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Edward S. Mocarski - One of the best experts on this subject based on the ideXlab platform.
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Recognizing limits of Z‐nucleic acid binding protein (ZBP1/DAI/DLM1) function
The FEBS journal, 2020Co-Authors: Heather S. Koehler, Yanjun Feng, Pratyusha Mandal, Edward S. MocarskiAbstract:Z-nucleic acid binding protein (ZBP)1 (also known as DAI and DLM1) is a pathogen sensor activated by double-strand character RNA to recruit receptor-interacting protein (RIP) Kinase via a RIP homotypic interaction motif. The activation of receptor-interacting protein Kinase (RIPK)3 and initiation of virus-induced necroptosis were initially reported in a landmark publication Upton et al. (Cell Host Microbe 11: 290, 2012) employing the DNA virus murine cytomegalovirus (MCMV). M45-encoded viral inhibitor of RIP activation prevents virus-induced necroptosis. Additional virus-encoded suppressors of necroptosis were then identified, including herpes simplex virus ICP6 and vaccinia virus E3L. Caspase-8 suppressors encoded by these DNA viruses block apoptosis, unleashing necroptosis mediated through Z-nucleic acid binding protein 1 (ZBP1) recruitment of RIPK3. These studies all utilized ZBP1-deficient mice generated by the Akira Lab (Zbp1-/- AK ) to bring the significance of virus-induced necroptosis to light. C57BL/6 mice were chosen as controls based on the assumption that mutant mice were congenic; however, these mice were recently found to display an unexpected innate immune deficit, lacking C57BL/6-specific NK1.1 and Ly49H natural killer cell subpopulations important in the early control of MCMV infection. Short nucleotide polymorphism analysis of Zbp1-/- AK breeders revealed a mixed genetic background (~ 71% C57BL/6 DNA and ~ 29% 129). Even though this level of 129 strain background does not alter ZBP1 cell-autonomous function as a sensor and mediator of necroptosis, it confounds innate immune response characteristics. In the future, genetic background must be carefully controlled before implicating ZBP1 function in response characteristics that shape immunity, inflammation, metabolism, and pathogenesis.
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recognizing limits of z nucleic acid binding protein zbp1 dai dlm1 function
FEBS Journal, 2020Co-Authors: Heather Koehler, Pratyusha Mandal, Yanjun Feng, Edward S. MocarskiAbstract:Z-nucleic acid binding protein (ZBP)1 (also known as DAI and DLM1) is a pathogen sensor activated by double-strand character RNA to recruit receptor-interacting protein (RIP) Kinase via a RIP homotypic interaction motif. The activation of receptor-interacting protein Kinase (RIPK)3 and initiation of virus-induced necroptosis were initially reported in a landmark publication Upton et al. (Cell Host Microbe 11: 290, 2012) employing the DNA virus murine cytomegalovirus (MCMV). M45-encoded viral inhibitor of RIP activation prevents virus-induced necroptosis. Additional virus-encoded suppressors of necroptosis were then identified, including herpes simplex virus ICP6 and vaccinia virus E3L. Caspase-8 suppressors encoded by these DNA viruses block apoptosis, unleashing necroptosis mediated through Z-nucleic acid binding protein 1 (ZBP1) recruitment of RIPK3. These studies all utilized ZBP1-deficient mice generated by the Akira Lab (Zbp1-/- AK ) to bring the significance of virus-induced necroptosis to light. C57BL/6 mice were chosen as controls based on the assumption that mutant mice were congenic; however, these mice were recently found to display an unexpected innate immune deficit, lacking C57BL/6-specific NK1.1 and Ly49H natural killer cell subpopulations important in the early control of MCMV infection. Short nucleotide polymorphism analysis of Zbp1-/- AK breeders revealed a mixed genetic background (~ 71% C57BL/6 DNA and ~ 29% 129). Even though this level of 129 strain background does not alter ZBP1 cell-autonomous function as a sensor and mediator of necroptosis, it confounds innate immune response characteristics. In the future, genetic background must be carefully controlled before implicating ZBP1 function in response characteristics that shape immunity, inflammation, metabolism, and pathogenesis.
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Caspase-8 restricts natural killer cell accumulation during MCMV Infection.
Medical microbiology and immunology, 2019Co-Authors: Yanjun Feng, Lisa P. Daley-bauer, Linda Roback, Marc Potempa, Lewis L Lanier, Edward S. MocarskiAbstract:Natural killer (NK) cells provide important host defense against herpesvirus infections and influence subsequent T cell control of replication and maintenance of latency. NK cells exhibit phases of expansion, contraction and memory formation in response to the natural mouse pathogen murine cytomegalovirus (MCMV). Innate and adaptive immune responses are tightly regulated in mammals to avoid excess tissue damage while preventing acute and chronic viral disease and assuring resistance to reinfection. Caspase (CASP)8 is an autoactivating aspartate-specific cysteine protease that initiates extrinsic apoptosis and prevents receptor interacting protein (RIP) Kinase (RIPK)1-RIPK3-driven necroptosis. CASP8 also promotes death-independent signal transduction. All of these activities make contributions to inflammation. Here, we demonstrate that CASP8 restricts NK cell expansion during MCMV infection but does not influence NK memory. Casp8-/-RIPk3-/- mice mount higher NK response levels than Casp8+/-RIPk3-/- littermate controls or WT C57BL/6 J mice, indicating that RIPK3 deficiency alone does not contribute to NK response patterns. MCMV m157-responsive Ly49H+ NK cells support increased expansion of both Ly49H- NK cells and CD8 T cells in Casp8-/-RIPk3-/- mice. Surprisingly, hyperaccumulation of NK cells depends on the pronecrotic Kinase RIPK1. RIPk1-/-Casp8-/-RIPk3-/- mice fail to show the enhanced expansion of lymphocytes observed in Casp8-/-RIPk3-/- mice even though development and homeostasis are preserved in uninfected RIPk1-/-Casp8-/-RIPk3-/- mice. Thus, CASP8 naturally regulates the magnitude of NK cell responses in response to infection where strong activation signals depend on another key regulator of death signaling, RIPK1. In addition, the strong NK cell response promotes survival of effector CD8 T cells during their expansion. Thus, hyperaccumulation of NK cells and crosstalk with T cells becomes amplified in the absence of extrinsic cell death machinery.
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Herpes simplex virus 1 ICP6 impedes TNF receptor 1-induced necrosome assembly during compartmentalization to detergent-resistant membrane vesicles.
The Journal of biological chemistry, 2018Co-Authors: Mohammed K. Ali, Linda Roback, Edward S. MocarskiAbstract:Receptor-interacting protein (RIP) Kinase 3 (RIPK3)-dependent necroptosis directs inflammation and tissue injury, as well as anti-viral host defense. In human cells, herpes simplex virus 1 (HSV1) UL39-encoded ICP6 blocks RIP homotypic interacting motif (RHIM) signal transduction, preventing this leakage form of cell death and sustaining viral infection. TNF receptor 1 (TNFR1)-induced necroptosis is known to require the formation of a RIPK1-RIPK3-mixed lineage Kinase domain-like pseudoKinase (MLKL) signaling complex (necrosome) that we find compartmentalizes exclusively to caveolin-1-associated detergent-resistant membrane (DRM) vesicles in HT-29 cells. Translocation proceeds in the presence of RIPK3 Kinase inhibitor GSK'840 or MLKL inhibitor necrosulfonomide but requires the Kinase activity, as well as RHIM signaling of RIPK1. ICP6 impedes the translocation of RIPK1, RIPK3, and MLKL to caveolin-1-containing DRM vesicles without fully blocking the activation of RIPK3 or phosphorylation of MLKL. Consistent with the important contribution of RIPK1 RHIM-dependent recruitment of RIPK3, overexpression of RHIM-deficient RIPK3 results in phosphorylation of MLKL, but this does not lead to either translocation or necroptosis. Combined, these data reveal a critical role of RHIM signaling in the recruitment of the MLKL-containing necrosome to membrane vesicle-associated sites of aggregation. A similar mechanism is predicted for other RHIM-containing signaling adaptors, Z-nucleic acid-binding protein 1 (ZBP1) (also called DAI and DLM1), and TIR domain-containing adapter-inducing interferon-β (TRIF).
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Mouse cytomegalovirus M36 and M45 death suppressors cooperate to prevent inflammation resulting from antiviral programmed cell death pathways.
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Lisa P. Daley-bauer, Yanjun Feng, William J. Kaiser, Linda Roback, Lynsey N. Crosby, A. Louise Mccormick, Edward S. MocarskiAbstract:The complex interplay between caspase-8 and receptor-interacting protein (RIP) Kinase RIP 3 (RIPK3) driving extrinsic apoptosis and necroptosis is not fully understood. Murine cytomegalovirus triggers both apoptosis and necroptosis in infected cells; however, encoded inhibitors of caspase-8 activity (M36) and RIP3 signaling (M45) suppress these antiviral responses. Here, we report that this virus activates caspase-8 in macrophages to trigger apoptosis that gives rise to secondary necroptosis. Infection with double-mutant ΔM36/M45mutRHIM virus reveals a signaling pattern in which caspase-8 activates caspase-3 to drive apoptosis with subsequent RIP3-dependent activation of mixed lineage Kinase domain-like (MLKL) leading to necroptosis. This combined cell death signaling is highly inflammatory, greater than either apoptosis induced by ΔM36 or necroptosis induced by M45mutRHIM virus. IL-6 production by macrophages is dramatically increased during double-mutant virus infection and correlates with faster antiviral responses in the host. Collaboratively, M36 and M45 target caspase-8 and RIP3 pathways together to suppress this proinflammatory cell death. This study reveals the effect of antiviral programmed cell death pathways on inflammation, shows that caspase-8 activation may go hand-in-hand with necroptosis in macrophages, and revises current understanding of independent and collaborative functions of M36 and M45 in blocking apoptotic and necroptotic cell death responses.
Demetrios G Vavvas - One of the best experts on this subject based on the ideXlab platform.
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Blocking the Necroptosis Pathway Decreases RPE and Photoreceptor Damage Induced by NaIO3
2018Co-Authors: Miin Roh, Joan W Miller, Hidetaka Matsumoto, Haijinag Lin, Alp Atik, Peggy Bouzika, Albert Alhatem, Demetrios G VavvasAbstract:Purpose: Sodium iodate (NaIO3) has been extensively used as a retinotoxin to induce RPE cell damage and degeneration of photoreceptors in vitro and in vivo. RIP-Kinase dependent programmed necrosis is an important redundant cell death pathway involved in photoreceptor cell death. We wanted to determine whether these pathways are actively involved in RPE and photoreceptor cell death after NaIO3 insult. Methods: ARPE-19 cells were exposed to different concentrations of NaIO3 in the presence or absence of various concentrations of a RIPK inhibitor (Nec-1) or a pan-caspase inhibitor (Z-VAD), individually or combined. Cell death was determined at different time points by MTT (Sigma-Aldrich), LDH (Promega) and TUNEL (Millipore) assay. C57BL/6 and RIP3-/- mice were treated with a peritoneal injection of NaIO3 and eyes were enucleated at day 3 or 7. TUNEL staining was used to evaluate photoreceptor cell death. Photoreceptor cell loss was evaluated by measuring the thickness of outer nuclear layer (ONL). Microglia in the ONL were quantified in a retinal whole mount with Iba-1 antibody. RPE degeneration was also assessed in a RPE whole mount, with ZO-1 antibody. Results: NaIO3 resulted in significant cell death of ARPE-19 cells. Treatment with Nec-1 resulted in better protection than treatment with Z-VAD (P
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Necrotic cone photoreceptor cell death in retinitis pigmentosa
Cell death & disease, 2015Co-Authors: Yusuke Murakami, Joan W Miller, Demetrios G Vavvas, Yasuhiro Ikeda, Shunji Nakatake, K.-h. Sonoda, Tatsuro IshibashiAbstract:Retinitis pigmentosa (RP) comprises a group of inherited retinal degenerations, resulting from rod and cone photoreceptor cell death. Genetic studies have identified mutations in more than 50 genes—most of which encode rod-related molecules—that are associated with RP. Although rod cells that harbor the deleterious mutations are expected to die, it remains a puzzle why cone cells also die in this disease, subsequent to rod degeneration. Because the loss of cone-mediated vision is the most debilitating aspect of RP, elucidating the mechanisms of cone cell death is critical towards developing novel therapeutics in RP. Apoptosis and necrosis are two major forms of cell death, which show distinct morphological appearance. Apoptosis is accompanied by the reduction of cellular volume and chromatin condensation, and necrosis is associated with cellular and organelle swelling, and plasma membrane rupture. Although necrosis was traditionally considered as an unregulated form of cell death, it is now known to have regulated components, such as those involving receptor-interacting protein (RIP) Kinases.1 In animal models of RP, rod cell death has been shown to occur mainly through apoptosis.2 Recent studies demonstrated that caspase-independent pathways, such as poly-ADP-ribose-polymerase, calpain and histone deacetylase, are commonly activated in dying rod cells in several models of RP.3, 4 In contrast, the mode of cone cell death is less characterized. We and others previously demonstrated that, in mouse models of RP, cone cell death is associated with necrotic features and it is substantially suppressed by RIP3 deficiency or the RIP Kinase inhibitor.5, 6 These findings indicated that the necrotic pathway is involved in cone cell death in RP, at least in part, and may be a novel therapeutic target (Figure 1). However, the relevancy of these findings in human pathology remains unclear. Figure 1 Rod and cone photoreceptor cell death in retinitis pigmentosa. Rod cell death due to the deleterious genetic mutations is associated with apoptosis, which involves the activation of caspase-independent pathways including poly-ADP-ribose-polymerase (PARP), ... In our recent study published in Cell Death and Discovery, we investigated the possible involvement of necrotic cone cell death in RP patients by examining the cone mosaic images obtained by the adaptive optics scanning laser ophthalmoscopy (AO-SLO).7 With the AO imaging system, the individual cone cells are visualized as bright spots in living human eyes. Using an automated measurement program of the cone spot size in AO-SLO images, we showed that there was a population of enlarged cone spots in the macula of RP patients. Cone enlargement was observed in a variety of RP patients and disease stage. The precise interpretation of these changes in AO-SLO images is challenging, however, taken together with the results from experimental studies, we propose that the enlarged spots may reflect the necrotic changes of cone cells in RP patients. Consistent with this idea, previous histological studies of postmortem RP patients' eyes demonstrated the necrotic changes of cone cells such as cell swelling and disrupted plasma membrane.8 Intracellular contents released from dying or dead cells act as damage-associated molecular patterns (DAMPs) to promote inflammatory responses and tissue injury. HMGB1 is one of the best-characterized DAMPs released from necrotic cells.9 In the vitreous of RP patients, we found that the HMGB1 levels were significantly elevated compared with those in controls. These findings support our idea that necrotic cell death is implicated in the degenerative process of RP. In animal models of RP, we previously demonstrated that RIP3 deficiency suppresses microglial activation during cone but not rod degeneration in rd10 mice, suggesting that DAMPs released from necrotic cone cells may enhance retinal inflammation.5 In human RP patients, intraocular inflammation measured by slit-lamp or laser flaremeter is inversely associated with central visual function.10 These findings indicate that cone cell death and inflammation are closely interconnected during cone degeneration in RP. Recent studies have shown that the cone cell death in RP is caused by the microenvironmental changes following rod degeneration, such as inflammation, oxidation and loss of trophic factors. Interestingly, Punzo et al.11 reported that, in four different models of RP the dying cones show gene expression profiles associated with starvation. In line with these findings, Ait-Ali et al.12 recently showed that rod-derived cone viability factor promotes cone cell survival by stimulating the glucose uptake and glycolysis. Because nutrient deprivation can lead to mitochondrial and cytoplasmic swelling, the necrotic cone cell death in RP may be caused by a nutrient shortage. Alternatively, as inflammatory cells express tumor necrosis factor-α and FAS ligand, which recruit RIP1 and activate RIP Kinase pathways, excessive inflammatory activation may exacerbate necrotic cone cell death in RP. It will be interesting to further investigate the mechanisms of cone cell death in several models and human patients with RP to identify the common therapeutic targets to prevent or delay the secondary cone degeneration in RP.
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RIP Kinase-mediated programmed necrosis
Neuroprotection and Neuroregeneration for Retinal Diseases, 2014Co-Authors: Yusuke Murakami, Maki Kayama, Joan W Miller, Demetrios G VavvasAbstract:Retinal ganglion cell (RGC) death is the ultimate cause of vision loss in glaucoma. Apoptosis has been thought to be a major form of cell death in various diseases including glaucoma; however, attempts to develop neuroprotective agents that target apoptosis have largely failed. Recent accumulating evidence has shown that non-apoptotic forms of cell death such as necrosis are also regulated by specific molecular machinery, such as those mediated by receptor-interacting protein (RIP) Kinases. In this review, we summarize recent advances in our understanding of RIP Kinase signaling and its roles in RGC loss. These data suggest that not only apoptosis but also necrosis is involved in RGC death and that combined targeting of these pathways may be an effective strategy for glaucoma.
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receptor interacting protein Kinase mediates necrotic cone but not rod cell death in a mouse model of inherited degeneration
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Yusuke Murakami, Toshio Hisatomi, Joan W Miller, Hidetaka Matsumoto, Miin Roh, Jun Suzuki, Yasuhiro Ikeda, Demetrios G VavvasAbstract:Retinitis pigmentosa comprises a group of inherited retinal photoreceptor degenerations that lead to progressive loss of vision. Although in most cases rods, but not cones, harbor the deleterious gene mutations, cones do die in this disease, usually after the main phase of rod cell loss. Rod photoreceptor death is characterized by apoptotic features. In contrast, the mechanisms and features of subsequent nonautonomous cone cell death remain largely unknown. In this study, we show that receptor-interacting protein (RIP) Kinase mediates necrotic cone cell death in rd10 mice, a mouse model of retinitis pigmentosa caused by a mutation in a rod-specific gene. The expression of RIP3, a key regulator of programmed necrosis, was elevated in rd10 mouse retinas in the phase of cone but not rod degeneration. Although rd10 mice lacking RIP3 developed comparable rod degeneration to control rd10 mice, they displayed a significant preservation of cone cells. Ultrastructural analysis of rd10 mouse retinas revealed that a substantial fraction of dying cones exhibited necrotic morphology, which was rescued by RIP3 deficiency. Additionally, pharmacologic treatment with a RIP Kinase inhibitor attenuated histological and functional deficits of cones in rd10 mice. Thus, necrotic mechanisms involving RIP Kinase are crucial in cone cell death in inherited retinal degeneration, suggesting the RIP Kinase pathway as a potential target to protect cone-mediated central and peRIPheral vision loss in patients with retinitis pigementosa.
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RIP Kinases, necroptosis and redundancy in neuronal cell death
Acta Ophthalmologica, 2012Co-Authors: Demetrios G Vavvas, Yusuke Murakami, Maki Kayama, Jw MillerAbstract:Purpose Neuronal cell death is the major cause of vision loss in many eye diseases. The exact mechanism remains unknown. Apoptosis has been thought to be the major form of regulated cell death and the main modality of neuronal cell death in degenerative ailments. However, neuroprotective strategies based on apoptosis have failed to materialize. We wanted to investigate the presence of alternative cell death modalities in various models of degenerative eye diseases. Methods Neuronal cell death was studied in a variety of animal models, including retinal detachment, RD10 juvenile degeneration, Cx3Cr1/CCL2/rd8 tRIPle mutant, optic nerve crush, and chemical toxicity models (NMDA, PolyI:C, Na-Iodate, Lipid peroxide, and chloroquine). Analysis of cell death was performed by transmission electron microscopy (TEM), TUNEL staining and standard molecular techniques. Results Caspase dependent apoptosis was the major cell death modality in most models of cell degeneration. However, RIP regulated necrosis accounted for a significant portion of cell death morphology. Under conditions of selective caspase inhibition, RIP regulated necrosis became the predominant cell death modality. Simultaneous caspase and RIPK inhibition lead to significant neuroprotection. Autophagy accounted for small portion of cell death in the models that it was examined. Conclusion RIP Kinase regulated necrosis (necroptosis) is a significant redundant cell death pathway in many animal models of ocular degenerative diseases. It becomes the predominant form of cell death under conditions of caspase inhibition. Combination treatments may be needed for successful neuroprotection. Commercial interest
Yanjun Feng - One of the best experts on this subject based on the ideXlab platform.
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Recognizing limits of Z‐nucleic acid binding protein (ZBP1/DAI/DLM1) function
The FEBS journal, 2020Co-Authors: Heather S. Koehler, Yanjun Feng, Pratyusha Mandal, Edward S. MocarskiAbstract:Z-nucleic acid binding protein (ZBP)1 (also known as DAI and DLM1) is a pathogen sensor activated by double-strand character RNA to recruit receptor-interacting protein (RIP) Kinase via a RIP homotypic interaction motif. The activation of receptor-interacting protein Kinase (RIPK)3 and initiation of virus-induced necroptosis were initially reported in a landmark publication Upton et al. (Cell Host Microbe 11: 290, 2012) employing the DNA virus murine cytomegalovirus (MCMV). M45-encoded viral inhibitor of RIP activation prevents virus-induced necroptosis. Additional virus-encoded suppressors of necroptosis were then identified, including herpes simplex virus ICP6 and vaccinia virus E3L. Caspase-8 suppressors encoded by these DNA viruses block apoptosis, unleashing necroptosis mediated through Z-nucleic acid binding protein 1 (ZBP1) recruitment of RIPK3. These studies all utilized ZBP1-deficient mice generated by the Akira Lab (Zbp1-/- AK ) to bring the significance of virus-induced necroptosis to light. C57BL/6 mice were chosen as controls based on the assumption that mutant mice were congenic; however, these mice were recently found to display an unexpected innate immune deficit, lacking C57BL/6-specific NK1.1 and Ly49H natural killer cell subpopulations important in the early control of MCMV infection. Short nucleotide polymorphism analysis of Zbp1-/- AK breeders revealed a mixed genetic background (~ 71% C57BL/6 DNA and ~ 29% 129). Even though this level of 129 strain background does not alter ZBP1 cell-autonomous function as a sensor and mediator of necroptosis, it confounds innate immune response characteristics. In the future, genetic background must be carefully controlled before implicating ZBP1 function in response characteristics that shape immunity, inflammation, metabolism, and pathogenesis.
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recognizing limits of z nucleic acid binding protein zbp1 dai dlm1 function
FEBS Journal, 2020Co-Authors: Heather Koehler, Pratyusha Mandal, Yanjun Feng, Edward S. MocarskiAbstract:Z-nucleic acid binding protein (ZBP)1 (also known as DAI and DLM1) is a pathogen sensor activated by double-strand character RNA to recruit receptor-interacting protein (RIP) Kinase via a RIP homotypic interaction motif. The activation of receptor-interacting protein Kinase (RIPK)3 and initiation of virus-induced necroptosis were initially reported in a landmark publication Upton et al. (Cell Host Microbe 11: 290, 2012) employing the DNA virus murine cytomegalovirus (MCMV). M45-encoded viral inhibitor of RIP activation prevents virus-induced necroptosis. Additional virus-encoded suppressors of necroptosis were then identified, including herpes simplex virus ICP6 and vaccinia virus E3L. Caspase-8 suppressors encoded by these DNA viruses block apoptosis, unleashing necroptosis mediated through Z-nucleic acid binding protein 1 (ZBP1) recruitment of RIPK3. These studies all utilized ZBP1-deficient mice generated by the Akira Lab (Zbp1-/- AK ) to bring the significance of virus-induced necroptosis to light. C57BL/6 mice were chosen as controls based on the assumption that mutant mice were congenic; however, these mice were recently found to display an unexpected innate immune deficit, lacking C57BL/6-specific NK1.1 and Ly49H natural killer cell subpopulations important in the early control of MCMV infection. Short nucleotide polymorphism analysis of Zbp1-/- AK breeders revealed a mixed genetic background (~ 71% C57BL/6 DNA and ~ 29% 129). Even though this level of 129 strain background does not alter ZBP1 cell-autonomous function as a sensor and mediator of necroptosis, it confounds innate immune response characteristics. In the future, genetic background must be carefully controlled before implicating ZBP1 function in response characteristics that shape immunity, inflammation, metabolism, and pathogenesis.
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Caspase-8 restricts natural killer cell accumulation during MCMV Infection.
Medical microbiology and immunology, 2019Co-Authors: Yanjun Feng, Lisa P. Daley-bauer, Linda Roback, Marc Potempa, Lewis L Lanier, Edward S. MocarskiAbstract:Natural killer (NK) cells provide important host defense against herpesvirus infections and influence subsequent T cell control of replication and maintenance of latency. NK cells exhibit phases of expansion, contraction and memory formation in response to the natural mouse pathogen murine cytomegalovirus (MCMV). Innate and adaptive immune responses are tightly regulated in mammals to avoid excess tissue damage while preventing acute and chronic viral disease and assuring resistance to reinfection. Caspase (CASP)8 is an autoactivating aspartate-specific cysteine protease that initiates extrinsic apoptosis and prevents receptor interacting protein (RIP) Kinase (RIPK)1-RIPK3-driven necroptosis. CASP8 also promotes death-independent signal transduction. All of these activities make contributions to inflammation. Here, we demonstrate that CASP8 restricts NK cell expansion during MCMV infection but does not influence NK memory. Casp8-/-RIPk3-/- mice mount higher NK response levels than Casp8+/-RIPk3-/- littermate controls or WT C57BL/6 J mice, indicating that RIPK3 deficiency alone does not contribute to NK response patterns. MCMV m157-responsive Ly49H+ NK cells support increased expansion of both Ly49H- NK cells and CD8 T cells in Casp8-/-RIPk3-/- mice. Surprisingly, hyperaccumulation of NK cells depends on the pronecrotic Kinase RIPK1. RIPk1-/-Casp8-/-RIPk3-/- mice fail to show the enhanced expansion of lymphocytes observed in Casp8-/-RIPk3-/- mice even though development and homeostasis are preserved in uninfected RIPk1-/-Casp8-/-RIPk3-/- mice. Thus, CASP8 naturally regulates the magnitude of NK cell responses in response to infection where strong activation signals depend on another key regulator of death signaling, RIPK1. In addition, the strong NK cell response promotes survival of effector CD8 T cells during their expansion. Thus, hyperaccumulation of NK cells and crosstalk with T cells becomes amplified in the absence of extrinsic cell death machinery.
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Mouse cytomegalovirus M36 and M45 death suppressors cooperate to prevent inflammation resulting from antiviral programmed cell death pathways.
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Lisa P. Daley-bauer, Yanjun Feng, William J. Kaiser, Linda Roback, Lynsey N. Crosby, A. Louise Mccormick, Edward S. MocarskiAbstract:The complex interplay between caspase-8 and receptor-interacting protein (RIP) Kinase RIP 3 (RIPK3) driving extrinsic apoptosis and necroptosis is not fully understood. Murine cytomegalovirus triggers both apoptosis and necroptosis in infected cells; however, encoded inhibitors of caspase-8 activity (M36) and RIP3 signaling (M45) suppress these antiviral responses. Here, we report that this virus activates caspase-8 in macrophages to trigger apoptosis that gives rise to secondary necroptosis. Infection with double-mutant ΔM36/M45mutRHIM virus reveals a signaling pattern in which caspase-8 activates caspase-3 to drive apoptosis with subsequent RIP3-dependent activation of mixed lineage Kinase domain-like (MLKL) leading to necroptosis. This combined cell death signaling is highly inflammatory, greater than either apoptosis induced by ΔM36 or necroptosis induced by M45mutRHIM virus. IL-6 production by macrophages is dramatically increased during double-mutant virus infection and correlates with faster antiviral responses in the host. Collaboratively, M36 and M45 target caspase-8 and RIP3 pathways together to suppress this proinflammatory cell death. This study reveals the effect of antiviral programmed cell death pathways on inflammation, shows that caspase-8 activation may go hand-in-hand with necroptosis in macrophages, and revises current understanding of independent and collaborative functions of M36 and M45 in blocking apoptotic and necroptotic cell death responses.
Yusuke Murakami - One of the best experts on this subject based on the ideXlab platform.
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RIP1 Kinase mediates angiogenesis by modulating macrophages in experimental neovascularization
2019Co-Authors: Takashi Ueta, Yusuke Murakami, Kenji Ishihara, Shoji Notomi, Jong Jer Lee, Daniel E. Maidana, Nikolaos Efstathiou, Eiichi Hasegawa, Kunihiro Azuma, Tetsuya ToyonoAbstract:ABSTRACT Inflammation plays an important role in pathologic angiogenesis. Receptor-interacting protein 1 (RIP1) is highly expressed in inflammatory cells and is known to play an important role in the regulation of apoptosis, necroptosis, and inflammation, however its role in angiogenesis remains elusive. Here, we show that RIP1 is abundantly expressed in infiltrating macrophages during angiogenesis, and genetic or pharmacological inhibition of RIP1 Kinase activity using Kinase-inactive RIP1K45A/K45A mice or necrostatin-1 attenuates angiogenesis in laser-induced choroidal neovascularization (CNV), Matrigel plug angiogenesis, and alkali injury-induced corneal neovascularization in mice. The inhibitory effect on angiogenesis was mediated by caspase activation through a Kinase-independent function of RIP1 and RIP3, and simultaneous caspase inhibition with RIP1 Kinase inhibition abrogated the effects of RIP1 Kinase inhibition on angiogenesis in vivo. Mechanistically, infiltrating macrophages are the key target for RIP1 Kinase inhibition to attenuate pathological angiogenesis, and we observed that the inhibition of RIP1 Kinase activity is associated with caspase activation in infiltrating macrophages and decreased expression of pro-angiogenic M2-like markers while M1 marker expressions were sustained. Similarly, in vitro, catalytic inhibition of RIP1 down-regulated M2 marker expressions in IL-4-activated bone marrow-derived macrophages, which was blocked by simultaneous caspase inhibition. Taken together, these results suggest a novel, non-necrotic function of RIP1 Kinase activity and suggest that RIP1-mediated modulation of macrophage activation may represent a therapeutic target for the control of angiogenesis-related diseases. Significance Pathological angiogenesis has been implicated in diverse pathologies. Infiltrating macrophages, especially those activated to M2-like phenotype are critically important to support angiogenesis. Whereas the role of RIP1 Kinase in the regulation of apoptosis, necroptosis, and inflammation have been well established, its role in angiogenesis remains elusive despite being abundantly expressed in angiogenesis-related infiltrating macrophages. This study demonstrated for the first time that RIP1 Kinase inhibition attenuates angiogenesis in multiple mouse models of pathological angiogenesis in vivo. Mechanistically, the inhibitory effect on angiogenesis depends on RIP Kinase inhibition-mediated caspase activation in infiltrating macrophages that suppresses M2-like polarization, thereby attenuating pathological angiogenesis.
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Combined inhibition of apoptosis and necrosis promotes transient neuroprotection of retinal ganglion cells and partial-axon regeneration after optic nerve damage
2018Co-Authors: Maki Kayama, Yusuke Murakami, Aristomenis Thanos, Yuki Morizane, Joan W Miller, Kumiko Omura, Edith R. Reshef, Andrea Gianni, Toru Nakazawa, Larry I. BenowitzAbstract:Retinal ganglion cell (RGC) death is the hallmark of glaucoma. Axonal injury is thought to precede RGC loss in glaucoma, and thus studies using an optic nerve (ON) crush model have been widely used to investigate mechanisms of cell death that are common to both conditions. Prior work has focused on the involvement of caspases in RGC death, but little is known about the contribution of other forms of cell death such as necrosis. In this study we show that receptor interacting protein (RIP) Kinase-mediated necrosis normally plays a role in RGC death and acts in concert with caspase-dependent apoptosis. The expression of RIP3, a key activator of RIP1 Kinase, as well as caspase activity, increased following ON injury. Caspase inhibition alone failed to provide substantial protection to injured RGCs and unexpectedly exacerbated necrosis. In contrast, pharmacologic or genetic inhibition of RIP Kinases in combination with caspase blockade delayed both apoptotic and necrotic RGC death, although RGCs still continued to die. Furthermore, inhibition of RIP1 Kinase promoted a moderate level of axon regeneration that was only minimal affected by caspase inhibition. In conclusion, multiple approaches are required for effective RGC death prevention and axonal regeneration. Further studies are needed to elucidate more effective long term strategies that can lead to sustained neuroprotection and regeneration.
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Necrotic cone photoreceptor cell death in retinitis pigmentosa
Cell death & disease, 2015Co-Authors: Yusuke Murakami, Joan W Miller, Demetrios G Vavvas, Yasuhiro Ikeda, Shunji Nakatake, K.-h. Sonoda, Tatsuro IshibashiAbstract:Retinitis pigmentosa (RP) comprises a group of inherited retinal degenerations, resulting from rod and cone photoreceptor cell death. Genetic studies have identified mutations in more than 50 genes—most of which encode rod-related molecules—that are associated with RP. Although rod cells that harbor the deleterious mutations are expected to die, it remains a puzzle why cone cells also die in this disease, subsequent to rod degeneration. Because the loss of cone-mediated vision is the most debilitating aspect of RP, elucidating the mechanisms of cone cell death is critical towards developing novel therapeutics in RP. Apoptosis and necrosis are two major forms of cell death, which show distinct morphological appearance. Apoptosis is accompanied by the reduction of cellular volume and chromatin condensation, and necrosis is associated with cellular and organelle swelling, and plasma membrane rupture. Although necrosis was traditionally considered as an unregulated form of cell death, it is now known to have regulated components, such as those involving receptor-interacting protein (RIP) Kinases.1 In animal models of RP, rod cell death has been shown to occur mainly through apoptosis.2 Recent studies demonstrated that caspase-independent pathways, such as poly-ADP-ribose-polymerase, calpain and histone deacetylase, are commonly activated in dying rod cells in several models of RP.3, 4 In contrast, the mode of cone cell death is less characterized. We and others previously demonstrated that, in mouse models of RP, cone cell death is associated with necrotic features and it is substantially suppressed by RIP3 deficiency or the RIP Kinase inhibitor.5, 6 These findings indicated that the necrotic pathway is involved in cone cell death in RP, at least in part, and may be a novel therapeutic target (Figure 1). However, the relevancy of these findings in human pathology remains unclear. Figure 1 Rod and cone photoreceptor cell death in retinitis pigmentosa. Rod cell death due to the deleterious genetic mutations is associated with apoptosis, which involves the activation of caspase-independent pathways including poly-ADP-ribose-polymerase (PARP), ... In our recent study published in Cell Death and Discovery, we investigated the possible involvement of necrotic cone cell death in RP patients by examining the cone mosaic images obtained by the adaptive optics scanning laser ophthalmoscopy (AO-SLO).7 With the AO imaging system, the individual cone cells are visualized as bright spots in living human eyes. Using an automated measurement program of the cone spot size in AO-SLO images, we showed that there was a population of enlarged cone spots in the macula of RP patients. Cone enlargement was observed in a variety of RP patients and disease stage. The precise interpretation of these changes in AO-SLO images is challenging, however, taken together with the results from experimental studies, we propose that the enlarged spots may reflect the necrotic changes of cone cells in RP patients. Consistent with this idea, previous histological studies of postmortem RP patients' eyes demonstrated the necrotic changes of cone cells such as cell swelling and disrupted plasma membrane.8 Intracellular contents released from dying or dead cells act as damage-associated molecular patterns (DAMPs) to promote inflammatory responses and tissue injury. HMGB1 is one of the best-characterized DAMPs released from necrotic cells.9 In the vitreous of RP patients, we found that the HMGB1 levels were significantly elevated compared with those in controls. These findings support our idea that necrotic cell death is implicated in the degenerative process of RP. In animal models of RP, we previously demonstrated that RIP3 deficiency suppresses microglial activation during cone but not rod degeneration in rd10 mice, suggesting that DAMPs released from necrotic cone cells may enhance retinal inflammation.5 In human RP patients, intraocular inflammation measured by slit-lamp or laser flaremeter is inversely associated with central visual function.10 These findings indicate that cone cell death and inflammation are closely interconnected during cone degeneration in RP. Recent studies have shown that the cone cell death in RP is caused by the microenvironmental changes following rod degeneration, such as inflammation, oxidation and loss of trophic factors. Interestingly, Punzo et al.11 reported that, in four different models of RP the dying cones show gene expression profiles associated with starvation. In line with these findings, Ait-Ali et al.12 recently showed that rod-derived cone viability factor promotes cone cell survival by stimulating the glucose uptake and glycolysis. Because nutrient deprivation can lead to mitochondrial and cytoplasmic swelling, the necrotic cone cell death in RP may be caused by a nutrient shortage. Alternatively, as inflammatory cells express tumor necrosis factor-α and FAS ligand, which recruit RIP1 and activate RIP Kinase pathways, excessive inflammatory activation may exacerbate necrotic cone cell death in RP. It will be interesting to further investigate the mechanisms of cone cell death in several models and human patients with RP to identify the common therapeutic targets to prevent or delay the secondary cone degeneration in RP.
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RIP Kinase-mediated programmed necrosis
Neuroprotection and Neuroregeneration for Retinal Diseases, 2014Co-Authors: Yusuke Murakami, Maki Kayama, Joan W Miller, Demetrios G VavvasAbstract:Retinal ganglion cell (RGC) death is the ultimate cause of vision loss in glaucoma. Apoptosis has been thought to be a major form of cell death in various diseases including glaucoma; however, attempts to develop neuroprotective agents that target apoptosis have largely failed. Recent accumulating evidence has shown that non-apoptotic forms of cell death such as necrosis are also regulated by specific molecular machinery, such as those mediated by receptor-interacting protein (RIP) Kinases. In this review, we summarize recent advances in our understanding of RIP Kinase signaling and its roles in RGC loss. These data suggest that not only apoptosis but also necrosis is involved in RGC death and that combined targeting of these pathways may be an effective strategy for glaucoma.
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receptor interacting protein Kinase mediates necrotic cone but not rod cell death in a mouse model of inherited degeneration
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Yusuke Murakami, Toshio Hisatomi, Joan W Miller, Hidetaka Matsumoto, Miin Roh, Jun Suzuki, Yasuhiro Ikeda, Demetrios G VavvasAbstract:Retinitis pigmentosa comprises a group of inherited retinal photoreceptor degenerations that lead to progressive loss of vision. Although in most cases rods, but not cones, harbor the deleterious gene mutations, cones do die in this disease, usually after the main phase of rod cell loss. Rod photoreceptor death is characterized by apoptotic features. In contrast, the mechanisms and features of subsequent nonautonomous cone cell death remain largely unknown. In this study, we show that receptor-interacting protein (RIP) Kinase mediates necrotic cone cell death in rd10 mice, a mouse model of retinitis pigmentosa caused by a mutation in a rod-specific gene. The expression of RIP3, a key regulator of programmed necrosis, was elevated in rd10 mouse retinas in the phase of cone but not rod degeneration. Although rd10 mice lacking RIP3 developed comparable rod degeneration to control rd10 mice, they displayed a significant preservation of cone cells. Ultrastructural analysis of rd10 mouse retinas revealed that a substantial fraction of dying cones exhibited necrotic morphology, which was rescued by RIP3 deficiency. Additionally, pharmacologic treatment with a RIP Kinase inhibitor attenuated histological and functional deficits of cones in rd10 mice. Thus, necrotic mechanisms involving RIP Kinase are crucial in cone cell death in inherited retinal degeneration, suggesting the RIP Kinase pathway as a potential target to protect cone-mediated central and peRIPheral vision loss in patients with retinitis pigementosa.
Joan W Miller - One of the best experts on this subject based on the ideXlab platform.
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Blocking the Necroptosis Pathway Decreases RPE and Photoreceptor Damage Induced by NaIO3
2018Co-Authors: Miin Roh, Joan W Miller, Hidetaka Matsumoto, Haijinag Lin, Alp Atik, Peggy Bouzika, Albert Alhatem, Demetrios G VavvasAbstract:Purpose: Sodium iodate (NaIO3) has been extensively used as a retinotoxin to induce RPE cell damage and degeneration of photoreceptors in vitro and in vivo. RIP-Kinase dependent programmed necrosis is an important redundant cell death pathway involved in photoreceptor cell death. We wanted to determine whether these pathways are actively involved in RPE and photoreceptor cell death after NaIO3 insult. Methods: ARPE-19 cells were exposed to different concentrations of NaIO3 in the presence or absence of various concentrations of a RIPK inhibitor (Nec-1) or a pan-caspase inhibitor (Z-VAD), individually or combined. Cell death was determined at different time points by MTT (Sigma-Aldrich), LDH (Promega) and TUNEL (Millipore) assay. C57BL/6 and RIP3-/- mice were treated with a peritoneal injection of NaIO3 and eyes were enucleated at day 3 or 7. TUNEL staining was used to evaluate photoreceptor cell death. Photoreceptor cell loss was evaluated by measuring the thickness of outer nuclear layer (ONL). Microglia in the ONL were quantified in a retinal whole mount with Iba-1 antibody. RPE degeneration was also assessed in a RPE whole mount, with ZO-1 antibody. Results: NaIO3 resulted in significant cell death of ARPE-19 cells. Treatment with Nec-1 resulted in better protection than treatment with Z-VAD (P
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Combined inhibition of apoptosis and necrosis promotes transient neuroprotection of retinal ganglion cells and partial-axon regeneration after optic nerve damage
2018Co-Authors: Maki Kayama, Yusuke Murakami, Aristomenis Thanos, Yuki Morizane, Joan W Miller, Kumiko Omura, Edith R. Reshef, Andrea Gianni, Toru Nakazawa, Larry I. BenowitzAbstract:Retinal ganglion cell (RGC) death is the hallmark of glaucoma. Axonal injury is thought to precede RGC loss in glaucoma, and thus studies using an optic nerve (ON) crush model have been widely used to investigate mechanisms of cell death that are common to both conditions. Prior work has focused on the involvement of caspases in RGC death, but little is known about the contribution of other forms of cell death such as necrosis. In this study we show that receptor interacting protein (RIP) Kinase-mediated necrosis normally plays a role in RGC death and acts in concert with caspase-dependent apoptosis. The expression of RIP3, a key activator of RIP1 Kinase, as well as caspase activity, increased following ON injury. Caspase inhibition alone failed to provide substantial protection to injured RGCs and unexpectedly exacerbated necrosis. In contrast, pharmacologic or genetic inhibition of RIP Kinases in combination with caspase blockade delayed both apoptotic and necrotic RGC death, although RGCs still continued to die. Furthermore, inhibition of RIP1 Kinase promoted a moderate level of axon regeneration that was only minimal affected by caspase inhibition. In conclusion, multiple approaches are required for effective RGC death prevention and axonal regeneration. Further studies are needed to elucidate more effective long term strategies that can lead to sustained neuroprotection and regeneration.
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Necrotic cone photoreceptor cell death in retinitis pigmentosa
Cell death & disease, 2015Co-Authors: Yusuke Murakami, Joan W Miller, Demetrios G Vavvas, Yasuhiro Ikeda, Shunji Nakatake, K.-h. Sonoda, Tatsuro IshibashiAbstract:Retinitis pigmentosa (RP) comprises a group of inherited retinal degenerations, resulting from rod and cone photoreceptor cell death. Genetic studies have identified mutations in more than 50 genes—most of which encode rod-related molecules—that are associated with RP. Although rod cells that harbor the deleterious mutations are expected to die, it remains a puzzle why cone cells also die in this disease, subsequent to rod degeneration. Because the loss of cone-mediated vision is the most debilitating aspect of RP, elucidating the mechanisms of cone cell death is critical towards developing novel therapeutics in RP. Apoptosis and necrosis are two major forms of cell death, which show distinct morphological appearance. Apoptosis is accompanied by the reduction of cellular volume and chromatin condensation, and necrosis is associated with cellular and organelle swelling, and plasma membrane rupture. Although necrosis was traditionally considered as an unregulated form of cell death, it is now known to have regulated components, such as those involving receptor-interacting protein (RIP) Kinases.1 In animal models of RP, rod cell death has been shown to occur mainly through apoptosis.2 Recent studies demonstrated that caspase-independent pathways, such as poly-ADP-ribose-polymerase, calpain and histone deacetylase, are commonly activated in dying rod cells in several models of RP.3, 4 In contrast, the mode of cone cell death is less characterized. We and others previously demonstrated that, in mouse models of RP, cone cell death is associated with necrotic features and it is substantially suppressed by RIP3 deficiency or the RIP Kinase inhibitor.5, 6 These findings indicated that the necrotic pathway is involved in cone cell death in RP, at least in part, and may be a novel therapeutic target (Figure 1). However, the relevancy of these findings in human pathology remains unclear. Figure 1 Rod and cone photoreceptor cell death in retinitis pigmentosa. Rod cell death due to the deleterious genetic mutations is associated with apoptosis, which involves the activation of caspase-independent pathways including poly-ADP-ribose-polymerase (PARP), ... In our recent study published in Cell Death and Discovery, we investigated the possible involvement of necrotic cone cell death in RP patients by examining the cone mosaic images obtained by the adaptive optics scanning laser ophthalmoscopy (AO-SLO).7 With the AO imaging system, the individual cone cells are visualized as bright spots in living human eyes. Using an automated measurement program of the cone spot size in AO-SLO images, we showed that there was a population of enlarged cone spots in the macula of RP patients. Cone enlargement was observed in a variety of RP patients and disease stage. The precise interpretation of these changes in AO-SLO images is challenging, however, taken together with the results from experimental studies, we propose that the enlarged spots may reflect the necrotic changes of cone cells in RP patients. Consistent with this idea, previous histological studies of postmortem RP patients' eyes demonstrated the necrotic changes of cone cells such as cell swelling and disrupted plasma membrane.8 Intracellular contents released from dying or dead cells act as damage-associated molecular patterns (DAMPs) to promote inflammatory responses and tissue injury. HMGB1 is one of the best-characterized DAMPs released from necrotic cells.9 In the vitreous of RP patients, we found that the HMGB1 levels were significantly elevated compared with those in controls. These findings support our idea that necrotic cell death is implicated in the degenerative process of RP. In animal models of RP, we previously demonstrated that RIP3 deficiency suppresses microglial activation during cone but not rod degeneration in rd10 mice, suggesting that DAMPs released from necrotic cone cells may enhance retinal inflammation.5 In human RP patients, intraocular inflammation measured by slit-lamp or laser flaremeter is inversely associated with central visual function.10 These findings indicate that cone cell death and inflammation are closely interconnected during cone degeneration in RP. Recent studies have shown that the cone cell death in RP is caused by the microenvironmental changes following rod degeneration, such as inflammation, oxidation and loss of trophic factors. Interestingly, Punzo et al.11 reported that, in four different models of RP the dying cones show gene expression profiles associated with starvation. In line with these findings, Ait-Ali et al.12 recently showed that rod-derived cone viability factor promotes cone cell survival by stimulating the glucose uptake and glycolysis. Because nutrient deprivation can lead to mitochondrial and cytoplasmic swelling, the necrotic cone cell death in RP may be caused by a nutrient shortage. Alternatively, as inflammatory cells express tumor necrosis factor-α and FAS ligand, which recruit RIP1 and activate RIP Kinase pathways, excessive inflammatory activation may exacerbate necrotic cone cell death in RP. It will be interesting to further investigate the mechanisms of cone cell death in several models and human patients with RP to identify the common therapeutic targets to prevent or delay the secondary cone degeneration in RP.
-
RIP Kinase-mediated programmed necrosis
Neuroprotection and Neuroregeneration for Retinal Diseases, 2014Co-Authors: Yusuke Murakami, Maki Kayama, Joan W Miller, Demetrios G VavvasAbstract:Retinal ganglion cell (RGC) death is the ultimate cause of vision loss in glaucoma. Apoptosis has been thought to be a major form of cell death in various diseases including glaucoma; however, attempts to develop neuroprotective agents that target apoptosis have largely failed. Recent accumulating evidence has shown that non-apoptotic forms of cell death such as necrosis are also regulated by specific molecular machinery, such as those mediated by receptor-interacting protein (RIP) Kinases. In this review, we summarize recent advances in our understanding of RIP Kinase signaling and its roles in RGC loss. These data suggest that not only apoptosis but also necrosis is involved in RGC death and that combined targeting of these pathways may be an effective strategy for glaucoma.
-
receptor interacting protein Kinase mediates necrotic cone but not rod cell death in a mouse model of inherited degeneration
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Yusuke Murakami, Toshio Hisatomi, Joan W Miller, Hidetaka Matsumoto, Miin Roh, Jun Suzuki, Yasuhiro Ikeda, Demetrios G VavvasAbstract:Retinitis pigmentosa comprises a group of inherited retinal photoreceptor degenerations that lead to progressive loss of vision. Although in most cases rods, but not cones, harbor the deleterious gene mutations, cones do die in this disease, usually after the main phase of rod cell loss. Rod photoreceptor death is characterized by apoptotic features. In contrast, the mechanisms and features of subsequent nonautonomous cone cell death remain largely unknown. In this study, we show that receptor-interacting protein (RIP) Kinase mediates necrotic cone cell death in rd10 mice, a mouse model of retinitis pigmentosa caused by a mutation in a rod-specific gene. The expression of RIP3, a key regulator of programmed necrosis, was elevated in rd10 mouse retinas in the phase of cone but not rod degeneration. Although rd10 mice lacking RIP3 developed comparable rod degeneration to control rd10 mice, they displayed a significant preservation of cone cells. Ultrastructural analysis of rd10 mouse retinas revealed that a substantial fraction of dying cones exhibited necrotic morphology, which was rescued by RIP3 deficiency. Additionally, pharmacologic treatment with a RIP Kinase inhibitor attenuated histological and functional deficits of cones in rd10 mice. Thus, necrotic mechanisms involving RIP Kinase are crucial in cone cell death in inherited retinal degeneration, suggesting the RIP Kinase pathway as a potential target to protect cone-mediated central and peRIPheral vision loss in patients with retinitis pigementosa.
