The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Rafael Radi - One of the best experts on this subject based on the ideXlab platform.
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fundamentals on the biochemistry of peroxynitrite and protein tyrosine Nitration
Redox biology, 2018Co-Authors: Silvina Bartesaghi, Rafael RadiAbstract:In this review we provide an analysis of the biochemistry of peroxynitrite and tyrosine Nitration. Peroxynitrite is the product of the diffusion-controlled reaction between superoxide (O2•-) and nitric oxide (•NO). This process is in competition with the enzymatic dismutation of O2•- and the diffusion of •NO across cells and tissues and its reaction with molecular targets (e.g. guanylate cyclase). Understanding the kinetics and compartmentalization of the O2•- / •NO interplay is critical to rationalize the shift of •NO from a physiological mediator to a cytotoxic intermediate. Once formed, peroxynitrite (ONOO- and ONOOH; pKa = 6,8) behaves as a strong one and two-electron oxidant towards a series of biomolecules including transition metal centers and thiols. In addition, peroxynitrite anion can secondarily evolve to secondary radicals either via its fast reaction with CO2 or through proton-catalyzed homolysis. Thus, peroxynitrite can participate in direct (bimolecular) and indirect (through secondary radical intermediates) oxidation reactions; through these processes peroxynitrite can participate as cytotoxic effector molecule against invading pathogens and/or as an endogenous pathogenic mediator. Peroxynitrite can cause protein tyrosine Nitration in vitro and in vivo. Indeed, tyrosine Nitration is a hallmark of the reactions of •NO-derived oxidants in cells and tissues and serves as a biomarker of oxidative damage. Protein tyrosine Nitration can mediate changes in protein structure and function that affect cell homeostasis. Tyrosine Nitration in biological systems is a free radical process that can be promoted either by peroxynitrite-derived radicals or by other related •NO-dependent oxidative processes. Recently, mechanisms responsible of tyrosine Nitration in hydrophobic biostructures such as membranes and lipoproteins have been assessed and involve the parallel occurrence and connection with lipid peroxidation. Experimental strategies to reveal the proximal oxidizing mechanism during tyrosine Nitration in given pathophysiologically-relevant conditions include mapping and identification of the tyrosine Nitration sites in specific proteins.
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biochemistry of protein tyrosine Nitration in cardiovascular pathology
Cardiovascular Research, 2007Co-Authors: Gonzalo Peluffo, Rafael RadiAbstract:Several pathologies of the cardiovascular system are associated with an augmented production of nitric oxide and/or superoxide-derived oxidants and/or alteration in the antioxidant detoxification pathways that lead to nitroxidative stress. One important consequence of these reactive intermediates at the biochemical level is the Nitration of protein tyrosines, which is performed through either of two of the relevant Nitration pathways that operate in vivo, namely peroxynitrite and heme peroxidase-dependent Nitration. Proteins nitrated at tyrosine residues have been detected in several compartments of the cardiovascular system. In this review a selection of nitrated proteins in plasma (fibrinogen, plasmin, Apo-1), vessel wall (Apo-B, cyclooxygenase, prostaglandin synthase, Mn-superoxide dismutase) and myocardium (myofibrillar creatine kinase, α-actinin, sarcoplasmic reticulum Ca 2+ ATPase) are analyzed in the context of cardiovascular disease. Nitration of tyrosine can affect protein function, which could directly link nitroxidative stress to the molecular alterations found in disease. While some proteins are inactivated by Nitration (e.g. Mn-SOD) others undergo a gain-of-function (e.g. fibrinogen) that can have an ample impact on the pathophysiology of the cardiovascular system. Nitrotyrosine is also emerging as a novel independent marker of cardiovascular disease. Pharmacological strategies directed towards inhibiting protein Nitration will assist to shed light on the relevance of this post-translational modification to human cardiovascular pathology.
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nitric oxide oxidants and protein tyrosine Nitration
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Rafael RadiAbstract:The occurrence of protein tyrosine Nitration under disease conditions is now firmly established and represents a shift from the signal transducing physiological actions of (.)NO to oxidative and potentially pathogenic pathways. Tyrosine Nitration is mediated by reactive nitrogen species such as peroxynitrite anion (ONOO(-)) and nitrogen dioxide ((.)NO2), formed as secondary products of (.)NO metabolism in the presence of oxidants including superoxide radicals (O2(.-)), hydrogen peroxide (H2O2), and transition metal centers. The precise interplay between (.)NO and oxidants and the identification of the proximal intermediate(s) responsible for Nitration in vivo have been under controversy. Despite the capacity of peroxynitrite to mediate tyrosine Nitration in vitro, its role on Nitration in vivo has been questioned, and alternative pathways, including the nitrite/H2O2/hemeperoxidase and transition metal-dependent mechanisms, have been proposed. A balanced analysis of existing evidence indicates that (i) different Nitration pathways can contribute to tyrosine Nitration in vivo, and (ii) most, if not all, Nitration pathways involve free radical biochemistry with carbonate radicals (CO3(.-)) and/or oxo-metal complexes oxidizing tyrosine to tyrosyl radical followed by the diffusion-controlled reaction with (.)NO2 to yield 3-nitrotyrosine. Although protein tyrosine Nitration is a low-yield process in vivo, 3-nitrotyrosine has been revealed as a relevant biomarker of (.)NO-dependent oxidative stress; additionally, site-specific Nitration focused on particular protein tyrosines may result in modification of function and promote a biological effect. Tissue distribution and quantitation of protein 3-nitrotyrosine, recognition of the predominant Nitration pathways and individual identification of nitrated proteins in disease states open new avenues for the understanding and treatment of human pathologies.
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cytochrome c Nitration by peroxynitrite
Journal of Biological Chemistry, 2000Co-Authors: Adriana Cassina, Bruce A Freeman, Harry Ischiropoulos, Roberto Hodara, Jose M Souza, Leonor Thomson, Laura Castro, Rafael RadiAbstract:Peroxynitrite (ONOO(-)), the product of superoxide (O(2)) and nitric oxide (.NO) reaction, inhibits mitochondrial respiration and can stimulate apoptosis. Cytochrome c, a mediator of these two aspects of mitochondrial function, thus represents an important potential target of ONOO(-) during conditions involving accelerated rates of oxygen radical and.NO generation. Horse heart cytochrome c(3+) was nitrated by ONOO(-), as indicated by spectral changes, Western blot analysis, and mass spectrometry. A dose-dependent loss of cytochrome c(3+) 695 nm absorption occurred, inferring that Nitration of a critical heme-vicinal tyrosine (Tyr-67) promoted a conformational change, displacing the Met-80 heme ligand. Nitration was confirmed by cross-reactivity with a specific antibody against 3-nitrotyrosine and by increased molecular mass compatible with the addition of a nitro-(-NO(2)) group. Mass analysis of tryptic digests indicated the preferential Nitration of Tyr-67 among the four conserved tyrosine residues in cytochrome c. Cytochrome c(3+) was more extensively nitrated than cytochrome c(2+) because of the preferential oxidation of the reduced heme by ONOO(-). Similar protein Nitration patterns were obtained by ONOO(-) reaction in the presence of carbon dioxide, whereupon secondary nitrating species arise from the decomposition of the nitroso-peroxocarboxylate (ONOOCO(2)(-)) intermediate. Peroxynitrite-nitrated cytochrome c displayed significant changes in redox properties, including (a) increased peroxidatic activity, (b) resistance to reduction by ascorbate, and (c) impaired support of state 4-dependent respiration in intact rat heart mitochondria. These results indicate that cytochrome c Nitration may represent both oxidative and signaling events occurring during .NO- and ONOO(-)-mediated cell injury.
Harry Ischiropoulos - One of the best experts on this subject based on the ideXlab platform.
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tyrosine Nitration localisation quantification consequences for protein function and signal transduction
Free Radical Research, 2001Co-Authors: Stan Greenacre, Harry IschiropoulosAbstract:The Nitration of free tyrosine or protein tyrosine residues generates 3-nitrotyrosine the detection of which has been utilised as a footprint for the in vivo formation of peroxynitrite and other reactive nitrogen species. The detection of 3-nitrotyrosine by analytical and immunological techniques has established that tyrosine Nitration occurs under physiological conditions and levels increase in most disease states. This review provides an updated, comprehensive and detailed summary of the tissue, cellular and specific protein localisation of 3-nitrotyrosine and its quantification. The potential consequences of Nitration to protein function and the pathogenesis of disease are also examined together with the possible effects of protein Nitration on signal transduction pathways and on the metabolism of proteins.
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cytochrome c Nitration by peroxynitrite
Journal of Biological Chemistry, 2000Co-Authors: Adriana Cassina, Bruce A Freeman, Harry Ischiropoulos, Roberto Hodara, Jose M Souza, Leonor Thomson, Laura Castro, Rafael RadiAbstract:Peroxynitrite (ONOO(-)), the product of superoxide (O(2)) and nitric oxide (.NO) reaction, inhibits mitochondrial respiration and can stimulate apoptosis. Cytochrome c, a mediator of these two aspects of mitochondrial function, thus represents an important potential target of ONOO(-) during conditions involving accelerated rates of oxygen radical and.NO generation. Horse heart cytochrome c(3+) was nitrated by ONOO(-), as indicated by spectral changes, Western blot analysis, and mass spectrometry. A dose-dependent loss of cytochrome c(3+) 695 nm absorption occurred, inferring that Nitration of a critical heme-vicinal tyrosine (Tyr-67) promoted a conformational change, displacing the Met-80 heme ligand. Nitration was confirmed by cross-reactivity with a specific antibody against 3-nitrotyrosine and by increased molecular mass compatible with the addition of a nitro-(-NO(2)) group. Mass analysis of tryptic digests indicated the preferential Nitration of Tyr-67 among the four conserved tyrosine residues in cytochrome c. Cytochrome c(3+) was more extensively nitrated than cytochrome c(2+) because of the preferential oxidation of the reduced heme by ONOO(-). Similar protein Nitration patterns were obtained by ONOO(-) reaction in the presence of carbon dioxide, whereupon secondary nitrating species arise from the decomposition of the nitroso-peroxocarboxylate (ONOOCO(2)(-)) intermediate. Peroxynitrite-nitrated cytochrome c displayed significant changes in redox properties, including (a) increased peroxidatic activity, (b) resistance to reduction by ascorbate, and (c) impaired support of state 4-dependent respiration in intact rat heart mitochondria. These results indicate that cytochrome c Nitration may represent both oxidative and signaling events occurring during .NO- and ONOO(-)-mediated cell injury.
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biological tyrosine Nitration a pathophysiological function of nitric oxide and reactive oxygen species
Archives of Biochemistry and Biophysics, 1998Co-Authors: Harry IschiropoulosAbstract:Analytical and immunological methodologies and occasionally both methodologies have been applied to detect and quantify 3-nitrotyrosine in almost every major organ system. In certain diseases increased levels of 3-nitrotyrosine have been correlated with elevated levels of other indices of oxidative stress. Numerous reports have established that Nitration is a biological process derived from the biochemical interaction of nitric oxide or nitric oxide-derived secondary products with reactive oxygen species. This article addresses critical issues regarding this biological process, namely the biochemical pathways for Nitration of tyrosine residuesin vivo,potential protein targets, and pathophysiological consequences of protein tyrosine Nitration.
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inactivation of tyrosine hydroxylase by Nitration following exposure to peroxynitrite and 1 methyl 4 phenyl 1 2 3 6 tetrahydropyridine mptp
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Jahan Ara, Serge Przedborski, Ali Naini, Vernice Jacksonlewis, Rosario R Trifiletti, Joel Horwitz, Harry IschiropoulosAbstract:The decrement in dopamine levels exceeds the loss of dopaminergic neurons in Parkinson’s disease (PD) patients and experimental models of PD. This discrepancy is poorly understood and may represent an important event in the pathogenesis of PD. Herein, we report that the rate-limiting enzyme in dopamine synthesis, tyrosine hydroxylase (TH), is a selective target for Nitration following exposure of PC12 cells to either peroxynitrite or 1-methyl-4-phenylpyridiniun ion (MPP+). Nitration of TH also occurs in mouse striatum after MPTP administration. Nitration of tyrosine residues in TH results in loss of enzymatic activity. In the mouse striatum, tyrosine Nitration-mediated loss in TH activity parallels the decline in dopamine levels whereas the levels of TH protein remain unchanged for the first 6 hr post MPTP injection. Striatal TH was not nitrated in mice overexpressing copper/zinc superoxide dismutase after MPTP administration, supporting a critical role for superoxide in TH tyrosine Nitration. These results indicate that tyrosine Nitration-induced TH inactivation and consequently dopamine synthesis failure, represents an early and thus far unidentified biochemical event in MPTP neurotoxic process. The resemblance of the MPTP model with PD suggests that a similar phenomenon may occur in PD, influencing the severity of parkisonian symptoms.
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kinetics of superoxide dismutase and iron catalyzed Nitration of phenolics by peroxynitrite
Archives of Biochemistry and Biophysics, 1992Co-Authors: Joseph S Beckman, Harry Ischiropoulos, Ling Zhu, Mark Van Der Woerd, Craig R Smith, Jun Chen, Joseph G Harrison, James C Martin, Michael TsaiAbstract:Superoxide dismutase and Fe3+EDTA catalyzed the Nitration by peroxynitrite (ONOO-) of a wide range of phenolics including tyrosine in proteins. Nitration was not mediated by a free radical mechanism because hydroxyl radical scavengers did not reduce either superoxide dismutase or Fe3+EDTA-catalyzed Nitration and nitrogen dioxide was not a significant product from either catalyst. Rather, metal ions appear to catalyze the heterolytic cleavage of peroxynitrite to form a nitronium-like species (NO2+). The calculated energy for separating peroxynitrous acid into hydroxide ion and nitronium ion is 13 kcal.mol-1 at pH 7.0. Fe3+EDTA catalyzed Nitration with an activation energy of 12 kcal.mol-1 at a rate of 5700 M-1.s-1 at 37 degrees C and pH 7.5. The reaction rate of peroxynitrite with bovine Cu,Zn superoxide dismutase was 10(5) M-1.s-1 at low superoxide dismutase concentrations, but the rate of Nitration became independent of superoxide dismutase concentration above 10 microM with only 9% of added peroxynitrite yielding nitrophenol. We propose that peroxynitrite anion is more stable in the cis conformation, whereas only a higher energy species in the trans conformation can fit in the active site of Cu,Zn superoxide dismutase. At high superoxide dismutase concentrations, phenolic Nitration may be limited by the rate of isomerization from the cis to trans conformations of peroxynitrite as well as by competing pathways for peroxynitrite decomposition. In contrast, Fe3+EDTA appears to react directly with the cis anion, resulting in greater Nitration yields.
Virinder Nohria - One of the best experts on this subject based on the ideXlab platform.
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safety and tolerability of different titration rates of retigabine ezogabine in patients with partial onset seizures
Epilepsy Research, 2013Co-Authors: Victor Biton, Martin J Brodie, Sarah E Derossett, Antonio Gilnagel, Virinder NohriaAbstract:Retigabine (RTG; international nonproprietary name)/ezogabine (EZG; US adopted name) is an antiepileptic drug (AED) that prolongs neuronal voltage-gated potassium-channel KCNQ2–5 (Kv 7.2–7.5) opening. This double-blind study evaluated different RTG/EZG dose-titration rates. Patients (N = 73) with partial-onset seizures receiving concomitant AEDs were randomized to one of three titration groups, all of which were initiated at RTG/EZG 300 mg/day divided into three equal doses. Fast-, medium-, and slow-titration groups received dose increments of 150 mg/day every 2, 4, and 7 days, respectively, achieving the target dose of 1200 mg/day after 13, 25, and 43 days, respectively. Safety assessments were performed throughout. Discontinuation rates due to treatment-emergent adverse events (TEAEs) were numerically higher in the fast- (10/23) and medium- (7/22) titration groups than in the slow-titration group (3/23) but statistical significance was achieved only for the high-titration group compared with the low-titration group (p = 0.024). Stratified analysis, with concomitant AEDs divided into enzyme inducers (carbamazepine, phenytoin, oxcarbazepine) or noninducers, showed that the risk of discontinuation due primarily to TEAEs was significantly higher in the fast- (p = 0.010) but not in the medium-titration group (p = 0.078) when compared with the slow-titration group. Overall, the slow-titration rate appeared to be best tolerated and was used in further efficacy and safety studies with RTG/EZG.
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Safety and tolerability of different titration rates of retigabine (ezogabine) in patients with partial-onset seizures.
Epilepsy research, 2013Co-Authors: Victor Biton, Antonio Gil-nagel, Martin J Brodie, Sarah E Derossett, Virinder NohriaAbstract:Retigabine (RTG; international nonproprietary name)/ezogabine (EZG; US adopted name) is an antiepileptic drug (AED) that prolongs neuronal voltage-gated potassium-channel KCNQ2-5 (Kv 7.2-7.5) opening. This double-blind study evaluated different RTG/EZG dose-titration rates. Patients (N=73) with partial-onset seizures receiving concomitant AEDs were randomized to one of three titration groups, all of which were initiated at RTG/EZG 300mg/day divided into three equal doses. Fast-, medium-, and slow-titration groups received dose increments of 150mg/day every 2, 4, and 7 days, respectively, achieving the target dose of 1200mg/day after 13, 25, and 43 days, respectively. Safety assessments were performed throughout. Discontinuation rates due to treatment-emergent adverse events (TEAEs) were numerically higher in the fast- (10/23) and medium- (7/22) titration groups than in the slow-titration group (3/23) but statistical significance was achieved only for the high-titration group compared with the low-titration group (p=0.024). Stratified analysis, with concomitant AEDs divided into enzyme inducers (carbamazepine, phenytoin, oxcarbazepine) or noninducers, showed that the risk of discontinuation due primarily to TEAEs was significantly higher in the fast- (p=0.010) but not in the medium-titration group (p=0.078) when compared with the slow-titration group. Overall, the slow-titration rate appeared to be best tolerated and was used in further efficacy and safety studies with RTG/EZG.
Ming-hui Zou - One of the best experts on this subject based on the ideXlab platform.
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Tyrosine Nitration of prostacyclin synthase is associated with enhanced retinal cell apoptosis in diabetes
The American Journal of Pathology, 2011Co-Authors: Ming-hui Zou, Mingkai Lin, Timothy J. Lyons, Zhonglin XieAbstract:The risk of diabetic retinopathy is associated with the presence of both oxidative stress and toxic eicosanoids. Whether oxidative stress actually causes diabetic retinopathy via the generation of toxic eicosanoids, however, remains unknown. The aim of the present study was to determine whether tyrosine Nitration of prostacyclin synthase (PGIS) contributes to retinal cell death in vitro and in vivo. Exposure of human retinal pericytes to heavily oxidized and glycated LDL (HOG-LDL), but not native forms of LDL (N-LDL), for 24 hours significantly increased pericyte apoptosis, accompanied by increased tyrosine Nitration of PGIS and decreased PGIS activity. Inhibition of the thromboxane receptor or cyclooxygenase-2 dramatically attenuated HOG-LDL–induced apoptosis without restoring PGIS activity. Administration of superoxide dismutase (to scavenge superoxide anions) or l-NG-nitroarginine methyl ester (l-NAME, a nonselective nitric oxide synthase inhibitor) restored PGIS activity and attenuated pericyte apoptosis. In Akita mouse retinas, diabetes increased intraretinal levels of oxidized LDL and glycated LDL, induced PGIS Nitration, enhanced apoptotic cell death, and impaired blood–retinal barrier function. Chronic administration of tempol, a superoxide scavenger, reduced intraretinal oxidized LDL and glycated LDL levels, PGIS Nitration, and retina cell apoptosis, thereby preserving the integrity of blood–retinal barriers. In conclusion, oxidized LDL-mediated PGIS Nitration and associated thromboxane receptor stimulation might be important in the initiation and progression of diabetic retinopathy.
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Nitration of prostacyclin synthase: mechanism and physiological implications
International Congress Series, 2002Co-Authors: Volker Ullrich, Andreas Daiber, Markus Bachschmid, Ming-hui ZouAbstract:Abstract In a series of investigations, we have provided evidence that prostacyclin synthase can be nitrated and inactivated under physiological conditions. Here, we address some pertinent questions on this process like the cause for selectivity, the cellular machinery of Nitration, ways of its inhibition and a possible physiological or pathophysiological significance. The underlying mechanism of heme-thiolate catalysis explains the selectivity of peroxynitrite for prostacyclin (PGI2)1 synthase. The cellular conditions primarily require superoxide formation by a tightly controlled release, distinct from autoxidation processes. None of the well-known inhibitors of peroxynitrite-mediated Nitrations and hydroxylations could block PGI2 synthase Nitration except ebselen, which, however, was ineffective in the presence of SH-groups. A physiological role may lie in the ability of superoxide to eliminate NO and, subsequently, PGI2 as mediators of vessel relaxation, of anti-adhesion properties and of differentiation. At the same time, the remaining prostacyclin endoperoxide (PGH2) causes constriction, adhesion and proliferation through activation of the thromboxane A2/PGH2 receptor. The smooth muscle-dependent formation of PGE2 from PGH2 will also stimulate P-selectin release for the immune response. Pathophysiological conditions mediated by peroxynitrite (PN) may prevail after activation of early immediate genes and formation of peroxynitrite at much higher levels than required for endothelial dysfunction.
Victor Biton - One of the best experts on this subject based on the ideXlab platform.
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safety and tolerability of different titration rates of retigabine ezogabine in patients with partial onset seizures
Epilepsy Research, 2013Co-Authors: Victor Biton, Martin J Brodie, Sarah E Derossett, Antonio Gilnagel, Virinder NohriaAbstract:Retigabine (RTG; international nonproprietary name)/ezogabine (EZG; US adopted name) is an antiepileptic drug (AED) that prolongs neuronal voltage-gated potassium-channel KCNQ2–5 (Kv 7.2–7.5) opening. This double-blind study evaluated different RTG/EZG dose-titration rates. Patients (N = 73) with partial-onset seizures receiving concomitant AEDs were randomized to one of three titration groups, all of which were initiated at RTG/EZG 300 mg/day divided into three equal doses. Fast-, medium-, and slow-titration groups received dose increments of 150 mg/day every 2, 4, and 7 days, respectively, achieving the target dose of 1200 mg/day after 13, 25, and 43 days, respectively. Safety assessments were performed throughout. Discontinuation rates due to treatment-emergent adverse events (TEAEs) were numerically higher in the fast- (10/23) and medium- (7/22) titration groups than in the slow-titration group (3/23) but statistical significance was achieved only for the high-titration group compared with the low-titration group (p = 0.024). Stratified analysis, with concomitant AEDs divided into enzyme inducers (carbamazepine, phenytoin, oxcarbazepine) or noninducers, showed that the risk of discontinuation due primarily to TEAEs was significantly higher in the fast- (p = 0.010) but not in the medium-titration group (p = 0.078) when compared with the slow-titration group. Overall, the slow-titration rate appeared to be best tolerated and was used in further efficacy and safety studies with RTG/EZG.
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Safety and tolerability of different titration rates of retigabine (ezogabine) in patients with partial-onset seizures.
Epilepsy research, 2013Co-Authors: Victor Biton, Antonio Gil-nagel, Martin J Brodie, Sarah E Derossett, Virinder NohriaAbstract:Retigabine (RTG; international nonproprietary name)/ezogabine (EZG; US adopted name) is an antiepileptic drug (AED) that prolongs neuronal voltage-gated potassium-channel KCNQ2-5 (Kv 7.2-7.5) opening. This double-blind study evaluated different RTG/EZG dose-titration rates. Patients (N=73) with partial-onset seizures receiving concomitant AEDs were randomized to one of three titration groups, all of which were initiated at RTG/EZG 300mg/day divided into three equal doses. Fast-, medium-, and slow-titration groups received dose increments of 150mg/day every 2, 4, and 7 days, respectively, achieving the target dose of 1200mg/day after 13, 25, and 43 days, respectively. Safety assessments were performed throughout. Discontinuation rates due to treatment-emergent adverse events (TEAEs) were numerically higher in the fast- (10/23) and medium- (7/22) titration groups than in the slow-titration group (3/23) but statistical significance was achieved only for the high-titration group compared with the low-titration group (p=0.024). Stratified analysis, with concomitant AEDs divided into enzyme inducers (carbamazepine, phenytoin, oxcarbazepine) or noninducers, showed that the risk of discontinuation due primarily to TEAEs was significantly higher in the fast- (p=0.010) but not in the medium-titration group (p=0.078) when compared with the slow-titration group. Overall, the slow-titration rate appeared to be best tolerated and was used in further efficacy and safety studies with RTG/EZG.
