The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform

Bernardino Ghetti - One of the best experts on this subject based on the ideXlab platform.

  • Regional differences in the vulnerability of substantia nigra dopaminergic neurons in Weaver mice.
    Acta neurobiologiae experimentalis, 2009
    Co-Authors: Joaquín Martí, Bernardino Ghetti, Shirley A. Bayer, M. C. Santa-cruz, Roger Serra, Vanessa Molina, José P. Hervás
    Abstract:

    Vulnerability of midbrain dopaminergic (DA) neurons in the Weaver Mouse was studied at postnatal (P) days 8 and 90, in chosen coronal levels throughout the anteroposterior (AP) extent of the substantia nigra pars compacta (SNc). Wild-type (+/+) and homozygous Weaver (wv/wv) mice used were the offspring of pregnant dams injected in several cases with tritiated thymidine on embryonic days 11-15. DA neurons were identified for their tyrosine hydroxylase immunoreactivity. Data reveal that at P8, the frequency of both +/+ and wv/wv late-generated DA cells increases from rostral to caudal SNc. No apparent DA-cell loss was observed at P8 in the mutant genotype, irrespective of the AP level considered. However, throughout the AP, there was a significant reduction in the number of these neurons at any level in 90-day-old Weavers. Comparison of P8 and P90 +/+ SNc suggests that cell death is not a major aspect in the developmental regulation of normal DA neurons, although numerical cell depletion in the postnatal development of Weaver SNc probably results from the amplification of a basal cell-death process, which affected all the coronal levels studied.

  • Purkinje cell age-distribution in fissures and in foliar crowns: A comparative study in the Weaver cerebellum
    Brain Structure & Function, 2007
    Co-Authors: Joaquín Martí, Bernardino Ghetti, Shirley A. Bayer, M. C. Santa-cruz, José P. Hervás
    Abstract:

    Generation and settling of Purkinje cells (PCs) are investigated in the Weaver Mouse cerebellum in order to determine possible relationships with the fissuration pattern. Tritiated thymidine was supplied to pregnant females at the time that these neurons were being produced. Autoradiography was then applied on brain sections obtained from control and Weaver offspring at postnatal (P) day 90. This makes it possible to assess the differential survival of neurons born at distinct embryonic times on the basis of the proportion of labeled cells located at the two foliar compartments: fissures and foliar crowns. Our data show that throughout the surface contour of the vermal lobes, generative programs of PCs were close between wild type and homozygous Weaver. Similar data were found in the lobules of the lateral hemisphere. On the other hand, the loss of PCs in Weaver cerebella can be related to foliar concavities or convexities depending on the vermal lobe or the hemispheric lobule studied. Lastly, we have obtained evidence that late-generated PCs of both normal and mutant mice were preferentially located in fissures. These quantitative relationships lead us to propose a model in which the final distribution of PCs through the vermal contour would be coupled to two factors: the cortical fissuration patterning and a “time-sequential effect” of Weaver mutation.

  • Dopamine Transporter‐Dependent and ‐Independent Endogenous Dopamine Release from Weaver Mouse Striatum In Vitro
    Journal of neurochemistry, 2002
    Co-Authors: Judith A. Richter, Bernardino Ghetti, D. J. Bare, J. R. Simon
    Abstract:

    The Weaver mutant Mouse (wv/wv) has an approximately 70% loss of nigrostriatal dopamine (DA) neurons, but the fractional DA release evoked by amphetamine (but not a high potassium level) has been shown to be greater from striatal slices of the Weaver compared with +/+ mice. In the present work we tested the hypothesis that fractional DA release from Weaver striatum would be greater when release was mediated by the DA transporter. Serotonin (5-HT)-stimulated fractional DA release was greater from Weaver than from +/+ striatum. The release evoked by 5-HT in the presence of 10 microM nomifensine (an antagonist of the DA transporter) was less than in its absence, but the difference between Weaver and +/+ striatum remained. In the presence of nomifensine, 1-(m-chlorophenyl)biguanide, classified as a 5-HT3 agonist, also induced a greater fractional release from Weaver compared with +/+ striatum. When veratridine was used at a low concentration (1 microM), the fractional evoked release of DA was higher from the Weaver in the presence and absence of nomifensine. These findings suggest that the reason for the difference in the responsiveness of the two genotypes to these release-inducing agents is not related to DA transporter function.

  • dopamine transporter dependent and independent endogenous dopamine release from Weaver Mouse striatum in vitro
    Journal of Neurochemistry, 2002
    Co-Authors: Judith A. Richter, Bernardino Ghetti, D. J. Bare, J. R. Simon
    Abstract:

    The Weaver mutant Mouse (wv/wv) has an approximately 70% loss of nigrostriatal dopamine (DA) neurons, but the fractional DA release evoked by amphetamine (but not a high potassium level) has been shown to be greater from striatal slices of the Weaver compared with +/+ mice. In the present work we tested the hypothesis that fractional DA release from Weaver striatum would be greater when release was mediated by the DA transporter. Serotonin (5-HT)-stimulated fractional DA release was greater from Weaver than from +/+ striatum. The release evoked by 5-HT in the presence of 10 microM nomifensine (an antagonist of the DA transporter) was less than in its absence, but the difference between Weaver and +/+ striatum remained. In the presence of nomifensine, 1-(m-chlorophenyl)biguanide, classified as a 5-HT3 agonist, also induced a greater fractional release from Weaver compared with +/+ striatum. When veratridine was used at a low concentration (1 microM), the fractional evoked release of DA was higher from the Weaver in the presence and absence of nomifensine. These findings suggest that the reason for the difference in the responsiveness of the two genotypes to these release-inducing agents is not related to DA transporter function.

  • Glial cell line-derived neurotrophic factor protects midbrain dopamine neurons from the lethal action of the Weaver gene: a quantitative immunocytochemical study
    Brain research. Developmental brain research, 1999
    Co-Authors: Jeffrey D Broome, Bernardino Ghetti, Katherine V. Wills, Paul A Lapchak, Laurel L Camp, Shirley A. Bayer
    Abstract:

    Glial cell line-derived neurotrophic factor (GDNF) has been shown to protect and repair midbrain dopamine neurons in vivo using animal models created with neurotoxins. The Weaver Mouse (wv/wv) has natural and spontaneous midbrain dopaminergic cell death which gives a unique opportunity to examine the effects of GDNF. The present study was designed to investigate a possible neuroprotective role by GDNF for midbrain dopamine neurons in the wv/wv. Weaver pups were given 1 μl injections on postnatal day 1. The wv/wv placebo group received a single unilateral injection into the right lateral ventricle of phosphate buffered saline (PBS) while the GDNF treated wv/wv mice received either 1.0 μg/μl or 10.0 μg/μl GDNF in PBS. All mice were sacrificed on postnatal day 20 and their brains were processed for tyrosine hydoxylase (TH) immunocytochemistry. When compared to the placebo group, the 1 μg GDNF group showed significantly less cell death on the injection side, but the contralateral side showed no significant sparing of TH neurons. The combined counts from both sides show significantly more TH staining neurons in the 1 μg GDNF group compared to placebo. When compared to placebo-injected controls, the 10 μg GDNF treated group showed significantly more TH staining neurons on the injected side, contralateral side, and combined. The results demonstrate that GDNF does protect Weaver dopaminergic midbrain neurons from the lethal action of the Weaver gene and the effect is positively correlated to dosage.

Nikolaos Matsokis - One of the best experts on this subject based on the ideXlab platform.

  • Anti-neuroinflammatory, protective effects of the synthetic microneurotrophin BNN-20 in the advanced dopaminergic neurodegeneration of "Weaver" mice.
    Neuropharmacology, 2019
    Co-Authors: Vasiliki Panagiotakopoulou, Konstantinos Botsakis, Theodora Mourtzi, Georgios T. Stathopoulos, Foteini Delis, Katerina Antoniou, Manolis Tzatzarakis, Aggeliki Dimopoulou, Nafsika Poulia, Nikolaos Matsokis
    Abstract:

    BNN-20 is a synthetic microneurotrophin, long-term (P1-P21) administration of which exerts potent neuroprotective effect on the "Weaver" Mouse, a genetic model of progressive, nigrostriatal dopaminergic degeneration. The present study complements and expands our previous work, providing evidence that BNN-20 fully protects the dopaminergic neurons even when administration begins at a late stage of dopaminergic degeneration (>40%). Since neuroinflammation plays a critical role in Parkinson's disease, we investigated the possible anti-neuroinflammatory mechanisms underlying the pharmacological action of BNN-20. The latter was shown to be microglia-mediated, at least in part. Indeed, BNN-20 induced a partial, but significant, reversal of microglia hyperactivation, observed in the untreated "Weaver" Mouse. Furthermore, it induced a shift in microglia polarization towards the neuroprotective M2 phenotype, suggesting a possible beneficial shifting of microglia activity. This observation was further supported by morphometric measurements. Moreover, BDNF levels, which were severely reduced in the "Weaver" Mouse midbrain, were restored to normal even after short-term BNN-20 administration. Experiments in "Weaver"/NGL (dual GFP/luciferase-NF-κВ reporter) mice using bioluminescence after a short BNN-20 treatment (P60-P74), have shown that the increase of BDNF production was specifically mediated through the TrkB-PI3K-Akt-NF-κB signaling pathway. Interestingly, long-term BNN-20 treatment (P14-P60) significantly increased dopamine levels in the "Weaver" striatum, which seems to be associated with the improved motor activity observed in the treated mutant animals. In conclusion, our findings suggest that BNN-20 may serve as a lead molecule for new therapeutic compounds for Parkinson's disease, combining strong anti-neuroinflammatory and neuroprotective properties, leading to elevated dopamine levels and improved motor activity.

  • increased sensitivity in the interaction of the dopaminergic adenosinergic system at the level of the adenylate cyclase activity in the striatum of the Weaver Mouse
    Neurochemistry International, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Panagopoulos, Nikolaos Matsokis, M Margariti, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • Increased sensitivity in the interaction of the dopaminergic/adenosinergic system at the level of the adenylate cyclase activity in the striatum of the "Weaver" Mouse.
    Neurochemistry international, 2016
    Co-Authors: Konstantinos Botsakis, Tondikidou, Nikolaos Panagopoulos, Margariti M, Nikolaos Matsokis, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • 17β-Estradiol/N-acetylcysteine interaction enhances the neuroprotective effect on dopaminergic neurons in the Weaver model of dopamine deficiency.
    Neuroscience, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Fevronia Angelatou, S. Theodoritsi, Konstantinos Grintzalis, I. Antonopoulos, Christos D. Georgiou, Marigoula Margarity, Nikolaos Panagopoulos
    Abstract:

    The Weaver Mouse, is a phenocopy of Parkinson's disease (PD) in which dopaminergic neurons degenerate gradually during development, reaching at P21 a neurodegeneration of 55%. Thus, the Weaver Mouse constitutes an appropriate in vivo PD model for investigating the effect of neuroprotective agents. In the present study, long-term treatment (from P1 to P21) with 17β-estradiol (17β-estradiol) significantly protected the dopaminergic neurons in the substantia nigra (SN) of Weaver Mouse by 54%, as was detected by immunohistochemical experiments, using the specific antibody against tyrosine hydroxylase (TH). This dopaminergic neuroprotection is in line with our biochemical results showing that 17β-estradiol treatment significantly decreased the high lipid peroxidation levels seen in the SN of Weaver Mouse, indicating high oxidative stress. Interestingly, co-administration of 17β-estradiol with N-acetylcysteine (NAC, precursor molecule of glutathione (GSH)) further significantly increased the survival of dopaminergic neurons in the SN (by 85%), with a parallel further decrease of lipid peroxidation to normal levels. Our results show the in vivo neuroprotective effect of 17β-estradiol, which is strongly enhanced by co administration of NAC, indicating a strong synergistic effect of the two drugs. Furthermore, the main mechanism underlying this neuroprotective action seems to be the reversal of the oxidative stress shown by the high peroxidation levels. These results could be of clinical relevance since both drugs are already used separately in the clinic, 17β-estradiol for treatment of PD and NAC as a mucolytic agent and for the treatment of several disorders.

  • blockade of adenosine a2a receptors downregulates darpp 32 but increases erk1 2 activity in striatum of dopamine deficient Weaver Mouse
    Neurochemistry International, 2010
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Ourania Pavlou, Paraskevi D. Poulou, Fevronia Angelatou
    Abstract:

    In the present study we investigated the signal transduction cascade modulated by adenosine A(2A) receptors under chronic dopamine deficiency in the "Weaver" Mouse. We determined the phosphorylation state of cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) at Thr34 and of Extracellular Signal-regulated Protein Kinases 1/2 (ERK1/2), under basal conditions and after in vivo stimulation of A(2A) receptors by administration of the agonist CGS21680. Our results revealed that the endogenous levels of phospho-DARPPP-32 and phospho-ERK1/2 are elevated in "Weaver" striatum probably as an adaptation phenomenon to gradual dopaminergic neurodegeneration appearing in this animal model, characterized as phenocopy of Parkinson's disease. Stimulation of A(2A) receptors by CGS21680 further increases phospho-DARPP-32 but downregulates significantly the elevated phospho-ERK1/2 levels bringing them close to those observed in wild type animals. Consistently, blockade of A(2A) receptors by MSX-3 (A(2A) receptor antagonist) downregulates phospho-DARPP-32 but significantly increases even more the phosphorylation/activation of ERK1/2. These results indicate that under chronic dopamine deficiency (a) the A(2A)/cAMP/PKA/DARPP-32 cascade is overactive due to the elevated endogenous phospho-DARPP-32 levels and (b) the A(2A) receptor modulatory effect on ERK1/2 signaling is dysregulated exerting opposing action compared to that observed in normal animals (Quiroz et al., 2006), i.e. in "Weaver" animals A(2A) receptor blockade increases the activity of ERK1/2 cascade. This could be of clinical relevance since A(2A) antagonists are already used in clinical trials for ameliorating Parkinson's disease (PD) symptoms.

Fevronia Angelatou - One of the best experts on this subject based on the ideXlab platform.

  • increased sensitivity in the interaction of the dopaminergic adenosinergic system at the level of the adenylate cyclase activity in the striatum of the Weaver Mouse
    Neurochemistry International, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Panagopoulos, Nikolaos Matsokis, M Margariti, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • Increased sensitivity in the interaction of the dopaminergic/adenosinergic system at the level of the adenylate cyclase activity in the striatum of the "Weaver" Mouse.
    Neurochemistry international, 2016
    Co-Authors: Konstantinos Botsakis, Tondikidou, Nikolaos Panagopoulos, Margariti M, Nikolaos Matsokis, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • 17β-Estradiol/N-acetylcysteine interaction enhances the neuroprotective effect on dopaminergic neurons in the Weaver model of dopamine deficiency.
    Neuroscience, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Fevronia Angelatou, S. Theodoritsi, Konstantinos Grintzalis, I. Antonopoulos, Christos D. Georgiou, Marigoula Margarity, Nikolaos Panagopoulos
    Abstract:

    The Weaver Mouse, is a phenocopy of Parkinson's disease (PD) in which dopaminergic neurons degenerate gradually during development, reaching at P21 a neurodegeneration of 55%. Thus, the Weaver Mouse constitutes an appropriate in vivo PD model for investigating the effect of neuroprotective agents. In the present study, long-term treatment (from P1 to P21) with 17β-estradiol (17β-estradiol) significantly protected the dopaminergic neurons in the substantia nigra (SN) of Weaver Mouse by 54%, as was detected by immunohistochemical experiments, using the specific antibody against tyrosine hydroxylase (TH). This dopaminergic neuroprotection is in line with our biochemical results showing that 17β-estradiol treatment significantly decreased the high lipid peroxidation levels seen in the SN of Weaver Mouse, indicating high oxidative stress. Interestingly, co-administration of 17β-estradiol with N-acetylcysteine (NAC, precursor molecule of glutathione (GSH)) further significantly increased the survival of dopaminergic neurons in the SN (by 85%), with a parallel further decrease of lipid peroxidation to normal levels. Our results show the in vivo neuroprotective effect of 17β-estradiol, which is strongly enhanced by co administration of NAC, indicating a strong synergistic effect of the two drugs. Furthermore, the main mechanism underlying this neuroprotective action seems to be the reversal of the oxidative stress shown by the high peroxidation levels. These results could be of clinical relevance since both drugs are already used separately in the clinic, 17β-estradiol for treatment of PD and NAC as a mucolytic agent and for the treatment of several disorders.

  • blockade of adenosine a2a receptors downregulates darpp 32 but increases erk1 2 activity in striatum of dopamine deficient Weaver Mouse
    Neurochemistry International, 2010
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Ourania Pavlou, Paraskevi D. Poulou, Fevronia Angelatou
    Abstract:

    In the present study we investigated the signal transduction cascade modulated by adenosine A(2A) receptors under chronic dopamine deficiency in the "Weaver" Mouse. We determined the phosphorylation state of cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) at Thr34 and of Extracellular Signal-regulated Protein Kinases 1/2 (ERK1/2), under basal conditions and after in vivo stimulation of A(2A) receptors by administration of the agonist CGS21680. Our results revealed that the endogenous levels of phospho-DARPPP-32 and phospho-ERK1/2 are elevated in "Weaver" striatum probably as an adaptation phenomenon to gradual dopaminergic neurodegeneration appearing in this animal model, characterized as phenocopy of Parkinson's disease. Stimulation of A(2A) receptors by CGS21680 further increases phospho-DARPP-32 but downregulates significantly the elevated phospho-ERK1/2 levels bringing them close to those observed in wild type animals. Consistently, blockade of A(2A) receptors by MSX-3 (A(2A) receptor antagonist) downregulates phospho-DARPP-32 but significantly increases even more the phosphorylation/activation of ERK1/2. These results indicate that under chronic dopamine deficiency (a) the A(2A)/cAMP/PKA/DARPP-32 cascade is overactive due to the elevated endogenous phospho-DARPP-32 levels and (b) the A(2A) receptor modulatory effect on ERK1/2 signaling is dysregulated exerting opposing action compared to that observed in normal animals (Quiroz et al., 2006), i.e. in "Weaver" animals A(2A) receptor blockade increases the activity of ERK1/2 cascade. This could be of clinical relevance since A(2A) antagonists are already used in clinical trials for ameliorating Parkinson's disease (PD) symptoms.

  • Blockade of adenosine A2A receptors downregulates DARPP-32 but increases ERK1/2 activity in striatum of dopamine deficient "Weaver" Mouse.
    Neurochemistry international, 2009
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Ourania Pavlou, Paraskevi D. Poulou, Fevronia Angelatou
    Abstract:

    In the present study we investigated the signal transduction cascade modulated by adenosine A(2A) receptors under chronic dopamine deficiency in the "Weaver" Mouse. We determined the phosphorylation state of cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) at Thr34 and of Extracellular Signal-regulated Protein Kinases 1/2 (ERK1/2), under basal conditions and after in vivo stimulation of A(2A) receptors by administration of the agonist CGS21680. Our results revealed that the endogenous levels of phospho-DARPPP-32 and phospho-ERK1/2 are elevated in "Weaver" striatum probably as an adaptation phenomenon to gradual dopaminergic neurodegeneration appearing in this animal model, characterized as phenocopy of Parkinson's disease. Stimulation of A(2A) receptors by CGS21680 further increases phospho-DARPP-32 but downregulates significantly the elevated phospho-ERK1/2 levels bringing them close to those observed in wild type animals. Consistently, blockade of A(2A) receptors by MSX-3 (A(2A) receptor antagonist) downregulates phospho-DARPP-32 but significantly increases even more the phosphorylation/activation of ERK1/2. These results indicate that under chronic dopamine deficiency (a) the A(2A)/cAMP/PKA/DARPP-32 cascade is overactive due to the elevated endogenous phospho-DARPP-32 levels and (b) the A(2A) receptor modulatory effect on ERK1/2 signaling is dysregulated exerting opposing action compared to that observed in normal animals (Quiroz et al., 2006), i.e. in "Weaver" animals A(2A) receptor blockade increases the activity of ERK1/2 cascade. This could be of clinical relevance since A(2A) antagonists are already used in clinical trials for ameliorating Parkinson's disease (PD) symptoms.

J. R. Simon - One of the best experts on this subject based on the ideXlab platform.

  • dopamine transporter dependent and independent endogenous dopamine release from Weaver Mouse striatum in vitro
    Journal of Neurochemistry, 2002
    Co-Authors: Judith A. Richter, Bernardino Ghetti, D. J. Bare, J. R. Simon
    Abstract:

    The Weaver mutant Mouse (wv/wv) has an approximately 70% loss of nigrostriatal dopamine (DA) neurons, but the fractional DA release evoked by amphetamine (but not a high potassium level) has been shown to be greater from striatal slices of the Weaver compared with +/+ mice. In the present work we tested the hypothesis that fractional DA release from Weaver striatum would be greater when release was mediated by the DA transporter. Serotonin (5-HT)-stimulated fractional DA release was greater from Weaver than from +/+ striatum. The release evoked by 5-HT in the presence of 10 microM nomifensine (an antagonist of the DA transporter) was less than in its absence, but the difference between Weaver and +/+ striatum remained. In the presence of nomifensine, 1-(m-chlorophenyl)biguanide, classified as a 5-HT3 agonist, also induced a greater fractional release from Weaver compared with +/+ striatum. When veratridine was used at a low concentration (1 microM), the fractional evoked release of DA was higher from the Weaver in the presence and absence of nomifensine. These findings suggest that the reason for the difference in the responsiveness of the two genotypes to these release-inducing agents is not related to DA transporter function.

  • Dopamine Transporter‐Dependent and ‐Independent Endogenous Dopamine Release from Weaver Mouse Striatum In Vitro
    Journal of neurochemistry, 2002
    Co-Authors: Judith A. Richter, Bernardino Ghetti, D. J. Bare, J. R. Simon
    Abstract:

    The Weaver mutant Mouse (wv/wv) has an approximately 70% loss of nigrostriatal dopamine (DA) neurons, but the fractional DA release evoked by amphetamine (but not a high potassium level) has been shown to be greater from striatal slices of the Weaver compared with +/+ mice. In the present work we tested the hypothesis that fractional DA release from Weaver striatum would be greater when release was mediated by the DA transporter. Serotonin (5-HT)-stimulated fractional DA release was greater from Weaver than from +/+ striatum. The release evoked by 5-HT in the presence of 10 microM nomifensine (an antagonist of the DA transporter) was less than in its absence, but the difference between Weaver and +/+ striatum remained. In the presence of nomifensine, 1-(m-chlorophenyl)biguanide, classified as a 5-HT3 agonist, also induced a greater fractional release from Weaver compared with +/+ striatum. When veratridine was used at a low concentration (1 microM), the fractional evoked release of DA was higher from the Weaver in the presence and absence of nomifensine. These findings suggest that the reason for the difference in the responsiveness of the two genotypes to these release-inducing agents is not related to DA transporter function.

  • The Weaver mutant Mouse as a model of nigrostriatal dysfunction.
    Molecular neurobiology, 1994
    Co-Authors: J. R. Simon, B Ghetti
    Abstract:

    The Weaver mutant Mouse has a genetic defect that results in the loss of dopamine neurons in the nigrostriatal pathway. Striatal tyrosine hydroxylase and dopamine content are reduced by 60-70%, and dopamine uptake is reduced by as much as 95%. Deficits in all three of these striatal dopamine markers are seen as early as postnatal d 3. The striatal dopamine systems in the Weaver apparently have the ability to compensate for this dopamine deficit. Thus, in the Weaver, in vitro resting release, as well as amphetamine-evoked fractional release of endogenous dopamine are increased. An additional change seen in the Weaver striatum is an elevated serotonin content. These alterations may play an adaptive role in attempting to compensate for the dopamine loss. In summary, the Weaver mutant Mouse has dramatic deficits in the nigrostriatal pathway, but also seems to develop certain adaptive mechanisms in dopaminergic and other transmitter systems that may compensate functionally for the dopamine deficit. Thus, the Weaver Mouse provides a unique animal model for studying naturally induced neuronal degeneration that complements those models using surgical and pharmacological protocols.

  • Is there a significant somatodendritic uptake of dopamine in the substantia nigra? Evidence from the Weaver mutant Mouse
    Neurochemistry international, 1993
    Co-Authors: J. R. Simon, Bernardino Ghetti
    Abstract:

    Slices of the substantia nigra from normal mice and from mice with the Weaver gene were used to study somatodendritic uptake of dopamine. The substantia nigra of the homozygous Weaver Mouse is deficient in both cell bodies and dendrites whereas the substantia nigra of the heterozygous Weaver Mouse is deficient only in dendrites. Accumulation of [3H]dopamine by nigral slices obtained from each genotype was not different from that observed in slices obtained from control mice. The observed accumulation of [3H]dopamine was apparently taking place predominantly into serotonergic and noradrenergic elements since significant reductions were obtained by both fluoxetine and desipramine at concentrations that were selective for the serotonin and norepinephrine carriers, respectively. In the absence, as well as in the presence of fluoxetine and desipramine, dopamine accumulation in the substantia nigra was only slightly attenuated by the known dopamine uptake blocker GBR 12909. These data argue against a significant presence of somatodendritic uptake systems for dopamine in the substantia nigra and suggest that caution be used in the interpretation of results from studies on dopamine release from nigral slices when [3H]dopamine has been used to preload the tissue. Under such experimental conditions, it is likely that a large proportion of the released tritium might come from neurons other than those which contain endogenous neurotransmitter dopamine.

Konstantinos Botsakis - One of the best experts on this subject based on the ideXlab platform.

  • Anti-neuroinflammatory, protective effects of the synthetic microneurotrophin BNN-20 in the advanced dopaminergic neurodegeneration of "Weaver" mice.
    Neuropharmacology, 2019
    Co-Authors: Vasiliki Panagiotakopoulou, Konstantinos Botsakis, Theodora Mourtzi, Georgios T. Stathopoulos, Foteini Delis, Katerina Antoniou, Manolis Tzatzarakis, Aggeliki Dimopoulou, Nafsika Poulia, Nikolaos Matsokis
    Abstract:

    BNN-20 is a synthetic microneurotrophin, long-term (P1-P21) administration of which exerts potent neuroprotective effect on the "Weaver" Mouse, a genetic model of progressive, nigrostriatal dopaminergic degeneration. The present study complements and expands our previous work, providing evidence that BNN-20 fully protects the dopaminergic neurons even when administration begins at a late stage of dopaminergic degeneration (>40%). Since neuroinflammation plays a critical role in Parkinson's disease, we investigated the possible anti-neuroinflammatory mechanisms underlying the pharmacological action of BNN-20. The latter was shown to be microglia-mediated, at least in part. Indeed, BNN-20 induced a partial, but significant, reversal of microglia hyperactivation, observed in the untreated "Weaver" Mouse. Furthermore, it induced a shift in microglia polarization towards the neuroprotective M2 phenotype, suggesting a possible beneficial shifting of microglia activity. This observation was further supported by morphometric measurements. Moreover, BDNF levels, which were severely reduced in the "Weaver" Mouse midbrain, were restored to normal even after short-term BNN-20 administration. Experiments in "Weaver"/NGL (dual GFP/luciferase-NF-κВ reporter) mice using bioluminescence after a short BNN-20 treatment (P60-P74), have shown that the increase of BDNF production was specifically mediated through the TrkB-PI3K-Akt-NF-κB signaling pathway. Interestingly, long-term BNN-20 treatment (P14-P60) significantly increased dopamine levels in the "Weaver" striatum, which seems to be associated with the improved motor activity observed in the treated mutant animals. In conclusion, our findings suggest that BNN-20 may serve as a lead molecule for new therapeutic compounds for Parkinson's disease, combining strong anti-neuroinflammatory and neuroprotective properties, leading to elevated dopamine levels and improved motor activity.

  • BNN-20, a synthetic microneurotrophin, strongly protects dopaminergic neurons in the "Weaver" Mouse, a genetic model of dopamine-denervation, acting through the TrkB neurotrophin receptor.
    Neuropharmacology, 2017
    Co-Authors: Konstantinos Botsakis, Theodora Mourtzi, Vasiliki Panagiotakopoulou, Malamati Vreka, Georgios T. Stathopoulos, Iosif Pediaditakis, Ioannis Charalampopoulos, A. Gravanis, Foteini Delis, Katerina Antoniou
    Abstract:

    Neurotrophic factors are among the most promising treatments aiming at slowing or stopping and even reversing Parkinson's disease (PD). However, in most cases, they cannot readily cross the human blood-brain-barrier (BBB). Herein, we propose as a therapeutic for PD the small molecule 17-beta-spiro-[5-androsten-17,2'-oxiran]-3beta-ol (BNN-20), a synthetic analogue of DHEA, which crosses the BBB and is deprived of endocrine side-effects. Using the “Weaver” Mouse, a genetic model of PD, which exhibits progressive dopaminergic neurodegeneration in the Substantia Nigra (SN), we have shown that long-term administration (P1-P21) of BNN-20 almost fully protected the dopaminergic neurons and their terminals, via i) a strong anti-apoptotic effect, probably mediated through the Tropomyosin receptor kinase B (TrkB) neurotrophin receptor's PI3K-Akt-NF-κB signaling pathway, ii) by exerting an efficient antioxidant effect, iii) by inducing significant anti-inflammatory activity and iv) by restoring Brain-Derived Neurotrophic Factor (BDNF) levels. By intercrossing “Weaver” with NGL mice (dual GFP/luciferase-NF-κΒ reporter mice, NF-κΒ.GFP.Luc), we obtained Weaver/NGL mice that express the NF-κB reporter in all somatic cells. Acute BNN-20 administration to Weaver/NGL mice induced a strong NF-κB-dependent transcriptional response in the brain as detected by bioluminescence imaging, which was abolished by co-administration of the TrkB inhibitor ANA-12. This indicates that BNN-20 exerts its beneficial action (at least in part) through the TrkB-PI3K-Akt-NF-κB signaling pathway. These results could be of clinical relevance, as they suggest BNN-20 as an important neuroprotective agent acting through the TrkB neurotrophin receptor pathway, mimicking the action of the endogenous neurotrophin BDNF. Thus BNN-20 could be proposed for treatment of PD.

  • increased sensitivity in the interaction of the dopaminergic adenosinergic system at the level of the adenylate cyclase activity in the striatum of the Weaver Mouse
    Neurochemistry International, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Panagopoulos, Nikolaos Matsokis, M Margariti, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • Increased sensitivity in the interaction of the dopaminergic/adenosinergic system at the level of the adenylate cyclase activity in the striatum of the "Weaver" Mouse.
    Neurochemistry international, 2016
    Co-Authors: Konstantinos Botsakis, Tondikidou, Nikolaos Panagopoulos, Margariti M, Nikolaos Matsokis, Fevronia Angelatou
    Abstract:

    Abstract The specific antagonistic interaction between dopamine D 1 and adenosine A 1 receptors (D 1 /A 1 ), as well as between dopamine D 2 and adenosine A 2a receptors (D 2 /A 2a ) exist not only at the receptor/receptor level, but also at the level of the secondary messengers. In this study, we examined the possible changes in these interactions at the level of cAMP formation in membrane preparation from “Weaver” Mouse striatum (a genetic model of Parkinson disease), by using specific agonists of these receptors. We also examined in the striatum of the “Weaver” Mouse the interaction between D 1 and D 2 dopamine receptors. Our results showed that in the striatum of “Weaver” mice: a) the cAMP synthesis induced by D 1 receptor activation (SKF 38393), was significantly reduced compared to control mice, while A 1 receptor activation (L-PIA) leaded to a more intense inhibition of the D 1 -induced cAMP-formation compared to the controls, b) the cAMP synthesis which was induced by A 2a receptor activation (CGS 21680), was significantly increased compared to the control mice. The specific D 2 receptor agonist Quinpirole, added in low concentrations, caused a significant reduction of the A 2a -induced cAMP formation, which was not observed in the control Mouse. Furthermore, the D 1 receptor induced cAMP synthesis was significantly higher in control compared to “Weaver” striatum, which was more efficiently downregulated by D 2 receptor agonist Quinpirole. These results suggest that the sensitivity to D 1 and A 2a receptor agonists is altered and that the interaction between D 1 /A 1 and D 2 /A 2a receptors is enhanced in the striatum of the “Weaver” mutation, while an uncoupling between D 1 and D 2 receptors was observed. Since the adenylate cyclase basal activity did not differ between “Weaver” and control striatum, the above-mentioned changes seem to be due to alterations in the function of the adenosine/dopamine receptors and their coupling to the G-proteins.

  • 17β-Estradiol/N-acetylcysteine interaction enhances the neuroprotective effect on dopaminergic neurons in the Weaver model of dopamine deficiency.
    Neuroscience, 2016
    Co-Authors: Konstantinos Botsakis, Nikolaos Matsokis, Fevronia Angelatou, S. Theodoritsi, Konstantinos Grintzalis, I. Antonopoulos, Christos D. Georgiou, Marigoula Margarity, Nikolaos Panagopoulos
    Abstract:

    The Weaver Mouse, is a phenocopy of Parkinson's disease (PD) in which dopaminergic neurons degenerate gradually during development, reaching at P21 a neurodegeneration of 55%. Thus, the Weaver Mouse constitutes an appropriate in vivo PD model for investigating the effect of neuroprotective agents. In the present study, long-term treatment (from P1 to P21) with 17β-estradiol (17β-estradiol) significantly protected the dopaminergic neurons in the substantia nigra (SN) of Weaver Mouse by 54%, as was detected by immunohistochemical experiments, using the specific antibody against tyrosine hydroxylase (TH). This dopaminergic neuroprotection is in line with our biochemical results showing that 17β-estradiol treatment significantly decreased the high lipid peroxidation levels seen in the SN of Weaver Mouse, indicating high oxidative stress. Interestingly, co-administration of 17β-estradiol with N-acetylcysteine (NAC, precursor molecule of glutathione (GSH)) further significantly increased the survival of dopaminergic neurons in the SN (by 85%), with a parallel further decrease of lipid peroxidation to normal levels. Our results show the in vivo neuroprotective effect of 17β-estradiol, which is strongly enhanced by co administration of NAC, indicating a strong synergistic effect of the two drugs. Furthermore, the main mechanism underlying this neuroprotective action seems to be the reversal of the oxidative stress shown by the high peroxidation levels. These results could be of clinical relevance since both drugs are already used separately in the clinic, 17β-estradiol for treatment of PD and NAC as a mucolytic agent and for the treatment of several disorders.