Renal nerves contribute to hypertension in Schlager BPH/2J mice

Schlager mice (BPH/2J) are hypertensive due to a greater contribution of the sympathetic nervous system (SNS) and renin-angiotensin system (RAS). The kidneys of BPH/2J are hyper-innervated suggesting renal nerves may contribute to the hypertension. We therefore determined the effect of bilateral renal denervation (RD) on hypertension in BPH/2J. Mean arterial pressure (MAP) was measured by radiotelemetry before and for 3 weeks after RD in BPH/2J and BPN/3J. The effects of pentolinium and enalaprilat were examined to determine the contribution of the SNS and RAS, respectively. After 3 weeks, MAP was −10.9 ± 2.1 mmHg lower in RD BPH/2J compared to baseline and −2.1 ± 2.2 mmHg in sham BPH/2J (P < 0.001, n = 8–10). RD had no effect in BPN/3J (P > 0.1). The depressor response to pentolinium was greater in BPH/2J than BPN/3J, but in both cases the response in RD mice was similar to sham. Enalaprilat decreased MAP more in RD BPH/2J compared to sham (−12 vs −3 mmHg, P < 0.001) but had no effect in BPN/3J. RD reduced renal noradrenaline in both strains but more so in BPH/2J. RD reduced renin mRNA and protein, but not plasma renin in BPH/2J to levels comparable with BPN/3J mice. We conclude that renal nerves contribute to hypertension in BPH mice as RD induced a sustained fall in MAP, which was associated with a reduction of intrarenal renin expression. The lack of inhibition of the depressor effects of pentolinium and enalaprilat by RD suggests that vasoconstrictor effects of the SNS or RAS are not involved

Sirtuin 1 activation : a neuroprotective strategy for in vivo cerebral oxidative stress ? Involvement of SIRT1 in the beneficial effects of poly(ADP-ribose)polymerase inhibition

Le stress oxydant (SO) est un mécanisme commun à l’ischémie cérébrale et au traumatisme crânien qui entraîne notamment l’hyperactivation délétère de la poly(ADP-ribose)polymérase (PARP), une enzyme NAD+-dépendante. Cette dernière est impliquée dans le déficit neurologique et la lésion cérébrale consécutifs à ces pathologies. In vitro, l’hyperactivation de la PARP diminue le taux cérébral de NAD+, son substrat, et l’activité de la sirtuin 1 (SIRT1), une enzyme également NAD+-dépendante. L’activation de la SIRT1 est bénéfique au cours d’un SO in vitro. Si les effets bénéfiques de l’inhibition de la PARP ont été démontrés in vivo au cours d’un SO cérébral, l’implication de la SIRT1 ainsi que son rôle dans les effets de l’inhibition de la PARP n’ont pas été explorés. Dans la première partie de ce travail, nous avons mis en évidence qu’un modèle de SO cérébral induit in vivo chez le rat par une injection intrastriatale de malonate entraîne un SO prolongé, un déficit neurologique et une activation de la PARP associée à une diminution du NAD+. Dans la deuxième partie de ce travail, nous avons montré que le 3-aminobenzamide (3AB), un inhibiteur de la PARP, ne permet pas de s’opposer à la chute du NAD+ dans ce modèle, ce qui suggère que le NAD+ pourrait être consommé par d’autres enzymes NAD+-dépendantes, dont la SIRT1. L’inhibition de la PARP par le 3AB a permis d’augmenter le rapport activité/expression nucléaire de la SIRT1 et a entraîné sa translocation cytoplasmique au cours du SO. Un prétraitement par le SRT1720, un activateur spécifique de la SIRT1, diminue le déficit neurologique et la lésion striatale 6 heures après le SO cérébral, ce qui suggère que l’activation de la SIRT1 est bénéfique dans les conséquences d’un SO cérébral in vivo. L’association de l’inhibiteur de la PARP avec l’activateur de la SIRT1 (3AB+SRT1720) n’a pas potentialisé les effets protecteurs de chaque monothérapie. L’EX527, un inhibiteur de la SIRT1, ne modifie pas le déficit et la lésion. En revanche, l’association de l’inhibiteur de la PARP avec l’inhibiteur de la SIRT1 (3AB+EX527) supprime la récupération neurologique ainsi que la réduction de la lésion, induites par l’inhibition de la PARP seule (3AB). Ces données suggèrent que l’activation de la SIRT1 est impliquée dans les effets bénéfiques de l’inhibition de la PARP in vivo au cours d’un SO cérébral. En conclusion, l’ensemble de ce travail a permis une meilleure caractérisation de la PARP et de la SIRT1 au cours d’un SO cérébral in vivo. La SIRT1 pourrait constituer une cible pharmacologique pour le traitement des pathologies cérébrales au cours desquelles un SO est présent. De plus, nous avons montré que les effets bénéfiques de l’inhibition de la PARP sur les conséquences fonctionnelles et histologiques induites par le SO cérébral sont liés à l’activation de la SIRT1.Oxidative stress (OS) is involved in cerebral ischemia and traumatic brain injury and results in deleterious activation of poly(ADP-ribose)polymerase (PARP), an NAD+-dependant enzyme. PARP is implicated in neurological deficit and brain injury post-ischemia and post-trauma. In vitro, PARP overactivation reduced both brain NAD+ levels, its substrate, and activity of sirtuin 1 (SIRT1), an other NAD+-dependant enzyme. SIRT1 activation is beneficial during in vitro OS. Even if the beneficial effects of PARP inhibition have been demonstrated, SIRT1 involvement during in vivo cerebral OS and its role in the beneficial effects of PARP inhibition have not been studied.In the first part, we demonstrated that in vivo cerebral OS induced by intrastriatal injection of malonate in rat promoted prolonged OS, neurological deficit, PARP activation and NAD+ decrease. In the second part, we showed that 3-aminobenzamide (3AB), a PARP inhibitor, did not reduce NAD+ loss, suggesting that NAD+ could be consumed by other NAD+-dependant enzymes, including SIRT1. The PARP inhibitor increased the nuclear SIRT1 activity/expression ratio and induced its cytoplasmic translocation during OS. SRT1720, a specific SIRT1 activator, reduced both neurological deficit and striatal lesion 6 hours after cerebral OS, suggesting that SIRT1 activation is beneficial on in vivo OS consequences. The combination of the PARP inhibitor with the SIRT1 activator (3AB + SRT1720) did not potentiate the neuroprotective effects of each strategy. EX527, a SIRT1 inhibitor, did not affect OS-induced deficit and lesion. However, association of the PARP inhibitor with the SIRT1 inhibitor (3AB + EX527) suppressed the neurological recovery and the reduction of lesion induced by 3AB alone. Our data suggested that SIRT1 activation is involved in the neuroprotective effects of PARP inhibition during in vivo cerebral OS. In conclusion, our work led to a better characterization of PARP and SIRT1 during in vivo cerebral OS. SIRT1 is a potential pharmacological target for the treatment of brain pathologies in which OS is present. In addition, SIRT1 activation is involved in the beneficial effects of PARP inhibition on functional and histological cerebral OS consequence

L'activation de la sirtuin 1 (une nouvelle stratégie neuroprotectrice pour le stress oxydant cérébral in vivo ? Implication dans les effets bénéfiques de l'inhibition de la poly(ADP-ribose)polymérase par le 3-aminobenzamide)

Le stress oxydant (SO) est un mécanisme commun à l ischémie cérébrale et au traumatisme crânien qui entraîne notamment l hyperactivation délétère de la poly(ADP-ribose)polymérase (PARP), une enzyme NAD+-dépendante. Cette dernière est impliquée dans le déficit neurologique et la lésion cérébrale consécutifs à ces pathologies. In vitro, l hyperactivation de la PARP diminue le taux cérébral de NAD+, son substrat, et l activité de la sirtuin 1 (SIRT1), une enzyme également NAD+-dépendante. L activation de la SIRT1 est bénéfique au cours d un SO in vitro. Si les effets bénéfiques de l inhibition de la PARP ont été démontrés in vivo au cours d un SO cérébral, l implication de la SIRT1 ainsi que son rôle dans les effets de l inhibition de la PARP n ont pas été explorés. Dans la première partie de ce travail, nous avons mis en évidence qu un modèle de SO cérébral induit in vivo chez le rat par une injection intrastriatale de malonate entraîne un SO prolongé, un déficit neurologique et une activation de la PARP associée à une diminution du NAD+. Dans la deuxième partie de ce travail, nous avons montré que le 3-aminobenzamide (3AB), un inhibiteur de la PARP, ne permet pas de s opposer à la chute du NAD+ dans ce modèle, ce qui suggère que le NAD+ pourrait être consommé par d autres enzymes NAD+-dépendantes, dont la SIRT1. L inhibition de la PARP par le 3AB a permis d augmenter le rapport activité/expression nucléaire de la SIRT1 et a entraîné sa translocation cytoplasmique au cours du SO. Un prétraitement par le SRT1720, un activateur spécifique de la SIRT1, diminue le déficit neurologique et la lésion striatale 6 heures après le SO cérébral, ce qui suggère que l activation de la SIRT1 est bénéfique dans les conséquences d un SO cérébral in vivo. L association de l inhibiteur de la PARP avec l activateur de la SIRT1 (3AB+SRT1720) n a pas potentialisé les effets protecteurs de chaque monothérapie. L EX527, un inhibiteur de la SIRT1, ne modifie pas le déficit et la lésion. En revanche, l association de l inhibiteur de la PARP avec l inhibiteur de la SIRT1 (3AB+EX527) supprime la récupération neurologique ainsi que la réduction de la lésion, induites par l inhibition de la PARP seule (3AB). Ces données suggèrent que l activation de la SIRT1 est impliquée dans les effets bénéfiques de l inhibition de la PARP in vivo au cours d un SO cérébral. En conclusion, l ensemble de ce travail a permis une meilleure caractérisation de la PARP et de la SIRT1 au cours d un SO cérébral in vivo. La SIRT1 pourrait constituer une cible pharmacologique pour le traitement des pathologies cérébrales au cours desquelles un SO est présent. De plus, nous avons montré que les effets bénéfiques de l inhibition de la PARP sur les conséquences fonctionnelles et histologiques induites par le SO cérébral sont liés à l activation de la SIRT1.Oxidative stress (OS) is involved in cerebral ischemia and traumatic brain injury and results in deleterious activation of poly(ADP-ribose)polymerase (PARP), an NAD+-dependant enzyme. PARP is implicated in neurological deficit and brain injury post-ischemia and post-trauma. In vitro, PARP overactivation reduced both brain NAD+ levels, its substrate, and activity of sirtuin 1 (SIRT1), an other NAD+-dependant enzyme. SIRT1 activation is beneficial during in vitro OS. Even if the beneficial effects of PARP inhibition have been demonstrated, SIRT1 involvement during in vivo cerebral OS and its role in the beneficial effects of PARP inhibition have not been studied.In the first part, we demonstrated that in vivo cerebral OS induced by intrastriatal injection of malonate in rat promoted prolonged OS, neurological deficit, PARP activation and NAD+ decrease. In the second part, we showed that 3-aminobenzamide (3AB), a PARP inhibitor, did not reduce NAD+ loss, suggesting that NAD+ could be consumed by other NAD+-dependant enzymes, including SIRT1. The PARP inhibitor increased the nuclear SIRT1 activity/expression ratio and induced its cytoplasmic translocation during OS. SRT1720, a specific SIRT1 activator, reduced both neurological deficit and striatal lesion 6 hours after cerebral OS, suggesting that SIRT1 activation is beneficial on in vivo OS consequences. The combination of the PARP inhibitor with the SIRT1 activator (3AB + SRT1720) did not potentiate the neuroprotective effects of each strategy. EX527, a SIRT1 inhibitor, did not affect OS-induced deficit and lesion. However, association of the PARP inhibitor with the SIRT1 inhibitor (3AB + EX527) suppressed the neurological recovery and the reduction of lesion induced by 3AB alone. Our data suggested that SIRT1 activation is involved in the neuroprotective effects of PARP inhibition during in vivo cerebral OS. In conclusion, our work led to a better characterization of PARP and SIRT1 during in vivo cerebral OS. SIRT1 is a potential pharmacological target for the treatment of brain pathologies in which OS is present. In addition, SIRT1 activation is involved in the beneficial effects of PARP inhibition on functional and histological cerebral OS consequencesPARIS5-Bibliotheque electronique (751069902) / SudocPARIS-BIUM-Bib. électronique (751069903) / SudocSudocFranceF

Neurological and Histological Consequences Induced by <i>In Vivo</i> Cerebral Oxidative Stress: Evidence for Beneficial Effects of SRT1720, a Sirtuin 1 Activator, and Sirtuin 1-Mediated Neuroprotective Effects of Poly(ADP-ribose) Polymerase Inhibition

<div><p>Poly(ADP-ribose)polymerase and sirtuin 1 are both NAD⁺-dependent enzymes. <i>In vitro</i> oxidative stress activates poly(ADP-ribose)polymerase, decreases NAD⁺ level, sirtuin 1 activity and finally leads to cell death. Poly(ADP-ribose)polymerase hyperactivation contributes to cell death. In addition, poly(ADP-ribose)polymerase inhibition restores NAD⁺ level and sirtuin 1 activity <i>in vitro</i>. <i>In vitro</i> sirtuin 1 induction protects neurons from cell loss induced by oxidative stress. In this context, the role of sirtuin 1 and its involvement in beneficial effects of poly(ADP-ribose)polymerase inhibition were evaluated <i>in vivo</i> in a model of cerebral oxidative stress induced by intrastriatal infusion of malonate in rat. Malonate promoted a NAD⁺ decrease that was not prevented by 3-aminobenzamide, a poly(ADP-ribose)polymerase inhibitor, at 4 and 24 hours. However, 3-aminobenzamide increased nuclear SIRT1 activity/expression ratio after oxidative stress. Malonate induced a neurological deficit associated with a striatal lesion. Both were reduced by 3-aminobenzamide and SRT1720, a sirtuin 1 activator, showing beneficial effects of poly(ADP-ribose)polymerase inhibition and sirtuin 1 activation on oxidative stress consequences. EX527, a sirtuin 1 inhibitor, given alone, modified neither the score nor the lesion, suggesting that endogenous sirtuin 1 was not activated during cerebral oxidative stress. However, its association with 3-aminobenzamide suppressed the neurological improvement and the lesion reduction induced by 3-aminobenzamide. The association of 3-aminobenzamide with SRT1720, the sirtuin 1 activator, did not lead to a better protection than 3-aminobenzamide alone. The present data represent the first demonstration that the sirtuin 1 activator SRT1720 is neuroprotective during <i>in vivo</i> cerebral oxidative stress. Furthermore sirtuin 1 activation is involved in the beneficial effects of poly(ADP-ribose)polymerase inhibition after <i>in vivo</i> cerebral oxidative stress.</p></div

Schematic interrelationship between PARP, SIRT1 and neuroprotection during <i>in vivo</i> cerebral oxidative stress.

<p>(A) in physiological conditions, PARP and SIRT1 are both NAD⁺-dependent enzymes whose activities are probably in balance; (B) in oxidative stress conditions, PARP is hyperactivated causing NAD⁺ decrease. (C) in oxidative stress conditions, EX527, a SIRT1 inhibitor, is not deleterious suggesting that an endogenous SIRT1 activation is not present when PARP is hyperactivated and NAD⁺ is consumed (B). (D) in oxidative stress conditions, SRT1720, a SIRT1 activator, is neuroprotective suggesting beneficial effects of an exogenous SIRT1 activation. (E) in oxidative stress conditions, PARP hyperactivation contributes to neurological deficit and striatal lesion showing a deleterious role of PARP. Its inhibition increases nuclear SIRT1 activity that may, partly, explain the neuroprotective effects of 3AB. (F) in oxidative stress conditions, neuroprotective effects of 3AB are suppressed by EX527, suggesting that SIRT1 activation is implicated in neuroprotective effect of PARP inhibition during <i>in vivo</i> cerebral oxidative stress.</p

Both 3-aminobenzamide and SRT1720 reduced striatal lesion whereas EX527 blocked beneficial effects of PARP inhibition.

<p>Effects of 3AB, SRT1720, EX527, 3AB+SRT1720 and 3AB+EX527 association on striatal lesion 6 hours after <i>in vivo</i> cerebral oxidative stress (n = 7−11). (A) Representative photographs. (B) Representative histograms. Data are presented as mean ± S.E.M. Differences were evaluated by two-way ANOVA followed by Student t-test group comparisons. * P < 0.05, ** P < 0.01.</p

3-aminobenzamide did not prevent NAD⁺ depletion consecutive to cerebral oxidative stress.

<p>Effects of 3-aminobenzamide (3AB) on NAD⁺ depletion 4 and 24 hours after <i>in vivo</i> cerebral oxidative stress (n = 7−9). Data are presented as mean ± S.E.M. Differences were evaluated by two-way ANOVA followed by Student t-test group comparisons. ***P < 0.001.</p

Dose-effect of SRT1720 and EX527 on PARP activity <i>in vitro</i>.

<p>Dose-effect of (A) SRT1720, a SIRT1 activator and (B) EX527, a SIRT1 inhibitor, on relative PAR production. Data are expressed in % of control as mean ± S.E.M. Differences were evaluated by one way-ANOVA followed by Dunnett test. * P < 0.05 and * P < 0.01.</p

3-aminobenzamide decreased nuclear SIRT1 expression without modifying its activity, demonstrating basal SIRT1 activity increase.

<p>Effects of 3-aminobenzamide (3AB) on (A) nuclear SIRT1 expression, (B) acetylated-histone H3 expression and (C) nuclear SIRT1 activity / expression ratio 6 hours after <i>in vivo</i> cerebral oxidative stress (n = 5−9). Data are presented as mean ± S.E.M. Differences were evaluated by two-way ANOVA followed by Student t-test group comparisons. **P < 0.01.</p