Jean-François Savouret

Resveratrol, a natural aryl hydrocarbon receptor antagonist, protects sperm from DNA damage and apoptosis caused by benzo(a)pyrene☆

Benzo(a)pyrene (BaP), an aryl hydrocarbon receptor (AhR) ligand present in cigarette smoke and car exhaust, is thought to have negative effects on male reproduction. We hypothesized that BaP damages sperm through AhR activation, phase I enzyme induction, DNA adduct formation, and increased germ cell apoptosis in the testis, and that resveratrol, a natural competitive inhibitor of the AhR found in some red wines, could prevent the adverse effects of BaP on sperm. Male Balb C mice were injected subcutaneously (s.c.) for 5 weeks with a range of BaP doses (0.5 mg/kg to 50 mg/kg). Live sperm were obtained from the vas deferens, counted, and stained to measure annexin-V positive (apoptotic) cells. In a subsequent study, mice were injected for 5 weeks with corn oil (control), BaP (5 mg/kg/week), or BaP plus resveratrol (50 mg/kg/week) (n = 3 per group). Immunohistochemistry (IHC) was performed on testis sections for the determination of CYP1A1, BaP diol epoxide (BPDE) DNA adducts, and apoptosis and the results quantified by using the HSCORE, a semiquantitative scoring system. Our results demonstrated that sperm counts after 5 weeks were inversely correlated to BaP dosage. BaP (0.5 to 5 mg/week) positively correlated with sperm apoptosis while higher doses increased sperm necrosis. CYP1A1 protein was observed mainly in interstitial cells of some testis sections, but there was no significant induction by BaP. BPDE DNA adducts were induced in all components of the seminiferous tubules by BaP and suppressed by resveratrol: median HSCORE (interquartile range) control 61 (52-71.5); BaP 213 (192-248), P = 0.01 compared to control; BaP plus resveratrol 83 (70-90). BaP significantly increased apoptosis, mainly in spermatogonia: medain HSCORE (interquartile range) BaP 189 (161-223) versus control 83 (57-93), P < 0.01; and this effect was abrogated by resveratrol. Median HSCORE for BaP plus resveratrol was 112 (range 99-121). In summary, BaP caused increased sperm cell BPDE DNA adduct formation and apoptosis in the mouse. The natural AhR antagonist, resveratrol diminished BaP-induced DNA adducts and apoptosis in seminiferous tubules.

Resveratrol decreases hyperalgesia induced by carrageenan in the rat hind paw

The effect of resveratrol, an aryl hydrocarbon receptor (AhR) antagonist, known to inhibit inducible cyclooxygenase-2 (COX2) and its transcription were examined in a model of hyperalgesia induced by carrageenan in the rat. Pretreatment with resveratrol did not reverse swelling and edema, but reversed the hyperalgesia induced by local tissue injury provoked by carrageenan. This reversal, occurring at resveratrol concentrations as low as 2 mg/kg, lasted for at least 48 hours. The link with COX2 activity inhibition and COX2 gene transcription, as well as a potential AhR inhibitory effect, remain to be established.

Postischemic treatment by trans‐resveratrol in rat liver ischemia‐reperfusion: A possible strategy in liver surgery

Liver ischemia‐reperfusion (I/R) injury occurs in many clinical conditions, including liver surgery and transplantation. Oxygen free radicals generated during I/R reduce endogenous antioxidant systems and contribute to hepatic injury. trans‐Resveratrol (trans‐3,5,4′‐trihydroxystilbene) is reported to have antioxidant properties. We investigated the effect of trans‐resveratrol on liver injury induced by I/R. After 1 hour of ischemia, administered 5 minutes before 3 hours of reperfusion, trans‐resveratrol was hepatoprotective at a low dose (0.02 mg/kg). It significantly decreased aminotransferase levels by about 40% and improved sinusoidal dilatation. trans‐Resveratrol preserved antioxidant defense by preventing total and reduced glutathione depletion caused by I/R. At 0.2 mg/kg, trans‐resveratrol significantly increased glutathione reductase, Cu/Zn–superoxide dismutase, and catalase activities. However, at a high dose (20 mg/kg), trans‐resveratrol became prooxidant with an aggravation of liver injury evaluated by aminotransferase release and histological analysis and associated with a depletion of total and reduced glutathione levels and a decrease of antioxidant enzyme activities. In conclusion, a prereperfusion treatment by trans‐resveratrol only at low doses decreases liver injury induced by I/R by protecting against antioxidant defense failure. This administration protocol could reduce liver damage during surgery or transplantation. Liver Transpl 14:451–459, 2008.

Promoter- and cell-specific responses to sex steroids.

Understanding the mechanisms of cellular trafficking of steroid hormone receptors not only yields important information per se but also permits the development of methods to analyze in vivo the different steps of agonist or antagonist action on the receptor. It has been shown that agonists and antagonists display different properties when acting through the same receptor on different hormone responsive elements (HREs) present in different genes. Besides this promoter-specific activity of different ligands, the presence of receptor-associated proteins modulates the activity of the receptors in different cells. All these mechanisms concur to a differential activity of various agonists and antagonists on the transcription of various genes expressed in different cells.