Testosterone-down-regulated Akt pathway during cardiac ischemia/reperfusion: a mechanism involving BAD, Bcl-2 and FOXO3a

Opposing effects of age and calorie restriction on molecular determinants of myocardial ischemic tolerance

We test the hypothesis that moderate calorie restriction (CR) reverses negative influences of age on molecular determinants of myocardial stress resistance. Postischemic contractile dysfunction, cellular damage, and expression of regulators of autophagy/apoptosis and of prosurvival and prodeath kinases were assessed in myocardium from young adult (YA; 2- to 4-month-old) and middle-aged (MA; 12-month-old) mice, and MA mice subjected to 14 weeks of 40% CR (MA-CR). Ventricular dysfunction after 25%±2%), as was cell death indicated by troponin I (TnI) efflux (1,701±214 ng vs. 785±102 ng in YA). MA hearts exhibited 30% and 65% reductions in postischemic Beclin1 and Parkin, respectively, yet 50% lower proapoptotic Bax and 85% higher antiapoptotic Bcl2, increasing the Bcl2/Bax ratio. Age did not influence Akt or p38-mitogen-activated protein kinase (MAPK) expression; reduced expression of increasingly phosphorylated ribosomal protein S6 kinase (p70S6K), increased expression of dephosphorylated glycogen synthase kinase 3β (GSK3β) and enhanced postischemic p38-MAPK phosphorylation. CR countered the age-related decline in ischemic tolerance, improving contractile recovery (60%±4%) and reducing cell death (123±22 ng of TnI). Protection was not associated with changes in Parkin or Bax, whereas CR partially limited the age-related decline in Beclin1 and further increased Bcl2. CR counteracted age-related changes in p70S6K, increased Akt levels, and reduced p38-MAPK (albeit increasing preischemic phosphorylation), and paradoxically reduced postischemic GSK3β phosphorylation. In summary, moderate age worsens cardiac ischemic tolerance; this is associated with reduced expression of autophagy regulators, dysregulation of p70S6K and GSK3β, and postischemic p38-MAPK activation. CR counters age effects on postischemic dysfunction/cell death; this is associated with reversal of age effects on p70S6K, augmentation of Akt and Bcl2 levels, and preischemic p38-MAPK activation. Age and CR thus impact on distinct determinants of ischemic tolerance, although p70S6K signaling presents a point of convergence.

Orchiectomy attenuates kidney fibrosis after ureteral obstruction by reduction of oxidative stress in mice

BACKGROUND/AIMS

Men are generally more prone to chronic kidney disease and progression to end-stage renal disease than women. However, the underlying mechanisms remain unclear. In this study, we investigated the role of reactive oxygen species and testosterone in the progression of renal fibrosis in mice with unilateral ureteral obstruction (UUO).

METHODS

Mice were subjected to either orchiectomy or sham operation 14 days before either UUO or sham surgery. Harvesting of the kidney was performed 7 days after the UUO surgery to measure the production of reactive oxygen species and expression of antioxidants such as catalase, copper-zinc superoxide dismutase, and manganese superoxide dismutase, as well as fibrosis markers including α-smooth muscle actin (α-SMA) and collagen.

RESULTS

UUO resulted in increased expression of α-SMA and collagen deposition in the kidneys of both female and male mice. These increases were significantly greater in males than females. Orchiectomy significantly reduced increases in α-SMA expression and collagen deposition when compared with intact male. UUO increased the production of hydrogen peroxide and lipid peroxidation along with the decreases in expression of manganese superoxide dismutase, copper-zinc superoxide dismutase, and catalase. These changes induced by UUO were significantly attenuated by orchiectomy.

CONCLUSION

Males are more susceptible to UUO-induced kidney fibrosis compared with females, and the higher susceptibility of males is obviated by orchiectomy along with reduction in oxidative stress.

Role of Akt-dependent pathway in resveratrol-mediated cardioprotection after trauma-hemorrhage

BACKGROUND

Resveratrol has been shown to have protective effects for patients in shock-like states, and Akt (protein kinase B) is known to play a role in pro-inflammatory events in response to injury. The aim of this study is to determine whether resveratrol provides cardioprotection mediated via an Akt-dependent pathway in trauma-hemorrhaged animals.

METHODS

Male Sprague-Dawley rats underwent trauma-hemorrhage and resuscitation. A single dose of resveratrol (30 mg/kg body weight) with or without a PI3K inhibitor (wortmannin) or vehicle was administered intravenously during the resuscitation. Two hours after either the trauma-hemorrhage or sham operation, the cardiac output, the positive maximal pressure increase of the left ventricle (+dP/dt(max)), and the negative maximal pressure decrease of the left ventricle (-dP/dt(max)) were measured. Cardiac myeloperoxidase (MPO) activity, interleukin (IL)-6, and intercellular adhesion molecule (ICAM)-1 levels, Akt activity, and apoptosis were measured. One-way ANOVA and Tukey's test were used for statistical analysis.

RESULTS

Cardiac output and ± dP/dt(max) decreased significantly after trauma-hemorrhage. Administration of resveratrol significantly improved these cardiac function parameters. Trauma-hemorrhage increased cardiac MPO activity, IL-6 levels, and ICAM-1 levels, and these parameters were significantly improved in the resveratrol-treated rats subjected to trauma-hemorrhage. Although trauma-hemorrhage decreased cardiac Akt phosphorylation (p-Akt), resveratrol treatment following trauma-hemorrhage prevented the same decrease in cardiac p-Akt. The increase in cardiac apoptosis was attenuated in rats that received resveratrol. Co-administration of wortmannin prevented the beneficial effects of resveratrol on the attenuation of pro-inflammatory responses and cardiac injury after trauma-hemorrhage.

CONCLUSION

Resveratrol attenuates cardiac injury following trauma-hemorrhage, which is, at least in part, due to its anti-inflammatory effects via Akt-dependent pathways.