Expression and Activity Patterns of Nitric Oxide Synthases and Antioxidant Enzymes Reveal a Substantial Heterogeneity Between Cardiac and Vascular Aging in the Rat

Abstract

We investigated the effects of aging and ischemia-reperfusion (I/R) injury on the expression and activity of nitric oxide (*NO) synthases and superoxide dismutase (SOD) isoforms. To this end we perfused excised hearts from young (6 months old) and old (31-34 months old) rats according to the Langendorff technique. The isolated hearts were, after baseline perfusion for 30 min, either subjected to 20 min of global no-flow ischemia followed by 40 min of reperfusion or were control-perfused (60 min normoxic perfusion). Both MnSOD and Cu,ZnSOD expression remained unchanged with increasing age and remained unaltered by I/R. However, SOD activity decreased from 7.55 +/- 0.1 U/mg protein in young hearts to 5.94 +/- 0.44 in old hearts (P<0.05). Furthermore, I/R led to a further decrease in enzyme activity (to 6.35 +/- 0.41 U/mg protein; P<0.05) in myocardium of young, but not in that of old animals. No changes in myocardial protein-bound 3-nitrotyrosine levels could be detected. Endothelial NOS (eNOS) expression and activity remained unchanged in aged left ventricles, irrespective of I/R injury. This was in steep contrast to peripheral (renal and femoral) arteries obtained from the same animals where a marked age-associated increase of eNOS protein expression could be demonstrated. Inducible NOS expression was undetectable either in the peripheral arteries or in the left ventricle, irrespective of age. In particular when associated with an acute pathology, which is furthermore limited to a certain time frame, changes in the aged myocardium with respect to enzymes crucially involved in maintaining the redox homeostasis, seem to be much less pronounced or even absent compared to the vascular aging process. This may point to heterogeneity in the molecular regulation of the cardiovascular aging process.

The hydrogen sulfide signaling system: changes during aging and the benefits of caloric restriction

“…The increased CSE protein expression with age in aorta is similar to changes in eNOS protein expression with age in peripheral arteries, although the increase in eNOS expression is typically larger (Cernadas et al 1998;Goettsch et al 2001;van der Loo et al 2005;van der Loo et al 2000). It has been proposed that the change in eNOS is a homeostatic correction for decreased NO bioavailability or NO concentration, and that this is caused by increased superoxide reacting with NO to form a peroxynitrite (van der Loo et al 2005;van der Loo et al 2000).…”

“…It has been proposed that the change in eNOS is a homeostatic correction for decreased NO bioavailability or NO concentration, and that this is caused by increased superoxide reacting with NO to form a peroxynitrite (van der Loo et al 2005;van der Loo et al 2000). Interestingly, NO and H 2 S can interact, and therefore changes in one system could impact the other (Hosoki et al 1997;Wang et al 2008).…”

“…At higher H 2 S concentrations, sufficient H 2 S may remain to activate K ATP channels, causing the second phase relaxation (Zhao et al 2001). The concentration of NO is reduced with age (Cernadas et al 1998;Goettsch et al 2001;van der Loo et al 2005;van der Loo et al 2000), and therefore it follows that less H 2 S would be required to significantly reduce free NO in tissue of older animals. This would have the effect of increasing the apparent sensitivity of the first-phase contraction to H 2 S, consistent with our observations.…”

“…Aging influences the action and/or efficacy of many signaling molecules, including norepinephrine and the more well-studied gasotransmitter NO (Lakatta 1993;Tanaka et al 2006;van der Loo et al 2000). A recent study of plasma H 2 S concentration in humans over 50-80 years of age reported that H 2 S levels may decline with age ), but whether aging affects the H 2 S signaling system is unknown.…”

“…Caloric restriction (CR) is an intervention that attenuates many effects of aging (Anderson and Weindruch 2010;Labinskyy et al 2006;Leeuwenburgh and Prolla 2006), including cardiovascular morbidity (van der Loo et al 2000), cross-linking of cardiac and skeletal muscle proteins (Leeuwenburgh et al 1997), mitochondrial dysfunction (Aspnes et al 1997;Payne et al 2003), loss of skeletal muscle mass (Payne et al 2003;van der Loo et al 2000), and endothelial dysfunction (Barja 2002;Castello et al 2005;Gredilla et al 2004;Gredilla et al 2001;Taddei et al 2006). Furthermore, CR attenuates the age-related impairment of the NO signaling system (Minamiyama et al 2007;Sharifi et al 2008;Yang et al 2004).…”