Aging increases DNase γ, an apoptosis-related endonuclease, in rat liver nuclei: effect of dietary restriction

Apoptotic DNase network: Mutual induction and cooperation among apoptotic endonucleases

DNA fragmentation produced by apoptotic DNases (endonucleases) leads to irreversible cell death. Although apoptotic DNases are simultaneously induced following toxic/oxidative cell injury and/or failed DNA repair, the study of DNases in apoptosis has generally been reductionist in approach, focusing on individual DNases rather than their possible cooperativity. Coordinated induction of DNases would require a mechanism of communication; however, mutual DNase induction or activation of DNases by enzymatic or non‐enzymatic mechanisms is not currently recognized. The evidence presented in this review suggests apoptotic DNases operate in a network in which members induce each other through the DNA breaks they produce. With DNA breaks being a common communicator among DNases, it would be logical to propose that DNA breaks from other sources such as oxidative DNA damage or actions of DNA repair endonucleases and DNA topoisomerases may also serve as triggers for a cooperative DNase feedback loop leading to elevated DNA fragmentation and subsequent cell death. Therefore, mutual induction of apoptotic DNases has serious implications for studies focused on activation or inhibition of specific DNases as a strategy for therapeutic intervention aimed at modulation of cell death.

Antioxidant and antiapoptotic activities of deprenyl and estradiol co-administration in aged rat kidney

Aging is a progressive degeneration process in living organisms. Deprenyl is an irreversible monoamine-oxidase B inhibitor which has antioxidant, antiapoptotic and neuroprotective effects. Estradiol is also a neuroprotective and antioxidant hormone. The objective of this study was to determine whether the antioxidative effects of deprenyl can suppress apoptotic activity, with or without estradiol, in aged female rat kidney. Wistar Albino female rats were divided into six groups as follows; young (3 months old) control, aged (24 months old) control, aged deprenyl treated, aged estradiol treated, aged deprenyl plus estradiol treated and sham. All rats except for the sham group were injected for 21 days. Determination of oxidative stress parameter was performed spectrophotometrically. To detect apoptotic cells, TUNEL staining and caspase-3 immunohistochemistry were performed. Deprenyl and estradiol administration, alone or in combination, decreased significantly the levels of lipid peroxidation relative to aged control and sham-injected rats. The number of TUNEL positive cells decreased significantly in deprenyl and estradiol-treated rats compared with aged control and sham rats. Deprenyl and estradiol replacement attenuated age-related changes in renal morphology. The results indicate that deprenyl treatment alone, or in combination with estradiol, may modulate age-related apoptotic changes in rat kidney by decreasing oxidative stress.

Suppression of apoptosis and oxidative stress by deprenyl and estradiol in aged rat liver

Aging is accompanied by significant structural and functional transformations of all organs and systems. Age-associated increase in apoptotic behavior may cause disease. Older cells are more susceptible to endogenous oxidative damage, and oxidative stress is a potent inducer of apoptosis. Deprenyl is an irreversible monoamine-oxidase B inhibitor which has anti-oxidant, anti-apoptotic and neuroprotective effects. Estrogen is also a neuroprotective and anti-oxidant hormone. The objectives of this study were to determine whether the anti-oxidative effects of deprenyl can suppress apoptotic activity, with or without estradiol, in aged female rat livers. In this study, ovariectomized female Wistar albino rats were divided into six groups as follows; young (3 months old) saline-treated control, aged (24 months old) saline-treated control, aged deprenyl treated, aged estradiol treated, aged deprenyl plus estradiol treated and aged sham controls. All rats except for the sham group were treated for 21 days. Determination of oxidative stress parameters was performed spectrophotometrically. To detect apoptotic cells, TUNEL staining was performed. The results were analyzed by one-way ANOVA post hoc Bonferroni test. Deprenyl and estradiol administration, alone or in combination, decreased significantly the levels of lipid peroxidation and increased superoxide dismutase activity in the liver relative to aged control and sham rats (P<0.05). The number of TUNEL positive cells decreased significantly in deprenyl and estradiol-treated rats compared with aged control and sham rats. The results indicate that deprenyl treatment alone, or in combination with estradiol, may modulate age-related apoptotic changes in rat liver by decreasing oxidative stress.

Effect of antioxidant diets on mitochondrial gene expression in rat brain during aging

Age-related increase of reactive oxygen species (ROS) is particularly detrimental in postmitotic tissues. Calorie restriction (CR) has been shown to exert beneficial effects, consistent with reduced ROS generation by mitochondria. Many antioxidant compounds also mimic such effects. N-acetyl cysteine (NAC) provides thiol groups to glutathione and to mitochondrial respiratory chain proteins; thus, it may counteract both ROS generation and effects. In the present study we investigated, in different rat brain areas during aging (6, 12, and 28 months), the effect of 1-year treatment with CR and dietary supplementation with NAC on the expression of subunit 39 kDa and ND-1 (mitochondrial respiratory complex I), subunit IV (complex IV), subunit alpha of F0F1-ATP synthase (complex V) and of adenine nucleotide translocator, isoform 1 (ANT-1). The observed age-related changes of expression were prevented by the dietary treatments. The present study provides further evidence for the critical role of mitochondria in the aging process.

Toward a unified theory of caloric restriction and longevity regulation

The diet known as calorie restriction (CR) is the most reproducible way to extend the lifespan of mammals. Many of the early hypotheses to explain this effect were based on it being a passive alteration in metabolism. Yet, recent data from yeast, worms, flies, and mammals support the idea that CR is not simply a passive effect but an active, highly conserved stress response that evolved early in life's history to increase an organism's chance of surviving adversity. This perspective updates the evidence for and against the various hypotheses of CR, and concludes that many of them can be synthesized into a single, unifying hypothesis. This has important implications for how we might develop novel medicines that can harness these newly discovered innate mechanisms of disease resistance and survival.

Acute stress response in calorie-restricted rats to lipopolysaccharide-induced inflammation

Calorie restriction (CR) reduces morbidity and mortality in a wide range of organisms, possibly through the stress response machinery. We analyzed the acute phase response of CR rats to lipopolysaccharide (LPS)-induced inflammatory challenge. Six-month-old male F344 rats, fed ad libitum (AL) or a 30% calorie-restricted diet from 6 weeks of age, received an intravenous LPS injection and were then sacrificed between 0 and 8 h. CR attenuated liver injury without reduction in the plasma concentrations of proinflammatory cytokines or nitric oxide (NO). Western blotting analysis of liver tissue demonstrated that CR did not affect the degradation of cytoplasmic I-kappaB and subsequent nuclear translocation of NF-kappaB, a key transcription factor after inflammatory challenge. We also analyzed the liver gene expression profiles at 0, 1 and 4 h with DNA arrays and cluster analysis. Compared with the AL group, CR upregulated the expression of several genes for inflammatory mediators or their related molecules at 0 h, but not at 1 or 4 h. CR downregulated genes for energy or xenobiotic metabolism and stress response proteins at 0 h. At 1 h, the relatively downregulated genes by CR were those for proteases and the ubiquitin-proteasome pathway. The present results suggest that CR attenuates liver injury without suppression of the proinflammatory response, and that the protective effect emerges from constitutively, rather than inductively, expressed gene products.