Physical exercise prevents cellular senescence in circulating leukocytes and in the vessel wall.

BACKGROUND: The underlying molecular mechanisms of the vasculoprotective effects of physical exercise are incompletely understood. Telomere erosion is a central component of aging, and telomere-associated proteins regulate cellular senescence and survival. This study examines the effects of exercising on vascular telomere biology and endothelial apoptosis in mice and the effects of long-term endurance training on telomere biology in humans. METHODS AND RESULTS: C57/Bl6 mice were randomized to voluntary running or no running wheel conditions for 3 weeks. Exercise upregulated telomerase activity in the thoracic aorta and in circulating mononuclear cells compared with sedentary controls, increased vascular expression of telomere repeat-binding factor 2 and Ku70, and reduced the expression of vascular apoptosis regulators such as cell-cycle-checkpoint kinase 2, p16, and p53. Mice preconditioned by voluntary running exhibited a marked reduction in lipopolysaccharide-induced aortic endothelial apoptosis. Transgenic mouse studies showed that endothelial nitric oxide synthase and telomerase reverse transcriptase synergize to confer endothelial stress resistance after physical activity. To test the significance of these data in humans, telomere biology in circulating leukocytes of young and middle-aged track and field athletes was analyzed. Peripheral blood leukocytes isolated from endurance athletes showed increased telomerase activity, expression of telomere-stabilizing proteins, and downregulation of cell-cycle inhibitors compared with untrained individuals. Long-term endurance training was associated with reduced leukocyte telomere erosion compared with untrained controls. CONCLUSIONS: Physical activity regulates telomere-stabilizing proteins in mice and in humans and thereby protects from stress-induced vascular apoptosis.

The PPAR-gamma agonist pioglitazone increases neoangiogenesis and prevents apoptosis of endothelial progenitor cells.

PPAR-gamma agonists (thiazolidinediones, TZDs) may improve endothelial function independently of insulin sensitizing. Bone marrow-derived endothelial progenitor cells (EPC) contribute to neoangiogenesis. Mice were treated with pioglitazone, 20mg/kg/day for 10 days. Treatment with TZD upregulated circulating Sca-1/VEGFR-2 positive EPC in the blood (235+/-60%) and the bone marrow (166+/-30%), cultured spleen-derived DiLDL/lectin positive EPC increased to 231+/-21% (n=24 per group). Upregulation of EPC was persistent after 20 days. TZD increased SDF-1-induced migratory capacity per number of EPC by 246+/-73% and increased expression of telomere repeat-binding factor 2 by 320+/-50%. In vivo neoangiogenesis was increased two-fold (214+/-42%, 20 days). The NOS inhibitor L-NAME did not inhibit the TZD-induced upregulation of EPC. EPC from TZD-treated animals showed reduced in vivo apoptosis (65+/-2.8% of vehicle). In cultured human EPC, pre-treatment with pioglitazone prevented H(2)O(2)-induced apoptosis. Inhibition of EPC apoptosis by TZD was abolished in the presence of wortmannin but not by LNMA. In summary, TZD upregulates both number and functional capacity of endothelial progenitor cells. Pioglitazone prevents apoptosis of EPC in mice as well as in human EPC in a PI3K-dependent but NO-independent manner. Reduction of EPC apoptosis by TZD may be a potentially beneficial mechanism for patients with vascular diseases.

Effects of physical exercise on myocardial telomere-regulating proteins, survival pathways, and apoptosis.

OBJECTIVES: The purpose of this study was to study the underlying molecular mechanisms of the protective cardiac effects of physical exercise. BACKGROUND: Telomere-regulating proteins affect cellular senescence, survival, and regeneration. METHODS: C57/Bl6 wild-type, endothelial nitric oxide synthase (eNOS)-deficient and telomerase reverse transcriptase (TERT)-deficient mice were randomized to voluntary running or no running wheel conditions (n = 8 to 12 per group). RESULTS: Short-term running (21 days) up-regulated cardiac telomerase activity to >2-fold of sedentary controls, increased protein expression of TERT and telomere repeat binding factor (TRF) 2, and reduced expression of the proapoptotic mediators cell-cycle-checkpoint kinase 2 (Chk2), p53, and p16. Myocardial and leukocyte telomere length did not differ between 3-week- and 6-month-old sedentary or running mice, but telomerase activity, TRF2 and TERT expression were persistently increased after 6 months and the expression of Chk2, p53, and p16 remained down-regulated. The exercise-induced changes were absent in both TERT(-/-) and eNOS(-/-) mice. Running increased cardiac expression of insulin-like growth factor (IGF)-1. Treatment with IGF-1 up-regulated myocardial telomerase activity >14-fold and increased the expression of phosphorylated Akt protein kinase and phosphorylated eNOS. To test the physiologic relevance of these exercise-mediated prosurvival pathways, apoptotic cardiomyopathy was induced by treatment with doxorubicin. Up-regulation of telomere-stabilizing proteins by physical exercise in mice reduced doxorubicin-induced p53 expression and potently prevented cardiomyocyte apoptosis in wild-type, but not in TERT(-/-) mice. CONCLUSIONS: Long- and short-term voluntary physical exercise up-regulates cardiac telomere-stabilizing proteins and thereby induces antisenescent and protective effects, for example, to prevent doxorubicin-induced cardiomyopathy. These beneficial cardiac effects are mediated by TERT, eNOS, and IGF-1.

Regulation of endothelial progenitor cells by prostaglandin E1 via inhibition of apoptosis.

Bone marrow derived endothelial progenitor cells (EPC) improve endothelial function and neoangiogenesis. Prostaglandin E1 (PGE1) is used for the treatment of patients with peripheral artery disease (PAD). However, the molecular effects are only partially understood. Treatment of C57/Bl6 mice with PGE1, 10 microg/kg BW increased the number of circulating Sca-1/VEGFR-2 positive EPC in the blood compared to vehicle (122+/-7% and 119+/-6% after 10 and 20 days). EPC in the bone marrow were upregulated to 125+/-11% (10 days) and 142+/-15% (20 days). PGE1 increased DiLDL/Lectin positive spleen-derived EPC to 170+/-20% and 174+/-14% after 10 and 20 days. Treatment with PGE1 enhanced in-vivo neoangiogenesis by 2-fold (disk assay, 218+/-27%). PGE1 enhanced the SDF-1 induced migratory capacity per number of EPC to 140+/-11%, 146+/-22% and 160+/-16% after 10, 14 and 20 days. Greater migratory capacity was associated with upregulation of expression of telomere repeat-binding factor (TRF2). EPC of PGE1-treated mice were characterized by reduced apoptosis. Similarly, PGE1 prevented H(2)O(2)-induced apoptosis in cultured human EPC. The effect is mediated by PI3-kinase. The effects of PGE1 on EPC were completely prevented by co-treatment with the NO-inhibitor L-NAME, 50 mg kg(-1) p.o. Treatment with the prostaglandin I2 derivative iloprost (10 microg/kg BW, 20 days) did not alter EPC numbers or function. Physical exercise is the basis of the treatment of patients with PAD. Voluntary running increased EPC numbers in mice. Treatment with PGE1 resulted in an additional increase of Sca-1/VEGFR-2- and DiLDL/lectin positive EPC as well as migration. n=10-24 for all groups, all effects p<0.05. In summary, prostaglandin E1 increases the number of EPC in the blood and the bone marrow in mice. The effect is additive to physical exercise, depends on nitric oxide and is characterized by reduction of PI3-kinase mediated apoptosis. PGE1-mediated upregulation of EPC is associated with improved EPC function and enhanced angiogenesis.