ABSTRACT
AIMS: Oxidative stress is known to induce early replicative senescence. Senescence has been proposed to work as a barrier to immortalization and tumor development. Here, we aimed to evaluate the impact of the loss of peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α), a master regulator of oxidative metabolism and mitochondrial reactive oxygen species (ROS) generation, on replicative senescence and immortalization in mouse embryonic fibroblasts (MEFs). RESULTS: We found that primary MEFs lacking PGC-1α showed higher levels of ROS than wild-type MEFs at all cell passages tested. The elevated production of ROS was associated with higher levels of oxidative DNA damage and the increased formation of DNA double-strand breaks. Evaluation of the induction of DNA repair systems in response to γ-radiation indicated that the loss of PGC-1α also resulted in a small but significant reduction in their activity. DNA damage induced the early activation of senescence markers, including an increase in the number of ß-galactosidase-positive cells, the induction of p53 phosphorylation, and the increase in p16 and p19 protein. These changes were, however, not sufficient to reduce proliferation rates of PGC-1α-deficient MEFs at any cell passage tested. Moreover, PGC-1α-deficient cells escaped replicative senescence. INNOVATION & CONCLUSION: PGC-1α plays an important role in the control of cellular senescence and immortalization.
Subject(s)
Cellular Senescence/radiation effects , DNA Repair , DNA/genetics , Fibroblasts/radiation effects , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , Animals , Biomarkers/metabolism , Cell Proliferation/genetics , Cell Proliferation/radiation effects , Cellular Senescence/genetics , Cyclin-Dependent Kinase Inhibitor p16/genetics , Cyclin-Dependent Kinase Inhibitor p16/metabolism , Cyclin-Dependent Kinase Inhibitor p19/genetics , Cyclin-Dependent Kinase Inhibitor p19/metabolism , DNA/metabolism , DNA Breaks, Double-Stranded/radiation effects , Embryo, Mammalian , Fibroblasts/cytology , Fibroblasts/metabolism , Gamma Rays , Gene Expression Regulation , Mice , Mice, Knockout , Mitochondria/metabolism , Mitochondria/radiation effects , Oxidative Stress , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/deficiency , Phosphorylation/radiation effects , Reactive Oxygen Species/metabolism , Tumor Suppressor Protein p53/genetics , Tumor Suppressor Protein p53/metabolism , beta-Galactosidase/genetics , beta-Galactosidase/metabolismABSTRACT
AIMS: Liver steatosis is associated with mitochondrial dysfunction and elevated reactive oxygen species (ROS) levels together with enhanced sensitivity to ischemia-reperfusion (IR) injury and limited response to preconditioning protocols. Here, we sought to determine whether the downregulation in the steatotic liver of peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), a master regulator of mitochondrial metabolism and ROS that is known to play a role in liver metabolic control, could be responsible for the sensitivity of the steatotic liver to ischemic damage. RESULTS: PGC-1α was induced in normal liver after exposure to an IR protocol, which was concomitant with an increase in the levels of antioxidant proteins. By contrast, its induction was severely blunted in the steatotic liver, resulting in a modest induction of antioxidant proteins. Livers of PGC-1α-/- mice on a chow diet were normal, but they exhibited an enhanced sensitivity to IR injury and also a lack of response to ischemic preconditioning (IPC), a phenotype that recapitulated the features of the steatotic liver in terms of liver damage, although the inflammatory response differed between both models. Utilizing an in vitro model of IPC, we found that PGC-1α expression was downregulated in hepatic cells cultured at 1% O2; whereas it was induced after reoxygenation (3% O2), and it was responsible for the recovery of antioxidant gene expression after the ischemic period. Innovation & Conclusion: PGC-1α plays an important role in the protection against IR injury in the liver, which is likely associated with its capacity to induce antioxidant gene expression. Antioxid. Redox Signal. 27, 1332-1346.
Subject(s)
Down-Regulation , Fatty Liver/pathology , Liver/blood supply , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , Animals , Antioxidants/metabolism , Cells, Cultured , Disease Models, Animal , Fatty Liver/genetics , Fatty Liver/metabolism , Gene Knockout Techniques , Hepatocytes , Ischemic Preconditioning , Mice , Reactive Oxygen Species/metabolism , Reperfusion Injury/genetics , Reperfusion Injury/metabolismABSTRACT
OBJECTIVES: To determine the prevalence of alcohol misuse among medical inpatients and the methods used by medical staff to evaluate alcohol consumption. METHODS: Multicenter, prospective, observational, cross-sectional study performed at 21 hospitals in Spain. All adult patients hospitalized in internal medicine wards on 12 March 2008 were eligible for study. Alcohol consumption was evaluated with the Alcohol Use Disorders Identification Test (AUDIT-C and AUDIT) and the Systematic Inventory of Alcohol Consumption questionnaire. Drinking patterns were determined according to clinical evaluation using ICD-10 criteria. Medical records were reviewed to gather information on the recording of alcohol use. RESULTS: We assessed 1039 inpatients, of whom 123 (12%) had unhealthy alcohol drinking patterns. Alcohol misuse was more frequent among males (odds ratio 5.20), younger patients (odds ratio, 14.17), median age patients (odds ratio, 2.99), and South Region (odds ratio, 1.77). Alcohol use during hospitalization was recorded in 603 inpatients (59%); quantitative records were performed in 28% of hazardous and harmful drinkers and in 41% of dependent patients. Lack of alcohol use recording was more frequent among females (odds ratio 1.73), median and older age groups (odds ratios 1.44 and 1.73, respectively), Northwest Regions (odds ratios 3.46). Patients from the East Region (odds ratio 0.47) had more frequently assessed the question in their medical records. CONCLUSIONS: Prevalence of alcohol misuse was higher in hospitalized patients than in the general population. Adequate quantitative recording was infrequent. We stress the need to implement measures to increase and improve the detection and recording of alcohol use.
