Genes encoding enzymes involved in fatty acids (FA) and glucose oxidation are transcriptionally regulated by peroxisome proliferator-activated receptors (PPAR), members of the nuclear receptor superfamily. Under conditions associated with O 2 deficiency, PPAR-α modulates substrate switch (between FA and glucose) aimed at the adequate energy production to maintain basic cardiac function. Both, positive and negative effects of PPAR-α activation on myoc ardial ischemia/reperfusion (I/R) injury have been reported. Moreover, the role of PPAR-mediated metabolic shifts in cardioprotective mechanisms of preconditioning (PC) is relatively less investigated. We explored the effects of PPAR-α upregulation mimicking a delayed “second window” of PC on I/R injury in the rat heart and potential downstream mechanisms involved. Pretreatment of rats with PPAR-α agonist WY-14643 (WY, 1 mg/kg, i.p.) 24 h prior to I/R reduced post-ischemic stunning, arrhythmias and the extent of lethal injury (infarct size) and ap optosis (caspase-3 expression) in isolated hearts exposed to 30-min global ischemia and 2-h reperfusion. Protection was associated with remarkably increased expression of PPAR- α target genes promoting FA utilization (medium-chain acyl-CoA de hydrogenase, pyruvate dehydrogenase kinase-4 and carnitine palmitoyltransferase I) and reduced expression of glucose transporter GLUT-4 responsible for glucose transport and metabolism. In addition, enhanced Akt phosphorylation and protein levels of eNOS, in conjunction with blunting of cardioprotection by NOS inhibitor L-NAME, were observed in the WY-treated hearts. Conclusions: upregulation of PPAR-α target metabolic genes involved in FA oxidation may underlie a delayed phase PC-like protection in the rat heart. Potential non-genomic effects of PPAR-α-mediated cardioprotection may involve activation of prosurvival PI3K/Akt pathway and its downstream targets such as eNOS and subsequently reduced apoptosis., T. Ravingerová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The purpose of this study was to determine the role of lipotoxicity in vascular smooth muscle (VSM). C1-BODIPY 500/510 C12 used to assess the ability of VSM A7r5 cells to transport long-chain fatty acids showed that lipid transport did not appear to limit metabolism. Thin layer chromatography revealed that storage of transported fatty acid occurred primarily as mono- and diglycerides and fatty acids but not as triglycerides. We used lipid-induced apoptosis as a measure of lipotoxicity and found that 1.5 mM palmitate (6.8:1) bound to albumin resulted in a 15-fold increase in the number of apoptotic cells compared to the control at 24 hours. This apoptosis did not seem to be due to an increase in reactive oxygen species (ROS) since VSM cells incubated in palmitate showed less ROS production than cells incubated in albumin only. Similar exposure to oleate did not significantly increase the number of apoptotic cells compared to the control. Oleate actually significantly attenuated the apoptosis induced by palmitate, suggesting that unsaturated fatty acids have a protective effect on cells undergoing palmitate-induced apoptosis. These results suggest that vascular smooth muscle is vulnerable to lipotoxicity and that this lipotoxicity may play a role in the development of atherosclerosis., H. M. Mattern, C. D. Hardin., and Obsahuje bibliografii a bibliografické odkazy