Naproxen and Diclofenac Attenuate Atorvastatin-induced Preconditioning of the Myocardium.

Statins reduce infarct size (IS) in ischemia-reperfusion injury of the myocardium. Inhibition of cyclooxygenase-2 (COX-2) attenuates this benefit. We investigated the effect of two widely used non-selective non-steroidal anti-inflammatory drugs (NSAIDs) with different degree of anti-COX-2 activity on atorvastatin-mediated preconditioning. Wistar rats received oral atorvastatin (10 mg∙kg-1∙day-1), naproxen (10 mg∙kg-1∙day-1), diclofenac (8 mg∙kg-1∙day-1), atorvastatin+naproxen, atorvastatin+diclofenac or water for three days. Hearts were then excised and perfused in the Langendorff system. Area at risk (AR) and IS were determined after 30 min of regional ischemia and 120 min of reperfusion. Atorvastatin reduced IS by 51.3% compared with controls (14.7 ± 3.9% vs. 30.2 ± 4.6% of the AR; P < 0.001). Naproxen and diclofenac alone did not alter IS compared to control. Diclofenac completely abrogated atorvastatin-mediated protection of the myocardium. Naproxen significantly attenuated but did not eliminate the IS reducing the effect of atorvastatin when compared with controls (P = 0.038). The difference in IS between the atorvastatin+naproxen group and the atorvastatin+diclofenac group showed a strong trend in reaching statistical significance (P = 0.058), but was not found to be significant. Our results suggest relatively small, but noticeable differences among non-selective NSAIDs in their potential to attenuate statin-mediated preconditioning.

PPAR-alpha activation as a preconditioning-like intervention in rats in vivo confers myocardial protection against acute ischaemia-reperfusion injury: involvement of PI3K-Akt.

Peroxisome proliferator-activated receptors (PPAR) regulate the expression of genes involved in lipid metabolism, energy production, and inflammation. Their role in ischaemia-reperfusion (I/R) is less clear, although research indicates involvement of PPARs in some forms of preconditioning. This study aimed to explore the effects of PPAR-α activation on the I/R injury and potential cardioprotective downstream mechanisms involved. Langendorff-perfused hearts of rats pretreated with the selective PPAR-α agonist WY-14643 (WY, pirinixic acid; 3 mg·(kg body mass)·day(-1); 5 days) were subjected to 30 min ischaemia - 2 h reperfusion with or without the phosphatidylinositol 3-kinase (PI3K)-Akt inhibitor wortmannin for the evaluation of functional (left ventricular developed pressure, LVDP) recovery, infarct size (IS), and reperfusion-induced arrhythmias. A 2-fold increase in baseline PPAR-α mRNA levels (qPCR) in the WY-treated group and higher post-I/R PPAR-α levels compared with those in untreated controls were accompanied by similar changes in the expression of PPAR-α target genes PDK4 and mCPT-1, regulating glucose and fatty acid metabolism, and by enhanced Akt phosphorylation. Post-ischaemic LVDP restoration in WY-treated hearts reached 60% ± 9% of the pre-ischaemic values compared with 24% ± 3% in the control hearts (P < 0.05), coupled with reduced IS and incidence of ventricular fibrillation that was blunted by wortmannin. Results indicate that PPAR-α up-regulation may confer preconditioning-like protection via metabolic effects. Downstream mechanisms of PPAR-α-mediated cardioprotection may involve PI3K-Akt activation.

Upregulation of CaMKIIδ during ischaemia-reperfusion is associated with reperfusion-induced arrhythmias and mechanical dysfunction of the rat heart: involvement of sarcolemmal Ca2+-cycling proteins.

Although Ca(2+)/calmodulin-dependent protein kinase II delta (CaMKIIδ) has been implicated in development of different phenotypes of myocardial ischaemia-reperfusion injury, its involvement in arrhythmogenesis and cardiac stunning is not sufficiently elucidated. Moreover, the mechanisms by which CaMKIIδ mediates disturbances in excitation-contraction coupling, are not exactly known. To investigate this, KN-93 (0.5 µmol/L), a CaMKII inhibitor, was administered before induction of global ischaemia and reperfusion in isolated Langendorff-perfused rat hearts. Expression of CaMKIIδ and the sarcollemal Ca(2+)-cycling proteins, known to be activated during reperfusion, was analyzed using immunoblotting. KN-93 reduced reperfusion-induced ectopic activity and the incidence of ventricular fibrillation. Likewise, the severity of arrhythmias was lower in KN-treated hearts. During the pre-ischaemia phase, neither inotropic nor chronotropic effects were elicited by KN-93, whereas post-ischaemic contractile recovery was significantly improved. Ischaemia-reperfusion increased the expression of CaMKIIδ and sodium-calcium exchanger (NCX1) proteins without any influence on the protein content of alpha 1c, a pore-forming subunit of L-type calcium channels (LTCCs). On the other hand, inhibition of CaMKII normalized changes in the expression of CaMKIIδ and NCX1. Taken together, CaMKIIδ seems to regulate its own turnover and to be an important component of cascade integrating NCX1, rather than LTCCs that promote ischaemia-reperfusion-induced contractile dysfunction and arrhythmias.

The role of PPAR in myocardial response to ischemia in normal and diseased heart.

Peroxisome proliferator-activated receptors (PPAR), ligand-activated transcription factors, belong to the nuclear hormone receptor superfamily regulating expression of genes involved in different aspects of lipid metabolism, inflammation and cardiac energy production. Activation of PPAR-α isoform by its natural ligands, fatty acids (FA) and eicosanoids, promotes mitochondrial FA oxidation as the primary ATP-generating pathway. On the other hand, PPAR-γ regulates lipid anabolism or storage, while, until recently, the function of PPAR-ß/δ has been less explored. Under conditions associated with acute or chronic oxygen deprivation, PPAR-α modulates expression of genes that determine substrate switch (FA vs. glucose) aimed at maintenance of basic cardiac function. Although PPAR-α and PPAR-γ synthetic agonists, hypolipidemic and antidiabetic drugs, have been reported to protect the heart against ischemia/reperfusion injury, it is still a matter of debate whether PPAR activation plays a beneficial or detrimental role in myocardial response to ischemia, in particular, in pathological conditions. This article reviews some findings demonstrating the impact of PPAR activation on cardiac resistance to ischemia in normal and pathologically altered heart. Specifically, it addresses the issue of susceptibility to ischemia in the diabetic myocardium, with particular regards to the role of PPAR. Finally, involvement of PPAR in the mechanisms of lipid-independent cardioprotective effects of some hypolipidemic drugs is also discussed.