Src tyrosine kinase is the trigger but not the mediator of ischemic preconditioning

Abstract

The signal cascade that triggers and mediates ischemic preconditioning (IPC) remains unclear. The present study investigated the role of the Src family of tyrosine kinases in IPC. Isolated and buffer-perfused rat hearts underwent IPC with three cycles of 5-min ischemia and 5-min reperfusion, followed by 30-min ischemia and 120-min reperfusion. The Src tyrosine kinase family-selective inhibitor PP1 was administered between 45 and 30 min before ischemia (early PP1 treatment) or for 15 min before IPC [early PP1-preconditioning (PC) treatment]. PP1 was also administered for 5 min before the sustained ischemia (late PP1 treatment) or after IPC (late PP1-PC treatment). Src kinase was activated after 30 min of ischemia in both the membrane and cytosolic fractions. Src kinase was also activated by IPC but was attenuated after the sustained ischemia. Early and late PP1 treatment inhibited Src activation after the sustained ischemia and reduced infarct size. Early PP1-PC inhibited Src activation after IPC but not after the sustained ischemia and blocked cardioprotection afforded by IPC. Late PP1-PC treatment abrogated IPC-induced activation of Src and protein kinase C (PKC)-epsilon in the membrane but not in the cytosolic fraction. This treatment modality abrogated Src activation after the sustained ischemia and failed to block cardioprotection afforded by IPC. These results suggest that Src kinase activation mediates ischemic injury but triggers IPC in the position either upstream of or parallel to membrane-associated PKC-epsilon.

ACh and adenosine activate PI3-kinase in rabbit hearts through transactivation of receptor tyrosine kinases

“…Indeed, Mockridge et al (24) found that PI3-kinase activation in a model of simulated ischemia-reperfusion in cardiomyocytes could be blocked by the Src kinase inhibitor PP2. PP2 also could block protection from IPC in rat heart (15). PP2 completely blocked Akt activation from ACh in the present study supporting a role for an Src kinase in this pathway.…”

Cardioprotection with palm tocotrienol: antioxidant activity of tocotrienol is linked with its ability to stabilize proteasomes

“…Markedly elevated levels of c-Src kinase activity were detected in human skin tumors (1). Myocardial ischemia-reperfusion caused an induction of c-Src protein expression (17); inhibition of c-Src with PPI reduces the extent of cellular injury.…”

“…At the end of reperfusion, a 10% (wt/vol) solution of triphenyltetrazolium chloride in phosphate buffer was infused into the aortic cannula for 20 min at 37°C (16,17). The hearts were excised and stored at Ϫ70°C.…”

The ubiquitin-proteasome system in cardiac physiology and pathology

“…We (176) have observed that degree of proteasome inhibition during reperfusion is dependent on length of ischemia and seems to correlate with levels of oxidized and ubiquitinated proteins and have suggested that the process known as dysregulation is occurring in which there is failure to degrade normal substrates of the proteasome. In support of this hypothesis, we (43) have recently shown that preservation of proteasome function with tocotrienol pretreatment decreases postischemic levels of phosphorylated c-SRC, which signals for ubiquitination and degradation by proteasome (93), and which is also known to be upregulated during ischemia and associated with poor outcomes (97). Further, we (51) have recently demonstrated that pretreatment of isolated hearts with the proteasome inhibitor lactacystin results in a greater accumulation of oxidized proteins and diminished degradation of oxidized actin in the postischemic heart, implying a mediatory role for proteasome.…”