Mechanisms of cardiac protection from ischemia/reperfusion injury: a role for caveolae and caveolin‐1

Abstract

Caveolae, small invaginations in the plasma membrane, contain caveolins (Cav) that scaffold signaling molecules including the tyrosine kinase Src. We tested the hypothesis that cardiac protection involves a caveolin-dependent mechanism. We used in vitro and in vivo models of ischemia-reperfusion injury, electron microscopy (EM), transgenic mice, and biochemical assays to address this hypothesis. We found that Cav-1 mRNA and protein were expressed in mouse adult cardiac myocytes (ACM). The volatile anesthetic, isoflurane, protected ACM from hypoxia-induced cell death and increased sarcolemmal caveolae. Hearts of wild-type (WT) mice showed rapid phosphorylation of Src and Cav-1 after isoflurane and ischemic preconditioning. The Src inhibitor PP2 reduced phosphorylation of Src (Y416) and Cav-1 in the heart and abolished isoflurane-induced cardiac protection in WT mice. Infarct size (percent area at risk) was reduced by isoflurane in WT (30.5+/-4 vs. 44.2+/-3, n=7, P<0.05) but not Cav-1(-/-) mice (46.6+/-5 vs. 41.7+/-3, n=7). Cav-1(-/-) mice exposed to isoflurane showed significant alterations in Src phosphorylation and recruitment of C-terminal Src kinase, a negative regulator of Src, when compared to WT mice. The results indicate that isoflurane modifies cardiac myocyte sarcolemmal membrane structure and composition and that activation of Src and phosphorylation of Cav-1 contribute to cardiac protection. Accordingly, therapies targeted to post-translational modification of Src and Cav-1 may provide a novel approach for such protection.

Caveolin-3 expression and caveolae are required for isoflurane-induced cardiac protection from hypoxia and ischemia/reperfusion injury

“…Concentrations of isoflurane (0.7%, 1.4%, and 2.8% vol/vol in air) were chosen based on the minimum alveolar concentrations (MAC) in rodents (where 1.4% vol/vol is equivalent to 1 MAC [24]). We have previously confirmed that 1.4% vol/vol isoflurane produces 0.165 ± 0.003 mM isoflurane in media in our metabolic chamber [15]. Cell death was quantified by counting trypan blue-stained cells with results expressed as a percentage of total cells counted ( Figure 1).…”

“…We have recently shown that isoflurane increases the recruitment and phosphorylation of Src kinase and caveolin-1 into myocardial caveolar fractions. We have also shown that this phosphorylation of Src and caveolin-1 are required for isoflurane-induced cardiac protection [15]; isoflurane increased the phosphorylation of caveolin-1 in a Src-dependent manner and caveolin-1 knockout mice were not able to be protected from myocardial ischemia/reperfusion injury by isoflurane. Importantly, myocytes isolated from these animals have normal caveolae (unpublished observations).…”

“…Cardiac myocytes (CM) express the muscle-specific isoform caveolin-3 [12] while other cell types in the heart express caveolin-1 and -2. Recent studies have shown: 1) the presence and interaction of all three caveolin isoforms in adult cardiac myocytes [13,14], 2) a signaling role for caveolin-1 in cardiac myocytes [15], and 3) that caveolins can scaffold proteins associated with cardiac protection [16,17].…”

Persistent eNOS activation secondary to caveolin-1 deficiency induces pulmonary hypertension in mice and humans through PKG nitration

“…Caveolin-1 deficiency was also seen in rat models of PH (22,23), and the cell-permeable Cav1 inhibitory peptide prevented the development of monocrotaline-induced PH (24). In addition, decreased expression of caveolin-1, predominantly in endothelial cells, was observed in lungs of patients with severe idiopathic pulmonary arterial hypertension (IPAH) (23,25). In the present study, we addressed the potentially important mechanism of pulmonary vascular remodeling and PH associated with caveolin-1 deficiency.…”

Intravenous administration of halogenated inhaled anesthetics—research tool or real application?

“…It has been demonstrated that isoflurane specifically interacts with caveolin, a protein-sequestered area in such regions of myocardial membrane (caveolae). 12 Will the anesthetic delivery by lipid infusion alter how the anesthetic partitions into such specific regions of membrane? Might the enhanced protection at apparently low anesthetic concentrations be due, in part, to the delivery or the alterations to specific regions of the cell membranes and organelles?…”