Confocal Microscopic Localization of Constitutive and Heat Shock–Induced Proteins HSP70 and HSP27 in the Rat Heart

Abstract

Background-Heat-shock treatment of rats elevates expression of heat-shock proteins, which play a role in improving the contractile recovery and reducing infarct size in hearts after ischemic injury. However, the location of these proteins in the heart is unknown. Methods and Results-Anesthetized rats were heat-shocked by elevation of body temperature to 42°C to 42.5°C for 15 minutes, followed by 24 hours of recovery. Control and heat-shocked hearts were extirpated and perfused briefly with saline followed by 2% paraformaldehyde in PBS. Confocal immunofluorescence microscopy of control hearts revealed that HSP27 was localized in cardiomyocytes in a pattern reminiscent of Z bands and was colocalized with neuronal markers in somata and axons. No obvious change in HSP27 content or distribution occurred after heat shock. Confocal microscopy revealed little or no HSP70 in control hearts. After heat shock, HSP70 was detected neither in cardiomyocytes nor in neuronal elements within the heart, but HSP70 was abundant in small blood vessels found between the ventricular cardiomyocytes. Conclusions-Heat shock induces a cell type-specific expression of HSP70 in blood vessels but not myocytes or intrinsic cardiac neurons, suggesting that blood vessels play a primary role in myocardial protection. (Circulation.

Insulin-induced myocardial protection in isolated ischemic rat hearts requires p38 MAPK phosphorylation of Hsp27

“…At 24 h after heat shock treatment, the Hsp27 distribution and abundance are minimally changed (40). In the current study, the abundance of Hsp27 is not significantly changed in the heart after insulin, heat shock, or heat shock and insulin treatments (Fig.…”

“…In contrast, at 1 h after heat shock, Hsp70 was detectable in cardiac tissue and appeared to be localized mostly in small capillaries and in perivascular cells between the cardiomyocytes (Fig. 3), and this localization is not different at 6 or 24 h after heat shock (40,42,43). At 1 h after induction, it is unlikely that sufficient mature Hsp70 has accumulated in the cells to provide protection from ischemiareperfusion injury.…”

“…4). As with Hsp70, an increase in protective proteins in blood vessels could be the first line of defense in protecting the heart from reactive oxygen species during reperfusion injury (40). After heat shock, Hsp27 appears to be localized with ␣-tubulin (Fig.…”

“…Hsp27 is constitutive in the myocardium and is associated with contractile elements, and after heat shock treatment, its abundance is minimally changed (40). However, engineered overexpression of Hsp27 in cardiomyocytes provides protection against simulated ischemia (48,68).…”

HSP70.1 and -70.3 are required for late-phase protection induced by ischemic preconditioning of mouse hearts

“…Alternatively, a recent study with confocal microscopy demonstrated that heat shock-induced stress-protein expression in rat heart increases HSP70 expression in microvascular blood vessels and not in cardiomyocytes (18). This study suggests that the cross tolerance to I/R injury after heat shock, mediated by HSP70 expression in the myocardium, may involve alterations in microvascular blood flow during ischemia or following restoration of flow to ischemic areas during reperfusion.…”