Specific heat shock proteins protect microtubules during simulated ischemia in cardiac myocytes

The protective effects of heat shock proteins (HSPs) during myocardial ischemia are now well documented, but little is known about the mechanisms of protection and the specificity of different HSPs. Because cytoskeletal injury plays a crucial role in the pathogenesis of irreversible ischemic damage, we tested whether overexpression of specific HSPs protects the integrity of microtubules during simulated ischemia in rat neonatal cardiac myocytes. Overexpression of specific HSPs was achieved by adenovirus-mediated transgene expression. Damage was assessed by comparing control cells to cells that were subjected to a simulated ischemia protocol. Microtubular integrity was measured by indirect immunofluorescence, confocal microscopy, and image analysis. Within 14 h of simulated ischemia, microtubular integrity decreased significantly in uninfected myocytes (from 24.6 +/- 1.2 to 13.2 +/- 0.4) and in myocytes infected with a control virus that expressed no transgene (from 25.9 +/- 1.8 to 13.1 +/- 1.4). Microtubular integrity after ischemia was significantly better preserved in cells overexpressing constitutive Hsp70 (21.7 +/- 1.6) or alpha(B)-crystallin (18.0 +/- 2.7) but not in cells overexpressing inducible Hsp70 (11.5 +/- 0.8) or Hsp27 (14.0 +/- 2.2). We conclude that specific HSPs protect the microtubules during simulated cardiac ischemia.