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Specific heat shock proteins protect microtubules during simulated ischemia in cardiac myocytes
W F Bluhm1, J L Martin, R Mestril
1Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093-0618, USA.
Abstract:
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 alphaB-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.
Insights
Specific heat shock proteins (HSPs) protect cardiac cell microtubules from damage during simulated ischemia. Constitutive Hsp70 and alphaB-crystallin showed protective effects, unlike inducible Hsp70 or Hsp27.
Area of Science:
- Cardiovascular Biology
- Cellular Stress Response
- Molecular Medicine
Background:
- Heat shock proteins (HSPs) are known to protect against myocardial ischemia.
- Mechanisms and specificity of HSP protection, particularly concerning cytoskeletal integrity, remain unclear.
- Cytoskeletal injury is a key factor in irreversible ischemic damage.
Purpose of the Study:
- To investigate whether specific HSPs protect microtubule integrity during simulated cardiac ischemia.
- To determine the differential protective effects of various HSPs against ischemia-induced cytoskeletal damage.
Main Methods:
- Adenovirus-mediated gene transfer was used to overexpress specific HSPs in rat neonatal cardiac myocytes.
- Simulated ischemia protocol was applied to assess damage.
- Microtubule integrity was quantified using indirect immunofluorescence, confocal microscopy, and image analysis.
Main Results:
- Microtubule integrity significantly decreased in control myocytes after 14 hours of simulated ischemia.
- Overexpression of constitutive Hsp70 and alphaB-crystallin significantly preserved microtubule integrity.
- Overexpression of inducible Hsp70 and Hsp27 did not provide significant protection.
Conclusions:
- Specific heat shock proteins, notably constitutive Hsp70 and alphaB-crystallin, protect microtubule integrity during simulated cardiac ischemia.
- These findings highlight the role of specific HSPs in mitigating cytoskeletal damage in ischemic conditions.
- Further research into HSP mechanisms could lead to novel therapeutic strategies for myocardial ischemia.