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Simultaneous induction of mitochondrial heat shock protein mRNAs in rat forebrain ischemia
1Department of Neurosurgery, Akita University School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan.
Abstract:
Several investigations have postulated evidence of the involvement of apoptosis in delayed neuronal death following brief periods of global cerebral ischemia. Apoptosis may be closely linked to mitochondrial dysfunction. Heat shock protein (HSP) 60 and HSP10 are mitochondrial matrix proteins induced by stress and form the chaperonin complex that is implicated in protein folding and assembly within the mitochondria. This study investigated the induction of these mitochondrial stress protein genes in the hippocampal CA1 region and less vulnerable regions following transient forebrain ischemia. In situ hybridization analysis revealed that the induction pattern of HSP60 mRNA was identical to that of HSP10 mRNA throughout the entire ischemic course. No changes occurred in the expression of both mRNAs after 2 min ischemia. Strong induction of both mRNAs occurred in the CA1 region after 10 min ischemia and persisted until 1 d after reperfusion. In contrast, induction of both mRNAs in the less vulnerable regions was terminated by 1 d after reperfusion. These results demonstrate that mitochondrial stress conditions persist concomitantly with cytosolic stress conditions in regions vulnerable to transient forebrain ischemia.
Insights
Mitochondrial stress proteins HSP60 and HSP10 are induced in vulnerable brain regions after ischemia. Their prolonged expression in the CA1 region suggests sustained mitochondrial dysfunction contributing to delayed neuronal death.
Area of Science:
- Neuroscience
- Cellular Biology
- Biochemistry
Background:
- Delayed neuronal death after cerebral ischemia is linked to apoptosis and mitochondrial dysfunction.
- Heat shock proteins (HSP) 60 and HSP10 are mitochondrial chaperones involved in protein folding.
- These proteins are induced by cellular stress.
Purpose of the Study:
- To investigate the induction of mitochondrial stress protein genes HSP60 and HSP10.
- To compare their expression patterns in vulnerable (hippocampal CA1) and less vulnerable brain regions following transient forebrain ischemia.
Main Methods:
- Transient forebrain ischemia was induced in a rodent model.
- In situ hybridization was used to analyze HSP60 and HSP10 mRNA expression.
- Expression levels were examined in the hippocampal CA1 region and other brain areas at various time points after ischemia.
Main Results:
- HSP60 and HSP10 mRNA induction patterns were identical throughout the ischemic course.
- No changes in expression were observed after 2 minutes of ischemia.
- Strong induction in the CA1 region persisted for 1 day post-reperfusion, while less vulnerable regions showed transient induction.
Conclusions:
- Mitochondrial stress conditions persist in ischemia-vulnerable brain regions.
- The sustained induction of HSP60 and HSP10 in the CA1 region suggests ongoing mitochondrial dysfunction.
- This supports the role of mitochondrial stress in delayed neuronal death following ischemia.