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Changes of Ca2+/calmodulin-dependent protein kinase-II after transient ischemia in gerbil hippocampus
T Zalewska1, B Zabłocka, K Domańska-Janik
1Department of Neurochemistry, Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.
Abstract:
Transient cerebral ischemia induces, besides delayed neurodegeneration in selected brain structures, a number of early responses which may mediate ischemic injury/repair processes. Here we report that 5 min exposure to cerebral ischemia in gerbils induces a rapid inhibition and subsequent translocation of Ca2+/calmodulin-dependent protein kinase II (CaMKII). These changes were partially reversible during a 24 h post-ischemic recovery. Concomitantly the total amount of the enzyme protein, as revealed by Western blotting (alpha-subunit specific), remained stable. This is consistent with our previous hypothesis, that the mechanism of ischemic CaMKII down-regulation involves a reversible posttranslational modification-(auto)phosphorylation, rather than the degradation of enzyme protein. The effectiveness of known modulators of post-ischemic outcome in counteracting CaMKII inhibition was tested. Three of these drugs, namely dizocilpine (MK-801), N-nitro-L-arginine methyl ester (L-NAME) and ginkgolide (BN52021), all significantly attenuated the enzyme response to ischemia, whereas an obvious diversity in the time-course of their actions implicates different mechanisms involved.
Insights
Transient cerebral ischemia rapidly inhibits Ca2+/calmodulin-dependent protein kinase II (CaMKII) in gerbils. This CaMKII inhibition is reversible and can be attenuated by specific drugs, suggesting potential therapeutic targets for ischemic brain injury.
Area of Science:
- Neuroscience
- Biochemistry
- Ischemic Stroke Research
Background:
- Transient cerebral ischemia triggers early cellular responses impacting brain injury and repair.
- Ca2+/calmodulin-dependent protein kinase II (CaMKII) is implicated in neuronal function and plasticity.
Purpose of the Study:
- To investigate the early changes in CaMKII activity and localization following transient cerebral ischemia.
- To explore the reversibility of these CaMKII changes and the potential of therapeutic interventions.
Main Methods:
- Gerbil model of transient cerebral ischemia (5 minutes).
- Western blotting to assess CaMKII protein levels and phosphorylation.
- Evaluation of drug effects (MK-801, L-NAME, BN52021) on CaMKII response.
Main Results:
- Ischemia rapidly inhibited and translocated CaMKII.
- These CaMKII alterations were partially reversible within 24 hours post-ischemia.
- Total CaMKII protein levels remained stable, suggesting post-translational modification rather than degradation.
- MK-801, L-NAME, and BN52021 attenuated the ischemic CaMKII response through distinct mechanisms.
Conclusions:
- Ischemic events induce rapid, reversible post-translational modifications of CaMKII.
- CaMKII inhibition is a key early event in ischemic brain injury.
- Targeting CaMKII pathways with drugs like MK-801, L-NAME, or BN52021 may offer neuroprotective strategies.