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Early and delayed neuroprotective effects of FK506 on experimental focal ischemia quantitatively assessed by
T Ebisu1, K Katsuta, A Fujikawa
1Department of Neurosurgery, Meiji University of Oriental Medicine, Kyoto, Japan. ebisu@muom.meiji-u.ac.jp
Abstract:
The immunosuppressive drug FK506 (tacrolimus) has been reported to be a powerful neuroprotective agent in the focal ischemia of animals. However, no report has been published concerning neuroprotective effect of this compound on the morphology in superacute stage. The separate analysis between early and delayed effects of FK506 on the morphology may be helpful in the study of the compound's mechanism of action which is still unknown. The goal of this study was to determine early and delayed effects of pharmacological treatment with FK506 in permanent MCA occlusion using magnetic resonance imaging (MRI). Nineteen rats were subjected to permanent MCA occlusion, and given either intravenous injection of placebo or 1 mg/kg FK506 immediately after occlusion. DWI and T(2)-weighted MRI were performed 3 and 24 h after MCA occlusion, and postmortem histological analysis was also performed. FK506 drastically reduced the ischemic damage in 3-h apparent diffusion coefficient (ADC) map. This is the first report to demonstrate the neuroprotective effects of FK506 on focal cerebral ischemia in superacute stage. In addition, postmortem ischemic damage tended to be smaller than ischemic area indicated by 3-h ADC map in the FK506 group, whereas there was an excellent equality between them in the placebo group, suggesting the possible effect of FK506 on the later ischemic period. Our findings provide direct evidence for the neuroprotective effect of FK506 on ischemic cell damage in both early stage and possibly later stage.
Insights
FK506 (tacrolimus) demonstrates significant neuroprotection in the superacute stage of focal cerebral ischemia. This immunosuppressive drug reduces early ischemic damage and shows potential for later-stage effects, offering new insights into its mechanism of action.
Area of Science:
- Neuroscience
- Pharmacology
- Radiology
Background:
- FK506 (tacrolimus) is a known neuroprotective agent in animal models of focal ischemia.
- The specific effects of FK506 on morphology during the superacute stage of ischemia remain under-investigated.
- Understanding early versus delayed effects of FK506 may elucidate its mechanism of action.
Purpose of the Study:
- To investigate the early and delayed neuroprotective effects of FK506 in a rat model of permanent middle cerebral artery (MCA) occlusion.
- To utilize magnetic resonance imaging (MRI) to assess morphological changes and ischemic damage.
Main Methods:
- Permanent MCA occlusion was induced in 19 rats.
- Animals received either FK506 (1 mg/kg IV) or placebo immediately after occlusion.
- Diffusion-weighted imaging (DWI) and T(2)-weighted MRI were performed at 3 and 24 hours post-occlusion, followed by histological analysis.
Main Results:
- FK506 significantly reduced ischemic damage as indicated by the 3-hour apparent diffusion coefficient (ADC) map.
- This study provides the first evidence of FK506's neuroprotective effect in the superacute phase of focal cerebral ischemia.
- Histological damage in the FK506 group was smaller than the 3-hour ADC map indicated, suggesting potential delayed protective effects, unlike the placebo group.
Conclusions:
- FK506 exhibits potent neuroprotective effects against ischemic cell damage in the early stages of focal cerebral ischemia.
- The findings suggest FK506 may also exert protective effects during the later stages of ischemia.
- This research offers direct evidence supporting FK506's role in mitigating ischemic brain injury.