geranylgeranylacetone and triphenyltetrazolium

Previous studies demonstrated the cytoprotective effect of geranylgeranylacetone (GGA), a heat shock protein (HSP) inducer, against ischemic insult. Protein kinase C (PKC) is thought to be an important factor that mediates the expression of heat shock protein 70 (HSP70) in vitro. However, the signaling pathways in the brain in vivo after oral GGA administration remain unclear. We measured and compared infarction volumes to investigate the effect of GGA on cerebral infarction induced by permanent middle cerebral artery (MCA) occlusion in rats. To clarify the relationship between PKC induction and HSP70 expression, we determined the amounts of HSP70 and PKC proteins after GGA administration by immunoblotting. We evaluated the effects of pretreatment with chelerythrine (CHE), a specific PKC inhibitor, on expressions of PKC and HSP70 proteins with immunoblotting. Neuroprotective effects of GGA (pretreatment with a single oral GGA dose (800 mg/kg) 48 h before ischemia) were prevented by CHE pretreatment, which indicates that PKC may mediate the GGA-dependent protection. Oral GGA-induced HSP70 expression induced PKC delta, and GGA pretreatment enhanced ischemia-induced HSP70, both of which were prevented by CHE pretreatment. These results suggest that a single oral dose of GGA induces PKC delta and promotes HSP70 expression in the brain and that GGA plays an important role in neuroprotection against cerebral ischemia.

Topics: Alkaloids; Animals; Benzophenanthridines; Blotting, Western; Cerebral Infarction; Disease Models, Animal; Diterpenes; Drug Interactions; Enzyme Inhibitors; Gene Expression; HSP70 Heat-Shock Proteins; Infarction, Middle Cerebral Artery; Male; Neuroprotective Agents; Phenanthridines; Protein Kinase C; Rats; Rats, Wistar; Tetrazolium Salts; Time Factors

The present study evaluated the neuroprotective effect of geranylgeranylacetone (GGA), which is known as an antiulcer agent and more recently as a heat shock protein (HSP) inducer, against cerebral infarction induced by permanent left middle cerebral artery (MCA) occlusion. GGA was given orally in various regimens prior to MCA occlusion in rats. Pretreatment with a single oral GGA dose (800 mg/kg) 48 h before ischemia significantly attenuated cerebral infarction volume (81.7+/-18.4 mm3 versus 369.1+/-70.2 mm3; P<.01). A significant increase in HSP70 immunoreactivity was found in the neocortex in GGA-treated animals with or without ischemia. Pretreatment with a single oral dose of GGA provides an important tool for exploring the mechanisms of neuroprotection against cerebral ischemic neuronal damage.

Topics: Animals; Cerebral Infarction; Diterpenes; Dose-Response Relationship, Drug; Gene Expression Regulation; HSP70 Heat-Shock Proteins; Immunohistochemistry; Infarction, Middle Cerebral Artery; Male; Neurologic Examination; Neuroprotective Agents; Rats; Tetrazolium Salts; Time Factors

Previous studies have strongly suggested that heat shock protein 70 (HSP70) has protective effects in ischemia/reperfusion in tissues such as brain, heart, and liver. This study was performed to assess the efficacy of the HSP70 inducer geranylgeranylacetone (GGA) in experiments involving permanent middle cerebral artery (MCA) occlusion. Male Balb/c mice were subjected to permanent MCA occlusion by direct occlusion through small craniectomy. Vehicle or GGA (200 or 1000 mg/kg) was injected intraperitoneally 1 h prior to the onset of ischemia. Infarct volumes were evaluated at 24 h of ischemia by using 2,3,5-triphenyltetrazolium chloride (TTC) staining. The effect of GGA on the induction of HSP70 was studied at 3 h after ischemia with fluorescence immunocytochemistry. The percentage of infarct volume in the control mice (n=10) was 23.0+/-4.0% (mean+/-SD) of the contralateral hemisphere, while those in the treated groups were 22.6+/-7.3% (200 mg/kg group; n=5, P>0.05) and 15.7+/-3.8% (1000 mg/kg group; n=5, P<0.05). Pretreatments with 1000 mg/kg of GGA enhanced the ischemia-related induction of HSP in the neurons and astrocytes in the boundary zone of infarct. The results demonstrate that GGA significantly reduces infarct volume due to permanent MCA occlusion when given 1 h prior to the induction of ischemia.

Topics: Animals; Brain Infarction; Brain Ischemia; Disease Models, Animal; Diterpenes; Dose-Response Relationship, Drug; Gene Expression Regulation; Glial Fibrillary Acidic Protein; HSP70 Heat-Shock Proteins; Immunohistochemistry; Male; Mice; Mice, Inbred BALB C; Neuroprotective Agents; Tetrazolium Salts