geranylgeranylacetone and Brain-Ischemia

We previously reported that heat shock protein 27 (HSP27) phosphorylation plays an important role in the activation of glucose-6-phosphate dehydrogenase (G6PD), resulting in the upregulation of the pentose phosphate pathway and antioxidant effects against cerebral ischemia-reperfusion injury. The present study investigated the effect of geranylgeranylacetone, an inducer of HSP27, on ischemia-reperfusion injury in male rats as a preliminary study to see if further research of the effects of geranylgeranylacetone on the ischemic stroke was warranted.. In all experiments, male Wistar rats were used. First, we conducted pathway activity profiling based on a gas chromatography-mass spectrometry to identify ischemia-reperfusion-related metabolic pathways. Next, we investigated the effects of geranylgeranylacetone on the pentose phosphate pathway and ischemia-reperfusion injury by real-time polymerase chain reaction (RT-PCR), immunoblotting, and G6PD activity, protein carbonylation and infarct volume analysis. Geranylgeranylacetone or vehicle was injected intracerebroventricularly 3 h prior to middle cerebral artery occlusion or sham operation.. Pathway activity profiling demonstrated that changes in the metabolic state depended on reperfusion time and that the pentose phosphate pathway and taurine-hypotaurine metabolism pathway were the most strongly related to reperfusion among 137 metabolic pathways. RT-PCR demonstrated that geranylgeranylacetone did not significantly affect the increase in HSP27 transcript levels after ischemia-reperfusion. Immunoblotting showed that geranylgeranylacetone did not significantly affect the elevation of HSP27 protein levels. However, geranylgeranylacetone significantly increase the elevation of phosphorylation of HSP27 after ischemia-reperfusion. In addition, geranylgeranylacetone significantly affected the increase in G6PD activity, and reduced the increase in protein carbonylation after ischemia-reperfusion. Accordingly, geranylgeranylacetone significantly reduced the infarct size (median 31.3% vs 19.9%, p = 0.0013).. As a preliminary study, these findings suggest that geranylgeranylacetone may be a promising agent for the treatment of ischemic stroke and would be worthy of further study. Further studies are required to clearly delineate the mechanism of geranylgeranylacetone-induced HSP27 phosphorylation in antioxidant effects, which may guide the development of new approaches for minimizing the impact of cerebral ischemia-reperfusion injury.

Topics: Animals; Brain Ischemia; Diterpenes; HSP27 Heat-Shock Proteins; Male; Neuroprotective Agents; Phosphorylation; Rats; Rats, Wistar; Reperfusion Injury

Cerebral ischemia and reperfusion (I/R) can trigger a cytotoxic cascade with overflow of reactive oxygen species, paradoxically causing neurological dysfunction, redox imbalance, inflammation and apoptosis. The present study aims to investigate the effect of geranylgeranylacetone(GGA) on cerebral I/R injury and the underlying mechanism. The results demonstrated that cerebral I/R increased the neurological function abnormality, brain edema, inflammation and oxidative injury in rats as well as the cognitive impairment, which was significantly reversed by GGA in a dose-dependent manner. GGA also suppressed the cell injury and apoptosis caused by cerebral I/R. Moreover, the protective effect of GGA was found to involve heat shock protein 90 (HSP90) and phosphorylated endothelial nitric oxide synthase (eNOS) expression and activity. Both the HSP90 and eNOS inhibitor abolished the effect of GGA. The data showed that GGA could protect rats against cerebral I/R injury, which may be related to the induction of HSP90 and activation of eNOS.

Topics: Animals; Apoptosis; Brain; Brain Edema; Brain Ischemia; Cognition Disorders; Disease Models, Animal; Diterpenes; HSP90 Heat-Shock Proteins; Malondialdehyde; Maze Learning; Neuroimmunomodulation; Neuroprotective Agents; Nitric Oxide Synthase Type III; Phosphorylation; Random Allocation; Rats, Sprague-Dawley; Reperfusion Injury; Treatment Outcome; Tumor Necrosis Factor-alpha

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