Browsing by Subject "p38MAPK"
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Item INVOLVEMENT OF P38 MAPK IN REACTIVE ASTROGLIOSIS INDUCED BY ISCHEMIC STROKE(2013-04-12) Roy Choudhury, GouravPurpose: Reactive astrogliosis is an important response during early phase of cerebral ischemia but as time progresses; these activated astrocytes develop into a glial scar. During acute phase of ischemia, astrocyte activation is beneficial as it limits the spread of infarct however in long term the glial scar developed becomes a barrier to migrating axons and hinder the recovery process. The hallmark of astrogliosis is an increase in the expression of GFAP (Glial fibrillary acidic protein). However the signaling events underlying these phenomenons have not been yet clearly elucidated. p38MAPK, a stress signaling Mitogen activate protein kinase plays an essential role in inflammation and has been widely reported to be activated during ischemic injury. Since inflammation is major determinant of events after ischemic injury in brain, we hypothesize that p38 MAPK plays a critical role in reactive astrogliosis after ischemic injury and its inhibition attenuates glial scar formation Methods: For in vitro studies rodent primary astrocytes were used and were subjected to Oxygen-glucose deprivation (OGD) for 3h. p38MAPK's role in astrocyte activation was determined pharmacologically with a p38 inhibitor (SB 239063) and genetically by an astrocyte specific p38 knockout. 24 hours following insult and the expression of GFAP was determined using Western blots. Wound healing and Transwell assay were used to determine role of P38 in astrocyte migration. For in vivo studies astrocyte specific conditional p38 knockout mice (p38KO) were used. Transient or Permanent middle cerebral artery occlusion (tMCAO or pMCAO) was performed to model ischemic stroke. Walk initiation, Negative geotaxis and Ladder rung walking test were used to determine motor dysfunction after MCAO. Astrogliosis morphometric analysis was to quantify glial scar in GFAP stained brain sections Results: In primary astrocyte cultures, hypoxia and scratch injury-induced astrogliosis was attenuated by both p38 inhibition and knockout of p38 MAPK. In vivo studies showed that p38KO mice after permanent MCAO had a significantly smaller glial scar compared to their wild type (WT) littermates. Results also indicated that p38KO mice performed significantly better in behavioral studies compared to their WT only in tMCAO Conclusions: p38MAPK plays an essential role in evolution of glial scar after ischemia and its inhibition attenuates glial scar formation. P38 inhibition significantly improves motor dysfunction in tMCAO but the protection is lost in pMCAOItem P38MAPK PROMOTES ASTROGLIOSIS AFTER FOCAL ISCHEMIC STROKE IN MICE(2013-04-12) Roy Choudhury, GouravPurpose: Patients surviving ischemic stroke are often left with long term functional disabilities suggesting that the ischemia associated pathology continues to persist in long term and limits recovery. One such reason for limited functional recovery is formation of glial scar. Glial scar is formed in response to ischemic injury and may protect the cerebral tissue from further injury during early phase of injury. But in long term, this glial scar establishes a physical and chemical barrier to the axonal migration and growth and hinders recovery. The events of a post ischemic brain are prominently influenced by inflammation and p38MAPK is an important signal transducer of cell's response to inflammatory mediators. So in our current study we hypothesize that astrocyte activation and glial scar formation after stroke is regulated by astrocytic p38MAPK and its inhibition will attenuate the glial scar formation Methods: Primary astrocyte cultures isolated from GFAP/p38 knockout mice and wild type littermates were used for in vitro studies. In vitro hypoxic condition (0.5% O2 and 5%CO2) was simulated by depriving Oxygen and glucose (OGD) for 3 hours. Wound healing and Transwell assay were used to determine role of p38MPAK in astrocyte migration. For in vivo studies, permanent middle cerebral artery occlusion (pMCAO) was conducted to induce ischemic stroke. Astrogliosis morphometric analysis was performed using nucleator method to quantify glial scar in GFAP stained brain sections Results: Results from in vitro studies indicated that p38MAPK knockout significantly attenuated OGD induced increase in glial fibrillary acidic protein (GFAP) expression and reduced astrocyte migration. In vivo studies showed that conditional GFAP/p38 knockout mice after MCAO had a significantly smaller glial scar compared to their wild type litter mates Conclusions: Astrocyte reactivation and glial scar formation in brain after ischemic injury is mediated p38MAPK and its inhibition attenuates glial scar