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Cyclooxygenase 2 inhibits SAPK activation in neuronal apoptosis
Bradley Miller1, Yu-Wen E Chang, Andrey Sorokin
1Department of Medicine, Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI 53226-0509, USA.
Abstract:
Cyclooxygenase 2 (COX-2) expressed in cultured neuronal PC12 cells under inducible promoter protects cells from trophic withdrawal apoptosis. Stimulation of SAPK is thought to play a significant role in initiation of PC12 cell death. We have therefore examined whether COX-2 expression inhibits trophic withdrawal-mediated activation of SAPK. SAPK activity increased during the first 6h after NGF removal in mock-transfected PC12 cells. COX-2 expression attenuated the increase of SAPK, as detected by Western blot analysis with phosphorylation state specific anti-SAPK antibodies and by SAPK activity assays. We propose that COX-2 attenuated SAPK activation by preventing activation of nNOS, which occurs, as we have shown before, via COX-2-mediated expression of dynein light chain (DLC). Activation of SAPK in neuronal cell death was attenuated by DLC expression. These observations support a role for NO production and SAPK activation in the neuronal death mechanisms.
Insights
Cyclooxygenase 2 (COX-2) expression protects neuronal PC12 cells from apoptosis. COX-2 inhibits stress-activated protein kinase (SAPK) activation, a key factor in neuronal cell death.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Neuronal cell death is implicated in various neurological disorders.
- Cyclooxygenase 2 (COX-2) is known to have protective roles in certain cellular contexts.
- Stress-activated protein kinase (SAPK) pathways are critical in initiating apoptosis.
Purpose of the Study:
- To investigate whether COX-2 expression inhibits trophic withdrawal-mediated activation of SAPK in PC12 cells.
- To elucidate the molecular mechanisms by which COX-2 influences SAPK activation and neuronal survival.
Main Methods:
- PC12 cells were cultured and transfected with an inducible COX-2 expression vector.
- Trophic withdrawal was induced by removing nerve growth factor (NGF).
- SAPK activation was assessed using Western blot analysis with phospho-specific antibodies and in vitro kinase assays.
Main Results:
- SAPK activity significantly increased within 6 hours of NGF removal in mock-transfected cells.
- COX-2 expression markedly attenuated the increase in SAPK activation.
- This inhibition was linked to the prevention of neuronal nitric oxide synthase (nNOS) activation, mediated by COX-2-induced dynein light chain (DLC) expression.
Conclusions:
- COX-2 plays a neuroprotective role by inhibiting SAPK activation during trophic withdrawal.
- The mechanism involves COX-2-mediated suppression of nNOS activation via DLC.
- NO production and SAPK activation are critical components of neuronal death pathways.