Cofilin Inhibition Restores Neuronal Cell Death in Oxygen–Glucose Deprivation Model of Ischemia

Abstract

Ischemia is a condition associated with decreased blood supply to the brain, eventually leading to death of neurons. It is associated with a diverse cascade of responses involving both degenerative and regenerative mechanisms. At the cellular level, the changes are initiated prominently in the neuronal cytoskeleton. Cofilin, a cytoskeletal actin severing protein, is known to be involved in the early stages of apoptotic cell death. Evidence supports its intervention in the progression of disease states like Alzheimer's and ischemic kidney disease. In the present study, we have hypothesized the possible involvement of cofilin in ischemia. Using PC12 cells and mouse primary cultures of cortical neurons, we investigated the potential role of cofilin in ischemia in two different in vitro ischemic models: chemical induced oxidative stress and oxygen-glucose deprivation/reperfusion (OGD/R). The expression profile studies demonstrated a decrease in phosphocofilin levels in all models of ischemia, implying stress-induced cofilin activation. Furthermore, calcineurin and slingshot 1L (SSH) phosphatases were found to be the signaling mediators of the cofilin activation. In primary cultures of cortical neurons, cofilin was found to be significantly activated after 1 h of OGD. To delineate the role of activated cofilin in ischemia, we knocked down cofilin by siRNA technique and tested the impact of cofilin silencing on neuronal viability. Cofilin siRNA-treated neurons showed a significant reduction of cofilin levels in all treatment groups (control, OGD and OGD/R). Additionally, cofilin siRNA reduced cofilin mitochondrial translocation and caspase 3 cleavage, with a concomitant increase in neuronal viability. These results strongly support the active role of cofilin in ischemia-induced neuronal degeneration and apoptosis. We believe that targeting this protein mediator has a potential for therapeutic intervention in ischemic brain injury and stroke.

Much More Than a Scaffold: Cytoskeletal Proteins in Neurological Disorders

“…Besides PAK4, the protein kinase D (PKD 1 and 2) also have been shown to inactivate the SSH1L-based dephosphorylation of cofilin [121][122][123]. On the contrary, Calcineurin, a Ca 2+ /calmodulin-dependent protein phosphatase, has been shown to activate it [124,125].…”

The Emerging Roles of the Calcineurin-Nuclear Factor of Activated T-Lymphocytes Pathway in Nervous System Functions and Diseases

“…Calcineurin signaling also mediated the activation of the cytoskeletal actin severing protein cofilin and the resulting neuronal death in oxygen-glucose deprivation/reperfusion and chemical induced oxidative stress, to in vitro models of ischemia [34]. Moreover, cyclosporine A prevented the apoptosis of astrocytes exposed to simulated ischemia in vitro via a calcineurin and Erk1/2-dependent mechanism [233] and through the inhibition of cytosolic phospholipase A2- (PLA2-) mediated release of arachidonic acid [234].…”

Neuroprotective Effects of Bioactive Compounds and MAPK Pathway Modulation in “Ischemia”—Stressed PC12 Pheochromocytoma Cells

“…To date more than 160 cellular substrates of ERK phosphorylation have been discovered, all of which are expressing a multitude of functions [ 228 ]. PC12 cells for example, were shown to possess substrates such as hypoxia inducible factor 1 (HIF 1 α) [ 229 ], nuclear factor-erythroid 2 p45-related factor 2 (Nrf 2 ) [ 230 ], the human heat shock protein 70 (HSP 70) [ 229 ], other protein kinase and phosphatases such as Rho kinase [ 231 ], protein phosphatase 1/2 A (PP-1/2A) [ 232 ], cytoskeletal proteins (Cofilin) [ 233 ] and different regulator proteins of apoptosis (caspase-3/9) [ 108 ]. Table 3 also demonstrates that, independent of insult duration, or time of reperfusion these seemingly distinct growth factors, exert a substantial degree of protection as attested by a significant reduction of apo-necrotic cell death.…”