Extracellular heat shock protein 72 protects schwann cells from hydrogen peroxide-induced apoptosis.

The cytoprotective role of extracellular heat shock protein (Hsp) 72 has been demonstrated in various cell types, including neuronal cells; however, few studies have investigated the actual role of Hsp72 in the survival of Schwann cells (SCs). In the present study, we investigated the effect of exogenous Hsp72 on Schwann cell apoptotic cell death induced by H₂O₂. We determined that extracellular exposure to Hsp72 reduced cell death in rat SCs in a dose-dependent manner, with the protection resulting from downregulation of apoptosis induced by H₂O₂ (as shown by TUNEL and annexin V flow cytometry analyses). Moreover, we observed that Hsp72 suppressed caspase-3 and -9 activation induced by H₂O₂. This was accompanied by upregulation of the antiapoptotic protein Bcl-2. These findings indicate that extracellular Hsp72 can afford neuroprotection to peripheral nerves via its ability to inhibit Schwann cell apoptosis and diminish oxidative stress-mediated injuries.