Heat shock protein B1 is required for the prolactin-induced cytoprotective effects on pancreatic islets.

The success of islet transplantation has improved lately. Unfortunately, it is still compromised by cell loss. We have shown that prolactin (PRL) inhibits beta-cell apoptosis and up-regulates the antiapoptotic Heat Shock Protein B1 (HSPB1) in human islets. Since its function in pancreatic islets has not been studied, we explored the role of HSPB1 in PRL-induced beta-cell survival. The significant PRL-induced cytoprotection in control cells was abrogated in HSPB1 silenced cells, overexpression of HSPB1 recovered survival. PRL-mediated inhibition of cytokine-induced caspase activities and cytokine-induced decrease of BCL-2/BAX ratio was significantly reverted in knocked-down cells. Kinetics of HSPB1 and HSF1 expression were studied in primary cultures of murine and human pancreatic islets. These findings are highly relevant for the improvement of clinical islet transplantation success rate since our results demonstrated a key role for HSPB1 pointing it as a promising target for beta-cell cytoprotection through the up-regulation of an endogenous protective pathway.