Hyperthermia increases HSP production in human PDMCs by stimulating ROS formation, p38 MAPK and Akt signaling, and increasing HSF1 activity

Background: Human placenta-derived multipotent cells (hPDMCs) are isolated from a source uncomplicated by ethical issues and are ideal for therapeutic applications because of their capacity for multilineage differentiation and proven immunosuppressive properties. It is known that heat shock preconditioning induces the upregulation of heat shock proteins (HSPs), which enhance survival and engraftment of embryonic stem cells (ESCs) during transplantation in live animal models, although whether heat shock preconditioning has the same effects in hPDMCs is unclear. Methods: The hPDMCs were isolated from placenta of healthy donors. The cells were treated with heat shock (43 °C, 15 min), followed by evaluation of cell viability. Furthermore, the HSPs expression was assessed by Western blot, qPCR. The reactive oxygen species (ROS) production and signal pathway activation were determined by flow cytometry and Western blot, respectively. The regulatory pathways involved in HSPs expression were examined by pretreatment with chemical inhibitors, and siRNAs of MAPK, Akt, and heat shock factor 1 (HSF1), followed by determination of HSPs expression. Results: This study demonstrates that heat shock treatment induced ROS generation and HPSs expression in hPDMCs. Heat shock stimulation also increased p38 MAPK and Akt phosphorylation. These effects were reduced by inhibitors of ROS, p38 MAPK and Akt. Moreover, we found that heat shock treatment enhanced nuclear translocation of the HSF1 in hPDMCs, representing activation of HSF1. Pretreatment of hPDMCs with ROS scavengers, SB203580 and Akt inhibitors also reduced the translocation of HSF1 induced by heat shock. Conclusions: Our data indicate that heat shock acts via ROS to activate p38 MAPK and Akt signaling, which subsequently activates HSF1, leading to HSP activation and contributing to the protective role of hPDMCs.