HSP70 induced by hyperosmotic stress partially protects LLC-PK1 cells against nephrotoxic drugs

Accumulation of HSP70 is related to the cytoprotection. It was evaluated whether hyperosmotic stress induces HSP70 accumulation in LLC-PK1 cells, and protects cells against toxicity provoked by cisplatin (Cis) and cyclosporine A (CyA). Cells were maintained in isosmotic (Iso) or hyperosmotic (H) culture medium for 24 h and then exposed to Cis or CyA for an additional period of 12 or 24 h (groups H+Cis and H+CyA). The H medium did not induce cell death and increased both HSP70 mRNA and protein levels, suggesting a role in cell adaptation to H condition. H medium produced partial cytoprotection against Cis and CyA compared with control cells. Despite the cytoprotection, there was a reduction in HSP70 mRNA and protein levels in H+Cis group. In contrast, the H+CyA group presented high levels of HSP70 mRNA and protein. The induction of HSP70 by H medium was associated with tolerance of LLC-PK1 cells against Cis and CyA cytotoxicity but this protection was induced by different mechanisms and depended on the characteristics of the drug used.