Age effect on HSP70: Decreased resistance to ischemic and oxidative stress in HDF

Background. Heat pre-conditioning results in induction of heat shock proteins including HSP70 that gives a cytoprotective effect against further stress. However, HSP70 induction is attenuated in aged cells. The lower HSP70-levels may contribute to the impaired stress response seen in the aged, and to the higher rates of chronic wounds in aged, which arise from repeated ischemia-reperfusion injury. The aim of this study was to investigate a possible connection by comparing the viability of heat pre-conditioned aged versus young human dermal fibroblasts (RDF) after exposure to stress. Materials and methods. Young (15-28) and aged (6177) HDF were heat pre-conditioned (42 degrees C, 1 h) and after recovery (1, 2, or 20 h) treated with carbonyl-cyanide-m-chlorophenythydrazone (hypoxic stress) or with hydrogen peroxide (oxidative stress) for 1 h. HSP70 levels were determined by Western blot. Cell damage was assessed by quantifying lactic dehydrogenase (LDH) in conditioned media. Aged HDF were transfected with HSP70-plasmid, consecutively heat preconditioned and exposed to oxidative stress. Results. HSP70 increased in heat pre-conditioned young HDF by 96, 189, and 237% after 1, 2, and 20-h recovery, respectively, and in aged HDF by 27,61, and 26%. LDH-release was only decreased in young HDF 20-h after heat-treatment compared with non-heat treated cells (P < 0.001). HSP70-transfection of aged HDF with plasmid reduced LDH-release by 29%. Conclusions. Heat pre-conditioning fails to protect aged HDF to oxidative or hypoxic stress due in part to impaired HSP70 induction compared to young. (c) 2005 Elsevier Inc. All rights reserved.