Increased expression of heat shock protein-70 protects A549 cells against hyperoxia

Abstract

Acute and chronic lung injury secondary to hyperoxia remains an important complication in critically ill patients, and, consequently, there is interest in developing strategies to protect the lung against hyperoxia. Heat shock proteins (HSPs) confer protection against a broad array of cytotoxic agents. In this study, we tested the hypothesis that increased expression of the 70-kDa HSP (HSP70) would protect cultured human respiratory epithelium against hyperoxia. Recombinant A549 cells were generated in which human HSP70 was increased by stable transfection with a plasmid containing human HSP70 cDNA under control of the cytomegalovirus promoter (A549-HSP70 cells). A549-HSP70 cells exposed to hyperoxia had greater acute survival rates and clonogenic capacity compared with wild-type A549 cells and with control cells stably transfected with the empty expression plasmid. Hyperoxia-mediated lipid peroxidation and ATP depletion were also attenuated in A549-HSP70 cells exposed to hyperoxia. Increased expression of HSP70 did not detectably alter mRNA levels of the intracellular antioxidants manganese superoxide dismutase, catalase, and glutathione peroxidase. Collectively, these data demonstrate a specific in vitro protective role for HSP70 against hyperoxia and suggest that potential mechanisms of protection involve attenuation of hyperoxia-mediated lipid peroxidation and ATP depletion.

Heat Shock–Induced Protection of Renal Proximal Tubular Epithelial Cells from Cold Storage and Rewarming Injury

“…For example, addition of recombinant HSP-70 has been shown to inhibit cytochrome C/dATP-mediated caspase activation (41) and to block cell death via reduced p38 kinase activation (42). In addition, an overexpression study in human lung adenocarcinoma cells demonstrated a specific role for HSP-70 in blocking hyperoxia-mediated lipid peroxidation and cell death (43). Despite the ability of HSP-70 overexpression to protect HK-2 cells, blocking of HSP-70 upregulation with siRNA did not inhibit the protective effect of heat shock.…”

Heat shock response and acute lung injury☆

“…Similarly, induction of Hsp70 by thermal stress protected cultured murine lung epithelial cells and bovine pulmonary artery endothelial cells from oxidant-mediated injury (11,129). Overexpression of Hsp70 via stable transfection also protects lung epithelial cells from the deleterious effects of hyperoxia (130) and peroxynitrite (9,131). Perhaps more compelling, direct delivery of the mature Hsp70 protein using a Tat-Hsp70 protein protects HSF1 null fibroblasts, which lack the intrinsic ability to mount a stress response and are therefore susceptible to hyperoxia-mediated cell death (132), against the deleterious effects of hyperoxia (133).…”

“…Hsp70 is the most highly induced stress protein in cells and tissues undergoing the stress response (3), and is known to be induced in patients with a variety of critical illnesses or injuries (140)(141)(142)(143). Microinjection of anti-Hsp70 antibody into cells impairs their ability to achieve thermotolerance (144), and increased expression of Hsp70 by gene transfer/transfection has been demonstrated to confer protection against in vitro toxicity secondary to lethal hyperthermia (145), endotoxin (8), nitric oxide (9), hyperoxia (130), and in vivo ischemia-reperfusion injury (146)(147)(148). In addition, in vitro delivery of mature Hsp70 into the intracellular compartment has been shown to protect fibroblasts against lethal thermal injury and hyperoxia (133), and neuronal cells against nitrosative stress and excitotoxicity (149).…”

Cellular response to oxidative stress: Signaling for suicide and survival*

“…These include direct oxidative damage (i.e., hydrogen peroxide or hypoxia reperfusion injury) as well as a variety of other stresses in which generation of ROS is implicated in cytotoxicity (i.e., chemotherapeutic agents, heat stress, cytokines) (Park et al, 1998;Preville et al, 1998;Wong et al, 1998;Chen et al, 1999;Creagh and Cotter, 1999;Komatsuda et al, 1999;Baek et al, 2000;Ding and Keller, 2001). In addition, elevated Hsp expression not only improves cell survival, but also reduces the oxidative damage to proteins, DNA, and lipids (Su et al, 1999;Yamamoto et al, 2000;Park et al, 1998).…”