Ky. Chong et al., STABLE OVEREXPRESSION OF THE CONSTITUTIVE FORM OF HEAT-SHOCK-PROTEIN-70 CONFERS OXIDATIVE PROTECTION, Journal of Molecular and Cellular Cardiology, 30(3), 1998, pp. 599-608
We have previously reported that thermal preconditioning confers an ox
idative resistance in rat heart-derived H9c2 myocytes. The development
of this resistance is associated with a co-expression of both inducib
le (hsp70i) and constitutive (hsp70c) forms of the 70-kD heat shock pr
oteins, suggesting an antioxidant role for these proteins. Overexpress
ion of hsp70i has been shown to render cells more tolerant to oxidativ
e challenge. The present study sought to determine whether increases i
n hsp70c. the constitutive member of this protein family, are also pos
itively correlated to oxidative protection. A rat cDNA encoding hsp70c
was inserted into a mammalian expression vector, allowing transcripti
on of the inserted gene to be regulated by a powerful cytomegaloviral
promoter. After introduction of this construct into H9c2 myocytes, sta
ble clones were obtained. Western and Northern blot analysis of the de
rived clones showed a two-fold increase in hsp70c mRNA and protein con
centrations. These clones were more resistant to thermal killing when
compared to control cells transfected with the vector alone, implicati
ng a functional role for the overexpressed hsp70c protein. hsp70c-enri
ched cells also exhibited a marked resistance to oxidative challenges,
including exposure to hydrogen peroxide (H2O2), hydroxyl radical, men
adione, and hypoxia/reoxygenation. These findings indicate that hsp70c
overexpression provides a protective effect against endogenous or exo
genously generated reactive oxygen species (ROS), suggesting that hsp7
0c actively participates in the heat shock-induced oxidative protectio
n. (C) 1998 Academic Press Limited.