Oxidative damage to Ca²⁺‐ATPase sarcoplasmic reticulum by HOCl and protective effect of some antioxidants

Abstract

Injury of rabbit skeletal sarcoplasmic reticulum (SR) induced by hypochlorous acid (HOCl) was studied. HOCl inhibited Ca2+-ATPase activity in a concentration-dependent manner (IC50=100 micromol/l). The concentration of 13.5 micromol/l HOCl reduced the level of sulfhydryl (SH) groups by 50%, yet it did not influence the enzyme activity. In comparison with SH group oxidation and enzyme activity inhibition, a significantly longer time was necessary for the generation of protein carbonyls in SR injured by HOCl. Protective effects of some antioxidants (stobadine, trolox, EGb 761, Pycnogenol) were studied in SR oxidatively injured by HOCl. Trolox and EGb 761 exerted a protective effect on ATPase activity and on SH groups of SR oxidatively modified by HOCl. Stobadine and Pycnogenol inhibited markedly protein carbonyl formation. Stobadine was the only antioxidant able to scavenge HOCl. In conclusion, the protective effects of antioxidants against decrease of Ca2+-ATPase activity induced by HOCl might be caused by protection of SH groups. The compounds with both antioxidant and Ca2+-ATPase protecting effect offer dual defense against tissue damage occurring, e.g. in aging process.

Oxidative injury induced by hypochlorous acid to Ca-ATPase from sarcoplasmic reticulum of skeletal muscle and protective effect of trolox

“…However, the ability of low HOCl concentrations (10-20 µmol/l) to oxidise plasma membrane thiols was reported by Schaur et al (1998). On the other hand, when SR was oxidised by HOCl, the SH reducing agents glutathione and dithiothreitol protected at least partially Ca-ATPase activity in our experiments (Strosova et al 2005a). Experiments of Favero et al (1998), when SR was oxidised by HOCl, indicated that SH groups might be involved in HOCl-induced injury.…”

“…A significant concentration-dependent protective effect of trolox on SR Ca-ATPase activity from rabbit muscle oxidised by HOCl was reported in our recent publication (Strosova et al 2005a). Maximum of the protective effect was observed at trolox concentration of 250 µmol/l.…”

“…In our recent publication, the concentration of HOCl which caused 50% decrease in SR Ca-ATPase activity from rabbit skeletal muscle was determined as 100 µmol/l (Strosova et al 2005a). Incubation with trolox (50-500 µmol/l) was without any effect on Ca-ATPase activity.…”

“…Previously we found that trolox, a water soluble derivative of α tocopherol, was able to prevent skeletal muscle sarcoplasmic reticulum (SR) Ca-ATPase activity decrease after oxidation of SR vesicles by HOCl (Strosova et al 2005a). In this work we analysed the protective effect of trolox on pure Ca-ATPase from the same source, with the aim to attempt to explain the mechanisms of this prevention.…”

Sarcoendoplasmic Reticulum Ca2+ ATPase. A Critical Target in Chlorine Inhalation–Induced Cardiotoxicity

“…HOCl exposure decreases SERCA activity, and this can be reversed by antioxidants (41). In turn, SCN 2 in biological fluids serves as a scavenger of HOCl.…”