THE PROTECTIVE EFFECTS OF DIHYDROLIPOAMIDE AND GLUTATHIONE AGAINST PHOTODYNAMIC DAMAGE BY AL-PHTALOCYANINE TETRASULFONATE

In spite of well-known ability of lipoamide/dihydrolipoamide (LipS(2)N H(2)/ Lip(SH)(2) NH2) and oxidized/reduced glutathione (GSSG/CSH) coup les to scavenge singlet oxygen(O-1(2)), the possible protective effect s of these compounds against photodynamical damage by Al-phtalocyanine tetrasulfonate (Al-PcS4) were examined. Using erythrocyte glutathione reductase, pig heart lipoamide dehydrogenase and hamster kidney fibro blast culture as model systems, we have found that protective effects of Lip(SH)(2)NH2 and LipS(2)NH(2) were close to that of azide, far exc eeding the effects of GSH and GSSG, and paralleling the rates of Al-Pc S4-sensitized photooxidation of these compounds. We have failed to obs erve a previously described (Devasagayam, T.P.A., et al. (1991)Biochim . Biophys. Acta 1088, 409-412) enhancement of damaging action of O-1(2 ) by GSH. These findings point out to the possibility of LipS(2)NH(2)/ Lip(SH)(2)NH2 to neutralize the side-effects of photodynamic therapy, and to a minor but definitely protective role of GSH.