Antioxidant properties of sulfinates: protective effect of hypotaurine on peroxynitrite-dependent damage.

It has been proposed that hypotaurine may function as an antioxidant in vivo. We investigated whether this compound can act as protective agent able to prevent damage from peroxynitrite, a strong oxidizing and nitrating agent that reacts with several biomolecules. The results showed that the compound efficiently protects tyrosine against nitration, alpha1-antiproteinase against inactivation, and human low-density lipoprotein against modification by peroxynitrite. Hypotaurine is also highly effective in inhibiting peroxynitrite-mediated nitration of tyrosine in the presence of added bicarbonate. This result suggests that hypotaurine could play an important role as protective agent under physiological conditions. Moreover, it was found that cysteine sulfinic acid, but not taurine, possesses protective properties against peroxynitrite-dependent damage similar to hypotaurine. These findings indicate that the protective effects exerted by these compounds may be attributable to the presence of the sulfinic group oxidizable into sulfonate by scavenging peroxynitrite and/or its derived species.