D-Penicillamine modulates hydrogen sulfide (H2S) pathway through selective inhibition of cystathionine-γ-lyase.

BACKGROUND AND
PURPOSE: Hydrogen sulfide (H2S) is a gasotransmitter produced from L-cysteine through the enzymatic action of cystathionine-γ-lyase (CSE) and/or cystathionine-β-synthase. D-Penicillamine is the d isomer of a dimethylated cysteine and has been used for the treatment of rheumatoid arthritis. AsD-penicillamine is structurally very similar to cysteine, we have investigated whether D-penicillamine, as a cysteine analogue, has an effect on the H2 S pathway. EXPERIMENTAL APPROACH: We tested the effect of D-penicillamine (0.01-1 mM) in mouse aortic rings mounted in isolated organ baths and determined whether it could affect H2 S biosynthesis. In particular, we investigated any possible inhibitor or donor behaviour by using recombinant enzyme-based assays and an in vivo approach. KEY
RESULTS: D-Penicillamine, per se, showed little or no vasodilator effect, and it cannot be metabolized as a substrate in place of l-cysteine. However, d-penicillamine significantly reduced L-cysteine-induced vasodilatation in a concentration-dependent manner through inhibition of H2 S biosynthesis, and this effect occurred at concentrations 10 times lower than those needed to induce the release of H2 S. In particular, D-penicillamine selectively inhibited CSE in a pyridoxal-5'-phosphate-dependent manner. CONCLUSIONS AND IMPLICATIONS: Taken together, our results suggest that D-penicillamine acts as a selective CSE inhibitor, leading to new perspectives in the design and use of specific pharmacological tools for H2 S research. In addition, the inhibitory effect of D-penicillamine on CSE could account for its beneficial action in rheumatoid arthritis patients, where H2 S has been shown to have a detrimental effect.