Sulfhydryl groups (SH)

Sulfhydryl groups, or thiols (-SH), are vital chemical moieties found on the amino acid cysteine and within the tripeptide glutathione. In proximal tubular cells, these groups are essential for maintaining the cellular redox balance, facilitating the function of various enzymes (such as Na+/K+-ATPase), and ensuring proper protein structure through disulfide bridge formation. Because the proximal tubule is a primary site for the concentration and reabsorption of toxins, these sulfhydryl groups are major targets for electrophilic metabolites and heavy metals like mercury, cadmium, and lead, which have a high affinity for sulfur. The covalent modification or depletion of these groups leads to oxidative stress, mitochondrial dysfunction, and eventual cell necrosis, manifesting clinically as nephrotoxicity. Therapeutic strategies often involve the use of thiol-donating agents to protect or restore these groups, thereby mitigating the damage caused by nephrotoxic insults.

Other names

Thiol groupsMercapto groups-SH groupsProtein sulfhydrylsEndogenous thiols

Drugs typically act by providing exogenous thiol sources to replenish depleted cellular pools (e.g., N-acetylcysteine) or by acting as chelating agents that sequester heavy metals to prevent their covalent binding to endogenous protein sulfhydryl groups.