The serine peptidase inhibitor TPCK induces several morphophysiological changes in the opportunistic fungal pathogen Candida parapsilosis sensu stricto.

Candida parapsilosis sensu stricto (C. parapsilosis) has emerged as the second/third commonest Candida species isolated from hospitals worldwide. Candida spp. possess numerous virulence attributes, including peptidases that play multiple roles in both physiological and pathological events. So, fungal peptidases are valid targets for new drugs development. With this premise in mind, we have evaluated the effect of serine peptidase inhibitors (SPIs) on both cell biology and virulence aspects of C. parapsilosis. First, five different SPIs, phenylmethylsulfonyl fluoride, benzamidine, 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride, N-α-tosyl-L-lysine chloromethyl ketone hydrochloride, and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) were tested, and TPCK showed the best efficacy to arrest fungal growth. Subsequently, the ability of TPCK to modulate physiopathological processes was investigated. Overall, TPCK was able to (i) inhibit the cell-associated serine peptidase activities, (ii) promote morphometric and ultrastructural alterations, (iii) induce an increase in the intracellular oxidation level, which culminates in a vigorous lipid peroxidation and accumulation of neutral lipids in cytoplasmic inclusions, (iv) modulate the expression/exposition of surface structures, such as mannose/glucose-rich glycoconjugates, N-acetylglucosamine-containing molecules, chitin, polypeptides and surface aspartic peptidases, (v) reduce the adhesion to either polystyrene or glass surfaces as well as to partially disarticulate the mature biofilm, (vi) block the fungal interaction with macrophages, and (vii) protect Galleria mellonella from fungal infection, enhancing larvae survivability. Altogether, these results demonstrated that TPCK induced several changes over fungal biology besides the interference with aspects associated to C. parapsilosis virulence and pathogenesis, which indicates that SPIs could be novel promising therapeutic agents in dealing with candidiasis.