Polyamine depletion down-regulates expression of the Trichomonas vaginalis cytotoxic CP65, a 65-kDa cysteine proteinase involved in cellular damage.

Recently, we found that inhibition of putrescine synthesis by ornithine decarboxylase (ODC) significantly increased Trichomonas vaginalis adherence mediated by protein adhesins. Surprisingly and unexpectedly, trichomonal contact-dependent cytotoxicity was absent. Therefore, a role for polyamine depletion on regulation of T. vaginalis cytotoxicity mediated by the cysteine proteinase (CP) of 65-kDa, CP65, was investigated. We performed cytotoxicity and cell-binding assays followed by zymograms, as well as Western blot and indirect immunofluorescence assays using specific anti-CP65 antibodies to detect CP65. Trichomonads grown in the presence of the ODC inhibitor, 1-4-diamino-2-butanone (DAB) had lower levels of cytotoxicity that corresponded with diminished CP65 proteolytic activity when compared to untreated organisms handled identically. Likewise, semiquantitative and qRT-PCR as well as Western blot and immunofluorescence assays showed decreased amounts of tvcp65 mRNA and CP65 protein in DAB-treated parasites. These effects were reversed by addition of exogenous putrescine. These data show a direct link between polyamine metabolism and expression of the cytotoxic CP65 proteinase involved in trichomonal host cellular damage.