The mechanism for differential effect of nelfinavir and indinavir on collagen metabolism in human skin fibroblasts

Prolidase-proline oxidase axis is engaged in apoptosis induction by birch buds flavonol santin in endometrial adenocarcinoma cell line

Cancer of the corpus uteri and cervix uteri, collectively ranks second among new cancer cases in women after breast cancer. Therefore, investigation of new anticancer agents and identifying new molecular targets presents a challenge to improve effectiveness of chemotherapy. In this study, antiproliferative activity of flavonoids derived from the buds of silver birch and downy birch was evaluated in endometrial cancer Ishikawa cells and cervical cancer HeLa cells. It was found that flavanol santin reduced viability of both cell lines better than other flavonoids, including apigenin and luteolin. Moreover, this activity was slightly higher than that induced by the chemotherapy drug, cisplatin. Santin promoted intrinsic and extrinsic apoptosis pathways in cancer cells, but it had low toxicity in normal fibroblasts. The mechanisms of impairing cancer cell viability included induction of oxidative proline catabolism, however in different ways in the cell lines used. In HeLa cells, increase of proline oxidation was due to activation of p53 leading to proline oxidase upregulation. In contrast, in Ishikawa cells, having basal proline oxidase level significantly higher than HeLa cells, santin treatment decreased its expression. Nevertheless, proline oxidation was induced in these cells since santin increased expression and activity of prolidase, an enzyme providing proline from protein degradation. In both cell lines, proline oxidation was associated with generation of reactive oxygen species leading to reduction in cell viability. Our findings reveal the involvement of proline oxidase in induction of apoptosis by santin and identify a role of prolidase in proline oxidase-dependent apoptosis.

Capsaicin up-regulates pro-apoptotic activity of thiazolidinediones in glioblastoma cell line

Capsaicin (N-vanillyl-8-methyl-alpha-nonenamide), a spicy, neurotoxic component of hot pepper is a ligand of vanilloid type-I (TRPV1) receptor of anti-cancer potential. However, molecular mechanism of its action is not fully understood. We found that capsaicin stimulated intrinsic and extrinsic pathway of apoptosis in human glioblastoma LN-18 cell line and this phenomenon was not dependent on TRPV1. Activation of peroxisome proliferator-activated receptor gamma (PPARγ), a ligand-dependent transcription factor, also induced apoptosis in glioblastoma cells. Although PPARγ ligands (thiazolidinediones - rosiglitazone, pioglitazone) promoted apoptosis in LN-18 cells, capsaicin augmented this effect. We found that capsaicin in a dose dependent manner induced expression of PPARγ in glioblastoma LN-18 cells. These findings suggest that capsaicin-dependent up-regulation of PPARγ represent the mechanism for augmentation of cell death by thiazolidinediones.

Proline-dependent regulation of collagen metabolism

This review is focused on recent data on the role of proline (Pro) in collagen biosynthesis and cellular metabolism. It seems obvious that one of the main substrates for collagen biosynthesis Pro is required to form collagen molecule. The question raised in this review is whether the Pro for collagen biosynthesis is synthesized "de novo", comes directly from degraded proteins or it is converted from other amino acids. Recent data provided evidence that extracellular Pro (added to culture medium) had significant, but relatively little impact on collagen biosynthesis in fibroblasts (the main collagen synthesized cells) cultured in the presence of glutamine (Gln). However, extracellular Pro drastically increased collagen biosynthesis in the cells cultured in Gln-free medium. It suggests that Pro availability determines the rate of collagen biosynthesis and demand for Pro in fibroblasts is predominantly met by conversion from Gln. The potential mechanism of this process as well as possible implication of this knowledge in pharmacotherapy of connective tissue diseases is discussed in this review.