Abundance of proline (Pro) in collagen molecule led us to investigate whether Pro supply affects collagen biosynthesis in human skin fibroblasts. Treatment of the cells with milimolar concentrations (5 and 10 mM) of Pro for 24 and 48 h contributed to increase in α1 subunit of collagen type I (COL1A1) expression in both cells and culture medium. However, the effect was more pronounced in glutamine-free medium. In such condition, Pro induced collagen expression by about twofold in the cells, while in the medium only by about 30% during 24 h incubation, compared to control. In the presence of glutamine (Gln), exogenous Pro stimulated intracellular collagen expression only by about 30% during 24 h of fibroblasts incubation, and it was not accompanied by adequate increase of collagen secretion into medium. Gln alone stimulated the processes by about 2–3 fold during the course of the experiment. Pro-dependent increase in collagen expression in Gln-free medium was accompanied by increase in prolidase activity and expression of pAkt. In both Gln-free medium and Gln-supplemented medium, Pro induced expression of p53 and HIF-1α. The data suggest that availability of Gln, as a substrate for Pro biosynthesis, determine the utilization of exogenous Pro for the collagen biosynthesis.
The mechanism for differential effects of human immune deficiency virus protease inhibitors (HIVPIs), nelfinavir (NEL) and indinavir (IND) on collagen metabolism disturbances was studied in human skin fibroblasts. It has been considered that HIVPIs‐dependent deregulation of collagen biosynthesis involves prolidase (an enzyme providing proline for collagen biosynthesis), glutamine (Gln) (a substrate for proline biosynthesis), nuclear factor‐κB (NF‐κB) (a transcription factor that inhibit expression of type I collagen genes), β1 integrin receptor and Akt signalling. It was found that NEL impaired collagen biosynthesis and the process was more pronounced in the presence of Gln, while IND stimulated collagen biosynthesis. NEL‐dependent inhibition of collagen biosynthesis was accompanied by massive intracellular accumulation of type I collagen, while IND slightly induced this process. This effect of NEL was reversed by ascorbic acid but not N‐acetylcysteine. The mechanism for the NEL‐dependent defect in collagen metabolism was found at the level of prolidase activity, β1 integrin signalling and NF‐κB. NEL inhibited expression of β1 integrin receptor, Akt and ERK1/2 and increased expression of p65 NF‐κB. However, inhibitors of p65 NF‐κB did not prevent NEL‐dependent inhibition of collagen biosynthesis suggesting that this transcription factor is not involved in studied mechanism. Using PI3K inhibitor wortmannin that prevent phosphorylation of Akt revealed that NEL‐dependent inhibition of Akt results in inhibition of collagen biosynthesis. The data suggest that differential effect of NEL and IND on collagen metabolism involves NEL‐dependent down‐regulation of Akt signalling and proline availability for collagen biosynthesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.