Cytoprotective effect of non-opiate leu-enkephalin analogues against the background of ornithine decarboxylase inhibitor exposure

The purpose of the study was to assess the involvement of the polyamine system in the implementation of the cytoprotective effect of non-opiate analogues of leu-enkephalin under conditions of oxidative stress. Material and methods. Rat pulmonary fibroblasts were incubated with the NALE peptide (Phe–D-Ala–Gly–Phe–Leu–Arg, 0.1 μM) and its structural analogue peptide G (Phe–D-Ala–Gly–Phe–Leu–Gly, 0. 1 µM), some series - with difluoromethylornithine (DFMO, 2 mM). Oxidative stress was modeled by adding H₂O₂ (100 μM) to the culture medium. The morphometric parameters of the nucleo-nucleolar apparatus of fibroblasts, the proliferative activity of cells, and the features of p53 expression were studied on monolayers. Results. Incubation of fibroblasts with hydrogen peroxide leads to a stress response of cells, as evidenced by the complete absence of mitotic activity, a significant decrease in cell culture density, an increase in the area of nuclei and an increase in the proportion of p53 + fibroblasts. Incubation with the ornithine decarboxylase synthesis blocker DFMO caused a deterioration in the condition of the cell culture: the mitotic index decreased, and the number of p53 + fibroblasts increased even more significantly. Pre-incubation (before adding H₂O₂) with NALE and G peptides reduced, but did not completely eliminate, the negative effect of hydrogen peroxide on cell culture. Preliminary co-incubation of cell monolayers with peptides and DFMO showed a more pronounced cytoprotective effect in OS. Thus, in the series with NALE, the indicators of the proportion of p53 + fibroblasts, culture density, and size of fibroblast nuclei did not differ from the control parameters; a significant increase in the total area of nucleoli in cell nuclei was recorded. In the series with peptide G, the indicators of the proportion of p53 + fibroblasts, the size of fibroblast nuclei, the number and total area of nucleoli were similar to the control indicators, and a significant increase in the cell culture density was revealed, compared to the control. Conclusions. The results of the study indicate a direct cytoprotective effect of peptides - non-opiate analogues of leu-enkephalin, including conditions of blockade of the polyamine system.

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