ИСТИНА

INTRODUCTION: Plant hormones and their natural and synthetic derivatives are promising objects of investigation because they may affect the viability and metabolism of human cells. Plant hormone gibberellic acid (gibberellin A3) (GA), a potent plant growth regulator, is commonly used in agriculture. It turned out that GA has different effects on the animal and human cells, depending on the object of study, concentrations, and application regimen. Many studies reported the toxic, carcinogenic and allergic effects of GA, but the others demonstrated that GA and its derivatives may have anti-inflammatory and anti-tumor activity and stimulate the secretion. Our previous study showed that GA induced swelling and expansion of Golgi complex in cultured normal and tumor human cells of epidermal origin, but these structural changes were not accompanied by an increased level of protein synthesis. We suggested that GA may induce specific cellular response in the form of UPR followed by the stress of ER. RESULTS: In this study, we investigated the ability of GA to induce the ER stress in the cultured human cell lines - immortalized non-tumorigenic keratinocytes HaCaT and epidermoid carcinoma A431 cells. Using RT-qPCR we showed that 2 mM of GA (24 h of treatment for both cell lines) induced the up-regulation of genes associated with ER stress - CHOP, sXBP1 and GRP78 in HaCaT and ATF4, CHOP, sXBP1 and GRP78 in A431 cells. Intracellular Ca2+ concentration was assayed by the Fluo-4 AM calcium probe. The addition of GA was accompanied by the influx of intracellular Ca2+ in both cell lines. However, Western blot analysis showed that the content of ER stress marker GRP78 increased mainly in A431 cells, as well as the autophagy marker LC3B-II. Simultaneously, GA increased the content of differentiation markers: involucrin – mainly in A431 cells, and filaggrin – in both cell lines. CONCLUSIONS: Thus, GA in millimolar concentrations induced mild ER stress followed by the activation of differentiation in cultured normal and tumor cell lines of epidermoid origin. The activation of differentiation is more prominent in tumor cells A431, then in immortalized normal cells HaCaT, because carcinoma cells originally have lower differentiation status. FINDINGS: This research was funded by Russian Foundation for Basic Research, grant number 19-015-00233 (to E. Smirnova) and the RUDN University Strategic Academic Leadership Program.