Arginine Deiminase of Streptococcus pyogenes M49-16 Disrupts the Confluence of the Monolayer and the Structure of the Actin Cytoskeleton of Endothelial Cells In Vitro

The actin cytoskeleton is involved in the regulation of the barrier function of the endothelium. The bioavailability of arginine is an important factor determining of actin cytoskeleton dynamics. Pathogenic microorganisms can use arginine-hydrolyzing enzymes to disrupt the confluences of the vascular endothelium for subsequent dissemination. In this study, the effect of streptococcal arginine deiminase on the human umbilical vein endothelial cells monolayer confluence and the actin cytoskeleton structure in vitro was studied. The original technique for obtaining supernatants by sonication destroyed streptococcal cells (SDSCs) of the original strain of Streptococcus pyogenes M49-16 and its isogenic mutant with the inactivated arginine deiminase gene S. pyogenes M49-16delArcA was used in this study. The changes in the L-arginine concentration were evaluated by the modified Sakaguchi colorimetric method. The structure of the actin cytoskeleton was analyzed after cells staining with fluorescent dye labeled phalloidin. The confluence of the endothelial cell monolayer was evaluated morphologically after staining the cells with crystal violet dye. It was found that in the presence of the parental strain-derived SDSC, a significant decrease in the arginine concentration in the endothelial cells culture medium caused dynamic changes in the actin cytoskeleton structure. After 48 hours, lamellae and stress fibers formed. After 72 hours, the content of F-actin decreased and the confluence of the monolayer of endothelial cells was disrupted. Such changes were not detected when cells were cultured under standard conditions and in the presence of mutant strain-derived SDSC. The results obtained show that pathogenic microbes can use arginine depletion to regulate endothelial barrier function and dissemination in the host organism.