Toxoplasma gondii shows high dissemination and migration properties across biological barriers infecting immunologically privileged organs. Toxoplasma uses different routes for dissemination; however, the mechanisms are not fully understood. Herein, we studied the effects of proteases present in excretion/secretion products (ESPs) of Toxoplasma on MDCK cell monolayers. Ultrastructural analysis showed that ESPs of Toxoplasma disrupt the intercellular junctions (IJ) of adjacent cells. The tight junction (TJ) proteins ZO-1, occludin, and claudin-1 suffered a progressive decrease in protein levels upon ESPs treatment. In addition, ESPs induced mislocalization of such TJ proteins, along with the adherent junction protein E-cadherin, and this was prevented by pre-treating the ESPs with protease inhibitors. Reorganisation of cytoskeleton proteins was also observed. Endocytosis inhibitors, Dyngo®-4a and Dynasore, impeded the modifications, suggesting that TJ proteins internalisation is triggered by the ESPs proteases hence contributing to the loss of IJ. The observed disruption in TJ proteins went in line with a decrease in the transepithelial electrical resistance of the monolayers, which was significantly blocked by pre-treating ESPs with metalloprotease and serine protease inhibitors. Moreover, exposure of cell monolayers to ESPs facilitated paracellular migration of tachyzoites. Our results demonstrate that Toxoplasma ESPs contain proteases that can disrupt the IJ of epithelial monolayers and this could facilitate the paracellular route for Toxoplasma tissue dissemination and migration.
Keywords: Toxoplasma gondii; excretion/secretion products; intercellular junctions; paracellular migration; proteases.
© 2020 John Wiley & Sons Ltd.