ZO-1 and -2 are required for TRPV1-modulated paracellular permeability

The tight junction-based paracellular pathway plays an important role in saliva secretion. zonula occludens (zo) proteins are submembranous proteins of tight junction complex; however,their function in salivary epithelium is poorly understood. here,we found that activation of transient receptor potential vanilloid subtype 1 (trpv1) by capsaicin increased rat saliva secretion both in vivo and ex vivo. meanwhile,trpv1 activation enlarged the width of tight junctions between neighboring acinar cells,increased the paracellular fiux of 4-kda fluorescein isothiocyanate (fitc)-dextran in submandibular gland (smg) tissues,and decreased transepithelial electric resistance (ter) in smg-c6 cells. zo-1,-2,and -3 were distributed principally to the apical lateral region of acinar cells in smg tissues and continuously encircled the peripheries of smg-c6 cells in the untreated condition. trpv1 activation obviously diminished zo-1 and -2 staining,but not zo-3 or β-catenin,at the cell-cell contacts ex vivo and in vitro. moreover,in untreated smg-c6 cells,zo-1 and -2 single or double knockdown by small interfering rna (sirna) increased the paracellular fiux of 4-kda fitc-dextran. in capsaicin-treated cells,zo-1 and -2 single or double knockdown abolished,whereas their re-expression restored,the capsaicin-induced increase in paracellular permeability. furthermore,trpv1 activation increased rhoa activity,and inhibition of either rhoa or rho kinase (rock) abolished the capsaicin-induced ter decrease as well as zo-1 and -2 redistribution. these results indicate that zo-1 and -2 play crucial roles in both basal salivary epithelial barrier function and trpv1-modulated paracellular transport. rhoa-rock signaling pathway is responsible for trpv1-modulated paracellular permeability as well as zo-1 and -2 redistribution. © international & american associations for dental research 2015.