21‐benzylidene digoxin effect on tight junctions proteins

Abstract

The importance of Na,K‐ATPase for the formation of junctional complexes is well established. The aim of this work is to characterize the biological effect of a digoxin derivative, 21‐benzylidene digoxin (21‐BD) on tight junctions. MDCK cells are treated with 5, 10 and 50 μM 21‐BD and the immunofluorescence of tight junctions (TJs) proteins α1 Na,K‐ATPase and the transepithelial electrical resistance (TEER) were performed. Treatment with 50 μM 21‐BD induces a sustained increase of the TEER for, at least, 87 h and that is dependent on the doses. As expected, TEER change is associated to alterations of the expression of the integral plasma membrane proteins claudin‐2 and 4, as well as the membrane peripheral protein ZO‐1 after 50μM 21‐BD treatment. We have observed the characteristic “chicken fence pattern” that corresponds to the localization of these proteins in the TJs. Also, 21‐BD treatment caused the increase of the membrane localization and α1 Na,K‐ATPase RNAm expression levels. Treatment with several cardiac steroids causes different effects on cell junctions. The cardiac steroids treatment causes disruption of TJs and only ouabain in low concentrations (10 nM) increases the sealing of TJs and accelerates cell polarity. The effect of 21‐BD on TJs have demonstrated that cardiac steroids other than ouabain can act as TJs enhancer and that it can has implications on cancer metastasis. Supported: CNPq, Fapemig, CAPES