Connexin 43 is involved in aldosterone-induced podocyte injury

Connexin43 (Cx43) belongs to a family of transmembrane proteins that build cell-to-cell channels in gap junctions, which play an essential role in intercellular communication, cell proliferation, differentiation and apoptosis. The aim of this study is to clarify the effect of Cx43 in aldosterone (Aldo)-induced podocyte injury and explore the possible molecular mechanism behind this effect.

Uninephrectomized Sprague-Dawley rats were given 1% NaCl (salt) in their water and an Aldo infusion (0.75 μg/h) for 28 days to induce podocyte injury. Podocytes were incubated in media containing either buffer or increasing concentrations of Aldo (10(-9) - 10(-7) M) for variable time periods. The podocytes were then examined and the mechanism of injury investigated using TUNEL assay, ELISA, immunofluorescence staining, western blot, RNA interference, and DCFDA fluorescence.

Here, we report that in vivo administration of Aldo caused greater numbers of TUNEL-positive podocytes, accompanied by increased Cx43 expression, but a reduction in WT1-positive podocytes. In vitro studies indicated that Aldo induces podocyte apoptosis in a dose- and time-dependent manner and is accompanied by increases in Cx43 expression, gap junction intercellular communication (GJIC), ROS production, and the Bax/Bcl-2 ratio. Silencing of Cx43 expression attenuates the increase of ROS production and the subsequent up-regulation of the Bax/Bcl-2 ratio, which partially inhibited the podocytes apoptosis.

Our study provides preliminary evidence that upregulation of Cx43 expression is involved in Aldo-induced podocyte injury, and that Cx43 is a potentially relevant therapeutic target for the treatment of chronic kidney diseases (CKD).