[TGF-beta1 reduces connexin43-mediated gap junctional intercellular communication in rat Leydig cells]

To observe the effects of TGF-beta on the expression of connexin43 (Cx43) and Cx43-mediated gap junctional intercellular communication (GJIC) in rat Leydig cells, and investigate the association of its effects on Leydig cells with its ability of changing GJIC.

Primarily cultured purified Leydig cells were divided into a blank control group, a positive control group (treated with the GJIC inhibitor Carbenoxolone), and four TGF-beta1 groups (treated with TGF-beta1 at the concentration of 1, 2, 5 and 10 ng/ml, respectively, for 20 hours). The localization and expression of Cx43 were detected by immunofluorescence and Western blot, and the changes in GJIC analyzed by FRAP assay.

Cx43 was expressed as scattered bright spots in the cytoplasm and membrane of Leydig cells. TGF-beta1 significantly elevated the expression of Cx43 in the cytoplasm, but caused no evident change in the membrane. Western blot showed an evident increase in the phosphorylation of Cx43 with the increased concentration of TGF-beta1 as compared with that of the blank control group (P < 0.05). After 20 hours of treatment with TGF-beta1 at 5 ng/ml, the fluorescence intensity of Leydig cells was markedly reduced (P < 0.01), with a mean fluorescence recovery rate of merely (43.58 +/- 1.87)%.

TGF-beta1 could significantly down-regulate GJIC between adjacent Leydig cells, and this inhibitory effect may be achieved by promoting the expression of Cx43 in the cytoplasm and elevating the phosphorylation of Cx43.