Down-regulation of the Expression of Senescence Proteins P16 and P21 by Activating Connexin 43 in the Smooth Muscle of Spiral Modiolar Artery of Guinea Pigs

  Objective  To analyze the correlation between connexin 43 (Cx43) and the expression of P16 and P21, aging-related proteins, and to investigate the possible role of Cx43 in the development of cell senescence with an aging model prepared by D-galactose (D-gal) intervention in the vascular smooth muscle cells (VSMCs) of guinea pig spiral modiolar artery (SMA).

  Methods  The VSMCs of guinea pig SMA were cultured with the adhesion method, and the markers of VSMCs were detected with immunofluorescence technique. The experiment has a control group, a D-gal group, and a group that received D-gal and gap junction agonist AAP10 intervention, hereafter referred to as the AAP10 group. Cell Counting Kit-8 (CCK-8) was used to check VSMC activity and to determine the concentration and duration of D-gal intervention. The mRNA expression of Cx43 in each group was checked with qRT-PCR. The expression of Cx43, P16 and P21 proteins in each group was examined with the Western blot. The expression and distribution of P16 and P21 proteins were examined with immunofluorescence assay.

  Results  Immunofluorescence results showed that the positive expression rate of cell actin (α-SM-actin) was over 90%. CCK-8 results showed that the optimal concentration of D-gal intervention was 30 mg/mL and the intervention duration was 48 h. qRT-PCR test showed that the mRNA expression of Cx43 in VSMCs in the D-gal group was significantly lower than that in the control group (P<0.01), while it is higher in the AAP10 group than that of the D-gal group (P<0.01); Western blot assay showed that the Cx43 expression level in VSMCs in the D-gal group was significantly lower than that in the control group (P<0.01) and the expression of P16 and P21 was significantly higher than that in the control group (P<0.01), the expression of Cx43 protein in AAP10 group was significantly up-regulated compared with that in the D-gal group (P<0.01), while the expression of P16 and P21 was down-regulated significantly (P<0.01); The results of immunofluorescence showed that P16 and P21 were mainly expressed in the cell nucleus. Semi-quantitative analysis of fluorescence intensity showed that the level of P16 and P21 protein in the D-gal group was significantly higher than that in the control group, and the fluorescence intensity of AAP10 group was significantly lower than that in the D-gal group (P<0.01).

  Conclusion  Up-regulation of Cx43 expression can reverse the D-gal-induced abnormal expression of P16 and P21, two aging-related proteins, in SMA. It is suggested that Cx43 on SMA may be involved in D-gal-induced cell senescence, which provides a theoretical basis and possible intervention target for the delay of cell senescence.