Glycated Serum Albumin Decreases Connexin 43 Phosphorylation in the Corpus Cavernosum

Abstract

Background: Glycated serum albumin (GSA) is an early glycosylation product that participates in diabetic vascular complications. This study aimed to examine the role of GSA in early damage to the corpus cavernosum and to identify the involved pathways. Methods: Nine male 8-week-old SD rats weighing 250-300 g were divided into the control (saline vehicle, n=3) and GSA (200 µg/kg, n=6) groups. Corpus cavernosum tissues were harvested. Phosphorylated and non-phosphorylated Cx43, eNOS, PI3K, and Akt were tested by immunohistochemistry and western blotting. Human umbilical vein endothelial cells (HUVECs) overexpressing or not Cx43 were used to analyze the Cx43 phosphorylation site (S368, S262, Y265, S255, and S279/282) by western blotting. Results: The expression of phosphorylated Cx43 in the penis was significantly lower in GSA-treated rats than in controls. The expression levels of p-Cx43, p-eNOS, p-PI3K, and p-Akt were significantly decreased in HUVECs exposed to GSA, both in a dose- and time-dependent manners. The most significant impact on all four proteins was observed with 1 μg/ml of GSA for 12 h. The phosphorylation at the S368, S262, Y265, S255, and S279/282 sites of Cx43 was downregulated to various degrees by GSA, and the S368 site was the most significantly suppressed phosphorylation site compared with the other sites. Conclusions: GSA decreased the expression of phosphorylated Cx43 in the corpus cavernosum of rats. This effect might be related to the decreased phosphorylation of p-eNOS, p-PI3K, and p-Akt, as well as by downregulation of phosphorylation at the S368 site. Funding Statement: This study was funded by the grant from the National Natural Science Foundation of China (No. 81771577 & No. 81401196) Declaration of Interests: All authors declare that they have no competing interests. Ethics Approval Statement: Human umbilical vein endothelial cells (HUVECs) were isolated from human umbilical cords, which were donated under informed consent from the mothers. All the procedures were approved by the Ethics Committee for Clinical Research at Galicia (China) and were performed according to the World Medical Association Declaration of Helsinki. This study was approved by the Institutional Animal Care and Use Committee. All procedures were conducted in accordance with the institutional guidelines.