Sodium-glucose co-transporter 1 and 2 expression in the mammary artery of patients with bypass surgery: role of the pro-inflammatory response and contribution to oxidative stress

Abstract Background Selective sodium-glucose cotransporter 2 (SGLT2) inhibitors have shown cardiovascular protection independently of glycemic control. Angiotensin II (Ang II) and H2O2 induced the expression of SGLT1 and 2 in cultured endothelial cells and isolated arteries to promote oxidative stress and endothelial dysfunction. However, the expression level and role of SGLT1 and 2 in human arteries remain poorly studied. Purpose This study examined the expression level of SGLT1 and 2 in the human internal mammary artery (IMA) obtained from bypass surgery patients, and, if so, determined the underlying mechanism and function. Methods IMAs were obtained from 40 bypass surgery patients (age 45 to 82). The expression level of target factors was assessed by Western blot analysis, immunofluorescence staining and RT-PCR, and the level of oxidative stress using dihydroethidium staining. Human kidney was used as a control tissue known to express SGLT1 and 2. Porcine coronary artery endothelial cells (CAEC) were cultured and studied at passage 1. Results Western blot analysis of 40 IMA samples indicated a high level of both SGLT1 and 2 in 16 and 17 IMAs, an intermediate level in 8 and 6 IMAs, and a low one in 16 and 17 IMAs, respectively. Immunofluorescence staining of IMA sections indicated that SGLT1 and 2 immunofluorescence signals were observed predominantly in the intima thickening and the media. The expression levels of SGLT1 and 2 were associated with p-p65 NF-kB signals but not angiotensin-converting enzyme (ACE), AT1R, MCP-1, VCAM-1. IMAs with a high expression level of SGLT1 and 2 had a high level of ROS throughout the arterial wall including the intima thickening and endothelium, which was inhibited by the antioxidant N-acetylcysteine, the ACE inhibitor perindoprilat, the AT1R antagonist losartan, and also by the dual SGLT1 and 2 inhibitor sotagliflozin and the selective SGLT2 inhibitor empagliflozin. Pro-inflammatory cytokines mRNA levels of IL-1β, TNF-α and IL-6 were detected in IMAs. Exposure of CAEC to either TNF-α, IL-1β or IL-6 caused a concentration-dependent upregulation of SGLT1 and 2. Conclusion The present findings indicate that SGLT1 and 2 expression is observed in some but not all IMAs of bypass surgery patients predominantly in the media, the intima thickening and the endothelium. High expression levels of SGLT1 and 2 are associated with NF-kB activation and oxidative stress that is prevented by a selective SGLT2 inhibitor and by a dual SGLT1/2 inhibitor. Since pro-inflammatory cytokines triggered SGLT1 and 2 expression in endothelial cells, the inflammatory burden of patients appears to be an important trigger regulating SGLT1/2 expression and the subsequent pro-oxidant response prompting pro-inflammatory and pro-thrombotic responses. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): This work was supported by an unrestricted research grant from Boehringer Ingelheim Pharma GmbH & Co. KG, Biberach, Germany.