Chlorogenic acid ameliorates non-proliferative diabetic retinopathy via alleviating retinal inflammation through targeting TNFR1 in retinal endothelial cells

As a prominent complication of diabetes mellitus (DM) affecting microvasculature, diabetic retinopathy (DR) originates from blood-retinal barrier (BRB) damage. Natural polyphenolic compound chlorogenic acid (CGA) has already been reported to alleviate DR. This study delves into the concrete mechanism of the CGA-supplied protection against DR and elucidates its key target in retinal endothelial cells. DM in mice was induced using streptozotocin (STZ). CGA mitigated BRB dysfunction, leukocytes adhesion and the formation of acellular vessels in vivo. CGA suppressed retinal inflammation and the release of tumor necrosis factor-α (TNFα) by inhibiting nuclear factor kappa-B (NFκB). Furthermore, CGA reduced the TNFα-initiated adhesion of peripheral blood mononuclear cell (PBMC) to human retinal endothelial cell (HREC). CGA obviously decreased the TNFα-upregulated expression of vascular cell adhesion molecule-1 (VCAM1) and intercellular adhesion molecule-1 (ICAM1), and abrogated the TNFα-induced NFκB activation in HRECs. All these phenomena were reversed by overexpressing type 1 TNF receptor (TNFR1) in HRECs. The CGA-provided improvement on leukocytes adhesion and retinal inflammation was disappeared in mice injected with an endothelial-specific TNFR1 overexpression adeno-associated virus (AAV). CGA reduced the interaction between TNFα and TNFR1 through binding to TNFR1 in retinal endothelial cells. In summary, excepting reducing TNFα expression via inhibiting retinal inflammation, CGA also reduced the adhesion of leukocytes to retinal vessels through decreasing VCAM1 and ICAM1 expression via blocking the TNFα-initiated NFκB activation by targeting TNFR1 in retinal endothelial cells. All of those mitigated retinal inflammation, ultimately alleviating BRB breakdown in DR.