Functional blocking of Ninjurin1 as a strategy for protecting endothelial cells in diabetes mellitus

Abstract

Ongoing efforts to remove pathological inflammatory stimuli are crucial for the protection of endothelial cells in diabetes. Nerve injury-induced protein 1 (Ninj1) is an adhesion molecule that not only contributes to inflammation but also regulates the apoptosis of endothelial cells. In the present study, Ninj1 was found highly expressed in endothelial cells in Type 2 diabetic mice and increased in high-glucose (HG) cultured HUVECs. Furthermore, we found that Ninj1 levels are up-regulated in endothelial cells in clinical specimens of diabetic patients when compared with nondiabetic tissues, indicating a biological correlation between Ninj1 and endothelial pathophysiology in diabetic condition. Functional blocking of Ninj1 promoted endothelial tube formation and eNOS phosphorylation in the HG condition. Additionally, blocking Ninj1 inhibited the activation of caspase-3 and increased the Bcl-2/Bax ratio, thus inhibiting HUVECs apoptosis induced by HG. HG-induced ROS overproduction, p38 MAPK and NF-κB activation, and the overexpression of, and genes were ameliorated after Ninj1 was blocked. Using the signaling pathway inhibitor LY294002, we found that Bcl-2 expression and eNOS phosphorylation after Ninj1 blockade were regulated via PI3K/Akt signaling pathway. The endothelial contents, α-SMAPECAM-1 vascular numbers, and blood perfusion in the hindlimb were markedly up-regulated after Ninj1 was blocked. According to our findings, functional blocking of Ninj1 shows protective effects on diabetic endothelial cells both and Thus, we consider Ninj1 to be a potential therapeutic target for preventing endothelial dysfunction in diabetes mellitus.

Ninjurin 1 dodecamer peptide containing the N-terminal adhesion motif (N-NAM) exerts proangiogenic effects in HUVECs and in the postischemic brain

“…The proangiogenic effect found in our siRNA-mediated Ninj1 KD experiments indicates that endogenous Ninj1 has a negative effect on angiogenesis, which is in keeping with a previous report that angiogenesis was enhanced after functionally blocking Ninj1 using a neutralizing antibody or siRNA in diabetic mice 15 . In addition, increase in the function and survival of endothelial cells following treatment with a Ninj1 antibody was reported in a similar diabetic animal model 20 . In the present study, we found that endogenous Ninj1 KD enhanced angiogenesis and that in that situation, N-NAM exerted no angiogenic effect, which suggested that the proangiogenic effects of N-NAM resulted from the suppression of endogenous Ninj1.…”

“…Given the importance of angiogenesis during recovery, N-NAM might be a useful starting point for the development of therapeutics that target neuro-recovery from postischemic damage. Attenuation of delayed inflammation by N-NAM may also contribute to promote functional recovery following cerebral ischemia since numerous reports, including ours, have demonstrated the anti-inflammatory effects of this peptide 17 – 20 , 22 . It is important to note here that since in the process of reparative angiogenesis, the interplay between the immune cells and growing blood vessels is important, pro-angiogenic effect is associated with anti-inflammatory effect if the postischemic brain.…”

“…In particular, treatment with a peptide harboring this motif markedly reduced myeloid cell migration in an EAE animal model 17 and activated T cells to enter the CNS 18 . In addition, an Ninj1-blocking peptide exerted anti-inflammatory effect in septic animal model 19 and anti-apoptotic and anti-inflammatory effects on endothelial cells in an animal model of diabetes mellitus 20 . That blocking peptide also regulated cell proliferation and migration in a genetic status of p53-dependent manner, which is wild type or mutant 21 .…”

Inhibition of miR-383 suppresses oxidative stress and improves endothelial function by increasing sirtuin 1

“…Excessive ROS generation contributes to EC malfunction in diabetes (28). Previous studies have shown that ROS generation partly contributes to HG-triggered cell death of ECs (29,30). OS normalization, resulting from use of antioxidants, reduces damage to vessels in patients with diabetes (31,32).…”

The Role of Ninjurin1 and Its Impact beyond the Nervous System

“…It is well documented that diabetes mellitus (DM), considered as a low-grade inflammatory disease, is one of the risk factors for endothelial dysfunction [43]. Furthermore, experimental and animal studies have demonstrated that Ninj1 expression was upregulated not only in ECs of type 2 diabetic mice and high-glucose (HG) cultured human umbilical vein ECs but also in ECs of clinical specimens for diabetics [44]. Moreover, in gain- and loss-of function experiments, Wang et al [44] elucidated that Ninj1 can facilitate the expression of proinflammatory genes, such as ICAM-1, VCAM-1, IL-6, and MCP-1, via modulating p38-MAPK and NF-κB pathways, and the formation of reactive oxygen species under HG condition.…”