Modulation of Immune Response by RAGE and TLR4 Signalling in PBMCs of Diabetic and Non‐Diabetic Patients

Abstract

Diabetes is associated with increased glucose levels and accumulation of glycated products. It is also associated with impairment in the immune response, such as increased susceptibility to infections. In this study, we assessed the possible interactions between TLR4 and RAGE signalling on apoptosis and on the expression of inflammatory cytokines in PBMC from individuals with and without diabetes. PBMCs were isolated from seven diabetic patients and six individuals without diabetes and stimulated in vitro with bacterial LPS (1 lg/ml) associated or not with BSA-AGE (200 lg/ml). This stimulation was performed for 6 h, both in the presence and in the absence of inhibitors of TLR4 (R. sphaeroides LPS, 20 lg/ml) and RAGE (blocking monoclonal antibody). Apoptosis at early and late stages was assessed by the annexin-V/PI staining using flow cytometry. Regulation of TNF-a and IL-10 gene expression was determined by RT-qPCR. PBMCs from diabetes patients tended to be more resistant apoptosis. There were no synergistic or antagonistic effects with the simultaneous activation of TLR4 and RAGE in PBMCs from either diabetes or non-diabetes group. Activation of TLR4 is more potent for the induction of TNF-a and IL-10; RAGE signalling had a negative regulatory effect on TNF-a expression induced by LPS. TLR and RAGE do not have relevant roles in apoptosis of PBMCs. The activation of TLR has greater role than RAGE in regulating the gene expression of IL-10 and TNF-a.

Sustained high glucose exposure sensitizes macrophage responses to cytokine stimuli but reduces their phagocytic activity

“…Mononuclear cells from diabetic patients secrete less IL-1 and IL-6 after LPS stimulation [ 15 , 16 ]. Increased glycation is known to inhibit IL-10 and TNFα production by immune cells [ 17 ], which suggests that the lower cytokine production may be a consequence of diabetes-mediated intrinsic defect in these cells. In our study, long-term HighGlu did not affect the differentiation of bone marrow cells into F4/80 + macrophages, but the function of these cells appears to be altered (see below).…”

Effect of hemoadsorption during cardiopulmonary bypass surgery – a blinded, randomized, controlled pilot study using a novel adsorbent

“…That could be based on an effect modification of comorbidities like diabetes mellitus (DM). There is good evidence that patients with DM are associated with an immunosuppressive condition and have poorer humoral response, including decreased cytokine production, and therefore have an increased susceptibility to infections [ 29 – 31 ]. Although there were no differences between both groups, the lowest levels of LPS-induced TNF-α release were found in HA-treated patients with DM.…”

Pattern recognition receptor‐mediated inflammation in diabetic vascular complications

“…In diabetes, high glucose (HG)-induced AGEs may activate TLRs and trigger inflammation. 8,14 The correlation between TLR activation and DVCs has been addressed in many studies. 70,[75][76][77] In addition, data from preclinical studies indicate that disrupting TLR activation provides beneficial effects in diabetic nephropathy 78 and cardiomyopathy.…”

“…11,13 In diabetes, persistently elevated levels of glucose accelerate the production of AGEs which may act as DAMPs to activate PRRs and incite chronic inflammation. 8,14…”