Toll-like receptor 4 in atherosclerosis

Increased toll-like receptor (TLR) 2 and TLR4 expression in monocytes from patients with type 1 diabetes: further evidence of a proinflammatory state

CONTEXT

Type 1 diabetes (T1DM) is associated with increased cardiovascular mortality. It is a pro-inflammatory state as evidenced by increased circulating biomarkers and monocyte activity. The toll-like receptors (TLRs) are pattern recognition receptors, expressed abundantly on monocytes. TLR2 and TLR4 are important in atherosclerosis. However, there is a paucity of data examining TLR2 and TLR4 expression in T1DM and examining its contribution to the proinflammatory state.

OBJECTIVE

Thus, we examined TLR2 and TLR4 expression in monocytes from T1DM patients compared with controls (n = 31 per group).

SETTING

The study was performed at the University of California Davis Medical Center.

PATIENTS

Healthy controls (n = 31) and T1DM patients (n = 31) were included in the study.

RESULTS

TLR2 and TLR4 surface expression and mRNA were significantly increased in T1DM monocytes compared with controls. Downstream targets of TLR, nuclear factor kappaB, myeloid differentiation factor 88, Trif, and phosphorylated IL-1 receptor-associated kinase were significantly up-regulated in T1DM. Finally, the release of IL-1beta and TNF-alpha was significantly increased in monocytes from T1DM compared with controls and correlated with TLR2 and TLR4 expression (P < 0.005). In addition, TLR2 and TLR4 expression was significantly correlated to glycosylated hemoglobin, carboxymethyllysine, and nuclear factor kappaB (P < 0.02).

CONCLUSION

Thus, we make the novel observation that TLR2 and TLR4 expression and signaling are increased in T1DM and contribute to the proinflammatory state.

Atrial extracellular matrix remodelling in patients with atrial fibrillation

Atrial fibrillation (AF) is the most frequent clinical arrhythmia. Atrial fibrosis is an important factor in initiating and maintaining AF. However, the collagen turnover and its regulation in AF has not been completely elucidated. We tested the hypothesis that the extracellular matrix changes are more severe in patients with permanent AF in comparison with those in patients in sinus rhythm (SR). Intraoperative biopsies from the right atrial appendages (RAA) and free walls (RFW) from 24 patients with AF undergoing a mini-Maze procedure and 24 patients in SR were investigated with qualitative and quantitative immunofluorescent and Western blot analyses. As compared with SR, all patients with AF exhibited dysregulations in collagen type I and type III synthesis/degradation. Tissue inhibitors of metalloproteinases (TIMP2) was significantly enhanced only in RAA-AF. As compared with SR, collagen VI, matrix metalloproteinases MMP2, MMP9 and TIMP1 were significantly increased while TIMP3 and TIMP4 remained unchanged in all AF groups. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a newly discovered MMPs inhibitor, was elevated in RFW as compared to RAA-AF (P<0.05) and RFW-SR (P<0.05). The level of transforming growth factor (TGF)-β1 was higher in AF than SR. Smad2 and phosphorylated Smad2 showed an elevation in RFW-AF as compared to RFW-SR, RAA-AF, and RAA-SR groups (P<0.05). Conclusions: Atrial fibrosis in AF is characterized by severe alterations in collagen I and III synthesis/degradation associated with disturbed MMP/TIMP systems and increased levels of RECK. TGF-β1 contributes to atrial fibrosis via TGF-β1-Smad pathway by phospho-rylating Smad2. These processes culminate in accumulations of fibrillar and non-fibrillar collagens leading to excessive atrial fibrosis and maintainance of AF.

Pellino proteins: novel players in TLR and IL-1R signalling

Members of the Toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) family play important roles in immunity and inflammation. They initiate common intracellular signalling cascades leading to the activation of nuclear factor-κB (NF-κB) and other transcription factors that stimulate the expression of a variety of genes that shape an appropriate immune response. TLR/IL-1R signalling involves multiple protein–protein interactions, but the mechanisms that regulate these interactions are still largely unclear. In this context, Pellino proteins have been suggested to function as evolutionary conserved scaffold proteins in TLR/IL-1R signalling. However, recently Pellino proteins were also proposed to function as novel ubiquitin ligases for IL-1R associated kinase 1 (IRAK-1). Here we review our current knowledge on the expression, biological role and mechanism of action of Pellino proteins in TLR/IL-1R-induced signalling.

Cellular, molecular and clinical aspects of vitamin E on atherosclerosis prevention

Randomised clinical trials and epidemiologic studies addressing the preventive effects of vitamin E supplementation against cardiovascular disease reported both positive and negative effects, and recent meta-analyses of the clinical studies were rather disappointing. In contrast to that, many animal studies clearly show a preventive action of vitamin E in several experimental settings, which can be explained by the molecular and cellular effects of vitamin E observed in cell cultures. This review is focusing on the molecular effects of vitamin E on the cells playing a role during atherosclerosis, in particular on the endothelial cells, vascular smooth muscle cells, monocytes/macrophages, T cells, and mast cells. Vitamin E may act by normalizing aberrant signal transduction and gene expression in antioxidant and non-antioxidant manners; in particular, over-expression of scavenger receptors and consequent foam cell formation can be prevented by vitamin E. In addition to that, the cellular effects of alpha-tocopheryl phosphate and of EPC-K1, a composite molecule between alpha-tocopheryl phosphate and l-ascorbic acid, are summarized.