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Hyperglycemia activates toll-like receptor 4 (TLR4) to induce inflammation in diabetic cardiomyopathy (DCM). However, the mechanisms of TLR4 activation remain unclear. Here we examine the role of myeloid differentiation 2 (MD2), a co-receptor of TLR4, in high glucose (HG)- and diabetes-induced inflammatory cardiomyopathy. We show increased MD2 in heart tissues of diabetic mice and serum of human diabetic subjects. MD2 deficiency in mice inhibits TLR4 pathway activation, which correlates with reduced myocardial remodeling and improved cardiac function. Mechanistically, we show that HG induces extracellular advanced glycation end products (AGEs), which bind directly to MD2, leading to formation of AGEs-MD2-TLR4 complex and initiation of pro-inflammatory pathways. We further detect elevated AGE-MD2 complexes in heart tissues and serum of diabetic mice and human subjects with DCM. In summary, we uncover a new mechanism of HG-induced inflammatory responses and myocardial injury, in which AGE products directly bind MD2 to drive inflammatory DCM. The mechanisms underlying cardiac inflammation in diabetic cardiomyopathy are incompletely understood. Here the authors show that advanced glycation end products bind to the TLR4 co-receptor MD2 initiating pro-inflammatory pathways. [ABSTRACT FROM AUTHOR]

Growing evidence indicates that angiotensin II (Ang II), a potent biologically active product of RAS, is a key regulator of renal inflammation and fibrosis. In this study, we tested the hypothesis that Ang II induces renal inflammatory injury and fibrosis through interaction with myeloid differentiation protein-2 (MD2), the accessory protein of toll-like receptor 4 (TLR4) of the immune system. Results indicated that in MD2−/− mice, the Ang II-induced renal fibrosis, inflammation and kidney dysfunction were significantly reduced compared to control Ang II-infused wild-type mice. Similarly, in the presence of small molecule MD2 specific inhibitor L6H21 or siRNA-MD2, the Ang II-induced increases of pro-fibrotic and pro-inflammatory molecules were prevented in tubular NRK-52E cells. MD2 blockade also inhibited activation of NF-κB and ERK. Moreover, MD2 blockade prevented the Ang II-stimulated formation of the MD2/TLR4/MyD88 signaling complex, as well as the increased surface binding of Ang II in NRK-52E cells. In addition, Ang II directly bound recombinant MD2 protein, rather than TLR4 protein. We conclude that MD2 is a significant contributor in the Ang II-induced kidney inflammatory injury in chronic renal diseases. Furthermore, MD2 inhibition could be a new and important therapeutic strategy for preventing progression of chronic renal diseases. [ABSTRACT FROM AUTHOR]

Surface proteins were compared in endothelial cells (EC) obtained from bovine peripheral lung, pulmonary artery and vein, and dorsal aorta using sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Galactose-containing glycoproteins [molecular weight (M) 160-220 and 40 kDa] binding to the Ricinus communis agglutinin (RCA) and peanut agglutinin (PNA) were selectively observed on pulmonary microvessel EC as compared to EC from pulmonary artery, pulmonary vein, and dorsal aorta. The unique RCA- and PNA-binding profiles of EC from the pulmonary artery and microvessels may be important in characterizing EC from different sites in the pulmonary circulation. The pulmonary microvessel EC monolayer was also 15-fold more restrictive to transendothelial flux of [C]sucrose (M=342 Da) than the pulmonary artery EC monolayer. In contrast, the microvessel EC were only six- and twofold more restrictive to the flux of larger tracer molecules, ovalbumin (M 43 kDa) and albumin (M=69 kDa) than pulmonary artery EC. The greater restrictiveness of pulmonary microvessel EC monolayer indicates a major phenotypic difference in the cultured pulmonary microvessel EC barrier function. [ABSTRACT FROM AUTHOR]