Intravascular heavy chain-modification of hyaluronan during endotoxic shock

Correlation of plasma TSG-6 with cardiac function, myocardial fibrosis, and prognosis in dilated cardiomyopathy patients with heart failure

OBJECTIVES

Tumor necrosis factor α stimulated gene 6 (TSG-6) protein is an inflammation-inducing protein. In recent years, TSG-6 protein has been found to play an anti-inflammatory and anti-fibrosis role in a variety of disease models. The level of TSG-6 protein in circulating blood is considered to be a biological indicator for the evaluation of acute coronary syndrome, severe infection, and other diseases, and it is closely related to the prognosis. The clinical correlation between TSG-6 protein and dilated cardiomyopathy (DCM) patients with heart failure has not been reported. This study aims to investigate the changes of plasma TSG-6 protein levels in cardiomyopathy patients with heart failure and its correlation with cardiac function, myocardial fibrosis, and prognosis.

METHODS

Based on the prospective studies, a number of 90 DCM patients with heart failure were selected as a DCM heart failure group from Dec.1, 2019 to Sept.1, 2020. Thirty-nine healthy people were served as a control group. Plasma TSG-6, Collagen Ⅰ, Collagen III, and α-smooth muscle actin (α-SMA) were measured with ELISA test. Echocardiography was used to evaluate the structure and function of the heart. DCM patients with heart failure were followed up for 3 months. The patients were assigned into 2 groups according to whether they had major adverse cardiovascular events (MACE). The general clinical data, plasma TSG-6, Collagen Ⅰ, Collagen III, and α-SMA protein levels were compared between the control group and the DCM heart failure group. At the same time, the correlation between plasma TSG-6 protein level and cardiac function grade, myocardial fibrosis or prognosis of patients in the DCM heart failure group was analyzed.

RESULTS

Compared with the control group, the heart rate, TSG-6, Collagen Ⅰ, Collage III, α-SMA, hemoglobin, atrial natriuretic peptide (NT-proBNP), hypersensitive C-reactive protein, aspartate aminotransferase, serum creatinine, lactate dehydrogenase, and left ventricular end diastolic diameter (LVEDD) increased significantly (all P<0.001). High-density lipoprotein, left ventricular short axis shortening rate (LVFS), and left ventricular ejection fraction (LVEF) decreased significantly in the DCM heart failure group (all P<0.001). Plasma levels of TSG-6 were positively correlated with NT-proBNP, Collagen Ⅰ, Collagen III, α-SMA, and LVEDD (all P<0.001), while they were negatively correlated with LVFS and LVEF (all P<0.001). With the increase of NYHA heart function classification, plasma levels of TSG-6, Collagen Ⅰ, Collagen III, and α-SMA increased significantly (all P<0.001). The increases in plasma levels of NT-proBNP and TSG-6 was associated with poor prognosis in DCM patients with heart failure (all P<0.05). The sensitivity and specificity of plasma NT-proBNP for evaluating the prognosis of DCM heart failure were 76.2% and 68.1%, respectively. The sensitivity and specificity of plasma TSG-6 for evaluating the prognosis of DCM heart failure were 95.2% and 66.7%, respectively. The sensitivity and specificity of plasma TSG-6 combined with NT-proBNP for prognostic evaluation of DCM heart failure were 85.7% and 81.2%, respectively. The specificity of plasma TSG-6 combined with NT-proBNP for the prognosis of heart failure was better than that of NT-proBNP or TSG-6 alone (P<0.001).

CONCLUSIONS

The plasma levels TSG-6 in DCM patients with heart failure increase significantly, and the plasma levels TSG-6 could be used as a new predictor for cardiac function, myocardial fibrosis, and prognosis.

Bacterial products in donor airways prevent the induction of lung transplant tolerance

Although postoperative bacterial infections can trigger rejection of pulmonary allografts, the impact of bacterial colonization of donor grafts on alloimmune responses to transplanted lungs remains unknown. Here, we tested the hypothesis that bacterial products present within donor grafts at the time of implantation promote lung allograft rejection. Administration of the toll-like receptor 2 (TLR2) agonist Pam₃ Cys₄ to Balb/c wild-type grafts triggered acute cellular rejection after transplantation into B6 wild-type recipients that received perioperative costimulatory blockade. Pam₃ Cys₄ -triggered rejection was associated with an expansion of CD8⁺ T lymphocytes and CD11c⁺ CD11b^hi MHC (major histocompatibility complex) class II⁺ antigen-presenting cells within the transplanted lungs. Rejection was prevented when lungs were transplanted into TLR2-deficient recipients but not when MyD88-deficient donors were used. Adoptive transfer of B6 wild-type monocytes, but not T cells, following transplantation into B6 TLR2-deficient recipients restored the ability of Pam₃ Cys₄ to trigger acute cellular rejection. Thus, we have demonstrated that activation of TLR2 by a bacterial lipopeptide within the donor airways prevents the induction of lung allograft tolerance through a process mediated by recipient-derived monocytes. Our work suggests that donor lungs harboring bacteria may precipitate an inflammatory response that can facilitate allograft rejection.

Inter-α-inhibitor heavy chain-1 has an integrin-like 3D structure mediating immune regulatory activities and matrix stabilization during ovulation

Inter-α-inhibitor is a proteoglycan essential for mammalian reproduction and also plays a less well-characterized role in inflammation. It comprises two homologous "heavy chains" (HC1 and HC2) covalently attached to chondroitin sulfate on the bikunin core protein. Before ovulation, HCs are transferred onto the polysaccharide hyaluronan (HA) to form covalent HC·HA complexes, thereby stabilizing an extracellular matrix around the oocyte required for fertilization. Additionally, such complexes form during inflammatory processes and mediate leukocyte adhesion in the synovial fluids of arthritis patients and protect against sepsis. Here using X-ray crystallography, we show that human HC1 has a structure similar to integrin β-chains, with a von Willebrand factor A domain containing a functional metal ion-dependent adhesion site (MIDAS) and an associated hybrid domain. A comparison of the WT protein and a variant with an impaired MIDAS (but otherwise structurally identical) by small-angle X-ray scattering and analytical ultracentrifugation revealed that HC1 self-associates in a cation-dependent manner, providing a mechanism for HC·HA cross-linking and matrix stabilization. Surprisingly, unlike integrins, HC1 interacted with RGD-containing ligands, such as fibronectin, vitronectin, and the latency-associated peptides of transforming growth factor β, in a MIDAS/cation-independent manner. However, HC1 utilizes its MIDAS motif to bind to and inhibit the cleavage of complement C3, and small-angle X-ray scattering-based modeling indicates that this occurs through the inhibition of the alternative pathway C3 convertase. These findings provide detailed structural and functional insights into HC1 as a regulator of innate immunity and further elucidate the role of HC·HA complexes in inflammation and ovulation.

Inter-α-inhibitor Ameliorates Endothelial Inflammation in Sepsis

PURPOSE

Vascular endothelial cells demonstrate severe injury in sepsis, and a reduction in endothelial inflammation would be beneficial. Inter-α-Inhibitor (IαI) is a family of abundant plasma proteins with anti-inflammatory properties and has been investigated in human and animal sepsis with encouraging results. We hypothesized that IαI may protect endothelia from sepsis-related inflammation.

METHODS

IαI-deficient or sufficient mice were treated with endotoxin or underwent complement-induced lung injury. VCAM-1 and ICAM-1 expression was measured in blood and lung as marker of endothelial activation. Human endothelia were exposed to activated complement C5a with or without IαI. Blood from human sepsis patients was examined for VCAM-1 and ICAM-1 and levels were correlated with blood levels of IαI.

RESULTS

IαI-deficient mice showed increased endothelial activation in endotoxin/sepsis- and complement-induced lung injury models. In vitro, levels of endothelial pro-inflammatory cytokines and cell growth factors induced by activated complement C5a were significantly decreased in the presence of IαI. This effect was associated with decreased ERK and NFκB activation. IαI levels were inversely associated with VCAM-1 and ICAM-1 levels in a human sepsis cohort.

CONCLUSIONS

IαI ameliorates endothelial inflammation and may be beneficial as a treatment of sepsis.