Hongyan Diao

The differential amino acid requirement within osteopontin in α4 and α9 integrin-mediated cell binding and migration

Osteopontin (OPN) contains at least two major integrin recognition domains, Arg159-Gly-Asp161 (RGD) and Ser162-Val-Val-Tyr-Gly-Leu-Arg168 (SVVYGLR), recognized by alphavbeta3 and alpha5beta1 and alpha4 and alpha9 integrins, respectively. OPN is specifically cleaved by thrombin and matrix metalloproteinase (MMP)-3 or MMP-7 at a position of Arg168/Ser169 (R/S) and Gly166/Leu167 (G/L), respectively. We in this study examined the requirement of residues within SVVYGLR for the alpha4 and alpha9 integrin recognition and how MMP-cleavage influences the integrin recognition. The residues, Val164, Tyr165, and Leu167 are critical for alpha4 and alpha9 integrin recognition in both cell adhesion and cell migration. The residue Arg168 is additionally required for alpha9 integrin recognition in cell adhesion and this explains why alpha9 integrin binds to only thrombin cleaved form of OPN. alpha4 integrin is able to bind to SVVYG (MMP-cleaved form of RAA OPN-N half), while alpha9 integrin is not, supporting the above notion that Arg168 is additionally required for alpha9 integrin-mediated cell adhesion. The residue Val163 is important for alpha4, but not for alpha9 integrin recognition in cell migration. Importantly, we found that the replacement of Arg168 by Ala (R168A mutant) induces the augmentation of cell migration via alpha4 and alpha9 integrins.

Syndecan-4 protects against osteopontin-mediated acute hepatic injury by masking functional domains of osteopontin

Osteopontin (OPN) is a T helper type 1 immunoregulatory cytokine that plays a critical role in various inflammatory disorders. OPN exerts proinflammatory reactions through interaction with integrin receptors. OPN function can be modulated by protease digestion. However, the molecular mechanisms that regulate OPN function in vivo have not been elucidated. There are two putative heparin-binding domains (HBDs) within the OPN molecule, which may bind both heparin and heparin-like glycosaminoglycans such as syndecan. We show that expression of OPN and syndecan-4 is significantly up-regulated after concanavalin-A (ConA) injection. Syndecan-4 binds to one of the HBDs of OPN, which overlaps with the thrombin cleavage site of OPN. When OPN is associated with syndecan-4, syndecan-4 masks both the thrombin cleavage and the integrin binding sites within OPN. Importantly, syndecan-4–deficient (Syn4KO) mice are more susceptible to hepatic injury, and the thrombin-cleaved form of OPN is significantly elevated in Syn4KO mice as compared with wild-type mice after ConA injection. Finally, we demonstrate that administration of purified syndecan-4 protects mice from ConA-induced hepatic injury. Thus, syndecan-4 is a critical intrinsic regulator of inflammatory reactions via its effects on OPN function and is a potential novel therapeutic tool for treating inflammatory diseases.

Endogenous Interleukin-6 Plays a Crucial Protective Role in Streptococcal Toxic Shock Syndrome via Suppression of Tumor Necrosis Factor Alpha Production

ABSTRACT During a Streptococcus pyogenes infection in interleukin-6 (IL-6)-deficient mice, there is elevation of serum tumor necrosis factor alpha (TNF-α) levels, muscular necrosis, and death compared with infection of C57BL/6 mice. Anti-TNF-α monoclonal antibody treatment decreased mortality and muscular necrosis in the infected IL-6-deficient mice. These results suggest that IL-6 plays a crucial protective role via suppression of TNF-α production in S. pyogenes infection.

Angiotensin II plasma levels are linked to disease severity and predict fatal outcomes in H7N9-infected patients

A novel influenza A (H7N9) virus of avian origin emerged in eastern China in the spring of 2013. This virus causes severe disease in humans, including acute and often lethal respiratory failure. As of January 2014, 275 cases of H7N9-infected patients had been reported, highlighting the urgency of identifying biomarkers for predicting disease severity and fatal outcomes. Here, we show that plasma levels of angiotensin II, a major regulatory peptide of the renin–angiotensin system, are markedly elevated in H7N9 patients and are associated with disease progression. Moreover, the sustained high levels of angiotensin II in these patients are strongly correlated with mortality. The predictive value of angiotensin II is higher than that of C-reactive protein and some clinical parameters such as the PaO2/FiO2 ratio (partial pressure of arterial oxygen to the fraction of inspired oxygen). Our findings indicate that angiotensin II is a biomarker for lethality in flu infections. Supplementary information The online version of this article (doi:10.1038/ncomms4595) contains supplementary material, which is available to authorized users.

Osteopontin regulates development and function of invariant natural killer T cells.

Invariant natural killer T (iNKT) cells belong to a subset of lymphocytes bridging innate and acquired immunity. We demonstrated that osteopontin (OPN) is involved in the activation of iNKT cells. In the present work, we examined whether OPN affects development and function of iNKT cells. We found that the number of peripheral iNKT cells was significantly reduced in OPN-deficient mice compared with wild-type mice. Although the number of thymic iNKT cells was not different between WT and OPN-deficient mice, intrathymic iNKT cell maturation was impaired in OPN-deficient mice. iNKT cell function was also significantly altered in OPN-deficient mice, as evidenced by (i) deficient down-regulation of iNKT cell receptor, (ii) reduction of IL-4 production while preserving production of IFN-γ, and (iii) reduction of Fas ligand (FasL) expression, leading to reduced Fas/FasL-dependent cytotoxicity against hepatocytes. Importantly, activation of the transcription factors NFAT2 (nuclear factor of activated T cells 2) and GATA-3 was impaired, whereas activation of T-bet was preserved in iNKT cells of OPN-deficient mice. These data collectively indicate that OPN plays a pivotal role not only in the development, but also in the function of iNKT cells.

Effect of Osteopontin Alleles on β-Glucan-Induced Granuloma Formation in the Mouse Liver

The granuloma formation is a host defense response against persistent irritants. Osteopontin is centrally involved in the formation of granulomas. Three osteopontin alleles, designated a, b, and c, have been found in mice. Here we used a murine model of zymosan (beta-glucan)-induced granuloma formation in the liver to determine possible functional differences between the osteopontin alleles in cell-mediated immunity. In contrast to mice with alleles a or c, mice with the allele b was defective in granuloma formation. As detected by mRNA expression, cytokines and chemokines known to be critically involved in granuloma formation were elicited in liver tissue, regardless of the osteopontin allele expressed. Alignment of the deduced amino acid sequences showed that unlike osteopontin c, b differs from a in 11 amino acids. All three osteopontin alleles had normal cell-binding properties. However, only the b allelic form was defective in the induction of cell migration as tested with dendritic cells. In conclusion, generation of a granulomatous response in mice depends critically on the presence of a functional osteopontin allele. Defective granuloma formation in mice with allele b is likely to be because of an impaired chemotactic function of the osteopontin b protein on immunocompetent cells.

The Serum Profile of Hypercytokinemia Factors Identified in H7N9-Infected Patients can Predict Fatal Outcomes

The novel avian origin influenza A (H7N9) virus has caused severe diseases in humans in eastern China since the spring of 2013. Fatal outcomes of H7N9 infections are often attributed to the severe pneumonia and acute respiratory distress syndrome (ARDS). There is urgent need to discover biomarkers predicting the progression of disease and fatal outcome of potentially lethal flu infections, based on sound statistical analysis. We discovered that 34 of the 48 cytokines and chemokines examined in this study were significantly elevated in the plasma samples from patients infected with H7N9. We report for the first time that the levels of MIF, SCF, MCP-1, HGF, and SCGF-β are highly positively linked to disease severity and the profile of mediators MIF, SCF, MCP-1, HGF, SCGF-β, IP-10, IL-18, and IFN-γ is an independent outcome predictor.

High salt diet stimulates gut Th17 response and exacerbates TNBS-induced colitis in mice

This study focuses on characterizing the effect of a high salt diet (HSD) on intestinal immunity and the risk of inflammatory bowel diseases (IBD). We found that mice on a HSD had an increased frequency of IL-17A producing cells in the intestinal lamina propria (LP) compared to mice on a normal diet (ND). Furthermore, most intestinal IL-17A producing cells were CD4+TCRβ+ cells. A HSD increased the LP T helper 17 (Th17) responses in both the small and large intestines but did not increase the Th17 response of other gut-associated lymphoid organ. Although, HSD did not change the percentage of regulatory T (Treg) cells, HSD significantly inhibit secretion of IL-10 and the suppressive function of Treg cells. Moreover, we found that HSD exacerbates trinitrobenzenesulfonic acid (TNBS) induced colitis, and Th17 response was significantly increased in the colonic LP of HSD TNBS-treated mice compared with the ND TNBS-treated mice. This study demonstrates that HSD stimulates the intestinal Th17 response but inhibits the function of Treg cells. Moreover, HSD exacerbates TNBS induced mice colitis, suggesting that HSD disrupts the intestinal immunity and increases the risk of IBD.

Severe H7N9 Infection Is Associated with Decreased Antigen-Presenting Capacity of CD14+ Cells

The outbreak of H7N9 human infection has caused concern worldwide, but the immunological characteristics of infected patients and the determinants of diverse outcomes remain to be thoroughly understood. In this study, twenty-three patients with H7N9 infections were classified into severe and mild cases. We found that severe patients were commonly lymphopenic with significantly lower levels of T cells, monocytes and related cytokine levels compared to the mild cases. The expression of HLA-DR on CD14+ cells were significantly lower in the severe infection group compared to the mild group (in acute phase: 34.65±4.88 vs. 10.37±1.69, p<0.001). Importantly, the expression of HLA-DR on CD14+ cells was negatively correlated with H7N9 infection severity. Furthermore, although the phagocytosis capabilities of monocyte were similar between two groups, the monocytes of severe infection patients had a lower antigen-presenting capacity. And some in vitro experiments suggested that the impaired antigen-presenting function is associated with lower activation of T cells in responses to immune stimulation. Our present study suggested that the severe H7N9 patients were in a state of immune decrease which presented with general lymphopenia and low antigen-presenting capacity resulting in impaired T cell response. Additionally, HLA-DR levels of CD14+ cells may be a potential biomarker for predicting H7N9 disease progression.

Natural killer T cells play a necessary role in modulating of immune-mediated liver injury by gut microbiota

Gut microbiota are implicated in many liver diseases. Concanavalin A (ConA)-induced hepatitis is a well-characterized murine model of fulminant immunological hepatic injury. Oral administration of pathogenic bacteria or gentamycin to the mice before ConA injection, liver injury and lymphocyte distribution in liver and intestine were assessed. Our data show that administration of pathogenic bacteria exacerbated the liver damage. There was more downregulation of activation-induced natural killer T (NKT) cells in the liver of pathogenic bacteria-treated ConA groups. Also, there was a negative correlation between the numbers of hepatic NKT cells and liver injury in our experiments. Moreover, intestinal dendritic cells (DCs) were increased in pathogenic bacteria–treated ConA groups. The activation of DCs in Peyers patches and the liver was similar to the intestine. However, depletion of gut gram-negative bacteria alleviated ConA-induced liver injury, through suppressed hepatic NKT cells activation and DCs homing in liver and intestine. In vitro experiments revealed that DCs promoted NKT cell cytotoxicity against hepatocyte following stimulation with pathogenic bacteria. Our study suggests that increased intestinal pathogenic bacteria facilitate immune-mediated liver injury, which may be due to the activation of NKT cells that mediated by intestinal bacterial antigens activated DCs.