T cell activation and function are critically regulated by positive and negative costimulatory molecules. Aberrant expression and function of costimulatory molecules have been associated with persistent activation of self-reactive T cells in autoimmune diseases such as rheumatoid arthritis (RA). In this study, initial analysis of costimulatory molecules led to the unexpected observation that, in addition to CD80, several negative regulators (e.g., CTLA-4, programmed death-1 (PD-1), and PD ligand-1) were overexpressed in synovial T cells and macrophages derived from RA patients as opposed to controls. The expression of CD80 and PD ligand-1 on monocytes could be induced in vitro by IFN-γ and TNF-α that were produced abundantly in RA-derived synovial fluid (SF). Furthermore, the soluble form of negative costimulatory molecules occurred at high concentrations in sera and SF of RA patients and correlated with titers of rheumatoid factor in RA patients. In particular, the levels of soluble PD-1 were found to correlate significantly with those of TNF-α in SF derived from RA patients. Detailed characterization of soluble PD-1 revealed that it corresponded to an alternative splice variant (PD-1Δex3) and could functionally block the regulatory effect of membrane-bound PD-1 on T cell activation. Our data indicate a novel pathogenic pathway in which overexpression of negative costimulatory molecules to restrict synovial inflammation in RA is overruled by the excessive production of soluble costimulatory molecules.

Osteopontin (OPN) is an extracellular matrix protein of pleiotropic properties and has been recently recognized as a potential inflammatory cytokine. In this study, we demonstrate, for the first time to our knowledge, that overexpression of OPN in synovial T cells is associated with local inflammatory milieu and that OPN acts as an important mediator in amplification and perpetuation of rheumatoid synovitis. The study revealed that mRNA expression of OPN was highly elevated in CD4 + synovial T cells derived from patients with RA, which correlated with increased OPN concentrations in synovial fluid (SF). The pattern of OPN overexpression was confined to rheumatoid synovium and correlated with coexpression of selected OPN receptors in synovial T cells, including integrins αv and β1 and CD44. RA-derived SF stimulated the expression of OPN in T cells, which was attributable to IL-10 present in SF and abrogated by anti-IL-10 antibody. Among the more than 300 autoimmune and inflammatory response genes examined, OPN selectively induced the expression of proinflammatory cytokines and chemokines known to promote migration and recruitment of inflammatory cells. Furthermore, it was evident that OPN activated transcription factor NF-κB in mononuclear cells. The study has important implications for understanding the role of OPN in rheumatoid synovitis and other inflammatory conditions.

The limited efficacy of current treatment methods and increased type 2 diabetes mellitus (T2DM) incidence constitute an incentive for investigating how metabolic homeostasis is maintained, to improve treatment efficacy and identify novel treatment methods. We analyzed a three-generation family of Chinese origin with the common feature of T2DM attacks and fatty pancreas (FP), alongside 19 unrelated patients with FP and 58 cases with T2DM for genetic variations in Enho, serum adropin, and relative Treg amounts. Functional studies with adropin knockout (AdrKO) in C57BL/6J mice were also performed. It showed serum adropin levels were significantly lower in FP and T2DM patients than in healthy subjects; relative Treg amounts were also significantly decreased in FP and T2DM patients, and positively associated with adropin (r=0.7220, P=0.0001). Sequencing revealed that the patients shared a Cys56Trp mutation in Enho. In vivo, adropin-deficiency was associated with increased severity of glucose homeostasis impairment and fat metabolism disorder. AdrKO mice exhibited reduced endothelial nitric oxide synthase (eNOS) phosphorylation (Ser1177), impaired glycosphingolipid biosynthesis, adipocytes infiltrating, and loss of Treg, and developed FP and T2DM. Adropin-deficiency contributed to loss of Treg and the development of FP disease and T2DM.

Osteopontin (OPN) is an extracellular matrix protein of pleiotropic properties and has been recently recognized as a potential inflammatory cytokine. In this study, we demonstrate, for the first time to our knowledge, that overexpression of OPN in synovial T cells is associated with local inflammatory milieu and that OPN acts as an important mediator in amplification and perpetuation of rheumatoid synovitis. The study revealed that mRNA expression of OPN was highly elevated in CD4 + synovial T cells derived from patients with RA, which correlated with increased OPN concentrations in synovial fluid (SF). The pattern of OPN overexpression was confined to rheumatoid synovium and correlated with coexpression of selected OPN receptors in synovial T cells, including integrins αv and β1 and CD44. RA-derived SF stimulated the expression of OPN in T cells, which was attributable to IL-10 present in SF and abrogated by anti-IL-10 antibody. Among the more than 300 autoimmune and inflammatory response genes examined, OPN selectively induced the expression of proinflammatory cytokines and chemokines known to promote migration and recruitment of inflammatory cells. Furthermore, it was evident that OPN activated transcription factor NF-κB in mononuclear cells. The study has important implications for understanding the role of OPN in rheumatoid synovitis and other inflammatory conditions.

Autoimmune pancreatitis may be related to PRSS1 gene mutations.