Synergistic costimulation by both B7 molecules regulates colitis pathogenesis

Vitamin D Increases CTLA-4 Gene Expression in Patients with Mild to Moderate Ulcerative Colitis

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disorder of the large intestine. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is a member of the immunoglobulin superfamily, which binds B7-1 and B7-2 on APCs (antigen-presenting cells), and induces APCs to produce an inhibitory signal to T cells. The aim of this study was to investigate the effect of vitamin D on CTLA-4 gene expression in whole blood samples of patients with UC.

METHODS

90 patients with mild to moderate UC were randomized to receive either a single injection of 7.5 mg vitamin D3 or 1 mL normal saline. 90 days following the intervention fold changes in CTLA-4 mRNA expression were determined and statistical comparisons between the two groups were performed.

RESULTS

Serum vitamin D increased significantly only in the vitamin D group. CTLA-4 fold changes were significantly higher in the vitamin D group compared with the placebo group (median ± IQR: 1.21 ± 2.3 vs. 1.00 ± 1.5, respectively; p = 0.007).

CONCLUSION

The results of this study revealed that vitamin D administration in patients with UC enhances the CTLA-4 gene expression.

Prevention of Injury-Induced Osteoarthritis in Rodent Temporomandibular Joint by Targeting Chondrocyte CaSR

Traumatic joint injuries produce osteoarthritic cartilage manifesting accelerated chondrocyte terminal differentiation and matrix degradation via unknown cellular and molecular mechanisms. Here we report the ability of biomechanical stress to increase expression of the calcium-sensing receptor (CaSR), a pivotal driver of chondrocyte terminal differentiation, in cultured chondrogenic cells subjected to fluid flow shear stress (FFSS) and in chondrocytes of rodent temporomandibular joint (TMJ) cartilage subjected to unilateral anterior cross-bite (UAC). In cultured ATDC5 cells or TMJ chondrocytes, FFSS induced Ca²⁺ loading and CaSR localization in endoplasmic reticulum (ER), casually accelerating cell differentiation that could be abrogated by emptying ER Ca²⁺ stores or CaSR knockdown. Likewise, acute chondrocyte-specific Casr knockout (KO) prevented the UAC-induced acceleration of chondrocyte terminal differentiation and matrix degradation in TMJ cartilage in mice. More importantly, local injections of CaSR antagonist, NPS2143, replicated the effects of Casr KO in preventing the development of osteoarthritic phenotypes in TMJ cartilage of the UAC-treated rats. Our study revealed a novel pathological action of CaSR in development of osteoarthritic cartilage due to aberrant mechanical stimuli and supports a therapeutic potential of calcilytics in preventing osteoarthritis in temporomandibular joints by targeting the CaSR. © 2018 American Society for Bone and Mineral Research.

Costimulation of Th17 cells: Adding fuel or putting out the fire in the inflamed gut?

Inflammatory bowel disease, typified by Crohn's disease and ulcerative colitis, is a common disorder characterized by recurrent and serious inflammation of the gastrointestinal tract. It is well documented that T cells play a pivotal role in the development of inflammatory bowel disease. Th17 cells are a unique T cell subpopulation implicated in inflammatory bowel disease and many other autoimmune/inflammatory diseases. However, the regulatory mechanism of Th17 activation and proliferation has not been defined completely. Recent studies have shown that the ligation of several costimulatory receptor-ligand pairs contributes to the activation, differentiation, and proliferation of T lymphocytes including the Th17 subset. In this review, we will discuss the emerging evidence on the role of Th17 cells in inflammatory bowel disease pathogenesis as well as the effect of costimulatory molecules on Th17 development and consider if the need for such costimulation of T lymphocytes provides a target for the development of novel therapeutic strategy.

Suppression of colon inflammation by CD80 blockade: evaluation in two murine models of inflammatory bowel disease

BACKGROUND

Human inflammatory bowel disease (IBD) is a chronic condition mediated by aberrant immune responses to the luminal antigens by activated CD4+ T cells. The CD80/CD86:CD28/CD152 costimulatory pathways transmit signals critical for T cell activation and suppression. Macrophages and epithelial cells are the chief antigen-presenting cells in the gut. Macrophages from the IBD colon express significantly elevated levels of CD80 and CD86 costimulatory molecules. The CD28-CD80 interaction primarily participates in breaking the tolerance and inducing the immune response in murine models of colitis. Blockade of CD80-costimulatory axis is an attractive strategy in the treatment of IBD.

METHODS

Incorporating the structural information of the CD80:CD152 complex together with the preferences of interface residues to form polyproline type II helix, we designed novel peptide agents that selectively blocked CD80 receptor interactions.

RESULTS

Administration of CD80 blocking agent at the time of adoptive transfer prevented the SCID mice from CD4+CD45Rb(high) T-cell mediated colitis. Significantly, CD80-CAP (competitive antagonist peptide) treatment suppressed established inflammation in TNBS-induced colitis, a model for Th1-mediated Crohn's disease. The colons of the mice receiving the CD80 blocking agent appeared unaffected macroscopically and exhibited negligible microscopic inflammation. The CD80-CAP treatment was associated with significantly reduced Th1 cytokines in the colon.

CONCLUSIONS

The CD80 blocking peptide appeared to mediate protection against colitis by inducing Th2 skewing of the cytokine response.