Effect of Dihydrotestosterone on Costimulatory Molecules in a Mouse Model of Graves’ Disease

Objective Graves’disease is the most common autoimmune thyroid disease and its prevalence and clinical manifestations are disparate between females and males.Costimulatory molecules play an essential role in regulating autoimmune responses.The objective of this study was to determine if expression of inhibitory molecules was correlated with treatment by dihydrotestosterone(DHT)in an in vivo BALB/c mouse model of experimental autoimmune Graves’disease.Methods Female BALB/c mice were immunized three times with thyroid stimulating hormone receptor A-subunit encoded by adenovirus to establish a Graves’disease model.Three different doses of DHT or a matching placebo were administered by implantation of slow-release pellets a week before the first immunization.Four weeks after the third immunization,the mice were euthanatized,and then the spleen and thymus were removed.Total thyroxine and free thyroxine levels in serum of mice were detected using a radioimmunoassay kit.Real-time polymerase chain reaction was performed to estimate the expression of costimulatory molecules in lymphocytes from the spleen and thymus.Flow cytometry was used to analyze the percentage of CD4^+T cells in splenic lymphocytes.Quantitative data were compared with unpaired t-tests.Correlation between two variables was analyzed using Analysis of Variance.Results Treatment with DHT can dramatically reduce total thyroxine and free thyroxine levels.Higher expression of programmed death-1 was found in the spleen of Graves’disease mice receiving 5 mg of DHT treatment(0.635±0.296 vs.0.327±0.212;t=2.714,P=0.014),similarly,T-cell immunoglobulin domain and mucin domain 3(TIM-3)in both the spleen(1.004±0.338 vs.0.646±0.314;t=2.205,P=0.022)and the thymus(0.263±0.127 vs.0.120±0.076;t=3.221,P=0.004)also increased after 5 mg of DHT treatment compared with the parallel placebo model mice.Moreover,the percentage of CD4^+T cells declined in the splenic lymphocytes of Graves’disease mice treated with 5 mg of DHT(19.90%±3.985%vs.24.05%±2.587%;t=2.804,P=0.012).A significant negative association was observed between expression of TIM-3 in the spleen and serum levels of total thyroxine(r=-0.7106,P=0.014)as well as free thyroxine(r=-0.6542,P=0.029).Conclusion This study demonstrates that DHT can ameliorate experimental autoimmune Graves’disease,which may occur by up-regulating expression of programmed death-1 and TIM-3 and inhibiting development of CD4^+T cells.

Axonal growth inhibitors and their receptors in spinal cord injury:from biology to clinical translation

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelinassociated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19(that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the Rho A/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

Scar-modulating treatments for central nervous system injury

Traumatic injury to the adult mammalian central nervous system（CNS） leads to complex cellular responses. Among them, the scar tissue formed is generally recognized as a major obstacle to CNS repair, both by the production of inhibitory molecules and by the physical impedance of axon regrowth. Therefore, scar-modulating treatments have become a leading therapeutic intervention for CNS injury. To date, a variety of biological and pharmaceutical treatments, targeting scar modulation, have been tested in animal models of CNS injury, and a few are likely to enter clinical trials. In this review, we summarize current knowledge of the scar-modulating treatments according to their specific aims：（1） inhibition of glial and fibrotic scar formation, and（2） blockade of the production of scar-associated inhibitory molecules. The removal of existing scar tissue is also discussed as a treatment of choice. It is believed that only a combinatorial strategy is likely to help eliminate the detrimental effects of scar tissue on CNS repair.

ERMAP is a B7 family-related molecule that negatively regulates T cell and macrophage responses

T cell activation and tolerance are tightly regulated by costimulatory and coinhibitory molecules.B7 family members play a crucial role in regulating immune responses.In this study,we identified erythroid membrane-associated protein(ERMAP)as a novel T cell inhibitory molecule.ERMAP shares significant sequence and structural homology with existing B7 family members in its extracellular domain.The ERMAP protein is expressed on the cell surface of resting and activated antigen-presenting cells(APCs)and in some tumor tissues.The putative ERMAP receptor is expressed on activated CD4 and CD8 T cells and macrophages.Both mouse and human ERMAP-IgG2a Fc(ERMAP-Ig)fusion proteins inhibit T cell functions in vitro.Administration of ERMAP-Ig protein ameliorates autoimmune diseases,including experimental autoimmune encephalomyelitis and type 1 diabetes,in mice.Anti-ERMAP antibody enhances macrophage phagocytosis of cancer cells in vitro.Furthermore,administration of an anti-ERMAP antibody inhibits tumor growth in mice likely by blocking the inhibitory effects of ERMAP on T cells and macrophages.Our results suggest that therapeutic interaction with the ERMAP inhibitory pathway may represent a novel strategy for treating patients with autoimmune disease or cancer.