Li-Tzu Yeh

Different Modulation of Ptpn22 in Effector and Regulatory T Cells Leads to Attenuation of Autoimmune Diabetes in Transgenic Nonobese Diabetic Mice

Ptpn22 encodes PEST domain–enriched tyrosine phosphatase (Pep), which negatively regulates TCR proximal signaling and is strongly associated with a variety of autoimmune diseases in humans. The net effect of Pep on the balance of immunity and tolerance is uncertain because of the simultaneous inhibition of TCR-mediated signaling of effector and regulatory T cells (Tregs). In this study, we generated transgenic NOD mice that overexpressed Pep in T cells. The transgenic mice had a significantly lower incidence of spontaneous autoimmune diabetes, which was accompanied by fewer IFN-γ–producing T cells, and an increased ratio of CD4+Foxp3+ Tregs to CD4+IFN-γ+ or to CD8+IFN-γ+ T cells, respectively, in pancreatic islets. Transgenic T cells showed markedly decreased TCR-mediated effector cell responses such as proliferation and Th1 differentiation. By contrast, the inhibitory effect of transgenic Pep on TCR signaling did not affect the differentiation of Tregs or their suppressive activity. Adoptive transfer experiments showed that transgenic splenocytes exhibited attenuated diabetogenic ability. To examine further the pathogenic features of transgenic T cells, we generated Ptpn22/BDC2.5 doubly transgenic mice and found reduced proliferation and Th1 differentiation in CD4+ T lymphocytes with additional Pep in pancreatic lymph nodes but not in inguinal lymph nodes of NOD/SCID recipients. This finding indicates that transgenic Pep attenuates T cell functions in an islet Ag–driven manner. Taken together, our results demonstrate that Pep overexpression in T cells attenuates autoimmune diabetes in NOD mice by preferentially modulating TCR signaling–mediated functions in diabetogenic T cells but not in Tregs.

Citral alleviates an accelerated and severe lupus nephritis model by inhibiting the activation signal of NLRP3 inflammasome and enhancing Nrf2 activation

IntroductionLupus nephritis (LN) is a major complication of systemic lupus erythematosus. NLRP3 inflammasome activation, reactive oxygen species (ROS) and mononuclear leukocyte infiltration in the kidney have been shown to provoke the acceleration and deterioration of LN, such as accelerated and severe LN (ASLN). Development of a novel therapeutic remedy based on these molecular events to prevent the progression of the disease is clinically warranted.MethodsCitral (3,7-dimethyl-2,6-octadienal), a major active compound in a Chinese herbal medicine Litsea cubeba, was used to test its renoprotective effects in a lipopolysaccharide (LPS)-induced mouse ASLN model by examining NLRP3 inflammasome activation, ROS and COX-2 production as well as Nrf2 activation. The analysis of mechanisms of action of Citral also involved its effects on IL-1β secretion and signaling pathways of NLRP3 inflammasome in LPS-primed peritoneal macrophages or J774A macrophages.ResultsAttenuated proteinuria, renal function impairment, and renal histopathology, the latter including intrinsic cell proliferation, cellular crescents, neutrophil influx, fibrinoid necrosis in the glomerulus, and peri-glomerular infiltration of mononuclear leukocytes as well as glomerulonephritis activity score were observed in Citral-treated ASLN mice. In addition, Citral inhibited NLRP3 inflammasome activation and levels of ROS, NAD(P)H oxidase subunit p47phox, or COX-2, and it enhanced the activation of nuclear factor E2-related factor 2 (Nrf2). In LPS-primed macrophages, Citral reduced ATP-induced IL-1β secretion and caspase-1 activation, but did not affect LPS-induced NLRP3 protein expression.ConclusionOur data show that Citral alleviates the mouse ASLN model by inhibition of the activation signal, but not the priming signal, of NLRP3 inflammasome and enhanced activation of Nrf2 antioxidant signaling.

B lymphocyte-induced maturation protein 1 (BLIMP-1) attenuates autoimmune diabetes in NOD mice by suppressing Th1 and Th17 cells

Aims/hypothesisRecent reports indicate that B lymphocyte-induced maturation protein 1 (BLIMP-1), encoded by the Prdm1 gene, expands its control over T cells and is associated with susceptibility to colitis in mice with T cell-specific BLIMP-1 deficiency. In this study, we aimed to investigate the potential role of BLIMP-1 in regulating autoimmune diabetes and T helper type 17 (Th17) cells.MethodsWe generated T cell-specific Blimp1 (also known as Prdm1) transgenic (Tg) or conditional knockout (CKO) NOD mice, in which Blimp1 is overexpressed or deleted in T cells, respectively. By side-by-side analysing these Tg or CKO mice, we further dissected the potential mechanisms of BLIMP-1-mediated modulation on autoimmune diabetes.ResultsOverproduction of BLIMP-1 in T cells significantly attenuated insulitis and the incidence of diabetes in NOD mice. Consistent with these results, the diabetogenic effect of splenocytes was remarkably impaired in Blimp1 Tg mice. Moreover, overproduction of BLIMP-1 repressed the proliferation and activation of lymphocytes and enhanced the function of regulatory T cells (Tregs) in NOD mice. In contrast, mice lacking BLIMP-1 in T cells markedly increased Th1 and Th17 cells, and developed highly proliferative and activated lymphocytes. Strikingly, overexpansion of Th1 and Th17 cells in CKO mice was significantly reduced by introducing a Blimp1 transgene, reinforcing the emerging role of BLIMP-1 in autoimmunity.Conclusions/interpretationWe conclude that BLIMP-1 orchestrates a T cell-specific modulation of autoimmunity by affecting lymphocyte proliferation and activation, Th1 and Th17 cell differentiation, and Treg function. Our results provide a theoretical basis for developing BLIMP-1-manipulated therapies for autoimmune diabetes.

T cell-specific BLIMP-1 deficiency exacerbates experimental autoimmune encephalomyelitis in nonobese diabetic mice by increasing Th1 and Th17 cells.

Recently, we demonstrated that B lymphocyte-induced maturation protein 1 (BLIMP-1) has a role in regulating the differentiation and effector function of Th1 and Th17 cells. As these cells play critical roles in the induction and pathogenesis of experimental autoimmune encephalomyelitis (EAE), we investigated the potential role of T cell BLIMP-1 in modulating MOG35-55-induced EAE. We established T cell-specific BLIMP-1 conditional knockout (CKO) NOD mice to dissect the role of BLIMP-1 in EAE using loss-of-function model. Our results indicate that EAE severity is dramatically exacerbated in CKO mice. The numbers of CNS-infiltrating Th1, Th17, IFN-γ(+)IL-17A(+), and IL-21(+)IL-17A(+) CD4(+) T cells are remarkably increased in brain and spinal cord of CKO mice. Moreover, the ratio of Tregs/effectors and IL-10 production of Tregs are significantly downregulated in CNS of CKO mice. We conclude that BLIMP-1 suppresses autoimmune encephalomyelitis via downregulating Th1 and Th17 cells and impairing Treg cells.

Tyrosine Phosphorylation of c-Maf Enhances the Expression of IL-4 Gene

Maf proteins are involved in a variety of biological processes, such as oncogenesis, lens development, and differentiation. In immune system, c-Maf transactivates IL-4 promoter, and ectopic expression of c-Maf skews primary T cell response toward the Th2 pathway. Numerous transcription factors are subjected to posttranslational modification. In this study, to our knowledge, we show for the first time that c-Maf is subjective to tyrosine phosphorylation in Th cells and that the level of its tyrosine phosphorylation positively correlates with IL-4 expression by peripheral Th cells, but is negatively associated with the severity of disease in NOD mice. c-Maf undergoes tyrosine phosphorylation at Tyr21, Tyr92, and Tyr131 residues in Th2 cells. Furthermore, tyrosine phosphorylation at these three residues is critical for the recruitment of c-Maf to IL-4 promoter and IL-4 production in Th cells. Taken together, this study sheds new light on the role of posttranslational modification of c-Maf in IL-4 production and Th cell-mediated autoimmune diseases.

Targeting tumour necrosis factor receptor 1 assembly reverses Th17-mediated colitis through boosting a Th2 response

Objective The soluble preligand assembly domain (PLAD) of tumour necrosis factor receptor 1 (TNFR1) interferes with receptor trimerisation to block downstream signalling, and mediates Th17 suppression. We explored the therapeutic potential of recombinant PLAD.Fc protein on a spontaneous experimental colitis. Design A T-cell-specific BLIMP-1 knockout mouse model with mixed Th1/Th17 responses, resembling human Crohns disease (CD) was established, and its colitogenic phenotype was characterised. Mice, 9 weeks old, were treated with PLAD.Fc protein at 5 mg/kg of body weight twice per week for 16 weeks, and presence of colitis was monitored by the appearance of diarrhoea, weight loss, and by histological colonic scoring. Activation status, cytokine profiles, and transcription factors in T cells were further analysed. Results The colitogenic phenotype in BLIMP-1 knockout mice was alleviated when an interleukin (IL)-23 knockdown transgene was introduced, indicating a therapeutic potential by downregulating IL-23-Th17 axis in these knockout mice. In PLAD.Fc-treated group, the mouse body weight remained stable and only mild disease scores were revealed. The percentage of naive CD4 T cells was increased and that of effector/memory CD4 T cells was decreased after PLAD.Fc-treatment. Moreover, the levels of IFN-γ, IL-17, IL-21, IL-22, IL-23R, granulocyte-macrophage colony-stimulating factor (GM-CSF) and TNF-α were diminished. Strikingly, Th2-associated cytokines (IL-4, IL-13 and IL-10) in sera, as well as percentages of Th2 cells, were increased in PLAD.Fc-treated mice. However, PLAD.Fc-mediated suppression of effector phenotypes in Th1/Th17 was abrogated after neutralising IL-10. Conclusions The Th2 cytokine milieu induced by PLAD.Fc rebalanced T-helper cell subsets and conferred a protection against colitis in BLIMP-1 knockout mice.

IL-1β in Irrigation Fluid and MRNA Expression in Synovial Tissue of the Knee Joint as Therapeutic Markers of Inflammation in Collagen Antibody-Induced Arthritis

Objective: We studied the relationship between the severity of inflammation and IL-1β production and relative expression level of IL-1β mRNA in irrigation fluid and synovial tissue obtained from the knee joint during the acute stage of a murine model of type II collagen antibody-induced arthritis (CAIA). This model is used to identify potential therapeutic markers for treating rheumatoid arthritis. Methods: Irrigation fluid and synovium tissue were harvested from the knee joint of BALB/c mice in acute stage of CAIA induction. The IL-1β protein level was measured by enzyme-linked immunosorbent assay, and the relative expression level of IL-1β mRNA was analyzed by reverse transcription-polymerase chain reaction. Two investigators analyzed expression levels and histopathological changes. Results: IL-1β concentration was higher in irrigation fluid from the knee joint than in the serum in the acute stage of CAIA. The relative expression level of IL-1β mRNA was elevated in synovial tissue. Histopathological changes in the knee joint and foot indicated similar severity. Conclusions: IL-1β concentration in irrigation fluid and relative expression level of IL-1β mRNA in the synovium have potential as therapeutic markers in studying and treating CAIA.

New insights into Blimp-1 in T lymphocytes: a divergent regulator of cell destiny and effector function

B lymphocyte-induced maturation protein-1 (Blimp-1) serves as a master regulator of the development and function of antibody-producing B cells. Given that its function in T lymphocytes has been identified within the past decade, we review recent findings with emphasis on its role in coordinated control of gene expression during the development, differentiation, and function of T cells. Expression of Blimp-1 is mainly confined to activated T cells and is essential for the production of interleukin (IL)-10 by a subset of forkhead box (Fox)p3+ regulatory T cells with an effector phenotype. Blimp-1 is also required to induce cell elimination in the thymus and critically modulates peripheral T cell activation and proliferation. In addition, Blimp-1 promotes T helper (Th) 2 lineage commitment and limits Th1, Th17 and follicular helper T cell differentiation. Furthermore, Blimp-1 coordinates with other transcription factors to regulate expression of IL-2, IL-21 and IL-10 in effector T lymphocytes. In CD8+ T cells, Blimp-1 expression is distinct in heterogeneous populations at the stages of clonal expansion, differentiation, contraction and memory formation when they encounter antigens. Moreover, Blimp-1 plays a fundamental role in coordinating cytokine receptor signaling networks and transcriptional programs to regulate diverse aspects of the formation and function of effector and memory CD8+ T cells and their exhaustion. Blimp-1 also functions as a gatekeeper of T cell activation and suppression to prevent or dampen autoimmune disease, antiviral responses and antitumor immunity. In this review, we discuss the emerging roles of Blimp-1 in the complex regulation of gene networks that regulate the destiny and effector function of T cells and provide a Blimp-1-dominated transcriptional framework for T lymphocyte homeostasis.

Diabetic Animal Models with Infectious Diseases: Focus on the Dysfunction of Immune System

Diabetes Mellitus (DM) is a metabolic disease that can lead to a variety of complications, such as neuropathy, retinopathy, nephropathy, and cardiovascular disease. Furthermore, pathogen infection accompanied by considerable morbidity and mortality is common among diabetic patients. Increased susceptibility to pathogen infection results from impaired immune responses, such as lower cytokine production and reduced function or migration of immune cells. However, existing clinical data remains controversial because multiple diabetes-related factors such as obesity, hyperglycemia, hyperinsulinemia, and other comorbidities also increase the risk of infection. In recent decades, several animal models have been used to investigate the role played by immune dysfunction in increasing susceptibility to pathogens and related diseases in diabetes. This review focuses on studies that used diabetic animal models to study infectious diseases and summarizes potential mechanisms underlying dysfunction of the immune system in diabetes patients.

A noncontact footpad thickness assay to evaluate rheumatoid disease

Measuring soft tissue thickness is an important step in rheumatoid disease research. The severity of mouse footpad swelling can be used as an indicator of disease progression. A noncontact footpad thickness assay, simplified geometry measurement system (SGMS), was developed that was able to reduce both intra- and interobserver variances during measurements. Three materials with five objects each were used in this study: hard blocks, soft sponges and mouse footpads. Thicknesses were measured using calipers or the SGMS. In the measurement of the hard block, there was no difference in measurement errors between calipers and SGMS. For the mouse footpad thickness, there was significant difference in intraobserver variances among three observers and a significant difference of interobserver variances between calipers and SGMS. In conclusions, this noncontact assay is reliable and highly reproducible for the assessment of inflammatory reactions when results are expressed as a gradual increase in footpad thickness.