Interleukin-33 ameliorates experimental colitis through promoting Th2/Foxp3⁺ regulatory T-cell responses in mice.

Crohn's disease (CD) is characterized by the activation of Th1 and Th17 cells and deficiency of regulatory T cells (Tregs), leading to intestine tissue injury and destruction. As a novel cytokine of the interleukin (IL)-1 family, the role and underlying mechanisms of IL-33 in CD remain poorly understood. Here, we assess the effects and mechanisms of IL-33 on the trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis that mimics human CD. We found that IL-33 levels were increased in the TNBS-treated mice, whereas recombinant IL-33 (rIL-33) administration substantially ameliorated TNBS-mediated colonic tissue injury and clinical symptoms of colitis. The protective effect of rIL-33 was partly associated with the markedly increased induction of Th2-type cytokines. Importantly, rIL-33 treatment resulted in prominently upregulated Foxp3 expression in the TNBS-treated mice, and depletion of Tregs significantly abrogated the impact of IL-33 on reducing the development of colitis. Notably, the level of CD103⁺ dendritic cells (DCs), which promotes development of Tregs, is also increased in mesenteric lymph node and lamina propria of rIL-33-treated mice. The impact of rIL-33 on CD103⁺ DC induction was the result of indirectly upregulating intestine epithelial cells that produce thymic stromal lymphopoietin and retinoic acid but do not directly act on DCs. In conclusion, our data provide clear evidence that IL-33 plays a protective role in TNBS-induced colitis, which is closely related to a Th1-to-Th2/Treg switch. Thus, IL-33 is a promising candidate for the development of new treatments for CD.

MiR-199a-3p modulates the function of dendritic cells involved in transplantation tolerance by targeting CD86.

Dendritic cells (DCs) are key components of the immune system, serving as antigen-presenting cells to activate adaptive immunity. Whereas mature DCs promote immune responses, immature DCs induce or maintain immunological tolerance by downregulating T-cell responses. Therefore, DCs are potent antigen (Ag)-presenting cells in the immune system. MicroRNAs are noncoding RNAs that posttranscriptionally regulate mRNA by binding the 3'-untranslated region (UTR) of these molecules, modulating their expression. Many recent studies have suggested a potential role of miRNAs in DCs maturation and differentiation, but the exact mechanisms governing this process are unclear. How and whether miR-199a-3p affects DC maturation has not been investigated. Here, we found that MiR-199a-3p levels are correlated with DC maturation, inflammatory cytokine secretion, and PI3K/AKT/NF-κB signaling pathway activity. In addition, we analyzed the stimulation of regulatory T-cells by DCs. Through this work, we determined CD86 to be targeted by miR-199a-3p, thereby linking it to DC maturation. miR-199a-3p therefore directly inhibits CD86 expression via 3'-UTR targeting, subsequently prolonging allograft survival in a mouse heart transplantation model. miR-199a-3p over-expression may therefore be a potential therapeutic strategy for use in organ transplantation or patients with autoimmune diseases.

Diagnostic value of circulating miRNA-122 for hepatitis B virus and/or hepatitis C virus-associated chronic viral hepatitis.

Background: The liver-specific microRNA-122 (miR-122) has been demonstrated as a powerful and promising biomarker of hepatic diseases. However, the researches on the accuracy of miR122 detection in chronic viral hepatitis have been inconsistent, leading us to conduct this meta-analysis to systematically summarize the diagnostic value of circulating miR-122 in patients with hepatitis B virus (HBV) and/or hepatitis C virus (HCV)-associated chronic viral hepatitis.Methods: A comprehensive literature search (updated to January 30, 2019) in PubMed, Cochrane library, EMBASE, CNKI, Wanfang, and CQVIP databases was performed to identify eligible studies. The sensitivity (SEN), specificity (SPE), positive and negative likelihood ratios (PLR and NLR), diagnostic odds ratio (DOR), and area under the curve (AUC) were pooled to explore the diagnostic performance of circulating miR-122. Subgroup and threshold effect analysis were further carried out to explore the heterogeneity.Results: Overall, 15 studies were finally included in this meta-analysis according to the exclusion and inclusion criteria. The pooled estimates indicated a moderately high diagnostic accuracy for circulating miR-122, with a sensitivity of 0.92 [95% confidence interval (CI), 0.86-0.95], a specificity of 0.84 (95% CI, 0.78-0.89), a PLR of 5.7 (95% CI, 4.7-8.1), a NLR of 0.1 (95% CI, 0.06-0.18), a DOR of 57 (95% CI 25-129), and an AUC of 0.93 (95% CI, 0.91-0.95). The subgroup analysis demonstrated that diagnostic accuracy was better for HCV-associated chronic viral hepatitis patients and non-Chinese compared with other subgroups. In addition, we found that serum might be a more promising matrix for detecting the expression of miR-122 than plasma.Conclusions: Our results demonstrated that circulating miR-122 have a relatively high diagnostic value for chronic viral hepatitis detection, especially in the patients with HCV-associated chronic viral hepatitis. However, further large cohort studies are still required to confirm our findings.

Anti-CCL25 antibody prolongs skin allograft survival by blocking CCR9 expression and impairing splenic T-cell function.

Chemokines, by virtue of their ability to recruit immune cells into allografts, play critical roles in acute transplantation rejection. CCR9 and its ligand, CCL25, is one of the key regulators of thymocyte migration and maturation in normal and inflammatory conditions. Moreover, several studies have revealed that high expression of CCR9 and CCL25 participated in many kinds of diseases. However, the role of CCR9 in allograft rejection is still unclear. In this study, we established a murine skin transplantation model of acute rejection. Our findings showed that the proportion of CCR9-expressing T cells was significantly increased in the spleen of allotransplanted mice compared with syngeneic transplantation. Furthermore, expression of CCL25 in allograft was similarly increased. Neutralization of CCL25 by intravenous injection of anti-CCL25 monoclonal antibody significantly prolonged skin allograft survival, decreased the number of infiltrating cells, and simultaneously suppressed the chemotactic ability and the proliferation of the splenic T cells in response to allogeneic antigens. Finally, blockade of CCL25 also diminished the secretion of IFN-γ by splenic T cells. These studies indicated that CCR9/CCL25 was involved in acute transplantation rejection and anti-CCL25 strategies might be useful in preventing acute rejection.

Flt3L combined with rapamycin promotes cardiac allograft tolerance by inducing regulatory dendritic cells and allograft autophagy in mice.

The induction of immune tolerance is still a formidable challenge in organ transplantation. Dendritic cells (DCs) play an important role in orchestrating immune responses by either mediating protective immune responses or inducing antigen specific tolerance. Previous studies demonstrated that the fms-like tyrosine kinase 3 receptor (Flt3) and its ligand (Flt3L) play an essential role in the regulation of DC commitment and development. Here, we report a synergic effect between Flt3L and low-dose rapamycin (Rapa) in the protection of allograft rejction. It was found that Flt3L combined with Rapa significantly prolonged murine cardiac allograft survival time as compared with that of untreated recipients or recipients treated with Rapa or Flt3L alone. Mechanistic studies revealed that Flt3L combined with low-dose of Rapa induced the generation of tolerogenic DCs along with the production of CD25(+) Foxp3(+) regulatory T cells and IL-10 secretion. We also observed enhanced autophagy in the cardiac allograft, which could be another asset contributing to the enhanced allograft survival. All together, these data suggest that Flt3L combined with low-dose of Rapa could be an effective therapeutic approach to induce tolerance in clinical setting of transplantation.

Blockade of IL-33 ameliorates Con A-induced hepatic injury by reducing NKT cell activation and IFN-γ production in mice.

IL-33, a recently described member of the IL-1 family, has been identified as a cytokine endowed with pro-Th2 type functions. To date, there are only limited data on its role in physiological and pathological hepatic immune responses. In this study, we examined the role of IL-33 in immune-mediated liver injury by exploring the model of concanavalin A (Con A)-induced hepatitis. We observed that the level of IL-33 expression in the liver was dramatically increased at 12 h after Con A injection. Meanwhile, ST2L, the receptor of IL-33, was significantly up-regulated in lymphocytes including T and natural killer T (NKT) cells, especially in NKT cells. Moreover, administration of recombinant IL-33 exacerbated Con A-induced hepatitis, while pretreatment of IL-33-blocking antibody or psST2-Fc plasmids showed a protective effect probably by inhibiting the activation of late stage of T cells and NKT cells and also decreasing the production of the cytokine IFN-γ. Furthermore, depletion of NKT cells abolished the protective effect of IL-33-blocking antibody, and IL-33 failed to exacerbate Con A-induced hepatitis in IFN-γ(-/-) mice. These data suggested the critical roles of NKT cells and IFN-γ in the involvement of IL-33 in Con A-induced hepatitis. Blockade of IL-33 may represent a novel therapeutic strategy through IL-33/ST2L signal to prevent immune-mediated liver injury.

Gene silencing of NALP3 protects against liver ischemia-reperfusion injury in mice.

Liver ischemia-reperfusion (I/R) injury is a multifactorial process that affects graft function after liver transplantation. Inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1ß, and IL-18, have been shown to play key roles in the pathophysiology of liver I/R injury. Studies have indicated that NALP3 (NACHT domain, leucine-rich repeat [LRR] domain, and pyrin domain [PYD]-containing protein-3) inflammasome is pivotal in the processing and releasing of IL-1ß and IL-18. The aim of this study was to test whether NALP3 silencing has a protective effect in murine liver I/R injury. Using a partial lobar liver warm ischemia model, mice were hydrodynamically injected with pNALP3shRNA, pshRNANC, or saline 48 hr before ischemia. Those mice pretreated with pNALP3shRNA showed decreased serum alanine aminotransferase levels; inhibited production of proinflammatory cytokines such as IL-1ß, IL-18, TNF-α, and IL-6 by downregulation of caspase-1 activation and NF-κB activity; as well as decreased release of HMGB1 (high-mobility group box-1) and inflammatory cell infiltration, leading to the prevention of liver I/R injury, when compared with controls. Histology revealed that pretreatment with pNALP3shRNA significantly ameliorated hepatocellular damage after I/R. Thus, by using a small hairpin RNA approach, our study confirms that NALP3 signaling is involved in liver I/R and that silencing of NALP3 can protect the liver from I/R injury by reducing IL-1ß, IL-18, TNF-α, IL-6, and HMGB1 release through downregulation of caspase-1 activation and NF-κB activity.