Reduced IL-35 levels are associated with increased platelet aggregation and activation in patients with acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Interleukin-35 Promote Osteogenesis and Inhibit Adipogenesis: Role of Wnt/β-Catenin and PPARγ Signaling Pathways

Mesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into several cell types, including cartilage, fat, and bone. It has been reported that the decision process of MSCs into fat and bone cells is competing and reciprocal. Interleukin (IL)-35 is an important effector protein in the Wnt/β-catenin signaling pathway that acts as a bone metabolism regulator. However, it is unclear whether IL-35 is also important for regulating MSC differentiation to fat and bone. In the current study, we evaluated the role of IL-35 in C3H10T1/2 cells, which are a good cell model for investigating osteogenesis and adipogenesis in bone marrows. The role of IL-35 on osteoblast proliferation and apoptosis was assessed using cell counting kit-8 assay and flow cytometry, respectively. Extracellular matrix mineralization and lipid accumulation were measured by Alizarin Red S staining and Oil Red O staining, respectively. The most important transcription factor of the process of osteogenesis Runx2 and Wnt/β-catenin signaling pathway components β-catenin and Axin2 were investigated in response to IL-35 treatment. Furthermore, the adipogenic markers PPAR-γ and C/EBPα were also investigated. Our observations showed that IL-35 could promote the proliferation of MSCs and inhibit the apoptosis of MSCs. We found that IL-35 treatment resulted in a dramatic stimulation of osteogenesis and inhibition of adipogenesis. Moreover, IL-35 enhanced Wnt/β-catenin pathway key component β-catenin as well as Axin2 expression during MSCs differentiated to osteoblasts. Our findings suggested that IL-35 might control the balance between osteogenic and adipogenic differentiation of progenitor cells through the Wnt/β-catenin-PPARγ signaling pathway, suggesting its potential application in providing an intervention in osteoporosis and obesity.

IL-35 expression in hepatocellular carcinoma cells is associated with tumor progression

IL-35 has recently been demonstrated to play significant roles in the progression of various malignant tumors. We investigated the expression of IL-35 in hepatocellular carcinoma (HCC) and the regulatory mechanisms in HCC progression. Tissue microarray from 75 HCC patients revealed that IL-35 was primarily localized in the cytoplasm of cancer cells and peri-tumoral hepatocytes. Quantitative analysis showed that IL-35 expression was significantly lower in patients in the advanced stages than in the early stages. Significantly lower expression of IL-35 was also observed in HCC patients with higher histological grades, larger tumor size, positive microvascular invasion and lymph node/distant metastasis. IL-35 over-expression in HepG2 cells significantly upregulated HLA-ABC and CD95, reduced activities of MMP-2 and MMP-9, and decreased cell migration, invasion and colony formation capacities. Our data indicated that decreased expression of IL-35 in tumor tissues might contribute to the progression of HCC, and IL-35 may serve as a new therapeutic target for HCC.

Interleukin-35 mitigates the function of murine transplanted islet cells via regulation of Treg/Th17 ratio

Pancreatic islet transplantation is a promising treatment for type 1 diabetes (T1D). Interleukin-35 (IL-35) is a recently discovered cytokine that exhibits potent immunosuppressive functions. However, the role of IL-35 in islet transplant rejection remains to be elucidated. In this study, we isolated islet cells of BALB/c mouse and purified CD4+ T cell subsets of a C57BL/6 mouse. The model for islet transplantation was established in vitro by co-culture of the islet cells and CD4+ T cells. IL-35 (20 ng/ml) was administered every other day. Following co-culture, the islet function and Treg/Th17 ratio were analyzed on days 1, 3, and 5. Furthermore, the Th17/Treg ratio was modulated (1:0–2), and the function of islet cells as well as proliferation of Th17 cells were analyzed. T cell sorting was performed using the magnetic bead sorting method; Treg and Th17 count using flow cytometry; cell proliferation detection using the carboxyfluorescein diacetate succinimidyl ester (CFSE) method, and islet function test using the sugar stimulation test. Results showed that Th17 counts increased in the co-culture system. However, after administration of IL-35, the number of Treg cells increased significantly compared to that in the control group (50.7% of total CD4+ T cells on day 5 in IL-35 group vs. 9.5% in control group) whereas the proliferation rate of Th17 cells was significantly inhibited (0.3% in IL-35 group vs. 7.2% in control group on day 5). Reducing the Th17/Treg ratio significantly improved the function of transplanted islets. Treg inhibited Th17 proliferation and IL-35 enhanced this inhibitory effect. IL-35 mitigates the function of murine transplanted islet cells via regulation of the Treg/Th17 ratio. This might serve as a potential therapeutic strategy for in-vivo islet transplant rejection and T1D.

IL-35 inhibits acute graft-versus-host disease in a mouse model

Acute graft-versus-host disease (aGVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our previous study found that the novel anti-inflammatory cytokine IL-35 could suppress aGVHD in patients after allo-HSCT. In this study, we used C57BL/6 (B6, H-2b) mice as donors and (B6×DBA/2) F1 (BDF1, H-2b×d) mice as recipients to create a model of aGVHD and explore the relationship between IL-35 and aGVHD. The mice receiving IL-35 survived longer than did the control mice. We observed that treatment with IL-35 and RAPA could reduce the incidence of aGVHD. Additionally, this treatment inhibited intestinal and thymic epithelial cell apoptosis and liver infiltration by the donor T-cells, thereby ameliorating the enteropathy and liver injury caused by aGVHD. We found that IL-35 and RAPA also markedly suppressed TNF-α and IL-17A expression and enhanced IFN-γ expression in the intestine and liver. We measured Tregs in spleen and found that IL-35 and RAPA treatment expanded the number of Tregs in spleen. We found that the phosphorylation of STAT1 and STAT4 were inhibited in mice with aGVHD. In contrast, STAT1 and STAT4 were phosphorylated when the mice were treated with IL-35. IL-35 may have therapeutic potential in the treatment of aGVHD after allo-HSCT.