The Deleterious Impact of Interleukin 9 to Hepatorenal Physiology

Perivascular Fibrosis Is Mediated by a KLF10-IL-9 Signaling Axis in CD4+ T Cells

BACKGROUND

Perivascular fibrosis, characterized by increased amount of connective tissue around vessels, is a hallmark for vascular disease. Ang II (angiotensin II) contributes to vascular disease and end-organ damage via promoting T-cell activation. Despite recent data suggesting the role of T cells in the progression of perivascular fibrosis, the underlying mechanisms are poorly understood.

METHODS

TF (transcription factor) profiling was performed in peripheral blood mononuclear cells of hypertensive patients. CD4-targeted KLF10 (Kruppel like factor 10)-deficient (Klf10^fl/flCD4^Cre+; [TKO]) and CD4-Cre (Klf10^+/+CD4^Cre+; (Cre)) control mice were subjected to Ang II infusion. End point characterization included cardiac echocardiography, aortic imaging, multiorgan histology, flow cytometry, cytokine analysis, aorta and fibroblast transcriptomic analysis, and aortic single-cell RNA-sequencing.

RESULTS

TF profiling identified increased KLF10 expression in hypertensive human subjects and in CD4+ T cells in Ang II-treated mice. TKO mice showed enhanced perivascular fibrosis, but not interstitial fibrosis, in aorta, heart, and kidney in response to Ang II, accompanied by alterations in global longitudinal strain, arterial stiffness, and kidney function compared with Cre control mice. However, blood pressure was unchanged between the 2 groups. Mechanistically, KLF10 bound to the IL (interleukin)-9 promoter and interacted with HDAC1 (histone deacetylase 1) inhibit IL-9 transcription. Increased IL-9 in TKO mice induced fibroblast intracellular calcium mobilization, fibroblast activation, and differentiation and increased production of collagen and extracellular matrix, thereby promoting the progression of perivascular fibrosis and impairing target organ function. Remarkably, injection of anti-IL9 antibodies reversed perivascular fibrosis in Ang II-infused TKO mice and C57BL/6 mice. Single-cell RNA-sequencing revealed fibroblast heterogeneity with activated signatures associated with robust ECM (extracellular matrix) and perivascular fibrosis in Ang II-treated TKO mice.

CONCLUSIONS

CD4+ T cell deficiency of Klf10 exacerbated perivascular fibrosis and multi-organ dysfunction in response to Ang II via upregulation of IL-9. Klf10 or IL-9 in T cells might represent novel therapeutic targets for treatment of vascular or fibrotic diseases.

Interleukin-9 in Immunopathology of Trypanosoma cruzi Experimental Infection

Chagas’ disease is a parasitosis caused by Trypanosoma cruzi, which affects approximately 8 million people worldwide. The balance between pro- and anti-inflammatory cytokines produced during immunological responses contributes to disease prognosis and progression. Parasite tissue persistence can induce chronic inflammatory stimuli, which can cause long-term tissue injury and fibrosis. Chronic Chagas’ patients exhibit increased levels of interleukin (IL)-9, an important cytokine in the regulation of inflammatory and fibrogenic processes. Data on the role of IL-9 in other pathologies are sometimes contradictory, and few studies have explored this cytokine’s influence in Chagas’ disease pathology. Hence, the aim of this study was to evaluate the role of IL-9 in the progression of T. cruzi infection in vivo and in vitro. In vitro infection demonstrated that IL-9 reduced the number of infected cells and decreased the multiplication of intracellular amastigotes in both C2C12 myoblasts and bone marrow-derived macrophages. In myoblasts, the increased production of nitric oxide (NO) was essential for reduced parasite multiplication, whereas macrophage responses resulted in increased IL-6 and reduced TGF-β levels, indicating that parasite growth restriction mechanisms induced by IL-9 were cell-type specific. Experimental infection of BALB/c mice with T. cruzi trypomastigotes of the Y strain implicated a major role of IL-9 during the chronic phase, as increased Th9 and Tc9 cells were detected among splenocytes; higher levels of IL-9 in these cell populations and increased cardiac IL-9 levels were detected compared to those of uninfected mice. Moreover, rIL9 treatment decreased serum IL-12, IL-6, and IL-10 levels and cardiac TNF-α levels, possibly attempting to control the inflammatory response. IL-9 neutralization increased cardiac fibrosis, synthesis of collagens I and III, and mastocyte recruitment in BALB/c heart tissue during the chronic phase. In conclusion, our data showed that IL-9 reduced the invasion and multiplication of T. cruzi in vitro, in both myoblasts and macrophages, favoring disease control through cell-specific mechanisms. In vivo, IL-9 was elevated during experimental chronic infection in BALB/c mice, and this cytokine played a protective role in the immunopathological response during this phase by controlling cardiac fibrosis and proinflammatory cytokine production.

IL-9: a novel pro-podocyte survival cytokine in FSGS

Progressive focal segmental glomerulosclerosis, characterized by podocyte loss, is often refractory to treatment and leads to progressive proteinuric chronic kidney disease. Interleukin-9 (IL-9) is reported to play important roles in innate and adaptive immunity in extrarenal inflammatory diseases. By using an IL-9 knockout mouse model, Xiong et al. demonstrate IL-9 as a novel pro-podocyte survival cytokine in the adriamycin nephropathy model of focal segmental glomerulosclerosis. Sequential in vitro and in vivo data corroborate a direct protective role, rather than an immunologic role, for IL-9 on podocyte survival. This commentary highlights these novel data and discusses the necessary steps for developing IL-9 as a potential novel therapeutic for focal segmental glomerulosclerosis.

Interleukin-9 protects from early podocyte injury and progressive glomerulosclerosis in Adriamycin-induced nephropathy

A wide spectrum of immunological functions has been attributed to Interleukin 9 (IL-9), including effects on the survival and proliferation of immune and parenchymal cells. In recent years, emerging evidence suggests that IL-9 expression can promote tissue repair in inflammatory conditions. However, data about the involvement of IL-9 in kidney tissue protection is very limited. Here, we investigated the role of IL-9 in Adriamycin-induced nephropathy (AN), a mouse model for proteinuric chronic kidney disease. Compared to wild type mice, IL-9 knockout (Il9^-/-) mice with AN displayed accelerated development of proteinuria, aggravated glomerulosclerosis and deterioration of kidney function. At an early stage of disease, the Il9^-/- mice already displayed a higher extent of glomerular podocyte injury and loss of podocyte number compared to wild type mice. In the kidney, T cells and innate lymphoid cells produced IL-9. However, selective deficiency of IL-9 in the innate immune system in Il9^-/-Rag2^-/- mice that lack T and B cells did not alter the outcome of AN, indicating that IL-9 derived from the adaptive immune system was the major driver of tissue protection in this model. Mechanistically, we could show that podocytes expressed the IL-9 receptor in vivo and that IL-9 signaling protects podocytes from Adriamycin-induced apoptosis in vitro. Finally, in vivo treatment with IL-9 effectively protected wild type mice from glomerulosclerosis and kidney failure in the AN model. The detection of increased serum IL-9 levels in patients with primary focal and segmental glomerulosclerosis further suggests that IL-9 production is induced by glomerular injury in humans. Thus, IL-9 confers protection against experimental glomerulosclerosis, identifying the IL-9 pathway as a potential therapeutic target in proteinuric chronic kidney disease.

Anaphylatoxins enhance Th9 cell recruitment via the CCL20-CCR6 axis in IgA nephropathy

BACKGROUND

CD4⁺ T cells are involved in the pathogenesis of immunoglobulin A nephropathy (IgAN); T helper (Th) 1, Th17 and Th22 cells promote the occurrence and amplification of inflammatory reactions, while regulatory T (Treg) cells produce the opposite effects. However, whether Th9 cells, a subset of CD4⁺ T cells, participate in IgAN development is still unknown.

METHODS

Human peripheral blood mononuclear cells (PBMCs) were isolated from IgAN patients for Th9 cells detection by flow cytometry. Wild-type (WT) mouse was used to establish an IgAN mouse model while C3aR and C5aR inhibitor treated IgAN mouse. Kidney disease and function was assessed by histology and albumin-to-creatinine ratio. C3aR and C5aR expression was examined by immunohistochemical (IHC) assay. Th9 cell proportions in the blood of IgAN mouse was detected. C3a, C5a and interleukin (IL)-9 levels were tested by ELISA. Moreover, co-culture system between human mesangial cells (HMCs) and CD4⁺ T cells were constructed with or without C3a, C5a and anti-CCL20 mAb stimulation for transwell assay to examine Th9 cell chemotaxis.

RESULTS

We observed the numbers of Th9 cell and the levels of IL-9 were increased in IgAN patients and IgAN mice. Furthermore, C3a and C5a level in serum and kidney, C3aR and C5aR expression was increased in IgAN mice compared to WT mice. Most interestingly, C3aR and C5aR inhibitor could reduce kidney damage, Th9 cell numbers and IL-9 levels. We also observed that C3a and C5a enhanced CCL20 production in HMCs. Notably, C3a and C5a also increased the recruitment of Th9 cells and IL-9 levels by HMCs through enhancing the CCL20-CCR6 pathway.

CONCLUSIONS

Our results support that C3a and C5a increase the production of CCL20 by HMCs and consequently augment Th9 cell recruitment and IL-9 levels, resulting in IgAN exacerbation.

Crosstalk network among multiple inflammatory mediators in liver fibrosis

Liver fibrosis is the common pathological basis of all chronic liver diseases, and is the necessary stage for the progression of chronic liver disease to cirrhosis. As one of pathogenic factors, inflammation plays a predominant role in liver fibrosis via communication and interaction between inflammatory cells, cytokines, and the related signaling pathways. Damaged hepatocytes induce an increase in pro-inflammatory factors, thereby inducing the development of inflammation. In addition, it has been reported that inflammatory response related signaling pathway is the main signal transduction pathway for the development of liver fibrosis. The crosstalk regulatory network leads to hepatic stellate cell activation and proinflammatory cytokine production, which in turn initiate the fibrotic response. Compared with the past, the research on the pathogenesis of liver fibrosis has been greatly developed. However, the liver fibrosis mechanism is complex and many pathways involved need to be further studied. This review mainly focuses on the crosstalk regulatory network among inflammatory cells, cytokines, and the related signaling pathways in the pathogenesis of chronic inflammatory liver diseases. Moreover, we also summarize the recent studies on the mechanisms underlying liver fibrosis and clinical efforts on the targeted therapies against the fibrotic response.