Interleukin-38 promotes skin tumorigenesis in an IL-1Rrp2-dependent manner

A Multifunctional Therapeutic Strategy Using P7C3 as A Countermeasure Against Bone Loss and Fragility in An Ovariectomized Rat Model of Postmenopausal Osteoporosis

By 2060, an estimated one in four Americans will be elderly. Consequently, the prevalence of osteoporosis and fragility fractures will also increase. Presently, no available intervention definitively prevents or manages osteoporosis. This study explores whether Pool 7 Compound 3 (P7C3) reduces progressive bone loss and fragility following the onset of ovariectomy (OVX)-induced osteoporosis. Results confirm OVX-induced weakened, osteoporotic bone together with a significant gain in adipogenic body weight. Treatment with P7C3 significantly reduced osteoclastic activity, bone marrow adiposity, whole-body weight gain, and preserved bone area, architecture, and mechanical strength. Analyses reveal significantly upregulated platelet derived growth factor-BB and leukemia inhibitory factor, with downregulation of interleukin-1 R6, and receptor activator of nuclear factor kappa-B (RANK). Together, proteomic data suggest the targeting of several key regulators of inflammation, bone, and adipose turnover, via transforming growth factor-beta/SMAD, and Wingless-related integration site/be-catenin signaling pathways. To the best of the knowledge, this is first evidence of an intervention that drives against bone loss via RANK. Metatranscriptomic analyses of the gut microbiota show P7C3 increased Porphyromonadaceae bacterium, Candidatus Melainabacteria, and Ruminococcaceae bacterium abundance, potentially contributing to the favorable inflammatory, and adipo-osteogenic metabolic regulation observed. The results reveal an undiscovered, and multifunctional therapeutic strategy to prevent the pathological progression of OVX-induced bone loss.

IL-38 Aggravates Atopic Dermatitis via Facilitating Migration of Langerhans cells

Atopic dermatitis (AD) is a common inflammation skin disease that involves dysregulated interplay between immune cells and keratinocytes. Interleukin-38 (IL-38), a poorly characterized IL-1 family cytokine, its role and mechanism in the pathogenesis of AD is elusive. Here, we show that IL-38 is mainly secreted by epidermal keratinocytes and highly expressed in the skin and downregulated in AD lesions. We generated IL-38 keratinocyte-specific knockout mice (K14Cre/+-IL-38f/f ) and induced AD models by 2,4-dinitrofluorobenzene (DNFB). Unexpectedly, after treatment with DNFB, K14Cre/+-IL-38f/f mice were less susceptible to cutaneous inflammation of AD. Moreover, keratinocyte-specific deletion of IL-38 suppressed the migration of Langerhans cells (LCs) into lymph nodes which results in disturbed differentiation of CD4+T cells and decreased the infiltration of immune cells into AD lesions. LCs are a type of dendritic cell that reside specifically in the epidermis and regulate immune responses. We developed LC-like cells in vitro from mouse bone marrow (BM) and treated with recombined IL-38. The results show that IL-38 depended on IL-36R, activated the phosphorylated expression of IRAK4 and NF-κB P65 and upregulated the expression of CCR7 to promoting the migration of LCs, nevertheless, the upregulation disappeared with the addition of IL-36 receptor antagonist (IL-36RA), IRAK4 or NF-κB P65 inhibitor. Furthermore, after treatment with IRAK4 inhibitors, the experimental AD phenotypes were alleviated and so IRAK4 is considered a promising target for the treatment of inflammatory diseases. Overall, our findings indicated a potential pathway that IL-38 depends on IL-36R, leading to LCs migration to promote AD by upregulating CCR7 via IRAK4/NF-κB and implied the prevention and treatment of AD, supporting potential clinical utilization of IRAK4 inhibitors in AD treatment.

Emerging functions and therapeutic targets of IL-38 in central nervous system diseases

Interleukin (IL)-38 is a newly discovered cytokine of the IL-1 family, which binds various receptors (i.e., IL-36R, IL-1 receptor accessory protein-like 1, and IL-1R1) in the central nervous system (CNS). The hallmark physiological function of IL-38 is competitive binding to IL-36R, as does the IL-36R antagonist. Emerging research has shown that IL-38 is abnormally expressed in the serum and brain tissue of patients with ischemic stroke (IS) and autism spectrum disorder (ASD), suggesting that IL-38 may play an important role in neurological diseases. Important advances include that IL-38 alleviates neuromyelitis optica disorder (NMOD) by inhibiting Th17 expression, improves IS by protecting against atherosclerosis via regulating immune cells and inflammation, and reduces IL-1β and CXCL8 release through inhibiting human microglial activity post-ASD. In contrast, IL-38 mRNA is markedly increased and is mainly expressed in phagocytes in spinal cord injury (SCI). IL-38 ablation attenuated SCI by reducing immune cell infiltration. However, the effect and underlying mechanism of IL-38 in CNS diseases remain inadequately characterized. In this review, we summarize the biological characteristics, pathophysiological role, and potential mechanisms of IL-38 in CNS diseases (e.g., NMOD, Alzheimer's disease, ASD, IS, TBI, and SCI), aiming to explore the therapeutic potential of IL-38 in the prevention and treatment of CNS diseases.

IL-38 regulates intestinal stem cell homeostasis by inducing WNT signaling and beneficial IL-1β secretion

The IL-1 Family member IL-38 has been characterized primarily as an antiinflammatory cytokine in human and mouse models of systemic diseases. Here, we examined the role of IL-38 in the murine small intestine (SI). Immunostaining of SI revealed that IL-38 expression partially confines to intestinal stem cells. Cultures of intestinal organoids reveal IL-38 functions as a growth factor by increasing organoid size via inducing WNT3a. In contrast, organoids from IL-38-deficient mice develop more slowly. This reduction in size is likely due to the downregulation of intestinal stemness markers (i.e., Fzd5, Ephb2, and Olfm4) expression compared with wild-type organoids. The IL-38 binding to IL-1R6 and IL-1R9 is still a matter of debate. Therefore, to analyze the molecular mechanisms of IL-38 signaling, we also examined organoids from IL-1R9-deficient mice. Unexpectedly, these organoids, although significantly smaller than wild type, respond to IL-38, suggesting that IL-1R9 is not involved in IL-38 signaling in the stem cell crypt. Nevertheless, silencing of IL-1R6 disabled the organoid response to the growth property of IL-38, thus suggesting IL-1R6 as the main receptor used by IL-38 in the crypt compartment. In organoids from wild-type mice, IL-38 stimulation induced low concentrations of IL-1β which contribute to organoid growth. However, high concentrations of IL-1β have detrimental effects on the cultures that were prevented by treatment with recombinant IL-38. Overall, our data demonstrate an important regulatory function of IL-38 as a growth factor, and as an antiinflammatory molecule in the SI, maintaining homeostasis.

The emerging role of IL-38 in diseases: A comprehensive review

INTRODUCTION

Interleukin-38 (IL-38) is a new type of anti-inflammatory cytokine, which is mainly expressed in the immunity-related organs and is involved in various diseases including cardiovascular and cerebrovascular diseases, lung diseases, viral infectious diseases and autoimmune diseases.

AIM

This review aims to detail the biological function, receptors and signaling of IL-38, which highlights its therapeutic potential in related diseases.

CONCLUSION

This article provides a comprehensive review of the association between interleukin-38 and related diseases, using interleukin-38 as a keyword and searching the relevant literature through Pubmed and Web of science up to July 2023.

Dexamethasone and OLT1177 Cooperate in the Reduction of Melanoma Growth by Inhibiting STAT3 Functions

The NLRP3 inflammasome is a multimolecular complex that processes inactive IL-1β and IL-18 into proinflammatory cytokines. OLT1177 is an orally active small compound that specifically inhibits NLRP3. Here, B16F10 melanoma were implanted in mice and treated with OLT1177 as well as combined with the glucocorticoid dexamethasone. At sacrifice, OLT1177 treated mice had significantly smaller tumors compared to tumor-bearing mice treated with vehicle. However, the combined treatment of OLT1177 plus dexamethasone revealed a greater suppression of tumor growth. This reduction was accompanied by a downregulation of nuclear and mitochondrial STAT3-dependent gene transcription and by a significant reduction of STAT3 Y705 and S727 phosphorylations in the tumors. In vitro, the human melanoma cell line 1205Lu, stimulated with IL-1α, exhibited significantly lower levels of STAT3 Y705 phosphorylation by the combination treatment, thus affecting the nuclear functions of STAT3. In the same cells, STAT3 serine 727 phosphorylation was also lower, affecting the mitochondrial functions of STAT3. In addition, metabolic analyses revealed a marked reduction of ATP production rate and glycolytic reserve in cells treated with the combination of OLT1177 plus dexamethasone. These findings demonstrate that the combination of OLT1177 and dexamethasone reduces tumor growth by targeting nuclear as well as mitochondrial functions of STAT3.

Interleukin-38 promotes skin tumorigenesis in an IL-1Rrp2-dependent manner

Interleukin-38 (IL-38) is strongly associated with chronic inflammatory diseases; however, its role in tumorigenesis is poorly understood. We demonstrated that expression of IL-38, which exhibits high expression in the skin, is downregulated in human cutaneous squamous cell carcinoma and 7,12-dimethylbenzanthracene/12-O-tetradecanoyl phorbol-13-acetate-induced mouse skin tumorigenesis. IL-38 keratinocyte-specific knockout mice displayed suppressed skin tumor formation and malignant progression. Keratinocyte-specific deletion of IL-38 was associated with reduced expression of inflammatory cytokines, leading to reduced myeloid cell infiltration into the local tumor microenvironment. IL-38 is dispensable for epidermal mutagenesis, but IL-38 keratinocyte-specific deletion reduces proliferative gene expression along with epidermal cell proliferation and hyperplasia. Mechanistically, we first demonstrated that IL-38 activates the c-Jun N-terminal kinase (JNK)/activator protein 1 signal transduction pathway to promote the expression of cancer-related inflammatory cytokines and proliferation and migration of tumor cells in an IL-1 receptor-related protein 2 (IL-1Rrp2)-dependent manner. Our findings highlight the role of IL-38 in the regulation of epidermal cell hyperplasia and pro-tumorigenic microenvironment through IL-1Rrp2/JNK and suggest IL-38/IL-1Rrp2 as a preventive and potential therapeutic target in skin cancer.