iRhom2 promotes lupus nephritis through TNF-α and EGFR signaling

E3 ubiquitin ligase TRIM31: A potential therapeutic target

Ubiquitination is a key mechanism for post-translational protein modification, affecting protein localization, metabolism, degradation and various cellular physiological processes. Dysregulation of ubiquitination is associated with the pathogenesis of various diseases, such as tumors and cardiovascular diseases, making it a primary area of interest in biochemical research and drug development endeavors. E3 ubiquitin ligases play a pivotal role in modulating the ubiquitination of substrate proteins through their unique recognition functions. TRIM31, a member of the TRIM family of E3 ubiquitin ligases, is aberrantly expressed in different pathophysiological conditions. The biological function of TRIM31 is associated with the occurrence and development of diverse diseases. TRIM31 has been demonstrated to inhibit inflammation by promoting ubiquitin-proteasome-mediated degradation of the sensing protein NLRP3 in the inflammasome. TRIM31 mediates ubiquitination of MAVS, inducing the formation of prion-like aggregates, and triggering innate antiviral immune responses. TRIM31 is also implicated in tumor pathophysiology through its ability to promote ubiquitination of the tumor suppressor protein p53. These findings indicate that TRIM31 is a potential therapeutic target, and subsequent in-depth research of TRIM31 is anticipated to provide information on its clinical application in therapy.

The interferon-rich skin environment regulates Langerhans cell ADAM17 to promote photosensitivity in lupus

The autoimmune disease lupus erythematosus (lupus) is characterized by photosensitivity, where even ambient ultraviolet radiation (UVR) exposure can lead to development of inflammatory skin lesions. We have previously shown that Langerhans cells (LCs) limit keratinocyte apoptosis and photosensitivity via a disintegrin and metalloprotease 17 (ADAM17)-mediated release of epidermal growth factor receptor (EGFR) ligands and that LC ADAM17 sheddase activity is reduced in lupus. Here, we sought to understand how the lupus skin environment contributes to LC ADAM17 dysfunction and, in the process, differentiate between effects on LC ADAM17 sheddase function, LC ADAM17 expression, and LC numbers. We show through transcriptomic analysis a shared IFN-rich environment in non-lesional skin across human lupus and three murine models: MRL/lpr, B6.Sle1yaa, and imiquimod (IMQ) mice. IFN-I inhibits LC ADAM17 sheddase activity in murine and human LCs, and IFNAR blockade in lupus model mice restores LC ADAM17 sheddase activity, all without consistent effects on LC ADAM17 protein expression or LC numbers. Anti-IFNAR-mediated LC ADAM17 sheddase function restoration is associated with reduced photosensitive responses that are dependent on EGFR signaling and LC ADAM17. Reactive oxygen species (ROS) is a known mediator of ADAM17 activity; we show that UVR-induced LC ROS production is reduced in lupus model mice, restored by anti-IFNAR, and is cytoplasmic in origin. Our findings suggest that IFN-I promotes photosensitivity at least in part by inhibiting UVR-induced LC ADAM17 sheddase function and raise the possibility that anifrolumab ameliorates lupus skin disease in part by restoring this function. This work provides insight into IFN-I-mediated disease mechanisms, LC regulation, and a potential mechanism of action for anifrolumab in lupus.

Mechanistic insight on the role of iRhom2-TNF-α-BAFF signaling pathway in various autoimmune disorders

iRhom2 is a crucial cofactor involved in upregulation of TNF receptors (TNFRs) and the pro-inflammatory cytokine tumor necrosis factor (TNF-) from the cell surface by ADAM17. Tumor necrosis factor- α converting enzyme (TACE) is another name given to ADAM17. Many membrane attached biologically active molecules are cleaved by this enzyme which includes TNFRs and the pro-inflammatory cytokine tumor necrosis factor- α. The TNF receptors are of two types TNFR1 and TNFR2. iRhom2 belongs to the pseudo-protease class of rhomboid family, its abundance is observed in the immune cells. Biological activity of ADAM17 is affected in multiple levels by the iRhom2. ADAM17 is trafficked into the Golgi apparatus by the action of iRhom2, where it gets matured proteolytically and is stimulated to perform its function on the cell surface. This process of activation of ADAM17 results in the protection of the organism from the cascade of inflammatory reactions, as this activation blocks the TNF- α mediated secretion responsible for inflammatory responses produced. Present paper illustrates about the iRhom2-TNF-α-BAFF signaling pathway and its correlation with several autoimmune disorders such as Rheumatoid Arthritis, Systemic Lupus Erythematosus, Hemophilia Arthropathy, Alzheimer's disease and Tylosis with esophageal cancer etc.

Th1-related transcription factors and cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an inflammatory disorder related to immunity dysfunction. The Th1 cell family including Th1 cells, transcription factor T-bet, and related cytokines IFNγ, TNFα, IL-2, IL-18, TGF-β, and IL-12 have been widely discussed in autoimmunity, such as SLE. In this review, we will comprehensively discuss the expression profile of the Th1 cell family in both SLE patients and animal models and clarify how the family members are involved in lupus development. Interestingly, T-bet-related age-associated B cells (ABCs) and low-dose IL-2 treatment in lupus were emergently discussed as well. Collection of the evidence will better understand the roles of the Th1 cell family in lupus pathogenesis, especially targeting IL-2 in lupus.

Epidermal growth factor receptor activation is essential for kidney fibrosis development

Fibrosis is the progressive accumulation of excess extracellular matrix and can cause organ failure. Fibrosis can affect nearly every organ including kidney and there is no specific treatment currently. Although Epidermal Growth Factor Receptor (EGFR) signaling pathway has been implicated in development of kidney fibrosis, underlying mechanisms by which EGFR itself mediates kidney fibrosis have not been elucidated. We find that EGFR expression increases in interstitial myofibroblasts in human and mouse fibrotic kidneys. Selective EGFR deletion in the fibroblast/pericyte population inhibits interstitial fibrosis in response to unilateral ureteral obstruction, ischemia or nephrotoxins. In vivo and in vitro studies and single-nucleus RNA sequencing analysis demonstrate that EGFR activation does not induce myofibroblast transformation but is necessary for the initial pericyte/fibroblast migration and proliferation prior to subsequent myofibroblast transformation by TGF-ß or other profibrotic factors. These findings may also provide insight into development of fibrosis in other organs and in other conditions.

DUSP2 inhibits the progression of lupus nephritis in mice by regulating the STAT3 pathway

One of the most severe side effects of systemic lupus erythematosus (SLE) is lupus nephritis (LN). To search for potential therapeutic targets in SLE is crucial for the progression of SLE. In this study, we selected C57BL/6J mice as controls and MRL/lpr mice as an LN model and obtained dual specificity phosphatase 2 (DUSP2)-overexpressed mice by injecting AAV-DUSP2 plasmid into the tail vein. Then, proteinuria, urea nitrogen, dsDNA and TNF-α, IL-6, and IL-1β levels were measured in each group of mice. In addition, renal histopathological damage was assessed by hematoxylin-eosin. Finally, STAT3 phosphorylation levels were detected by Western blot assay. The results showed that DUSP2 could reduce proteinuria, urea nitrogen, dsDNA and TNF-α, IL-6, and IL-1β levels and improve renal tissue injury in mice with LN. Mechanistically, DUSP2 inhibited STAT3 phosphorylation. These results demonstrated that DUSP2 played a role in ameliorating LN, which provided potential targets for LN research.

Analysis of the function of ADAM17 in iRhom2 curly-bare and tylosis with esophageal cancer mutant mice

Tylosis with oesophageal cancer (TOC) is a rare familial disorder caused by cytoplasmic mutations in inactive rhomboid 2 (iRhom2 or iR2, encoded by Rhbdf2). iR2 and the related iRhom1 (or iR1, encoded by Rhbdf1) are key regulators of the membrane-anchored metalloprotease ADAM17, which is required for activating EGFR ligands and for releasing pro-inflammatory cytokines such as TNFα (or TNF). A cytoplasmic deletion in iR2, including the TOC site, leads to curly coat or bare skin (cub) in mice, whereas a knock-in TOC mutation (toc) causes less severe alopecia and wavy fur. The abnormal skin and hair phenotypes of iR2cub/cub and iR2toc/toc mice depend on amphiregulin (Areg) and Adam17, as loss of one allele of either gene rescues the fur phenotypes. Remarkably, we found that iR1-/- iR2cub/cub mice survived, despite a lack of mature ADAM17, whereas iR2cub/cub Adam17-/- mice died perinatally, suggesting that the iR2cub gain-of-function mutation requires the presence of ADAM17, but not its catalytic activity. The iR2toc mutation did not substantially reduce the levels of mature ADAM17, but instead affected its function in a substrate-selective manner. Our findings provide new insights into the role of the cytoplasmic domain of iR2 in vivo, with implications for the treatment of TOC patients.

Exploring the potential mechanisms of Shiwei Hezi pill against nephritis based on the method of network pharmacology

Objective: We aimed to reveal the potential active ingredients, targets and pathways of Shiwei Hezi pill (SHP) in the treatment of nephritis based on systematic network pharmacology. Methods: The online database was used to screen the common targets of SHP and nephritis, and the interaction between targets was analyzed. Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed using the Bioinformatics website. Molecular docking was carried out to verify the correlation between core ingredients and key targets. Cytoscape 3.6.1 was applied to perform protein-protein interactions (PPT) network construction and data visualization. Results: A total of 82 active ingredients in SHP were screened, and 140 common targets of SHP and nephritis were obtained. Our results demonstrated that TNF, AKT1 and PTGS2 might be the key targets of SHP in the treatment of nephritis. GO enrichment analysis yielded 2163 GO entries (p < 0.05), including 2,014 entries of the biological process (BP) category, 61 entries of the cell composition (CC) category and 143 entries of the molecular function (MF) category. KEGG pathway enrichment analysis produced 186 signaling pathways (p < 0.05), involving the AGE-RAGE, IL-17and TNF signaling pathways. The results of molecular docking showed that three active ingredients in SHP (quercetin, kaempferol and luteolin) could effectively bind to the TNF, AKT1 and PTGS2 targets. Conclusion: The effective active ingredients in SHP may regulate multiple signaling pathways through multiple targets, thereby exhibiting a therapeutic effect on nephritis.

The ADAM17 sheddase complex regulator iTAP/Frmd8 modulates inflammation and tumor growth

The metalloprotease ADAM17 is a sheddase of key molecules, including TNF and epidermal growth factor receptor ligands. ADAM17 exists within an assemblage, the "sheddase complex," containing a rhomboid pseudoprotease (iRhom1 or iRhom2). iRhoms control multiple aspects of ADAM17 biology. The FERM domain-containing protein iTAP/Frmd8 is an iRhom-binding protein that prevents the precocious shunting of ADAM17 and iRhom2 to lysosomes and their consequent degradation. As pathophysiological role(s) of iTAP/Frmd8 have not been addressed, we characterized the impact of iTAP/Frmd8 loss on ADAM17-associated phenotypes in mice. We show that iTAP/Frmd8 KO mice exhibit defects in inflammatory and intestinal epithelial barrier repair functions, but not the collateral defects associated with global ADAM17 loss. Furthermore, we show that iTAP/Frmd8 regulates cancer cell growth in a cell-autonomous manner and by modulating the tumor microenvironment. Our work suggests that pharmacological intervention at the level of iTAP/Frmd8 may be beneficial to target ADAM17 activity in specific compartments during chronic inflammatory diseases or cancer, while avoiding the collateral impact on the vital functions associated with the widespread inhibition of ADAM17.

The prognostic value of RHBDF2 in Pan-Cancer, and its correlation with cell Adhesion of Hepatocellular Carcinoma

The impact of RHBDF2 on the expression and potential function in many cancers is still unknown. Therefore, the expression and methylation modification of RHBDF2 were evaluated across TCGA cancers in this study. Moreover, two methods, COX regression and Kaplan-Meier, were utilized for analyses of the prognoses of RHBDF2 in patients. Besides, the association between RHBDF2 and immune microenvironment, mutation, tumor mutation burden and microsatellite instability was analyzed with Pearson correlation. We verified RHBDF2 expression in hepatocellular carcinoma (HCC) compared with normal cell and tissue samples, detected the effects of RHBDF2 knockdown on biological functions in HCC cells, and detected CD4, CD8 and CD68 expression in hepatocellular carcinoma tissues and paired normal tissues. Given these results, the significant mRNA overexpression and promoter hypomethylation of RHBDF2 in various tumor types was showed, and a clear relationship between RHBDF2 overexpression and unfavourable overall survival and progression-free survival was observed, including liver hepatocellular carcinoma (LIHC), glioma (GBMLGG) and pancreatic adenocarcinoma (PAAD). Additionally, hypomethylation of RHBDF2 can affect the overall survival in some tumors. Furthermore, a clear correlation between RHBDF2 and infiltration of immune cells, immune-related molecules, TMB and MSI was observed. Besides, RHBDF2 expression is upregulated in HCC cells and tissues, and RHBDF2 knockdown could decrease the cell adhesion ability of HCC cells. More importantly, the expression of CD4, CD8 and CD68 was higher in HCC tissues. Altogether, the research denoted that RHBDF2 can be a prognostic biomarker for cancers according to these results and participate in cell adhesion of HCC cells.

Elevated expression of receptors for EGF, PDGF, transferrin and folate within murine and human lupus nephritis kidneys

OBJECTIVE

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease where the body's immune system targets cells and tissue in numerous organs, including the kidneys. Lupus nephritis (LN) is a highly heterogeneous disease, and diagnosis is difficult because clinical manifestations vary widely among patients. Comprehensive proteomic studies reported recently in LN have identified several urinary proteins which are also cell-surface receptors. If indeed these receptor proteins are also hyper-expressed within the kidneys, ligands to these receptors may be useful for drug targeting.

METHODS

scRNA sequence data analysis and immunohistochemistry were performed on LN kidneys for expression of four implicated receptors, EGFR, FOL2R2, PDGF-RB, and TFRC.

RESULTS

In reported scRNA sequencing studies from 21 LN patients and 3 healthy control renal biopsies or renal-infiltrating immune cells from 24 LN biopsies, EGFR, FOLR2, PDGF-Rb, and TFRC were all hyper expressed within LN kidneys in comparison to healthy kidneys, either within resident renal cells or infiltrating leukocytes. Immunohistochemistry staining of murine lupus renal biopsies from lupus mice revealed EGFR, FOLR2, TFRC and PDGF-RB were elevated in LN kidneys. Immunohistochemistry staining of human Class II, Class III, and Class IV kidney tissue sections revealed EGFR, TFRC, and PDGF-RB were significantly elevated in proliferative LN kidneys.

CONCLUSION

These findings underscore the potential of EGFR, TFRC, FOLR2, and PDGF-RB as promising receptors for potential drug-targeting in LN.

Macrophages in Lupus Nephritis: Exploring a potential new therapeutic avenue

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE) that occurs in about half of patients. LN is characterized by glomerular deposition of immune complexes, leading to subendothelial, mesangial and subepithelial electron dense deposits, triggering immune cell infiltration and glomerular as well as tubulointerstitial injury. Monocytes and macrophages are abundantly present in inflammatory lesions, both in glomeruli and the tubulointerstitium. Here we discuss how monocytes and macrophages are involved in this process and how monocytes and macrophages may represent specific therapeutic targets to control LN.

Immunomodulatory role of metalloproteinase ADAM17 in tumor development

ADAM17 is a member of the a disintegrin and metalloproteinase (ADAM) family of transmembrane proteases involved in the shedding of some cell membrane proteins and regulating various signaling pathways. More than 90 substrates are regulated by ADAM17, some of which are closely relevant to tumor formation and development. Besides, ADAM17 is also responsible for immune regulation and its substrate-mediated signal transduction. Recently, ADAM17 has been considered as a major target for the treatment of tumors and yet its immunomodulatory roles and mechanisms remain unclear. In this paper, we summarized the recent understanding of structure and several regulatory roles of ADAM17. Importantly, we highlighted the immunomodulatory roles of ADAM17 in tumor development, as well as small molecule inhibitors and monoclonal antibodies targeting ADAM17.

1,25-dihydroxyvitamin D3 ameliorates lupus nephritis through inhibiting the NF-κB and MAPK signalling pathways in MRL/lpr mice

Background

Lupus nephritis (LN) is a common and serious complication of systemic lupus erythematosus (SLE). However, the aetiology and pathogenesis of LN remain unknown. 1,25-dihydroxyvitamin D3 [1,25-(OH)2-VitD3] is the active form of vitamin D, and it has been shown to perform important functions in inflammatory and immune-related diseases. In this study, we investigated the time-dependent effects of 1,25-dihydroxyvitamin D3 and explored the underlying mechanism in MRL/lpr mice, a well-studied animal model of LN.

Methods

Beginning at 8 weeks of age, 24-h urine samples were collected weekly to measure the levels of protein in the urine. We treated female MRL/lpr mice with 1,25-dihydroxyvitamin D3 (4 μg/kg) or 1% DMSO by intraperitoneal injection twice weekly for 3 weeks beginning at the age of 11 weeks. The mice were separately sacrificed, and serum and kidney samples were collected at the ages of 14, 16, 18, and 20 weeks to measure creatinine (Cr) levels, blood urea nitrogen (BUN) levels, histological damage, immunological marker (A-ds DNA, C1q, C3, IgG, IgM) levels, and inflammatory factor (TNF-α, IL-17, MCP-1) levels. Furthermore, the nuclear factor kappa B (NF-κB) and the mitogen-activated protein kinase (MAPK) signalling pathways were also assessed to elucidate the underlying mechanism.

Results

We found that MRL/lpr mice treated with 1,25-dihydroxyvitamin D3 displayed significantly attenuated LN. VitD3-treated mice exhibited significantly improved renal pathological damage and reduced proteinuria, BUN, SCr, A-ds DNA antibody and immune complex deposition levels (P < 0.05) compared with untreated MRL/lpr mice. Moreover, 1,25-dihydroxyvitamin D3 inhibited the complement cascade, inhibited the release of proinflammatory cytokines, such as TNF-α, IL-17, and MCP-1, and inhibited NF-κB and MAPK activation (P < 0.05).

Conclusion

1,25-dihydroxyvitamin D3 exerts a protective effect against LN by inhibiting the NF-κB and MAPK signalling pathways, providing a potential treatment strategy for LN. Interestingly, the NF-κB and MAPK signalling pathways are time-dependent mediators of LN and may be associated with lupus activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02870-z.

The Amphiregulin/EGFR axis protects from lupus nephritis via downregulation of pathogenic CD4+ T helper cell responses

Systemic lupus erythematosus (SLE) is a common autoimmune disorder with a complex and poorly understood immuno-pathogenesis. Lupus nephritis (LN) is a frequent and difficult to treat complication, which causes high morbidity and mortality. The multifunctional cytokine amphiregulin (AREG) has been implicated in SLE pathogenesis, but its function in LN currently remains unknown. We thus studied the model of pristane-induced LN and found increasing renal and systemic AREG expression during the course of disease. Importantly, renal injury was significantly aggravated in the absence of AREG, revealing a net anti-inflammatory role. Analyses of immune responses showed dual effects. On the one hand, AREG enhanced activation of pro-inflammatory myeloid cells, which however did not play a major role for the course of LN. More importantly, on the other hand, AREG strongly suppressed pathogenic cytokine production by T helper effector cells. This effect was more general in nature and could be reproduced in response to antigen immunization. Since AREG has been postulated to downregulate T cell responses via enhancing Treg suppressive capacity, we followed up on this aspect. Interestingly, however, in vitro studies revealed potential direct and Treg independent effects of AREG on T helper effector cells. In favor of this notion, we found significantly enhanced T cell responses and consecutive aggravation of LN, only if epidermal growth factor receptor (EGFR) signaling was abrogated in total T cells, but not if the EGFR was absent on Tregs alone. Finally, we also found enhanced AREG expression in plasma and renal biopsies of patients with LN, supporting the relevance of our findings for human disease. In summary, our data identify AREG as an anti-inflammatory mediator of LN via broad downregulation of pathogenic T cell immunity. These findings further highlight the AREG/EGFR axis as a potential therapeutic target.

The E3 ubiquitin-protein ligase Trim31 alleviates non-alcoholic fatty liver disease by targeting Rhbdf2 in mouse hepatocytes

Systemic metabolic syndrome significantly increases the risk of morbidity and mortality in patients with non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). However, no effective therapeutic strategies are available, practically because our understanding of its complicated pathogenesis is poor. Here we identify the tripartite motif-containing protein 31 (Trim31) as an endogenous inhibitor of rhomboid 5 homolog 2 (Rhbdf2), and we further determine that Trim31 directly binds to Rhbdf2 and facilitates its proteasomal degradation. Hepatocyte-specific Trim31 ablation facilitates NAFLD-associated phenotypes in mice. Inversely, transgenic or ex vivo gene therapy-mediated Trim31 gain-of-function in mice with NAFLD phenotypes virtually alleviates severe deterioration and progression of steatohepatitis. The current findings suggest that Trim31 is an endogenous inhibitor of Rhbdf2 and downstream cascades in the pathogenic process of steatohepatitis and that it may serve as a feasible therapeutical target for the treatment of NAFLD/NASH and associated metabolic disorders.

Nonalcoholic steatohepatitis (NASH) is a chronic liver disease with complex disease mechanisms. Here the authors report that the E3 ubiquitin-protein ligase Trim31 mitigates development of NASH via inhibition of rhomboid 5 homolog 2 (Rhbdf2) in mice.

Deficiency of inactive rhomboid protein 2 (iRhom2) attenuates diet-induced hyperlipidaemia and early atherogenesis

AIMS

Atherosclerosis is a chronic inflammatory disease of the arterial vessel wall and anti-inflammatory treatment strategies are currently pursued to lower cardiovascular disease burden. Modulation of recently discovered inactive rhomboid protein 2 (iRhom2) attenuates shedding of tumour necrosis factor-alpha (TNF-α) selectively from immune cells. The present study aims at investigating the impact of iRhom2 deficiency on the development of atherosclerosis.

METHODS AND RESULTS

Low-density lipoprotein receptor (LDLR)-deficient mice with additional deficiency of iRhom2 (LDLR-/-iRhom2-/-) and control (LDLR-/-) mice were fed a Western-type diet (WD) for 8 or 20 weeks to induce early or advanced atherosclerosis. Deficiency of iRhom2 resulted in a significant decrease in the size of early atherosclerotic plaques as determined in aortic root cross-sections. LDLR-/-iRhom2-/- mice exhibited significantly lower serum levels of TNF-α and lower circulating and hepatic levels of cholesterol and triglycerides compared to LDLR-/- mice at 8 weeks of WD. Analyses of hepatic bile acid concentration and gene expression at 8 weeks of WD revealed that iRhom2 deficiency prevented WD-induced repression of hepatic bile acid synthesis in LDLR-/- mice. In contrast, at 20 weeks of WD, plaque size, plaque composition, and serum levels of TNF-α or cholesterol were not different between genotypes.

CONCLUSION

Modulation of inflammation by iRhom2 deficiency attenuated diet-induced hyperlipidaemia and early atherogenesis in LDLR-/- mice. iRhom2 deficiency did not affect diet-induced plaque burden and composition in advanced atherosclerosis in LDLR-/- mice.

Congenital iRHOM2 deficiency causes ADAM17 dysfunction and environmentally directed immunodysregulatory disease

We report a pleiotropic disease due to loss-of-function mutations in RHBDF2, the gene encoding iRHOM2, in two kindreds with recurrent infections in different organs. One patient had recurrent pneumonia but no colon involvement, another had recurrent infectious hemorrhagic colitis but no lung involvement and the other two experienced recurrent respiratory infections. Loss of iRHOM2, a rhomboid superfamily member that regulates the ADAM17 metalloproteinase, caused defective ADAM17-dependent cleavage and release of cytokines, including tumor-necrosis factor and amphiregulin. To understand the diverse clinical phenotypes, we challenged Rhbdf2-/- mice with Pseudomonas aeruginosa by nasal gavage and observed more severe pneumonia, whereas infection with Citrobacter rodentium caused worse inflammatory colitis than in wild-type mice. The fecal microbiota in the colitis patient had characteristic oral species that can predispose to colitis. Thus, a human immunodeficiency arising from iRHOM2 deficiency causes divergent disease phenotypes that can involve the local microbial environment.

The pseudoprotease iRhom1 controls ectodomain shedding of membrane proteins in the nervous system

Proteolytic ectodomain shedding of membrane proteins is a fundamental mechanism to control the communication between cells and their environment. A key protease for membrane protein shedding is ADAM17, which requires a non-proteolytic subunit, either inactive Rhomboid 1 (iRhom1) or iRhom2 for its activity. While iRhom1 and iRhom2 are co-expressed in most tissues and appear to have largely redundant functions, the brain is an organ with predominant expression of iRhom1. Yet, little is known about the spatio-temporal expression of iRhom1 in mammalian brain and about its function in controlling membrane protein shedding in the nervous system. Here, we demonstrate that iRhom1 is expressed in mouse brain from the prenatal stage to adulthood with a peak in early postnatal development. In the adult mouse brain iRhom1 was widely expressed, including in cortex, hippocampus, olfactory bulb, and cerebellum. Proteomic analysis of the secretome of primary neurons using the hiSPECS method and of cerebrospinal fluid, obtained from iRhom1-deficient and control mice, identified several membrane proteins that require iRhom1 for their shedding in vitro or in vivo. One of these proteins was 'multiple-EGF-like-domains protein 10' (MEGF10), a phagocytic receptor in the brain that is linked to the removal of amyloid β and apoptotic neurons. MEGF10 was further validated as an ADAM17 substrate using ADAM17-deficient mouse embryonic fibroblasts. Taken together, this study discovers a role for iRhom1 in controlling membrane protein shedding in the mouse brain, establishes MEGF10 as an iRhom1-dependent ADAM17 substrate and demonstrates that iRhom1 is widely expressed in murine brain.

ADAM17 orchestrates Interleukin-6, TNFα and EGF-R signaling in inflammation and cancer

It was realized in the 1990s that some membrane proteins such as TNFα, both TNF receptors, ligands of the EGF-R and the Interleukin-6 receptor are proteolytically cleaved and are shed from the cell membrane as soluble proteins. The major responsible protease is a metalloprotease named ADAM17. So far, close to 100 substrates, including cytokines, cytokine receptors, chemokines and adhesion molecules of ADAM17 are known. Therefore, ADAM17 orchestrates many different signaling pathways and is a central signaling hub in inflammation and carcinogenesis. ADAM17 plays an important role in the biology of Interleukin-6 (IL-6) since the generation of the soluble Interleukin-6 receptor (sIL-6R) is needed for trans-signaling, which has been identified as the pro-inflammatory activity of this cytokine. In contrast, Interleukin-6 signaling via the membrane-bound Interleukin-6 receptor is mostly regenerative and protective. Probably due to its broad substrate spectrum, ADAM17 is essential for life and most of the few human individuals identified with ADAM17 gene defects died at young age. Although the potential of ADAM17 as a therapeutic target has been recognized, specific blockade of ADAM17 is not trivial since the metalloprotease domain of ADAM17 shares high structural homology with other proteases, in particular matrix metalloproteases. Here, the critical functions of ADAM17 in IL-6, TNFα and EGF-R pathways and strategies of therapeutic interventions are discussed.

Serum Amphiregulin and Heparin-Binding Epidermal Growth Factor as Biomarkers in Patients with Idiopathic Inflammatory Myopathy

Background. The epidermal growth factors amphiregulin (AREG) and heparin-binding epidermal growth factor (HB-EGF) are implicated in the pathogenesis of several autoimmune diseases, but their clinical and pathological roles in idiopathic inflammatory myopathy (IIM) are unclear. Methods. Serum AREG and HB-EGF levels were measured by ELISA in patients with IIM (n = 37), systemic sclerosis (n = 17), and rheumatoid arthritis (n = 10), and for seven age- and sex-matched healthy controls (HCs). Associations between serum AREG or HB-EGF levels and the clinical parameters were analyzed. Results. Serum AREG levels in IIM patients were significantly elevated compared to those in HCs (median, 20.7 and 10.7 pg/mL, respectively; p = 0.025). In particular, serum AREG levels in IIM patients with interstitial lung disease (ILD) were higher than those of HCs (22.4 pg/mL, p = 0.027). The disease duration in patients with elevated serum AREG levels was significantly shorter compared to those who had normal serum AREG levels (7 and 21 months, respectively; p = 0.0012). Serum HB-EGF levels were significantly increased in IIM patients with elevated CK levels (136.2 pg/mL; p = 0.020) and patients with anti-Mi-2 antibody (183.7 pg/mL; p = 0.045) compared to those in HCs (74.9 pg/mL). Conclusion. These results suggested that AREG could be a promising biomarker associated with early-phase IIM-related ILD, and that HB-EGF expression was associated with muscle injury and regeneration in IIM.

Key metalloproteinase-mediated pathways in the kidney

Matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs) belong to the metzincin family of zinc-containing multidomain molecules, and can act as soluble or membrane-bound proteases. These enzymes inactivate or activate other soluble or membrane-expressed mediator molecules, which enables them to control developmental processes, tissue remodelling, inflammatory responses and proliferative signalling pathways. The dysregulation of MMPs and ADAMs has long been recognized in acute kidney injury and in chronic kidney disease, and genetic targeting of selected MMPs and ADAMs in different mouse models of kidney disease showed that they can have detrimental and protective roles. In particular, MMP-2, MMP-7, MMP-9, ADAM10 and ADAM17 have been shown to have a mainly profibrotic effect and might therefore represent therapeutic targets. Each of these proteases has been associated with a different profibrotic pathway that involves tissue remodelling, Wnt-β-catenin signalling, stem cell factor-c-kit signalling, IL-6 trans-signalling or epidermal growth factor receptor (EGFR) signalling. Broad-spectrum metalloproteinase inhibitors have been used to treat fibrotic kidney diseases experimentally but more targeted approaches have since been developed, including inhibitory antibodies, to avoid the toxic side effects initially observed with broad-spectrum inhibitors. These advances not only provide a solid foundation for additional preclinical studies but also encourage further translation into clinical research.

Long non-coding RNA expression profiles in neutrophils revealed potential biomarker for prediction of renal involvement in SLE patients

OBJECTIVE

The long non-coding RNA plays an important role in inflammation and autoimmune diseases. The aim of this study is to screen and identify abnormally expressed lncRNAs in peripheral blood neutrophils of SLE patients as novel biomarkers and to explore the relationship between lncRNAs levels and clinical features, disease activity and organ damage.

METHODS

RNA-seq technology was used to screen differentially expressed lncRNAs in neutrophils from SLE patients and healthy donors. Based on the results of screening, candidate lncRNA levels in neutrophils of 88 SLE patients, 35 other connective disease controls, and 78 healthy controls were qualified by real-time quantitative polymerase chain reaction.

RESULTS

LncRNA expression profiling revealed 360 up-regulated lncRNAs and 224 down-regulated lncRNAs in neutrophils of SLE patients when compared with healthy controls. qPCR assay validated that the expression of Lnc-FOSB-1:1 was significantly decreased in neutrophils of SLE patients when compared with other CTD patients or healthy controls. It correlated negatively with SLE Disease Activity Index 2000 (SLEDAI-2K) score (r = -0.541, P < 0.001) and IFN scores (r = -0.337, P = 0.001). More importantly, decreased Lnc-FOSB-1:1 expression was associated with lupus nephritis. Lower baseline Lnc-FOSB-1:1 level was associated with higher risk of future renal involvement (within an average of 2.6 years) in patients without renal disease at baseline (P = 0.019).

CONCLUSION

LncRNA expression profile in neutrophils of SLE patients revealed differentially expressed lncRNAs. Validation study on Lnc-FOSB-1:1 suggest that it is a potential biomarker for prediction of near future renal involvement.

Targeted truncation of the ADAM17 cytoplasmic domain in mice results in protein destabilization and a hypomorphic phenotype

A disintegrin and metalloprotease 17 (ADAM17) is a cell-surface metalloprotease that serves as the principle sheddase for tumor necrosis factor α (TNFα), interleukin-6 receptor (IL-6R), and several ligands of the epidermal growth factor receptor (EGFR), regulating these crucial signaling pathways. ADAM17 activation requires its transmembrane domain, but not its cytoplasmic domain, and little is known about the role of this domain in vivo. To investigate, we used CRISPR-Cas9 to mutate the endogenous Adam17 locus in mice to produce a mutant ADAM17 lacking its cytoplasmic domain (Adam17Δcyto). Homozygous Adam17Δcyto animals were born at a Mendelian ratio and survived into adulthood with slightly wavy hair and curled whiskers, consistent with defects in ADAM17/EGFR signaling. At birth, Adam17Δcyto mice resembled Adam17−/− mice in that they had open eyes and enlarged semilunar heart valves, but they did not have bone growth plate defects. The deletion of the cytoplasmic domain resulted in strongly decreased ADAM17 protein levels in all tissues and cells examined, providing a likely cause for the hypomorphic phenotype. In functional assays, Adam17Δcyto mouse embryonic fibroblasts and bone-marrow-derived macrophages had strongly reduced ADAM17 activity, consistent with the reduced protein levels. Nevertheless, ADAM17Δcyto could be stimulated by PMA, a well-characterized posttranslational activator of ADAM17, corroborating that the cytoplasmic domain of endogenous ADAM17 is not required for its rapid response to PMA. Taken together, these results provide the first evidence that the cytoplasmic domain of ADAM17 plays a pivotal role in vivo in regulating ADAM17 levels and function.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

iRHOM2: A Regulator of Palmoplantar Biology, Inflammation, and Viral Susceptibility

The palmoplantar epidermis is a specialized area of the skin that undergoes high levels of mechanical stress. The palmoplantar keratinization and esophageal cancer syndrome, tylosis with esophageal cancer, is linked to mutations in RHBDF2 encoding the proteolytically inactive rhomboid protein, iRhom2. Subsequently, iRhom2 was found to affect palmoplantar thickening to modulate the stress keratin response and to mediate context-dependent stress pathways by p63. iRhom2 is also a direct regulator of the sheddase, ADAM17, and the antiviral adaptor protein, stimulator of IFN genes. In this perspective, the pleiotropic functions of iRhom2 are discussed with respect to the skin, inflammation, and the antiviral response.

Lipidomics Revealed Aberrant Metabolism of Lipids Including FAHFAs in Renal Tissue in the Progression of Lupus Nephritis in a Murine Model

Lupus nephritis (LN) is an inflammatory renal disease of patients with systemic lupus erythematosus with lots of immune complexes deposited in kidneys. Accumulated studies have demonstrated the close relationships among dyslipidaemia, inflammation, and autoimmune response, and oxidative stress in the patients. Lipids play numerous important roles in biological process and cellular functions. Herein, shotgun lipidomics was employed to quantitatively analyze cellular lipidomes in the renal tissue of MRL/lpr mice in the progression of LN (including pre-LN and LN state) with/without treated with glucocorticoids (GCs). The levels of cytokines (i.e., TNF-α (Tumor necrosis factor alpha) and IL-6 (Interleukin 6)) in the serum were measured by ELISA (enzyme-linked immunosorbent assay) kits. Renal histopathological changes and C3 deposition in the glomeruli of the mice were also determined. Lipidomics analysis revealed that the ectopic fat deposition and the aberrant metabolism of lipids that were relevant to oxidative stress (e.g., 4-hydroxyalkenal, ceramide, lysophospholipid species, etc.) always existed in the development of LN. Moreover, the anti-inflammatory FAHFA (fatty acid ester of hydroxyl fatty acid) species in the kidney tissue could largely reflect the severity of LN. Thus, they were a potential early biomarker for LN. In addition, the study also revealed that treatment with GCs could prevent the progression of LN, but greatly aggravate the aberrant metabolism of the lipids, particularly when used for a long time.

Strategies to Target ADAM17 in Disease: From its Discovery to the iRhom Revolution

For decades, disintegrin and metalloproteinase 17 (ADAM17) has been the object of deep investigation. Since its discovery as the tumor necrosis factor convertase, it has been considered a major drug target, especially in the context of inflammatory diseases and cancer. Nevertheless, the development of drugs targeting ADAM17 has been harder than expected. This has generally been due to its multifunctionality, with over 80 different transmembrane proteins other than tumor necrosis factor α (TNF) being released by ADAM17, and its structural similarity to other metalloproteinases. This review provides an overview of the different roles of ADAM17 in disease and the effects of its ablation in a number of in vivo models of pathological conditions. Furthermore, here, we comprehensively encompass the approaches that have been developed to accomplish ADAM17 selective inhibition, from the newest non-zinc-binding ADAM17 synthetic inhibitors to the exploitation of iRhom2 to specifically target ADAM17 in immune cells.

The Threshold Effect: Lipopolysaccharide-Induced Inflammatory Responses in Primary Macrophages Are Differentially Regulated in an iRhom2-Dependent Manner

A well-controlled innate immune response is characterized by a rapid yet self-limiting inflammatory response. Although much is known about the range of inflammatory stimuli capable of triggering an innate immune response, the mechanisms which govern the degree of inflammation induced by inflammatory insults and the mechanisms in place to reset or maintain homeostasis are poorly understood. Tumor necrosis factor (TNF) is a potent early response pro-inflammatory cytokine produced by immune cells following a broad range of insults spanning autoimmunity and metabolic diseases to pathogenic infections. Previous studies have shown that a disintegrin and metalloproteinase (ADAM) 17 controls the release of soluble TNF and epidermal growth factor receptor signaling. Utilizing a genetic model of ADAM17 deficiency through the deletion of its regulator, the inactive rhomboid 2 (iRhom2), we show that loss of ADAM17 activity in innate immune cells leads to decreased expression of various cytokines in response to low levels of pathogen-associated molecular pattern (PAMP) stimulation but not at high-dose stimulation. In addition, TNF receptor (TNFR) 1/2-deficient bone marrow-derived macrophages yielded significantly reduced TNF expression following low levels of PAMP stimulation, suggesting that signaling through the TNFRs in immune cells drives a feed-forward regulatory mechanism wherein low levels of TNF allow sustained enhancement of TNF expression in an iRhom2/ADAM17-dependent manner. Thus, we demonstrate that inflammatory expression of TNF and IL1β is differentially regulated following high or low doses of PAMP stimulation, invoking the activation of a previously unknown regulatory mechanism of inflammation.

Decreased serum ACE2 levels in patients with connective tissue diseases

Objective

To evaluate serum concentration and activity of angiotensin-converting enzyme 2 (ACE2) in patients with connective tissue diseases (CTDs).

Methods

Serum samples from healthy subjects and patients with SLE, systemic sclerosis (SSc), primary Sjögren’s syndrome (SS) and RA were collected. The concentration and activity of ACE2 were measured by ELISA and fluorometric method, respectively, and analysed for associations with clinical features and concurrent medications.

Results

In total, 66 SLE, 55 SSc, 31 SS and 31 RA patients were involved. ACE2 concentration was significantly decreased in patients with either of the four CTDs compared with healthy subjects. The concentration was not linked to special clinical features expect that it was slightly lower in patients with lupus nephritis than those without. In SLE patients, ACE2 concentration elevated with the increase of glucocorticoids, and was not associated with other treatments. Different from the concentration, ACE2 activity was increased in CTD patients. A weak correlation of ACE2 activity with SLE disease activity index score was also observed.

Conclusion

The clinical significance of ACE2 concentration and activity looks quite different among CTD patients. Preliminary data suggest ACE2 levels are not affected by most of the treatments.

Neonatal Hyperoxia Downregulates Claudin-4, Occludin, and ZO-1 Expression in Rat Kidney Accompanied by Impaired Proximal Tubular Development

Hyperoxia is essential to manage in preterm infants but causes injury to immature kidney. Previous study indicates that hyperoxia causes oxidative damage to neonatal kidney and impairs renal development. However, the underlying mechanisms by which neonatal hyperoxia effects on immature kidney still need to be elucidated. Tight junction, among which the representative proteins are claudin-4, occludin, and ZO-1, plays a crucial role in nephrogenesis and maintaining renal function. Inflammatory cytokines are involved in the pleiotropic regulation of tight junction proteins. Here, we investigated how neonatal hyperoxia affected the expression of key tight junction proteins and inflammatory factors (IL-6 and TNF-α) in the developing rat kidneys and elucidated their correlation with renal injury. We found claudin-4, occludin, and zonula occludens-1 (ZO-1) expression in proximal tubules was significantly downregulated after neonatal hyperoxia. The expression of these tight junction proteins was positively correlated with that of IL-6 and TNF-α, while claudin-4 expression was positively correlated with injury score of proximal tubules in mature kidneys. These findings indicated that impaired expression of tight junction proteins in kidney might be a potential mechanism of hyperoxia-induced nephrogenic disorders. It provides new insights to further study oxidative renal injury and development disorders and will be helpful for seeking potential therapeutics for hyperoxia-induced renal injury in the future.

The Role of iRhom2 in Metabolic and Cardiovascular-Related Disorders

Chronic obesity is associated with metabolic imbalance leading to diabetes, dyslipidemia, and cardiovascular diseases (CVDs), in which inflammation is caused by exposure to inflammatory stimuli, such as accumulating sphingolipid ceramides or intracellular stress. This inflammatory response is likely to be prolonged by the effects of dietary and blood cholesterol, thereby leading to chronic low-grade inflammation and endothelial dysfunction. Elevated levels of pro-inflammatory cytokines such as tumor necrosis factor (TNF) are predictive of CVDs and have been widely studied for potential therapeutic strategies. The release of TNF is controlled by a disintegrin and metalloprotease (ADAM) 17 and both are positively associated with CVDs. ADAM17 also cleaves most of the ligands of the epidermal growth factor receptor (EGFR) which have been associated with hypertension, atherogenesis, vascular dysfunction, and cardiac remodeling. The inactive rhomboid protein 2 (iRhom2) regulates the ADAM17-dependent shedding of TNF in immune cells. In addition, iRhom2 also regulates the ADAM17-mediated cleavage of EGFR ligands such as amphiregulin and heparin-binding EGF-like growth factor. Targeting iRhom2 has recently become a possible alternative therapeutic strategy in chronic inflammatory diseases such as lupus nephritis and rheumatoid arthritis. However, what role this intriguing interacting partner of ADAM17 plays in the vasculature and how it functions in the pathologies of obesity and associated CVDs, are exciting questions that are only beginning to be elucidated. In this review, we discuss the role of iRhom2 in cardiovascular-related pathologies such as atherogenesis and obesity by providing an evaluation of known iRhom2-dependent cellular and inflammatory pathways.

Dysfunctional Rhbdf2 of proopiomelanocortin mitigates ambient particulate matter exposure-induced neurological injury and neuron loss by antagonizing oxidative stress and inflammatory reaction

Ambient particulate matter (PM_2.5)-induced metabolic syndromes is a critical contributor to the pathological processes of neurological diseases, but the underlying molecular mechanisms remain poorly understood. The rhomboid 5 homolog 2 (Rhbdf2), an essential regulator in the production of TNF-α, has recently been confirmed to exhibit a key role in regulating inflammation-associated diseases. Thus, we examined whether Rhbdf2 contributes to hypothalamic inflammation via NF-κB associated inflammation activation in long-term PM_2.5-exposed mice. Specifically, proopiomelanocortin-specific Rhbdf2 deficiency (Rhbdf2^Pomc) and corresponding littermates control mice were used for the current study. After 24 weeks of PM_2.5 inhalation, systemic-metabolism disorder was confirmed in WT mice in terms of impaired glucose tolerance, increased insulin resistance, and high blood pressure. Markedly, PM_2.5-treated Rhbdf2^Pomc mice displayed a significantly opposite trend in these parameters compared with those of the controls group. We next confirmed hypothalamic injury accompanied by abnormal POMC neurons loss, as indicated by increased inflammatory cytokines, chemokines, and oxidative-stress levels and decreased antioxidant activity. These results were further supported by blood routine examination. In summary, our findings suggest that Rhbdf2 plays an important role in exacerbating PM_2.5-stimulated POMC neurons loss associated hypothalamic injury, thus providing a possible target for blocking pathological development of air pollution-associated diseases.

IL-38: A novel cytokine in systemic lupus erythematosus pathogenesis

IL‐38 is a newly identified cytokine that belongs to the IL‐1 family. In our previous study, we found elevated plasma levels of IL‐38 in patients with systemic lupus erythematosus (SLE). However, the clear relationship of IL‐38 expression in plasma, peripheral blood mononuclear cells (PBMCs) and clinical and laboratory features needs elucidation. Additionally, we evaluated the possible role of IL‐38 in regulating production of inflammatory cytokines in PBMCs in vitro. A pristane‐induced murine lupus model was used to further demonstrate the effects of IL‐38 on cytokines in vivo and discuss the significance of IL‐38 in lupus development. The results showed that mRNA expression of IL‐38 in PBMCs of patients with SLE was elevated compared with volunteers, and expression of IL‐38 in both plasma and PBMCs was strongly related to clinical features, such as haematuria and proteinuria, and correlated with a SLEDAI score. Plasma levels of TNF‐α, IL‐1β, IL‐6 and IL‐23 were elevated in patients with SLE and were related to plasma levels of IL‐38. In vitro, PBMCs of patients with SLE stimulated with IL‐38 showed a decreased expression of the four inflammatory cytokines compared with PBMCs of patients without treatment. Interestingly, IL‐38 administration in lupus mice significantly reduced the development of lupus, such as reduced proteinuria, improved histological examinations of the kidneys and down‐regulated inflammatory cytokines. In conclusion, IL‐38 may suppress synthesis of pro‐inflammatory cytokines and therefore regulate lupus pathogenesis.

iRhom2: An Emerging Adaptor Regulating Immunity and Disease

The rhomboid family are evolutionary conserved intramembrane proteases. Their inactive members, iRhom in Drosophila melanogaster and iRhom1 and iRhom2 in mammals, lack the catalytic center and are hence labelled “inactive” rhomboid family members. In mammals, both iRhoms are involved in maturation and trafficking of the ubiquitous transmembrane protease a disintegrin and metalloprotease (ADAM) 17, which through cleaving many biologically active molecules has a critical role in tumor necrosis factor alpha (TNFα), epidermal growth factor receptor (EGFR), interleukin-6 (IL-6) and Notch signaling. Accordingly, with iRhom2 having a profound influence on ADAM17 activation and substrate specificity it regulates these signaling pathways. Moreover, iRhom2 has a role in the innate immune response to both RNA and DNA viruses and in regulation of keratin subtype expression in wound healing and cancer. Here we review the role of iRhom2 in immunity and disease, both dependent and independent of its regulation of ADAM17.

MicroRNA-16 directly binds to DEC2 and inactivates the TLR4 signaling pathway to inhibit lupus nephritis-induced kidney tissue hyperplasia and mesangial cell proliferation

Lupus nephritis (LN) is the most serious manifestation of systemic lupus erythematosus (SLE) and a major risk of mortality. This research focused on the function of microRNA-16 (miR-16) in LN development. Fcgamma receptor II-b-deficient (Fcgr2b^-/-) mice with the natural potential to develop SLE- and LN-like diseases were used. Gain- and loss-of-function studies were performed to explore the function of miR-16 in pathological symptoms in mouse kidney tissues and the proliferation of mesangial cells (SV40 MES-13). The putative downstream molecules of miR-16 were explored. Consequently, poor expression of miR-16 was found in kidney tissues. Upregulation of miR-16 inhibited tissue hyperplasia, inflammatory infiltration, glomerular injury and fibrosis but increased cell apoptosis in mouse kidney tissues, and it inhibited proliferation but promoted apoptosis of MES-13 cells as well. miR-16 directly bound to DEC2 and inactivated the TLR4 signaling. DEC2 blocked the protective roles of miR-16 in MES-13 cells. The enhanced proliferation in MES-13 cells following miR-16 inhibition was reversed by chloroquine phosphate, a TLR4 antagonist. To sum up, miR-16 was evidenced to have a potent protective capacity in LN through relieving the LN symptoms in kidney tissues and reducing proliferation of mesangial cells, during which DEC2 silencing and TLR4 signaling deficit were involved.

Amphiregulin Aggravates Glomerulonephritis via Recruitment and Activation of Myeloid Cells

BACKGROUND

Recent studies have identified the EGF receptor (EGFR) ligand amphiregulin (AREG) as an important mediator of inflammatory diseases. Both pro- and anti-inflammatory functions have been described, but the role of AREG in GN remains unknown.

METHODS

The nephrotoxic nephritis model of GN was studied in AREG^-/- mice after bone marrow transplantation, and in mice with myeloid cell-specific EGFR deficiency. Therapeutic utility of AREG neutralization was assessed. Furthermore, AREG's effects on renal cells and monocytes/macrophages (M/M) were analyzed. Finally, we evaluated AREG expression in human renal biopsies.

RESULTS

Renal AREG mRNA was strongly upregulated in murine GN. Renal resident cells were the most functionally relevant source of AREG. Importantly, the observation that knockout mice showed significant amelioration of disease indicates that AREG is pathogenic in GN. AREG enhanced myeloid cell responses via inducing chemokine and colony stimulating factor 2 (CSF2) expression in kidney resident cells. Furthermore, AREG directly skewed M/M to a proinflammatory M1 phenotype and protected them from apoptosis. Consequently, anti-AREG antibody treatment dose-dependently ameliorated GN. Notably, selective abrogation of EGFR signaling in myeloid cells was sufficient to protect against nephritis. Finally, strong upregulation of AREG expression was also detected in kidneys of patients with two forms of crescentic GN.

CONCLUSIONS

AREG is a proinflammatory mediator of GN via (1) enhancing renal pathogenic myeloid cell infiltration and (2) direct effects on M/M polarization, proliferation, and cytokine secretion. The AREG/EGFR axis is a potential therapeutic target for acute GN.

Macrophage metabolic reprogramming presents a therapeutic target in lupus nephritis

IgG antibodies cause inflammation and organ damage in autoimmune diseases such as systemic lupus erythematosus (SLE). We investigated the metabolic profile of macrophages isolated from inflamed tissues in immune complex (IC)-associated diseases, including SLE and rheumatoid arthritis, and following IgG Fcγ receptor cross-linking. We found that human and mouse macrophages undergo a switch to glycolysis in response to IgG IC stimulation, mirroring macrophage metabolic changes in inflamed tissue in vivo. This metabolic reprogramming was required to generate a number of proinflammatory mediators, including IL-1β, and was dependent on mTOR and hypoxia-inducible factor (HIF)1α. Inhibition of glycolysis, or genetic depletion of HIF1α, attenuated IgG IC-induced activation of macrophages in vitro, including primary human kidney macrophages. In vivo, glycolysis inhibition led to a reduction in kidney macrophage IL-1β and reduced neutrophil recruitment in a murine model of antibody-mediated nephritis. Together, our data reveal the molecular mechanisms underpinning FcγR-mediated metabolic reprogramming in macrophages and suggest a therapeutic strategy for autoantibody-induced inflammation, including lupus nephritis.

Update on the cellular and molecular aspects of lupus nephritis

Recent progress has highlighted the involvement of a variety of innate and adaptive immune cells in lupus nephritis. These include activated neutrophils producing extracellular chromatin traps that induce type I interferon production and endothelial injury, metabolically-rewired IL-17-producing T-cells causing tissue inflammation, follicular and extra-follicular helper T-cells promoting the maturation of autoantibody-producing B-cells that may also sustain the formation of germinal centers, and alternatively activated monocytes/macrophages participating in tissue repair and remodeling. The role of resident cells such as podocytes and tubular epithelial cells is increasingly recognized in regulating the local immune responses and determining the kidney function and integrity. These findings are corroborated by advanced, high-throughput genomic studies, which have revealed an unprecedented amount of data highlighting the molecular heterogeneity of immune and non-immune cells implicated in lupus kidney disease. Importantly, this research has led to the discovery of putative pathogenic pathways, enabling the rationale design of novel treatments.

The molecular, cellular and pathophysiological roles of iRhom pseudoproteases

iRhom proteins are catalytically inactive relatives of rhomboid intramembrane proteases. There is a rapidly growing body of evidence that these pseudoenzymes have a central function in regulating inflammatory and growth factor signalling and consequent roles in many diseases. iRhom pseudoproteases have evolved new domains from their proteolytic ancestors, which are integral to their modular regulation and functions. Although we cannot yet conclude the full extent of their molecular and cellular mechanisms, there is a clearly emerging theme that they regulate the stability and trafficking of other membrane proteins. In the best understood case, iRhoms act as regulatory cofactors of the ADAM17 protease, controlling its function of shedding cytokines and growth factors. It seems likely that as the involvement of iRhoms in human diseases is increasingly recognized, they will become the focus of pharmaceutical interest, and here we discuss what is known about their molecular mechanisms and relevance in known pathologies.

Protecting the kidney in systemic lupus erythematosus: from diagnosis to therapy

Lupus nephritis (LN) is a common manifestation of systemic lupus erythematosus that can lead to irreversible renal impairment. Although the prognosis of LN has improved substantially over the past 50 years, outcomes have plateaued in the USA in the past 20 years as immunosuppressive therapies have failed to reverse disease in more than half of treated patients. This failure might reflect disease complexity and heterogeneity, as well as social and economic barriers to health-care access that can delay intervention until after damage has already occurred. LN progression is still poorly understood and involves multiple cell types and both immune and non-immune mechanisms. Single-cell analysis of intrinsic renal cells and infiltrating cells from patients with LN is a new approach that will help to define the pathways of renal injury at a cellular level. Although many new immune-modulating therapies are being tested in the clinic, the development of therapies to improve regeneration of the injured kidney and to prevent fibrosis requires a better understanding of the mechanisms of LN progression. This mechanistic understanding, together with the development of clinical measures to evaluate risk and detect early disease and better access to expert health-care providers, should improve outcomes for patients with LN.

Gene-function studies in systemic lupus erythematosus

PURPOSE OF REVIEW

The aim of this review is to discuss recent developments in our understanding of how systemic lupus erythematosus (SLE)-associated genes contribute to autoimmunity.

RECENT FINDINGS

Gene-function studies have revealed mechanisms through which SLE-associated alleles of IFIH1, TNFAIP3, IRF5, and PRDM1 likely contribute to the development of autoimmunity. Novel research has identified Mac-1 (encoded by ITGAM), CaMK4, and iRhom2 as plausible therapeutic targets in lupus nephritis.

SUMMARY

The work discussed in this review has broad implications for our understanding of the pathogenesis of SLE and for the development of novel therapeutic strategies.

Inactive Rhomboid Protein 2 Mediates Intestinal Inflammation by Releasing Tumor Necrosis Factor-α

BACKGROUND

Tumor necrosis factor (TNF)-α is a major proinflammatory cytokine that plays a key role in inflammatory bowel disease (IBD). Inactive rhomboid protein 2 (iRhom2) is essential for activating TNF-α-converting enzyme (TACE) in immune cells, which regulates TNF-α release. The aim of the study was to investigate the role of iRhom2 in intestinal inflammation in IBD.

METHODS

The expression of iRhom2 and TACE in lipopolysaccharide (LPS)-stimulated COLO 205 and RAW 264.7 cells was assessed by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. The expression of iRhom2 and TACE in the colonic tissue of IBD patients and 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-treated mice was determined by RT-PCR and immunohistochemistry. To assess the role of iRhom2 in intestinal inflammation, colitis was induced in wild-type and iRhom2-/- mice by the administration of TNBS enema.

RESULTS

In LPS-stimulated COLO 205 and RAW 264.7 cells, the mRNA and protein levels of TACE and iRhom2 were upregulated. The expression of TACE and iRhom2 in the colon of the IBD patients and TNBS-treated mice was significantly enhanced. The inflammatory cells that expressed high levels of iRhom2 in the colon were identified as macrophages. Finally, iRhom2 deficiency ameliorated TNBS-induced colitis by inhibiting TNF-α release.

CONCLUSIONS

iRhom2 has an important role in intestinal inflammation through TNF-α secretion in immune cells, which suggests that iRhom2 could be a novel therapeutic target for IBD.

LNA-anti-miR-150 ameliorated kidney injury of lupus nephritis by inhibiting renal fibrosis and macrophage infiltration

Background

The prevalence of lupus nephritis (LN) remains high despite various emerging monoclonal antibodies against with targeting systemic lupus erythematosus (SLE). Renal fibrosis is the main feature of late stage LN, and novel therapeutic agents are still needed. We previously reported that microRNA (miR)-150 increases in renal biopsies of American LN patients and that miR-150 agonist promotes fibrosis in cultured kidney cells. Presently, we aim to verify whether locked nucleic acid (LNA)-anti-miR-150 can ameliorate LN in mice and to investigate its corresponding mechanisms.

Methods

We first observed natural history and renal miR-150 expression in female Fcgr2b^−/− mice of a spontaneously developed LN model. We then verified miR-150 renal absorption and determined the dose of the suppressed miR-150 by subcutaneous injection of LNA-anti-miR-150 (2 and 4 mg/kg). Thirdly, we investigated the therapeutic effects of LNA-anti-miR-150 (2 mg/kg for 8 weeks) on LN mice and the corresponding mechanisms by studying fibrosis-related genes, cytokines, and kidney resident macrophages. Lastly, we detected the expression of renal miR-150 and the mechanism-associated factors in renal biopsies from new onset untreated LN patients.

Results

Fcgr2b^−/− mice developed SLE indicated by positive serum autoantibodies at age 19 weeks and LN demonstrated by proteinuria at age 32 weeks. Renal miR-150 was overexpressed in LN mice compared to wild type mice. FAM-labeled LNA-anti-miR-150 was absorbed by both glomeruli and renal tubules. LNA-anti-miR-150 suppressed the elevated renal miR-150 levels in LN mice compared to the scrambled LNA without systemic toxicity. Meanwhile, serum double strand-DNA antibody, proteinuria, and kidney injury were ameliorated. Importantly, the elevated renal pro-fibrotic genes (transforming growth factor-β1, α-smooth muscle antibody, and fibronectin) and decreased anti-fibrotic gene suppressor of cytokine signal 1 were both reversed. Renal pro-inflammatory cytokines (interferon-γ, interleukin-6, and tumor necrosis factor-α) and macrophages were also decreased. In addition, the changes of renal miR-150 and associated proteins shown in LN mice were also seen in human subjects.

Conclusions

LNA-anti-miR-150 may be a promising novel therapeutic agent for LN in addition to the current emerging monoclonal antibodies, and its renal protective mechanism may be mediated by anti-fibrosis and anti-inflammation as well as reduction of the infiltrated kidney resident macrophages.

Lupus nephritis: challenges and progress

PURPOSE OF REVIEW

The management of lupus nephritis remains unsatisfactory due to insufficiently effective treatment regimens and the dearth of reliable predictors of disease onset or progression to guide individualized therapeutic decisions. This review summarizes new findings related to lupus nephritis over the last 18 months and discusses clinical needs that should be considered to advance trials of mechanism-based therapeutic strategies.

RECENT FINDINGS

Collaborative teams are addressing how to improve disease definitions and are developing predictive models for disease onset, disease response and risk of flare in individual patients. More attention is being paid to clinical trial design. Advanced technologic approaches are allowing the analysis of small amounts of human tissue and urine in unprecedented detail so as to discover new pathogenic mechanisms and identify disease biomarkers. Novel therapies continue to be tested in disease models and include new strategies to protect renal tissue from cell damage and fibrosis.

SUMMARY

The collaborative efforts of patients, clinical and translational researchers, the pharmaceutical industry and funding sources are needed to advance therapies for lupus nephritis. Specialized clinical centers can then deliver optimal and more personalized patient care that will improve patient outcomes.

iRhom2 inhibits bile duct obstruction-induced liver fibrosis

Chronic liver disease can induce prolonged activation of hepatic stellate cells, which may result in liver fibrosis. Inactive rhomboid protein 2 (iRhom2) is required for the maturation of A disintegrin and metalloprotease 17 (ADAM17, also called TACE), which is responsible for the cleavage of membrane-bound tumor necrosis factor-α (TNF-α) and its receptors (TNFRs). Here, using the murine bile duct ligation (BDL) model, we showed that the abundance of iRhom2 and activation of ADAM17 increased during liver fibrosis. Consistent with this, concentrations of ADAM17 substrates were increased in plasma samples from mice after BDL and in patients suffering from liver cirrhosis. We observed increased liver fibrosis, accelerated disease progression, and an increase in activated stellate cells after BDL in mice lacking iRhom2 (Rhbdf2^-/- ) compared to that in controls. In vitro primary mouse hepatic stellate cells exhibited iRhom2-dependent shedding of the ADAM17 substrates TNFR1 and TNFR2. In vivo TNFR shedding after BDL also depended on iRhom2. Treatment of Rhbdf2^-/- mice with the TNF-α inhibitor etanercept reduced the presence of activated stellate cells and alleviated liver fibrosis after BDL. Together, these data suggest that iRhom2-mediated inhibition of TNFR signaling protects against liver fibrosis.

Role of ADAM17 in kidney disease

It is known that the renin-angiotensin system plays a major role in the pathophysiology of cardiovascular disease and renal injury. Within the renin-angiotensin system, angiotensin-converting enzyme 2 (ACE2) cleaves ANG II to generate ANG(1–7) peptide, which counteracts the adverse effects of ANG II accumulation. ACE2 can undergo cleavage or shedding to release the catalytically active ectodomain into the circulation by a disintegrin and metalloprotease (ADAM)17, also known as TNF-α-converting enzyme. ADAM17 is involved in many pathological processes such as cancer, inflammatory diseases, neurological diseases, cardiovascular diseases, atherosclerosis, diabetes, and hypertension. Clinical and experimental studies have shown that ADAM17 is involved in chronic kidney disease (CKD) with a proinflammatory and profibrotic role, suggesting that it could be an important mediator of CKD progression. ADAM17 inhibition attenuates fibrosis and inflammation, suggesting that its inhibition may be a possible new valuable therapeutic tool in fibrotic kidney disease treatment. In addition, in renal disease, some experimental studies have demonstrated that ADAM17 is differently expressed in the kidney. Thus, ADAM17 is highly expressed in distal renal tubules and increased in the whole kidney in diabetic models. In this article, we will review the role of ADAM17 under physiological and pathological conditions. We will mainly focus on the importance of ADAM17 in the context of CKD.

Novel functions of inactive rhomboid proteins in immunity and disease

iRhoms are related to a family of intramembrane serine proteinases called rhomboids but lack proteolytic activity. In mammals, there are two iRhoms, iRhom1 and iRhom2, which have similar domain structures and overlapping specificities as well as distinctive functions. These catalytically inactive rhomboids are essential regulators for the maturation and trafficking of the disintegrin metalloprotease ADAM17 from the endoplasmic reticulum to the cell surface, and are required for the cleavage and release of a variety of membrane-associated proteins, including the IL-6 receptor, l-selectin, TNF, and EGFR ligands. iRhom2-dependent regulation of ADAM17 function has been recently implicated in the development and progression of several autoimmune diseases including rheumatoid arthritis, lupus nephritis, as well as hemophilic arthropathy. In this review, we discuss our current understanding of iRhom biology, their implications in autoimmune pathologies, and their potential as therapeutic targets.