Regulation of age-associated B cells by IRF5 in systemic autoimmunity.

Age-associated B cells (ABCs) are a subset of B cells dependent on the transcription factor T-bet that accumulate prematurely in autoimmune settings. The pathways that regulate ABCs in autoimmunity are largely unknown. SWAP-70 and DEF6 (also known as IBP or SLAT) are the only two members of the SWEF family, a unique family of Rho GTPase-regulatory proteins that control both cytoskeletal dynamics and the activity of the transcription factor IRF4. Notably, DEF6 is a newly identified human risk variant for systemic lupus erythematosus. Here we found that the lupus syndrome that developed in SWEF-deficient mice was accompanied by the accumulation of ABCs that produced autoantibodies after stimulation. ABCs from SWEF-deficient mice exhibited a distinctive transcriptome and a unique chromatin landscape characterized by enrichment for motifs bound by transcription factors of the IRF and AP-1 families and the transcription factor T-bet. Enhanced ABC formation in SWEF-deficient mice was controlled by the cytokine IL-21 and IRF5, whose variants are strongly associated with lupus. The lack of SWEF proteins led to dysregulated activity of IRF5 in response to stimulation with IL-21. These studies thus elucidate a previously unknown signaling pathway that controls ABCs in autoimmunity.

Shifting diets and the rise of male-biased inequality on the Central Plains of China during Eastern Zhou.

Farming domesticated millets, tending pigs, and hunting constituted the core of human subsistence strategies during Neolithic Yangshao (5000-2900 BC). Introduction of wheat and barley as well as the addition of domesticated herbivores during the Late Neolithic (∼2600-1900 BC) led to restructuring of ancient Chinese subsistence strategies. This study documents a dietary shift from indigenous millets to the newly introduced cereals in northcentral China during the Bronze Age Eastern Zhou Dynasty (771-221 BC) based on stable isotope analysis of human and animal bone samples. Our results show that this change affected females to a greater degree than males. We find that consumption of the newly introduced cereals was associated with less consumption of animal products and a higher rate of skeletal stress markers among females. We hypothesized that the observed separation of dietary signatures between males and females marks the rise of male-biased inequality in early China. We test this hypothesis by comparing Eastern Zhou human skeletal data with those from Neolithic Yangshao archaeological contexts. We find no evidence of male-female inequality in early farming communities. The presence of male-biased inequality in Eastern Zhou society is supported by increased body height difference between the sexes as well as the greater wealth of male burials.

Glucocorticoid Signaling: An Update from a Genomic Perspective.

Glucocorticoid hormones (GC) regulate essential physiological functions including energy homeostasis, embryonic and postembryonic development, and the stress response. From the biomedical perspective, GC have garnered a tremendous amount of attention as highly potent anti-inflammatory and immunosuppressive medications indispensable in the clinic. GC signal through the GC receptor (GR), a ligand-dependent transcription factor whose structure, DNA binding, and the molecular partners that it employs to regulate transcription have been under intense investigation for decades. In particular, next-generation sequencing-based approaches have revolutionized the field by introducing a unified platform for a simultaneous genome-wide analysis of cellular activities at the level of RNA production, binding of transcription factors to DNA and RNA, and chromatin landscape and topology. Here we describe fundamental concepts of GC/GR function as established through traditional molecular and in vivo approaches and focus on the novel insights of GC biology that have emerged over the last 10 years from the rapidly expanding arsenal of system-wide genomic methodologies.

Targeting the RhoA-ROCK pathway to reverse T-cell dysfunction in SLE.

OBJECTIVES: Deregulated production of interleukin (IL)-17 and IL-21 contributes to the pathogenesis of autoimmune disorders such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Production of IL-17 and IL-21 can be regulated by ROCK2, one of the two Rho kinases. Increased ROCK activation was previously observed in an SLE cohort. Here, we evaluated ROCK activity in a new SLE cohort, and an RA cohort, and assessed the ability of distinct inhibitors of the ROCK pathway to suppress production of IL-17 and IL-21 by SLE T cells or human Th17 cells. METHODS: ROCK activity in peripheral blood mononuclear cells (PBMCs) from 29 patients with SLE, 31 patients with RA and 28 healthy controls was determined by ELISA. SLE T cells or in vitro-differentiated Th17 cells were treated with Y27632 (a pan-ROCK inhibitor), KD025 (a selective ROCK2 inhibitor) or simvastatin (which inhibits RhoA, a major ROCK activator). ROCK activity and IL-17 and IL-21 production were assessed. The transcriptional profile altered by ROCK inhibitors was evaluated by NanoString technology. RESULTS: ROCK activity levels were significantly higher in patients with SLE and RA than healthy controls. Th17 cells exhibited high ROCK activity that was inhibited by Y27632, KD025 or simvastatin; each also decreased IL-17 and IL-21 production by purified SLE T cells or Th17 cells. Immune profiling revealed both overlapping and distinct effects of the different ROCK inhibitors. CONCLUSIONS: ROCK activity is elevated in PBMCs from patients with SLE and RA. Production of IL-17 and IL-21 by SLE T cells or Th17 cells can furthermore be inhibited by targeting the RhoA-ROCK pathway via both non-selective and selective approaches.

Glucocorticoid receptor represses proinflammatory genes at distinct steps of the transcription cycle.

Widespread anti-inflammatory actions of glucocorticoid hormones are mediated by the glucocorticoid receptor (GR), a ligand-dependent transcription factor of the nuclear receptor superfamily. In conjunction with its corepressor GR-interacting protein-1 (GRIP1), GR tethers to the DNA-bound activator protein-1 and NF-κB and represses transcription of their target proinflammatory cytokine genes. However, these target genes fall into distinct classes depending on the step of the transcription cycle that is rate-limiting for their activation: Some are controlled through RNA polymerase II (PolII) recruitment and initiation, whereas others undergo signal-induced release of paused elongation complexes into productive RNA synthesis. Whether these genes are differentially regulated by GR is unknown. Here we report that, at the initiation-controlled inflammatory genes in primary macrophages, GR inhibited LPS-induced PolII occupancy. In contrast, at the elongation-controlled genes, GR did not affect PolII recruitment or transcription initiation but promoted, in a GRIP1-dependent manner, the accumulation of the pause-inducing negative elongation factor. Consistently, GR-dependent repression of elongation-controlled genes was abolished specifically in negative elongation factor-deficient macrophages. Thus, GR:GRIP1 use distinct mechanisms to repress inflammatory genes at different stages of the transcription cycle.

Role of transcriptional coregulator GRIP1 in the anti-inflammatory actions of glucocorticoids.

Inhibition of cytokine gene expression by the hormone-activated glucocorticoid receptor (GR) is the key component of the anti-inflammatory actions of glucocorticoids, yet the underlying molecular mechanisms remain obscure. Here we report that glucocorticoid repression of cytokine genes in primary macrophages is mediated by GR-interacting protein (GRIP)1, a transcriptional coregulator of the p160 family, which is recruited to the p65-occupied genomic NFκB-binding sites in conjunction with liganded GR. We created a mouse strain enabling a conditional hematopoietic cell-restricted deletion of GRIP1 in adult animals. In this model, GRIP1 depletion in macrophages attenuated in a dose-dependent manner repression of NFκB target genes by GR irrespective of the upstream Toll-like receptor pathway responsible for their activation. Furthermore, genome-wide transcriptome analysis revealed a broad derepression of lipopolysaccharide (LPS)-induced glucocorticoid-sensitive targets in GRIP1-depleted macrophages without affecting their activation by LPS. Consistently, conditional GRIP1-deficient mice were sensitized, relative to the wild type, to a systemic inflammatory challenge developing characteristic signs of LPS-induced shock. Thus, by serving as a GR corepressor, GRIP1 facilitates the anti-inflammatory effects of glucocorticoids in vivo.

Glucocorticoid receptor coordinates transcription factor-dominated regulatory network in macrophages.

BACKGROUND: Inflammation triggered by infection or injury is tightly controlled by glucocorticoid hormones which signal via a dedicated transcription factor, the Glucocorticoid Receptor (GR), to regulate hundreds of genes. However, the hierarchy of transcriptional responses to GR activation and the molecular basis of their oftentimes non-linear dynamics are not understood. RESULTS: We investigated early glucocorticoid-driven transcriptional events in macrophages, a cell type highly responsive to both pro- and anti-inflammatory stimuli. Using whole transcriptome analyses in resting and acutely lipopolysaccharide (LPS)-stimulated macrophages, we show that early GR target genes form dense networks with the majority of control nodes represented by transcription factors. The expression dynamics of several glucocorticoid-responsive genes are consistent with feed forward loops (FFL) and coincide with rapid GR recruitment. Notably, GR binding sites in genes encoding members of the KLF transcription factor family colocalize with KLF binding sites. Moreover, our gene expression, transcription factor binding and computational data are consistent with the existence of the GR-KLF9-KLF2 incoherent FFL. Analysis of LPS-downregulated genes revealed striking enrichment in multimerized Zn-fingers- and KRAB domain-containing proteins known to bind nucleic acids and repress transcription by propagating heterochromatin. This raises an intriguing possibility that an increase in chromatin accessibility in inflammatory macrophages results from broad downregulation of negative chromatin remodelers. CONCLUSIONS: Pro- and anti-inflammatory stimuli alter the expression of a vast array of transcription factors and chromatin remodelers. By regulating multiple transcription factors, which propagate the initial hormonal signal, GR acts as a coordinating hub in anti-inflammatory responses. As several KLFs promote the anti-inflammatory program in macrophages, we propose that GR and KLFs functionally cooperate to curb inflammation.

Mechanisms of Epigenomic and Functional Convergence Between Glucocorticoid- and IL4-Driven Macrophage Programming.

Macrophages adopt distinct phenotypes in response to environmental cues, with type-2 cytokine interleukin-4 promoting a tissue-repair homeostatic state (M2IL4). Glucocorticoids, widely used anti-inflammatory therapeutics, reportedly impart a similar phenotype (M2GC), but how such disparate pathways may functionally converge is unknown. We show using integrative functional genomics that M2IL4 and M2GC transcriptomes share a striking overlap mirrored by a shift in chromatin landscape in both common and signal-specific gene subsets. This core homeostatic program is enacted by transcriptional effectors KLF4 and the GC receptor, whose genome-wide occupancy and actions are integrated in a stimulus-specific manner by the nuclear receptor cofactor GRIP1. Indeed, many of the M2IL4:M2GC-shared transcriptomic changes were GRIP1-dependent. Consistently, GRIP1 loss attenuated phagocytic activity of both populations in vitro and macrophage tissue-repair properties in the murine colitis model in vivo. These findings provide a mechanistic framework for homeostatic macrophage programming by distinct signals, to better inform anti-inflammatory drug design.

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.

Immediate mediators of the inflammatory response are poised for gene activation through RNA polymerase II stalling.

The kinetics and magnitude of cytokine gene expression are tightly regulated to elicit a balanced response to pathogens and result from integrated changes in transcription and mRNA stability. Yet, how a single microbial stimulus induces peak transcription of some genes (TNFalpha) within minutes whereas others (IP-10) require hours remains unclear. Here, we dissect activation of several lipopolysaccharide (LPS)-inducible genes in macrophages, an essential cell type mediating inflammatory response in mammals. We show that a key difference between the genes is the step of the transcription cycle at which they are regulated. Specifically, at TNFalpha, RNA Polymerase II initiates transcription in resting macrophages, but stalls near the promoter until LPS triggers rapid and transient release of the negative elongation factor (NELF) complex and productive elongation. In contrast, no NELF or polymerase is detectible near the IP-10 promoter before induction, and LPS-dependent polymerase recruitment is rate limiting for transcription. We further demonstrate that this strategy is shared by other immune mediators and is independent of the inducer and signaling pathway responsible for gene activation. Finally, as a striking example of evolutionary conservation, the Drosophila homolog of the TNFalpha gene, eiger, displayed all of the hallmarks of NELF-dependent polymerase stalling. We propose that polymerase stalling ensures the coordinated, timely activation the inflammatory gene expression program from Drosophila to mammals.

GRIP1-associated SET-domain methyltransferase in glucocorticoid receptor target gene expression.

Transcriptional regulators such as the glucocorticoid receptor (GR) recruit multiple cofactors to activate or repress transcription. Although most cofactors are intrinsically bifunctional, little is known about the molecular mechanisms dictating the specific polarity of regulation. Furthermore, chromatin modifications thought to be confined to silent loci appear in actively transcribed genes suggesting that similar enzymatic activities may mediate constitutive and transient chromatin states. GRIP1, a GR ligand-dependent coregulator of the p160 family can potentiate or inhibit transcription but the molecular contexts and mechanisms that enable GRIP1 corepressor activity are poorly understood. In a yeast 2-hybrid screen with GRIP1 repression domain (RD)-containing fragment, we repeatedly isolated the C-terminal region of a SET domain-containing protein subsequently identified as histone H4 lysine 20 trimethyltransferase, Suv4-20h1. We cloned a full-length Suv4-20h1 and dissected its interaction with GRIP1 in yeast, in vitro, and in mammalian cells. Strict nuclear localization and high salt concentration required for Suv4-20h1 extraction were consistent with its tight association with chromatin. Overexpression of Suv4-20h1 in human U2OS and A549 cells expressing integrated and endogenous GR, respectively, antagonized ligand-dependent induction of a subset of GR target genes, whereas Suv4-20h1 siRNA-mediated depletion had a reciprocal effect. Inhibition of GR transactivation required both the GRIP1 interacting region of Suv4-20h1 and its catalytic activity. Thus, Suv4-20h1 known exclusively as a factor involved in constitutive heterochromatin maintenance, actively participates in hormone-dependent transcriptional regulation affecting GR target gene expression in a promoter- and cell type-specific manner.

Transcription cofactor GRIP1 differentially affects myeloid cell-driven neuroinflammation and response to IFN-ß therapy.

Macrophages (MФ) and microglia (MG) are critical in the pathogenesis of multiple sclerosis (MS) and its mouse model, experimental autoimmune encephalomyelitis (EAE). Glucocorticoids (GCs) and interferon ß (IFN-ß) are frontline treatments for MS, and disrupting each pathway in mice aggravates EAE. Glucocorticoid receptor-interacting protein 1 (GRIP1) facilitates both GR and type I IFN transcriptional actions; hence, we evaluated the role of GRIP1 in neuroinflammation. Surprisingly, myeloid cell-specific loss of GRIP1 dramatically reduced EAE severity, immune cell infiltration of the CNS, and MG activation and demyelination specifically during the neuroinflammatory phase of the disease, yet also blunted therapeutic properties of IFN-ß. MФ/MG transcriptome analyses at the bulk and single-cell levels revealed that GRIP1 deletion attenuated nuclear receptor, inflammatory and, interestingly, type I IFN pathways and promoted the persistence of a homeostatic MG signature. Together, these results uncover the multifaceted function of type I IFN in MS/EAE pathogenesis and therapy, and an unexpectedly permissive role of myeloid cell GRIP1 in neuroinflammation.

RNA-seq Analysis of Peri-Implant Tissue Shows Differences in Immune, Notch, Wnt, and Angiogenesis Pathways in Aged Versus Young Mice.

The number of total joint replacements (TJRs) in the United States is increasing annually. Cementless implants are intended to improve upon traditional cemented implants by allowing bone growth directly on the surface to improve implant longevity. One major complication of TJR is implant loosening, which is related to deficient osseointegration in cementless TJRs. Although poor osseointegration in aged patients is typically attributed to decreased basal bone mass, little is known about the molecular pathways that compromise the growth of bone onto porous titanium implants. To identify the pathways important for osseointegration that are compromised by aging, we developed an approach for transcriptomic profiling of peri-implant tissue in young and aged mice using our murine model of osseointegration. Based on previous findings of changes of bone quality associated with aging, we hypothesized that aged mice have impaired activation of bone anabolic pathways at the bone-implant interface. We found that pathways most significantly downregulated in aged mice relative to young mice are related to angiogenic, Notch, and Wnt signaling. Downregulation of these pathways is associated with markedly increased expression of inflammatory and immune genes at the bone-implant interface in aged mice. These results identify osseointegration pathways affected by aging and suggest that an increased inflammatory response in aged mice may compromise peri-implant bone healing. Targeting the Notch and Wnt pathways, promoting angiogenesis, or modulating the immune response at the peri-implant site may enhance osseointegration and improve the outcome of joint replacement in older patients. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

In vitro responses to platelet-rich-plasma are associated with variable clinical outcomes in patients with knee osteoarthritis.

Autologous blood-derived products such as platelet-rich plasma (PRP) are widely used to treat musculoskeletal conditions, including knee osteoarthritis (OA). However, the clinical outcomes after PRP administration are often variable, and there is limited information about the specific characteristics of PRP that impact bioactivity and clinical responses. In this study, we aimed to develop an integrative workflow to evaluate responses to PRP in vitro, and to assess if the in vitro responses to PRP are associated with the PRP composition and clinical outcomes in patients with knee OA. To do this, we used a coculture system of macrophages and fibroblasts paired with transcriptomic analyses to comprehensively characterize the modulation of inflammatory responses by PRP in vitro. Relying on patient-reported outcomes and achievement of minimal clinically important differences in OA patients receiving PRP injections, we identified responders and non-responders to the treatment. Comparisons of PRP from these patient groups allowed us to identify differences in the composition and in vitro activity of PRP. We believe that our integrative workflow may enable the development of targeted approaches that rely on PRP and other orthobiologics to treat musculoskeletal pathologies.

Altered function and differentiation of age-associated B cells contribute to the female bias in lupus mice.

Differences in immune responses to viruses and autoimmune diseases such as systemic lupus erythematosus (SLE) can show sexual dimorphism. Age-associated B cells (ABC) are a population of CD11c+T-bet+ B cells critical for antiviral responses and autoimmune disorders. Absence of DEF6 and SWAP-70, two homologous guanine exchange factors, in double-knock-out (DKO) mice leads to a lupus-like syndrome in females marked by accumulation of ABCs. Here we demonstrate that DKO ABCs show sex-specific differences in cell number, upregulation of an ISG signature, and further differentiation. DKO ABCs undergo oligoclonal expansion and differentiate into both CD11c+ and CD11c- effector B cell populations with pathogenic and pro-inflammatory function as demonstrated by BCR sequencing and fate-mapping experiments. Tlr7 duplication in DKO males overrides the sex-bias and further augments the dissemination and pathogenicity of ABCs, resulting in severe pulmonary inflammation and early mortality. Thus, sexual dimorphism shapes the expansion, function and differentiation of ABCs that accompanies TLR7-driven immunopathogenesis.

Serine-threonine kinase ROCK2 regulates germinal center B cell positioning and cholesterol biosynthesis.

Germinal center (GC) responses require B cells to respond to a dynamic set of intercellular and microenvironmental signals that instruct B cell positioning, differentiation, and metabolic reprogramming. RHO-associated coiled-coil-containing protein kinase 2 (ROCK2), a serine-threonine kinase that can be therapeutically targeted by ROCK inhibitors or statins, is a key downstream effector of RHOA GTPases. Although RHOA-mediated pathways are emerging as critical regulators of GC responses, the role of ROCK2 in B cells is unknown. Here, we found that ROCK2 was activated in response to key T cell signals like CD40 and IL-21 and that it regulated GC formation and maintenance. RNA-Seq analyses revealed that ROCK2 controlled a unique transcriptional program in GC B cells that promoted optimal GC polarization and cholesterol biosynthesis. ROCK2 regulated this program by restraining AKT activation and subsequently enhancing FOXO1 activity. ATAC-Seq (assay for transposase-accessible chromatin with high-throughput sequencing) and biochemical analyses revealed that the effects of ROCK2 on cholesterol biosynthesis were instead mediated via a novel mechanism. ROCK2 directly phosphorylated interferon regulatory factor 8 (IRF8), a crucial mediator of GC responses, and promoted its interaction with sterol regulatory element-binding transcription factor 2 (SREBP2) at key regulatory regions controlling the expression of cholesterol biosynthetic enzymes, resulting in optimal recruitment of SREBP2 at these sites. These findings thus uncover ROCK2 as a multifaceted and therapeutically targetable regulator of GC responses.

Negative elongation factor complex enables macrophage inflammatory responses by controlling anti-inflammatory gene expression.

Studies on macrophage gene expression have historically focused on events leading to RNA polymerase II recruitment and transcription initiation, whereas the contribution of post-initiation steps to macrophage activation remains poorly understood. Here, we report that widespread promoter-proximal RNA polymerase II pausing in resting macrophages is marked by co-localization of the negative elongation factor (NELF) complex and facilitated by PU.1. Upon inflammatory stimulation, over 60% of activated transcriptome is regulated by polymerase pause-release and a transient genome-wide NELF dissociation from chromatin, unexpectedly, independent of CDK9, a presumed NELF kinase. Genetic disruption of NELF in macrophages enhanced transcription of AP-1-encoding Fos and Jun and, consequently, AP-1 targets including Il10. Augmented expression of IL-10, a critical anti-inflammatory cytokine, in turn, attenuated production of pro-inflammatory mediators and, ultimately, macrophage-mediated inflammation in vivo. Together, these findings establish a previously unappreciated role of NELF in constraining transcription of inflammation inhibitors thereby enabling inflammatory macrophage activation.

A second catalytic domain in the Elp3 histone acetyltransferases: a candidate for histone demethylase activity?

A new subfamily of two-domain histone acetyltransferases (HATs) related to Elp3 has been identified. In addition to a HAT domain in the C terminus, these proteins have an N-terminal domain similar to the catalytic domain of S-adenosylmethionine radical enzymes. Two-domain organization is preserved in evolution, suggesting that both enzymatic activities are functionally or mechanistically coupled and directed towards highly conserved substrates. The functional implications of this similarity and a possible role for Elp3-related proteins as histone demethylases are discussed.

Gene-specific mechanisms direct glucocorticoid-receptor-driven repression of inflammatory response genes in macrophages.

The glucocorticoid receptor (GR) potently represses macrophage-elicited inflammation, however, the underlying mechanisms remain obscure. Our genome-wide analysis in mouse macrophages reveals that pro-inflammatory paused genes, activated via global negative elongation factor (NELF) dissociation and RNA Polymerase (Pol)2 release from early elongation arrest, and non-paused genes, induced by de novo Pol2 recruitment, are equally susceptible to acute glucocorticoid repression. Moreover, in both cases the dominant mechanism involves rapid GR tethering to p65 at NF-kB-binding sites. Yet, specifically at paused genes, GR activation triggers widespread promoter accumulation of NELF, with myeloid cell-specific NELF deletion conferring glucocorticoid resistance. Conversely, at non-paused genes, GR attenuates the recruitment of p300 and histone acetylation, leading to a failure to assemble BRD4 and Mediator at promoters and enhancers, ultimately blocking Pol2 initiation. Thus, GR displays no preference for a specific pro-inflammatory gene class; however, it effects repression by targeting distinct temporal events and components of transcriptional machinery.

iRhom2 promotes lupus nephritis through TNF-α and EGFR signaling.

Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-α and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney diseases. Here, we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b-/- mice from developing severe kidney damage without altering anti-double-stranded DNA (anti-dsDNA) Ab production by simultaneously blocking HB-EGF/EGFR and TNF-α signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-α and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b-/- mice, alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-α or EGFR signaling protected Fcgr2b-/- mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-α and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a target for selective and simultaneous dual inhibition of 2 major pathological pathways in the effector arm of the disease.