Cell type specific IL-27p28 (IL-30) deletion uncovers an unexpected pro-inflammatory property of IL-30 in autoimmune inflammation

IL-27 is an IL-12 family cytokine with potent immunoregulatory properties, capable of modulating inflammatory responses, including autoimmunity. While extensive studies have been performed to investigate the major target cells of IL-27 mediating its functions, the source of IL-27 especially during tissue specific autoimmune inflammation has not formally been tested. IL-27p28 subunit, also known as IL-30, was initially discovered as an IL-27-specific subunit, and its expression has thus been used as a surrogate for IL-27. However, there is emerging evidence that IL-27p28 can be secreted without Ebi3, a subunit that forms IL-27 with IL-27p28. Furthermore, IL-27p28 was also reported to act as a negative regulator antagonizing IL-27. In this study, we utilized various cell type specific IL-27p28-deficient mouse models and examined the major source of IL-27p28 in T cell mediated autoimmune neuroinflammation. We found that dendritic cell-derived IL-27p28 is dispensable for the disease development but that IL-27p28 expressed by infiltrating and CNS resident APC subsets, namely, infiltrating monocytes, microglia, and astrocytes, play an essential role in limiting inflammation. Unexpectedly, we observed that cell type specific IL-27p28 deficiency expressing severe disease phenotype is associated with dysregulated IL-27p28 expression in otherwise unaffected APC subsets, suggesting that disproportionate IL-27p28 expressed may increase disease susceptibility. Indeed, systemic recombinant IL-30 administration also induced severe disease. Taken together, our results uncover a pro-inflammatory property of IL-30 that supports encephalitogenic immunity in vivo.

Redox regulation of PTPN22 affects the severity of T cell dependent autoimmune inflammation

Chronic autoimmune diseases are associated with mutations in PTPN22, a modifier of T cell receptor signaling. As with all protein tyrosine phosphatases the activity of PTPN22 is redox regulated, but if or how such regulation can modulate inflammatory pathways in vivo is not known. To determine this, we created a mouse with a cysteine-to-serine mutation at position 129 in PTPN22 (C129S), a residue proposed to alter the redox regulatory properties of PTPN22 by forming a disulfide with the catalytic C227 residue. The C129S mutant mouse showed a stronger T cell-dependent inflammatory response and development of T cell dependent autoimmune arthritis due to enhanced TCR signaling and activation of T cells, an effect neutralized by a mutation in Ncf1, a component of the NOX2 complex. Activity assays with purified proteins suggest that the functional results can be explained by an increased sensitivity to oxidation of the C129S mutated PTPN22 protein. We also observed that the disulfide of native PTPN22 can be directly reduced by the thioredoxin system, while the C129S mutant lacking this disulfide was less amenable to reductive reactivation. In conclusion, we show that PTPN22 functionally interacts with Ncf1 and is regulated by oxidation via the non-catalytic C129 residue and oxidation-prone PTPN22 leads to increased severity in the development of T cell-dependent autoimmunity.Significance statementA hitherto unstudied aspect of PTPN22 biology is its regulation by cell redox states. Here we created a mouse model where PTPN22 was mutated to respond differentially to redox levels in vivo and found that PTPN22 function is regulated by reactive oxygen species and that redox regulation of PTPN22 impacts T-cell-dependent autoimmune inflammation.

Regnase-1 deficiency restrains Klebsiella pneumoniae infection by regulation of a Type I interferon response

Excessive inflammatory responses can cause collateral tissue damage or autoimmune inflammation, sometimes with severe morbidity or mortality. During host defense responses, numerous negative feedback mechanisms are established to prevent excessive unchecked inflammation. However, this restraint can sometimes come at the cost of suboptimal infection control, and we do not fully understand how this balance is maintained during different infection settings. The endoribonuclease Regnase-1 (Reg1, Zc3h12a, MCPIP1) is an RNA binding protein (RBP) that binds and degrades many target mRNA transcripts. Reg1 is a potent feedback regulator of IL-17 and LPS signal transduction, among other stimuli. Consequently, Reg1 deficiency exacerbates autoimmune inflammation in multiple mouse models, but on the other hand, reduced Reg1 improves immunity to fungal infection. To date, the role of Reg1 in bacterial immunity is poorly defined. Here, we show that mice deficient in Reg1 are more resistant to pulmonary Klebsiella pneumoniae (KP) infection. Unexpectedly, effects of Reg1 deficiency were not due to accelerated eradication of bacteria or increased pro-inflammatory cytokine expression. Rather, alveolar macrophages from Reg1-deficient mice showed enrichment of Type I IFN-related genes upon KP infection, accompanied by increased Ifnb1 expression. Surprisingly, the stability of Ifnb1 mRNA was not altered by Reg1-deficiency; rather, mRNA encoding its upstream regulator IRF7 appeared to be a more prominent target. Thus, impaired Reg1 induces Type I IFN and enhances resistance to KP, raising the possibility that Reg1 could be a potential clinical target in acute bacterial infections.

PREVALENCE OF PERIODONTAL DISEASES IN PATIENTS WITH GOUT

Gout is a systemic disease characterized by an inflammatory reaction at the sites of deposition of sodium monourate crystals in individuals with hyperuricemia and is caused by external factors and (or) genetic factors. Patients with gout often have comorbidities such as cardiovascular disease (including hypertension), diabetes and chronic kidney disease, and dental disease. In the professional literature there are almost no studies of periodontal tissues in patients with gout. The aim of our study was to investigate the prevalence of periodontal disease in patients with gout. The participants were divided into 2 groups: the main one included 150 patients with gout, and the comparative one included 80 people without rheumatic pathology. The age of the subjects ranged from 30 to 50 years or more. The clinical examination was performed according to a standard scheme, which included history taking and analysis of patient’s complaints. According to the results obtained, the patients with gout showed a significantly higher prevalence of periodontal disease in all age groups, compared with individuals with rheumatic pathology. A high percentage of periodontal pathology was observed in the young participants of the main group. The larges share in the structure of periodontal diseases among the patients with gout was represented by advanced generalized periodontitis class I and II, and parodontosis, while the individuals without rheumatic pathology demonstrated a higher percentage of initial stages of periodontal disease. With age, both groups demonstrated the increase in the prevalence of periodontal disease, but in patients with gout, this process was more intense. It can be concluded that systemic disorders associated with gout, among which chronic autoimmune inflammation, oxidative stress, endothelial dysfunction and a high risk of atherosclerosis are very common, can be regarded as predictors of both rapid progression and aggravation of destructive inflammatory lesions of the periodontium.

Hematopoietic Stem Cells Undergo Immune Training and Constitute a Long-Term Reservoir for Hyper-Inflammatory Macrophages in a Mouse Model of Chronic Autoimmunity

Auto-immune diseases (AD) are characterized by repeated flares of disease activity separated by periods of remission. Cycles of AD remission and relapse can occur even with therapeutic intervention and contribute to AD morbidity. Paradoxically, during remission myeloid cells retain increased expression of genes related to interferon signaling and antigen presentation. Given the relatively short lifespan of myeloid cells, these observations imply the existence of a clonal reservoir fueling AD relapse. Recent literature describes hematopoietic stem cells (HSC) as a cellular source for trained myeloid cells in response to immune stimuli. Thus, we hypothesize that HSC may also retain a long-term memory of chronic autoimmune inflammation, thereby providing a continuous supply of myeloid cells that promote AD pathogenesis. To test this hypothesis, we have combined high-throughput molecular and cytokine profiling approaches with functional assays to address heritable changes in immune function using the pristane-induced mouse model of systemic lupus erythematosus (SLE). Eight weeks after pristane injection, we observe significant myeloid lineage expansion in the bone marrow (BM), including mature myeloid cells, granulocyte/monocyte progenitors (GMP) and multipotent progenitor (MPP) populations. To understand the impact of SLE-like disease on the molecular programming of the hematopoietic system, we performed RNA-seq analyses of BM Mon and HSC. As anticipated, BM Mon activated inflammatory programs and antigen presentation genes, which overlapped with gene signatures of human monocytes from SLE patients. HSC also activated innate defense gene programs resembling signatures of trained immunity, thus establishing the potential for autoimmune inflammation to induce immune training in HSC. To establish whether these molecular programs potentiate myeloid cell function, we generated BM-derived macrophages (BMDM) from control and pristane-induced mice. BMDMs from pristane-induced mice exhibited significantly increased capacity to kill Mycobacterium avium. Further, co-culture of T cells with BMDMs from pristane-induced mice significantly boosted T cell proliferation, indicative of enhanced antigen presentation. To establish whether HSC from pristane-induced mice propagate molecular memory of SLE-like disease to myeloid progeny, we transplanted stringently enriched (LSK/SLAM/CD34 -/EPCR +) long-term (LT)-HSC into lethally irradiated recipient mice. 18 weeks post transplant, mice transplanted with LT-HSC from pristane-induced donors had a small but significant reduction in donor BM HSC chimerism but did not exhibit overt changes in lineage output. Strikingly, BMDMs from pristane-induced donors showed increased bacterial killing and inflammatory cytokine generation following M. avium challenge, as well as increased capacity to induce antigen-specific T cell proliferation. Thus, LT-HSC retain and pass on altered functional properties to myeloid cells, even in the absence of AD activity. To characterize the molecular mechanisms underlying HSC-propagated alterations in myeloid cell function, we ran RNA-seq on donor-derived GMP and BMDMs. Notably, GMP derived from pristane-induced donor LT-HSC had increased expression of Fos and Jun/b/d, key molecular drivers of immune training in stem cells. Likewise, pristane-induced donor BMDMs maintained increased expression of IFN-regulated genes including MHC-I, a gene also overexpressed in PBMCs from human SLE patients. Consistent with these findings, re-stimulation of recipient mice with pristane led to a significant increase in cytokine-producing lymph node T cells versus recipient mice transplanted with control HSC, further supporting a model of immune training. Overall, these data show that chronic autoimmune inflammation can induce in HSC a heritable trained immunity phenotype that is transmitted to myeloid progeny, enhancing their functional activity. Ongoing studies are establishing the capacity for this phenotype to exacerbate AD. We are also testing the importance of molecular players identified above in establishing AD-related immune training and assessing the potential for therapeutic interventions to disrupt HSC memory in this setting. Our data thus stand to establish a new paradigm for trained immunity in HSC as a key contributor to AD pathology and relapse. Disclosures No relevant conflicts of interest to declare.

Mechanisms of brain protection against autoimmune inflammation

A significant number of unique antigens expressed in the brain can activate an adaptive immune response, increasing the risk of autoimmune inflammation in the central nervous system (CNS). As a result, a complex protection system exists in the CNS to prevent autoimmune reactions. In addition to the blood-brain- and blood-cerebrospinal fluid-barriers, we discuss complex systems of antigen drainage and circulation of antigen-presenting cells in the CNS. Moreover, the interaction of the CNS with the peripheral immune system typically occurs in specific areas (choroid plexuses, perivascular spaces, and brain meninges), and resident cells of the innate immune system (macrophages, microglia, astrocytes) have limited opportunities for antigen presentation and do not migrate to regional lymph nodes. There are signs of activation of adaptive immunity against CNS antigens in normal conditions, which, however, do not lead to autoimmune diseases. The review covers the mechanisms of maintaining natural immune self-tolerance in the CNS and their failure in autoimmune CNS pathology.

cDC1 Dependent Accumulation of Memory T Cells Is Required for Chronic Autoimmune Inflammation in Murine Testis

As an immune privilege site, there are various types of immune cells in the testis. Previous research has been focused on the testicular macrophages, and much less is known about the T cells in the testis. Here, we found that T cells with memory phenotypes were the most abundant leukocyte in the testis except for macrophages. Our results showed that the proportion of testicular T cells increases gradually from birth to adulthood in mice and that the primary type of T cells changed from γδTCR+ T cells to αβTCR+ T cells. In addition, under homeostatic conditions, CD8+ T cells are the dominant subgroup and have different phenotypic characteristics from CD4+ T cells. We found that cDC1, but not cDC2, is necessary for the presence of T cells in the testis under physiological state. A significant decrease of T cells does not have a deleterious effect on the development of the testis or spermatogenesis. However, cDC1-dependent T cells play an indispensable role in chronic autoimmune orchitis of the testis. Collectively, our multifaceted data provide a comprehensive picture of the accumulation, localization, and function of testicular T cells.

The m6A reader IMP2 directs autoimmune inflammation through an IL-17– and TNFα-dependent C/EBP transcription factor axis

Excessive cytokine activity underlies many autoimmune conditions, particularly through the interleukin-17 (IL-17) and tumor necrosis factor–α (TNFα) signaling axis. Both cytokines activate nuclear factor κB, but appropriate induction of downstream effector genes requires coordinated activation of other transcription factors, notably, CCAAT/enhancer binding proteins (C/EBPs). Here, we demonstrate the unexpected involvement of a posttranscriptional “epitranscriptomic” mRNA modification [N6-methyladenosine (m6A)] in regulating C/EBPβ and C/EBPδ in response to IL-17A, as well as IL-17F and TNFα. Prompted by the observation that C/EBPβ/δ-encoding transcripts contain m6A consensus sites, we show that Cebpd and Cebpb mRNAs are subject to m6A modification. Induction of C/EBPs is enhanced by an m6A methylase “writer” and suppressed by a demethylase “eraser.” The only m6A “reader” found to be involved in this pathway was IGF2BP2 (IMP2), and IMP2 occupancy of Cebpd and Cebpb mRNA was enhanced by m6A modification. IMP2 facilitated IL-17–mediated Cebpd mRNA stabilization and promoted translation of C/EBPβ/δ in response to IL-17A, IL-17F, and TNFα. RNA sequencing revealed transcriptome-wide IL-17–induced transcripts that are IMP2 influenced, and RNA immunoprecipitation sequencing identified the subset of mRNAs that are directly occupied by IMP2, which included Cebpb and Cebpd. Lipocalin-2 (Lcn2), a hallmark of autoimmune kidney injury, was strongly dependent on IL-17, IMP2, and C/EBPβ/δ. Imp2−/− mice were resistant to autoantibody-induced glomerulonephritis (AGN), showing impaired renal expression of C/EBPs and Lcn2. Moreover, IMP2 deletion initiated only after AGN onset ameliorated disease. Thus, posttranscriptional regulation of C/EBPs through m6A/IMP2 represents a previously unidentified paradigm of cytokine-driven autoimmune inflammation.