IL-2 Treatment Research Articles

Contribution of IL-33/ILC2-mediated Th2 cytokines during the progression of minimal change disease.

Minimal change disease (MCD) is a common type of nephrotic syndrome with high recurrence rate. This study aims to explore the impacts of interleukin (IL)-33 in MCD and to discuss its potential mechanism. In adriamycin (ADM) and puromycin aminonucleoside (PAN)-induced MCD rat model, IL-33 was used for treatment. H&E staining was applied for detecting histological changes. Critical proteins were examined by western blot. Corresponding commercial kits tested oxidative stress- and inflammation-related factors. Cell apoptosis was measured by TUNEL assay. ADM-induced podocyte injury model was establish to mimic MCD in vitro. Cell proliferation and apoptosis were detected by CCK-8 and TUNEL assays. Finally, podocyte was stimulated by innate lymphoid type-2 cells-secreted Th2 cytokines (ILC2s: IL-13 and IL-5 respectively), with or without incubation with M1 macrophage medium to further explore the immune-regulation of ILC2s behind the inflammatory environment of MCD. It was found that PAN-induced kidney jury, inflammation, oxidative stress and apoptosis were severer than ADM, and IL-33 treatment significantly alleviated the above injuries in PAN and ADM-induced MCD rat model. Moreover, IL-33 reversed the reduced viability and increased oxidative stress and apoptosis in ADM-induced podocyte injury model. Further, the capacities of IL-13 alone in inducing M1/M2 macrophage polarization, apoptosis, inflammation, kidney injury and reducing cell viability are stronger than IL-5. However, IL-13 reversed reduced cell viability and stimulated apoptosis, inflammation, kidney injury mediated by co-incubation with M1-conditioned medium. Collectively, IL-33 might protect against immunologic injury in MCD via mediating ILC2s-secreted IL-13.

Regulation of Cytotoxic Immune Effector Function by AJ3 Probiotic Bacteria in Amyotrophic Lateral Sclerosis (ALS).

Our recent studies indicated that amyotrophic lateral sclerosis (ALS) patients suffer from significantly elevated levels of interferon-gamma (IFN-γ) secretion by natural killer (NK) and CD8+ T cells, which may be responsible for the immune-pathologies seen in central nervous system and in peripheral organs of the patients. In order to counter such elevated induction of IFN-γ in patients we designed a treatment strategy to increase anti-inflammatory cytokine interleukin-10 (IL-10) by the use of probiotic strains which significantly increase the levels of IL-10. Therefore, in this paper we demonstrate disease specific functions of Al-Pro (AJ3) formulated for the adjunct treatment of auto-immune diseases including ALS, and compared the function with CA/I-Pro (AJ4) for the treatment of cancer and viral diseases, and NK-CLK (AJ2) for maintenance of immune balance and promotion of disease prevention. The three different formulations of probiotic bacteria have distinct profiles of activation of peripheral blood mononuclear cells (PBMCs), NK, and CD8+ T cells, and their induced activation is different from those mediated by either IL-2 or IL-2 + anti-CD16 monoclonal antibodies (mAbs) or IL-2 + anti-CD3/CD28 mAbs. IL-2 + anti-CD16 mAb activation of PBMCs and NK cells had the highest IFN-γ/IL-10 ratio, whereas IL-2 combination with sAJ4 had the next highest followed by IL-2 + sAJ2 and the lowest was seen with IL-2 + sAJ3. Accordingly, the highest secretion of IFN-γ was seen when the PBMCs and NK cells were treated with IL-2 + sAJ4, intermediate for IL-2 + sAJ2 and the lowest with IL-2 + sAJ3. The levels of IFN-γ induction and the ratio of IFN-γ to IL-10 induced by different probiotic bacteria formulation in the absence of IL-2 treatment remained much lower when compared to those treated in the presence of IL-2. Of note is the difference between NK cells and CD8+ T cells in which synergistic induction of IFN-y by IL-2 + sAJ4 was significantly higher in NK cells than those seen by CD8+ T cells. Based on these results, sAJ3 should be effective in alleviating auto-immunity seen in ALS since it will greatly regulate the levels and function of IFN-γ negatively, decreasing overactivation of cytotoxic immune effectors and prevention of death in motor neurons.

IL-4 induces reparative phenotype of RPE cells and protects against retinal neurodegeneration via Nrf2 activation

Retinal degeneration is a kind of neurodegeneration characterized by progressive neuronal death and dysfunction of retinal pigment epithelium (RPE) cells, leading to permanent visual impairment. It still lacks effective therapeutic options and new drugs are highly warranted. In this study, we found the expression of IL-4, a critical regulator of immunity, was reduced in both patients and mouse models. Importantly, exogenous intravitreal IL-4 application could exert a novel neuroprotective effect, characterized by well-preserved RPE layer and neuroretinal structure, as well as amplified wave-amplitudes in ERG. The RNA-seq analysis revealed that IL-4 treatment suppressed the essential oxidative and pro-inflammatory pathways in the degenerative retina. Particularly, IL-4 upregulated the IL-4Rα on RPE cells and induced a reparative phenotype via the activation of Nrf2 both in vitro and in vivo. Furthermore, the Nrf2-/- mice displayed no recovery in response to IL-4 application, highlighting a significant role of Nrf2 in IL-4-mediated protection. Our data provides evidence that IL-4 protects against retinal neurodegeneration by its antioxidant and anti-inflammatory property through IL-4Rα upregulation and Nrf2 activation in RPE cells. The IL-4/IL-4Rα-Nrf2 axis maybe the potential targets for the development of novel therapies for neurodegenerative diseases.

The Use of IL-17 and IL-23 Inhibitors in Swedish Clinical Practice: A Register-Based Analysis

Background: Interleukin (IL) inhibitors have made completely cleared skin achievable for many patients with moderate to severe psoriasis in clinical trial settings. Few observational studies assess treatment response in accordance with treatment goals in guidelines. Objectives: The aim of the study was to analyze the treatment response of IL-17/IL-23 inhibitors in clinical practice and the proportions of patients that reach the treatment target of the Psoriasis Area and Severity Index (PASI) < 3 and the Dermatology Life Quality Index (DLQI) ≤5. Methods: A longitudinal, observational study based on the Swedish National Registry for Systemic Treatment of Psoriasis, PsoReg. Patients using IL-17/IL-23 inhibitors with assessments of PASI, DLQI, and EQ-5D before (maximum 6 months) and after (3–12 months) initiation of IL-17/IL-23 were included. Results: In total, 333 patients using IL-17/IL-23 inhibitors were included. Eighty percent (n = 266) received IL-17 inhibitors, and 20% (n = 67) received IL-23 inhibitors. Sixty-six percent of patients reached both PASI <3 and DLQI ≤5, 23% reached one target, and 11% reached none. The mean (SD) PASI, DLQI, and EQ-5D improvements were 6.75 (6.99), 7.14 (7.97), and 0.126 (0.296), respectively. There was no statistically significant difference in outcomes between IL-17 and IL-23 inhibitor treatment groups. Conclusions: IL-17/IL-23 inhibitors are effective in clinical practice, but there is still an unmet therapeutic need in moderate to severe psoriasis.

Maturation and specialization of group 2 innate lymphoid cells through the lung-gut axis.

Innate lymphoid cells (ILC) are abundant in mucosal tissues. They serve critical functions in anti-pathogen response and tissue homeostasis. However, the heterogenous composition of ILCs in mucosal sites and their various maturation trajectories are less well known. In this study, we characterize ILC types and functions from both the lung and the small intestine, and identify their tissue-specific markers. We find that ILC2s residing in the lung express CCR2, whereas intestinal ILC2s express CCR4. Through the use of CCR2 and CCR4 reporter mice, we show that ILC2s undergo translocation via the lung-gut axis upon IL-33 treatment. This trajectory of ILC2s is also observed at the postnatal stage. Allergen-induced activation of lung ILC2s affects the homeostasis of gut ILC2s. Together, our findings implicate that ILCs display tissue-specific features in both the lung and gut, and ILC2s mature along the lung-gut axis in particular homeostatic and inflammatory conditions.

IL-21 signaling promotes the establishment of KSHV infection in human tonsil lymphocytes by increasing differentiation and targeting of plasma cells.

Factors influencing Kaposi's sarcoma-associated herpesvirus (KSHV) transmission and the early stages of KSHV infection in the human immune system remain poorly characterized. KSHV is known to extensively manipulate the host immune system and the cytokine milieu, and cytokines are known to influence the progression of KSHV-associated diseases. Our previous work identified the early targeting of plasma cells for KSHV infection. In this study, we examine whether IL-21, a cytokine known to profoundly influence plasma cell fate, influences the early stages of KSHV infection in B lymphocytes. Using our unique model of ex vivo KSHV infection in tonsil lymphocytes, we investigate the influence of IL-21 supplementation, IL-21 neutralization, the distribution of IL-21 receptor on B cell subsets and IL-21 secreting T cell subsets on the establishment of KSHV infection in human B cells. We show that IL-21 signaling promotes KSHV infection by promoting both total plasma cell numbers and increasing KSHV infection in plasma cells as early as 3 days post-infection. We further demonstrate that the synergistic effect of KSHV infection and IL-21 treatment on plasma cell frequencies is due to differentiation of new plasma cells from naïve B cell precursors. We examine T cells secreting IL-21 in our tonsil specimens and determine that IL-21 producing CD8+ central memory T cells are correlated with plasma cell frequencies and KSHV targeting of plasma cells. These results demonstrate the novel finding that differentiation of new plasma cells is involved in the early stages of KSHV infection in B cells, and that IL-21 signaling can potentiate this effect thereby increasing the overall magnitude of KSHV infection at early timepoints. These results suggest that IL-21 signaling represents a host-level susceptibility factor for the establishment of KSHV infection.

Adenosine kinase promotes post-infarction cardiac repair by epigenetically maintaining reparative macrophage phenotype

Pro-inflammatory and reparative macrophages are crucial in clearing necrotic myocardium and promoting cardiac repair after myocardial infarction (MI), respectively. Extracellular adenosine has been demonstrated to modulate macrophage polarization through adenosine receptors. However, the role of intracellular adenosine in macrophage polarization has not been explored and adenosine kinase (ADK) is a major enzyme regulating intracellular adenosine levels. Here, we aimed to elucidate the role of ADK in macrophage polarization and its subsequent impact on MI. We demonstrated that ADK was upregulated in bone marrow-derived macrophages (BMDMs) after IL-4 treatment and was highly expressed in the infarct area at day 7 post-MI, especially in macrophages. Compared with wild-type mice, myeloid-specific Adk knockout mice showed increased infarct size, limited myofibroblast differentiation, reduced collagen deposition and more severe cardiac dysfunction after MI, which was related to impaired reparative macrophage phenotype in MI tissue. We found that ADK deletion or inhibition significantly decreased the expression of reparative genes, such as Arg1, Ym1, Fizz1, and Cd206 in BMDMs after IL-4 treatment. The increased intracellular adenosine due to Adk deletion inhibited transmethylation reactions and decreased the trimethylation of H3K4 in BMDMs after IL-4 treatment. Mechanistically, we demonstrated that Adk deletion suppressed reparative macrophage phenotype through decreased IRF4 expression, which resulted from reduced levels of H3K4me3 on the Irf4 promotor. Together, our study reveals that ADK exerts a protective effect against MI by promoting reparative macrophage polarization through epigenetic mechanisms.

The Role of MRE11 in the IL-6/STAT3 Pathway of Lung Cancer Cells.

MRE11 is a pivotal protein for ATM activation during double-strand DNA break. ATM kinase activations may act as lung cancer biomarkers. The IL-6/STAT3 pathway plays an important role in tumor metastasis, including lung cancer. However, the mechanism between MRE11 and the IL-6/STAT3 pathway is still unclear. In this study, we discovered that MRE11 can interact with STAT3 under IL-6 treatment and regulate STAT3 Tyr705 phosphorylation. After the knockdown of MRE11 in lung cancer cells, we discovered that IL-6 or the conditional medium of THP-1 cells can induce the mRNA expression of STAT3 downstream genes, including CCL2, in the control cells, but not in MRE11-knockdown lung cancer cells. Moreover, CCL2 secretion was lower in MRE11-knockdown lung cancer cells than in control cells after treatment with the conditional medium of RAW264.7 cells. In addition, MRE11 deficiency in lung cancer cells decreases their ability to recruit RAW 264.7 cells. Furthermore, MRE11 is a potential target for lung cancer therapy.

Absolute decrease in regulatory T cells and low-dose interleukin-2 therapy: restoring and expanding regulatory T cells to treat systemic sclerosis: a 24-week study.

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular lesions, immunological alterations and tissue fibrosis. There is some evidence of an imbalance between T-cell subsets in this disease. Interleukin (IL)-2 is a cytokine that can regulate the activity of immune cells and there is evidence that low-dose IL-2 therapy can be used to treat immune diseases. To investigate the changes of peripheral lymphocyte subsets, especially T helper (Th)17 and regulatory T (Treg) cells and the effects of low-dose IL-2 therapy in patients with SSc. In total, 66 patients with SSc and 49 sex- and age-matched healthy controls (HCs), were enrolled. The absolute numbers of peripheral lymphocyte subsets in these individuals were determined by flow cytometry. The 66 patients, were divided into 2 groups: 23 (the IL-2 group) were treated with low-dose (5.0 × 105 IU) IL-2 by subcutaneous injection daily for 5 days combined with conventional therapy, while the remaining 23 patients received conventional therapy only. Compared with HCs, the absolute numbers of peripheral T, CD4+ T, CD8+ T, natural killer and Treg cells were significantly lower in patients with SSc, with the most dramatic difference seen in both the absolute number and percentage of Treg cells in these patients, including new (previously untreated) cases, resulting in an imbalance (elevated ratio) between Th17 and Treg cells. At Week 24 after commencement of IL-2 treatment, Treg cells were markedly increased and tended to restore the balance of Th17 to Treg cells compared with baseline. Erythrocyte sedimentation rate, C-reactive protein, modified Rodnan Skin Score and visual analogue scale score were significantly decreased in both the IL-2 and non-IL-2 groups, indicating disease improvement. Notably, compared with those in the non-IL-2 group, patients treated with IL-2 had greater improvement. Our study showed that the absolute numbers of peripheral Treg cells together with total T, CD4+ T, CD8+ T and NK is significantly decreased, leading to an imbalance of Th17 to Treg cells in patients with SSc, and that low-dose IL-2 treatment could restore the balance of the two immune cells and reduce disease activity without obvious adverse effects.

Mechanism and Experimental Verification of the Use of Rhodiola crenulata to Cytokine Storm Based on Network Pharmacology and Molecular Docking

Objective: To identify the potential biological mechanisms by which Rhodiola crenulata (RC) treats cytokine storm (CS) using network pharmacology, molecular docking, and experimental verification. Methods: The ingredients and targets of RC were collected from the Organchem database. CS-related genes were collected using the GeneCards and OMIM databases. Cytoscape 3.7.2 software was used to construct the RC-CS network diagram. These data were inputted into the STRING database to construct a protein–protein interaction network. we performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes enrichment analysis using DAVID and R software. Molecular docking of the active ingredient and pathway-related targets was carried out using AutoDock Vina and PyMOL, and then a CS model was established in rats induced by lipopolysaccharide for in vivo experimental verification. Results: The network pharmacology results showed that kaempferol was the most important active component of RC in the treatment of CS, and IL6 and STAT3 were identified as key targets. Molecular docking results showed that RC active components kaempferol had a good binding ability to IL6/STAT3. At the same time, compared with the model group, different doses of kaempferol could down-regulate the expression of inflammatory factors ( P &lt; .05), and protect against systemic inflammatory response multiple organ damage. Conclusion: This study preliminarily revealed that RC can prevent and treat CS by regulating the expression of inflammatory factors, inhibiting the systemic inflammatory response induced by lipopolysaccharide, and providing a theoretical basis for the study of its pharmacodynamic material basis and mechanism of action.

IL-2 receptor engineering enhances regulatory T cell function suppressed by calcineurin inhibitor

Clinical trials utilizing regulatory T cell (Treg) therapy in organ transplantation have shown promising results, however, the choice of a standard immunosuppressive regimen is still controversial. Calcineurin inhibitors (CNIs) are one of the most common immunosuppressants for organ transplantation, although they may negatively affect Tregs by inhibiting IL-2 production by conventional T cells. As a strategy to replace IL-2 signaling selectively in Tregs, we have introduced an engineered orthogonal IL-2 (ortho IL-2) cytokine/cytokine receptor (R) pair that specifically binds with each other but does not bind with their wild-type counterparts. Murine Tregs were isolated from recipients and retrovirally transduced with ortho IL-2Rβ during ex vivo expansion. Transduced Tregs (ortho Tregs) were transferred into recipient mice in a mixed hematopoietic chimerism model with tacrolimus administration. Ortho IL-2 treatment significantly increased the ortho IL-2Rβ(+) Treg population in the presence of tacrolimus without stimulating other T cell subsets. All the mice treated with tacrolimus plus ortho IL-2 achieved heart allograft tolerance, even after tacrolimus cessation, whereas those receiving tacrolimus treatment alone did not. These data demonstrate that Treg therapy can be adopted into a CNI-based regimen by utilizing cytokine receptor engineering.

Allelic Variants of HLA-C Upstream Region, PSORS1C3, MICA, TNFA and Genes Involved in Epidermal Homeostasis and Barrier Function Influence the Clinical Response to Anti-IL-12/IL-23 Treatment of Patients with Psoriasis.

Several biologic therapies have been developed to treat moderate-to-severe psoriasis, with patients exhibiting different clinical benefits, possibly due to the heterogeneity of pathogenic processes underlying their conditions. Ustekinumab targets the IL-12/IL-23-p40 subunit and inhibits type-1 and type-17 T-cell responses. Although ustekinumab is effective as both short- and long-term treatment, therapeutic response varies considerably among patients. Ustekinumab biosimilars will be commercialized in the very next future, likely broadening the use of this drug in the treatment of psoriasis patients. Our pharmacogenomic study evaluated the influence of 417 single-nucleotide polymorphisms (SNPs) in psoriasis-risk alleles on the clinical response to ustekinumab in a cohort of 152 patients affected by moderate-to-severe plaque-type psoriasis. Differences in SNP pattern characterizing HLA-Cw6+ or HLA-Cw6- patients, showing high or low responses to ustekinumab, were also analysed. We identified twelve SNPs in HLA-C upstream region (rs12189871, rs4406273, rs9348862 and rs9368670), PSORS1C3 (rs1265181), MICA (rs2523497), LCE3A-B intergenic region (rs12030223, rs6701730), CDSN (rs1042127, rs4713436), CCHCR1 (rs2073719) and in TNFA (rs1800610) genes associated with excellent response to ustekinumab. We also found that HLA-Cw6+ and HLA-Cw6- patients carried out distinct patterns of SNPs associated with different clinical responses. The assessment of HLA-C alleles, together with other genetic variants, could be helpful for defining patients who better benefit from anti-IL-12/IL-23 therapy.

Wnt and Notch Pathways Regulate Stemness of Myeloid Leukemia Cells Via IL33/ST2 Signaling

Therapy-resistant leukemic stem cells (LSCs) are a main cause of relapse in chronic and acute myeloid leukemia (CML and AML) patients. Stemness, a cellular state of LSCs characterized by their quiescence, pluripotency, and long-term self-renewal capacity, is thought to have major implications on therapy resistance and outcome in myeloid leukemias. However, signaling pathways that induce stemness are often not specific for LSCs and shared with normal hematopoietic stem cells (HSCs). Therefore, LSCs are difficult to be targeted therapeutically. IL-33/ST2 signaling may be a potential target to eradicate CML and AML LSCs. To investigate the ST2 gene (IL1RL1) expression in different hematological malignancies, we used the MILE gene expression dataset containing 2096 samples. The IL1RL1 high expressing samples (n=62) were exclusively represented by myeloid leukemias (CML and AML), and 50% of the IL1RL1 high samples harbored either the BCR/ABL1 (CML) or the AML1/ETO (AML) oncogenes. We confirmed the result from the MILE database by analyzing the ST2 protein expression on FACS-sorted CD34+ LSCs from AML and CML patient samples. Indeed, AML1/ETO and BCR/ABL1 harboring LSCs expressed ST2, while healthy hematopoietic stem cells (HSCs) and LSCs harboring other oncogenes were ST2-negative. Transfecting the ST2-negative cell line Ramos with the AML1/ETO and BCR/ABL1 oncogenes induced ST2-expression. Next, we performed a gene set enrichment analysis (GSEA), comparing the IL1RL1 high vs. IL1RL1 low samples in the MILE dataset. Genes involved in stemness (p<0.01), Wnt- (p<0.001), and NF-ΚB (p=0.054) signaling were upregulated, while the Notch-pathway (p<0.05) was downregulated. Since the NF-ΚB is a known downstream pathway of ST2, we hypothesized that Wnt and/or Notch signaling pathways regulate ST2 expression. Therefore, we treated FACS-sorted CD34+ AML1/ETO expressing LSCs with the Wnt pathway inhibitor XAV939 or HES1 and NOTCH1 shRNAs, silencing the Notch pathway. Treatment with XAV939 led to a decrease in ST2 expression in these cells, while silencing HES1 and NOTCH1 enhanced ST2-expression. To analyze the molecular mechanisms induced by IL-33/ST2 signaling, we performed a transcriptomic analysis using FACS-sorted CD34+ AML1/ETO LSCs upon treatment with or without IL-33. In total, 377 genes were up- and 139 genes downregulated after IL-33 stimulation. IL-33-induced genes were involved in the positive regulation of NF-ΚB (p<0.05) and canonical Wnt (p<0.001) signaling pathways, and the regulation of stem cell division and maintenance (p<0.001). To functionally test whether IL-33/ST2 signaling triggers stemness in myeloid leukemia, we performed a colony forming assay using CD34+ AML1/ETO or BCR/ABL1 expressing LSCs from leukemia patient samples. The colony numbers increased 1.5-3fold upon IL-33 treatment in three consecutive platings, indicating an increase in stem cell numbers. IL-33 had no effect on colony numbers of HSCs and LSCs harboring other oncogenes. To test the in vivo relevance of IL-33/ST2 signaling in leukemia development, we used a congenic AML1/ETO9a (AE9a) or BCR/ABL1 (CML) mouse model. Briefly, we transduced ST2-negative HSCs originating from BL/6 or ST2-knockout (ST2-/-) mice with AE9a-GFP or BCR/ABL1-GFP and transplanted those cells into recipients. In both models, the LSCs strongly expressed ST2, but IL-33/ST2 signaling had no influence on the disease development. Stemness supports resistance against standard therapy in both, AML and CML. Since we were able to show that IL-33/ST2 signaling promotes stemness in AML1/ETO and BCR/ABL1 LSCs, we hypothesized that IL-33 addition protects LSCs from treatment with standard therapeutics. Indeed, IL-33 rescued the reduced colony forming capacity of LSCs that were either treated with the chemotherapeutic agent cytarabine (AML1/ETO LSCs) or the tyrosine kinase inhibitor Nilotinib (BCR/ABL1 LSCs). Furthermore, ST2-deficiency led to a reduced LSC count in CML mice compared to control mice when treated with Nilotinib (p=0.047). We showed that ST2 is expressed on AML1/ETO and BCR/ABL1 harboring LSCs and that activated IL-33/ST2 signaling induced stemness in these LSCs. Targeting IL-33/ST2 signaling in these specific subtypes of AML and CML may eliminate LSCs and overcome resistance towards chemotherapy or TKIs. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Heme and Iron Aggravate Tissue Damage in Sickle Cell Disease By Driving Macrophage Functional Reprogramming through the Coordinated Suppression of Efferocytosis and Mitochondrial Metabolism

Introduction: Sickle cell disease (SCD) is hallmarked by an underlying chronic inflammatory status, which is in part driven by pro-inflammatory macrophages. Macrophages are highly plastic immune cells which integrate and respond to a variety of signals they are exposed to in the surrounding microenvironment. One of these stimuli is represented by heme released upon hemolysis, which acts as damage-associated molecular pattern to stimulate macrophage inflammatory phenotypic switching through TLR4 signaling and ROS production (Vinchi et al., Blood 2016). Heme-induced pro-inflammatory activation program in macrophages promotes sterile inflammation and aggravates hepatic fibrosis in SCD, contributing to the inflammatory landscape and organ damage typically associated with this disease. While previous studies addressed heme ability to induce inflammatory cytokine production in macrophages, how heme alters cell functional properties remains unexplored. Macrophage functions such as immune cell recruitment ability and apoptotic cell clearance are relevant in the context of SCD, where tissue damage and cell apoptosis occur frequently due to vaso-occlusive episodes, hypoxia and ischemic injury. Methods: Here we analyzed macrophage response to apoptotic stimuli in vivo, in mouse models of heme overload and SCD, as well as in vitro, in bone-marrow-derived macrophages (BMDMs), to unveil the impact of hemolysis on macrophage functional properties. Results: Our results demonstrate that, in addition to inflammatory activation, heme severely alters macrophage functional response to apoptotic cell damage by exacerbating their immune cell recruitment ability and impairing their efferocytic capacity. We show that exposure to heme excess drives defective efferocytosis of apoptotic neutrophils in BMDMs and mouse model of heme overload. This is fully recapitulated in SCD mice, where limited efferocytosis contributes to impaired apoptotic cell clearance and exacerbated tissue damage. Mechanistically, altered efferocytosis depends on heme-driven activation of TLR4 signaling pathway and the suppression of the nuclear transcription factor PPARγ and its coactivator PGC1α, which lead to reduced expression of efferocytic receptors and impaired mitochondrial dynamics and functions. This results in limited recognition/engulfment of apoptotic cells and decreased shift to aerobic mitochondrial fatty acid β-oxidation and anti-inflammatory IL-4 and IL-10 release, with consequent inhibition of continual efferocytosis, inflammation resolution and tissue repair. Heme-driven changes are associated with cell metabolic skewing towards glycolysis and pentose phosphate pathway and reduced reliance on mitochondrial fatty acid oxidation and TCA cycle. Macrophages pre-loaded with fatty acids showed decreased oxygen consumption rate and ATP production after heme exposure, indicating that heme-altered mitochondrial dynamics impair lipid catabolism via limited mitochondrial oxidative phosphorylation. Overall, heme induces macrophage phenotypic and functional reprogramming through the coordinated suppression of efferocytosis, via efferocytosis receptor downregulation, and fatty acid β-oxidation, via altered mitochondrial dynamics. We further demonstrate that heme-impaired efferocytosis and tissue damage promote autoimmunity through anti-nuclear antibody production against 'self' secondary necrotic cells, potentially explaining the increasing evidence of autoimmune diseases in SCD patients. Finally, hemopexin-mediated heme scavenging and anti-inflammatory IL-4 treatment improve tissue damage in hemolytic mice through macrophage rewiring. Defective efferocytosis is reproduced in vitro by macrophage exposure to SCD patients' plasma and rescued by heme scavenging via haptoglobin/hemopexin and PPARγ/PGC1α modulation via PPARα agonist or IL-4. Conclusion: Our data indicate that the therapeutic improvement of heme-altered macrophage functional properties via heme scavenging or PPARγ/PGC1α modulation significantly promotes the resolution of inflammation and ameliorates tissue damage associated with SCD pathophysiology. Thus, macrophage functional rewiring offers potentially valuable therapeutic strategies for SCD patients to improve tissue damage resolution upon vaso-occlusive crisis and ischemic events and prevent autoimmune conditions.

Low-Dose IL-2 Attenuated Depression-like Behaviors and Pathological Changes through Restoring the Balances between IL-6 and TGF-β and between Th17 and Treg in a Chronic Stress-Induced Mouse Model of Depression.

Microglia activation, increased IL-6 and decreased TGF-β were found in depressed patients or in animal models of depression. IL-6 enhances T helper 17 cell differentiation, thereby causing an imbalance between Th17 and Treg cells, which induces neuroinflammation and neuronal dysfunction. However, whether imbalances between IL-6 and TGF-β and between Th17 and Treg occur in depression and whether depression can be improved upon restoring these imbalances are unknown. Treg promoter IL-2 (1500UI/0.1 mL/day) was used to treat a mouse model of depression induced by chronic unpredictable mild stress (CUMS). The behavior and concentrations of IL-6, TGF-β, Th17, IL-17A, IL-17Rc, Treg-related factors (helios and STAT5), astrocyte A1 phenotype S100β, microglia M1 phenotype Iba-1, indoleamine-2,3-dioxygenase (IDO) enzyme, corticosterone (CORT) and neurotransmitters were evaluated. When compared to controls, CUMS reduced sucrose preference, the number of entries into and the time spent in the open arms of the elevated plus maze and the exploration in the "open field", while it increased the immobility time in tail suspension, which was ameliorated by IL-2 treatment. RoRα, S100β, IL-17A, IL-17Rc, IL-6, Iba-1, IDO enzyme and CORT concentrations were significantly increased, and Helios, FoxP3+, STAT5 and TGF-β were significantly decreased by CUMS, which were significantly attenuated by IL-2 when compared to the CUMS group. The NE, DA and 5-HT contents and those of their metabolites were decreased by CUMS, which returned to control levels after IL-2 treatment. The study demonstrated that imbalances between IL-6 and TGF-β and between Th17and Treg occurred in the hippocampus of the depression model. IL-2 attenuated depression- and anxiety-like behaviors and normalized the neurotransmitter concentration and the activity of the IDO enzyme, astrocytes and microglia through restoring both balances, but it did not decrease the CORT concentration.

Costimulation blockade in combination with IL-2 permits regulatory T cell sparing immunomodulation that inhibits autoimmunity

Blockade of CD28 costimulation with CTLA-4-Ig/Abatacept is used to dampen effector T cell responses in autoimmune and transplantation settings. However, a significant drawback of this approach is impaired regulatory T cell homeostasis that requires CD28 signaling. Therefore, strategies that restrict the effects of costimulation blockade to effector T cells would be advantageous. Here we probe the relative roles of CD28 and IL-2 in maintaining Treg. We find provision of IL-2 counteracts the regulatory T cell loss induced by costimulation blockade while minimally affecting the conventional T cell compartment. These data suggest that combining costimulation blockade with IL-2 treatment may selectively impair effector T cell responses while maintaining regulatory T cells. Using a mouse model of autoimmune diabetes, we show combined therapy supports regulatory T cell homeostasis and protects from disease. These findings are recapitulated in humanised mice using clinically relevant reagents and provide an exemplar for rational use of a second immunotherapy to offset known limitations of the first.

Abstract 15292: Il21R-AS1 Long Non-Coding RNA as Potential Regulator in Therapeutic Angiogenesis in Peripheral Arterial Disease

Background: Peripheral arterial disease (PAD) is the major complication of systemic atherosclerosis. The clinical complications are intermittent claudication (IC) or its more severe form, critical limb ischemia (CLI). Potential therapeutic agents, to treat PAD failed in clinical studies. Vascular endothelial growth factor (VEGF) induced significant edema with no clinical benefit. Still today, no medical therapy exists to improve perfusion in PAD. Our lab has been studying the role of the interleukin-21 receptor (IL21R) in therapeutic angiogenesis. IL21 is undergoing clinical studies but its ability to be a therapeutic may be limited. IL21R transcribes a single human long non-coding RNA, the IL21R- antisense 1 (IL21R-AS1), with no mice homolog. Its role in PAD is not established yet. Hypothesis: IL21R-AS1 can serve as an activator of IL21R signaling to mediate hypoxia-induced angiogenesis without increasing vascular permeability. Methods and Results: Plasma from patients with IC, CLI, and non-PAD controls was obtained from whole blood. IL21R-AS1 was elevated in the plasma of patients with CLI. IL21R-AS1 expression was higher in endothelial cells (ECs) under hypoxia (2% O 2 ) serum starvation (HSS), an in vitro model of PAD. To reduce the expression of IL21R-AS1 cells were transfected with gapmeR, and for the overexpression, IL21-AS1 pCMV-TnT plasmid was used. The knockdown of the IL21R-AS1 decreased tube formation in angiogenesis assay performed on growth factor reduced matrigel, while the overexpression of the lncRNA was pro-angiogenic in hypoxic endothelial cells. We detected IL21R-AS1 in the cytoplasm and showed its translocation to the cell surface in HSS. More importantly, in ECs under HSS, we detected IL21R-AS1 in IL21R immunoprecipitation samples; suggesting a direct interaction between IL21R-AS1 and the IL21R. Both IL21 treatment and IL21R-AS1 overexpression increased transendothelial resistance (TER) in hypoxic ECs, in contrast to the permeability induced by VEGF as measured by ECIS (Endothelial Cell Impedance Sensing). Conclusion: Collectively our data suggest that the lncRNA IL21R-AS1 serves as an activator of the IL21R that can mediate angiogenesis but without inducing vascular leakage.

Promotion of a synthetic degradation of activated STAT6 by PARP-1 inhibition: roles of poly(ADP-ribosyl)ation, calpains and autophagy

BackgroundWe reported that PARP-1 regulates genes whose products are crucial for asthma, in part, by controlling STAT6 integrity speculatively through a calpain-dependent mechanism. We wished to decipher the PARP-1/STAT6 relationship in the context of intracellular trafficking and promoter occupancy of the transcription factor on target genes, its integrity in the presence of calpains, and its connection to autophagy.MethodsThis study was conducted using primary splenocytes or fibroblasts derived from wild-type or PARP-1−/− mice and Jurkat T cells to mimic Th2 inflammation.ResultsWe show that the role for PARP-1 in expression of IL-4-induced genes (e.g. gata-3) in splenocytes did not involve effects on STAT6 phosphorylation or its subcellular trafficking, rather, it influenced its occupancy of gata-3 proximal and distal promoters in the early stages of IL-4 stimulation. At later stages, PARP-1 was crucial for STAT6 integrity as its inhibition, pharmacologically or by gene knockout, compromised the fate of the transcription factor. Calpain-1 appeared to preferentially degrade JAK-phosphorylated-STAT6, which was blocked by calpastatin-mediated inhibition or by genetic knockout in mouse fibroblasts. The STAT6/PARP-1 relationship entailed physical interaction and modification by poly(ADP-ribosyl)ation independently of double-strand-DNA breaks. Poly(ADP-ribosyl)ation protected phosphorylated-STAT6 against calpain-1-mediated degradation. Additionally, our results show that STAT6 is a bonafide substrate for chaperone-mediated autophagy in a selective and calpain-dependent manner in the human Jurkat cell-line. The effects were partially blocked by IL-4 treatment and PARP-1 inhibition.ConclusionsThe results demonstrate that poly(ADP-ribosyl)ation plays a critical role in protecting activated STAT6 during Th2 inflammation, which may be synthetically targeted for degradation by inhibiting PARP-1.

Abstract 11914: VSIG4+ Resident Tissue Macrophages Govern Cardiac Remodeling and Function After Acute Myocardial Infarction in Mice

Introduction. Resident tissue macrophages (RTM) are essential cellular hubs regulating tissue homeostasis beyond their classical immune surveillance functions. Of note, after acute myocardial infarction (AMI), cardiac RTM have been shown to inhibit fibrosis, promote angiogenesis, and foster the anti-inflammatory response to injury by interacting with other immune cell types, such as monocytes and T lymphocytes, to drive them towards pro-healing phenotypes. Hypothesis. Using Single Cell RNA Sequencing, we identified a new subpopulation of cardiac RTM characterized by the expression of VSIG4 (B7 family-related protein V-set and Ig domain-containing 4). In this work, we hypothesized that VSIG4+ RTM display protective function in the infarcted heart. Method and results. Visg4 deficient mice showed adverse cardiac remodeling and worsened cardiac function at day 14 and 28 after the onset of ischemia when compared to their wild-type littermates. Echocardiography-based transthoracic injection of FACS-sorted cardiac VISG4+ macrophages into infarcted hearts 2 weeks post-AMI, improved cardiac function in both WT and Vsig4 -/- mice, underlying the protective role of VSIG4+ RTM in this pathological setting. Conversely, injection of Vsig4 -/- macrophages impaired cardiac function in WT and Vsig4 -/- animals. VSIG4 deficiency is associated with a higher number of neutrophils, inflammatory monocytes and macrophages but also with a reduction in the amount of CCR5+ regulatory T lymphocytes in the cardiac tissue without any changes in blood, bone marrow and spleen. In cultured peritoneal macrophages, a prototypical example of RTM, IL4 and IL13 stimulation improved VSIG4 mRNA and protein levels through IL4 receptor alpha and IL13 receptor alpha1 activation. IL4 and IL13 treatment also increased secretion of CCL3 and CCL4, two chemokine ligands of CCR5, these effects were blunted in VSIG4 deficient macrophages. Conclusion. VSIG4+ RTM are key regulators of cardiac remodeling after AMI likely through their ability to hamper inflammation and recruit protective regulatory T cells in infarcted heart.

IL-33-ILC2 axis promotes anti-tumor CD8+ T cell responses via OX40 signaling

Group 2 innate lymphoid cells (ILC2s) are resident cells and participate in innate and adaptive immunity. In the tumor microenvironment (TME), ILC2s contribute to both tumorigenesis and inhibition of tumor growth, but the true role of ILC2s in TME construction remains unclear. We show that IL-33 treatment induces an anti-tumor effect in vivo in a mouse model of melanoma in which ILC2s and CD8+ T cells infiltrate into tumor tissue. This anti-tumor effect is dependent on CD8+ T cells, however, IL-33 does not act directly on CD8+ T cells because the cells lack ST2, the receptor for IL-33. ILC2s and CD8+ T cells in tumors of IL-33-treated mice express OX40 ligand (OX40L) and OX40, respectively, and in vivo blockade of OX40L-OX40 interaction canceled the anti-tumor effect of IL-33. Co-culture of CD8+ T cells expressing OX40 with IL-33-stimulated ILC2 expressing OX40L promoted cell activation and proliferation of CD8+ T cells, which was significantly suppressed by administration of anti-OX40L blocking antibody. Thus, the IL-33-ILC2 axis promotes CD8+ T cell responses via OX40/OX40L interaction and exerts an anti-tumor effect.