scholarly journals IL4 Reduces Epileptogenesis Susceptibility Acutely After TBI: The Role of Macrophage/Microglia Polarization

2021 ◽  
Author(s):  
Mozhdeh Radpour ◽  
Bahar Khoshkroodian ◽  
Tara Asgari ◽  
Hamid Gholami Pourbadie ◽  
Mohammad Sayyah
Keyword(s):  
Lesion Size ◽  
Interleukin 4 ◽  
Lesion Volume ◽  
Arginase 1 ◽  
Generalized Seizures ◽  
Ptz Kindling ◽  
Tnf Α ◽  
Inflammatory Phenotype ◽  
Anti Inflammatory ◽  
Post Traumatic Epilepsy

Abstract Traumatic brain injury (TBI) is responsible for 5% of all epilepsy cases, which are known as post-traumatic epilepsy. Macrophage/microglia are key players in TBI pathogenesis. They are activated after TBI, transform to inflammatory phenotype (M1) and trigger neuroinflammation, which provokes epileptogenesis. Interleukin-4 (IL-4) is a well-known polarizer of macrophage/microglia to the anti-inflammatory phenotype (M2). We tested the effect of IL-4 on the rate of epileptogenesis, brain expression of inflammatory and anti-inflammatory cytokines, and the lesion size in traumatic rats. Trauma was exerted to temporo-parietal cortex of rats by Controlled Cortical Impact. Thereafter, rats received a single dose (100ng/rat) of IL-4 through intracerebroventricular injection. After 24h, pentylenetetrazole (PTZ) kindling started and development of generalized seizures was recorded. Level of TNF-α, TGF-β, IL-10, and arginase-1 (Arg-1) was measured in the brain by immunoblotting at 6h, 12h, 24h, 48h, and 5 days after TBI. The lesion size and cell survival were determined by staining. Traumatic rats were kindled by 5±1 PTZ injections (significantly less than 11±2 injections of control and sham-operated rats, p<0.001). IL-4 did not change kindling rate in sham-operated rats but inhibited acceleration of kindling rate in traumatic rats (13±1 PTZ injections, p<0.001). IL-4 decreased post-TBI overexpression of TNF-α (6h, p<0.001) whereas upregulated post-TBI expression of TGF-β (48h, p<0.001), IL-10 (24h, p<0.05; 48h, p<0.01), and Arg-1 (24h, p<0.001). IL-4 decreased lesion volume and number of dead neurons. IL-4 suppresses TBI-induced acceleration of epileptogenesis in rats by directing macrophage/microglia to the anti-inflammatory M2 phenotype and inhibition of neuronal death.

scholarly journals Central Nervous System Barriers Impact Distribution and Expression of iNOS and Arginase-1 in Infiltrating Macrophages During Neuroinflammation

2021 ◽  
Vol 12 ◽  
Author(s):  
Daniela C. Ivan ◽  
Sabrina Walthert ◽  
Giuseppe Locatelli
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Differential Distribution ◽  
General Ability ◽  
Border Regions ◽  
Arginase 1 ◽  
Tnf Α ◽  
Inflammatory Phenotype ◽  
Anti Inflammatory

In multiple sclerosis (MS) and other neuroinflammatory diseases, monocyte-derived cells (MoCs) traffic through distinct central nervous system (CNS) barriers and gain access to the organ parenchyma exerting detrimental or beneficial functions. How and where these MoCs acquire their different functional commitments during CNS invasion remains however unclear, thus hindering the design of MS treatments specifically blocking detrimental MoC actions. To clarify this issue, we investigated the distribution of iNOS+ pro-inflammatory and arginase-1+ anti-inflammatory MoCs at the distinct border regions of the CNS in a mouse model of MS. Interestingly, MoCs within perivascular parenchymal spaces displayed a predominant pro-inflammatory phenotype compared to MoCs accumulating at the leptomeninges and at the intraventricular choroid plexus (ChP). Furthermore, in an in vitro model, we could observe the general ability of functionally-polarized MoCs to migrate through the ChP epithelial barrier, together indicating the ChP as a potential CNS entry and polarization site for MoCs. Thus, pro- and anti-inflammatory MoCs differentially accumulate at distinct CNS barriers before reaching the parenchyma, but the mechanism for their phenotype acquisition remains undefined. Shedding light on this process, we observed that endothelial (BBB) and epithelial (ChP) CNS barrier cells can directly regulate transcription of Nos2 (coding for iNOS) and Arg1 (coding for arginase-1) in interacting MoCs. More specifically, while TNF-α+IFN-γ stimulated BBB cells induced Nos2 expression in MoCs, IL-1β driven activation of endothelial BBB cells led to a significant upregulation of Arg1 in MoCs. Supporting this latter finding, less pro-inflammatory MoCs could be found nearby IL1R1+ vessels in the mouse spinal cord upon neuroinflammation. Taken together, our data indicate differential distribution of pro- and anti-inflammatory MoCs at CNS borders and highlight how the interaction of MoCs with CNS barriers can significantly affect the functional activation of these CNS-invading MoCs during autoimmune inflammation.

scholarly journals Short-chain fatty acids contribute to neuropathic pain via regulating microglia activation and polarization

2021 ◽  
Vol 17 ◽  
pp. 174480692199652
Author(s):  
Feng Zhou ◽  
Xian Wang ◽  
Baoyu Han ◽  
Xiaohui Tang ◽  
Ru Liu ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuropathic Pain ◽  
Thermal Hyperalgesia ◽  
Short Chain Fatty Acids ◽  
Antibiotic Administration ◽  
Tnf Α ◽  
Microglia Polarization ◽  
Inflammatory Phenotype ◽  
Phenotype Markers ◽  
Anti Inflammatory

Microglia activation and subsequent pro-inflammatory responses play a key role in the development of neuropathic pain. The process of microglia polarization towards pro-inflammatory phenotype often occurs during neuroinflammation. Recent studies have demonstrated an active role for the gut microbiota in promoting microglial full maturation and inflammatory capabilities via the production of Short-Chain Fatty Acids (SCFAs). However, it remains unclear whether SCFAs is involved in pro-inflammatory/anti-inflammatory phenotypes microglia polarization in the neuropathic pain. In the present study, chronic constriction injury (CCI) was used to induce neuropathic pain in mice, the mechanical withdrawal threshold, thermal hyperalgesia were accomplished. The levels of microglia markers including ionized calcium-binding adaptor molecule 1 (Iba1), cluster of differentiation 11b (CD11b), pro-inflammatory phenotype markers including CD68, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and anti-inflammatory phenotype markers including CD206, IL-4 in the hippocampus and spinal cord were determined on day 21 after CCI. The results showed that CCI produced mechanical allodynia and thermal hyperalgesia, and also increased the expressions of microglia markers (Iba1, CD11b) and pro-inflammatory phenotype markers (CD68, IL-1β, and TNF-α), but not anti-inflammatory phenotype marker (CD206, IL-4) in the hippocampus and spinal cord, accompanied by increased SCFAs in the gut. Notably, antibiotic administration reversed these abnormalities, and its effects was also bloked by SCFAs administration. In conclusion, data from our study suggest that CCI can lead to mechanical and thermal hyperalgesia, while SCFAs play a key role in the pathogenesis of neuropathic pain by regulating microglial activation and subsequent pro-inflammatory phenotype polarization. Antibiotic administration may be a new treatment for neuropathic pain by reducing the production of SCFAs and further inhibiting the process of microglia polarization.

scholarly journals Comparative Phenotypic and Functional Analyses of the Effects of IL-10 or TGF-β on Porcine Macrophages

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1098
Author(s):  
Tania Carta ◽  
Elisabetta Razzuoli ◽  
Floriana Fruscione ◽  
Susanna Zinellu ◽  
Dionigia Meloni ◽  
...  
Keyword(s):  
Macrophage Polarization ◽  
Phagocytic Cells ◽  
Mhc Ii ◽  
Tnf Α ◽  
Regulated Expression ◽  
Inflammatory Phenotype ◽  
Anti Inflammatory ◽  
Functional Analyses ◽  
The Impact ◽  
Immunosuppressive Cytokines

Macrophages are phagocytic cells involved in maintaining tissue homeostasis and defense against pathogens. Macrophages may be polarized into different functionally specialized subsets. M2c macrophages arise following stimulation with IL-10 or TGF-β and mediate anti-inflammatory and tissue repair functions. M2c macrophages remain poorly characterized in the pig, thus we investigated the impact of these regulatory cytokines on porcine monocyte-derived macrophages (moMΦ). The phenotype and functionality of these cells was characterized though confocal microscopy, flow cytometry, ELISA, and RT-qPCR. Both cytokines induced CD14 and MHC II DR down-regulation and reduced IL-6, TNF-α, and CD14 expression, suggestive of an anti-inflammatory phenotype. Interestingly, neither IL-10 or TGF-β were able to trigger IL-10 induction or release by moMΦ. Differences between these cytokines were observed: stimulation with IL-10, but not TGF-β, induced up-regulation of both CD16 and CD163 on moMΦ. In addition, IL-10 down-regulated expression of IL-1β and IL-12p40 4h post-stimulation and induced a stronger impairment of moMΦ ability to respond to either TLR2 or TLR4 agonists. Overall, our results provide an overview of porcine macrophage polarization by two immunosuppressive cytokines, revealing differences between IL-10 and TGF-β, and reporting some peculiarity of swine, which should be considered in translational studies.

scholarly journals PTX-3 Secreted by Intra-Articular-Injected SMUP-Cells Reduces Pain in an Osteoarthritis Rat Model

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2420
Author(s):  
Minju Lee ◽  
Gee-Hye Kim ◽  
Miyeon Kim ◽  
Ji Min Seo ◽  
Yu Mi Kim ◽  
...  
Keyword(s):  
Scale Up ◽  
Therapeutic Effects ◽  
Arginase 1 ◽  
Inflammatory Phenotype ◽  
Monosodium Iodoacetate ◽  
M1 Phenotype ◽  
Interleukin 1Α ◽  
Anti Inflammatory ◽  
Factor Α ◽  
Inflammatory Macrophages

Mesenchymal stem cells (MSCs) are accessible, abundantly available, and capable of regenerating; they have the potential to be developed as therapeutic agents for diseases. However, concerns remain in their further application. In this study, we developed a SMall cell+Ultra Potent+Scale UP cell (SMUP-Cell) platform to improve whole-cell processing, including manufacturing bioreactors and xeno-free solutions for commercialization. To confirm the superiority of SMUP-Cell improvements, we demonstrated that a molecule secreted by SMUP-Cells is capable of polarizing inflammatory macrophages (M1) into their anti-inflammatory phenotype (M2) at the site of injury in a pain-associated osteoarthritis (OA) model. Lipopolysaccharide-stimulated macrophages co-cultured with SMUP-Cells expressed low levels of M1-phenotype markers (CD11b, tumor necrosis factor-α, interleukin-1α, and interleukin-6), but high levels of M2 markers (CD163 and arginase-1). To identify the paracrine action underlying the anti-inflammatory effect of SMUP-Cells, we employed a cytokine array and detected increased levels of pentraxin-related protein-3 (PTX-3). Additionally, PTX-3 mRNA silencing was applied to confirm PTX-3 function. PTX-3 silencing in SMUP-Cells significantly decreased their therapeutic effects against monosodium iodoacetate (MIA)-induced OA. Thus, PTX-3 expression in injected SMUP-Cells, applied as a therapeutic strategy, reduced pain in an OA model.

scholarly journals Anti-Inflammatory Strategy for M2 Microglial Polarization Using Retinoic Acid-Loaded Nanoparticles

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Marta Machado-Pereira ◽  
Tiago Santos ◽  
Lino Ferreira ◽  
Liliana Bernardino ◽  
Raquel Ferreira
Keyword(s):  
Nitric Oxide ◽  
Retinoic Acid ◽  
Inflammatory Diseases ◽  
Polymeric Nanoparticles ◽  
Microglial Cells ◽  
Interleukin 4 ◽  
Microglial Polarization ◽  
Postsynaptic Protein ◽  
Arginase 1 ◽  
Anti Inflammatory

Inflammatory mechanisms triggered by microglial cells are involved in the pathophysiology of several brain disorders, hindering repair. Herein, we propose the use of retinoic acid-loaded polymeric nanoparticles (RA-NP) as a means to modulate microglia response towards an anti-inflammatory and neuroprotective phenotype (M2). RA-NP were first confirmed to be internalized by N9 microglial cells; nanoparticles did not affect cell survival at concentrations below 100 μg/mL. Then, immunocytochemical studies were performed to assess the expression of pro- and anti-inflammatory mediators. Our results show that RA-NP inhibited LPS-induced release of nitric oxide and the expression of inducible nitric oxide synthase and promoted arginase-1 and interleukin-4 production. Additionally, RA-NP induced a ramified microglia morphology (indicative of M2 state), promoting tissue viability, particularly neuronal survival, and restored the expression of postsynaptic protein-95 in organotypic hippocampal slice cultures exposed to an inflammatory challenge. RA-NP also proved to be more efficient than the free equivalent RA concentration. Altogether, our data indicate that RA-NP may be envisioned as a promising therapeutic agent for brain inflammatory diseases.

scholarly journals Perilla Leaf Extract (PLE) Attenuates COPD Airway Inflammation via the TLR4/Syk/PKC/NF-κB Pathway In Vivo and In Vitro

2022 ◽  
Vol 12 ◽  
Author(s):  
Jiqiao Yuan ◽  
Xuyu Li ◽  
Nan Fang ◽  
Ping Li ◽  
Ziqian Zhang ◽  
...  
Keyword(s):  
Airway Inflammation ◽  
Airflow Limitation ◽  
Interleukin 4 ◽  
Inflammatory Factors ◽  
Chronic Obstructive ◽  
Potential Mechanism ◽  
Tnf Α ◽  
Anti Inflammatory

Chronic obstructive pulmonary disease (COPD) is a complex and heterogeneous disease characterized by persistent airflow limitation but still lacking effective treatments. Perilla frutescens (L.) Britt., an important traditional medicinal plant with excellent antioxidant and anti-inflammatory properties, is widely used for the treatment of respiratory disease in China. However, its protective activity and mechanism against COPD airway inflammation have not been fully studied. Here, the anti-inflammatory effects of the PLE were investigated, and its underlying mechanisms were then elucidated. The presented results suggested a notable effect of the PLE on airway inflammation of COPD, by significantly ameliorating inflammatory cell infiltration in lung tissue, lessening leukocytes (lymphocytes, neutrophils, and macrophages) and inflammatory mediators (interleukin 4 (IL-4), IL-6, IL-17A, interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α)) in the bronchoalveolar lavage fluid (BALF) of cigarette smoke (CS)/lipopolysaccharide (LPS)-induced COPD mice in vivo and inhibiting the production of inflammatory factors (nitric oxide (NO), IL-6, and TNF-α) and intracellular reactive oxygen species (ROS) in LPS-stimulated RAW264.7 cells in vitro. For further extent, PLE treatment significantly suppressed the expression and phosphorylation of TLR4, Syk, PKC, and NF-κB p65 in vivo and their mRNA in vitro. Subsequently, by co-treating with their inhibitors in vitro, its potential mechanism via TLR4/Syk/PKC/NF-κB p65 signals was disclosed. In summary, the obtained results indicated a noteworthy effective activity of the PLE on COPD inflammation, and partly, the TLR4/Syk/PKC/NF-κB p65 axis might be the potential mechanism.

scholarly journals Secoiridoid Glucosides and Anti-Inflammatory Constituents from the Stem Bark of Fraxinus chinensis

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5911
Author(s):  
Hao-Chiun Chang ◽  
Shih-Wei Wang ◽  
Chin-Yen Chen ◽  
Tsong-Long Hwang ◽  
Ming-Jen Cheng ◽  
...  
Keyword(s):  
Gouty Arthritis ◽  
Dimethyl Ester ◽  
Stem Bark ◽  
Human Neutrophils ◽  
No Production ◽  
Necrosis Factor Alpha ◽  
Arginase 1 ◽  
Tnf Α ◽  
Anti Inflammatory ◽  
Fraxinus Chinensis

Qin Pi (Fraxinus chinensis Roxb.) is commercially used in healthcare products for the improvement of intestinal function and gouty arthritis in many countries. Three new secoiridoid glucosides, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), and 3′′,4′′-di-O-methyl-demethyloleuropein (3), have been isolated from the stem bark of Fraxinus chinensis, together with 23 known compounds (4–26). The structures of the new compounds were established by spectroscopic analyses (1D, 2D NMR, IR, UV, and HRESIMS). Among the isolated compounds, (8E)-4′′-O-methylligstroside (1), (8E)-4′′-O-methyldemethylligstroside (2), 3′′,4′′-di-O-methyldemethyloleuropein (3), oleuropein (6), aesculetin (9), isoscopoletin (11), aesculetin dimethyl ester (12), fraxetin (14), tyrosol (21), 4-hydroxyphenethyl acetate (22), and (+)-pinoresinol (24) exhibited inhibition (IC50 ≤ 7.65 μg/mL) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leuckyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 1, 9, 11, 14, 21, and 22 inhibited fMLP/CB-induced elastase release with IC50 ≤ 3.23 μg/mL. In addition, compounds 2, 9, 11, 14, and 21 showed potent inhibition with IC50 values ≤ 27.11 μM, against lipopolysaccharide (LPS)-induced nitric oxide (NO) generation. The well-known proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), were also inhibited by compounds 1, 9, and 14. Compounds 1, 9, and 14 displayed an anti-inflammatory effect against NO, TNF-α, and IL-6 through the inhibition of activation of MAPKs and IκBα in LPS-activated macrophages. In addition, compounds 1, 9, and 14 stimulated anti-inflammatory M2 phenotype by elevating the expression of arginase 1 and Krüppel-like factor 4 (KLF4). The above results suggested that compounds 1, 9, and 14 could be considered as potential compounds for further development of NO production-targeted anti-inflammatory agents.

scholarly journals MAO-A Inhibition by Metaxalone Reverts IL-1β-Induced Inflammatory Phenotype in Microglial Cells

2021 ◽  
Vol 22 (16) ◽  
pp. 8425
Author(s):  
Giovanni Pallio ◽  
Angela D’Ascola ◽  
Luigi Cardia ◽  
Federica Mannino ◽  
Alessandra Bitto ◽  
...  
Keyword(s):  
Neurological Disorders ◽  
Monoamine Oxidase A ◽  
Microglial Cells ◽  
Peroxisome Proliferator ◽  
Necrosis Factor Alpha ◽  
Peroxisome Proliferator Activated Receptor ◽  
Tnf Α ◽  
Mao A ◽  
Inflammatory Phenotype ◽  
Anti Inflammatory

Experimental and clinical studies have suggested that several neurological disorders are associated with the occurrence of central nervous system neuroinflammation. Metaxalone is an FDA-approved muscle relaxant that has been reported to inhibit monoamine oxidase A (MAO-A). The aim of this study was to investigate whether metaxalone might exert antioxidant and anti-inflammatory effects in HMC3 microglial cells. An inflammatory phenotype was induced in HMC3 microglial cells through stimulation with interleukin-1β (IL-1β). Control cells and IL-1β-stimulated cells were subsequently treated with metaxalone (10, 20, and 40 µM) for six hours. IL-1β stimulated the release of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), but reduced the anti-inflammatory cytokine interleukin-13 (IL-13). The upstream signal consisted of an increased priming of nuclear factor-kB (NF-kB), blunted peroxisome proliferator-activated receptor gamma (PPARγ), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression. IL-1β also augmented MAO-A expression/activity and malondialdehyde levels and decreased Nrf2 mRNA expression and protein levels. Metaxalone decreased MAO-A activity and expression, reduced NF-kB, TNF-α, and IL-6, enhanced IL-13, and also increased PPARγ, PGC-1α, and Nrf2 expression. The present experimental study suggests that metaxalone has potential for the treatment of several neurological disorders associated with neuroinflammation.

scholarly journals C16, a novel sinomenine derivatives, promoted macrophage reprogramming toward M2-like phenotype and protected mice from endotoxemia

2021 ◽  
Vol 35 ◽  
pp. 205873842110267
Author(s):  
Ping Ni ◽  
Yue-Qin Liu ◽  
Jin-Yu Man ◽  
Wang Li ◽  
Shan-Shan Xue ◽  
...  
Keyword(s):  
Peritoneal Macrophages ◽  
Enzyme Linked Immunosorbent Assay ◽  
Phenotype Correlation ◽  
Arginase 1 ◽  
Tnf Α ◽  
Anti Inflammatory ◽  
Factor Α ◽  
Correlation Factors ◽  
M2 Phenotype

Macrophage plays a critical part in host defense, tissue repair, and anti-inflammation; Macrophage reprogramming is responsible for disease development or regression. We aimed to clarify the effect of sinomenine-4-hydroxy-palmitate (C16), on macrophage reprogramming and anti-inflammatory in endotoxemia model. According to a structure modification of SIN (Sinomenine), C16 was found. Then, based on the endotoxin model, the mice liver and kidney toxicity was evaluated and serum cytokines level of IL-6 (Interleukin-6), TNF-α (Tumor necrosis factor-α), and IL-1β (Interleukin-1β) were measured by ELISA (Enzyme linked immunosorbent assay). Then, we confirmed the effect of C16 on macrophages reprogramming, we used the flow cytometry to test the effect of C16 on macrophages apoptosis in vitro. Then, iNOS (Inducible nitric oxide synthase), M1-type related cytokines, such as IL-1β, TNF-α, and M2-type related cytokines, such as Arg-1 (Arginase-1), CD206, Fizz1, and Ym1 was detected, which expressed in ANA-1 and primary peritoneal macrophages. To further explore the molecular mechanism of C16 in reprogramming of macrophages from M1 toward M2 phenotype, the expression of STAT1 (signal transducer and activator of Transcription 1), STAT3, ERK1/2 (extracellular signal regulated kinase1/2), AKT, p38, and its corresponding phosphorylation were determined by western blot. Our results demonstrated that C16 improved the survival rate of LPS- (lipopolysaccharide) challenged mice and decreased the inflammatory cytokines expression; After C16 treatment, the expression of M1 phenotype correlation factors decreased significantly, while the expression of M2 phenotype correlation factors increased significantly at different levels compared with normal group. It indicated that C16 reprogram macrophages phenotype from M1 toward M2 following LPS stimulus. Furthermore, the results also showed that C16 showed anti-inflammatory effect by inhibiting LPS-induced p38, AKT and STAT1 phosphorylation and contributing ERK1/2 activation. C16 promoted macrophage reprogramming toward M2-like phenotype via p-p38/p-AKT or STAT1 signals pathway and C16 might be a valid candidate for inflammatory disease.

The Hypoxia Inducible Factor-2/Arginase-1 Axis Plays An Adaptive Role In Gvhd

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2006-2006
Author(s):  
Rena Feinman ◽  
Iriana Colorado ◽  
Jenny Zilberberg ◽  
Thobekile T Ndlovu ◽  
Moshe Z Miller ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Hypoxia Inducible Factor ◽  
Mrna Levels ◽  
Split Dose ◽  
Arginase 1 ◽  
Inflammatory Phenotype ◽  
Inflammatory Bowel ◽  
Anti Inflammatory ◽  
Lethal Irradiation

Abstract The intestinal epithelium is a primary target of graft-versus-host disease (GVHD). The hypoxia-signaling pathway has been implicated as an adaptive response in the intestinal epithelium in numerous models of inflammatory bowel disease, such as colitis and T-cell induced diarrhea. The transcription factor family, hypoxia-inducible factor (HIF) has emerged as master regulators of the transcriptional response to hypoxic stress in normal and transformed cells. HIF heterodimers consist of an oxygen-labile α subunit (HIF-1α, HIF-2α) and a constitutively expressed HIF-1β subunit that mediate a wide spectrum of physiological and cellular adaptive responses, including angiogenesis, metabolic adaption, and erythropoiesis. HIF-1 has recently been implicated as a gut-protective factor in inflammatory bowel disease models by maintaining intestinal homeostasis. HIF-1 can also skew the differentiation of T cells to regulatory T cells (Treg) via the induction of FoxP3, thereby attenuating T-cell driven colitis. Although HIF-1 and HIF-2 share many overlapping functions, HIF-1 has been implicated in the inflammatory phenotype of M1 macrophages via inducible nitric oxide synthase (iNOS) whereas HIF-2 is involved in the anti-inflammatory phenotype of M2 macrophages via arginase-1 (Arg1). Based on these findings and that mucosal inflamed tissues are hypoxic, we hypothesized that the induction of the hypoxia-signaling pathway may limit GVHD-induced mucosal inflammation and injury. To determine the adaptive roles of HIF-1 and HIF-2 in GVHD, we first tested the major histocompatibility complex (MHC)-haploidentical C567BL/6 (B6,H2b) -> B6xDBA/2 (B6D2)F1 (H2b/d) model in which donor spenocytes (2x107) and anti-Thy1 + C’ treated (T- cell depleted) bone marrow (ATBM) cells (5x106) are transplanted into B6D2F1 recipients after exposure to lethal irradiation (11Gy, split dose). B6 ATBM cells transplanted alone into B6D2F1 mice served as a negative control for all comparisons. Realtime PCR analysis demonstrated a modest increase in ileal mucosal HIF-2α expression 8 days (d) post-transplant (p<0.027). In contrast, HIF-1α mRNA levels were not induced. However, both HIF-1α and HIF-2α protein levels were upregulated 2-fold and 5-fold, respectively, in the ileal mucosa of B6D2F1 recipients receiving ATBM plus splenocytes, as determined by western blotting. Notably, Arg1 mRNA levels (HIF-2 target) were markedly upregulated during GVHD (p<0.018), whereas iNOS mRNA levels (HIF-1α target) were downregulated (p<0.01). Increased HIF-2α and Arg1 expression in the ileum as a consequence of GVHD was also observed in two MHC H2b-matched, minor histocompatability antigen (miHA)-mismatched models. BALB.B and CXB-2 mice were exposed to lethal irradiation (9Gy, split dose) and transplanted with B6 ATBM cells alone or along with host-presensitized B6 CD4+ T cells. After 8d, HIF-2α and HIF-1α mRNA ileal levels were increased and decreased, respectively, in both models undergoing GVHD. Similarly, Arg1 transcripts were increased by 12-fold (p<0.03) and 6.1 fold (p<0.007), respectively in B6->BALB.B and B6->CXB-2 models. However, after 20d post-transplant, a 4- and 3-fold decrease in Arg1 mRNA levels occurred in both models. Likewise, two anti-inflammatory, Treg-associated cytokines, interleukin-10 (IL-10) and transforming growth factor beta (TGFβ) mRNA expression were elevated by 2-and 7-fold, respectively, after d8 in B6->BALB.B mice. TGFβ levels returned to baseline (p<0.05 vs d8) after 20d and IL-10 mRNA levels were reduced by 2.5 fold (p<0.029 vs d8). Lastly, in an ELISpot assay, the addition of a prolyl hydroxylase inhibitor, dimethyloxaloylgylcine (DMOG), a HIF activator, reduced the alloreactive interferon-γ response to vehicle levels (p>0.001) in a B6 anti-B6D2F1 mixed lymphocyte reaction. Taken together, our data suggest that HIF-2/Arg1 axis confers an anti-inflammatory response in the ileum after 8d of GVHD. However, after 20d, this response is inversely correlated with the lethality of the GVHD response. The amelioration of alloreactivity by DMOG suggests that the persistent activation of HIF may be necessary to dampen GVHD. Further studies will delineate the contribution of the HIF-2 response in the maintenance of intestinal homeostasis and limiting T cell alloreactivity. Disclosures: Zilberberg: Onyx Pharmaceuticals: Research Funding. Dziopa:Onyx Pharmaceuticals: Research Funding.

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