Damage-associated Pattern Molecules Research Articles

Inflammasome: structure, biological functions, and therapeutic targets.

Inflammasomes are a group of protein complex located in cytoplasm and assemble in response to a wide variety of pathogen-associated molecule patterns, damage-associated molecule patterns, and cellular stress. Generally, the activation of inflammasomes will lead to maturation of proinflammatory cytokines and pyroptotic cell death, both associated with inflammatory cascade amplification. A sensor protein, an adaptor, and a procaspase protein interact through their functional domains and compose one subunit of inflammasome complex. Under physiological conditions, inflammasome functions against pathogen infection and endogenous dangers including mtROS, mtDNA, and so on, while dysregulation of its activation can lead to unwanted results. In recent years, advances have been made to clarify the mechanisms of inflammasome activation, the structural details of them and their functions (negative/positive) in multiple disease models in both animal models and human. The wide range of the stimuli makes the function of inflammasome diverse and complex. Here, we review the structure, biological functions, and therapeutic targets of inflammasomes, while highlight NLRP3, NLRC4, and AIM2 inflammasomes, which are the most well studied. In conclusion, this review focuses on the activation process, biological functions, and structure of the most well-studied inflammasomes, summarizing and predicting approaches for disease treatment and prevention with inflammasome as a target. We aim to provide fresh insight into new solutions to the challenges in this field.

Complement C3 Enhances LPS-Elicited Neuroinflammation and Neurodegeneration Via the Mac1/NOX2 Pathway

Recent studies showed increased expression of complements in various neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases. However, the mechanism regulating the expression of complements and their roles in the pathogenesis of neurodegeneration are unclear. We hypothesized that acute neuroinflammation increases the expression and activation of brain complements, which, in turn, participate in chronic neuroinflammation and progressive neurodegeneration. We initially focused on the complement component C3, because C3 can activate microglia by binding to C3 receptors and attaching to damaged neurons destined to be phagocytosed by microglia. We found that complement C3 is upregulated in lipopolysaccharide (LPS)-stimulated neuron/glial cultures. Mechanistic studies revealed that microglia-released proinflammatory factors initiated the enhanced expression of C3 in astroglia during acute neuroinflammation. On the other hand, the sustained C3 expression during chronic neuroinflammation requires releasing damage-associated molecule patterns (DAMPs) from damaged/degenerating brain cells. Our results suggested that DAMPs might act on microglial integrin receptor Mac1 to trigger the activation of NADPH oxidase (NOX2). Activated microglial NOX2 increases the production of extracellular reactive oxygen species (ROS), elevating the levels of intracellular ROS of astroglia and sustaining the astroglial C3 expression. This was supported by the findings showing reduced C3 expression and attenuated neurodegeneration in LPS-treated neuron/glial cultures prepared from mice deficient in Mac1 or NOX2. LPS-induced neurodegeneration and oxidative stress are significantly reduced in C3 KO neuron/glial cultures and mouse brains. Together, this study provides the first evidence demonstrating the role of C3 in regulating chronic neuroinflammation and in driving progressive neurodegeneration.

Enhanced Immunogenic Cell Death and Antigen Presentation via Engineered Bifidobacterium bifidum to Boost Chemo-immunotherapy.

The immunogenic cell death (ICD) of tumor cells has aroused great interest in the field of immunotherapy, mainly due to the production of plentiful tumor-associated antigens (TAAs) and damage-associated molecule patterns. However, doxorubicin (DOX)-induced tumor-specific T-cell-mediated immune response is usually very weak because of antigen presentation deficiency and the immunosuppressive tumor microenvironment (ITME). Herein, the probiotic Bifidobacterium bifidum (Bi) was covalently modified with DOX-loaded CaP/SiO2 nanoparticles (DNPs@Bi) for tumor therapy. On one hand, the pH-responsive release of DOX could induce chemotherapy and ICD in the ITME. On the other hand, tumor-targeting Bi is able to significantly enhance the presentation of TAAs from B16F10 cells to DCs via Cx43-dependent gap junctions. Due to the combination of enhanced ICD and TAAs presentation, the maturation of DCs and the infiltration of cytotoxic T lymphocytes in the ITME were stimulated. As a result, in vivo antitumor experiments demonstrated that DNPs@Bi prolonged the survival rate and significantly inhibited the tumor progression and metastasis. This strategy of bacterial-driven hypoxia-targeting delivery systems offers a promising approach to tumor chemo-immunotherapy.

PS-BPB04-2: P2RX7 DEFICIENCY OR P2RX7 ANTAGONISM BLUNTS ANGIOTENSIN II-INDUCED HYPERTENSION, VASCULAR INJURY AND CD8+ T CELL ACTIVATION

Objectives: Innate and adaptive immune cells contribute to hypertension and end-organ damage. High blood pressure (BP) causes cardiovascular injury and the release of damage-associated molecule patterns such as adenosine triphosphate (ATP). ATP can bind to the purinergic receptor P2X7 (P2RX7) on innate immune cells triggering interleukin-1β; release, which drives further immune activation. Elevated plasma ATP levels was observed in hypertensive patients. We hypothesized that P2rx7 knockout or P2RX7 antagonism would blunt angiotensin II (AngII)-induced BP elevation and cardiovascular injury through decreased immune activation. Design and method: Ten-to-12-week-old male C57BL/6J wild-type (WT) and P2rx7-/- mice were infused or not with AngII (1000 ng/kg/min) for 14 days. A second group of AngII-infused WT mice was also infused with the P2RX7 antagonist AZ10606120 (694 ng/kg/min) or vehicle. BP was determined by telemetry, plasma ATP using a bioluminescence assay, mesenteric artery function using pressurized myography, cardiac left ventricle (LV) function and mass by ultrasound and activated immune T cell infiltration in aortic perivascular adipose tissue (PVAT) by flow cytometry. Results: Plasma ATP was 2.2 fold higher in AngII-infused compared to sham-treated mice (P < 0.05). AngII-induced systolic BP elevation was reduced by P2rx7 deficiency (12 mm Hg, P < 0.05) or P2RX7 antagonism (27 mm Hg, P < 0.01). AngII induced a 26% decrease in LV fractional shortening (FS, P < 0.05) and a 1.5 fold increase in LV mass/body weight (BW) in WT mice (P < 0.001), which were exaggerated in P2rx7-/- mice (FS: 38% lower and LVmass/BW: 1.14 fold higher, P < 0.05), but not in mice receiving AZ10606120. AngII treatment caused a 26% reduction in the dilatation response of mesenteric arteries to acetylcholine in WT mice (P < 0.05), but not in P2rx7-/- or AZ10606120-treated mice. AngII promoted a 3.8 fold increase in CD69+CD8+ T cell infiltration in aortic PVAT of WT mice (P < 0.001), but not in P2rx7-/- or AZ10606120-treated mice. Conclusion: P2rx7 knockout or antagonism attenuates AngII-induced BP elevation, vascular injury, and infiltration of activated CD8+ T cells into aortic PVAT. P2rx7 knockout exacerbated AngII-induced cardiac dysfunction and hypertrophy, whereas P2RX7 antagonism did not.

Research progress on Mincle as a multifunctional receptor.

Macrophage-induced C-type lectin (Mincle), a lipopolysaccharide-induced protein, is widely expressed on antigen-presenting cells. Mincle acts as a pattern recognition receptor that recognizes pathogen-associated molecular patterns of pathogens such as bacteria and fungi, mainly glycolipids, which induces an acquired immune response against microbial infection. Interestingly, Mincle can also identify patterns of lipid damage-associated molecule patterns released by injured cells, such as Sin3-associated protein 130 and β-glucosylceramides, which induces sterile inflammation and ultimately accelerates the progression of stroke, obesity, hepatitis, kidney injury, autoimmune diseases and tumors by promoting tissue inflammation. This article will review the various functions of Mincle, such as mediating sterile inflammation of tissues to accelerate disease progression, initiating immune responses to fight infection and promoting tumor progression.

Multifunctional Magnetic Nanoclusters Can Induce Immunogenic Cell Death and Suppress Tumor Recurrence and Metastasis.

Metastasis is the predominant cause of cancer deaths due to solid organ malignancies; however, anticancer drugs are not effective in treating metastatic cancer. Here we report a nanotherapeutic approach that combines magnetic nanocluster-based hyperthermia and free radical generation with an immune checkpoint blockade (ICB) for effective suppression of both primary and secondary tumors. We attached 2,2'-azobis(2-midinopropane) dihydrochloride (AAPH) molecules to magnetic iron oxide nanoclusters (IONCs) to form an IONC-AAPH nanoplatform. The IONC can generate a high level of localized heat under an alternating magnetic field (AMF), which decomposes the AAPH on the cluster surface and produces a large number of carbon-centered free radicals. A combination of localized heating and free radicals can effectively kill tumor cells under both normoxic and hypoxic conditions. The tumor cell death caused by the combination of magnetic heating and free radicals led to the release or exposure of various damage-associated molecule patterns, which promoted the maturation of dendritic cells. Treating the tumor-bearing mice with IONC-AAPH under AMF not only eradicated the tumors but also generated systemic antitumor immune responses. The combination of IONC-AAPH under AMF with anti-PD-1 ICB dramatically suppressed the growth of untreated distant tumors and induced long-term immune memory. This IONC-AAPH based magneto-immunotherapy has the potential to effectively combat metastasis and control cancer recurrence.

Abstract 118: P2X7 Receptor Contributes To Angiotensin II-induced Hypertension, Vascular Injury And Cd8 + T Cell Activation

Introduction: Innate and adaptive immune cells contribute to hypertension and end-organ damage. High blood pressure (BP) causes cardiovascular injury and the release of damage-associated molecule patterns such as adenosine triphosphate (ATP). ATP can bind to the purinergic receptor P2X7 (P2RX7) on innate immune cells triggering interleukin-1β release, which drives further immune activation. Hypothesis: We hypothesized that P2rx7 knockout or P2RX7 antagonism would blunt angiotensin II (AngII)-induced BP elevation and cardiovascular injury through decreased immune activation. Methods: Ten-to-12-week-old male C57BL/6J wild-type (WT) and P2rx7 -/- mice were infused or not with AngII (1000 ng/kg/min) for 14 days. A second group of AngII-infused WT mice was also infused with the P2RX7 antagonist AZ10606120 (694 ng/kg/min) or vehicle. BP was determined by telemetry, plasma ATP using a bioluminescence assay, mesenteric artery function using pressurized myography, cardiac left ventricle (LV) function and mass by ultrasound and activated immune T cell infiltration in aortic perivascular adipose tissue (PVAT) by flow cytometry. Results: AngII increased plasma ATP in WT mice (4.4±1.2 vs 2.0±0.9 μM, P <0.05). AngII-induced systolic BP elevation was reduced by P2rx7 deficiency (164±3 vs 176±2 mm Hg, P <0.05) or P2RX7 antagonism (143±5 vs 170±5 mm Hg, P <0.01). AngII decreased LV fractional shortening (FS, 32.5±3.1% vs 43.8±2.4%, P <0.05) and increased LV mass/body weight (BW) in WT mice (LVmass/BW, 6.3±0.2 vs 4.2±0.2 mg/g, P <0.001), which were exaggerated in P2rx7 -/- (FS: 20.2±3.1% and LVmass/BW: 7.2±0.5 mg/g, P <0.05), but not in mice receiving AZ10606120. AngII reduced the dilatation response of mesenteric arteries to acetylcholine in WT (61±7 vs 83±4%, P <0.05), but not in P2rx7 -/- or AZ10606120-treated mice. AngII increased CD69 + CD8 + T cell infiltration in aortic PVAT of WT (60±16 vs 16±3 cells/aortic PVAT, P <0.001), but not in P2rx7 -/- or AZ10606120-treated mice. Conclusion: P2rx7 knockout or antagonism attenuates AngII-induced BP elevation, vascular injury, and infiltration of activated CD8 + T cells into aortic PVAT. P2rx7 knockout exacerbated AngII-induced cardiac dysfunction and hypertrophy, whereas P2RX7 antagonism did not.

The Role of Inflammasomes in Osteoarthritis and Secondary Joint Degeneration Diseases.

Osteoarthritis is age-related and the most common form of arthritis. The main characteristics of the disease are progressive loss of cartilage and secondary synovial inflammation, which finally result in pain, joint stiffness, and functional disability. Similarly, joint degeneration is characteristic of systemic inflammatory diseases such as rheumatoid arthritis and gout, with the associated secondary type of osteoarthritis. Studies suggest that inflammation importantly contributes to the progression of the disease. Particularly, cytokines TNFα and IL-1β drive catabolic signaling in affected joints. IL-1β is a product of inflammasome activation. Inflammasomes are inflammatory multiprotein complexes that propagate inflammation in various autoimmune and autoinflammatory conditions through cell death and the release of inflammatory cytokines and damage-associated molecule patterns. In this article, we review genetic, marker, and animal studies that establish inflammasomes as important drivers of secondary arthritis and discuss the current evidence for inflammasome involvement in primary osteoarthritis. The NLRP3 inflammasome has a significant role in the development of secondary osteoarthritis, and several studies have provided evidence of its role in the development of primary osteoarthritis, while other inflammasomes cannot be excluded. Inflammasome-targeted therapeutic options might thus provide a promising strategy to tackle these debilitating diseases.

Pegylated liposomal mitoxantrone modulates tumor immune landscape to boost PD-L1 blockade therapy

Nanoparticles have great advantages in overcoming the delivery barriers for chemotherapeutics, but the effect on overall tumor immune landscape after drug delivery is still poorly understood. Here, we employed pegylated liposomal mitoxantrone (PL-MIT), an antitumor nanomedicine commercially approved by National Medical Products Administration, to systematically investigate its effects on tumor immune landscape. We found PL-MIT is able to significantly enhance multiple damage-associated molecule patterns (DAMPs) signals in tumors in vivo and evoke strong antitumor immunity by promoting the dendritic cells maturation and T cells infiltration. More importantly, we found that in addition to up-regulating the expression of PD-L1 on tumor cells, PL-MIT tends to induce high expression of PD-L1 on myeloid-derived suppressor cells (MDSC), especially on granulocytic MDSC (G-MDSC), which is unfavorable for the antitumor immunity. Under the guidance of these results, we combined the PL-MIT treatment with anti-PD-L1 antibody and found that the antitumor efficacy was further improved in anti-PD-L1 antibody-insensitive tumors. In summary, our study provides a new insight for the guiding of combination of nanomedicine and antitumor immunotherapy by investigating the impact of nanomedicine on the tumor immune landscape.

The Innate Cellular Immune Response in Xenotransplantation.

Xenotransplantation is very attractive strategy for addressing the shortage of donors. While hyper acute rejection (HAR) caused by natural antibodies and complement has been well defined, this is not the case for innate cellular xenogeneic rejection. An increasing body of evidence suggests that innate cellular immune responses contribute to xenogeneic rejection. Various molecular incompatibilities between receptors and their ligands across different species typically have an impact on graft outcome. NK cells are activated by direct interaction as well as by antigen dependent cellular cytotoxicity (ADCC) mechanisms. Macrophages are activated through various mechanisms in xenogeneic conditions. Macrophages recognize CD47 as a “marker of self” through binding to SIRPα. A number of studies have shown that incompatibility of porcine CD47 against human SIRPα contributes to the rejection of xenogeneic target cells by macrophages. Neutrophils are an early responder cell that infiltrates xenogeneic grafts. It has also been reported that neutrophil extracellular traps (NETs) activate macrophages as damage-associated pattern molecules (DAMPs). In this review, we summarize recent insights into innate cellular xenogeneic rejection.

Abstract 13: P2X7 Receptor Knockout Attenuates Angiotensin II-Induced Hypertension, Vascular Injury And CD8 + T Cell Infiltration

Background: The P2X7 receptor (P2RX7) recognizes damage associated molecule patterns such as adenosine triphosphate (ATP), and triggers the activation of immune cells. Elevated plasma ATP levels have been observed in hypertensive patients, providing a potential mechanism for P2RX7 activation. Additionally, a hypomorphic polymorphism for P2X7 is correlated with a decreased risk for essential hypertension in Chinese post-menopausal women. However, it is unknown whether P2RX7 activation contributes to angiotensin (Ang) II-induced blood pressure (BP) elevation and vascular damage. We hypothesized that P2rx7 knockout would blunt Ang II-induced BP elevation, vascular injury, and infiltration of activated immune T cells into perivascular adipose tissue (PVAT). Methods: Ten-to-12-week-old male C57BL/6J male wild-type (WT) and P2rx7 -/- mice were infused or not with Ang II (1000ng/kg/min) for 14 days. BP was determined by telemetry, mesenteric artery function and remodeling using pressurized myography, aortic stiffening by ultrasound and infiltration of activated immune T cells in aortic PVAT by flow cytometry. Results: Ang II-infused P2rx7 -/- mice display a reduced systolic BP (164±3 vs. 176±2 mm Hg, P <0.05) and pulse pressure (37±4 vs. 53±3 mm Hg, P <0.001) in comparison to WT mice. Aortic stiffening occurred in WT mice treated with Ang II, demonstrated by an increased pulse wave velocity (7.7±0.7 vs. 5.9±0.3 m/s, P <0.05), accompanied by a 3.8-fold increased infiltration of activated CD8 + T cells in aortic PVAT (60±16 vs 16±3 cells/aortic PVAT, P <0.001), which were both absent in P2rx7 -/- mice (6.4±1.4 vs 5.5±1.1 m/s and 27±7 vs 16±3 cells/aortic PVAT). In addition, the frequency of IFN-γ producing CD8 + T cells in the spleen of Ang II-treated WT mice increased (2.6±0.2% vs 1.2±0.2%), which did not occur in P2rx7 -/- mice (1.7±0.3% vs 1.7±0.2%). Ang II-infusion induced mesenteric artery endothelial dysfunction in WT mice (61±7 vs 83±4% relaxation response to acetylcholine, P <0.05), which was absent in P2rx7 -/- mice (89±3 vs 90±3%). Conclusion: P2rx7 knockout attenuates Ang II-induced hypertension, vascular injury, and infiltration of activated CD8 + T cells into aortic PVAT.

Short- and long-distance signaling in plant defense.

When encountering microbial pathogens, plant cells can recognize danger signals derived from pathogens, activate plant immune responses and generate cell-autonomous as well as non-cell-autonomous defense signaling molecules, which promotes defense responses at the infection site and in the neighboring cells. Meanwhile, local damages can result in the release of immunogenic signals including damage-associated molecule patterns and phytocytokines, which also serve as danger signals to potentiate immune responses in cells surrounding the infection site. Activation of local defense responses further induces the production of long-distance defense signals, which can move to distal tissue to activate systemic acquired resistance. In this review, we summarize current knowledge on various signaling molecules involved in short- and long-distance defense signaling, and emphasize the roles of regulatory proteins involved in the processes.

Augmenter of Liver Regeneration Reduces Ischemia Reperfusion Injury by Less Chemokine Expression, Gr-1 Infiltration and Oxidative Stress.

Hepatic ischemia reperfusion injury (IRI) is a major complication in liver resection and transplantation. Here, we analyzed the impact of recombinant human augmenter of liver regeneration (rALR), an anti-oxidative and anti-apoptotic protein, on the deleterious process induced by ischemia reperfusion (IR). Application of rALR reduced tissue damage (necrosis), levels of lipid peroxidation (oxidative stress) and expression of anti-oxidative genes in a mouse IRI model. Damage associated molecule pattern (DAMP) and inflammatory cytokines such as HMGB1 and TNFα, were not affected by rALR. Furthermore, we evaluated infiltration of inflammatory cells into liver tissue after IRI and found no change in CD3 or γδTCR positive cells, or expression of IL17/IFNγ by γδTCR cells. The quantity of Gr-1 positive cells (neutrophils), and therefore, myeloperoxidase activity, was lower in rALR-treated mice. Moreover, we found under hypoxic conditions attenuated ROS levels after ALR treatment in RAW264.7 cells and in primary mouse hepatocytes. Application of rALR also led to reduced expression of chemo-attractants like CXCL1, CXCL2 and CCl2 in hepatocytes. In addition, ALR expression was increased in IR mouse livers after 3 h and in biopsies from human liver transplants with minimal signs of tissue damage. Therefore, ALR attenuates IRI through reduced neutrophil tissue infiltration mediated by lower expression of key hepatic chemokines and reduction of ROS generation.

Reprograming of peripheral Foxp3+ regulatory T cell towards Th17-like cell in patients with active systemic lupus erythematosus

Treg is essential to limit the extend and duration of the immune response, but its stability is still under debate. Here we demonstrate that IL-17-producing Treg cells (Th17-like cells) increased in peripheral blood of patients with Systemic Lupus Erythematosus (SLE). Notably, the Th17-like cells from patient with active SLE were characterized with some phenotype and function of Th17 cells. Upon stimulation, Helios-Foxp3 + CD4+ T cells decrease Foxp3 expression but increase expression of IL-17 and RORγt. Damage associated molecule pattern and inflammatory cytokines are important for induction of IL-17 expression in Treg cells. The Th17-like cells from patients with active SLE lose suppressive function and have robust response to stimulation of autoantigens. We also observed that the level of Th17-like cells in peripheral blood is closely associated with the clinical index of SLE. These findings suggest that instability of Treg plays a critical role in pathogenesis of autoimmune diseases.

Embryonic Stem Cell‐Derived Exosomes Inhibit Doxorubicin‐Induced Pyroptosis in Cardiac Cells

Doxorubicin (Dox) is a potent antineoplastic drug used to treat various cancers. Unfortunately, Dox administration is limited due to induction of adverse cardiotoxicity (DIC), which is mediated through oxidative stress, ER stress, and inflammation. However, it is unknown whether Dox induces an inflammasomne‐mediated cell death, called “pyroptosis” in heart. Pyroptosis occurs via activation of TLR‐4 receptor and generation of NLRP3 inflammasome in response to damage‐associated pattern molecules (DAPMs). This would follow‐up with stimulation of caspase‐1 cascade and secretion of pro‐inflammatory cytokines from the dead cells. This study is undertaken to determine whether Dox generates pyroptosis in cardiac cell culture model. Furthermore, to elucidate the protective effects of embryonic stem cell‐derived exosomes (ES‐Exos) in inhibiting pyroptotic cell death. For this purpose, we designed a cell culture model using H9c2 cadiomyoblasts. To generate DIC, H9c2 were exposed to Dox (2 μM for 24 hrs) to induce pyroptosis and accordingly treated with exosomes (10 μg for additional 24 hrs). Cells were assigned into 4 groups: Control, Dox, Dox+ES‐Exos, and Dox+MEF‐Exos (as negative control). According to western blot analysis, immunohistochemical staining and ELISA data, Dox administration caused significant increase in expression of inflammasome markers, TLR‐4 and NLRP3, (p<0.05), pyroptotic markers, caspase‐1, IL1‐β, Caspase‐11, and gasdermin‐D, (p<0.05), as well as pro‐inflammatory cytokines, TNF‐α and IL‐6, (p<0.05) in H9c2 cells. Conversely, increased pyroptosis and inflammation post‐Dox treatment were attenuated significantly upon ES‐Exos treatment in H9c2 cells (p<0.05). However, MEF‐Exos treatment did not make significant changes vs Dox group (non‐significant vs Dox). Overall, our data shows Dox induces pyroptosis and inflammation within cardiac cells, which can be inhibited following treatment with ES‐exosomes. The significance of this study is a new mechanistic insight on the pathophysiological role of NLRP3 inflammasome‐mediated pyroptosis in Dox‐induced cardiotoxicity.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Citrullinated fibrinogen impairs immunomodulatory function of bone marrow mesenchymal stem cells by triggering toll-like receptor

Bone marrow mesenchymal stem cells (BMSC) have been shown to possess immunomodulatory activities, while its role in rheumatoid arthritis (RA) remains unknown. Citrullinated fibrinogen (cfb) has been considered as a specific autoantigen in RA pathogenesis. Our study aims to determine the role of cfb on immunomodulatory function of BMSC. We demonstrated the specific role of toll-like receptor 4 (TLR4)-NFκB pathway in the pro-inflammatory response of BMSC to cfb with increased production of interleukin (IL)-6, IL-8 and chemokine CC motif ligand 2 (CCL2). Moreover, cfb impaired BMSC-mediated suppression of peripheral blood mononuclear cells (PBMC) proliferation and reduced the production of the key immunomodulatory molecule indoleamine 2,3-dioxygenase (IDO) in BMSC. We have uncovered a previously unrecognized role of cfb in interfering BMSC-mediated immunoregulation in RA. Cfb could act as a damage-associated molecule pattern (DAMP) for BMSC and thereby contribute to the propagation of inflammation in RA.

CD39 deficiency in murine liver allografts promotes inflammatory injury and immune-mediated rejection

Adenosine triphosphate (ATP), an essential metabolic energy source, is released following cell apoptosis or necrosis. It acts as a damage-associated molecule pattern to stimulate innate immune cells. The ectonucleotidase CD39 regulates immune activation by hydrolysis of extracellular ATP. We have shown previously that CD39 expression by donor livers helps protect syngeneic grafts with extended (24h) cold preservation time from ischemia reperfusion injury. Given its immune regulatory properties, we hypothesized that CD39 expression in donor livers might modulate transplant tolerance that occurs following mouse allogeneic liver transplantation (LTx). Livers from C57BL/6 (B6) wild-type (WT) or CD39 KO mice were transplanted into normal C3H recipients with minimal (approximately 1h) cold ischemia. Serum alanine aminotransferase levels at day 4 post-LTx were significantly higher in animals given CD39KO compared with WT livers. Moreover, IFN-γ production by liver-infiltrating CD8+ T cells at day 4 was significantly higher in CD39KO than in WT grafts. Furthermore, splenic T cells from CD39KO liver recipients exhibited greater proliferative responses to donor alloantigens than those from mice given WT grafts. By contrast, there was a concomitant significant reduction in the frequency of regulatory T cells (Treg) in CD39KO than in WT livers. Whereas WT liver allografts survived >100days, no CD39KO grafts survived beyond 40days (median survival time [MST]: WT: >100days vs CD39KO: 8days; p<0.01). In addition, soluble CD39 administration significantly prolonged CD39KO liver allograft survival (MST: 27.5days). These novel data suggest that CD39 expression in liver allografts modulates tissue injury, inflammation, anti-donor effector T cell responses and Treg infiltration and can suppress transplant rejection.

NLRP3 Inflammasome Mediates Chronic Mild Stress-Induced Depression in Mice via Neuroinflammation.

Background:Evidence from both clinical and experimental research indicates that the immune-brain interaction plays a pivotal role in the pathophysiology of depression. A multi-protein complex of the innate immune system, the NLRP3 inflammasome regulates cleavage and secretion of proinflammatory cytokine interleukin-1β. The inflammasome detects various pathogen-associated molecule patterns and damage-associated molecule patterns, which then leads to a series of immune-inflammatory reactions.Methods:To explore the role of inflammasome activation in the underlying biological mechanisms of depression, we established a mouse model of depression with unpredictable chronic mild stress.Results:Mice subjected to chronic mild stress for 4 weeks had significantly higher serum corticosterone levels, serum interleukin-1β levels, and hippocampal active interleukin-1β protein levels. They also displayed depressive-like symptoms, including decreased sucrose preference and increased immobility time. Moreover, the hippocampi of chronic mild stress-exposed mice had significantly higher activity of caspase-1, which accompanied by higher protein levels of NLRP3 and the apoptotic speck-containing protein with a card. Pretreatment with the NLRP3 inflammasome inhibitor VX-765 decreased serum and hippocampal levels of interleukin-1β protein and significantly moderated the depressive-like behaviors induced by chronic mild stress.Conclusions:These data suggest the NLRP3 inflammasome mediates stress-induced depression via immune activation. Future procedures targeting the NLRP3 inflammasome may have promising effects in the prevention and treatment of depression.

Abstract 630: Induction of anti-melanoma immunity after intralesional ablative therapy

Abstract Immunotherapeutic strategies incorporating intralesional (IL) ablative therapy to elicit a tumor specific immune response are under investigation as a non-surgical option to induce tumor regression of cutaneous neoplasms. Rose Bengal (RB) is a water-soluble xanthene dye that was originally used as an intravenous liver diagnostic and is in use by ophthalmologists to stain damaged cells in the eye. In murine models of breast cancer and melanoma, we have shown that IL injection of PV-10 (10% RB in saline solution) leads to ablation of injected tumors and regression of non-injected bystander tumors. In these models, increased anti-tumor T cell responses were measured, supporting the induction of systemic anti-tumor immunity after tumor ablation with PV-10. In our ongoing phase I clinical trial exploring melanoma regression in patients, IL PV-10 has led to a significant decrease of melA positive melanoma cells in the biopsies of both PV10-injected and non-injected lesions. This regression correlated with increased circulating CD3+T cells (p=0.03) in peripheral blood mononuclear cells (PBMC). T cells purified from PBMC from a melanoma patient produced increased IFN-gamma in response to autologous tumor after treatment with PV-10. Ex vivo models implemented to investigate this phenomenon indicate that the cytotoxicity induced by PV-10 is not apoptosis-dependent as evidenced by Annexin staining of melanoma cells following PV-10 treatment. PV-10 directly induced necrosis of melanoma cells at 50 uM, but was not toxic to healthy fibroblasts at the same dose. Further preclinical translational testing has shown that treatment of murine B16 cells with PV-10 leads to release of HMGB1, a soluble Damage Associated Molecule Pattern (DAMP) that is important for activation of dendritic cells (DCs). In the murine B16 melanoma model, there is a significant increase in the number of DCs infiltrating the tumor-draining lymph nodes after IL injection of PV-10. These findings suggest that PV-10 treatment leads to the release of DC activating factors and DC recruitment. Further studies to determine the role of PV-10 on T cell activation are ongoing. In sum, these clinical and preclinical results increase our understanding of the cytotoxic and immunological mechanisms that may play a role in systemic immunity induced by PV-10 tumor ablation. Citation Format: Hao Liu, Krithika Kodumudi, Amy Weber, Amod A. Sarnaik, Shari Pilon-Thomas. Induction of anti-melanoma immunity after intralesional ablative therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 630. doi:10.1158/1538-7445.AM2014-630

CD39 Is Critical for Inducing Tolerance in Murine Allogeneic Liver Transplantation.

Background: ATP is abundant in the cell cytosol and important for cell metabolism. Once cells die or are injured, ATP is released into the extracellular space and activates immune cells as a DAMP (damage-associated molecule pattern). CD39 regulates immune activation by hydrolysis of extracellular (e)ATP. We have found that conventional mouse liver myeloid(m) DC express comparatively high levels of surface CD39 and that this contributes to protection of the liver from cold ischemia reperfusion injury after syngeneic liver transplantation (LTx). We hypothesized that CD39 might play an important role in “spontaneous” transplant tolerance after allogeneic mouse LTx. METHODS: 10-12 week-old male B6 WT or CD39 KO (B6 background) livers were transplanted orthotopically into normal 10-12 week-old male C3H mice. Graft rejection was assessed by host survival and histology and also by serum ALT on day 4 after LTx. Incidences of regulatory T cells (Treg) and IFN-γ+ CD8+ T cells in the graft were quantified by flow cytometry at day 4 post LTx. Anti-donor T cell proliferative responses were evaluated by CFSE-MLR. RESULTS: Whereas all the WT B6 liver transplanted C3H mice survived more than 100 days, animals that received CD39KO livers all died within 40 days (MST: WT: >100d vs CD39 KO 8d; p<0.01). Serum ALT at day 4 post LTx was significantly higher in mice given CD39KO livers than in those with WT livers (WT: 480±226 IU/l vs CD39KO 860±484IU/l; p<0.05). The frequency of Treg in liver graft non-parenchymal cells after LTx was significantly lower in CD39KO livers than in WT livers (WT: 3.4±0.5% vs CD39KO 2.6±0.2%; p<0.05). Moreover IFN-γ production by CD8+ liver T cells was significantly higher in CD39KO allografts than in WT allografts (WT: 38.8±1.7% vs CD39KO 46.6±2.0%; p<0.05). Splenic T cells from CD39KO liver transplant recipients exhibited greater proliferation against donor splenocytes than those from WT liver allografted mice (WT: 27.2±5.8% vs CD39KO 36.3±5.7%; p<0.05). CONCLUSION: CD39 deficiency in liver grafts induces stronger anti-donor T cell responses and breaks “spontaneous” tolerance after mouse liver Tx. CD39 may be an important molecule for promoting liver allograft tolerance.