scholarly journals A Novel View of the Role of Prostaglandin E2 (PGE2) in Facilitating Engraftment of HSPCs By Activating the NOX2-ROS-Nlrp3 Inflammasome Axis to Incorporate the CXCR4 Receptor into Membrane Lipid Rafts

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 3-3
Author(s):  
Magdalena Kucia ◽  
Kamila Bujko ◽  
Arjun Thapa ◽  
Janina Ratajczak ◽  
Mariusz Z Ratajczak
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Nlrp3 Inflammasome ◽  
Membrane Lipid ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Hematopoietic Stem ◽  
Cxcr4 Receptor ◽  
Nlrp3 Inflammasomes

Background . It is known that prostaglandin E2 (PGE2) increases the homing and engraftment of hematopoietic stem/progenitor cells (HSPCs). However, aside from its role in upregulation of CXCR4 receptor expression on the surface of these cells, the exact mechanism has not been proposed. We have demonstrated in the past that an important step enabling the migration of HSPCs is the incorporation of CXCR4 into membrane lipid rafts on the leading surface (leading edge, in two dimensions) of migrating cells, which facilitates its interaction with cell migration signaling pathways (Wysoczynski M et al. Incorporation of CXCR4 into membrane lipid rafts primes homing-related responses of hematopoietic stem/progenitor cells to an SDF-1 gradient. Blood. 2005;105(1):40-48). Recently, we reported that Nlrp3 inflammasome-deficient HSPCs show a defect in lipid raft formation that results in defective migration of these cells in response to an SDF-1 gradient and their defective homing and engraftment after transplantation (Adamiak, M et al. Nlrp3 Inflammasome Signaling Regulates the Homing and Engraftment of Hematopoietic Stem Cells (HSPCs) by Enhancing Incorporation of CXCR4 Receptor into Membrane Lipid Rafts. Stem Cell Rev and Rep (2020). https://doi.org/10.1007/s12015-020-10005-w). An important activator of Nlrp3 inflammasomes is reactive oxygen species (ROS). Importantly, the enzyme that generates ROS, known as NADPH oxidase 2 (NOX2), is also associated with cell membrane lipid rafts. Hypothesis. Given the known roles of PGE2, membrane lipid rafts, and the Nlrp3 inflammasome in migration, homing, and engraftment of HSPCs, we hypothesized that PGE2 signaling promotes Nlrp3 inflammasome activation in a Nox2-ROS-dependent manner that results in incorporation of CXCR4 into membrane lipid rafts, which better explains the role of PGE2 in these phenomena.Materials and Methods. To test this hypothesis, murine SKL and human CD34+ cells enriched for HSPCs were stimulated with PGE2 to evaluate activation of genes of the Nlrp3 inflammasome complex at the mRNA and protein levels. Next, HSPCs from Nox2-KO mice were tested for membrane lipid raft formation in functional chemotaxis assays in response to SDF-1 gradients under conditions promoting membrane lipid raft formation. Formation of membrane lipid rafts in Nox2-KO cells was also evaluated by confocal analysis in the presence or absence of PGE2. Finally, the effect of the PGE2-Nox2-Nlrp3 inflammasome axis on the formation of membrane lipid rafts was evaluated in the presence of the ROS scavenger N-acethyl-cysteine (NAC). Results. We provide for the first time evidence that PGE2 activates Nlrp3 inflammasomes in HSPCs in a Nox2-ROS-dependent manner. This Nlrp3 inflammasome activation increases at the leading surface of migrating HSPCs with incorporation of the CXCR4 receptor into membrane lipid rafts. Formation of membrane lipid rafts was absent in Nox2-KO and Nlrp3-KO mouse HSPCs and in normal wild type cells after their exposure to NAC. Moreover, we also observed that Nox2-KO and Nlrp3-KO mice had a lower basal level of CXCR4 expression. Conclusions. Our results for the first time explain the role of PGE2 in promoting homing and migration of HSPCs, which occurs in response to PGE2 by activation of the Nox2-ROS-Nlrp3 inflammasome axis and thereby promotes incorporation of the CXCR4 receptor into membrane lipid rafts. Moreover, basal expression of the CXCR4 receptor was at a low level on the surface of HSPCs from Nlrp3-KO mice. Thus, our results provide evidence for the importance of the Nox2-ROS-Nlrp3 inflammasome axis in PGE2-mediated homing and engraftment of HSPCs and the role of PGE2-mediated lipid raft formation for optimal responsiveness of CXCR4 to SDF-1 in the BM microenvironment. Disclosures No relevant conflicts of interest to declare.

scholarly journals Modulation of Purinergic Signaling Prior to Transplantation Both in Hematopoietic Stem Progenitor Cells (HSPCs) or Recipient Bone Marrow (BM) Microenvironment - As Novel Strategies to Accelerate and Facilitate HSPCs Homing and Engraftment

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3809-3809
Author(s):  
Mateusz Adamiak ◽  
Arjun Thapa ◽  
Kamila Bujko ◽  
Katarzyna Brzeźniakiewicz-Janus ◽  
Janina Ratajczak ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Lipid Raft ◽  
Nlrp3 Inflammasome ◽  
Ex Vivo ◽  
Purinergic Signaling ◽  
Membrane Lipid ◽  
Short Exposure ◽  
Heme Oxygenase 1 ◽  
Dependent Manner ◽  
Hematopoietic Stem

Abstract Background. The success rate of hematopoietic stem cell transplantation strongly depends on the number of transplanted hematopoietic stem/progenitor cells (HSPCs) and their speed of engraftment after infusion to the myeloablated transplant recipient. Therefore, clinical outcomes will benefit from accelerating the speed of homing and engraftment rate of transplanted HSPCs. This is important when the number of available HSPCs is low, as seen after poor harvest from BM, poor mobilization efficiency of the donor, and a low number of HSPCs present in the available umbilical cord blood (UCB) unit for an adult recipient. Our recent research demonstrated that purinergic signaling involving extracellular adenosine triphosphate (eATP) and its extracellular metabolite adenosine (eAdo) play a significant opposite role in homing/engraftment of HSPCs - reviewed in Curr Opin Hematol 2021, 28:251-261. To explain this eATP released from the cells of conditioned for transplantation by myeloablation recipient's BM facilitates homing of HSPCs, and subsequently becomes metabolized by cell surface ectonucleotidases CD39 and CD73 to eAdo, that inhibits this process. Therefore, eATP and eAdo upregulated in PB and BM modulate homing/engraftment in i) infused to the recipient donor-derived HSPCs and ii) in recipient BM microenvironment - in an opposite way. We also reported that the beneficial effect of eATP on homing/engraftment of HSPCs depends on the promotion of membrane lipid raft formation on the surface of HSPCs that incorporate homing receptors for their optimal interaction with BM released homing chemoattractants. This process is promoted by eATP activated Nlrp3 inflammasome. On the other hand, Nlrp3 inflammasome and membrane lipid raft formation are inhibited by eAdo in heme oxygenase-1 (HO-1)-dependent manner (Leukemia 2020; 34:1512-1523). Hypothesis. We hypothesized that proper modulation of eATP - eAdo signaling both at the level of transplanted HSPCs and recipient BM microenvironment will speed up the seeding efficiency of transplanted cells to BM niches. Material and Methods. We exposed HSPCs before transplantation ex vivo to i) exogenous eATP or ii) small molecular CD39 and CD73 inhibitors. We also inhibited CD39 and CD73 in transplant recipients BM at the time of myeloablative conditioning. In addition, we also activated ex vivo Nlrp3 inflammasome in HSPCs to be transplanted by specific activator nigericin. In control experiments, eATP stimulated Nlrp3 inflammasome activity was inhibited by the HO-1 activator that is CoPP. Homing of HSPCs was evaluated by measuring a number of donor-derived fluorochrome-labeled cells and clonogenic progenitors in BM of myeloablated hosts at 24 hours after transplantation. Early engraftment was assessed by counting the number of CFU-S and clonogeneic progenitors 12 days after transplantation and by evaluating kinetics of recovery of PB hematopoietic cell counts. Finally, while activation of Nlrp3 inflammasome was assessed by immunofluorescence assay, membrane lipid raft formation was evaluated by confocal microscopy. Results. We noticed that homing and engraftment of HSPCs was significantly accelerated after i) short exposure before transplantation to eATP, ii) inhibition of eAdo formation by CD39, and CD73 inhibitors, and iii) activation of Nlrp3 inflammasome by nigericin. Similarly, inhibition of eAdo formation in recipient BM microenvironment of transplanted mice by CD39 and CD73 inhibitors also improved homing and engraftment efficiency. This correlated with activation in the eATP-dependent manner of Nlrp3 inflammasome in HSPCs followed by membrane lipid raft formation. In the BM microenvironment, upregulation of eATP and inhibition of eAdo also enhanced expression of homing chemoattractants. Conclusions. Since all purinergic signaling modifiers employed in our studies are non-toxic against HSPCs, our data obtained in the animal model indicates that modulation of purinergic signaling before transplantation in HSPCs as well as in BM of the myeloablated recipient would significantly accelerate hematopoietic recovery after hematopoietic transplantation. Disclosures No relevant conflicts of interest to declare.

A Novel Evidence That PNH Affected Cells Residing in Bone Marrow (BM) Due to Impaired Incorporation of CXCR4 and VLA-4 Into Membrane Lipid Rafts Show Defective SDF-1- and VCAM-1-Mediated Retention in BM What Leads to Their Increased Motility and Impaired Interaction with the BM Stem Cell Niches

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1256-1256
Author(s):  
Kasia Mierzejewska ◽  
Cesar Rodriguez ◽  
Vivek R. Sharma ◽  
Magdalena Kucia ◽  
Jaroslaw P. Maciejewski ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Stem Cell ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Research Funding ◽  
Membrane Lipid ◽  
Proper Function ◽  
Hematopoietic Stem ◽  
Cxcr4 Receptor ◽  
Stem Cell Niches

Abstract Abstract 1256 Background. Hematopoietic stem progenitor cells (HSPCs) are retained in bone marrow (BM) niches due to the stromal-derived growth factor-1 (SDF-1)–CXCR4 receptor axis and interactions between Very Late Antigen-4 (VLA-4 or a4b1integrin) and its ligand, Vascular Adhesion Molecule-1 (VCAM-1 or CD106). While HSPCs express CXCR4 and VLA-4, their corresponding ligands, SDF-1 and VCAM-1, are expressed by cells in the BM microenvironment (e.g., osteoblasts and fibroblasts). Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired hemolytic anemia that results from the expansion of hematopoietic stem cells with a mutation in one of the enzymes (PIG-A) responsible for glycosylphosphatidylinositol (GPI anchor) biosynthesis, which is a post-translation modification of proteins associated with lipid rafts on the cell membrane surface. Some of these proteins are involved in the resistance of erythrocytes to lysis by the final product of complement cascade (CC) activation, C5b-C9, also known as the membrane attack complex (MAC). Furthermore, as we reported, the CXCR4 receptor, which binds a-chemokine stromal derived factor-1 (SDF-1) is also associated with lipid rafts (Blood 2005;105:40–8) similarly as VLA-4 (a4b1integrin). Recently we demonstrated that the bioactive lipid sphingosine-1-phosphate (S1P), which is a major chemoattractant directing egress of HSPCs from bone marrow (BM) into peripheral blood (PB) during mobilization, is released from lyzed erythrocytes in C5b-C9/MAC-dependent manner (Leukemia 2010;24:976–85). We also demonstrated that PNH affected HSPCs are preferentially mobilized into PB which suggests their defective retention in BM microenvironment (Leukemia 2012;26:1722). Hypothesis. To explain preferential mobilization of PNH patients HSPCs into PB we hypothesized that BM residing HSPCs may have a defective adhesion in BM niches due to defect in lipid raft formation that are required for a proper function of CXCR4-SDF-1 and VLA-4-VCAM-1 retention axes. Experimental strategies. To address this issue we employed for adhesion, chemotaxis and lipid raft formation assays PIG-A mutated human K-562 and TF-1 cells and more importantly BM MNC derived from PNH patients (n=3). PNH affected HSPCs were sorted by FACS as CD34+FLAER− and normal unaffected HSPCs as CD34+FLAER+cell population. Using these cells we studied their i) adhesiveness to immobilized SDF-1 (CXCR4 ligand), VCAM-1 (VLA-4 ligand), fibronectin and BM stroma cells, ii) chemotactic responsiveness in Transwell assays to SDF-1 gradient, iii) ability to incorporate CXCR4 and VLA-4 receptors into membrane lipid rafts and iv) activation of signaling pathways relevant to cell adhesion/migration (MAPKp42/44 and AKT) in response to SDF-1 stimulation. Results. We found that both PIG-A mutated human K-562 and TF-1 cells and more important CD34+FLAER− HSPCs derived from BM of PNH patients in contrast to normal CD34+FLAER+HSPCs show defective adhesion to immobilized SDF-1, VCAM-I, fibronectin and BM stroma cells. This corresponded with weak responsiveness of these cells in chemotactic assays to SDF-1 gradient and weaker phosphorylation of MAPK042/44 and AKT after SDF-1 stimulation. Finally, direct confocal microscopy studies demonstrated defect in incorporation of CXCR4 and VLA-4 into membrane lipid rafts in CD34+FLAER− cells isolated from BM of PNH patients. Conclusions. Based on these observations, we propose a novel view of the pathogenesis of PNH and the expansion of PNH-affected cells in BM microenvironment. Accordingly, the lack of PIG-A protein, which plays an important role in lipid raft formation a proper function of CXCR4 and VLA-4, confers an adhesion defect and an advantage to PNH-affected HSPCs, which become more mobile. These PNH-mutated HSPCs over time may outcompete normal HSPCs for their niches in BM, due to their increased motility, and contribute to the PNH type of hematopoiesis. Defective retention of PNH affected HSPCs and they proper interaction with stem cell niches in BM may lead with time in some of the cases to their malignant transformation. We propose also that drugs that increase BM level of S1P and thus prevent egress of PNH HSPCs from their niches could be employed in PNH treatment along with CC inhibitors (Eculizumab). Disclosures: Maciejewski: NIH: Research Funding; Aplastic Anemia&MDS International Foundation: Research Funding.

scholarly journals Flotillin-dependent lipid-raft microdomains are required for functional phagolysosomes against fungal infections

2019 ◽  
Author(s):  
Franziska Schmidt ◽  
Andreas Thywißen ◽  
Marie Röcker ◽  
Cristina Cunha ◽  
Zoltán Cseresnyés ◽  
...  
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Fungal Infections ◽  
Pathogenic Fungus ◽  
Cell Transplant ◽  
Hematopoietic Stem ◽  
Essential Components ◽  
Human Pathogenic Fungus ◽  
Lipid Raft Microdomains

SUMMARYLipid rafts form signaling platforms on biological membranes with incompletely characterized role in immune response to infection. Here we report that lipid raft microdomains are essential components of the phagolysosomal membrane of macrophages. Genetic deletion of the lipidraft chaperons flotillin-1 and flotillin-2 demonstrate that the assembly of both major defense complexes vATPase and NADPH oxidase on the phagolysosomal membrane requires lipid rafts. Furthermore, we discovered a new virulence mechanism leading to the dysregulation of lipid-raft formation by melanized wild-type conidia of the important human-pathogenic fungusAspergillus fumigatus. This results in reduced phagolysosomal acidification. Phagolysosomes with ingested melanized conidia contain a reduced amount of free Ca2+ions as compared to phagolysosomes with melanin-free conidia. In agreement with a role of Ca2+for generation of functional lipid rafts, we show that Ca2+-dependent calmodulin activity is required for lipid-raft formation on the phagolysosome. We identified a single nucleotide polymorphism in the humanFLOT1gene that results in heightened susceptibility for invasive aspergillosis in hematopoietic stem-cell transplant recipients. Collectively, flotillin-dependent lipid rafts on the phagolysosomal membrane play an essential role in protective antifungal immunity in humans.

Microglia NLRP3 Inflammasomes Activation Involving Diabetic Neuroinflammation in Diabetic Mice and BV2 Cells

2021 ◽  
Vol 27 ◽  
Author(s):  
Yuan Li ◽  
Haifeng Zhang ◽  
Mingyuan Liu ◽  
Weiying Guo ◽  
Lu Yu
Keyword(s):  
Proinflammatory Cytokines ◽  
Nlrp3 Inflammasome ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Diabetic Mice ◽  
Continuous Release ◽  
Bv2 Cells ◽  
Physiological Values ◽  
Nlrp3 Inflammasomes

Background: Hyperglycemia-induced microglia activation can cause a continuous release of proinflammatory cytokines, which gradually damages neurons and contributes to central diabetic neuroinflammation. Objective: This study aimed to illustrate the possible mechanism related to NLRP3 inflammasome and the aggravation of diabetes neuroinflammation. Methods: The targeted proteins from BV2 cells and brain tissues were tested by Western blot or immunohistochemistry. Cytokines from cell supernatant and serum were detected by ELISA. Meanwhile, cytoplasm and mitochondria ROS were determined by DCFHDA and Mito sox Red, respectively. Results: In vitro, BV2 cells were stimulated by different glucose concentrations (5.5 to 65 mM/L) above physiological values and maintained for different periods (12 to 48h). The proinflammatory cytokines IL-1β，IL18，IL6，TNFα and cytoplasm ROS were significantly increased in a dose-dependent manner, while mitochondrial ROS was unaffected. NLRP3 inflammasomes, MAPKs, and NF-κB pathways were obviously activated at the concentration of 35 mM/L for 12h. Inhibition assay using specific inhibitors indicated that the treatment of glucose (35 mM/L for 12h) could stimulate NLRP3 inflammasome activation via ROS/JNK MAPKs/NF-κB pathway. In STZ induced diabetes mice models, microglia NLRP3, ASC, and caspase-1 proteins were highly expressed, and serum cytokines IL-1β, IL6, IL18, and TNFα were remarkably increased. Conclusion: Microglia NLRP3 inflammasomes activation involves diabetic neuroinflammation in diabetic mice and BV2 cells via ROS/JNK MAPKs/NF-κB pathways.

scholarly journals Role of NLRP3 Inflammasomes in Neuroinflammation Diseases

2020 ◽  
pp. 1-5
Author(s):  
Sen Lin ◽  
Xifan Mei
Keyword(s):  
Nlrp3 Inflammasome ◽  
Current Knowledge ◽  
Inflammasome Activation ◽  
Protein Signaling ◽  
Caspase 1 ◽  
Nlrp3 Inflammasome Activation ◽  
Inflammatory Immune Response ◽  
Nlrp3 Inflammasomes ◽  
Pro Inflammatory Cytokines

<b><i>Background:</i></b> Inflammasomes are large intracellular multi-protein signaling complexes that are formed in the cytosolic compartment as an inflammatory immune response to endogenous danger signals. The formation of the inflammasome enables activation of an inflammatory protease caspase-1 and pyroptosis initiation with the subsequent cleaving of the pro-inflammatory cytokines interleukin (IL)-1β and proIL-18 to produce active forms. The inflammasome complex consists of a nod-like receptor, the adapter apoptosis-associated speck-like protein, and caspase-1. Dysregulation of NLRP3 inflammasome activation is involved in neuroinflammation disease pathogenesis, although its role in SCI development and progression remains controversial due to the inconsistent findings described. <b><i>Summary:</i></b> In this review, we summarize the current knowledge on the contribution of the NLRP3 inflammasome on potential neuroinflammation diseases therapy.

scholarly journals Hematopoiesis is regulated by cholesterol efflux pathways and lipid rafts: connections with cardiovascular diseases

2019 ◽  
Vol 61 (5) ◽  
pp. 667-675 ◽  
Author(s):  
Pooranee K. Morgan ◽  
Longhou Fang ◽  
Graeme I. Lancaster ◽  
Andrew J. Murphy
Keyword(s):  
Cell Membrane ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Cholesterol Efflux ◽  
Receptor Occupancy ◽  
Cholesterol Homeostasis ◽  
Hematopoietic Stem ◽  
Stem And Progenitor Cells ◽  
Feedback Pathways

Lipid rafts are highly ordered regions of the plasma membrane that are enriched in cholesterol and sphingolipids and play important roles in many cells. In hematopoietic stem and progenitor cells (HSPCs), lipid rafts house receptors critical for normal hematopoiesis. Lipid rafts also can bind and sequester kinases that induce negative feedback pathways to limit proliferative cytokine receptor cycling back to the cell membrane. Modulation of lipid rafts occurs through an array of mechanisms, with optimal cholesterol efflux one of the major regulators. As such, cholesterol homeostasis also regulates hematopoiesis. Increased lipid raft content, which occurs in response to changes in cholesterol efflux in the membrane, can result in prolonged receptor occupancy in the cell membrane and enhanced signaling. In addition, certain diseases, like diabetes, may contribute to lipid raft formation and affect cholesterol retention in rafts. In this review, we explore the role of lipid raft-related mechanisms in hematopoiesis and CVD (specifically, atherosclerosis) and discuss how defective cholesterol efflux pathways in HSPCs contribute to expansion of lipid rafts, thereby promoting myelopoiesis and thrombopoiesis. We also discuss the utility of cholesterol acceptors in contributing to lipid raft regulation and disruption, and highlight the potential to manipulate these pathways for therapeutic gain in CVD as well as other disorders with aberrant hematopoiesis.

Impaired Engraftment of Hematopoietic Stem/Progenitor Cells (HSPC) in Immunodefcient Mice Supports an Important Role of Complement System for Optimal Homing.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 338-338
Author(s):  
Reca Ryan ◽  
Marcin Wysoczynski ◽  
Janina Ratajczak ◽  
Mariusz Z. Ratajczak
Keyword(s):  
Progenitor Cells ◽  
Lipid Rafts ◽  
Membrane Lipid ◽  
Scid Mice ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Human Cd34 ◽  
Cell Counts ◽  
Cd34 Cells

Abstract Recently we demonstrated that conditioning for transplantation (radio-chemotherapy) activates complement (C) in bone marrow (BM) and that the third complement component (C3) cleavage fragments (C3a and desArgC3a) increase responsiveness of hematopoietic stem/progenitor cells (HSPC) to stromal-derived factor (SDF)-1 gradient by enhancing the incorporation of CXCR4 into membrane lipid rafts – what enables its better interaction with small GTPases from the Rho/Rac family (Blood2003, 101, 3784, Blood2005, 105, 40–48). Based on these data we hypothesized that C could affect the homing/engraftment of HSPC. Thus we performed transplant experiments in several strains of immunodeficient animals. First, we noticed that lethally irradiated NOD/SCID mice engrafted worse with wt HSPC as compared to wt animals (~30% decrease in a presence of donor-derived clonogeneic CFU-GM in marrow cavities 24 hrs after transplantation). This impaired engraftment correlated with the lack of C activation in BM after conditioning for transplantation by lethal irradiation. The lack of C activation in NOD/SCID mice after conditioning for transplant could be explained by a lack of IgM antibodies that activate C by classical IgM-dependent pathway. Next, to learn more on the molecular mechanisms of C cascade activation during conditioning for transplantation and the role of the C3a-C3aR axis in engraftment of HSPC we studied engraftment i) of wild type (wt) murine HSPC in immunodeficient mice (C3−/− and C3aR−/−) and ii) murine HSPC derived from C3aR−/− or C3−/− deficient mice in wild type littermates. The engraftment of HSPC was evaluated by i) recovery of peripheral blood cell counts in transplanted animals, ii) number of CFU-S colonies and iii) number of clonogeneic progenitors in marrow cavities 16 day after transplantation. We noticed that both C3−/− and C3aR−/− mice had impaired engraftment with wt HSPC. At the same time HSPC from C3aR−/− mice but not C3−/− animals showed poor engraftment in wt recipients. This suggests that i) C3aR expressed on HSPC interacts with C3a generated during C-activation in BM environment and ii) that this interaction is important for optimal homing of HSPC. To support further this notion, human CD34+ cells were exposed to nontoxic doses of C3aR antagonist SB290157 and transplanted into NOD/SCID mice. Subsequently, 24 hrs after transplantation cells were isolated from the marrow cavities and stimulated to grow human CFU-GM colonies. By employing this assay we noticed reduced engraftment of human CD34+ cells (~30%, p<0.0001) as compared to mice transplanted with control CD34+ cells unexposed to SB290157. These data allow for the following conclusions: i) C is activated in BM during conditioning for transplantation by irradiation ii) C is activated after exposure of a natural neoepitope in damaged marrow which is recognized by natural IgM activating C via the classical pathway, iii) C3 cleavage product C3a binds to C3aR on transplanted HSPC and increases incorporation of CXCR4 into membrane lipid rafts enhancing responsiveness of HSPC to an SDF-1 gradient, and finally iv) a proper interplay between the C system and SDF-1-CXCR axis ensures optimal homing of HSPC.

scholarly journals MCL Plays an Anti-Inflammatory Role inMycobacterium tuberculosis-Induced Immune Response by Inhibiting NF-κB and NLRP3 Inflammasome Activation

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Qingwen Zhang ◽  
Xinru Jiang ◽  
Weigang He ◽  
Kailin Wei ◽  
Jinxia Sun ◽  
...  
Keyword(s):  
Immune Response ◽  
Inflammatory Response ◽  
Nlrp3 Inflammasome ◽  
Inflammatory Responses ◽  
Inhibitory Effect ◽  
Drug Candidate ◽  
Inflammasome Activation ◽  
Dependent Manner ◽  
Nlrp3 Inflammasome Activation

Mycobacterium tuberculosis(Mtb) remains a significant menace to global health as it induces granulomatous lung lesions and systemic inflammatory responses during active tuberculosis (TB). Micheliolide (MCL), a sesquiterpene lactone, was recently reported to have a function of relieving LPS-induced inflammatory response, but the regulative role of MCL on the immunopathology of TB still remains unknown. In this experiment, we examined the inhibitory effect of MCL on Mtb-induced inflammatory response in mouse macrophage-like cell line Raw264.7 by downregulating the activation of nuclear factor kappa B (NF-κB) and NLRP3 inflammasome. Evidences showed that MCL decreased the secretion of Mtb-induced inflammatory cytokines (IL-1βand TNF-α) in a dose-dependent manner. Meanwhile, MCL dramatically suppressed Mtb-induced activation of iNOS and COX2 as well as subsequent production of NO. Furthermore, MCL inhibited Mtb-induced phosphorylation of Akt (Ser 473) in Raw264.7. According to our results, MCL plays an important role in modulating Mtb-induced inflammatory response through PI3K/Akt/NF-κB pathway and subsequently downregulating the activation of NLRP3 inflammasome. Therefore, MCL may represent as a potential drug candidate in the adjuvant treatment of TB by regulating host immune response.

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