Publications by authors named "Richard R Kew"

25 Publications

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Group IIA Secreted Phospholipase A Plays a Central Role in the Pathobiology of COVID-19.

medRxiv 2021 Feb 23. Epub 2021 Feb 23.

There is an urgent need to identify cellular and molecular mechanisms responsible for severe COVID-19 disease accompanied by multiple organ failure and high mortality rates. Here, we performed untargeted/targeted lipidomics and focused biochemistry on 127 patient plasma samples, and showed high levels of circulating, enzymatically active secreted phospholipase A Group IIA (sPLA -IIA) in severe and fatal COVID-19 disease compared with uninfected patients or mild illness. Machine learning demonstrated that sPLA -IIA effectively stratifies severe from fatal COVID-19 disease. We further introduce a PLA-BUN index that combines sPLA -IIA and blood urea nitrogen (BUN) threshold levels as a critical risk factor for mitochondrial dysfunction, sustained inflammatory injury and lethal COVID-19. With the availability of clinically tested inhibitors of sPLA -IIA, our study opens the door to a precision intervention using indices discovered here to reduce COVID-19 mortality.
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http://dx.doi.org/10.1101/2021.02.22.21252237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7924289PMC
February 2021

The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Authors:
Richard R Kew

Front Endocrinol (Lausanne) 2019 10;10:470. Epub 2019 Jul 10.

Department of Pathology, Stony Brook Cancer Center, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, United States.

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both and . Recent studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis and augments neutrophilic inflammation . This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.
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http://dx.doi.org/10.3389/fendo.2019.00470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6635842PMC
July 2019

Vitamin D-binding protein deficiency in mice decreases systemic and select tissue levels of inflammatory cytokines in a murine model of acute muscle injury.

J Trauma Acute Care Surg 2018 06;84(6):847-854

From the Department of Pathology (R.R.K., T.T., J.E.D.), Stony Brook University School of Medicine, Stony Brook, New York; and Division of Trauma, Department of Surgery (J.A.V., R.S.J.), Stony Brook University School of Medicine, Stony Brook, New York.

Background: Severe acute muscle injury results in massive cell damage, causing the release of actin into extracellular fluids where it complexes with the vitamin D-binding protein (DBP). We hypothesized that a systemic DBP deficiency would result in a less proinflammatory phenotype.

Methods: C57BL/6 wild-type (WT) and DBP-deficient (DBP-/-) mice received intramuscular injections of either 50% glycerol or phosphate-buffered saline into thigh muscles. Muscle injury was assessed by histology. Cytokine levels were measured in plasma, muscle, kidney, and lung.

Results: All animals survived the procedure, but glycerol injection in both strains of mice showed lysis of skeletal myocytes and inflammatory cell infiltrate. The muscle inflammatory cell infiltrate in DBP-deficient mice had remarkably few neutrophils as compared with WT mice. The neutrophil chemoattractant CXCL1 was significantly reduced in muscle tissue from DBP-/- mice. However, there were no other significant differences in muscle cytokine levels. In contrast, plasma obtained 48 hours after glycerol injection revealed that DBP-deficient mice had significantly lower levels of systemic cytokines interleukin 6, CCL2, CXCL1, and granulocyte colony-stimulating factor. Lung tissue from DBP-/- mice showed significantly decreased amounts of CCL2 and CXCL1 as compared with glycerol-treated WT mice. Several chemokines in kidney homogenates following glycerol-induced injury were significantly reduced in DBP-/- mice: CCL2, CCL5, CXCL1, and CXCL2.

Conclusions: Acute muscle injury triggered a systemic proinflammatory response as noted by elevated plasma cytokine levels. However, mice with a systemic DBP deficiency demonstrated a change in their cytokine profile 48 hours after muscle injury to a less proinflammatory phenotype.
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http://dx.doi.org/10.1097/TA.0000000000001875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5970036PMC
June 2018

Loss of acid ceramidase in myeloid cells suppresses intestinal neutrophil recruitment.

FASEB J 2018 05 19;32(5):2339-2353. Epub 2017 Dec 19.

Department of Medicine, Stony Brook University, Stony Brook, New York, USA.

Bioactive sphingolipids are modulators of immune processes and their metabolism is often dysregulated in ulcerative colitis, a major category of inflammatory bowel disease (IBD). While multiple axes of sphingolipid metabolism have been investigated to delineate mechanisms regulating ulcerative colitis, the role of acid ceramidase (AC) in intestinal inflammation is yet to be characterized. Here we demonstrate that AC expression is elevated selectively in the inflammatory infiltrate in human and murine colitis. To probe for mechanistic insight into how AC up-regulation can impact intestinal inflammation, we investigated the selective loss of AC expression in the myeloid population. Using a model of intestinal epithelial injury, we demonstrate that myeloid AC conditional knockout mice exhibit impairment of neutrophil recruitment to the colon mucosa as a result of defective cytokine and chemokine production. Furthermore, the loss of myeloid AC protects from tumor incidence in colitis-associated cancer (CAC) and inhibits the expansion of neutrophils and granulocytic myeloid-derived suppressor cells in the tumor microenvironment. Collectively, our results demonstrate a tissue-specific role for AC in regulating neutrophilic inflammation and cytokine production. We demonstrate novel mechanisms of how granulocytes are recruited to the colon that may have therapeutic potential in intestinal inflammation, IBD, and CAC.-Espaillat, M. P., Snider, A. J., Qiu, Z., Channer, B., Coant, N., Schuchman, E. H., Kew, R. R., Sheridan, B. S., Hannun, Y. A., Obeid, L. M. Loss of acid ceramidase in myeloid cells suppresses intestinal neutrophil recruitment.
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http://dx.doi.org/10.1096/fj.201700585RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6207279PMC
May 2018

Sepsis in the Critically Ill-Does Gender Matter?

Crit Care Med 2017 11;45(11):1957-1959

Department of Surgery, Stony Brook University School of Medicine, Stony Brook, NY Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY.

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http://dx.doi.org/10.1097/CCM.0000000000002671DOI Listing
November 2017

Sphingolipids in neutrophil function and inflammatory responses: Mechanisms and implications for intestinal immunity and inflammation in ulcerative colitis.

Adv Biol Regul 2017 Jan 14;63:140-155. Epub 2016 Nov 14.

Department of Medicine, Stony Brook University, Stony Brook, NY 11794, USA; Northport Veterans Affairs Medical Center, Northport, NY 11768, USA. Electronic address:

Bioactive sphingolipids are regulators of immune cell function and play critical roles in inflammatory conditions including ulcerative colitis. As one of the major forms of inflammatory bowel disease, ulcerative colitis pathophysiology is characterized by an aberrant intestinal inflammatory response that persists causing chronic inflammation and tissue injury. Innate immune cells play an integral role in normal intestinal homeostasis but their dysregulation is thought to contribute to the pathogenesis of ulcerative colitis. In particular, neutrophils are key effector cells and are first line defenders against invading pathogens. While the activity of neutrophils in the intestinal mucosa is required for homeostasis, regulatory mechanisms are equally important to prevent unnecessary activation. In ulcerative colitis, unregulated neutrophil inflammatory mechanisms promote tissue injury and loss of homeostasis. Aberrant neutrophil function represents an early checkpoint in the detrimental cycle of chronic intestinal inflammation; thus, dissecting the mechanisms by which these cells are regulated both before and during disease is essential for understanding the pathogenesis of ulcerative colitis. We present an analysis of the role of sphingolipids in the regulation of neutrophil function and the implication of this relationship in ulcerative colitis.
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http://dx.doi.org/10.1016/j.jbior.2016.11.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5292058PMC
January 2017

Identification of the gC1qR sites for the HIV-1 viral envelope protein gp41 and the HCV core protein: Implications in viral-specific pathogenesis and therapy.

Mol Immunol 2016 06 23;74:18-26. Epub 2016 Apr 23.

The Departments of Medicine, Stony Brook University, Stony Brook, NY 11794, United States; The Departments of Pathology, Stony Brook University, Stony Brook, NY 11794, United States. Electronic address:

A substantial body of evidence accumulated over the past 20 years supports the concept that gC1qR is a major pathogen-associated pattern recognition receptor (PRR). This conclusion is based on the fact that, a wide range of bacterial and viral ligands are able to exploit gC1qR to either suppress the host's immune response and thus enhance their survival, or to gain access into cells to initiate disease. Of the extensive array of viral ligands that have affinity for gC1qR, the HIV-1 envelope glycoprotein gp41, and the core protein of hepatitis C virus (HCV) are of major interest as they are known to contribute to the high morbidity and mortality caused by these pathogens. While the HCV core protein binds gC1qR and suppresses T cell proliferation resulting in a significantly diminished immune response, the gp41 employs gC1qR to induce the surface expression of the NK cell ligand, NKp44L, on uninfected CD4(+) T cells, thereby rendering them susceptible to autologous destruction by NKp44 receptor expressing NK cells. Because of the potential for the design of peptide-based or antibody-based therapeutic options, the present studies were undertaken to define the gC1qR interaction sites for these pathogen-associated molecular ligands. Employing a solid phase microplate-binding assay, we examined the binding of each viral ligand to wild type gC1qR and 11 gC1qR deletion mutants. The results obtained from these studies have identified two major HCV core protein sites on a domain of gC1qR comprising of residues 144-148 and 196-202. Domain 196-202 in turn, is located in the last half of the larger gC1qR segment encoded by exons IV-VI (residues 159-282), which was proposed previously to contain the site for HCV core protein. The major gC1qR site for gp41 on the other hand, was found to be in a highly conserved region encoded by exon IV and comprises of residues 174-180. Interestingly, gC1qR residues 174-180 also constitute the cell surface-binding site for soluble gC1qR (sgC1qR), which can bind to the cell surface in an autocrine/paracrine manner via surface expressed fibrinogen or other membrane molecules. The identification of the sites for these viral ligands should therefore provide additional targets for the design of peptide-based or antigen-based therapeutic strategies.
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http://dx.doi.org/10.1016/j.molimm.2016.03.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4987126PMC
June 2016

Enhanced recognition of plasma proteins in a non-native state by complement C3b. A possible clearance mechanism for damaged proteins in blood.

Mol Immunol 2015 Mar 15;64(1):55-62. Epub 2014 Nov 15.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794, USA. Electronic address:

Complement C3 is a key fluid-phase protein of the immune system that covalently tags pathogenic cells and molecules for subsequent clearance. Previously, we reported that complement activation results in the formation of multiple C3b:plasma protein complexes in serum. However, it is not known if C3b attaches to any plasma protein in close proximity or preferentially binds damaged proteins. The objective of this study was to determine if C3b couples to plasma proteins in a non-native state and if this could be a potential mechanism to detect and clear damaged proteins from the blood. Using a purified in vitro system with alternative pathway proteins C3, factors B and D it was observed that guanidinium-HCl denaturation of three purified plasma proteins (albumin, alpha-1 proteinase inhibitor, vitamin D binding protein) greatly increased their capacity to form covalent complexes with C3b. However, native vitamin D binding protein, covalently attached to C3b, still retained the ability to bind its natural ligand G-actin, indicating that C3b links to plasma proteins in their native configuration but denaturation substantially increases this interaction. Serum complement activation generated a large number of C3b:plasma protein complexes that bound red blood cell membranes, suggesting a CR1-mediated clearance mechanism. Thermally denatured (60°C) serum activated the alternative pathway when added to fresh serum as evidenced by factor B cleavage and iC3b generation, but this heat-treated serum could not generate the pro-inflammatory peptide C5a. These results show that C3 recognizes and tags damaged plasma proteins for subsequent removal from the blood without triggering proinflammatory functions.
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http://dx.doi.org/10.1016/j.molimm.2014.10.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4282830PMC
March 2015

Cell migration to CXCL12 requires simultaneous IKKα and IKKβ-dependent NF-κB signaling.

Biochim Biophys Acta 2014 Sep 18;1843(9):1796-1804. Epub 2014 Apr 18.

Biochemistry and Cell Biology Dept., Stony Brook University, Stony Brook, New York 11794-5215, USA.

CXCL12 and its unique receptor CXCR4, is critical for the homing of a variety of cell lineages during both development and tissue repair. CXCL12 is particularly important for the recruitment of hemato/lymphopoietic cells to their target organs. In conjunction with the damage-associated alarmin molecule HMGB1, CXCL12 mediates immune effector and stem/progenitor cell migration towards damaged tissues for subsequent repair. Previously, we showed that cell migration to HMGB1 simultaneously requires both IKKβ and IKKα-dependent NF-κB activation. IKKβ-mediated activation maintains sufficient expression of HMGB1's receptor RAGE, while IKKα-dependent NF-κB activation ensures continuous production of CXCL12, which complexes with HMGB1 to engage CXCR4. Here using fibroblasts and primary mature macrophages, we show that IKKβ and IKKα are simultaneously essential for cell migration in response to CXCL12 alone. Non-canonical NF-κB pathway subunits RelB and p52 are also both essential for cell migration towards CXCL12, suggesting that IKKα is required to drive non-canonical NF-κB signaling. Flow cytometric analyses of CXCR4 expression show that IKKβ, but not IKKα, is required to maintain a critical threshold level of this CXCL12 receptor. Time-lapse video microscopy experiments in primary MEFs reveal that IKKα is required both for polarization of cells towards a CXCL12 gradient and to establish a basal level of velocity towards CXCL12. In addition, CXCL12 modestly up-regulates IKKα-dependent p52 nuclear translocation and IKKα-dependent expression of the CXCL12 gene. On the basis of our collective results we posit that IKKα is needed to maintain the basal expression of a critical protein co-factor required for cell migration to CXCL12.
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http://dx.doi.org/10.1016/j.bbamcr.2014.04.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096130PMC
September 2014

Generation of multiple fluid-phase C3b:plasma protein complexes during complement activation: possible implications in C3 glomerulopathies.

J Immunol 2014 Feb 23;192(3):1220-30. Epub 2013 Dec 23.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794;

The complement system is tightly regulated to safeguard against tissue damage that results from unwanted activation. The key step of C3 cleavage to C3b is regulated by multiple mechanisms that control the initiation and extent of activation. This study demonstrated that C3b:plasma protein complexes form in the fluid-phase during complement activation. Several different plasma proteins displayed a discrete high molecular SDS-resistant band when any of the three complement activating pathways were triggered in normal human serum or plasma. Serum depleted of individual complement proteins revealed that C3 and factors B and D were essential for complex formation. Inactivation of the thioester bond in C3 also prevented complex formation. In vitro, complexes could be generated using four purified proteins-C3, factor B, factor D, and target protein-and Mg(2+) to allow C3 convertase formation. These studies showed that the complexes consisted of a plasma protein covalently bound to C3b in a 1:1 molar ratio; the C3b portion was rapidly degraded by factors H and I. Analysis of plasma samples from patients with dense deposit disease and C3 glomerulonephritis demonstrated that C3b:protein complexes form spontaneously in the blood of patients with dense deposit disease and, to a lesser extent, in C3 glomerulonephritis patients, but not in healthy controls. This finding supports the underlying hypothesis that these C3 glomerulopathies are diseases of fluid-phase complement dysregulation. These complexes could normally function as a passive mechanism to intercept C3b from depositing on host cells. However, excessive generation and/or defective clearance of fluid-phase C3b:protein complexes may have pathological consequences.
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http://dx.doi.org/10.4049/jimmunol.1302288DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897554PMC
February 2014

Soluble gC1qR is an autocrine signal that induces B1R expression on endothelial cells.

J Immunol 2014 Jan 6;192(1):377-84. Epub 2013 Dec 6.

Department of Medicine, Stony Brook University, Stony Brook, NY 11794;

Bradykinin (BK) is one of the most potent vasodilator agonists known and belongs to the kinin family of proinflammatory peptides. BK induces its activity via two G protein-coupled receptors: BK receptor 1 (B1R) and BK receptor 2. Although BK receptor 2 is constitutively expressed on endothelial cells (ECs), B1R is induced by IL-1β. The C1q receptor, receptor for the globular heads of C1q (gC1qR), which plays a role in BK generation, is expressed on activated ECs and is also secreted as soluble gC1qR (sgC1qR). Because sgC1qR can bind to ECs, we hypothesized that it may also serve as an autocrine/paracrine signal for the induction of B1R expression. In this study, we show that gC1qR binds to ECs via a highly conserved domain consisting of residues 174-180, as assessed by solid-phase binding assay and deconvolution fluorescence microscopy. Incubation of ECs (24 h, 37 °C) with sgC1qR resulted in enhancement of B1R expression, whereas incubation with gC1qR lacking aa 174-180 and 154-162 had a diminished effect. Binding of sgC1qR to ECs was through surface-bound fibrinogen and was inhibited by anti-fibrinogen. In summary, our data suggest that, at sites of inflammation, sgC1qR can enhance vascular permeability by upregulation of B1R expression through de novo synthesis, as well as rapid translocation of preformed B1R.
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http://dx.doi.org/10.4049/jimmunol.1302031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3876932PMC
January 2014

Circulating complexes of the vitamin D binding protein with G-actin induce lung inflammation by targeting endothelial cells.

Immunobiology 2014 Mar 14;219(3):198-207. Epub 2013 Oct 14.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA. Electronic address:

This study investigated the actin scavenger function of the vitamin D binding protein (DBP) in vivo using DBP null (-/-) mice. Intravenous injection of G-actin into wild-type (DBP+/+) and DBP-/- mice showed that contrary to expectations, DBP+/+ mice developed more severe acute lung inflammation. Inflammation was restricted to the lung and pathological changes were clearly evident at 1.5 and 4h post-injection but were largely resolved by 24h. Histology of DBP+/+ lungs revealed noticeably more vascular leakage, hemorrhage and thickening of the alveolar wall. Flow cytometry analysis of whole lung homogenates showed significantly increased neutrophil infiltration into DBP+/+ mouse lungs at 1.5 and 4h. Increased amounts of protein and leukocytes were also noted in bronchoalveolar lavage fluid from DBP+/+ mice 4h after actin injection. In vitro, purified DBP-actin complexes did not activate complement or neutrophils but induced injury and death of cultured human lung microvascular endothelial cells (HLMVEC) and human umbilical vein endothelial cells (HUVEC). Cells treated with DBP-actin showed a significant reduction in viability at 4h, this effect was reversible if cells were cultured in fresh media for another 24h. However, a 24-h treatment with DBP-actin complexes showed a significant increase in cell death (95% for HLMVEC, 45% for HUVEC). The mechanism of endothelial cell death was via both caspase-3 dependent (HUVEC) and independent (HLMVEC) pathways. These results demonstrate that elevated levels and/or prolonged exposure to DBP-actin complexes may induce endothelial cell injury and death, particularly in the lung microvasculature.
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http://dx.doi.org/10.1016/j.imbio.2013.10.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946638PMC
March 2014

Neutrophil recruitment to the lung in both C5a- and CXCL1-induced alveolitis is impaired in vitamin D-binding protein-deficient mice.

J Immunol 2013 Jul 10;191(2):848-56. Epub 2013 Jun 10.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794, USA.

Knowledge of how neutrophils respond to chemotactic signals in a complex inflammatory environment is not completely understood. Moreover, even less is known about factors in physiological fluids that regulate the activity of chemoattractants. The vitamin D-binding protein (DBP) has been shown to significantly enhance chemotaxis to complement activation peptide C5a using purified proteins in vitro, and by ex vivo depletion of DBP in physiological fluids, but this function has not been determined in vivo. DBP null ((-/-)) mice were used to investigate how a systemic absence of this plasma protein affects leukocyte recruitment in alveolitis models of lung inflammation. DBP(-/-) mice had significantly reduced (~50%) neutrophil recruitment to the lungs compared with their wild-type DBP(+/+) counterparts in three different alveolitis models, two acute and one chronic. The histology of DBP(-/-) mouse lungs also showed significantly less injury than wild-type animals. The chemotactic cofactor function of DBP appears to be selective for neutrophil recruitment, but, in contrast to previous in vitro results, in vivo DBP can enhance the activity of other chemoattractants, including CXCL1. The reduced neutrophil response in DBP(-/-) mice could be rescued to wild-type levels by administering exogenous DBP. Finally, in inflammatory fluids, DBP binds to G-actin released from damaged cells, and this complex may be the active chemotactic cofactor. To our knowledge, results show for the first time that DBP is a significant chemotactic cofactor in vivo and not specific for C5a, suggesting that this ubiquitous plasma protein may have a more significant role in neutrophil recruitment than previously recognized.
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http://dx.doi.org/10.4049/jimmunol.1202941DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3702662PMC
July 2013

The IKKα-dependent NF-κB p52/RelB noncanonical pathway is essential to sustain a CXCL12 autocrine loop in cells migrating in response to HMGB1.

J Immunol 2012 Mar 27;188(5):2380-6. Epub 2012 Jan 27.

Department of Pathology, Stony Brook University Medical Center, Stony Brook, NY 11794, USA.

HMGB1 is a chromatin architectural protein that is released by dead or damaged cells at sites of tissue injury. Extracellular HMGB1 functions as a proinflammatory cytokine and chemoattractant for immune effector and progenitor cells. Previously, we have shown that the inhibitor of NF-κB kinase (IKK)β- and IKKα-dependent NF-κB signaling pathways are simultaneously required for cell migration to HMGB1. The IKKβ-dependent canonical pathway is needed to maintain expression of receptor for advanced glycation end products, the ubiquitously expressed receptor for HMGB1, but the target of the IKKα non-canonical pathway was not known. In this study, we show that the IKKα-dependent p52/RelB noncanonical pathway is critical to sustain CXCL12/SDF1 production in order for cells to migrate toward HMGB1. Using both mouse bone marrow-derived macrophages and mouse embryo fibroblasts (MEFs), it was observed that neutralization of CXCL12 by a CXCL12 mAb completely eliminated chemotaxis to HMGB1. In addition, the HMGB1 migration defect of IKKα KO and p52 KO cells could be rescued by adding recombinant CXCL12 to cells. Moreover, p52 KO MEFs stably transduced with a GFP retroviral vector that enforces physiologic expression of CXCL12 also showed near normal migration toward HMGB1. Finally, both AMD3100, a specific antagonist of CXCL12's G protein-coupled receptor CXCR4, and an anti-CXCR4 Ab blocked HMGB1 chemotactic responses. These results indicate that HMGB1-CXCL12 interplay drives cell migration toward HMGB1 by engaging receptors of both chemoattractants. This novel requirement for a second receptor-ligand pair enhances our understanding of the molecular mechanisms regulating HMGB1-dependent cell recruitment to sites of tissue injury.
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http://dx.doi.org/10.4049/jimmunol.1102454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3288724PMC
March 2012

Cofactor regulation of C5a chemotactic activity in physiological fluids. Requirement for the vitamin D binding protein, thrombospondin-1 and its receptors.

Mol Immunol 2011 Dec 19;49(3):495-503. Epub 2011 Oct 19.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA.

Factors in physiological fluids that regulate the chemotactic activity of complement activation peptides C5a and C5a des Arg are not well understood. The vitamin D binding protein (DBP) has been shown to significantly enhance chemotaxis to C5a/C5a des Arg. More recently, platelet-derived thrombospondin-1 (TSP-1) has been shown to facilitate the augmentation of C5a-induced chemotaxis by DBP. The objective of this study was to better characterize these chemotactic cofactors and investigate the role that cell surface TSP-1 receptors CD36 and CD47 may play in this process. The chemotactic activity in C-activated normal serum, citrated plasma, DBP-depleted serum or C5 depleted serum was determined for both normal human neutrophils and U937 cell line transfected with the C5a receptor (U937-C5aR). In addition, levels of C5a des Arg, DBP and TSP-1 in these fluids were measured by RIA or ELISA. Results show that there is a clear hierarchy with C5a being the essential primary signal (DBP or TSP-1 will not function in the absence of C5a), DBP the necessary cofactor and TSP-1 a dependent tertiary factor, since it cannot function to enhance chemotaxis to C5a without DBP. Measurement of the C5a-induced intracellular calcium flux confirmed the same hierarchy observed with chemotaxis. Moreover, analysis of bronchoalveolar lavage fluid (BALF) from patients with the adult respiratory distress syndrome (ARDS) demonstrated that C5a-dependent chemotactic activity is significantly decreased after anti-DBP treatment. Finally, results show that TSP-1 utilizes cell surface receptors CD36 and CD47 to augment chemotaxis, but DBP does not bind to TSP-1, CD36 or CD47. The results clearly demonstrate that C5a/C5a des Arg needs both DBP and TSP-1 for maximal chemotactic activity and suggest that the regulation of C5a chemotactic activity in physiological fluids is more complex than previously thought.
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http://dx.doi.org/10.1016/j.molimm.2011.09.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3224156PMC
December 2011

DNA alkylating therapy induces tumor regression through an HMGB1-mediated activation of innate immunity.

J Immunol 2011 Mar 7;186(6):3517-26. Epub 2011 Feb 7.

Graduate Program in Molecular and Cellular Biology, Stony Brook University, Stony Brook, NY 11974, USA.

Dysregulation of apoptosis is associated with the development of human cancer and resistance to anticancer therapy. We have previously shown in tumor xenografts that DNA alkylating agents induce sporadic cell necrosis and regression of apoptosis-deficient tumors. Sporadic tumor cell necrosis is associated with extracellular release of cellular content such as the high mobility group box 1 (HMGB1) protein and subsequent recruitment of innate immune cells into the tumor tissue. It remained unclear whether HMGB1 and the activation of innate immunity played a role in tumor response to chemotherapy. In this study, we show that whereas DNA alkylating therapy leads to a complete tumor regression in an athymic mouse tumor xenograft model, it fails to do so in tumors deficient in HMGB1. The HMGB1-deficient tumors have an impaired ability to recruit innate immune cells including macrophages, neutrophils, and NK cells into the treated tumor tissue. Cytokine array analysis reveals that whereas DNA alkylating treatment leads to suppression of protumor cytokines such as IL-4, IL-10, and IL-13, loss of HMGB1 leads to elevated levels of these cytokines upon treatment. Suppression of innate immunity and HMGB1 using depleting Abs leads to a failure in tumor regression. Taken together, these results indicate that HMGB1 plays an essential role in activation of innate immunity and tumor clearance in response to DNA alkylating agents.
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http://dx.doi.org/10.4049/jimmunol.1003267DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3066027PMC
March 2011

Inhibitor of NF-kappa B kinases alpha and beta are both essential for high mobility group box 1-mediated chemotaxis [corrected].

J Immunol 2010 Apr 15;184(8):4497-509. Epub 2010 Mar 15.

Vita-Salute San Raffaele University, School of Medicine, San Raffaele Scientific Institute, Milano, Italy.

Inhibitor of NF-kappaB kinases beta (IKKbeta) and alpha (IKKalpha) activate distinct NF-kappaB signaling modules. The IKKbeta/canonical NF-kappaB pathway rapidly responds to stress-like conditions, whereas the IKKalpha/noncanonical pathway controls adaptive immunity. Moreover, IKKalpha can attenuate IKKbeta-initiated inflammatory responses. High mobility group box 1 (HMGB1), a chromatin protein, is an extracellular signal of tissue damage-attracting cells in inflammation, tissue regeneration, and scar formation. We show that IKKalpha and IKKbeta are each critically important for HMGB1-elicited chemotaxis of fibroblasts, macrophages, and neutrophils in vitro and neutrophils in vivo. By time-lapse microscopy we dissected different parameters of the HMGB1 migration response and found that IKKalpha and IKKbeta are each essential to polarize cells toward HMGB1 and that each kinase also differentially affects cellular velocity in a time-dependent manner. In addition, HMGB1 modestly induces noncanonical IKKalpha-dependent p52 nuclear translocation and p52/RelB target gene expression. Akin to IKKalpha and IKKbeta, p52 and RelB are also required for HMGB1 chemotaxis, and p52 is essential for cellular orientation toward an HMGB1 gradient. RAGE, a ubiquitously expressed HMGB1 receptor, is required for HMGB1 chemotaxis. Moreover, IKKbeta, but not IKKalpha, is required for HMGB1 to induce RAGE mRNA, suggesting that RAGE is at least one IKKbeta target involved in HMGB1 migration responses, and in accord with these results enforced RAGE expression rescues the HMGB1 migration defect of IKKbeta, but not IKKalpha, null cells. Thus, proinflammatory HMGB1 chemotactic responses mechanistically require the differential collaboration of both IKK-dependent NF-kappaB signaling pathways.
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http://dx.doi.org/10.4049/jimmunol.0903131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2915896PMC
April 2010

Identification of two distinct cell binding sequences in the vitamin D binding protein.

Biochim Biophys Acta 2010 May 6;1803(5):623-9. Epub 2010 Mar 6.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA.

The vitamin D binding protein (DBP) is a multifunctional, albumin-like plasma protein that often requires cell surface binding to mediate some of its diverse functions. DBP binds to several different molecules on the external face of the plasma membrane indicating that it may possess distinct cell binding sequences. In this report, surface plasmon resonance was utilized to evaluate the relative binding of the human myeloid cell line U937 to immobilized recombinant expressed DBP in order to identify cell localization sequences. U937 cells showed robust binding to immobilized native DBP, but essentially no interaction when sensor chips were coated with beta(2)-microglobulin or BSA. The cell-DBP interaction was completely eliminated if cells were pretreated with soluble DBP. Recombinant DBP domains and truncated domains were next evaluated to determine the location of cell binding regions. Domains I (amino acids 1-191) and III (379-458), but not domain II (192-378), could support cell binding. Further evaluation of domain I, using truncated proteins and overlapping peptides, demonstrated that a single amino acid sequence, residues 150-172 (NYGQAPLSLLVSYTKSYLSMVGS), mediated cell binding. The domain III cell binding region was investigated using truncated versions of domain III fused to full-length domain II that served as a scaffold. These experiments indicated that the cell binding sequence is located in the first portion of that domain (379-402: ELSSFIDKGQELCADYSENTFTEY). Overlapping peptides spanning this sequence could partially block cell binding only when used in combination. We conclude that DBP contains two cell localization sequences that may be required for some of the multiple functions of this protein.
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http://dx.doi.org/10.1016/j.bbamcr.2010.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2856814PMC
May 2010

Upregulation of vitamin D binding protein (Gc-globulin) binding sites during neutrophil activation from a latent reservoir in azurophil granules.

Mol Immunol 2007 Mar 20;44(9):2370-7. Epub 2006 Nov 20.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA.

Vitamin D binding protein (DBP) is a multifunctional plasma transport protein that is also found on the surface of many cell types. Cell surface DBP significantly enhances chemotactic activity of complement (C) peptides C5a and C5a des Arg. However, both DBP binding and C5a chemotaxis enhancement can vary among neutrophil donors. To test if activation during cell purification is responsible for this variability, neutrophils were isolated using both standard and lipopolysaccharide (LPS)-free protocols. Cells isolated by the LPS-free method had no DBP-enhanced chemotaxis to C5a or DBP binding to plasma membranes. Moreover, neutrophils treated with LPS bound more avidity to immobilized DBP than sham-treated cells. Subcellular fractionation of neutrophils (standard protocol) revealed a heavy plasma membrane (HM) band that contained components of light plasma membranes and all three granules. The HM band possessed most of the DBP binding activity (58%), and activation of cells with ionomycin greatly increased DBP binding to HM. Azurophil granules contained 33% of the total DBP binding sites and there was a highly significant positive correlation (r=0.988) between release of the granule marker myeloperoxidase and DBP binding. These results indicate that fusion of granules with the plasma membrane forms HM that contains DBP binding sites.
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http://dx.doi.org/10.1016/j.molimm.2006.10.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1819475PMC
March 2007

CD44 and annexin A2 mediate the C5a chemotactic cofactor function of the vitamin D binding protein.

J Immunol 2005 Oct;175(7):4754-60

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794, USA.

The vitamin D binding protein (DBP) is a plasma protein that significantly enhances the chemotactic activity of C5a and C5a(desArg) (cochemotactic activity). The objective of this study was to investigate how DBP mediates this process using neutrophils and U937 cells transfected with the C5a receptor (U937-C5aR cells) and comparing chemotaxis to C-activated serum (DBP dependent) vs purified C5a (DBP independent). Binding to the cell surface is essential for this protein to function as a chemotactic cofactor, and DBP binds to a chondroitin sulfate proteoglycan (CSPG) on neutrophil plasma membrane preparations. To determine whether a CSPG also functions to mediate cochemotactic activity, U937-C5aR cells were grown in chlorate to inhibit CSPG sulfation or treated with chondroitinase AC. Either treatment significantly inhibited chemotaxis only to C-activated serum. CD44 is a major cell surface CSPG on leukocytes, and functions to facilitate chemotaxis. Treatment of cells with anti-CD44 blocks chemotaxis of neutrophils and U937-C5aR cells to C-activated serum but not purified C5a. DBP binds to CD44 on the cell surface as evidenced by coimmunoprecipitation, confocal microscopy, and cell binding studies. Annexin A2 associates with CD44 in lipid rafts; therefore, its potential role in mediating cochemotactic activity was investigated. Results demonstrate that anti-A2 inhibits neutrophil and U937-C5aR chemotaxis specifically to C-activated serum, blocks DBP binding to cells, and colocalizes with anti-DBP on the cell surface. These results provide clear evidence that CD44 and annexin A2 mediate the C5a chemotactic cofactor function of DBP.
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http://dx.doi.org/10.4049/jimmunol.175.7.4754DOI Listing
October 2005

Chemotaxis of human monocyte-derived dendritic cells to complement component C1q is mediated by the receptors gC1qR and cC1qR.

Mol Immunol 2006 Mar 2;43(9):1402-7. Epub 2005 Sep 2.

Department of Medicine, Stony Brook University School of Medicine, Stony Brook, NY 11794-8161, USA.

Dendritic cells (DCs) are recruited to inflammatory sites where they phagocytose and process antigens for subsequent presentation to the T lymphocytes in the lymphoid tissue. Several leukocyte chemoattractants and their specific receptors have been shown to induce the migration of DC. The complement protein C1q has multiple immune functions including acting as a chemoattractant for neutrophils, eosinophils and mast cells. Therefore, the objective of this study was to determine if soluble C1q can induce chemotaxis of DC. Culturing cells in GM-CSF and IL-4 for 5 to 7 days generated human monocyte-derived DCs. In addition, LPS was added from day 5 to 7 to induce DC maturation. Cells were classified as either immature or mature DC by assessing the cell surface markers by flow cytometry, phagocytosis of dextran-FITC and T cell proliferation in an allogenic MLR. Immature DCs express the C1q receptors (C1qR), gC1qR and cC1qR/CR and, accordingly, display a vigorous migratory response to soluble C1q with maximal cell movement observed at 10-50nM. In contrast, mature DCs neither express C1qR nor do move to a gradient of soluble C1q. Varying the concentration gradient of C1q (checkerboard assay) showed that the protein largely induces a chemotactic response. Finally, blocking gC1qR and cC1qR/CR by using specific antibodies abolished the chemotactic response to C1q but had no effect on a different chemoattractant C5a. These results clearly demonstrate that C1q functions as a chemotactic factor for immature DC, and migration is mediated through ligation of both gC1qR and cC1qR/CR.
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http://dx.doi.org/10.1016/j.molimm.2005.07.030DOI Listing
March 2006

Selective inhibition of the C5a chemotactic cofactor function of the vitamin D binding protein by 1,25(OH)2 vitamin D3.

Mol Immunol 2006 Mar 22;43(8):1109-15. Epub 2005 Aug 22.

Department of Pathology, Health Sciences Center, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA.

The Vitamin D binding protein (DBP) is a multifunctional plasma protein that can significantly enhance the chemotactic response to complement fragment C5a. The chemotactic cofactor function of DBP requires cell surface binding in order to mediate this process. The goal of this study was to investigate the effect of ligating DBP with its two primary physiological ligands, Vitamin D and G-actin, on both binding to neutrophils and the ability to enhance chemotaxis to C5a. There was no difference in neutrophil binding between of the holo (bound) forms versus the apo (unbound) form of radioiodinated DBP, indicating that the cell binding region of DBP is likely distinct from the Vitamin D sterol and G-actin binding sites. Likewise, G-actin, 25(OH)D3, and G-actin plus 25(OH)D3 bound to DBP did not alter its capacity to enhance chemotaxis toward C5a. However, the active form of Vitamin D (1,25(OH)2D3) completely eliminated the chemotactic cofactor function of DBP. Dose-response curves demonstrated that as little as 1pM 1,25(OH)2D3 significantly inhibited chemotaxis enhancement. Moreover, at physiological concentrations 1,25(OH)2D3 needs to be bound to DBP to mediate the inhibitory effect. Neutrophil chemotaxis to optimal concentrations of C5a, formyl peptide, CXCL8 or leukotriene B4 was not altered by 1,25(OH)2D3, indicating that the active vitamin does not have a global inhibitory effect on neutrophil chemotaxis. Finally, inhibition of cell surface alkaline phosphatase (AP) with sodium orthovanadate completely reversed the inhibitory effect of 1,25(OH)2D3. These results indicate that the cell binding and co-chemotactic functions of DBP are not altered when the protein binds G-actin and/or Vitamin D. Furthermore, the co-chemotactic signal from DBP can be eliminated or counteracted by 1,25(OH)2D3.
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http://dx.doi.org/10.1016/j.molimm.2005.07.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1403830PMC
March 2006

Identification of a region in the vitamin D-binding protein that mediates its C5a chemotactic cofactor function.

J Biol Chem 2004 Dec 14;279(51):53282-7. Epub 2004 Oct 14.

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794-8691, USA.

The vitamin D-binding protein (DBP), also known as group-specific component or Gc-globulin, is a multifunctional plasma protein that can significantly enhance the leukocyte chemotactic activity to C5a and C5a des-Arg. DBP is a member of the albumin gene family and has a triple domain modular structure with extensive disulfide bonding that is characteristic of this protein family. The goal of this study was to identify a region in DBP that mediates the chemotactic cofactor function for C5a. Full-length and truncated versions of DBP (Gc-2 allele) were expressed in Escherichia coli using a glutathione S-transferase fusion protein expression system. The structure of the expressed proteins was confirmed by SDS-PAGE and immunoblotting, whereas protein function was verified by quantitating the binding of [(3)H]vitamin D. Dibutyryl cAMP-differentiated HL-60 cells were utilized to test purified natural DBP and recombinant expressed DBP (reDBP) for their ability to enhance chemotaxis and intracellular Ca(2+) flux to C5a. Natural and full-length reDBP (458 amino acid residues) as well as truncated reDBPs that contained the N-terminal domain I (domains I and II, residues 1-378; domain I, residues 1-191) significantly enhanced both cell movement and intracellular Ca(2+) concentrations in response to C5a. Progressive truncation of DBP domain I localized the chemotactic enhancing region between residues 126-175. Overlapping peptides corresponding to this region were synthesized, and results indicate that a 20-amino-acid sequence (residues 130-149, 5'-EAFRKDPKEYANQFMWEYST-3') in domain I of DBP is essential for its C5a chemotactic cofactor function.
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http://dx.doi.org/10.1074/jbc.M411462200DOI Listing
December 2004

Protease-activated receptor-2 (PAR-2) expression in human fibroblasts is regulated by growth factors and extracellular matrix.

J Invest Dermatol 2004 Nov;123(5):832-9

Department of Medicine, Stony Brook University School of Medicine, Stony Brook, New York, USA.

Many cell types express a membrane receptor, activated by trypsin-like proteases, termed protease-activated receptor-2 (PAR-2). Previous studies describing PAR-2 expression on fibroblasts have been conflicting. In this report, we investigated in vitro PAR-2 expression on several fibroblast cell lines using flow cytometry, immunohistology, and immunoblots of cell lysates. Consistent PAR-2 expression was detected in cultured fibroblasts, although we observed heterogeneity of cellular expression among the cell lines. Some fibroblast lines expressed PAR-2 predominantly as an intracellular protein with differing cytoplasmic staining patterns, whereas other fibroblast lines displayed PAR-2 primarily as a cell surface receptor. Immunoblots of cell lysates with polyclonal anti-PAR-2 demonstrated a 44 kDa band, the predicted molecular weight for the PAR-2 core protein. Furthermore, we noted that expression of PAR-2 was subject to regulation. Fibroblasts grown within a collagen matrix downregulated receptor expression whereas increased PAR-2 expression was observed by the addition of fibroblast growth factors PDGF-BB and TGF-beta. This study may explain the previous inconsistencies in PAR-2 expression observed on tissue fibroblasts. Results indicate that the degree of fibroblast proliferation, attenuated by extracellular matrix and upregulated by growth factors, influences whether fibroblasts express PAR-2 and, thus, would be responsive to protease signaling.
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http://dx.doi.org/10.1111/j.0022-202X.2004.23445.xDOI Listing
November 2004

Platelet-derived thrombospondin-1 is necessary for the vitamin D-binding protein (Gc-globulin) to function as a chemotactic cofactor for C5a.

J Immunol 2004 Sep;173(6):4130-6

Department of Pathology, Stony Brook University School of Medicine, Stony Brook, NY 11794, USA.

The chemotactic activity of C5a and C5a des Arg can be enhanced significantly by the vitamin D-binding protein (DBP), also known as Gc-globulin. DBP is a multifunctional 56-kDa plasma protein that binds and transports several diverse ligands. The objective of this study was to investigate the mechanisms by which DBP functions as a chemotactic cofactor for C5a using neutrophils and U937 cells transfected with the C5aR (U937-C5aR cells). The results demonstrate that U937-C5aR cells show C5a chemotactic enhancement only to DBP in serum, but, unlike mature neutrophils, this cell line cannot respond to DBP in plasma or to purified DBP. Analysis by SDS-PAGE and isoelectric focusing revealed no structural difference between DBP in serum compared with DBP in plasma. However, plasma supplemented with either serum, DBP-depleted serum, or activated platelet releasate provides a required factor and permits DBP to function as a chemotactic cofactor for C5a. Fractionation of activated platelet releasate revealed that the additional factor possessed the properties of thrombospondin-1 (TSP-1). Finally, purified TSP-1 alone could reproduce the effect of serum or platelet releasate, whereas Abs to TSP-1 could block these effects. These results provide clear evidence that TSP-1 is needed for DBP to function as a chemotactic cofactor for C5a.
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http://dx.doi.org/10.4049/jimmunol.173.6.4130DOI Listing
September 2004