Essential Role Of Neutrophils Research Articles

The leukotriene B4 /BLT1-dependent neutrophil accumulation exacerbates immune complex-mediated glomerulonephritis.

Crescent formation is the most important pathological finding that defines the prognosis of nephritis. Although neutrophils are known to play an important role in the progression of crescentic glomerulonephritis, such as anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, the key chemoattractant for neutrophils in ANCA-associated glomerulonephritis has not been identified. Here, we demonstrate that a lipid chemoattractant, leukotriene B4 (LTB4 ), and its receptor BLT1 are primarily involved in disease pathogenesis in a mouse model of immune complex-mediated crescentic glomerulonephritis. Circulating neutrophils accumulated into glomeruli within 1 h after disease onset, which was accompanied by LTB4 accumulation in the kidney cortex, leading to kidney injury. LTB4 was produced by cross-linking of Fc gamma receptors on neutrophils. Mice deficient in BLT1 or LTB4 biosynthesis exhibited suppressed initial neutrophil infiltration and subsequent thrombotic glomerulonephritis and renal fibrosis. Depletion of neutrophils before, but not after, disease onset prevented proteinuria and kidney injury, indicating the essential role of neutrophils in the early phase of glomerulonephritis. Administration of a BLT1 antagonist before and after disease onset almost completely suppressed induction of glomerulonephritis. Finally, we found that the glomeruli from patients with ANCA-associated glomerulonephritis contained more BLT1-positive cells than glomeruli from patients with other etiologies. Taken together, the LTB4 -BLT1 axis is the key driver of neutrophilic glomerular inflammation, and will be a novel therapeutic target for the crescentic glomerulonephritis.

Role of neutrophils in type 2 diabetes and associated atherosclerosis.

The development of cardiovascular diseases associated with Type-2 diabetes remains one of the most challenging public health burdens in the developed world. Early onset of metabolic deficiencies, namely dysregulated glucose homeostasis, peripheral insulin resistance, and impaired insulin production are accompanied by both innate and adaptive immune responses that culminate in a state of chronic, low-grade inflammation. Neutrophils are a critical component of the innate immune system which offer frontline defense against pathogens through a variety of potent effector functions. Recent data indicate an essential role of neutrophils in various disease processes that contribute to the development of Type-2 diabetes and atherosclerosis. In this brief review, we aim to distill the most relevant clinical and pre-clinical literature that investigates the role of neutrophils as an important mediator for the Type-2 diabetes/atherosclerosis connection.

Essential Role of Neutrophils in the Protective Immune Response Induced by a Live Attenuated Leishmania Vaccine.

No licensed vaccine exists against visceral leishmaniasis (VL), a disease caused by the Leishmania donovani parasite. We have previously reported both macrophages and dendritic cells play important role in the protection induced by a live attenuated centrin gene-deleted L. donovani (LdCen-/- ) parasite vaccine. The role of neutrophils in orchestrating the initial innate response to pathogens is widely recognized. To investigate the early interaction of LdCen-/- with neutrophils, we immunized mice intradermally in the ear pinna with LdCen-/- Compared with LdWT infection, LdCen-/- parasites induced higher recruitment of neutrophils to the ear dermis and ear draining lymph nodes (dLN) as early as 6-18 h after immunization, which were predominantly proinflammatory in nature. Neutrophils from ear dLN of LdCen-/- -immunized mice exhibited heightened expression of costimulatory molecules and attenuated expression of coinhibitory molecules necessary for higher T cell activation. Further phenotypic characterization revealed heterogeneous neutrophil populations containing Nα and Nβ subtypes in the ear dLN. Of the two, the parasitized Nα subset from LdCen-/- -immunized mice exhibited much stronger Ag-specific CD4+ T cell proliferation ex vivo. Adoptive transfer of neutrophils bearing LdCen-/- parasites induced an increased Th1 response in naive mice. Importantly, neutrophil depletion significantly abrogated Ag-specific CD4+ T cell proliferation in LdCen-/- -immunized mice and impaired protection against virulent challenge. Conversely, replenishing of neutrophils significantly restored the LdCen-/- -induced host-protective response. These results suggest that neutrophils are indispensable for protective immunity induced by LdCen-/- parasite vaccine.

VISTA deficiency protects from immune complex-mediated glomerulonephritis by inhibiting neutrophil activation

V-type immunoglobulin domain-containing suppressor of T-cell activation (VISTA) is a negative checkpoint regulator of T cells. We assessed VISTA deficient mice in the murine nephrotoxic nephritis models of acute and chronic immune-complex mediated glomerulonephritis. We show that VISTA deficiency protects from crescentic glomerulonephritis, with no effect on the nephritogenic adaptive immune response. The early neutrophil influx was unaffected but proteinuria was reduced suggesting a reduction in neutrophil activation. In vivo, there was reduced neutrophil degranulation in VISTA deficienct mice and, in vitro, VISTA-deficient neutrophils had an impaired response to immune complexes but not to fMLP or PMA. Mice with a genetic deficiency of neutrophils due to myeloid-specific deletion of myeloid cell leukemia 1 (Mcl-1) were also protected from crescentic glomerulonephritis, indicating an essential role for neutrophils. Therefore, VISTA deficiency inhibits neutrophil activation by immune complexes and neutrophil-dependent crescentic glomerulonephritis. This suggests that VISTA is a therapeutic target for inflammatory disease. However, this would need to be balanced against a potential enhancing effect on autoimmunity.

Pseudomonas aeruginosa rugose small-colony variants evade host clearance, are hyper-inflammatory, and persist in multiple host environments.

Pseudomonas aeruginosa causes devastating infections in immunocompromised individuals. Once established, P. aeruginosa infections become incredibly difficult to treat due to the development of antibiotic tolerant, aggregated communities known as biofilms. A hyper-biofilm forming clinical variant of P. aeruginosa, known as a rugose small-colony variant (RSCV), is frequently isolated from chronic infections and is correlated with poor clinical outcome. The development of these mutants during infection suggests a selective advantage for this phenotype, but it remains unclear how this phenotype promotes persistence. While prior studies suggest RSCVs could survive by evading the host immune response, our study reveals infection with the RSCV, PAO1ΔwspF, stimulated an extensive inflammatory response that caused significant damage to the surrounding host tissue. In both a chronic wound model and acute pulmonary model of infection, we observed increased bacterial burden, host tissue damage, and a robust neutrophil response during RSCV infection. Given the essential role of neutrophils in P. aeruginosa-mediated disease, we investigated the impact of the RSCV phenotype on neutrophil function. The RSCV phenotype promoted phagocytic evasion and stimulated neutrophil reactive oxygen species (ROS) production. We also demonstrate that bacterial aggregation and TLR-mediated pro-inflammatory cytokine production contribute to the immune response to RSCVs. Additionally, RSCVs exhibited enhanced tolerance to neutrophil-produced antimicrobials including H2O2 and the antimicrobial peptide LL-37. Collectively, these data indicate RSCVs elicit a robust but ineffective neutrophil response that causes significant host tissue damage. This study provides new insight on RSCV persistence, and indicates this variant may have a critical role in the recurring tissue damage often associated with chronic infections.

The Essential Role of Neutrophils during Infection with the Intracellular Bacterial Pathogen Listeria monocytogenes.

Neutrophils have historically been characterized as first responder cells vital to host survival because of their ability to contain and eliminate bacterial and fungal pathogens. However, recent studies have shown that neutrophils participate in both protective and detrimental responses to a diverse array of inflammatory and infectious diseases. Although the contribution of neutrophils to extracellular infections has been investigated for decades, their specific role during intracellular bacterial infections has only recently been appreciated. During infection with the Gram-positive intracellular pathogen Listeria monocytogenes, neutrophils are recruited from the bone marrow to sites of infection where they use novel bacterial-sensing pathways leading to phagocytosis and production of bactericidal factors. This review summarizes the requirement of neutrophils during L. monocytogenes infection by examining both neutrophil trafficking and function during primary and secondary infection.

Abstract 4977: An essential role for neutrophils in lung cancer promotion .

Abstract Lung cancer is the leading cause of cancer death worldwide, and cigarette smoking is the principal cause of it. Cigarette smoke-induced lung cancer is characterized by a deregulated inflammatory tumor microenvironment. Tumor cells produce various cytokines and chemokines that attract leukocytes. Leukocytes (innate and adaptive immune cells) can amplify parenchymal innate immune responses, and have been shown to contribute to tumor promotion. In addition, smokers with chronic obstructive pulmonary disease (COPD), an inflammatory disease of the lung, have an increased risk of lung cancer compared to smokers without COPD. These facts suggest a strong link between COPD-type inflammation and lung cancer promotion. In histopathologic specimens of lung and in bronchoalveolar lavage fluid (BALF) from COPD patients, neutrophils and macrophages are prominent. Neutrophils are among the first cells to arrive at sites of inflammation, and the increased number of tumor-associated neutrophils is linked to poorer outcome in patients with lung cancer. We have previously shown that COPD-like airway inflammation promotes lung cancer in a K-ras mutant mouse model of lung cancer (CC-LR). This was associated with severe neutrophilic influx due to increased level of neutrophil chemoattractant, KC, which was partially inhibited by using a natural non-specific anti-inflammatory agent, curcumin 1% in diet, and resulted in significant tumor suppression. To further study the role of neutrophil in lung tumorigenesis, we depleted neutrophils in CC-LR mice using an anti-neutrophil antibody, mLy6G, 5mg/kg twice a week by intraperitoneal injection. This resulted in complete lung neutrophil depletion and 68% (3.2-fold) reduction in lung surface tumor number. Neutrophil elastase (NE) is a potent elastolytic enzyme produced by neutrophils at the site of inflammation. It participates actively in COPD development and might contribute to tumor progression by activating proteolytic cascades. The concentration of NE in tumor extracts was also found to be linked to the invasiveness of lung cancer. Therefore, we crossed the CC-LR mice with NE knock out (KO) mice. We have found that lack of NE significantly inhibited lung cancer development by 43% (1.7-fold) without changing the BALF inflammatory cell component of the CC-LR mice. We further inhibited the main receptor for neutrophil chemo-attractant KC, CXCR2, using a selective inhibitor, SB332235Z, 50 mg/kg orally twice daily by gavage. Similarly, this also resulted in significant suppression of neutrophil recruitment into the lung of CC-LR mice followed by significant (∼64%, 2.8-fold) tumor reduction. We conclude that lung cancer promotion by inflammation partly mediated by activation of IL-8/CXCR2 pathway and subsequent recruitment of neutrophils and release of neutrophil elastase. This provides a baseline for future clinical trails using IL-8/CXCR2 pathway or NE inhibitors in patients with lung cancer. Citation Format: Lei Gong, Amber C. Cumpian, Cesar E. Ochoa, Daniel J. Lapid, Seyedeh Golsar Mirabolfathinejad, Maria Miguelina De la Garza, Seyed Javad Moghaddam. An essential role for neutrophils in lung cancer promotion . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4977. doi:10.1158/1538-7445.AM2013-4977

Essential Role for Neutrophils in Pathogenesis and Adaptive Immunity in Chlamydia caviae Ocular Infections

Trachoma, the world's leading cause of preventable blindness, is produced by chronic ocular infection with Chlamydia trachomatis, an obligate intracellular bacterium. While many studies have focused on immune mechanisms for trachoma during chronic stages of infection, less research has targeted immune mechanisms in primary ocular infections, events that could impact chronic responses. The goal of this study was to investigate the function of neutrophils during primary chlamydial ocular infection by using the guinea pig model of Chlamydia caviae inclusion conjunctivitis. We hypothesized that neutrophils help modulate the adaptive response and promote host tissue damage. To test these hypotheses, guinea pigs with primary C. caviae ocular infections were depleted of neutrophils by using rabbit antineutrophil antiserum, and immune responses and immunopathology were evaluated during the first 7 days of infection. Results showed that neutrophil depletion dramatically decreased ocular pathology, both clinically and histologically. The adaptive response was also altered, with increased C. caviae-specific IgA titers in tears and serum and decreased numbers of CD4(+) and CD8(+) T cells in infected conjunctivae. Additionally, there were changes in conjunctival chemokines and cytokines, such as increased expression of IgA-promoting interleukin-5 and anti-inflammatory transforming growth factor β, along with decreased expression of T cell-recruiting CCL5 (RANTES). This study, the first to investigate the role of neutrophils in primary chlamydial ocular infection, indicates a previously unappreciated role for neutrophils in modulating the adaptive response and suggests a prominent role for neutrophils in chlamydia-associated ocular pathology.

Essential Role for Neutrophils but not Alveolar Macrophages at Early Time Points followingAspergillus fumigatusInfection

Alveolar macrophages and neutrophils mediate innate immune defense against the opportunistic fungal pathogen Aspergillus fumigatus and are believed to be essential for host survival following inhalation of fungal spores (conidia). Although alveolar macrophages are postulated to kill inhaled conidia and neutrophils are believed to act against hyphae, the relative contribution of alveolar macrophages and neutrophils to early defense against A. fumigatus remain incompletely defined. To more precisely characterize the contributions of alveolar macrophages and neutrophils in antifungal host defense, we selectively depleted each cell population at different times following pulmonary challenge with conidia. Mice depleted of alveolar macrophages prior to pulmonary A. fumigatus infection recruited neutrophils normally and restricted hyphal tissue invasion. In contrast, neutrophil depletion prior to or within 3 h after infection was associated with high mortality. Neutrophil depletion at later time points, however, was associated with nearly normal survival rates. Our studies suggest that neutrophils, but not alveolar macrophages, provide essential anticonidial defense and that a brief period of influx into the respiratory tree is sufficient to prevent conidial germination and invasive disease.

Essential role of neutrophils in anti‐type II collagen antibody and lipopolysaccharide‐induced arthritis

In mice arthritis model induced by anti-type II collagen (CII) antibodies and lipopolysaccharide (LPS), most of cells that infiltrated into the joint space were neutrophils. To investigate the role of neutrophils in the pathogenesis of arthritis, we depleted the neutrophils in vivo by injection of the antibody against Gr-1 expressed mainly on neutrophils. The neutrophil depletion completely inhibited the arthritis development. Furthermore, neutrophil depletion in mice that had already developed arthritis ameliorated the disease. These results showed that neutrophils are indispensable not only for the development, but also for the maintenance of arthritis. Next, we tried to develop arthritis in C5-deficient mice to investigate the involvement of C5a, one of chemotactic factors for neutrophils. C5-deficient mice showed significant reduction in arthritis development in comparison with wild type mice. Injection of pertussis toxin (Ptx) into the mice, which inhibits the signals from the inhibitory G-protein coupled-receptors including the C5a receptor, suppressed the development of arthritis. Furthermore, Ptx also ameliorated the arthritis when injected into mice that had already developed the disease. These results suggest the important role of chemotactic factors involving C5a and inhibitory G-protein (Gi)-coupled receptors not only in the development, but also in the maintenance of arthritis.

Essential role of neutrophils in initiation of arthritis

Essential role of neutrophils in initiation of arthritis

Essential Role of Neutrophils in Germ Cell-Specific Apoptosis Following Ischemia/Reperfusion Injury of the Mouse Testis1

This study investigates the role of neutrophils in ischemia-induced aspermatogenesis in the mouse. Previous studies in the rat have demonstrated that ischemia-inducing testicular torsion followed by torsion repair and reperfusion resulted in germ cell-specific apoptosis. This was correlated with an increase in neutrophil adhesion to subtunical venules, an increase in reactive oxygen species, and increased expression of several apoptosis-associated molecules. In the present investigation, wild-type C57BL/6 mice were subjected to various degrees and duration of testicular torsion. A torsion of 720 degrees for 2 h caused disruption of the seminiferous epithelium and significantly reduced testis weight and daily sperm production. An immunohistochemical method specific for apoptotic nuclei indicated that these effects were due to germ cell-specific apoptosis. An increase in myeloperoxidase (MPO) activity and an increase in the number of neutrophils adhering to testicular subtunical venules after torsion repair/reperfusion demonstrated an increase in neutrophil recruitment to the testis. In contrast, E-selectin knockout mice and wild-type mice rendered neutropenic showed a significant decrease in neutrophil recruitment as evidenced by MPO activity and microscopic examination of subtunical venules. Importantly, germ cell-specific apoptosis was also reduced. Thus, germ cell-specific apoptosis is observed after ischemia/reperfusion of the murine testis, and this apoptosis is directly linked to the recruitment of neutrophils to subtunical venules. Endothelial cell adhesion molecules, particularly E-selectin, play an important role in mediating this pathology.

Essential role of neutrophils in the initiation and progression of a murine model of rheumatoid arthritis.

Neutrophils are prominent participants in the joint inflammation of human rheumatoid arthritis (RA) patients, but the extent of their role in the inductive phase of joint inflammation is unknown. In the K/BxN mouse RA model, transfer of autoreactive Ig from the K/BxN mouse into mice induces a rapid and profound joint-specific inflammatory response reminiscent of human RA. We observed that after K/BxN serum transfer, the earliest clinical signs of inflammation in the ankle joint correlated with the presence of neutrophils in the synovial regions of recipient mouse ankle joints. In this study, we investigated the role of neutrophils in the early inflammatory response to transferred arthritogenic serum from the K/BxN transgenic mouse. Mice were treated with a neutrophil-depleting mAb before and following transfer of arthritogenic serum and scored for clinical indications of inflammation and severity of swelling in ankle joints and front paws. In the absence of neutrophils, mice were completely resistant to the inflammatory effects of K/BxN serum. Importantly, depletion of neutrophils in diseased recipient mice up to 5 days after serum transfer reversed the inflammatory reaction in the joints. Transfer of serum into mice deficient in the generation of nitrogen or oxygen radicals (inducible NO synthase 2 or gp91(phox) genes, respectively) gave normal inflammatory responses, indicating that neither pathway is essential for disease induction. These studies have identified a critical role for neutrophils in initiating and maintaining inflammatory processes in the joint.

Mechanisms underlying hematopoietic stem cell mobilization induced by the CXC chemokine interleukin-8.

The CXC chemokine interleukin-8 induces rapid mobilization of hematopoietic progenitor cells in mice and monkeys. Antibodies against the beta 2-integrin leukocyte function-associated antigen-1 completely blocked interleukin-8-induced mobilization. This was not due to a direct effect on the hematopoietic progenitor cells, as leukocyte function-associated antigen-1 was found not to be expressed on hematopoietic progenitor cells. Additional experiments showed that interleukin-8 induces the rapid release of the metalloproteinase gelatinase B, concurrent with the mobilization of hematopoietic progenitor cells. Mobilization could be completely prevented by anti-gelatinase B antibodies. Because neutrophils express leukocyte function-associated antigen-1 and high affinity interleukin-8 receptors, and release gelatinase B upon stimulation with interleukin-8, we hypothesized that neutrophils are key mediators in interleukin-8-induced stem cell mobilization. Further studies showed that mobilization by interleukin-8 was completely absent in mice rendered neutropenic with anti-granulocytic antibodies. Taken together, these data are consistent with an essential role for neutrophils in interleukin-8-induced stem cell mobilization.