The Role of Neutrophils during Mild and Severe Influenza Virus Infections of Mice

Neutrophils have been implicated in both protective and pathological responses following influenza virus infections. We have used mAb 1A8 (anti-Ly6G) to specifically deplete LyG6high neutrophils and induce neutropenia in mice infected with virus strains known to differ in virulence. Mice were also treated with mAb RB6-8C5 (anti-Ly6C/G or anti-Gr-1), a mAb widely used to investigate the role of neutrophils in mice that has been shown to bind and deplete additional leukocyte subsets. Using mAb 1A8, we confirm the beneficial role of neutrophils in mice infected with virus strains of intermediate (HKx31; H3N2) or high (PR8; H1N1) virulence whereas treatment of mice infected with an avirulent strain (BJx109; H3N2) did not affect disease or virus replication. Treatment of BJx109-infected mice with mAb RB6-8C5 was, however, associated with significant weight loss and enhanced virus replication indicating that other Gr-1+ cells, not neutrophils, limit disease severity during mild influenza infections

Macrophage CD74 contributes to MIF-induced pulmonary inflammation

<p>Abstract</p> <p>Background</p> <p>MIF is a critical mediator of the host defense, and is involved in both acute and chronic responses in the lung. Neutralization of MIF reduces neutrophil accumulation into the lung in animal models. We hypothesized that MIF, in the alveolar space, promotes neutrophil accumulation via activation of the CD74 receptor on macrophages.</p> <p>Methods</p> <p>To determine whether macrophage CD74 surface expression contributes MIF-induced neutrophil accumulation, we instilled recombinant MIF (r-MIF) into the trachea of mice in the presence or absence of anti-CD74 antibody or the MIF specific inhibitor, ISO-1. Using macrophage culture, we examined the downstream pathways of MIF-induced activation that lead to neutrophil accumulation.</p> <p>Results</p> <p>Intratracheal instillation of r-MIF increased the number of neutrophils as well as the concentration of macrophage inflammatory protein 2 (MIP-2) and keratinocyte-derived chemokine (KC) in BAL fluids. CD74 was found to be expressed on the surface of alveolar macrophages, and MIF-induced MIP-2 accumulation was dependent on p44/p42 MAPK in macrophages. Anti-CD74 antibody inhibited MIF-induced p44/p42 MAPK phosphorylation and MIP-2 release by macrophages. Furthermore, we show that anti-CD74 antibody inhibits MIF-induced alveolar accumulation of MIP-2 (control IgG vs. CD74 Ab; 477.1 ± 136.7 vs. 242.2 ± 102.2 pg/ml, p < 0.05), KC (1796.2 ± 436.1 vs. 1138.2 ± 310.2 pg/ml, p < 0.05) and neutrophils (total number of neutrophils, 3.33 ± 0.93 × 10⁴vs. 1.90 ± 0.61 × 10⁴, p < 0.05) in our mouse model.</p> <p>Conclusion</p> <p>MIF-induced neutrophil accumulation in the alveolar space results from interaction with CD74 expressed on the surface of alveolar macrophage cells. This interaction induces p44/p42 MAPK activation and chemokine release. The data suggest that MIF and its receptor, CD74, may be useful targets to reduce neutrophilic lung inflammation, and acute lung injury.</p

Hydrodynamic delivery of siRNA in a mouse model of sepsis

The use of siRNA in vivo as well as in animal models has become more widespread in recent years, leading to further questions as to the best mode of delivery that will achieve optimal knockdown. While the exact mechanism of siRNA uptake at a cellular level has yet to be fully elucidated, various delivery techniques are being researched, including the use of viral vectors of shRNA, liposome encapsulations, and hydrodynamic delivery of naked siRNA. We describe the use of hydrodynamic administration as a technique to deliver, in vivo, naked siRNA constructs into experimental animals as a method of transient gene knockdown. This method may prove useful in situations where knockout animals do not exist, or to determine the effect of gene knockdown at specific time points during an experiment. © 2008 Humana Press

Hydrodynamic delivery of siRNA in a mouse model of sepsis

The use of siRNA in vivo as well as in animal models has become more widespread in recent years, leading to further questions as to the best mode of delivery that will achieve optimal knockdown. While the exact mechanism of siRNA uptake at a cellular level has yet to be fully elucidated, various delivery techniques are being researched, including the use of viral vectors of shRNA, liposome encapsulations, and hydrodynamic delivery of naked siRNA. We describe the use of hydrodynamic administration as a technique to deliver, in vivo, naked siRNA constructs into experimental animals as a method of transient gene knockdown. This method may prove useful in situations where knockout animals do not exist, or to determine the effect of gene knockdown at specific time points during an experiment. © 2008 Humana Press

Endothelial cells response to neutrophil‐derived extracellular vesicles miRNAs in anti‐PR3 positive vasculitis

In vasculitis disorders, inflammation affects blood vessels. Granulomatosis with polyangiitis (GPA) is a chronic systemic vasculitis distinguished by the presence of anti‐proteinase‐3 autoantibodies (anti‐PR3). In this study we analyzed the molecular signature of human umbilical endothelial cells (HUVECs) in response to neutrophil‐derived extracellular vesicles (EVs). EVs were obtained from anti‐PR3‐activated neutrophils, purified and characterized by flow cytometry, nanoparticle tracking and miRNA screening. HUVECs were stimulated with EVs and miRNA/mRNA expression was measured. Cell culture media proteins were identified by antibody microarrays and selected cytokines were measured. Comparison of differentially expressed miRNAs/mRNAs between non‐stimulated and EV‐stimulated HUVECs revealed two regulatory patterns. Significant up‐regulation of 14 mRNA transcripts (including CXCL8, DKK1, IL1RL1, ANGPT‐2, THBS1 and VCAM‐1) was accompanied by 11 miRNAs silencing (including miR‐661, miR‐664a‐3p, miR‐377‐3p, miR‐30d‐5p). Significant down‐regulation was observed for nine mRNA transcripts (including FASLG, CASP8, STAT3, GATA3, IRAK1 and IL6) and accompanied by up‐regulation of 10 miRNAs (including miR‐223‐3p, miR‐142‐3p, miR‐211‐5p). Stimulated HUVECs released IL‐8, Dickkopf‐related protein 1 (DKK‐1), soluble interleukin (IL)‐1 like receptor‐1 (ST2), growth differentiation factor 15 (GDF‐15), angiopoietin‐2, endoglin, thrombospondin‐1 and vascular adhesion molecule‐1 (VCAM‐1). Moreover, transfection of HUVECs with mimics of highly expressed in EVs miR‐223‐3p or miR‐142‐3p, stimulated production of IL‐8, ST2 and endoglin. Cytokines released by HUVECs were also elevated in blood of patients with GPA. The most increased were IL‐8, DKK‐1, ST2, angiopoietin‐2 and IL‐33. In‐vitro stimulation of HUVECs by neutrophil‐derived EVs recapitulates contribution of endothelium in autoimmune vasculitis. Proinflammatory phenotype of released cytokines corresponds with the regulatory network of miRNAs/mRNAs comprising both EVs miRNA and endothelial cell transcripts