Neutrophil and Eosinophil DNA Extracellular Trap Formation: Lessons From Pathogenic Fungi

Fungal infections represent a worldwide health problem. Fungal pathogens are responsible for a variety of conditions, including superficial diseases, allergic pathologies and potentially lethal invasive infections. Neutrophils and eosinophils have been implicated as effector cells in several pathologies. Neutrophils are major effector cells involved in the control of fungal infections and exhibit a plethora of antifungal mechanisms, such as phagocytosis, reactive oxygen species production, degranulation, extracellular vesicle formation, and DNA extracellular trap (ET) release. Eosinophils are polymorphonuclear cells classically implicated as effector cells in the pathogenesis of allergic diseases and helminthic infections, although their roles as immunomodulatory players in both innate and adaptive immunity are currently recognized. Eosinophils are also endowed with antifungal activities and are abundantly found in allergic conditions associated with fungal colonization and sensitization. Neutrophils and eosinophils have been demonstrated to release their nuclear and mitochondrial DNA in response to many pathogens and pro-inflammatory stimuli. ETs have been implicated in the killing and control of many pathogens, as well as in promoting inflammation and tissue damage. The formation of ETs by neutrophils and eosinophils has been described in response to pathogenic fungi. Here, we provide an overview of the mechanisms involved in the release of neutrophil and eosinophil ETs in response to fungal pathogens. General implications for understanding the formation of ETs and the roles of ETs in fungal infections are discussed.

Elastase modifies bleomycin-induced pulmonary fibrosis in mice

Pulmonary fibrosis (PF) is characterized by excessive accumulation of collagen in the lungs. Emphysema is characterized by loss of the extracellular matrix (ECM) and alveolar enlargement. We studied the co-participation of elastase-induced mild emphysema in bleomycin-induced PF in mice by analyzing oxidative stress, inflammation and lung histology. C57BL/6 mice were divided into four groups: control; bleomycin (0.1U/mouse); elastase (using porcine pancreatic elastase (PPE)+bleomycin (3U/mouse 14 days before 0.1U/mouse of bleomycin; PPE+B); elastase (3U/mouse). Mice were humanely sacrificed 7, 14 and 21 days after treatment with bleomycin or vehicle. PF was observed 14 days and 21 days after bleomycin treatment but was observed after 14 days only in the PPE+B group. In the PPE+B group at 21 days, we observed many alveoli and alveolar septa with few PF areas. We also observed marked and progressive increases of collagens 7, 14 and 21 days after bleomycin treatment whereas, in the PPE+B group, collagen deposition was observed only at 14 days. There was a reduction in activities of the antioxidant enzymes superoxide dismutase (p<0.05), catalase (p<0.01) and glutathione peroxidase (p<0.01) parallel with an increase in nitrite (p<0.01) 21 days after bleomycin treatment compared with the control group. These endpoints were also reduced (p<0.05, p<0.05 and p<0.01, respectively) and increased (p<0.01) in the PPE+B group at 21 days compared with the control group. Interleukin (IL)-1β expression was upregulated (p<0.01) whereas IL-6 was downregulated (p<0.05) in the PPE+B group at 21 days compared with the control group. PF and emphysema did not coexist in our model of lung disease and despite increased levels of oxidative stress and inflammatory markers after combined stimulus (elastase and bleomycin) overall histology was improved to that of the nearest control group.

LPS induces eosinophil migration via CCR3 signaling through a mechanism independent of RANTES and Eotaxin

Mounting evidence suggests that lipopolysaccharide (LPS) modulates bronchoconstriction and eosinophil function in asthma. We have investigated the role of different chemokines in the eosinophil influx to the pleural cavity after LPS stimulation. Expression of mRNA for eotaxin, regulated on activation, normal T cells expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-2, and monocyte chemotactic protein (MCP)-1 was increased in cells recovered from the mouse pleural cavity 6 h after LPS administration. Eotaxin and RANTES, but not MIP-1alpha, protein levels were also increased in cell-free pleural washes recovered 6 h after LPS stimulation (LPW). Antimurine eotaxin and antimurine RANTES antibodies (Abs) failed to inhibit LPS-induced eosinophil influx into mouse pleural cavity in vivo. Pertussis toxin inhibited LPW-induced eosinophil shape change in vitro, suggesting the involvement of G protein-coupled receptors in LPW signaling. Blockade of CCR3 receptors diminished eosinophil shape change induced by LPW fractions in vitro and LPS-induced eosinophil accumulation in vivo. To investigate further contribution of CC chemokines, we administered a 35-kD CC chemokine neutralizing protein (vCKBP) in vivo. vCKBP inhibited the eosinophil accumulation induced by eotaxin and ovalbumin, but did not block that induced by LPS or LPW. Our data suggest that LPS-induced eosinophil accumulation depends on G protein-coupled CCR3 receptor activation, through a mechanism independent of eotaxin, RANTES, or other vCKBP-inhibitable CC chemokines.