Depletion of Neutrophils Promotes the Resolution of Pulmonary Inflammation and Fibrosis in Mice Infected with Paracoccidioides brasiliensis

Abstract

Chronic stages of paracoccidioidomycosis (PCM) are characterized by granulomatous lesions which promote the development of pulmonary fibrosis leading to the loss of respiratory function in 50% of patients; in addition, it has been observed that neutrophils predominate during these chronic stages of P. brasiliensis infection. The goal of this study was to evaluate the role of the neutrophil during the chronic stages of experimental pulmonary PCM and during the fibrosis development and tissue repair using a monoclonal specific to this phagocytic cell. Male BALB/c mice were inoculated intranasally with 1.5x106 P. brasiliensis yeast cells. A monoclonal antibody specific to neutrophils was administered at 4 weeks post-inoculation followed by doses every 48h during two weeks. Mice were sacrificed at 8 and 12 weeks post-inoculation to assess cellularity, fungal load, cytokine/chemokine levels, histopathological analysis, collagen and expression of genes related to fibrosis development. Depletion of neutrophils was associated with a significant decrease in the number of eosinophils, dendritic cells, B cells, CD4-T cells, MDSCs and Treg cells, fungal load and levels of most of the pro-inflammatory cytokines/chemokines evaluated, including IL-17, TNF-α and TGF-β1. Recovery of lung architecture was also associated with reduced levels of collagen, high expression of TGF-β3, matrix metalloproteinase (MMP)-12 and -14, and decreased expression of tissue inhibitor metalloproteinase (TIMP)-2, and MMP-8. Depletion of neutrophils might attenuate lung fibrosis and inflammation through down-regulating TGF-β1, TNF-α, IL-17, MMP-8 and TIMP-2. These results suggest that neutrophil could be considered as a therapeutic target in pulmonary fibrosis induced by P. brasiliensis.

Revealing Dynamics of Accumulation of Systemically Injected Liposomes in the Skin by Intravital Microscopy

“…31 Briefly, mice were injected i.p. with 180 μ g of the antibody 2 days prior to injection of EPC/DSPE-PEG/DiR/DiI liposomes.…”

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

“…This is supported by another murine study that demonstrated that neutrophil‐elastase‐deficient mice present a significant reduction in fibroblast and myofibroblast accumulation in comparison to wild type mice and that elastase deficiency protected mice from asbestos‐induced pulmonary fibrosis (Gregory et al., ). Moreover, a mouse model of pulmonary fibrosis induced by chronic fungal infection with Paracoccidioides brasiliensis showed that depletion of neutrophils could attenuate pulmonary fibrosis and inflammation (Puerta‐Arias, Pino‐Tamayo, Arango, & Gonzalez, ). This suggests that, at least in these models, the pro‐inflammatory activity of neutrophils, possibly through the production of neutrophil elastase and other compounds, can promote tissue injury leading to a continuous activation of myofibroblasts in an attempt to heal the tissue, therefore promoting fibrosis.…”

The role of myeloid-derived suppressor cells in chronic infectious diseases and the current methodology available for their study

“…All of these depletion strategies have disadvantages and are not applicable during infectious diseases. Antibody administration depletes both MDSCs and their pro‐inflammatory counterparts; in fact, the administration of anti‐Ly6G is a common strategy to induce neutropenia during infectious disease . The same goes for CCR2‐DTR mice.…”