Impairment of neutrophil migration to remote inflammatory site during lung histoplasmosis

The Role of the Interleukin-17 Axis and Neutrophils in the Pathogenesis of Endemic and Systemic Mycoses

Systemic and endemic mycoses are considered life-threatening respiratory diseases which are caused by a group of dimorphic fungal pathogens belonging to the genera Histoplasma, Coccidioides, Blastomyces, Paracoccidioides, Talaromyces, and the newly described pathogen Emergomyces. T-cell mediated immunity, mainly T helper (Th)1 and Th17 responses, are essential for protection against these dimorphic fungi; thus, IL-17 production is associated with neutrophil and macrophage recruitment at the site of infection accompanied by chemokines and proinflammatory cytokines production, a mechanism that is mediated by some pattern recognition receptors (PRRs), including Dectin-1, Dectine-2, TLRs, Mannose receptor (MR), Galectin-3 and NLPR3, and the adaptor molecules caspase adaptor recruitment domain family member 9 (Card9), and myeloid differentiation factor 88 (MyD88). However, these PRRs play distinctly different roles for each pathogen. Furthermore, neutrophils have been confirmed as a source of IL-17, and different neutrophil subsets and neutrophil extracellular traps (NETs) have also been described as participating in the inflammatory process in these fungal infections. However, both the Th17/IL-17 axis and neutrophils appear to play different roles, being beneficial mediating fungal controls or detrimental promoting disease pathologies depending on the fungal agent. This review will focus on highlighting the role of the IL-17 axis and neutrophils in the main endemic and systemic mycoses: histoplasmosis, coccidioidomycosis, blastomycosis, and paracoccidioidomycosis.

The ethanolic extract of Terminalia argentea Mart. & Zucc. bark reduces the inflammation through the modulation of cytokines and nitric oxide mediated by the downregulation of NF-κB

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia argentea Mart. & Zucc. (Combretaceae), popularly known as "capitão do campo", is native from the Brazilian cerrado, which is used in folk medicine to treat inflammatory diseases.

AIM OF THE STUDY

We aimed to investigate the anti-inflammatory effects, toxicity and mechanisms of action regarding the use of the hydroalcoholic extract of T. argentea bark.

MATERIALS AND METHODS

Toxicity was determinate in vitro using the macrophage lineage J774.1 without LPS. Cells were treated with 0.5; 2; 8; 32 and 125 μg/mL of the plant extract. Cell viability was assessed by MTT colorimetric assay. The production of nitrite and cytokines was also determined in the supernatants. A NF-κB reporter assay using RAW macrophages was employed to elucidate the impact of the plant extract on the expression of such molecule. In mice, toxicity was assessed by orally given an intermediate to high concentration of the plant extract on a single dose (1000 or 5000 mg/kg) or low and intermediate doses (300 or 1000 mg/kg) twice daily for 14 days. Blood samples were collected for biochemical analysis. The anti-inflammatory activity was assessed using the air-pouch model with or without pre-inoculation with the inflammatory stimuli LPS (0.5 μg/mL), followed by treatment with plant extract at 5, 60 or 300 mg/kg administered in the air pouch (subcutaneous injection). After 4 h, mice were euthanized and the air pouches washed with 2 mL heparinized PBS (10 IU/mL). Then, the local production in the air pouch wash of cytokines, total proteins and leukocytes was assessed.

RESULTS

No signals of toxicity were observed either in cells or mice. Regardless the concentration used in vitro, the extract exhibited a significant anti-inflammatory activity, as perceived by the reduction of the inflammatory cytokines IL-1β, TNF-α and IL-6 and nitrites on cell supernatants. This was concomitant with a downregulation in NF-κB and elevated levels of IL-10. In mice, similar effects were observed, especially when the plant extract was given at 300 mg/kg, inhibiting the release of IL-1β, TNF-α, IL-6 and proteins, as well as increasing the release of IL-10.

CONCLUSIONS

Altogether, our results demonstrated that the hydroalcoholic extract of T. argentea bark has anti-inflammatory activity without inducing toxicity in cells or living animals. This activity seems to be chiefly influenced by a downregulation in NF-κB, inflammatory cytokines and production of nitrite along with augmented concentration of IL-10.

Approaches to Evaluate Lung Inflammation in Translational Research

Inflammation is a common feature in several types of lung disease and is a frequent end point to validate lung disease models, evaluate genetic or environmental impact on disease severity, or test the efficacy of new therapies. Questions relevant to a study should be defined during experimental design and techniques selected to specifically address these scientific queries. In this review, the authors focus primarily on the breadth of techniques to evaluate lung inflammation that have both clinical and preclinical applications. Stratification of approaches to assess lung inflammation can diminish weaknesses inherent to each technique, provide data validation, and increase the reproducibility of a study. Specialized techniques (eg, imaging, pathology) often require experienced personnel to collect, evaluate, and interpret the data; these experts should be active contributors to the research team through reporting of the data. Scoring of tissue lesions is a useful method to transform observational pathologic data into semiquantitative or quantitative data for statistical analysis and enhanced rigor. Each technique to evaluate lung inflammation has advantages and limitations; understanding these parameters can help identify approaches that best complement one another to increase the rigor and translational significance of data.