Cow Dung Smoke Exposure Enhances Non-Typeable Haemophilus influenza Adherence to Human Airway Epithelial Cells

Abstract

Background:

Nearly half of the world's population uses biomass fuel for the purposes of cooking and heating. Smoke-derived from biomass increases the risk of the development of lung diseases, including pneumonia, COPD, airway tract infections, and lung cancer. Yet, only a small number of experimental studies have been conducted on the impact of animal dung smoke on airway epithelial cells. This is in part due to the lack of a standard procedure for the preparation of, and exposure to animal dung smoke. Here, we generated cow dung smoke extract (CDSE) and investigated the effects of CDSE in PAFR expression and adhesion of nontypeable Haemophilus influenza (NTHi) to human bronchial epithelial cells (BEAS-2Bs).

Methods:

Cow dung collected from a local farmhouse was sun-dried, crushed and rolled in a paper with a sterile cotton wool filter at one of the end, similar to a filtered-cigarette. The cow dung rolls were then burned in a water aspirator to collect the smoke particles. The retained smoke particles were then dissolved in dimethyl-sulfoxide to prepare cow dung smoke extract. The BEAS2B cells were exposed to different concentrations of CDSE for 4 h at 37degrees C and 5% CO₂. Parallel exposures of BEAS-2B cells to CSE were also performed for comparison. The cells were then challenged with NTHi labeled with fluorescein isothiocyanate. The PAFR expression levels and NTHi adhesion were determined using immunofluorescence. Comparisons between groups were performed using one-way analysis of variance (ANOVA) with Dunnet's post-hoc test was performed using GraphPad Prism version 5.0 (GraphPad Software, La Jolla CA; www.graphpad.com). P < 0.05 was considered statistically significant.

Results:

A simple and cost-effective method, using a water aspirator, was used to prepare the cow dung smoke extract. Similar to cigarette smoke extract exposure, we observed a dose-dependent increase in PAFR expression on human airway epithelial cells that were subjected to cow dung extract over a concentration range of 0.0001% to 1% (v/v). Furthermore, the CDSE exposure increased the NTHi adhesion by 1.9 times (P<0.001) in vitro, which was attenuated by the PAFR antagonist, WEB2086.

Conclusions:

Cow dung smoke exposure has the potential to increase the susceptibility to NTHi infection via the PAFR induction.