Monomethylarsonous Acid (MMAIII) Has an Adverse Effect on the Innate Immune Response of Human Bronchial Epithelial Cells to Pseudomonas aeruginosa

RESEARCH ARTICLE Monomethylarsonous Acid (MMAIII) Has an Adverse Effect on the Innate Immune Response of Human Bronchial Epithelial Cells to Pseudomonas aeruginosa Emily G. Notch1,2*, Britton C. Goodale1, Roxanna Barnaby1, Bonita Coutermarsh1, Brent Berwin1, Vivien F. Taylor3, Brian P. Jackson3, Bruce A. Stanton1 1 Department of Microbiology and Immunology, Center for Environmental Health Sciences, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America, 2 Department of Physical and Biological Sciences, Western New England University, Springfield, Massachusetts, United States of America, 3 Department of Earth Sciences, Dartmouth College, Hanover, New Hampshire, United States of America * OPEN ACCESS Citation: Notch EG, Goodale BC, Barnaby R, Coutermarsh B, Berwin B, Taylor VF, et al. (2015) Monomethylarsonous Acid (MMAIII) Has an Adverse Effect on the Innate Immune Response of Human Bronchial Epithelial Cells to Pseudomonas aeruginosa. PLoS ONE 10(11): e0142392. doi:10.1371/journal.pone.0142392 Editor: Shama Ahmad, University of Alabama at Birmingham, UNITED STATES Received: June 18, 2015 Accepted: October 21, 2015 Published: November 10, 2015 Copyright: © 2015 Notch et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Arsenic is the number one contaminant of concern with regard to human health according to the World Health Organization. Epidemiological studies on Asian and South American populations have linked arsenic exposure with an increased incidence of lung disease, including pneumonia, and chronic obstructive pulmonary disease, both of which are associated with bacterial infection. However, little is known about the effects of low dose arsenic exposure, or the contributions of organic arsenic to the innate immune response to bacterial infection. This study examined the effects on Pseudomonas aeruginosa (P. aeruginosa) induced cytokine secretion by human bronchial epithelial cells (HBEC) by inorganic sodium arsenite (iAsIII) and two major metabolites, monomethylarsonous acid (MMAIII) and dimethylarsenic acid (DMAV), at concentrations relevant to the U.S. population. Neither iAsIII nor DMAV altered P. aeruginosa induced cytokine secretion. By contrast, MMAIII increased P. aeruginosa induced secretion of IL-8, IL-6 and CXCL2. A combination of iAsIII, MMAIII and DMAV (10 pbb total) reduced IL-8 and CXCL1 secretion. These data demonstrate for the first time that exposure to MMAIII alone, and a combination of iAsIII, MMAIII and DMAV at levels relevant to the U.S. may have negative effects on the innate immune response of human bronchial epithelial cells to P. aeruginosa. Data Availability Statement: All relevant data are within the paper. Funding: This work was supported by grant P42 ES007373 from the National Institute of Environmental Health Sciences (http://www.niehs.nih. gov/) [B.A.S.; Superfund Research Program (SRP) Project 3]. E.G.N. was supported by a postdoctoral fellowship from P42 ES007373 (SRP, Training Core), and by grant R01 HL074175 (http://www.nih.gov/). The funders had no role in study design, data Introduction According to the World Health Organization (WHO) and the Agency for Toxic Substances and Disease Registry (ATSDR) arsenic is the number one contaminant of concern for human health worldwide [1]. Hundreds of millions of people worldwide are exposed to arsenic via their drinking water, many at doses higher than the WHO maximum contaminant level of PLOS ONE | DOI:10.1371/journal.pone.0142392 November 10, 2015 1 / 16 MMA Alters Cytokine Secretion in HBEC collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exists. 10 ppb [2]. The United States Geological Survey has reported that more than 25 million people in the U.S. are exposed to well water with arsenic concentrations exceeding 10 ppb, the current EPA standard for public water supplies [3,4]. Although the level of arsenic in water in the U.S. is generally lower than in Asia and South America, levels of arsenic in well water in Maine have been measured as high as 3,100 ppb and blood levels of total arsenic ranging from 0.23 to 8.58 ppb have been measured in a rural North Carolina population indicating exposure via food and drinking water [3,5]. Recently, rice, and rice-based products including toddler formulas and energy bars have been identified as major contributors to arsenic exposure [6–9]. For people with low levels of arsenic exposure via drinking water, food constitutes 54–80% of the exposure risk [10]. Many rice and rice based food products contain significant amounts of organic species of arsenic [9,11]. This is cause for concern as little is currently known about the impact of organic forms of arsenic exposure on human health. Some studies have indicated that trivalent DMA and MMA are more toxic than inorganic arsenic, however these studies were done at high concentrations in animal models, and toxicity varies by species and oxidation state [12]. For example, MMAIII (180 ppb) has been shown to inhibit cholesterol biosynthesis and inhibit steroid receptor binding to DNA response elements in mammalian cells [13,14]. However, to our knowledge there are no studies that have examined the effects of low levels of organic arsenic exposure on the innate immune response. Although animal studies examining immune response have been conducted using low levels of arsenite in the drinking water, because arsenite is metabolized in the liver it is not possible to determine if the reported effects are the result of arsenite, MMA or DMA [15]. Arsenic exposure in Asia and South America has been linked with a variety of lung diseases including pneumonia, chronic obstructive pulmonary disease (COPD), bronchiectasis, chronic bronchitis and lung cancer [16–18]. Pneumonia, bronchiectasis and COPD are frequently associated with the opportunistic pathogen, Pseudomonas aeruginosa (P. aeruginosa), one of the leading causes of nosocomial infections throughout the world [19,20]. While it has been shown that low-level exposure to arsenic in zebrafish and mice alters the immune response to viral and bacterial pathogens, little is known about the mechanisms by which this alteration occurs [15,21]. In addition, nothing is known about effects of low levels of arsenic on the innate immune function of human lung. Accordingly, the goal of this study was to examine the impact of low levels of arsenic and methylated metabolites on P. aeruginosa induced cytokine secretion in primary human bronchial epithelial cells (HBEC). P. aeruginosa lung infections stimulate the secretion of several cytokines by HBEC including IL-8, IL-6, CXCL1 and CXCL2 [22–24]. These cytokines are chemotactic, an (...truncated)