Fine particulate matter (PM_2.5) enhances allergic sensitization in BALB/c mice

ABSTRACT

Ambient particulate matter (PM), a component of air pollution, exacerbates airway inflammation and hyperreactivity in asthmatic patients. Studies showed that PM possesses adjuvant-like properties that enhance the allergic inflammatory response; however, the mechanism (or mechanisms) by which PM enhances the allergic response remains to be determined. The aim of this study was to assess how exposure to fine PM collected from Sacramento, CA, shapes the allergic airway immune response in BALB/c mice undergoing sensitization and challenge with ovalbumin (OVA). Eight-week-old BALB/c male mice were sensitized/challenged with phosphate-buffered saline (PBS/PBS; n = 6), PM/PBS (n = 6), OVA/OVA (n = 6), or OVA + PM/OVA (n = 6). Lung tissue, bronchoalveolar lavage fluid (BALF), and plasma were analyzed for cellular inflammation, cytokines, immunoglobulin E, and heme oxygenase-1 (HO-1) expression. Mice in the OVA + PM/OVA group displayed significantly increased airway inflammation compared to OVA/OVA animals. Total cells, macrophages, and eosinophils recovered in BALF were significantly elevated in the OVA + PM/OVA compared to OVA/OVA group. Histopathological grading indicated that OVA + PM/OVA treatment induced significant inflammation compared to OVA/OVA. Both immunoglobulin (Ig) E and tumor necrosis factor (TNF) α levels were significantly increased in OVA/OVA and OVA + PM /OVA groups compared to PBS/PBS control. The number of HO-1 positive alveolar macrophages was significantly elevated in lungs of mice treated with OVA + PM /OVA compared to OVA/OVA. Our findings suggest that fine PM enhances allergic inflammatory response in pulmonary tissue through mechanisms involving increased oxidative stress.

Acknowledgments

We acknowledge Dale Uyeminami, Imelda Espiritu, Janice Peake, Alexa Pham, Esther Patchin, Jocelyn Claude, and Katherine Johnson for their valuable help through this experiment.

Funding

This work was supported by the National Institute for Occupational Safety and Health (NIOSH)-funded Western Center for Agricultural Health and Safety (NIOSH OHO7550), the University of California Davis Graduate Research Mentorship Fellowship, and a National Institute of Health Pharmacology T32 Training Grant (T32GM099608).

Author Contributions

ARC performed experiments, analyzed data, and interpreted the results. KEP provided overall experimental design and guidance. KJB collected, extracted, and analyzed particulate matter samples. SSJ provided extensive feedback and editing. The article was read, revised, and approved by all authors.

Competing Interests

The authors do not have competing interests.

Additional information

Funding

This work was supported by the National Institute for Occupational Safety and Health (NIOSH)-funded Western Center for Agricultural Health and Safety (NIOSH OHO7550), the University of California Davis Graduate Research Mentorship Fellowship, and a National Institute of Health Pharmacology T32 Training Grant (T32GM099608).