The synergistic effects of PM2.5 and high-fat diet on Th1/Th2 balance in model mice with asthma.

Background: Particulate matter, ambient particulate matter with an aerodynamic equivalent diameter ≤2.5 µm (PM_2.5) is closely associated with asthma, and a high-fat diet is also a risk factor for the condition. In many cities in China, exposure to PM_2.5 and consumption of a high-fat diet coexist. The Th1/Th2 balance is the immunological foundation for the onset and progression of asthma, and it is more accurate to describe asthma symptoms in terms of changes in this balance. Therefore, the aim of this study was to investigate the effects of PM_2.5 and high-fat diet the combined effects on Th1/Th2 balance in asthma immune.

Methods: Given this background, our study examined the effects of PM_2.5 and high-fat diets on the Th1/Th2 balance and proposed potential molecular mechanisms for asthma development induced by these factors. In this study, male BALB/c mice and ovalbumin (OVA)-sensitized asthma mice subjected to either a normal or high-fat diet were exposed to PM_2.5 or filtered air for one month. We evaluated the effects of PM_2.5 and high-fat diets on asthma using histopathology, enzyme-linked immunosorbent assays, transcriptome sequencing, and quantitative polymerase chain reaction (PCR).

Results: We found that PM_2.5 exposure increased the secretion of Th2-related inflammatory mediators, while a high-fat diet increased the secretion of Th1-related inflammatory mediators. However, the combined effects still predominantly favored a Th2 skew. PM_2.5 exposure shifted the Th1/Th2 balance toward Th2, whereas a high-fat diet shifted it toward Th1. The combination of PM_2.5 exposure and a high-fat diet resulted in a less pronounced Th2 polarization compared to PM_2.5 exposure alone.

Conclusions: PM_2.5 exposure and short-term high-fat diet both exacerbate asthma but there is an opposite direction of modulation of the Th1/Th2 balance.