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PM2.5 Extracts Induce INFγ-Independent Activation of CIITA, MHCII, and Increases Inflammation in Human Bronchial
Héctor Jirau-Colón1,2, Braulio D Jiménez-Vélez1,2
1Department of Biochemistry, University of Puerto Rico Medical Sciences Campus, San Juan 00935, Puerto Rico.
Abstract:
The capacity of particulate matter (PM) to enhance and stimulate the expression of pro-inflammatory mediators has been previously demonstrated in non-antigen-presenting cells (human bronchial epithelia). Nonetheless, many proposed mechanisms for this are extrapolated from known canonical molecular pathways. This work evaluates a possible mechanism for inflammatory exacerbation after exposure to PM2.5 (from Puerto Rico) and CuSO4, using human bronchial epithelial cells (BEAS-2B) as a model. The induction of CIITA, MHCII genes, and various pro-inflammatory mediators was investigated. Among these, the phosphorylation of STAT1 Y701 was significantly induced after 4 h of PM2.5 exposure, concurrent with a slight increase in CIITA and HLA-DRα mRNA levels. INFγ mRNA levels remained low amidst exposure time, while IL-6 levels significantly increased at earlier times. IL-8 remained low, as expected from attenuation by IL-6 in the known INFγ-independent inflammation pathway. The effects of CuSO4 showed an increase in HLA-DRα expression after 8 h, an increase in STAT1 at 1 h, and RF1 at 8 h We hypothesize and show evidence that an inflammatory response due to PM2.5 extract exposure in human bronchial epithelia can be induced early via an alternate non-canonical pathway in the absence of INFγ.
Insights
Particulate matter (PM2.5) exposure in human bronchial cells can trigger early inflammation via a non-canonical pathway, independent of INFγ. This study reveals a novel mechanism for PM-induced inflammatory responses.
Area of Science:
- Environmental Health
- Immunology
- Cell Biology
Background:
- Particulate matter (PM) exposure is known to induce pro-inflammatory mediators in human bronchial epithelial cells.
- Existing mechanisms often rely on canonical molecular pathways, but alternative pathways may exist.
Purpose of the Study:
- To investigate a potential non-canonical inflammatory pathway induced by PM2.5 exposure in human bronchial epithelial cells (BEAS-2B).
- To evaluate the role of CIITA, MHCII genes, and pro-inflammatory mediators in response to PM2.5 and CuSO4.
Main Methods:
- Exposure of BEAS-2B cells to PM2.5 (Puerto Rico) and CuSO4.
- Analysis of STAT1 phosphorylation, CIITA, MHCII genes (HLA-DRα), and cytokine mRNA levels (INFγ, IL-6, IL-8).
Main Results:
- PM2.5 exposure induced STAT1 Y701 phosphorylation and increased CIITA and HLA-DRα mRNA early on.
- IL-6 levels increased early with PM2.5, while IL-8 remained low.
- CuSO4 exposure showed delayed effects on HLA-DRα, STAT1, and RF1 expression.
Conclusions:
- PM2.5 exposure can initiate an early inflammatory response in human bronchial epithelia through an alternative, non-canonical pathway.
- This pathway appears to operate independently of INFγ, suggesting a novel mechanism for PM-induced inflammation.
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