The MUC5B Mucin Is Involved in Paraquat-Induced Lung Inflammation

Abstract EN

Objective.

Paraquat (PQ), a widely used toxic herbicide, induces lung inflammation through mechanisms that remain incompletely understood.

In a previous study, we found that the plasma MUC5B mucin level was implicated in PQ poisoning in patients.

Here, we hypothesize that MUC5B is a critical mediator in PQ-induced cell inflammation.

Methods.

A mouse model of PQ-induced lung injury was used to examine the MUC5B expression level.

A549 cells (alveolar epithelial cells line) were exposed to PQ in dose-dependent and time-dependent manners.

Cell viability was detected by CCK-8 assays.

The expression levels of MUC5B were examined by dot blot enzyme-linked immunosorbent assay (ELISA) and RT-qPCR.

Western blotting was used to detect the levels of proteins in the MAPK and NF-κB pathways.

Inflammatory factors in the cell culture medium were measured by ELISA.

NF-κB and MAPK pathway inhibitors and MUC5B siRNA (siMUC5B) were used to determine the function of MUC5B.

Finally, N-acetyl-cysteine (NAC) was added and its regulatory effect on the MAPK-NF-κB-MUC5B pathway was examined in PQ-induced cell inflammation.

Results.

MUC5B was significantly upregulated accompanying the increases in TNF-α and IL-6 secretion following PQ treatment in mouse and also in A549 cells after treatment with 50 μM PQ at 24 hours.

Furthermore, MAPK and NF-κB pathway inhibitors could dramatically decrease the expression of MUC5B and the secretion of TNF-α and IL-6.

Importantly, siMUC5B could significantly attenuate the secretion of TNF-α and IL-6 induced by PQ.

As expected, the addition of NAC efficiently suppresses the TNF-α and IL-6 secretion stimulated from PQ and also downregulated ERK, JNK, and p65 phosphorylation (ERK/JNK MAPK and NF-κB pathways) as well as MUC5B expression.

Conclusion.

Our findings suggest that MUC5B participates in the process of PQ-induced cell inflammation and is downstream of the NF-κB and MAPK pathways.

NAC can attenuate PQ-induced cell inflammation at least in part by suppressing the MAPK-NF-κB-MUC5B pathway.

These results nominate MUC5B as a new biomarker and therapeutic target for PQ-induced lung inflammation.