Microplastics amplify the pro-inflammatory response to fungal mycelial fragments and spores in neutrophil-like cells

HDPE combined with fungal fragments induced significant release of IL-6 and IL-8 while the mixtures with fungal spores induced only IL-6 release from the neutrophil-like cells. Most importantly, we observed a trend of decreasing IL-6 levels with increasing doses of HDPE microplastics in mixture with fungal particles, indicating possible dysregulation of the pro-inflammatory response. The tested doses of HDPE microplastics in mixture with fungal particles showed no significant acute effects on the cell viability. Using HEK293-TLR reporter cells, we found no significant activation of TLR2 and TLR4 by HDPE microplastics, fungal particles, or their combination, suggesting that the release of IL-6 and IL-8 is induced through other innate immune-signaling pathways. Taken together, fungal particles as microbial contaminants, seem to be the main drivers of the immune responses triggered by exposure to mixed HDPE microplastics and fungal particles. Among these, fungal mycelial fragments appear to be the most potent compared to fungal spores that are typically monitored for risk assessments.