Top-down generated micro- and nanoplastics reduce macrophage viability without eliciting a pro-inflammatory response

Area of Science:

• Environmental Science
• Toxicology
• Immunology

Background:

• Micro- and nanoplastic particles (MNPs) are ubiquitous environmental contaminants.
• Human exposure to MNPs is inevitable through various routes.
• The immunotoxic effects of fragmented MNPs on macrophages are not well understood.

Purpose of the Study:

• To investigate the cytotoxic and pro-inflammatory effects of fragmented MNPs on human macrophages.
• To assess the impact of different MNP types, sizes, and concentrations on macrophage responses.

Main Methods:

• Human THP-1 macrophages were exposed to fragmented PVC, PP, PA6.6, and primary PS particles, as well as TiO2.
• Particle uptake was analyzed using flow cytometry and confocal microscopy.
• Macrophage responses were measured via lysosomal and mitochondrial activity, LDH leakage, NF-κB activity, and cytokine secretion.

Main Results:

• Macrophages took up PS particles in a concentration-, time-, and size-dependent manner.
• MNPs increased lysosomal activity, indicating potential accumulation.
• Fragmented MNPs induced cytotoxicity (decreased mitochondrial activity, increased LDH leakage) but not significant pro-inflammatory cytokine release (IL-6, IL-1β, TNF-α).

Conclusions:

• Fragmented MNPs exhibit cytotoxic potential towards human macrophages at higher concentrations.
• A direct pro-inflammatory response by macrophages to fragmented MNPs was not observed.
• Physico-chemically altered MNPs may indirectly affect immune system functioning, necessitating further research.