Differential sensitivity of hemocyte subpopulations (mytilus edulis) to aged polyethylene terephthalate micro-and-nanoplastic particles

Hemocytes of bivalve mollusks play a crucial role in cell-mediated immunity and serve as valuable models for investigating plastic particle-induced responses. Different subpopulations of hemocytes, such as hyalinocytes and granulocytes, exhibit distinct morphological and functional characteristics, including internal cell signaling pathways that regulate various cellular processes. Despite growing research on biological responses to plastic particle exposure, systematic cellular-level analyses are still limited. Hence, this study focused on assessing the responses of hemocyte subpopulations (Mytilus edulis) to chemically aged polyethylene terephthalate (APET) microplastic (MPs) and nanoplastic (NPs) particle exposure. Two different size ranges were utilized: APET MPs (D50 = 1.4 µm and D90 = 3.1 µm) and APET NPs (D50 = 0.57 µm and D90 = 1.1 µm). In-vitro experiments were carried out using environmentally relevant concentrations: C1: 10 particles/mL; C2: 10^3 particles/mL; and C3: 10^5 particles/mL. Characterization of the APET particles was conducted through a combination of techniques, such as Single Particle Extinction and Scattering (SPES), Raman Spectroscopy, Scanning Electron Microscopy (SEM), and Dynamic Light Scattering (DLS). To evaluate the underlying mechanisms induced by exposure to APET in-vitro, an in-depth assessment was carried out across multiple cellular effect endpoints, including lysosomal stability, reactive oxygen species (ROS) production, cellular mortality, and morphological parameters, such as cell size and complexity. The responses of the hemocyte subpopulations were assessed using flow cytometry at various time points (6h, 12h, 24h, and 48h). Particle size and concentration-dependent lysosomal destabilization were observed at particular time points. While elevated ROS levels were more pronounced in granulocytes exposed to the highest concentration of nano-sized plastic particles. Both APET MPs and NPs induce significant increases in cellular mortality, particularly after 24h of exposure at high concentrations. Current findings offer mechanistic insights into the differential sensitivities of bivalve hemocytes under environmentally relevant exposure conditions, highlighting implications for their functional integrity. Also see: https://micro2024.sciencesconf.org/558712/document