UNRAVELING THE MOLECULAR MECHANISMS OF MICROPLASTICS INTERNALIZATION AND THEIR INTRACELLULAR IMPACT

In recent years, microplastics (MPs) in our environment has become a critical concern. These tiny plastic particles, measuring less than 5 millimeters, result from the fragmentation of larger plastic debris due to UV-light-induced oxidation, mechanical abrasion, and temperature fluctuations. Nowadays plastics, have led us into what many refer to as “Plasticene” since their mid-20th century discovery. Despite widespread recognition of the detrimental effects of MPs, including impacts on fertility, hepatic function, immune response, and gene expression patterns, understanding their cellular-level effects remains challenging due to their diverse characteristics, including size, composition, and target specificity. In this work we aim to elucidate the molecular mechanisms underlying the internalization of MPs of different sizes (5 and 0.5 microns), using distinct cell cultures: GT1-7 (human hypothalamic neurons) and 3T3-L1 (murine pre-adipocytes). First, we assessed the toxicity of both types of MPs and we found no significant effects on cell viability for either cell line, except for a slight reduction at the highest concentration in GT1-7 cells. Using fluorescence microscopy, we found that larger particles exhibit minimal cellular uptake compared to their smaller counterparts. To understand the predominant internalization mechanism, we conducted inhibition experiments on macropinocytosis, clathrindependent and caveolin-dependent endocytosis via flow cytometry. Then, combining optical and electron microscopy techniques, we examined the intracellular localization of MPs. This allowed us to identify interactions between MPs and intracellular organelles, such as lysosomes and mitochondria, potentially compromising cellular health. Through this research we hope to enhance our understanding of MPs actions at the cellular level. Furthermore, our findings will inform strategies for mitigating the impact of MPs on both human health and the environment.