Microplastics, tiny plastic particles less than 5 mm in size, are ubiquitous in the environment and can even be found in human blood, placenta, and lungs. A new study reveals that when these microplastics become degraded by ultraviolet (UV) light, they can cause a concerning type of cell death called lysosome-deregulated cell death. This finding provides important insights into the potential health risks of microplastics, especially as they undergo weathering in the environment. Microplastics are a growing environmental concern, and understanding their impacts on human health is crucial.
The Threat of Degraded Microplastics
Microplastics are a ubiquitous environmental pollutant, and human exposure to them is unavoidable. These tiny plastic particles can enter our bodies through ingestion, inhalation, or even absorption through the skin. What’s more, microplastics have been detected in human blood, placenta, and lungs, raising serious concerns about their potential health impacts.
The Importance of Surface Degradation
A key factor that can influence the toxicity of microplastics is their surface degradation. As microplastics are exposed to environmental factors like UV light and waves, their physical and chemical properties can change. This surface degradation is a crucial consideration when evaluating the risks of microplastics to human health.
Lysosome-Deregulated Cell Death
In this new study, researchers focused on the effects of degraded polyethylene (PE) microplastics on two types of immune cells: murine macrophages and human monocytes. They found that degraded PE microplastics induced a form of cell death that was not accompanied by the activation of caspase-3, a key enzyme involved in apoptosis (programmed cell death).
Further investigation revealed that degraded PE microplastics disrupted the normal function of lysosomes, which are organelles within cells that play a crucial role in recycling and breaking down cellular components. This lysosomal dysfunction led to the accumulation of autophagosomes (structures involved in the autophagy process) and the inhibition of autophagy flux, ultimately causing cell death.
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The Role of Iron and Ferroptosis
The researchers also found that the cytotoxic effects of degraded PE microplastics were mitigated by the addition of an iron chelator, deferoxamine. This suggests that the release of iron from damaged lysosomes may contribute to the cell death induced by degraded microplastics, potentially through a process called ferroptosis – a form of iron-dependent cell death.
Implications and Future Research
This study provides valuable insights into the potential health risks posed by degraded microplastics. The findings highlight the importance of considering the physicochemical properties of environmental microplastics, especially their surface degradation, when assessing their impact on human health. Further research is needed to understand the precise mechanisms by which degraded microplastics induce lysosomal dysfunction and cell death, as well as to explore the potential link to ferroptosis.
As microplastics continue to accumulate in the environment, understanding their effects on human health is crucial. This new study contributes to the growing body of evidence that the weathering and degradation of microplastics can have significant consequences for biological systems, including the potential to disrupt critical cellular processes and lead to harmful health outcomes.
Author credit: This article is based on research by Sota Manabe, Yuya Haga, Hirofumi Tsujino, Yudai Ikuno, Haruyasu Asahara, Kazuma Higashisaka, and Yasuo Tsutsumi.
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