Nikhil Prasad Fact checked by:Thailand Medical News Team May 30, 2024 1 month, 4 weeks, 1 hour, 9 minutes ago
Medical News: Global plastic production has surged exponentially, reaching nearly 475 million tons in 2021, with projections to climb to 550 million tons by 2026. This increase has led to a significant rise in microplastic (MP) contamination in our environment. Microplastics, resulting from the degradation of larger plastic debris, present a growing ecological concern due to their persistent nature and slow chemical breakdown. Human exposure to MPs occurs through both ingestion and inhalation, raising alarms about their potential health impacts as recently covered in numerous
Medical News reports. (Refer To Read Also section at the end of the article).
Despite widespread speculation regarding the health consequences of MP exposure, there is limited direct evidence linking MPs to specific human diseases, except in heavily contaminated industrial settings. However, emerging clinical data suggests potential health risks, such as increased severity of inflammatory bowel disease and higher risks of cardiovascular events in patients with detectable MPs in their bodies.
Study Methods
To investigate the effects of MPs on the immune response to SARS-CoV-2 infection, researchers from QIMR Berghofer Medical Research Institute, Brisbane-Australia, Institut National de Recherche Agronomique, Unité Mixte de Recherche-France and the Australian Infectious Disease Research Centre, Global Virus Network (GVN) Center of Excellence, Brisbane-Australia utilized a mouse model of mild COVID-19. Female C57BL/6J mice were inoculated intranasally with a suspension of azide-free 1 μm polystyrene MP beads and a SARS-CoV-2 omicron BA.5 inoculum. The host response to this co-delivery was analyzed using histopathology and RNA-Seq at 2- and 6-days post-infection (dpi).
Study Findings
-
Initial Effects of MP Inoculation
MP exposure induced mild inflammation in the lungs at 2 dpi. RNA-Seq analysis identified 341 differentially expressed genes (DEGs) indicating a mild pro-inflammatory response. Notably, interstitial macrophages and dendritic cells showed reduced abundance, while alveolar epithelial cells appeared more transcriptionally active. These findings suggest a modest inflammatory response and slight proliferation of lung epithelial cells.
-Resolution of MP Effects
By 6 dpi, the inflammatory response to MPs had largely resolved, with only seven DEGs remaining. This indicates that the lung response to a single MP exposure is transient and resolves within a week.
-
Impact of MPs on SARS-CoV-2 Infection
SARS-CoV-2 infection in the mACE2-hACE2 mouse model using the omicron BA.5 variant did not significantly alter MP clearance from the lungs, although clearance was slightly slower in infected mice. Viral titers and RNA levels in the respiratory tract were unaffected by MP presence.
Dysregulation of Immune Responses
-Suppression of Innate Immunity at 2 dpi
At 2 dpi, MP exposure suppressed innate immune responses, evidenced by reduced type I interferon (IFN) signatures and diminished phagocytosis activities. This suppression is likely due to MPs inhibiting the efferocytosis process, where macrophages engulf apoptotic cells. This inhibition potentially led to reduced activation of plasmacytoid dendriti
c cells (pDCs), which are key producers of type I IFNs during viral infections.
-Increased Pro-inflammatory Signatures at 6 dpi
By 6 dpi, MPs induced an increase in pro-inflammatory cytokines such as TNF, IL-1β, IL-1α, OSM, IL-17A, and IL-6. These cytokines are commonly associated with severe COVID-19 cases. The overall pro-inflammatory environment suggested a shift towards a "cytokine release syndrome" (CRS) profile, which is a hallmark of severe COVID-19.
Mechanistic Insights
The suppression of early innate immune responses, followed by a delayed pro-inflammatory response, may be attributed to MPs interfering with the efferocytosis process. This interference can lead to secondary necrosis of infected cells, promoting inflammation. Additionally, MPs induced stress responses, as seen by the upregulation of heat shock protein 70 (Hsp70) genes, which are markers of cellular stress.
This study highlights the dual role of MPs in modulating immune responses during SARS-CoV-2 infection. Initially, MPs suppress protective innate immune responses, which could hinder early viral clearance. However, this suppression transitions into a heightened pro-inflammatory state, resembling CRS observed in severe COVID-19 cases. Despite these transcriptional changes, no overt clinical or histopathological alterations were detected in the mouse model, suggesting that MP-induced dysregulation was mild in this setting.
The findings underscore the potential for MPs to exacerbate inflammatory processes in disease contexts, raising concerns about the broader health implications of chronic MP exposure. Future research should focus on understanding the long-term effects of realistic MP doses and exploring the impacts of different MP shapes, sizes, and compositions.
Conclusion
Microplastics can dysregulate innate immune responses to SARS-CoV-2 infection in the lungs, initially suppressing pro-inflammatory activities and later promoting a CRS-like profile. These findings contribute to the growing body of evidence suggesting that MPs may influence disease outcomes, highlighting the need for further investigation into the health impacts of chronic MP exposure.
The study findings were published in the peer reviewed journal: Frontiers in Immunology.
https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2024.1382655/full
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Read Also:
https://www.thailandmedical.news/news/microplastics-found-in-human-blood-a-new-health-threat
https://www.thailandmedical.news/news/microplastics-found-in-testicular-tissue
https://www.thailandmedical.news/news/covid-19-news-indian-researchers-warn-that-microplastics-in-waste-water-could-be-aiding-sars-cov-2-transmission
https://www.thailandmedical.news/news/microplastics-found-in-human-digestive-systems-and-faeces-across-the-world,-new-study-reveals.
https://www.thailandmedical.news/news/health-warning:-plastic-teabags-release-microscopic-particles-into-tea
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