In Vivo Tissue Distribution of Polystyrene or Mixed Polymer Microspheres and Metabolomic Analysis after Oral Exposure in Mice.

BACKGROUND: Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored. OBJECTIVES: This study aims to investigate the impacts of polymer microspheres on tissue metabolism in mice by assessing the microspheres ability to translocate across the gut barrier and enter into systemic circulation. Specifically, we wanted to examine microsphere accumulation in different organ systems, identify concentration-dependent metabolic changes, and evaluate the effects of mixed microsphere exposures on health outcomes. METHODS: To investigate the impact of ingested microspheres on target metabolic pathways, mice were exposed to either polystyrene (5µm) microspheres or a mixture of polymer microspheres consisting of polystyrene (5µm), polyethylene (1-4µm), and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid) (5µm). Exposures were performed twice a week for 4 weeks at a concentration of either 0, 2, or 4mg/week via oral gastric gavage. Tissues were collected to examine microsphere ingress and changes in metabolites. RESULTS: In mice that ingested microspheres, we detected polystyrene microspheres in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolic differences that occurred in the colon, liver, and brain, which showed differential responses that were dependent on concentration and type of microsphere exposure. DISCUSSION: This study uses a mouse model to provide critical insight into the potential health implications of the pervasive issue of plastic pollution. These findings demonstrate that orally consumed polystyrene or mixed polymer microspheres can accumulate in tissues such as the brain, liver, and kidney. Furthermore, this study highlights concentration-dependent and polymer type-specific metabolic changes in the colon, liver, and brain after plastic microsphere exposure. These results underline the mobility within and between biological tissues of MPs after exposure and emphasize the importance of understanding their metabolic impact. https://doi.org/10.1289/EHP13435.

In Vivo Tissue Distribution of Microplastics and Systemic Metabolomic Alterations After Gastrointestinal Exposure.

Global plastic use has consistently increased over the past century with several different types of plastics now being produced. Much of these plastics end up in oceans or landfills leading to a substantial accumulation of plastics in the environment. Plastic debris slowly degrades into microplastics (MPs) that can ultimately be inhaled or ingested by both animals and humans. A growing body of evidence indicates that MPs can cross the gut barrier and enter into the lymphatic and systemic circulation leading to accumulation in tissues such as the lungs, liver, kidney, and brain. The impacts of mixed MPs exposure on tissue function through metabolism remains largely unexplored. To investigate the impact of ingested MPs on target metabolomic pathways, mice were subjected to either polystyrene microspheres or a mixed plastics (5 µm) exposure consisting of polystyrene, polyethylene and the biodegradability and biocompatible plastic, poly-(lactic-co-glycolic acid). Exposures were performed twice a week for four weeks at a dose of either 0, 2, or 4 mg/week via oral gastric gavage. Our findings demonstrate that, in mice, ingested MPs can pass through the gut barrier, be translocated through the systemic circulation, and accumulate in distant tissues including the brain, liver, and kidney. Additionally, we report on the metabolomic changes that occur in the colon, liver and brain which show differential responses that are dependent on dose and type of MPs exposure. Lastly, our study provides proof of concept for identifying metabolomic alterations associated with MPs exposure and adds insight into the potential health risks that mixed MPs contamination may pose to humans.

Comparison of a micro-electro-mechanical system airflow sensor with the pneumotach in the forced oscillation technique.

PURPOSE: This study supports the use of thin-film micro-electro-mechanical system (MEMS) airflow sensors in the forced oscillation technique. MATERIALS AND METHODS: The study employed static testing using air flow standards and computer-controlled sound attenuations at 8 Hz. Human feasibility studies were conducted with a testing apparatus consisting of a pneumotach and thin-film MEMS air flow sensors in series. Short-time Fourier transform spectra were obtained using SIGVIEW software. RESULTS: Three tests were performed, and excellent correlations were observed between the probes. The thin-film MEMS probe showed superior sensitivity to higher frequencies up to 200 Hz. CONCLUSION: The results suggest that lower-cost thin-film MEMS can be used for forced oscillation technique applications (including home care devices) that will benefit patients suffering from pulmonary diseases such as asthma, COPD, and cystic fibrosis.

Post-diarrhea chronic intestinal symptoms and irritable bowel syndrome in North American travelers to Mexico.

OBJECTIVES: Irritable bowel syndrome (IBS) has been reported to complicate bacterial diarrhea. Because of the frequency of international travel and the common occurrence of bacterial diarrhea, we studied the occurrence of chronic gastrointestinal complaints and post-diarrhea IBS in North U.S. travelers to Mexico. METHODS: One hundred and sixty-nine healthy students were followed prospectively for 5 wk for the occurrence and etiology of diarrhea while studying for 5 wk in Mexico. Subjects recorded their symptoms during travel and completed a gastrointestinal symptom questionnaire 6 months after returning to the United States to determine the presence of IBS using the Rome II criteria. RESULTS: Ninety-seven (57%) subjects returned a completed questionnaire. Sixty-one (63%) developed diarrhea while in Mexico, mostly due to enterotoxigenic and enteroaggregative Escherichia coli. Six months after travel the following chronic symptoms were reported: loose stools, abdominal pain, and fecal urgency in 17 (18%), 17 (18%), and 9 (9%) respectively. Of the 60 patients surveyed who had acquired diarrhea in Mexico, 7 (11%) met the criteria for IBS 6 months later of which 6 (10%) were newly diagnosed. No identified pathogen in the initial illness was associated with the development of IBS. CONCLUSIONS: Chronic gastrointestinal complaints including IBS are common in returning travelers having experienced diarrhea. Postinfectious complications of traveler's diarrhea require further study for etiology and strategy for prevention.

Modification of haemophiliac haemorrhage pain by transcutaneous electrical nerve stimulation.

Haemophiliacs suffer considerable pain when they bleed into their joints. This study investigated the use of transcutaneous electrical nerve stimulation (TENS) for relief of such pain. Thirty-six haemophiliac patients received either active or placebo TENS treatment. The intensity of pain was assessed before and after treatment using the McGill Pain Questionnaire. After 25 min of active treatment, 71% of the subjects reported at least 50% pain relief as measured by the McGill Pain Questionnaire. This compares with only 25% pain relief experienced by the placebo group.

Modification of induced ischaemic pain by transcutaneous electrical nerve stimulation.

Endurance to ischaemic pain was assessed in healthy subjects receiving either continuous or trains of transcutaneous electrical nerve stimulation (TENS) at different intensity levels. Control subjects received no stimulation. Self-reports of pain thresholds and pain tolerance levels were obtained, and on-going pain was assessed by means of two linear pain scales. At the end of each trial, descriptions of intolerable pain were obtained using the McGill Pain Questionnaire. High intensity continuous stimulation raised pain tolerances and endurance of pain, but was associated with higher levels of reported pain when tolerance was reached. Low intensity trains of stimulation raised pain thresholds and tolerance levels but did not increase endurance to induced ischaemic pain. Our results suggest that the response to induced ischaemic pain can be selectively modified by peripheral electrical stimulation depending on its temporal and intensity characteristics.