Abstract Body: Introduction: Over the past few decades, plastics have been widely used in many products. Recently, the potential ingestion of plastic debris called microplastics and nanoplastics (MNPs) and their toxicity to organs and tissues have been reported. They can enter the bloodstream not only by ingestion, but also by inhalation and dermal contact. MNPs are emerging as a potential risk factor for cerebrovascular events such as myocardial infarction and stroke in recent clinical study. However, the relationship between MNPs exposure and ischemic stroke is not well elucidated. In this study, we investigated the effect of MNPs on ischemic stroke using the transient middle cerebral artery occlusion (tMCAO) model in mice.
Methods: We used 12-week-old male C57BL/6J mice. Mice (n = 48) were divided into four groups based on the materials administered. After daily pretreatment with either pure water as vehicle, polystyrene (PS, 150 mg/kg/day), polyethylene (PE, 150 mg/kg/day), and polyvinyl chloride (PVC, 150 mg/kg/day) for 35 days, mice were subjected to tMCAO for 60 minutes. Treatment with MNPs was continued until postoperative day 2. As a safety study, we measured the body weight and blood pressure during the pretreatment. We compared Garcia score, neurological deficit score (NDS), rotarod performance (% baseline), and infarction volume (% ipsilateral) between the groups 3 days after tMCAO.
Results: No significant side effects such as weight loss or blood pressure changes were observed during pretreatment. Garcia scores were significantly lower in the PE (7.5 ± 4.0) and PVC (9.1 ± 2.1) groups compared to the vehicle group (11.9 ± 3.7) on day 3 (Fig. A, P<0.05, respectively). Similarly, NDS was significantly higher in the PE (2.5 ± 1.3) and PVC (2.3 ± 0.5) groups compared to the vehicle group (1.4 ± 1.0) on day 3 (Fig. B, P<0.05). There was a significant difference in rotarod performance between PE (55.6%) and vehicle (100.2%) groups on day 3 (Fig. C, P<0.05). Infarct volumes were significantly larger in the PE (30.2%) and PVC (27.3%) groups compared to the vehicle group (14.2%) on day 3 (Fig. D, P<0.05). These results were not confirmed in the PS group.
Conclusions: This preliminary study revealed the potential negative effects of microplastics and nanoplastics on ischemic stroke in mice. Future research should evaluate the long-term outcomes and the mechanisms by which microplastics and nanoplastics exacerbate the ischemic stroke.