I had trouble finding the actual paper, but I think this is a preprint:
The in vivo study involves injecting nanoplastics directly into the brain of mice along with human α-synuclein fibrils, so is one step up from in vitro work but still quite artificial.
In sum, it does not demonstrate that nanoplastics in the environment, or even those that might be directly administered to mice, e.g. in food, have any effect on Parkinson's-like symptoms or pathology.
Edit: I should add that laboratory mice are often in contact with plastics that they chew on. So it's highly unlikely that ingesting plastics has any effect on mouse models of Parkinson's as this would have been noted decades ago.
Doesn't it only mean there were no control group? Just like when they found out that mice suddenly started dying less when they raised lab temp a bit.
However, mice that have human α-synuclein have been around for decades, and nobody has (so far) noticed any effect of plastics on the development of Parkinsonism in these mice, neither are there any claims that Parkinsonism is more prevalent in people who have plastic implants of one kind or another.
Note that people ingest plastics all the time, e.g. through the breakdown of toothbrush bristles.
Plastics are found in human blood/lungs/breast milk/placenta etc, so the concern is much stronger than just accidental ingestion from a toothbrush.
Read about effects of xenoestrogens, which a bunch of these plastics apparentlt are, and cross check with some realities of today.
Yes, I appreciate the risk of plasticisers, and these should be addressed.
However, by the time an item made of plastic has become a "microplastic", these plasticisers have been leached out.