Specific microRNAs that are contained in tiny, cell-derived vesicles called exosomes may be biomarkers of Parkinson’s disease, according to a study.
The study, “Circulating exosomal miRNAs as diagnostic biomarkers in Parkinson’s disease,” was published in the journal European Review for Medical and Pharmacological Sciences.
MicroRNAs (miRNAs) are tiny bits of RNA that bind to messenger RNA (mRNA) — a molecule generated from DNA that contains the information to make proteins — to regulate gene expression, which is the process by which information in a gene is synthesized to create a working product, like a protein.
Abnormal plasma levels of miRNAs have been found in Parkinson’s patients. For example, while miR-505 — also implicated in cancer and hypertension — was reduced, miR-331-5p — also involved in cancer and chemotherapy resistance — was elevated in these patients.
In the cerebrospinal fluid, which fills the brain and spinal cord, miRNAs contained in exosomes may have diagnostic value for Parkinson’s patients. However, little is known about exosomal miRNAs from blood plasma, which have been suggested as a useful approach to diagnose Alzheimer’s.
Aiming to address this, researchers at Cangzhou Central Hospital in China collected blood from 52 Parkinson’s patients and 48 healthy participants used as controls. Parkinson’s patients included 28 men, at a mean age of 65.6 years with a mean disease duration of 5.3 years. Healthy individuals included 26 men, at a mean age of 61.2 years.
Among the used Parkinson’s medications, a levodopa/carbidopa combination was taken by all patients. Comtan (entacapone) was also common, taken by 20 patients (38.5%), while Zelapar (selegiline) was taken by 10 (19.2%), and Requip (ropinirole) taken by nine (17.3%).
Exosomes were isolated from blood samples, which were then analyzed for their levels of protein and miRNAs.
The exosomes were round or oval-shaped and contained the exosomal protein markers CD9, CD63, and Tsg101, confirming the presence of these tiny vesicles in plasma.
Among nine different miRNAs, the level of exosomal miR-331-5p was significantly higher and that of miR-505 was significantly lower in Parkinson’s patients than in healthy controls. In patients, miR-331-5p was mainly packaged in exosomes, which, according to the researchers, may mean it is later transferred to Parkinson’s-related cells to influence disease development.
In turn, miR-505 was essentially found in the plasma, indicating it may not be transferred to Parkinson’s by exosomes, but rather by other cells. However, this theory needs to be further studied, the team said.
These results provide “solid evidence that exosomal miR-331-5p and miR-505 could be biomarkers for [Parkinson’s],” the researchers wrote, and that “exosomal miR-331-5p and miR-505 have diagnostic values for [Parkinson’s].”
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