Analysis of Cerebrospinal Fluid Soluble TREM2 and Polymorphisms in Sporadic Parkinson’s Disease in a Chinese Population

Background Triggering receptor expressed on myeloid cells 2 ( TREM2 ) is a microglial surface receptor that mediates the degradation disorder of amyloid β (Aβ) in Alzheimer’s disease. However, the role of TREM2 in Parkinson’s disease (PD) and α-Synclein (α-Syn) degradation is largely unknown. Methods In this case-control study on Chinese population, we sequenced for polymorphisms in exon 2 of the TREM2 gene in 1,292 individuals, PD cases (n = 612), healthy controls (n = 680) by Sanger sequence, and compared the distribution of allelic frequencies between the two groups by the Fisher’s exact test. Additionally, we developed and used the enzyme-linked immunosorbent assay to evaluated soluble TREM2 (sTREM2) levels in the cerebrospinal fluid (CSF), and plasma in partial of sequenced groups (55 PD and 40 healthy controls) analyzed their relationship with total a-syn (t-a-Syn). Results Two novel variants were detected in exon 2 of the TREM2 gene, namely, p.S81 N, p.G58D; however, these were not significantly associated with PD (612 PD and 680 healthy controls). sTREM2 in CSF was significantly upregulated in PD patients compared to healthy controls (433.1 ± 24.7 pg/mL vs. 275.2 ± 17.9 pg/mL, p < 0.0001), but not in plasma (281.7 ± 29.3 pg/mL vs. 257.8 ± 16.5 pg/mL, p = 0.805). In PD patients, sTREM2 was positively correlated with t-α-syn ( r = 0.62, p = 0.0001) in CSF, but not in plasma ( r = 0.02, p = 0.89). Conclusions Although it may not indicate that exon 2 polymorphisms of TREM2 play a role in the pathogenesis of PD in the Chinese population, our findings described above highlight the relevance of CSF sTREM2 as a promising biomarker and are extremely possible to the therapeutic target for PD in the future.