Role of Apolipoprotein E, Cathepsin D, and Brain-Derived Neurotrophic Factor in Parkinson’s Disease: A Study from Eastern India

Cathepsins and Parkinson's disease: insights from Mendelian randomization analyses

Background

Parkinson's disease (PD), the second most prevalent neurodegenerative condition, has a multifaceted etiology. Cathepsin-cysteine proteases situated within lysosomes participate in a range of physiological and pathological processes, including the degradation of harmful proteins. Prior research has pointed towards a potential link between cathepsins and PD; however, the precise causal relationship between the cathepsin family and PD remains unclear.

Methods

This study employed univariate and multivariate Mendelian randomization (MR) analyses to explore the causal relationship between the nine cathepsins and Parkinson's disease (PD) risk. For the primary analysis, genome-wide association study (GWAS) summary statistics for the plasma levels of the nine cathepsins and PD was obtained from the INTERVAL study and the International Parkinson's Disease Genomics Consortium. GWAS for PD replication analysis were obtained from the FinnGen consortium, and a meta-analysis was performed for the primary and replication analyses to evaluate the association between genetically predicted cathepsin plasma levels and PD risk. After identifying significant MR estimates, genetic co-localization analyses were conducted to determine whether shared or distinct causal variants influenced both cathepsins and PD.

Results

Elevated cathepsin B levels were associated with a decreased risk of PD in univariate MR analysis (odds ratio [OR] = 0.890, 95% confidence interval [CI]: 0.831-0.954, pFDR = 0.009). However, there was no indication that PD affected cathepsin B levels (OR = 0.965, 95% CI: 0.858-1.087, p = 0.852). In addition, after adjusting for the remaining cathepsins, cathepsin B levels independently and significantly contributed to the reduced risk of PD in multivariate MR analysis (OR = 0.887, 95% CI: 0.823-0.957, p = 0.002). The results of the replication MR analysis with the FinnGen GWAS for PD (OR = 0.921, 95% CI: 0.860-0.987, p = 0.020) and meta-analysis (OR = 0.905, 95% CI: 0.862-0.951, p < 0.001) were consistent with those of the primary analysis. Colocalization analysis did not provide any evidence of a shared causal variant between cathepsins and PD (PP.H4.abf = 0.005).

Conclusion

This genetic investigation supports the hypothesis that cathepsin B exerts a protective effect against PD. The quantification of cathepsin B levels could potentially serve as a predictive biomarker for susceptibility to PD, providing new insights into the pathomechanisms of the disease and possible interventions.

Association Between Dystonia-Related Genetic Loci and Parkinson's Disease in Eastern China

Background

Parkinson's disease (PD) and dystonia are closely related in terms of pathophysiology and clinical manifestations, but their common genetic characteristics remain unclear. Some genome-wide association studies (GWASs) and replication studies have revealed correlations between single nucleotide polymorphisms (SNPs) of the ARSG, BDNF, NALCN, OR4X2, KIAA1715, and OR4B1 genes and dystonia. This study was conducted to assess the association between these genetic loci and PD in a population from Eastern China.

Methods

We genotyped the SNPs (rs11655081 of ARSG; rs6265 of BDNF; rs61973742, rs1338051, rs9518384, and rs9518385 of NALCN; rs67863238 of OR4X2; rs10930717 of KIAA1715; and rs35875350 of OR4B1) in a cohort of 474 patients with PD and 439 healthy controls from East China. To determine the genotypes of these SNPs, we used an Agena MassARRAY Typer 4.0. Odds ratios (ORs) and 95% CIs were computed to evaluate the correlations between these SNPs and the risk of PD.

Results

There were significant differences in the genotype distribution (OR = 0.649, 95% CI = 0.478–0.880) and minor allele frequency (MAF) (OR = 0.703, 95% CI = 0.533–0.929) of SNP rs61973742 (NALCN) between patients with PD and healthy controls. A significant difference was detected in the genotype distribution of rs11655081 (ARSG) (OR = 1.486, 95% CI = 1.080–2.045).

Conclusion

Single nucleotide polymorphisms rs11655081 (ARSG) and rs61973742 (NALCN) may be associated with PD. The C allele of rs11655081 may increase the risk of PD, whereas the G allele of rs61973742 may be a protective factor.

APOE rs405509 polymorphism and Parkinson's disease risk in the Chinese population

Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder with complex etiology involving both genetic and environmental factors. Apolipoprotein E (ApoE) rs405509 (-219 T/G), a promoter SNP, controls the expression of APOE gene, and plays a modifier effect of APOE ε4 on the susceptibility of Alzheimer's disease. In this study, we investigate the association between APOE rs405509 polymorphism and the susceptibility of PD in a Chinese population. A total of 1020 subjects were collected including 510 sporadic PD patients (mean age: 63.11 ± 9.28 years) and 510 healthy control subjects (mean age: 62.97 ± 9.09 years). APOE rs405509 polymorphism was genotyped using a TaqMan genotyping method. The Hardy-Weinberg Equilibrium (HWE) was calculated for the control group by Chi-square (χ2) test. The strength of this association between the APOE rs405509 polymorphism and PD risk was evaluated with crude odds ratios (ORs) and 95 % confidence intervals (CIs) using a logistic regression analysis. The T allele frequency was 0.84 and 0.70 in the PD and control groups, respectively. T allele carriers of rs405509 were associated with an increased overall risk of PD and in male subjects in the allele, recessive, and additive genetic models. Similar results in female subjects were found in the allele and recessive genetic models. In conclusion, our study suggests that the APOE rs405509 T allele is correlated with increased susceptibility of PD in a Chinese population.

Cathepsins in the Pathophysiology of Mucopolysaccharidoses: New Perspectives for Therapy

Cathepsins (CTSs) are ubiquitously expressed proteases normally found in the endolysosomal compartment where they mediate protein degradation and turnover. However, CTSs are also found in the cytoplasm, nucleus, and extracellular matrix where they actively participate in cell signaling, protein processing, and trafficking through the plasma and nuclear membranes and between intracellular organelles. Dysregulation in CTS expression and/or activity disrupts cellular homeostasis, thus contributing to many human diseases, including inflammatory and cardiovascular diseases, neurodegenerative disorders, diabetes, obesity, cancer, kidney dysfunction, and others. This review aimed to highlight the involvement of CTSs in inherited lysosomal storage disorders, with a primary focus to the emerging evidence on the role of CTSs in the pathophysiology of Mucopolysaccharidoses (MPSs). These latter diseases are characterized by severe neurological, skeletal and cardiovascular phenotypes, and no effective cure exists to date. The advance in the knowledge of the molecular mechanisms underlying the activity of CTSs in MPSs may open a new challenge for the development of novel therapeutic approaches for the cure of such intractable diseases.