Colonic Leucine-Rich Repeat Kinase 2 Expression Is Increased and Associated With Disease Severity in Patients With Parkinson's Disease

Abstract

Background: Mutations in leucine-rich repeat kinase 2 (LRRK2) comprise a common genetic risk factor for Parkinson's disease (PD) and inflammatory bowel disease (IBD). We investigated the expression of LRRK2 in colonic biopsies obtained from a cohort of PD patients and healthy controls.

Methods: A cohort of 51 PD patients and 40 age- and gender-matched controls who have colonic biopsied samples were recruited. Among these participants, 26 individuals (12 PD patients and 14 controls) had a series of colon biopsies. For the patients with PD, the first biopsies were taken before the PD diagnosis. The colonic expression of LRRK2 was assayed by immunohistochemical staining.

Results: The fraction of LRRK2-positive cells among the total cell count in biopsied colonic tissues was significantly higher in PD patients than controls (0.81% ± 0.53% vs. 0.45% ± 0.39%; P = 0.02). Colonic LRRK2 immunoreactivity was higher in those with LRRK2 genetic variants compared to those with wild type LRRK2 (2.44% ± 1.15% vs. 0.21 ± 0.13%, P < 0.01). Age had no effect on LRRK2 expression (P = 0.96). LRRK2 expression correlated with disease severity in regards to motor symptoms measured by the UPDRS part III scores (r = 6335, P < 0.001) and cognitive dysfunction measured by the mini-mental status examination scores (r = -0.5774, P < 0.001). PD patients in the prodromal phase had a steeper increase in colonic LRRK2 expression compared to controls during the serial colon biopsy assessment (P < 0.01).

Conclusion: Colonic LRRK2 expression was increased in PD patients compared to controls, and the expression level correlated with disease severity.

Keywords: Parkinson’s disease; biomarker (BM); colon biopsy; inflammatory bowel diseases; leucine-rich repeat kinase 2.

FIGURE 1

LRRK2 expression in colonic biopsies from PD patients and age- and gender-matched controls. (A) Original view of the represented colonic biopsy tissues. (B) All nuclei are circled with green lines, and the LRRK2-positive staining detected as positive events are circled in red lines (arrows) by the StrataQuest Analysis software version 6 (TissueGnostics, Vienna, Austria). (C) Distribution histograms of the LRRK2-positive ratio in PD patients and controls. (D) Representative pictures of LRRK2-positive cells in the submucosa of colonic samples from one 72-year-old male PD patient and one 71-year-old male control participant. Positive events are indicated by arrows. The pictures on the right are the magnification of the framed areas on the left. Scale bar: 100 μm. (E) The fractions of LRRK2-positive cells in the total cell counts in colonic biopsies were significantly higher in PD patients than controls (P = 0.004 by Mann-Whitney U-test). (F) The fractions of LRRK2-positive cells in the total cell counts in colonic biopsies from PD patients with wild type or genetic variant in LRRK2. *P < 0.05; **P < 0.01.

FIGURE 2

Correlation of colonic LRRK2 expression with clinical severity in PD. (A) Age did not correlate with LRRK2 expression in colonic biopsies. (B,C) Correlation of colonic LRRK2 expression with Hoehn-Yaht stage and UPDRS part III motor score. (D) Correlation of colonic LRRK2 expression with MMSE score.

FIGURE 3

Time-sequential serial analysis of LRRK2 expression in colonic biopsies from patients with PD and controls. (A) Individual data for colonic LRRK2 expression from the serial study. (B) Grouping analysis of colonic LRRK2 expression was significantly different between PD patients and controls in individual time serial groups.