ABSTRACT
Objective:To investigate the effect of LRRK2G2019S mutation on activation of microglia after iron deprivation and its mechanism.Methods:(1) Microglia were differentiated from human induced pluripotent stem cells (IPSC) with the help of hematopoietic progenitor cells (HPC) and identified by immunofluorescent staining, and α-synuclein (α-syn) A53T mutant protein was obtained by protein purification technology. (2) Microglia were divided into control group, α-syn group, α-syn+ deferoxamine (DFO) group; phosphate buffer solution (PBS), 1 μmol/L purified α-syn A53T mutant protein, 1 μmol/L purified α-syn A53T mutant protein+30 mmol/L DFO were given respectively for 24 h. Fe 2+ concentration was detected by colorimetry, Rab35 protein expression was detected by Western blotting, intracellular reactive oxygen species (ROS) level was detected by flow cytometry, and interleukin-6 ( IL-6), tumor necrosis factor-α ( TNF-α) and transforming growth factor-β ( TGF-β) mRNA expressions were detected by real time-PCR (RT-PCR); microglia culture supernatant (MCS) in the 3 groups were transfered to SH-SY5Y cells, and SH-SY5Y cell apoptosis was detected by flow cytometry. (3) Bidirectional DNA sequencing was used to detect leucine rich repeat kinase 2 ( LRRK2) gene mutations in microglia treated with 1 μmol/L purified α-syn A53T mutant protein. Microglia were divided into control group, α-syn group and α-syn+GSK3357679A group, and treated with corresponding drugs for 24 h, respectively (LRRK2 inhibitor GSK3357679A concentration: 10 nmol/L), and LRRK2 protein expression was detected by Western blotting; microglia were divided into control group, α-syn group, α-syn+GSK3357679A, and α-syn+GSK3357679A+DFO group, and treated with corresponding drugs for 24 h, Rab35 protein expression was detected by Western blotting, intracellular ROS level was detected by flow cytometry, and IL-6, TNF-α and TGF-β mRNA expressions were detected by RT-PCR. (4) Microglia were divided into control group, α-syn group, α-syn+rapamycin (RAPA) group, and treated with corresponding drugs for 24 h (concentration of autophagy inducer RAPA: 50 nmol/L); protein expressions of Rab35, P62 and microtubule-associated protein light chain 3 II (LC3II) were detected by Western blotting; intracellular ROS level was detected by flow cytometry, and IL-6, TNF-α and TGF-β mRNA expressions were detected by RT-PCR. (5) Microglia were divided into control group, α-syn group, and α-syn+Rab35 group, and treated with corresponding drugs for 24 h (concentration of Rab35 overexpressed plasmids: 1 μg/mL); Rab35, P62, and LC3II protein expressions were detected by Western blotting; ROS level was detected by flow cytometry, and IL-6, TNF-α and TGF-β mRNA expressions were detected by RT-PCR. Results:(1) Immunofluorescent staining showed negative neuronal nuclei (NeuN) expression and positive ionized calcium-binding adapter molecule 1 (Iba1) expression in microglia, and high LRRK2 expression; PcDNA3.1-SNCA-A53T expression plasmid was constructed and α-syn A53T mutant protein was purified. (2) The Fe 2+ concentration in α-syn group was significantly higher than that in control group, and the Fe 2+ concentration in α-syn+DFO group was significantly lower than that in α-syn group ( P<0.05); the Rab35 protein and TGF-β mRNA expressions in control group, α-syn group and α-syn+DFO group were decreased successively, while the IL-6 and TNF-α mRNA expressions were increased successively, with significant differences ( P<0.05); ROS level and SH-SY5Y cell apoptosis rate in control group, α-syn group, α-syn+DFO group were increased successively. (3) Bidirectional DNA sequencing showed that the LRRK2G2019S mutation in microglia was the most obvious after α-syn A53T mutant protein stimulation; compared with the control group, the α-syn group had significantly increased LRRK2 protein expression, while the α-syn+GSK3357679A group had significantly decreased LRRK2 protein expression compared with α-syn group ( P<0.05); compared with the control group, the α-syn group had significantly decreased Rab35 protein and TGF-β mRNA expressions, and statistically increased IL-6 and TNF-α mRNA expressions ( P<0.05); compared with α-syn group, the α-syn+GSK3357679A group had significantly increased Rab35 protein and TGF-β mRNA expressions, and statistically decreased IL-6 and TNF-α mRNA expressions ( P<0.05); compared with α-syn+GSK3357679A group, α-syn+GSK3357679A+DFO group had significantly increased IL-6 and TNF-α mRNA expressions, and significantly decreased Rab35 protein and TGF-β mRNA expressions ( P<0.05). The α-syn group had higher ROS level than the control group, the α-syn+GSK3357679A group had lower ROS level than the α-syn group, and the α-syn+GSK3357679A+DFO group had higher ROS level than the α-syn+GSK3357679A group. (4) Compared with the control group, the α-syn group had significantly decreased Rab35 and LC3II protein, and TGF-β mRNA expressions, and significantly increased P62 protein, IL-6 and TNF-α mRNA expressions ( P<0.05); compared with α-syn group, the α-syn+RAPA group had significantly increased Rab35 and LC3II protein, and TGF-β mRNA expressions, and significantly decreased P62 protein, and IL-6 and TNF-α mRNA expressions ( P<0.05); the α-syn group had higher ROS level than the control group and α-syn+RAPA group. (5) Compared with the control group, the α-syn group had significantly decreased Rab35 and LC3II protein, and TGF-β mRNA expressions, and statistically increased P62 protein, and IL-6 and TNF-α mRNA expressions ( P<0.05); compared with the α-syn group, the α-syn+Rab35 group had significantly increased Rab35 and LC3II protein, and TGF-β mRNA expressions, and significantly decreased P62 protein, and IL-6 and TNF-α mRNA expressions ( P<0.05). The α-syn group had higher ROS level than the control group and α-syn+Rab35 group. Conclusion:LRRK2G2019S can induce neuroinflammation by inhibiting Rab35-related autophagy under iron deprivation, and Rab35 is expected to be a key factor in intervening neuroinflammation.
ABSTRACT
BACKGROUND AND PURPOSE: It is essential to develop a reliable predictive serum biomarker for Parkinson's disease (PD). The accumulation of alpha-synuclein (αSyn) and up-regulated expression of Rab35 participate in the etiology of PD. The purpose of this investigation was to determine whether the combined assessment of serum αSyn and Rab35 is a useful predictive biomarker for PD. METHODS: Serum levels of αSyn or Rab35 were determined in serum samples from 59 sporadic PD patients, 19 progressive supranuclear palsy (PSP) patients, 20 multiple system atrophy (MSA) patients, and 60 normal controls (NC). Receiver operating characteristics (ROC) curves were calculated to determine the diagnostic accuracy of αSyn or/and Rab35 in discriminating PD patients from NC or atypical parkinsonian patients. RESULTS: The levels of αSyn and Rab35 were increased in PD patients. The serum level of Rab35 was positively correlated with that of αSyn in PD patients. Compared to analyzing αSyn or Rab35 alone, the combined analysis of αSyn and Rab35 produced a larger area under the ROC curve and performed better in discriminating PD patients from NC, MSA patients, or PSP patients. When age was dichotomized at 55, 60, 65, or 70 years, the combined assessment of αSyn and Rab35 for classifying PD was better in the group below the cutoff age than in the group above the cutoff age. CONCLUSIONS: Combined assessment of serum αSyn and Rab35 is a better biomarker for discriminating PD patients from NC or atypical parkinsonian patients, and is a useful predictive biomarker for younger sporadic PD patients.