Dynamic changes of locus coeruleus damage in Parkinson's disease-like mice induced by paraquat / 中华劳动卫生职业病杂志

Objective: To observe the dynamic changes of brainstem locus coeruleus (LC) damage in Parkinson' s disease (PD) -like mice by paraquat (PQ) . Methods: In October 2019, 36 male C57BL/6 mice were randomly divided into the exposure group and the control group, with 18 mice in each group. The mice in the exposure group were given intraperitoneal injection of 15 mg/kg PQ, and the mice in the control group were given intraperitoneal injection of 0.9% saline, twice a week for 8 weeks. Neurobehavioral changes (pole climbing test, swimming test, open field test, tail hanging test, high plus maze test and water maze test) were observed at 4 weeks, 6 weeks and 8 weeks, respectively, and the changes of motor ability, emotion and cognitive function were evaluated. The brain tissue of mice were taken and stained with Hematoxylin-Eosin (HE) to observe the pathological changes of LC. Nissl staining was used to detect the changes of neuronal Nissl bodies in LC. Immunohistochemistry (IHC) staining was used to detect the expression of neuron nuclear antigen (NeuN) , dopamine (DA) neurons and norepinephrine (NE) neuron markers tyrosine hydroxylase (TH) , α-synuclein (α-syn) in substantia nigra (SN) and LC. The expression levels of NeuN, TH and α-syn in the midbrain and brainstem were detected by Western blotting. TUNEL staining was used to detect neuronal apoptosis in LC. Results: Compared with the 4th week of PQ exposure group, the time of pole climbing and swimming immobility were gradually increased, the ratio of open arm residence time of high plus maze test and the number of times of the platform and the residence time of platform quadrant in water maze test were gradually decreased (P<0.05) in the exposure group with the progress of exposure time. The results of HE and Nissl staining showed that the neurons in LC gradually arranged loosely, the nucleus were deeply stained, the cytoplasm was pyknosis, and the number of Nissl bodies gradually decreased (P<0.05) in the exposure group with the progress of exposure time. IHC results showed that the number of NeuN and TH positive cells in SN and LC of mice were gradually decreased, and the positive expression of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. Western blotting results showed that the expression levels of NeuN and TH in the midbrain and brainstem were gradually decreased, and the expression level of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. TUNEL staining showed that the apoptosis rates of neurons in LC were gradually increased (P<0.05) in the exposure group with the progress of exposure time. Conclusion: PQ induces progressive damage in the LC area of PD-like mice, which may be caused by the abnormal accumulation of pathological α-syn in the LC area.

Preliminary study on time-dependent changes of intestinal tract and brain-gut axis in mice model of Parkinson's disease induced by paraquat / 中华劳动卫生职业病杂志

Objective: To observe the intestinal time-dependent changes in Parkinson's disease (PD) mouse model constructed by intraperitoneal injection of paraquat (PQ) and to establish the brain-gut axis connection initially. Methods: In October 2019, 48 mice were randomly divided into treated group and control groups: treated 4-week (P-4) group, treated 6-week (P-6) group, treated 8-week (P-8) group, control 4-week (C-4) group, control 6-week (C-6) group, and control 8-week (C-8) group. The treated group was injected with 15 mg/kg PQ solution and the control group was injected with 0.9% saline (0.2 ml/20 g) by intraperitoneal injection twice a week. After the initial state (0 weeks) and the treatment at the end of 4, 6 and 8 weeks, the mood changes and motor functions of mice were assessed by neurobehavioral tests (open field test, pole climbing test, tail suspension test and elevated plus maze test) . And the number of fecal pellets for 1 h and water content were calculated to assess the functional status of the gastrointestinal tract. Western blotting experiments were performed to detect the expression levels of α-synuclein (α-syn) and tyrosine hydroxylase (TH) in the nigrostriatal region of the mouse brain, the tight junction markers zonula occludens-1 (ZO-1) and Occludin, the inflammatory markers of integrin αM subunit (CD11b) , inducible nitric oxide synthase (iNOS) , high mobility group box 1 (HMGB1) , interleukin-1β (IL-1β) , and the neuronal markers βⅢ-tubulin and α-syn protein in the colon.Immunohistochemical staining was performed to detect the expression levels of colonic tight junction proteins ZO-1 and Occludin. Immunofluorescence staining was performed to detect the expression levels of TH in the substantia nigra region of the midbrain, and the co-localization of colonic intestine neuronal marker (βⅢ-tubulin) and Ser129 α-syn in the colonic. Results: Compared with the initial state (0 weeks) and C-8 group, mice in the P-8 group had significantly higher pole climbing test scores and resting time, and significantly lower total active distance, mean active speed, percentage of open arm entry and 1 h fecal instances (P<0.05) . After poisoning, the 1 h fecal water content of model mice first increased and then decreased, the P-4 and P-6 groups were significantly higher than the simultaneous point control group, and the P-8 groups were significantly lower than the initial state (P<0.05) . Compared with control, P-4 and P-6 groups, the expression levels of ZO-1 and Occludin in the P-8 group were significantly decreased (P<0.05) . Compared with control group, the expression levels of CD11b and IL-1β in the P-4 group were significantly increased (P<0.05) . Compared with control and P-4 group, the expression levels of CD11b, iNOS, HMGB1 and IL-1β in the P-6 and P-8 groups were significantly increased (P<0.05) . Compared with the control and P-4 groups, the expression levels of βⅢ-tubulin in the colon of mice in the P-8 group were significantly decreased, and the expression levels of α-syn and Ser129 α-syn were significantly increased (P<0.05) . The expression level of Ser129 α-syn in the colon of model mice was negatively correlated with the expression level of βⅢ-tubulin (r(s)=-0.9149, 95%CI: -0.9771--0.7085, P<0.001) . Ser129 α-syn and βⅢ-tubulin co-localization in the colonic intermuscular plexus region increased gradually with the time of exposure. Compared with the control, P-4 and P-6 groups, the expression level of TH in the nigrostriatal region of the brain was significantly decreased, and the expression levels of α-syn and Ser129 α-syn were significantly increased in the P-8 group (P<0.05) . Correlation analysis showed that the relative expression level of Ser129 α-syn in the nigrostriatal region of the brain was negatively correlated with the expression level of TH in the model mice (r(s)=-0.9716, 95% CI: -0.9925--0.8953, P<0.001) . Conclusion: The PD mouse model is successfully established by PQ, and the intestinal function of the model mice is reduced in a time-dependent manner. And on this basis, it is preliminary determined that the abnormal aggregation of α-syn may be an important substance connecting the brain-gut axis.