BAG3 promotes autophagy and suppresses NLRP3 inflammasome activation in Parkinson's disease.

Background: Neuroinflammation mediated by microglia plays a key role in the pathogenesis of Parkinson's disease (PD), and our previous studies showed this was significantly inhibited by enhanced autophagy. In the autophagy pathway, Bcl2-associated athanogene (BAG)3 is a prominent co-chaperone, and we have shown BAG3 can regulate autophagy to clear the PD pathogenic protein α-synuclein. However, the connection between BAG3 and microglia mediated neuroinflammation is not clear. Methods: In this study, we explored whether BAG3 regulated related neuroinflammation and its original mechanism in PD. An inflammatory model of PD was established by injecting adeno-associated virus (AAV)-BAG3 into the bilateral striatum of C57BL/6 male mice to induce overexpression of BAG3, followed by injection of lipopolysaccharide (LPS). The striatum was extracted at 3 days after injection of LPS for Western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR), and immunohistochemical staining was performed at 21 days after injection. At the same time, LPS was used to induce activation of BV2 cells to verify the effect of BAG3 in vitro. Results: Overexpression of BAG3 reduced LPS-induced pyroptosis by reducing activation of caspase-1, the NOD-like receptor family, and the pyrin domain-containing 3 (NLRP3) inflammasome, and by release of interleukin (IL)-1ß and tumor necrosis factor (TNF)-α. The LPS-induced inflammatory environment inhibits autophagy, and overexpression of BAG3 can restore autophagy, which may be the mechanism by which BAG3 reduces neuronal inflammation in PD. Conclusions: Our results demonstrate BAG3 promotes autophagy and suppresses NLRP3 inflammasome formation in PD.

Correlations between retinal nerve fiber layer thickness and cognitive progression in Parkinson's disease: A longitudinal study.

BACKGROUND: Retinal abnormalities measured by optical coherence tomography (OCT) have been detected in both Parkinson's disease (PD) and Alzheimer's disease (AD). Cognitive impairment is not only found in AD, but 75-90% of PD patients will also develop dementia in the late stage of disease. We assessed whether baseline retinal nerve fiber layer (RNFL) thickness predicted worsening of cognitive status over time and the correlation between RNFL thickness and the detailed impaired cognitive domains in PD. METHODS: RNFL thickness was measured using high-definition OCT in 78 non-dementia PD patients. Clinical and cognitive assessments were performed at baseline and at 3.61 ± 0.65 years follow-up. Linear mixed-effects models were used to examine associations between RNFL thickness and the changes in cognitive test scores, after adjusting for age, sex, disease duration and education. RESULTS: Analysis of outcomes according to baseline RNFL tertiles showed worse performance in global cognitive tests, delayed memory, and executive functions in patients with a thin RNFL. During follow-up, greater cognitive deterioration was found in thin RNFL tertile patients. Lower baseline average RNFL thickness was associated with greater annualized decline in Mini-Mental State Examination and Montreal Cognitive Assessment. CONCLUSION: The correlation between RNFL thickness and cognitive dysfunction suggests that OCT may be useful for predicting cognitive dysfunction in PD patients.

Fatigue correlates with sleep disturbances in Parkinson disease.

BACKGROUND: Many Parkinson disease (PD) patients complain about chronic fatigue and sleep disturbances during the night. The objective of this study is to determine the relationship between fatigue and sleep disturbances by using polysomnography (PSG) in PD patients. METHODS: Two hundred and thirty-two PD patients (152 with mild fatigue and 80 with severe fatigue) were recruited in this study. Demographic information and clinical symptoms were collected. Fatigue severity scale (FSS) was applied to evaluate the severity of fatigue, and PSG was conducted in all PD patients. FSS ≥4 was defined as severe fatigue, and FSS <4 was defined as mild fatigue. Multivariate logistic regression and linear regression models were used to investigate the associations between fatigue and sleep disturbances. RESULTS: Patients with severe fatigue tended to have a longer duration of disease, higher Unified Parkinson Disease Rating Scale score, more advanced Hoehn and Yahr stage, higher daily levodopa equivalent dose, worse depression, anxiety, and higher daytime sleepiness score. In addition, they had lower percentage of rapid eye movement (REM) sleep (P = 0.009) and were more likely to have REM sleep behavior disorder (RBD) (P = 0.018). Multivariate logistic regression analyses found that the presence of RBD and proportion of REM sleep were the independent predictors for fatigue. After the adjustment of age, sex, duration, body mass index, severity of disease, scores of Hamilton Rating Scale for Depression, Hamilton Anxiety Rating Scale, and other sleep disorders, proportion of REM sleep and degree of REM sleep without atonia in patients with PD were still associated with FSS score. CONCLUSION: Considering the association between fatigue, RBD, and the altered sleep architecture, fatigue is a special subtype in PD and more studies should be focused on this debilitating symptom.

Effect of Rapid Eye Movement Sleep Behavior Disorder on Obstructive Sleep Apnea Severity and Cognition of Parkinson's Disease Patients.

BACKGROUND: Rapid eye movement (REM) sleep behavior disorder (RBD) and obstructive sleep apnea (OSA) are the most common sleep disorders in Parkinson's disease (PD). The aim of this study was to identify whether RBD could alleviate OSA severity in PD patients and its effect on cognitive impairment. METHODS: From February 2014 to May 2017, we recruited 174 PD patients from the Second Affiliated Hospital of Soochow University, all of whom underwent polysomnography (PSG). We collected clinical data, PSG results, and compared information between patients with and without RBD or OSA by analysis of covariance. We also investigated the effect of these sleep disorders on cognitive impairment using linear regression. RESULTS: We grouped participants as follows: PD only (n = 53), PD + OSA (n = 29), PD + RBD (n = 61), and PD + RBD + OSA (n = 31). Minimum oxygen saturation (SaO2) during whole sleep and in REM sleep was higher in PD + RBD + OSA patients than that in PD + OSA patients. PD + RBD patients had worse Mini-Mental Status Examination and Montreal Cognitive Assessment (MoCA) scores than those in the PD group (P < 0.001), especially in visuospatial/executive, attention, and memory functions. The PD + OSA group performed worse than the PD group in the delayed recall domain. After adjusting for age, sex, body mass index, education, disease severity, and other sleep disorders, MoCA was negatively associated with OSA (ß = -0.736, P = 0.043) and RBD (ß = -2.575,P < 0.001). The severity of RBD (tonic/phasic electromyography activity) and OSA (apnea-hypopnea index/oxygen desaturation index/minimum SaO2) were also associated with MoCA. The adjusted ß values of RBD-related parameters were higher than that for OSA. CONCLUSIONS: We found that RBD alleviated OSA severity; however, RBD and OSA together exacerbated PD cognitive impairment. Further studies are needed to evaluate whether OSA treatment can improve cognition in PD.

A role of BAG3 in regulating SNCA/α-synuclein clearance via selective macroautophagy.

Many studies reveal that BAG3 plays a critical role in the regulation of protein degradation via macroautophagy. However, it remains unknown whether BAG3 affects the quality control of α-synuclein (SNCA), a Parkinson's disease-related protein. In this study, we demonstrated the increases of BAG3 expression in the ventral midbrain of SNCAA53T transgenic mice and also in MG132-treated PC12 cells overexpressing wild-type SNCA (SNCAWT-PC12). Moreover, we showed that BAG3 overexpression was sufficient to enhance the autophagy activity while knockdown of Bag3 reduced it in SNCAWT-PC12 cells. Immunoprecipitation revealed that BAG3 interacted with heat shock protein 70 and sequestosome 1. The immunostaining also showed the perinuclear accumulation and colocalization of BAG3 with these 2 proteins, as well as with LC3 dots in tyrosine hydroxylase-positive neurons in the midbrain of SNCAA53T mice. BAG3 overexpression was able to modulate SNCA degradation via macroautophagy which was prevented by Atg5 knockdown. Taken together, these results indicate that BAG3 plays a relevant role in regulating SNCA clearance via macroautophagy, and the heat shock protein 70-BAG3-sequestosome 1 complex may be involved in this process.

A pivotal role of FOS-mediated BECN1/Beclin 1 upregulation in dopamine D2 and D3 receptor agonist-induced autophagy activation.

Autophagy dysfunction is implicated in the pathogenesis of Parkinson disease (PD). BECN1/Beclin 1 acts as a critical regulator of autophagy and other cellular processes; yet, little is known about the function and regulation of BECN1 in PD. In this study, we report that dopamine D2 and D3 receptor (DRD2 and DRD3) activation by pramipexole and quinpirole could enhance BECN1 transcription and promote autophagy activation in several cell lines, including PC12, MES23.5 and differentiated SH-SY5Y cells, and also in tyrosine hydroxylase positive primary midbrain neurons. Moreover, we identified a novel FOS (FBJ murine osteosarcoma viral oncogene homolog) binding sequence (5'-TGCCTCA-3') in the rat and human Becn1/BECN1 promoter and uncovered an essential role of FOS binding in the enhancement of Becn1 transcription in PC12 cells in response to the dopamine agonist(s). In addition, we demonstrated a critical role of intracellular Ca2+ elevation, followed by the enhanced phosphorylation of CAMK4 (calcium/calmodulin-dependent protein kinase IV) and CREB (cAMP responsive element binding protein) in the increases of FOS expression and autophagy activity. More importantly, pramipexole treatment ameliorated the SNCA/α-synuclein accumulation in rotenone-treated PC12 cells that overexpress wild-type or A53T mutant SNCA by promoting autophagy flux. This effect was also demonstrated in the substantia nigra and the striatum of SNCAA53T transgenic mice. The inhibition of SNCA accumulation by pramipexole was attenuated by cotreatment with the DRD2 and DRD3 antagonists and Becn1 siRNAs. Thus, our findings suggest that DRD2 and DRD3 agonist(s) may induce autophagy activation via a BECN1-dependent pathway and have the potential to reduce SNCA accumulation in PD.

TNF compromises lysosome acidification and reduces α-synuclein degradation via autophagy in dopaminergic cells.

Tumor necrosis factor-α (TNF) is increasingly implicated as a critical pro-inflammatory cytokine involved in chronic inflammation and neurodegeneration of Parkinson's disease (PD). However, the cellular and molecular events that lead to dopaminergic neuron degeneration are not fully understood. In this study, we demonstrated that microglia-released and recombinant TNF disrupted α-synuclein (α-SYN) degradation and caused its accumulation in PC12 cells and midbrain neurons. At subtoxic doses, recombinant TNF was found to increase the number of LC3 puncta dots and LC3II protein level, associated with the increases of P62 protein level. Inhibition of lysosomal degradation with Bafilomycin A1 pretreatment abrogated the TNF-induced elevation in LC3II protein level whereas autophagy inhibitor 3-methyladenine did not affect it. Moreover, TNF led to a marked increase in the number of yellow LC3 dots with a marginal elevation in red-only dots in RFP-GFP-tandem fluorescent LC3 (tf-LC3) transfected PC12 cells, implying the impairment in autophagic flux. Furthermore, TNF treatment reduced lysosomal acidification, as LysoTracker Red fluorescence and LysoSensor fluorescence shift from blue to yellow was markedly decreased in TNF-treated PC12 cells. Co-treatment with mammalian target of rapamycin kinase complex 1 (mTORC1) inhibitor PP242, which activated transcription factor EB (TFEB) signaling and lysosome biogenesis, partially rescued the accumulation of α-SYN in PC12 cells and midbrain neurons. Taken together, our results demonstrated that at subtoxic levels, TNF was able to impair autophagic flux and result in α-SYN accumulation by compromising lysosomal acidification in dopaminergic cells. This may represent a novel mechanism for TNF-induced dopaminergic neuron degeneration in PD.