Antidepressant-Like Action of Single Facial Injection of Botulinum Neurotoxin A is Associated with Augmented 5-HT Levels and BDNF/ERK/CREB Pathways in Mouse Brain

The present study was designed to examine the therapeutic effects of Botulinum neurotoxin A(BoNT/A)on depression-like behaviors in mice and to explore the potential mechanisms.These results revealed that a single facial injection of BoNT/A induced a rapid and prolonged improvement of depression-like behaviors in naive and space-restriction-stressed(SRS)mice,reflected by a decreased duration of immobility in behavioral despair tests.BoNT/A significantly increased the 5-hydroxytryptamine(5-HT)levels in several brain regions,including the hippocampus and hypothalamus,in SRS mice.BoNT/A increased the expression of the N-methyl-Daspartate receptor subunits NR1 and NR2 B in the hippocampus,which were significantly decreased in SRS mice.Furthermore,BoNT/A significantly increased the expression of brain-derived neurotrophic factor(BDNF)in the hippocampus,hypothalamus,prefrontal cortex,and amygdala,which were decreased in SRS mice.Finally,BoNT/A transiently increased the levels of phosphorylated extracellular signal-regulated kinase(p-ERK)and cAMPresponse element binding protein(p-CREB),which were suppressed in the hippocampus of SRS mice.Collectively,these results demonstrated that BoNT/A treatment has antidepressant-like activity in mice,and this is associated with increased 5-HT levels and the activation of BDNF/ERK/CREB pathways in the hippocampus,supporting further investigation of BoNT/A therapy in depression.

Thioredoxin-Interacting Protein(TXNIP) Regulates Parkin/PINK1-mediated Mitophagy in Dopaminergic Neurons Under High-glucose Conditions: Implications for Molecular Links Between Parkinson’s Disease and Diabetes

Patients with diabetes mellitus have a higher risk of developing Parkinson’s disease(PD). However, the molecular links between PD and diabetes remain unclear.In this study, we investigated the roles of thioredoxininteracting protein(TXNIP) in Parkin/PINK1-mediated mitophagy in dopaminergic(DA) cells under high-glucose(HG) conditions. In streptozotocin-induced diabetic mice,TXNIP was upregulated and autophagy was inhibited in the midbrain, while the loss of DA neurons was accelerated by hyperglycemia. In cultured PC12 cells under HG, TXNIP expression was upregulated and the intracellular reactive oxygen species(ROS) levels increased, leading to cell death. Autophagic flux was further blocked and PINK1 expression was decreased under HG conditions. Parkin expression in the mitochondrial fraction and carbonyl cyanide 3-chlorophenylhydrazone(CCCP)-induced co-localization of COX IV(marker for mitochondria) and LAMP1(marker for lysosomes) were also significantly decreased by HG. Overexpression of TXNIP was sufficient to decrease the expression of both PINK1 and Parkin in PC12 cells, while knockdown of the expression of TXNIP by si RNA decreased intracellular ROS and attenuated cellular injury under HG. Moreover, inhibition of TXNIP improved the CCCP-induced co-localization of COX IV and LAMP1 in PC12 cells under HG. Together, these results suggest that TXNIP regulates Parkin/PINK1-mediated mitophagy under HG conditions, and targeting TXNIP may be a promising therapeutic strategy for reducing the risk of PD under hyperglycemic conditions.