Brain-derived neurotrophic factor regulates LYN kinase-mediated myosin light chain kinase activation to modulate nonmuscle myosin II activity in hippocampal neurons.

Myosins belong to a large superfamily of actin-dependent molecular motors. Nonmuscle myosin II (NM II) is involved in the morphology and function of neurons, but little is known about how NM II activity is regulated. Brain-derived neurotrophic factor (BDNF) is a prevalent neurotrophic factor in the brain that encourages growth and differentiation of neurons and synapses. In this study, we report that BDNF upregulates the phosphorylation of myosin regulatory light chain (MLC2), to increases the activity of NM II. The role of BDNF on modulating the phosphorylation of MLC2 was validated by using Western blotting in primary cultured hippocampal neurons. This result was confirmed by injecting BDNF into the dorsal hippocampus of mice and detecting the phosphorylation level of MLC2 by Western blotting. We further perform coimmunoprecipitation assay to confirm that this process depends on the activation of the LYN kinase through binding with tyrosine kinase receptor B, the receptor of BDNF, in a kinase activity-dependent manner. LYN kinase subsequently phosphorylates MLCK, further promoting the phosphorylation of MLC2. Taken together, our results suggest a new molecular mechanism by which BDNF regulates MLC2 activity, which provides a new perspective for further understanding the functional regulation of NM II in the nervous system.

[Meta-analysis and GRADE evaluation of Shuxuetong Injection in treatment of stroke in progressive].

This study aims to systematically evaluate the efficacy and safety of Shuxuetong Injection in the treatment of stroke in progressive. Randomized controlled trials of Shuxuetong Injection in the treatment of stroke in progressive were searched from CNKI, Wanfang, VIP, CMB, PubMed and EMbase. After strict literature screening, data extraction and quality evaluation, a total of 22 articles were included for analysis by RevMan 5.3. The Meta-analysis showed that Shuxuetong Injection combined with conventional treatment was superior to the conventional treatment alone in the major outcome indicators including effective rate(RR=1.27, 95%CI[1.20, 1.33], Z=9.18, P<0.000 01), deterioration rate(RR=0.38, 95%CI[0.22, 0.68], Z=3.31, P=0.000 9), NIHSS scores(MD=-3.89, 95%CI[-4.34,-3.43], Z=16.83, P<0.000 01), CSS scores(MD=-5.59, 95%CI[-6.42,-4.76], Z=13.20, P<0.000 01) and activity of daily living scores(MD=12.02, 95%CI[10.31, 13.72], Z=13.83, P<0.000 01), mortality during treatment was not increased(RR=0.40, 95%CI[0.13, 1.26], Z=1.56, P=0.12). Moreover, Shuxuetong Injection combined with conventional treatment further reduced the secondary outcome indicators including fibrinogen(MD=-0.35, 95%CI[-0.58,-0.13], Z=3.09, P=0.002), triglyceride(MD=-0.38, 95%CI[-0.67,-0.10], Z=2.65, P=0.008), low density lipoprotein cholesterol(MD=-0.72, 95%CI[-0.83,-0.61], Z=12.64, P<0.000 01), serum hypersensitive C-reactive protein(MD=-4.41, 95%CI[-6.96,-1.86], Z=3.38, P=0.000 7), and interleukin-6(MD=-5.43, 95%CI[-6.91,-3.96], Z=7.22, P<0.000 01). GRADE evaluation results showed that the major outcome indicators had low quality of evidence. Shuxuetong Injection in the treatment of stroke in progressive can improve the clinical effective rate, reduce the deterioration rate, improve the neurological function and activity of daily living, down-regulate the levels of fibrinogen, triglyceride, low density lipoprotein cholesterol and alleviate the inflammatory response. Although most studies have reported no adverse reactions, there are selective reports. The safety of Shuxuetong Injection needs to be further verified by more high-quality randomized controlled trial.

[Meta-analysis of Tanreqing Injection in adjuvant treatment of stroke-associated pneumonia].

To systematically evaluate the efficiency and safety of Tanreqing Injection in the treatment of stroke-associated pneumonia(SAP). Seven domestic and foreign databases(CNKI, Wanfang, VIP, CBM, PubMed, Cochrane Library, EMbase) were retrieved from the establishment to July 2020. According to the inclusion and exclusion criteria, randomized controlled trial of the effect of Tanreqing Injection in the treatment of SAP was selected. NoteExpress software was used to screen out literatures. RevMan 5.4 software was used for data analysis. GRADE system was used to evaluate the evidence quality of the outcome indicators. A total of 1 755 cases in 21 studies were retrieved, including 879 cases in experimental group and 876 cases in control group. In general, the quality of stu-dies received was not high. According to Meta-analysis,(1) in terms of shortening the length of hospital stay, Tanreqing Injection combined with conventional western medicine was better than conventional western medicine(MD=-4.04, 95%CI[-4.43,-3.65], P<0.000 01);(2) in terms of increasing effective rate, Tanreqing Injection combined with conventional western medicine was better than conventional western medicine(RR=1.22, 95%CI[1.17, 1.27], P<0.000 01);(3) in terms of reducing inflammation indicators, Tanreqing Injection combined with conventional western medicine was better than conventional western medicine(MD_(CRP)=-10.75, 95%CI[-15.61,-5.88], P<0.000 01; MD_(WBC count)=-1.62, 95%CI[-2.55,-0.69], P=0.000 6; MD_(PCT)=-0.58, 95%CI[-0.89,-0.26], P=0.000 3];(4) in terms of improving symptoms and signs, Tanreqing Injection combined with conventional wes-tern medicine was better than conventional western medicine(MD_(cough)=-2.73, 95%CI[-4.93,-0.53], P=0.02; MD_(antipyretic)=-1.07, 95%CI[-1.17,-0.98), P<0.000 01];(5) in terms of decreasing the NIHSS scores, Tanreqing Injection combined with conventional western medicine was better than conventional western medicine(MD=-3.02, 95%CI[-4.91,-1.13], P=0.002);(6) in terms of adverse reactions, there was no statistically significant difference between Tanreqing Injection combined with conventio-nal western medicine compared with conventional western medicine treatment(RR=1.19, 95%CI[0.61,2.29], P=0.61). GRADE system showed that the evidence levels of above outcome indicators were low and extremely low. The results proved that Tanreqing Injection combined with conventional western medicine had a good advantage in the treatment of SAP, with better observation indicators better than western medicine conventional treatment, and no increase in the incidence of adverse reactions. However, this study had certain limitations. The overall quality of the included studies was low, which affected the reliability of the results. Therefore, the conclusions of this study shall be used cautiously.

miR-181a Participates in Contextual Fear Memory Formation Via Activating mTOR Signaling Pathway.

Long-term memory formation has been proven to require gene expression and new protein synthesis. MicroRNAs (miRNAs), as an endogenous small non-coding RNAs, inhibit the expression of their mRNA targets, through which involve in new memory formation. In this study, elevated miR-181a levels were found to be responsible for hippocampal contextual fear memory consolidation. Using a luciferase reporter assay, we indicated that miR-181a targets 2 upstream molecules of mTOR pathway, namely, PRKAA1 and REDD1. Upregulated miR-181a can downregulate the PRKAA1 and REDD1 protein levels and promote mTOR activity to facilitate hippocampal fear memory consolidation. These results indicate that miR-181a is involved in hippocampal contextual fear memory by activating the mTOR signaling pathway. This work provides a novel evidence for the role of miRNAs in memory formation and demonstrates the implication of mTOR signaling pathway in miRNA processing in the adult brain.

Ubiquitin C-Terminal Hydrolase L1 (UCH-L1) Promotes Hippocampus-Dependent Memory via Its Deubiquitinating Effect on TrkB.

Multiple studies have established that brain-derived neurotrophic factor (BDNF) plays a critical role in the regulation of synaptic plasticity via its receptor, TrkB. In addition to being phosphorylated, TrkB has also been demonstrated to be ubiquitinated. However, the mechanisms of TrkB ubiquitination and its biological functions remain poorly understood. In this study, we demonstrate that ubiquitin C-terminal hydrolase L1 (UCH-L1) promotes contextual fear conditioning learning and memory via the regulation of ubiquitination of TrkB. We provide evidence that UCH-L1 can deubiquitinate TrkB directly. K460 in the juxtamembane domain of TrkB is the primary ubiquitination site and is regulated by UCH-L1. By using a peptide that competitively inhibits the association between UCH-L1 and TrkB, we show that the blockade of UCH-L1-regulated TrkB deubiquitination leads to increased BDNF-induced TrkB internalization and consequently directs the internalized TrkB to the degradation pathway, resulting in increased degradation of surface TrkB and attenuation of TrkB activation and its downstream signaling pathways. Moreover, injection of the peptide into the DG region of mice impairs hippocampus-dependent memory. Together, our results suggest that the ubiquitination of TrkB is a mechanism that controls its downstream signaling pathways via the regulation of its endocytosis and postendocytic trafficking and that UCH-L1 mediates the deubiquitination of TrkB and could be a potential target for the modulation of hippocampus-dependent memory.SIGNIFICANCE STATEMENT Ubiquitin C-terminal hydrolase L1 (UCH-L1) has been demonstrated to play important roles in the regulation of synaptic plasticity and learning and memory. TrkB, the receptor for brain-derived neurotrophic factor, has also been shown to be a potent regulator of synaptic plasticity. In this study, we demonstrate that UCH-L1 functions as a deubiquitinase for TrkB. The blockage of UCH-L1-regulated deubiquitination of TrkB eventually results in the increased degradation of surface TrkB and decreased activation of TrkB and its downstream signaling pathways. In vivo, UCH-L1-regulated TrkB deubiquitination is necessary for hippocampus-dependent memory. Overall, our study provides novel insights into the mechanisms of UCH-L1-mediated neurobiological functions and suggests that ubiquitination is an important regulatory signal for TrkB functions.

HDAC7 Ubiquitination by the E3 Ligase CBX4 Is Involved in Contextual Fear Conditioning Memory Formation.

Histone acetylation, an epigenetic modification, plays an important role in long-term memory formation. Recently, histone deacetylase (HDAC) inhibitors were demonstrated to promote memory formation, which raises the intriguing possibility that they may be used to rescue memory deficits. However, additional research is necessary to clarify the roles of individual HDACs in memory. In this study, we demonstrated that HDAC7, within the dorsal hippocampus of C57BL6J mice, had a late and persistent decrease after contextual fear conditioning (CFC) training (4-24 h), which was involved in long-term CFC memory formation. We also showed that HDAC7 decreased via ubiquitin-dependent degradation. CBX4 was one of the HDAC7 E3 ligases involved in this process. Nur77, as one of the target genes of HDAC7, increased 6-24 h after CFC training and, accordingly, modulated the formation of CFC memory. Finally, HDAC7 was involved in the formation of other hippocampal-dependent memories, including the Morris water maze and object location test. The current findings facilitate an understanding of the molecular and cellular mechanisms of HDAC7 in the regulation of hippocampal-dependent memory.SIGNIFICANCE STATEMENT The current findings demonstrated the effects of histone deacetylase 7 (HDAC7) on hippocampal-dependent memories. Moreover, we determined the mechanism of decreased HDAC7 in contextual fear conditioning (CFC) through ubiquitin-dependent protein degradation. We also verified that CBX4 was one of the HDAC7 E3 ligases. Finally, we demonstrated that Nur77, as one of the important targets for HDAC7, was involved in CFC memory formation. All of these proteins, including HDAC7, CBX4, and Nur77, could be potential therapeutic targets for preventing memory deficits in aging and neurological diseases.