Will Sirtuins Be Promising Therapeutic Targets for TBI and Associated Neurodegenerative Diseases?

Serum exosomes miR-206 and miR-549a-3p as potential biomarkers of traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of death and disability worldwide. However, effective diagnostic, therapeutic and prognostic biomarkers are still lacking. Our research group previously revealed through high-throughput sequencing that the serum exosomes miR-133a-3p, miR-206, and miR-549a-3p differ significantly in severe TBI (sTBI), mild or moderate TBI (mTBI), and control groups. However, convincing experimental evidence is lacking. To solve this problem, we used qPCR in this study to further verify the expression levels of serum exosomes miR-133a-3p, miR-206 and miR-549a-3p in TBI patients. The results showed that the serum exosomes miR-206 and miR-549a-3p showed good predictive value as biomarkers of TBI. In addition, in order to further verify whether serum exosomes miR-206 and miR-549a-3p can be used as potential biomarkers in patients with TBI and to understand the mechanism of their possible effects, we further determined the contents of SOD, BDNF, VEGF, VEGI, NSE and S100β in the serum of TBI patients. The results showed that, serum exosomes miR-206 and miR-549a-3p showed good correlation with BDNF, NSE and S100β. In conclusion, serum exosomes miR-206 and miR-549a-3p have the potential to serve as potential biomarkers in patients with TBI.

Caffeine improves mitochondrial dysfunction in the white matter of neonatal rats with hypoxia-ischemia through deacetylation: a proteomic analysis of lysine acetylation

Aims

White matter damage (WMD) is linked to both cerebral palsy and cognitive deficits in infants born prematurely. The focus of this study was to examine how caffeine influences the acetylation of proteins within the neonatal white matter and to evaluate its effectiveness in treating white matter damage caused by hypoxia-ischemia.

Main methods

We employed a method combining affinity enrichment with advanced liquid chromatography and mass spectrometry to profile acetylation in proteins from the white matter of neonatal rats grouped into control (Sham), hypoxic-ischemic (HI), and caffeine-treated (Caffeine) groups.

Key findings

Our findings included 1,999 sites of lysine acetylation across 1,123 proteins, with quantifiable changes noted in 1,342 sites within 689 proteins. Analysis of these patterns identified recurring sequences adjacent to the acetylation sites, notably YKacN, FkacN, and G * * * GkacS. Investigation into the biological roles of these proteins through Gene Ontology analysis indicated their involvement in a variety of cellular processes, predominantly within mitochondrial locations. Further analysis indicated that the acetylation of tau (Mapt), a protein associated with microtubules, was elevated in the HI condition; however, caffeine treatment appeared to mitigate this over-modification, thus potentially aiding in reducing oxidative stress, inflammation in the nervous system, and improving mitochondrial health. Caffeine inhibited acetylated Mapt through sirtuin 2 (SITR2), promoted Mapt nuclear translocation, and improved mitochondrial dysfunction, which was subsequently weakened by the SIRT2 inhibitor, AK-7.

Significance

Caffeine-induced changes in lysine acetylation may play a key role in improving mitochondrial dysfunction and inhibiting oxidative stress and neuroinflammation.

Dehydroevodiamine ameliorates neurological dysfunction after traumatic brain injury in mice via regulating the SIRT1/FOXO3a/Bim pathway

BACKGROUND

Traumatic Brain Injury (TBI) poses a considerable public health challenge, resulting in mortality, disability, and economic strain. Dehydroevodiamine (DEDM) is a natural compound derived from a traditional Chinese herbal medicine. Prior studies have substantiated the neuroprotective attributes of this compound in the context of TBI. Nevertheless, a comprehensive comprehension of the exact mechanisms responsible for its neuroprotective effects remains elusive. It is imperative to elucidate the precise intrinsic mechanisms underlying the neuroprotective actions of DEDM.

PURPOSE

The aim of this investigation was to elucidate the mechanism underlying DEDM treatment in TBI utilizing both in vivo and in vitro models. Specifically, our focus was on comprehending the impact of DEDM on the Sirtuin1 (SIRT1) / Forkhead box O3 (FOXO3a) / Bcl-2-like protein 11 (Bim) pathway, a pivotal player in TBI-induced cell death attributed to oxidative stress.

STUDY DESIGN AND METHODS

We established a TBI mouse model via the weight drop method. Following continuous intraperitoneal administration, we assessed the neurological dysfunction using the Modified Neurological Severity Score (mNSS) and behavioral assay, followed by sample collection. Secondary brain damage in mice was evaluated through Nissl staining, brain water content measurement, Evans blue detection, and Western blot assays. We scrutinized the expression levels of oxidative stress-related indicators and key proteins for apoptosis. The intricate mechanism of DEDM in TBI was further explored through immunofluorescence, Co-immunoprecipitation (Co-IP) assays, real-time quantitative PCR (RT-qPCR), dual-luciferase assays and western blotting. Additionally, we further investigated the specific therapeutic mechanism of DEDM in an oxidative stress cell model.

RESULTS

The results indicated that DEDM effectively ameliorated oxidative stress and apoptosis post-TBI, mitigating neurological dysfunction and brain injury in mice. DEDM facilitated the deacetylation of FOXO3a by up-regulating the expression of the deacetylase SIRT1, consequently suppressing Bim expression. This mechanism contributed to the alleviation of neurological injury and symptom improvement in TBI-afflicted mice. Remarkably, SIRT1 emerged as a central mediator in the overall treatment mechanism.

CONCLUSIONS

DEDM exerted significant neuroprotective effects on TBI mice by modulating the SIRT1/FOXO3a/Bim pathway. Our innovative research provides a basis for further exploration of the clinical therapeutic potential of DEDM in the context of TBI.

Roles of Histone Acetyltransferases and Deacetylases in the Retinal Development and Diseases

The critical role of epigenetic modification of histones in maintaining the normal function of the nervous system has attracted increasing attention. Among these modifications, the level of histone acetylation, modulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), is essential in regulating gene expression. In recent years, the research progress on the function of HDACs in retinal development and disease has advanced remarkably, while that regarding HATs remains to be investigated. Here, we overview the roles of HATs and HDACs in regulating the development of diverse retinal cells, including retinal progenitor cells, photoreceptor cells, bipolar cells, ganglion cells, and Müller glial cells. The effects of HATs and HDACs on the progression of various retinal diseases are also discussed with the highlight of the proof-of-concept research regarding the application of available HDAC inhibitors in treating retinal diseases.

Dietary energy restriction in neurological diseases: what's new?

Energy-restricted diet is a specific dietary regimen, including the continuous energy-restricted diet and the intermittent energy-restricted diet. It has been proven effective not only to reduce weight and extend the lifespan in animal models, but also to regulate the development and progression of various neurological diseases such as epilepsy, cerebrovascular diseases (stroke), neurodegenerative disorders (Alzheimer's disease and Parkinson's disease) and autoimmune diseases (multiple sclerosis). However, the mechanism in this field is still not clear and a systematic neurological summary is still missing. In this review, we first give a brief summary of the definition and mainstream strategies of energy restrictions. We then review evidence about the effects of energy-restricted diet from both animal models and human trials, and update the current understanding of mechanisms underlying the biological role of energy-restricted diet in the fight against neurological diseases. Our review thus contributes to the modification of dietary regimen and the search for special diet mimics.

Adiponectin/AdiopR1 signaling prevents mitochondrial dysfunction and oxidative injury after traumatic brain injury in a SIRT3 dependent manner

Mitochondrial dysfunction and oxidative injury, which contribute to worsening of neurological deficits and poor clinical outcomes, are hallmarks of secondary brain injury after TBI. Adiponectin (APN), beyond its well-established regulatory effects on metabolism, is also essential for maintaining normal brain functions by binding APN receptors that are ubiquitously expressed in the brain. Currently, the significance of the APN/APN receptor (AdipoR) signaling pathway in secondary injury after TBI and the specific mechanisms have not been conclusively determined. In this study, we found that APN knockout aggravated brain functional deficits, increased brain edema and lesion volume, and exacerbated oxidative stress as well as apoptosis after TBI. These effects were significantly alleviated after APN receptor agonist (AdipoRon) treatment. Moreover, we found that AdipoR1, rather than AdipoR2, mediated the protective effects of APN/AdipoR signaling against oxidative stress and brain injury after TBI. In neuron-specific AdipoR1 knockout mice, mitochondrial damage was more severe after TBI, indicating a potential association between APN/AdipoR1 signaling inactivation and mitochondrial damage. Mechanistically, neuron-specific knockout of SIRT3, the most important deacetylase in the mitochondria, reversed the neuroprotective effects of AdipoRon after TBI. Then, PRDX3, a critical antioxidant enzyme in the mitochondria, was identified as a vital downstream target of the APN/SIRT3 axis to alleviate oxidative injury after TBI. Finally, we revealed that APN/AdipoR1 signaling promotes SIRT3 transcription by activating the AMPK-PGC pathway. In conclusion, APN/AdipoR1 signaling plays a protective role in post-TBI oxidative damage by restoring the SIRT3-mediated mitochondrial homeostasis and antioxidant system.

Will Sirtuin 2 Be a Promising Target for Neuroinflammatory Disorders?

Neuroinflammatory disorder is a general term that is associated with the progressive loss of neuronal structure or function. At present, the widely studied diseases with neuroinflammatory components are mainly divided into neurodegenerative and neuropsychiatric diseases, namely, Alzheimer’s disease, Parkinson’s disease, depression, stroke, and so on. An appropriate neuroinflammatory response can promote brain homeostasis, while excessive neuroinflammation can inhibit neuronal regeneration and damage the central nervous system. Apart from the symptomatic treatment with cholinesterase inhibitors, antidepressants/anxiolytics, and neuroprotective drugs, the treatment of neuroinflammation is a promising therapeutic method. Sirtuins are a host of class III histone deacetylases, that require nicotinamide adenine dinucleotide for their lysine residue deacetylase activity. The role of sirtuin 2 (SIRT2), one of the sirtuins, in modulating senescence, myelin formation, autophagy, and inflammation has been widely studied. SIRT2 is associated with many neuroinflammatory disorders considering it has deacetylation properties, that regulate the entire immune homeostasis. The aim of this review was to summarize the latest progress in regulating the effects of SIRT2 on immune homeostasis in neuroinflammatory disorders. The overall structure and catalytic properties of SIRT2, the selective inhibitors of SIRT2, the relationship between immune homeostasis and SIRT2, and the multitasking role of SIRT2 in several diseases with neuroinflammatory components were discussed.

SIRT4 Is Highly Expressed in Retinal Müller Glial Cells

Sirtuin 4 (SIRT4) is one of seven mammalian sirtuins that possesses ADP-ribosyltransferase, lipoamidase and deacylase activities and plays indispensable role in metabolic regulation. However, the role of SIRT4 in the retina is not clearly understood. The purpose of this study was to explore the location and function of SIRT4 in the retina. Therefore, immunofluorescence was used to analyze the localization of SIRT4 in rat, mouse and human retinas. Western blotting was used to assess SIRT4 and glutamine synthetase (GS) protein expression at different developmental stages in C57BL/6 mice retinas. We further analyzed the retinal structure, electrophysiological function and the expression of GS protein in SIRT4-deficient mice. Excitotoxicity was caused by intravitreal injection of glutamate (50 nmol) in mice with long-term intraperitoneal injection of resveratrol (20 mg/Kg), and then retinas were subjected to Western blotting and paraffin section staining to analyze the effect of SIRT4 on excitotoxicity. We show that SIRT4 co-locates with Müller glial cell markers (GS and vimentin). The protein expression pattern of SIRT4 was similar to that of GS, and both increased with development. There were no significant retinal structure or electrophysiological function changes in 2-month SIRT4-deficient mice, while the expression of GS protein was decreased. Moreover, long-term administration of resveratrol can upregulate the expression of SIRT4 and GS while reducing the retinal injury caused by excessive glutamate. These results suggest that SIRT4 is highly expressed in retinal Müller glial cells and is relevant to the expression of GS. SIRT4 does not appear to be essential in retinal development, but resveratrol, as an activator of SIRT4, can upregulate GS protein expression and protect the retina from excitotoxicity.

Gongjin-Dan Enhances Neurite Outgrowth of Cortical Neuron by Ameliorating H2O2-Induced Oxidative Damage via Sirtuin1 Signaling Pathway

Gongjin-dan (GJD) is a multiherbal formula produced from 10 medicinal herbs and has been traditonally used as an oriental medicine to treat cardiovascular diseases, alcoholic hepatitis, mild dementia, and anemia. Additionally, increasing evidence suggests that GJD exerts neuroprotective effects by suppressing inflammation and oxidative stress-induced events to prevent neurological diseases. However, the mechanism by which GJD prevents oxidative stress-induced neuronal injury in a mature neuron remains unknown. Here, we examined the preventive effect and mechanism of GJD on primary cortical neurons exposed to hydrogen peroxide (H2O2). In the neuroprotection signaling pathway, Sirtuin1 is involved in neuroprotective action as a therapeutic target for neurological diseases. After pre-treatment with GJD at three concentrations (10, 25, and 50 µg/mL) and stimulation by H2O2 (30 µM) for 24 h, the influence of GJD on Sirtuin1 activation was assessed using immunocytochemistry, real-time PCR, western blotting, and flow cytometry. GJD effectively ameliorated H2O2-induced neuronal death against oxidative damage through Sirtuin1 activation. In addition, GJD-induced Sirtuin1 activation accelerated elongation of new axons and formation of synapses via increased expression of nerve growth factor and brain-derived neurotrophic factor, as well as regeneration-related genes. Thus, GJD shows potential for preventing neurological diseases via Sirtuin1 activation.

Regulation of Hypoxic Signaling and Oxidative Stress via the MicroRNA-SIRT2 Axis and Its Relationship with Aging-Related Diseases

The sirtuin family of nicotinamide adenine dinucleotide-dependent deacetylase and ADP-ribosyl transferases plays key roles in aging, metabolism, stress response, and aging-related diseases. SIRT2 is a unique sirtuin that is expressed in the cytosol and is abundant in neuronal cells. Various microRNAs were recently reported to regulate SIRT2 expression via its 3'-untranslated region (UTR), and single nucleotide polymorphisms in the miRNA-binding sites of SIRT2 3'-UTR were identified in patients with neurodegenerative diseases. The present review highlights recent studies into SIRT2-mediated regulation of the stress response, posttranscriptional regulation of SIRT2 by microRNAs, and the implications of the SIRT2-miRNA axis in aging-related diseases.

PPARα and PPARγ Signaling Is Enhanced in the Brain of the Naked Mole-Rat, a Mammal that Shows Intrinsic Neuroprotection from Oxygen Deprivation

Naked mole-rats (NMRs) are a long-lived animal that do not develop age-related diseases including neurodegeneration and cancer. Additionally, NMRs have a profound ability to consume reactive oxygen species (ROS) and survive long periods of oxygen deprivation. Here, we evaluated the unique proteome across selected brain regions of NMRs at different ages. Compared to mice, we observed numerous differentially expressed proteins related to altered mitochondrial function in all brain regions, suggesting that the mitochondria in NMRs may have adapted to compensate for energy demands associated with living in a harsh, underground environment. Keeping in mind that ROS can induce polyunsaturated fatty acid peroxidation under periods of neuronal stress, we investigated docosahexaenoic acid (DHA) and arachidonic acid (AA) peroxidation under oxygen-deprived conditions and observed that NMRs undergo DHA and AA peroxidation to a far less extent compared to mice. Further, our proteomic analysis also suggested enhanced peroxisome proliferator-activated receptor (PPAR)-retinoid X receptor (RXR) activation in NMRs via the PPARα-RXR and PPARγ-RXR complexes. Correspondingly, we present several lines of evidence supporting PPAR activation, including increased eicosapetenoic and omega-3 docosapentaenoic acid, as well as an upregulation of fatty acid-binding protein 3 and 4, known transporters of omega-3 fatty acids and PPAR activators. These results suggest enhanced PPARα and PPARγ signaling as a potential, innate neuroprotective mechanism in NMRs.

The protective mechanism of SIRT1 on cartilage through regulation of LEF-1

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative disease that suppresses middle-aged and older people worldwide. Silent information regulator 1(SIRT-1) is associated with several age-related diseases, such as cardiovascular diseases, neurodegenerative diseases and tumors, etc. The protective role of SIRT-1 in bone and joint diseases has become increasingly well known.

OBJECTIVE

To explore the relationship between SIRT-1 and its related factors in OA.

METHODS

Fresh tibial plateau specimens were collected from 30 patients with knee OA who underwent total knee arthroplasty. According to the results of Safranin O Fast Green Staining, hematoxylin-eosin staining and the OARSI grade developed by the International Association for the Study of Osteoarthropathy, the specimens were divided into the mild group, moderate group and severe group, and the damage of cartilage was evaluated. SIRT-1 protein levels in cartilage samples were analyzed by immunohistochemistry. Then, take 60 8-week-old female C57BL/6 J mice and apply the Destabilization of the medial meniscus (DMM) to induce OA. Mice were randomly divided into normal group (sham), model group (model), and post-modeling drug administration group (srt), and each group was further divided into 2 weeks after modeling (2 W) and 8 weeks after modeling (8 W) according to the time after surgery. The degenerative degree of a knee joint in mouse knee cartilage samples was evaluated using Safranin O Fast Green Staining and OARSI grade. Immunohistochemical techniques assessed the protein levels of SIRT-1, β-catenin, LEF-1, MMP-13 and Collagen II in cartilage samples. The protein levels of β-catenin, LEF-1 and MMP-13 in the samples were assessed by the immunohistofluorescence technique. The mRNA expression of SIRT-1 and LEF-1 in mouse cartilage samples was evaluated by real-time quantitative polymerase chain reaction (qPCR).

RESULTS

In the human cartilage samples, according to the results of Safranin O Fast Green Staining, compared with the mild group, the moderate group and the severe group showed damage cartilage layer structure, the number of chondrocytes decreased, the cell hypertrophic, the cartilage surface discontinuous, and the OARSI grade increased. The severe group had severe cartilage injury and the highest OARSI grade. In the mice cartilage samples, according to immunohistochemical analysis, the protein levels of β-catenin, LEF-1 and MMP-13 in cartilage specimens of model 2 W and model 8 W groups were significantly increased than the sham 2 W and sham 8 W groups. The protein levels of SIRT-1 and Collagen II were significantly decreased (P < 0.05), the results of srt 2 W and srt 8 W groups were between the sham group and the model group. According to immunofluorescence analysis, the protein levels of β-catenin, LEF-1 and MMP-13 in model 2 W and model 8 W groups were significantly increased than sham 2 W and sham 8 W groups. The results of srt 2w and srt 8w groups were between the sham group and the model group. According to the real-time qPCR results: Compared with sham 2 W and sham 8 W groups, the mRNA expression of SIRT-1 in model 2 W and model 8 W groups was significantly decreased, while the mRNA expression of LEF-1 was significantly increased. In contrast, the results of srt 2 W and srt 8 W groups were between the sham group and the model group.

CONCLUSION

SRT-1720, as a specific activator of SIRT-1, does increase the protein level of SIRT-1. SIRT-1 may play a protective role in cartilage by regulating the expression of LEF-1 and related inflammatory factors in OA.

Discoveries of the specific expression of lncRNAs and mRNAs in hippocampus of rats after traumatic brain injury

Objects

Explore the relationship between the neural function deficit and the changes of lncRNA and mRNA in hippocampus after traumatic brain injury (TBI) in rats.

Methods

Twenty male rats weighted 200-240 grams were randomly divided into sham group and TBI group. Neurologic severity score (NSS) was performed after operation, and the hippocampus of rats was collected for long non-coding RNAs (lncRNAs), mRNAs microarray detection, real-time quantitative PCR Detecting System (Q-PCR), western blot (WB) detection, and serum biochemical detection.

Results

The NSS score of the TBI group was significantly higher than the sham group. Compared with the sham group, 270 lncRNAs changed in the TBI group, of which 224 were up-regulated and 46 were down-regulated. Among up-regulated lncRNAs, mRNAs were distributed in upstream of 22 lncRNAs, downstream of 17 lncRNAs, overlapping regions of 48 lncRNAs, and antisense chains of 21 lncRNAs. Among down-regulated lncRNAs, mRNAs were distributed in upstream of 6 lncRNAs, downstream of 3 lncRNAs, overlapping regions of 10 lncRNAs, and antisense chains of 8 lncRNAs. Compared with the sham group, 1054 mRNA changed in the TBI group, of which 921 mRNA were up-regulated and 133 mRNA were down-regulated. The expression changes of ENSRNOT000063054, ENSRNOT000052790, ENSRNOT00000054410, ENSRNOT000063242, and ENSRNOT000069411 IncRNA regulate the expression of Top2a, RT1-CE11, Papss2, Stk32a, and Grid2 gene.

Conclusion

The present study detected the differential expression of lncRNAs and mRNAs in hippocampi of rats subjected to TBI, and discussed their relation, primarily.

Sirtuins, a potential target in Traumatic Brain Injury and relevant experimental models

Traumatic brain injury (TBI) can simply be defined as a violent external injury to the head causing brain dysfunction. The primary injury occurs immediately on impact whereas the secondary injury begins minutes to months after impact. TBI affects a vast majority of population worldwide yet, there isn't any therapeutic intervention available. Sirtuins (SIRTs) are important regulator proteins found in humans. In several neurodegenerative diseases, SIRTs have proven its neuroprotective actions. Owing to the pathophysiological similarities in these diseases and TBI, SIRTs may serve as a potential target for therapeutic intervention in TBI. This review aims to describe the relevance of SIRTs as a potential pharmacological target in TBI. Also, the experimental animal model of TBI explored to understand the role of SIRTs in TBI have been discussed.

Transcriptional profiling of microglia in the injured brain reveals distinct molecular features underlying neurodegeneration

Neurotrauma has been recognized as a risk factor for neurodegenerative diseases, and sex difference of the incidence and outcome of neurodegenerative diseases has long been recognized. Past studies suggest that microglia could play a versatile role in both health and disease. So far, the microglial mechanisms underlying neurodegeneration and potentially lead to sex-specific therapies are still very open. Here we applied whole transcriptome analysis of microglia acutely isolated at different timepoints after a cortical stab wound injury to gain insight into genes that might be dysregulated and transcriptionally different between males and females after cortical injury. We found that microglia displayed distinct temporal and sexual molecular signatures of transcriptome after cortical injury. Hypotheses and gene candidates that we presented in the present study could be worthy to be examined to explore the roles of microglia in neurotrauma and in sex-biased neurodegenerative diseases.