Tetrahydrocurcumin provides neuroprotection in rats after traumatic brain injury: autophagy and the PI3K/AKT pathways as a potential mechanism

The role of tetrahydrocurcumin in disease prevention and treatment

In recent decades, natural compounds derived from herbal medicine or dietary sources have played important roles in prevention and treatment of various diseases and have attracted more and more attention. Curcumin, extracted from the Curcumae Longae Rhizoma and widely used as food spice and coloring agent, has been proven to possess high pharmacological value. However, the pharmacological application of curcumin is limited due to its poor systemic bioavailability. As a major active metabolite of curcumin, tetrahydrocurcumin (THC) has higher bioavailability and stability than curcumin. Increasing evidence confirmed that THC had a wide range of biological activities and significant treatment effects on diseases. In this paper, we reviewed the research progress on the biological activities and therapeutic potential of THC on different diseases such as neurological disorders, metabolic syndromes, cancers, and inflammatory diseases. The extensive pharmacological effects of THC involve the modulation of various signaling transduction pathways including MAPK, JAK/STAT, NF-κB, Nrf2, PI3K/Akt/mTOR, AMPK, Wnt/β-catenin. In addition, the pharmacokinetics, drug combination and toxicology of THC were discussed, thus providing scientific basis for the safe application of THC and the development of its dietary supplements and drugs.

Neuroinflammation Plays a Potential Role in the Medulla Oblongata After Moderate Traumatic Brain Injury in Mice as Revealed by Nontargeted Metabonomics Analysis

Moderate traumatic brain injury (mTBI) involves a series of complex pathophysiological processes in not only the area in direct contact with mechanical violence but also in other brain regions far from the injury site, which may be important factors influencing subsequent neurological dysfunction or death. The medulla oblongata (MO) is a key area for the maintenance of basic respiratory and circulatory functions, whereas the pathophysiological processes after mTBI have rarely drawn the attention of researchers. In this study, we established a closed-head cortical contusion injury model, identified 6 different time points that covered the acute, subacute, and chronic phases, and then used nontargeted metabolomics to identify and analyze the changes in differential metabolites (DMs) and metabolic pathways in the MO region. Our results showed that the metabolic profile of the MO region underwent specific changes over time: harmaline, riboflavin, and dephospho-coenzyme A were identified as the key DMs and play important roles in reducing inflammation, enhancing antioxidation, and maintaining homeostasis. Choline and glycerophospholipid metabolism was identified as the key pathway related to the changes in MO metabolism at different phases. In addition, we confirmed increases in the levels of inflammatory factors and the activation of astrocytes and microglia by Western blot and immunofluorescence staining, and these findings were consistent with the nontargeted metabolomic results. These findings suggest that neuroinflammation plays a central role in MO neuropathology after mTBI and provide new insights into the complex pathophysiologic mechanisms involved after mTBI.

Curcumin in the treatment of inflammation and oxidative stress responses in traumatic brain injury: a systematic review and meta-analysis

Background and aim

Traumatic brain injury (TBI), a leading cause of high morbidity and mortality, represents a significant global public health challenge. Currently, no effective treatment for TBI exists. Curcumin, an active compound extracted from the root of Curcuma longa, has demonstrated neuroprotective properties both in vitro and in vivo. Notably, it has shown potential in reducing oxidative stress and inflammation and enhancing redox balance. This paper conducts a systematic review and meta-analysis to explore curcumin's role in TBI animal models extensively. The findings offer valuable insights for future human clinical trials evaluating curcumin as a therapeutic supplement or nutraceutical in TBI management.

Methods

Comprehensive literature searches were conducted across MEDLINE, Embase, Cochrane, Web of Science, and Google Scholar databases. These searches aimed to identify relevant manuscripts in all languages, utilizing the keywords "curcumin" and "traumatic brain injury."

Results

The final quantitative analysis included 18 eligible articles corresponding to animal studies. The analysis revealed that curcumin significantly reduced inflammatory cytokines, including IL-1β (p = 0.000), IL-6 (p = 0.002), and TNF-α (p = 0.000), across various concentrations, time points, and administration routes. Additionally, curcumin markedly enhanced the activity of oxidative stress markers such as SOD (p = 0.000), Sir2 (p = 0.000), GPx (p = 0.000), and Nrf2 (p = 0.000), while reducing MDA (p = 0.000), 4-HNE (p = 0.001), and oxyprotein levels (p = 0.024). Furthermore, curcumin improved cerebral edema (p = 0.000) and upregulated neuroprotective factors like synapsin I (p = 0.019), BDNF (p = 0.000), and CREB (p = 0.000), without reducing mNSS (p = 0.144). About autophagy and apoptosis, curcumin increased the activity of Beclin-1 (p = 0.000) and Bcl-2 (p = 0.000), while decreasing caspase-3 (p = 0.000), the apoptosis index (p = 0.000), and P62 (p = 0.002).

Conclusion

Curcumin supplementation positively affects traumatic brain injury (TBI) by alleviating oxidative stress and inflammatory responses and promoting neuroprotection. It holds potential as a therapeutic agent for human TBI. However, this conclusion necessitates further substantiation through high-quality literature and additional randomized controlled trials (RCTs).

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/. The registration number of PROSPERO: CRD42023452685.

Protective Effects of Plant-Derived Compounds Against Traumatic Brain Injury

Inflammation in the nervous system is one of the key features of many neurodegenerative diseases. It is increasingly being identified as a critical pathophysiological primitive mechanism associated with chronic neurodegenerative diseases following traumatic brain injury (TBI). Phytochemicals have a wide range of clinical properties due to their antioxidant and anti-inflammatory effects. Currently, there are few drugs available for the treatment of neurodegenerative diseases other than symptomatic relief. Numerous studies have shown that plant-derived compounds, in particular polyphenols, protect against various neurodegenerative diseases and are safe for consumption. Polyphenols exert protective effects on TBI via restoration of nuclear factor kappa B (NF-κB), toll-like receptor-4 (TLR4), and Nod-like receptor family proteins (NLRPs) pathways. In addition, these phytochemicals and their derivatives upregulate the phosphatidylinositol-3-Kinase/Protein Kinase B (PI3K/AKT) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways, which have critical functions in modulating TBI symptoms. There is supporting evidence that medicinal plants and phytochemicals are protective in different TBI models, though future clinical trials are needed to clarify the precise mechanisms and functions of different polyphenolic compounds in TBI.

Tetrahydrocurcumin Protects Against GSK3β/PTEN/PI3K/Akt-Mediated Neuroinflammatory Responses and Microglial Polarization Following Traumatic Brain Injury

Tetrahydrocurcumin (THC) and microglial polarization play crucial roles in neuroprotection during traumatic brain injury (TBI). However, whether THC regulates microglial polarization in TBI is unknown. Thus, we intended to analyze the functions and mechanism of THC in nerve injury after TBI via the regulation of microglial polarization. A TBI rat model was established, and modified neurological function score (mNSS), brain water content, Nissl staining, and Fluoro-Jade B (FJB) staining were used to evaluate neurological function. The expression of the M1-linked markers CD16 and CD86, as well as the M2-associated markers CD206 and YM-1, was analyzed via qRT-PCR, western blotting, and immunofluorescence. The levels of inflammatory cytokines were assessed via ELISA. Primary microglia were isolated from the brain and treated with lipopolysaccharide (LPS) to induce injury. TUNEL staining was used to measure primary microglial apoptosis. The expression of GSK3β, PTEN, and PI3K/Akt pathway proteins was detected via western blotting. TBI induced nerve injury, while THC improved neurological function recovery after TBI. Further analysis indicated that THC enhanced M2 microglial polarization and attenuated the inflammatory reaction mediated by microglia both in vitro and in vivo. Moreover, we found that THC promoted the M2 microglial phenotype through upregulating GSK3β expression. Additionally, we proved that GSK3β activated the PI3K/Akt pathway by phosphorylating PTEN. In conclusion, we demonstrated that THC protected against nerve injury after TBI via microglial polarization via the GSK3B/PTEN/PI3K/Akt signaling axis, suggesting the potential of THC for TBI treatment by promoting microglial M2 polarization.

The neuroprotection of controlled decompression after traumatic epidural intracranial hypertension through suppression of autophagy via PI3K/Akt signaling pathway

Acute intracranial hypertension (AIH) is a common and tricky symptom that inflicts upon patients after traumatic brain injury (TBI). A variety of clinical options have been applied for the management of AIH, such as physiotherapy, medication, surgery and combination therapy. Specifically, controlled decompression (CDC) alleviates the extent of brain injury and reduces the incidence of a series of post-TBI complications, thereby enhancing the prognosis of patients suffering from acute intracranial hypertension. The objective of the present project is to illuminate the potential molecular mechanism that underlies the neuroprotective effects of CDC in a rat model of traumatic epidural intracranial hypertension (TEIH). Herein, we observed the functional recovery, the degree of brain edema, the level of apoptosis, the expressions of neuronal cell autophagy-related signaling pathway proteins (including Akt, p-Akt, LC3 and Beclin-1) in rat TEIH model at 24 h post-surgery. The results showed in comparison with rapid decompression (RDC), CDC reduced the degree of brain edema, diminished the level of cellular apoptosis and enhanced neurological function, and whereas the neuroprotective effect of CDC could be reversed by rapamycin (Rap). The expressions of Beclin-1 and LC3 in CDC group were significantly lower than those of RDC group, and the expression levels of these two proteins were significantly elevated after the addition of Rap. The expression of p-Akt in CDC group was considerably enhanced than RDC group. After the addition of LY294002, a PI3K/Akt pathway inhibitor, p-Akt protein expression was reduced, and the neuroprotective effect of the rats was markedly inhibited. Taken together, our data demonstrate the superior neuroprotective effect of CDC with regard to alleviating early brain edema, improving the neurological status, suppressing apoptosis and inhibiting neuronal autophagy via triggering PI3K/Akt signaling pathway.

Curcuminoids as Cell Signaling Pathway Modulators: A Potential Strategy for Cancer Prevention

Despite substantial advancements in curative modern medicine in the last few decades, cancer risk and casualty rates have continued to mount globally. The exact reason for cancer's onset and progression is still unknown. However, skeletal and functional abnormalities in the genetic code are assumed to be the primary cause of cancer. Many lines of evidence reported that some medicinal plants can be utilized to curb cancer cell proliferation with a safe, fruitful, and cost-efficient perspective. Curcuminoid, isolated from Curcuma longa, have gotten a lot of focus due to their anticancer potential as they reduce tumor progression, invasion, and dissemination. Further, they modulated signal transduction routes like MAPK, PI3K/Akt/mTOR, JAK/STAT, and Wnt/β-catenin, etc., and triggered apoptosis as well as actuated autophagy in malignant cells without altering the normal cells, thus preventing cancer progression. Besides, Curcuminoid also regulate the function and expression of anti-tumor and carcinogenic miRNAs. Clinical studies also reported the therapeutic effect of Curcuminoid against various cancer through decreasing specific biomarkers like TNF-α, Bcl-2, COX-2, PGE2, VEGF, IκKβ, and various cytokines like IL-12p70, IL-10, IL-2, IFN-γ levels and increasing in p53 and Bax levels. Thus, in the present review, we abridged the modulation of several signal transduction routes by Curcuminoids in various malignancies, and its modulatory role in the initiation of tumor-suppressive miRNAs and suppression of the oncogenic miRNAs are explored. Additionally, various pharmacokinetic approaches have been projected to address the Curcuminoids bioavailability like the use of piperine as an adjuvant; nanotechnology- based Curcuminoids preparations utilizing Curcuminoids analogues are also discussed.

Evaluation of Glycogen Synthase Kinase Pathway for Assessing the Antidepressant-like Effect of Glucosamine as a Radioprotector in Rats: Behavioral and Biochemical Studies

Radiotherapy is a very important tool in the treatment of cancer; nevertheless, its side effects are a hindrance to its use. The present study is designed to evaluate glucosamine effects against radiation-induced brain oxidative stress and depression-like effect in rats. Four groups of female Wister rats were used as control, irradiated (4 × 2 Gy), glucosamine (1 g/kg P.O), and glucosamine + irradiated group. The behavioral responses are estimated. The brain hippocampi of the rats are separated to evaluate oxidative stress biochemical parameters and glycogen synthase kinase pathway in addition to the biogenic amines. Irradiation exposure led to disturbances in the behavioral assessments (forced swimming test, light-dark box, and open field test) and a significant decrease in brain GSH, neurotransmitters (serotonin, norepinephrine, and dopamine), phosphatidylinositol 3 kinase (PI3K), and phosphorylated protein kinase-B (p-AKT) levels. Additionally, MDA and ROS levels increased significantly post-irradiation along with the phosphorylated glycogen synthase kinase (p-GSK3). Glucosamine administration before irradiation caused improvement in the behavioral valuations and the biochemical parameters in the brain as well. Glucosamine might be used as a radioprotector to improve brain function and as an antidepressant drug. It could be promising as a future therapy in managing depression occurring during radiotherapy.

Curcumin, inflammation, and neurological disorders: How are they linked?

Background

Despite the extensive research in recent years, the current treatment modalities for neurological disorders are suboptimal. Curcumin, a polyphenol found in Curcuma genus, has been shown to mitigate the pathophysiology and clinical sequalae involved in neuroinflammation and neurodegenerative diseases.

Methods

We searched PubMed database for relevant publications on curcumin and its uses in treating neurological diseases. We also reviewed relevant clinical trials which appeared on searching PubMed database using 'Curcumin and clinical trials'.

Results

This review details the pleiotropic immunomodulatory functions and neuroprotective properties of curcumin, its derivatives and formulations in various preclinical and clinical investigations. The effects of curcumin on neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), brain tumors, epilepsy, Huntington's disorder (HD), ischemia, Parkinson's disease (PD), multiple sclerosis (MS), and traumatic brain injury (TBI) with a major focus on associated signalling pathways have been thoroughly discussed.

Conclusion

This review demonstrates curcumin can suppress spinal neuroinflammation by modulating diverse astroglia mediated cascades, ensuring the treatment of neurological disorders.

Positive Tetrahydrocurcumin-Associated Brain-Related Metabolomic Implications

Tetrahydrocurcumin (THC) is a metabolite of curcumin (CUR). It shares many of CUR's beneficial biological activities in addition to being more water-soluble, chemically stable, and bioavailable compared to CUR. However, its mechanisms of action have not been fully elucidated. This paper addresses the preventive role of THC on various brain dysfunctions as well as its effects on brain redox processes, traumatic brain injury, ischemia-reperfusion injury, Alzheimer's disease, and Parkinson's disease in various animal or cell culture models. In addition to its strong antioxidant properties, the effects of THC on the reduction of amyloid β aggregates are also well documented. The therapeutic potential of THC to treat patterns of mitochondrial brain dysmorphic dysfunction is also addressed and thoroughly reviewed, as is evidence from experimental studies about the mechanism of mitochondrial failure during cerebral ischemia/reperfusion injury. THC treatment also results in a dose-dependent decrease in ERK-mediated phosphorylation of GRASP65, which prevents further compartmentalization of the Golgi apparatus. The PI3K/AKT signaling pathway is possibly the most involved mechanism in the anti-apoptotic effect of THC. Overall, studies in various animal models of different brain disorders suggest that THC can be used as a dietary supplement to protect against traumatic brain injury and even improve brain function in Alzheimer's and Parkinson's diseases. We suggest further preclinical studies be conducted to demonstrate the brain-protective, anti-amyloid, and anti-Parkinson effects of THC. Application of the methods used in the currently reviewed studies would be useful and should help define doses and methods of THC administration in different disease conditions.

Sinomenine Protects against Early Brain Injury by Inhibiting Microglial Inflammatory Response via Nrf2-Dependent Pathway after Subarachnoid Hemorrhage

Microglial activation and sustained inflammation plays an important role in the processes of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Sinomenine (SIN) has been demonstrated to have neuroprotective effects in the traumatic brain injury (TBI) model. However, the role of SIN in SAH-induced EBI and its latent mechanisms remain unclear. This study was carried out to explore the role of SIN on SAH-induced EBI and its effects on the microglial inflammatory response following SAH. In this study, a model of SAH in rats was established. Modified neurological severity scores (mNSS), encephaledema, and Nissl staining were employed to determine the effects of SIN. Western blot and immunofluorescence analysis were performed to evaluate nuclear factor erythroid 2-related factor 2 (Nrf2) expression. Nrf2-related downstream proteins, including heme oxygenase-1 (HO-1) and quinine oxidoreductase-1 (NQO-1), were detected with immunohistochemistry analyses and Real-Time Quantitative Polymerase Chain Reaction (RT-qPCR). Microglia activation and associated inflammatory factors, factor-kappa B (NF-κB), interleukin-1β (IL-1β), and interleukin-6 (IL-6), were assessed after SAH. The results showed that SIN administration improved neurobehavior function, and attenuated neural apoptosis and brain edema after SAH. In addition, SIN inhibited microglial action and the subsequent inflammatory response after SAH through the upregulated expression of HO-1 and NQO-1 via activation of the Nrf2 pathway. These results demonstrated that SIN supplementation provided protection against SAH-induced neuronal apoptosis by microglial inflammatory response regulation and possible involvement of the Nrf2 pathway.

TrkB agonist N-acetyl serotonin promotes functional recovery after traumatic brain injury by suppressing ferroptosis via the PI3K/Akt/Nrf2/Ferritin H pathway

Ferroptosis is a form of regulated cell death that is mainly triggered by iron-dependent lipid peroxidation. A growing body of evidence suggests that ferroptosis is involved in the pathophysiology of traumatic brain injury (TBI), and tropomyosin-related kinase B (TrkB) deficiency would mediate TBI pathologies. As an agonist of TrkB and an immediate precursor of melatonin, N-acetyl serotonin (NAS) exerts several beneficial effects on TBI, but there is no information regarding the role of NAS in ferroptosis after TBI. Here, we examined the effect of NAS treatment on TBI-induced functional outcomes and ferroptosis. Remarkably, the administration of NAS alleviated TBI-induced neurobehavioral deficits, lesion volume, and neurodegeneration. NAS also rescued TBI-induced mitochondrial shrinkage, the changes in ferroptosis-related molecule expression, and iron accumulation in the ipsilateral cortex. Similar results were obtained with a well-established ferroptosis inhibitor, liproxstatin-1. Furthermore, NAS activated the TrkB/PI3K/Akt/Nrf2 pathway in the mouse model of TBI, while inhibition of PI3K and Nrf2 weakened the protection of NAS against ferroptosis both in vitro and in vivo, suggesting that a possible pathway linking NAS to the action of anti-ferroptosis was TrkB/PI3K/Akt/Nrf2. Given that ferritin H (Fth) is a known transcription target of Nrf2, we then investigated the effects of NAS on neuron-specific Fth knockout (Fth-KO) mice. Strikingly, Fth deletion almost abolished the protective effects of NAS against TBI-induced ferroptosis and synaptic damage, although Fth deletion-induced susceptibility toward ferroptosis after TBI was reversed by an iron chelator, deferoxamine. Taken together, these data indicate that the TrkB agonist NAS treatment appears to improve brain function after TBI by suppressing ferroptosis, at least in part, through activation of the PI3K/Akt/Nrf2/Fth pathway, providing evidence that NAS is likely to be a promising anti-ferroptosis agent for further treatment for TBI.

Neuroprotective effect of naringenin-loaded solid lipid nanoparticles against streptozocin-induced neurotoxicity through autophagy blockage

Autophagy is a pivotal contributing factor to modulate the progression of neurodegenerative diseases. Although naringenin (Nar) has shown beneficial effects against neurodegenerative diseases, its poor solubility and bioavailability have limited its application. The present research aimed to design a nanostructured formulation of Nar to achieve an enhanced therapeutic effect. Herein, Nar-loaded solid lipid nanoparticles (Nar-SLNs) were prepared and characterized. Then, PC12 cells were exposed to streptozocin (STZ) and/or Nar and Nar-SLNs in vitro to clarify the protective effect of Nar and its nanoformulation against STZ-stimulated neurotoxicity. The empty SLNs and Nar-SLNs indicated a narrow polydispersity index value with a negative zeta potential. As determined by the scanning electron microscopy images, the nanoparticles had a spherical shape and were less than 20 nm in size. FTIR results demonstrated the interaction between Nar and SLNs and supported the presence of Nar in the nanoparticle. The nanoformulation revealed an initial burst release followed by a sustained release manner. Treatment of PC12 cells with STZ resulted in mitochondrial dysfunction and increased autophagic markers, including LC3-II, Beclin1, Akt, ATG genes, and accumulation of miR-21 and miR-22. Both Nar and Nar-SLNs pre-treatment improved cell survival and augmented mitochondrial membrane potential, accompanied by reduced autophagic markers expression. However, Nar-SLNs were more effective than free Nar. As a result, our findings suggested that SLNs effectively enhance the neuroprotective effect of Nar, and Nar-SLNs may be a promising candidate to suppress or prevent STZ-elicited neurotoxicity. PRACTICAL APPLICATIONS: According to the beneficial effect of Nar in the management of neurodegenerative diseases, we evaluated the protective effect of Nar and Nar-SLNs against STZ-stimulated neurotoxicity and analyzed the role of autophagy in STZ-stimulated neurotoxicity. Our results proposed that Nar-SLNs could be a promising option for neurological disorders prevention through autophagy suppression.

The contribution of altered neuronal autophagy to neurodegeneration

Defects in cellular functions related to altered protein homeostasis and associated progressive accumulation of pathological intracellular material is a critical process involved in the pathogenesis of many neurodegenerative disorders, including Alzheimer's disease and Parkinson's disease. Autophagy is an essential mechanism that ensures neuronal health by removing long-lived proteins or defective organelles and by doing so prevents cell toxicity and death within the central nervous system. Abundant evidence has shown that neuronal autophagy pathways are altered in Alzheimer's disease, Parkinson's disease and traumas of the central nervous system including Spinal Cord Injury and Traumatic Brain Injury. In this review, we aimed to summarize the latest studies on the role that altered neuronal autophagy plays in brain health and these pathological conditions, and how this knowledge can be leveraged for the development of novel therapeutics against them.

New insights into the interplay between autophagy and oxidative and endoplasmic reticulum stress in neuronal cell death and survival

Autophagy is a dynamic process that maintains the normal homeostasis of cells by digesting and degrading aging proteins and damaged organelles. The effect of autophagy on neural tissue is still a matter of debate. Some authors suggest that autophagy has a protective effect on nerve cells, whereas others suggest that autophagy also induces the death of nerve cells and aggravates nerve injury. In mammals, oxidative stress, autophagy and endoplasmic reticulum stress (ERS) constitute important defense mechanisms to help cells adapt to and survive the stress conditions caused by physiological and pathological stimuli. Under many pathophysiological conditions, oxidative stress, autophagy and ERS are integrated and amplified in cells to promote the progress of diseases. Over the past few decades, oxidative stress, autophagy and ERS and their interactions have been a hot topic in biomedical research. In this review, we summarize recent advances in understanding the interactions between oxidative stress, autophagy and ERS in neuronal cell death and survival.

Nutraceuticals as Modulators of Autophagy: Relevance in Parkinson’s Disease

Dietary supplements and nutraceuticals have entered the mainstream. Especially in the media, they are strongly advertised as safe and even recommended for certain diseases. Although they may support conventional therapy, sometimes these substances can have unexpected side effects. This review is particularly focused on the modulation of autophagy by selected vitamins and nutraceuticals, and their relevance in the treatment of neurodegenerative diseases, especially Parkinson’s disease (PD). Autophagy is crucial in PD; thus, the induction of autophagy may alleviate the course of the disease by reducing the so-called Lewy bodies. Hence, we believe that those substances could be used in prevention and support of conventional therapy of neurodegenerative diseases. This review will shed some light on their ability to modulate the autophagy.

Natural products attenuate PI3K/Akt/mTOR signaling pathway: A promising strategy in regulating neurodegeneration

BACKGROUND

As common, progressive, and chronic causes of disability and death, neurodegenerative diseases (NDDs) significantly threaten human health, while no effective treatment is available. Given the engagement of multiple dysregulated pathways in neurodegeneration, there is an imperative need to target the axis and provide effective/multi-target agents to tackle neurodegeneration. Recent studies have revealed the role of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) in some diseases and natural products with therapeutic potentials.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating various neuronal disorders via the PI3K/Akt/mTOR signaling pathway.

STUDY DESIGN AND METHODS

A systematic and comprehensive review was done based on the PubMed, Scopus, Web of Science, and Cochrane electronic databases. Two independent investigators followed the PRISMA guidelines and included papers on PI3K/Akt/mTOR and interconnected pathways/mediators targeted by phytochemicals in NDDs.

RESULTS

Natural products are multi-target agents with diverse pharmacological and biological activities and rich sources for discovering and developing novel therapeutic agents. Accordingly, recent studies have shown increasing phytochemicals in combating Alzheimer's disease, aging, Parkinson's disease, brain/spinal cord damages, depression, and other neuronal-associated dysfunctions. Amongst the emerging targets in neurodegeneration, PI3K/Akt/mTOR is of great importance. Therefore, attenuation of these mediators would be a great step towards neuroprotection in such NDDs.

CONCLUSION

The application of plant-derived secondary metabolites in managing and/or treating various neuronal disorders through the PI3K/Akt/mTOR signaling pathway is a promising strategy towards neuroprotection.

Protective Effect of GM1 Attenuates Hippocampus and Cortex Apoptosis After Ketamine Exposure in Neonatal Rat via PI3K/AKT/GSK3β Pathway

Ketamine is a widely used analgesic and anesthetic in obstetrics and pediatrics. Ketamine is known to promote neuronal death and cognitive dysfunction in the brains of humans and animals during development. Monosialotetrahexosyl ganglioside (GM1), a promoter of brain development, exerts neuroprotective effects in many neurological disease models. Here, we investigated the neuroprotective effect of GM1 and its potential underlying mechanism against ketamine-induced apoptosis of rats. Seven-day-old Sprague Dawley (SD) rats were randomly divided into the following four groups: (1) group C (control group: normal saline was injected intraperitoneally); (2) group K (ketamine); (3) group GM1 (GM1 was given before normal saline injection); and (4) GM1+K group (received GM1 30 min before continuous exposure to ketamine). Each group contained 15 rats, received six doses of ketamine (20 mg/kg), and was injected with saline every 90 min. The Morris water maze (MWM) test, the number of cortical and hippocampal cells, apoptosis, and AKT/GSK3β pathway were analyzed. To determine whether GM1 exerted its effect via the PI3K/AKT/GSK3β pathway, PC12 cells were incubated with LY294002, a PI3K inhibitor. We found that GM1 protected against ketamine-induced apoptosis in the hippocampus and cortex by reducing the expression of Bcl-2 and Caspase-3, and by increasing the expression of Bax. GM1 treatment increased the expression of p-AKT and p-GSK3β. However, the anti-apoptotic effect of GM1 was eliminated after inhibiting the phosphorylation of AKT. We showed that GM1 lessens ketamine-induced apoptosis in the hippocampus and cortex of young rats by regulating the PI3K/AKT/GSK3β pathway. Taken together, GM1 may be a potential preventive treatment for the neurotoxicity caused by continuous exposure to ketamine.

Impact of Curcumin on Traumatic Brain Injury and Involved Molecular Signaling Pathways

Traumatic Brain Injury (TBI) is one of the main causes of mortality and morbidity worldwide with no suitable treatment. The present study was designed to review the present literature about the protective effects of curcumin and the underlying mechanism against TBI. All published English language papers from beginning to 2019 were selected in this study. The findings indicate that curcumin may be effective against TBI outcomes by modulating the molecular signaling pathways involved in oxidative stress, inflammation, apoptosis, and autophagy. However, more experimental studies should be done to identify all mechanisms involved in the pathogenesis of TBI. Patents for Curcumin and chronic inflammation and traumatic brain injury management (WO2017097805A1 and US9101580B2) were published. In conclusion, the present study confirmed the potential therapeutic impact of curcumin for treating TBI.

Curcumin Metabolite Tetrahydrocurcumin in the Treatment of Eye Diseases

Curcumin is one of the most valuable natural products due to its pharmacological activities. However, the low bioavailability of curcumin has long been a problem for its medicinal use. Large studies have been conducted to improve the use of curcumin; among these studies, curcumin metabolites have become a relatively new research focus over the past few years. Additionally, accumulating evidence suggests that curcumin or curcuminoid metabolites have similar or better biological activity than the precursor of curcumin. Recent studies focus on the protective role of plasma tetrahydrocurcumin (THC), a main metabolite of curcumin, against tumors and chronic inflammatory diseases. Nevertheless, studies of THC in eye diseases have not yet been conducted. Since ophthalmic conditions play a crucial role in worldwide public health, the prevention and treatment of ophthalmic diseases are of great concern. Therefore, the present study investigated the antioxidative, anti-inflammatory, antiangiogenic, and neuroprotective effects of THC on four major ocular diseases: age-related cataracts, glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR). While this study aimed to show curcumin as a promising potential solution for eye conditions and discusses the involved mechanistic pathways, further work is required for the clinical application of curcumin.

MFG-E8 attenuates inflammation in subarachnoid hemorrhage by driving microglial M2 polarization

Increasing evidence suggests that microglial polarization plays an important role in the pathological processes of neuroinflammation following subarachnoid hemorrhage (SAH). Previous studies indicated that milk fat globule-epidermal growth factor-8 (MFG-E8) has potential anti-apoptotic and anti-inflammatory effects in cerebral ischemia. However, the effects of MFG-E8 on microglial polarization have not been evaluated after SAH. Therefore, the aim of this study was to explore the role of MFG-E8 in anti-inflammation, and its effects on microglial polarization following SAH. We established the SAH model via prechiasmatic cistern blood injection in mice. Double-immunofluorescence staining, western blotting and quantitative real-time polymerase chain reaction (q-PCR) were performed to investigate the expression and cellular distribution of MFG-E8. Two different dosages (1 and 5 μg) of recombinant human MFG-E8 (rhMFG-E8) were injected intracerebroventricularly (i.c.v.) at 1 h after SAH. Brain water content, neurological scores, beam-walking score, Fluoro-Jade C (FJC), and terminal deoxynucleotidyl transferase dUTP nick endlabeling staining (TUNEL) were measured at 24 h. Suppression of MFG-E8, integrin β3 and phosphorylation of STAT3 were achieved by specific siRNAs (500 pmol/5 μl) and the STAT3 inhibitor Stattic (5 μM). The potential signaling pathways and microglial polarization were measured by immunofluorescence labeling and western blotting. SAH induction increased the levels of inflammatory mediators and the proportion of M1 cells, and caused neuronal apoptosis in mice at 24 h. Treatment with rhMFG-E8 (5 μg) remarkably decreased brain edema, improved neurological functions, reduced the levels of proinflammatory factors, and promoted the microglial to shift to M2 phenotype. However, knockdown of MFG-E8 and integrin β3 via siRNA abolished the effects of MFG-E8 on anti-inflammation and M2 phenotype polarization. The STAT3 inhibitor Stattic further clarified the role of rhMFG-E8 in microglial polarization by regulating the protein levels of the integrin β3/SOCS3/STAT3 pathway. rhMFG-E8 inhibits neuronal inflammation by transformation the microglial phenotype toward M2 and its direct protective effect on neurons after SAH, which may be mediated by modulation of the integrin β3/SOCS3/STAT3 signaling pathway, highlighting rhMFG-E8 as a potential therapeutic target for the treatment of SAH patients.

Obstacles against the Marketing of Curcumin as a Drug

Among the extensive public and scientific interest in the use of phytochemicals to prevent or treat human diseases in recent years, natural compounds have been highly investigated to elucidate their therapeutic effect on chronic human diseases including cancer, cardiovascular disease, and neurodegenerative disease. Curcumin, an active principle of the perennial herb Curcuma longa, has attracted an increasing research interest over the last half-century due to its diversity of molecular targets, including transcription factors, enzymes, protein kinases, growth factors, inflammatory cytokines, receptors, and it's interesting pharmacological activities. Despite that, the clinical effectiveness of the native curcumin is weak, owing to its low bioavailability and rapid metabolism. Preclinical data obtained from animal models and phase I clinical studies done in human volunteers confirmed a small amount of intestinal absorption, hepatic first pass effect, and some degree of intestinal metabolism, might explain its poor systemic availability when it is given via the oral route. During the last decade, researchers have attempted with new pharmaceutical methods such as nanoparticles, liposomes, micelles, solid dispersions, emulsions, and microspheres to improve the bioavailability of curcumin. As a result, a significant number of bioavailable curcumin-based formulations were introduced with a varying range of enhanced bioavailability. This manuscript critically reviews the available scientific evidence on the basic and clinical effects and molecular targets of curcumin. We also discuss its pharmacokinetic and problems for marketing curcumin as a drug.

Tetrahydrocurcumin mitigates acute hypobaric hypoxia-induced cerebral oedema and inflammation through the NF-κB/VEGF/MMP-9 pathway

High-altitude cerebral oedema (HACE) is a potentially fatal manifestation of high-altitude sickness and is caused partly by inflammation and the blood-brain barrier disruption. Tetrahydrocurcumin (THC) has been reported to exert effective antioxidative and anti-inflammatory effects; This study sought to elucidate the underlying mechanism of THC in mitigating HACE using a mouse model. Our results revealed that prophylactic administration of THC (40 mg/kg) for 3 days significantly alleviated the increase in brain water content (BWC), interleukin-1β (IL-1β) and TNF-α levels caused by acute hypobaric hypoxia (AHH). Additionally, superoxide dismutase (SOD) activity was increased by THC to enhance the ability to resist hypoxia. Histological and ultrastructural analysis of the cerebrum revealed that THC administration mitigated AHH-induced pericellular oedema and reduced the perivascular space, resulting in the simultaneous remission of oedema and protection of mitochondria in the cerebrum. In vitro, astrocytes exposed to hypoxia (4% O₂ ) for 24 hr exhibited and increase in IL-1β expression followed by an increase in vascular endothelial growth factor (VEGF) levels. Furthermore, THC administration remarkably downregulated VEGF, matrix metallopeptidase-9 (MMP-9), and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) expression, both in vivo and in vitro. Our data highlight the potential prophylactic activity of THC in HACE, it effectively mitigates AHH-induced cerebral oedema and inflammation is associated with the inhibition of the NF-κB/ VEGF/MMP-9 pathways.

Epothilone B Facilitates Peripheral Nerve Regeneration by Promoting Autophagy and Migration in Schwann Cells

The search for drugs that can facilitate axonal regeneration and elongation following peripheral nerve injury has been an area of increasing interest in recent years. Epothilone B (EpoB) is an FDA-approved antineoplastic agent, which shows the capacity to induce α-tubulin polymerization and to improve the stability of microtubules. Recently, it has been increasingly recognized that EpoB has a regenerative effect in the central nervous system. However, the information currently available regarding the potential therapeutic effect of EpoB on peripheral nerve regeneration is limited. Here, we used a rat sciatic crush injury model system to determine that EpoB strikingly improved axonal regeneration and recovery of function. Also, EpoB (1 nM) did not result in significant apoptosis in Schwann cells (SCs) and showed little effect on their viability either. Interestingly, EpoB (1 nM) significantly enhanced migration in SCs, which was inhibited by autophagy inhibitors 3-methyladenine (3-MA). Since PI3K/Akt signaling has been implicated in regulating autophagy, we further examined the involvement of PI3K/Akt in the process of EpoB-induced SC migration. We found that EpoB (1 nM) significantly inhibited phosphorylation of PI3K and Akt in SCs. Further studies showed that both EpoB-enhanced migration and autophagy were increased/inhibited by inhibition/activation of PI3K/Akt signaling with LY294002 or IGF-1. In conclusion, EpoB can promote axonal regeneration following peripheral nerve injury by enhancing the migration of SCs, with this activity being controlled by PI3K/Akt signaling-mediated autophagy in SCs. This underscores the potential therapeutic value of EpoB in enhancing regeneration and functional recovery in cases of peripheral nerve injury.

Curcumin in Health and Diseases: Alzheimer's Disease and Curcumin Analogues, Derivatives, and Hybrids

Worldwide, Alzheimer’s disease (AD) is the most common neurodegenerative multifactorial disease influencing the elderly population. Nowadays, several medications, among them curcumin, are used in the treatment of AD. Curcumin, which is the principal component of Curcuma longa, has shown favorable effects forsignificantly preventing or treating AD. During the last decade, the scientific community has focused their research on the optimization of therapeutic properties and on the improvement of pharmacokinetic properties of curcumin. This review summarizes bibliographical data from 2009 to 2019 on curcumin analogues, derivatives, and hybrids, as well as their therapeutic, preventic, and diagnostic applications in AD. Recent advances in the field have revealed that the phenolic hydroxyl group could contribute to the anti-amyloidogenic activity. Phenyl methoxy groups seem to contribute to the suppression of amyloid-β peptide (Aβ₄₂) and to the suppression of amyloid precursor protein (APP) andhydrophobic interactions have also revealed a growing role. Furthermore, flexible moieties, at the linker, are crucial for the inhibition of Aβ aggregation. The inhibitory activity of derivatives is increased with the expansion of the aromatic rings. The promising role of curcumin-based compounds in diagnostic imaging is highlighted. The keto-enol tautomerism seems to be a novel modification for the design of amyloid-binding agents. Molecular docking results, (Q)SAR, as well as in vitro and in vivo tests highlight the structures and chemical moieties that are correlated with specific activity. As a result, the knowledge gained from the existing research should lead to the design and synthesis ofinnovative and multitargetedcurcumin analogues, derivatives, or curcumin hybrids, which would be very useful drug and tools in medicine for both diagnosis and treatment of AD.

Neuroprotective Effects and Treatment Potential of Incretin Mimetics in a Murine Model of Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is a commonly occurring injury in sports, victims of motor vehicle accidents, and falls. TBI has become a pressing public health concern with no specific therapeutic treatment. Mild TBI (mTBI), which accounts for approximately 90% of all TBI cases, may frequently lead to long-lasting cognitive, behavioral, and emotional impairments. The incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are gastrointestinal hormones that induce glucose-dependent insulin secretion, promote β-cell proliferation, and enhance resistance to apoptosis. GLP-1 mimetics are marketed as treatments for type 2 diabetes mellitus (T2DM) and are well tolerated. Both GLP-1 and GIP mimetics have shown neuroprotective properties in animal models of Parkinson's and Alzheimer's disease. The aim of this study is to evaluate the potential neuroprotective effects of liraglutide, a GLP-1 analog, and twincretin, a dual GLP-1R/GIPR agonist, in a murine mTBI model. First, we subjected mice to mTBI using a weight-drop device and, thereafter, administered liraglutide or twincretin as a 7-day regimen of subcutaneous (s.c.) injections. We then investigated the effects of these drugs on mTBI-induced cognitive impairments, neurodegeneration, and neuroinflammation. Finally, we assessed their effects on neuroprotective proteins expression that are downstream to GLP-1R/GIPR activation; specifically, PI3K and PKA phosphorylation. Both drugs ameliorated mTBI-induced cognitive impairments evaluated by the novel object recognition (NOR) and the Y-maze paradigms in which neither anxiety nor locomotor activity were confounds, as the latter were unaffected by either mTBI or drugs. Additionally, both drugs significantly mitigated mTBI-induced neurodegeneration and neuroinflammation, as quantified by immunohistochemical staining with Fluoro-Jade/anti-NeuN and anti-Iba-1 antibodies, respectively. mTBI challenge significantly decreased PKA phosphorylation levels in ipsilateral cortex, which was mitigated by both drugs. However, PI3K phosphorylation was not affected by mTBI. These findings offer a new potential therapeutic approach to treat mTBI, and support further investigation of the neuroprotective effects and mechanism of action of incretin-based therapies for neurological disorders.

Modulation of autophagy in traumatic brain injury

Traumatic brain injury (TBI) is defined as a traumatically induced structural injury or physiological disruption of brain function as a result of external forces, leading to adult disability and death. A growing body of evidence reveals that alterations in autophagy-related proteins exist extensively in both experimentally and clinically after TBI. Of note, the autophagy pathway plays an essential role in pathophysiological processes, such as oxidative stress, inflammatory response, and apoptosis, thus contributing to neurological properties of TBI. With this in mind, this review summarizes a comprehensive overview on the beneficial and detrimental effects of autophagy in pathophysiological conditions and how these activities are linked to the pathogenesis of TBI. Moreover, the relationship between oxidative stress, inflammation, apoptosis, and autophagy occur TBI. Ultimately, multiple compounds and various drugs targeting the autophagy pathway are well described in TBI. Therefore, autophagy flux represents a potential clinical therapeutic value for the treatment of TBI and its complications.

Role of Autophagy on Heavy Metal-Induced Renal Damage and the Protective Effects of Curcumin in Autophagy and Kidney Preservation

Curcumin is a hydrophobic polyphenol compound extracted from the rhizome of turmeric. The protective effect of curcumin on kidney damage in multiple experimental models has been widely described. Its protective effect is mainly associated with its antioxidant and anti-inflammatory properties, as well as with mitochondrial function maintenance. On the other hand, occupational or environmental exposure to heavy metals is a serious public health problem. For a long time, heavy metals-induced nephrotoxicity was mainly associated with reactive oxygen species overproduction and loss of endogenous antioxidant activity. However, recent studies have shown that in addition to oxidative stress, heavy metals also suppress the autophagy flux, enhancing cell damage. Thus, natural compounds with the ability to modulate and restore autophagy flux represent a promising new therapeutic strategy. Furthermore, it has been reported in other renal damage models that curcumin’s nephroprotective effects are related to its ability to regulate autophagic flow. The data indicate that curcumin modulates autophagy by classic signaling pathways (suppression of protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and/or by stimulation of adenosine monophosphate-activated protein kinase (AMPK) and extracellular signal-dependent kinase (ERK) pathways). Moreover, it allows lysosomal function preservation, which is crucial for the later stage of autophagy. However, future studies of autophagy modulation by curcumin in heavy metals-induced autophagy flux impairment are still needed.

The Relationship Between Autophagy and Brain Plasticity in Neurological Diseases

Autophagy, a catabolic degradation system, is utilized for destroying and recycling the damaged or unnecessary cellular components. Brain plasticity refers to the remarkable characteristics of brain neurons that change their structure and function according to previous experience. This review was performed by searching the relevant articles in databases of SCIENCEDIRECT, PUBMED, and Web of Science, from respective inception to January 2019. Here, we review the neuroprotective effect of autophagy in neurological diseases and the mechanism of autophagy in brain plasticity. Moreover, the mechanism of autophagy in the process of brain plasticity can provide the possibility for the development of new treatment methods in the future, thus benefiting patients with neurological diseases. In summary, autophagy and brain plasticity play important roles in neurological diseases.

Multi-Dimensional Mapping of Brain-Derived Extracellular Vesicle MicroRNA Biomarker for Traumatic Brain Injury Diagnostics

The diagnosis and prognosis of traumatic brain injury (TBI) is complicated by variability in the type and severity of injuries and the multiple endophenotypes that describe each patient's response and recovery to the injury. It has been challenging to capture the multiple dimensions that describe an injury and its recovery to provide clinically useful information. To address this challenge, we have performed an open-ended search for panels of microRNA (miRNA) biomarkers, packaged inside of brain-derived extracellular vesicles (EVs), that can be combined algorithmically to accurately classify various states of injury. We mapped GluR2+ EV miRNA across a variety of injury types, injury intensities, history of injuries, and time elapsed after injury, and sham controls in a pre-clinical murine model (n = 116), as well as in clinical samples (n = 36). We combined next-generation sequencing with a technology recently developed by our lab, Track Etched Magnetic Nanopore (TENPO) sorting, to enrich for GluR2+ EVs and profile their miRNA. By mapping and comparing brain-derived EV miRNA between various injuries, we have identified signaling pathways in the packaged miRNA that connect these biomarkers to underlying mechanisms of TBI. Many of these pathways are shared between the pre-clinical model and the clinical samples, and present distinct signatures across different injury models and times elapsed after injury. Using this map of EV miRNA, we applied machine learning to define a panel of biomarkers to successfully classify specific states of injury, paving the way for a prognostic blood test for TBI. We generated a panel of eight miRNAs (miR-150-5p, miR-669c-5p, miR-488-3p, miR-22-5p, miR-9-5p, miR-6236, miR-219a.2-3p, miR-351-3p) for injured mice versus sham mice and four miRNAs (miR-203b-5p, miR-203a-3p, miR-206, miR-185-5p) for TBI patients versus healthy controls.

Downregulation of microRNA-200c-3p reduces damage of hippocampal neurons in epileptic rats by upregulating expression of RECK and inactivating the AKT signaling pathway

OBJECTIVE

The aim of this study is to investigate the role of mircoRNA-200c-3p (miR-200c-3p) on hippocampal neuron injury in epileptic rats through the regulation of the AKT signaling pathway by targeting RECK.

METHODS

The epilepsy rat model was induced by intraperitoneal injection of lithium chloride-pilocarpine. Successful modeled rats were injected with miR-200c-3p inhibitors, inhibitors NC, siRNA-negative control (NC) and RECK-siRNA. The astrocyte activation, levels of oxidative stress indexes, contents of inflammatory factors and the AKT signaling pathway-related proteins in hippocampus tissues were evaluated.

RESULTS

High expression of miR-200c-3p and low expression of RECK were found in the hippocampus tissues of epileptic rats. Downregulation of miR-200c-3p or upregulation of RECK decreased apoptosis of hippocampal neurons, expression of GFAP, content of MDA and increased the activities of GSH-Px and SOD, decreased expression of TNF-α, IL-1β and IL-6 as well as expression of p-PI3K/t-PI3K and p-Akt/t-Akt in hippocampus tissues of epileptic rats.

CONCLUSION

Our study provides evidence that downregulation of miR-200c-3p reduces damage of hippocampal neurons in epileptic rats by upregulating RECK and inactivating the AKT signaling pathway.

Roles of PI3K/AKT/GSK3 Pathway Involved in Psychiatric Illnesses

Psychiatric illnesses may be qualified to the cellular impairments of the function for survival or death in neurons, which may consequently appear as abnormalities in the neuroplasticity. The molecular mechanism has not been well understood, however, it seems that PI3K, AKT, GSK3, and their downstream molecules have crucial roles in the pathogenesis. Through transducing cell surviving signal, the PI3K/AKT/GSK3 pathway may organize an intracellular central network for the action of the synaptic neuroplasticity. In addition, the pathways may also regulate cell proliferation, cell migration, and apoptosis. Several lines of evidence have supported a role for this signaling network underlying the development and treatment for psychiatric illnesses. Indeed, the discovery of molecular biochemical phenotypes would represent a breakthrough in the research for effective treatment. In this review, we summarize advances on the involvement of the PI3K/AKT/GSK3 pathways in cell signaling of neuronal cells. This study may provide novel insights on the mechanism of mental disorder involved in psychiatric illnesses and would open future opportunity for contributions suggesting new targets for diagnostic and/or therapeutic procedures.

Protective effect of ginsenoside Rg1 on LPS-induced apoptosis of lung epithelial cells

Sepsis-induced acute lung injury (ALI) is a life-threatening medical condition with high mortality and morbidity in the critical care units. Though, it was commonly accepted that inflammation and apoptosis of lung epithelial cells played an essential role in the pathogenesis of ALI, the underlying mechanism remain unknown. In our study, we found that LPS-induced cell apoptosis could be counteracted by elevated cell autophagy. In LPS-treated MLE-12 cells, suppression of autophagy via 3-MA could aggravate LPS-induced apoptosis, while activation of autophagy via Rapamycin could effectively impair the apoptosis of MLE-12 cells induced by LPS. In order to further discover the molecular regulation mechanism between apoptosis and autophagy in LPS-treated MLE-12 cells, we demonstrated that autophagy could induced the expression of Nrf2, followed with the decrease of p-p65. Targeted inhibition of Nrf2 could induce enlarged cell apoptosis via increasing the level of p-p65. In addition, we demonstrated that ginsenoside Rg1 protected MLE-12 cells from LPS-induced apoptosis via augmenting autophagy and inducing the expression of Nrf2. Our data implicates that activation of autophagy and Nrf2 by ginsenoside Rg1 may provide a preventive and therapeutic strategy for ALI.

Turmeric Extract Supplementation Reduces Tau Protein Level in Repetitive Traumatic Brain Injury Model

BACKGROUND:

Repetitive traumatic brain injury (RTBI) has gained much attention in this decade, especially in contact sports athletes and military personals. This injury is correlated with early neurodegenerative changes that are marked with the increased of tau protein. Turmeric extract (TE) is a well-known anti-inflammation and antioxidant that decreases tau protein expression in neurodegenerative disease.

AIM:

This study aimed to prove the effect of TE on tau protein level after RTBI.

METHODS:

Forty Sprague Dawley mice were divided into four groups, i.e. negative sham control group, the control group, and two treatment groups. A weight drop model was used by applying a 40-gram mass that was dropped from a 1-meter height onto the vertex of the head, with a total frequency of 12 times, divided into 4 days (day 0, 1, 3, and 7; 3 traumas on each day). TE was given to all treatment groups with 500 mg/kg BW doses once daily. The first treatment group had TE for seven days along the trauma. The second treatment group had pretreatment TE extract, given from seven days before first trauma and continued along the trauma protocol days. Tau protein level was measured on brain and serum using ELISA method.

RESULTS:

There was a significant reduction of tau protein level in both treatment groups compared to trauma group, either in serum or brain, but we also found significant differences regarding brain tau level between the treatment and pretreatment group.

CONCLUSION:

This study might provide evidence of with the role of pretreatment TE in RTBI.

Overexpression of microRNA-183 promotes apoptosis of substantia nigra neurons via the inhibition of OSMR in a mouse model of Parkinson's disease

The present study aimed to investigate the effect of microRNA-183 (miR-183) on substantia nigra neurons by targeting oncostatin M receptor (OSMR) in a mouse model of Parkinson’s disease (PD). The positive expression rates of OSMR and the apoptosis of substantia nigra neurons were detected by immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling, respectively. Substantia nigra neurons in normal and PD mice were cultured in vitro. The association between miR-183 and OSMR was verified using a dual luciferase reporter gene assay. The expression of miR-183 and the phosphoinositide 3-kinase-Akt signaling pathway-associated genes were detected by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Cell apoptosis was detected by flow cytometry. OSMR is the target gene of miR-183. The number of OSMR-positive cells and the apoptotic rate of substantia nigra neurons were increased in the PD group. Neurons transfected with miR-183 mimic exhibited elevated expression levels of miR-183, B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) and caspase-9 and increased apoptotic rate, and reduced expression levels of OSMR, Akt, phosphorylated (p-)Akt, glycogen synthase kinase-3 (GSK-3β), p-GSK-3β, Bcl-2, insulin-like growth factor 1 (IGF-1), mammalian target of rapamycin (mTOR) and p-mTOR. The miR-183 inhibitor decreased the expression levels of miR-183, Bax and caspase-9 and the apoptotic rate; however, increased the expression of OSMR, Akt, p-Akt, GSK-3β, p-GSK-3β, Bcl-2, IGF-1, mTOR and p-mTOR. The results of the present study provide evidence that the overexpression of miR-183 promotes the apoptosis of substantia nigra neurons by inhibiting the expression of OSMR.

Curcumin: A naturally occurring autophagy modulator

Autophagy is a self-degradative process that plays a pivotal role in several medical conditions associated with infection, cancer, neurodegeneration, aging, and metabolic disorders. Its interplay with cancer development and treatment resistance is complicated and paramount for drug design since an autophagic response can lead to tumor suppression by enhancing cellular integrity and tumorigenesis by improving tumor cell survival. In addition, autophagy denotes the cellular ability of adapting to stress though it may end up in apoptosis activation when cells are exposed to a very powerful stress. Induction of autophagy is a therapeutic option in cancer and many anticancer drugs have been developed to this aim. Curcumin as a hydrophobic polyphenol compound extracted from the known spice turmeric has different pharmacological effects in both in vitro and in vivo models. Many reports exist reporting that curcumin is capable of triggering autophagy in several cancer cells. In this review, we will focus on how curcumin can target autophagy in different cellular settings that may extend our understanding of new pharmacological agents to overcome relevant diseases.

Recombinant milk fat globule-EGF factor-8 reduces apoptosis via integrin β3/FAK/PI3K/AKT signaling pathway in rats after traumatic brain injury

Accumulating evidence suggests neuronal apoptosis has the potential to lead to more harmful effects in the pathological processes following traumatic brain injury (TBI). Previous studies have established that milk fat globule-EGF factor-8 (MFG-E8) provides neuroprotection through modulation of inflammation, oxidative stress, and especially apoptosis in cerebral ischemia and neurodegenerative disease. However, the effects of MFG-E8 on neuronal apoptosis in TBI have not yet been investigated. Therefore, we explored the role of MFG-E8 on anti-apoptosis and its potential mechanism following TBI. In the first set of experiments, adult male Sprague–Dawley (SD) rats were randomly divided into Sham and TBI groups that were each further divided into five groups representing different time points (6 h, 24 h, 72 h, and 7 days) (n = 9 each). Western blotting, quantitative real-time PCR, and immunofluorescence staining were performed to identify the expression and cellular localization of MFG-E8. In the second set of experiments, four groups were randomly assigned: Sham group, TBI + Vehicle group, and TBI + rhMFG-E8 (1 and 3 µg) (n = 15). Recombinant human MFGE8 (rhMFG-E8) was administrated as two concentrations through intracerebroventricular (i.c.v.) injection at 1 h after TBI induction. Brain water content, neurological severity score, western blotting, and immunofluorescence staining were measured at 24 and 72 h following TBI. In the final set of experiments, MFG-E8 siRNA (500 pmol/3 µl), integrin β3 siRNA (500 pmol/3 µl), and PI3K inhibitor LY294002 (5 and 20 µM) were injected i.c.v. and thereafter rats exposed to TBI. Western blotting, immunofluorescence staining, brain water content, neurological severity score, and Fluoro-Jade C (FJC) staining were used to investigate the effect of the integrin-β3/FAK/PI3K/AKT signaling pathway on MFG-E8-mediated anti-apoptosis after TBI. The expression of MFG-E8 was mainly located in microglial cells and increased to peak at 24 h after TBI. Treatment with rhMFG-E8 (3 µg) markedly decreased brain water content, improved neurological deficits, and reduced neuronal apoptosis at 24 and 72 h after TBI. rhMFG-E8 significantly enhanced the expression of integrin-β3/FAK/PI3K/AKT pathway-related components. Administration of integrin-β3 siRNA and LY294002 (5 and 20 µM) abolished the effect of rhMFG-E8 on anti-apoptosis and neuroprotection after TBI. This study demonstrated for the first time that rhMFG-E8 inhibits neuronal apoptosis and offers neuroprotection. This is suggested to occur through the modulation of the integrin-β3/FAK/PI3K/AKT signaling pathway, highlighting rhMFG-E8 as a potentially promising therapeutic strategy for TBI patients.

Baicalin provides neuroprotection in traumatic brain injury mice model through Akt/Nrf2 pathway

Background

The neuroprotective effects of Baicalin have been confirmed in several central nervous system (CNS) diseases. However, its possible effect on traumatic brain injury (TBI) model is still not clear. The present study is aimed to investigate the role and the underling mechanisms of 7-D-glucuronic acid-5,6-dihydroxyflavone (Baicalin) on TBI model.

Methods

The weight-drop model of TBI in Institute of Cancer Research mice was treated with Baicalin intraperitoneally at 30 minutes after TBI. LY294002 (LY) (a commonly used PI3K/Akt pathway inhibitor) was injected into the left ventricle at 30 minutes before TBI. All mice were euthanized at 24 hours after TBI to collect the brain tissue for a series of tests except for neurological function, which was measured at 2 hours and 1 and 3 days post-TBI.

Results

Baicalin administration significantly improved neurobehavioral function, alleviated brain edema, and reduced apoptosis-positive cells by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay accompanied with the upregulation of B-cell lymphoma 2 (Bcl-2) and downregulation of Bcl-2-associated X protein (Bax) and cleaved-caspase 3 by Western blot. Besides, TBI-induced oxidant stress status was also restored in the Baicalin group by measuring malondialdehyde (MDA) content, glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels in the injured brain cortex. Furthermore, translocation of Nrf2 to the nucleus was dramatically enhanced by Baicalin verified by immunofluorescence and Western blot analyses. Accordingly, its downstream antioxidative enzymes nicotinamide adenine dinucleotide phosphate:quinine oxidoreductase 1 (NQO-1) and heme oxygenase 1 (HO-1) were also activated by Baicalin confirmed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. However, cotreatment with Baicalin and LY could partly abolish Baicalin-induced activation of Nrf2 and its neuroprotective effects in TBI.

Conclusion

This study demonstrates that Baicalin provides a neuroprotective effect in TBI mice model via activating the Akt/Nrf2 pathway.

Pathophysiology and treatment of cerebral edema in traumatic brain injury

Cerebral edema (CE) and resultant intracranial hypertension are associated with unfavorable prognosis in traumatic brain injury (TBI). CE is a leading cause of in-hospital mortality, occurring in >60% of patients with mass lesions, and ∼15% of those with normal initial computed tomography scans. After treatment of mass lesions in severe TBI, an important focus of acute neurocritical care is evaluating and managing the secondary injury process of CE and resultant intracranial hypertension. This review focuses on a contemporary understanding of various pathophysiologic pathways contributing to CE, with a subsequent description of potential targeted therapies. There is a discussion of identified cellular/cytotoxic contributors to CE, as well as mechanisms that influence blood-brain-barrier (BBB) disruption/vasogenic edema, with the caveat that this distinction may be somewhat artificial since molecular processes contributing to these pathways are interrelated. While an exhaustive discussion of all pathways with putative contributions to CE is beyond the scope of this review, the roles of some key contributors are highlighted, and references are provided for further details. Potential future molecular targets for treating CE are presented based on pathophysiologic mechanisms. We thus aim to provide a translational synopsis of present and future strategies targeting CE after TBI in the context of a paradigm shift towards precision medicine. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".

Tetrahydrocurcumin ameliorates free fatty acid-induced hepatic steatosis and improves insulin resistance in HepG2 cells

Elevated levels of free fatty acids (FFAs) in the liver, resulting from either increased lipolysis or imbalanced FFAs flux, is a key pathogenic factor of hepatic steatosis. This study was conducted to examine the therapeutic effect of tetrahydrocurcumin (THC), a naturally occurring curcuminoid and a metabolite of curcumin, on oleic acid (OA)-induced steatosis in human hepatocellular carcinoma cells and to elucidate the underlying mechanism. HepG2 cells were incubated with OA to induce steatosis, and then treated with various concentrations of THC. The results showed that THC treatment significantly decreased lipid accumulation in OA-treated HepG2 cells, possibly, by inhibiting the expression of the lipogenic proteins, sterol regulatory element-binding protein 1 (SREBP-1c), peroxisome proliferator-activated receptor gamma (PPARγ), fatty acid synthase (FAS), and fatty acid-binding protein 4 (FABP4). Moreover, THC attenuated OA-induced hepatic lipogenesis in an adenosine monophosphate–activated protein kinase (AMPK)-dependent manner, which was reversed by pretreatment with an AMPK inhibitor. THC promoted lipolysis and upregulated the expression of genes involved in β-oxidation. Glucose uptake and insulin signaling impaired in HepG2 cells incubated with OA were abated by THC treatment, including phosphorylation of the insulin receptor substrate 1 (IRS-1)/phosphoinositide 3-kinase (PI3K)/Akt and downstream signaling pathways, forkhead box protein O1 (FOXO1) and glycogen synthase kinase 3 β (GSK3β), which are involved in gluconeogenesis and glycogen synthesis, respectively. Altogether, these results demonstrated the novel therapeutic benefit of THC against hepatic steatosis and, consequently, a potential treatment for non-alcoholic fatty liver disease (NAFLD).

Ketamine ameliorates oxidative stress-induced apoptosis in experimental traumatic brain injury via the Nrf2 pathway

Background

Ketamine can act as a multifunctional neuroprotective agent by inhibiting oxidative stress, cellular dysfunction, and apoptosis. Although it has been proven to be effective in various neurologic disorders, the mechanism of the treatment of traumatic brain injury (TBI) is not fully understood. The aim of this study was to investigate the neuroprotective function of ketamine in models of TBI and the potential role of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in this putative protective effect.

Materials and methods

Wild-type male mice were randomly assigned to five groups: Sham group, Sham + ketamine group, TBI group, TBI + vehicle group, and TBI + ketamine group. Marmarou’s weight drop model in mice was used to induce TBI, after which either ketamine or vehicle was administered via intraperitoneal injection. After 24 h, the brain samples were collected for analysis.

Results

Ketamine significantly ameliorated secondary brain injury induced by TBI, including neurological deficits, brain water content, and neuronal apoptosis. In addition, the levels of malondialdehyde (MDA), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were restored by the ketamine treatment. Western blotting and immunohistochemistry showed that ketamine significantly increased the level of Nrf2. Furthermore, administration of ketamine also induced the expression of Nrf2 pathway-related downstream factors, including hemeoxygenase-1 and quinine oxidoreductase-1, at the pre- and post-transcriptional levels.

Conclusion

Ketamine exhibits neuroprotective effects by attenuating oxidative stress and apoptosis after TBI. Therefore, ketamine could be an effective therapeutic agent for the treatment of TBI.

Sevoflurane post-conditioning attenuates traumatic brain injury-induced neuronal apoptosis by promoting autophagy via the PI3K/AKT signaling pathway

Background

Sevoflurane post-conditioning exerts nerve-protective effects through inhibiting caspase-dependent neuronal apoptosis after a traumatic brain injury (TBI). Autophagy that is induced by the endoplasmic reticulum stress plays an important role in the secondary neurological dysfunction after a TBI. However, the relationship between autophagy and caspase-dependent apoptosis as well as the underlying nerve protection mechanism that occurs with sevoflurane post-conditioning following a TBI remains unclear.

Methods

The Feeney TBI model was used to induce brain injury in rats. Evaluation of the modified neurological severity scores, measurement of brain water content, Nissl staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay were used to determine the neuroprotective effects of the sevoflurane post-conditioning. Both immunofluorescence and Western blot analyses were used to detect the expression of autophagy-related proteins microtubule-associated protein 1 light chain 3-II and Beclin-1, pro-apoptotic factors, as well as the activation of the phosphatidylinositide 3-kinase/protein kinase B (PI3K/AKT) signaling pathway within the lesioned cortex.

Results

Autophagy and neuronal apoptosis were activated in the lesioned cortex following the TBI. Sevoflurane post-conditioning enhanced early autophagy, suppressed neuronal apoptosis, and alleviated brain edema, which improved nerve function after a TBI (all P < 0.05). Sevoflurane post-conditioning induced the activation of PI3K/AKT signaling after the TBI (P < 0.05). The neuroprotective effects of sevoflurane post-conditioning were reversed through the autophagy inhibitor 3-methyladenine treatment.

Conclusion

Neuronal apoptosis and the activation of autophagy were involved in the secondary neurological injury following a TBI. Sevoflurane post-conditioning weakened the TBI-induced neuronal apoptosis by regulating autophagy via PI3K/AKT signaling.

Ganglioside GM1 protects against high altitude cerebral edema in rats by suppressing the oxidative stress and inflammatory response via the PI3K/AKT-Nrf2 pathway

High altitude cerebral edema (HACE) is a severe type of acute mountain sickness (AMS) that occurs in response to a high altitude hypobaric hypoxic (HH) environment. GM1 monosialoganglioside can alleviate brain injury under adverse conditions including amyloid-β-peptide, ischemia and trauma. However, its role in HACE-induced brain damage remains poorly elucidated. In this study, GM1 supplementation dose-dependently attenuated increase in rat brain water content (BWC) induced by hypobaric chamber (7600 m) exposurefor 24 h. Compared with the HH-treated group, rats injected with GM1 exhibited less brain vascular leakage, lower aquaporin-4 and higher occludin expression, but they also showed increase in Na+/K+-ATPase pump activities. Importantly, HH-incurred consciousness impairment and coordination loss also were ameliorated following GM1 administration. Furthermore, the increased oxidative stress and decrease in anti-oxidant stress system under the HH condition were also reversely abrogated by GM1 treatment via suppressing accumulation of ROS, MDA and elevating the levels of SOD and GSH. Simultaneously, GM1 administration also counteracted the enhanced inflammation in HH-exposed rats by muting pro-inflammatory cytokines IL-1β, TNF-α, and IL-6 levels in serum and brain tissues. Subsequently, GM1 potentiated the activation of the PI3K/AKT-Nrf2 pathway. Cessation of this pathway by LY294002 reversed GM1-mediated inhibitory effects on oxidative stress and inflammation, and ultimately abrogated the protective role of GM1 in abating brain edema, cognitive and motor dysfunction. Overall, GM1 may afford a protective intervention in HACE by suppressing oxidative stress and inflammatory response via activating the PI3K/AKT-Nrf2 pathway, implying a promising agent for the treatment of HACE.

ERK1/2/mTOR/Stat3 pathway-mediated autophagy alleviates traumatic brain injury-induced acute lung injury

Acute lung injury (ALI) is one of several complications in patients with traumatic brain injury (TBI). Autophagy is a primary homeostatic process that promotes cell survival under stress. Accumulating evidence implicates autophagy in the pathogenesis of ALI under various conditions. However, the role of autophagy in TBI-induced ALI remains unknown. The aim of this study was to adjust autophagy with pharmacological agents to determine its functional significance in TBI-induced ALI. Rats were preconditioned with autophagy promoter rapamycin or inhibitor 3-methyladenine before they were challenged with TBI. Extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor U0126, mechanistic target of rapamycin (mTOR) inhibitor rapamycin, and signal transducer and activator of transcription 3 (Stat3) inhibitor S31-201 were used to test the role of ERK1/2/mTOR/Stat3 signaling pathway in regulating autophagy. Autophagy is activated in lung tissues after TBI. Enhancement of autophagy suppressed apoptosis, inflammation and oxidative stress in lung tissues, which were activated after TBI, whereas inhibition of autophagy aggravated these critical pathological changes. Autophagy also improved TBI-induced impairment in pulmonary barrier function, oxygenation function and static compliance. Furthermore, TBI-induced autophagy was mediated by ERK1/2/mTOR/Stat3 pathway, which may serve to reduce ALI and improve pulmonary barrier function, oxygenation function and static compliance. These findings are important for the prevention and treatment of TBI-induced ALI.

Impaired autophagic flux is associated with the severity of trauma and the role of A2AR in brain cells after traumatic brain injury

Recent studies have shown that after traumatic brain injury (TBI), the number of autophagosomes is markedly increased in brain cells surrounding the wound; however, whether autophagy is enhanced or suppressed by TBI remains controversial. In our study, we used a controlled cortical impact system to establish models of mild, moderate and severe TBI. In the mild TBI model, the levels of autophagy-related protein 6 (Beclin1) and autophagy-related protein 12 (ATG12)-autophagy-related protein 5 (ATG5) conjugates were increased, indicating the enhanced initiation of autophagy. Furthermore, the level of the autophagic substrate sequestosome 1 (SQSTM1) was decreased in the ipsilateral cortex. This result, together with the results observed in tandem mRFP-GFP-LC3 adeno-associated virus (AAV)-infected mice, indicates that autophagosome clearance was also increased after mild TBI. Conversely, following moderate and severe TBI, there was no change in the initiation of autophagy, and autophagosome accumulation was observed. Next, we used chloroquine (CQ) to artificially impair autophagic flux in the injured cortex of the mild TBI model and found that the severity of trauma was obviously exacerbated. In addition, autophagic flux and trauma severity were significantly improved in adenosine A_2A receptor (A_2AR) knockout (KO) mice subjected to moderate TBI. Thus, A_2AR may be involved in regulating the impairment of autophagic flux in response to brain injury. Our findings suggest that whether autophagy is increased after TBI is associated with whether autophagic flux is impaired, and the impairment of autophagic flux exacerbates the severity of trauma. Furthermore, A_2AR may be a target for alleviating the impairment in autophagic flux after TBI.

RETRACTED: Dexmedetomidine exerts neuroprotective effect via the activation of the PI3K/Akt/mTOR signaling pathway in rats with traumatic brain injury

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 3A, 5C and 7A which appear to have a similar phenotype as many other publications, as detailed here: https://pubpeer.com/publications/7D9475A7397928053FFE9442F8E943; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Several additional suspected image duplication issues were also identified in Figures 3A, 5A, and 7A. The journal requested the corresponding authors comment on these concerns and provide the raw data. The authors were unable to provide a satisfactory explanation or the raw data. The Supervision Committee of the National Natural Science Foundation of China launched an investigation into several papers of Jiangsu Normal University, including this one, and found evidence of "Falsification of pictures or data, fabrication of research process, use of others' signatures without consent, and false information in project final reports", as detailed here: https://www.nsfc.gov.cn/publish/portal0/tab442/info85495.htm. The Academic Committee at Jiangsu Normal University requested retraction of the article. The Editor-in-Chief assessed the case and decided to retract the article.