Adenosine monophosphate-activated protein kinase modulation by berberine attenuates mitochondrial deficits and redox imbalance in experimental diabetic neuropathy

Advances of traditional Chinese medicine preclinical mechanisms and clinical studies on diabetic peripheral neuropathy

CONTEXT

Diabetic peripheral neuropathy (DPN) results in an enormous burden and reduces the quality of life for patients. Considering there is no specific drug for the management of DPN, traditional Chinese medicine (TCM) has increasingly drawn attention of clinicians and researchers around the world due to its characteristics of multiple targets, active components, and exemplary safety.

OBJECTIVE

To summarize the current status of TCM in the treatment of DPN and provide directions for novel drug development, the clinical effects and potential mechanisms of TCM used in treating DPN were comprehensively reviewed.

METHODS

Existing evidence on TCM interventions for DPN was screened from databases such as PubMed, the Cochrane Neuromuscular Disease Group Specialized Register (CENTRAL), and the Chinese National Knowledge Infrastructure Database (CNKI). The focus was on summarizing and analyzing representative preclinical and clinical TCM studies published before 2023.

RESULTS

This review identified the ameliorative effects of about 22 single herbal extracts, more than 30 herbal compound prescriptions, and four Chinese patent medicines on DPN in preclinical and clinical research. The latest advances in the mechanism highlight that TCM exerts its beneficial effects on DPN by inhibiting inflammation, oxidative stress and apoptosis, endoplasmic reticulum stress and improving mitochondrial function.

CONCLUSIONS

TCM has shown the power latent capacity in treating DPN. It is proposed that more large-scale and multi-center randomized controlled clinical trials and fundamental experiments should be conducted to further verify these findings.

Targeting autophagy with natural products as a potential therapeutic approach for diabetic microangiopathy

As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people's health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.

Berberine inhibits NLRP3 inflammasome activation and proinflammatory macrophage M1 polarization to accelerate peripheral nerve regeneration

Berberine (BBR) has demonstrated potent anti-inflammatory effects by modulating macrophage polarization. Nevertheless, the precise mechanisms through which berberine regulates post-injury inflammation within the peripheral nerve system remain elusive. This study seeks to elucidate the role of BBR and its underlying mechanisms in inflammation following peripheral nerve injury (PNI). Adult male C57BL/6J mice subjected to PNI were administered daily doses of berberine (0, 60, 120, 180, 240 ​mg/kg) via gavage from day 1 through day 28. Evaluation of the sciatic function index (SFI) and paw withdrawal threshold revealed that BBR dose-dependently enhanced both motor and sensory functions. Immunofluorescent staining for anti-myelin basic protein (anti-MBP) and anti-neurofilament-200 (anti-NF-200), along with histological staining comprising hematoxylin-eosin (HE), luxol fast blue (LFB), and Masson staining, demonstrated that BBR dose-dependently promoted structural regeneration. Molecular analyses including qRT-PCR, Western blotting, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence confirmed that inactivation of the NLRP3 inflammasome by MCC950 shifted macrophages from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, while also impeding macrophage infiltration. Furthermore, BBR significantly downregulated the expression of the NLRP3 inflammasome and its associated molecules in macrophages, thereby mitigating NLRP3 inflammasome activation-induced macrophage M1 polarization and inflammation. In summary, BBR's neuroprotective effects were concomitant with the suppression of inflammation after PNI, achieved through the inhibition of NLRP3 inflammasome activation-induced macrophage M1 polarization.

Research progress of traditional Chinese medicine monomer in treating diabetic peripheral neuropathy: A review

Diabetes peripheral neuropathy is one of the most common complications of diabetes. Early symptoms are insidious, while late symptoms mainly include numbness, pain, swelling, and loss of sensation in the limbs, which can lead to disability, foot ulcers, amputation, and so on. At present, the pathogenesis is also complex and diverse, and it is not yet clear. Western medicine treatment mainly focuses on controlling blood sugar and nourishing nerves, but the effect is not ideal. In recent years, it has been found that many drug monomers have shown good therapeutic and prognostic effects in the prevention and treatment of diabetes peripheral neuropathy, and related research has become a hot topic. To understand the specific mechanism of action of traditional Chinese medicine monomers in treatment, this article provides a review of their mechanism research and key roles. It mainly includes flavonoids, phenols, terpenes, saponins, alkaloids, polysaccharides, etc. By nuclear factor-κB (NF-κB), the signaling pathways of adenosine monophosphate-activated protein kinase (AMPK), Nrf2/ARE, SIRT1/p53, etc, can play a role in lowering blood sugar, antioxidant, anti-inflammatory, inhibiting cell apoptosis, and autophagy, promoting sciatic nerve regeneration, and have great potential in the prevention and treatment of this disease. A systematic summary of its related mechanisms of action was conducted, providing ideas for in-depth research and exploration of richer traditional Chinese medicine components, and also providing a relatively complete theoretical reference for clinical research on diabetes peripheral neuropathy treatment.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

Targeted metabolomics reveals the aberrant energy status in diabetic peripheral neuropathy and the neuroprotective mechanism of traditional Chinese medicine JinMaiTong

Diabetic peripheral neuropathy (DPN) is a common and devastating complication of diabetes, for which effective therapies are currently lacking. Disturbed energy status plays a crucial role in DPN pathogenesis. However, the integrated profile of energy metabolism, especially the central carbohydrate metabolism, remains unclear in DPN. Here, we developed a metabolomics approach by targeting 56 metabolites using high-performance ion chromatography-tandem mass spectrometry (HPIC-MS/MS) to illustrate the integrative characteristics of central carbohydrate metabolism in patients with DPN and streptozotocin-induced DPN rats. Furthermore, JinMaiTong (JMT), a traditional Chinese medicine (TCM) formula, was found to be effective for DPN, improving the peripheral neurological function and alleviating the neuropathology of DPN rats even after demyelination and axonal degeneration. JMT ameliorated DPN by regulating the aberrant energy balance and mitochondrial functions, including excessive glycolysis restoration, tricarboxylic acid cycle improvement, and increased adenosine triphosphate (ATP) generation. Bioenergetic profile was aberrant in cultured rat Schwann cells under high-glucose conditions, which was remarkably corrected by JMT treatment. In-vivo and in-vitro studies revealed that these effects of JMT were mainly attributed to the activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and downstream peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Our results expand the therapeutic framework for DPN and suggest the integrative modulation of energy metabolism using TCMs, such as JMT, as an effective strategy for its treatment.

Natural products as pharmacological modulators of mitochondrial dysfunctions for the treatment of diabetes and its complications: An update since 2010

Diabetes, characterized as a well-known chronic metabolic syndrome, with its associated complications pose a substantial and escalating health and healthcare challenge on a global scale. Current strategies addressing diabetes are mainly symptomatic and there are fewer available curative pharmaceuticals for diabetic complications. Thus, there is an urgent need to identify novel pharmacological targets and agents. The impaired mitochondria have been associated with the etiology of diabetes and its complications, and the intervention of mitochondrial dysfunction represents an attractive breakthrough point for the treatments of diabetes and its complications. Natural products (NPs), with multicenter characteristics, multi-pharmacological activities and lower toxicity, have been caught attentions as the modulators of mitochondrial functions in the therapeutical filed of diabetes and its complications. This review mainly summarizes the recent progresses on the potential of 39 NPs and 2 plant-extracted mixtures to improve mitochondrial dysfunction against diabetes and its complications. It is expected that this work may be useful to accelerate the development of innovative drugs originated from NPs and improve upcoming therapeutics in diabetes and its complications.

Diabetic Neuropathy: An Overview of Molecular Pathways and Protective Mechanisms of Phytobioactives

Diabetic neuropathy (DN) is a common and debilitating complication of diabetes mellitus that affects the peripheral nerves and causes pain, numbness, and impaired function. The pathogenesis of DN involves multiple molecular mechanisms, such as oxidative stress, inflammation, and pathways of advanced glycation end products, polyol, hexosamine, and protein kinase C. Phytochemicals are natural compounds derived from plants that have various biological activities and therapeutic potential. Flavonoids, terpenes, alkaloids, stilbenes, and tannins are some of the phytochemicals that have been identified as having protective potential for diabetic neuropathy. These compounds can modulate various cellular pathways involved in the development and progression of neuropathy, including reducing oxidative stress and inflammation and promoting nerve growth and repair. In this review, the current evidence on the effects of phytochemicals on DN by focusing on five major classes, flavonoids, terpenes, alkaloids, stilbenes, and tannins, are summarized. This compilation also discusses the possible molecular targets of numerous pathways of DN that these phytochemicals modulate. These phytochemicals may offer a promising alternative or complementary approach to conventional drugs for DN management by modulating multiple pathological pathways and restoring nerve function.

Preparation, characterization, and pharmacological application of oral Honokiol-loaded solid lipid nanoparticles for diabetic neuropathy

Honokiol is a phytochemical component with a variety of pharmacological properties. However, the major limitation of Honokiol is its poor solubility and low oral bioavailability. In this study, we formulated and characterized oral Honokiol-loaded solid lipid nanoparticles (SLNs) to enhance bioavailability and then evaluated their effectiveness in experimental diabetic neuropathy (DN). The finalized formulation has a spherical morphology, a particle size (PS) of 121.31 ± 9.051 nm, a polydispersity index (PDI) of 0.249 ± 0.002, a zeta potential (ZP) of -20.8 ± 2.72 mV, and an entrapment efficiency (% EE) of 88.66 ± 2.30 %. In-vitro release data shows, Honokiol-SLNs displayed a sustained release profile at pH (7.4). The oral bioavailability of Honokiol-SLNs was remarkably greater (8-fold) than Honokiol-Pure suspension. The neuroprotective property of Honokiol-SLNs was initially demonstrated against hydrogen peroxide H2O2-stimulated PC12 (pheochromocytoma) cells. Furthermore, results of in-vivo studies demonstrated that treatment with Honokiol-SLNs significantly (p < 0.001) suppressed oxidative stress by inhibition of nuclear factor kappa B (NF-κB) and significant (p < 0.001) upregulation of nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling in the spinal cord. The expression of transient receptor potential melastatin 8(TRPM8) and transient receptor potential vanilloid 1 (TRPV1) was significantly (p < 0.001) downregulated. Honokiol-SLNs inhibited apoptosis by significant (p < 0.001) downregulation of cleaved caspase-3 expression in the spinal cord. These findings demonstrate that Honokiol-SLNs providedbetter neuroprotection in DN because of higher oral bioavailability.

PGC1α: an emerging therapeutic target for chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN)-mediated paresthesias are a common complication in cancer patients undergoing chemotherapy. There are currently no treatments available to prevent or reverse CIPN. Therefore, new therapeutic targets are urgently needed to develop more effective analgesics. However, the pathogenesis of CIPN remains unclear, and the prevention and treatment strategies of CIPN are still unresolved issues in medicine. More and more studies have demonstrated that mitochondrial dysfunction has become a major factor in promoting the development and maintenance of CIPN, and peroxisome proliferator-activated receptor gamma (PPARγ) coactivator 1α (PGC1α) plays a significant role in maintaining the mitochondrial function, protecting peripheral nerves, and alleviating CIPN. In this review, we highlight the core role of PGC1α in regulating oxidative stress and maintaining normal mitochondrial function and summarize recent advances in its therapeutic effects and mechanisms in CIPN and other forms of peripheral neuropathy. Emerging studies suggest that PGC1α activation may positively impact CIPN mitigation by modulating oxidative stress, mitochondrial dysfunction, and inflammation. Therefore, novel therapeutic strategies targeting PGC1α could be a potential therapeutic target in CIPN.

Piceatannol promotes neuroprotection by inducing mitophagy and mitobiogenesis in the experimental diabetic peripheral neuropathy and hyperglycemia-induced neurotoxicity

Piceatannol (PCN), a SIRT1 activator, regulates multiple oxidative stress mechanism and has anti-inflammatory potential in various inflammatory conditions. However, its role in Diabetic insulted peripheral neuropathy (DN) remains unknown. Oxidative stress and mitochondrial dysfunction are major contributing factors to DN. Myriad studies have proven that sirtuin1 (SIRT1) stimulation convalesce nerve functions by activating mitochondrial functions like mitochondrial biogenesis and mitophagy. Diabetic neuropathy (DN) was provoked by injecting streptozotocin (STZ) at a dose of 55 mg/kg, i.p to male Sprague Dawley (SD) rats. Mechanical, thermal hyperalgesia was evaluated by using water immersion, Vonfrey Aesthesiometer, and Randall Sellito Calipers. Motor, sensory nerve conduction velocity was measured using Power Lab 4sp system whereas The Laser Doppler system was used to evaluate nerve blood flow. To induce hyperglycemia for the in vitro investigations, high glucose (HG) (30 mM) conditions were applied to Neuro2a cells. At doses of 5 and 10 µM, PCN was examined for its role in SIRT1 and Nrf2 activation. HG-induced N2A cells, reactive oxygen exposure, mitochondrial superoxides and mitochondrial membrane potentials were restored by PCN exposure, and their neurite outgrowth was enhanced. Peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis was induced by increased SIRT1 activation by piceatannol. SIRT1 activation also enhanced Nrf2-mediated antioxidant signalling. Our study results inferred that PCN administration can counteract the decline in mitochondrial function and antioxidant activity in diabetic rats and HG-exposed N2A cells by increasing the SIRT1 and Nrf2 activities.

The impact of oxidative stress-induced mitochondrial dysfunction on diabetic microvascular complications

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycaemia, with absolute insulin deficiency or insulin resistance as the main cause, and causes damage to various target organs including the heart, kidney and neurovascular. In terms of the pathological and physiological mechanisms of DM, oxidative stress is one of the main mechanisms leading to DM and is an important link between DM and its complications. Oxidative stress is a pathological phenomenon resulting from an imbalance between the production of free radicals and the scavenging of antioxidant systems. The main site of reactive oxygen species (ROS) production is the mitochondria, which are also the main organelles damaged. In a chronic high glucose environment, impaired electron transport chain within the mitochondria leads to the production of ROS, prompts increased proton leakage and altered mitochondrial membrane potential (MMP), which in turn releases cytochrome c (cyt-c), leading to apoptosis. This subsequently leads to a vicious cycle of impaired clearance by the body's antioxidant system, impaired transcription and protein synthesis of mitochondrial DNA (mtDNA), which is responsible for encoding mitochondrial proteins, and impaired DNA repair systems, contributing to mitochondrial dysfunction. This paper reviews the dysfunction of mitochondria in the environment of high glucose induced oxidative stress in the DM model, and looks forward to providing a new treatment plan for oxidative stress based on mitochondrial dysfunction.

Activation of SIRT1 by silibinin improved mitochondrial health and alleviated the oxidative damage in experimental diabetic neuropathy and high glucose-mediated neurotoxicity

BACKGROUND

Silibinin (SBN), a sirtuin 1 (SIRT1) activator, has been evaluated for its anti-inflammatory activity in many inflammatory diseases. However, its role in diabetes-induced peripheral neuropathy (DPN) remains unknown. The SIRT1 activation convalesces nerve functions by improving mitochondrial biogenesis and mitophagy.

METHODS

DPN was induced by streptozotocin (STZ) at a dose of 55 mg/kg, i.p. in the male SD rats whereas neurotoxicity was induced in Neuro2A cells by 30 mM (high glucose) glucose. Neurobehavioural (nerve conduction velocity and nerve blood flow) western blot, immunohistochemistry, and immunocytochemistry were performed to evaluate the protein expression and their cellular localisation.

RESULTS

Two-week SBN treatment improved neurobehavioural symptoms, SIRT1, PGC-1α, and TFAM expression in the sciatic nerve and HG insulted N2A cells. It has also maintained the mitophagy by up-regulating PARL, PINK1, PGAM5, LC3 level and provided antioxidant defence by upregulating Nrf2.

CONCLUSION

SBN has shown neuroprotective potential in DPN through SIRT1 activation and antioxidant mechanism.

PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose

BACKGROUND

Oxidative stress mediated by hyperglycemia damages cell-reparative processes such as mitophagy. Down-regulation of mitophagy is considered to be a susceptible factor for diabetes mellitus (DM) and its complications. However, the role of mitophagy in DM-associated periodontitis has not been fully elucidated. Apoptosis of human gingival epithelial cells (hGECs) is one of the representative events of DM-associated periodontitis. Thus, this study aimed to investigate PTEN-induced putative kinase 1 (PINK1)-mediated mitophagy activated in the process of high glucose (HG)-induced hGECs apoptosis.

METHODS

For dose-response studies, hGECs were incubated in different concentrations of glucose (5.5, 15, 25, and 50 mmol/L) for 48 h. Then, hGECs were challenged with 25 mmol/L glucose for 12 h and 48 h, respectively. Apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL), caspase 9 and mitochondrial membrane potential (MMP). Subsequently, autophagy was evaluated by estimating P62, LC3 II mRNA levels, LC3 fluorescent puncta and LC3-II/I ratio. Meanwhile, the involvement of PINK1-mediated mitophagy was assessed by qRT-PCR, western blotting and immunofluorescence. Finally, hGECs were transfected with shPINK1 and analyzed by MMP, caspase 9 and annexin V-FITC apoptosis.

RESULTS

The number of TUNEL-positive cells and caspase 9 protein were significantly increased in cells challenged with HG (25 mmol/L) for 48 h (HG 48 h). MMP was impaired both at HG 12 h and HG 48 h, but the degree of depolarization was more serious at HG 48 h. The autophagy improved as the amount of LC3 II increased and p62 decreased in HG 12 h. During this process, HG 12 h treatment induced PINK1-mediated mitophagy. PINK1 silencing with HG 12 h resulted in MMP depolarization and cell apoptosis.

CONCLUSIONS

These results suggested that loss of the PINK1 gene may cause mitochondrial dysfunction and increase sensitivity to HG-induced apoptosis of hGECs at the early stage. PINK1 mediated mitophagy attenuates early apoptosis of gingival epithelial cells induced by high glucose.

The role of AMPK-dependent pathways in cellular and molecular mechanisms of metformin: a new perspective for treatment and prevention of diseases

Metformin can suppress gluconeogenesis and reduce blood sugar by activating adenosine monophosphate-activated protein kinase (AMPK) and inducing small heterodimer partner (SHP) expression in the liver cells. The main mechanism of metformin’s action is related to its activation of the AMPK enzyme and regulation of the energy balance. AMPK is a heterothermic serine/threonine kinase made of a catalytic alpha subunit and two subunits of beta and a gamma regulator. This enzyme can measure the intracellular ratio of AMP/ATP. If this ratio is high, the amino acid threonine 172 available in its alpha chain would be activated by the phosphorylated liver kinase B1 (LKB1), leading to AMPK activation. Several studies have indicated that apart from its significant role in the reduction of blood glucose level, metformin activates the AMPK enzyme that in turn has various efficient impacts on the regulation of various processes, including controlling inflammatory conditions, altering the differentiation pathway of immune and non-immune cell pathways, and the amelioration of various cancers, liver diseases, inflammatory bowel disease (IBD), kidney diseases, neurological disorders, etc. Metformin’s activation of AMPK enables it to control inflammatory conditions, improve oxidative status, regulate the differentiation pathways of various cells, change the pathological process in various diseases, and finally have positive therapeutic effects on them. Due to the activation of AMPK and its role in regulating several subcellular signalling pathways, metformin can be effective in altering the cells’ proliferation and differentiation pathways and eventually in the prevention and treatment of certain diseases.

Renoprotective potential of myo-inositol on diabetic kidney disease: Focus on the role of the PINK1/Parkin pathway and mitophagy receptors

Recent studies have emphasized the role of mitochondria in renal function as well as in renal injury. Poor mitochondrial quality control mechanisms including mitochondrial fusion, fission and mitophagy are major contributors for progression of diabetic renal injury. The current study is aimed to evaluate the protective role of myo-inositol (MI) against diabetic nephropathy (DN) by utilizing high glucose exposed NRK 52E cell and streptozotocin (STZ) induced DN model. MI supplementation (at doses 37.5 and 75 mg/kg) ameliorated albuminuria and enhanced the renal function as indicated significant improvement in urinary creatinine and urea levels. On the other hand, the western blot analysis of both in vitro and in vivo studies has revealed poor mitophagy in renal cells which was reversed upon myo-inositol treatment. Apart from targeting the canonical PINK1/Parkin pathway, we also focused on the role mitophagy receptors prohibitin (PHB) and NIP3-like protein (NIX). A significant reduction in expression of NIX and PHB2 was observed in renal tissue of diabetic control rats and high glucose exposed NRK 52E cells. Myo-inositol treatment resulted in positive modulation of PINK1/Parkin pathway as well as PHB2 and NIX. Myo-inositol also enhanced the mitochondrial biogenesis in renal tissue of diabetic rat by upregulating Nrf2/SIRT1/PGC-1α axis. The current study thus underlines the renoprotective effect myo-inositol, upregulation of mitophagy proteins and mitochondrial biogenesis upon myo-inositol treatment.

Berberine Alleviate Cisplatin-Induced Peripheral Neuropathy by Modulating Inflammation Signal via TRPV1

Chemotherapy induced peripheral neuropathy (CIPN) is a severe neurodegenerative disorder caused by chemotherapy drugs. Berberine is a natural monomer compound of Coptis chinensis, which has anti-tumor effect and can improve neuropathy through anti-inflammatory mechanisms. Transient receptor potential vanilloid (TRPV1) can sense noxious thermal and chemical stimuli, which is an important target for the study of pathological pain. In both vivo and in vitro CIPN models, we found that berberine alleviated peripheral neuropathy associated with dorsal root ganglia inflammation induced by cisplatin. We confirmed that berberine mediated the neuroinflammatory reaction induced by cisplatin by inhibiting the overexpression of TRPV1 and NF-κB and activating the JNK/p38 MAPK pathways in early injury, which inhibited the expression of p-JNK and mediated the expression of p38 MAPK/ERK in late injury in vivo. Moreover, genetic deletion of TRPV1 significantly reduced the protective effects of berberine on mechanical and heat hyperalgesia in mice. In TRPV1 knockout mice, the expression of NF-κB increased in late stage, and berberine inhibited the overexpression of NF-κB and p-ERK in late injury. Our results support berberine can reverse neuropathic inflammatory pain response induced by cisplatin, TRPV1 may be involved in this process.

Research progress on the pharmacological effects of berberine targeting mitochondria

Berberine is a natural active ingredient extracted from the rhizome of Rhizoma Coptidis, which interacts with multiple intracellular targets and exhibits a wide range of pharmacological activities. Previous studies have preliminarily confirmed that the regulation of mitochondrial activity is related to various pharmacological actions of berberine, such as regulating blood sugar and lipid and inhibiting tumor progression. However, the mechanism of berberine's regulation of mitochondrial activity remains to be further studied. This paper summarizes the molecular mechanism of the mitochondrial quality control system and briefly reviews the targets of berberine in regulating mitochondrial activity. It is proposed that berberine mainly regulates glycolipid metabolism by regulating mitochondrial respiratory chain function, promotes tumor cell apoptosis by regulating mitochondrial apoptosis pathway, and protects cardiac function by promoting mitophagy to alleviate mitochondrial dysfunction. It reveals the mechanism of berberine's pharmacological effects from the perspective of mitochondria and provides a scientific basis for the application of berberine in the clinical treatment of diseases.

Neurobiological Opportunities in Diabetic Polyneuropathy

This review highlights a selection of potential translational directions for the treatment of diabetic polyneuropathy (DPN) currently irreversible and without approved interventions beyond pain management. The list does not include all diabetic targets that have been generated over several decades of research but focuses on newer work. The emphasis is firstly on approaches that support the viability and growth of peripheral neurons and their ability to withstand a barrage of diabetic alterations. We include a section describing Schwann cell targets and finally how mitochondrial damage has been a common element in discussing neuropathic damage. Most of the molecules and pathways described here have not yet reached clinical trials, but many trials have been negative to date. Nonetheless, these failures clear the pathway for new thoughts over reversing DPN.

Natural products as geroprotectors: An autophagy perspective

Over the past decade, significant attention has been given to repurposing Food and Drug Administration approved drugs to treat age-related diseases. In contrast, less consideration has been given to natural bioactive compounds. Consequently, there have been limited attempts to translate these compounds. Autophagy is a fundamental biological pathway linked to aging, and numerous strategies to enhance autophagy have been shown to extend lifespan. Interestingly, there are a number of natural products that are reported to modulate autophagy, and here we describe a number of them that activate autophagy through diverse molecular and cellular mechanisms. Among these, Urolithin A, Spermidine, Resveratrol, Fatty Acids and Phospholipids, Trehalose and Lithium are featured in detail. Finally, we outline possible strategies to optimise and increase the translatability of natural products, with the overall aim of delaying the ageing process and improving human healthspan.

Quercetin Attenuates Diabetic Peripheral Neuropathy by Correcting Mitochondrial Abnormality via Activation of AMPK/PGC-1α Pathway in vivo and in vitro

The AMPK/PGC-1α pathway-mediated mitochondrial dysfunction has been supposed to play a crucial role in pathogenesis of diabetic peripheral neuropathy (DPN). The present study investigated the neuroprotective potential of quercetin, a natural AMPK activator. Streptozotocin (STZ)-induced diabetic rats that developed DPN phenotype were orally administrated with quercetin (30 and 60 mg/kg per day) for 6 weeks. The morphologic changes in the sciatic nerves (SN), the pathological structure of neurons in dorsal root ganglion (DRG), and the expressions of myelin proteins were assessed. The ATP content and the mitochondrial ultrastructure were measured. Furthermore, key proteins in the AMPK/PGC-1α pathway were determined. As a result, quercetin administration at both doses improved the paw withdrawal threshold, nerve conduction velocity, and the pathologic changes in SN and DRG of DPN rats. The expressions of myelin basic protein and myelin protein zero were also increased by quercetin. The oxidative stress, decreased ATP generation, and morphological changes of mitochondria were corrected by quercetin. In vitro study found that quercetin treatment significantly decreased the high-glucose-induced generation of reactive oxygen species, as well as attenuated the mitochondrial morphologic injuries and oxidative DNA damages of RSC96 cells. Quercetin treatment promoted the expressions of phosphorylated AMPK, PGC-1α, SIRT1, NRF1, and TFAM under hyperglycemic state in vivo and in vitro. This study revealed that the neuroprotective effect of quercetin was mainly related to mitochondrial protection by activation of the AMPK/PGC-1α pathway for the first time and proved quercetin as a potential therapeutic agent in the management of diabetic neuropathy.

Carvacrol abates NLRP3 inflammasome activation by augmenting Keap1/Nrf-2/p62 directed autophagy and mitochondrial quality control in neuropathic pain

Objectives: We aimed to evaluate the effect of carvacrol (CRC), a phenolic monoterpene with high nutritional value on NLRP3 activation against chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain (NP) in rats and in lipopolysacharide (LPS) induced neuroinflammation in neuro2a (N2A) cells. Methods: NP was induced in male SD rats by performing CCI and CRC (30 and 60 mg/kg, p.o) was administered for 14 days. Behavioural and functional parameters were evaluated using standard procedures. Various molecular experimentations were conducted to evaluate the efficacy of CRC against CCI induced neuropathy and in LPS (1 μg/ml) primed and ATP (5 μM) treated N2A cells.Results: CCI resulted in marked development of hyperalgesia and allodynia. Further, CCI rats, LPS and ATP treated N2A cells showed enhanced expression of NLRP3, ASC, Caspase-1 and IL-1β. In addition, CCI rats exhibited diminished levels of Nrf-2 with an increase in Keap1 expression. Also, CCI animals manifested with compromised mitochondrial function along with decreased autophagy markers and enhanced p62 levels when compared to sham rats. However, CRC administration significantly ameliorated these changes suggesting NLRP3 inhibition by CRC may be attributed to activation of autophagy via Keap1/Nrf-2/p62 forward feedback loop and augmentation of mitochondrial quality control. Intriguingly, pretreatment of CRC (50 and 100 μM) to LPS and ATP treated N2A cells resulted in decreased colocalization of NLRP3 and ASC.Discussion: These findings revealed the neuroprotective potential of CRC against CCI induced NP and delineate the critical role of autophagy and mitochondrial quality control in NLRP3 regulation.

Neuroprotective effect of paeonol in streptozotocin-induced diabetes in rats

BACKGROUND

Diabetic neuropathy is one of the most common microvascular complication of diabetes. It is associated with neuronal dysfunction and pain. Paeonol is an important natural product reported for its antioxidant, anti-inflammatory and antidiabetic activities.

AIM

The present research was planned to study effect of paeonol in diabetic peripheral neuropathy in rats.

METHODS

Diabetes was induced in Sprague Dawley rats by using Streptozotocin (55 mg/kg, i.p.). After six weeks, diabetic animals were treated daily with paeonol at a dose of 50, 100 and 200 mg/kg for four weeks. At the end of the treatment, plasma glucose, mechanical allodynia, mechanical hyperalgesia, thermal hyperalgesia and nerve conduction velocities were recorded. Oxidative stress parameters were studied in sciatic nerve. Histopathology study of sciatic nerve, NF-κB and MCP-1 expression were also studied at the end of study.

KEY FINDINGS

Paeonol treatment significantly lowered the plasma glucose levels, mechanical allodynia, mechanical hyperalgesia and thermal hyperalgesia as compared to diabetic control group. Paeonol treatment also enhanced the motor and sensory nerve conduction velocity. Paeonol treated diabetic animals showed significant changes in oxidative stress parameters. Histopathology study indicated that paeonol treatment prevented the neuronal damage, lowered demyelination and leukocyte infiltration. NF-κB and MCP-1 expression was significantly decreased in sciatic nerve of diabetic animals treated with paeonol.

SIGNIFICANCE

Results of the present study indicate that paeonol may be considered as effective option for management of diabetic neuropathy.

Electroacupuncture Alleviates Diabetic Peripheral Neuropathy by Regulating Glycolipid-Related GLO/AGEs/RAGE Axis

Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes mellitus (DM) and affects over one-third of all patients. Neuropathic pain and nerve dysfunction induced by DM is related to the increase of advanced glycation end products (AGEs) produced by reactive dicarbonyl compounds in a hyperglycemia environment. AGEs induce the expression of pro-inflammatory cytokines via the main receptor (RAGE), which has been documented to play a crucial role in the pathogenesis of diabetic peripheral neuropathy. Electroacupuncture (EA) has been reported to have a positive effect on paralgesia caused by various diseases, but the mechanism is unclear. In this study, we used high-fat-fed low-dose streptozotocin-induced rats as a model of type 2 diabetes (T2DM). Persistent metabolic disorder led to mechanical and thermal hyperalgesia, as well as intraepidermal nerve fiber density reduction and nerve demyelination. EA improved neurological hyperalgesia, decreased the pro-inflammatory cytokines, reduced the generation of AGEs and RAGE, and regulated the glyoxalase system in the EA group. Taken together, our study suggested that EA plays a role in the treatment of T2DM-induced DPN, and is probably related to the regulation of metabolism and the secondary influence on the GLO/AGE/RAGE axis.

Berberine elevates mitochondrial membrane potential and decreases reactive oxygen species by inhibiting the Rho/ROCK pathway in rats with diabetic encephalopathy

OBJECTIVES

Diabetic encephalopathy (DE) is a serious complication of diabetes mainly occurring in the elderly patients. Berberine (BBR) is an isoquinoline alkaloids extracted from Coptis chinensis that is applied in the treatment of diabetes clinically. This study explored the possible mechanism of BBR in relieving DE.

METHODS

Wistar rats were injected with streptozotocin and fed a high fat diet to establish the model of DE. The model rats were treated with BBR. The body weight, blood glucose and insulin of rats were measured, and Morris water maze test was conducted to evaluate the learning and memory abilities. The pathological conditions of cortical tissues were detected. The cortical mitochondria membrane potential (MMP) and reactive oxygen species (ROS) were monitored. The expressions of Rho/ROCK pathway-related genes of rat cortex were detected. The changes of MMP and ROS were detected after the treatment of Rho/ROCK pathway activator.

RESULTS

The body weight of model rats changed little, and levels of blood glucose and insulin were increased. The spatial learning and memory abilities were impaired, with disordered cortical neurons, and obvious neurons apoptosis and glia proliferation. BBR alleviated cognitive dysfunction and pathological damage in rats with DE. BBR enhanced cortical MMP and suppressed ROS. BBR treatment inhibited the Rho/ROCK pathway. Activation of the Rho/ROCK pathway reversed the effects of BBR on MMP and ROS.

CONCLUSION

BBR elevated MMP and reduced ROS in rats with DE by inhibiting the Rho/ROCK pathway. This study may offer novel insights for the management of DE.

Huang Lian Jie Du Tang attenuates paraquat-induced mitophagy in human SH-SY5Y cells: A traditional decoction with a novel therapeutic potential in treating Parkinson's disease

Huang Lian Jie Du Tang (HLJDT) is a traditional Chinese medical decoction for heat-fire clearing and detoxication. Theoretically, the cause of Parkinson's disease (PD) has been attributed to the dysregulations of internal wind, phlegm, fire, and stasis. Thus, HLJDT has been used to treat PD. However, the molecular mechanism is unknown. Besides, paraquat (PQ) as an herbicide has been known to impair midbrain dopaminergic neurons, resemblance to the pathology of PD. Thus, the molecular mechanism of HLJDT in treating PD and PQ-induced in vitro PD model was investigated in this study. Primarily, the dose-response of PQ (0.1∼1 mM)-induced neurotoxicity for 24 h was performed in the human neuroblastoma SH-SY5Y cells. The LD₅₀ of PQ is around 0.3 mM and was applied throughout the following experiments. The neutral red assay was used to estimate cell viability. Co-transfection of the mitochondrial marker and proapoptotic factor genes were applied to measure the release of mitochondrial proapoptotic factors during PQ intoxication and HLJDT protection. The fluorescent dyes were used to detect mitochondrial membrane potential and free radical formation. Western blot and dot-blot analysis and immunocytochemistry were used to estimate the level of proteins related to apoptosis and mitophagy. PINK1 gene silencing was used to determine the significance of mitophagy during PQ intoxication. In this study, HLJDT attenuated PQ-induced apoptosis in SH-SY5Y cells. HLJDT reversed PQ-induced decreased mitochondrial membrane potential and suppressed PQ-induced increased cytosolic and mitochondrial free radical formations and mitochondrial proapoptotic factor releases. Furthermore, HLJDT mitigated PQ-induced increases in full-length PINK1, phosphorylations of Parkin and ubiquitin, mitochondrial translocation of phosphorylated Parkin, and mitophagy. PINK1 gene silencing attenuated PQ-induced neurotoxicity. Therefore, HLJDT attenuated PQ-induced cell death by regulating mitophagy.

Chronic hyperglycemia impairs mitochondrial unfolded protein response and precipitates proteotoxicity in experimental diabetic neuropathy: focus on LonP1 mediated mitochondrial regulation

BACKGROUND

Disturbed mitochondrial homeostasis has been identified to contribute to the pathogenesis of diabetic neuropathy (DN). However, the role of Mitochondrial Lon peptidase 1 (Lonp1) and Heat shock proteins (HSP's) in DN remains elusive. Here we studied the role of these proteins in experimental DN.

METHODS

Rats were injected with STZ (55 mg/kg, ip) to induce diabetes. After confirmation of diabetes, animals were maintained for 8 weeks to develop neuropathy. Resveratrol was administered at two dose levels 10 and 20 mg/kg for last 2 weeks. Neuronal PC12 cells was challenged with 30 mM of β-D glucose to evaluate the molecular changes.

RESULTS

Diabetic rats showed reduced expression of various mitochondrial proteases in dorsal root ganglions (DRG). This effect may increase proteotoxicity and diminish electron transport chain (ETC) activity as evident by increased protein oxidation and reduced ETC complexes activities under diabetic condition. In particular, we focused on our efforts to characterize the expression pattern of Lonp1 which was found to be significantly (p < 0.01 vs. control group) under expressed in DRG of diabetic rats. We used Resveratrol to characterize the importance of Lonp1 in regulation of mitochondrial function. High glucose (HG) (30 mM) exposed PC12 cells suggested that Resveratrol treatment attenuated the HG induced mitochondrial damage via induction of mitochondrial proteases. Moreover, siRNA directed against Lonp1 has impaired the activity of Resveratrol in attenuating the HG induced mitochondrial dysfunction.

CONCLUSION

These results would signify the importance of modulating mitochondrial proteases for the therapeutic management of DN.

AMPK in microvascular complications of diabetes and the beneficial effects of AMPK activators from plants

BACKGROUND

Diabetes mellitus is a multifactorial disorder with the risk of micro- and macro-vascular complications. High glucose-induced derangements in metabolic pathways are primarily associated with the initiation and progression of secondary complications namely, diabetic nephropathy, neuropathy, and retinopathy. Adenosine monophosphate-activated protein kinase (AMPK) has emerged as an attractive therapeutic target to treat various metabolic disorders including diabetes mellitus. It is a master metabolic regulator that helps in maintaining cellular energy homeostasis by promoting ATP-generating catabolic pathways and inhibiting ATP-consuming anabolic pathways. Numerous pharmacological and plant-derived bioactive compounds that increase AMP-activated protein kinase activation has shown beneficial effects by mitigating secondary complications namely retinopathy, nephropathy, and neuropathy.

PURPOSE

The purpose of this review is to highlight current knowledge on the role of AMPK and its activators from plant origin in diabetic microvascular complications.

METHODS

Search engines such as Google Scholar, PubMed, Science Direct and Web of Science are used to extract papers using relevant key words. Papers mainly focusing on the role of AMPK and AMPK activators from plant origin in diabetic nephropathy, retinopathy, and neuropathy was chosen to be highlighted.

RESULTS

According to results, decrease in AMPK activation during diabetes play a causative role in the pathogenesis of diabetic microvascular complications. Some of the plant-derived bioactive compounds were beneficial in restoring AMPK activity and ameliorating diabetic microvascular complications.

CONCLUSION

AMPK activators from plant origin are beneficial in mitigating diabetic microvascular complications. These pieces of evidence will be helpful in the development of AMPK-centric therapies to mitigate diabetic microvascular complications.

Berberine Ameliorates Subarachnoid Hemorrhage Injury via Induction of Sirtuin 1 and Inhibiting HMGB1/Nf-κB Pathway

Excessive cerebral inflammation plays a key role in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Berberine, an isoquinoline alkaloid isolated from Chinese herb Coptis chinensis, possesses anti-inflammatory, and neuroprotective effects. Here we evaluated the beneficial effects of berberine against SAH-induced inflammatory response and the subsequent brain injury. Our data showed that berberine treatment significantly inhibited microglia activation and proinflammatory cytokines release. Concomitant with suppressed cerebral inflammation, berberine mitigated the subsequent brain injury as demonstrated by improved neurological behavior, reduced brain edema, and decreased neural apoptosis. Moreover, berberine significantly inhibited high mobile group box 1 (HMGB1)/nuclear factor-κB (Nf-κB)-dependent pathway and enhanced sirtuin 1 (SIRT1) expression after SAH. Treatment with ex527, a selective SIRT1 inhibitor, reversed berberine-induced SIRT1 activation and inhibitory effects on HMGB1/Nf-κB activation. In addition, ex527 pretreatment abated the anti-inflammatory and neuroprotective effects of berberine on SAH. Taken together, these findings suggest that berberine provides beneficial effects against SAH-triggered cerebral inflammation by inhibiting HMGB1/Nf-κB pathway, which may be modulated by SIRT1 activation.

Mitochondrial biogenesis: An update

In response to the energy demand triggered by developmental signals and environmental stressors, the cells launch the mitochondrial biogenesis process. This is a self‐renewal route, by which new mitochondria are generated from the ones already existing. Recently, considerable progress has been made in deciphering mitochondrial biogenesis‐related proteins and genes that function in health and in pathology‐related circumstances. However, an outlook on the intracellular mechanisms shared by the main players that drive mitochondrial biogenesis machinery is still missing. Here, we provide such a view by focusing on the following issues: (a) the role of mitochondrial biogenesis in homeostasis of the mitochondrial mass and function, (b) the signalling pathways beyond the induction/promotion, stimulation and inhibition of mitochondrial biogenesis and (c) the therapeutic applications aiming the repair and regeneration of defective mitochondrial biogenesis (in ageing, metabolic diseases, neurodegeneration and cancer). The review is concluded by the perspectives of mitochondrial medicine and research.

The onset speed of hyperglycemia is important to the development of neuropathic hyperalgesia in streptozotocin-induced diabetic rats

Diabetic neuropathic hyperalgesia is one of the most common diabetes complications. The physiopathological mechanism of hyperalgesia and the reason by which this condition affects only part of the diabetic patients still unclear. We tested whether an adaptation of primary afferent neurons to hyperglycemia could prevent the development of hyperalgesia. Hyperglycemia was induced in male Wistar rats by a daily administration of a low dose of streptozotocin (STZ), during five consecutive days. Glycemia and mechanical nociceptive thresholds were measured at days 0, 3, 7 and 14 after starting the streptozotocin treatment. In parallel, dorsal root ganglia (DRG) neurons were collected from healthy male Wistar rats and cultured in different glucose concentrations (mimicking slow or fast increase of hyperglycemia), and used for calcium imaging and Western blot analyses. Rats with a slow increase of glycemia did not develop hyperalgesia, while rats with a fast increase of glycemia developed hyperalgesia. DRG neurons suddenly incubated in DMEM containing a high glucose concentration showed a significant increase of calcium influx. However, DRG neurons incubated in DMEM and receiving increasing doses of glucose had the same calcium influx observed in control neurons. The activation of AMPK (α1/α2) was greater in L5-L6 DRG of hyperglycemic and non-hyperalgesic rats, when compared with hyperglycemic and hyperalgesic rats. Our data suggest that the onset speed of hyperglycemia could be related to the development of diabetic neuropathic hyperalgesia, as a maladaptive consequence associated with low activation of AMPK (α1/α2) in peripheral nociceptive neurons when the glycemia suddenly increases.

A Metabolic Insight Into the Neuroprotective Effect of Jin-Mai-Tong (JMT) Decoction on Diabetic Rats With Peripheral Neuropathy Using Untargeted Metabolomics Strategy

Jin-Mai-Tong (JMT) decoction is a traditional Chinese compound prescription for treating diabetic peripheral neuropathy (DPN). The aim of this study is to investigate the neuroprotective effect of JMT decoction on diabetic rats with peripheral neuropathy and to elucidate the potential mechanism based on a metabolomics approach. Sprague-Dawley (SD) rats were randomly divided into four groups: control group, Streptozotocin (STZ) induced model group, JMT low dose (JMT-L) treated group and JMT high dose (JMT-H) treated group. After 12 weeks of treatment, behavioral changes, small fiber loss, and histopathological damages of sciatic nerves were estimated. Serum samples were collected for untargeted metabolomics analysis based on UPLC/QTOF-MS and multivariate statistics. As a result, JMT treatment at two dosages (13.9 and 27.8 g/kg⋅d) evidently improved the mechanical pain threshold (P < 0.05), increased the intraepidermal nerve fiber density (IENFD) and subepidermal nerve fiber density (SNFD) (P < 0.05), and renovated the demyelination and axonal atrophy of sciatic nerves on DPN rats. Furthermore, metabolomics study revealed that the serum metabolic profiles altered significantly among the control group and the STZ-induced model group. A total of 21 metabolites were identified as potential biomarkers related to the therapeutic effect of JMT decoction. Among them, 16 biomarkers were found in both JMT-H and JMT-L treated groups, while the five others were specific to JMT-H group. These metabolites mainly involved in lipid metabolism, tricarboxylic acid (TCA) cycle, amino acid metabolism, and so on. Besides, correlation analysis indicated that both mechanical pain threshold and distal nerve fiber density were negatively correlated with the serum levels of metabolites from lipid metabolism and TCA cycle. In conclusion, the results demonstrated that JMT decoction has an obvious protective effect against DPN, which could be mediated via ameliorating the metabolic disorders in diabetic rats with peripheral neuropathy.

Berberine for prevention of dementia associated with diabetes and its comorbidities: A systematic review

BACKGROUND

A growing number of epidemiological studies indicate that metabolic syndrome (MetS) and its associated features play a key role in the development of certain degenerative brain disorders, including Alzheimer's disease and vascular dementia. Produced by several different medicinal plants, berberine is a bioactive alkaloid with a wide range of pharmacological effects, including antidiabetic effects. However, it is not clear whether berberine could prevent the development of dementia in association with diabetes.

OBJECTIVE

To give an overview of the therapeutic potential of berberine as a treatment for dementia associated with diabetes.

SEARCH STRATEGY

Database searches A and B were conducted using PubMed and ScienceDirect. In search A, studies on berberine's antidementia activities were identified using "berberine" and "dementia" as search terms. In search B, recent studies on berberine's effects on diabetes were surveyed using "berberine" and "diabetes" as search terms.

INCLUSION CRITERIA

Clinical and preclinical studies that investigated berberine's effects associated with MetS and cognitive dysfunction were included.

DATA EXTRACTION AND ANALYSIS

Data from studies were extracted by one author, and checked by a second; quality assessments were performed independently by two authors.

RESULTS

In search A, 61 articles were identified, and 22 original research articles were selected. In search B, 458 articles were identified, of which 101 were deemed relevant and selected. Three duplicates were removed, and a total of 120 articles were reviewed for this study. The results demonstrate that berberine exerts beneficial effects directly in the brain: enhancing cholinergic neurotransmission, improving cerebral blood flow, protecting neurons from inflammation, limiting hyperphosphorylation of tau and facilitating β-amyloid peptide clearance. In addition, evidence is growing that berberine is effective against diabetes and associated disorders, such as atherosclerosis, cardiomyopathy, hypertension, hepatic steatosis, diabetic nephropathy, gut dysbiosis, retinopathy and neuropathy, suggesting indirect benefits for the prevention of dementia.

CONCLUSION

Berberine could impede the development of dementia via multiple mechanisms: preventing brain damages and enhancing cognition directly in the brain, and indirectly through alleviating risk factors such as metabolic dysfunction, and cardiovascular, kidney and liver diseases. This study provided evidence to support the value of berberine in the prevention of dementia associated with MetS.

Proteomic profiling of the neurons in mice with depressive-like behavior induced by corticosterone and the regulation of berberine: pivotal sites of oxidative phosphorylation

Chronic corticosterone (CORT) stress is an anxiety and depression inducing factor that involves the dysfunction of glucocorticoid receptor (GR), brain-derived neurotrophic factor (BDNF), and neuronal plasticity. However, the regulation of proteomic profiles in neurons suffering CORT stress is remaining elusive. Thus, the proteomic profiles of mouse neuronal C17.2 stem cells were comprehensively investigated by TMT (tandem mass tag)-labeling quantitative proteomics. The quantitative proteomics conjugated gene ontology analysis revealed the inhibitory effect of CORT on the expression of mitochondrial oxidative phosphorylation-related proteins, which can be antagonized by berberine (BBR) treatment. In addition, animal studies showed that changes in mitochondria by CORT can affect neuropsychiatric activities and disturb the physiological functions of neurons via disordering mitochondrial oxidative phosphorylation. Thus, the mitochondrial energy metabolism can be considered as one of the major mechanism underlying CORT-mediated depression. Since CORT is important for depression after traumatic stress disorder, our study will shed light on the prevention and treatment of depression as well as posttraumatic stress disorder (PTSD).

Berberine attenuated the cytotoxicity induced by t-BHP via inhibiting oxidative stress and mitochondria dysfunction in PC-12 cells

Neurodegenerative diseases all share several common features such as involvement of oxidative damage and mitochondrial dysfunction in pathogenesis. Oxidative stress induced by overproduction of mitochondrial reactive oxygen species (ROS) or impairment of the antioxidant deficiency results in mitochondrial dysfunction and initiation of the cell death cascade. Berberine (BBR), a traditional Chinese medicine, has been reported to exert anti-oxidative stress and anti-apoptosis effect in CNS diseases. However, the mechanism of BBR on regulating mitophagy and protecting mitochondrial function under oxidative stress remains unclear. In present study, we evaluated the beneficial effects of BBR on the tert-butyl hydroperoxide (t-BHP)-induced cytotoxicity. Furthermore, we explored the protective role of BBR in mitochondrial function and mitophagy under oxidative stress in PC-12 cells. Our results demonstrated that BBR effectively inhibited t-BHP-induced apoptosis which is associated with the decreased leakage of lactate dehydrogenase (LDH) and ROS overproduction. Moreover, BBR significantly suppressed cytochrome c expression, upregulated the ratio of Bcl-2/Bax, and ameliorated mitochondrial dysfunction by optimizing mitochondria membrane potential (ΔΨm) status and ATP production. In addition, BBR reduced the expression of autophagy-specific marker LC3, SQTM1/p62, and maintained lysosome normal function which involved the restoration of upstream signaling pathway AKT and mTOR phosphorylation level. Collectively, these findings suggested that BBR protects PC-12 cells from oxidative injury through inhibiting ROS level, mitochondria dysfunction, and mitophagy via PI3K/AKT/mTOR signaling pathways, which suggest a potential therapeutic strategy for oxidative stress and neurotoxic damages.

Therapeutic and biological activities of berberine: The involvement of Nrf2 signaling pathway

Since the beginning of the 21st century, studies have focused on developing drugs from naturally occurring compounds. Berberine (Brb) as a plant-derived compound is of interest. It is an isoquinone alkaloid which is derived from Berberis aristata, Berberis aquifolium and Berberis vulgaris. This plant-derived compound has a variety of pharmacological effects such as antioxidant, anti-inflammatory, antidiabetic, antidiarrheal, antitumor, antimicrobial, and anti-inflammatory. Various studies have demonstrated the therapeutic and biological activities of Brb, but there is a lack of a precise review to manifest the signaling pathway of action of Brb. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a highly conserved pathway which mainly involves in preservation of redox balance. At the present review, we describe the therapeutic and biological activities of Brb as well as the relevant mechanisms specially focused on the Nrf2 signaling pathway.

Pharmacological interventions targeting Wnt/β-catenin signaling pathway attenuate paclitaxel-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a disabling pain condition which occurs as a consequence of cancer chemotherapy with anti-cancer agents like paclitaxel, oxaliplatin, etc. Despite immense research in the pathological pathways involved in CIPN, treatment options still remain limited. Recently, pathological involvement of Wnt signaling has been investigated in various neuropathic pain models, however there are no reports as yet on the role of Wnt signaling in CIPN. In the present study, we have investigated the neuroprotective effects of Wnt signaling inhibitors namely LGK974 (Porcupine inhibitor), NSC668036 (Disheveled inhibitor) and PNU76454 (β-catenin inhibitor) in paclitaxel-induced neuropathic pain. Paclitaxel (2 mg/kg, i. p.) was administered to male Sprague Dawley rats on four alternate days. After 21 days, paclitaxel-treated rats showed reduced behavioral pain thresholds (cold allodynia, heat & mechanical hyperalgesia) and nerve functions (nerve conduction velocity and nerve blood flow). Moreover, Wnt signaling proteins (Wnt3a, β-catenin, c-myc and Dvl1), inflammatory marker (matrix metalloproteinase 2) and endoplasmic reticulum stress marker (GRP78) were found to be upregulated in the sciatic nerves of paclitaxel-treated rats accompanied with loss of intraepidermal nerve fiber density as compared to the control rats. Intrathecal administration of Wnt inhibitors (each at dose of 10 and 30 μM) for three consecutive days to paclitaxel-treated rats, significantly improved behavioral pain thresholds and nerve functional parameters by inhibition of Wnt signaling, inflammation, endoplasmic reticulum stress and improvement of intraepidermal nerve fiber density. All these results suggested the neuroprotective potential of Wnt signaling inhibitors in CIPN.

Berberine as a potential autophagy modulator

Today, pharmacognosy is considered a valuable science in the prevention and treatment of diseases. Among herbals, Berberine is an isoquinoline alkaloid found in the Berberis species. Surprisingly, it shows antimicrobial, antiviral, antidiarrheal, antipyretic, and anti-inflammatory potential. Furthermore, it diminishes drug resistance in cancer therapy and enhances tumor suppression in part through autophagy and cell cycle arrest mechanisms. In the present review, we discuss the effect of berberine on diverse cellular pathways and describe how berberine acts as an autophagy modulator to adjust physiologic and pathologic conditions and diminishes drug resistance in cancer therapy.

Ameliorative Effect of Berberine on Neonatally Induced Type 2 Diabetic Neuropathy via Modulation of BDNF, IGF-1, PPAR-γ, and AMPK Expressions

Neonatal-streptozotocin (n-STZ)-induced diabetes mimics most of the clinicopathological symptoms of type 2 diabetes mellitus (T2DM) peripheral neuropathy. Berberine, a plant alkaloid, is reported to have antidiabetic, antioxidant, anti-inflammatory, and neuroprotective potential. The aim of the present study was to investigate the potential of berberine against n-STZ-induced painful diabetic peripheral polyneuropathy by assessing various biochemical, electrophysiological, morphological, and ultrastructural studies. Type 2 diabetes mellitus was produced neonatal at the age of 2 days (10-12 g) by STZ (90 mg/kg intraperitoneal). After confirmation of neuropathy at 6 weeks, rats were treated with berberine (10, 20, and 40 mg/kg). Administration of n-STZ resulted in T2DM-induced neuropathic pain reflected by a significant alterations (P < .05) in hyperalgesia, allodynia, and motor as well as sensory nerve conduction velocities whereas berberine (20 and 40 mg/kg) treatment significantly attenuated (P < .05) these alterations. Berberine treatment significantly inhibited (P < .05) STZ-induced alterations in aldose reductase, glycated hemoglobin, serum insulin, hepatic cholesterol, and triglyceride levels. The elevated oxido-nitrosative stress and decreased Na-K-ATPase and pulse Ox levels were significantly attenuated (P < .05) by berberine. It also significantly downregulated (P < .05) neural tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 messenger RNA (mRNA), and protein expressions both. Streptozotocin-induced downregulated mRNA expressions of brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF-1), and peroxisome proliferator-activated receptors-γ (PPAR-γ) in sciatic nerve were significantly upregulated (P < .05) by berberine. Western blot analysis revealed that STZ-induced alterations in adenosine monophosphate protein kinase (AMPK; Thr-172) and protein phosphatase 2C-α protein expressions in dorsal root ganglia were inhibited by berberine. It also attenuated histological and ultrastructural alterations induced in sciatic nerve by STZ. In conclusion, berberine exerts its neuroprotective effect against n-STZ-induced diabetic peripheral neuropathy via modulation of pro-inflammatory cytokines (TNF α, IL-1β, and IL-6), oxido-nitrosative stress, BDNF, IGF-1, PPAR-γ, and AMPK expression to ameliorate impaired allodynia, hyperalgesia, and nerve conduction velocity during T2DM.

Pharmacologic Inhibition of Porcupine, Disheveled, and β-Catenin in Wnt Signaling Pathway Ameliorates Diabetic Peripheral Neuropathy in Rats

Wnt signaling pathway has been investigated extensively for its diverse metabolic and pain-modulating mechanisms; recently its involvement has been postulated in the development of neuropathic pain. However, there are no reports as yet on the involvement of Wnt signaling pathway in one of the most debilitating neurovascular complication of diabetes, namely, diabetic peripheral neuropathy (DPN). Thus, in the present study, involvement of Wnt signaling was investigated in DPN using Wnt signaling inhibitors namely LGK974 (porcupine inhibitor), NSC668036 (disheveled inhibitor), and PNU74654 (β-catenin inhibitor). Diabetes was induced by a single intraperitoneal injection of streptozotocin (50 mg/kg) to male Sprague-Dawley rats. Diabetic rats after 6 weeks of diabetes induction showed increased expression of Wnt signaling proteins in the spinal cord (L4-L6 lumbar segment), dorsal root ganglions and sciatic nerves. Subsequent increase in inflammation, endoplasmic reticulum stress and loss of intraepidermal nerve fiber density was also observed, leading to neurobehavioral and nerve functional deficits in diabetic rats. Intrathecal administration of Wnt signaling inhibitors (each at doses of 10 and 30 µmol/L) in diabetic rats showed improvement in pain-associated behaviors (heat, cold, and mechanical hyperalgesia) and nerve functions (motor, sensory nerve conduction velocities, and nerve blood flow) by decreasing the expression of Wnt pathway proteins, inflammatory marker, matrix metalloproteinase 2, endoplasmic reticulum stress marker, glucose-regulated protein 78, and improving intraepidermal nerve fiber density. All these results signify the neuroprotective potential of Wnt signaling inhibitors in DPN. PERSPECTIVE: This study emphasizes the involvement of Wnt signaling pathway in DPN. Blockade of this pathway using Wnt inhibitors provided neuroprotection in experimental DPN in rats. This study may provide a basis for exploring the therapeutic potential of Wnt inhibitors in DPN patients.

Berberine Ameliorates High Glucose-Induced Cardiomyocyte Injury via AMPK Signaling Activation to Stimulate Mitochondrial Biogenesis and Restore Autophagic Flux

Background: Type II diabetes (T2D)-induced cardiomyocyte hypertrophy is closely linked to the impairment of mitochondrial function. Berberine has been shown to be a promising effect for hypoglycemia in T2D models. High glucose-induced cardiomyocyte hypertrophy in vitro has been reported. The present study investigated the protective effect and the underlying mechanism of berberine on high glucose-induced H9C2 cell line.

Methods: High glucose-induced H9C2 cell line was used to mimic the hyperglycemia resulting in cardiomyocyte hypertrophy. Berberine was used to rescue in this model and explore the mechanism in it. Confocal microscopy, immunofluorescence, RT-PCR, and western blot analysis were performed to evaluate the protective effects of berberine in high glucose-induced H9C2 cell line.

Results: Berberine dramatically alleviated hypertrophy of H9C2 cell line and significantly ameliorated mitochondrial function by rectifying the imbalance of fusion and fission in mitochondrial dynamics. Furthermore, berberine further promoted mitogenesis and cleared the damaged mitochondria via mitophagy. In addition, berberine also restored autophagic flux in high glucose-induced cardiomyocyte injury via AMPK signaling pathway activation.

Conclusion: Berberine ameliorates high glucose-induced cardiomyocyte injury via AMPK signaling pathway activation to stimulate mitochondrial biogenesis and restore autophagicflux in H9C2 cell line.

Cellular stress response mechanisms of Rhizoma coptidis: a systematic review

Rhizoma coptidis has been used in China for thousands of years with the functions of heating dampness and purging fire detoxification. But the underlying molecular mechanisms of Rhizoma coptidis are still far from being fully elucidated. Alkaloids, especially berberine, coptisine and palmatine, are responsible for multiple pharmacological effects of Rhizoma coptidis. In this review, we studied on the effects and molecular mechanisms of Rhizoma coptidis on NF-κB/MAPK/PI3K–Akt/AMPK/ERS and oxidative stress pathways. Then we summarized the mechanisms of these alkaloid components of Rhizoma coptidis on cardiovascular and cerebrovascular diseases, diabetes and diabetic complications. Evidence presented in this review implicated that Rhizoma coptidis exerted beneficial effects on various diseases by regulation of NF-κB/MAPK/PI3K–Akt/AMPK/ERS and oxidative stress pathways, which support the clinical application of Rhizoma coptidis and offer references for future researches.