Botanical Drug Puerarin Attenuates 6-Hydroxydopamine (6-OHDA)-Induced Neurotoxicity via Upregulating Mitochondrial Enzyme Arginase-2

Integrating metabolomics and network pharmacology analysis to explore mechanism of Pueraria lobata against pulmonary fibrosis: Involvement of arginine metabolism pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Pueraria lobata (Willd.) Ohwi is a typical medicinal and edible plant with a long application history in China and Southeast Asia. As a widely used traditional medicine, P. lobata exhibits the properties of anti-inflammatory, antipyretic, antioxidant, relieving cough and asthma. Particularly, the increasing evidence indicates that the P. lobata has the therapeutic effect on fibrotic-related diseases in terms of metabolic regulation. However, the mechanisms of P. lobata on pulmonary fibrosis (PF) has not been thoroughly explored.

AIM OF THE STUDY

This study aimed to explore the effect of arginine metabolites of P. lobata against PF model by integrating metabolomics and network pharmacology analysis. It might provide a new idea for the target finding of P. lobata anti-pulmonary fibrosis.

MATERIALS AND METHODS

In this study, the Sprague Dawley (SD) rats were randomly divided into five experimental groups: saline-treated control group, bleomycin-induced fibrosis group, prednisolone acetate group, P. lobata 3.2 g/kg group and P. lobata 6.4 g/kg group. The therapeutic effect of P. lobata on bleomycin-induced PF in rats was evaluated by clinical symptoms such as lung function, body weight, hematoxylin eosin staining (HE), Masson staining and hydroxyproline assay. Next, the plasma metabolomics analysis was carried out by LC-MS to explore the pathological differences between the group of control, PF and P. lobata-treated rats. Then, the network pharmacology study coupled with experimental validation was conducted to analysis the results of metabolic research. We constructed the "component-target-disease" network of P. lobata in the treatment of PF. In addition, the molecular docking method was used to verify the interaction between potential active ingredients and core targets of P. lobata. Finally, we tested NOS2 and L-OT in arginine-related metabolic pathway in plasma of the rats by enzyme-linked immunosorbent assay (ELISA). Real-time PCR was performed to observe the level of TNF-α mRNA and MMP9 mRNA. And we tested the expression of TNF-α and MMP9 by Western blot analysis.

RESULTS

Our findings revealed that P. lobata improved lung function and ameliorated the pathological symptoms, such as pathological damage, collagen deposition, and body weight loss in PF rats. Otherwise, the plasma metabolomics were employed to screen the differential metabolites of amino acids, lipids, flavonoids, arachidonic acid metabolites, glycoside, etc. Finally, we found that the arginine metabolism signaling mainly involved in the regulating of P. lobata on the treatment of PF rats. Furtherly, the network pharmacology predicted that the arginine metabolism pathway was contained in the top 20 pathways. Next, we integrated metabolomics and network pharmacology that identified NOS2, MMP9 and TNF-α as the P. lobata regulated hub genes by molecular docking. Importantly, it indicated a strong affinity between the puerarin and the NOS2. P. lobata attenuated TNF-α, MMP-9 and NOS2 levels, suppressed TNF-α and MMP-9 protein expression, and decreased L-OT and NOS2 content in PF rats. These results indicated that the effects of P. lobata may ameliorated PF via the arginine metabolism pathway in rats. Therefore, P. lobata may be a potential therapeutic agent to ameliorated PF.

CONCLUSION

In this work, we used metabolomics and network pharmacology to explore the mechanisms of P. lobata in the treatment of PF. Finally, we confirmed that P. lobata alleviated BLM-induced PF in rats by regulating arginine metabolism pathway based on reducing the L-OT and NOS2-related signal molecular. The search for the biomarkers finding of arginine metabolism pathway revealed a new strategy for P. lobata in the treatment of PF.

Pharmacological mechanisms of puerarin in the treatment of Parkinson's disease: An overview

Puerarin, a monomer of traditional Chinese medicine, is a key component of Pueraria radix. Both clinical and experimental researches demonstrated that puerarin has therapeutic effects on Parkinson's disease (PD). Puerarin's pharmacological mechanisms include: 1) Anti-apoptosis. Puerarin inhibits cell apoptosis through the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (Akt) and c-Jun N-terminal kinase (JNK) signaling pathways. Puerarin also exerts a hormone-like effect against cell apoptosis; 2) Anti-oxidative stress injury. Puerarin inhibits the Nrf2 nuclear exclusion through the GSK-3β/Fyn pathway to promote the Nrf2 accumulation in the nucleus, and then promotes the antioxidant synthesis through the Nrf2/ARE signaling pathway to protect against oxidative stress; 3) Neuroprotective effects by intervening in the ubiquitin-proteasome system (UPS) and autophagy-lysosomal pathway (ALP). Puerarin significantly enhances the activity of chaperone-mediated autophagy (CMA), which downregulates the expression of α-synuclein, reduces its accumulation, and thus improves the function of damaged neurons. Additionally, puerarin increases proteasome activity and decreases ubiquitin-binding proteins, thereby preventing toxic accumulation of intracellular proteins; 4) Alleviating inflammatory response. Puerarin inhibits the conversion of microglia to the M1 phenotype while inducing the transition of microglia to the M2 phenotype. Furthermore, puerarin promotes the secretion of anti-inflammatory factor and inhibits the expression of pro-inflammatory factors; 5) Increasing the levels of dopamine and its metabolites. Puerarin could increase the levels of dopamine, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum; 6) Promoting neurotrophic factor expression and neuronal repair. Puerarin increases the expression of glial cell-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), thereby exerting a neuroprotective effect. Moreover, the regulation of the gut microbiota by puerarin may be a potential mechanism for the treatment of PD. The current review discusses the molecular mechanisms of puerarin, which may provide insight into the active components of traditional Chinese medicine in the treatment of PD.

Investigating the Potential Therapeutic Mechanisms of Puerarin in Neurological Diseases

Plants and their derived phytochemicals have a long history of treating a wide range of illnesses for several decades. They are believed to be the origin of a diverse array of medicinal compounds. One of the compounds found in kudzu root is puerarin, a isoflavone glycoside commonly used as an alternative medicine to treat various diseases. From a biological perspective, puerarin can be described as a white needle crystal with the chemical name of 7-hydroxy-3-(4-hydroxyphenyl)-1-benzopyran-4-one-8-D-glucopyranoside. Besides, puerarin is sparingly soluble in water and produces no color or light yellow solution. Multiple experimental and clinical studies have confirmed the significant therapeutic effects of puerarin. These effects span a wide range of pharmacological effects, including neuroprotection, hepatoprotection, cardioprotection, immunomodulation, anticancer properties, anti-diabetic properties, anti-osteoporosis properties, and more. Puerarin achieves these effects by interacting with various cellular and molecular pathways, such as MAPK, AMPK, NF-κB, mTOR, β-catenin, and PKB/Akt, as well as different receptors, enzymes, and growth factors. The current review highlights the molecular mechanism of puerarin as a neuroprotective agent in the treatment of various neurodegenerative and neurological diseases. Extensive cellular, animal, and clinical research has provided valuable insights into its effectiveness in conditions such as Alzheimer's disease, Parkinson's disease, epilepsy, cerebral stroke, depression, and more.

Potential implications of polyphenolic compounds in neurodegenerative diseases

Neurodegenerative diseases are common chronic diseases related to progressive damage to the nervous system. Current neurodegenerative diseases present difficulties and despite extensive research efforts to develop new disease-modifying therapies, there is still no effective treatment for halting the neurodegenerative process. Polyphenols are biologically active organic compounds abundantly found in various plants. It has been reported that plant-derived dietary polyphenols may improve some disease states and promote health. Emerging pieces of evidence indicate that polyphenols are associated with neurodegenerative diseases. This review aims to overview the potential neuroprotective roles of polyphenols in most common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, epilepsy, and ischemic stroke.

Neuroprotective Mechanisms of Puerarin in Central Nervous System Diseases: Update

Due to global population aging and modern lifestyle changes, the incidence of central nervous system (CNS) disorders, such as neurodegenerative diseases, neuropsychiatric disorders, and cerebrovascular diseases, is increasing and has become a major public health challenge. Current medications commonly used in the clinic are far from satisfactory and may cause serious side effects. Therefore, the identification of novel drugs for the effective management of CNS diseases is very urgent. Puerarin, a highly bioactive ingredient isolated from Pueraria lobata, is known to possess a broad spectrum of pharmacological properties including anti-diabetic, anti-inflammatory, anti-antioxidant, neuroprotective, and cardioprotective features. However, its clinical application is limited due to its poor water solubility. Since puerarin has demonstrated a wide range of neuroprotective functions in various CNS diseases, such as Alzheimer’s disease, Parkinson’s disease, cerebral ischemia, depression, and spinal cord injury, it has been attracting increasingly intense attention worldwide. In this review, we intend to extensively summarize the research progress on neuroprotective mechanisms of puerarin in recent years and discuss the future directions of its application in CNS disease treatment.

Targeting Mitochondria by Plant Secondary Metabolites: A Promising Strategy in Combating Parkinson's Disease

Parkinson’s disease (PD) is one of the most prevalent and debilitating neurodegenerative conditions, and is currently on the rise. Several dysregulated pathways are behind the pathogenesis of PD; however, the critical targets remain unclear. Accordingly, there is an urgent need to reveal the key dysregulated pathways in PD. Prevailing reports have highlighted the importance of mitochondrial and cross-talked mediators in neurological disorders, genetic changes, and related complications of PD. Multiple pathophysiological mechanisms of PD, as well as the low efficacy and side effects of conventional neuroprotective therapies, drive the need for finding novel alternative agents. Recently, much attention has been paid to using plant secondary metabolites (e.g., flavonoids/phenolic compounds, alkaloids, and terpenoids) in the modulation of PD-associated manifestations by targeting mitochondria. In this line, plant secondary metabolites have shown promising potential for the simultaneous modulation of mitochondrial apoptosis and reactive oxygen species. This review aimed to address mitochondria and multiple dysregulated pathways in PD by plant-derived secondary metabolites.

Botanical Drug Puerarin Ameliorates Liposaccharide-Induced Depressive Behaviors in Mice via Inhibiting RagA/mTOR/p70S6K Pathways

BACKGROUND

The depressive symptom hallmarks the progression of the neurodegenerative diseases, especially Alzheimer's disease. Bacterial infection is related to inflammation and depression. The present project thereby examined whether botanical drug puerarin could attenuate liposaccharide- (LPS-) induced depressive behaviors in mice.

METHODS

Adult male C57BL/6N mice were sequentially treated with LPS and puerarin and evaluated for the depressive behaviors by tail suspension test and forced swim test. The brain tissues were profiled for the molecular targets of puerarin by next-generation RNA sequencing technique. Candidate targets were further verified in LPS-treated mice, neural stem cells, and highly differentiated PC12 cell line.

RESULTS

Puerarin ameliorated LPS-induced depression in the mice. RNA sequencing profiles revealed that puerarin altered the expression of 16 genes while markedly downregulated Ras-related GTP-binding protein A (RagA) in LPS-treated mice. The effect of puerarin on RagA expression was confirmed by immunostaining, Western blot, and quantitative real-time PCR (qRT-PCR). Biochemical studies showed that puerarin inhibited RagA/mTOR/p70S6K pathway, attenuated the accumulation of mTORC1 in close proximity to lysosome, and reduced the production of proinflammatory cytokines.

CONCLUSIONS

Botanical drug puerarin attenuated inflammation and depressive behaviors in LPS-challenged mice by inhibiting RagA/mTOR/p70S6K pathways. Puerarin may be a lead compound for the new antidepressant drugs.

The effects of the M2a macrophage-induced axonal regeneration of neurons by arginase 1

BACKGROUND

Spinal cord injury (SCI) is a challenge worldwide, but there are no effective treatments or therapeutic methods in the clinic. Recent studies have shown that type I arginase (Arginase1, Arg1) is closely associated with the treatment of SCI. The classical treatment for SCI involves filling the local area of SCI with activated M2a macrophages to allow the repair and regeneration of some synapses, but the specific mechanism of action of Arg1 is not clear.

METHOD

In the present study, we first induced the polarization of RAW264.7 macrophages to M2a-type cells using IL-4 and constructed an Arg1 knockout cell line through the use of shRNA; we used these cells to treat a rat model of SCI. Finally, the present study explored the mechanism and pathway by which Arginase 1 regulates spinal repair by immunoblotting and immunohistochemistry.

RESULT

Suspended M2a (Arg1-/+) macrophages were transplanted into the injury site in a rat model of contusion SCI. Compared with the model group and the shArg1 group, the shScramble (shSc) group exhibited higher Basso, Beattie, Bresnahan motor function scores, more compact structures and more Nissl bodies. Immunohistochemical results showed that the shSc group expressed higher levels of NeuN (a neuronal marker) and tau (an axonal marker), as well as the up-regulation of Cdc42, N-WASP, Arp2/3 and tau, as determined by Western blot.

CONCLUSION

The study found that the polarization of M2a macrophages promoted the expression of Arginase 1, which restored axonal regeneration, promoted axonal regeneration, and promoted the structural and functional recovery of the contused spinal cord.

Puerarin improves hepatic glucose and lipid homeostasis in vitro and in vivo by regulating the AMPK pathway

Obesity is an increasingly concerning global health issue, which is accompanied by disruption of glucose and lipid metabolisms. The aim of this study was to uncover the potential and molecular actions of puerarin, a phytochemical, for alleviating metabolic dysfunctions of glucose and lipid metabolisms. A rat model fed a high fat and high fructose diet and a HepG2 cell model challenged with fructose combined with free fatty acid were utilized to identify the effects of puerarin on obesity-associated insulin resistance and hepatic steatosis. The molecular mechanisms underlying puerarin treatment effects were further investigated using qRT-PCR and western blotting. Results show that puerarin significantly ameliorated features of obesity in rats, including bodyweight, hyperlipidemia, hyperglycemia, glucose/insulin intolerance, insulin resistance, hepatic steatosis, and oxidative stress, which are related to the activation of AMPK and PI3K/Akt pathways in the liver. Puerarin reduced lipid accumulation and caused a reduction of the mRNA expression of lipogenic genes such as SREBP-1c, FAS, SCD-1, and HMGCR, and an increment in the phosphorylation of AMPK and ACC in HepG2 cells. Moreover, puerarin ameliorated insulin resistance by increasing GLUT4 mRNA expression and activating the PI3K/Akt pathway. Treatment with the AMPK inhibitor compound C partially abolished the beneficial effects of puerarin on lipid accumulation and insulin resistance in HepG2 cells, which indicated that the protective effects of puerarin partially depend on the AMPK pathway. The present study indicates that puerarin shows potential as a functional food therapeutic for the treatment of obesity.

Neuroprotective effects of natural compounds on neurotoxin-induced oxidative stress and cell apoptosis

OBJECTIVES

Overproduction of reactive species, notably reactive oxygen (ROS) and nitrogen (RNS) species, along with the failure of balancing effects of endogenous antioxidant defenses result in destruction of cellular structures, lipids, proteins, and genetic material, which lead to oxidative stress. Oxidative stress-induced neuronal apoptosis plays a pivotal role in pathogenesis of neurodegeneration. Antioxidants represent one of the medical choice strategies for protecting against this unbalanced oxidation-antioxidation status. Recently, natural compounds with neuroprotective potential that can scavenge free radicals and protect cells from oxidative damage have received extensive attention.

METHODS

In this review, we summarized the detailed research progress on the medicinal plants-derived natural compounds with potential anti-oxidation effects and their molecular mechanisms on modulating the neurotoxin (6-OHDA, H₂O₂, glutamate, Aβ)-induced oxidative stress and cell apoptosis.

RESULTS

The natural compounds that efficacious in modulating reactive species production and mitochondrial function include flavonoids, glucosides, alkaloids, polyphenols, lignans, coumarins, terpenoids, quinones and others. They decreased the neurotoxin-induced oxidative damage and apoptosis by (1) decreasing ROS/RNS generation, lipid peroxidation, caspase-3 and caspase-9 activities, LDH release, the ratio of Bax/Bcl-2, Ca²⁺ influx and cytochrome c release, (2) elevating MMP, and (3) restoring endogenous antioxidant enzymatic activities (CAT, GSH-Px, GSR, SOD). And they exerted neuroprotective effects against cell damages and apoptosis by modulating the oxidative cascades of different signaling pathways (Nrf2/HO-1, NF-κB, MAPKs, PI3K/Akt, GSK-3β) and preventing mitochondria-dependent apoptosis pathways.

DISCUSSION

The present work reviews the role of oxidative stress in neurodegeneration, highlighting the potential anti-oxidation effects of natural compounds as a promising approach to develop innovative neuroprotective strategy.

Botanical Drug Puerarin Promotes Neuronal Survival and Neurite Outgrowth against MPTP/MPP+-Induced Toxicity via Progesterone Receptor Signaling

Background

Progesterone receptor (PR) modulates neuroprotective and regenerative responses in Parkinson's disease and related neurological diseases.

Objectives

The present study was designed to determine whether botanical drug puerarin could exhibit neuroprotective and neurorestorative activities via PR signaling.

Methods

The neuroprotective and neurotrophic activities of puerarin were investigated in MPTP-lesioned mice and MPP⁺-challenged primary rat midbrain neurons. Rotarod performance test and tail suspension test were used to assess motor functions. Tyrosine hydroxylase (TH) and PR were determined by immunostaining, Western blotting, and luciferase reporter assays. Neurite outgrowth was assessed by fluorescence staining and immunostaining.

Results

Puerarin effectively ameliorated the MPTP-induced motor abnormalities in MPTP-lesioned mice and protected primary rat midbrain neurons against MPP⁺-induced toxicity via PR signaling although progesterone exhibited the neuroprotection. PR antagonist mifepristone (RU486) diminished the neuroprotection of puerarin in MPTP-lesioned mice and MPP⁺-induced primary rat midbrain neurons. Moreover, puerarin promoted the differentiation of primary rat midbrain neurons and potentiated NGF to induce neuritogenesis in PC12 cells. RU486 and PR-siRNA could inhibit the effect of puerarin. Puerarin and progesterone could enhance the PR promoter.

Conclusion

Puerarin attenuated MPTP- and MPP⁺-induced toxicity and potentiated neurite outgrowth via PR. These results suggested that puerarin may become an alternative hormone for suppressing MPTP- and MPP⁺-induced toxicity in neurodegenerative diseases.

Puerarin suppresses MPP+/MPTP-induced oxidative stress through an Nrf2-dependent mechanism

In this study, we hypothesized that anti-parkinsonian effect of puerarin is attributable to its antioxidant properties via Nrf2-dependent glutathione (GSH) biosynthesis mechanism. Experimentally, we found that puerarin attenuated 1-methyl-4-phenylpyridinium (MPP⁺)-induced oxidative stress through elevating biosynthetic capacity of GSH in PC12 cells. Mechanistically, puerarin suppressed Fyn phosphorylation by GSK-3β-dependent mechanism in MPP⁺-challenged PC12 cells. Furthermore, puerarin induced accumulation of Nrf2 in the nucleus via inhibiting its nuclear exclusion. In parallel, puerarin up-regulated antioxidant response element (ARE)-driven catalytic subunits from glutamate cysteine ligase (GCLc) expression at levels of transcription and translation. Most interestingly, pharmacological inhibitor of GSK-3β or Fyn shRNA blocked puerarin-induced Nrf2 activation in MPP⁺-challenged PC12 cells. Concomitantly, puerarin ameliorated motor deficits and inhibited oxidative stress in the ventral midbrain in MPTP-intoxicated wild-type (WT) mice, but failed to attenuate MPTP neurotoxicity and up-regulate GCLc gene in Nrf2-knockout (Nrf2^-/-) mice, suggesting that anti-parkinsonian effect of puerarin was dependent on Nrf2. Additionally, puerarin regulated Fyn and GSK-3β phosphorylation in the ventral midbrain in MPTP-intoxicated WT mice. Collectively, the results of the study provide molecular insights into the potential therapeutic action of puerarin in Parkinson's disease, suggesting that puerarin may be a promising candidate for the treatment of Parkinson's disease.

A Pharmacological Appraisal of Neuroprotective and Neurorestorative Flavonoids Against Neurodegenerative Diseases

BACKGROUND & OBJECTIVE

Alzheimer's disease (AD) and Parkinson's disease (PD) affect an increasing number of the elderly population worldwide. The existing treatments mainly improve the core symptoms of AD and PD in a temporary manner and cause alarming side effects. Naturally occurring flavonoids are well-documented for neuroprotective and neurorestorative effects against various neurodegenerative diseases. Thus, we analyzed the pharmacokinetics of eight potent natural products flavonoids for the druggability and discussed the neuroprotective and neurorestorative effects and the underlying mechanisms.

CONCLUSION

This review provides valuable clues for the development of novel therapeutics against neurodegenerative diseases.

Potential link between the RagA-mTOR-p70S6K axis and depressive-behaviors during bacterial liposaccharide challenge

BACKGROUND

Bacterial infection is a potential risk factor for depression. However, little is known about the mechanistic link between bacterial endotoxin and depressive-like behaviors. The aim of the present study was to clarify whether liposaccharide (LPS) could induce depressive-like behaviors in mice via sequentially activating small GTPase RagA, mammalian target of rapamycin (mTOR), and p70S6K.

METHODS

C57BL/6 N mice were treated with 0.83 mg/kg LPS by intraperitoneal injection for 24 h. The animals were assessed for depressive-like behaviors by forced swim test and tail suspension test. The expression levels of RagA, mTOR, and p70S6K were determined in mice, primary cortical neurons, neural stem cells, and PC12 cells.

RESULTS

LPS effectively induced depressive-like behaviors in mice. Biochemical examination revealed that LPS not only upregulated RagA expression but also activated mTOR/p70S6K pathway in mouse brains. LPS challenge also achieved a similar effect in primary cortical neurons, neural stem cells, and PC12 cells. Following the silencing of RagA expression with specific siRNA, LPS failed to induce mTORC1 translocation to the lysosomal membranes in PC12 cells. These results suggested that LPS might sequentially upregulate RagA and activate mTOR and p70S6K pathways in mice and neural stem cells.

CONCLUSIONS

This study for the first time demonstrated that LPS might induce depressive-like behaviors in mice via the upregulation of RagA and subsequent activation of mTOR/p70S6K pathway. Such information may highlight the RagA-mTOR-p70S6K signaling cascade as a novel therapeutic target for the development of new anti-depressant therapeutics.

Study on antrodia camphorata polysaccharide in alleviating the neuroethology of PD mice by decreasing the expression of NLRP3 inflammasome

Parkinson's disease (PD) is a neurodegenerative disease, and the role of neuroinflammation in the pathogenesis and progression of PD has been confirmed. The polysaccharides and triterpenoids of antrodia camphorata (a polyporous fungus) harbor diverse and powerful pharmacological effects. In this study, 6-hydroxydopamine was used to construct a PD mouse model. After antrodia camphorata polysaccharide (ACP) intervention, neurobehavioral changes were detected, neurotransmitter changes in striatum were determined by high-performance liquid chromatography, the alterations of striatal NOD-like receptor pyrin domain containing three (NLRP3) were examined by immunohistochemistry, and the expression of NLRP3, IL-1β, Caspase-1, and proCaspase-1 were detected by western blot. To be specific, the items of neurobehavioral test included open field activity, rotary test, pole test, gait analysis, and swimming test. As a result, 6-hydroxydopamine could lead to PD-like lesions, including tremor, stiffness, attenuated spontaneous activity, and bradykinesia in mice, and the expression of tyrosine hydroxylase in the striatum was decreased. After ACP intervention, the neuroethology of mice was significantly improved, as demonstrated by the elevated levels of dopamine in the striatum and the decreased expression of dopamine in the striatum in NLRP3 inflammasome. NLRP3 inflammasome played an important role in neuroinflammation in PD mice. ACP could reduce the activation of NLRP3 and expression of related inflammatory factors.

Puerarin protects against high-fat high-sucrose diet-induced non-alcoholic fatty liver disease by modulating PARP-1/PI3K/AKT signaling pathway and facilitating mitochondrial homeostasis

As yet, there was no effective pharmacological therapy approved for non-alcoholic fatty liver disease (NAFLD). Here, we aimed to evaluate the therapeutic potential of puerarin against NAFLD and explored the underlying mechanisms. C57BL/6J mice were fed with a high-fat high-sucrose (HFHS) diet with or without puerarin coadministration intragastrically. The levels of hepatocellular injury, steatosis, fibrosis, and mitochondrial and metabolism alteration were detected. First, puerarin ameliorated histopathologic abnormalities due to HFHS. We observed a marked increase in hepatic lipid content, inflammation, and fibrosis level, which were attenuated by puerarin. Possible mechanisms were related to puerarin-mediated activation of PI3K/AKT pathway and further improvement in fatty acid metabolism. Puerarin restored the NAD+ content and beneficially affected the hepatic mitochondrial function, which attenuated HFHS-induced steatosis and metabolic disturbances. Finally, hepatic PARP-1 was activated due to excessive fat intake. Puerarin attenuated the PARP-1 expression in HFHS-fed mice, and PJ34, the PARP inhibitor, could mimic these protections of puerarin. However, pharmacological inhibition of PI3K disabled the protection of puerarin or PJ34 toward NAD+ refilling and mitochondrial homeostasis. In conclusion, our findings indicated that puerarin could be a promising and practical therapeutic strategy in NAFLD through modulating PARP-1/PI3K/AKT signaling pathway and further facilitating mitochondrial function.

Puerarin alters the function of monocytes/macrophages and exhibits chondroprotection in mice

Recent studies have suggested that puerarin may impede osteoclastogenesis and facilitate bone regeneration, in addition to attenuating tissue inflammation. The present study investigated the therapeutic effects of puerarin on inflammatory responses and monocyte recruitment in in vitro and in vivo osteoarthritis (OA) models. Puerarin treatment increased the proliferation of OA chondrocytes, as determined by Cell Counting Kit‑8 assay. In addition, the present results suggested that puerarin suppressed the interleukin‑1β‑induced production of inflammatory cytokines in OA chondrocytes and monocytes/macrophages, as assessed by ELISA. In a mouse model of mono‑iodoacetate‑induced OA, the present histological analyses suggested that administration with puerarin attenuated the inflammatory profile of OA joints and reduced cartilage destruction. Using flow cytometry, a decreased number of myeloid‑derived C‑C chemokine receptor 2+/lymphocyte Ag 6C+ monocytes was identified in the blood of OA mice treated with puerarin compared with control OA mice. Furthermore, quantitative real‑time polymerase chain reaction analysis suggested that puerarin treatment decreased C‑C chemokine ligand 2 expression in arthritic tissues. Collectively, the results suggested that puerarin treatment limited the recruitment of inflammatory monocytes. In summary, the present study provided pre‑clinical evidence that puerarin may serve as a potential target in the treatment of OA.

Puerarin prevents tumor necrosis factor-α-induced apoptosis of PC12 cells via activation of the PI3K/Akt signaling pathway

Tumor necrosis factor-α (TNF-α), a potential proinflammatory cytokine, is an important component involved in neuronal apoptosis associated with neuroinflammation in the central nervous system. It has been reported that puerarin possesses pharmacological effects, such as anti-apoptotic, antioxidant, anti-osteoporosis, anti-inflammatory, cardioprotective and neuroprotective actions. The aim of the present study was to explore the effect of puerarin on apoptosis induced by TNF-α (3×10⁵ U/l) and its detailed mechanisms in PC12 cells. MTT and flow cytometric assays were performed to evaluate cell cytotoxicity and apoptosis, respectively. An enzymatic assay was used to detect the activity of caspase-3 and caspase-9. Western blot analysis was performed to assess changes in the levels of proteins, including B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, Akt and phosphorylated Akt. The results showed that puerarin (25 and 50 µM) significantly suppressed TNF-α-induced apoptosis in PC12 cells. The TNF-α-induced in crease in the Bax/Bcl-2 ratio was markedly inhibited by pre-treatment with puerarin for 2 h. In addition, puerarin decreased the level of TNF-α-induced cleaved caspase-3. Furthermore, puerarin inhibited the TNF-α-induced decrease in the phosphorylation of Akt, which was abolished by LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, suggesting that the PI3K/Akt pathway participated in the suppressive effect of puerarin. Taken together, these findings indicated that puerarin prevented TNF-α-induced apoptosis in PC12 cells via activating of the PI3K/Akt signaling pathway, suggesting that puerarin may be a potential neuroprotective drug in the clinical treatment of neuroinflammation via anti-apoptotic mechanisms.

Cystatin C as a potential therapeutic mediator against Parkinson's disease via VEGF-induced angiogenesis and enhanced neuronal autophagy in neurovascular units

Cystatin C (CYS C, Cst3) is an endogenous cysteine protease inhibitor that plays neuroprotective roles in neurodegenerative diseases. We aimed to explore the association of CYS C with Parkinson’s disease (PD) models and investigate its involvement in the role of neurovascular units (NVUs) in PD neuro-pathogenesis. We used A53T α-synuclein (SNCA) transgenic mice and 6-hydroxydopamine-lesioned DAergic PC12 cells as experimental PD models to investigate the mechanisms behind this association. The injections of CYS C were administered to the right substantia nigra (SN) of A53T SNCA transgenic mice to measure the effects of CYS C in transgenic A53T SNCA mice. To explore the angiogenesis in vivo and in vitro, we used the chick embryo chorioallantoic membrane (CAM) assay and tube formation (TF) assay. We found that CYS C has a neuroprotective effect in this in vivo PD model. We observed increased VEGF, NURR1 and autophagy markers LC3B and decreased SNCA and apoptosis marker cleaved CASP3 in different brain regions of CYS C-treated A53T SNCA transgenic mice. In vitro, we observed that CYS C-induced VEGF, a secreted protein, attenuated 6-OHDA-lesioned DAergic PC12 cell degeneration by regulating p-PKC-α/p-ERK1/2-Nurr1 signaling and inducing autophagy. VEGF-mediated angiogenesis was markedly enhanced in the conditioned media of 6-OHDA-lesioned PC12 cells with CYS C-overexpression, whereas blockage of autophagy in CYS C-overexpressing PC12 cells significantly downregulated VEGF expression and the associated angiogenesis. Our data indicate that CYS C displays dual neuronal–vascular functions, promoting PC12 cell survival and angiogenesis via regulating the level of secreted VEGF in NVUs. Our study provides evidence that may aid in the development of an alternative approach for the treatment of PD through modulation of CYS C-mediated neuronal-vascular pathways.

Plant Natural Product Puerarin Ameliorates Depressive Behaviors and Chronic Pain in Mice with Spared Nerve Injury (SNI)

Simultaneous relief of the pain from body and brain remains an ongoing challenge. The aim of the present study was to clarify whether plant-derived isoflavone puerarin could ameliorate comorbid depression and pain. We investigated the effects of puerarin on depressive-like behaviors and neuropathic pain in C57BL/6 N mice with spared nerve injury (SNI). After SNI surgery, mice were allowed to recover spontaneously for 7 days and subsequently treated with puerarin, anti-depressant citalopram, and analgesic ibuprofen, alone or in combination, for 8 or 14 days. Forced swim test and tail suspension test were used to assess depressive-like behaviors, whereas von Frey filament test was used to estimate the sensitivity to the mechanical stimulation. Our results suggested that puerarin effectively ameliorated depression and pain in SNI mice although citalopram exhibited anti-depressant activity. In contrast, ibuprofen showed lesser activities against SNI-induced depression and pain. Further mechanistic studies revealed the uniqueness of puerarin as follows: (1) puerarin did not recover SNI-induced depletion of reduced glutathione and loss of superoxide dismutase (SOD), whereas citalopram and ibuprofen showed somewhat antioxidant activities; (2) puerarin markedly promoted the activation of CREB pathway although puerarin and citalopram activated ERK pathway to the same extent; (3) puerarin rapidly and persistently induced brain-derived neurotrophic factor (BDNF) expression whereas citalopram only induced BDNF expression after a prolonged stimulation. Collectively, these results suggest that puerarin may ameliorate the SNI-induced depression and pain via activating ERK, CREB, and BDNF pathways. Puerarin may serve as new lead compound for the development of novel therapeutics for depression and pain comorbidity.

Contra-directional Coupling of Nur77 and Nurr1 in Neurodegeneration: A Novel Mechanism for Memantine-Induced Anti-inflammation and Anti-mitochondrial Impairment

Recent evidence suggests that nerve growth factor IB (Nur77) and nuclear receptor related1 (Nurr1) are differentially involved in dopaminergic neurodegeneration. Since memantine has shown clinically relevant efficacy in Parkinson's disease (PD) and displayed a potent protective effect on dopaminergic neurons in experimental PD models, we asked if it exerts its neuroprotection by regulating Nur77 and Nurr1 signaling. We adopted a well-established in vitro PD model, 6-hydroxydopamine (OHDA)-lesioned PC12 cells, to test our hypothesis. Different concentrations of memantine were incubated with 6-OHDA-lesioned PC12 cells, and Nur77/Nurr1 and their related signaling molecules were examined by Western blot and immunocytochemistry. Nur77-deficient PC12 cells were used to verify the influences of Nur77 on neurodegeneration and memantine-mediated neuroprotection. We found that memantine reversed Nur77 upregulation and restored Nurr1 downregulation in 6-OHDA-lesioned PC12 cells. 6-OHDA incubation caused Nur77 translocation from the nucleus to cytosol and induced co-localization of Cyt c/HSP60/Nur77 in the cytosol. Memantine strongly reduced the sub-cellular translocations of Nur77/Cyt c/HSP60 under 6-OHDA-induced oxidative condition. Knockdown of Nur77 enhanced the viability of PC12 cells exposed to 6-OHDA, while memantine-induced neuroprotection was much less in the cells with Nur77 knockdown than in those without it. We conclude that Nur77 plays a crucial role in modulating mitochondrial impairment and contributes to neurodegeneration under the experimental PD condition. Memantine effectively suppresses such Nur77-mediated neurodegeneration and promotes survival signaling through post-translational modification of Nurr1. Nur77 and Nurr1 present a contra-directionally coupling interaction in memantine-mediated neuroprotection.