Sulfuretin protects against cytokine-induced beta-cell damage and prevents streptozotocin-induced diabetes

Synthesis, characterization and biological evaluation of aurones as potential neuroprotective agents

Aim: To synthesize aurone (Ar) derivatives and to demonstrate their effects against diabetes mellitus (DM) and neurodegeneration. Materials & methods: Five Ar (A-E) derivatives were synthesized, characterized by proton NMR and screened for antioxidant, anti-diabetic and anti-cholinesterase activities. They were further evaluated for neuroprotective effects in streptozotocin (STZ)-induced neurodegenerative model. Results: Among the aurone derivatives ArE demonstrated significant reversal of cognitive impairment, oxidative stress and neuroinflammation. Biochemical analysis revealed anti-diabetic and neuroprotective effects, possibly through downregulation of inflammatory markers and upregulation of antioxidant enzymes. Conclusion: Synthesized Ar (A-E) exhibits promising therapeutic potential against STZ-induced neurodegeneration and DM by modulating inflammatory and oxidative pathways, suggesting a novel avenue for disease management.

A comprehensive review of medicinal Toxicodendron (Anacardiaceae): Botany, traditional uses, phytochemistry and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Comprising of about 30 species, the genus Toxicodendron (Anacardiaceae) are mainly distributed in East Asia and North America. Among them, 13 species have been traditionally used as folk medicines in Asia and other parts of the world to treat blood diseases, abnormal bleeding, skin diseases, gastrointestinal diseases, liver diseases, bone injury, lung diseases, neurological diseases, cardiovascular diseases, tonic, cancer, eye diseases, menstrual irregularities, inflammation, rheumatism, diabetes mellitus, rattlesnake bite, internal parasites, contraceptive, vomiting and diarrhea.

AIM OF THE STUDY

To date, no comprehensive review on Toxicodendron has been published and the scientific basis of the traditional medicinal benefits of Toxicodendron have been less reported. Therefore, this review aims to provide a reference for further research and development on medicinal purpose of Toxicodendron by summarizing the works (from 1980 to 2023), and focusing on its botany, traditional uses, phytochemistry and pharmacology.

MATERIALS AND METHODS

The names of the species were from The Plant List Database (http://www.theplantlist.org), World Flora Online (http://www.worldfloraonline.org), Catalogue of Life Database (https://www.catalogueoflife.org/) and Plants for A Future Database (https://pfaf.org/user/Default.aspx). And the search terms "Toxicodendron" and "the names of 31 species and their synonyms" were used to search for information from electronic databases such as Web of Science, Scopus, Google Scholar, Science Direct, PubMed, Baidu Scholar, Springer, and Wiley Online Library. Moreover, PhD and MSc dissertations were also used to support this work.

RESULTS

These species on Toxicodendron are widely used in folkloric medicine and modern pharmacological activities. So far, approximately 238 compounds, mainly phenolic acids and their derivatives, urushiols, flavonoids and terpenoids, are extracted and isolated from Toxicodendron plants, commonly, T. trichocarpum, T. vernicifluum, T. succedaneum, and T. radicans. Among them, phenolic acids and flavonoids are the main compound classes that show pharmacological activities in Toxicodendron plants both in vitro and in vivo. Furthermore, the extracts and single compounds of these species show a wide range of activities, such as antioxidant, antibacterial, anti-inflammatory, anti-tumor, liver protection, fat reduction, nerve protection, and treatment of blood diseases.

CONCLUSIONS

Selected species of Toxicodendron have been used as herbal medicines in the Southeast Asian for a long time. Furthermore, some bioactive constituents have been identified from them, so plants in this genus may be potential new drugs. The existing research on Toxicodendron has been reviewed, and the phytochemistry and pharmacology provide theoretical basis for some of the traditional medicinal uses. Therefore, in this review, the traditional medicinal, phytochemical and modern pharmacology of Toxicodendron plants are summarized to help future researchers to find new drug leads or to get a better understanding of structure-activity relationships.

Recent Trends in the Antidiabetic Prominence of Natural and Synthetic Analogues of Aurones

Natural products are a boundless source for the development of pharmaceutical agents against a wide range of human diseases. Accordingly, naturally occurring aurones possess various biological benefits, such as anticancer, antioxidant, antimicrobial, antidiabetic, anti-inflammatory, antiviral and neuroprotective effects. In addition, various studies have revealed that aurones are potential templates for the regulation of diabetes mellitus and its associated complications. Likewise, certain aurones and their analogues have been found to be remarkable kinase inhibitors of DARK2, PPAR-γ, PTPM1, AGE, α-amylase and α-glucosidase, which represents a promising approach for the treatment of chronic metabolic disorders such as diabetes. Therefore, in our present study, we provide a detailed account of the advances in aurones as antidiabetic agents over the past decade.

Activation of Nrf2 by sulfuretin stimulates chondrocyte differentiation and increases bone lengths in zebrafish

Elongation of most bones occur at the growth plate through endochondral ossification in postnatal mammals. The maturation of chondrocyte is a crucial factor in longitudinal bone growth, which is regulated by a complex network of paracrine and endocrine signaling pathways. Here, we show that a phytochemical sulfuretin can stimulate hypertrophic chondrocyte differentiation in vitro and in vivo. We found that sulfuretin stabilized nuclear factor (erythroid-derived 2)-like 2 (Nrf2), stimulated its transcriptional activity, and induced expression of its target genes. Sulfuretin treatment resulted in an increase in body length of zebrafish larvae and induced the expression of chondrocyte markers. Consistently, a clinically available Nrf2 activator, dimethyl fumarate (DMF), induced the expression of hypertrophic chondrocyte markers and increased the body length of zebrafish. Importantly, we found that chondrocyte gene expression in cell culture and skeletal growth in zebrafish stimulated by sulfuretin were significantly abrogated by Nrf2 depletion, suggesting that such stimulatory effects of sulfuretin were dependent on Nrf2, at least in part. Taken together, these data show that sulfuretin has a potential use as supporting ingredients for enhancing bone growth. [BMB Reports 2023; 56(9): 496-501].

An update of aurones: food resource, health benefit, biosynthesis and application

Aurones are a subclass of active flavonoids characterized with a scaffold of 2-benzylidene-3(2H)-benzofuranone. This type of chemicals are widely distributed in fruit, vegetable and flower, and contribute to human health. In this review, we summarize the natural aurones isolated from dietary plants. Their positive effects on immunomodulation, antioxidation, cancer prevention as well as maintaining the health status of cardiovascular, nervous system and liver organs are highlighted. The biosynthesis strategies of plant-derived aurones are elaborated to provide solutions for their limited natural abundance. The potential application of natural aurones in food coloration are also discussed. This paper combines the up-to-date information and gives a full image of dietary aurones.

Discovery of blood-brain barrier permeant amine-functionalized aurones as inhibitors of activated microglia

Sulfuretin, a naturally occurring aurone is reported to inhibit macrophage and microglia activation. A series of aurones incorporating basic amines and lipophilic functionalities at ring A and/or ring B were synthesized to improve upon present sulfuretin activity towards targeting brain microglia while overcoming the blood-brain barrier (BBB). Evaluation of the ability of the aurones to inhibit lipopolysaccharide (LPS)-stimulated nitric oxide (NO) secretion by murine BV-2 microglia has identified several inhibitors showing significant NO reduction at 1 to 10 µM. Potent inhibitors were represented by aurones with bulky, planar moieties at ring A (3f) or at ring B (1e and 1f) and having a pendant piperidine at ring B (1a, 2a, 2b, and 3f). The active aurones inhibited the BV-2 microglia polarizing towards the M1 state as indicated by attenuation of IL-1β and TNF-α secretions in LPS-activated microglia but did not induce the microglia towards the M2 state. The aurones 2a, 2b, and 1f showed high passive BBB permeability in the parallel artificial membrane permeability assay (PAMPA) owing to their optimal lipophilicities. 2a, being non-cell toxic, BBB permeant and potent, represents a new lead for the development of aurones as inhibitors of activated microglia.

Sulfuretin exerts anti-depressive effects in the lipopolysaccharide-induced depressive mouse models

BACKGROUND

Herb-derived therapeutics is an attractive strategy to treat depression. Here we report the ameliorating effects of Sulfuretin, an anti-inflammatory compound in a depressive mouse model.

METHODS

Immobility times were obtained in the tail suspension test and forced swim test performed from day 14 to day 16. Quantitative real-time PCR (qRT-PCR) and Western blot were used to measure brain-derived neurotrophic factor (BDNF) and the extracellular signal-regulated kinase (ERK) pathway of the hippocampus tissue on day 17. SL327 was used to block the ERK pathway in mice to evaluate the interaction between Sulfuretin and the ERK pathway. Mice were treated with Sulfuretin for 14 days before lipopolysaccharide (LPS) injection (0.83 mg/kg/day, i.p.) for two days.

RESULTS

Behavior tests showed that Sulfuretin dose-dependently decreased immobility times correlated with depression symptoms. BDNF levels and ERK signaling were significantly restored in the Sulfuretin-treated mice, showing the improvement of brain function. Blocking the p-ERK signaling abrogated the effects of Sulfuretin in improving behaviors and levels of BDNF.

CONCLUSION

Our study suggests that Sulfuretin exhibits anti-depressive function in LPS-induced depressive mice, in which the ERK signaling plays an essential role.

Integrating Ethnobotany, Phytochemistry, and Pharmacology of Cotinus coggygria and Toxicodendron vernicifluum: What Predictions can be Made for the European Smoketree?

The smoketree (Cotinus coggygria) is a historically known medicinal plant from Southeast Europe. Its ethnomedicinal use in skin and mucosal lesions is commonly accepted across countries. Other utilizations reported locally include fever reduction, cardiac diseases, hypertension, urinary diseases, cough, asthma, hemorrhoids, diabetes, numbness of arm, liver disease, and cancer. Departing from the smoketree's traditional uses, this review summarizes investigations on the phytochemistry and bioactivity of the plant. In vitro and in vivo experiments supporting wound-healing, anti-inflammatory, antibacterial, cytotoxic, antioxidative, hepatoprotective, and antidiabetic effects are presented. Metabolites from smoketree that are responsible for the main pharmacological effects of smoketree are pointed out. Furthermore, the review performs a comparison between C. coggygria and the lacquer tree (Toxicodendron vernicifluum). The latter is a comprehensively studied species used in Asian phytotherapy, with whom the European smoketree shares a consistent pool of secondary metabolites. The comparative approach aims to open new perspectives in the research of smoketree and anticipates an optimized use of C. coggygria in therapy. It also points out the relevance of a chemosystematic approach in the field of medicinal plants research.

Design, synthesis, and biological evaluation of a novel dual peroxisome proliferator-activated receptor alpha/delta agonist for the treatment of diabetic kidney disease through anti-inflammatory mechanisms

Diabetic kidney disease (DKD) is a major feature of the final stage of nearly all cause types of diabetes mellitus (DM). To date, few safe and effective drugs are available to treat. Peroxisome proliferator-activated receptors (PPARs), comprised of three members: PPAR-α, PPAR-δ and PPAR-γ, play a protective role in the DKD through glycemic control and lipid metabolism, whereas systemic activation of PPAR-γ causes serious side-effects in clinical trials. GFT505 is a dual PPAR-α/δ agonist, and the selectivity against PPAR-γ is still to be improved. Sulfuretin has been shown to suppress the expression of PPAR-γ and improve the pathogenesis of diabetic complications. In this study, by hybridizing the carboxylic acid of GFT505 and the parent nucleus of sulfuretin, we pioneeringly designed and synthetized a series of novel dual PPAR-α/δ agonists, expecting to provide a better benefit/risk ratio for PPARs. Of all the synthesized compounds, compound 12 was identified with highly activity on PPAR-α/δ and higher selectivity against PPAR-γ than that of GFT505 (EC₅₀: hPPAR-α: 0.26 μM vs.0.76 μM; hPPAR-δ: 0.50 μM vs.0.73 μM; hPPAR-γ: 4.22 μM vs.2.79 μM). The molecular docking studies also depicted good binding affinity of compound 12 for PPAR-α and PPAR-δ compared to GFT505. Furthermore, compound 12 exhibited an evidently renoprotective effect on the DKD through inhibiting inflammatory process, which might at least partly via JNK/NF-κB pathways in vivo and in vitro. Overall, compound 12 hold therapeutic promise for DKD.

Efficacy of a Novel Herbal Formulation (F2) on the Management of Obesity: In Vitro and In Vivo Study

Background

Currently, obesity and its comorbidities have become a serious threat to human health necessitating urgent development of safe and effective therapy for their management.

Materials and Methods

In this research, a novel polyherbal formulation (F2) was prepared by mixing specific proportions of royal jelly and lemon juice with ethanol extracts of Orostachys japonicus, Rhus verniciflua, and Geranium thunbergii. The antioxidant activity was assessed using DPPH and ABTS assay methods. The antiobesity potential of the F2 was assessed in vitro using 3T3-L1 fibroblast and in vivo using a high-fat diet (HFD) fed C57BL/6J mice model. F2 was administered in mice at the dose of 23 mg/kg and 46 mg/kg, twice daily by oral gavage. A well-accepted antiobesity agent, Garcinia cambogia (GC), at 200 mg/kg was used as a positive control.

Results

F2 was observed to exhibit synergistic antiadipogenic activity in 3T3-L1 cells. This inhibition was reinforced by the downregulation of specific adipogenic transcription factors. Furthermore, F2 was also found to reduce mice body weight gain, food efficiency ratio, fasting blood glucose level, fat deposition into the liver, and mass of white adipose tissue. F2 also played a role in the excretion of fat consumed by the mice. For most of the assays performed, the F2 (46 mg/kg) was comparable to the positive control GC (200 mg/kg). In addition, potential and synergistic antioxidant activity was observed on F2.

Conclusion

The results revealed that the formulation F2 exhibited potential antiobesity activity through the inhibition of adipocyte differentiation, dietary fat absorption, and reduction of free fatty acids deposition in tissues.

Reduction of blood glucose by plant extracts and their use in the treatment of diabetes mellitus; discrepancies in effectiveness between animal and human studies

ETHNOPHARMACOLOGICAL RELEVANCE

The global problem of diabetes, together with the limited access of large numbers of patients to conventional antidiabetic medicines, continues to drive the search for new agents. Ancient Asian systems such as traditional Chinese medicine, Japanese Kampo medicine, and Indian Ayurvedic medicine, as well as African traditional medicine and many others have identified numerous plants reported anecdotally to treat diabetes; there are probably more than 800 such plants for which there is scientific evidence for their activity, mostly from studies using various models of diabetes in experimental animals.

AIM OF THE REVIEW

Rather than a comprehensive coverage of the literature, this article aims to identify discrepancies between findings in animal and human studies, and to highlight some of the problems in developing plant extract-based medicines that lower blood glucose in patients with diabetes, as well as to suggest potential ways forward.

METHODS

In addition to searching the 2018 PubMed literature using the terms 'extract AND blood glucose, a search of the whole literature was conducted using the terms 'plant extracts' AND 'blood glucose' AND 'diabetes' AND 'double blind' with 'clinical trials' as a filter. A third search using PubMed and Medline was undertaken for systematic reviews and meta-analyses investigating the effects of plant extracts on blood glucose/glycosylated haemoglobin in patients with relevant metabolic pathologies.

FINDINGS

Despite numerous animal studies demonstrating the effects of plant extracts on blood glucose, few randomised, double-blind, placebo-controlled trials have been conducted to confirm efficacy in treating humans with diabetes; there have been only a small number of systematic reviews with meta-analyses of clinical studies. Qualitative and quantitative discrepancies between animal and human clinical studies in some cases were marked; the factors contributing to this included variations in the products among different studies, the doses used, differences between animal models and the human disease, and the impact of concomitant therapy in patients, as well as differences in the duration of treatment, and the fact that treatment in animals may begin before or very soon after the induction of diabetes.

CONCLUSION

The potential afforded by natural products has not yet been realised in the context of treating diabetes mellitus. A systematic, coordinated, international effort is required to achieve the goal of providing anti-diabetic treatments derived from medicinal plants.

Probiotic mediated NF-κB regulation for prospective management of type 2 diabetes

Diabetes and other lifestyle disorders have been recognized as the leading cause of morbidity and mortality globally. Nuclear factor kappa B (NF-κB) is a major factor involved in the early pathobiology of diabetes and studies reveal that hyperglycemic conditions in body leads to NF-κB mediated activation of several cytokines, chemokines and inflammatory molecules. NF-κB family comprises of certain DNA-binding protein factors that elicit the transcription of pro-inflammatory molecules. Various studies have identified NF-κB as a promising target for diabetic management. Probiotics have been proposed as bio-therapeutic agents for treatment of inflammatory disorders and many other chronic clinical stages. The precise mechanisms by which probiotics acts is yet to be fully understood, however research findings have indicated their role in NF-κB modulation. The current review highlights NF-κB as a bio-therapeutic target for probable management of type 2 diabetes through probiotic intervention.

Glucose-lowering effect of Gryllus bimaculatus powder on streptozotocin-induced diabetes through the AKT/mTOR pathway

This study was carried out to elucidate the antidiabetic effects of Gryllus bimaculatus powder using a streptozotocin (STZ)-induced rat model of type I diabetes. Administration of the insect powder significantly rescued representative diabetes markers (i.e., insulin and C-peptide) in STZ-treated rats. Improved glucose tolerance test (GTT) and insulin tolerance test (ITT) results were also observed, indicating that Gryllus bimaculatus powder exerts antidiabetic effects. Gryllus bimaculatus powder administration rescued STZ-induced alterations in both islet morphology and insulin staining patterns. The extract increased antiapoptotic Bcl2 expression and decreased proapoptotic Bax and active caspase 3 expressions. In addition, the Gryllus bimaculatus powder supplementation enhanced AKT/mTOR pathway, a key marker of the state of anabolic metabolism, and its downstream effector, mTOR. Collectively, our results suggest that Gryllus bimaculatus contributes to the maintenance of pancreatic β-cell function and morphology against a diabetic state through the regulations against apoptosis and anabolic metabolism.

Rhus verniciflua leaf extract suppresses obesity in high-fat diet-induced obese mice

Background

Obesity is a serious health problem in the world. We thought that the activity and safety of natural plants and/or foods are very important in the management of therapy for obesity. Rhus verniciflua (R. verniciflua) is also known as lacquer tree in Japan and Korea, and it is consumed as food ingredients and/or traditional herbal medicine. We prepared an extract from R. verniciflua leaves (Rv-PEM01-99) to develop a new functional food material and/or nutritional supplements.

Objective

This study evaluated the anti-obesity effects of the Rv-PEM01-99 in high-fat diet (HFD)-induced obese mice.

Design

Six-week-old male C57BL/6J mice were divided into three groups: group I (HFD group), group II (HFD + 1% Rv-PEM01-99 group), and group III (HFD + 2% Rv-PEM01-99 group). Throughout the 56-day treatment period, body weights of these mice were checked twice a week. After 56 days, blood biochemical analyses were performed.

Results

In animal studies, no death or abnormalities in food consumption were observed between groups I, II, and III. Body weight gain in the groups administered Rv-PEM01-99 was less than that in group I. In particular, body weight gain in group III was significantly less than that in group I after 52 days of Rv-PEM01-99 administration. In addition, intra-abdominal fat and leptin levels in group III were significantly lower than those in group I. HPLC and LC/MS analysis showed a quercetin derivative as an active compound in Rv-PEM01-99.

Conclusion

Rv-PEM01-99, containing a quercetin derivative, showed anti-obesity effect in HFD-fed mice. It could therefore be useful as food material and/or nutritional supplement for management of obesity.

Sulfuretin Prevents Obesity and Metabolic Diseases in Diet Induced Obese Mice

The global obesity epidemic and associated metabolic diseases require alternative biological targets for new therapeutic strategies. In this study, we show that a phytochemical sulfuretin suppressed adipocyte differentiation of preadipocytes and administration of sulfuretin to high fat diet-fed obese mice prevented obesity and increased insulin sensitivity. These effects were associated with a suppressed expression of inflammatory markers, induced expression of adiponectin, and increased levels of phosphorylated ERK and AKT. To elucidate the molecular mechanism of sulfuretin in adipocytes, we performed microarray analysis and identified activating transcription factor 3 (Atf3) as a sulfuretin-responsive gene. Sulfuretin elevated Atf3 mRNA and protein levels in white adipose tissue and adipocytes. Consistently, deficiency of Atf3 promoted lipid accumulation and the expression of adipocyte markers. Sulfuretin’s but not resveratrol’s anti-adipogenic effects were diminished in Atf3 deficient cells, indicating that Atf3 is an essential factor in the effects of sulfuretin. These results highlight the usefulness of sulfuretin as a new anti-obesity intervention for the prevention of obesity and its associated metabolic diseases.

HX-1171 attenuates pancreatic β-cell apoptosis and hyperglycemia-mediated oxidative stress via Nrf2 activation in streptozotocin-induced diabetic model

Streptozotocin (STZ) acts specifically on pancreatic beta cells, inducing cell destruction and cell dysfunction, resulting in diabetes. Many studies have reported that nuclear factor-erythroid 2-related factor 2 (Nrf2), a main regulator of antioxidant expression, prevents and improves diabetes-related diseases. In this study, we investigated the antidiabetic effect of the newly discovered Nrf2 activator, HX-1171, in the STZ-induced diabetic mouse model. HX-1171 enhanced insulin secretion by reducing STZ-induced cell apoptosis, and decreased intracellular reactive oxygen species (ROS) generation by upregulating the expression of antioxidant enzymes through Nrf2 activation in INS-1 pancreatic beta cells. In STZ-induced diabetic mice, HX-1171 administration significantly lowered blood glucose levels and restored blood insulin levels. In the STZ-only injected mice, the pancreatic islets showed morphological changes and loss of function, whereas the HX-1171-treated group was similar to that of the control group. These results suggest that HX-1171 may be developed as a promising therapeutic agent for diabetes-related diseases.

Cytoprotective effect of flavonoid-induced autophagy on bisphosphonate mediated cell death in osteoblast

With rapid economic growth and further developments in medical science, the entry into the aging population is currently increasing, as is the number of patients with metabolic diseases, such as hypertension, hyperlipidemia, heart disease, and diabetes. The current treatments for metabolic bone diseases, which are also on the rise, cause negative side effects. Bisphosphonates, which are used to treat osteoporosis, inhibit the bone resorption ability of osteoclasts and during prolonged administration, cause bisphosphonate‐related osteonecrosis of the jaw (BRONJ). Numerous studies have shown the potential role of natural plant products as flavonoids in the protection against osteoporosis and in the influence of bone remodeling. Autophagy occurs after the degradation of cytoplasmic components within the lysosome and serves as an essential cytoprotective response to pathologic stress caused by certain diseases. In the present study, we hypothesized that the cytoprotective effects of flavonoids might be related to those associated with autophagy, an essential cytoprotective response to the pathologic stress caused by certain diseases, in osteoblasts. We demonstrated the cytoprotective effect of flavonoid‐induced autophagy against the toxicity of zoledronate and the induction of autophagy by flavonoids to support osteogenic transcription factors, leading to osteoblast differentiation and bone formation. Further studies are necessary to clarify the connections between autophagy and osteogenesis. It would be helpful to shed light on methodological challenges through molecular biological studies and new animal models. The findings of the current study may help to delineate the potential role of flavonoids in the treatment of metabolic bone disease.

Sulfuretin Attenuates MPP⁺-Induced Neurotoxicity through Akt/GSK3β and ERK Signaling Pathways

Parkinson's disease (PD) is the second most common neurodegenerative disease. It is caused by the death of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress and mitochondrial dysfunction contribute to the loss of dopaminergic neurons in PD. Sulfuretin is a potent antioxidant that is reported to be beneficial in the treatment of neurodegenerative diseases. In this study, we examined the protective effect of sulfuretin against 1-methyl-4-phenyl pyridinium (MPP⁺)-induced cell model of PD in SH-SY5Y cells and the underlying molecular mechanisms. Sulfuretin significantly decreased MPP⁺-induced apoptotic cell death, accompanied by a reduction in caspase 3 activity and polyADP-ribose polymerase (PARP) cleavage. Furthermore, it attenuated MPP⁺-induced production of intracellular reactive oxygen species (ROS) and disruption of mitochondrial membrane potential (MMP). Consistently, sulfuretin decreased p53 expression and the Bax/Bcl-2 ratio. Moreover, sulfuretin significantly increased the phosphorylation of Akt, GSK3β, and ERK. Pharmacological inhibitors of PI3K/Akt and ERK abolished the cytoprotective effects of sulfuretin against MPP⁺. An inhibitor of GSK3β mimicked sulfuretin-induced protection against MPP⁺. Taken together, these results suggest that sulfuretin significantly attenuates MPP⁺-induced neurotoxicity through Akt/GSK3β and ERK signaling pathways in SH-SY5Y cells. Our findings suggest that sulfuretin might be one of the potential candidates for the treatment of PD.

Exploration of Underlying Mechanism of Anti-adipogenic Activity of Sulfuretin

Sulfuretin is a natural flavonoid found in the plant Rhus verniciflua STOKES. The plant has been traditionally used as medicinal agent for antiviral, cathartic, diaphoretic, anti-rheumatic and sedative activities in East Asia. In this study we isolated and identified sulfuretin from R. verniciflua and investigated its anti-adipogenic activity against 3T3-L1 preadipocytes cells. We evaluated the effects of sulfuretin on the adipogenic transcription factors like peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), fatty acid synthase (FAS), Fabp4, adiponectin and zinc fingerprint protein (Zfp) 521 by gene expression (real-time QPCR) and Western blot analysis. Sulfuretin treatment at Day 0 and 2 showed significant reduction of lipid production in 3T3-L1 cells in concentration dependent manner. Gene expression analysis (real-time PCR) revealed that sulfuretin inhibited the both major adipogenic factors (C/EBPα, C/EBPβ and PPARγ) and minor adipogenic factors (sterol regulatory element-binding protein (SREBP1c), adiponectin, FAS, Fabp4, Zfp423, and Ebf1). Western blot analysis showed the increased expression of β-catenin and suppression of PPARγ after sulfuretin treatment. Overall, sulfuretin is a natural flavonoid having potent anti-adipogenic activity through the suppression of major adipogenic factors C/EBPα, C/EBPβ and PPARγ, which initiate adipogenesis.

Antidiabetic, hypolipidemic and hepatoprotective effects of Arctium lappa root's hydro-alcoholic extract on nicotinamide-streptozotocin induced type 2 model of diabetes in male mice

OBJECTIVE

Arctium lappa (burdock), (A. lappa) root has hypoglycemic and antioxidative effects, and has been used for treatment of diabetes in tradition medicine. This study was conducted to evaluate the antidiabetic and hypolipidemic properties of A. lappa root extract on nicotinamide-streptozotocin (NA-STZ)-induced type2 diabetes in mice.

MATERIALS AND METHODS

In this investigation, 70 adult male NMRI mice (30-35g) randomly divided into 7 groups (n=10) as follow: 1-control, 2-type 2 diabetic mice, 3-diabetic mice that received glibenclamide (0.25 mg/kg) as an anti-diabetic drug, 4, 5, 6 and 7- diabetic and normal animals that were pre-treated with 200 and 300 mg/kg A. lappa root extract, respectively, for 28 days. Diabetes has been induced by intraperitoneal injection of NA and STZ. Finally, the blood sample was taken and insulin, glucose, SGOT, SGPT, alkaline phosphatase, leptin and lipid levels was evaluated.

RESULTS

Induction of diabetes decreased the level of insulin, leptin and high density lipoprotein (HDL) and increased the level of other lipids, glucose, and hepatic enzymes significantly (p<0.05). Administration of both doses of the extract significantly decreased the level of triglyceride, very low density lipoprotein, glucose and alkaline phosphatase in diabetic mice (p<0.05). Insulin levels increased in animals treated with 200 mg/kg (p<0.05) and HDL and leptin levels increased in animals treated with 300 mg/kg of the extract (p<0.01).

CONCLUSION

The results showed that A. lappa root extract, at specific doses, has an anti-diabetic effect through its hypolipidemic and insulinotropic properties. Hence, this plant extract may be beneficial in the treatment of diabetes.

Chrysin induces cell apoptosis via activation of the p53/Bcl-2/caspase-9 pathway in hepatocellular carcinoma cells

Chrysin is a major active ingredient of flavonoids, known to exhibit protective effects against various types of cancer. However, the anticancer role of chrysin against hepatocellular carcinoma (HCC) and the underlying molecular mechanisms remain unclear. In order to evaluate the effects of chrysin on cell viability and apoptosis in human HCC, HepG2 and QGY7701 cells were used in the present study. Cell viability was monitored using an MTT assay. In addition, an Annexin V-fluorescein isothiocyanate/propidium iodide kit was used for the labeling of the apoptotic cells, which were then measured using flow cytometry. Western blotting was used to examine the protein expression of p53, B-cell lymphoma-2 (Bcl-2), Bcl-2-associated X (Bax), Bcl-2-associated death promoter (Bad), Bcl-2 homologous antagonist/killer (Bak), caspases-3 and -9, and cleaved-caspases-3 and -9. The results of the present study revealed that chrysin suppressed the cell viability of HepG2 and QGY7701 cells in a concentration-dependent manner. In addition, chrysin induced significant apoptosis in HepG2 and QGY7701 cells. Furthermore, it was demonstrated that chrysin treatment increased the expression of proapoptotic proteins, including p53, Bax, Bad and Bak, while it decreased the protein level of antiapoptotic protein Bcl-2. It was also demonstrated that chrysin induced apoptosis in the HCC cells by regulating the p53/Bcl-2/caspase-9 signaling pathway. In conclusion, the results of the present study suggested that chrysin may be a potential candidate agent for the induction of cell apoptosis in human HCC.

Challenges and issues with streptozotocin-induced diabetes - A clinically relevant animal model to understand the diabetes pathogenesis and evaluate therapeutics

Streptozotocin (STZ) has been extensively used over the last three decades to induce diabetes in various animal species and to help screen for hypoglycemic drugs. STZ induces clinical features in animals that resemble those associated with diabetes in humans. For this reason STZ treated animals have been used to study diabetogenic mechanisms and for preclinical evaluation of novel antidiabetic therapies. However, the physiochemical characteristics and associated toxicities of STZ are still major obstacles for researchers using STZ treated animals to investigate diabetes. Another major challenges in STZ-induced diabetes are sustaining uniformity, suitability, reproducibility and induction of diabetes with minimal animal lethality. Lack of appropriate use of STZ was found to be associated with increased mortality and animal suffering. During STZ use in animals, attention should be paid to several factors such as method of preparation of STZ, stability, suitable dose, route of administration, diet regimen, animal species with respect to age, body weight, gender and the target blood glucose level used to represent hyperglycemia. Therefore, protocol for STZ-induced diabetes in experimental animals must be meticulously planned. This review highlights specific skills and strategies involved in the execution of STZ-induced diabetes model. The present review aims to provide insight into diabetogenic mechanisms of STZ, specific toxicity of STZ with its significance and factors responsible for variations in diabetogenic effects of STZ. Further this review also addresses ways to minimize STZ-induced mortality, suggests methods to improve STZ-based experimental models and best utilize them for experimental studies purported to understand diabetes pathogenesis and preclinical evaluation of drugs.

Sulfuretin induces osteoblast differentiation through activation of TGF-β signaling

The identification and examination of potential determinants controlling the progression of cell fate toward osteoblasts can be intriguing subjects. In this study, the effects of sulfuretin, a major compound isolated from Rhus verniciflua Stokes, on osteoblast differentiation were investigated. Treatments of sulfuretin induced alkaline phosphatase (ALP) activity in mesenchymal C3H10T1/2 cells and mineralization in preosteoblast MC3T3-E1 cells. Pro-osteogenic effects of sulfuretin were consistently observed in freshly isolated primary bone marrow cells. In mechanical studies, sulfuretin specifically induced expression of TGF-β target genes, such as SMAD7 and PAI-1, but not other signaling pathway-related genes. Similar to the results of gene expression analysis, reporter assays further demonstrated TGF-β-specific induction by sulfuretin. Furthermore, disruption of TGF-β signaling using treatment with TGF-β-specific inhibitor, SB-431542, and introduction of SMAD2/3 small interfering RNA impaired the effects of sulfuretin in inducing ALP activity and expression of ALP mRNA. Together, these data indicate that the pro-osteogenic effects of sulfuretin are mediated through activation of TGF-β signaling, further supporting the potential of sulfuretin in the prevention of bone-related diseases such as bone fracture and osteoporosis.

Bougainvillea spectabilis Exhibits Antihyperglycemic and Antioxidant Activities in Experimental Diabetes

The study investigates the effects of aqueous extract of Bougainvillea spectabilis leaves on blood glucose, glycosylated hemoglobin, lipid profile, oxidative stress, and on DNA damage, if any, as well as on liver and kidney functions in streptozotocin-induced diabetes in Wistar rats. Daily administration of the aqueous extract of B spectabilis leaves for 28 days resulted in significant reduction in hyperglycemia and hyperlipidemia as evident from restoration of relevant biochemical markers following extract administration. The extract also exhibited significant antioxidant activity as evidenced from the enzymatic and nonenzymatic responses and DNA damage markers. The extract restored kidney and liver functions to normal and proved to be nontoxic. A marked improvement in the histological changes of tissues was also observed. The present study documented antihyperglycemic, antihyperlipidemic, and antioxidative potentials of the aqueous extract of B spectabilis leaves without any toxicity in streptozotocin-treated Wistar rats.

Involvement of the Nrf2/HO-1 signaling pathway in sulfuretin-induced protection against amyloid beta25-35 neurotoxicity

Sulfuretin, one of the major flavonoid glycosides found in the stem bark of Albizzia julibrissin and heartwood of Rhus verniciflua, is a known anti-oxidant. We previously demonstrated that sulfuretin inhibits neuronal death via reactive oxygen species (ROS)-dependent mechanisms in human SH-SY5Y cells, although other relevant mechanisms of action of this compound remain largely uncharacterized. As part of our ongoing exploration of the pharmacological actions of sulfuretin, we studied the neuroprotective effects of sulfuretin against amyloid beta (Aβ)-induced neurotoxicity in human SH-SY5Y and primary hippocampal neuron cells and investigated the possible mechanisms involved. Specifically, we found in the present study that sulfuretin significantly attenuates the decrease in cell viability, release of lactate dehydrogenase, and accumulation of ROS associated with Aβ25-35-induced neurotoxicity in neuronal cells. Furthermore, sulfuretin stimulated the activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a downstream target of phosphatidylinositol 3-kinases (PI3K)/Akt. We demonstrated that sulfuretin induces the expression of heme oxygenase-1 (HO-1), an anti-oxidant response gene. Notably, we found that the neuroprotective effects of sulfuretin were diminished by an Nrf2 small interfering RNA (siRNA), the HO-1 inhibitor zinc protoporphyrin IX (ZnPP), as well as the PI3K/Akt inhibitor LY294002. Taken together, these results indicated that sulfuretin protects neuronal cells from Aβ25-35-induced neurotoxicity through activation of Nrf/HO-1 and PI3K/Akt signaling pathways. Our results also indicate that sulfuretin-induced induction of Nrf2-dependent HO-1 expression via the PI3K/Akt signaling pathway has preventive and/or therapeutic potential for the management of Alzheimer's disease.

Pharmacokinetic Profile of Eight Phenolic Compounds and Their Conjugated Metabolites after Oral Administration of Rhus verniciflua Extracts in Rats

Rhus verniciflua (Toxicodendron vernicifluum) is a medicinal tree popularly used in Asian countries such as China, Japan, and Korea as a food additive or herbal medicine because of its beneficial effects. R. verniciflua extract (RVE) contains diverse phenolic compounds, such as flavonoids, as its major biological active constituents. In this study, the pharmacokinetic profiles of eight phenolic compounds were investigated following oral administration of RVE to rats. The eight phenolic compounds were 2,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, fisetin, fustin, butin, sulfuretin, taxifolin, and garbanzol. The plasma concentrations of the eight compounds were determined by using a liquid chromatography-triple-quadrupole mass spectrometer before and after treatment with β-glucuronidase. When 1.5 g/kg RVE was administered, the eight compounds were all detected in plasma, mainly as conjugated forms. These pharmacokinetic data would be useful for understanding the pharmacological effects of RVE.

Polyphenols isolated from Broussonetia kazinoki prevent cytokine-induced β-cell damage and the development of type 1 diabetes

The axis of nuclear factor κB (NF-κB)-inducible NO synthase (iNOS)-nitric oxide plays a key role in cytokine- and streptozotocin-mediated pancreatic β-cell damage. In this study, we investigated the effects of kazinol C and isokazinol D isolated from Broussonetia kazinoki on the β-cell viability and function. RINm5F cells and primary islets were used for in vitro and ex vivo cytokine toxicity experiments, respectively. For type 1 diabetes induction, mice were injected with multiple low-dose streptozotocin (MLDS). Cytokine-induced toxicity was completely abolished in both RINm5F cells and islets that were pretreated with either kazinol C or isokazinol D. Both kazinols inhibited the NF-κB signaling pathway, thereby inhibiting cytokine-mediated iNOS induction, nitric oxide production, apoptotic cell death and defects in insulin secretion. Moreover, the occurrence of diabetes in MLDS-treated mice was efficiently attenuated in kazinol-pretreated mice. Immunohistochemical analysis revealed that the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive apoptotic cells and nuclear p65-positive cells were significantly decreased in kazinol-pretreated mice. Our results suggest that kazinol C and isokazinol D block the NF-κB pathway, thus reducing the extent of β-cell damage. Therefore, kazinol C and isokazinol D may have therapeutic value in delaying pancreatic β-cell damage in type 1 diabetes.

Effects of luteolin on retinal oxidative stress and inflammation in diabetes

These studies are the first to show that luteolin can inhibit diabetes-induced retinal abnormalities that are postulated in the development of diabetic retinopathy.

Chrysin protects against focal cerebral ischemia/reperfusion injury in mice through attenuation of oxidative stress and inflammation

Inflammation and oxidative stress play an important part in the pathogenesis of focal cerebral ischemia/reperfusion (I/R) injury, resulting in neuronal death. The signaling pathways involved and the underlying mechanisms of these events are not fully understood. Chrysin, which is a naturally occurring flavonoid, exhibits various biological activities. In this study, we investigated the neuroprotective properties of chrysin in a mouse model of middle cerebral artery occlusion (MCAO). To this end, male C57/BL6 mice were pretreated with chrysin once a day for seven days and were then subjected to 1 h of middle cerebral artery occlusion followed by reperfusion for 24 h. Our data show that chrysin successfully decreased neurological deficit scores and infarct volumes, compared with the vehicle group. The increases in glial cell numbers and proinflammatory cytokine secretion usually caused by ischemia/reperfusion were significantly ameliorated by chrysin pretreatment. Moreover, chrysin also inhibited the MCAO-induced up-regulation of nuclear factor-kappa B (NF-κB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), compared with the vehicle. These results suggest that chrysin could be a potential prophylactic agent for cerebral ischemia/reperfusion (I/R) injury mediated by its anti-inflammatory and anti-oxidative effects.

Integrating traditional medicine into modern inflammatory diseases care: multitargeting by Rhus verniciflua Stokes

Despite the fact that numerous researches were performed on prevention and treatment of inflammation related diseases, the overall incidence has not changed remarkably. This requires new approaches to overcome inflammation mediated diseases, and thus traditional medicine could be an efficacious source for prevention and treatment of these diseases. In this review, we discuss the contribution of traditional medicine, especially Rhus verniciflua Stokes, to modern medicine against diverse inflammation mediated diseases. Traditionally, this remedy has been used in Eastern Asia for the treatment of gastric problems, hepatic disorders, infectious diseases, and blood disorders. Modern science has provided the scientific basis for the use of Rhus verniciflua Stokes against such disorders and diseases. Various chemical constituents have been identified from this plant, including phenolic acid, and flavonoids. Cell-based studies have exhibited the potential of this as antibacterial, antioxidant, neuroprotective, anti-inflammatory, growth inhibitory, and anticancer activities. Enormous animal studies have shown the potential of this against proinflammatory diseases, neurodegenerative diseases, diabetes, liver diseases, and chemical insults. At the molecular level, this medicinal plant has been shown to modulate diverse cell-signaling pathways. In clinical studies, Rhus verniciflua Stokes has shown efficacy against various cancer patients such as colorectal, gastric, hepatic, renal, pancreatic, and pulmonary cancers. Thus, this remedy is now exhibiting activities in the clinic.

The efficacy of SPA0355 in protecting β cells in isolated pancreatic islets and in a murine experimental model of type 1 diabetes

Cytokines activate several inflammatory signals that mediate β-cell destruction. We recently determined that SPA0355 is a strong anti-inflammatory compound, thus reporting its efficacy in protecting β cells from various insults. The effects of SPA0355 on β-cell survival were studied in RINm5F cells and primary islets. The protective effects of this compound on the development of type 1 diabetes were evaluated in non-obese diabetic (NOD) mice. SPA0355 completely prevented cytokine-induced nitric oxide synthase (iNOS) expression and cytotoxicity in RINm5F cells and isolated islets. The molecular mechanism of SPA0355 inhibition of iNOS expression involves the inhibition of nuclear factor κB and Janus kinase signal transducer and activator of transcription pathways. The protective effects of SPA0355 against cytokine toxicity were further demonstrated by normal insulin secretion and absence of apoptosis of cytokine-treated islets. In experiments with NOD mice, the occurrence of diabetes was efficiently reduced when the mice were treated with SPA0355. Therefore, SPA0355 might be a valuable treatment option that delays the destruction of pancreatic β cells in type 1 diabetes.

Butein is a novel anti-adipogenic compound

Rhus verniciflua Stokes (RVS) has been used as a traditional herbal medicine for its various biological activities including anti-adipogenic effects. Activity-guided separation led to the identification of the anti-adipogenic functions of butein. Butein, a novel anti-adipogenic compound, robustly suppressed lipid accumulation and inhibited expression of adipogenic markers. Molecular studies showed that activated transforming growth factor-β (TGF-β) and suppressed signal transducer and activator of transcription 3 (STAT3) signaling pathways were mediated by butein. Analysis of the temporal expression profiles suggests that TGF-β signaling precedes the STAT3 in the butein-mediated anti-adipogenic cascade. Small interfering RNA-mediated silencing of STAT3 or SMAD2/3 blunted the inhibitory effects of butein on adipogenesis indicating that an interaction between two signaling pathways is required for the action of butein. Upon butein treatments, stimulation of TGF-β signaling was still preserved in STAT3 silenced cells, whereas regulation of STAT3 signaling by butein was significantly impaired in SMAD2/3 silenced cells, further showing that TGF-β acts upstream of STAT3 in the butein-mediated anti-adipogenesis. Taken together, the present study shows that butein, a novel anti-adipogenic compound from RVS, inhibits adipocyte differentiation through the TGF-β pathway followed by STAT3 and peroxisome proliferator-activated receptor γ signaling, further implicating potential roles of butein in TGF-β- and STAT3-dysregulated diseases.

Sulfuretin-induced miR-30C selectively downregulates cyclin D1 and D2 and triggers cell death in human cancer cell lines

Sulfuretin (3',4',6'-trihydroxyaurone), one of the key flavonoids isolated from Rhus verniciflua, is known to suppress inflammation and oxidative stress. However, the anti-cancer properties of sulfuretin as well as its mechanism of action remain poorly understood. Here, we show that the expression of miR-30C is markedly enhanced in sulfuretin-stimulated cells, consequently promoting apoptosis and cell cycle arrest in human cancer cell lines. The transient transfection of pre-miR-30C resulted in greater than 70% growth inhibition in PC-3 cells and provided strong evidence that miR-30C selectively suppresses the expression of cyclin D1 and D2, but not cyclin D3. Target validation analysis revealed that 3'-UTR of cyclin D2 is a direct target of miR-30C, whereas suppression by miR-30C of cyclin D1 may occur through indirect mRNA regulation. In addition, silencing miR-30C expression partially reversed sulfuretin-induced cell death. Taken together, our data suggest that miR-30C, a tumor suppressor miRNA, contributes to anti-cancer properties of sulfuretin by negatively regulating cyclin D1 and D2, providing important implications of sulfuretin and miR-30C for the therapeutic intervention of human cancers.

Anti-inflammatory therapy in type 1 diabetes

Type 1 diabetes (T1D) is a multi-factorial, organ-specific autoimmune disease in genetically susceptible individuals, which is characterized by a selective and progressive loss of insulin-producing β-cells. Cells mediating innate as well as adaptive immunity infiltrate pancreatic islets, thereby generating an aberrant inflammatory process called insulitis that can be mirrored by a pathologic autoantibody production and autoreactive T-cells. In tight cooperation with infiltrating innate immune cells, which secrete high levels of pro-inflammatory cytokines like IL-1β, TNFα, and INFγ effector T-cells trigger the fatal destruction process of β-cells. There is ongoing discussion on the contribution of inflammation in T1D pathogenesis, ranging from a bystander reaction of autoimmunity to a dysregulation of immune responses that initiate inflammatory processes and thereby actively promoting β-cell death. Here, we review recent advances in anti-inflammatory interventions in T1D animal models and preclinical studies and discuss their mode of action as well as their capacity to interfere with T1D development.

Myricetin protects against cytokine-induced cell death in RIN-m5f β cells

Cytokine-induced cell death is recognized as a major cause of progressive β-cell loss. Tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interferon γ (IFN-γ) in combination trigger a series of events that lead to β-cell death. In the past few decades, the use of myricetin as an anti-inflammatory and cytoprotective agent has gained much attention. The present study focused on the protective roles of myricetin against cytokine-induced cell death in insulin-secreting RIN-m5f β cells. The results showed that myricetin (especially at concentrations of 10 μM and 20 μM) increased cell viability and decreased cell apoptosis induced by the cytokine mixture of TNF-α (10 ng/mL), IL-1β (5 ng/mL), and IFN-γ (1000 IU/mL) for 3 days. Moreover, the cytokines increased the total and p65 subunit levels of nuclear factor κB, decreased inhibitor κB α levels, stimulated the accumulation of nitric oxide, increased cytochrome c release from mitochondria, and induced reactive oxygen species generation; myricetin (especially at the concentration of 20 μM) abolished all of these parameters. These results suggest that myricetin might have therapeutic value for preventing β-cell death.

Cytoprotective effect of Coreopsis tinctoria extracts and flavonoids on tBHP and cytokine-induced cell injury in pancreatic MIN6 cells

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Coreopsis tinctoria flowering tops infusion is traditionally used in Portugal for treating the symptoms of diabetes. Recent studies have revealed its antihyperglycemic activity when administered for 3 weeks to a STZ-induced glucose intolerance model in the rat and glucose tolerance regain was even clearer and pancreatic function recovery was achieved when administering Coreopsis tinctoria flavonoid-rich AcOEt fraction. In this study we aimed to evaluate the protective effect of Coreopsis tinctoria flowering tops aqueous extract, AcOEt fraction and the pure compounds marein and flavanomarein, against beta-cell injury, in a mouse insulinoma cell line (MIN6) challenged with pro-oxidant tert-butyl-hydroperoxide (tBHP) or cytokines.

MATERIALS AND METHODS

The protective effects of Coreopsis tinctoria flowering tops extracts and pure compounds were evaluated through pre-incubating MIN6 cells with samples followed by treatment with tBHP (400 μM for 2 h) after which viability was determined through ATP measurements. In order to assess whether plant extracts were involved in decreasing reactive oxygen species, superoxide anion production was determined through a lucigenin-enhanced chemiluminescent method. Lastly, the direct influence of Coreopsis tinctoria extracts and main compounds on cell survival/apoptosis was determined measuring caspase 3 and 7 cleavage induced by cytokines.

RESULTS

Coreopsis tinctoria flowering tops extracts (25-100 μg/mL) and pure compounds (200-400 μM), when pre-incubated with MIN6 cells did not present any cytotoxicity, instead they increased cell viability in a dose dependent manner when challenged with tBHP. Treatment with this pro-oxidant also showed a rise in superoxide radical anion formation in MIN6 cells. This increase was significantly reduced by treatment with superoxide dismutase enzyme (SOD) but not by pre-treatment with Coreopsis tinctoria flowering tops extracts. Caspase 3/7 activation measurements show that Coreopsis tinctoria flowering tops extracts, as well as marein and flavanomarein, significantly inhibit apoptosis.

CONCLUSIONS

Coreopsis tinctoria extracts and pure compounds show cytoprotection that seems to be due to inhibition of the apoptotic pathway, and not through a decrease on superoxide radical production.