Biological effects of the plant-derived polyphenol resveratrol in human articular cartilage and chondrosarcoma cells

Anti-Inflammatory Effects of Dietary Polyphenols through Inhibitory Activity against Metalloproteinases

Matrix metalloproteinases (MMPs) are zinc-dependent metalloproteinases that play important roles in a variety of diseases, including cancer, cardiovascular disease, diabetes, obesity, and brain diseases. Dietary polyphenols are thought to have a variety of beneficial effects on these diseases characterized by inflammation. Clinical studies have demonstrated that MMPs are in most cases upregulated in various inflammatory diseases, including osteoarthritis, rheumatoid arthritis, inflammatory bowel disease, and Alzheimer's disease. Studies using patient-derived human samples, animal studies, and cellular experiments have suggested that polyphenols may be beneficial against inflammatory diseases by suppressing MMP gene expression and enzyme activity. One important mechanism by which polyphenols exert their activity is the downregulation of reactive oxygen species that promote MMP expression. Another important mechanism is the direct binding of polyphenols to MMPs and their inhibition of enzyme activity. Molecular docking analyses have provided a structural basis for the interaction between polyphenols and MMPs and will help to explore new polyphenol-based drugs with anti-inflammatory properties.

Protective Effect of Resveratrol on Knee Osteoarthritis and its Molecular Mechanisms: A Recent Review in Preclinical and Clinical Trials

Osteoarthritis (OA) is one of the progressing chronic joint associated with by many complex factors such as age, obesity, and trauma. Knee osteoarthritis (KOA) is the most common type of OA. KOA is characterized by articular cartilage destruction and degeneration, synovial inflammation, and abnormal subchondral bone changes. To date, no practical clinical approach has been able to modify the pathological progression of KOA. Drug therapy is limited to pain control and may lead to serious side effects when taken for a long time. Therefore, searching for safer and more reliable treatments has become necessary. Interestingly, more and more research has focused on natural products, and monomeric compounds derived from natural products have received much attention as drug candidates for KOA treatment. Resveratrol (RES), a natural phenolic compound, has various pharmacological and biological activities, including anti-cancer, anti-apoptotic, and anti-decay. Recently, studies on the effects of RES on maintaining the normal homeostasis of chondrocytes in KOA have received increasing attention, which seems to be attributed to the multi-targeted effects of RES on chondrocyte function. This review summarizes preclinical trials, clinical trials, and emerging tissue engineering studies of RES for KOA and discusses the specific mechanisms by which RES alleviates KOA. A better understanding of the pharmacological role of RES in KOA could provide clinical implications for intervention in the development of KOA.

Antioxidant Effects of Resveratrol in Intervertebral Disk

Intervertebral disk (IVD) degeneration (IVDD) can cause various spinal degenerative diseases. Cumulative evidence has indicated that IVDD can result from inflammation, apoptosis, autophagy, biomechanical changes and other factors. Currently, lack of conservative treatment for degenerative spinal diseases leads to an urgent demand for clinically applicable medication to ameliorate the progression of IVDD. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a polyphenol compound extracted from red wine or grapes, has shown protective effects on IVD, alleviating the progression of IVDD. Resveratrol has been demonstrated as a scavenger of free radicals both in vivo and in vitro. The antioxidant effects of resveratrol are likely attributed to its regulation on mitochondrial dysfunction or the elimination of reactive oxygen species. This review will summarize the mechanisms of the reactive oxygen species production and elaborate the mechanisms of resveratrol in retarding IVDD progression, providing a comprehensive understanding of the antioxidant effects of resveratrol in IVD.

Leptin Induced TLR4 Expression via the JAK2-STAT3 Pathway in Obesity-Related Osteoarthritis

Obesity is considered as a risk factor of osteoarthritis (OA), but the precise relationship is still poorly understood. Leptin, one of the most relevant factors secreted by adipose tissues, plays an important role in the pathogenesis of OA. Our aim was to investigate the regulation and molecular mechanism of the leptin signaling pathway in obesity-related OA. SD rats were fed with a high-fat diet (HFD) for 5, 15, and 27 weeks. The levels of leptin in serum increased from W5, while in the synovial fluid increased from W15. The histological evaluation showed that the pathological changes of OA occurred at 27 weeks rather than 5 or 15 weeks. We also found that leptin induced CD14/TLR4 activation by the JAK2-STAT3 signaling pathway to promote OA. Moreover, silencing SOCS3 enhanced leptin-induced JAK2-STAT3-CD14/TLR4 activation in rat primary chondrocytes. Our findings indicated that leptin may be one of the initiating factors of obesity-related OA. TLR4 is at least partially regulated by leptin through the JAK2-STAT3-CD14 pathway. Meanwhile, SOCS3 acting as a negative feedback inhibitor of leptin signaling presented a potential therapeutic prospect for obesity-related OA. Our study provided new evidence suggesting the key role of leptin in mediating obesity-related OA process and its underlying mechanisms.

Chondrocyte Aging: The Molecular Determinants and Therapeutic Opportunities

Osteoarthritis (OA) is a joint degenerative disease that is an exceedingly common problem associated with aging. Aging is the principal risk factor for OA, but damage-related physiopathology of articular chondrocytes probably drives the mechanisms of joint degeneration by a progressive decline in the homeostatic and regenerative capacity of cells. Cellular aging is the manifestation of a complex interplay of cellular and molecular pathways underpinned by transcriptional, translational, and epigenetic mechanisms and niche factors, and unraveling this complexity will improve our understanding of underlying molecular changes that affect the ability of the articular cartilage to maintain or regenerate itself. This insight is imperative for developing new cell and drug therapies for OA disease that will target the specific causes of age-related functional decline. This review explores the key age-related changes within articular chondrocytes and discusses the molecular mechanisms that are commonly perturbed as cartilage ages and degenerates. Current efforts and emerging potential therapies in treating OA that are being employed to halt or decelerate the aging processes are also discussed.

Emerging Natural-Product-Based Treatments for the Management of Osteoarthritis

Osteoarthritis (OA) is a complex degenerative disease in which joint homeostasis is disrupted, leading to synovial inflammation, cartilage degradation, subchondral bone remodeling, and resulting in pain and joint disability. Yet, the development of new treatment strategies to restore the equilibrium of the osteoarthritic joint remains a challenge. Numerous studies have revealed that dietary components and/or natural products have anti-inflammatory, antioxidant, anti-bone-resorption, and anabolic potential and have received much attention toward the development of new therapeutic strategies for OA treatment. In the present review, we provide an overview of current and emerging natural-product-based research treatments for OA management by drawing attention to experimental, pre-clinical, and clinical models. Herein, we review current and emerging natural-product-based research treatments for OA management.

Herbal Remedies as Potential in Cartilage Tissue Engineering: An Overview of New Therapeutic Approaches and Strategies

It is estimated that by 2023, approximately 20% of the population of Western Europe and North America will suffer from a degenerative joint disease commonly known as osteoarthritis (OA). During the development of OA, pro-inflammatory cytokines are one of the major causes that drive the production of inflammatory mediators and thus of matrix-degrading enzymes. OA is a challenging disease for doctors due to the limitation of the joint cartilage's capacity to repair itself. Though new treatment approaches, in particular with mesenchymal stem cells (MSCs) that integrate the tissue engineering (TE) of cartilage tissue, are promising, they are not only expensive but more often do not lead to the regeneration of joint cartilage. Therefore, there is an increasing need for novel, safe, and more effective alternatives to promote cartilage joint regeneration and TE. Indeed, naturally occurring phytochemical compounds (herbal remedies) have a great anti-inflammatory, anti-oxidant, and anabolic potential, and they have received much attention for the development of new therapeutic strategies for the treatment of inflammatory diseases, including the prevention of age-related OA and cartilage TE. This paper summarizes recent research on herbal remedies and their chondroinductive and chondroprotective effects on cartilage and progenitor cells, and it also emphasizes the possibilities that exist in this research area, especially with regard to the nutritional support of cartilage regeneration and TE, which may not benefit from non-steroidal anti-inflammatory drugs (NSAIDs).

Resveratrol counteracts IL-1β-mediated impairment of extracellular matrix deposition in 3D articular chondrocyte constructs

When aiming at cell-based therapies in osteoarthritis (OA), proinflammatory conditions mediated by cytokines such as IL-1β need to be considered. In recent studies, the phytoalexin resveratrol (RSV) has exhibited potent anti-inflammatory properties. However, long-term effects on 3D cartilaginous constructs under inflammatory conditions with regard to tissue quality, especially extracellular matrix (ECM) composition, have remained unexplored. Therefore, we employed long-term model cultures for cell-based therapies in an in vitro OA environment and evaluated effects of RSV. Pellet constructs made from expanded porcine articular chondrocytes were cultured with either IL-1β (1-10 ng/ml) or RSV (50 μM) alone, or a cotreatment with both agents. Treatments were applied for 14 days, either directly after pellet formation or after a preculture period of 7 days. Culture with IL-1β (10 ng/ml) decreased pellet size and DNA amount and severely compromised glycosaminoglycan (GAG) and collagen content. Cotreatment with RSV distinctly counteracted the proinflammatory catabolism and led to partial rescue of the ECM composition in both culture systems, with especially strong effects on GAG. Marked MMP13 expression was detected in IL-1β-treated pellets, but none upon RSV cotreatment. Expression of collagen type I was increased upon IL-1β treatment and still observed when adding RSV, whereas collagen type X, indicating hypertrophy, was detected exclusively in pellets treated with RSV alone. In conclusion, RSV can counteract IL-1β-mediated degradation and distinctly improve cartilaginous ECM deposition in 3D long-term inflammatory cultures. Nevertheless, potential hypertrophic effects should be taken into account when considering RSV as cotreatment for articular cartilage repair techniques.

Resveratrol Exerts Anti-Osteoarthritic Effect by Inhibiting TLR4/NF-κB Signaling Pathway via the TLR4/Akt/FoxO1 Axis in IL-1β-Stimulated SW1353 Cells

Purpose

Osteoarthritis (OA) is associated with chronic low-grade inflammation. Resveratrol exerts protective effects on OA through its anti-inflammatory property; however, the mechanism of resveratrol on anti-inflammatory signaling pathways has not been fully elucidated yet. The aim of the present study was to investigate whether resveratrol-mediated PI3K/Akt expression is linked to TLR4/NF-κB pathway and the role of TLR4/Akt/FoxO1 axis in the anti-osteoarthritic effect of resveratrol.

Methods

SW1353 cells stimulated by IL-1β (10 ng/mL) were cultured in the presence or absence of resveratrol (50 μM) and then treated with TLR4 siRNA, PI3K inhibitor LY294002 or FoxO1 siRNA, respectively. The associated proteins of TLR4 signaling pathways and TLR4/Akt/FoxO1 axis were evaluated by Western blot. The level of IL-6 in the supernatant was detected by ELISA.

Results

IL-1β treatment increased the expression of TLR4/NF-κB and phosphorylation of PI3K/Akt and FoxO1, while additional resveratrol further upregulated the expression of PI3K/Akt and FoxO1 phosphorylation but downregulated TLR4 signals in SW1353 cells. Further analyses by the inhibition of TLR4, PI3K/Akt and FoxO1 signaling pathways, respectively, showed that the activation of TLR4 can induce PI3K/Akt phosphorylation, which increases the phosphorylation of FoxO1 and inactivates it. Next, inactivated-FoxO1 can reduce the expression of TLR4, which forms a self-limiting mechanism of inflammation. Resveratrol treatment can upregulate PI3K/Akt phosphorylation and inactivate FoxO1, thereby reducing TLR4 and inflammation.

Conclusion

This study reveals that TLR4/Akt/FoxO1 inflammatory self-limiting mechanism may exist in IL-1β-stimulated SW1353 cells. This study reveals a novel cross-talk mechanism which is between integrated PI3K/Akt/FoxO1 signaling network and TLR4-driven innate responses in IL-1β-stimulated SW1353 cells. Resveratrol may exert anti-OA effect by enhancing the self-limiting mechanism of inflammation through TLR4/Akt/FoxO1 axis.

Resveratrol inhibits the development of obesity-related osteoarthritis via the TLR4 and PI3K/Akt signaling pathways

Aim of the study: Obesity leads to mild, chronic inflammation which is a primary risk factor for osteoarthritis (OA). Resveratrol exerts a protective effect on OA through its anti-inflammatory properties, but the precise mechanism remains unknown. The present study aimed to investigate the mechanism by which resveratrol alleviates obesity-related OA, and whether it is linked to the TLR4 and PI3K/Akt signaling pathways. Materials and methods: C57BL/6J male mice were fed a high-fat diet (HFD) with or without resveratrol treatment and knee joints were collected for analysis. In addition, IL-1β-induced SW1353 cells were used to study in vitro the reciprocal effects of TLR4 and PI3K/Akt pathways. Results: Resveratrol inhibited the development of OA in mice fed a HFD. TLR4 and PI3K/Akt signaling pathways were both activated in the articular cartilage; resveratrol treatment down-regulated TLR4 but up-regulated PI3K/Akt signaling. Further in vitro results showed that the effect of resveratrol alone on activation of PI3K/Akt was attenuated but not abolished by the TLR4 inhibitor CLI-095, and resveratrol failed to reduce TLR4 protein expression in IL-1β stimulated cells pretreated with the PI3K inhibitor LY294002. Conclusions: Resveratrol may exert an anti-osteoarthritic effect by inhibiting TLR4 via the activation of PI3K/Akt signaling pathways. Resveratrol has potential as a drug for OA prevention.

Natural products as important tyrosine kinase inhibitors

As an important source of drugs, natural products play an important role in the discovery and development of new drugs. More than 60% of anti-tumor drugs are closely related to natural products. At the same time, as the main cause of tumors, the abnormal activity of tyrosine kinase has become an important target for clinical treatment. Although, small molecule targeted drugs dominate the cancer treatment. Natural active products are driving the development of new tyrosine kinase inhibitors with their unique mode of action and molecular structure diversity. Obtaining new chemical entities with tyrosine kinase inhibitory activity from natural active products will bring new breakthroughs in the research of anticancer drugs. In this paper, different tyrosine kinases are mainly classified as targets, and natural products and derivatives which have been found to inhibit tyrosine kinase activity have been described. It is hoped that by analyzing the different aspects of the source, structural characteristics, mechanism of action and biological activity of these natural products, we will find new members that can be developed into drugs and promote the development of anti-tumor drugs.

Resveratrol protects against asthma-induced airway inflammation and remodeling by inhibiting the HMGB1/TLR4/NF-κB pathway

The aim of the present study was to explore the protective role of resveratrol (RES) in asthma-induced airway inflammation and remodeling, as well as its underlying mechanism. An asthma rat model was induced by ovalbumin (OVA) treatment. Rats were randomly assigned into sham, asthma, 10 µmol/l RES and 50 µmol/l RES groups. The amount of inflammatory cells in rat bronchoalveolar lavage fluid (BALF) was detected. Pathological lesions in lung tissues were accessed by hematoxylin and eosin (H&E), and Masson's trichrome staining. Levels of inflammatory factors in lung homogenate were detected via ELISA. The blood serum of asthmatic and healthy children was also collected for analysis. Reverse transcription-quantitative polymerase chain reaction was performed to detect high mobility group box 1 (HMGB1), Τoll-like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (MyD88) and NF-κB expression in asthmatic and healthy children, as well as rats of the different groups. H&E staining demonstrated that multiple inflammatory cell infiltration into the rat airway epithelium of the asthma group occurred whilst the 50 µmol/l RES group displayed alleviated pathological lesions. Masson staining indicated that there was an increased airway collagen deposition area in the asthma and 10 µmol/l RES groups compared with the 50 µmol/l RES group. The number of inflammatory cells in BALF extracted from rats of the asthma and 10 µmol/l RES groups was higher compared with the 50 µmol/l RES group. Treatment with 50 µmol/l RES significantly decreased the thicknesses of the airway wall and smooth muscle. ELISA results illustrated that interleukin (IL)-1, IL-10 and tumor necrosis factor-α (TNF-α) levels were elevated, whereas IL-12 level was reduced in lung tissues of the asthma and 10 µmol/l RES groups whilst the 50 µmol/l RES group demonstrated the opposite trend. HMGB1, TLR4, MyD88 and NF-κB mRNA levels were remarkably elevated in rats of the asthma and 10 µmol/l RES groups compared with the 50 µmol/l RES group. Serum levels of IL-1, IL-10 and TNF-α were elevated, whereas IL-12 was reduced in asthmatic children compared with healthy children. The present results demonstrated that a large dose of RES alleviated asthma-induced airway inflammation and airway remodeling by inhibiting the release of inflammatory cytokines via the HMGB1/TLR4/NF-κB pathway.

Efficacy and safety of co-administration of resveratrol with meloxicam in patients with knee osteoarthritis: a pilot interventional study

Background and aim

Resveratrol shows remarkable anti-inflammatory activities in experimental models. This study aims to evaluate the effect of resveratrol, as an adjuvant with meloxicam (Mlx), on the pain and functional activity during a 90-day period and monitor the adverse effects on kidney and liver functions, lipid profile, and hematological markers.

Patients and methods

This study was a double-blind, placebo-controlled, randomized multi-center study that involved 110 patients with knee osteoarthritis (OA) and was performed at Sulaimani City, Iraq, from December 2016 to September 2017. To assess the effects of Mlx with or without resveratrol, pain severity and functional disability were evaluated at baseline and after 90 days using the Western Ontario and McMaster Universities Osteoarthritis Index. Fasting blood was collected to evaluate the lipid profile markers, hematological picture, and liver and kidney functions, in addition to vitamin D level.

Results

Resveratrol significantly improves pain, functions, and associated symptoms compared with placebo. The clinical and biochemical markers indicated that 500 mg/day of resveratrol, as an adjuvant with Mlx, is safe and well tolerated by the knee OA patients.

Conclusion

Resveratrol, as an “add-on” medication with Mlx, was superior in terms of safety and efficacy to Mlx alone for the treatment of pain and improvement of physical function in patients with knee OA.

Cellular pharmacodynamic effects of Pycnogenol® in patients with severe osteoarthritis: a randomized controlled pilot study

BACKGROUND

The standardized maritime pine bark extract (Pycnogenol®) has previously shown symptom alleviating effects in patients suffering from moderate forms of knee osteoarthritis (OA). The cellular mechanisms for this positive impact are so far unknown. The purpose of the present randomized pilot controlled study was to span the knowledge gap between the reported clinical effects of Pycnogenol® and its in vivo mechanism of action in OA patients.

METHODS

Thirty three patients with severe OA scheduled for a knee arthroplasty either received 100 mg of Pycnogenol® twice daily or no treatment (control group) three weeks before surgery. Cartilage, synovial fluid and serum samples were collected during surgical intervention. Relative gene expression of cartilage homeostasis markers were analyzed in the patients' chondrocytes. Inflammatory and cartilage metabolism mediators were investigated in serum and synovial fluid samples.

RESULTS

The oral intake of Pycnogenol® downregulated the gene expression of various cartilage degradation markers in the patients' chondrocytes, the decrease of MMP3, MMP13 and the pro-inflammatory cytokine IL1B were statistically significant (p ≤ 0.05). Additionally, protein concentrations of ADAMTS-5 in serum were reduced significantly (p ≤ 0.05) after three weeks intake of the pine bark extract.

CONCLUSIONS

This is the first report about positive cellular effects of a dietary supplement on key catabolic and inflammatory markers in patients with severe OA. The results provide a rational basis for understanding previously reported clinical effects of Pycnogenol® on symptom scores of patients suffering from OA.

TRIAL REGISTRATION

ISRCTN10754119 . Retrospectively registered 08/10/2015.

In vitro polyphenol effects on apoptosis: An update of literature data

Polyphenols are secondary plant metabolites which have been studied extensively for their health-promoting properties, and which could also exert pharmacological activities ranging from anti-inflammatory effects, to cytotoxic activity against cancer cells. The main mechanism for programmed cell death is represented by apoptosis, and its dysregulation is involved in the etiopathology of cancer. As such, substances able to induce apoptosis in cancer cells could be used as new anticancer agents. The aim of this paper is to review literature data on the apoptotic effects of polyphenols and the molecular mechanisms through which they induce these effects in cancer cells. In addition, a brief summary of the new delivery forms used to increase the bioavailability, and clinical impact of polyphenols is provided. The studies reported show that many polyphenol rich plant extracts, originating from food and herbal medicine, as well as isolated polyphenols administered individually or in combination, can regulate cell apoptosis primarily through intrinsic and extrinsic mechanisms of action in in vitro conditions. Due to these promising results, the use of polyphenols in the treatment of cancer should therefore be deeply investigated. In particular, because of the low number of clinical trials, further studies are required to evaluate the anticancer activity of polyphenols in in vivo conditions.

Beneficial effect of resveratrol on phenotypic features and activity of osteoarthritic osteoblasts

Background

Osteoarthritis (OA) is a complex disease, which affects multiple tissues, namely the subchondral bone, articular cartilage and synovial membrane. Alterations of the subchondral bone include an increased, yet under mineralized osteoid matrix, abnormal osteoblast cell phenotype including elevated alkaline phosphatase (ALP) activity, increased release of osteocalcin (OC) and transforming growth factor β-1 (TGF-β1). Previous studies have demonstrated an inhibition of the canonical Wnt signaling (cWnt) pathway in OA osteoblasts (Ob). As resveratrol (RSV) has been shown to upregulate the Wnt signaling pathway in different cell systems, we hypothesized that RSV could be beneficial for OA Ob.

Method

We prepared primary human Ob using the subchondral bone plate of tibial plateaus of OA patients undergoing total knee arthroplasty, or tibial plateaus of normal individuals at autopsy. Sirtuin 1 (Sirt1) expression in normal and OA subchondral bone tissue was evaluated by immunohistochemical analysis. Expression of genes was evaluated by qRT-PCR and protein production by western blot analysis. ALP activity and osteocalcin secretion were evaluated respectively with substrate hydrolysis and enzyme immunoassay. Mineralization levels were evaluated with alizarin red staining. Wnt/β-catenin signaling was evaluated by target gene expression using the TOPflash TCF/lef luciferase reporter assay and intracellular signaling using β-catenin levels in western blot analysis. Extracellular signal-regulated kinase (Erk)1/2 and the Smad1/5/8 pathways were evaluated by western blot analysis.

Results

Sirt1 expression and production were reduced in OA subchondral bone tissue compared to normal tissue. RSV upregulated Sirt1 and its activity, and reduced the expression of leptin. RSV increased Erk1/2 phosphorylation in OA Ob; however, it had no effect on Smad 1/5/8 phosphorylation. RSV had little effect on cell proliferation and only slightly affected the Bax/Bcl2 ratio. The expression of Runx2/Cbfa1 and peroxisome proliferator-activated receptor (PPAR)γ were not affected by increasing doses of RSV. The endogenous increased ALP activity and OC release observed in OA Ob compared to normal Ob were partly corrected only for ALP at high RSV levels but not for OC release. In contrast, RSV increased the mineralization of OA Ob. Moreover, whereas Wnt3a stimulates the Wnt/β-catenin pathway in these cells, RSV further increased the response to Wnt3a.

Conclusion

These data indicate that RSV promotes Sirt1 levels, inhibits the endogenous expression of leptin by OA osteoblasts and can promote the Wnt/β-catenin and Erk1/2 signaling pathways, which are altered in these cells.

Induction of sirtuin-1 signaling by resveratrol induces human chondrosarcoma cell apoptosis and exhibits antitumor activity

Chondrosarcoma is a malignant primary bone tumor. Sirtuin-1 (SIRT1), which is a member of sirtuin family, plays a dual role either in cancer promotion or suppression. There is no report about the role of SIRT1 in the human chondrosarcoma cells. Resveratrol is a potent activator of SIRT1. However, its effects on chondrosarcoma have not been extensively studied. Here, we investigated the role of SIRT1 induction by resveratrol in human chondrosarcoma cell growth and tumor progression. Resveratrol significantly decreased cell viability and induced cell apoptosis in human chondrosarcoma cells in a dose-dependent manner. The protein expression and activity of SIRT1 were activated after treatment with resveratrol. Resveratrol significantly inhibited NF-κB signaling by deacetylating the p65 subunit of NF-κB complex, which could be reversed by siRNA-SIRT1 transfection or deacetylation inhibitor MS-275. Resveratrol induced-apoptosis involved a caspase-3-mediated mechanism. Both siRNA-SIRT1 transfection and MS-275 significantly inhibited the resveratrol-induced caspase-3 cleavage and activity in human chondrosarcoma cells. Moreover, in vivo chondrosarcoma xenograft study revealed a dramatic reduction in tumor volume and the increased SIRT1 and cleaved caspase-3 expressions in tumors by resveratrol treatment. These results suggest that resveratrol induces chondrosarcoma cell apoptosis via a SIRT1-activated NF-κB deacetylation and exhibits anti-chondrosarcoma activity in vivo.

Resveratrol inhibits the IL-1β-induced expression of MMP-13 and IL-6 in human articular chondrocytes via TLR4/MyD88-dependent and -independent signaling cascades

The natural polyphenolic compound, resveratrol, has been shown to exhibit anti-osteoarthritic activity. Therefore it is hypothesized that resveratrol may serve as a nutritional supplement to counteract osteoarthritis (OA). However, the mechanisms responsible for these anti-osteoarthritic effects have not yet been fully elucidated. The aim of this study was to determine whether the biological effects of resveratrol against interleukin (IL)-1β‑induced inflammation in human articular chondrocytes involved both Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)-dependent and -independent signaling pathways. Human articular chondrocytes derived from patients with OA were stimulated with IL-1β, and then co-treated with resveratrol. Cell viability was subsequently evaluated by MTS assays, and the concentrations of matrix metalloproteinase (MMP)-13 and the pro-inflammatory factor, IL-6, were detected in culture supernatants using ELISA. The mRNA and protein levels of downstream mediators of TLR4/MyD88-dependent and -independent signaling pathways were also assayed by RT-qPCR and western blot analysis, respectively. Our results revealed that resveratrol prevented the IL-1β-induced reduction in cell viability. Furthermore, stimulation of the chondrocytes with IL-1β resulted in a significant upregulation of TLR4 and downstream targets of both TLR4/MyD88-dependent and -independent signaling pathways that are associated with the synthesis of MMP-13 and IL-6. Correspondingly, IL-1β-induced catabolic and inflammatory responses were effectively reversed by resveratrol. Taken together, these data suggest that resveratrol exerted protective effects against matrix degradation and inflammation in OA-affected chondrocytes by inhibiting both TLR4/MyD88-dependent and -independent signaling pathways. Thus, resveratrol represents a potential treatment for OA and warrants further investigation.

Oral Administration of Resveratrol Alleviates Osteoarthritis Pathology in C57BL/6J Mice Model Induced by a High-Fat Diet

Obesity has been associated with osteoarthritis (OA) due to increased mass and metabolic factors which are independent of the biomechanical contribution to joint load. Resveratrol, a natural polyphenolic compound, exerts protective effects on OA through its anti-inflammatory property. However, the mechanism of resveratrol on obesity-related OA is unclear. To investigate the effect and possible mechanism of oral resveratrol on obesity-related OA, we fed C57BL/6J mice with a high-fat diet (HFD) for 16 weeks to establish obesity-related OA model; then two doses (22.5 mg/kg and 45 mg/kg) of resveratrol were given by gavage for additional 12 weeks. Mice with HFD significantly increased body weights compared to the control mice, while resveratrol treatment did not cause obvious weight loss. Histological assessments showed that resveratrol at 45 mg/kg significantly improved OA symptoms. Levels of serum IL-1β and leptin were decreased by resveratrol treatment and positively correlated with Mankin scores. Moreover, resveratrol significantly inhibited the expression of TLR4 and TRAF6 in cartilage. These results suggest that HFD induced obesity can lead to the occurrence of OA, and resveratrol may alleviate OA pathology by decreasing the levels of systematic inflammation and/or inhibiting TLR4 signaling pathway in cartilage. Thus, resveratrol might be a promising therapeutic treatment for obesity-related OA.

The synovial microenvironment of osteoarthritic joints alters RNA-seq expression profiles of human primary articular chondrocytes

Osteoarthritis (OA) is a disabling degenerative joint disease that prompts pain and has limited treatment options. To permit early diagnosis and treatment of OA, a high resolution mechanistic understanding of human chondrocytes in normal and diseased states is necessary. In this study, we assessed the biological effects of OA-related changes in the synovial microenvironment on chondrocytes embedded within anatomically intact cartilage from joints with different pathological grades by next generation RNA-sequencing (RNA-seq). We determined the transcriptome of primary articular chondrocytes derived from anatomically unaffected knees and ankles, as well as from joints affected by OA. The GALAXY bioinformatics platform was used to facilitate biological interpretations. Comparisons of patient samples by k-means, hierarchical clustering and principal component analyses together reveal that primary chondrocytes exhibit OA grade-related differences in gene expression, including genes involved in cell-adhesion, ECM production and immune response. We conclude that diseased synovial microenvironments in joints with different histopathological OA grades directly alter gene expression in chondrocytes. One ramification of this finding is that anatomically intact cartilage from OA joints is not an ideal source of healthy chondrocytes, nor should these specimens be used to generate a normal baseline for the molecular characterization of diseased joints.

Intracellular Delivery of Poorly Soluble Polyphenols: Elucidating the Interplay of Self-Assembling Nanocarriers and Human Chondrocytes

Increased molecular understanding of multifactorial diseases paves the way for novel therapeutic approaches requiring sophisticated carriers for intracellular delivery of actives. We designed and characterized self-assembling lipid-core nanocapsules for coencapsulation of two poorly soluble natural polyphenols curcumin and resveratrol. The polyphenols were identified as high-potential therapeutic candidates intervening in the intracellular inflammation cascade of chondrocytes during the progress of osteoarthritis. To elucidate the interplay between chondrocytes and nanocapsules and their therapeutic effect, we pursued a complementary analytical approach combining label-free visualization with biological assays. Primary human chondrocytes did not show any adverse effects upon nanocapsule application and coherent anti-Stokes Raman scattering images visualized their intracellular uptake. Further, by systematically blocking different uptake mechanisms, an energy independent uptake into the cells could be identified. Additionally, we tested the therapeutic effect of the polyphenol-loaded carriers on inflamed chondrocytes. Treatment with nanocapsules resulted in a major reduction of nitric oxide levels, a well-known apoptosis trigger during the course of osteoarthritis. For a more profound examination of this protective effect on joint cells, we pursued studies with atomic force microscopy investigations. Significant changes in the cell cytoskeleton as well as prominent dents in the cell membrane upon induced apoptosis were revealed. Interestingly, these effects could not be detected for chondrocytes which were pretreated with the nanocapsules. Overall, besides presenting a sophisticated carrier system for joint application, these results highlight the necessity of establishing combinatorial analytical approaches to elucidate cellular uptake, the interplay of codelivered drugs and their therapeutic effect on the subcellular level.

Biological Effects of the Herbal Plant-Derived Phytoestrogen Bavachin in Primary Rat Chondrocytes

The aim of this study was to examine the anabolic and anticatabolic functions of bavachin in primary rat chondrocytes. With bavachin treatment, chondrocytes survived for 21 d without cell proliferation, and the proteoglycan content and extracellular matrix increased. Short-term monolayer culture of chondrocytes showed that gene induction of both aggrecan and collagen type II, major extracellular matrix components, was significantly upregulated by bavachin. The expression and activities of cartilage-degrading enzymes such as matrix metalloproteinases and a disintegrin and metalloproteinase with thrombospondin motifs were inhibited significantly by bavachin, while tissue inhibitors of metalloprotease were significantly upregulated. Bavachin inhibits the expression of inducible nitric oxide synthase, a representative catabolic factor, and downregulated the expression of nitric oxide, cyclooxygenase-2, and prostaglandin E2 in a dose-dependent manner in chondrocytes. Our results suggest that the bavachin has anabolic and potent anticatabolic biological effects on chondrocytes, which may have considerable promise in treating articular cartilage degeneration in the future.

Effects of resveratrol on collagen type II protein in the superficial and middle zone chondrocytes of porcine articular cartilage

ETHNOPHARMACOLOGICAL RELEVANCE

Resveratrol (RSV) was first isolated in 1940 from the roots of white hellebore (Veratrum grandiflorum (Maxim. ex Miq) O. Loes) and in 1963 from the roots of Japanese knotweed (Polygonum cuspidatum Siebold & Zucc.). These species have been used traditionally to treat arthritis, gout or inflammation. RSV (3,5,4-trihydroxystilbene) is a polyphenolic phytoalexin compound found in various plants, such as grape vines, berries, peanuts, seeds and roots; the highest concentration is in the skin of red grapes. This component of red wine has potent anti-inflammatory properties and may reduce the side effects of non-steroidal anti-inflammatory drugs that are currently used for pain amelioration in osteoarthritis (OA). In early degeneration of articular cartilage, which may lead to OA there is a loss of the tensile properties, indicative of damage to the fibrillar network. Damage to this fibrillar meshwork, made up of primarily collagen type II (90-95%), may be a critical event in the pathology of many arthritides, due in part to the very slow rate of collagen turnover within the cartilage. Collagen type II is the pre-dominant protein of the cartilage middle zone matrix mainly responsible for tensile strength of articular cartilage. The aim of the study was to investigate the effects of RSV on the expression of collagen type II from the superficial and middle zone chondrocytes of porcine articular cartilage.

MATERIALS AND METHODS

Porcine articular chondrocytes were isolated from the superficial and middle zone of articular cartilage, cultured as monolayers in serum-free chemically defined medium for four days. Effects of RSV on porcine articular chondrocytes were studied by assessing expression of collagen type II mRNA by RT-PCR and protein levels of collagen type II by ELISA; as well as localisation of collagen type II on cartilage tissue sections using immunohistochemistry.

RESULTS

RSV significantly stimulated the expression of collagen type II at the mRNA and protein levels in the superficial and middle zone. Immunohistochemistry revealed that collagen type II was present along the whole cartilage tissue sections. The staining was strong in the superficial zone, mild in the middle zone and less around hypertrophic chondrocytes in the deep zone. Histological analysis confirmed that cartilage slices were obtained from specific articular cartilage zones.

CONCLUSION

This study revealed the importance of RSV in the regulation of collagen type II protein in different zones of articular cartilage.

Resveratrol Enhances Cardiomyocyte Differentiation of Human Induced Pluripotent Stem Cells through Inhibiting Canonical WNT Signal Pathway and Enhancing Serum Response Factor-miR-1 Axis

Resveratrol (trans-3,5,4′-trihydroxystilbene) (RSV) is a natural polyphenol with protective effects over cardiac tissues and can affect cell survival and differentiation in cardiac stem cells transplantation. However, whether this agent can affect cardiomyocytes (CMs) differentiation of induced pluripotent stem cells (iPSCs) is not yet clear. This study explored whether RSV can affect CMs differentiation of human iPSCs. Under embryoid bodies (EBs) condition, the effect of RSV on the change of pluripotent markers, endoderm markers, mesoderm markers, and ectoderm markers was measured using qRT-PCR. Under CM differentiation culture, the effect of RSV on CM specific markers was also measured. The regulative role of RSV over canonical Wnt signal pathway and serum response factor- (SRF-) miR-1 axis and the functions of these two axes were further studied. Results showed that RSV had no effect on the self-renewal of human iPSCs but could promote mesoderm differentiation. Under CM differentiation culture, RSV could promote CM differentiation of human iPSCs through suppressing canonical Wnt signal pathway and enhancing SRF-miR-1 axis.

The impact of polyphenols on chondrocyte growth and survival: a preliminary report

Background

Imbalances in the functional binding of fibroblast growth factors (FGFs) to their receptors (FGFRs) have consequences for cell proliferation and differentiation that in chondrocytes may lead to degraded cartilage. The toxic, proinflammatory, and oxidative response of cytokines and FGFs can be mitigated by dietary polyphenols.

Objective

We explored the possible effects of polyphenols in the management of osteoarticular diseases using a model based on the transduction of a mutated human FGFR3 (G380R) in murine chondrocytes. This mutation is present in most cases of skeletal dysplasia and is responsible for the overexpression of FGFR3 that, in the presence of its ligand, FGF9, results in toxic effects leading to altered cellular growth.

Design

Different combinations of dietary polyphenols derived from plant extracts were assayed in FGFR3 (G380R) mutated murine chondrocytes, exploring cell survival, chloride efflux, extracellular matrix (ECM) generation, and grade of activation of mitogen-activated protein kinases.

Results

Bioactive compounds from Hibiscus sabdariffa reversed the toxic effects of FGF9 and restored normal growth, suggesting a probable translation to clinical requests in humans. Indeed, these compounds activated the intracellular chloride efflux, increased ECM generation, and stimulated cell proliferation. The inhibition of mitogen-activated protein kinase phosphorylation was interpreted as the main mechanism governing these beneficial effects.

Conclusions

These findings support the rationale behind the encouragement of the development of drugs that repress the overexpression of FGFRs and suggest the dietary incorporation of supplementary nutrients in the management of degraded cartilage.

Resveratrol protects rabbit articular chondrocyte against sodium nitroprusside-induced apoptosis via scavenging ROS

This study aims to investigate the mechanism by which resveratrol (RV) prevents sodium nitroprusside (SNP)-induced chondrocyte apoptosis, which is a characteristic feature of osteoarthritis (OA). Rabbit articular chondrocytes were pre-incubated with 100 μM RV for 18 h before 1.5 mM SNP co-treatment for 6 h. Cell viability was evaluated by CCK-8. Annexin V/PI double staining and Hoechst 33258 staining were used to determine the fashion of SNP-induced chondrocytes death. Mitochondrial membrane potential (ΔΨm) was measured by using flow cytometry (FCM) with TMRM and Rhodamine 123 staining. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels were confirmed by FCM analysis with DCFH-DA and DAF-FM DA staining. Cytoskeleton proteins of chondrocytes co-stained with Actin-Trakcer Green and Tubulin-Trakcer Red were validated by confocal microscopy. SNP induced time- and dose-dependent chondrocytes apoptosis with decline of ΔΨm, activation of caspases as well as cytoskeletal remodeling. SNP induced a significant induction of both ROS and NO. RV remarkably prevented SNP-induced ROS production and apoptosis as well as cytoskeletal remodeling, but did not prevent SNP-induced NO production. Pretreatment with NO scavengers did not significantly prevent SNP-induced apoptosis and cytoskeletal remodeling. SNP induces NO-independent ROS production which dominates rabbit articular chondrocyte apoptosis, and RV protects chondrocytes against SNP-induced apoptosis via scavenging ROS instead of NO.

Resveratrol suppresses TPA-induced matrix metalloproteinase-9 expression through the inhibition of MAPK pathways in oral cancer cells

BACKGROUND

Naturally occurring agents, such as resveratrol, have been determined to benefit health. Numerous studies have demonstrated that resveratrol has antioxidative, cardioprotective, and neuroprotective properties. However, the effect of resveratrol exerts on the metastasis of oral cancer cells remains unclear. In this study, we investigated the effect the anti-invasive activity of resveratrol on a human oral cancer cell line (SCC-9) in vitro and the underlying mechanisms.

METHODS

Cell viability was examined by MTT assay, whereas cell motility was measured by migration and wound-healing assays. Zymography, reverse-transcriptase polymerase chain reaction (PCR), and promoter assays confirmed the inhibitory effects of resveratrol on matrix metalloproteinase-9 (MMP-9) expression in oral cancer cells.

RESULTS

We established that various concentrations (0-100 μM) of resveratrol inhibited the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced migration capacities of SCC-9 cells and caused no cytotoxic effects. Zymography and Western blot analyses suggested that resveratrol inhibited TPA-induced MMP-9 gelatinolytic activity and protein expression. In addition, the results indicated that resveratrol inhibited the phosphorylation of c-Jun N-terminal kinase (JNK)1/2 and extracellular-signal-regulated kinase (ERK)1/2 involved in downregulating protein expression and the transcription of MMP-9.

CONCLUSION

In summary, resveratrol inhibited MMP-9 expression and oral cancer cell metastasis by downregulating JNK1/2 and ERK1/2 signals pathways and, thus, exerts beneficial effects in chemoprevention.

The potential for dietary factors to prevent or treat osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease for which there are no disease-modifying drugs. It is a leading cause of disability in the UK. Increasing age and obesity are both major risk factors for OA and the health and economic burden of this disease will increase in the future. Focusing on compounds from the habitual diet that may prevent the onset or slow the progression of OA is a strategy that has been under-investigated to date. An approach that relies on dietary modification is clearly attractive in terms of risk/benefit and more likely to be implementable at the population level. However, before undertaking a full clinical trial to examine potential efficacy, detailed molecular studies are required in order to optimise the design. This review focuses on potential dietary factors that may reduce the risk or progression of OA, including micronutrients, fatty acids, flavonoids and other phytochemicals. It therefore ignores data coming from classical inflammatory arthritides and nutraceuticals such as glucosamine and chondroitin. In conclusion, diet offers a route by which the health of the joint can be protected and OA incidence or progression decreased. In a chronic disease, with risk factors increasing in the population and with no pharmaceutical cure, an understanding of this will be crucial.

Protective effect of resveratrol against IL-1β-induced inflammatory response on human osteoarthritic chondrocytes partly via the TLR4/MyD88/NF-κB signaling pathway: an "in vitro study"

Resveratrol is a natural polyphenolic compound that prevents inflammation in chondrocytes and animal models of osteoarthritis (OA) via yet to be defined mechanisms. The purpose of this study was to determine whether the protective effect of resveratrol on IL-1β-induced human articular chondrocytes was associated with the TLR4/MyD88/NF-κB signaling pathway by incubating human articular chondrocytes (harvested from osteoarthritis patients) with IL-1β before treatment with resveratrol. Cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and TNFα levels in culture supernatants were measured by ELISA(Enzymelinked immunosorbent assay). The levels of TLR4 and its downstream signaling targets (MyD88 and TRAF6) and IL-1β were assessed by measuring the levels of mRNA and protein expression by real-time RT-PCR and western blot analysis, respectively, in addition to assessing NF-κB activation. In addition, TLR4 siRNA was used to block TLR4 expression in chondrocytes further demonstrating that resveratrol prevented IL-1β-mediated inflammation by TLR4 inhibition. We found that resveratrol prevented IL-1β-induced reduction in cell viability. Stimulation of chondrocytes with IL-1β caused a significant up-regulation of TLR4 and its downstream targets MyD88 and TRAF6 resulting in NF-κB activation associated with the synthesis of IL-1β and TNFα. These IL-1β-induced inflammatory responses were all effectively reversed by resveratrol. Furthermore, activation of NF-κB in chondrocytes treated with TLR4 siRNA was significantly attenuated, but not abolished, and exposure to resveratrol further reduced NF-κB translocation. These data suggested that resveratrol prevented IL-1β-induced inflammation in human articular chondrocytes at least in part by inhibiting the TLR4/MyD88/NF-κB signaling pathway suggesting that resveratrol has the potential to be used as a nutritional supplement to counteract OA symptoms.

Significance of epigenetic landscape in cartilage regeneration from the cartilage development and pathology perspective

Regenerative therapies for cartilage defects have been greatly advanced by progress in both the stem cell biology and tissue engineering fields. Despite notable successes, significant barriers remain including shortage of autologous cell sources and generation of a stable chondrocyte phenotype using progenitor cells. Increasing demands for the treatment of degenerative diseases, such as osteoarthritis and rheumatoid arthritis, highlight the importance of epigenetic remodeling in cartilage regeneration. Epigenetic regulatory mechanisms, such as microRNAs, DNA methylation, and histone modifications, have been intensively studied due to their direct regulatory role on gene expression. However, a thorough understanding of the environmental factors that initiate these epigenetic events may provide greater insight into the prevention of degenerative diseases and improve the efficacy of treatments. In other words, if we could identify a specific factor from the environment and its downstream signaling events, then we could stop or retard degradation and enhance cartilage regeneration. A more operational definition of epigenetic remodeling has recently been proposed by categorizing the signals during the epigenetic process into epigenators, initiators, and maintainers. This review seeks to compile and reorganize the existing literature pertaining to epigenetic remodeling events placing emphasis on perceiving the landscape of epigenetic mechanisms during cartilage regeneration with the new operational definition, especially from the environmental factors' point of view. Progress in understanding epigenetic regulatory mechanisms could benefit cartilage regeneration and engineering on a larger scale and provide more promising therapeutic applications.

Resveratrol inhibits the growth of gastric cancer by inducing G1 phase arrest and senescence in a Sirt1-dependent manner

Resveratrol, a naturally occurring polyphenolic compound, has been reported to exert anticancer activity by affecting diverse molecular targets. In this study, we examined the effects and the underlying mechanisms of resveratrol on gastric cancer. We found that resveratrol inhibited the proliferation of gastric cancer cells in a dose-dependent manner. At the concentration of 25 and 50 µM, resveratrol inhibited the cell viability and diminished the clonogenic potential of gastric cancer cells. Resveratrol treatment arrested gastric cancer cells in the G1 phase and led to senescence instead of apoptosis. Regulators of the cell cycle and senescence pathways, including cyclin D1, cyclin-dependent kinase (CDK4 and 6), p21 and p16, were dysregulated by resveratrol treatment. The inhibitory effects of resveratrol on gastric cancer were also verified in vivo using a nude mice xenograft model. Resveratrol (40 mg/kg/d) exerted inhibitory activities on gastric cancer development and significantly decreased the fractions of Ki67-positive cells in the tumor specimens from the nude mice. After resveratrol treatment, the induction of senescence and the changes in the expression of the regulators involved in the cell cycle and senescence pathways were similar to what we observed in vitro. However, the depletion of Sirtuin (Sirt)1 reversed the above-described effects of resveratrol both in vitro and in vivo. Our data suggest that resveratrol inhibits gastric cancer in a Sirt1-dependent manner and provide detailed evidence for the possibility of applying resveratrol in gastric cancer prevention and therapy.

Resveratrol Inhibits Nitric Oxide-Induced Apoptosis via the NF-Kappa B Pathway in Rabbit Articular Chondrocytes

Resveratrol (trans-3,4'-trihydroxystillbene), a naturally occurring polyphenolic antioxidant found in grapes and red wine, elicits diverse biochemical responses and demonstrates anti-aging, anti-inflammatory, and anti-proliferative effects in several cell types. Previously, resveratrol was shown to regulate differentiation and inflammation in rabbit articular chondrocytes, while the direct production of nitric oxide (NO) in these cells by treatment with the NO donor sodium nitroprusside (SNP) led to apoptosis. In this study, the effect of resveratrol on NO-induced apoptosis in rabbit articular chondrocytes was investigated. Resveratrol dramatically reduced NO-induced apoptosis in chondrocytes, as determined by phase-contrast microscopy, the MTT assay, FACS analysis, and DAPI staining. Treatment with resveratrol inhibited the SNP-induced expression of p53 and p21 and reduced the expression of procaspase-3 in chondrocytes, as detected by western blot analysis. SNP-induced degradation of I-kappa B alpha (IκB-α) was rescued by resveratrol treatment, and the SN50 peptide-mediated inhibition of NF-kappa B (NF-κB) activity potently blocked SNP-induced caspase-3 activation and apoptosis. Our results suggest that resveratrol inhibits NO-induced apoptosis through the NF-κB pathway in articular chondrocytes.

A current review of molecular mechanisms regarding osteoarthritis and pain

Osteoarthritis afflicts millions of individuals across the world resulting in impaired quality of life and increased health costs. To understand this disease, physicians have been studying risk factors, such as genetic predisposition, aging, obesity, and joint malalignment; however have been unable to conclusively determine the direct etiology. Current treatment options are short-term or ineffective and fail to address pathophysiological and biochemical mechanisms involved with cartilage degeneration and the induction of pain in arthritic joints. OA pain involves a complex integration of sensory, affective, and cognitive processes that integrate a variety of abnormal cellular mechanisms at both peripheral and central (spinal and supraspinal) levels of the nervous system Through studies examined by investigators, the role of growth factors and cytokines has increasingly become more relevant in examining their effects on articular cartilage homeostasis and the development of osteoarthritis and osteoarthritis-associated pain. Catabolic factors involved in both cartilage degradation in vitro and nociceptive stimulation include IL-1, IL-6, TNF-α, PGE2, FGF-2 and PKCδ, and pharmacologic inhibitors to these mediators, as well as compounds such as RSV and LfcinB, may potentially be used as biological treatments in the future. This review explores several biochemical mediators involved in OA and pain, and provides a framework for the understanding of potential biologic therapies in the treatment of degenerative joint disease in the future.

Regioselective hydroxylation of trans-resveratrol via inhibition of tyrosinase from Streptomyces avermitilis MA4680

Secreted tyrosinase from melanin-forming Streptomyces avermitilis MA4680 was involved in both ortho-hydroxylation and further oxidation of trans-resveratrol, leading to the formation of melanin. This finding was confirmed by constructing deletion mutants of melC(2) and melD(2) encoding extracellular and intracellular tyrosinase, respectively; the melC2 deletion mutant did not produce piceatannol as well as melanin, whereas the melD2 deletion mutant oxidized resveratrol and synthesized melanin with the same yields, suggesting that MelC2 is responsible for ortho-hydroxylation of resveratrol. Extracellular tyrosinase (MelC2) efficiently converted trans-resveratrol into piceatannol in the presence of either tyrosinase inhibitors or reducing agents such as catechol, NADH, and ascorbic acid. Reducing agents slow down the dioxygenase reaction of tyrosinase. In the presence of catechol, the regio-specific hydroxylation of trans-resveratrol was successfully performed by whole cell biotransformation, and further oxidation of trans-resveratrol was efficiently blocked. The yield of this ortho-hydroxylation of trans-resveratrol was dependent upon inhibitor concentration. Using 1.8 mg of wild-type Streptomyces avermitilis cells, the conversion yield of 100 μM trans-resveratrol to piceatannol was 78% in 3 h in the presence of 1 mM catechol, indicating 14 μM piceatannol h(-1) DCW mg(-1) specific productivity, which was a 14-fold increase in conversion yield compared to that without catechol, which is a remarkably higher reaction rate than that of P450 bioconversion. This method could be generally applied to biocatalysis of various dioxygenases.