Inhibition of STAT3 signaling induces apoptosis and suppresses growth of lung cancer: good and bad.

Signal transducer and activator of transcription 3 (STAT3) modulates a variety of genes involved in the regulation of critical functions, including cell proliferation, differentiation, apoptosis, angiogenesis, metastasis, and immunity. For many cancers, elevated levels of STAT3 signaling have been associated with a poor prognosis and the development of chemotherapy resistance. In this study, we investigated the inhibitory effects of a novel small-molecule inhibitor of STAT3, STX-0119, on the cell viability and survival of human lung cancer cells. STX-0119 inhibited activated STAT3 and the expression of STAT3-regulated oncoproteins such as c-Myc, cyclin D1, and survivin in lung cancer cells. STX-0119 also decreased the amount of STAT3 in the nuclear fraction as well as induced apoptosis of these lung cancer cell lines as evidenced by increases in apoptotic cells (Annexin V positive) and poly (ADP-ribose) polymerase (PARP) cleavage. The efficacy of STX-0119 in a mouse xenograft model was confirmed. However, a hematological side effect, which had not been previously reported, was observed. The level of white blood cells was significantly lowered when treated at the dose at which STX-0119 alone showed a significant tumor-suppressive effect. In conclusion, we suggest that STX-0119 may be a potent therapeutic agent against lung cancer. Consideration of the side effect suggests, it is necessary to study whether low-dose STX-0119 is effective for lung treatment with a combination of classic lung cancer therapeutics.

Design, synthesis, and effects of novel phenylpyrimidines as glucagon receptor antagonists.

The hormone glucagon increases blood glucose levels through increasing hepatic glucose output. In diabetic patients, dysregulation of glucagon secretion contributes to hyperglycemia. Thus, the inhibition of glucagon receptor is one target for the treatment of hyperglycemia in type 2 diabetes. Here we designed and synthesized a series of small molecules based on phenylpyrimidine. Of these, the compound (R)-7a most significantly decreased the glucagon-induced cAMP production and glucagon-induced glucose production during in vitro and in vivo assays. In addition, (R)-7a showed good efficacy in glucagon challenge tests and lowered blood glucose levels in diabetic db/db mice. Our results suggest that the compound (R)-7a could be a potential glucose-lowering agent for treating type 2 diabetes.

Kartogenin inhibits pain behavior, chondrocyte inflammation, and attenuates osteoarthritis progression in mice through induction of IL-10.

Osteoarthritis (OA) is a major degenerative joint condition that causes articular cartilage destruction. It was recently found that enhancement of chondroclasts and suppression in Treg cell differentiation are involved in the pathogenesis of OA. Kartogenin (KGN) is a small drug-like molecule that induces chondrogenesis in mesenchymal stem cells (MSCs). This study aimed to identify whether KGN can enhance severe pain behavior and improve cartilage repair in OA rat model. Induction of OA model was loaded by IA-injection of MIA. In the OA rat model, treatment an intra-articular injection of KGN. Pain levels were evaluated by analyzing PWL and PWT response in animals. Histological analysis and micro-CT images of femurs were used to analyze cartilage destruction. Gene expression was measured by real-time PCR. Immunohistochemistry was analyzed to detect protein expression. KGN injection significantly decreased pain severity and joint destruction in the MIA-induced OA model. KGN also increased mRNA levels of the anti-inflammatory cytokine IL-10 in OA patients' chondrocytes stimulated by IL-1ß. Decreased chondroclast expression, and increased Treg cell expression. KGN revealed therapeutic activity with the potential to reduce pain and improve cartilage destruction. Thus, KGN could be a therapeutic molecule for OA that inhibits cartilage damage.

Streptavidin-mirror DNA tetrahedron hybrid as a platform for intracellular and tumor delivery of enzymes.

Despite the extremely high substrate specificity and catalytically amplified activity of enzymes, the lack of efficient cellular internalization limits their application as therapeutics. To overcome this limitation and to harness enzymes as practical biologics for targeting intracellular functions, we developed the streptavidin-mirror DNA tetrahedron hybrid as a platform for intracellular delivery of various enzymes. The hybrid consists of streptavidin, which provides a stoichiometrically controlled loading site for the enzyme cargo and an L-DNA (mirror DNA) tetrahedron, which provides the intracellular delivery potential. Due to the cell-penetrating ability of the mirror DNA tetrahedron of this hybrid, enzymes loaded on streptavidin can be efficiently delivered into the cells, intracellularly expressing their activity. In addition, we demonstrate tumor delivery of enzymes in an animal model by utilizing the potential of the hybrid to accumulate in tumors. Strikingly, the hybrid is able to transfer the apoptotic enzyme specifically into tumor cells, leading to strong suppression of tumor growth without causing significant damage to other tissues. These results suggest that the hybrid may allow anti-proliferative enzymes and proteins to be utilized as anticancer drugs.

Gingerenone A Attenuates Monocyte-Endothelial Adhesion via Suppression of I Kappa B Kinase Phosphorylation.

During the early stages of atherosclerosis, monocytes bind and migrate into the endothelial layer, promoting inflammation within the aorta. In order to prevent the development of atherosclerosis, it is critical to inhibit such inflammation. The therapeutic effects of ginger have been investigated in several models of cardiovascular disease. However, although a number of previous studies have focused on specific compounds, the mechanisms of action responsible remain unclear. Here, we investigated five major compounds present in ginger, and observed that gingerenone A exhibited the strongest inhibitory effects against tumor necrosis factor (TNF)-α and lipopolysaccharide (LPS) induced monocyte-endothelial adhesion. Furthermore, gingerenone A significantly suppressed the expression of TNF-α and LPS-induced vascular cell adhesion molecule-1 (VCAM-1) and chemokine (C-C motif) ligand 2 (CCL2), key mediators of the interaction between monocytes, and endothelial cells. Transactivation of nuclear factor-κB (NF-κB), which is a key transcription factor of VCAM-1 and CCL2, was induced by TNF-α and LPS, and inhibited by treatment of gingerenone A. Gingerenone A also inhibited the phosphorylation of NF-κB inhibitor (IκB) α and IκB Kinase. Taken together, these results demonstrate that gingerenone A attenuates TNF-α and LPS-induced monocyte adhesion and the expression of adhesion factors in endothelial cells via the suppression of NF-κB signaling. J. Cell. Biochem. 119: 260-268, 2018. © 2017 Wiley Periodicals, Inc.

A major daidzin metabolite 7,8,4'-trihydroxyisoflavone found in the plasma of soybean extract-fed rats attenuates monocyte-endothelial cell adhesion.

Among many functional foods and their phytochemicals, ingestion of soybean (Glycine max) is highly correlated to reduced risk of cardiovascular diseases. Validation of potential health benefits of functional foods requires information about the bioavailability and metabolism of bioactive compounds. In this context, several phase I and II metabolites of isoflavones were target-analyzed in the plasma of rats acutely supplemented with soybean embryo extract. A daidzein metabolite, 7,8,4'-trihydroxyisoflavone (7,8,4'-THI), was found to have the highest average area under curve value (574.3±112.8). Therefore, its potential prevention effect on atherosclerosis was investigated using monocyte-endothelial cell adhesion assay. Different from its precursor daidzein or daidzin, 7,8,4'-THI attenuated adhesion of THP-1 monocytes to tumor necrosis factor-alpha (TNF-α) stimulated human umbilical vein endothelial cells (HUVECs). In addition, 7,8,4'-THI significantly downregulated TNF-α stimulated the expression of vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 and phosphorylation of IκB kinase and IκBα involved in the initiation of atherosclerosis in HUVECs. Therefore, 7,8,4'-THI, a highly bioavailable hydroxylated isoflavone metabolite, has potential anti-atherosclerotic effect via inhibiting monocyte-endothelial adhesion.

5-(3',4'-Dihydroxyphenyl-γ-valerolactone), a Major Microbial Metabolite of Proanthocyanidin, Attenuates THP-1 Monocyte-Endothelial Adhesion.

Several metabolomics of polymeric flavan-3-ols have reported that proanthocyanidins are extensively metabolized by gut microbiota. 5-(3',4'-dihydroxyphenyl)-γ-valerolactone (DHPV) has been reported to be the major microbial metabolite of proanthocyanidins. We demonstrated that DHPV has stronger prevention effect on tumor necrosis factor (TNF)-α-stimulated adhesion of THP-1 human monocytic cells to human umbilical vein endothelial cells compared to its potential precursors such as procyanidin A1, A2, B1 and B2, (+)catechin, (-)epicatechin and its microbial metabolites such as 3-(3,4-dihydroxyphenyl)propionic acid and 2-(3,4-dihydroxyphenyl)acetic acid. Mechanism study showed that DHPV prevents THP-1 monocyte-endothelial cell adhesion by downregulating TNF-α-stimulated expressions of the two biomarkers of atherosclerosis such as vascular cell adhesion molecule-1 and monocyte chemotactic protein-1, activation of nuclear factor kappa B transcription and phosphorylation of I kappa-B kinase and IκBα. We suggested that DHPV has higher potentiality in prevention of atherosclerosis among the proanthocyanidin metabolites.

Systemic structure-activity relationship study of phenyl polyyne diols as potential chemopreventive agents.

The present study reports the cancer chemopreventive activities of phenyl polyyne diols derived from polyacetylene triol. Thirty-seven analogues based on a 1-phenylhexa-2,4-diyne-1,6-diol scaffold were prepared and their effects on QR activity were elucidated, as well as their cytotoxicities. We found that most of the derivatives based on phenylhexa-2,4-diyne-1,6-diol exhibited good QR induction activity and relatively low cytotoxicity and systemic structure-activity relationship was revealed. In particular, 4-fluorophenyl, 3-chlorophenyl, and 3,4-dioxolophenyl derivatives showed the best profiles in terms of QR induction, cytotoxicity, and CI.

Dehydroglyasperin C suppresses TPA-induced cell transformation through direct inhibition of MKK4 and PI3K.

Bioactive natural compounds from plant-derived sources have received substantial interest due to their potential therapeutic and preventive effects toward various human diseases. Licorice (Glycyrrhiza), a frequently-used component in traditional oriental medicines, has been incorporated into recipes not only to enhance taste, but also to treat various conditions including inflammation, chronic fatigue syndrome, and even cancer. Dehydroglyasperin C (DGC) is a major isoflavone found in the root of licorice. In the present study, we investigated the cancer chemopreventive effect of DGC and the underlying molecular mechanisms involved, by analyzing its effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced neoplastic cell transformation and cyclooxygenase (COX)-2 expression in JB6 P+ mouse epidermal cells. DGC treatment attenuated TPA-induced activator protein-1 (AP-1) and nuclear factor-κB (NF-κB) transcriptional activation, two major regulators of TPA-induced cell transformation, and COX-2 expression. TPA-induced phosphorylation of p38, JNK1/2 and Akt was also suppressed by DGC. Kinase assay data revealed that DGC inhibited the kinase activity of MKK4 and PI3K and this outcome was due to direct physical binding with DGC. Notably, DGC bound directly to MKK4 and PI3K in an ATP-competitive manner. Taken together, these results suggest that DGC exhibits cancer chemopreventive potential via its inhibitory effect on TPA-induced neoplastic cell transformation and COX-2 modulation through regulation of the MKK4 and PI3K pathways.

Characteristics of urinary retention in female inpatients managed with medical treatments.

PURPOSE: We aimed to analyze the characteristics of urinary retention (UR) in female inpatients managed with medical treatments. MATERIALS AND METHODS: We retrospectively analyzed the medical records of female inpatients referred to the department of urology for UR at our institution from January 2009, to December 2014. UR was defined as a difficulty in self-voiding despite a sufficient urine volume or >300-mL postvoid residual. The data included patients' age, body mass index (BMI), ambulatory status, medical and surgical history, classes of taking drugs, and urinary tract infection. RESULTS: A total of 182 women were included as retention group, mean age of 72.64±12.94 years and BMI of 22.94±3.10 kg/m(2). In the chi-square analysis, cardiovascular disorders (p=0.000), diabetes mellitus (p=0.008), metastatic malignancy (p=0.008), chronic renal disorders (p=0.028) were found significantly. In the multiple logistic regression analysis, cardiovascular disorders (p=0.002; odds ratio [OR], 0.491), metastatic malignancy (p=0.013; OR, 2.616) were found to increase the risk of UR. The most common surgical history was anti-incontinence surgery (7.2%). In term of medication use, the most prescribed agents were nonsteroidal anti-inflammatory drugs (NSAIDs) (53.8%). The patients taking multiple drugs with antimuscarinic effects except of NSAIDs, narcotics and diuretics were 48 (26.4%). Urinary tract infection was identified in 43 patients (23.6%). CONCLUSIONS: UR in females managed with medical treatments could be occurred occasionally. We think that thorough attentions are needed for UR to patients with cardiovascular disorders including diabetes mellitus, metastatic malignancy, chronic renal disorders urinary tract infection, and more careful interests when managing with drugs with antimuscarinic effects.

Identification of dialkyl diacetylene diols with potent cancer chemopreventive activity.

An increasing importance of chemoprevention for controlling cancer risks prompted the discovery of new active cancer chemopreventive agents. In this study, we designed and synthesized substituted hexa-2,4-diyne-1,6-diols, more structurally simplified, tunable, and easily preparable than natural gymnasterkoreaynes, and evaluated their cancer chemopreventive activities by measuring concentration of doubling quinone reductase activity (CD), cell viability, and chemopreventive index (CI). Most of the diols exhibited good CD activity and low cytotoxicity. In particular, tetradeca-5,7-diyne-4,9-diol and 2-methyltetradeca-5,7-diyne-4,9-diol showed the best cancer chemopreventive activity, approximately equipotent to that of sulforaphane. And, by synthesizing optically active stereoisomers of selected active compounds, the effect of stereochemistry was also studied. Eventually, we produced a chemopreventive compound for in vivo study.

Brown Pine Leaf Extract and Its Active Component Trans-Communic Acid Inhibit UVB-Induced MMP-1 Expression by Targeting PI3K.

Japanese red pine (Pinus densiflora) is widely present in China, Japan, and Korea. Its green pine leaves have traditionally been used as a food as well as a coloring agent. After being shed, pine leaves change their color from green to brown within two years, and although the brown pine leaves are abundantly available, their value has not been closely assessed. In this study, we investigated the potential anti-photoaging properties of brown pine leaves for skin. Brown pine leaf extract (BPLE) inhibited UVB-induced matrix metalloproteinase-1 (MMP-1) expression to a greater extent than pine leaf extract (PLE) in human keratinocytes and a human skin equivalent model. HPLC analysis revealed that the quantity of trans-communic acid (TCA) and dehydroabietic acid (DAA) significantly increases when the pine leaf color changes from green to brown. BPLE and TCA elicited reductions in UVB-induced MMP-1 mRNA expression and activator protein-1 (AP-1) transactivation by reducing DNA binding activity of phospho-c-Jun, c-fos and Fra-1. BPLE and TCA also inhibited UVB-induced Akt phosphorylation, but not mitogen activated protein kinase (MAPK), known regulators of AP-1 transactivation. We additionally found that BPLE and TCA inhibited phosphoinositide 3-kinase (PI3K), the upstream kinase of Akt, in vitro. In summary, both BPLE and its active component TCA exhibit protective effects against UVB-induced skin aging. Taken together, these findings underline the potential for BPLE and TCA to be utilized as anti-wrinkling agents and cosmetic ingredients, as they suppress UVB-induced MMP-1 expression.

20-O-ß-D-glucopyranosyl-20(S)-protopanaxadiol, a metabolite of ginsenoside Rb1, enhances the production of hyaluronic acid through the activation of ERK and Akt mediated by Src tyrosin kinase in human keratinocytes.

The aim of the present study was to determine the mechanisms through which 20-O-ß-D-glucopyranosyl-20(S)-protopanaxadiol (20GPPD) promotes the production of hyaluronic acid (HA) in human keratinocytes. 20GPPD is the primary bioactive metabolite of Rb1, a major ginsenoside found in ginseng (Panax ginseng). We sought to elucidate the underlying mechanisms behind the 20GPPD-induced production of HA. We found that 20GPPD induced an increase in HA production by elevating hyaluronan synthase 2 (HAS2) expression in human keratinocytes. The phosphorylation of extracellular signal-regulated kinase (ERK) and Akt was also enhanced by 20GPPD in a dose-dependent manner. The pharmacological inhibition of ERK (using U0126) or Akt (using LY294002) suppressed the 20GPPD-induced expression of HAS2, whereas treatment with an epidermal growth factor receptor (EGFR) inhibitor (AG1478) or an intracellular Ca2+ chelator (BAPTA/AM) did not exert any observable effects. The increased Src phosphorylation was also confirmed following treatment with 20GPPD in the human keratinocytes. Following pre-treatment with the Src inhibitor, PP2, both HA production and HAS2 expression were attenuated. Furthermore, the 20GPPD-enhanced ERK and Akt signaling decreased following treatment with PP2. Taken together, our results suggest that Src kinase plays a critical role in the 20GPPD-induced production of HA by acting as an upstream modulator of ERK and Akt activity in human keratinocytes.

Cocoa phytochemicals: recent advances in molecular mechanisms on health.

Recent reports on cocoa are appealing in that a food commonly consumed for pure pleasure might also bring tangible benefits for human health. Cocoa consumption is correlated with reduced health risks of cardiovascular diseases, hypertension, atherosclerosis, and cancer, and the health-promoting effects of cocoa are mediated by cocoa-driven phytochemicals. Cocoa is rich in procyanidins, theobromine, (-)-epicatechin, catechins, and caffeine. Among the phytochemicals present in consumed cocoa, theobromine is most available in human plasma, followed by caffeine, (-)-epicatechin, catechin, and procyanidins. It has been reported that cocoa phytochemicals specifically modulate or interact with specific molecular targets linked to the pathogenesis of chronic human diseases, including cardiovascular diseases, cancer, neurodegenerative diseases, obesity, diabetes, and skin aging. This review summarizes comprehensive recent findings on the beneficial actions of cocoa-driven phytochemicals in molecular mechanisms of human health.

Anthocyanins in the ripe fruits of Rubus coreanus Miquel and their protective effect on neuronal PC-12 cells.

Phenolics of the fresh ripe fruits of Rubus coreanus Miquel were extracted and separated into anthocyanin and the non-anthocyanin fractions, which were used for the evaluation for antioxidant capacity and neuroprotective effects. The anthocyanin fraction accounted for approximately 47-55% of the total antioxidant capacity of the whole extract and had significantly higher free radical-scavenging capacity than the non-anthocyanin fraction. Furthermore, the anthocyanins alleviated intracellular oxidative stress, as assayed by in vitro fluorescent measurements. The anthocyanins showed neuroprotective effects on PC-12 cells in vitro against oxidative stress in a dose-dependent manner. Triple quadrupole LC/MS and Q-TOF LC/MS analyses revealed four major anthocyanins; cyanidin 3-O-sambubioside, cyanidin 3-O-glucoside, cyanidin 3-O-xylosylrutinoside, and cyanidin 3-O-rutinoside in increasing order of amounts. These results demonstrated that anthocyanins are the major components and contributors to the antioxidant capacity of ripe R. coreanus Miquel fruits. Further studies are warranted to determine whether consumption of the fruits reduces oxidative stress in the brain and promotes health.

The Prostate Cancer Detection Rate on the Second Prostate Biopsy according to Prostate-Specific Antigen Trend.

PURPOSE: To identify the prostate cancer detection rate on the patients who had second prostate biopsy out of the patients who were reported negative in their first biopsy. MATERIALS AND METHODS: From July 2006 to February 2012, prostate biopsy was performed on 843 patients with over 4 ng/ml and on 618 biopsy negative patients PSA was performed from between 6 months and 9 months after biopsy. On 164 patients, second biopsy was performed, and 42 patients were selected. If there was less than 10% change between PSA before the prostate biopsy and PSA measured during 6 to 9 months after the first biopsy it was considered as no change. If above 10% increase, it was considered increase and if above 10% decrease it was considered as decrease. RESULTS: The cancer detection rate in PSA increase group was 20%, the detection rate in no change in PSA level but still over the normal range group 8.3%, and that in the PSA decrease group was 0%. When comparing prostate cancer group and non-cancer group, it is more probable to have prostate cancer when they are older, prostate volume is smaller and PSA density is higher. CONCLUSIONS: The second biopsy is strongly recommended when PSA level shows no change or increase, age is older, prostate volume is smaller or PSA density is higher.

Neuroprotective effect of caffeoylquinic acids from Artemisia princeps Pampanini against oxidative stress-induced toxicity in PC-12 cells.

Phenolics in dry Artemisia princeps Pampanini, an herbal plant traditionally consumed as food ingredients in Korea was extracted, fractionated, and quantified as well as evaluated for its neuroprotection for PC-12 cells. Whole extract had 5,852 mg gallic acid equivalents/100 g of total phenolics and 6,274 mg and 9,698 mg vitamin C equivalents/100 g of antioxidant capacities assayed by DPPH and ABTS radicals, respectively. The fraction extracted with n-butanol had the highest levels of total phenolics and antioxidant capacity than the other fractions (n-hexane, chloroform, ethyl acetate, and water). Using a reversed-phase HPLC system, caffeoylquinic acid (CQA) and its derivatives such as 3-CQA, 4-CQA, 5-CQA, 1,5-diCQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA were isolated and quantified. The whole extract and its n-butanol fraction yielded 3,5-diCQA with the highest amount, which consisted of approximately 36.8% and 33.5%, respectively. The whole extract, the n-butanol fraction, and 3,5-diCQA showed neuroprotective effect on PC-12 cells under the insult of amyloid ß peptide in a dose-dependent manner. Treatments of the whole extract and the n-butanol fraction for PC-12 cells under oxidative stress increased approximately 1.6 and 2.4 times higher cell viability, compared with the control without treatments. For PC-12 cells treated with 3,5-diCQA, intracellular oxidative stress decreased by 51.3% and cell viability increased up to 2.8 times compared to the control with oxidative insult of amyloid ß peptide only. These results indicate that phenolics from A. princeps Pampanini alleviated the oxidative stress and enhanced the viability of PC-12 cells, suggesting that it may be applied as a dietary antineurodegenerative agent in functional foods.

Cocoa polyphenols suppress TNF-α-induced vascular endothelial growth factor expression by inhibiting phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase kinase-1 (MEK1) activities in mouse epidermal cells.

Cocoa polyphenols have antioxidant and anti-inflammatory effects. TNF-α is a pro-inflammatory cytokine that has a vital role in the pathogenesis of inflammatory diseases such as cancer and psoriasis. Vascular endothelial growth factor (VEGF) expression is associated with tumorigenesis, CVD, rheumatoid arthritis and psoriasis. We tested whether cocoa polyphenol extract (CPE) inhibited TNF-α-induced VEGF expression in promotion-sensitive JB6 mouse epidermal cells. CPE significantly inhibited TNF-α-induced up-regulation of VEGF via reducing TNF-α-induced activation of the nuclear transcription factors activator protein-1 (AP-1) and NF-κB, which are key regulators of VEGF expression. CPE also inhibited TNF-α-induced phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinase. CPE blocked activation of their downstream kinases, p70 kDa ribosomal protein S6 kinase and p90 kDa ribosomal protein S6 kinase. CPE suppressed phosphoinositide 3-kinase (PI3K) activity via binding PI3K directly. CPE did not affect TNF-α-induced phosphorylation of mitogen-activated protein kinase kinase-1 (MEK1) but suppressed TNF-α-induced MEK1 activity. Collectively, these results indicate that CPE reduced TNF-α-induced up-regulation of VEGF by directly inhibiting PI3K and MEK1 activities, which may contribute to its chemopreventive potential.

Quercetin, the active phenolic component in kiwifruit, prevents hydrogen peroxide-induced inhibition of gap-junction intercellular communication.

We evaluated the effects of the two main kiwifruit cultivars (gold kiwifruit (GOK) and green kiwifruit (GRK)) and their active phenolic compound, quercetin, on H2O2-induced inhibition of gap-junction intercellular communication (GJIC) in WB-F344 rat liver epithelial cells. We found that both GOK and GRK protect WB-F344 cells from H2O2-induced inhibition of GJIC. The extracellular signal-regulated protein kinase 1/2 (ERK1/2)-connexin 43 (Cx43) signalling pathway is crucial for the regulation of GJIC, and both GOK and GRK blocked the H2O2-induced phosphorylation of Cx43 and ERK1/2 in WB-F344 cells. Quercetin alone attenuated the H2O2-mediated ERK1/2-Cx43 signalling pathway and consequently reversed H2O2-mediated inhibition of GJIC in WB-F344 cells. A free radical-scavenging assay using 1,1-diphenyl-2-picrylhydrazyl showed that the scavenging activity of quercetin was higher than that of a synthetic antioxidant, butylated hydroxytoluene, per mol, suggesting that the chemopreventive effect of quercetin on H2O2-mediated inhibition of ERK1/2-Cx43 signalling and GJIC may be mediated through its free radical-scavenging activity. Since the carcinogenicity of reactive oxygen species such as H2O2 is attributable to the inhibition of GJIC, GOK, GRK and quercetin may have chemopreventive potential by preventing the inhibition of GJIC.

Improved assay for determining the total radical-scavenging capacity of antioxidants and foods.

Free radicals play a crucial role in the pathophysiology of human diseases such as cancer, atherosclerosis, and neurodegenerative diseases, and considerable attention has been focused on functional foods (or nutraceuticals) that are able to decrease the concentrations of free radicals and consequently protect against these diseases. The present study investigated an improved quantitative assay to measure antioxidant activity using the stable and fast-reacting chromogenic indicator [2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS). The ABTS-radical-scavenging activities of various antioxidants and apple extracts were measured in 96-well plates, and plots thereof were linearly interpolated, with the total radical-scavenging capacity quantified as the area under the curve. The first order of linear regression was obtained in a relationship between the absorbance reduction and various concentrations of the tested sample, and the total radical-scavenging capacity was expressed as the vitamin-C-equivalent antioxidant capacity. The advantages of this quantitative assay are that, first, it is fast, sensitive and confers little variation from experimental errors for single or mixed antioxidants; second, a large number of samples in a low quantity at a time can be run using 96-well plates.