6-O-angeloylplenolin inhibits osteoclastogenesis in vitro via suppressing c-Src/NF-κB/NFATc1 pathways and ameliorates bone resorption in collagen-induced arthritis mouse model.

One of the effective therapeutic strategies to treat rheumatoid arthritis (RA)-related bone resorption is to target excessive activation of osteoclasts. We discovered that 6-O-angeloylplenolin (6-OAP), a pseudoguaianolide from Euphorbia thymifolia Linn widely used for the treatment of RA in traditional Chinese medicine, could inhibit RANKL-induced osteoclastogenesis and bone resorption in both RAW264.7 cells and BMMs from 1 µM and protect a collagen-induced arthritis (CIA) mouse model from bone destruction in vivo. The severity of arthritis and bone erosion observed in paw joints and the femurs of the CIA model were attenuated by 6-OAP administered at both dosages (1 or 5 mg/kg, i.g.). BMD, Tb.N and BV/TV were also improved by 6-OAP treatment. Histological analysis and TRAP staining of femurs further confirmed the protective effects of 6-OAP on bone erosion, which is mainly due to reduced osteoclasts. Molecular docking indicated that c-Src might be a target of 6-OAP and phosphorylation of c-Src was suppressed by 6-OAP treatment. CETSA and SPR assay further confirmed the potential interaction between 6-OAP and c-Src. Three signaling molecules downstream of c-Src that are vital to the differentiation and function of osteoclasts, NF-κB, c-Fos and NFATc1, were also suppressed by 6-OAP in vitro. In summary, the results demonstrated that the function of c-Src was disrupted by 6-OAP, which led to the suppression of downstream signaling vital to osteoclast differentiation and function. In conclusion, 6-OAP has the potential to be further developed for the treatment of RA-related bone erosion.

Antiproliferative effect of Potentilla fulgens on glioblastoma cancer cells through downregulation of Akt/mTOR signaling pathway.

BACKGROUND: Glioblastoma multiforme (GBM) is the most aggressive brain tumor that is common among adults. This aggression is due to increased invasion, migration, proliferation, angiogenesis, and decreased apoptosis. Plant-based compounds have a high potential to be used as an anticancer agent due to their various mechanisms and less undesirable side effects. Potentilla fulgens is a medicinal plant, and methanolic root extract of P. fulgens (PRE) has anti-inflammatory and anticancer properties. OBJECTIVE: In this study, we aimed to investigate antiproliferative effect of PRE on U118 and T98G glioblastoma cancer cells and to reveal which molecular signaling pathways regulate this mechanism of action. MATERIALS AND METHODS: The effect of PRE on cell viability of GBM cells was investigated by MTT assay. Involvement of PRE with cell growth and survival signaling pathways, phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR and c-Src/signal transducer and activator of transcription 3 (STAT3), was examined using Western Blot. RESULTS: PRE reduced cell viability of GBM and human dermal fibroblast (HDF) cells in a dose-and time-independent manner. PI3K expression/phosphorylation level remained unchanged in both GBM and HDF cells after PRE treatment, but Akt/mTOR signaling pathway was downregulated in PRE-treated cells. PRE treatment did not affect c-Src expression/phosphorylation level in GBM cells; however, expression of c-Src was suppressed in HDF cells. Similar results were observed for STAT3 expression and phosphorylation status. CONCLUSION: PRE has the ability to suppress cell viability in GBM cells, by targeting the Akt/mTOR signaling pathway.

Controlling non small cell lung cancer progression by blocking focal adhesion kinase-c-Src active site with Rosmarinus officinalis L. phytocomponents: An in silico and in vitro study.

Background: Non small cell lung cancer (NSCLC) is a global, fatal oncological malady to which conventional and targeted therapies proved less effective with consequent side effects; hence, phytocomponents from herbal sources may provide potent alternative and should be tested for cancer intervention. Activation and overexpression of proto-oncogene tyrosine kinase Src (c-Src) and focal adhesion kinase (FAK) lead to cell proliferation and invasion. Hence, in the present investigation, in silico analysis was carried out to identify molecular intervention of phytocomponents in blocking the active site and thus inhibiting c-Src and FAK activation, which in turn could control progression of NSCLC. Materials and Methods: In silico analysis was carried out using Molegro Virtual Docker, Molegro Molecular Viewer, and ClusPro server for ligand-protein and protein-protein interaction study. Phytochemical analysis and assay for antioxidant activity of hydroalcoholic extract of Rosmarinus officinalis L. were carried out using standard phytochemical tests, high-performance thin-layer chromatography, and 2, 2-diphenyl-1-picrylhydrazyl assay. Effectiveness of extract in arresting cell proliferation was confirmed using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay on A549 cell line. Results: In silico analysis indicated effective binding of rosmarinic acid to the active site of target proteins FAK and c-Src, blocking their activity. MTT assay revealed potent antiproliferative activity of hydroalcoholic extract which acted in dose-dependent manner. Phytochemical analysis confirmed that the extract was rich in phytocomponents and had antioxidant activity of 94.9%, which could therefore effectively eliminate free radicals and inhibit cell progression. Conclusion: In silico and in vitro studies confirmed that phytocomponents present in hydroalcoholic extract of R. officinalis L. could effectively block the active site of target proteins and thus controlled cell proliferation on NSCLC cells, suggesting herb as an effective alternative medicine for the treatment of NSCLC.

Anti-osteoporosis effect of Semen Cuscutae in ovariectomized mice through inhibition of bone resorption by osteoclasts.

ETHNOPHARMACOLOGICAL RELEVANCE: Semen Cuscutae, called Tu-si-zi in Chinese, is a kind of dried mature seed in the Convolvulaceae family. It mainly distributes in China, Korea, Pakistan, Vietnam, India and Thailand. It is used as a kidney-tonifying drug for treatment of aging related diseases such as osteoporosis in traditional Chinese medicine. However, the exact mechanisms on bone resorption are poorly studied. AIM OF THE STUDY: The aim of this study was to investigate the potential effect of Semen Cuscutae on ovariectomy (OVX)-induced osteoporosis in mice and clarify the exact mechanisms by which Semen Cuscutae exert the anti-osteoporosis effect. MATERIALS AND METHODS: Qualitative and quantitative analyses of Semen Cuscutae were performed by UPLC-Q-TOF-MS and HPLC-MS/MS, respectively. Changes in bone mineral density (BMD) induced by OVX in mice were measured by dual-energy X-ray absorptiometry and micro-computed tomography (µCT). Tartrate-resistant acid phosphatase (TRAP) staining as well as hematoxylin and eosin (HE) staining were used to observe bone microarchitectural changes. ELISA kits were used to assess the therapeutic effects of Semen Cuscutae on the serum levels of osteoprotegerin (OPG), tartrate-resistant acid phosphatase 5b (TRACP-5b), and receptor activator of nuclear factor-κB (RANKL). The effect of Semen Cuscutae on primary cell viability was assessed using CCK-8 and anti-tartrate phosphatase assays. TRAP staining and actin ring staining were used to observe the effect of Semen Cuscutae on osteoclast differentiation. Western blotting was used to measure the effects of Semen Cuscutae on expressions of NFATC1, c-Src kinase, and c-fos. RESULTS: Results from UPLC-Q-TOF-MS showed that the main components of Semen Cuscutae were flavonoid compounds that included quercitrin, quercetin, hyperoside, caffeic acid, rutin, chlorogenic acid, luteolin, apigenin, kaempferol, isoquercetin, cryptochlorogenic acid, isorhamnetin-3-O-glucoside, and astragalin. After the Semen Cuscutae extract was orally administered to OVX mice, bone density increased (P < 0.01) and bone microstructure was significantly improved (P < 0.01 or 0.05). Additionally, Semen Cuscutae exhibited a significant descending effect in the levels of serum TRACP-5b and RANKL, while there was a significant increase in OPG in the Semen Cuscutae group compared with the OVX group, especially at high doses. Moreover, we found that increasing of c-fos, c-Src kinase, and NFATC1 protein expressions were reversed by Semen Cuscutae in vitro and in vivo. CONCLUSIONS: Our results showed that Semen Cuscutae exhibited anti-osteoporosis effects through the c-fos/c-Src kinase/NFATC1 signaling pathway.

Inhibition of SYK and cSrc kinases can protect bone and cartilage in preclinical models of osteoarthritis and rheumatoid arthritis.

The pathophysiology of osteoarthritis (OA) includes the destruction of subchondral bone tissue and inflammation of the synovium. Thus, an effective disease-modifying treatment should act on both of these pathogenetic components. It is known that cSrc kinase is involved in bone and cartilage remodeling, and SYK kinase is associated with the inflammatory component. Thus the aim of this study was to characterize the mechanism of action and efficacy of a small molecule multikinase inhibitor MT-SYK-03 targeting SYK and cSrc kinases among others in different in vitro and in vivo arthritis models. The selectivity of MT-SYK-03 kinase inhibition was assayed on a panel of 341 kinases. The compound was evaluated in a set of in vitro models of OA and in vivo OA and RA models: surgically-induced arthritis (SIA), monosodium iodoacetate-induced arthritis (MIA), collagen-induced arthritis (CIA), adjuvant-induced arthritis (AIA). MT-SYK-03 inhibited cSrc and SYK with IC50 of 14.2 and 23 nM respectively. Only five kinases were inhibited > 90% at 500 nM of MT-SYK-03. In in vitro OA models MT-SYK-03 reduced hypertrophic changes of chondrocytes, bone resorption, and inhibited SYK-mediated inflammatory signaling. MT-SYK-03 showed preferential distribution to joint and bone tissue (in rats) and revealed disease-modifying activity in vivo by halving the depth of cartilage erosion in rat SIA model, and increasing the pain threshold in rat MIA model. Chondroprotective and antiresorptive effects were shown in a monotherapy regime and in combination with methotrexate (MTX) in murine and rat CIA models; an immune-mediated inflammation in rat AIA model was decreased. The obtained preclinical data support inhibition of cSrc and SYK as a viable strategy for disease-modifying treatment of OA. A Phase 2 clinical study of MT-SYK-03 is to be started.

L-Theanine Down-Regulates the JAK/STAT3 Pathway to Attenuate the Proliferation and Migration of Vascular Smooth Muscle Cells Induced by Angiotensin II.

L-Theanine, a green tea amino acid derivative, has cardiovascular qualities. The focus of the current evaluation was to examine the suppression of L-theanine on cultured vascular smooth muscle cell (VSMC) proliferation and migration that is prompted by angiotensin II (Ang II). The VSMCs were treated with non-cytotoxic concentrations of L-theanine and then stimulated with Ang II. The CCK-8 and Transwell chamber assays were monitored on the proliferation and migration rate, respectively. We discovered that L-theanine (50 and 100 µM) significantly halted Ang II-induced VSMC proliferation and migration. This was joined by a decline in the amount of cyclin D1. An additional discovery was that L-theanine lowered the proportion of S-phase cells, whereas the number of G1/G0-phase cells in Ang II-stimulated VSMCs was elevated, based on flow cytometry. Western blotting analyses indicated that L-theanine had no impact on extracellular-signal-regulated kinase 1/2 (ERK1/2) activation prompted by Ang II. Nevertheless, L-theanine significantly lowered Ang II-prompted phosphorylation of Janus kinase 2 (JAK2), c-Src tyrosine kinase, and signal transducer and activators of transcription 3 (STAT3). The outcomes revealed that L-theanine subdued the Ang II-prompted proliferation and migration of VSMC, partly via the obstruction of the JAK/STAT3 pathway instead of via just the ERK pathway.

Acetylcholine-dependent upregulation of TASK-1 channels in thalamic interneurons by a smooth muscle-like signalling pathway.

KEY POINTS: The ascending brainstem transmitter acetylcholine depolarizes thalamocortical relay neurons while it induces hyperpolarization in local circuit inhibitory interneurons. Sustained K+ currents are modulated in thalamic neurons to control their activity modes; for the interneurons the molecular nature of the underlying ion channels is as yet unknown. Activation of TASK-1 K+ channels results in hyperpolarization of interneurons and suppression of their action potential firing. The modulation cascade involves a non-receptor tyrosine kinase, c-Src. The present study identifies a novel pathway for the activation of TASK-1 channels in CNS neurons that resembles cholinergic signalling and TASK-1 current modulation during hypoxia in smooth muscle cells. ABSTRACT: The dorsal part of the lateral geniculate nucleus (dLGN) is the main thalamic site for state-dependent transmission of visual information. Non-retinal inputs from the ascending arousal system and inhibition provided by γ-aminobutyric acid (GABA)ergic local circuit interneurons (INs) control neuronal activity within the dLGN. In particular, acetylcholine (ACh) depolarizes thalamocortical relay neurons by inhibiting two-pore domain potassium (K2P ) channels. Conversely, ACh also hyperpolarizes INs via an as-yet-unknown mechanism. By using whole cell patch-clamp recordings in brain slices and appropriate pharmacological tools we here report that stimulation of type 2 muscarinic ACh receptors induces IN hyperpolarization by recruiting the G-protein ßγ subunit (Gßγ), class-1A phosphatidylinositol-4,5-bisphosphate 3-kinase, and cellular and sarcoma (c-Src) tyrosine kinase, leading to activation of two-pore domain weakly inwardly rectifying K+ channel (TWIK)-related acid-sensitive K+ (TASK)-1 channels. The latter was confirmed by the use of TASK-1-deficient mice. Furthermore inhibition of phospholipase Cß as well as an increase in the intracellular level of phosphatidylinositol-3,4,5-trisphosphate facilitated the muscarinic effect. Our results have uncovered a previously unknown role of c-Src tyrosine kinase in regulating IN function in the brain and identified a novel mechanism by which TASK-1 channels are activated in neurons.

Natural-Based Indirubins Display Potent Cytotoxicity toward Wild-Type and T315I-Resistant Leukemia Cell Lines.

Drug resistance in chronic myelogenous leukemia (CML) requires the development of new CML chemotherapeutic drugs. Indirubin, a well-known mutikinase inhibitor, is the major active component of "Danggui Longhui Wan", a Chinese traditional medicine used for the treatment of CML symptoms. An in-house collection of indirubin derivatives was screened at 1 µM on wild-type and imatinib-resistant T315I mutant CML cells. Herein are reported that only 15 analogues of the natural 6-bromoindirubin displayed potent cytotoxicity in the submicromolar range. Kinase assays in vitro show that eight out of the 15 active molecules strongly inhibited both c-Src and Abl oncogenic kinases in the nanomolar range. Most importantly, these eight molecules blocked the activity of T315I mutant Abl kinase at the submicromolar level and with analogue 22 exhibiting inhibitory activity at the low nanomolar range. Docking calculations suggested that active indirubins might inhibit T315I Abl kinase through an unprecedented binding to both active and Src-like inactive conformations. Analogue 22 is the first derivative of a natural product identified as an inhibitor of wild-type and imatinib-resistant T315I mutant Abl kinases.

Ginkgetin Blocks Constitutive STAT3 Activation and Induces Apoptosis through Induction of SHP-1 and PTEN Tyrosine Phosphatases.

Ginkgetin, a biflavone from Ginkgo biloba leaves, is known to exhibit antiinflammatory, antifungal, neuroprotective, and antitumor activities, but its precise mechanism of action has not been fully elucidated. Because the aberrant activation of STAT3 has been linked with regulation of inflammation, proliferation, invasion, and metastasis of tumors, we hypothesized that ginkgetin modulates the activation of STAT3 in tumor cells. We found that ginkgetin clearly suppressed constitutive phosphorylation of STAT3 through inhibition of the activation of upstream JAK1 and c-Src kinases and nuclear translocation of STAT3 on both A549 and FaDu cells. Treatment with sodium pervanadate reversed the ginkgetin-induced down-modulation of STAT3, thereby indicating a critical role for a PTP. We also found that ginkgetin strongly induced the expression of the SHP-1 and PTEN proteins and its mRNAs. Further, deletion of SHP-1 and PTEN genes by siRNA suppressed the induction of SHP-1 and PTEN, and reversed the inhibition of STAT3 activation. Ginkgetin induced apoptosis as characterized by an increased accumulation of cells in subG1 phase, positive Annexin V binding, loss of mitochondrial membrane potential, down-regulation of STAT3-regulated gene products, and cleavage of PARP. Overall, ginkgetin abrogates STAT3 signaling pathway through induction of SHP-1 and PTEN proteins, thus attenuating STAT3 phosphorylation and tumorigenesis.

Pharmit: interactive exploration of chemical space.

Pharmit (http://pharmit.csb.pitt.edu) provides an online, interactive environment for the virtual screening of large compound databases using pharmacophores, molecular shape and energy minimization. Users can import, create and edit virtual screening queries in an interactive browser-based interface. Queries are specified in terms of a pharmacophore, a spatial arrangement of the essential features of an interaction, and molecular shape. Search results can be further ranked and filtered using energy minimization. In addition to a number of pre-built databases of popular compound libraries, users may submit their own compound libraries for screening. Pharmit uses state-of-the-art sub-linear algorithms to provide interactive screening of millions of compounds. Queries typically take a few seconds to a few minutes depending on their complexity. This allows users to iteratively refine their search during a single session. The easy access to large chemical datasets provided by Pharmit simplifies and accelerates structure-based drug design. Pharmit is available under a dual BSD/GPL open-source license.

Blockage of STAT3 Signaling Pathway by Morusin Induces Apoptosis and Inhibits Invasion in Human Pancreatic Tumor Cells.

OBJECTIVES: Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor implicated in carcinogenesis. Here, we investigated the role of morusin, the major prenylflavonoid, isolated from Chinese herbal medicine in abrogating the constitutive STAT3 activation in human pancreatic tumor cells. METHODS: The effect of morusin on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation, and apoptosis was examined. RESULTS: Morusin specifically inhibited constitutive STAT3 activation both at tyrosine residue 705 and serine residue 727 in 4 pancreatic tumor cells. The inhibition of STAT3 was mediated through the suppression of activation of upstream JAK1, JAK2, and c-Src kinases. Morusin led to the accumulation of the cells in different phases of the cell cycle and caused induction of apoptosis and loss of mitochondrial membrane potential. Morusin downregulated the expression of various STAT3-regulated gene products; this correlated with induction of caspase-3 activation and anti-invasive effects. Treatment with the protein tyrosine phosphatase inhibitor pervanadate reversed the morusin-induced downregulation of STAT3, thereby suggesting the involvement of a protein tyrosine phosphatase. CONCLUSIONS: Morusin is a novel blocker of STAT3 activation and thus may have potential in negative regulation of growth and metastasis of pancreatic tumor cells.

Histochemical evidence of zoledronate inhibiting c-src expression and interfering with CD44/OPN-mediated osteoclast adhesion in the tibiae of mice.

The purpose of this study was to investigate the effect of zoledronate (ZA) on osteoclast functions and viability in the tibiae of 8-week-old male mice. After weekly intravenous administration of ZA (125 µg/kg body weight) for 8 weeks, the mice were fixed by transcardial perfusion of 4% paraformaldehyde under anesthesia, and their tibiae were extracted for histochemical analysis. Compared with the control group, many tartrate-resistant acidic phosphatase-positive osteoclasts were found on the surface of the trabecular bone, but cartilage cores were obviously increased in the metaphysis of the ZA group. Osteoclasts of both groups showed similar expression of cathepsin K and matrix metalloproteinase-9. However, hardly any expression of c-src, a gene necessary for ruffled border formation and bone resorption, was found in osteoclasts of the ZA group. Moreover, no expression of CD44 or osteopontin (OPN) was observed in osteoclasts of the ZA group. Taken together, our findings suggest that ZA administration decreases the bone resorption ability of osteoclasts by inhibiting c-src expression and suppressing osteoclast adhesion by interfering with CD44/OPN binding.

Dehydroepiandrosterone Activation of G-protein-coupled Estrogen Receptor Rapidly Stimulates MicroRNA-21 Transcription in Human Hepatocellular Carcinoma Cells.

Little is known about the regulation of the oncomiR miR-21 in liver. Dehydroepiandrosterone (DHEA) regulates gene expression as a ligand for a G-protein-coupled receptor and as a precursor for steroids that activate nuclear receptor signaling. We report that 10 nm DHEA increases primary miR-21 (pri-miR-21) transcription and mature miR-21 expression in HepG2 cells in a biphasic manner with an initial peak at 1 h followed by a second, sustained response from 3-12 h. DHEA also increased miR-21 in primary human hepatocytes and Hep3B cells. siRNA, antibody, and inhibitor studies suggest that the rapid DHEA-mediated increase in miR-21 involves a G-protein-coupled estrogen receptor (GPER/GPR30), estrogen receptor α-36 (ERα36), epidermal growth factor receptor-dependent, pertussis toxin-sensitive pathway requiring activation of c-Src, ERK1/2, and PI3K. GPER antagonist G-15 attenuated DHEA- and BSA-conjugated DHEA-stimulated pri-miR-21 transcription. Like DHEA, GPER agonists G-1 and fulvestrant increased pri-miR-21 in a GPER- and ERα36-dependent manner. DHEA, like G-1, increased GPER and ERα36 mRNA and protein levels. DHEA increased ERK1/2 and c-Src phosphorylation in a GPER-responsive manner. DHEA increased c-Jun, but not c-Fos, protein expression after 2 h. DHEA increased androgen receptor, c-Fos, and c-Jun recruitment to the miR-21 promoter. These results suggest that physiological concentrations of DHEA activate a GPER intracellular signaling cascade that increases pri-miR-21 transcription mediated at least in part by AP-1 and androgen receptor miR-21 promoter interaction.

The hydrolysed products of iridoid glycosides can enhance imatinib mesylate-induced apoptosis in human myeloid leukaemia cells.

Several studies have demonstrated that deregulated activation of signal transducer and activator of transcription 3 (STAT3) has been associated with survival, proliferation, chemoresistance and angiogenesis of tumour cells. Thus, inhibition of STAT3 expression could be a potent therapeutic approach for cancer treatment. Using several leukaemia cell lines, the effect of the hydrolysed-catalpol (H-catalpol) and hydrolysed-aucubin (H-aucubin) products on the STAT3 signalling pathway, inhibition of BCR-ABL activation, cellular proliferation and potentiation of imatinib mesylate-induced apoptosis was investigated. We found that iridoid glycosides (catalpol and aucubin) did not exert any cytotoxicity in the tumour cells, whereas both H-catalpol and H-aucubin exhibited significant cytotoxic effects on K562 human myeloid leukaemia cells. Indeed, H-catalpol and H-aucubin down-regulated BCR-ABL phosphorylation and inhibited constitutive STAT3 activation through abrogating upstream JAK2 and c-Src and constitutive STAT5 activation leading to apoptosis through caspase-3 activation. Hydrolysed-catalpol enhanced the apoptosis induced by imatinib mesylate and this correlated with down-regulation of gene products that mediate cell proliferation (cyclin D1), and cell survival (Bcl-2, Bcl-xL and survivin); all known to be regulated by the STAT3. Overall, our results provide novel insight into the role of hydrolysed iridoids in potentially treating leukaemia through the modulation of STAT3 signalling pathway.

A Discovery Strategy for Selective Inhibitors of c-Src in Complex with the Focal Adhesion Kinase SH3/SH2-binding Region.

The c-Src tyrosine kinase co-operates with the focal adhesion kinase to regulate cell adhesion and motility. Focal adhesion kinase engages the regulatory SH3 and SH2 domains of c-Src, resulting in localized kinase activation that contributes to tumor cell metastasis. Using assay conditions where c-Src kinase activity required binding to a tyrosine phosphopeptide based on the focal adhesion kinase SH3-SH2 docking sequence, we screened a kinase-biased library for selective inhibitors of the Src/focal adhesion kinase peptide complex versus c-Src alone. This approach identified an aminopyrimidinyl carbamate compound, WH-4-124-2, with nanomolar inhibitory potency and fivefold selectivity for c-Src when bound to the phospho-focal adhesion kinase peptide. Molecular docking studies indicate that WH-4-124-2 may preferentially inhibit the 'DFG-out' conformation of the kinase active site. These findings suggest that interaction of c-Src with focal adhesion kinase induces a unique kinase domain conformation amenable to selective inhibition.

Substrate activity screening with kinases: discovery of small-molecule substrate-competitive c-Src inhibitors.

Substrate-competitive kinase inhibitors represent a promising class of kinase inhibitors, however, there is no methodology to selectively identify this type of inhibitor. Substrate activity screening was applied to tyrosine kinases. By using this methodology, the first small-molecule substrates for any protein kinase were discovered, as well as the first substrate-competitive inhibitors of c-Src with activity in both biochemical and cellular assays. Characterization of the lead inhibitor demonstrates that substrate-competitive kinase inhibitors possess unique properties, including cellular efficacy that matches biochemical potency and synergy with ATP-competitive inhibitors.

Interaction between a CSK gene variant and fish oil intake influences blood pressure in healthy adults.

Blood pressure is a heritable determinant of cardiovascular disease (CVD) risk. Recent genome-wide association studies have identified several single-nucleotide polymorphisms (SNPs) associated with blood pressure, including rs1378942 in the c-Src tyrosine kinase (CSK) gene. Fish oil supplementation provides inconsistent protection from CVD, which may reflect genetic variation. We investigated the effect of rs1378942 genotype interaction with fish oil dosage on blood pressure measurements in the MARINA (Modulation of Atherosclerosis Risk by Increasing doses of N-3 fatty Acids) study, a parallel, double-blind, controlled trial in 367 participants randomly assigned to receive treatment with 0.45, 0.9, and 1.8 g/d eicosapentaenoic acid [EPA (20:5n-3)] and docosahexaenoic acid [DHA (22:6n-3)] (1.51:1) or an olive oil placebo for 12 mo. A total of 310 participants were genotyped. There were no significant associations with blood pressure measures at baseline; however, the interaction between genotype and treatment was a significant determinant of systolic blood pressure (SBP) (P = 0.010), diastolic blood pressure (DBP) (P = 0.037), and mean arterial blood pressure (MABP) (P = 0.014). After the 1.8 g/d dose, noncarriers of the rs1378942 variant allele showed significantly lower SBP (P = 0.010), DBP (P = 0.016), and MABP (P = 0.032) at follow-up, adjusted for baseline values, than did carriers. We found no evidence of SNP genotype association with endothelial function (brachial artery diameter and flow-mediated dilatation), arterial stiffness (carotid-femoral pulse wave velocity and digital volume pulse), and resting heart rate. A high intake of EPA and DHA could help protect noncarriers but not carriers of the risk allele. Dietary recommendations to reduce blood pressure in the general population may not necessarily benefit those most at risk. This trial was registered at controlled-trials.com as ISRCTN66664610.

Chemopreventive activity of plant flavonoid isorhamnetin in colorectal cancer is mediated by oncogenic Src and ß-catenin.

Analysis of the Polyp Prevention Trial showed an association between an isorhamnetin-rich diet and a reduced risk of advanced adenoma recurrence; however, the mechanism behind the chemoprotective effects of isorhamnetin remains unclear. Here, we show that isorhamnetin prevents colorectal tumorigenesis of FVB/N mice treated with the chemical carcinogen azoxymethane and subsequently exposed to colonic irritant dextran sodium sulfate (DSS). Dietary isorhamnetin decreased mortality, tumor number, and tumor burden by 62%, 35%, and 59%, respectively. MRI, histopathology, and immunohistochemical analysis revealed that dietary isorhamnetin resolved the DSS-induced inflammatory response faster than the control diet. Isorhamnetin inhibited AOM/DSS-induced oncogenic c-Src activation and ß-catenin nuclear translocation, while promoting the expression of C-terminal Src kinase (CSK), a negative regulator of Src family of tyrosine kinases. Similarly, in HT-29 colon cancer cells, isorhamnetin inhibited oncogenic Src activity and ß-catenin nuclear translocation by inducing expression of csk, as verified by RNA interference knockdown of csk. Our observations suggest the chemoprotective effects of isorhamnetin in colon cancer are linked to its anti-inflammatory activities and its inhibition of oncogenic Src activity and consequential loss of nuclear ß-catenin, activities that are dependent on CSK expression.

Molecular mechanisms underlying the apoptotic effect of KCNB1 K+ channel oxidation.

Potassium (K(+)) channels are targets of reactive oxygen species in the aging nervous system. KCNB1 (formerly Kv2.1), a voltage-gated K(+) channel abundantly expressed in the cortex and hippocampus, is oxidized in the brains of aging mice and of the triple transgenic 3xTg-AD mouse model of Alzheimer's disease. KCNB1 oxidation acts to enhance apoptosis in mammalian cell lines, whereas a KCNB1 variant resistant to oxidative modification, C73A-KCNB1, is cytoprotective. Here we investigated the molecular mechanisms through which oxidized KCNB1 channels promote apoptosis. Biochemical evidence showed that oxidized KCNB1 channels, which form oligomers held together by disulfide bridges involving Cys-73, accumulated in the plasma membrane as a result of defective endocytosis. In contrast, C73A-mutant channels, which do not oligomerize, were normally internalized. KCNB1 channels localize in lipid rafts, and their internalization was dynamin 2-dependent. Accordingly, cholesterol supplementation reduced apoptosis promoted by oxidation of KCNB1. In contrast, cholesterol depletion exacerbated apoptotic death in a KCNB1-independent fashion. Inhibition of raft-associating c-Src tyrosine kinase and downstream JNK kinase by pharmacological and molecular means suppressed the pro-apoptotic effect of KCNB1 oxidation. Together, these data suggest that the accumulation of KCNB1 oligomers in the membrane disrupts planar lipid raft integrity and causes apoptosis via activating the c-Src/JNK signaling pathway.

25-Methoxyhispidol A, a novel triterpenoid of Poncirus trifoliata, inhibits cell growth via the modulation of EGFR/c-Src signaling pathway in MDA-MB-231 human breast cancer cells.

The fruit of Poncirus trifoliata (Rutaceae) has been used a medicinal food and traditional medicine. Recently we reported the isolation of 25-methoxyhispidol A (25-MHA) as a novel triterpenoid from the immature fruit of P. trifoliata with the potential growth inhibition of cancer cells. However, the molecular mechanisms on the anti-proliferative activity in cancer cells remain to be elucidated. In the present study, we investigated the anti-proliferative activity and mechanisms of actions mediated by 25-MHA in estrogen receptor (ER)-negative MDA-MB-231 human breast cancer cells. 25-MHA exhibited the growth inhibitory activity against MDA-MB-231 cells with the cell cycle arrest in the G0/G1 phase. The cell cycle arrest in the G0/G1 by 25-MHA was well correlated with the downregulation of cyclin D1, cyclin dependent kinase (CDK4), CDK2, cyclin A, phosphorylated retinoblastoma protein (pRb), and induction of cdk inhibitor p21(WAF1/Cip1) protein. 25-MHA also suppressed the activation of c-Src/epidermal growth factor receptor (EGFR)/Akt signaling, and consequently led to the inactivation of mTOR and its downstream signal molecules including 4E-binding protein (4E-BP) and p70 S6 kinase. These findings suggest that 25-MHA-mediated inhibitory activity of human breast cancer cell growth might be related with the cell cycle arrest and modulation of signal transduction pathways.