Robust GRK2/3/6-dependent desensitization of oxytocin receptor in neurons.

Oxytocin plays critical roles in the brain as a neuromodulator, regulating social and other affective behavior. However, the regulatory mechanisms controlling oxytocin receptor (OXTR) signaling in neurons remain unexplored. In this study, we have identified robust and rapid-onset desensitization of OXTR response in multiple regions of the mouse brain. Both cell autonomous spiking response and presynaptic activation undergo similar agonist-induced desensitization. G-protein-coupled receptor kinases (GRK) GRK2, GRK3, and GRK6 are recruited to the activated OXTR in neurons, followed by recruitment of ß-arrestin-1 and -2. Neuronal OXTR desensitization was impaired by suppression of GRK2/3/6 kinase activity but remained unaltered with double knockout of ß-arrestin-1 and -2. Additionally, we observed robust agonist-induced internalization of neuronal OXTR and its Rab5-dependent recruitment to early endosomes, which was impaired by GRK2/3/6 inhibition. This work defines distinctive aspects of the mechanisms governing OXTR desensitization and internalization in neurons compared to prior studies in heterologous cells.

Structural and Functional Characterization of a Novel Scorpion Toxin that Inhibits NaV1.8 via Interactions With the DI Voltage Sensor and DII Pore Module.

Voltage-gated sodium channel NaV1.8 regulates transmission of pain signals to the brain. While NaV1.8 has the potential to serve as a drug target, the molecular mechanisms that shape NaV1.8 gating are not completely understood, particularly mechanisms that couple activation to inactivation. Interactions between toxin producing animals and their predators provide a novel approach for investigating NaV structure-function relationships. Arizona bark scorpions produce Na+ channel toxins that initiate pain signaling. However, in predatory grasshopper mice, toxins inhibit NaV1.8 currents and block pain signals. A screen of synthetic peptide toxins predicted from bark scorpion venom showed that peptide NaTx36 inhibited Na+ current recorded from a recombinant grasshopper mouse NaV1.8 channel (OtNaV1.8). Toxin NaTx36 hyperpolarized OtNaV1.8 activation, steady-state fast inactivation, and slow inactivation. Mutagenesis revealed that the first gating charge in the domain I (DI) S4 voltage sensor and an acidic amino acid (E) in the DII SS2 - S6 pore loop are critical for the inhibitory effects of NaTx36. Computational modeling showed that a DI S1 - S2 asparagine (N) stabilizes the NaTx36 - OtNaV1.8 complex while residues in the DI S3 - S4 linker and S4 voltage sensor form electrostatic interactions that allow a toxin glutamine (Q) to contact the first S4 gating charge. Surprisingly, the models predicted that NaTx36 contacts amino acids in the DII S5 - SS1 pore loop instead of the SS2 - S6 loop; the DII SS2 - S6 loop motif (QVSE) alters the conformation of the DII S5 - SS1 pore loop, enhancing allosteric interactions between toxin and the DII S5 - SS1 pore loop. Few toxins have been identified that modify NaV1.8 gating. Moreover, few toxins have been described that modify sodium channel gating via the DI S4 voltage sensor. Thus, NaTx36 and OtNaV1.8 provide tools for investigating the structure-activity relationship between channel activation and inactivation gating, and the connection to alternative pain phenotypes.

Gender-Based Vegetarian and Nonvegetarian Dietary Impact on Cardiac Autonomic Function of Heart Rate Variability.

Objective: Cardiovascular disease is one among the major mortality threats throughout the world. Autonomic activity of the nervous system can be examined by heart rate variability (HRV) analysis. Association of sympathetic and parasympathetic activities is directly related to HRV modulation. The aim of the study is to determine variations in HRV parameters among adult/adolescent male and female subjects due to vegetarian and nonvegetarian diet.Method: Ninety undergraduate students in each male and female group (N = 180) volunteered for the study. Based upon food habits, male and female subjects were categorized into four groups. Short-term (5-minute) heart rate recordings were measured from the subjects in a seated position before breakfast with minimum of 12 hours' fasting. Two-way analysis of variance was performed among the time and frequency domain variables.Results: Time domain variables are observed as significant (p < 0.05) between vegetarian males and females and also (p < 0.05) between male vegetarian and female nonvegetarians for standard deviation of NN intervals. Frequency domain HRV indices such as low frequency (LF; p = 0.01), high frequency (HF; p = 0.0001), and LF/HF (p < 0.001) resulted between male and female vegetarians. Significance of LF (p = 0.02), HF (p < 0.0001), and LF/HF (p < 0.01) was measured between male vegetarians and female nonvegetarians. LF (p = 0.02), HF (p = 0.04), and LF/HF (p = 0.002) resulted between nonvegetarian males and females. HF (p = 0.05) was enumerated between male vegetarians and nonvegetarians.Conclusions: Significant predominance of sympathetic cardiac activity was observed among male nonvegetarian consumers more than female vegetarians. Analysis demonstrates that the gender-based influence of vegetarian and nonvegetarian diet has significant correlation under HRV measurements.

4,4'-Diisothiocyanatostilbene-2,2'-disulfonate modulates voltage-gated K+ current and influences cell cycle arrest in androgen sensitive and insensitive human prostate cancer cell lines.

The stilbene derivative, 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), an anion channel blocker is used in the present study to evaluate its modulatory effect on voltage-gated K+ current (IK) in human prostate cancer cell lines (LNCaP and PC-3). Voltage-gated K+ (KV) channels in the plasma membrane are critically involved in the proliferation of tumor cells. Therefore, KV channels are considered as a novel potential target for cancer treatment. The results of the present study show that the external perfusion of DIDS activates IK in a concentration-dependent manner, although the known K+ channel blocker TEA failed to block the DIDS activated IK in PC-3 cells. Whereas, in LNCaP cells, the higher concentration of DIDS blocked IK, though this effect was not completely recovered after washout. The difference in function of DIDS might be due to the expression of different Kv channel isoforms in LNCaP and PC-3 cells. Further, the anticancer studies show that treatment of DIDS significantly induced G2/M phase cell cycle arrest and induced moderate and low level of cell death in LNCaP and PC-3 cells respectively. This finding reveals that DIDS modulates IK and exerts cell cycle arrest and cell death in LNCaP and PC-3 cells.

Modulatory Effect of Selected Dietary Phytochemicals on Delayed Rectifier K+ Current in Human Prostate Cancer Cells.

Phytochemicals are ubiquitous in naturally occurring dietary elements that exhibits diverse pharmacological properties over various pathological disorders, including cancer. Voltage gated K+ (KV) channel in the plasma membrane contributes to wide range of cellular processes including cancer progression. Therefore, modulation of KV channel is being considered as a novel potential target for cancer therapy. The whole cell patch clamp technique was used to record the modulatory effect of chrysin, naringenin, caffeic acid, gallic acid, and zingerone on delayed rectifier potassium current (IK) in human prostate cancer cells LNCaP and PC-3. Among the tested compounds, zingerone blocked IK in a concentration-dependent manner in LNCaP cells and estimated the IC50 value of 141 µM and Emax was 81.3%. Further analysis of KV channel activation kinetics showed that zingerone induces a positive shift in the activation curve in LNCaP cells, whereas the inhibitory effect of gallic acid on IK was significantly less potent than the inhibition caused by zingerone. However, chrysin, naringenin, and caffeic acid did not modulate the KV channel conductance in LNCaP or PC-3 cells. Our findings confirmed that not all the tested phytochemicals to be effective modulators of IK and suggested that IK inhibitory effect of zingerone and gallic acid may be responsible for their anticancer effects in prostate cancer cells.

Piperine blocks voltage gated K+ current and inhibits proliferation in androgen sensitive and insensitive human prostate cancer cell lines.

Piperine is an attractive therapeutic alkaloid from black pepper that exhibits a broad spectrum of pharmacological properties over various pathological disorders including cancer. Voltage gated K+ (KV) channels play an important role in regulating cancer cell proliferation and are considered as potential target for cancer treatment. However, the implication of piperine in KV associated anticancer activities on human prostate cancer cells LNCaP and PC-3 remains unrevealed. The electrophysiological and pharmacological data identifies that both androgen sensitive (LNCaP) and insensitive (PC-3) prostate cancer cells typically expressed voltage gated K+ current (IK). This current was significantly blocked by piperine in a concentration-dependent manner with an IC50 value 39.91 µM in LNCaP and 49.45 µM in PC-3 cells. Analysis of voltage-dependence of activation kinetics showed that piperine induces a positive shift in the relative activation curve in both the cells. Piperine also depolarized the resting membrane potential by an average of 10.2 mV and 8.3 mV in LNCaP and PC-3 cells, respectively. The anticancer studies showed that, treatment with piperine concentration dependently induced G1 phase cell cycle arrest and apoptosis in LNCaP and PC-3 cells. These results unravel that the IK inhibition might be responsible for the anticancer effect of piperine on androgen sensitive and insensitive human prostate cancer cells.

Why does NiOOH cocatalyst increase the oxygen evolution activity of α-Fe2O3?

Nickel oxyhydroxide (NiOOH) is known to increase the oxygen evolution reaction (OER) performance of hematite (Fe2O3) photoanodes. In recent experimental studies, it has been reported that the increased OER activity is related to the activation of the hematite (α-Fe2O3) surface by NiOOH rather than the activity of NiOOH itself. In this study, we investigate the reason behind the higher activity and the low overpotentials for NiOOH-Fe2O3 photoanodes using first principles calculations. To study the activity of possible catalytic sites, different geometries with NiOOH as a cluster and as a strip geometry on hematite (110) surfaces are studied. Density functional theory + U calculations are carried out to determine the OER activity at different sites of these structures. The geometry with a continuous strip of NiOOH on hematite is stable and is able to explain the activity. We found that the Ni atoms at the edge sites of the NiOOH cocatalyst are catalytically more active than Ni atoms on the basal plane of the cocatalyst; the calculated overpotentials are as low as 0.39 V.

Anticancer mechanism of troxerutin via targeting Nrf2 and NF-κB signalling pathways in hepatocarcinoma cell line.

Troxerutin (TX), a bioflavonoid widely present in various fruits and vegetables, has shown to exhibit numerous pharmacological properties including anti-neoplastic and anti-cancer activities. Nrf2 and NF-κB are the key transcription factors that regulate oxidative stress and inflammation, therefore we assessed whether TX modulate these pathways and its downstream proteins in HuH-7 hepatocarcinoma cells. TX induced apoptotic cellular and nuclear changes were examined by fluorescence staining techniques, agarose gel electrophoresis and flow cytometry. Oxidative stress was determined through biochemical analysis of antioxidant enzymes and lipid peroxidation profile. The protein expressions of NF-κB and Nrf2 pathway regulators, cell proliferation markers and apoptotic pathway mediators were evaluated by performing immunoblotting, immunocytochemistry and molecular docking. Our results revealed that TX inhibits the growth of HuH-7 cells in a concentration and time-dependent manner. TX treated HuH-7 cells exhibited increased heme oxygenase (HO)-1 protein expression, augmented nuclear translocation of Nrf2, and reduced oxidative stress. Furthermore, TX suppressed the expression of IKKß which subsequently inhibited the nuclear translocation of NF-κB (p65 subunit), and thus downregulated NF-κB mediated inflammatory responses, proliferation and cell survival. Collectively, our results indicate that TX exerts anti-cancer effect in HuH-7 hepatocarcinoma cells possibly through simultaneous regulation of the molecular signalling pathways, Nrf2 and NF-κB.

Hypodipsic-hypernatremia syndrome in an adult with polycythemia: a case report.

BACKGROUND: Hypernatremia is a very common electrolyte disorder and is frequently encountered in out-patient as well as in-hospital settings. We describe an adult who was found to have unexplained relative polycythemia and episodic hypernatremia. A diagnosis of idiopathic hypodipsic-hypernatremia syndrome was made and the patient was managed with a water-drinking schedule. CASE PRESENTATION: A 24-year-old South African-Indian man was found to have polycythemia in association with episodes of hypernatremia. Investigations indicated that he had relative polycythemia. He experienced no thirst at a time when his serum sodium concentration was found to be 151 mmol/L. Further testing indicated that his renal response to arginine vasopressin was intact and magnetic resonance imaging of his brain revealed no hypothalamic lesions. A diagnosis of idiopathic hypodipsic-hypernatremia syndrome was made and he was managed with a water-drinking schedule that corrected his hypernatremia. CONCLUSION: Hypodipsia should always be considered when a patient without physical or cognitive disability presents with unexplained episodic hypernatremia or with relative polycythemia.

Troxerutin subdues hepatic tumorigenesis via disrupting the MDM2-p53 interaction.

Hepatocellular carcinoma (HCC) is the leading cause of cancer death worldwide that lacks proper medical prognosis and treatment. In the present study, the anti-tumoral potential of troxerutin (TX), an ethnomedicine, was examined in relation to its effects on the promoter 2-acetylaminofluorene (2-AAF) in N-nitrosodiethylamine (NDEA) initiated HCC, as compared to its effects on HCC induced by NDEA alone. Liver samples from each experimental group were collected and evaluated for histological, biochemical and cellular characterization. The protein expressions of apoptotic and cell proliferation markers were determined via immunohistochemistry and western blotting. Molecular docking was also performed to delineate the inhibitory mechanism of TX on HCC. The results show that only higher doses of TX showed a significant reduction in the incidence of hepatic nodule formation, and they also counteracted NDEA plus 2-AAF induced alterations in the enzymic status. The frequencies of glutathione-S-transferase and proliferating cell nuclear antigen, markers of S phase progression, were markedly reduced during TX treatment. TX also modulated the imbalance in the MDM2-p53 interaction. The molecular docking results confirmed the interaction of TX with the upstream kinases that regulate apoptosis. This study provides evidence that a copious dose of TX is required to counteract the differential mitoinhibitory effect of 2-AAF in NDEA initiated hepatomas, and TX exhibits an anti-tumoral effect via suppressing oxidative stress, regulating liver function enzymes, inhibiting inflammatory responses and modulating MDM2-p53 interactions, thus inducing apoptosis, and thereby suggesting that TX may provide promising therapeutic effects for the chemoprevention of HCC.

The in vivo antineoplastic and therapeutic efficacy of troxerutin on rat preneoplastic liver: biochemical, histological and cellular aspects.

PURPOSE: Troxerutin (TXER), a trihydroxyethylated derivative of the natural bioflavonoid rutin, abundantly found in tea, various fruits and vegetables, is known to exhibit ample pharmacological properties. In the present investigation, we examined the antineoplastic, therapeutic efficacy and furthermore the possible mechanisms of action of TXER against NAFLD/NASH progression to hepatocarcinogenesis. METHODS: The effect of TXER (12.5, 25 or 50 mg/kg b.w/day) was evaluated on the nitrosodiethylamine (NDEA) model of hepatocarcinogenesis in rats, after 16 weeks of oral treatment, with special focus on liver specific enzymes, xenobiotic metabolizing enzymes, antioxidant status, lipid peroxidation profile, DNA damage, fibrosis, cell proliferation and inflammatory status. RESULTS: Administration of TXER to hepatocellular carcinoma-bearing rats restored the enzyme activities and the hepatic architecture. Furthermore, TXER significantly curtailed NDEA-induced DNA damage, cell proliferation, inflammation, fibrosis and hepatic hyperplasia. CONCLUSION: This study provides the evidence that troxerutin exerts a significant therapeutic effect against liver cancer by modulating liver function enzymes, xenobiotic enzymes, oxidative damage, inhibiting cell proliferation, suppressing inflammatory response and induction of apoptosis.

Molecular aspects and chemoprevention of dimethylaminoazobenzene-induced hepatocarcinogenesis: A review.

The lipophilic azo dye dimethylaminoazobenzene (DAB) is a potent hepatocarcinogen accounted as a group-2B carcinogen causing risk to humans. DAB is commonly used as a coloring agent in food, pharmaceuticals, beverages, soap and polishes. The exploration of DAB-induced hepatocarcinogenesis in animal models helped to an extent to perceive the histological, biochemical and molecular mechanisms of DAB carcinogenesis and also the severity of DAB exposure to humans. In experimental animal models, it is well-proved that the procarcinogen DAB is predominantly metabolized by cytochrome P450 enzymes giving rise to the formation of toxic electrophiles and reactive oxygen species (ROS), which further forms DNA adducts leading to the development of hepatic tumors. Recently, research evidence suggests that dietary phytochemicals and plant polyphenols are promising agents to control the incidence of DAB-induced hepatocarcinogenesis by preventing the generation of toxic electrophiles and ROS thereby inhibiting the formation of DNA adducts. This review highlights the role of specific dietary factors, biotransformation of DAB, phenotypic and genotypic alterations, and significance of certain chemopreventive agents against DAB-induced hepatocarcinogenesis.