Effects of ginsenoside Rg3 on α9α10 nicotinic acetylcholine receptor-mediated ion currents

Ginsenosides is a low molecular weight substance found in ginseng as one of the active ingredients. Ginsenosides, like other herbal medicines, has a wide range of neuropharmacological actions including neuroprotective effects. The α9α10 nicotinic acetylcholine receptor is one of numerous nicotinic acetylcholine receptors that exists as a heteropentameric form in auditory hair cells of the cochlea. In this study, we report the effects of ginsenosides on rat α9α10 nicotinic acetylcholine receptor-mediated ion currents using the two-electrode voltage clamp technique. Treatment with acetylcholine evoked inward currents (IACh) in oocytes heterologously expressing the α9α10 nicotinic acetylcholine receptor. Ginsenosides blocked IACh in order of potency of Rg3> Rb2> CK>Re = Rg2> Rf>Rc> Rb1> Rg1 with reversible manners, and the blocking effect of Rg3 on IACh was same after pre-application than co-application of Rg3. The half maximal inhibitory concentration (IC50) of Rg3 was 39.6 ± 4.9 µm. Rg3-induced IACh inhibition was not affected by acetylcholine concentration and was independent of membrane holding potential. Although the inhibitory effect of Rg3 on IACh was abolished in oocytes expressing α9 subunit alone, indicating that the presence of α10 subunit might be required for Rg3-induced regulations of α9α10 nicotinic acetylcholine receptor channel activity. These results indicate that α10 subunit of α9α10 nicotinic acetylcholine receptor might play an important role in Rg3-induced regulation of the α9α10 nicotinic acetylcholine receptor.

Relationship between chewing ability and depressive symptoms

OBJECTIVE

Depression, as one of the most common mental health problems, has many related factors. Recent studies have suggested chewing difficulties as a risk factor for depression in the elderly. This study seeks to investigate whether chewing ability is associated with depressive symptoms in a Korean population.

METHODS

This study used data from the Fifth Korean National Health and Nutrition Examination Survey (KNHANES V) conducted in 2010. Self-reported questionnaires assessed depressive symptoms and chewing ability for the purposes of this study. A total of 6,255 subjects aged over 19 years were included for this study (2,704 males and 3,551 females).

RESULTS

Comparing depressive symptoms with chewing ability (i.e., very poor, poor, moderate, good, and very good), the adjusted odds ratios (ORs) and confidence intervals (CI) were 1.05 (95% CI: 0.84-1.32) for good vs. very good (as a reference), 1.31 (95% CI: 1.00-1.73) for moderate vs. very good, 1.41 (95% CI: 1.12-1.78) for poor vs. very good, and 1.76 (95% CI: 1.16-2.76) for very poor vs. very good.

CONCLUSION

This study suggests that subjects with reduced chewing ability were more susceptible to having depressive symptoms.

Differential effects of ginsenoside metabolites on slowly activating delayed rectifier K(+) and KCNQ1 K(+) channel currents

Channels formed by the co-assembly of the KCNQ1 subunit and the mink (KCNE1) subunit underline the slowly activating delayed rectifier K⁺ channels (I_Ks) in the heart. This K⁺ channel is one of the main pharmacological targets for the development of drugs against cardiovascular disease. Panax ginseng has been shown to exhibit beneficial cardiovascular effects. In a previous study, we showed that ginsenoside Rg3 activates human KCNQ1 K⁺ channel currents through interactions with the K318 and V319 residues. However, little is known about the effects of ginsenoside metabolites on KCNQ1 K⁺ alone or the KCNQ1 + KCNE1 K⁺ (I_Ks) channels. In the present study, we examined the effect of protopanaxatriol (PPT) and compound K (CK) on KCNQ1 K⁺ and I_Ks channel activity expressed in Xenopus oocytes. PPT more strongly inhibited the I_Ks channel currents than the currents of KCNQ1 K⁺ alone in concentration- and voltage-dependent manners. The IC₅₀ values on I_Ks and KCNQ1 alone currents for PPT were 5.18±0.13 and 10.04±0.17 μM, respectively. PPT caused a leftward shift in the activation curve of I_Ks channel activity, but minimally affected KCNQ1 alone. CK exhibited slight inhibition on I_Ks and KCNQ1 alone K⁺ channel currents. These results indicate that ginsenoside metabolites show limited effects on I_Ks channel activity, depending on the structure of the ginsenoside metabolites.

Relationship between cognitive impairment and depression in dialysis patients

PURPOSE

Patients with chronic kidney disease frequently show cognitive dysfunction. The association of depression and cognitive function is not well known in maintenance dialysis patients. We evaluated cognitive impairment and depression, as well as their relationship in regards to methods of dialysis, maintenance hemodialysis (MHD) and chronic peritoneal dialysis (CPD).

MATERIALS AND METHODS

Fifty-six maintenance dialysis patients were recruited and their clinical and laboratory data were collected. The Korean version of the mini-mental state exam (K-MMSE) was applied to screen the patient's cognitive function, while the Korean version of the Beck Depression Inventory (K-BDI) was used for depression screening.

RESULTS

The average age of the participants was 54.2±10.2 years; 29 (51.8%) were female. The average dialysis vintage was 4.2±3.8 years. The CPD group showed significantly higher K-MMSE score (27.8±2.9 vs. 26.1±3.1, p=0.010) and lower K-BDI score (12.0±8.4 vs. 20.2±10.4, p=0.003) compared with the MHD group. The percentage of patients with depression symptoms was higher in the MHD group (51.7% vs. 18.5%). There was a negative correlation between cognitive function and prevalence of depressive symptoms. Depression and education level were shown to be independent predictors for cognitive impairment in multivariate analysis.

CONCLUSION

Cognitive impairment was closely correlated with depression. It is important to detect cognitive impairment and depression early in maintenance dialysis patients with simple bedside screening tools.

Activation of lysophosphatidic Acid receptor is coupled to enhancement of ca(2+)-activated potassium channel currents

The calcium-activated K(+) (BKCa) channel is one of the potassium-selective ion channels that are present in the nervous and vascular systems. Ca(2+) is the main regulator of BKCa channel activation. The BKCa channel contains two high affinity Ca(2+) binding sites, namely, regulators of K(+) conductance, RCK1 and the Ca(2+) bowl. Lysophosphatidic acid (LPA, 1-radyl-2-hydroxy-sn-glycero-3-phosphate) is one of the neurolipids. LPA affects diverse cellular functions on many cell types through G protein-coupled LPA receptor subtypes. The activation of LPA receptors induces transient elevation of intracellular Ca(2+) levels through diverse G proteins such as Gαq/11, Gαi, Gα12/13, and Gαs and the related signal transduction pathway. In the present study, we examined LPA effects on BKCa channel activity expressed in Xenopus oocytes, which are known to endogenously express the LPA receptor. Treatment with LPA induced a large outward current in a reversible and concentration-dependent manner. However, repeated treatment with LPA induced a rapid desensitization, and the LPA receptor antagonist Ki16425 blocked LPA action. LPA-mediated BKCa channel activation was also attenuated by the PLC inhibitor U-73122, IP3 inhibitor 2-APB, Ca(2+) chelator BAPTA, or PKC inhibitor calphostin. In addition, mutations in RCK1 and RCK2 also attenuated LPA-mediated BKCa channel activation. The present study indicates that LPA-mediated activation of the BKCa channel is achieved through the PLC, IP3, Ca(2+), and PKC pathway and that LPA-mediated activation of the BKCa channel could be one of the biological effects of LPA in the nervous and vascular systems.

Differential effects of ginsenoside metabolites on HERG k channel currents

The human ether-a-go-go-related gene (HERG) cardiac K⁺ channels are one of the representative pharmacological targets for development of drugs against cardiovascular diseases such as arrhythmia. Panax ginseng has been known to exhibit cardioprotective effects. In a previous report we demonstrated that ginsenoside Rg₃ regulates HERG K⁺ channels by decelerating deactivation. However, little is known about how ginsenoside metabolites regulate HERG K⁺ channel activity. In the present study, we examined the effects of ginsenoside metabolites such as compound K (CK), protopanaxadiol (PPD), and protopanaxatriol (PPT) on HERG K⁺ channel activity by expressing human α subunits in Xenopus oocytes. CK induced a large persistent deactivating-tail current (I_{deactivating-tail}) and significantly decelerated deactivating current decay in a concentration-dependent manner. The EC₅₀ for persistent I_{deactivating-tail} was 16.6±1.3 μM. In contrast to CK, PPT accelerated deactivating-tail current deactivation. PPD itself had no effects on deactivating-tail currents, whereas PPD inhibited ginsenoside Rg₃-induced persistent I_{deactivating-tail} and accelerated HERG K⁺ channel deactivation in a concentration-dependent manner. These results indicate that ginsenoside metabolites exhibit differential regulation on I_{deactivating-tail} of HERG K⁺ channel.

Effects of Minor Ginsenosides, Ginsenoside Metabolites, and Ginsenoside Epimers on the Growth of Caenorhabditis elegans

In the previous report, we have demonstrated that ginsenoside Rc, one of major ginsenosides, is a major component for the restoration for normal growth of worms in cholesterol-deprived medium. In the present study, we further investigated the roles of minor ginsenosides, such as ginsenoside Rh₁ and Rh₂, ginsenoside metabolites such as compound K (CK), protopanaxadiol (PPD), and protopanaxatriol (PPT) and ginsenoside epimers such as 20(R)- and 20(S)-ginsenoside Rg₃ in cholesterol-deprived medium. We found that ginsenoside Rh₁ almost restored normal growth of worms in cholesterol-deprived medium in F1 generation. However, supplement of ginsenoside Rh₂ caused a suppression of worm growths in cholesterol-deprived medium. In addition, CK and PPD also slightly restored normal growth of worms in cholesterol-deprived medium but PPT not. In experiments using ginsenoside epimers, supplement of 20(S)- but not 20(R)-ginsenoside Rg₃ in cholesterol-deprived medium also almost restored worm growth. These results indicate that the absence or presence of carbohydrate component at backbone of ginsenoside, the number of carbohydrate attached at carbon-3, and the position of hydroxyl group at carbon-20 of ginsenoside might plays important roles in restoration of worm growth in cholesterol-deprived medium.

Effects of Ginsenoside Metabolites on GABAA Receptor-Mediated Ion Currents

In a previous report, we demonstrated that ginsenoside Rc, one of major ginsenosides from Panax ginseng, enhances γ-aminobutyric acid (GABA) receptor_A (GABA_A)-mediated ion channel currents. However, little is known about the effects of ginsenoside metabolites on GABA_A receptor channel activity. The present study investigated the effects of ginsenoside metabolites on human recombinant GABA_A receptor (α₁β₁γ_2s) channel activity expressed in Xenopus oocytes using a two-electrode voltage clamp technique. M4, a metabolite of protopanaxatriol ginsenosides, more potently inhibited the GABA-induced inward peak current (I_GABA) than protopanaxadiol (PPD), a metabolite of PPD ginsenosides. The effect of M4 and PPD on I_GABA was both concentration-dependent and reversible. The half-inhibitory concentration (IC₅₀) values of M4 and PPD were 17.1±2.2 and 23.1±8.6 μM, respectively. The inhibition of I_GABA by M4 and PPD was voltage-independent and non-competitive. This study implies that the regulation of GABA_A receptor channel activity by ginsenoside metabolites differs from that of ginsenosides.

Inhibitory Effects of Ginsenoside Metabolites, Compound K and Protopanaxatriol, on GABAC Receptor-Mediated Ion Currents

Ginsenosides, one of the active ingredients of Panax ginseng, show various pharmacological and physiological effects, and they are converted into compound K (CK) or protopanaxatriol (M4) by intestinal microorganisms. CK is a metabolite derived from protopanaxadiol (PD) ginsenosides, whereas M4 is a metabolite derived from protopanaxatriol (PT) ginsenosides. The γ-aminobutyric acid receptor_C (GABA_C) is primarily expressed in retinal bipolar cells and several regions of the brain. However, little is known of the effects of ginsenoside metabolites on GABA_C receptor channel activity. In the present study, we examined the effects of CK and M4 on the activity of human recombinant GABA_C receptor (ρ1) channels expressed in Xenopus oocytes by using a 2-electrode voltage clamp technique. In oocytes expressing GABA_C receptor cRNA, we found that CK or M4 alone had no effect in oocytes. However, co-application of either CK or M4 with GABA inhibited the GABA-induced inward peak current (I_GABA). Interestingly, pre-application of M4 inhibited I_GABA more potently than CK in a dose-dependent and reversible manner. The half-inhibitory concentration (IC₅₀) values of CK and M4 were 52.1±2.3 and 45.7±3.9 µM, respectively. Inhibition of I_GABA by CK and M4 was voltage-independent and non-competitive. This study implies that ginsenoside metabolites may regulate GABA_C receptor channel activity in the brain, including in the eyes.

Resveratrol Inhibits GABAC ρ Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

Resveratrol is a phytoalexin found in grapes, red wine, and berries. Resveratrol has been known to have many beneficial health effects, such as anti-cancer, neuroprotective, anti-inflammatory, and life-prolonging effects. However, relatively little is known about the effects of resveratrol on the regulation of ligand-gated ion channels. We have previously reported that resveratrol regulates subsets of homomeric ligand-gated ion channels such as those of 5-HT_3A receptors. The γ-aminobutyric acid_C (GABA_C) receptor is mainly expressed in retinal bipolar cells and plays an important role in visual processing. In the present study, we examined the effects of resveratrol on the channel activity of homomeric GABA_C receptor expressed in Xenopus oocytes injected with cRNA encoding human GABA_C ρ subunits. Our data show that the application of GABA elicits an inward peak current (I_GABA) in oocytes that express the GABA_C receptor. Resveratrol treatment had no effect on oocytes injected with H₂O or with GABA_C receptor cRNA. Co-treatment with resveratrol and GABA inhibited I_GABA in oocytes with GABA_C receptors. The inhibition of I_GABA by resveratrol was in a reversible and concentration-dependent manner. The IC₅₀ of resveratrol was 28.9±2.8 µM in oocytes expressing GABA_C receptor. The inhibition of I_GABA by resveratrol was in voltage-independent and non-competitive manner. These results indicate that resveratrol might regulate GABA_C receptor expression and that this regulation might be one of the pharmacological actions of resveratrol on the nervous system.

Abstract TP182: Bone Mass Loss May Be A Predictor Of Silent Cerebral Infarct And Cerebral White Matter Change In Community-dwelling Adults Without Stroke And Dementia

Background: Loss of bone and muscle mass, fall and fractures are common conditions after stroke. Possible association between reduced bone density and cognitive impairment in postmenopausal women are well recognized. However, the relationship between bone mass loss and silent infarcts and cerebral white matter changes remains unknown.

Methods: Bone densitometry measured by Dual-energy X-ray absorptiometry of lumbar spine and hip and brain CT scan were performed for 650 subjects (458 female, mean age 63±7.8 years; 192 male, 61.5±8.5 years) among 650 stroke- and dementia-free adults older than 50 years recruited for early health check-up program, a part of PRESENT project between January 2009 and December 2010. Assessment of vascular risk factors and physical examination by in-person interview and were also taken by neurologist, and trained nurses.

Result: In unadjusted analysis, the odds ratio (OR) for silent cerebral infarcts and/or cerebral white matter changes in men with osteoporosis was 3.8 (95% CI, 1.62-8.86; p = 0.002) and 2.2 (95% CI, 1.35-3.53; p=0.002) in women as compared to subjects with normal bone density. Even after adjustment for age, education, hypertension, DM, hypercholesterolemia, and current smoking, the OR was 3.8 (95% CI, 1.43-10.3; p = 0.008) for men and 1.9 (95% CI, 1.10-3.18; p=0.02), for women.

Conclusion: These findings suggest that loss of bone mass may be a predictor of silent cerebral infarcts and cerebral white matter changes in community dwelling, apparently healthy adults.

Gintonin, a ginseng-derived lysophosphatidic acid receptor ligand, potentiates ATP-gated P2X₁ receptor channel currents

Ginseng, the root of Panax ginseng C.A. Meyer, is used as a general tonic. Recently, we isolated a novel ginsengderived lysophosphatidic acid (LPA) receptor ligand, gintonin. Gintonin activates G protein-coupled LPA receptors with high affinity in cells endogenously expressing LPA receptors, e.g., Xenopus oocytes. P2X receptors are ligandgated ion channels activated by extracellular ATP, and 7 receptor subtypes (P2X1-P2X7) have been identified. Most of the P2X1 receptors are expressed in the smooth muscles of genitourinary organs involved in reproduction. A main characteristic of the P2X1 receptor is rapid desensitization after repeated ATP treatment of cells or tissues expressing P2X1 receptors. In the present study, we examined the effect of gintonin on P2X1 receptor channel activity. P2X1 receptors were heterologously expressed in Xenopus oocytes. ATP treatment of oocytes expressing P2X1 receptors induced large inward currents (I ATP ), but repetitive ATP treatments induced a rapid desensitization of I ATP . Gintonin treatment after P2X1 receptor desensitization potentiated I ATP in a concentration-dependent manner. We further examined the signaling transduction pathways involved in gintonin-mediated potentiation of I ATP . Gintoninmediated I ATP potentiation was blocked by Ki16425, an LPA1/3 receptor antagonist, a PKC inhibitor, a PLC inhibitor, and a PI4-Kinase inhibitor but not by a calcium chelator. In addition, mutations of the phosphoinositide binding site of the P2X1 receptor greatly attenuated the gintonin-mediated I ATP potentiation. These results indicate that G protein-coupled LPA receptor activation by gintonin is coupled to the potentiation of the desensitized P2X1 receptor through a phosphoinositide-dependent pathway.

Gintonin, a ginseng-derived novel ingredient, evokes long-term potentiation through N-methyl-D-aspartic acid receptor activation: involvement of LPA receptors

Ginseng has been shown to have memory-improving effects in human. However, little is known about the active components and the molecular mechanisms underlying its effects. Recently, we isolated novel lysophosphatidic acids (LPAs)-ginseng protein complex derived from ginseng, gintonin. Gintonin activates G protein-coupled LPA receptors with high affinity. Gintonin activated Ca²⁺-activated Clchannels in Xenopus oocytes through the activation of endogenous LPA receptor. In the present study, we investigated whether the activation of LPA receptor by gintonin is coupled to the regulation of N-methyl-D-aspartic acid (NMDA) receptor channel activity in Xenopus oocytes expressing rat NMDA receptors. The NMDA receptor-mediated ion current (I ( NMDA )) was measured using the two-electrode voltage-clamp technique. In oocytes injected with cRNAs encoding NMDA receptor subunits, gintonin enhanced I ( NMDA ) in a concentration-dependent manner. Gintonin-mediated I ( NMDA ) enhancement was blocked by Ki16425, an LPA1/3 receptor antagonist. Gintonin action was blocked by a PLC inhibitor, IP₃ receptor antagonist, Ca²⁺ chelator, and a tyrosine kinase inhibitor. The site-directed mutation of Ser1308 of the NMDA receptor, which is phosphorylated by protein kinase C (PKC), to an Ala residue, or co-expression of receptor protein tyrosine phosphatase with the NMDA receptor attenuated gintonin action. Moreover, gintonin treatment elicited a transient elevation of [Ca²⁺](i) in cultured hippocampal neurons and elevated longterm potentiation (LTP) in both concentration-dependent manners in rat hippocampal slices. Gintonin-mediated LTP induction was abolished by Ki16425. These results indicate that gintonin-mediated I ( NMDA ) potentiation and LTP induction in the hippocampus via the activation of LPA receptor might be responsible for ginseng-mediated improvement of memory-related brain functions.

Pharmacokinetics and in vivo potency of soluble epoxide hydrolase inhibitors in cynomolgus monkeys

BACKGROUND AND PURPOSE

Soluble epoxide hydrolase inhibitors (sEHIs) possess anti-inflammatory, antiatherosclerotic, antihypertensive and analgesic properties. The pharmacokinetics (PK) and pharmacodynamics in terms of inhibitory potency of sEHIs were assessed in non-human primates (NHPs). Development of a sEHI for use in NHPs will facilitate investigations on the role of sEH in numerous chronic inflammatory conditions.

EXPERIMENTAL APPROACH

PK parameters of 11 sEHIs in cynomolgus monkeys were determined after oral dosing with 0.3 mg·kg(-1). Their physical properties and inhibitory potency in hepatic cytosol of cynomolgus monkeys were examined. Dose-dependent effects of the two inhibitors 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) and the related acetyl piperidine derivative, 1-trifluoromethoxyphenyl-3-(1-acetylpiperidin-4-yl) urea (TPAU), on natural blood eicosanoids, were determined.

KEY RESULTS

Among the inhibitors tested, TPPU and two 4-(cyclohexyloxy) benzoic acid urea sEHIs displayed high plasma concentrations (>10 × IC(50)), when dosed orally at 0.3 mg·kg(-1). Although the 4-(cyclohexyloxy) benzoic acid ureas were more potent against monkey sEH than piperidyl ureas (TPAU and TPPU), the latter compounds showed higher plasma concentrations and more drug-like properties. The C(max) increased with dose from 0.3 to 3 mg·kg(-1) for TPPU and from 0.1 to 3 mg·kg(-1) for TPAU, although it was not linear over this range of doses. As an indication of target engagement, ratios of linoleate epoxides to diols increased with TPPU administration.

CONCLUSION AND IMPLICATIONS

Our data indicate that TPPU is suitable for investigating sEH biology and the role of epoxide-containing lipids in modulating inflammatory diseases in NHPs.

Delayed treatment with human umbilical cord blood-derived stem cells attenuates diabetic renal injury

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide. Excess accumulation of extracellular matrix and the epithelial-to-mesenchymal transition contribute to renal fibrosis, which is associated with DKD. The present study examined whether delayed treatment with human umbilical cord blood-derived stem cells (hUCB-SC) showed a therapeutic effect on DKD progression. Experimental diabetes was induced by intraperitoneal injection of streptozotocin (STZ; 50 mg/kg) into 6-week-old male Sprague-Dawley rats. Age-matched control rats received an equivalent volume of sodium citrate buffer alone. At 4 weeks after the STZ injection when diabetic renal injury had developed, hUCB-SC were administered (1 × 10(6) cells/rat) through the tail vein. Four weeks after administering the hUCB-SC, rats were sacrificed and we measured indices of DKD, including urinary protein excretion as well as fibronectin, α-smooth muscle actin (α-SMA), and E-cadherin mRNA, and protein expression. Diabetic rats developed significantly increased urinary protein excretion and renal hypertrophy compared to those in control rats. Renal expression of fibronectin and α-SMA mRNA, and protein were increased significantly in diabetic rats compared to those in the controls. E-cadherin protein expression in diabetic kidneys decreased significantly. Intravenously administered hUCB-SC effectively reduced proteinuria, renal fibronectin, and α-SMA up-regulation, as well as renal E-cadherin down-regulation in diabetic rats without a significant effect on blood glucose. Engrafted hUCB-SC in diabetic kidneys were confirmed by human DNA PKcs. The results demonstrated that delayed treatment with hUCB-SC attenuated the progression of diabetic renal injury.

Ischemic stroke among the patients with end-stage renal disease who were undergoing maintenance dialysis

PURPOSE

In spite of higher incidence of stroke in end-stage renal disease (ESRD) patients compared to general population, the risk factor for stroke which is specific to ESRD is not fully understood. The ESRD patients who develop stroke may have certain additional risk factors compared to ESRD patients without stroke. We used registered data of Hallym Stroke Registry to elucidate the factors which affect development of ischemic stroke among the dialysis patients.

MATERIALS AND METHODS

We recruited patients with acute ischemic stroke in ESRD patients undergoing maintenance dialysis. Dialysis patients without stroke were selected as control group with age and gender matching. We compared the demographic features, stroke risk factors, and laboratory findings in ESRD patients with or without ischemic stroke.

RESULTS

The total of 25 patients with ESRD developed ischemic stroke. Fifty ESRD patients without stroke were chosen as the control group. The mean age of acute ischemic stroke patients was 59.80±9.94 and male gender was 48%. The most common ischemic stroke subtype was small vessel occlusion (n=12), followed by large artery atherosclerosis (n=7). The patients with stroke had more frequent history of hypertension and higher systolic/diastolic blood pressure at the time of admission than the ESRD patients without stroke. Total cholesterol and LDL-cholesterol levels were significantly lower in the stroke group. In multivariate analysis, LDL-cholesterol was found to be the only risk factor for ischemic stroke.

CONCLUSION

The results of our study reveal that LDL-cholesterol is associated with greater risk for ischemic stroke in the patients on dialysis.

Inhibitory effects of dextrorotatory morphinans on the human 5-HT(3A) receptor expressed in Xenopus oocytes: Involvement of the N-terminal domain of the 5-HT(3A) receptor

We previously developed a series of dextromethorphan (DM, 3-methoxy-17-methylmorphinan) analogs modified at positions 3 and 17 of the morphinan ring system. Recent reports have shown that DM attenuates abdominal pain caused by irritable bowel syndrome, and multidrug regimens that include DM prevent nausea/vomiting following cancer surgery. However, little is known regarding the molecular mechanisms underlying the beneficial effects of DM. Here, we investigated the effects of DM, 3 of its analogs (AM, 3-allyloxy-17-methoxymorphian; CM, 3-cyclopropyl-17-methoxymorphinan; and DF, 3-methyl-17-methylmorphinan), and 1 of its metabolites (HM, 3-methoxymorphinan) on the activity of the human 5-HT(3A) receptor channel expressed in Xenopus laevis oocytes, using the 2-microelectrode voltage clamp technique. We found that intra-oocyte injection of human 5-HT(3A) receptor cRNAs elicited an inward current (I(5-HT)) in the presence of 5-HT. Cotreatment with AM, CM, DF, DM, or HM inhibited I(5-HT) in a dose-dependent, voltage-independent, and reversible manner. The IC(50) values for AM, CM, DF, DM, and HM were 24.5±1.4, 21.5±4.2, 132.6±35.8, 181.3±23.5, and 191.3±31.5μM, respectively. The IC(50) values of AM and CM were 7-fold lower than that of DM, and mechanistic analysis revealed that DM, DF, HM, AM, and CM were competitive inhibitors of I(5-HT). Point mutations of Arg241 in the N-terminal, but not amino acids in the pore region, to other amino acid residues attenuated or abolished DM- and DM-analog-induced inhibition of I(5-HT). Together, these results demonstrated that dextrorotatory morphinans might regulate 5-HT(3A) receptor channel activity via interaction with its N-terminal domain.

Effects of protopanaxatriol-ginsenoside metabolites on rat N-methyl-d-aspartic Acid receptor-mediated ion currents

Ginsenosides are low molecular weight glycosides found in ginseng that exhibit neuroprotective effects through inhibition of N-methyl-D-aspartic acid (NMDA) receptor channel activity. Ginsenosides, like other natural compounds, are metabolized by gastric juices and intestinal microorganisms to produce ginsenoside metabolites. However, little is known about how ginsenoside metabolites regulate NMDA receptor channel activity. In the present study, we investigated the effects of ginsenoside metabolites, such as compound K (CK), protopanaxadiol (PPD), and protopanaxatriol (PPT), on oocytes that heterologously express the rat NMDA receptor. NMDA receptor-mediated ion current (I_NMDA) was measured using the 2-electrode voltage clamp technique. In oocytes injected with cRNAs encoding NMDA receptor subunits, PPT, but not CK or PPD, reversibly inhibited I_NMDA in a concentration-dependent manner. The IC₅₀ for PPT on I_NMDA was 48.1±4.6 µM, was non-competitive with NMDA, and was independent of the membrane holding potential. These results demonstrate the possibility that PPT interacts with the NMDA receptor, although not at the NMDA binding site, and that the inhibitory effects of PPT on I_NMDA could be related to ginseng-mediated neuroprotection.

Spin-density matrix elements for γp→K*0Σ+ at Eγ=1.85-3.0 GeV with evidence for the κ(800) meson exchange

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.

Morphological changes of the lateral meniscus in end-stage lateral compartment osteoarthritis of the knee

OBJECTIVE

The aim of this study was to evaluate the morphological changes of the lateral meniscus in end-stage lateral compartment osteoarthritis (OA) of the knee.

METHODS

One hundred fifty-eight knee joints from 133 patients that subsequently underwent total knee joint arthroplasty from January 2008 to December 2009 were enrolled. There were 26 men and 107 women. Their ages ranged from 56 to 81 (mean 67.4 ± 6.5 years). All study participants had complete obliteration of the lateral joint space identified by weight-bearing radiography. Meniscal position was assessed by measuring meniscal subluxation and meniscal height. The meniscal morphology was assessed using a modification of the whole-organ magnetic resonance imaging score (WORMS). The frequency of different meniscal morphology and their respective positions was calculated.

RESULTS

The predominant type (42.4%, 53.8% and 52.5% in the anterior horn, mid-body and posterior horn, respectively) of abnormal meniscal morphology was a complete maceration/destruction or complete resection. The anterior horn of non-macerated lateral meniscus was more subluxed than that of the non-macerated medial meniscus in patients with lateral OA.

CONCLUSION

This study suggests that the lateral meniscus in persons with end-stage lateral OA are mostly macerated or destroyed. Also, unlike isolated end-staged medial compartment OA, the anterior horn of the lateral meniscus in isolated end-stage lateral OA is commonly affected.

Profiling of differentially expressed genes in haemophilia A with inhibitor

Inhibitor development is the most significant complication in the therapy of haemophilia A (HA) patients. In spite of many studies, not much is known regarding the mechanism underlying inhibitor development. To understand the mechanism, we analysed profiles of differentially expressed genes (DEGs) between inhibitor and non-inhibitor HA via a microarray technique. Twenty unrelated Korean HAs were studied: 11 were non-inhibitor and nine were HA with inhibitor (≥5 BU mL(-1)). Microarray analysis was conducted using a Human Ref-8 expression Beadchip system (Illumina) and the data were analysed using Beadstudio software. We identified 545 DEGs in inhibitor HA as compared with the non-inhibitor patients; 384 genes were up-regulated and 161 genes were down-regulated. Among them, 75 genes whose expressions were altered by at least two-fold (>+2 or <-2) were selected and classified via the PANTHER classification method. The expressions of signal transduction and immunity-related genes differed significantly in the two groups. For validation of the DEGs, semi-quantitative RT-PCR (semi-qRT-PCR) was conducted with the six selected DEGs. The results corresponded to the microarray data, with the exception of one gene. We also examined the expression of the genes associated with the antigen presentation process via real-time PCR. The average levels of IL10, CTLA4 and TNFα slightly reduced, whereas that of IFNγ increased in the inhibitor HA group. We are currently unable to explain whether this phenomenon is a function of the inhibitor-inducing factor or is an epiphenomenon of antibody production. Nevertheless, our results provide a possible explanation for inhibitor development.

Resveratrol enhances 5-hydroxytryptamine type 3A receptor-mediated ion currents: the role of arginine 222 residue in pre-transmembrane domain I

Resveratrol, which is found in grapes, red wine, and berries, has many beneficial health effects, such as anti-cancer, neuro-protective, anti-inflammatory, and life-prolonging effects. However, the cellular mechanisms by which resveratrol acts are relatively unknown, especially in terms of possible regulation of receptors involved in synaptic transmission. 5-Hydroxytryptamine type 3A (5-HT(3A)) receptor is one of several ligand-gated ion channels involved in fast synaptic transmission. In the present study, we investigated the effect of resveratrol on mouse 5-HT(3A) receptor channel activity. 5-HT(3A) receptor was expressed in Xenopus oocytes, and the current was measured using a two-electrode voltage clamp technique. Treatment of resveratrol itself had no effect on the oocytes injected with H(2)O as well as on the oocytes injected with 5-HT(3A) receptor cRNA. In the oocytes injected with 5-HT(3A) receptor cRNA, co- or pre-treatment of resveratrol with 5-HT potentiated 5-HT-induced inward peak current (I(5-HT)) with concentration-, reversible, and voltage-independent manners. The EC(50) of resveratrol was 28.0±2.4 µM. The presence of resveratrol caused a leftward shift of 5-HT concentration-response curve. Protein kinase C (PKC) activator or inhibitor had no effect on resveratrol action on I(5-HT). Site-directed mutations of pre-transmembrane domain 1 (pre-TM1) such as R222A, R222D, R222E, R222K, and R222T abolished or attenuated resveratrol-induced enhancement of I(5-HT), indicating that resveratrol might interact with pre-TM1 of 5-HT(3A) receptor. These results indicate that resveratrol might regulate 5-HT(3A) receptor channel activity via interaction with the N-terminal domain and these results further show that resveratrol-mediated regulation of 5-HT(3A) receptor channel activity might be one of cellular mechanisms of resveratrol action.

Functional expression and characterization in Xenopus laevis oocytes of the ABCG2 transporter derived from A549 human lung adenocarcinoma cells

We cloned the ATP-binding cassette sub-family G member 2 (ABCG2) transporter, the most recently identified among several major human multidrug-resistance pumps, from A549 human lung adenocarcinoma cells in order to characterize its function and substrate specificity. In a previous report, we confirmed that a stem cell-like side population of A549 cells highly expressed the ABCG2 gene and had a unique ability to resist the anticancer drug methotrexate (MTX). In this study, ABCG2 cDNA was cloned by RT-PCR and converted into cRNA by an in vitro transcription system for expression in Xenopus laevis (X. laevis) oocytes. The transcribed cRNA of the ABCG2 gene was injected into the oocytes under the absence of cofactors or heterologous partner proteins or some lipids from the media. A high expression of ABCG2 was observed on the oocyte surface by immunofluorescence and confocal laser microscopy. We tested the functional effect of ABCG2 expression on drug efflux by directly injecting MTX into X. laevis oocytes. The drug concentration within the oocytes was quantified with LC-MS/MS; the analysis showed that the accumulation of MTX was significantly decreased in the X. laevis oocytes expressing ABCG2 compared with the control oocytes not expressing ABCG2. These findings show that the ABCG2 protein has an important role in the efflux of MTX through the cell membrane of X. laevis oocytes. Therefore, it might be that ABCG2, abundantly expressed in the stem cell population of A549 cells, can modulate resistance to MTX in lung cancer therapy.

Inhibitory Effects of Quercetin on Muscle-type of Nicotinic Acetylcholine Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

The flavonoid quercetin is a low molecular weight compound generally found in apple, gingko, tomato, onion and other red-colored fruits and vegetables. Like other flavonoids, quercetin has diverse pharmacological actions. However, relatively little is known about the influence of quercetin effects in the regulation of ligand-gated ion channels. Previously, we reported that quercetin regulates subsets of nicotinic acetylcholine receptors such as α3β4, α7 and α9α10. Presently, we investigated the effects of quercetin on muscle-type of nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding human fetal or adult muscle-type of nicotinic acetylcholine receptor subunits. Acetylcholine treatment elicited an inward peak current (I(ACh)) in oocytes expressing both muscle-type of nicotinic acetylcholine receptors and co-treatment of quercetin with acetylcholine inhibited I(ACh). Pre-treatment of quercetin further inhibited I(ACh) in oocytes expressing adult and fetal muscle-type nicotinic acetylcholine receptors. The inhibition of I(ACh) by quercetin was reversible and concentration-dependent. The IC(50) of quercetin was 18.9±1.2 µM in oocytes expressing adult muscle-type nicotinic acetylcholine receptor. The inhibition of I(ACh) by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate human muscle-type nicotinic acetylcholine receptor channel activity and that quercetin-mediated regulation of muscle-type nicotinic acetylcholine receptor might be coupled to regulation of neuromuscular junction activity.