Identification of cis-acting promoter sequences required for expression of the glycerol-3-phosphate acyltransferase 1 gene in mice

Glycerol-3-phosphate acyltransferase 1 (GPAT1) is a rate limiting enzyme in de novo glycerophospholipid synthesis. The murine GPAT1 promoter sequence (the "classical" sequence) was reported previously. However, the organization of this DNA sequence does not fully match the mouse genome sequences on NCBI/GenBank. Here we have identified net cis-acting promoter sequences for the mouse GPAT1 gene: promoter 1a which includes part of the classical sequence and the downstream promoter 1b. Promoter 1a facilitates transcription of two alternative GPAT1 transcript variants, GPAT1-V1 and V2, while promoter 1b produces a third transcript variant, GPAT1-V3. Upstream stimulating factor-1 (USF-1) controlled both promoters whereas sterol regulatory element-binding protein-1 (SREBP-1) exclusively regulated promoter 1a activity in vitro. Feeding increased GPAT1-V1 and V2, but not V3 mRNA levels in mouse liver. The obese condition of db/db mice did not alter the hepatic expression levels of any of the three GPAT1 variants. Feeding enhanced hepatic mRNA levels, intranuclear protein levels and promoter 1a-binding levels of SREBP-1, but not of USF-1. Thus, promoter 1a was exclusively activated by routine feeding in vivo. Our results indicate differential roles of the two promoters in the regulation of hepatic GPAT1 gene expression in mice.

NO-1886, a lipoprotein lipase activator, attenuates contraction of rat intestinal ring preparations

Various intestinal symptoms or diseases are closely associated with intestinal motility, which may be altered by metabolic disturbances associated with diabetes and obesity. It is therefore important that drugs used in the treatment of metabolic disorders should not have any adverse effects on the intestine. In the present study, we examined whether [4-(4-bromo-2-cyano-phenylcarbamoyl)-benzyl]-phosphonic acid diethyl ester (NO-1886), a lipoprotein lipase activator with anti-diabetic and/or anti-obese activity, affects stimulant-induced intestinal contractility. Administration of NO-1886 to intestinal ring preparations of ileum, rectum and colon isolated from Wistar rats attenuated or relaxed contraction induced by a high K+ environment or acetylcholine (ACh). This effect of NO-1886 was dependent on extracellular Ca(2+) and intracellular myosin light chain kinase activity. Our results also showed that ACh-induced colonic contraction was significantly higher in the obese Otsuka Long-Evans Tokushima Fatty (OLETF) than in the non-obese Long-Evans Tokushima Otsuka (LETO) rats. The hypercontractility observed in the colons of OLETF rats occurred concomitantly with an elevation in muscarinic M3 ACh receptor protein levels. Administration of NO-1886 attenuated the obesity-induced hypercontractility of the colonic rings of OLETF rats. Thus, intestinal contractile system would be a novel pharmacological target of the lipoprotein lipase activator NO-1886.

The effects of losartan on signal-averaged P wave in patients with atrial fibrillation

BACKGROUND

Losartan has recently been reported to suppress atrial structural remodeling. However, few reports exist on signal-averaged electrocardiography (ECG) for preventing atrial electrical remodeling. We examined the effect of losartan on atrial electricity by using signal-averaged ECG of P waves.

METHODS

The subjects comprised 40 patients with essential hypertension complicated with symptomatic paroxysmal atrial fibrillation. The patients received pilsicainide for the complication; they were defibrillated and divided into two subgroups for antihypertensive therapy: calcium antagonist-administrated (CB) and losartan-administrated (LOS) groups. We recorded the signal-averaged electrocardiography of P waves and calculated (1) filtered P wave duration (PD), (2) the voltage integral for the entire P wave (integral-p), and (3) the root mean square voltages of the terminal 40, 30, and 20 ms (RMS-40, RMS-30, and RMS-20). Procollagen C propeptide type I (PIP) and A- and B-type natriuretic peptide (ANP and BNP, respectively) levels in the groups were measured before and after antihypertensive agent administration.

RESULTS

RMS-20 increased significantly and PD decreased significantly in the LOS group 24 weeks after antihypertensive drug administration; however, they remained unchanged in the CB group. Integral-p decreased significantly in both groups, and the decrease rate was significantly higher in the LOS group. Serum BNP levels decreased significantly only in the LOS group.

CONCLUSIONS

Losartan inhibits atrial remodeling by inhibiting left atrial fibrosis as indicated by the procollagen C propeptide type I, ANP, and BNP levels. Signal-averaged ECG demonstrated that losartan suppresses atrial fibrillation recurrence by improving atrial conduction disturbance.

Hyperglycemia impairs isoflurane-induced adenosine triphosphate-sensitive potassium channel activation in vascular smooth muscle cells

BACKGROUND

Isoflurane activates vascular adenosine triphosphate sensitive potassium (K(ATP)) channels, and may induce vasodilation. In the present study, we investigated whether hyperglycemia modifies isoflurane activation of vascular K(ATP) channel.

METHODS

We used a cell-attached patch-clamp configuration to test the effects of isoflurane on K(ATP) channel activity in vascular smooth muscle cells (VSMCs) after incubation for 24 h in medium containing normal glucose (NG, 5.5 mM D-glucose), L-glucose (LG, 5.5 mM D-glucose plus 17.5 mM L-glucose), or high glucose (HG, 23 mM D-glucose). Superoxide levels in aortas were measured by the lucigenin-enhanced chemiluminescence technique.

RESULTS

Isoflurane-induced open probabilities were significantly reduced in VSMCs from arteries incubated in HG (0.06 +/- 0.01) compared with NG (0.17 +/- 0.02; P < 0.05) and LG (0.15 +/- 0.02; P < 0.05). Pretreatment of VSMCs with protein kinase C (PKC) inhibitors, calphostin C and PKC inhibitor 20-28, greatly reduced HG inhibition of isoflurane-induced K(ATP) channel activity. In addition, a PKC activator, PMA, mimicked the effects of HG. Superoxide release was significantly increased in arteries incubated in HG (18.3 +/- 11.5 relative light units (RLU) x s(-1) x mg(-1); P < 0.05 versus NG). Coincubated with polyethylene glycol-superoxide dismutase (250 U/mL), a cell-permeable superoxide scavenger, greatly reduced the HG-induced increase of superoxide, but failed to reduce HG inhibition of isoflurane-induced K(ATP) channel activity.

CONCLUSIONS

Our results suggest that the metabolic stress of hyperglycemia can impair isoflurane-induced vascular K(ATP) channel activity mediated by excessive activation of PKC. This could impede the coronary vasodilation response to isoflurane, causing ischemia or hypoxia in patients with perioperative hyperglycemia.

Reactive oxygen species induced by diamide inhibit insulin-induced ATP-sensitive potassium channel activation in cultured vascular smooth muscle cells

Both insulin resistance and reactive oxygen species (ROS) have been reported to play essential pathophysiological roles in cardiovascular diseases. However, the mechanistic link between ROS and insulin resistance in the vasculature remains unclear. Recently we have shown that insulin causes KATP channel activation mediated by PI3K in cultured vascular smooth muscle cells (VSMCs). KATP channel in VSMCs is critical in the regulation of vascular tonus. Here we examined the effects of ROS induced by a thol-oxidizing agent, diamide, on the insulin signalling pathway and KATP channel activities in cultured VSMCs (A10 cells). Diamide (100 microM) increased intercellular ROS and extracellular signal-regulated kinases (ERK) activity. Treatment with 100 M diamide suppressed significantly insulin-induced IRS and Akt phosphorylation. In addition to IRS and Akt, diamide inhibited insulin receptor auto-phosphorylation. Patch-clamp study showed that diamide suppressed insulin-induced but did not pinacidil-induced KATP channel activities in A10 cells. From these data, we conclude that ROS inhibit critical insulin signal transduction components including IRS and Akt, and these effects cause down-regulation of insulin's action in the vasculature including KATP channel activation. This study may contribute to our understanding of mechanisms of insulin resistance-associated cardiovascular disease.

Micronutrient deficiencies and anemia among preschool children in rural Vietnam

The prevalence of trace elements deficiencies, vitamin A deficiency, anemia, and their relationships were investigated in a cross sectional study involving 243 children aged from 12 to 72 months in rural Vietnam. Serum levels of copper, zinc, selenium and magnesium were determined by inductively coupled plasma mass spectrometer and that of retinol by high performance liquid chromatography. Hemoglobin concentration in whole blood was measured by the cyanmethemoglobin method. The prevalence of deficiencies in zinc, selenium, magnesium, and copper was 86.9%, 62.3%, 51.9%, and 1.7%, respectively. On the other hand, 55.6% were anemic and 11.3% had vitamin A deficiency. Deficiency in two or more micronutrient was found in 79.4% of the children. Parameters associated significantly with anemia were selenium deficiency (OR 2.80 95% CI 1.63-4.80, p=0.0002) and serum retinol<1.05 micromol/L (OR 1.83, 95% CI 1.10-3.05, p=0.021). Magnesium deficiency (OR 3.09 95% CI 1.36-7.03) was found to be a risk factor for zinc deficiency and vice versa. The results indicate that micronutrient deficiencies are prevalent among preschool children in Vietnam. In addition, the results also demonstrate a strong relationship between selenium deficiency and anemia. Clearly, sustainable strategies are urgently required to overcome the problems in the country.

The effects of extracellular pH on vasopressin inhibition of ATP-sensitive K+ channels in vascular smooth muscle cells

BACKGROUND

Arginine vasopressin (AVP) inhibits ATP-sensitive potassium (K(ATP)) channels and may help to restore vascular tone in patients with vasodilatory shock. In the present study, we investigated whether extracellular acidification modifies the inhibition of vascular K(ATP) channels by AVP.

METHODS

We used a cell-attached patch-clamp configuration to investigate the effects of extracellular pH (pH(o)) on AVP-K(ATP) channel interaction in rat aortic smooth muscle cells.

RESULTS

Bath application of AVP significantly inhibited extracellular acidification (pH(o) = 6.5)-induced K(ATP) channel activity in a concentration-dependent manner, with an half-maximal inhibitory concentration (IC50) value of 16.8 pM. Furthermore, bath application of AVP significantly inhibited pinacidil-induced K(ATP) channel activity at mild (pH(o) = 7.0) and severe (pH(o) = 6.5) extracellular acidification, with IC50 values of 266.7 and 21.4 pM, respectively, but failed to significantly inhibit at normal pH (pH(o) = 7.4) or under alkalosis (pH(o) = 9.0). Augmentation of AVP inhibition of vascular K(ATP) channels during extracellular acidification was eliminated by pretreatment with OPC-21268, a specific blocker of the V1 receptor, but not by a V2 blocker, OPC-31260. AVP-induced inhibition was also suppressed by pretreatment with a protein kinase C inhibitor, calphostin C.

CONCLUSIONS

Our results suggest that AVP inhibits extracellular acidification-induced vascular K(ATP) channel activity, and that the inhibitory effects of AVP on vascular K(ATP) channels are enhanced by extracellular acidification via the V1 receptor-protein kinase C cell-signaling pathway. The potent inhibition of vascular K(ATP) channels by AVP under acidic conditions may make it suitable for management of vasodilatory shock.

Insulin activates ATP-sensitive potassium channels via phosphatidylinositol 3-kinase in cultured vascular smooth muscle cells

The effects of insulin on the vasculature are significant because insulin resistance is associated with hypertension. To increase the understanding of the effects of insulin on the vasculature, we analyzed changes in potassium ion transport in cultured vascular smooth muscle cells (VSMCs). Using the potential-sensitive fluorescence dye bis-(1,3-dibutylbarbituric acid)trimethine oxonol [DiBAC4(3)], we found that insulin induced membrane hyperpolarization after 2 min in A10 cells. Insulin-induced hyperpolarization was suppressed by glibenclamide, an ATP-sensitive potassium (K(ATP)) channel blocker. Using a cell-attached patch clamp experiment, the K(ATP) channel was activated by insulin in both A10 cells and isolated VSMCs from rat aortas, indicating that insulin causes membrane hyperpolarization via K(ATP) channel activation. These effects were not dependent on intracellular ATP concentration, but wortmannin, a phosphatidylinositol 3-kinase (PI3-K) inhibitor, significantly suppressed insulin-induced K(ATP) channel activation. In addition, insulin enhanced phosphorylation of insulin receptor, insulin receptor substrate (IRS)-1 and protein kinase B (Akt) after 2 min. These data suggest that K(ATP) channel activation by insulin is mediated by PI3-K. Furthermore, using a nitric oxide synthase (NOS) inhibitor, we found that NOS might play an important role downstream of PI3-K in insulin-induced K(ATP) channel activation. This study may contribute to our understanding of mechanisms of insulin resistance-associated hypertension.

Vibrio parahaemolyticus elevates interferon alpha production in intestinal-like epithelial Caco-2 cells

Vibrio parahaemolyticus is the leading cause of gastroenteritis from seafood consumption. We tried to determine how the gene expression levels of intestinal-like epithelial cells (Caco-2 cells) and mouse intestinal loop mucosal cells change upon infection with this bacterium. Since we found the robust production of interferon alpha (IFN-alpha) by the V. parahaemolyticus infection, we also assessed the upregulation of a number of IFN-stimulated genes (ISGs). The expressions of IFN protein were determined by Western blotting, and the gene expressions of Caco-2 cells after V. parahaemolyticus infection were determined by quantitative real-time reverse-transcription polymerase chain reaction. Three ISGs (i.e., IFN-alpha-inducible protein 15, IFN-alpha-inducible protein 6-16, and IFN-induced protein with tetratricopeptide repeats 1) were upregulated by V. parahaemolyticus infection. Infection induced the production of IFN-alpha, but not IFN-beta or IFN-gamma. The upregulation of the 3 ISGs was suppressed by treatment with a neutralizing IFN-alpha antibody. Moreover, the production of infection-induced IFN-alpha was found in the mouse intestinal loop mucosal cells. V. parahaemolyticus infection of Caco-2 cells results in IFN-alpha production and the expression of IFN-regulated genes.

The nucleoside and nucleotide mixture (OG-VI) rescues intestinal-like epithelial cells from the cytotoxicity of chemotherapeutic agents

Immune cells and cells undergoing rapid turn-over can obtain exogenous nucleotides via salvage synthesis. We evaluated whether or not the balanced nucleoside and nucleotide mixture OG-VI, could rescue intestinal epithelial-like Caco-2 cells from the cytotoxic effects of several chemotherapeutic agents, in the presence and absence of glutamine (Gln). Cells were exposed to 5-fluorouracil (5FU), methotrexate (MTX) or 6-mercaptopurine (6MP), after which proliferation and cell cycle analyses were performed. Following exposure to the chemotherapeutic agents, we observed that cells treated with OG-VI proliferated well, whereas those without the supplement did not proliferate. Furthermore, following treatment with either 5FU or MTX, we observed that the number of cells in the G0/G1 phase decreased and those in the S phases increased. However, these cell cycle alterations were prevented by the addition of OG-VI. With the exception of 6MP-treated cells, we did not observe any effects on proliferation or cell cycle regulation that could be ascribed to the presence of Gln. Thus, we have demonstrated that OG-VI rescues cells from the cytotoxic effects of several chemotherapeutic agents.

The phytoestrogen ginsensoside Re activates potassium channels of vascular smooth muscle cells through PI3K/Akt and nitric oxide pathways

In vascular smooth muscle cells, large-conductance Ca(2+)-activated K(+) channels (K(Ca) channels) play a pivotal role in determining membrane potential, and thereby the vascular tone. Ginsenoside Re, a phytochemical from ginseng, is reported to activate this channel, but its precise mechanism is unsolved. Patch clamp studies showed that ginsenoside Re activates K(Ca) channels in the arterial smooth muscle cell line A10 in a dose-dependent manner. The channel-opening effect of ginsenoside Re was inhibited by 1 microM L-NIO, an inhibitor of eNOS, but not by 3 microM SMTC, an inhibitor of nNOS, indicating that ginsenoside Re activated K(Ca) channels through activation of eNOS. SH-6 (10 microM), an Akt inhibitor, and wortmannin, a PI3-kinase inhibitor, completely blocked activation of K(Ca) channels by ginsenoside Re, indicating that it activates eNOS via a c-Src/PI3-kinase/Akt-dependent mechanism. In addition, the ginsenoside Re-induced activation of eNOS and K(Ca) channel was blocked by 10 microM ICI 182, 780, an inhibitor of membrane estrogen receptor-alpha, suggesting that eNOS activation occurs via a non-genomic pathway of this receptor. In conclusion, ginsenoside Re releases NO via a membrane sex steroid receptors, resulting in K(Ca) channel activation in vascular smooth muscle cells, promoting vasodilation and preventing severe arterial contraction.

Development of a new water sterilization device with a 365 nm UV-LED

Ultraviolet (UV) irradiation is an effective disinfection method. In sterilization equipment, a low-pressure mercury lamp emitting an effective germicidal UVC (254 nm) is used as the light source. However, the lamp, which contains mercury, must be disposed of at the end of its lifetime or following damage due to physical shock or vibration. We investigated the suitability of an ultraviolet light-emitting diode at an output wavelength of 365 nm (UVA-LED) as a sterilization device, comparing with the other wavelength irradiation such as 254 nm (a low-pressure mercury lam) and 405 nm (LED). We used a commercially available UVA-LED that emitted light at the shortest wavelength and at the highest output energy. The new sterilization system using the UVA-LED was able to inactivate bacteria, such as Escherichia coli DH5 alpha, Enteropathogenic E. coli, Vibrio parahaemolyticus, Staphylococcus aureus, and Salmonella enterica serovar Enteritidis. The inactivations of the bacteria were dependent on the accumulation of UVA irradiation. Taking advantage of the safety and compact size of LED devices, we expect that the UVA-LED sterilization device can be developed as a new type of water sterilization device.

Deficiency of Cbl-b gene enhances infiltration and activation of macrophages in adipose tissue and causes peripheral insulin resistance in mice

OBJECTIVE

c-Cbl plays an important role in whole-body fuel homeostasis by regulating insulin action. In the present study, we examined the role of Cbl-b, another member of the Cbl family, in insulin action.

RESEARCH DESIGN AND METHODS

C57BL/6 (Cbl-b(+/+)) or Cbl-b-deficient (Cbl-b(-/-)) mice were subjected to insulin and glucose tolerance tests and a hyperinsulinemic-euglycemic clamp test. Infiltration of macrophages into white adipose tissue (WAT) was assessed by immunohistochemistry and flow cytometry. We examined macrophage activation using co-cultures of 3T3-L1 adipocytes and peritoneal macrophages.

RESULTS

Elderly Cbl-b(-/-) mice developed glucose intolerance and peripheral insulin resistance; serum insulin concentrations after a glucose challenge were always higher in elderly Cbl-b(-/-) mice than age-matched Cbl-b(+/+) mice. Deficiency of the Cbl-b gene significantly decreased the uptake of 2-deoxyglucose into WAT and glucose infusion rate, whereas fatty liver was apparent in elderly Cbl-b(-/-) mice. Cbl-b deficiency was associated with infiltration of macrophages into the WAT and expression of cytokines, such as tumor necrosis factor-alpha, interleukin-6, and monocyte chemoattractant protein (MCP)-1. Co-culture of Cbl-b(-/-) macrophages with 3T3-L1 adipocytes induced leptin expression and dephosphorylation of insulin receptor substrate 1, leading to impaired glucose uptake in adipocytes. Furthermore, Vav1, a key factor in macrophage activation, was highly phosphorylated in peritoneal Cbl-b(-/-) macrophages compared with Cbl-b(+/+) macrophages. Treatment with a neutralizing anti-MCP-1 antibody improved peripheral insulin resistance and macrophage infiltration into WAT in elderly Cbl-b(-/-) mice.

CONCLUSIONS

Cbl-b is a negative regulator of macrophage infiltration and activation, and macrophage activation by Cbl-b deficiency contributes to the peripheral insulin resistance and glucose intolerance via cytokines secreted from macrophages.

Physical exercise-associated gene expression signatures in peripheral blood

OBJECTIVE

To assess response to physical stress, gene expression profiles in peripheral blood cells were analyzed using an original microarray carrying 1467 stress-responsive complementary DNA probes.

DESIGN

Gene expression was analyzed at 4, 24, and 48 hours after exercising on a cycle ergometer at 60% VO2 max for 1 hour (aerobic exercise) or until exhausted (exhaustive exercise).

SETTING

Institute of Health Biosciences, University of Tokushima Graduate School.

PARTICIPANTS

Twelve healthy male students of the postgraduate or undergraduate school.

INTERVENTIONS

The volunteers performed the aerobic or exhaustive exercise on a cycle ergometer.

MAIN OUTCOME MEASUREMENTS

Detection of aerobic exercise-responsive or exhaustive exercise-responsive genes in peripheral blood cells.

RESULTS

Aerobic and exhaustive exercise transiently changed the expression of 21 and 16 genes, respectively, with the peak at 4 hours. Only 2 genes significantly responded to both types of exercise. Exhaustive but not aerobic exercise produced a secondary response with significantly altered expression of 14 genes at 24 hours. Five of those genes encode receptors for neurotransmitters (HTR1A, CHRNB2, GABRB3, GABRG3, and LOC51289).

CONCLUSIONS

The behavior of the individual genes shown here may be informative to objectively assess acute physical stress and exhaustion-associated responses.

Angiotensin II Decreases Glucose Uptake by Downregulation of GLUT1 in the Cell Membrane of the Vascular Smooth Muscle Cell Line A10

Recent evidence suggests a crosstalk between angiotensin II (Ang II) and insulin. However, whether this crosstalk affects glucose uptake, particularly in terms of actin filament involvement, has not yet been studied in vascular smooth muscle cells. Pretreatment of cells with either Ang II or cytochalasin D disarranged actin filaments in a time-dependent manner and inhibited glucose uptake. However, insulin increased actin reorganization and glucose uptake. Membrane fractionation studies showed that Ang II decreased GLUT-1 at the cell membrane, whereas it increased GLUT-1 in the cytoplasm, indicating that Ang II may cause internalization of GLUT-1 via actin disorganization, consequently decreasing glucose uptake. The effects of Ang II on glucose uptake and actin reorganization were blocked by AT1 receptor antagonist, but not by AT2 antagonist. Either P38 or ERK1/2 inhibitors partially reversed the Ang II-inhibited actin reorganization and glucose uptake, suggesting that MAPK signaling pathways could be involved as downstream events in Ang II signaling, and this signaling may interfere with insulin-induced actin reorganization and glucose uptake. These data imply that Ang II induces insulin resistance by decreasing glucose uptake via disarrangement of actin filaments, which provides a novel insight into understanding of insulin resistance by Ang II at the molecular level.

Transforming growth factor beta stimulates rheumatoid synovial fibroblasts via the type II receptor

Transforming growth factor (TGF)-beta regulates the function of fibroblasts, and has been shown to have a role in the pathogenesis of rheumatoid arthritis (RA) because several studies have demonstrated the presence of TGF-beta in the synovial tissue and synovial fluids of RA patients. In this study, we examined the expression of TGF-beta receptors in synovial fibroblasts of patients with RA and demonstrated the significance in functional responses of synovial fibroblasts to TGF-beta in this disorder. Transforming growth factor beta1 stimulated the expression of connective tissue growth factor (CTGF) in fibroblasts of patients with RA more than in those of patients with osteoarthritis (OA). Transforming growth factor beta1 induced the chemotactic migration of RA synovial fibroblasts and inhibited their proliferation significantly more than OA synovial fibroblasts. Both RA and OA synovial fibroblasts expressed detectable amounts of TGF-beta receptor type II mRNA, but the expression was higher in RA patients than in OA patients, as assessed by reverse transcriptase-polymerase chain reaction. There was no significant difference in the expression of TGF-beta receptor type I or type III in synovial fibroblasts between RA and OA patients. These results indicate that synovial fibroblasts of RA patients express the increased TGF-beta receptor type II, which is associated with altered responses to TGF-beta observed in CTGF expression, chemotaxis, and proliferation of RA synovial fibroblasts, and may have an important role in the pathogenesis of RA.

Catecholamine-induced stimulation of growth in Vibrio species

AIMS

To evaluate the effect of norepinephrine (NE) and related compounds on the growth of bacteria, we have examined the effect of the neuroendocrine hormone NE and related compounds on the growth of Vibrio parahaemolyticus and other human-pathogenic Vibrio species (Vibrio cholerae, Vibrio vulnificus, and Vibrio mimicus).

METHODS AND RESULTS

The effects on bacterial growth were examined using the serum-based medium and viable cells were counted using agar plates. We have shown that NE and its related compounds stimulate growth of V. parahaemolyticus in serum-based medium. This NE-induced growth stimulation was dependent upon the presence of transferrin. NE also stimulated growth of V. mimicus, but not V. cholerae and V. vulnificus.

CONCLUSIONS

These results suggest that the Vibrio species differ in their ability to respond to NE.

SIGNIFICANCE AND IMPACT OF THE STUDY

It is possible that NE and related compounds modulate the pathogenicity of V. parahaemolyticus and V. mimicus.

Transcription factors Csx/Nkx2.5 and GATA4 distinctly regulate expression of Ca2+ channels in neonatal rat heart

The cardiac transcription factors Csx/Nkx2.5 and GATA4 play important roles in vertebrate heart development. Although mutations of Csx/Nkx2.5 or GATA4 are associated with various congenital heart diseases, their mechanism of action on cardiomyocyte function is not completely elucidated. In this study, we therefore investigated the actions of these transcription factors on the electrophysiological features and expression of ion channels in cardiomyocytes. Genes for transcription factors Csx/Nkx2.5 and GATA4 were transfected into rat neonatal cardiomyocytes by adenoviral infection. Action potentials, L-, T-type Ca(2+) channels and hyperpolarization-activated cation current (I(h)) of rat neonatal myocytes were recorded by patch clamp technique after adenoviral infection. Expression of ion channels was confirmed by real-time PCR. In Csx/Nkx2.5 overexpression myocytes, the spontaneous beating rate was markedly increased with an up-regulation of the Ca(v)3.2 T-type Ca(2+) channel, while in GATA4 overexpression myocytes, the T-type Ca(2+) channel was unchanged. On the other hand, the L-type Ca(2+) channel was down-regulated by both Csx/Nkx2.5 and GATA4 overexpression; the level of Ca(v)1.3 mRNA was dramatically decreased by Csx/Nkx2.5 overexpression. These results indicate that Csx/Nkx2.5 and GATA4 play important roles on the generation of pacemaker potentials modulating voltage-dependent Ca(2+) channels in the neonatal cardiomyocyte.

Isoflurane activates sarcolemmal adenosine triphosphate-sensitive potassium channels in vascular smooth muscle cells: a role for protein kinase A

BACKGROUND

Recent evidence indicates that vascular adenosine triphosphate-sensitive potassium (K(ATP)) channels in vascular smooth muscle cells are critical in the regulation of vascular tonus under both physiologic and pathophysiologic conditions. Studies of the interaction of volatile anesthetics with vascular K(ATP) channels have been limited. In the current study, the authors investigated the molecular mechanism of isoflurane's action on vascular K(ATP) channels.

METHODS

Electrophysiologic experiments were performed using cell-attached and inside-out patch clamp techniques to monitor native vascular K(ATP) channels, and recombinant K(ATP) channels comprised of inwardly rectifying potassium channel subunits (Kir6.1) and the sulfonylurea receptor (SUR2B). Isometric tension experiments were performed in rat thoracic aortic rings without endothelium.

RESULTS

Application of isoflurane (0.5 mM) to the bath solution during cell-attached recordings induced a significant increase in K(ATP) channel activity, which was greatly reduced by pretreatment with a selective inhibitor of protein kinase A (PKA), Rp-cAMPS (100 microM). In inside-out patches, isoflurane did not activate K(ATP) channels. Isoflurane significantly activated wild-type recombinant SUR2B/Kir6.1 in cell-attached patches. Isoflurane-induced activation of wild-type channels was diminished in the PKA-insensitive mutant SUR2B-T633A/Kir6.1, SUR2B-S1465A/Kir6.1, and SUR2B/Kir6.1-S385A. In addition, the authors demonstrated that isoflurane-induced PKA activation was associated with isoflurane-induced decreases in isometric tension in the rat aorta.

CONCLUSION

These results indicate that isoflurane activates K(ATP) channels via PKA activation. PKA-dependent vasodilation induced by isoflurane also was observed in isometric tension experiments. Analysis of expressed vascular-type K(ATP) channels suggested that PKA-mediated phosphorylation of both Kir6.1 and SUR2B subunits plays a pivotal role in isoflurane-induced vascular K(ATP) channel activation.

Visualization of cardiac dipole using a current density map: detection of cardiac current undetectable by electrocardiography using magnetocardiography

A close relationship exists between electric current and the magnetic field. However, electricity and magnetism have different physical characteristics, and magnetocardiography (MCG) may provide information on cardiac current that is difficult to obtain by electrocardiography (ECG). In the present study, we investigated the issue of whether the current density map method, in which cardiac current is estimated from the magnetic gradient, facilitates the visualization of cardiac current undetectable by ECG. The subjects were 50 healthy adults (N group), 40 patients with left ventricular overloading (LVO group), 15 patients with right ventricular overloading (RVO group), 10 patients with an old inferior myocardial infarction (OMI group), and 30 patients with diabetes mellitus (DM group). MCGs were recorded with a second derivative superconducting quantum interference device (SQUID) gradiometer using liquid helium. Isopotential maps and current density maps from unipolar precordial ECG leads and MCGs, respectively, were prepared, and the cardiac electric current was examined. The current density map at the ventricular depolarization phase showed one peak of current density in the N group. However, in the OMI group, the current density map showed multiple peaks of current density areas. In the RVO group, two peaks of current densities were detected at the right superior region and left thoracic region and these two diploles appeared to be from the right and left ventricular derived cardiac currents, respectively. Moreover, there was a significant correlation between the magnitude of the current density from the right ventricle and the systolic pulmonary arterial pressure. The current density map at the ventricular repolarization phase in the N group showed only a single current source. However, abnormal current sources in the current density maps were frequently detected even in patients showing no abnormalities on isopotential maps in the LVO, DM, and OMI groups. The findings herein suggest that opposing dipoles of the ventricular depolarization and repolarization vectors were summed and evaluated as a single dipole in the electrocardiogram. However, MCG facilitated the detection of multiple dipoles because of its superior spatial resolution as well as difference in physical properties between magnetic and electrical fields. Our results suggest that MCG with a current density map is useful for detecting cardiac current undetectable by ECG in an early stage.

Angiotensin II inhibits insulin-induced actin stress fiber formation and glucose uptake via ERK1/2

There is crosstalk in intracellular signaling between Angiotensin II (Ang II) and insulin. We hypothesized that the underlying mechanism might be related to changes in cytoskeleton. In the presence of 100 nM of Ang II, insulin-induced glucose uptake was decreased and insulin-induced actin filament organization was inhibited. PKC inhibitors, including GF109203x and p38MAPK inhibitor (SB203580) neither improved insulin-induced actin reorganization nor glucose uptake. In contrast, the Ang II-induced inhibition of glucose uptake and actin filament disorganization was reversed by 10 micromol ERK 1/2 MAPK inhibitor (PD98059). Pretreatment of Ang II increased ERK1/2 phosphorylation and inhibited insulin-induced Akt phosphorylation. The effect of Ang II on ERK1/2 phosphorylation was blocked by Ang II type 1 receptor antagonists, RNH6270 and PD98059 but not by SB203580 or Guanosine-5'-O-(2-ThioDiphosphate), a G-protein inhibitor. We next tested the effect of broad-spectrum matrix metalloproteinase (MMP) inhibitor (GM6001) on Ang II-inhibition of insulin signaling pathway. GM6001 did not improve Ang II-induced actin filament disorganization and did not inhibit ERK1/2 phosphorylation. From these data in L6 myotube, we conclude that Ang II negatively regulates the insulin signal not through MMP signaling pathway but specifically through MMP-independent ERK1/2 activation pathway, providing an alternative molecular mechanism for angiotensin-induced insulin resistance.

Differential effects of etomidate and midazolam on vascular adenosine triphosphate-sensitive potassium channels: isometric tension and patch clamp studies

BACKGROUND

The aim of this study was to investigate the effects of two imidazoline-derived intravenous anesthetics, etomidate and midazolam, on vascular adenosine triphosphate-sensitive potassium (KATP) channel activity.

METHODS

In isolated rat aorta, isometric tension was recorded to examine the anesthetic effects on vasodilator response to levcromakalim, a selective KATP channel opener. Using the patch clamp method, the anesthetic effects were also examined on the currents through (1) native vascular KATP channels, (2) recombinant KATP channels with different combinations of various types of inwardly rectifying potassium channel (Kir6.0 family: Kir6.1, 6.2) and sulfonylurea receptor (SUR1, 2A, 2B) subunits, (3) SUR-deficient channels derived from a truncated isoform of Kir6.2 subunit (Kir6.2DeltaC36 channels), and (4) mutant Kir6.2DeltaC36 channels with reduced sensitivity to adenosine triphosphate (Kir6.2DeltaC36-K185Q channels).

RESULTS

Etomidate (> or = 10 m), but not midazolam (up to 10 m), inhibited the levcromakalim-induced vasodilation, which was sensitive to glibenclamide (IC50: 7.21 x 10 m; maximum inhibitory concentration: 1.22 x 10 m). Etomidate (> or = 3 x 10 m), but not midazolam (up to 10 m), inhibited the native KATP channel activity in both cell-attached and inside-out configurations with IC50 values of 1.68 x 10 m and 1.52 x 10 m, respectively. Etomidate (10 m) also inhibited the activity of various types of recombinant SUR/Kir6.0KATP channels, Kir6.2DeltaC36 channels, and Kir6.2DeltaC36-K185Q channels with equivalent potency.

CONCLUSIONS

Clinical concentrations of etomidate, but not midazolam, inhibit the KATP channel activity in vascular smooth muscle cells. The inhibition is presumably through its effects on the Kir6.0 subunit, but not on the SUR subunit, with the binding site different from adenosine triphosphate at the amino acid level.

Vitamin A deficiency induces a decrease in EEG delta power during sleep in mice

Recent report (Maret, S., Franken, P., Dauvilliers, Y., Ghyselinck, N.B., Chambon, P., Tafti, M., 2005. Retinoic acid signaling affects cortical synchrony during sleep. Science 310, 111-113.) has suggested that vitamin A (retinol and its derivatives) is genetically involved in the electroencephalogram (EEG) delta oscillation during sleep. However, this finding has not yet been confirmed by other studies. In this study, we attempted to record the sleep EEG and behavior, and to quantify striatal monoamines in mice fed a vitamin A-deficient (VAD) diet for 4 weeks, in order to clarify the linkage between the delta oscillation and vitamin A. VAD mice demonstrated a significant decrease in the delta power of the EEG. However, 6-h sleep deprivation caused the recovery of the delta power in VAD mice to a level similar to that of the control. VAD also caused the decrease of spontaneous activity throughout 24-h period. Furthermore, dihydroxyphenylacetic acid, a metabolite of dopamine, was decreased significantly in the striatal tissue of VAD mice. Our present results suggest that the deficiency of vitamin A causes the attenuation of delta power in NREM sleep and spontaneous activity. These attenuations may be related to the alteration of striatal dopaminergic function.

BCAA-enriched snack improves nutritional state of cirrhosis

OBJECTIVE

A late evening snack improves the catabolic state in patients with advanced liver cirrhosis. We tested whether long-term (3 mo) late evening snacking that included a branched-chain amino acid (BCAA)-enriched nutrient mixture produces a better nutritional state and better quality of life than ordinary food in patients with hepatitis C virus-positive liver cirrhosis.

METHODS

In a multicenter, randomized study, 48 patients with liver cirrhosis received late-evening supplementation with the BCAA-enriched nutrient mixture or ordinary food, such as a rice ball or bread, for 3 mo. During the study period, each patient was instructed on energy and protein intake. Blood biochemical data, nitrogen balance, respiratory quotient, and health-related quality of life (Short Form 36 questionnaire) were evaluated at baseline and at the end of the study.

RESULTS

Total and late-evening energy intakes were similar in the two groups at 3 mo. Serum albumin level, nitrogen balance, and respiratory quotient were significantly improved by the BCAA mixture but not by ordinary food. The parameters of the Short Form 36 did not statistically significantly improve over 3 mo in either group.

CONCLUSION

Long-term oral supplementation with a BCAA mixture is better than ordinary food in a late evening snack at improving the serum albumin level and the energy metabolism in patients with cirrhosis.