Carnosic acid alleviates depression-like behaviors on chronic mild stressed mice via PPAR-γ-dependent regulation of ADPN/FGF9 pathway.

RATIONALE: The pathway of adiponectin (ADPN)/fibroblast growth factor 9 (FGF9) was recently thought as a key role in the development of depression. ADPN is crucially regulated by peroxisome proliferator-activated receptor-gamma (PPAR-γ). Natural material carnosic acid (CA) has been applied for therapeutics of mental disorders. OBJECTIVES: To evaluate the antidepressive effect of CA in stress-treated mice and define whether its effects is involved in the regulation of ADPN/FGF9 pathway. METHODS: In vivo study, the levels of ADPN and FGF9 in both serum and hippocampus tissues, the expressions of ADPN receptor 2 (AdipoR2) in hippocampus and PPAR-γ in abdominal adipose, as well as the pathological changes of hippocampus were determined in 28-day period of chronic unpredictable mild stress (CUMS)-induced depression model of male ICR (Institute of Cancer Research) mice or adipo-/- mice. In vitro study, the level of ADPN and the mRNA expressions of both ADPN and PPAR-γ were determined in mouse 3T3-L1 preadipocytes. RESULTS: In vivo study, treatment with CA (50 or 100 mg/kg per day) for 21 days markedly suppressed depressive-like behaviors, the elevating levels of FGF9 and decreasing levels of ADPN in both serum and hippocampus tissues, the downregulating protein and mRNA expressions of AdipoR2 in hippocampus and PPAR-γ in abdominal adipose, as well as the pathological injury of hippocampus induced by CUMS in male ICR mice. The antidepressive effects of CA were markedly attenuated in male CUMS-treated adipo-/- mice. In vitro study, incubation with CA (3-30 µmol/L) for 24 h could concentration-dependently upregulate the mRNA expressions of both PPAR-γ and ADPN as well as increase the level of ADPN. The experiments using PPAR-γ-specific inhibitor GW9662 and transient transfection with mutated PPAR-γ-binding site promotor constructs showed that the activation of PPAR-γ mediated CA-induced ADPN expression in adipocytes. CONCLUSIONS: CA could significantly improve stress-induced depressive disorder, which may be related to regulating the dysfunction of ADPN-FGF9 pathway via activating PPAR-γ in adipocytes.

The correlation between adiponectin and FGF9 in depression disorder.

Adiponectin (ADPN) and fibroblast growth factor 9 (FGF9) has been reported as anti-depressive and pro-depressive factor, respectively. However, it is unknown whether there is directly interaction between ADPN and FGF9 in depression. The present study aims to investigate the correlation between ADPN and FGF9 in depression disorder. Firstly, the decreased level of ADPN and the increased level of FGF9 in plasma of depressive patients compared with non-depressive subjects were observed. Furthermore, these is a significant negative correlation between the ratio of ADPN to FGF9 and the total score of Hamilton Depression Scale in total investigated subjects. The similar changes of ADPN and FGF9 were also observed in elder adiponectin gene knockout (Adipo-/-) mice with an increasing trend to depressive-like behaviors. Secondly, the decreasing level of ADPN and increasing level of FGF9 in plasma and hippocampus tissues were observed in chronic unpredictable mild stress (CUMS)-induced depression in ICR mice with significant depressive-like behaviors and hippocampus damage, which attenuated by injection of recombinant ADPN or FGF9 antibody into lateral ventricle. In Adipo-/- mice, injection of FGF9 antibody into lateral ventricle also attenuated CUMS-induced depressivelike behaviors. The protein expression of FGF receptor 3 (FGFR3), the main receptor of FGF9, was significantly down-regulated in hippocampus tissues of CUMS-treated mice, which could be attenuated by treatment with either recombinant ADPN or anti-FGF9. In summary, the present results suggest that ADPN maybe a key negative regulator of FGF9/FGFR3 in depressive disorder and the dysfunction of ADPN-FGF9 pathway plays a key role in stress-induced depression.

Effect of Ginkgo biloba extract-761 on motor functions in permanent middle cerebral artery occlusion rats.

BACKGROUND: Ginkgo biloba extract (EGb-761) has been in use to treat variety of ailments including memory loss and emotional disorders usually experienced after ischemic stroke. However, data regarding its protective role in stroke associated motor dysfunction is scarce. PURPOSE: The present work was designed to investigate the long-term effects of EGb-761 on the motor dysfunctions associated with permanent middle cerebral artery occlusion (pMCAO) in rats. STUDY DESIGN/METHODS: Focal ischemic stroke was induced in male Sprague-Dawley rats by pMCAO. These rats were orally administered with EGb-761 (25, 50, 100 mg/kg) and positive control butylphthalide (50 mg/kg) for up to 28 consecutive days. The motor function was evaluated by assessing neurological scores, rotarod performance and gait analysis after 7, 14, 21 and 28 days. After 28 days, the histological examination of in frontal cortex and hippocampus was also carried out. RESULTS: EGb-761 treatment significantly improved motor function with better outcome in coordination and gait impairment rats. EGb-761 (25, 50, 100 mg/kg) treatment for 28 days significantly decreased the neurological scores. After 28 days of treatment EGb-761 (50 and 100 mg/kg) significantly increased the latency in rotarod test, walk speed, and the body rotation, whereas, decreased the stride time and the left posterior swing length in gait were observed. EGb-761 (50, 100 mg/kg). EGb-761 (50, 100 mg/kg) significantly improved the pathological changes related to pMCAO. CONCLUSIONS: EGb 761 could improve motor function especially gait impairments among pMCAO rat model related to the decreased neuronal damage. Therefore, it might be the potential to be explored further as an effective therapeutic drug to treat post stroke motor dysfunctions.

Involvement of dimethylarginine dimethylaminohydrolase-2 in visfatin-enhanced angiogenic function of endothelial cells.

BACKGROUND: Visfatin, a new adipocytokine, was reported to promote angiogenesis. Dimethylarginine dimethylaminohydrolase (DDAH), which could regulate vascular endothelial growth factor (VEGF) expression in endothelial cells, is thought as a novel modulator of angiogenesis. The aim of the study was to investigate the role of DDAH2 in visfatin-induced angiogenesis in human umbilical vein endothelial cells (HUVECs). METHODS AND RESULTS: Visfatin could concentration- and time-dependently enhance cell migration and tube formation reflecting angiogenic capability of HUVECs. Moreover, visfatin upregulated both mRNA and protein expressions of DDAH2 and VEGF. Angiogenic effects of visfatin were attenuated by DDAH2 small interfering RNA. Visfatin-induced protein kinase B (Akt) phosphorylation and phosphoinositide 3 kinase (PI3K) inhibitors could suppress visfatin-induced upregulation of DDAH2 and VEGF expressions. CONCLUSIONS: Taken together, our results demonstrate that PI3K/Akt-mediated upregulation of DDAH2 expression plays a critical role in visfatin-promoted angiogenesis via regulating VEGF-dependent pathway.

All-trans retinoic acid inhibits cobalt chloride-induced apoptosis in PC12 cells: role of the dimethylarginine dimethylaminohydrolase/asymmetric dimethylarginine pathway.

Previous studies have shown that the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) and its specific hydrolase dimethylarginine dimethylaminohydrolase (DDAH) are involved in the regulation of apoptosis in different cell types. In the present study, we investigated the role of the DDAH/ADMA pathway in cobalt chloride (CoCl(2))-induced apoptosis and the antiapoptotic effect of all-trans retinoic acid (atRA) in undifferentiated pheochromocytoma (PC12) cells. Treatment of CoCl(2) (125 microM) for 48 hr significantly induced the apoptosis of PC12 cells, concomitantly with increased intracellular reactive oxygen species (ROS) production and caspase-3 activity. CoCl(2) treatment also decreased the activity of DDAH and the expression of DDAH2 (mRNA and protein), resulting in an increased level of ADMA. All these alterations induced by CoCl(2) were attenuated by atRA (0.1, 1, or 10 microM). Interestingly, the antiapoptotic effects of atRA were inhibited by DDAH2 small RNA interference. In contrast, DDAH2 overexpression inhibited the proapoptotic effects of CoCl(2). We also found that treatment of exogenous ADMA (3, 10, or 30 microM) induced the apoptosis of PC12 cells in a concentration- and time-dependent manner, which was inhibited by the antioxidant or the caspase-3 inhibitor. These findings suggest that the modulation of the DDAH/ADMA/ROS pathway plays an important role in CoCl(2)-induced apoptosis and the antiapoptotic effects of atRA in undifferentiated PC12 cells.

Asymmetric dimethylarginine induces tissue factor expression in monocytes via NF-kappaB-dependent pathway: Role in acute coronary syndromes.

Asymmetric dimethylarginine (ADMA), a major endogenous inhibitor of nitric oxide synthase, is recently defined as an independent cardiovascular risk factor. Tissue factor (TF) expression and procoagulant activity (PCA) of peripheral monocytes are increased in patients with acute coronary syndromes (ACS), which resulted in blood procoagulant state tending to thrombus formation. In the present study, we tested the hypothesis that ADMA contribute to TF expression of peripheral monocytes in ACS. Twenty patients with unstable angina (UA), 20 patients with stable angina (SA) and 20 control subjects were recruited. Monocytic cell line THP-1 was incubated with different concentrations of ADMA (1-10microM) for various periods (6-24h). Our results showed that plasma level of ADMA in patients with UA was significantly higher than those in patients with SA or in the control group, and positively correlated with TF antigen level and PCA of circulating monocytes. Adjusting for all patient characteristics, we confirmed these findings in multivariate regression analyses. In cultured THP-1 cells, ADMA transcriptionally upregulated both TF antigen expression and PCA in a concentration-dependent manner. The experiments using nuclear factor-kappaB (NF-kappaB) inhibitor and transient transfection with wild-type and mutated TF promotor constructs showed that the NF-kappaB is an important transcriptional regulator of ADMA-induced TF expression. Our results suggest that elevated plasma level of ADMA induces TF expression in monocytes via NF-kappaB-dependent pathway, which contributes to procoagulant phenotype of circulating monocytes in ACS.

Protection of capsaicin against hypoxia-reoxygenation-induced apoptosis of rat hippocampal neurons.

The aim of this study was to investigate the effect of capsaicin on hypoxia-reoxygenation (H/R)-induced apoptosis in primary rat hippocampal neurons. Three hours of hypoxia (1% O2) and subsequent reoxygenation for 24 h significantly increased the apoptotic death of hippocampal neurons, as evidenced by increases in both TUNEL-positive cell number and caspase-3 activity. Pretreatment with capsaicin (3-30 micromol/L) or the caspase-3-specific inhibitor acetyl-DEVD-CHO (100 micromol/L) markedly attenuated H/R-induced apoptosis in hippocampal neurons. Capsaicin also markedly induced the phosphorylation of Akt. The phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (10 micromol/L) prevented any capsaicin-induced survival effect in hippocampal neurons. Intracellular levels of reactive oxygen species (ROS), which were greatly increased after H/R, were significantly inhibited by capsaicin, pyrrolidine dithiocarbamate (PDTC) (50 micromol/L), and LY294002. Taken together, these data suggest that capsaicin protects against H/R-induced apoptosis of hippocampal neurons via the PI3K/Akt-mediated signaling pathway, which is related to the inhibition of oxidative stress and caspase-3 activation.

Rutaecarpine inhibits hypoxia/reoxygenation-induced apoptosis in rat hippocampal neurons.

Our previous studies showed that rutaecarpine (Rut) protected against myocardial ischemia/reperfusion (I/R) injury, which was associated with activation of transient receptor potential vanilloid subtype 1 (TRPV1). Recently, TRPV1 activation was also reported to exert neuroprotective effects. The present study was to investigate the effect of Rut on hypoxia/reoxygenation (H/R)-induced apoptosis in primary rat hippocampal neurons. Three-hour hypoxia (1% O2) and consequent 24-h reoxygenation significantly increased the apoptotic death of hippocampal neurons as evidenced by increases in both TUNEL-positive cell number and caspase-3 activity. However, pretreatment with Rut (1-10microM) or caspase-3 specific inhibitor DEVD-CHO could markedly attenuate H/R-induced apoptosis in neurons. Rut markedly induced the phosphorylation of Akt and PI3K inhibitor LY294002 prevented the survival effect of Rut on neurons. Intracellular oxidative stress was significantly induced after H/R, which was inhibited by Rut and LY294002 as well as antioxidant PDTC. TRPV1 antagonist capsazepine or intracellular Ca2+ chelator BAPTA/AM could abolish these effects of Rut mentioned above. In summary, the present data suggest that Rut inhibits H/R-induced apoptosis of hippocampal neurons via TRPV1-[Ca2+]i-dependent and PI3K/Akt signaling pathway, which is related to inhibiting oxidative stress and caspase-3 activation.

Expression of small-conductance calcium-activated potassium channels (SK3) in skeletal muscle: regulation by muscle activity.

The type 3 small conductance calcium-activated potassium channel (SK3) is expressed in embryonic and adult denervated skeletal muscles where it contributes to hyperexcitability. This study aimed at determining the role of muscle activity in regulating SK3 channels. Soleus muscles of adult rats were denervated by cutting the sciatic nerve. In reinnervation studies, the soleus nerve was crushed: in one group, muscles were reinnervated with electrically silent axons, by chronic sciatic nerve perfusion with tetrodotoxin. Several groups of denervated muscles were subjected to chronic direct electrical stimulation, using either fast (100 Hz) or slower patterns (20 or 30 Hz). The SK3 mRNA and protein levels in soleus muscle were determined by reverse transcriptional-PCR, Western blot and immunofluorescence. Both denervated and reinnervated-paralysed soleus muscles displayed similar up-regulation of SK3 mRNA and protein. Reinnervation with electrically active axons instead inhibited SK3 up-regulation. Chronic muscle direct stimulation in vivo, irrespective of the pattern used, reversed the denervation-induced up-regulation of SK3 expression or prevented it when initiated at the time of denervation. Chronic electrical stimulation of denervated muscles also completely prevented the development of the after-hyperpolarization (AHP) following the action potential, normally induced in the muscle fibres by denervation. We conclude that action potential activity evoked by motor neurones in muscle fibres is both necessary and sufficient to account for the physiological down-regulation of SK3 channels in the non-junctional membrane of skeletal muscle.

Calcitonin gene-related peptide-mediated antihypertensive and anti-platelet effects by rutaecarpine in spontaneously hypertensive rats.

We have previously reported that Chinese traditional medicine rutaecarpine (Rut) produced a sustained hypotensive effect in phenol-induced and two-kidney, one-clip hypertensive rats. The aims of this study are to determine whether Rut could exert antihypertensive and anti-platelet effects in spontaneously hypertensive rats (SHR) and the underlying mechanisms. In vivo, SHR were given Rut and the blood pressure was monitored. Blood was collected for the measurements of calcitonin gene-related peptide (CGRP), tissue factor (TF) concentration and activity, and platelet aggregation, and the dorsal root ganglia were saved for examining CGRP expression. In vitro, the effects of Rut and CGRP on platelet aggregation were measured, and the effect of CGRP on platelet-derived TF release was also determined. Rut exerted a sustained hypotensive effect in SHR concomitantly with the increased synthesis and release of CGRP. The treatment of Rut also showed an inhibitory effect on platelet aggregation concomitantly with the decreased TF activity and TF antigen level in plasma. Study in vitro showed an inhibitory effect of Rut on platelet aggregation in the presence of thoracic aorta, which was abolished by capsazepine or CGRP(8-37), an antagonist of vanilloid receptor or CGRP receptor. Exogenous CGRP was able to inhibit both platelet aggregation and the release of platelet-derived TF, which were abolished by CGRP(8-37). The results suggest that Rut exerts both antihypertensive and anti-platelet effects through stimulating the synthesis and release of CGRP in SHR, and CGRP-mediated anti-platelet effect is related to inhibiting the release of platelet-derived TF.

Role of endogenous nitric oxide synthase inhibitor in gastric mucosal injury.

To explore the role of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) in gastric mucosal injury, 3 models of gastric mucosal injury induced by ethanol, indomethacin, or cold stress were used in rats. The cultured human gastric mucosal epithelial cell line GES-1 infected by Helicobacter pylori (Hp) was selected to mimic human gastric mucosal injury. Gastric mucosal ulcer index (UI), levels of ADMA and NO, and activity of dimethylarginine dimethylaminohydrolase (DDAH) were determined in the mucosal injury models; in Hp-infected or ADMA-treated GES-1 cells, levels of ADMA, NO, and TNF-alpha and activity of DDAH were measured. The results showed that UI and levels of ADMA were markedly increased and accompanied by significantly decreased DDAH activity in the mucosal injury models. Incubation of GES-1 cells with Hp increased levels of TNF-alpha and ADMA and decreased activity of DDAH. Administration of ADMA also increased levels of TNF-alpha. The results suggest that ADMA plays an important role in facilitating gastric mucosal injury, an effect which is associated with inhibiting NO synthesis and inducing inflammatory reaction.

[Differentiation of 2 endothelial progenitor cells in vitro and inhibitory effect of asymmetric dimethylarginine on its proliferation].

OBJECTIVE: To investigate the Methods for culturing two types of endothelial progenitor cells (EPC) from human umbilical cord blood and study their differentiation traits and the depressant effect of asymmetric dimethylarginine (ADMA) on its proliferation. METHODS: Mononuclear cells were isolated from fresh cord blood by 6% hydroxyethyl starch(HES) and density gradient centrifugation.Isolated cells were cultured in the medium supplemented with vascular endothelial growth factors (VEGF) and basic fibroblast growth factors (bFGF). The growth characteristics and biological features of the cells were observed at different time points and identified by morphology,immunofluorescence staining,reverse transcription polymerase chain reaction (RT-PCR), and flow cytometry.Attached cells were incubated with different concentrations of ADMA (1,5, and 10 micromol/L) for 24,48, and 72 hours. Methylthiazoletetrazolium (MTT) assay and quantified colony forming units (CFUs) were used to assess the proliferation of endothelial progenitor cells. RESULTS: The attached cells were divided into 2 types:early EPC and late EPC. Early EPC changed from small sized round cells to spindle shaped cells and late EPC formed a typical cobblestone-like cells. Fluorescence microscopy showed that EPC were positive for both Dil-acLDL uptake and FITC-UEA-I binding.RT-PCR and FACS showed the difference of endothelial cell-specific,gene expression and changed AC133,CD34, and KDR among different times.Incubation of EPC with ADMA dose and time-dependently decreased the number and the proliferation of EPC. CONCLUSION: There are 2 types of EPC from a source of human umbilical cord blood and ADMA may depress the EPC proliferation, providing a basis for further research.

Involvement of the endothelial DDAH/ADMA pathway in nitroglycerin tolerance: the role of ALDH-2.

Previous studies have shown that nitroglycerin (GTN) tolerance is closely related to an oxidative stress-induced decrease in activity of mitochondrial isoforms of aldehyde dehydrogenase (ALDH-2), and prolonged GTN treatment causes endothelial dysfunction. Asymmetric dimethylarginine (ADMA), a major endogenous NO synthase (NOS) inhibitor, could inhibit NO production and induce oxidative stress in endothelial cells. ADMA and its major hydrolase dimethylarginine dimethylaminohydrolase (DDAH) have recently been thought of as a novel regulatory system of endothelium function. The aim of the present study was to determine whether the DDAH/ADMA pathway is involved in the development of GTN tolerance in endothelial cells. Tolerance, reflected by the decrease in cyclic GMP (cGMP) production, was induced by exposure of human umbilical vein endothelial cells (HUVECs) to GTN (10 microM) for 16 h. While the treatment increased reactive oxygen species (ROS) production/malondialdehyde (MDA) concentration and decreased ALDH-2 activity as well as cGMP production, it markedly increased the level of ADMA in culture medium and decreased DDAH activity in endothelial cells. Exogenous ADMA significantly enhanced ROS production/MDA concentration and inhibited ALDH-2 activity, and overexpression of DDAH2 could significantly suppress GTN-induced oxidative stress and inhibition of ALDH-2 activity, which is also attenuated by L-arginine. Therefore, our results suggest for the first time that the endothelial DDAH/ADMA pathway plays an important role in the development/maintenance of GTN tolerance.

Asymmetric dimethylarginine induces TNF-alpha production via ROS/NF-kappaB dependent pathway in human monocytic cells and the inhibitory effect of reinioside C.

Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase (NOS) inhibitor, has been implicated in vascular inflammation through induction of reactive oxygen species (ROS) and proinflammatory genes in endothelial cells. However, relatively few attentions have been paid to the effect of ADMA on monocytes, one of the important cells throughout all stages of atherosclerosis. In the present study, we found that reinioside C, the main component extracted from Polygala fallax Hemsl., dose-dependently inhibited tumor necrosis factor-alpha (TNF-alpha) production induced by ADMA in monocytes, Furthermore, reinioside C attenuated ADMA-induced generation of reactive oxygen species and activation of nuclear factor-kappaB (NF-kappaB) activity in monocytes in a dose-dependent manner, this effect was inhibited by l-arginine (NOS substrate) and PDTC (inhibitor of NF-kappaB). These data suggest that reinioside C could attenuate the increase of TNF-alpha induced by exogenous ADMA through inhibition ROS/NF-kappaB pathway in monocytes.

Reduction of NO- and EDHF-mediated vasodilatation in hypertension: role of asymmetric dimethylarginine.

Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase (NOS), and endothelial dysfunction is related to the elevation of ADMA level in hypertension. Besides the NO-mediated pathway, the endothelium-derived hyperpolarizing factor (EDHF)-mediated pathway is involved in endothelial dysfunction. The aims of the present study were to evaluate the changes of endothelium-dependent dilatation of arteries in hypertension and the role of ADMA in NO- and EDHF-mediated vasodilatation. The great omental arteries were isolated from essential hypertensive and normotensive patients, and mesenteric arteries were isolated from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. NO-, EDHF-, and prostaglandin (PGI(2))-mediated endothelium-dependent vasodilatation were measured, and plasma concentrations of ADMA were determined in rats. Cultured endothelial cells were treated with ADMA (1-10 microM) for 48 h, and the mRNA and protein level of small-conductance Ca(2+)-activated K(+) channel 3 (SK3), which has been thought to be a key mediator of EDHF, was determined. Both NO- and EDHF-mediated endothelium-dependent responses were decreased in the great omental arteries of hypertensive patients and mesenteric arteries of SHR. Plasma levels of ADMA were significantly increased in SHR. In cultured endothelial cells, the expressions of SK3 mRNA and protein were concentration-dependently down-regulated in the presence of ADMA. The present study suggests that the inhibitory effect of ADMA on endothelial function not only involves NO-mediated endothelium-dependent vasodilatation but also the EDHF-mediated pathways in hypertensive animals and humans, and that ADMA can down-regulate the expression of SK3 channels in endothelial cells.

Down-regulation of endogenous nitric oxide synthase inhibitors on endothelial SK3 expression.

OBJECTIVES: To investigate role of endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) in down-regulation of the expression of endothelial SK3 in atherosclerosis. METHODS: Apolipoprotein E deficient (apo E(-/-)) mice aged 11 approximately 12 weeks were treated with ADMA (5 mg/kg per day, subcutaneous injection) for 4 weeks. Cultured human umbilical venous endothelial cells (HUVECs) were treated with different concentrations of lysophosphatidylcholine (LPC) or ADMA for 48 h. Plasma levels of ADMA were determined by high performance liquid chromatogram (HPLC); protein and mRNA levels of SK3 in the aortas of mice and cultured cells were detected by immunofluorescence, western blot and RT-PCR, respectively. RESULTS: Concomitantly with the elevated plasma levels of ADMA, the expressions of both SK3 protein and mRNA in aortas of apo E(-/-) mice were significantly reduced in comparison to those of the wild-type mice. Moreover, 4-week treatment of ADMA made levels of SK3 expression even lower. In cultured HUVECs, either LPC or ADMA notably decreased the expressions of both SK3 protein and mRNA in a concentration dependent manner. CONCLUSIONS: Endogenous ADMA may be an important factor for down-regulation of the expression of endothelial SK3 in atherosclerotic animals.

Reduction of asymmetric dimethylarginine involved in the cardioprotective effect of losartan in spontaneously hypertensive rats.

Previous studies have indicated that nitric oxide synthase (NOS) inhibitors can induce an increase of blood pressure and exacerbate myocardial injury induced by ischemia and reperfusion, whereas angiotensin II receptor antagonists protect the myocardium against injury induced by ischemia and reperfusion. Isolated hearts from male spontaneously hypertensive rats (SHR) or male Wistar-Kyoto rats (WKY) were subjected to 20 min global ischemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure, and its first derivatives (+/-dP/dt(max)) were recorded, and serum concentrations of asymmetric dimethylarginine (ADMA) and NO and the release of creatine kinase in coronary effluent were measured. The level of ADMA was significantly increased and the concentration of NO was decreased in SHR. Ischemia and reperfusion significantly inhibited the recovery of cardiac function and increased the release of creatine kinase, and ischemia and reperfusion-induced myocardial injury in SHR was aggravated compared with WKY. Vasodilation responses to acetylcholine of aortic rings were decreased in SHR. Treatment with losartan (30 mg/kg) for 14 days significantly lowered blood pressure, elevated the plasma level of NO, and decreased the plasma concentration of ADMA in SHR. Treatment with losartan significantly improved endothelium-dependent relaxation and cardiac function during ischemia and reperfusion in SHR. Exogenous ADMA also aggravated myocardial injury induced by ischemia and reperfusion in isolated perfused heart of WKY, as shown by increasing creatine kinase release and decreasing cardiac function. The present results suggest that the protective effect of losartan on myocardial injury induced by ischemia and reperfusion is related to the reduction of ADMA levels.

[Effect of asymmetric dimethylarginine on the activation of hepatic stellate cells and its mechanism].

OBJECTIVE: To investigate the effect of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, on the activation of hepatic stellate cells (HSCs) and its mechanism. METHODS: Primary HSCs isolated from SD rats were cultured and treated with different concentrations (1, 3 or 10micromol/L) of ADMA for various periods (12 approximately 48h). Expression of alpha-smooth muscle actin (alpha-SMA) and synthesis of type-I collagens in HSC were determined. Messenger RNA levels of the transforming growth factor-beta1 (TGF-beta(1)) in the HSCs were determined using RT-PCR. Intracellular reactive oxidant species (ROS) production was measured using oxidant-sensitive fluorescent indicator. Activation of nuclear factor-kappaB (NF-kappaB) was detected by electrophoretic mobility shift assay (EMSA). RESULTS: ADMA could increase alpha-SMA-positive cells ratio and Type I collagens production of HSCs in a concentration- and time-dependent manner, concomitant with the increase of the TGF-beta(1) mRNA level. Treatment with ADMA (10micromol/L) significantly increased the intracellular ROS production and activated NF-kappaB. Such effects of ADMA on the level of TGF-beta(1) mRNA could be markedly attenuated by pretreatment with antioxidant pyrrolidine dithiocarbamate (25micromol/L). CONCLUSION: ADMA can induce the HSC activation by increasing TGF-beta(1) expression through ROS-NF-kappaB-dependent pathway. Therefore, ADMA should be a novel and endogenous activator of HSC, which may be involved in the development of liver fibrosis.

Decrease in endogenous CGRP release in nitroglycerin tolerance: role of ALDH-2.

In the present study, we tested whether the decreased release of calcitonin gene-related peptide (CGRP) observed in nitroglycerin tolerance is associated with the decrease in aldehyde dehydrogenase (ALDH-2) activity. We further investigated the possible involvement of reactive oxygen species in the decrease in ALDH-2 activity. Tolerance was induced by exposure of isolated rat thoracic aortas and human umbical vein endothelial cells (HUVEC) to nitroglycerin in vitro or by pretreatment with nitroglycerin for 8 days in vivo. Pretreatment with ALDH-2 inhibitors and nitroglycerin significantly attenuated vasodilator responses to nitroglycerin concomitantly with a decrease in the release of CGRP from the isolated thoracic aorta. Nitroglycerin produced a depressor effect concomitantly with an increase in plasma concentrations of CGRP, and the effect of nitroglycerin was attenuated after pretreatment with an inhibitor of ALDH-2 or nitroglycerin for 8 days. Exposure of HUVEC to nitroglycerin for 16 h increased reactive oxygen species production and decreased ALDH-2 activity as well as cGMP production in a time-and concentration-dependent manner. Pretreatment with an ALDH-2 inhibitor also significantly decreased the cGMP production. However, tolerance to nitroglycerin in HUVEC was restored in the presence of N-acetylcysteine or captopril. The present results suggest that nitrate tolerance is, at least partially, associated with a decrease in endogenous CGRP release via a decrease in ALDH-2 activity as a result of stimulation of reactive oxygen species production.

Effect of asymmetric dimethylarginine on atherogenesis and erythrocyte deformability in apolipoprotein E deficient mice.

Previous investigations have shown that the level of asymmetric dimethylarginine (ADMA) was increased in hypercholesterolemic animal and humans, and the decreased erythrocyte deformability has been suggested to be a factor contributing to atherogenesis. In the present study, we investigated the effect of ADMA, endogenous or exogenous, on atherogenesis and erythrocyte deformability in apolipoprotein E deficient (ApoE-/-) mice. On a regular chow diet, ApoE-/- mice or C57BL/6 J mice at 12 weeks of age were treated with ADMA (5 mg/kg/day) for 4 weeks. Atherosclerotic lesion area, erythrocyte deformability, plasma lipids and asymmetric dimethylarginine (ADMA) level were determined. Plasma concentrations of triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C), total cholesterol (TC), ADMA, and atherosclerotic lesion area were significantly increased, and the level of plasma high-density lipoprotein-cholesterol (HDL-C), erythrocyte deformability in ApoE-/- mice were markedly decreased compared with that of C57BL/6J mice (P<0.05 or P<0.01). Exogenous ADMA treatment increased the plasma TG level, produced atherosclerotic lesions, and decreased erythrocyte deformability in C57BL/6J mice (P<0.05 or P<0.01). Treatment with exogenous ADMA further increased the plasma TG level and lesion areas, and decreased erythrocyte deformability in ApoE-/- mice. In vitro, exogenous ADMA caused a decrease of erythrocyte deformability in a concentration-dependent manner, and the effect of ADMA was reversed by L-arginine. The present results suggest that endogenous ADMA is an important contributor to the development of atherosclerosis and that reduction of erythrocyte deformability and impaired endothelial function induced by ADMA may be an important factor facilitating atherosclerotic lesions.