17 beta-Estradiol attenuates voltage-dependent Ca2+ currents in A7r5 vascular smooth muscle cell line

Effects of N-acetylcysteine against systemic and renal hemodynamic effects of endotoxin in healthy humans

OBJECTIVE

Systemic inflammation causes vasodilation and impairs the vascular response to catecholamines. There is evidence that altered vasoreactivity is associated with increased production of free radicals. We studied the influence of systemic doses of the antioxidant N-acetylcysteine on inflammatory cytokines and renal plasma flow and on the systemic pressor response to norepinephrine during experimental endotoxemia.

DESIGN

A double-blind, placebo-controlled crossover study.

SETTING

Medical University of Vienna, Clinical Pharmacology, Vienna General Hospital, AKH.

SUBJECTS

Eight healthy, male humans.

INTERVENTIONS

Intravenous administration of Escherichia coli endotoxin (lipopolysaccharide, 20 IU/kg) on two separate study days with concomitant intravenous infusion of placebo or N-acetylcysteine (150 mg/kg loading dose; 15 mg/kg/hr continuous infusion), respectively.

MEASUREMENTS AND MAIN RESULTS

Measurements of inflammatory cytokines, of renal plasma flow by the para-aminohippurate-clearance method, and of the systemic pressor response to norepinephrine were taken at baseline and after endotoxin. Lipopolysaccharide increased body temperature and plasma concentrations of tumor necrosis factor-alpha, which was mitigated during N-acetylcysteine infusions. Likewise, the lipopolysaccharide-induced increases in renal plasma flow and decreases in blood pressure were attenuated, and the hyporeactivity of pulse rate to norepinephrine 4 hrs after lipopolysaccharide was improved by N-acetylcysteine.

CONCLUSION

High doses of N-acetylcysteine might exert protective effects on systemic hemodynamics and on the reactivity to catecholamines in humans challenged by lipopolysaccharide. This action of the antioxidant N-acetylcysteine is paralleled by humoral anti-inflammatory mechanisms and may be useful in patients with systemic inflammation.

Endotoxemia-mediated induction of cardiac inducible nitric-oxide synthase expression accounts for the hypotensive effect of ethanol in female rats

We have recently shown that intragastric (i.g.) ethanol lowers blood pressure (BP) in conscious female rats via a reduction in cardiac output (CO). However, the mechanisms implicated in these hemodynamic effects of ethanol are not known. Therefore, we tested the hypothesis that ethanol-evoked endotoxemia mediates the reduction in CO via enhanced myocardial inducible nitric-oxide synthase (iNOS) expression. Immunoblot (myocardial iNOS), biochemical (plasma endotoxin and nitrite/nitrate), and integrative [BP, heart rate, CO, stroke volume (SV), and total peripheral resistance (TPR)] studies were conducted in conscious female rats that received i.g. ethanol (1 g/kg) in the absence or presence of 1400W (N-(3-[aminomethyl]benzyl) acetamidine) or ampicillin to selectively inhibit iNOS and to eliminate endogenous endotoxin, respectively. Ethanol-evoked hypotension coincided with reductions in CO and SV and increases in: 1) TPR, 2) plasma endotoxin and nitrite/nitrate, and 3) myocardial iNOS expression. These effects of ethanol were virtually abolished in rats pretreated with ampicillin (200 mg/kg/day for 2 days by gavage) or with 1400W (5 mg/kg i.p.) except for the increase in plasma endotoxin, which persisted in 1400W-pretreated rats. These findings yield insight into the mechanistic role of endotoxin-myocardial iNOS signaling in the cardiodepressant action of ethanol, which accounts for its hypotensive effect in conscious female rats.

Effect of 5-HT(2) receptor blockade on cadmium-induced acute toxicity

The protective effect of 5-HT(2) receptor blockade with ketanserin or ritanserin against cadmium liver injury was investigated. Male Wistar rats were injected intraperitoneally with a sublethal dose of cadmium (3.5 mg/kg body weight). Rats were treated with normal saline (group I), ketanserin (3 mg/kg body weight; group II), or ritanserin (3 mg/kg body weight; group III) 2 hr prior and 4 hr after cadmium administration and killed at different time points. Hematoxylin/eosin-stained liver sections were assessed for necrosis, apoptosis, peliosis, mitoses, and inflammatory infiltration. Apoptosis was also quantified by the TUNEL assay. Nonparenchymal liver cells and activated Kupffer cells were identified histochemically. Necrosis, hepatocyte apoptosis, nonparenchymal cell apoptosis, and macroscopic and microscopic peliosis were markedly reduced or minimized in ketanserin- or ritanserin-treated rats. The observed protective effect was almost identical for both ketanserin and ritanserin administration. 5-HT(2) receptor blockade exerts a protective effect against acute cadmium-induced hepatotoxicity.

The modulatory role of androgens and progestins in the induction of vasorelaxation in human umbilical artery

Sex steroids have been described as protectors of the cardiovascular system and one of their relevant actions is inhibition of vascular tone. However, this information has been derived from animal models. The aim of this study was to investigate the vasorelaxant properties of several progestins and androgens on the vascular tone of human umbilical artery (HUA) to elucidate their potential regulatory role on fetoplacental blood flow. HUA rings, obtained from umbilical cords at vaginal deliveries and cesarean section from term uncomplicated pregnancies, were isometrically recorded and precontracted with either KCl or serotonin. Subsequently, dehydroepiandrosterone, testosterone, progesterone and some of their 5-reduced metabolites were added at different noncumulative concentrations on KCl-induced precontraction. There were significant differences in the vasorelaxing responses to these steroids; excluding 5alpha-pregnandione, the remaining steroids induced concentration-dependent vasorelaxations. In general, androgens were more potent than progestins, with 5beta-dihydrotestosterone being the most potent one. These vasorelaxations remained unaffected by inhibitors of transcription and translation, selective steroid receptor antagonists, a nitric oxide synthase inhibitor or specific blockers of K(+) channels. Interestingly, the serotonin contraction was significantly less sensitive to steroid-induced vasorelaxation. Moreover, the contraction evoked by Ca(2+) in depolarized tissues (by KCl-Ca(2+) free solution) was prevented by steroids. These data, taken together, suggest that sex steroids (particularly androgens) induce an acute (nongenomically-mediated) vasorelaxing effect on the HUA which may be mediated by: (i) a nitric oxide-independent pathway; and/or (ii) a decrease in external Ca(2+) influx by inactivating Ca(2+) channels, but not by activating K(+) channels.

Morphologic features in the regenerating liver—a comparative intravital, lightmicroscopical and ultrastructural analysis with focus on hepatic stellate cells

Different cell types play a role in the liver regeneration. The present study reveals morphological key steps of liver regeneration by correlating intravital, light, and electron microscopic with immunohistochemistry results focusing on hepatic stellate cells (HSCs). In Lewis rats, liver regeneration was induced by a 2/3-hepatectomy. Animals (n = 7 each) were killed after 0, 1, 2, 3, 4, 7, and 14 days. Morphological features were investigated by light microscopy, immunohistochemistry [alpha-smooth muscle actin (alpha-SMA), Desmin, vascular endothelial growth factor (VEGF)/VEGF receptor, Ki-67, ssDNA], intravital microscopy (sinusoid density, number of hepatocytes, and HSC), and electron microscopy focussed on cell-to-cell interactions. During liver regeneration, HSC were activated at day 3 showing a loss of autofluorescence and simultaneously an increased alpha-SMA expression and direct cell contact to hepatocytes. HSC activation was followed by increasing VEGF expression and sinusoid density. After 14 days, liver architecture and ultrastructure was restored and HSCs were deactivated showing decreased alpha-SMA expression as well as increased apoptosis and no more direct cell contact to hepatocytes. HSCs play a central role in the regenerating liver by governing angiogenesis and extracellular matrix remodeling. A direct cell contact to hepatocytes seems to be essential for HSC activation, whereas deactivation is accompanied by loosening of hepatocyte contact and increased apoptosis.

Prostacyclin in liver disease: a potential therapeutic option

Complex molecular and cellular mechanisms are involved in the initiation and progression of hepatic fibrosis. Recent studies have shown that hepatic stellate cells, endothelin, cytokines and prostacyclin play crucial roles in this pathology. Prostacyclin exerts vasorelaxant, antioxidant and antifibrotic properties that prevent the development of fibrosis and cirrhosis in liver diseases. In this editorial, the authors discuss some of the molecular and cellular mechanisms involved in the initiation and progression of liver fibrosis and the role played by prostacyclin in counteracting it. At the moment, however, only limited information is available from clinical studies demonstrating the effectiveness of prostacyclin in liver diseases and this makes it difficult to draw any conclusions; further efforts are necessary to verify whether prostacyclin, alone or in combination with other drugs, may be a valid therapeutic option in liver diseases.

Inhibitory effect of peroxiredoxin II (Prx II) on Ras-ERK-NFkappaB pathway in mouse embryonic fibroblast (MEF) senescence

Intracellular reactive oxygen species (ROS) were attenuated by the expression of peroxiredoxin II (Prx II). Cellular senescence as judged by senescence-associated (SA)-beta-galactosidase (Gal) positive cell formation was increased in Prx II-deficient mouse embryonic fibroblast (MEF). Ras expression was increased following passages. The level of Ras expression was higher in Prx II-/- MEF than wild type MEF. ERK activity was also augmented by the deletion of Prx II. SA-beta-Gal-positive cell formation was reduced by PD98059, ERK inhibitor. Activated nuclear transcription factor, nuclear factor-kappaB (NFkappaB) by the deletion of Prx II was inhibited by the treatment with PD98059. In contrast, no changes in SA-beta-Gal-positive cell formation were detected by NFkappaB inhibitor, N-alpha-tosyl-L-phenylalanyl chloromethyl ketone (TPCK). Collectively, results suggest that Prx II deletion activate Ras-ERK-NFkappaB pathways and cellular senescence in Prx II-/- MEF cells was mediated by ERK activation but not by NFkappaB activation.

Potential role of female sex hormones in the pathophysiology of migraine

Clinical evidence indicates that female sex steroids may contribute to the high prevalence of migraine in women, as well as changes in the frequency or severity of migraine attacks that are in tandem with various reproductive milestones in women's life. While female sex steroids do not seem to be involved in the pathogenesis of migraine per se, they may modulate several mediators and/or receptor systems via both genomic and non-genomic mechanisms; these actions may be perpetuated at the central nervous system, as well as at the peripheral (neuro)vascular level. For example, female sex steroids have been shown to enhance: (i) neuronal excitability by elevating Ca(2+) and decreasing Mg(2+) concentrations, an action that may occur with other mechanisms triggering migraine; (ii) the synthesis and release of nitric oxide (NO) and neuropeptides, such as calcitonin gene-related peptide CGRP, a mechanism that reinforces vasodilatation and activates trigeminal sensory afferents with a subsequent stimulation of pain centres; and (iii) the function of receptors mediating vasodilatation, while the responses of receptors inducing vasoconstriction are attenuated. The serotonergic, adrenergic and gamma-aminobutyric acid (GABA)-ergic systems are also modulated by sex steroids, albeit to a varying degree and with potentially contrasting effects on migraine outcome. Taken together, female sex steroids seem to be involved in an array of components implicated in migraine pathogenesis. Future studies will further delineate the extent and the clinical relevance of each of these mechanisms, and will thus expand the knowledge on the femininity of migraine.

Role of oxidative stress in experimental sepsis and multisystem organ dysfunction

Massive increase in radical species can lead to oxidative stress, promoting cell injury and death. This review focuses on experimental evidence of oxidative stress in critical illnesses, sepsis and multisystem organ dysfunction. Oxidative stress could negatively affect organ injury and thus overall survival of experimental models. Based on this experimental evidence, we could improve the rationale of supplementation of antioxidants alone or in combination with standard therapies aimed to reduce oxidative stress as novel adjunct treatment in critical care.

Interleukin-10 Gene Transfer: Prevention of Multiple Organ Injury in a Murine Cecal Ligation and Puncture Model of Sepsis

INTRODUCTION

The aim of this study was to determine the effect of immunoregulatory cytokine interleukin-10 (IL-10) gene therapy on multiple organ injury (MOI) induced by a cecal ligation and puncture (CLP) model of sepsis in mice.

METHODS

Male Balb/c mice subjected to CLP were treated with either an hIL-10-carrying vector or an empty control vector. We assessed the degree of lung, liver, and kidney tissue destruction biochemically by measuring myeloperoxidase (MPO) and malondialdehyde (MDA) activity. Histologic assessments were based on neutrophil infiltration in lung and liver tissue. IL-10 protein expression was examined immunohistochemically, and ultrastructural changes in the liver were studied by transmission electron microscopy. We analyzed the expression of tumor necrosis factor-alpha (TNFalpha) mRNA by reverse transcription polymerase chain reaction 3, 8, and 24 hours after CLP in all organs.

RESULTS

Organ damage was significantly reduced by hIL-10 gene transfer, which was associated at the tissue level with reduced MPO activity in the liver, lung, and kidney and decreased leukocyte sequestration and MDA formation in the lung. The liver MDA was not significantly higher in the hIL-10 gene therapy group than in the controls and seemed not to be affected by hIL-10 gene transfer. The reduced portal tract neutrophilic infiltration and preserved ultrastructure of the hepatocytes also showed that tissue function was not impaired. The lung and kidney TNFalpha mRNA expression was suppressed markedly in the hIL-10 gene therapy group, but liver TNFalpha mRNA expression varied over time.

CONCLUSIONS

These findings showed that IL-10 gene therapy significantly attenuated sepsis-induced MOI.

Hepatic effects of influxed endothelin-1 from portal vein: in situ portal vein infusion model using dogs

BACKGROUND/PURPOSE

Endothelin-1 is a potent vasoconstrictor formed by vascular endothelium. This study was designed to investigate the hepatic effect of endothelin-1 produced by portal vascular endothelium.

METHODS

Portal venous pressure, portal venous flow, hepatic arterial flow, tissue blood flow, and tissue oxygen pressure were measured during portal vein endothelin-1 infusion in dogs at rates of 1.0 to 5.0 ng/kg per minute. Sinusoidal width during maximal infusion was determined morphometrically. Serum concentrations of mitochondrial glutamic oxaloacetic transaminase and endothelin-1 in portal and hepatic venous blood were also measured.

RESULTS

Intraportal endothelin-1 infusion dose-dependently increased portal venous pressure and reduced portal venous and hepatic arterial blood flow. Tissue blood flow and oxygen pressure also decreased. Endothelin-1 also significantly increased serum mitochondrial glutamic oxaloacetic transaminase and constricted hepatic sinusoids. These changes reversed after completion of infusion.

CONCLUSIONS

Intraportal endothelin-1 caused circulatory and histological changes in hepatic sinusoids that may suggest the role of endothelin-1 formed by portal venous bed epithelium.

Medroxyprogesterone acetate attenuates long-term effects of 17beta-estradiol in coronary arteries from hyperlipidemic rabbits

OBJECTIVE

The progestin component in hormone replacement treatment may oppose the effects of estrogen on vascular function. This study examined the effect of long-term treatment with 17beta-estradiol (E(2)) alone and in combination with two progestins on K(+) and Ca(2+)-mediated mechanisms in coronary arteries.

METHODS

Watanabe heritable hyperlipidemic rabbits were treated orally with either E(2) (4 mg/day), medroxyprogesterone acetate (MPA) (10 mg/day), norethindrone acetate (NETA) (2 mg/day), E(2)+MPA, E(2)+NETA, or placebo for 16 weeks (n=10 in each group). Coronary arteries were used for mRNA and myograph studies.

RESULTS

E(2) increased vasodilatation induced by sodium nitroprusside and decreased vasocontraction induced by potassium. The first but not the latter response was opposed by MPA. The combination of MPA and E(2), but neither compound alone enhanced nimodipine-induced vasodilatation and increased the expression of L-type voltage-gated Ca(2+) channel mRNA. NETA had no opposing effects. Hormone treatment did not affect large-conductance Ca(2+) activated or ATP-sensitive K(+) channels or cGMP-dependent protein kinase mRNA expression. Hyperlipidemia had no effect on vascular reactivity.

CONCLUSION

When E(2) is administered with MPA, effects of E(2) on nitric oxide and Ca(2+)-mediated vascular reactivity in rabbit coronary arteries are modulated. The results suggest that the progestin component in hormone replacement treatment may interfere with the supposed beneficial vascular effects of estrogen.

Effects of estradiol on phenylephrine contractility associated with intracellular calcium release in rat aorta

The ability of estradiol to affect phenylephrine-induced contraction and the subsequent increase in resting tone, associated with capacitative Ca(2+) entry across the plasma membrane, was evaluated in rat aortic rings incubated in Ca(2+)-free solution. The incubation with estradiol (1-100 nM, 5 min) inhibited both the phenylephrine-induced contraction and the IRT. Neither cycloheximide (1 microM; inhibitor of protein synthesis) nor tamoxifen (1 microM; blocker of estrogenic receptors) modified the effects of estradiol. Estradiol (100 microM) also blocked the contractile response to serotonin (10 microM) but not to caffeine (10 mM). In addition, estradiol (100 microM) inhibited the contractile responses to cyclopiazonic acid (1 microM; selective Ca(2+)-ATPase inhibitor) associated with capacitative Ca(2+) influx through non-L-type Ca(2+) channels. Finally, estradiol inhibited the Ca(2+)-induced increases in intracellular free Ca(2+) (after pretreatment with phenylephrine) in cultured rat aorta smooth muscle cells incubated in Ca(2+)-free solution. In conclusion, estradiol interfered in a concentration-dependent manner with Ca(2+)-dependent contractile effects mediated by the stimuli of alpha(1)-adrenergic and serotonergic receptors and inhibited the capacitative Ca(2+) influx through both L-type and non-L-type Ca(2+) channels. Such effects are in essence nongenomic and not mediated by the intracellular estrogenic receptor.

Ontogeny and pathway of formation of 5alpha-androstane-3alpha,17beta-diol in the testes of the immature brushtail possum Trichosurus vulpecula

The testicular androgen 5alpha;-androstane-3alpha,17beta-diol (androstanediol) mediates virilisation in pouch young of a marsupial, the tammar wallaby, and is the principal androgen formed in immature rodent testes. To chart the pattern of androstanediol formation in another marsupial species, the testes or fragments of testes from brushtail possums (Trichosurus vulpecula) that spanned the age range from early pouch young to mature adults were incubated with (3)H-progesterone and the products were identified by high-performance liquid chromatography. The only 19-carbon steroids identified in pouch young and adult testes were the Delta(4)-3-keto-steroids testosterone and androstenedione. However, androstanediol and another 5alpha-reduced androgen (androsterone) were synthesised by testes from Day 87-200 males and these appeared to be formed from the 5alpha-reduction and 3-keto reduction of testosterone and androstenedione. In the prostate and glans penis of the immature male, (3)H-androstanediol was converted to dihydrotestosterone. We conclude that the timing of androstanediol formation in the possum testis resembles the process in rodents rather than in the tammar wallaby and that any androstanediol in the circulation probably acts in target tissues via conversion to dihydrotestosterone.

Attenuation of acute phase shear stress by somatostatin improves small-for-size liver graft survival

The major concern of living donor liver transplantation is small-for-size graft injury at the early phase after transplantation. Novel therapeutic strategies should be developed. To investigate the protective effect of somatostatin related to hemodynamic stress on small-for-size liver graft injury, we applied a treatment regimen of low-dose somatostatin in a rat orthotopic liver transplantation model using small-for-size grafts (median, 38.7%; range, 35-42%). Somatostatin was given at 5 minutes before total hepatectomy and immediately after reperfusion in the recipient (20 microg/kg). Graft survival, portal hemodynamics, intragraft gene expression and hepatic ultrastructural changes were compared between the rats with or without somatostatin treatment. Seven-day graft survival rates in the somatostatin treatment group were significantly improved compared to the control group (66.7% vs. 16.7%, P = 0.036). In the treatment group, portal pressure and hepatic surface blood flow were significantly decreased within the first 30 minutes after reperfusion, whereas in the control group, transient portal hypertension and excessive hepatic blood flow were observed. Intragraft expression (both messenger RNA and protein) of endothelin-1 was significantly downregulated accompanied with upregulation of heme oxygenase-1 and A20. Better preservation of liver function was found in the treatment group. Hepatic ultrastructure, especially the integrity of sinusoids, was well protected in the treatment group. In conclusion, low-dose somatostatin rescues small-for-size grafts from acute phase injury in liver transplantation by attenuation of acute-phase shear stress that resulted from transient portal hypertension.

Modulation of mitochondrial Ca(2+) uptake by estrogen receptor agonists and antagonists

Ca(2+) uptake by mitochondria is a key element in the control of cellular Ca(2+) homeostasis and Ca(2+)-dependent phenomena. It has been known for many years that this Ca(2+) uptake is mediated by the mitochondrial Ca(2+) uniporter, a specific Ca(2+) channel of the inner mitochondrial membrane. We have shown previously that this channel is strongly activated by a series of natural phytoestrogenic flavonoids. We show here that several agonists and antagonists of estrogen receptors (ERs) also modulate the activity of the uniporter. The specific alpha-ER agonist 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT) was the strongest activator, increasing the rate of mitochondrial Ca(2+) uptake in permeabilized HeLa cells by 10-fold at 2 microM. Consistently, PPT largely increased the histamine-induced mitochondrial [Ca(2+)] peak and reduced the cytosolic one. Diethylstilbestrol and 17-beta-estradiol (but not 17-alpha-estradiol) were active at pharmacological concentrations while the beta-estrogen-receptor agonist 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) was little effective. The ER modulators tamoxifen and 4-hydroxy-tamoxifen inhibited mitochondrial Ca(2+) uptake (IC(50) 2.5+/-1.5 and 2.5+/-1.4 microM, mean+/-s.d., respectively) both in the presence and in the absence of PPT, but raloxifene and the pure estrogen antagonist ICI 182,780 produced no effect. Activation by PPT was immediate and inhibition by tamoxifen or 4-hydroxy-tamoxifen required only 5 min to reach maximum. Tamoxifen did not modify mitochondrial membrane potential and PPT induced a slow mitochondrial depolarization at higher concentrations than those required to activate mitochondrial Ca(2+) uptake. These results suggest that some kind of ER or related protein located in mitochondria controls the activity of the Ca(2+) uniporter by a nongenomic mechanism. This novel mechanism of action of estrogen agonists and antagonists can provide a new interpretation for several previously reported effects of these compounds.

Portal hypertension: from pathophysiology to clinical practice

Portal hypertension (PHT) is responsible for the more severe and often lethal complications of cirrhosis such as bleeding oesophageal varices, ascites, renal dysfunction and hepatic encephalopathy. Because of the combined impact of these complications, PHT remains the most important cause of morbidity and mortality in patients with cirrhosis. Over the years, it has become clear that a decrease in portal pressure is not only protective against the risk of variceal (re)bleeding but is also associated with a lower long-term risk of developing complications and an improved long-term survival. A milestone in therapy was the introduction of non-selective beta-blockers for the prevention of bleeding and rebleeding of gastro-esophageal varices. However, in practice, less than half the patients under beta-blockade are protected from these risks, supporting the overall demand for innovation and expansion of our therapeutic armamentarium. Recent advances in the knowledge of the pathophysiology of cirrhotic PHT have directed future therapy towards the increased intrahepatic vascular resistance, which, in part, is determined by an increased hepatic vascular tone. This increased vasculogenic component provides the rationale for the potential use of therapies aimed at increasing intrahepatic vasorelaxing capacity via gene therapy, liver-selective nitric oxide donors and statines on the one hand, and at antagonizing excessive intrahepatic vasoconstrictor force through the use of endothelin antagonists, angiotensin blockers, alpha(1) adrenergic antagonists or combined alpha(1)- and non-selective beta-blockers or somatostatin analogues on the other. The focus of this review is to give an update on the pathophysiology of PHT in order to elucidate these potential novel strategies subsequently.

Estrogen-induced contraction of coronary arteries is mediated by superoxide generated in vascular smooth muscle

Although previous studies demonstrated beneficial effects of estrogen on cardiovascular function, the Women's Health Initiative has reported an increased incidence of coronary heart disease and stroke in postmenopausal women taking hormone replacement therapy. The objective of the present study was to identify a molecular mechanism whereby estrogen, a vasodilatory hormone, could possibly increase the risk of cardiovascular disease. Isometric contractile force recordings were performed on endothelium-denuded porcine coronary arteries, whereas molecular and fluorescence studies identified estrogen signaling molecules in coronary smooth muscle. Estrogen (1-1,000 nM) relaxed arteries in an endothelium-independent fashion; however, when arteries were pretreated with agents to uncouple nitric oxide (NO) production from NO synthase (NOS), estrogen contracted coronary arteries with an EC(50) of 7.3 +/- 4 nM. Estrogen-induced contraction was attenuated by reducing superoxide (O(2)(-)). Estrogen-stimulated O(2)(-) production was detected in NOS-uncoupled coronary myocytes. Interestingly, only the type 1 neuronal NOS isoform (nNOS) was detected in myocytes, making this protein a likely target mediating both estrogen-induced relaxation and contraction of endothelium-denuded coronary arteries. Estrogen-induced contraction was completely inhibited by 1 muM nifedipine or 10 muM indomethacin, indicating involvement of dihydropyridine-sensitive calcium channels and contractile prostaglandins. We propose that a single molecular mechanism can mediate the dual and opposite effect of estrogen on coronary arteries: by stimulating type 1 nNOS in coronary arteries, estrogen produces either vasodilation via NO or vasoconstriction via O(2)(-).

The endothelin/nitric oxide balance determines small-for-size liver injury after reduced-size rat liver transplantation

Small-for-size (SFS) liver graft injury is probably related to microcirculatory disorders due to an imbalance of vasoconstricting, e.g. endothelin (ET)-1, and vasorelaxing mediators, e.g. nitric oxide (NO). We studied the role of ET-1/NO balance and the effect of an endothelin A receptor (ETAR) antagonist on SFS injury after liver resection and reduced-size liver transplantation (RSLT). One hundred twenty-six Lewis rats were divided into five groups: (I) 70% liver resection, (II) 70% liver resection treated with the ETAR antagonist LU 135252 (1 mg/kg b.w. i.v.), (III) RSLT (30% residual liver volume), (IV) RSLT treated with the ETAR antagonist, (V) sham operation. Liver microcirculation was measured by intravital microscopy. ET-1, ETAR, endothelial NO-synthase (eNOS), activation of Kupffer cells (KCs) and parenchymal injury were studied by immunohistology. Survival and liver function were followed up to 14 days. RSLT led to increased ET-1, ETAR and decreased eNOS protein expression, accompanied by activation of KC, reduced perfusion rate, vasoconstriction and elevated sinusoidal blood flow, as well as hepatocellular damage, impaired liver function and impaired survival. ETAR blockade (groups II + IV) improved the ET-1/NO balance, attenuated microcirculatory disorders and improved hepatocellular apoptosis and liver function. Microcirculatory disorders related to an ET-1/NO imbalance may contribute to SFS liver injury. Maintenance of ET-1/NO balance by blocking ETAR reduces SFS injury by protecting liver microcirculation, thus reducing hepatocellular damage.

Evidence that 17alpha-estradiol is biologically active in the uterine tissue: antiuterotonic and antiuterotrophic action

BACKGROUND

17alpha-Estradiol has been considered as the hormonally inactive isomer of 17beta-estradiol. Recently, nongenomic (smooth muscle relaxation) and genomic (light estrogenic activity) effects of 17alpha-estradiol have been reported, but no reports have yet determined its possible antiestrogenic activity. Therefore, this study investigated: the nongenomic action of 17alpha-estradiol on uterine contractile activity and its potential agonist-antagonist activity on uterine growth.

METHODS

Uterine rings from rats were isometrically recorded. Different concentrations (0.2-200 microM) of 17alpha-estradiol were tested on spontaneous contraction and equimolarly compared with 17beta-estradiol. To examine the mechanism of 17alpha-estradiol action, its effect was studied in presence of beta2-antagonist (propranolol), antiestrogens (tamoxifen and ICI 182,780) or inhibitors of protein synthesis (cycloheximide) and transcription (actinomycin D). Moreover, contractions induced by high potassium (KCl) solution or calcium in depolarized tissues by KCl-calcium free solution were exposed to 17alpha-estradiol. Collaterally, we performed an uterotrophic assay in adult ovariectomized rats measuring the uterine wet weight. The administration for three days of 0.3 microM/day/Kg 17beta-estradiol was equimolarly compared with the response produced by 17alpha-estradiol. Antiuterotrophic activity was assayed by administration of 0.3 microM/day/Kg 17beta-estradiol and various doses ratios (1:1, 1:3, 1:5, and 1:100) of 17alpha-estradiol.

RESULTS

The estradiol isomers elicited an immediate relaxation, concentration-dependent and reversible on spontaneous contraction. 17alpha-Estradiol presented lower potency than 17beta-estradiol although it did not antagonize 17beta-estradiol-induced relaxation. Relaxation to 17alpha-estradiol was not inhibited by propranolol, tamoxifen, ICI 182,780, cycloheximide or actinomycin D. The KCl contractions were also sensitive to 17alpha-estradiol-induced relaxation and calcium contractions in depolarized tissues were markedly prevented by 17alpha-estradiol, implying a reduction of extracellular calcium influx through voltage-operated calcium channels (VOCCs). Uterotrophic assay detected significant increase in uterine weight using 17alpha-estradiol, which was significantly minor as compared with 17beta-estradiol. 17alpha-Estradiol, at all doses ratios, significantly antagonized the hypertrophic response of 17beta-estradiol.

CONCLUSION

17alpha-Estradiol induces a relaxing effect, which may be independent of the classical estrogen receptor, nongenomic action, apparently mediated by inactivation of VOCCs. 17alpha-Estradiol is also a weak estrogen agonist (uterotrophic response); likewise, 17alpha-estradiol may act as an antiestrogen (antiuterotrophic response). The overall data document a nongenomic relaxing action and a novel antiestrogenic action of 17alpha-estradiol, which are relevant in estrogen-mediated uterine physiology.

Effect of estrogen therapy on cerebral arteries during stroke in female rats

OBJECTIVE

To investigate the effect of estrogen therapy on the structural and functional properties of the middle cerebral artery during ischemia and reperfusion.

DESIGN

Ovariectomized (OVX; n = 8) and ovariectomized with estrogen therapy (OVX+EST; n = 8) female Sprague-Dawley rats were exposed to 1 hour of ischemia using a model of temporary focal ischemia of the middle cerebral artery with 24 hours of reperfusion and compared to sham controls (CTL; n = 8). After occlusion and reperfusion, right middle cerebral arteries were removed from the brain and mounted on glass cannulas in a chamber that allowed for control over transmural pressure and measurement of lumen diameter. Lumen diameter was measured in response to increased transmural pressure (myogenic tone) as well as response to nitro-L-arginine, serotonin, and nifedipine. Cerebrovascular reactivity was compared to other stroke outcome measures, including infarct volume (%) and neurologic deficit.

RESULTS

Serum estrogen was increased in OVX+EST rats (60.5 +/- 18.2 pg/mL) compared to OVX (0.2 +/- 0.2 pg/mL P < 0.05 vs OVX+EST) and CTL animals (1.3 +/- 1.0 pg/mL P > 0.05 vs OVX). OVX showed significantly less myogenic tone at 75 mm Hg (13.8 +/- 3.6%, P < 0.05 vs CTL) than CTL (29.8 +/- 4.7%) that was partially restored by estrogen therapy (21.2 +/- 4.5; P > 0.05). At serotonin concentrations of 10(-7) M, 3 x 10(-7) M, and 10(-6) M, the vessels from ischemic OVX rats showed significantly greater constriction (20.9 +/- 2.1%, 35.0 +/- 3.9%, and 39.4 +/- 3.4%, respectively) compared to nonischemic CTL rats (6.3 +/- 1.1%, 11.3 +/- 1.8%, and 16.8 +/- 2.5%, respectively P < 0.05). Estrogen therapy resulted in intermediate responses (18.2 +/- 5.3%, 25.2 +/- 6.6%, and 28.2 +/- 6.5%, respectively) that were not significantly different from the other groups. In addition, ischemia resulted in significantly greater dilation in response to 0.01 microM nifedipine in vessels from OVX animals (51.1 +/- 8.0%) compared to nonischemic CTL (18.0 +/- 3.8%; P < 0.05) and estrogen therapy resulted in an intermediate response (38.0 +/- 10.6; P > 0.05). Both reactivity to nitro-L-arginine and passive distensibility were not different among groups. There were no differences in percent infarct or neurologic deficit between ischemic groups.

CONCLUSIONS

The influence of ischemia and reperfusion on vessel function was more dominant than that of estrogen therapy. However, estrogen therapy seemed to partially restore vessel function to similar levels as nonischemic vessels.

17beta-estradiol attenuates alpha, beta-meATP-induced currents in rat dorsal root ganglion neurons

The effects of 17beta-estradiol on the alpha,beta-me ATP-induced currents were studied on dorsal root ganglion (DRG) neurons using whole-cell recording technique. Three types of currents (transient, sustained or biphasic) were evoked by alpha,beta-me ATP in acutely dissociated DRG neurons. When neurons were pre-incubated with 17beta-estradiol (10-1000 nM) for 4 min, an inhibition of the transient current and the transient component of the biphasic current was observed. In contrast, 17beta-estradiol did not have any significant effect on the sustained current evoked by alpha,beta-meATP. The inhibitory effects were concentration-dependent, reversible and could be blocked by the estradiol receptor inhibitor, ICI 182,780 (1 microM). However, bovine serum albumin-conjugated 17beta-estradiol (17beta-estradiol-BSA, 10 nM) failed to mimic the effects of 17beta-estradiol. 17alpha-estradiol, the inactive isoform, did not have significant effects on alphabeta-meATP-induced currents, either. Sustained currents induced by ATP (100 microM) in nodose ganglion (NG), superior cervical ganglion (SCG) and otic ganglion (OTG) neurons were not affected by 17beta-estradiol. These results suggest that the female gonadal hormone, 17beta-estradiol, might participate in control of pain by modulating P2X3 receptor-mediated events in sensory neurons.

N-Acetyl-Cysteine Attenuates Endotoxin-Induced Adhesion Molecule Expression in Human Whole Blood

Leukocyte adhesion to endothelial cells plays a pivotal role in the early stage of endotoxin shock. The attenuation of the leukocyte response to endotoxin may contribute to the prevention of further organ dysfunction. Recent evidence implies that N-acetyl-cysteine (NAC) attenuates endotoxin-induced pathophysiological changes. We investigated the effect of NAC on the expression of CD11b and CD62L in endotoxin-stimulated human whole blood. NAC (>10 mM) significantly inhibited the lipopolysaccharide (LPS)-induced upregulation of CD11b in a concentration-dependent manner. However, NAC did not affect the LPS-induced downregulation of CD62L. We also analyzed the effect of NAC on interleukin-8 (IL-8)-induced expression of CD11b in human whole blood. IL-8 (10 ng/mL) significantly upregulated the expression of CD11b, and the IL-8-induced upregulation was significantly attenuated by NAC (>10 mM) in a dose-dependent manner. We conclude that NAC attenuates the increased expression of CD11b in either LPS or IL-8-stimulated human whole blood.

Relaxations to oestrogen receptor subtype selective agonists in rat and mouse arteries

It has been recently reported that the oestrogen receptor alpha agonist PPT (4,4',4"-(4-propyl-[1H]-pyrazole-1,3,5-triyl) tris-phenol) is more potent than the oestrogen receptor beta agonist DPN (2,3-bis(4-hydroxyphenyl)-propionitrile) at producing relaxations in rat mesenteric artery. We have investigated the relaxant actions of PPT and DPN in rat and mouse aorta and mesenteric artery. In rat aortic rings contracted with KCl (40 mM), the oestrogen receptor beta agonist DPN produced significantly greater relaxations than the oestrogen receptor alpha agonist PPT. In wild-type (WT) mouse aorta, the same result was found, but in WT mouse mesenteric artery, as in rat mesenteric artery, DPN was significantly less potent than PPT in females but had similar potency to PPT in males. Relaxations to DPN also occurred in aorta from nitric oxide synthase-3-knockout (NOS-3-KO) mice, and in denuded aorta from both mouse and rat. Hence, in the mouse mesenteric artery, as in the rat mesenteric artery, PPT is at least as potent as DPN at producing relaxations; however, DPN was much more potent than PPT in the rat and mouse aorta. Effects of oestrogen receptor subtype selective agonists are tissue dependent. In addition, actions are largely endothelium-independent.

Kupffer Cell Ablation Improves Hepatic Microcirculation after Trauma and Sepsis

BACKGROUND

Macrophages undergo maladaptive alterations after trauma. In this study, we assessed the role of Kupffer cells in hepatic microcirculatory response to endothelin-1 (ET-1) after femur fracture (FFx) and cecal ligation and puncture (CLP).

METHODS

Sprague-Dawley rats (200-300 g) underwent sham, FFx, CLP, or FFx + CLP. To ablate Kupffer cells, group 1 animals were treated with gadolinium chloride, and group 2 animals received saline. Hepatic microcirculation was assessed by intravital microscopy. Liver mitochondrial redox state and tissue oxygen (tPo2) were determined by NADH and ruthenium fluorescence, respectively. Liver damage was estimated by alanine aminotransferase levels. Differences were assessed using analysis of variance followed by Student-Newman-Keuls post hoc test.

RESULTS

After 10 minutes of ET-1, CLP and FFx + CLP caused significant reduction in hepatic perfusion index (2.5-fold and 5-fold vs. sham, p < 0.05, respectively), redox state (36% and 45% vs. sham, p < 0.01, respectively), tPo2 (10% and 12% vs. sham, p < 0.05, respectively), and more liver damage compared with sham and FFx-treated animals. Kupffer cell depletion restored microcirculation, redox state, and tPo2 and abrogated hepatocellular damage.

CONCLUSION

Kupffer cells contribute directly to hepatic microcirculatory dysfunction and liver injury after inflammatory stress. Furthermore, Kupffer cell depletion ameliorates the microcirculatory perturbations of trauma and sepsis. Thus, modulation of Kupffer cell response may prove beneficial.

Acute relaxation of mouse duodenum [correction of duodenun] by estrogens. Evidence for an estrogen receptor-independent modulation of muscle excitability

17-beta-Estradiol, the stereoisomer 17-alpha-estradiol and the synthetic estrogen diethylstilbestrol (DES), all caused a rapid (<3 min) dose-dependent reversible relaxation of mouse duodenal spontaneous activity, reduced basal tone and depressed the responses to CaCl(2) and KCl. The steroidal antiestrogen 7alpha-[9-[(4,4,5,5,5,-pentafluoropenty)sulphinyl]nonyl]-estra-1,3,5(19)-triene-3,17beta-diol (ICI182,780) failed to either mimic or prevent the effect of 17-beta-estradiol. The effect of estrogens was unrelated to activation of nitric oxide (NO), mitogen-activated protein kinase (MAPK), protein kinase A (PKA), protein kinase G (PKG) or protein kinase C (PKC). Estrogen-induced relaxation was partially reversed by 1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]-pyridine-3-carboxilic acid methyl ester (BAY-K8644), depolarization, or by application of tetraethylammonium or 4-aminopyridine, but not by glibenclamide, apamin, charybdotoxin, paxilline or verruculogen. The effects of BAY-K8644 and K(+) channel blockers were synergistic, and allowed relaxed tissues to recover spontaneous activity and basal tone. We hypothesize that the rapid non-genomic spasmolytic effect of estrogens on mouse duodenal muscle might be triggered by an estrogen-receptor-independent mechanism likely involving activation of tetraethylamonium- and 4-aminopyridine-sensitive K(+) channels and inhibition of L-type Ca2(+) channels on the smooth muscle cells.

The effects of N-acetylcysteine on oxidative stress in organophosphate poisoning model

Organophosphate compounds act by irreversible inhibition of cholinesterase. In addition to their muscarinic, nicotinic, and central nervous system effects, some organophosphate insecticides cause oxidative stress by increasing lipid peroxidation in erythrocytes and by increasing levels of the enzymes superoxide dismutase and catalase. In this study, the effects of an antioxidant, N-acetylcysteine (NAC), in organophosphate poisoning were investigated. After obtaining Animal Ethics Committee approval, 16 male Wistar rats were divided into 2 groups. Following anesthesia, rats were tracheostomized and mechanically ventilated. Invasive hemodynamic monitoring was begun and all rats were injected with 70 mg/kg of dichlorvos (DDVP) intraperitoneally. The rats in group 1 received placebo intravenous 0.9% NaCl and the rats in group 2 received 150 mg/kg intravenous NAC. Blood samples were obtained before injection of DDVP and 60 minutes after injection to determine levels of malondialdehyde, superoxide dismutase, and catalase. Hemodynamic data and biochemistry test results were compared by analysis of variance and Wilcoxon test. P<.05 was regarded as statistically significant. Superoxide dismutase and malondialdehyde levels were significantly increased in group 1 while no difference was observed in group 2. It was concluded that organophosphate compounds might cause oxidative stress by interfering with antioxidant defense mechanisms in erythrocytes and that NAC might prevent increased lipid peroxidation. In addition to classic treatments, drugs with antioxidant effects might therefore be promising in the treatment of organophosphate poisoning.

FTY720 attenuates hepatic ischemia-reperfusion injury in normal and cirrhotic livers

Hepatic ischemia-reperfusion injury is an inevitable consequence during liver surgery. The outcome is particularly poor in cirrhotic livers, which are more prone to hepatic ischemia-reperfusion injury. We aim to study whether FTY720 could attenuate hepatic ischemia-reperfusion injury both in normal and in cirrhotic livers. We applied a 70% liver-ischemia (60 min) model in rats with normal or cirrhotic livers. FTY720 was given 20 min before ischemia and 10 min before reperfusion (1 mg/kg, i.v.). Liver tissues and blood were sampled at 20 min, 60 min, 90 min, 6 h and 24 h after reperfusion for detection of MAPK-Egr-1, Akt pathways and caspase cascade. Hepatic ultrastructure and apoptosis were also compared. FTY720 significantly improved liver function in the rats with normal and cirrhotic livers. Akt pathway was activated at 6 and 24 h after reperfusion. FTY720 significantly down-regulated Egr-1, ET-1, iNOS and MIP-2 accompanied with up-regulation of A20, IL-10, HO-1 and Hsp70. MAPK (Raf-MEK-Erk) pathway was down-regulated. Hepatic ultrastructure was well maintained and fewer apoptotic liver cells were found in the FTY720 groups. In conclusion, FTY720 attenuates ischemia-reperfusion injury in both normal and cirrhotic livers by activation of cell survival Akt signaling and down-regulation of Egr-1 via Raf-MEK-Erk pathway.

Augmented sympathetic vasoconstriction in exercising forearms of postmenopausal women is reversed by oestrogen therapy

Sympathetic vasoconstriction is normally attenuated in exercising muscles of young men and women. Recent evidence indicates that such modulation, termed functional sympatholysis, may be impaired in older men. Whether a similar impairment occurs in older women, and what role oestrogen deficiency might play in this impairment, are not known. Based on the strong positive correlation between circulating oestrogen levels and functional sympatholysis previously reported in female rats, we hypothesized that sympatholysis would be impaired in oestrogen-deficient postmenopausal women, and that this impairment would be reversed by oestrogen replacement. To test these hypotheses, we measured vasoconstrictor responses in the forearms of pre- and postmenopausal women using near infrared spectroscopy to detect decreases in muscle oxygenation in response to reflex activation of sympathetic nerves evoked by lower body negative pressure (LBNP). In eight premenopausal women, LBNP decreased muscle oxygenation by 20 +/- 1% in resting forearm, but only by 3 +/- 2% in exercising forearm (P < 0.05). In contrast, in eight postmenopausal women, LBNP decreased muscle oxygenation by 15 +/- 3% in resting forearm, and by 12 +/- 4% in exercising forearm (P > 0.05). After 1 month of transdermal oestradiol replacement in these women, the normal effect of exercise to blunt sympathetic vasoconstriction was restored (rest, -19 +/- 3%; exercise, -2 +/- 3%; P < 0.05). These data indicate that functional sympatholysis is impaired in oestrogen-deficient postmenopausal women. The effect of short-term unopposed oestrogen replacement to correct this impairment implicates a role for oestrogen in the sympathetic neural control of muscle haemodynamics during exercise.

The attenuation of hepatic microcirculatory alterations by exogenous substitution of nitric oxide by s-nitroso-human albumin after hemorrhagic shock in the rat

Hepatic microcirculatory disorders such as narrowing of sinusoids after hemorrhagic shock play a major role in the pathogenesis of organ failure. It is known that the balance of vasoactive mediators such as endothelin and nitric oxide (NO) regulate microvascular perfusion, including the diameter of hepatic sinusoids. The present study was designed to evaluate the role of exogenous substitution of NO by S-nitroso-albumin (S-NO-HSA) in the prevention of pathophysiological alterations of hepatic microcirculation. Anesthetized Sprague-Dawley rats were instrumented for invasive hemodynamic monitoring. Hemorrhagic shock was induced by bleeding to a mean arterial pressure (MAP) of 40 mmHg and was maintained for 60 min. Thereafter, the animals were resuscitated with shed blood and Ringer's solution. During the first hour of resuscitation, S-NO-HSA or pure HSA was infused continuously (10 micromol/kg/h) and hepatic microcirculation was detected by intravital epifluorescence microscopy either 5 or 24 h after the insult. Results were compared with a sham-treated group (n = 6-8 per group). Shock-induced microcirculatory narrowing of sinusoids was significantly reduced in the S-NO-HSA group compared with the HSA group both at 5 and 24 h (HSA: 9.3 +/- 0.2 microm; S-NO-HSA: 12.1 +/- 0.2 microm, P < 0.05). Sinusoidal perfusion was significantly higher in the S-NO-HSA group than in the HSA group (HSA: 50,934 +/- 1,382 microm3/s; S-NO-HSA: 78,120 +/- 2,348 microm3/s, P < 0.05). Reversible leukocyte adhesion to sinusoidal endothelium, an indicator of the inflammatory response, was significantly reduced in the S-NO-HAS-treated group. The findings of this study in a rat model of hemorrhagic shock suggest that NO substitution by S-NO-HSA during resuscitation attenuates both early and late hepatic microcirculatory disturbances as well as the increase in leukocyte adherence.

Effect of Trolox on altered vasoregulatory gene expression in hepatic ischemia/reperfusion

This study was designed to investigate the effect of Trolox, a hydrophilic analogue of vitamin E, on the alteration of vasoregulatory gene expression during hepatic ischemia and reperfusion (I/R). Rats were subjected to 60 min of hepatic ischemia in vivo. The rats were treated intravenously with Trolox (2.5 mg/kg) or the vehicle as a control 5 min before reperfusion. Liver samples were obtained 5 h after reperfusion for a RT-PCR analysis on the mRNA for the genes of interest. These mRNA peptides are endothelin-1 (ET-1), potent vasoconstrictor peptide, its receptor ET(A) and ET(B), vasodilator endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), heme oxygenase-1 (HO-1), tumor necrosis factor-alpha (TNF-alpha) and cyclooxygenase-2 (COX-2). It was seen that serum alanine aminotransferase and lipid peroxidation levels were markedly increased after I/R and Trolox significantly suppressed this increase. In contrast, the glutathione concentration decreased in the I/R group, and this decrease was inhibited by Trolox. ET-1 mRNA expression was increased by I/R, an increase which was prevented by Trolox. The mRNA levels for ET(A) receptor was significantly decreased, whereas ET(B) receptor transcript increased in the I/R group. The increase in ET(A) was prevented by Trolox. The mRNA levels for iNOS and HO-1 significantly increased in the I/R group and Trolox attenuated this increase. There were no significant differences in eNOS mRNA expression among any of the experimental groups. The mRNA levels for COX-2 and TNF-alpha significantly increased in I/R group and Trolox also attenuated this increase. Our findings suggest that I/R induces an imbalanced hepatic vasoregulatory gene expression and Trolox ameliorates this change through its free radical scavenging activity.

Involvement of atrial natriuretic peptide in blood pressure reduction induced by estradiol in spontaneously hypertensive rats

The aim of the present study was to determine the involvement of atrial natriuretic peptide (ANP) in blood pressure (BP) alterations induced by estradiol treatment. Spontaneously hypertensive rats (SHR) and Wistar rats (WR) were ovariectomized and, after 3 weeks, were injected daily for 4 days with estradiol benzoate (E2; 5 microg/100 g/day) or a vehicle. One day after the last injection, the animals were decapitated, blood was collected, and both right and left atrial appendages were quickly removed for determination of ANP by radioimmunoassay (RIA), or used for ANP mRNA determination. Estradiol treatment induced a significant reduction of blood pressure in SHR, but not in WR. This reduction was correlated with the increase of plasma ANP levels that were significantly increased in E2-treated, compared with vehicle-treated, SHR. E2-treated SHR showed significant increases in ANP concentration in the right and left atria compared to the vehicle-treated animals. These observations were confirmed by ANP mRNA. In summary, the present study shows that short-term estradiol treatment reduces the blood pressure of ovariectomized SHR, but not of WR. This reduction was highly correlated with increased plasma estradiol and ANP levels. These results suggest that ANP is involved in mediating the effect of estradiol on blood pressure reduction.

Hepatic microvascular dysfunction during evolution of dietary steatohepatitis in mice

In alcoholic steatohepatitis, hepatic microvascular changes have pathogenic significance for hepatocellular function, perisinusoidal fibrosis, and portal hypertension. It is unclear whether similar changes occur in other forms of steatohepatitis. We therefore examined whether hepatic microvascular dysfunction occurs in fibrosing steatohepatitis induced by feeding mice a high-fat methionine- and choline-deficient (MCD) diet. Using in vivo microscopic--as well as histological and electron microscopic--methods, together with measurements of alanine aminotransferase (ALT), lipid content, and oxidative stress, hepatic microvascular structure and function were studied in relation to inflammatory and fibrotic changes during evolution of steatohepatitis. At 3 weeks of MCD diet intake, serum ALT was elevated and hepatic steatosis was pronounced. By 5 weeks, necroinflammatory change was noteworthy, and by 8 weeks perisinusoidal fibrosis was established. Compared with mice receiving the high-fat diet supplemented with methionine and choline (controls), levels of hepatic lipid and lipoperoxides were elevated at 3 weeks and beyond. The numbers of perfused sinusoids were significantly reduced at each time point. Enlarged, fat-laden hepatocytes together with perivascular fibrosis narrowed sinusoidal lumens, making vessels tortuous and impairing sinusoidal perfusion. At 3 and 5 weeks, MCD diet caused significant increases in phagocytic activity of macrophages in centrilobular regions. By 8 weeks, macrophage activity was less striking, but the number of leukocytes adherent to the sinusoidal lining had increased 5-fold compared with controls. In conclusion, these results are consistent with a dysfunctional hepatic microvasculature. Thus, microvascular changes may contribute to progressive liver injury in metabolic and toxic forms of steatohepatitis.

REMOTE TRAUMA SENSITIZES HEPATIC MICROCIRCULATION TO ENDOTHELIN VIA CAVEOLIN INHIBITION OF eNOS ACTIVITY

This study addresses the microvascular mechanisms by which a remote, mild stress such as blunt trauma sensitizes the liver to injury. Rats received closed femur fracture (FFx), and 24 h later livers were isolated and perfused at a similar starting flow rate for assessment of vascular response to endothelin-1 (ET-1). Sinusoidal volumetric flow (QS), red blood cell velocity (VRBC), and sinusoidal diameter (Ds) were determined by intravital microscopy. Baseline portal resistance in livers from FFx rats was not changed. The FFx group showed a lower baseline VRBC (322.9 +/- 26.4 and 207.3 +/- 17.2 microm/s in sham and FFx,) and QS (28.4 +/- 4.2 and 17.6 +/- 2.1 pL/s in sham and FFx, P < 0.05). ET-1 caused a decrease in the VRBC in sham but no change after FFx. In contrast, Ds was unchanged by ET-1 in sham but decreased in FFx (10.3 +/- 0.4 to 10.7 +/- 0.5 vs. 10.6 +/- 0.4 to 9.0 +/- 0.4 microm at 10 min in sham and FFx groups, P < 0.05). The overall result of these changes was a greater decrease in sinusoidal flow in FFx compared with sham. There was no significant change in mRNA for ET-1, endothelin A (ETA) receptor, or iNOS (inducible nitric oxide synthase) in FFx compared with sham. However, endothelin B (ETB) receptor mRNA and eNOS (endothelial nitric oxide synthase) mRNA were increased in the FFx group (ETB, 54.81 +/- 8.08 in sham vs. 83.28 +/- 8.19 in FFx; eNOS, 56.11 +/- 2.53 in sham vs. 83.31 +/- 5.51 in FFx; P < 0.05) while the levels of these proteins remained unchanged. Caveolin-1 (cav-1) protein levels were elevated in FFx, and coimmunoprecipitation with both ETB and eNOS showed increased associations with these proteins, suggesting a possible inactivation of eNOS. The eNOS activity was also blunted in FFx animals in the presence of increased cav-1 expression. Taken together, these results demonstrate that remote trauma sensitizes the liver to the sinusoidal constrictor effect of ET-1. We propose that this hyperresponsiveness occurs as a result of uncoupling of the ETB receptor from eNOS activity mediated by interaction of eNOS and possibly the ETB receptor with increased caveolin-1. This vascular sensitization that occurs after FFx may contribute to the exacerbation of injury during subsequent stresses.

FK 409 ameliorates small-for-size liver graft injury by attenuation of portal hypertension and down-regulation of Egr-1 pathway

OBJECTIVE

To investigate whether low-dose nitric oxide donor FK 409 could attenuate small-for-size graft injury in liver transplantation using small-for-size grafts.

SUMMARY BACKGROUND DATA

The major concern of live donor liver transplantation is small-for-size graft injury at the early phase after transplantation. Novel therapeutic strategies should be investigated.

METHODS

We employed a rat orthotopic liver transplantation model using small-for-size (40%) graft. FK 409 was given at 30 minutes before graft harvesting (2 mg/kg) to the donor and immediately after reperfusion (1 mg/kg) to the recipient (FK group). Graft survival, intragraft genes expression, portal hemodynamics, and hepatic ultrastructural changes were compared between the 2 groups.

RESULTS

Seven-day graft survival rates in the FK group were significantly improved compared with those of rats not receiving FK 409 (control group; 80% versus 28.6%, P = 0.018). In the FK group, portal pressure was significantly decreased within the first 60 minutes after reperfusion whereas in the control group, transient portal hypertension was observed. Intragraft expression (both mRNA and protein) of early growth response-1, endothelin-1, endothelin-1 receptor A, tumor necrosis factor-alpha, macrophage-inflammatory protein-2, and inducible nitric oxide synthase was significantly down-regulated accompanied with up-regulation of heme oxygenase-1, A20, interferon-gamma-inducible protein-10, and interleukin-10 during the first 24 hours after reperfusion. Hepatic ultrastructure, especially the integrity of sinusoids was well protected in the FK group.

CONCLUSIONS

Low-dose FK 409 rescues small-for-size grafts in liver transplantation by attenuation of portal hypertension and amelioration of acute phase inflammatory response by down-regulation of Egr-1, together with prior induction of heat shock proteins.

Endothelium-dependent and independent enhancement of vascular contractility in the ovariectomized rabbit

OBJECTIVE

Estrogen suppresses contractile response and increases vasodilator response, partly by modulating endothelial function. However, the effect of estrogen on the contractility of vascular smooth muscle remains to be elucidated. We investigated the effect of a long-term estrogen deficiency on vascular contractility and the Ca(2+) sensitivity of the contractile apparatus in arterial smooth muscle.

METHODS

Female rabbits were divided into the following three groups: control group, an ovariectomized group (OVX), and a group supplemented with 17beta-estradiol after ovariectomy (OVX+E2). Twelve weeks later, the mesenteric artery was isolated, and the vascular contractility was evaluated.

RESULTS

In OVX, the contractile responses to phenylephrine and 118 mM potassium were enhanced, and the basal release of nitric oxide decreased in the strips with endothelium compared with either OVX+E2 or control. An enhancement of contraction was also observed in the strips without endothelium. However, the extent of enhancement was smaller than that observed in the presence of endothelium. The simultaneous measurement of calcium ([Ca(2+)](i)) and tension revealed no significant difference in the [Ca(2+)](i) elevations induced by phenylephrine among the three groups. In the alpha-toxin permeabilized strips, the Ca(2+)-tension relationships obtained both with and without phenylephrine and guanosine triphosphate were similar among the three groups. No difference in the myosin expression and the histology of vascular tissue was observed among the three groups.

CONCLUSION

Long-term estrogen deficiency increased the vascular tone mainly by enhancing smooth muscle contractility. Endothelial dysfunction is considered to play a minor role in the augmentation of vascular tone.

Expression of hepatic vascular stress genes following ischemia/reperfusion and subsequent endotoxemia

Hepatic ischemia and reperfusion (I/R) predisposes the liver to secondary stresses such as endotoxemia, possibly via dysregulation of the hepatic microcirculation secondary to an imbalanced regulation of the vascular stress genes. In this study, the effect of hepatic I/R on the hepatic vasoregulatory gene expression in response to endotoxin was determined. Rats were subjected to 90 min of hepatic ischemia and 6 h of reperfusion. Lipopolysaccharide (LPS, 1 mg/kg) was injected intraperitoneally after reperfusion. Plasma and liver samples were obtained 6 h after reperfusion for serum aminotransferase assays and RT-PCR analysis of the mRNA for the genes of interest: endothelin-1 (ET-1), its receptors ET A and ET B, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), heme oxygenase-1 (HO-1), cyclooxygenase-2 (COX-2), and tumor necrosis factor-alpha (TNF-alpha). The activities of serum aminotransferases were significantly increased in the I/R group. This increase was markedly potentiated by LPS treatment. The ET-1 mRNA was increased by LPS alone, and this increase was significantly greater in both the I/R alone and I/R + LPS groups compared to the sham. There were no significant differences in ET A receptor mRNA levels among any of the experimental groups. ET B mRNA was increased by both LPS alone and I/R alone, with no significant difference between the I/R alone and I/R + LPS groups. The eNOS and HO-1 transcripts were increased by I/R alone and further increased by I/R + LPS. The iNOS mRNA levels were increased by I/R alone, but increased significantly more by both LPS alone and I/R + LPS compared to I/R alone. The TNF-alpha mRNA levels showed no change with I/R alone, but were increased by both LPS alone and I/R + LPS. The COX-2 expression was increased significantly by I/R alone and significantly more by I/R + LPS. Taken collectively, significantly greater induction of the vasodilator genes over the constriction forces was observed with I/R + LPS. These results may partly explain the increased susceptibility of ischemic livers to injury as a result of endotoxemia.

Improved Hepatic Perfusion After Iloprost Infusion in Patients with HCV Chronic Infection: A Pilot Study with Possible Therapeutic Implications

We performed a pilot study to evaluate whether portal flow volume (PFV) changed in subjects with chronic hepatitis C virus (HCV) infection with respect to control patients after infusion of iloprost, a prostacyclin analog. Six subjects with chronic HCV infection and arteriopathy of the lower limbs (CHCVIA) and 4 control patients affected only by HCV infection (CHCV) were studied with color Doppler sonography. CHCVIA patients were examined before and after 3 days of iloprost infusion, and CHCV patients were examined before and after 3 days with no treatment. In each patient, PFV was obtained after calculating portal flow velocity (PV), portal diameter, and portal vein cross-sectional area. The mean difference between basal and final values of the PFV of CHCVIA patients was significant (p = 0.03), as was the difference in the PFV (final values expressed as percent of basal values) in CHCVIA patients compared with those obtained in the CHCV patients (p = 0.01). We have observed significant improvement in hepatic perfusion in CHCVIA patients compared with CHCV patients after iloprost infusion. In light of these results, we suggest some possible therapeutic implications in patients with HCV infection. Further studies are necessary to confirm this hypothesis.

Vasodilator mRNA levels are increased in the livers of portal hypertensive NO-synthase 3-deficient mice

BACKGROUND/AIMS

Nitric oxide synthase (NOS) 3-deficient (NOS-3 KO) mice have an increased systemic arterial pressure but develop portal hypertension to the same extent as wildtype (WT) mice. We hypothesized that other vasodilators in the portal circulation compensate for the lack in NOS-3 activity. We used quantitative PCR as a screening method to identify mediators that possibly compensate for NOS-3 in NOS-3 KO mice.

METHODS

Mean arterial pressure (MAP) and portal venous pressure (PVP) were measured in the anaesthetized animal. mRNA levels in whole liver tissue were determined by quantitative RT-PCR.

RESULTS

NOS-3 KO mice had a significantly higher mean arterial pressure than WT mice, but portal venous pressure did not differ. Bile duct ligation (BDL) induced a drop in MAP and a rise in PVP in both groups. Bile duct ligation induced a significant increase in mRNA levels of the cannabinoid receptor (CB)-1, adrenomedullin and NOS-2 in the liver of NOS-3 KO and WT mice. Nitric oxide synthase-1 and NOS-3 mRNA levels were elevated in BDL WT mice compared with sham-operated WT mice. Higher mRNA levels of CB-1, NOS-1 and the adrenomedullin receptor were found in sham-operated NOS-3 KO mice compared with sham-operated WT mice.

CONCLUSIONS

We used quantitative PCR as a screening method to identify vasodilative mediators that might be involved in the compensation for the lack of NOS-3 activity in NOS-3 KO mice. Elevated mRNA levels in sham-operated NOS-3 KO mice compared with sham-operated WT mice were demonstrated for CB-1, NOS-1 and the adrenomedullin receptor.

Systemic, pulmonary, and hepatosplanchnic effects of N-acetylcysteine during long-term porcine endotoxemia

OBJECTIVE

Controversial data have been reported on the effects of N-acetylcysteine in patients with septic shock. We therefore investigated the systemic, pulmonary, and hepatosplanchnic hemodynamic, gas exchange, and metabolic effects of N-acetylcysteine during long-term, volume-resuscitated, hyperdynamic porcine endotoxemia, which mimics the features of hyperdynamic human sepsis.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Investigational animal laboratory.

SUBJECTS

Eighteen pigs were randomized to receive endotoxin alone (controls, n = 9) or endotoxin plus N-acetylcysteine (n = 9).

INTERVENTIONS

Anesthetized, mechanically ventilated, and instrumented animals received continuous intravenous endotoxin and were resuscitated with hydroxyethylstarch to keep mean arterial pressure >60 mm Hg. After 12 hrs of endotoxemia, they were randomized to receive either placebo or N-acetylcysteine (150 mg/kg loading dose over 1 hr followed by 20 mg.kg-1.hr-1 for 11 hrs).

MEASUREMENTS AND MAIN RESULTS

Before as well as 12, 18, and 24 hrs after starting the endotoxin infusion, systemic, pulmonary, and hepatosplanchnic hemodynamics, oxygen exchange, and metabolism as well as nitric oxide, glutathione, and 8-isoprostane concentrations were assessed. N-acetylcysteine failed to improve any of the variables of the systemic, pulmonary, or hepatosplanchnic hemodynamics, gas exchange, and metabolism. Although N-acetylcysteine significantly elevated glutathione concentration, it did not influence the 8-isoprostane concentrations and even further reduced hepatic venous pH.

CONCLUSIONS

Despite the increased glutathione concentration, N-acetylcysteine did not improve systemic, pulmonary, and hepatosplanchnic hemodynamics, oxygen exchange, and metabolism. When compared with previous reports in the literature, a different timing of N-acetylcysteine administration and/or an ongoing or even N-acetylcysteine-induced aggravation of oxidative stress may account for this result.

Gender, sex hormones, and vascular tone

The greater incidence of hypertension and coronary artery disease in men and postmenopausal women compared with premenopausal women has been related, in part, to gender differences in vascular tone and possible vascular protective effects of the female sex hormones estrogen and progesterone. However, vascular effects of the male sex hormone testosterone have also been suggested. Estrogen, progesterone, and testosterone receptors have been identified in blood vessels of human and other mammals and have been localized in the plasmalemma, cytosol, and nuclear compartments of various vascular cells, including the endothelium and the smooth muscle. The interaction of sex hormones with cytosolic/nuclear receptors triggers long-term genomic effects that could stimulate endothelial cell growth while inhibiting smooth muscle proliferation. Activation of plasmalemmal sex hormone receptors may trigger acute nongenomic responses that could stimulate endothelium-dependent mechanisms of vascular relaxation such as the nitric oxide-cGMP, prostacyclin-cAMP, and hyperpolarization pathways. Additional endothelium-independent effects of sex hormones may involve inhibition of the signaling mechanisms of vascular smooth muscle contraction such as intracellular Ca2+ concentration and protein kinase C. The sex hormone-induced stimulation of the endothelium-dependent mechanisms of vascular relaxation and inhibition of the mechanisms of vascular smooth muscle contraction may contribute to the gender differences in vascular tone and may represent potential beneficial vascular effects of hormone replacement therapy during natural and surgically induced deficiencies of gonadal hormones.

Role of kupffer cells in the vasoregulatory gene expression during hepatic ischemia/reperfusion

Hepatic microcirculatory failure is a major component of reperfusion injury in the liver. Recent data provided some evidence that endothelium-derived vasoconstrictors and vasodilators may be functionally important to the control of the total hepatic blood flow under these conditions of circulatory failure. Since Kupffer cells provide signals that regulate the hepatic response in ischemia/reperfusion (I/R), the aim of this study was to investigate the role of Kupffer cells in the I/R-induced imbalance of vasoregulatory gene expression. Rats were subjected to 60 min hepatic ischemia, followed by 5 h of reperfusion. The Kupffer cells were inactivated by gadolinium chloride (GdCl3, 7.5 mg/kg body weight, intravenously) 1 day prior to ischemia. Liver samples were obtained 5 hrs after reperfusion for RT-PCR analysis of the mRNA for genes of interest: endothelin-1 (ET-1), its receptors ETA and ETB, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1). ET-1 mRNA expression was increased by I/R. mRNA levels for ETA receptors showed no change, whereas ETB receptor transcripts increased in the I/R group. The increases in ET-1 and ETB mRNA were not prevented by the GdCl3 pretreatment. The mRNA levels for iNOS and eNOS significantly increased within the I/R group with no significant difference between the I/R group and the GdCl3-treated I/R group. HO-1 mRNA expression significantly increased in the I/R group and this increase was attenuated by GdCl3. In conclusion, we have demonstrated that an imbalance in hepatic vasoregulatory gene expression occurs during I/R. Our findings suggest that the activation of Kupffer cells is not required for I/R-induced hepatic microvascular dysfunction.

Age-related reduction in estrogen receptor-mediated mechanisms of vascular relaxation in female spontaneously hypertensive rats

Hypertension increases with aging, and changes in vascular estrogen receptors (ERs) may play a role in age-related hypertension in women. We tested whether age-related increases in blood pressure in female spontaneously hypertensive rats (SHRs) are associated with reduction in amount and/or vascular relaxation effects of estrogen and ER. Arterial pressure and plasma estradiol were measured in adult (12 weeks) and aging (16 months) female SHRs, and thoracic aorta was isolated for measurement of active stress, 45Ca2+ influx, and ERs. Arterial pressure was greater and plasma estradiol was less in aging females than in adult females. In aorta of adult females, Western blots revealed alpha- and beta-ERs that were slightly reduced in aging rats. In endothelium-intact vascular strips, phenylephrine (Phe; 10(-5) mol/L) caused greater active stress in aging rats (9.3+/-0.2) than in adult rats (6.2+/-0.3x10(4) N/m2). 17beta-estradiol (E2) caused relaxation of Phe contraction and stimulation of vascular nitrite/nitrate production, which was reduced in aging rats. In endothelium-denuded strips, E2 still caused relaxation of Phe contraction, which was smaller in aging rats than adult rats. KCl (51 mmol/L), which stimulates Ca2+ influx, produced greater active stress in aging rats (9.1+/-0.3) than in adult rats (5.9+/-0.2x10(4) N/m2). E2 caused relaxation of KCl contraction and inhibition of Phe- and KCl-induced 45Ca2+ influx, which were reduced in aging rats. Thus, aging in female SHR is associated with reduction in ER-mediated NO production from endothelial cells and decrease in inhibitory effects of estrogen on Ca2+ entry mechanisms of smooth muscle contraction. The age-related decrease in ER-mediated vascular relaxation may explain the increased vascular contraction and arterial pressure associated with aging in females.

The effect of N-acetylcysteine on nuclear factor-kappa B activation, interleukin-6, interleukin-8, and intercellular adhesion molecule-1 expression in patients with sepsis

OBJECTIVE

Expression of inflammatory mediators is controlled in part at the transcriptional level via nuclear factor-kappa B. Inhibition of nuclear factor-kappa B activation may be beneficial in critically ill patients. N-acetylcysteine is an antioxidant that inhibits nuclear factor-kappa B activation in vitro. In this pilot study we investigated the effect of N-acetylcysteine on nuclear factor-kappa B activation and circulating cytokine and adhesion molecules in patients with sepsis.

DESIGN

Prospective, randomized, double blind, placebo-controlled pilot trial.

SETTING

Eight-bed intensive care unit in a university teaching hospital.

PATIENTS

Twenty consecutive patients within 12 hrs of fulfilling the consensus criteria for sepsis.

INTERVENTIONS

A bolus of 150 mg/kg N-acetylcysteine in 100 mL of 0.9% saline over 15 mins, then 50 mg/kg in 100 mL of 0.9% saline over 4 hrs as a loading dose, and then a maintenance infusion of 50 mg/kg in 200 mL of 0.9% saline over each 24-hr period for a total of 72 hrs, or an equivalent volume of saline.

MEASUREMENTS AND MAIN RESULTS

Nuclear factor-kappa B activation was measured in mononuclear leukocytes using electrophoretic mobility shift assay, at baseline and 24, 48, 72, and 96 hrs later. Activation decreased significantly in patients treated with N-acetylcysteine (p =.016) but not placebo and was significantly reduced at 72 hrs compared with both preinfusion values (p =.028) and patients receiving placebo (p =.01). Plasma interleukin-6, interleukin-8, and soluble intercellular adhesion molecule-1 concentrations were measured using enzyme immunoassay. Interleukin-6 concentrations were high initially and then decreased in all patients, regardless of whether they received N-acetylcysteine or placebo. Interleukin-8 decreased significantly only in those who received N-acetylcysteine (p =.0081). Soluble intercellular adhesion molecule-1 concentrations remained unchanged in all patients.

CONCLUSIONS

Administration of N-acetylcysteine results in decreased nuclear factor-kappa B activation in patients with sepsis, associated with decreases in interleukin-8 but not interleukin-6 or soluble intercellular adhesion molecule-1. These pilot data suggest that antioxidant therapy with N-acetylcysteine may be useful in blunting the inflammatory response to sepsis. Further studies are warranted.

Malaria

PURPOSE OF REVIEW

This review addresses recent developments that relate to the pathogenesis of severe malaria and its treatment, and also highlights the increase in the global burden of malaria and provides a summary of clinical trials of malaria vaccines.

RECENT FINDINGS

Malaria, one of the world's most important parasitic infections, is on the increase globally. This has resulted in an increase in the morbidity and mortality from malaria in endemic areas, a resurgence in areas where it was previous eradicated, and an increase in imported malaria in Europe and North America. Mortality from severe malaria continues to be high, even when effective drugs are available, because most deaths occur within hours of admission to hospital. In severe malaria, the presence of acidosis is the most important prognostic factor in children and adults. A number of therapies have resulted in clinical improvements and the correction of acidosis in phase I and II studies, but larger trials are required to examine the effect on mortality. More malaria vaccines are now in phase I or II trials; however, available data do not yet promise an imminent impact on malaria control.

SUMMARY

Recent developments include a better understanding of the pathogenesis of severe malaria, and have given rise to a number of novel therapeutic strategies that should be examined in larger phase III trials. Similarly, there has been considerable progress in the field of vaccine development.