Does brain histamine contribute to the development of hypertension in spontaneously hypertensive rats?

Summary Histaminergic neurons of the brain have been implicated in genetic hypertension. We investigated the effect of inhibition of histamine synthesis by -fluoromethylhistidine (-FMH), the irreversible inhibitor of histidine decarboxylase, on the development and maintenance of hypertension in spontaneously hypertensive rats.Young (3-week-old) and adult (7-week-old) rats were treated with -fluoromethylhistidine for 29 and 13 days, respectively. Treatment of spontaneously hypertensive rats and normotensive Wistar-Kyoto rats with -fluoromethylhistidine led to a pronounced decrease in the histidine decarboxylase activity and in the histamine concentration in the brain (hypothalamus, brainstem, cortex —midbrain). In adult spontaneously hypertensive rats, the development of hypertension was not influenced by -fluoromethylhistidine. In young spontaneously hypertensive rats, -fluoromethylhistidine led to a transient delay in the development of hypertension which was followed by a transient tendency to increased blood pressure.It is concluded that histaminergic neurons of the brain play only a subordinate role, if any at all, in the development of hypertension in spontaneously hypertensive rats.This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung     

α-Adrenoceptor-mediated inhibition of noradrenaline release in rabbit brain cortex slices

Summary Brain cortex slices from rabbits were preincubated with [³H]noradrenaline and then superfused and stimulated electrically at 3Hz. In the presence of cocaine 30 M, unlabelled noradrenaline, -methylnoradrenaline, clonidine, oxymetazoline, xylazine and guanabenz decreased, whereas yohimbine, corynanthine, phentolamine, tolazoline and azapetine increased the stimulation-evoked overflow of tritium. Phenylephrine and prazosin had no effect on the evoked overflow except at concentrations that greatly accelerated the basal outflow of tritium. The results indicate that the noradrenergic axons of rabbit brain cortex are endowed with presynaptic -adrenoceptors which are exclusively of the ₂-type. Addition of various concentrations of cocaine, addition of pargyline, or stimulation at different current strengths was used to obtain either a high or a low stimulation-evoked overflow of tritium. Independently of the method used, a low evoked overflow coincided with a large percentage inhibition produced by 0.1M clonidine, whereas a high evoked overflow coincided with a smaller percentage inhibition produced by clonidine. The results indicate that drugs which block the re-uptake of noradrenaline diminish the presynaptic inhibitory effect of -adrenergic agonists by increasing the biophase concentration of released noradrenaline.     

α1-Adrenoceptor activation of PKC-ε causes heterologous desensitization of thromboxane receptors in the aorta of spontaneously hypertensive rats

Background and Purpose

In the aorta of adult spontaneously hypertensive (SHR), but not in that of normotensive Wistar-Kyoto (WKY), rats, previous exposure to phenylephrine inhibits subsequent contractions to PGE₂. The present experiments were designed to examine the mechanism(s) underlying this inhibition.

Experimental Approach

Isometric tension was measured in isolated rings of SHR and WKY aortae. Gene expression and protein presence were measured by quantitative real-time PCR and Western blotting respectively.

Key Results

In aorta of 18 weeks SHR, but not age-matched WKY, pre-exposure to phenylephrine inhibited subsequent contractions to PGE₂ that were mediated by thromboxane prostanoid (TP) receptors. This inhibition was not observed in preparations of pre-hypertensive 5-week-old SHR, and was significantly larger in those of 36- than 18-week-old SHR. Pre-exposure to the PKC activator, phorbol 12,13-dibutyrate, also inhibited subsequent contractions to PGE₂ in SHR aortae. The selective inhibitor of PKC-ε, ε-V1-2, abolished the desensitization caused by pre-exposure to phenylephrine. Two molecular PKC bands were detected and their relative intensities differed in 36-week-old WKY and SHR vascular smooth muscle. The mRNA expressions of PKC-α, PKC-ε, PK-N2 and PKC-ζ and of G protein-coupled kinase (GRK)-2, GRK4 and β-arrestin2 were higher in SHR than WKY aortae.

Conclusions and Implications

These experiments suggest that in the SHR but not the WKY aorta, α₁-adrenoceptor activation desensitizes TP receptors through activation of PKC-ε. This heterologous desensitization is a consequence of the chronic exposure to high arterial pressure.Tables of Links

Lack of epinine formation in adrenal medulla and brain of rats during cold exposure and inhibition of dopamine β-hydroxylase

Summary Cold exposure of rats for 4 h and simultaneous inhibition of dopamine -hydroxylase by FLA-63 (25 mg/kg) led to a reduction of the catecholamine content of the adrenal medulla by 46% and of the brain by 68%. Additional injections of 5 mg/kg FLA-63 4 and 9 h after beginning of the experiments, respectively, kept the catecholamine content on this low level (brain) or decreased in further (adrenal medulla). Administration of 5 mg/kg (-)DOPA together with the mono-amine oxidase inhibitor pargyline (50 mg/kg) 24 h after the first injection of FLA-63 stimulated the resynthesis. It amounted for the adrenal medulla to 20 g/kg body weight/8 h and for the brain to 45 ng/g tissue wet weight/8 h. Paper chromatographic analyses of the extracts of adrenal medulla and brain, respectively, performed at each time of the different injections, clearly identified adrenaline, noradrenaline and dopamine (in traces) in the adrenal medulla as well as noradrenaline and dopamine in the brain; epinine on the contrary could not be demonstrated, not even in traces. Since at least 25 ng of epinine can be detected with certainty by our method, it can be concluded that epinine is not formed in amounts greater than 75 ng/pair adrenal glands or 37.5 ng/brain. The present results support the view that the main pathway of adrenaline biosynthesis in the suprarenal medulla and the brain proceeds via noradrenaline and not via epinine.     

Effect of age on the prejunctional α-adrenoceptor-mediated feedback in the heart of spontaneously hypertensive rats and normotensive Wistar Kyoto rats

Summary The prejunctional ₂-adrenoceptor-mediated feed-back in the heart of pithed young and adult spontaneously hypertensive rats (SHR) and corresponding normotensive Wistar Kyoto rats (WKY) was studied. After electrical stimulation of the sympathetic outflow from the spinal cord to the heart, B-HT 920 induced an inhibition of the cardiac response, which was significant at stimulation frequencies up to 1 Hz in young SHR and WKY and up to 2 Hz in the adult animals. Rauwolscine produced a potentiation of the cardiac response to electrical stimulation in SHR, which was significant from 0.2–10 Hz in young SHR and from 0.1–10 Hz in adult SHR. In young WKY, rauwolscine did not potentiate the increase in heart rate to sympathetic nerve stimulation, whereas in adult WKY ₂-adrenoceptor blockade by rauwolscine significantly potentiated the cardiac response to electrical stimulation at frequencies in the range of 0.2–10 Hz. In SHR the potentiation of the cardiac response to sympathetic nerve stimulation by rauwolscine was much stronger than in WKY.These results suggest that in adult animals the prejunctional ₂-adrenoceptor mediated feedback is more developed than in young rats. In contrast with young WKY, a significant endogenous feedback can be demonstrated in adult WKY. In SHR, however, the physiological role of prejunctional ₂-adrenoceptors is much more important.     

Brain α4β2 nicotinic acetylcholine receptors are involved in the secretion of noradrenaline and adrenaline from adrenal medulla in rats

Recently, we reported that intracerebroventricularly (i.c.v.) administered (±)-epibatidine (a non-selective agonist of nicotinic acetylcholine receptors) elevates plasma noradrenaline and adrenaline through brain nicotinic acetylcholine receptor-mediated mechanisms in rats. In the present study, we characterized the receptors involved in these responses using selective agonists and antagonists of nicotinic acetylcholine receptor subtypes in anesthetized rats. (±)-Epibatidine (5 and 10 nmol/animal, i.c.v.) and (−)-nicotine (250 and 500 nmol/animal, i.c.v.) both elevated plasma noradrenaline and adrenaline (adrenaline > noradrenaline) but the former was more efficient than the latter. The (±)-epibatidine (5 nmol/animal, i.c.v.)-induced elevation of plasma catecholamines was reduced by dihydro-β-erythroidine (a selective antagonist of α4β2 nicotinic acetylcholine receptors) (100 and 300 nmol/animal, i.c.v.), while methyllycaconitine (a selective antagonist of α7 nicotinic acetylcholine receptors) (100 and 300 nmol/animal, i.c.v.) had no effect on the (±)-epibatidine-induced responses. RJR-2403 (a selective agonist of α4β2 nicotinic acetylcholine receptors) (2.5 and 5 μmol/animal, i.c.v.) elevated plasma noradrenaline and adrenaline (adrenaline > noradrenaline), while PNU-282987 (a selective agonist of α7 nicotinic acetylcholine receptors) (2.5 and 5 μmol/animal, i.c.v.) had no effect. Furthermore, the RJR-2403 (5 μmol/animal, i.c.v.)-induced responses were abolished by acute bilateral adrenalectomy. Immunohistochemical procedures demonstrated the expression of α4 and β2 nicotinic acetylcholine receptor subunits on the spinally projecting hypothalamic paraventricular neurons. Taken together, brain α4β2 nicotinic acetylcholine receptors seem to be involved in the secretion of noradrenaline and adrenaline from adrenal medulla in rats.     

Activation of β2-adrenoceptors by isoprenaline and adrenaline enhances noradrenaline release in cortical kidney slices of young spontaneously hypertensive rats

Summary The aim of the present study was to investigate -adrenoceptor modulation of noradrenaline release from sympathetic nerves in superfused cortical kidney slices of 4-week-old spontaneously hypertensive rats (SHR) and age-matched controls (WKY). After preincubation with ³H-noradrenaline the kidney slices were electrically stimulated in superfusion chambers. The stimulation induced (S-I) outflow of radioactivity was mainly composed of unmetabolized 3H-noradrenaline in both strains and thus taken as an index of noradrenaline release. There was a frequency-dependent (1.25–20 Hz) increase in the S-1 outflow of radioactivity. At all stimulation frequencies tested S-I outflow of radioactivity was similar or even slightly lower in SHR than in WKY kidney slices in either the absence or presence of cocaine (10 mol/l). The non-selective -adrenoceptor agonists isoprenaline (0.l gmol/1) and adrenaline (0.01 and 0.1 mol/l) enhanced S-I outflow of radioactivity. The facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) were blocked by the selective ₂-adrenoceptor antagonist ICI 118551 (0.1 mol/l) but not by the selective ₁-adrenoceptor antagonist atenolol (0.3 mol/l). The cell-permeable CAMP analogue 8-bromo-cAMP (300 mol/l) enhanced S-1 outflow of radioactivity to a similar extent in both SHR and WKY kidney slices. A combination of 8-bromo-cAMP (300 mol/l) and adrenaline (0.1 mol/l) did not enhance S-1 outflow of radioactivity to a greater extent than 8-bromo cAMP (300 mol/l) alone in both strains. However, the facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) but not that of adrenaline (0.01 mol/l) were significantly greater in SHR than in WKY. The results suggest that stimulation of prejunctional ₂-adrenoceptors by adrenaline even in the absence of a-adrenoceptor blockade enhances noradrenaline release in kidney cortex of young SHR and WKY. This ₂-adrenoceptor mediated effect may possibly be dependent on cAMP formation. The greater facilitatory effects of isoprenaline (0.1 mol/l) and adrenaline (0.1 mol/l) in SHR as compared to WKY are in accord with receptor binding studies which show a higher density of ₂-adrenoceptors in SHR than in WKY kidney cortex.Abbreviations SHR Spontaneously hypertensive rats - WKY WistarKyoto rats - cAMP 3-5-cyclic adenosine monophosphate - S-I stimulation induced Send offprint requests to: L. C. Rump     

Effect of the AT₁ receptor antagonist losartan on diurnal variation in pain threshold in spontaneously hypertensive rats

Angiotensin (AT) II plays a key role in the regulation of blood pressure and water-salt balance and modulates nociception. Peptides based on AT influence central functions through the activation of AT?, AT? or AT? receptors. The aim of this study was to elucidate the role of AT? receptors in diurnal variation in nociception in spontaneously hypertensive rats (SHR). Male Wistar rats (16 weeks old) and SHR were caged individually and exposed to light from 08:00 to 20:00 h. The tail cuff method for noninvasive measurement of arterial blood pressure (ABP), paw pressure test for the determination of pain threshold and rotarod test to study motor coordination were used. Chronic treatment was administered to the SHR with the AT? receptor antagonist losartan (10 mg/kg/day, s.c.) for 14 days. Spontaneously hypertensive rats showed lower pain threshold and smaller day-night variations of nociception as compared to Wistar rats. Chronic losartan decreased the ABP and produced an inverted diurnal pattern of nociception in SHR, increasing the pain threshold at 03:00 h. Neither strain differences nor changes in motor coordination after losartan treatment were observed in SHR. Our results suggest that SHR have disturbances in diurnal variation in nociception and that the AT? receptor plays a role in the regulation of the circadian rhythm of mechanical pain threshold in SHR.     

Slow dissociation of partial agonists from the D₂ receptor is linked to reduced prolactin release

In this study we investigated the correlation between affinity, efficacy, peripheral receptor occupancy, and kinetic properties of D? dopamine receptor ligands with time-course evaluations of prolactin release in rat blood. We profiled typical and atypical antipsychotic antagonists at D? receptors, the partial agonist aripiprazole, and four novel partial agonist compounds with different properties. Clozapine and quetiapine revealed lower prolactin release and fast dissociation kinetics, linking fast dissociation and prolactin-sparing properties. Surprisingly, haloperidol, a highly prolactin-releasing antagonist, shared intermediate dissociation properties. Factors other than kinetic properties may thus contribute to prolactin-releasing properties of antagonists. Partial agonists sharing similar efficacies and receptor occupancies differed markedly in their ability to induce hyperprolactinaemia. Aripiprazole moderately released prolactin even at high receptor occupancies, with slow dissociation from D? receptors. Other compounds displaying low affinities and fast dissociations released prolactin substantially, although less than haloperidol. The effect augmented after repeated administrations. Compounds with high affinities and slow dissociation rates stimulated moderate prolactin release at high receptor occupancies, reaching a ceiling effect at 50-60% occupancy. Moreover, the effect developed tolerance. In conclusion, we investigated the affinity and kinetic properties of D? partial agonists associated with their ability to induce prolactin release in blood. We propose that for D? partial agonists, at comparable intrinsic activities and peripheral occupancies, the prolactin-releasing properties are linked to their kinetic rate properties. Differently from D? antagonists, partial agonists display slow dissociation and high affinity associated with a low prolactin release profile.     

GABAergic modulation of catecholamine release from cultured bovine adrenal chromaffin cells. Evidence for the involvement of Cl−-dependent Ca2+ entry

Summary The mode by which GABA facilitates the basal and stimulation-evoked catecholamine (CA) release from cultured bovine adrenal chromaffin cells was investigated. Muscimol, a GABA_A receptor agonist, facilitated ⁴⁵Ca uptake in a concentration-related manner. When GABA and acetylcholine (ACh) were simultaneously applied, additive increase in ⁴⁵Ca uptake was observed. Similar effect on ⁴⁵Ca uptake was observed in the presence of GABA and veratridine, although ⁴⁵Ca uptake induced by a rather low concentration of veratridine was more than additively enhanced by GABA. GABA-evoked CA release was also more than additively enhanced by BayK 8644 whereas there was only an additive effect on ⁴⁵Ca uptake. Substitution of extracellular Cl^– by sucrose (low Cl^– medium) during the stimulation with GABA enhanced GABA-evoked CA release. Substitution of extracellular Cl^– for more than 1 h abolished GABA-evoked CA release and ⁴⁵Ca uptake. At this time, the concentration-response curve for veratridine-evoked CA release was shifted to left and GABA no longer enhanced veratridine-evoked CA release at any concentration of veratridine. GABA-induced facilitation of ⁴⁵Ca uptake in the presence of low concentration of veratridine was also inhibited by long-term treatment with low Cl^– medium. These results suggest that the C^–-dependent process linked to GABA_A receptor acts on voltage-sensitive Ca²⁺ channels in chromaffin cells to elicit and modulate CA release. Send offprint requests to A. Tsujimoto at the above address     

α2-Adrenoceptor mediated inhibition of the release of radiolabelled 5-hydroxytryptamine and noradrenaline from slices of the dorsal region of the rat brain

Summary Possible local interactions between noradrenergic and serotonergic systems in the dorsal raphe region of the rat were investigated by studying the effects of various drugs on depolarization (20 mmol/l K⁺)-induced release of [³H]5-hydroxytryptamine (5-HT) and [³H]noradrenaline (NA) in vitro using a superfusion method. Exogenous 5-HT did not influence the release of [³H]NA. However, NA (in the presence of 10 mol/l desipramine) as well as the selective ₂-adrenoceptor agonists clonidine and oxymetazoline strongly inhibited [³H]5-HT release. The selective ₁-adrenoceptor agonists phenylephrine and methoxamine did not affect the release of either [³H]5-HT or [⁵H]NA. The inhibition by NA of both [³H]5-HT and [⁵H]NA release was not affected by the -adrenoceptor antagonist sotalol nor by the selective ₁-adrenoceptor antagonist prazosin. However, phentolamine and the selective ₂-adrenoceptor antagonists yohimbine and rauwolscine competitively antagonized the inhibitory effect of NA on [³H]NA release (respective pA₂-values 7.5 and 8.3) and on [³H]5-HT release (respective pA₂-values 7.7 and 8.2). Moreover, the release of [³H]NA and also, but to a lesser extent, that of [³H]5-HT were increased by the antagonists. It is concluded that the release of both 5-HT and NA in the dorsal raphe region may be subject to presynaptic inhibition by NA via activation of ₂-adrenoceptors.Send offprint requests to A. L. Frankhuijzen     

Gαq-protein carboxyl terminus imitation polypeptide GCIP-27 attenuates proliferation of vascular smooth muscle cells and vascular remodeling in spontaneously hypertensive rats

Gq-protein is located at the convergent point in signal transduction pathways leading to vascular remodeling. The carboxyl terminus of Gα-subunit plays a vital role in G-protein-receptor interaction. The present study was designed to explore the effects of a synthetic Gαq carboxyl terminus imitation peptide, namely GCIP-27, on vascular smooth muscle cells (VSMC) in vitro and vascular remodeling in spontaneous hypertensive rats (SHR). Hyperplasia and hypertrophy of VSMC wre determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, [(3)H]-thymidine and [(3)H]-leucine incorporation, and [Ca(2+)](i) was measured with Fluo-3/AM staining. Systolic blood pressure (SBP), the ratio of media thickness to lumen diameter (MT/LD) of aorta, collagen content, and phospholipase C activity in aorta were measured in SHR. GCIP-27 (3-100 μg/l) significantly decreased proliferation activity, protein content, incorporation of [(3)H]-thymidine and [(3)H]-leucine, and [Ca(2+)](i) level in VSMC. SBP, MT/LD, collagen content, and phospholipase C activity in aorta of SHR were decreased significantly in GCIP-27 (7, 20, 60 μg/kg)-treated groups and losartan (6 mg/kg) group compared with vehicle group. In conclusion, GCIP-27 could inhibit vascular remodeling effectively in vitro and in vivo.     

Special focus on the role of α(1D)-adrenoreceptors in the assessment of renal tubular sodium re-absorptive responses in spontaneously hypertensive rats subjected to high sodium diet

α(1D)-adrenoceptors are involved in the genesis/maintenance of hypertension in spontaneously hypertensive rats (SHR). This study aims to investigate the role of α(1D)-adrenoceptors in the antinatriuretic and antidiuretic responses in SHR subjected to high sodium (SHRHNa) and normal sodium (SHRNNa) intake for six weeks. Renal inulin clearance study was performed in which the antinatriuretic and antidiuretic responses to phenylephrine were examined in the presence and absence of α(?D)-adrenoceptors blocker BMY7378. Data, mean±S.E.M. were subjected to ANOVA with significance at p<0.05. Results show that feeding SHR for six weeks with high salt did not cause any change in blood pressure. SHRHNa had higher (all p<0.05) urine flow rate (UFR), fractional and absolute excretion of sodium (FE(Na) and U(Na)V) compared to SHRNNa. Phenylephrine infusion produced significant reduction in UFR, FE(Na) and U(Na)V in both SHRHNa and SHRNNa. The antidiuretic and antinatriuretic responses to phenylephrine in both groups were attenuated in the presence of BMY7378. Moreover, the antidiuretic and antinatriuretic responses to phenylephrine and BMY7378 were independent on any significant changes in renal and glomerular hemodynamics in both groups. Thus we conclude that high sodium intake did not bring any further increase in blood pressure of SHR, however, it results in exaggerated natriuresis and diuresis in SHRHNa. Irrespective of dietary sodium changes, α?-adrenoceptors are involved in mediating the antinatriuretic and antidiuretic responses to phenylephrine in SHR. Further, high sodium intake did not significantly influence the functionality of α(?D)-adrenoceptors in mediating the adrenergically induced antinatriuresis and antidiuresis.     

Cytosolic phospholipase A₂ inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation

The protective potential of nortriptyline has been reported in a few experimental models of brain ischemia, both in vivo and in vitro. However, the detailed molecular mechanisms of the protective action of the drug are still unresolved. The aim of the present study was to determine whether treatment with low or medium concentrations of nortriptyline (0.1–10 µM) might have an effect on cPLA₂ protein and/or mRNA expression in ischemic astrocytes, and whether this influence might be related to its potential positive influence on cell viability. On the 21^st day in vitro, primary cultures of rat cortical astrocytes were subjected to ischemia-simulating conditions (combined oxygen glucose deprivation, OGD) for 24 h and exposed to nortriptyline. The drug at concentrations of 0.1 and 1 µM attenuated the expression of cPLA₂ (both the phosphorylated and unphosphorylated forms) together with a significant decrease in the cPLA₂ mRNA level in ischemic astrocytes. We have demonstrated that nortriptyline influences a decrease in cPLA_2-mediated arachidonic acid (AA) release through a mechanism that appears to involve the attenuation of both PKC and Erk1/2 kinase expression. Nortriptyline also significantly prevented mitochondrial depolarization in ischemic astrocytes. Moreover, the antidepressant protected glial cells against OGD-induced apoptosis and necrosis. Our findings document a role for cPLA₂ expression attenuation and AA release inhibition in the protective effect of nortriptyline in ischemic astrocytes.     

Controlled release of insulin from self-assembling nanofiber hydrogel, PuraMatrix?: application for the subcutaneous injection in rats

The concept of this research is, using the acetyl-(Arg-Ala-Asp-Ala)?-CONH? peptide hydrosol (PuraMatrix?, PM), to develop an new injectable formula of controlled insulin delivery for subcutaneous injection. PM has sol-gel phase transition behavior, and was developed as a scaffold in the field of tissue engineering. The aqueous media of the PM including insulin changed from a sol to a gel phase with increasing ion strength of phosphate ion and pH in working environments in vitro and in vivo. In this study, we examined the in vitro insulin dissolution behavior and the in vivo pharmacokinetics and pharmacodynamics after subcutaneous administration of PM-insulin sol (PM-Isol). In the in vitro release study, after PM-Isol was converted to a gel phase (PM-Igel), PM concentration-dependent and controlled release of insulin were observed at the final concentrations of PM between 0.1% and 2.0% (w/v). The PM-Isol is changed to gel form in vivo, and exhibited a sustained-release pharmacokinetics of insulin, where PM concentration-dependent prolongation of efficacy was found. The plasma glucose level markedly decreased, and the lowest plasma glucose level was maintained up to 24h when 2.0% (w/v) PM-Isol was administered subcutaneously to rats. The PM-Isol, we developed here, is applicable for the wild-type of insulin, and increased the bioavailability and hypoglycemic efficacy of insulin after subcutaneous injection. Hence, the PM is a useful inactive ingredient to produce various types of control-released system of insulin by making just a few changes in PM content of the formulation.     

Monocrotaline-induced pulmonary arterial hypertension is attenuated by TNF-α antagonists via the suppression of TNF-α expression and NF-κB pathway in rats

Inflammation is involved in various types of human pulmonary arterial hypertension (PAH), especially in PAH-associated connective tissue diseases. Although the pathogenesis of pulmonary hypertension has still remained largely unclear, TNF-α has been reported as a key pro-inflammatory cytokine in severe pulmonary hypertension and emphysema. The aim of this study was to investigate the effect of a TNF-α antagonist, recombinant TNF-α receptor II:IgG Fc fusion protein (rhTNFRFc), on the development of monocrotaline (MCT)-induced PAH in rats. Our results revealed that treatment of rhTNFRFc in these rats had favorable effects on mPAP levels, hemodynamics and pulmonary vascular remodeling, preventing PAH development at 3 weeks following MCT. Furthermore, rhTNFRFc treatment resulted in markedly reduced expression of TNF-α via the inhibition of NF-κB activity in rat lungs. These results demonstrated that rhTNFRFc attenuated the process of MCT-induced PAH through its anti-inflammatory property. Although further studies are needed to define the appropriate treatment regimen, our findings suggest that rhTNFRFc might provide therapeutic benefits for PAH patients.     

Enhancement of the hypothalamic–pituitary–adrenal axis but not cytokine responses to stress challenges imposed during withdrawal from acute alcohol exposure in Sprague–Dawley rats

Rationale  

Alcohol withdrawal is associated with reduced activity, increased anxiety, and other signs of distress.     

6,6'-Bieckol, isolated from marine alga Ecklonia cava, suppressed LPS-induced nitric oxide and PGE₂ production and inflammatory cytokine expression in macrophages: the inhibition of NFκB

Ecklonia cava is an edible brown alga that contains high levels of phlorotannins, which are unique marine polyphenolic compounds. In the present study, we investigated the anti-inflammatory effects and the underlying molecular mechanism of phlorotannin 6,6′-bieckol, which is an active component isolated from E. cava, on lipopolysaccharide (LPS)-stimulated primary macrophages and RAW 264.7 macrophage cells. 6,6′-Bieckol was found to inhibit nitric oxide (NO) and prostaglandin E₂ (PGE₂) production and to suppress the LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the mRNA and protein levels. In addition, 6,6′-bieckol downregulated the production and mRNA expression of the inflammatory cytokines TNF-α and IL-6. Moreover, pretreatment with 6,6′-bieckol decreased LPS-induced transactivation of nuclear factor-kappa B (NFκB) and nuclear translocation of p50 and p65 subunits of NFκB. Furthermore, chromatin immunoprecipitation assay revealed that 6,6′-bieckol inhibited LPS-induced NFκB binding to the TNF-α and IL-6 promoters. Taken together, these data suggest that the anti-inflammatory properties of 6,6′-bieckol are related to the down-regulation of iNOS, COX-2, and pro-inflammatory cytokines through the negative regulation of the NFκB pathway in LPS-stimulated macrophages.