The p38 MAPK inhibitor, SB203580, abrogates ischaemic preconditioning in rat heart but timing of administration is critical

There is debate concerning the involvement of p38 mitogen activated protein kinase (MAPK) in the mediation of ischaemic preconditioning. Pharmacological inhibition of p38 MAPK with SB203580 has been reported to block preconditioning in some studies but not in others. We hypothesised that this divergence could be due to differences in the timing of inhibitor administration. Isolated rat hearts were perfused in the Langendorff mode and subjected to 35 min regional ischaemia followed by 120 min reperfusion. Hearts were then double stained with Evans' blue and triphenyltetrazolium chloride to determine risk (R) and infarct zones (I), expressed as I/R% ratios. Preconditioned hearts were subjected to 2 times 5 min global ischaemia with 10 min intervening reperfusion. SB203580 10 μ M was perfused either during the preconditioning protocol (PC+SB-early), just prior to and during the first 15 min of the lethal ischaemia (PC+SB-late) or prior to regional ischaemia in the absence of preconditioning. Ischaemic preconditioning significantly limited infarct size (I/R 38.9 ± 3.0% in control vs 13.4 ± 2.4%, P < 0.01). In the PC+SB-early group, preconditioning was still fully protective (I/R% 14.6 ± 1.0). However, in the PC+SB-late group, SB203580 completely blocked the protection afforded by preconditioning (I/R% 33.6 ± 4.4%, P < 0.01 vs 13.4 ± 2.4% in preconditioned hearts, p < 0.05). SB203580 alone did not affect infarct size when given prior to and during regional ischaemia (I/R 36.2 ± 2.7%). These histological data are corroborated by a significant increase in p38 MAPK activation in the preconditioned hearts during sustained ischaemia in comparison with the controls. In conclusion the activation of p38 MAPK during lethal ischaemia, but not during the ischaemic preconditioning protocol, is essential for the mediation of protection and may resolve some of the earlier controversy surrounding the use of SB203580 in preconditioning studies. Received: 28 June 2000, Returned for revision: 21 July 2000, Revision received: 9 August 2000, Accepted: 13 September 2000     

Interleukin-1β up-regulates tumor necrosis factor receptors in the mouse airways

Cytokines like interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα), released during the inflammatory process, play important roles in the development of airway hyperresponsiveness. The effects of these cytokines are mediated by cell surface receptors, specific for each cytokine. The expression of cytokine receptors is a dynamic process, where receptors can be up- or down-regulated in response to changes in the environment. One such environmental factor is the presence of cytokines per se. The present study was designed to evaluate the effects of IL-1β on the expression of its corresponding receptor IL-1 RI, as well as on the closely related TNFα receptors TNF RI and TNF RII in airways using a mouse organ culture assay and intranasal inoculation model. Immunohistochemical staining was used to quantify expressional differences between fresh and cultured tracheal segments. In the fresh, uncultured, segments, IL-1 RI and TNF RI were seen in the epithelial layer and TNF RI in the smooth muscle layer. After 4 days of culture, the expression of TNF RI decreased in the epithelial layer, whereas the corresponding expression of IL-1 RI and TNF RI in the smooth muscle remained unchanged. When culture was performed in the presence of IL-1β, the expression of IL-1 RI and TNF RI in the epithelial cells and TNF RI in the smooth muscle cells increased. TNF RII was not detected in either fresh or cultured trachea, but after treatment with IL-1β an expression was found in both the epithelial layer and in the smooth muscle cells. The IL-1β-induced increased expression, on TNF RI and TNF RII in the smooth muscle ex vivo and in the lung parenchyma after intranasal challenge in vivo, was verified at the mRNA level using real-time RT PCR. To summarize, presence of IL-1β increases the expression of IL-1 R1 and TNF RI and induces expression of TNF RII in the airway wall. It is not inconceivable that these alterations of the IL-1 and TNF receptors may have important functional implications for the development of hyperresponsiveness in inflammatory airway diseases like asthma.     

Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes

G. Taimor, K.-D. Schlüter, K. Frischkopf, M. Flesch, S. Rosenkranz and H. M. Piper. Autocrine Regulation of TGF β Expression in Adult Cardiomyocytes. Journal of Molecular and Cellular Cardiology (1999)31 , 2127–2136. As shown before, TGF β acts in an autocrine manner on the induction of hypertrophic responsiveness to β -adrenoceptor stimulation in cultured ventricular cardiomyocytes of adult rat. We now investigated how TGF β expression and activation is regulated in these cultures and how β -adrenoceptor stimulation influences TGF β -mRNA expression. It was found that freshly isolated cardiomyocytes secrete latent TGF β in the culture medium. Supplementation of the cultures with 20% FCS resulted in activation of the secreted TGFβ to 4.1±0.2 ng/ml active TGF β after 6 days. Presence of the protease inhibitor aprotinin (50μ g/ml) reduced TGF β activity by 44±5% (n=5, P<0.05). In cultures supplemented with 5% FCS, TGF β was not activated. Active TGF β downregulated its mRNA-expression: after 6 days TGF β₁-mRNA was reduced to 55.1±11.0%, TGFβ₂ -mRNA to 30.1±16.5%, and TGF β₃-mRNA to 0.3±0.4% in 20% FCS-cultures as compared to their expression in freshly isolated cells (n=4, P<0.05). TGFβ -mRNA expression did not change in cultures without active TGF β. Isoprenaline (1 μ m) increased TGF β₁-mRNA only in cultures which had been pre-exposed to active TGF β. This effect was also seen when hearts from normal mice were compared with hearts from transgenic mice overexpressing TGFβ₁ : only in hearts from transgenic animals perfusion with isoprenaline increased TGFβ₁ -mRNA. In conclusion, isolated cardiomyocytes release latent TGF β, which is activated by external proteases. Active TGF β downregulates its own mRNA expression. Preexposure to TGF β is necessary for a β -adrenoceptor-mediated increase in TGF β₁-mRNA in cardiomyocytes.     

Duration of Action of Inhaled vs. Intravenous β2-Adrenoceptor Agonists in an Anaesthetized Guinea-pig Model

We compared the duration of action of the short-acting α₂-adrenoceptor agonist salbutamol and the long-acting α₂-adrenoceptor agonists salmeterol and formoterol when administered iv or by inhalation in a histamine-induced bronchoconstriction model in the guinea-pig. Following aerosol dosing, maximal bronchoprotector effects were seen for salbutamol, salmeterol and formoterol at concentrations of 1 mg/ml, 100 μ g/ml and 30 μ g/ml respectively, giving a potency order of formoterol > salmeterol > salbutamol. All displayed similar maximum effects in this system. A maximal concentration of salbutamol showed bronchoprotection at 1 h but not at 3 h post-dosing whereas maximal concentrations of formoterol and salmeterol showed protection up to 5 h post-aqueous-aerosol dosing, giving a duration order of salmeterol > formoterol > salbutamol. All three α₂-adrenoceptor agonists showed dose-dependent bronchoprotection and duration of action following intravenous administration; salbutamol and salmeterol were equipotent and both were less potent than formoterol. Bronchoprotection obtained with sub-maximal concentrations of all three α₂-adrenoceptor agonists faded within 30 min following iv administration, but this could be extended by increasing the doses. These results demonstrate that the route of administration is important in determining the duration of action of α₂-adrenoceptor agonists in the lung. Furthermore, such findings lend support to the suggestion that the physico-chemical characteristics of salmeterol govern its duration of action rather than sustained binding of this agonist to a α₂-adrenoceptor exo-site.     

The Long and Short of β2-agonists

For patients whose asthma is not adequately controlled with inhaled corticosteroid (ICS) therapy alone, increasing the dose of ICS or the addition of a long-acting β₂-agonist is recommended. Greater improvements in lung function are achieved with the addition of a long-acting β₂-agonist to ICS therapy, rather than doubling the dose of ICS. Formoterol and salmeterol have a similarly long duration of effect (up to 12 h). However, as a result of their different chemical structures, there are marked pharmacological differences in the mechanism of action which affect their speeds of onset. These differences amount to a more rapid onset of effect for formoterol compared with salmeterol. Long-acting β₂-agonists appear to be well tolerated at elevated doses. These two features (tolerability at high doses and rapid onset of effect) support the use of formoterol as a reliever medication in addition to use in maintenance therapy. The long-acting β₂-agonists can be considered as beneficial additions to ICS therapy for the management of moderate-to-severe asthma.     

An Immortalized Myocyte Cell Line, HL-1, Expresses a Functional δ -Opioid Receptor

The present study characterizes opioid receptors in an immortalized myocyte cell line, HL-1. Displacement of [³H]bremazocine by selective ligands for the mu (μ), delta (δ), and kappa (κ) receptors revealed that only the δ -selective ligands could fully displace specific [³H]bremazocine binding, indicating the presence of only the δ -receptor in these cells. Saturation binding studies with the δ -antagonist naltrindole afforded a B_maxof 32 fmols/mg protein and a K_Dvalue for [³H]naltrindole of 0.46 n . The binding affinities of variousδ ligands for the receptor in HL-1 cell membranes obtained from competition binding assays were similar to those obtained using membranes from a neuroblastoma×glioma cell line, NG108-15. Finally, various δ -agonists were found to stimulate the binding of [³⁵S]GTP γ S, confirming coupling of the cardiac δ -receptor to G-protein. DADLE (D-Ala-D-Leu-enkephalin) was found to be the most efficacious in this assay, stimulating the binding of [³⁵S]GTP γ S to 27% above basal level. The above results indicate that the HL-1 cell line contains a functionally coupled δ -opioid receptor and therefore provides an in vitro model by which to study the direct effects of opioids on cardiac opioid receptors.     

Association of β2-adrenoceptor Gln27Glu variant with body weight but not hypertension

β₂-Adrenoceptor (β₂-ADR)-mediated vasodilatation decreases vascular reactivity and blood pressure (BP) and chromosome 5 where its gene (ADRB2R) resides and shows linkage to hypertension (HT). A Gln27Glu ADRB2R variant confers resistance to agonist-induced desensitization and enhanced vasodilator response to isoprenaline. Therefore, we carried out a case-control study in a cohort of HT and normotensive (NT) Anglo-Celtic Australian white subjects whose parents had a similar BP status as the subjects. Glu27 frequency was 0.41 in 108 HT and 0.42 in 141 NT (χ² = 0.05, P = .82). Within the HT group, the Glu27 allele was more prevalent in 61 subjects who were overweight (body mass index [BMI] ≥ 25 kg/m²) compared with 41 who were lean (BMI <25 kg/m²); ie, 0.49 v 0.31, respectively (χ² = 6.4, P = .012). Furthermore, Glu27 tracked with elevation in BMI in these subjects: 24 ± 4 kg/m², 27 ± 5 kg/m², and 28 ± 5 kg/m² for Gln/Gln, Gln/Glu, and Glu/Glu, respectively (P = .0058 by one-way ANOVA). Thus, the Gln27Glu β₂-ADR variant is excluded in HT, but might influence body weight.     

δβ -Thalassaemia in Two Yugoslavian Families

Members of two Yugoslavian families were found to have δβ-thalassaemia. Interaction of β-thalassaemia with δβ-thalassaemia occurred in two young children producing a clinical condition which is somewhat less severe than that of homozygous β-thalassaemia. Results from biosynthetic analyses indicate that the degree of globin chain imbalance in double heterozygotes for β- and δβ-thalassaemia is similar to that in homozygous β-thalassaemia. Fetal haemoglobin of all heterozygotes contained ^Gγ and ^Aγ chains in an average ratio of about 2:3 whereas that in the two double heterozygotes had ^Gγ and ^Aγ chains in a ratio of 3:2.     

Phosphorylation of Phospholamban at Threonine-17 in the Absence and Presence of β -Adrenergic Stimulation in Neonatal Rat Cardiomyocytes

The site-specific phospholamban phosphorylation was studied with respect to the interplay of cAMP- and Ca²⁺signaling in neonatal rat cardiomyocytes. To elucidate the signal pathway(s) for the activation of Ca²⁺/calmodulin-dependent protein kinase (CaMKII) we studied Thr17 phosphorylation of phospholamban in dependence of Ca²⁺channel activation by S(-)-Bay K8644 and in dependence of the depletion of the sarcoplasmic reticulum Ca²⁺stores by ryanodine or thapsigargin in the absence or presence of β -adrenergic stimulation. The isoproterenol (0.1 μ )-induced Thr17 phosphorylation was potentiated 2.5-fold in presence of 1 μ S(-)-Bay K8644. Interestingly, S(-)-Bay K8644 alone was also able to induce Thr17 phosphorylation in a dose- and time-dependent fashion. Ryanodine (1.0 μ ) reduced both the isoproterenol (0.1μ ) and S(-)-Bay K8644-(1 μ ) mediated Thr17 phosphorylation by about 90%. Thapsigargin (1 μ ) diminished the S(-)-Bay K8644 and isoproterenol-associated Thr17 phosphorylation by 53.5±6.3% and 92.5±11.1%, respectively. Ser16 phosphorylation was not affected under these conditions. KN-93 reduced the Thr17 phosphorylation by S(-)-Bay K8644 and isoproterenol to levels of 1.1±0.3% and 8.6±2.1%, respectively. However, the effect of KN-93 was attenuated (47.8±3.6%) in isoproterenol prestimulated cells. Protein phosphatase inhibition by okadaic acid increased exclusively the Ser16 phosphorylation. In summary, our results reflect a cross-talk between β -adrenoceptor stimulation and intracellular Ca²⁺at the level of CaMKII-mediated phospholamban phosphorylation in neonatal rat cardiomyocytes. We report conditions which exclusively produce Thr17 or Ser16 phosphorylation. We postulate that Ca²⁺transport systems of the sarcoplasmic reticulum are critical determinants for the activation of CaMKII that catalyzes phosphorylation of phospholamban.     

Adenosine modulates β-adrenergic signal transduction in guinea-pig heart ventricular membranes

The mechanism of the antiadrenergic action of adenosine in the heart was investigated by examining the effects of phenylisopro-pyladenosine (PIA), an adenosine A₁ receptor agonist, on β-adrenergic receptor and non-receptor elicited increases in adenylyl cyclase activity of guinea-pig ventricular membranes. These membranes contained adenosine A₁ receptors (≈ 80 fmol/mg) and at least one ADP-ribosylated G protein with a molecular weight of approximately 40 kDa. PIA attenuated isoproterenol-enhanced adenylyl cyclase activity and [³H]GDP release in this membrane preparation. However, PIA had no significant effect on GPP(NP)P or forskolin activated adenylyl cyclase. Additionally, PIA did not change the sensitivity of the cyclase to either magnesium or GTP in these membranes. The inhibition of isoproterenol-enhanced activity appeared to be dependent on the activation state of the enzyme such that the degree of PIA inhibition decreased with increasing isoproterenol concentration. These data suggest that adenosine inhibition of catecholamine-stimulated adenylyl cyclase activity occurs predominantly by modulating β-adrenergic receptor signal transduction and that subunits of G_i may be involved in this action.     

The temporal relationship between p38 MAPK and HSP27 activation in ischaemic and pharmacological preconditioning

An ischaemic preconditioning protocol and subsequent sustained ischaemia were characterized by activation and attenuation of p38 MAPK phosphorylation, respectively. However, the significance of events downstream of p38 MAPK needs investigation. Therefore the temporal relationship between phosphorylation of p38 MAPK and its downstream substrate HSP27 was studied during either an ischaemic or –adrenergic preconditioning protocol and during sustained ischaemia.Isolated rat hearts were preconditioned (with or without a p38 MAPK inhibitor, SB203580) with 1 × 5 min or 3 × 5 min global ischaemia or 5 min –adrenergic stimulation (10^–7 M isoproterenol), followed by 25 min sustained ischaemia and 30 min reperfusion. Hearts were freeze–clamped at different time intervals and fractionated to determine p38 MAPK and HSP27 phosphorylation, via Western blotting.Significant phosphorylation of cytosolic p38 MAPK and membrane (myo–fibrillar) HSP27 occurred at the end of the first preconditioning episode. However, p38 MAPK phosphorylation disappeared during subsequent preconditioning episodes, while HSP27 phosphorylation was maintained for the duration of the protocol. Similar changes in p38 MAPK and HSP27 occurred with 5 min –adrenergic preconditioning. After 25 min ischaemia, significant phosphorylation of cytosolic and membrane HSP27 was observed, while p38 MAPK phosphorylation was attenuated in ischaemic and –adrenergic preconditioned compared to non–preconditioned hearts. SB203580–induced abolishment of p38 MAPK and HSP27 phosphorylation during the triggering phase of both preconditioning protocols reversed the changes in these parameters seen after sustained ischaemia.The results suggest that p38 MAPK activation triggers HSP27 phosphorylation during both the preconditioning protocols and during sustained ischaemia. Protection of preconditioned hearts during sustained ischaemia was characterized by phosphorylation of both cytosolic and myofibrillar HSP27.     

Tumor necrosis factor-α in liver transplantation and resection: No evidence for a key role in ischemia-reperfusion injury

Experimental studies have shown that liver ischemia-reperfusion induces Kupffer cell activation and tumor necrosis factor-α (TNFα) release. The aim of this work was to determine whether severe hepatic ischemia and subsequent reperfusion triggers TNFα release in man. Serum TNFα was measured before and 3, 10, 30, 60, 120 min after revascularization and postoperatively at day 1 and 2 in 11 patients with orthotopic liver transplantation (group 1 and 4 patients with liver resection with vascular occlusion (group 2). In group 1, TNFα levels decreased during the first few minutes of reperfusion, then increased slightly to peak at 120 min (40 ± 13 pg/ml). Primary non-function occurred in 1 patient in whom low peroperative levels of TNFα levels were measured. In group 2, no significant changes in TNFα levels were observed. These data, in a small number of patients: (a) show that hepatic ischemia reperfusion does not result in major TNFα production; (b) do not support a primary pathogenic role for TNFα in damage after ischemia-reperfusion in humans.     

Differential Hemodynamic Effects of β-Adrenoceptor Blockers,Ca Antagonists and Combined α-β-Receptor Blockade in Ischemic Heart Disease

ABSTRACT. The hemodynamic responses to 3 different therapeutical regimens: β-adrenoceptor blockade, calcium inflow inhibition and combined α-β-blockade were evaluated in 3 matched randomized groups of patients with ischemic heart disease and typical exercise-induced angina. The groups consisted of 22, 16 and 15 men, mean age 55–59 years. They were studied at rest and during ischemia-inducing exercise, before and after single oral doses of 100 mg metoprolol, 10 mg nifedipine and 200 mg labetalol. Pressures in the brachial artery and the pulmonary circulation were recorded by means of percutaneously introduced catheters. Cardiac output was determined according to the Fick principle. Metoprolol reduced mean arterial pressures, heart rate and cardiac output. Systemic vascular resistance and left ventricular filling pressure increased. Nifedipine resulted under all conditions in a distinct reduction of systemic vascular resistance and arterial pressures and a slight increase in heart rate and cardiac output. Left ventricular filling pressure was significantly lowered, the more the higher the initial level. The effect of labetalol was similar to that of nifedipine; however, cardiac output was unchanged and heart rate was slightly reduced. Left ventricular filling pressure was significantly lower. It is apparent that suppression of adrenergic stimulation by β-receptor blockade alone may have adverse hemodynamic effects in ischemic heart disease and prompt further functional deterioration. Conversely, both calcium and combined α-β-receptor blockade tend to improve left ventricular function by lowering both left ventricular preload and total systemic vascular resistance. The results strongly suggest that in patients in whom β-receptor blockers appear indicated, their adverse hemodynamic effects can be offset by concomitant α₁-receptor blockade or vasodilation without losing symptomatic efficacy. Combined α-β-receptor blockade has the advantage over calcium antagonists alone to prevent any increase in adrenergic activity and related hyperkinetic response.     

Hemoglobinopathies in the dogon country: Presence of βs, βc,and δa'genes

The population of the Dogon, located in Mali, is divided in an endogamic Noble class and two endogamic servant castes (Tanners and Blacksmiths). We find that the polymorphic frequencies of β^c, β^s, and, unexpectedly, a mutation of the δ-chain (δ^A'), are geographically (valley vs. plateau) as well as social status dependent. © 1994 Wiley-Liss, Inc.     

The Cardiac β -Adrenoceptor-G-protein(s)-adenylyl Cyclase System in Monocrotaline-treated Rats

In rats, injection of the alkaloid monocrotaline (MCT) causes right ventricular hypertrophy and cardiac failure. In order to study whether, in MCT-treated rats, changes in the cardiac β -adrenoceptor-G-protein(s)-adenylyl cyclase system might be comparable to those found in human primary pulmonary hypertension, we assessed in right and left ventricles from MCT-treated rats the components of the β -adrenoceptor system: the receptor number and subtype distribution (by (-)-[¹²⁵I]iodocyanopindolol binding), the G-proteins (by quantitative Western blotting), and the activity of adenylyl cyclase. A single injection of 60 mg/kg i.p. MCT caused in rats right ventricular hypertrophy (RVH); part of the rats developed cardiac failure (RVF). In these rats the cardiac β -adrenoceptor-G-protein(s)-adenylyl cyclase system was markedly changed β -adrenoceptors were desensitized due to a decrease in receptor number, an uncoupling of the receptor from the G_s-adenylyl cyclase system, a decrease in G_sand a decrease in the activity of the catalytic unit of adenylyl cyclase. In general, these changes were more pronounced in right ventricles v left ventricles, and in rats with RVF v rats with RVH. On the other hand, cardiac muscarinic receptors and G_iappeared not to be altered. We conclude that in MCT-treated rats changes in the cardiac β -adrenoceptor-G-protein(s)-adenylyl cyclase system occur that resemble those observed in human primary pulmonary hypertension. Thus, MCT-treated rat appears to be a suitable animal model to study in more detail the pathophysiology of the development of right heart failure, and to identify new therapeutic possibilities.     

Thymosin-α1, but not interferon-α, specifically inhibits anchorage-independent growth of hepatitis B viral transfected HepG2 cells

Background: Thymosin-α₁ is a biological response modifier that has been used clinically, alone and in combination with interferon-α for the treatment of chronic hepatitis B viral infection. Both immunomodulatory and immediate intracelluilar mechanisms have been postulated to explain the effect of these two agents on HBV-infected hepatocytes.Methods: In this study, hepatitis B transfected HepG2 hepatoblastoma cells (HepG2-Nu2), derived from 2.2.15 cells, were used as an in vitro model to determine the efficacy of thymosin-α₁ and interferon-α, individually and combined, a proliferation inhibitors of HBV-infected cells. For comparison, parental HepG2 cells and an SV40-transfected HepG2 cell line (HepG2P9T2) were also evaluated.Results: In a clonogenic soft agar assay, thymosin-α₁ inhibited the anchorage-independent growth of the HepG2-Nu2 cells by 40% compared with untreated controls, but did not inhibit parental HepG2 or HepG2P9T2 clonal growth. The response was dose dependent over concentrations spanning three log units. In comparison, 10 000 units/ml of interferon-α inhibited parental HepG2, HepG2-N4Z and HepG2P9T2 by 33%, 41% and 87%, respectively. The combination of thymosin-α₁ and interferon-α consistently inhibited HepG2-Nu2 clonal growth more effectively than either treatment alone, reaching maximum inhibition levels of 51%.Conclusions: Thymosin-α₁ specifically inhibits the tumorigenic growth of HBV-transfected HepG2 cells in contrast to the general inhibition displayed by interferon-α. This panel of cell lines may be an important resource for dissecting the mechanism by which thymosin, alone or in combination with other drugs, influences HBV-infected hepatocytes and/or HBV-associated carcinoma.