Calcium-dependent epidermal growth factor receptor transactivation mediates the angiotensin II-induced mitogen-activated protein kinase activation in vascular smooth muscle cells

We have recently reported that angiotensin II (Ang II)-induced mitogen-activated protein kinase (MAPK) activation is mainly mediated by Ca2+-dependent activation of a protein tyrosine kinase through Gq-coupled Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMC). In the present study, we found Ang II rapidly induced the tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and its association with Shc and Grb2. These reactions were inhibited by the EGF receptor kinase inhibitor, AG1478. The Ang II-induced phosphorylation of the EGF receptor was mimicked by a Ca2+ ionophore and completely inhibited by an intracellular Ca2+ chelator. Thus, AG1478 abolished the MAPK activation induced by Ang II, a Ca2+ ionophore as well as EGF but not by a phorbol ester or platelet-derived growth factor-BB in the VSMC. Moreover, Ang II induced association of EGF receptor with catalytically active c-Src. This reaction was not affected by AG1478. These data indicate that Ang II induces Ca2+-dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.

Endothelin receptor subtype B mediates synthesis of nitric oxide by cultured bovine endothelial cells

Endothelins (ET) produce endothelium-dependent vasodilation through nitric oxide (NO) synthesis. The present study was designed to elucidate the cellular mechanism by which ET induces synthesis and release of endothelium-derived NO by cultured bovine endothelial cells (EC). Binding studies revealed that bovine EC membrane had the binding sites of a novel agonist (BQ3020) for non-isopeptide-selective receptor subtype (ETB). Affinity labeling studies showed a major labeled band with the apparent molecular mass of 50 kD. Northern blot analysis demonstrated the expression of mRNA for ETB receptor. BQ3020 rapidly and dose dependently induced formation of inositol-1,4,5-triphosphate and increased intracellular Ca2+ concentrations in fura-2-loaded cells. Concomitantly, BQ3020 dose dependently stimulated production of both nitrate/nitrite (NOx) and cyclic GMP; a highly significant correlation existed between NOx and cGMP production. The stimulatory effect on NOx and cGMP production by ETB agonist was inhibited by NO synthase inhibitor monomethyl-L-arginine; this effect was reversed by coaddition of L-arginine, but not D-arginine. NOx and cGMP production stimulated by BQ3020 was inhibited by pretreatment with pertussis toxin. ETB agonist-induced NOx production was blocked by a calmodulin inhibitor and an intracellular Ca2+ chelator, but not by an extracellular Ca2+ chelator or a Ca2+ channel blocker. These data suggest that endothelins stimulate ETB receptor-mediated phosphoinositide breakdown via pertussis toxin-sensitive G-protein(s), which triggers release of intracellular Ca2+, thereby activating Ca2+/calmodulin-dependent NO synthase in EC.

Clinical experience with a bioartificial liver in the treatment of severe liver failure. A phase I clinical trial

OBJECTIVE

The purpose of this study was to develop a bioartificial liver (BAL) to treat patients with severe liver failure until they can be either transplanted or recover spontaneously.

SUMMARY BACKGROUND DATA

Severe acute liver failure is associated with high mortality. Liver transplantation has emerged as an effective therapy for patients who did not respond to standard management. However, because of the donor organ shortage and urgent need for transplantation, many patients die before they can be transplanted and others do not survive after transplantation, primarily because of intracranial hypertension.

METHODS

Three groups of patients with severe acute liver failure were treated with the BAL. In group 1 (n = 18) were patients with fulminant hepatic failure (FHF), in group 2 (n = 3) were patients with primary nonfunction (PNF) of a transplanted liver, and in group 3 (n = 10) were patients with acute exacerbation of chronic liver disease. Patients in groups 1 and 2 were candidates for transplantation at the time they entered the study, whereas patients in group 3 were not.

RESULTS

In group 1, 16 patients were "bridged" successfully to transplantation, 1 patient was bridged to recovery without a transplant, and 1 patient died because of concomitant severe pancreatitis. In group 2, all patients were bridged successfully to retransplantation. In group 3, two patients were supported to recovery and successful transplants at later dates; the other eight patients, although supported temporarily with the BAL, later died because they were not candidates for transplantation.

CONCLUSIONS

The authors' clinical experience with the BAL has yielded encouraging results. A randomized, controlled, prospective trial (phase II-III) is being initiated to determine the efficacy of the system.

Specific receptors for adrenomedullin in cultured rat vascular smooth muscle cells

The effects of synthetic rat adrenomedullin (rAM), a novel vasorelaxant peptide originally isolated from human pheochromocytoma, on receptor binding and cAMP generation were studied in cultured rat vascular smooth muscle cells (VSMC). A binding study using [125I]rAM revealed the presence of a single class of high-affinity (Kd 1.3 x 10(-8) M) binding sites for rAM in VSMC. The apparent Ki of rat calcitonin gene-related peptide (rCGRP) was 3 x 10(-7) M. Affinity labeling of VSMC membranes with [125I]rAM revealed two distinct labeled bands with apparent molecular weights of 120 and 70 kDa, both of which were abolished by excess unlabeled rAM or rCGRP, rAM stimulated cAMP formation with an approximate EC50 of 10(-8) M, the effect of which was additive with isoproterenol, but not with rCGRP. The rAM-induced cAMP response was unaffected by propranolol, indomethacin, or quinacrine, but inhibited by a CGRP receptor antagonist, human CGRP[8-37]. These data suggest that VSMC possesses specific AM receptors functionally coupled to adenylate cyclase with which CGRP interacts.

Identification of an essential signaling cascade for mitogen-activated protein kinase activation by angiotensin II in cultured rat vascular smooth muscle cells. Possible requirement of Gq-mediated p21ras activation coupled to a Ca2+/calmodulin-sensitive tyrosine kinase

In cultured rat vascular smooth muscle cells, angiotensin II (Ang II) induced a rapid increase in mitogen-activated protein kinase (MAPK) activity through the Ang II type 1 receptor, which was insensitive to pertussis toxin but was abolished by the phospholipase C inhibitor, U73122. The Ang II-induced MAPK activation was not affected by the protein kinase C inhibitor, GF109203X, and was only partially impaired by pretreatment with a phorbol ester, whereas both treatments completely prevented MAPK activation by the phorbol ester. Intracellular Ca2+ chelation by TMB-8, but not extracellular Ca2+ chelation or inhibition of Ca2+ influx, abolished Ang II-induced MAPK activation. The calmodulin inhibitor, calmidazolium, and the tyrosine kinase inhibitor, genistein, completely blocked MAPK activation by Ang II as well as by the Ca2+ ionophore A23187. Ang II caused a rapid increase in the binding of GTP to p21(ras), and this was inhibited by genistein, TMB-8, and calmidazolium but not by pertussis toxin or GF109203X. These data suggest that Ang II-induced MAPK activation through the Ang II type 1 receptor could be mediated by p21(ras)activation through a currently unidentified tyrosine kinase that lies downstream of Gq-coupled Ca2+/calmodulin signals.

Activation of MAPKs by angiotensin II in vascular smooth muscle cells. Metalloprotease-dependent EGF receptor activation is required for activation of ERK and p38 MAPK but not for JNK

In cultured vascular smooth muscle cells (VSMC), the vasculotrophic factor, angiotensin II (AngII) activates three major MAPKs via the G(q)-coupled AT1 receptor. Extracellular signal-regulated kinase (ERK) activation by AngII requires Ca(2+)-dependent "transactivation" of the EGF receptor that may involve a metalloprotease to stimulate processing of an EGF receptor ligand from its precursor. Whether EGF receptor transactivation also contributes to activation of other members of MAPKs such as p38MAPK and c-Jun N-terminal kinase (JNK) by AngII remains unclear. In the present study, we have examined the effects of a synthetic metalloprotease inhibitor BB2116, and the EGF receptor kinase inhibitor AG1478 on AngII-induced activation of MAPKs in cultured VSMC. BB2116 markedly inhibited ERK activation induced by AngII or the Ca(2+) ionophore without affecting the activation by EGF or PDGF. BB2116 as well as HB-EGF neutralizing antibody inhibited the EGF receptor transactivation by AngII, suggesting a critical role of HB-EGF in the metalloprotease-dependent EGF receptor transactivation. In addition to the ERK activation, activation of p38MAPK and JNK by AngII was inhibited by an AT1 receptor antagonist, RNH6270. and EGF markedly activate p38MAPK, whereas but not EGF markedly activates JNK, indicating the possible contribution of the EGF receptor transactivation to the p38MAPK activation. The findings that both BB2116 and AG1478 specifically inhibited activation of p38MAPK but not JNK by AngII support this hypothesis. From these data, we conclude that ERK and p38MAPK activation by AngII requires the metalloprotease-dependent EGF receptor transactivation, whereas the JNK activation is regulated without involvement of EGF receptor transactivation.

Cellular mechanism of endothelin-1 release by angiotensin and vasopressin

Release of endothelin-1, a novel potent vasoconstrictor peptide originally isolated from endothelial cells, from cultured bovine endothelial cells has been shown to be stimulated by arginine vasopressin and angiotensin II. To elucidate the cellular mechanism by which endothelin-1 is released by these vasoconstrictors, we tested the effects of several compounds on the agonist-induced endothelin-1 release and studied the changes of cytosolic free Ca2+ concentrations and phosphoinositide breakdown by these agonists in cultured bovine endothelial cells. Protein kinase C inhibitors (H-7, staurosporine), an intracellular Ca2+ chelator, and an inhibitor of phospholipase C (neomycin), all abolished the agonist-induced endothelin-1 release, whereas the Ca2+ channel blocker nicardipine was ineffective. Although synthetic 1,2-diglyceride (diolein) dose dependently stimulated endothelin-1 release, downregulation of protein kinase C after pretreatment with phorbol ester resulted in decreased effects to increase endothelin-1 release by the agonists. Both arginine vasopressin and angiotensin II induced immediate and transient increases in intracellular Ca2+ levels of fura-2-loaded endothelial cells as well as formation of inositol trisphosphate; the agonist-induced intracellular Ca2+ increases were not affected either by nicardipine or by chelating extracellular Ca2+. The arginine vasopressin- and angiotensin II-induced intracellular Ca2+ increases, inositol trisphosphate formation, and endothelin-1 release were completely abolished by V1-receptor antagonist and saralasin, respectively. It is concluded that arginine vasopressin and angiotensin II stimulate the release of endothelin-1 by a common mechanism, involving receptor-mediated mobilization of intracellular Ca2+ and activation of protein kinase C in endothelial cells.

Mechanotransduction of rat aortic vascular smooth muscle cells requires RhoA and intact actin filaments

The growth-promoting effect of mechanical stress on vascular smooth muscle cells (VSMCs) has been implicated in the progress of vascular disease in hypertension. Extracellular signal-regulated kinases (ERKs) have been implicated in cellular responses, such as vascular remodeling, induced by mechanical stretch. However, it remains to be determined how mechanical stretch activates ERKs. The cytoskeleton seems the most likely candidate for force transmission into the interior of the cell. Therefore, we examined (1) whether the cytoskeleton involves mechanical stretch-induced signaling, (2) whether Rho is activated by stretch, and (3) whether Rho mediates the stretch-induced signaling in rat cultured VSMCs. Mechanical stretch activated ERKs, with a peak response observed at 20 minutes, followed by a significant increase in DNA synthesis. Treatment with the ERK kinase-1 inhibitor, PD98059, inhibited the stretch-induced increase in DNA synthesis. Cytochalasin D, which selectively disrupts the network of actin filaments, markedly inhibited stretch-induced ERK activation. In the control state, RhoA was observed predominantly in the cytosolic fraction, but it was translocated in part to the particulate fraction in response to mechanical stretch. Botulinum C3 exoenzyme, which inactivates Rho p21 (known to participate in the reorganization of the actin cytoskeleton), attenuated stretch-induced ERK activation. Inhibition of Rho kinase (p160ROCK) also suppressed stretch-induced ERK activation dose dependently. Our results suggest that mechanotransduction in VSMCs is dependent on intact actin filaments, that Rho is activated by stretch, and that Rho/p160ROCK mediates stretch-induced ERK activation and vascular hyperplasia.

Non-contact, two-dimensional measurement of tissue circulation in choroid and optic nerve head using laser speckle phenomenon

A new apparatus has been developed using the laser speckle phenomenon for non-contact, two-dimensional analysis of tissue circulation in the choroid and optic nerve head (ONH). The fundus was illuminated by a diode laser spot and its image speckle was detected by an image sensor. The difference between the average of the speckle intensity (Imean) and the speckle intensity for successive scannings was calculated, and the ratio of Imean to this difference was defined as normalized blur (NB), which is a quantitative index of blood velocity. The results were displayed on color graphic monitors showing the two-dimensional variation of the NB level in the measurement field. In the rabbit, this apparatus was used to study the relationship between the results of NB measurement and the choroidal blood flow determined by the microsphere technique, the relationship between NB obtained from the ONH tissue free of visible surface vessels and the ocular perfusion pressure (OPP) after a lethal injection of pentobarital, and the effect of intraocular pressure (IOP) on the NB in the choroid or in the ONH. A stepwise reduction in the OPP was introduced by elevating the IOP manometrically. The relative decrease in the average NB over the field measured, NBav, in the choroid with the reduction in OPP showed a significant correlation with the relative change in the blood flow rate determined using the microsphere technique (r = 0.60, P < 0.001). NBav in the ONH had a good correlation with the OPP after a lethal injection of pentobarbital (r = 0.98, P < 0.001). NBav in the choroid decreased with reduction in the OPP. Although NBav in the ONH was little affected by OPP change when OPP was above 40 mmHg, at OPP levels below 40 mmHg, NBav in the ONH decreased along with a reduction in the OPP. These results suggest that by using the present apparatus, the blood velocity in the choroid or ONH under various conditions can be studied non-invasively in the living eye.

Intracellular signaling of angiotensin II-induced p70 S6 kinase phosphorylation at Ser(411) in vascular smooth muscle cells. Possible requirement of epidermal growth factor receptor, Ras, extracellular signal-regulated kinase, and Akt

Activation of p70 S6 kinase (p70(S6K)) by growth factors requires multiple signal inputs involving phosphoinositide 3-kinase (PI3K), its effector Akt, and an unidentified kinase that phosphorylates Ser/Thr residues (Ser(411), Ser(418), Ser(424), and Thr(421)) clustered at its autoinhibitory domain. However, the mechanism by which G protein-coupled receptors activate p70(S6K) remains largely uncertain. By using vascular smooth muscle cells in which we have demonstrated Ras/extracellular signal-regulated kinase (ERK) activation through Ca(2+)-dependent, epidermal growth factor (EGF) receptor transactivation by G(q)-coupled angiotensin II (Ang II) receptor, we present a unique cross-talk required for Ser(411) phosphorylation of p70(S6K) by Ang II. Both p70(S6K) Ser(411) and Akt Ser(473) phosphorylation by Ang II appear to involve EGF receptor transactivation and were inhibited by dominant-negative Ras, whereas the phosphorylation of p70(S6K) and ERK but not Akt was sensitive to the MEK inhibitor. By contrast, the phosphorylation of p70(S6K) and Akt but not ERK was sensitive to PI3K inhibitors. Similar inhibitory pattern on these phosphorylation sites by EGF but not insulin was observed. Taken together with the inhibition of Ang II-induced p70(S6K) activation by dominant-negative Ras and the MEK inhibitor, we conclude that Ang II-initiated activation of p70(S6K) requires both ERK cascade and PI3K/Akt cascade that bifurcate at the point of EGF receptor-dependent Ras activation.

Involvement of PYK2 in angiotensin II signaling of vascular smooth muscle cells

-PYK2, a recently identified Ca2+-sensitive tyrosine kinase, has been implicated in extracellular signal-regulated kinase (ERK) activation via several G protein-coupled receptors. We have reported that angiotensin II (Ang II) induces Ca2+-dependent transactivation of the epidermal growth factor receptor (EGFR) which serves as a scaffold for preactivated c-Src and downstream adaptors (Shc/Grb2), leading to ERK activation in cultured rat vascular smooth muscle cells (VSMC). Herein we demonstrate the involvement of PYK2 in this cascade. Ang II rapidly induced tyrosine phosphorylation of PYK2, whose effect was completely inhibited by an AT1 receptor antagonist and an intracellular Ca2+ chelator. A Ca2+ ionophore also induced PYK2 tyrosine phosphorylation to a level comparable with that by Ang II, whereas phorbol ester-induced phosphorylation was less than that by Ang II. Moreover, PYK2 formed a complex coprecipitable with catalytically active c-Src after Ang II stimulation. Although a selective EGFR kinase inhibitor completely abolished Ang II-induced recruitment of Grb2 to EGFR and markedly attenuated Ang II-induced ERK activation, it had no effect on Ang II-induced PYK2 tyrosine phosphorylation or its association with c-Src and Grb2. These data suggest that the AT1 receptor uses Ca2+-dependent PYK2 to activate c-Src, thereby leading to EGFR transactivation, which preponderantly recruits Grb2 in rat VSMC.

Structure-activity relationship of adrenomedullin, a novel vasodilatory peptide, in cultured rat vascular smooth muscle cells

Vascular smooth muscle cells (VSMC) from rat aorta possess specific receptors for a novel potent vasorelaxant peptide, adrenomedullin (AM). To elucidate its receptor coupling to guanine nucleotide-binding stimulatory protein and the structural requirement of the AM molecule to its vascular receptors, we have studied the effects of guanine nucleotides on [125I]human (h) AM binding and adenylate cyclase activity in cultured rat VSMC, and the effects of various synthetic hAM analogs on [125I]hAM binding and the cAMP response. Guanosine 5'-O-(3-thiotriphosphate) dose dependently inhibited [125I]hAM binding to rat VSMC membranes. hAM stimulated adenylate cyclase activity, and its effect was additive with GTP. hAM-induced cAMP formation was abrogated by pretreatment with cholera toxin, but not by that with pertussis toxin. Intact hAM-(1-52)-NH2 and N-terminal truncated derivatives [hAM-(13-52)-NH2, hAM-(16-52)-NH2] almost equally inhibited [125I]hAM binding and stimulated cAMP formation, whereas removal of C-terminal Tyr52 residue [hAM-(1-51)-NH2] remarkably decreased receptor-binding activity and the cAMP response. The effects of hAM-(1-52)-OH, hAM-(1-51)-OH, and a linear hAM analog ([carbamoylmethyl-Cys16,21]hAM-NH2) were far less potent on receptor binding and the cAMP response than that of hAM-(1-52)-NH2. The C-terminal fragment [hAM-(33-52)-NH2] and the N-terminal fragment [hAM-(1-10)-OH] had neither receptor-binding nor adenylate cyclase activity. hAM-(22-52)-NH2 had no agonistic effect, but showed an antagonistic effect on the hAM-induced cAMP response. These data suggest that vascular AM receptors are functionally coupled to adenylate cyclase via guanine nucleotide-binding stimulatory protein. Studies of the structure-activity relationship of hAM revealed that the cyclic structure formed by the disulfide bridge and amidation of the C-terminal residue of the AM molecule are critical for receptor binding and subsequent cAMP generation and suggest that the C-terminal fragment hAM-(22-52)-NH2 may be an antagonist for vascular AM receptors.

Signal transduction of angiotensin II type 1 receptor through receptor tyrosine kinase

In cultured vascular smooth muscle cells, the angiotensin II (AngII) type-1 (AT(1)) receptor generates growth-promoting signals via the epidermal growth factor (EGF) receptor system. This 'transactivation' mechanism now appears to be utilized by a variety of G-protein-coupled receptors in many cells. The AngII-induced EGF receptor transactivation leads to activation of downstream signaling molecules including Ras, ERK, c-fos, Akt/protein kinase B, and p70 S6 kinase. We propose three possible mechanisms may be involved in the transactivation, (i) an upstream tyrosine kinase, (ii) reactive oxygen species, and (iii) a juxtacrine activation of the EGF receptor ligand. Whether the EGF receptor signal transduction induced by AngII plays an essential role in cardiovascular remodeling remains to be investigated.

Induction of nitric oxide synthase gene by interleukin-1 beta in cultured rat cardiocytes

BACKGROUND

Impaired myocardial contractility in septic shock is protracting, which may be caused by cytokine-induced nitric oxide (NO) synthesis in the heart. However, the cellular mechanism by which cytokines induce nitric oxide synthase (NOS) in cardiocytes remains obscure.

METHODS AND RESULTS

We studied the effect of human recombinant interleukin-1 beta (IL-1 beta) on synthesis of NO2-/NO3- (NOx) and the expression of NOS mRNA and protein in cultured neonatal rat cardiocytes. IL-1 beta dose-dependently (0.1 to 10 ng/mL) stimulated NOx production as a function of time (6 to 48 hours). Northern blot analysis using complementary DNAs for rat brain-type constitutive (c) NOS and mouse macrophage-type inducible (i) NOS as probes showed that IL-1 beta induced expression of mRNA for iNOS but not for cNOS, starting after 6 hours and reaching a maximum after 48 hours in cardiocytes. IL-1 beta similarly induced iNOS mRNA expression in cultured adult rat cardiocytes in a time-dependent manner. Western blot analysis using specific antibody against the N-terminal fragment of mouse iNOS revealed the expression of 130-kD iNOS-like protein in IL-1 beta-treated cardiocytes. Northern blotting and immunocytochemical study revealed that IL-1 beta-induced iNOS mRNA and iNOS-like immunoreactivity were exclusively localized to cardiac myocytes but also to nonmyocytes, to a lesser extent. NG-mono-methyl-L-arginine, an NOS inhibitor, completely blocked the IL-1 beta-induced NOx production, whose effect was reversed by L-arginine but not by D-arginine. Dexamethasone inhibited the IL-1 beta-induced NOx production as well as iNOS mRNA expression. Cycloheximide and actinomycin D completely inhibited the IL-1 beta-induced NOx production and iNOS mRNA expression. Neither a calmodulin inhibitor (W-7), a protein kinase C inhibitor (calphostin C), nor a Ca2+ channel antagonist (nicardipine) showed any effect on the IL-1 beta-induced NOx production.

CONCLUSIONS

These data demonstrate that IL-1 beta induces macrophage-type iNOS mRNA expression mainly by cardiac myocytes but also by nonmyocytes to a lesser extent, and subsequent de novo protein synthesis of iNOS leads to excessive local production of NO by cardiocytes.

Role of necroptosis in the pathogenesis of solid organ injury

Necroptosis is a type of regulated cell death dependent on the activity of receptor-interacting serine/threonine-protein (RIP) kinases. However, unlike apoptosis, it is caspase independent. Increasing evidence has implicated necroptosis in the pathogenesis of disease, including ischemic injury, neurodegeneration, viral infection and many others. Key players of the necroptosis signalling pathway are now widely recognized as therapeutic targets. Necrostatins may be developed as potent inhibitors of necroptosis, targeting the activity of RIPK1. Necrostatin-1, the first generation of necrostatins, has been shown to confer potent protective effects in different animal models. This review will summarize novel insights into the involvement of necroptosis in specific injury of different organs, and the therapeutic platform that it provides for treatment.

L-arginine infusion induces hypotension and diuresis/natriuresis with concomitant increased urinary excretion of nitrite/nitrate and cyclic GMP in humans

1. The vascular endothelium produces endothelium-derived relaxing factor (EDRF) or nitric oxide (NO), which exerts vasodilation through cyclic guanosine monophosphate (cGMP) as a second messenger. To determine whether EDRF has any vasodilating and natriuretic action in man, the present study examined the effects of L-arginine (L-Arg), a substrate for NO, on the responses of mean blood pressure (MBP) and heart rate (HR); plasma concentrations of cGMP, atrial natriuretic factor (ANF) and nitrite/nitrate (NOx); urinary excretion of sodium, cGMP and NOx; and urinary flow in eight normal male subjects. These parameters were compared with those following saline infusion in the same subjects. Clearance of para-aminohippuric acid (PAH) and inulin was studied in five normal subjects. 2. Infusion of L-Arg (30 g) caused a significant fall in MBP (-8 mmHg) with a concomitant rise in HR (10 beats/min), while saline infusion had no effects on these parameters. 3. Neither L-Arg nor saline infusion caused appreciable changes in plasma concentrations of ANF or NOx. Plasma cGMP concentrations increased significantly during (1.7-fold) and after (1.9-fold) L-Arg infusion, but only slightly (1.3-fold) during saline infusion. 4. Urine flow increased more remarkably following L-Arg infusion than that following saline infusion. Remarkable increases in urinary excretion of sodium and fractional excretion of sodium were observed after L-Arg infusion compared with those after saline infusion. Natriuresis was associated with enhanced urinary excretion of cGMP and Nox. Urinary Nox excretion showed positive correlations with urinary flow (r = 0.69, P less than 0.001) and with urinary cGMP excretion (r = 0.60, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

A role for transcriptional repressors in targeting the yeast Swi/Snf complex

Genetic and biochemical studies indicate that the evolutionarily conserved Swi/Snf complex acts at a subset of genes to help transcriptional activators function on chromatin templates. The mechanism by which this complex is targeted to specific chromosomal loci remains unknown. We show that Swi/Snf is required for expression of the yeast histone HTA1-HTB1 locus because of the role of Hir1p and Hir2p corepressors in negatively regulating transcription. Snf5p, Snf2p/Swi2p, and Swi3p, three components of the yeast Swi/Snf complex, coimmunoprecipitate with each Hir protein, and Snf5p is maximally associated with the HTA1-HTB1 promoter when the Hir-based repression system is intact and the Swi/Snf complex is functional. The data support a role for the Hir repressors in the gene-specific targeting of Swi/Snf.

Fulminant hepatic failure in rats: survival and effect on blood chemistry and liver regeneration

A reproducible experimental animal model of fulminant hepatic failure (FHF) resembling the clinical condition is needed. We have developed such a model in the rat by combining resection of the two anterior liver lobes (68% liver mass) with ligation of the right lobes pedicle (24% liver mass), resulting in liver necrosis; the remaining two omental lobes (8% liver mass) are left intact. Adult Sprague-Dawley rats (250-300 g) were used. Survival time was determined in 60 rats. Because maintenance of body temperature at 37 degrees C shortened survival time by half, FHF rats were not warmed during the postinduction period and were allowed to gradually enter a state of mild to moderate hypothermia (29-32 degrees C). Additionally, 42 FHF rats were killed in batches of six rats each 2, 6, 12, 18, 24, 30, and 36 hours postoperatively to evaluate changes in blood chemistry (glucose, lactate, liver function tests, prothrombin time) and to assess liver regenerative response in the residual omental liver lobes (weight, protein content, incorporation of bromodeoxyuridine [BrdU], expression of proliferation cell nuclear antigen [PCNA], mitotic activity), plasma levels of hepatocyte growth factor (HGF) and transforming growth factor beta (TGF-beta1), and tissue expression of the HGF and it's receptor c-met. Rats undergoing partial hepatectomy of 68% (PH; n = 42) and a sham operation (SO; n = 42) served as controls. All SO and PH controls survived. PH rats showed only transient decreases in body temperature, signs of modest early hepatic dysfunction (hyperlactemia, hyperammonemia, prolonged PT time), and normal restitution of liver mass. All FHF rats became comatose by 24 hours postoperatively. Most animals (90%) died within 24-48 hours postoperatively (mean, 39 +/- 11 hours). Changes in blood chemistry reflected rapid development of liver failure. Plasma HGF levels were markedly elevated and at all time points were higher than in PH controls (P < .05). At the same time, expression of HGF and c-met messenger RNA in the remnant liver was delayed. Plasma TGF-beta1 levels increased early (18 hours) and remained twofold to threefold higher than that of PH and SO controls (P < .05). There was only a 20% increase in the weight of the remnant liver lobes due to swelling. No hepatocytes stained positively for BrdU and PCNA, and none showed mitotic figures. In contrast, all PH controls showed vigorous liver regeneration. In conclusion, we have developed and characterized a novel model of FHF in rats that has a number of physiological and biochemical features seen clinically in FHF, including severely impaired ability of the residual liver tissue to regenerate.

Mechanical stretch stimulates growth of vascular smooth muscle cells via epidermal growth factor receptor

We have studied whether activation of epidermal growth factor receptor (EGFR) is involved in stretch-induced extracellular signal-regulated kinase 1/2 (ERK1/2) activation and protein synthesis in cultured rat vascular smooth muscle cells (VSMC). Cyclic stretch (1 Hz) induced a rapid (within 5 min) phosphorylation of ERK1/2, an effect that was time and strength dependent and inhibited by an EGFR kinase inhibitor (AG-1478) but not by a platelet-derived growth factor receptor kinase inhibitor (AG-1296). The stretch rapidly (within 2 min) induced tyrosine phosphorylation of several proteins, among which 180-kDa protein was shown to be EGFR as revealed by blockade with AG-1478 as well as immunoprecipitation with anti-EGFR antibody coupled with immunoblotting with anti-phosphotyrosine antibody. The stretch rapidly (within 2 min) induced association of tyrosine-phosphorylated EGFR with adaptor proteins (Shc/Grb2) as revealed by coprecipitation with glutathione-S-transferase-Grb2 fusion protein coupled with immunoblotting with anti-phosphotyrosine, anti-EGFR, and anti-Shc antibodies. Transfection of a dominant-negative mutant of H-Ras also inhibited stretch-induced ERK1/2 activation. Treatment with a stretch-activated ion channel blocker (Gd(3+)) and an intracellular Ca(2+) antagonist (TMB-8) inhibited stretch-induced phosphorylation of EGFR and ERK1/2. Treatment with AG-1478 and a mitogen-activated protein kinase kinase inhibitor (PD-98059), but not AG-1296, blocked [(3)H]leucine uptake stimulated by a high level of stretch. These data suggest that ERK1/2 activation by mechanical stretch requires Ca(2+)-sensitive EGFR activation mainly via stretch-activated ion channels, thereby leading to VSMC growth.

Quantitative analysis of regular and irregular astigmatism induced by pterygium

PURPOSE

To quantitatively evaluate the influence of pterygium and its removal surgery on both regular and irregular corneal astigmatism.

METHODS

In 19 eyes of 19 patients undergoing pterygium surgery, videokeratographic measurements were taken before and 1 month after surgery. Using Fourier harmonic analysis, dioptric data on mire rings were decomposed into spherical, regular astigmatism, and irregular astigmatism (decentration and higher order irregularity) components. The distance between the line of sight and the advancing edge of pterygium was measured, and the eyes were classified into two groups: large pterygium group (the distance <2.0 mm, n = 7) and small pterygium group (> or =2.0 mm, n = 12). Fifteen eyes of 15 subjects served as age-matched normal control eyes.

RESULTS

Before surgery, the magnitudes of regular astigmatism and higher order irregular astigmatism showed significant correlation with the size of pterygium. Regular astigmatism, asymmetry, and higher order irregularity in the large pterygium group were significantly greater than those of normal control eyes. The pterygium removal surgery significantly improved these changes, but regular astigmatism and higher order irregularity in the large pterygium group still remained significantly greater than those in the normal control eyes.

CONCLUSION

Pterygium induces a significant amount of regular and irregular astigmatism in proportion to its size. The removal surgery can improve these changes, but corneal distortion does not normalize completely in eyes with advanced pterygium.

A novel ETA antagonist (BQ-123) inhibits endothelin-1-induced phosphoinositide breakdown and DNA synthesis in rat vascular smooth muscle cells

The effects of a novel cyclic pentapeptide (BQ-123), an endothelin (ET) antagonist selective for the ETA receptor subtype, on phosphoinositide breakdown and DNA synthesis stimulated by ET-1 were studied in cultured rat vascular smooth muscle cells (VSMC). BQ-123 competitively inhibited the binding of [125I]ET-1 to VSMC with the apparent Ki of 4 x 10(-9) M. BQ-123 dose-dependently inhibited formation of inositol-1,4,5-trisphosphate and [3H]thymidine uptake stimulated by ET-1. These data suggest that the ET-1-induced DNA synthesis in VSMC is mainly mediated by ETA receptor subtype.

A possible association between suspected restrictive pattern as assessed by ordinary pulmonary function test and the metabolic syndrome

BACKGROUND

Impaired restrictive pulmonary function has been reported to be associated with insulin resistance and metabolic abnormalities. However, the possible association of restrictive pulmonary defect with metabolic syndrome (MetS) is not well understood. We examined the association in comparison with C-reactive protein (CRP), which is a predictor for MetS.

METHODS

We recruited 2,396 apparently healthy adults and investigated the associations among pulmonary function, metabolic abnormality, and MetS, as defined by three different criteria. Abnormal pulmonary function was evaluated by both continuous pulmonary function variables including the percentage of predicted FVC (%PFVC) and a clinical category defined according to the American Thoracic Society/European Respiratory Society guidelines.

RESULTS

CRP and %PFVC, but not FEV1/FVC ratio, were significantly correlated with metabolic abnormalities even after adjustment for confounders including waist circumference. After adjustment for age, sex, and height, the odds ratios (ORs) of a restrictive pattern (RP), as defined by a reduced FVC and a normal FEV1/FVC ratio using the lower limit of normal and RP substitutively defined by reduced FVC and an FEV1/FVC ratio of > or = 85% for MetS, were 1.76 to 2.52 (p < 0.05 to < 0.0001) and 1.87 to 2.28 (p < 0.05 to < 0.01), respectively. The obstructive pattern (OP) was not significantly associated with any MetS criteria. A moderate-to-severe RP, but not a high CRP level (> 3.0 mg/L), was consistently associated with the three MetS criteria (OR, 2.08 to 3.57; p < 0.05 to < 0.01), even after adjustment for confounders.

CONCLUSION

Impaired restrictive pulmonary function, but not OP, might be associated with metabolic disorders and MetS in a severity-dependent manner.

Recurrence-free survival more than 10 years after liver resection for hepatocellular carcinoma

BACKGROUND

High recurrence rates after liver resection with curative intent for hepatocellular carcinoma (HCC) remain a problem. The characterization of long-term survivors without recurrence after liver resection may help improve the therapeutic strategy for HCC.

METHODS

A nationwide Japanese database was used to analyse 20 811 patients with HCC who underwent liver resection with curative intent.

RESULTS

The 10-year recurrence-free survival rate after liver resection for HCC with curative intent was 22.4 per cent. Some 281 patients were recurrence-free after more than 10 years. The HCCs measured less than 5 cm in 83.2 per cent, a single lesion was present in 91.7 per cent, and a simple nodular macroscopic appearance was found in 73.3 per cent of these patients; histologically, most HCCs showed no vascular invasion or intrahepatic metastases. Multivariable analysis revealed tumour differentiation as the strongest predictor of death from recurrent HCC within 5 years.

CONCLUSION

Long-term recurrence-free survival is possible after liver resection for HCC, particularly in patients with a single lesion measuring less than 5 cm with a simple nodular appearance and low tumour marker levels.

Involvement of reactive oxygen species in the activation of tyrosine kinase and extracellular signal-regulated kinase by angiotensin II

Reactive oxygen species (ROS) have been proposed to mediate vascular hypertrophy induced by angiotensin II (Ang II). Recently, we and others have shown that growth-promoting signals by Ang II involve protein tyrosine kinase (PTK) and extracellular signal-regulated kinase (ERK). However, whether ROS contribute to the Ang II-induced PTK and/or ERK activation in vascular smooth muscle cells (VSMCs) remains largely unclear. Here, we have investigated the possible involvement of ROS in Ang II-induced PTK and ERK activation. In the presence of a NADH/NADPH oxidase inhibitor, diphenyleneiodonium (DPI) or an antioxidant, alpha-tocopherol, Ang II-induced protein tyrosine phosphorylation of two major proteins (p120, p70) and ERK activation were markedly reduced, whereas ERK activation by epidermal growth factor was unaffected. DPI also inhibited Ang II-induced H2O2 production and PTK activation. In this regard, H2O2 and a membrane permeable thiol-oxidizing agent, diamide, stimulated protein tyrosine phosphorylation of p120 and p70, and ERK activation in VSMCs. H2O2 also enhanced PTK activity. From these data, we conclude that ROS play a critical role in the Ang II-induced PTK and ERK activation in VSMCs, thereby contributing to vascular growth associated with enhanced Ang II activity.