Identification of Nck interacting proteins in vascular smooth muscle cells

The adaptor molecule Nck has been demonstrated to mediate Angiotensin II (AngII)-induced stimulation of p21-activated kinase (PAK) and c-Jun NH2-terminal kinase (JNK) in vascular smooth muscle cells (VSMC). We have previously demonstrated, that immunoprecipitation of Nck from VSMC stimulated by AngII yielded an unidentified 100 kD phosphotyrosine (pTyr) protein. The present study was aimed at identifying the Nck-associated 100 kD pTyr protein in VSMC. Several candidate proteins of appropriate size, that had been shown previously either to bind to Nck or had been implicated in signal transduction pathways leading to activation of PAK or JNK were tested for association with Nck in VSMC. The first candidate protein we tested was Git1, which did not bind to Nck in VSMC upon stimulation by AngII. However, we identified dynamin as a 100 kD protein that was bound to Nck in VSCM via interaction with the third Nck-SH3 domain. However, dynamin was not tyrosine phosphorylated by AngII treatment and seemed to be distinct from the 100 kD phosphotyrosine protein that was found in Nck immunoprecipitates. Future work will now have to identify the Nck-associated 100 kD pTyr protein and functional studies will have to address its role in AngII signaling.

Effect of tracheal occlusion on peripheric pulmonary vessel muscularization in a fetal rabbit model for congenital diaphragmatic hernia

OBJECTIVE

This study was undertaken to evaluate the effects on peripheric pulmonary vessel muscularization by tracheal occlusion (TO) performed at different gestational ages in fetal rabbits with surgically induced diaphragmatic hernia.

STUDY DESIGN

In 23 New Zealand white does, both ovarian end fetuses underwent surgical creation of diaphragmatic hernia at 23 days of gestation (pseudoglandular phase). At 26, 27, or 28 days 1 fetus underwent TO, the contralateral one underwent a sham operation for a total of 46 fetuses. At 30 days (alveolar phase), fetuses were harvested together with 1 nonoperated internal control. Lungs were processed for vascular morphometry. Proportionate medial thickness and muscularization of intra-acinar vessels were evaluated.

RESULTS

Late TO (day 28; saccular phase) normalizes the lung-to-body weight ratio and causes significant medial thinning in vessels up to 35 microm diameter.

CONCLUSION

Tracheal occlusion decreases muscularization of intra-acinar pulmonary vessels in a gestational age-dependent fashion, with maximal effect when TO is performed at 28 days.

Properties of engineered vascular constructs made from collagen, fibrin, and collagen–fibrin mixtures

Vascular constructs were formed by embedding rat aortic smooth muscle cells in three-dimensional matrices of Type I collagen, fibrin, or a mixture of collagen and fibrin in a 1:1 ratio, at total matrix protein concentrations of 2 and 4 mg/ml. Morphological and mechanical properties were evaluated after 6 days in culture, and the effect of cyclic mechanical strain on collagen-fibrin mixture constructs was also studied. Constructs made with the lower protein concentration compacted to the greatest degree, and fibrin was found to enhance gel compaction. Each matrix type exhibited a characteristic stress-strain profile. Pure collagen had the highest linear modulus and pure fibrin had the lowest. The ultimate tensile stress was strongly dependent on the degree of gel compaction, and collagen-fibrin mixtures at 2mg/ml total protein content exhibited the highest values. Application of cyclic mechanical strain to collagen-fibrin mixture constructs caused a significant increase in gel compaction and a decrease in cell proliferation. The linear modulus, ultimate tensile stress and toughness of the constructs were all augmented by mechanical strain. These results demonstrate that the properties of engineered vascular tissues can be modulated by the combination of selected extracellular matrix components, and the application of mechanical stimulation.

Haemangiomas are formed by cells expressing high levels of alphavbeta3 integrin and lacking acetylated LDL uptake

Haemangiomas are benign tumours occurring in up to 12% of Caucasians, particularly in infancy and childhood. In the present study, two variant cell lines were isolated from murine endothelioma cells. One variant, named t.End.1V(high), represented 16.9% of the parental cell population and was selected by virtue of high expression levels of integrin alphavbeta3 and reduced capacity to endocytose acetylated low-density lipoproteins (Ac-LDLs). A second variant, named t.End.1V(low), represented 38.8% of the parental endothelioma cell line, expressed low levels of alphavbeta3 integrin, and was able to endocytose Ac-LDL. These phenotypic modifications were stable and correlated with specific morphological and functional properties of the two variant cell lines. While the t.End.1V(high) cells induced the formation of large haemangiomas when injected subcutaneously into mice, the t.End.1V(low) cells formed haemangiocytomas. When compared with t.End.1V(low) cells, the t.End.1V(high) cells showed increased migratory capacity, lacked an inflammatory response, and formed cord-like structures in fibrin gels. In contrast, the t.End.1V(low) cells organized into cysts with a lumen in fibrin gels. They rarely formed blood-filled haemangiomas in vivo and recruited host smooth muscle cells, a phenomenon typical for vessel wall maturation of resting cells. These data suggest that Ac-LDL uptake and the level of alphavbeta3 integrin expression are linked to the ability of endothelial cells to form large haemangiomas in vivo.

Tissue distribution of ACE2 protein, the functional receptor for SARS coronavirus. A first step in understanding SARS pathogenesis

Severe acute respiratory syndrome (SARS) is an acute infectious disease that spreads mainly via the respiratory route. A distinct coronavirus (SARS-CoV) has been identified as the aetiological agent of SARS. Recently, a metallopeptidase named angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for SARS-CoV. Although ACE2 mRNA is known to be present in virtually all organs, its protein expression is largely unknown. Since identifying the possible route of infection has major implications for understanding the pathogenesis and future treatment strategies for SARS, the present study investigated the localization of ACE2 protein in various human organs (oral and nasal mucosa, nasopharynx, lung, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver, kidney, and brain). The most remarkable finding was the surface expression of ACE2 protein on lung alveolar epithelial cells and enterocytes of the small intestine. Furthermore, ACE2 was present in arterial and venous endothelial cells and arterial smooth muscle cells in all organs studied. In conclusion, ACE2 is abundantly present in humans in the epithelia of the lung and small intestine, which might provide possible routes of entry for the SARS-CoV. This epithelial expression, together with the presence of ACE2 in vascular endothelium, also provides a first step in understanding the pathogenesis of the main SARS disease manifestations.

Acute coronary syndromes: Virchow's triad revisited

The acute coronary syndromes (ACS), which include unstable angina, non-ST-segment and ST-segment elevation acute myocardial infarction, all share common pathophysiology processes that are characterized by coronary plaque disruption with superimposed thrombus formation, leading to myocardial ischaemia. A greater understanding of these processes has enable us to correlate the abnormalities in arterial vessel wall substrates ('vessel abnormalities'), rheologic and biomechanical conditions ('abnormal flow'), and blood thrombogenicity ('abnormal blood constituents') to the contribution of coronary plaque disruption and subsequent thrombosis, with the basic concepts of Virchow's triad for thrombus formation (thrombogenesis) described about 150 years ago. This improved understanding has led to the identification of newer therapeutic targets and, hence, novel pharmacological agents targeting different components of Virchow's triad, particularly in altering thrombus formation and plaque vulnerability.

Evidence for functionally active protease-activated receptor-3 (PAR-3) in human vascular smooth muscle cells

The present study investigates whether vascular smooth muscle cells of the human saphenous vein (SMC) express a functionally active protease-activated receptor-3 (PAR-3). PAR-3 mRNA was detected by RT-PCR. In the presence of thrombin, a rapid and transient increase in PAR-3 mRNA was observed. Stimulation of SMC with thrombin or the synthetic PAR-3-activating peptide, TFRGAP, resulted in transient mobilization of intracellular calcium. After a preceding challenge with thrombin, the calcium signal to TFRGAP was abolished, suggesting cleavage and subsequent desensitization of PAR-3 by thrombin. Activation of PAR-3 by TFRGAP elicited a time-dependent activation of the extracellular-signal-regulated kinase (ERK)-1/2 with a maximum response 10-20 min after stimulation. At 200 microM, TFRGAP increased [3H]-thymidine incorporation into cellular DNA about two-fold. These data indicate that PAR-3 is expressed in human SMC and triggers intracellular signaling. Thus, in the SMC PAR-3 might contribute to thrombin-induced responses.

Presence of Cx37 and lack of desmin in smooth muscle cells are early markers for arteriogenesis

In search of early structural markers of arteriogenesis, we studied the expression of gap junction proteins as well as of contractile and cytoskeletal proteins in smooth muscle cells (SMCs) during coronary collateral vessel growth induced by chronic occlusion of the left circumflex artery (LCx) in the dog heart. We used confocal microscopy with antibodies against connexin37 (Cx37), alpha-smooth muscle actin (alpha-SM actin), calponin, desmin and vinculin. The quantitative confocal analysis of immunofluorescence intensity showed that (1) in normal vessels (NV), Cx37 was present in endothelium only, not in SMC. Calponin, alpha-SM actin, desmin and vinculin were evenly expressed in SMC. (2) In early growing V (EV) with minimal intima formation, alpha-SM actin, calponin and vinculin showed little change in SMC, but desmin was 3.3 times lower than in NV, and Cx37 was induced (NV 0 arbitrary units/microm2, EV 50.3). (3) In actively growing V (AV), alpha-SM actin, calponin and vinculin were 3-, 3.3- and 2.9-fold lower, respectively, in the neointima as compared to the media. However, Cx37 was 48.2 AU/microm2 in the media and 15.8 AU/microm2 in the neointima. Desmin was almost absent in the neointima and 5-fold reduced in the media. SMC, strongly positive for alpha-SM actin and calponin, expressed Cx37. Our findings indicate that induction of Cx37 and reduction of desmin precede the phenotypic changes of SMCs, which are characterized by down-regulation of alpha-SM actin, calponin and vinculin, and the formation of a neointima. An altered expression of Cx37 and desmin, therefore, are early markers for arteriogenesis in dog heart.

Lysosomal deposition of Abeta in cultures of brain vascular smooth muscle cells is enhanced by iron

Recently, we found that brain vascular smooth muscle cells from Tg2576 mice over-expressed the APP transgene in culture, secreted amyloid-beta peptide (Abeta) and accumulated Abeta intracellularly. Now we detected this intracellular Abeta inside lysosomes, which were also rich in C-terminal domain of APP, but not in endoplasmic reticulum, Golgi apparatus, or trans-Golgi network. Treatment of cultures with ferrous ions (50-150 microM) increased the proportion of muscle cells with Abeta immunoreactive granules and the amounts of intracellular Abeta1-40 and Abeta1-42 in a dose-dependent manner. This increase of intracellular Abeta1-40 by iron was inhibited by alpha-tocopherol, but not by a water-soluble antioxidant melatonin. The increase of intracellular Abeta1-42 by iron was not inhibited by alpha-tocopherol or melatonin. Cell treatment with iron did not alter the lysosomal localization of Abeta immunoreactivity. Cell treatment with iron (II and III), copper (II), zinc (II) and aluminum (III) increased cellular levels of carbonyls. However, the effect of zinc on Abeta accumulation in cultures was weak, and there were no effects of copper and aluminum. The data suggest that iron may be the factor that triggers vascular amyloidosis. Lysosomal accumulation of APP and Abeta initiates deposition of amyloid in blood vessels in Tg2576 mice.

Control of actin dynamics by p38 MAP kinase – Hsp27 distribution in the lamellipodium of smooth muscle cells

We investigated the role of the p38 mitogen-activated protein kinase (p38 MAPK) in the PDGF-BB-induced cytoskeleton remodeling that occurs during the migration of porcine aortic smooth muscle cells (SMC). We showed that p38 MAPK controlled the polymerization of actin that is required for PDGF-induced lamellipodia formation and migration. To investigate the mechanism of action of p38 MAPK, we explored its cellular localization and that of its indirect substrate, the heat shock protein Hsp27, during SMC spreading on fibronectin in the presence and absence of PDGF. Spreading of SMC on fibronectin activated p38 MAPK in a sustained manner only in the presence of PDGF. In these conditions, Hsp27 and p38 MAPK were localized all over the lamellipodia. A transiently phosphorylated form of p38 MAPK was observed at the leading edge, whereas p38 MAPK remained phosphorylated at the base of the lamellipodia. Phosphorylated Hsp27 was excluded from the leading edge and restricted to the base of the lamellipodia. These results were confirmed by Triton X-100 extraction of particulate membrane fraction. Displacement of Hsp27 from the leading edge by cytochalasin D treatment suggests that nonphosphorylated Hsp27 caps barbed ends in vivo. Our data indicate that nonphosphorylated Hsp27 might contribute to the formation of a short, branched actin network at the leading edge, whereas phosphorylated Hsp27 might stabilize the actin network at the base of lamellipodia, which is composed of long, unbranched actin filaments.

Complement 3 is involved in the synthetic phenotype and exaggerated growth of vascular smooth muscle cells from spontaneously hypertensive rats

Vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) show the synthetic phenotype and exaggerated growth in comparison with VSMCs from normotensive Wistar-Kyoto (WKY) rats. We investigated genes associated with the synthetic phenotype and exaggerated growth of VSMCs from SHR by microarray. Expression of 1300 transcripts was evaluated by microarray with total mRNA extracted from mid-layer aortic smooth muscle of 3-week-old SHR/Izumo and WKY/Izumo rats. mRNAs encoding sodium-dependent neurotransmitter transporter, epidermal growth factor precursor, EEF2, leptin receptor long-isoform b, clathrin assembly protein short form, and preprocomplement 3 (pre-pro-C3) were expressed only in aortic smooth muscle from SHR by microarray and by reverse-transcription polymerase chain reaction analysis. Pre-pro-C3 mRNA was detected only in cultured VSMCs from SHR. Exogenous C3 changed VSMCs to the synthetic phenotype. Antisense oligodeoxynucleotides (ODN) to C3 reduced the higher level of DNA synthesis in VSMCs from SHR. Antisense ODN to C3 increased expression of SM22alpha mRNA and decreased expression of osteopontin and matrix Gla mRNAs. It also decreased expression of growth factor mRNAs in VSMCs from SHR. In conclusion, we have shown that C3, independent of other complement molecules, has direct effects on the phenotype of VSMCs and stimulates growth of these cells. C3 is produced only by VSMCs from SHR. Therefore, C3 may be the gene underlying the synthetic phenotype and exaggerated growth of VSMCs from SHR. C3 may be a new target for the treatment of hypertension.

Distribution of actin and myosin in the cochlear microvascular bed

OBJECTIVE

Previous studies of the microvascular bed of the rat inner ear showed vascular constriction after i.v. application of endothelin-1 (ET-1). Luminal narrowing together with multiple circumscribed constrictions were observed on vascular corrosion casts of initial and small calibre veins. These constrictions were interpreted as being caused by contractile cytoplasmic fibrils, most probably of pericytes; pericytes reportedly respond to ET-1 and the frequency, distribution and dimension of pericytes and their cytoplasmic processes closely corresponded to the constrictions observed. In the present study we analysed the distribution of actin and myosin in order to directly show the presence of contractile cytoplasmic fibrils.

MATERIAL AND METHODS

We performed standard immunostaining for actin, smooth muscle actin, smooth muscle myosin and tropomyosin in the cochlea. We used different fixation protocols (methacarn, neutral formalin, Bouin's fluid) and compared observations in two species (rat and guinea pig).

RESULTS

Immunohistochemistry confirmed the presence of contractile cytoplasmic fibrils in cochlear pericytes and vascular smooth muscle cells. Microvessels in the cochlea were much better provided with contractile fibrils in rats compared to guinea pigs. The distribution of contractile fibrils in rats corresponded well to the luminal constrictions observed on vascular corrosion casts.

CONCLUSIONS

Our results support the assumption that active myofibrillar contraction (in response to ET-1 stimulation of pericytes) causes luminal constriction in cochlear microvessels. Contraction of myofibrils can be influenced by intrinsic or extrinsic agents, which offers new therapeutic regimens to govern cochlear blood flow. As the frequency of contractile cells on cochlear microvessels varied with the species studied, evaluation of human material will be the next step.

Matrix Metalloproteinase-2-Mediated Inhibition of Na + -Dependent Ca 2 + Uptake by Superoxide Radicals (O 2 . − ) in Microsomes of Pulmonary Smooth Muscle

Treatment of microsomes (preferably enriched with endoplasmic reticulum) isolated from bovine pulmonary artery smooth muscle tissue with the O2*- -generating system (hypoxanthine (HPX) plus xanthine oxidase (XO)), markedly stimulated matrix metalloproteinase-2 (MMP-2) activity and also enhanced Ca2+ ATPase activity and ATP-dependent Ca2+ uptake. Pretreatment with superoxide dismutase (SOD) and tissue inhibitor of metalloproteinase (TIMP-2) (50 microg ml(-1)), preserved the increase in MMP-2 activity, Ca2+ ATPase activity and also ATP-dependent Ca2+ uptake in the microsomes. In contrast, Na+-dependent Ca2+ uptake in the microsomes was found to be inhibited by the O2*- - generating system. Additionally, O2*- -induced inhibition of Na+-dependent Ca2+ uptake was reversed by SOD and TIMP-2 (50 microg ml(-1)). Electron microscopy revealed that treatment with the O2*- -generating system did not cause any noticeable damage to the microsomes. O2*- -induced changes in MMP-2 activity, ATP-dependent Ca2+ uptake and Na+-dependent Ca2+ uptake, were not reversed upon pretreatment of the microsomes with a low dose (5 microg ml(-1)) of TIMP-2 which, on the contrary, reversed MMP-2 (1 microg ml(-1))-mediated alteration on these parameters. The inhibition of Na+-dependent Ca2+ uptake by O2*- and MMP-2, overpowered the stimulation of ATP-dependent Ca2+ uptake in the microsomes. Treatment of TIMP-2 (5 microg ml(-1)) with the O2*- -generating system abolished the inhibitory effect of TIMP-2 (5 microg ml(-1)) on MMP-2 (1 microg ml(-1)) (measured by (14)C-gelatin degradation). Overall, the present study suggests that O2*- inactivated TIMP-2, the ambient inhibitor of MMP-2, leading to activation of the ambient proteinase, MMP-2, which subsequently stimulated Ca2+ ATPase activity and ATP-dependent Ca2+ uptake, but inhibited Na+-dependent Ca2+ uptake, resulting in a marked decrease in Ca2+ uptake in the smooth muscle microsomes.

Non-helical type IV collagen polypeptides in human placenta

Our previous reports showed that cultured human cells secrete non-disulfide-bonded non-helical alpha1(IV) and alpha2(IV) chains under physiological conditions. In the present report we show that the alpha(IV) chains in non-helical form were reactive to lectin ABA (Agaricus bisporus agglutinin), whereas the alpha(IV) chains secreted in triple-helical form were not. These results indicate that ABA could be used to distinguish the two conformational isomers of type IV collagen polypeptides. An alpha1(IV) chain isolated from human placenta with an antibody-coupled column showed a positive reaction to ABA, indicating that gelatin form of the type IV collagen alpha1(IV) chain is produced and retained in the tissue in vivo. A possible significance of the gelatin form is discussed from the finding that the non-helical alpha1(IV) chain purified with EDTA-free buffer contained degraded polypeptides including NC1-size domain and showed an apparent inhibition against activated pro-MMP-9. This is the first report to show that a gelatin form of protein exists in vivo.

[Fluorescence quantification of intracellular calcium of rat smooth muscle cells]

OBJECTIVE

To explore the kinetic changes of calcium in rat smooth muscle cells and establish a method for quantification of intracellular calcium.

METHODS

Rat mesenteric arteriolar smooth muscle cells (ASMCs) were isolated and the kinetic changes of calcium were measured using highly sensitive Ca2+ fluorescent probe indo-1 with laser scanning confocal microscopy (LSCM). The dissociation constant values (Kd) of the fluorescent probe indo-1 was measured at 37 degrees Celsius, and according to the conversion formula from fluorescence intensity to concentration, the concentration of Ca2+ was calculated.

RESULTS

Analysis of the fluorescent images using LSCM showed that [Ca2+]i in the ASMCs were significantly elevated in response to stimulation with dexamethasone, and spontaneous calcium waves as well as intracellular calcium overloading were observed occasionally.

CONCLUSION

Fluorescence quantification with LSCM is applicable for detecting the kinetic changes of intracellular [Ca2+]i.

The source of heme for vascular heme oxygenase II: de novo heme biosynthesis in rat aorta

Heme is an essential prosthetic group or substrate for many proteins, including hemoglobin, and hemo enzymes such as nitric oxide synthase, soluble guanylyl cyclase, and heme oxygenase (HO). HO is responsible for the breakdown of heme into equimolar amounts of biliverdin, iron, and carbon monoxide, the latter of which is thought to play a role in the regulation of vascular tone. It is not clear whether the source of heme for cardiovascular functions is derived from uptake from the extracellular milieu or synthesis. In this study, we tested the hypothesis that blood vessels obtain their supply of heme for HO through de novo synthesis. Adult male Sprague–Dawley rat aorta was incubated at 37 °C in Krebs' solution with 1 µM [14C]δ-aminolevulinic acid (ALA). [14C]ALA uptake was linear for about 30 min and reached a plateau at approximately 100 min. The radioactivity was incorporated into porphyrins and heme as determined by esterification of14C-labelled metabolites and thin-layer chromatography. The first and rate-limiting step of heme biosynthesis is catalyzed by ALA synthase (ALA-S), the activity of which was determined in rat aorta using a radiometric assay, ~250 nmol·(g wet mass)–1·h–1. Inducing HO-1 in rat aorta with S-nitroso-N-acetyl penicil la mine (500 µM) did not increase ALA-S activity as compared with basal activity levels of the enzyme. It appears that there is a sufficient amount of heme available under basal ALA-S activity conditions to meet the increased demand for heme resulting from HO-1 induction. These observations indicate that the complete enzymatic pathway for de novo heme biosynthesis resides in rat aorta and furthermore indicate that de novo heme synthesis is capable of supplying a substantial portion of the heme substrate for HO in the aorta.Key words: heme biosynthesis, vasculature, carbon monoxide, heme oxygenase, δ-aminolevulinic acid synthase.

Proinflammatory phenotype of coronary arteries promotes endothelial apoptosis in aging

Previously we demonstrated that aging in coronary arteries is associated with proinflammatory phenotypic changes and decreased NO bioavailability, which, we hypothesized, promotes vascular disease by enhancing endothelial apoptosis. To test this hypothesis we characterized proapoptotic alterations in the phenotype of coronary arteries of aged (26 mo old) and young (3 mo old) F344 rats. DNA fragmentation analysis and TUNEL assay showed that in aged vessels there was an approximately fivefold increase in the number of apoptotic endothelial cells. In aged coronary arteries there was an increased expression of TNFα, TNFβ, and caspase 9 (microarray, real-time PCR), as well as increased caspase 9 and caspase 3 activity, whereas expression of TNFR1, TNFα-converting enzyme (TACE), Bcl-2, Bcl-X(L), Bid, Bax, caspase 8, and caspase 3 were unchanged. In vessel culture (18 h) incubation of aged coronary arteries with a TNF blocking antibody or the NO donor S-nitroso-penicillamine (SNAP) decreased apoptotic cell death. Incubation of young arteries with exogenous TNFα increased caspase 9 activity and elicited endothelial apoptosis, which was attenuated by SNAP. Inhibition of NO synthesis in cultured young coronary arteries also induced apoptotic cell death and potentiated the apoptotic effect of TNFα. Thus we propose that age-related upregulation of TNFα and caspase 9 and decreased bioavailability of NO promote endothelial apoptosis in coronary arteries that may lead to impaired endothelial function and ischemic heart disease in the elderly.

Changes in the vascular beta-adrenoceptor-activated signalling pathway in 2Kidney-1Clip hypertensive rats

1. beta-Adrenoceptor (beta-AR)-mediated vasodilation, which plays an important physiological role in the regulation of vascular tone, is decreased in two-kidney, one clip (2K-1C) renal hypertension. In this study, downstream pathways related to vascular beta-AR activation were evaluated in 2K-1C rats. 2. Relaxation responses to isoprenaline, forskolin and 8-Br-cAMP were diminished in aortas without endothelium from 2K-1C when compared to those in normotensive two kidney (2K). Basal adenosine-3',5'-monophosphate (cAMP), as well as isoprenaline-induced increase in cAMP levels, was not different between 2K and 2K-1C aortas. 3. Contractile responses to caffeine, after depletion and reloading of intracellular Ca(2+) stores, were greater in 2K-1C than in 2K. The presence of isoprenaline during the Ca(2+)-reloading period abolished the differences between groups by increasing caffeine contraction in 2K without changing this response in 2K-1C aortas. Inhibition of the sarcolemmal Ca(2+)ATPase with thapsigargin markedly attenuated isoprenaline vasodilation in both 2K and 2K-1C and abolished the differences between groups. 4. Blockade of ATP-sensitive K(+) channels (K(ATP)) channels with glibenclamide significantly decreased isoprenaline vasodilation in 2K-1C without affecting this response in 2K. Both vascular gene and protein expression of protein kinase A (PKA), as well as phosphoserine-containing proteins, were increased in 2K-1C vs 2K rats. 5. In conclusion, decreased isoprenaline vasodilation in 2K-1C hypertensive rats is related to impaired modulation of the sarcolemmal Ca(2+)ATPase activity. Moreover, K(ATP) channels may play a compensatory role on isoprenaline-induced relaxation in renal hypertension. Both Ca(2+)ATPase and K(ATP) channel functional alterations, associated with decreased beta-AR vasodilation, are paralleled by an upregulation of protein kinase A (PKA) and phosphoserine proteins expression.

Effect of mycophenolate mofetil on glomerulosclerosis and renal oxidative stress in rats

BACKGROUND/AIMS

Mycophenolate mofetil (MMF) is known to attenuate glomerulosclerosis in experimental models of renal failure. We investigated whether this is mediated by reduction of oxidative stress.

METHODS

Effects of MMF on oxidative stress are studied in an experimental rat model (NA model) involving unilateral nephrectomy and two intravenous injections with adriamycin (2 mg/kg). Rats are sacrificed after 2 and 6 weeks. Glomerulosclerosis and tubulointerstitial lesions are demonstrated by histological techniques. Presence of macrophages/monocytes (ED1) and myofibroblasts (alpha-SMA) is demonstrated by immunohistochemistry. Oxidative stress is evaluated by enzymatic measurements (AOE), spectrofluorometry (TBARS), immunohistochemistry (MDA and HNE) and histology (ferric iron deposition).

RESULTS

The NA model shows proteinuria, hypercholesterolemia, beginning glomerulosclerosis, tubulointerstitial sclerosis and tubular dilatation, glomerular, periglomerular and interstitial presence of alpha-SMA and increased presence of macrophages/monocytes after 6 weeks. Oxidative stress in renal cortex is apparent (increased cortex TBARS concentration, increased glomerular presence of MDA and HNE, decreased activity of antioxidant enzymes, ferric iron deposition in proximal tubules) after 6 weeks. MMF administration results in a decrease of glomerulosclerosis, interstitial sclerosis, glomerular and periglomerular expression of alpha-SMA and the number of ED1-positive cells in tubulointerstitium and glomeruli. Proteinuria and cholesterolemia are not decreased. TBARS level, and activities of catalase, Mn and Cu/Zn superoxide dismutase as well as the presence of ferric iron in the proximal tubules are not changed by MMF treatment. Cortex activity of glutathione peroxidase returns to normal.

CONCLUSION

MMF has a favorable effect on glomerular and interstitial fibrosis in the NA model of kidney disease, but not on proteinuria and cholesterolemia. Improvement of fibrosis cannot be explained by major changes in oxidative stress or antioxidant defense.

Elemental maps in human allantochorial placental vessels cells. 4. Isoproterenol and sodium nitroprusside effects

The ionic channels (particularly, K+ and Ca2+ channels) regulate, via the membrane potential, the ionic distribution into the vascular cells. Micro-particule induced X-ray emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMCs) and of vascular endothelial cells (VECs) in the placental human allantochorial vessels in a physiological medium (Hanks' solution) modified by the addition of a NO donor (sodium nitroprusside, SNP) and of a beta-adrenergic stimulator (isoproterenol, ISO). The addition of SNP or ISO induced no modification of the Na, K, Cl, P, S, Mg and Ca concentrations in VSMCs. In VECs, a same effect was observed except an increase of the Mg concentration with ISO. Theses results indicated a retroactive control (active feedback) of the internal ionic distribution by endothelial factors, ionic channels and exchangers.

Interferon regulatory factor-1 mediates PPARgamma-induced apoptosis in vascular smooth muscle cells

OBJECTIVE

Peroxisome proliferator-activated receptor gamma (PPARgamma) possesses general beneficial effects on the cardiovascular system, such as inhibition of vascular lesion formation and atherosclerosis. However, molecular mechanisms for these effects are yet to be fully defined. The aim of this study is to elucidate whether interferon regulatory factor-1 (IRF-1), a transcriptional factor with anti-proliferative and pro-apoptotic properties, mediates PPARgamma-induced apoptosis in vascular smooth muscle cells (VSMCs).

METHODS AND RESULTS

Using Northern and Western blot analyses, we documented that PPARgamma ligands, including ciglitazone, troglitazone, and GW7845, significantly increased IRF-1 expression in VSMCs; however, the PPARalpha ligand (Wy14643) and PPARdelta ligand (GW0742) did not affect its expression. PPARgamma-induced IRF-1 expression was abrogated by pretreatment with the PPARgamma antagonist GW9662. In contrast, adenoviral expression of PPARgamma in VSMCs dramatically increased IRF-1 level. Furthermore, PPARgamma activation increased IRF-1 promoter activity but did not affect IRF-1 mRNA stability. Finally, reducing IRF-1 expression by antisense technology attenuated PPARgamma-induced VSMC apoptosis through decreasing cyclin-dependent kinase inhibitor p21(cip1) and caspase-3 activity.

CONCLUSIONS

Our data demonstrate that IRF-1 is a novel PPARgamma target gene and mediates PPARgamma-induced VSMC apoptosis.

Vascular non-endothelial nitric oxide induced by swimming exercise stress in rats

1. Herein, we report the effects of acute or chronic forced swimming on vascular responsiveness to angiotensin (Ang) II. 2. The possible involvement of locally produced substances, such as nitric oxide (NO) and prostanoids, in these effects were studied in rat thoracic aorta and superior mesenteric arteries. 3. Chronic, but not acute, swimming reduced the efficacy (maximal effect; Emax) of AngII in thoracic aorta and mesenteric arteries, either with intact or denuded endothelium. 4. The efficacy of AngII was reduced in the presence of indomethacin in mesenteric arteries, but not in the aorta, from either control or chronically stressed rats. 5. Treatment with NG-monomethyl-l-arginine reversed the effect of chronic stress on the response to AngII, suggesting that chronic stress may increase non-endothelial NO activity in both the aorta and mesenteric arteries. 6. The effects of acute and chronic stress on vascular reactivity were selective for AngII because no changes were observed on the effects of phenylephrine.

Insulin stimulates glucose transport via nitric oxide/cyclic GMP pathway in human vascular smooth muscle cells

OBJECTIVE

In cultured human vascular smooth muscle cells, insulin increases cyclic GMP production by inducing nitric oxide (NO) synthesis. The aim of the present study was to determine whether in these cells the insulin-stimulated NO/cyclic GMP pathway plays a role in the regulation of glucose uptake.

METHODS AND RESULTS

Glucose transport in human vascular smooth muscle cells was measured as uptake of 2-deoxy-d-[3H]glucose, cyclic GMP synthesis was checked by radioimmunoassay, and GLUT4 recruitment into the plasma membrane was determined by immunofluorescence. Insulin-stimulated glucose transport and GLUT4 recruitment were blocked by an inhibitor of NO synthesis and mimicked by NO-releasing drugs. Insulin- and NO-elicited glucose uptake were blocked by inhibitors of soluble guanylate cyclase and cyclic GMP-dependent protein kinase; furthermore, glucose transport was stimulated by an analog of cyclic GMP.

CONCLUSIONS

Our results suggest that insulin-elicited glucose transport (and the corresponding GLUT4 recruitment into the plasma membrane) in human vascular smooth muscle cells is mediated by an increased synthesis of NO, which stimulates the production of cyclic GMP and the subsequent activation of a cyclic GMP-dependent protein kinase.

Evidence for protein kinase C-mediated activation of Rho-kinase in a porcine model of coronary artery spasm

OBJECTIVE

We have recently demonstrated that protein kinase C (PKC) and Rho-kinase play important roles in coronary vasospasm in a porcine model. However, it remains to be examined whether there is an interaction between the two molecules to cause the spasm.

METHODS AND RESULTS

A segment of left porcine coronary artery was chronically treated with IL-1beta-bound microbeads in vivo. Two weeks after the operation, phorbol ester caused coronary spasm in vivo and coronary hypercontractions in vitro at the IL-1beta-treated segment; both were significantly inhibited by hydroxyfasudil, a specific Rho-kinase inhibitor. Guanosine 5'-[gamma-thio]triphosphate (GTPgammaS), which activates Rho with a resultant activation of Rho-kinase, enhanced Ca2+ sensitization of permeabilized vascular smooth muscle cells, which were resistant to the blockade of PKC by calphostin C. The GTPgammaS-induced Ca2+ sensitization was greater in the spastic segment than in the control segment. Western blot analysis revealed that only PKCdelta isoform was activated during the hypercontraction.

CONCLUSIONS

These results demonstrate that PKC and Rho-kinase coexist on the same intracellular signaling pathway, with PKC located upstream on Rho-kinase, and that among the PKC isoforms, only PKCdelta may be involved. Thus, the strategy to inhibit Rho-kinase rather than PKC may be a more specific and useful treatment for coronary spasm.

Direct interaction between the actin-binding protein filamin-A and the inwardly rectifying potassium channel, Kir2.1

The role of filamins in actin cross-linking and membrane stabilization is well established, but recently their ability to interact with a variety of transmembrane receptors and signaling proteins has led to speculation of additional roles in scaffolding and signal transduction. Here we report a direct interaction between filamin-A and Kir2.1, an isoform of inwardly rectifying potassium channel expressed in vascular smooth muscle and an important regulator of vascular tone. Yeast two-hybrid screening of a porcine coronary artery cDNA library using the carboxyl terminus of Kir2.1 as bait yielded cDNA encoding a fragment of filamin-A (residues 2481-2647). Interaction between filamin-A and Kir2.1 was confirmed by in vitro overlay assay of membrane-bound Kir2.1 with glutathione S-transferase fusion protein of the isolated filamin clone. Additionally, antibodies directed against Kir2.1 coimmunoprecipitated filamin-A from arterial smooth muscle cell lysates, and immunocytochemical analysis of individual arterial smooth muscle cells showed that Kir2.1 and filamin co-localize in "hotspots" at the cell membrane. Interaction with filamin-A was found to have no effect on Kir2.1 channel behavior but, rather, increased the number of functional channels resident within the membrane. We conclude that filamin-A is potentially an important regulator of Kir2.1 surface expression and location within vascular smooth muscle.

Functional regulation of tissue plasminogen activator on the surface of vascular smooth muscle cells by the type-II transmembrane protein p63 (CKAP4)

We have demonstrated that tissue plasminogen activator (tPA) binds specifically to human vascular smooth muscle cells (VSMC) in a functionally relevant manner, both increasing plasminogen activation and decreasing tPA inhibition (Ellis, V., and Whawell, S. A. (1997) Blood 90, 2312-2322; Werner, F., Razzaq, T. M., and Ellis, V. (1999) J. Biol. Chem. 274, 21555-21561). To further understand this system we have now identified and characterized the protein responsible for this binding. Rat VSMC were surface-labeled with 125I, and cell lysates were subjected to an affinity chromatography scheme based on the previously identified tPA binding characteristics. A single radiolabeled protein of 63 kDa bound specifically and was eluted at low pH. This protein was isolated from large scale preparations of VSMC and unambiguously identified as the rat homologue of the human type-II transmembrane protein p63 (CKAP4) by matrix-assisted laser desorption ionization and nano-electrospray tandem mass spectrometry of tryptic fragments. In confirmation of this, a monoclonal antibody raised against authentic human p63 recognized the isolated protein in Western blotting. Immunofluorescence microscopy demonstrated that p63 was located principally in the endoplasmic reticulum but was also detected in significant quantities on the surface of human VSMC. In support of the hypothesis that p63 is the functional tPA binding site on VSMC, an anti-p63 monoclonal antibody was found to block tPA binding. Furthermore, heterologous expression of an N-terminally truncated mutant of p63, which targets exclusively to the plasma membrane, led to an increase in tPA-catalyzed plasminogen activation. Therefore, p63 on the surface of VSMC may contribute to the functional regulation of the plasminogen activation system in the vessel wall.

Diverse Contribution of Bone Marrow Cells to Neointimal Hyperplasia After Mechanical Vascular Injuries

We and others have suggested that bone marrow-derived progenitor cells may contribute to the pathogenesis of vascular diseases. On the other hand, it was reported that bone marrow cells do not participate substantially in vascular remodeling in other experimental systems. In this study, three distinct types of mechanical vascular injuries were induced in the same mouse whose bone marrow had been reconstituted with that of GFP or LacZ mice. All injuries are known to cause smooth muscle cell (SMC) hyperplasia. At 4 weeks after wire-mediated endovascular injury, a significant number of the neointimal and medial cells derived from bone marrow. In contrast, marker-positive cells were seldom detected in the lesion induced by perivascular cuff replacement. There were only a few bone marrow-derived cells in the neointima after ligation of the common carotid artery. These results indicate that the origin of intimal cells is diverse and that contribution of bone marrow-derived cells to neointimal hyperplasia depends on the type of model.

Apolipoprotein D inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell proliferated by preventing translocation of phosphorylated extracellular signal regulated kinase 1/2 to the nucleus

OBJECTIVE

Elevated apolipoprotein D (apoD) levels are associated with reduced proliferation of cancer cells. We therefore investigated whether apoD, which occurs free or associated with HDL, suppresses vascular smooth muscle cell (VSMC) proliferation, which is related to the pathobiology of disease.

METHODS AND RESULTS

Intense immunoreactivity for apoD was observed in human atherosclerotic plaque but not in normal coronary artery. However, an increase in apoD mRNA was seen in quiescent relative to proliferating fetal lamb aortic VSMCs, and in the rat aortic VSMC line (A10), we demonstrated uptake of apoD from serum. Stable transfection of apoD in A10 cells in the absence of serum did not influence VSMC proliferation assessed by [3H]-thymidine incorporation. ApoD, administered at a dose of 100 ng/mL, completely inhibited basal as well as platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation (P<0.01) but had no effect on fibroblast growth factor-induced VSMC proliferation. ApoD did not suppress PDGF-BB or fibroblast growth factor-2-induced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 but selectively inhibited PDGF-BB-mediated ERK1/2 nuclear translocation.

CONCLUSIONS

Our data suggest that apoD selectively modulates the proliferative response of VSMC to growth factors by a mechanism related to nuclear translocation of ERK1/2.

Vascular endothelial growth factor-D expression in human atherosclerotic lesions

OBJECTIVE

Vascular endothelial growth factor-D (VEGF-D) is a recently characterized member of the VEGF family, but its expression in atherosclerotic lesions remains unknown. We studied the expression of VEGF-D and its receptors (VEGFR-2 and VEGFR-3) in normal and atherosclerotic human arteries, and compared that to the expression pattern of VEGF-A.

METHODS

Human arterial samples (n=39) obtained from amputation operations and fast autopsies were classified according to the stage of atherosclerosis and studied by immunohistochemistry. The results were confirmed by in situ hybridization and RT-PCR.

RESULTS

We found that while VEGF-A expression increased during atherogenesis, VEGF-D expression remained relatively stable only decreasing in complicated lesions. In normal arteries and in early lesions VEGF-D was mainly expressed in smooth muscle cells, whereas in complicated atherosclerotic lesions the expression was most prominent in macrophages and also colocalized with plaque neovascularization. By comparing the staining profiles of different antibodies, we found that proteolytic processing of VEGF-D was efficient in the vessel wall. VEGFR-2, but not VEGFR-3, was expressed in the vessel wall at every stage of atherosclerosis.

CONCLUSIONS

Our results suggest that in large arteries VEGF-D is mainly expressed in smooth muscle cells and that it may have a role in the maintenance of vascular homeostasis. However, in complicated lesions it was also expressed in macrophages and may contribute to plaque neovascularization. The constitutive expression of VEGFR-2 in arteries suggests that it may be one of the principal mediators of the VEGF-D effects in large arteries.

Functional effects of novel anti-ClC-3 antibodies on native volume-sensitive osmolyte and anion channels in cardiac and smooth muscle cells

Whether ClC-3 encodes volume-sensitive organic osmolyte and anion channels (VSOACs) remains controversial. We have shown previously that native VSOACs in some cardiac and vascular myocytes were blocked by a commercial anti-ClC-3 carboxy terminal antibody (Alm C592-661 antibody), although recent studies have raised questions related to the specificity of Alm C592-661 antibody. Therefore, we have developed three new anti-ClC-3 antibodies and investigated their functional effects on native VSOACs in freshly isolated canine pulmonary artery smooth muscle cells (PASMCs) and guinea pig cardiac myocytes. These new antibodies produced a common prominent immunoreactive band with an apparent molecular mass of 90-92 kDa in the guinea pig heart and PASMCs, and a similar molecular mass immunoreactive band was observed in the brain from homozygous Clcn3+/+ mice but not from homozygous Clcn3-/- mice. VSOACs elicited by hypotonic cell swelling in PASMCs and guinea pig atrial myocytes were nearly completely abolished by intracellular dialysis with two new anti-ClC-3 antibodies specifically targeting the ClC-3 carboxy (C670-687 antibody) and amino terminus (A1-14 antibody). This inhibition of native VSOACs can be attributed to a specific interaction with endogenous ClC-3, because 1) preabsorption of the antibodies with corresponding antigens prevented the inhibitory effects, 2) extracellular application of a new antibody raised against an extracellular epitope (Ex133-148) of ClC-3 failed to inhibit native VSOACs in PASMCs, 3) intracellular dialysis with an antibody targeting Kv1.1 potassium channels failed to inhibit native VSOACs in guinea pig atrial myocytes, and 4) anti-ClC-3 C670-687 antibody had no effects on swelling-induced augmentation of the slow component of the delayed rectifying potassium current in guinea pig ventricular myocytes, although VSOACs in the same cells were inhibited by the antibody. These results confirm that endogenous ClC-3 is an essential molecular entity responsible for native VSOACs in PASMCs and guinea pig cardiac myocytes.

Differential localisation of the renin–angiotensin system in de-novo lesions and in-stent restenotic lesions in in-vivo human coronary arteries

OBJECTIVE

Different components of the renin-angiotensin system (RAS) have been demonstrated in atherosclerotic plaques. However, the involvement of the RAS in in-stent restenosis is not clear. We studied the differential immunolocalisation of angiotensin converting enzyme (ACE) and the angiotensin II type 1 (AT1) receptor in de-novo stenotic lesions and in-stent restenotic lesions in human coronary arteries.

METHODS

Using a pullback atherectomy catheter, biopsies from de-novo coronary lesions (n=19) and in-stent restenotic lesions (n=19) were obtained. The biopsies were immunostained for vascular smooth muscle cells (VSMCs), macrophages, ACE and the AT1 receptor.

RESULTS

In biopsies from de-novo stenotic lesions ACE-positive macrophages were more numerous than in in-stent restenotic lesions (P=0.002). Moreover, in the latter lesions, ACE-positive macrophages decreased when the time interval of stent implantation was longer. On the other hand, in-stent restenotic lesions contained predominantly young VSMCs, which abundantly expressed AT1 receptors.

CONCLUSIONS

Lesional ACE expression is not a prominent feature of in-stent restenotic lesions. In contrast, AT1 receptors are abundantly expressed on young VSMCs. In de-novo lesions ACE and AT1 receptors were found on macrophages and VSMCs, which were present in all specimens.

Role of Crk-associated substrate in the regulation of vascular smooth muscle contraction

A pool of actin monomers is induced to polymerize into actin filaments during contractile stimulation of smooth muscle. The inhibition of actin dynamics by actin polymerization inhibitors depresses active force generation in smooth muscle. In this study, we hypothesized that Crk-associated substrate plays a role in the regulation of contraction and actin dynamics in vascular smooth muscle. Antisense or sense oligodeoxynucleotides for Crk-associated substrate were introduced into carotid smooth muscle tissues by chemical loading. The treatment of smooth muscle strips with antisense oligodeoxynucleotides inhibited the expression of Crk-associated substrates; it did not influence the expression of actin, myosin heavy chain, and paxillin. Sense oligodeoxynucleotides did not affect the expression of these proteins in smooth muscle tissues. Force generation in response to stimulation with norepinephrine or KCl was significantly lower in antisense-treated muscle strips than in sense-treated strips or in muscle strips not treated with oligodeoxynucleotides. The downregulation of Crk-associated substrate did not attenuate increases in phosphorylation of the 20-kDa regulatory light chain of myosin in response to stimulation with norepinephrine. The increase in F-actin/G-actin ratio during contractile stimulation was significantly inhibited in antisense-treated smooth muscle strips. Contractile activation of smooth muscle increased the association of profilin with actin monomers; the depletion of Crk-associated substrate inhibited the increases in the profilin-actin complex in response to contractile stimulation. These results suggest that Crk-associated substrate is a necessary molecule of signaling cascades that regulate active force generation in smooth muscle. This molecule may regulate actin dynamics in smooth muscle in response to contractile stimulation.

Chronic physiological shear stress inhibits tumor necrosis factor-induced proinflammatory responses in rabbit aorta perfused ex vivo

BACKGROUND

Regions in the vasculature exposed to steady laminar flow have a lower likelihood for atherosclerosis than regions exposed to disturbed flow with low shear stress. We previously found that laminar flow of short duration inhibited tumor necrosis factor (TNF)-alpha-mediated proinflammatory signaling in cultured endothelial cells (ECs). However, mechanisms responsible for the atheroprotective effects of physiological shear stress remain undefined. Therefore, we examined the effects of chronic shear stress on TNF-alpha-induced inflammatory responses using an ex vivo perfusion organ culture system.

METHODS AND RESULTS

Rabbit aortas were exposed to low or normal shear stress (0.4 or 12 dyne/cm2) at a constant pressure for 24 to 26 hours. EC and vascular smooth muscle cell (VSMC) proteins were selectively purified. After exposure to low shear stress, TNF-alpha (50 ng/mL, 6 hours) specifically stimulated vascular cell adhesion molecule (VCAM)-1 expression in ECs but not VSMCs. TNF-alpha-stimulated VCAM expression was inhibited significantly by preexposure to normal shear stress. Normal shear stress inhibited TNF (15 minutes) activation of mitogen-activated protein (MAP) kinases (c-Jun NH2-terminal kinase [JNK], p38, extracellular signal-regulated kinase [ERK]) in ECs. Specific pharmacological inhibitors of JNK and p38 but not ERK significantly inhibited TNF-induced VCAM expression. Normal shear stress prevented the association of TNF receptor (TNFR)-1 with TNFR-associated factor (TRAF)-2. There was no effect of low or normal shear stress on TNF-alpha-induced nuclear factor-kappaB activation. A nitric oxide synthesis inhibitor, NG-nitro-l-arginine methyl ester, did not reverse the inhibitory effects of shear stress on VCAM expression.

CONCLUSIONS

These results suggest that physiological shear stress is antiinflammatory by specifically inhibiting MAP kinase signaling and inhibiting TRAF-2 interaction with TNFR-1.

Emergence of smooth muscle cell endothelin B-mediated vasoconstriction in lambs with experimental congenital heart disease and increased pulmonary blood flow

BACKGROUND

Endothelin-1 (ET-1) has been implicated in the pathophysiology of pulmonary hypertension. In 1-month-old lambs with increased pulmonary blood flow, we have demonstrated early alterations in the ET-1 cascade. The objective of this study was to investigate the role of potential later alterations of the ET cascade in the pathophysiology of pulmonary hypertension secondary to increased pulmonary blood flow.

METHODS AND RESULTS

Eighteen fetal lambs underwent in utero placement of an aortopulmonary vascular graft (shunt) and were studied 8 weeks after spontaneous delivery. Compared with age-matched control lambs, lung tissue ET-1 levels were increased in shunt lambs (317.2+/-113.8 versus 209.8+/-61.8 pg/g, P<0.05). In shunt lambs (n=9), exogenous ET-1 induced potent pulmonary vasoconstriction, which was blocked by the ETA receptor antagonist PD 156707 (n=3). This pulmonary vasoconstriction was mimicked by exogenous Ala1,3,11,15 ET-1 (4 Ala ET-1), the ETB receptor agonist, and was blocked by the ETB receptor antagonist BQ 788 (n=3). However, in control lambs (n=7), ET-1 and 4 Ala ET-1 did not change pulmonary vascular tone. In contrast to 4-week-old shunt lambs, immunohistochemistry revealed the emergence of ETB receptors on smooth muscle cells in the vasculature of 8-week-old shunt lambs.

CONCLUSIONS

Over time, increased pulmonary blood flow and/or pressure results in the emergence of ETB-mediated vasoconstriction, which coincides with the emergence of ETB receptors on smooth muscle cells. These data suggest an important role for ETB receptors in the pathophysiology of pulmonary hypertension in this animal model of increased pulmonary blood flow.

Aldehydes mediate tissue factor induction: A possible mechanism linking lipid peroxidation to thrombotic events

Tissue factor (TF), which is expressed in atherosclerotic plaques and colocalizes with oxidized lipids, initiates the thrombogenic process. We have analyzed the effect of aldehydes derived from peroxidation of polyunsaturated fatty acids on TF expression in human vascular smooth muscle cells (HVSMC). Our results demonstrate that hexanal and 2,4-decadienal (2,4-DDE), two apolar aldehydes, increase TF expression. Exposure of HVSMC to hexanal for 2 h led to TF protein levels up to seven times higher than untreated cells whereas 2,4-DDE for 30 min led to them being up to 2.2 times higher. This induction of TF antigen by aldehydes correlates with an increase in TF mRNA levels. Electrophoretic mobility shift assays (EMSAs) showed that the binding activity of the transcription factor AP-1 (c-Fos/c-Jun) to TF promoter was elevated in response to these oxidation products. This enhancement was associated to an increase of c-fos transcriptional activity, which was reversible by pretreatment with simvastatin. We conclude that the induction of TF by aldehydes might contribute to the severity of atherogenesis.

Absence of p53 leads to accelerated neointimal hyperplasia after vascular injury

OBJECTIVE

It has been suggested that deregulated expression of the tumor suppressor protein p53 may play a role in the pathogenesis of occlusive vascular remodeling. However, the role of p53 in cell proliferation and apoptosis in vascular lesions has been controversial.

METHODS AND RESULTS

We tested the potential involvement of p53-mediated molecular signaling in lesion formation using a mouse model of vascular injury that may resemble balloon angioplasty. A large wire was inserted into the femoral artery of p53+/+ and p53-/- mice. There was no significant difference in the occurrence of rapid-onset apoptosis, that is, 4 hours after injury. At 2 weeks, the number of proliferating cells in the lesion of p53-/- mice was significantly higher than that observed in p53+/+ mice. The frequency of apoptotic cells was significantly lower in p53-/- mice than in p53+/+ mice. At 4 weeks, the neointimal hyperplasia of p53-/- mice was greater than that of p53+/+ mice. There was no significant difference in the frequency of apoptosis in the lesions.

CONCLUSIONS

These results indicate a crucial role of p53 in pathological vascular remodeling after mechanical injury and provide the basis for the development of new therapies targeting p53 for a prophylactic treatment of vascular diseases.

Elemental maps in human allantochorial placental vessels cells: 2. MgCl2 and MgSO4 effects

Extracellular magnesium salts are known to interfere with ionic channels in the cellular membranes. The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K+ and Ca2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro-Particule Induced X-ray Emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMC) and of vascular endothelial cells (VEC) in the placental human allantochorial vessels in a physiological medium (Hanks' solution) modified by the addition of 2 mM MgCl2 or 2 mM MgSO4 which block the calcium-sensitive K+ channels (K(Ca)), the ATP-sensitive K+ channels (K(ATP)) and the voltage-sensitive K+ (K(df)) and Ca2+ channels. In VSMC (media layer), the addition of MgCl2 induced no modification of the K, Cl, P, S and Ca concentrations but increased the Na and Mg concentrations and the addition of MgSO4 only significantly increased the Mg concentration, the other ion concentrations remaining constant. In endothelium (VEC), MgCl2 or MgSO4 addition implicated the same observations as in VSMC. These results confirmed the blockage of K(df), K(Ca), K(ATP) and Ca channels in VSMC and VEC by magnesium salts, the relationship between Mg2+ ions and internal Na and demonstrated the possible intervention of a Na+/Mg2+ exchanger.

Analysis of the polycystins in aortic vascular smooth muscle cells

The leading cause of death in autosomal dominant polycystic kidney disease (ADPKD) is cardiovascular. However, little is known about the pathogenesis of these manifestations. The present study was undertaken to characterize the ADPKD proteins, the polycystins, in vascular smooth muscle cells. It was demonstrated that the expression of polycystin-1 is developmentally regulated, whereas polycystin-2 has a more constant level of expression. A polycystin-1 subpopulation was immunoprecipitated by polycystin-2, indicating an in vivo interaction of these two proteins. Analysis with glycosidase and cell surface biotinylation indicates that some polycystin-1 products, but not polycystin-2, are located on the plasma membrane. Immunofluorescence showed that most of the polycystin-1 and polycystin-2 was cytoplasmic but that persistent polycystin-1 staining was located in proximity to the cell surface after a Triton-X extraction, whereas no clear surface localization of polycystin-2 was detected. Immuno-gold electron microscopy revealed that polycystin-1 was localized at the plasma membrane and sarcoplasmic reticulum, whereas polycystin-2 was mainly located in the sarcoplasmic reticulum. Both polycystins were found to be associated with dense plaques. These observations are consistent with an important role of the polycystins in the development, maintenance, and function of the myoelastic arterial organization and with the vascular phenotype associated with ADPKD.

Arterial smooth muscle cell heterogeneity: implications for atherosclerosis and restenosis development

During atheromatous plaque formation or restenosis after angioplasty, smooth muscle cells (SMCs) migrate from the media toward the intima, where they proliferate and undergo phenotypic changes. The mechanisms that regulate these phenomena and, in particular, the phenotypic modulation of intimal SMCs have been the subject of numerous studies and much debate during recent years. One view is that any SMCs present in the media could undergo phenotypic modulation. Alternatively, the seminal observation of Benditt and Benditt that human atheromatous plaques have the features of a monoclonal or an oligoclonal lesion has led to the hypothesis that a predisposed, medial SMC subpopulation could play a crucial role in the production of intimal thickening. The presence of a distinct SMC population in the arterial wall implies that under normal conditions, SMCs are phenotypically heterogeneous. The concept of SMC heterogeneity is gaining wider acceptance, as shown by the increasing number of publications on this subject. In this review, we discuss the in vitro studies that demonstrate the presence of distinct SMC subpopulations in arteries of various species, including humans. Their specific features and their regulation will be highlighted. Finally, the relevance of an atheroma-prone phenotype to intimal thickening formation will be discussed.

Crucial role of type 2 inositol 1,4,5-trisphosphate receptors for acetylcholine-induced Ca2+ oscillations in vascular myocytes

OBJECTIVE

The aim of this study was to correlate the expression of InsP3R subtypes in native vascular and visceral myocytes with specific Ca2+-signaling patterns.

METHODS AND RESULTS

By Western blot and immunostaining, we showed that rat portal vein expressed InsP3R1 and InsP3R2 but not InsP3R3, whereas rat ureter expressed InsP3R1 and InsP3R3 but not InsP3R2. Acetylcholine induced single Ca2+ responses in all ureteric myocytes but only in 50% of vascular myocytes. In the remaining vascular myocytes, the first transient peak was followed by Ca2+ oscillations. By correlating Ca2+ signals and immunostaining, we revealed that oscillating vascular cells expressed both InsP3R1 and InsP3R2 whereas nonoscillating vascular cells expressed only InsP3R1. Acetylcholine-induced oscillations were not affected by inhibitors of ryanodine receptors, Ca2+-ATPases, Ca2+ influx, and mitochondrial Ca2+ uniporter but were inhibited by intracellular infusion of heparin. Using specific antibodies against InsP3R subtypes, we showed that acetylcholine-induced Ca2+ oscillations were specifically blocked by the anti-InsP3R antibody. These data were supported by antisense oligonucleotides targeting InsP3R2, which selectively inhibited Ca2+ oscillations.

CONCLUSIONS

Our results suggest that in native smooth muscle cells, a differential expression of InsP3R subtypes encodes specific InsP3-mediated Ca2+ responses and that the presence of the InsP3R2 subtype is required for acetylcholine-induced Ca2+ oscillations in vascular myocytes.

Cholesterol dependence of vascular ERK1/2 activation and growth in response to stretch: role of endothelin-1

OBJECTIVE

Stretch-induced growth of the vascular wall plays a role in hypertension and neointima formation. Its signal pathways involve integrins, cytoskeleton, membrane receptors, and ion channels, some of which are organized in cholesterol-rich, membrane domains such as lipid rafts or caveolae. This study tested the role of rafts/caveolae in stretch-induced vascular growth by manipulation of membrane cholesterol contents.

METHODS AND RESULTS

Growth and protein synthesis were induced by mechanical stretch of rat portal veins in vitro. Sucrose gradient centrifugation showed stretch-induced tyrosine phosphorylation primarily in fractions containing caveolin-1. Disruption of membrane caveolae with use of methyl-beta-cyclodextrin (mbetacd) reduced weight gain, protein synthesis, and DNA synthesis to levels in unstretched, control veins. These effects were partially reversed by restoration of cellular cholesterol contents. Inhibited growth was associated with abolished activation of extracellular signal-regulated kinase (ERK) 1/2 in response to stretch and endothelin-1 (ET-1) but not to angiotensin II. Inhibition of ET-1 type A (ETA) receptors by RF139317 or endothelin-converting enzyme by phosphoramidone abolished stretch-induced ERK1/2 activation, which was, however, unaffected by removal of the endothelium.

CONCLUSIONS

Stretch-induced growth signaling in vascular smooth muscle depends on cholesterol-rich, membrane microdomains by a mechanism involving ETA receptors that respond to endogenous ET-1 production.

Tumor necrosis factor-alpha promotes macrophage-induced vascular smooth muscle cell apoptosis by direct and autocrine mechanisms

OBJECTIVE

We have previously shown that human macrophages induce human plaque vascular smooth muscle cell (VSMC) apoptosis by cell-cell proximity, Fas-L, and nitric oxide (NO), thereby predisposing to plaque rupture. This study sought to analyze whether tumor necrosis factor-alpha (TNF-alpha) contributes additionally to macrophage-induced VSMC apoptosis.

METHODS AND RESULTS

Macrophage-induced VSMC apoptosis was examined in direct coculture. Antagonistic antibodies to TNF-receptor (R1) inhibited VSMC apoptosis, and preincubation of monocytes and VSMCs indicated that TNF-R1 on both cell types contributed to macrophage-induced VSMC apoptosis. Correspondingly, both monocytes and VSMCs expressed TNF-R1, and macrophages expressed cell surface TNF-alpha. Two NO donors upregulated VSMC surface TNF-R1, and exogenous TNF-alpha induced VSMC apoptosis synergistically with the NO donor diethylenetriamine/NO, indicating that NO sensitizes VSMCs to TNF-alpha. Neutralizing anti-TNF-R1 antibodies inhibited macrophage activation assessed by Fas-L expression and NO secretion.

CONCLUSIONS

TNF-alpha promotes macrophage-induced VSMC apoptosis by autocrine and direct pathways.

Induction of tissue factor in the arterial wall during recurrent thrombus formation

OBJECTIVE

Tissue factor (TF) is normally expressed at low levels in the media of blood vessels, but it is readily induced after vessel injury. It is not known whether vascular damage per se or thrombus formation is responsible for this phenomenon.

METHODS AND RESULTS

Cyclic flow variations (CFVs), attributable to recurrent thrombus formation, were induced in stenotic rabbit carotid arteries with endothelial injury. CFVs were observed for 30 minutes and 2, 4, and 8 hours in different groups of animals. Another group of rabbits pretreated with hirudin before inducing arterial damage to inhibit thrombus formation was observed for 8 hours. Arterial sections were immunostained for TF. Undamaged arteries served as controls. In additional rabbits, in situ hybridization experiments were performed. No TF expression was observed in the media of control vessels, whereas a progressive increase in TF mRNA and protein expression was observed in carotid arteries as CFVs progressed. No increase in TF expression was observed in animals pretreated with hirudin. In vitro experiments demonstrated that TF mRNA is induced in smooth muscle cells stimulated with activated platelets as well as with some platelet-derived mediators.

CONCLUSIONS

This phenomenon may contribute to sustain intravascular thrombus formation after the initial thrombogenic stimulus.

Potassium channels in human umbilical artery cells

OBJECTIVE

To identify K+ channels of smooth muscle of human umbilical artery using the patch-clamp technique and to study their effect on resting tone of umbilical artery rings.

METHODS

Whole-cell and single-channel patch-clamp recordings in enzymatically isolated smooth muscle cells were made. Measurements of developed isometric force were performed on intact tissue.

RESULTS

Delayed rectifier K+ channels (KDR) and large-conductance Ca2+-activated K+ channels (BKCa) contribute to the whole-cell voltage- and time-dependent outward K+ current, as it was specifically inhibited by 5 mM 4-aminopyridine (4-AP; KDR blocker) (92 +/- 4% at 0 mV, n = 7), by 1 mM tetraethylammonium (TEA; BKCa blocker) (71 +/- 4% at +60 mV, n = 4), and by 200 nM iberiotoxin (BKCa blocker) (64 +/- 7% at +60 mV, n = 4). In outside-out patches, BKCa channels had a single-channel conductance of 132 +/- 4 pS (n = 24) in asymmetric K+ conditions and 216 +/- 4 pS (n = 4) in a symmetric K+ gradient. The activity of the BKCa channels was significantly augmented by 1 microM Ca2+ in the inside-out configuration. 4-AP had no effect on resting tone of intact arterial rings. TEA produced contraction of arterial rings whereas phloretin, an activator of BKCa, relaxed them, which means that BKCa channels are functional in intact tissue and are involved in the maintenance of resting tone in this human vessel.

CONCLUSION

The identities of K+ channels in the human umbilical artery were shown using the patch-clamp technique, and the physiologic effect of K+ channels on resting tone was documented.

Insulin signaling in the vasculature

An abnormal vasodilation is a major defect observed in the arteries of diabetic and hypertensive individuals. Myosin bound phosphatase (MBP) dephosphorylates myosin light chains which play a dominant role in vascular smooth muscle (VSM) contraction. Using two distinct approaches, we have demonstrated that insulin rapidly stimulates MBP and simultaneously inhibits RhoA/Rho kinase signaling via the nitric oxide (NO)/cGMP signaling pathway. Insulin activates MBP by decreasing Thr695 phosphorylation of myosin-bound subunit (MBS) via two different but cross-talking signaling pathways. Firstly, insulin inactivates Rho kinase by blocking RhoA activation and translocation to the membrane fraction via increased cGMP/cGK-1( mediated RhoA phosphorylation and decreased geranylgeranylation. Secondly, insulin induces iNOS expression via PI3-kinase signaling leading to generation of NO/cGMP which activates MBP via cGK-1( mediated inhibition of MBSThr695 phosphorylation via Rho kinase inactivation. MBP activation prevents agonist induced MLC20 phosphorylation as well as VSMC contraction. VSMCs isolated from SHR and diabetic rats exhibit elevations in Rho kinase, which increases MBS Thr695 phosphorylation and inhibits MBP. The defects appear to be at the level of PI3-kinase activation due to impaired insulin-induced IRS-1 tyrosine phosphorylation because of increased association of active Rho kinase with the IRS-1 leading to increased IRS-1 serine phosphorylation, which interrupts with downstream insulin signaling.

Prediction of cell type-specific gene modules: identification and initial characterization of a core set of smooth muscle-specific genes

Genes that are expressed in the same subset of cells potentially constitute a module regulated by shared cis-regulatory elements and a distinct set of transcription factors. Identifying such units is an important entry point to the molecular study of cell differentiation. We developed a general method to classify cell type-specific genes from expressed sequence tag (EST) data, and we optimized it for identification of smooth muscle cell (SMC)-specific genes. Expression profiles were derived from the quantitative distribution of EST data in mouse, and genes were classified based on their profile similarity to known reference genes, in this case smooth muscle myosin heavy chain. A large majority (>90%) of known SMC-specific genes were identified, together with novel candidates. Extensive experimental validation confirmed SMC-specific expression of candidates, for example, lipoma preferred partner (LPP) and a novel SMC-specific putative monoamine oxidase, SMAO. Our method performed considerably better than other computational methods in an objective cross validation comparison. The total number of SMC-specific genes is estimated to be approximately 50.

New expression profiles of voltage-gated ion channels in arteries exposed to high blood pressure

The diameters of small arteries and arterioles are tightly regulated by the dynamic interaction between Ca(2+) and K(+) channels in the vascular smooth muscle cells. Calcium influx through voltage-gated Ca(2+) channels induces vasoconstriction, whereas the opening of K(+) channels mediates hyperpolarization, inactivation of voltage-gated Ca(2+) channels, and vasodilation. Three types of voltage-sensitive ion channels have been highly implicated in the regulation of resting vascular tone. These include the L-type Ca(2+) (Ca(L)) channels, voltage-gated K(+) (K(V)) channels, and high-conductance voltage- and Ca(2+)-sensitive K(+) (BK(Ca)) channels. Recently, abnormal expression profiles of these ion channels have been identified as part of the pathogenesis of arterial hypertension and other vasospastic diseases. An increasing number of studies suggest that high blood pressure may trigger cellular signaling cascades that dynamically alter the expression profile of arterial ion channels to further modify vascular tone. This article will briefly review the properties of Ca(L), K(V), and BK(Ca) channels, present evidence that their expression profile is altered during systemic hypertension, and suggest potential mechanisms by which the signal of elevated blood pressure may result in altered ion channel expression. A final section will discuss emerging concepts and opportunities for the development of new vasoactive drugs, which may rely on targeting disease-specific changes in ion channel expression as a mechanism to lower vascular tone during hypertensive diseases.

Smooth muscle cell migration stimulated by interleukin 6 is associated with cytoskeletal reorganization

BACKGROUND

Interleukin 6 (IL-6) is elevated in the arterial wall in atherosclerosis and restenosis after angioplasty. An important contributor to these pathologies is migration of vascular smooth muscle cells (VSMC), which is often associated with cytoskeletal reorganization initiated by growth factors and chemokines. We recently reported that IL-6 stimulated migration of VSMC. Here, we examined the cytoskeleton of VSMC and cytoskeletal associated proteins to determine potential mechanisms associated with IL-6 induced migration.

MATERIALS AND METHODS

Studies were performed in VSMC cultured from rat aortas.

RESULTS

IL-6 significantly stimulated VSMC migration. IL-6 induced actin polymerization, and tyrosine phosphorylation of focal adhesion-associated cytoskeletal proteins including focal adhesion kinase (FAK) and paxillin. Cytochalasin D, an inhibitor of actin polymerization, blocked phosphorylation of FAK and paxillin as well as cell motility induced by the cytokine.

CONCLUSIONS

Collectively, these data demonstrate for the first time that IL-6 stimulates VSMC motility which correlated with induction of actin cytoskeletal reorganization and tyrosine phosphorylation of FAK and paxillin.

Genomic profiles and predictive biological networks in oxidant-induced atherogenesis

Atherogenic stimuli trigger complex responses in vascular smooth muscle cells (VSMCs) that culminate in activation/repression of overlapping signal transduction cascades involving oxidative stress. In the case of benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon present in tobacco smoke, the atherogenic response involves interference with redox homeostasis by oxidative intermediates of BaP metabolism. The present studies were conducted to define genomic profiles and predictive gene biological networks associated with the atherogenic response of murine (aortic) VSMCs to BaP. A combined oxidant-antioxidant treatment regimen was used to identify redox-sensitive targets during the early course of the atherogenic response. Gene expression profiles were defined using cDNA microarrays coupled to analysis of variance and several clustering methodologies. A predictor algorithm was then applied to gain insight into critical gene-gene interactions during atherogenesis. Supervised and nonsupervised analyses identified clones highly regulated by BaP, unaffected by antioxidant, and neutralized by combined chemical treatments. Lymphocyte antigen-6 complex, histocompatibility class I component factors, secreted phosphoprotein, and several interferon-inducible proteins were identified as novel redox-regulated targets of BaP. Predictor analysis confirmed these relationships and identified immune-related genes as critical molecular targets of BaP. Redox-dependent patterns of gene deregulation indicate that oxidative stress plays a prominent role during the early stages of BaP-induced atherogenesis.

Enhanced smooth muscle cell coverage of microvessels exposed to increased hemodynamic stresses in vivo

During vascular remodeling in adult organisms, new capillary growth is often coupled with the adaptation of arterioles and venules, a process that requires the recruitment and differentiation of precursor cells into smooth muscle. We studied the in vivo adaptation of microvessels in the presence of elevated pressure and circumferential wall stress using a ligation strategy for mesenteric microvascular networks. Acute pressure increases of 42.6+/-18% and 17.1+/-2.3% were respectively elicited in the 25- to 30-microm-diameter venules and arterioles supplying the networks. Wall shear rates were not significantly changed; however, diameters were increased in >10-microm-diameter venules and >20-microm-diameter arterioles. Smooth muscle cell contractile phenotype was determined in all microvessels by observing the expression of smooth muscle myosin heavy chain (SM-MHC; a marker of fully differentiated smooth muscle) and smooth muscle alpha-actin (a marker for all smooth muscle, including immature smooth muscle of fibroblast/pericyte lineage). The ratio of SM-MHC positive vessel length to smooth muscle alpha-actin-positive vessel length increased >2-fold after 5 and 10 days of the ligation treatment. Smooth muscle proliferation was studied by bromodeoxyuridine incorporation, and the increase in SM-MHC-labeled microvessel length density was accompanied by no measurable change in proliferation of SM-MHC-labeled cells 5 and 10 days after ligation. These results indicate that after a period of 5 or 10 days, mesenteric microvessels <40 microm in diameter exposed to elevated pressure and wall strain exhibit an enhanced coverage of mature, fully differentiated smooth muscle cells.