Role of acellular collagen matrix surgisis in the endoscopic management of ureteropelvic junction obstruction

PURPOSE

To investigate the role of acellular collagen matrix (Surgisis during endopyelotomy.

MATERIALS AND METHODS

Nine female pigs (25-35 kg) were enrolled in our protocol. The pigs were categorized as follows. Group I (N = 3) had endopyelotomy + insertion of SIS, Group II (N = 3) creation of UPJ stricture + endopyelotomy + insertion of SIS, and Group III (N = 3) Davis intubated ureterotomy using SIS. The contralateral side served as a control for each group (one pig in each group). In three pigs (two in Group III and one in Group II), Surgisis was treated with India ink prior to insertion at the endopyelotomy site. An endopyelotomy stent (14/8 F x 24 cm) was used to stent the ureteropelvic junction (UPJ) for 4 weeks. Four weeks after the stent was removed, laparoscopic nephroureterectomy was performed, and the animals were euthanized. Histopathologic analysis of the Surgisis-regenerated segment of the UPJ was performed using hematoxylin and eosin, reticular (collagen), smooth muscle actin, and S-100 (nerve) stains.

RESULTS

All animals tolerated the procedure. The mean operative time was 162 minutes. One pig (Group II) developed pyonephrosis; one pig (Group III) developed significant ascites and was sacrificed 2 week before the end of the experiment. Histopathologic analysis showed complete epithelializaton at 8 weeks. Reticular stain demonstrated abundant collagen matrix in the submucosa. Smooth muscle staining revealed myofibroblastic proliferation within the SIS-regenerated tissue adjacent to disorganized smooth muscle cells. India ink-stained SIS-regenerated tissue did not show smooth muscle cells. The S-100 stain did not demonstrate neurons at 8 weeks; however, in three pigs, peristaltic activity was noted across the UPJ.

CONCLUSION

The use of acellular collagen matrix in the endoscopic management of UPJ obstruction is a promising technique. The abundance of myofibroblasts and absence of abundant smooth muscle regeneration indicates a need to investigate the role of growth factors in SIS regeneration of host tissue.

Stimulation of arteriogenesis in skeletal muscle by microbubble destruction with ultrasound

BACKGROUND

The application of ultrasound to microbubbles in skeletal muscle creates capillary ruptures. We tested the hypothesis that this bioeffect could be used to stimulate the growth and remodeling of new arterioles via natural repair processes, resulting in an increase in skeletal muscle nutrient blood flow.

METHODS AND RESULTS

Pulsed ultrasound (1 MHz) was applied to exposed rat gracilis muscle after intravenous microbubble injection. Capillary rupturing was visually verified by the presence of red blood cells in the muscle, and animals were allowed to recover. Ultrasound-microbubble-treated and contralateral sham-treated muscles were harvested 3, 7, 14, and 28 days later. Arterioles were assessed by smooth muscle alpha-actin staining, and skeletal muscle blood flow was measured with 15- micro m fluorescent microspheres. An approximately 65% increase in arterioles per muscle fiber was noted in treated muscles compared with paired sham-treated control muscles at 7 and 14 days after treatment. This increase in arterioles occurred across all studied diameter ranges at both 7 and 14 days after treatment. Arterioles per muscle fiber in sham-treated and untreated control muscles were comparable, indicating that the surgical intervention itself had no significant effect. Hyperemia nutrient blood flow in treated muscles was increased 57% over that in paired sham-treated control muscles.

CONCLUSIONS

Capillary rupturing via microbubble destruction with ultrasound enhances arterioles per muscle fiber, arteriole diameters, and maximum nutrient blood flow in skeletal muscle. This method has the potential to become a clinical tool for stimulating blood flow to organs affected by occlusive vascular disease.

Smooth muscle progenitor cells in human blood

BACKGROUND

Recent animal data suggest that vascular smooth muscle cells within the neointima of the vessel wall may originate from bone marrow, providing indirect evidence for circulating smooth muscle progenitor cells (SPCs). Evidence for circulating SPCs in human subjects does not exist, and the mechanism whereby such putative SPCs may home to sites of plaque formation is presently not understood but is likely to involve expression of specific surface adhesion molecules, such as integrins. In this study, we aimed to culture smooth muscle outgrowth cells (SOCs) from SPCs in human peripheral blood and characterize surface integrin expression on these cells.

METHODS AND RESULTS

Human mononuclear cells isolated from buffy coat were seeded on collagen type 1 matrix and outgrowth cells selected in endothelial growth medium (EGM-2) or EGM-2 and platelet-derived growth factor BB. Selection in platelet-derived growth factor BB-enriched medium caused rapid outgrowth and expansion of SOC to >40 population doublings in a 4-month period. These SOCs were positive for smooth muscle cell-specific alpha actin (alphaSMA), myosin heavy chain, and calponin on immunofluorescence and Western blotting and were also positive for CD34, Flt1, and Flk1 receptor but negative for Tie-2 receptor expression, suggesting a potential bone marrow angioblastic origin. In contrast, endothelial outgrowth cells (EOCs) grown in EGM-2 alone and the initial MNC population were negative for these smooth muscle-specific markers. Integrin alpha5beta1 expression by FACS and Western blotting was significantly increased in SOCs compared with EOCs, and this was confirmed by 8-fold greater adhesion of SOC to fibronectin (P<0.001), an effect that could be decreased using an alpha5beta1 antibody. Finally, SOC showed a significantly greater in vitro proliferative potential compared with EOCs of similar passage (P<0.001).

CONCLUSIONS

This study demonstrates for the first time outgrowth of smooth muscle cells with a specific growth, adhesion, and integrin profile from putative SPC in human blood. These data have implications for our understanding of adult vascular smooth muscle cell differentiation, proliferation, and homing.

Connexin37 is the major connexin expressed in the media of caudal artery

OBJECTIVE

To determine the connexins (Cxs) involved in intercellular coupling within vascular muscle, the present study has quantified mRNA and protein expression for Cx37, Cx40, Cx43, and Cx45 in the caudal artery (CA) and thoracic aorta (ThA) of the rat.

METHODS AND RESULTS

Real-time polymerase chain reaction and immunohistochemistry identified Cx37 as the most abundantly expressed Cx in the CA, with fine punctate staining observed in the media. Conversely, mRNA for Cx43 was 40-fold greater in the ThA than in the CA, with punctate staining in the endothelium and media of the ThA but confined to the endothelium in the CA. Western blotting confirmed the differences in the relative amounts of Cx43 between the 2 vessels. For both arteries, Cx45 was expressed to a lesser degree in the media but not in the endothelium, whereas Cx40 was found only in the endothelium. Cx37, Cx40, and Cx43 were expressed in the endothelium of both vessels, although the density of Cx40 plaques was significantly greater in the CA.

CONCLUSIONS

The demonstration of Cx37 as the dominant Cx in the media of the CA highlights the potential heterogeneity in Cx involvement in vascular smooth muscle.

Leptin inhibits angiotensin II-induced intracellular calcium increase and vasoconstriction in the rat aorta

Besides its role in body weight control leptin may also act as a vasoactive hormone. This study was designed to investigate whether leptin modifies angiotensin II (ANG II)-induced vascular responses. The expression of functional leptin receptors (OB-Rb) was detected in vascular smooth muscle cells (VSMCs) from adult Wistar rats by RT-PCR. Immunocytochemistry and Western blot analysis further showed the expression of OB-R protein in VSMCs. The ANG II (10(-7) mol/liter)-induced increase in intracellular Ca(2+) was blocked (P < 0.01) by leptin (10(-8) mol/liter). Moreover, in calcium-free buffer leptin was able to inhibit 65% of the ANG II-induced calcium release from intracellular stores. In endothelium-denuded aortic rings from adult Wistar rats no effect of leptin on basal tension was observed. However, the ANG II-induced isometric contraction was reduced (P < 0.05) by leptin (10(-8) mol/liter). The experiments were also performed in age- and sex-matched Zucker rats, in which no effect of leptin on ANG II-induced calcium increase and vasoconstriction was observed. It is concluded that leptin blocks the vasoconstrictor action of ANG II and inhibits the ANG II-induced increase in intracellular Ca(2+) in VSMCs through OB-Rb. These findings provide new insight into the physiological effects of leptin on blood pressure regulation.

Human umbilical cord and fetal membranes co-express leptin and its receptor genes

Leptin, protein product of the ob gene, not only regulates food intake and energy expenditure but also has a number of other actions in the body. Leptin actions are mediated by its receptors that have either a long or a truncated intracellular domain, which is coupled to signal transduction pathways. Previous studies have demonstrated that human placenta expresses both leptin and its receptors. However, it is not known whether human umbilical cord and fetal membranes are also sites of expression of these molecules. Therefore, the present study investigated leptin and its receptor expression in these tissues from term pregnancy. Reverse-transcription polymerase chain reaction (RT-PCR) amplified expected size fragments of leptin and also its short and long receptor isoforms from umbilical cord and fetal membranes. The authenticity of PCR-amplified fragments was confirmed by Southern blot hybridization with corresponding cDNA probes. Western blotting revealed that the transcripts were translated into 16-kDa leptin, and 125-kDa (long) and 100-kDa (short) leptin receptor isoforms. However, the long form is present in umbilical cord and the short form in the fetal membranes. Immunocytochemistry revealed that leptin and its receptor isoforms were present in endothelial cells and smooth muscle of umbilical veins and artery, myofibroblasts in Wharton's jelly, amnion covering the cord, amnion and chorion in reflected fetal membranes and decidua from membranes. Amnion, however, contained the highest levels of leptin and its receptor immunostaining. In summary, term pregnancy human umbilical cord and fetal membranes co-express leptin and its receptor genes, which supports the hypothesis that leptin is an autocrine and paracrine regulator in these tissues.

Content and activity of cAMP response element-binding protein regulate platelet-derived growth factor receptor-alpha content in vascular smooth muscles

Experiments in vascular smooth muscle cells (SMCs) indicate that the transcription factor cAMP response element-binding protein (CREB), the cyclic nucleotide response element-binding protein, suppresses expression of the platelet-derived growth factor-alpha receptor gene (PDGFRalpha). Adenovirus-mediated expression of constitutively active CREB mutants decreases PDGFRalpha mRNA, PDGFRalpha protein, and PDGFRalpha promoter-luciferase reporter activity in cultured SMCs. Expression of dominant negative CREB protein, A-CREB, increases PDGFRalpha protein content and the PDGFRalpha-promoter activity in SMCs. Active CREB prevents activation of PDGFRalpha promoter-luciferase reporter activity by CCAAT/enhancer-binding protein-delta (C/EBPdelta), shown to mediate IL-1beta stimulation of PDGFRalpha expression. Exposure of cultured SMCs to high glucose or reactive oxidant stress, which decrease CREB protein content and activity, increases PDGFRalpha protein content and promoter activity. Expression of active CREB blunts reactive oxidant stress-induced PDGFRalpha accumulation in SMCs. Loss of CREB protein in aortic walls of rats with streptozotocin-induced diabetes is accompanied by an increase in PDGFRalpha content. In Ob/Ob mice (which demonstrate reduced aortic wall CREB content vs. Ob/- controls), treatment with the peroxisomal proliferator-activated receptor gamma rosiglitazone increases CREB content and decreases PDGFRalpha content in the aortic wall. Thus, both in vitro and in vivo loss of CREB content and activity and subsequent accumulation of PDGFRalpha may contribute to SMC activation during diabetes.

G-protein-coupled receptors in human atherosclerosis: comparison of vasoconstrictors (endothelin and thromboxane) with recently de-orphanized (urotensin-II, apelin and ghrelin) receptors

Endothelin (ET)-1 and thromboxane (Tx) levels are increased in human atherosclerosis. One of the aims of this study was to understand how receptors for a peptide mediator (ET-1) with a long physiological half life, would differ from a lipid mediator (TxA(2)), with a short physiological half life, in human coronary artery disease (CAD). Secondly, to determine if receptor protein is present in human coronary artery vascular smooth muscle for the recently adopted peptide orphan receptors for urotensin-II, apelin and ghrelin. The ET(A) receptor subtype predominated in the medial smooth muscle layer of both non-diseased coronary artery (NCA) and CAD. However, this subtype was present at relatively low density in the proliferated intimal layer of CAD. The ET(B) receptor protein was not altered with CAD, compared with NCA. Tx receptor density was significantly (P<0.05) increased in both the media and intima of CAD, compared with NCA. There was no alteration in receptor density, on the medial smooth muscle for urotensin-II and apelin with CAD. Interestingly, receptor density for the novel vasodilator peptide ghrelin was significantly (P<0.05) increased (approx. 4 fold) with CAD, compared with NCA. The alteration of receptor density with disease for Tx and ghrelin provides novel therapeutic targets for the treatment of atherosclerosis. In conclusion, while some GPCR are altered, others remain unchanged with human atherosclerosis. The increase in vasoconstrictor Tx receptor density with disease suggests the importance of Tx receptor antagonism. Intriguingly, the increase in receptor density for the novel vasodilator ghrelin, identified from post-genomic research, may potentially be beneficial with human atherosclerosis.

Prevention of accelerated atherosclerosis by angiotensin-converting enzyme inhibition in diabetic apolipoprotein E-deficient mice

BACKGROUND

Atherosclerosis is a major complication of diabetes, but the mechanisms by which diabetes promotes macrovascular disease have not been fully delineated. Although several animal studies have demonstrated that inhibition of ACE results in a decrease in the development of atherosclerotic lesions, information about the potential benefits of these agents on complex and advanced atherosclerotic lesions as observed in long-term diabetes is lacking. The aim of this study was to evaluate whether treatment with the ACE inhibitor perindopril affects diabetes-induced plaque formation in the apolipoprotein E (apoE)-deficient mouse.

METHODS AND RESULTS

Diabetes was induced by injection of streptozotocin in 6-week-old apoE-deficient mice. Diabetic animals received treatment with perindopril (4 mg x kg(-1) x d(-1)) or no treatment for 20 weeks. Nondiabetic apoE-deficient mice were used as controls. Induction of diabetes was associated with a 4-fold increase in plaque area compared with nondiabetic animals. This accelerated atherosclerosis was associated with a significant increase in aortic ACE expression and activity and connective tissue growth factor and vascular cell adhesion molecule-1 expression. Perindopril treatment inhibited the development of atherosclerotic lesions and diabetes-induced ACE, connective tissue growth factor, and vascular cell adhesion molecule-1 overexpression in the aorta.

CONCLUSIONS

The activation of the local renin-angiotensin system in the diabetic aorta and the reduction in atherosclerosis with ACE inhibitor treatment provides further evidence that the renin-angiotensin system plays a pivotal role in the development and acceleration of atherosclerosis in diabetes.

ET-1 receptor gene expression and distribution in L1 and L2 cells from hypertensive sheep pulmonary artery

We examined gene and surface expression and activity of the endothelin (ET)-1 receptors (ETA and ETB) in subendothelial (L1) and inner medial (L2) cells from the main pulmonary artery of sheep with continuous air embolization (CAE)-induced chronic pulmonary hypertension (CPH). According to quantitative real-time RT-PCR, basal gene expression of both receptors was significantly higher in L2 than L1 cells, and hypertensive L2 cells showed significantly higher gene expression of ETB than controls. Expression of both genes in hypertensive L1 cells was similar to controls. Fluorescence-activated cell sorter analysis confirmed the increased distribution of ET(B) in hypertensive L2 cells. Although only the ETA receptors in control L2 cells showed significant binding of [125I]-labeled ET-1 at 1 h, both receptors bound ET-1 to hypertensive cells. Exposure to exogenous ET-1 for 18 h revealed that only the L2 cells internalized ET-1, and internalization by hypertensive L2 cells was significantly reduced when compared with controls. Treatment with ETA (BQ-610) and ETB (BQ-788) receptor antagonists demonstrated that both receptors contributed to internalization of ET-1 in control L2 cells, whereas in hypertensive cells only when both receptor antagonists were used in combination was significant suppression of ET-1 internalization found. We conclude that in sheep receiving CAE, alterations in ETB receptors in cells of the L2 layer may contribute to the maintenance of CPH via alterations in their expression, distribution, and activity.

Heterogeneity of smooth muscle cell populations cultured from pig coronary artery

OBJECTIVE

Heterogeneous smooth muscle cell (SMC) populations have been described in the arteries of several species. We have investigated whether SMC heterogeneity is present in the porcine coronary artery, which is widely used as a model of restenosis.

METHODS AND RESULTS

By using 2 isolation methods, distinct medial populations were identified: spindle-shaped SMCs (S-SMCs) after enzymatic digestion, with a "hill-and-valley" growth pattern, and rhomboid SMCs (R-SMCs) after explantation, which grow as a monolayer. Moreover, the intimal thickening that was induced after stent implantation yielded a large proportion of R-SMCs. R-SMCs exhibited high proliferative and migratory activities and high urokinase activity and were poorly differentiated compared with S-SMCs. Heparin and transforming growth factor-beta2 inhibited proliferation and increased differentiation in both populations, whereas fibroblast growth factor-2 and platelet-derived growth factor-BB had the opposite effect. In addition, S-SMCs treated with fibroblast growth factor-2 or platelet-derived growth factor-BB or placed in coculture with coronary artery endothelial cells acquired a rhomboid phenotype. This change was reversible and was also observed with S-SMC clones, suggesting that it depends on phenotypic modulation rather than on selection.

CONCLUSIONS

Our results show that 2 distinct SMC subpopulations can be recovered from the pig coronary artery media. The study of these subpopulations will be useful for understanding the mechanisms of restenosis.

Type 5 phosphodiesterase expression in the human vagina

OBJECTIVES

It has been demonstrated that clitoral and vaginal tissues express nitric oxide synthase isoforms in a way that parallels that of the penile corpus cavernosum. Considering the role of the vagina in the female sexual response and the anatomic connection between the clitoris and the anterosuperior vaginal wall, our aim was to study the distribution of type 5 phosphodiesterase (PDE5) in the anterosuperior wall of the human vagina.

METHODS

Immunohistochemistry was performed on the vaginal tissue of 14 women obtained at autopsy and on exfoliated cells of the vaginal epithelium obtained from 5 healthy female donors. Specific antibodies against PDE5 were tested on both paraffin sections and cytologic smears. Immunoblotting experiments were performed in parallel with the same antibodies.

RESULTS

The histologic analysis of human cadaveric vaginal tissue revealed that PDE5 immunoreactivity was mostly localized in the smooth muscle of vessels, forming a pseudocavernous tissue in the vaginal wall and endothelium. The Skene periurethral glands and vaginal epithelium were also positive for the antibody. The latter finding was confirmed using exfoliated cells of the vaginal epithelium harvested in vivo.

CONCLUSIONS

The presence and tissue distribution of PDE5 in the human vagina suggest that the integrated system of nitric oxide synthase-PDE5 may play a physiologic role not only in the male sexual response but also in female sexual arousal.

The CXC chemokine cCAF stimulates precocious deposition of ECM molecules by wound fibroblasts, accelerating development of granulation tissue

BACKGROUND

During wound repair, fibroblasts orchestrate replacement of the provisional matrix formed during clotting with tenascin, cellular fibronectin and collagen III. These, in turn, are critical for migration of endothelial cells, keratinocytes and additional fibroblasts into the wound site. Fibroblasts are also important in the deposition of collagen I during scar formation. The CXC chemokine chicken Chemotactic and Angiogenic Factor (cCAF), is highly expressed by fibroblasts after wounding and during development of the granulation tissue, especially in areas where extracellular matrix (ECM) is abundant. We hypothesized that cCAF stimulates fibroblasts to produce these matrix molecules.

RESULTS

Here we show that this chemokine can stimulate precocious deposition of tenascin, fibronectin and collagen I, but not collagen III. Studies in culture and in vivo show that tenascin stimulation can also be achieved by the N-terminal 15 aas of the protein and occurs at the level of gene expression. In contrast, stimulation of fibronectin and collagen I both require the entire molecule and do not involve changes in gene expression. Fibronectin accumulation appears to be linked to tenascin production, and collagen I to decreased MMP-1 levels. In addition, cCAF is chemotactic for fibroblasts and accelerates their migration.

CONCLUSIONS

These previously unknown functions for chemokines suggest that cCAF, the chicken orthologue of human IL-8, enhances healing by rapidly chemoattracting fibroblasts into the wound site and stimulating them to produce ECM molecules, leading to precocious development of granulation tissue. This acceleration of the repair process may have important application to healing of impaired wounds.

Model of nitric oxide diffusion in an arteriole: impact of hemoglobin-based blood substitutes

Administration of hemoglobin-based oxygen carriers (HBOCs) frequently results in vasoconstriction that is primarily attributed to the scavenging of endothelium-derived nitric oxide (NO) by cell-free hemoglobin. The ensuing pressor response could be caused by the high NO reactivity of HBOC in the vascular lumen and/or the extravasation of hemoglobin molecules. There is a need for quantitative understanding of the NO interaction with HBOC in the blood vessels. We developed a detailed mathematical model of NO diffusion and reaction in the presence of an HBOC for an arteriolar-size vessel. The HBOC reactivity with NO and degree of extravasation was studied in the range of 2-58 x 10(6) M(-1) x s(-1) and 0-100%, respectively. The model predictions showed that the addition of HBOC reduced the smooth muscle (SM) NO concentration in the activation range (12-28 nM) for soluble guanylate cyclase, a major determinant of SM contraction. The SM NO concentration was significantly reduced when the extravasation of HBOC molecules was considered. The myoglobin present in the parenchymal cells scavenges NO, which reduces the SM NO concentration.

Abdominal aortic healing associated with a thin-walled Dacron-covered endovascular graft in a canine model

PURPOSE

To characterize the healing response associated with an experimental endovascular graft (EVG) by examining the lumen of the prosthesis and the native vessel wall responses after implantation in a canine model.

METHODS

An endovascular graft (EVG) constructed of hookless self-expanding nitinol springs covered by an ultrathin Dacron fabric was placed in the abdominal aorta of 8 dogs following femoral artery catheterization. After 12 weeks, specimens were subjected to histological and immunocytochemical testing to quantitatively and qualitatively analyze the cellular makeup of the luminal and abluminal tissues.

RESULTS

Gross examination revealed a glistening, thrombus-free luminal surface on all prostheses, which was confirmed by scanning electron microscopy. The EVGs were well incorporated into the aortic wall, leaving a concentric, smooth flow surface. Immunocytochemistry verified the presence of von Willebrand factor-positive endothelial cells on the luminal surface and alpha-smooth muscle cell actin-positive smooth muscle and/or fibroblast cells in the subendothelial space. A sparse inflammatory response and a paucity of proliferating nuclear cell antigen-positive cells were noted within the neomedial lining adjacent to the graft material. In addition, a rich vaso vasorum-like plexus of microvessels was evident within the neomedial tissue. The native vessel wall upon which the EVG impinged was largely unaffected. CONCLUSIONS; These data demonstrate that placement of an experimental EVG in the canine abdominal aorta elicits a healing response that is distinct from interpositional vascular grafts. Results from this study have particular relevance to the proximal and distal anastomotic neck regions.

Neuropeptide Y Y1 and neuropeptide Y Y2 receptors in human cardiovascular tissues

mRNA encoding the human NPY Y1 and NPY Y2 receptors were detected in cerebral, meningeal, and coronary arteries using reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, the trigeminal and superior cervical ganglia were positive for both receptors. In some arteries and in SK-N-MC cells only mRNA encoding the NPY Y1 was detected. Besides the expected NPY Y1 PCR products, an additional 97 bp longer amplicon originating from an alternative splicing event was found in most tissues studied. Antibodies directed against the NPY Y1 receptor revealed immunostaining mainly in the smooth muscle layer of blood vessels whereas antibodies against the NPY Y2 receptor showed immunostaining in nerve cell bodies.

Induction of apoptosis in vascular smooth muscle cells by mechanical stretch

We studied the response of porcine vascular smooth muscle cells (PVSMCs) to cyclic sinusoidal stretch at a frequency of 1 Hz. Cyclic stretch with an area change of 25% caused an increase in PVSMC apoptosis, which was accompanied by sustained activation of c-Jun NH(2)-terminal kinases (JNK) and the mitogen-activated protein kinase p38. Cyclic stretch with an area change of 7% had no such effect. Infection of PVSMCs with recombinant adenoviruses expressing constitutively active forms of upstream molecules that activate JNK and p38 also led to apoptosis. The simultaneous blockade of both JNK and p38 pathways with adenovirus-mediated expression of dominant-negative mutants of c-Jun and p38 caused a significant decrease (to 1/2) of the apoptosis induced by 25% cyclic stretch. The 25% stretch also caused sustained clustering of tumor necrosis factor-alpha (TNF-alpha) receptor-1 and its association with TNF-alpha receptor-associated factor-2 (TRAF-2). Overexpressing the wild-type TRAF-2 in PVSMCs caused an increase in apoptosis. In contrast, the expression of a dominant-negative mutant of TRAF-2 attenuated stretch-induced apoptois. These results support the hypothesis that circumferential overload under hypertensive conditions induces a clustering of death receptors that cause vascular smooth muscle cell apoptosis.

Production of the long pentraxin PTX3 in advanced atherosclerotic plaques

Elevated plasma levels of the pentraxin protein family member C-reactive protein (CRP) are associated with increased risk of cardiovascular disease in both healthy and high-risk subjects. The long pentraxin family member, pentraxin 3 (PTX3), was recently described. Like CRP, PTX3 is induced by acute inflammatory stimuli and is increased in the blood of patients with acute myocardial infarction. Unlike CRP, it is expressed in a wide range of cell types, but not in hepatocytes. In this study, we have investigated the expression of PTX3 in atherosclerosis. Immunohistochemical staining of advanced atherosclerotic lesions revealed strong expression of PTX3. In contrast, no PTX3 expression was observed in nonatherosclerotic internal mammary arteries. By staining serial sections with cell type- and PTX3-specific antibodies, we observed that PTX3 was produced principally by macrophages and endothelial cells. Infrequent expression by smooth muscle cells was also observed. Our results suggest that PTX3 may contribute to the pathogenesis of atherosclerosis.

Increases in endothelial Ca(2+) activate K(Ca) channels and elicit EDHF-type arteriolar dilation via gap junctions

In skeletal muscle arterioles, the pathway leading to non-nitric oxide (NO), non-prostaglandin-mediated endothelium-derived hyperpolarizing factor (EDHF)-type dilations is not well characterized. To elucidate some of the steps in this process, simultaneous changes in endothelial intracellular Ca(2+) concentration ([Ca(2+)](i)) and the diameter of rat gracilis muscle arterioles (approximately 60 microm) to acetylcholine (ACh) were measured by fura 2 microfluorimetry (in the absence of NO and prostaglandins). ACh elicited rapid increases in endothelial [Ca(2+)](i) (101 +/- 7%), followed by substantial dilations (73 +/- 2%, coupling time: 1.3 +/- 0.2 s) that were prevented by endothelial loading of an intracellular Ca(2+) chelator [1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid]. Arteriolar dilations to ACh were also inhibited by intraluminal administration of the Ca(2+)-activated K(+) (K(Ca)) channel blockers charybdotoxin plus apamin or by palmitoleic acid, an uncoupler of myoendothelial gap junctions without affecting changes in endothelial [Ca(2+)](i). The presence of large conductance K(Ca) channels on arteriolar endothelial cells was demonstrated with immunohistochemisty. We propose that in skeletal muscle arterioles, EDHF-type mediation is evoked by an increase in endothelial [Ca(2+)](i), which by activating endothelial K(Ca) channels elicits hyperpolarization that is conducted via myoendothelial gap junctions to the smooth muscle resulting in decreases in [Ca(2+)](i) and consequently dilation.

Identification of urocortin mRNA and peptide in the human endometrium

Urocortin is a 40-amino acid peptide belonging to the corticotropin-releasing factor (CRF) family. In human reproductive tissues, urocortin expression has been previously demonstrated in the ovary, in the placenta and fetal membranes and in pregnant uterine tissues, while no data are available on the expression of the peptide in the nonpregnant uterus. In this study, urocortin expression was evaluated by both immunohistochemistry and reverse transcription-polymerase chain reaction, in human uterine tissues and cells at different phases of the menstrual cycle. Urocortin was immunolocalized in endometrial epithelial and stromal cells, as well as in the myometrium, and in vascular smooth muscle cells. No differences between proliferative and secretory phase were observed. These results were confirmed by reverse transcription-polymerase chain reaction analysis of isolated endometrial epithelial and stromal cells, and myometrial specimens. These findings open new questions on the roles played by urocortin in the human uterus.

Cyclic mechanical stretch induces VEGF and FGF-2 expression in pulmonary vascular smooth muscle cells

Vascular endothelial growth factor (VEGF) and basic (b) fibroblast growth factor (FGF-2/bFGF) are involved in vascular development and angiogenesis. Pulmonary artery smooth muscle cells express VEGF and FGF-2 and are subjected to mechanical forces during pulsatile blood flow. The effect of stretch on growth factor expression in these cells is not well characterized. We investigated the effect of cyclic stretch on the expression of VEGF and FGF-2 in ovine pulmonary artery smooth muscle cells. Primary confluent cells from 6-wk-old lambs were cultured on flexible silicon membranes and subjected to cyclic biaxial stretch (1 Hz; 5-25% stretch; 4-48 h). Nonstretched cells served as controls. Expression of VEGF and FGF-2 was determined by Northern blot analysis. Cyclic stretch induced expression of both VEGF and FGF-2 mRNA in a time- and amplitude-dependent manner. Maximum expression was found at 24 h and 15% stretch (VEGF: 1.8-fold; FGF-2: 1.9-fold). These results demonstrate that mechanical stretch regulates VEGF and FGF-2 gene expression, which could play a role in pulmonary vascular development or in postnatal pulmonary artery function or disease.

DNA binding-independent induction of IkappaBalpha gene transcription by PPARalpha

PPARs are ligand-activated transcription factors that regulate energy homeostasis. In addition, PPARs furthermore control the inflammatory response by antagonizing the nuclear factor-kappaB (NF-kappaB) signaling pathway. We recently demonstrated that PPARalpha activators increase IkappaBalpha mRNA and protein levels in human aortic smooth muscle cells. Here, we studied the molecular mechanisms by which PPARalpha controls IkappaBalpha expression. Using transient transfection assays, it is demonstrated that PPARalpha potentiates p65-stimulated IkappaBalpha transcription in a ligand-dependent manner. Site-directed mutagenesis experiments revealed that PPARalpha activation of IkappaBalpha transcription requires the NF-kappaB and Sp1 sites within IkappaBalpha promoter. Chromatin immunoprecipitation assays demonstrate that PPARalpha activation enhances the occupancy of the NF-kappaB response element in IkappaBalpha promoter in vivo. Overexpression of the oncoprotein E1A failed to inhibit PPARalpha-mediated IkappaBalpha promoter induction, suggesting that cAMP response element binding protein-binding protein/p300 is not involved in this mechanism. By contrast, a dominant-negative form of VDR-interacting protein 205 (DRIP205) comprising its two LXXLL motifs completely abolished PPARalpha ligand-mediated activation. Furthermore, cotransfection of increasing amounts of DRIP205 relieved this inhibition, suggesting that PPARalpha requires DRIP205 to regulate IkappaBalpha promoter activity. By contrast, DRIP205 is not involved in PPARalpha-mediated NF-kappaB transcriptional repression. Taken together, these data provide a molecular basis for PPARalpha-mediated induction of IkappaBalpha and demonstrate, for the first time, that PPARalpha may positively regulate gene transcription in the absence of functional PPAR response elements.

Cloning of a differentially expressed tropomyosin isoform from cultured rabbit aortic smooth muscle cells

The four known tropomyosin genes have highly conserved DNA and amino acid sequences, and at least 18 isoforms are generated by alternative RNA splicing in muscle and non-muscle cells. No rabbit tropomyosin nucleotide sequences are known, although protein sequences for alpha- and beta-tropomyosin expressed by rabbit skeletal muscle have been described. Subtractive hybridisation was used to select for genes differentially expressed in rabbit aortic smooth muscle cells (SMC), during the change in cell phenotype in primary culture that is characterised by a loss of cytoskeletal filaments and contractile proteins. This led to the cloning of a tropomyosin gene predominantly expressed in rabbit SMC during this change. The full-length cDNA clone, designated "rabbit TM-beta", contains an open reading frame of 284 amino acids, 5' untranslated region (UTR) of 117 base pairs and 3' UTR of 79 base pairs. It is closely related to the beta-gene isoforms in other species, with the highest homology in DNA and protein sequences to the human fibroblast isoform TM-1 (91.7% identity in 1035 bp and 93.3% identity in the entire 284 amino acid sequence of the protein). It differs from rabbit skeletal muscle beta-tropomyosin (81.7% homology at the protein level) mainly in two regions at amino acids 189-213 and 258-283 suggesting alternative splicing of exons 6a for 6b and 9d for 9a. Since this TM-beta gene was the only gene strongly enough expressed in SMC changing phenotype to be observed by the subtractive hybridisation screen, it likely plays a significant role in this process.

Induction of atherosclerotic plaque rupture in apolipoprotein E-/- mice after adenovirus-mediated transfer of p53

BACKGROUND

The presence of the tumor-suppressor gene p53 in advanced atherosclerotic plaques and the sensitivity to p53-induced cell death of smooth muscle cells isolated from these plaques have fueled speculation about the role of p53 in lesion destabilization and plaque rupture. In this study, we describe a strategy to promote (thrombotic) rupture of preexisting atherosclerotic lesions using p53-induced lesion remodeling.

METHODS AND RESULTS

Carotid atherogenesis was initiated in apolipoprotein E knockout mice by placement of a perivascular silastic collar. The resulting plaques were incubated transluminally with recombinant adenovirus carrying either a p53 or beta-galactosidase (lacZ) transgene. p53 transfection was restricted to the smooth muscle cell-rich cap of the plaque and led to an increase in cap cell apoptosis 1 day after transfer. p53 overexpression resulted in a marked decrease in the cellular and extracellular content of the cap, reflected by a markedly reduced cap/intima ratio (0.21+/-0.04 versus 0.46+/-0.03, P<0.001). The latter is a characteristic feature of plaque vulnerability to rupture, and whereas spontaneous rupture of p53-treated lesions was rare, it was found in 40% of cases after treatment with the vasopressor compound phenylephrine (P=0.003).

CONCLUSIONS

We have demonstrated a potential role of p53-induced remodeling in atherosclerotic plaque destabilization. Being the first example of inducible rupture at a predefined location, this model offers a unique opportunity to delineate the processes that precede rupture and to evaluate plaque-stabilizing therapies.

Altered dye diffusion and upregulation of connexin37 in mouse aortic endothelium deficient in connexin40

Connexin40 (Cx40), connexin37 (Cx37) and connexin43 (Cx43) are subunit proteins of gap junction channels in the vascular wall which are presumably involved in the propagation of vasomotor signals. In this study we have investigated in Cx40-deficient versus wild-type aortic endothelium to which extent loss of Cx40 impairs intercellular communication. We show in Cx40-deficient mice that expression of both Cx37 and Cx43 protein was increased approximately 3- and 2-fold over the level in wild-type endothelium, respectively. Furthermore, Cx37 immunosignals were distributed more homogeneously on contacting plasma membranes in Cx40-deficient versus with wild-type endothelium. Cx43 was not detected in endothelium but only in smooth muscle cells of the vessel wall. Iontophoretic injection of Lucifer Yellow or neurobiotin into aortic endothelium of Cx40-deficient mice showed extensive intercellular transfer of neurobiotin but not of Lucifer Yellow. In contrast, intercellular spreading of Lucifer Yellow was observed in endothelium of wild-type aorta. As shown by electron microscopy, gap junctions in Cx40-deficient endothelium were morphologically different from those of wild-type vessels. These results demonstrate that dye diffusibility of endothelial gap junctions is different in Cx40-deficient and wild-type mice, although Cx40-deficient mice retain the capability of intercellular communication. Apparently, Cx40-deficient endothelial cells upregulate and redistribute Cx37 as a molecular adaptation to the lack of Cx40.

cGMP-dependent protein kinase expression restores contractile function in cultured vascular smooth muscle cells

Vascular diseases, such as atherosclerosis and restenosis following angioplasty or transplantation, are due to abnormal vascular smooth muscle growth and gene expression. The smooth muscle cells (SMC) in response to injury lose their contractile function, become highly proliferative and synthesize and secrete extracellular matrix proteins. Similar changes in the phenotypic properties of vascular SMC occur during in vitro culture. In this report, we examined whether restoration of the expression of the major receptor protein for nitric oxide (NO) signaling in smooth muscle, the guanosine 3':5' cyclic monophosphate (cGMP)-dependent protein kinase (PKG), reestablished contractile function to cultured rat aortic SMC. Contractile function was monitored using the silicone polymer wrinkle assay used previously to determine contractility in cultured mesangial cells. Noncontractile rat aortic smooth muscle cells transfected with the cDNA encoding the type I isoform of PKG, but not those transfected with empty vector, formed discreet wrinkles on the substratum in response to serum indicative of contraction. Treatment of the PKG-expressing SMC with sodium nitroprusside (SNP), an NO donor, and with cGMP analogs, or with the adenylyl cyclase activator, forskolin, and with adenosine 3':5' cyclic monophosphate (cAMP) analogs reduced wrinkling. The expression of a major PKG substrate protein involved in smooth muscle relaxation, heat shock-related protein-20 (HSP20), was also reestablished in PKG-expressing SMC. Treatment of the PKG-expressing SMC with nitroprusside resulted in phosphorylation of HSP20. Collectively, these results indicate that PKG expression is important to establish contractility to SMC in culture.

Transient receptor potential channels regulate myogenic tone of resistance arteries

Elevation of intravascular pressure causes depolarization and constriction (myogenic tone) of small arteries and arterioles, and this response is a key element in blood flow regulation. However, the nature of pressure-induced depolarization has remained elusive. In the present study, we provide evidence that a transient receptor potential channel (TRPC6) homologue has a major role in this depolarizing response to pressure. Antisense oligodeoxynucleotides to TRPC6 decreased TRPC6 protein expression and greatly attenuated arterial smooth muscle depolarization and constriction caused by elevated pressure in intact cerebral arteries. Suppressing the expression of this channel protein also reduced the current density of a major cation current in resistance artery smooth muscle cells. We propose that TRPC6 channels play an essential role in regulation of myogenic tone.

ET(A) and ET(B) receptors modulate the proliferation of human pulmonary artery smooth muscle cells

We determined the distribution of ET(A) and ET(B) receptors in pulmonary arteries from pulmonary hypertensive patients and control subjects, using in vitro autoradiography, and investigated their role in mediating the proliferative effects of endothelin-1 (ET-1) on distal human pulmonary artery smooth muscle cells (PASMCs). Distal arteries possessed more medial [(125)I]-ET-1 binding sites (105 +/- 10 versus 45 +/- 6 amol/mm(2); p < 0.001) and a greater proportion of ET(B) receptors than proximal arteries (36 +/- 3% versus 3 +/- 1%; p < 0.001). Receptor density in distal arteries and lung parenchyma was twofold greater (p < 0.05) in pulmonary hypertensive patients than in control subjects. ET-1 (10(-9)-10(-7) mol/L) stimulated DNA synthesis (147 +/- 10% of control subjects; p < 0.05) and attenuated the antiproliferative action of cicaprost and forskolin on PASMCs, these effects being mediated via ET(A) and ET(B) receptors. Serum-stimulated proliferation was attenuated by inhibiting either endogenous ET-1 release with phosphoramidon (10(-5) mol/L) or its action with PD145065 (10(-5) mol/L). Cicaprost (10(-10)-10(-7) mol/L) inhibited ET-1 release from PASMCs (49 +/- 16% of control after 24 h; p < 0.001) and increased intracellular cAMP levels, whereas ET(B) receptor stimulation selectively reduced cAMP levels. In conclusion, ET(A) and ET(B) receptors are differentially distributed in human pulmonary arteries. Both receptors promote the proliferation of PASMCs in vitro and may contribute to vascular remodeling in pulmonary hypertension.

Evidence for activation of the renin-angiotensin system in the human prostate: increased angiotensin II and reduced AT(1) receptor expression in benign prostatic hyperplasia

The expression and cellular localization of angiotensin II (Ang II) and AT(1) receptor proteins were examined in the normal human prostate and benign prostatic hyperplasia (BPH) by immunohistochemistry. In the normal prostate, Ang II immunoreactivity was localized to the basal layer of the epithelium and AT(1) receptor immunostaining was found predominantly on stromal smooth muscle and also on vascular smooth muscle of prostatic blood vessels. Ang II immunoreactivity was markedly increased in hyperplastic acini in BPH compared with acini in the normal prostate (normal: 7.4+/-0.2%, n=5 vs. BPH: 22.7+/-1.9%, n=5, p<0.001). However, AT(1) receptor immunoreactivity was significantly decreased in BPH compared with the normal prostate [normal: 16.4+/-2.2%, n=4 vs. BPH: 9.4+/-1.3%, n=5, p<0.05 (p=0.025)]. The present study demonstrates the presence of Ang II peptide in the basal layer of the epithelium and AT(1) receptors on stromal smooth muscle, suggesting that Ang II may mediate paracrine functions on cellular growth and smooth muscle tone in the human prostate. Furthermore, AT(1) receptor down-regulation in BPH may be due to receptor hyperstimulation by increased local levels of Ang II in BPH. These data extend previous findings in support of the novel concept that overactivity of the renin-angiotensin system (RAS) may be involved in the pathophysiology of BPH.

Expression and localization of tissue factor pathway inhibitor-2 in normal and atherosclerotic human vessels

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type, serine protease inhibitor with inhibitory activity toward activated factor XI, plasma kallikrein, plasmin, certain matrix metalloproteinases, and the tissue factor:activated factor VII complex. In this study, we investigated TFPI-2 expression and localization in normal and atherosclerotic human arteries by using in situ hybridization and immunohistochemical techniques. In healthy human blood vessels, TFPI-2 was detected in the vascular endothelium alone. In human atherosclerotic tissues, TFPI-2 expression was assigned to macrophages, T cells, endothelial cells, and smooth muscle cells. Western blot analysis for TFPI-2 confirmed its production by cultured human aortic smooth muscle cells, U937 cells (monocytes), and Jurkat (T cell) cell lines. Reverse transcription-polymerase chain reaction revealed similar TFPI-2 expression levels in both monocytes and macrophages in culture. Electron microscopic study with immunogold labeling revealed the association of TFPI-2 antigen with both the extracellular matrix and plasma membranes. TFPI-2 antigen was detected in some areas of atheroma that also stained positively for both tissue factor and factor VII. Moreover, detection of TFPI-2 in close spatial proximity to plasmin/plasminogen on macrophages, on endothelial cells, and in matrix-rich areas highlighted its possible functional significance in the regulation of plasmin activity and downstream proteolytic mechanisms that occur in the atherosclerotic lesion.

[Role of elastin in the development of vascular function. Knock-out study of the elastin gene in mice]

The elastic fibres endow extensible tissues with resiliency, such as in blood vessels, heart, skin and lung. Elastic fibres are made of microfibrils, and mainly elastin (90%) which provides the fibre with elasticity. Beside the biomechanical role of elastin, a close correlation between elastin and elastic fibre network disorganisation and vascular smooth muscle cell (VSMC) growth disregulation has been known for several years through the description and study of several human or animal polyfeatured or obstructive vascular diseases, such as supravalvular aortic stenosis (SVAS) and Williams syndrome (WS), both related to heterozygous mutations or deletion in the elastin gene. The study of mice knock-out for the elastin gene (homozygous or heterozygous) leads to think that elastin should now be seen as an important elastic component providing extensible tissues with resiliency, as well as a major developmental regulator of VSMC life cycle and smooth muscle tissue organisation. Further developments in the area of preventive therapy of SVAS, WS or other inherited muscular disorders are likely to arise from these results.

Smitin, a novel smooth muscle titin-like protein, interacts with myosin filaments in vivo and in vitro

Smooth muscle cells use an actin-myosin II-based contractile apparatus to produce force for a variety of physiological functions, including blood pressure regulation and gut peristalsis. The organization of the smooth muscle contractile apparatus resembles that of striated skeletal and cardiac muscle, but remains much more poorly understood. We have found that avian vascular and visceral smooth muscles contain a novel, megadalton protein, smitin, that is similar to striated muscle titin in molecular morphology, localization in a contractile apparatus, and ability to interact with myosin filaments. Smitin, like titin, is a long fibrous molecule with a globular domain on one end. Specific reactivities of an anti-smitin polyclonal antibody and an anti-titin monoclonal antibody suggest that smitin and titin are distinct proteins rather than differentially spliced isoforms encoded by the same gene. Smitin immunofluorescently colocalizes with myosin in chicken gizzard smooth muscle, and interacts with two configurations of smooth muscle myosin filaments in vitro. In physiological ionic strength conditions, smitin and smooth muscle myosin coassemble into irregular aggregates containing large sidepolar myosin filaments. In low ionic strength conditions, smitin and smooth muscle myosin form highly ordered structures containing linear and polygonal end-to-end and side-by-side arrays of small bipolar myosin filaments. We have used immunogold localization and sucrose density gradient cosedimentation analyses to confirm association of smitin with both the sidepolar and bipolar smooth muscle myosin filaments. These findings suggest that the titin-like protein smitin may play a central role in organizing myosin filaments in the contractile apparatus and perhaps in other structures in smooth muscle cells.

Heart-specific genes revealed by expressed sequence tag (EST) sampling

BACKGROUND

Cardiovascular diseases are the primary cause of death worldwide; the identification of genes specifically expressed in the heart is thus of major biomedical interest. We carried out a comprehensive analysis of gene-expression profiles using expressed sequence tags (ESTs) to identify genes overexpressed in the human adult heart. The initial set of genes expressed in the heart was constructed by clustering and assembling ESTs from heart cDNA libraries. Expression profiles were then generated for each gene by counting their cognate ESTs in all libraries. Differential expression was assessed by applying a previously published statistical procedure to these profiles.

RESULTS

We identified 35 cardiac-specific genes overexpressed in the heart, some of which displayed significant coexpression. Some genes had no previously recognized cardiac function. Of the 35 genes, 32 were mapped back onto the human genome sequence. According to Online Mendelian Inheritance in Man (OMIM), five genes were previously known as heart-disease genes and one gene was located in the locus of a bleeding disorder. Analysis of the promoter regions of this collection of genes provides the first list of putative regulatory elements associated with differential cardiac expression.

CONCLUSION

This study shows that ESTs are still a powerful tool to identify differentially expressed genes. We present a list of genes specifically expressed in the human heart, one of which is a candidate for a bleeding disorder. In addition, we provide the first set of putative regulatory elements, the combination of which appears correlated with heart-specific gene expression.

Ultraviolet light-irradiated collagen III modulates expression of cytoskeletal and surface adhesion molecules in rat aortic smooth muscle cells in vitro

Systemic and pulmonary hypertension is characterised by structural reconstruction of the vascular wall which includes hypertrophy and hyperplasia of vascular smooth muscle cells (VSMCs) and fibroproduction. We hypothesise that these changes are stimulated by non-enzymatic modification of collagen molecules in the injured vascular wall by radicals. We exposed collagen III to ultraviolet (UV) light irradiation which, as indicated by fluorescence and electrophoretic analyses, resulted in its fragmentation. Both irradiated and control unmodified collagen were adsorbed on culture dishes and seeded with VSMCs derived from the rat thoracic aorta. During the first week after seeding, the cells on the modified collagen attained significantly higher population density (by 15-83%), higher mitotic index (by 31-135%) and higher BrdU labelling index (by 32%). However, these cells were less resistant to spontaneous and trypsin-mediated detachment from the growth support. As revealed using enzyme-linked immunosorbent assay in 3-day-old cultures, the cells growing on the irradiated collagen exhibited a lower concentration of beta-1 integrins (-10%, measured per milligram of protein), vinculin (-18%), talin (-6%) and vimentin (-15%). Immunofluorescence staining showed that these molecules were distributed more diffusely and less organised into focal adhesion plaques or cytoskeletal fibres. The concentration of two adhesion molecules of immunoglobulin type, ICAM-1 and VCAM-1, was increased by 11% and 16%, respectively. The concentration of alpha-v integrins and alpha-actin was unchanged; the latter, however, formed fewer distinct microfilament bundles in cells on the modified collagen. Our results suggest that the VSMCs growing on UV-modified collagen are more prone to escape the growth control mediated by cell-extracellular matrix contact and can bind the cells of the immune system.

cDNA microarray analysis of vascular gene expression after nitric oxide donor infusions in rats: implications for nitrate tolerance mechanisms

Vascular nitrate tolerance is often accompanied by changes in the activity and/or expression of a number of proteins. However, it is not known whether these changes are associated with the vasodilatory properties of nitrates, or with their tolerance mechanisms. We examined the hemodynamic effects and vascular gene expressions of 2 nitric oxide (NO) donors: nitroglycerin (NTG) and S-nitroso-N-acetylpenicillamine (SNAP). Rats received 10 microg/min NTG, SNAP, or vehicle infusion for 8 hours. Hemodynamic tolerance was monitored by the maximal mean arterial pressure (MAP) response to a 30-microg NTG or SNAP bolus challenge dose (CD) at various times during infusion. Gene expression in rat aorta after NTG or SNAP treatment was determined using cDNA microarrays, and the relative differences in expression after drug treatment were evaluated using several statistical techniques. MAP response of the NTG CD was attenuated from the first hour of NTG infusion (P <.001, analysis of variance [ANOVA]), but not after SNAP (P >.05, ANOVA) or control infusion (P >.05, ANOVA). Student t-statistics revealed that 447 rat genes in the aorta were significantly altered by NTG treatment (P <.05). An adjusted t-statistic approach using resampling techniques identified a subset of 290 genes that remained significantly different between NTG treatment vs control. In contrast, SNAP treatment resulted in the up-regulation of only 7 genes and the down-regulation of 34 genes. These results indicate that continuous NTG infusion induced widespread changes in vascular gene expression, many of which are consistent with the multifactorial and complex mechanisms reported for nitrate tolerance.

L-type Ca2+ channels in fetal and adult ovine cerebral arteries

Recently, we reported that, whereas in cerebral arteries of the adult a majority of norepinephrine (NE)-induced increase in intracellular Ca2+ concentration ([Ca2+]i) comes from release of the sarcoplasmic reticulum (SR) Ca2+ stores, in the fetus the SR Ca2+ stores are relatively small, and NE-induced increase in [Ca2+]i results mainly from activation of plasma membrane L-type Ca2+ channels (20). In an effort to establish further the role of L-type Ca2+ channels in the developing cerebral arteries, we tested the hypothesis that, in the fetus, increased reliance on plasmalemmal L-type Ca2+ channels is mediated, in part, by increased L-type Ca2+ channel density. We used 3H-labeled (+)isopropyl-4-(2,1,3-benzoxadiazol-4-y1)-1,4-dihydro-(2,6-dimethyl-5-methoxycarbonyl)pyridine-3-carboxylate (PN200-110, isradipine) to measure L-type Ca2+ channel density (Bmax) in the cerebral arteries, common carotid artery (CCA), and descending aortae of fetal (approximately 140 gestation days), newborn (7-10 days), and adult sheep. In the cerebral and common carotid arteries, B(max) values (fmol/mg protein) of fetuses and newborns were significantly greater than those of adults. Western immunoblotting assay also revealed that the density of L-type Ca2+ channel protein in the cerebral arteries and CCA was about twofold greater in the fetus than the adult. Finally, compared with the adult, fetal cerebral arteries demonstrated a significantly greater maximum tension and [Ca2+]i in response to stimulation with the L-type Ca2+ channel agonist Bay K 8644. In addition, Bay K 8644-stimulated fetal vessels demonstrated a maximal tension and [Ca2+]i similar to that observed in response to stimulation with 10(-4) NE. These results support the idea that fetal cerebrovascular smooth muscle relies more on extracellular Ca2+ and L-type Ca2+ channels for contraction than does the adult and that this increased reliance is mediated, in part, by greater L-type Ca2+ channel density. This may have important implications in the regulation of cerebral blood flow in the developing organism.

Functional and compositional studies of arteries stored in University of Wisconsin solution compared with Krebs-Bülbring buffer

Endothelium-dependent and -independent vasorelaxation in ring segments of rabbit thoracic aorta is reduced and noradrenaline-induced vasoconstriction unaltered after prolonged storage in University of Wisconsin solution (UW) compared to arteries stored in extracellular-type solutions such as Krebs-Bülbring buffer (KBB). The aims of the present study were to determine whether angiotensin-II-induced vasoconstriction, alterations in myosin light chains, protein synthetic capacity, and subcellular structures are altered after 8 days of UW storage at 4 degrees C. The present study showed reduced contractility to angiotensin II, following 8 days of cold storage in UW, that was not reversed in the presence of a nitric oxide synthase inhibitor, N(G)-nitro-l-arginine methyl ester (100 microM). Measurements of contractile protein ratios in the same tissues after cold storage in UW or KBB did not show any significant alterations in smooth muscle myosin light chains or protein synthetic capacity (reflected by total RNA). It is concluded that reductions in vasoconstriction in UW-stored tissue are unlikely to be due to increased release of nitric oxide nor reduced availability of myosin light chains for phosphorylation and vasoconstriction.

Changes in expression of P2 receptors in rat and mouse pancreas during development and ageing

In view of the evidence for a role for extracellular ATP in both pancreatic endocrine and exocrine functions, we have investigated the expression of P2X and P2Y receptors in this tissue in neonate and aged rat and mouse. Using immunohistochemistry it was shown that P2X(1), P2X(4), P2X(7), P2Y(1) and P2Y(2) receptors were present in different regions of the rat and mouse pancreas; P2X(3) and P2X(6) receptors were not found, and P2X(5) immunolabelling was only found in some nerves. The pancreatic vasculature of both rat and mouse expressed P2X(1), P2X(2), P2Y(1) and P2Y(2) receptors in the smooth muscle. P2X(1) and P2X(4) receptors were absent in the islets of the neonate pancreas, but were progressively upregulated with age after birth. In contrast, the greatest expression of P2Y(1) in cells from the duct system was in neonate pancreas, while there was no P2Y(1) expression in aged rat pancreas. P2X(7) receptors had a consistent pattern of distribution in all of the groups examined, being located in the outer periphery of the islet. Using antibodies raised against insulin, somatostatin and glucagon, double-labelling immunofluorescence was used to identify P2X(7)-positive cells in different islet of Langerhans cell populations. Our results demonstrated a clear immunoreaction to P2X(7) receptors in islet alpha cells, while no P2X(7) was expressed in beta and delta cells. The significance of the differential expression of P2 receptors in the pancreas during development and ageing, and a possible role for the proliferation and death of the islet cell population are discussed.

Tissue kallikrein and bradykinin B2 receptor in human uterus in luteal phase and in early and late gestation

This study was addressed to evaluate the temporospatial pattern of key components of the kallikreinkinin system in human uterus in luteal phase (n = 7), early pregnancy (isolated spontaneous abortions, n = 11; ectopic pregnancies, n = 9), idiopathic preterm deliveries (n = 5), and term gestations (n = 12). Tissue kallikrein mRNA and protein and the type 2 bradykinin receptor (B2R) protein were expressed in luminal and glandular epithelium and in endothelial cells of stromal and myometrial blood vessels, while tissue kallikrein mRNA and B2R, but not tissue kallikrein protein, were observed in decidual cells and in arteriolar and myometrial muscle. A greater signal intensity for tissue kallikrein mRNA and protein and of B2R protein was observed in the early pregnancy samples. The sites and variations of the tissue kallikrein mRNA and protein and of the B2R protein in the human uterus and in fallopian tubes during the luteal phase and in pregnancy coincide with those described for other vasoactive effectors such as nitric oxide, prostacyclins, growth factors, and renin. The uterine localization of the main enzyme and receptor of the tissue kallikrein-kinin system in key sites for embryo attachment, implantation, placentation, maintenance of placental blood flow, and parturition supports the notion that the kallikreinkinin system participates in these processes, probably through vasodilation, increased vasopermeability, enhanced matrix degradation, stimulation of cell proliferation, and myometrial contractility.

Transforming growth factor-beta 1 stimulates vascular smooth muscle cell L-proline transport by inducing system A amino acid transporter 2 (SAT2) gene expression

Transforming growth factor-beta1 (TGF-beta 1) is a multifunctional cytokine that contributes to arterial remodelling by stimulating vascular smooth muscle cell (SMC) growth and collagen synthesis at sites of vascular injury. Since l-proline is essential for the synthesis of collagen, we examined whether TGF-beta 1 regulates the transcellular transport of l-proline by vascular SMCs. l-Proline uptake by vascular SMCs was primarily sodium-dependent, pH-sensitive, blocked by neutral amino acids and alpha-(methylamino)isobutyric acid, and exhibited trans-inhibition. Treatment of SMCs with TGF-beta 1 stimulated l-proline transport in a concentration- and time-dependent manner. The TGF-beta 1-mediated l-proline uptake was inhibited by cycloheximide or actinomycin D. Kinetic studies indicated that TGF-beta 1-induced l-proline transport was mediated by an increase in transport capacity independent of any changes in the affinity for l-proline. TGF-beta 1 stimulated the expression of system A amino acid transporter 2 (SAT2) mRNA in a time-dependent fashion that paralleled the increase in l-proline transport. Reverse transcriptase PCR failed to detect the presence of SAT1 or amino acid transporter 3 (ATA3) in either untreated or TGF-beta 1-treated SMCs. These results demonstrate that l-proline transport by vascular SMCs is mediated predominantly by the SAT and that TGF-beta 1 stimulates SMC l-proline uptake by inducing the expression of the SAT2 gene. The ability of TGF-beta 1 to induce SAT2 expression may function to provide SMCs with the necessary levels of l-proline required for collagen synthesis and cell growth.

Lipoprotein (a) binds and inactivates tissue factor pathway inhibitor: a novel link between lipoproteins and thrombosis

Lipoprotein (a) [Lp(a)] has been associated with both anti-fibrinolytic and atherogenic effects. However, no direct link currently exists between this atherogenic lipoprotein and intravascular coagulation. The current study examined the binding and functional effects of Lp(a), its lipoprotein constituents, apoliprotein (a) [apo(a)] and low-density lipoprotein (LDL), and lysine-plasminogen (L-PLG), which shares significant homology with apo(a), on tissue factor pathway inhibitor (TFPI), a major regulator of tissue factor-mediated coagulation. Results indicate that Lp(a), apo(a), and PLG but not LDL bound recombinant TFPI (rTFPI) in vitro and that apo(a) bound to a region spanning the last 37 amino acid residues of the c-terminus of TFPI. The apparent binding affinity for TFPI was much higher for Lp(a) (KD approximately 150 nM) compared to PLG (KD approximately 800 nM) and nanomolar concentrations of apo(a) (500 nM) inhibited PLG binding to TFPI. Lp(a) also inhibited in a concentration-dependent manner rTFPI activity and endothelial cell surface TFPI activity in vitro, whereas PLG had no such effect. Moreover physiologic concentrations of PLG (2 microM) had no effect on the concentration-dependent inhibition of TFPI activity induced by Lp(a). In human atherosclerotic plaque, apo(a) and TFPI immunostaining were shown to coexist in smooth muscle cell-rich areas of the intima. These data suggest a novel mechanism whereby Lp(a) through its apo(a) moiety may promote thrombosis by binding and inactivating TFPI.

Elevating high-density lipoprotein cholesterol in apolipoprotein E-deficient mice remodels advanced atherosclerotic lesions by decreasing macrophage and increasing smooth muscle cell content

BACKGROUND

HDL cholesterol levels are inversely correlated with coronary heart disease risk in humans, and in animal studies, HDL elevation decreases formation and progression of foam-cell lesions. The potential for HDL to affect preexisting advanced atherosclerotic lesions is not known. To approach this issue, we used a novel mouse aortic transplantation model.

METHODS AND RESULTS

ApoE-deficient (EKO) mice were fed a Western-type diet for 6 months, and thoracic aortic segments containing advanced lesions replaced segments of the abdominal aorta of 4-month-old EKO syngeneic mice not expressing (plasma HDL cholesterol approximately 26 mg/dL) or expressing (HDL approximately 64 mg/dL) a human apoAI (hAI) transgene. Both types of recipients had comparable non-HDL cholesterol levels. Five months after transplantation, mice were killed and grafts analyzed. Compared with lesion area in pretransplant mice (0.14+/-0.04 mm(2), mean+/-SEM), there was progression in the EKO recipients (0.39+/-0.06 mm(2), P<0.01). Compared with EKO recipients, hAI/EKO recipients had retarded progression (0.24+/-0.04 mm(2), P<0.05). Immunostaining for CD68 and other macrophage-associated proteins, monocyte chemoattractant protein-1, acyl coenzyme A:cholesterol acyltransferase, and tissue factor, in lesions of pretransplant and EKO recipient mice showed abundant macrophages. In contrast, compared with any other group, lesional macrophage area in hAI/EKO mice decreased >80% (P<0.003), and smooth muscle cell content (alpha-actin staining) increased >300% (P<0.006). The decrease in macrophages and increase in smooth muscle cells was primarily in the superficial subendothelial layer.

CONCLUSIONS

Increasing HDL cholesterol levels in EKO mice retards progression of advanced atherosclerotic lesions and remodels them to a more stable-appearing phenotype.

Vascular calcification: expression patterns of the osteoblast-specific gene core binding factor alpha-1 and the protective factor matrix gla protein in human atherogenesis

OBJECTIVE

Increasing evidence suggests that vascular calcification is a regulated process. We studied the vascular expression pattern of a key factor in mineralization and a counteracting, protective factor. Based on the phenotype of null mice, Core binding factor alpha-1 (Cbfa-1) plays a pivotal role in bone formation, whereas Matrix Gla Protein (MGP) is a potent inhibitor of vascular calcification.

METHODS

We investigated the expression of MGP and Cbfa-1 in cultured, human monocytic cells, endothelial cells and smooth muscle cells (SMC), as well as in normal and atherosclerotic vessel specimens.

RESULTS

In cultured cells MGP is expressed in endothelial cells and SMC, whereas Cbfa-1 mRNA is predominantly present in macrophages and to a lesser extent in SMC. In the normal vessel wall MGP expression is high at the luminal side and declines toward the center of the media, whereas Cbfa-1 is absent. Moderate, diffuse calcification of the aorta media was observed only in those regions where MGP is low or absent. In atherosclerotic lesions MGP is expressed in endothelial cells and SMC that form fibrous caps, but is never present in macrophages. Cbfa-1 is synthesized in regions without MGP, it is associated with calcified areas and Cbfa-1 may be considered a marker for osteoprogenitor-like cells in the vessel wall.

CONCLUSIONS

Our observations on MGP expression confirm and extend published data and are consistent with a protective function of MGP. Cbfa-1 expression is absent in normal medial SMC and co-localizes with neointimal macrophages and focal calcifications.

Clinical importance of vascular LH/hCG receptors--a review

It was believed for a long time that functional LH/hCG receptors were present only in gonads. Recent studies have demonstrated, however, that these receptors are also present in several nongonadal organs in the human body. Uterus is one of them. Besides two uterine layers, endothelial cells and smooth muscle of blood vessels in the uterus also contain these receptors. In vivo administration of hCG decreased vascular resistance in the human uterus and in vitro treatment increased vasodilatory and decreased vasoconstrictive eicosanoids in the vessels. These findings led us to investigate whether hCG administration to patients with signs of threatened abortion has any beneficial effect. Patients were treated with either magnesium or progesterone and/or hCG. The results showed that the frequency of patients reaching second trimester was higher when hCG was used, which was paralleled by a significant decrease in uterine vascular resistance. Patients who reached term after treatment had decreased incidence of preterm delivery and intrauterine growth retardation. In conclusion, we suggest that uterine vascular LH/hCG receptors play an important role in the peri-implantation period by increasing uterine blood flow through vasodilatation and also perhaps through angiogenesis and trophoblast invasion, resulting in therapeutic benefit.

Calcium signalling through nucleotide receptor P2X1 in rat portal vein myocytes

1. ATP-mediated Ca2+ signalling was studied in freshly isolated rat portal vein myocytes by means of a laser confocal microscope and the patch-clamp technique. 2. In vascular myocytes held at -60 mV, ATP induced a large inward current that was supported mainly by activation of P2X1 receptors, although other P2X receptor subtypes (P2X3, P2X4 and P2X5) were revealed by reverse transcription-polymerase chain reaction. 3. Confocal Ca2+ measurements revealed that ATP-mediated Ca2+ responses started at initiation sites where spontaneous or triggered Ca2+ sparks were not detected, whereas membrane depolarizations triggered Ca2+ waves by repetitive activation of Ca2+ sparks from a single initiation site. 4. ATP-mediated Ca2+ responses depended on Ca2+ influx through non-selective cation channels that activated, in turn, Ca2+ release from the intracellular store via ryanodine receptors (RYRs). Using specific antibodies directed against the RYR subtypes, we show that ATP-mediated Ca2+ release requires, at least, RYR2, but not RYR3. 5. Our results suggest that, in vascular myocytes, Ca2+ influx through P2X1 receptors may trigger Ca2+-induced Ca2+ release at intracellular sites where RYRs are not clustered.

Clinical data supporting the importance of vascular LH/hCG receptors of uterine blood vessels

Recent studies revealed functional extragonadal gonadotropin receptors at several sites of the human body. The human chorionic gonadotropin/luteinizing hormone (hCG/LH) receptor messenger RNA and protein were found in the endothelial and vascular smooth muscle layers of the human uterine arteries. In vivo administration of hCG decreased the blood flow resistance in the human uterus and in vitro increased vasodilating eicosanoids in the vascular wall. These findings initiated a further study investigating whether the administration of hCG to patients with signs of threatened abortion has any beneficial effect. The patients were treated with either magnesium or progesterone and/or hCG. The results showed that the rate of patients reaching second trimester was higher when hCG was included in the treatment protocol, and a parallel significant decrease in uterine blood flow resistance was also found. Analyzing the long-term results, the rate of preterm and growth-retarded deliveries was lower when hCG was administered in the first trimester. As a conclusion, the uterine vascular LH/hCG receptors play a significant role in the peri-implantation period. The hCG might also participate in angiogenesis, enhancing long-term clinical results.

Platelet-derived growth factor receptors expressed in response to injury of differentiated vascular smooth muscle in vitro: effects on Ca2+ and growth signals

Vascular smooth muscle cells (VSMCs) in the intact vascular wall are differentiated for contraction, whereas the response to vascular injury involves transition towards a synthetic phenotype, with increased tendency for proliferation. Platelet-derived growth factor (PDGF) is thought to be important for this process. We investigated expression and functional coupling of PDGF receptors (PDGFRs) alpha and beta in rat tail arterial rings kept in organ culture, in order to capture early events in the phenotypic transition. In freshly dissected rings no PDGFR immunoreactivity was found in medial VSMCs, whereas PDGFR alpha was detected in nerve fibres. After organ culture for 1-4 days PDGFR alpha and beta as well as phospholipase Cgamma2 (PLCgamma2), known to couple to PDGFR, were expressed in VSMCs within 100 microm of the cut ends. Calponin, a marker for the contractile phenotype, was decreased near the injured area, suggesting that cells were in transition towards synthetic phenotype. In these cells, which showed functional Ca2+-release from the sarcoplasmic reticulum, PDGF-AB (100 ng x mL(-1)) had no effect on [Ca2+]i, whereas cultured VSMCs obtained from explants of rat tail arterial rings responded to PDGF-AB with an increase in [Ca2+]i. However, PDGFR within the cultured rings coupled to growth signalling pathways, as PDGF-AB caused a tyrphostin AG1295-sensitive activation of extracellular signal-regulated kinases 1 and 2 and of [3H]-thymidine incorporation. Thus, early expression of PDGFR in VSMC adjacent to sites of vascular injury coincides with signs of dedifferentiation. These receptors couple to growth signalling, but do not activate intracellular Ca2+ release.

Expression and localization of the contractile prostaglandin F receptor in pregnant rat myometrium in late gestation, labor, and postpartum

A polyclonal antibody was raised against amino acids 7-18 in the first extracellular loop of rat prostaglandin F (FP) receptor to monitor expression and localization in pregnant rat myometrium at Gestational Days 16, 18, 20, 21, 21.5, 22 (delivery), and 23 (1-day postpartum; n = 5 per group). The antibody recognized a protein of approximately 43 kDa on Western blot analysis in both membrane (soluble and nonsoluble) and cytosolic fractions of myometrium on each day of gestation. Expression of FP protein increased significantly (P < 0.05) during late gestation in both soluble membrane and cytosolic fractions, being significantly greater at Day 21.5 than at Day 20 of gestation in the soluble membrane fraction and in the cytosolic fraction of tissues collected during labor compared with those obtained before labor. The total concentration of FP receptor in the membrane (soluble plus nonsoluble) remained high throughout late gestation and fell significantly (P < 0.05) in the postpartum period. The FP receptor in the soluble membrane fraction (compared to the total membrane FP receptor) was significantly (P < 0.05) higher in late gestation than earlier, whereas the ratio of FP protein in cytosolic to that in the total membrane was significantly (P < 0.05) higher on Day 23 than earlier in gestation, suggesting a dynamic movement of FP with advancing gestational age. Immunoreactive FP receptor localized to circular and longitudinal smooth muscle at all gestational ages, but changes in intracellular localization were observed in late gestation with a staining pattern similar to alpha-actin, suggesting an association with myofibrils. Our study suggests an increase in FP-receptor protein in myometrium with advancing gestation and a marked elevation at term. This supports a role for uterine FP receptors in mediation of uterine contractility at term.

NG2 proteoglycan is expressed exclusively by mural cells during vascular morphogenesis

Immunofluorescence mapping demonstrates that the NG2 proteoglycan is invariably expressed by the mural cell component of mouse neovascular structures. This pattern is independent of the developmental mechanism responsible for formation of the vasculature (vasculogenesis or angiogenesis). Thus, NG2 is expressed in the embryonic heart by cardiomyocytes, in developing macrovasculature by smooth muscle cells, and in nascent microvessels by vascular pericytes. Due to the scarcity of proven markers for developing pericytes, NG2 is especially useful for identification of this cell type. The utility of NG2 as a pericyte marker is illustrated by two observations. First, pericytes are associated with endothelial tubes at an early point in microvessel development. This early interaction between pericytes and endothelial cells has important implications for the role of pericytes in the development and stabilization of microvascular tubes. Second, the pericyte to endothelial cell ratio in developing capillaries varies from tissue to tissue. Because the extent of pericyte investment is likely to affect the physical properties of the vessel in question, it is important to understand the mechanisms that control this process. Additional insight into these and other aspects of vascular morphogenesis should be possible through use of NG2 as a mural cell marker.