The regulation of human vascular smooth muscle extracellular matrix protein production by alpha- and beta-adrenoceptor stimulation

β-Adrenoceptor Signaling Activation Improves Bladder Fibrosis by Inhibiting Extracellular Matrix Deposition of Bladder Outlet Obstruction

BACKGROUND

Partial bladder outlet obstruction (pBOO) causes deposition of extracellular matrix (ECM), promotes bladder fibrosis, and decreases bladder compliance.

METHODS

To investigate the effect of β-adrenoceptor (ADRB) on the ECM deposition of pBOO rat model and explore its underlying mechanism, human bladder smooth muscle cells (hBSMCs) were exposed to the pathological hydrostatic pressure (100 cm H2O) for 6 h, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were employed. Then the rats of sham operation and pBOO model were treated with vehicle or ADRB agonists for 3 weeks, and the alterations of the bladder were observed via Masson staining and immunohistochemical analysis.

RESULTS

100 cm H2O hydrostatic pressure significantly upregulated the expression of collagen I (COL1), collagen III (COL3) and fibronectin (FN), and downregulated the expression of ADRB2 and ADRB3 of hBSMCs at 6 h. The agonists of ADRB2 and ADRB3, Formoterol and BRL 37344, decreased COL1 and FN expression of hBSMCs under 100 cm H2O for 6 h compared with the cells exposed to hydrostatic pressure only. As the classic downstream pathways of ADRB, the EPAC pathway inhibited COL1 and FN expression of hBSMCs via regulating SMAD3 and SMAD2 activities, respectively. In pBOO rats, Procaterol (ADRB2 agonist), and Mirabegron (ADRB3 agonist) inhibited the formation of collagen and decreased the expression of FN and COL1 in the bladders of pBOO rats.

CONCLUSIONS

The bladder fibrosis of pBOO and deposition of hBSMCs ECM under hydrostatic pressure were regulated by ADRB2, and ADRB3 via EPAC/SMAD2/FN and EPAC/SMAD3/COL1 pathways, these findings pave an avenue for effective treatment of pBOO.

Propranolol Reduces the Development of Lesions and Rescues Barrier Function in Cerebral Cavernous Malformations: A Preclinical Study

[Figure: see text].

The effects of repeated binge drinking on arterial stiffness and urinary norepinephrine levels in young adults

OBJECTIVES

The aim of this study was to investigate the effect of repeated binge drinking and moderate alcohol consumption in young adults on arterial stiffness and sympathetic activity.

METHODS

We enrolled 49 healthy young adults, free of cardiovascular diseases (25 men; age: 23.5 ± 0.4 years; BMI: 23.4 ± 0.4 kg/m; mean ± S.E). Individuals included were those with a history of repeated binge drinking (>2 years duration; n = 20), drank at moderate levels (MODs, >5 years duration; n = 16) and abstained from alcohol (last 2-3 years; n = 13). Arterial stiffness was assessed using carotid to femoral pulse wave velocity (cfPWV) and sympathetic activity was assessed using 24-h urinary norepinephrine levels. Also measured was aortic SBP and augmentation index (AIx), a measure of wave reflection.

RESULTS

Binge drinkers and MODs had higher cfPWV than alcohol abstainers (0.6 and 0.5 m/s, respectively; P ≤ 0.04). In addition, binge drinkers had higher urinary norepinephrine levels than MODs and alcohol abstainers (P < 0.05). Higher cfPWV were correlated with higher norepinephrine levels (r = 0.35. P = 0.02). Aortic SBP (P = 0.2) and AIx (P = 0.96) were similar among binge drinkers, MODs and alcohol abstainers.

CONCLUSION

Our findings suggest that repeated exposure to alcohol, regardless of drinking pattern, may increase aortic arterial stiffness in healthy young adults. In addition, sympathetic activation, reflected by increased 24-h urinary norepinephrine levels, may contribute to alcohol-induced arterial stiffening in young adults.

Increased pulse wave velocity in persons with spinal cord injury: the effect of the renin-angiotensin-aldosterone system

Increased pulse wave velocity (PWV), a marker of cardiovascular disease (CVD), has been reported in otherwise healthy individuals with spinal cord injury (SCI) compared with age-matched uninjured controls. Due to decentralized descending sympathetic vascular control, individuals with injuries above T6 are prone to orthostatic hypotension and, as a result, depend on the renin-angiotensin-aldosterone system (RAAS) to maintain orthostatic blood pressure (BP). The purpose of this study was to determine resting PWV, a noninvasive surrogate of central arterial stiffness, in individuals with cervical (C4-T1; n = 11) and thoracic (T6-T12; n = 11) SCI, compared with age-matched controls (controls; n = 11). Next, our aim was to describe group differences in BP, plasma norepinephrine (NE), and renin response to head-up tilt (HUT). Finally, we sought to determine the relationship between PWV and the orthostatic change in BP, NE, and the plasma renin during HUT among the groups. PWV was significantly increased in both cervical (8.81 ± 1.91 m/s) and thoracic (7.36 ± 1.58 m/s) SCI compared with the controls (5.53 ± 0.95 m/s; P < 0.05). The change from supine to 60° HUT in BP and NE was significantly reduced and change in plasma renin was significantly increased in the cervical group compared with the thoracic and control groups. Group affiliation and change in plasma renin were significant predictors of PWV (R² = 0.63, P = 0.001). These data suggest that dependency on the RAAS for orthostatic BP maintenance may be associated with increased PWV and risk of CVD in the SCI population.NEW & NOTEWORTHY Our novel findings suggest that increased arterial stiffness in individuals with SCI may be due to greater dependency on the RAAS to maintain hemodynamic stability during an orthostatic challenge. Asymptomatic orthostatic hypotension can occur in persons with SCI during transition from the supine to the seated position and during other upright activities of daily living; however, it is seldom addressed by clinicians.

Erectile dysfunction is associated with defective L-cysteine/hydrogen sulfide pathway in human corpus cavernosum and penile arteries

H₂S signaling was proposed to participate in erectile physiology. L-cysteine (CYS)/H₂S pathway stimulation causes cGMP-dependent relaxation of human corpus cavernosum (HCC) and penile arteries (HPRA). The aim was to evaluate the impact of ED on CYS/H₂S pathway at functional and molecular level in human penile vascular tissues. NaHS- and CYS-induced responses were evaluated in HCC and HPRA from organ donors without ED (NoED, n = 29) and from ED patients undergoing penile prosthesis insertion (n = 45). cGMP accumulation and cystathionine β-synthase and cystathionine γ-lyase expression were also determined. NaHS-induced relaxations were slightly but significantly impaired in HCC but not in HPRA from ED patients. In contrast, CYS-induced relaxations were markedly impaired in HCC (E_max 67.6 ± 4.9% vs 46.2 ± 4.6%, P < 0.01) and HPRA (E_max 80.8 ± 4.0% vs 48.1 ± 8.6%, P < 0.05) from men with ED. Impairment of CYS-induced responses was observed even after separating diabetic ED patients. In HPRA from ED patients, CYS- but not NaHS-induced vasodilation was significantly associated to endothelial function measured as vasodilatory capacity of acetylcholine (ACh) in these preparations (r² = 0.481, P < 0.01). Impairment of CYS-induced relaxations was related to significant reduction in CYS-induced accumulation of cGMP in cavernosal tissue. Furthermore, the expression of H₂S synthesizing enzymes was significantly reduced in HCC from ED patients with respect to NoED. This was confirmed by immunofluorescence in HCC and HPRA sections. ED involves impairment of CYS/H₂S pathway in penile vascular tissues associated with decreased expression of H₂S generating enzymes, CBS and CSE. These evidences support a therapeutic potential for modulation of CYS/H₂S signaling in the management of ED.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Morphology, Biochemistry, and Pathophysiology of MENX-Related Pheochromocytoma Recapitulate the Clinical Features

Pheochromocytomas (PCCs) are tumors arising from neural crest-derived chromaffin cells. There are currently few animal models of PCC that recapitulate the key features of human tumors. Because such models may be useful for investigations of molecular pathomechanisms and development of novel therapeutic interventions, we characterized a spontaneous animal model (multiple endocrine neoplasia [MENX] rats) that develops endogenous PCCs with complete penetrance. Urine was longitudinally collected from wild-type (wt) and MENX-affected (mutant) rats and outputs of catecholamines and their O-methylated metabolites determined by mass spectrometry. Adrenal catecholamine contents, cellular ultrastructure, and expression of phenylethanolamine N-methyltransferase, which converts norepinephrine to epinephrine, were also determined in wt and mutant rats. Blood pressure was longitudinally measured and end-organ pathology assessed. Compared with wt rats, mutant animals showed age-dependent increases in urinary outputs of norepinephrine (P = .0079) and normetanephrine (P = .0014) that correlated in time with development of tumor nodules, increases in blood pressure, and development of hypertension-related end-organ pathology. Development of tumor nodules, which lacked expression of N-methyltransferase, occurred on a background of adrenal medullary morphological and biochemical changes occurring as early as 1 month of age and involving increased adrenal medullary concentrations of dense cored vesicles, tissue contents of both norepinephrine and epinephrine, and urinary outputs of metanephrine, the metabolite of epinephrine. Taken together, MENX-affected rats share several biochemical and pathophysiological features with PCC patients. This model thus provides a suitable platform to study the pathogenesis of PCC for preclinical translational studies aimed at the development of novel therapies for aggressive forms of human tumors.

Tetrahydrobiopterin lowers muscle sympathetic nerve activity and improves augmentation index in patients with chronic kidney disease

Chronic kidney disease (CKD) is characterized by overactivation of the sympathetic nervous system (SNS) that contributes to cardiovascular risk. Decreased nitric oxide (NO) bioavailability is a major factor contributing to SNS overactivity in CKD, since reduced neuronal NO leads to increased central SNS activity. Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide synthase that increases NO bioavailability in experimental models of CKD. We conducted a randomized, double-blinded, placebo-controlled trial testing the benefits of oral sapropterin dihydrochloride (6R-BH4, a synthetic form of BH4) in CKD. 36 patients with CKD and hypertension were randomized to 12 wk of 1) 200 mg 6R-BH4 twice daily + 1 mg folic acid once daily; vs. 2) placebo + folic acid. The primary endpoint was a change in resting muscle sympathetic nerve activity (MSNA). Secondary endpoints included arterial stiffness using pulse wave velocity (PWV) and augmentation index (AIx), endothelial function using brachial artery flow-mediated dilation and endothelial progenitor cells, endothelium-independent vasodilatation (EID), microalbuminuria, and blood pressure. We observed a significant reduction in MSNA after 12 wk of 6R-BH4 (-7.5 ± 2.1 bursts/min vs. +3.2 ± 1.3 bursts/min; P = 0.003). We also observed a significant improvement in AIx (by -5.8 ± 2.0% vs. +1.8 ± 1.7 in the placebo group, P = 0.007). EID increased significantly (by +2.0 ± 0.59%; P = 0.004) in the 6R-BH4 group, but there was no change in endothelial function. There was a trend toward a reduction in diastolic blood pressure by -4 ± 3 mmHg at 12 wk with 6R-BH4 (P = 0.055). 6R-BH4 treatment may have beneficial effects on SNS activity and central pulse wave reflections in hypertensive patients with CKD.

Syndecan-1 regulates vascular smooth muscle cell phenotype

OBJECTIVE

We examined the role of syndecan-1 in modulating the phenotype of vascular smooth muscle cells in the context of endogenous inflammatory factors and altered microenvironments that occur in disease or injury-induced vascular remodeling.

METHODS AND RESULTS

Vascular smooth muscle cells (vSMCs) display a continuum of phenotypes that can be altered during vascular remodeling. While the syndecans have emerged as powerful and complex regulators of cell function, their role in controlling vSMC phenotype is unknown. Here, we isolated vSMCs from wild type (WT) and syndecan-1 knockout (S1KO) mice. Gene expression and western blotting studies indicated decreased levels of α-smooth muscle actin (α-SMA), calponin, and other vSMC-specific differentiation markers in S1KO relative to WT cells. The spread area of the S1KO cells was found to be greater than WT cells, with a corresponding increase in focal adhesion formation, Src phosphorylation, and alterations in actin cytoskeletal arrangement. In addition, S1KO led to increased S6RP phosphorylation and decreased AKT and PKC-α phosphorylation. To examine whether these changes were present in vivo, isolated aortae from aged WT and S1KO mice were stained for calponin. Consistent with our in-vitro findings, the WT mice aortae stained higher for calponin relative to S1KO. When exposed to the inflammatory cytokine TNF-α, WT vSMCs had an 80% reduction in syndecan-1 expression. Further, with TNF-α, S1KO vSMCs produced increased pro-inflammatory cytokines relative to WT. Finally, inhibition of interactions between syndecan-1 and integrins αvβ3 and αvβ5 using the inhibitory peptide synstatin appeared to have similar effects on vSMCs as knocking out syndecan-1, with decreased expression of vSMC differentiation markers and increased expression of inflammatory cytokines, receptors, and osteopontin.

CONCLUSIONS

Taken together, our results support that syndecan-1 promotes vSMC differentiation and quiescence. Thus, the presence of syndecan-1 would have a protective effect against vSMC dedifferentiation and this activity is linked to interactions with integrins αvβ3 and αvβ5.

Regulation of aortic extracellular matrix synthesis via noradrenergic system and angiotensin II in juvenile rats

CONTEXT

Extracellular matrix (ECM) synthesis regulation by sympathetic nervous system (SNS) or angiotensin II (ANG II) was widely reported, but interaction between the two systems on ECM synthesis needs further investigation.

OBJECTIVE

We tested implication of SNS and ANG II on ECM synthesis in juvenile rat aorta.

MATERIALS AND METHODS

Sympathectomy with guanethidine (50 mg/kg, subcutaneous) and blockade of the ANG II AT1 receptors (AT1R) blocker with losartan (20 mg/kg/day in drinking water) were performed alone or in combination in rats. mRNA and protein synthesis of collagen and elastin were examined by Q-RT-PCR and immunoblotting.

RESULTS

Collagen type I and III mRNA were increased respectively by 62 and 43% after sympathectomy and decreased respectively by 31 and 60% after AT1R blockade. Combined treatment increased collagen type III by 36% but not collagen type I. The same tendency of collagen expression was observed at mRNA and protein levels after the three treatments. mRNA and protein level of elastin was decreased respectively by 63 and 39% and increased by 158 and 15% after losartan treatment. Combined treatment abrogates changes induced by single treatments.

DISCUSSION AND CONCLUSION

The two systems act as antagonists on ECM expression in the aorta and combined inhibition of the two systems prevents imbalance of mRNA and protein level of collagen I and elastin induced by single treatment. Combined inhibition of the two systems prevents deposit or excessive reduction of ECM and can more prevent cardiovascular disorders.

Physiological regulation of extracellular matrix collagen and elastin in the arterial wall of rats by noradrenergic tone and angiotensin II

The interactions between the effects of the sympathetic nervous system (SNS) and angiotensin II (ANG II) on vascular extracellular matrix (ECM) synthesis were determined in rats.

The mRNA and protein content of collagen I, collagen III and elastin in the abdominal aorta (AA) and femoral artery (FA) was investigated in Wistar–Kyoto rats treated for 5 weeks with guanethidine, a sympathoplegic, losartan, an ANG II AT1 receptor (AT1R) blocker, or both. The effects of noradrenaline (NE) and ANG II on collagen III and elastin mRNA, and the receptor involved, were tested in cultured vascular smooth muscle cells (VSMCs) in vitro.

Guanethidine increased collagen types I and III and decreased elastin, while losartan had an opposite effect, although without effect on collagen III. The combination of treatments abrogated changes induced by simple treatment with collagen I and elastin, but increased collagen III mRNA in AA and not in FA. NE stimulated collagen III mRNA via β receptors and elastin via α1 and α2 receptors. ANG II stimulated collagen III but inhibited elastin mRNA via AT1R.

Overall, SNS and ANG II exert opposite and antagonistic effects on major components of ECM in the vascular wall. This may be of relevance for the choice of a therapeutic strategy in vascular diseases.

Hypertension in pheochromocytoma: characteristics and treatment

Pheochromocytoma is a tumor of the chromaffin cells in the adrenal medulla and sympathetic paraganglia, which synthesizes and secretes catecholamines. Norepinephrine, epinephrine, and dopamine all act on their target receptors, which causes a physiologic change in the body. High circulating levels of catecholamines can lead to severe hypertension and can have devastating effects on multiple body systems (eg, cardiovascular, cerebrovascular), and can lead to death if untreated. Although surgical treatment represents the only modality of ultimate cure, pharmacologic preoperative treatment remains the mainstay of successful outcome.

Time to re-appraise the role of alpha-1 adrenoceptor antagonists in the management of hypertension?

The role of alpha-1 adrenoceptor antagonists (alpha-blockers) in the management of hypertension continues to evolve. Recent data support their use as add-on therapy in uncontrolled hypertension when used in combination with all other major classes of antihypertensive drug and there is increasing evidence suggesting that they have modest but significant beneficial effects on lipid and glucose metabolism. The availability of extended-release formulations has contributed to an excellent tolerability profile. New data from an observational analysis of the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) suggest that doxazosin gastrointestinal therapeutic system (GITS) used as a third-line antihypertensive agent lowered blood pressure and caused modest reductions in plasma lipids. Furthermore, use of doxazosin in ASCOT was not associated with an increased risk of heart failure, in contrast to the earlier finding of the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). Overall, currently available data support the use of alpha-blockers as safe, well tolerated and effective add-on antihypertensive drugs, which have additional favourable metabolic effects.

Effect of celiprolol on prevention of cardiovascular events in vascular Ehlers-Danlos syndrome: a prospective randomised, open, blinded-endpoints trial

BACKGROUND

Vascular Ehlers-Danlos syndrome is a rare severe disease that causes arterial dissections and ruptures that can lead to early death. No preventive treatment has yet been validated. Our aim was to assess the ability of celiprolol, a β(1)-adrenoceptor antagonist with a β(2)-adrenoceptor agonist action, to prevent arterial dissections and ruptures in vascular Ehlers-Danlos syndrome.

METHODS

Our study was a multicentre, randomised, open trial with blinded assessment of clinical events in eight centres in France and one in Belgium. Patients with clinical vascular Ehlers-Danlos syndrome were randomly assigned to 5 years of treatment with celiprolol or to no treatment. Randomisation was done from a centralised, previously established list of sealed envelopes with stratification by patients' age (≤32 years or >32 years). 33 patients were positive for mutation of collagen 3A1 (COL3A1). Celiprolol was administered twice daily and uptritrated by 100 mg steps every 6 months to a maximum of 400 mg per day. [DOSAGE ERROR CORRECTED]. The primary endpoints were arterial events (rupture or dissection, fatal or not). This study is registered with ClinicalTrials.gov, number NCT00190411.

FINDINGS

53 patients were randomly assigned to celiprolol (25 patients) or control groups (28). Mean duration of follow-up was 47 (SD 5) months, with the trial stopped early for treatment benefit. The primary endpoints were reached by five (20%) in the celiprolol group and by 14 (50%) controls (hazard ratio [HR] 0·36; 95% CI 0·15-0·88; p=0·040). Adverse events were severe fatigue in one patient after starting 100 mg celiprolol and mild fatigue in two patients related to dose uptitration.

INTERPRETATION

We suggest that celiprolol might be the treatment of choice for physicians aiming to prevent major complications in patients with vascular Ehlers-Danlos syndrome. Whether patients with similar clinical presentations and no mutation are also protected remains to be established.

FUNDING

French Ministry of Health, Programme Hospitalier de Recherche Clinique 2001.

Factors influencing arterial stiffness in pheochromocytoma and effect of adrenalectomy

The aim of the study was to evaluate arterial stiffness and its modulating factors measured by carotid-femoral pulse wave velocity (PWV) and central augmentation index (AI) in patients with pheochromocytoma (PHEO) before and after surgery. Forty-five patients with PHEO and 45 healthy controls were investigated using an applanation tonometer (SphygmoCor, AtCor Medical). The gender, age, BMI and lipid profiles were comparable among both groups. The main difference in basic characteristic was as expected for fasting plasma glucose (P<0.001) and all blood pressure modalities. PWV in PHEO was significantly higher than in controls (7.2+/-1.4 vs. 5.8+/-0.5 ms(-1); P<0.001). Between-group difference in PWV remained significant even after the adjustment for age, heart rate, fasting plasma glucose and each of brachial (P<0.001) and 24 h blood pressure parameters (P<0.01). The difference in AI between groups did not reach the statistical significance (19+/-14 vs. 16+/-13%; NS). In multiple regression analysis, age (P<0.001), mean blood pressure (P=0.002), high-sensitive C-reactive protein (hs-CRP) (P=0.007) and 24 h urine norepinephrine (P=0.007) were independently associated with PWV in PHEO. In addition, 27 patients with PHEO were studied 1 year after tumor removal. Successful tumor removal led to a significant decrease in PWV (7.0+/-1.2 vs. 6.0+/-1.1 ms(-1); P<0.001). In conclusion, patients with PHEO have an increase in PWV, which is reversed by the successful tumor removal. Age, mean blood pressure, hs-CRP and norepinephrine levels are independent predictors of PWV.

Adipocyte extracellular matrix composition, dynamics and role in obesity

The central role of the adipose tissue in lipid metabolism places specific demands on the cell structure of adipocytes. The protein composition and dynamics of the extracellular matrix (ECM) is of crucial importance for the functioning of those cells. Adipogenesis is a bi-phasic process in which the ECM develops from a fibrillar to a laminar structure as cells move from the commitment phase to the growth phase characterized by storage of vast amounts of triglycerides. Mature adipocytes appear to spend a lot of energy on the maintenance of the ECM. ECM remodeling is mediated by a balanced complement of constructive and destructive enzymes together with their enhancers and inhibitors. ECM remodeling is an energy costing process regulated by insulin, by the energy metabolism, and by mechanical forces. In the obese, overgrowth of adipocytes may lead to instability of the ECM, possibly mediated by hypoxia.

Cardiovascular complications in patients with pheochromocytoma: a mini-review

Phaeochromocytomas are rare neuroendocrine tumours secreting high levels of catecholamines, able to exert serious metabolic and cardiovascular effects. The serious and potentially lethal cardiovascular complications of these tumours are due to the potent effects of secreted catecholamines, especially noradrenaline, the main transmitter released from sympathetic nerve terminals. Hypertension, tachycardia, pallor, headache and anxiety, usually dominate the clinical presentation. Occasionally, patients with predominantly epinephrine-secreting tumours present hypotension or even shock. Other cardiovascular complications of pheochromocytoma include ischaemic heart disease, acute myocardial infarction, cardiac arrhythmias, heart failure due to toxic cardiomyopathy, or pulmonary edema. Catecholamines have been shown to influence the extracellular matrix with collagen deposition and subsequent fibrosis in the arterial wall and in the myocardium. These morphofunctional changes of the myocardium and of arterial wall can be emphasized by ultrasound imaging. Indeed, ultrasound imaging of the myocardium and arterial wall not only identifies wall thickness but also contains information on texture that may be revealed by acoustic tissue characterization. The latter can be quantified through videodensitometric analysis of echographic images or through ultrasonic integrated backscatter signal analysis. This paper reviews cardiovascular complications in patients with pheochromocytoma and utility of the new ultrasound technique as backscatter signal. It is useful for evaluating preclinical pathological morphofunctional changes of the myocardium and arterial wall, characterized by increased collagen content in pheochromocytoma patients. The recognition of early catecholamine-induced alterations in patients with pheochromocytoma, is important to prevent at least morbidity and mortality, before surgical treatment.

Quantification of the temporal evolution of collagen orientation in mechanically conditioned engineered cardiovascular tissues

Load-bearing soft tissues predominantly consist of collagen and exhibit anisotropic, non-linear visco-elastic behavior, coupled to the organization of the collagen fibers. Mimicking native mechanical behavior forms a major goal in cardiovascular tissue engineering. Engineered tissues often lack properly organized collagen and consequently do not meet in vivo mechanical demands. To improve collagen architecture and mechanical properties, mechanical stimulation of the tissue during in vitro tissue growth is crucial. This study describes the evolution of collagen fiber orientation with culture time in engineered tissue constructs in response to mechanical loading. To achieve this, a novel technique for the quantification of collagen fiber orientation is used, based on 3D vital imaging using multiphoton microscopy combined with image analysis. The engineered tissue constructs consisted of cell-seeded biodegradable rectangular scaffolds, which were either constrained or intermittently strained in longitudinal direction. Collagen fiber orientation analyses revealed that mechanical loading induced collagen alignment. The alignment shifted from oblique at the surface of the construct towards parallel to the straining direction in deeper tissue layers. Most importantly, intermittent straining improved and accelerated the alignment of the collagen fibers, as compared to constraining the constructs. Both the method and the results are relevant to create and monitor load-bearing tissues with an organized anisotropic collagen network.

Hypertension and microvascular remodelling

In the present review, microvascular remodelling refers to alterations in the structure of resistance vessels contributing to elevated systemic vascular resistance in hypertension. We start with some historical aspects, underscoring the importance of Folkow's contribution made half a century ago. We then move to some basic concepts on the biomechanics of blood vessels, and explicit the definitions proposed by Mulvany for specific forms of remodelling, especially inward eutrophic and inward hypertrophic. The available evidence for the existence of remodelled resistance vessels in hypertension comes next, with relatively more weight given to human, in comparison with animal data. Mechanisms are discussed. The impact of antihypertensive drug treatment on remodelling is described, again with emphasis on human data. Some details are given on the three studies to date which point to remodelling of subcutaneous resistance arteries as an independent predictor of cardiovascular risk in hypertensive patients. We terminate by considering the potential role of remodelling in the pathogenesis of end-organ damage and in the perpetuation of hypertension.

Effects of ACE inhibition and beta-blockade on female genital structures in spontaneously hypertensive rats

INTRODUCTION AND AIM

This study evaluated the possible differences between an angiotensin converting enzyme (ACE) inhibitor and a beta-blocker concerning their potential protective role on female external genitalia in spontaneously hypertensive rats (SHR).

MAIN OUTCOME MEASURES

Morphological changes in the clitoris after antihypertensive treatments.

METHODS

For 6 months, SHR received no treatment; SHR + ramipril (RAM), SHR + atenolol (AT), and control Wistar Kyoto (WKY) rats received no treatment. Clitorises were processed for immunohistochemistry using anti-alpha-smooth muscle actin (alpha-SMA), anti-collagen I and III, anti-transforming growth factor beta(1) (TGFbeta(1)), and anti-endothelial nitric oxide synthase (eNOS) antibodies.

RESULTS

SHR + RAM and SHR + AT presented significantly lower blood pressure in both groups vs. untreated SHR. Compared with WKY, alpha-SMA was increased in the arteries and in the cavernous spaces of the clitoris together with a marked increase in wall/lumen ratio in clitoral vessels in untreated SHR. All these alterations were diminished in SHR + AT (P < 0.01). SHR + RAM presented differences with respect to SHR + AT in the reduction of these variables. TGFbeta(1) expression in the vessel wall from the clitoris and collagen I and III deposition in the interstitium from the clitoris in untreated SHR were significantly more (P < 0.01) than in WKY. While SHR + AT showed a mild decrease in these variables, SHR + RAM presented a significant reduction (P < 0.01) in TGFbeta(1) expression interstitial fibrosis and in both types of collagens. Positive immunostaining of eNOS in the sinusoidal endothelium from the clitoris was less (P < 0.01) in untreated SHR (3.4 +/- 1.3%) and SHR + AT (5.1 +/- 1.2%) than in SHR + RAM (17.2 +/- 1.6%) and WKY (15.9 +/- 1.7%). Untreated SHR and SHR + AT presented more surrounding connective tissue at the perineurium in the clitoris (P < 0.01) than SHR + RAM.

CONCLUSION

ACE inhibition provided a considerable protective role on the female external genitalia structures in SHR by a mechanism that may be, at least in part, independent of the degree of blood pressure lowering.

The role of myoendothelial gap junctions in the formation of arterial aneurysms: the hypothesis of "connexin 43:40 stoichiometry"

Heterocellular myoendothelial gap junctions (MEGJs) are essential in coordinating and regulating vasomotion. Little is known about their potential role in disease states. We discuss how alteration in the Cx 43:40 expression ratio at the level of MEGJs may begin a chain of reactions in the arterial wall resulting in an aneurysm formation. In this model, we assumed that aneurysm is a chronic arterial disease associated with medial degeneration and intimal hyperplasia. It also was assumed that MEGJs are composed of Cx43 and Cx40 in different stoichiometry and that the characteristic of a given junction is in the favor of its most abundantly expressed constituent. The hypothesis of Cx 43:40 stoichiometry indicates that impaired MEGJs may play a role in the pathogenesis of arterial aneurysms. Cx43 upregulation and Cx40 downregulation (increased Cx 43:40 stoichiometry) may induce a cascade of inflammatory, electrical, metabolic and proliferative derangements in the arterial wall, which finally lead to the matrix degradation, intimal hyperplasia, endothelial-medial dissociation and loss of endothelium-dependent hyperpolarizing currents, irregular vasomotion, impaired growth factor activation, and arterial sympathetic deprivation. The final consequence of these alterations is aneurysm formation.

Treatment of vascular smooth muscle cells with estradiol and beta-adrenergic agonists has an additive effect on cAMP levels, but no additive effect on inhibition of collagen synthesis

Several studies have suggested that increased cell levels of cAMP result in decreased rates of collagen synthesis. Oestrogen treatment of vascular smooth muscle cells (VSMCs) has been shown to cause increased levels of cAMP and decreased rates of collagen synthesis. Beta-adrenergic agonists are also known to increase cellular levels of cAMP in VSMCs, although the effect of beta-adrenergic agonists on collagen synthetic rates in VSMCs is unknown. Since beta-agonists and oestrogens are commonly used clinical agents these studies were conducted to determine the potential of these agents to have an additive effect on cell cAMP levels and inhibition of collagen synthetic rates. When VSMCs were treated with both oestrogen and isoproterenol there was an additive effect on cellular cAMP levels although the observed decrease in collagen synthetic rates was the same as observed in cells treated with just oestrogen. Treatment of VSMCs with propranolol inhibited isoproterenol-induced changes in cAMP but had no effect on either oestrogen-induced increases in cAMP levels or inhibition of collagen synthesis. The cellular location of cAMP following beta-adrenergic agonist treatment was different from the distribution of cAMP in control or oestrogen-treated VSMCs. This difference in cellular distribution of cAMP may partially explain the absence of collagen synthesis inhibition following beta-adrenergic agonist treatment of VSMCs.

Sympathectomy Causes Aggravated Lesions and Dedifferentiation in Large Rabbit Atherosclerotic Arteries without Involving Nitric Oxide

Previously [Histochem J 1997;29:279-286], we found that sympathectomy induced neointima formation in ear but not cerebral arteries of genetically hyperlipidemic rabbits. To clarify the influence of sympathetic nerves in atherosclerosis, and whether their influence involves vascular NO activity, we studied groups of normocholesterolemic intact (NI) and sympathectomized (NS), and hypercholesterolemic intact (HI) and sympathectomized (HS) rabbits (diet/6-hydroxydopamine for 79 days). Segments of basilar (BA) and femoral (FA) arteries were studied histochemically, to evaluate differentiation (anti-desmin, anti-vimentin, anti-h-caldesmon, and nuclear dye), by confocal microscopy, and by in vitro myography. In BAs, staining of NI and NS groups was similar. In hypercholesterolemic groups, a small neointima developed, more frequently in HS segments where smooth muscle cells (SMCs) positive for all antibodies appeared to be migrating into the neointima. In FAs, SMCs stained for the three antibodies in the NI group, but we observed desmin- and h-caldesmon-negative, vimentin-positive cells in some external medial layers of the NS, HI and HS groups, identical to adventitial fibroblasts. Large neointimas of the HS group contained vimentin-positive and largely desmin- and h-caldesmon-negative cells. Relaxation of BA or FA segments to acetylcholine was not decreased by sympathectomy. Sympathectomy increased the contraction of resting FAs to nitro-L-arginine (p = 0.0379). Thus, sympathectomy aggravates the tendency for FA SMCs to migrate and dedifferentiate, increasing atherosclerotic lesions, without decreasing NO activity, but has only minor effects on BAs.

The role of the alpha-1 adrenoceptor in modulating human mesangial cell matrix production

BACKGROUND

The sympathetic nervous system is frequently activated in hypertension and may modify various aspects of renal function. Whether modulation of the sympathetic nervous system directly influences the development of renal fibrosis is yet to be established. The current study investigates the role of the alpha-1 adrenoceptor on human mesangial cell scarring.

METHODS

Human mesangial cells were injured with macrophage-conditioned medium (MPCM) and treated with doxazosin for 1 or 3 days.

RESULTS

alpha-1 Adrenoceptor antagonist doxazosin of 2 micromol/l reduced fibronectin protein in MPCM-injured female mesangial cells by 31 +/- 1.03% (P < 0.001) and by 9.5 +/- 0.3% (P = 0.01) in male mesangial cells. The differential response between sexes was significant (P = 0.004). alpha-1B Adrenoceptors were detected in human mesangial cells by reverse transcription-polymerase chain reaction with expression in female cells being 87% higher than in males (P = 0.04). Injury with MPCM reduced alpha-1B adrenoceptor mRNA expression in both cell types. Doxazosin had no effect on the protein levels of transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta), however, a small reduction in tumour necrosis factor-alpha (TNF-alpha) levels was observed. Doxazosin had no effect on the modulators of matrix turnover matrix metalloproteinases MMP3, MMP9 and tissue inhibitor of matrix metalloproteinases (TIMP-1), although a significant reduction in tissue plasminogen activator (tPA); (36.5 +/- 2.6%, P < 0.001) was observed. Doxazosin caused an up-regulation of kallikrein expression, both at mRNA and protein levels. Co-treatment with the bradykinin B2 receptor antagonist HOE140 was able to attenuate the effects of doxazosin treatment on fibronectin levels.

CONCLUSION

These data suggest that inhibition of alpha-1B adrenoceptors in mesangial cells exerts an anti-fibrotic effect in a sex-specific manner via modulation of the kallikrein-kinin/plasminogen activator system.

Respective contribution of age, mean arterial pressure, and body weight on central arterial distensibility in SHR

In spontaneously hypertensive rats (SHR), carotid and aortic distensibilities measured at operational blood pressure (BP) are reduced. Increased body weight and mean arterial pressure (MAP) are both known to reduce distensibility independently. However, whether, after adjustment to body weight and mean BP, distensibility remains reduced in SHR has never been investigated. Carotid and abdominal aorta distensibilities were measured under anesthesia in SHR at 5, 12, 52, and 78 wk of age, and measurements were compared with age-matched normotensive Wistar rats. Each age group was composed of 9 or 10 animals. We determined distensibility using echo-tracking techniques of high resolution. Compared with Wistar rats, carotid and aortic distensibilities measured at operational MAP are reduced in SHR. This reduction is accentuated with age, particularly for the carotid artery. After adjustment to body weight and MAP, carotid and aortic distensibilities become identical in Wistar and SHR (or even slightly increased in SHR) but continue to be reduced with age, mainly for the carotid artery. In conclusion, in SHR, age and high BP do not have a parallel and similar influence on the reduction of arterial distensibility. Aging constantly reduces arterial distensibility, whereas MAP levels contribute to maintenance of arterial function.

Fructose overload modifies vascular morphology and prostaglandin production in rats

1. A fructose (Fru)-enriched diet induces a mild increase in blood pressure associated with hyperglycaemia, hypertriglyceridaemia, and insulin resistance, resembling the human 'syndrome X', being an useful model to study hypertension and type 2 diabetes. 2. A sustained elevation of blood pressure is associated with cardiovascular structural modifications such as left ventricular hypertrophy and increased wall thickness:lumen diameter ratio in blood vessels. 3. Prostanoids (PR), metabolites of arachidonic acid through the cyclooxygenase pathway, include vasoactive substances synthesized and released by the vessel walls. 4. The aim of the present study was to analyse, in Fru-treated rats: (i) the morphology of mesenteric vessels and; (ii) the PR production in aorta and mesenteric vessels, in order to assess whether these parameters are related with the haemodynamic alterations observed in this experimental model. 5. Blood pressure, glycaemia and triglyceridaemia, were significantly elevated in both (4 and 22 weeks) Fru-treated groups. Meanwhile body and heart weight as well as insulinaemia were similar between experimental animals and controls. 6. The mesenteric vessels of Fru-treated rats (22 weeks) showed an increased thickness and area of the media when compared with the controls; meanwhile, the lumen diameter was similar in both groups. 7. The Fru treatment for 4 weeks did not modify PR production in aorta, whereas in the mesenteric bed it diminished prostaglandin (PG) E(2) release significantly compared with the controls. However, in the group treated for 22 weeks, Fru reduced PGI(2) production in the aorta, as assessed by 6-keto-PGF(1)alpha measurements. Meanwhile, in the mesenteric bed, the chronic Fru treatment decreased PGE(2) release but, rather surprisingly, increased the output of PGI(2) when compared with its corresponding controls. 8. In conclusion, the present study shows the existence of an alteration in the morphology of mesenteric vessels in Fru-treated rats, which could be related to an increase in peripheral resistance and the consequent mild hypertension observed in this model. However, a diminished release of vasodilator PRs, such as PGE(2) in mesenteric vessels at 4 and 22 weeks and PGI(2) in aorta at 22 weeks could further impair the vessel response. The increase in PGI(2) observed in the chronic group in mesenteric vessels could be attributed to a compensatory mechanism.

Gene expression profiles in response to the activation of adrenoceptors in A7r5 aortic smooth muscle cells

1. Vascular adrenoceptors play an important role in vascular physiology and pathophysiology, such as hypertension, atherosclerosis and restenosis after angioplasty. To define the changes in the ene expression in vascular smooth muscle cells in response to the activation of alpha1- or beta-adrenoceptors, a DNA microarray was used. 2. First, the existence of alpha1- and beta-adrenoceptors in A7r5 aortic smooth muscle cells was confirmed by radioligand binding. Then, the inhibitory effects of phenylephrine (an alpha1-adrenoceptor agonist) and isoproterenol (a beta-adrenoceptor agonist) on the proliferation of A7r5 cells were determined by [3H]-thymidine incorporation. 3. The A7r5 cells were treated with 10 micromol/L phenylephrine or 1 micromol/L isoproterenol for 24 h and changes in gene expression were detected with the DNA microarray. Only 14 and 20 genes were identified after treatment of cells with phenylephrine and isoproterenol, respectively, and most genes displayed decreased expression. The changed genes could be grouped into five major functional categories: cell signalling/communication, cell structure/motility, cell/organism defence, gene/protein expression and metabolism. The gene expression profile in response to the activation of alpha1-adrenoceptors was very different from that following activation of beta-adrenoceptors. Interestingly, many phenylephrine-responsive genes were associated with metabolism, whereas many isoproterenol-responsive genes encoded cell signalling and structure proteins. This means that adrenoceptors may modulate multiple aspects of biological function in vascular smooth muscle cells. 4. Collectively, the activation of both alpha1-adrenoceptors (with phenylephrine) and beta-adrenoceptors (with isoproterenol) inhibited the proliferation of A7r5 cells, but microarray data revealed that the mechanisms may be different: the activation of alpha1-adrenoceptors could induce the expression of metabolic genes, resulting in the inhibition of proliferation, whereas activation of beta-adrenoceptors altered the expression of genes that encoded cell signalling and structure proteins to inhibit cell proliferation.

Norepinephrine-induced changes in cardiac transforming growth factor-beta isoform expression pattern of female and male rats

Transforming growth factor-beta (TGF-beta) is a ubiquitous growth-regulating protein with an essential role in tissue repair and formation of extracellular matrix (ECM). To better understand the role of different isoforms of TGF-beta in the cardiac remodeling process induced by norepinephrine (NE), the expression of TGF-beta1, TGF-beta2, and TGF-beta3 was studied and compared with the expression of collagen. NE (0.1 mg/kg. h) was intravenously infused in female and male Sprague-Dawley rats for several time periods, and freshly obtained ventricular myocardium after 1 day was dissociated into myocyte and nonmyocyte fractions. Prazosin (0.1 mg/kg x h) and metoprolol (1 mg/kg. h) were used to block alpha- and beta-adrenoceptors, respectively. After NE infusion, the three isoforms of TGF-beta were differentially induced as far as the magnitude and the time course is concerned. The increased expression of TGF-beta2 started earlier with a maximum after 12 hours and was more pronounced (10-fold elevation) than that of the other two isoforms, with a clear specificity for the left ventricle in female hearts. This specificity was also seen in male rats with 16-fold elevation of TGF-beta2 after 1 day of NE-stimulation. The increase of TGF-beta2 was significant only in the myocyte fraction obtained from female as well as from male hearts. The expression of the mRNA of all TGF-beta isoforms of collagen type I and type III, and of the matrix metalloproteinase (MMP)-2 and its inhibitor TIMP-2 was reduced predominantly by alpha-adrenoceptor blockade with prazosin. The increase in TGF-beta isoforms correlated with that of the mRNA expression of collagens, MMP-2 and TIMP-2.

Acute mechanoadaptation of vascular smooth muscle cells in response to continuous arteriolar vasoconstriction: implications for functional remodeling

Arterioles exposed to norepinephrine (NE) for 4 h exhibit incomplete relaxation on removal of the agonist. We hypothesized that this is due to a mechanoadaptation process associated with active repositioning of vascular smooth muscle cells (VSMCs) within the vascular wall. Isolated arterioles were exposed to NE (10(-5.5) M) for either 5 min (n = 7) or 4 h (n = 13). During the 5-min exposure, vessel diameter was reduced to 61 +/- 2.6%, and cells shortened to 76.3 +/- 3.8% of control. After NE removal, vessel diameter and cell length returned to control values, which indicated that during acute vasoconstriction cells shorten and relengthen in a reversible fashion. In contrast, when NE exposure lasted 4 h, vessels did not return to control diameter, but VSMCs returned to control length after NE removal. During the 4-h constriction, 56% of the VSMCs began returning to control length, and the overlap between VSMCs increased, which indicated that cellular repositioning had occurred in the presence of the maintained constriction. Thus, in response to prolonged constriction, VSMCs undergo a mechanoadaptation process involving "length autoregulation" that would be energetically favorable for maintenance of a reduced diameter and may provide a mechanism for the development of eutrophic remodeling of the vascular wall.

Adrenergic mechanisms and remodeling of subcutaneous small resistance arteries in humans

BACKGROUND

Vascular structural alterations in small resistance arteries of patients with essential hypertension (EH) are mostly characterized by inward eutrophic remodeling. In fact, no difference in the smooth muscle cell volume (CV) between normotensive subjects (NT) and essential hypertensive patients was observed. However, experimental models of hypertension with chronic infusion of agonists of adrenergic receptors were characterized by the presence of smooth muscle cell hypertrophy or hyperplasia. Recently, we have observed the presence of vascular smooth muscle cell hypertrophy in patients with renovascular hypertension.

OBJECTIVE

The aim of the study to investigate the structural characteristics of subcutaneous small resistance arteries of NT, of EH, and of patients with phaeochromocytoma (Phaeo).

PATIENTS AND METHODS

Thirty Phaeo, 30 NT and 30 EH were included in the study. A biopsy of subcutaneous fat was taken from all subjects. Small resistance arteries (relaxed diameter 160-280 microm) were dissected and mounted on a micromyograph and the media : lumen ratio was calculated. In nine Phaeo, nine NT and 13 EH the cell volume was measured by an unbiased stereological principle, the 'disector' method. RESULTS No difference in smooth muscle cell volume was observed between groups. However, inward remodeling in Phaeo was less marked than in EH, although the increase in media : lumen ratio was similar compared with NT. However, the lack of changes in media cross-sectional area, compared with NT, suggest that there has been little hypertrophy, the changes observed thus being eutrophic.

CONCLUSIONS

Our data show, based on a reasonably large sample, that a pronounced activation of the adrenergic system is not associated with vascular smooth muscle cell hypertrophy or hyperplasia in humans. It is therefore possible that adrenergic mechanisms may have a relevant role in the development of eutrophic remodeling in small vessels.

Norepinephrine induces hepatic fibrogenesis in leptin deficient ob/ob mice

Leptin's actions on certain cells require a leptin-inducible neurotransmitter, norepinephrine (NE). NE modulates hepatic fibrosis. Therefore, decreased NE may explain why leptin deficiency inhibits hepatic fibrosis. We manipulated adrenergic activity in leptin-deficient ob/ob mice, leptin-sufficient, dopamine beta-hydroxylase deficient (Dbh(-/-)) mice, and HSC cultures to determine if leptin requires NE to activate HSC and induce hepatic fibrosis. ob/ob mice have chronic liver injury, but reduced numbers of HSC. Supplemental leptin increases HSC, suggesting that leptin-dependent, injury-related factors permit expansion of HSC populations. NE also increases HSC numbers and activation, normalizing fibrogenesis. When fed hepatotoxic diets, NE-deficient Dbh(-/-) mice fail to accumulate activated HSC and have impaired fibrogenesis unless treated with adrenergic agonists. NE acts directly on HSC to modulate leptin's actions because leptin increases HSC proliferation and prazosin, an alpha-adrenoceptor antagonist, inhibits this. Thus, leptin permits injury-related increases in adrenergic activity and requires NE to activate HSC and induce hepatic fibrogenesis.

Norepinephrine and neuropeptide Y promote proliferation and collagen gene expression of hepatic myofibroblastic stellate cells

The mechanisms initiating and perpetuating the fibrogenic response in the injured liver are not well understood. Hepatic stellate cells are activated by liver injury to become proliferative and fibrogenic myofibroblasts. Emerging evidence suggests that the sympathetic nervous system may play a role in the development of cirrhosis. It is not known, however, whether this requires a direct interaction between sympathetic neurotransmitters and stellate cell receptors, or results indirectly, from sympathetic effects on the vasculature. Using cultured hepatic stellate cells, we show that the sympathetic neurotransmitters, norepinephrine and neuropeptide Y, markedly stimulate the proliferation of activated, myofibroblastic, hepatic stellate cells. Norepinephrine, but not neuropeptide Y, also induces collagen gene expression. In conclusion, physiologically relevant concentrations of sympathetic neurotransmitters directly modulate the phenotype of hepatic stellate cells. This suggests that targeted interruption of sympathetic nervous system signaling in hepatic stellate cells may be useful in constraining the fibrogenic response to liver injury.

TGFbeta1 enhances formation of cellular Abeta/apoE deposits in vascular myocytes

Brain injury increases the risk of Alzheimer's disease (AD) through unknown mechanisms. We studied deposition of amyloid-beta protein (Abeta) in cells exposed to transforming growth factor beta1 (TGFbeta1), a cytokine that regulates cell metabolism during brain injury, and apolipoproteinE (apoE), the major lipid transporter in the brain. The studies were conducted by using brain vascular smooth muscle cells that are engaged in beta-amyloidosis in vivo and produce Abeta in cell culture. We found that cell treatment with TGFbeta1 together with apoE4 strongly increased the amount of cellular Abeta. The intracellular Abeta co-localized with apoE but not with TGFbeta, similarly as in vascular beta-amyloid. Some cellular Abeta/apoE deposits increased in size and persisted in culture even after the TGFbeta1 and apoE4 were removed. The appearance of cellular deposits of Abeta was associated with increased production of the amyloid-beta precursor protein and cellular retention of its mature form. The results suggest that the concomitant presence of apoE and TGFbeta1 can trigger vascular beta-amyloidosis by inducing intracellular formation of stable Abeta/apoE deposits.

Effect of antihypertensive treatment on small artery remodeling in hypertension

Blood vessels are remodeled in hypertension both structurally and functionally. The changes that occur in their structure, mechanical properties, and function contribute to blood pressure elevation and to complications of hypertension. We studied the remodeling of small arteries in experimental animals and humans. Smooth muscle cells of small arteries are restructured around a smaller lumen, with significant remodeling of the extracellular matrix and collagen and fibronectin deposition. Interestingly, there is no evidence of net growth of the vascular wall (which results in so-called eutrophic remodeling), particularly in the milder forms of human essential hypertension. Hypertrophic remodeling and increased small artery stiffness may be found in more severe forms of hypertension. Almost all hypertensive patients have vascular structural remodeling. However, only some exhibit endothelial dysfunction. This is particularly true in mild hypertension, in which endothelial dysfunction is less common. A 1-year treatment of hypertensive patients with angiotensin converting enzyme inhibitors, angiotensin AT1 receptor antagonists, and long acting calcium channel blockers corrected small artery structure and, to variable degrees depending on the agents used, impaired endothelial function. In contrast, beta blockers did not improve structure, function, or mechanics of vessels. When beta-blocker-treated patients were switched to an AT1 receptor antagonist, small artery structure and impaired endothelial function were corrected. The vascular protective action of some antihypertensive agents may contribute to improve outcome for hypertensive patients, although this is presently unproven.

Acetylcholine promotes the proliferation and collagen gene expression of myofibroblastic hepatic stellate cells

The mechanisms that initiate and perpetuate the fibrogenic response, during liver injury, are unclear. Animal studies, however, strongly support a role for the autonomic nervous system (ANS) in wound healing. Therefore, the ANS may also mediate the development of cirrhosis. Hepatic stellate cells (HSC), the liver's major matrix-producing cells, are activated by injury to become proliferative, fibrogenic myofibroblasts. HSC respond to sympathetic neurotransmitters by changing phenotype, suggesting that HSC may be the cellular effectors of ANS signals that modulate hepatic fibrogenesis during recovery from liver damage. We show here that the parasympathetic neurotransmitter acetylcholine markedly stimulates the proliferation of myofibroblastic HSC and induces HSC collagen gene expression in these cells. By extending evidence that HSC are direct targets of the ANS, these results support the proposed neuroglial role of HSC in the liver and suggest that interrupting ANS signalling may be useful in constraining the fibrogenic response to liver injury.

Resistance artery mechanics and composition in angiotensin II-infused rats: effects of aldosterone antagonism

BACKGROUND

Angiotensin (Ang) II stimulates aldosterone production, which may mediate some of the effects of Ang II.

OBJECTIVE

To test whether Ang II-induced structural and mechanical changes in resistance arteries may be prevented by the non-selective aldosterone receptor blocker, spironolactone, independently of reduction in blood pressure.

METHODS

Male Sprague-Dawley rats received Ang II [120 ng/kg per min subcutaneously (s.c.)] with or without spironolactone or hydralazine (25 mg/kg per day). Two additional groups received aldosterone (750 ng/h s.c.) with or without spironolactone. After 2 weeks, third-order mesenteric arteries were dissected and studied by pressurized myograph. Deposition of collagen type I/III in the vascular wall was evaluated by confocal immunofluorescence microscopy.

RESULTS

Ang II increased blood pressure significantly (P <0.01); this was partially prevented by spironolactone (P <0.01) and nearly normalized by hydralazine (P <0.01). Media thickness, media:lumen ratio and media cross-sectional area of mesenteric resistance arteries increased under Ang II or aldosterone (P <0.01) and this was partially prevented by spironolactone (P <0.01), but not by hydralazine. Compared with the control or Ang II + spironolactone groups, rats treated with Ang II with or without hydralazine presented stiffer vessels, with leftward shift of the stress-strain relationship and a raised slope of the incremental elastic modulus-stress relationship (P <0.05). Confocal microscopy demonstrated enhanced deposition of collagen type I/III in the media of arteries from rats infused with Ang II or aldosterone, an effect that was prevented partially by spironolactone but unaffected by hydralazine.

CONCLUSION

Ang II-induced vascular alterations in structure, mechanics and composition were partially prevented by spironolactone, independently of blood pressure reduction, providing further evidence that some actions of Ang II on resistance arteries are mediated by aldosterone.

Aetiology and pathogenesis of benign prostatic hyperplasia

PURPOSE OF REVIEW

Prostatic hyperplasia predominantly involves the stromal compartment of the gland and affects more than 70% of men of 70 years or older with or without obstructive symptoms of benign prostatic hyperplasia. A consensus view is emerging concerning the factors and control systems that modulate cell proliferation and connective tissue biology in the prostate. The purpose of this review is to discuss some of the recent work contributing to the latter in the context of the aetiology of benign prostatic hyperplasia.

RECENT FINDINGS

Studies over the last 3-5 years have identified transforming growth factor beta, fibroblast growth factor and insulin-like growth factor family members as key regulators of cell proliferation and extracellular matrix turnover with interrelated activities. Recently, oestrogens, adrenergic signalling and inflammatory processes have been shown to impact and potentially perturb the balance between the activities of the above factors. These agents are all subject to alteration with age and as such are candidates for potential triggers of the initiation of stromal hyperplasia.

SUMMARY

The current model for the control and dysregulation of prostatic stromal growth is discussed in relation to the pathogenesis of benign prostatic hyperplasia and future directions for research.

Vascular and cardiac benefits of angiotensin receptor blockers

Angiotensin II not only is a vasoconstrictor, but it also affects cell growth and apoptosis, inflammation, fibrosis, and coagulation. Blockade of the renin-angiotensin system, either with inhibitors of the generation of angiotensin (angiotensin-converting enzyme [ACE] inhibitors) or with blockers of angiotensin receptors, reduces blood pressure and inhibits other pathophysiological actions. These other effects provide benefits in coronary heart disease, heart failure, diabetic nephropathy, and stroke beyond blood pressure reduction. These benefits were first demonstrated with ACE inhibitors. However, the mechanism of action of angiotensin receptor blockers, which block angiotensin II stimulation at the angiotensin type 1 receptor but not at the type 2 receptor, may have advantages, particularly for endothelial dysfunction and vascular remodeling, as well as cardiac and renal protection. Recent multicenter trials suggest that ACE inhibitors and angiotensin receptor blockers may reduce morbidity and mortality associated with cardiovascular and renal disease beyond blood pressure reduction. Several studies with different angiotensin receptor blockers, including comparisons with ACE inhibitors, are under way, and should provide further guidance for their clinical use.