Alpha-adrenergic blockers: mechanism of action, blood pressure control, and effects of lipoprotein metabolism

Identifying mitigating strategies for endothelial cell dysfunction and hypertension in response to VEGF receptor inhibitors

Vascular endothelial growth factor receptor inhibitors (VEGFRis) improve cancer survival but are associated with treatment-limiting hypertension, often attributed to endothelial cell (EC) dysfunction. Using phosphoproteomic profiling of VEGFRi-treated ECs, drugs were screened for mitigators of VEGFRi-induced EC dysfunction and validated in primary aortic ECs, mice, and canine cancer patients. VEGFRi treatment significantly raised systolic blood pressure (SBP) and increased markers of endothelial and renal dysfunction in mice and canine cancer patients. α-Adrenergic-antagonists were identified as drugs that most oppose the VEGFRi proteomic signature. Doxazosin, one such α-antagonist, prevented EC dysfunction in murine, canine, and human aortic ECs. In mice with sorafenib-induced-hypertension, doxazosin mitigated EC dysfunction but not hypertension or glomerular endotheliosis, while lisinopril mitigated hypertension and glomerular endotheliosis without impacting EC function. Hence, reversing EC dysfunction was insufficient to mitigate VEGFRi-induced-hypertension in this mouse model. Canine cancer patients with VEGFRi-induced-hypertension were randomized to doxazosin or lisinopril and both agents significantly decreased SBP. The canine clinical trial supports safety and efficacy of doxazosin and lisinopril as antihypertensives for VEGFRi-induced-hypertension and the potential of trials in canines with spontaneous cancer to accelerate translation. The overall findings demonstrate the utility of phosphoproteomics to identify EC-protective agents to mitigate cardio-oncology side effects.

Facile Synthesis of Some New Peptidomimetic β3 -and β2,3 -Amino Alcohols Possessing Pyridyl Moiety via Reductive Ring Opening of Pyridyl-isoxazolidines

Regio- and stereoselective 1,3-dipolar cycloadditions of C-(3-pyridyl)-N-phenylnitrone (2) with variedly substituted dipolarophiles (3, 4) were carried out to obtain substituted pyridyl-isoxazolidines (5-8). Reductive cleavage of pyridyl-isoxazolidines (5-8) with ammonium formate, methanol-THF solvents, at ambient temperature, in the presence of Pd/C provided a facile route for the synthesis of β3 -and β2,3 -amino alcohols (9-12), with a substitution pattern having pronounced influence on torsional angles. The obtained compounds (9-12) are valuable scaffolds which can be utilized for peptidomimetics. Thus, the present methodology for reductive opening of isoxazolidine ring avoids the disadvantages of using expensive apparatus and hazards involved in the use of hydrogen gas. The preferential formation of amino-alcohols in case of bicyclic isoxazolidines (8a-c), which precludes any recyclization is rationalized by DFT calculations.

First-line diuretics versus other classes of antihypertensive drugs for hypertension

BACKGROUND

Different first-line drug classes for patients with hypertension are often assumed to have similar effectiveness with respect to reducing mortality and morbidity outcomes, and lowering blood pressure. First-line low-dose thiazide diuretics have been previously shown to have the best mortality and morbidity evidence when compared with placebo or no treatment. Head-to-head comparisons of thiazides with other blood pressure-lowering drug classes would demonstrate whether there are important differences.

OBJECTIVES

To compare the effects of first-line diuretic drugs with other individual first-line classes of antihypertensive drugs on mortality, morbidity, and withdrawals due to adverse effects in patients with hypertension. Secondary objectives included assessments of the need for added drugs, drug switching, and blood pressure-lowering.

SEARCH METHODS

Cochrane Hypertension's Information Specialist searched the Cochrane Hypertension Specialized Register, CENTRAL, MEDLINE, Embase, and trials registers to March 2021. We also checked references and contacted study authors to identify additional studies. A top-up search of the Specialized Register was carried out in June 2022.

SELECTION CRITERIA

Randomized active comparator trials of at least one year's duration were included. Trials had a clearly defined intervention arm of a first-line diuretic (thiazide, thiazide-like, or loop diuretic) compared to another first-line drug class: beta-blockers, calcium channel blockers, alpha adrenergic blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor blockers, direct renin inhibitors, or other antihypertensive drug classes. Studies had to include clearly defined mortality and morbidity outcomes (serious adverse events, total cardiovascular events, stroke, coronary heart disease (CHD), congestive heart failure, and withdrawals due to adverse effects).

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included 20 trials with 26 comparator arms randomizing over 90,000 participants. The findings are relevant to first-line use of drug classes in older male and female hypertensive patients (aged 50 to 75) with multiple co-morbidities, including type 2 diabetes. First-line thiazide and thiazide-like diuretics were compared with beta-blockers (six trials), calcium channel blockers (eight trials), ACE inhibitors (five trials), and alpha-adrenergic blockers (three trials); other comparators included angiotensin II receptor blockers, aliskiren (a direct renin inhibitor), and clonidine (a centrally acting drug). Only three studies reported data for total serious adverse events: two studies compared diuretics with calcium channel blockers and one with a direct renin inhibitor. Compared to first-line beta-blockers, first-line thiazides probably result in little to no difference in total mortality (risk ratio (RR) 0.96, 95% confidence interval (CI) 0.84 to 1.10; 5 trials, 18,241 participants; moderate-certainty), probably reduce total cardiovascular events (5.4% versus 4.8%; RR 0.88, 95% CI 0.78 to 1.00; 4 trials, 18,135 participants; absolute risk reduction (ARR) 0.6%, moderate-certainty), may result in little to no difference in stroke (RR 0.85, 95% CI 0.66 to 1.09; 4 trials, 18,135 participants; low-certainty), CHD (RR 0.91, 95% CI 0.78 to 1.07; 4 trials, 18,135 participants; low-certainty), or heart failure (RR 0.69, 95% CI 0.40 to 1.19; 1 trial, 6569 participants; low-certainty), and probably reduce withdrawals due to adverse effects (10.1% versus 7.9%; RR 0.78, 95% CI 0.71 to 0.85; 5 trials, 18,501 participants; ARR 2.2%; moderate-certainty). Compared to first-line calcium channel blockers, first-line thiazides probably result in little to no difference in total mortality (RR 1.02, 95% CI 0.96 to 1.08; 7 trials, 35,417 participants; moderate-certainty), may result in little to no difference in serious adverse events (RR 1.09, 95% CI 0.97 to 1.24; 2 trials, 7204 participants; low-certainty), probably reduce total cardiovascular events (14.3% versus 13.3%; RR 0.93, 95% CI 0.89 to 0.98; 6 trials, 35,217 participants; ARR 1.0%; moderate-certainty), probably result in little to no difference in stroke (RR 1.06, 95% CI 0.95 to 1.18; 6 trials, 35,217 participants; moderate-certainty) or CHD (RR 1.00, 95% CI 0.93 to 1.08; 6 trials, 35,217 participants; moderate-certainty), probably reduce heart failure (4.4% versus 3.2%; RR 0.74, 95% CI 0.66 to 0.82; 6 trials, 35,217 participants; ARR 1.2%; moderate-certainty), and may reduce withdrawals due to adverse effects (7.6% versus 6.2%; RR 0.81, 95% CI 0.75 to 0.88; 7 trials, 33,908 participants; ARR 1.4%; low-certainty). Compared to first-line ACE inhibitors, first-line thiazides probably result in little to no difference in total mortality (RR 1.00, 95% CI 0.95 to 1.07; 3 trials, 30,961 participants; moderate-certainty), may result in little to no difference in total cardiovascular events (RR 0.97, 95% CI 0.92 to 1.02; 3 trials, 30,900 participants; low-certainty), probably reduce stroke slightly (4.7% versus 4.1%; RR 0.89, 95% CI 0.80 to 0.99; 3 trials, 30,900 participants; ARR 0.6%; moderate-certainty), probably result in little to no difference in CHD (RR 1.03, 95% CI 0.96 to 1.12; 3 trials, 30,900 participants; moderate-certainty) or heart failure (RR 0.94, 95% CI 0.84 to 1.04; 2 trials, 30,392 participants; moderate-certainty), and probably reduce withdrawals due to adverse effects (3.9% versus 2.9%; RR 0.73, 95% CI 0.64 to 0.84; 3 trials, 25,254 participants; ARR 1.0%; moderate-certainty). Compared to first-line alpha-blockers, first-line thiazides probably result in little to no difference in total mortality (RR 0.98, 95% CI 0.88 to 1.09; 1 trial, 24,316 participants; moderate-certainty), probably reduce total cardiovascular events (12.1% versus 9.0%; RR 0.74, 95% CI 0.69 to 0.80; 2 trials, 24,396 participants; ARR 3.1%; moderate-certainty) and stroke (2.7% versus 2.3%; RR 0.86, 95% CI 0.73 to 1.01; 2 trials, 24,396 participants; ARR 0.4%; moderate-certainty), may result in little to no difference in CHD (RR 0.98, 95% CI 0.86 to 1.11; 2 trials, 24,396 participants; low-certainty), probably reduce heart failure (5.4% versus 2.8%; RR 0.51, 95% CI 0.45 to 0.58; 1 trial, 24,316 participants; ARR 2.6%; moderate-certainty), and may reduce withdrawals due to adverse effects (1.3% versus 0.9%; RR 0.70, 95% CI 0.54 to 0.89; 3 trials, 24,772 participants; ARR 0.4%; low-certainty). For the other drug classes, data were insufficient. No antihypertensive drug class demonstrated any clinically important advantages over first-line thiazides.

AUTHORS' CONCLUSIONS

When used as first-line agents for the treatment of hypertension, thiazides and thiazide-like drugs likely do not change total mortality and likely decrease some morbidity outcomes such as cardiovascular events and withdrawals due to adverse effects, when compared to beta-blockers, calcium channel blockers, ACE inhibitors, and alpha-blockers.

Updates on Pharmacologic Management of Microvascular Angina

Microvascular angina (MVA), historically called cardiac syndrome X, refers to angina with nonobstructive coronary artery disease. This female-predominant cardiovascular disorder adds considerable health-related costs due to repeated diagnostic angiography and frequent hospital admissions. Despite the high prevalence of this diagnosis in patients undergoing coronary angiography, it is still a therapeutic challenge for cardiologists. Unlike obstructive coronary artery disease, with multiple evidence-based therapies and management guidelines, little is known regarding the management of MVA. During the last decade, many therapeutic interventions have been suggested for the treatment of MVA. However, there is a lack of summarization tab and update of current knowledge about pharmacologic management of MVA, mostly due to unclear pathophysiology. In this article, we have reviewed the underlying mechanisms of MVA and the outcomes of various medications in patients with this disease. Contrary to vasospastic angina in which normal angiogram is observed as well, nitrates are not effective in the treatment of MVA. Beta-blockers and calcium channel blockers have the strongest evidence of improving the symptoms. Moreover, the use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, statins, estrogen, and novel antianginal drugs has had promising outcomes. Investigations are still ongoing for vitamin D, omega-3, incretins, and n-acetyl cysteine, which have resulted in beneficial initial outcomes. We believe that the employment of the available results and results of the future large-scale trials into cardiac care guidelines would help reduce the global cost of cardiac care tremendously.

Novel roles of phentolamine in protecting axon myelination, muscle atrophy, and functional recovery following nerve injury

Incomplete functional recovery after peripheral nerve injury (PNI) often results in devastating physical disabilities in human patients. Despite improved progress in surgical and non-surgical approaches, achieving complete functional recovery following PNI remains a challenge. This study demonstrates that phentolamine may hold a significant promise in treating nerve injuries and denervation induced muscle atrophy following PNI. In a sciatic nerve crush injury mouse model, we found that phentolamine treatment enhanced motor and functional recovery, protected axon myelination, and attenuated injury-induced muscle atrophy in mice at 14 days post-injury (dpi) compared to saline treatment. In the soleus of phentolamine treated animals, we observed the downregulation of phosphorylated signal transducer and activator of transcription factor 3 (p-STAT3) as well as muscle atrophy-related genes Myogenin, muscle ring finger 1 (MuRF-1), and Forkhead box O proteins (FoxO1, FoxO3). Our results show that both nerve and muscle recovery are integral components of phentolamine treatment-induced global functional recovery in mice at 14 dpi. Moreover, phentolamine treatment improved locomotor functional recovery in the mice after spinal cord crush (SCC) injury. The fact that phentolamine is an FDA approved non-selective alpha-adrenergic blocker, clinically prescribed for oral anesthesia reversal, hypertension, and erectile dysfunction makes this drug a promising candidate for repurposing in restoring behavioral recovery following PNI and SCC injuries, axonal neuropathy, and muscle wasting disorders.

Pre-Operative Selective vs Non-Selective α-Blockade in Pheochromocytoma-Paraganglioma Patients Undergoing Surgery: A Meta-Analysis

The main objective of this systematic review and meta-analysis was to review, assess and report on the studies that have evaluated selective alpha blockade (SAB) vs. non-selective alpha blockade (NSAB) therapy in patients undergoing surgery for pheochromocytomas and paragangliomas (PPGL). We performed a systematic search of electronic databases. A meta-analysis was conducted to examine the effectiveness of the two blockades. RevMan 5.3 was used for the meta-analysis. Of the eight articles that met the inclusion criteria, there was only one randomized control trial. Meta-analysis showed that there was no significant difference between the groups SAB and NSAB with regard to intra-operative systolic blood pressure (SBP) >160 mm Hg (relative risk (RR) 0.95 [95% CI 0.57, 1.56] P = 0·83) and intra-operative vasopressor requirement (RR 1.10 [95% CI 0.96, 1.26] P = 0·16). Meta-analysis revealed that there was a significant difference between the groups (SAB vs NSAB) with respect to post-operative vasopressor requirement (RR 1.66 [95% CI 1.0, 2.74] P = 0·05). There was no significant difference between the groups with respect to post-operative complications (RR 0.84 [95% CI 0.58, 1.22] P = 0·36). In conclusion, as patients blocked selectively may have a higher incidence of vasodilator requirement intra-operatively, NSAB offers some haemodynamic advantage over SAB. However, NSAB's real clinical benefit cannot be ascertained with the current studies as this difference did not result in any significant advantage over SAB with regard to morbidity or mortality.

The sympathetic/beta-adrenergic pathway mediates irisin regulation of cardiac functions in zebrafish

Irisin is a 23 kDa myokine encoded in its precursor, fibronectin type III domain containing 5 (FNDC5). The exercise-induced increase in the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α) promotes FNDC5 mRNA, followed by the proteolytic cleavage of FNDC5 to release irisin from the skeletal or cardiac muscle into the blood. Irisin is abundantly expressed in skeletal and cardiac muscle and plays an important role in feeding, modulates appetite regulatory peptides, and regulates cardiovascular functions in zebrafish. In order to determine the potential mechanisms of acute irisin effects, in this research, we explored whether adrenergic or muscarinic pathways mediate the cardiovascular effects of irisin. Propranolol (100 ng/g B·W) alone modulated cardiac functions, and when injected in combination with irisin (0.1 ng/g B·W) attenuated the effects of irisin in regulating cardiovascular functions in zebrafish at 15 min post-injection. Atropine (100 ng/g B·W) modulated cardiovascular physiology in the absence of irisin, while it was ineffective in influencing irisin-induced effects on cardiovascular functions in zebrafish. At 1 h post-injection, irisin downregulated PGC-1 alpha mRNA, myostatin-a and myostatin-b mRNA expression in zebrafish heart and skeletal muscle. Propranolol alone had no effect on the expression of these mRNAs in zebrafish and did not alter the irisin-induced changes in expression. At 1 h post-injection, irisin siRNA downregulated PGC-1 alpha, troponin C and troponin T2D mRNA expression, while upregulating myostatin a and b mRNA expression in zebrafish heart and skeletal muscle. Atropine alone had no effects on mRNA expression, and was unable to alter effects on mRNA expression of siRNA. Overall, this research identified a role for the sympathetic/beta-adrenergic pathway in regulating irisin effects on cardiovascular physiology and cardiac gene expression in zebrafish.

Alpha-1 blocker use increased risk of subsequent renal cell carcinoma: A nationwide population-based study in Taiwan

Elevated Renal cell carcinoma (RCC) risk has been associated with the use of several antihypertensive medications but has not yet been elucidated in the populations prescribed alpha-1 blockers that are commonly used in the treatment of hypertension and lower urinary tract symptoms associated with benign prostatic hyperplasia (LUTS-BPH). The aim of the present study was to investigate the association between alpha-1 blocker use and the risk of developing RCC using a nationwide population-based database in Taiwan. Patients who were treated with alpha-1 blockers for at least 28 days were identified through the Taiwan National Health Insurance Research Database from 2000 to 2010. The unexposed participants were matched with the exposed cases according to age, sex, and index year at a ratio of 3:1. Cox proportional hazards regression, stratified by sex and comorbidities and adjusted for age, was performed to estimate hazard ratios (HRs) for the risk of subsequent RCC. Among 2,232,092 subjects, patients who received alpha-1 blocker treatment had a higher risk of RCC than the unexposed group. Taking into account hypertension and BPH, the adjusted HR was significantly higher in male alpha-1 blocker users who had no BPH and either the presence (HR: 1.63, 95% confidence interval [CI] = 1.22–2.18) or absence (HR: 2.31, 95% CI = 1.40–3.81) of hypertension than in men not receiving these drugs. Taken together, male alpha-1 blocker users who had no comorbidity of BPH exhibited an increased risk for developing RCC independent of hypertension. Further study is warranted to elucidate the underlying mechanisms of this association.

The effect of epinephrine on the perfusion index during ultrasound-guided supraclavicular brachial plexus block: a randomized controlled trial

The perfusion index (PI) is an objective tool used to assess a successful nerve block. Epinephrine is a widely used adjuvant to local anesthetics, and it may affect PI values because of the vasoconstrictive property. The aim of this study was to investigate the influence of epinephrine on PI as an indicator of a successful block in ultrasound-guided supraclavicular brachial plexus block (SCBPB). In this randomized controlled trial, 82 adult patients underwent upper limb surgery under SCBPB were recruited between July 2018 and March 2019 in a single tertiary care center. Participants were randomly assigned to one of two groups: non-epinephrine group (n = 41) or epinephrine group (5 mcg ml⁻¹, n = 41). The primary outcome was the comparison of the “PI ratio 10,” which was defined as the ratio of the PI 10 to the baseline. Receiver operating characteristic (ROC) curves were constructed to determine the accuracy of the PI in predicting the block success at each time interval. The PI ratio 10 was 2.7 (1.9–4.0) in non-epinephrine group and 3.3 (2.2–4.4) in epinephrine group (median difference: 0.4; 95% confidence interval [CI] − 1.1 to 0.2; P = 0.207). The ROC curves compared without group identification were not significantly different over time. The cut-off value for the PI and PI ratio at 5 min (PI ratio 5) were 7.7 (area under the ROC [AUROC]: 0.89, 95% CI 0.83–0.94) and 1.6 (AUROC: 0.94, 95% CI 0.90–0.98), respectively. The perineural epinephrine did not affect the PI following a SCBPB. The PI ratio 5 > 1.6 might be considered as a relatively accurate predictor of a successful SCBPB.

Trial registration: This study was registered at the Clinical Trial Registry of Korea (https://cris.nih.go.kr. CriS No. KCT0003006).

Synthesis, Molecular Modeling of Novel Substituted Pyridazinones and their Vasorelaxant Activities

BACKGROUND

Hypertension, one of the most common cardiovascular diseases that can cause coronary disease, stroke, myocardial infarction, and sudden death, it is the major contributor to cardiac failure as well as renal insufficiency.

OBJECTIVES

As there are many cardio-active pyridazinone-base derivatives in clinical use, therefore, we aimed to synthesize a new series of pyridazin-3-ones and evaluate their vasorelaxant activity.

METHODS

A new series of synthesized compounds were carried out first by the synthesis of 6- flouroarylpyridazinones by cyclization of 3-(4-flourobenzoyl) propionic acid with hydrazine hydrate or arylhydrazines to provide the corresponding pyridazinone derivatives 2a-d. Mannich reaction was performed using morpholine or piperidine formaldehyde to obtain compounds 3a,b. On the other hand, reaction of 2a with various chloroacetamide intermediates, in dimethylformamide and potassium carbonate as a catalyst, afforded the target compounds 5a-c. The aromatic acid hydrazide intermediates 6a-g were prepared in 50-90% yield, by reacting to the prepared esters with hydrazine hydrate under reflux in ethanol. The two compounds 8a,b were prepared via condensation of 7a,b with ethyl chloroacetate in dry acetone. Finally, the target 2,4,6-trisubstituted pyridazinones 9a-c derivatives were obtained by the reaction of 7a with the appropriate aromatic aldehyde or substituted acetophenones. The new compounds were then evaluated for their vasorelaxant properties using isolated thoracic rat aortic rings. In addition, a homology model was built and molecular modeling simulation of these compounds into the active sites of the newly created α1a-adrenoceptor model was performed in order to predict and rationalize their affinities toward this receptor.

RESULTS

Among these compounds; 5a was the most potent, it exhibited approximately two-times the activity of prazosin (IC50 = 0.250, 0.487 mmol, respectively) also, fourteen compounds were more potent than prazosin.

Oxygen in the Tumor Microenvironment: Mathematical and Numerical Modeling

There are many reasons to try to achieve a good grasp of the distribution of oxygen in the tumor microenvironment. The lack of oxygen - hypoxia - is a main actor in the evolution of tumors and in their growth and appears to be just as important in tumor invasion and metastasis. Mathematical models of the distribution of oxygen in tumors which are based on reaction-diffusion equations provide partial but qualitatively significant descriptions of the measured oxygen concentrations in the tumor microenvironment, especially when they incorporate important elements of the blood vessel network such as the blood vessel size and spatial distribution and the pulsation of local pressure due to blood circulation. Here, we review our mathematical and numerical approaches to the distribution of oxygen that yield insights both on the role of the distribution of blood vessel density and size and on the fluctuations of blood pressure.

Angiocrine signals regulate quiescence and therapy resistance in bone metastasis

Bone provides supportive microenvironments for hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) and is a frequent site of metastasis. While incidences of bone metastases increase with age, the properties of the bone marrow microenvironment that regulate dormancy and reactivation of disseminated tumor cells (DTCs) remain poorly understood. Here, we elucidate the age-associated changes in the bone secretome that trigger proliferation of HSCs, MSCs, and DTCs in the aging bone marrow microenvironment. Remarkably, a bone-specific mechanism involving expansion of pericytes and induction of quiescence-promoting secretome rendered this proliferative microenvironment resistant to radiation and chemotherapy. This bone-specific expansion of pericytes was triggered by an increase in PDGF signaling via remodeling of specialized type H blood vessels in response to therapy. The decline in bone marrow pericytes upon aging provides an explanation for loss of quiescence and expansion of cancer cells in the aged bone marrow microenvironment. Manipulation of blood flow — specifically, reduced blood flow — inhibited pericyte expansion, regulated endothelial PDGF-B expression, and rendered bone metastatic cancer cells susceptible to radiation and chemotherapy. Thus, our study provides a framework to recognize bone marrow vascular niches in age-associated increases in metastasis and to target angiocrine signals in therapeutic strategies to manage bone metastasis.

Radiation and chemotherapy induce bone-specific expansion of vascular niches, which promotes therapy resistance.

Anticancer activities of a β-amino alcohol ligand and nanoparticles of its copper(ii) and zinc(ii) complexes evaluated by experimental and theoretical methods

2-(2-(2-Hydroxyethylamino)ethylamino)cyclohexanol (HEAC) and copper and zinc complexes, [Cu(HEAC)Cl]Cl (1), [Cu(HEAC)Br]Br (2), [Zn(HEAC)Cl₂] (3), were prepared and identified by elemental analysis, FT-IR, UV-Vis, ¹H NMR spectroscopy and single-crystal X-ray diffraction. Also nanoparticles of 1–3 were prepared for anticancer studies by ultrasonic irradiation. Particle size and morphology of the nano particles are investigated by PXRD and SEM, respectively. X-ray analysis revealed that the ionic complexes 1 and 2 are isostructural. In the structure of complexes 1 and 2, the metal atom has a CuN₂O₂X (X: Cl (1), Br (2)) environment with square-pyramidal geometry, containing the tetradentate N₂O₂-donor HEAC. The bond length of the axial position in the square-pyramidal geometry of 1 and 2 is elongated. Complex 3 has a ZnN₂OCl₂ environment with trigonal bipyramidal geometry around the zinc atom in which the HEAC acts as mer-N₂O-donor. The ability of HEAC and nano particles 1–3 to interact with the nine biomacromolecules (BRAF kinase, CatB, DNA gyrase, HDAC7, rHA, RNR, TrxR, TS and Top II) are investigated by docking calculations. For examination of the docking results, the in vitro activities of four compounds against the human leukemia cell line K562 were investigated by evaluation of IC₅₀ values and mode of cell death (apoptosis). The thermodynamic stability of the compounds along with the charge distribution pattern were studied by DFT and NBO analysis, respectively.

Nano particles of copper and zinc complexes with an amino alcohol ligand were prepared under ultrasonic irradiation and their anticancer activates were investigated along with the docking studies and DFT calculations.

Pulsation-limited oxygen diffusion in the tumour microenvironment

Hypoxia is central to tumour evolution, growth, invasion and metastasis. Mathematical models of hypoxia based on reaction-diffusion equations provide seemingly incomplete descriptions as they fail to predict the measured oxygen concentrations in the tumour microenvironment. In an attempt to explain the discrepancies, we consider both the inhomogeneous distribution of oxygen-consuming cells in solid tumours and the dynamics of blood flow in the tumour microcirculation. We find that the low-frequency oscillations play an important role in the establishment of tumour hypoxia. The oscillations interact with consumption to inhibit oxygen diffusion in the microenvironment. This suggests that alpha-blockers-a class of drugs used to treat hypertension and stress disorders, and known to lower or even abolish low-frequency oscillations of arterial blood flow -may act as adjuvant drugs in the radiotherapy of solid tumours by enhancing the oxygen effect.

Hypertension in Patients with Cardiac Transplantation

Hypertension is a common complication among post cardiac transplant recipients affecting more than 95% of patients. Increased blood pressure poses a significant cardiovascular morbidity and mortality in these patients; it should be identified quickly and needs to be managed appropriately. Understanding the pathophysiology and contributing factors to this disease in these complex and unique patients is the key to appropriate treatment selection.

Metabolic effects of prazosin on skeletal muscle insulin resistance in glucocorticoid-treated male rats

High-dose glucocorticoids (GC) induce skeletal muscle atrophy, insulin resistance, and reduced muscle capillarization. Identification of treatments to prevent or reverse capillary rarefaction and metabolic deterioration caused by prolonged elevations in GCs would be therapeutically beneficial. Chronic administration of prazosin, an α₁-adrenergic antagonist, increases skeletal muscle capillarization in healthy rodents and, recently, in a rodent model of elevated GCs and hyperglycemia. The purpose of this study was to determine whether prazosin administration would improve glucose tolerance and insulin sensitivity, through prazosin-mediated sparing of capillary rarefaction, in this rodent model of increased GC exposure. Prazosin was provided in drinking water (50 mg/l) to GC-treated or control rats (400 mg implants of either corticosterone or a wax pellet) for 7 or 14 days (n = 5-14/group). Whole body measures of glucose metabolism were correlated with skeletal muscle capillarization (C:F) at 7 and 14 days in the four groups of rats. Individual C:F was found to be predictive of insulin sensitivity (r² = 0.4781), but not of glucose tolerance (r² = 0.1601) and compared with water only, prazosin treatment decreased insulin values during oral glucose challenge by approximately one-third in corticosterone (Cort)-treated animals. Cort treatment, regardless of duration, induced significant glycolytic skeletal muscle atrophy (P < 0.05), decreased IRS-1 protein content (P < 0.05), and caused elevations in FOXO1 protein expression (P < 0.05), which were unaffected with prazosin administration. In summary, it appears that α₁-adrenergic antagonism improves Cort-induced skeletal muscle vascular impairments and reduces insulin secretion during an oral glucose tolerance test, but is unable to improve the negative alterations directly affecting the myocyte, including muscle size and muscle signaling protein expression.

Blood flow controls bone vascular function and osteogenesis

While blood vessels play important roles in bone homeostasis and repair, fundamental aspects of vascular function in the skeletal system remain poorly understood. Here we show that the long bone vasculature generates a peculiar flow pattern, which is important for proper angiogenesis. Intravital imaging reveals that vessel growth in murine long bone involves the extension and anastomotic fusion of endothelial buds. Impaired blood flow leads to defective angiogenesis and osteogenesis, and downregulation of Notch signalling in endothelial cells. In aged mice, skeletal blood flow and endothelial Notch activity are also reduced leading to decreased angiogenesis and osteogenesis, which is reverted by genetic reactivation of Notch. Blood flow and angiogenesis in aged mice are also enhanced on administration of bisphosphonate, a class of drugs frequently used for the treatment of osteoporosis. We propose that blood flow and endothelial Notch signalling are key factors controlling ageing processes in the skeletal system.

Formation of new blood vessels and bone is coupled. Here the authors show that blood flow represents a key regulator of angiogenesis and endothelial Notch signalling in the bone, and that reactivation of Notch signalling in the endothelium of aged mice rejuvenates the bone.

Renal Denervation

Sympathetic nervous system over-activity is closely linked with elevation of systemic blood pressure. Both animal and human studies suggest renal sympathetic nerves play an important role in this respect. Historically, modulation of sympathetic activity has been used to treat hypertension. More recently, catheter based renal sympathetic denervation was introduced for the management of treatment resistant hypertension. Sound physiological principles and surgical precedent underpin renal denervation as a therapy for treatment of resistant hypertension. Encouraging results of early studies led to a widespread adoption of the procedure for management of this condition. Subsequently a sham controlled randomised controlled study failed to confirm the benefit of renal denervation leading to a halt in its use in most countries in the world. However, critical analysis of the sham-controlled study indicates a number of flaws. A number of lessons have been learnt from this and other studies which need to be applied in future trials to ascertain the actual role of renal denervation in the management of treatment resistant hypertension before further implementation. This chapter deals with all these issues in detail.

The Specific α1-Adrenergic Receptor Antagonist Prazosin Influences the Urine Proteome

Urine, reflecting many changes in the body, is a better source than blood for biomarker discovery. However, even under physiological conditions, the urine proteome often varies. Understanding how various regulating factors affect urine proteome helps link changes to urine proteome with urinary biomarkers of physiological conditions as well as corresponding diseases. To evaluate the possible impact of α1-adrenergic receptor on urine proteome, this study investigated effects of the specific inhibitor prazosin on the urine proteome in a rat model by using tandem mass tagging and two-dimensional liquid chromatography-tandem mass spectrometry. A total of 775 proteins were identified, approximately half of which were influenced by prazosin treatment, indicating that the sympathetic nervous system exerts a significant impact on urine proteome. Eight significantly changed proteins were previously annotated as urinary candidate biomarkers. Angiotensinogen, haptoglobin, and beta-2 microglobulin, which were reported to be associated with blood pressure, were validated via Western blot. Prazosin is widely used in clinical practice; thus, these protein changes should be considered when studying corresponding diseases such as hypertension, post-traumatic stress disorder and benign prostatic hyperplasia. The related physiological activities of α1-receptors, controlling blood pressure and fear response might significantly affect the urine proteome and warrant further biomarker studies.

Pharmacologic Treatment of Pediatric Hypertension

Prevalence of hypertension is increasing in children and adolescents. Uncontrolled hypertension in children not only causes end organ damage but also increases the risk of adult hypertension and cardiovascular disease. Clinical trials have proven efficacy of antihypertensive medications in children. These medications are well tolerated by children with acceptable safety profile. The choice of agent is usually driven by underlying etiology of hypertension, profile of its side effects, and clinician's preference. This article will review currently available pediatric data on mechanism of action, common adverse effects, pediatric indication, recent clinical trial, and newer drugs in the common classes of antihypertensive medications.

The role of the kidney and the sympathetic nervous system in hypertension

Nearly one-third of the world's population has hypertension. The human and societal impact of hypertension is enormous. Primary hypertension accounts for 95 % of cases of hypertension in adults. The pathogenesis of primary hypertension is complex. The kidney and the sympathetic nervous system play important roles in the development and maintenance of hypertension. This review discusses their respective roles, the interaction between the two, implications of sympathetic overactivity in kidney disease and therapeutic interventions that have been developed on the basis of this knowledge, especially modulation of the sympathetic nervous system.

Treatment of benign prostatic hyperplasia with Croton membranaceus in an experimental animal model

ETHNOPHARMACOLOGICAL RELEVANCE

Croton membranaceus leaf extracts are used in the Bahamas to aromatize tobacco. In Nigeria it is used to improve digestion and in Ghana, the root extract is used for the treatment of benign prostatic hyperplasia (BPH). Despite claims of efficacy no data exists to support this. The aim of this study was to determine if Croton membranaceus aqueous root extract (CMARE) could attenuate the development of BPH in an animal model.

MATERIALS AND METHODS

Fifty (50) adult male Sprague-Dawley rats weighing 200-250g were randomly divided into 5 groups. Group 1 served as the control and received normal saline p.o. Groups 2-5 were castrated and injected with 5mg/kg b.wt. testosterone propionate subcutaneously for 28 days. Group 2 (model group) had no further treatment. Group 3 was simultaneously given 0.5mg/kg b.wt. finasteride p.o. throughout. Groups 4 and 5 received 30mg/kg b.wt. [low dose (LD)] and 300mg/kg b.wt. [high dose (HD)] CMARE, respectively, for 28 days. Rats were sacrificed at the end of the study and all prostate organs harvested. Wet weights, volumes and prostatic index (PI) were determined. Tissues were histologically examined. Serum prostate specific antigen (PSA) and dihydrotestosterone (DHT) levels were determined.

RESULTS

Prostate volume of the control group was 0.67±0.23cm(3). The model, finasteride, CMARE LD and HD groups had the following volumes: 0.92±0.12, 0.84±0.16, 0.79±0.16 and 0.80±0.19cm(3), respectively. Only the model group showed significant statistical differences with the control (p=0.007). PI for control, model, finasteride, LD and HD groups was as follows: 0.19±0.04, 0.30±0.04, 0.25±0.04, 0.21±0.05 and 0.22±0.05. No statistical differences between the control PI and the CMARE treated groups were observed. Histologically, the model group had massive growth of columnar stromal and epithelial cells. CMARE and finasteride attenuated this growth with a resultant thin layer of stromal and epithelial cells similar to the control. PSA levels were significantly lower in the treatment groups.

CONCLUSION

CMARE reduces stromal and epithelial cell growth, and subsequently shrinks enlarged prostate. This is the first scientific proof validating the anecdotal evidence of CMARE efficacy in the management of BPH.

Synthesis, antimicrobial and molecular docking studies of enantiomerically pure N-alkylated β-amino alcohols from phenylpropanolamines

Enantiomerically pure N-alkylated β-amino alcohols 1a, 1a', 1c, 1c', 1d, 1d', 1e and 1e', with ee 100% have been synthesized from phenylpropanolamines 2. Effect of the neighboring chiral environment on the newly formed chiral center has been studied experimentally and concluded that the newly formed chiral center's absolute configuration is opposite to the adjacent (α- or β-) chiral environment. The antimicrobial activity of the synthesized β-amino alcohols were screened using in vitro disc diffusion method and variable antimicrobial activities were shown for 1a, 1a', 1c, 1c', 1d, 1d', 1e &1e' and amongst them 1d &1d' exhibited significant activity against bacteria and fungi. In silico studies revealed all the synthesized β-amino alcohols 1a-e and 1a'-e' have shown good binding energies ranging from -7.38 to -6.09 kJ/mol towards the target receptor DNA topoisomerase IV and 1d' has shown maximum binding energy -7.38 kJ/mol.

Tamsulosin treatment for benign prostatic hyperplasia and risk of severe hypotension in men aged 40-85 years in the United States: risk window analyses using between and within patient methodology

OBJECTIVE

To characterize risk of hypotension requiring admission to hospital in middle aged and older men treated with tamsulosin for benign prostatic hyperplasia.

DESIGN

Population based retrospective cohort study (between patient methodology) and self controlled case series (within patient methodology).

SETTING

Healthcare claims data from the IMS Lifelink database in the United States.

PARTICIPANTS

Men aged 40-85 years with private US healthcare insurance entering the cohort at their first dispensing for tamsulosin or for a 5α reductase inhibitor (5ARI) between January 2001 and June 2011 after a minimum of six months' enrolment.

MAIN OUTCOMES MEASURES

Hypotension requiring admission to hospital. Cox proportional hazards models estimated rate ratios at time varying intervals during follow-up: weeks 1-4, 5-8, and 9-12 after tamsulosin initiation; weeks 1-4, 5-8, and 9-12 after restarting tamsulosin (after a four week gap); and maintenance tamsulosin treatment (remaining exposed person time). Covariates included age, calendar year, demographics, antihypertensive use, healthcare use, and a Charlson comorbidity score. A self controlled case series, having implicit control for time invariant covariates, was additionally conducted.

RESULTS

Among 383,567 new users of study drugs (tamsulosin 297,596; 5ARI 85,971), 2562 admissions to hospital for severe hypotension were identified. The incidence for hypotension was higher for tamsulosin (42.4 events per 10,000 person years) than for 5ARIs (31.3 events per 10,000 person years) or all accrued person time (29.1 events per 10,000 person years). After tamsulosin initiation, the cohort analysis identified an increased rate of hypotension during weeks 1-4 (rate ratio 2.12 (95% confidence interval 1.29 to 3.04)) and 5-8 (1.51 (1.04 to 2.18)), and no significant increase at weeks 9-12. The rate ratio for hypotension also increased at weeks 1-4 (1.84 (1.46 to 2.33)) and 5-8 (1.85 (1.45 to 2.36)) after restarting tamsulosin, as did maintenance tamsulosin treatment (1.19 (1.07 to 1.32)). The self controlled case series gave similar results as the cohort analysis.

CONCLUSIONS

We observed a temporal association between tamsulosin use for benign prostatic hyperplasia and severe hypotension during the first eight weeks after initiating treatment and the first eight weeks after restarting treatment. This association suggests that physicians should focus on improving counseling strategies to warn patients regarding the "first dose phenomenon" with tamsulosin.

Dysregulation of the autonomic nervous system predicts the development of the metabolic syndrome

CONTEXT

Stress is suggested to lead to metabolic dysregulations as clustered in the metabolic syndrome. Although dysregulation of the autonomic nervous system is found to associate with the metabolic syndrome and its dysregulations, no longitudinal study has been performed to date to examine the predictive value of this stress system in the development of the metabolic syndrome.

OBJECTIVE

We examined whether autonomic nervous system functioning predicts 2-year development of metabolic abnormalities that constitute the metabolic syndrome.

DESIGN

Data of the baseline and 2-year follow-up assessment of a prospective cohort: the Netherlands Study of Depression and Anxiety was used.

SETTING

Participants were recruited in the general community, primary care, and specialized mental health care organizations.

PARTICIPANTS

A group of 1933 participants aged 18-65 years.

MAIN OUTCOME MEASURES

The autonomic nervous system measures included heart rate (HR), respiratory sinus arrhythmia (RSA; high RSA reflecting high parasympathetic activity), pre-ejection period (PEP; high PEP reflecting low sympathetic activity), cardiac autonomic balance (CAB), and cardiac autonomic regulation (CAR). Metabolic syndrome was based on the updated Adult Treatment Panel III criteria and included high waist circumference, serum triglycerides, blood pressure, serum glucose, and low high-density lipoprotein (HDL) cholesterol.

RESULTS

Baseline short PEP, low CAB, high HR, and CAR were predictors of an increase in the number of components of the metabolic syndrome during follow-up. High HR and low CAB were predictors of a 2-year decrease in HDL cholesterol, and 2-year increase in diastolic and systolic blood pressure. Short PEP and high CAR also predicted a 2-year increase in systolic blood pressure, and short PEP additionally predicted 2-year increase in diastolic blood pressure. Finally, a low baseline RSA was predictive for subsequent decreases in HDL cholesterol.

CONCLUSION

Increased sympathetic activity predicts an increase in metabolic abnormalities over time. These findings suggest that a dysregulation of the autonomic nervous system is an important predictor of cardiovascular diseases and diabetes through dysregulating lipid metabolism and blood pressure over time.

Role of brainstem thyrotropin-releasing hormone-triggered sympathetic overactivation in cardiovascular mortality in type 2 diabetic Goto-Kakizaki rats

Sympathetic hyperactivity has an important role in cardiovascular mortality in patients with type 2 diabetes (T2D). Thyrotropin-releasing hormone (TRH)-containing fibers innervate autonomic motor and premotor nuclei of the brainstem and spinal cord that regulate cardiovascular functions. We compared cardiovascular responses to application of TRH-analog in the brainstem of Wistar and T2D Goto-Kakizaki (GK) rats. GK rats exhibited basal systolic hypertension (152±2 mm Hg) and had a significantly potentiated, dose-related hypertensive response to intracisternal (i.c.) injection of the TRH-analog RX77368 (10-60 ng). In GK rats only, i.c. RX77368 (30-60 ng) markedly increased heart rate (HR; +88 b.p.m.) and induced acute cardiac mortality (100%), concurrent with extreme hyperglycemia (>26 mmol l(-1)), increased plasma H(2)O(2) and 8-isoprostane, and enhanced heart expression of NADPH oxidase 4 and vascular cell adhesion molecule-1 mRNAs. GK rats also had elevated basal plasma epinephrine, higher adrenal gene expression of tyrosine hydroxylase and dopamine β-hydroxylase (DβH), and greater plasma catecholamine and adrenal DβH responses to i.c. TRH-analog, compared with Wistar rats. In GK rats, hexamethonium blocked i.c. RX77368-induced hypertensive and tachycardic responses, and reduced mortality by 86%, whereas phentolamine abolished the hypertensive response but enhanced tachycardia (+160 b.p.m.), and reduced mortality by 50%. The angiotensin II type 1 receptor antagonist irbesartan prevented i.c. RX77368-induced increases in blood pressure, HR and mortality. In conclusion, sympathetic overactivation triggered by brainstem TRH contributes to the mechanism of cardiovascular morbidity and mortality in T2D, which involves heightened cardiac inflammation and peripheral oxidative stress responses to sympathetic drive, and a mediating role of the renin-angiotensin system.

Hypertension in kidney transplant recipients

Arterial hypertension is frequently observed in renal transplant recipients. Its pathogenesis is multifactorial in most cases. Calcineurin inhibitors (CNI) can increase peripheral vascular resistance by inducing arteriolar vasoconstriction and can cause extracellular fluid expansion by reducing the glomerular filtration rate (GFR), activating the renin-angiotensin system (RAS), and by inactivating the atrial natriuretic peptide. Glucocorticoids can impair urinary water and salt excretion. Poor graft function can lead to increased extracellular volume and inappropriate production of renin. Native kidneys, older age of the donor and transplant renal artery stenosis (TRAS) may also contribute to the development of hypertension. Arterial hypertension not only can increases the risk for cardiovascular events but can also deteriorate renal allograft function. A number of studies have shown that the higher the levels of blood pressure are, the higher is the risk of graft failure. On the other hand, a good control of blood pressure may prevent many cardiovascular and renal complications. Appropriate lifestyle modification is the first step for treating hypertension. Calcium channel blockers (CCB) and renin-angiotensin system (RAS) inhibitors are the most frequently used antihypertensive agents, but in many cases, a combination of these and other drugs is required to obtain good control of hypertension.

Sympathetic neural adaptation to hypocaloric diet with or without exercise training in obese metabolic syndrome subjects

OBJECTIVE

Sympathetic nervous system (SNS) overactivity contributes to the pathogenesis and target organ complications of obesity. This study was conducted to examine the effects of lifestyle interventions (weight loss alone or together with exercise) on SNS function.

RESEARCH DESIGN AND METHODS

Untreated men and women (mean age 55 +/- 1 year; BMI 32.3 +/- 0.5 kg/m(2)) who fulfilled Adult Treatment Panel III metabolic syndrome criteria were randomly allocated to either dietary weight loss (WL, n = 20), dietary weight loss and moderate-intensity aerobic exercise (WL+EX, n = 20), or no treatment (control, n = 19). Whole-body norepinephrine kinetics, muscle sympathetic nerve activity by microneurography, baroreflex sensitivity, fitness (maximal oxygen consumption), metabolic, and anthropometric measurements were made at baseline and 12 weeks.

RESULTS

Body weight decreased by -7.1 +/- 0.6 and -8.4 +/- 1.0 kg in the WL and WL+EX groups, respectively (both P < 0.001). Fitness increased by 19 +/- 4% (P < 0.001) in the WL+EX group only. Resting SNS activity decreased similarly in the WL and WL+EX groups: norepinephrine spillover by -96 +/- 30 and -101 +/- 34 ng/min (both P < 0.01) and muscle sympathetic nerve activity by -12 +/- 6 and -19 +/- 4 bursts/100 heart beats, respectively (both P < 0.01), but remained unchanged in control subjects. Blood pressure, baroreflex sensitivity, and metabolic parameters improved significantly and similarly in the two lifestyle intervention groups.

CONCLUSIONS

The addition of moderate-intensity aerobic exercise training to a weight loss program does not confer additional benefits on resting SNS activity. This suggests that weight loss is the prime mover in sympathetic neural adaptation to a hypocaloric diet.

Effect of alpha1-adrenergic receptors in cardiac pathophysiology

Compelling evidence now exists that proves adrenergic blockade is at the center of neurohormonal antagonism in heart failure (HF). Catecholamines are well known to act through both beta- and alpha-adrenergic receptors (ARs), which mediate their effects through distinct receptor pathways. Beta-AR blockers are commonly used in the treatment of HF and have distinct receptor affinity profiles. The recent COMET trial comparing 2 important beta-blocking drugs showed a distinct advantage for carvedilol in decreasing the risk of mortality from HF. The mechanism of action for carvedilol differs from metoprolol tartrate in its ability to block both alpha- and beta-ARs, leading to renewed interest in the potential role of alpha-ARs in the progression of HF. In contrast, however, the ALLHAT study discontinued use of doxazosin, an alpha1-receptor blocker because of an increase in cardiovascular events among patients using this drug. The results of these studies appear to be in contrast with respect to the role of alpha-ARs in regards to cardiovascular pathophysiology. Further study of the alpha-receptor and understanding the role of alpha-ARs in HF is necessary to understand the therapeutic effect of alpha-blockade. This article reviews our understanding of the alpha-AR in HF.

Doxazosin, an alpha-1 antagonist, prevents further progression of the advanced atherosclerotic lesion in hypercholesterolemic hamsters

The aim of this study was to examine the effect of doxazosin (DOX) on the further progression and regression of the advanced atherosclerotic lesion in the hypercholesterolemic hamster. Thirty-six, male F(1)B Golden Syrian hamsters, 10 weeks of age, were divided into 3 groups of 12 and fed a nonpurified hypercholesterolemic diet (HCD) containing 10% coconut oil and 0.1% cholesterol (wt/wt) for 9 months (HCD 9). One group of hamsters was euthanized at 9 months and their aortas were collected, fixed, and stored until analysis. The remaining hamsters were either maintained on the HCD for an additional 6 months (HCD 15) or fed the HCD plus 20 mg/kg/d DOX for the 6 months. At the end of the study (15 months), the DOX-treated hamsters had significantly lower plasma total cholesterol (TC) (-68%), low-density lipoprotein-cholesterol (LDL-C) (-73%), and triglycerides (TG) (-74%) compared with the HCD 15. The lumenal narrowing and intimal thickening atherosclerotic lesions were significantly less in the DOX-treated hamsters compared with the HCD 15 (-66% and -70%, respectively). These data suggest that DOX treatment prevents further progression of the advanced atherosclerotic lesion possibly by lowering plasma TC, LDL-C, and TG in hypercholesterolemic hamsters.

Reduction of the soluble cyclic GMP vasorelaxing system in the vascular wall of stroke-prone spontaneously hypertensive rats: effect of the alpha1 -receptor blocker doxazosin

OBJECTIVE

The aim of the present study was to analyse the nitric oxide (NO)/cyclic GMP (cGMP) relaxing system in spontaneously hypertensive rats of the stroke-prone substrain (SHRSP).

DESIGN

The study was performed in 20-week-old SHRSP rats. A group of normotensive Wistar-Kyoto (WKY) rats was used as control.

RESULTS

The endothelium-dependent relaxation to acetylcholine was reduced in SHRSP rats (n = 15). No modifications in the expression of the endothelial nitric oxide synthase were found in the vascular wall of WKY rats (n = 15) and SHRSP rats. SHRSP rats demonstrated an impaired relaxing response to the NO-donor sodium nitroprusside that was accompanied by a reduction in the level of the main second messenger of NO, cyclic GMP. The expression of the soluble guanylate cyclase (sGC) beta1-subunit was markedly reduced in the vascular wall of SHRSP rats. In the experimental model of SHRSP, an increased concentration of catecholamines has been reported. Therefore, we evaluated the effect of an alpha1-receptor blocker, doxazosin, on the NO/cGMP system. Doxazosin [10 mg/kg body weight (bw) per day for 15 days, n = 15] reduced mean arterial pressure (MAP) in SHRSP rats. Treatment with doxazosin preserved the endothelium-independent relaxation response to sodium nitroprusside in aortic segments from SHRSP rats which was associated with an increased expression of the sGC beta1-subunit. A dose of doxazosin (1 mg/kg bw per day, n = 15) that did not modify MAP partially prevented sGC protein expression in the vascular wall.

CONCLUSIONS

Independently of the endothelial NO-generating system, impaired vasorelaxation could also result from vascular smooth muscle cell layer dysfunction. Doxazosin treatment improved the endothelial-independent relaxation and preserved the cGMP generating system in the vascular wall of SHRSP rats.

Alpha-adrenergic receptors regulate human lymphocyte amiloride-sensitive sodium channels

Two independent signal transduction pathways regulate lymphocyte amiloride-sensitive sodium channels (ASSCs), one utilizing cAMP as a second messenger and the other utilizing a GTP-binding protein. This implies that two plasma membrane receptors play a role in the regulation of lymphocyte ASSCs. In this study, we tested the hypothesis that alpha1- and alpha2-adrenergic receptors independently regulate lymphocyte ASSCs via the two previously identified second messengers. Direct measurements indicated that norepinephrine increased lymphocyte cAMP and activated ASSCs. The alpha2-specific inhibitor, yohimbine, blocked this activation, thereby linking alpha2-adrenergic receptors to ASSC regulation via cAMP. The alpha1-specific ligand, terazosin, acted as an agonist and activated lymphocyte ASSCs but inhibited ASSC current that had been preactivated by norepinephrine or 8-(4-chlorophenylthio) (CPT)-cAMP. Terazosin had no effect on the lymphocyte whole cell ASSC currents preactivated by treatment with pertussis toxin. This finding indirectly links alpha1-adrenergic receptors to lymphocyte ASSC regulation via GTP-binding proteins. Terazosin had no direct inhibitory or stimulatory effects on alpha,beta,gamma-endothelial sodium channels reconstituted into planar lipid bilayers and expressed in Xenopus oocytes, ruling out a direct interaction between terazosin and the channels. These findings support the hypothesis that both alpha1- and alpha2-adrenergic receptors independently regulate lymphocyte ASSCs via GTP-binding proteins and cAMP, respectively.

Effects of doxazosin on functional alterations of isolated coronary arteries from cholesterol-fed rabbits

Anti-hypertensive treatment is much less successful at reducing coronary artery disease than at reducing mortality from stroke and congestive heart failure. The effects of the alpha-adrenergic antagonist doxazosin on progression of atheromatous lesions and functional responses of isolated coronary arteries from cholesterol-fed rabbits have been investigated. Normotensive rabbits were fed either a standard chow (control, n = 8) or a 1% cholesterol-rich diet (n = 16) for 20 weeks. After 3 weeks the cholesterol-fed animals were assigned randomly to two groups either given placebo capsules (n = 8) or treated with doxazosin (5 mg kg-1 day-1; n = 8). Doxazosin reduced the mean arterial blood pressure by 10% that of the control and placebo-treated cholesterol-fed rabbits, but did not affect the plasma cholesterol, triacylglycerol and phospholipid levels, which were, after 20 weeks, severalfold increased in the cholesterol-fed rabbits compared with controls. Histological examination showed atheromatous lesions in proximal (but not distal) coronary arteries from both groups of cholesterol-fed rabbits. Doxazosin either had no effect on reduced contractions to 125 mmol L-1 potassium saline solution or increased contractions to 5-hydroxytryptamine in proximal isolated coronary arteries from the cholesterol-fed rabbits. It did, however, abolish the hyper-responsiveness of the large atheromatous coronary arteries to noradrenaline. In both vehicle-and doxazosin-treated cholesterol-fed rabbits the maximum relaxation and sensitivity to acetylcholine were significantly reduced in proximal segments compared with the control group, whereas responses to acetylcholine in distal coronary segments were not significantly different. The relaxation to sodium nitroprusside, adenosine diphosphate and isoprenaline in proximal and distal coronary arteries were similar in the three experimental groups. These results indicate that treatment of normotensive cholesterol-fed rabbits with doxazosin prevents the hyper-responsiveness to noradrenaline of proximal coronary arteries, although it does not prevent the progression of other functional alterations observed in the coronary circulation.

Effects of doxazosin, an alpha 1-adrenergic inhibitor, on plasma lipid and lipoprotein levels, low density lipoprotein metabolism and cholesterol absorption in cynomolgus monkeys

The mechanism(s) by which doxazosin, an alpha 1 inhibitor, regulates plasma low density lipoprotein cholesterol (LDL-C) and apolipoprotein B (apo B) levels were investigated in 'normocholesterolemic' (average total cholesterol (TC) of 218 mg/dl) and 'hypercholesterolemic' (average TC of 350 mg/dl) cynomolgus monkeys. Twelve weeks of doxazosin treatment (1 mg/kg per day) significantly reduced plasma TC and LDL-C levels in both groups while high density lipoprotein cholesterol and apolipoprotein A-I concentrations rose. Despite these changes in plasma lipids, LDL and HDL lipid composition was not affected by doxazosin. The reduction in LDL-C and apo B in the doxazosin-treated 'hypercholesterolemic' group was associated with a significant increase in both receptor-dependent and -independent LDL apo B fractional catabolic rates. Similar associations were noted in the 'normocholesterolemic' group. LDL apo B production or transport rate was not affected by doxazosin. Cholesterol absorption was also significantly reduced by doxazosin which may also contribute to lowering plasma LDL-C levels. These studies suggest that doxazosin treatment can produce beneficial changes in the plasma lipid profile over a wide rage of plasma cholesterol levels by up-regulating LDL fractional clearance.