β-Blockers in the Treatment of Hypertension: Are There Clinically Relevant Differences?

Beta-blocker efficacy for intra- and interdialytic hypertension patients: a systematic review and meta-analysis

PURPOSE

Intradialytic hypertension affects 5-15% of hemodialysis patients, yet relevant studies are relatively scarce. It is also associated with higher interdialytic blood pressure. Beta-blockers can be preferred as antihypertensive drugs due to their superior blood pressure control, decreased risk of cardiovascular events, improved endothelial cell function, and decreased noradrenaline levels. Through this study, beta-blocker antihypertensive effects in intra- and interdialytic hypertension were analyzed.

METHODS

Systematic review and meta-analysis were performed following PRISMA guidelines. We registered our PROSPERO protocol (Registration ID: CRD42023446184) and included relevant full-text clinical trials or RCTs from 2008 to 2023 with predetermined keywords and criteria from multiple databases including PUBMED, COCHRANE, SCOPUS, and citation searching. Seven eligible articles were included in this review study.

RESULTS

Four studies with 82 participants for intradialytic hypertension evaluation were included. Meta-analysis showed a decrease in SBP in intradialytic hypertensive patients after beta-blocker intervention, with a significant estimated mean difference of - 15.19 mmHg (P < 0.00001; 95% CI - 19.47 to - 10.91). Supporting previous data, SBP remains constant between pre- and post-dialysis with beta-blocker therapy, with an insignificant estimated mean difference of - 2.72 mmHg (P = 0.29; 95% CI - 7.80 to 2.36). Whereas five studies with 142 participants were included for interdialytic hypertension evaluation. Meta-analysis shows a significant decrease in SBP before to after therapy, with an estimated mean difference of - 10.92 (P < 0.0001; 95% CI - 16.33 to - 5.51).

CONCLUSION

Beta-blocker treatment resulted in significant reductions in post-hemodialysis systolic blood pressure among intra- and interdialytic hypertensive patients.

Therapeutic Options for Migraines in the Microsurgical Patient: A Scoping Review

BACKGROUND

There exists an increasing array of treatments proposed to prevent, alleviate, and abort symptoms of a migraine; however, for patients who undergo reconstructive microsurgery, caution must be taken to preserve vascular integrity. This study is the first-to-date scoping review of vascular and bleeding risk of current migraine therapies, with the purpose of identifying potential therapeutic agents for postoperative migraine management appropriate for microsurgical patients.

METHODS

Currently available migraine therapeutics were compiled from the UpToDate software system and the American Academy of Family Physicians. A PubMed literature review was performed for each therapeutic's effect on bleeding or vascular involvement. Data were compiled into tables of abortive, symptom-controlling and prophylactic, and nonpharmacologic treatments. Expert microsurgeons reviewed the data to provide recommendations for optimized patient care.

RESULTS

Triptans and other ergot derivatives demonstrated strong evidence of vasoconstriction and were greatly advised against for immediate postmicrosurgical use. Novel pharmaceutical therapies such as lasmiditan and calcitonin gene-related peptide antagonists have no literature indicating potential for vasoconstriction or hematoma and remain an investigational option for abortive medical treatment. For symptom control, acetaminophen appears the safest option, with clinical judgment and further research needed for use of nonsteroidal antiinflammatory drugs. Alternative treatment techniques may include migraine prophylaxis with botulinum toxin injection or nutraceutical treatment by means of magnesium supplementation or coenzyme Q10 administration, minimizing the need for additional medication in the postoperative setting.

CONCLUSIONS

Patients undergoing reconstructive microsurgery have a unique medical profile limiting the therapeutic options available to treat migraines. This review provides preliminary evidence to be considered as a guide for prescribing therapeutics for migraine in the postoperative setting.

Cardioprotective effects of Talinum paniculatum (Jacq.) Gaertn. in doxorubicin-induced cardiotoxicity in hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

Talinum paniculatum (Jacq.) Gaertn. (Talinaceae) is a medicinal species that is widely distributed throughout Brazil. Popularly known as "major-gomes," the species is used in folk medicine for the treatment of cardiovascular disorders.

AIM OF THE STUDY

To evaluate the effect of an ethanolic extract of T. paniculatum (EETP) in rats with renovascular hypertension and heart failure and determine its chemical composition.

MATERIALS AND METHODS

First, EETP was obtained, and its chemical profile was analyzed by LC-DAD-MS. The acute toxicity was evaluated in female Wistar rats. The model of renovascular hypertension was established in male Wistar rats by combining the Goldblatt 2K1C method and intraperitoneal doxorubicin administration for 6 weeks. The animals were then treated daily with EETP (30, 100, and 300 mg/kg) or metoprolol (25 mg/kg) by gavage for 28 days. The negative control group was treated with vehicle (filtered water). The sham group consisted of animals that were not subjected to 2K1C or cardiotoxicity and were treated with vehicle. Renal function was evaluated on days 1, 14, and 28. At the end of treatment, the electrocardiographic profile, blood pressure, and mesenteric vascular reactivity were investigated. Serum urea, creatinine, angiotensin converting enzyme, nitrotyrosine, malondialdehyde, nitrite, aldosterone, and sodium and potassium levels were measured. The heart, aorta artery, liver, and right kidney were collected, weighed, and processed for histopathological analysis. Cardiac chambers also underwent morphometric analysis.

RESULTS

No signs of toxicity were observed in female Wistar rats. Thirty-two compounds were annotated from EETP, including flavonoids, chlorogenic acids, and saponins. EETP treatment resulted in a significant cardiorenal-protective response, normalizing electrocardiographic and hemodynamic alterations, and preventing ventricle remodeling. These effects were associated with serum antioxidant activity and angiotensin-converting enzyme (ACE) inhibition.

CONCLUSION

The present study demonstrated that EETP may exert cardioprotective effects through serum antioxidant activity and ACE inhibition, preventing alterations of hemodynamic and endothelial function, and reducing damage to cardiac structure. Thus, EETP, especially at the 100 and 300 mg/kg doses, may be useful for preventing doxorubicin-induced cardiotoxicity in hypertensive patients.

Comparative cardioprotective effects of carvedilol versus atenolol in a rat model of cardiorenal syndrome type 4

The incidence of chronic kidney disease is escalating; cardiorenal syndrome (CRS) type 4 is gaining a major health concern causing significant morbidity and mortality, putting major burdens on the healthcare system. This study was designed to compare the cardioprotective effects of carvedilol versus atenolol against CRS type 4 induced by subtotal 5/6 nephrectomy in rats and to explore the underlying mechanisms. Immediately after surgery, carvedilol (20 mg/kg/day) or atenolol (20 mg/kg/day) was added to drinking water for 10 weeks. Carvedilol was more effective than atenolol in improving kidney functions, decreasing elevated blood pressures, attenuating cardiac hypertrophy, reducing serum brain natriuretic peptide, and diminished cardiac fibrous tissue deposition. However, carvedilol was equivalent to atenolol in modulating β1-adrenergic receptors (β1ARs) and cardiac diacylglycerol (DAG) signaling, but carvedilol was superior in modulating β-arrestin2, phosphatidyl inositol 4,5 bisphosphates (PIP2), and caspase 3 levels. Carvedilol has superior cardioprotective effects than atenolol in a rat model of CRS type 4. These protective effects are mediated through modulating cardiac β1ARs/β-arrestin2/PIP2/DAG as well as abating cardiac apoptotic signaling pathways (caspase3/pS473 protein kinase B (Akt)).

Beta-Blockers Use and Risk of Breast Cancer in Women with Hypertension

BACKGROUND

The risk of breast cancer among hypertensive patients who use beta-blockers has attracted attention. However, the evidence is inconsistent and investigation of the dose-specific associations for subtypes of beta-blockers is limited.

METHODS

By incorporating Swedish national registers, breast cancer risk was estimated in women with hypertension who used nonselective beta-blockers and beta-1 selective blockers compared with propensity score-matched nonusers. The cumulative defined daily dose was used to study the dose-response association. Test of interaction between beta-blocker use and other antihypertensive medications was performed.

RESULTS

Hypertensive patients taking beta-1 selective blockers (metoprolol, atenolol, bisoprolol) had an increased risk of breast cancer with a HR and 95% confidence interval (CI) of 2.39 (1.95-2.94), 2.31 (1.46-3.64), and 3.02 (2.09-4.36), respectively. All of the observed associations were dose-dependent (P _trend < 0.0001). No significant association was found for the nonselective beta-blocker (propranolol) except that among users of agents acting on the renin-angiotensin system, those who used propranolol had increased breast cancer risk. Modification of agents acting on the renin-angiotensin system on breast cancer risk was also observed for atenolol.

CONCLUSIONS

The increased risk of breast cancer associates with the use of beta-1 selective blockers in a dose-response manner.

IMPACT

Breast cancer surveillance is recommended for hypertensive female patients using beta-1 selective blockers.

Effects of Propranolol on Growth, Lipids and Energy Metabolism and Oxidative Stress Response of Phaeodactylum tricornutum

Simple Summary

In the past two decades, increasing attention has been directed to investigate the incidence and consequences of pharmaceuticals in the aquatic environment. Propranolol is a non-selective β-adrenoceptor blocker used in large quantities worldwide to treat cardiovascular conditions. Diatoms (model organism) exposed to this compound showed evident signs of oxidative stress, a significant reduction of the autotrophic O₂ production and an increase in the heterotrophic mitochondrial respiration. Additionally, diatoms exposed to propranolol showed a consumption of its storage lipids. In ecological terms this will have cascading impacts in the marine trophic webs, where these organisms are key elements, through a reduction of the water column oxygenation and essential fatty acid availability to the heterotrophic organisms that depend on these primary producers. In ecotoxicological terms, diatoms photochemical and fatty acid traits showed to be potential good biomarkers for toxicity assessment of diatoms exposed to this widespread pharmaceutical compound.

Abstract

Present demographic trends suggest a rise in the contributions of human pharmaceuticals into coastal ecosystems, underpinning an increasing demand to evaluate the ecotoxicological effects and implications of drug residues in marine risk assessments. Propranolol, a non-selective β-adrenoceptor blocker, is used worldwide to treat high blood pressure conditions and other related cardiovascular conditions. Although diatoms lack β-adrenoceptors, this microalgal group presents receptor-like kinases and proteins with a functional analogy to the animal receptors and that can be targeted by propranolol. In the present work, the authors evaluated the effect of this non-selective β-adrenoceptor blocker in diatom cells using P. tricornutum as a model organism, to evaluate the potential effect of this compound in cell physiology (growth, lipids and energy metabolism and oxidative stress) and its potential relevance for marine ecosystems. Propranolol exposure leads to a significant reduction in diatom cell growth, more evident in the highest concentrations tested. This is likely due to the observed impairment of the main primary photochemistry processes and the enhancement of the mitochondrial respiratory activity. More specifically, propranolol decreased the energy transduction from photosystem II (PSII) to the electron transport chain, leading to an increase in oxidative stress levels. Cells exposed to propranolol also exhibited high-dissipated energy flux, indicating that this excessive energy is efficiently diverted, to some extent, from the photosystems, acting to prevent irreversible photoinhibition. As energy production is impaired at the PSII donor side, preventing energy production through the electron transport chain, diatoms appear to be consuming storage lipids as an energy backup system, to maintain essential cellular functions. This consumption will be attained by an increase in respiratory activity. Considering the primary oxygen production and consumption pathways, propranolol showed a significant reduction of the autotrophic O₂ production and an increase in the heterotrophic mitochondrial respiration. Both mechanisms can have negative effects on marine trophic webs, due to a decrease in the energetic input from marine primary producers and a simultaneous oxygen production decrease for heterotrophic species. In ecotoxicological terms, bio-optical and fatty acid data appear as highly efficient tools for ecotoxicity assessment, with an overall high degree of classification when these traits are used to build a toxicological profile, instead of individually assessed.

Survey of Pharmacological Activity and Pharmacokinetics of Selected β-Adrenergic Blockers in Regard to Their Stereochemistry

The present survey concentrates on pharmacodynamics and pharmacokinetics of selected β-adrenergic blockers from the point of view of their stereochemistry. It could be shown that the activity in the arylaminoethanol and aryloxyaminopropanol group of β-blockers is higher in their (–)-enantiomers as compared with the (+)-enantiomers. The stereoisomers differ also in other types of bioactivity as well as in toxicity. The particular pharmacokinetic stages such as resorption, distribution, and metabolism are discussed in regard to their stereochemistry.

Assessing the environmental hazard of individual and combined pharmaceuticals: acute and chronic toxicity of fluoxetine and propranolol in the crustacean Daphnia magna

Pharmaceuticals are widespread emerging contaminants and, like all pollutants, are present in combination with others in the ecosystems. The aim of the present work was to evaluate the toxic response of the crustacean Daphnia magna exposed to individual and combined pharmaceuticals. Fluoxetine, a selective serotonin re-uptake inhibitor widely prescribed as antidepressant, and propranolol, a non-selective β-adrenergic receptor-blocking agent used to treat hypertension, were tested. Several experimental trials of an acute immobilization test and a chronic reproduction test were performed. Single chemicals were first tested separately. Toxicity of binary mixtures was then assessed using a fixed ratio experimental design. Five concentrations and 5 percentages of each substance in the mixture (0, 25, 50, 75, and 100%) were tested. The MIXTOX model was applied to analyze the experimental results. This tool is a stepwise statistical procedure that evaluates if and how observed data deviate from a reference model, either concentration addition (CA) or independent action (IA), and provides significance testing for synergism, antagonism, or more complex interactions. Acute EC50 values ranged from 6.4 to 7.8 mg/L for propranolol and from 6.4 to 9.1 mg/L for fluoxetine. Chronic EC50 values ranged from 0.59 to 1.00 mg/L for propranolol and from 0.23 to 0.24 mg/L for fluoxetine. Results showed a significant antagonism between chemicals in both the acute and the chronic mixture tests when CA was adopted as the reference model, while absence of interactive effects when IA was used.

Insights into the regulation of the MXR response in haemocytes of the Mediterranean mussel (Mytilus galloprovincialis)

This study investigated functional and transcriptional modulation of the Multixenobiotic resistance (MXR) system as a cytoprotective mechanism contributing to the physiological chemoresistance of haemocytes in the Mediterranean mussel. Basal transport activity was assessed using the model substrate rhodamine 123 and specific inhibitors for the MXR-related transporters P-glycoprotein (ABCB mRNA) and Multidrug resistance-related protein (ABCC mRNA). Results showed that MXR activity in mussel haemocytes was mainly supported by the Mrp-mediated efflux. In agreement, ABCC was expressed at higher levels than ABCB. Activation of the cyclic-AMP (cAMP) dependent protein kinase A (PKA) resulted in increased rhodamine efflux, which was counteracted by the selective PKA inhibitor H89. Although serotonin, a physiological modulator of cAMP/PKA signaling and ABCB transcription in haemocytes, did not affect basal MXR transport, the environmental pharmaceuticals fluoxetine, propranolol, and carbamazepine, which interact in different ways with the adrenergic and serotoninergic pathways, were showed to act as modulators and substrates of MXR-related transporters and to affect cell viability. While the increased MXR activity may have lowered the cytotoxic effects of propranolol and carbamazepine, the lack of MXR efflux induction by fluoxetine may play a role in the observed cytotoxicity of the compound.

Human pharmaceuticals in the marine environment: Focus on exposure and biological effects in animal species

Marine waters have been poorly investigated for the occurrence of pharmaceutical contamination. Recent data confirm that pharmaceuticals occur widely in marine and coastal environments; therefore, assessment of potential risk to marine species needs further efforts. The present study represents the first extensive review of pharmaceutical contamination in marine environments addressing the effects on the marine biota analyzed at the molecular, cellular, and individual levels. Because pharmaceuticals differ from conventional pollutants, being designed to interact with specific physiological pathways at low doses, the most recent evidence on modes of action and physiological alterations on marine animal species are discussed. Data on spatial distributions of pharmaceuticals in waters and sediments, as well as bioaccumulation rates, are also presented. The present review also seeks to expand knowledge of how the quality of coastal and marine environments could be efficiently monitored to anticipate possible health and environmental risks.

Shotgun proteomics to unravel marine mussel (Mytilus edulis) response to long-term exposure to low salinity and propranolol in a Baltic Sea microcosm

Pharmaceuticals, among them the β-adrenoceptor blocker propranolol, are an important group of environmental contaminants reported in European waters. Laboratory exposure to pharmaceuticals on marine species has been performed without considering the input of the ecosystem flow. To unravel the ecosystem response to long-term exposure to propranolol we have performed long-term exposure to propranolol and low salinity in microcosms. We applied shotgun proteomic analysis to gills of Mytilus edulis from those Baltic Sea microcosms and identified 2071 proteins with a proteogenomic strategy. The proteome profiling patterns from the 587 highly reproductive proteins among groups define salinity as a key factor in the mussel's response to propranolol. Exposure at low salinity drives molecular mechanisms of adaptation based on a decrease in the abundance of several cytoskeletal proteins, signalling and intracellular membrane trafficking pathway combined with a response towards the maintenance of transcription and translation. The exposure to propranolol combined with low salinity modulates the expression of structural proteins including cilia functions and decreases the expression of membrane protein transporters. This study reinforces the environment concerns of the impact of low salinity in combination with anthropogenic pollutants and anticipates critical physiological conditions for the survival of the blue mussel in the northern areas.

BIOLOGICAL SIGNIFICANCE

Applying shotgun proteomic analysis to M. edulis gills samples from a long-term microcosm exposure to propranolol and following a proteogenomic identification strategy, we have identified 2071 proteins. The proteomic analysis unrevealed which molecular mechanisms drive the adaptation to low salinity stress and how salinity modulates the effects of exposure to propranolol. These results reinforce the idea of the impact of low salinity in combination with anthropogenic pollutants and anticipate critical physiological condition.

A multibiomarker approach to explore interactive effects of propranolol and fluoxetine in marine mussels

A multi-biomarker approach, including several lysosomal parameters, activity and mRNA expression of antioxidant enzymes, and DNA damage, was employed to investigate the nominal effects of 0.3 ng/L fluoxetine (FX) and 0.3 ng/L propranolol (PROP) alone or in combination (0.3 ng/L FX + 0.3 ng/L PROP) on Mediterranean mussels after a 7 day treatment. FX co-exposure appears to facilitate PROP bioaccumulation because PROP only accumulated in digestive gland of FX + PROP treated mussels. Lysosomal parameters were significantly impaired by FX + PROP treatment, while no clear antioxidant responses at the catalytic and transcriptional levels were observed. Biomarker responses led to a "medium stress level" diagnosis in FX + PROP treated mussels, according to the Expert System, whereas 0.3 ng/L PROP or FX alone did not induce consistent stress conditions. These findings suggest vulnerability of coastal marine mussels to FX and PROP contamination at environmentally relevant levels.

The mode of action (MOA) approach reveals interactive effects of environmental pharmaceuticals on Mytilus galloprovincialis

Aquatic organisms are unintentionally exposed to a large number of pharmaceutical residues in their natural habitats. Ecotoxicological studies have agreed that these compounds are not harmful to aquatic organisms, as their environmental concentrations are typically too low. However, recent reports have shown biological effects at such low concentrations when biological endpoints related to the therapeutic effects are assessed. Therefore, conservation of molecular targets is now addressed as a key aspect for the development of more efficient test strategies for pharmaceutical environmental risk assessment, providing the rationale for the mode of action (MOA) approach. In the present study the MOA approach was used to investigate the interactive effects of fluoxetine (FX) and propranolol (PROP) on the Mediterranean mussels (Mytilus galloprovincialis). Indeed, organisms in the environment are exposed to pharmaceutical mixtures throughout their lifetime, and particular combinations may be of concern. The antidepressant FX increases serotonin (5-HT) levels in the synaptic cleft by inhibiting 5-HT reuptake. PROP, a prototypical β-adrenoceptor antagonist, also blocks 5-HT1 receptors, which are negatively coupled to cAMP-mediated signaling. Cell signaling alterations potentially triggered by 5-HT1 receptor occupation were therefore assessed after a 7-day mussel exposure to FX or PROP, alone or in combination, each at 0.3 ng/L concentration. FX decreased cAMP levels and PKA activities in digestive gland and mantle/gonads, in agreement with an increased occupation of 5-HT1 receptors. PROP caused a decrease in cAMP levels and PKA activities in digestive gland and an increase in cAMP levels in mantle/gonads, consistent with a differential expression of adrenergic and 5-HT receptors in the two tissues. Co-exposure to FX and PROP provides significant indications for antagonistic effects of the pharmaceuticals, consistent with a direct (PROP) and indirect (FX) action on the same molecular target. Interestingly, FX induced over-expression of a 5-HT1 gene product, and PROP counteracted such increase when the mixture was administered, while having per se no effect. Finally, mRNA expression of the ABCB gene encoding the MXR-related transporter P-glycoprotein was reduced by both pharmaceuticals in the digestive gland, while decreased by FX, increased by PROP, and not affected by the mixture in mantle/gonads. Since transcription of this gene product is under cAMP/PKA modulation, the impairment of regulatory pathways triggered by low concentrations of pharmaceuticals have the potential to affect the ability of animals to elaborate strategies of defense or adaptation toward further stress factors. In this specific case, the pharmaceutical mixture limits the detrimental effects of the single compounds.

The decline effect in cardiovascular medicine: is the effect of cardiovascular medicine and stent on cardiovascular events decline over the years?

The term decline effect is referred to a diminution of scientifically discovered effects over time. Reasons for the decline effect are multifaceted and include publication bias, selective reporting, outcomes reporting bias, regression to the mean, scientific paradigm shift, overshadowing and habituation, among others. Such effects can be found in cardiovascular medicines through medications (e.g., aspirin, antithrombotics, proton pump inhibitor, beta-blockers, statins, estrogen/progestin, angiotensin converting enzyme inhibitor etc.), as well as with interventional devices (e.g., angioplasty, percutaneous coronary intervention, stents). The scientific community should understand the various dimensions of the decline effects, and effective steps should be undertaken to prevent or recognize such decline effects in cardiovascular medicines.

Meta-analysis of the comparative effects of different classes of antihypertensive agents on brachial and central systolic blood pressure, and augmentation index

AIMS

Brachial systolic blood pressure (bSBP) exceeds aortic pressure by a variable amount, and estimated central systolic blood pressure (cSBP) may be a better indicator of cardiovascular risk than bSBP. We undertook a systematic review and meta-analysis to compare the effect of single and multiple antihypertensive agents on bSBP, cSBP and augmentation index (AIx).

METHODS

A random effects meta-analysis was performed on 24 randomized controlled trials of antihypertensives with measurements of bSBP, cSBP and/or AIx. Separate analyses were performed for drug comparisons with or without placebo, and drug combinations.

RESULTS

In the placebo vs. drug meta-analysis, antihypertensive therapy reduced bSBP more than cSBP and there was no statistically significant evidence of heterogeneity by drug class, although the number of individual studies was small. In placebo-adjusted drug vs. drug comparison, treatment with β-blockers, omapatrilat and thiazide diuretics lowered cSBP significantly less than bSBP (i.e. central to brachial amplification decreased), whereas other monotherapies lowered cSBP and bSBP to similar extents. Sample sizes were too small and effect estimates insufficiently precise to allow firm conclusions to be made regarding comparisons between individual drug classes. Antihypertensive combinations that included β-blockers decreased central to brachial amplification. β-Blockers increased AIx, whereas all other antihypertensive agents reduced AIx to similar extents.

CONCLUSIONS

A reduction in central to brachial amplification by some classes of antihypertensive drug will result in lesser reductions in cSBP despite achievement of target bSBP. This effect could contribute to differences in outcomes in randomized clinical trials when β-blocker- and/or diuretic-based antihypertensive therapy are compared with other regimens.

Cyclic-AMP mediated regulation of ABCB mRNA expression in mussel haemocytes

Background

The multixenobiotic resistance system (MXR) allows aquatic organisms to cope with their habitat despite high pollution levels by over-expressing membrane and intracellular transporters, including the P-glycoprotein (Pgp). In mammals transcription of the ABCB1 gene encoding Pgp is under cAMP/PKA-mediated regulation; whether this is true in mollusks is not fully clarified.

Methodology/Principal Findings

cAMP/PKA regulation and ABCB mRNA expression were assessed in haemocytes from Mediterranean mussels (Mytilus galloprovincialis) exposed in vivo for 1 week to 0.3 ng/L fluoxetine (FX) alone or in combination with 0.3 ng/L propranolol (PROP). FX significantly decreased cAMP levels and PKA activity, and induced ABCB mRNA down-regulation. FX effects were abolished in the presence of PROP. In vitro experiments using haemocytes treated with physiological agonists (noradrenaline and serotonin) and pharmacological modulators (PROP, forskolin, dbcAMP, and H89) of the cAMP/PKA system were performed to obtain clear evidence about the involvement of the signaling pathway in the transcriptional regulation of ABCB. Serotonin (5-HT) decreased cAMP levels, PKA activity and ABCB mRNA expression but increased the mRNA levels for a putative 5-HT₁ receptor. Interestingly, 5-HT₁ was also over-expressed after in vivo exposures to FX. 5-HT effects were counteracted by PROP. Forskolin and dbcAMP increased PKA activity as well as ABCB mRNA expression; the latter effect was abolished in the presence of the PKA inhibitor H89.

Conclusions

This study provides the first direct evidence for the cAMP/PKA-mediated regulation of ABCB transcription in mussels.

Effect of Tulbaghia violacea on the blood pressure and heart rate in male spontaneously hypertensive Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Tulbaghia violacea Harv. (Alliaceae) is a small bulbous herb which belongs to the family Alliaceae, most commonly associated with onions and garlic. In South Africa, this herb has been traditionally used in the treatment of various ailments, including fever, colds, asthma, paralysis, hypertension and stomach problems. The aim of this study was to evaluate the effect of methanol leaf extracts (MLE) of Tulbaghia violacea on the blood pressure (BP) and heart rate (HR) in anaesthetized male spontaneously hypertensive rats; and to find out the mechanism(s) by which it acts.

MATERIALS AND METHODS

The MLE of Tulbaghia violacea (5-150mg/kg), angiotensin I human acetate salt hydrate (ang I, 3.1-100μg/kg), angiotensin II human (ang II, 3.1-50μg/kg), phenylephrine hydrochloride (phenylephrine, 0.01-0.16mg/kg) and dobutamine hydrochloride (dobutamine, 0.2-10.0μg/kg) were infused intravenously, while the BP and HR were measured via a pressure transducer connecting the femoral artery and the Powerlab.

RESULTS

Tulbaghia violacea significantly (p<0.01) reduced the systolic, diastolic, and mean arterial BP; and HR dose-dependently. Ang I, ang II, phenylephrine and dobutamine all increased the BP dose-dependently. The hypertensive effect of ang I and the HR-increasing effect of dobutamine were significantly (p<0.01) decreased by their co-infusion with Tulbaghia violacea (60mg/kg). However, the co-infusion of ang II or phenylephrine with Tulbaghia violacea (60mg/kg) did not produce any significant change in BP or HR when compared to the infusion of either agent alone in the same animal.

CONCLUSIONS

Tulbaghia violacea reduced BP and HR in the SHR. The reduction in BP may be due to actions of the MLE on the ang I converting enzyme (ACE) and β(1) adrenoceptors.

The β-blocker propranolol affects cAMP-dependent signaling and induces the stress response in Mediterranean mussels, Mytilus galloprovincialis

Widespread occurrence of pharmaceuticals is reported in aquatic systems, posing concerns for the health of aquatic wildlife and a theoretical risk to humans. A recent concept was developed for the identification of highly active compounds amongst the environmental pharmaceuticals, based on their mode of action, the homology between human targets and possible targets in the environment, and the importance of the affected pathway for the target species. In line with this approach, this study investigated whether propranolol (PROP) affects the cAMP-dependent pathway in Mediterranean mussels, Mytilus galloprovincialis. PROP is a prototypical β-adrenoceptor antagonist, and these receptors exist in bivalves and show gross pharmacological properties similar to their mammalian counterparts. PROP also acts as a 5-HT1 receptor antagonist, which is the sole 5-HT receptor reported in bivalves to date. Importantly, β-adrenoceptor and 5HT-1 receptor subtypes are positively and negatively coupled to cAMP-mediated signaling, respectively. PROP was administered as either l-PROP or dl-PROP. A wide range of concentrations was tested including low (0.3, 3 and 30ng/L) and high (300ng/L) environmental ranges, and a concentration 5-fold above the maximum reported environmental level (30,000ng/L). After a 7-day exposure, mussel cAMP levels and PKA activities were significantly reduced in digestive gland, increased in mantle/gonads and unaffected in gills. Similar patterns were observed for the mRNA expression of the ABCB1 gene encoding the membrane transporter P-glycoprotein, hypothesised to be under PKA modulation. The effects on the digestive gland are consistent with PROP blocking β-adrenoceptors. The observed increased cAMP levels in the mantle/gonad tissue support PROP blocking 5-HT1 receptors. Catalase and glutathione-S tranferase were differently affected by PROP in the two tissues. Mussel haemocyte lysosome membrane stability, a sensitive biomarker of animal health status, was concentration-dependently reduced following PROP exposure. Our observations provide evidence for PROP affecting cell signaling in M. galloprovincialis. Moreover, the chemical interacts with specific and evolutionally conserved biochemical pathways for which it was designed. The mode of action of PROP in mussels is related with its therapeutic properties in humans, based upon these conserved human targets. It also induced a stress response, and all these effects were displayed at the lowest concentrations tested.

Effect of low sodium intake and β-blockade on renin synthesis and secretion in mice with unilateral ureteral ligation

We previously reported that sodium depletion increased renin secretion from the normal kidney in mice. We postulated that the combined procedures of sodium depletion and β-adrenoceptor blockade would affect the activity of the renin-angiotensin system. To test this hypothesis, we investigated the interaction of low sodium intake (LSI) and propranolol (PRO) on renin synthesis and secretion. To prevent the influence of tubule flow on renin secretion, mice with a left hydronephrotic kidney were used. LSI increased plasma renin concentration (PRC) 5.6-fold in the right renal vein (P<0.01). There was no net increase of PRC in the left renal vein. Tissue renin concentration (TRC) was elevated 3.6-fold and 1.3-fold in the right and left kidneys (P<0.01), respectively. After administration of PRO, PRC decreased by 34% in the right renal vein and 47% in the aorta (P<0.05); TRC was reduced by 37.5% in the right and 29.3% in the hydronephrotic kidneys (P<0.05). The combination of LSI and PRO increased PRC 3.4-fold and 1.8-fold in the right (P<0.01) and left renal veins (P<0.05), respectively. TRC increased 3.4-fold in the right (P<0.01) but only 61% in the left kidneys (P<0.05). The pattern in change of renin mRNA levels was similar to TRC but the absolute amount was smaller. There were correlations between PRC and renin mRNA, and between TRC and renin mRNA in both kidneys (P<0.001). Thus, LSI increased renin synthesis in both kidneys. However, there was no apparent renin secretion in the hydronephrotic kidney. PRO treatment suppressed renin synthesis and renin secretion, irrespective of hydronephrosis and LSI. The macula densa is critical for renin secretion under all of the circumstances studied.

Clinical updates on carvedilol: a first choice beta-blocker in the treatment of cardiovascular diseases

IMPORTANCE OF THE FIELD

Carvedilol, a non-selective beta-blocker, has recently drawn attention because of its therapeutic benefits over other prescribed analogues for the treatment of cardiovascular diseases (CVDs).

AREAS COVERED IN THIS REVIEW

The present review attempts to present the clinical efficacy of carvedilol in comparison to other available beta-blockers. The literature search was carried out in three electronic databases (Unbound Medline, Pubmed and Sciencedirect) and internet search engines (Scirus and Google Scholar) without time constraints to ensure maximum literature coverage.

WHAT THE READER WILL GAIN

A relatively large number of comparative studies have revealed that carvedilol has advantage over traditional beta-blockers with respect to hemodynamic and metabolic effects, due to its unique non-selective alpha-/beta-adrenoceptor affinity. Such results indicate its safe and effective therapeutic application particularly in patients with complicated CVDs, even in pediatric and geriatric patients.

TAKE HOME MESSAGE

The therapeutic profile of carvedilol indicates its suitability for treatment of complicated CVDs than other non-selective beta-blockers. However, there is a limitation in terms of its dose due to its low bioavailability (approximately 25%). Therefore, there is still need for bioavailability enhancement and dose reduction to further improve the therapeutic efficacy of the drug.

Real-time optoacoustic monitoring and three-dimensional mapping of a human arm vasculature

We present our findings from a real-time laser optoacoustic imaging system (LOIS). The system utilizes a Q-switched Nd:YAG laser; a standard 128-channel ultrasonic linear array probe; custom electronics and custom software to collect, process, and display optoacoustic (OA) images at 10 Hz. We propose that this system be used during preoperative mapping of forearm vessels for hemodialysis treatment. To demonstrate the real-time imaging capabilities of the system, we show OA images of forearm vessels in a volunteer and compare our results to ultrasound images of the same region. Our OA images show blood vessels in high contrast. Manipulations with the probe enable us to locate and track arteries and veins of a forearm in real time. We also demonstrate the ability to combine a series of OA image slices into a volume for spatial representation of the vascular network. Finally, we use frame-by-frame analysis of the recorded OA video to measure dynamic changes of the crossection of the ulnar artery.