Angiotensin receptor blockers versus angiotensin-converting enzyme inhibitors: where do we stand now?

Sustained Activation of CLR/RAMP Receptors by Gel-Forming Agonists

Background: Adrenomedullin (ADM), adrenomedullin 2 (ADM2), and CGRP family peptides are important regulators of vascular vasotone and integrity, neurotransmission, and fetoplacental development. These peptides signal through CLR/RAMP1, 2, and 3 receptors, and protect against endothelial dysfunction in disease models. As such, CLR/RAMP receptor agonists are considered important therapeutic candidates for various diseases. Methods and Results: Based on the screening of a series of palmitoylated chimeric ADM/ADM2 analogs, we demonstrated a combination of lipidation and accommodating motifs at the hinge region of select peptides is important for gaining an enhanced receptor-activation activity and improved stimulatory effects on the proliferation and survival of human lymphatic endothelial cells when compared to wild-type peptides. In addition, by serendipity, we found that select palmitoylated analogs self-assemble to form liquid gels, and subcutaneous administration of an analog gel led to the sustained presence of the peptide in the circulation for >2 days. Consistently, subcutaneous injection of the analog gel significantly reduced the blood pressure in SHR rats and increased vasodilation in the hindlimbs of adult rats for days. Conclusions: Together, these data suggest gel-forming adrenomedullin analogs may represent promising candidates for the treatment of various life-threatening endothelial dysfunction-associated diseases such as treatment-resistant hypertension and preeclampsia, which are in urgent need of an effective drug.

Tβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin β4 (Tβ4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for Tβ4 and (or) its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by 2 successive enzymes, meprin α and prolyl oligopeptidase. We also discussed the possible mechanisms involved in the Tβ4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, Tβ4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, Tβ4 and Ac-SDKP have antifibrotic and anti-inflammatory properties in the arteries, heart, lungs, and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of Tβ4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular, and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.

Consequences of continuing renin angiotensin aldosterone system antagonists in the preoperative period: a systematic review and meta-analysis

Background

Patients who use angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin II receptor blockers (ARBs) are prone to developing side effects like hypotension and even refractory hypotension during anesthesia use, and whether ACEIs/ARBs should be continued or discontinued in such patients remains debatable. The present systematic review and meta-analysis was conducted to clarify the consequences of continuing or withholding these drugs, especially with regards to the incidence of intraoperative hypotension, in patients who continue to use ACEIs/ARBs on the day of their scheduled surgery.

Methods

Studies with data pertinent to the incidence of intraoperative hypotension during anesthesia use in patients who continued the use of ACEIs/ARBs on the day of their scheduled surgery were considered for inclusion.

Results

Thirteen studies reporting on the incidences of intraoperative hypotension between patients who continued receiving ACEIs/ARBs and those who did not on the day of their surgical procedure were included. The pooled effects showed that hypotension during anesthesia was more likely to develop in patients who continued to take ACEIs/ARBs when compared to those who did not (RR = 1.41, 95% CI: 1.21–1.64). However, there were no significant differences between these groups of patients with regards to postoperative complications including ST-T abnormalities, myocardial injury, myocardial infarction, stroke, major adverse cardiac events, acute kidney injury, or death (RR = 1.25, 95% CI: 0.76–2.04). The differences remained similar in subgroup analyses and sensitivity analyses.

Conclusions

No sufficient available evidence to recommend discontinuing ACEIs/ARBs on the day of surgery was found in this literature review and meta-analysis. However, anesthetists should be cautious about the risk for intraoperative hypotension in patients chronically receiving ACEIs/ARBs, and should know how to treat it effectively.

Possible vasculoprotective role of linagliptin against sodium arsenite-induced vascular endothelial dysfunction

Vascular endothelial dysfunction (VED) interrupts the integrity and function of endothelial lining through enhanced markers of oxidative stress and decrease endothelial nitric oxide synthase (eNOS) expression. The main aim of the present study has been designed to investigate the possible vasculoprotective role of linagliptin against sodium arsenite-induced VED. Sodium arsenite (1.5 mg/kg, i.p., 2 weeks) abrogated the acetylcholine-induced, endothelium-dependent vasorelaxation by depicting the decrease in serum nitrite/nitrate concentration, reduced glutathione level, and simultaneously enhance the thiobarbituric acid reactive substances (TBARS) level, superoxide level, and tumor necrosis factor-alpha. These elevated markers interrupt the integrity of endothelial lining of thoracic aorta which was assessed histologically. The study elicits dose dependent effect of linagliptin (1.5 mg/kg, i.p. and 3 mg/kg, i.p.) or atorvastatin (30 mg/kg, p.o.) treatment, improved the endothelium-dependent independent relaxation, improve the integrity of endothelium lining which was assessed histologically by enhancing the serum nitrite/nitrate level, reduced glutathione level and simultaneously decreasing the TBARS level, superoxide anion level and tumor necrosis factor-alpha (TNF-α) level. L-NAME (25 mg/kg, i.p.), eNOS inhibitor, abrogated the ameliorative potential of linagliptin. However, the ameliorative potential of linagliptin has been enhanced by l-arginine (200 mg/kg, i.p.) which elicits that ameliorative potential of linagliptin was through eNOS signaling cascade and it may be concluded that linagliptin 3 mg/kg, i.p. has more significantly activated the eNOS and decreased the oxidative markers than linagliptin 1.5 mg/kg, i.p. and prevented sodium arsenite-induced VED.

Association between Withholding Angiotensin Receptor Blockers in the Early Postoperative Period and 30-day Mortality

Background:

Despite widespread use, there is limited information to guide perioperative management of angiotensin receptor blockers (ARBs).

Methods:

In this retrospective cohort study, the authors evaluated the patterns of postoperative ARB use in veterans regularly prescribed ARBs admitted for noncardiac surgery at the Veterans Affairs Healthcare system between 1999 and 2011. Multivariable and propensity score–matched Cox proportional hazards models were used to determine the independent effect of failure to resume ARB by postoperative day 2 on the primary outcome of all-cause 30-day mortality.

Results:

Out of 1,167,482 surgical admissions, 30,173 inpatient surgical admissions met inclusion criteria. Approximately 10,205 patients (33.8%) in the cohort did not resume ARB by day 2. Those that resumed ARB had a 30-day mortality rate of 1.3% (260 of 19,968), whereas 3.2% (323 of 10,205) died in the group that withheld ARB. The unadjusted hazard ratio (HR) for 30-day mortality was 2.45 (95% CI, 2.08 to 2.89; P < 0.001) for those that withheld ARB compared with those that resumed, whereas the multivariable adjusted HR was 1.74 (95% CI, 1.47 to 2.06; P < 0.001). When restricted to a propensity score–matched subset of 19,490, the HR was similar (1.47; 95% CI, 1.22 to 1.78; P < 0.001). Withholding ARB in younger patients increased mortality risk (HR = 2.52; 95% CI, 1.69 to 3.76; P < 0.001 for age <60 yr) compared with older patients (HR = 1.42; 95% CI, 1.09 to 1.85; P = 0.01 for age >75 yr).

Conclusions:

Postoperative delay in resuming ARB is common, particularly in patients who are frail after surgery. Withholding ARB is strongly associated with increased 30-day mortality, especially in younger patients, although residual confounding may be present.

Perspectives for angiotensin profiling with liquid chromatography/mass spectrometry to evaluate ACE/ACE2 balance in endothelial dysfunction and vascular pathologies

Vascular injury, characterized by endothelial dysfunction, inflammation, structural remodeling, thrombosis and calcification leads to cardiovascular diseases. Angiotensin (Ang) II (1-8) - synthesized mainly by angiotensin converting enzyme (ACE) is the best characterized mediator of the renin-angiotensin system (RAS). This peptide initially identified by its vasoactive properties was found to play a major role in vascular response to insult. However, recent discovery of angiotensin converting enzyme 2 (ACE2) that produces vasoprotective Ang-(1-7) peptide highlighted complexity of the system and suggested that balance between ACE/Ang II and ACE2/Ang-(1-7) is fundamental in maintaining vascular homeostasis and its disorders are associated with cardiovascular pathology. There is therefore a need to develop methods for comprehensive analysis of biologically active Ang peptides and their metabolites of ACE/Ang II and ACE2/Ang-(1-7) axes. Liquid chromatography/mass spectrometry (LC/MS) is an analytical technique that offers potential for specific, simultaneous analysis of Ang peptides. With sensitivity added by application of preconcentration nanochromatography reaching picomolar concentrations, practically all Ang peptides identified so far could be quantified in biological samples. Ang profiling is important not only for understanding their physiological or pathological role but could also serve as an early diagnostic biomarker of endothelial dysfunction and cardiovascular pathology. It could also be used for monitoring the efficacy of the RAS-targeted therapies. Although, the methodology requires further improvements to adopt it for routine application, Ang peptide profiling with targeted LC/MS analysis might assess functional balance between ACE/Ang II and ACE2/Ang-(1-7) axes, facilitate our understanding of the cardiovascular pathology and enhance biomarker portfolio in cardiovascular diseases.

Divergent Roles of Matrix Metalloproteinase 2 in Pathogenesis of Thoracic Aortic Aneurysm

Objective—

Aortic aneurysm, focal dilation of the aorta, results from impaired integrity of aortic extracellular matrix (ECM). Matrix metalloproteinases (MMPs) are traditionally known as ECM-degrading enzymes. MMP2 has been associated with aneurysm in patients and in animal models. We investigated the role of MMP2 in thoracic aortic aneurysm using 2 models of aortic remodeling and aneurysm.

Approach and Results—

Male 10-week-old MMP2-deficient (MMP2 −/− ) and wild-type mice received angiotensin II (Ang II, 1.5 mg/kg/day) or saline (Alzet pump) for 4 weeks. Although both genotypes exhibited dilation of the ascending aorta after Ang II infusion, MMP2 −/− mice showed more severe dilation of the thoracic aorta and thoracic aortic aneurysm. The Ang II–induced increase in elastin and collagen (mRNA and protein) was markedly suppressed in MMP2 −/− thoracic aorta and smooth muscle cells, whereas only mRNA levels were reduced in MMP2 −/− -Ang II abdominal aorta. Consistent with the absence of MMP2, proteolytic activities were lower in MMP2 −/− -Ang II compared with wild-type-Ang II thoracic and abdominal aorta. MMP2-deficiency suppressed the activation of latent transforming growth factor-β and the Smad2/3 pathway in vivo and in vitro. Intriguingly, MMP2 −/− mice were protected against CaCl 2 -induced thoracic aortic aneurysm, which triggered ECM degradation but not synthesis.

Conclusions—

This study reveals the dual role of MMP2 in ECM degradation, as well as ECM synthesis. Moreover, the greater susceptibility of the thoracic aorta to impaired ECM synthesis, compared with vulnerability of the abdominal aorta to aberrant ECM degradation, provides an insight into the regional susceptibility of the aorta to aneurysm development.

Development of a sensitive, accurate and robust liquid chromatography/mass spectrometric method for profiling of angiotensin peptides in plasma and its application for atherosclerotic mice

Quantification of angiotensin (Ang) peptides in biological matrices is a challenge due to their low picomolar (pM) concentration and poor analytical performance of current methods. This work aimed to select an optimal strategy for liquid chromatography/mass spectrometry (LC/MS) quantification of major angiotensins in plasma of wild type and atherosclerotic mice. Optimal LC/MS set-up for Ang quantification was chosen, based on analytical performance, from: nanoflow/orbitrap, nanoflow/triple quadrupole and preconcentration nanoflow/triple quadrupole. The best LC/MS configuration (preconcentration nanoflow/triple quadrupole) was validated and used for measurement of angiotensins (Ang I, II, III, IV and (1-7)) in plasma of 6-month-old atherosclerotic apolipoprotein E/LDL receptor double knock-outs (ApoE/LDLR (--/--)) and wild type C57BL/6J (WT) mice. The method established for Ang quantification was selective, accurate and highly sensitive with LLOQ of 5pgmL(-1). The peak area intra-day precisions for Ang II and Ang-(1-7) were in the range 3.0-5.1 and 3.5-5.8, respectively, with corresponding accuracy of 95.4-103.5% and 95.6-106.3%. Plasma angiotensin profile was substantially modified in ApoE/LDLR knock-out mice with increase in concentration of Ang II from 37.6±21.3pgmL(-1) in WT to 200.2±47.6pgmL(-1). Concentrations of Ang I, III and IV were also increased 3-10 fold in ApoE/LDLR (--/--) mice while that of Ang-(1-7) was unchanged. We conclude that the method developed could be effectively used for accurate, comprehensive profiling of angiotensin peptides in mouse plasma. We identified substantial changes in renin-angiotensin system in a genetic mouse model of atherosclerosis consistent with the overactivation of angiotensin converting enzyme (ACE) and the impairment of ACE2.

Is reversal of endothelial dysfunction still an attractive target in modern cardiology?

Although the endothelium has a number of important functions, the term endothelial dysfunction is commonly used to describe impairment in its vasodilatory capacity. There have been numerous studies evaluating the relationship between endothelial dysfunction and cardiovascular disease, however assessment of endothelial function is perhaps still primarily thought of as a research tool and has not reached widespread clinical acceptance. In this review we explore the relationship between endothelial dysfunction and cardiovascular disease, its prognostic significance, methods of pharmacological reversal of endothelial dysfunction, and ask the question, is reversal of endothelial dysfunction still an attractive target in modern cardiology?

Loss of Timp3 gene leads to abdominal aortic aneurysm formation in response to angiotensin II

Aortic aneurysm is dilation of the aorta primarily due to degradation of the aortic wall extracellular matrix (ECM). Tissue inhibitors of metalloproteinases (TIMPs) inhibit matrix metalloproteinases (MMPs), the proteases that degrade the ECM. Timp3 is the only ECM-bound Timp, and its levels are altered in the aorta from patients with abdominal aortic aneurysm (AAA). We investigated the causal role of Timp3 in AAA formation. Infusion of angiotensin II (Ang II) using micro-osmotic (Alzet) pumps in Timp3(-/-) male mice, but not in wild type control mice, led to adverse remodeling of the abdominal aorta, reduced collagen and elastin proteins but not mRNA, and elevated proteolytic activities, suggesting excess protein degradation within 2 weeks that led to formation of AAA by 4 weeks. Intriguingly, despite early up-regulation of MMP2 in Timp3(-/-)Ang II aortas, additional deletion of Mmp2 in these mice (Timp3(-/-)/Mmp2(-/-)) resulted in exacerbated AAA, compromised survival due to aortic rupture, and inflammation in the abdominal aorta. Reconstitution of WT bone marrow in Timp3(-/-)/Mmp2(-/-) mice reduced inflammation and prevented AAA in these animals following Ang II infusion. Treatment with a broad spectrum MMP inhibitor (PD166793) prevented the Ang II-induced AAA in Timp3(-/-) and Timp3(-/-)/Mmp2(-/-) mice. Our study demonstrates that the regulatory function of TIMP3 is critical in preventing adverse vascular remodeling and AAA. Hence, replenishing TIMP3, a physiological inhibitor of a number of metalloproteinases, could serve as a therapeutic approach in limiting AAA development or expansion.

The differential effect of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers with respect to foot ulcer and limb amputation in those with diabetes

Diabetic foot ulcers (DFU) or lower extremity amputation (LEA) are complications of diabetes. In those with diabetes, angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) are commonly used to prevent the progression of kidney disease. Recent studies have indicated that angiotensin may affect angiogenesis and wound repair. Our goal was to evaluate in those with diabetes the likelihood of developing a DFU or LEA among users of ACEi or ARB using a retrospective cohort design of general practices in the United Kingdom. We studied 40,342 individuals at least 35 years of age with diabetes who were first prescribed ACEi or ARB between 1995 and 2006. A total of 35,153 individuals were treated with ACEi, 12,437 individuals with ARB, and 7,310 both. The hazard ratio for DFU was 0.50 (95% confidence intervals: 0.43, 0.59), showing an increased risk of DFU for those using ACEi vs. ARB. The hazard ratio for LEA was 0.72 (0.48, 1.01). However, among those with lower extremity peripheral arterial disease the hazard ratio was 0.45 (0.22, 0.91) for the new onset of a LEA. In conclusion, among those with diabetes, exposure to ACEi as compared with ARB increases the risk of developing a DFU or LEA.

Deeply discounted medications: Implications of generic prescription drug wars

OBJECTIVE

To describe the history of generic prescription pricing programs at major pharmacy chains and their potential implications on prescribing, quality of care, and patient safety.

DATA SOURCES

Publicly available generic prescription discount program drug lists as of May 1, 2009.

SUMMARY

Fierce competition among major pharmacy chains such as Walgreens, CVS, and Walmart has led to a generic prescription pricing war with unclear public health implications. Introduced in 2006, currently 7 of the 10 largest pharmacy chains advertise a version of a deeply discounted medication (DDM) program, accounting for more than 25,000 locations nationally. By early 2008, almost 70 million Americans had used these programs. Although DDM programs lower drug costs for many patients, DDM formularies include potentially ineffective or harmful medications, have the potential to influence physician prescribing behavior, and may impair pharmacists' ability to review complete drug-dispensing records.

CONCLUSION

DDMs are widespread but have the potential for unintended consequences on patients, providers, and the health care system. A systematic review of DDMs needs to evaluate the clinical, economic, and system-level implications of such programs.

Angiotensin receptor blockers: role in hypertension management, cardiovascular risk reduction, and nephropathy

BACKGROUND

The renin-angiotensin system (RAS) plays a central pathogenic role in the development of hypertension and associated vascular disorders. However, whether the two main classes of agents that blunt RAS activity-angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs)-yield comparable cardioprotective and renoprotective effects in high-risk patients is controversial.

METHOD

An analysis of several controlled clinical trials provides evidence that, in patients with or without heart failure, ARBs provide protective effects and improvements in prognosis compared with those achieved with ACEIs.

RESULTS

This article describes the critical studies that examine the cardioprotective and renoprotective efficacy of ARBs and identifies the populations and doses at which these agents are most effective.

DISCUSSION

In the clinical setting, ARBs may be a valuable alternative to ACEI therapy. Because of their tolerability profile, ARBs or ARB combination therapy may be an option for patients susceptible to ACEI-related adverse events.

Age-dependent differential crosstalk between alpha(1)-adrenergic and angiotensin receptors

BACKGROUND

Previous reports of crosstalk between alpha(1)- adrenergic receptors (alpha(1)-AR) and angiotensin receptors (ATR) have pointed to the existence of physiological regulation between the sympathetic nervous system and the renin-angiotensin system at the receptor level. This regulation may have an important role in the control of blood pressure and may be modified in different cardiovascular pathologies. Aging is considered to be an independent cardiovascular risk factor. Nevertheless, neither the variation in physiological action or interaction of signal transduction between these two receptors as a result of aging has been established. To clarify these aspects, the interaction between alpha(1)-AR and ATR was evaluated.

METHODS

The inotropic response of alpha(1)-AR to agonists was assessed in the presence and absence of angiotensin II using the left atria of 3.5-, 12-, 18- and 24-month-old (young adult, middle aged, elderly and aged, respectively) male Wistar rats. In the four age groups of rat hearts, the activities of tyrosine kinase were measured when just the AT(1)R subtype was activated, or when both alpha(1)-AR and AT(1)R were activated. The activities of cytosolic phospholipase A(2) and the levels of cyclic GMP were investigated when just the AT(2)R subtype was activated, or when both alpha(1)-AR and AT(2)R were activated.

RESULTS

No effect was found on the cumulative concentration-response curve for phenylephrine when AT(1)R was activated in 3.5- or 12-month-old rats. However, in 18- and 24-month-old rats, the maximum positive inotropic response and the negative logarithm of the effective 50% concentration increased markedly. No effect was found on the cumulative concentration response curve induced by phenylephrine when AT(2)R was activated. The activities of tyrosine kinase increased significantly in 3.5- and 12-month-old rats, but there was no difference in 18- and 24-month-old rats when alpha(1)-AR and AT(1)R were both activated compared with when just AT(1)R was activated. Cytosolic phospholipase A(2) activity and cyclic GMP levels decreased significantly when both alpha(1)-AR and AT(2)R were activated compared with when just AT(2)R was activated.

CONCLUSIONS

In the isolated left atria of elderly and aged rats, the activation of AT(1)R enhanced the positive inotropic response induced by the activation of alpha(1)-AR. The activation of AT(2)R had no effect on the positive inotropic response induced by the activation of alpha(1)-AR. The action of alpha(1)-AR increased the signal transduction of AT(1)R in young-adult and middle-aged rat hearts but had no effect in elderly and aged hearts. The action of alpha(1)-AR had no effect on AT(2)R signal transduction.

Association between renin-angiotensin-aldosterone system genotypes and haplotypes and risk of ischemic stroke of atherosclerotic etiology

OBJECTIVE

The association of renin C-4063T and angiotensinogen (AGT) T174M, AGT M235T and AGT A-6G polymorphisms with ischemic stroke of atherosclerotic etiology was investigated in 329 Tunisian patients with stroke and 444 controls.

MATERIALS AND METHODS

Genotyping was performed using PCR-RFLP and the contributions of polymorphisms to the risk of stroke were analyzed using haplotype and multivariate regression analysis.

RESULTS

AGT 235T and AGT-6G allele and AGT 235T/T, AGT-6A/G and AGT-6G/G genotype frequencies were higher in patients. Linkage disequilibrium (LD) was noted for AGT174T with AGT235M and AGT(-6)A in patients, while AGT235M was in LD with AGT(-6)A in controls and AGT235T was in LD with AGT(-6)G in both groups. The AGT 174T/235T/-6A and AGT 174T/235M/-6G haplotypes were positively and negatively associated with stroke respectively. Multivariate regression analysis identified AGT 174T/235M/-6A, AGT 174T/235T/-6G, AGT 174T/235T/-6A and AGT 174M/235T/-6A haplotypes to be significantly associated with an increased risk of stroke.

CONCLUSIONS

Renin-angiotensin-aldosterone system polymorphisms influence the risk of atherosclerotic stroke in Tunisians.

Angiotensin II type-2 (AT2) receptor antagonism alters cardiovascular responses to static exercise and simultaneously changes glutamate/GABA levels within the ventrolateral medulla

Angiotensin II receptors (Ang II), classified into AT1 and AT2 subtypes, are located in different regions of the central nervous system, including the cardiovascular control centers in the medulla oblongata. We previously reported the role of Ang II AT1 receptors within the medulla on cardiovascular responses and glutamate/GABA neurotransmission during the exercise pressor reflex [Patel, D., Böhlke, M., Phattanarudee, S., Kabadi, S., Maher, T.J., Ally, A., 2008. Cardiovascular responses and neurotransmitter changes during blockade of angiotensin II receptors within the ventrolateral medulla. Neurosci. Res. 60 (3), 340-348]. In this study, we investigated the role of the AT2 receptor subtype within the ventrolateral medullary region (VLM) in modulating increases in mean arterial pressure (MAP) and heart rate (HR) in response to static skeletal muscle contraction.

METHODS

Using microdialysis methods in anesthetized rats, we administered AR-AT2 antagonists into the rostral (RVLM) and caudal (CVLM) VLM and determined its effects on cardiovascular responses and glutamate/GABA neurotransmission following muscle contraction. Bilateral microdialysis of a selective AT2 antagonist, PD 123319 (10 microM), for 30 min into the RVLM augmented MAP and HR responses during a static muscle contraction. Simultaneously, the drug increased glutamate and decreased GABA levels within the RVLM. After 60 min of discontinuation of the drug, only MAP and HR values but not the neurotransmitter levels in response to a muscle contraction returned to baseline. In contrast, bilateral microdialysis of the drug into the CVLM attenuated cardiovascular responses during a static muscle contraction, decreased glutamate and increased GABA. However, only the cardiovascular responses recovered after 60 min of discontinuation of the drug. These results demonstrate that AT2 within both RVLM and CVLM plays important differential roles in modulating neurotransmission and cardiovascular function during the exercise pressor reflex.

ACE-inhibitor, AT1-receptor-antagonist, or both? A clinical pharmacologist's perspective after publication of the results of ONTARGET

Clinical Pharmacology is commonly accepted to be a bridging discipline between basic science observations and clinical practice. Today, it should be a major task of the clinical pharmacologist in academia to provide support in the interpretation of preclinical and clinical study data, to develop evidence-based treatment guidelines and to serve as drug expert supporting all disciplines of clinical medicine with specific pharmacological and therapeutic knowledge. The results of the ONTARGET-trial confront both researchers and clinicians with the unexpected truth that AT(1)-receptor-blockade with an angiotensin-receptor-blocker (ARB) does not seem to have superior therapeutic benefit compared with an ACE-inhibitor (ACE-I) at reducing fatal and nonfatal cardiovascular events. The combination of the two drugs was associated with more adverse events without an increase in benefit. Therefore, the crucial question 'ACE-I, ARB, or both?' requires a new and critical appraisal depending on the medical indication for which these renin-angiotensin-system (RAS)-inhibitors are used: In a population of high-risk patients suffering from cardiovascular disease or diabetes mellitus, the evidence to favor an ARB over an ACE-I is still limited after ONTARGET and because of the higher costs for ARBs one can rather support the old therapeutic advice that ARBs are equally effective as ACE-Is and therefore therapeutic alternatives for patients with ACE-I intolerance. With respect to a very moderate additive BP-lowering effect of dual therapy with an ACE-I and an ARB seen in metaanalysis which was not even clearly attributable to dual RAS-inhibition and the increased adverse event rate in the combination treatment group of ONTARGET, this regimen seems not to be recommendable for the treatment of hypertension. Dual-RAS-blockade using an ACE-I-ARB-combination is an effective therapy to treat proteinuria and might be of therapeutic benefit especially in diabetic patients without concomitant diseases. There may be a therapeutic rationale to prefer ARBs over ACE-Is in well-selected patients with congestive heart failure (CHF) because a considerable amount of angiotensin II (Ang II) is produced independent of angiotensin-conversion-enzyme (ACE) in the failing heart and is therapeutically unaffected by ACE-I treatment. The results of the Val-HeFt and the CHARM-added-study revealed additive effects of an ARB on heart failure related morbidity and mortality when added to existing therapy with an ACE-I suggesting a role for ACE-I-ARB-combination treatment in well selected heart failure patients. Independent of the medical indication for its use, the concept of dual RAS-blockade with an ARB-ACE-I-combination should clinically be used with caution and a close monitoring of potassium levels and kidney function. Although the results of ONTARGET revealed equity of ramipril and telmisartan at reducing fatal and nonfatal cardiovascular events, we should not forget that pharmacologically not all ARBs are the same and the question if the study results of ONTARGET with telmisartan are transferable to the complete class of ARBs still merits further investigation.

Oral heart failure medications: an update for home health clinicians

Heart failure in the United States is a growing epidemic, with approximately 550,000 new cases per year. An increasing number of patients are treated at home with drugs that require a working knowledge of both the syndrome and the various therapeutic agents in use. New understanding of the syndrome has led to a paradigm shift from treating signs and symptoms to increasing long-term survival. This article focuses on the syndrome as it relates to common agents prescribed for the patient in the home setting.

Perinatal 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure sensitizes offspring to angiotensin II-induced hypertension

In utero and lactational exposure of mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to cardiac hypertrophy and hydronephrosis in adulthood. We tested the hypothesis that perinatal TCDD exposure increases the susceptibility to cardiovascular disease when offspring are exposed to a common cardiovascular disease risk factor, angiotensin II (Ang II). Pregnant C57BL/6N mice were exposed to corn oil (control) or 6.0 microg/kg TCDD on gestation day 14.5. Male offspring were then exposed to a subpressor (0.1 mg/kg/day) or pressor (0.7 mg/kg/day) dose of Ang II at 3.5 months and cardiac morphology and blood pressure analyzed, respectively. Perinatal TCDD exposure increased left ventricular cavity dilation during diastole, and wall thickness during diastole and systole. While Ang II stimulated an increase in wall thickness, the degree of increase was equivalent between control and TCDD offspring. In contrast, perinatal TCDD exposure did not alter basal blood pressure. However, Ang II increased systolic blood pressure more rapidly and to a greater degree in TCDD offspring. Further, Ang II stimulated renal myofibroblast differentiation and collagen deposition to a greater degree, and tended to increase procollagen I mRNA in TCDD offspring, compared to controls. These data suggest that perinatal TCDD exposure increases the susceptibility of offspring to renal fibrosis and hypertension in adulthood.

Cytochrome P450 and gene activation--from pharmacology to cholesterol elimination and regression of atherosclerosis

BACKGROUND

Lipoproteins are closely associated with the atherosclerotic vascular process. Elevated levels of high-density lipoprotein cholesterol (HDL-C) and apolipoprotein AI (apo AI) in plasma indicate a low probability of coronary heart disease (CHD) together with enhanced longevity, and elevated levels of low-density lipoprotein-cholesterol (LDL-C) and apo B indicate an increased risk of CHD and death. Studies linking gene activation and the induction of cytochrome P450 with elevated plasma levels of apo AI and HDL-C and lowered plasma levels of LDL-C presented a new potential approach to prevent and treat atherosclerotic disease.

OBJECTIVE AND METHODS

This is a review aimed at clarifying the effects of P450-enzymes and gene activation on cholesterol homeostasis, the atherosclerotic vascular process, prevention and regression of atherosclerosis and the manifestation of atherosclerotic disease, particularly CHD, the leading cause of death in the world.

RESULTS

P450-enzymes maintain cellular cholesterol homeostasis. They respond to cholesterol accumulation by enhancing the generation of hydroxycholesterols (oxysterols) and activating cholesterol-eliminating mechanisms. The CYP7A1, CYP27A1, CYP46A1 and CYP3A4 enzymes generate major oxysterols that enter the circulation. The oxysterols activate-via nuclear receptors-ATP-binding cassette (ABC) A1 and other genes, leading to the elimination of excess cholesterol and protecting arteries from atherosclerosis. Several drugs and nonpharmacologic compounds are ligands for the liver X receptor, pregnane X receptor and other receptors, activate P450 and other genes involved in cholesterol elimination, prevent or regress atherosclerosis and reduce cardiovascular events.

CONCLUSIONS

P450-enzymes are essential in the physiological maintenance of cholesterol balance. They activate mechanisms which eliminate excess cholesterol and counteract the atherosclerotic process. Several drugs and nonpharmacologic compounds induce P450 and other genes, prevent or regress atherosclerosis and reduce the occurrence of non-fatal and fatal CHD and other atherosclerotic diseases.

Review: The therapeutic role of RAS blockade in chronic heart failure

Cardiovascular disease represents a continuum that starts with risk factors such as hypertension and progresses to atherosclerosis, end-organ damage, and ultimately to chronic heart failure (CHF) and premature death. Renin-angiotensin system (RAS) blockade with angiotensin converting enzyme (ACE) inhibitors and/or angiotensin II type 1 receptor blockers (ARBs) has turned out to be beneficial at all stages of this continuum. Several mechanisms govern the progression of structural myocardial damage to end-stage CHF. Chronic neuroendocrine activation fosters left ventricular remodeling and dilatation and leads to clinical symptoms of CHF via forward/backward failure. RAS inhibition is a cornerstone of neuroendocrine blockade in CHF patients, and combined RAS blockade is especially effective in patients presenting with repetitive cardiac decompensations. This review focuses on the therapeutic role of inhibitors of different RAS components in chronic heart failure caused by systolic left ventricular dysfunction.

Cardiovascular responses and neurotransmitter changes during blockade of angiotensin II receptors within the ventrolateral medulla

Angiotensin II (Ang II) receptors are located in different regions of the brain, particularly within the cardiovascular control centers in the brainstem. These Ang II receptors are divided into AT1 and AT2 subtypes. We investigated the role of AT1 receptor subtype within the rostral (RVLM) and caudal (CVLM) ventrolateral medulla on cardiovascular responses and glutamate/GABA neurotransmission during static exercise using microdialysis in anesthetized rats. Bilateral microdialysis of a selective AT1 receptor antagonist, ZD7155 (10 microM), for 30 min into the RVLM attenuated increases in mean arterial pressure (MAP) and heart rate (HR) during a static muscle contraction. Glutamate concentrations within the RVLM decreased while GABA levels increased simultaneously during the contraction period when compared to those before ZD7155. After 60 min of discontinuation of ZD7155, MAP, HR, glutamate, and GABA levels in response to another muscle contraction returned to baseline levels. Conversely, bilateral microdialysis of ZD7155 into the CVLM potentiated cardiovascular responses during a static muscle contraction; glutamate concentrations increased while GABA levels within the CVLM decreased. All responses recovered after 60 min of discontinuation of ZD7155. These results demonstrate that medullary AT1 receptors play an important role in modulating both neurotransmission and cardiovascular function during static exercise.