Controlled evaLuation of Angiotensin Receptor Blockers for COVID-19 respIraTorY disease (CLARITY): statistical analysis plan for a randomised controlled Bayesian adaptive sample size trial

The CLARITY trial (Controlled evaLuation of Angiotensin Receptor Blockers for COVID-19 respIraTorY disease) is a two-arm, multi-centre, randomised controlled trial being run in India and Australia that investigates the effectiveness of angiotensin receptor blockers in addition to standard care compared to placebo (in Indian sites) with standard care in reducing the duration and severity of lung failure in patients with COVID-19. The trial was designed as a Bayesian adaptive sample size trial with regular planned analyses where pre-specified decision rules will be assessed to determine whether the trial should be stopped due to sufficient evidence of treatment effectiveness or futility. Here, we describe the statistical analysis plan for the trial and define the pre-specified decision rules, including those that could lead to the trial being halted. The primary outcome is clinical status on a 7-point ordinal scale adapted from the WHO Clinical Progression scale assessed at day 14. The primary analysis will follow the intention-to-treat principle. A Bayesian adaptive trial design was selected because there is considerable uncertainty about the extent of potential benefit of this treatment.

Trial registration

ClinicalTrials.gov NCT04394117. Registered on 19 May 2020Clinical Trial Registry of India CTRI/2020/07/026831

Version and revisions

Version 1.0. No revisions.

No dynamic changes in plasma ACE2 activity in patients with acute coronary syndrome

Background

Angiotensin converting enzyme 2 (ACE2) is expressed in the human myocardium and blood vessels and degrades the vasoconstrictor peptide angiotensin (Ang) II. Plasma ACE2 activity is elevated in patients with cardiovascular disease (CVD) and is a predictor of major adverse cardiovascular events (MACE) in obstructive coronary artery disease. However, it is unknown whether acute coronary syndrome (ACS) causes dynamic changes in plasma ACE2 activity.

Purpose

We investigated dynamic changes in serial troponin-T and plasma ACE2 activity in patients presenting with ACS who underwent invasive coronary angiography (ICA).

Methods

Consecutive patients admitted with ACS from October-November 2019 were screened. Those meeting the Fourth Universal Definition of Myocardial Infarction who had both ICA and serial troponin-T testing were included. The study was approved by the hospitals Human Research Ethics Committee. All patients had routine plasma samples taken over 3 time-points for measurement of troponin-T; the same sample was used to measure plasma ACE2 activity. Catalytic ACE2 activity was measured using a validated, sensitive quenched fluorescent substrate-based assay. Serial median troponin and ACE2 activity levels were analysed using the Friedman test for repeated measures.

Results

Forty-nine patients were included. The mean age of participants was 63.9±11.0 years, and 36 (74%) patients were male. Overall, 16 (36%) patients presented with ST-elevation myocardial infarction (STEMI) and 29 (74%) with non-ST-elevation myocardial infarction (NSTEMI). Twenty-nine (59%) patients had a history of hypertension and 14 (29%) a history of ischaemic heart disease; 13 (27%) with priorMI, 11 (22%) had previous PCI and 2 (4%) had prior coronary artery bypass grafting. Over the 3 time points, there was a clear rise in median troponin-T levels representing myocardial injury (p<0.001), with no change in median plasma ACE2 activity (p=0.23, table 1). There was no difference in median ACE2 activity in those presenting with STEMI vs. NSTEMI (6.9 [2.1–9.5] vs. 6.0 [1.8–12.1], p=0.87), nor in those who underwent PCI to a culprit lesion compared to those who did not have a culprit lesion stented (5.8 [0.9–10.5] vs. 7.3 [2.8–14.9], p=0.37).

Conclusions

Patients with ACS had higher plasma ACE2 levels compared to levels previously reported in healthy controls. There were no dynamic changes in ACE2 activity in the setting of ACS, despite a significant rise in troponin-T. These results suggest that plasma ACE2 levels reflect underlying endothelial dysfunction rather than acute myocardial injury or infarction. Studies are now underway to assess if plasma ACE2 activity in ACS predicts MACE.

Funding Acknowledgement

Type of funding sources: None. Table 1

P5740ACE2 activity level is associated with embolic stroke of undetermined source

Background

ACE2 activity levels correlate with adverse left atrial remodelling in patients with atrial fibrillation (AF). Several biochemical and structural markers have been associated with embolic stroke of undetermined source (ESUS). The relationship between ACE2 activity and ESUS is unknown.

Purpose

Randomised controlled trials failed to demonstrate a clear benefit of oral anticoagulation in an unselected ESUS population. As selective use of oral anticoagulation guided by biomarker risk-profiling may benefit these patients, we evaluated the association between ACE2 activity and ESUS.

Methods

This prospective case control study compared patients with ESUS against a control group matched for vascular risk factors. ESUS was diagnosed following cerebral vascular imaging and 24 hours of cardiac monitoring to exclude AF. Blood samples were collected for measurement of ACE2 activity, D-Dimer and high sensitivity troponin T (hsTnT).

Results

A total of 51 patients in the ESUS group were compared with 47 patients in the Control group. ACE2 activity and D-Dimer levels were significantly higher in the ESUS group. There was a significant but weak positive correlation between ACE2 activity and hsTnT (r=0.20, p<0.05). Left atrial volume index (LAVI) on echocardiography was significantly higher in the ESUS group. On regression modelling adjusting for LAVI, only ACE2 activity remained significant for ESUS, with a 20% rise in odds for every 4 unit increase in ACE2 activity (OR 1.20; 95% CI: 1.01 - 1.36, p=0.04).

Participant characteristics Control (n=47) ESUS (n=51) P value Age (years) 65.65±6.78 67.20±6.89 0.26 Female gender 22 (45.8) 19 (38.0) 0.43 Hypertension 22 (45.8) 24 (48.0) 0.83 Diabetes mellitus 9 (18.8) 12 (24.0) 0.53 CHA2DS2VASc score 2 (1–3) 2 (1–3) 0.50 LA size & Biomarkers   LA volume index (ml/m2) 36.5 (32.6–42.5) 39.1 (36.2–46.0) 0.04   ACE2 (pmol/ml/min) 7.24 (2.66–14.64) 10.16 (4.54–18.80) 0.04   D-Dimer (mg/L) 0.35 (0.3–0.5) 0.40 (0.30–0.60) 0.02   hsTroponin T (ng/L) 7.0 (5–10) 9.00 (6.0–13.5) 0.05 Values are expressed as mean ± standard deviation, median (IQR), or n (%).

Median ACE2 activity

Conclusion(s)

ACE2 activity is associated with ESUS independent of left atrial volume and correlate with elevated Troponin. Further studies are warranted to investigate the utility of ACE2 activity in identifying ESUS patients that may benefit from oral anticoagulation.

Acknowledgement/Funding

This study received project funding from the Eastern Health Foundation

Left ventricular hypertrophy and cognitive function: a systematic review

Cognitive impairment is common in patients with hypertension. Left ventricular hypertrophy (LVH) is recognised as a marker of hypertension-related organ damage and is a strong predictor of coronary artery disease, heart failure and stroke. There is evidence that LVH is independently associated with cognitive impairment, even after adjustment for the presence of hypertension. We conducted a systematic review that examined cognitive impairment in adults with LVH. Independent searches were performed in Ovid MEDLINE, Ovid psycInfo and PubMed with the terms left ventricular hypertrophy and cognition. Seventy-three studies were identified when both searches were combined. After limiting the search to studies that were: (1) reported in English; (2) conducted in humans; (3) in adults aged 50 years and older; and (4) investigated the relationship between LVH and cognitive performance, nine papers were included in this systematic review. The majority of studies found an association between LVH and cognitive performance. Inspection of results indicated that individuals with LVH exhibited a lower performance in cognitive tests, when compared to individuals without LVH. Memory and executive functions were the cognitive domains that showed a specific vulnerability to the presence of LVH. A possible mechanism for the relationship between LVH and cognition is the presence of cerebral white matter damage. White matter lesions occur frequently in patients with LVH and may contribute to cognitive dysfunction. Together, the results of this review suggest that memory impairment and executive dysfunction are the cognitive domains that showed a particular association with the presence of LVH.

Beta-blockers are under-prescribed in patients with chronic obstructive pulmonary disease and co-morbid cardiac disease

The use of beta-blockers in patients with chronic obstructive pulmonary disease and co-morbid cardiovascular disease is controversial, despite increasing evidence to support their use as safe and efficacious. This study retrospectively assessed the rates of beta-blocker prescription in patients admitted to two Australian tertiary hospitals for acute exacerbation of chronic obstructive pulmonary disease. This revealed that less than half of patients (45%) with known cardiac indications were receiving beta-blocker therapy, evident across all degrees of airways disease severity. Further work is needed to ensure that medical management of this patient group is optimised.

Age adjusted Charlson Co-morbidity Index is an independent predictor of mortality over long-term follow-up in infective endocarditis

BACKGROUND

Infective endocarditis (IE) is associated with high morbidity and mortality. The epidemiology of IE is changing, affecting more elderly patients with increased medical comorbidities. We aimed to assess the ability of the age adjusted Charlson Co-morbidity Index (ACCI) to predict early and late outcomes.

METHODS

Between 1998 and 2010, adult patients with definite IE according to the modified Duke criteria were identified. The primary outcome was in-hospital and all-cause mortality. The secondary outcome was predictors of the primary outcome incorporating ACCI.

RESULTS

148 patients with IE were followed up for a mean of 3.8 ± 3 years. The mean age was 57 ± 17 years and 66% were male. In-hospital mortality and all-cause mortality were 24 and 47% respectively. Comorbid conditions included diabetes mellitus (DM) (21%); ischaemic heart disease (16%); heart failure (HF) (14%); renal failure (eGFR <60 ml/min/1.73 m(2)) (19%); and anaemia (64%). The most common causative organism was Staphylococcus aureus (53%). ACCI was >3 in 59% of patients. Cardiac surgery was performed in 45% of patients. On Cox regression analysis, ACCI >3 (HR=3.0 [1.5-6.0], p<0.002), new onset HF (HR=2.2 [1.3-3.6], p<0.003), anaemia (HR=1.8 [1.1-3.2], p=0.04) and age-per decade (HR=1.4 [1.1-1.7]. p=0.004) were independently associated with all-cause mortality. ACCI >3 was the strongest predictor of in-hospital mortality (OR=8.4 [2.8-24], p<0.001). Of the individual ACCI components, prior HF, DM with complications and metastatic disease were independent predictors of all-cause mortality.

CONCLUSION

In-hospital and all-cause mortality of IE remain high. An ACCI >3 was a strong predictor of mortality, in addition to age, new HF and anaemia.

Global longitudinal strain is a strong independent predictor of all-cause mortality in patients with aortic stenosis

AIMS

To assess the capacity of global longitudinal strain (GLS) in patients with aortic stenosis (AS) to (i) detect the subclinical left ventricular (LV) dysfunction [LV ejection fraction (LVEF) ≥50% patients]; (ii) predict all-cause mortality and major adverse cardiac events (MACE) (all patients), and (iii) provide incremental prognostic information over current risk markers.

METHODS AND RESULTS

Patients with AS (n = 146) and age-matched controls (n = 12) underwent baseline echocardiography to assess AS severity, conventional LV parameters and GLS via speckle tracking echocardiography. Baseline demographics, symptom severity class and comorbidities were recorded. Outcomes were identified via hospital record review and subject/physician interview. The mean age was 75 ± 11, 62% were male. The baseline aortic valve (AV) area was 1.0 ± 0.4 cm(2) and LVEF was 59 ± 11%. In patients with a normal LVEF (n = 122), the baseline GLS was controls -21 ± 2%, mild AS -18 ± 3%, moderate AS -17 ± 3% and severe AS -15 ± 3% (P< 0.001). GLS correlated with the LV mass index, LVEF, AS severity, and symptom class (P< 0.05). During a median follow-up of 2.1 (inter-quartile range: 1.8-2.4) years, there were 20 deaths and 101 MACE. Unadjusted hazard ratios (HRs) for GLS (per %) were all-cause mortality (HR: 1.42, P< 0.001) and MACE (HR: 1.09, P< 0.001). After adjustment for clinical and echocardiographic variables, GLS remained a strong independent predictor of all-cause mortality (HR: 1.38, P< 0.001).

CONCLUSIONS

GLS detects subclinical dysfunction and has incremental prognostic value over traditional risk markers including haemodynamic severity, symptom class, and LVEF in patients with AS. Incorporation of GLS into risk models may improve the identification of the optimal timing for AV replacement.

A comparison of precipitants and mortality when acute decompensated heart failure occurs in the community and hospital settings

AIM

We aimed to compare the precipitants of acute decompensated heart failure (ADHF) among patients admitted with diagnoses inclusive of ADHF (community patients) and patients admitted without ADHF but who developed it during their stay (hospital patients).

METHODS

This was a prospective, analytical, observational study undertaken in the Austin Hospital, a major metropolitan teaching hospital (September 2008-February 2010). Consecutive patients admitted to a general medicine unit, and diagnosed and treated for ADHF were enrolled. The unit medical staff completed a specifically designed data collection document.

RESULTS

Three hundred and fifty-nine patients were enrolled (42.9% male, mean age 81.9 years). The community (n=312) and hospital (n=47) patient groups did not differ in age, gender, risk variables (living alone, cognitive impairment, multiple medications, compliance), cardiac failure medication use or cause of known heart failure (ischaemia, hypertension, valve dysfunction, 'other') (p>0.05). The ADHF precipitants comprised infection (39.8% patients), myocardial ischaemia (17.3%), tachyarrhythmia (16.2%), non-compliance with fluid and salt restriction (9.2%), non-compliance with medication (6.7%), renal failure (5.8%), medication reduction (5.0%), intravenous fluid complication (3.9%) and 'other' causes (13.9%). Significantly more hospital patients had their ADHF precipitated by intravenous fluid complications (25.5% versus 0.6%, p<0.001). Hospital patients also had a significantly greater death rate (25.5% versus 9.3%, p<0.01).

CONCLUSION

Acute decompensated heart failure precipitated in hospital is a dangerous condition with a high mortality. While infection and myocardial ischaemia are the common precipitants, complications of intravenous fluid use, an iatrogenic condition, may be considerable and are potentially avoidable.

Progression of aortic stenosis in elderly patients over long-term follow up

BACKGROUND

The natural history of aortic stenosis (AS) in elderly patients remains poorly defined. In an elderly cohort over long-term follow-up, we assessed: 1) rates and predictors of hemodynamic progression and 2) composite aortic valve replacement (AVR) or death endpoint.

METHODS

Consecutive Department of Veterans' Affairs patients with AS (>60 years) were prospectively enrolled between 1988 and 1994 (n=239) and followed until 2008. Patients with ≥ 2 trans-thoracic echocardiograms >6 months apart were included in the progression analysis (n=147). Baseline demographics, comorbidities and echocardiography parameters were recorded. Follow-up was censored at AVR/death.

RESULTS

The age of patients was 73 ± 6 years; 82% were male. Baseline AS severity was mild (67%), moderate (23%) and severe (10%). Follow-up was 6.5 ± 4 years (range: 1-17 years). Annualized mean aortic valve gradient progression rates were: mild AS 4 ± 4 mmHg/year; moderate AS 6 ± 5 mmHg/year and severe AS 10 ± 8 mmHg/year (p<0.001). Five-year event-free survival was 66 ± 5%, 23 ± 7% and 20 ± 10% for mild, moderate and severe AS respectively. Progression to severe AS occurred in 35% and 74% of patients with mild and moderate AS respectively. Independent predictors of rapid progression were: baseline AS severity (per grade) (OR 2.6, p=0.001), aortic valve calcification (per grade) (OR 2.1, p=0.01), severe renal impairment (OR 4.0, p=0.04) and anemia (OR 2.3, p=0.05).

CONCLUSIONS

In elderly patients, hemodynamic progression of AS is predicted by AS severity, renal function, aortic valve calcification and history of anemia. These factors identify patients at high risk of rapid hemodynamic progression, for whom more frequent clinical and echocardiographic surveillance is advisable.

Review article: the pathophysiological roles of the renin-angiotensin system in the gastrointestinal tract

BACKGROUND

The renin-angiotensin system (RAS) is a homeostatic pathway widely known to regulate cardiovascular and renal physiology; however, little is known about its influence in gastrointestinal tissues.

AIM

To elicit the anatomical distribution and physiological significance of the components of the RAS in the gastrointestinal tract.

METHODS

An extensive online literature review including Pubmed and Medline.

RESULTS

There is evidence for RAS involvement in gastrointestinal physiology and pathophysiology, with all the components required for autonomous regulation identified throughout the gastrointestinal tract. The RAS is implicated in the regulation of glucose, amino acid, fluid and electrolyte absorption and secretion, motility, inflammation, blood flow and possibly malignant disease within the gastrointestinal tract. Animal studies investigating the effects of RAS blockade in a range of conditions including inflammatory bowel disease, functional gut disorders, gastrointestinal malignancy and even intestinal ischaemia have been encouraging to date. Given the ready availability of drugs that modify the RAS and their excellent safety profile, an opportunity exists for investigation of their possible therapeutic role in a variety of human gastrointestinal diseases.

CONCLUSIONS

The gastrointestinal renin-angiotensin system appears to be intricately involved in a number of physiological processes, and provides a possible target for novel investigative and therapeutic approaches.

Chronic kidney disease: cardiac and renal angiotensin-converting enzyme (ACE) 2 expression in rats after subtotal nephrectomy and the effect of ACE inhibition

Renin-angiotensin system blockade slows but does not prevent the cardiovascular complications of chronic kidney disease (CKD). Angiotensin-converting enzyme (ACE) 2 is differentially regulated in acute kidney injury, with increased cardiac ACE2 but decreased kidney ACE2 levels. This study investigated the effect of long-term ACE inhibition on cardiac and renal ACE2 in rats with CKD induced by subtotal nephrectomy (STNx). Sprague-Dawley rats had sham (control) or STNx surgery. Control rats received vehicle (n = 9) and STNx rats ramipril (1 mg kg(-1) day(-1); n = 10) or vehicle (n = 10) for 28 days. Subtotal nephrectomy resulted in impaired creatinine clearance (P < 0.05), proteinuria (P < 0.05), renal fibrosis (P < 0.05) and reduced renal cortical ACE2 mRNA (P < 0.05) and activity (P < 0.05). In rats with CKD, ramipril improved creatinine clearance (P < 0.05) and was associated with an increase in cortical but not medullary ACE2 activity (P < 0.05). Compared with control rats, STNx rats were hypertensive (P < 0.01), with increased left ventricular end-diastolic pressure (LVEDP; P < 0.01), left ventricular hypertrophy (LVH; P < 0.05) and interstitial (P < 0.05) and perivascular fibrosis (P < 0.01). In rats with CKD, ramipril decreased blood pressure (P < 0.001) and reduced LVEDP (P < 0.01), LVH (P < 0.01) and perivascular fibrosis (P < 0.05) but did not significantly reduce interstitial fibrosis. There was no change in cardiac ACE2 in rats with CKD compared with control rats. In rats with CKD, ACE inhibition had major benefits to reduce blood pressure and cardiac hypertrophy and to improve creatinine clearance, but did not significantly impact on cardiac ACE2, cardiac interstitial fibrosis, renal fibrosis or proteinuria. Thus, in rats with CKD, renal ACE2 deficiency and lack of activation of cardiac ACE2 may contribute to the progression of cardiac and renal tissue injury. As long-term ACE inhibition only partly ameliorated the adverse cardio-renal effects of CKD, adjunctive therapies that lead to further increases in ACE2 activity may be needed to combat the cardio-renal complications of CKD.

Angiotensin II mediates epithelial-to-mesenchymal transformation in tubular cells by ANG 1-7/MAS-1-dependent pathways

Epithelial-to-mesenchymal transformation (EMT) of tubular cells into a myofibroblastic phenotype is an important mediator of renal scarring in chronic nephropathy. This study examines the role of the renin-angiotensin system (RAS) in this process. NRK-52E cells were exposed to angiotensin (ANG) II and ANG 1-7 in the presence or absence of inhibitors and agonists of RAS signaling. EMT was assessed at 3 days by expression of alpha-smooth muscle actin (alpha-SMA) and E-cadherin and the induction of a myofibroblastic phenotype. Expression of fibrogenic growth factors and matrix proteins was assessed by RT-PCR and immunofluorescence microscopy. To confirm findings in vivo, rats were also infused with ANG 1-7 (24 microg*kg(-1)*h(-1)) or saline via an osmotic minipump for 10 days, and renal fibrogenesis was then assessed. Treatment of NRK-52E cells with ANG II induced characteristic changes of EMT. Selective blockade of the AT(1) receptor or the AT(2) receptor failed to inhibit ANG II-induced EMT. However, blockade of the ANG 1-7 receptor, Mas-1, was able to prevent ANG II-dependent EMT. To confirm these findings, both ANG 1-7 and the selective Mas receptor agonist, AVE-0991, were able to induce NRK-52E cells in a dose-dependent manner. Exposing cells to recombinant ACE2 was also able to induce EMT. In addition, an infusion of ANG 1-7 induced the tubular expression of alpha-SMA and the expression of matrix proteins in the kidney. ANG II is a potent stimulus for EMT, but not through conventional pathways. This study points to the possible limitations of conventional RAS blockade, which not only fails to antagonize this pathway, but also may enhance it via augmenting the synthesis of ANG 1-7.

ACE2 and AT4R are present in diseased human blood vessels

A growing body of evidence suggests that the angiotensin II fragments, Ang(1-7) and Ang(3-8), have a vasoactive role, however ACE2, the enzyme that produces Ang(1-7), or AT4R, the receptor that binds Ang (3-8), have yet been simultaneously localised in both normal and diseased human conduit blood vessels. We sought to determine the immunohistochemical distribution of ACE2 and the AT4R in human internal mammary and radial arteries from patients undergoing coronary artery bypass surgery. We found that ACE2 positive cells were abundant in both normal and diseased vessels, being present in neo-intima and in media. ACE2 positive immunoreactivity was not present in the endothelial layer of the conduit vessels, but was clearly evident in small newly formed angiogenic vessels as well as the vaso vasorum. Endothelial AT4R immunoreactivity were rarely observed in either normal and diseased arteries, but AT4R positive cells were observed adjacent to the internal elastic lamine in the internal mammary artery, in the neo-intima of radial arteries, as well as in the media of both internal mammary artery and radial artery. AT4R was abundant in vaso vasorum and within small angiogenic vessels. Both AT4R and ACE2 co-localised with smooth muscle cell alpha actin. This study identifies smooth muscle cell alpha actin positive ACE2 and AT4R in human blood vessels as well as in angiogenic vessels, indicating a possible role for these enzymes in pathological disease.

Acute kidney injury in the rat causes cardiac remodelling and increases angiotensin-converting enzyme 2 expression

Patients with kidney failure are at high risk of a cardiac death and frequently develop left ventricular hypertrophy (LVH). The mechanisms involved in the cardiac structural changes that occur in kidney failure are yet to be fully delineated. Angiotensin-converting enzyme (ACE) 2 is a newly described enzyme that is expressed in the heart and plays an important role in cardiac function. This study assessed whether ACE2 plays a role in the cardiac remodelling that occurs in experimental acute kidney injury (AKI). Sprague-Dawley rats had sham (control) or subtotal nephrectomy surgery (STNx). Control rats received vehicle (n = 10), and STNx rats received the ACE inhibitor (ACEi) ramipril, 1 mg kg(-1) day(-1) (n = 15) or vehicle (n = 13) orally for 10 days after surgery. Rats with AKI had polyuria (P < 0.001), proteinuria (P < 0.001) and hypertension (P < 0.001). Cardiac structural changes were present and characterized by LVH (P < 0.001), fibrosis (P < 0.001) and increased cardiac brain natriuretic peptide (BNP) mRNA (P < 0.01). These changes occurred in association with a significant increase in cardiac ACE2 gene expression (P < 0.01) and ACE2 activity (P < 0.05). Ramipril decreased blood pressure (P < 0.001), LVH (P < 0.001), fibrosis (P < 0.01) and BNP mRNA (P < 0.01). These changes occurred in association with inhibition of cardiac ACE (P < 0.05) and a reduction in cardiac ACE2 activity (P < 0.01). These data suggest that AKI, even at 10 days, promotes cardiac injury that is characterized by hypertrophy, fibrosis and increased cardiac ACE2. Angiotensin-converting enzyme 2, by promoting the production of the antifibrotic peptide angiotensin(1-7), may have a cardioprotective role in AKI, particularly since amelioration of adverse cardiac effects with ACE inhibition was associated with normalization of cardiac ACE2 activity.

Chronic liver injury in rats and humans upregulates the novel enzyme angiotensin converting enzyme 2

BACKGROUND

Angiotensin converting enzyme (ACE) 2 is a recently identified homologue of ACE that may counterregulate the actions of angiotensin (Ang) II by facilitating its breakdown to Ang 1-7. The renin-angiotensin system (RAS) has been implicated in the pathogenesis of cirrhosis but the role of ACE2 in liver disease is not known.

AIMS

This study examined the effects of liver injury on ACE2 expression and activity in experimental hepatic fibrosis and human cirrhosis, and the effects of Ang 1-7 on vascular tone in cirrhotic rat aorta.

METHODS

In sham operated and bile duct ligated (BDL) rats, quantitative reverse transcriptase-polymerase chain reaction was used to assess hepatic ACE2 mRNA, and western blotting and immunohistochemistry to quantify and localise ACE2 protein. ACE2 activity was quantified by quenched fluorescent substrate assay. Similar studies were performed in normal human liver and in hepatitis C cirrhosis.

RESULTS

ACE2 mRNA was detectable at low levels in rat liver and increased following BDL (363-fold; p < 0.01). ACE2 protein increased after BDL (23.5-fold; p < 0.05) as did ACE2 activity (fourfold; p < 0.05). In human cirrhotic liver, gene (>30-fold), protein expression (97-fold), and activity of ACE2 (2.4 fold) were increased compared with controls (all p < 0.01). In healthy livers, ACE2 was confined to endothelial cells, occasional bile ducts, and perivenular hepatocytes but in both BDL and human cirrhosis there was widespread parenchymal expression of ACE2 protein. Exposure of cultured human hepatocytes to hypoxia led to increased ACE2 expression. In preconstricted rat aorta, Ang 1-7 alone did not affect vascular tone but it significantly enhanced acetylcholine mediated vasodilatation in cirrhotic vessels.

CONCLUSIONS

ACE2 expression is significantly increased in liver injury in both humans and rat, possibly in response to increasing hepatocellular hypoxia, and may modulate RAS activity in cirrhosis.

Thiazolidinediones and congestive heart failure--exacerbation or new onset of left ventricular dysfunction?

BACKGROUND

Patients with diabetes mellitus have a high incidence of coronary heart disease and congestive heart failure (CHF). Thiazolidinediones (TZD) are a new class of pharmacological agents for the treatment of Type 2 diabetes mellitus, which have many beneficial cardiovascular effects. Peripheral oedema and weight gain have been reported in 4.8% of subjects on TZDs alone, with a higher incidence noted in those receiving combination insulin therapy (up to 15%), but there is limited data on the occurrence of CHF.

METHODS AND RESULTS

In this paper, we report on six cases of TZD-induced fluid retention with symptoms and signs of peripheral oedema and/or CHF that occurred in subjects attending our diabetic clinic. The predominant finding in all cases was of diastolic dysfunction. All subjects were obese and hypertensive, with 5/6 having the additional risk factor of LVH, 5/6 subjects had microvascular complications, whilst 3/6 were also on insulin therapy.

CONCLUSION

We suggest that obese, hypertensive diabetics may benefit from echocardiographic screening prior to commencement of TZDs, as these agents may exacerbate underlying undiagnosed left ventricular diastolic dysfunction.

Renoprotective effects of vasopeptidase inhibition in an experimental model of diabetic nephropathy

AIMS

Although ACE inhibitors slow progression of diabetic renal disease, the mortality and morbidity is still high. As other hormonal factors are involved, inhibition of vasopeptidases could further reduce progression. We studied dual inhibition of angiotensin converting enzyme and neutral endopeptidase in a model of progressive diabetic renal injury. The major endpoints were reductions in systemic blood pressure, albuminuria and renal structural injury.

METHODS

Diabetic spontaneously hypertensive rats were treated with the ACE inhibitor perindopril (mg.kg(-1).day(-1)) or the vasopeptidase inhibitor omapatrilat at doses of 10 (oma10) and 40 (oma40) mg.kg(-1).day(-1) for 32 weeks. In vivo ACE and NEP inhibition was quantitated by in vitro autoradiography. Renal structural injury was assessed by measurement of the glomerulosclerotic (GS) index and tubulointerstitial area (TI). The expression of transforming growth factor beta, beta-inducible gene-h3 and nephrin were also quantitated.

RESULTS

Despite a similar reduction in blood pressure by perindopril and oma10, greater attenuation of albuminuria was afforded by oma10, with a complete amelioration observed with oma40. Oma40 lead to a 33% reduction in renal NEP binding and this was associated with less albuminuria and prevention of GS, TI area and overexpression of TGFbeta and betaig-h3. Diabetes-associated reduction in nephrin expression was restored by both drugs.

CONCLUSION/INTERPRETATION

These findings suggest that other vasoactive mechanisms in addition to angiotensin II are important in the prevention of diabetic nephropathy, and that vasopeptidase inhibition might confer an advantage over blockade of the RAS alone in the treatment of diabetic renal disease.

Evidence for cardioprotective, renoprotective, and vasculoprotective effects of vasopeptidase inhibitors in disease

In both the natriuretic peptide and renin-angiotensin systems, peptidases play an important role in the inactivation or activation of the system. Angiotensin-converting enzyme is responsible for the conversion of angiotensin I to angiotensin II, while neutral endopeptidase is one of the pathways involved in the degradation of the natriuretic peptides. The vasopeptidase inhibitors, which simultaneously inhibit neutral endopeptidase and angiotensin-converting enzyme, appear to offer distinct therapeutic advantages in treating hypertension, heart failure, and endothelial dysfunction.

Vasopeptidase inhibition attenuates the progression of renal injury in subtotal nephrectomized rats

BACKGROUND

Vasopeptidase inhibitors are a new class of cardiovascular compounds that inhibit both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The aim of the present study was to explore the effects of omapatrilat, a vasopeptidase inhibitor, on renal function and pathology in subtotally nephrectomized (STNx) rats.

METHODS

STNx rats were randomized to four groups and treated for 12 weeks: no treatment (N = 14); omapatrilat at a low dose of 10 mg/kg (L, N = 12) and at a high dose of 40 mg/kg (H, N = 10); or an ACE inhibitor, fosinopril, at a dose of 10 mg/kg (N = 12). Sham-operated rats were used as control animals (N = 12).

RESULTS

Elevated blood pressure in STNx rats (174 +/- 9 mm Hg) was reduced by omapatrilat in a dose-dependent manner (L, 121 +/- 3 mm Hg; H, 110 +/- 3 mm Hg) and by fosinopril (149 +/- 5 mm Hg). Proteinuria in STNx rats (246 +/- 73 mg/day) was reduced by treatment with fosinopril (88 +/- 21 mg/day) and was normalized by treatment with omapatrilat (L, 30 +/- 4 mg/day; H, 20 +/- 2 mg/day vs. control 25 +/- 1 mg/day). Decreased glomerular filtration rates, elevated plasma urea and creatinine and glomerulosclerosis, and tubulointerstitial fibrosis were ameliorated by omapatrilat and fosinopril to a similar degree. Compared with fosinopril, omapatrilat treatment was associated with increased plasma renin activity and decreased renal ACE and NEP binding in a dose-dependent manner.

CONCLUSION

These findings suggest that vasopeptidase inhibition may provide a useful strategy for the treatment of progressive renal disease.

In-vitro and in-vivo inhibition of rat neutral endopeptidase and angiotensin converting enzyme with the vasopeptidase inhibitor gemopatrilat

OBJECTIVES

Vasopeptidase inhibitors are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). The aim of this study was to characterize in-vitro and in-vivo inhibition of NEP and ACE in the rat with the vasopeptidase inhibitor gemopatrilat.

DESIGN AND METHODS

In-vitro NEP and ACE inhibition was studied by radioinhibitory binding assay using rat renal membranes and the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A, respectively (n = 3 per curve). In-vivo NEP and ACE inhibition was studied using in-vitro autoradiography in rats that received oral gemopatrilat (1, 3, 10 mg/kg; n = 4 per dose) and were killed 1 h later, or received oral gemopatrilat (3, 10 mg/kg) and were killed at time points 1, 2, 4, 8, 18, 24 and 48 h (n = 4 per time point).

RESULTS

Gemopatrilat caused a concentration-dependent displacement of specific radioligands from renal membrane NEP (IC50 305 +/- 5.4 nmol/I) and ACE (IC50 3.6 +/- 0.02 nmol/). In the dose-response study gemopatrilat (1, 3 and 10 mg/kg) caused significant inhibition of plasma ACE (P< 0.01), and renal ACE and NEP (3, 10 mg/kg, P < 0.01). In the time course experiment, gemopatrilat (10 mg/kg) increased plasma renin activity for 8 h (P< 0.01) and inhibited plasma ACE (P< 0.05), renal NEP (P< 0.01) and renal ACE (P< 0.05) for 48 h.

CONCLUSIONS

Gemopatrilat is a potent in-vitro vasopeptidase inhibitor that also causes prolonged inhibition of circulating and renal ACE and renal NEP after a single oral dose. The data suggest that gemopatrilat may be a useful addition to existing vasopeptidase inhibitors in the treatment of cardiovascular disease.

Thirst in elderly subjects

The hormonal changes associated with ageing, the occurrence of other medical condition and the use of medications increases the likelihood of conditions such as hyper- and hypo-natremia. Awareness of the homeostatic changes with age and the relations with disease and drugs will lead better management of fluid disorders in the elderly patient and hopefully a reduction in morbidity and mortality.

Beneficial renal and cardiac effects of vasopeptidase inhibition with S21402 in heart failure

S21402 is a vasopeptidase inhibitor that simultaneously inhibits neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE). This study determined whether chronic treatment with S21402 produced different effects on sodium and water excretion, hormonal parameters, and cardiovascular structure compared with selective inhibition of ACE and NEP in a rat model of myocardial infarction-induced congestive heart failure (CHF). CHF rats received the vasopeptidase inhibitor (S21402, 100 mg. kg(-1). d(-1)), an ACE inhibitor (captopril, 50 mg. kg(-1). d(-1)), a NEP inhibitor (SCH42495, 60 mg. kg(-1). d(-1)), or vehicle for 4 weeks. S21402 alone caused a diuresis and natriuresis (P<0.01) in CHF. After 4 weeks, blood pressure was lowered by captopril but not other treatments (P<0.01). Both S21402 and captopril increased plasma renin activity (P<0.01), all treatment lowered plasma aldosterone (P<0.05) and plasma natriuretic peptide levels were unchanged. In the kidney, S21402 inhibited NEP and ACE (P<0.01), SCH42495 inhibited NEP (P<0.01), and captopril inhibited ACE (P<0.01). Heart mass was reduced by all active treatments; captopril reduced left ventricular mass (P<0.01), SCH42495 reduced right ventricular mass (P<0.01), and S21402 decreased left (P<0.05) and right ventricular mass (P<0.01), atrial mass (P<0.05), and lung mass (P<0.01). In CHF, vasopeptidase inhibition with S21402 produces effects that differ from those of selective NEP or ACE inhibition. S21402 improved sodium and water excretion, reduced pulmonary congestion, and attenuated both right and left ventricular remodeling. These effects, which occurred in the absence of any hypotensive action, suggest that S21402 may offer several advantages over ACE inhibition alone in the treatment of heart failure.

Vasopressin V1a receptor antagonism does not reverse adrenocorticotrophin-induced hypertension in the rat

1. The role of arginine vasopressin (AVP) was examined in adrenocorticotrophin (ACTH)-induced hypertension in Sprague-Dawley rats using the non-peptide AVP V1a receptor antagonist OPC 21268. 2. In an acute study, six rats were pretreated with ACTH for 11 days and direct arterial blood pressure (4 h), plasma osmolality and electrolyte concentrations were measured after OPC 21268 gavage. In a chronic study, 40 rats were randomly divided into four groups: (i) sham injection + sham gavage; (ii) ACTH + sham gavage; (iii) sham injection + OPC 21268; or (iv) ACTH + OPC-21268 for 16 days. Systolic blood pressure (SBP), water intake, urine volume (UV), urine osmolality and electrolytes, food intake, bodyweight and plasma osmolality and electrolyte concentrations were measured. 3. In the acute study, direct mean arterial blood pressure did not change with OPC 21268 (122+/-2 and 120+/-3 mmHg at 0 and 240 min, respectively). 4. In the chronic study, OPC 21268 did not affect ACTH-induced rises in blood pressure (from 125+/-2 (control) to 145+/-5 mmHg (group 4) compared with 122+/-3 (control) to 149+/-5 mmHg (group2)). Water intake and UV increased (from 29+/-2 to 83+/-6 mL/day; and from 5+/-1 to 36+/-5 mL/day, respectively) and the change in bodyweight decreased from 0+/-2 to -107+/-7 g. 5. These results suggest that AVP (at the V1a receptor) does not play a significant role in the maintenance of ACTH-induced hypertension.

Antihypertensive and antihypertrophic effects of omapatrilat in SHR

Vasopeptidase inhibitors, such as omapatrilat are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). In normotensive rats, a single dose of oral omapatrilat (10 mg/kg) and 1 mg/kg inhibited plasma ACE (P < .01) for 24 h and increased plasma renin activity for 8 h (P < .01). In vitro autoradiography using the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A showed omapatrilat (10 mg/kg) caused rapid and potent inhibition of renal NEP and ACE, respectively, for 24 h (P < .01). In spontaneously hypertensive rats, 10 days of oral omapatrilat (40 mg/kg/day) reduced blood pressure (vehicle 237 +/- 4 mm Hg; omapatrilat, 10 mg/kg, 212 +/- 4 mm Hg; omapatrilat 40 mg/kg, 197 +/- 4 mm Hg, P < .01) in a dose-dependent manner (10 v 40 mg/kg, P < .01). Left ventricular hypertrophy was significantly reduced by high-dose omapatrilat (vehicle 2.76 +/- 0.03 mg/g body weight; omapatrilat, 10 mg/kg, 2.71 +/- 0.02 mg/g; omapatrilat 40 mg/kg, 2.55 +/- 0.02 mg/g, P < .01) and omapatrilat also increased kidney weight compared to vehicle (both doses, P < .01). Omapatrilat caused significant inhibition of plasma ACE and increased plasma renin activity (both doses, P < .01), and in vitro autoradiographic studies indicated sustained inhibition of renal ACE and NEP (both doses, P < .01). Omapatrilat is a potent vasopeptidase inhibitor, and its antihypertensive effects are associated with inhibition of NEP and ACE at the tissue level and beneficial effects on cardiovascular structure. Relating the degree of tissue inhibition to physiologic responses may allow further definition of the role of local renin angiotensin and natriuretic peptide systems in the beneficial effects of vasopeptidase inhibitors.

Effects of neutral endopeptidase inhibition in the rat remnant kidney model

The orally active neutral metalloendopeptidase (NEP) inhibitor SCH34826 was given by oral gavage in a dose of 90 mg/kg twice daily for 3 days to rats with subtotal nephrectomy (n = 7) and effects were compared to a placebo group receiving phosphate buffer (n = 5). Inhibition of neutral endopeptidase in the remnant kidney was measured by in vitro autoradiography using the specific radioligand [125I]-SCH 47896. Treatment with the NEP inhibitor SCH34826 caused a 60% reduction in the neutral endopeptidase radioligand-binding site density in the kidneys of the SCH34826-treated animals compared to the placebo group (81.6+/-3.7 versus 214.5+/-4.2 dpm/mm2, p<0.01). This was associated with a marked increase in urinary atrial natriuretic peptide (ANP) from 3,930+/-295 to 9,094+/-1,089 pg/24 h in the SCH34826-treated group (p<0.01). Concomitantly there was a transient increase in natriuresis in the SCH34826-treated group [baseline 2.03+/-0.55 to 3.77+/-0.58 mmol/24 h on treatment day 1 (p = 0.02) and 2.58+/-0.19 mmol/24 h on treatment day 3 (p = 0.09)] which was not observed in the placebo group. Urinary protein excretion, glomerular filtration rate (determined by 99mTc-DTPA clearance), systemic blood pressure, plasma ANP concentration and urinary cyclic GMP excretion were not changed by SCH34826 treatment. These results suggest that oral administration of the NEP inhibitor SCH34826 inhibits renal neutral endopeptidase, increases urinary ANP and modulates natriuresis without alteration of systemic blood pressure, plasma ANP and renin level, glomerular filtration or protein excretion.

Reversal of cardiac hypertrophy and fibrosis by S21402, a dual inhibitor of neutral endopeptidase and angiotensin converting enzyme in SHRs

OBJECTIVE

The major advantage of dual inhibitors of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) is their ability to lower blood pressure irrespective of renin or volume status. The aim of this study was to determine whether dual NEP/ACE inhibition produces different effects on cardiovascular structure and fibrosis, hormonal parameters and inhibition of tissue enzymes compared with selective inhibition of ACE and NEP in the spontaneously hypertensive rat (SHR).

METHODS

Male SHRs received the dual NEP/ACE inhibitor (S21402, 100 mg/kg per day), the ACE inhibitor (captopril, 50 mg/kg per day), the NEP inhibitor (SCH42495, 60 mg/kg per day) or vehicle for 2 weeks.

RESULTS

S21402 produced equivalent blood pressure lowering effects to captopril (vehicle, 220 +/- 1 mmHg; S21402, 189 +/- 2 mmHg; captopril, 187 +/- 3 mmHg), but was a more effective antihypertensive agent than SCH42495 (214 +/- 2 mmHg, P< 0.01). All treatments reduced left ventricular mass (P< 0.05) and cardiac fibrosis (P< 0.01). S21402 inhibited renal NEP and ACE (P< 0.01), SCH42495 inhibited renal NEP (P < 0.01), and captopril inhibited renal ACE (P< 0.01). Captopril and S21402 increased plasma renin activity (P< 0.05), but the rise with S21402 was attenuated compared with that caused by captopril (P< 0.01). All treatments reduced plasma aldosterone levels (P< 0.01), and NEP inhibition with SCH42495 and S21402 increased plasma atrial natriuretic peptide (ANP; P< 0.05).

CONCLUSIONS

These results indicate that selective NEP inhibition has major benefits in the regression of cardiac hypertrophy and reduction of fibrosis but has limited antihypertensive effects. The dual NEP/ACE inhibitor S21402 offered no advantage over the selective ACE inhibitor in terms of blood pressure reduction, or attenuation of cardiac hypertrophy and fibrosis, but did increase plasma ANP and blunted the reactive rise in renin with ACE inhibition. Further studies are needed to determine whether more complete blockade of the renin-angiotensin system with dual NEP/ACE inhibition results in additional benefits in terms of morbidity and mortality in cardiovascular disease.

Vasopressin receptor antagonism--a therapeutic option in heart failure and hypertension

The precise role of vasopressin in the pathophysiology of cardiovascular disease is controversial, but this peptide hormone is important for several reasons. Firstly, circulating concentrations of vasopressin are elevated in heart failure and some forms of hypertension. Secondly, there is evidence that vasopressin is synthesized not only in the hypophysial-pituitary axis but also in peripheral tissues including the heart where it acts as a paracrine hormone. Thirdly, vasopressin has vasoconstrictor, mitogenic, hyperplastic and renal fluid retaining properties which, by analogy with angiotensin II, may have deleterious effects when present in chronic excess. Finally, the availability of orally active non-peptide vasopressin receptor antagonists allows vasopressin receptor antagonism to be considered as a therapeutic option in cardiovascular disease.

Passive ventricular constraint amends the course of heart failure: a study in an ovine model of dilated cardiomyopathy

OBJECTIVE

Dilated cardiomyopathy (DCM) is associated with a progressive deterioration in cardiac function. We hypothesised that some of the deleterious effects of DCM could be reduced by mechanically limiting the degree of cardiac dilatation.

METHODS

A Transonic 20A cardiac output (CO) flow-probe was implanted in the pulmonary artery of 12 adult (52 +/- 4 kg) sheep. Early heart failure was created by rapid right ventricular (RV) pacing for 21 days at a rate which resulted in an initial 10% decrease in CO (to a maximum of 190 bpm). A custom polyester jacket (Acorn Cardiovascular, St Paul, MN) was then placed, via a partial lower sternotomy, on the ventricular epicardium of all sheep. Animals were randomised either to jacket retention (wrap) or removal (sham). Pacing was recommenced at a higher rate (that initiated a further 10% decrease in CO) for 28 days. Haemodynamic and echocardiographic parameters were determined at baseline, implant and at termination.

RESULTS

At termination, the left ventricular fractional shortening was significantly higher (p = 0.03), the degree of mitral valve regurgitation lower (scaled 0-3) (p = 0.03) and the left ventricular long axis area smaller (p = 0.02) in the wrap animals compared with sham.

CONCLUSIONS

In this model of heart failure, ventricular constraint with a polyester jacket diminished the deterioration in cardiac function associated with progressive dilated cardiomyopathy. These results suggest that maintainance of a more normal cardiac size and shape may be beneficial in patients with dilated cardiomyopathy.

Pustular vasculitis of the hands

A case of pustular vasculitis of the hands with evidence of systemic involvement is described. A 64-year-old woman presented with a 2-day history of large, tense bullae arranged symmetrically over the dorsum of the three radial digits and extending on to the radial aspect of the dorsum of each hand. The bullae caused some discomfort and prevented normal use of her hands. There was no response to antibiotic therapy initiated prior to referral to hospital. Initial investigations revealed a raised white cell count with a neutrophilia, a raised erythrocyte sedimentation rate and a raised C-reactive protein. Abnormalities of liver function were detected. Aspirates from the bullae and blood cultures were sterile. The histology of debrided tissue demonstrated a florid neutrophilic dermal infiltrate with many blood vessels associated with prominent fibrin. A diagnosis of pustular vasculitis of the hands was made. The bullae were surgically debrided and treatment with oral corticosteroids was started. Two days after commencement of oral prednisolone, a crusted pustule appeared on her upper cutaneous lip. There was rapid resolution of both the vasculitis of the hands and the pustule on her upper lip following an increase in the dose of oral prednisolone. The patient was discharged on the seventeenth day following admission.

In vivo and in vitro characterisation of a nonpeptide vasopressin V(1A) and V(2) receptor antagonist (YM087) in the rat

This paper reports the in vitro and in vivo characterisation of a nonpeptide, orally active, vasopressin V(1A) and V(2) receptor antagonist, YM087 (methyl-1,4,5,6-tetrahydroimidazo[4, 5-d][1]benzoazepine-6-carbonyl)-2-phenylbenzanilide monohydrochloride) in the rat. YM087 dose dependently displaced the vasopressin V(1A) receptor antagonist radioligand, 125I-labelled [d(CH(2))(5),sarcosine(7)]vasopressin at vasopressin V(1A) receptors in liver and kidney medulla membranes and caused a concentration dependent displacement of the vasopressin V(2) receptor antagonist radioligand [3H]desGly-NH(2)(9)[d(CH(2))(5), D-Ile(2), Ile(4)]vasopressin at vasopressin V(2) receptors in kidney medulla membranes. In vitro binding kinetic studies showed YM087 acted as a competitive antagonist at liver V(1A) and kidney V(1A) and V(2) vasopressin receptors. Oral administration of YM087 (0.1-3 mg/kg) dose dependently inhibited vasopressin binding to liver V(1A) and kidney V(1A) and V(2) vasopressin receptors over 24 h. Oral YM087 (1-3 mg/kg/day) for 7 days in normotensive rats caused a dose dependent aquaresis with no effect on systolic blood pressure. These results show that YM087 is an orally effective vasopressin V(1A) and V(2) receptor antagonist that may be useful in the treatment of conditions characterised by vasoconstriction and fluid retention such as congestive heart failure.

Localization of the insulin-like growth factor system in a rat model of heart failure induced by myocardial infarction

Although cardiac effects of growth hormone (GH) and insulin-like growth factor (IGF)-I have been reported in experimental models of heart failure and in human dilated cardiomyopathy, the IGF system has not been comprehensively assessed in the failing heart. We therefore localized the IGF system in the left ventricle during congestive heart failure after myocardial infarction (MI) in the rat. The left anterior descending coronary artery was ligated in adult female Sprague-Dawley rats and hearts were examined after 6 months when congestive heart failure had developed. In situ hybridization histochemistry was used to localize mRNA for the components of the IGF system in the left ventricle of sham and congestive heart failure animals. We were able to detect changes in the spatial distribution of mRNA for IGF-I and IGF binding proteins 3, 4, 5, and 6 in the left ventricle during congestive heart failure after MI. IGF-I and the binding proteins were predominantly increased in the infarct/peri-infarct area of the left ventricle. Other components of the IGF system were indistinguishable from the low to undetectable levels in sham-operated rats. These results demonstrate that the IGF system is altered in the failing heart and suggest that the IGF system plays an important role in the response of the heart to MI and consequent failure.

Vasopressin V2 receptor enhances gain of baroreflex in conscious spontaneously hypertensive rats

The aim of the present study was to determine the receptor subtype involved in arginine vasopressin (AVP)-induced modulation of baroreflex function in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats using novel nonpeptide AVP V1- and V2-receptor antagonists. Baroreceptor heart rate (HR) reflex was investigated in both SHR and WKY rats which were intravenously administered the selective V1- and V2-receptor antagonists OPC-21268 and OPC-31260, respectively. Baroreflex function was assessed by obtaining alternate pressor and depressor responses to phenylephrine and sodium nitroprusside, respectively, to construct baroreflex curves. In both SHR and WKY rats baroreflex activity was tested before and after intravenous administration of vehicle (20% DMSO), OPC-21268 (10 mg/kg), and OPC-31260 (1 and 10 mg/kg). Vehicle did not significantly alter basal mean arterial pressure (MAP) and HR values or baroreflex function in SHR or WKY rats. The V1-receptor antagonist had no significant effect on resting MAP or HR values or on baroreflex parameters in both groups of rats, although this dose was shown to significantly inhibit the pressor response to AVP (5 ng iv; ANOVA, P < 0.05). In SHR but not WKY rats the V2-receptor antagonist significantly attenuated the gain (or slope) of the baroreflex curve (to 73 +/- 3 and 79 +/- 7% of control for 1 and 10 mg/kg, respectively), although AVP-induced pressor responses were also attenuated with the higher dose of the V2-receptor antagonist. These findings suggest that AVP tonically enhances baroreflex function through a V2 receptor in the SHR.

Clinical management of carpal tunnel syndrome: a 12-year review of outcomes

Carpal tunnel syndrome (CTS) is a disorder frequently encountered by occupational health care specialists. The health care management of this disorder has involved a diverse set of clinical procedures. The present article is a review of the literature related to CTS with an emphasis on occupational-related CTS. MEDLINE, Cumulative Index to Nursing and Allied Health Literature, PsycLIT, and NIOSHTIC databases from 1985-1997 were searched for treatment outcome studies related to CTS. Treatments of interest included surgery, physical therapy, drug therapy, chiropractic treatment, biobehavioral interventions, and occupational rehabilitation. A systematic review of the effects of these interventions on symptoms, medical status, function, return to work, psychological well-being, and patient satisfaction was completed. Compared to other treatments, the majority of studies assessed the effects of surgical interventions. Endoscopic release was associated with higher levels of physical functioning and fewer days to return to work when compared to open release. Limited evidence indicated: 1) steroid injections and oral use of B6 were associated with pain reduction; 2) in comparison to splinting, range of motion exercises appeared to be associated with less pain and fewer days to return to work; 3) cognitive behavior therapy yielded reductions in pain, anxiety, and depression; and, 4) multidisciplinary occupational rehabilitation was associated with a higher percentage of chronic cases returning to work than usual care. Workers' compensation status was associated with increased time to return to work following surgery. Conclusions are preliminary due to the small number of well-controlled studies, variability in duration of symptoms and disability, and the broad range of reported outcome measures. While there are several opinions regarding effective treatment, there is very little scientific support for the range of options currently used in practice. Despite the emerging evidence of the multivariate nature of CTS, the majority of outcome studies have focused on single interventions directed at individual etiological factors or symptoms and functional limitations secondary to CTS.

Salt induces myocardial and renal fibrosis in normotensive and hypertensive rats

BACKGROUND

The detrimental effects of high dietary salt intake may not only involve effects on blood pressure and organ hypertrophy but also lead to tissue fibrosis independently of these factors.

METHODS AND RESULTS

The effect of a normal (1%) or high (8%) sodium chloride diet on myocardial and renal fibrosis was assessed by quantitative histomorphometry in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The effect of salt on transforming growth factor-beta1 (TGF-beta1) gene expression was assessed by Northern blot hybridization. A high-salt diet from 8 to 16 weeks of age resulted in increased blood pressure and left ventricular and renal hypertrophy in both WKYs and SHRs. Marked interstitial fibrosis was demonstrated in the left ventricle (LV), glomeruli, and renal tubules and in intramyocardial arteries and arterioles but not in the right ventricle. The collagen volume fraction increased significantly after high-salt diet in the LV, intramyocardial arteries and arterioles, glomeruli, and peritubular areas in both WKYs and SHRs. In the kidneys, glomerular and peritubular type IV collagen was also increased. There was overexpression of TGF-beta1 mRNA in the LV and kidneys in both rat strains after a high-salt diet (all P<0.001).

CONCLUSIONS

High dietary salt led to widespread fibrosis and increased TGF-beta1 in the heart and kidney in normotensive and hypertensive rats. These results suggest a specific effect of dietary salt on fibrosis, possibly via TGF-beta1-dependent pathways, and further suggest that excessive salt intake may be an important direct pathogenic factor for cardiovascular disease.

Dual inhibition of neutral endopeptidase and angiotensin-converting enzyme in rats with hypertension and diabetes mellitus

It has been suggested that combined inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) may lower blood pressure more effectively than either treatment alone, independent of the degree of salt and volume status or the activity of the renin-angiotensin system. The effects of NEP inhibition in hypertension associated with diabetes mellitus are largely unknown. We therefore compared ACE inhibition, NEP inhibition, and dual NEP/ACE inhibition in diabetic hypertensive rats. Spontaneously hypertensive rats (SHR) aged 9 to 10 weeks were injected with either streptozotocin (45 mg/kg) or citrate buffer and randomized to receive either the ACE inhibitor captopril (25 mg/kg BID), the NEP inhibitor SCH 42495 (30 mg/kg BID), the dual NEP/ACE inhibitor S 21402 (25 or 50 mg/kg BID), or vehicle by gavage for 4 weeks. A group of diabetic SHR was also allocated to receive the combination of SCH 42495 (30 mg/kg BID) and captopril (25 mg/kg BID). The degree of renal NEP inhibition was determined by autoradiography, and plasma renin activity (PRA) was determined by radioimmunoassay. In diabetic SHR, the dual NEP/ACE inhibitor (50 mg/kg BID), as well as the combination of the NEP inhibitor and the ACE inhibitor, reduced systolic blood pressure more effectively than the ACE inhibitor (P<0.001) or the NEP inhibitor (P<0.001) alone. In nondiabetic SHR, the dual NEP/ACE inhibitor and the ACE inhibitor were equally effective, while the NEP inhibitor had only slight blood pressure lowering effects. Relative heart weight decreased in parallel to the changes in blood pressure. Renal NEP was clearly inhibited (70% to 92%; P<0.001) by both the NEP inhibitor and the dual NEP/ACE inhibitor. Both the ACE inhibitor and the dual NEP/ACE inhibitor increased PRA, but the stimulating effect of dual NEP/ACE inhibition on PRA was less than that observed with ACE inhibition alone (P<0.05). Albuminuria in diabetic SHR was lower during treatment with both the dual NEP/ACE inhibitor (50 mg/kg BID) and the combination of NEP inhibition and ACE inhibition compared with vehicle treatment (P<0.05). In conclusion, the present study shows that hypertension in SHR with streptozotocin-induced diabetes is modulated by natriuretic peptides and thus is sensitive to NEP inhibition. The increased efficacy of dual NEP/ACE inhibition on blood pressure in diabetic SHR, compared with ACE or NEP inhibition alone, suggests that this therapeutic approach may prove beneficial in the treatment of hypertension associated with diabetes mellitus and other forms of volume-dependent hypertension.

Long-term effects of nonpeptide vasopressin V2 antagonist OPC-31260 in heart failure in the rat

The hormone arginine vasopressin (AVP) contributes to water retention and vasoconstriction in congestive heart failure (CHF) through effects at the V2 and V1a receptors, respectively. The effect of long-term V2 receptor (V2R) blockade using OPC-31260 was assessed in a rat model of postinfarction-induced CHF. Rats underwent coronary artery ligation or sham operation and were treated for 6 mo with oral OPC-31260 (10 mg . kg-1 . day-1) or vehicle. CHF was characterized by left ventricular remodeling and impaired systolic function, increased cardiac and lung weight, and elevated plasma atrial natriuretic peptide; plasma AVP and plasma renin activity were not increased. Chronic V2R blockade increased urine volume (P < 0.01) and decreased urine osmolality (P < 0.01) but had no natriuretic effects. V2R blockade did not activate the renin-angiotensin system but increased plasma AVP in CHF (P < 0.01). V2R blockade did not influence cardiac remodeling, cardiac function, or survival. These results suggest that AVP plays a major role in water retention through the renal V2R in a rat model of CHF. V2R blockade using OPC-31260 may represent an alternative to standard diuretic therapy in the management of water retention that characterizes heart failure.

Occupational upper extremity disorders in the federal workforce. Prevalence, health care expenditures, and patterns of work disability

Upper extremity disorders (UEDs) account for a significant number of work-related illnesses in the US workforce. Little information exists on the distribution of UEDs, their associated health care and indemnity costs, or patterns of work disability. The study presented is an analysis of upper extremity claims within the federal workforce. In this study, the universe consisted of all claims accepted by the US Department of Labor, Office of Workers' Compensation Programs (OWCP), from October 1, 1993, through September 30, 1994. A total of 185,927 claims of notices of injury were processed during the study period, and of these, 8,147 or 4.4% had an UED diagnosis coded according to the International Classification of Diseases, Clinical Modification (ICD-9-CM). 5,844 claims involved a single UED diagnosis and were the only claims field by these employees between October 1, 1990, and September 30, 1994. These single claims with single diagnoses comprised the sample for further analysis. Mononeuritis and enthesopathies of the upper limb were the most common diagnoses, accounting for 43% and 31% of the claims, respectively. Women had a higher proportion of carpal tunnel syndrome, "unspecified" mononeuritis, and "unspecified" enthesopathies. The majority of claimants for both the mononeuritis- and enthesopathy-related diagnoses were between 31 and 50 years of age, received only health care benefits, and did not incur wage loss. Health care costs for mononeuritis and enthesopathy claims were $12,228,755 (M = $2,849). Carpal tunnel syndrome (CTS) and enthesopathy of the elbow were the most costly diagnoses, accounting for 57% and 16% of the total, respectively. Surgical services represented the highest expenditures in CTS claims. Physical therapy accounted for the majority of health care costs for enthesopathy cases. The mean number of workdays lost for CTS and enthesopathy claims were 84 and 79, and the average indemnity costs were $4,941 and $4,477, respectively. These findings indicate that while UEDs represent a relatively small percentage of all workers' compensation cases, the health care and indemnity costs are considerable. Also mean duration and pattern of work disability revealed that these disorders can result in chronic work disability similar to that observed in low back pain. The results highlight the need to determine whether interventions that account for the majority of costs significantly impact long-term outcomes. There is also a need to identify risk factors for prolonged disability in those who experience problems with delayed recovery.

Vasopressin V1a and V2 receptor mRNA in deoxycorticosterone acetate-salt hypertension in the rat

1. Vasopressin V1a and V2 receptors are differentially regulated in deoxycorticosterone acetate-salt hypertension. This paper investigated whether the changes were due to transcription changes in receptor mRNA assessed by in situ hybridization histochemistry (liver V1a receptor) and by reverse transcription-polymerase chain reaction (kidney V1a and V2 receptor). 2. Systolic blood pressure and plasma vasopressin levels were significantly elevated in deoxycorticosterone acetate-salt rats (n = 24) compared with water-control (n = 28) and salt-control rats (n = 28) (P < 0.001). Plasma sodium was elevated in deoxycorticosterone acetate-salt rats compared with both control groups (P < 0.01) and plasma osmolality was elevated in deoxycorticosterone acetate-salt rats compared with water-control rats (P < 0.05). 3. Binding kinetic studies demonstrated downregulation of liver V1a and kidney V2 receptors in deoxycorticosterone acetate-salt rats compared with water-control and salt-control rats (P < 0.05). This was not associated with any change in liver V1a receptor mRNA (P = 0.95), or in kidney V1a (P = 0.79) or V2 receptor mRNA (P = 0.96). 4. In deoxycorticosterone acetate-salt hypertension, downregulation of liver V1a and kidney V2 receptors occurs in the setting of stable vasopressin gene transcription. These results suggest that changes in receptor processing may be responsible for the differential regulation of vasopressin receptors that occurs in deoxycorticosterone acetate-salt hypertension.

New hormonal blockade strategies in cardiovascular disease

The circulation is controlled by overlapping haemodynamic, structural and neurohumoral mechanisms. Many hormonal vasoactive substances, mostly derived from endothelial cells, are also growth regulators. Although neurohormonal systems are involved in normal physiological compensatory responses they often become maladaptive in conditions such as congestive heart failure. The success of blocking the renin angiotensin system by angiotensin converting enzyme (ACE) inhibitors has led to efforts to block other hormonal systems. Neutral endopeptidase (NEP), the major enzymatic pathway for degradation of natriuretic peptides, has a similar catalytic site to ACE. This has led to compounds that simultaneously inhibit both enzymes. Such dual ACE/NEP inhibitors show promise in experimental hypertension and heart failure. Similar dual NEP/ECE (endothelin converting enzyme) inhibitors are becoming available. The hormone vasopressin has dual actions on the vasculature and the kidney via specific membrane receptors. Specific orally active vasopressin receptor antagonists have been developed and their therapeutic potential in hypertension, heart failure and oedematous states are being explored.

High-dose cyclophosphamide, etoposide and carboplatin with autologous bone marrow support for metastatic breast cancer: long-term results

We report long-term results of high-dose cyclophosphamide, etoposide and carboplatin with ABMT in 20 patients with metastatic breast cancer. Median age of the group was 41 years, ECOG performance status = 0 in 18 patients and 1 in two patients. Twelve patients had received adjuvant chemotherapy. Predominant sites of metastases were lung (eight), chest wall (four), liver (four), bone (three) and lymph nodes (three). Response to pretransplant chemotherapy was complete (CR) in four patients, partial (PR) in 10 patients and stable (SD) in five patients. After high-dose chemotherapy eight patients were in CR, six PR, four SD and one progressive disease. Two patients died of regimen-related toxicities (candidal sepsis and alveolar hemorrhage). With a median follow-up period of 55 months (minimum 48 months), 12 patients have died of recurrent breast cancer, one died of toxicity of salvage chemotherapy, two are alive with disease, two are alive and free of progressive disease. One patient with relapsed disease was lost to follow-up. Median event-free survival is 6 months and median overall survival is 17 months. All three of the long-term disease-free survivors had predominantly nodal disease. Two of these three patients presented with metastatic disease and received high-dose chemotherapy with ABMT as part of initial therapy for breast cancer; two of three attained CR to standard-dose cytoreductive therapy; none received doxorubicin-containing adjuvant chemotherapy.

Susceptibility to atrial fibrillation: a study in an ovine model of pacing-induced early heart failure

INTRODUCTION

The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing-induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters.

METHODS AND RESULTS

Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF threshold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6-week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA ERP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology.

CONCLUSION

In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.

Rationale and pharmacology of angiotensin II receptor antagonists: current status and future issues

BACKGROUND

The renin-angiotensin system consists of a cascade of substrate-enzyme interactions that culminates with the production of angiotensin II, the active peptide responsible for all the known effects of the renin-angiotensin system. Blocking this enzymatic cascade has been the focus of considerable research to the extent that the renin-angiotensin system is implicated in the control of blood pressure, sodium and water homeostasis, and cardiovascular function and structure.

ANGIOTENSIN CONVERTING ENZYME INHIBITORS

Angiotensin converting enzyme (ACE) inhibitors provide one way of blocking the renin-angiotensin system, and to this end the compounds have proved efficacious in the treatment of hypertension and cardiovascular disease. However, these compounds are limited in the extent to which they block the renin-angiotensin system, partly due to recently described alternate pathways for the genesis of angiotensin II and also because ACE is not a very specific enzyme and has multiple other potential substrates including bradykinin, tachykinins, neurotensin substance P, and others.

ANGIOTENSIN II RECEPTORS

The development of angiotensin II receptor antagonists represents a new way to block the renin-angiotensin system at the receptor level. Irbesartan is a new angiotensin II receptor antagonist that provides specific and insurmountable antagonism of the AT1 receptor subtype, demonstrating a greater than 8500-fold specificity for the AT1 receptor, the subtype which mediates all the known actions of angiotensin, compared to the AT2 receptor. Comparative studies have demonstrated that irbesartan is 10 times more potent than losartan and slightly more potent than E3174, losartan's active metabolite. Preclinical pharmacological studies in a variety of animal models have demonstrated that irbesartan provides a dose-dependent, insurmountable blockade of angiotensin and reductions in blood pressure, urinary protein and glomerular sclerosis score.