Racial differences in biologic predictors of severe asthma: Data from the Severe Asthma Research Program

BACKGROUND

Biologic factors are known to contribute to asthma severity. It is unknown whether these factors differentially contribute to asthma severity in black compared with white subjects.

OBJECTIVE

We sought to assess the extent to which racial disparities between black and white subjects with severe asthma are attributable to physiologic, immunoinflammatory, and sociodemographic variables.

METHODS

Black and white asthmatic adults enrolled in a cross-sectional study focused on severe asthma were evaluated. Severe asthma was identified by using the American Thoracic Society definition. After initial univariable analyses, unconditional logistic regression models were used to estimate the probability of having severe asthma for black and white subjects.

RESULTS

Differences in severe asthma in black compared with white subjects were observed. In univariable analysis IgE level was not associated with severe asthma in black or white subjects, whereas in multivariable analysis IgE level was significantly associated with severe asthma for black subjects (P = .014) but not for white subjects. The odds of having severe asthma more than doubled for black subjects with 2 or more family members with asthma (P = .026), whereas the odds of severe asthma for white participants with a strong family history of asthma decreased by almost half (P = .05). Atopy was negatively associated with severe asthma in both races in univariable analysis but remained significant only in black subjects, whereas comorbidities were associated with severe asthma in white subjects.

CONCLUSION

Biologic factors were distinctly associated with severe asthma only in black subjects. Studies that incorporate comprehensive evaluation of biologic factors associated with asthma might lead to the development of therapies that target biologic abnormalities in black subjects.

A biohybrid artificial lung prototype with active mixing of endothelialized microporous hollow fibers

Acute respiratory distress syndrome (ARDS) affects nearly 150,000 patients per year in the US, and is associated with high mortality ( approximately 40%) and suboptimal options for patient care. Mechanical ventilation and extracorporeal membrane oxygenation are limited to short-term use due to ventilator-induced lung injury and poor biocompatibility, respectively. In this report, we describe the development of a biohybrid lung prototype, employing a rotating endothelialized microporous hollow fiber (MHF) bundle to improve blood biocompatibility while MHF mixing could contribute to gas transfer efficiency. MHFs were surface modified with radio frequency glow discharge (RFGD) and protein adsorption to promote endothelial cell (EC) attachment and growth. The MHF bundles were placed in the biohybrid lung prototype and rotated up to 1,500 revolutions per minute (rpm) using speed ramping protocols to condition ECs to remain adherent on the fibers. Oxygen transfer, thrombotic deposition, and EC p-selectin expression were evaluated as indicators of biohybrid lung functionality and biocompatibility. A fixed aliquot of blood in contact with MHF bundles rotated at either 250 or 750 rpm reached saturating pO(2) levels more quickly with increased rpm, supporting the concept that fiber rotation would positively contribute to oxygen transfer. The presence of ECs had no effect on the rate of oxygen transfer at lower fiber rpm, but did provide some resistance with increased rpm when the overall rate of mass transfer was higher due to active mixing. RFGD followed by fibronectin adsorption on MHFs facilitated near confluent EC coverage with minimal p-selectin expression under both normoxic and hyperoxic conditions. Indeed, even subconfluent EC coverage on MHFs significantly reduced thrombotic deposition adding further support that endothelialization enhances, blood biocompatibility. Overall these findings demonstrate a proof-of-concept that a rotating endothelialized MHF bundle enhances gas transfer and biocompatibility, potentially producing safer, more efficient artificial lungs.

Mass-spectrometric analysis of hydroperoxy- and hydroxy-derivatives of cardiolipin and phosphatidylserine in cells and tissues induced by pro-apoptotic and pro-inflammatory stimuli

Oxidation of two anionic phospholipids--cardiolipin (CL) in mitochondria and phosphatidylserine (PS) in extramitochondrial compartments--is important signaling event, particularly during the execution of programmed cell death and clearance of apoptotic cells. Quantitative analysis of CL and PS oxidation products is central to understanding their molecular mechanisms of action. We combined the identification of diverse phospholipid molecular species by ESI-MS with quantitative assessments of lipid hydroperoxides using a fluorescence HPLC-based protocol. We characterized CL and PS oxidation products formed in a model system (cyt c/H(2)O(2)), in apoptotic cells (neurons, pulmonary artery endothelial cells) and mouse lung under inflammatory/oxidative stress conditions (hyperoxia, inhalation of single walled carbon nanotubes). Our results demonstrate the usefulness of this approach for quantitative assessments, identification of individual molecular species and structural characterization of anionic phospholipids that are involved in oxidative modification in cells and tissues.

Aldosterone status associated with insulin resistance in patients with heart failure--data from the ALOFT study

BACKGROUND

Aldosterone has a key role in the pathophysiology of heart failure. In around 50% of such patients, aldosterone "escapes" from inhibition by drugs that interrupt the renin-angiotensin axis; such patients have a worse clinical outcome. Insulin resistance is a risk factor in heart failure and cardiovascular disease. The relation between aldosterone status and insulin sensitivity was investigated in a cohort of heart failure patients.

METHODS

302 patients with New York Heart Association (NYHA) class II-IV heart failure on conventional therapy were randomised in the ALiskiren Observation of heart Failure Treatment study (ALOFT), designed to test the safety of a directly acting renin inhibitor. Plasma aldosterone and 24-hour urinary aldosterone excretion, as well as fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were measured. Subjects with aldosterone escape and high urinary aldosterone were identified according to previously accepted definitions.

RESULTS

20% of subjects demonstrated aldosterone escape and 34% had high urinary aldosterone levels. At baseline, there was a positive correlation between fasting insulin and plasma (r = 0.22 p<0.01) and urinary aldosterone(r = 0.19 p<0.03). Aldosterone escape and high urinary aldosterone subjects both demonstrated higher levels of fasting insulin (p<0.008, p<0.03), HOMA-IR (p<0.06, p<0.03) and insulin-glucose ratios (p<0.006, p<0.06) when compared to low aldosterone counterparts. All associations remained significant when adjusted for potential confounders.

CONCLUSIONS

This study demonstrates a novel direct relation between aldosterone status and insulin resistance in heart failure. This observation merits further study and may identify an additional mechanism that contributes to the adverse clinical outcome associated with aldosterone escape.

Coordinated regulation of dimethylarginine dimethylaminohydrolase-1 and cationic amino acid transporter-1 by farnesoid X receptor in mouse liver and kidney and its implication in the control of blood levels of asymmetric dimethylarginine

Asymmetric dimethylarginine (ADMA) is a potent endogenous inhibitor of endothelial nitric-oxide synthase (eNOS), and increased plasma concentrations of ADMA have been regarded as a risk factor for a number of cardiovascular diseases. Circulating ADMA is largely taken up by liver and kidney via system y(+) carriers of the cationic amino acid (CAT) family and subsequently metabolized by dimethylarginine dimethylaminohydrolases (DDAHs). As such, agents targeted at enhancing ADMA metabolism may prove to be useful in the prevention and/or treatment of various types of cardiovascular disease. Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily and plays an important role in the maintenance of cholesterol and bile acid homeostasis. We report here that treatment of mice with an FXR agonist 3-(2,6-dichlorophenyl)-4-(3'-carboxy-2-chlorostilben-4-yl)oxymethyl-5-isopropylisoxazole; GW4064) led to increased expression of DDAH-1 and CAT-1 in both liver and kidney. In cultured human hepatocytes and kidney proximal tubular epithelial cells, GW4064 increased CAT-1 expression, and this was associated with a significant increase in the cellular uptake of ADMA. Promoter analyses suggest that CAT-1 is a likely target of FXR, and a functional FXR response element was found in the promoter region of CAT-1 gene. These data suggest that FXR may play an important role in regulating blood levels of ADMA via coordinated regulation of DDAH-1 and CAT-1 in liver and kidney.

Cytochrome c/cardiolipin relations in mitochondria: a kiss of death

Recently, phospholipid peroxidation products gained a reputation as key regulatory molecules and participants in oxidative signaling pathways. During apoptosis, a mitochondria-specific phospholipid, cardiolipin (CL), interacts with cytochrome c (cyt c) to form a peroxidase complex that catalyzes CL oxidation; this process plays a pivotal role in the mitochondrial stage of the execution of the cell death program. This review is focused on redox mechanisms and essential structural features of cyt c's conversion into a CL-specific peroxidase that represent an interesting and maybe still unique example of a functionally significant ligand change in hemoproteins. Furthermore, specific characteristics of CL in mitochondria--its asymmetric transmembrane distribution and mechanisms of collapse, the regulation of its synthesis, remodeling, and fatty acid composition--are given significant consideration. Finally, new concepts in drug discovery based on the design of mitochondria-targeted inhibitors of cyt c/CL peroxidase and CL peroxidation with antiapoptotic effects are presented.

Influence of smoking status on progression of endothelial dysfunction. TREND Investigators. Trial on Reversing Endothelial Dysfunction

BACKGROUND

Cigarette smoking is a major risk factor for developing coronary artery disease and is associated with increased coronary morbidity and mortality in patients with established atherosclerosis. This report describes the influence of smoking on coronary endothelial function in normotensive patients with coronary artery disease, but without left ventricular dysfunction, severe hypercholesterolemia, or insulin-dependent diabetes mellitus.

METHODS

Placebo-treated patients (n = 54) from a larger study assessing coronary endothelial function were classified at baseline as smokers or nonsmokers for this subgroup analysis. Patients underwent coronary angiography at baseline and again after 6-month follow-up.

RESULTS

At baseline, there was a trend for a greater decrease in target segment diameter (n = 54) in smokers compared with nonsmokers (-17.2 +/- 5.3% vs. -8.0 +/- 2.5%, acetylcholine 10(-4) mol/l). All measured coronary artery segments (n = 202) showed similar responses (-7.3 +/- 2.7% vs. -3.8 +/- 1.3%, acetylcholine 10(-4) mmol/l, for smokers vs. nonsmokers, respectively). After 6 months, smokers showed an even greater vasoconstrictor response to acetylcholine whereas nonsmokers did not (-21.7 +/- 5.3% vs. -8.3 +/- 2.5%, acetylcholine 10(-4) mmol/l). The vasodilatory response to nitroglycerin was similar in smokers and nonsmokers.

CONCLUSIONS

In current smokers, a marked decline in endothelium-dependent vasomotor response was observed over a 6-month period.

The anti-ischemic potential of angiotensin-converting enzyme inhibition: insights from the heart outcomes prevention evaluation trial

Therapy with an angiotensin-converting enzyme (ACE) inhibitor is established for reducing excessive blood pressure, reducing mortality in patients with congestive heart failure (CHF), preventing the development of CHF in patients with asymptomatic left ventricular (LV) dysfunction, and preventing death and CHF when initiated early after the onset of acute myocardial infarction (MI). Although these benefits have been attributed largely to hemodynamic mechanisms, recent preclinical and clinical evidence reveal ACE inhibition as potent in preventing ischemic events and in blocking an array of ischemic processes, including atherogenesis. A major contributor to this new evidence is the large, placebo-controlled Heart Outcomes Prevention Evaluation (HOPE) trial, which found that the ACE inhibitor ramipril ( 10 mg daily) prevented MI and other ischemic events in patients with a broad range of cardiovascular (CV) risks (including coronary artery disease, stroke, peripheral vascular disease, or diabetes plus one additional risk factor) but no LV dysfunction or history of heart failure at baseline. The data from the HOPE trial suggest a greatly expanded role for ramipril in the prevention and management of CV disease.

Eplerenone improves prognosis in postmyocardial infarction diabetic patients with heart failure: results from EPHESUS

BACKGROUND

The Epleronone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) trial demonstrated that selective aldosterone blockade with eplerenone significantly reduced total mortality by 15%, combined cardiovascular (CV) mortality/CV hospitalization by 13%, CV mortality by 17% and sudden cardiac death by 21%, vs. placebo when added to standard care in patients with left ventricular systolic dysfunction (LVSD) and signs of congestive heart failure (CHF) following acute myocardial infarction (AMI). We retrospectively evaluated the effect of eplerenone vs. placebo in a subset of 1483 diabetic patients with LVSD and signs of CHF following AMI.

METHODS

Diabetic status was determined from medical histories at screening. Analyses were based on time to first occurrence of an event. Results were based on a Cox's proportional hazards regression model stratified by region with treatment, subgroup and treatment-by-subgroup interaction as factors. The 95% confidence intervals for the risk ratios were based on the Wald's test.

RESULTS

Treatment with eplerenone in diabetic patients with CHF following AMI reduced the risk of the primary endpoint, a composite of CV mortality or CV hospitalization, by 17% (p = 0.031). The absolute risk reduction of the primary endpoint was greater in the diabetic cohort (5.1%) than in the non-diabetic cohort (3%). Hyperkalaemia occurred more often with eplerenone than with placebo (5.6 vs. 3%, p = 0.015). Among the diabetic cohorts, the prespecified endpoint of 'any CV disorder' occurred in 28% of the eplerenone group and 35% of the placebo group (p = 0.007).

CONCLUSION

Eplerenone treatment may reduce adverse CV events in diabetic patients with LVSD and signs of CHF following AMI.