Aptamer proteomics for biomarker discovery in heart failure with reduced ejection fraction

Background

Though current heart failure (HF) biomarkers are highly prognostic, systematically characterizing associations between circulating proteins and risk of subsequent events may improve clinical risk prediction and illuminate new biological pathways. Large-scale assays measuring thousands of proteins now enable unbiased proteomic investigation in clinical trials.

Purpose

To identify and replicate serum proteins associated with HF events in patients with chronic HF with reduced ejection fraction (HFrEF), and to develop and validate a proteomic risk score.

Methods

Serum levels of 4076 proteins were measured at baseline in the ATMOSPHERE (n=1261, 487 events over 6 years) and PARADIGM-HF (n=1257, 287 events over 4 years) trials of chronic HFrEF using a modified aptamer-based proteomics assay. Proteins associated with the primary endpoint, HF hospitalization or cardiovascular death, were identified in the ATMOSPHERE discovery cohort (false discovery rate<0.05) by Cox regression adjusted for age, sex, treatment arm, and anticoagulant use, and replicated in PARADIGM-HF (Bonferroni-corrected p<0.05). A proteomic risk score was derived in ATMOSPHERE using Cox LASSO penalized regression and evaluated in PARADIGM-HF compared to the MAGGIC clinical risk score and N-terminal pro-B-type natriuretic peptide (NT-proBNP). For proteins associated with the primary endpoint, pathway analysis was conducted using Ingenuity Pathway analysis and an exploratory two-sample Mendelian randomization was performed using genetic and outcome data from both trials and protein quantitative trait loci from deCODE to infer which identified proteins contribute to HF prognosis.

Results

We identified 377 serum proteins associated with the primary endpoint in ATMOSPHERE and replicated 167 in PARADIGM-HF. Prognostic proteins included known HF biomarkers Growth Differentiation Factor 15, NT-proBNP, and Angiopoietin-2, and also a previously unrecognized HF biomarker: Sushi, Von Willebrand Factor Type A, EGF And Pentraxin Domain Containing 1 (SVEP1) (HR 1.60 [95% CI 1.44–1.79] per standard deviation [SD], p=2x10–17) (Table 1). Proteins related to hepatic fibrosis, granulocyte adhesion, and inhibition of matrix metalloproteinases were over-represented. A 64-protein risk score derived in ATMOSPHERE predicted clinical events in PARADIGM-HF with greater discrimination (c-statistic 0.70) than the MAGGIC clinical score (c-statistic 0.61), NT-proBNP (c-statistic 0.65), or both (c-statistic 0.66) (Figure 1). Genetically predicted levels of NT-proBNP, WISP2, FSTL1, and CTSS were associated with the primary endpoint by Mendelian randomization.

Conclusions

We identify SVEP1, an extracellular matrix protein known to cause inflammation in vascular smooth muscle cells, as a previously unrecognized HF biomarker. A 64-protein score improved risk discrimination compared with NT-proBNP and may assist in identifying high-risk patients for clinical trials or disease management programs.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): The ATMOSPHERE and PARADIGM-HF trials were sponsored by Novartis

Alkaline phosphatase and bilirubin combined are a powerful predictor of outcome in patients with heart failure and reduced ejection fraction: an analysis of the ATMOSPHERE and PARADIGM-HF trials

Introduction

Bilirubin is a recognized predictor of adverse outcomes in patients with heart failure and reduced ejection fraction (HFrEF), possibly because it is a marker of congestion. Alkaline phosphatase (ALP) is an enzyme produced in many tissues including the biliary ducts and elevated levels are also associated with congestion.

Purpose

To examine the prognostic value of ALP alone and in combination with bilirubin in patients with HFrEF.

Methods

The study population was ambulatory patients with HFrEF enrolled in 2 recent clinical trials with similar inclusion and exclusion criteria: ATMOSPHERE (derivation cohort) and PARADIGM-HF (validation). Cut points to define elevated bilirubin and alkaline phosphatase were >17mg/dL and >120 U/L respectively. The composite of cardiovascular death or HF hospitalization, its components, and all-cause death related to elevation of one, other or both of bilirubin and ALP was examined using Cox regression. Univariable and multivariable models with adjustment for other recognized prognostic variables including NT-proBNP were analyzed.

Results

Of 7016 patients with HFrEF enrolled in ATMOSPHERE, 6870 had a measurement of both bilirubin and ALP at baseline: mean age 63 years, 22% women, mean LVEF 28% and proportion NYHA class III/IV 37%. Bilirubin and ALP were both normal in 4810 (70.0%) patients, bilirubin was elevated in 1393 (20.3%), ALP was elevated in 360 (5.2%) and both were elevated in 307 (4.5%) patients. Patients with elevation of both ALP and bilirubin were older, had lower systolic blood pressure, higher heart rate, higher NT-pro BNP, more clinical features of congestion, more atrial fibrillation and a greater proportion were treated with diuretics and digoxin. The primary endpoint rates (per 100 person-years) were 10.4 (95% CI 9.9–11.0) when both markers were normal, 15.1 (13.9–16.4) when bilirubin was elevated, 12.4 (10.4–14.9) when alkaline phosphatase was elevated, and 25.6 (22.0–29.9) when both markers were elevated (Figure 1). The adjusted hazard ratios (95% CI) were (both biomarkers normal = reference): elevated bilirubin 1.19 (1.07–1.31), P=0.001; elevated ALP 1.03 (0.84–1.26), P=0.81; both elevated 1.45 (1.21–1.73), P<0.001. Elevation of both bilirubin and ALP was a significant independent predictor of the components of the primary outcome and all-cause death, the corresponding hazard ratios for all cause death were 1.12 (0.99–1.25), p=0.06; 1.19 (0.96–1.47), p=0.12; and 1.51 (1.25–1.82), p<0.001. These findings were validated in PARADIGM-HF (Table 1).

Conclusions

Elevation of ALP in combination with elevated bilirubin identifies a small group of patients at very high risk of adverse outcomes. This may reflect more significant congestion. ALP and bilirubin, inexpensive and routinely measured biochemical tests, are useful prognostic markers in patients with HFrEF.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship.

Impact of changes in tricuspid regurgitation on clinical outcomes following mitral valve teer compared to guideline-directed medical therapy: a sub-analysis of the COAPT trial

Funding Acknowledgements

Type of funding sources: None.

OnBehalf

Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients with Functional Mitral Regurgitation (COAPT)

Background

Prior studies suggest tricuspid regurgitation (TR) diminishes/resolves following mitral valve surgery and thus do not require treatment and may not influence outcomes.

Purpose

  We sought to evaluate the change in TR (ΔTR) and its association with outcomes after transcatheter edge-to-edge repair (TEER) compared with guideline-directed medical therapy (GDMT) in the COAPT trial.

Methods

Patients from the COAPT trial with echo core lab TR assessment at baseline and 30-day follow-up (n = 504) were included and divided into 2 groups: those whose TR worsened (ΔTR-INC) and those with no change or improvement in TR (ΔTR-SAME/DEC).  Two-year composite endpoints of death or heart failure hospitalization (HFH) and the individual components were analyzed, after excluding events occurring within the first 30 days.

Results

ΔTR-SAME/DEC occurred in 430 pts (228 TEER, 202 GDMT) while ΔTR-INC was noted in 74 pts (38 TEER, 36 GDMT) (Figure 1A). From 30 days to 2 years, ΔTR-INC pts had a higher rate of the composite outcome of death or HFH compared with ΔTR-SAME/DEC (p = 0.006, Figure 1B). Both 2-year death (HR 1.52, 95% CI 1.01-2.27; p = 0.04) and HFH (HR 1.52, 95% CI 1.04-2.22; p = 0.03) were associated with ΔTR-INC. Assessed by treatment group (Figure 1C and 1D), the relationship between ΔTR-INC and composite death or HFH was significant in GDMT alone pts (HR 1.86, 95% CI 1.21-2.86) but not in TEER pts (HR 1.33, 95% CI 0.79-2.23), although interaction testing demonstrated consistency between the two treatments  (Pint = 0.31). 

Conclusions

Worsening TR at 30 days occurred in ∼15% of pts in the COAPT trial whether they were treated with TEER or GDMT alone. DTRINC was associated with increased death and HFH during 2-year follow-up. Abstract Figure 1

1386Reduction of mitral regurgitation in patients with heart failure and secondary mitral regurgitation: relationship between changes in brain natriuretic peptide and outcomes from the COAPT trial

Background

Brain natriuretic peptide (BNP) is a well-established predictor of hospitalization and death in patients with heart failure (HF). In the COAPT trial, treatment of patients with HF and secondary mitral regurgitation (SMR) with transcatheter mitral valve repair (TMVr) reduced the 2-year rates of all-cause mortality and HF hospitalization compared with maximally-tolerated guideline-directed medical therapy (GDMT) alone. Whether these improvements in outcomes were reflected in serial changes in BNP levels has not been reported.

Purpose

Herein, we report the first results of serial changes in BNP levels by treatment group in patients from the COAPT trial.

Methods

614 patients with HF and 3+ or 4+ SMR were randomized 1:1 to TMVr + GDMT or GDMT alone. Key inclusion criteria included NYHA functional class II-IVa (ambulatory), ischemic or non-ischemic cardiomyopathy with LVEF 20%-50% and LVESD ≤70 mm. Baseline BNP or NT-proBNP levels were drawn at baseline and at 6 and 12 months. For the present analysis NT-proBNP (pg/ml) values were converted to BNP values (pg/ml) using a ratio of 7 to 1.

Results

At baseline, mean values of BNP were not significantly different between treatment groups (945 pg/ml vs. 964 pg/ml in the TMVr + GDMT and GDMT groups respectively, p=0.84). At 6 months, mean values of BNP in the TMVr + GDMT group were significantly lower than in the GDMT alone group (690 pg/ml vs 893 pg/ml, p=0.02) but not at 12 months (584 pg/ml vs. 728 pg/ml, p=0.22). By analysis of covariance, BNP decreased to a greater degree after TMVr + GDMT compared with GDMT only at both 6 and 12 months (least squares mean differences of −121 pg/ml and −166 pg/ml respectively, both p<0.05) (Figure).

Change in BNP level from baseline

Conclusions

In patients with HF and 3+ or 4+ SMR enrolled in the COAPT trial, reduction of SMR with TMVr reduced BNP compared with maximally-tolerated GDMT only, a change which paralleled the reductions noted in all-cause mortality and HF hospitalizations with TMVr.

Acknowledgement/Funding

Abbott

IPL576,092, a novel anti-inflammatory compound, inhibits leukocyte infiltration and changes in lung function in response to allergen challenge

IPL576,092, a lead compound from a novel class of polyhydroxylated sterols, was tested in models of allergen-induced bronchoconstriction and airway inflammation. In a rat ovalbumin lung inflammation model, orally administered IPL576,092 significantly inhibited the challenge-mediated increase in total bronchoalveolar lavage leukocyte numbers, and macrophage and lymphocyte infiltration (1-10 mg/kg/day). There was a similar trend towards inhibition of eosinophil and neutrophil accumulation. Sheep were treated with IPL576,092 by inhalation (400 microg/kg/day), and lung resistance and airway hyper-responsiveness (AHR) were determined after Ascaris suum challenge. IPL576,092 significantly reduced the early and late phase bronchoconstrictor responses by 63+/-4.6 and 84+/-4.6%, respectively. IPL576,092 also blocked AHR (2.2+/-5.7% change from pre-challenge PC400), whereas control animals showed a 62.2+/-2.6% decrease in the PC400 (p<0.05). Oral IPL576,092 (5 mg/kg/day) also significantly decreased hyper-reactivity in mice. In a guinea pig model, IPL576,092 (5 mg/kg/day) significantly protected against allergen-induced increases in lung resistance (11.4+/-2.3 control versus 4.8+/-01.5 IPL576,092, area under the curve) and inhibited the increase in lung elastance (280+/-58 control versus 167+/-52 IPL576,092, p<0.05). IPL576,092, unlike dexamethasone, did not significantly decrease rat serum corticosterone levels or thymus and spleen weights, supporting a mechanism of action different from classic glucocorticoids. IPL576,092 significantly attenuates characteristics of an asthmatic response, indicating therapeutic potential for this drug class.

Respiratory drive during carbachol challenge in allergic sheep

Diaphragmatic activity is the standard assessment of respiratory neural output but is difficult to measure and cannot be used for long-term clinical monitoring. The tidal breathing minute ventilation (V') and mean inspiratory flow (VT/tI) reflect respiratory drive and can be monitored non-invasively using respiratory inductive plethysmography (RIP). Recent findings indicate that peak inspiratory acceleration (PIA) correlates to diaphragmatic activity during CO2 rebreathing in piglets. The aim of the present study was to assess whether tidal breathing peak inspiratory acceleration reflects respiratory drive during carbachol challenge. Aerosolized carbachol was administered to 15 allergic sheep until pulmonary resistance increased by at least 400%. After threshold dose, slight increases in V' and VT/tI were seen (8 and 5%, respectively; P=NS), while PIA increased by 30% (P<0.05). The change in PIA was closely correlated to changes in V'[bar over] and VT/tI (r=0.73, P<0.01 and r=0.88, P<0.001, respectively). In conclusion, peak inspiratory acceleration reflected respiratory drive during bronchoprovocation. Further, this new measure of drive has the potential to accurately estimate drive in chronic obstructive lung disease where intrinsic positive end expiratory pressure prevents accurate selection of beginning inspiration necessary for computation of, e.g. VT/tI.

Fluorescence spectroscopic investigation of effect of excipients on epidermal barrier and transdermal systems

Excipients are often used in transdermal formulations to overcome the formidable barrier offered by the epidermis in order to achieve the target flux. In this study we describe the use of frequency-domain fluorescence spectroscopy to characterize the effect of two commonly used excipients, propyleneglycol monolaurate (PGML) and oleic acid on stratum corneum and in a silicone-based transdermal delivery system. Fluorescence lifetime and limiting anisotropy for the probe 1,6-diphenyl-1,3,5-hexatriene in isolated human epidermis were measured as a function of formulation treatment. The drop in lifetime ranged from 0.5 to 2.3 ns, indicative of an increased dielectric constant of the lipophilic barrier exposed to all formulations. This increase is due to increased partitioning of the polar excipients from the delivery system into the stratum corneum. The limiting anisotropy showed a drop of 0.1 in the case of the epidermis exposed to oleic acid formulation and not the PGML formulations, indicative of the different modes of action for these two excipients. The fluorescence data suggested fluidization of the silicone matrix by both oleic acid and PGML. The dynamic fluorescence measurements described in this study are a powerful way to screen formulations while gaining valuable mechanistic insight into the mode of flux enhancement in transdermal formulations.

Characterization of the stratum corneum lipid matrix using fluorescence spectroscopy

Using fluorescence techniques, we studied the dynamics of the lipid bilayer matrix of human stratum corneum (SC) and compared the results with that of distearoyl-phosphatidylcholine (DSPC). We employed a series of 9-anthroyloxy fatty acids (AF) that partitioned into the bilayer, enabling us to evaluate this structure as a function of depth within the lamellae. With AF probes, the re-orientation of the fluorophore is known to be affected by the polarity, hydrogen bonding, and rigidity of the surrounding medium, altering the emission maximum and lifetime in the excited state. In addition, we evaluated quenching, in which iodide collides with the fluorophore, revealing information on the accessibility of the fluorophore located in the bilayer. The emission and lifetime data showed that the reorientation of the fluorophore in SC was more hindered than in DSPC, indicating that SC bilayers were more rigid than DSPC bilayers. Quenching data of both SC and DSPC indicated that the deeper the fluorophore was positioned in the bilayer, the less accessible it was to iodide, pointing to a gradient in accessibility. In addition, the quenching results also showed that the SC is less accessible to iodide than in DSPC. The observed differences in bilayer rigidity and quencher accessibility between the two systems can be explained by differences in lipid composition and hydration. Whereas the DSPC bilayer consists of phospholipids, SC bilayers are composed of more anhydrous lipids like cholesterol and ceramides, which form a tight bilayer packing. In this way SC lipids exist in a relatively anhydrous and rigid environment, forming an effective diffusion barrier to water and ions.

The influence of an electric field on ion and water accessibility to stratum corneum lipid lamellae

PURPOSE

To study ion transport through stratum corneum (SC) lipid lamellae under passive and iontophoretic conditions.

METHODS

Iodide ion transport was measured by fluorescence quenching. Since the process involves diffusion of an iodide ion to the fluorophore located within the SC lamellae, the accessibility of iodide ions was measured. Moreover, the use of anthroyloxy fatty acid probes, provided information as a function of depth within the lamellae.

RESULTS

Fluorescence quenching by iodide ions increased with iontophoretic current density, suggesting increased ion accessibility within the SC lamellae. In addition, at constant current, quenching decreased as the fluorophore was located deeper within the lamellae. This gradient in ion accessibility suggests that more iodide is found near the head-group than near the core of the SC lipid lamellae. Results obtained in the absence of iodide also show increased water accessibility during iontophoresis.

CONCLUSIONS

These results show that in the presence of an applied electric field the SC lipid lamellae interior becomes more accessible to water and ions. These results imply that during iontophoresis, ion and water transport through human skin is associated, at least in part, with the SC lipid lamellae.

Activation of NMDA and muscarinic receptors induces nur-77 mRNA in hippocampal neurons

Using in situ hybridization, we show that the expression of the immediately-early gene, nur-77, increases rapidly and transiently in hippocampal neurons following activation of muscarinic and N-methyl-D-aspartate receptors and after hippocampal long-term potentiation (LTP). On the basis of these results we hypothesize that nur-77 may coordinate with other transcription factors to initiate subsequent changes in hippocampal gene expression associated with plasticity-related activation of N-methyl-D-aspartate and muscarinic receptors.

Effect of PGML excipient mixture in a transdermal system on the in vitro transport of estradiol across skin

PURPOSE

To measure the effect of a combination of excipients from a silicone based pressure sensitive adhesive (PSA) on drug transport across skin.

METHODS

Partitioning of propylene glycol monolaurate (PG-ML) from silicone PSA and a solution formulation into the stratum corneum (SC) was measured using radiolabeled PG-ML. Transport of a model drug, estradiol, as well as PG-ML across skin were measured in vitro using heat separated epidermis from human cadaver skin.

RESULTS

The PG-ML partitioning into SC showed a saturation and was independent of the formulation. The local dielectric of the lipid bilayers of the SC showed an increase as a result of PG-ML uptake, as determined by the decrease in fluorescence lifetime of a lipophilic probe incorporated into the SC. However, there was no alteration of lipid packing in SC.

CONCLUSIONS

The PG-ML and estradiol transport showed a good correlation over 3 days, suggesting that the two species are co-transported across the epidermis.

Fluorescence spectroscopy of 9-anthroyloxy fatty acids in solvents

A series of anthroyloxy fatty acid (AF) fluorescent probes, with the anthroyloxy group covalently linked at various positions along the alkyl chain, were studied in solvents exhibiting a wide range of polarity and hydrogen-bond donor (Hd) and acceptor (Ha) ability. These probes were sensitive to the solvent polarity as reflected by the Stokes' shift observed in steady state fluorescence. As determined by multi-linear regression analysis of the observed Stokes' shift and solvent parameters, such as orientation polarizability (delta f), Hd and Ha of the solvents, all the probes were sensitive to the Hd of solvents but were not affected by the Ha of solvents except the 2-AF. Due to the proximity of the polar headgroup to the fluorophore, it appears that some intramolecular hydrogen-bonding is present in 2-AF, an interaction that is sensitive to the pH of the solvent, but is less sensitive to the Hd and Ha of the solvents. Fluorescence lifetimes measured by the multi-frequency phase-modulation technique in mixtures of hexane and ethanol reflect a modified Stern-Volmer behavior suggesting the second solvent, ethanol, specifically interacts with the probe, in part through collisional quenching. Also, the lifetime data were sensitive to very low concentrations of the second solvent (0-0.1%, by vol.). The results from this study provide insight into the intrinsic differences between the different AF positions that must be taken into consideration while investigating the dynamics of lipid bilayer systems. Moreover, this study illustrates the utility and resolving power of lifetime based measurements needed for the interpretation of heterogeneous biophysical environments.

Brain-derived neurotrophic factor expression after long-term potentiation

Long-term potentiation (LTP) of perforant-path dentate granule cell synapses, in awake rats, was followed by a time-dependent expression of brain-derived neurotrophic factor (BDNF) mRNA in dentate granule cells. This BDNF expression was blocked by the N-methyl-D-aspartate (NMDA) antagonist dizocilpine maleate (MK-801), which also blocked LTP induction, and by sodium pentobarbital, which shortens LTP persistence. These results suggest that BDNF may participate in the NMDA-receptor mediated cascade of events that result in LTP stabilization.

Fluorescence anisotropy studies on the interaction of the short chain n-alkanols with stratum corneum lipid liposomes (SCLL) and distearoylphosphatidylcholine (DSPC)/distearoylphosphatidic acid (DSPA) liposomes

Previously, the action of the short chain n-alkanols (from C1 to C5) and isopropanol as possible enhancers on the transport of lipophilic and polar/ionic permeants across hairless mouse skin was investigated. In the present study, the steady-state fluorescence anisotropy was measured as a means of estimating the changes in fluidity caused by the n-alkanols at different depths in the stratum corneum lipid liposomes (SCLL). Some selected experiments with the distearoylphosphatidylcholine (DSPC)/distearoylphosphatidic acid (DSPA) liposomes were performed for relative comparisons. The effects of the n-alkanols on polarity sensitive parameters such as fluorescence lifetimes, fluorescence quantum yield ratios, and emission maxima were studied in the SCLL. The polarity of the bilayer decreased as the fluorescent probe was placed closer to the bilayer center and the n-alkanols did not alter this gradient. Assessment of the depth-dependent effects of the n-alkanols using SCLL showed that most of the significant changes in fluidity induced by the n-alkanols were observed at intermediate depths (C2-C9) and there was little or no increase in fluidity in the deep hydrophobic region close to the bilayer center. These results suggest that the short chain n-alkanols work as effective 'fluidizing' agents at the intermediate depths (C2-C9) in the bilayer.

Inhibition of antigen-induced airway and cutaneous responses by heparin: a pharmacodynamic study

We have previously shown that heparin attenuates the acute bronchoconstrictor response and immediate cutaneous reaction (ICR) to antigen in allergic sheep. In the present investigation, we studied the pharmacodynamics of the antiallergic action of heparin. Specific lung resistance (sRL) was measured in eight sheep, allergic to Ascaris suum antigen, before and 5 min after inhalation challenge with the antigen. On different experiment days, antigen challenge was repeated after pretreatment with 1) aerosol heparin (1,000 U/kg) administered < or = 20 min, 6 h, 12 h, and 24 h and 2) intravenous heparin (1,000 U/kg) administered < or = 20 min, 1 h, 6 h, and 12 h before antigen challenge. sRL increased by 374 +/- 116% (SE) above baseline with antigen alone. Both aerosol and intravenous heparin attenuated the antigen effects on sRL in a time-dependent fashion. Prolonging the lag time between pretreatment and antigen challenge decreased the inhibitory effect of aerosol heparin; delta sRL was 31 +/- 29, 99 +/- 38, 142 +/- 40, and 306 +/- 60% for < or = 20-min, 6-h, 12-h, and 24-h pretreatment protocols, respectively. In contrast, prolonging the lag time increased the inhibitory effect of intravenous heparin: delta sRL was 246 +/- 64, 66 +/- 26, and 76 +/- 32% for < or = 20 min, 1 h, and 6 h, respectively. In seven additional sheep pretreatment with intravenous heparin (1,000 U/kg) attenuated the ICR also in a time-dependent manner; the inhibitory effect of heparin on ICR to antigen was enhanced 60% by increasing the heparin pretreatment interval from 20 to 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between sphingosine and cholesteryl sulfate in epidermal lipids

Free sphingosine, a material with multiple and potent biological activities, is known to occur in high concentration in mammalian epidermis. In the present study, thin-layer chromatography showed that in lipid extracts of human and pig stratum corneum, sphingosine forms a relatively stable compound with endogenous cholesteryl sulfate. NMR spectrometry of sphingosine and its hydrochloride, sulfate, and mixtures with cholesteryl or dodecyl sulfate showed that interaction with the organic sulfates constituted simple salt formation. Under neutral or weakly acidic conditions, such salts were only slightly dissociated and migrated on thin-layer chromatograms as discrete compounds. Thin-layer chromatography revealed undissociated salt formation between several long-chain bases and organic sulfates, and showed that their interaction is stoichiometric. However, undissociated salts were not formed between long-chain bases and fatty acids or phosphatidic acid. Undissociated salt formation may therefore be specific for organic bases and sulfates. It was concluded that the free sphingosine in the stratum corneum may be present as its cholesteryl sulfate salt and in this form be unavailable for permeation into the viable epidermal cells.

Partition of sodium dodecyl sulfate into stratum corneum lipid liposomes

Synthetic detergents produce deleterious effects on human skin as the result of being taken up by the stratum corneum (SC). The present study aimed to determine to what extent a typical detergent enters the SC lipid lamellae, and what effect this might have on the physical properties of the lipids. These effects were studied in large unilamellar liposomes prepared from SC lipids (50% by weight of epidermal ceramides, 28% cholesterol, 17% free fatty acids, and 5% cholesteryl sulfate) by extrusion through successive polycarbonate filters of decreasing pore size, finally 400 nm. Freeze-fracture electron microscopy and light-scattering particle size analysis indicated a uniform liposome diameter averaging 230 nm. Partitioning of sodium dodecyl sulfate (SDS) into the lipid phase from aqueous buffer solutions was measured using the SC lipid liposomes and [U-14C]SDS. The partition coefficient was 416, 450, and 588 at pH 8.5 and 524, 507, and 807 at pH 7 for three different concentrations (0.1%, 0.02%, and 0.004%) of SDS. This high degree of partitioning into the liposomes is consistent with the high level of SDS partitioning seen in full SC. At the maximum, the SDS represented 18% of the liposomal lipids. Preparation of stable liposomes from SC lipids to which 10% or 20% of SDS had been added confirmed the ability of the liposomes to survive these high concentrations of surfactant. The permeability of the liposomes was enhanced as a result of SDS partitioning into the bilayers, as measured by the increased release of trapped [U-14C]glucose from these vesicles, and by their increased permeability to water in osmotic shock experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Lamellar structures formed by stratum corneum lipids in vitro: a deuterium nuclear magnetic resonance (NMR) study

Hydrated lipid mixtures consisting of stratum corneum ceramides, cholesterol, specifically deuterated palmitic acid, and cholesteryl sulfate were investigated by solid-state 2H NMR spectroscopy at different temperatures. The mole ratio of cholesterol to ceramides was varied from 1 to 0. 2H NMR spectra from these mixtures showed powder patterns with quadrupolar splittings smaller than those obtained from control mixtures containing dipalmitoylphosphatidylcholine (DPPC) instead of the ceramides. This result is attributed to the rigid amide group of the ceramides, with a planar configuration, which could prevent close packing of the alpha-methylenes of the acyl chains. There was a gradual loss of symmetry in the powder pattern as the amount of cholesterol was decreased and the amount of ceramides (or DPPC) was increased concomitantly. The loss was more pronounced in the ceramide-containing samples. This phenomenon is interpreted as a decrease in the axial reorientation rate of the alpha-deuterated palmitic acid in the bilayers, presumably caused by the increased hydrogen bonding resulting from the high amount of hydroxyl-bearing ceramides. Spectra obtained at temperatures above 60 degrees C indicated the formation of a hexagonal phase (HII) by the ceramide-containing mixtures. Spectra of the omega-deuterated palmitic acid in the mixture containing 76 mol% ceramides and no cholesterol indicated phase separation into a more rigid phase and a more mobile phase in the temperature range of 25 to 60 degrees C. The bilayer configuration of lipids at 25 degrees C was confirmed by thin-section electron microscopy.

Structures formed by epidermal lipids in vitro

The extracellular membranous structures of stratum corneum constitute the major barrier to percutaneous penetration. These intercellular lipid lamellae are devoid of phospholipids and are unique in their lipid composition. In this article, some of the recent investigations of the structures formed by the stratum corneum lipids in vitro are discussed with relevance to the barrier function of epidermis. These studies have provided some insight into the dramatic physical changes that occur in the membranous structures of the epidermis during the formation of the stratum corneum.

Deuterium NMR investigation of polymorphism in stratum corneum lipids

The intercellular lipid lamellae of stratum corneum constitute the major barrier to percutaneous penetration. Deuterium magnetic resonance and freeze-fracture electron microscopic investigation of hydrated lipid mixtures consisting of ceramides, cholesterol, palmitic acid and cholesteryl sulfate and approximating the stratum corneum intercellular lipid composition, revealed thermally induced polymorphism. The transition temperature of bilayer to hexagonal transition decreased as the ratio of cholesterol to ceramides in these mixtures was lowered. Lipid mixtures in which the stratum corneum ceramides were replaced by synthetic dipalmitoylphosphatidylcholine did not show any polymorphism throughout the temperature range used in the present study. The ability of the ceramide-containing samples to form hexagonal structures establishes a plausible mechanism for the assembly of the stratum corneum intercellular lamellae during the final stages of epidermal differentiation. Also, the bilayer to hexagonal phase transition of these nonpolar lipid mixtures could be used to enhance the penetration of drugs through skin.

Interaction between corneocytes and stratum corneum lipid liposomes in vitro

Small unilamellar vesicles were made from a mixture of epidermal ceramides (45%), cholesterol (35%), free fatty acids (15%) and cholesteryl sulfate (5%). Isolated corneocytes prepared from pig epidermis were added to the liposomes and the interaction between corneocytes and liposomes was studied by (1) thin-section electron microscopy and (2) monitoring the release of aqueous contents of the vesicles by following the fluorescence intensity of carboxyfluorescein entrapped in the vesicles. The vesicles adsorbed readily onto the corneocytes and slowly transformed into lamellar sheets. Enhanced fluorescence intensity indicated a corneocyte-induced membrane fusion process that resulted in the release of aqueous contents of the vesicles. The results suggest a cohesive role for the corneocyte cell envelope, which consists of a monomolecular layer of lipids covalently bound to the outside of a cross-linked protein envelope. This may be one of the major factors in the reassembly of extruded membranous disks into lamellar sheets which occurs during the final stages of epidermal differentiation.

Preparation of model membranes for skin permeability studies using stratum corneum lipids

Liposomes were prepared from stratum corneum lipids consisting of epidermal ceramides (55% by weight), cholesterol (25%), free fatty acids (15%), and cholesteryl sulfate (5%). Multiple lamellae were formed by air-drying the liposomal suspensions on hydrophilic filter disks, and water permeabilities through these filter-supported lamellae were measured using a diffusion cell. Ultrastructure of the lipid lamellae was characterized by scanning and thin-section electron microscopy. Water flux data and ultrastructure of the model membranes are discussed in relation to stratum corneum, the horny layer of the epidermis that constitutes the epidermal barrier.

Pharmacological profile of MDL 26,024GO: a novel antiasthmatic agent

MDL 26,024GO was shown to be an orally absorbed mediator release inhibitor in the rat PCA and PPA tests. In addition, the compound was shown to both elicit and inhibit elicitation of the Bezold-Jarisch reflex in the dog. MDL 26,024GO also significantly reduced Ascaris-induced changes in pulmonary mechanics in cynomolgus monkeys. The compound inhibited both early and late phase antigen induced-changes in Ascaris-sensitive sheep, as well as the increased airway hyperreactivity which normally follows antigen challenge. These results suggest the compound may have therapeutic potential in the treatment of asthma.

Should the patella be resurfaced in total knee arthroplasty? Efficacy of patellar resurfacing

To assess the long-term efficacy of patellar resurfacing, 100 knees were evaluated in 84 patients. The operations were performed between 1978 and 1982. The follow-up period ranged from 60 to 103 months. The diagnosis was degenerative joint disease (DJD) in 83%, rheumatoid arthritis in 12%, and miscellaneous in 5% of the knees. The implant (47 knees) and nonimplant (53 knees) groups were comparable with respect to age, body size, and length of follow-up period. The analysis revealed equivocal results. Considering all diagnostic categories combined, rest pain was marginally better in the resurfaced group (p = 0.04), but this difference resulted from an unequal distribution of subjects between mild and zero pain categories. Pain with walking, maximum walking distance, ability to climb stairs and rise from a chair, active arc of motion, extensor lag, and quadriceps strength were similar in the two groups. When the DJD group was considered separately, no significant difference emerged. There was little evidence to support a recommendation for routine patellar resurfacing in total knee arthroplasty.