New solutions to old problems: A practical approach to identify samples with intravenous fluid contamination in clinical laboratories

OBJECTIVES

Contamination with intravenous (IV) fluids is a common cause of specimen rejection or erroneous results in hospitalized patients. Identification of contaminated samples can be difficult. Common measures such as failed delta checks may not be adequately sensitive nor specific. This study aimed to determine detection criteria using commonly ordered tests to identify IV fluid contamination and validate the use of these criteria.

METHODS

Confirmed contaminated and non-contaminated samples were used to identify patterns in laboratory results to develop criteria to detect IV fluid contamination. The proposed criteria were implemented at a tertiary care hospital laboratory to assess performance prospectively for 6 months, and applied to retrospective chemistry results from 3 hospitals and 1 community lab to determine feasibility and flagging rates. The algorithm was also tested at an external institution for transferability.

RESULTS

The proposed algorithm had a positive predictive value of 92 %, negative predictive value of 91 % and overall agreement of 92 % when two or more criteria are met (n = 214). The flagging rates were 0.03 % to 0.07 % for hospital and 0.003 % for community laboratories.

CONCLUSIONS

The proposed algorithm identified true contamination with low false flagging rates in tertiary care urban hospital laboratories. Retrospective and prospective analysis suggest the algorithm is suitable for implementation in clinical laboratories to identify samples with possible IV fluid contamination for further investigation.

Imprecision of high-sensitivity cardiac troponin assays at the female 99th-percentile

BACKGROUND

An analytical benchmark for high-sensitivity cardiac troponin (hs-cTn) assays is to achieve a coefficient of variation (CV) of ≤ 10.0 % at the 99th percentile upper reference limit (URL) used for the diagnosis of myocardial infarction. Few prospective multicenter studies have evaluated assay imprecision and none have determined precision at the female URL which is lower than the male URL for all cardiac troponin assays.

METHODS

Human serum and plasma matrix samples were constructed to yield hs-cTn concentrations near the female URLs for the Abbott, Beckman, Roche, and Siemens hs-cTn assays. These materials were sent (on dry ice) to 35 Canadian hospital laboratories (n = 64 instruments evaluated) participating in a larger clinical trial, with instructions for storage, handling, and monthly testing over one year. The mean concentration, standard deviation, and CV for each instrument type and an overall pooled CV for each manufacturer were calculated.

RESULTS

The CVs for all individual instruments and overall were ≤ 10.0 % for two manufacturers (Abbott CVpooled = 6.3 % and Beckman CVpooled = 7.0 %). One of four Siemens Atellica instruments yielded a CV > 10.0 % (CVpooled = 7.7 %), whereas 15 of 41 Roche instruments yielded CVs > 10.0 % at the female URL of 9 ng/L used worldwide (6 cobas e411, 1 cobas e601, 4 cobas e602, and 4 cobas e801) (CVpooled = 11.7 %). Four Roche instruments also yielded CVs > 10.0 % near the female URL of 14 ng/L used in the United States (CVpooled = 8.5 %).

CONCLUSIONS

The number of instruments achieving a CV ≤ 10.0 % at the female 99th-percentile URL varies by manufacturer and by instrument. Monitoring assay precision at the female URL is necessary for some assays to ensure optimal use of this threshold in clinical practice.

Effect of a High-Sensitivity Troponin I and Associated Diagnostic Protocol on Emergency Department Length of Stay: A Retrospective Cohort Study

Background

The objective of this study was to assess the introduction of a high-sensitivity troponin I (hs-TnI) assay and its associated accelerated protocol on emergency department (ED) length of stay (LOS) for patients presenting with chest pain, compared to an accelerated diagnostic protocol using conventional troponin (TnI) testing.

Methods

We conducted a retrospective cohort study of all adults with a primary presenting complaint of chest pain of cardiac origin and a Canadian Triage and Acuity Scale score of 2 or 3, between November 8, 2019 and November 9, 2021, to a tertiary-care urban Canadian ED. The primary outcome was ED LOS. Secondary outcomes included consultation proportions and major adverse cardiac events within 30 days of the index ED visit.

Results

A total of 2640 patients presenting with chest pain were included, with 1333 in the TnI group and 1307 in the hs-TnI group. Median ED LOS decreased significantly, from 392 minutes for the TnI group, and 371 minutes for the hs-TnI group (median difference = 21 minutes; 95% confidence interval: 5.3, 36.7). The numbers of consultations and admissions were not statistically different between study periods. The major adverse cardiac events outcomes did not change following the implementation of the hs-TnI test (13.6% vs 13.1%; P = 0.71).

Conclusions

The implementation of an accelerated chest pain protocol using an hs-TnI assay in a tertiary-care Canadian ED was associated with a modest reduction of LOS for all patients, and a substantial reduction of LOS for patients undergoing serial troponin testing. This strategy was safe, with no increase in adverse outcomes.

Ex vivo hemolysis: three cases demonstrating mechanically-induced hemolysis from the extracorporeal circuit during hemodialysis

Sporadic mechanically-induced hemolysis associated with kinks in extracorporeal blood circuits during hemodialysis is a rare but potentially serious complication that exhibits laboratory features consistent with both in vivo and in vitro hemolysis. Misclassification of clinically significant hemolysis as in vitro can lead to inappropriate test cancellation and delayed medical interventions. Here, we report three cases of hemolysis attributed to kinked hemodialysis blood lines, which we have defined as "ex vivo" hemolysis. All three cases demonstrated an initial mixed picture of laboratory features consistent with both classifications of hemolysis. Specifically, absent features of in vivo hemolysis on blood film smear despite normal potassium led to the misclassification of these samples as in vitro hemolysis and their cancellation. A proposed mechanism for these overlapping laboratory features is the recirculation of damaged red blood cells from the kinked or pinched hemodialysis line back into the patient circulation producing an "ex vivo" hemolysis presentation. In two of the three cases, the patients developed acute pancreatitis as a result of hemolysis and required urgent medical follow up. We developed a decision pathway to help laboratories in identifying and handling these samples by recognizing that in vitro and in vivo hemolysis have overlapping laboratory features. These cases highlight the need for laboratorians and the clinical care team to be vigilant about mechanically-induced hemolysis from the extracorporeal circuit during hemodialysis. Communication is critical to identify the cause of hemolysis in these patients and prevent unnecessary delays in result reporting.

Centralization of multisite reagent lot-to-lot validation for Ortho Clinical Vitros chemistry instruments

OBJECTIVE

Reagent lot-to-lot comparisons are recommended by accreditation bodies to ensure that the performance of each reagent lot meets acceptable standards for quality patient results. The general approach is comprised of performing quality control (QC) and patient comparison between the old and new reagent lots and evaluating against a pre-defined criteria. Reagent lot comparison practices are often variable despite using the same instrument across different laboratories. This is costly, time consuming, and can lead to variability in acceptance criteria. While Clinical & Laboratory Standards Institute (CLSI) has a recommended guideline for reagent lot validation, it is often difficult to execute for small and rural laboratories due to limited resources. Defining the analytes required for detailed validation is important to allocate appropriate resources to ensure quality patient results. The goal of this study was to develop a standardized approach to reagent lot validation and optimize lab resources on Vitros chemistry instruments.

DESIGN AND METHOD

This study consists of a retrospective and prospective analysis of reagent lot changes in dry slide chemistry analyzers (Ortho Clinical Diagnostics Vitros). Two years of retrospective reagent lot comparison data was obtained at a single site. A prospective study was conducted by assessing aliquots of 10 patient sample pools at 9 sites with Vitros analyzers.

RESULTS

Of the 19 chemistry analytes evaluated, albumin, sodium, and total protein showed significant differences between reagent lots and also exceeded the pre-defined acceptance criteria.

CONCLUSION

For these analytes, our recommendations are to perform a comprehensive lot validation with QC and patient samples. A simple lot validation with a reflex approach comprised of initially assaying QC can be adapted for the more stable analytes to allow achieving quality patient result in a resource constraint rural environment.

Hydroxocobalamin interference in routine laboratory tests: Development of a protocol for identifying samples and reporting results from patients treated with CyanokitTM

OBJECTIVES

Hydroxocobalamin (OHCob) is an antidote for cyanide poisoning in patients rescued from house fires and is known to cause interference with certain laboratory tests. Consensus is lacking on the extent of this interference and on how to handle these samples. The objectives of this study were to characterize OHCob interference across a wide range of laboratory tests and to develop protocols for identifying and reporting these samples.

DESIGNS & METHODS

Patient plasma samples (n = 5) were spiked with OHCob (1.5 mg/mL) and compared to controls without this drug. A series of analytes were measured using chemistry, urinalysis, coagulation, hematology, and blood gas instruments. Dose-response testing was performed on a subset of assays that showed interferences ≥10%.

RESULTS

Of the 77 analytes evaluated, 27 (35%) showed interference from OHCob, with chemistry and coagulation analytes showing the greatest effects. Of those affected, 22 analytes had a positive interference, whereas 5 analytes had negative interference. Dose-response studies showed dose-dependent increases and/or decreases consistent with initial spiking studies. Although red in colour, plasma samples with OHCob did not trigger hemolysis index flags, necessitating a special sample identification and reporting protocol.

CONCLUSION

OHCob had significant effects on several analytes across different instruments. These findings led to the development of special sample handling and reporting protocols to identify OHCob samples and ensure only accurate results are released. It is vital for emergency departments to document and notify their laboratories whenever blood samples from these patients are drawn.

Analytical Concordance of Diverse Point-of-Care and Central Laboratory Troponin I Assays

BACKGROUND

Cardiac troponin I (cTnI) 99th percentile cutoffs, used in the diagnosis of acute myocardial infarction, are not standardized across cTnI assays. We compared 3 point-of-care (POC) and 1 central laboratory contemporary cTnI assays against the Abbott high-sensitivity (hs) cTnI to evaluate the analytical concordance and the feasibility of using a single cutoff value for all assays.

METHODS

Fresh blood samples collected from 102 inpatients in the coronary care unit were measured on central laboratory instruments (Beckman Coulter DxI AccuTnI+3 TnI, Abbott Architect hs-TnI) and cTnI POC analyzers (Alere Triage Troponin I, Radiometer AQT90, Abbott i-STAT). Agreement and correlation between the contemporary cTnI assays and hs-cTnI assay were assessed using regression analysis. Proportional bias was assessed using Bland-Altman plots. Concordance between the contemporary cTnI and hs-cTnI assays was determined by diagnostic contingency tables at specific cutoffs.

RESULTS

Most POC cTnI assays had excellent correlation with the Abbott hs-cTnI method (r ² = 0.955-0.970) except for Alere Triage (r ² = 0.617), while proportional bias is evident between all cTnI assays. Overall concordance between POC contemporary cTnI assays and hs-cTnI assay was 80% to 90% at their respective 99th percentile cutoffs. The concordance increased to 90% to 95% when a fixed cutoff of 0.03 to 0.05 ng/mL was used across the assays.

CONCLUSIONS

This study demonstrates poor analytical concordance between cTnI assays at the 99th percentile and supports the notion of a single clinical decision limit for cTnI and consequently standardization of diagnostic protocols despite the analytical differences among these assays.

Milrinone therapeutic drug monitoring in a pediatric population: Development and validation of a quantitative liquid chromatography-tandem mass spectrometry method

BACKGROUND

Milrinone is a potent selective phosphodiesterase type III inhibitor which stimulates myocardial function and improves myocardial relaxation. Although therapeutic monitoring is crucial to maintain therapeutic outcome, little data is available. A proof-of-principle study has been initiated in our institution to evaluate the clinical impact of optimizing milrinone dosing through therapeutic drug monitoring (TDM) in children following cardiac surgery. We developed a robust LC-MS/MS method to quantify milrinone in serum from pediatric patients in real-time.

METHODS

A liquid-liquid extraction procedure was used to prepare samples for analysis prior to measurement by LC-MS/MS. Performance characteristics, such as linearity, limit of quantitation (LOQ) and precision, were assessed. Patient samples were acquired post-surgery and analyzed to determine the concentration-time profile of the drug as well as to track turn-around-times.

RESULTS

Within day precision was <8.3% across 3 levels of QC. Between-day precision was <12%. The method was linear from 50 to 800μg/l; the lower limit of quantification was 22μg/l. Comparison with another LC-MS/MS method showed good agreement. Using this simplified method, turnaround times within 3-6h were achievable, and patient drug profiles demonstrated that some milrinone levels were either sub-therapeutic or in the toxic range, highlighting the importance for milrinone TDM.

CONCLUSIONS

This simplified and quick method proved to be analytically robust and able to provide therapeutic monitoring of milrinone in real-time in patients post-cardiac surgery.

Clinical impact of improved point-of-care glucose monitoring in neonatal intensive care using Nova StatStrip: Evidence for improved accuracy, better sensitivity, and reduced test utilization

OBJECTIVES

Studies have demonstrated improved analytical performance of the Nova StatStrip glucose meter, but limited data is available on its clinical performance in critically ill neonates in the neonatal intensive care unit (NICU).

DESIGN AND METHODS

A retrospective charge review was conducted on 651 neonates admitted to the NICU over 2 years. Demographics, sample collection information, and clinical details were recorded. Glucose measurements were performed at the bedside using either the Nova StraStrip or LifeScan SureStep Flexx meters as well as corresponding measurements of laboratory venous plasma glucose. Performance was analyzed by receiver operator characteristic (ROC) curves for detecting hypoglycemia and critical glucose levels.

RESULTS

Linear regression analysis comparing StatStrip and laboratory venous plasma glucose samples demonstrated significantly tighter agreement (r(2)=0.7994) and accuracy (mean bias=0.13mmol/L) than SureStep (r(2)=0.6845 and mean bias=0.53mmol/L). StatStrip also showed improved sensitivity for detecting critical low glucose values ≤3.0mmol/L (80.9 vs 68.9%, p<0.05). ROC curve analysis further demonstrated excellent performance of StatStrip at this cutoff with an AUC of 0.98. Overall, neonates were also tested significantly less frequently with the StatStrip meter by 24% compared to SureStep.

CONCLUSIONS

Implementation of StatStrip led to better agreement with venous plasma glucose, improved detection of critical low glucose results, and more efficient test utilization. This study demonstrates the importance of accurate and sensitive glucose monitoring in the NICU.

Complex Biological Profile of Hematologic Markers across Pediatric, Adult, and Geriatric Ages: Establishment of Robust Pediatric and Adult Reference Intervals on the Basis of the Canadian Health Measures Survey

BACKGROUND

In a collaboration between the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) and the Canadian Health Measures Survey (CHMS), we determined reference value distributions using an a priori approach and created a comprehensive database of age- and sex-stratified reference intervals for clinically relevant hematologic parameters in a large household population of children and adults.

METHODS

The CHMS collected data and blood samples from 11 999 respondents aged 3–79 years. Hematology markers were measured with either the Beckman Coulter HmX or Siemens Sysmex CA-500 Series analyzers. After applying exclusion criteria and removing outliers, we determined statistically relevant age and sex partitions and calculated reference intervals, including 90% CIs, according to CSLI C28-A3 guidelines.

RESULTS

Hematology marker values showed dynamic changes from childhood into adulthood as well as between sexes, necessitating distinct partitions throughout life. Most age partitions were necessary during childhood, reflecting the hematologic changes that occur during growth and development. Hemoglobin, red blood cell count, hematocrit, and indices (mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration) increased with age, but females had lower hemoglobin and hematocrit starting at puberty. Platelet count gradually decreased with age and required multiple sex partitions during adolescence and adulthood. White blood cell count remained relatively constant over life, whereas fibrinogen increased slightly, requiring distinct age and sex partitions.

CONCLUSIONS

The robust dataset generated in this study has allowed observation of dynamic biological profiles of several hematology markers and the establishment of comprehensive age- and sex-specific reference intervals that may contribute to accurate monitoring of pediatric, adult, and geriatric patients.

Complex Reference Values for Endocrine and Special Chemistry Biomarkers across Pediatric, Adult, and Geriatric Ages: Establishment of Robust Pediatric and Adult Reference Intervals on the Basis of the Canadian Health Measures Survey

BACKGROUND

Defining laboratory biomarker reference values in a healthy population and understanding the fluctuations in biomarker concentrations throughout life and between sexes are critical to clinical interpretation of laboratory test results in different disease states. The Canadian Health Measures Survey (CHMS) has collected blood samples and health information from the Canadian household population. In collaboration with the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER), the data have been analyzed to determine reference value distributions and reference intervals for several endocrine and special chemistry biomarkers in pediatric, adult, and geriatric age groups.

METHODS

CHMS collected data and blood samples from thousands of community participants aged 3 to 79 years. We used serum samples to measure 13 immunoassay-based special chemistry and endocrine markers. We assessed reference value distributions and, after excluding outliers, calculated age- and sex-specific reference intervals, along with corresponding 90% CIs, according to CLSI C28-A3 guidelines.

RESULTS

We observed fluctuations in biomarker reference values across the pediatric, adult, and geriatric age range, with stratification required on the basis of age for all analytes. Additional sex partitions were required for apolipoprotein AI, homocysteine, ferritin, and high sensitivity C-reactive protein.

CONCLUSIONS

The unique collaboration between CALIPER and CHMS has enabled, for the first time, a detailed examination of the changes in various immunochemical markers that occur in healthy individuals of different ages. The robust age- and sex-specific reference intervals established in this study provide insight into the complex biological changes that take place throughout development and aging and will contribute to improved clinical test interpretation.

Biochemical Marker Reference Values across Pediatric, Adult, and Geriatric Ages: Establishment of Robust Pediatric and Adult Reference Intervals on the Basis of the Canadian Health Measures Survey

BACKGROUND

Biological covariates such as age and sex can markedly influence biochemical marker reference values, but no comprehensive study has examined such changes across pediatric, adult, and geriatric ages. The Canadian Health Measures Survey (CHMS) collected comprehensive nationwide health information and blood samples from children and adults in the household population and, in collaboration with the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER), examined biological changes in biochemical markers from pediatric to geriatric age, establishing a comprehensive reference interval database for routine disease biomarkers.

METHODS

The CHMS collected health information, physical measurements, and biosamples (blood and urine) from approximately 12 000 Canadians aged 3–79 years and measured 24 biochemical markers with the Ortho Vitros 5600 FS analyzer or a manual microplate. By use of CLSI C28-A3 guidelines, we determined age- and sex-specific reference intervals, including corresponding 90% CIs, on the basis of specific exclusion criteria.

RESULTS

Biochemical marker reference values exhibited dynamic changes from pediatric to geriatric age. Most biochemical markers required some combination of age and/or sex partitioning. Two or more age partitions were required for all analytes except bicarbonate, which remained constant throughout life. Additional sex partitioning was required for most biomarkers, except bicarbonate, total cholesterol, total protein, urine iodine, and potassium.

CONCLUSIONS

Understanding the fluctuations in biochemical markers over a wide age range provides important insight into biological processes and facilitates clinical application of biochemical markers to monitor manifestation of various disease states. The CHMS-CALIPER collaboration addresses this important evidence gap and allows the establishment of robust pediatric and adult reference intervals.

Glycogen synthase kinase-3β inhibition augments diabetic endothelial progenitor cell abundance and functionality via cathepsin B: a novel therapeutic opportunity for arterial repair

Progenitor cell therapy is hindered in patients with diabetes mellitus (DM) due to cellular senescence. Glycogen synthase kinase-3β (GSK3β) activity is increased in DM, potentially exacerbating impaired cell-based therapies. Thus, we aimed to determine if and how GSK3β inhibitors (GSKi) can improve therapeutic efficacy of endothelial progenitor cells (EPC) from patients with DM. Patients with DM had fewer EPCs and increased rates of apoptosis. DM EPCs also exhibited higher levels of GSK3β activity resulting in increased levels of phosphorylated β-catenin. Proteomic profiling of DM EPCs treated with GSKi identified 37 nonredundant, differentially regulated proteins. Cathepsin B (cathB) was subsequently confirmed to be differentially regulated and showed 40% less baseline activity in DM EPCs, an effect reversed by GSKi treatment. Finally, in vivo efficacy of cell-based therapy was assessed in a xenotransplant femoral wire injury mouse model. Administration of DM EPCs reduced the intima-to-media ratio, an effect that was further augmented when DM EPCs were pretreated with GSKi yet absent when cathB was antagonized. In DM, increased basal GSK3β activity contributes to accelerated EPC cellular senescence, an effect reversed by small molecule antagonism of GSK3β, which enhanced cell-based therapy after vascular injury.

Insulin-degrading enzyme deficiency in bone marrow cells increases atherosclerosis in LDL receptor-deficient mice

BACKGROUND

Insulin-degrading enzyme (IDE), a protease implicated in several chronic diseases, associates with the cytoplasmic domain of the macrophage Type A scavenger receptor (SR-A). Our goal was to investigate the effect of IDE deficiency (Ide(-/-)) on diet-induced atherosclerosis in low density lipoprotein-deficient (Ldlr(-/-)) mice and on SR-A function.

METHODS

Irradiated Ldlr(-/-) or Ide(-/-)Ldlr(-/-) mice were reconstituted with wild-type or Ide(-/-) bone marrow and, 6 weeks later, were placed on a high-fat diet for 8 weeks.

RESULTS

After 8 weeks on a high-fat diet, male Ldlr(-/-) recipients of Ide(-/-) bone marrow had more atherosclerosis, higher serum cholesterol and increased lesion-associated β-amyloid, an IDE substrate, and receptor for advanced glycation end products (RAGE), a proinflammatory receptor for β-amyloid, compared to male Ldlr(-/-) recipients of wild-type bone marrow. IDE deficiency in male Ldlr(-/-) recipient mice did not affect atherosclerosis or cholesterol levels and moderated the effects of IDE deficiency of bone marrow-derived cells. No differences were seen between Ldlr(-/-) and Ide(-/-)Ldlr(-/-) female mice reconstituted with Ide(-/-) or wild-type bone marrow. IDE deficiency in macrophages did not alter SR-A levels, cell surface SR-A, or foam cell formation.

CONCLUSION

IDE deficiency in bone marrow-derived cells results in larger atherosclerotic lesions, increased lesion-associated Aβ and RAGE, and higher serum cholesterol in male, Ldlr(-/-) mice.

Extracellular HSP27 acts as a signaling molecule to activate NF-κB in macrophages

Heat shock protein 27 (HSP27) shows attenuated expression in human coronary arteries as the extent of atherosclerosis progresses. In mice, overexpression of HSP27 reduces atherogenesis, yet the precise mechanism(s) are incompletely understood. Inflammation plays a central role in atherogenesis, and of particular interest is the balance of pro- and anti-inflammatory factors produced by macrophages. As nuclear factor-kappa B (NF-κB) is a key immune signaling modulator in atherogenesis, and macrophages are known to secrete HSP27, we sought to determine if recombinant HSP27 (rHSP27) alters NF-κB signaling in macrophages. Treatment of THP-1 macrophages with rHSP27 resulted in the degradation of an inhibitor of NF-κB, IκBα, nuclear translocation of the NF-κB p65 subunit, and increased NF-κB transcriptional activity. Treatment of THP-1 macrophages with rHSP27 yielded increased expression of a variety of genes, including the pro-inflammatory factors, IL-1β, and TNF-α. However, rHSP27 also increased the expression of the anti-inflammatory factors IL-10 and GM-CSF both at the mRNA and protein levels. Our study suggests that in macrophages, activation of NF-κB signaling by rHSP27 is associated with upregulated expression and secretion of key pro- and anti-inflammatory cytokines. Moreover, we surmise that it is the balance in expression of these mediators and antagonists of inflammation, and hence atherogenesis, that yields a favorable net effect of HSP27 on the vessel wall.

Abstract 544: Extracellular Heat Shock Protein 27 Inhibits Foam Cell Formation by Targeting Scavenger Receptor-A in the Vessel Wall

Background: We showed that injection of recombinant heat shock protein 27 (rHSP27) into ApoE -/- mice reduces atherosclerosis lesions and total serum cholesterol levels. Extracellular HSP27 also interacts with scavenger receptor (SR)-A and inhibits acLDL uptake in macrophages, but the role of SR-A in HSP27 atheroprotection remains unclear.

Purpose: To elucidate the mechanism of HSP27 atheroprotection by exploring if the presence of SR-A is required to facilitate its salutary effects.

Methods/Results: rHSP27 treatment of bone-marrow derived macrophages from ApoE -/- mice reduced acLDL uptake (38%, p<0.05) using flow cytometry - effects not observed (p=0.171) in cells from ApoE -/- SR-A -/- mice. rHSP27 reduced acLDL binding (38%, p<0.01) and uptake (34%, p<0.01) in THP-1 macrophages associated with downregulation of SR-A transcript (46%, p<0.01) and total protein levels (63%, p<0.001). Flow cytometry and confocal microscopy revealed reduction in SR-A expression at the cell surface. To explore the signaling involved, NF-kB activation was assessed in THP-1 cells stably transfected with an NF-kB reporter. rHSP27 increased NF-kB activity (7 fold, p<0.001) and induced translocation of the NF-kB p65 subunit from the cytosol to the nucleus - effects that were inhibited (p<0.05) by the NF-kB antagonist, BAY. Addition of BAY inhibited the effect of rHSP27 on SR-A gene and protein expression and acLDL uptake (p<0.05). To explore the importance of SR-A in HSP27 atheroprotection, rHSP25 (mouse homologue) or PBS was administered to ApoE -/- and ApoE -/- SR-A -/- mice for 3 weeks on a high fat diet. Treatment of ApoE -/- mice revealed reductions of en face aortic lesions (39%, p<0.001), SR-A expression in the intima, and total serum cholesterol levels (32%, p<0.01). In the absence of SR-A, HSP27 atheroprotection was abolished (p=0.79) despite similar decreases in serum cholesterol levels (25%, p<0.05).

Conclusions: Extracellular HSP27 inhibits foam cells by downregulating SR-A expression via an NF-κB-dependent mechanism. HSP27 atheroprotection requires the presence of SR-A expression in vivo. In the absence of SR-A, loss of atheroprotection occurs despite reductions in total serum cholesterol levels, suggesting SR-A as a novel target for HSP27 in the vessel wall.

Role of myosin light chain kinase in cardiotrophin-1-induced cardiac myofibroblast cell migration

Chemotactic movement of myofibroblasts is recognized as a common means for their sequestration to the site of tissue injury. Following myocardial infarction (MI), recruitment of cardiac myofibroblasts to the infarct scar is a critical step in wound healing. Contractile myofibroblasts express embryonic smooth muscle myosin, α-smooth muscle actin, as well as collagens I and III. We examined the effects of cardiotrophin-1 (CT-1) in the induction of primary rat ventricular myofibroblast motility. Changes in membrane potential (Em) and Ca2+entry were studied to reveal the mechanisms for induction of myofibroblast migration. CT-1-induced cardiac myofibroblast cell migration, which was attenuated through the inhibition of JAK2 (25 μM AG490), and myosin light chain kinase (20 μM ML-7). Inhibition of K+channels (1 mM tetraethylammonium or 100 μM 4-aminopyridine) and nonselective cation channels by 10 μM gadolinium (Gd3+) significantly reduced migration in the presence of CT-1. CT-1 treatment caused a significant increase in myosin light chain phosphorylation, which could be inhibited by incubation in Ca2+-free conditions or by application of AG490, ML-7, and W7 (100 μM; calmodulin inhibitor). Monitoring myofibroblast membrane potential with potentiometric fluorescent DiBAC4( 3 ) dye revealed a biphasic response to CT-1 consisting of an initial depolarization followed by hyperpolarization. Increased intracellular Ca2+, as assessed by fluo 3, occurred immediately after membrane depolarization and attenuated at the time of maximal hyperpolarization. CT-1 exerts chemotactic effects via multiple parallel signaling modalities in ventricular myofibroblasts, including changes in membrane potential, alterations in intracellular calcium, and activation of a number of intracellular signaling pathways. Further study is warranted to determine the precise role of K+currents in this process.

Tissue deposition of the insect repellent DEET and the sunscreen oxybenzone from repeated topical skin applications in rats

Insect repellent N,N-diethyl-m-toluamide (DEET) and sunscreen oxybenzone are capable of enhancing skin permeation of each other when applied simultaneously. We carried out a cellular study in rat astrocytes and neurons to assess cell toxicity of DEET and oxybenzone and a 30-day study in Sprague-Dawley rats to characterize skin permeation and tissue disposition of the compounds. Cellular toxicity occurred at 1 µg/mL for neurons and 7-day treatment for astrocytes and neurons. DEET and oxybenzone permeated across the skin to accumulate in blood, liver, and brain after repeated topical applications. DEET disappeared from the application site faster than oxybenzone. Combined application enhanced the disposition of DEET in liver. No overt sign of behavioral toxicity was observed from several behavioral testing protocols. It was concluded that despite measurable disposition of the study compounds in vivo, there was no evidence of neurotoxicological deficits from repeated topical applications of DEET, oxybenzone, or both.

Cardiac fibroblast to myofibroblast differentiation in vivo and in vitro: expression of focal adhesion components in neonatal and adult rat ventricular myofibroblasts

In fibrosing hearts, myofibroblasts are associated with cardiac extracellular matrix remodeling. Expression of key genes in the transition of cardiac fibroblast to myofibroblast phenotype in post-myocardial infarction heart and in vitro has not been well addressed. Contractile, focal adhesion-associated, receptor proteins, fibroblast growth factor-2 (FGF-2) expression, and motility were compared to assess phenotype in adult and neonatal rat cardiac fibroblasts and myofibroblasts. Neonatal and adult fibroblasts undergo phenotypic transition to myofibroblastic cells, marked by increased alpha-smooth muscle actin (alphaSMA), smooth muscle myosin heavy chain (SMemb), extra domain-A (ED-A) fibronectin, paxillin, tensin, FGF-2, and TbetaRII receptor. Elevated ED-A fibronectin confirmed fibroblast to supermature myofibroblastic phenotype transition. Presence of myofibroblasts in vivo was noted in sections of healed infarct scar after myocardial infarction, and their expression is similar to that in culture. Thus, cultured neonatal and adult cardiac fibroblasts transition to myofibroblasts in vitro and share expression profiles of cardiac myofibroblasts in vivo. Reduced motility with in vitro passage reflects enhanced production of focal adhesions.

The participation of the Na+-Ca2+ exchanger in primary cardiac myofibroblast migration, contraction, and proliferation

Cardiac ventricular myofibroblast motility, proliferation, and contraction contribute to post-myocardial infarct wound healing, infarct scar formation, and remodeling of the ventricle remote to the site of infarction. The Na+-Ca2+ exchanger (NCX1) is involved in altered calcium handling in cardiac myocytes during cardiac remodeling associated with heart failure, however, its role in cardiac myofibroblast cell function is unexplored. In this study we investigated the involvement of NCX1 as well as the role of non-selective-cation channels (NSCC) in cardiac myofibroblast cell function in vitro. Immunofluorescence and Western blots revealed that P1 cells upregulate alpha-smooth muscle actin (alphaSMA) and embryonic smooth muscle myosin heavy chain (SMemb) expression. NCX1 mRNA and proteins as well as Ca(v)1.2a protein are also expressed in P1 myofibroblasts. Myofibroblast motility in the presence of 50 ng/ml PDGF-BB was blocked with AG1296. Myofibroblast motility, contraction, and proliferation were sensitive to KB-R7943, a specific NCX1 reverse-mode inhibitor. In contrast, only proliferation and contraction, but not motility were sensitive to nifedipine, while gadolinium (NSCC blocker) was only associated with decreased motility. ML-7 treatment was associated with inhibition of the chemotactic response and contraction. Thus cardiac myofibroblast chemotaxis, contraction, and proliferation were sensitive to different pharmacologic treatments suggesting that regulation of transplasmalemmal calcium movements may be important in growth factor receptor-mediated processes. NCX1 may represent an important moiety in suppression of myofibroblast functions.

Differential and combined effects of cardiotrophin-1 and TGF-β1 on cardiac myofibroblast proliferation and contraction

Myofibroblasts respond to an array of signals from mitogens and cytokines during the course of wound healing following a myocardial infarction (MI), and these signals may coordinate ventricular myofibroblast proliferation. Furthermore, myofibroblasts are contractile and contribute to wound contraction by imparting mechanical tension on surrounding extracellular matrix. Although TGF-β1, CT-1, and PDGF-BB participate in various stages of post-MI wound healing, their combined net effect(s) on myofibroblast function is unknown. We investigated myofibroblast proliferation, expression of cell cycle proteins, and contractile function of cells treated with TGF-β1 and/or CT-1. We confirmed that TGF-β1 (10 ng/ml) suppresses proliferation of these cells, whereas CT-1 (10 ng/ml) and, for comparative purposes, PDGF-BB (1 ng/ml) treatments were associated with proliferation. Specific TGF-β1 treatment ablated CT-1-induced myofibroblast proliferation. TGF-β1 effects were specific, as they were suppressed by either TGF-β-neutralizing antibody or viral Smad7 overexpression. TGF-β1 treatment also increased expression of p27 and decreased expression of cyclin E and Cdk2 in primary cells. CT-1 (10 ng/ml) treatment of myofibroblasts had no effect on collagen gel deformation versus controls, whereas TGF-β1 (10 ng/ml) and PDGF (10 ng/ml) treatments were associated with significant cell contraction; again, TGF-β1-mediated contraction was unaffected by CT-1. Alone, CT-1 and TGF-β1 treatments exert opposing effects on myofibroblast function, whereas in combination TGF-β1-mediated effects supersede those of CT-1 (and PDGF-BB). Thus TGF-β1 and CT-1 exert differential effects on myofibroblast proliferation and contraction in vitro, and we suggest that a balance of these effects may be important for the execution of normal cardiac wound healing.