Assessing the performance of ChatGPT in bioethics: a large language model's moral compass in medicine

Chat Generative Pre-Trained Transformer (ChatGPT) has been a growing point of interest in medical education yet has not been assessed in the field of bioethics. This study evaluated the accuracy of ChatGPT-3.5 (April 2023 version) in answering text-based, multiple choice bioethics questions at the level of US third-year and fourth-year medical students. A total of 114 bioethical questions were identified from the widely utilised question banks UWorld and AMBOSS. Accuracy, bioethical categories, difficulty levels, specialty data, error analysis and character count were analysed. We found that ChatGPT had an accuracy of 59.6%, with greater accuracy in topics surrounding death and patient-physician relationships and performed poorly on questions pertaining to informed consent. Of all the specialties, it performed best in paediatrics. Yet, certain specialties and bioethical categories were under-represented. Among the errors made, it tended towards content errors and application errors. There were no significant associations between character count and accuracy. Nevertheless, this investigation contributes to the ongoing dialogue on artificial intelligence's (AI) role in healthcare and medical education, advocating for further research to fully understand AI systems' capabilities and constraints in the nuanced field of medical bioethics.

Cholesterol deficiency as a mechanism for autism: A valproic acid model

Dysregulated cholesterol metabolism represents an increasingly recognized feature of autism spectrum disorder (ASD). Children with fetal valproate syndrome caused by prenatal exposure to valproic acid (VPA), an anti-epileptic and mood-stabilizing drug, have a higher incidence of developing ASD. However, the role of VPA in cholesterol homeostasis in neurons and microglial cells remains unclear. Therefore, we examined the effect of VPA exposure on regulation of cholesterol homeostasis in the human microglial clone 3 (HMC3) cell line and the human neuroblastoma cell line SH-SY5Y. HMC3 and SH-SY5Y cells were each incubated in increasing concentrations of VPA, followed by quantification of mRNA and protein expression of cholesterol transporters and cholesterol metabolizing enzymes. Cholesterol efflux was evaluated using colorimetric assays. We found that VPA treatment in HMC3 cells significantly reduced ABCA1 mRNA, but increased ABCG1 and CD36 mRNA levels in a dose-dependent manner. However, ABCA1 and ABCG1 protein levels were reduced by VPA in HMC3. Furthermore, similar experiments in SH-SY5Y cells showed increased mRNA levels for ABCA1, ABCG1, CD36, and 27-hydroxylase with VPA treatment. VPA exposure significantly reduced protein levels of ABCA1 in a dose-dependent manner, but increased the ABCG1 protein level at the highest dose in SH-SY5Y cells. In addition, VPA treatment significantly increased cholesterol efflux in SH-SY5Y, but had no impact on efflux in HMC3. VPA differentially controls the expression of ABCA1 and ABCG1, but regulation at the transcriptional and translational levels are not consistent and changes in the expression of these genes do not correlate with cholesterol efflux in vitro.

Fostering student and faculty scholarship in an accelerated three-year medical school

Background: In acknowledgement of the importance of research competency in academic medicine, an extracurricular student research program and faculty development researcher pathway was developed to promote scholarly productivity at New York University (NYU) Long Island School of Medicine (LISOM), a three-year accelerated Liaison Committee on Medical Education (LCME)-accredited medical school. The aim was to enhance medical students’ and faculty scholarly productivity, by creating new training programs targeting research skills and academic collaboration. Impact was assessed by initial review of the extracurricular student research program and faculty development researcher pathway. Methods: Electronic surveys via Google were sent out to all current (n = 72) students on 9/20/2021 and the faculty identified based on their primary appointment to NYU LISOM in the learning management system on 9/17/2021 to determine participation in research, presentation of research findings, satisfaction with the program, and research opportunities for students.  Student scholarly productivity was tracked using PubMed, restricted to search years 2020 through 2022.  For the faculty development researcher pathway, publications were tracked for each participant before and after completion of the program, with pre- and post-completion dates ranging from 2012 through 2020.  Results: Student survey results (29 responses out of 72) indicated 28% of students were involved in research with institutional faculty and 59% were interested in starting a research project. Most students involved in extracurricular research were satisfied with their experience and eight students have publications with faculty.  For the faculty development researcher pathway, 35% of the participants increased publications after program graduation. Conclusions: Outcomes from the student research program and faculty researcher pathway were positive regarding student research engagement and faculty scholarly productivity, though long-term outcomes are yet to be evaluated. Progress will be tracked as students continue through undergraduate and graduate medical education, and as both students and faculty progress throughout their career.

Effect of oxytocin on lipid accumulation under inflammatory conditions in human macrophages

INTRODUCTION AND AIMS

Oxytocin (OT) is a neuropeptide hormone secreted by the posterior pituitary gland. Deficits in OT action have been observed in patients with behavioral and mood disorders, some of which correlate with an increased risk of cardiovascular disease (CVD). Recent research has revealed a wider systemic role that OT plays in inflammatory modulation and development of atherosclerotic plaques. This study investigated the role that OT plays in cholesterol transport and foam cell formation in LPS-stimulated THP-1 human macrophages.

METHODS

THP-1 differentiated macrophages were treated with media, LPS (100 ng/ml), LPS + OT (10 pM), or LPS + OT (100 pM). Changes in gene expression and protein levels of cholesterol transporters were analyzed by real time quantitative PCR (RT-qPCR) and Western blot, while oxLDL uptake and cholesterol efflux capacity were evaluated with fluorometric assays.

RESULTS

RT-qPCR analysis revealed a significant increase in ABCG1 gene expression upon OT + LPS treatment, compared to LPS alone (p = 0.0081), with Western blotting supporting the increase in expression of the ABCG1 protein. Analysis of oxLDL uptake showed a significantly lower fluorescent value in LPS + OT (100pM) -treated cells when compared to LPS alone (p < 0.0001). While not statistically significant (p = 0.06), cholesterol efflux capacity increased with LPS + OT treatment.

CONCLUSION

We demonstrate here that OT can attenuate LPS-mediated lipid accumulation in THP-1 macrophages. These findings support the hypothesis that OT could be used to reduce pro-inflammatory and potentially atherogenic changes observed in patients with heightened CVD risk. This study suggests further exploration of OT effects on monocyte and macrophage cholesterol handling in vivo.

Gut bacterial taxonomic abundances vary with cognition, personality, and mood in the Wisconsin Longitudinal Study

Animal studies have shown that the gut microbiome can influence memory, social behavior, and anxiety-like behavior. Several human studies show similar results where variation in the gut microbiome is associated with dementia, depression, and personality traits, though most of these studies are limited by small sample size and other biases. Here, we analyzed fecal samples from 313 participants in the Wisconsin Longitudinal Study, a randomly selected population-based cohort of older adults, with measured psycho-cognitive dimensions (cognition, mood, and personality) and key confounders. 16s V4 sequencing showed that Megamonas is associated with all measured psycho-cognitive traits, Fusobacterium is associated with cognitive and personality traits, Pseudoramibacter_Eubacterium is associated with mood and personality traits, Butyvibrio is associated with cognitive traits, and Cloacibacillus is associated with mood traits. These findings are robust to sensitivity analyses and provide novel evidence of shared relationships between the gut microbiome and multiple psycho-cognitive traits in older adults, confirming some of the animal literature, while also providing new insights. While we addressed some of the weaknesses in prior studies, further studies are necessary to elucidate temporal and causal relationships between the gut microbiome and multiple psycho-cognitive traits in well-phenotyped, randomly-selected population-based samples.

Idiopathic pulmonary fibrosis: Molecular mechanisms and potential treatment approaches

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive disease with high mortality that commonly occurs in middle-aged and older adults. IPF, characterized by a decline in lung function, often manifests as exertional dyspnea and cough. Symptoms result from a fibrotic process driven by alveolar epithelial cells that leads to increased migration, proliferation, and differentiation of lung fibroblasts. Ultimately, the differentiation of fibroblasts into myofibroblasts, which synthesize excessive amounts of extracellular matrix proteins, destroys the lung architecture. However, the factors that induce the fibrotic process are unclear. Diagnosis can be a difficult process; the gold standard for diagnosis is the multidisciplinary conference. Practical biomarkers are needed to improve diagnostic and prognostic accuracy. High-resolution computed tomography typically shows interstitial pneumonia with basal and peripheral honeycombing. Gas exchange and diffusion capacity are impaired. Treatments are limited, although the anti-fibrotic drugs pirfenidone and nintedanib can slow the progression of the disease. Lung transplantation is often contraindicated because of age and comorbidities, but it improves survival when successful. The incidence and prevalence of IPF has been increasing and there is an urgent need for improved therapies. This review covers the detailed cellular and molecular mechanisms underlying IPF progression as well as current treatments and cutting-edge research into new therapeutic targets.

The role of interferon-γ in cardiovascular disease: an update

PURPOSE

Cardiovascular disease (CVD) is the leading cause of death, globally, and its prevalence is only expected to rise due to the increasing incidence of co-morbidities such as obesity and diabetes. Medical treatment of CVD is directed primarily at slowing or reversing the underlying atherosclerotic process by managing circulating lipids with an emphasis on control of low-density lipoprotein (LDL) cholesterol. However, over the past several decades, there has been increasing recognition that chronic inflammation and immune system activation are important contributors to atherosclerosis. This shift in focus has led to the elucidation of the complex interplay between cholesterol and cellular secretion of cytokines involved in CVD pathogenesis. Of the vast array of cytokine promoting atherosclerosis, interferon (IFN)-γ is highly implicated and, therefore, of great interest.

METHODS

Literature review was performed to further understand the effect of IFN-γ on the development of atherosclerotic CVD.

RESULTS

IFN-γ, the sole member of the type II IFN family, is produced by T cells and macrophages, and has been found to induce production of other cytokines and to have multiple effects on all stages of atherogenesis. IFN-γ activates a variety of signaling pathways, most commonly the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway, to induce oxidative stress, promote foam cell accumulation, stimulate smooth muscle cell proliferation and migration into the arterial intima, enhance platelet-derived growth factor expression, and destabilize plaque. These are just a few of the contributions of IFN-γ to the initiation and progression of atherosclerotic CVD.

CONCLUSION

Given the pivotal role of IFN-γ in the advancement of CVD, activation of its signaling pathways is being explored as a driver of atherosclerosis. Manipulation of this key cytokine may lead to novel therapeutic avenues for CVD prevention and treatment. A number of therapies are being explored with IFN-γ as the potential target.

The gut microbiome and psycho-cognitive traits

The idea that trillions of bacteria inhabit our gut is somewhat unnerving, yet these bacteria may have a greater influence on our behavior than previously thought. Accumulating data strongly suggest that these gut commensal organisms have a strong inter-relationship with our brain and behavior, including cognitive function, mood, and personality. In this chapter, we discuss the role of the gut microbiome in the development of human personality, mood and mood disorders, and cognition, with a particular emphasis on the current consensus and controversies in the literature surrounding the behavioral effects of bioactive metabolites, microbial ratio shifts, and neurotransmitter synthesis facilitated by the microbiome.

Adenosine and the Cardiovascular System

Adenosine is an endogenous nucleoside with a short half-life that regulates many physiological functions involving the heart and cardiovascular system. Among the cardioprotective properties of adenosine are its ability to improve cholesterol homeostasis, impact platelet aggregation and inhibit the inflammatory response. Through modulation of forward and reverse cholesterol transport pathways, adenosine can improve cholesterol balance and thereby protect macrophages from lipid overload and foam cell transformation. The function of adenosine is controlled through four G-protein coupled receptors: A₁, A_2A, A_2B and A₃. Of these four, it is the A_2A receptor that is in a large part responsible for the anti-inflammatory effects of adenosine as well as defense against excess cholesterol accumulation. A_2A receptor agonists are the focus of efforts by the pharmaceutical industry to develop new cardiovascular therapies, and pharmacological actions of the atheroprotective and anti-inflammatory drug methotrexate are mediated via release of adenosine and activation of the A_2A receptor. Also relevant are anti-platelet agents that decrease platelet activation and adhesion and reduce thrombotic occlusion of atherosclerotic arteries by antagonizing adenosine diphosphate-mediated effects on the P2Y12 receptor. The purpose of this review is to discuss the effects of adenosine on cell types found in the arterial wall that are involved in atherosclerosis, to describe use of adenosine and its receptor ligands to limit excess cholesterol accumulation and to explore clinically applied anti-platelet effects. Its impact on electrophysiology and use as a clinical treatment for myocardial preservation during infarct will also be covered. Results of cell culture studies, animal experiments and human clinical trials are presented. Finally, we highlight future directions of research in the application of adenosine as an approach to improving outcomes in persons with cardiovascular disease.

Cholesterol efflux alterations in adolescent obesity: role of adipose-derived extracellular vesical microRNAs

BACKGROUND

Macrophage cholesterol efflux capacity has been identified as a predictor for cardiovascular disease. We assessed the relationship between adipocyte-derived extracellular vesicle microRNAs and macrophage cholesterol efflux capacity.

METHODS

We assessed an adolescent cohort (n = 93, Age, median (IQR) = 17 (3) year, Female = 71, Male = 22) throughout the BMI continuum (BMI = 45.2 (13.2) kg/m²) for: (1) cholesterol efflux capacity and lipoprotein profiles; (2) adipocyte-derived extracellular vesicle microRNAs in serum; (3) the role of visceral adipose tissue extracellular vesicle in regulation of cholesterol efflux and cholesterol efflux gene expression in THP-1 macrophages in vitro.

RESULTS

Efflux capacity was significantly associated with HDL (r = 0.30, p = 0.01) and LDL (r = 0.33, p = 0.005) particle size. Multivariate-analysis identified six microRNAs associated (p < 0.05) with cholesterol efflux capacity: miR-3129-5p (Beta = 0.695), miR-20b (0.430), miR9-5p (0.111), miR-320d (- 0.190), miR301a-5p (0.042), miR-155-5p (0.004). In response to increasing concentrations (1 μg/mL vs. 3 μg/mL) of VAT extracellular vesicle, cholesterol efflux (66% ± 10% vs. 49% ± 2%; p < 0.01) and expression of ABCA1 (FC = 1.9 ± 0.8 vs 0.5 ± 0.2; p < 0.001), CD36 (0.7 ± 0.4 vs. 2.1 ± 0.8, p = 0.02), CYP27A1 (1.4 ± 0.4 vs. 0.9 ± 0.5; p < 0.05), and LXRA (1.8 ± 1.1 vs. 0.5 ± 0.2; p < 0.05) was altered in THP-1 cells in vitro.

CONCLUSION

Adipocyte-derived extracellular vesicle microRNAs may, in part, be involved macrophage cholesterol efflux regulation.

Accelerated Atherosclerosis in Rheumatoid Arthritis: Mechanisms and Treatment

Background:

Rheumatoid arthritis (RA) is a chronic systemic autoimmune inflammatory disorder that increases the risk of developing cardiovascular disease. There is accumulating evidence that the RA disease state accelerates the formation of atherosclerotic plaques. Treatments for RA improve joint symptomatology and may reduce inflammation, but consideration of their effects on the cardiovascular system is generally low priority.

Objective:

Since cardiovascular disease is the leading cause of mortality in RA patients, the impact of RA therapies on atherosclerosis is an area in need of attention and the focus of this review.

Results:

The drugs used to treat RA may be analgesics, conventional disease-modifying anti-rheumatic drugs, and/or biologics, including antibodies against the cytokine tumor necrosis factor-α. Pain relievers such as nonselective non-steroidal anti-inflammatory drugs and cyclooxygenase inhibitors may adversely affect lipid metabolism and cyclooxygenase inhibitors have been associated with increased adverse cardiovascular events, such as myocardial infarction and stroke. Methotrexate, the anchor disease-modifying anti-rheumatic drug in RA treatment has multiple atheroprotective advantages and is often combined with other therapies. Biologic inhibitors of tumor necrosis factor-α may be beneficial in preventing cardiovascular disease because tumor necrosis factor-α promotes the initiation and progression of atherosclerosis. However, some studies show a worsening of the lipid profile in RA with blockade of this cytokine, leading to higher total cholesterol and triglycerides.

Conclusion:

Greater understanding of the pharmacologic activity of RA treatments on the atherosclerotic process may lead to improved care, addressing both damages to the joints and heart.

Oxytocin: Potential to mitigate cardiovascular risk

Cardiovascular disease (CVD) remains the leading cause of death worldwide, despite multiple treatment options. In addition to elevated lipid levels, oxidative stress and inflammation are key factors driving atherogenesis and CVD. New strategies are required to mitigate risk and most urgently for statin-intolerant patients. The neuropeptide hormone oxytocin, synthesized in the brain hypothalamus, is worthy of consideration as a CVD ancillary treatment because it moderates factors directly linked to atherosclerotic CVD such as inflammation, weight gain, food intake and insulin resistance. Though initially studied for its contribution to parturition and lactation, oxytocin participates in social attachment and bonding, associative learning, memory and stress responses. Oxytocin has shown promise in animal models of atherosclerosis and in some human studies as well. A number of properties of oxytocin make it a candidate CVD treatment. Oxytocin not only lowers fat mass and cytokine levels, but also improves glucose tolerance, lowers blood pressure and relieves anxiety. Further, it has an important role in communication in the gut-brain axis that makes it a promising treatment for obesity and type 2 diabetes. Oxytocin acts through its receptor which is a class I G-protein-coupled receptor present in cells of the vascular system including the heart and arteries. While oxytocin is not used for heart disease at present, residual CVD risk remains in a substantial portion of patients despite multidrug regimens, leaving open the possibility of using the endogenous nonapeptide as an adjunct therapy. This review discusses the possible role for oxytocin in human CVD prevention and treatment.

Amyloid toxicity in Alzheimer's disease

A major feature of Alzheimer's disease (AD) pathology is the plaque composed of aggregated amyloid-β (Aβ) peptide. Although these plaques may have harmful properties, there is much evidence to implicate soluble oligomeric Aβ as the primary noxious form. Aβ oligomers can be generated both extracellularly and intracellularly. Aβ is toxic to neurons in a myriad of ways. It can cause pore formation resulting in the leakage of ions, disruption of cellular calcium balance, and loss of membrane potential. It can promote apoptosis, cause synaptic loss, and disrupt the cytoskeleton. Current treatments for AD are limited and palliative. Much research and effort is being devoted to reducing Aβ production as an approach to slowing or preventing the development of AD. Aβ formation results from the amyloidogenic cleavage of human amyloid precursor protein (APP). Reconfiguring this process to disfavor amyloid generation might be possible through the reduction of APP or inhibition of enzymes that convert the precursor protein to amyloid.

Exosomes in Cholesterol Metabolism and Atherosclerosis

OBJECTIVE

Exosomes are small secreted membrane vesicles formed in the late endocytic compartments by inward budding. Interest in these extracellular vesicles and their role in atherosclerosis is growing, as they can affect multiple cellular processes that lead to lipid overload, cytokine secretion and cellular adhesion. Exosomes protect and transport lipids, proteins, and RNAs, fostering intercellular communication among different cell types involved in atherogenesis such as macrophages, endothelium and smooth muscle. Their molecular composition reflects their cell type of origin, but they share attributes because they are enriched in proteins of their endosomal source.

CONCLUSION

This review will describe the current state of our knowledge of exosome involvement in the development of atherosclerosis. The transfer of signaling molecules, lipids, mRNAs, and microRNAs via exosomes with effects on monocyte and macrophage cholesterol metabolism, endothelial cell and platelet activation and smooth muscle proliferation will be discussed. Finally, therapeutic potential of exosomes and clinical application will be explored.

COX-2-dependent and independent effects of COX-2 inhibitors and NSAIDs on proatherogenic changes in human monocytes/macrophages

It is the second decade of controversy regarding the cardiovascular effects of cyclo-oxygenase-2 (COX-2) inhibitors. At this time, celecoxib is the only available COX-2-specific inhibitor for treatment of pain and inflammation. Therefore, the present study was designed primarily to determine the impact of celecoxib on cholesterol handling (uptake via scavenger receptors and efflux from the cells) and foam cell formation in human THP-1 macrophages, followed by comparison to rofecoxib and other non-steroidal anti-inflammatory drugs (NSAIDs). THP-1 human macrophages and peripheral blood mononuclear cells were incubated with: celecoxib, rofecoxib, naproxen (at 5, 10, 25 µM) and acetaminophen (0.5 mM, 1 mM)±oxidized low-density lipoprotein (oxLDL, 25 µg/mL). Scavenger receptors: CD36, LOX-1, SR-A1, and CXCL16 and cholesterol efflux proteins: ATP-binding cassette transporter (ABC) A1 and G1, and 27-hydroxylase were detected. The adhesion of monocytes to cultured endothelial cells with/ without COX-2 inhibitors/NSAIDs was also analyzed. The presence of celecoxib and rofecoxib (at high concentrations) significantly decreased expression of 27-hydroxylase and ABCA1, interfering with normal cholesterol outflow from macrophages. Acetaminophen and the non-specific COX inhibitor naproxen had no significant effect on these proteins. Only celecoxib had a profound effect on the class B scavenger receptor CD36 and the class E receptor LOX1. We demonstrate that in contrast to celecoxib, rofecoxib and naproxen increased adhesive properties of monocytes to endothelial cells. This work might contribute to our understanding of multiple mechanisms underlying elevated cardiovascular risk upon the use of COX-2 inhibitors and uncover new possibilities to enhance the safety profile of existing COX-2 inhibitors.

1: COMPARATIVE EFFECT OF SELECTIVE AND NON-SELECTIVE COX-2 INHIBITORS ON LIPID ACCUMULATION IN HUMAN MACROPHAGES

Purpose of Study

It is the second decade of controversy regarding the cardiovascular (CV) effects of cycloxygenase-2 (COX-2) inhibitors. COX-2 inhibitors possess anti-inflammatory and analgesic effects comparable with conventional non-steroidal anti-inflammatory drugs, but produce fewer gastrointestinal adverse effects. Here we demonstrate that only selective COX-2 inhibitors cause disruption of the delicate balance between cholesterol efflux and influx that leads to lipid overload and macrophage foam cell formation (FCF).

Methods Used

THP-1 human macrophages were incubated with: celecoxib (10 µM, 25 µM); rofecoxib (10 µM, 25 µM); naproxen (10 µM, 25 µM); acetaminophen (0.5 mM, 1 mM)±oxidized low density lipoprotein (oxLDL, 25 µg/ml, 48 h) or 5 µg/ml (Dil)-oxLDL. FCF (% oil red O stained cells) and oxLDL accumulation were determined (fluorescent intensity). Scavenger receptors: CD36, LOX-1, SR-A1 and CXCL16 and cholesterol efflux proteins: ATP-binding cassette transporter (ABC) A1 and ABCG1 were detected in macrophages by QRT-PCR and immunocytochemistry.

Summary of Results

Celecoxib decreased ABCA1 and ABCG1 message in a concentration dependent manner: 68.2±13.36% for ABCA1 and 65.7±13.36% for ABCG1 (control set at 100%, n=6, P<0.01). Neither naproxen nor acetaminophen significantly affected expression of cholesterol efflux proteins. Both specific and nonspecific COX-2 inhibitors had a significant impact on expression of scavenger receptors CD36, LOX-1 and SR-A1–nearly double control (n=6, P<0.05). However, only specific COX-2 inhibitors significantly increased FCF in THP-1 differentiated macrophages (62.2±5.2% for celecoxib and 56.3±3.4% for rofecoxib vs. 33.5±5.1% for untreated cells, P<0.05).

Conclusions

Here we report that only specific COX-2 inhibitors might contribute to atherogenesis by promoting lipid overload and lipoprotein accumulation. This may explain, in part, the increased CV risk in patients taking COX-2 inhibitors for extended periods. Despite increased scavenger receptor expression, naproxen and acetaminophen do not impact lipid content, perhaps because efflux pathways remain intact.

MP1: CORRECTING ATHEROGENIC EFFECTS OF LUPUS PLASMA ON MACROPHAGES WITH RESVERATROL AND MYCOPHENOLATE

Purpose of Study

Premature atherosclerosis with coronary artery disease is a major cause of morbidity in Systemic Lupus Erythematosus (SLE). SLE patient plasma induces a pro-atherogenic profile of cholesterol transport genes in macrophages. A common immunosuppressive treatment for SLE, mycophenolate (MMF) reduces scavenger receptors thus reducing lipid influx. We have demonstrated atheroprotective properties of the polyphenol resveratrol on cholesterol efflux. This study determines whether MMF and resveratrol work synergistically to regulate cholesterol transport in macrophages exposed to pro-atherogenic SLE plasma.

Methods Used

THP-1 human macrophages (106/ml) were incubated in 10% SLE plasma with: media (control); MMF (1 µg/ml); resveratrol (50 µM); and MMF+resveratrol. After 24 h incubation, total RNA and protein were isolated. Message level of scavenger receptors CD36, LOX1, and SRA1; and efflux proteins 27-hydroxylase, ATP binding cassette transporter (ABC)A1, and ABCG1 were evaluated by QRT-PCR and confirmed by immunoblot. Cholesterol efflux was measured by Amplex Red Cholesterol Assay kit run±cholesterol esterase.

Summary of Results

In 10% SLE plasma, MMF suppressed efflux genes ABCA1 and ABCG1 (58.38±3.5% and 72.98±3.3%) vs. SLE plasma alone (p<0.0001) while MMF+resveratrol corrected this suppression. In SLE plasma, MMF+resveratrol decreased ScrA1 and LOX-1 by 15±2.5% and 47±1.0%, respectively vs. resveratrol alone (p<0.0001). SLE plasma promoted cholesterol accumulation in THP-1 macrophages and prevented efflux into medium. It increased the ratio of cholesterol esters to free cholesterol (ChE/FC). Resveratrol decreased intracellular cholesterol and restored ChE/FC ratios to that of cells in healthy control plasma.

Conclusions

MMF and resveratrol exhibit complimentary effects on macrophages exposed to SLE plasma. Both agents combined restore cholesterol influx and efflux gene expression to that of cells treated with control plasma. Resveratrol additionally reverses cholesterol accumulation caused by SLE plasma. Further evaluation of resveratrol+MMF in atherosclerosis in SLE may lead to improved treatment.

10: CHOLESTEROL FLUX PATHWAY ABNORMALITIES INDUCED BY PLASMA FROM PATIENTS WITH CHRONIC KIDNEY DISEASE

Purpose of Study

Chronic kidney disease (CKD) is a known risk factor for cardiovascular disease (CVD). Patients with CKD have a high prevalence of atherosclerosis. However, CVD risk associated with CKD is not entirely explained by standard lipid profile or liver handling of cholesterol, as evidenced by the resistance to statin benefits seen in later stages of CKD. This study aims to detect changes in expression of cholesterol transport proteins in the setting of CKD and to determine if such changes adversely affect lipid handling by macrophages leading to cholesterol overload and atheromatous foam cell formation.

Methods Used

THP-1 human macrophages (106/ml) were incubated for 18 h–24 h with plasma obtained from 10 CKD patients (7 male, 3 female) or 10 healthy control subjects (4 male, 6 female). CKD patients were not on dialysis and had not received renal transplant. Following incubation, mRNA was isolated and reverse transcribed. The resulting cDNA was subjected to quantitative real-time PCR using specific primers for ATP binding cassette transporter (ABC)A1 (cholesterol efflux protein) and CD36, (a scavenger receptor with the capacity to endocytose oxidized LDL).

Summary of Results

PCR analysis showed that ABCA1 mRNA was reduced by 23±5% (p<0.0001) while CD36 mRNA was decreased by 36±7% (p<0.0001) in macrophages exposed to CKD plasma as compared to healthy control.

Conclusions

These findings suggest a different mechanism of lipid dysregulation associated with CKD that may explain the pathogenesis of elevated CVD risk in CKD and lack of response to statins. This mechanism, through pro-atherogenic suppression of ABCA1, differs from our finding in autoimmune rheumatic diseases where, in addition to lowering of ABCA1, augmentation of CD36 was also observed. In CKD, a paradoxical decrease in CD36 could compromise macrophage clearance of lipids, increasing vulnerability to lipoprotein thrombi in kidney. Further lowering of monocyte CD36 with statins would be of little benefit if CD36 is already low in CKD. Defining changes in lipid handling in CKD could lead to novel, targeted CVD treatment approaches in the CKD population.

11: THE ADENOSINE A2A RECEPTOR AGONIST UK-432,097 STIMULATES ANTI-ATHEROGENIC REVERSE CHOLESTEROL TRANSPORT PROTEINS IN THP-1 HUMAN MACROPHAGES

Purpose of Study

Methotrexate (MTX) is an anti-rheumatic drug with atheroprotective properties mediated through adenosine release and activation of the adenosine A2A receptor (A2AR). A2AR ligation increases reverse cholesterol transport via upregulation of cholesterol efflux proteins ATP-binding cassette transporter (ABC)A1 and ABCG1, liver X receptor (LXR) and cholesterol 27-hydroxylase. MTX is non-specific and associated with adverse effects on liver and kidney. Therefore, this study examines the anti-atherogenic efficacy of a specific A2AR agonist, UK-432,097, a drug with an established safety profile in humans.

Methods Used

THP-1 human macrophages were incubated in the following conditions: (1) RPMI media (untreated control); (2) dimethyl sulfoxide vehicle control; (3) UK-432,097 (100 nM); (4) ZM-241385 (1 µM) (A2AR antagonist)+UK-432,097 (100 nM). Gene expression analysis was performed using QRT-PCR for cholesterol efflux genes, normalized to the housekeeping gene GAPDH. Western blotting was performed using specific antibodies. All data were analyzed by one-way ANOVA with P values <0.05 considered significant.

Summary of Results

Following 6 h exposure to UK-432,097, mRNA and protein levels of ABCA1 increased by 88.75±5.4% and by 56.34±12.4% above control (P<0.01), respectively. ABCG1 expression increased by 58.42±6.32% and 65.45±5.24% vs. control (P<0.01), respectively. Following 18 h incubation in UK-432,097, 27-hydroxylase mRNA and protein increased by 46.45±3.4% and 50.27±8.9% (P<0.01), respectively. Message and protein level of LXRα were upregulated to 155.80±4.9% and 157.98±12.9% (n=3, P<0.01), respectively. A2AR blockade with ZM-241385 negated the effect of UK-432,097. UK-432,097 decreased oxidized LDL uptake by 28.9% in THP-1 macrophages (P<0.01).

Conclusions

This study demonstrates that UK-432,097 increases anti-atherogenic reverse cholesterol transport proteins with concomitant reduction in oxidized lipid accumulation in THP-1 macrophages. Since MTX is already being used in clinical trials to reduce cardiovascular risk, our results encourage further studies of specific A2AR agonists as cardioprotective treatment in high risk individuals.

Application of angiotensin II to healthy rat sciatic nerve can produce neuropathy without associated vasculopathy

Elevated angiotensin II (AII) levels have been associated with hypertension, diabetes, and polyneuropathy. It is unknown whether AII applied to healthy nerve can be used to model a confined neuronal injury by producing localized vasculopathy and associated neuropathy. In this study, angiotensin II (2.2 μg/ml) or saline was infused constantly via osmotic pump onto the sciatic nerve of 20 rats for 12 weeks. Nerve conduction studies were repeated every 4 weeks, and sciatic nerve was collected for pathological analysis at 12 weeks. Animals infused with AII showed a significant decrease in nerve fiber diameter (P < 0.001), axon diameter (P < 0.001), and myelin thickness (P < 0.001), despite the absence of electrophysiological changes. Surprisingly, there was no significant difference in vessel diameter or wall thickness. AII can cause structural alterations in healthy nerve without associated changes in vasculature, implying the existence of additional previously unrecognized mechanisms of AII-induced neuronal injury.

The effect of subacute denervation on the electrical anisotropy of skeletal muscle: implications for clinical diagnostic testing

OBJECTIVE

Applied electrical current flows preferentially along rather than across muscle fibers, a characteristic called anisotropy. In this study, we investigate the alteration in muscle anisotropy after denervation.

METHODS

Eight adult male rats underwent sciatic nerve crush and the gastrocnemius was harvested from 1 to 2.5 weeks later. Muscle from 12 additional healthy rats was also obtained. Multifrequency electrical impedance measurements were made on the tissue and its conductivity and relative permittivity (i.e., its polarizability) calculated. Anisotropy of the tissue was determined by calculating conductivity and permittivity differences, subtracting transverse from longitudinal values. Muscle fiber and blood vessel quantification were also performed.

RESULTS

The mean conductivity difference for sciatic crush animals was higher (p<0.05) than for the healthy animals across the frequency spectrum, due to a greater increase in longitudinal conductivity than in transverse conductivity. For example, at 10 kHz, the conductivity difference was 0.15S/m for healthy animals and 0.29 S/m for post-crush animals. Relative permittivity difference values, however, were similar between groups. There was a strong correlation of conductivity anisotropy to muscle fiber size but not to blood vessel area.

CONCLUSIONS

Anisotropy of muscle conductivity increases markedly after subacute denervation injury.

SIGNIFICANCE

This alteration in anisotropy has direct relevance to the clinical application of electrical impedance myography. We also speculate that it may impact other forms of diagnostic testing, including needle electromyography and magnetic resonance imaging.

Motor unit number estimation in the rat tail using a modified multipoint stimulation technique

Motor unit number estimation (MUNE) of the rodent hindlimb has been used mainly for following the progression of motor neuron disorders. By performing MUNE in the tail, however, progression of axonal neuropathy could also be assessed, as both proximal and distal regions would be available for study. In this investigation, three raters performed a modified multipoint stimulation MUNE technique in the tails of 14 healthy adult rats. The technique was straightforward to perform, with a relatively narrow range of motor unit number estimates of 40 +/- 16 (standard deviation) for the proximal tail and 21 +/- 11 for the distal tail. Intrarater reliability coefficients were 0.31 (P = 0.033) and 0.32 (P = 0.028) for the proximal and distal tail, respectively. Interrater reliability coefficients were 0.22 (P = 0.086) and 0.44 (P = 0.004). These reliability assessments, along with the relatively low motor unit estimates and narrow range of values, support the idea that rat tail MUNE may have utility in the evaluation of rodent models of neuromuscular disease, including length-dependent neuropathy.

Changes in mouse mu opioid receptor Exon 7/8-like immunoreactivity following food restriction and food deprivation in rats

Opioid agonists and antagonists respectively increase and decrease food intake. That selective mu opioid antagonists are more effective than antisense probes directed against the mu opioid receptor (MOR-1) gene in reducing deprivation-induced feeding suggests a role for isoforms. Both food restriction and deprivation alter protein and mRNA levels of opioid peptides and receptors. Antisera directed against Exon 4 of the MOR-1-like immunoreactivity (LI) (Exon 4) clone or directed against mouse Exons 7/8 (mE7/8-LI) revealed high levels of immunoreactivity in brain nuclei related to feeding behavior. Therefore, the present study assessed MOR-1LI and mE7/8-LI in hypothalamic and extrahypothalamic sites in rats exposed to ad libitum feeding, food restriction (2, 7, 14 days), or food deprivation (24, 48 h). MOR-1-LI displayed robust reactivity, but was insensitive to food restriction or deprivation. mE7/8-LI, both in terms of cell counts and relative optical density, was significantly and selectively increased in the dorsal and ventral parvocellular subdivisions of the hypothalamic paraventricular nucleus in food-restricted (14 days) rats, but all other restriction or deprivation regimens were ineffective in other hypothalamic nuclei. In contrast, significant and site-specific decreases in relative optical density in the rostral part of the nucleus tractus solitarius (NTS) were observed in food-restricted (2, 7 days) or food-deprived (24, 48 h) animals, but these regimens were ineffective in the other extrahypothalamic sites. This study indicates the sensitivity of this mE7/8-LI probe in the hypothalamic parvocellular paraventricular nucleus and rostral NTS to food restriction and deprivation in rats.

Dexamethasone treatment and ICAM-1 deficiency impair VEGF-induced angiogenesis in adult brain

BACKGROUND

Infusion of exogenous vascular endothelial growth factor (VEGF) into adult brain at doses above 60 ng/day induces dramatic angiogenesis accompanied by vascular leak and inflammation. Blood vessels formed by this treatment are dilated and tortuous, exhibiting a pathological morphology. Pathological VEGF-induced angiogenesis is preceded by vascular leak and inflammation, which have been proposed to mediate subsequent angiogenesis.

METHODS

To test this hypothesis, we infused VEGF into the brains of adult rats to induce pathological angiogenesis. Some of these rats were treated with dexamethasone, a potent anti-inflammatory glucocorticoid, to inhibit inflammation and edema.

RESULTS

We demonstrate that inhibition of inflammation by treatment with dexamethasone significantly attenuated VEGF-induced pathological angiogenesis. To present converging evidence that inflammation may be important in this angiogenic process, we also demonstrate that mice genetically deficient in the inflammatory mediator intercellular adhesion molecule-1 have attenuated VEGF-induced angiogenesis. These same mice showed normal amounts of physiological angiogenesis in response to enriched environments, however, suggesting that a generalized reduction in vascular plasticity could not account for their poor angiogenic response to VEGF.

CONCLUSIONS

Taken together, the data from these experiments suggest that the inflammation which occurs before or during VEGF-induced pathological brain angiogenesis plays a contributory role in the pathological angiogenic process.

BDNF: a missing link between sympathetic dysfunction and inflammatory disease?

Nerve growth factor (NGF) plays a role in sympathetic neuron integrity and survival. Brain-derived neurotrophic factor (BDNF) also has trophic effects on sympathetic neurons. We report here the serendipitous finding that co-treatment of hippocampus with BDNF and the NGF antagonist TrkA-Fc leads to perivascular inflammation and marked vasoconstriction. This effect is not observed with either reagent alone or in combination with other control proteins. Because NGF supports sympathetic neuron health, we tested the hypothesis that BDNF combined with sympathetic compromise caused this effect. Superior cervical ganglia were removed bilaterally with concurrent BDNF infusion into hippocampus. Perivascular inflammation was observed at 3 days, but not 12 days post treatment, when sympathetic terminals had receded, suggesting that the presence of these terminals was necessary for inflammation. Since sympathetic dysfunction may lead to compensatory overactivity of norepinephrine (NE) signaling, we co-infused BDNF with NE in the hippocampus and observed perivascular inflammation. In humans, sympathetic overactivity has been reported in a variety of vascular diseases. Some of these diseases, e.g. primary Raynaud's, are not accompanied by serious inflammatory disease whereas others, such as scleroderma and systemic lupus, are. We speculate that BDNF may contribute to the transformation of sympathetic dysfunction to inflammatory disease.

VEGF-mediated inflammation precedes angiogenesis in adult brain

Vascular endothelial growth factor (VEGF) has been shown to induce angiogenesis when infused continuously into adult rat brain tissue. In addition, VEGF has been shown to enhance permeability in brain vasculature. Adult rats were continuously infused with mouse VEGF into neocortex for up to 7 days. We studied the development of VEGF-induced vasculature in rat neocortex and evaluated the temporal expression of a wide variety of markers for inflammation and vascular leak in relation to the angiogenic response using immunohistochemistry and Western blot analysis. We report here that VEGF-mediated inflammation in brain is characterized by upregulation of ICAM-1 and the chemokine MIP-1alpha, as well as a preferential extravasation of monocytes. VEGF causes a dramatic breakdown of the blood-brain barrier, which is characterized by decreased investment of the vasculature with astroglial endfeet. Perivascular cells, in contrast, increase around the newly formed cerebrovasculature. In addition, breakdown of the blood-brain barrier, leukocyte extravasation, and extracellular matrix deposition occur before vascular proliferation. Furthermore, administration of low doses of VEGF induces permeability and inflammation without appreciable vascular proliferation.