Seth Truran

Human microvascular dysfunction and apoptotic injury induced by AL amyloidosis light chain proteins.

Light chain amyloidosis (AL) involves overproduction of amyloidogenic light chain proteins (LC) leading to heart failure, yet the mechanisms underlying tissue toxicity remain unknown. We hypothesized that LC induces endothelial dysfunction in non-AL human microvasculature and apoptotic injury in human coronary artery endothelial cells (HCAECs). Adipose arterioles (n = 34, 50 ± 3 yr) and atrial coronary arterioles (n = 19, 68 ± 2 yr) from non-AL subjects were cannulated. Adipose arteriole dilator responses to acetylcholine/papaverine were measured at baseline and 1 h exposure to LC (20 μg/ml) from biopsy-proven AL subjects (57 ± 11 yr) without and with antioxidant cotreatment. Coronary arteriole dilation to bradykinin/papaverine was measured post-LC exposure. HCAECs were exposed to 1 or 24 h of LC. LC reduced dilation to acetylcholine (10(-4) M: 41.6 ± 7 vs. 85.8 ± 2.2% control, P < 0.001) and papaverine (81.4 ± 4.6 vs. 94.8 ± 1.3% control, P < 0.01) in adipose arterioles and to bradykinin (10(-6) M: 68.6 ± 6.2 vs. 90.9 ± 1.6% control, P < 0.001) but not papaverine in coronary arterioles. There was an increase in superoxide and peroxynitrite in arterioles treated with LC. Adipose arteriole dilation was restored by cotreatment with polyethylene glycol-superoxide dismutase and tetrahydrobiopterin but only partially restored by mitoquinone (mitochondria-targeted antioxidant) and gp91ds-tat (NADPH oxidase inhibitor). HCAECs exposed to LC showed reduced NO and increased superoxide, peroxynitrite, annexin-V, and propidium iodide compared with control. Brief exposure to physiological amounts of LC induced endothelial dysfunction in human adipose and coronary arterioles and increased apoptotic injury in coronary artery endothelial cells likely as a result of oxidative stress, reduced NO bioavailability, and peroxynitrite production. Microvascular dysfunction and injury is a novel mechanism underlying AL pathobiology and is a potential target for therapy.

Exenatide Protects against Glucose and Lipid-Induced Endothelial Dysfunction: Evidence for Direct Vasodilation Effect of GLP-1 Receptor Agonists in Humans

GLP-1 receptor (GLP-1R) agonists may improve endothelial function (EF) via metabolic improvement and direct vascular action. The current study determined the effect of GLP-1R agonist exenatide on postprandial EF in type 2 diabetes and the mechanisms underlying GLP-1R agonist–mediated vasodilation. Two crossover studies were conducted: 36 participants with type 2 diabetes received subcutaneous exenatide or placebo for 11 days and EF, and glucose and lipid responses to breakfast and lunch were determined; and 32 participants with impaired glucose tolerance (IGT) or diet-controlled type 2 diabetes had EF measured before and after intravenous exenatide, with or without the GLP-1R antagonist exendin-9. Mechanisms of GLP-1R agonist action were studied ex vivo on human subcutaneous adipose tissue arterioles and endothelial cells. Subcutaneous exenatide increased postprandial EF independent of reductions in plasma glucose and triglycerides. Intravenous exenatide increased fasting EF, and exendin-9 abolished this effect. Exenatide elicited eNOS activation and NO production in endothelial cells, and induced dose-dependent vasorelaxation and reduced high-glucose or lipid-induced endothelial dysfunction in arterioles ex vivo. These effects were reduced with AMPK inhibition. In conclusion, exenatide augmented postprandial EF in subjects with diabetes and prevented high-glucose and lipid-induced endothelial dysfunction in human arterioles. These effects were largely direct, via GLP-1R and AMPK activation.

Prognostic implication of late gadolinium enhancement on cardiac MRI in light chain (AL) amyloidosis on long term follow up.

BackgroundLight chain amyloidosis (AL) is a rare plasma cell dyscrasia associated with poor survival especially in the setting of heart failure. Late gadolinium enhancement (LGE) on cardiac MRI was recently found to correlate with myocardial amyloid deposition but the prognostic role is not established. The aim is to determine the prognostic significance of LGE in AL by comparing long term survival of AL patients with and without LGE.MethodsTwenty nine consecutive patients (14 females; 62 ± 11 years) with biopsy-proven AL undergoing cardiac MRI with gadolinium as part of AL workup were included. Survival was prospectively followed 29 months (median) following MRI and compared between those with and without LGE by Kaplan-Meier and log-rank analyses.ResultsLGE was positive in 23 subjects (79%) and negative in 6 (21%). Left ventricular ejection fraction was 66 ± 17% in LGE-positive and 69 ± 12% in LGE-negative patients (p = 0.8). Overall 1-year mortality was 36%. On follow-up, 14/23 LGE-positive and none of LGE-negative patients died (log rank p = 0.0061). Presenting New York Heart Association heart failure class was also associated with poor survival (p = 0.0059). Survival between two LGE groups stratified by heart failure class still showed a significant difference by a stratified log-rank test (p = 0.04).ConclusionLate gadolinium enhancement is common and is associated with poor long-term survival in light chain amyloidosis, even after adjustment for heart failure class presentation. The prognostic significance of late gadolinium enhancement in this disease may be useful in patient risk-stratification.

Systemic and microvascular oxidative stress induced by light chain amyloidosis

Light chain amyloidosis (AL) is a plasma cell dyscrasia associated with production of amyloidogenic immunoglobulin light chains (LC). Despite its often fatal course, the mechanism of injury remains unknown. We tested the hypothesis that AL is associated with oxidative stress by comparing serum protein carbonyl (a marker of protein oxidation and oxidative stress) in AL subjects (n=23, 60 ± 11 years) vs. controls (n=9, 54 ± 2 years); we also measured superoxide production (n=11) and dilator response to sodium nitroprusside (SNP, n=6) in isolated non-AL human adipose arterioles exposed to LC (20 μg/mL) purified from AL subjects for 1 h vs. control. Protein carbonyl was higher in AL patients (0.19 ± 0.04 vs. 0.003 ± 0.003 nmol/mg control, p=0.002). Post-exposure to LC proteins, arteriole superoxide was higher (1.89 ± 0.36 times control, p=0.03) with impaired dilation to SNP (10(-4) M, 54 ± 6 vs. 86 ± 4%, p=0.01, logEC50 -3.7 ± 0.2 vs. -6.7 ± 0.6, p=0.002). AL is associated with systemic oxidative stress and brief acute exposure to AL light chain proteins induces oxidative stress and microvascular dysfunction in human adipose arterioles. This novel mechanism of injury may be important in AL pathophysiology.

Intraventricular dyssynchrony in light chain amyloidosis: a new mechanism of systolic dysfunction assessed by 3-dimensional echocardiography

BackgroundLight chain amyloidosis (AL) is a rare but often fatal disease due to intractable heart failure. Amyloid deposition leads to diastolic dysfunction and often preserved ejection fraction. We hypothesize that AL is associated with regional systolic dyssynchrony. The aim is to compare left ventricular (LV) regional synchrony in AL subjects versus healthy controls using 16-segment dyssynchrony index measured from 3-dimension-al (3D) echocardiography.MethodsCardiac 3D echocardiography full volumes were acquired in 10 biopsy-proven AL subjects (60 ± 3 years, 5 females) and 10 healthy controls (52 ± 1 years, 5 females). The LV was subdivided into 16 segments and the time from end-diastole to the minimal systolic volume for each of the 16 segments was expressed as a percent of the cycle length. The standard deviations of these times provided a 16-segment dyssynchrony index (16-SD%). 16-SD% was compared between healthy and AL subjects.ResultsLeft ventricular ejection fraction was comparable (control vs. AL: 62.4 ± 0.6 vs. 58.6 ± 2.8%, p = NS). 16-SD% was significantly higher in AL versus healthy subjects (5.93 ± 4.4 vs. 1.67 ± 0.87%, p = 0.003). 16-SD% correlated with left ventricular mass index (R 0.45, p = 0.04) but not to left ventricular ejection fraction.ConclusionLight chain amyloidosis is associated with left ventricular regional systolic dyssynchrony. Regional dyssynchrony may be an unrecognized mechanism of heart failure in AL subjects.

Adipose and leptomeningeal arteriole endothelial dysfunction induced by β-amyloid peptide: a practical human model to study Alzheimer's disease vasculopathy.

BACKGROUND Evidence point to vascular dysfunction and hypoperfusion as early abnormalities in Alzheimers disease (AD); probing their mechanistic bases can lead to new therapeutic approaches. We tested the hypotheses that β-amyloid peptide induces endothelial dysfunction and oxidative stress in human microvasculature and that response will be similar between peripheral adipose and brain leptomeningeal arterioles. NEW METHOD Abdominal subcutaneous arterioles from living human subjects (n=17) and cadaver leptomeningeal arterioles (n=6) from rapid autopsy were exposed to Aβ1-42 (Aβ) for 1-h and dilation response to acetylcholine/papaverine were measured and compared to baseline response. Adipose arteriole reactive oxygen species (ROS) production and nitrotyrosine content were measured. COMPARISON WITH EXISTING METHODS Methods described allow direct investigation of human microvessel functional response that cannot be replicated by human noninvasive imaging or post-mortem histology. RESULTS Adipose arterioles exposed to 2 μM Aβ showed impaired dilation to acetylcholine that was reversed by antioxidant polyethylene glycol superoxide dismutase (PEG-SOD) (Aβ-60.9 ± 6%, control-93.2 ± 1.8%, Aβ+PEGSOD-84.7 ± 3.9%, both p<0.05 vs. Aβ). Aβ caused reduced dilation to papaverine. Aβ increased adipose arteriole ROS production and increased arteriole nitrotyrosine content. Leptomeningeal arterioles showed similar impaired response to acetylcholine when exposed to Aβ (43.0 ± 6.2% versus 81.1 ± 5.7% control, p<0.05). CONCLUSION Aβ exposure induced adipose arteriole endothelial and non-endothelial dysfunction and oxidative stress that were reversed by antioxidant treatment. Aβ-induced endothelial dysfunction was similar between peripheral adipose and leptomeningeal arterioles. Ex vivo living adipose and cadaver leptomeningeal arterioles are viable, novel and practical human tissue models to study Alzheimers vascular pathophysiology.

Nanoliposomes protect against AL amyloid light chain protein-induced endothelial injury.

Abstract Context: A newly-recognized pathogenic mechanism underlying light chain amyloidosis (AL) involves endothelial dysfunction and cell injury caused by misfolded light chain proteins (LC). Nanoliposomes (NL) are artificial phospholipid vesicles that could attach to misfolded proteins and reduce tissue injury. Objective: To test whether co-treatment with NL reduces LC-induced endothelial dysfunction and cell death. Methods: Abdominal subcutaneous adipose arterioles from 14 non-AL subjects were cannulated; dilator response to acetylcholine and papaverine were measured at baseline and following 1-hour exposure to LC (20 µg/mL, 2 purified from AL subjects’ urine, 1 from human recombinant LC [AL-09]) ± NL (phosphatidylcholine/cholesterol/phosphatidic acid 70/25/5 molar ratio) or NL alone. Human aortic artery endothelial cells (HAEC) were exposed to Oregon Green-labeled LC ± NL for 24 hours and intracellular LC and apoptosis (Hoechst stain) were measured. Circular dichroism spectroscopy was performed on AL-09 LC ± NL to follow changes in secondary structure and protein thermal stability. Results: LC caused impaired dilation to acetylcholine that was restored by NL (control – 94.0 ± 1.8%, LC – 65.0 ± 7.1%, LC + NL – 95.3 ± 1.8%, p ≤ 0.001 LC versus control or LC + NL). NL protection was inhibited by L-NG-nitroarginine methyl ester. NL increased the beta sheet structure of LC, reduced endothelial cell internalization of LC and protected against LC-induced endothelial cell death. Conclusions: LC induced human adipose arteriole endothelial dysfunction and endothelial cell death, which were reversed by co-treatment with NL. This protection may partly be due to enhancing LC protein structure and reducing LC internalization. Nanoliposomes represent a promising new class of agents to ameliorate tissue injury from protein misfolding diseases such as AL.

Nanoliposomes protect against human arteriole endothelial dysfunction induced by β-amyloid peptide

We tested whether nanoliposomes containing phosphatidylcholine, cholesterol and phosphatidic acid (NLPA) prevent β-amyloid 1-42 (Aβ42) fibrillation and Aβ42-induced human arteriole endothelial dysfunction. NLPA abolished Aβ42 fibril formation (thioflavin-T fluorescence/electron microscopy). In ex-vivo human adipose and leptomeningeal arterioles, Aβ42 impaired dilator response to acetylcholine that was reversed by NLPA; this protection was abolished by L-NG-nitroarginine methyl ester. Aβ42 reduced human umbilical vein endothelial cell NO production that was restored by NLPA. Nanoliposomes prevented Aβ42 amyloid formation, reversed Aβ42-induced human microvascular endothelial dysfunction and may be useful in Alzheimer’s disease.

Oxidative Stress Alters the Morphology and Toxicity of Aortic Medial Amyloid

The aggregation and fibril deposition of amyloid proteins have been implicated in a range of neurodegenerative and vascular diseases, and yet the underlying molecular mechanisms are poorly understood. Here, we use a combination of cell-based assays, biophysical analysis, and atomic force microscopy to investigate the potential involvement of oxidative stress in aortic medial amyloid (AMA) pathogenesis and deposition. We show that medin, the main constituent of AMA, can induce an environment rich in oxidative species, increasing superoxide and reducing bioavailable nitric oxide in human cells. We investigate the role that this oxidative environment may play in altering the aggregation process of medin and identify potential posttranslational modification sites where site-specific modification and interaction can be unambiguously demonstrated. In an oxidizing environment, medin is nitrated at tyrosine and tryptophan residues, with resultant effects on morphology that lead to longer fibrils with increased toxicity. This provides further motivation to investigate the role of oxidative stress in AMA pathogenicity.

Monosialoganglioside-Containing Nanoliposomes Restore Endothelial Function Impaired by AL Amyloidosis Light Chain Proteins.

Background Light chain amyloidosis (AL) is associated with high mortality, especially in patients with advanced cardiovascular involvement. It is caused by toxicity of misfolded light chain proteins (LC) in vascular, cardiac, and other tissues. There is no treatment to reverse LC tissue toxicity. We tested the hypothesis that nanoliposomes composed of monosialoganglioside, phosphatidylcholine, and cholesterol (GM1 ganglioside–containing nanoliposomes [NLGM1]) can protect against LC‐induced human microvascular dysfunction and assess mechanisms behind the protective effect. Methods and Results The dilator responses of ex vivo abdominal adipose arterioles from human participants without AL to acetylcholine and papaverine were measured before and after exposure to LC (20 μg/mL) with or without NLGM1 (1:10 ratio for LC:NLGM1 mass). Human umbilical vein endothelial cells were exposed for 18 to 20 hours to vehicle, LC with or without NLGM1, or NLGM1 and compared for oxidative and nitrative stress response and cellular viability. LC impaired arteriole dilator response to acetylcholine, which was restored by co‐treatment with NLGM1. LC decreased endothelial cell nitric oxide production and cell viability while increasing superoxide and peroxynitrite; these adverse effects were reversed by NLGM1. NLGM1 increased endothelial cell protein expression of antioxidant enzymes heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1 and increased nuclear factor, erythroid 2 like 2 (Nrf‐2) protein. Nrf‐2 gene knockdown reduced antioxidant stress response and reversed the protective effects of NLGM1. Conclusions NLGM1 protects against LC‐induced human microvascular endothelial dysfunction through increased nitric oxide bioavailability and reduced oxidative and nitrative stress mediated by Nrf‐2–dependent antioxidant stress response. These findings point to a potential novel therapeutic approach for light chain amyloidosis.