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

Abstract

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.

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

“…2 Recently, we showed that ex-vivo human leptomeningeal arterioles acutely exposed to soluble b-amyloid peptide 1-42 (Ab42), a major peptide implicated in AD, demonstrate endothelial dysfunction, and that this effect was similar in human abdominal subcutaneous adipose arterioles. 3 We showed similar induction of human arteriole endothelial dysfunction with exposure to light chain proteins derived from patients with AL amyloidosis, [4][5][6] suggesting common vascular toxicity among amyloidogenic proteins despite differences in amino acid composition. When nanoliposomes of less than 100 nM size composed of phospholipids phosphatidylcholine, cholesterol and phosphatidic acid (NLPA) were cotreated with amyloidogenic light chains, endothelial dysfunction was reversed and the b-sheet structure of the light chain protein was altered.…”

“…The methods for arteriole preparation were previously published. 6 Arterioles ($80-250 mM diameter) were isolated from adipose tissue (living donors) or leptomeningeal tissue (cadaver donors), cannulated and pressurized until a final pressure of 60 mm Hg. Arteriole diameters were measured using videomicrometers.…”

Diagnostic utility of cardiac troponin T level in patients with cardiac amyloidosis

“…Increased LV filling pressure, which causes increased wall stress due to diastolic dysfunction in cardiac amyloidosis, compresses myocardial capillaries, with subsequent decrease in their lumen. Endothelial function is impaired by microvascular toxicity induced by light chain in AL amyloidosis 27, 28. These mechanisms cause functional myocardial ischaemia, subclinical impairment of LV systolic function, and cardiac troponin release.…”

Clinical and prognostic significance of serum levels of von Willebrand factor and ADAMTS-13 antigens in AL amyloidosis

“…Preclinical evidence indicates that toxic light chains may directly cause microvascular dysfunction, and the injury caused by light chains may induce apoptotic injury to ECs. 11,12 A more detailed functional study of the vascular function in patients with AL amyloidosis is required and, although some data have been published, 13 our group is further investigating the functional and clinical consequences of AL amyloidosis in the arterial vessels.…”

“…Light chains may be directly toxic to the ECs and may thus alter vascular function. [9][10][11][12] There are limited data on endothelial function in patients with AL amyloidosis. 9,13 The study of the vascular function is complex, and surrogate markers of endothelial activation could be useful in understanding the potential role of endothelium in the development of symptoms and complications of AL amyloidosis.…”