Carbamylated low‐density lipoprotein induces oxidative stress and accelerated senescence in human endothelial progenitor cells

Abstract

Carbamylated low-density lipoprotein (cLDL) plays a role in atherosclerosis. In this study we evaluate the effect of uremia on LDL carbamylation and the effect of cLDL and oxidized LDL (oxLDL; 200 μg/ml) on number, function, and genomic stability of endothelial progenitor cells (EPCs) obtained from healthy volunteers. cLDL was generated after incubation of native LDL (nLDL) with uremic serum from patients with chronic kidney disease (CKD) stages 2-4. Oxidative stress was measured by flow cytometry and fluorescent microscopy, mitochondrial depolarization by flow cytometry, senescence by β-galactosidase activity and telomere length, and DNA damage by phosphorylated histone H2AX (γH2AX). The percentage of cLDL by uremic serum was related to the severity of CKD. Compared with nLDL, cLDL induced an increase in oxidative stress (62±5 vs. 8±3%, P<0.001) and cells with mitochondrial depolarization (73±7 vs. 9±5%, P<0.001), and a decrease in EPC proliferation and angiogenesis. cLDL also induced accelerated senescence (73±16 vs. 12±9%, P<0.001), which was associated with a decrease in the expression of γH2AX (62±9 vs. 5±3%, P<0.001). The degree of injury induced by cLDL was comparable to that observed with oxLDL. This study supports the hypothesis that cLDL triggers genomic damage in EPCs, resulting in premature senescence. We can, therefore, hypothesize that EPCs injury by cLDL contributes to an increase in atherosclerotic disease in CKD.

Aging and Atherosclerosis

“…These cells from aged animals are accompanied by reduced expression of cell surface markers and cytokines for chemotaxis, such as C-X-C chemokine receptor type 4, 27,32 decreased hypoxia-inducible factor 1A, 33,34 as well as increased oxidative stress and inflammation. 35,36 …”

“…48 -50 Shortened telomeres are evident in atherosclerosis, observed in plaque VSMCs 23 and ECs 51 relative to the normal vessel wall, and in circulating EPCs. 36 Also, telomeres in leukocytes are shorter in patients with atherosclerosis compared with control subjects 52,53 and are inversely correlated to cardiovascular disease risks in patients with subclinical diseases. 54,55 Short telomeres and low levels of telomerase expression and activity are functionally important in VSMC senescence, as ectopic telomerase expression can dramatically increase lifespan of both plaque and normal VSMCs.…”

Aging and uremia: Is there cellular and molecular crossover?

“…The same group went on to demonstrate that indoxyl sulphate stimulated sene scence of cultured human aortic smooth muscle cells via an oxidative stress mechanism [74] . Carracedo et al [80] evaluated the effects of uremia on lowdensity lipoprotein (LDL) carbamylation and the effect of carbamylated LDL (cLDL) and oxidized LDL on the number, function, and genomic stability of endothelial progenitor cells (EPCs) obtained from healthy volunteers. EPCs were exposed to cLDL generated after incubation of native LDL (nLDL) with uremic serum from patients with CKD stages 24.…”

Carbamylation-Derived Products: Bioactive Compounds and Potential Biomarkers in Chronic Renal Failure and Atherosclerosis

“…In addition, macrophage scavenger receptors recognize cLDLs (17,49 ). cLDLs have been reported to promote the adhesion of monocytes on endothelial cells (50 ), induce endothelial cell death (51,52 ), stimulate the proliferation of vascular smooth muscle cells (53 ), and induce oxidative stress and accelerated senescence in human endothelial progenitor cells (54 ). Carbamylated HDLs have been reported to contribute to the atherosclerotic process by promoting foam cell formation (55 ).…”