L-citrulline and L-arginine supplementation has been shown to have several beneficial effects on the cardiovascular system. Nitric oxide (NO) protects against the progression of atherosclerosis and is synthesized by nitric oxide synthase (NOS), which converts L-arginine (L-Arg) into L-citrulline (L-Cit). Our previous study revealed that chronic administration of a combination of L-Cit and L- Arg has a better therapeutic effect on high cholesterol-induced atherosclerosis in rabbits. We investigated how L-Arg and L-Cit affect endothelial function, aging and atherosclerosis. Following a 3-day stimulation of human umbilical venous endothelial cells (HUVECs) with high glucose (HG: 22 mM) and L-Arg (300 μM), L-Cit (300 μM) or L-Arg plus L-Cit (LALC: each 150 μM) supplementation, endothelial senescence and function were evaluated. These amino acids were also administered to dyslipidemic type 2 diabetic (ZDFM) rats fed a high cholesterol diet. They were fed L-Arg or L-Cit or LALC for four weeks. Aortic senescence was investigated by measuring senescence-associated ß-galactosidase (SA-ß-gal), telomerase activity, DNA damage and p16INK4a protein expression. Only L-Cit and LALC supplementation retarded the HG-induced endothelial senescence, as evaluated by SA-ß-gal activity, a widely used marker of cellular senescence, p16INK4a expression, a senescence-related protein, and DNA damage. Under HG conditions, L-Cit and LCLA restored telomerase activity to levels observed under normal glucose (NG) conditions. Under HG conditions, L-Cit decreased ROS production, as measured by CM-H2DCFDA and the expression of p67phox, a major component of NADPH oxidase. Under HG conditions, L-Cit and LALC increased NO production, as measured by DAF-2AM. Endothelial NO synthase (eNOS) and phosphorylated eNOS were decreased under HG conditions and L-Cit and LALC significantly increased these levels. Arginase 2 protein expression increased under the HG conditions, and L-Cit and LALC significantly attenuated this effect. In ZDFM rats, SA-ß-gal activity was detected on the aortic endothelial surface; however, L-Cit and LALC reduced these levels. L-Cit and LALC both decreased the proportion of senescent cells. Furthermore, treatment with LALC for 4 weeks increased plasma NO production. Therefore conclusively, L-citrulline supplementation rescued NO levels better than L-arginine supplementation by inhibiting ROS production and arginase 2 protein expression. Consequently, L-Cit and LCLA supplementation retaeded HG-induced endothelial senescence.

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<b><i>Background:</i></b> Coagulant factor Xa inhibitors (XaIs) are prescribed for patients with atrial fibrillation for years. <b><i>Methods:</i></b> Human umbilical venous endothelial cells (HUVECs) were cultured with or without (w/wo) a XaI (rivaroxaban) under high glucose (HG: 22 mM). Endothelial senescence was investigated by assessing senescence-associated-β-galactosidase (SA-β-gal), p53, and telomere length. Endothelial function and atherosclerosis were examined by nitric oxide-related-products (NOx: NO₂^– and NO₃^–), O₂^–, endothelial NO synthase (eNOS), NADPH oxidase (p22^phox), and ICAM1. PAR1 (protease-activated receptor 1) and PAR2, which were reported to regulate eNOS phosphorylation, were inhibited by small interfering RNAs (siRNAs). Thirty-two male dyslipidemic type 2 diabetic rats (ZFDM LepR^fa/fa) were fed a high-cholesterol diet w/wo XaI (50 µg/day/kg) for 1–4 weeks. <b><i>Results:</i></b> SA-β-gal, p53, p21, and p16^INK4a were increased by HG and restored by XaI (50 nM) in HUVECs. XaI restored telomerase activity and preserved telomere length. XaI suppressed O₂^–, p22^phox, and ICAM1 and restored NOx and eNOS. XaI decreased PAR1 following elevation by HG, which was confirmed by PAR1 siRNA and PAR2 siRNA. In in vivo experiments, plasma glucose, total cholesterol, and triglycerides were increased for 4 weeks but were not changed by XaI. XaI decreased SA-β-gal and telomerase and preserved telomere length in the aortic endothelium. XaI activated eNOS, inhibited p22^phox, increased plasma NOx, and decreased O₂^–. <b><i>Conclusion:</i></b> Rivaroxaban prevents replicative senescence in HUVECs and aortic endothelial cells in dyslipidemic diabetic mice. It restores endothelial function and prevents the progression of atherosclerosis.