CKD Increases Carbonylation of HDL and Is Associated with Impaired Antiaggregant Properties
Authors: Florens Nans , Calzada Catherine , Lemoine Sandrine , Boulet Marie Michèle , Guillot Nicolas , Barba Christophe , Roux Julie , Delolme Fréderic , Page Adeline , Poux Jean Michel , Laville Maurice , Moulin Philippe , Soulère Laurent , Guebre-Egziabher Fitsum , Juillard Laurent , Soulage Christophe O. 
Published: June 2020

Significance Statement
CKD is associated with increased oxidative stress that correlates with the occurrence of cardiovascular events. Oxidative stress induces modifications that particularly affect circulating lipoproteins such as HDL that exhibit atheroprotective properties in vitro. However, information about the antithrombotic properties of HDL in CKD is lacking. The authors demonstrate that HDL from a CKD rabbit model and patients on hemodialysis exhibited an impaired ability to inhibit platelet aggregation, suggesting that properties of altered HDL may contribute to the increased cardiovascular risk in this patient population. They also describe the putative role of carbonylation by 4-hydroxynonenal adduction in these properties. This study provides important insights into the potential implication of HDL modifications in atherothrombosis and cardiovascular morbidity and mortality among patients on dialysis.

Background
CKD is associated with increased oxidative stress that correlates with occurrence of cardiovascular events. Modifications induced by increased oxidative stress particularly affect circulating lipoproteins such as HDL that exhibit antiatheromatous and antithrombotic properties in vitro.

Methods
To explore the specific role of oxidative modifications of HDL in CKD and their effect on the platelet-targeting antiaggregant properties of HDL, we used a CKD (5/6 nephrectomy) rabbit model. For ex vivo assessment of the antiaggregant properties of HDL, we collected blood samples from 15 healthy volunteers, 25 patients on hemodialysis, and 20 on peritoneal dialysis. We analyzed malondialdehyde, 4-hydroxynonenal (HNE), and 4-hydroxy-2-hexenal protein adduct levels. Platelet aggregation and activation were assessed by aggregometry, thromboxane B2 assay, or FACS. We modified HDL from controls by incubating it overnight at 37°C with 100 µM of HNE.

Results
HDL from CKD rabbits and patients on hemodialysis had HNE adducts. The percentage of platelet aggregation or activation induced by collagen was significantly higher when platelets were incubated with HDL from CKD rabbit and hemodialysis groups than with HDL from the control group. In both rabbits and humans, platelet aggregation and activation were significantly higher in the presence of HNE-modified HDL than with HDL from their respective controls. Incubation of platelets with a blocking antibody directed against CD36 or with a pharmacologic inhibitor of SRC kinases restored the antiaggregative phenotype in the presence of HDL from CKD rabbits, patients on hemodialysis and peritoneal dialysis, and HNE-modified HDL.

Conclusions
HDL from CKD rabbits and patients on hemodialysis exhibited an impaired ability to inhibit platelet aggregation, suggesting that altered HDL properties may contribute to the increased cardiovascular risk in this population.