Chronic kidney disease and atherosclerosis: effect of carbamoylated albumin on macrophage cholesterol effux

• Grant number: 21/13639-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2022
• End date: December 31, 2022
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Marisa Passarelli
• Grantee: Gabriela Bueno Mello de Jesus
• Host Institution: Faculdade de Medicina (FM). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Cardiovascular disease (CVD) is the leading cause of mortality in individuals with chronic kidney disease (CKD). The gradual loss of renal function is influenced and also affects traditional risk factors for CVD; however, the control of blood pressure and dyslipidemia is not able to prevent cardiovascular morbidity and mortality. This is attributed to the action of non-classical risk factors, which include oxidative stress, the formation of advanced glycation products (AGEs), and the modification of proteins by carbamoylation, resulting from uremic stress. AGEs alter lipid homeostasis in macrophages, due to their interaction with the AGER receptor, which triggers oxidative, inflammatory, and endoplasmic reticulum stress, ultimately capable of eliciting a greater intracellular degradation of the HDL receptor, ABCA -1. As a consequence, there is impairment in macrophage cholesterol efflux mediated by apo A-I and HDL, with intracellular accumulation of toxic sterols. These effects are long-lasting and persist even after the removal of AGE-albumin from the culture medium, suggesting the existence of "cellular memory". Albumin carbamoylation is independently related to the risk of morbidity and mortality in CKD, and recent evidence points to its action on the negative modulation of HDL-mediated cholesterol efflux, according to the evolution of CKD. In the present investigation, we propose to detail the action and duration of the effect of carbamoylated albumin on cholesterol efflux and ABCA-1 receptor expression in macrophages. Fatty acid-free bovine albumin will be modified "in vitro" by carbamoylation by incubating with different concentrations of potassium cyanate, for 4 h at 37ºC; control albumin will be incubated in the presence of phosphate buffer only. Bone-marrow-derived macrophages (BMDMs) will be incubated for 48 h with control or carbamoylated albumin followed by immediate incubation with cholesterol acceptors or after different time intervals in culture medium only (in the absence of carbamoylated albumin or control). Cholesterol efflux will be determined after 6 h of incubation with apo A-I or HDL2. The ABCA-1 content will be determined by immunoblot. The results will be important to understanding the pathophysiology of atherosclerosis in CKD, which involves the action of uremic toxins as a risk component.(AU)