Chronic kidney disease : a complex network of leukocyte dysfunction and inflammation

Abstract

Chronic kidney disease (CKD) is a common medical condition with a prevalence of up to 13% worldwide. The insidious loss of renal function develops over time to reach end stage renal disease (ESRD) when the kidneys are unable to remove toxins and interventions such as dialysis or kidney transplantation are mandatory. These patients are at increased risk of morbidity and mortality, essentially due to cardiovascular diseases and infections, which arise from alterations in both the innate and adaptive immune responses. This thesis focuses on the functional aberrations in leukocytes, inflammation and outcomes of medical interventions in CKD patients. In paper I, we investigated the impact of blood-membrane interaction on circulating basophils and neutrophils in hemodialysis patients (stage 5D) using dialyzers with two different pore sizes; high-flux and low-flux. Passage through the low-flux dialyzer induced a significant up-regulation of the activation marker CD63 on basophils, while this was not the case in high-flux dialysis. No significant differences were observed in the expression of neutrophil activation markers (CD11b, the active epitope of CD11b, and CD88), either comparing the two dialyzers, or compared to healthy controls. In paper II, we analyzed the proliferation of lymphocytes and production of pro-inflammatory molecules following in vitro stimulation of whole blood from pre-dialysis (CKD stage 3-4), hemodialysis patients (stage 5D), and healthy individuals. We found a similar absolute number of lymphoblasts, and CD4+ and CD8+ subpopulation in response to stimulation when comparing the three groups. However, levels of selected cytokines were lower in the staphylococcus enterotoxin A (SEA)-, influenza A vaccine (IAV)-, and pokeweed mitogen (PWM)-stimulated supernatants from hemodialysis patients compared to those in pre-dialysis and healthy controls. In paper III, we aimed to investigate whether the decreased in vitro cytokine production results from dysfunction of T cells per se. We analyzed the T lymphocyte profile in CKD patients (stage 5D) following stimulation of isolated CD4+ cells with an antigen-independent stimulator (SEA). The proportion of CD4+CD25+FOXP3+ (Treg) and CD4+GATA3+ (Th2) cells was significantly lower in patients. Levels of Interleukin (IL)-4 were significantly lower in supernatants from patients, while Interferon (IFN)-γ levels were higher. IL-10 levels did not differ, comparing patients to healthy individuals. In paper IV, we performed a clinical trial for 12 weeks with the vitamin D receptor activator (VDRA)-paricalcitol and placebo in patients with moderate CKD (stage 3- 4). We observed that selected pro-inflammatory cytokines decreased following VDRA treatment but not in the placebo group. Micro RNAs: 432-5p, 495-3p, and 576-5p were also significantly down regulated in the active treated group compared to the placebo group.

In conclusion, we demonstrate that chronic renal impairment and hemodialysis leads to a high inflammatory state and alteration in the function of innate and adaptive immune cells. Moreover, we show that treatment with active vitamin D-paricalcitol has a positive impact on dampening inflammatory molecules and miRs involved in atherosclerosis and inflammation. Altogether, these findings provide us with a better understanding of potential factors orchestrating the higher prevalence of cardiovascular diseases and infections, as well as the progression of CKD.