Leukocyte dysfunction and inflammatory markers in patients with chronic kidney disease and patients on dialysis
Abstract: Patients with chronic kidney disease (CKD) and patients on dialysis are at risk for serious infectious complications. This is partly due to leukocyte dysfunction, which is a consequence of both uremic retention solutes and of dialysis. Paper I describes functions of in vivo extravasated monocytes and neutrophils (CD11b/CD18 expression, respiratory burst and apoptosis) from patients on high-flux hemodialysis/hemodiafiltration (HD/HDF) and healthy subjects. In contrast to our previous observations in patients on low-flux HD, CKD and peritoneal dialysis, we found similar mobilization of CD11b/CD18 and also in the apoptotic rate in patients on high-flux HD/HDF and in healthy subjects, which can be interpreted as a preserved leukocyte function in this dialysis population. CD11b/CD18 is an important adhesion molecule for leukocyte transmigration and phagocytosis. There were differences in the respiratory burst between patients and healthy subject, which could be due to leukocyte refractoriness when challenged with a strong inflammatory stimulus. Paper II describes the concentrations of important chemokines for neutrophils; IL-8 and matrix metalloproteinase-9/neutrophil gelatinase-associated lipocalin (MMP-9/NGAL), and monocytes; monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha) in the peripheral circulation and at the site of interstitial inflammation in patients on high-flux HD/HDF, compared with healthy subjects. We found similar (IL-8, MMP-9/NGAL and MIP-1alpha) or even higher (MCP-1) concentrations of these chemokines at the site of interstitial inflammation in patients on high-flux HD/HDF compared with healthy subjects. One of the mechanisms for the preserved leukocyte function demonstrated in Paper I could be an equal production of chemokines at the site of inflammation, which has not been demonstrated for patients with CKD or patients on low-flux HD. Paper III describes the CD11b/CD18 mobilization and gene transcription of transforming growth factor beta (TGFbeta), CD40, IL-1 receptor-associated kinase-1 (IRAK-1), IL8 and IL12A by in vitro lipopolysaccharide (LPS) stimulation and in vivo extravasation of neutrophils. We found a similar fold change in gene transcription of TGFbeta, CD40 and IRAK-1, as well as a similar range of CD11b/CD18 mobilization by LPS stimulation and extravasation, indicating a potential use of in vitro LPS stimulation as a model for studying in vivo activation of neutrophils. Paper IV describes the transcriptional regulation after LPS stimulation of neutrophils from patients with CKD stage 3-5 and healthy subjects. In patients with CKD, there is a weak LPS-mediated up-regulation or even a down-regulation of important proinflammatory mediators, among these superoxide dismutase 2 (SOD2), whereas in healthy subjects there is a strong up-regulation. SOD2 is of central importance for both the up-regulation of other proinflammatory mediators and neutrophil respiratory burst, which is demonstrated by inhibition of SOD2 in differentiated HL60 cells and subsequent analysis of gene transcription fold change and respiratory burst after PMA stimulation. The impaired up-regulation of SOD2 following LPS stimulation could be one of the mechanisms responsible for neutrophil dysfunction observed in CKD patients.
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