Phenotypic and functional properties of HLA-DRhi intermediate monocytes in health and chronic kidney disease
Cormican, Sarah
Cormican, Sarah
Loading...
Repository DOI
Publication Date
2022-03-25
Type
Thesis
Downloads
Citation
Abstract
Chronic kidney disease (CKD) is a common condition, characteristed by reduced renal function and frequently associated with progressive loss of glomerular filtration, ultimately reaching end stage renal disease (ESRD). Cardiovascular disease and mortality are increased in CKD, partly due to chronic inflammation, one aspect of which is abnormalities of the peripheral blood monocyte repertoire. Monocytes are generally classified into three subsets defined by relative expression of CD14 and CD16 and termed the classical, intermediate and nonclassical subsets. Recently, our group reported that intermediate monocytes are comprised of two distinct subpopulations based on relative expression of major histocompatibility complex II protein, HLA-DR. These subpopulations were termed HLA-DRmid IMs and HLA-DRhi intermediate monocytes. Recently reported data indicate that this monocyte subpopulation is increased in CKD compared to healthy volunteers. The major aims of this work were to determine if renal impairment is independently associated with an increase in circulating HLA-DRhi intermediate monocytes and to deterime if numbers of this novel intermediate monocyte subpopulation are associated with risk of CKD progression. The study also aimed to determine the impact of haemodialysis initation on the peripheral blood monocyte repertoire. Finally, we also aimed to determine the phenotypic and functional properties of HLA-DRhi intermediate monocytes with regard to chemotaxis, endothelial adhesion, antigen presentation and cytokine production and to determine whether CKD modulates these activities in HLA-DRhi IMs or in other monocyte populations. Results of a previous cross-sectional study of monocyte subset and intermediate monocyte subpopulation numbers were used for a follow-up analysis to determine the association between baseline monocyte profiles and subsequent eGFR decline. Subjects with CKD, patient controls, healthy volunteers and patients with ESRD were recruited by informed consent in Merlin Park University Hospital, Galway University Hospital and the Clinical Research Facility, Galway. Peripheral blood mononuclear cells and serum were isolated from blood samples for phenotypic and functional studies of chemotaxis, endothelial adhesion and cytoine production. Serum samples were also isolated and used for ELISA analyses. In the follow-up analysis of a previously recruited study cohort, HLA-DRhi intermediate monocytes at baseline were associated with subsequent rate of decline in renal function. HLA-DRhi intermediate monocytes were confirmed to be numerically increased in CKD compared to an age- and co-morbidity-matched patient control group. Haemodialysis XI initiation did not affect total intermediate monocyte or intermediate monocyte subpopulation numbers, but an increase in the proportion of nonclassical monocytes was observed following haemodialysis initiation. HLA-DRhi intermediate monocytes were characterised by distinct expression patterns of various surface proteins related to chemotaxis, endothelial adhesion and antigen presentation. Of note, HLA-DRhi intermediate monocytes expressed CCR5, CD11b, CD11c, CD40 and HLA-DQ at a higher level than all other subpopulations. They also expressed CX3CR1 at a high level, comparable to that expressed by nonclassical monocytes. Monocytes from subjects with CKD demonstrated enhanced migration in response to a CCL5 or CX3CL1 gradient. This was not specific to the HLA-DRhi intermediate monocyte subpopulation. Monocyte-endothelial adhesion was also observed to increase in CKD and was partially dependent on CX3CL1-CX3CR1 binding. HLA-DRhi intermediate monocytes were observed to be the most potent producers of the pro-inflammatory cytokines TNF-a and IL- 1b in response to lipopolysaccharide stimulation in a large cohort of subjects with and without CKD. This characteristic was preserved in subjects with CKD but overall cytokine production was not increased in CKD. The observations made within this thesis provide evidence that HLA-DRhi intermediate monocytes are of distinct pathophysiological significance to the progression and cardiovascular complications of CKD. Further work will be required to determine other functional properties of HLA-DRhi intermediate monocytes. Analysis of the gene expression profile of this monocyte subpopulation compared to other monocytes would be of value. Preliminary observations within this thesis also suggest a role for evaluating the presence of intermediate monocyte subpopulations within the renal parenchyma. Furthermore, the results presented indicate that HLA-DRhi intermediate monocytes may be of clinical relevance, either as a prognostic marker or as a therapeutic target. Overall, the observations within this thesis significantly extend the current level of understanding of monocyte biology in CKD.
Publisher
NUI Galway
Publisher DOI
Rights
Attribution-NonCommercial-NoDerivs 3.0 Ireland