Elham Dadfar

Expression of neutrophil SOD2 is reduced after lipopolysaccharide stimulation: a potential cause of neutrophil dysfunction in chronic kidney disease

BACKGROUND Neutrophils from patients with chronic kidney disease (CKD) are dysfunctional and thus a contributing factor to the risk of infections. The mechanisms for leucocyte dysfunction in CKD are not fully understood. It is known that lipopolysaccharide (LPS) activates transcription of several genes encoding proinflammatory cytokines. We therefore aimed to study the effect of LPS on neutrophil expression of genes related to the inflammatory response to address the hypothesis that LPS-induced gene transcriptions are altered in CKD patients. METHODS We analysed gene expression of LPS-stimulated neutrophils from 30 patients with CKD and 15 healthy controls. Superoxide dismutase-2 (SOD2), IL1A, IL-1R1, IL-1R2 and IL8RA gene expression from both neutrophils and differentiated HL60 cells were measured by quantitative polymerase chain reaction. Differentiated HL60 cells were stimulated with phorbol-12-myristate-7-acetate (PMA) after inhibition of SOD2 by small interfering RNA followed by respiratory burst assessment using flow cytometry. RESULTS LPS stimulation induced a significant mobilization of CD11b on neutrophils from CKD and healthy controls. Upregulation of SOD2, IL1A, IL-1R1 and IL-1R2 gene expression in neutrophils from healthy controls after LPS stimulation was contrasted by no change in gene transcription (IL-1R1 and IL-1R2) or even a downregulation in patients with CKD (SOD2 and IL1A). Inhibition of SOD2 reduced the PMA-induced respiratory burst and IL1A, IL-1R1, IL-1R2 and IL8RA gene expression in neutrophil-differentiated HL60 cells. CONCLUSIONS Because of the critical role of SOD2 in the generation of hydrogen peroxide during phagocytosis, downregulation of SOD2 gene expression after LPS stimulation in neutrophils from patients with CKD indicates a potential mechanism for neutrophil dysfunction and cytokine dysregulation in these patients.

Activation of Wnt/β-Catenin Pathway in Monocytes Derived from Chronic Kidney Disease Patients

Patients with chronic kidney disease (CKD) have significantly increased morbidity and mortality resulting from infections and cardiovascular diseases. Since monocytes play an essential role in host immunity, this study was directed to explore the gene expression profile in order to identify differences in activated pathways in monocytes relevant to the pathophysiology of atherosclerosis and increased susceptibility to infections. Monocytes from CKD patients (stages 4 and 5, estimated GFR <20 ml/min/1.73 m2) and healthy donors were collected from peripheral blood. Microarray gene expression profile was performed and data were interpreted by GeneSpring software and by PANTHER tool. Western blot was done to validate the pathway members. The results demonstrated that 600 and 272 genes were differentially up- and down regulated respectively in the patient group. Pathways involved in the inflammatory response were highly expressed and the Wnt/β-catenin signaling pathway was the most significant pathway expressed in the patient group. Since this pathway has been attributed to a variety of inflammatory manifestations, the current findings may contribute to dysfunctional monocytes in CKD patients. Strategies to interfere with this pathway may improve host immunity and prevent cardiovascular complications in CKD patients.

Newly recruited human monocytes have a preserved responsiveness towards bacterial peptides in terms of CD11b up-regulation and intracellular hydrogen peroxide production.

The transmigration of peripheral human monocytes to the interstitium is a fundamental step in the host‐defence mechanism against infections. Little is known about the state of function of in vivo transmigrated interstitial monocytes prior to differentiation into macrophages and dendritic cells. We hypothesized that newly recruited interstitial monocytes have a preserved responsiveness against bacterial‐related peptides, giving them a specific role in the immediate defence against invading pathogens. In order to test this hypothesis, we explored the responsiveness of in vivo transmigrated as well as peripheral monocytes, in terms of CD11b expression and H2O2 production towards the bacterial‐related peptide formylmethionylleucylphenylalanine (fMLP) by the use of a skin chamber technique. In addition, we analysed the concentration of interleukin (IL)‐8, monocyte chemotactic protein‐1 (MCP‐1) and tumour necrosis factor (TNF)‐α in the skin blister exudates and in the circulation. We demonstrate that in vivo‐transmigrated monocytes had a fivefold higher CD11b expression compared to monocytes obtained from the peripheral circulation. fMLP exposure induced a significantly higher CD11b expression on transmigrated cells compared to peripheral monocytes. In addition, newly recruited monocytes had a preserved H2O2 production. The interstitial concentration of IL‐8, MCP‐1 and TNF‐α was significantly higher in blister exudates compared to that in the peripheral circulation. Thus, in vivo transmigrated human monocytes preserve their capacity to respond towards bacterial peptides in terms of CD11b up‐regulation and H2O2 generation. These data strengthen a role for newly recruited interstitial human monocytes in the immediate defence against invading pathogens.

Granulocyte Extravasation and Recruitment to Sites of Interstitial Inflammation in Patients with Renal Failure

Background: We have shown that leukocytes collected from sites of interstitial inflammation in patients on hemodialysis have a disturbed expression of CD11b compared to cells from healthy subjects. The aim of the present study was to study adhesion molecule expression on granulocytes in the peripheral circulation and at sites of interstitial inflammation in patients with renal failure. Methods: Two skin blisters were raised in 10 patients and 19 healthy subjects and interstitial exudates collected (0 h). Skin chambers were applied and exposed to buffer or serum for 10 h in order to induce an intermediate and an intense interstitial inflammation. Cells and blister fluid were collected for determination of leukocyte count, CD11b/CD62L expression, interleukin-8 (IL-8) concentration in the interstitium and blister activity in terms of CD11b up-regulation. Results: At the sites of intermediate and intense inflammation, granulocytes from patients with renal failure showed significantly higher expression of CD62L (p < 0.01 and p < 0.001, respectively) and significantly lower expression of CD11b (p < 0.0001 and p < 0.0001, respectively) compared to corresponding cells from healthy subjects. The interstitial concentration of IL-8 was significantly lower at the sites of intermediate (p < 0.005) and intense inflammation (p < 0.05) in patients with renal failure compared to in healthy subjects. In order to explore whether the decreased CD11b expression observed in patients is due to the interstitial milieu, blister exudates from patients and healthy subjects were incubated with leukocytes from healthy blood donors. Blister exudates from patients had a similar capacity to mobilize CD11b on granulocytes in vitro compared with blister exudates from healthy subjects. There was no consistent correlation between the expression of adhesion molecules on granulocytes in the interstitium and the concentration of IL-8 or the total interstitial concentration of chemotactic mediators. Conclusion: Constitutive cellular determinants are probably involved in the disturbed expression of adhesion molecules on granulocytes at sites of interstitial inflammation in patients with renal failure.

Monocyte and Neutrophil Chemotactic Activity at the Site of Interstitial Inflammation in Patients on High-Flux Hemodialysis or Hemodiafiltration

Background/Aims: We have observed a difference between patients on low-flux hemodialysis (HD) or peritoneal dialysis and patients on hemodiafiltration (HDF) or high-flux HD in the capacity of transmigrated leukocytes to mobilize CD11b in response to inflammatory stimuli compared with healthy subjects. This could be due to different interstitial chemokine concentrations. Methods: We measured concentrations of circulating and interstitial macrophage inflammatory protein-1α (MIP-1α), matrix metalloproteinase-9 (MMP-9)/neutrophil gelatinase-associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) in 10 patients on HDF or high-flux HD and 11 healthy subjects by using immunoassay. Results: The interstitial concentrations of MIP-1α, MMP-9/NGAL and IL-8 were similar in patients and healthy subjects, while the corresponding concentration of MCP-1 was significantly higher in patients on HDF or high-flux HD as compared with healthy subjects (p < 0.01). Conclusion: We suggest that an equal or higher concentration of chemokines in the interstitium in patients with HDF or high-flux HD might be one mechanism responsible for the preserved function of transmigrated leukocytes.

In vivo transmigrated monocytes from patients with stable coronary artery disease have a reduced expression of CD11b

Coronary artery disease (CAD) is characterized by infiltration of monocyte derived cells in the intima of the vessel wall. We hypothesized that accumulation of these cells is caused partly by an altered monocyte transmigration process in CAD. To gain insight into this issue we applied the skin blister method that allows collection of in vivo transmigrated cells at sites of local inflammation. Nineteen patients with stable CAD and 19 matched controls were enrolled. Markers of inflammation and gradients of chemokines, as well as adhesion molecule expression and up‐regulation capacity, were studied. The expression of inflammatory markers, such as C‐reactive protein, interleukin (IL)‐6, tumour necrosis factor‐α and IL‐10, was similar in patients and controls, indicating that patients were in a stable phase of the disease. Expression of adhesion molecules, CD11b and very late activation antigen‐4, on peripheral monocytes did not differ between patients and controls. However, following in vivo transmigration, monocytes in patients with CAD had a significantly reduced expression and mobilization of CD11b. The effect on CD11b could not be reproduced by in vitro stimulation with blister fluid, representing a local inflammatory milieu, or in an in vitro system of transmigration. These findings point towards differences in monocyte CD11b expression and availability at an inflammatory site between patients with CAD and healthy controls.