Neutrophil degranulation and severely impaired extracellular trap formation at the basis of susceptibility to infections of hemodialysis patients

Abstract

Background Chronic kidney disease patients are at increased risk of mortality with cardiovascular diseases and infections as the two leading causes of death for end-stage kidney disease treated with hemodialysis (HD). Mortality from bacterial infections in HD patients is estimated to be 100–1000 times higher than in the healthy population. Methods We comprehensively characterized highly pure circulating neutrophils from HD and healthy donors. Results Protein levels and transcriptome of HD patients’ neutrophils indicated massive neutrophil degranulation with a dramatic reduction in reactive oxygen species (ROS) production during an oxidative burst and defective oxidative cellular signaling. Moreover, HD neutrophils exhibit severely impaired ability to generate extracellular NET formation (NETosis) in NADPH oxidase-dependent or independent pathways, reflecting their loss of capacity to kill extracellular bacteria. Ectopic hydrogen peroxidase (H2O2) or recombinant human SOD-1 (rSOD-1) partly restores and improves the extent of HD dysfunctional neutrophil NET formation. Conclusions Our report is one of the first singular examples of severe and chronic impairment of NET formation leading to substantial clinical susceptibility to bacteremia that most likely results from the metabolic and environmental milieu typical to HD patients and not by common human genetic deficiencies. In this manner, aberrant gene expression and differential exocytosis of distinct granule populations could reflect the chronic defect in neutrophil functionality and their diminished ability to induce NETosis. Therefore, our findings suggest that targeting NETosis in HD patients may reduce infections, minimize their severity, and decrease the mortality rate from infections in this patient population.

NETs-Induced Thrombosis Impacts on Cardiovascular and Chronic Kidney Disease

“…Some authors observed increased NETs production by neutrophils isolated from dialysis patients upon phorbol-12-myristate-13-acetate (PMA) stimulation, 148,149 along with increased PAD4 levels in serum 149 or increased NE activity in both resting and PMA-stimulated neutrophils. 148 In contrast, others reported a decreased NETs formation capacity of isolated neutrophils from dialysis patients upon stimulation with PMA, lipopolysaccharide, or the Ca 2+ ionophore A23187 compared with healthy controls 15 (Table 2). The latter was observed along with a reduced PAD4 expression in neutrophils as well as a reduced capacity of agonist-induced ROS production, a decreased basal cellular content of the neutrophil granule proteins myeloperoxidase, NE, and MMP-9 (matrix metallopeptidase-9) but an increased surface expression of activation and degranulation markers (CD66b, CD15, CD18) by isolated neutrophils.…”

“…Based on these latter findings, it was suggested that neutrophils from hemodialysis patients have a constant potent immune activation, which leads to substantial neutrophil degranulation, a subsequent limited preservation of degranulation capacity and a malfunctioning ROS cascade, and thereby a reduction in both NADPH oxidase-dependent and NADPH oxidase-independent NET formation. 15 Another study also concluded on an increased basal activation of neutrophils in hemodialysis patients upon observation of increased NETs formation, ROS production, surface activation marker expression, and H3cit levels by unstimulated neutrophils when isolated from hemodialysis patients compared to controls, along with a reduced fold-upregulation of NET formation upon neutrophil stimulation with PMA 135 (Table 2). Overall, reasons for the divergent findings on NETs formation capacity of neutrophils isolated from dialysis patients (being either increased or decreased upon PMA stimulation) remain currently unclear.…”

“…Multiple groups reported a signature of increased neutrophil activation in blood of patients with CKD with increased expression of CD11b 12,13 and its interaction partner CD18, 14,15 2 integrins with important role in neutrophil adhesion to activated endothelium. Furthermore, circulating neutrophils from patients with CKD on hemodialysis showed increased expression of the activation markers CD35, 135 CD66b and CD15.…”

“…7 They display chronic low-grade inflammation 8 and enhanced serum titers of NETs inducers like interleukin (IL)8 9–11 and show increased expression of neutrophil activation markers on circulating blood neutrophils. 12–15…”

“…7 They display chronic low-grade inflammation 8 and enhanced serum titers of NETs inducers like interleukin (IL)8 [9][10][11] and show increased expression of neutrophil activation markers on circulating blood neutrophils. [12][13][14][15] Central to thromboinflammation is the loss of the antithrombotic and anti-inflammatory functions of endothelial cells, leading to dysregulation of coagulation, complement, platelet activation, and leukocyte recruitment. Binding between platelets and recruited neutrophils advances changes in neutrophil function promoting arrest at sites of thrombus formation but also initiation of thrombosis through NETs formation.…”