Endotoxin, Neutrophil Function and Albumin in Renal Insufficiency
Condition: Chronic Renal Insufficiency; Acute Renal Failure
MeSH terms: Renal Insufficiency; Acute Kidney Injury; Renal Insufficiency, Chronic
Study type: Observational

Summary: 
      Chronic kidney disease is widespread in the western world with bacterial infection and sepsis
      as common complication. It has been shown that innate immune defence, represented by
      dysfunction of neutrophil granulocytes, is impaired in chronic kidney disease. Another impact
      of chronic kidney disease on innate immunity is the chronic activation of neutrophils leading
      to high levels of inflammatory cytokines, thus contributing to protein oxidation. Oxidation
      of human serum albumin (HSA), the major plasma protein, occurs in chronic kidney disease and
      leads to further activation of neutrophils. Another important impact of HSA oxidation is the
      decrease of its binding capacity leading to impaired detoxification ability of albumin. This
      includes reduced clearance of endotoxin, a major component of the gram negative bacterial
      cell wall. Circulating endotoxin is recognized by complex formation with lipopolysaccharide
      binding protein (LBP) followed by binding to CD14 and toll-like receptor (TLR) 4. High
      systemic endotoxin levels occur in chronic kidney disease and may be the result of decreased
      clearance ability of HSA and increased gut permeability in combination with intestinal
      bacterial overgrowth. High systemic endotoxin is associated with worse outcome in several
      diseases and could be used as predictor for mortality in chronic kidney disease patients.

      Endotoxemia in renal insufficiency leads to impaired neutrophil function and to increased
      albumin oxidation. Oxidized albumin is not able to bind endotoxin adequately any more, which
      leads to a further increase in oxidative stress and neutrophil dysfunction, resulting in a
      vicious cycle.

      195 patients with renal dysfunction will be enrolled and divided into 5 groups. Additionally,
      samples of 25 age and sex-matched healthy controls will be collected.

      This concept will change the understanding of several aspects of chronic kidney disease and
      will potentially help to stratify patients into different groups at risk according to their
      endotoxin status, and their immune and albumin dysfunction. The results of this study will
      have important implications into the development of novel therapeutic strategies
    

Detailed description: 
      Laboratory methods Endotoxin will be detected by an adapted limulus amoebocyte lysate assay.
      LBP and sCD14 will be determined by means of ELISA. HPLC will be used to determine nitrate,
      nitrite, albumin fractions, albumin binding capacity, iNOS expression and energy status of
      neutrophils. For investigation of oxidation driven by leukocyte derived myeloperoxidase, mass
      spectrometry analysis will be used. Carbonyl contents of proteins will be detected by ELISA.
      Neutrophil function and TLR2, 4 and 9 expression will be studied by flow cytometrical
      analysis. For cell culture tests, freshly isolated neutrophils or differentiated HL60 cells
      will be used and incubated with albumin and/or endotoxin. Stool samples will be used for
      16srDNA sequencing of the gut microbiome.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        1. 50 predialytic patients (a) 25 patients with an eGFR between 30 and 45 (KDIGO 3B) and
             (b) 25 patients with an eGFR between 15 and 30 (KDIGO 4)

          2. 50 patients undergoing hemodialysis or hemodiafiltration for ESRD (a) 25 patients
             under therapy with sevelamer and (b) 25 patients without sevelamer

          3. (a) 25 patients undergoing peritoneal dialysis for ESRD without signs of infection and
             (b) 25 patients undergoing peritoneal dialysis for ESRD with peritonitis

          4. 25 patients with acute renal failure

          5. 45 patients after kidney transplantation (a) 15 patients with an eGFR > 45, (b) 15
             patients with an eGFR between 30 and 45 and (c) 15 patients with an eGFR < 30

          6. 25 age and sex-matched healthy controls
      
Biospecimen description: 
      Serum, Plasma, Urine
    
Keywords: endotoxin; neutrophil function; albumin function