#2411 Inflammation in hypervolemic hemodialysis patients is linked to increased caspase-4 activity

Abstract

Abstract Background and Aims Hypervolemia is associated with inflammation in hemodialysis patients (HD). How hypervolemia triggers inflammation is not entirely known. We hypothesized that hypervolemia affects signaling via the NF-kB transcription factor system and thus analyzed the phosphorylated forms of RelA and RelB in immune cells of hypervolemic (H) and normovolemic (N) patients. Further on, we speculated that the higher inflammatory load in H in comparison to N patients could affect the sensor of intracellular LPS activity, namely caspase-4. Method Forty HD patients were categorized by bioimpedance measurement in normovolemic (N; 23) and hypervolemic (H; 17) groups. A caspase activity assay in combination with a specific Caspase-4/-5 inhibitor was used to detect Caspase-4/-5 activity in isolated PBMCs by flow-cytometry. The transcription factors RelA (pS529) and RelB (pS552) were analyzed by phopho-flow cytometry. Endotoxin as well as IL-6 and TNF-α were detected by ELISA technique. Results Hypervolemic patients were older and had more frequent diabetes. Although the endotoxin levels (EU/ml) in the serum of both groups were not different (N: 3.3 ± 1.6 vs. H 2.9 ± 1.4), Caspase-4/-5 activity (frequency of CD14+Caspase-4+), linked to intracellular endotoxin detection, was significantly elevated in H patients (N: 52 + 17% vs. H: 65 + 17%, p < 0.01). While the frequency and expression density of Rel A expressing immune cells were not different, the monocytic frequency of cells staining positive for RelB (pS552) was significantly elevated in N patients (N: 37.7 ± 27.1 vs. H: 20.4 ± 17.1, p=0.038). Among inflammatory cytokines (pg/ml) measured in the serum of patients, only IL-6 (N: 5.8 ± 10.5 vs H: 7.2 ± 6.8, p = 0.01) but not TNF-α (N: 7.7 ± 1.1 vs. H: 7.5 ± 0.7, p = 0.580) was increased in H patients. Conclusion The lower frequency of pRelB-positive monocytes in hypervolemic patients may be linked to a functional impairment to resolve inflammatory circles. The elevated caspase-4/-5 activity in H patients, however, can be interpreted as a higher intracellular LPS-load in H patients. Therefore, both higher inflammatory load and lower inflammatory resolution capacities are characteristics of H patients.