Abstract: TH-PO287

Antioxidant Regulation of Alarmin Redox and Function during Sepsis

Session Information

Category: Acute Kidney Injury

  • 001 AKI: Basic

Authors

  • Abdulmahdi, Wasan, New York Medical College, Valhalla, New York, United States
  • Patel, Devika, New York Medical College, Valhalla, New York, United States
  • Rabadi, May M., Columbia University Medical Center, New York, New York, United States
  • Azar, Tala F., New York Medical College, Valhalla, New York, United States
  • Jules, Edson, New York Medical College, Valhalla, New York, United States
  • Papanagnou, Anastasios, Westchester Medical Center, Bayside, New York, United States
  • Ratliff, Brian B., New York Medical College, Valhalla, New York, United States
Background

During sepsis, oxidative stress is enhanced and the alarmin High Mobility Group Box 1 protein (HMGB1) is released into the circulation from immune, endothelial and kidney epithelial cells. Once in the circulation, HMGB1 can promote systemic inflammation, with the kidney particularly susceptible to damage. However, the severity of the pro-damage signal mediated by HMGB1 is dependent on the alarmin’s redox state. Thus, we examined HMGB1 redox in kidney cells during sepsis and the ability of endogenous antioxidants to regulate HMGB1 oxidation.

Methods

Lipopolysaccharide (LPS) was administered at different doses to cells and animals to mimic different severities of sepsis. During LPS treatment, reactive oxygen species (ROS) generation was examined in cell cultures and in animals. After 24 hours of LPS treatment, HMGB1 redox state was examined in the nuclear and cytoplasmic compartments of kidney cells and in the plasma using a HMGB1 redox detection assay and also by mass spectrometry (LC-MS/MS) analysis. Glutathione and thioredoxin inhibitors were administered to endothelial and proximal tubule cell cultures to determine their impact on HMGB1 redox during LPS treatment. In addition, HMGB1 (of varying redox state) was isolated from mice that had received high or low LPS dose and was re-introduced to healthy mice for analysis of the alarmin’s pro-inflammatory effects.

Results

CellROX and MitoSOX labeling of LPS-stressed endothelial and proximal tubule cells demonstrated increased ROS generation in cells as sepsis severity increased. Consequently, HMGB1 oxidation increased in the cytoplasm of kidney cells and was maintained after its release into the circulation, with the degree of oxidation dependent on the severity of sepsis. The greater the oxidation of HMGB1, the greater the ability of the alarmin to stimulate pro-inflammatory cyto-/chemokine release. Highly oxidized HMGB1 also increased mitochondrial ATP production. Administration of glutathione and thioredoxin inhibitors to cell cultures enhanced HMGB1 oxidation during sepsis in endothelial and proximal tubule cells.

Conclusion

In conclusion, as sepsis severity increases, ROS generation and HMGB1 oxidation increases in kidney cells, which enhances HMGB1’s pro-inflammatory signaling. Conversely, the glutathione and thioredoxin systems work to maintain the protein in its reduced state