Abstract 168: Circulating Blood Neutrophils Are the Main Source of Plasma Nampt After Cardiac Arrest

Introduction: Nampt functions as a novel extracellular damage-associated molecular pattern. It has been shown to be released from many cell types including neutrophils, adipocytes, and hepatocytes. In a mouse model of cardiac arrest, increased plasma Nampt correlates with inflammation, cardiovascular dysfunction and poor survival. However, the source of plasma Nampt after cardiac arrest is unknown.

Hypothesis: We hypothesize that plasma Nampt is released from blood neutrophils.

Methods: Circulating blood neutrophils from C57/BL6 mice were depleted by intraperitoneal injection of 500 μg murinized Ly-6G (1A8) antibody. 48 hours later, mice were subjected to 8 min KCl-induced cardiac arrest followed by resuscitation. Saline-treated mice served as the control group. Blood neutrophil counts were measured at 48 h after injection. Plasma NAMPT concentration at 4 h post-resuscitation was measured by ELISA.

Results: Ly-6G antibody induces a nearly complete depletion of blood neutrophils at 48 h after injection. Neutrophil counts were 1.17 ± 0.07 for saline control mice and 0.12 ± 0.01 (10 ⁶ /ml) for Ly-6G treated mice (p < 0.01). Plasma eNampt concentrations at 4h post-ROSC were significantly lower in Ly-6G treated mice compared to control mice. Plasma concentration of NAMPT decreased from 12.67 ± 0.39 ng/ml for saline-treated mice to 5.34 ± 1.41 ng/ml for Ly-6G treated mice (p < 0.01).

Conclusion: Circulating blood neutrophils are sufficiently depleted by Ly-6G antibody, and neutrophils are the major contributor to plasma NAMPT during cardiac arrest. The study of neutrophil depletion on post-resuscitation inflammatory cytokine and mouse survival is ongoing.