Reducing leukocyte trafficking preserves hepatic function after sepsis.

INTRODUCTION

Leukocyte trafficking may induce hepatic dysfunction in sepsis. Herein, we hypothesize that reduction in leukocyte adhesion and, hence, leukocyte-endothelial interaction by activated protein C (aPC) may preserve hepatic function after sepsis.

METHODS

Rats underwent sham or cecal ligation and puncture, followed by saline or aPC (1 mg/kg intravenously) infusion, twice daily for 4 days. Cytokine levels were determined by enzyme-linked immunosorbent assay. Liver function and injury were assessed by bile production and plasma aspartate transaminase, respectively. In parallel experiments, neutrophils were labeled with Rhodamine 6G, and trafficking determined by cell motion tracking using intravital microscopy. Leukocyte trafficking and traveling velocity were computed at baseline and at 10 minutes and 40 minutes after endothelin-1 infusion.

RESULTS

Sepsis induced 90% mortality and elevated levels of interleukin (IL)-2 (167 pg/mL +/- 39 pg/mL vs. 68 pg/mL +/- 2 pg/mL, p < 0.05), IL-6 (5,806 pg/mL +/- 3,389 pg/mL vs. 0 pg/mL +/- 0 pg/mL, p < 0.05), and IL-8 (492 pg/mL +/- 22 pg/mL vs. 21 pg/mL +/- 17 pg/mL, p < 0.05). Aspartate transaminase levels increased (227 IU/L +/- 14 IU/L vs. 51 IU/L +/- 7 IU/L, p < 0.05) in cecal ligation and puncture animals, whereas bile production decreased by fivefold compared with sham (436 microg/kg/h +/- 247 microg/kg/h vs. 2,357 microg/kg/h +/- 147 microg/kg/h, p < 0.05). Hepatic leukocyte adhesion increased threefold in septic animals (42.7 WBC per image +/- 7.3 WBC per image vs. 14.8 WBC per image +/- 3.8 WBC per image, p < 0.01), whereas leukocyte velocity decreased compared with sham (10.5 microm/s +/- 2.2 microm/s vs. 22.3 microm/s +/- 2.4 microm/s, p < 0.01). By contrast, aPC treatment reduced mortality to 60%, attenuated inflammatory cytokines, reduced leukocyte trafficking, and preserved hepatic function.

CONCLUSIONS

Our data demonstrate that sepsis may, in part, induce hepatic dysfunction by augmenting leukocyte trafficking into hepatic sinusoids. Treatment with aPC attenuated leukocyte trafficking and, in doing so, preserved hepatic function and improved survival. Collectively, these data suggest an important role for protein C-dependent leukocyte-endothelial interaction in sepsis.