Alterations in hepatic microcirculation, mitochondrial redox state and tissue oxygenation after trauma and sepsis

Introduction: Hepatic microcirculatory dysfunction and mismatch of blood supply to metabolic demand play an important role in liver failure after stress. Here, we assessed hepatic microcirculation in response to the vasoregulator Endothelin-1 (ET-1) after femur fracture (FFx) and cecal ligation and puncture (CLP). We hypothesized that sequential stress causes hepatic microcirculatory dysfunction leading to altered mitochondrial redox state and tissue PO2 (tPO2). Methods: Male Sprague-Dawley rats (200–300 g, n = 4/groups) underwent sham surgery, FFx, CLP and FFx+CLP. Using intravital microscopy, hepatic microcirculation was assessed by sinusoidal volumetric flow (pL/sec) and perfusion index (PI, pL/sec/200μm). Changes in hepatic mitochondrial redox state and liver tPO2 were determined by NADH autofluorescence (AU, arbitrary unit) and ruthenium (Ru, AU) fluorescence, respectively. Western blot analysis was used to determine ETA/ETB receptor protein expression (AU). Differences among groups were compared using one-way ANOVA followed by Student-Newman-Keuls post hoc test. Results: After 10 minutes of intraportal ET-1 infusion, liver microcirculation was altered in CLP and FFx+CLP groups (Table, values are mean ± SE). TABLE—ABSTRACT 24GroupFlowPINADHRuETAETBSham21 ± 3160 ± 19109 ± 7177 ± 50 ± 09 ± 3FFx19 ± 1155 ± 15101 ± 10148 ± 80 ± 038 ± 8CLP9 ± 2∗69 ± 14∗153 ± 10∗190 ± 6∗0 ± 036 ± 16FFx+CLP5 ± 0.8∗28 ± 4∗160 ± 12∗202 ± 7∗52 ± 8§58 ± 12§∗p < 0.05 vs. sham and FFx,§p < 0.05 vs. sham, FFx, and CLP. Sequential stress also led to increased NADH and Ruthenium fluorescence intensity, indicating a reduction in O2 availability. Vasoactive receptor proteins ETA and ETB were upregulated after injury. Conclusion: Our data suggest that sepsis and sequential stress result in liver microcirculatory disturbances leading to altered global hepatic perfusion, and contribute toward a reduction in O2 supply. These changes in the liver microcirculation, mediated in part by Endothelin-1, may play an important role in the development of liver failure after inflammatory stress.