Background: Trauma and hypovolemic shock are associated with mitochondrial dysfunction and septic complications. We hypothesize that hypovolemic shock and resuscitation results in peripheral blood mononuclear cell (PBMC) mitochondrial dysfunction that is linked to immunosuppression.
Methods: With the use of a decompensated shock model, Long-Evans rats were bled to a mean arterial pressure of 40 mm Hg until the blood pressure could no longer be maintained without fluid infusion. Shock was sustained by incremental infusion of lactated Ringer's solution until 40% of the shed volume had been returned (severe shock). Animals were resuscitated with four times the shed volume in lactated Ringer's solution over 60 minutes (resuscitation). Control animals underwent line placement but were not hemorrhaged. Animals were randomized to control (n = 5), severe shock (n = 5), or resuscitation (n = 6) groups. At each time point, PBMC were isolated for mitochondrial function analysis using flow cytometry and high-resolution respirometry. Immune function was evaluated by quantifying serum interleukin 6 (IL-6) and tumor necrosis factor (TNF-α) after PBMC stimulation with lipopolysaccharide. The impact of plasma on mitochondrial function was evaluated by incubating PBMCs harvested following severe shock with control plasma. PBMCs from control animals were likewise mixed with plasma collected following resuscitation. Student's t test and Pearson correlations were performed (significance, p < 0.05).
Results: Following resuscitation, PBMCs demonstrated significant bioenergetic failure with a marked decrease in basal, maximal, and adenosine triphosphate-linked respiration. Mitochondrial membrane potential also decreased significantly by 50% following resuscitation. Serum IL-6 increased, while lipopolysaccharide stimulated TNF-α production decreased dramatically following shock and resuscitation. Observed mitochondrial dysfunction correlated significantly with IL-6 and TNF-α levels. PBMCs demonstrated significant mitochondrial recovery when incubated in control serum, whereas control PBMCs developed depressed function when incubated with serum collected following severe shock.
Conclusion: Mitochondrial dysfunction following hemorrhagic shock and resuscitation was associated with the inhibition of PBMC response to endotoxin that may lead to an immunosuppressed state.