Enhanced enzymatic degradation of tryptophan by indoleamine 2,3-dioxygenase contributes to the tryptophan-deficient state seen after major trauma.

Decreased lymphocyte proliferation, lymphopenia, immunodepression, and opportunistic infections are common after major trauma. Early alimentation in these patients corrects lymphopenia, enhances immunity, and reduces the incidence of infections, but the underlying mechanisms are poorly understood. Tryptophan is essential for the production and function of rapidly proliferating cells such as lymphocytes. Tryptophan is enzymatically degraded by indoleamine 2,3-dioxygenase (IDO), whose activity is solely dependent on expression of interferon-gamma (IFN-gamma). Because increased expression of IFN-gamma has been reported in trauma patients, we investigated whether enhanced IDO-mediated tryptophan degradation is associated with lymphopenia and poor outcomes after major trauma. The incidence of bacteremic sepsis (BS), adult respiratory distress syndrome (ARDS), multiple organ dysfunction/failure syndromes (MODS/MOF), and death was prospectively documented in 22 trauma patients with a mean ISS of 24.9 +/- 2.2. Sequential blood samples were obtained from admission through postinjury day 10. Five patients developed BS, three of whom developed ARDS; two of the three ARDS patients developed MOF and died on day 10. Trauma patients had significantly lower tryptophan levels (days 1-10), higher kynurenine:tryptophan ratios (days 1-2), and fewer lymphocytes (days 1-4) than healthy volunteers (P < 0.05). Although patients with poor outcomes (i.e., BS, ARDS, MOF, and death) had significantly lower tryptophan levels and greater lymphopenia on several days after injury, the sample size was too small to draw any definitive conclusions. These data indicate that decreased plasma tryptophan levels and lymphopenia typically occur after major trauma. A concomitant increase in kynurenine suggests that the observed tryptophan deficiency is caused, in part, by IDO-mediated tryptophan degradation.

Recombinant human interleukin-1alpha increases serum albumin, Gc-globulin, and alpha1-antitrypsin levels in burned mice.

The response to thermal injury is a complex physiologic process requiring communication between sites of injury and distant target organs. The liver, one of these target organs, synthesizes a family of secretory proteins, the acute phase proteins, that carries out specific immunoprotective functions. In this study we investigated the effects of daily recombinant human interleukin-1alpha (rhIL-1alpha) administration on the serum levels of negatively regulated, i.e., albumin and Gc-globulin and positively regulated, i.e., alpha1-antitrypsin, acute phase proteins in a murine model of thermal injury. Adult CF-1 female mice underwent a 6.5-seconds, 20% total burn surface area, full thickness steam injury, and received either intraperitoneal rhIL-1alpha (20 microg x kg(-1) x day(-1)) or diluent for 10 days. Seven and 14 days after injury, mice were sacrificed, and serum albumin, Gc-globulin and alpha1-antitrypsin levels were measured by crossed immunoelectrophoresis technique. Thermal injury significantly lowered serum albumin levels, tended to decrease Gc-globulin levels, and increased serum alpha1-antitrypsin levels. Daily rhIL-1alpha administration after burn injury prevented hypoalbuminemia, and increased serum levels of Gc-globulin and alpha1-antitrypsin. IL-1 therapy might be helpful to maintain the homeostasis and immunity of the host after thermal injury.