Heme oxygenase-1/CO protect against post-traumatic suppression of adaptive immune responses (IRC8P.475)

Abstract

Abstract Traumatic injury induces a systemic dysregulated immuno-inflammatory response that contributes to mortality. This response includes an upregulation of pro-inflammatory cytokines by innate cells and an independent suppression of adaptive immunity characterized by reduced Th1 responses. Heme oxygenase-1 (HO-1) and its byproduct, carbon monoxide (CO), are protective against injury-induced inflammation and end-organ damage, but their beneficial role in the dysregulation of adaptive responses following trauma is unknown. To investigate this, B6 mice received multiple-trauma or no manipulation, and were given either vehicle or a HO-1 inducer (Cobalt protoporphyrin, CoPP; 5mg/kg) prior to injury. Another cohort received either room air or CO (250ppm) for 4 hours directly post-injury. At 48hr post-trauma, Tcell functions were assessed by ex-vivo mitogen-induced Tcell proliferation and Th1 cytokine release (IL-2 and IFN-γ). As expected after injury, a near 50% reduction in Tcell proliferation was seen in vehicle- or air-treated trauma mice, compared to uninjured controls (p=0.007). A parallel reduction in Tcell IL-2 and IFN-γ release was observed. In clear contrast, CoPP or CO treatment prevented trauma-induced reductions in Tcell proliferation and cytokine release (fold difference 0.90±0.10 and 1.21±0.16 to uninjured controls, respectively). Overall, HO-1 represents an endogenous protective pathway that can be exploited following trauma to preserve normal immune functions & survival.