Nlrx1 Attenuates Damage Following Traumatic Brain Injury Through Negatively Regulating Nf-Kb Signaling

Mechanical trauma to the CNS results in the disruption of the cellular microenvironment leading to massive necrotic and apoptotic loss of neuronal and glia populations. The progressive cascade of secondary events, including ischemia, inflammation, excitotoxicity and free radial release contribute to neural tissue damage. Members of the NLR family of pattern recognition receptors are essential mediators of the host immune response. Recently, our lab and others identified a novel sub-group of NLRs that function as negative regulators of inflammation. One of the members of this sub-group, NLRX1, is a potent regulator of interferon, NF-κB, ROS production and autophagy. Thus, we hypothesized that NLRX1 attenuates Traumatic Brain Injury (TBI) through the negative regulation of overzealous innate immune system signaling. To evaluate this hypothesis, we utilized Nlrx1 −/− mice in a controlled cortical impact (CCI) injury model. The Nlrx1 −/− mice exhibited significantly larger brain lesions and increased motor deficits following CCI injury. We also observed significant proliferation of microglia within the Nlrx1 −/− lesions compared to wild type animals. Mechanistically, our data indicates that NLRX1 attenuates TBI progression through the microglia compartment via negative regulation of NF-κB signaling and IL-6 production. Together, our data extends the function of NLRX1 beyond its currently characterized role in host-pathogen defense and identifies this highly novel NLR as a significant modulator of TBI progression.