Immune regulatory role of reactive oxygen species (ROS) in sepsis

About This Grant

Project Summary Sepsis and septic shock are the leading causes of morbidity and mortality among critically ill patients in intensive care units (ICUs), leading to extraordinary healthcare costs annually. Numerous attempts have been made to identify more specific and effective therapeutic strategies and pharmacological agents for the treatment of sepsis. None has proven effective to date. Thus, there is still a critical need for targeted and effective therapy to reduce mortality from this disease. The objective of this study is to elucidate the role of ROS in modulating IL-1β bioactivity in sepsis. The hypothesis is that ROS-induced irreversible oxidation and its modulation by S-glutathionylation are key regulatory mechanisms controlling IL-1β bioactivity in sepsis. There is overwhelming evidence that ROS and oxidative stress play significant roles in the pathogenesis of sepsis-associated multiple organ failures. Antioxidants, such as N-acetylcysteine (NAC), due to their anti- inflammatory property, have been proposed for the treatment of sepsis. However, the results of the related clinical trials with septic patients have generally been incongruous and disappointing. It turns out that, besides their pro-inflammatory and pro-injury roles in the pathogenesis of sepsis, ROS can also elicit anti-inflammatory effects by inhibiting IL-1β bioactivity. NAC ameliorates oxidative stress and ROS-induced tissue damage. However, such treatment also augments IL-1β bioactivity and IL-1β-mediated pro-inflammatory responses, thereby contributing to the ineffectiveness and even adverse effect of NAC-based sepsis therapy. In this study, it is proposed that combined treatment with NAC and IL-1 receptor antagonist, anakinra, will effectively attenuate sepsis pathogenesis. The premise is strongly supported by the preliminary finding that NAC treatment decreased sepsis-induced mortality more effectively in IL1R1 deficient mice than in WT mice. In current study, the role of ROS-elicited oxidation in modulating IL-1β bioactivity will be further investigated in a murine model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). First, the effects of co- treatment with NAC and anakinra on sepsis pathogenesis will be examined in detail (Aim 1). Mechanistically, to elucidate the role of IL-1β irreversible oxidation in sepsis, the levels of irreversibly oxidized (inactive) IL-1β in septic mice will be measured, and the impact of IL-1β irreversible oxidation on CLP-induced sepsis will be determined (Aim 2). Additionally, the roles of S-glutathionylation and Grx1 in regulating the irreversible oxidation and deactivation of IL-1β in sepsis will be investigated (Aim 3). Finally, the ROS-mediated regulation of IL-1β bioactivity and its correlation with disease severity will be explored using plasma samples from human sepsis patients (Aim 4). Together, the experiments proposed in these four specific aims will advance our understanding of the molecular control of IL-1β activity in general and provide insights into the mechanism of action of ROS-induced irreversible oxidation in controlling IL-1β bioactivity in sepsis, with the ultimate goal of solidifying the combinatorial treatment with NAC and anakinra as a novel therapeutic strategy for sepsis.