Effects of O-GlcNAcylation (O-GlcNAc) on the release of inflammatory mediators and abnormal vascular reactivity in mice with systemic inflammatory response syndrome (SIRS) and sepsis

Abstract

O-GlcNAcylation (O-GlcNAc) is an unusual form of glycosylation, where a simple sugar N-acetyl-glucosamine (GlcNAc) is added to the hydroxyl group (O) of serine (Ser) and threonine (Thr) residues in nuclear and cytoplasmic proteins. Increased O-GlcNAc reduces the release of inflammatory mediators as interleukin1² (IL-1²), interleukin-6 (IL-6) and tumor necrosis factor (TNF-±) as well as the activity of the transcription factor kappa B nuclear factor (NF-ºB) in cells of the immune system. The initial events of the Systemic Inflammatory Response Syndrome (SIRS), a serious condition related to systemic inflammation, organ dysfunction, and organ failure, as well as in sepsis, a complex inflammatory response due to an infectious insult, involve the release of inflammatory cells, increased levels of cytokines and increased production of reactive oxygen species (ROS). The hypothesis of this study is that increased modification by O-GlcNAc decreases the levels of IL-1², IL-6 and TNF-± as well as NF-kB activation and ROS production in arteries from animals with SIRS (mild and severe) and moderate and severe sepsis, therefore reducing the risk of cardiovascular complications. SIRS/endotoxemia will be induced by lipopolysaccharide (LPS) administration and sepsis will be induced by cecal ligation and puncture. The effects of glucosamine and OGA inhibitors (that increase O-GlcNAc-modified proteins) or vehicle on SIRS/sepsis-associated survival/mortality, production and release of cytokines by inflammatory and vascular cells, vascular reactivity and changes in blood pressure will be determined. Vascular reactivity will be determined in thoracic aortic rings and cytokines levels/NF-kB activation will be measured by ELISA and western blot analyses, respectively. This study is scientifically important since O-GlcNAc is an additional mechanism that control intracellular signaling and SIRS/sepsis represents 40% to 70 % of death among hospitalized patients in intensive care units. Studies on the effects of O-GlcNAc in pathophysiological conditions are essential to clarify the role of this post-translational modification in SIRS/sepsis. This study includes various experimental strategies (physiological, pharmacological, biochemical, cellular and molecular techniques) to define the effects of O- GlcNAc on SIRS/sepsis-associated vascular dysfunction and inflammatory process. (AU)