We have made the seminal observation that O-linked ?-N-acetylglucosamine (O-GlcNAc) modification of proteins induced by three distinct and independent stimuli, 17-? estradiol (E2), glucosamine (GlcN) and the selective O-GlcNAcase inhibitor O-(acetamido-2-deoxy-D-glucopyranosylidene) amino-N-phenylcarbamate (PUGNAc), has anti-inflammatory effects in balloon injured rat carotid arteries. These novel observations provide provocative evidence that enhanced O-GlcNAc modification of proteins has anti-inflammatory and vasoprotective effects in the setting of acute endoluminal vascular injury. We have strong evidence that increased protein O-GlcNAc modification in response to GlcN treatment is associated with attenuation of TNF-a-induced expression of inflammatory mediators in isolated rat aortic smooth muscle cells (RASMCs) in a manner previously reported for E2. We have utilized the TNF-a-treated RASMC as an in vitro model of the acute vascular injury response and have begun to define the mechanisms by which interventions that stimulate protein O-GlcNAc modification, i.e., E2 and GlcN, inhibit inflammatory responses to TNF-a. We have focused on the NF?B signaling pathway, which is known to be activated by both TNF-a and acute vascular injury. Initial experiments demonstrated that GlcN inhibits TNF-a-induced NF?B activation in RASMCs. Subsequent studies showed that pretreatment with GlcN inhibits TNF-a-induced phosphorylation and degradation of I?Ba in RASMCs, while E2 pretreatment is associated with an initial reduction, followed by an accelerated reappearance of I?Ba in TNF-a treated cells, likely reflecting new protein synthesis mediated by activated NF?B. The current study will test directly the hypothesis that O-GlcNAc modification of proteins, including I?Ba, plays a mechanistic role in regulating the inflammatory response to endoluminal arterial injury in vivo and to TNF-a stimulation in isolated RASMCs in vitro.
The Specific Aims are:
Specific Aim 1 : To test the hypothesis that increasing protein O-GlcNAc modification protects arteries from inflammatory stress related to acute endoluminal injury in vivo via inhibition of NF?B signaling.
Specific Aim 2 : To test the hypothesis that increasing protein O-GlcNAc modification inhibits TNF-a-induced inflammatory responses in RASMCs in vitro via inhibition of NF:B signaling and define the precise sites in the NF?B signaling cascade that are responsible for this effect.
Specific Aim 3 : To identify specific protein targets of O-GlcNAc modification in RASMCs that play a functional role in the anti-inflammatory effects of GlcN and E2. Upon successful completion of these Aims, cellular/molecular mechanisms responsible for the anti-inflammatory and vasoprotective actions of O-GlcNAc modification will be elucidated and will be related to the extent of the injury response (i.e., inflammation and neointima formation). We postulate that O-GlcNAc modification represents a novel mechanism of vasoprotection that may lend itself to the development of new strategies for the prevention and treatment of cardiovascular disease.
This proposal will test the hypothesis that a novel mechanism, O-linked acetylglucosamine (O-GlcNAc) modification of proteins, has anti-inflammatory and vasoprotective effects in injured arteries and cytokine- stimulated smooth muscle cells (SMCs) and will identify the specific proteins that are responsible for these protective effects.
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