Studies of post-translational modification by β-N-acetyl-D-glucosamine (O-GlcNAc) are hampered by a lack of efficient tools such as O-GlcNAc specific antibodies that can be employed for detection, isolation, and site localization. We have obtained a large panel of O-GlcNAcspecific IgG MAbs having a broad spectrum of binding partners by combining three-component immunogen methodology with hybridoma technology. Immunoprecipitation followed by largescale shotgun proteomics led to the identification of more than 200 mammalian O-GlcNAc modified proteins, including a large number of novel glycoproteins. A substantial number of the glycoproteins were only enriched by one of the antibodies and this observation combined with results of inhibition ELISAs suggests that the antibodies in addition to their O-GlcNAcdependence also appear to have different, but overlapping, local peptide determinants. The MAbs made it possible to delineate differentially modified proteins of liver in response to traumahemorrhage and resuscitation in a rat model.

Inflammation plays a major role in vascular disease. We have shown that leukocyte infiltration and inflammatory mediator expression contribute to vascular remodeling after endoluminal injury. This study tested whether increasing protein O-linked-N-acetylglucosamine (O-GlcNAc) levels with glucosamine (GlcN) and O-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino-N-phenylcarbamate (PUGNAc) inhibits acute inflammatory and neointimal responses to endoluminal arterial injury. Ovariectomized rats were treated with a single injection of GlcN (0.3 mg/g ip), PUGNAc (7 nmol/g ip) or vehicle (V) 2 h before balloon injury of the right carotid artery. O-GlcNAc-modified protein levels decreased markedly in injured arteries of V-treated rats at 30 min, 2 h, and 24 h after injury but returned to control (contralateral uninjured) levels after 14 days. Both GlcN and PUGNAc increased O-GlcNAc-modified protein levels in injured arteries compared with V controls at 30 min postinjury; the GlcN-mediated increase persisted at 24 h but was not evident at 14 days. Proinflammatory mediator expression increased markedly after injury and was reduced significantly (30-50%) by GlcN and PUGNAc. GlcN and PUGNAc also inhibited infiltration of neutrophils and monocytes in injured arteries. Chronic (14 days) treatment with GlcN reduced neointima formation in injured arteries by 50% compared with V controls. Acute GlcN and PUGNAc treatment increases O-GlcNAc-modified protein levels and inhibits acute inflammatory responses in balloon-injured rat carotid arteries; 14 day GlcN treatment inhibits neointima formation in these vessels. Augmenting O-GlcNAc modification of proteins in the vasculature may represent a novel anti-inflammatory and vasoprotective mechanism.

Changes in the levels of O-linked N-acetylglucosamine (O-GlcNAc) on nucleocytoplasmic protein have been associated with a number of age-related diseases such as Alzheimer's and diabetes; however, there is relatively little information regarding the impact of age on tissue O-GlcNAc levels. Therefore, the goal of this study was to determine whether senescence was associated with alterations in O-GlcNAc in heart, aorta, brain and skeletal muscle and if so whether there were also changes in the expression of enzymes critical in regulating O-GlcNAc levels, namely, O-GlcNAc transferase (OGT), O-GlcNAcase and glutamine:fructose-6-phosphate amidotransferase (GFAT). Tissues were harvested from 5-and 24-month old Brown-Norway rats; UDP-GlcNAc, a precursor of O-GlcNAc was assessed by HPLC, O-GlcNAc and OGT levels were assessed by immunoblot analysis and GFAT1/2, OGT, O-GlcNAcase mRNA levels were determined by RT-PCR. In the 24-month old animals serum insulin and triglyceride levels were significantly increased compared to the 5-month old group; however, glucose levels were unchanged. Protein O-GlcNAc levels were significantly increased with age (30-107 %) in all tissues examined; however, paradoxically the expression of OGT, which catalyzes O-GlcNAc formation, was decreased by ~30% in the heart, aorta and brain. In the heart increased O-GlcNAc was associated with increased UDP-GlcNAc levels and elevated GFAT mRNA while in other tissues we found no difference in UDP-GlcNAc or GFAT mRNA levels. These results demonstrate that senescence is associated with increased O-GlcNAc levels in multiple tissues and support the notion that dysregulation of pathways leading to O-GlcNAc formation may play an important role in the development of age-related diseases.

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An early and rapid response to severe injury or trauma is the development of hyperglycemia, which has long been thought to be an essential survival response by providing fuel for vital organ systems and facilitating mobilization of interstitial fluid reserves by increasing osmolarity. However, glucose can also be metabolized via the hexosamine biosynthesis pathway (HBP), leading to the synthesis of uridine diphosphate N-acetyl-glucosamine(UDP-GlcNAc). UDP-GlcNAc is a substrate for the addition, via an O-linkage, of a single N-acetylglucosamine to serine or threonine residues of nuclear and cytoplasmic proteins (O-glycosylation, O-GlcNAc). There is increasing appreciation that protein O-glycosylation is a highly dynamic posttranslational modification that plays a key role in signal transduction pathways. Sustained increases in O-GlocNAc have been implicated in the development of diabetes and diabetic complications; however, recent studies have demonstrated that stress leads to a transient increase in O-GlcNAc levels that is associated with increased tolerance to stress. Indeed, activation of pathways leading to O-GlcNAc formation improves cell survival after I/R injury, whereas inhibition of O-GlcNAc formation decreases cell survival. In addition, in rodent models of trauma-hemorrhage, increasing O-GlcNAc levels during resuscitation improves cardiac function and organ perfusion and attenuates the inflammatory response. At the cellular level, increasing O-GlcNAc levels attenuates nuclear factor-kappaB activation. It is noteworthy that other metabolic-based treatments for severe injury such as glucose-insulin-potassium and glutamine also lead to increased HBP flux and O-GlcNAc levels. The goal of this review is to summarize our current understanding of the role of the HBP and O-GlcNAc on the regulation of cell function and survival and to present evidence to support the notion that activation of these pathways represents a novel treatment strategy for severe injury and trauma.

Objective We have previously shown that increasing protein O-linked β-N-acetylglucosamine (O-GlcNAc) levels by different mechanisms reduced inflammatory responses and improved organ function 2 hours after trauma-hemorrhage (T-H). The aim of the study was to evaluate the effects of O-GlcNAc levels on survival, inflammation and organ damage 24 hours after T-H. Design Prospective, randomized, controlled study. Setting Animal research laboratory. Subjects Male, adult Sprague-Dawley rats. Interventions Overnight fasted animals were subjected to either sham surgery (SH) or (T-H) and during the resuscitation phase received glucosamine (270 mg/Kg, GlcN) to increase O-GlcNAc synthesis or O-(2-Acetamido-2-deoxy-D-glucopyranosylidene)amino N-phenyl Carbamate, (7mg/Kg, PUGNAc) to inhibit O-GlcNAc removal, or mannitol as control (CON). Measurements and main results Survival was followed up for 24 hours. Surviving rats were euthanized and inflammatory responses, and end organ injuries were assessed. Both GlcN and PUGNAc increased 24 hours survival compared to controls (CON: 53%, GN: 85%, PUGNAc: 86%, logrank test, p<0.05). PUGNAc attenuated the T-H induced increase in serum IL-6 (SH: 8±6, CON: 181±36, PUGNAc: 42±22 pg/mL, p<0.05), ALT (SH: 95±14, CON: 297±56, PUGNAc: 126±21 IU, p<0.05), AST (SH: 536±110, CON: 1661±215, PUGNAc: 897±155 IU, p<0.05) and LDH (SH: 160±18, CON: 1499±311, PUGNAc: 357±99 IU, p<0.05); however, GlcN had no effect on these serum parameters. Furthermore, PUGNAc but not GlcN maintained O-GlcNAc levels in liver and lung and significantly attenuated the NF-κB DNA activation in the liver. In the liver and heart, increased iNOS expression was also attenuated in the PUGNAc treated group. Conclusions These results demonstrate that increasing O-GlcNAc with either GlcN or PUGNAc improved 24 hour survival after T-H. However, only PUGNAc treatment attenuated significantly the subsequent tissue injury and inflammatory responses, suggesting that inhibition of O-GlcNAc removal may represent a new therapeutic approach for the treatment of hypovolemic shock.

We have previously shown that glucosamine administration resulted in higher cardiac output and improved tissue perfusion after trauma-hemorrhage with resuscitation in rats, which was associated with the increased levels of protein O-linked-N-acetylglucosamine (O-GlcNAc). The purpose of the study was to evaluate the effect of glucosamine on the survival, without resuscitation, in rats. Adult male rats underwent midline laparotomy and 55% of total blood volume was withdrawn for 25 min under isoflurane anesthesia. At the end of the hemorrhage period, 2.5 mL of 150 mM glucosamine or equivalent osmolarity of mannitol solution was injected intravenously for 10 min. The survival time, mean blood pressure, heart rate, and central body temperature were monitored continuously; then, the O-GlcNAc levels in heart, brain, liver, and muscle were measured by means of Western blot analysis. Glucosamine administration significantly increased the survival rate in comparison with mannitol administration (percentage of survival after 2 h, 47% vs. 20%; P < 0.05). The mean arterial pressure was significantly higher in the glucosamine group for 18 min after treatment. The protein O-GlcNAc levels, assessed 30 min after glucosamine treatment, were significantly increased in the heart, brain, and liver. These data demonstrate that i.v. glucosamine administration improves the survival rate after trauma-hemorrhage without resuscitation; this effect may be related to the glucosamine-induced increase in protein O-glycosylation. Furthermore, the increase in mean arterial pressure may suggest a vasoactive and/or positive inotropic effect of glucosamine in hypovolemic shock.

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