Lipopolysaccharide (LPS)-stimulated iNOS Induction Is Increased by Glucosamine under Normal Glucose Conditions but Is Inhibited by Glucosamine under High Glucose Conditions in Macrophage Cells

O-GlcNAcylation in ischemic diseases

Protein glycosylation is an extensively studied field, with the most studied forms being oxygen or nitrogen-linked N-acetylglucosamine (O-GlcNAc or N-GlcNAc) glycosylation. Particular residues on proteins are targeted by O-GlcNAcylation, which is among the most intricate post-translational modifications. Significantly contributing to an organism's proteome, it influences numerous factors affecting protein stability, function, and subcellular localization. It also modifies the cellular function of target proteins that have crucial responsibilities in controlling pathways related to the central nervous system, cardiovascular homeostasis, and other organ functions. Under conditions of acute stress, changes in the levels of O-GlcNAcylation of these proteins may have a defensive function. Nevertheless, deviant O-GlcNAcylation nullifies this safeguard and stimulates the advancement of several ailments, the prognosis of which relies on the cellular milieu. Hence, this review provides a concise overview of the function and comprehension of O-GlcNAcylation in ischemia diseases, aiming to facilitate the discovery of new therapeutic targets for efficient treatment, particularly in patients with diabetes.

O-GlcNAcylation: a pro-survival response to acute stress in the cardiovascular and central nervous systems

O-GlcNAcylation is a unique monosaccharide modification that is ubiquitously present in numerous nucleoplasmic and mitochondrial proteins. The hexosamine biosynthesis pathway (HBP), which is a key branch of glycolysis, provides the unique sugar donor UDP-GlcNAc for the O-GlcNAc modification. Thus, HBP/O-GlcNAcylation can act as a nutrient sensor to perceive changes in nutrient levels and trigger O-GlcNAc modifications of functional proteins in cellular (patho-)physiology, thereby regulating diverse metabolic processes. An imbalance in O-GlcNAcylation has been shown to be a pathogenic contributor to dysfunction in metabolic diseases, including type 2 diabetes, cancer, and neurodegeneration. However, under acute stress conditions, protein O-GlcNAc modification exhibits rapid and transient upregulation, which is strongly correlated with stress tolerance and cell survival. In this context, we discuss the metabolic, pharmacological and genetic modulation of HBP/O-GlcNAc modification in the biological system, the beneficial role of O-GlcNAcylation in regulating stress tolerance for cardioprotection, and neuroprotection, which is a novel and rapidly growing field. Current evidence suggests that transient activation of the O-GlcNAc modification represents a potent pro-survival signalling pathway and may provide a promising strategy for stress-related disorder therapy.

Purine Metabolism and Hexosamine Biosynthetic Pathway Abnormalities in Diarrheal Weaned Piglets Identified Using Metabolomics

Post-weaning diarrhea significantly contributes to the high mortality in pig production, but the metabolic changes in weaned piglets with diarrhea remain unclear. This study aimed to identify the differential metabolites in the urine of diarrheal weaned piglets and those of healthy weaned piglets to reveal the metabolic changes associated with diarrhea in weaned piglets. Nine 25-day-old piglets with diarrhea scores above 16 and an average body weight of 5.41 ± 0.18 kg were selected for the diarrhea group. Corresponding to the body weight and sex of the diarrhea group, nine 25-month-old healthy piglets with similar sex and body weights of 5.49 ± 0.21 kg were selected as the control group. Results showed that the serum C-reactive protein and cortisol of piglets in the diarrhea group were higher than those in the control group (p < 0.05). The mRNA expression of TNF-α, IFN-γ in the jejunum and colon, and IL-1β in the jejunum were increased in diarrhea piglets (p < 0.05), accompanied by a reduction in the mRNA expression of ZO-1, ZO-2, and CLDN1 in the jejunum and colon (p < 0.05); mRNA expression of OCLN in the colon also occurred (p < 0.05). Metabolomic analysis of urine revealed increased levels of inosine, hypoxanthine, guanosine, deoxyinosin, glucosamine, glucosamine-1-p, N-Acetylmannosamine, chitobiose, and uric acid, identified as differential metabolites in diarrhea piglets compared to the controls. In summary, elevated weaning stress and inflammatory disease were associated with the abnormalities of purine metabolism and the hexosamine biosynthetic pathway of weaned piglets. This study additionally indicated the presence of energy metabolism-related diseases in diarrheal weaned piglets.

Characterization and anti-tumor activities of polysaccharide isolated from Brassica rapa L. via activation of macrophages through TLR2-and TLR4-Dependent pathways

We have previously shown the immunostimulatory effects by Nozawana (Brassica rapa L.). In this report, we determined the characteristics of Nozawana polysaccharide (NPS) and evaluated the immunomodulatory effects and anti-tumor activity of NPS mediated by macrophage activation. The molecular weight of NPS was determined by gel filtration chromatography with an average molecular weight of approximately 100.6 kDa. HPLC analysis showed that NPS contained glucose, galacturonic acid, galactose, and arabinose. NPS increased cytokine and nitric oxide (NO) production by macrophages in a Toll-like receptor (TLR)2 and TLR4-dependent manner. Furthermore, NPS induced apoptosis significantly against 4T1 murine breast cancer cells cultured in conditioned medium from NPS-treated macrophages through tumor necrosis factor-α. In tumor-bearing mouse model, tumor growth was significantly reduced in NPS-treated mice compared with control mice. These results support the potential use of NPS as an immunotherapeutic material found in health food products.

Carfilzomib Mitigates Lipopolysaccharide/D-Galactosamine/Dimethylsulfoxide-Induced Acute Liver Failure in Mice

Acute liver failure (ALF) is a disease accompanied by severe liver inflammation. No effective therapy is available yet apart from liver transplantation; therefore, developing novel treatments for ALF is urgently required. Inflammatory mediators released by NF-кB activation play an essential role in ALF. Proteasome inhibitors have many medical uses, such as reducing inflammation and NF-кB inhibition, which are believed to account for most of their repurposing effects. This study was undertaken to explore the possible protective effects and the underlying mechanisms of carfilzomib, a proteasome inhibitor, in a mouse model of ALF induced by lipopolysaccharide/D-galactosamine/dimethylsulfoxide (LPS/GalN/DMSO). Carfilzomib dose-dependently protected mice from LPS/GalN/DMSO-induced liver injury, as indicated by the decrease in serum alanine aminotransferase and aspartate aminotransferase levels. LPS/GalN/DMSO increased TNF-α, NF-кB, lipid peroxidation, NO, iNOS, cyclooxygenase-II, myeloperoxidase, and caspase-3 levels. Carfilzomib administration mitigated LPS/GalN/DMSO-induced liver damage by decreasing the elevated levels of TNF-α, NF-кB, lipid peroxidation, nitric oxide, iNOS, cyclooxygenase-II, myeloperoxidase, caspase-3, and histopathological changes. A restored glutathione level was also observed in the carfilzomib-treated LPS/GalN/DMSO mice. Our results demonstrate that carfilzomib protects against LPS/GalN/DMSO-induced ALF by inhibiting NF-кB, decreasing inflammatory mediators, oxidative/nitrosative stress, neutrophil recruitment, and apoptosis, suggesting that carfilzomib may be a potential therapeutic agent for ALF.

Shuttle between arginine and lysine: influence on cancer immunonutrition

Amino acids which are essential nutrients for all cell types' survival are also recognised to serve as opportunistic/alternative fuels in cancers auxotrophic for specific amino acids. Accordingly, restriction of amino acids has been utilised as a therapeutic strategy in these cancers. Contrastingly, amino acid deficiencies in cancer are found to greatly impair immune functions, increasing mortality and morbidity rates. Dietary and supplemental amino acids in such conditions have revealed their importance as 'immunonutrients' by modulating cellular homeostasis processes and halting malignant progression. L-arginine specifically has attracted interest as an immunonutrient by acting as a nodal regulator of immune responses linked to carcinogenesis processes through its versatile signalling molecule, nitric oxide (NO). The quantum of NO generated directly influences the cytotoxic and cytostatic processes of cell cycle arrest, apoptosis, and senescence. However, L-lysine, a CAT transporter competitor for arginine effectively limits arginine input at high L-lysine concentrations by limiting arginine-mediated effects. The phenomenon of arginine-lysine antagonism can, therefore, be hypothesised to influence the immunonutritional effects exerted by arginine. The review highlights aspects of lysine's interference with arginine-mediated NO generation and its consequences on immunonutritional and anti-cancer effects, and discusses possible alternatives to manage the condition. However, further research that considers monitoring lysine levels in arginine immunonutritional therapy is essential to conclude the hypothesis.

Agarwood oil nanoemulsion counteracts LPS-induced inflammation and oxidative stress in RAW264.7 mouse macrophages

PURPOSE

Oxidative stress and inflammation are key pathophysiological features of chronic respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Agarwood oil obtained from Aquilaria trees has promising antioxidant and anti-inflammatory activities. However, its clinical application is hampered by poor solubility. A viable approach to overcome this involves formulation of oily constituents into emulsions. Here, we have investigated the antioxidant and anti-inflammatory potential of an agarwood oil-based nanoemulsion (DE'RAAQSIN) against lipopolysaccharide (LPS)-induced RAW264.7 mouse macrophages in vitro.

METHODS

The antioxidant and anti-inflammatory activity of DE'RAAQSIN was assessed by measuring the levels of ROS and nitric oxide (NO) produced, using the DCF-DA assay and the Griess reagent assay, respectively. The molecular pathways activated by DE'RAAQSIN were investigated via qPCR.

RESULTS

LPS stimulation of RAW264.7 cells increased the production of nitric oxide (NO) and ROS and resulted in the overexpression of the inducible nitric oxide synthase (iNOS) gene. Furthermore, LPS induced the upregulation of the expression of key proinflammatory genes (IL-6, TNF-α, IL-1β, and CXCL1) and of the antioxidant gene heme oxygenase-1 (HO-1). DE'RAAQSIN demonstrated potent antioxidant and anti-inflammatory activity by significantly reducing the levels of ROS and of secreted NO, simultaneously counteracting the LPS-induced overexpression of iNOS, IL-6, TNF-α, IL-1β, and HO-1. These findings were corroborated by in silico activity prediction and physicochemical analysis of the main agarwood oil components.

CONCLUSIONS

We propose DE'RAAQSIN as a promising alternative managing inflammatory disorders, opening the platform for further studies aimed at understanding the effectiveness of DE'RAAQSIN.

Evaluation of Glycogen Synthase Kinase Pathway for Assessing the Antidepressant-like Effect of Glucosamine as a Radioprotector in Rats: Behavioral and Biochemical Studies

Radiotherapy is a very important tool in the treatment of cancer; nevertheless, its side effects are a hindrance to its use. The present study is designed to evaluate glucosamine effects against radiation-induced brain oxidative stress and depression-like effect in rats. Four groups of female Wister rats were used as control, irradiated (4 × 2 Gy), glucosamine (1 g/kg P.O), and glucosamine + irradiated group. The behavioral responses are estimated. The brain hippocampi of the rats are separated to evaluate oxidative stress biochemical parameters and glycogen synthase kinase pathway in addition to the biogenic amines. Irradiation exposure led to disturbances in the behavioral assessments (forced swimming test, light-dark box, and open field test) and a significant decrease in brain GSH, neurotransmitters (serotonin, norepinephrine, and dopamine), phosphatidylinositol 3 kinase (PI3K), and phosphorylated protein kinase-B (p-AKT) levels. Additionally, MDA and ROS levels increased significantly post-irradiation along with the phosphorylated glycogen synthase kinase (p-GSK3). Glucosamine administration before irradiation caused improvement in the behavioral valuations and the biochemical parameters in the brain as well. Glucosamine might be used as a radioprotector to improve brain function and as an antidepressant drug. It could be promising as a future therapy in managing depression occurring during radiotherapy.

Hexosamine biosynthetic pathway and O-GlcNAc cycling of glucose metabolism in brain function and disease

Impaired brain glucose metabolism is considered a hallmark of brain dysfunction and neurodegeneration. Disruption of the hexosamine biosynthetic pathway (HBP) and subsequent O-linked N-acetylglucosamine (O-GlcNAc) cycling has been identified as an emerging link between altered glucose metabolism and defects in the brain. Myriads of cytosolic and nuclear proteins in the nervous system are modified at serine or threonine residues with a single N-acetylglucosamine (O-GlcNAc) molecule by O-GlcNAc transferase (OGT), which can be removed by β-N-acetylglucosaminidase (O-GlcNAcase, OGA). Homeostatic regulation of O-GlcNAc cycling is important for the maintenance of normal brain activity. Although significant evidence linking dysregulated HBP metabolism and aberrant O-GlcNAc cycling to induction or progression of neuronal diseases has been obtained, the issue of whether altered O-GlcNAcylation is causal in brain pathogenesis remains uncertain. Elucidation of the specific functions and regulatory mechanisms of individual O-GlcNAcylated neuronal proteins in both normal and diseased states may facilitate the identification of novel therapeutic targets for various neuronal disorders. The information presented in this review highlights the importance of HBP/O-GlcNAcylation in the neuronal system and summarizes the roles and potential mechanisms of O-GlcNAcylated neuronal proteins in maintaining normal brain function and initiation and progression of neurological diseases.

How do different bile acid derivatives affect rat macrophage function - Friends or foes?

Due to an increased need for new immunomodulatory agents, many previously known molecules have been structurally modified in order to obtain new drugs, preserving at the same time some of the benevolent characteristics of the parent molecule. This study aimed to evaluate the immunomodulatory potential of a selected library of bile acid derivatives (BAD) using a broad spectrum of assays, evaluating rat peritoneal macrophages viability, cell membrane damage, lysosomal and adhesion function, and nitric oxide and cytokine production as a response to lipopolysaccharide stimulation. Also, in silico studies on two bile acid-activated receptors were conducted and the results were related to the observed in vitro effects. All tested BAD exerted significant toxicity in concentrations higher than 10 μM, which was determined based on mitochondria and cell membrane damage in a panel of assays. On the other hand, at lower concentrations, the tested BAD proved to be immunomodulatory since they affected lysosomal function, cell adhesion capacities and the ability to produce inflammatory cytokines in response to a stimulus. One of the compounds proved to exhibit significant toxicity toward macrophages, but also caused a concentration-dependent decrease in nitric oxide levels and was identified as a potential farnesoid X receptor agonist.

Diversity-oriented synthesis of diterpenoid alkaloids yields a potent anti-inflammatory agent

BACKGROUND

The diterpenoid alkaloids belong to a highly esteemed group of natural compounds, which display significant biological activities. It is a productive strategy to expand the chemical space of these intriguing natural compounds for drug discovery.

METHODS

We prepared a series of new derivatives bearing diverse skeletons and functionalities from the diterpenoid alkaloids deltaline and talatisamine based on a diversity-oriented synthesis strategy. The anti-inflammatory activity of these derivatives was initially screened and evaluated by the release of nitric oxide (NO), tumor necrosis factor (TNF-α), and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-activated RAW264.7 cells. Futhermore, the anti-inflammatory activity of the representative derivative 31a was validated in various inflammatory animal models, including phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mice ear edema, LPS-stimulated acute kidney injury, and collagen-induced arthritis (CIA).

RESULTS

It was found that several derivatives were able to suppress the secretion of NO, TNF-α, and IL-6 in LPS-activated RAW264.7 cells. Compound 31a, one of the representative derivatives named as deltanaline, demonstrated the strongest anti-inflammatory effects in LPS-activated macrophages and three different animal models of inflammatory diseases by inhibiting nuclear factor kappa-B (NF-κB)/mitogen-activated protein kinase (MAPK) signaling and inducing autophagy.

CONCLUSION

Deltanaline is a new structural compound derived from natural diterpenoid alkaloids, which may serve as a new lead compound for the treatment of inflammatory diseases.

Crosstalk of TNF-α, IFN-γ, NF-kB, STAT1 and redox signaling in lipopolysaccharide/D-galactosamine/dimethylsulfoxide-induced fulminant hepatic failure in mice

Purpose

The clinical study of fulminant hepatic failure is challenging due to its high mortality and relative rarity, necessitating reliance on pre-clinical models to gain insight into its pathophysiology and develop potential therapies.

Methods and Results

In our study, the combination of the commonly used solvent dimethyl sulfoxide to the current-day model of lipopolysaccharide/d-galactosamine-caused fulminant hepatic failure was found to cause significantly greater hepatic damage, as indicated by alanine aminotransferase level. The effect was dose-dependent, with the maximum increase in alanine aminotransferase observed following 200 μl/kg dimethyl sulfoxide co-administration. Co-administration of 200 μl/kg dimethyl sulfoxide also remarkably increased histopathological changes induced by lipopolysaccharide/d-galactosamine. Importantly, alanine aminotransferase levels and survival rate in the 200 μl/kg dimethyl sulfoxide co-administration groups were both greater than those in the classical lipopolysaccharide/d-galactosamine model. We found that dimethyl sulfoxide co-administration aggravated lipopolysaccharide/d-galactosamine-caused liver damage by stimulating inflammatory signaling, as indicated by tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) levels. Further, nuclear factor kappa B (NF-kB) and transcription factor activator 1 (STAT1) were upregulated, as was neutrophil recruitment, indicated by myeloperoxidase activity. Hepatocyte apoptosis was also increased, and greater nitro-oxidative stress was noted, as determined based on nitric oxide, malondialdehyde, and glutathione levels.

Conclusion

Co-treatment with low doses of dimethyl sulfoxide enhanced the lipopolysaccharide/d-galactosamine-caused hepatic failure in animals, with higher toxicity and greater survival rates. The current findings also highlight the potential danger of using dimethyl sulfoxide as a solvent in experiments involving the hepatic immune system, suggesting that the new lipopolysaccharide/d-galactosamine/dimethyl sulfoxide model described herein could be used for pharmacological screening with the goal to better understand hepatic failure and evaluate treatment approaches.

Extract of Pinus densiflora needles suppresses acute inflammation by regulating inflammatory mediators in RAW264.7 macrophages and mice

CONTEXT

Pinus densiflora Siebold & Zucc. (Pinaceae) needle extracts ameliorate oxidative stress, but research into their anti-inflammatory effects is limited.

OBJECTIVE

To investigate antioxidant and anti-inflammatory effects of a Pinus densiflora needles (PINE) ethanol extract in vitro and in vivo.

MATERIALS AND METHODS

We measured levels of reactive oxygen species (ROS), superoxide dismutase (SOD) and inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW264.7 cells at various PINE concentrations (25, 50 and 100 μg/mL; but 6.25, 12.5 and 25 μg/mL for interleukin-1β and prostaglandin E₂ (PGE₂)). Thirty ICR mice were randomized to six groups: vehicle, control, PINE pre-treatment (0.1, 0.3 and 1 mg/left ear for 10 min followed by arachidonic acid treatment for 30 min) and dexamethasone. The posttreatment ear thickness and myeloperoxidase (MPO) activity were measured.

RESULTS

PINE 100 μg/mL significantly decreased ROS (IC₅₀, 70.93 μg/mL, p < 0.01), SOD (IC₅₀, 30.99 μg/mL, p < 0.05), malondialdehyde (p < 0.01), nitric oxide (NO) (IC₅₀, 27.44 μg/mL, p < 0.01) and tumour necrosis factor-alpha (p < 0.05) levels. Interleukin-1β (p < 0.05) and PGE₂ (p < 0.01) release decreased significantly with 25 μg/mL PINE. PINE 1 mg/ear inhibited LPS-stimulated expression of cyclooxygenase-2 and inducible NO synthase in RAW264.7 macrophages and significantly inhibited ear oedema (36.73-15.04% compared to the control, p < 0.01) and MPO activity (167.94-105.59%, p < 0.05).

DISCUSSION AND CONCLUSIONS

PINE exerts antioxidant and anti-inflammatory effects by inhibiting the production of inflammatory mediators. Identified flavonoids such as taxifolin and quercetin glucoside can be attributed to effect of PINE.

Chronically Elevated O-GlcNAcylation Limits Nitric Oxide Production and Deregulates Specific Pro-Inflammatory Cytokines

Inflammation is the immune response to harmful stimuli, including pathogens, damaged cells and toxic compounds. However, uncontrolled inflammation can be detrimental and contribute to numerous chronic inflammatory diseases, such as insulin resistance. At the forefront of this response are macrophages, which sense the local microenvironment to respond with a pro-inflammatory, M1-polarized phenotype, or anti-inflammatory, M2-polarized phenotype. M1 macrophages upregulate factors like pro-inflammatory cytokines, to promote inflammatory signaling, and inducible Nitric Oxide Synthase (iNOS), to produce nitric oxide (NO). The generated NO can kill microorganisms to protect the body, but also signal back to the macrophage to limit pro-inflammatory cytokine production to maintain macrophage homeostasis. Thus, the tight regulation of iNOS in macrophages is critical for the immune system. Here, we investigated how elevation of the nutrient-sensitive posttranslational modification, O-GlcNAc, impacts M1 polarized macrophages. We identified increased gene expression of specific pro-inflammatory cytokines (Il-6, Il-1β, Il-12) when O-GlcNAc cycling was blocked. We further uncovered an interaction between O-GlcNAc and iNOS, with iNOS being an OGT target in vitro. Analysis of M1 polarized bone marrow derived macrophages deficient in the enzyme that removes O-GlcNAc, O-GlcNAcase (OGA), revealed decreased iNOS activity as measured by a reduction in NO release. Further, elevated O-GlcNAc acted on Il-6 expression through the iNOS pathway, as iNOS inhibitior L-NIL raised wildtype Il-6 expression similar to OGA deficient cells but had no further effect on the hyper-O-GlcNAcylated cells. Thus O-GlcNAc contributes to macrophage homeostasis through modulation of iNOS activity.

Hexokinase 1 cellular localization regulates the metabolic fate of glucose

The product of hexokinase (HK) enzymes, glucose-6-phosphate, can be metabolized through glycolysis or directed to alternative metabolic routes, such as the pentose phosphate pathway (PPP) to generate anabolic intermediates. HK1 contains an N-terminal mitochondrial binding domain (MBD), but its physiologic significance remains unclear. To elucidate the effect of HK1 mitochondrial dissociation on cellular metabolism, we generated mice lacking the HK1 MBD (ΔE1HK1). These mice produced a hyper-inflammatory response when challenged with lipopolysaccharide. Additionally, there was decreased glucose flux below the level of GAPDH and increased upstream flux through the PPP. The glycolytic block below GAPDH is mediated by the binding of cytosolic HK1 with S100A8/A9, resulting in GAPDH nitrosylation through iNOS. Additionally, human and mouse macrophages from conditions of low-grade inflammation, such as aging and diabetes, displayed increased cytosolic HK1 and reduced GAPDH activity. Our data indicate that HK1 mitochondrial binding alters glucose metabolism through regulation of GAPDH.

Protein O-GlcNAcylation Regulates Innate Immune Cell Function

Metabolite-mediated protein posttranslational modifications (PTM) represent highly evolutionarily conserved mechanisms by which metabolic networks participate in fine-tuning diverse cellular biological activities. Modification of proteins with the metabolite UDP-N-acetylglucosamine (UDP-GlcNAc), known as protein O-GlcNAcylation, is one well-defined form of PTM that is catalyzed by a single pair of enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Previous studies have discovered critical roles of protein O-GlcNAcylation in many fundamental biological activities via modifying numerous nuclear and cytoplasmic proteins. A common mechanism by which O-GlcNAc affects protein function is through the cross-regulation between protein O-GlcNAcylation and phosphorylation. This is of particular importance to innate immune cell functions due to the essential role of protein phosphorylation in regulating many aspects of innate immune signaling. Indeed, as an integral component of cellular metabolic network, profound alteration in protein O-GlcNAcylation has been documented following the activation of innate immune cells. Accumulating evidence suggests that O-GlcNAcylation of proteins involved in the NF-κB pathway and other inflammation-associated signaling pathways plays an essential role in regulating the functionality of innate immune cells. Here, we summarize recent studies focusing on the role of protein O-GlcNAcylation in regulating the NF-κB pathway, other innate immune signaling responses and its disease relevance.

Targeting Protein O-GlcNAcylation, a Link between Type 2 Diabetes Mellitus and Inflammatory Disease

Unresolved hyperglycaemia, a hallmark of type 2 diabetes mellitus (T2DM), is a well characterised manifestation of altered fuel homeostasis and our understanding of its role in the pathologic activation of the inflammatory system continues to grow. Metabolic disorders like T2DM trigger changes in the regulation of key cellular processes such as cell trafficking and proliferation, and manifest as chronic inflammatory disorders with severe long-term consequences. Activation of inflammatory pathways has recently emerged as a critical link between T2DM and inflammation. A substantial body of evidence has suggested that this is due in part to increased flux through the hexosamine biosynthetic pathway (HBP). The HBP, a unique nutrient-sensing metabolic pathway, produces the activated amino sugar UDP-GlcNAc which is a critical substrate for protein O-GlcNAcylation, a dynamic, reversible post-translational glycosylation of serine and threonine residues in target proteins. Protein O-GlcNAcylation impacts a range of cellular processes, including inflammation, metabolism, trafficking, and cytoskeletal organisation. As increased HBP flux culminates in increased protein O-GlcNAcylation, we propose that targeting O-GlcNAcylation may be a viable therapeutic strategy for the prevention and management of glucose-dependent pathologies with inflammatory components.

O-GlcNAcylation regulation of cellular signaling in cancer

O-GlcNAcylation is a post-translational modification occurring on serine/threonine residues of nuclear and cytoplasmic proteins, mediated by the enzymes OGT and OGA which catalyze the addition or removal of the UDP-GlcNAc moieties, respectively. Structural changes brought by this modification lead to alternations of protein stability, protein-protein interactions, and phosphorylation. Importantly, O-GlcNAcylation is a nutrient sensor by coupling nutrient sensing with cellular signaling. Elevated levels of OGT and O-GlcNAc have been reported in a variety of cancers and has been linked to regulation of multiple cancer signaling pathways. In this review, we discuss the most recent findings on the role of O-GlcNAcylation as a metabolic sensor in signaling pathways and immune response in cancer.

Actions of Klotho on hippocampal neuronal cells

Klotho gene was originally recognized as a putative aging-suppressor and its prominent age-regulating effects are mostly attributed to the modulation of mineral homeostasis in the kidney. However, recent studies link alterations in hippocampal Klotho expression with cognitive impairment and neurodegenerative diseases. This suggests that hippocampal neurons require Klotho for health and proper functionality. Klotho protects against neuronal dysfunction and regulates several intracellular signaling pathways including oxidative stress response, inflammation, DNA damage, autophagy, endoplasmic reticulum stress response, and multiple types of cell death. Specifically, this chapter covers the current knowledge as to how Klotho protein affects the hippocampal neuronal cells, with special attention paid to underlying molecular mechanisms, and thus influences hippocampal development, hippocampal-dependent cognition, behavior, and motor skills as well as mediates neurodegenerative processes.

Inhibition of O-GlcNAcylation protects from Shiga toxin-mediated cell injury and lethality in host

Shiga toxins (Stxs) produced by enterohemorrhagic Escherichia coli (EHEC) are the major virulence factors responsible for hemorrhagic colitis, which can lead to life-threatening systemic complications including acute renal failure (hemolytic uremic syndrome) and neuropathy. Here, we report that O-GlcNAcylation, a type of post-translational modification, was acutely increased upon induction of endoplasmic reticulum (ER) stress in host cells by Stxs. Suppression of the abnormal Stx-mediated increase in O-GlcNAcylation effectively inhibited apoptotic and inflammatory responses in Stx-susceptible cells. The protective effect of O-GlcNAc inhibition for Stx-mediated pathogenic responses was also verified using three-dimensional (3D)-cultured spheroids or organoids mimicking the human kidney. Treatment with an O-GlcNAcylation inhibitor remarkably improved the major disease symptoms and survival rate for mice intraperitoneally injected with a lethal dose of Stx. In conclusion, this study elucidates O-GlcNAcylation-dependent pathogenic mechanisms of Stxs and demonstrates that inhibition of aberrant O-GlcNAcylation is a potential approach to treat Stx-mediated diseases.

O-GlcNAcylation in Chronic Lymphocytic Leukemia and Other Blood Cancers

In the past decade, aberrant O-GlcNAcylation has emerged as a new hallmark of cancer. O-GlcNAcylation is a post-translational modification that results when the amino-sugar β-D-N-acetylglucosamine (GlcNAc) is made in the hexosamine biosynthesis pathway (HBP) and covalently attached to serine and threonine residues in intracellular proteins by the glycosyltransferase O-GlcNAc transferase (OGT). O-GlcNAc moieties reflect the metabolic state of a cell and are removed by O-GlcNAcase (OGA). O-GlcNAcylation affects signaling pathways and protein expression by cross-talk with kinases and proteasomes and changes gene expression by altering protein interactions, localization, and complex formation. The HBP and O-GlcNAcylation are also recognized to mediate survival of cells in harsh conditions. Consequently, O-GlcNAcylation can affect many of the cellular processes that are relevant for cancer and is generally thought to promote tumor growth, disease progression, and immune escape. However, recent studies suggest a more nuanced view with O-GlcNAcylation acting as a tumor promoter or suppressor depending on the stage of disease or the genetic abnormalities, proliferative status, and state of the p53 axis in the cancer cell. Clinically relevant HBP and OGA inhibitors are already available and OGT inhibitors are in development to modulate O-GlcNAcylation as a potentially novel cancer treatment. Here recent studies that implicate O-GlcNAcylation in oncogenic properties of blood cancers are reviewed, focusing on chronic lymphocytic leukemia and effects on signal transduction and stress resistance in the cancer microenvironment. Therapeutic strategies for targeting the HBP and O-GlcNAcylation are also discussed.

Design, Synthesis, and In Vitro and In Vivo Biological Evaluation of Limonin Derivatives for Anti-Inflammation Therapy

In this study, limonin derivatives were used to design new anti-inflammatory compounds with high pharmacological activity and low toxicity. A total of 23 new limonin derivatives were discovered, synthesized, and screened for their anti-inflammatory activity against lipopolysaccharide (LPS)-treated RAW 264.7 cells. Of them, compound f4 was found to be the most active, with a higher efficiency compared with limonin and celecoxib. Subsequently, we studied the mechanism underlying the activity of f4 and found that it inhibited proinflammatory cytokines by blocking the NF-κB/MAPK signaling pathway in LPS-treated RAW 264.7 cells as well as mice. In conclusion, f4 may be a promising anti-inflammatory lead compound.

Regulation of Nuclear Factor-kappaB Function by O-GlcNAcylation in Inflammation and Cancer

Nuclear factor-kappaB (NF-κB) is a pleiotropic, evolutionarily conserved transcription factor family that plays a central role in regulating immune responses, inflammation, cell survival, and apoptosis. Great strides have been made in the past three decades to understand the role of NF-κB in physiological and pathological conditions. Carcinogenesis is associated with constitutive activation of NF-κB that promotes tumor cell proliferation, angiogenesis, and apoptosis evasion. NF-κB is ubiquitously expressed, however, its activity is under tight regulation by inhibitors of the pathway and through multiple posttranslational modifications. O-GlcNAcylation is a dynamic posttranslational modification that controls NF-κB-dependent transactivation. O-GlcNAcylation acts as a nutrient-dependent rheostat of cellular signaling. Increased uptake of glucose and glutamine by cancer cells enhances NF-κB O-GlcNAcylation. Growing evidence indicates that O-GlcNAcylation of NF-κB is a key molecular mechanism that regulates cancer cell proliferation, survival and metastasis and acts as link between inflammation and cancer. In this review, we are attempting to summarize the current understanding of the cohesive role of NF-κB O-GlcNAcylation in inflammation and cancer.

Nanosensor Chemical Cytometry for Characterizing the Efflux Heterogeneity of Nitric Oxide from Macrophages

Macrophages are a critical part of the human immune response, and their collective heterogeneity is implicated in disease progression and prevention. A nondestructive, label-free tool does not currently exist for profiling the dynamic, antigenic responses of single macrophages in a collection to correlate with specific molecular expression and correlated biophysical properties at the cellular level, despite the potential for diagnosis and therapeutics. Herein, we develop a nanosensor chemical cytometry (NCC) that can profile the heterogeneity of inducible nitric oxide synthase (iNOS) responses from macrophage populations. By integrating a near-infrared (nIR) fluorescent nanosensor array and collagen layer with microfluidics, the cellular lensing effect of the macrophage was utilized to characterize both nitric oxide (NO) efflux and refractive index (RI) changes at a single-cell level. Using a parallel, multichannel approach, distinct iNOS heterogeneities of macrophages can be monitored at an attomolar (10^-18 mol) sensitivity in a nondestructive and real-time manner with a throughput of exceeding the 200 cells/frame. We demonstrate that estimated mean NO efflux rates of macrophage populations are elevated from 342 (σ = 199) to 464 (σ = 206) attomol/cell·hr with a 3% larger increase in the heterogeneity, and estimated RI of macrophage decrease from 1.366 (σ = 0.015) to 1.359 (σ = 0.009) with trimodal subpopulations under lipopolysaccharide (LPS) activation. These measured values are also in good agreement with Griess assay results and previously reported measurements. This work provides an efficient strategy for single-cell analysis of macrophage populations for cellular manufacturing and biopharmaceutical engineering.

Impact of a long-term high-glucose environment on pro-inflammatory responses in macrophages stimulated with lipopolysaccharide

Cumulative evidence has established that macrophages orchestrate inflammatory responses that crucially contribute to the pathogenesis of insulin-resistant obesity and type 2 diabetes. In the present study, we examined the impact of hyperglycemia on macrophage pro-inflammatory responses under an inflammatory stimulus. To conduct this study, RAW264.7 macrophages were cultured under normal- (5.5 mM) or high-glucose (22 or 40 mM) conditions for 7 days and stimulated with lipopolysaccharide (LPS). Long-term exposure to high glucose significantly enhanced the increase in the production of pro-inflammatory cytokines, including tumor necrosis-α, interleukin (IL)-1β, and IL-6, when macrophages were stimulated with LPS. The LPS-induced increases in inducible nitric oxide (NO) synthase (iNOS) expression and NO production were also significantly enhanced by long-term exposure of macrophages to high glucose. Treatment with N-acetyl-L-cysteine, a widely used thiol-containing antioxidant, blunted the enhancement of the LPS-induced upregulation of pro-inflammatory cytokine production, iNOS expression, and NO production in macrophages. When intracellular reactive oxygen species (ROS) were visualized using the fluorescence dye 5-(and-6)-chloromethyl-2',7'-dichlorofluorescein diacetate, acetyl ester, a significant increase in ROS generation was found after stimulation of macrophages with LPS, and this increased ROS generation was exacerbated under long-term high-glucose conditions. LPS-induced translocation of phosphorylated nuclear factor-κB (NF-κB), a transcription factor regulating many pro-inflammatory genes, into the nucleus was promoted under long-term high-glucose conditions. Altogether, the present results indicate that a long-term high-glucose environment can enhance activation of NF-κB in LPS-stimulated macrophages possibly due to excessive ROS production, thereby leading to increased macrophage pro-inflammatory responses.

A sweet spot for macrophages: Focusing on polarization

Macrophages are a type of functionally plastic cells that can create a pro-/anti-inflammatory microenvironment for organs by producing different kinds of cytokines, chemokines, and growth factors to regulate immunity and inflammatory responses. In addition, they can also be induced to adopt different phenotypes in response to extracellular and intracellular signals, a process defined as M1/M2 polarization. Growing evidence indicates that glycobiology is closely associated with this polarization process. In this research, we review studies of the roles of glycosylation, glucose metabolism, and key lectins in the regulation of macrophages function and polarization to provide a new perspective for immunotherapies for multiple diseases.

Sophoridine Inhibits the Tumour Growth of Non-Small Lung Cancer by Inducing Macrophages M1 Polarisation via MAPK-Mediated Inflammatory Pathway

Lung cancer is one of the most common and lethal neoplasms for which very few efficacious treatments are currently available. M1-like polarised tumour-associated macrophages (TAMs) are key mediators to modulate the tumour microenvironment, which play a key role in inhibiting cancer cell growth. Sophoridine, a naturally occurring alkaloid, exerts multiple pharmacological activities including anti-tumour and anti-inflammatory activities, but it has not been characterised as a regulator of tumour microenvironment towards NSCLC. Herein, the regulatory effects of sophoridine on the polarisation of THP-1 cells into TAMs and the anti-tumour effects of sophoridine-stimulated M1 polarised macrophages towards lung cancer cells were carefully investigated both in vitro and in vivo. The results showed that sophoridine could significantly promote M1 polarisation of RAW264.7 and THP-1-derived macrophages, leading to increased expression of pro-inflammatory cytokines and the M1 surface markers CD86 via activating MAPKs signaling pathway. Further investigations showed that sophoridine-stimulated RAW264.7 and THP-1-derived M1 macrophages effectively induced cell apoptosis as well as inhibited the cell colony formation and cell proliferation in both H460 and Lewis lung cancer cells. In Lewis-bearing mice model, sophoridine (15 or 25 mg/kg) significantly inhibited the tumour growth and up-regulated the expression of CD86/F4/80 in tumour tissues. Collectively, the findings clearly demonstrate that sophoridine promoted M1-like polarisation in vitro and in vivo, suggesting that sophoridine held a great therapeutic potential for treating lung cancer.

Chronic Effects of a High Sucrose Diet on Murine Gastrointestinal Nutrient Sensor Gene and Protein Expression Levels and Lipid Metabolism

The gastrointestinal tract (GIT) plays a key role in regulating nutrient metabolism and appetite responses. This study aimed to identify changes in the GIT that are important in the development of diet related obesity and diabetes. GIT samples were obtained from C57BL/6J male mice chronically fed a control diet or a high sucrose diet (HSD) and analysed for changes in gene, protein and metabolite levels. In HSD mice, GIT expression levels of fat oxidation genes were reduced, and increased de novo lipogenesis was evident in ileum. Gene expression levels of the putative sugar sensor, slc5a4a and slc5a4b, and fat sensor, cd36, were downregulated in the small intestines of HSD mice. In HSD mice, there was also evidence of bacterial overgrowth and a lipopolysaccharide activated inflammatory pathway involving inducible nitric oxide synthase (iNOS). In Caco-2 cells, sucrose significantly increased the expression levels of the nos2, iNOS and nitric oxide (NO) gas levels. In conclusion, sucrose fed induced obesity/diabetes is associated with changes in GI macronutrient sensing, appetite regulation and nutrient metabolism and intestinal microflora. These may be important drivers, and thus therapeutic targets, of diet-related metabolic disease.

Glucose transporter 4 mediates LPS-induced IL-6 production in osteoblasts under high glucose conditions

PURPOSE

Diabetes causes hyperglycemic disorders due to insufficient activity of insulin, and it also increases blood glucose level. Recent studies have reported the relationship between diabetes and periodontal disease. Periodontitis is advanced by inflammatory cytokines stimulated with LPS. The purpose of this study was to investigate the effects of hyperglycemia on the expression of inflammatory cytokines induced by LPS in osteoblasts.

METHODS

Cells were cultured for 7 and 14 days in the presence or absence of LPS and glucose. The expression mRNA level of IL-6, RANKL and OCN was determined using real-time PCR. The protein expression of IL-6 and RANKL was also measured using ELISA.

RESULTS

LPS and glucose increased the mRNA expression of IL-6, coupled with a decrease in the mRNA expression of OCN, which is associated with IL-6 and glucose. It also increased the protein expression of IL-6 compared to LPS. However, LPS+Glucose did not affect the mRNA and protein expression of RANKL. Furthermore, GLUT4 inhibitor, WZB117, blocked the stimulatory effect of glucose on LPS-induced IL-6 mRNA expression. WZB117 did not affect LPS-reduced OCN mRNA expression.

CONCLUSION

These results suggest that high glucose levels increase LPS-induced IL-6 expression mediated by GLUT4.

Lipopolysaccharide Induces GFAT2 Expression to Promote O-Linked β-N-Acetylglucosaminylation and Attenuate Inflammation in Macrophages

Glycosylation with O-linked β-N-acetylglucosamine (O-GlcNAcylation) is a reversible posttranslational modification that regulates the activity of intracellular proteins according to glucose availability and its metabolism through the hexosamine biosynthesis pathway. This modification has been involved in the regulation of various immune cell types, including macrophages. However, little is known concerning the mechanisms that regulate the protein O-GlcNAcylation level in these cells. In the present work, we demonstrate that LPS treatment induces a marked increase in protein O-GlcNAcylation in RAW264.7 cells, bone marrow-derived and peritoneal mouse macrophages, as well as human monocyte-derived macrophages. Targeted deletion of OGT in macrophages resulted in an increased effect of LPS on NOS2 expression and cytokine production, suggesting that O-GlcNAcylation may restrain inflammatory processes induced by LPS. The effect of LPS on protein O-GlcNAcylation in macrophages was associated with an increased expression and activity of glutamine fructose 6-phosphate amidotransferase (GFAT), the enzyme that catalyzes the rate-limiting step of the hexosamine biosynthesis pathway. More specifically, we observed that LPS potently stimulated GFAT2 isoform mRNA and protein expression. Genetic or pharmacological inhibition of FoxO1 impaired the LPS effect on GFAT2 expression, suggesting a FoxO1-dependent mechanism. We conclude that GFAT2 should be considered a new LPS-inducible gene involved in regulation of protein O-GlcNAcylation, which permits limited exacerbation of inflammation upon macrophage activation.

Glucosamine regulates hepatic lipid accumulation by sensing glucose levels or feeding states of normal and excess

Dose-dependent lipid accumulation was induced by glucose in HepG2 cells. GlcN also exerted a promotory effect on lipid accumulation in HepG2 cells under normal glucose conditions (NG, 5 mM) and liver of normal fed zebrafish larvae. High glucose (HG, 25 mM)-induced lipid accumulation was suppressed by l-glutamine-d-fructose 6-phosphate amidotransferase inhibitors. ER stress inhibitors did not suppress HG or GlcN-mediated lipid accumulation. HG and GlcN stimulated protein expression, DNA binding and O-GlcNAcylation of carbohydrate-responsive element-binding protein (ChREBP). Furthermore, both HG and GlcN increased nuclear sterol regulatory element-binding protein-1 (SREBP-1) levels in HepG2 cells. In contrast to its stimulatory effect under NG, GlcN suppressed lipid accumulation in HepG2 cells under HG conditions. Similarly, GlcN suppressed lipid accumulation in livers of overfed zebrafish. In addition, GlcN activity on DNA binding and O-GlcNAcylation of ChREBP was stimulatory under NG and inhibitory under HG conditions. Moreover, GlcN enhanced ChREBP, SREBP-1c, ACC, FAS, L-PK and SCD-1 mRNA expression under NG but inhibited HG-induced upregulation in HepG2 cells. The O-GlcNAc transferase inhibitor, alloxan, reduced lipid accumulation by HG or GlcN while the O-GlcNAcase inhibitor, PUGNAc, enhanced lipid accumulation in HepG2 cells and liver of zebrafish larvae. GlcN-induced lipid accumulation was inhibited by the AMPK activator, AICAR. Phosphorylation of AMPK (p-AMPK) was suppressed by GlcN under NG while increased by GlcN under HG. PUGNAc downregulated p-AMPK while alloxan restored GlcN- or HG-induced p-AMPK inhibition. Our results collectively suggest that GlcN regulates lipogenesis by sensing the glucose or energy states of normal and excess fuel through AMPK modulation.

O-GlcNAcylation and its role in the immune system

O-linked-N-acetylglucosaminylation (O-GlcNAcylation) is a type of glycosylation that occurs when a monosaccharide, O-GlcNAc, is added onto serine or threonine residues of nuclear or cytoplasmic proteins by O-GlcNAc transferase (OGT) and which can be reversibly removed by O-GlcNAcase (OGA). O-GlcNAcylation couples the processes of nutrient sensing, metabolism, signal transduction and transcription, and plays important roles in development, normal physiology and physiopathology. Cumulative studies have indicated that O-GlcNAcylation affects the functions of protein substrates in a number of ways, including protein cellular localization, protein stability and protein/protein interaction. Particularly, O-GlcNAcylation has been shown to have intricate crosstalk with phosphorylation as they both modify serine or threonine residues. Aberrant O-GlcNAcylation on various protein substrates has been implicated in many diseases, including neurodegenerative diseases, diabetes and cancers. However, the role of protein O-GlcNAcylation in immune cell lineages has been less explored. This review summarizes the current understanding of the fundamental biochemistry of O-GlcNAcylation, and discusses the molecular mechanisms by which O-GlcNAcylation regulates the development, maturation and functions of immune cells. In brief, O-GlcNAcylation promotes the development, proliferation, and activation of T and B cells. O-GlcNAcylation regulates inflammatory and antiviral responses of macrophages. O-GlcNAcylation promotes the function of activated neutrophils, but inhibits the activity of nature killer cells.

Anti-Inflammatory Effects of Fucoxanthinol in LPS-Induced RAW264.7 Cells through the NAAA-PEA Pathway

Palmitoylethanolamide (PEA) is an endogenous lipid mediator with powerful anti-inflammatory and analgesic functions. PEA can be hydrolyzed by a lysosomal enzyme N-acylethanolamine acid amidase (NAAA), which is highly expressed in macrophages and other immune cells. The pharmacological inhibition of NAAA activity is a potential therapeutic strategy for inflammation-related diseases. Fucoxanthinol (FXOH) is a marine carotenoid from brown seaweeds with various beneficial effects. However, the anti-inflammatory effects and mechanism of action of FXOH in lipopolysaccharide (LPS)-stimulated macrophages remain unclear. This study aimed to explore the role of FXOH in the NAAA–PEA pathway and the anti-inflammatory effects based on this mechanism. In vitro results showed that FXOH can directly bind to the active site of NAAA protein and specifically inhibit the activity of NAAA enzyme. In an LPS-induced inflammatory model in macrophages, FXOH pretreatment significantly reversed the LPS-induced downregulation of PEA levels. FXOH also substantially attenuated the mRNA expression of inflammatory factors, including inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), and markedly reduced the production of TNF-α, IL-6, IL-1β, and nitric oxide (NO). Moreover, the inhibitory effect of FXOH on NO induction was significantly abolished by the peroxisome proliferator-activated receptor α (PPAR-α) inhibitor GW6471. All these findings demonstrated that FXOH can prevent LPS-induced inflammation in macrophages, and its mechanisms may be associated with the regulation of the NAAA-PEA-PPAR-α pathway.

Toll-like receptor 4/nuclear factor-kappa B pathway is involved in activating microphages by polysaccharides isolated from Fagopyrum esculentum

Buckwheat polysaccharide fractions (BPFs) isolated from seeds of Fagopyrum esculentum have shown extensive immunomodulatory activities including activation of immune system. In this study, the immuno-modulation effects of BPFs on microphages were investigated. The obtained results show that BPFs can activate microphages as indicated by significant increases in the activity of inducible nitric oxide synthase (12.6 ± 1.30 U/mg prot), nuclear factor-kappa B (NF-κB) protein levels, and secretion of nitric oxide (NO) (21.5 ± 1.20 μmol/ml) and tumor necrosis factor-alpha (TNF-α) (71.2 ± 18.20 pg/ml). Moreover, blocking toll-like receptor 4 (TLR4)/NF-κB pathway using a specific antibody to TLR4 or inhibitor of NF-κB led to the significant inhibitory immuno-modulation effect on microphages as indicated by the decrease in the secretion level of NO and TNF-α. It is demonstrated that BPFs can activate microphages and TLR4/NF-κB pathway is involved in the induction of NO and TNF-α in macrophages by BPFs.

Acute Increase in O-GlcNAc Improves Survival in Mice With LPS-Induced Systemic Inflammatory Response Syndrome

Sepsis is a systemic inflammatory response syndrome (SIRS) resulting from a severe infection that is characterized by immune dysregulation, cardiovascular derangements, and end-organ dysfunction. The modification of proteins by O-linked N-acetylglucosamine (O-GlcNAcylation) influences many of the key processes that are altered during sepsis, including the production of inflammatory mediators and vascular contractility. Here, we investigated whether O-GlcNAc affects the inflammatory response and cardiovascular dysfunction associated with sepsis. Mice received an intraperitoneal injection of lipopolysaccharide (LPS, 20 mg/Kg) to induce endotoxic shock and systemic inflammation, resembling sepsis-induced SIRS. The effects of an acute increase in O-GlcNAcylation, by treatment of mice with glucosamine (GlcN, 300 mg/Kg, i.v.) or thiamet-G (ThG, 150 μg/Kg, i.v.), on LPS-associated mortality, production and release of cytokines by macrophages and vascular cells, vascular responsiveness to constrictors and blood pressure were then determined. Mice under LPS-induced SIRS exhibited a systemic and local inflammatory response with increased levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor (TNF-α), as well as severe hypotension and vascular hyporesponsiveness, characterized by reduced vasoconstriction to phenylephrine. In addition, LPS increased neutrophil infiltration in lungs and produced significant lethality. Treatment with GlcN and ThG reduced systemic inflammation and attenuated hypotension and the vascular refractoriness to phenylephrine, improving survival. GlcN and ThG also decreased LPS-induced production of inflammatory cytokines by bone marrow-derived macrophages and nuclear transcription factor-kappa B (NF-κB) activation in RAW 264.7 NF-κB promoter macrophages. Treatment of mice with ThG increased O-glycosylation of NF-κB p65 subunit in mesenteric arteries, which was associated with reduced Ser⁵³⁶ phosphorylation of NF-κB p65. Finally, GlcN also increased survival rates in mice submitted to cecal ligation and puncture (CLP), a sepsis model. In conclusion, increased O-GlcNAc reduces systemic inflammation and cardiovascular disfunction in experimental sepsis models, pointing this pathway as a potential target for therapeutic intervention.

CTRP9 induces iNOS expression through JAK2/STAT3 pathway in Raw 264.7 and peritoneal macrophages

The C1q tumor necrosis factor (TNF)-related proteins 9 (CTRP9), an adipocyte-derived cytokine, affects a number of physiological processes, including immune function and inflammation. We investigated whether CTRP9 affects the expression of inflammation-related genes in Raw 264.7 and peritoneal macrophages. The CTRP9-induced expression of iNOS increased in a time- and dose-dependent manner. LPS and CTRP9 promote the expression of iNOS jointly in Raw 264.7 and peritoneal macrophages. CTRP9 induced the phosphorylation of JAK2 and STAT3 in Raw 264.7 and peritoneal macrophages. VX509 (JAK2 inhibitor) reduced the CTRP9-induced iNOS protein production. In addition, the CTRP9-induced phosphorylation of JAK2 and STAT3 was dramatically reduced by VX509. Collectively, these results suggest that JAK2/STAT3 signaling is involved in the CTRP9-induced expression of iNOS.

Therapeutic Effect of Glucosamine on an Atopic Dermatitis Animal Model

Background

Recent studies have reported that glucosamine (GlcN) showed therapeutic effects in allergic diseases such as asthma and rhinitis, and its mechanisms include the suppression of T helper type 2 immune responses and the nuclear factor-κB pathway.

Objective

We aimed to investigate the effect of GlcN on atopic dermatitis (AD) in an animal model.

Methods

Twenty-five BALB/c mice were divided into five groups (groups A~E). Group A was the phosphate-buffered saline (PBS)-treated group without AD induction. Group B was the PBS control group with AD induction. Groups C to E were the AD induction groups, which were treated with three different doses of GlcN (10 mg, 20 mg, and 40 mg, respectively). Histopathological examination was performed after GlcN administration. Interleukin (IL)-4, IL-13, and IL-17 cytokine levels were measured by enzyme-linked immunosorbent assay using skin biopsy specimens. Serum total immunoglobulin E (IgE) concentrations were measured before and after administration with GlcN or PBS.

Results

Clinical dermatitis scores decreased with increasing GlcN dose (p<0.001). Concentrations of tissue IL-13 and IL-17 decreased after GlcN administration (each group: p=0.002 and p<0.001, respectively), but the concentrations of tissue IL-4 did not show differences across groups. Serum IgE levels tended to be lower after GlcN administration (p=0.004). Histopathological scores were not significantly different among groups B~E (p=0.394).

Conclusion

GlcN improved AD symptoms and decreased tissue IL-13, IL-17, and serum total IgE levels in an animal model.

Structure and Immunomodulatory Activity of Microparticulate Mushroom Sclerotial β-Glucan Prepared from Polyporus rhinocerus

In this study, an immunologically active novel microparticulate mushroom β-glucan (PRA-1p) was prepared using an alkali-soluble glucan PRA-1 by an emulsification and cross-linking method. PRA-1 was a hyperbranched (1→3),(1→6)-β-d-glucan with a degree of branching of 0.89, isolated from the sclerotia of Polyporus rhinocerus. PRA-1 had a rod-like conformation, while PRA-1p exhibited a monodisperse and homogeneous spherical conformation with a diameter ranging from 0.3 to 2.0 μm in water. PRA-1p significantly induced nitric oxide and reactive oxygen species production as well as morphological changes of murine macrophages (RAW 264.7 cells) and upregulated their phagocytic activity. Furthermore, PRA-1p treatment markedly enhanced the secretion of cytokines, including cutaneous T cell-attracting chemokine 27, granulocyte-colony-stimulating factor, monocyte chemoattractant protein 1, macrophage inflammatory protein 1α, macrophage inflammatory protein 2, regulated on activation, normal T cell expressed and secreted, soluble tumor necrosis factor receptor 1, and tissue inhibitors of metalloproteinases. Activation of RAW 264.7 cells triggered by PRA-1p was associated with activation of inducible nitric oxide synthase, nuclear factor κB, extracellular signal-regulated kinase, and protein kinase B. This work suggests that novel PRA-1p derived from the mushroom sclerotia of P. rhinocerus has potential application as an immunostimulatory agent.

O-GlcNAcylation in immunity and inflammation: An intricate system (Review)

Chronic, low‑grade inflammation associated with obesity and diabetes result from the infiltration of adipose and vascular tissue by immune cells and contributes to cardiovascular complications. Despite an incomplete understanding of the mechanistic underpinnings of immune cell differentiation and inflammation, O‑GlcNAcylation, the addition of O‑linked N‑acetylglucosamine (O‑GlcNAc) to cytoplasmic, nuclear and mitochondrial proteins by the two cycling enzymes, the O‑linked N‑acetylglucosamine transferase (OGT) and the O‑GlcNAcase (OGA), may contribute to fine‑tune immunity and inflammation in both physiological and pathological conditions. Early studies have indicated that O‑GlcNAcylation of proteins play a pro‑inflammatory role in diabetes and insulin resistance, whereas subsequent studies have demonstrated that this post‑translational modification could also be protective against acute injuries. These studies suggest that diverse types of insults result in dynamic changes to O‑GlcNAcylation patterns, which fluctuate with cellular metabolism to promote or inhibit inflammation. In this review, the current understanding of O‑GlcNAcylation and its adaptive modulation in immune and inflammatory responses is summarized.

Emerging role of glycosylation in the polarization of tumor-associated macrophages

Tumors are formed by several cell types interacting in a complex environment of soluble and matrix molecules. The crosstalk between the cells and extracellular components control tumor fate. Macrophages are highly plastic and diverse immune cells that are known to be key regulators of this complex network, which is mostly because they can adjust their metabolism and reprogram their phenotype and effector function. Here, we review the studies that disclose the central role of metabolism and tumor microenvironment in shaping the phenotype and function of macrophages, highlighting the importance of the hexosamine biosynthetic pathway. We further discuss growing evidence of nutrient-sensitive protein modifications such as O-GlcNAcylation and extracellular glycosylation in the function and polarization of tumor-associated macrophages.

Glucosamine improves survival in a mouse model of sepsis and attenuates sepsis-induced lung injury and inflammation

The aim of the current study was to investigate the effects of glucosamine (GlcN) on septic lethality and sepsis-induced inflammation using animal models of mice and zebrafish. GlcN pretreatment improved survival in the cecal ligation and puncture (CLP)-induced sepsis mouse model and attenuated lipopolysaccharide (LPS)-induced septic lung injury and systemic inflammation. GlcN suppressed LPS-induced M1-specific but not M2-specific gene expression. Furthermore, increased expressions of inflammatory genes in visceral tissue of LPS-injected zebrafish were suppressed by GlcN. GlcN suppressed LPS-induced activation of mitogen-activated protein kinase (MAPK) and NF-κB in lung tissue. LPS triggered a reduction in O-GlcNAc levels in nucleocytoplasmic proteins of lung, liver, and spleen after 1 day, which returned to normal levels at day 3. GlcN inhibited LPS-induced O-GlcNAc down-regulation in mouse lung and visceral tissue of zebrafish. Furthermore, the O-GlcNAcase (OGA) level was increased by LPS, which were suppressed by GlcN in mouse and zebrafish. OGA inhibitors suppressed LPS-induced expression of inflammatory genes in RAW264.7 cells and the visceral tissue of zebrafish. Stable knockdown of Oga via short hairpin RNA led to increased inducible nitric oxide synthase (iNOS) expression in response to LPS with or without GlcN in RAW264.7 cells. Overall, our results demonstrate a protective effect of GlcN on sepsis potentially through modulation of O-GlcNAcylation of nucleocytoplasmic proteins.

Glucosamine prevents polarization of cytotoxic granules in NK-92 cells by disturbing FOXO1/ERK/paxillin phosphorylation

Glucosamine (GlcN) is a naturally occurring derivative of glucose and an over-the-counter food additive. However, the mechanism underlying GlcN action on cells is unknown. In this study, we investigated the effect of GlcN on natural killer (NK) cells. We demonstrate that GlcN affects NK-92 cell cytotoxicity by altering the distribution of cathepsin C, a cysteine protease required for granzyme processing in cytotoxic granules. The relocation of cathepsin C due to GlcN was shown to be accompanied by a decrease in the intracellular enzyme activity and its extracellular secretion. Similarly, the relocation of endosomal aspartic cathepsin E was observed. Furthermore, we elucidated that repositioning of cathepsin C is a consequence of altered signaling pathways of cytotoxic granule movement. The inhibition of phosphorylation upstream and downstream of ERK by GlcN disturbed the polarized release of cytotoxic vesicles. Considerable changes in the ERK phosphorylation dynamics, but not in those of p38 kinase or JNK, were observed in the IL2-activated NK-92 cells. We found decreased phosphorylation of the transcription factor FOXO1 and simultaneous prolonged phosphorylation of ERK as well as its nuclear translocation. Additionally, a protein downstream of the ERK phosphorylation cascade, paxillin, was less phosphorylated, resulting in a diffuse distribution of cytotoxic granules. Taken together, our results suggest that dietary GlcN affects signaling pathway activation of NK-92 immune cells.

Too sweet to resist: Control of immune cell function by O-GlcNAcylation

O-linked β-N-acetyl glucosamine modification (O-GlcNAcylation) is a dynamic, reversible posttranslational modification of cytoplasmic and nuclear proteins. O-GlcNAcylation depends on nutrient availability and the hexosamine biosynthetic pathway (HBP), which produces the donor substrate UDP-GlcNAc. O-GlcNAcylation is mediated by a single enzyme, O-GlcNAc transferase (OGT), which adds GlcNAc and another enzyme, O-GlcNAcase (OGA), which removes O-GlcNAc from proteins. O-GlcNAcylation controls vital cellular processes including transcription, translation, the cell cycle, metabolism, and cellular stress. Aberrant O-GlcNAcylation has been implicated in various pathologies including Alzheimer's disease, diabetes, obesity, and cancer. Growing evidences indicate that O-GlcNAcylation plays crucial roles in regulating immunity and inflammatory responses, especially under hyperglycemic conditions. This review will highlight the emerging functions of O-GlcNAcylation in mammalian immunity under physiological and various pathological conditions.

Glucosamine has an antiallergic effect in mice with allergic asthma and rhinitis

BACKGROUND

Glucosamine (GlcN) is generally used as a dietary supplement because of its antiinflammatory effects. We evaluated the antiallergic effect of GlcN in mice with allergic asthma and rhinitis.

METHODS

Thirty-two mice were allocated equally into 4 groups (n = 8). In group A (control), we performed intraperitoneal/intranasal challenge using sterile saline. In group B (asthma/rhinitis), we used ovalbumin for intraperitoneal/intranasal challenge to induce allergic asthma and rhinitis. In groups C and D (GlcN treatment), mice were given 1% and 5% GlcN throughout the period of ovalbumin challenge, respectively. We measured serum total and ovalbumin-specific immunoglobulin E (IgE), cytokine titers (interleukin-1, -4, -5, -6, -10, and -17; tumor necrosis factor-α; and interferon-γ), and the number of inflammatory cells (eosinophils, neutrophils, lymphocytes) in bronchoalveolar lavage (BAL) fluid. We also performed histopathologic examination of the lung and nasal cavity. Finally, we performed real-time polymerase chain reaction for the genes Bcl-2, EC-SOD, VEGF, caspase-3, Bax, COX-2, Hif-1α, and heme oxygenase-1.

RESULTS

Compared with group B, group D had significant serum total and ovalbumin-specific IgE decreases after GlcN treatment (p < 0.05). Titers for IL-4, IL-5, IL-6, and IL-17 in BAL fluid were significantly decreased in group D (p < 0.05). Eosinophils in BAL fluid were significantly decreased in group D compared with group B (p < 0.05). Groups C and D showed significant improvement of inflammation compared with group B. Group D had significant downregulation of EC-SOD, Bax, Hif-1α, and heme oxygenase-1 compared with group B.

CONCLUSION

GlcN had a significant antiallergic effect in mice with allergic asthma and rhinitis.