AGE-RAGE interaction and oxidative stress in obesity-related renal dysfunction

Associations between obesity and hyperuricemia combing mendelian randomization with network pharmacology

Objective

Obesity has become a global health issue and a risk factor for hyperuricemia. However, the associations between obesity and hyperuricemia are sometimes confounding. In the present study, we performed mendelian randomization (MR) analysis to study their relationship and investigate the underlying mechanism by network pharmacology.

Method

Body mass index (BMI) and uric acid related to single nucleotide polymorphism were selected as instrumental variables for MR analysis. Three robust analytical methods are used for bidirectional MR analysis such as inverse-variance weighting, weighted median and MR-Egger regression. Then, we further performed sensitivity analysis to evaluate the horizontal pleiotropy, heterogeneities, and stability. The targets related to obesity and hyperuricemia were collected, screened and further conducted for Kyoto Encyclopedia of Genes and Genomes pathway enrichment to explore the mechanism of obesity and hyperuricemia using network pharmacology.

Results

The positive causality was indicated between BMI and hyperuricemia based on inverse variance-weighted analysis [odds ratio:1.23, 95% confidence interval: 1.11 to 1.30 for each standard deviation increase in BMI (4.6 kg/m2)]. Conversely, hyperuricemia did not influence BMI. 235 intersected targets from obesity and hyperuricemia were collected. Insulin resistance were the top 1 key target. The mechanism between obesity and hyperuricemia are associated with important pathways including adipocytokine signaling pathway, insulin resistance and cholesterol metabolism et al.

Conclusions

Our MR analysis supported the causal association between obesity and hyperuricemia based on availablegenome-wide association analysis summary statistics. Obesity leads to hyperuricemia via insulin resistance, which is a key link in the huge network pathways using network pharmacology.

Relevance of oxidative stress biomarkers, hemoglobin A1c, troponin-I, and angiotensin-converting enzyme metabolism to blood pressure in acute myocardial infarction: a case-control study

The aim was to investigate this relationship by calculating 1) the correlation between peak troponin-C (peak-cTnI), levels of oxidative stress biomarkers, including lipid peroxidation products (malondialdehyde (MDA), conjugated dienes (CD)), and antioxidant enzyme activity (glutathione peroxidase (GPx)), and HbA1c and 2) the correlation between HbA1c and serum angiotensin-converting enzyme (ACE) activity, and its impact on the rate pressure product (RPP) in acute myocardial infarction (AMI). A case-control study was performed in 306 AMI patients having undergone coronary angiography and on 410 controls. GPx activity was reduced in association with increased MDA and CD in patients. Peak-cTnI was positively correlated with HbA1c, MDA, and CD levels. Serum ACE activity was negatively correlated with GPx. HbA1c was positively correlated with ACE activity and RPP. Linear regression analysis showed that peak-cTnI, ACE activity and HbA1c are significant predictors of AMI. Elevated HbA1c and peak-cTnI levels are associated with RPP elevation causing AMI. In conclusions, patients with elevated HbA1c, elevated ACE activity and cTnI are at increased risk of AMI with increasing RPP. Patients at risk of AMI can be identified at an early stage if the biomarkers HbA1c, ACE activity, and cTnI are measured and preventive measures are taken in a targeted manner.

Fisetin treatment alleviates kidney injury in mice with diabetes-exacerbated atherosclerosis through inhibiting CD36/fibrosis pathway

Diabetes-related vascular complications include diabetic cardiovascular diseases (CVD), diabetic nephropathy (DN) and diabetic retinopathy, etc. DN can promote the process of end-stage renal disease. On the other hand, atherosclerosis accelerates kidney damage. It is really an urge to explore the mechanisms of diabetes-exacerbated atherosclerosis as well as new agents for treatment of diabetes-exacerbated atherosclerosis and the complications. In this study we investigated the therapeutic effects of fisetin, a natural flavonoid from fruits and vegetables, on kidney injury caused by streptozotocin (STZ)-induced diabetic atherosclerosis in low density lipoprotein receptor deficient (LDLR-/-) mice. Diabetes was induced in LDLR-/- mice by injecting STZ, and the mice were fed high-fat diet (HFD) containing fisetin for 12 weeks. We found that fisetin treatment effectively attenuated diabetes-exacerbated atherosclerosis. Furthermore, we showed that fisetin treatment significantly ameliorated atherosclerosis-enhanced diabetic kidney injury, evidenced by regulating uric acid, urea and creatinine levels in urine and serum, and ameliorating morphological damages and fibrosis in the kidney. In addition, we found that the improvement of glomerular function by fisetin was mediated by reducing the production of reactive oxygen species (ROS), advanced glycosylation end products (AGEs) and inflammatory cytokines. Furthermore, fisetin treatment reduced accumulation of extracellular matrix (ECM) in the kidney by inhibiting the expression of vascular endothelial growth factor A (VEGFA), fibronectin and collagens, while enhancing matrix metalloproteinases 2 (MMP2) and MMP9, which was mainly mediated by inactivating transforming growth factor β (TGFβ)/SMAD family member 2/3 (Smad2/3) pathways. In both in vivo and in vitro experiments, we demonstrated that the therapeutic effects of fisetin on kidney fibrosis resulted from inhibiting CD36 expression. In conclusion, our results suggest that fisetin is a promising natural agent for the treatment of renal injury caused by diabetes and atherosclerosis. We reveal that fisetin is an inhibitor of CD36 for reducing the progression of kidney fibrosis, and fisetin-regulated CD36 may be a therapeutic target for the treatment of renal fibrosis.

AGE-RAGE axis culminates into multiple pathogenic processes: a central road to neurodegeneration

Advanced glycation end-products (AGEs; e.g., glyoxal, methylglyoxal or carboxymethyl-lysine) are heterogenous group of toxic compounds synthesized in the body through both exogenous and endogenous pathways. AGEs are known to covalently modify proteins bringing about loss of functional alteration in the proteins. AGEs also interact with their receptor, receptor for AGE (RAGE) and such interactions influence different biological processes including oxidative stress and apoptosis. Previously, AGE-RAGE axis has long been considered to be the maligning factor for various human diseases including, diabetes, obesity, cardiovascular, aging, etc. Recent developments have revealed the involvement of AGE-RAGE axis in different pathological consequences associated with the onset of neurodegeneration including, disruption of blood brain barrier, neuroinflammation, remodeling of extracellular matrix, dysregulation of polyol pathway and antioxidant enzymes, etc. In the present article, we attempted to describe a new avenue that AGE-RAGE axis culminates to different pathological consequences in brain and therefore, is a central instigating component to several neurodegenerative diseases (NGDs). We also invoke that specific inhibitors of TIR domains of TLR or RAGE receptors are crucial molecules for the therapeutic intervention of NGDs. Clinical perspectives have also been appropriately discussed.

Network Pharmacology Study to Interpret Signaling Pathways of Ilex cornuta Leaves against Obesity

Ilex cornuta Leaves (ICLs) are a representative and traditional prescription for controlling obesity. Nevertheless, the corresponding therapeutic compounds and related pharmacological mechanisms of such medication remain undocumented. The compounds from ICLs were identified by gas chromatography-mass spectrum (GC-MS), and SwissADME confirmed their physicochemical properties. Next, the target proteins related to compounds or obesity-associated proteins were retrieved from public databases. RPackage constructed the protein–protein interaction (PPI) network, a bubble chart, and signaling pathways–target proteins–compounds (STC) network. Lastly, a molecular docking test (MDT) was performed to evaluate the affinity between target proteins and ligands from ICLs. GC-MS detected a total of 51 compounds from ICLs. The public databases identified 219 target proteins associated with selective compounds, 3028 obesity-related target proteins, and 118 overlapping target proteins. Moreover, the STC network revealed 42 target proteins, 22 signaling pathways, and 39 compounds, which were viewed to be remedially significant. The NOD-like receptor (NLR) signaling pathway was considered a key signaling pathway from the bubble chart. In parallel, the MDT identified three target proteins (IL6, MAPK1, and CASP1) on the NLR signaling pathway and four compounds against obesity. Overall, four compounds from ICLs might show anti-obesity synergistic efficacy by inactivating the NLR signaling pathway.

Exploiting Common Aspects of Obesity and Alzheimer's Disease

Alzheimer’s disease (AD) is an example of age-related dementia, and there are still no known preventive or curative measures for this disease. Obesity and associated metabolic changes are widely accepted as risk factors of age-related cognitive decline. Insulin is the prime mediator of metabolic homeostasis, which is impaired in obesity, and this impairment potentiates amyloid-β (Aβ) accumulation and the formation of neurofibrillary tangles (NFTs). Obesity is also linked with functional and morphological alterations in brain mitochondria leading to brain insulin resistance (IR) and memory deficits associated with AD. Also, increased peripheral inflammation and oxidative stress due to obesity are the main drivers that increase an individual’s susceptibility to cognitive deficits, thus doubling the risk of AD. This enhanced risk of AD is alarming in the context of a rapidly increasing global incidence of obesity and overweight in the general population. In this review, we summarize the risk factors that link obesity with AD and emphasize the point that the treatment and management of obesity may also provide a way to prevent AD.

Pentoxifylline mitigates renal glycoxidative stress in obese mice by inhibiting AGE/RAGE signaling and increasing glyoxalase levels

AIM

The pharmacological properties of pentoxifylline have been re-evaluated, particularly in chronic kidney disease in diabetes, favored by its anti-inflammatory action. Definitive evidences of renal outcomes are lacking, which indicates the need for investigation of novel mechanisms of action of pentoxifylline. We postulated that components associated with the metabolism of advanced glycation end products (AGEs) may be modulated by pentoxifylline, which consequently decreases the detrimental effects of obesity on kidneys.

MAIN METHODS

C57BL-6J mice were fed a high-fat diet for 14 weeks and treated with 50 mg/kg pentoxifylline during the last 7 weeks. Changes in the renal levels of AGE metabolism-associated components were investigated, with particular focus on the receptor for AGEs (RAGE), its downstream components, and components related to AGE detoxification, including glyoxalase 1 (GLO 1).

KEY FINDINGS

Pentoxifylline reduced body weight gain, improved insulin sensitivity and glucose tolerance, downregulated biomarkers of glycoxidative stress, and enhanced plasma paraoxonase 1 activity. In the kidneys, pentoxifylline inhibited glomerular expansion, lipid deposition, reduced pro-inflammatory cytokine levels, and induced the activation of AMP-activated protein kinase. Pentoxifylline inhibited the renal accumulation of AGEs and reduced the levels of RAGE and its downstream components, and consequently mitigated oxidative stress and apoptosis. Pentoxifylline also increased the renal levels of GLO 1 and the activities of antioxidant enzymes. Urinary albumin levels were observed to be lowered, which reconfirmed the antialbuminuric effects of pentoxifylline.

SIGNIFICANCE

The novel mechanisms of action help explain the renoprotective effects of pentoxifylline and the attenuation of obesity-associated renal complications related to glycoxidative stress.

Syzygium aromaticum Reduces Diabetes-induced Glucotoxicity via the NRF2/Glo1 Pathway

Advanced glycation end products and methylglyoxal are known to show increased levels in diabetic conditions and induce diverse metabolic disorders. However, the antiglycation ability of the bark of Syzygium aromaticum is not yet studied. In this study, we determined the inhibitory effects of S. aromaticum on AGE formation. Moreover, S. aromaticum showed breakage and inhibitory ability against the formation of AGE-collagen crosslinks. In SV40 MES13 cells, treatment with the S. aromaticum extract significantly ameliorated MG-induced oxidative stress as well as cytotoxicity. Furthermore, in the S. aromaticum extract-treated group, there was a reduction in levels of several diabetic markers, such as blood glucose, kidney weight, and urinary albumin to creatinine ratio in streptozotocin-induced diabetic rats. Treatment with the S. aromaticum extract significantly increased the expression of nuclear factor erythroid 2-related factor 2, a transcription factor involved in the expression of antioxidant enzymes. Moreover, the treatment significantly upregulated the expression of glyoxalase 1 and downregulated the expression of receptor for AGEs. These results suggest that the S. aromaticum extract might ameliorate diabetes-induced renal damage by inhibiting the AGE-induced glucotoxicity and oxidative stress through the Nrf2/Glo1 pathway.

New Insights into the Pathogenesis of Diabetic Nephropathy: Proximal Renal Tubules Are Primary Target of Oxidative Stress in Diabetic Kidney

Diabetic nephropathy is a major source of end-stage renal failure, affecting about one-third cases of diabetes mellitus. It has long been accepted that diabetic nephropathy is mainly characterized by glomerular defects, while clinical observations have implied that renal tubular damage is closely linked to kidney dysfunction at the early stages of diabetic nephropathy. In this study, we conducted pathohistological analyses focusing on renal tubular lesions in the early-stage diabetic kidney with the use of a streptozotocin (STZ)-induced diabetes mellitus mouse model. The results revealed that histological alterations in renal tubules, shown by a vacuolar nucleic structure, accumulations of PAS-positive substance, and accelerated restoration stress, occur initially without the presence of glomerular lesions in the early-stage diabetic kidney, and that these tubular defects are localized mainly in proximal renal tubules. Moreover, enhanced expression of RAGE, suggesting an aberrant activation of AGEs-RAGE signaling pathway, and accumulation of oxidative modified mitochondria through the impaired autophagy/lysosome system, were also seen in the damaged diabetic proximal renal tubules. Our findings indicate that proximal tubular defects are the initial pathological events increasingly linked to the progression of diabetic nephropathy, and that controlling renal tubular damage could be an effective therapeutic strategy for the clinical treatment of diabetic nephropathy.

Measurement and Clinical Significance of Lipid Peroxidation as a Biomarker of Oxidative Stress: Oxidative Stress in Diabetes, Atherosclerosis, and Chronic Inflammation

Endothelial dysfunction is one of the initial steps in the pathogenesis of atherosclerosis and development of cardiovascular disease in patients with diabetes mellitus. Several risk factors are associated with endothelial dysfunction and atherosclerosis, such as hypertension, dyslipidaemia, inflammation, oxidative stress, and advanced glycation-end products. Among these risk factors, oxidative stress is the largest contributor to the formation of atherosclerotic plaques. Measurement of reactive oxygen species (ROS) is still difficult, and assays for the measurement of ROS have failed to show a consistent correlation between pathological states and oxidative stress. To solve this problem, this review summarizes the current knowledge on biomarkers of oxidative stress, especially lipid peroxidation, and discusses the roles of oxidative stress, as measured by indices of lipid peroxidation, in diabetes mellitus, atherosclerosis, and chronic inflammation.

MitoQ supplementation prevent long-term impact of maternal smoking on renal development, oxidative stress and mitochondrial density in male mice offspring

To investigate the effect of maternal MitoQ treatment on renal disorders caused by maternal cigarette smoke exposure (SE). We have demonstrated that maternal SE during pregnancy increases the risk of developing chronic kidney disease (CKD) in adult offspring. Mitochondrial oxidative damage contributes to the adverse effects of maternal smoking on renal disorders. MitoQ is a mitochondria-targeted antioxidant that has been shown to protect against oxidative damage-related pathologies in many diseases. Female Balb/c mice (8 weeks) were divided into Sham (exposed to air), SE (exposed to cigarette smoke) and SEMQ (exposed to cigarette smoke with MitoQ supplemented from mating) groups. Kidneys from the mothers were collected when the pups weaned and those from the offspring were collected at 13 weeks. Maternal MitoQ supplementation during gestation and lactation significantly reversed the adverse impact of maternal SE on offspring’s body weight, kidney mass and renal pathology. MitoQ administration also significantly reversed the impact of SE on the renal cellular mitochondrial density and renal total reactive oxygen species in both the mothers and their offspring in adulthood. Our results suggested that MitoQ supplementation can mitigate the adverse impact of maternal SE on offspring’s renal pathology, renal oxidative stress and mitochondrial density in mice offspring.

AGEs-RAGE overexpression in a patient with smoking-related idiopathic nodular glomerulosclerosis

We report a case of smoking-related idiopathic nodular glomerulosclerosis (ING) with overexpression of glomerular advanced glycation end products (AGEs) and their receptor (RAGE). A 59-year-old Japanese man with nephrotic syndrome, who had a smoking history of one pack of cigarettes per day for approximately 40 years, presented with a 3-year history of urinalysis abnormalities without clinical evidence of diabetic mellitus. The patient's leg edema progressively worsened over the previous 2 years, and he was admitted to our hospital. Renal biopsy showed mesangial expansion with diabetic Kimmelstiel-Wilson-like nodular lesions, glomerular basement thickening, and arteriosclerosis. No electron-dense deposits, fibrils, or microtubule deposits were seen in the glomeruli on electron microscopy. Skin AGE level measured using AGE reader was higher in this case than the average level in age-matched Caucasians. In addition, immunohistochemical analysis revealed that N-carboxymethyl lysine, one of the major AGEs, and RAGE were overexpressed and podocin expression was decreased in the peripheral area of the glomerular nodular lesions. These observations suggest that AGEs-RAGE system may be activated in smoking-related ING, possibly leading to the progression of renal dysfunction.

Activation of the AGE/RAGE system in the brains of rats and in SH-SY5Y cells exposed to high level of fluoride might connect to oxidative stress

To explore the mechanisms by which chronic fluorosis damages the brain, we determined the levels of the advanced glycation end-products (AGEs), the receptor for AGE (RAGE), NADPH oxidase-2 (NOX2), reactive oxygen species (ROS) and malondialdehyde (MDA) in the brains of rats and/or SH-SY5Y cells exposed to different levels of sodium fluoride (5 or 50 ppm in the drinking water for 3 or 6 months and in the incubation medium for as long as 48 h, respectively). The levels of AGEs, RAGE and NOX2 protein and mRNA were measured by an Elisa assay, Western blotting and real-time PCR, respectively. The ROS content was assessed by fluorescein staining and MDA by thiobarbituric acid-reactive substance assay. In comparison to the unexposed controls, the protein and mRNA levels of AGEs, RAGE and NOX2 in the brains of rats after 6 months of exposure and in SH-SY5Y cells following high-dose exposure to fluoride were elevated. In contrast, no significant changes in these parameters were detected in the rats exposed for 3 months. In addition, the levels of ROS and MDA in the SH-SY5Y cells exposed to high-dose of fluoride were elevated in a manner that correlated positively with the levels of AGE/RAGE. In conclusion, our present results indicate that excessive fluoride can activate the AGE/RAGE pathway, which might in turn enhance oxidative stress.

Lycopene supplementation reduces TNF-α via RAGE in the kidney of obese rats

Background:

The kidney is a target organ for injuries caused by advanced glycation end products (AGEs) in obesity. The receptor of AGEs (RAGE) is proinflammatory and appears to have a role in the pathogenesis of renal disease due to obesity.

Objective:

The aim was to verify the effect of obesity on renal damage and the effect of lycopene on these complications

Design and Methods:

Male Wistar rats were randomly assigned to receive a control diet (C, n=7) or a high-fat diet plus sucrose (HD+S, n=14) for 6 weeks. After this period, the HD+S animals were randomized into two groups: HD+S (n=7) and HD+S supplemented with lycopene (HD+S+L, n=7). The animals received maize oil (C and HD+S) or lycopene (HD+S+L) for a 6-week period.

Results:

The HD+S and HD+S+L animals demonstrated insulin resistance (OGTT glucose after 150 min; C: 117.6±3.9<HD+S: 138.1±5.1=HD+S+L: 137.8±5.2 mg dl⁻¹; P=0.01); however, no changes were seen in fasting glucose, plasma lipids, blood pressure or renal function. Renal concentrations of RAGE and TNF-α increased in the HD+S group and lycopene supplementation restored these to control group values (RAGE: C: 3.1±0.3=DH+S+L: 3.1±0.3<DH+S: 3.6±0.4 μg g⁻¹; P=0.014; TNF-α: C: 227.8±2.7=DH+S+L: 227.4±2.2<DH+S: 238.7±3.0 pg/ml; P=0.014).

Conclusions:

Lycopene may be beneficial in the prevention and treatment of oxidative stress and inflammation in the kidney due to obesity.

Purple sweet potato color ameliorates kidney damage via inhibiting oxidative stress mediated NLRP3 inflammasome activation in high fat diet mice

Inflammation plays a crucial role in the pathogenesis of obesity. Purple sweet potato color (PSPC) has potential anti-inflammation efficacy. We evaluated the effect of PSPC on kidney injury induced by high fat diet (HFD) and explored the mechanism underlying these effects. The results showed that PSPC (700 mg/kg per day) reduced body weight, ratio of urine albumin to creatinine, inflammatory cell infiltration, and Collagen IV accumulation in mice fed an HFD (60% fat food) for 20 weeks. PSPC significantly reduced the expression level of kidney NLRP3 inflammasome including NLRP3 and ASC and Caspase-1, and resulted in decline of IL-1β. Moreover, PSPC inhibited the activation of I kappa B kinase β (IKKβ) and the nuclear translocation of nuclear factor kappa beta (NF-κB). Additionally, PSPC decreased the expression level of oxidative stress-associated AGE receptor (RAGE) and thioredoxin interacting protein (TXNIP) in the upstream of NLRP3 inflammasome. These data imply that the beneficial effects of PSPC on HFD-induced kidney dysfunction and damage are mediated through NLRP3 signaling pathways, suggesting a potential target for the prevention of obesity.

Supplementation with a juice powder concentrate and exercise decrease oxidation and inflammation, and improve the microcirculation in obese women: randomised controlled trial data

Obesity and sedentary lifestyle are associated with increased oxidative stress, inflammation and vessel dysfunction. Previous research has shown that an encapsulated fruit/berry/vegetable juice powder (FBV) supplement or controlled exercise training improve the markers of redox biology, low-grade inflammation and circulation. The aim of the present study was to assess the effects of 8 weeks of supplementation with FBV or placebo, and a single bout of controlled walking on the markers of oxidation, inflammation and skin capillary microcirculation in forty-two obese pre-menopausal women (41 (SD 5) years, non-smokers and BMI 34·5 (SD 3·8) kg/m(2)) using a randomised, double-blind, placebo-controlled design. All assessments were made before and after 8 weeks of capsule supplementation, and pre- and post-30 min of controlled treadmill walking at 70 % of VO2max. Venous blood was collected for the determination of carbonyl proteins (CP), oxidised LDL (ox-LDL), total oxidation status (TOS) of lipids, malondialdehyde, TNF-α and IL-6. Capillary blood flow, O2 saturation of Hb (SO2Hb) and the relative concentration of Hb (rHb) were assessed at a 2 mm skin depth. Following 8 weeks of supplementation, compared with placebo, the FBV group had a significant (P< 0·05) reduction in CP, ox-LDL, TOS and TNF-α, and a significant increase in blood flow, SO2Hb and rHb. Independent of supplementation, moderate exercise significantly increased blood flow and rHb, with a trend towards increased SO2Hb. Compared with placebo, 8 weeks of supplementation with FBV decreased the markers of systemic oxidation and inflammation. Both FBV supplementation and a single walking bout improved the markers of the microcirculation in these obese women.

IL-1β, RAGE and FABP4: targeting the dynamic trio in metabolic inflammation and related pathologies

Within the past decade, inflammatory and lipid mediators, such as IL-1β, FABP4 and RAGE, have emerged as important contributors to metabolic dysfunction. As growing experimental and clinical evidence continues to tie obesity-induced chronic inflammation with dysregulated lipid, insulin signaling and related pathologies, IL-1β, FABP4 and RAGE each are being independently implicated as culprits in these events. There are also convincing data that molecular pathways driven by these molecules are interconnected in exacerbating metabolic consequences of obesity. This article highlights the roles of IL-1β, FABP4 and RAGE in normal physiology as well as focusing specifically on their contribution to inflammation, insulin resistance, atherosclerosis, Type 2 diabetes and cancer. Studies implicating the interconnection between these pathways, current and emerging therapeutics, and their use as potential biomarkers are also discussed. Evidence of impact of IL-1β, FABP4 and RAGE pathways on severity of metabolic dysfunction underlines the strong links between inflammatory events, lipid metabolism and insulin regulation, and offers new intriguing approaches for future therapies of obesity-driven pathologies.

Radical roles for RAGE in the pathogenesis of oxidative stress in cardiovascular diseases and beyond

Oxidative stress is a central mechanism by which the receptor for advanced glycation endproducts (RAGE) mediates its pathological effects. Multiple experimental inquiries in RAGE-expressing cultured cells have demonstrated that ligand-RAGE interaction mediates generation of reactive oxygen species (ROS) and consequent downstream signal transduction and regulation of gene expression. The primary mechanism by which RAGE generates oxidative stress is via activation of NADPH oxidase; amplification mechanisms in the mitochondria may further drive ROS production. Recent studies indicating that the cytoplasmic domain of RAGE binds to the formin mDia1 provide further support for the critical roles of this pathway in oxidative stress; mDia1 was required for activation of rac1 and NADPH oxidase in primary murine aortic smooth muscle cells treated with RAGE ligand S100B. In vivo, in multiple distinct disease models in animals, RAGE action generates oxidative stress and modulates cellular/tissue fate in range of disorders, such as in myocardial ischemia, atherosclerosis, and aneurysm formation. Blockade or genetic deletion of RAGE was shown to be protective in these settings. Indeed, beyond cardiovascular disease, evidence is accruing in human subjects linking levels of RAGE ligands and soluble RAGE to oxidative stress in disorders such as doxorubicin toxicity, acetaminophen toxicity, neurodegeneration, hyperlipidemia, diabetes, preeclampsia, rheumatoid arthritis and pulmonary fibrosis. Blockade of RAGE signal transduction may be a key strategy for the prevention of the deleterious consequences of oxidative stress, particularly in chronic disease.

Croix CM, Watkins SC, Fleming AM, Champion HC, Mason RP, Freeman BA, Kelley EE. Obesity-induced tissue free radical generation: an in vivo immuno-spin trapping study

Assessment of tissue free radical production is routinely accomplished by measuring secondary by-products of redox reactions and/or diminution of key antioxidants such as reduced thiols. However, immuno-spin trapping, a newly developed immunohistochemical technique for detection of free radical formation, is garnering considerable interest as it allows for the visualization of 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-adducted molecules. Yet, to date, immuno-spin trapping reports have utilized in vivo models in which successful detection of free radical adducts required exposure to lethal levels of oxidative stress not reflective of chronic inflammatory disease. To study the extents and anatomic locations of more clinically relevant levels of radical formation, we examined tissues from high-fat (HF) diet-fed mice, a model of low-grade chronic inflammation known to demonstrate enhanced rates of reactive species production. Mice subjected to 20 weeks of HF diet displayed increased free radical formation (anti-DMPO mean fluorescence staining) in skeletal muscle (0.863±0.06 units vs 0.512±0.07 units), kidney (0.076±0.0036 vs 0.043±0.0025), and liver (0.275±0.012 vs 0.135±0.014) compared to control mice fed normal laboratory chow (NC). Western blot analysis of tissue homogenates confirmed these results showing enhanced DMPO immunoreactivity in HF mice compared to NC samples. The obesity-related results were confirmed in a rat model of pulmonary hypertension and right heart failure in which intense immunodetectable radical formation was observed in the lung and right ventricle of monocrotaline-treated rats compared to saline-treated controls. Combined, these data affirm the utility of immuno-spin trapping as a tool for in vivo assessment of altered extents of macromolecule oxidation to radical intermediates under chronic inflammatory conditions.