RAGE Inhibitors as Alternatives to Dexamethasone for Managing Cerebral Edema Following Brain Tumor Surgery

Resection of brain tumors frequently causes injury to the surrounding brain tissue that exacerbates cerebral edema by activating an inflammatory cascade. Although corticosteroids are often utilized peri-operatively to alleviate the symptoms associated with brain edema, they increase operative morbidities and suppress the efficacy of immunotherapy. Thus, novel approaches to minimize cerebral edema caused by neurosurgical procedures will have significant utility in the management of patients with brain tumors. We have studied the role of the receptor for advanced glycation end products (RAGE) and its ligands on inflammatory responses to neurosurgical injury in mice and humans. Blood-brain barrier (BBB) integrity and neuroinflammation were characterized by Nanostring, flow cytometry, qPCR, and immunoblotting of WT and RAGE knockout mice brains subjected to surgical brain injury (SBI). Human tumor tissue and fluid collected from the resection cavity of patients undergoing craniotomy were also analyzed by single-cell RNA sequencing and ELISA. Genetic ablation of RAGE significantly abrogated neuroinflammation and BBB disruption in the murine SBI model. The inflammatory responses to SBI were associated with infiltration of S100A9-expressing myeloid-derived cells into the brain. Local release of pro-inflammatory S100A9 was confirmed in patients following tumor resection. RAGE and S100A9 inhibitors were as effective as dexamethasone in attenuating neuroinflammation. However, unlike dexamethasone and S100A9 inhibitor, RAGE inhibition did not diminish the efficacy of anti-PD-1 immunotherapy in glioma-bearing mice. These observations confirm the role of the RAGE axis in surgically induced neuroinflammation and provide an alternative therapeutic option to dexamethasone in managing post-operative cerebral edema.

Impairing RAGE signaling promotes survival and limits disease pathogenesis following SARS-CoV-2 infection in mice

Cellular and molecular mechanisms driving morbidity following SARS-CoV-2 infection have not been well defined. The receptor for advanced glycation end products (RAGE) is a central mediator of tissue injury and contributes to SARS-CoV-2 disease pathogenesis. In this study, we temporally delineated key cell and molecular events leading to lung injury in mice following SARS-CoV-2 infection and assessed efficacy of therapeutically targeting RAGE to improve survival. Early following infection, SARS-CoV-2 replicated to high titers within the lungs and evaded triggering inflammation and cell death. However, a significant necrotic cell death event in CD45^– populations, corresponding with peak viral loads, was observed on day 2 after infection. Metabolic reprogramming and inflammation were initiated following this cell death event and corresponded with increased lung interstitial pneumonia, perivascular inflammation, and endothelial hyperplasia together with decreased oxygen saturation. Therapeutic treatment with the RAGE antagonist FPS-ZM1 improved survival in infected mice and limited inflammation and associated perivascular pathology. Together, these results provide critical characterization of disease pathogenesis in the mouse model and implicate a role for RAGE signaling as a therapeutic target to improve outcomes following SARS-CoV-2 infection.

RAGE signaling antagonist suppresses mouse macrophage foam cell formation

The engagement of the receptor for advanced glycation end-products (receptor for AGEs, RAGE) with diverse ligands could elicit chronic vascular inflammation, such as atherosclerosis. Binding of cytoplasmic tail RAGE (ctRAGE) to diaphanous-related formin 1 (Diaph1) is known to yield RAGE intracellular signal transduction and subsequent cellular responses. However, the effectiveness of an inhibitor of the ctRAGE/Diaph1 interaction in attenuating the development of atherosclerosis is unclear. In this study, using macrophages from Ager+/+ and Ager-/- mice, we validated the effects of an inhibitor on AGEs-RAGE-induced foam cell formation. The inhibitor significantly suppressed AGEs-RAGE-evoked Rac1 activity, cell invasion, and uptake of oxidized low-density lipoprotein, as well as AGEs-induced NF-κB activation and upregulation of proinflammatory gene expression. Moreover, expression of Il-10, an anti-inflammatory gene, was restored by this antagonist. These findings suggest that the RAGE-Diaph1 inhibitor could be a potential therapeutic drug against RAGE-related diseases, such as chronic inflammation and atherosclerosis.

Targeting RAGE to prevent SARS-CoV-2-mediated multiple organ failure: Hypotheses and perspectives

A novel infectious disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was detected in December 2019 and declared as a global pandemic by the World Health. Approximately 15% of patients with COVID-19 progress to severe pneumonia and eventually develop acute respiratory distress syndrome (ARDS), septic shock and/or multiple organ failure with high morbidity and mortality. Evidence points towards a determinant pathogenic role of members of the renin-angiotensin system (RAS) in mediating the susceptibility, infection, inflammatory response and parenchymal injury in lungs and other organs of COVID-19 patients. The receptor for advanced glycation end-products (RAGE), a member of the immunoglobulin superfamily, has important roles in pulmonary pathological states, including fibrosis, pneumonia and ARDS. RAGE overexpression/hyperactivation is essential to the deleterious effects of RAS in several pathological processes, including hypertension, chronic kidney and cardiovascular diseases, and diabetes, all of which are major comorbidities of SARS-CoV-2 infection. We propose RAGE as an additional molecular target in COVID-19 patients for ameliorating the multi-organ pathology induced by the virus and improving survival, also in the perspective of future infections by other coronaviruses.

Lipopolysaccharides induce a RAGE-mediated sensitization of sensory neurons and fluid hypersecretion in the upper airways

Thoracic dorsal root ganglia (tDRG) contribute to fluid secretion in the upper airways. Inflammation potentiates DRG responses, but the mechanisms remain under investigation. The receptor for advanced glycation end-products (RAGE) underlies potentiation of DRG responses in pain pathologies; however, its role in other sensory modalities is less understood. We hypothesize that RAGE contributes to electrophysiological and biochemical changes in tDRGs during inflammation. We used tDRGs and tracheas from wild types (WT), RAGE knock-out (RAGE-KO), and with the RAGE antagonist FPS-ZM1, and exposed them to lipopolysaccharides (LPS). We studied: capsaicin (CAP)-evoked currents and action potentials (AP), tracheal submucosal gland secretion, RAGE expression and downstream pathways. In WT neurons, LPS increased CAP-evoked currents and AP generation, and it caused submucosal gland hypersecretion in tracheas from WT mice exposed to LPS. In contrast, LPS had no effect on tDRG excitability or gland secretion in RAGE-KO mice or mice treated with FPS-ZM1. LPS upregulated full-length RAGE (encoded by Tv1-RAGE) and downregulated a soluble (sRAGE) splice variant (encoded by MmusRAGEv4) in tDRG neurons. These data suggest that sensitization of tDRG neurons contributes to hypersecretion in the upper airways during inflammation. And at least two RAGE variants may be involved in these effects of LPS.

Increased Expression of S100B and RAGE in a Mouse Model of Bile Duct Ligation-induced Liver Fibrosis

BACKGROUND

Liver fibrosis is defined as the accumulation of the extracellular matrix and scar formation. The receptor for advanced glycation end products (RAGE) has been demonstrated to participate in fibrogenesis. S100B is a ligand of RAGE and exerts extracellular functions by inducing a series of signal transduction cascades. However, the involvement of S100B and RAGE in cholestasis-induced liver fibrosis remains unclear. In this study, we investigated S100B and RAGE expression during liver fibrosis in mice that underwent common bile duct ligation (BDL).

METHODS

BDL was performed in 10-week-old male C57BL/6J mice with sham control (n = 26) and BDL (n = 26) groups. Expression levels of S100B, RAGE and fibrotic markers in the livers from both groups at week 1 and 3 after BDL were examined by western blot and quantitative real-time reverse transcription polymerase chain reaction analysis. Liver fibrotic changes were examined by histological and ultrastructural analysis.

RESULTS

Histological staining with Sirius Red and the evaluation of the messenger RNA expression of fibrotic markers showed noticeable periportal fibrosis and bile duct proliferation. S100B was mainly present in bile duct epithelial cells, and its expression was upregulated in proportion to the ductular reaction during fibrogenesis by BDL. RAGE expression was also increased, and interestingly, triple immunofluorescence staining and transmission electron microscopy showed that both S100B and RAGE were expressed in proliferating bile duct epithelial cells and activated hepatic stellate cells (HSCs) of the BDL livers. In addition, in rat HSCs (HSC-T6), treatment with recombinant S100B protein significantly increased fibrotic markers in a dose-dependent manner, and RAGE small interfering RNA (siRNA) suppressed S100B-stimulated upregulation of fibrotic markers compared with cells treated with scramble siRNA and S100B.

CONCLUSION

These findings suggest that the increased expression of S100B and RAGE and the interaction between S100B and RAGE may play an important role in ductular reaction and liver fibrosis induced by BDL.

Magic Peptide: Unique Properties of the LRR11 Peptide in the Activation of Leukotriene Synthesis in Human Neutrophils

Neutrophil-mediated innate host defense mechanisms include pathogen elimination through bacterial phagocytosis, which activates the 5-lipoxygenase (5-LOX) product synthesis. Here, we studied the effect of synthetic oligodeoxyribonucleotides (ODNs), which mimic the receptor-recognized sites of bacterial (CpG-ODNs) and genomic (G-rich ODNs) DNAs released from the inflammatory area, on the neutrophil functions after cell stimulation with Salmonella typhimurium. A possible mechanism for ODN recognition by Toll-like receptor 9 (TLR9) and RAGE receptor has been proposed. We found for the first time that the combination of the magic peptide LRR11 from the leucine-rich repeat (LRR) of TLR9 with the CpG-ODNs modulates the uptake and signaling from ODNs, in particular, dramatically stimulates 5-LOX pathway. Using thickness shear mode acoustic method, we confirmed the specific binding of CpG-ODNs, but not G-rich ODN, to LRR11. The RAGE receptor has been shown to play an important role in promoting ODN uptake. Thus, FPS-ZM1, a high-affinity RAGE inhibitor, suppresses the synthesis of 5-LOX products and reduces the uptake of ODNs by neutrophils; the inhibitor effect being abolished by the addition of LRR11. The results obtained revealed that the studied peptide-ODN complexes possess high biological activity and can be promising for the development of effective vaccine adjuvants and antimicrobial therapeutics.

DNA aptamer raised against receptor for advanced glycation end products suppresses renal tubular damage and improves insulin resistance in diabetic mice

OBJECTIVE

Interaction of advanced glycation end products (AGEs) with the receptor RAGE plays a role in diabetic nephropathy. However, effects of RAGE-aptamer on tubular damage remain unknown. We examined whether RAGE-aptamer inhibited tubular damage in KKAy/Ta mice, obese type 2 diabetic mice with insulin resistance.

MATERIALS AND METHODS

Male 8-week-old KKAy/Ta mice received continuous intraperitoneal infusion of either control-aptamer or RAGE-aptamer for 8 weeks. Blood biochemistry and blood pressure, and urinary N-acetyl-β-D-glucosaminidase (NAG) activity and albumin excretion levels were monitored. Kidney and adipose tissue samples were obtained for immunohistochemical analyses.

RESULTS

Although RAGE-aptamer did not affect blood glucose, blood pressure, body weight, or serum creatinine values, it significantly inhibited the increase in urinary NAG activity and HOMA-IR in diabetic mice at 12 and 16 and at 16 weeks old, respectively. Furthermore, compared with control-aptamer-treated mice, renal carboxymethyllysine, RAGE, and NADPH oxidase-driven superoxide generation were significantly decreased in RAGE-aptamer-treated mice at 12 weeks old with subsequent amelioration of histological alterations in glomerular and interstitial area, while adipose tissue adiponectin expression was increased.

CONCLUSION

Our present results suggest that RAGE-aptamer could inhibit tubular injury in obese type 2 diabetic mice partly by suppressing the AGE-RAGE-oxidative stress axis and improving insulin resistance.

Receptor for Advanced Glycation End Products (RAGE) Mediates Cognitive Impairment Triggered by Pneumococcal Meningitis

Pneumococcal meningitis is a life-threatening infection of the central nervous system (CNS), and half of the survivors of meningitis suffer from neurological sequelae. We hypothesized that pneumococcal meningitis causes CNS inflammation via the disruption of the blood-brain barrier (BBB) and by increasing the receptor for advanced glycation end product (RAGE) expression in the brain, which causes glial cell activation, leading to cognitive impairment. To test our hypothesis, 60-day-old Wistar rats were subjected to meningitis by receiving an intracisternal injection of Streptococcus pneumoniae or artificial cerebrospinal fluid as a control group and were treated with a RAGE-specific inhibitor (FPS-ZM1) in saline. The rats also received ceftriaxone 100 mg/kg intraperitoneally, bid, and fluid replacements. Experimental pneumococcal meningitis triggered BBB disruption after meningitis induction, and FPS-ZM1 treatment significantly suppressed BBB disruption. Ten days after meningitis induction, surviving animals were free from infection, but they presented increased levels of TNF-α and IL-1β in the prefrontal cortex (PFC); high expression levels of RAGE, amyloid-β (Aβ1-42), and microglial cell activation in the PFC and hippocampus; and memory impairment, as evaluated by the open-field, novel object recognition task and Morris water maze behavioral tasks. Targeted RAGE inhibition was able to reduce cytokine levels, decrease the expression of RAGE and Aβ1-42, inhibit microglial cell activation, and improve cognitive deficits in meningitis survivor rats. The sequence of events generated by pneumococcal meningitis can persist long after recovery, triggering neurocognitive decline; however, RAGE blocker attenuated the development of brain inflammation and cognitive impairment in experimental meningitis.

JNK modulates RAGE/β-catenin signaling and is essential for allergic airway inflammation in asthma

As a leading cause of occupational asthma, toluene diisocyanate (TDI)-induced asthma is an inflammatory disease of the airways with one of the most significant characteristics involving inflammation, in which the receptor of advanced glycation end products (RAGE) plays an extremely important role. However, the mechanism underlying the upregulation of RAGE is still unknown. The aim of the present study was to examine whether JNK mediates β-catenin stabilization via activation of RAGE in asthma. Herein from the results by analyzing the blood from healthy donors and patients with asthma, it was found that the expression of RAGE and p-JNK is highly correlated and elevated concomitantly with the severity of bronchial asthma. Additionally, upon sensitizing and challenging the mice with TDI, we found that RAGE inhibitor (FPS-ZM1) and JNK inhibitor (SP600125) significantly reduced the TDI-induced asthma inflammation in vivo. Furthermore, SP600125 also considerably restored RAGE and p-JNK expression. Besides, the in vitro results from TDI-HSA treatment of 16HBE cells reveal that therapeutic inhibition of JNK reduced TDI driving RAGE expression and β-catenin translocation, while treatment with Anisomycin, a JNK agonist, showed the opposite effect. Moreover, genetic knockdown of RAGE does not contribute to JNK phosphorylation, indicating that JNK functions upstream of RAGE. Collectively, these findings highlight a role for JNK signaling in RAGE/β-catenin regulation and have important therapeutic implications for the treatment of TDI induced asthma.

The Development of Maillard Reaction, and Advanced Glycation End Product (AGE)-Receptor for AGE (RAGE) Signaling Inhibitors as Novel Therapeutic Strategies for Patients with AGE-Related Diseases

Advanced glycation end products (AGEs) are generated by nonenzymatic modifications of macromolecules (proteins, lipids, and nucleic acids) by saccharides (glucose, fructose, and pentose) via Maillard reaction. The formed AGE molecules can be catabolized and cleared by glyoxalase I and II in renal proximal tubular cells. AGE-related diseases include physiological aging, neurodegenerative/neuroinflammatory diseases, diabetes mellitus (DM) and its complications, autoimmune/rheumatic inflammatory diseases, bone-degenerative diseases, and chronic renal diseases. AGEs, by binding to receptors for AGE (RAGEs), alter innate and adaptive immune responses to induce inflammation and immunosuppression via the generation of proinflammatory cytokines, reactive oxygen species (ROS), and reactive nitrogen intermediates (RNI). These pathological molecules cause vascular endothelial/smooth muscular/connective tissue-cell and renal mesangial/endothelial/podocytic-cell damage in AGE-related diseases. In the present review, we first focus on the cellular and molecular bases of AGE–RAGE axis signaling pathways in AGE-related diseases. Then, we discuss in detail the modes of action of newly discovered novel biomolecules and phytochemical compounds, such as Maillard reaction and AGE–RAGE signaling inhibitors. These molecules are expected to become the new therapeutic strategies for patients with AGE-related diseases in addition to the traditional hypoglycemic and anti-hypertensive agents. We particularly emphasize the importance of “metabolic memory”, the “French paradox”, and the pharmacokinetics and therapeutic dosing of the effective natural compounds associated with pharmacogenetics in the treatment of AGE-related diseases. Lastly, we propose prospective investigations for solving the enigmas in AGE-mediated pathological effects.

RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin

We addressed the involvement of the receptor for advanced glycation end products (RAGE) in the impairment of the cellular cholesterol efflux elicited by glycated albumin. Albumin was isolated from type 1 (DM1) and type 2 (DM2) diabetes mellitus (HbA1c > 9%) and non-DM subjects (C). Moreover, albumin was glycated in vitro (AGE-albumin). Macrophages from Ager null and wild-type (WT) mice, or THP-1 transfected with siRNA-AGER, were treated with C, DM1, DM2, non-glycated or AGE-albumin. The cholesterol efflux was reduced in WT cells exposed to DM1 or DM2 albumin as compared to C, and the intracellular lipid content was increased. These events were not observed in Ager null cells, in which the cholesterol efflux and lipid staining were, respectively, higher and lower when compared to WT cells. In WT, Ager, Nox4 and Nfkb1, mRNA increased and Scd1 and Abcg1 diminished after treatment with DM1 and DM2 albumin. In Ager null cells treated with DM-albumin, Nox4, Scd1 and Nfkb1 were reduced and Jak2 and Abcg1 increased. In AGER-silenced THP-1, NOX4 and SCD1 mRNA were reduced and JAK2 and ABCG1 were increased even after treatment with AGE or DM-albumin. RAGE mediates the deleterious effects of AGE-albumin in macrophage cholesterol efflux.

Inhibition of RAGE by FPS-ZM1 alleviates renal injury in spontaneously hypertensive rats

The current study was designed to examine the protection of RAGE-specific inhibitor FPS-ZM1 against renal injury in spontaneously hypertensive rats (SHR) and investigate the underlying mechanism. The adult male SHR were treated with FPS-ZM1 via oral gavages for 12 weeks, and age-matched male Wistar-Kyoto rats (WKY) were used as control. Treatment of SHR with FPS-ZM1 slightly reduced blood pressure, and significantly improved baroreflex sensitivity in SHR. Treatment of SHR with FPS-ZM1 improved renal function, evidenced by increased glomerular filtration rate and renal blood flow, and reduced plasma creatinine, blood urea nitrogen and urine albumin excretion rate. Histology results revealed that treatment of SHR with FPS-ZM1 alleviated renal injury and reduced tubulointerstitial fibrosis. Treatment of SHR with FPS-ZM1 suppressed activation of NF-κB and reduced expression of pro-inflammatory cytokines including Tnf, Il6, and Il1b. Treatment of SHR with FPS-ZM1 abated oxidative stress and downregulated mRNA levels of components of NADPH oxidase (Nox) including Cyba, Nox1, Nox2, Nox4 and Ncf1 in kidneys. In addition, treatment of SHR with FPS-ZM1 reduced renal AngII levels, downregulated mRNA expression of Ace and upregulated expression of Agtr2. In conclusion, treatment with FPS-ZM1 alleviated hypertension-related renal dysfunction, possibly by suppressing NF-κB-mediated inflammation, abating Nox-mediated oxidative stress, and improving local renal renin-angiotensin system (RAS).

Pyrogallol-Phloroglucinol-6,6-Bieckol Alleviates Obesity and Systemic Inflammation in a Mouse Model by Reducing Expression of RAGE and RAGE Ligands

Ecklonia cava (E. cava) can alleviate diet-induced obesity in animal models, and phlorotannins contained in E. cava help prevent hypertrophy-induced adipocyte differentiation. Receptor for advanced glycation end-products (RAGE) is well known to induce hypertrophy of visceral fat and to trigger inflammation substantially. While the relationship between RAGE and obesity and inflammation has been well-characterized, few studies describe the effects of phlorotannin on RAGE. In this study, we investigated the anti-obesity effects of pyrogallol-phloroglucinol-6,6-bieckol (PPB)-a single compound from the ethanoic extract of E. cava-mediated by a reduction in the inflammation caused by RAGE and RAGE ligands. In visceral fat, PPB (i) significantly inhibited RAGE ligands, (ii) reduced the expression of RAGE, and (iii) reduced the binding ratio between RAGE and RAGE ligands. Under lower expression of RAGE, RAGE ligands and their cognate binding, the differentiation of macrophages found in visceral fat into M1-type-the pro-inflammatory form of this immune cell-was reduced. As the M1-type macrophage decreased, pro-inflammatory cytokines, which cause obesity, decreased in visceral fat. The results of this study highlight the anti-obesity effects of PPB, with the effects mediated by reductions in RAGE, RAGE ligands, and inflammation.

Short-term pharmacologic RAGE inhibition differentially affects bone and skeletal muscle in middle-aged mice

Loss of bone and muscle mass are two major clinical complications among the growing list of chronic diseases that primarily affect elderly individuals. Persistent low-grade inflammation, one of the major drivers of aging, is also associated with both bone and muscle dysfunction in aging. Particularly, chronic activation of the receptor for advanced glycation end products (RAGE) and elevated levels of its ligands high mobility group box 1 (HMGB1), AGEs, S100 proteins and Aβ fibrils have been linked to bone and muscle loss in various pathologies. Further, genetic or pharmacologic RAGE inhibition has been shown to preserve both bone and muscle mass. However, whether short-term pharmacologic RAGE inhibition can prevent early bone and muscle loss in aging is unknown. To address this question, we treated young (4-mo) and middle-aged (15-mo) C57BL/6 female mice with vehicle or Azeliragon, a small-molecule RAGE inhibitor initially developed to treat Alzheimer's disease. Azeliragon did not prevent the aging-induced alterations in bone geometry or mechanics, likely due to its differential effects [direct vs. indirect] on bone cell viability/function. On the other hand, Azeliragon attenuated the aging-related body composition changes [fat and lean mass] and reversed the skeletal muscle alterations induced with aging. Interestingly, while Azeliragon induced similar metabolic changes in bone and skeletal muscle, aging differentially altered the expression of genes associated with glucose uptake/metabolism in these two tissues, highlighting a potential explanation for the differential effects of Azeliragon on bone and skeletal muscle in middle-aged mice. Overall, our findings suggest that while short-term pharmacologic RAGE inhibition did not protect against early aging-induced bone alterations, it prevented against the early effects of aging in skeletal muscle.

Novel findings of 18β-glycyrrhetinic acid on sRAGE secretion through inhibition of transient receptor potential canonical channels in high-glucose environment

Enhancing soluble receptor for advanced glycation endproducts (sRAGE) is considered as a potent strategy for diabetes therapy. sRAGE secretion is regulated by calcium and transient receptor potential canonical (TRPC) channels. However, the role of TRPC channels in diabetes remains unknown. 18β-Glycyrrhetinic acid (18β-GA), produced from liquorice, has shown antidiabetic properties. This study was aimed to investigate the effect of 18β-GA on sRAGE secretion via TRPC channels in high glucose (HG)-induced THP-1 cells. HG treatment enhanced TRPC3 and TRPC6 expression and consequently caused reactive oxygen species (ROS) accumulation mediated through p47 nicotinamide-adenine dinucleotide phosphate oxidase and inducible nitric oxide synthase (iNOS) associated with uncoupling protein 2 (UCP2) decline and lower sRAGE secretion. Interestingly, 18β-GA showed the dramatic effects similar to Pyr3 or 2-aminoethyl diphenyl borinate inhibitors and effectively reversed HG-elicited mechanisms including that blocking TRPC3 and TRPC6 protein expressions, suppressing intracellular [Ca2+] concentration, decreasing expressions of ROS, p47s, and iNOS, but increasing UCP2 level and promoting sRAGE secretion. Therefore, 18β-GA provides a potential implication to diabetes mellitus and its complications.

Papaverine identified as an inhibitor of high mobility group box 1/receptor for advanced glycation end-products interaction suppresses high mobility group box 1-mediated inflammatory responses

The interaction of high mobility group box 1 (HMGB1), which is secreted from immune and dying cells during cellular infection and injury, and receptor for advanced glycation end-products (RAGE) appears to be critical for acute and chronic inflammatory disorders. Here we designed a unique cyclic β-hairpin peptide (Pepb2), which mimics the predicted RAGE-binding domain of HMGB1. Pepb2 competitively inhibited HMGB1/RAGE interaction. We then identified papaverine as a Pepb2 mimetic by in silico 3D-structural similarity screening from the DrugBank library. Papaverine was found to directly inhibit HMGB1/RAGE interaction. It also suppressed the HMGB1-mediated production of pro-inflammatory cytokines, IL-6 and TNF-α, in mouse macrophage-like RAW264.7 cells and bone marrow-derived macrophages. In addition, papaverine attenuated mortality in cecal ligation puncture-induced sepsis model mice. Taken together, these findings indicate that papaverine could become a useful therapeutic against HMGB1/RAGE-mediated sepsis and other inflammatory diseases.

Inhibition of RAGE Axis Signaling: A Pharmacological Challenge

The Receptor for Advanced Glycation End Products (RAGE) is an important cell surface receptor, which belongs to the IgG super family and is now considered as a pattern recognition receptor. Because of its relevance in many human clinical settings, it is now pursued as a very attractive therapeutic target. However, particular features of this receptor such as a wide repertoire of ligands with different binding domains, the existence of many RAGE variants as well as the presence of cytoplasmatic adaptors leading a diverse signaling, are important limitations in the search for successful pharmacological approaches to inhibit RAGE signaling. Therefore, the present review aimed to display the most promising approaches to inhibit RAGE signaling, and provide an up to date review of progress in this area.

Dietary Advanced Glycation Endproducts Induce an Inflammatory Response in Human Macrophages in Vitro

Advanced glycation endproducts (AGEs) can be found in protein- and sugar-rich food products processed at high temperatures, which make up a vast amount of the Western diet. The effect of AGE-rich food products on human health is not yet clear and controversy still exists due to possible contamination of samples with endotoxin and the use of endogenous formed AGEs. AGEs occur in food products, both as protein-bound and individual molecules. Which form exactly induces a pro-inflammatory effect is also unknown. In this study, we exposed human macrophage-like cells to dietary AGEs, both in a protein matrix and individual AGEs. It was ensured that all samples did not contain endotoxin concentrations > 0.06 EU/mL. The dietary AGEs induced TNF-alpha secretion of human macrophage-like cells. This effect was decreased by the addition of N(ε)-carboxymethyllysine (CML)-antibodies or a receptor for advanced glycation endproducts (RAGE) antagonist. None of the individual AGEs induce any TNF-alpha, indicating that AGEs should be bound to proteins to exert an inflammatory reaction. These findings show that dietary AGEs directly stimulate the inflammatory response of human innate immune cells and help us define the risk of regular consumption of AGE-rich food products on human health.

Efficient Expression of an Alzheimer's Disease Vaccine Candidate in the Microalga Schizochytrium sp. Using the Algevir System

Alzheimer's disease (AD) is the most common neurodegenerative disease, where β-amyloid (Aβ) plays a key role in forming conglomerated senile plaques. The receptor of advanced glycation end products (RAGE) is considered a therapeutic target since it transports Aβ into the central nervous system, favoring the pathology progression. Due to the lack of effective therapies for AD, several therapeutic approaches are under development, being vaccines considered a promising alternative. Herein, the use of the Algevir system was explored to produce in the Schizochytrium sp. microalga the LTB:RAGE vaccine candidate. Algevir relies in an inducible geminiviral vector and led to yields of up to 380 µg LTB:RAGE/g fresh weight biomass at 48-h post-induction. The Schizochytrium-produced LTB:RAGE vaccine retained its antigenic activity and was highly stable up to temperatures of 60 °C. These data demonstrate the potential of Schizochytrium sp. as a platform for high production of thermostable recombinant antigens useful for vaccination against AD.

Receptor for Advanced Glycation End-Products (RAGE) Blockade Do Damage to Neuronal Survival via Disrupting Wnt/β-Catenin Signaling in Spinal Cord Injury

Wnt signaling are recognized key factors in neuronal development, cell proliferation and axonal guidance. However, RAGE effect on wnt signaling after spinal cord injury (SCI) are poorly understood. Our study aims to explore RAGE blockade effect on wnt signaling after SCI. We constructed Allen SCI model and micro-injected with RAGE neutralizing antibody or IgG after injury. We determined β-catenin, wnt3a and its receptor frizzled-5 via Western blot. We determined β-catenin/NeuN expression at 2 weeks after SCI via immunofluorescence (IF). We found that β-catenin, wnt3a and wnt receptor frizzled5 expression were activated after SCI at 3 days after injury. However, RAGE blockade inhibit β-catenin, wnt3a and frizzled5 expression. We found that β-catenin accumulation in NeuN cells were activated after SCI via IF, however, RAGE blockade reduced β-catenin and NeuN positive cells. RAGE blockade attenuated number of survived neurons and decreased area of spared white matter around the epicenter. RAGE signaling may involved in disrupting wnt signaling to aids neuronal recovery after SCI.

Exendin-4, a glucagon-like peptide-1 receptor agonist downregulates hepatic receptor for advanced glycation end products in non-alcoholic steatohepatitis rat model

CONTEXT

Exendin-4, a glucagon-like peptide-1 receptor agonist has been shown to have curative effects on hepatic steatosis in murine models.

OBJECTIVE

The present study aimed to elucidate the effect of Exendin-4 on hepatic receptor for advanced glycation end products (RAGE) mRNA expression in non-alcoholic steatohepatitis (NASH) rat model induced by high-fat diet.

METHODS

NASH was induced by high-fat diet intake, and Exendin-4 was given in two different doses. After 12 weeks, liver enzyme levels, hepatic triglycerides, antioxidant enzymes and malondialdehyde (MDA) levels, and mRNA RAGE was detected using RT-PCR.

RESULTS

Exendin-4 in high dose reduced significantly liver enzymes activity, hepatic triglycerides, MDA levels and hepatic mRNA RAGE expression levels with significantly higher antioxidant enzymes activity.

CONCLUSIONS

Our results give further insights into the mechanisms underlying the curative role of Exendin-4 in NASH, suggesting that interference with RAGE may be a useful therapeutic approach to NASH.

Astrocyte´s RAGE: More Than Just a Question of Mood

BACKGROUND

Adequate function of the nervous system depends on the balance of glianeuron complex interactions. Astrocytes, in particular, are key elements in this process due to the significant participation of these cells in essential properties of the nervous system such as neuroinflammation, regulation of neurotransmitters, release of gliotransmitters and control of synaptic plasticity, among others. Astrocytes express the receptor for advanced glycation end products (RAGE) which is very important in the recognition of endogenous molecules released in the context of infection, physiological stress or chronic inflammation. RAGE can bind several advanced glycation end products, S100 proteins, HMGB1, amyloid-β and other additional DAMP molecules. The nuclear factorkappa B (NF-κB) transcription pathway is the main intracellular signaling pathway activated by the RAGE receptor, inducing an increase in the expression and release of proinflammatory cytokines. Due to its numerous interactions, RAGE is suspected to be involved in various physiological and pathological processes.

CONCLUSION

It is plausible that a prolonged exposure to RAGE ligands or abnormally increased concentrations of some ligands may induce lengthy periods of intracellular proinflammatory activation, which may induce the appearance of reactive astrocytes involved in the development and/or progression of neurodegenerative disorders. Blocking or reducing the duration of activation of RAGE/NF-κB signaling in astrocytes may become an important therapeutic alternative for the treatment of neurodegenerative disorders in the future.

The impact of RAGE inhibition in animal models of bacterial sepsis: a systematic review and meta-analysis

Objective To evaluate the impact of inhibition of the receptor for advanced glycation end products (RAGE) on the outcome of bacterial sepsis in animal models. Methods Relevant publications were identified by systematic searches of PubMed, ISI Web of Science and Elsevier-Scopus databases. Results A total of Eleven studies with moderate quality were selected for analysis. A meta-analysis of survival rates revealed a significant advantage of RAGE inhibition in comparison with controls (HR 0.67, 95% CI 0.52-0.86). This effect was most pronounced in polymicrobial infection (HR 0.28, 95% CI 0.14-0.55), followed by Gram positive (G+) bacterial infection (HR 0.70, 95% CI 0.50-0.97) and Gram negative (G-) bacterial infection (HR 0.89, 95% CI 0.58-1.38). For G+ bacterial infection, RAGE inhibition decreased bacterial outgrowth and dissemination, inflammatory cell influx, plasma cytokine levels, and pulmonary injury. Conclusions RAGE inhibition appears to have a beneficial impact on the outcome of sepsis in animal models, although there are discrepancies between different types of infection.

Gamma-linolenic acid ameliorated glycation-induced memory impairment in rats

CONTEXT

γ-Linolenic acid (GLA) is an important constituent of anti-ageing supplements.

OBJECTIVE

The current study investigates the anti-ageing effect of GLA in Sprague-Dawley rats.

MATERIALS AND METHODS

GLA (0.1, 0.2, 0.4, 2, 10, 20 and 24 μM) was initially evaluated for its effect on the formation of advanced glycation end products (AGEs) in vitro. For in vivo assessment (1, 5 or 15 mg/kg), the rat model of accelerated ageing was developed using d-fructose (1000 mg/kg (i.p.) plus 10% in drinking water for 40 days). Morris water maze was used to evaluate impairment in learning and memory. The blood of treated animals was used to measure glycosylated haemoglobin (HbA1c) levels. The interaction of GLA with active residues of receptor of AGE (RAGE) was analyzed using AutoDock Vina.

RESULTS

Our data showed that GLA inhibited the production of AGEs (IC₅₀ = 1.12 ± 0.05 μM). However, this effect was more significant at lower tested doses. A similar pattern was also observed in in vivo experiments, where the effect of fructose was reversed by GLA only at lowest tested dose of 1 mg/kg. The HbA1c levels also revealed significant reduction at lower doses (1 and 5 mg/kg). The in silico data exhibited promising interaction of GLA with active residues (Try72, Arg77 and Gln67) of RAGE.

CONCLUSION

The GLA, at lower doses, possesses therapeutic potential against glycation-induced memory decline.

[Receptor for advanced glycation end products upregulates MUC5AC expression and promotes mucus overproduction in mice with toluene diisocyanate-induced asthma]

OBJECTIVE

To explore the role of the receptor for advanced glycation end products (RAGE) in regulating the expression of MUC5AC and mucus production in a mouse model of toluene diisocyanate (TDI)?induced asthma.

METHODS

BALB/c mice were randomly divided into control group, vehicle (AOO) group, TDI?induced asthma group and RAGE inhibitor (FPS?ZM1) group. PAS staining, Western blotting, and immunohistochemistry were used to analyze the changes in mucus production and MUC5AC expression in the airway of the mice, and the expression of p?ERK was detected with Western blotting. In vitro cultured human bronchial epithelial cell line 16HBE was transfected with lentiviral vector carrying short hairpin RNA targeting RAGE (shRNA?RAGE) and subsequently challenged with a TDI?human serum albumin (TDI-HSA) conjugate, and the changes in cellular MUC5AC mRNA expression as detected using RT-PCR; the protein expressions of ERK and p?ERK in the cells were examined with Western blotting. The effect of ERK inhibitor U0126 pretreatment on MUC5AC mRNA expression was also analyzed in the cells.

RESULTS

Compared with the control mice, TDI-induced asthmatic mice showed significantly higher rates of PAS positivity and increased MUC5AC and p?ERK expressions in the airway (P<0.05). Treatment with FPS?ZM1 significantly decreased PAS positivity and lowered MUC5AC and p?ERK expressions in the airway of the asthmatic mice (P<0.05). Exposure of 16HBE cells to TDI?HSA caused a significant increase in MUC5AC mRNA expression and p?ERK protein expression (P<0.05), while RAGE knockdown obviously suppressed TDI?HSA-induced upregulation of p-ERK and MUC5AC mRNA (P<0.05). Treatment with the ERK inhibitor U0126 also lowered TDI?HSA?induced up?regulation of MUC5AC mRNA in the cells (P<0.05).

CONCLUSION

RAGE signaling induces MUC5AC expression via extracellular signal-regulated kinase pathway to promote mucus overproduction in mice with TDI-induced asthma.

Inhibition of the receptor for advanced glycation end-products (RAGE) protects from secondhand smoke (SHS)-induced intrauterine growth restriction IUGR in mice

Intrauterine growth restriction (IUGR) is a disease affecting 10% of all pregnancies. IUGR is associated with maternal, fetal, or placental abnormalities. Studies investigating the effects of secondhand smoke (SHS) exposure and IUGR are limited. The receptor for advanced glycation end-products (RAGE) is a pro-inflammatory transmembrane receptor increased by SHS in the placenta. We tested the hypothesis that inhibition of RAGE during SHS exposure protects from smoke-induced IUGR. C57BL/6 mice were exposed to SHS or SHS + semi-synthetic glycosaminoglycan ethers (SAGEs) known to inhibit RAGE signaling. Trophoblast cells were treated with cigarette smoke extract (CSE) with or without SAGEs in order to address the effects of RAGE inhibition during trophoblast invasion in vitro. SHS-treated mice demonstrated a significant reduction in fetal weight (7.35-fold, P ≤ 0.0001) and placental weight (1.13-fold, P ≤ 0.0001) compared with controls. Mice co-treated with SHS and SAGEs were protected from SHS-induced fetal weights decreases. SHS treatment of C57BL/6 mice activated placental extracellular signal-regulated kinase (ERK) (3.0-fold, P ≤ 0.05), JNK (2.4-fold, P ≤ 0.05) and p38 (2.1-fold, P ≤ 0.05) and the expression of inflammatory mediators including TNF-α (1.34-fold, P ≤ 0.05) and IL-1β (1.03-fold, P ≤ 0.05). SHS-mediated activation of these molecules was reduced to basal levels when SAGE was co-administered. Invasion of trophoblast cells decreased 92% (P < 0.002) when treated with CSE and CSE-mediated invasion was completely reversed by SAGEs. We conclude that RAGE inhibition protects against fetal weight loss during SHS-induced IUGR. These studies provide insight into tobacco-mediated IUGR development and clarify avenues that may be helpful in the alleviation of placental complications.

Therapeutic Effectiveness of Anti-RAGE Antibody Administration in a Rat Model of Crush Injury

Crush injury patients often have systemic inflammatory response syndrome that leads to multiple organ failure. Receptor for advanced glycation endproducts (RAGE) functions as a pattern recognition receptor that regulates inflammation. We evaluated the effects of anti-RAGE antibody in a crush injury model. Pressure was applied to both hindlimbs of rats for 6 h by 3.0-kg blocks and then released. Animals were randomly divided into the sham (RAGE-Sh) group, crush (RAGE-Ctrl) group or anti-RAGE antibody-treated crush (RAGE-Tx) group. Samples were collected at 3, 6 and 24 h after releasing pressure. In the RAGE-Ctrl group, fluorescent immunostaining in the lung showed upregulated RAGE expression at 3 h. The serum soluble RAGE (sRAGE) level, which reflects the amount of RAGE expression in systemic tissue, increased at 6 h. Serum interleukin 6 (IL-6; systemic inflammation marker) increased immediately at 3 h. Histological analysis revealed lung injury at 6 and 24 h. Administration of anti-RAGE antibody before releasing compression inhibited upregulated RAGE expression in the lung alveoli, suppressed RAGE-associated mediators sRAGE and IL6, attenuated the lung damage and improved the 7-day survival rate. Collectively, our results indicated that the use of anti-RAGE antibody before releasing compression is associated with a favourable prognosis following crush injury.

Targeted inhibition of RAGE in substantia nigra of rats blocks 6-OHDA-induced dopaminergic denervation

The receptor for advanced glycation endproducts (RAGE) is a pattern-recognition receptor associated with inflammation in most cell types. RAGE up-regulates the expression of proinflammatory mediators and its own expression via activation of NF-kB. Recent works have proposed a role for RAGE in Parkinson's disease (PD). In this study, we used the multimodal blocker of RAGE FPS-ZM1, which has become available recently, to selectively inhibit RAGE in the substantia nigra (SN) of rats intracranially injected with 6-hydroxydopamine (6-OHDA). FPS-ZM1 (40 μg per rat), injected concomitantly with 6-OHDA (10 μg per rat) into the SN, inhibited the increase in RAGE, activation of ERK1/2, Src and nuclear translocation of NF-kB p65 subunit in the SN. RAGE inhibition blocked glial fibrillary acidic protein and Iba-1 upregulation as well as associated astrocyte and microglia activation. Circulating cytokines in serum and CSF were also decreased by FPS-ZM1 injection. The loss of tyrosine hydroxylase and NeuN-positive neurons was significantly inhibited by RAGE blocking. Finally, FPS-ZM1 attenuated locomotory and exploratory deficits induced by 6-OHDA. Our results demonstrate that RAGE is an essential component in the neuroinflammation and dopaminergic denervation induced by 6-OHDA in the SN. Selective inhibition of RAGE may offer perspectives for therapeutic approaches.

RAGE-Aptamer Blocks the Development and Progression of Experimental Diabetic Nephropathy

The interaction of advanced glycation end products (AGEs) and their receptor (RAGE) plays a central role in diabetic nephropathy. We screened DNA aptamers directed against RAGE (RAGE-aptamers) in vitro and examined the effects on the development and progression of diabetic nephropathy in streptozotocin-induced diabetic rats. RAGE-aptamer bound to RAGE with a K_d of 5.68 nmol/L and resultantly blocked the binding of AGEs to RAGE. When diabetic rats received continuous intraperitoneal injection of RAGE-aptamer from week 7 to 11 of diabetes, the increases in renal NADPH oxidase activity, oxidative stress generation, AGE, RAGE, inflammatory and fibrotic gene and protein levels, macrophage and extracellular matrix accumulation, and albuminuria were significantly suppressed, which were associated with improvement of podocyte damage. Two-week infusion of RAGE-aptamer just after the induction of diabetes also inhibited the AGE-RAGE-oxidative stress system and MCP-1 levels in the kidneys of 8-week-old diabetic rats and simultaneously ameliorated podocyte injury and albuminuria. Moreover, RAGE-aptamer significantly suppressed the AGE-induced oxidative stress generation and inflammatory and fibrotic reactions in human cultured mesangial cells. The findings suggest that continuous infusion of RAGE-aptamer could attenuate the development and progression of experimental diabetic nephropathy by blocking the AGE-RAGE axis.

Meadowsweet Teas as New Functional Beverages: Comparative Analysis of Nutrients, Phytochemicals and Biological Effects of Four Filipendula Species

In recent years, the increased popularity of functional beverages such as herbal teas and decoctions has led to the search for new sources of raw materials that provide appropriate taste and functionality to consumers. The objective of this study was to investigate the nutritional, phytochemical profiles and bioactivities of possible functional beverages produced from F. ulmaria and its alternative substitutes (F. camtschatica, F. denudata, F. stepposa). The investigated decoctions were analyzed regarding their macronutrient, carbohydrate, organic acid, amino acid and mineral composition. Quantification of the main phenolic compounds in the decoctions of meadowsweet floral teas was performed by a microcolumn RP-HPLC-UV procedure; the highest content was revealed in F. stepposa tea. The investigation of the essential oil of four meadowsweet teas revealed the presence of 28 compounds, including simple phenols, monoterpenes, sesquiterpenes and aliphatic components. The dominance of methyl salicylate and salicylaldehyde was noted in all samples. Studies on the water soluble polysaccharides of Filipendula flowers allowed us to establish their general affiliation to galactans and/or arabinogalactans with an admixture of glucans of the starch type and galacturonans as minor components. The bioactivity data demonstrated a good ability of meadowsweet teas to inhibit amylase, α-glucosidase and AGE formation. Tea samples showed antioxidant properties by the DPPH•, ABTS•+ and Br• free radicals scavenging assays and the carotene bleaching assay, caused by the presence of highly active ellagitannins. The anti-complement activity of the water-soluble polysaccharide fraction of meadowsweet teas indicated their possible immune-modulating properties. Filipendula beverage formulations can be expected to deliver beneficial effects due to their unique nutritional and phytochemical profiles. Potential applications as health-promoting functional products may be suggested.

HMGB1 Promotes Intraoral Palatal Wound Healing through RAGE-Dependent Mechanisms

High mobility group box 1 (HMGB1) is tightly connected to the process of tissue organization upon tissue injury. Here we show that HMGB1 controls epithelium and connective tissue regeneration both in vivo and in vitro during palatal wound healing. Heterozygous HMGB1 (Hmgb1^+/-) mice and Wild-type (WT) mice were subjected to palatal injury. Maxillary tissues were stained with Mallory Azan or immunostained with anti-HMGB1, anti-proliferating cell nuclear antigen (PCNA), anti-nuclear factor-κB (NF-κB) p50 and anti-vascular endothelial growth factor (VEGF) antibodies. Palatal gingival explants were cultured with recombinant HMGB1 (rHMGB1) co-treated with siRNA targeting receptor for advanced glycation end products (RAGEs) for cell migration and PCNA expression analysis. Measurement of the wound area showed differences between Hmgb1^+/- and WT mice on Day 3 after wounding. Mallory Azan staining showed densely packed of collagen fibers in WT mice, whereas in Hmgb1^+/- mice weave-like pattern of low density collagen bundles were present. At three and seven days post-surgery, PCNA, NF-κB p50 and VEGF positive keratinocytes of WT mice were greater than that of Hmgb1^+/- mice. Knockdown of RAGE prevents the effect of rHMGB1-induced cell migration and PCNA expression in gingival cell cultures. The data suggest that HMGB1/RAGE axis has crucial roles in palatal wound healing.

iRAGE as a novel carboxymethylated peptide that prevents advanced glycation end product-induced apoptosis and endoplasmic reticulum stress in vascular smooth muscle cells

Advanced glycation end-products (AGE) and the receptor for AGE (RAGE) have been linked to numerous diabetic vascular complications. RAGE activation promotes a self-sustaining state of chronic inflammation and has been shown to induce apoptosis in various cell types. Although previous studies in vascular smooth muscle cells (VSMC) showed that RAGE activation increases vascular calcification and interferes with their contractile phenotype, little is known on the potential of RAGE to induce apoptosis in VSMC. Using a combination of apoptotic assays, we showed that RAGE stimulation with its ligand CML-HSA promotes apoptosis of VSMC. The formation of stress granules and the increase in the level of the associated protein HuR point toward RAGE-dependent endoplasmic reticulum (ER) stress, which is proposed as a key contributor of RAGE-induced apoptosis in VSMC as it has been shown to promote cell death via numerous mechanisms, including up-regulation of caspase-9. Chronic NF-κB activation and modulation of Bcl-2 homologs are also suspected to contribute to RAGE-dependent apoptosis in VSMC. With the goal of reducing RAGE signaling and its detrimental impact on VSMC, we designed a RAGE antagonist (iRAGE) derived from the primary amino acid sequence of HSA. The resulting CML peptide was selected for the high glycation frequency of the primary sequence in the native protein in vivo. Pretreatment with iRAGE blocked 69.6% of the increase in NF-κB signaling caused by RAGE activation with CML-HSA after 48h. Preincubation with iRAGE was successful in reducing RAGE-induced apoptosis, as seen through enhanced cell survival by SPR and reduced PARP cleavage. Activation of executioner caspases was 63.5% lower in cells treated with iRAGE before stimulation with CML-HSA. To our knowledge, iRAGE is the first antagonist shown to block AGE-RAGE interaction and we propose the molecule as an initial candidate for drug discovery.

DNA aptamer raised against advanced glycation end products (AGEs) improves glycemic control and decreases adipocyte size in fructose-fed rats by suppressing AGE-RAGE axis

Advanced glycation end products (AGEs) decrease adiponectin expression and suppress insulin signaling in cultured adipocytes through the interaction with a receptor for AGEs (RAGE) via oxidative stress generation. We have recently found that high-affinity DNA aptamer directed against AGE (AGE-aptamer) prevents the progression of experimental diabetic nephropathy by blocking the harmful actions of AGEs in the kidney. This study examined the effects of AGE-aptamer on adipocyte remodeling, AGE-RAGE-oxidative stress axis, and adiponectin expression in fructose-fed rats. Although AGE-aptamer treatment by an osmotic mini pump for 8 weeks did not affect serum insulin levels, it significantly decreased average fasting blood glucose and had a tendency to inhibit body weight gain in fructose-fed rats. Furthermore, AGE-aptamer significantly suppressed the increase in adipocyte size and prevented the elevation in AGEs, RAGE, and an oxidative stress marker, 8-hydroxydeoxyguanosine (8-OHdG), levels in adipose tissues of fructose-fed rats at 14-week-old, while it restored the decrease in adiponectin mRNA levels. Our present study suggests that AGE-aptamer could improve glycemic control and prevent adipocyte remodeling in fructose-fed rats partly by suppressing the AGE-RAGE-mediated oxidative stress generation. AGE-aptamer might be a novel therapeutic strategy for fructose-induced metabolic derangements.

Effect of TTP488 in patients with mild to moderate Alzheimer's disease

BACKGROUND

TTP488, an antagonist at the Receptor for Advanced Glycation End products, was evaluated as a potential treatment for patients with mild-to-moderate Alzheimer's disease (AD). A previous report describes decreased decline in ADAS-cog (delta = 3.1, p = 0.008 at 18 months, ANCOVA with multiple imputation), relative to placebo, following a 5 mg/day dose of TTP488. Acute, reversible cognitive worsening was seen with a 20 mg/day dose. The present study further evaluates the efficacy of TTP488 by subgroup analyses based on disease severity and concentration effect analysis.

METHODS

399 patients were randomized to one of two oral TTP488 doses (60 mg for 6 days followed by 20 mg/day; 15 mg for 6 days followed by 5 mg/day) or placebo for 18 months. Pre-specified primary analysis, using an ITT population, was on the ADAS-cog11. Secondary analyses included as a key secondary variable the Clinical Dementia Rating-Sum of Boxes (CDR-SB), and another secondary variable of the ADCS-ADL.

RESULTS

On-treatment analysis demonstrated numerical differences favoring 5 mg/day over placebo, with nominal significance at Month 18 (delta = 2.7, p = 0.03). Patients with mild AD, whether defined by MMSE or ADAS-cog, demonstrated significant differences favoring 5 mg/day on ADAS-cog and trends on CDR-sb and ADCS-ADL at Month 18. TTP488 plasma concentrations of 7.6-16.8 ng/mL were associated with a decreased decline in ADAS-cog over time compared to placebo. Worsening on the ADAS-cog relative to placebo was evident at 46.8-167.0 ng/mL.

CONCLUSIONS

Results of these analyses support further investigation of 5 mg/day in future Phase 3 trials in patients with mild AD.