Therapeutic potential of targeting the receptor for advanced glycation end products (RAGE) by small molecule inhibitors

CYP2E1 mediated advanced oxidation protein products exacerbate acetaminophen induced drug-derived liver injury in vitro and in vivo

Drug-induced liver injury (DILI) is prevalent in the treatment of chronic kidney disease (CKD). Advanced oxidation protein products (AOPPs) are markers of CKD progression and participate in the occurrence and development of liver diseases. However, the mechanisms underlying the regulation of DILI in CKD have not been established. Herein, we demonstrate the involvement of Cytochrome p450 2E1 (CYP2E1) in DILI induced by AOPPs is exacerbated by exposure to acetaminophen (APAP). We used a adenine-induced CKD model, a model of DILI induced by APAP, and the AOPPs model was generated by intraperitoneal injection. The decline in renal function was associated with a significantly increased concentration of Scr, BUN and AOPPs, and renal tissue fibrosis. The ALT, AST, and AOPPs levels and liver tissue necrosis increased significantly in CKD model group compared with the sodium carboxymethyl cellulose (CMCNa) group. In the AOPPs model, compared to the PBS controls, ALT, AST, and AOPP levels, and liver tissue necrosis increased significantly. In HepG2 or L0-2 cell lines, cell survival was significantly reduced in the AOPP + APAP treatment and CYP2E1 protein expression was increased. FPS-ZM1 or NAC attenuated the hepatocyte toxicity induced by AOPP + APAP and suppression of CYP2E1 expression. AOPPs exacerbated APAP-induced DILI through CYP2E1 signaling pathways. Protein uremic toxins, such as AOPPs, can modify drug toxicity in patients with CKD. This study provides new a rationale to reduce the generation of DILIs in clinical treatment in patients with CKD. AOPPs targeting may present a novel approach to reduce the occurrence of DILI.

High mobility group box-1: A therapeutic target for analgesia and associated symptoms in chronic pain

The number of patients with chronic pain continues to increase against the background of an ageing society and a high incidence of various epidemics and disasters. One factor contributing to this situation is the absence of truly effective analgesics. Chronic pain is a persistent stress for the organism and can trigger a variety of neuropsychiatric symptoms. Hence, the search for useful analgesic targets is currently being intensified worldwide, and it is anticipated that the key to success may be molecules involved in emotional as well as sensory systems. High mobility group box-1 (HMGB1) has attracted attention as a therapeutic target for a variety of diseases. It is a very unique molecule having a dual role as a nuclear protein while also functioning as an inflammatory agent outside the cell. In recent years, numerous studies have shown that HMGB1 acts as a pain inducer in primary sensory nerves and the spinal dorsal horn. In addition, HMGB1 can function in the brain, and is involved in the symptoms of depression, anxiety and cognitive dysfunction that accompany chronic pain. In this review, we will summarize recent research and discuss the potential of HMGB1 as a useful drug target for chronic pain.

The RAGE Axis: A Relevant Inflammatory Hub in Human Diseases

In 1992, a transcendental report suggested that the receptor of advanced glycation end-products (RAGE) functions as a cell surface receptor for a wide and diverse group of compounds, commonly referred to as advanced glycation end-products (AGEs), resulting from the non-enzymatic glycation of lipids and proteins in response to hyperglycemia. The interaction of these compounds with RAGE represents an essential element in triggering the cellular response to proteins or lipids that become glycated. Although initially demonstrated for diabetes complications, a growing body of evidence clearly supports RAGE's role in human diseases. Moreover, the recognizing capacities of this receptor have been extended to a plethora of structurally diverse ligands. As a result, it has been acknowledged as a pattern recognition receptor (PRR) and functionally categorized as the RAGE axis. The ligation to RAGE leads the initiation of a complex signaling cascade and thus triggering crucial cellular events in the pathophysiology of many human diseases. In the present review, we intend to summarize basic features of the RAGE axis biology as well as its contribution to some relevant human diseases such as metabolic diseases, neurodegenerative, cardiovascular, autoimmune, and chronic airways diseases, and cancer as a result of exposure to AGEs, as well as many other ligands.

HMGB1/RAGE axis in tumor development: unraveling its significance

High mobility group protein 1 (HMGB1) plays a complex role in tumor biology. When released into the extracellular space, it binds to the receptor for advanced glycation end products (RAGE) located on the cell membrane, playing an important role in tumor development by regulating a number of biological processes and signal pathways. In this review, we outline the multifaceted functions of the HMGB1/RAGE axis, which encompasses tumor cell proliferation, apoptosis, autophagy, metastasis, and angiogenesis. This axis is instrumental in tumor progression, promoting tumor cell proliferation, autophagy, metastasis, and angiogenesis while inhibiting apoptosis, through pivotal signaling pathways, including MAPK, NF-κB, PI3K/AKT, ERK, and STAT3. Notably, small molecules, such as miRNA-218, ethyl pyruvate (EP), and glycyrrhizin exhibit the ability to inhibit the HMGB1/RAGE axis, restraining tumor development. Therefore, a deeper understanding of the mechanisms of the HMGB1/RAGE axis in tumors is of great importance, and the development of inhibitors targeting this axis warrants further exploration.

Novel Glycomimetics Protect against Glycated Low-Density Lipoprotein-Induced Vascular Calcification In Vitro via Attenuation of the RAGE/ERK/CREB Pathway

Heparan sulphate (HS) can act as a co-receptor on the cell surface and alterations in this process underpin many pathological conditions. We have previously described the usefulness of mimics of HS (glycomimetics) in protection against β-glycerophosphate-induced vascular calcification and in the restoration of the functional capacity of diabetic endothelial colony-forming cells in vitro. This study aims to investigate whether our novel glycomimetic compounds can attenuate glycated low-density lipoprotein (g-LDL)-induced calcification by inhibiting RAGE signalling within the context of critical limb ischemia (CLI). We used an established osteogenic in vitro vascular smooth muscle cell (VSMC) model. Osteoprotegerin (OPG), sclerostin and glycation levels were all significantly increased in CLI serum compared to healthy controls, while the vascular calcification marker osteocalcin (OCN) was down-regulated in CLI patients vs. controls. Incubation with both CLI serum and g-LDL (10 µg/mL) significantly increased VSMC calcification vs. controls after 21 days, with CLI serum-induced calcification apparent after only 10 days. Glycomimetics (C2 and C3) significantly inhibited g-LDL and CLI serum-induced mineralisation, as shown by a reduction in alizarin red (AR) staining and alkaline phosphatase (ALP) activity. Furthermore, secretion of the osteogenic marker OCN was significantly reduced in VSMCs incubated with CLI serum in the presence of glycomimetics. Phosphorylation of cyclic AMP response element-binding protein (CREB) was significantly increased in g-LDL-treated cells vs. untreated controls, which was attenuated with glycomimetics. Blocking CREB activation with a pharmacological inhibitor 666-15 replicated the protective effects of glycomimetics, evidenced by elevated AR staining. In silico molecular docking simulations revealed the binding affinity of the glycomimetics C2 and C3 with the V domain of RAGE. In conclusion, these findings demonstrate that novel glycomimetics, C2 and C3 have potent anti-calcification properties in vitro, inhibiting both g-LDL and CLI serum-induced VSMC mineralisation via the inhibition of LDLR, RAGE, CREB and subsequent expression of the downstream osteogenic markers, ALP and OCN.

Thinking outside the black box: are the brain endothelial cells the new main target in Alzheimer's disease?

The blood-brain barrier is the interface through which the brain interacts with the milieu and consists mainly of a sophisticated network of brain endothelial cells that forms blood vessels and selectively moves molecules inside and outside the brain through multiple mechanisms of transport. Although brain endothelial cell function is crucial for brain homeostasis, their role in neurodegenerative diseases has historically not been considered with the same importance as other brain cells such as microglia, astroglia, neurons, or even molecules such as amyloid beta, Tau, or alpha-synuclein. Alzheimer's disease is the most common neurodegenerative disease, and brain endothelial cell dysfunction has been reported by several groups. However, its impairment has barely been considered as a potential therapeutic target. Here we review the most recent advances in the relationship between Alzheimer's disease and brain endothelial cells commitment and analyze the possible mechanisms through which their alterations contribute to this neurodegenerative disease, highlighting their inflammatory phenotype and the possibility of an impaired secretory pattern of brain endothelial cells that could contribute to the progression of this ailment. Finally, we discuss why shall brain endothelial cells be appreciated as a therapeutic target instead of solely an obstacle for delivering treatments to the injured brain in Alzheimer's disease.

Modulating the RAGE-Induced Inflammatory Response: Peptoids as RAGE Antagonists

While the primary pathology of Alzheimer's disease (AD) is defined by brain deposition of amyloid-β (Aβ) plaques and tau neurofibrillary tangles, chronic inflammation has emerged as an important factor in AD etiology. Upregulated cell surface expression of the receptor for advanced glycation end-products (RAGE), a key receptor of innate immune response, is reported in AD. In parallel, RAGE ligands, including Aβ aggregates, HMGB1, and S100B, are elevated in AD brain. Activation of RAGE by these ligands triggers release of inflammatory cytokines and upregulates cell surface RAGE. Despite such observation, there are currently no therapeutics that target RAGE for treatment of AD-associated neuroinflammation. Peptoids, a novel class of potential AD therapeutics, display low toxicity, facile blood-brain barrier permeability, and resistance to proteolytic degradation. In the current study, peptoids were designed to mimic Aβ, a ligand that binds the V-domain of RAGE, and curtail RAGE inflammatory activation. We reveal the nanomolar binding capability of peptoids JPT1 and JPT1a to RAGE and demonstrate their ability to attenuate lipopolysaccharide-induced pro-inflammatory cytokine production as well as upregulation of RAGE cell surface expression. These results support RAGE antagonist peptoid-based mimics as a prospective therapeutic strategy to counter neuroinflammation in AD and other neurodegenerative diseases.

Advances in Biomarkers for Diagnosis and Treatment of ARDS

Acute respiratory distress syndrome (ARDS) is a common and fatal disease, characterized by lung inflammation, edema, poor oxygenation, and the need for mechanical ventilation, or even extracorporeal membrane oxygenation if the patient is unresponsive to routine treatment. In this review, we aim to explore advances in biomarkers for the diagnosis and treatment of ARDS. In viewing the distinct characteristics of each biomarker, we classified the biomarkers into the following six categories: inflammatory, alveolar epithelial injury, endothelial injury, coagulation/fibrinolysis, extracellular matrix turnover, and oxidative stress biomarkers. In addition, we discussed the potential role of machine learning in identifying and utilizing these biomarkers and reviewed its clinical application. Despite the tremendous progress in biomarker research, there remain nonnegligible gaps between biomarker discovery and clinical utility. The challenges and future directions in ARDS research concern investigators as well as clinicians, underscoring the essentiality of continued investigation to improve diagnosis and treatment.

In Silico Interactions of Natural and Synthetic Compounds with Key Proteins Involved in Alzheimer's Disease: Prospects for Designing New Therapeutics Compound

Memory impairment is a result of multiple factors including amyloid-beta (Aβ) accumulation. Several receptors are mediated for Aβ transport and signaling. Moreover, blood lipids are involved in Aβ signaling pathway through these receptors. Mediated blood lipid level by statins aims to regulate Aβ signaling cascade. First, the structure of receptors was taken from the RCSB PDB database and prepared with MGLTools and AutoDock tool 4. Second, the ligand was prepared for docking through AutoDock Vina. The binding affinity was calculated, and the binding sites were determined through LigPlot+ software. Besides, pharmacokinetic properties were calculated through multiple software. Finally, a molecular dynamics (MD) simulation was conducted to evaluate ligands stability along with clustering analysis to evaluate proteins connection. Our molecular docking and dynamic analyses revealed silymarin as a potential inhibitor of acetylcholinesterase (AChE), P-glycoprotein, and angiotensin-converting enzyme 2 (ACE2) with 0.704, 0.85, and 0.83 Å for RMSD along with -114.27, -107.44, and -122.51 kcal/mol for free binding energy, respectively. Moreover, rosuvastatin and quercetin have more stability compared to silymarin and donepezil in complex with P-glycoprotein and ACE2, respectively. Eventually, based on clustering and pharmacokinetics analysis, silymarin, rosuvastatin, and quercetin are suggested to be involved in peripheral clearance of Aβ. The bioactivity effects of mentioned statins and antioxidants are predicted to be helpful in treating memory impairment in Alzheimer's disease (AD). Nevertheless, mentioned drug effect could be improved by nanoparticles to facilitate penetration of the blood-brain barrier (BBB).

Discovery of acylated isoquercitrin derivatives as potent anti-neuroinflammatory agents in vitro and in vivo

Neuroinflammation is considered as an important pathological mechanism in neurodegenerative diseases. The natural isoquercitrin (IQ) was reported to have potential anti-neuroinflammatory activity. The acylation of glycoside in IQ enhanced its hydrophobicity, which was expected to enhance the protective effect against inflammation. In this study, three carboxylic acids with anti-neuroinflammatory effects including cinnamic acid, ibuprofen (IBU) and acetylsalicylic acid were introduced into the 6''-OH of IQ through the corresponding vinyl esters intermediates (8a-8c). Ultimately, the acylated IQ derivatives (Compound 9a-9c) were obtained with 35-42% yields using immobilized lipase Novozym 435 as catalyst. Subsequently, their anti-neuroinflammatory activities were evaluated in lipopolysaccharide (LPS)-induced BV2 cells. Compound 9b improved cell viability in the range of ≤50 μM and significantly decreased NO, PGE2 production and TNF-α, IL-1β release and oxidative stress level with a concentration-dependent manner. Also, it could downregulate iNOS, COX-2, TNF-α and IL-1β expression levels, approximately 40% reduction were achieved when 15μM compound 9b was employed. In addition, compound 9b resisted phosphorylation and degradation of IkBαs, suppressing the activation of NF-κB signaling pathway, exhibiting excellent neuroinflammatory inhibition. Moreover, the administration of compound 9b (30, 60 mg/kg) alleviated behavioral disorders and neuronal damages in LPS-induced neuroinflammatory mice. Meanwhile, the decreased TNF-α, IL-1β release, expression and the inhibited glial cells activation were obtained in compound 9b-treated group, which was superior to that of IQ or IBU. Overall, these findings demonstrated that compound 9b, formed by the introduction of ibuprofen into IQ, can serve as a novel promising therapeutic agent for anti-neuroinflammation.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

RAGE Inhibitors in Neurodegenerative Diseases

Nonenzymatic reactions of reducing sugars with primary amino groups of amino acids, proteins, and nucleic acids, followed by oxidative degradations would lead to the formation of advanced glycation endproducts (AGEs). The AGEs exert multifactorial effects on cell damage leading to the onset of neurological disorders. The interaction of AGEs with the receptors for advanced glycation endproducts (RAGE) contribute to the activation of intracellular signaling and the expression of the pro-inflammatory transcription factors and various inflammatory cytokines. This inflammatory signaling cascade is associated with various neurological diseases, including Alzheimer's disease (AD), secondary effects of traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and diabetic neuropathy, and other AGE-related diseases, including diabetes and atherosclerosis. Furthermore, the imbalance of gut microbiota and intestinal inflammation are also associated with endothelial dysfunction, disrupted blood-brain barrier (BBB) and thereby the onset and progression of AD and other neurological diseases. AGEs and RAGE play an important role in altering the gut microbiota composition and thereby increase the gut permeability and affect the modulation of the immune-related cytokines. The inhibition of the AGE-RAGE interactions, through small molecule-based therapeutics, prevents the inflammatory cascade of events associated with AGE-RAGE interactions, and thereby attenuates the disease progression. Some of the RAGE antagonists, such as Azeliragon, are currently in clinical development for treating neurological diseases, including AD, although currently there have been no FDA-approved therapeutics based on the RAGE antagonists. This review outlines the AGE-RAGE interactions as a leading cause of the onset of neurological diseases and the current efforts on developing therapeutics for neurological diseases based on the RAGE antagonists.

Contributions of the receptor for advanced glycation end products axis activation in gastric cancer

Compelling shreds of evidence derived from both clinical and experimental research have demonstrated the crucial contribution of receptor for advanced glycation end products (RAGE) axis activation in the development of neoplasms, including gastric cancer (GC). This new actor in tumor biology plays an important role in the onset of a crucial and long-lasting inflammatory milieu, not only by supporting phenotypic changes favoring growth and dissemination of tumor cells, but also by functioning as a pattern-recognition receptor in the inflammatory response to Helicobacter pylori infection. In the present review, we aim to highlight how the overexpression and activation of the RAGE axis contributes to the proliferation and survival of GC cells as and their acquisition of more invasive phenotypes that promote dissemination and metastasis. Finally, the contribution of some single nucleotide polymorphisms in the RAGE gene as susceptibility or poor prognosis factors is also discussed.

Blockade of receptor for advanced glycation end-products with azeliragon ameliorates streptozotocin-induced diabetic neuropathy

Treatment options for diabetic neuropathy are suboptimal, so development of a new therapeutic strategy is urgent. We focused on the role of receptor for advanced glycation end-products (RAGE) in diabetic neuropathy. We elaborated the effects of azeliragon (orally available small-molecule antagonist of RAGE) on streptozotocin (STZ)-induced mechanical hypersensitivity in mice. A reduction in mechanical nociceptive threshold observed 28 days after STZ treatment was improved by single administration of azeliragon (10 and 30 mg/kg) at 3 h, but this effect disappeared at 24 h. Conversely, repeat administration (three times; days 28, 30, and 32) of azeliragon (30 mg/kg) enhanced the antinociceptive effect significantly compared with that obtained upon single administration, and this effect persisted at least up to 24 h. The antinociceptive effect of azeliragon (30 mg/kg) was almost comparable with that of pregabalin (30 mg/kg). These drug treatments had no effect on blood glucose levels. Our findings suggest that RAGE might be an effective target for diabetic neuropathy treatment.

Electroacupuncture inhibits the expression of HMGB1/RAGE and alleviates injury to the primary motor cortex in rats with cerebral ischemia

Background

The high-mobility group box 1 (HMGB1)/receptor for advanced glycation end products (RAGE) signaling pathway holds promise as a potential therapeutic target for ischemic brain injury. The effects of FPS-ZM1 and electroacupuncture (EA) on activation of the HMGB1/RAGE signaling pathway after cerebral ischemia remain uncertain.

Methods

Middle cerebral artery occlusion (MCAO) model was established. Neurological function was assessed using Longa scores. Nissl staining was used to observe the morphology of neurons. The expression levels of HMGB1 and RAGE were assayed with immunofluorescence staining and western blot.

Results

The results showed that EA and FPS-ZM1 could reduce the neural function score and neurons cell injury in cerebral ischemia rats by inhibiting the expression of HMGB1 and RAGE in primary motor cortex (M1) region. In addition, EA combined with FPS-ZM1 had a better therapeutic effect.

Conclusions

The HMGB1/RAGE pathway could be activated after cerebral ischemia. Both EA and FPS-ZM1 improved neurological deficits and attenuated neuronal damage in rats. They had synergistic effects. These interventions were observed to mitigate brain damage by suppressing the activation of HMGB1/RAGE.

Therapeutic Potential of Targeting the HMGB1/RAGE Axis in Inflammatory Diseases

High mobility group box 1 (HMGB1) is a nuclear protein that can interact with a receptor for advanced glycation end-products (RAGE; a multi-ligand immunoglobulin receptor) and mediates the inflammatory pathways that lead to various pathological conditions, such as cancer, diabetes, neurodegenerative disorders, and cardiovascular diseases. Blocking the HMGB1/RAGE axis could be an effective therapeutic approach to treat these inflammatory conditions, which has been successfully employed by various research groups recently. In this article, we critically review the structural insights and functional mechanism of HMGB1 and RAGE to mediate inflammatory processes. More importantly, current perspectives of recent therapeutic approaches utilized to inhibit the communication between HMGB1 and RAGE using small molecules are also summarized along with their clinical progression to treat various inflammatory disorders. Encouraging results are reported by investigators focusing on HMGB1/RAGE signaling leading to the identification of compounds that could be useful in further clinical studies. We highlight the current gaps in our knowledge and future directions for the therapeutic potential of targeting key molecules in HMGB1/RAGE signaling in the pathophysiology of inflammatory diseases.

Advanced Glycation End Products in Health and Disease

Advanced glycation end products (AGEs), formed through the nonenzymatic reaction of reducing sugars with the side-chain amino groups of lysine or arginine of proteins, followed by further glycoxidation reactions under oxidative stress conditions, are involved in the onset and exacerbation of a variety of diseases, including diabetes, atherosclerosis, and Alzheimer’s disease (AD) as well as in the secondary stages of traumatic brain injury (TBI). AGEs, in the form of intra- and interprotein crosslinks, deactivate various enzymes, exacerbating disease progression. The interactions of AGEs with the receptors for the AGEs (RAGE) also result in further downstream inflammatory cascade events. The overexpression of RAGE and the AGE-RAGE interactions are especially involved in cases of Alzheimer’s disease and other neurodegenerative diseases, including TBI and amyotrophic lateral sclerosis (ALS). Maillard reactions are also observed in the gut bacterial species. The protein aggregates found in the bacterial species resemble those of AD and Parkinson’s disease (PD), and AGE inhibitors increase the life span of the bacteria. Dietary AGEs alter the gut microbiota composition and elevate plasma glycosylation, thereby leading to systemic proinflammatory effects and endothelial dysfunction. There is emerging interest in developing AGE inhibitor and AGE breaker compounds to treat AGE-mediated pathologies, including diabetes and neurodegenerative diseases. Gut-microbiota-derived enzymes may also function as AGE-breaker biocatalysts. Thus, AGEs have a prominent role in the pathogenesis of various diseases, and the AGE inhibitor and AGE breaker approach may lead to novel therapeutic candidates.