A multimodal RAGE-specific inhibitor reduces amyloid β-mediated brain disorder in a mouse model of Alzheimer disease

Astrocyte-derived CHI3L1 signaling impairs neurogenesis and cognition in the demyelinated hippocampus

Cognitive dysfunction is a feature in multiple sclerosis (MS), a chronic inflammatory demyelinating disorder. A notable aspect of MS brains is hippocampal demyelination, which is closely associated with cognitive decline. However, the mechanisms underlying this phenomenon remain unclear. Chitinase-3-like (CHI3L1), secreted by activated astrocytes, has been identified as a biomarker for MS progression. Our study investigates CHI3L1's function within the demyelinating hippocampus and demonstrates a correlation between CHI3L1 expression and cognitive impairment in patients with MS. Activated astrocytes release CHI3L1 in reaction to induced demyelination, which adversely affects the proliferation and differentiation of neural stem cells and impairs dendritic growth, complexity, and spine formation in neurons. Our findings indicate that the astrocytic deletion of CHI3L1 can mitigate neurogenic deficits and cognitive dysfunction. We showed that CHI3L1 interacts with CRTH2/receptor for advanced glycation end (RAGE) by attenuating β-catenin signaling. The reactivation of β-catenin signaling can revitalize neurogenesis, which holds promise for therapy of inflammatory demyelination.

Cornuside ameliorates cognitive impairments via RAGE/TXNIP/NF-κB signaling in Aβ1-42 induced Alzheimer's disease mice

Cornuside has been discovered to improve learning and memory in AD mice, however, its underlying mechanism was not fully understood. In the present study, we established an AD mice model by intracerebroventricular injection of Aβ1-42, which were treated with cornuside (3, 10, 30 mg/kg) for 2 weeks. Cornuside significantly ameliorated cognitive function of AD mice in series of behavioral tests, including Morris water maze test, nest building test, novel object recognition test and step-down test. Additionally, cornuside could attenuate neuronal injury, and promote cholinergic synaptic transmission by restoring the level of acetylcholine (ACh) via inhibiting acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), as well as facilitating choline acetyltransferase (ChAT). Furthermore, cornuside inhibited oxidative stress levels amplified as decreased malondialdehyde (MDA), by inhibiting TXNIP expression, improving total anti-oxidative capacity (TAOC), raising activities of superoxide dismutase (SOD) and catalase (CAT). Cornuside also reduced the activation of microglia and astrocytes, decreased the level of proinflammatory factors TNF-α, IL-6, IL-1β, iNOS and COX2 via interfering RAGE-mediated IKK-IκB-NF-κB phosphorylation. Similar anti-oxidative and anti-inflammatory effects were also found in LPS-stimulated BV2 cells via hampering RAGE-mediated TXNIP activation and NF-κB nuclear translocation. Virtual docking revealed that cornuside could interact with the active pocket of RAGE V domain directly. In conclusion, cornuside could bind to the RAGE directly impeding the interaction of Aβ and RAGE, and cut down the expression of TXNIP inhibiting ROS production and oxidative stress, as well as hamper NF-κB p65 mediated the inflammation.

Semaphorin3C identified as mediator of neuroinflammation and microglia polarization after spinal cord injury

Excessive neuroinflammation after spinal cord injury (SCI) is a major hurdle during nerve repair. Although proinflammatory macrophage/microglia-mediated neuroinflammation plays important roles, the underlying mechanism that triggers neuroinflammation and aggravating factors remain unclear. The present study identified a proinflammatory role of semaphorin3C (SEMA3C) in immunoregulation after SCI. SEMA3C expression level peaked 7 days post-injury (dpi) and decreased by 14 dpi. In vivo and in vitro studies revealed that macrophages/microglia expressed SEMA3C in the local microenvironment, which induced neuroinflammation and conversion of proinflammatory macrophage/microglia. Mechanistic experiments revealed that RAGE/NF-κB was downstream target of SEMA3C. Inhibiting SEMA3C-mediated RAGE signaling considerably suppressed proinflammatory cytokine production, reversed polarization of macrophages/microglia shortly after SCI. In addition, inhibition of SEMA3C-mediated RAGE signaling suggested that the SEMA3C/RAGE axis is a feasible target to preserve axons from neuroinflammation. Taken together, our study provides the first experimental evidence of an immunoregulatory role for SEMA3C in SCI via an autocrine mechanism.

Role of Epigenetic Modulation in Neurodegenerative Diseases: Implications of Phytochemical Interventions

Epigenetics defines changes in cell function without involving alterations in DNA sequence. Neuroepigenetics bridges neuroscience and epigenetics by regulating gene expression in the nervous system and its impact on brain function. With the increase in research in recent years, it was observed that alterations in the gene expression did not always originate from changes in the genetic sequence, which has led to understanding the role of epigenetics in neurodegenerative diseases (NDDs) including Alzheimer's disease (AD) and Parkinson's disease (PD). Epigenetic alterations contribute to the aberrant expression of genes involved in neuroinflammation, protein aggregation, and neuronal death. Natural phytochemicals have shown promise as potential therapeutic agents against NDDs because of their antioxidant, anti-inflammatory, and neuroprotective effects in cellular and animal models. For instance, resveratrol (grapes), curcumin (turmeric), and epigallocatechin gallate (EGCG; green tea) exhibit neuroprotective effects through their influence on DNA methylation patterns, histone acetylation, and non-coding RNA expression profiles. Phytochemicals also aid in slowing disease progression, preserving neuronal function, and enhancing cognitive and motor abilities. The present review focuses on various epigenetic modifications involved in the pathology of NDDs, including AD and PD, gene expression regulation related to epigenetic alterations, and the role of specific polyphenols in influencing epigenetic modifications in AD and PD.

The critical role of RAGE in severe influenza infection: A target for control of inflammatory response in the disease

Controlling the excessive inflammatory response is one of the key ways to reduce the severity and mortality of severe influenza virus infections. RAGE is involved in inflammatory responses and acute lung injuries. Here, we investigated the role of RAGE and its potential application as a target for severe influenza treatment through serological correlation analysis for influenza patients, and treatment with the RAGE inhibitor FPS-ZM1 on A549 cells or mice with influenza A (H1N1) infection. The results showed high levels of RAGE were correlated with immunopathological injury and severity of influenza, and FPS-ZM1 treatment increased the viability of A549 cells with influenza A infection and decreased morbidity and mortality of influenza A virus infection in mice. The RAGE/NF-κb inflammatory signaling pathway is a major targeting pathway for FPS-ZM1 treatment in severe influenza. These findings provide further insights into the immune injury of severe influenza and a potential targeting candidate for the disease treatment.

Tracking mitochondrial Cu(I) fluctuations through a ratiometric fluorescent probe in AD model cells: Towards understanding how AβOs induce mitochondrial Cu(I) dyshomeostasis

Mitochondrial copper signaling pathway plays a role in Alzheimer's disease (AD), especially in relevant Amyloid-β oligomers (AβOs) neurotoxicity and mitochondrial dysfunction. Clarifying the relationship between mitochondrial copper homeostasis and both of mitochondrial dysfunction and AβOs neurotoxicity is important for understanding AD pathogenesis. Herein, we designed and synthesized a ratiometric fluorescent probe CHC-NS4 for Cu(I). CHC-NS4 possesses excellent ratiometric response, high selectivity to Cu(I) and specific ability to target mitochondria. Under mitochondrial dysfunction induced by oligomycin, mitochondrial Cu(I) levels gradually increased, which may be related to inhibition of ATP7A-mediated Cu(I) exportation and/or high expression of COX. On this basis, CHC-NS4 was further utilized to visualize the fluctuations of mitochondrial Cu(I) levels during progression of AD model cells induced by AβOs. It was found that mitochondrial Cu(I) levels were gradually elevated during the AD progression, which depended on not only AβOs concentration but also incubation time. Moreover, endocytosis maybe served as a prime pathway mode for mitochondrial Cu(I) dyshomeostasis induced by AβOs during AD progression. These results have provided a novel inspiration into mitochondrial copper biology in AD pathogenesis.

Development of Receptor for Advanced Glycation End Products (RAGE) ligands through target directed dynamic combinatorial chemistry: a novel class of possible antagonists

RAGE is a transmembrane receptor of immunoglobulin family that can bind various endogenous and exogenous ligands, initiating the inflammatory downstream signaling pathways, including inflammaging. Therefore, RAGE represents an attractive drug target for age-related diseases. For the development of small-molecule RAGE antagonists, we employed protein-templated dynamic combinatorial chemistry (ptDCC) using RAGE's VC1 domain as a template, the first application of this approach in the context of RAGE. The affinities of DCC hits were validated using microscale thermophoresis. Subsequent screening against AGE2 (glyceraldehyde-modified AGE)-sRAGE (solubleRAGE) (AGE2-BSA/sRAGE) interaction using ELISA tests led to the identification of antagonists with micromolar potency. Our findings not only demonstrate the successful application of ptDCC on RAGE but also highlight its potential to address the pressing need for alternative strategies for the development of small-molecule RAGE antagonists, an area of research that has experienced a slowdown in recent years.

S100b treatment overcomes RAGE signaling deficits in myoblasts on advanced glycation end-product cross-linked collagen and promotes myogenic differentiation

Advanced glycation end-products (AGEs) stochastically accrue in skeletal muscle and on collagen over an individual's lifespan, stiffening the muscle and modifying the stem cell (MuSC) microenvironment while promoting proinflammatory, antiregenerative signaling via the receptor for advanced glycation end-products (RAGEs). In the present study, a novel in vitro model was developed of this phenomenon by cross linking a 3-D collagen scaffold with AGEs and investigating how myoblasts responded to such an environment. Briefly, collagen scaffolds were incubated with d-ribose (0, 25, 40, 100, or 250 mM) for 5 days at 37°C. C2C12 immortalized mouse myoblasts were grown on the scaffolds for 6 days in growth conditions for proliferation, and 12 days for differentiation and fusion. Human primary myoblasts were also used to confirm the C2C12 data. AGEs aberrantly extended the DNA production stage of C2C12s (but not in human primary myoblasts) which is known to delay differentiation in myogenesis, and this effect was prevented by RAGE inhibition. Furthermore, the differentiation and fusion of myoblasts were disrupted by AGEs, which were associated with reductions in integrins and suppression of RAGE. The addition of S100b (RAGE agonist) recovered the differentiation and fusion of myoblasts, and the addition of RAGE inhibitors (FPS-ZM1 and Azeliragon) inhibited the differentiation and fusion of myoblasts. Our results provide novel insights into the role of the AGE-RAGE axis in skeletal muscle aging, and future work is warranted on the potential application of S100b as a proregenerative factor in aged skeletal muscle.NEW & NOTEWORTHY Collagen cross-linked by advanced glycation end-products (AGEs) induced myoblast proliferation but prevented differentiation, myotube formation, and RAGE upregulation. RAGE inhibition occluded AGE-induced myoblast proliferation, while the delivery of S100b, a RAGE ligand, recovered fusion deficits.

Targeting the heparan sulfate-binding site of RAGE with monoclonal antibodies

Heparan sulfate (HS) plays its biological functions by interacting with hundreds of secreted extracellular and transmembrane proteins. Interaction with HS has been shown to be required for the normal function of many HS-binding proteins. Receptor for advanced glycation end-product (RAGE) is such a protein, whose activation requires HS-induced oligomerization. Using RAGE as an exemplary protein, we show here the workflow of a simple method of developing and characterizing mAbs that targets the HS-binding site. We found that HS-binding site of RAGE is quite immunogenic as 18 out of 94 anti-RAGE mAbs target various epitopes within the HS-binding site. Sequence analysis found that a common feature of anti-HS-binding site mAbs is the presence of abundant acidic residues (range between 6 to 11) in the complementarity determining region, suggesting electrostatic interaction plays an important role in promoting antigen-antibody interaction. Interestingly, mAbs targeting different epitopes within the HS-binding site blocks HS-RAGE interaction to different degrees, and the inhibitory effect is highly consistent among mAbs that target the same epitope. Functional assay revealed that anti-HS-binding site mAbs show different potency in inhibiting osteoclastogenesis, and the inhibitory potency does not have a simple correlation with the affinity and the epitope. Our study demonstrates that developing HS-binding site targeting mAbs should be applicable to most HS-binding proteins. By targeting this unique functional site, these mAbs might find therapeutic applications in treating various human diseases.

Interactions between nanoparticles and pathological changes of vascular in Alzheimer's disease

Emerging evidence suggests that vascular pathological changes play a pivotal role in the pathogenesis of Alzheimer's disease (AD). The dysfunction of the cerebral vasculature occurs in the early course of AD, characterized by alterations in vascular morphology, diminished cerebral blood flow (CBF), impairment of the neurovascular unit (NVU), vasculature inflammation, and cerebral amyloid angiopathy. Vascular dysfunction not only facilitates the influx of neurotoxic substances into the brain, triggering inflammation and immune responses but also hampers the efflux of toxic proteins such as Aβ from the brain, thereby contributing to neurodegenerative changes in AD. Furthermore, these vascular changes significantly impact drug delivery and distribution within the brain. Therefore, developing targeted delivery systems or therapeutic strategies based on vascular alterations may potentially represent a novel breakthrough in AD treatment. This review comprehensively examines various aspects of vascular alterations in AD and outlines the current interactions between nanoparticles and pathological changes of vascular.

Cyclophilin A is a ligand for RAGE in thrombo-inflammation

AIMS

Cyclophilin A (CyPA) induces leucocyte recruitment and platelet activation upon release into the extracellular space. Extracellular CyPA therefore plays a critical role in immuno-inflammatory responses in tissue injury and thrombosis upon platelet activation. To date, CD147 (EMMPRIN) has been described as the primary receptor mediating extracellular effects of CyPA in platelets and leucocytes. The receptor for advanced glycation end products (RAGE) shares inflammatory and prothrombotic properties and has also been found to have similar ligands as CD147. In this study, we investigated the role of RAGE as a previously unknown interaction partner for CyPA.

METHODS AND RESULTS

Confocal imaging, proximity ligation, co-immunoprecipitation, and atomic force microscopy were performed and demonstrated an interaction of CyPA with RAGE on the cell surface. Static and dynamic cell adhesion and chemotaxis assays towards extracellular CyPA using human leucocytes and leucocytes from RAGE-deficient Ager-/- mice were conducted. Inhibition of RAGE abrogated CyPA-induced effects on leucocyte adhesion and chemotaxis in vitro. Accordingly, Ager-/- mice showed reduced leucocyte recruitment and endothelial adhesion towards CyPA in vivo. In wild-type mice, we observed a downregulation of RAGE on leucocytes when endogenous extracellular CyPA was reduced. We furthermore evaluated the role of RAGE for platelet activation and thrombus formation upon CyPA stimulation. CyPA-induced activation of platelets was found to be dependent on RAGE, as inhibition of RAGE, as well as platelets from Ager-/- mice showed a diminished activation and thrombus formation upon CyPA stimulation. CyPA-induced signalling through RAGE was found to involve central signalling pathways including the adaptor protein MyD88, intracellular Ca2+ signalling, and NF-κB activation.

CONCLUSION

We propose RAGE as a hitherto unknown receptor for CyPA mediating leucocyte as well as platelet activation. The CyPA-RAGE interaction thus represents a novel mechanism in thrombo-inflammation.

Post-translational modifications of beta-amyloid alter its transport in the blood-brain barrier in vitro model

One of the hallmarks of Alzheimer's disease (AD) is the accumulation of beta-amyloid peptide (Aβ) leading to formation of soluble neurotoxic Aβ oligomers and insoluble amyloid plaques in various parts of the brain. Aβ undergoes post-translational modifications that alter its pathogenic properties. Aβ is produced not only in brain, but also in the peripheral tissues. Such Aβ, including its post-translationally modified forms, can enter the brain from circulation by binding to RAGE and contribute to the pathology of AD. However, the transport of modified forms of Aβ across the blood-brain barrier (BBB) has not been investigated. Here, we used a transwell BBB model as a controlled environment for permeability studies. We found that Aβ42 containing isomerized Asp7 residue (iso-Aβ42) and Aβ42 containing phosphorylated Ser8 residue (pS8-Aβ42) crossed the BBB better than unmodified Aβ42, which correlated with different contribution of endocytosis mechanisms to the transport of these isoforms. Using microscale thermophoresis, we observed that RAGE binds to iso-Aβ42 an order of magnitude weaker than to Aβ42. Thus, post-translational modifications of Aβ increase the rate of its transport across the BBB and modify the mechanisms of the transport, which may be important for AD pathology and treatment.

N-acetylserotonin alleviates retinal ischemia-reperfusion injury via HMGB1/RAGE/NF-κB pathway in rats

AIM

To observe the effects of N-acetylserotonin (NAS) administration on retinal ischemia-reperfusion (RIR) injury in rats and explore the underlying mechanisms involving the high mobility group box 1 (HMGB1)/receptor for advanced glycation end-products (RAGE)/nuclear factor-kappa B (NF-κB) signaling pathway.

METHODS

A rat model of RIR was developed by increasing the pressure of the anterior chamber of the eye. Eighty male Sprague Dawley were randomly divided into five groups: sham group (n=8), RIR group (n=28), RIR+NAS group (n=28), RIR+FPS-ZM1 group (n=8) and RIR+NAS+ FPS-ZM1 group (n=8). The therapeutic effects of NAS were examined by hematoxylin-eosin (H&E) staining, and retinal ganglion cells (RGCs) counting. The expression of interleukin 1 beta (IL-1β), HMGB1, RAGE, and nod-like receptor 3 (NLRP3) proteins and the phosphorylation of nuclear factor-kappa B (p-NF-κB) were analyzed by immunohistochemistry staining and Western blot analysis. The expression of HMGB1 protein was also detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

H&E staining results showed that NAS significantly reduced retinal edema and increased the number of RGCs in RIR rats. With NAS therapy, the HMGB1 and RAGE expression decreased significantly, and the activation of the NF-κB/NLRP3 pathway was antagonized along with the inhibition of p-NF-κB and NLRP3 protein expression. Additionally, NAS exhibited an anti-inflammatory effect by reducing IL-1β expression. The inhibitory of RAGE binding to HMGB1 by RAGE inhibitor FPS-ZM1 led to a significant decrease of p-NF-κB and NLRP3 expression, so as to the IL-1β expression and retinal edema, accompanied by an increase of RGCs in RIR rats.

CONCLUSION

NAS may exhibit a neuroprotective effect against RIR via the HMGB1/RAGE/NF-κB signaling pathway, which may be a useful therapeutic target for retinal disease.

Blood-brain barrier transporters: An overview of function, dysfunction in Alzheimer's disease and strategies for treatment

The blood-brain-barrier (BBB) has a major function in maintaining brain homeostasis by regulating the entry of molecules from the blood to the brain. Key players in BBB function are BBB transporters which are highly expressed in brain endothelial cells (BECs) and critical in mediating the exchange of nutrients and waste products. BBB transporters can also influence drug delivery into the brain by inhibiting or facilitating the entry of brain targeting therapeutics for the treatment of brain disorders, such as Alzheimer's disease (AD). Recent studies have shown that AD is associated with a disrupted BBB and transporter dysfunction, although their roles in the development in AD are not fully understand. Modulation of BBB transporter activity may pose a novel approach to enhance the delivery of drugs to the brain for enhanced treatment of AD. In this review, we will give an overview of key functions of BBB transporters and known changes in AD. In addition, we will discuss current strategies for transporter modulation for enhanced drug delivery into the brain.

Skin autofluorescence, reflecting accumulation of advanced glycation end products, and the risk of dementia in a population-based cohort

Conditions such as hyperglycemia and oxidative stress lead to the formation of advanced glycation end products (AGEs), which are harmful compounds that have been implicated in dementia. Within the Rotterdam Study, we measured skin AGEs as skin autofluorescence, reflecting long-term accumulation of AGEs, and determined their association with the risk of dementia and with brain magnetic resonance imaging (MRI) measures. Skin autofluorescence was measured between 2013 and 2016 in 2922 participants without dementia. Of these, 1504 also underwent brain MRI, on which measures of brain atrophy and cerebral small vessel disease were assessed. All participants were followed for the incidence of dementia until 2020. Of 2922 participants (mean age 72.6 years, 57% women), 123 developed dementia. Higher skin autofluorescence (per standard deviation) was associated with an increased risk of dementia (hazard ratio 1.21 [95% confidence interval 1.01-1.46]) and Alzheimer's disease (1.19 [0.97-1.47]), independently of age and other studied potential confounders. Stronger effects were seen in apolipoprotein E (APOE) ε4 carriers (1.34 [0.98-1.82]) and in participants with diabetes (1.35 [0.94-1.94]). Participants with higher skin autofluorescence levels also had smaller total brain volumes and smaller hippocampus volumes on MRI, and they had more often lacunes. These results suggest that AGEs may be involved in dementia pathophysiology.

Loss of Direct Vascular Contact to Astrocytes in the Hippocampus as an Initial Event in Alzheimer's Disease. Evidence from Patients, In Vivo and In Vitro Experimental Models

Alzheimer's disease (AD) is characterized by the accumulation of aggregated amyloid peptides in the brain parenchyma and within the walls of cerebral vessels. The hippocampus-a complex brain structure with a pivotal role in learning and memory-is implicated in this disease. However, there is limited data on vascular changes during AD pathological degeneration in this susceptible structure, which has distinctive vascular traits. Our aim was to evaluate vascular alterations in the hippocampus of AD patients and PDAPP-J20 mice-a model of AD-and to determine the impact of Aβ40 and Aβ42 on endothelial cell activation. We found a loss of physical astrocyte-endothelium interaction in the hippocampus of individuals with AD as compared to non-AD donors, along with reduced vascular density. Astrocyte-endothelial interactions and levels of the tight junction protein occludin were altered early in PDAPP-J20 mice, preceding any signs of morphological changes or disruption of the blood-brain barrier in these mice. At later stages, PDAPP-J20 mice exhibited decreased vascular density in the hippocampus and leakage of fluorescent tracers, indicating dysfunction of the vasculature and the BBB. In vitro studies showed that soluble Aβ40 exposure in human brain microvascular endothelial cells (HBMEC) was sufficient to induce NFκB translocation to the nucleus, which may be linked with an observed reduction in occludin levels. The inhibition of the membrane receptor for advanced glycation end products (RAGE) prevented these changes in HBMEC. Additional results suggest that Aβ42 indirectly affects the endothelium by inducing astrocytic factors. Furthermore, our results from human and mouse brain samples provide evidence for the crucial involvement of the hippocampal vasculature in Alzheimer's disease.

Communal interaction of glycation and gut microbes in diabetes mellitus, Alzheimer's disease, and Parkinson's disease pathogenesis

Diabetes and its complications, Alzheimer's disease (AD), and Parkinson's disease (PD) are increasing gradually, reflecting a global threat vis-à-vis expressing the essentiality of a substantial paradigm shift in research and remedial actions. Protein glycation is influenced by several factors, like time, temperature, pH, metal ions, and the half-life of the protein. Surprisingly, most proteins associated with metabolic and neurodegenerative disorders are generally long-lived and hence susceptible to glycation. Remarkably, proteins linked with diabetes, AD, and PD share this characteristic. This modulates protein's structure, aggregation tendency, and toxicity, highlighting renovated attention. Gut microbes and microbial metabolites marked their importance in human health and diseases. Though many scientific shreds of evidence are proposed for possible change and dysbiosis in gut flora in these diseases, very little is known about the mechanisms. Screening and unfolding their functionality in metabolic and neurodegenerative disorders is essential in hunting the gut treasure. Therefore, it is imperative to evaluate the role of glycation as a common link in diabetes and neurodegenerative diseases, which helps to clarify if modulation of nonenzymatic glycation may act as a beneficial therapeutic strategy and gut microbes/metabolites may answer some of the crucial questions. This review briefly emphasizes the common functional attributes of glycation and gut microbes, the possible linkages, and discusses current treatment options and therapeutic challenges.

Neuroprotective potential of formononetin, a naturally occurring isoflavone phytoestrogen

The increased prevalence of neurological illnesses is a burgeoning challenge to the public healthcare system and presents greater financial pressure. Formononetin, an O-methylated isoflavone, has gained a lot of attention due to its neuroprotective potential explored in several investigations. Formononetin is widely found in legumes and several types of clovers including Trifolium pratense L., Astragalus membranaceus, Sophora tomentosa, etc. Formononetin modulates various endogenous mediators to confer neuroprotection. It prevents RAGE activation that results in the inhibition of neuronal damage via downregulating the level of ROS and proinflammatory cytokines. Furthermore, formononetin also increases the expression of ADAM-10, which affects the pathology of neurodegenerative disease by lowering tau phosphorylation, maintaining synaptic plasticity, and boosting hippocampus neurogenesis. Besides these, formononetin also increases the expression of antioxidants, Nrf-2, PI3K, ApoJ, and LRP1. Whereas, reduces the expression of p65-NF-κB and proinflammatory cytokines. It also inhibits the deposition of Aβ and MAO-B activity. An inhibition of Aβ/RAGE-induced activation of MAPK and NOX governs the protection elicited by formononetin against inflammatory and oxidative stress-induced neuronal damage. Besides this, PI3K/Akt and ER-α-mediated activation of ADAM10, ApoJ/LRP1-mediated clearance of Aβ, and MAO-B inhibition-mediated preservation of dopaminergic neurons integrity are the major modulations produced by formononetin. This review covers the biosynthesis of formononetin and key molecular pathways modulated by formononetin to confer neuroprotection.

Inhibition of the HMGB1/RAGE axis protects against cisplatin-induced ototoxicity via suppression of inflammation and oxidative stress

As an anti-tumor drug widely used in the clinic, cisplatin is limited by its ototoxic side effects associated with various factors, including inflammatory responses. Receptor for Advanced Glycation Endproducts (RAGE) recognizes damage-associated molecular patterns (DAMPs) and promotes stress and inflammation. This study intended to determine the potential behavior of the HMGB1/RAGE axis after cisplatin injury and whether it has a protective effect after inhibiting this pathway. We used FPS-ZM1, a RAGE inhibitor, to modulate the axis of HMGB1/RAGE in neonatal mouse cochlear explants and C57BL/6 mice in vivo. Apoptosis was identified by Annexin V-FITC/PI assay, Cleaved Caspase-3, and TUNEL staining. Reactive oxygen species (ROS) level was assessed by MitoSOX Red and CellROX Green assay. The expression of proteins associated with the HMGB1/RAGE axis and apoptosis was observed by western blotting. The expression of inflammatory cytokines was evaluated by qPCR. The protective effect of HMGB1/RAGE knockdown was also assessed on cisplatin-induced ototoxicity. These results demonstrated that cisplatin could activate the HMGB1/RAGE pathway in cochlear hair cells and release inflammatory factors. Pretreatment with FPS-ZM1 alleviated cisplatin-induced ototoxicity in vivo and in vitro. Knocking down HMGB1 and RAGE achieved specific protective effects. Altogether, inhibiting HMGB1/RAGE axis can reverse the increase of ROS accumulation, the activation of apoptosis, and the production of inflammatory reactions after cisplatin injury. FPS-ZM1 could resist the ototoxicity of cisplatin by suppressing the HMGB1/RAGE signal pathway, and it may be considered the new otoprotective potential strategy for hearing loss.

Receptor for advanced glycation end-products: Biological significance and imaging applications

The receptor for advanced glycation end-products (RAGE or AGER) is a transmembrane, immunoglobulin-like receptor that, due to its multiple isoform structures, binds to a diverse range of endo- and exogenous ligands. RAGE activation caused by the ligand binding initiates a cascade of complex pathways associated with producing free radicals, such as reactive nitric oxide and oxygen species, cell proliferation, and immunoinflammatory processes. The involvement of RAGE in the pathogenesis of disorders such as diabetes, inflammation, tumor progression, and endothelial dysfunction is dictated by the accumulation of advanced glycation end-products (AGEs) at pathologic states leading to sustained RAGE upregulation. The involvement of RAGE and its ligands in numerous pathologies and diseases makes RAGE an interesting target for therapy focused on the modulation of both RAGE expression or activation and the production or exogenous administration of AGEs. Despite the known role that the RAGE/AGE axis plays in multiple disease states, there remains an urgent need to develop noninvasive, molecular imaging approaches that can accurately quantify RAGE levels in vivo that will aid in the validation of RAGE and its ligands as biomarkers and therapeutic targets. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Biosensing.

Music compensates for altered gene expression in age-related cognitive disorders

Extensive literature has explored the beneficial effects of music in age-related cognitive disorders (ACD), but limited knowledge exists regarding its impact on gene expression. We analyzed transcriptomes of ACD patients and healthy controls, pre-post a music session (n = 60), and main genes/pathways were compared to those dysregulated in mild cognitive impairment (MCI) and Alzheimer's disease (AD) as revealed by a multi-cohort study (n = 1269 MCI/AD and controls). Music was associated with 2.3 times more whole-genome gene expression, particularly on neurodegeneration-related genes, in ACD than in controls. Co-expressed gene-modules and pathways analysis demonstrated that music impacted autophagy, vesicle and endosome organization, biological processes commonly dysregulated in MCI/AD. Notably, the data indicated a strong negative correlation between musically-modified genes/pathways in ACD and those dysregulated in MCI/AD. These findings highlight the compensatory effect of music on genes/biological processes affected in MCI/AD, providing insights into the molecular mechanisms underlying the benefits of music on these disorders.

Enhanced expression of RAGE/NADPH oxidase signaling pathway and increased level of oxidative stress in brains of rats with chronic fluorosis and the protective effects of blockers

This investigation was designed to examine the potential involvement of RAGE/NADPH oxidase signaling in the damage to the brain caused by chronic fluorosis. Sprague-Dawley rats were divided randomly into 9 groups each containing 20 animals, Controls (C); rats receiving low (i.e., 10 ppm) (LF) or high does ( i.e., 50 ppm) (HF) of fluoride in their drinking water; and these same groups injected with FPS-ZM1, an inhibitor of RAGE, (CF, LFF and HFF, respectively) or administered EGb761, an active ingredient of Ginkgo biloba extract, intragastrically (CE, LFE, and HFE). Following 3 and 6 months of such treatment, the spatial learning and memory of the animals were assessed with the Morris water maze test; the levels of malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide dismutase (SOD) assayed by biochemical methods; and the levels of proteins related to the RAGE/NADPH pathway determined by Western blot and of the corresponding mRNAs by qPCR. After 6 months, the spatial learning and memory of the LF and HF groups had declined; their brain contents of MDA and H2O2 increased and SOD activity decreased; and the levels of the RAGE, gp91, P47, phospho-P47phox and P22 proteins and corresponding mRNAs in their brains were all elevated. Interestingly, all of these pathological changes caused by fluorosis could be attenuated by both FPS-ZM1 and EGb761. These findings indicate that the brain damage induced by fluorosis may be caused, at least in part, by enhanced RAGE/NADPH oxidase signaling and that FPS-ZM1 or EGb761 might be of clinical value in connection with the treatment of this condition.

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.

Preserving cognitive function in patients with Alzheimer's disease: The Alzheimer's disease neuroprotection research initiative (ADNRI)

The global trend toward aging populations has resulted in an increase in the occurrence of Alzheimer's disease (AD) and associated socioeconomic burdens. Abnormal metabolism of amyloid-β (Aβ) has been proposed as a significant pathomechanism in AD, supported by results of recent clinical trials using anti-Aβ antibodies. Nonetheless, the cognitive benefits of the current treatments are limited. The etiology of AD is multifactorial, encompassing Aβ and tau accumulation, neuroinflammation, demyelination, vascular dysfunction, and comorbidities, which collectively lead to widespread neurodegeneration in the brain and cognitive impairment. Hence, solely removing Aβ from the brain may be insufficient to combat neurodegeneration and preserve cognition. To attain effective treatment for AD, it is necessary to (1) conduct extensive research on various mechanisms that cause neurodegeneration, including advances in neuroimaging techniques for earlier detection and a more precise characterization of molecular events at scales ranging from cellular to the full system level; (2) identify neuroprotective intervention targets against different neurodegeneration mechanisms; and (3) discover novel and optimal combinations of neuroprotective intervention strategies to maintain cognitive function in AD patients. The Alzheimer's Disease Neuroprotection Research Initiative's objective is to facilitate coordinated, multidisciplinary efforts to develop systemic neuroprotective strategies to combat AD. The aim is to achieve mitigation of the full spectrum of pathological processes underlying AD, with the goal of halting or even reversing cognitive decline.

Local perfusion of capillaries reveals disrupted beta-amyloid homeostasis at the blood-brain barrier in Tg2576 murine Alzheimer's model

BACKGROUND

Parenchymal accumulation of beta-amyloid (Aβ) characterizes Alzheimer's disease (AD). Aβ homeostasis is maintained by two ATP-binding cassette (ABC) transporters (ABCC1 and ABCB1) mediating efflux, and the receptor for advanced glycation end products (RAGE) mediating influx across the blood-brain barrier (BBB). Altered transporter levels and disruption of tight junctions (TJ) were linked to AD. However, Aβ transport and the activity of ABCC1, ABCB1 and RAGE as well as the functionality of TJ in AD are unclear.

METHODS

ISMICAP, a BBB model involving microperfusion of capillaries, was used to assess BBB properties in acute cortical brain slices from Tg2576 mice compared to wild-type (WT) controls using two-photon microscopy. TJ integrity was tested by vascularly perfusing biocytin-tetramethylrhodamine (TMR) and quantifying its extravascular diffusion as well as the diffusion of FM1-43 from luminal to abluminal membranes of endothelial cells (ECs). To assess ABCC1 and ABCB1 activity, calcein-AM was perfused, which is converted to fluorescent calcein in ECs and gets actively extruded by both transporters. To probe which transporter is involved, probenecid or Elacridar were applied, individually or combined, to block ABCC1 and ABCB1, respectively. To assess RAGE activity, the binding of 5-FAM-tagged Aβ by ECs was quantified with or without applying FPS-ZM1, a RAGE antagonist.

RESULTS

In Tg2576 mouse brain, extravascular TMR was 1.8-fold that in WT mice, indicating increased paracellular leakage. FM1-43 staining of abluminal membranes in Tg2576 capillaries was 1.7-fold that in WT mice, indicating reduced TJ integrity in AD. While calcein was undetectable in WT mice, its accumulation was significant in Tg2576 mice, suggesting lower calcein extrusion in AD. Incubation with probenecid or Elacridar in WT mice resulted in a marked calcein accumulation, yet probenecid alone had no effect in Tg2576 mice, implying the absence of probenecid-sensitive ABC transporters. In WT mice, Aβ accumulated along the luminal membranes, which was undetectable after applying FPS-ZM1. In contrast, marginal Aβ fluorescence was observed in Tg2576 vessels, and FPS-ZM1 was without effect, suggesting reduced RAGE binding activity.

CONCLUSIONS

Disrupted TJ integrity, reduced ABCC1 functionality and decreased RAGE binding were identified as BBB alterations in Tg2576 mice, with the latter finding challenging the current concepts. Our results suggest to manage AD by including modulation of TJ proteins and Aβ-RAGE binding.

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.

Blood-Brain Barrier Breakdown in Alzheimer's Disease: Mechanisms and Targeted Strategies

The blood-brain barrier (BBB) is a unique and selective feature of the central nervous system's vasculature. BBB dysfunction has been observed as an early sign of Alzheimer's Disease (AD) before the onset of dementia or neurodegeneration. The intricate relationship between the BBB and the pathogenesis of AD, especially in the context of neurovascular coupling and the overlap of pathophysiology in neurodegenerative and cerebrovascular diseases, underscores the urgency to understand the BBB's role more deeply. Preserving or restoring the BBB function emerges as a potentially promising strategy for mitigating the progression and severity of AD. Molecular and genetic changes, such as the isoform ε4 of apolipoprotein E (ApoEε4), a significant genetic risk factor and a promoter of the BBB dysfunction, have been shown to mediate the BBB disruption. Additionally, receptors and transporters like the low-density lipoprotein receptor-related protein 1 (LRP1), P-glycoprotein (P-gp), and the receptor for advanced glycation end products (RAGEs) have been implicated in AD's pathogenesis. In this comprehensive review, we endeavor to shed light on the intricate pathogenic and therapeutic connections between AD and the BBB. We also delve into the latest developments and pioneering strategies targeting the BBB for therapeutic interventions, addressing its potential as a barrier and a carrier. By providing an integrative perspective, we anticipate paving the way for future research and treatments focused on exploiting the BBB's role in AD pathogenesis and therapy.

Blood-brain barrier dysfunction and Alzheimer's disease: associations, pathogenic mechanisms, and therapeutic potential

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by the accumulation of amyloid-beta (Aβ), hyperphosphorylation of tau, and neuroinflammation in the brain. The blood-brain barrier (BBB) limits solutes from circulating blood from entering the brain, which is essential for neuronal functioning. Focusing on BBB function is important for the early detection of AD and in-depth study of AD pathogenic mechanisms. However, the mechanism of BBB alteration in AD is still unclear, which hinders further research on therapeutics that target the BBB to delay the progression of AD. The exact timing of the vascular abnormalities in AD and the complex cause-and-effect relationships remain uncertain. Thus, it is necessary to summarize and emphasize this process. First, in this review, the current evidence for BBB dysfunction in AD is summarized. Then, the interrelationships and pathogenic mechanisms between BBB dysfunction and the risk factors for AD, such as Aβ, tau, neuroinflammation, apolipoprotein E (ApoE) genotype and aging, were analyzed. Finally, we discuss the current status and future directions of therapeutic AD strategies targeting the BBB. We hope that these summaries or reviews will allow readers to better understand the relationship between the BBB and AD.

Oxidative Stress in Health and Disease

Oxidative stress, resulting from the excessive intracellular accumulation of reactive oxygen species (ROS), reactive nitrogen species (RNS), and other free radical species, contributes to the onset and progression of various diseases, including diabetes, obesity, diabetic nephropathy, diabetic neuropathy, and neurological diseases, such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Oxidative stress is also implicated in cardiovascular disease and cancer. Exacerbated oxidative stress leads to the accelerated formation of advanced glycation end products (AGEs), a complex mixture of crosslinked proteins and protein modifications. Relatively high levels of AGEs are generated in diabetes, obesity, AD, and other I neurological diseases. AGEs such as Ne-carboxymethyllysine (CML) serve as markers for disease progression. AGEs, through interaction with receptors for advanced glycation end products (RAGE), initiate a cascade of deleterious signaling events to form inflammatory cytokines, and thereby further exacerbate oxidative stress in a vicious cycle. AGE inhibitors, AGE breakers, and RAGE inhibitors are therefore potential therapeutic agents for multiple diseases, including diabetes and AD. The complexity of the AGEs and the lack of well-established mechanisms for AGE formation are largely responsible for the lack of effective therapeutics targeting oxidative stress and AGE-related diseases. This review addresses the role of oxidative stress in the pathogenesis of AGE-related chronic diseases, including diabetes and neurological disorders, and recent progress in the development of therapeutics based on antioxidants, AGE breakers and RAGE inhibitors. Furthermore, this review outlines therapeutic strategies based on single-atom nanozymes that attenuate oxidative stress through the sequestering of reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Discovery of Potential RAGE inhibitors using Receptor-Based Pharmacophore Modeling, High Throughput Virtual Screening and Docking Studies

Receptor for Advanced Glycation End products (RAGE) is a transmembrane receptor that can bind to various endogenous and exogenous ligands and initiate the inflammatory downstream signaling pathways. So far RAGE has been involved in various disorders including cardiovascular and neurodegenerative diseases, cancer, and diabetes. Blocking the interactions between RAGE and its ligands is a therapeutic approach to treat these conditions. In this context, we effectively utilized the receptor-based-pharmacophore modeling to discover structurally diverse molecular compounds having potential to effectively bind with RAGE. Two pharmacophore models were developed on V-domain of RAGE using Phase application of Schrodinger suite. The developed pharmacophoric features were used for screening of 1.8 million drug-like molecules downloaded from ChEMBL database. The molecules were scrutinized according to their molecular weight as well as clogP values. Phase screening was performed to find out the molecules that matched the developed pharmacophoric features that were further selected to analyze their binding modes using high-throughput virtual screening, extra precision docking studies and MM-GBSA ΔG binding calculations. These analyses provided ten hit RAGE inhibitory molecules that can bind to two different shallow binding sites on the V-domain of RAGE. Among the obtained compounds two compounds ChEMBL501494 and ChEMBL4081874 were found with best binding free energies that proved their receptor-ligand complex stability within their respective binding cavity on RAGE. Therefore, these molecules could be utilized for further designing and optimizing the future class of potential RAGE inhibitors.

The VCAM1-ApoE pathway directs microglial chemotaxis and alleviates Alzheimer's disease pathology

In Alzheimer's disease (AD), sensome receptor dysfunction impairs microglial danger-associated molecular pattern (DAMP) clearance and exacerbates disease pathology. Although extrinsic signals, including interleukin-33 (IL-33), can restore microglial DAMP clearance, it remains largely unclear how the sensome receptor is regulated and interacts with DAMP during phagocytic clearance. Here, we show that IL-33 induces VCAM1 in microglia, which promotes microglial chemotaxis toward amyloid-beta (Aβ) plaque-associated ApoE, and leads to Aβ clearance. We show that IL-33 stimulates a chemotactic state in microglia, characterized by Aβ-directed migration. Functional screening identified that VCAM1 directs microglial Aβ chemotaxis by sensing Aβ plaque-associated ApoE. Moreover, we found that disrupting VCAM1-ApoE interaction abolishes microglial Aβ chemotaxis, resulting in decreased microglial clearance of Aβ. In patients with AD, higher cerebrospinal fluid levels of soluble VCAM1 were correlated with impaired microglial Aβ chemotaxis. Together, our findings demonstrate that promoting VCAM1-ApoE-dependent microglial functions ameliorates AD pathology.

Increased alpha-synuclein and neuroinflammation in the substantia nigra triggered by systemic inflammation are reversed by targeted inhibition of the receptor for advanced glycation end products (RAGE)

The receptor for advanced glycation end products (RAGE) is a protein of the immunoglobulin superfamily capable of regulating inflammation. Considering the role of this receptor in the initiation and establishment of neuroinflammation, and the limited understanding of the function of RAGE in the maintenance of this condition, this study describes the effects of RAGE inhibition in the brain, through an intranasal treatment with the antagonist FPS-ZM1, in an animal model of chronic neuroinflammation induced by acute intraperitoneal injection of lipopolysaccharide (LPS). Seventy days after LPS administration (2 mg/kg, i.p.), Wistar rats received, intranasally, 1.2 mg of FPS-ZM1 over 14 days. On days 88 and 89, the animals were submitted to the open-field test and were killed on day 90 after the intraperitoneal injection of LPS. Our results indicate that blockade of encephalic RAGE attenuates LPS-induced chronic neuroinflammation in different brain regions. Furthermore, we found that intranasal FPS-ZM1 administration reduced levels of gliosis markers, RAGE ligands, and α-synuclein in the substantia nigra pars compacta. Additionally, the treatment also reversed the increase in S100 calcium-binding protein B (RAGE ligand) in the cerebrospinal fluid and the cognitive-behavioral deficits promoted by LPS-less time spent in the central zone of the open-field arena (more time in the lateral zones), decreased total distance traveled, and increased number of freezing episodes. In summary, our study demonstrates the prominent role of RAGE in the maintenance of a chronic neuroinflammatory state triggered by a single episode of systemic inflammation and also points to possible future RAGE-based therapeutic approaches to treat conditions in which chronic neuroinflammation and increased α-synuclein levels could play a relevant role, such as in Parkinson's disease.

RAGE/SNAIL1 signaling drives epithelial-mesenchymal plasticity in metastatic triple-negative breast cancer

Epithelial/Mesenchymal (E/M) plasticity plays a fundamental role both in embryogenesis and during tumorigenesis. The receptor for advanced glycation end products (RAGE) is a driver of cell plasticity in fibrotic diseases; however, its role and molecular mechanism in triple-negative breast cancer (TNBC) remains unclear. Here, we demonstrate that RAGE signaling maintains the mesenchymal phenotype of aggressive TNBC cells by enforcing the expression of SNAIL1. Besides, we uncover a crosstalk mechanism between the TGF-β and RAGE pathways that is required for the acquisition of mesenchymal traits in TNBC cells. Consistently, RAGE inhibition elicits epithelial features that block migration and invasion capacities. Next, since RAGE is a sensor of the tumor microenvironment, we modeled acute acidosis in TNBC cells and showed it promotes enhanced production of RAGE ligands and the activation of RAGE-dependent invasive properties. Furthermore, acute acidosis increases SNAIL1 levels and tumor cell invasion in a RAGE-dependent manner. Finally, we demonstrate that in vivo inhibition of RAGE reduces metastasis incidence and expands survival, consistent with molecular effects that support the relevance of RAGE signaling in E/M plasticity. These results uncover new molecular insights on the regulation of E/M phenotypes in cancer metastasis and provide rationale for pharmacological intervention of this signaling axis.

RAGE inhibition blunts insulin-induced oncogenic signals in breast cancer

The receptor for advanced glycation end products (RAGE) is implicated in diabetes and obesity complications, as well as in breast cancer (BC). Herein, we evaluated whether RAGE contributes to the oncogenic actions of Insulin, which plays a key role in BC progression particularly in obese and diabetic patients. Analysis of the publicly available METABRIC study, which collects gene expression and clinical data from a large cohort (n = 1904) of BC patients, revealed that RAGE and the Insulin Receptor (IR) are co-expressed and associated with negative prognostic parameters. In MCF-7, ZR75 and 4T1 BC cells, as well as in patient-derived Cancer-Associated Fibroblasts, the pharmacological inhibition of RAGE as well as its genetic depletion interfered with Insulin-induced activation of the oncogenic pathway IR/IRS1/AKT/CD1. Mechanistically, IR and RAGE directly interacted upon Insulin stimulation, as shown by in situ proximity ligation assays and coimmunoprecipitation studies. Of note, RAGE inhibition halted the activation of both IR and insulin like growth factor 1 receptor (IGF-1R), as demonstrated in MCF-7 cells KO for the IR and the IGF-1R gene via CRISPR-cas9 technology. An unbiased label-free proteomic analysis uncovered proteins and predicted pathways affected by RAGE inhibition in Insulin-stimulated BC cells. Biologically, RAGE inhibition reduced cell proliferation, migration, and patient-derived mammosphere formation triggered by Insulin. In vivo, the pharmacological inhibition of RAGE halted Insulin-induced tumor growth, without affecting blood glucose homeostasis. Together, our findings suggest that targeting RAGE may represent an appealing opportunity to blunt Insulin-induced oncogenic signaling in BC.

RAGE inhibitor TTP488 (Azeliragon) suppresses metastasis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic cancer subtype, which is generally untreatable once it metastasizes. We hypothesized that interfering with the Receptor for Advanced Glycation End-products (RAGE) signaling with the small molecule RAGE inhibitors (TTP488/Azeliragon and FPS-ZM1) would impair TNBC metastasis and impair fundamental mechanisms underlying tumor progression and metastasis. Both TTP488 and FPS-ZM1 impaired spontaneous and experimental metastasis of TNBC models, with TTP488 reducing metastasis to a greater degree than FPS-ZM1. Transcriptomic analysis of primary xenograft tumor and metastatic tissue revealed high concordance in gene and protein changes with both drugs, with TTP488 showing greater potency against metastatic driver pathways. Phenotypic validation of transcriptomic analysis by functional cell assays revealed that RAGE inhibition impaired TNBC cell adhesion to multiple extracellular matrix proteins (including collagens, laminins, and fibronectin), migration, and invasion. Neither RAGE inhibitor impaired cellular viability, proliferation, or cell cycle in vitro. Proteomic analysis of serum from tumor-bearing mice revealed RAGE inhibition affected metastatic driver mechanisms, including multiple cytokines and growth factors. Further mechanistic studies by phospho-proteomic analysis of tumors revealed RAGE inhibition led to decreased signaling through critical BC metastatic driver mechanisms, including Pyk2, STAT3, and Akt. These results show that TTP488 impairs metastasis of TNBC and further clarifies the signaling and cellular mechanisms through which RAGE mediates metastasis. Importantly, as TTP488 displays a favorable safety profile in human studies, our study provides the rationale for evaluating TTP488 in clinical trials to treat or prevent metastatic TNBC.

The Ephrin tyrosine kinase a3 (EphA3) is a novel mediator of RAGE-prompted motility of breast cancer cells

BACKGROUND

The receptor for advanced glycation-end products (RAGE) and its ligands have been implicated in obesity and associated inflammatory processes as well as in metabolic alterations like diabetes. In addition, RAGE-mediated signaling has been reported to contribute to the metastatic progression of breast cancer (BC), although mechanistic insights are still required. Here, we provide novel findings regarding the transcriptomic landscape and the molecular events through which RAGE may prompt aggressive features in estrogen receptor (ER)-positive BC.

METHODS

MCF7 and T47D BC cells stably overexpressing human RAGE were used as a model system to evaluate important changes like cell protrusions, migration, invasion and colony formation both in vitro through scanning electron microscopy, clonogenic, migration and invasion assays and in vivo through zebrafish xenografts experiments. The whole transcriptome of RAGE-overexpressing BC cells was screened by high-throughput RNA sequencing. Thereafter, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses allowed the prediction of potential functions of differentially expressed genes (DEGs). Flow cytometry, real time-PCR, chromatin immunoprecipitation, immunofluorescence and western blot assays were performed to investigate the molecular network involved in the regulation of a novel RAGE target gene namely EphA3. The clinical significance of EphA3 was explored in the TCGA cohort of patients through the survivALL package, whereas the pro-migratory role of EphA3 signaling was ascertained in both BC cells and cancer-associated fibroblasts (CAFs). Statistical analysis was performed by t-tests.

RESULTS

RNA-seq findings and GSEA analysis revealed that RAGE overexpression leads to a motility-related gene signature in ER-positive BC cells. Accordingly, we found that RAGE-overexpressing BC cells exhibit long filopodia-like membrane protrusions as well as an enhanced dissemination potential, as determined by the diverse experimental assays. Mechanistically, we established for the first time that EphA3 signaling may act as a physical mediator of BC cells and CAFs motility through both homotypic and heterotypic interactions.

CONCLUSIONS

Our data demonstrate that RAGE up-regulation leads to migratory ability in ER-positive BC cells. Noteworthy, our findings suggest that EphA3 may be considered as a novel RAGE target gene facilitating BC invasion and scattering from the primary tumor mass. Overall, the current results may provide useful insights for more comprehensive therapeutic approaches in BC, particularly in obese and diabetic patients that are characterized by high RAGE levels.

High-mobility group box 1 (HMGB1) crosses the BBB bidirectionally

High-mobility group box 1 (HMGB1) is a ubiquitous protein that regulates transcription in the nucleus, and is an endogenous damage-associated molecular pattern molecule that activates the innate immune system. HMGB1 activates the TLR4 and RAGE recepto, inducing downstream signals reminiscent of cytokines that have been found to cross the blood-brain barrier (BBB). Blood HMGB1 increases in stroke, sepsis, senescence, alcohol binge drinking and other conditions. Here, we examined the ability of HMGB1 radioactively labeled with iodine (I-HMGB1) to cross the BBB. We found that I-HMGB1 readily entered into mouse brain from the circulation with a unidirectional influx rate of 0.654 μl/g-min. All brain regions tested took up I-HMGB1; uptake was greatest by the olfactory bulb and least in the striatum. Transport was not reliably inhibited by unlabeled HMGB1 nor by inhibitors of TLR4, TLR2, RAGE, or CXCR4. Uptake was enhanced by co-injection of wheatgerm agglutinin, suggestive of involvement of absorptive transcytosis as a mechanism of transport. Induction of inflammation/neuroinflammation with lipopolysaccharide is known to increase blood HMGB1; we report here that brain transport is also increased by LPS-induced inflammation. Finally, we found that I-HMGB1 was also transported in the brain-to-blood direction, with both unlabeled HMGB1 or lipopolysaccharide increasing the transport rate. These results show that HMGB1 can bidirectionally cross the BBB and that those transport rates are enhanced by inflammation. Such transport provides a mechanism by which HMGB1 levels would impact neuroimmune signaling in both the brain and periphery.

MRP8/14 Is a Molecular Signature Triggered by Dopamine in HIV Latent Myeloid Targets That Increases HIV Transcription and Distinguishes HIV+ Methamphetamine Users with Detectable CSF Viral Load and Brain Pathology

There is a significant overlap between HIV infection and substance-use disorders. Dopamine (DA) is the most abundantly upregulated neurotransmitter in methamphetamine abuse, with receptors (DRD1-5) that are expressed by neurons as well as by a large diversity of cell types, including innate immune cells that are the targets of HIV infection, making them responsive to the hyperdopaminergic environment that is characteristic of stimulant drugs. Therefore, the presence of high levels of dopamine may affect the pathogenesis of HIV, particularly in the brain. The stimulation of HIV latently infected U1 promonocytes with DA significantly increased viral p24 levels in the supernatant at 24 h, suggesting effects on activation and replication. Using selective agonists to different DRDs, we found that DRD1 played a major role in activating viral transcription, followed by DRD4, which increased p24 with a slower kinetic rate compared to DRD1. Transcriptome and systems biology analyses led to the identification of a cluster of genes responsive to DA, where S100A8 and S100A9 were most significantly correlated with the early increase in p24 levels following DA stimulation. Conversely, DA increased the expression of these genes' transcripts at the protein level, MRP8 and MRP14, respectively, which form a complex also known as calprotectin. Interestingly, MRP8/14 was able to stimulate HIV transcription in latent U1 cells, and this occurred via binding of the complex to the receptor for an advanced glycosylation end-product (RAGE). Using selective agonists, both DRD1 and DRD4 increased MRP8/14 on the surface, in the cytoplasm, as well as secreted in the supernatants. On the other hand, while DRD1/5 did not affect the expression of RAGE, DRD4 stimulation caused its downregulation, offering a mechanism for the delayed effect via DRD4 on the p24 increase. To cross-validate MRP8/14 as a DA signature with a biomarker value, we tested its expression in HIV+ Meth users' postmortem brain specimens and peripheral cells. MRP8/14+ cells were more frequently identified in mesolimbic areas such as the basal ganglia of HIV+ Meth+ cases compared to HIV+ non-Meth users or to controls. Likewise, MRP8/14+ CD11b+ monocytes were more frequent in HIV+ Meth users, particularly in specimens from participants with a detectable viral load in the CSF. Overall, our results suggest that the MRP8 and MRP14 complex may serve as a signature to distinguish subjects using addictive substances in the context of HIV, and that this may play a role in aggravating HIV pathology by promoting viral replication in people with HIV who use Meth.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Clinical Manifestation of AGE-RAGE Axis in Neurodegenerative and Cognitive Impairment Disorders

The receptor of Advanced Glycation Endproducts (RAGE) and Advanced Glycation Endproducts (AGE) have multiple functions in our body and their restraint are being observed in neurodegenerative and memory impairment disorders. The review of different pathways allows an understanding of the probable mechanism of neurodegeneration and memory impairment involving RAGE and AGE. Commonly we observe AGE accumulation in neural cells and tissues but the extent of accumulation increases with the presence of memory impairment disorder. The presence of AGEs can also be seen in morbid accumulation, pathological structures in the form of amyloid clots, and nervous fibrillary tangles in Alzheimer's Disease (AD) and memory impairment disease.Many neuropathological and biochemical aspects of AD are explained by AGEs, including widespread protein crosslinking, glial activation of oxidative stress, and neuronal cell death. Oxidative stress is due to different reasons and glycation end products set in motion and form or define various actions which are normally due to AGE changes in a pathogenic cascade. By regulating the transit of ß-amyloid in and out of the brain or altering inflammatory pathways, AGE and it's ensnare receptor such as soluble RAGE may function as blockage or shield AD development. RAGE activates the transcription-controlling factor Necrosis Factor (NF-κB) and increases the protraction of cytokines, like a higher number of Tumor Necrosis Factor (TNF-α) and Interleukin (IL-I) by inducing several signal transduction cascades. Furthermore, binding to RAGE can pro-activate reactive oxygen species (ROS), which is popularly known to cause neuronal death.

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.

Effect of β-amyloid on blood-brain barrier properties and function

The deposition of beta-amyloid (Aβ) aggregates in the brain, accompanied by impaired cognitive function, is a characteristic feature of Alzheimer's disease (AD). An important role in this process is played by vascular disorders, in particular, a disturbance of the blood-brain barrier (BBB). The BBB controls the entry of Aβ from plasma to the brain via the receptor for advanced glycation end products (RAGE) and the removal of brain-derived Aβ via the low-density lipoprotein receptor-related protein (LRP1). The balance between the input of Aβ to the brain from the periphery and its output is disturbed during AD. Aβ changes the redox-status of BBB cells, which in turn changes the functioning of mitochondria and disrupts the barrier function of endothelial cells by affecting tight junction proteins. Aβ oligomers have the greatest toxic effect on BBB cells, and oligomers are most rapidly transferred by transcytosis from the brain side of the BBB to the blood side. Both the cytotoxic effect of Aβ and the impairment of barrier function are partly due to the interaction of Aβ monomers and oligomers with membrane-bound RAGE. AD therapies based on the disruption of this interaction or the creation of decoys for Aβ are being developed. The question of the transfer of various Aβ isoforms through the BBB is important, since it can influence the development of AD. It is shown that the rate of input of Aβ40 and Aβ42 from the blood into the brain is different. The actual question of the transfer of pathogenic Aβ isoforms with post-translational modifications or mutations through the BBB still remains open.

Unveiling new secrets in Parkinson's disease: The glycatome

We are witnessing a considerable increase in the incidence of Parkinson's disease (PD), which may be due to the general ageing of the population. While there is a plethora of therapeutic strategies for this disease, they still fail to arrest disease progression as they do not target and prevent the neurodegenerative process. The identification of disease-causing mutations allowed researchers to better dissect the underlying causes of this disease, highlighting, for example, the pathogenic role of alpha-synuclein. However, most PD cases are sporadic, which is making it hard to unveil the major causative mechanisms of this disease. In the recent years, epidemiological evidence suggest that type-2 diabetes mellitus (T2DM) individuals have higher risk and worst outcomes of PD, allowing to raise the hypothesis that some dysregulated processes in T2DM may contribute or even trigger the neurodegenerative process in PD. One major consequence of T2DM is the unprogrammed reaction between sugars, increased in T2DM, and proteins, a reaction named glycation. Pre-clinical reports show that alpha-synuclein is a target of glycation, and glycation potentiates its pathogenicity which contributes for the neurodegenerative process. Moreover, it triggers, anticipates, or aggravates several PD-like motor and non-motor complications. A given profile of proteins are differently glycated in diseased conditions, altering the brain proteome and leading to brain dysfunction and neurodegeneration. Herein we coin the term Glycatome as the profile of glycated proteins. In this review we report on the mechanisms underlying the association between T2DM and PD, with particular focus on the impact of protein glycation.

Regulation of the Blood-Brain Barrier in Health and Disease

The neurovascular unit is a dynamic microenvironment with tightly controlled signaling and transport coordinated by the blood-brain barrier (BBB). A properly functioning BBB allows sufficient movement of ions and macromolecules to meet the high metabolic demand of the central nervous system (CNS), while protecting the brain from pathogenic and noxious insults. This review describes the main cell types comprising the BBB and unique molecular signatures of these cells. Additionally, major signaling pathways for BBB development and maintenance are highlighted. Finally, we describe the pathophysiology of BBB diseases, their relationship to barrier dysfunction, and identify avenues for therapeutic intervention.

Regulation of beta-amyloid for the treatment of Alzheimer's disease: Research progress of therapeutic strategies and bioactive compounds

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is difficult to treat. Extracellular amyloid is the principal pathological criterion for the diagnosis of AD. Amyloid β (Aβ) interacts with various receptor molecules on the plasma membrane and mediates a series of signaling pathways that play a vital role in the occurrence and development of AD. Research on receptors that interact with Aβ is currently ongoing. Overall, there are no effective medications to treat AD. In this review, we first discuss the importance of Aβ in the pathogenesis of AD, then summarize the latest progress of Aβ-related targets and compounds. Finally, we put forward the challenges and opportunities in the development of effective AD therapies.

The process of methylglyoxal-induced retinal capillary endothelial cell degeneration in rats

Methylglyoxal, a highly reactive dicarbonyl compound, is increased and accumulated in patients with diabetic mellitus. Methylglyoxal forms advanced glycation end products (AGE), contributing to the pathogenesis of diabetic complications, including diabetic retinopathy. Recent studies have shown that methylglyoxal induces diabetic retinopathy-like abnormalities in retinal vasculature. In this study, we investigated the processes and mechanisms of methylglyoxal-induced retinal capillary endothelial cell degeneration in rats. Morphological changes in vascular components (endothelial cells, pericytes, and basement membranes) were assessed in the retinas 2, 7, and 14 days after intravitreal injection of methylglyoxal. Intravitreal methylglyoxal injection induced retinal capillary endothelial cell degeneration in a dose- and time-dependent manner. Changes in the shape and distribution of pericytes occurred before the initiation of capillary regression in the retinas of methylglyoxal-injected eyes. The receptor for AGEs (RAGEs) antagonist FPS-ZM1, and the matrix metalloproteinase (MMP) inhibitor GM6001 significantly attenuated methylglyoxal-induced capillary endothelial cell degeneration. FPS-ZM1 failed to prevent pathological changes in pericytes in methylglyoxal-injected eyes. In situ zymography revealed that MMP activity was enhanced at sites of blood vessels with reduced pericyte coverage in methylglyoxal-injected eyes. These results suggest that intravitreal methylglyoxal injection induces pathological changes in pericytes before the initiation of capillary endothelial cell degeneration via an AGE-RAGE-independent pathway. The capillary endothelial cell degeneration is mediated by activating the AGE-RAGE pathway and increasing MMP activity in endothelial cells by impairing pericyte function in the retina.

Updated Understanding of the Glial-Vascular Unit in Central Nervous System Disorders

The concept of the glial-vascular unit (GVU) was raised recently to emphasize the close associations between brain cells and cerebral vessels, and their coordinated reactions to diverse neurological insults from a "glio-centric" view. GVU is a multicellular structure composed of glial cells, perivascular cells, and perivascular space. Each component is closely linked, collectively forming the GVU. The central roles of glial and perivascular cells and their multi-level interconnections in the GVU under normal conditions and in central nervous system (CNS) disorders have not been elucidated in detail. Here, we comprehensively review the intensive interactions between glial cells and perivascular cells in the niche of perivascular space, which take part in the modulation of cerebral blood flow and angiogenesis, formation of the blood-brain barrier, and clearance of neurotoxic wastes. Next, we discuss dysfunctions of the GVU in various neurological diseases, including ischemic stroke, spinal cord injury, Alzheimer's disease, and major depression disorder. In addition, we highlight the possible therapies targeting the GVU, which may have potential clinical applications.

Neuroprotection of Food Bioactives in Neurodegenerative Diseases: Role of the Gut Microbiota and Innate Immune Receptors

Gut-brain connections may be mediated by an assortment of microbial molecules, which can subsequently traverse intestinal and blood-brain barriers and impact neurological function. Pattern recognition receptors (PRRs) are important innate immune proteins in the gut. Gut microbiota act in concert with the PRRs is a novel target for regulating host-microbe signaling and immune homeostasis, which may involve the pathogenesis of neurodegenerative diseases. Natural food bioactives bestow a protective advantage on neurodegenerative diseases through immunomodulatory effects of the modified gut microbiota or alterations in the landscape of microbiota-produced metabolites via PRRs modulation. In this review, we discuss the effect of natural food bioactives on the gut microbiota and the role of PRRs in the gut-brain crosstalk. We focused on the neuroprotective mechanisms of natural bioactive compounds behind the action of the gut microbiota and PRRs. Research advances in natural food bioactives as antineurodegeneration agents were also presented.

MiR-146a-5p Contributes to Microglial Polarization Transitions Associated With AGEs

M1/M2 polarization transitions of microglial phenotypes determine the states of neuroinflammation, which is critical in the pathophysiology of diabetic encephalopathy. This study aims to investigate the effects of advanced glycation end products (AGEs) on the microglial polarization state, the role of miR-146a-5p in the regulation of microglial polarization, and the underlying signaling pathways. BV-2 cells were incubated with N-ε-carboxymethyl lysine (CML), one kind of Advanced Glycation End Products (AGEs), to induce polarization. CD11b and iNOS and CD206 and Arg-1 were used to evaluate M1 and M2 microglia, respectively. The mRNA and protein expression levels of miR-146a-5p, transcription factor NF-κB, and inflammasome NLRP3 were measured. High and low expression of miR-146a-5p in the BV-2 cell line was generated by lentivirus transfection technology. RAGE, TLR-4, and NF-κB antagonists were applied to evaluate the underlying signaling pathways. Compared with the control group, CML upregulated the M1 phenotype and downregulated the M2 phenotype. These effects were reversed by overexpression of miR-146a. Furthermore, the expression of inflammasome NLRP3 and NF-κB was upregulated in the CML group and was reduced after miR-146a overexpression. And then overexpression of miR-146a effects was reversed by inhibition miR-146a expression. An NF-κB antagonist (PDTC), a RAGE antagonist (FPS-ZMI), and a TLR-4 antagonist (TLI-095) all reversed the polarization state induced by CML. In summary, CML induced polarization transitions to M1 phenotype and promoted inflammasome NLRP3 expression in BV-2 cells. The RAGE or TLR-4/miR-146a/NLRP3/NF-кB pathway might participate in the regulation of CML-induced BV-2 polarization.

Pharmacological Targeting of the RAGE-NFκB Signalling Axis Impedes Monocyte Activation under Diabetic Conditions through the Repression of SHP-2 Tyrosine Phosphatase Function

Monocytes play a vital role in the development of cardiovascular diseases. Type 2 diabetes mellitus (T2DM) is a major CVD risk factor, and T2DM-induced aberrant activation and enhanced migration of monocytes is a vital pathomechanism that leads to atherogenesis. We recently reported the upregulation of SHP-2 phosphatase expression in mediating the VEGF resistance of T2DM patient-derived monocytes or methylglyoxal- (MG, a glucose metabolite and advanced glycation end product (AGE) precursor) treated monocytes. However, the exact mechanisms leading to SHP-2 upregulation in hyperglycemic monocytes are unknown. Since inflammation and accumulation of AGEs is a hallmark of T2DM, we hypothesise that inflammation and AGE-RAGE (Receptor-for-AGEs) signalling drive SHP-2 expression in monocytes and blockade of these pathways will repress SHP-2 function. Indeed, monocytes from T2DM patients revealed an elevated SHP-2 expression. Under normoglycemic conditions, the serum from T2DM patients strongly induced SHP-2 expression, indicating that the T2DM serum contains critical factors that directly regulate SHP-2 expression. Activation of pro-inflammatory TNFα signalling cascade drove SHP-2 expression in monocytes. In line with this, linear regression analysis revealed a significant positive correlation between TNFα expression and SHP-2 transcript levels in T2DM monocytes. Monocytes exposed to MG or AGE mimetic AGE-BSA, revealed an elevated SHP-2 expression and co-treatment with an NFκB inhibitor or genetic inhibition of p65 reversed it. The pharmacological inhibition of RAGE was sufficient to block MG- or AGE-BSA-induced SHP-2 expression and activity. Confirming the importance of RAGE-NFκB signalling in regulating SHP-2 expression, the elevated binding of NFκB to the SHP-2 promoter-induced by MG or AGE-BSA-was reversed by RAGE and NFκB inhibition. Besides, we detected elevated RAGE levels in human and murine T2DM monocytes and monocytes exposed to MG or AGE-BSA. Importantly, MG and AGE-BSA treatment of non-T2DM monocytes phenocopied the aberrant pro-migratory phenotype of T2DM monocytes, which was reversed entirely by either SHP-2- or RAGE inhibition. In conclusion, these findings suggest a new therapeutic approach to prevent accelerated atherosclerosis in T2DM patients since inhibiting the RAGE-NFκB-SHP-2 axis impeded the T2DM-driven, SHP-2-dependent monocyte activation.