The novel RAGE interactor PRAK is associated with autophagy signaling in Alzheimer's disease pathogenesis

MK5 Regulates Microglial Activation and Neuroinflammation in Experimental Stroke Models

OBJECTIVE

Microglial activation plays a crucial role in neuroinflammation following ischemic stroke. This study was conducted to investigate the role and potential mechanisms of MK5 within microglial cells in the inflammatory response following ischemic stroke in mice in vivo and in vitro.

METHODS

Microglia-specific conditional MK5 knockout (MK5 cKO) mice and their control mice (MK5f/f) were subjected to middle cerebral artery occlusion (MCAO). BV2 cells (a mouse microglial cell line) were transfected with small interfering RNA (siRNA) to knock down MK5 levels and subsequently exposed to oxygen-glucose deprivation/reperfusion (OGD/R) to simulate ischemic conditions in vitro. Following MCAO, behavioral tests and infarct volume measurements were conducted. Levels of cytokines and microglial markers were evaluated using qPCR and Western blotting, while immunofluorescence was employed to observe microglial activation. Additionally, Western blotting was performed to assess the phosphorylation of HSP27 and NF-κB.

RESULTS

Compared to the control group, the knockout of the MK5 gene in microglia significantly exacerbated neurological deficits and increased infarct volume in MCAO mice. The loss of the MK5 promoted inflammation by upregulating pro-inflammatory factors and downregulating anti-inflammatory factors, while also enhancing microglial activation in both MCAO mice and BV2 microglial cells subjected to OGD/R. Furthermore, the knockout of the MK5 gene in microglia reduced the phosphorylation levels of HSP27 and increased the phosphorylation levels of NF-κB in the aforementioned models.

CONCLUSION

Microglial MK5 plays a critical role in the ischemic neuroinflammatory response by regulating the phosphorylation of HSP27 and NF-κB, positioning it as a potential target for stroke treatment.

Extracellular vesicles derived from monomeric α-synuclein-treated microglia ameliorate neuroinflammation by delivery of miRNAs targeting PRAK

Parkinson's disease (PD) is characterized by the formation of Lewy body, which mainly contains misfolded α-synuclein. Microglial activation plays a role in neurodegeneration. The pathologically oligomeric α-synuclein promotes inflammatory microglia, while physiologically monomeric α-synuclein induces anti-inflammatory microglia, the relationship between these two forms in activating microglia and the molecular mechanism is essentially unknown. In this study, using in vivo and in vitro models, we challenged primary or BV2 microglia with exogenous stimuli including α-synuclein. We examined microglial activation and the underlying mechanism by Western blot, RT-PCR, ELISA, IF, FCM, miRNA sequencing and bioinformatic analysis. Oligomeric α-synuclein activatedmicroglia via theinvolvement of the PRAK/MK5 pathway. The specific PRAK inhibitor GLPG0259 could mitigate microglial activation insulted by oligomeric α-synuclein. Monomeric α-synuclein regulated theanti-inflammatory microglia by delivering microglia-derived extracellular vesicles (EVs) in vitro and in vivo. Furthersequencingand bioinformatic analysis of microglial EVs-associated miRNAs indicatedthatmost of these miRNAs targeted PRAK. These results suggest that PRAK serves as an intersection in microglial activation when challenged with conformationally different α-synuclein. EVs derived from microglia treated with monomeric α-synuclein promote anti-inflammatory microglia by delivering miRNAs that target PRAK into recipient microglia.

Exosomes Derived from M2 Microglial Cells Modulated by 1070-nm Light Improve Cognition in an Alzheimer's Disease Mouse Model

Near-infrared photobiomodulation has been identified as a potential strategy for Alzheimer's disease (AD). However, the mechanisms underlying this therapeutic effect remain poorly characterize. Herein, it is illustrate that 1070-nm light induces the morphological alteration of microglia from an M1 to M2 phenotype that secretes exosomes, which alleviates the β-amyloid burden to improve cognitive function by ameliorating neuroinflammation and promoting neuronal dendritic spine plasticity. The results show that 4 J cm-2 1070-nm light at a 10-Hz frequency prompts microglia with an M1 inflammatory type to switch to an M2 anti-inflammatory type. This induces secretion of M2 microglial-derived exosomes containing miR-7670-3p, which targets activating transcription factor 6 (ATF6) during endoplasmic reticulum (ER) stress. Moreover, it is found that miR-7670-3p reduces ATF6 expression to further ameliorate ER stress, thus attenuating the inflammatory response and protecting dendritic spine integrity of neurons in the cortex and hippocampus of 5xFAD mice, ultimately leading to improvements in cognitive function. This study highlights the critical role of exosomes derive from 1070-nm light-modulated microglia in treating AD mice, which may provide a theoretical basis for the treatment of AD with the use of near-infrared photobiomodulation.

Design, synthesis and pharmacological evaluation of β-carboline derivatives as potential antitumor agent via targeting autophagy

A series of novel β-carboline derivatives was designed, synthesized and evaluated as potential anticancer agents. Among them, compound 6g showed the most potent antiproliferative activity against the 786-0, HT-29 and 22RV1 cell lines with IC₅₀ values of 2.71, 2.02, and 3.86 μM, respectively. The antitumor efficiency of compound 6gin vivo was also evaluated, and the results revealed that compound 6g significantly suppressed tumor development and reduced tumor weight in a mouse colorectal cancer homograft model. Further investigation on mechanisms of action demonstrated that compound 6g inhibited HCT116 cell growth by stimulating the ATG5/ATG7-dependent autophagic pathway. These molecules might be served as candidates for further development of colorectal cancer therapy agent.

Impairment of insulin signaling pathway PI3K/Akt/mTOR and insulin resistance induced AGEs on diabetes mellitus and neurodegenerative diseases: a perspective review

Insulin resistance is common in type 2 diabetes mellitus (T2DM), neurodegenerative diseases, cardiovascular diseases, kidney diseases, and polycystic ovary syndrome. Impairment in insulin signaling pathways, such as the PI3K/Akt/mTOR pathway, would lead to insulin resistance. It might induce the synthesis and deposition of advanced glycation end products (AGEs), reactive oxygen species, and reactive nitrogen species, resulting in stress, protein misfolding, protein accumulation, mitochondrial dysfunction, reticulum function, and metabolic syndrome dysregulation, inflammation, and apoptosis. It plays a huge role in various neurodegenerative diseases like Parkinson's disease, Alzheimer's disease, Huntington's disease, and Amyloid lateral sclerosis. In this review, we intend to focus on the possible effect of insulin resistance in the progression of neurodegeneration via the impaired P13K/Akt/mTOR signaling pathway, AGEs, and receptors for AGEs.

Rab31, a receptor of advanced glycation end products (RAGE) interacting protein, inhibits AGE induced pancreatic β-cell apoptosis through the pAKT/BCL2 pathway

Receptor of advanced glycation end products (RAGE) mediates diverse signal transduction following ligand stimulation and plays an important role in diabetes complications and aging associated disease. We have previously verified that advanced glycation end products (AGE) bind to RAGE to cause pancreatic β-cell apoptosis through the mitochondrial pathway. However, the direct interacting protein(s) of RAGE in β cells has never been appreciated. In the present study, we utilized GST pull-down assay combined with mass spectrometry to identify the interacting proteins of the RAGE intracellular domain (C-terminal 43 amino acid of RAGE). Overall four RAGE interacting proteins, including Rab31, were identified with scores over 160. Rab31 was detected in three β-cell lines and confirmed to have interacted with RAGE via co-immunoprecipitation and immunostaining assays. This interaction was further enhanced by glycation-serum (GS) stimulation due to membrane distribution of Rab31 following treatment with GS. We further confirmed that Rab31 promoted RAGE endocytosis and inhibited GS-induced β-cell apoptosis through the pAKT/BCL2 pathway. These findings reveal a new RAGE interaction protein Rab31 that prevents AGE/RAGE-induced pancreatic β-cell apoptosis. Rab31 is therefore a promising therapeutic target for preserving functional β cells under diabetes conditions.

Role and Therapeutic Potential of RAGE Signaling in Neurodegeneration

Activation of the receptor for advanced glycation end products (RAGE) has been shown to play an active role in the development of multiple neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis. Although originally identified as a receptor for advanced glycation end products, RAGE is a pattern recognition receptor able to bind multiple ligands. The final outcome of RAGE signaling is defined in a context and cell type specific manner and can exert both neurotoxic and neuroprotective functions. Contributing to the complexity of the RAGE signaling network, different RAGE isoforms with distinctive signaling capabilities have been described. Moreover, multiple RAGE ligands bind other receptors and RAGE antagonism can significantly affect their signaling. Here, we discuss the outcome of celltype specific RAGE signaling in neurodegenerative pathologies. In addition, we will review the different approaches that have been developed to target RAGE signaling and their therapeutic potential. A clear understanding of the outcome of RAGE signaling in a cell type- and disease-specific manner would contribute to advancing the development of new therapies targeting RAGE. The ability to counteract RAGE neurotoxic signaling while preserving its neuroprotective effects would be critical for the success of novel therapies targeting RAGE signaling.

Neuroprotective Effects of Endogenous Secretory Receptor for Advanced Glycation End-products in Brain Ischemia

The receptor for advanced glycation end-products (RAGE) is expressed on human brain endothelial cells (HBEC) and is implicated in neuronal cell death after ischemia. We report that endogenous secretory RAGE (esRAGE) is a splicing variant form of RAGE that functions as a decoy against ischemia-induced neuronal cell damage. This study demonstrated that esRAGE was associated with heparan sulphate proteoglycans on HBEC. The parabiotic experiments between human esRAGE overexpressing transgenic (Tg), RAGE knockout (KO), and wild-type (WT) mice revealed a significant neuronal cell damage in the CA1 region of the WT side of parabiotic WT→WT mice, but not of Tg→WT mice, 7 days after bilateral common carotid artery occlusion. Human esRAGE was detected around the CA1 neurons in the WT side of the parabiotic Tg→WT pair, but not in the KO side of the Tg→KO pair. To elucidate the dynamic transfer of esRAGE into the brain, we used the blood-brain barrier (BBB) system (PharmaCo-Cell) with or without RAGE knockdown in endothelial cells. A RAGE-dependent transfer of esRAGE was demonstrated from the vascular to the brain side. These findings suggested that esRAGE is associated with heparan sulphate proteoglycans and is transferred into the brain via BBB to exert its neuroprotective effects in ischemia.

Advanced Glycation End Products (AGEs), Glutathione and Breast Cancer: Factors, Mechanism and Therapeutic Interventions

Background:

Advanced Glycation End products (AGEs) are basically the end result of glycation of proteins and/or lipids in the presence of sugars. Specific cases of hyperglycemia have been reported with increased propensity of generation of AGEs. Many chronic and deadly diseases such as diabetes, cancer and neurodegenerative disorders have been known to be caused as a result of generation of AGEs. The role of glutathione (GSH) metabolism and its intricate association with AGEs have also been well established in breast cancer prognosis and treatment. To understand the etiology, mechanism and production of AGEs along with clinical relevance of Receptors for Advanced Glycation End-products (RAGE) and RAGE ligands, their interplay with GSH is of paramount importance especially in relation to breast cancer.

Methods:

The available literature using PubMed, National Library of Medicine database, Web of Science and SCOPUS indexed, Science Direct and other prestigious journals have been systematically reviewed using the keywords: advanced glycation end-products, breast cancer, glutathione RAGE, and AGEs inhibitors. This narrative review of all the relevant papers with significant citations has led us to have greater insight into the action mechanism and potential therapeutic significance of AGEs inhibitors.

Results:

Targeting breast cancer with the specific immunoglobulins and with other therapeutic interventions is needed to inhibit the generation of AGEs and manage glutathione expression, thus having strong implications in the management of breast cancer. Many RAGE ligands such as HMGB1, S100P, S100A8, S100A9 etc. have been known to enhance RAGE expression which may further lead to increased proliferation, migration and metastatic nature of tumor cells. Hence, RAGE and RAGE ligands in a close linkup with GSH may prove to be effective therapeutic markers of severity of breast cancer and for angiogenesis of tumor.

Conclusion:

This review provides a strong platform to comprehend the etiology, mechanism and production of AGEs and glutathione along with the agents which can block their production, paving a way for the therapeutic intervention and an amicable solution to treat and manage breast cancer.

TREM2 in Alzheimer's Disease: Microglial Survival and Energy Metabolism

Alzheimer’s disease (AD) is the leading cause of age-related dementia among the elderly population. Recent genetic studies have identified rare variants of the gene encoding the triggering receptor expressed on myeloid cells-2 (TREM2) as significant genetic risk factors in late-onset AD (LOAD). TREM2 is specifically expressed in brain microglia and modulates microglial functions in response to key AD pathologies such as amyloid-β (Aβ) plaques and tau tangles. In this review article, we discuss recent research progress in our understanding on the role of TREM2 in microglia and its relevance to AD pathologies. In addition, we discuss evidence describing new TREM2 ligands and the role of TREM2 signaling in microglial survival and energy metabolism. A comprehensive understanding of TREM2 function in the pathogenesis of AD offers a unique opportunity to explore the potential of this microglial receptor as an alternative target in AD therapy.

Depression and sterile inflammation: Essential role of danger associated molecular patterns

Stress is a major risk factor for psychiatric disorder including major depressive disorder (MDD) and can induce inflammation, which is known to be dysregulated in depression. Several clinical and pre-clinical studies have demonstrated a strong association between depressive symptoms and the expression of factors that increase inflammation. Conversely, administration of anti-inflammatory agents has been shown to ameliorate depressive symptoms, demonstrating the importance of inflammation as a mediator of depression. Although it is clear that inflammation plays a role in the pathophysiology of depression, the mechanism by which inflammation is activated in mood disorders remains unclear. To address this issue, studies have investigated the role of pattern recognition receptor (PRR) activation in stress-induced inflammation and mood disorders. However, the identification of the endogenous factors, referred to as danger-associated molecular patterns (DAMP) that activate these receptors remains understudied. Here we review the role of DAMPs in depression and highlight the clinical evidence for elevation of DAMP signaling in MDD patients and in pre-clinical animal stress models of depression.

A High Content Screen in Macrophages Identifies Small Molecule Modulators of STING-IRF3 and NFkB Signaling

We screened a library of bioactive small molecules for activators and inhibitors of innate immune signaling through IRF3 and NFkB pathways with the goals of advancing pathway understanding and discovering probes for immunology research. We used high content screening to measure the translocation from the cytoplasm to nucleus of IRF3 and NFkB in primary human macrophages; these transcription factors play a critical role in the activation of STING and other pro-inflammatory pathways. Our pathway activator screen yielded a diverse set of hits that promoted nuclear translocation of IRF3 and/or NFkB, but the majority of these compounds did not cause activation of downstream pathways. Screening for antagonists of the STING pathway yielded multiple kinase inhibitors, some of which inhibit kinases not previously known to regulate the activity of this pathway. Structure-activity relationships (SARs) and subsequent chemical proteomics experiments suggested that MAPKAPK5 (PRAK) is a kinase that regulates IRF3 translocation in human macrophages. Our work establishes a high content screening approach for measuring pro-inflammatory pathways in human macrophages and identifies novel ways to inhibit such pathways; among the targets of the screen are several molecules that may merit further development as anti-inflammatory drugs.

Molecular and functional signatures in a novel Alzheimer's disease mouse model assessed by quantitative proteomics

Background

Alzheimer’s disease (AD), the most common neurodegenerative disorder, is characterized by the deposition of extracellular amyloid plaques and intracellular neurofibrillary tangles. To understand the pathological mechanisms underlying AD, developing animal models that completely encompass the main features of AD pathologies is indispensable. Although mouse models that display pathological hallmarks of AD (amyloid plaques, neurofibrillary tangles, or both) have been developed and investigated, a systematic approach for understanding the molecular characteristics of AD mouse models is lacking.

Methods

To elucidate the mechanisms underlying the contribution of amyloid beta (Aβ) and tau in AD pathogenesis, we herein generated a novel animal model of AD, namely the AD-like pathology with amyloid and neurofibrillary tangles (ADLP^APT) mice. The ADLP^APT mice carry three human transgenes, including amyloid precursor protein, presenilin-1, and tau, with six mutations. To characterize the molecular and functional signatures of AD in ADLP^APT mice, we analyzed the hippocampal proteome and performed comparisons with individual-pathology transgenic mice (i.e., amyloid or neurofibrillary tangles) and wild-type mice using quantitative proteomics with 10-plex tandem mass tag.

Results

The ADLP^APT mice exhibited accelerated neurofibrillary tangle formation in addition to amyloid plaques, neuronal loss in the CA1 area, and memory deficit at an early age. In addition, our proteomic analysis identified nearly 10,000 protein groups, which enabled the identification of hundreds of differentially expressed proteins (DEPs) in ADLP^APT mice. Bioinformatics analysis of DEPs revealed that ADLP^APT mice experienced age-dependent active immune responses and synaptic dysfunctions.

Conclusions

Our study is the first to compare and describe the proteomic characteristics in amyloid and neurofibrillary tangle pathologies using isobaric label-based quantitative proteomics. Furthermore, we analyzed the hippocampal proteome of the newly developed ADLP^APT model mice to investigate how both Aβ and tau pathologies regulate the hippocampal proteome. Because the ADLP^APT mouse model recapitulates the main features of AD pathogenesis, the proteomic data derived from its hippocampus has significant utility as a novel resource for the research on the Aβ-tau axis and pathophysiological changes in vivo.

Electronic supplementary material

The online version of this article (10.1186/s13024-017-0234-4) contains supplementary material, which is available to authorized users.

MK5: A novel regulator of cardiac fibroblast function?

MAP kinase-activated protein kinases (MKs), protein serine/threonine kinases downstream of the MAPKs, regulate a number of biological functions. MK5 was initially identified as a substrate for p38 MAPK but subsequent studies revealed that MK5 activity is regulated by atypical MAPKs ERK3 and ERK4. However, the roles of these MAPKs in activating MK5 remain controversial. The interactome and physiological function of MK5 are just beginning to be understood. Here, we provide an overview of the structure-function of MK5 including recent progress in determining its role in cardiac structure and function. The cardiac phenotype of MK5 haplodeficient mice, and the effect of reduced MK5 expression on cardiac remodeling, is also discussed. © 2017 IUBMB Life, 69(10):785-794, 2017.

Relationship between Advanced Glycation End Products and Steroidogenesis in PCOS

BACKGROUND

Women with PCOS have elevated levels of the harmful Advanced Glycation End Products (AGEs), which are highly reactive molecules formed after glycation of lipids and proteins. Additionally, AGEs accumulate in the ovaries of women with PCOS potentially contributing to the well-documented abnormal steroidogenesis and folliculogenesis.

MAIN BODY

A systematic review of articles and abstracts available in PubMed was conducted and presented in a systemic manner. This article reports changes in steroidogenic enzyme activity in granulosa and theca cells in PCOS and PCOS-models. It also described the changes in AGEs and their receptors in the ovaries of women with PCOS and presents the underlying mechanism(s) whereby AGEs could be responsible for the PCOS-related changes in granulosa and theca cell function thus adversely impacting steroidogenesis and follicular development. AGEs are associated with hyperandrogenism in PCOS possibly by altering the activity of various enzymes such as cholesterol side-chain cleavage enzyme cytochrome P450, steroidogenic acute regulatory protein, 17α-hydroxylase, and 3β-hydroxysteroid dehydrogenase. AGEs also affect luteinizing hormone receptor and anti-Mullerian hormone receptor expression as well as their signaling pathways in granulosa cells.

CONCLUSIONS

A better understanding of how AGEs alter granulosa and theca cell function is likely to contribute meaningfully to a conceptual framework whereby new interventions to prevent and/or treat ovarian dysfunction in PCOS can ultimately be developed.

Direct interaction of beta-amyloid with Na,K-ATPase as a putative regulator of the enzyme function

By maintaining the Na⁺ and K⁺ transmembrane gradient mammalian Na,K-ATPase acts as a key regulator of neuronal electrotonic properties. Na,K-ATPase has an important role in synaptic transmission and memory formation. Accumulation of beta-amyloid (Aβ) at the early stages of Alzheimer’s disease is accompanied by reduction of Na,K-ATPase functional activity. The molecular mechanism behind this phenomenon is not known. Here we show that the monomeric Aβ(1-42) forms a tight (K_d of 3 μM), enthalpy-driven equimolar complex with α1β1 Na,K-ATPase. The complex formation results in dose-dependent inhibition of the enzyme hydrolytic activity. The binding site of Aβ(1-42) is localized in the “gap” between the alpha- and beta-subunits of Na,K-ATPase, disrupting the enzyme functionality by preventing the subunits from shifting towards each other. Interaction of Na,K-ATPase with exogenous Aβ(1-42) leads to a pronounced decrease of the enzyme transport and hydrolytic activity and Src-kinase activation in neuroblastoma cells SH-SY5Y. This interaction allows regulation of Na,K-ATPase activity by short-term increase of the Aβ(1-42) level. However prolonged increase of Aβ(1-42) level under pathological conditions could lead to chronical inhibition of Na,K-ATPase and disruption of neuronal function. Taken together, our data suggest the role of beta-amyloid as a novel physiological regulator of Na,K-ATPase.