CLIC1 function is required for beta-amyloid-induced generation of reactive oxygen species by microglia

CLIC1 and IFITM2 expression in brain tissue correlates with cognitive impairment via immune dysregulation in sepsis and Alzheimer's disease

BACKGROUND

Sepsis, a life-threatening condition driven by dysregulated host responses to infection, is associated with long-term cognitive impairments resembling Alzheimer's disease (AD). However, the molecular mechanisms linking sepsis-induced cognitive dysfunction and AD remain unclear. We hypothesized that shared genetic pathways underlie cognitive deficits in both conditions.

METHODS

Cecal ligation and puncture (CLP) in C57BL/6 J mice modeled sepsis-induced cognitive decline and amyloid pathology. Brain tissue datasets (GSE33000 for AD; GSE135838 for sepsis) were analyzed via Weighted Gene Co-expression Network Analysis (WGCNA), machine learning, and functional enrichment. Key genes were validated through ROC analysis, immune infiltration profiling, and in vivo/in vitro experiments.

RESULTS

Sepsis accelerated cognitive decline and AD-like pathology in mice. Bioinformatics identified CLIC1 and IFITM2 as co-diagnostic genes linked to immune dysregulation in both sepsis and AD. Immune infiltration revealed reduced neutrophils/NK cells, M1 macrophage polarization, and naïve-to-memory B cell shifts in sepsis versus AD. CLIC1 and IFITM2 were upregulated in CLP mice and cytokine-stimulated human cerebral endothelial cells, aligning with bioinformatics predictions.

CONCLUSION

CLIC1 and IFITM2, pivotal in immune cell activation, emerged as shared biomarkers of sepsis-related cognitive impairment and AD. These findings highlight immune-driven molecular intersections in cognitive deficits, offering novel targets for mechanistic research and therapeutic development.

Targeting the NLRP3 inflammasome in Parkinson's disease: From molecular mechanism to therapeutic strategy

Parkinson's disease is the second most common neurodegenerative disease, characterized by substantial loss of dopaminergic (DA) neurons, the formation of Lewy bodies (LBs) in the substantia nigra, and pronounced neuroinflammation. The nucleotide-binding domain like leucine-rich repeat- and pyrin domain-containing protein 3 (NLRP3) inflammasome is one of the pattern recognition receptors (PRRs) that function as intracellular sensors in response to both pathogenic microbes and sterile triggers associated with Parkinson's disease. These triggers include reactive oxygen species (ROS), misfolding protein aggregation, and potassium ion (K+) efflux. Upon activation, it recruits and activates caspase-1, then processes the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18, which mediate neuroinflammation in Parkinson's disease. In this review, we provide a comprehensive overview of NLRP3 inflammasome, detailing its structure, activation pathways, and the factors that trigger its activation. We also explore the pathological mechanisms by which NLRP3 contributes to Parkinson's disease and discuss potential strategies for targeting NLRP3 as a therapeutic approach.

Circular RNA APP contributes to Alzheimer's disease pathogenesis by modulating microglial polarization via miR-1906/CLIC1 axis

BACKGROUND

Abnormal microglial polarization phenotypes contribute to the pathogenesis of Alzheimer's disease (AD). Circular RNAs (circRNAs) have garnered increasing attention due to their significant roles in human diseases. Although research has demonstrated differential expression of circRNAs in AD, their specific functions in AD pathogenesis remain largely unexplored.

METHODS

CircRNA microarray was performed to identify differentially expressed circRNAs in the hippocampus of APP/PS1 and WT mice. The stability of circAPP was assessed via RNase R treatment assay. CircAPP downstream targets miR-1906 and chloride intracellular channel 1 (CLIC1) were identified using bioinformatics and proteomics, respectively. RT-PCR assay was conducted to detect the expression of circAPP, miR-1906 and CLIC1. Morris water maze (MWM) test, passive avoidance test and novel object recognition task were used to detect cognitive function of APP/PS1 mice. Microglial M1/M2 polarization and AD pathology were assessed using Western blot, flow cytometry and Golgi staining assays. CLIC1 expression and channel activity were evaluated using Western blot and functional chloride channel assays, respectively. The subcellular location of circAPP was assessed via FISH and RT-PCR assays. RNA pull-down assay was performed to detect the interaction of miR-1906 with circAPP and 3' untranslated region (3'UTR) of CLIC1 mRNA.

RESULTS

In this study, we identified a novel circRNA, named circAPP, that is encoded by amyloid precursor protein (APP) and is implicated in AD. CircAPP is a stable circRNA that was upregulated in Aβ-treated microglial cells and the hippocampus of APP/PS1 mice. Downregulation of circAPP or CLIC1, or overexpression of miR-1906 in microglia modulated microglial M1/M2 polarization in Aβ-treated microglial cells and the hippocampus of APP/PS1 mice, and improved AD pathology and the cognitive function of APP/PS1 mice. Further results revealed that circAPP was mainly distributed in the cytoplasm, and circAPP could regulate CLIC1 expression and channel activity by interacting with miR-1906 and affecting miR-1906 expression, thereby regulating microglial polarization in AD.

CONCLUSIONS

Taken together, our study elucidates the regulatory role of circAPP in AD microglial polarization via miR-1906/CLIC1 axis, and suggests that circAPP may act as a critical player in AD pathogenesis and represent a promising therapeutic target for AD.

Identification of an ionic mechanism for ERα-mediated rapid excitation in neurons

The major female ovarian hormone, 17β-estradiol (E2), can alter neuronal excitability within milliseconds to regulate a variety of physiological processes. Estrogen receptor-α (ERα), classically known as a nuclear receptor, exists as a membrane-bound receptor to mediate this rapid action of E2, but the ionic mechanisms remain unclear. Here, we show that a membrane channel protein, chloride intracellular channel protein-1 (Clic1), can physically interact with ERα with a preference to the membrane-bound ERα. Clic1-mediated currents can be enhanced by E2 and reduced by its depletion. In addition, Clic1 currents are required to mediate the E2-induced rapid excitations in multiple brain ERα populations. Further, genetic disruption of Clic1 in hypothalamic ERα neurons blunts the regulations of E2 on female body weight balance. In conclusion, we identified the Clic1 chloride channel as a key mediator for E2-induced rapid neuronal excitation, which may have a broad impact on multiple neurobiological processes regulated by E2.

Chloride intracellular channel 4 participates in the regulation of lipopolysaccharide-induced inflammatory responses in human bronchial epithelial cells

The airway epithelium is located at the interactional boundary between the external and internal environments of the organism and is often exposed to harmful environmental stimuli. Inflammatory response that occurs after airway epithelial stress is the basis of many lung and systemic diseases. Chloride intracellular channel 4 (CLIC4) is abundantly expressed in epithelial cells. The purpose of this study was to investigate whether CLIC4 is involved in the regulation of lipopolysaccharide (LPS)-induced inflammatory response in airway epithelial cells and to clarify its potential mechanism. Our results showed that LPS induced inflammatory response and decreased CLIC4 levels in vivo and in vitro. CLIC4 silencing aggravated the inflammatory response in epithelial cells, while overexpression of CLIC4 combined with LPS exposure significantly decreased the inflammatory response compared with cells exposed to LPS without CLIC4 overexpression. By labeling intracellular chloride ions with chloride fluorescent probe MQAE, we showed that CLIC4 mediated intracellular chloride ion-regulated LPS-induced cellular inflammatory response.

A CLIC1 network coordinates matrix stiffness and the Warburg effect to promote tumor growth in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) features substantial matrix stiffening and reprogrammed glucose metabolism, particularly the Warburg effect. However, the complex interplay between these traits and their impact on tumor advancement remains inadequately explored. Here, we integrated clinical, cellular, and bioinformatics approaches to explore the connection between matrix stiffness and the Warburg effect in PDAC, identifying CLIC1 as a key mediator. Elevated CLIC1 expression, induced by matrix stiffness through Wnt/β-catenin/TCF4 signaling, signifies poorer prognostic outcomes in PDAC. Functionally, CLIC1 serves as a catalyst for glycolytic metabolism, propelling tumor proliferation. Mechanistically, CLIC1 fortifies HIF1α stability by curbing hydroxylation via reactive oxygen species (ROS). Collectively, PDAC cells elevate CLIC1 levels in a matrix-stiffness-responsive manner, bolstering the Warburg effect to drive tumor growth via ROS/HIF1α signaling. Our insights highlight opportunities for targeted therapies that concurrently address matrix properties and metabolic rewiring, with CLIC1 emerging as a promising intervention point.

Upregulation of NADPH-oxidase, inducible nitric oxide synthase and apoptosis in the hippocampus following impaired insulin signaling in the rats: Development of sporadic Alzheimer's disease

NADPH-oxidase (NOX) is a multi-subunit enzyme complex. The upregulation of NOX causes massive production of superoxide (O2¯), which avidly reacts with nitric oxide (NO) and increases cellular reactive oxygen/nitrogen species (ROS/RNS). Increased ROS/RNS plays pivotal role in the sporadic Alzheimer's disease (sAD) development and brain damage following impaired insulin signaling. Hence, this study aimed to examine early-time course of changes in NOX and NOS expression, and apoptotic proteins in the rats hippocampi following insulin signaling impairment [induced by STZ injection; intraperitoneal (IP) or in cerebral ventricles (ICV)]. Early effects (1, 3, or 6 weeks) on the NOX activity, translocation of NOX subunits from cytosol to the membrane, NO-synthases [neuronal-, inducible- and endothelial-NOS; nNOS, iNOS and eNOS], The Rac-1 protein expression, levels of NO and O2¯, cytochrome c release, caspase-3 and 9 activations (cleavage) were studied. STZ injection (in both models) increased NOX activity, O2¯ production, and enhanced cytosolic subunits translocation into membrane. The iNOS but not nNOS and eNOS expression and NO levels were increased in STZ treated rats. Finally, STZ injection increased cytochrome c release, caspase-3 and 9 activations in a manner that was significantly associated with levels of O2¯ and NO in the hippocampus. ICV-STZ administration resulted in significant profound changes over the IP route. In conclusion, impairment in insulin function induces early changes in ROS/RNS contents through NOX and iNOS upregulation and neuronal apoptosis in the hippocampus. Our results could mechanistically explain the role of impaired insulin function in the development of sAD.

Retrograde AAV-mediated gene modulation reveals chloride intracellular channel proteins as potent regulators of retinal ganglion cell death

Most projection neurons, including retinal ganglion cells (RGCs), undergo cell death after axotomy proximal to the cell body. Specific RGC subtypes, such as ON-OFF direction selective RGCs (ooDSGCs) are particularly vulnerable, whereas intrinsically photosensitive RGCs (ipRGCs) exhibit resilience to axonal injury. Through the application of RNA sequencing and fluorescent in situ hybridization, we show that the expression of chloride intracellular channel protein 1 and 4 (Clic1 and Clic4) are highly increased in the ooDSGCs after axonal injury. Toward determining a gene's role in RGCs, we optimized the utility and efficacy of adenovirus associated virus (AAV)-retro expressing short hairpin RNA (shRNA). Injection of AAV2-retro into the superior colliculus results in efficient shRNA expression in RGCs. Incorporating histone H2B gene fused with mGreenLantern results in bright nuclear reporter expression, thereby enhancing single RGC identification and cell quantitation in live retinas. Lastly, we demonstrate that AAV2-retro mediated knockdown of both Clic1 and Clic4 promotes RGC survival after injury. Our findings establish an integrated use of AAV2-retro-shRNA and real-time fundus imaging and reveal CLICs' contribution to RGC death.

Chloride ions in health and disease

Chloride is a key anion involved in cellular physiology by regulating its homeostasis and rheostatic processes. Changes in cellular Cl- concentration result in differential regulation of cellular functions such as transcription and translation, post-translation modifications, cell cycle and proliferation, cell volume, and pH levels. In intracellular compartments, Cl- modulates the function of lysosomes, mitochondria, endosomes, phagosomes, the nucleus, and the endoplasmic reticulum. In extracellular fluid (ECF), Cl- is present in blood/plasma and interstitial fluid compartments. A reduction in Cl- levels in ECF can result in cell volume contraction. Cl- is the key physiological anion and is a principal compensatory ion for the movement of the major cations such as Na+, K+, and Ca2+. Over the past 25 years, we have increased our understanding of cellular signaling mediated by Cl-, which has helped in understanding the molecular and metabolic changes observed in pathologies with altered Cl- levels. Here, we review the concentration of Cl- in various organs and cellular compartments, ion channels responsible for its transportation, and recent information on its physiological roles.

Chloride intracellular channel (CLIC) proteins function as fusogens

Chloride Intracellular Channel (CLIC) family members uniquely transition between soluble and membrane-associated conformations. Despite decades of extensive functional and structural studies, CLICs' function as ion channels remains debated, rendering our understanding of their physiological role incomplete. Here, we expose the function of CLIC5 as a fusogen. We demonstrate that purified CLIC5 directly interacts with the membrane and induces fusion, as reflected by increased liposomal diameter and lipid and content mixing between liposomes. Moreover, we show that this activity is facilitated by acidic pH, a known trigger for CLICs' transition to a membrane-associated conformation, and that increased exposure of the hydrophobic inter-domain interface is crucial for this process. Finally, mutation of a conserved hydrophobic interfacial residue diminishes the fusogenic activity of CLIC5 in vitro and impairs excretory canal extension in C. elegans in vivo. Together, our results unravel the long-sought physiological role of these enigmatic proteins.

Proteomic Analysis to Identify Prospective Biomarkers of Treatment Outcome After Microvascular Decompression for Trigeminal Neuralgia: A Preliminary Study

Trigeminal neuralgia (TN) is a severe neuropathic facial pain disorder, often caused by vascular or neuronal compression of the trigeminal nerve. In such cases, microvascular decompression (MVD) surgery can be used to treat TN, but pain relief is not guaranteed. The molecular mechanisms that affect treatment response to MVD are not well understood. In this exploratory study, we performed label-free quantitative proteomic profiling of plasma and cerebrospinal fluid samples from patients undergoing MVD for TN, then compared the proteomic profiles of patients graded as responders (n = 7) versus non-responders (n = 9). We quantified 1,090 proteins in plasma and 1,087 proteins in the cerebrospinal fluid, of which 12 were differentially regulated in the same direction in both sample types. Functional analyses of differentially regulated proteins in protein-protein interaction networks suggested pathways of the immune system, axon guidance, and cellular stress response to be associated with response to MVD. These findings suggest potential biomarkers of response to MVD, as well as possible mechanisms of variable treatment success in TN patients. PERSPECTIVE: This exploratory study evaluates proteomic profiles in plasma and cerebrospinal fluid of patients undergoing microvascular decompression surgery for trigeminal neuralgia. Differential expression of proteins between surgery responders versus non-responders may serve as biomarkers to predict surgical success and provide insight into surgical mechanisms of pain relief in trigeminal neuralgia.

The Cl- transporter ClC-7 is essential for phagocytic clearance by microglia

Microglia, professional phagocytic cells of the brain, rely upon the appropriate activation of lysosomes to execute their immune and clearance functions. Lysosomal activity is, in turn, modulated by a complex network of over 200 membrane and accessory proteins that relay extracellular cues to these key degradation centers. The ClC-7 chloride (Cl-)-proton (H+) antiporter (also known as CLCN7) is localized to the endolysosomal compartments and mutations in CLCN7 lead to osteopetrosis and neurodegeneration. Although the functions of ClC-7 have been extensively investigated in osteoclasts and neurons, its role in microglia in vivo remains largely unexamined. Here, we show that microglia and embryonic macrophages in zebrafish clcn7 mutants cannot effectively process extracellular debris in the form of apoptotic cells and β-amyloid. Despite these functional defects, microglia develop normally in clcn7 mutants and display normal expression of endosomal and lysosomal markers. We also find that mutants for ostm1, which encodes the β-subunit of ClC-7, have a phenotype that is strikingly similar to that of clcn7 mutants. Together, our observations uncover a previously unappreciated role of ClC-7 in microglia and contribute to the understanding of the neurodegenerative phenotypes that accompany mutations in this channel.

Salivary Chloride Intracellular Channel 1 (CLIC1) as a Hub of Gene-Gene Interactome of Periodontitis With Diabetes Mellitus

Background and introduction Periodontal disease is one of the most prevalent chronic conditions that affects the oral cavity. Identifying and predicting biomarkers is essential for the prevention of high-morbidity oral diseases. The genomic interaction network identifies common hub genes involved in crucial protein formation in periodontal inflammation. Diabetes mellitus is a metabolic disorder that has a double-edged sword relationship with periodontitis. Chloride intracellular channel 1 (CLIC1) was identified as a hub gene linking the pathogenesis of periodontitis and diabetes mellitus using a bioinformatic tool. Therefore, this current study aimed to assess the concentration of the pro-inflammatory biomarker CLIC1 in saliva among individuals with periodontal health and those with periodontal disease linked to diabetes mellitus. Materials and methods Differentially expressed genes (DEGs) in periodontitis were identified using datasets retrieved from the Gene Expression Omnibus (GEO) database. DEGs were combined to build the network, and GeneMANIA was used to find and rank the interconnecting genes. CLIC1 was identified as the hub gene, and clinical validation was done using patient samples. The study involved 30 participants. Based on clinical and radiographic periodontal findings, they were split into three groups: healthy (group 1, n=10), with periodontitis but no diabetes mellitus (group 2, n=10), and with periodontitis and diabetes mellitus (group 3, n=10). The collection of saliva samples, followed by quantifying these samples, was performed using an enzyme-linked immunosorbent assay (ELISA). Results From network graph analysis, it was discovered that CLIC1 functions as a hub gene in the majority of toll-like receptor pathways. The mean concentration of CLIC1 in saliva increased consistently as the disease was observed in periodontitis patients and periodontitis patients with diabetes mellitus.  Conclusion CLIC1 concentrations were positively correlated with periodontitis in individuals with diabetes. Therefore, CLIC1 could be a diagnostic biomarker for patients with periodontitis. However, large-scale studies are needed to confirm more positive associations.

Microglia in Glioma

Myeloid cells are fundamental constituents of the brain tumor microenvironment. In this chapter, we describe the state-of-the-art knowledge on the role of microglial cells in the cross-talk with the most common and aggressive brain tumor, glioblastoma. We report in vitro and in vivo studies related to glioblastoma patients and glioma models to outline the symbiotic interactions that microglia develop with tumoral cells, highlighting the heterogeneity of microglial functions in shaping the brain tumor microenvironment.

Multi-omics analysis reveals CLIC1 as a therapeutic vulnerability of gliomas

Introduction: Despite advances in comprehending cancer biology, malignant gliomas remain incurable. The present work conducted a multi-omics analysis for investigating the significance of chloride intracellular channel 1 (CLIC1) in gliomas. Methods: Multi-omics data of glioma covering transcriptomics, genomics, DNA methylation and single-cell transcriptomics from multiple public cohorts were enrolled for analyzing CLIC1. In vitro experiments were conducted to measure apoptosis and cell mobility in U251 and U373 glioma cells following transfection of CLIC1 siRNAs. Results: Elevated CLIC1 expression was proven to stably and independently estimate worse survival outcomes. CLIC1 expression was higher in more advanced stage, wild-type IDH and unmethylated MGMT samples. Tumorigenic and anticancer immunity pathways were remarkably enriched in CLIC1-up-regulated tumors. Additionally, CLIC1 was positively linked with cancer-immunity cycle, stromal activation, DNA damage repair and cell cycle. Suppressing CLIC1 resulted in apoptosis and attenuated cell motility of glioma cells. More frequent genomic alterations were found in CLIC1-up-regulated tumors. CLIC1 expression presented a remarkably negative connection to DNA methylation. High CLIC1 expression samples were more sensitive to camptothecin, cisplatin, doxorubicin, erlotinib, paclitaxel, rapamycin, clofarabine, tanespimycin, methotrexate, everolimus, TAK-733, trametinib and AZD8330. Tumors with upregulated CLIC1 presented abundant immune cell infiltration, higher expression of immune-checkpoints and -modulators and similar transcriptome profiling, indicative of well response to immune-checkpoint blockade (ICB). Nevertheless, due to elevated TIDE score, tumors with CLIC1 upregulation appeared to be resistant to ICB. Single-cell analysis unveiled that CLIC1 was expressed ubiquitously in tumor cells and tumor microenvironment. Conclusions: Overall, CLIC1 was a promising treatment vulnerability in glioma.

Biophysical characterization of chloride intracellular channel 6 (CLIC6)

Chloride intracellular channels (CLICs) are a family of proteins that exist in soluble and transmembrane forms. The newest discovered member of the family CLIC6 is implicated in breast, ovarian, lung gastric, and pancreatic cancers and is also known to interact with dopamine-(D(2)-like) receptors. The soluble structure of the channel has been resolved, but the exact physiological role of CLIC6, biophysical characterization, and the membrane structure remain unknown. Here, we aimed to characterize the biophysical properties of this channel using a patch-clamp approach. To determine the biophysical properties of CLIC6, we expressed CLIC6 in HEK-293 cells. On ectopic expression, CLIC6 localizes to the plasma membrane of HEK-293 cells. We established the biophysical properties of CLIC6 by using electrophysiological approaches. Using various anions and potassium (K+) solutions, we determined that CLIC6 is more permeable to chloride-(Cl-) as compared to bromide-(Br-), fluoride-(F-), and K+ ions. In the whole-cell configuration, the CLIC6 currents were inhibited after the addition of 10 μM of IAA-94 (CLIC-specific blocker). CLIC6 was also found to be regulated by pH and redox potential. We demonstrate that the histidine residue at 648 (H648) in the C terminus and cysteine residue in the N terminus (C487) are directly involved in the pH-induced conformational change and redox regulation of CLIC6, respectively. Using qRT-PCR, we identified that CLIC6 is most abundant in the lung and brain, and we recorded the CLIC6 current in mouse lung epithelial cells. Overall, we have determined the biophysical properties of CLIC6 and established it as a Cl- channel.

Novel diagnostic biomarkers of oxidative stress, immunological characterization and experimental validation in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative condition causing cognitive decline. Oxidative stress (OS) is believed to contribute to neuronal death and dysfunction in AD. We conducted a study to identify differentially expressed OS-related genes (DEOSGs) through bioinformatics analysis and experimental validation, aiming to develop a diagnostic model for AD. We analyzed the GSE33000 dataset to identify OS regulator expression profiles and create molecular clusters (C1 and C2) associated with immune cell infiltration using 310 AD samples. Cluster analysis revealed significant heterogeneity in immune infiltration. The 'WGCNA' algorithm identified cluster-specific and disease-specific differentially expressed genes (DGEs). Four machine learning models (random forest (RF), support vector machine (SVM), generalized linear model (GLM) and extreme gradient boosting (XGB)) were compared, with GLM performing the best (AUC = 0.812). Five DEOSGs (NFKBIA, PLCE1, CLIC1, SLCO4A1, TRAF3IP2) were identified based on the GLM model. AD subtype prediction accuracy was validated using nomograms and calibration curves. External datasets (GSE122063 and GSE106241) confirmed the expression levels and clinical significance of important genes. Experimental validation through RT-qPCR showed increased expression of NFKBIA, CLIC1, SLCO4A1, TRAF3IP2, and decreased expression of PLCE1 in the temporal cortex of AD mice. This study provides insights for AD research and treatment, particularly focusing on the five model-related DEOSGs.

Targeting Clic1 for the treatment of obesity: A novel therapeutic strategy to reduce food intake and body weight

OBJECTIVE

Despite great advances in obesity therapeutics in recent years, there is still a need to identify additional therapeutic targets for the treatment of this disease. We previously discovered a signature of genes, including Chloride intracellular channel 1 (Clic1), whose expression was associated with drug-induced weight gain, and in these studies, we assess the effect of Clic1 inhibition on food intake and body weight in mice.

METHODS

We studied the impact of Clic1 inhibition in mouse models of binge-eating, diet-induced obese mice and genetic models of obesity (Magel2 KO mice).

RESULTS

Clic1 knockout (KO) mice ate significantly less and had a lower body weight than WT littermates when either fed chow or high fat diet. Furthermore, pharmacological inhibition of Clic1 in diet-induced obese mice resulted in suppression of food intake and promoted highly efficacious weight loss. Clic1 inhibition also reduced food intake in binge-eating models and hyperphagic Magel2 KO mice. We observed that chronic obesity resulted in a significant change in subcellular localization of Clic1 with an increased ratio of Clic1 in the membrane in the obese state. These observations provide a novel therapeutic strategy to block Clic1 translocation as a potential mechanism to reduce food intake and lower body weight.

CONCLUSIONS

These studies attribute a novel role of Clic1 as a driver of food intake and overconsumption. In summary, we have identified hypothalamic expression of Clic1 plays a key role in food intake, providing a novel therapeutic target to treat overconsumption that is the root cause of modern obesity.

Immunological characterization and diagnostic models of RNA N6-methyladenosine regulators in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia, and it displays both clinical and molecular variability. RNA N6-methyladenosine (m6A) regulators are involved in a wide range of essential cellular processes. In this study, we aimed to identify molecular signatures associated with m6A in Alzheimer's disease and use those signatures to develop a predictive model. We examined the expression patterns of m6A regulators and immune features in Alzheimer's disease using the GSE33000 dataset. We examined the immune cell infiltration and molecular groups based on m6A-related genes in 310 Alzheimer's disease samples. The WGCNA algorithm was utilized to determine differently expressed genes within each cluster. After evaluating the strengths and weaknesses of the random forest model, the support vector machine model, the generalized linear model, and eXtreme Gradient Boosting, the best machine model was selected. Methods such as nomograms, calibration curves, judgment curve analysis, and the use of independent data sets were used to verify the accuracy of the predictions made. Alzheimer's disease and non-disease Alzheimer's groups were compared to identify dysregulated m6A-related genes and activated immune responses. In Alzheimer's disease, two molecular clusters linked to m6A were identified. Immune infiltration analysis indicated substantial variation in protection between groups. Cluster 1 included processes like the Toll-like receptor signaling cascade, positive regulation of chromatin binding, and numerous malignancies; cluster 2 included processes like the cell cycle, mRNA transport, and ubiquitin-mediated proteolysis. With a lower residual and root mean square error and a larger area under the curve (AUC = 0.951), the Random forest machine model showed the greatest discriminative performance. The resulting random forest model was based on five genes, and it performed well (AUC = 0.894) on external validation datasets. Accuracy in predicting Alzheimer's disease subgroups was also shown by analyses of nomograms, calibration curves, and decision curves. In this research, we methodically outlined the tangled web of connections between m6A and AD and created a promising prediction model for gauging the correlation between m6A subtype risk and AD pathology.

Human amygdala involvement in Alzheimer's disease revealed by stereological and dia-PASEF analysis

Alzheimer's disease (AD) is characterized by the accumulation of pathological amyloid-β (Aβ) and Tau proteins. According to the prion-like hypothesis, both proteins can seed and disseminate through brain regions through neural connections and glial cells. The amygdaloid complex (AC) is involved early in the disease, and its widespread connections with other brain regions indicate that it is a hub for propagating pathology. To characterize changes in the AC as well as the involvement of neuronal and glial cells in AD, a combined stereological and proteomic analysis was performed in non-Alzheimer's disease and AD human samples. The synaptic alterations identified by proteomic data analysis could be related to the volume reduction observed in AD by the Cavalieri probe without neuronal loss. The pathological markers appeared in a gradient pattern with the medial region (cortical nucleus, Co) being more affected than lateral regions, suggesting the relevance of connections in the distribution of the pathology among different brain regions. Generalized astrogliosis was observed in every AC nucleus, likely related to deposits of pathological proteins. Astrocytes might mediate phagocytic microglial activation, whereas microglia might play a dual role since protective and toxic phenotypes have been described. These results highlight the potential participation of the amygdala in the disease spreading from/to olfactory areas, the temporal lobe and beyond. Proteomic data are available via ProteomeXchange with identifier PXD038322.

Intracellular chloride channel 1 and tumor

As the major intracellular anion, chloride plays an important role in maintaining intracellular and extracellular ion homeostasis, osmotic pressure, and cell volume. Intracellular chloride channel 1, which has the physiological role of forming membrane proteins in the lipid bilayer and playing ion channels, is a hot research topic in recent years. It has been found that CLIC1 does not only act as an ion channel but also participates in cell cycle regulation, apoptosis, and intracellular oxidation; thus, it participates in the proliferation, invasion, and migration of various tumor cells in various systems throughout the body. At the same time, CLIC1 is highly expressed in tumor cells and is associated with malignancy and a poor prognosis. This paper reviews the pathological mechanisms of CLIC1 in systemic diseases, which is important for the early diagnosis, treatment, and prognosis of systemic diseases associated with CLIC1 expression.

Post-translational modifications and protein quality control of mitochondrial channels and transporters

Mitochondria play a critical role in energy metabolism and signal transduction, which is tightly regulated by proteins, metabolites, and ion fluxes. Metabolites and ion homeostasis are mainly mediated by channels and transporters present on mitochondrial membranes. Mitochondria comprise two distinct compartments, the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM), which have differing permeabilities to ions and metabolites. The OMM is semipermeable due to the presence of non-selective molecular pores, while the IMM is highly selective and impermeable due to the presence of specialized channels and transporters which regulate ion and metabolite fluxes. These channels and transporters are modulated by various post-translational modifications (PTMs), including phosphorylation, oxidative modifications, ions, and metabolites binding, glycosylation, acetylation, and others. Additionally, the mitochondrial protein quality control (MPQC) system plays a crucial role in ensuring efficient molecular flux through the mitochondrial membranes by selectively removing mistargeted or defective proteins. Inefficient functioning of the transporters and channels in mitochondria can disrupt cellular homeostasis, leading to the onset of various pathological conditions. In this review, we provide a comprehensive overview of the current understanding of mitochondrial channels and transporters in terms of their functions, PTMs, and quality control mechanisms.

Chloride Intracellular Channel Protein 2 Promotes Microglial Invasion: A Link to Microgliosis in the Parkinson's Disease Brain

Activated microglia potentially cause neurodegeneration in Parkinson's disease (PD). Matrix metalloproteinase (MMP)-9 plays a crucial role in the pathogenesis of PD, but the modulator of microglial release of MMP-9 remains obscure. Given the modulatory effect of chloride intracellular channel protein 2 (CLIC2) on MMPs, we aimed to determine the role of CLIC2 in regulating microglial MMP expression and activation. We found that CLIC2 is expressed in microglia and neurons in rat brain tissue and focused on the function of CLIC2 in primary cultured microglia. Exposure to recombinant CLIC2 protein enhanced microglial invasion activity, and its knockdown abolished this activity. Moreover, increased activation of MMP-9 was confirmed by the addition of the CLIC2 protein, and CLIC2 knockdown eliminated this activation. Additionally, increased expression of CLIC2 was observed in PD-modeled tissue. In conclusion, CLIC2 increases MMP-9 activity in the microglia, which are involved in PD pathogenesis.

Human antimicrobial peptide LL-37 contributes to Alzheimer's disease progression

As a prime mover in Alzheimer's disease (AD), microglial activation requires membrane translocation, integration, and activation of the metamorphic protein chloride intracellular channel 1 (CLIC1), which is primarily cytoplasmic under physiological conditions. However, the formation and activation mechanisms of functional CLIC1 are unknown. Here, we found that the human antimicrobial peptide (AMP) LL-37 promoted CLIC1 membrane translocation and integration. It also activates CLIC1 to cause microglial hyperactivation, neuroinflammation, and excitotoxicity. In mouse and monkey models, LL-37 caused significant pathological phenotypes linked to AD, including elevated amyloid-β, increased neurofibrillary tangles, enhanced neuronal death and brain atrophy, enlargement of lateral ventricles, and impairment of synaptic plasticity and cognition, while Clic1 knockout and blockade of LL-37-CLIC1 interactions inhibited these phenotypes. Given AD's association with infection and that overloading AMP may exacerbate AD, this study suggests that LL-37, which is up-regulated upon infection, may be a driving force behind AD by acting as an endogenous agonist of CLIC1.

Chloride intracellular channel 1 promotes esophageal squamous cell carcinoma proliferation via mTOR signalling

OBJECTIVES

To investigate the clinical significance of Chloride Intracellular Channel 1 (CLIC1) expression in esophageal squamous cell carcinoma (ESCC) and its functional contribution and molecular mechanisms to the progression of ESCC.

METHODS

CLIC1 expression was analyzed by immunohistochemistry (IHC) in a cohort of 86 ESCC tissue specimens and paired normal adjacent esophageal tissues. Associations between clinicopathological features of ESCC and CLIC1 expression were determined. In vitro analyses examined CLIC1 expression in the ESCC cell lines KYSE150 and TE1 using RT-PCR and Western blotting. The downstream pathways of CLIC1 were detected by lentiviral shRNA knockdown and subsequent proteomic analyses. CLIC1 siRNA knockdown was performed in ESCC cell lines KYSE150 and TE1 and the functional effects of CLIC1 on the growth and proliferation of ESCC cells were evaluated combined with cell viability and colony formation assays; the mTOR signaling pathway-related proteins were detected by Western blotting based on the previous proteomic data.

RESULTS

CLIC1 expression was significantly increased in ex vivo ESCC tissues compared with corresponding normal tissues, and the up-regulation was associated with clinical tumor node metastasis (TNM) classifications. Knockdown of CLIC1 inhibited in vitro cell proliferation of ESCC cell lines KYSE150 and TE1. CLIC1 knockdown down-regulated the protein expression of p-mTOR and the downstream targets Rictor and p-4EBP1 in both KYSE150 and TE1 cell lines. And the CLIC1 knockdown induced inhibition of cell proliferation on ESCC cells could be rescued by mTOR overexpression.

CONCLUSIONS

CLIC1 expression increases during esophageal carcinogenesis and it may functionally contribute to the progression of ESCC through growth promotion effects by promoting the mTOR and downstream signaling pathway. CLIC1 therefore constitutes a candidate molecular biomarker of ESCC.

Endocannabinoid signaling in microglia

Microglia, the innate immune cells of the central nervous system (CNS), execute their sentinel, housekeeping and defense functions through a panoply of genes, receptors and released cytokines, chemokines and neurotrophic factors. Moreover, microglia functions are closely linked to the constant communication with other cell types, among them neurons. Depending on the signaling pathway and type of stimuli involved, the outcome of microglia operation can be neuroprotective or neurodegenerative. Accordingly, microglia are increasingly becoming considered cellular targets for therapeutic intervention. Among signals controlling microglia activity, the endocannabinoid (EC) system has been shown to exert a neuroprotective role in many neurological diseases. Like neurons, microglia express functional EC receptors and can produce and degrade ECs. Interestingly, boosting EC signaling leads to an anti-inflammatory and neuroprotective microglia phenotype. Nonetheless, little evidence is available on the microglia-mediated therapeutic effects of EC compounds. This review focuses on the EC signals acting on the CNS microglia in physiological and pathological conditions, namely on the CB1R, CB2R and TRPV1-mediated regulation of microglia properties. It also provides new evidence, which strengthens the understanding of mechanisms underlying the control of microglia functions by ECs. Given the broad expression of the EC system in glial and neuronal cells, the resulting picture is the need for in vivo studies in transgenic mouse models to dissect the contribution of EC microglia signaling in the neuroprotective effects of EC-derived compounds.

Trilobatin rescues cognitive impairment of Alzheimer's disease by targeting HMGB1 through mediating SIRT3/SOD2 signaling pathway

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with cognitive impairment that currently is uncurable. Previous study shows that trilobatin (TLB), a naturally occurring food additive, exerts neuroprotective effect in experimental models of AD. In the present study we investigated the molecular mechanisms underlying the beneficial effect of TLB on experimental models of AD in vivo and in vitro. APP/PS1 transgenic mice were administered TLB (4, 8 mg· kg-1 ·d-1, i.g.) for 3 months; rats were subjected to ICV injection of Aβ25-35, followed by administration of TLB (2.5, 5, 10 mg· kg-1 ·d-1, i.g.) for 14 days. We showed that TLB administration significantly and dose-dependently ameliorated the cognitive deficits in the two AD animal models, assessed in open field test, novel object recognition test, Y-maze test and Morris water maze test. Furthermore, TLB administration dose-dependently inhibited microglia and astrocyte activation in the hippocampus of APP/PS1 transgenic mice accompanied by decreased expression of high-mobility group box 1 (HMGB1), TLR4 and NF-κB. In Aβ25-25-treated BV2 cells, TLB (12.5-50 μM) concentration-dependently increased the cell viability through inhibiting HMGB1/TLR4/NF-κB signaling pathway. HMGB1 overexpression abrogated the beneficial effects of TLB on BV2 cells after Aβ25-35 insults. Molecular docking and surface plasmon resonance assay revealed that TLB directly bound to HMGB1 with a KD value of 8.541×10-4 M. Furthermore, we demonstrated that TLB inhibited Aβ25-35-induced acetylation of HMGB1 through activating SIRT3/SOD2 signaling pathway, thereby restoring redox homeostasis and suppressing neuroinflammation. These results, for the first time, unravel a new property of TLB: rescuing cognitive impairment of AD via targeting HMGB1 and activating SIRT3/SOD2 signaling pathway.

Predictable fold switching by the SARS-CoV-2 protein ORF9b

Extant fold-switching proteins remodel their secondary structures and change their functions in response to environmental stimuli. These shapeshifting proteins regulate biological processes and are associated with a number of diseases, including tuberculosis, cancer, Alzheimer's, and autoimmune disorders. Thus, predictive methods are needed to identify more fold-switching proteins, especially since all naturally occurring instances have been discovered by chance. In response to this need, two high-throughput predictive methods have recently been developed. Here we test them on ORF9b, a newly discovered fold switcher and potential therapeutic target from the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Promisingly, both methods correctly indicate that ORF9b switches folds. We then tested the same two methods on ORF9b1, the ORF9b homolog from SARS-CoV-1. Again, both methods predict that ORF9b1 switches folds, a finding consistent with experimental binding studies. Together, these results (a) demonstrate that protein fold switching can be predicted using high-throughput computational approaches and (b) suggest that fold switching might be a general characteristic of ORF9b homologs.

Influence of Nitric Oxide-Cyclic GMP and Oxidative STRESS on Amyloid-β Peptide Induced Decrease of Na,K-ATPase Activity in Rat Hippocampal Slices

Amyloid-β peptide (Aβ) has been shown to cause synaptic dysfunction and can render neurons vulnerable to excitotoxicity and oxidative stress. Na,K-ATPase plays an important role to maintain cell ionic equilibrium and it can be modulated by N-methyl-D-aspartate (NMDA)-nitric oxide (NO)-cyclic GMP pathway. Disruption of NO synthase (NOS) activity and reactive oxygen species (ROS) production could lead to changes in Na,K-ATPase isoforms' activities that may be detrimental to the cells. Our aim was to evaluate the signaling pathways of Aβ in relation to NMDA-NOS-cyclic GMP versus oxidative stress on α₁-/α_2,3-Na,K-ATPase activities in rat hippocampal slices. Aβ_1-40 induced a concentration-dependent increase of NOS activity and increased cyclic guanosine monophosphate (cGMP), TBARS (thiobarbituric acid reactive substances), and 3-Nitrotyrosine (3-NT)-modified protein levels in rat hippocampal slices. The increase in NOS activity and cyclic GMP levels induced by Aβ_1-40 was completely blocked by MK-801 (inhibitor of NMDA receptor) and L-NAME (inhibitor of NOS) pre-treatment but changes in TBARS levels were only partially blocked by both compounds. The Aβ treatment also decreased Na,K-ATPase activity which was reverted by N-nitro-L-arginine methyl ester hydrochloride (L-NAME) but not by MK-801 pre-treatment. The decrease in enzyme activity induced by Aβ was isoform-specific since only α₁-Na,K-ATPase was affected. These findings suggest that the activation of NMDA-NOS signaling cascade linked to α_2,3-Na,K-ATPase activity may mediate an adaptive, neuroprotective response to Aβ in rat hippocampus.

Chloride intracellular channels as novel biomarkers for digestive system tumors (Review)

Digestive system malignant tumors are common tumors, and the traditional treatment methods for these tumors include surgical resection, radiotherapy, chemotherapy, and molecularly targeted drugs. However, diagnosis remains challenging, and the early detection of postoperative recurrence is complicated. Therefore, it is necessary to explore novel biomarkers to facilitate clinical diagnosis and treatment. Accumulating evidence supports the crucial role of chloride channels in the development of multiple types of cancers. Given that chloride channels are widely expressed and involved in cell proliferation, apoptosis and cell cycle, among other processes, they may serve as a promising diagnostic and therapeutic target. Chloride intracellular channels (CLICs) are a class of chloride channels that are upregulated or downregulated in certain types of cancer. Furthermore, in certain cases, during cell cycle progression, the localization and function of the cytosolic form of the transmembrane proteins of CLICs are also altered, which may provide a key target for cancer therapy. The aim of the present review was to focus on CLICs as biomarkers for digestive system tumors.

Transmembrane Chloride Intracellular Channel 1 (tmCLIC1) as a Potential Biomarker for Personalized Medicine

Identification of potential pathological biomarkers has proved to be essential for understanding complex and fatal diseases, such as cancer and neurodegenerative diseases. Ion channels are involved in the maintenance of cellular homeostasis. Moreover, loss of function and aberrant expression of ion channels and transporters have been linked to various cancers, and to neurodegeneration. The Chloride Intracellular Channel 1 (CLIC1), CLIC1 is a metamorphic protein belonging to a partially unexplored protein superfamily, the CLICs. In homeostatic conditions, CLIC1 protein is expressed in cells as a cytosolic monomer. In pathological states, CLIC1 is specifically expressed as transmembrane chloride channel. In the following review, we trace the involvement of CLIC1 protein functions in physiological and in pathological conditions and assess its functionally active isoform as a potential target for future therapeutic strategies.

N-3 PUFA Prevent Oxidative Stress in a Rat Model of Beta-Amyloid-Induced Toxicity

Polyunsaturated fatty acids (PUFA) are involved in brain disorders associated to amyloid beta (Aβ) toxicity for which oxidative stress, neurochemical dysfunctions, and neuroinflammation are underlying mechanisms. Here, mechanisms through which lifelong exposure to n-3 PUFA-enriched or n-6/n-3 balanced diets could elicit a protective role in a rat model of Aβ-induced toxicity were investigated. To this aim, we quantified hippocampal reactive oxygen species (ROS) amount, 8-hydroxy-2'-deoxyguanosine and interleukin-10 levels, NADPH oxidase (NOX) 1, NOX2, superoxide dismutase 1, and glutathione contents, as well as plasmatic malondialdehyde. Moreover, in the same experimental groups, we assessed tryptophan, serotonin, and its turnover, kynurenine, and noradrenaline amounts. Results showed increased hippocampal ROS and NOX2 levels, serotonin turnover, kynurenine, and noradrenaline contents in Aβ-treated rats. Both n-6/n-3 balanced and n-3 PUFA enriched diets reduced ROS production, NOX1 and malondialdehyde levels, serotonin turnover, and kynurenine amount in Aβ-injected rats, while increasing NOX2, superoxide dismutase 1, and serotonin contents. No differences in plasmatic coenzyme Q10, reduced glutathione (GSH) and tryptophan levels were detected among different experimental groups, whereas GSH + oxidized glutathione (GSSG) levels were increased in sham animals fed with n-3 PUFA enriched diet and in Aβ-treated rats exposed to both n-6/n-3 balanced and n-3 enriched diets. In addition, Aβ-induced decrease of interleukin-10 levels was prevented by n-6/n-3 PUFA balanced diet. N-3 PUFA enriched diet further increased interleukin-10 and 8-hydroxy-2'-deoxyguanosine levels. In conclusion, our data highlight the possible neuroprotective role of n-3 PUFA in perturbation of oxidative equilibrium induced by Aβ-administration.

Proteomic analysis reveals rotator cuff injury caused by oxidative stress

Background and aims:

Rotator cuff tendinopathy is common and is related to pain and dysfunction. However, the pathological mechanism of rotator cuff injury and shoulder pain is unclear. Objective: to investigate the pathological mechanism of rotator cuff injury and shoulder pain, and screen out the marker proteins related to rotator cuff injury by proteomics.

Methods:

Subacromial synovium specimens were collected from patients undergoing shoulder arthroscopic surgery. The experimental group were patients with rotator cuff repair surgery, and the control group were patients with habitual dislocation of the shoulder joint. Pathological examination was performed, and then followed by non-labeled quantitative proteomic detection. Finally, from analysis of the biological information of the samples, specific proteins related to rotator cuff injury and shoulder pain were deduced by functional analysis of differential proteins.

Results:

All the patients in experimental groups were representative. A large number of adipocytes and inflammatory cells were found in the pathological sections of the experimental group; the proteomics analysis screen identified 80 proteins with significant differences, and the analysis of protein function revealed that S100A11 (p = 0.011), PLIN4 (p = 0.017), HYOU1 (p = 0.002) and CLIC1 (p = 0.007) were closely related to oxidative stress and chronic inflammation.

Conclusion:

Rotator cuff injury is closely related to oxidative stress and chronic inflammatory response, and the results suggest that the expression of S100A11, PLIN4, HYOU1 and CLIC1 in the synovium of rotator cuff injury provides a new marker for the study of its pathological mechanism.

A mini-review on ion fluxes that regulate NLRP3 inflammasome activation

The activation of NLR family pyrin domain containing 3 (NLRP3) inflammasome can be induced by a wide spectrum of activators. This is unlikely achieved by the binding of different activators directly to the NLRP3 protein itself, as the activators found so far show different forms of chemical structures. Previous studies have shown that these activators can induce potassium ion (K+) and chloride ion (Cl-) efflux, calcium (Ca2+) and other ion mobilization, mitochondrial dysfunction, and lysosomal disruption, all of which are believed to cause NLRP3 inflammasome activation; how these events are induced by the activators and how they coordinate with each other in inducing the NLRP3 inflammasome activation are not fully understood. Increasing evidence suggests that the coordinated change of intracellular ion concentrations may be a common mechanism for the NLRP3 activation by different activators. In this mini-review, we present a brief summary of the current knowledge about how different ionic flows (including K+, sodium ion, Ca2+, magnesium ion, manganese ion, zinc ion, iron ion, and Cl-) are involved in regulating the NLRP3 inflammasome activation in macrophages.

Effect of Combined Electroacupuncture and Selegiline Treatment in Alzheimer's Disease: An Animal Model

The complexity of pathological mechanisms in Alzheimer's disease (AD) poses significant challenges to the development of corresponding drugs. Symptom-specific pharmacological interventions and alternative treatments provide promising treatment possibilities. Therefore, we considered a combination of selegiline (SEL) and electroacupuncture (EA). We used an animal model with AD to investigate the effect of a combination of these treatments on cognitive function. 5XFAD mice received a week of SEL treatment and 2 weeks of EA. Novel object recognition and Y-maze tests were subsequently performed to assess their cognitive functions. To determine the molecular action of the combination treatment, Western blots, Aβ_1-42 enzyme-linked immunosorbent assays (ELISA), and micro-positron-emission tomography were also performed to assess pathological markers and processes. The results were assessed based on the difference between untreated transgenic, SEL-treated, and SEL- and EA-treated groups of mice. Mice in the combined treatment group demonstrated significantly better cognitive functions, and lesser neuroinflammation than the comparative groups. In addition, mice treated with a combination of SEL and EA did not demonstrate a direct modulation of insoluble Aβ but demonstrated greater glucose metabolism. Our findings demonstrated that SEL combined with EA treatment was associated with better cognitive functioning due to inhibition of neuroinflammation and increased glucose metabolism relative to the comparative groups in a mouse model with AD.

Sequenced Combinations of Cisplatin and Selected Phytochemicals towards Overcoming Drug Resistance in Ovarian Tumour Models

In the present study, cisplatin, artemisinin, and oleanolic acid were evaluated alone, and in combination, on human ovarian A2780, A2780^ZD0473R, and A2780^cisR cancer cell lines, with the aim of overcoming cisplatin resistance and side effects. Cytotoxicity was assessed by MTT reduction assay. Combination index (CI) values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. Moreover, 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780^cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism, and biosynthetic processes and drug resistance and detoxification. Results indicate that appropriately sequenced combinations of cisplatin with artemisinin (ART) and oleanolic acid (OA) may provide a means to reduce side effects and circumvent platinum resistance.

Chloride intracellular channel 4 participate in the protective effect of Ginkgolide B in MPP+ injured MN9D cells: insight from proteomic analysis

Background

Ginkgolide B (GB), the extract of G. biloba leaves, has been shown to be protective against many neurological disorders, including Parkinson’s disease (PD). Efforts have been made to synthesized ginkgolides analogs and derivatives with more targeted and smaller molecular weight. In the present study, four GB derivatives (GBHC-1-GBHC-4) were synthesized, and their protective roles in N-methyl-4-phenylpyridinium (MPP +) injured MN9D dopaminergic neuronal cell line were evaluated. Also, cell response mechanisms upon these GB derivatives treatment were analyzed by iTRAQ proteomics.

Methods

MN9D cells were treated with MPP + to induce in vitro cell models of PD. Four GB derivatives (GBHC-1-GBHC-4) were synthesized, and their protective roles on cell viability and apoptosis in in vitro PD model cells were evaluated by CCK8 assay, fluorescence-activated cell sorting and DAPI staining, respectively. The proteomic profiles of MPP+ injured MN9D cells pretreated with or without GB and GB derivatives were detected using the isobaric tags for relative and absolute quantification (iTRAQ) labeling technique.

Results

Pretreatment with GBHC-1-GBHC-4 noticeably increased cell viability and attenuated cell apoptosis in MPP+ -injured MN9D cells. Using proteomic analysis, we identified differentially expressed proteins upon GB and GB derivatives treatment. Chloride intracellular channel 4 (CLIC4) and “protein processing in endoplasmic reticulum” pathways participated in the protective roles of GB and GBHC-4. GB and GBHC-4 pretreatment could significantly reverse MPP+ -induced CLIC4 expression and translocation from cytoplasm to nucleus of MN9D cells.

Conclusions

Quantitative comparative proteomic analysis identified differentially expressed proteins associated with GB and GB derivatives. We further verified the expression of CLIC4 by western blotting and immunocytochemistry assay. This bio-information on the identified pathways and differentially expressed proteins such as CLIC4 provide more targeted directions for the synthesis of more effective and targeted GB derivatives for the treatment of neurological disorders.

Predicting Clinical Dementia Rating Using Blood RNA Levels

The Clinical Dementia Rating (CDR) is commonly used to assess cognitive decline in Alzheimer's disease patients and is included in the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset. We divided 741 ADNI participants with blood microarray data into three groups based on their most recent CDR assessment: cognitive normal (CDR = 0), mild cognitive impairment (CDR = 0.5), and probable Alzheimer's disease (CDR ≥ 1.0). We then used machine learning to predict cognitive status using only blood RNA levels. Only one probe for chloride intracellular channel 1 (CLIC1) was significant after correction. However, by combining individually nonsignificant probes with p-values less than 0.1, we averaged 87.87% (s = 1.02) predictive accuracy for classifying the three groups, compared to a 55.46% baseline for this study due to unequal group sizes. The best model had an overall precision of 0.902, recall of 0.895, and a receiver operating characteristic (ROC) curve area of 0.904. Although we identified one significant probe in CLIC1, CLIC1 levels alone were not sufficient to predict dementia status and cannot be used alone in a clinical setting. Additional analyses combining individually suggestive, but nonsignificant, blood RNA levels were significantly predictive and may improve diagnostic accuracy for Alzheimer's disease. Therefore, we propose that patient features that do not individually predict cognitive status might still contribute to overall cognitive decline through interactions that can be elucidated through machine learning.

Identification of Conserved Proteomic Networks in Neurodegenerative Dementia

Data-driven analyses are increasingly valued in modern medicine. We integrate quantitative proteomics and transcriptomics from over 1,000 post-mortem brains from six cohorts representing Alzheimer's disease (AD), asymptomatic AD, progressive supranuclear palsy (PSP), and control patients from the Accelerating Medicines Partnership - Alzheimer's Disease consortium. We define robust co-expression trajectories related to disease progression, including early neuronal, microglial, astrocyte, and immune response modules, and later mRNA splicing and mitochondrial modules. The majority of, but not all, modules are conserved at the transcriptomic level, including module C3, which is only observed in proteome networks and enriched in mitogen-activated protein kinase (MAPK) signaling. Genetic risk enriches in modules changing early in disease and indicates that AD and PSP have distinct causal biological drivers at the pathway level, despite aspects of similar pathology, including synaptic loss and glial inflammatory changes. The conserved, high-confidence proteomic changes enriched in genetic risk represent targets for drug discovery.

CLIC1 Protein Accumulates in Circulating Monocyte Membrane during Neurodegeneration

Pathologies that lead to neurodegeneration in the central nervous system (CNS) represent a major contemporary medical challenge. Neurodegenerative processes, like those that occur in Alzheimer’s disease (AD) are progressive, and at the moment, they are unstoppable. Not only is an adequate therapy missing but diagnosis is also extremely complicated. The most reliable method is the measurement of beta amyloid and tau peptides concentration in the cerebrospinal fluid (CSF). However, collecting liquid samples from the CNS is an invasive procedure, thus it is not suitable for a large-scale prevention program. Ideally, blood testing is the most manageable and appropriate diagnostic procedure for a massive population screening. Recently, a few candidates, including proteins or microRNAs present in plasma/serum have been identified. The aim of the present work is to propose the chloride intracellular channel 1 (CLIC1) protein as a potential marker of neurodegenerative processes. CLIC1 protein accumulates in peripheral blood mononuclear cells (PBMCs), and increases drastically when the CNS is in a chronic inflammatory state. In AD patients, both immunolocalization and mRNA quantification are able to show the behavior of CLIC1 during a persistent inflammatory state of the CNS. In particular, confocal microscopy analysis and electrophysiological measurements highlight the significant presence of transmembrane CLIC1 (tmCLIC1) in PBMCs from AD patients. Recent investigations suggest that tmCLIC1 has a very specific role. This provides an opportunity to use blood tests and conventional technologies to discriminate between healthy individuals and patients with ongoing neurodegenerative processes.

Intracellular Chloride Channels: Novel Biomarkers in Diseases

Ion channels are integral membrane proteins present on the plasma membrane as well as intracellular membranes. In the human genome, there are more than 400 known genes encoding ion channel proteins. Ion channels are known to regulate several cellular, organellar, and physiological processes. Any mutation or disruption in their function can result in pathological disorders, both common or rare. Ion channels present on the plasma membrane are widely acknowledged for their role in various biological processes, but in recent years, several studies have pointed out the importance of ion channels located in intracellular organelles. However, ion channels located in intracellular organelles are not well-understood in the context of physiological conditions, such as the generation of cellular excitability and ionic homeostasis. Due to the lack of information regarding their molecular identity and technical limitations of studying them, intracellular organelle ion channels have thus far been overlooked as potential therapeutic targets. In this review, we focus on a novel class of intracellular organelle ion channels, Chloride Intracellular Ion Channels (CLICs), mainly documented for their role in cardiovascular, neurophysiology, and tumor biology. CLICs have a single transmembrane domain, and in cells, they exist in cytosolic as well as membranous forms. They are predominantly present in intracellular organelles and have recently been shown to be localized to cardiomyocyte mitochondria as well as exosomes. In fact, a member of this family, CLIC5, is the first mitochondrial chloride channel to be identified on the molecular level in the inner mitochondrial membrane, while another member, CLIC4, is located predominantly in the outer mitochondrial membrane. In this review, we discuss this unique class of intracellular chloride channels, their role in pathologies, such as cardiovascular, cancer, and neurodegenerative diseases, and the recent developments concerning their usage as theraputic targets.

Proteomics and bioinformatics approaches for the identification of plasma biomarkers to detect Parkinson's disease

The aim of the present study was to screen for biomarkers of Parkinson's disease (PD) using proteomics and bioinformatics approaches. PD patients were divided into three groups: Those without surgery (PD1 group); those who had undergone deep brain stimulation (DBS) surgery without electrode stimulation (PD2 group); and those who had undergone DBS surgery with 1 month of electrode stimulation (PD3 group). The non-Parkinson control group (CK group) was also involved. Quantitative proteomic analysis of human sera was performed through the use of tandem mass tag markers and liquid chromatography-mass spectrometry (LC-MS)-based techniques. For the proteins with quantitative information, a systematic bioinformatics analysis was then performed, including protein annotation, functional classification, functional enrichment and cluster analysis based on functional enrichment. Of the 739 proteins identified, quantitative information was available for 644. With regard to differential expression, 18 upregulated and 21 downregulated proteins were screened in the PD1/CK comparison group; 12 upregulated and 12 downregulated proteins in the PD2/PD1 comparison group; and 16 upregulated and 19 downregulated proteins in the PD3/PD2 comparison group. Coiled-coil domain-containing protein 154 (CCDC154) and tripartite motif-containing protein 3 (TRIM3) were key proteins involved in the molecular mechanisms of PD, participating in intracellular vesicle, ubiquitin protein ligase and transition metal ion-binding activities. After DBS surgery, desert hedgehog protein (DHH) was downregulated, whereas neuropilin-2 (NRP2) was upregulated; these participated in the ensheathment of neurons and the semaphorin receptor complex, respectively. The expression level of chloride intracellular channel protein 1 (CLIC1) was increased after 1 month of electrode stimulation following DBS. By combining proteomic approaches and LC-MS methods, significant proteins including CCDC154, TRIM3, DHH, NRP2 and CLIC1 were detected with high specificity and sensitivity. These may be used as novel biomarkers for early diagnosis of PD and the future development of treatments.

The inhibition of chloride intracellular channel 1 enhances Ca2+ and reactive oxygen species signaling in A549 human lung cancer cells

Chloride intracellular channel 1 (CLIC1) is a promising therapeutic target in cancer due to its intrinsic characteristics; it is overexpressed in specific tumor types and its localization changes from cytosolic to surface membrane depending on activities and cell cycle progression. Ca²⁺ and reactive oxygen species (ROS) are critical signaling molecules that modulate diverse cellular functions, including cell death. In this study, we investigated the function of CLIC1 in Ca²⁺ and ROS signaling in A549 human lung cancer cells. Depletion of CLIC1 via shRNAs in A549 cells increased DNA double-strand breaks both under control conditions and under treatment with the putative anticancer agent chelerythrine, accompanied by a concomitant increase in the p-JNK level. CLIC1 knockdown greatly increased basal ROS levels, an effect prevented by BAPTA-AM, an intracellular calcium chelator. Intracellular Ca²⁺ measurements clearly showed that CLIC1 knockdown significantly increased chelerythrine-induced Ca²⁺ signaling as well as the basal Ca²⁺ level in A549 cells compared to these levels in control cells. Suppression of extracellular Ca²⁺ restored the basal Ca²⁺ level in CLIC1-knockdown A549 cells relative to that in control cells, implying that CLIC1 regulates [Ca²⁺]_i through Ca²⁺ entry across the plasma membrane. Consistent with this finding, the L-type Ca²⁺ channel (LTCC) blocker nifedipine reduced the basal Ca²⁺ level in CLIC1 knockdown cells to that in control cells. Taken together, our results demonstrate that CLIC1 knockdown induces an increase in the intracellular Ca²⁺ level via LTCC, which then triggers excessive ROS production and consequent JNK activation. Thus, CLIC1 is a key regulator of Ca²⁺ signaling in the control of cancer cell survival.

Repurposed Biguanide Drugs in Glioblastoma Exert Antiproliferative Effects via the Inhibition of Intracellular Chloride Channel 1 Activity

The lack of in-depth knowledge about the molecular determinants of glioblastoma (GBM) occurrence and progression, combined with few effective and BBB crossing-targeted compounds represents a major challenge for the discovery of novel and efficacious drugs for GBM. Among relevant molecular factors controlling the aggressive behavior of GBM, chloride intracellular channel 1 (CLIC1) represents an emerging prognostic and predictive biomarker, as well as a promising therapeutic target. CLIC1 is a metamorphic protein, co-existing as both soluble cytoplasmic and membrane-associated conformers, with the latter acting as chloride selective ion channel. CLIC1 is involved in several physiological cell functions and its abnormal expression triggers tumor development, favoring tumor cell proliferation, invasion, and metastasis. CLIC1 overexpression is associated with aggressive features of various human solid tumors, including GBM, in which its expression level is correlated with poor prognosis. Moreover, increasing evidence shows that modification of microglia ion channel activity, and CLIC1 in particular, contributes to the development of different neuropathological states and brain tumors. Intriguingly, CLIC1 is constitutively active within cancer stem cells (CSCs), while it seems less relevant for the survival of non-CSC GBM subpopulations and for normal cells. CSCs represent GBM development and progression driving force, being endowed with stem cell-like properties (self-renewal and differentiation), ability to survive therapies, to expand and differentiate, causing tumor recurrence. Downregulation of CLIC1 results in drastic inhibition of GBM CSC proliferation in vitro and in vivo, making the control of the activity this of channel a possible innovative pharmacological target. Recently, drugs belonging to the biguanide class (including metformin) were reported to selectively inhibit CLIC1 activity in CSCs, impairing their viability and invasiveness, but sparing normal stem cells, thus representing potential novel antitumor drugs with a safe toxicological profile. On these premises, we review the most recent insights into the biological role of CLIC1 as a potential selective pharmacological target in GBM. Moreover, we examine old and new drugs able to functionally target CLIC1 activity, discussing the challenges and potential development of CLIC1-targeted therapies.

Physiology of Microglia

Microglial cells derive from fetal macrophages which immigrate into and disseminate throughout the central nervous system (CNS) in early embryogenesis. After settling in the nerve tissue, microglial progenitors acquire an idiosyncratic morphological phenotype with small cell body and moving thin and highly ramified processes currently defined as "resting or surveillant microglia". Physiology of microglia is manifested by second messenger-mediated cellular excitability, low resting membrane conductance, and expression of receptors to pathogen- or damage-associated molecular patterns (PAMPs and DAMPs), as well as receptors to classical neurotransmitters and neurohormones. This specific physiological profile reflects adaptive changes of myeloid cells to the CNS environment.

Microglia in Alzheimer's Disease: A Role for Ion Channels

Alzheimer's disease is the most common form of dementia, it is estimated to affect over 40 million people worldwide. Classically, the disease has been characterized by the neuropathological hallmarks of aggregated extracellular amyloid-β and intracellular paired helical filaments of hyperphosphorylated tau. A wealth of evidence indicates a pivotal role for the innate immune system, such as microglia, and inflammation in the pathology of Alzheimer's disease. The over production and aggregation of Alzheimer's associated proteins results in chronic inflammation and disrupts microglial clearance of these depositions. Despite being non-excitable, microglia express a diverse array of ion channels which shape their physiological functions. In support of this, there is a growing body of evidence pointing to the involvement of microglial ion channels contributing to neurodegenerative diseases such as Alzheimer's disease. In this review, we discuss the evidence for an array of microglia ion channels and their importance in modulating microglial homeostasis and how this process could be disrupted in Alzheimer's disease. One promising avenue for assessing the role that microglia play in the initiation and progression of Alzheimer's disease is through using induced pluripotent stem cell derived microglia. Here, we examine what is already understood in terms of the molecular underpinnings of inflammation in Alzheimer's disease, and the utility that inducible pluripotent stem cell derived microglia may have to advance this knowledge. We outline the variability that occurs between the use of animal and human models with regards to the importance of microglial ion channels in generating a relevant functional model of brain inflammation. Overcoming these hurdles will be pivotal in order to develop new drug targets and progress our understanding of the pathological mechanisms involved in Alzheimer's disease.

Mutual Influence of ROS, pH, and CLIC1 Membrane Protein in the Regulation of G1-S Phase Progression in Human Glioblastoma Stem Cells

Glioblastoma (GB) is the most lethal, aggressive, and diffuse brain tumor. The main challenge for successful treatment is targeting the cancer stem cell (CSC) subpopulation responsible for tumor origin, progression, and recurrence. Chloride Intracellular Channel 1 (CLIC1), highly expressed in CSCs, is constitutively present in the plasma membrane where it is associated with chloride ion permeability. In vitro, CLIC1 inhibition leads to a significant arrest of GB CSCs in G₁ phase of the cell cycle. Furthermore, CLIC1 knockdown impairs tumor growth in vivo Here, we demonstrate that CLIC1 membrane localization and function is specific for GB CSCs. Mesenchymal stem cells (MSC) do not show CLIC1-associated chloride permeability, and inhibition of CLIC1 protein function has no influence on MSC cell-cycle progression. Investigation of the basic functions of GB CSCs reveals a constitutive state of oxidative stress and cytoplasmic alkalinization compared with MSCs. Both intracellular oxidation and cytoplasmic pH changes have been reported to affect CLIC1 membrane functional expression. We now report that in CSCs these three elements are temporally linked during CSC G₁-S transition. Impeding CLIC1-mediated chloride current prevents both intracellular ROS accumulation and pH changes. CLIC1 membrane functional impairment results in GB CSCs resetting from an allostatic tumorigenic condition to a homeostatic steady state. In contrast, inhibiting NADPH oxidase and NHE1 proton pump results in cell death of both GB CSCs and MSCs. Our results show that CLIC1 membrane protein is crucial and specific for GB CSC proliferation, and is a promising pharmacologic target for successful brain tumor therapies. Mol Cancer Ther; 17(11); 2451-61. ©2018 AACR.

Integrative Analysis of Hippocampus Gene Expression Profiles Identifies Network Alterations in Aging and Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder contributing to rapid decline in cognitive function and ultimately dementia. Most cases of AD occur in elderly and later years. There is a growing need for understanding the relationship between aging and AD to identify shared and unique hallmarks associated with the disease in a region and cell-type specific manner. Although genomic studies on AD have been performed extensively, the molecular mechanism of disease progression is still not clear. The major objective of our study is to obtain a higher-order network-level understanding of aging and AD, and their relationship using the hippocampal gene expression profiles of young (20-50 years), aging (70-99 years), and AD (70-99 years). The hippocampus is vulnerable to damage at early stages of AD and altered neurogenesis in the hippocampus is linked to the onset of AD. We combined the weighted gene co-expression network and weighted protein-protein interaction network-level approaches to study the transition from young to aging to AD. The network analysis revealed the organization of co-expression network into functional modules that are cell-type specific in aging and AD. We found that modules associated with astrocytes, endothelial cells and microglial cells are upregulated and significantly correlate with both aging and AD. The modules associated with neurons, mitochondria and endoplasmic reticulum are downregulated and significantly correlate with AD than aging. The oligodendrocytes module does not show significant correlation with neither aging nor disease. Further, we identified aging- and AD-specific interactions/subnetworks by integrating the gene expression with a human protein-protein interaction network. We found dysregulation of genes encoding protein kinases (FYN, SYK, SRC, PKC, MAPK1, ephrin receptors) and transcription factors (FOS, STAT3, CEBPB, MYC, NFKβ, and EGR1) in AD. Further, we found genes that encode proteins with neuroprotective function (14-3-3 proteins, PIN1, ATXN1, BDNF, VEGFA) to be part of the downregulated AD subnetwork. Our study highlights that simultaneously analyzing aging and AD will help to understand the pre-clinical and clinical phase of AD and aid in developing the treatment strategies.