Ethanol-induced ceramide production causes neuronal apoptosis by increasing MCL-1S-mediated ER-mitochondria contacts.

Heavy alcohol consumption causes neuronal cell death and cognitive impairment. Neuronal cell death induced by ethanol may result from increased production of the sphingolipid metabolite ceramide. However, the molecular mechanisms of neuronal cell death caused by ethanol-induced ceramide production have not been elucidated. Therefore, we investigated the mechanism through which ethanol-induced ceramide production causes neuronal cell apoptosis using human induced-pluripotent stem cell-derived neurons and SH-SY5Y cells and identified the effects of ceramide on memory deficits in C57BL/6 mice. First, we found that ethanol-induced ceramide production was decreased by inhibition of the de novo synthesis pathway, mediated by serine palmitoyltransferase (SPT). The associated alterations of the molecules related to the ceramide pathway suggest that the elevated level of ceramide activated protein phosphatase 1 (PP1), which inhibited the nuclear translocation of serine/arginine-rich splicing factor 1 (SRSF1). This led to aberrant splicing of myeloid cell leukemia 1 (MCL-1) pre-mRNA, which upregulated MCL-1S expression. Our results demonstrated that the interaction of MCL-1S with the inositol 1, 4, 5-trisphosphate receptor (IP3R) increases calcium release from the endoplasmic reticulum (ER) and then activated ER-bound inverted formin 2 (INF2). In addition, we discovered that F-actin polymerization through INF2 activation promoted ER-mitochondria contacts, which induced mitochondrial calcium influx and mitochondrial reactive oxygen species (mtROS) production. Markedly, MCL-1S silencing decreased mitochondria-associated ER membrane (MAM) formation and prevented mitochondrial calcium influx and mtROS accumulation, by inhibiting INF2-dependent actin polymerization interacting with mitochondria. Furthermore, the inhibition of ceramide production in ethanol-fed mice reduced MCL-1S expression, neuronal cell death, and cognitive impairment. In conclusion, we suggest that ethanol-induced ceramide production may lead to mitochondrial calcium overload through MCL-1S-mediated INF2 activation-dependent MAM formation, which promotes neuronal apoptosis.

Prenatal glucocorticoid exposure selectively impairs neuroligin 1-dependent neurogenesis by suppressing astrocytic FGF2-neuronal FGFR1 axis.

Exposure to maternal stress irreversibly impairs neurogenesis of offspring by inducing life-long effects on interaction between neurons and glia under raging differentiation process, culminating in cognitive and neuropsychiatric abnormalities in adulthood. We identified that prenatal exposure to stress-responsive hormone glucocorticoid impaired neurogenesis and induced abnormal behaviors in ICR mice. Then, we used human induced pluripotent stem cell (iPSC)-derived neural stem cell (NSC) to investigate how neurogenesis deficits occur. Following glucocorticoid treatment, NSC-derived astrocytes were found to be A1-like neurotoxic astrocytes. Moreover, cortisol-treated astrocytic conditioned media (ACM) then specifically downregulated AMPA receptor-mediated glutamatergic synaptic formation and transmission in differentiating neurons, by inhibiting localization of ionotropic glutamate receptor (GluR)1/2 into synapses. We then revealed that downregulated astrocytic fibroblast growth factor 2 (FGF2) and nuclear fibroblast growth factor receptor 1 (FGFR1) of neurons are key pathogenic factors for reducing glutamatergic synaptogenesis. We further confirmed that cortisol-treated ACM specifically decreased the binding of neuronal FGFR1 to the synaptogenic NLGN1 promoter, but this was reversed by FGFR1 restoration. Upregulation of neuroligin 1, which is important in scaffolding GluR1/2 into the postsynaptic compartment, eventually normalized glutamatergic synaptogenesis and subsequent neurogenesis. Moreover, pretreatment of FGF2 elevated neuroligin 1 expression and trafficking of GluR1/2 into the postsynaptic compartment of mice exposed to prenatal corticosterone, improving spatial memory and depression/anxiety-like behaviors. In conclusion, we identified neuroligin 1 restoration by astrocytic FGF2 and its downstream neuronal nuclear FGFR1 as a critical target for preventing prenatal stress-induced dysfunction in glutamatergic synaptogenesis, which recovered both neurogenesis and hippocampal-related behaviors.

Cyanidin 3-O-arabinoside suppresses DHT-induced dermal papilla cell senescence by modulating p38-dependent ER-mitochondria contacts.

BACKGROUND: Androgenetic alopecia (AGA) is a genetic disorder caused by dihydrotestosterone (DHT), accompanied by the senescence of androgen-sensitive dermal papilla cells (DPCs) located in the base of hair follicles. DHT causes DPC senescence in AGA through mitochondrial dysfunction. However, the mechanism of this pathogenesis remains unknown. In this study, we investigated the protective role of cyanidins on DHT-induced mitochondrial dysfunction and DPC senescence and the regulatory mechanism involved. METHODS: DPCs were used to investigate the effect of DHT on mitochondrial dysfunction with MitoSOX and Rhod-2 staining. Senescence-associated ß-galactosidase activity assay was performed to examine the involvement of membrane AR-mediated signaling in DHT-induced DPC senescence. AGA mice model was used to study the cyanidins on DHT-induced hair growth deceleration. RESULTS: Cyanidin 3-O-arabinoside (C3A) effectively decreased DHT-induced mtROS accumulation in DPCs, and C3A reversed the DHT-induced DPC senescence. Excessive mitochondrial calcium accumulation was blocked by C3A. C3A inhibited p38-mediated voltage-dependent anion channel 1 (VDAC1) expression that contributes to mitochondria-associated ER membrane (MAM) formation and transfer of calcium via VDAC1-IP3R1 interactions. DHT-induced MAM formation resulted in increase of DPC senescence. In AGA mice models, C3A restored DHT-induced hair growth deceleration, which activated hair follicle stem cell proliferation. CONCLUSIONS: C3A is a promising natural compound for AGA treatments against DHT-induced DPC senescence through reduction of MAM formation and mitochondrial dysfunction.

Melatonin restores Muc2 depletion induced by V. vulnificus VvpM via melatonin receptor 2 coupling with Gαq.

BACKGROUND: Melatonin (5-methoxy-N-acetyltryptamine), a hormone produced in the pineal gland, has a variety of biological functions as an antioxidant, but a functional role of melatonin in the regulation of intestinal mucin (Muc) production during bacterial infection has yet to be described in detail. In this study, we investigate the effects of melatonin during Muc2 repression elicited by the Gram-negative bacterium V. vulnificus. METHODS: Mucus-secreting human HT29-MTX cells were used to study the functional role of melatonin during Muc2 depletion induced by the recombinant protein (r) VvpM produced by V. vulnificus. The regulatory effects of melatonin coupling with melatonin receptor 2 (MT2) on the production of reactive oxygen species (ROS), the activation of PKCδ and ERK, and the hypermethylation of the Muc2 promoter as induced by rVvpM were examined. Experimental mouse models of V. vulnificus infection were used to study the role of melatonin and how it neutralizes the bacterial toxin activity related to Muc2 repression. RESULTS: Recombinant protein (r) VvpM significantly reduced the level of Muc2 in HT29-MTX cells. The repression of Muc2 induced by rVvpM was significantly restored upon a treatment with melatonin (1 µM), which had been inhibited by the knockdown of MT2 coupling with Gαq and the NADPH oxidase subunit p47 phox. Melatonin inhibited the ROS-mediated phosphorylation of PKCδ and ERK responsible for region-specific hypermethylation in the Muc2 promoter in rVvpM-treated HT29-MTX cells. In the mouse models of V. vulnificus infection, treatment with melatonin maintained the level of Muc2 expression in the intestine. In addition, the mutation of the VvpM gene from V. vulnificus exhibited an effect similar to that of melatonin. CONCLUSIONS: These results demonstrate that melatonin acting on MT2 inhibits the hypermethylation of the Muc2 promoter to restore the level of Muc2 production in intestinal epithelial cells infected with V. vulnificus.

Ethanol-activated CaMKII signaling induces neuronal apoptosis through Drp1-mediated excessive mitochondrial fission and JNK1-dependent NLRP3 inflammasome activation.

BACKGROUND: Neurodegeneration is a representative phenotype of patients with chronic alcoholism. Ethanol-induced calcium overload causes NOD-like receptor protein 3 (NLRP3) inflammasome formation and an imbalance in mitochondrial dynamics, closely associated with the pathogenesis of neurodegeneration. However, how calcium regulates this process in neuronal cells is poorly understood. Therefore, the present study investigated the detailed mechanism of calcium-regulated mitochondrial dynamics and NLRP3 inflammasome formation in neuronal cells by ethanol. METHODS: In this study, we used the SK-N-MC human neuroblastoma cell line. To confirm the expression level of the mRNA and protein, real time quantitative PCR and western blot were performed. Co-immunoprecipitation and Immunofluorescence staining were conducted to confirm the complex formation or interaction of the proteins. Flow cytometry was used to analyze intracellular calcium, mitochondrial dysfunction and neuronal apoptosis. RESULTS: Ethanol increased cleaved caspase-3 levels and mitochondrial reactive oxygen species (ROS) generation associated with neuronal apoptosis. In addition, ethanol increased protein kinase A (PKA) activation and cAMP-response-element-binding protein (CREB) phosphorylation, which increased N-methyl-D-aspartate receptor (NMDAR) expression. Ethanol-increased NMDAR induced intracellular calcium overload and calmodulin-dependent protein kinase II (CaMKII) activation leading to phosphorylation of dynamin-related protein 1 (Drp1) and c-Jun N-terminal protein kinase 1 (JNK1). Drp1 phosphorylation promoted Drp1 translocation to the mitochondria, resulting in excessive mitochondrial fission, mitochondrial ROS accumulation, and loss of mitochondrial membrane potential, which was recovered by Drp1 inhibitor pretreatment. Ethanol-induced JNK1 phosphorylation activated the NLRP3 inflammasome that induced caspase-1 dependent mitophagy inhibition, thereby exacerbating ROS accumulation and causing cell death. Suppressing caspase-1 induced mitophagy and reversed the ethanol-induced apoptosis in neuronal cells. CONCLUSIONS: Our results demonstrated that ethanol upregulated NMDAR-dependent CaMKII phosphorylation which is essential for Drp1-mediated excessive mitochondrial fission and the JNK1-induced NLRP3 inflammasome activation resulting in neuronal apoptosis. Video abstract.

Identification and characterization of Vibrio vulnificus plpA encoding a phospholipase A2 essential for pathogenesis.

The marine bacterium Vibrio vulnificus causes food-borne diseases, which may lead to life-threatening septicemia in some individuals. Therefore, identifying virulence factors in V. vulnificus is of high priority. We performed a transcriptome analysis on V. vulnificus after infection of human intestinal HT29-methotrexate cells and found induction of plpA, encoding a putative phospholipase, VvPlpA. Bioinformatics, biochemical, and genetic analyses demonstrated that VvPlpA is a phospholipase A2 secreted in a type II secretion system-dependent manner. Compared with the wild type, the plpA mutant exhibited reduced mortality, systemic infection, and inflammation in mice as well as low cytotoxicity toward the human epithelial INT-407 cells. Moreover, plpA mutation attenuated the release of actin and cytosolic cyclophilin A from INT-407 cells, indicating that VvPlpA is a virulence factor essential for causing lysis and necrotic death of the epithelial cells. plpA transcription was growth phase-dependent, reaching maximum levels during the early stationary phase. Also, transcription factor HlyU and cAMP receptor protein (CRP) mediate additive activation and host-dependent induction of plpA Molecular biological analyses revealed that plpA expression is controlled via the promoter, P plpA , and that HlyU and CRP directly bind to P plpA upstream sequences. Taken together, this study demonstrated that VvPlpA is a type II secretion system-dependent secretory phospholipase A2 regulated by HlyU and CRP and is essential for the pathogenicity of V. vulnificus.

High Glucose-Induced Reactive Oxygen Species Stimulates Human Mesenchymal Stem Cell Migration Through Snail and EZH2-Dependent E-Cadherin Repression.

BACKGROUND/AIMS: Glucose plays an important role in stem cell fate determination and behaviors. However, it is still not known how glucose contributes to the precise molecular mechanisms responsible for stem cell migration. Thus, we investigate the effect of glucose on the regulation of the human umbilical cord blood-derived mesenchymal stem cell (hUCB-MSC) migration, and analyze the mechanism accompanied by this effect. METHODS: Western blot analysis, wound healing migration assays, immunoprecipitation, and chromatin immunoprecipitation assay were performed to investigate the effect of high glucose on hUCB-MSC migration. Additionally, hUCB-MSC transplantation was performed in the mouse excisional wound splinting model. RESULTS: High concentration glucose (25 mM) elicits hUCB-MSC migration compared to normal glucose and high glucose-pretreated hUCB-MSC transplantation into the wound sites in mice also accelerates skin wound repair. We therefore elucidated the detailed mechanisms how high glucose induces hUCB-MSC migration. We showed that high glucose regulates E-cadherin repression through increased Snail and EZH2 expressions. And, we found high glucose-induced reactive oxygen species (ROS) promotes two signaling; JNK which regulates γ-secretase leading to the cleavage of Notch proteins and PI3K/Akt signaling which enhances GSK-3ß phosphorylation. High glucose-mediated JNK/Notch pathway regulates the expression of EZH2, and PI3K/Akt/GSK-3ß pathway stimulates Snail stabilization, respectively. High glucose enhances the formation of EZH2/Snail/HDAC1 complex in the nucleus, which in turn causes E-cadherin repression. CONCLUSION: This study reveals that high glucose-induced ROS stimulates the migration of hUCB-MSC through E-cadherin repression via Snail and EZH2 signaling pathways.

Ethanol-induced PGE2 up-regulates Aß production through PKA/CREB signaling pathway.

Ethanol abuse aggravates dementia-associated cognitive defects through the progression of Alzheimer's disease (AD) pathophysiology. Beta-site APP-cleaving enzyme 1 (BACE1) has been considered as a key regulator of AD pathogenesis by controlling amyloid beta peptide (Aß) accumulation. In addition, previous studies reported that endoplasmic reticulum (ER) stress and neuroinflammation have been proposed in ethanol-induced neurodegeneration. Thus, we investigated the role of ER stress and PGE2, a neuroinflammation mediator, in the ethanol-stimulated BACE1 expression and Aß production. Using the human-derived neuroblastoma cell line SK-N-MC, the results show that ethanol up-regulated BACE1 expression in a dose-dependent manner. Ethanol stimulated reactive oxygen species (ROS) production, which induced CHOP expression and eIF2α phosphorylation. PBA (an ER stress inhibitor) attenuated the ethanol-increased cyclooxygenase-2 (COX-2) expression and PGE2 production. By using salubrinal (an eIF2α dephosphorylation inhibitor) or EIF2A siRNA, we found that eIF2α phosphorylation mediated the ethanol-induced COX-2 expression. In addition, COX-2-induced BACE1 up-regulation was abolished by NS-398 (a selective COX-2 inhibitor). And, PF-04418948 (an EP-2 receptor inhibitor) pretreatment reduced ethanol-induced PKA activation and CREB phosphorylation as well as ethanol-stimulated Aß production. Furthermore, 14-22 amide (a PKA inhibitor) pretreatment or CREB1 siRNA transfection suppressed the ethanol-induced BACE1 expression. In conclusion, ethanol-induced eIF2α phosphorylation stimulates COX-2 expression and PGE2 production which induces the BACE1 expression and Aß production via EP-2 receptor-dependent PKA/CREB pathway.

Enhancement of high glucose-induced PINK1 expression by melatonin stimulates neuronal cell survival: Involvement of MT2 /Akt/NF-κB pathway.

Hyperglycemia is a representative hallmark and risk factor for diabetes mellitus (DM) and is closely linked to DM-associated neuronal cell death. Previous investigators reported on a genome-wide association study and showed relationships between DM and melatonin receptor (MT), highlighting the role of MT signaling by assessing melatonin in DM. However, the role of MT signaling in DM pathogenesis is unclear. Therefore, we investigated the role of mitophagy regulators in high glucose-induced neuronal cell death and the effect of melatonin against high glucose-induced mitophagy regulators in neuronal cells. In our results, high glucose significantly increased PTEN-induced putative kinase 1 (PINK1) and LC-3B expressions; as well it decreased cytochrome c oxidase subunit 4 expression and Mitotracker™ fluorescence intensity. Silencing of PINK1 induced mitochondrial reactive oxygen species (ROS) accumulation and mitochondrial membrane potential impairment, increased expressions of cleaved caspases, and increased the number of annexin V-positive cells. In addition, high glucose-stimulated melatonin receptor 1B (MTNR1B) mRNA and PINK1 expressions were reversed by ROS scavenger N-acetyl cysteine pretreatment. Upregulation of PINK1 expression in neuronal cells is suppressed by pretreatment with MT2 receptor-specific inhibitor 4-P-PDOT. We further showed melatonin stimulated Akt phosphorylation, which was followed by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) phosphorylation and nuclear translocation. Silencing of PINK1 expression abolished melatonin-regulated mitochondrial ROS production, cleaved caspase-3 and caspase-9 expressions, and the number of annexin V-positive cells. In conclusion, we have demonstrated the melatonin stimulates PINK1 expression via an MT2 /Akt/NF-κB pathway, and such stimulation is important for the prevention of neuronal cell apoptosis under high glucose conditions.

Vibrio vulnificus VvpE Stimulates IL-1ß Production by the Hypomethylation of the IL-1ß Promoter and NF-κB Activation via Lipid Raft-Dependent ANXA2 Recruitment and Reactive Oxygen Species Signaling in Intestinal Epithelial Cells.

An inflammatory response is a hallmark of necrosis evoked by bacterial pathogens. Vibrio vulnificus, VvpE, is an elastase that is responsible for tissue necrosis and inflammation; however, the molecular mechanism by which it regulates host cell death has not been characterized. In the present study, we investigate the cellular mechanism of VvpE with regard to host cell death and the inflammatory response of human intestinal epithelial (INT-407) cells. The recombinant protein (r)VvpE (50 pg/ml) caused cytotoxicity mainly via necrosis coupled with IL-1ß production. The necrotic cell death induced by rVvpE is highly susceptible to the knockdown of annexin A (ANXA)2 and the sequestration of membrane cholesterol. We found that rVvpE induces the recruitment of NADPH oxidase 2 and neutrophil cytosolic factor 1 into membrane lipid rafts coupled with ANXA2 to facilitate the production of reactive oxygen species (ROS). The bacterial signaling of rVvpE through ROS production is uniquely mediated by the phosphorylation of redox-sensitive transcription factor NF-κB. The silencing of NF-κB inhibited IL-1ß production during necrosis. rVvpE induced hypomethylation and region-specific transcriptional occupancy by NF-κB in the IL-1ß promoter and has the ability to induce pyroptosis via NOD-, LRR-, and pyrin domain-containing 3 inflammasome. In a mouse model of V. vulnificus infection, the mutation of the vvpE gene from V. vulnificus negated the proinflammatory responses and maintained the physiological levels of the proliferation and migration of enterocytes. These results demonstrate that VvpE induces the hypomethylation of the IL-1ß promoter and the transcriptional regulation of NF-κB through lipid raft-dependent ANXA2 recruitment and ROS signaling to promote IL-1ß production in intestinal epithelial cells.

Oleic acid enhances the motility of umbilical cord blood derived mesenchymal stem cells through EphB2-dependent F-actin formation.

The role of unsaturated fatty acids (UFAs) is essential for determining stem cell functions. Eph/Ephrin interactions are important for regulation of stem cell fate and localization within their niche, which is significant for a wide range of stem cell behavior. Although oleic acid (OA) and Ephrin receptors (Ephs) have critical roles in the maintenance of stem cell functions, interrelation between Ephs and OA has not been explored. Therefore, the present study investigated the effect of OA-pretreated UCB-MSCs in skin wound-healing and underlying mechanism of Eph expression. OA promoted the motility of UCB-MSCs via EphB2 expression. OA-mediated GPR40 activation leads to Gαq-dependent PKCα phosphorylation. In addition, OA-induced phosphorylation of GSK3ß was followed by ß-catenin nuclear translocation in UCB-MSCs. Activation of ß-catenin was blocked by PKC inhibitors, and OA-induced EphB2 expression was suppressed by ß-cateninsiRNA transfection. Of those Rho-GTPases, Rac1 was activated in an EphB2-dependent manner. Accordingly, knocking down EphB2 suppressed F-actin expression. In vivo skin wound-healing assay revealed that OA-treated UCB-MSCs enhanced skin wound repair compared to UCB-MSCs pretreated with EphB2siRNA and OA. In conclusion, we showed that OA enhances UCB-MSC motility through EphB2-dependent F-actin formation involving PKCα/GSK3ß/ß-catenin and Rac1 signaling pathways.

VvpE mediates the intestinal colonization of Vibrio vulnificus by the disruption of tight junctions.

The disruption of gastrointestinal tight junctions and their colonization evoked by enteric pathogens are hallmarks of the pathogenesis. Vibrio (V.) vulnificus, VvpE, is an elastase which is responsible for host surface adherence and vascular permeability; however, the functional roles of VvpE in the pathogenesis of V. vulnificus (WT) are poorly understood. In the present study, we have investigated the role of VvpE in regulation of intestinal tight junctions and the colonization of WT. We found that mutation of the vvpE gene from V. vulnificus (vvpE mutant) prevents intestinal tight/adherens junction dysregulation due to a WT infection and maintains the physiological level of the epithelial paracellular permeability. Interestingly, the vvpE mutant exhibited defective intestinal colonization abilities, whereas WT colonization was significantly elevated in the ileum in a time-dependent manner. Finally, the vvpE mutant negated the enterotoxicity, the breakdown of red blood cells, and pro-inflammatory responses, all of which are induced by the WT infection. In addition, the results of a LC-MS/MS analysis showed that VvpE contributes to WT pathogenesis in multiple ways by interacting with intestinal proteins, including ß-globin, Annexin A2, Annexin A4, F-actin, and intelectin-1b. These results demonstrate that VvpE plays important role in promoting the tight junction disruption and intestinal colonization of V. vulnificus and that it also has the ability to interact with the intestinal proteins responsible for microbial pathogenesis.

Novel Pathway for Hypoxia-Induced Proliferation and Migration in Human Mesenchymal Stem Cells: Involvement of HIF-1α, FASN, and mTORC1.

The control of stem cells by oxygen signaling is an important way to improve various stem cell physiological functions and metabolic nutrient alteration. Lipid metabolism alteration via hypoxia is thought to be a key factor in controlling stem cell fate and function. However, the interaction between hypoxia and the metabolic and functional changes to stem cells is incompletely described. This study aimed to identify hypoxia-inducible lipid metabolic enzymes that can regulate umbilical cord blood (UCB)-derived human mesenchymal stem cell (hMSC) proliferation and migration and to demonstrate the signaling pathway that controls functional change in UCB-hMSCs. Our results indicate that hypoxia treatment stimulates UCB-hMSC proliferation, and expression of two lipogenic enzymes: fatty acid synthase (FASN) and stearoyl-CoA desaturase-1 (SCD1). FASN but not SCD1 is a key enzyme for regulation of UCB-hMSC proliferation and migration. Hypoxia-induced FASN expression was controlled by the hypoxia-inducible factor-1 alpha (HIF-1α)/SCAP/SREBP1 pathway. Mammalian target of rapamycin (mTOR) was phosphorylated by hypoxia, whereas inhibition of FASN by cerulenin suppressed hypoxia-induced mTOR phosphorylation as well as UCB-hMSC proliferation and migration. RAPTOR small interfering RNA transfection significantly inhibited hypoxia-induced proliferation and migration. Hypoxia-induced mTOR also regulated CDK2, CDK4, cyclin D1, cyclin E, and F-actin expression as well as that of c-myc, p-cofilin, profilin, and Rho GTPase. Taken together, the results suggest that mTORC1 mainly regulates UCB-hMSC proliferation and migration under hypoxia conditions via control of cell cycle and F-actin organization modulating factors. In conclusion, the HIF-1α/FASN/mTORC1 axis is a key pathway linking hypoxia-induced lipid metabolism with proliferation and migration in UCB-hMSCs. Stem Cells 2015;33:2182-2195.

Melatonin enhances the human mesenchymal stem cells motility via melatonin receptor 2 coupling with Gαq in skin wound healing.

Melatonin, a circadian rhythm-promoting molecule, has a variety of biological functions, but the functional role of melatonin in the motility of mesenchymal stem cells (MSCs) has yet to be studied. In a mouse skin excisional wound model, we found that transplantation of umbilical cord blood (UCB)-MSCs pretreated with melatonin enhanced wound closure, granulation, and re-epithelialization at mouse skin wound sites, where relatively more UCB-MSCs which were engrafted onto the wound site were detected. Thus, we identified the signaling pathway of melatonin, which affects the motility of UCB-MSCs. Melatonin (1 µm) significantly increased the motility of UCB-MSCs, which had been inhibited by the knockdown of melatonin receptor 2 (MT2). We found that Gαq coupled with MT2 and that the binding of Gαq to MT2 uniquely stimulated an atypical PKC isoform, PKCζ. Melatonin induced the phosphorylation of FAK and paxillin, which were concurrently downregulated by blocking of the PKC activity. Melatonin increased the levels of active Cdc42 and Arp2/3, and it has the ability to stimulate cytoskeletal reorganization-related proteins such as profilin-1, cofilin-1, and F-actin in UCB-MSCs. Finally, a lack of MT2 expression in UCB-MSCs during a mouse skin transplantation experiment resulted in impaired wound healing and less engraftment of stem cells at the wound site. These results demonstrate that melatonin signaling via MT2 triggers FAK/paxillin phosphorylation to stimulate reorganization of the actin cytoskeleton, which is responsible for Cdc42/Arp2/3 activation to promote UCB-MSCs motility.

AutoPepVax, a Novel Machine-Learning-Based Program for Vaccine Design: Application to a Pan-Cancer Vaccine Targeting EGFR Missense Mutations.

The current epitope selection methods for peptide vaccines often rely on epitope binding affinity predictions, prompting the need for the development of more sophisticated in silico methods to determine immunologically relevant epitopes. Here, we developed AutoPepVax to expedite and improve the in silico epitope selection for peptide vaccine design. AutoPepVax is a novel program that automatically identifies non-toxic and non-allergenic epitopes capable of inducing tumor-infiltrating lymphocytes by considering various epitope characteristics. AutoPepVax employs random forest classification and linear regression machine-learning-based models, which are trained with datasets derived from tumor samples. AutoPepVax, along with documentation on how to run the program, is freely available on GitHub. We used AutoPepVax to design a pan-cancer peptide vaccine targeting epidermal growth factor receptor (EGFR) missense mutations commonly found in lung adenocarcinoma (LUAD), colorectal adenocarcinoma (CRAD), glioblastoma multiforme (GBM), and head and neck squamous cell carcinoma (HNSCC). These mutations have been previously targeted in clinical trials for EGFR-specific peptide vaccines in GBM and LUAD, and they show promise but lack demonstrated clinical efficacy. Using AutoPepVax, our analysis of 96 EGFR mutations identified 368 potential MHC-I-restricted epitope-HLA pairs from 49,113 candidates and 430 potential MHC-II-restricted pairs from 168,669 candidates. Notably, 19 mutations presented viable epitopes for MHC I and II restrictions. To evaluate the potential impact of a pan-cancer vaccine composed of these epitopes, we used our program, PCOptim, to curate a minimal list of epitopes with optimal population coverage. The world population coverage of our list ranged from 81.8% to 98.5% for MHC Class II and Class I epitopes, respectively. From our list of epitopes, we constructed 3D epitope-MHC models for six MHC-I-restricted and four MHC-II-restricted epitopes, demonstrating their epitope binding potential and interaction with T-cell receptors. AutoPepVax's comprehensive approach to in silico epitope selection addresses vaccine safety, efficacy, and broad applicability. Future studies aim to validate the AutoPepVax-designed vaccines with murine tumor models that harbor the studied mutations.

Sodium butyrate ameliorates high glucose-suppressed neuronal mitophagy by restoring PRKN expression via inhibiting the RELA-HDAC8 complex.

Damaged mitochondria accumulation in diabetes is one of the main features that contribute to increased incidence of cognitive impairment by inducing apoptosis. Butyrate is a major metabolite produced by microbiota that has neuroprotective effects by regulating mitochondrial function. However, detailed mechanisms underlying how butyrate can regulate neuronal mitophagy remain unclear. Here, we examined the regulatory effects of sodium butyrate (NaB) on high glucose-induced mitophagy dysregulation, neuronal apoptosis, and cognitive impairment and its underlying mechanisms in human-induced pluripotent stem cell-derived neurons, SH-SY5Ys, and streptozotocin (STZ)-induced diabetic mice. In our results, diabetic mice showed gut-microbiota dysbiosis, especially a decreased number of butyrate-producing bacteria and reduced NaB plasma concentration. NaB ameliorated high glucose-induced neuronal mitochondrial dysfunction by recovering PRKN/Parkin-mediated mitophagy. High glucose-induced reactive oxygen species (ROS) and -inhibited PRKAA/AMPKα stimulated the RELA/p65-HDAC8 complex, which downregulated PRKN protein expression by binding to the PRKN promoter region. NaB restored PRKN expression by blocking RELA nuclear translocation and directly inhibiting HDAC8 in the nucleus. In addition, HDAC8 overexpression inhibited the positive effect of NaB on high glucose-induced mitophagy dysfunction and neuronal apoptosis. Oral administration of NaB improved cognitive impairment in diabetic mice by restoring mitophagy in the hippocampus. Taken together, NaB ameliorates neuronal mitophagy through PRKN restoration by inhibiting RELA-HDAC8 complexes, suggesting that NaB is an important substance for protecting neuronal apoptosis in diabetes-associated cognitive impairment.

Transcription Factor EB-Mediated Lysosomal Function Regulation for Determining Stem Cell Fate under Metabolic Stress.

Stem cells require high amounts of energy to replicate their genome and organelles and differentiate into numerous cell types. Therefore, metabolic stress has a major impact on stem cell fate determination, including self-renewal, quiescence, and differentiation. Lysosomes are catabolic organelles that influence stem cell function and fate by regulating the degradation of intracellular components and maintaining cellular homeostasis in response to metabolic stress. Lysosomal functions altered by metabolic stress are tightly regulated by the transcription factor EB (TFEB) and TFE3, critical regulators of lysosomal gene expression. Therefore, understanding the regulatory mechanism of TFEB-mediated lysosomal function may provide some insight into stem cell fate determination under metabolic stress. In this review, we summarize the molecular mechanism of TFEB/TFE3 in modulating stem cell lysosomal function and then elucidate the role of TFEB/TFE3-mediated transcriptional activity in the determination of stem cell fate under metabolic stress.

Melatonin-mediated FKBP4 downregulation protects against stress-induced neuronal mitochondria dysfunctions by blocking nuclear translocation of GR.

The physiological crosstalk between glucocorticoid and melatonin maintains neuronal homeostasis in regulating circadian rhythms. However, the stress-inducing level of glucocorticoid triggers mitochondrial dysfunction including defective mitophagy by increasing the activity of glucocorticoid receptors (GRs), leading to neuronal cell death. Melatonin then suppresses glucocorticoid-induced stress-responsive neurodegeneration; however, the regulatory mechanism of melatonin, i.e., associated proteins involved in GR activity, has not been elucidated. Therefore, we investigated how melatonin regulates chaperone proteins related to GR trafficking into the nucleus to suppress glucocorticoid action. In this study, the effects of glucocorticoid on suppressing NIX-mediated mitophagy, followed by mitochondrial dysfunction, neuronal cell apoptosis, and cognitive deficits were reversed by melatonin treatment by inhibiting the nuclear translocation of GRs in both SH-SY5Y cells and mouse hippocampal tissue. Moreover, melatonin selectively suppressed the expression of FKBP prolyl isomerase 4 (FKBP4), which is a co-chaperone protein that works with dynein, to reduce the nuclear translocation of GRs among the chaperone proteins and nuclear trafficking proteins. In both cells and hippocampal tissue, melatonin upregulated melatonin receptor 1 (MT1) bound to Gαq, which triggered the phosphorylation of ERK1. The activated ERK then enhanced DNA methyltransferase 1 (DNMT1)-mediated hypermethylation of FKBP52 promoter, reducing GR-mediated mitochondrial dysfunction and cell apoptosis, the effects of which were reversed by knocking down DNMT1. Taken together, melatonin has a protective effect against glucocorticoid-induced defective mitophagy and neurodegeneration by enhancing DNMT1-mediated FKBP4 downregulation that reduced the nuclear translocation of GRs.

TRIM16-mediated lysophagy suppresses high-glucose-accumulated neuronal Aß.

ABBREVIATIONS: Aß: amyloid ß; AD: Alzheimer disease; AMPK: 5' adenosine monophosphate-activated protein kinase; CTSB: cathepsin B; CTSD: cathepsin D; DM: diabetes mellitus; ESCRT: endosomal sorting complex required for transport; FBXO27: F-box protein 27; iPSC-NDs: induced pluripotent stem cell-derived neuronal differentiated cells; LAMP1: lysosomal-associated membrane protein 1; LMP: lysosomal membrane permeabilization; LRSAM1: leucine rich repeat and sterile alpha motif containing 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; p-MAPT/tau: phosphorylated microtubule associated protein tau; ROS: reactive oxygen species; STZ: streptozotocin; TFE3: transcription factor E3; TFEB: transcription factor EB; TRIM16: tripartite motif containing 16; UBE2QL1: ubiquitin conjugating enzyme E2 Q family like 1; VCP: valosin containing protein.

High glucose-mediated VPS26a down-regulation dysregulates neuronal amyloid precursor protein processing and tau phosphorylation.

BACKGROUND AND PURPOSE: The relationship between hyperglycaemia-induced retromer dysfunction impairing intracellular trafficking and Alzheimer's disease (AD) remains unclear, although diabetes mellitus (DM) is considered a risk factor for AD. Here, we investigated the effects of high glucose on the retromer and defined the dysregulation of mechanisms of amyloid precursor protein (APP) processing and tau phosphorylation. EXPERIMENTAL APPROACH: We used human induced-pluripotent stem cell-derived neuronal differentiated cells and SH-SY5Ys exposed to high glucose to identify the underlying mechanisms. Streptozotocin-induced diabetic mice were used to elucidate whether the retromer contributes to the AD-like pathology. KEY RESULTS: We found that vacuolar protein sorting-associated protein 26a (VPS26a) was decreased in the hippocampus of diabetic mice and high glucose-treated human neuronal cells. High glucose down-regulated VPS26a through ROS/NF-κB/DNA methyltransferase1-mediated promoter hypermethylation. VPS26a recovery blocked retention of APP and cation-independent mannose-6-phosphate receptor in endosomes and promoted transport to the trans-Golgi, which decreased Aß levels, and improved cathepsin D activity, reducing p-tau levels, respectively. Retromer enhancement ameliorated synaptic deficits, astrocyte over-activation, and cognitive impairment in diabetic mice. CONCLUSION AND IMPLICATIONS: In conclusion, VPS26a is a promising candidate for the inhibition of DM-associated AD pathogenesis by modulating APP processing and tau phosphorylation.