Autophagy and KRT8/keratin 8 protect degeneration of retinal pigment epithelium under oxidative stress

Retinal light damage: From mechanisms to protective strategies

Visible light serves as a crucial medium for vision formation.;however, prolonged or excessive exposure to light is recognized as a significant etiological factor contributing to retinal degenerative diseases. The retina, with its unique structure and adaptability, relies on the homeostasis of cellular functions to maintain visual health. Under normal conditions, the retina can mount adaptive responses to various insults, including light-induced damage. Unfortunately, exposure to intense and excessive light triggers a cascade of pathological alterations in retinal photoreceptor cells, pigment epithelial cells, ganglion cells, and glial cells. These alterations encompass disruption of intracellular REDOX and Ca²⁺ homeostasis, pyroptosis, endoplasmic reticulum stress, autophagy, and the release of inflammatory cytokines, culminating in irreversible retinal damage. We first delineate the mechanisms of retinal light damage through 4 main avenues: mitochondria function, endoplasmic reticulum stress, cell autophagy, and inflammation. Subsequently, we discuss protective strategies against retinal light damage, aiming to guide research toward the prevention and treatment of light-induced retinal conditions.

NLRP3 and autophagy in retinal ganglion cell inflammation in age-related macular degeneration: potential therapeutic implications

Retinal degenerative diseases were a large group of diseases characterized by the primary death of retinal ganglion cells (RGCs). Recent studies had shown an interaction between autophagy and nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) inflammasomes, which may affect RGCs in retinal degenerative diseases. The NLRP3 inflammasome was a protein complex that, upon activation, produces caspase-1, mediating the apoptosis of retinal cells and promoting the occurrence and development of retinal degenerative diseases. Upregulated autophagy could inhibit NLRP3 inflammasome activation, while inhibited autophagy can promote NLRP3 inflammasome activation, which leaded to the accelerated emergence of drusen and lipofuscin deposition under the neurosensory retina. The activated NLRP3 inflammasome could further inhibit autophagy, thus forming a vicious cycle that accelerated the damage and death of RGCs. This review discussed the relationship between NLRP3 inflammasome and autophagy and its effects on RGCs in age-related macular degeneration, providing a new perspective and direction for the treatment of retinal diseases.

Autophagy in dry AMD: A promising therapeutic strategy for retinal pigment epithelial cell damage

Dry age-related macular degeneration (AMD) is a prevalent clinical condition that leads to permanent damage to central vision and poses a significant threat to patients' visual health. Although the pathogenesis of dry AMD remains unclear, there is consensus on the role of retinal pigment epithelium (RPE) damage. Oxidative stress and chronic inflammation are major contributors to RPE cell damage, and the NOD-like receptor thermoprotein structural domain-associated protein 3 (NLRP3) inflammasome mediates the inflammatory response leading to apoptosis in RPE cells. Furthermore, lipofuscin accumulation results in oxidative stress, NLRP3 activation, and the development of vitelliform lesions, a hallmark of dry AMD, all of which may contribute to RPE dysfunction. The process of autophagy, involving the encapsulation, recognition, and transport of accumulated proteins and dead cells to the lysosome for degradation, is recognized as a significant pathway for cellular self-protection and homeostasis maintenance. Recently, RPE cell autophagy has been discovered to be closely linked to the development of macular degeneration, positioning autophagy as a cutting-edge research area in the realm of dry AMD. In this review, we present an overview of how lipofuscin, oxidative stress, and the NLRP3 inflammasome damage the RPE through their respective causal mechanisms. We summarized the connection between autophagy, oxidative stress, and NLRP3 inflammatory cytokines. Our findings suggest that targeting autophagy improves RPE function and sustains visual health, offering new perspectives for understanding the pathogenesis and clinical management of dry AMD.

Hu-Zhang Qing-Mai Formulation anti-oxidative stress alleviates diabetic retinopathy: Network pharmacology analysis and in vitro experiment

BACKGROUND

In this study, the potential mechanism of the Hu-Zhang Qing-Mai Formulation (HZQMF) on diabetic retinopathy (DR) in inhibiting oxidative stress was explored through network pharmacology analysis and in vitro experiments.

METHODS

The Traditional Chinese Medicine Systematic Pharmacology Analysis Platform was used to retrieve the active pharmaceutical ingredients and targets of HZQMF. DR-related genes and oxidative stress-related genes were obtained from PharmGKB, TTD, OMIM, GeneCards, and Drugbank. STRING was used to construct a protein-protein interaction network to screen core targets. Gene ontology and Kyoto encyclopedia of genes and genomes enrichment analyses were performed using R 4.0.3. Network topology analysis was carried out using Cytoscape 3.8.2. Finally, we looked into how well the main API protected human retinal pigment epithelial cells from damage brought on by hydrogen peroxide (H2O2).

RESULTS

Quercetin (Que) was identified as the primary API of HZQMF through network pharmacology analysis, while JUN, MAPK1, and STAT3 were identified as the primary hub genes. Kyoto encyclopedia of genes and genomes enrichment analysis showed that the AGE-RAGE signaling pathway may be crucial to the therapeutic process. In vitro experiments confirmed that Que increased cell vitality and inhibited apoptosis.

CONCLUSION

Que might significantly reduce H2O2-induced ARPE-19 cell injury by inhibiting apoptosis-related genes of the AGE-RAGE pathway (JUN, MAPK1, STAT3). This study lays the foundation for further research on HZQMF in treating DR.

Phosphorylation of KRT8 (keratin 8) by excessive mechanical load-activated PKN (protein kinase N) impairs autophagosome initiation and contributes to disc degeneration

Excessive mechanical load (overloading) is a well-documented pathogenetic factor for many mechano stress-induced pathologies, i.e. intervertebral disc degeneration (IDD). Under overloading, the balance between anabolism and catabolism within nucleus pulposus (NP) cells are badly thrown off, and NP cells undergo apoptosis. However, little is known about how the overloading is transduced to the NP cells and contributes to disc degeneration. The current study shows that conditional knockout of Krt8 (keratin 8) within NP aggravates load-induced IDD in vivo, and overexpression of Krt8 endows NP cells greater resistance to overloading-induced apoptosis and degeneration in vitro. Discovery-driven experiments shows that phosphorylation of KRT8 on Ser43 by overloading activated RHOA-PKN (protein kinase N) impedes trafficking of Golgi resident small GTPase RAB33B, suppresses the autophagosome initiation and contributes to IDD. Overexpression of Krt8 and knockdown of Pkn1 and Pkn2, at an early stage of IDD, ameliorates disc degeneration; yet only knockdown of Pkn1 and Pkn2, when treated at late stage of IDD, shows a therapeutic effect. This study validates a protective role of Krt8 during overloading-induced IDD and demonstrates that targeting overloading activation of PKNs could be a novel and effective approach to mechano stress-induced pathologies with a wider window of therapeutic opportunity.Abbreviations: AAV: adeno-associated virus; AF: anulus fibrosus; ANOVA: analysis of variance; ATG: autophagy related; BSA: bovine serum albumin; cDNA: complementary deoxyribonucleic acid; CEP: cartilaginous endplates; CHX: cycloheximide; cKO: conditional knockout; Cor: coronal plane; CT: computed tomography; Cy: coccygeal vertebra; D: aspartic acid; DEG: differentially expressed gene; DHI: disc height index; DIBA: dot immunobinding assay; dUTP: 2'-deoxyuridine 5'-triphosphate; ECM: extracellular matrix; EDTA: ethylene diamine tetraacetic acid; ER: endoplasmic reticulum; FBS: fetal bovine serum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GPS: group-based prediction system; GSEA: gene set enrichment analysis; GTP: guanosine triphosphate; HE: hematoxylin-eosin; HRP: horseradish peroxidase; IDD: intervertebral disc degeneration; IF: immunofluorescence staining; IL1: interleukin 1; IVD: intervertebral disc; KEGG: Kyoto encyclopedia of genes and genomes; KRT8: keratin 8; KD: knockdown; KO: knockout; L: lumbar vertebra; LBP: low back pain; LC/MS: liquid chromatograph mass spectrometer; LSI: mouse lumbar instability model; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MMP3: matrix metallopeptidase 3; MRI: nuclear magnetic resonance imaging; NC: negative control; NP: nucleus pulposus; PBS: phosphate-buffered saline; PE: p-phycoerythrin; PFA: paraformaldehyde; PI: propidium iodide; PKN: protein kinase N; OE: overexpression; PTM: post translational modification; PVDF: polyvinylidene fluoride; qPCR: quantitative reverse-transcriptase polymerase chain reaction; RHOA: ras homolog family member A; RIPA: radio immunoprecipitation assay; RNA: ribonucleic acid; ROS: reactive oxygen species; RT: room temperature; TCM: rat tail compression-induced IDD model; TCS: mouse tail suturing compressive model; S: serine; Sag: sagittal plane; SD rats: Sprague-Dawley rats; shRNA: short hairpin RNA; siRNA: small interfering RNA; SOFG: safranin O-fast green; SQSTM1: sequestosome 1; TUNEL: terminal deoxynucleotidyl transferase dUTP nick end labeling; VG/ml: viral genomes per milliliter; WCL: whole cell lysate.

Keratin8 Deficiency Aggravates Retinal Ganglion Cell Damage Under Acute Ocular Hypertension

Purpose

Keratin 8/18 (KRT8/18), paired members of the intermediate filament family, have shown vital functions in regulating physiological activities more than supporting the mechanic strength for cells and organelles. However, the KRT8/18 presence in retinal ganglion cells (RGCs) and functions on neuroprotection in a mouse model of acute ocular hypertension (AOH) are unknown and worthy of exploration.

Methods

We identified the existence of KRT8/18 in normal human and mouse retinas and primary RGCs. KRT8/18 levels were detected after AOH modeling. The adeno-associated virus (AAV) system was intravitreally used for selective KRT8 knockdown in RGCs. The histological changes, the loss and dysfunction of RGCs, and the gliosis in retinas were detected. The markers of cell apoptosis and MAPK pathways were investigated.

Results

KRT8/18 existed in all retinal layers and was highly expressed in RGCs, and they increased after AOH induction. The KRT8 knockdown in RGCs caused no histopathological changes and RGC loss in retinas without AOH modeling. However, after the KRT8 deficiency, AOH significantly promoted the loss of whole retina and inner retina thickness, the reduction, apoptosis, and dysfunction of RGCs, and the glial activation. Besides, downregulated Bcl-2 and upregulated cleaved-Caspase 3 were found in the AOH retinas with KRT8 knockdown, which may be caused by the increased phosphorylation level of MAPK pathways (JNK, p38, and ERK).

Conclusions

The KRT8 deficiency promoted RGC apoptosis and neurodegeneration by abnormal activation of MAPK pathways in AOH retinas. Targeting KRT8 may serve as a novel treatment for saving RCGs from glaucomatous injuries.

Natural products: protective effects against ischemia-induced retinal injury

Ischemic retinal damage, a common condition associated with retinal vascular occlusion, glaucoma, diabetic retinopathy, and other eye diseases, threatens the vision of millions of people worldwide. It triggers excessive inflammation, oxidative stress, apoptosis, and vascular dysfunction, leading to the loss and death of retinal ganglion cells. Unfortunately, minority drugs are available for treating retinal ischemic injury diseases, and their safety are limited. Therefore, there is an urgent need to develop more effective treatments for ischemic retinal damage. Natural compounds have been reported to have antioxidant, anti-inflammatory, and antiapoptotic properties that can be used to treat ischemic retinal damage. In addition, many natural compounds have been shown to exhibit biological functions and pharmacological properties relevant to the treatment of cellular and tissue damage. This article reviews the neuroprotective mechanisms of natural compounds involve treating ischemic retinal injury. These natural compounds may serve as treatments for ischemia-induced retinal diseases.

The apoptotic effects of soybean agglutinin were induced through three different signal pathways by down-regulating cytoskeleton proteins in IPEC-J2 cells

Soybean agglutinin (SBA) is a main anti-nutritional factor in soybean. SBA exhibits its anti-nutritional functions by binding to intestinal epithelial cells. Keratin8 (KRT8), Keratin18 (KRT18) and Actin (ACTA) are the representative SBA-specific binding proteins. Such cytoskeletal proteins act a crucial role in different cell activities. However, limited reports reveal what the signal transduction pathway of apoptosis caused by SBA when binding to KRT8, KRT18 and ACTA. We aimed to evaluate the effects of SBA on cell apoptosis and the expression of the cytoskeletal protein (KRT8, KRT18 and ACTA), reveal the roles of these cytoskeletal proteins or their combinations on SBA-induced cell apoptosis in IPEC-J2 cell line, evaluate the influences of SBA on the mitochondria, endoplasmic reticulum stress and death receptor-mediated apoptosis signal pathway and to show the roles of KRT8, KRT18 and ACTA in different apoptosis signal pathways induced by SBA. The results showed that SBA induced the IPEC-J2 cell apoptosis and decreased the mRNA expression of KRT8, KRT18 and ACTA (p < 0.05). The degree of effect of three cytoskeleton proteins on cell apoptosis was ACTA > KRT8 > KRT18. The roles of these three cytoskeletal proteins on IPEC-J2 apoptotic rates had a certain accumulation effect. SBA up-regulated mitochondrial fission variant protein (FIS1) and fusion protein (Mfn2) promoted CytC and AIF in mitochondria to enter the cytoplasm, activated caspase-9 and caspase-3, damaged or declined mitochondrial function and reduced ATP synthesis (p < 0.05). Also, SBA up-regulated the expression of GRP78, XBP-1, eIF2α, p-eIF2α and CHOP (p < 0.05), down-regulated the expression level of ASK1 protein (p < 0.05). SBA led to the recruitment of FADD to the cytoplasmic membrane and increased the expression of FasL, resulting in caspase-8 processing. SBA up-regulated the expression level of Bax protein and decreased cytosolic Bcl-2 and Bid (p < 0.05). In addition, there was a significant negative correlation between the gene expression of cytoskeleton proteins and apoptosis, as well as the expression of key proteins of apoptosis-related signal transduction pathways. In conclusion, SBA induced the activation of the mitochondria, endoplasmic reticulum stress and the death receptor-mediated apoptosis signal pathway and the crosstalk between them. The effect of SBA on these three pathways was mainly exhibited via down-regulation of the mRNA expression of the three cytoskeletal expressions. This study elucidates the molecular mechanism and signaling pathway of SBA that lead to apoptosis from the perspective of cell biology and molecular biology and provides a new perspective on the toxicity mechanism of other food-derived anti-nutrients, medical gastrointestinal health and related cancer treatment.

Azithromycin, a potent autophagy inhibitor for cancer therapy, perturbs cytoskeletal protein dynamics

BACKGROUND

Autophagy plays an important role in tumour cell growth and survival and also promotes resistance to chemotherapy. Hence, autophagy has been targeted for cancer therapy. We previously reported that macrolide antibiotics including azithromycin (AZM) inhibit autophagy in various types of cancer cells in vitro. However, the underlying molecular mechanism for autophagy inhibition remains unclear. Here, we aimed to identify the molecular target of AZM for inhibiting autophagy.

METHODS

We identified the AZM-binding proteins using AZM-conjugated magnetic nanobeads for high-throughput affinity purification. Autophagy inhibitory mechanism of AZM was analysed by confocal microscopic and transmission electron microscopic observation. The anti-tumour effect with autophagy inhibition by oral AZM administration was assessed in the xenografted mice model.

RESULTS

We elucidated that keratin-18 (KRT18) and α/β-tubulin specifically bind to AZM. Treatment of the cells with AZM disrupts intracellular KRT18 dynamics, and KRT18 knockdown resulted in autophagy inhibition. Additionally, AZM treatment suppresses intracellular lysosomal trafficking along the microtubules for blocking autophagic flux. Oral AZM administration suppressed tumour growth while inhibiting autophagy in tumour tissue.

CONCLUSIONS

As drug-repurposing, our results indicate that AZM is a potent autophagy inhibitor for cancer treatment, which acts by directly interacting with cytoskeletal proteins and perturbing their dynamics.

Autophagy in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of visual impairment in the aging population with limited understanding of its pathogenesis and a lack of effective treatment. The progression of AMD is initially characterized by atrophic alterations in the retinal pigment epithelium, as well as the formation of lysosomal lipofuscin and extracellular drusen deposits. Damage caused by chronic oxidative stress, protein aggregation and inflammatory processes may lead to geographic atrophy and/or choroidal neovascularization and fibrosis. The role of macroautophagy/autophagy in AMD pathology is steadily emerging. This review describes selective and secretory autophagy and their role in drusen biogenesis, senescence-associated secretory phenotype, inflammation and epithelial-mesenchymal transition in the pathogenesis of AMD.Abbreviations: Aβ: amyloid-beta; AMBRA1: autophagy and beclin 1 regulator 1; AMD: age-related macular degeneration; ATF6: activating transcription factor 6; ATG: autophagy related; BACE1: beta-secretase 1; BHLHE40: basic helix-loop-helix family member e40; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; C: complement; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CARD: caspase recruitment domain; CDKN2A/p16: cyclin dependent kinase inhibitor 2A; CFB: complement factor B; DELEC1/Dec1; deleted in esophageal cancer 1; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; EMT: epithelial-mesenchymal transition; ER: endoplasmic reticulum; ERN1/IRE1: endoplasmic reticulum to nucleus signaling 1; FUNDC1: FUN14 domain containing 1; GABARAP: GABA type A receptor-associated protein; HMGB1: high mobility group box 1; IL: interleukin; KEAP1: kelch like ECH associated protein 1; LAP: LC3-associated phagocytosis; LAMP2: lysosomal associated membrane protein 2; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NFE2L2: NFE2 like bZIP transcription factor 2; NLRP3; NLR family pyrin domain containing 3; NFKB/NFκB: nuclear factor kappa B; OPTN: optineurin; PARL: presenilin associated rhomboid like; PGAM5: PGAM family member 5, mitochondrial serine/threonine protein phosphatase; PINK1: PTEN induced kinase 1; POS: photoreceptor outer segment; PPARGC1A: PPARG coactivator 1 alpha; PRKN: parkin RBR E3 ubiquitin protein ligase; PYCARD/ASC: PYD and CARD domain containing; ROS: reactive oxygen species; RPE: retinal pigment epithelium; SA: secretory autophagy; SASP: senescence-associated secretory phenotype; SEC22B: SEC22 homolog B, vesicle trafficking protein; SNAP: synaptosome associated protein; SNARE: soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1/p62: sequestosome 1; STX: syntaxin; TGFB2: transforming growth factor beta 2; TRIM16: tripartite motif containing 16; TWIST: twist family bHLH transcription factor; Ub: ubiquitin; ULK: unc-51 like autophagy activating kinase; UPR: unfolded protein response; UPS: ubiquitin-proteasome system; V-ATPase: vacuolar-type H+-translocating ATPase; VIM: vimentin.

Repeated Topical Administration of 3 nm Cerium Oxide Nanoparticles Reverts Disease Atrophic Phenotype and Arrests Neovascular Degeneration in AMD Mouse Models

Increased oxidative stress in the retina and retinal pigment epithelium is implicated in age-related macular degeneration (AMD). Antioxidant cerium oxide nanoparticles (CeO2NPs) have been used to treat degenerative retinal pathologies in animal models, although their delivery route is not ideal for chronic patient treatment. In this work, we prepared a formulation for ocular topical delivery that contains small (3 nm), nonaggregated biocompatible CeO2NPs. In vitro results indicate the biocompatible and protective character of the CeO2NPs, reducing oxidative stress in ARPE19 cells and inhibiting neovascularization related to pathological angiogenesis in both HUVEC and in in vitro models of neovascular growth. In the in vivo experiments, we observed the capacity of CeO2NPs to reach the retina after topical delivery and a subsequent reversion of the altered retinal transcriptome of the retinal degenerative mouse model DKOrd8 toward that of healthy control mice, together with signs of decreased inflammation and arrest of degeneration. Furthermore, CeO2NP eye drops' treatment reduced laser-induced choroidal neovascular lesions in mice by lowering VEGF and increasing PEDF levels. These results indicate that CeO2NP eye drops are a beneficial antioxidant and neuroprotective treatment for both dry and wet forms of AMD disease.

Proteostasis in aging-associated ocular disease

Vision impairment has devastating consequences for the quality of human life. The cells and tissues associated with the visual process must function throughout one's life span and maintain homeostasis despite exposure to a variety of insults. Maintenance of the proteome is termed proteostasis, and is vital for normal cellular functions, especially at an advanced age. Here we describe basic aspects of proteostasis, from protein synthesis and folding to degradation, and discuss the current status of the field with a particular focus on major age-related eye diseases: age-related macular degeneration, cataract, and glaucoma. Our intent is to allow vision scientists to determine where and how to harness the proteostatic machinery for extending functional homeostasis in the aging retina, lens, and trabecular meshwork. Several common themes have emerged despite these tissues having vastly different metabolisms. Continued exposure to insults, including chronic stress with advancing age, increases proteostatic burden and reduces the fidelity of the degradation machineries including the ubiquitin-proteasome and the autophagy-lysosome systems that recognize and remove damaged proteins. This "double jeopardy" results in an exponential accumulation of cytotoxic proteins with advancing age. We conclude with a discussion of the challenges in maintaining an appropriate balance of protein synthesis and degradation pathways, and suggest that harnessing proteostatic capacities should provide new opportunities to design interventions for attenuating age-related eye diseases before they limit sight.

Melatonin ameliorates nickel induced autophagy in mouse brain: diminution of oxidative stress

Nickel（Ni) is a neurotoxic environmental pollutant. Oxidative stress is thought to be the main mechanism behind the development of Ni neurotoxicity. Melatonin (Mt) has significant efficacy as an antioxidant. In this paper, we investigated the damage that Ni causes to the autophagy of the nervous system. Furthermore, Mt has can intervene upon the damage caused by Ni, which can protect the nervous system. Herein, we randomly divided 80 8-week-old male wild-type C57BL/6N mice into four groups, including the C group, Ni group, Mt group, and Mt+Ni group. Ni was gavaged at a concentration of 10mg/kg, while was Mt was administered at a concentration of 2mg/kg for 21 days at 0.1ml/10g body weight of the mice. Histopathological and ultrastructural observations demonstrated altered states, such as neuronal atrophy, as well as typical autophagic features in the Ni group. Mt was able to intervene effectively in Ni-induced neurotoxicity. The antioxidant capacity assay also demonstrated that Ni can lead to a large amount of reactive oxygen species (ROS) production within the mouse brain. Furthermore, the same Mt was effective at reducing ROS production. In order to further illustrate this point, we added the broad-spectrum phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 to NS20Y cells. The presence of inhibitors effectively demonstrates that, within the PI3K/AKT/mTOR pathway, autophagy occurs. In conclusion, these data suggest that Ni causes oxidative stress damage and induces autophagy within the mouse brain by inhibiting the PI3K/AKT/mTOR pathway, and that Mt can effectively alleviate the oxidative stress caused by Ni, and reducing Ni induces autophagy in the mouse brain through the PI3K/AKT/mTOR pathway.

Biomarkers as Predictive Factors of Anti-VEGF Response

Age-related macular degeneration is the main cause of irreversible vision in developed countries, and intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections are the current gold standard treatment today. Although anti-VEGF treatment results in important improvements in the course of this disease, there is a considerable number of patients not responding to the standardized protocols. The knowledge of how a patient will respond or how frequently retreatment might be required would be vital in planning treatment schedules, saving both resource utilization and financial costs, but today, there is not an ideal biomarker to use as a predictive response to ranibizumab therapy. Whole blood and blood mononuclear cells are the samples most studied; however, few reports are available on other important biofluid samples for studying this disease, such as aqueous humor. Moreover, the great majority of studies carried out to date were focused on the search for SNPs in genes related to AMD risk factors, but miRNAs, proteomic and metabolomics studies have rarely been conducted in anti-VEGF-treated samples. Here, we propose that genomic, proteomic and/or metabolomic markers could be used not alone but in combination with other methods, such as specific clinic characteristics, to identify patients with a poor response to anti-VEGF treatment to establish patient-specific treatment plans.

Decorin Protects Retinal Pigment Epithelium Cells from Oxidative Stress and Apoptosis via AMPK-mTOR-Regulated Autophagy

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss among the elderly worldwide with unidentified pathogenesis and limited therapeutic options. Oxidative stress-induced damage to the retinal pigment epithelium (RPE) is central in the development and progression of AMD. Decorin (DCN), a small leucine-rich proteoglycan, possesses powerful antifibrotic, anti-inflammatory, and antiangiogenic properties. DCN has also been reported to serve a cytoprotective role in various cell types, but its protective effects against H₂O₂-induced oxidative stress and apoptosis in ARPE-19 cells remain unclear. In this study, we showed that DCN significantly attenuated the increase in cell viability loss, apoptosis rate, and reactive oxygen species (ROS) levels in ARPE-19 cells induced by H₂O₂. Furthermore, DCN activated the AMPK/mTOR pathway to promote autophagy while genetic inhibition of autophagy-related gene 5 (ATG5) hindered autophagic process and diminished the protective role of DCN against oxidative stress in ARPE-19 cells. Collectively, these results suggest that DCN could protect RPE cells from H₂O₂-induced oxidative stress and apoptosis via autophagy promotion, thus providing the therapeutic potential for AMD prevention and treatment.

Autophagosome-lysosome fusion is facilitated by plectin-stabilized actin and keratin 8 during macroautophagic process

Autophagy is a lysosome-mediated degradative process that removes damaged proteins and organelles, during which autophagosome-lysosome fusion is a key step of the autophagic flux. Based on our observation that intermediate cytofilament keratin 8 (KRT8) enhances autophagic clearance in cells under oxidative stress condition, we investigated whether KRT8 supports the cytoplasmic architectural networks to facilitate the vesicular fusion entailing trafficking onto filamentous tracks. We found that KRT8 interacts with actin filaments via the cytolinker, plectin (PLEC) during trafficking of autophagosome. When PLEC was knocked down or KRT8 structure was collapsed by phosphorylation, autophagosome-lysosome fusion was attenuated. Inhibition of actin polymerization resulted in accumulation of autophagosomes owing to a decrease in autophagosome and lysosome fusion. Furthermore, myosin motor protein was found to be responsible for vesicular trafficking along the actin filaments to entail autolysosome formation. Thus, the autophagosome-lysosome fusion is aided by PLEC-stabilized actin filaments as well as intermediate cytofilament KRT8 that supports the structural integrity of actin filaments during macroautophagic process under oxidative stress condition.

Deletion of Asrgl1 Leads to Photoreceptor Degeneration in Mice

The asparaginase and isoaspartyl peptidase 1 (ASRGL1) is an L-asparaginase and beta-aspartyl peptidase enzyme that may be involved in the formation of L-aspartate, a neurotransmitter that can operate as an excitatory neurotransmitter in some brain regions. Although variants in ASRGL1 have been reported in retinitis pigmentosa (RP) patients, the in vivo functions and mechanisms of ASRGL in RP remains unknown due to the lack of suitable disease models. To explore the role of ASRGL in RP, we generated an Asrgl1 knockout mouse model (Asrgl1 KO) using the CRISPR/Cas9 technique. Asrgl1 ablation in mice led to an attenuated electroretinogram (ERG) response around 8 months. The thickness of the outer nuclei layer (ONL) started to decrease around 9 months in Asrgl1 KO mice and gradually intensified at 12 and 15 months. Immunostaining revealed thinner inner segment (IS) and thinner outer segment (OS) as well as the progressive degeneration of rod and cone cells in Asrgl1 KO mice. One hundred forty-nine transcriptional differentially expressed genes (DEGs) were found by RNA-seq in Asrgl1 KO retina. These DEGs were linked to a number of biological processes that were considerably enriched, including gastrointestinal disease and organismal injury and abnormalities. By analysis of canonical pathways, glucocorticoid receptor signaling was the most significant canonical pathway altered in Asrgl1 KO retina. Several molecules, including NFE2L2, IL-4, Foxp3, and Fos, were in the central nodes of the interaction network in Asrgl1 KO retina. In summary, our study provided a knockout mouse model for a better understanding of the molecular mechanism for ASRGL1-related RP.

Association of Keratin 8 Level in Aqueous Humor With Outcomes of Intravitreal Ranibizumab Treatment for Neovascular Age-Related Macular Degeneration

Purpose

To investigate keratin 8 (KRT8) level in the aqueous humor (AH) of patients with neovascular age-related macular degeneration (nAMD) and elucidate its association with intravitreal ranibizumab (IVR) treatment outcomes.

Methods

This prospective study involved 58 eyes of treatment-naïve nAMD patients treated with three IVR doses monthly and whose AH samples were collected at baseline and two months after the initial treatment. KRT8 level was determined using the enzyme-linked immunosorbent assay and compared with that of the control group, which comprised patients who underwent cataract surgery during the same period. The nAMD-affected eyes were classified into responder (dry) and poor responder (persistent fluid) groups, according to optical coherence tomography (OCT) findings at month three. Additionally, associations between the KRT8 level and IVR treatment outcomes were analyzed.

Results

The baseline KRT8 level was significantly higher in the AMD group than in the control group. In the AMD group, responders demonstrated significant differences between the KRT8 level at the baseline and month two, whereas poor responders exhibited no significant change. Regression analysis revealed that a higher KRT8 level at month two was significantly associated with persistent fluid upon OCT at months three and six.

Conclusions

Monitoring aqueous KRT8 level may facilitate early determination of the therapeutic effects of IVR in nAMD patients and reflect the conditions of retinal pigment epithelium during the disease course.

Translational Relevance

Monitoring aqueous KRT8 may aid early determination of therapeutic effects of IVR in neovascular AMD patients and reflect the health conditions of retinal pigment epithelium.

A role for Snail-MnSOD axis in regulating epithelial-to-mesenchymal transition markers expression in RPE cells

Age-related macular degeneration (AMD) is a common cause of vision loss. The epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, accompanied by oxidative damage, plays a crucial role in AMD. It is well known that manganese superoxide dismutase (MnSOD) encoded by SOD2 is a critical molecule in fighting against oxidative stress, and Snail encoded by SNAI1 is the essential transcription factor for EMT. However, the effect of MnSOD on EMT and the underlying mechanism in RPE cells remains unknown. In this study, we found that MnSOD knockdown triggered the EMT by upregulating Snail, while MnSOD overexpression reversed EMT even with TGFβ treatment in RPE cells, and the anti-oxidative stress activity of MnSOD mediated this observation. In addition, Snail depletion increased both expression and activity of MnSOD while Snail overexpression decreased MnSOD expression and activity, and Dual-luciferase reporter and ChIP assays showed that Snail directly bound to E-box (CACCTG) in the SOD2 promoter. Moreover, MnSOD over-expression and Snail interference co-treatment strengthened the anti-oxidation and EMT reversing. Therefore, our findings demonstrate that MnSOD prevents EMT of RPE cells in AMD through inhibiting oxidative injury to RPE. Moreover, a critical EMT transcription factor, Snail, functions as a new negative transcriptional factor of SOD2. Herein, the Snail-MnSOD axis forms a mutual loop in the development of AMD, which may be a novel systemic treatment target for preventing AMD.

Targeting senescent retinal pigment epithelial cells facilitates retinal regeneration in mouse models of age-related macular degeneration

Although age-related macular degeneration (AMD) is a multifactorial disorder with angiogenic, immune, and inflammatory components, the most common clinical treatment strategies are antiangiogenic therapies. However, these strategies are only applicable to neovascular AMD, which accounts for less than 20% of all AMD cases, and there are no FDA-approved drugs for the treatment of dry AMD, which accounts for ~ 80% of AMD cases. Here, we report that the elimination of senescent cells is a potential novel therapeutic approach for the treatment of all types of AMD. We identified senescent retinal pigment epithelium (RPE) cells in animal models of AMD and determined their contributions to retinal degeneration. We further confirmed that the clearance of senescent RPE cells with the MDM2-p53 inhibitor Nutlin-3a ameliorated retinal degeneration. These findings provide new insights into the use of senescent cells as a therapeutic target for the treatment of AMD.

Alterations of endometrial epithelial-mesenchymal transition and MAPK signalling components in women with PCOS are partially modulated by metformin in vitro

Growing evidence suggests that epithelial-mesenchymal transition (EMT) and its regulator mitogen-activated protein kinase (MAPK) contribute to endometria-related reproductive disorders. However, the regulation of EMT and MAPK signalling components in the endometrium from polycystic ovary syndrome (PCOS) patients has not been systematically investigated and remains elusive. In humans, how metformin induces molecular alterations in the endometrial tissues under PCOS conditions is not completely clear. Here, we recruited 7 non-PCOS patients during the proliferative phase (nPCOS), 7 non-PCOS patients with endometrial hyperplasia (nPCOSEH), 14 PCOS patients during the proliferative phase (PCOS) and 3 PCOS patients with endometrial hyperplasia (PCOSEH). Our studies demonstrated that compared with nPCOS, PCOS patients showed decreased Claudin 1 and increased Vimentin and Slug proteins. Similar to increased Slug protein, nPCOSEH and PCOSEH patients showed increased N-cadherin protein. Western blot and immunostaining revealed increased epithelial phosphorylated Cytokeratin 8 (p-CK 8) expression and an increased p-CK 8:CK 8 ratio in PCOS, nPCOSEH and PCOSEH patients compared to nPCOS patients. Although nPCOSEH and PCOSEH patients showed increased p-ERK1/2 and/or p38 protein levels, the significant increase in p-ERK1/2 expression and p-ERK1/2:ERK1/2 ratio was only found in PCOS patients compared to nPCOS patients. A significant induction of the membrane ERβ immunostaining was observed in the epithelial cells of PCOS and PCOSEH patients compared to nPCOS and nPCOSEH patients. While in vitro treatment with metformin alone increased Snail and decreased Claudin 1, N-cadherin and α-SMA proteins, concomitant treatment with metformin and E2 increased the expression of CK 8 and Snail proteins and decreased the expression of Claudin 1, ZO-1, Slug and α-SMA proteins. Our findings suggest that the EMT contributes to the switch from a healthy state to a PCOS state in the endometrium, which might subsequently drive endometrial injury and dysfunction. We also provide evidence that metformin differentially modulates EMT protein expression in PCOS patients depending on oestrogenic stimulation.

Nicotinamide suppresses bevacizumab-induced epithelial-mesenchymal transition of ARPE-19 cells by attenuating oxidative stress

AIM

To investigate the effects of nicotinamide (NAM) on bevacizumab (BEV)-induced epithelial-mesenchymal transition (EMT) of human retinal pigment epithelial cells (ARPE-19) and the underling mechanisms.

METHODS

ARPE-19 cells were treated with BEV for 24, 48, and 72h, and the variation degrees of EMT-related markers (fibronectin, α-SMA, vimentin, and ZO-1) were assessed by Western blotting to select the optimal treatment time point which exhibited the most obvious changes of EMT-related markers for the subsequent experiments. Furthermore, NAM was added to the medium, the mRNA and protein levels of the EMT-related markers were then measured. The accumulation of reactive oxygen species (ROS) and H₂O₂ and the total antioxidant capacity (TAC) of the cells were also measured to evaluate the level of oxidative stress.

RESULTS

After being treated with BEV for 72h, the protein expression levels of EMT-related markers in ARPE-19 cells showed significant changes. Meanwhile the levels of ROS and H₂O₂ were obviously increased, and the TAC of ARPE-19 cells was decreased. Totally 72h was chosen to be the optimal treatment time point in subsequent experiments. Furthermore, NAM inhibited BEV-induced EMT by downregulating fibronectin, α-SMA, and vimentin and upregulating ZO-1, decreased the accumulation of ROS and H₂O₂, and enhanced TAC in BEV-treated ARPE-19 cells.

CONCLUSION

This study demonstrates that NAM suppressed BEV-induced EMT in ARPE-19 cells by attenuating oxidative stress. Hence, NAM may be a potential therapeutic agent for alleviating neovascular fibrosis of the ocular fundus after anti-vascular endothelial growth factor therapy.

KRT8 (keratin 8) attenuates necrotic cell death by facilitating mitochondrial fission-mediated mitophagy through interaction with PLEC (plectin)

Dysregulation of mitochondrial homeostasis and accumulation of damaged mitochondria cause degenerative diseases such as age-related macular degeneration (AMD). We studied the effects of the intermediate cytofilament KRT8 (keratin 8) on mitochondrial homeostasis in relation to the morphology and function of mitochondria in retinal pigment epithelial cells under oxidative stress. When the mitochondria were damaged owing to oxidative stress, the damaged mitochondria were readily disposed of via mitophagy following mitochondrial fission. During this process, KRT8 was found to physically interact with the mitochondria through PLEC (plectin) and facilitate the mitochondrial fission-mediated mitophagy. However, the association between PLEC-anchoring mitochondria and KRT8 was dwindled by KRT8 phosphorylation under oxidative stress. The efficient KRT8-facilitated mitophagy flux suppressed the accumulation of damaged mitochondria and consequently diminished necrotic cell death under oxidative stress. Thus, by facilitating mitophagy, KRT8 protects RPE cells against necrotic cell death due to oxidative stress.

The CD36 Ligand-Promoted Autophagy Protects Retinal Pigment Epithelial Cells from Oxidative Stress

The retinal pigment epithelium (RPE) performs many functions that maintain photoreceptor health. Oxidative damage to the RPE is a critical component in the pathogenesis of eye diseases such as age-related macular degeneration (AMD). Ligands of the cluster of differentiation 36 (CD36) have previously preserved photoreceptor integrity in mouse models of AMD. The cytoprotective effect of the CD36 ligand MPE-001 on RPE cells has now been elucidated employing a model of oxidative stress. Sodium iodate (NaIO₃) induced formation of reactive oxygen species and apoptosis in human RPE cells, which were decreased by MPE-001 without affecting antioxidant enzyme transcription. Immunoblotting and immunostaining assays showed a restorative effect of MPE-001 on the autophagic flux disrupted by NaIO₃, which was associated with an increase in syntaxin 17-positive mature autophagosomes. The cytoprotective effect of MPE-001 was completely abolished by the autophagy inhibitors wortmannin and bafilomycin A1. In conclusion, we report for the first time an autophagy-dependent protection of RPE cells from oxidative stress by a CD36 ligand.

H2S exposure-induced oxidative stress promotes LPS-mediated hepatocyte autophagy through the PI3K/AKT/TOR pathway

Hydrogen sulfide (H₂S), a common air pollutant and toxic gas, is detrimental to organisms and the environment. Exposure to highly concentrated H₂S can induce oxidative stress and autophagy. However, the mechanism underlying the liver damage caused by H₂S has not been identified. Lipopolysaccharide (LPS), the key component of endotoxin, can induce oxidative stress and autophagy. For this experiment, we used one-day-old chickens as model organisms to evaluate the effects of H₂S combined with LPS on oxidative stress and autophagy. The four groups (control group, LPS group, H₂S group and H₂S-LPS group) were observed by electron microscopy, detected by oxidative stress kit, analyzed by quantitative real-time quantitative PCR, and analyzed by Western blot. We found that the activities of antioxidant enzymes (superoxide dismutase, antioxidant glutathione, catalase, and glutathione peroxidase) decreased in the H₂S group compared to those in the control group; however, malondialdehyde levels in the H₂S group increased. Molecular-level studies showed that the expression of genes associated with the PI3K/ AKT/ TOR pathways in the H₂S group decreased, whereas the expression of other autophagy-related genes (Beclin1, ATG5 and the ratio of LC3-II/ LC3-I) increased compared to that in the control group. These findings suggest that H₂S caused oxidative stress and induced autophagy through the PI3K/ AKT/ TOR pathway in chicken liver cells. Additionally, exposure to H₂S aggravated LPS-induced oxidative stress and autophagy injury. Capsule: Aerial exposure to H₂S can cause oxidative stress in chicken livers and induce autophagy through the PI3K/AKT/TOR pathway, and can aggravate LPS-induced oxidative stress and autophagy.

Hydrogen Sulfide Protects Retinal Pigment Epithelial Cells from Oxidative Stress-Induced Apoptosis and Affects Autophagy

Age-related macular degeneration (AMD) is a major cause of visual impairment and blindness among the elderly. AMD is characterized by retinal pigment epithelial (RPE) cell dysfunction. However, the pathogenesis of AMD is still unclear, and there is currently no effective treatment. Accumulated evidence indicates that oxidative stress and autophagy play a crucial role in the development of AMD. H2S is an antioxidant that can directly remove intracellular superoxide anions and hydrogen peroxide. The purpose of this study is to investigate the antioxidative effect of H2S in RPE cells and its role in autophagy. The results show that exogenous H2S (NaHS) pretreatment effectively reduces H2O2-induced oxidative stress, oxidative damage, apoptosis, and inflammation in ARPE-19 cells. NaHS pretreatment also decreased autophagy levels raised by H2O2, increased cell viability, and ameliorated cell morphological damage. Interestingly, the suppression of autophagy by its inhibitor 3-MA showed an increase of cell viability, amelioration of morphology, and a decrease of apoptosis. In summary, oxidative stress causes ARPE-19 cell injury by inducing cell autophagy. However exogenous H2S is shown to attenuate ARPE-19 cell injury, decrease apoptosis, and reduce the occurrence of autophagy-mediated by oxidative stress. These findings suggest that autophagy might play a crucial role in the development of AMD, and exogenous H2S has a potential value in the treatment of AMD.

Regulation of FN1 degradation by the p62/SQSTM1-dependent autophagy-lysosome pathway in HNSCC

Epithelial–mesenchymal transition (EMT) is involved in both physiological and pathological processes. EMT plays an essential role in the invasion, migration and metastasis of tumours. Autophagy has been shown to regulate EMT in a variety of cancers but not in head and neck squamous cell carcinoma (HNSCC). Herein, we investigated whether autophagy also regulates EMT in HNSCC. Analyses of clinical data from three public databases revealed that higher expression of fibronectin-1 (FN1) correlated with poorer prognosis and higher tumour pathological grade in HNSCC. Data from SCC-25 cells demonstrated that rapamycin and Earle’s balanced salt solution (EBSS) promoted autophagy, leading to increased FN1 degradation, while 3-methyladenine (3-MA), bafilomycin A1 (Baf A1) and chloroquine (CQ) inhibited autophagy, leading to decreased FN1 degradation. On the other hand, autophagic flux was blocked in BECN1 mutant HNSCC Cal-27 cells, and rapamycin did not promote autophagy in Cal-27 cells; also in addition, FN1 degradation was inhibited. Further, we identified FN1 degradation through the lysosome-dependent degradation pathway using the proteasome inhibitor MG132. Data from immunoprecipitation assays also showed that p62/SQSTM1 participated as an autophagy adapter in the autophagy–lysosome pathway of FN1 degradation. Finally, data from immunoprecipitation assays demonstrated that the interaction between p62 and FN1 was abolished in p62 mutant MCF-7 and A2780 cell lines. These results indicate that autophagy significantly promotes the degradation of FN1. Collectively, our findings clearly suggest that FN1, as a marker of EMT, has adverse effects on HNSCC and elucidate the autophagy–lysosome degradation mechanism of FN1.

Autophagy Genes for Wet Age-Related Macular Degeneration in a Finnish Case-Control Study

Age-related macular degeneration is an eye disease that is the main cause of legal blindness in the elderly in developed countries. Despite this, its pathogenesis is not completely known, and many genetic, epigenetic, environmental and lifestyle factors may be involved. Vision loss in age-related macular degeneration (AMD) is usually consequence of the occurrence of its wet (neovascular) form that is targeted in the clinic by anti-VEGF (vascular endothelial growth factor) treatment. The wet form of AMD is associated with the accumulation of cellular waste in the retinal pigment epithelium, which is removed by autophagy and the proteosomal degradation system. In the present work, we searched for the association between genotypes and alleles of single nucleotide polymorphisms (SNPs) of autophagy-related genes and wet AMD occurrence in a cohort of Finnish patients undergoing anti-VEGF therapy and controls. Additionally, the correlation between treatment efficacy and genotypes was investigated. Overall, 225 wet AMD patients and 161 controls were enrolled in this study. Ten SNPs (rs2295080, rs11121704, rs1057079, rs1064261, rs573775, rs11246867, rs3088051, rs10902469, rs73105013, rs10277) in the mTOR (Mechanistic Target of Rapamycin), ATG5 (Autophagy Related 5), ULK1 (Unc-51-Like Autophagy Activating Kinase 1), MAP1LC3A (Microtubule Associated Protein 1 Light Chain 3 α), SQSTM1 (Sequestosome 1) were analyzed with RT-PCR-based genotyping. The genotype/alleles rs2295080-G, rs11121704-C, rs1057079-C and rs73105013-T associated with an increased, whereas rs2295080-TT, rs2295080-T, rs11121704-TT, rs1057079-TT, rs1057079-T, rs573775-AA and rs73105013-C with a decreased occurrence of wet AMD. In addition, the rs2295080-GG, rs2295080-GT, rs1057079-TT, rs11246867-AG, rs3088051-CC and rs10277-CC genotypes were a positively correlated cumulative number of anti-VEGF injections in 2 years. Therefore, variability in autophagy genes may have an impact on the risk of wet AMD occurrence and the efficacy of anti-VEGF treatment.

Cysteinyl leukotriene receptor 1 modulates autophagic activity in retinal pigment epithelial cells

The retinal pigment epithelium (RPE), which is among the tissues in the body that are exposed to the highest levels of phagocytosis and oxidative stress, is dependent on autophagy function. Impaired autophagy and continuous cellular stress are associated with various disorders, such as dry age-related macular degeneration (AMD), a disease for which effective therapies are lacking. Cysteinyl leukotriene receptor (CysLTR) 1 is a potential modulator of autophagy; thus, the aim of this study was to investigate the role of CysLTR1 in autophagy regulation in the RPE cell line ARPE-19. The polarized ARPE-19 monolayer exhibited expression of CysLTR1, which was colocalized with β-tubulin III. In ARPE-19 cells, autophagic activity was rhythmically regulated and was increased upon CysLTR1 inhibition by Zafirlukast (ZK) treatment. H₂O₂ affected the proautophagic regulatory effect of ZK treatment depending on whether it was applied simultaneously with or prior to ZK treatment. Furthermore, mRNA levels of genes related to the leukotriene system, autophagy and the unfolded protein response were positively correlated. As CysLTR1 is involved in autophagy regulation under basal and oxidative stress conditions, a dysfunctional leukotriene system could negatively affect RPE functions. Therefore, CysLTR1 is a potential target for new treatment approaches for neurodegenerative disorders, such as AMD.

Ilimaquinone inhibits neovascular age-related macular degeneration through modulation of Wnt/β-catenin and p53 pathways

Neovascular age-related macular degeneration (nAMD) is a common cause of irreversible vision loss in the elderly. Anti-vascular endothelial growth factor has been effective in treating pathological ocular neovascularization, but it has limitations including the need for repeated intraocular injections for the maintenance of therapeutic effects in most patients and poor or non-response to this agent in some patients. in vitro cellular studies were conducted using retinal pigment epithelial cell lines (ARPE-19 and hTERT-RPE1), human umbilical vein endothelial cells (HUVECs), and human umbilical vein smooth muscle cells (HUVSMCs). in vivo efficacy of ilimaquinone (IQ) was tested in laser-induced choroidal neovascularization mouse and rabbit models. Tissue distribution study was performed in male C57BL6/J mice. IQ, 4,9-friedodrimane-type sesquiterpenoid isolated from the marine sponge, repressed the expression of angiogenic/inflammatory factors and restored the expression of E-cadherin in retinal pigment epithelial cells by inhibiting the Wnt/β-catenin pathway. In addition, it selectively inhibited proliferation and tube formation of HUVECs by activating the p53 pathway. Topical and intraperitoneal administration of IQ significantly reduced choroidal neovascularization in rabbits and mice with laser-induced choroidal neovascularization. Notably, IQ by the oral route of exposure was highly permeable to the eyes and suppressed abnormal vascular leakage by downregulation of β-catenin and stabilization of p53 in vivo. Our findings demonstrate that IQ functions through regulation of p53 and Wnt/β-catenin pathways with conceivable advantages over existing cytokine-targeted anti-angiogenic therapies.

LACTB Regulates PIK3R3 to Promote Autophagy and Inhibit EMT and Proliferation Through the PI3K/AKT/mTOR Signaling Pathway in Colorectal Cancer

Background

Colorectal cancer (CRC) is one of the most common aggressive malignancies. LACTB functions as a tumor suppressor, and previous findings have demonstrated that LACTB can inhibit epithelial-to-mesenchymal transition (EMT) and proliferation of breast cancer and CRC cells. However, few studies have investigated the roles of LACTB in autophagy and proliferation in CRC. The current study aimed to identify the roles of LACTB in EMT and proliferation associated with autophagy in CRC and to elucidate the probable molecular mechanisms through which LACTB are involved in these processes.

Materials and Methods

Transwell invasion, MTT, transmission electron microscopy, RNA-seq, immunoprecipitation, immunohistochemistry and Western blotting assays were performed to evaluate the migratory, invasive, proliferative and autophagic abilities of CRC cells, and the levels of active molecules involved in PI3K/AKT signaling were examined through Western blotting analysis. In addition, the in vivo function of LACTB was assessed using a tumor xenograft model.

Results

Weaker LACTB expression was found in CRC tissue samples than in nonmalignant tissue samples, and LACTB inhibited cell invasion, migration, and proliferation by promoting autophagy in vitro. Furthermore, the regulatory effects of LACTB on autophagy and EMT were partially attributed to the PI3K/AKT signaling pathway. The in vivo results also showed that LACTB modulated CRC tumorigenesis.

Conclusion

LACTB can regulate the activity of PIK3R3 to influence the level of PI3K, and it also promotes autophagy and inhibits EMT and proliferation in part through the PI3K/AKT/mTOR signaling pathway.

SNAP29 mediates the assembly of histidine-induced CTP synthase filaments in proximity to the cytokeratin network

Under metabolic stress, cellular components can assemble into distinct membraneless organelles for adaptation. One such example is cytidine 5'-triphosphate synthase (CTPS, for which there are CTPS1 and CTPS2 forms in mammals), which forms filamentous structures under glutamine deprivation. We have previously demonstrated that histidine (His)-mediated methylation regulates the formation of CTPS filaments to suppress enzymatic activity and preserve the CTPS protein under glutamine deprivation, which promotes cancer cell growth after stress alleviation. However, it remains unclear where and how these enigmatic structures are assembled. Using CTPS-APEX2-mediated in vivo proximity labeling, we found that synaptosome-associated protein 29 (SNAP29) regulates the spatiotemporal filament assembly of CTPS along the cytokeratin network in a keratin 8 (KRT8)-dependent manner. Knockdown of SNAP29 interfered with assembly and relaxed the filament-induced suppression of CTPS enzymatic activity. Furthermore, APEX2 proximity labeling of keratin 18 (KRT18) revealed a spatiotemporal association of SNAP29 with cytokeratin in response to stress. Super-resolution imaging suggests that during CTPS filament formation, SNAP29 interacts with CTPS along the cytokeratin network. This study links the cytokeratin network to the regulation of metabolism by compartmentalization of metabolic enzymes during nutrient deprivation.

The Metastasis Potential Promoting Capacity of Cancer-Associated Fibroblasts Was Attenuated by Cisplatin via Modulating KRT8

Background

Cancer-associated fibroblasts (CAFs) are an essential component of tumor microenvironment. They are attracting increasing attentions due to their crucial role in tumor growth, drug-resistance and metastasis. Cisplatin is a first-line chemotherapy drug applying in various types of cancer. There are intensive studies on cisplatin's effect on tumor cells, however, its effect on CAFs remains poorly understood. In the present study, we investigated the effect of cisplatin on CAFs.

Methods

Cell migration was detected by wound healing assay. Cell invasion was performed by the transwell assay. mRNA expression was detected by quantitative PCR, and protein expression was detected by Western blotting. Tumor growth was measured using BALB/c nude mice tumor models.

Results

Cisplatin attenuated the promoting capacity of CAFs on lung cancer cell migration and invasion, via suppressing CAFs' effect on metastasis-related genes including Twist1, vascular endothelial growth factor receptor (VEGFR), MMP2, and AKT signaling pathway. Keratin 8 (KRT8) was identified as a target of cisplatin. KRT8 upregulation in CAFs is responsible for the inhibitory effect of cisplatin on lung cancer cells metastasis potential through AKT pathway suppression. The stimulation of AKT by AKT activator SC79 reversed KRT8's effect on cell migration. Importantly, in vivo study also showed that CAFs enhanced tumor growth significantly, and cisplatin effectively abrogated the promoting effect of CAFs on tumor growth.

Conclusion

Our results revealed a novel mechanism that cisplatin attenuated the metastasis promoting effect of CAFs via KRT8/AKT signaling pathway. This finding highlights KRT8 in CAFs as a potential therapeutic candidate for metastasis treatment.

KRT8 phosphorylation regulates the epithelial-mesenchymal transition in retinal pigment epithelial cells through autophagy modulation

Proliferative vitreoretinopathy (PVR) is a severe ocular disease which results in complex retinal detachment and irreversible vision loss. The epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is considered to be critical in the pathogenesis of PVR. In this study, we focused on the potential impact of keratin 8 (KRT8) phosphorylation and autophagy on TGF-β2-induced EMT of RPE cells and explored the relationship between them. Using immunofluorescence and Western blot analysis, the co-localization of KRT8 and autophagy marker, as well as the abundance of phosphorylated KRT8 (p-KRT8) expression, was observed within subretinal and epiretinal membranes from PVR patients. Moreover, during TGF-β2-induced EMT process, we found that p-KRT8 was enhanced in RPE cells, which accompanied by an increase in autophagic flux. Inhibition of autophagy with pharmacological inhibitors or specific siRNAs was associated with a reduction in cell migration and the synthesis of several EMT markers. In the meantime, we demonstrated that p-KRT8 was correlated with the autophagy progression during the EMT of RPE cells. Knockdown the expression or mutagenesis of the critical phosphorylated site of KRT8 would induce autophagy impairment, through affecting the fusion of autophagosomes and lysosomes. Therefore, this study may provide a new insight into the pathogenesis of PVR and suggests the potential therapeutic value of p-KRT8 in the prevention and treatment of PVR.

Novel ADAM-17 inhibitor ZLDI-8 inhibits the metastasis of hepatocellular carcinoma by reversing epithelial-mesenchymal transition in vitro and in vivo

AIMS

Epithelial-mesenchymal transition (EMT) is one of the important regulators of metastasis in advanced hepatocellular carcinoma (HCC). Blocking the Notch signaling pathway and then reversing the EMT process is a hot spot in clinical tumor research. Here, we aimed to investigate the effect and underlying mechanisms of ADAM-17 (a key cleavage enzyme of Notch pathway) inhibitor ZLDI-8 we found before on the metastasis of hepatocellular carcinoma in vitro and in vivo.

MAIN METHODS

The cell viability of HCC cells was evaluated by MTT and colony formation assays. Migration and invasion were assessed respectively with wound healing and transwell assays. The expression and location of proteins were detected by western blot and immunofluorescence, respectively. The effects of ZLDI-8 on metastasis of liver cancer in vivo were investigated in a tail vein injection model.

KEY FINDINGS

In the present work, ZLDI-8 significantly inhibited proliferation, migration, invasion and EMT phenotype of highly aggressive MHCC97-H and LM3 cells. Moreover, ZLDI-8 could inhibit the migration and invasion of HepG2 and Bel7402 cells induced by TGF-β1. ZLDI-8 suppressed the protein expression of interstitial markers and increased that of epithelial markers. Meanwhile, ZLDI-8 decreased the expression of proteins in the Notch signaling pathway. Finally, ZLDI-8 blocks metastasis in the lung metastasis model in vivo.

SIGNIFICANCE

ZLDI-8 suppressed the metastasis of hepatocellular carcinoma, which was associated with reversing the EMT process and regulating Notch signaling pathway. The study laid the foundation for the discovery of drugs that reverse EMT to inhibit advanced HCC metastasis.

Autophagy and Age-Related Eye Diseases

Background

Autophagy is a catabolic process that depends on the lysosome. It is usually used to maintain cellular homeostasis, survival and development by degrading abnormal substances and dysfunctional organelles, especially when the cell is exposed to starvation or other stresses. Increasing studies have reported that autophagy is associated with various eye diseases, of which aging is one of the important factors.

Objective

To summarize the functional and regulatory role of autophagy in ocular diseases with aging, and discuss the possibility of autophagy-targeted therapy in age-related diseases.

Methods

PubMed searches were performed to identify relevant articles published mostly in the last 5 years. The key words were used to retrieve including “autophagy”, “aging”, “oxidative stress AND autophagy”, “dry eye AND autophagy”, “corneal disease AND autophagy”, “glaucoma AND autophagy”, “cataract AND autophagy”, “AMD AND autophagy”, “cardiovascular diseases AND autophagy”, “diabetes AND autophagy”. After being classified and assessed, the most relevant full texts in English were chosen.

Results

Apart from review articles, more than two research articles for each age-related eye diseases related to autophagy were retrieved. We only included the most relevant and recent studies for summary and discussion.

Conclusion

Autophagy has both protective and detrimental effects on the progress of age-related eye diseases. Different types of studies based on certain situations in vitro showed distinct results, which do not necessarily coincide with the actual situation in human bodies completely. It means the exact role and regulatory function of autophagy in ocular diseases remains largely unknown. Although autophagy as a potential therapeutic target has been proposed, many problems still need to be solved before it applies to clinical practice.

Knockdown of cytokeratin 8 overcomes chemoresistance of chordoma cells by aggravating endoplasmic reticulum stress through PERK/eIF2α arm of unfolded protein response and blocking autophagy

Chordoma is a malignant primary osseous spinal tumor with pronounced chemoresistance. However, the mechanisms of how chordoma cells develop chemoresistance are still not fully understood. Cytokeratin 8 (KRT8) is a molecular marker of notochordal cells, from which chordoma cells were believed to be originated. In this study, we showed that either doxorubicin or irinotecan promoted KRT8 expression in both CM319 and UCH1 cell lines, accompanied by an increased unfolded protein response and autophagy activity. Then, siRNA-mediated knockdown of KRT8 chemosensitized chordoma cells in vitro. Mechanistic studies showed that knockdown of KRT8 followed by chemotherapy aggravated endoplasmic reticulum stress through PERK/eIF2α arm of unfolded protein response and blocked late-stage autophagy. Moreover, suppression of the PERK/eIF2α arm of unfolded protein response using PERK inhibitor GSK2606414 partially rescued the apoptotic chordoma cells but did not reverse the blockage of the autophagy flux. Finally, tumor xenograft model further confirmed the chemosensitizing effects of siKRT8. This study represents the first systematic investigation into the role of KRT8 in chemoresistance of chordoma and our results highlight a possible strategy of targeting KRT8 to overcome chordoma chemoresistance.

The Regulation of NFE2L2 (NRF2) Signalling and Epithelial-to-Mesenchymal Transition in Age-Related Macular Degeneration Pathology

Age-related macular degeneration (AMD) is a mounting cause of loss of sight in the elderly in the developed countries, a trend enhanced by the continual ageing of the population. AMD is a multifactorial and only partly understood, malady. Unfortunately, there is no effective treatment for most AMD patients. It is known that oxidative stress (OS) damages the retinal pigment epithelium (RPE) and contributes to the progression of AMD. We review here the potential importance of two OS-related cellular systems in relation to AMD. First, the nuclear factor erythroid 2-related factor 2 (NFE2L2; NRF2)-mediated OS response signalling pathway is important in the prevention of oxidative damage and a failure of this system could be critical in the development of AMD. Second, epithelial-to-mesenchymal transition (EMT) represents a change in the cellular phenotype, which ultimately leads to the fibrosis encountered in RPE, a characteristic of AMD. Many of the pathways triggering EMT are promoted by OS. The possible interconnections between these two signalling routes are discussed here. From a broader perspective, the control of NFE2L2 and EMT as ways of preventing OS-derived cellular damage could be potentially valuable in the therapy of AMD.

Gene expression profiling in the hippocampus of adolescent rats after chronic alcohol administration

In South Korea, the average age of onset of alcohol drinking is 13.3 years and half of adolescents drink alcohol more than once a month; 8.45% of the Korean adolescent population become future high-risk alcohol drinkers. Chronic alcohol abuse causes physical and psychiatric health problems such as alcohol addiction, liver disease, stroke and cognitive impairments. This study aimed to investigate the effect of alcohol on gene expression and their function in the hippocampus of adolescent rats. After chronic alcohol administration in male (control, n = 6; alcohol, n = 6) Sprague-Dawley rats for 6 weeks, we analysed up- or down-regulated genes using RNA-sequencing technology. We found 83 genes more than 1.5-fold up- or down-regulated in the alcohol-treated group. Among them, genes (Dnai1, Cfap206 and Dnah1) associated with cilium movement were up-regulated in the alcohol-treated group. Mlf1, related to cell cycle arrest, was also up-regulated in the alcohol-treated group. On the other hand, genes (Smad3 and Plk5) involved in negative regulation of cell proliferation were down-regulated in the hippocampus by chronic alcohol administration. In addition, expression levels of genes associated with oxidative stress (Krt8 and Car3) and migration (Vim) were changed by chronic alcohol administration. These results pave a path for a better understanding of the neuromolecular mechanisms mediated by chronic alcohol exposure in the hippocampus of adolescents and negative pathology due to chronic alcohol abuse.

Oxidative stress causes Alu RNA accumulation via PIWIL4 sequestration into stress granules

The Alu element, the most abundant transposable element, is transcribed to Alu RNA. We hypothesized that the PIWI protein regulates the expression of Alu RNA in retinal pigment epithelial (RPE) cells, where accumulated Alu RNA leads to macular degeneration. Alu transcription was induced in RPE cells treated with H₂O₂. At an early stage of oxidative stress, PIWIL4 was translocated into the nucleus; however, subsequently it was sequestered into cytoplasmic stress granules, resulting in the accumulation of Alu RNA. An elevated amount of Alu RNA was positively correlated with the disruption of the epithelial features of RPE via induction of mesenchymal transition. Therefore, we suggest that oxidative stress causes Alu RNA accumulation via PIWIL4 sequestration into the cytoplasmic stress granules.

Interplay between Autophagy and the Ubiquitin-Proteasome System and Its Role in the Pathogenesis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a complex eye disease with many pathogenesis factors, including defective cellular waste management in retinal pigment epithelium (RPE). Main cellular waste in AMD are: all-trans retinal, drusen and lipofuscin, containing unfolded, damaged and unneeded proteins, which are degraded and recycled in RPE cells by two main machineries—the ubiquitin-proteasome system (UPS) and autophagy. Recent findings show that these systems can act together with a significant role of the EI24 (etoposide-induced protein 2.4 homolog) ubiquitin ligase in their action. On the other hand, E3 ligases are essential in both systems, but E3 is degraded by autophagy. The interplay between UPS and autophagy was targeted in several diseases, including Alzheimer disease. Therefore, cellular waste clearing in AMD should be considered in the context of such interplay rather than either of these systems singly. Aging and oxidative stress, two major AMD risk factors, reduce both UPS and autophagy. In conclusion, molecular mechanisms of UPS and autophagy can be considered as a target in AMD prevention and therapeutic perspective. Further work is needed to identify molecules and effects important for the coordination of action of these two cellular waste management systems.

Autophagy resists EMT process to maintain retinal pigment epithelium homeostasis

Proliferative vitreoretinopathy (PVR) is the most serious fibrous complication that causes vision loss after intraocular surgery, and there is currently no effective treatment in clinical. Autophagy is an important cell biological mechanism in maintaining the homeostasis of tissues and cells, resisting the process of EMT. However, it is still unclear whether autophagy could resist intraocular fibrosis and prevent PVR progression. In this study, we investigated the expression of mesenchymal biomarkers in autophagy deficiency cells and found these proteins were increased. The mesenchymal protein transcription factor Twist can bind to autophagy related protein p62 and promote the degradation of Twist, which reduced the expression of mesenchymal markers. By constructing an EMT model of retinal pigment epithelial (RPE) cells in vitro, we found that autophagy was activated in the EMT process of RPE cells. Moreover, in autophagy deficient RPE cell line via knockdown autophagy related protein 7 (Atg7), the expression of epithelial marker claudin-1 was suppressed and the mesenchymal markers were increased, accompanied by an increase in cell migration and contractility. Importantly, RPE epithelial properties can be maintained by promoting autophagy and effectively reversing TFG-β2-induced RPE fibrosis. These observations reveal that autophagy may be an effective way to treat PVR.

Effect of BMP15 and/or AMH during in vitro maturation of oocytes from involuntarily culled dairy cows

The high metabolic activity to which the dairy cattle are exposed to maintain milk production altered steroid metabolism that affects reproductive physiology and reduce oocyte competence. Our aims were (a) to characterize the competence of immature oocytes collected from dairy cattle based on the expression of genes in cumulus cells (CCs) and (b) to improve oocyte competence to support preimplantation embryo development by the supplementation of maturation medium with bone morphogenetic protein 15 (BMP15) and/or anti-mullerian hormone (AMH). Oocyte donors were identified at the moment of ovary collection and grouped by involuntarily culled dairy cows (Holstein breed) or beef cattle. The embryo development speed to blastocyst of the cull dairy cattle versus beef cattle (control group) was lower. Besides, <10% of oocytes (with CC biopsies) derived from dairy cattle were able to develop to the blastocyst stage. In addition, a higher level of expression and a positive correlation were observed in the expression of most of the genes evaluated (LUM, KRT18, KRT8, CLIC3, BMPR1B, and SLC38A3) in the cumulus-oocyte complexes that produced blastocysts versus those which did not develop correctly (arrested development). Further, use of BMP15 in the maturation of oocytes from dairy cattle seems to increase competence, modulating the expression of OCT4, SOX2, CDX2, GATA6, and TP1 in resulting blastocysts.

CRB2 mutation causes autosomal recessive retinitis pigmentosa

Retinitis pigmentosa (RP), the most common form of inherited retinal dystrophies, exhibits significant genetic heterogeneity. The crumbs homolog 2 (CRB2) protein, together with CRB1 and CRB3, belongs to the Crumbs family. Given that CRB1 mutations account for 4% of RP cases, the role of CRB2 mutations in RP etiology has long been hypothesized but never confirmed. Herein, we report the identification of CRB2 as a novel RP causative gene in a Chinese consanguineous family and have analyzed its pathogenic effects. Comprehensive ophthalmic and systemic evaluations confirmed the clinical diagnosis of the two patients in this family as RP. WES revealed a homozygous missense mutation, CRB2 p.R1249G, to segregate the RP phenotype, which was highly conserved among multiple species. In vitro cellular study revealed that this mutation not only interrupted the stability of the transcribed CRB2 mRNA and the encoded CRB2 protein, but also interfered with the wild type CRB2 mRNA/protein and decreased their expression. This mutation was also shown to trigger epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE) cells, thus impairing regular RPE phagocytosis and induce RPE degeneration and apoptosis. Thus, we conclude that CRB2 p.R1249G mutation causes RP via accelerating EMT, dysfunction and loss of RPE cells, and establish CRB2 as a novel Crumbs family member associated with non-syndromic RP. We provide important hints for understanding of CRB2 defects and retinopathy, and for the involvement of EMT of RPE cells in RP pathogenesis.

PCV2 infection aggravates ochratoxin A-induced nephrotoxicity via autophagy involving p38 signaling pathway in vivo and in vitro

Ochratoxin A (OTA) is reported to induce nephrotoxicity in animals and humans. Porcine circovirus type 2 (PCV2) could induce porcine dermatitis and nephropathy syndrome. To date, little is known whether virus infection aggravates mycotoxin-induced toxicity. This work aimed to study the effects of PCV2 infection on OTA-induced nephrotoxicity and its mechanism in vivo and vitro. The results in vivo showed that PCV2 infection aggravated OTA-induced poor growth performance, nephrotoxicity, p38 phosphorylation and autophagy as demonstrated by Atg5, LC3 II and p62 protein expressions in kidney of pigs. The results in vitro indicated that PCV2 infection significantly aggravated OTA-induced nephrotoxicity as demonstrated by cell viabilities, annexin V/PI binding and caspase 3 activities, and induced p38 phosphorylation and autophagy in PK15 cells. p38 inhibitor decreased Atg5 and LC3 protein expression induced by PCV2 infection and OTA combined treatment. Adding autophagy inhibitor 3-MA or CQ alleviated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Atg5-specific siRNA eliminated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Taken together, these data indicate that in vivo and in vitro PCV2 infection aggravated OTA-induced nephrotoxicity via p38-mediated autophagy.

Cytokeratin 8/18 protects breast cancer cell lines from TRAIL-induced apoptosis

TNF-related apoptosis inducing ligand (TRAIL) induces apoptosis by engaging its death receptors (DRs) 4 and/or 5 on targeted cells. Clinical attempts to stimulate this apoptotic pathway for cancer therapy, including the use of recombinant human TRAIL (rhTRAIL) or receptor agonistic antibodies, have been underway for over a decade. Unfortunately, these agents have only shown limited therapeutic effects due largely to tumor resistance arising from mechanisms yet to be defined. Here we show that intermediate filament proteins, keratin 8 and keratin 18 (K8/K18), negatively regulate TRAIL induced apoptosis. K8/K18 protein levels are consistently higher in TRAIL-resistant cells compared to TRAIL-sensitive cells in a panel of breast cancer cell lines. Blockade of K8 increased expression of DR5 on the surface of targeted cells and sensitized the cells to TRAIL-induced apoptosis. Conversely, ectopic expression of K8/K18 downregulated DR5 protein expression. K8/K18 appears to negatively regulate apoptosis signaling via DR5 in breast cancer cells. Our findings warrant additional studies to determine if K8/K18 could be a predictor of tumor resistance to DR5-targeted therapies.

Forkhead box O proteins: Crucial regulators of cancer EMT

The epithelial-mesenchymal transition (EMT) is an acknowledged cellular transition process in which epithelial cells acquire mesenchymal-like properties that endow cancer cells with increased migratory and invasive behavior. Forkhead box O (FOXO) proteins have been shown to orchestrate multiple EMT-associated pathways and EMT-related transcription factors (EMT-TFs), thereby modulating the EMT process. The focus of the current review is to evaluate the latest research progress regarding the roles of FOXO proteins in cancer EMT. First, a brief overview of the EMT process in cancer and a general background on the FOXO family are provided. Next, we present the interactions between FOXO proteins and multiple EMT-associated pathways during malignancy development. Finally, we propose several novel potential directions for future research. Collectively, the information compiled herein should serve as a comprehensive repository of information on this topic and should aid in the design of additional studies and the future development of FOXO proteins as therapeutic targets.

Effects of ochratoxin A on ER stress, MAPK signaling pathway and autophagy of kidney and spleen in pigs

Ochratoxin A (OTA), a worldwide mycotoxin found in food and feeds, is a potent nephrotoxin and immunotoxin in animals and humans. This research was conducted to evaluate whether endoplasmic reticulum (ER) stress, MAPK signaling pathway and autophagy were induced by OTA in kidney and spleen of pigs. Twenty-seven crossbred pigs randomly allocated to 3 groups were fed for 42 days ad libitum a basal diet without (Con group, 0.00 μg OTA/kg) and with supplementation of OTA at 400 (OTA-L group) and 800 μg/kg (OTA-H group). From each group, 6 pigs were randomly selected for blood collection on days 0, 21, and 42 and 3 pigs were randomly selected for tissue collection on day 42. The results showed that OTA at 400 and 800 μg/kg diets significantly increased OTA concentrations in serum and kidney and spleen induced the histopathological lesions of kidney and spleen, decreased TCR-stimulated T lymphocyte viabilities and IL-2 concentration, increased TNF-α concentration, and decreased T-AOC levels. OTA increased glucose regulated protein 78, p38, and ERK1/2 phosphorylation, and LC3 II and Atg5 protein expression in kidney and spleen of pigs. These results provide new insights into the relationship between OTA and ER stress, p38 and ERK1/2 MAPK signaling pathway and autophagy in pigs.