Protective effect of polypeptides from larva of housefly (Musca domestica) on hydrogen peroxide-induced oxidative damage in HepG2 cells

Novel antioxidant peptides identified from coix seed by molecular docking, quantum chemical calculations and invitro study in HepG2 cells

The aim of the study was to identify potent antioxidant peptides sourced from coix seed, analyze the structure-activity relationship through molecular docking and quantum chemical calculation. Molecular docking results showed that among thirteen peptides selected in silico, eight had favourable binding interaction with the Keap1-Kelch domain (2FLU). Promising peptides with significant binding scores were further evaluated using quantum calculation. It was shown that peptide FFDR exhibited exceptional stability, with a high energy gap of 5.24 eV and low Highest Occupied Molecular Orbitals (HOMO) and Lowest Unoccupied Molecular Orbitals (LUMO) values. Furthermore, FFDR displayed the capacity to enhance the expression of Nrf2-Keap1 antioxidant genes (CAT, SOD, GSH-Px) and improved cellular redox balance by increasing reduced glutathione (GSH) while reducing oxidized glutathione (GSSG) and malonaldehyde (MDA) levels. These findings highlight the potential of coix seed peptides in developing novel, effective and stable antioxidant-based functional foods.

Bioactive compounds and biological activity in edible insects: A review

New strategies to combat hunger are a current and urgent demand. The increase in population has generated a high demand for products and services that affect food production, cultivation areas, and climate. Viable and sustainable alternative sources have been sought to meet food quality requirements. In this context, edible insects are a good source of macro-nutrients, and bioactive compounds confer biological properties that improve their nutritional aspects and benefit human health. This review aims to present the benefits and contributions of edible insects from the point of view of the biological contribution of macronutrients, and bioactive compounds, as well as consider some anti-nutritional aspects reported in edible insects. It was found that insects possess most of the macronutrients necessary for human life and are rich in bioactive compounds commonly found in plants. These bioactive compounds can vary significantly depending on the developmental stage, diet, and species of edible insects. However, they also contain phytochemicals in which anti-nutrients predominate, which can adversely affect humans with allergenic reactions or reduced nutrient viability when consumed in high amounts or for prolonged periods. Hydrocyanide, oxalates, soluble oxalate, and phytate are the most studied anti-nutrients. However, the doses at which they occur are far below the limits in foods. In addition, anti-nutrient levels decrease significantly in processing, such as oven-drying and defatting methods. However, there are few studies, so more trials are needed to avoid generalizing. Therefore, edible insects can be considered complete food.

Grub polypeptide extracts protect against oxidative stress through the NRF2-ARE signaling pathway

Grub polypeptide extracts (GPEs) have antioxidant effects; however, their underlying molecular mechanisms are unknown. This study explored the antioxidant molecular mechanism of GPE via the nuclear factor-erythroid 2-related factor 2 (NRF2)-antioxidant response element (ARE) signaling pathway in C2C12 muscle satellite cells exposed to oxidative stress. The effects of GPE/or H2O2 on C2C12 were investigated by the MTT (3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) viability assay and immunofluorescence and small interfering RNA (siRNA) analyses. The cell viability, cell damage, intracellular reactive oxygen species (ROS) levels, and NRF2 signaling pathways related to proteins were measured. GPE significantly increased the antioxidant capacity of cells, evident by increased cell viability and decreased lactate dehydrogenase leakage, DNA damage, malondialdehyde content, and ROS level. GPE also markedly increased mRNA expression levels and activities of antioxidant enzymes including superoxidase 1 and 2, catalase, and glutathione peroxidase. In addition, GPE increased the gene and protein expression of NRF2 and heme oxygenase 1 by promoting NRF2 translocation from the cytoplasm to the nucleus and activating NRF2-ARE signaling pathways. The antioxidant effects of GPE through these signaling pathways were further confirmed by NRF2-specific siRNA silencing. Thus, GPE enhances antioxidant capacity and alleviates oxidative damage of C2C12 cells via the NRF2-ARE signaling pathway.

The Protective Effects of Protein-Enriched Fraction from Housefly (Musca domestica) against Aged-Related Brain Aging

The Musca domestica larvae are well known for its multifunctions and great nutritional value. The present study aimed at investigating the beneficial effect of Musca domestica larvae extract (Mde) against memory impairment, structural damage and oxidative stress in aged rats. Twenty-month-old rats were gavaged with Mde for 2 mo. Morris Water Maze test indicated Mde prevented aging-induced spatial learning and memory dysfunction in the aged rats. Mde supply was also found to attenuate age-associated changes of brain histology that observed by light microscopy and transmission electron microscopy. Moreover, the increase of antioxidant capacity, glutathione peroxidase (GPx) activity, superoxide dismutase (SOD) activity, as well as the decreased methane dicarboxylic aldehyde (MDA) levels, were consistent with these results. Hence, we propose that oral administration of Mde could improve memory impairment via antioxidant action, and Mde has the potential to act as an excellent food supplement or medicine for the attenuation of brain aging.

A newly isolated strain of Halomonas sp. (HA1) exerts anticancer potential via induction of apoptosis and G2/M arrest in hepatocellular carcinoma (HepG2) cell line

Marine bacterial strains are of great interest for their ability to produce secondary metabolites with anticancer potentials. Isolation, identification, characterization and anticancer activities of isolated bacteria from El-Hamra Lake, Wadi El-Natrun (Egypt) were the objectives of this study. The isolated bacteria were identified as a moderately halophilic alkaliphilic strain. Ethyl acetate extraction was performed and identified by liquid chromatography-mass spectrophotometry (LC–MS–MS) and nuclear magnetic resonance analysis (NMR). Cytotoxicity of the extract was assessed on the HepG2 cell line and normal human peripheral lymphocytes (HPBL) in vitro. Halomonas sp. HA1 extract analyses revealed anticancer potential. Many compounds have been identified including cyclo-(Leu-Leu), cyclo-(Pro-Phe), C17-sphinganine, hexanedioic acid, bis (2-ethylhexyl) ester, surfactin C14 and C15. The extract exhibited an IC₅₀ of 68 ± 1.8 μg/mL and caused marked morphological changes in treated HepG2 cells. For mechanistic anticancer evaluation, 20 and 40 µg/mL of bacterial extract were examined. The up-regulation of apoptosis-related genes' expression, P53, CASP-3, and BAX/BCL-2 at mRNA and protein levels proved the involvement of P53-dependant mitochondrial apoptotic pathway. The anti-proliferative properties were confirmed by significant G₂/M cell cycle arrest and PCNA down-regulation in the treated cells. Low cytotoxicity was observed in HPBL compared to HepG2 cells. In conclusion, results suggest that the apoptotic and anti-proliferative effects of Halomonas sp. HA1 extract on HepG2 cells can provide it as a candidate for future pharmaceutical industries.

Terapia Larval con Musca Domestica en el Tratamiento de la úlcera Leishmánicaen un Modelo Murino

La leishmaniosis es una enfermedad con gran impacto en salud pública dado a las características de las lesiones tegumentarias. El tratamiento experimental con terapia larval (TL) ha mostrado su uso potencial para la cura de la leishmaniosis, sin embargo, se han utilizado especies de moscas para TL en heridas causadas por Leishmania que no son de fácil colecta y cultivo bajo condiciones de laboratorio como Lucilia sericata o Calliphora vicina. El objetivo del presente trabajo fue usar una especie de mosca de fácil colecta, y de alta fecundidad como la Musca domestica para aplicarlas en TL de úlceras leishmánicas. Se realizó un estudio cuali-cuantitativo, de tipo descriptivo, mediante un diseño experimental empleado un modelo animal (Mesocricetus auratus), infectado con Leishmania amazonensis para evaluar el efecto terapéutico de la TL y comparar los resultados con el tratamiento químico antimonial de la droga experimental “Ulamina”. Se evidencia cicatrización y cura de la úlcera leishmánica en el 66,66 % de los animales tratados con TL en aplicación simple y del 100 % en TL combinada con Ulamina. El uso combinado de TL+Ulamina, muestra un efecto potenciador de la cura clínica de las úlceras, pero con persistente inflamación. Se observó una efectividad óptima de la TL con M. domestica, sobre las úlceras, aunque no se evidenció un efecto sobre L. amazonensis dado a la presencia de amastigotes en los frotis y a los amplicones obtenidos de 480 bp desde las improntas de los animales.

Housefly Pupae-Derived Antioxidant Peptides Exerting Neuroprotective Effects on Hydrogen Peroxide-Induced Oxidative Damage in PC12 Cells

In this study, two antioxidant peptides were identified and characterized from the alcalase-hydrolysate of housefly (Musca domestica L.) pupae guided by ABTS cation radical scavenging activity. Peptides sequences were identified as DFTPVCTTELGR (DR12, 1338.48 Da) and ARFEELCSDLFR (AR12, 1485.66 Da) using nano-liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both DR12 and AR12 exert strong ABTS cation radical scavenging ability with EC₅₀ values of 0.39 and 0.35 mM, respectively. Moreover, AR12 can effectively protect PC12 cells from oxidative damage induced by hydrogen peroxide (H₂O₂) by decreasing intracellular reactive oxygen species (ROS) and malonaldehyde (MDA), recovering cellular mitochondrial membrane potential (MMP), and increasing the activity of intracellular superoxide dismutase (SOD). Stability tests suggest that AR12 is competent for the challenge of heating, acid, alkali or simulated gastrointestinal (GI) digestion and exhibits great activity to remove ABTS cation radical. DR12 shows a great stability against heating, but its antioxidative ability declines after being treated with acid, alkali or simulated GI digestion. In general, both DR12 and AR12 identified from housefly pupae hydrolysate stand a chance of being potential antioxidants or precursors to antioxidants and AR12 might be applied in the field of neuroprotection.

Identification of proteins in housefly (Musca domestica) larvae powder by LC-MS/MS and their potential medical relevance

Housefly larvae (HL) powder was used to cure wounds centuries ago for its good nutritional and pharmacological values. At present, most of the medical studies are about the crude extracts of HL, while the specific pharmacological material basis is still unclear. We ground third-instar Musca domestica larvae into a powder, degreasing and preparing the protein extract. The protein extract was subjected to enzymatic hydrolysis, and the enzymatic hydrolysis products were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). We identified a variety of highly trusted proteins (false discovery rate is less than or equal to 1%), including catalysis-related proteins, antioxidant proteins and antimicrobial peptides, which may be closely related to the anti-tumor, anti-bacterial, anti-oxidant and other pharmacological effects of HL. We identified the amino acid sequences of these proteins, and further confirmed HL's protective effect on APP/PS1 transgenic Alzheimer's mice. The results of this work provide material basis for further medical research on HL.

Housefly larvae (HL) powder was used to cure wounds centuries ago for its good nutritional and pharmacological values.

Housefly (Musca domestica) larvae powder, preventing oxidative stress injury via regulation of UCP4 and CyclinD1 and modulation of JNK and P38 signaling in APP/PS1 mice

Housefly (Musca domestica) Larvae powder (HL) is rich in antioxidants. As oxidative stress is considered as one of the main pathogenesis in Alzheimer's Disease (AD), this study was designed to explore the protective effects of HL as an antioxidant on APP/PS1 mice. 2-Month-old APP/PS1 mice were divided into a model control (MC) group, a Donepezil group and a HL group, and C57BL/6 mice were used as the normal control (NC) group. After 180 days of treatment, the memory ability was measured by Morris Water Maze (MWM). The presence of Aβ and the expression of Uncoupling Protein 4 (UCP4) and CyclinD1 were detected by immunohistochemistry. The expressions of Superoxide Dismutase 1 (SOD1), Catalase (CAT) and Mitogen-activated Protein Kinase (MAPK) signal pathways were measured by western blotting. Compared with untreated APP/PS1 mice, the memory abilities of the HL-treated mice were significantly improved. Furthermore, the HL treatment not only down-regulated the deposition of Aβ and the expression of CylinD1, but also increased both the mRNA and protein levels of SOD, CAT, and UCP4, and enhanced the phosphorylation of JNK and P38 MAPK activation. In conclusion, these results suggest that HL may have a protective effect against memory impairment and prevent oxidative stress-induced injury via the regulation of UCP4 and CyclinD1 and the modulation of JNK and P38 MAPK signaling in AD.

Toxicological characteristics of edible insects in China: A historical review

Edible insects are ideal food sources, which contain important nutrients and health-promoting compounds. With a rapid development of industrial insect farming, insect-derived food is a novel and emerging food industry. Edible insects have been traditionally consumed in various communities, while continuously gaining relevance in today's society; however, they currently remain underutilized. Although there are a large number of literature on edible insects, these literature primarily focus on the nutritional value edible insects. The toxicity assessment data of edible insects remain incomprehensive, especially for the new national standard that is currently in effect; and many data and conclusions are not accurately specified/reported. Therefore, we performed a literature review and summarized the data on the toxicological assessment of edible insects in China. The review first describes the research progress on safety toxicological assessment, and then offers references regarding the development of 34 edible insect species in China. These data can be a platform for the development of future toxicological assessment strategies, which can be carried out by a multidisciplinary team, possibly consisting of food engineers, agronomists, farmers, and so on, to improve the acceptability of edible insects.

Immunological adjuvant effect of the peptide fraction from the larvae of Musca domestica

BACKGROUND

The larvae of Musca domestica (Diptera: Muscidae) have been used traditionally for malnutritional stagnation, decubital necrosis, osteomyelitis, ecthyma and lip scald and also to treat coma and gastric cancer in the traditional Chinese medicine. Its immunomodulatory effects in naïve mice in relation to the traditional uses were also reported. However, the immunological adjuvant potentials of this insect have not yet been studied.

METHODS

The peptide fraction from the larvae of Musca domestica L. (MDPF) was evaluated for its adjuvant potentials on the immune responses to ovalbumin (OVA) and avian influenza vaccine (rL-H5) by determining antigen-specific antibody titers, splenocyte proliferation, activity of natural killer (NK) cell, the secretion of cytokines from splenocytes in the immunized mice.

RESULTS

MDPF significantly enhanced not only the concanavalin A (Con A)-, lipopolysaccharide (LPS)- and antigen-stimulated splenocyte proliferation, but serum antigen-specific IgG, IgG1, IgG2a, and IgG2b antibody titers in the mice immunized with OVA and rL-H5. MDPF also remarkably promoted the killing activities of NK cells in splenocytes from the mice immunized with rL-H5. Furthermore, MDPF significantly promoted the production of Th1 (IL-2 and IFN-γ) and Th2 (IL-10) cytokines from splenocytes in the immunized mice.

CONCLUSIONS

The results indicated that MDPF had a potential to increase both cellular and humoral immune responses and elicit a balanced Th1/Th2 response, and that MDPF may be a safe and efficacious vaccine adjuvant candidate.

Effect of Musca domestic maggot polypeptide extract on HUVEC dysfunction induced by early-activated macrophages

CONTEXT

Musca domestica Linn. maggot is a traditional Chinese medicine. In our previous studies, Musca domestica maggot protein-enriched fraction and polypeptide extract (molecular weight <30 kD) were found to reverse endothelial cell dysfunction in atherosclerotic lesions.

OBJECTIVE

This study determines whether and how M. domestica maggot polypeptide extract affects the dysfunction of human umbilical vein endothelial cells (HUVEC) induced by macrophages (Mϕ).

MATERIALS AND METHODS

HUVEC and early-activated THP-1 Mϕ (incubated with LPS of 1 μg/ml for 2 h) were co-cultured in a Transwell system. The effects of Musca domestica maggot polypeptide extract (with increasing concentrations, i.e., 1.0, 2.5, 5.0, 10.0, 20.0, and 40.0 µg/ml) on the proliferation and migration HUVEC and their secretion of vascular endothelial growth factor (VEGF) were determined by flow cytometry, modified Boyden chamber assay, and enzyme-linked immunosorbent assay (ELISA) after incubation for 24 h.

RESULTS

Musca domestica maggot polypeptide extract decreased the proliferation of HUVEC in a concentration-dependent manner, with a 50% effective concentration (EC50) of 22.16 ± 1.48 µg/ml, and effectively inhibited HUVEC migration (EC50 = 35.15 ± 2.03 µg/ml) and VEGF secretion (EC50 = 28.64 ± 1.29 µg/ml).

DISCUSSION AND CONCLUSION

Musca domestica maggot polypeptide extract can inhibit the dysfunction of HUVEC induced by early-activated THP-1 Mϕ.

Anti-Oxidant and Anti-Adipogenic Effects of Ethanol Extracts from Wheat Germ and Wheat Germ Fermented with Aspergillus oryzae

Most of the wheat germ in cereal grains is removed during the milling process. Various physiological effects have been reported for bioactive substances in wheat germ such as phenolic acids and flavonoids. In this study, the anti-oxidant and anti-adipogenic effects of ethanol extracts from wheat germ (WGE) and wheat germ fermented with Aspergillus oryzae (F-WGE) were investigated in HepG2 and 3T3-L1 cells. The anti-oxidant activity of F-WGE was demonstrated by a dose-dependent increase in the enhanced scavenging capacity of hydroxyl radicals and Cu²⁺-chelating activity compared to WGE. WGE and F-WGE treatment at doses between 10 and 400 μg/mL did not affect the viability of HepG2 and 3T3-L1 cells. Intracellular ROS levels from Cu²⁺-induced oxidative stress were significantly decreased by F-WGE treatment in HepG2 cells compared to WGE. Lipid accumulation was increased in 3T3-L1 adipocytes by 100 μM Fe²⁺ treatment, but the accumulation was strongly inhibited by 100 μg/mL of WGE and F-WGE treatment. These results suggest that changes in bioactive substances during the fermentation of wheat germ can potentiate scavenging activities against transition metal-induced oxidative stress and lipid accumulation in 3T3-L1 adipocytes. Therefore, we propose that F-WGE is a novel food materials and provided scientific evidences for its efficacy in the development of functional foods.

Cloning, expression, and purification of a new antimicrobial peptide gene from Musca domestica larva

Musca domestica (Diptera: Muscidae), the housefly, exhibits unique immune defences and can produce antimicrobial peptides upon stimulation with bacteria. Based on the cDNA library constructed using the suppression subtractive hybridization (SSH) method, a 198-bp antimicrobial peptide gene, which we named MDAP-2, was amplified by rapid amplification of cDNA ends (RACE) from M. domestica larvae stimulated with Salmonella pullorum (Enterobacteriaceae: Salmonella). In the present study, the full-length MDAP-2 gene was cloned and inserted into a His-tagged Escherichia coli prokaryotic expression system to enable production of the recombinant peptide. The recombinant MDAP-2 peptide was purified using Ni-NTA HisTrap FF crude column chromatography. The bacteriostatic activity of the recombinant purified MDAP-2 protein was assessed. The results indicated that MDAP-2 had in vitro antibacterial activity against all of the tested Gram- bacteria from clinical isolates, including E. coli (Enterobacteriaceae: Escherichia), one strain of S. pullorum (Enterobacteriaceae: Salmonella), and one strain of Pasteurella multocida. DNA sequencing and BLAST analysis showed that the MDAP-2 antimicrobial peptide gene was not homologous to any other antimicrobial peptide genes in GenBank. The antibacterial mechanisms of the newly discovered MDAP-2 peptide warrant further study.

Anti-tumor and immunomodulatory activity of peptide fraction from the larvae of Musca domestica

ETHNOPHARMACOLOGICAL RELEVANCE

The larvae of Musca domestica (Diptera: Muscidae) have been used traditionally for malnutritional stagnation, decubital necrosis, osteomyelitis, ecthyma and lip scald and also to treat coma and gastric cancer in the traditional Chinese medicine. Its in vitro antitumor activity and immunomodulatory effect in naïve mice in relation to the traditional uses were also reported. However, the in vivo antitumor effect of this insect and its mechanism of action have not yet been well studied. The objectives of this study were to evaluate the in vivo antitumor potential of the peptide fraction from Musca domestica larvae (MDPF) and to elucidate its immunological mechanisms.

MATERIALS AND METHODS

The mice inoculated with sarcoma S180 cells were orally administered with MDPF at three doses for 10 days. The effects of MDPF on the growth of mouse S180 sarcoma, splenocyte proliferation, the activity of natural killer (NK) cells and cytotoxic T lymphocytes (CTLs), production and mRNA expression of cytokines from splenocytes, and serum antigen-specific antibody levels in tumor-bearing mice were measured.

RESULTS

MDPF could significantly not only inhibit the growth of mouse transplanted S180 sarcoma, but also promote splenocytes proliferation, NK cell and CTL activity from splenocytes, and enhance serum antigen-specific IgG, IgG2a and IgG2b antibody levels in S180-bearing mice. MDPF also significantly promoted the production of IFN-γ and up-regulated the mRNA expression levels of IFN-γ and Th1 transcription factors T-bet and STAT-4 in splenocytes from the S180-bearing mice. However, Th2 cytokine IL-10 and transcription factors GATA-3 and STAT-6 were not significantly changed both at transcriptional and protein levels following MDPF treatment.

CONCLUSIONS

MDPF significantly inhibit the growth of transplantable tumor in mice and its in vivo antitumor activity might be achieved by switching-on of Th1-based protective cell-mediated immunity. MDPF could act as antitumor agent with immunomodulatory activity.

Two xanthones from Swertia punicea with hepatoprotective activities in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Swertia punicea Hemsl. (Gentianaceae) is more commonly known as "Ganyan-cao" and used mainly as a traditional Chinese folk medicine for the treatment of acute bilious hepatitis, cholecystitis, fever, intoxification and jaundice.

MATERIALS AND METHODS

The active hepatoprotective constituents of Swertia punicea were purified using various column chromatography techniques. The structures of two isolated compounds were determined on the basis of spectroscopic data interpretation such as NMR analysis. The hepatoprotective activities of isolated compounds were evaluated by using hepatotoxicity in vitro and dimethylnitrosamine-induced rat hepatic fibrosis in vivo, respectively.

RESULTS

Two xanthones, 1, 7-dihydroxy-3, 4, 8-trimethoxyxanthone (1) and bellidifolin (2) were isolated from the stems of Swertia punicea. The compounds 1 and 2 exhibited notable hepatoprotective activities against carbon tetrachloride (CCl4) -induced HepG2 cell damage, and effectively alleviated the levels of aspartate transaminase (AST), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and malonic dialdehyde (MDA) induced by CCl₄ in a concentration-dependent manner. Co-treatment with compound 2 significantly increased the cell viability compared with N-acetyl-p-aminophenol (APAP) treatment. Compound 2 also alleviated APAP-induced hepatotoxicity by increasing glutathione (GSH) content and decreasing hydroxyl free radical (·OH) levels and reactive oxygen specises (ROS) production. In addition, the protective effect of compound 1 significantly alleviated DMN-induced liver inflammation and fibrosis. Oral administration of compound 1 recovered the reduction of albumin (ALB) and reversed the elevation of serum alanine transaminase (ALT), AST and total bilirubin (TBIL) in dimethylnitrosamine (DMN)-induced fibrotic rats. Severe oxidative stress induced in fibrotic rats was evidenced by a 1.5-fold elevation in MDA and a fall in the SOD activity, and treatment with compound 1 protected against these adverse effects. Recovery of rat liver tissue against DMN-induced hepatocellular necrosis, inflammatory changes and hepatic fibrosis by compound 1 is also confirmed by H&E and Masson stained histopathological evaluation of liver tissue.

CONCLUSION

Two xanthones from Swertia punicea exhibited hepatoprotective activities in vitro (compounds 1 and 2) and in vivo (compound 1), respectively.

Rapamycin attenuates visible light-induced injury in retinal photoreceptor cells via inhibiting endoplasmic reticulum stress

An extended exposure of the retina to visible light may lead to photochemical damage in retinal photoreceptor cells. The exact mechanism of retinal light damage remains unknown, and an effective therapy is still unavailable. Here, we demonstrated that rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), markedly protected 661W photoreceptor cells from visible light exposure-induced damage at the nanomolar level. We also observed by transmission electron microscopy that light exposure led to severe endoplasmic reticulum (ER) stress in 661W cells as well as abnormal endomembranes and ER membranes. In addition, obvious upregulated ER stress markers were monitored by western blot at the protein level and by quantitative reverse transcription-polymerase chain reaction (RT-PCR) at the mRNA level. Interestingly, rapamycin pretreatment significantly suppressed light-induced ER stress and all three major branches of the unfolded protein response (UPR), including the RNA-dependent protein kinase-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and activating transcription factor 6 (ATF6) pathways both at the protein and mRNA levels. Additionally, the inhibition of ER stress by rapamycin was further confirmed with a dithiothreitol (DTT; a classical ER stress inducer)-damaged 661W cell model. Meanwhile, our results also revealed that rapamycin was able to remarkably inhibit the activation of mTOR and its downstream factors eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), p-4EBP1, p70, p-p70, and phosphorylated ribosomal protein S6 kinase (p-S6K) in the light-injured 661W cells. Thus, these data indicate that visible light induces ER stress in 661W cells; whereas the mTOR inhibitor, rapamycin, effectively protects 661W cells from light injury through suppressing the ER stress pathway.