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African swine fever virus (ASFV) is a highly pathogenic swine DNA virus with high mortality that causes African swine fever (ASF) in domestic pigs and wild boars. For efficient viral infection, ASFV has developed complex strategies to evade key components of antiviral innate immune responses. However, the immune escape mechanism of ASFV remains unclear. Upon ASFV infection, cyclic GMP-AMP (2',3'-cGAMP) synthase (cGAS), a cytosolic DNA sensor, recognizes ASFV DNA and synthesizes the second messenger 2',3'-cGAMP, which triggers interferon (IFN) production to interfere with viral replication. In this study, we demonstrated a novel immune evasion mechanism of ASFV EP364R and C129R, which blocks cellular cyclic 2',3'-cGAMP-mediated antiviral responses. ASFV EP364R and C129R with nuclease homology inhibit IFN-mediated responses by specifically interacting with 2',3'-cGAMP and exerting their phosphodiesterase (PDE) activity to cleave 2',3'-cGAMP. Particularly notable is that ASFV EP364R had a region of homology with the stimulator of interferon genes (STING) protein containing a 2',3'-cGAMP-binding motif and point mutations in the Y76S and N78A amino acids of EP364R that impaired interaction with 2',3'-cGAMP and restored subsequent antiviral responses. These results highlight a critical role for ASFV EP364R and C129R in the inhibition of IFN responses and could be used to develop ASFV live attenuated vaccines.

2,3‐Butanediol (2,3‐BDO) is a promising bulk chemical owing to its high potential in industrial applications. Here, we engineered Klebsiella oxytoca for the economic production of 2,3‐BDO using mixed sugars from renewable biomass. First, to improve xylose consumption, the xylose transporter gene (xylE) was integrated into the methylglyoxal synthase A (mgsA)‐coding gene loci, and the engineered CHA004 strain showed much faster consumption of xylose than wild‐type (WT) strain with 1.4‐fold increase of overall sugar consumption rate. To further improve sugar utilization, we performed adaptive laboratory evolution for 90 days. The evolved strain (CHA006) was evaluated by cultivating it in the media containing single‐ or mixed‐sugars, and it was clearly observed that CHA006 has improved sugar consumption and 2,3‐BDO production than those of the parental strain. Finally, we demonstrated the superiority of CHA006 by culturing in two lignocellulosic hydrolysates derived from sunflower or pine tree. Particularly, in the pine tree hydrolysate containing xylose, glucose, galactose, and mannose, the CHA006 strain showed much improved consumption rates for all sugars, and 2,3‐BDO productivity (0.73 g L−1 hr−1) increased by 3.2‐fold compared to WT strain. We believe that the engineered CHA006 strain can be a potential host in the development of economic bioprocess for 2,3‐BDO through efficient utilization of mixed sugars derived from lignocellulosic biomass.

Leuconostoccitreum, a hetero-fermentative type of lactic acid bacteria, is a crucial probiotic candidate because of its ability to promote human health. However, inefficient gene manipulation tools limit its utilization in bioindustries. We report, for the first time, the development of a CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) interference (CRISPRi) system for engineering L. citreum. For reliable expression, the expression system of synthetic single guide RNA (sgRNA) and the deactivated Cas9 of Streptococcus pyogenes (SpdCas9) were constructed in a bicistronic design (BCD) platform using a high-copy-number plasmid. The expression of SpdCas9 and sgRNA was optimized by examining the combination of two synthetic promoters and Shine&ndash, Dalgarno sequences, the strong expression of sgRNA and the weak expression of SpdCas9 exhibited the most significant downregulation (20-fold decrease) of the target gene (sfGFP), without cell growth retardation caused by SpdCas9 overexpression. The feasibility of the optimized CRISPRi system was demonstrated by modulating the biosynthesis of riboflavin. Using the CRISPRi system, the expression of ribF and folE genes was downregulated (3.3-fold and 5.6-fold decreases, respectively), thereby improving riboflavin production. In addition, the co-expression of the rib operon was introduced and the production of riboflavin was further increased up to 1.7 mg/L, which was 1.53 times higher than that of the wild-type strain.

The lactic acid bacteria (LAB) Leuconostoc citreum are non-sporulating hetero-fermentative bacteria that play an important role in the fermented food industry. In this study, for the enhanced and reliable production of recombinant proteins in L. citreum, we developed a bicistronic design (BCD) expression system which includes a short leader peptide (1st cistron) followed by target genes (2nd cistron) under the control of a single promoter. Using superfolder green fluorescent protein (sfGFP) as a reporter, the functionality of BCD in L. citreum was verified. Further, to improve the expression in BCD, we tried to engineer a Shine-Dalgarno sequence (SD2) for the 2nd cistron and a promoter by FACS screening of random libraries, and both strong SD2 (eSD2) and promoter (P710V4) were successfully isolated. The usefulness of the engineered BCD with P710V4 and eSD2 was further validated using three model proteins—glutathione-s-transferase, human growth hormone, and α-amylase. All examined proteins were successfully produced with levels highly increased compared with those in the original BCD as well as the monocistronic design (MCD) expression system.

Increased behind-the-meter (BTM) solar generation causes additional errors in short-term load forecasting. To ensure power grid reliability, it is necessary to consider the influence of the behind-the-meter distributed resources. This study proposes a method to estimate the size of behind-the-meter assets by region to enhance load forecasting accuracy. This paper proposes a semi-supervised approach to BTM capacity estimation, including PV and battery energy storage systems (BESSs), to improve net load forecast using a probabilistic approach. A co-optimization is proposed to simultaneously optimize the hidden BTM capacity estimation and the expected improvement to the net load forecast. Finally, this paper presents a net load forecasting method that incorporates the results of BTM capacity estimation. To describe the efficiency of the proposed method, a study was conducted using actual utility data. The numerical results show that the proposed method improves the load forecasting accuracy by revealing the gross load pattern and reducing the influence of the BTM patterns.

Most skin damage caused by ultraviolet B (UVB) radiation is owing to the generation of reactive oxygen species. Phytochemicals can act as antioxidants against UVB-induced oxidative stress. This study investigated the protective effects of the flavone galangin against UVB-induced oxidative damage in human keratinocytes. Galangin efficiently scavenged free radicals and reduced UVB-induced damage to cellular macromolecules, such as DNA, lipids, and proteins. Furthermore, galangin rescued cells undergoing apoptosis induced by UVB radiation via recovering mitochondrial polarization and down-regulating apoptotic proteins. These results showed that galangin protects human keratinocytes against UVB radiation-induced cellular damage and apoptosis via its antioxidant effects.

Excessive ultraviolet (UV) radiation, a constituent of sunlight, can induce multiple types of skin damage. We recently demonstrated that americanin B, a lignin compound, protected cells against hydrogen peroxide (H2O2)-induced damage by exerting antioxidant effects and inhibiting apoptosis. In this study, we investigated the ability of americanin B to protect against cell injury induced by UVB (280-320nm), the most harmful UV wavelengths, in human HaCaT keratinocytes. Americanin B absorbed UVB, eliminated UVB-induced intracellular reactive oxygen species (ROS), and decreased the extent of UVB-induced oxidative modification of lipids, proteins, and DNA. In addition, americanin B inhibited UVB-induced apoptosis, as indicated by reductions in apoptotic body formation and DNA fragmentation. Furthermore, americanin B reversed the depolarization of the mitochondrial membrane induced by UVB exposure. These protective activities were associated with down-regulation of apoptosis-promoting proteins, Bax, caspase-9, and caspase-3 and up-regulation of an apoptosis inhibitor, Bcl-2. These results suggest that americanin B can protect human keratinocytes against UVB-induced cell damage.

Fucoxanthin, a natural carotenoid, is abundant in seaweed with antioxidant properties. This study investigated the role of fucoxanthin in the induction of antioxidant enzymes involved in the synthesis of reduced glutathione (GSH), synthesized by glutamate-cysteine ligase catalytic subunit (GCLC) and glutathione synthetase (GSS), via Akt/nuclear factor-erythroid 2-related (Nrf2) pathway in human keratinocytes (HaCaT) and elucidated the underlying mechanism. Fucoxanthin treatment increased the mRNA and protein levels of GCLC and GSS in HaCaT cells. In addition, fucoxanthin treatment promoted the nuclear translocation and phosphorylation of Nrf2, a transcription factor for the genes encoding GCLC and GSS. Chromatin immune-precipitation and luciferase reporter gene assays revealed that fucoxanthin treatment increased the binding of Nrf2 to the antioxidant response element (ARE) sequence and transcriptional activity of Nrf2. Fucoxanthin treatment increased phosphorylation of Akt (active form), an up-regulator of Nrf2 and exposure to LY294002, a phosphoinositide 3-kinase (PI3K)/Akt inhibitor, suppressed the fucoxanthin-induced activation of Akt, Nrf2, resulting in decreased GCLC and GSS expression. In accordance with the effects on GCLC and GSS expression, fucoxanthin induced the level of GSH. In addition, fucoxanthin treatment recovered the level of GSH reduced by ultraviolet B irradiation. Taken together, these findings suggest that fucoxanthin treatment augments cellular antioxidant defense by inducing Nrf2-driven expression of enzymes involved in GSH synthesis via PI3K/Akt signaling.

Glutathione S-transferase π-1 (GSTP-1) is a member of the glutathione S-transferase enzyme superfamily, which catalyzes the conjugation of electrophiles to glutathione during the process of detoxification. In this study, the epigenetic alterations of GSTP-1 expression in human colorectal cancers and the underlying mechanisms were investigated. In 10 colon cancer patients, proteomic analysis revealed that expression of GSTP-1 protein was higher in tumor tissues than in paired adjacent normal tissues. Likewise, in 7 of 10 colon cancer patients, GSTP-1 protein expression was more than 1.5-fold higher in tumor tissues than in adjacent normal tissues, as determined by western blotting. Immunohistochemical data confirmed that GSTP-1 protein was expressed at higher levels in colon cancer tissues compared to normal mucosa. GSTP-1 enzyme activity was closely correlated with GSTP-1 protein expression in colon cancer patients. Consistent with this, GSTP-1 mRNA, protein and activity levels were higher in the colorectal cancer cell lines Caco-2, HCT-116, HT-29, SNU-407 and SNU-1033 compared to the normal colon cell line FHC. Methylation-specific PCR results indicated that the high levels of GSTP-1 in human colorectal cancer cell lines were likely due to the lower degree of promoter methylation in colon cancer cell lines compared to the normal colon cell line, consistent with findings in colon cancer patients. Moreover, the levels of specific activator-protein complexes and histone marks were higher in human colorectal cancer cells compared to the normal human colon cell line, whereas the repressor protein complexes exhibited the opposite pattern. Furthermore, chromatin immunoprecipitation assays demonstrated that expression levels of the transcription factors AP-1 and SP-1 were correlated with the upregulation of GSTP-1 expression in colorectal cancer cells. Finally, knockdown of GSTP-1 promoted the sensitivity of SNU-407 cells to the anticancer agent 5-fluorouracil. These data indicate that GSTP-1 may serve as a clinically useful biomarker of colon cancer and a target for anti-colon cancer drugs.

Previously we demonstrated that phloroglucinol (1,3,5-trihydroxybenzene) protected human HaCaT keratinocytes against ultraviolet B (UVB, 280-320 nm)-induced oxidative stress in vitro by scavenging intracellular reactive oxygen species (ROS). The current study investigated whether phloroglucinol could similarly protect the mouse skin against UVB-induced oxidative tissue damage in vivo.Male 7-week-old Balb/c mice were divided into the following untreated normal control, phloroglucinol only-treated, vehicle plus UVB (30 or 60 mJ/cm(2))-exposed, and phloroglucinol (10 or 50 mg/ml) plus UVB (30 or 60 mJ/cm(2))-treated groups. Following UVB exposure, phloroglucinol or phosphate buffered saline vehicle was applied to the dorsal skin of each mouse daily for 3 days. Studies were conducted at 24 h after the last of the UVB exposures. Histopathological analyses of dorsal skin lesions were performed on all mice. In addition, the levels of UVB-provoked injury to cellular components, including DNA, proteins, and lipids were detected by levels of 8-oxoguanine (8-oxoG), protein carbonyls, and 8-isoprostane. Apoptosis were assessed by using western blot for B-cell lymphoma-2-associated X protein (Bax) and activated caspase-3 expression, by using immunohistochemistry.UVB radiation increased the thickness of the epidermis and the dermis, and also stimulated the accumulation of mast cells in the irradiated skin. However, treatment with phloroglucinol significantly decreased all of these parameters. Furthermore, phloroglucinol decreased UVB-provoked injury to cellular components, including DNA, proteins, and lipids; down-regulated the expression of phospho-histone H2A.X in the injured skin; and reduced the UVB-generated levels of 8-oxoG, protein carbonyls, and 8-isoprostane, which are all markers of oxidative stress. In addition, phloroglucinol attenuated the UVB-induced expression of the pro-apoptotic proteins, Bax protein, and activated caspase-3.These results suggest that phloroglucinol safeguards the mouse skin against UVB-induced oxidative stress and apoptosis.

The present study investigated the cytotoxic and apoptotic effects of an ethanol extract derived from the marine brown alga Dictyopteris undulata against human colon adenocarcinoma cells. The Dictyopteris undulata extract (DUE) showed cytotoxic activity against SW480 cells in a dose-dependent manner, with 50% inhibition of cell viability at a concentration of 40 μg/mL. DUE also induced programmed cell death in SW480 cells, as evidenced by apoptotic body formation, DNA fragmentation, an increase in the population of apoptotic sub-G1 phase cells, and mitochondrial membrane depolarization. Moreover, DUE significantly modulated the expression of apoptosisassociated proteins, resulting in a decrease in B cell lymphoma-2 expression and an increase in Bcl-2-associated X protein expression, as well as the activation of caspase-9 and caspase-3. Furthermore, DUE showed apoptotic cell death in two other colon cancer cell lines, SNU407 and HT29. These observations suggest that DUE may prove useful as a therapeutic agent for the attenuation of colon cancer.

Our previous work demonstrated that an ethyl acetate extract derived from Sargassum muticum (Yendo) Fenshol (SME) protected human HaCaT keratinocytes against ultraviolet B (UVB)-induced oxidative stress by increasing antioxidant activity in the cells, thereby inhibiting apoptosis.The aim of the current study was to further elucidate the anti-apoptotic mechanism of SME against UVB-induced cell damage.The expression levels of several apoptotic-associated and mitogen-activated kinase (MAPK) signaling proteins were determined by western blot analysis of UVB-irradiated HaCaT cells with or without prior SME treatment. In addition, the loss of mitochondrial membrane potential (Δψm) was detected using flow cytometry or confocal microscopy and the mitochondria membrane-permeate dye, JC-1. Apoptosis was assessed by quantifying DNA fragmentation and apoptotic body formation. Furthermore, cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.SME absorbed electromagnetic radiation in the UVB range (280-320 nm) of the UV/visible light spectrum. SME also increased Bcl-2 and Mcl-1 expression in UVB-irradiated cells and decreased the Bax expression. Moreover, SME inhibited the UVB-induced disruption of mitochondrial membrane potential and prevented UVB-mediated increases in activated caspase-9 and caspase-3 (an apoptotic initiator and executor, respectively) levels. Notably, treatment with a pan-caspase inhibitor enhanced the anti-apoptotic effects of SME in UVB-irradiated cells. Finally, SME reduced the UVB-mediated phosphorylation of p38 MAPK and JNK, and prevented the UVB-mediated dephosphorylation of Erk1/2 and Akt.The present results indicate that SME safeguards HaCaT keratinocytes from UVB-mediated apoptosis by inhibiting a caspase-dependent signaling pathway.

The aim of the present study was to elucidate the protective properties of 3,4-dihydroxybenzoic acid (DBA) isolated from Cladophora wrightiana Harvey (a green alga) against ultraviolet B (UVB)-induced damage to human HaCaT keratinocytes. DBA exhibited scavenging actions against the 1,1-diphenyl-2-picrylhydrazyl radical, the superoxide anion, and the hydroxyl radical. Furthermore, DBA decreased the levels of intracellular reactive oxygen species generated by hydrogen peroxide or UVB treatment of the cells. DBA also decreased the UVB-augmented levels of phospho-histone H2A.X and the extent of comet tail formation, which are both indications of DNA damage. In addition, the compound safeguarded keratinocytes from UVB-induced injury by reversing the production of apoptotic bodies, overturning the disruption of mitochondrial membrane potential, increasing the expression of the anti-apoptotic protein, B-cell lymphoma 2, and decreasing the expression of the pro-apoptotic proteins, Bcl-2-associated X and cleaved caspase-3. Taken together, these results demonstrate that DBA isolated from a green alga protects human keratinocytes against UVB-induced oxidative stress and apoptosis.

We investigated the protective effects of chlorogenic acid (CGA), a polyphenol compound, on oxidative damage induced by UVB exposure on human HaCaT cells. In a cell-free system, CGA scavenged 1,1-diphenyl-2-picrylhydrazyl radicals, superoxide anions, hydroxyl radicals, and intracellular reactive oxygen species (ROS) generated by hydrogen peroxide and ultraviolet B (UVB). Furthermore, CGA absorbed electromagnetic radiation in the UVB range (280-320 nm). UVB exposure resulted in damage to cellular DNA, as demonstrated in a comet assay; pre-treatment of cells with CGA prior to UVB irradiation prevented DNA damage and increased cell viability. Furthermore, CGA pre-treatment prevented or ameliorated apoptosis-related changes in UVB-exposed cells, including the formation of apoptotic bodies, disruption of mitochondrial membrane potential, and alterations in the levels of the apoptosis-related proteins Bcl-2, Bax, and caspase-3. Our findings suggest that CGA protects cells from oxidative stress induced by UVB radiation.

Fucodiphlorethol G (6'-[2,4-dihydroxy-6-(2,4,6-trihydroxyphenoxy)phenoxy]biphenyl-2,2',4,4',6-pentol) is a compound purified from Ecklonia cava, a brown alga that is widely distributed offshore of Jeju Island. This study investigated the protective effects of fucodiphlorethol G against oxidative damage-mediated apoptosis induced by ultraviolet B (UVB) irradiation. Fucodiphlorethol G attenuated the generation of 2, 2-diphenyl-1-picrylhydrazyl radicals and intracellular reactive oxygen species in response to UVB irradiation. Fucodiphlorethol G suppressed the inhibition of human keratinocyte growth by UVB irradiation. Additionally, the wavelength of light absorbed by fucodiphlorethol G was close to the UVB spectrum. Fucodiphlorethol G reduced UVB radiation-induced 8-isoprostane generation and DNA fragmentation in human keratinocytes. Moreover, fucodiphlorethol G reduced UVB radiation-induced loss of mitochondrial membrane potential, generation of apoptotic cells, and active caspase-9 expression. Taken together, fucodiphlorethol G protected human keratinocytes against UVB radiation-induced cell damage and apoptosis by absorbing UVB radiation and scavenging reactive oxygen species.

In this study, we investigated the molecular mechanisms underlying the anti-proliferative effects of Compound K, with specific reference to histone modification. Exposure of HT-29 human colon cancer cells to Compound K resulted in time-dependent inhibition of histone deacetylase (HDAC) activity, mRNA and protein expression. Compound K treatment induced unmethylation of the RUNX3 promoter region such as TSA treatment and an accumulation of acetylated histones H3 and H4 within the total cellular chromatin, resulting in an enhanced ability of these histones to bind to the promoter sequences of the tumor suppressor gene Runt-related transcription factor 3 (RUNX3). Treatment of cells with Compound K increased the mRNA and protein expression of RUNX3, as well as p21, a downstream target of RUNX3. These alterations were consistent with cell cycle arrest at the G0/G1 phases and induction of apoptosis. Our results provide new insights into the mechanisms of Compound K action in human colorectal cancer cells and suggest that HDAC inhibition presents a novel approach to prevent or treat colorectal cancer.

6'-O-galloylpaeoniflorin (GPF) is a galloylated derivate of paeoniflorin and a key chemical constituent of the peony root, a perennial flowering plant that is widely used as an herbal medicine in East Asia. This study is the first investigation of the cytoprotective effects of GPF against hydrogen peroxide (H2O2)-induced cell injury and death in human HaCaT keratinocytes. GPF demonstrated a significant scavenging capacity against the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, H2O2-generated intracellular reactive oxygen species (ROS), the superoxide anion radical (O2 (-)), and the hydroxyl radical (•OH). GPF also safeguarded HaCaT keratinocytes against H2O2-provoked apoptotic cell death and attenuated oxidative macromolecular damage to DNA, lipids, and proteins. The compound exerted its cytoprotective actions in keratinocytes at least in part by decreasing the number of DNA strand breaks, the levels of 8-isoprostane (a stable end-product of lipid peroxidation), and the formation of carbonylated protein species. Taken together, these results indicate that GPF may be developed as a cytoprotector against ROS-mediated oxidative stress.

Exposure to solar UVB radiation can lead to the formation of DNA lesions such as cyclobutane pyrimidine dimers (CPDs). Nucleotide excision repair (NER) is critical for the repair of CPDs induced by UV radiation. The purpose of this study was to investigate the ability of phloroglucinol to protect against the formation of UVB-induced CPDs in vitro and in vivo. Exposure to UVB radiation increased the number of CPDs in both HaCaT keratinocytes and mouse skin; however, these increases were reduced by treatment with phloroglucinol. Expression levels of xeroderma pigmentosum complementation group C (XPC) and excision repair cross-complementation 1 (ERCC1), which are essential components of the NER pathway, were reduced following UVB exposure, although phloroglucinol treatment recovered these levels in both HaCaT keratinocytes and mouse skin. Phloroglucinol also inhibited UVB-induced reductions in binding of the transcription factors specificity protein 1 to the XPC promoter. These results demonstrate that phloroglucinol can protect cells against UVB-induced DNA damage by inducing NER.

The purpose of this study was to assess the protective effects of an ethanol extract derived from the red alga Gracilaria bursa-pastoris (Gmelin) Silva (GBE) on ultraviolet B (UVB)-irradiated human HaCaT keratinocytes. GBE exhibited scavenging activity against intracellular reactive oxygen species that were induced by either hydrogen peroxide or UVB radiation. In addition, both the superoxide anion and the hydroxyl radical were scavenged by GBE in cell-free systems. GBE absorbed light in the UVB range (280-320 nm) of the electromagnetic spectrum and lessened the extent of UVB-induced oxidative damage to cellular lipids, proteins, and DNA. Finally, GBE-treated keratinocytes showed a reduction in UVB-induced apoptosis, as exemplified by fewer apoptotic bodies. These results suggest that GBE exerts cytoprotective actions against UVB-stimulated oxidative stress by scavenging ROS and absorbing UVB rays, thereby attenuating injury to cellular constituents and preventing cell death.

We evaluated the cytoprotective effects of americanin B, a lignan compound, against hydrogen peroxide (H2O2)-induced cell damage. Americanin B decreased the level of DPPH radicals, superoxide anions, hydroxyl radicals, and intracellular reactive oxygen species. Americanin B also attenuated DNA damage induced by H2O2 treatment, as shown by the inhibition of formation of comet tails, indicative of DNA strand breakage, and prevented the oxidation of protein and peroxidation of lipid, as determined by protein carbonyls and 8-isoprostane. Furthermore, americanin B protected against H2O2-induced apoptotic cell death, as determined by a reduction in the numbers of apoptotic bodies stained with Hoechst 33342. These findings suggest that americanin B protects cells against oxidative damage by exerting antioxidant effects and inhibiting apoptosis.

The cytoprotective effects of 6'-O-galloylpaeoniflorin against injury and death of human HaCaT keratinocytes resulting from ultraviolet B radiation were investigated. 6'-O-galloylpaeoniflorin exhibited the capacity to scavenge intracellular reactive oxygen species (ROS) generated by ultraviolet B radiation. 6'-O-galloylpaeoniflorin also attenuated ultraviolet B-induced oxidative macromolecular damage to DNA, lipids, and proteins, decreasing the number of DNA strand breaks, the level of 8-isoprostane (a biomarker of lipid peroxidation), and the level of protein carbonylation. Moreover, 6'-O-galloylpaeoniflorin rescued HaCaT cells from ultraviolet induced cell death, by downregulating the mitochondrial apoptotic pathway. Taken together, these results indicate that 6'-O-galloylpaeoniflorin has the potential to be developed as a medical agent against ROS-mediated skin diseases.

This study investigated the cytoprotective effect of Ecklonia cava-derived eckol against H2O2-induced mitochondrial dysfunction in Chang liver cells. While H2O2 augmented levels of mitochondrial reactive oxygen species (ROS), eckol decreased it. Eckol also attenuated high intracellular Ca(2+) levels stimulated by H2O2 and recovered H2O2-diminished ATP levels and succinate dehydrogenase activity. Eckol time-dependently increased the expression of manganese superoxide dismutase (Mn SOD), a mitochondrial antioxidant enzyme with cytoprotective effect against oxidative stress. Eckol recovered Mn SOD expression and activity that were decreased by H2O2. Finally, eckol induced Mn SOD through phosphorylated AMP-activated protein kinase (AMPK) and forkhead box O3a (FoxO3a). Specific silencing RNAs (siRNAs) against FoxO3a and AMPK reduced eckol-stimulated Mn SOD expression, and diethyldithiocarbamate (Mn SOD inhibitor) and siRNA against Mn SOD reduced the cytoprotective effect of eckol against H2O2-provoked cell death. These results demonstrate that eckol protects cells from mitochondrial oxidative stress by activating AMPK/FoxO3a-mediated induction of Mn SOD.

The cytoprotective mechanism of 7, 8-dihydroxyflavone (DHF) against oxidative stress-induced cell damage with respect to its stimulatory effect on the expression of heme oxygenase-1 (HO-1), a potent antioxidant enzyme, was investigated in the present study. Up-regulation of HO-1 expression by DHF was both dose and time dependent in lung fibroblast V79-4 cells. DHF also increased the protein expression level of the transcription factor nuclear factor erythroid-2-related factor 2 (Nrf2), and induced the translocation of Nrf2 from the cytosol into the nucleus, leading to elevated HO-1 expression. The siNrf2 RNA-transfection attenuated HO-1 expression induced by DHF treatment. In addition, DHF induced the activation of extracellular signal-regulated kinase (ERK), while U0126 (a specific pharmacological inhibitor of ERK kinase) abrogated DHF-activated Nrf2 and HO-1 expression. This suggests that DHF increased the levels of Nrf2 and HO-1 via ERK-dependent pathways. Furthermore, DHF significantly prevented the reduction of cell viability in response to oxidative stress; however, U0126 attenuated the protective effect of DHF. Taken together, these results demonstrate that DHF protected cells from oxidative stress via the activation of an ERK/Nrf2/HO-1 signaling pathway.

This study investigated the effect of 7,8-dihydroxyflavone (DHF) on the expression and activity of heme oxygenase-1 (HO-1), an enzyme with potent antioxidant properties, as well as the molecular mechanisms involved. DHF markedly upregulated HO-1 mRNA and protein expression in human keratinocytes (HaCaT cells), resulting in increased HO-1 activity. DHF also increased the protein level of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates HO-1 expression by binding to the antioxidant response element (ARE) within the HO-1 gene promoter, in a time-dependent manner. Moreover, DHF decreased the expression of Kelch-like ECH-associated protein 1, a repressor of Nrf2 activity, and induced the translocation of Nrf2 from the cytosol into the nucleus, thereby allowing its association with the ARE site. DHF activated extracellular-regulated kinase (ERK) and protein kinase B (PKB, Akt) in keratinocytes, while the ERK and Akt inhibitors attenuated DHF-enhanced Nrf2 and HO-1 expression. DHF also protected the keratinocytes against hydrogen peroxide- and ultraviolet B-induced oxidative damage, while HO-1, ERK and Akt inhibitors markedly suppressed DHF-mediated cytoprotection. Taken together, the results suggested that DHF activates ERK- and Akt-Nrf2 signaling cascades in HaCaT cells, leading to the upregulation of HO-1 and cytoprotection against oxidative stress.

The modified guanine base 8-oxoguanine (8-oxoG) is abundantly produced by oxidative stress, can contribute to carcinogenesis, and can be removed from DNA by 8-oxoguanine DNA glycosylase-1 (OGG1), which acts as an 8-oxoG glycosylase and endonuclease. This study investigated the mechanism by which 7,8-dihydroxyflavone (DHF) inhibits oxidative stress-induced 8-oxoG formation in hamster lung fibroblasts (V79-4). DHF significantly reduced the amount of 8-oxoG induced by hydrogen peroxide (H2O2) and elevated the levels of OGG1 mRNA and protein. DHF increased the binding of nuclear factor erythroid 2-related factor 2 (Nrf2) to antioxidant response element sequences in the upstream promoter region of OGG1. Moreover, DHF increased the nuclear levels of Nrf2, small Maf proteins, and the Nrf2/small Maf complex, all of which are decreased by H2O2treatment. Likewise, the level of phosphorylated Akt, which activates Nrf2, was decreased by H2O2treatment but restored by DHF treatment. The levels of OGG1 and nuclear translocation of Nrf2 protein were decreased upon treatment with PI3K inhibitor or Akt inhibitor, and DHF treatment did not restore OGG1 and nuclear Nrf2 levels in these inhibitor-treated cells. Furthermore, PI3K and Akt inhibitors abolished the protective effects of DHF in cells undergoing oxidative stress. These data indicate that DHF induces OGG1 expression via the PI3K-Akt pathway and protects cells against oxidative DNA base damage by activating DNA repair systems.

Background: Oxidative stress damages to cells or tissues, however, cellular defense systems including heme oxygenase-1 (HO-1) protects them against oxidative s tress. Flavonoid compounds can activate cellular defense mechanisms against oxidative stress and it can reduce cell damages. In the present study, the cytoprotective effects of morin (3,5,7,2’,4’-pentahydroxyflavone), in terms of HO-1 enzyme, against the oxidative stress and its involved mechanisms was elucidated. Methods: RT-PCR and western blot analysis were assessed to detect the mRNA and protein expression, respectively. Cell viability was measured by using MTT test. The immunocytochemistry was performed to define location of target protein. Electrophoretic mobility shift assay performed to measure transcription factor-promoter site binding activity. Results: Morin elevated mRNA and protein levels of HO-1 in human lens epithelial cells (HLE-B3). HO-1 inhibitor ZnPP attenuated the protective effect of morin against H2O2-induced cytotoxicity. Morin increased the protein level of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which up-regulates HO-1 expression by binding to the antioxidant response element (ARE) within the HO-1 gene promoter. Moreover, morin induced the translocation of Nrf2 from the cytosol into the nucleus. Morin activated extracellular-regulated kinase (ERK), while ERK inhibitor attenuated morin-enhanced Nrf2 and HO-1 expression. Conclusions: Morin activates ERK-Nrf2 signaling cascades in HLE-B3 cells, leading to the up-regulation of HO-1 and cytoprotection against oxidative stress. (J Cancer Prev 2013;18:249-256)

Hydrogen peroxide (H2O2) can induce cell damage by generating reactive oxygen species (ROS), resulting in DNA damage and cell death. The aim of this study is to elucidate the protective effects of fisetin (3,7,3′,4′,-tetrahydroxy flavone) against H2O2-induced cell damage. Fisetin reduced the level of superoxide anion, hydroxyl radical in cell free system, and intracellular ROS generated by H2O2. Moreover, fisetin protected against H2O2-induced membrane lipid peroxidation, cellular DNA damage, and protein carbonylation, which are the primary cellular outcomes of H2O2 treatment. Furthermore, fisetin increased the level of reduced glutathione (GSH) and expression of glutamate-cysteine ligase catalytic subunit, which is decreased by H2O2. Conversely, a GSH inhibitor abolished the cytoprotective effect of fisetin against H2O2-induced cells damage. Taken together, our results suggest that fisetin protects against H2O2-induced cell damage by inhibiting ROS generation, thereby maintaining the protective role of the cellular GSH system.