Doxorubicin (DOX), a common chemotherapeutic agent, suffers serious adverse effects including hepatotoxicity. Mokko lactone (ML) is a guainolide sesquiterpene with promising biological activities. The study aimed to evaluate the protection offered by ML against hepatotoxicity induced by DOX in rats. Our data indicated ML exhibited protective effects as evidenced by ameliorating the rise in serum activities of alanine transaminase, aspartate transaminase and alkaline phosphatase. This was confirmed histologically as ML prevented DOX-induced pathological alteration in liver architecture. Further, ML administration significantly prevented malondialdehyde accumulation, glutathione depletion and superoxide dismutase and catalase exhaustion. Antioxidant action of ML was associated with enhanced expression of the nuclear translocation of NF-E2-related factor 2 (Nrf2) and a lower expression of forkhead box protein O1 (FOXO1). Also, ML showed potent anti-inflammatory activities highlighted by decreased expression of interleukin 6, tumor necrosis factor α and nuclear factor κB (NF-κB). The anti-apoptotic effects of ML were associated with decreased Bax and enhanced Bcl-2 mRNA expression in liver tissues. ML caused a significant up-regulation in the expression of silent information regulator 1 (Sirt-1). Therefore, it can be concluded that ML prevents liver injury caused by DOX. This could partially be due to the ML regulatory activities on Sirt-1/FOXO1/NF-κB axis.

Pomegranate (Punica granatum L.), a nutrient-rich unique fruit, has been used for centuries for the prevention and treatment of various inflammation-driven diseases. Based on our previous study, a characterized pomegranate emulsion (PE) exhibited a striking inhibition of dimethylbenz(a)anthracene (DMBA)-initiated rat mammary tumorigenesis via antiproliferative and apoptosis-inducing mechanisms. The objective of the present work is to investigate the anti-inflammatory mechanism of action of PE during DMBA rat mammary carcinogenesis by evaluating the expression of cyclooxygenase-2 (COX-2), heat shock protein 90 (HSP90), nuclear factor-κB (NF-κB) and nuclear factor erythroid 2p45 (NF-E2)-related factor 2 (Nrf2). Mammary tumor samples were harvested from our previous chemopreventive study in which PE (0.2-5.0 g/kg) was found to reduce mammary tumorigenesis in a dose-dependent manner. The expressions of COX-2, HSP90, NF-κB, inhibitory κBα (IκBα) and Nrf2 were detected by immunohistochemical techniques. PE decreased the expression of COX-2 and HSP90, prevented the degradation of IκBα, hindered the translocation of NF-κB from cytosol to nucleus and increased the expression and nuclear translocation of Nrf2 during DMBA-induced mammary tumorigenesis. These findings, together with our previous results, indicate that PE-mediated prevention of DMBA-evoked mammary carcinogenesis may involve anti-inflammatory mechanisms through concurrent but differential regulation of two interrelated molecular pathways, namely NF-κB and Nrf2 signaling.

Doxorubicin (DOX), a commonly utilized anthracycline antibiotic, suffers deleterious side effects such as cardiotoxicity. Mokko lactone (ML) is a naturally occurring guainolide sesquiterpene with established antioxidant and anti-inflammatory actions. This study aimed at investigating the protective effects of ML in a DOX-induced cardiotoxicity model in rats. Our results indicated that ML exerted protection against cardiotoxicity induced by DOX as indicated by ameliorating the rise in serum troponin and creatine kinase-MB levels and lactate dehydrogenase activity. Histological assessment showed that ML provided protection against pathological alterations in heart architecture. Furthermore, treatment with ML significantly ameliorated DOX-induced accumulation of malondialdehyde and protein carbonyl, depletion of glutathione, and exhaustion of superoxide dismutase and catalase. ML's antioxidant effects were accompanied by increased nuclear translocation of NF-E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression. Moreover, ML exhibited significant anti-inflammatory activities as evidenced by lowered nuclear factor κB, interleukin-6, and tumor necrosis factor-α expression. ML also caused significant antiapoptotic actions manifested by modulation in mRNA expression of Bax, Bcl-2, and caspase-3. This suggests that ML prevents heart injury induced by DOX via its antioxidant, anti-inflammatory, and antiapoptotic activities.

This study investigated the protective effect and the molecular mechanism of piceatannol on hydrogen peroxide (H2O2)-induced retinal pigment epithelium cell (ARPE-19) damage. Piceatannol treatment significantly inhibited H2O2-induced RPE cell death and reactive oxygen species (ROS) generation by 64.4% and 75.0%, respectively. Results of flow cytometry showed that H2O2-induced ARPE-19 cells apoptosis was ameliorated by piceatannol supplementation, along with decreased relative protein expressions of Bax/Bcl-2, Cleave-Caspase-3, and Cleave-PARP. Moreover, piceatannol treatment induced NF-E2-related factor 2 (Nrf2) signaling activation, which was evidenced by increased transcription of anti-oxidant genes, glutamate-cysteine ligase catalytic subunit (GCLc), SOD, and HO-1. Knockdown of Nrf2 through targeted siRNA alleviated piceatannol-mediated HO-1 transcription, and significantly abolished piceatannol-mediated cytoprotection. LY294002 (PI3K inhibitor) dramatically blocked piceatannol-mediated increasing of Nrf2 nuclear translocation, HO-1 expression, and cytoprotective activity, indicating the involvement of PI3K/Akt pathway in the cytoprotective effect of piceatannol. The results from this suggest the potential of piceatannol in reducing the risk of age-related macular degeneration.

Due to metastatic potential and drug resistance, cancer stem cells (CSCs) have become a critical target for the development of chemotherapeutic agents. Recent studies showed that CSCs highly express NF-E2-related factor 2 (Nrf2)-mediated antioxidant enzymes and thereby retain relatively low levels of reactive oxygen species (ROS). Since anticancer agents usually utilize ROS as an arsenal for killing cancer cells, we hypothesized that inhibition of Nrf2 activity could increase the sensitivity of CSCs to anticancer drugs, and thus enhancing their therapeutic efficacy. We found that MCF-7-derived CSCs with a CD44high/CD24low phenotype formed mammospheres and highly expressed Nrf2 compared to the adherent parental MCF-7 cells. In a separate experiment, we screened 89 different edible plant extracts for inhibitory activity against the Nrf2 signaling pathway by using an antioxidant response element (ARE)-luciferase assay system. Among those extracts, Castanea crenata (chestnut) leaf extract significantly decreased the nuclear translocation of Nrf2 and protein expression of antioxidant enzymes in MCF-7-derived CSCs. The combined treatment of the CSCs with chestnut leaf extract and paclitaxel resulted in more effective cell death than the treatment with paclitaxel alone. These findings suggest that the chestnut leaf extract or its constituents could increase the susceptibility of breast CSCs to an anticancer drug, paclitaxel, through inhibition of the Nrf2 signaling pathway, and could be utilized as an adjuvant for chemotherapy.

Salmonella enterica serovar Typhimurium (S. Typhimurium) has evolved mechanisms to evade the host's nutritional immunity and thus promote bacterial growth by using the iron in the host. However, the detailed mechanisms of S. Typhimurium induce dysregulation of iron homeostasis and whether Lactobacillus johnsonii L531 can alleviate the iron metabolism disorder caused by S. Typhimurium has not been fully elucidated. Here, we show that S. Typhimurium activated the expression of iron regulatory protein 2 (IRP2), transferrin receptor 1, and divalent metal transporter protein 1 and suppressed the expression of iron exporter ferroportin, which resulted in iron overload and oxidative stress, inhibiting the key antioxidant proteins NF-E2-related factor 2, Heme Oxygenase-1, and Superoxide Dismutase in vitro and in vivo. L. johnsonii L531 pretreatment effectively reversed these phenomena. IRP2 knockdown inhibited iron overload and oxidative damage induced by S. Typhimurium in IPEC-J2 cells, while IRP2 overexpression promoted iron overload and oxidative damage caused by S. Typhimurium. Interestingly, the protective effect of L. johnsonii L531 on iron homeostasis and antioxidant function was blocked following IRP2 overexpression in Hela cells, demonstrating that L. johnsonii L531 attenuates disruption of iron homeostasis and consequent oxidative damage caused by S. Typhimurium via the IRP2 pathway, which contributes to the prevention of S. Typhimurium diarrhea in mice.

Exercise-induced reactive oxygen and nitrogen species are increasingly considered as beneficial health promotion. Astaxanthin (ASX) has been recognized as a potent antioxidant suitable for human ingestion. We investigated whether ASX administration suppressed antioxidant enzyme activity in moderate-intensity exercise. Seven-week-old male C57BL/6 mice (n = 8/group) were treated with ASX (5, 15, and 30 mg/kg BW) combined with 45 min/day moderate-intensity swimming training for four weeks. Results showed that the mice administrated with 15 and 30 mg/kg of ASX decreased glutathione peroxidase, catalase, malondialdehyde, and creatine kinase levels in plasma or muscle, compared with the swimming control group. Beyond that, these two (15 and 30 mg/kg BW) dosages of ASX downregulated gastrocnemius muscle erythroid 2p45 (NF-E2)-related factor 2 (Nrf2). Meanwhile, mRNA of Nrf2 and Nrf2-dependent enzymes in mice heart were also downregulated in the ASX-treated groups. However, the mice treated with 15 or 30 mg/kg ASX had increased constitutive nitric oxidase synthase and superoxide dismutase activity, compared with the swimming and sedentary control groups. Our findings indicate that high-dose administration of astaxanthin can blunt antioxidant enzyme activity and downregulate transcription of Nrf2 and Nrf2-dependent enzymes along with attenuating plasma and muscle MDA.

Olive tree (Olea europaea L.) leaves are an abundant source of bioactive compounds with several beneficial effects for human health. Recently, the effect of olive leaf extract in obesity has been studied. However, the molecular mechanism in preventing obesity-related inflammation has not been elucidated. Obesity is a state of chronic low-grade inflammation and is associated with an increase of pro-inflammatory M1 macrophages infiltration in the adipose tissue. In the current study, we explored Olea europaea L. leaf extract (OLE) anti-inflammatory activity using an in vitro model of obesity-induced inflammation obtained by stimulating murine macrophages RAW 264.7 with high dose of the free fatty acid palmitate. We found that OLE significantly suppressed the induction of pro-inflammatory mediators, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1β, nitric oxide (NO), prostaglandin E2 (PGE2) and reactive oxygen species (ROS), while it enhanced the anti-inflammatory cytokine, IL-10. Moreover, we demonstrated that OLE reduced the oxidative stress induced by palmitate in macrophages by regulating the NF-E2-related factor 2 (NRF2)-Kelch-like ECH-associated protein 1 (KEAP1) pathway. Finally, we showed that OLE promoted the shift of M1 macrophage toward less inflammatory M2-cells via the modulation of the associated NF-κB and proliferator-activated receptor gamma (PPARγ) signaling pathways. Thereby, our findings shed light on the potential therapeutic feature of OLE in recovering obesity-associated inflammation via regulating M1/M2 status.

5-hydroxyeicosatetraenoic acid (5-HETE) and 5-hydroxyeicosapentaenoic acid (5-HEPE) are major metabolites produced by 5-lipoxygenase (5-LOX) from arachidonic acid (AA) and eicosapentaenoic acid (EPA). Effects of hydroxides on endothelial cells are unclear, although 5-LOX is known to increase at arteriosclerotic lesions. To investigate the effects of hydroxides on human umbilical vein endothelial cells (HUVECs), the cells were treated with 50 μM each of AA, EPA, 5-HETE, and 5-HEPE. Treatment of HUVECs with 5-HETE and 5-HEPE, rather than with AA and EPA, increased the nuclear translocation of NF-E2 related factor 2 (Nrf2) and upregulated the expression of heme oxygenase-1 and cystine/glutamate transporter regulated by Nrf2. Reactive oxygen species (ROS) generation was markedly elevated in HUVECs after treatment with 5-HETE and 5-HEPE, and the pretreatment with α-tocopherol abrogated ROS levels similar to those in the vehicle control. However, ROS generation was independent of Nrf2 activation induced by 5-HETE and 5-HEPE. 5-HETE was converted to 5-oxo-eicosatetraenoic acid (5-oxo-ETE) in HUVECs, and 5-oxo-ETE increased Nrf2 activation. These results suggest that 5-HETE works as an Nrf2 activator through the metabolite 5-oxo-ETE in HUVECs. Similarly, 5-HEPE works in the same way, because 5-HEPE is metabolized to 5-oxo-eicosapentaenoic acid through the same pathway as that for 5-HETE.

Non-alcoholic fatty liver disease (NAFLD) affects more than 70% of patients with type 2 diabetes mellitus (T2DM) and has become one of the most common metabolic liver diseases worldwide. To date, treatments specifically targeting NAFLD do not exist. Oxidative stress and insulin resistance have been implicated in the pathogenesis of NAFLD in diabetes. Accordingly, the goal of this present study was to determine whether Ellagic acid (EA), a natural antioxidant polyphenol found in berries and nuts, mitigates hepatic oxidative stress and insulin resistance in T2DM rats, and thus alleviates NAFLD. Using adult female Goto Kakizaki (GK) rats, a non-obese and spontaneous model of T2DM, we found that EA treatment significantly lowered fasting blood glucose and reduced insulin resistance, as shown by a 21.8% reduction in the homeostasis model assessment index of insulin resistance (HOMA-IR), while triglyceride and total cholesterol levels remained unchanged. Increased hepatic lipid accumulation and oxidative stress present in diabetic GK rats was markedly reduced with EA treatment. This effect was associated with a downregulation of the NADPH oxidase subunit, p47-phox, and overexpression of NF-E2-related factor-2 (NRF2). Moreover, EA was able to decrease the hepatic expression of hypoxia-inducible factor (HIF-α), a transcription factor linked to hypoxia and hepatic steatosis. We further showed that EA treatment activated an insulin signaling pathway in the liver, as evidenced by increased levels of phosphorylated Akt (Ser 473). In conclusion, our results demonstrate that EA diminishes blood glucose levels and potently suppress NAFLD in diabetic rats via mechanisms that involve reductions in p47-phox and HIF-α, upregulation of NRF2 and enhancement of the Akt signaling pathway in the liver. Together, these results reveal that EA improves hepatic insulin sensitivity and lipid metabolism as a result of its antioxidant effects. This implies an anti-diabetic effect of EA with beneficial effects for the treatment of hepatic complications in T2DM.

This study was designed to investigate the hepatoprotective effect of bamboo stems using in vitro and in vivo experimental liver damage models. Ethyl acetate fraction of 80% ethanol extract of Phyllostachys nigra stem (PN3) containing polyphenols had a higher NQO1-ARE reporter gene activity as monitored by the activity of the NF-E2-related factor (Nrf2) antioxidant pathway in cells in comparison to extracts from other species and under other conditions. The Nrf2 was translocated from the cytosol to the nucleus in response to PN3, followed by induction of the Nrf2 target gene expression, including HO-1, GCL, and NQO-1 in HepG2 cells. Phosphorylation of Nrf2 in HepG2 cells was enhanced in PN3, which was mediated by PKCδ, ERK, and p38 MAPK. Consequently, PN3 inhibited arachidonic acid (AA) + iron-induced reactive oxygen species generation and glutathione depletion, and, thus, highlighted their role in cytotoxicity. Treatment with major polyphenols of PN3, including catechin, chlorogenic acid, caffeic acid, and p-coumaric acid, also improved AA + iron-mediated oxidative stress and, thus, improved cell viability. Treatment with phenylhydrazine in mice, i.e., the iron overload liver injury model, increased plasma alanine aminotransferase and aspartate aminotransferase levels and changed histological features in mice-a response that was almost completely blocked by PN3 administration. Moreover, PN3 extract mitigated phenylhydrazine-induced oxidative stress and inflammatory responses. Conclusively, PN3 can exert a hepatoprotective effect against iron overload-induced acute liver damage due to its antioxidant properties.