Nrf2 protects against furosemide-induced hepatotoxicity

Ganoderma lucidum Polysaccharides Ameliorate Acetaminophen-Induced Acute Liver Injury by Inhibiting Oxidative Stress and Apoptosis along the Nrf2 Pathway

The excessive employment of acetaminophen (APAP) is capable of generating oxidative stress and apoptosis, which ultimately result in acute liver injury (ALI). Ganoderma lucidum polysaccharides (GLPs) exhibit hepatoprotective activity, yet the protective impact and potential mechanism of GLPs in relation to APAP-induced ALI remain ambiguous. The intention of this research was to scrutinize the effect of GLPs on APAP-induced ALI and to shed light on their potential mechanism. The results demonstrated that GLPs were capable of notably alleviating the oxidative stress triggered by APAP, as shown through a significant drop in the liver index, the activities of serum ALT and AST, and the amounts of ROS and MDA in liver tissue, along with an increase in the levels of SOD, GSH, and GSH-Px. Within these, the hepatoprotective activity at the high dose was the most conspicuous, and its therapeutic efficacy surpassed that of the positive drug (bifendate). The results of histopathological staining (HE) and apoptosis staining (TUNEL) indicated that GLPs could remarkably inhibit the necrosis of hepatocytes, the permeation of inflammatory cells, and the occurrence of apoptosis induced by APAP. Moreover, Western blot analysis manifested that GLPs enhanced the manifestation of Nrf2 and its subsequent HO-1, GCLC, and NQO1 proteins within the Nrf2 pathway. The results of qPCR also indicated that GLPs augmented the expression of antioxidant genes Nrf2, HO-1, GCLC, and NQO1. The results reveal that GLPs are able to set off the Nrf2 signaling path and attenuate ALI-related oxidative stress and apoptosis, which is a potential natural medicine for the therapy of APAP-induced liver injury.

Restoration and preservation effects of mung bean antioxidant peptides on H2O2-induced WRL-68 cells via Keap1-Nrf2 pathway

Mung bean antioxidant peptides (MBAPs) were prepared from mung bean protein hydrolysate, and four peptide sequences including Ser-Asp-Arg-Thr-Gln-Ala-Pro-His (~953 Da), Ser-His-Pro-Gly-Asp-Phe-Thr-Pro-Val (~956 Da), Ser-Asp-Arg-Trp-Phe (~710 Da), and Leu-Asp-Arg-Gln-Leu (~644 Da) were identified. The effects of MBAPs on the oxidation-induced normal human liver cell line WRL-68 were analyzed to determine the mechanism protecting the oxidation-induced injury. The results showed that the cells were subjected to certain oxidative damage by H2O2 induction, as evidenced by decreased cell number and viability, overproduction of intracellular ROS, and decreased mitochondrial membrane potential. Compared with the H2O2-induced group, the MBAP-treated oxidation-induced group exhibited significantly higher cell number and viability, and the intracellular ROS was similar to that of the control group, suggesting that MBAP scavenges excessive intracellular free radicals after acting on the oxidation-induced cells. Combined with Western blotting results, it was concluded that the MBAP-treated oxidation-induced group also significantly promoted the expression of proteins related to the kelch-like ech-related protein 1 (Keap1)/ nuclear factor e2-related factor 2 (Nrf2) signaling pathway, which resulted in an approximately 2-fold increase in antioxidant enzymes, and a decrease in malondialdehyde content of approximately 55% compared to oxidatively-induced cells, leading to the recovery of both cell morphology and viability. These results suggest that MBAPs scavenge intracellular free radicals and improve oxidative stress in hepatocytes through the expression of Keap1/Nrf2 pathway-related protein, thereby reducing oxidative attack on the liver. Therefore, MBAP is applied as a nutritional ingredient in the functional food field, and this study provides a theoretical basis for the high utilization of mung bean proteins.

The role of Nrf2 signaling pathway in the mud crab (Scylla paramamosain) in response to Vibrio parahaemolyticus infection

The transcription factor Nrf2 plays vital roles in detoxification and antioxidant enzymes against oxidative stress. However, the function of Nrf2 in crustaceans is not well studied. In this study, a novel Nrf2 gene from the mud crab (Sp-Nrf2) was identified. It was encoded 245 amino acids. Sp-Nrf2 expression was ubiquitously expressed in all tested tissues, with the highest expression level in the gill. Sp-Nrf2 protein was mainly located in the nucleus. The expression levels of Sp-Nrf2, and antioxidant-related genes (HO-1 and NQO-1) were induced after Vibrio parahaemolyticus infection, indicating that Nrf2 signaling pathway was involved in the responses to bacterial infection. Over-expression of Sp-Nrf2 could improve cell viability after H₂O₂ exposure, indicating that Sp-Nrf2 might relieve oxidative stress. Silencing of Sp-Nrf2 in vivo decreased HO-1 and NQO-1 expression. Moreover, knocking down Sp-Nrf2 in vivo can increase malondialdehyde content and the mortality of mud crabs after V. parahaemolyticus infection. Our results indicated that Nrf2 signaling pathway played a significant role in immune response against bacterial infection.

Immunomodulatory Potential of Diuretics

In this review, diuretics and their immunomodulatory functions are described. The effects on the immune response of this group of drugs are reported in patients suffering from hypertension and under experimental conditions involving animal models and cell line studies. The pathogenesis of hypertension is strongly connected to chronic inflammation. The vast majority of diuretics modulate the immune response, changing it in favor of the anti-inflammatory response, but depending on the drug, these effects may differ. This topic is significantly important in medical practice regarding the treatment of patients who have coexisting diseases with chronic inflammatory pathogenesis, including hypertension or chronic heart failure. In patients with metabolic syndrome, allergies, or autoimmune disorders, the anti-inflammatory effect is favorable, because of the overstimulation of their immune system. Otherwise, in the geriatric population, it is important to find the proper anti- and pro-inflammatory balance to avoid an enhancement of immune response suppression, which can result in reducing the risk of serious infections that can occur due to the age-diminished function of the immune system. This article is intended to facilitate the selection of an antihypertensive drug that depends on the patient's immune situation.

Modeling the Bioactivation and Subsequent Reactivity of Drugs

Electrophilically reactive drug metabolites are implicated in many adverse drug reactions. In this mechanism-termed bioactivation-metabolic enzymes convert drugs into reactive metabolites that often conjugate to nucleophilic sites within biological macromolecules like proteins. Toxic metabolite-product adducts induce severe immune responses that can cause sometimes fatal disorders, most commonly in the form of liver injury, blood dyscrasia, or the dermatologic conditions toxic epidermal necrolysis and Stevens-Johnson syndrome. This study models four of the most common metabolic transformations that result in bioactivation: quinone formation, epoxidation, thiophene sulfur-oxidation, and nitroaromatic reduction, by synthesizing models of metabolism and reactivity. First, the metabolism models predict the formation probabilities of all possible metabolites among the pathways studied. Second, the exact structures of these metabolites are enumerated. Third, using these structures, the reactivity model predicts the reactivity of each metabolite. Finally, a feedfoward neural network converts the metabolism and reactivity predictions to a bioactivation prediction for each possible metabolite. These bioactivation predictions represent the joint probability that a metabolite forms and that this metabolite subsequently conjugates to protein or glutathione. Among molecules bioactivated by these pathways, we predicted the correct pathway with an AUC accuracy of 89.98%. Furthermore, the model predicts whether molecules will be bioactivated, distinguishing bioactivated and nonbioactivated molecules with 81.06% AUC. We applied this algorithm to withdrawn drugs. The known bioactivation pathways of alclofenac and benzbromarone were identified by the algorithm, and high probability bioactivation pathways not yet confirmed were identified for safrazine, zimelidine, and astemizole. This bioactivation model-the first of its kind that jointly considers both metabolism and reactivity-enables drug candidates to be quickly evaluated for a toxicity risk that often evades detection during preclinical trials. The XenoSite bioactivation model is available at http://swami.wustl.edu/xenosite/p/bioactivation.

Roots and stems of Kadsura coccinea extract induced developmental toxicity in zebrafish embryos/larvae through apoptosis and oxidative stress

CONTEXT

Although the roots and stems of Kadsura coccinea (Lem.) A. C. Smith. [Schisandraceae] are herbs and traditional foods in Li nationality, its toxicity remains unclear.

OBJECTIVE

To study developmental toxicity of K. coccinea consumption and explain underlying mechanisms.

MATERIALS AND METHODS

Zebrafish were applied to assess LC₅₀ values of hydroethanol extract (KCH) and water extract (KCW) of Kadsura coccinea. In further study, three concentrations groups of KCH (3.75, 7.5 and 15 μg/mL for embryo, 7.5, 15 and 30 μg/mL for larvae) and control group (n = 30) were administered. At specific stages of zebrafish development, spontaneous movement, hatching rate, etc., were measured. Gene expressions related to developmental toxicity were examined.

RESULTS

The LC₅₀ value of KCH (24 or 45 μg/mL) was lower than KCW (1447 or 2011 μg/mL) in embryos or larvae. The inhibited spontaneous movement (20%), hatching rate (20%), body length (12%) and eye area (30%) were observed after KCH treatment. Moreover, the decreased liver areas (25%) and fluorescence intensity (33%), increased ALT (37%) and AST levels (42%) were found in larvae treated with KCH (30 μg/mL). The increased ROS (89%), MDA concentrations (30%), apoptosis generation (62%) and decreased T-SOD activity (16%) were also observed. The represented genes of developmental hepatotoxicity, oxidative stress and apoptosis in zebrafish were activated after KCH (15 or 30 μg/mL) treatment.

DISCUSSION AND CONCLUSIONS

These results demonstrate that KCH has developmental toxicity on zebrafish. Our study provides a scientific basis for further research on the toxicity of Kadsura coccinea.

Nrf2 in Neoplastic and Non-Neoplastic Liver Diseases

Simple Summary

Although the Keap1-Nrf2 pathway represents a powerful cell defense mechanism against a variety of toxic insults, its role in acute or chronic liver damage and tumor development is not completely understood. This review addresses how Nrf2 is involved in liver pathophysiology and critically discusses the contrasting results emerging from the literature. The aim of the present report is to stimulate further investigation on the role of Nrf2 that could lead to define the best strategies to therapeutically target this pathway.

Abstract

Activation of the Keap1/Nrf2 pathway, the most important cell defense signal, triggered to neutralize the harmful effects of electrophilic and oxidative stress, plays a crucial role in cell survival. Therefore, its ability to attenuate acute and chronic liver damage, where oxidative stress represents the key player, is not surprising. On the other hand, while Nrf2 promotes proliferation in cancer cells, its role in non-neoplastic hepatocytes is a matter of debate. Another topic of uncertainty concerns the nature of the mechanisms of Nrf2 activation in hepatocarcinogenesis. Indeed, it remains unclear what is the main mechanism behind the sustained activation of the Keap1/Nrf2 pathway in hepatocarcinogenesis. This raises doubts about the best strategies to therapeutically target this pathway. In this review, we will analyze and discuss our present knowledge concerning the role of Nrf2 in hepatic physiology and pathology, including hepatocellular carcinoma. In particular, we will critically examine and discuss some findings originating from animal models that raise questions that still need to be adequately answered.

Polysaccharide from Echinacea purpurea reduce the oxidant stress in vitro and in vivo

Echinacea purpurea polysaccharides (EPPS) were extracted through water extract and alcohol precipitate method. Three polysaccharides were purified by DEAE cellulose, named EPPS-1, EPPS-2 and EPPS-3. The antioxidant activities in three polysaccharides were screened by free radical scavenging test and EPPS-3 possessed the best antioxidant function. Then the antioxidant activities of EPPS-3 were further explored in oxidative damage model in vitro and in vivo for the first time. The results showed that the antioxidases and the metabolism content were significantly improved in EPPS-3 group. EPPS-3 could protect hepatic tissue from the injury of CCl₄ compared with the oxidative damage model. The mechanism research demonstrated that EPPS-3 restrained cell apoptosis and promoted Nrf2 cell signal pathway to play an antioxidant impact. Therefore, EPPS-3 an ingredient could be served as amazing gift for food industry and feed additive.

Discovery of natural flavonoids as activators of Nrf2-mediated defense system: Structure-activity relationship and inhibition of intracellular oxidative insults

Continuous overproduction of reactive oxygen species (ROS), termed as oxidative stress, plays a crucial role in the onset and progression of many human diseases. Activation of nuclear transcription factor erythroid 2-related factor (Nrf2) by small molecules could eliminate ROS, and thus block the pathogenesis of oxidative stress-induced diseases. In this study, a natural flavonoid library was established and tested for their potential Nrf2 inducing effects. Based on QR inducing effect of flavonoids, their structure-activity relationship (SAR) on Nrf2 induction was summarized, and twenty flavonoids were firstly identified to be potential activators of Nrf2-mediated defensive response. Then, 7-O-methylbiochanin A (7-MBA) was further investigated for its capability on the Nrf2 activation and prevention against oxidative insults in human lung epithelial cells. Further studies indicated that 7-MBA activated Nrf2 signaling pathway and protected human lung epithelial Beas-2B cells against sodium arsenite [As(III)]-induced cytotoxicity in an Nrf2-dependent manner. Activation of Nrf2 by 7-MBA upregulated intracellular antioxidant capacity, which was produced by enhancement of Nrf2 stabilization, blockage of Nrf2 ubiquitination, as well as Nrf2 phosphorylation by mitogen-activated protein kinase (MAPK), protein kinase C (PKC), protein kinase R-like endoplasmic reticulum kinase (PERK), and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). Taken together, 7-MBA is a novel isoflavone-type Nrf2 activator displaying potential preventive effect against oxidative damages in human lung epithelial cells.

Detoxifying effect of pyridoxine on acetaminophen-induced hepatotoxicity via suppressing oxidative stress injury

The detoxifying effect of pyridoxine against acetaminophen (APAP)-induced hepatotoxicity was investigated. HepG2 cells were co-treated with APAP and pyridoxine to compare with betaine or methionine for 24 h. LDH, ALT and AST activities were measured to determine direct cells damage in vitro and in vivo. Lipid peroxidation, antioxidant enzymes activity, and glutathione level were measured. Cytochrome c releaseand procaspase-3, cleaved caspase-3, Bcl-2, or Bax protein levels were measured to determine APAP-induced apoptotic cell death. Pyridoxine treatment significantly increased cell viability and decreased leakage of LDH activity against APAP-induced hepatotoxicity in HepG2 cells. ALT and AST activities were dose-dependently reduced by pyridoxine treatment compared to APAP-treated group. Significant increases in activities of GST and GPx were observed after co-treatment with APAP and pyridoxine. Although APAP-induced Nrf2 and HO-1 expression levels were gradually reduced in HepG2 cells by pyridoxine treatment, induction of antioxidant enzymes activities were dose-dependently increased. These protected effects of pyridoxine against APAP-induced hepatoxicity were closely associated with suppression of APAP-induced oxidative stress and apoptotic cell death in HepG2 cells. These data indicated that the protective action of pyridoxine against hepatic cell injuries was involved in the direct antioxidant activity which provides a pivotal mechanism for its potential hepatoprotective action.

A multi-functional nanoplatform for efficacy tumor theranostic applications

Nanomaterials with multiple functions have become more and more popular in the domain of cancer research. MoS₂ has a great potential in photothermal therapy, X-ray/CT imaging and drug delivery. In this study, a water soluble MoS₂ nanosystem (MoS₂-PEG) was synthesized and explored in drug delivery, photothermal therapy (PTT) and X-ray imaging. Doxorubicin (DOX) was loaded onto MoS₂-PEG with a high drug loading efficiency (~69%) and obtained a multifunctional drug delivery system (MoS₂-PEG/DOX). As the drug delivery, MoS₂-PEG/DOX could efficiently cross the cell membranes, and escape from the endosome via NIR light irradiation, lead to more apoptosis in MCF-7 cells, and afford higher antitumor efficacy without obvious toxic effects to normal organs owing to its prolonged blood circulation and 11.6-fold higher DTX uptake of tumor than DOX. Besides, MoS₂-PEG/DOX not only served as a drug delivery system, but also as a powerful PTT agent for thermal ablation of tumor and a strong X-ray contrast agent for tumor diagnosis. In the in vitro and in vivo studies, MoS₂-PEG/DOX exhibited excellent tumor-targeting efficacy, outstanding synergistic anti-cancer effect of photothermal and chemotherapy and X-ray imaging property, demonstrating that MoS₂-PEG/DOX had a great potential for simultaneous diagnosis and photothermal-chemotherapy in cancer treatment.

Role of endoplasmic reticulum stress in drug-induced toxicity

Drug‐induced toxicity is a key issue for public health because some side effects can be severe and life‐threatening. These adverse effects can also be a major concern for the pharmaceutical companies since significant toxicity can lead to the interruption of clinical trials, or the withdrawal of the incriminated drugs from the market. Recent studies suggested that endoplasmic reticulum (ER) stress could be an important event involved in drug liability, in addition to other key mechanisms such as mitochondrial dysfunction and oxidative stress. Indeed, drug‐induced ER stress could lead to several deleterious effects within cells and tissues including accumulation of lipids, cell death, cytolysis, and inflammation. After recalling important information regarding drug‐induced adverse reactions and ER stress in diverse pathophysiological situations, this review summarizes the main data pertaining to drug‐induced ER stress and its potential involvement in different adverse effects. Drugs presented in this review are for instance acetaminophen (APAP), arsenic trioxide and other anticancer drugs, diclofenac, and different antiretroviral compounds. We also included data on tunicamycin (an antibiotic not used in human medicine because of its toxicity) and thapsigargin (a toxic compound of the Mediterranean plant Thapsia garganica) since both molecules are commonly used as prototypical toxins to induce ER stress in cellular and animal models.

Evaluation of kudzu root extract-induced hepatotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE

Kudzu root, the root of Pueraria lobata (Willd.) Ohwi, has been used as food and medicine for centuries, but few studies indicate that kudzu root may cause liver damage.

AIM OF STUDY

We studied the hepatotoxicity of kudzu root extract in mice, HepG2 cells and mice hepatocytes.

MATERIALS AND METHODS

Mice were administrated with kudzu root extract (10mg/day) for 4 weeks, and then the biochemical analysis and histopathological changes were carried out. To explore the potential mechanism by which kudzu root extract-induced hepatotoxicity, HepG2 cells and mice hepatocytes were co-cultured with kudzu root extract or puerarin, which is a kudzu root isoflavone, for 2h.

RESULTS

The increase of serum ALT and AST and histopathological changes in treated mice revealed that kudzu root extract was hepatotoxic. The increase of LDH leakage for HepG2 cells and mice hepatocytes further confirmed hepatotoxicity of kudzu root extract. Kudzu root extract and puerarin significantly up-regulated Mt1 mRNA involved in the acute phase response and Bax which is crucial for apoptosis. Gclc, Nrf2 and Ho-1 mRNA expressions did not change in treatment group.

CONCLUSIONS

Kudzu root extract may be hepatotoxic and caution may be required for its use.

Keap1-Nrf2 pathway: A promising target towards lung cancer prevention and therapeutics

Objectives

Drugs for targeted therapy have become a new strategy of adjuvant therapy for treatment of lung cancer. The Keap1 (kelch-like ECH-associated protein 1)–Nrf2 (nuclear factor erythroid 2-related factor 2) pathway is recognized to be critical in regulating genes related to the cellular protective response and protecting cells from oxidative damages and toxic insult.

Methods

Pubmed, Embase, OVID, and the Cochrane Library databases were searched from the beginning of each database without any limitations to the date of publication. Search terms were “Nrf2” or “Keap1” and “Lung cancer”.

Results

The upregulation of Nrf2 had been closely related to tumor protection and drug resistance. The aberrant state of Keap1 or Nrf2 that were frequently found in lung cancer conferred a poor prognosis. Nrf2 could prevent cells from undergoing oncogenesis as a tumor suppressor, while it could also promote cancer progression and resistance to chemotherapeutic drugs as an oncogene, depending on the different stages of tumor progression. Target Nrf2 signaling by specific chemicals showed it could prevent tumor growth or combat chemoresistance.

Conclusions

Increasing evidence has demonstrated the dual roles of the Keap1–Nrf2 pathway in tumor initiation and progression. In this paper, we provide a comprehensive overview of the potency of the Keap1–Nrf2 pathway as an antitumor target, and the current status of Nrf2 activators or inhibitors for therapeutic approaches. Further studies are required to clarify the role of Nrf2 in lung cancer at different tumor stages, in order to maximize the efficacy of Keap1–Nrf2 targeting agents.

Discovery of direct inhibitors of Keap1-Nrf2 protein-protein interaction as potential therapeutic and preventive agents

The Keap1–Nrf2–ARE pathway is an important antioxidant defense mechanism that protects cells from oxidative stress and the Keap1–Nrf2 protein–protein interaction (PPI) has become an important drug target to upregulate the expression of ARE-controlled cytoprotective oxidative stress response enzymes in the development of therapeutic and preventive agents for a number of diseases and conditions. However, most known Nrf2 activators/ARE inducers are indirect inhibitors of Keap1–Nrf2 PPI and they are electrophilic species that act by modifying the sulfhydryl groups of Keap1׳s cysteine residues. The electrophilicity of these indirect inhibitors may cause "off-target" side effects by reacting with cysteine residues of other important cellular proteins. Efforts have recently been focused on the development of direct inhibitors of Keap1–Nrf2 PPI. This article reviews these recent research efforts including the development of high throughput screening assays, the discovery of peptide and small molecule direct inhibitors, and the biophysical characterization of the binding of these inhibitors to the target Keap1 Kelch domain protein. These non-covalent direct inhibitors of Keap1–Nrf2 PPI could potentially be developed into effective therapeutic or preventive agents for a variety of diseases and conditions.

The role of the c-Jun N-terminal kinases 1/2 and receptor-interacting protein kinase 3 in furosemide-induced liver injury

1. The mechanisms of furosemide (FS) hepatotoxicity were explored in mice. Specifically, C57Bl/6 J mice were treated with 500 mg FS/kg bodyweight, and c-Jun N-terminal kinase (JNK) activation and receptor-interacting protein kinase 3 (RIP3) expression were measured by western blotting. Co-treatment with FS and the JNK inhibitor SP600125 was also performed, and FS-induced liver injury was compared in wild-type and RIP3 knockout (KO) mice. 2. JNK phosphorylation and RIP3 expression were increased in livers from the FS-treated mice as early as 6 h after treatment and persisted until at least 24 h. JNK phosphorylation was also observed in primary mouse hepatocytes and human HepaRG cells treated with FS. 3. Phosphorylated JNK translocated into mitochondria in livers, but no evidence of mitochondrial damage was observed. 4. SP600125-treated mice, SP600125 co-treated primary mouse hepatocytes and RIP3 KO mice were not protected against FS hepatotoxicity. These data show that, although JNK activation and RIP3 expression are induced by FS, neither contributes to the liver injury.