Regulation of Sirt1/Nrf2/TNF-α signaling pathway by luteolin is critical to attenuate acute mercuric chloride exposure induced hepatotoxicity

An update of Nrf2 activators and inhibitors in cancer prevention/promotion

NF-E2-related factor 2 (Nrf2) protein is a basic-region leucine zipper transcription factor that defends against endogenous or exogenous stressors. By inducing several cytoprotective and detoxifying gene expressions, Nrf2 can increase the sensitivity of the cells to oxidants and electrophiles. Transient Nrf2 activation, by its specific activators, has protective roles against carcinogenesis and cancer development. However, permanent activation of Nrf2 promotes various cancer properties, comprising malignant progression, chemo/radio resistance, and poor patient prognosis. Taken together, these findings suggest that reaching an optimal balance between paradoxical functions of Nrf2 in malignancy may render a selective improvement to identify therapeutic strategies in cancer treatment. In this review, we describe lately discovered Nrf2 inducers and inhibitors, and their chemopreventive and/or anticancer activities.

The Nrf2 pathway signifies one of the most significant cell defense procedures against exogenous or endogenous stressors. Certainly, by increasing the expression of several cytoprotective genes, the transcription factor Nrf2 can shelter cells and tissues from multiple sources of damage including electrophilic, xenobiotic, metabolic, and oxidative stress. Notably, the aberrant activation or accumulation of Nrf2, a common event in many tumors, confers a selective advantage to cancer cells and is connected to malignant progression, therapy resistance, and poor prognosis. Therefore, lately, Nrf2 has arisen as a hopeful target in treatment of cancer, and many struggles have been made to detect therapeutic strategies intended at disrupting its pro-oncogenic role. By summarizing the outcomes from past and recent studies, this review provided an overview concerning the Nrf2 pathway and the molecular mechanisms causing Nrf2 hyperactivation in cancer cells. Finally, this paper also described some of the most promising therapeutic approaches that have been successfully employed to counteract Nrf2 activity in tumors, with a particular emphasis on the development of natural compounds and the adoption of drug repurposing strategies.

Dietary phenolic-type Nrf2-activators: implications in the control of toxin-induced hepatic disorders

Numerous studies have exemplified the importance of nuclear factor erythroid 2-related factor 2 (Nrf2) activation in the alleviation of toxin-induced hepatic disorders primarily through eliminating oxidative stress. Whereafter, increasingly more efforts have been contributed to finding Nrf2-activators, especially from dietary polyphenols. The present review summarized the phenolic-type Nrf2-activators published in the past few decades, analyzed their effectiveness based on their structural characteristics and outlined their related mechanisms. It turns out that flavonoids are the largest group of phenolic-type Nrf2-activators, followed by nonflavonoids and phenolic acids. When counting on subgroups, the top three types are flavonols, flavones, and hydroxycinnamic acids, with curcuminoids having the highest effective doses. Moreover, most polyphenols work through the phosphorylation of Nrf2. Besides, mitogen-activated protein kinases (MAPKs) and protein kinase B (Akt) are the frequent targets of these Nrf2-activators, which indirectly mediate the behavior of Nrf2. However, current data are not sufficient to conclude any structure-activity relationship.

Post-treatment With Irisin Attenuates Acute Kidney Injury in Sepsis Mice Through Anti-Ferroptosis via the SIRT1/Nrf2 Pathway

Kidney is one of the most vulnerable organs in sepsis, resulting in sepsis-associated acute kidney injury (SA-AKI), which brings about not only morbidity but also mortality of sepsis. Ferroptosis is a new kind of death type of cells elicited by iron-dependent lipid peroxidation, which participates in pathogenesis of sepsis. The aim of this study was to verify the occurrence of ferroptosis in the SA-AKI pathogenesis and demonstrate that post-treatment with irisin could restrain ferroptosis and alleviate SA-AKI via activating the SIRT1/Nrf2 signaling pathway. We established a SA-AKI model by cecal ligation and puncture (CLP) operation and an in vitro model in LPS-induced HK2 cells, respectively. Our result exhibited that irisin inhibited the level of ferroptosis and ameliorated kidney injury in CLP mice, as evidenced by reducing the ROS production, iron content, and MDA level and increasing the GSH level, as well as the alteration of ferroptosis-related protein (GPX4 and ACSL4) expressions in renal, which was consistent with the ferroptosis inhibitor ferrostatin-1 (Fer-1). Additionally, we consistently observed that irisin inhibited ROS accumulation, iron production, and ameliorated mitochondrial dysfunction in LPS-stimulated HK-2 cells. Furthermore, our result also revealed that irisin could activate SIRT1/Nrf2 signaling pathways both in vivo and vitro. However, the beneficial effects of irisin were weakened by EX527 (an inhibitor of SIRT1) in vivo and by SIRT1 siRNA in vitro. In conclusion, irisin could protect against SA-AKI through ferroptotic resistance via activating the SIRT1/Nrf2 signaling pathway.

Activation of the GPX4/TLR4 Signaling Pathway Participates in the Alleviation of Selenium Yeast on Deltamethrin-Provoked Cerebrum Injury in Quails

Deltamethrin (DLM) is a member of pyrethroid pesticide widely applied for agriculture and aquaculture, and its residue in the environment seriously threatens the bio-safety. The cerebrum might be vulnerable to pesticide-triggered oxidative stress. However, there is no specific antidote for treating DLM-triggered cerebral injury. Selenium (Se) is an essential trace element functionally forming selenoprotein glutathione peroxidase (GPX) in antioxidant defense. Se yeast (SY) is a common and effective organic form of Se supplement with high selenomethionine content. Accordingly, this study focused on investigating the therapeutic potential of SY on DLM-induced cerebral injury in quails after chronically exposing to DLM and exploring the underlying mechanisms. Quails were treated with/without SY (0.4 mg kg^-1 SY added in standard diet) in the presence/absence of DLM (45 mg kg^-1 body weight intragastrically) for 12 weeks. The results showed SY supplementation ameliorated DLM-induced cerebral toxicity. Concretely, SY elevated the content of Se and increased GPX4 level in DLM-treated quail cerebrum. Furthermore, SY enhanced antioxidant defense system by upregulating nuclear factor-erythroid-2-related factor 2 (Nrf2) associated members. Inversely, SY diminished the changes of apoptosis- and inflammation-associated proteins and genes including toll-like receptor 4 (TLR4). Collectively, our results suggest that dietary SY protects against DLM-induced cerebral toxicity in quails via positively regulating the GPX4/TLR4 signaling pathway. GPX4 may be a potential therapeutic target for insecticide-induced biotoxicity.

Galangin Reverses H2O2-Induced Dermal Fibroblast Senescence via SIRT1-PGC-1α/Nrf2 Signaling

UV radiation and H₂O₂ are the primary factors that cause skin aging. Both trigger oxidative stress and cellular aging. It has been reported that deacetylase silent information regulator 1 (SIRT1), a longevity gene, enhances activation of NF-E2-related factor-2 (Nrf2), as well as its downstream key antioxidant gene hemeoxygenase-1 (HO-1), to protect cells against oxidative damage by deacetylating the transcription coactivator PPARγ coactivator-1α (PGC-1α). Galangin, a flavonoid, possesses anti-oxidative and anti-inflammatory potential. In the present study, we applied Ultraviolet B/H₂O₂-induced human dermal fibroblast damage as an in vitro model and UVB-induced photoaging of C57BL/6J nude mice as an in vivo model to investigate the underlying dermo-protective mechanisms of galangin. Our results indicated that galangin treatment attenuates H₂O₂/UVB-induced cell viability reduction, dermal aging, and SIRT1/PGC-1α/Nrf2 signaling activation. Furthermore, galangin treatment enhanced Nrf2 activation and nuclear accumulation, in addition to inhibiting Nrf2 degradation. Interestingly, upregulation of antioxidant response element luciferase activity following galangin treatment indicated the transcriptional activation of Nrf2. However, knockdown of SIRT1, PGC-1α, or Nrf2 by siRNA reversed the antioxidant and anti-aging effects of galangin. In vivo evidence further showed that galangin treatment, at doses of 12 and 24 mg/kg on the dorsal skin cells of nude mice resulted in considerably reduced UVB-induced epidermal hyperplasia and skin senescence, and promoted SIRT1/PGC-1α/Nrf2 signaling. Furthermore, enhanced nuclear localization of Nrf2 was observed in galangin-treated mice following UVB irradiation. In conclusion, our data indicated that galangin exerts anti-photoaging and antioxidant effects by promoting SIRT1/PGC-1α/Nrf2 signaling. Therefore, galangin is a potentially promising agent for cosmetic skin care products against UV-induced skin aging.

N-Acetylcysteine Alleviated the Deltamethrin-Induced Oxidative Cascade and Apoptosis in Liver and Kidney Tissues

Deltamethrin (DLM) is a synthetic pyrethroid with anti-acaricide and insecticidal properties. It is commonly used in agriculture and veterinary medicine. Humans and animals are exposed to DLM through the ingestion of polluted food and water, resulting in severe health issues. N-acetylcysteine (NAC) is a prodrug of L-cysteine, the precursor to glutathione. It can restore the oxidant-antioxidant balance. Therefore, this research aimed to examine whether NAC may protect broiler chickens against oxidative stress, at the level of biochemical and molecular alterations caused by DLM intoxication. The indicators of liver and kidney injury in the serum of DLM-intoxicated and NAC-treated groups were examined. Furthermore, lipid peroxidation, antioxidant markers, superoxide dismutase activity, and apoptotic gene expressions (caspase-3 and Bcl-2) were investigated. All parameters were significantly altered in the DLM-intoxicated group, suggesting that DLM could induce oxidative damage and apoptosis in hepato-renal tissue. The majority of the changes in the studied parameters were reversed when NAC therapy was used. In conclusion, by virtue of its antioxidant and antiapoptotic properties, NAC enabled the provision of significant protection effects against DLM-induced hepato-renal injury.

Crateva unilocalaris Buch. shoots attenuate D-galactose-induced brain injury and cognitive disorders of mice through PI3K/Akt/Nrf2 pathway

Crateva unilocalaris Buch. shoots are traditionally served as vegetable with many health-promoting benefits. The aim of the current investigation was designed to study the preventive effect of ethanol extract from...

Selenium alleviates mercury chloride-induced liver injury by regulating mitochondrial dynamics to inhibit the crosstalk between energy metabolism disorder and NF-κB/NLRP3 inflammasome-mediated inflammation

Mercury (Hg) is a persistent heavy metal contaminant with definite hepatotoxicity. Selenium (Se) has been shown to alleviate liver damage induced by heavy metals. Therefore, the present study aimed to explore the mechanism of the antagonistic effect of Se on mercury chloride (HgCl2)-induced hepatotoxicity in chickens. Firstly, we confirmed that Se alleviated HgCl2-induced liver injury through histopathological observation and liver function analyzation. The results also showed that Se prevented HgCl2-induced liver lipid accumulation and dyslipidemia by regulating the gene expression related to lipid as well as glucose metabolism. Moreover, Se blocked the nuclear factor kappa B (NF-κB)/NLR family pyrin domain containing 3 (NLRP3) inflammasome signaling pathway, which was the key to alleviate the inflammation caused by HgCl2. Mechanically, Se inhibited immoderate mitochondrial division, fusion, and biogenesis caused by HgCl2, and also improved mitochondrial respiration, which were essential for preventing energy metabolism disorder and inflammation. In conclusion, our results suggested that Se inhibited energy metabolism disorder and inflammation by regulating mitochondrial dynamics, thereby alleviating HgCl2-induced liver injury in chickens. These results are expected to provide potential intervention and therapeutic targets for diseases caused by inorganic mercury poisoning.

Luteolin Confers Cerebroprotection after Subarachnoid Hemorrhage by Suppression of NLPR3 Inflammasome Activation through Nrf2-Dependent Pathway

Luteolin (LUT) possesses multiple biologic functions and has beneficial effects for cardiovascular and cerebral vascular diseases. Here, we investigated the protective effects of LUT against subarachnoid hemorrhage (SAH) and the involvement of underlying molecular mechanisms. In a rat model of SAH, LUT significantly inhibited SAH-induced neuroinflammation as evidenced by reduced microglia activation, decreased neutrophil infiltration, and suppressed proinflammatory cytokine release. In addition, LUT markedly ameliorated SAH-induced oxidative damage and restored the endogenous antioxidant systems. Concomitant with the suppressed oxidative stress and neuroinflammation, LUT significantly improved neurologic function and reduced neuronal cell death after SAH. Mechanistically, LUT treatment significantly enhanced the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2), while it downregulated nod-like receptor pyrin domain-containing 3 (NLRP3) inflammasome activation. Inhibition of Nrf2 by ML385 dramatically abrogated LUT-induced Nrf2 activation and NLRP3 suppression and reversed the beneficial effects of LUT against SAH. In neurons and microglia coculture system, LUT also mitigated oxidative stress, inflammatory response, and neuronal degeneration. These beneficial effects were associated with activation of the Nrf2 and inhibitory effects on NLRP3 inflammasome and were reversed by ML385 treatment. Taken together, this present study reveals that LUT confers protection against SAH by inhibiting NLRP3 inflammasome signaling pathway, which may be modulated by Nrf2 activation.

The Antioxidant Transcription Factor Nrf2 in Cardiac Ischemia-Reperfusion Injury

Nuclear factor erythroid-2 related factor 2 (Nrf2) is a transcription factor that controls cellular defense responses against toxic and oxidative stress by modulating the expression of genes involved in antioxidant response and drug detoxification. In addition to maintaining redox homeostasis, Nrf2 is also involved in various cellular processes including metabolism and inflammation. Nrf2 activity is tightly regulated at the transcriptional, post-transcriptional and post-translational levels, which allows cells to quickly respond to pathological stress. In the present review, we describe the molecular mechanisms underlying the transcriptional regulation of Nrf2. We also focus on the impact of Nrf2 in cardiac ischemia-reperfusion injury, a condition that stimulates the overproduction of reactive oxygen species. Finally, we analyze the protective effect of several natural and synthetic compounds that induce Nrf2 activation and protect against ischemia-reperfusion injury in the heart and other organs, and their potential clinical application.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

A study on Wistar Albino rats: investigating protective role of ramelteon on liver damage caused by methotrexate

Methotrexate is an important immunosuppressive and antineoplastic drug and is widely used for treatment. However, hepatotoxicity is one of the major adverse effects of methotrexate. In this study, it was aimed to investigate whether ramelteon has a possible protective effect on hepatotoxicity induced by methotrexate. Thirty-two Wistar albino rats were equally divided into four groups: control, methotrexate, methotrexate + ramelteon, and ramelteon. Following a single dose of 20 mg/kg, methotrexate (i.p.), either saline or ramelteon 10 mg/kg (orally) was administered for 7 days. After treatment, animals were sacrificed, and histopathological analyses were evaluated with Hematoxylin-eosin (H-E), immunohistological analyses were evaluated with Interleukın-1 Beta (IL-1β) and Caspase 3 (CAS-3), biochemical analyzes were evaluated with Total Oxidant Status (TOS), Total antioxidants status (TAS), Oxidative Stress Index (OSI), aspartate aminotransferase (AST), alanine aminotransferase (ALT) activities, at last genetical analyses were evaluated with Sirtuin-1 (SIRT-1) - P53 gene expressions. In the control and ramelteon groups, normal histological structures were observed, while histopathological findings were observed in the methotrexate group. Increasing levels of IL-1β staining, CAS-3 staining, p53 gene expression, TOS, OSI, AST and ALT were observed in methotrexate group while were observed decreasing levels of TAS and SIRT-1 gene expression (p < 0.05). However, ramelteon reduced the increased findings in methotrexate-induced hepatotoxicity (p < 0.05). The results of the present study showed that ramelteon protects against methotrexate induced hepatotoxicity in rats via SIRT-1 signaling by histological, immunohistological, biochemical and genetical analyses.

Toxicological effects of deltamethrin on quail cerebrum: Weakened antioxidant defense and enhanced apoptosis

Deltamethrin is the most common type II synthetic pyrethroid insecticide, and has posed widespread residues to environment. However, whether deltamethrin has potential toxic effects on quail cerebrum remains greatly obscure. Accordingly, we investigated the impact of chronic exposure to deltamethrin on oxidative stress and apoptosis in quail cerebrum. Quails upon 12-week exposure of deltamethrin (0, 15, 30, or 45 mg/kg body weight intragastric administration) were used as a cerebrum injury model. The results showed that deltamethrin treatment led to cerebral injury dose-dependently through the weakened antioxidant defense by downregulating nuclear factor erythroid-2-related factor 2 (Nrf2) and its downstream proteins levels and mRNA expression. Furthermore, deltamethrin treatment induced apoptosis in cerebrum by decreasing B-cell lymphoma gene 2 (Bcl-2) level, as well as increasing Jun N-terminal kinase3, caspase-3, and Bcl-2-associated X protein levels. Simultaneously, toll-like receptor 4 (TLR4) downstream inflammation-related genes or proteins were significantly up-regulated by deltamethrin dose-dependently. Altogether, our study demonstrated that chronic exposure to deltamethrin induces inflammation and apoptosis in quail cerebrums by promoting oxidative stress linked to inhibition of the Nrf2/TLR4 signaling pathway. These results provide a novel knowledge on the chronic toxic effect of deltamethrin, and establish a theoretical foundation for the evaluation of pesticide-induced health risk.

The aggravation of allergic airway inflammation with dibutyl phthalate involved in Nrf2-mediated activation of the mast cells

Dibutyl phthalate (DBP)-an organic pollutant-is ubiquitous in the environment. DBP as an immune adjuvant is related to the development of multiple allergic diseases. However, the current research involving DBP-induced pulmonary toxicity remains poorly understood. Therefore, this research aimed to explore the adverse effect and potential mechanism of DBP exposure on the lungs in rats. In our study, ovalbumin was used to build a rat model of allergic airway inflammation to study any harmful effect of DBP exposure on lung tissues. Rats were treated by intragastric administration of DBP (500 mg kg^-1 or 750 mg kg^-1) and/or subcutaneous injection of SFN (4 mg kg^-1). The results of histopathological analysis, cell count, and myeloperoxidase showed that DBP promoted the inflammatory damage of lungs. In the lung tissues, the detection of terminal deoxynucleotidyl transferase dUNT nick end labeling and oxidative stress indices showed that DBP significantly increased the level of apoptosis and oxidative stress. Western blot analysis indicated that DBP raised the expression level of thymic stromal lymphopoietin and reduced the nuclear expression level of nuclear factor-erythroid-2-related factor 2 (Nrf2), which was further verified by quantitative real-time PCR. Meanwhile, DBP treatment markedly up-regulated the inflammatory cytokines such as IL-4 and IL-13, and rat mast cell protease-2, a marker secreted by mast cells (MCs). Conversely, sulforaphane, a Nrf2 inducer, ameliorated the pulmonary damage induced by DBP in the above. Altogether, our data provides a new insight into the impacts of the activation of MCs on the DBP-induced pulmonary toxicity as well as the safety evaluation of DBP.

Morin protects against acrylamide-induced neurotoxicity in rats: an investigation into different signal pathways

The presented study investigates the effects of morin against toxicity induced by acrylamide (ACR) in the brains of Sprague Dawley rats. In this study, neurotoxicity was induced by orally administering 38.27 mg/kg/b.w ACR to rats through gastric gavage for 10 days. Morin was administered at the same time and at different doses (50 and 100 mg/kg/b.w) with ACR. Biochemical and Western blot analyses showed that ACR increased malondialdehyde (MDA), p38α mitogen-activated protein kinase (p38α MAPK), nuclear factor kappa-B (NF-κB), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), p53, caspase-3, bcl-2 associated X protein (Bax), Beclin-1, light chain 3A (LC3A), and light chain 3B (LC3B) levels and decreased those of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), b-cell lymphoma-2 (Bcl-2), mammalian target of rapamycin (mTOR), phosphoinositide 3-kinase (PI3K), and protein kinase B (Akt) in brain tissue and therefore induced neurotoxicity by causing oxidative stress, inflammation, apoptosis, and autophagy. On the other hand, it was determined that morin positively affected the levels of these markers by displaying antioxidant, anti-inflammatory, anti-apoptotic, and anti-autophagic properties and had a protective effect on ACR-induced neurotoxicity. As a result, morin is an effective substance against brain damage caused by ACR, yet further studies are needed to use it effectively.

Potential Effects of Dietary Isoflavones on Drug-Induced Liver Injury

Numerous prescribed drugs and herbal and dietary supplements have been reported to cause drug-induced acute liver injury, which is a frequent cause of acute liver failure (ALF). It is a tremendous challenge with ever-increasing drug application in the medication system for huge populations. Drug-induced acute liver injury can lead to diverse pathologies similar to acute and chronic hepatitis, acute liver failure, biliary obstruction, fatty liver disease, and so on. Recently, extensive work demonstrated that isoflavones play an essential and protecting role in drug-induced liver injury (DILI). The isoflavones mediated hepatoprotection by modulating specific genes linked with control of cellular redox homeostasis and inflammatory responses. Isoflavones upregulate oxidative stress-responsive nuclear factor erythroid 2-like 2 (Nrf2), downregulate inflammatory nuclear factor-κB (NF-κB) signaling pathways, and modulate a balance between cell survival and death. Moreover, isoflavones actively inhibit the expression of cytochromes P450 (CYPs) enzyme during drug metabolism. Moreover, isoflavones are also linked with farnesoid X receptor (FXR) activation and signal transducer and activator of transcription factor 3 (STAT3) phosphorylation in hepatoprotection DILI. In vivo and in vitro studies clearly stated that isoflavones bear strong antioxidant potential and promising agents for hepatotoxicity prevention and stressed their potential role as therapeutic supplements in DILI. The current review will elaborate on isoflavones’ preventive and therapeutic potential concisely and highlight various molecular targets to exert a protective effect on DILI.

Inflammation response after the cessation of chronic arsenic exposure and post-treatment of natural astaxanthin in liver: potential role of cytokine-mediated cell-cell interactions

Ongoing groundwater arsenic contamination throughout China was first recognized in the 1960s. Groundwater arsenic contamination is a high risk for human and animal health worldwide. Apart from drinking water, diet is the second pathway for arsenic to enter the human body and eventually cause liver injury. Natural astaxanthin extracted from the green algae Haematococcus pluvialis has dominated the nutraceutical market for potential health benefits. Nevertheless, the molecular mechanism underlying the protective effect post astaxanthin against arsenic-induced hepatotoxicity remains largely obscure. In this study, we investigate the effect of natural astaxanthin (derived from Haemotococcus pluvialis) on oxidative stress and liver inflammatory response in rats after the cessation of chronic arsenic exposure. Wistar rats were given astaxanthin (250 mg kg-1) daily for 2 weeks after the cessation of exposure to sodium arsenite (300 μg L-1, drinking water, 24 weeks) by intragastric administration. The results showed that post treatment with astaxanthin attenuated liver injury induced by long-term exposure to arsenic in rats. Most importantly, post treatment with astaxanthin decreased the increasing of inflammatory cytokine NF-κB, tumor necrosis factor-α, interleukin-1β, oxidative stress level, and total arsenic content in livers of rats exposed to arsenic. In addition, post treatment with astaxanthin reversed the increasing of protein levels of alpha-smooth muscle actin and collagen Iα1, which are the activation markers of hepatic stellate cells (HSCs). Collectively, these data demonstrate that post astaxanthin treatment attenuates inflammation response in the liver after the cessation of chronic arsenic exposure via inhibition of cytokine-mediated cell-cell interactions. Daily ingestion of natural astaxanthin might be a potential and beneficial candidate for the treatment of liver damage after the cessation of chronic exposure to sodium arsenite.

Sirtuins as molecular targets, mediators, and protective agents in metal-induced toxicity

Metal dyshomeostasis, and especially overexposure, is known to cause adverse health effects due to modulation of a variety of metabolic pathways. An increasing body of literature has demonstrated that metal exposure may affect SIRT signaling, although the existing data are insufficient. Therefore, in this review we discuss the available data (PubMed-Medline, Google Scholar) on the influence of metal overload on sirtuin (SIRT) signaling and its association with other mechanisms involved in metal-induced toxicity. The existing data demonstrate that cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), aluminium (Al), hexavalent chromium (Cr^VI), manganese (Mn), iron (Fe), and copper (Cu) can inhibit SIRT1 activity. In addition, an inhibitory effect of Cd, Pb, As, and Fe on SIRT3 has been demonstrated. In turn, metal-induced inhibition of SIRT was shown to affect deacetylation of target proteins including FOXO, PGC1α, p53 and NF-kB. Increased acetylation downregulates PGC1α signaling pathway, resulting in cellular altered redox status and increased susceptibility to oxidative stress, as well as decreased mitochondrial biogenesis. Lower rates of LKB1 deacetylation may be responsible for metal-induced decreases in AMPK activity and subsequent metabolic disturbances. A shift to the acetylated FOXO results in increased expression of pro-apoptotic genes which upregulates apoptosis together with increased p53 signaling. Correspondingly, decreased NF-kB deacetylation results in upregulation of target genes of proinflammatory cytokines, enzymes, and cellular adhesion molecules thus promoting inflammation. Therefore, alterations in sirtuin activity may at least partially mediate metal-induced metabolic disturbances that have been implicated in neurotoxicity, nephrotoxicity, cardiotoxicity, and other toxic effects of heavy metals.

Antioxidant and anti-inflammatory properties of alpha-lipoic acid protect against valproic acid-induced liver injury

Valproic acid (VPA) is one of the most used antiepileptic drugs despite of its many adverse effects such as anemia, leucopenia, thrombocytopenia, and liver toxicity. The hepatoprotective effect of alpha-lipoic acid (ALA) was confirmed. The aim of this study was to detect the protective effect of ALA against the adverse effects of VPA. To study this, 30 white albino Wistar male rats were divided into four groups. Group I was the control group; Group II included rats that received ALA (100 mg·kg-1·day-1) orally for 14 days; Group III and Group IV included rats that received VPA (500 mg·kg-1·day-1) for 15 days intraperitoneally, but Group IV rats received ALA (100 mg·kg-1·day-1) orally for 14 days prior to VPA. Blood samples were collected and livers were excised from rats for colorimetric analysis and quantitative real-time PCR. The rats that received VPA showed leucopenia, thrombocytopenia, a significant decrease of superoxide dismutase, glutathione, nuclear factor erythroid 2-related factor 2, and sirtuin 1, besides a significant increase of malondialdehyde and tumor necrosis factor α. Prior treatment with ALA prevented all these results; ALA protected against VPA-induced liver damage and hematological disturbance via antioxidant and anti-inflammatory properties.

Molecular mechanism of heavy metals (Lead, Chromium, Arsenic, Mercury, Nickel and Cadmium) - induced hepatotoxicity - A review

Heavy metals pose a serious threat if they go beyond permissible limits in our bodies. Much heavy metal's viz. Lead, Chromium, Arsenic, Mercury, Nickel, and Cadmium pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. They cause the generation of ROS which in turn causes numerous injuries and undesirable changes in the liver. Epidemiological studies have shown an increase in the levels of such heavy metals in the environment posing a serious threat to human health. Epigenetic alterations have been seen in the event of exposure to such heavy metals. Apoptosis, caspase activation as well as ultrastructural changes in the hepatocytes have also been seen due to heavy metals. Inflammation involving TNF-alpha, pro-inflammatory cytokines, MAPK, ERK pathways have been seen in the event of heavy metal hepatotoxicity. All these have shown that these heavy metals pose a serious threat to human health in particular and the environment as a whole.

The protective effect of Veronica ciliata Fisch. Extracts on relieving oxidative stress-induced liver injury via activating AMPK/p62/Nrf2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Veronica ciliata Fisch. existed in various Tibetan medicine prescriptions, which was recorded to treat liver diseases in the Tibetan medicine roll of Chinese materia medica.

HYPOTHESIS/PURPOSE

The current study aimed to examine the effect of active constituents from V.ciliata relieving oxidative stress-mediated liver injury and clarify the underlying mechanism.

MATERIALS AND METHODS

tert-Butyl hydroperoxide (BHP) induced liver injury in mice model was established to evaluate the hepatoprotective effect of ethyl acetate extract of V. ciliata (EAFVC). Serum and liver indicators, as well as the histopathological change of liver were examined. Next, the constituents of EAFVC were separated and characterized by high-speed countercurrent chromatography (HSCCC) and Ultra performance liquid chromatography-mass spectrometer (UPLC-MS), respectively. Based on the above, the antioxidant activity of EAFVC and two fractions was evaluated using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2, 2'-azino-bis (3-ethylbenzothiazoli- ne-6-sulfonic acid) (ABTS) free radical scavenging assays. The hepatoprotective activity of EAFVC and its fractions/compounds attenuating ethanol-induced hepatocyte damage in BRL-3A cells was evaluated using the MTT method. The effect of the fraction and compounds with the strongest protective activity on ethanol-induced cytotoxicity, reactive oxygen species (ROS) accumulation, and glutathione (GSH) depletion was investigated. mRNA expression of nuclear factor-E2-related factor 2 (Nrf2) and nuclear factor of κB (NF-κB), as well as their downstream target genes, was determined by RT-qPCR. Finally, the potential mechanism of fraction 1 and luteolin on the AMPK/p62/Nrf2 signal pathway was studied using western blotting.

RESULTS

Firstly, EAFVC could relieve liver impairment induced by t-BHP in mice. Next, fraction 1 enriched with polyphenolic compounds and luteolin derived from EAFVC were screened to yield the highest hepatoprotective activity against ethanol-induced hepatocyte damage. Further study demonstrated that fraction 1 and luteolin relieved BRL-3A cells damage by decreasing the aspartate aminotransferase (AST), alanine transaminase (ALT) and lactate dehydrogenase (LDH) activities, ROS accumulation, as well as the depletion of GSH. Also, we determined that fraction 1 and luteolin suppressed inflammation and apoptosis of BRL-3A cells. The mechanistic studies indicated that fraction 1 could attenuate oxidative stress, inflammation, and apoptosis by activating AMPK phosphorylation, which promotes autophagy associated protein expression (LC3-B, Beclin1 and p62) as well as promote phosphorylation of p62 -dependent autophagic degradation of Keap1, to induce Nrf2 dissociation from Keap1 and translocate to nuclear. Nrf2 in the nuclear activate cytoprotective related genes to exert hepatoprotective function. Finally, we found that luteolin activated the protein expression of p-AMPK, p-p62, p62, Nrf2, and its downstream target genes.

CONCLUSIONS

This study clarified that fraction 1 enriched phenolic compounds could attenuate ethanol-induced liver injury in BRL-3A cells via activating AMPK/p62/Nrf2 pathway. Luteolin could serve as the major bioactive component in the therapeutic effect of fraction 1. These active constituents in V. ciliata could be used as the potential drugs targeted activation of AMPK or p62 for relieving oxidative stress-mediated liver disorders.

Hesperetin modulates the Sirt1/Nrf2 signaling pathway in counteracting myocardial ischemia through suppression of oxidative stress, inflammation, and apoptosis

Hesperetin (HSP) is a natural flavonoid that offers useful curative effects for cardiovascular diseases, but its effect on myocardial ischemia and its precise mechanism remains unclear. The aim of this study is to explore the potential cardioprotective mechanism of HSP on myocardial ischemia caused by isoproterenol (ISO). Adult male Kunming mice were randomly divided into five groups: control, ISO, low-dose HSP (L-HSP, 25 mg/kg/d), high-dose HSP (H-HSP, 50 mg/kg/d), and verapamil (VER) group. Treatment groups of mice received HSP or VER for seven days, and the groups other than the control group were injected with ISO (100 mg/kg/d) subcutaneously for two consecutive days to establish a model of myocardial ischemia. Electrocardiogram and heart-histology changes were used to assess changes in myocardial architecture. The activities and the content of oxidative stress markers and inflammatory cytokines were determined and assayed using kits respectively. The expressions of proteins associated with apoptosis and the Sirt1/Nrf2 pathway were evaluated by Western blotting. The results demonstrate that VER, L-HSP and H-HSP significantly reduced the J-point displacement, heart rate, cardiac pathomorphological changes, and the levels of creatine kinase, lactated dehydrogenase, malonaldehyde, interleukin-6, and tumor necrosis factor-α in serum while promoting the activation of superoxide dismutase, catalase, glutathione in serum in the ISO-treated animals. Furthermore, L-HSP and H-HSP also reversed the ISO-induced apoptosis and the changes in the Sirt1/Nrf2 signaling pathway, as evident from the levels of proteins Bax, Bcl-2, caspase-3, Sirt1, Nrf2, NQO-1, and HO-1. In conclusion, HSP plays a protective role in ISO-induced myocardial ischemia by modulating oxidative stress, inflammation, and apoptosis via Sirt1/Nrf2 pathway activation.

Ziziphus spina-christi leaf extract attenuates mercuric chloride-induced liver injury in male rats via inhibition of oxidative damage

Heavy metal contamination including mercury (Hg) has become one of the most serious environmental problems facing humans and other living organisms. Here, the hepatoprotective effects of Z. spina-christi leaf extract (ZCE) against inorganic mercury salt (mercuric chloride; HgCl₂)-induced hepatotoxicity model was investigated in rats. Mercury concentration, liver function markers, oxidative stress markers, inflammation, cell death indicators, and histopathology were assessed. ZCE protected against HgCl₂-induced hepatotoxicity, decreased Hg concentration, lipid peroxidation, and nitric oxide, increased glutathione, superoxide dismutase, catalase, and glutathione recycling enzymes (peroxidase and reductase), and upregulated nuclear factor-erythroid 2-related factor 2 (Nrf2) gene expression in HgCl₂-intoxicated rat hepatic tissue. Nrf2 downstream gene and heme oxygenase-1 were also upregulated, confirming that hepatoprotection by ZCE against HgCl₂-induced liver damage involved activation of the Nrf2/antioxidant response element pathway. ZCE also decreased the expression and production of pro-inflammatory cytokines and pro-apoptotic proteins and increased anti-apoptotic protein Bcl-2. Immunohistochemical analysis of liver tissues of HgCl₂-treated rats confirmed the alternations of apoptotic-related protein expression. Our data demonstrated that post-administration of ZCE attenuated HgCl₂-induced liver damage by activating the Nrf2/HO-1 signaling pathway. Therefore, administering this extract may be a novel therapeutic strategy for inorganic mercury intoxication.

Vitamin E and Lactobacillus Provide Protective Effects Against Liver Injury Induced by HgCl2: Role of CHOP, GPR87, and mTOR Proteins

BACKGROUND AND OBJECTIVE

Mercury is one of the most harmful heavy metals and its toxicity causes severe multi-organ dysfunction. This study was designed to explore novel molecular pathways involved in the hepatoprotective effect of vitamin E (Vit-E) and Lactobacillius plantarum (Lac-B) against mercury toxicity.

METHOD

Acute hepatotoxicity was induced by administration of high dose of mercuric chloride (HgCl2) in male rats, Vit-E or/and Lac-B were given along with HgCl2 for 2 weeks. The effects of those antioxidants were studied focusing on their anti-apoptotic, anti-oxidative stress and anti-inflammatory eficacies. Histopathological examinations were also conducted.

RESULTS

The administration of HgCl2 induced liver injury which manifested by elevation in serum ALT and AST. Liver MDA, caspase-3 and TNF-α levels were markedly increased; whereas, GSH level and SOD activity were declined. HgCl2 significantly elevated the expressions of hepatic CHOP, GPR87, NF-κB and mTOR. Histopathological examination revealed massive hepatocyte degeneration following HgCl2 administration. Treatment with Vit-E or/and Lac-B restored the normal levels of the previously mentioned parameters, as well as improved hepatic architecture.

CONCLUSION

Vit-E and Lac-B provided protective effect against HgCl2-induced hepatotoxicity via reduction of oxidative stress and inflammation, and downregulation of CHOP, GPR87, NF-κB and mTOR proteins' expressions.

Identification of Beilschmiedia tsangii Root Extract as a Liver Cancer Cell-Normal Keratinocyte Dual-Selective NRF2 Regulator

Transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) plays a crucial role in regulating the expression of genes participating in cellular defense mechanisms against oxidative or xenobiotic insults. However, there is increasing evidence showing that hyperactivation of NRF2 is associated with chemoresistance in several cancers, including hepatocellular carcinoma (HCC), thus making NRF2 an attractive target for cancer therapy. Another important issue in cancer medication is the adverse effects of these substances on normal cells. Here, we attempted to identify a dual-selective NRF2 regulator that exerts opposite effects on NRF2-hyperactivated HCC cells and normal keratinocytes. An antioxidant response element driven luciferase reporter assay was established in Huh7 and HaCaT cells as high-throughput screening platforms. Screening of 3,000 crude extracts from the Taiwanese Indigenous Plant Extract Library resulted in the identification of Beilschmiedia tsangii (BT) root extract as a dual-selective NRF2 regulator. Multiple compounds were found to contribute to the dual-selective effects of BT extract on NRF2 signaling in two cell lines. BT extract reduced NRF2 protein level and target gene expression levels in Huh7 cells but increased them in HaCaT cells. Furthermore, notable combinatory cytotoxic effects of BT extract and sorafenib on Huh7 cells were observed. On the contrary, sorafenib-induced inflammatory reactions in HaCaT cells were reduced by BT extract. In conclusion, our results suggest that the combination of a selective NRF2 activator and inhibitor could be a practical strategy for fine-tuning NRF2 activity for better cancer treatment and that plant extracts or partially purified fractions could be a promising source for the discovery of dual-selective NRF2 regulators.

Berberine ameliorates doxorubicin-induced cognitive impairment (chemobrain) in rats

AIMS

Cognitive decline is one of the most challenging issues for cancer survivors undergoing doxorubicin (DOX) based chemotherapy. Oxidative stress and inflammation primarily through tumor necrosis factor-alpha (TNF-α) are considered the key contributors to DOX-induced chemobrain. Berberine (BBR) has attracted much interest because of its anti-oxidative, anti-inflammatory and anti-apoptotic actions. This study aimed to evaluate the potential neuroprotective effect of BBR in DOX-induced neurodegeneration and cognitive deficits.

MATERIALS AND METHODS

Chemobrain was induced by DOX i.p. injection at the dose of 2 mg/kg, once/week, for four consecutive weeks. Rats were treated with BBR (100 mg/kg, p.o.) for 5 days/week for four consecutive weeks.

KEY FINDINGS

BBR significantly attenuated behavioral defects in DOX-induced cognitive impairment. Besides, BBR reversed histopathological abnormalities. Mechanistically, it reversed DOX-induced neuroinflammation by attenuating NF-κB gene and protein expression in addition to diminishing expression of pro-inflammatory mediators (TNF-α and IL-1β), as well as apoptotic related factors (Bax, Bcl2 and Bax/Bcl2 ratio). Additionally, BBR activated the anti-oxidative defense via upregulating the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and manganese superoxide dismutase (MnSOD). BBR improved synaptic plasticity through cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF). These effects were related through the modulation of Sirtuin1 (SIRT1) expression.

SIGNIFICANCE

BBR is highlighted to induce neuroprotection against DOX-induced cognitive decline through modulating brain growth factors and imposing an anti-inflammatory, anti-apoptotic and anti-oxidative effects.

Food-Derived Pharmacological Modulators of the Nrf2/ARE Pathway: Their Role in the Treatment of Diseases

Oxidative stress, which refers to unbalanced accumulation of reactive oxygen species (ROS) levels in cells, has been linked to acute and chronic diseases. Nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) pathway plays a vital role in regulating cytoprotective genes and enzymes in response to oxidative stress. Therefore, pharmacological regulation of Nrf2/ARE pathway is an effective method to treat several diseases that are mainly characterized by oxidative stress and inflammation. Natural products that counteract oxidative stress by modulating Nrf2 have contributed significantly to disease treatment. In this review, we focus on bioactive compounds derived from food that are Nrf2/ARE pathway regulators and describe the molecular mechanisms for regulating Nrf2 to exert favorable effects in experimental models of diseases.

The protective role of luteolin against the methotrexate-induced hepato-renal toxicity via its antioxidative, anti-inflammatory, and anti-apoptotic effects in rats

Methotrexate (MTX) is frequently used drug in treatment of cancer and autoimmune diseases. Unfortunately, MTX has many side effects including the hepato-renal toxicity. In this study, we hypothesized that Luteolin (Lut) exhibits protective effect against the MTX-induced hepato-renal toxicity. In order to investigate our hypothesis, the experiment was designed to examine the effect of exposure of male rats to MTX (20 mg/kg, i.p., at day 9) alone or together with Lut (50 mg/kg, oral for 14 days) compared to the control rats (received saline). The findings demonstrated that MTX treatment induced significant increases in the liver and kidney functions markers in serum samples including Aspartate transaminase (AST), Alanine transaminase (ALT), creatinine, urea and uric acid. MTX also mediated an oxidative stress expressed by elevated malondialdehyde (MDA) level and decreased level of reduced glutathione (GSH), antioxidant enzyme activities, and downregulation of the Nrf2 gene expression as an antioxidant trigger. Moreover, the inflammatory markers (NF-κB, TNF-α, and IL-1β) were significantly elevated upon MTX treatment. In addition, MTX showed an apoptotic response mediated by elevating the pro-apoptotic (Bax) and lowering the anti-apoptotic (Bcl-2) proteins. All of these changes were confirmed by the observed alterations in the histopathological examination of the hepatic and renal tissues. Lut exposure significantly reversed all the MTX-induced changes in the measured parameters suggesting its potential protective role against the MTX-induced toxicity. Finally, our findings concluded the antioxidative, anti-inflammatory and anti-apoptotic effects of Lut as a mechanism of its protective role against the MTX-induced hepato-renal toxicity in rats.

Hexavalent chromium induced heart dysfunction via Sesn2-mediated impairment of mitochondrial function and energy supply

Hexavalent chromium (Cr(VI)), the most toxic valence state of chromium, is widely present in industrial effluents and wastes. Although previous study has reported that Cr(VI) can cause cytomembrane structure impairment by aggravating lipid peroxidation in the heart, the detailed mechanism of Cr(VI)-induced heart dysfunction is still unclear. Sesn2, a novel antioxidant and stress-inducible molecule, is evidenced to protect against various cardiometabolic diseases such as atherosclerosis and cardiomyopathy. To define the potential mechanism of heart dysfunction induced by chronic Cr(VI) exposure, Wistar rats were intraperitoneal injected with potassium dichromate (K₂Cr₂O₇) for 35 d in the present study. The data showed that chronic K₂Cr₂O₇ exposure caused dose-dependently hematological variations, oxidative stress, dysfunction, and disorganized structure of heart, cardiomyocyte apoptosis, ATP depletion, and mitochondria impairment in rats. In addition, the expressions of Drp1 and Bax were increased by K₂Cr₂O₇. However, the suppression of Mfn2, PGC-1α, Sesn2, nuclear Nrf2, HO-1, and NQO1 protein levels was observed in K₂Cr₂O₇-treated rat hearts. In conclusion, these results demonstrate that chronic K₂Cr₂O₇ exposure dose-dependently causes heart dysfunction, and the molecular mechanism of this event is associated with the loss of Sesn2 mediated mitochondrial function and energy supply impairment.

Co-administration of Luteolin mitigated toxicity in rats' lungs associated with doxorubicin treatment

Doxorubicin (DOX), is a drug against lung malignancies with undesirable side effect including oxidative, inflammatory and apoptotic effects. Luteolin (LUT), present in fruits and vegetables is pharmacologically active against oxido-inflammatory and apoptotic responses. The present study examined the effect of LUT on DOX-induced lungs and blood dysfunction in Wistars rat (sex: male; 10 weeks old, 160 ± 5 g). Randomly grouped (n = 10) rats were treated as follows: control, LUT alone (100 mg/kg; per os), DOX (2 mg/kg; i. p), and co-treated rats with LUT (50 or 100 mg/kg) and DOX for two consecutive weeks. DOX alone adversely altered the final body and relative organ weights, red and white blood cell and platelet counts. DOX significantly (p > 0.05) reduced lungs antioxidant capacity, and anti-inflammatory cytokines; increased biomarkers of oxidative stress, caspase-3 activity, and pro-inflammatory cytokine. Morphological damages accompanied these biochemical alterations in the lung of experimental rats. Co-treatment with LUT, dose-dependently reversed DOX-mediated changes in rats' survival, toxic responses, and diminished oxidative stress in rat's lungs. Furthermore, co-treatment with LUT resulted in the reduction of pro-inflammatory cytokines and apoptotic biomarkers, increased red and white blood cell, platelet counts and abated pathological injuries in rat lungs treated with DOX alone. In essence, our findings indicate that LUT dose-dependently mitigated DOX-induced toxicities in the lungs and haematopoietic systems. Supplementation of patients on DOX-chemotherapy with phytochemicals exhibiting antioxidant activities, specifically LUT, could circumvent the onset of unintended toxic responses in the lungs and haematopoietic system exposed to DOX.

Enriched environment housing improved the laying hen's resistance to transport stress via modulating the heat shock protective response and inflammation

An enriched environment can promote adaptability of animals to cope with complex environments. A total of 18-week-old 216 laying hens were randomly divided into 2 groups; of which, one group was housed in conventional battery cages (CC, n = 36), and the others were housed in furnished cages (FC, n = 180). At the end of 64 wk of age, 24 chickens of each group were selected for 4-hour transport treatment. The spleen tissues of laying hens were collected before transportation (BT), immediately after transportation, and at 48 h after transportation to detect the expression of the heat shock protective response signaling pathway and inflammatory factors. Serum samples were collected to detect the content of immune cytokines. Transport stress decreased heat shock proteins (HSP; including Small HSP, HSP27, HSP40, HSP60, HS70, HSP90, HSP110) in the CC group (P < 0.05), whereas there was no significant difference in the expression of HSP (except for Small HSP and HSP40) in the FC group (P > 0.05) immediately after transportation. At 48 h after transportation, mRNA levels of HSP (except for Small HSP and HSP40) in the FC group were upregulated, which were higher than those at BT (P < 0.05). The changes in HSP60, HSP70, and HSP90 protein levels had similar tendencies. The results showed that housing in furnished cages alleviated the inhibition of expression of HSP in the hens' spleen induced by transport stress. In addition, the hens housed in the FC group had lower expression levels of proinflammatory factors (nuclear transcription factor-kappa B, inducible nitric oxide synthase, cyclooxygenase-2, prostaglandin E synthase, inflammatory cytokines [IL-1β and IL-6], and tumor necrosis factor alpha) (P < 0.05). We suggest that the enriched environment can reduce transport stress damage in laying hens and improve resistance to transport stress by regulating expression of heat shock response proteins and inflammatory cytokines.

Luteolin abates reproductive toxicity mediated by the oxido-inflammatory response in Doxorubicin-treated rats

The anti-neoplastic use of Doxorubicin (DOX) is hampered by several limitations, including reproductive toxicity. Luteolin (LUT)–a phytochemical-biological benefits include antioxidative and anti-inflammatory actions. Here we examined the protective effect of LUT against DOX-induced reproductive toxicity in an in vivo model—male albino Wistar rats—randomly assigned to five groups and treated as follows: Control (corn oil 2 mL/kg; per os), LUT (100 mg/kg; per os), DOX (2 mg/kg) by intraperitoneal injections, co-treated groups received LUT (50 and 100 mg/kg) with DOX. Treatment with DOX alone, significantly (p > 0.05), reduced biomarkers of testicular function, reproductive hormone levels, testicular and epididymal antioxidant, and anti-inflammatory cytokine. DOX increased (p > 0.05) sperm morphological abnormalities, as well as reactive oxygen and nitrogen species, lipid peroxidation, xanthine oxidase, a pro-inflammatory cytokine, and apoptotic biomarkers. Furthermore, testicular and epididymal histological lesion complemented the observed biochemical changes in treated rats. LUT co-treatment resulted in a dosage-dependent improvement in rats’ survivability, antioxidants capacity, reduction in biomarkers of oxidative stress, pro-inflammatory cytokines, and apoptosis in rat’s testis and epididymis. Also, LUT treatment resulted in improved histological features in the testis and epididymis, relative to DOX alone treated rats. LUT co-treatment abated DOX-mediated reproductive organ injuries associated with pro-oxidative, inflammatory, and apoptotic mechanisms. LUT supplementation may serve as a phyto-protective agent in alleviating male reproductive organ toxic injuries associated with Doxorubicin therapy.

Dibutyl phthalate induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway

Dibutyl phthalate (DBP), an important plastic contaminant in the environment, is known to cause organ toxicity. Although current research has shown that DBP-induced organ toxicity is associated with oxidative stress, the toxic effect of DBP on the lungs have not been fully elucidated. Therefore, we investigated the potential mechanism by which DBP induces pulmonary toxicity using a model of DBP-induced allergic airway inflammation in rats. The results showed that chronic exposure to DBP induced histopathological damage, inflammation, oxidative stress, apoptosis, and increased the protein levels of thymic stromal lymphopoietin (TSLP) and its downstream protein Janus kinase 1 (JAK1) and signal transducer and activator of transcription 6 (STAT6). Moreover, DBP exposure inhibited nuclear factor-erythroid-2-related factor 2 (Nrf2) and levels of its target genes NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Additionally, using in vitro experiments, we found that DBP induced oxidative stress, reduced cell viability, and inhibited the Nrf2/HO-1/NQO1 pathway in mouse alveolar type II epithelial cell line. Overall, these data demonstrate that DBP induces allergic airway inflammation in rats via inhibition of the Nrf2/TSLP/JAK1 pathway.

Hexavalent chromium induces renal apoptosis and autophagy via disordering the balance of mitochondrial dynamics in rats

The use of hexavalent chromium (Cr(VI)) in many industrial processes has resulted in serious environmental pollution problems. Cr(VI) causes organ toxicity in animals after ingestion or inhalation. However, the exact mechanism by which Cr(VI) produces kidney damage remains elusive. Herein, we investigated whether Cr(VI)-induced kidney damage is related to the disorder of mitochondrial dynamics. In this study, 28 male rats were divided into four groups and intraperitoneally injected with 0, 2, 4, and 6 mg/kg body weight potassium dichromate for 5 weeks. Experiment included analysis of renal histopathology and ultrastructure, determination of biochemical indicators, and measurement of related protein content. The results showed that Cr(VI) induced kidney injury through promotion of oxidative stress, apoptosis, and disorder of mitochondrial dynamics in a dose-dependent manner. The protein levels of the silent information regulator two ortholog 1 (Sirt1), peroxisome proliferation-activated receptor-g coactivator-1a (PGC-1a), and autophagy-related proteins were significantly decreased after Cr(VI) exposure. These findings suggest that Cr(VI) leads to the disorder of mitochondrial dynamics by inhibiting the Sirt1/PGC-1a pathway, which leads to renal apoptosis and autophagy in rats.

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.

Regulation of Nrf2/ARE Pathway by Dietary Flavonoids: A Friend or Foe for Cancer Management?

The nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cell signaling mechanism in maintaining redox homeostasis in humans. The role of dietary flavonoids in activating Nrf2/ARE in relation to cancer chemoprevention or cancer promotion is not well established. Here we summarize the dual effects of flavonoids in cancer chemoprevention and cancer promotion with respect to the regulation of the Nrf2/ARE pathway, while underlying the possible cellular mechanisms. Luteolin, apigenin, quercetin, myricetin, rutin, naringenin, epicatechin, and genistein activate the Nrf2/ARE pathway in both normal and cancer cells. The hormetic effect of flavonoids has been observed due to their antioxidant or prooxidant activity, depending on the concentrations. Reported in vitro and in vivo investigations suggest that the activation of the Nrf2/ARE pathway by either endogenous or exogenous stimuli under normal physiological conditions contributes to redox homeostasis, which may provide a mechanism for cancer chemoprevention. However, some flavonoids, such as luteolin, apigenin, myricetin, quercetin, naringenin, epicatechin, genistein, and daidzein, at low concentrations (1.5 to 20 µM) facilitate cancer cell growth and proliferation in vitro. Paradoxically, some flavonoids, including luteolin, apigenin, and chrysin, inhibit the Nrf2/ARE pathway in vitro. Therefore, even though flavonoids play a major role in cancer chemoprevention, due to their possible inducement of cancer cell growth, the effects of dietary flavonoids on cancer pathophysiology in patients or appropriate experimental animal models should be investigated systematically.

Hexavalent chromium induces mitochondrial dynamics disorder in rat liver by inhibiting AMPK/PGC-1α signaling pathway

Occupational exposure to hexavalent chromium (Cr(VI)) can cause cytotoxicity and carcinogenicity. In this study, we established a liver injury model in rats via intraperitoneal injection of potassium dichromate (0, 2, 4, and 6 mg/kg body weight) for 35 d to investigate the mechanism of Cr(VI)-induced liver injury. We found that Cr(VI) induced hepatic histopathological lesions, oxidative stress, and apoptosis and reduced the expression of mitochondrial-related regulatory factors such as adenosine 5'-monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in a dose-dependent manner. Furthermore, Cr(VI) promoted mitochondrial division and inhibited fusion, leading to increased expression of caspase-3 and production of mitochondrial reactive oxygen species. Our study demonstrates that long-term exposure to Cr(VI) induces mitochondrial dynamics disorder by inhibiting AMPK/PGC-1α signaling pathway in rat liver.

Inflammasome/NF-κB translocation inhibition via PPARγ agonist mitigates inorganic mercury induced nephrotoxicity

Mercury (Hg) pollution poses global human health and environmental risks. However, still knowledge gaps exist on both exposures and health effects. Here, we combined transcriptome sequencing technique to further investigate the specific mechanisms of inorganic Hg toxicity in the kidney. Strikingly, transcriptomic analysis revealed that 4174 unigenes (including 2646 upregulated and 1528 downregulated unigenes) were differentially expressed under acute HgCl₂ (5 mg/kg) exposure in the kidney. Additionally, we observed that HgCl₂ selectively induced tumor necrosis factor superfamily (TNFSF) to participate in renal damage, which was consistent with the high-throughput sequencing data. The phenomenon is accompanied by NLRP3 inflammasome and NF-κB signal activation in the kidney. Simultaneously, ELISA results shown that TNF-α, IL-1β and IL-6 concentrations in the kidney were significant increased. KEGG enrichment analysis showed that peroxisome proliferators-activated receptors (PPAR) signaling pathway might be vital toxic mechanism of Hg in the kidney. Then, our data showed that PPARγ agonist (GW 1929) attenuated HgCl₂ (15 μg/ml)-induced apoptosis and NLRP3 inflammasome activation via decreasing translocation of NF-κB and increasing Bcl2 levels in vitro. Along with this, we demonstrated that PPARγ antagonists (GW9662) effectively aggravated HgCl₂-induced nephrotoxicity. Overall, our results suggested that PPARγ signaling pathway is considered to be a protective mechanism to combat against HgCl₂-triggered NLRP3 inflammasome activation and apoptosis.

GRP78 effectively protect hypoxia/reperfusion-induced myocardial apoptosis via promotion of the Nrf2/HO-1 signaling pathway

Myocardial infarction is a major cause of death worldwide. Despite our understanding of the pathophysiology of myocardial infarction and the therapeutic options for treatment have improved substantially, acute myocardial infarction remains a leading cause of morbidity and mortality. Recent findings revealed that GRP78 could protect myocardial cells against ischemia reperfusion injury‐induced apoptosis, but the exact function and molecular mechanism remains unclear. In this study, we aimed to explore the effects of GRP78 on hypoxia/reperfusion (H/R)‐induced cardiomyocyte injury. Intriguingly, we first observed that GRP78 overexpression significantly protected myocytes from H/R‐induced apoptosis. On mechanism, our work revealed that GRP78 protected myocardial cells from hypoxia/reperfusion‐induced apoptosis via the activation of the Nrf2/HO‐1 signaling pathway. We observed the enhanced expression of Nrf2/HO‐1 in GRP78 overexpressed H9c2 cell, while GRP78 deficiency dramatically antagonized the expression of Nrf2/HO‐1. Furthermore, we found that blocked the Nrf2/HO‐1 signaling by the HO‐1 inhibitor zinc protoporphyrin IX (Znpp) significantly retrieved H9c2 cells apoptosis that inhibited by GRP78 overexpression. Taken together, our findings revealed a new mechanism by which GRP78 alleviated H/R‐induced cardiomyocyte apoptosis in H9c2 cells via the promotion of the Nrf2/HO‐1 signaling pathway.

Luteolin protects against testicular injury induced by lead acetate by activating the Nrf2/HO-1 pathway

Lead (Pb) is a toxic heavy metal that is harmful to humans, especially male reproductive organs. Luteolin (LUT) is a naturally occurring flavonoid with numerous biological activities. Our aim was to investigate the possible reproprotective effect of LUT against testicular deficits induced by Pb intoxication. In the present study, 28 rats were distributed into 4 groups: control, LUT (50 mg/kg), lead acetate (PbAc, 20 mg/kg), and LUT + PbAc groups, in which rats were pre-treated with LUT 3 hr before PbAc injection. All animals were treated for 7 days. Oxidative stress, inflammatory and apoptotic markers along with histopathological changes have been examined using spectrophotometric, ELISA, real-time PCR, and histopathological methods. PbAc injection elevated Pb concentration in testicular tissue and decreased levels of sex hormones. PbAc intoxication exacerbated lipoperoxidation and nitric oxide formation, depleted superoxide dismutase, and catalase activities along with glutathione and its originated enzymes (glutathione peroxidase and glutathione reductase). At the molecular level, PbAc deactivated nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 in the testicular tissue. In addition, PbAc toxicity induced inflammatory and apoptotic cascades in testicular tissue as evidenced by the increased tumor necrosis factor-alpha, interleukin-1 beta, inducible nitric oxide synthase, Bax, and caspase 3, while Bcl-2 was declined. Histopathological examination of testicular tissue also revealed that PbAc caused degeneration alterations in spermatogenic cells, the spermatogenic epithelial cells were disconnected from the basement membrane, and the seminiferous tubules were vacuolated. Remarkably, pre-treatment with LUT minimized significantly the testicular damage induced by PbAc. Therefore, we conclude that LUT may have a beneficial effect against PbAc-induced testicular injury through preventing oxidative challenge, inflammation, and finally apoptosis.

Low dose of luteolin activates Nrf2 in the liver of mice at start of the active phase but not that of the inactive phase

A flavone luteolin has various health-promoting activities. Several studies reported that high dose of luteolin activates the Nrf2/ARE pathway in the liver. However, the effect of the low dose of luteolin that can be taken from a dietary meal on the Nrf2 activation remain unclear. It is expected that the flavonoid metabolism possesses a circadian rhythm, since nutritional metabolism processes daily cycle. In this study we investigated whether an administration affects the Nrf2 activation. ICR mice were orally administered 0.01–10 mg/kg body weight of luteolin once a day for 7 days at two time-points: at the start of active phase (ZT12) or at that of inactive phase (ZT0). Luteolin increased the nuclear translocation of Nrf2, resulting in the increases in its target gene products HO-1 and NQO1 at ZT12 but not at ZT0. The expression level of Nrf2 was lower at ZT12 than at ZT0 in the liver. We also found that the level of luteolin aglycon in the plasma is higher at ZT12 than at ZT0. These results suggest that the low dose of luteolin can activate Nrf2 pathway and the aglycon form of luteolin may mainly contribute to activate the Nrf2 pathway at ZT12 in the liver.

Deltamethrin induces liver fibrosis in quails via activation of the TGF-β1/Smad signaling pathway

Deltamethrin (DLM) is an important member of the pyrethroid pesticide family, and its widespread use has led to serious environmental and health problems. Exposure to DLM causes pathological changes in the liver of animals and humans and can lead to liver fibrosis. However, the mechanism of DLM-induced liver fibrosis remains unclear. Therefore, to address its potential molecular mechanisms, we used both in vivo and in vitro methods. Quails were treated in vivo by intragastric administration of different concentrations of DLM (0, 15, 30, or 45 mg kg^-1), and the chicken liver cancer cell line LMH was treated in vitro with various doses of DLM (0, 50, 200, or 800 μg mL^-1). We found that DLM treatment in vivo induced liver fibrosis in a dose-dependent manner through the promotion of oxidative stress, activation of transforming growth factor-β1 (TGF-β1) and phosphorylation of Smad2/3. Treatment of LMH cells with different concentrations of DLM similarly induced oxidative stress and also decreased cell viability. Collectively, our study demonstrates that DLM-induced liver fibrosis in quails occurs via activation of the TGF-β1/Smad signaling pathway.

Sulforaphane prevents chromium-induced lung injury in rats via activation of the Akt/GSK-3β/Fyn pathway

Chromium (Cr) is an internationally recognized carcinogenic hazard that causes serious pulmonary toxicity. However, Cr-induced pulmonary toxicity lacks effective treatment to date. Sulforaphane (SFN), a well-known organosulfur compound, has gained increasing attention because of its unique biological function. This study investigates if SFN could decrease K₂Cr₂O₇-induced pulmonary toxicity and a potential mechanism involved using a rat 35-day Cr-induced pulmonary toxicity model and the mouse alveolar type II epithelial cell line (MLE-12). The results showed that SFN prevented Cr-induced oxidative stress, histopathological lesions, inflammation, apoptosis, and changes in protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK-3β) levels in vivo and in vitro. However, SFN can not play the protective effect against K₂Cr₂O₇-induced cell injury after treating by an Akt-specific inhibitor (MK-2206 2HCl) in MLE-12 cells. Furthermore, SFN increased the expression of nuclear factor-E2-related factor-2 (Nrf2) phase II detoxification enzymes. Collectively, this study demonstrates that SFN prevents K₂Cr₂O₇-induced lung toxicity in rats through enhancing Nrf2-mediated exogenous antioxidant defenses via activation of the Akt/GSK-3β/Fyn signaling pathway. SFN may be a novel natural substance to cure Cr-induced lung toxicity.

Luteolin protects against lead acetate-induced nephrotoxicity through antioxidant, anti-inflammatory, anti-apoptotic, and Nrf2/HO-1 signaling pathways

Lead (Pb) is one of the most common heavy metal pollutants affecting living organisms. It induces nephrotoxicity with significant alterations in renal structure and function. Luteolin (LUT) a flavonoid present in various plant products is well known for exhibiting numerous pharmacological properties. We evaluated the protective efficacy of LUT against Pb-induced renal injury in male Wistar rats. Four experimental groups: control, LUT (50 mg/kg, orally), PbAc (20 mg/kg, i.p.), LUT + PbAc (at the aforementioned doses) were maintained for 7 days. PbAc administration significantly increased renal Pb accumulation, urea, and creatinine levels in serum, and induced renal histological alterations. Additionally, compared to the control rats, PbAc-treated rats exhibited significantly low levels of antioxidant enzyme activity and expression (SOD, CAT, GPx and GR), as well as high MDA levels. Moreover, PbAc exposure downregulated Nfe212 and Homx1 mRNA expression and significantly increased inflammatory marker (TNF-α, IL-1β and NO) levels in renal tissue. PbAc significantly upregulated the synthesis of apoptotic related proteins and downregulated antiapoptotic protein expression. Notably, LUT pretreatment of PbAc-treated rats provided significant nephroprotection and reversed the alterations in the abovementioned parameters. In conclusion, LUT provided significant protection against PbAc intoxication via antioxidant, anti-inflammatory, and anti-apoptotic activities by activating the Nrf2/ARE signaling pathway.

Mast cell stabilizer modulates Sirt1/Nrf2/TNF pathway and inhibits oxidative stress, inflammation, and apoptosis in rat model of cyclophosphamide hepatotoxicity

Objectives: Cyclophosphamide (CYC) is the most common cytotoxic alkylating agent which considered as chemotherapy but its clinical usefulness is challenged with different forms of organ damage including hepatotoxicity. Hepatic mast cells (MC) have an important role in the pathophysiology of liver toxicity. We aimed to evaluate the possible protective effect of mast cell stabilizer, ketotifen in CYC induced-hepatotoxicity.Materials and methods: Twenty-four adult male albino Wistar rats were divided into four groups: control group, ketotifen group (received ketotifen 10 mg/kg/day, p.o.) for 14 days, CYC group (received CYC 200 mg/kg i.p.) as a single dose at the ninth day and ketotifen plus CYC group (received ketotifen and CYC). We measured serum enzyme biomarkers [alanine transaminase (ALT) and aspartate transaminase (AST)], total antioxidant capacity (TAC), interluken-1β (IL-1β), tissue malondialdehyde (MDA), nitric oxide (NOx), reduced glutathione (GSH), P-glycoprotein (P-gp), Sirtuin type 1 (Sirt1) and Nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Furthermore; histological changes, tumor necrosis factor (TNF) and caspase-3 immuno-expressions were evaluated.Results: CYC group showed hepatotoxic effect in the form of a significant increase in ALT, AST, MDA, NOx, IL-1β levels; TNF and caspase-3 immuno-expression. Moreover; it showed toxic histological changes of marked liver injury meanwhile, there is a significant decrease in TAC, GSH, P-gp, Sirt1, and Nrf2 levels. Ketotifen showed a significant improvement in all parameters.Conclusion: Mast cell stabilizer, ketotifen possesses potent ameliorative effects against the hepatotoxic effect of CYC by reducing oxidative stress, inflammatory process, and apoptosis through regulation of Sirt1/Nrf2/TNF pathway.

Protective effects of morin against acrylamide-induced hepatotoxicity and nephrotoxicity: A multi-biomarker approach

Acrylamide (ACR) is a heat-induced carcinogen substance that is found in some foods due to cooking or other thermal processes. The aim of present study was to assess the probable protective effects of morin against ACR-induced hepatorenal toxicity in rats. The rats were treated with ACR (38.27 mg/kg b.w., p.o.) alone or with morin (50 and 100 mg/kg b.w., p.o.) for 10 consecutive days. Morin treatment attenuated the ACR-induced liver and kidney tissue injury by diminishing the serum AST, ALP, ALT, urea and creatinine levels. Morin increased activities of SOD, CAT and GPx and levels of GSH, and suppressed lipid peroxidation in ACR induced tissues. Histopathological changes and immunohistochemical expressions of p53, EGFR, nephrin and AQP2 in the ACR-induced liver and kidney tissues were decreased after administration of morin. In addition, morin reversed the changes in levels of apoptotic, autophagic and inflammatory parameters such as caspase-3, bax, bcl-2, cytochrome c, beclin-1, LC3A, LC3B, p38α MAPK, NF-κB, IL-1β, IL-6, TNF-α and COX-2 in the ACR-induced toxicity. Morin also affected the protein levels by regulating the PI3K/Akt/mTOR signaling pathway and thus alleviated ACR-induced apoptosis and autophagy. Overall, these findings may shed some lights on new approaches for the treatment of ACR-induced hepatotoxicity and nephrotoxicity.