Nrf2 Knockdown Disrupts the Protective Effect of Curcumin on Alcohol-Induced Hepatocyte Necroptosis

Lytic cell death in metabolic liver disease

Regulated cell death is intrinsically associated with inflammatory liver disease and is pivotal in governing outcomes of metabolic liver disease. Different types of cell death may coexist as metabolic liver disease progresses to inflammation, fibrosis, and ultimately cirrhosis. In addition to apoptosis, lytic forms of hepatocellular death, such as necroptosis, pyroptosis and ferroptosis elicit strong inflammatory responses due to cell membrane permeabilisation and release of cellular components, contributing to the recruitment of immune cells and activation of hepatic stellate cells. The control of liver cell death is of fundamental importance and presents novel opportunities for potential therapeutic intervention. This review summarises the underlying mechanism of distinct lytic cell death modes and their commonalities, discusses their relevance to metabolic liver diseases of different aetiologies, and acknowledges the limitations of current knowledge in the field. We focus on the role of hepatocyte necroptosis, pyroptosis and ferroptosis in non-alcoholic fatty liver disease, alcohol-associated liver disease and other metabolic liver disorders, as well as potential therapeutic implications.

Effective Nephroprotection Against Acute Kidney Injury with a Star-Shaped Polyglutamate-Curcuminoid Conjugate

The lack of effective pharmacological treatments for acute kidney injury (AKI) remains a significant public health problem. Given the involvement of apoptosis and regulated necrosis in the initiation and progression of AKI, the inhibition of cell death may contribute to AKI prevention/recovery. Curcuminoids are a family of plant polyphenols that exhibit attractive biological properties that make them potentially suitable for AKI treatment. Now, in cultured tubular cells, we demonstrated that a crosslinked self-assembled star-shaped polyglutamate (PGA) conjugate of bisdemethoxycurcumin (St-PGA-CL-BDMC) inhibits apoptosis and necroptosis induced by Tweak/TNFα/IFNγ alone or concomitant to caspase inhibition. St-PGA-CL-BDMC also reduced NF-κB activation and subsequent gene transcription. In vivo, St-PGA-CL-BDMC prevented renal cell loss and preserved renal function in mice with folic acid-induced AKI. Mechanistically, St-PGA-CL-BDMC inhibited AKI-induced apoptosis and expression of ferroptosis markers and also decreased the kidney expression of genes involved in tubular damage and inflammation, while preserving the kidney expression of the protective factor, Klotho. Thus, due to renal accumulation and attractive pharmacological properties, the application of PGA-based therapeutics may improve nephroprotective properties of current AKI treatments.

Curcumin Protects Human Trophoblast HTR8/SVneo Cells from H2O2-Induced Oxidative Stress by Activating Nrf2 Signaling Pathway

Pregnancy complications are associated with oxidative stress induced by accumulation of trophoblastic ROS in the placenta. We employed the human trophoblast HTR8/SVneo cell line to determine the effect of curcumin pre-treatment on H₂O₂-induced oxidative damage in HTR8/Sveo cells. Cells were pretreated with 2.5 or 5 μM curcumin for 24 h, and then incubated with 400 μM H₂O₂ for another 24 h. The results showed that H₂O₂ decreased the cell viability and induced excessive accumulation of reactive oxygen species (ROS) in HTR8/Sveo cells. Curcumin pre-treatment effectively protected HTR8/SVneo cells against oxidative stress-induced apoptosis via increasing Bcl-2/Bax ratio and decreasing the protein expression level of cleaved-caspase 3. Moreover, curcumin pre-treatment alleviated the excessive oxidative stress by enhancing the activity of antioxidative enzymes. The antioxidant effect of curcumin was achieved by activating Nrf2 and its downstream antioxidant proteins. In addition, knockdown of Nrf2 by Nrf2-siRNA transfection abolished the protective effects of curcumin on HTR8/SVneo cells against oxidative damage. Taken together, our results show that curcumin could protect HTR8/SVneo cells from H₂O₂-induced oxidative stress by activating Nrf2 signaling pathway.

DNA-PKcs promotes alcohol-related liver disease by activating Drp1-related mitochondrial fission and repressing FUNDC1-required mitophagy

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a novel housekeeper of hepatic mitochondrial homeostasis outside the DNA repair process. In this study, DNA-PKcs was upregulated in the livers of mice that were exposed to alcohol; the expression of DNA-PKcs positively correlated with hepatic steatosis, fibrosis, apoptosis, and mitochondrial damage. Functional studies revealed that liver-specific DNA-PKcs knockout (DNA-PKcs LKO ) mice were protected from chronic ethanol-induced liver injury and mitochondrial damage. Mechanistic investigations established that DNA-PKcs promoted p53 activation, which elevated dynamin-related protein 1 (Drp1)-related mitochondrial fission but repressed FUN14 domain containing 1 (FUNDC1)-required mitophagy. Excessive fission and defective mitophagy triggered mtDNA damage, mitochondrial respiratory inhibition, mROS overproduction, cardiolipin oxidation, redox imbalance, calcium overload, and hepatic mitochondrial apoptosis. In contrast, the deletion of DNA-PKcs rescued these phenotypic alterations, which alleviated the susceptibility of hepatocytes to alcohol-induced cytotoxicity. Additionally, we also showed that orphan nuclear receptor subfamily 4 group A member 1 (NR4A1) was the upstream signal for DNA-PKcs activation and that the genetic ablation of NR4A1 ameliorated the progression of alcohol-related liver disease (ARLD); these results were similar to those obtained in DNA-PKcs knockout mice. Collectively, our results identified the NR4A1/DNA-PKcs/p53 axis as a novel signaling pathway responsible for ARLD pathogenesis that acts by activating Drp1-related mitochondrial fission and restricting FUNDC1-required mitophagy. The findings have potential implications for new approaches for ARLD therapy.

Protective effects of curcumin against chronic alcohol-induced liver injury in mice through modulating mitochondrial dysfunction and inhibiting endoplasmic reticulum stress

Background

Curcumin is a major active ingredient extracted from powdered dry rhizome of Curcuma longa. In Ayurveda and traditional Chinese medicine, it has been used as a hepatoprotective agent for centuries. However, the underlying mechanisms are not clear.

Objective

The present study is to investigate the hepatoprotective effects of curcumin in chronic alcohol-induced liver injury and explore its mechanism.

Design

Alcohol-exposed Balb/c mice were treated with curcumin (75 and 150 mg/kg) once per day for 8 weeks. Tissue from individual was fixed with formaldehyde for pathological examination. The activities of mitochondrial antioxidant enzymes, Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase, were determined. The level of mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (MPTP) opening was also determined. The expression of PGC-1α, NRF1, Mn-SOD, GRP78, PERK, IRE1α, nuclear NF-κB, and phosphorylated IκBα was quantified by western blot. The contents of TNF-α, IL-1β, and IL-6 in the liver were measured using the ELISA method.

Results

Curcumin significantly promoted hepatic mitochondrial function by reducing the opening of MPTP, thus increasing the MMP, promoting the activity of Na⁺/k⁺-ATPase, Ca²⁺-ATPase, and Ca²⁺/Mg²⁺-ATPase, and attenuating oxidative stress. Curcumin upregulated the expression of PGC-1α, NRF1, and Mn-SOD, and downregulated the expression of GRP78, PERK, and IRE1α in hepatic tissue. Curcumin also attenuated inflammation by inhibiting the IκBα–NF-κB pathway, which reduced the production of TNF, IL-1β, and IL-6.

Conclusion

Curcumin attenuates alcohol-induced liver injury via improving mitochondrial function and attenuating endoplasmic reticulum stress and inflammation. This study provides strong evidence for the beneficial effects of curcumin in the treatment of chronic alcohol-induced liver injury.

Shared pathways for neuroprogression and somatoprogression in neuropsychiatric disorders

Activated immune-inflammatory, oxidative and nitrosative stress (IO&NS) pathways and consequent mitochondrial aberrations are involved in the pathophysiology of psychiatric disorders including major depression, bipolar disorder and schizophrenia. They offer independent and shared contributions to pathways underpinning medical comorbidities including insulin resistance, metabolic syndrome, obesity and cardiovascular disease - herein conceptualized as somatoprogression. This narrative review of human studies aims to summarize relationships between IO&NS pathways, neuroprogression and somatoprogression. Activated IO&NS pathways, implicated in the neuroprogression of psychiatric disorders, affect the pathogenesis of comorbidities including insulin resistance, dyslipidaemia, obesity and hypertension, and by inference, metabolic syndrome. These conditions activate IO&NS pathways, exacerbating neuroprogression in psychiatric disorders. The processes whereby proinflammatory cytokines, nitrosative and endoplasmic reticulum stress, NADPH oxidase isoforms, PPARγ inactivation, SIRT1 deficiency and intracellular signalling pathways impact lipid metabolism and storage are considered. Through associations between body mass index, chronic neuroinflammation and FTO expression, activation of IO&NS pathways arising from somatoprogression may contribute to neuroprogression. Early evidence highlights the potential of adjuvants targeting IO&NS pathways for treating somatoprogression and neuroprogression.

Myalgic encephalomyelitis/chronic fatigue syndrome: From pathophysiological insights to novel therapeutic opportunities

Myalgic encephalomyelitis (ME) or chronic fatigue syndrome (CFS) is a common and disabling condition with a paucity of effective and evidence-based therapies, reflecting a major unmet need. Cognitive behavioural therapy and graded exercise are of modest benefit for only some ME/CFS patients, and many sufferers report aggravation of symptoms of fatigue with exercise. The presence of a multiplicity of pathophysiological abnormalities in at least the subgroup of people with ME/CFS diagnosed with the current international consensus "Fukuda" criteria, points to numerous potential therapeutic targets. Such abnormalities include extensive data showing that at least a subgroup has a pro-inflammatory state, increased oxidative and nitrosative stress, disruption of gut mucosal barriers and mitochondrial dysfunction together with dysregulated bioenergetics. In this paper, these pathways are summarised, and data regarding promising therapeutic options that target these pathways are highlighted; they include coenzyme Q₁₀, melatonin, curcumin, molecular hydrogen and N-acetylcysteine. These data are promising yet preliminary, suggesting hopeful avenues to address this major unmet burden of illness.

Necroptosis signaling in liver diseases: An update

The apoptosis alternate cell death pathways are extensively studied in recent years and their significance has been well recognized. With identification of newer cell death pathways, the therapeutic opportunities to modulate cell death have indeed further extended. Necroptosis, among other apoptosis alternate pathways, has been immensely studied recently in different hepatic disease models. Receptor-interacting protein 1 (RIPK1), RIPK3 and mixed lineage kinase domain like (MLKL) seemed to be the key players to mediate necroptosis pathway. Initially, necroptosis seemed to be following the typical pathway. But recently diverse pathways and outcomes have been observed. With recent studies reporting diverse outcomes, the necroptosis signalling has become a lot more interesting and intricate. The typical RIPK1 signalling followed by RIPK3 and MLKL might not always be strictly followed. Although, necroptosis signalling has been intensively investigated in various disease conditions; however, there is still a need to further elaborate and understand the unique scaffolding and kinase properties and other signalling interactions of necroptosis signalling molecules.

Polymorphism in the Promoter Region of NFE2L2 Gene Is a Genetic Marker of Susceptibility to Cirrhosis Associated with Alcohol Abuse

Alcoholic liver disease (ALD) is a highly prevalent spectrum of pathologies caused by alcohol overconsumption. Morbidity and mortality related to ALD are increasing worldwide, thereby demanding strategies for early diagnosis and detection of ALD predisposition. A potential candidate as a marker for ALD susceptibility is the transcription factor nuclear factor erythroid-related factor 2 (Nrf2), codified by the nuclear factor erythroid 2-related factor 2 gene (NFE2L2). Nrf2 regulates expression of proteins that protect against oxidative stress and inflammation caused by alcohol overconsumption. Here, we assessed genetic variants of NFE2L2 for association with ALD. Specimens from patients diagnosed with cirrhosis caused by ALD were genotyped for three NFE2L2 single nucleotide polymorphisms (SNP) (SNPs: rs35652124, rs4893819, and rs6721961). Hematoxylin & eosin and immunohistochemistry were performed to determine the inflammatory score and Nrf2 expression, respectively. SNPs rs4893819 and rs6721961 were not specifically associated with ALD, but analysis of SNP rs35652124 suggested that this polymorphism predisposes to ALD. Furthermore, SNP rs35652124 was associated with a lower level of Nrf2 expression. Moreover, liver samples from ALD patients with this polymorphism displayed more severe inflammatory activity. Together, these findings provide evidence that the SNP rs35652124 variation in the Nrf2-encoding gene NFE2L2 is a potential genetic marker for susceptibility to ALD.

Gallic acid protects against ethanol-induced hepatocyte necroptosis via an NRF2-dependent mechanism

Alcoholic liver disease (ALD), featured by excessive hepatocyte death and inflammation, is a prevalent disease that causes heavy health burdens worldwide. Hepatocyte necroptosis is a central event that promotes inflammation in ALD. At molecular levels, inhibition of nuclear factor (erythroid - derived 2) - like 2 (NRF2) was an important trigger for cell necroptosis. The protective effects of gallic acid (GA) on liver diseases caused by multiple factors have been elucidated, however, the role of GA in ALD remained unclear. Therefore, this study was aimed to investigate the anti-ALD effects of GA and further reveal the molecular mechanisms. Results showed that GA could effectively recover cell viability and reduce the release of aspartate transaminase, alanine transaminase, and lactic dehydrogenase by ethanol-stimulated hepatocytes. More importantly, GA limited hepatocyte necroptosis under ethanol stimulation, which was characterized by reduced expression of distinct necroptotic signals receptor-interacting protein 1 (RIP1) and RIP3 and release of high mobility group box protein 1. Mechanistically, GA could induce NRF2 expression in ethanol-incubated hepatocytes, which was a molecular basis for GA to suppress ethanol-induced hepatocyte necroptosis. In conclusion, this study demonstrated that GA improved ethanol-induced hepatocyte necroptosis in vitro. Further, NRF2 activation might be requisite for GA to exert its protective effects.

Lycopene attenuates aluminum-induced hippocampal lesions by inhibiting oxidative stress-mediated inflammation and apoptosis in the rat

Aluminum (Al) causes hippocampal lesions by oxidative stress, which is widely accepted as the primary pathogenesis of Al neurotoxicity. Lycopene (LYC), a naturally carotenoid, has received extensive attention due to its antioxidant effect. In this study, the neuroprotective effects and mechanisms of LYC against aluminum chloride (AlCl₃)-induced hippocampal lesions were explored. First, oral administration of LYC (4 mg/kg) alleviated AlCl₃-induced (150 mg/kg) cognition impairment and histopathological changes of the hippocampus in rats. Then, LYC significantly attenuated AlCl₃-induced oxidative stress, presenting as the reduced reactive oxygen species, malondialdehyde and 8-hydroxy-2'-deoxyguanosine levels, and increased glutathione level and superoxide dismutase activity. Moreover, LYC also protected the hippocampus from AlCl₃-induced apoptosis and neuroinflammation, as assessed by protein levels of p53, Bcl-2-associated X protein (Bax), B-cell lymphoma gene 2 (Bcl-2), Cytochrome c (Cyt c), cleaved caspase-3 and nuclear factor kappa B, as well as the mRNA levels of Bax, Bcl-2, tumor necrosis factor alpha, interleukin-6 and interleukin-1 beta. Finally, LYC increased nuclear factor-erythroid-2-related factor 2 (Nrf2) nuclear translocation and its downstream gene expression, including heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, glutamate cysteine ligase catalytic subunit and superoxide dismutase 1, which were involved in antioxidant, anti-apoptosis, and anti-inflammation. Overall, our findings demonstrate LYC attenuates Al-induced hippocampal lesions by inhibiting oxidative stress-mediated inflammation and apoptosis in the rat.

Nrf2 Suppresses Allergic Lung Inflammation by Attenuating the Type 2 Innate Lymphoid Cell Response

The Keap1-Nrf2 system plays a pivotal role in the oxidative stress response by inducing a number of cytoprotective genes. Under stress, damaged epithelial cells release cytokines that activate type 2 innate lymphoid cells (ILC2s), which mediate the allergic immune response. In this article, we investigated the role of the Keap1-Nrf2 pathway in ILC2 homeostasis and allergic inflammation using Nrf2 knockout mice. ILC2s from Nrf2-deficient mice showed a transient, upregulated IL-33 response and underwent hyperproliferation in response to a combined stimulation of IL-33 with IL-2, IL-7, or TSLP. This enhanced proliferation was correlated with an increased activation of downstream signals, including JAK1, Akt, and Erk1/2. In contrast, activating Nrf2 with a chemical inducer (CDDO-Im) decreased the viability of the wild-type but not of the Nrf2-deficient ILC2s. This effect on viability resembled that exerted by the corticosteroid dexamethasone; however, unlike the latter, the Nrf2-dependent cell death was mediated by neither caspase 3-dependent apoptosis nor necroptosis. Using a mouse intratracheal IL-33 administration allergy model, we found that the activation of Nrf2 by CDDO-Im in vivo decreased the number of pulmonary ILC2s and eosinophils. These findings indicated that Nrf2 is an important regulator of the allergic response by determining the survival and death of ILC2s, and these findings suggest that Nrf2 activation is a potential therapeutic strategy for steroid-resistant allergy alleviation.

The Role of Nrf2 in Liver Disease: Novel Molecular Mechanisms and Therapeutic Approaches

Oxidative stress and inflammation are the most important pathogenic events in the development and progression of liver diseases. Nuclear erythroid 2-related factor 2 (Nrf2) is the master regulator of the cellular protection via induction of anti-inflammatory, antioxidant, and cyto-protective genes expression. Multiple studies have shown that activation or suppression of this transcriptional factor significantly affect progression of liver diseases. Comprehensive understanding the roles of Nrf2 activation/expression and the outcomes of its activators/inhibitors are indispensable for defining the mechanisms and therapeutic strategies against liver diseases. In this current review, we discussed recent advances in the function and principal mechanisms by regulating Nrf2 in liver diseases, including acute liver failure, hepatic ischemia-reperfusion injury (IRI), alcoholic liver disease (ALD), viral hepatitis, non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and hepatocellular carcinoma (HCC).

Nanoemulsions improve the efficacy of turmeric in palmitate- and high fat diet-induced cellular and animal models

Turmeric is a well-known functional food exhibiting multiple biological activities in health and disease. However, low aqueous solubility and poor bioavailability limit its therapeutic potential. Herein, we investigated the utility of nanoemulsions as a carrier to improve the efficacy of turmeric. Compared with turmeric extract (TE), 5% TE-loaded nanoemulsion (TE-NE), which contains 20-fold lower curcumin content than TE, achieved similar inhibition of palmitate-induced lipotoxicity in HepG2 cells. Exposure of HepG2 cells to 5% TE-NE also suppressed the palmitate-induced accumulation of lipid vacuoles and reactive oxygen species comparably with TE, and was accompanied by decreased levels of sterol regulatory element-binding protein (SREBP)-1, peroxisome proliferator-activated receptor-γ2 (PPAR-γ2), cleaved caspase-3, and poly (ADP-ribose) polymerase (PARP). Consistent with these effects in HepG2 cells, oral administration of 5% TE-NE to mice fed a high fat diet (HFD) markedly suppressed lipid accumulation in liver, leading to a significant reduction in body weight and adipose tissue weight, equivalent to the effects observed with TE. Compared with TE, 5% TE-NE also equivalently inhibited the levels of SREBP-1, PPAR-γ2, cleaved caspase-3, and PARP in the liver of mice fed a HFD. Furthermore, TE and 5% TE-NE significantly improved serum lipid profiles in a similar manner. These observations indicate that nanoemulsions can improve the efficacy of turmeric, thereby eliciting more potent biological efficacy against palmitate- and high fat diet (HFD)-induced cellular damage.

Bioactivity, Health Benefits, and Related Molecular Mechanisms of Curcumin: Current Progress, Challenges, and Perspectives

Curcumin is a principal curcuminoid of turmeric (Curcuma longa), which is commonly used as a spice in cooking and a yellow pigment in the food processing industry. Recent studies have demonstrated that curcumin has a variety of biological activities and pharmacological performances, providing protection and promotion of human health. In addition to presenting an overview of the gut metabolism of curcumin, this paper reviews the current research progress on its versatile bioactivity, such as antioxidant, anti-inflammatory, and immune-regulatory activities, and also intensively discusses its health benefits, including the protective or preventive effects on cancers and diabetes, as well as the liver, nervous system, and cardiovascular systems, highlighting the potential molecular mechanisms. Besides, the beneficial effects of curcumin on human are further stated based on clinical trials. Considering that there is still a debate on the beneficial effects of curcumin, we also discuss related challenges and prospects. Overall, curcumin is a promising ingredient of novel functional foods, with protective efficacy in preventing certain diseases. We hope this comprehensive and updated review will be helpful for promoting human-based studies to facilitate its use in human health and diseases in the future.

Cancer Cell Metabolism Featuring Nrf2

Although the major role of Nrf2 has long been established as a transcription factor for providing cellular protection against oxidative stress, multiple pieces of research and reviews now claim exactly the opposite. The dilemma - "to activate or inhibit" the protein requires an immediate answer, which evidently links cellular metabolism to the causes and purpose of cancer. Profusely growing cancerous cells have prolific energy requirements, which can only be fulfilled by modulating cellular metabolism. This review highlights the cause and effect of Nrf2 modulation in cancer that in turn channelize cellular metabolism, thereby fulfilling the energy requirements of cancer cells. The present work also highlights the purpose of genetic mutations in Nrf2, in relation to cellular metabolism in cancer cells, thus pointing out a newer approach where parallel mutations may be the key factor to decide whether to activate or inhibit Nrf2.

Targeting Nrf-2 is a promising intervention approach for the prevention of ethanol-induced liver disease

Alcoholic liver disease (ALD) remains to be a worldwide health problem. It is generally accepted that oxidative stress plays critical roles in the pathogenesis of ALD, and antioxidant therapy represents a logical strategy for the prevention and treatment of ALD. Nuclear factor erythroid-derived 2-like 2 (NFE2L2 or Nrf-2) is essential for the antioxidant responsive element (ARE)-mediated induction of endogenous antioxidant enzymes such as heme oxygenase 1 (HO-1) and glutamate-cysteine ligase [GCL, the rate-limiting enzyme in the synthesis of glutathione (GSH)]. Activation of Nrf-2 pathway by genetic manipulation or pharmacological agents has been demonstrated to provide protection against ALD, which suggests that targeting Nrf-2 may be a promising approach for the prevention and treatment of ALD. Herein, we review the relevant literature about the potential hepatoprotective roles of Nrf-2 activation against ALD.

Nrf2 in alcoholic liver disease

Alcoholic liver disease (ALD) is a leading cause of morbidity and mortality of liver disorders and a major health issue globally. ALD refers to a spectrum of liver pathologies ranging from steatosis, steatohepatitis, fibrosis, cirrhosis and even hepatocellular carcinoma. Various mechanisms, including oxidative stress, protein and DNA modification, inflammation and impaired lipid metabolism, have been implicated in the pathogenesis of ALD. Further, reactive oxygen species (ROS) in particular, have been identified as a key component in the initiation and progression of ALD. Nuclear factor erythroid 2 like 2 (Nrf2) is a master regulator of the intracellular adaptive antioxidant response to oxidative stress, and aids in the detoxification of a variety of toxicants. Given its cytoprotective role, Nrf2 has been extensively studied as a therapeutic target for ALD. Paradoxically, however, emerging evidence have revealed that Nrf2 may be implicated in the progression of ALD. In this review, we summarize the role of Nrf2 in the development of ALD and discuss the underlying mechanisms. Clearly, more comprehensive studies with proper animal and cell models and in human are needed to verify the potential therapeutic role of Nrf2 in ALD.

The in vivo evidence for regulated necrosis

Necrosis is a hallmark of several widespread diseases or their direct complications. In the past decade, we learned that necrosis can be a regulated process that is potentially druggable. RIPK3- and MLKL-mediated necroptosis represents by far the best studied pathway of regulated necrosis. During necroptosis, the release of damage-associated molecular patterns (DAMPs) drives a phenomenon referred to as necroinflammation, a common consequence of necrosis. However, most studies of regulated necrosis investigated cell lines in vitro in a cell autonomous manner, which represents a non-physiological situation. Conclusions based on such work might not necessarily be transferrable to disease states in which synchronized, non-cell autonomous effects occur. Here, we summarize the current knowledge of the pathophysiological relevance of necroptosis in vivo, and in light of this understanding, we reassess the morphological classification of necrosis that is generally used by pathologists. Along these lines, we discuss the paucity of data implicating necroptosis in human disease. Finally, the in vivo relevance of non-necroptotic forms of necrosis, such as ferroptosis, is addressed.

Oroxylin A inhibits ethanol-induced hepatocyte senescence via YAP pathway

OBJECTIVES

Oroxylin A, a natural flavonoid isolated from Scutellaria baicalensis, has been reported to have anti-hepatic injury effects. However, the effects of oroxylin A on alcoholic liver disease (ALD) remains unclear. The aim of this study was to elucidate the effects of oroxylin A on ALD and the potential mechanisms.

MATERIALS AND METHODS

Male ICR mice and human hepatocyte cell line LO₂ were used. Yes-associated protein (YAP) overexpression and knockdown were achieved using plasmid and siRNA technique. Cellular senescence was assessed by analyses of the senescence-associated β-galactosidase (SA-β-gal), senescence marker p16, p21, Hmga1, cell cycle and telomerase activity.

RESULTS

Oroxylin A alleviated ethanol-induced hepatocyte damage by suppressing activities of supernatant marker enzymes. We found that oroxylin A inhibited ethanol-induced hepatocyte senescence by decreasing the number of SA-β-gal-positive LO₂ cells and reducing the expression of senescence markers p16, p21 and Hmga1 in vitro. Moreover, oroxylin A affected the cell cycle and telomerase activity. Of importance, we revealed that YAP pharmacological inhibitor verteporfin or YAP siRNA eliminated the effect of oroxylin A on ethanol-induced hepatocyte senescence in vitro, and this was further supported by the evidence in vivo experiments.

CONCLUSION

Therefore, these aggregated data suggested that oroxylin A relieved alcoholic liver injury possibly by inhibiting the senescence of hepatocyte, which was dependent on its activation of YAP in hepatocytes.

Antioxidant Effect of Barley Sprout Extract via Enhancement of Nuclear Factor-Erythroid 2 Related Factor 2 Activity and Glutathione Synthesis

We previously showed that barley sprout extract (BSE) prevents chronic alcohol intake-induced liver injury in mice. BSE notably inhibited glutathione (GSH) depletion and increased inflammatory responses, revealing its mechanism of preventing alcohol-induced liver injury. In the present study we investigated whether the antioxidant effect of BSE involves enhancing nuclear factor-erythroid 2 related factor 2 (Nrf2) activity and GSH synthesis to inhibit alcohol-induced oxidative liver injury. Mice fed alcohol for four weeks exhibited significantly increased oxidative stress, evidenced by increased malondialdehyde (MDA) level and 4-hydroxynonenal (4-HNE) immunostaining in the liver, whereas treatment with BSE (100 mg/kg) prevented these effects. Similarly, exposure to BSE (0.1–1 mg/mL) significantly reduced oxidative cell death induced by t-butyl hydroperoxide (t-BHP, 300 μM) and stabilized the mitochondrial membrane potential (∆ψ). BSE dose-dependently increased the activity of Nrf2, a potential transcriptional regulator of antioxidant genes, in HepG2 cells. Therefore, increased expression of its target genes, heme oxygenase-1 (HO-1), NADPH quinone oxidoreductase 1 (NQO1), and glutamate-cysteine ligase catalytic subunit (GCLC) was observed. Since GCLC is involved in the rate-limiting step of GSH synthesis, BSE increased the GSH level and decreased both cysteine dioxygenase (CDO) expression and taurine level. Because cysteine is a substrate for both taurine and GSH synthesis, a decrease in CDO expression would further contribute to increased cysteine availability for GSH synthesis. In conclusion, BSE protected the liver cells from oxidative stress by activating Nrf2 and increasing GSH synthesis.

Nrf2 activation is required for curcumin to induce lipocyte phenotype in hepatic stellate cells

Hepatic fibrosis is a reversible scarring response that commonly occurs with chronic liver injury. During hepatic fibrogenesis, the major effector hepatic stellate cells (HSCs) become activated, featured by disappeared intracellular lipid droplets, decreased retinoid storage, and dysregulated expression of genes associated with lipid and retinoid metabolism. Compelling evidence suggested that recovery of retinoid droplets could inhibit HSC activation, while the precise molecular basis underlying the phenotypical switch still remained unclear. In this study, curcumin increased the abundance of lipid droplets and content of triglyceride in activated HSCs. In addition, curcumin could concentration-dependently regulate genes associated with lipid and retinoid metabolism. Further, consistent results were obtained from in vivo experiments. Curcumin increased Nrf2 expression and nuclear translocation, and its binding activity to DNA, which might be associated with suppression of Kelch-like ECH-associated protein 1 in HSCs. Of interest was that Nrf2 overexpression plasmids, in contract to Nrf2 siRNA, strengthened the effect of curcumin on induction of lipocyte phenotype. In in vivo system, Nrf2 knockdown mediated by Nrf2 shRNA lentivirus not only accelerated the lipid degradation in HSCs but also promoted the progression of CCl₄-induced hepatic fibrosis in mice. Noteworthily, Nrf2 knockdown abolished the protective effect of curcumin. In conclusion, curcumin could induce lipocyte phenotype of activated HSCs via activating Nrf2. Nrf2 could be a target molecule for antifibrotic strategy.

Involvement of the activation of Nrf2/HO-1, p38 MAPK signaling pathways and endoplasmic reticulum stress in furazolidone induced cytotoxicity and S phase arrest in human hepatocyte L02 cells: modulation of curcumin

Furazolidone (FZD) is extensively used as the antiprotozoal and antibacterial drug in clinic. The previous study has shown that curcumin pretreatment could improve FZD induced cytotoxicity by inhibiting oxidative stress and mitochondrial apoptotic pathway. The current study aimed to investigate the potential roles of endoplasmic reticulum (ER) stress, p38 mitogen-activated protein kinases (p38 MAPK) signaling pathway in curcumin against FZD cytotoxicity by using human hepatocyte L02 cells. The results showed that curcumin could markedly attenuate FZD induced cytotoxicity. Compared with FZD alone group, curcumin pretreatment significantly reduced the expression of phospho (p)-p38, cyclin D1, p-checkpoint kinase 1 (ChK1) and breast cancer associated gene 1 (BRCA1) protein, followed to attenuate S phase arrest. Meanwhile, curcumin pretreatment prevented FZD induced ER stress, evidenced by the inhibition of glucose-regulated protein 78 and DNA damage inducible gene 153/C/EBP-homologous protein (GADD153/CHOP) protein expression. Moreover, compared with the control, FZD exposure activated the protein and mRNA expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1), which were further activated by curcumin treatment. These results reveal that curcumin could prevent FZD induced cytotoxicity and S phase arrest, which may involve the activation of Nrf2/HO-1 pathway and the inhibition of p38 MAPK pathway and ER stress.