Aging-related NOX4-Nrf2 redox imbalance increases susceptibility to cisplatin-induced acute kidney injury by regulating mitophagy

BACKGROUND

During aging, excessive ROS production in the kidneys leads to redox imbalance, which contributes to oxidative damage and impaired organ homeostasis. However, whether and how aging-related NOX4-Nrf2 redox imbalance increases susceptibility to cisplatin-induced acute kidney injury remain largely unknown.

METHODS

In this study, we used cisplatin-challenged aging mouse models and senescent HK-2 cells to investigate the effects and mechanisms of aging on susceptibility to cisplatin-induced acute kidney injury.

RESULTS

In vivo, we found that cisplatin stimulation caused more severe renal damage, oxidative stress, mitochondrial dysfunction and mitophagy impairment in aging mice than in young mice. Moreover, Nrf2 deficiency aggravated cisplatin-induced acute kidney injury by exacerbating NOX4-Nrf2 redox imbalance and defective mitophagy. In vitro experiments on D-gal-treated human renal tubular epithelial cells (HK-2) demonstrated that senescent renal epithelial cells exhibited increased susceptibility to cisplatin-induced apoptosis, NOX4-Nrf2 redox imbalance-mediated oxidative stress and defective mitophagy. Mechanistically, we found that knockdown of Nrf2 in HK2 cells resulted in increased ROS and aggravated mitophagy impairment, whereas these effects were reversed in NOX4-knockdown cells.

CONCLUSION

The present study indicates that NOX4-Nrf2 redox imbalance is critical for mitophagy deficiency in aged renal tubular epithelial cells and is a therapeutic target for alleviating cisplatin-induced acute kidney injury in elderly patients.

Melatonin alleviates particulate matter-induced liver fibrosis by inhibiting ROS-mediated mitophagy and inflammation via Nrf2 activation

OBJECTIVE

Fine particulate matter (PM2.5) is a source of pollution worldwide, that causes inflammation and liver fibrosis. Melatonin, as the predominant hormone secreted by the pineal gland, can inhibit PM2.5-induced lung injury by activating nuclear factor erythroid 2-related factor 2 (Nrf2) to inhibit ferroptosis. However, the possible role of melatonin in PM2.5-induced liver damage remains unclear.

EXPERIMENTAL APPROACH

In vitro, the effects of melatonin on PM2.5-induced oxidative stress and LX-2 cell activation were examined. In vivo, a PM2.5-induced inflammation and liver fibrosis mouse model was used to evaluate the hepatoprotective effect of melatonin.

RESULTS

In vitro, melatonin induced the expression of Nrf2 and its downstream genes and inhibited PM2.5-induced reactive oxygen species (ROS) production and mitochondrial damage. Melatonin also ameliorated the PM2.5-induced oxidative stress and fibrogenic marker upregulation. However, the antifibrotic effect of melatonin was abolished in siNrf2-treated LX-2 cells. In vivo, we observed mitochondrial abnormalities and mitochondrial fragmentation, which were accompanied by increased PTEN-induced kinase 1 (PINK1) and Parkin expression, in PM2.5-treated mouse hepatocytes. These changes were partially reversed by melatonin. In addition, melatonin activated the Nrf2 signaling pathway and protected against PM2.5-induced oxidative stress. Furthermore, melatonin alleviated inflammation and liver fibrosis. Moreover, Nrf2-KO mice exhibited more severe inflammation and liver fibrosis after PM2.5 exposure than wild-type mice, and the protective effect of melatonin on PM2.5- treated Nrf2-KO mice was greatly compromised.

CONCLUSION

These data suggest that melatonin effectively inhibits PM2.5-induced liver fibrosis by activating Nrf2 and inhibiting ROS-mediated mitophagy and inflammation.

Activation of Nrf2 signalling pathway by tectoridin protects against ferroptosis in particulate matter-induced lung injury

BACKGROUND AND PURPOSE

Our previous research showed that ferroptosis plays a crucial role in the pathophysiology of PM2.5-induced lung injury. The present study aimed to investigate the protective role of the Nrf2 signalling pathway and its bioactive molecule tectoridin in PM2.5-induced lung injury by regulating ferroptosis.

EXPERIMENTAL APPROACH

We examined the regulatory effect of Nrf2 on ferroptosis in PM2.5-induced lung injury and Beas-2b cells using Nrf2-knockout (KO) mice and Nrf2 siRNA transfection. The effects and underlying mechanisms of tectoridin on PM2.5-induced lung injury were evaluated in vitro and in vivo.

KEY RESULTS

Nrf2 deletion increased iron accumulation and ferroptosis-related protein expression in vivo and vitro, further exacerbating lung injury and cell death in response to PM2.5 exposure. Tectoridin activated Nrf2 target genes and ameliorated cell death caused by PM2.5. In addition, tectoridin prevented lipid peroxidation, iron accumulation and ferroptosis in vitro, but in siNrf2-treated cells, these effects almost disappeared. In addition, tectoridin effectively mitigated PM2.5-induced respiratory system damage, as evaluated by HE, PAS, and inflammatory factors. Tectoridin also augmented the antioxidative Nrf2 signalling pathway and prevented changes in ferroptosis-related morphological and biochemical indicators, including MDA levels, GSH depletion and GPX4 and xCT downregulation, in PM2.5-induced lung injury. However, the effects of tectoridin on ferroptosis and respiratory injury were almost abolished in Nrf2-KO mice.

CONCLUSION AND IMPLICATIONS

Our data proposed the protective effect of Nrf2 activation on PM2.5-induced lung injury by inhibiting ferroptosis-mediated lipid peroxidation and highlight the potential of tectoridin as a PM2.5-induced lung injury treatment.

Xanthohumol protect against acetaminophen-induced hepatotoxicity via Nrf2 activation through the AMPK/Akt/GSK3β pathway

OBJECTIVE

Acetaminophen (APAP) is one of the world's popular and safe painkillers, and overdose can cause severe liver damage and even acute liver failure. The effect and mechanism of the xanthohumol on acetaminophen-induced hepatotoxicity remains unclear.

METHODS

The hepatoprotective effects of xanthohumol were studied using APAP-induced HepG2 cells and acute liver injury of mouse, seperately.

RESULTS

In vitro, xanthohumol inhibited H2O2- and acetaminophen-induced cytotoxicity and oxidative stress. Xanthohumol up-regulated the expression of Nrf2. Further mechanistic studies showed that xanthohumol triggered Nrf2 activation via the AMPK/Akt/GSK3β pathway to exert a cytoprotective effect. In vivo, xanthohumol significantly ameliorated acetaminophen-induced mortality, the elevation of ALT and AST, GSH depletion, MDA formation and histopathological changes. Xanthohumol effectively suppressed the phosphorylation and mitochondrial translocation of JNK, mitochondrial translocation of Bax, the activation o cytochrome c, AIF secretion and Caspase-3. In vivo, xanthohumol increased Nrf2 nuclear transcription and AMPK, Akt and GSK3β phosphorylation in vivo. In addition, whether xanthohumol protected against acetaminophen-induced liver injury in Nrf2 knockout mice has not been illustated.

CONCLUSION

Thus, xanthohumol exerted a hepatoprotective effect by inhibiting oxidative stress and mitochondrial dysfunction through the AMPK/Akt/GSK3β/Nrf2 antioxidant pathway.

Daphnetin ameliorates PM2.5-induced airway inflammation by inhibiting NLRP3 inflammasome-mediated pyroptosis in CS-exposed mice

Epidemiologic studies have shown that fine particulate matter 2.5 (PM2.5) exaggerates airway inflammation associated with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Daphnetin (Daph) is a natural compound with a variety of biological activities. At present, there are limited data on whether Daph can protect against cigarette smoke (CS)-induced chronic obstructive pulmonary disease (COPD) and PM2.5-CS-induced AECOPD. Therefore, this study systematically evaluated the effects of Daph on CS-induced COPD and PM2.5-CS-induced AECOPD and determined its mechanism of action. First, in vitro studies showed that PM2.5 exacerbated cytotoxicity and NLRP3 inflammasome-mediated pyroptosis induced by low-dose cigarette smoke extracts (CSE). However, the effect was reversed by si-NLRP3 and MCC950. Similar results were obtained in PM2.5-CS-induced AECOPD mice. The results of the mechanistic studies suggested that blocking NLRP3 abolished PM2.5 combined with cigarette induced cytotoxicity, lung damage, NLRP3 inflammasome activation and pyroptosis in vitro and in vivo. Second, Daph suppressed the expression of NLRP3 inflammasome and pyroptosis in BEAS-2B cells. Third, Daph significantly protected against CS-induced COPD and PM2.5-CS-induced AECOPD by inhibiting the NLRP3 inflammasome and pyroptosis in mice. Our findings identified the NLRP3 inflammasome as a critical contributor to PM2.5-CS-induced airway inflammation, and Daph as a negative regulator of NLRP3-mediated pyroptosis, which has implications for the pathophysiology of AECOPD.

The promoting effect and mechanism of Nrf2 on cell metastasis in cervical cancer

BACKGROUND

Cervical cancer (CC) has poor prognosis and high mortality rate for its metastasis during the disease progression. Epithelial-mesenchymal transition (EMT) and anoikis are initial and pivotal steps during the metastatic process. Although higher levels of Nrf2 are associated with aggressive tumor behaviors in cervical cancer, the detailed mechanism of Nrf2 in cervical cancer metastasis, especially EMT and anoikis, remains unclear.

METHODS

Immunohistochemistry (IHC) was used to examine Nrf2 expression in CC. Wound healing assay and transwell analysis were used to evaluate the migration ability of CC cells. Western blot, qTR-PCR and immunofluorescent staining were used to verify the expression level of Nrf2, the EMT associated markers and anoikis associated proteins. Flow cytometry assays and cell counting were used to detect the apoptosis of cervical cancer cells. The lung and lymph node metastatic mouse model were established for studies in vivo. The interaction between Nrf2 and Snail1 was confirmed by rescue-of-function assay.

RESULTS

When compared with cervical cancer patients without lymph node metastasis, Nrf2 was highly expressed in patients with lymph node metastasis. And Nrf2 was proved to enhance the migration ability of HeLa and SiHa cells. In addition, Nrf2 was positively correlated with EMT processes and negatively associated with anoikis in cervical cancer. In vivo, a xenograft assay also showed that Nrf2 facilitated both pulmonary and lymphatic distant metastasis of cervical cancer. Rescue-of-function assay further revealed the mechanism that Nrf2 impacted the metastasis of CC through Snail1.

CONCLUSION

Our fundings established Nrf2 plays a crucial role in the metastasis of cervical cancer by enhancing EMT and resistance to anoikis by promoting the expression of Snail1, with potential value as a therapeutic candidate.

UBE2E2 enhances Snail-mediated epithelial-mesenchymal transition and Nrf2-mediated antioxidant activity in ovarian cancer

Dissemination of ovarian cancer (OvCa) cells can lead to inoperable metastatic lesions in the bowel and omentum, which have a poor prognosis despite surgical and chemotherapeutical options. A better understanding of the mechanisms underlying metastasis is urgently needed. In this study, bioinformatics analyses revealed that UBE2E2, a less-studied ubiquitin (Ub)-conjugating enzyme (E2), was upregulated in OvCa and was associated with poor prognosis. Subsequently, we performed western blot analysis and IHC staining with 88 OvCa and 26 normal ovarian tissue samples, which further confirmed that UBE2E2 protein is highly expressed in OvCa tissue but weakly expressed in normal tissue. Furthermore, the silencing of UBE2E2 blocked OvCa cell migration, epithelial-mesenchymal transition (EMT) and metastasis in vitro, whereas UBE2E2 overexpression exerted the opposite effects. Mechanistically, UBE2E2 promoted p62 accumulation and increased the activity of the Nrf2-antioxidant response element (ARE) system, which ultimately activated the Snail signaling pathway by inhibiting the ubiquitin-mediated degradation of Snail. Additionally, co-IP and immunofluorescence demonstrated that a direct interaction exists between UBE2E2 and Nrf2, and the N-terminal of UBE2E2 (residues 1-52) is required and sufficient for its interaction with Nrf2 protein. Mutations in the active site cysteine (Cys139) impaired both the function and cellular distribution of UBE2E2. More importantly, the deletion of UBE2E2 reduced tumorigenicity and metastasis in xenograft OvCa mouse models. Taken together, our findings reveal the role of the UBE2E2-Nrf2-p62-Snail signaling axis in OvCa and thus provides novel therapeutic targets for the prevention of OvCa metastasis.

PM2.5 increases susceptibility to acute exacerbation of COPD via NOX4/Nrf2 redox imbalance-mediated mitophagy

The increasing abundance of fine particulate matter (PM2.5) in the environment has increased susceptibility to acute exacerbation of COPD (AECOPD). During PM2.5 exposure, excessive reactive oxygen species (ROS) production triggers a redox imbalance, which contributes to damage to organelles and disruption of homeostasis. At present, there are limited data on whether NOX4/Nrf2 redox imbalance increases susceptibility to acute exacerbation of COPD (AECOPD), and the underlying mechanism is unclear. Therefore, the current study was aimed to evaluate the role of NOX4/Nrf2 redox balance on AECOPD induced by PM2.5-CS-exposure. Here, we report that PM2.5 exacerbates cytotoxicity by enhancing NOX4/Nrf2 redox imbalance-mediated mitophagy. First, exposure to a low-dose of PM2.5 (200 μg/ml) significantly exacerbated oxidative stress and mitochondrial damage by increasing the ROS overproduction, enhancing the excessive NOX4/Nrf2 redox imbalance, decreasing the mitochondrial membrane potential (MMP), and enhancing the mitochondrial fragmentation that were caused by a low-dose of CSE (2.5%). Second, coexposure to PM2.5 and CSE (PM2.5-CSE) induced excessive mitophagy. Third, PM2.5 exacerbated CS-induced COPD, as shown by excessive inflammatory cell infiltration, inflammatory cytokine production and mucus hypersecretion, goblet cell hyperplasia, NOX4/Nrf2 redox imbalance, and mitophagy, these effects triggered excessive ROS production and mitochondrial damage in mice. Mechanistically, PM2.5-CS-induced excessive levels of mitophagy by triggering redox imbalance, leading to greater cytotoxicity and AECOPD; however, reestablishing the NOX4/Nrf2 redox balance via NOX4 blockade or mitochondria-specific ROS inhibitor treatment alleviated this cytotoxicity and ameliorated AECOPD. PM2.5 may exacerbate NOX4/Nrf2 redox imbalance and subsequently enhance mitophagy by increasing the ROS and mito-ROS levels, thereby increasing susceptibility to AECOPD.

PM2.5 inhibits system Xc- activity to induce ferroptosis by activating the AMPK-Beclin1 pathway in acute lung injury

Urban airborne fine particulate matter (PM2.5) is a global pollution source that has been strongly related to multiple respiratory diseases involving various types of regulated cell death (RCD). However, the role of ferroptosis, a novel form of RCD, in PM2.5-induced acute lung injury (ALI), has not been elucidated. Herein, we define the role and mechanism of ferroptosis in a PM2.5-induced ALI model. First, we demonstrated that lipid peroxidation and iron accumulation were significantly enhanced in ALI models and were accompanied by activation of the AMP-activated protein kinase (AMPK)-Beclin1 signaling pathway and inhibition of the key subunit SLC7A11 of System Xc-. However, these abnormalities were partially reversed by ferroptosis inhibitors. We further revealed that Beclin1 knockdown or overexpression ameliorated or exacerbated PM2.5-induced ferroptosis, respectively. Mechanistically, we verified that Beclin1 blocks System Xc- activity to trigger ferroptosis by directly binding to SLC7A11. Finally, knockdown of Beclin1 by AAV-shRNA or inhibition of AMPK, an upstream activator of Beclin1, ameliorated PM2.5-induced ferroptosis and ALI. Taken together, our results revealed that ferroptosis plays a novel role in PM2.5-induced ALI and elucidated the specific mechanism involving the AMPK-Beclin1 pathway and System Xc-, which may provide new insight into the toxicological effects of PM2.5 on respiratory problems.

Leonurine hydrochloride alleviates ferroptosis in cisplatin-induced acute kidney injury by activating the Nrf2 signaling pathway

BACKGROUND AND PURPOSE

Increasing evidence suggests that ferroptosis plays a key role in the pathophysiology of acute kidney injury (AKI) induced by cisplatin. The Nrf2 signaling pathway regulates oxidative stress and lipid peroxidation and positively regulates cisplatin-induced AKI (CI-AKI). However, its effect as well as an alkaloid compound leonurine hydrochloride (LH) on ferroptosis after CI-AKI remain unclear.

EXPERIMENTAL APPROACH

The anti-ferroptotic effects of Nrf2 and LH were assessed using a mouse model of cisplatin-induced AKI. In vitro, the potential effects of LH on erastin- and RSL3-induced HK-2 human PTEC ferroptosis were examined.

KEY RESULTS

As expected, Nrf2 deletion induced ferroptosis-related protein expression and iron accumulation in vivo, further aggravating CI-AKI. LH activated Nrf2 and prevented iron accumulation, lipid peroxidation and ferroptosis in vitro, while these effects were abolished in siNrf2-treated cells. Moreover, LH potently ameliorated cisplatin-induced renal damage, as indicated by the assessment of SCr, BUN, KIM-1, and NGAL. Importantly, LH activated the Nrf2 antioxidative signaling pathway and prohibited changes in ferroptosis-related morphological and biochemical indicators, such as the MDA level, SOD and GSH depletion and GPX4 and xCT downregulation, in CI-AKI. Moreover, Nrf2 KO mice were more susceptible to ferroptosis after CI-AKI than control mice, and the protective effects of LH on AKI and ferroptosis were largely abolished in Nrf2 KO mice.

CONCLUSION AND IMPLICATIONS

These data suggest that the renal protective effects of Nrf2 activation on CI-AKI are achieved at least partially by inhibiting lipid peroxide-mediated ferroptosis and highlight the potential of LH as a CI-AKI treatment.

Leonurine inhibits the TXNIP/NLRP3 and NF-κB pathways via Nrf2 activation to alleviate carrageenan-induced pleurisy in mice

Oxidative stress and inflammation play important roles in pleurisy. Leonurine (Leo) has been confirmed to exert antioxidative and antiinflammatory effects in many preclinical experiments, but these effects have not been studied in pleurisy. The aim of this study was to explore the therapeutic effect and mechanism of Leo in a carrageenan (CAR)-induced pleurisy model. In this study, we found that the increase of reactive oxygen species (ROS), myeloperoxidase (MPO), and malondialdehyde (MDA) and decrease of glutathione (GSH) induced by CAR could be reversed by the treatment of Leo. Leo effectively reduced the levels of proinflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and the percentages of mature macrophages and increased the levels of antiinflammatory cytokines (IL-10). Furthermore, Western blotting revealed that Leo significantly activated the Nrf2 pathway to restrain the thioredoxin-interacting protein/NOD-like receptor protein 3 (TXNIP/NLRP3) and nuclear factor kappa-B (NF-κB) pathways. However, the protective effect of Leo was significantly weakened in Nrf2-deficient mice. These results indicate that Leo confers potent protection against CAR-induced pleurisy by inhibiting the TXNIP/NLRP3 and NF-κB pathways dependent on Nrf2, which may serve as a promising agent for attenuating pleurisy.

Amentoflavone Ameliorates Carrageenan-Induced Pleurisy and Lung Injury by Inhibiting the NF-κB/STAT3 Pathways via Nrf2 Activation

Many natural flavonoids can activate nuclear factor erythroid 2-related factor 2 (Nrf2), which is pivotal for alleviating various diseases related to inflammation and oxidative stress, including pleurisy. Amentoflavone (AMF), a biflavonoid extracted from many plants, has some beneficial bioactivities, especially anti-inflammatory and antioxidative activities. We aimed to investigate whether AMF protects against pleurisy and lung injury induced by carrageenan (Car) by activating Nrf2. Pleurisy was induced in wild-type (WT) and Nrf2-deficient (Nrf2^-/-) mice. Then, pleural exudate and lung tissue were collected for biochemical analysis, H&E staining, immunocytochemistry and western blotting. Our results indicated that AMF protected against Car-induced pleurisy and lung injury. The Wright-Giemsa and H&E staining results showed that AMF alleviated inflammatory effusion and pathological injury. In addition, AMF decreased SOD and GSH depletion and MDA and MPO generation in the lung tissue of mice. AMF activated Nrf2 through keap-1 dissociation and subsequently increased heme oxygenase-1 (HO-1), NAD(P)H-quinone oxidoreductase 1 (NQO1), and γ-glutamylcysteine ligase (GCL) levels. Furthermore, AMF suppressed IL-1β and TNF-α levels and increased IL-10 levels in pleural exudate by blocking the proinflammatory NF-κB, signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase (ERK) pathways induced by Car. However, these antioxidative and anti-inflammatory effects were weakened in Nrf2^-/- mice. Moreover, AMF failed to suppress the NF-κB and STAT3 pathways in Nrf2^-/- mice. Our results demonstrated that AMF exerted anti-inflammatory and antioxidative effects in Car-induced lung injury and pleurisy in a Nrf2-dependent manner.

Enterobacter cloacae aggravates metabolic disease by inducing inflammation and lipid accumulation

It is well known that gut microbiota imbalance can promote the development of metabolic disease. Enterobacter cloacae (E. cloacae) is a kind of opportunistic pathogen in the intestine. Therefore, we hypothesized that E. cloacae accelerated the development of metabolic disease. To answer this question, we used E. cloacae to induce disease in guinea pigs. We used H&E staining to detect the pathological changes of liver and aorta and used Oil Red O staining to evaluate the lipid accumulation in the liver. And that we used a kit to detect AST content and used Western blot to detect protein levels in the liver. We found that E. cloacae could induce liver pathological changes and lipid accumulation as well as aortic wall pathological changes in guinea pigs. And E. cloacae increased the liver index to 5.94% and the serum AST level to 41.93 U/L. Importantly, E. cloacae activated liver high mobility group protein (HMGB1)/toll-like receptor 4 (TLR4)/myeloiddifferentiationfactor88 (MYD88)/nuclear factor-kappa B (NF-κB) signal and sterol regulatory element-binding protein 1c (SREBP-1c) and inhibited AMP-activated protein kinase (AMPK). We conclude that E. cloacae promote nonalcoholic fatty liver disease (NAFLD) by inducing inflammation and lipid accumulation, and E. cloacae also promote atherosclerosis. These findings are important for study on the pathogenesis and drug screening of NAFLD and atherosclerosis.

Nrf2 Signaling Pathway Mediates the Protective Effects of Daphnetin Against D-Galactose Induced-Premature Ovarian Failure

Oxidative damage can lead to severe ovarian dysfunctions and even premature ovarian failure. Nrf2, a significant transcription factor that regulates the oxidative stress response of cells, declines with age. Daphnetin, as a kind of natural Chinese herbal medicine, can activate Nrf2 and further promote the antioxidant defense of cells. However, whether Daphnetin treatment can protect ovary from premature ovarian failure and the specific mechanism involved are not understood. This study aimed to investigate the protective function of Daphnetin against the ovarian aging induced by D-galactose in wild-type and Nrf2^−/− mice. Female C57BL/6 mice with Wild-type and Nrf2^−/− were divided into five groups separately and the premature ovarian failure model were established by D-galactose and then Daphnetin and VE were given for treatment. After 42 days, ovaries tissue and serum were collected for biochemical determination, H&E staining, Immunohistochemical staining and western blot analysis. In the WT-POF group, ovarian function was broke, and the expression of the ovarian senescence-associated protein P16 and the level of oxidative stress were significantly increased, while the expression of the anti-senescence protein klotho was significantly decreased. In addition, the expression of Nrf2 and the antioxidases GCLC, HO-1 and NQO1 were decreased, but TXNIP and NLRP3 were significantly increased. Furthermore, the characteristics of premature ovarian failure were more significant in Nrf2 knockout mice than in wild-type mice, especially the expression of NLRP3 and TXNIP. Moreover, daphnetin, an Nrf2 activator, rescued d-gal-induced POF in a dose-dependent manner, while the protective effect was weakened or even lost in Nrf2 knockout mice. Our results suggested that daphnetin is likely to be a candidate drug for premature ovarian failure treatment and it is mostly possible referred to the molecular mechanism of increasing Nrf2 expression and inhibiting NLRP3 activation in the ovarian aging process.

Farrerol Ameliorated Cisplatin-Induced Chronic Kidney Disease Through Mitophagy Induction via Nrf2/PINK1 Pathway

Previously, Our study has showed that farrerol can activate Nrf2 and ameliorate cisplatin-induced acute kidney injury (AKI). Mitophagy reportedly can prevent diabetic nephropathy, cisplatin-induced AKI and other related nephropathy. In this study, we evaluated the correlation between mitophagy and the protective effect of the Nrf2 activator farrerol on cisplatin-induced CKD by using C57BL/6 wild-type and Nrf2 knockout mice. We confirmed that Nrf2 and PINK1/Parkin-mediated mitophagy was significantly increased on the 3rd day of cisplatin stimulation but was reduced on the 38th day of cisplatin stimulation. Similar to previous results, farrerol activated Nrf2 on the 38th day of cisplatin administration, subsequently stimulating the Nrf2-targeted antioxidant enzymes HO-1 and NQO1. In addition, farrerol triggered PINK1/Parkin-mediated mitophagy by recruiting the receptor proteins LC3 and p62/SQSTM1, thereby eliminating damaged mitochondria. Furthermore, genetic deletion of Nrf2 reduced PINK1/Parkin-mediated mitophagy activation and led to increased renal tubular necrosis and renal fibrosis. We also found that farrerol alleviated inflammation and renal fibrosis by inhibiting p-NF-κB/NLRP3 and TGF-β/Smad signaling. These data indicated that farrerol effectively inhibited cisplatin-induced inflammation and renal fibrosis by activating Nrf2 and PINK1/Parkin-mediated mitophagy, which provides a potential novel therapeutic target for CKD.

Protective effect of miR-146 against kidney injury in diabetic nephropathy rats through mediating the NF-κB signaling pathway

The article "Protective effect of miR-146 against kidney injury in diabetic nephropathy rats through mediating the NF-κB signaling pathway", H.-Y. Yu, L.-F. Meng, X.-H. Lu, L.-H. Liu, X. Ci, Z. Zhuo, published in Eur Rev Med Pharmacol Sci 2020; 24 (6): 3215-3222-DOI: 10.26355/eurrev_202003_20688-PMID: 32271439, has been retracted by the authors due to some inaccuracies (some data cannot be repeated by further research). The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/20688.

Daphnetin ameliorated GM-induced renal injury through the suppression of oxidative stress and apoptosis in mice

Gentamicin (GM), an aminoglycoside antibiotic, is one of the most effective drugs used in the treatment of various types of bacterial infections, but the major adverse effect and drug-induced nephrotoxicity of GM limit its clinical applications. Daphnetin (Daph) is a natural coumarin derivative that is clinically used to treat rheumatoid arthritis and coagulopathy and exhibits antioxidant effects. However, the effect of Daph on GM-induced nephrotoxicity has not yet been elucidated. This study investigated Daph-mediated protection against GM-induced nephrotoxicity in mice and explored the underlying mechanisms of GM-induced renal dysfunction in mice. We found that Daph treatment significantly reduced GM-induced nephrotoxicity mainly by ameliorating renal injury in mice and attenuating cell damage in vitro. Mechanistically, we found that Daph upregulated the expression level of Nrf2 and its regulated antioxidant enzymes HO-1, NQO1, GCLC and GCLM in vivo and in vitro. GM upregulated the expression levels of NOX4, cleaved Caspase-3 and p53 and the BAX/BCL2 ratio in vivo to stimulate oxidative stress and apoptosis. However, Daph treatment significantly improved the oxidative stress and apoptosis caused by GM, thereby exerting antioxidative and antiapoptotic effects. Our study was the first to suggest that the natural product Daph protects against GM-induced nephrotoxicity through the activation of Nrf2 which regulates oxidative stress and apoptosis. The pharmacological activation of Nrf2 may be useful as a novel therapy to prevent renal injury.

Hyperoside relieves particulate matter-induced lung injury by inhibiting AMPK/mTOR-mediated autophagy deregulation

Autophagy-mediated cell death plays a critical role in the pathogenesis of PMs-induced lung injury. Hyperoside (Hyp), a flavonoid glycosides, is known to exert protective effects on many diseases by inhibiting autophagic activity. The current study aimed to explore the protective effect and mechanism of Hyp against PMs-induced lung injury in PM2.5 challenged Beas-2b cells in vitro and BALB/C mice in vivo. In vitro, we found that the organic solvent-extractable fraction of SRM1649b (O-PMs) caused more severe cytotoxicity in Beas-2b cells than the water solvent-extractable fraction of SRM1649b (W-PMs). O-PMs treatment dose-dependently upregulated the expression of autophagy markers (beclin-1, p62, atg3 and LC3II) and apoptotic proteins. This cytotoxicity of O-PMs was attenuated by Hyp pretreatment in parallel with downregulation of the expression of autophagy markers, apoptotic proteins, and p-AMPK and upregulation of p-mTOR expression. Notably, the therapeutic effect of Hyp was attenuated by pretreated with AICAR (an AMPK inducer), but enhanced by CC and 3-MA treatment. In vivo, Hyp reduced pathological lung injury and decreased the levels of PMs-induced inflammatory cytokines (TNF-α and IL-6), and the number of total cells in the BALF by inhibiting AMPK/mTOR signaling. Furthermore, cotreatment with AICAR (500 mg/kg) reduced but did not abrogate the pulmonary protective effect of Hyp. These findings indicate that Hyp protects against PMs-induced lung injury by suppressing autophagy deregulation and apoptosis through regulation of the AMPK/mTOR pathway.

Diosmetin induces apoptosis in ovarian cancer cells by activating reactive oxygen species and inhibiting the Nrf2 pathway

The fatality rate of ovarian cancer ranks first among gynecological tumors, and the prognosis is poor. Diosmetin (Dio), a natural flavonoid obtained from citrus fruits, has been shown to have anti-tumor effects in lung, liver, and skin cancers. We aimed to investigate the effects of Dio on ovarian cancer A2780 and SKOV3 cells along with the underlying mechanisms. Our data showed that Dio inhibited the proliferation, migration, and invasion of these cells and induced their apoptosis. Moreover, Dio upregulated the levels of Bax and cleaved Caspase-3 and PARP while downregulating the level of Bcl2. Mechanistically, our results revealed that Dio inhibited Nrf2 and induced the production of reactive oxygen species (ROS). The ROS scavenger N-acetyl-L-cysteine (NAC) suppressed the inhibitory effect of Dio on the proliferation of the ovarian cancer cells. Additionally, overexpression of Nrf2 partially suppressed the Dio-induced apoptosis and proliferation inhibition in these cells. These findings indicate that Dio exerts an anti-tumor activity by upregulating ROS levels and inhibiting Nrf2, indicating that Dio is a promising chemotherapeutic candidate for the treatment of ovarian cancer.

Protective effect of miR-146 against kidney injury in diabetic nephropathy rats through mediating the NF-κB signaling pathway

OBJECTIVE

To study the protective effect of micro ribonucleic acid (miR)-146 against kidney injury in diabetic nephropathy (DN) rats through the nuclear factor-κB (NF-κB) signaling pathway.

MATERIALS AND METHODS

In this experiment, 30 adult Sprague-Dawley rats with 5-6 weeks old and weighing 20-30 g were selected and randomly divided into control group (n=10), model group (n=10), and miR-146 Mimic group (n=10, DN rat model + miR-146 Mimic). The serum levels of creatinine (Cr) and blood urea nitrogen (BUN) in the three groups were detected using the full-automatic biochemical analyzer. The protein expression levels of phosphorylated-inhibitor of NF-κB (p-IκB), p-P65, P65, and Tubulin were detected via Western blotting. The messenger RNA (mRNA) of P65 was determined using quantitative Polymerase Chain Reaction (qPCR). Positive expression of p-IκB in tissues was determined using immunohistochemistry. Moreover, the contents of inflammatory factors tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 were detected using the enzyme-linked immunosorbent assay (ELISA) kits. Finally, the apoptosis was detected through Annexin V-fluorescein isothiocyanate (FITC) and propidium iodide (PI) dual-fluorescence labeling.

RESULTS

The serum levels of Cr and BUN were significantly higher in the model group than those in the control group (p<0.01), while they were significantly lower in miR-146 Mimic group than those in the model group (p<0.05). The levels of p-IκB and p-P65/P65 significantly increased in the model group compared with those in the control group (p<0.01), while they remarkably declined in the miR-146 Mimic group compared with those in the model group (p<0.05). The results of qPCR showed that the mRNA level of P65 had no significant difference among the three groups (p>0.05). The immunohistochemical assay showed that the positive expression of p-IκB in tissues was consistent with those of the protein level as Western blotting revealed. The rats in the model group had evidently increased levels of TNF-α, IL-1β, and IL-6 compared with the control group (p<0.01), while miR-146 Mimic group had evidently decreased levels of them compared with the model group (p<0.01). Finally, apoptosis was enhanced in the model group compared with that in the control group, while it was remarkably inhibited in the miR-146 Mimic group.

CONCLUSIONS

MiR-146 can inhibit the NF-κB signaling pathway, lower the levels of TNF-α, IL-1β, and IL-6, and reduce the apoptosis, thereby exerting a protective effect against kidney injury in DN.

Daphnetin triggers ROS-induced cell death and induces cytoprotective autophagy by modulating the AMPK/Akt/mTOR pathway in ovarian cancer

BACKGROUND

Ovarian cancer is one of the most common gynecological malignancies in the world. Daphnetin (Daph) was previously reported to possess antitumor potential, but its potential and molecular mechanisms in ovarian cancer remain poorly understood.

PURPOSE

In the current study, we aimed to explore the antitumor effect and detailed mechanisms of Daph in ovarian cancer cells.

METHODS

The cytotoxic effect of Daph on ovarian cells was determined in vitro and in vivo. Cell growth, proliferation, apoptosis and ROS generation were measured by CCK8 assays, colony formation assays and flow cytometry. Western blotting was used to evaluate the related signal proteins. Immunofluorescence and transmission electron microscopy were used to evaluate markers of autophagy and autophagic flux. The antitumor effects were observed in the A2780 xenograft model. Moreover, Daph-induced autophagy was observed by enhanced LC3-II accumulation and endogenous LC3 puncta, and an autophagy inhibitor further enhanced the antitumor efficacy of Daph, which indicated that the cytoprotective role of autophagy in ovarian cancer.

RESULTS

We found that Daph exhibited antitumor effects by inducing ROS-dependent apoptosis in ovarian cancer, which could be reversed by N-acetyl cysteine (NAC). The AMPK/Akt/mTOR pathway was involved in Daph-mediated cytoprotective autophagy, and when Daph-mediated the expression level of AMPK and autophagy were blocked, there was robust inhibition of cell proliferation and induction of apoptosis. In addition, in the A2780 xenograft model, combined treatment with Daph and an autophagy inhibitor showed obvious synergetic effects on the inhibition of cell viability and promotion of apoptosis, without any side effects.

CONCLUSION

Our results suggest that Daph triggers ROS-induced cell apoptosis and induces cytoprotective autophagy by modulating the AMPK/Akt/mTOR pathway. Moreover, the combination of Daph and autophagy inhibitor may be a potential therapeutic strategy for ovarian cancer.

Daphnetin Attenuated Cisplatin-Induced Acute Nephrotoxicity With Enhancing Antitumor Activity of Cisplatin by Upregulating SIRT1/SIRT6-Nrf2 Pathway

Cisplatin (CDDP) is a widely used drug for cancer treatment that exhibits major side effects in normal tissues, such as nephrotoxicity in kidneys. The Nrf2 signaling pathway, a regulator of mitochondrial dysfunction, oxidative stress and inflammation, is a potential therapeutic target in CDDP-induced nephrotoxicity. We explored the underlying mechanisms in wild-type (WT) and Nrf2^−/− mice on CDDP-induced renal dysfunction in vivo. We found that Nrf2 deficiency aggravated CDDP-induced nephrotoxicity, and Daph treatment significantly ameliorated the renal injury characterized by biochemical markers in WT mice and reduced the CDDP-induced cell damage. In terms of the mechanism, Daph upregulated the SIRT1 and SIRT6 expression in vivo and in vitro. Furthermore, Daph inhibited the expression level of NOX4, whereas it activated Nrf2 translocation and antioxidant enzymes HO-1 and NQO1, and alleviated oxidative stress and mitochondrial dysfunction. Moreover, Daph suppressed CDDP-induced NF-κB and MAPK inflammation pathways, as well as p53 and cleaved caspase-3 apoptosis pathways. Notably, the protective effects of Daph in WT mice were completely abrogated in Nrf2^−/− mice. Moreover, Daph enhanced, rather than attenuated, the tumoricidal effect of CDDP.

The role of Nrf2 in acute kidney injury: Novel molecular mechanisms and therapeutic approaches

Acute kidney injury (AKI) is a common clinical syndrome that is related to high morbidity and mortality. Oxidative stress, including the production of reactive oxygen species (ROS), appears to be the main element in the occurrence of AKI and the cause of the progression of chronic kidney disease (CKD) into end-stage renal disease (ESRD). Nuclear factor erythroid 2 related factor 2 (Nrf2) is a significant regulator of redox balance that has been shown to improve kidney disease by eliminating ROS. To date, researchers have found that the use of Nrf2-activated compounds can effectively reduce ROS, thereby preventing or retarding the progression of various types of AKI. In this review, we summarized the molecular mechanisms of Nrf2 and ROS in AKI and described the latest findings on the therapeutic potential of Nrf2 activators in various types of AKI.

Enhanced Keap1-Nrf2/Trx-1 axis by daphnetin protects against oxidative stress-driven hepatotoxicity via inhibiting ASK1/JNK and Txnip/NLRP3 inflammasome activation

BACKGROUND

Oxidative stress-triggered fatal hepatotoxicity is an essential pathogenic factor in acute liver failure (ALF).

AIMS

To investigate the protective effect of daphnetin (Daph) on tert-butyl hydroperoxide (t-BHP) and acetaminophen (APAP)-induced hepatotoxicity through altering Nrf2/Trx-1 pathway activation.

MATERIALS AND METHODS

In vivo, male C57BL/6 mice with Wild-type (WT) and Nrf2^-/- were divided into five groups and acute liver injury model were established by APAP or LPS/GalN after injection with Daph (20, 40, or 80 mg/kg), seperately. Then, liver tissue and serum were collected for biochemical determination, TUNEL and H & E staining, and western blot analysis. In vitro, HepG2 cells were used to investigate the protective effect and mechanism of daphnetin against ROS and apoptosis induced by t-BHP via apoptosis detection, western blot, immunofluorescence analysis, and sgRNA transfection.

RESULTS

Our results indicated that Daph efficiently inhibited t-BHP-stimulated hepatotoxicity, and modulated Trx-1 expression and Nrf2 activation which decreased Keap1-overexpression in HepG2 cells. Moreover, Daph inhibited t-BHP-excited hepatotoxicity and enhanced Trx-1 expression, which was reversed in Nrf2^-/- HepG2 cells. In vivo, a survival rate analysis first suggested that Daph significantly reduced the lethality induced by APAP or GalN/LPS in a Nrf2-dependent or -independent manner by using Nrf2^-/- mice, respectively. Next, further results implicated that Daph not only effectively alleviated APAP-induced an increase of ALT and AST levels, histopathological changes, ROS overproduction, malondialdehyde (MDA) formation and GSH/GSSG reduction, but it also relieved hepatic apoptosis by strengthening the suppression of cleaved-caspase-3 and expression of P53 protein. Additionally, Daph attenuated mitochondrial dysfunction by suppressing ASK1/JNK activation and decreasing apoptosis-inducing factor (AIF) and Cytochrome c release and Bax mitochondrial translocation. Daph inhibited inflammatory responses by inactivating the thioredoxin-interacting protein (Txnip)/NLRP3 inflammasome. Furthermore, Daph efficiently enhanced Nrf2 nuclear translocation and Trx-1 expression. However, these effects in WT mice were eliminated in Nrf2^-/- mice.

CONCLUSIONS

These investigations demonstrated that Daph treatment has protective potential against oxidative stress-driven hepatotoxicity by inhibition of ASK1/JNK and Txnip/NLRP3 activation, which may be strongly related to the Nrf2/Trx-1 upregulation.

Pterostilbene prevents LPS-induced early pulmonary fibrosis by suppressing oxidative stress, inflammation and apoptosis in vivo

Early pulmonary fibrosis after acute lung injury leads to poor prognosis and high mortality. Pterostilbene (Pts), a bioactive component in blueberries, possesses anti-inflammatory, antioxidative and antifibrotic properties. However, the effects of Pts on lipopolysaccharide (LPS)-induced pulmonary fibrosis are still unknown. In our study, the Pts group showed lower lung injury and fibrosis scores, and lower levels of hydroxyproline and protein (collagen I and transforming growth factor-β) than the scores and levels in mice treated with LPS. MMP-1 was the degrading enzyme of collagen I and LPS caused the inhibition of MMP-1, disturbing the degradation of collagen. Additionally, Pts remarkably reversed the LPS-induced inhibition of interleukin-10 and the release of tumor necrosis factor-α, interleukin-6 and interleukin-1β. In terms of cellular pathways, Pts treatment ameliorated LPS-activated nuclear factor kappa B (NF-κB) and NOD-like receptor NLRP3 signaling. Besides, LPS-induced low levels of A20 could be activated by Pts. In addition, Pts treatment reversed the high levels of Caspase-3, poly ADP-ribose polymerase (PARP) and Bcl2-associated X protein (Bax) expression and the low levels of B cell lymphoma/lewkmia-2 (Bcl2) that had been induced by LPS. Moreover, oxidative stress is also involved in the pathogenesis of fibrosis. Our findings indicate that LPS injection triggered the production of myeloperoxidase (MPO) and malondialdehyde (MDA) and the depletion of superoxide dismutase (SOD) and glutathione (GSH), and that these effects were notably reversed by treatment with Pts. In addition, Pts induced the dissociation of Kelch-like epichlorohydrin-associated protein-1 (Keap-1) and NF-E2 related factor-2 (Nrf2) and the activation of downstream genes (heme oxygenase-1, NAD(P)H:quinine oxidoreductase, glutamate-cysteine ligase catalytic subunit and glutamate-cysteine ligase modifier). In conclusion, oxidative stress, apoptosis and inflammation are involved in early pulmonary fibrosis and Pts exerts a protective effect by activating Keap-1/Nrf2, inhibiting caspase-dependent A20/NF-κB and NLRP3 signaling pathways.

Isoorientin Attenuates Cisplatin-Induced Nephrotoxicity Through the Inhibition of Oxidative Stress and Apoptosis via Activating the SIRT1/SIRT6/Nrf-2 Pathway

Cisplatin (CDDP) is a widely used chemotherapeutic agent for various solid tumors, but its severe side effects, particularly nephrotoxicity, limit its clinical application. Isoorientin (Iso) is a flavonoid-like compound known to have antioxidant effects. As oxidative injury plays a vital role in CDDP-induced acute kidney injury (AKI), the effect of Iso on CDDP-induced nephrotoxicity has not yet been researched. We assessed the effects of Iso against CDDP-induced nephrotoxicity in vitro using mTEC cells and further explored the mechanisms underlying CDDP-induced renal dysfunction in vivo in WT and Nrf2^-/- mice. The results showed that Iso treatment significantly reduced CDDP-induced nephrotoxicity via attenuating cell damage in vitro and via ameliorating renal injury, as determined by biochemical markers, in mice. The molecular mechanism underlying this protection was also investigated. Iso up-regulated the expression levels of SIRT1 and SIRT6 in vivo and in vitro. In addition, Iso activated Nrf2 translocation and the expression levels of its downstream antioxidant enzymes, such as HO-1 and NQO1, whereas it inhibited the expression level of NOX4, thus decreasing oxidative stress. Notably, the protective effects of Iso observed in WT mice were completely abolished in Nrf2^-/- mice. Collectively, these data indicate that the protective effect of Iso on CDDP-induced nephrotoxicity by SIRT1- and SIRT6-mediated Nrf2 activation regulates oxidative stress, inflammation and apoptosis. The absence of Nrf2 exacerbates CDDP-induced renal damage, and the pharmacological activation of Nrf2 may represent a novel therapy to prevent kidney injury.

Isoliquiritigenin exerts antioxidative and anti-inflammatory effects via activating the KEAP-1/Nrf2 pathway and inhibiting the NF-κB and NLRP3 pathways in carrageenan-induced pleurisy

Pleurisy refers to a pleural disease caused by pathogenic factors that stimulate the pleura associated with pleural inflammation and oxidative stress. Isoliquiritigenin (ISL), a flavonoid from the liquorice compound, possesses antioxidative and anti-inflammatory properties. In the current study, we investigated the protective effects of ISL on carrageenan-induced pleurisy and lung injury in mice. The mice were intraperitoneally injected with ISL (30 mg kg^-1) twice (each time interval of 12 h), followed by exposure to Car 1 h after the second dose of ISL. Our results indicated that ISL treatment significantly alleviated carrageenan-induced histopathological damage and increased levels of inflammatory cell exudation, protein leakage, and pro-inflammatory mediators. Meanwhile, ISL inhibited reactive oxygen species (ROS) generation, MDA and MPO formation, and SOD and GSH depletion induced by carrageenan. In addition, it decreased the GSSG level and GSSG-to-GSH ratio. In terms of the mechanism, ISL inhibited NOX2 and NOX4 levels, caused the dissociation of KEAP-1 and Nrf2, and activated the downstream genes HO-1, NQO1, GCLC and GCLM, thus decreasing oxidative stress. In addition, ISL exerts protective effects against inflammation by suppressing the NOD-like receptor protein 3 (NLRP3)/NF-κB pathway and the high levels of iNOS and COX-2. In summary, our results reinforce the hypothesis that ISL exerts protective effects on carrageenan-induced pleurisy and lung injury in a manner that can be attributed to Nrf2-mediated antioxidative activities and NLRP3/NF-κB-mediated anti-inflammatory activities.

Isoalantolactone Enhances the Antimicrobial Activity of Penicillin G against Staphylococcus aureus by Inactivating β-lactamase during Protein Translation

β-Lactamase-positive Staphylococcus aureus is one of the most prevalent multidrug-resistant pathogens worldwide and is associated with increasing threats to clinical therapeutics and public health. Here, we showed that isoalantolactone (IAL), in combination with penicillin G, exhibited significant synergism against 21 β-lactamase-positive S. aureus strains (including methicillin resistant S. aureus). An enzyme inhibition assay, a checkerboard minimum inhibitory concentration (MIC) assay, a growth curve assay, a time-killing assay, a RT-PCR assay and Circular Dichroism (CD) spectroscopy were performed on different β-lactamases or β-lactamase-positive S. aureus strains, in vitro, to confirm the mechanism of inhibition of β-lactamase and the synergistic effects of the combination of penicillin G and IAL. All the fractional inhibitory concentration (FIC) indices of penicillin G, in combination with IAL, against β-lactamase-positive S. aureus, were less than 0.5, and ranged from 0.10 ± 0.02 to 0.38 ± 0.17. The survival rate of S. aureus-infected mice increased significantly from 35.29% to 88.24% within 144 h following multiple compound therapy approaches. Unlike sulbactam, IAL inactivated β-lactamase during protein translation, and the therapeutic effect of combination therapy with IAL and penicillin G was equivalent to that of sulbactam with penicillin G. Collectively, our results indicated that IAL is a promising and leading drug that can be used to restore the antibacterial effect of β-lactam antibiotics such as penicillin G and to address the inevitable infection caused by βlactamase-positive S. aureus.

Farrerol Attenuates Cisplatin-Induced Nephrotoxicity by Inhibiting the Reactive Oxygen Species-Mediated Oxidation, Inflammation, and Apoptotic Signaling Pathways

Cisplatin is a chemotherapy drug that is often used in clinical practice, but its frequent use often leads to nephrotoxicity. Therefore, we urgently need a drug that reduces the nephrotoxicity induced by cisplatin. Farrerol reportedly has antioxidant potential, but its renal protective effects and potential mechanisms remain unclear. In this study, we used both cell and mouse models to determine the mechanism of farrerol in cisplatin-induced nephrotoxicity. The in vitro experiments revealed that farrerol improved cisplatin-induced nephrotoxicity and reactive oxygen species (ROS) production via nuclear factor erythrocyte 2-related factor 2 (Nrf2) activation. Moreover, farrerol effectively activated Nrf2 and subsequently increased the expression of Nrf2-targeted antioxidant enzymes, including heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO1), but inhibited Kelch-like ECH-associated protein 1 (Keap1) and NADPH oxidase type 4 (NOX4). Furthermore, farrerol attenuated the phosphorylation of C-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 mitogen-activated protein kinase (p38); the activation of phosphorylated nuclear factor-κB (p-NF-κB) and nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3); and the expression of phosphorylated p53 (p-p53), Bax, and cleaved caspase-3. In vivo, farrerol significantly improved cisplatin-induced renal damage, as demonstrated by the recovery of blood urea nitrogen (BUN), serum creatinine (SCr), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and pathological damage. Moreover, farrerol inhibited inflammatory and apoptotic protein expression in vivo. Notably, farrerol exerted slight protection in Nrf2-knockout mice compared with wild-type mice. These findings indicate that farrerol can effectively activate Nrf2 and can serve as a therapeutic target in the treatment of acute kidney injury (AKI).

Oridonin Sensitizes Cisplatin-Induced Apoptosis via AMPK/Akt/mTOR-Dependent Autophagosome Accumulation in A549 Cells

AMPK-mediated autophagy and Akt/mTOR pathways play important roles in current cancer treatments. Oridonin (Ori), an ent-kaurane diterpenoid isolated from Isodon rubescens, exerts extensive anti-tumor potential and controversial effects on autophagy. In this study, we investigated the effect of Ori on the autophagy, apoptosis, and AMPK/Akt/mTOR pathways and determined whether Ori was related to the increased cisplatin sensitivity observed in A549 cells. First, we found that Ori suppressed Akt/mTOR, Bcl2 and autophagy flux with enhanced levels of Atg3, P62, and LC3II, which was also shown as the accumulation of autophagosomes. AMPK and pro-apoptotic proteins (caspase3, Bax, and PARP) were activated in Ori-treated cells. With the pretreatment of compound c (AMPK inhibitor), the activation of autophagosomes, apoptosis and the inhibition of Akt/mTOR pathways induced by Ori were all reversed. The Ori-activated apoptosis-related markers mentioned previously and the cell-killing effect were restrained by 3-MA (inhibitor of autophagosomes) treatment. Therefore, we hypothesized that the Ori-induced pro-apoptotic effect was mediated by AMPK/Akt/mTOR-dependent accumulation of impaired autophagosomes. Furthermore, Ori could increase the sensitivity of cisplatin through its increased cell-killing, autophagy-suppressing and apoptosis-inducing activities. In addition to sensitizing cisplatin, Ori also alleviated cisplatin-induced acute renal injury in vivo, manifested as depleted BUN, CRE, kidney index, and weight loss compared to the cisplatin group. In summary, apart from its protective effect on cisplatin-induced nephrotoxicity, Ori enhanced cisplatin sensitivity via its pro-apoptotic activity mediated by AMPK/Akt/mTOR-dependent autophagosome activation, which may be a potential therapeutic target for non-small cell lung cancer.

Oridonin protects LPS-induced acute lung injury by modulating Nrf2-mediated oxidative stress and Nrf2-independent NLRP3 and NF-κB pathways

Background

Oxidative stress and the resulting inflammation are essential pathological processes in acute lung injury (ALI). Nuclear factor erythroid 2-related factor 2 (Nrf2), a vital transcriptional factor, possesses antioxidative potential and has become a primary target to treat many diseases. Oridonin (Ori), isolated from the plant Rabdosia Rrubescens, is a natural substance that possesses antioxidative and anti-inflammatory effects. Our aim was to study whether the anti-inflammatory and antioxidant effects of Ori on LPS-induced ALI were mediated by Nrf2.

Methods

MTT assays, Western blotting analysis, a mouse model, and hematoxylin-eosin (H & E) staining were employed to explore the mechanisms by which Ori exerts a protective effect on LPS-induced lung injury in RAW264.7 cells and in a mouse model.

Results

Our results indicated that Ori increased the expression of Nrf2 and its downstream genes (HO-1, GCLM), which was mediated by the activation of Akt and MAPK. Additionally, Ori inhibited LPS-induced activation of the pro-inflammatory pathways NLRP3 inflammasome and NF-κB pathways. These two pathways were also proven to be Nrf2-independent by the use of a Nrf2 inhibitor. In keeping with these findings, Ori alleviated LPS-induced histopathological changes, the enhanced production of myeloperoxidase and malondialdehyde, and the depleted expression of GSH and superoxide dismutase in the lung tissue of mice. Furthermore, the expression of LPS-induced NLRP3 inflammasome and NF-κB pathways was more evident in Nrf2-deficient mice but could still be reversed by Ori.

Conclusions

Our results demonstrated that Ori exerted protective effects on LPS-induced ALI via Nrf2-independent anti-inflammatory and Nrf2-dependent antioxidative activities.

Hesperetin relieves cisplatin-induced acute kidney injury by mitigating oxidative stress, inflammation and apoptosis

Although cisplatin is an effective anticancer drug, its clinical application is limited due to various side effects, especially nephrotoxicity. In this study, we investigated the protective effects and possible mechanisms of hesperetin on cisplatin-induced kidney damage. In vitro, hesperetin significantly attenuated oxidative stress-induced apoptosis by reducing ROS levels in cisplatin-treated HK-2 cells. Simultaneously, hesperetin activated the Nrf2 signaling pathway and regulated its downstream genes, including NQO1 and HO-1. In vivo, hesperetin could significantly attenuate cisplatin-induced nephrotoxicity, blood urea nitrogen (BUN) and serum creatinine (SCr). Furthermore, hesperetin clarifies cisplatin-induced oxidative stress by reducing MDA/MPO levels and increasing SOD/GSH levels. In addition, from the histopathological analysis of the kidney, hesperetin significantly reduced the nephrotoxicity caused by cisplatin compared with the cisplatin group. Moreover, western blotting of renal tissue revealed that hesperetin activates Nrf2 in a dose-dependent manner, attenuates the MAPK signaling pathway against inflammation, and inhibits the expression of apoptotic proteins to protect kidneys from AKI caused by cisplatin. Altogether, these findings suggest that hesperetin may be a potential protectant against cisplatin-induced nephrotoxicity.

Pterostilbene Activates the Nrf2-Dependent Antioxidant Response to Ameliorate Arsenic-Induced Intracellular Damage and Apoptosis in Human Keratinocytes

The NF-E2 p45-related factor 2 (Nrf2), a transcription factor that regulates the cellular adaptive response to oxidative stress, is a target for limiting tissue damage from exposure to environmental toxins, including arsenic. In the current study, we determine whether Pterostilbene (Pts), as a potent activator of Nrf2, has a protective effect on arsenic-induced cytotoxicity and apoptosis in human keratinocytes. Human keratinocytes (HaCaT) or mouse epidermal cells (JB6) were pretreated with Pts for 24 h prior to arsenic treatment. Harvested cells were analyzed by MTT, DCFH-DA, commercial kits, Flow cytometry assay and western blot analysis. Our results demonstrated that Pts effectively regulated the viability in HaCaT and JB6 cells, decreased the reactive oxygen species (ROS) generation and lipid peroxidation (MDA), and improved the NaAsO₂-induced depletion of superoxide dismutase (SOD). Moreover, Pts treatment further dramatically inhibited NaAsO₂-induced apoptosis, specifically the mitochondrial mediation of apoptosis, which coincided with the effective recovery of NaAsO₂-induced mitochondrial membrane potential (ΔΨm) depolarization and cytochrome c release from the mitochondria. Furthermore, arsenic-induced decrease of anti-apoptotic factor Bcl-2 and Bcl-xl, and increase of pro-apoptotic factor Bax and Bad, as well as survival signal related factor caspase 3 activation were reversed by Pts treatment. Further mechanistic studies confirmed that Pts increased antioxidant enzyme expression in a dose-dependent manner, which was related to Nrf2 nuclear translocation. In addition, the effects of Pts on NaAsO₂-induced cell viability were largely weakened when Nrf2 was knocked down. Together, our results provide evidence for the use of Pts to activate the Nrf2 pathway to alleviate arsenic-induced dermal damage.

Farrerol Ameliorates APAP-induced Hepatotoxicity via Activation of Nrf2 and Autophagy

Farrerol has been shown to have antioxidative potential via Nrf2 activation, which in turn is involved in the prevention of hepatotoxicity. The purpose of the current study was to explore the protective effect of farrerol against acetaminophen-induced hepatotoxicity and its underlying mechanisms. Mice were used to evaluate the hepatoprotective effect of farrerol on liver injury induced by acetaminophen in vivo. HepG2 cells were utilized to further determine the functional role and mechanisms by which Nrf2 and autophagy are involved in the hepatoprotective effect of farrerol in vitro. We found that treatment with farrerol leads to a significant reduction in acetaminophen-induced hepatotoxicity by decreasing mortality, histopathological liver changes, and ALT and AST levels. Furthermore, farrerol effectively suppressed mitochondrial dysfunction by reducing JNK phosphorylation, Bax mitochondrial translocation, AIF and cytochrome c release. Further investigations revealed that the activation of Nrf2 and the induction of autophagy via the AMPK/AKT pathway by farrerol contributed to its hepatoprotective activity in vitro. In addition, farrerol inhibited acetaminophen-induced the mortality and histopathological changes in WT mice were evidently alleviated but not abrogated in Nrf2 ^-/- mice, which attributed to the induction of autophagy. Together, farrerol has protective potential against acetaminophen-induced hepatotoxicity which may be associated with activation of Nrf2 and autophagy.

Isoorientin Ameliorates APAP-Induced Hepatotoxicity via Activation Nrf2 Antioxidative Pathway: The Involvement of AMPK/Akt/GSK3β

Oxidative stress has been highlighted as therapeutic targets for acetaminophen (APAP)-induced hepatotoxicity. Isoorientin (Iso), a well-known flavonoid-like compound, has been shown to have antioxidant potential. However, the effect of Iso on APAP-induced liver injury has not yet been elucidated. The present study investigated the hepatoprotective effect of Iso and its underlying mechanism. C57BL/6J mice were used to evaluate the hepatoprotective effect of Iso in vivo and HepG2 cells were utilized to further decipher the mechanisms of Iso -induced Nrf2 activation. We found that Iso treatment significantly reduced APAP-induced hepatotoxicity by reducing the lethality, histopathological liver changes, and alanine transaminase (ALT) and aspartate aminotransferase (AST) levels in serum. These effects were accompanied by decreased malondialdehyde (MDA) formation and myeloperoxidase level (MPO), and by decreased superoxide dismutase (SOD) and glutathione (GSH) depletion. Moreover, Iso induced Nrf2 activation and translocation as well as upstream AMPK/Akt/GSK3β activation. Furthermore, Iso effectively alleviated mitochondrial dysfunction by reducing c-jun N-terminal kinase phosphorylation and translocation, Bax mitochondrial translocation, and apoptosis-inducing factor and cytochrome c release. Further mechanistic investigations revealed that the activation of Nrf2 by Iso via the AMPK/Akt/GSK3β pathway contributed to the hepatoprotective activity of Iso in vitro. In addition, the Iso-mediated inhibition of APAP-induced the lethality, histopathological changes and mitochondrial dysfunction observed in WT mice was nearly absent in Nrf2^-/- mice. In summary, Iso ameliorated APAP-induced hepatotoxicity by activating Nrf2 via the AMPK/Akt/GSK3β pathway.

Pterostilbene Reduces Acetaminophen-Induced Liver Injury by Activating the Nrf2 Antioxidative Defense System via the AMPK/Akt/GSK3β Pathway

BACKGROUND/AIMS

Pterostilbene (Pts), a natural dimethylated analog of resveratrol from blueberries, exerts antioxidative and anti-apoptotic effects in various diseases. This study aims to investigate the protective effects and mechanism of Pts against acetaminophen (APAP)-induced hepatotoxicity in vivo.

METHODS

C57BL/6 mice were treated with APAP or APAP+Pts. HepG2 cells were used to further explore the underlying mechanisms in vitro. The effects of Pts on hepatotoxicity were measured by commercial kits, Hematoxylin and Eosin (H&E) straining, TUNEL assay, Western blot analysis, and Flow cytometry assay.

RESULTS

In vivo, Pts treatment effectively protected against APAP-induced severe liver injury by decreasing the lethality rate, the serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels, liver histological injury, liver malondialdehyde (MDA) formation and myeloperoxidase (MPO) levels and by increasing liver glutathione (GSH) and superoxide dismutase (SOD) levels. Moreover, in Pts-treated mice, the nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway was activated; however, APAP-induced c-Jun NH2-terminal kinase (JNK) activation, mitochondrial Bcl-2 Associated X Protein (Bax) translocation, apoptosis-inducing factor (AIF) levels and cytochrome c release were attenuated. In vitro, Pts was found to reverse hydrogen peroxide (H2O2) -induced cytotoxicity, reactive oxygen species (ROS) production and apoptosis that depended on Nrf2 activation. Moreover, Pts induced a dose-dependent increase in the phosphorylation of AMP-activated protein kinase (AMPK), serine/threonine kinase (Akt), and glycogen synthase kinase 3β (GSK3β) in HepG2 cells. Moreover, Pts protect against APAP or H2O2-induced toxicity were effectively attenuated or abolished in HepG2 Nrf2-/- cells and Nrf2-/- mice.

CONCLUSION

Our data suggest that Pts protects against APAP-induced toxicity by activating Nrf2 via the AMPK/Akt/GSK3β pathway.

Licochalcone A Upregulates Nrf2 Antioxidant Pathway and Thereby Alleviates Acetaminophen-Induced Hepatotoxicity

Acetaminophen (APAP) overdose-induced fatal hepatotoxicity is majorly characterized by overwhelmingly increased oxidative stress while enhanced nuclear factor-erythroid 2-related factor 2 (Nrf2) is involved in prevention of hepatotoxicity. Although Licochalcone A (Lico A) upregulates Nrf2 signaling pathway against oxidative stress-triggered cell injury, whether it could protect from APAP-induced hepatotoxicity by directly inducing Nrf2 activation is still poorly elucidated. This study aims to explore the protective effect of Lico A against APAP-induced hepatotoxicity and its underlying molecular mechanisms. Our findings indicated that Lico A effectively decreased tert-butyl hydroperoxide (t-BHP)- and APAP-stimulated cell apoptosis, mitochondrial dysfunction and reactive oxygen species generation and increased various anti-oxidative enzymes expression, which is largely dependent on upregulating Nrf2 nuclear translocation, reducing the Keap1 protein expression, and strengthening the antioxidant response element promoter activity. Meanwhile, Lico A dramatically protected against APAP-induced acute liver failure by lessening the lethality; alleviating histopathological liver changes; decreasing the alanine transaminase and aspartate aminotransferase levels, malondialdehyde formation, myeloperoxidase level and superoxide dismutase depletion, and increasing the GSH-to-GSSG ratio. Furthermore, Lico A not only significantly modulated apoptosis-related protein by increasing Bcl-2 expression, and decreasing Bax and caspase-3 cleavage expression, but also efficiently alleviated mitochondrial dysfunction by reducing c-jun N-terminal kinase phosphorylation and translocation, inhibiting Bax mitochondrial translocation, apoptosis-inducing factor and cytochrome c release. However, Lico A-inhibited APAP-induced the lethality, histopathological changes, hepatic apoptosis, and mitochondrial dysfunction in WT mice were evidently abrogated in Nrf2^-/- mice. These investigations firstly implicated that Lico A has protective potential against APAP-induced hepatotoxicity which may be strongly associated with the Nrf2-mediated defense mechanisms.

Diosmetin Alleviates Lipopolysaccharide-Induced Acute Lung Injury through Activating the Nrf2 Pathway and Inhibiting the NLRP3 Inflammasome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a common clinical syndrome of diffuse lung inflammation with high mortality rates and limited therapeutic methods. Diosmetin, an active component from Chinese herbs, has long been noticed because of its antioxidant and anti-inflammatory activities. The aim of this study was to evaluate the effects of diosmetin on LPS-induced ALI model and unveil the possible mechanisms. Our results revealed that pretreatment with diosmetin effectively alleviated lung histopathological changes, which were further evaluated by lung injury scores. Diosmetin also decreased lung wet/dry ratios, as well as total protein levels, inflammatory cell infiltration and proinflammatory cytokine (eg. TNF-α, IL-1β and IL-6) overproduction in bronchoalveolar lavage fluid (BALF). Additionally, increased MPO, MDA and ROS levels induced by LPS were also markly suppressed by diosmetin. Furthermore, diosmetin significantly increased the expression of Nrf2 along with its target gene HO-1 and blocked the activation of NLRP3 inflammasome in the lung tissues, which might be central to the protective effects of diosmetin. Further supporting these results, in vitro experiments also showed that diosmetin activated Nrf2 and HO-1, as well as inhibited the NLRP3 inflammasome in both RAW264.7 and A549 cells. The present study highlights the protective effects of diosmetin on LPS-induced ALI via activation of Nrf2 and inhibition of NLRP3 inflammasome, bringing up the hope of its application as a therapeutic drug towards LPS-induced ALI.

Isoliquiritigenin Activates Nuclear Factor Erythroid-2 Related Factor 2 to Suppress the NOD-Like Receptor Protein 3 Inflammasome and Inhibits the NF-κB Pathway in Macrophages and in Acute Lung Injury

Among the cellular response mechanisms, the nuclear factor erythroid-2 related factor 2 (Nrf2) pathway is considered a survival pathway that alleviates oxidative injury, while both the NOD-like receptor protein 3 (NLRP3) and NF-κB pathways are pro-inflammatory pathways that cause damage to cells. These pathways are implicated in the development and resolution of acute lung injury (ALI). Isoliquiritigenin (ISL), a flavonoid from the liquorice compound, is suggested to be a regulator of the above pathways, but the mechanisms of how the NLRP3/NF-κB pathway interacts with Nrf2 and its protective effects in ALI remain unknown. In the present study, ISL inhibited reactive oxygen species (ROS) generation and cytotoxicity induced by t-BHP and pro-inflammatory enzymes production induced by LPS in RAW 264.7 cells. Such cytoprotective effects coincided with the induction of AMP-activated protein kinase (AMPK)/Nrf2/antioxidant response element (ARE) signaling and the suppression of the NLRP3 and NF-κB pathways. Consistent with these findings, ISL treatment significantly alleviated lung injury in LPS-induced ALI mice, which was reflected by reductions in histopathological changes, pulmonary edema, and protein leakage. At the same time, the increased levels of inflammatory cell exudation and pro-inflammatory mediators, the enhanced production of ROS, myeloperoxidase, and malondialdehyde, and the depleted expression of GSH and superoxide dismutase induced by LPS were ameliorated by ISL. Furthermore, ISL notably activated AMPK/Nrf2/ARE signaling and inhibited LPS-induced NLRP3 and NF-κB activation in the lung. Moreover, although inhibition of the LPS-induced histopathological changes and ROS production were attenuated in Nrf2-deficient mice, the repression of the NLRP3 and NF-κB pathways by ISL was Nrf2-dependent and Nrf2-independent, respectively. In conclusion, our results are the first to highlight the beneficial role and relevant mechanisms of ISL in LPS-induced ALI and provide novel insight into its application.

Asiatic Acid Exhibits Anti-inflammatory and Antioxidant Activities against Lipopolysaccharide and d-Galactosamine-Induced Fulminant Hepatic Failure

Inflammation and oxidative stress are essential for the pathogenesis of fulminant hepatic failure (FHF). Asiatic acid (AA), which is a pentacyclic triterpene that widely occurs in various vegetables and fruits, has been reported to possess antioxidant and anti-inflammatory properties. In this study, we investigated the protective effects of AA against lipopolysaccharide (LPS) and d-galactosamine (GalN)-induced FHF and the underlying molecular mechanisms. Our findings suggested that AA treatment effectively protected against LPS/d-GalN-induced FHF by lessening the lethality; decreasing the alanine transaminase and aspartate aminotransferase levels, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α production, malondialdehyde formation, myeloperoxidase level and reactive oxygen species generation (i.e., H₂O₂, NO, and O2−), and increasing the glutathione and superoxide dismutase contents. Moreover, AA treatment significantly inhibited mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathway activation via the partial induction of programmed cell death 4 (PDCD4) protein expressions, which are involved in inflammatory responses. Furthermore, AA treatment dramatically induced the expression of the glutamate-cysteine ligase modifier subunit, the glutamate-cysteine ligase catalytic subunit, heme oxygenase-1, and NAD (P) H: quinoneoxidoreductase 1 (NQO1), which are largely dependent on activation of the nuclear factor-erythroid 2-related factor 2 (Nrf2) through the induction of AMP-activated protein kinase (AMPK) and glycogen synthase kinase-3β (GSK3β) phosphorylation. Accordingly, AA exhibited protective roles against LPS/d-GalN-induced FHF by inhibiting oxidative stress and inflammation. The underlying mechanism may be associated with the inhibition of MAPK and NF-κB activation via the partial induction of PDCD4 and upregulation of Nrf2 in an AMPK/GSK3β pathway activation-dependent manner.

Betulin exhibits anti-inflammatory activity in LPS-stimulated macrophages and endotoxin-shocked mice through an AMPK/AKT/Nrf2-dependent mechanism

Continued oxidative stress can lead to chronic inflammation, which in turn could mediate most chronic diseases including cancer. Nuclear factor erythroid 2-related factor (Nrf2), a critical transcriptional activator for antioxidative responses, has envolved to be an attractive drug target for the treatment or prevention of human diseases. In the present study, we investigated the effects and mechanisms of betulin on Nrf2 activation and its involvement in the lipopolysaccharide (LPS)-triggered inflammatory system. In macrophages, betulin activated the Nrf2 signaling pathway and increased Nrf2-targeted antioxidant and detoxifying enzymes, including NADPH, quinine oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), γ-glutamyl cysteine synthetase catalytic subunit (GCLC) and modifier subunit (GCLM) in a dose and time dependent manner. Importantly, we found betulin-induced activation of Nrf2 is AMPK/AKT/GSK3β dependent, as pharmacologically inactivating AMPK blocked the activating effect of betulin on AKT, GSK3β and Nrf2. Furthermore, betulin attenuated LPS-induced inflammatory mediators (iNOS and COX-2) and MAPK inflammatory signaling pathway. The effect of betulin on HO-1 and NQO1 upregulation, iNOS and COX-2 the downregulation, and survival time extension was largely weakened when Nrf2 was depleted in vitro and in vivo. Our results demonstrate that the AMPK/AKT/Nrf2 pathways are essential for the anti-inflammatory effects of betulin in LPS-stimulated macrophages and endotoxin-shocked mice.

Daphnetin-mediated Nrf2 antioxidant signaling pathways ameliorate tert-butyl hydroperoxide (t-BHP)-induced mitochondrial dysfunction and cell death

Daphnetin (Daph), a natural coumarin derivative isolated from plants of the Genus Daphne, possesses abundant biological activities, such as anti-inflammatory, antioxidant and anticancer properties. In the present study, we focused on investigating the protective effect of Daph against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage, mitochondrial dysfunction and the involvement of underlying molecular mechanisms. Our findings indicated that Daph effectively inhibited t-BHP-stimulated cytotoxicity, cell apoptosis, and mitochondrial dysfunction, which are associated with suppressed reactive oxygen species (ROS) generation, decreased malondialdehyde (MDA) formation, increased superoxide dismutase (SOD) levels and glutathione (GSH)/GSSG (oxidized GSH) ratio. Further investigation indicated that Daph significantly suppressed cytochrome c release and NLRP3 inflammasome activation and modulated apoptosis-related protein Bcl-2, Bax, and caspase-3 expression. Moreover, Daph dramatically induced the expression of the glutamate-cysteine ligase modifier (GCLM) subunit and the glutamate-cysteine ligase catalytic (GCLC) subunit, heme oxygenase-1 (HO-1), and NAD (P) H: quinone oxidoreductase (NQO1), which is largely dependent on upregulating the nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation, reducing the Keap1 protein expression, and strengthening the antioxidant response element (ARE) promoter activity. Additionally, Daph remarkably activated a c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) phosphorylation, but ERK and JNK inhibitor pretreatment exhibited an evident decrease of the level of Daph-enhanced Nrf2 nuclear translocation. Furthermore, Daph exposure suppressed t-BHP-induced cytotoxicity and ROS overproduction, which are mostly blocked in Nrf2 knockout RAW 264.7 cells and peritoneal macrophages. Accordingly, Daph exhibited protective roles against t-BHP-triggered oxidative damage and mitochondrial dysfunction by the upregulation of Nrf2 antioxidant signaling pathways, which may be involved in the activation of JNK and ERK.

Xanthohumol ameliorates lipopolysaccharide (LPS)-induced acute lung injury via induction of AMPK/GSK3β-Nrf2 signal axis

Abundant natural flavonoids can induce nuclear factor-erythroid 2 related factor 2 (Nrf2) and/or AMP-activated protein kinase (AMPK) activation, which play crucial roles in the amelioration of various inflammation- and oxidative stress-induced diseases, including acute lung injury (ALI). Xanthohumol (Xn), a principal prenylflavonoid, possesses anti-inflammation and anti-oxidant activities. However, whether Xn could protect from LPS-induced ALI through inducing AMPK/Nrf2 activation and its downstream signals, are still poorly elucidated. Accordingly, we focused on exploring the protective effect of Xn in the context of ALI and the involvement of underlying molecular mechanisms. Our findings indicated that Xn effectively alleviated lung injury by reduction of lung W/D ratio and protein levels, neutrophil infiltration, MDA and MPO formation, and SOD and GSH depletion. Meanwhile, Xn significantly lessened histopathological changes, reactive oxygen species (ROS) generation, several cytokines secretion, and iNOS and HMGB1 expression, and inhibited Txnip/NLRP3 inflammasome and NF-κB signaling pathway activation. Additionally, Xn evidently decreased t-BHP-stimulated cell apoptosis, ROS generation and GSH depletion but increased various anti-oxidative enzymes expression regulated by Keap1-Nrf2/ARE activation, which may be associated with AMPK and GSK3β phosphorylation. However, Xn-mediated inflammatory cytokines and ROS production, histopathological changes, Txnip/NLRP3 inflammasome and NF-κB signaling pathway in WT mice were remarkably abrogated in Nrf2^-/- mice. Our experimental results firstly provided a support that Xn effectively protected LPS-induced ALI against oxidative stress and inflammation damage which are largely dependent upon upregulation of the Nrf2 pathway via activation of AMPK/GSK3β, thereby suppressing LPS-activated Txnip/NLRP3 inflammasome and NF-κB signaling pathway.

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Xn protects LPS-induced acute lung injury via anti-inflammation and anti-oxidant.

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Xn induces expressions of GCLC, GCLM, HO-1, NQO-1 and Trx-1.

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Xn blocks NF-κB and Txnip/NLRP3 inflammasome activation.

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Xn upregulates AMPK/GSK3β-Nrf2 signal axis.

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Xn-attenuated acute lung injury is effectively abrogated in Nrf2-/- mice.

Nrf2-mediated liver protection by esculentoside A against acetaminophen toxicity through the AMPK/Akt/GSK3β pathway

Acetaminophen (APAP) overdose accounts for the majority of acute liver failure cases, and oxidative stress plays a key role in its toxic effects. Esculentoside A (EsA) has anti-oxidant activities, but its therapeutic potential for APAP hepatotoxicity remains unknown. This study aimed to assess the protective effects and mechanism of EsA against APAP-induced hepatotoxicity in vitro and in vivo. In vitro, EsA treatment inhibited APAP- or H2O2-induced cytotoxicity, H2O2 and O2- production, glutathione (GSH) depletion and apoptosis dependent on nuclear factor erythroid-2-related factor 2 (Nrf2) activation in HepG2 cells. Moreover, EsA significantly increased the phosphorylation of AMP-activated protein kinase (AMPK) and serine/threonine kinase (Akt), as well as glycogen synthase kinase 3 beta (GSK-3β) inhibitory phosphorylation at Ser9. Furthermore, an AMPK inhibitor (compound c) abolished the effects of EsA on AKT phosphorylation, GSK-3β inactivation, Nrf2 nuclear translocation and cytoprotection. With regard to APAP-induced acute liver injury, EsA attenuated the APAP-stimulated increases in the serum ALT and AST levels, as well as centrilobular necrosis and GSH depletion in the mice. In addition, it decreased the GSSG level, GSSG-to-GSH ratio, and the phosphorylation and mitochondrial translocation of c-Jun N-terminal kinase (JNK). Further, the protective potential of EsA against mitochondrial dysfunction was exhibited not only by inhibiting Bax mitochondrial translocation and the release of mitochondrial inter-membrane proteins, such as apoptosis-inducing factor (AIF), but also by activating Nrf2/HO-1. Collectively, our findings suggest that EsA has protective potential against APAP toxicity by potentiating the Nrf2-regulated survival mechanism through the AMPK/Akt/GSK3β pathway.

Tenuigenin exhibits anti-inflammatory activity via inhibiting MAPK and NF-κB and inducing Nrf2/HO-1 signaling in macrophages

Tenuigenin (TNG), isolated from the root of the Chinese herb Polygala tenuifolia, possesses various biological and pharmacological activities, including anti-oxidation and anti-inflammation activities. In this study, we aimed to further investigate whether its anti-inflammatory activity is associated with the inhibition of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in lipopolysaccharide (LPS)-induced RAW 264.7 cells. Our results showed that TNG treatment dramatically reduced prostaglandin E2 (PGE2) and NO production, decreased iNOS and COX-2 gene expression, inhibited JNK1/2, ERK1/2, p38 and NF-κB (p65) phosphorylation, and blocked IκBα phosphorylation and degradation. Further studies revealed that TNG dramatically up-regulated heme oxygenase (HO)-1 and nuclear factor erythroid 2-related factor 2 (Nrf2) expression, which was related to the induction of Nrf2 nuclear translocation and decreased Keap1 protein expression. Additionally, treatment with JNK1/2, ERK1/2 or p38 inhibitors had no effect on the TNG-induced HO-1 protein expression. Furthermore, the LPS-induced iNOS and COX-2 expression levels were inhibited by TNG, which was partially reversed by the HO-1-siRNA and HO-1 inhibitors. Together, these results showed that TNG's anti-inflammatory activity is related to the inhibition of iNOS and COX-2 expression via down-regulation of the MAPK and NF-κB, and up-regulation of the Nrf2/HO-1 signaling pathways.