Persistent Activation Of Nrf2 Research Articles

Assessing the mechanisms and adjunctive therapy for arsenic-induced liver injury in rats.

Environmental arsenic exposure is a significant global public health concern. Previous studies have demonstrated the association between arsenic-induced liver injury and oxidative stress as well as ferroptosis. However, the knowledge of the interactions among these mechanisms remains limited. Moreover, there is a lack of research on potential therapeutic interventions for liver injury resulting from arsenic exposure. To address these limitations, we established a rat model with liver injury caused by arsenic exposure and investigated the impact of the nuclear factor E2-related factor 2 (Nrf2)/glutathione peroxidase 4 (GPx4) signaling pathway and ferroptosis on arsenic-induced liver injury. Our findings revealed that arsenic increased Nrf2 expression and decreased GPx4 expression in the rat liver. This was accompanied by a substantial generation of reactive oxygen species and disruption of the antioxidant defense system, ultimately promoting liver injury through ferroptosis. Subsequently, we conducted intervention experiments using Rosa roxburghii Tratt (RRT) in rats exposed to arsenic. The results showed that the detrimental effects mentioned earlier were partially alleviated following RRT intervention. This study offers preliminary evidence that persistent activation of Nrf2 by arsenic triggers an adaptive antioxidant response, leading to liver injury through the promotion of ferroptosis. Additionally, we discovered that RRT inhibits Nrf2-mediated adaptive antioxidant responses by reducing hepatic ferroptosis, thereby mitigating liver injury caused by arsenic exposure in rats. Our study contributes to a deeper understanding of the molecular mechanisms underlying liver injury resulting from arsenic exposure. Furthermore, our findings may facilitate the identification of a potential edible and medicinal plant extracts that could be utilized to develop a more effective adjunctive treatment approach.

Oltipraz, the activator of nuclear factor erythroid 2-related factor 2 (Nrf2), protects against the formation of BAPN-induced aneurysms and dissection of the thoracic aorta in mice by inhibiting activation of the ROS-mediated NLRP3 inflammasome

BackgroundThoracic aortic aneurysm and dissection (TAAD) is caused by the apoptosis and phenotypic transformation of vascular smooth muscle cells (VSMCs). The dysfunction of VSMCs affects their secretion of chemokines such as monocyte chemoattractant protein-1 (MCP-1) to recruit the infiltration of macrophages which release proinflammatory cytokines and matrix metalloproteinases (MMPs) to accelerate the process of TAAD formation. Approach and resultsWe analyzed the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) in aortic tissues of TAAD patients and the β-aminopropionitrile fumarate (BAPN)-induced mouse model, and the levels of Nrf2 were elevated in both aortic lesions. Treatment with the Nrf2 activator oltipraz protects against the formation of BAPN-induced aneurysm and dissection, as demonstrated by a higher survival rate, postponing the time of aortic rupture, and inhibiting aortic luminal dilation. In addition, the thoracic aortas of BAPN-treated mice inhibited the apoptosis and phenotypic transformation of VSMCs. When treated with oltipraz, they had reduced macrophage infiltration proinflammatory cytokines and MMPs. Furthermore, oltipraz treatment promoted the translocation of Nrf2 and downregulated the NLRP3 pathway. ConclusionNrf2 plays a crucial role in protecting against TAAD development, and persistent activation of Nrf2 is a promising therapeutic strategy against the progression of TAAD.

FSH-inhibited autophagy protects against oxidative stress in goat Sertoli cells through p62-Nrf2 pathway

Oxidative stress is a common cause of male infertility. Sertoli cells are one of the target cells of oxidative injury, which leads to impaired testicular function. Follicle-stimulating hormone (FSH) is critical in Sertoli cell function. However, the role of FSH in the response of goat Sertoli cells to H2O2-induced oxidative stress has not been studied yet. To investigate this response, we established an oxidative stress model using goat Sertoli cells. FSH pretreatment significantly enhanced the decreased cell viability (p < 0.05) caused by oxidative injury and inhibited autophagic flux. FSH significantly increased p62 mRNA and protein levels (p < 0.01). Further investigations revealed that FSH also increased the expression level and nuclear translocation of Nrf2 in Sertoli cells (p < 0.01), which resulted in increased antioxidant enzyme activity (p < 0.05). In contrast, treatment with siNrf2 and sip62 abolished this protective effect of FSH. These findings suggest that FSH protects Sertoli cells against oxidative stress via the p62-Nrf2 pathway, and that p62 accumulation maintains persistent activation of Nrf2. Thus, p62 and Nrf2 are required for FSH-mediated protective role in H2O2-induced Sertoli cell injury. The findings reveal new mechanisms by which FSH protects against oxidative injury in goat Sertoli cells.

Abstract 2369: The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression

Abstract Basal-like breast cancer (BLBC) is an aggressive malignancy with a poor prognosis. Persistent activation of NRF2 and STAT3 is considered to stimulate the aggressive behavior of BLBC. An online database, NRF2-ome predicted the possibility of interplay between NRF2 and STAT3 based on domain motif interactions. However, cooperation between NRF2 and STAT3 and its implications for breast cancer progression remain elusive. Immunoprecipitation and in situ proximity analyses revealed that NRF2 and STAT3 directly interact with each other, which predominantly occurred in the nucleus of human breast cancer cells. After confirming the physical interaction between STAT3 and NRF2, we examined whether this could influence the expression or stability of each transcription factor. While silencing of NRF2 failed to alter the STAT3 expression, STAT3 knockdown facilitated degradation of NRF2. Of note, silencing of STAT3 did not affect the mRNA expression of NRF2, suggesting that STAT3-induced accumulation of NRF2 is attributable to stabilization of the preexisting protein. As the NRF2-STAT3 complex was found to accumulate predominantly in the nucleus, we speculate that NRF2 could bind to a functionally active phosphorylated form of STAT3 (P-STAT3Y705). The substitution of Y705 of STAT3 with the non-phosphorylatable phenylalanine (STAT3Y705F) abolished interaction with NRF2. Notably, the dimeric form, but not a monomeric form, of STAT3 interacts directly with the Neh1 and Neh3 domains of NRF2. Next, we investigated the functional significance of STAT3- NRF2 interaction in BLBC growth in vivo. STAT3 knockdown significantly reduced expression of NRF2 in the xenograft tumor tissues derived from MDA-MB-231 human breast cancer cells. Tumors derived from cells transfected with the non-specific control siRNA showed a pronounced interaction between STAT3 and NRF2, whereas such interaction was abolished in the STAT3-silenced xenograft tumor. Analysis of the TCGA multi-omics data showed that high levels of STAT3 and NRF2 mRNA transcripts were correlated with elevated expression of P-STAT3Y705 and NRF2 target proteins in breast cancer patients. Next generation RNA sequencing analysis identified the gene encoding interleukin-23A (IL-23A) upregulated by concurrent binding of STAT3 and NRF2 to its promoter. IL-23A is markedly overexpressed in BLBC, compared with other subtypes of breast cancer. Combined silencing of NRF2 and STAT3 inhibited BLBC growth to a greater extent than that achieved with single siRNA transfection. IL-23A depletion by siRNA also showed the similar phenotypic changes to those caused by double knockdown of both transcription factors. In conclusion, these findings suggest that the STAT3-NRF2 interaction accelerates BLBC growth and progression by augmenting IL-23A expression, which underscores the importance of subtype-specific molecular pathways in human breast cancer. Citation Format: Su-Jung Kim, Soma Saeidi, Nam-Chul Cho, Seung Hyeon Kim, Han-Byoel Lee, Wonshik Han, Hye-Kyung Na, Young-Joon Surh. The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2369.

Persistent activation of Nrf2 in a p62-dependent non-canonical manner aggravates lead-induced kidney injury by promoting apoptosis and inhibiting autophagy

IntroductionLead (Pb) is an environmental toxicant that poses severe health risks to humans and animals, especially renal disorders. Pb-induced nephrotoxicity has been attributed to oxidative stress, in which apoptosis and autophagy are core events. ObjectivesNuclear factor erythroid 2-related factor 2 (Nrf2) acts as a major contributor to counteract oxidative damage, while hyperactivation or depletion of Nrf2 pathway can cause the redox imbalance to induce tissue injury. This study was performed to clarify the function and mechanism of Nrf2 in Pb-triggered kidney injury. Methods and resultsFirst, data showed that Pb exposure activates Nrf2 pathway in primary rat proximal tubular cells. Next, Pb-induced Nrf2 activation was effectively regulated by pharmacological modulation or siRNA-mediated knockdown in vitro and in vivo assays. Notably, Pb-triggered cytotoxicity, renal injury and concomitant apoptosis were improved by Nrf2 downregulation, confirming that Pb-induced persistent Nrf2 activation contributes to nephrotoxicity. Additionally, Pb-triggered autophagy blockage was relieved by Nrf2 downregulation. Mechanistically, we found that Pb-induced persistent Nrf2 activation is attributed to reduced Nrf2 ubiquitination and nuclear-cytoplasmic loss of Keap1 in a p62-dependent manner. ConclusionsIn conclusion, these findings highlight the dark side of persistent Nrf2 activation and potential crosstalk among Pb-induced persistent Nrf2 activation, apoptosis and autophagy blockage in Pb-triggered nephrotoxicity.

Persistent activation of Nrf2 promotes a vicious cycle of oxidative stress and autophagy inhibition in cadmium-induced kidney injury

Nuclear factor erythroid 2-related factor 2 (Nrf2) serves as the master regulator of antioxidant signaling and inhibition or hyperactivation of Nrf2 pathway will result in the redox imbalance to induce tissue injury. Herein, we established cadmium (Cd)-exposed rat kidney injury model by intraperitoneal injection with CdCl2 (1.5 mg/kg body weight) and cytotoxicity model of NRK-52E cells by CdCl2 (5 μM) exposure to reveal the role of Nrf2 hyperactivation in Cd-induced nephrotoxicity. Data from the in vitro and in vivo study showed that Cd caused Nrf2 nuclear retention due to nuclear-cytoplasmic depletion of Kelch-like ECH-associated protein 1 (Keap1) and Sequestosome-1(SQSTM1/p62) accumulation, leading to the persistent activation of Nrf2. Moreover, we established inhibited models of Cd-induced prolonged Nrf2 activation using siRNA-mediated gene silencing in vitro and pharmacological inhibition in vivo for subsequent assays. First, Cd-induced cytotoxicity, renal injury and concomitant oxidative stress were markedly alleviated by Nrf2 inhibition. Second, Cd-induced autophagy inhibition was notably alleviated by Nrf2 inhibition. Further, we revealed underlying molecular mechanisms of the crosstalk between persistent activation of Nrf2 and autophagy inhibition in Cd-induced nephrotoxicity. Data showed that Cd-induced lysosomal dysfunction evidenced by impaired lysosomal biogenesis and degradation capacity was markedly recovered by Nrf2 inhibition. Meanwhile, Cd-impaired autophagosome-lysosome fusion was obviously restored by Nrf2 inhibition. In conclusion, our findings revealed that persistent activation of Nrf2 promoted a vicious cycle of oxidative stress and autophagy inhibition in Cd-induced nephrotoxicity.

Sulforaphane Prevents Angiotensin II-Induced Cardiomyopathy by Activation of Nrf2 Through Epigenetic Modification

Nuclear factor erythroid 2-related factor (Nrf2) is an important regulator of cellular antioxidant defense. We previously showed that SFN prevented Ang II-induced cardiac damage via activation of Nrf2. Furthermore, SFN treatment resulted in persistent activation of Nrf2 for at least another 3 months after withdrawing SFN. However, the underlying mechanism of SFN’s persistent cardiac protection remains unclear. This study aimed to explore the potential of SFN in activating cardiac Nrf2 through epigenetic mechanisms. Wild-type mice were injected subcutaneously with Ang II (0.5 mg/kg) every other day for 2 months, with or without SFN (0.5 mg/kg) treatment for 5 days each week for 3 months, and then kept for another 3 month. Administration of a subpressor dose of Ang II induced cardiac inflammatory factor expression, oxidative damage, fibrosis, and cardiac remodeling and dysfunction, all of which were effectively improved by SFN treatment, coupled with an upregulation of Nrf2 and downstream genes (CAT, HO-1). Bisulfite genome sequencing (BGS) and chromatin immunoprecipitation (ChIP) were then performed to detect the methylation level of the first 15 CpGs and histone H3 acetylation (Ac-H3) status in the Nrf2 promoter region, respectively. The results showed that SFN reduced Ang II-induced CpG hypermethylation and promoted Ac-H3 accumulation in the Nrf2 promoter region, accompanied by the inhibition of global DNMT and HDAC activity, and a decreased protein expression of key DNMT and HDAC enzymes: DNMT3a, DNMT3b and HDAC2, HDAC3, HDAC5. Taken together, SFN exerts its cardioprotective effect through epigenetic modification of Nrf2, which may partially contribute to long-term activation of cardiac Nrf2. Funding Statement: This work was supported by the National Natural Science Foundation of China (Grant number 395 81570344); National Key RD the Education Department Foundation of Jilin Province (Grant number JJKH20201036KJ); the Fundamental Research Funds for the Central Universities of Jilin University; the Health and Family Planning Commission of Jilin Province Foundations (Grant number 2016Q034 and 2017J11) and the Jilin Provincial Science and Technology Foundations (Grant number 20180414039GH and 20190201200JC). Declaration of Interests: The authors report no conflicts of interest in this work. Ethics Approval Statement: All animal procedures were approved by the Animal Care and Use Committee of the Chinese Academy of Medical Sciences (Beijing, China).

NFE2L2/KEAP1 Mutations Correlate with Higher Tumor Mutational Burden Value/PD-L1 Expression and Potentiate Improved Clinical Outcome with Immunotherapy.

Abnormalities in the KEPA1-NRF2 pathway have a role in cancer progression, metastasis, and resistance to chemo- and radiotherapies. Persistent activation of NRF2 associates with poor prognosis across different cancer types. However, the beneficial therapeutic strategy to harness this pathway in cancer remains unclear. This study aimed to investigate the clinical outcome with immunotherapy in NFE2L2/KEAP1 mutant population. We investigated the correlation between NFE2L2/KEAP1 mutations and tumor mutational burden (TMB) and programmed death-ligand 1 (PD-L1) expression status to identify the therapeutic vulnerability. For this purpose, relevance analysis with TMB value was performed in 9,040 patients with cancer, and relevance analysis with PD-L1 expression was performed in 3,457 patients. The Memorial Sloan Kettering Cancer Center (MSKCC) database and real-world evidence were used to assess the immunotherapy response in NFE2L2/KEAP1 mutant subsets. NFE2L2/KEAP1 mutations occurred in various cancers, and the highest mutation incidences occurred in lung squamous cell carcinoma (LUSC) at 19.16% (NFE2L2) and 10.31% (KEAP1). We confirmed that higher TMB value and PD-L1 expression were associated with NFE2L2/KEAP1 mutations compared with wild-type, especially in non-small lung cancer. MSKCC database analysis showed the improved survival of patients with NFE2L2/KEAP1 mutant with immunotherapy compared with other treatments (median overall survival 22.52 VS 12.89, p = .0034). Real-world evidence further confirmed the efficacy of immunotherapy in the mutant population. Our study revealed that patients with NFE2L2/KEAP1 mutant could achieve improved outcomes from immunotherapy than the other treatments. These findings may broaden the application of immune checkpoint blockade to patients harboring NFE2L2/KEAP1 mutations. NFE2L2/KEAP1 alterations occur frequently in multiple cancer types and are associated with poor prognosis; however, the efficacious strategy to inhibit this pathway in cancer is poorly understood. This study was designed to analyze the mutational characteristics of NFE2L2/KEAP1 alterations in 9,243 Chinese patients. The highest mutation incidences occurred in lung squamous cell carcinoma at 19.16% (NFE2L2) and 10.31% (KEAP1). Relevance analysis showed the NFE2L2/KEAP1 mutant subsets were associated with higher tumor mutational burden value and programmed death-ligand 1 expression. Clinical data further confirmed NFE2L2/KEAP1 mutations correlate with improved outcome with immunotherapy. These findings suggest the clinical application of immunotherapy in the NFE2L2/KEAP1 mutant population.

DC32, a Dihydroartemisinin Derivative, Ameliorates Collagen-Induced Arthritis Through an Nrf2-p62-Keap1 Feedback Loop.

Artemisinins have been reported to have diverse functions, such as antimalaria, anticancer, anti-inflammation, and immunoregulation activities. DC32 [(9α,12α-dihydroartemisinyl) bis(2′-chlorocinnmate)], a dihydroartemisinin derivative possessing potent immunosuppressive properties, was synthesized in our previous study. Collagen-induced arthritis (CIA) in DBA/1 mice and inflammatory model in NIH-3T3 cells were established to evaluate the effect of DC32 on RA and discover the underlying mechanisms. The results showed that DC32 could markedly alleviate footpad inflammation, reduce cartilage degradation, activate the Nrf2/HO-1 signaling pathway, and increase the transcription of p62 in DBA/1 mice with CIA. Further mechanistic exploration with NIH-3T3 cells indicated that DC32 could increase the transcription, expression, and nuclear translocation of Nrf2. In addition, DC32 promoted degradation of Keap1 protein and upregulated HO-1 and p62 expression. Furthermore, the effect of DC32 on Keap1 degradation could be prevented by p62 knockdown using siRNA. Administration of DC32 could inhibit the activation of Akt/mTOR and ERK, and pretreatment of NIH-3T3 cells with the autophagy inhibitor 3-methyladenine (3-MA) attenuated the degradation of Keap1 induced by DC32. These results suggest that DC32 inhibits the degradation of Nrf2 by promoting p62-mediated selective autophagy and that p62 upregulation contributed to a positive feedback loop for persistent activation of Nrf2. In summary, our present study demonstrated that DC32 significantly suppressed rheumatoid arthritis (RA) via the Nrf2-p62-Keap1 feedback loop by increasing the mRNA and protein levels of Nrf2 and inducing p62 expression. These findings provide new mechanisms for artemisinins in RA treatment and a potential strategy for discovering antirheumatic drugs.

Fyn kinase is a novel modulator of erythropoietin signaling and stress erythropoiesis.

The signaling cascade induced by the interaction of erythropoietin (EPO) with its receptor (EPO-R) is a key event of erythropoiesis. We present here data indicating that Fyn, a Src-family-kinase, participates in the EPO signaling-pathway, since Fyn-/- mice exhibit reduced Tyr-phosphorylation of EPO-R and decreased STAT5-activity. The importance of Fyn in erythropoiesis is also supported by the blunted responsiveness of Fyn-/- mice to stress erythropoiesis. Fyn-/- mouse erythroblasts adapt to reactive oxygen species (ROS) by activating the redox-related-transcription-factor Nrf2. However, since Fyn is a physiologic repressor of Nrf2, absence of Fyn resulted in persistent-activation of Nrf2 and accumulation of nonfunctional proteins. ROS-induced over-activation of Jak2-Akt-mTOR-pathway and repression of autophagy with perturbation of lysosomal-clearance were also noted. Treatment with Rapamycin, a mTOR-inhibitor and autophagy activator, ameliorates Fyn-/- mouse baseline erythropoiesis and erythropoietic response to oxidative-stress. These findings identify a novel multimodal action of Fyn in the regulation of normal and stress erythropoiesis.

NRF2 Activation Impairs Quiescence and Bone Marrow Reconstitution Capacity of Hematopoietic Stem Cells.

Tissue stem cells are maintained in quiescence under physiological conditions but proliferate and differentiate to replenish mature cells under stressed conditions. The KEAP1-NRF2 system plays an essential role in stress response and cytoprotection against redox disturbance. To clarify the role of the KEAP1-NRF2 system in tissue stem cells, we focused on hematopoiesis in this study and used Keap1-deficient mice to examine the effects of persistent activation of NRF2 on long-term hematopoietic stem cells (LT-HSCs). We found that persistent activation of NRF2 due to Keap1 deficiency did not change the number of LT-HSCs but reduced their quiescence in steady-state hematopoiesis. During hematopoietic regeneration after bone marrow (BM) transplantation, persistent activation of NRF2 reduced the BM reconstitution capacity of LT-HSCs, suggesting that NRF2 reduces the quiescence of LT-HSCs and promotes their differentiation, leading to eventual exhaustion. Transient activation of NRF2 by an electrophilic reagent also promotes the entry of LT-HSCs into the cell cycle. Taken together, our findings show that NRF2 drives the cell cycle entry and differentiation of LT-HSCs at the expense of their quiescence and maintenance, an effect that appears to be beneficial for prompt recovery from blood loss. We propose that the appropriate control of NRF2 activity by KEAP1 is essential for maintaining HSCs and guarantees their stress-induced regenerative response.

Nrf2 promotes the development of fibrosis and tumorigenesis in mice with defective hepatic autophagy

Autophagy is an intracellular lysosomal degradation process that plays an important role in regulating normal physiological functions of the liver. The purpose of the present study was to investigate the mechanism(s) by which the loss of hepatic autophagy leads to liver inflammation, fibrosis and tumorigenesis. Hepatocyte-specific Atg5 knockout mice were generated by crossing Atg5 Flox/Flox mice with albumin Cre mice. These mice were also crossed with Nrf2 knockout mice to generate Atg5 Flox/Flox, Albumin Cre(+)/Nrf2(-/-) double knockout mice. These mice were housed for various time points up to 15 months, and blood and liver tissues were harvested for biochemical and histological analysis. Hepatocyte-specific deletion of Atg5 resulted in increased apoptosis, inflammation and fibrosis in the liver. Increased apoptosis in hepatocyte-specific Atg5 knockout mice was likely due to accumulation of aberrant polyubiquitinated proteins (proteotoxicity) and disruption of the homeostasis of pro-and anti-apoptotic proteins. All of these pathological changes started as early as one month and persisted for 12-15 months. At 9-15 months of age, these mice also developed hepatocellular adenomas. Interestingly, deletion of Nrf2 in Atg5 liver-specific knockout mice markedly abolished these pathological changes, indicating a key role for this transcription factor in the mechanism of hepatic pathology. Our results provide genetic evidence that loss of autophagy in hepatocytes causes cell death resulting in liver inflammation, fibrosis and tumorigenesis. We also demonstrate that persistent activation of Nrf2 is critical for liver inflammation, fibrosis and eventual tumorigenesis that occur in mice with defects in hepatocyte autophagy.

Phosphorylation of p62 Activates the Keap1-Nrf2 Pathway during Selective Autophagy

The Keap1-Nrf2 system and autophagy are both involved in the oxidative-stress response, metabolic pathways, and innate immunity, and dysregulation of these processes is associated with pathogenic processes. However, the interplay between these two pathways remains largely unknown. Here, we show that phosphorylation of the autophagy-adaptor protein p62 markedly increases p62's binding affinity for Keap1, an adaptor of the Cul3-ubiquitin E3 ligasecomplex responsible for degrading Nrf2. Thus, p62 phosphorylation induces expression of cytoprotective Nrf2 targets. p62 is assembled on selective autophagic cargos such as ubiquitinated organelles and subsequently phosphorylated in an mTORC1-dependent manner, implying coupling of the Keap1-Nrf2 system to autophagy. Furthermore, persistent activation of Nrf2 through accumulation of phosphorylated p62 contributes to the growth of human hepatocellular carcinomas (HCCs). These results demonstrate that selective autophagy and the Keap1-Nrf2 pathway are interdependent, and that inhibitors of the interaction between phosphorylated p62 and Keap1 have potential as therapeutic agents against human HCC.

Application of Interleukin-22 Mediates Protection in Experimental Acetaminophen-Induced Acute Liver Injury

Acetaminophen (APAP, paracetamol)-induced hepatotoxicity, although treatable by timely application of N-acetylcysteine, can be fatal. Because it is among the common causes of acute liver failure in intensive care units and in light of its gradually increasing incidence, the need for novel therapeutic strategies aimed at severe intoxication is apparent. Recently, it has been shown that IL-22, a STAT3-activating cytokine, has the capability to mediate liver protection. Herein, the protective potential of IL-22 in murine APAP-induced hepatotoxicity was assessed. Intravenous administration of prophylactic IL-22 significantly reduced serum alanine aminotransferase levels and histopathologic damage in APAP-induced liver injury, a process that coincided with increased hepatocyte proliferation invivo. Concomitant gene expression analysis revealed hepatic induction of genes prototypically up-regulated by the IL-22/STAT3 axis, among others suppressor of cytokine signaling-3, lipocalin-2, and α1-antichymotrypsin. Notably, in a translational setting of therapeutic treatment 2 hours after APAP, IL-22 supported protection in the context of suboptimal N-acetylcysteine dosing. IL-22 likewise connected to augmented hepatocyte proliferation in this experimental setting. As detected by analysis of inflammatory cytokine production, systemically applied IL-22 did not display acute immunomodulation/stimulation in otherwise untreated or endotoxemic mice. Those latter observations clearly confirm acute tolerability of systemically applied IL-22. Observations presented altogether suggest that therapeutic IL-22 administration is a conceivable tissue-protective regimen aimed at hard-to-treat patients with severe APAP-induced hepatotoxicity.

Deficiency in the nuclear factor E2-related factor 2 renders pancreatic β-cells vulnerable to arsenic-induced cell damage

Chronic human exposure to inorganic arsenic (iAs), a potent environmental oxidative stressor, is associated with increased prevalence of type 2 diabetes, where impairment of pancreatic β-cell function is a key pathogenic factor. Nuclear factor E2-related factor 2 (Nrf2) is a central transcription factor regulating cellular adaptive response to oxidative stress. However, persistent activation of Nrf2 in response to chronic oxidative stress, including inorganic arsenite (iAs3+) exposure, blunts glucose-triggered reactive oxygen species (ROS) signaling and impairs glucose-stimulated insulin secretion (GSIS). In the current study, we found that MIN6 pancreatic β-cells with stable knockdown of Nrf2 (Nrf2-KD) by lentiviral shRNA and pancreatic islets isolated from Nrf2-knockout (Nrf2−/−) mice exhibited reduced expression of several antioxidant and detoxification enzymes in response to acute iAs3+ exposure. As a result, Nrf2-KD MIN6 cells and Nrf2−/− islets were more susceptible to iAs3+ and monomethylarsonous acid (MMA3+)-induced cell damage, as measured by decreased cell viability, augmented apoptosis and morphological change. Pretreatment of MIN6 cells with Nrf2 activator tert-butylhydroquinone protected the cells from iAs3+-induced cell damage in an Nrf2-dependent fashion. In contrast, antioxidant N‐acetyl cysteine protected Nrf2-KD MIN6 cells against acute cytotoxicity of iAs3+. The present study demonstrates that Nrf2-mediated antioxidant response is critical in the pancreatic β-cell defense mechanism against acute cytotoxicity by arsenic. The findings here, combined with our previous results on the inhibitory effect of antioxidants on ROS signaling and GSIS, suggest that Nrf2 plays paradoxical roles in pancreatic β-cell dysfunction induced by environmental arsenic exposure.

Persistent Activation of Nrf2 through p62 in Auditory Cells

Objective: Oxidative stress affects auditory cellular functions. The Nrf2/Keap1 signaling pathway is the main pathway responsible for cell defense against oxidative stress. The purposes of this study were to elucidate how Keap1 and Nrf2 provide molecular foundation for a possible crosstalk between autophagy and necrosis pathways in auditory cells. Method: We used auditory cell line (HEI-OC1) in this study. The viability of HEI-OC1 was determined by cell viability assays. The samples after treatment of HEI-OC1 were analyzed by a flow cytometer. Immunofluorescent confocal laser microscopy was used. Western blot was performed. HEI-OC1 was transfected with Nrf2, Keap1 and p62 siRNA. Results: H2O2 treatment resulted in time-dependent accumulation of LC3-II and the expression of GFP-LC3 in HEI-OC1 cells. Autophagic vacuoles were confirmed under transmission electron microscope in H2O2-treated HEI-OC1. Necrosis and autophagy were coincidentally identified in H2O2-treated HEI-OC1 cells. There were significant differences of cell viability between H2O2 only and H2O2 and Rapamycin-treated cells. The knockdown of p62 by siRNA, which loses its ability to interact with Keap1, had no effect on Nrf2 stability, demonstrating that p62-mediated Nrf2 up regulation is Keap1 dependent. These findings demonstrate that p62 could be a molecular hub of the Nrf2/Keap1 pathway in auditory cells. Conclusion: We demonstrated a promotion of autophagy through the mTOR signaling pathway to enhance cell survival in auditory cells under oxidative stress. A crosstalk between Nrf2/Keap1 pathway in the autophagy related-p62 are also presented. The selective autophagy substrate p62 activates the oxidative stress responsive factor Nrf2 through inactivation of keap1.

Liver-Specific Loss of Atg5 Causes Persistent Activation of Nrf2 and Protects Against Acetaminophen-Induced Liver Injury

Autophagy is an evolutionarily conserved biological process that degrades intracellular proteins and organelles including damaged mitochondria through the formation of autophagosome. We have previously demonstrated that pharmacological induction of autophagy by rapamycin protects against acetaminophen (APAP)-induced liver injury in mice. In contrast, in the present study, we found that mice with the liver-specific loss of Atg5, an essential autophagy gene, were resistant to APAP-induced liver injury. Hepatocyte-specific deletion of Atg5 resulted in mild liver injury characterized by increased apoptosis and compensatory hepatocyte proliferation. The lack of autophagy in the Atg5-deficient mouse livers was confirmed by increased p62 protein levels and the absence of LC3-lipidation as well as autophagosome formation. Analysis of histological and clinical chemistry parameters indicated that the Atg5 liver-specific knockout mice are resistant to APAP overdose (500 mg/kg). Further investigations revealed that the bioactivation of APAP is normal in Atg5 liver-specific knockout mice although they had lower CYP2E1 expression. There was an increased basal hepatic glutathione (GSH) content and a faster recovery of GSH after APAP treatment due to persistent activation of Nrf2, a transcriptional factor regulating drug detoxification and GSH synthesis gene expression. In addition, we found significantly higher hepatocyte proliferation in the livers of Atg5 liver-specific knockout mice. Taken together, our data suggest that persistent activation of Nrf2 and increased hepatocyte proliferation protect against APAP-induced liver injury in Atg5 liver-specific knockout mice.

Liver Specific Knockout Atg5 Causes Persistent Activation of Nrf2 and Protects Against Acetaminophen‐Induced Liver Injury

Autophagy is a biological process which degrades intracellular proteins and organelles including damaged mitochondria through the formation of autophagosome. We previously demonstrated that pharmacological induction of autophagy protected against acetaminophen (APAP)‐induced liver injury. To our surprise, in the present study, we found that mice with the liver‐specific knockout of Atg5, an essential autophagy gene, were not more susceptible but rather more resistant to APAP‐induced liver injury. The lack of autophagy in the Atg5‐knockout mouse livers was confirmed by increased p62 protein levels and the absence of LC3‐lipidation as well as autophagosome formation. We also found that Nrf2, a transcriptional factor regulating drug detoxification and glutathione (GSH) synthesis gene expression, was persistently activated in the Atg5 knockout mouse livers. As a result, there were more unconjugated free hepatic GSH and less protein adducts formation in APAP‐treated Atg5 knockout mouse livers than in wild type mouse. In addition, we found that hepatocyte proliferation was significantly increased in Atg5 knockout mouse livers, which might also attenuate APAP‐induced liver injury by promoting liver regeneration. In conclusion, we found that persistent activation of Nrf2 and increased hepatocytes proliferation protected against APAP‐induced liver injury in Atg5‐liver specific knockout mice.

Persistent activation of Nrf2 through p62 in hepatocellular carcinoma cells

Persistent activation of Nrf2 through p62 in hepatocellular carcinoma cells

Persistent activation of Nrf2 through p62 in hepatocellular carcinoma cells

Suppression of autophagy is always accompanied by marked accumulation of p62, a selective autophagy substrate. Because p62 interacts with the Nrf2-binding site on Keap1, which is a Cullin 3-based ubiquitin ligase adapter protein, autophagy deficiency causes competitive inhibition of the Nrf2-Keap1 interaction, resulting in stabilization of Nrf2 followed by transcriptional activation of Nrf2 target genes. Herein, we show that liver-specific autophagy-deficient mice harbor adenomas linked to both the formation of p62- and Keap1-positive cellular aggregates and induction of Nrf2 targets. Importantly, similar aggregates were identified in more than 25% of human hepatocellular carcinomas (HCC), and induction of Nrf2 target genes was recognized in most of these tumors. Gene targeting of p62 in an HCC cell line markedly abrogates the anchorage-independent growth, whereas forced expression of p62, but not a Keap1 interaction-defective mutant, resulted in recovery of the growth defect. These results indicate the involvement of persistent activation of Nrf2 through the accumulation of p62 in hepatoma development.