Eupatilin induces Sestrin2-dependent autophagy to prevent oxidative stress

Eupatilin suppresses osteoclastogenesis and periodontal bone loss by inhibiting the MAPKs/Siglec-15 pathway

Periodontitis is a widely prevalent oral disease around the world characterized by the disruption of the periodontal ligament and the subsequent development of periodontal pockets, as well as the loss of alveolar bone, and may eventually lead to tooth loss. This research aims to assess the suppressive impact of Eupatilin, a flavone obtained from Artemisia argyi, on osteoclastogenesis in vitro and periodontitis in vivo. We found that Eupatilin can efficiently obstruct the differentiation of Raw264.7 and bone marrow-derived macrophages (BMDMs) induced by RANKL, leading to the formation of mature osteoclasts. Consistently, bone slice resorption assay showed that Eupatilin significantly inhibited osteoclast-mediated bone resorption in a dose-dependent manner. Eupatilin also downregulated the expression of osteoclast-specific genes and proteins in Raw264.7 and BMDMs. RNA sequencing showed that Eupatilin notably downregulated the expression of Siglec-15. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses identified significantly enriched pathways in DEGs, including MAPK signaling pathway. And further mechanistic investigations confirmed that Eupatilin repressed MAPKs/NF-κBsignaling pathways. It was found that Siglec-15 overexpression reversed the inhibitory impact of Eupatilin on the differentiation of osteoclasts. Furthermore, activating MAPK signaling pathway reversed the downregulation of Siglec-15 and the inhibition of osteoclastogenesis by Eupatilin. To sum up, Eupatilin reduced the expression of Siglec-15 by suppressing MAPK signaling pathway, ultimately leading to the inhibition of osteoclastogenesis. Meanwhile, Eupatilin suppressed the alveolar bone resorption caused by experimentalperiodontitis in vivo. Eupatilin exhibits potential therapeutic effects in the treatment of periodontitis, rendering it a promising pharmaceutical agent.

Eupatilin attenuates doxorubicin-induced cardiotoxicity by activating the PI3K-AKT signaling pathway in mice

Eupatilin is a pharmacologically active flavonoid with a variety of biological activities, such as anticancer, anti-inflammatory, antioxidant, neuroprotective, anti-allergic and cardioprotective effects. However, whether eupatilin has protective effects on doxorubicin-induced cardiotoxicity remains unknown. Thus, this study aimed to investigate the role of eupatilin in doxorubicin-induced cardiotoxicity. Mice were exposed to a single dose of doxorubicin (15 mg/kg) to generate doxorubicin-induced cardiotoxicity or normal saline as a control. To explore the protective effects, mice were intraperitoneally injected with eupatilin daily for 7 days. Then, we examined the changes in cardiac function, inflammation, apoptosis, and oxidative stress to evaluate the effects of eupatilin on doxorubicin-induced cardiotoxicity. Additionally, RNA-seq analysis was introduced to explore the potential molecular mechanisms. Eupatilin ameliorated doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and cardiomyocyte apoptosis and ameliorated doxorubicin-induced cardiac dysfunction. Mechanistically, eupatilin activated the PI3K-AKT signaling pathway, as evidenced by RNA-seq analysis and Western blot analysis. This study provides the first evidence that eupatilin ameliorates doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and apoptosis. Pharmacotherapy with eupatilin provides a novel therapeutic regimen for doxorubicin-induced cardiotoxicity.

Eupatilin inhibits xanthine oxidase in vitro and attenuates hyperuricemia and renal injury in vivo

Uric acid (UA) is the final metabolite of purines in the liver that can cause hyperuricemia at high levels. The kidneys are the main excretory organs for UA. The excessive accumulation of UA in the kidneys causes the development of hyperuricemia that often leads to renal injury. Eupatilin (Eup) is a flavonoid natural product that possesses various pharmacological properties such as antioxidant, anti-cancer, and anti-inflammatory. We were interested in exploring the potential role of Eup in lowering UA and nephroprotective. We initially investigated the effects of Eup on xanthin oxidase (XOD) activity in vitro, followed by investigating its ability to lower UA levels, anti-inflammatory effects, nephroprotective effects, and the underlying mechanisms using hyperuricemia rats sustained at high UA level. The results showed that Eup had an inhibitory effect on XOD activity in vitro and significantly reduced serum UA, creatinine, BUN, IL-1β and IL-6 levels in hyperuricemic rats, ameliorating inflammation, renal oxidative stress and pathological injury. Furthermore, Eup inhibited ADA and XOD enzyme activities in the liver and serum and modulated GLUT9, URAT1 and ABCG2 protein expression in the kidneys and ileum. Our findings provide a scientific basis for suggesting Eup as an option for a potential treatment for hyperuricemia.

Eupatilin inhibits pulmonary fibrosis by activating Sestrin2/PI3K/Akt/mTOR dependent autophagy pathway

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a progressive chronic inflammatory disease with poor clinical outcomes and ineffective drug treatment options. Eupatilin is a major component extracted from the traditional herbal medicine Artemisia asiatica Nakai. Notably, it was demonstrated to have an anti-fibrosis effect in endometrial fibrosis, vocal fold, and hepatic fibrosis. Its role and mechanism in IPF remain unclear.

METHODS

This study used the TGF-β1-induced human embryonic lung fibroblasts (MRC-5) activation, IPF lung fibroblasts, and bleomycin-induced lung fibrosis mice model. Western blot, immunofluorescence staining, quantitative real time-PCR, hematoxylin and eosin staining, Masson's trichrome staining, and immunohistochemistry were used to evaluate the effects of eupatilin on fibroblast activation, pulmonary fibrosis, and autophagy. The autophagosomes were observed with a transmission electron microscope (TEM). RNA sequencing was used to determine the signaling pathway and key regulator related to autophagy.

RESULTS

Eupatilin significantly decreased the expression of Col1A1, fibronectin, α-SMA, and SQSTM1/p62. In contrast, it increased the expression of LC3B II/I and the number of autophagosomes in TGF-β1 treated MRC-5, IPF lung fibroblasts, and bleomycin-induced lung fibrosis mice model; it also alleviated bleomycin-induced lung fibrosis. The KEGG pathway mapping displayed that PI3K/Akt and Sestrin2 were associated with the enhanced fibrogenic process. Eupatilin suppressed the phosphorylation of PI3K/Akt/mTOR. Autophagy inhibitor 3-methyladenine (3-MA) and Akt activator SC-79 abrogated the anti-fibrotic effect of eupatilin. Sestrin2 expression was also downregulated in TGF-β1 treated lung fibroblasts and lung tissues of the bleomycin-induced pulmonary fibrosis mice model. Furthermore, eupatilin promoted Sestrin2 expression, and the knockdown of Sestrin2 significantly aggravated the degree of fibrosis, increased the phosphorylation of PI3K/Akt/mTOR, and decreased autophagy.

CONCLUSION

These findings indicate that eupatilin ameliorates pulmonary fibrosis through Sestrin2/PI3K/Akt/mTOR-dependent autophagy pathway.

Sestrin2 in diabetes and diabetic complications

Diabetes is a global health problem which is accompanied with multi-systemic complications. It is of great significance to elucidate the pathogenesis and to identify novel therapies of diabetes and diabetic complications. Sestrin2, a stress-inducible protein, is primarily involved in cellular responses to various stresses. It plays critical roles in regulating a series of cellular events, such as oxidative stress, mitochondrial function and endoplasmic reticulum stress. Researches investigating the correlations between Sestrin2, diabetes and diabetic complications are increasing in recent years. This review incorporates recent findings, demonstrates the diverse functions and regulating mechanisms of Sestrin2, and discusses the potential roles of Sestrin2 in the pathogenesis of diabetes and diabetic complications, hoping to highlight a promising therapeutic direction.

Evaluation of maternal serum sestrin-2 levels in intrauterine growth restriction

BACKGROUND

Sestrin-2 (SESN2) is a antioxidant protein that can be activated by a number of conditions, including DNA damage and hypoxia.

AIMS

Our objective was to evaluate maternal serum SESN2 levels in patients with intrauterine growth restriction (IUGR) and its association with adverse perinatal outcomes.

METHODS

This prospective study included a total of 87 pregnant women admitted to our tertiary care center between 2018 August and 2019 July. The study group consisted of a total of 44 patients who had been diagnosed with IUGR. Forty-three low-risk and gestational age-matched pregnant women were taken as control group. Demographic data, maternal serum SESN2 levels, and maternal-neonatal outcomes were evaluated. SESN2 levels were analyzed by the enzyme-linked immunosorbent assay (ELISA) method and compared between groups.

RESULTS

Maternal serum SESN2 levels were significantly higher in the IUGR group compared to control group (22.38 ng/ml vs. 13.0 ng/ml, p < 0.001). In correlation analysis, a negative significant correlation was found between SESN2 levels and gestational week at delivery (r = - 0.387, p < 0.001). The ideal cut-off value for detecting IUGR was 9.5 ng/ml, and the area under the curve was 0.719 (95%CI: 0.610-0.827). Birth interval, gestational week at birth, birth weight, and 1-5-min Apgar scores were lower in the IUGR group (p < 0.001).

CONCLUSIONS

Maternal serum SESN2 levels are elevated in IUGR and are associated with adverse neonatal outcome. Considering that SESN2 is involved in pathogenesis, it can be used as a new marker for the evaluation of IUGR.

Eupatilin Ameliorates Lipopolysaccharide-Induced Acute Kidney Injury by Inhibiting Inflammation, Oxidative Stress, and Apoptosis in Mice

Acute kidney injury (AKI) is a common complication of sepsis. Eupatilin (EUP) is a natural flavone with multiple biological activities and has beneficial effects against various inflammatory disorders. However, whether EUP has a favorable effect on septic AKI remains unknown. Here, we examined the effect of EUP on lipopolysaccharide (LPS)-evoked AKI in mice. LPS-evoked renal dysfunction was attenuated by EUP, as reflected by reductions in serum creatinine and blood urea nitrogen levels. LPS injection also induced structural damage such as tubular cell detachment, tubular dilatation, brush border loss of proximal tubules, and upregulation of tubular injury markers. However, EUP significantly ameliorated this structural damage. EUP decreased serum and renal cytokine levels, prevented macrophage infiltration, and inhibited mitogen-activated protein kinase and NF-κB signaling cascades. Lipid peroxidation and DNA oxidation were increased after LPS treatment. However, EUP mitigated LPS-evoked oxidative stress through downregulation of NPDPH oxidase 4 and upregulation of antioxidant enzymes. EUP also inhibited p53-mediated apoptosis in LPS-treated mice. Therefore, these results suggest that EUP ameliorates LPS-evoked AKI through inhibiting inflammation, oxidative stress, and apoptosis.

Eupatilin Improves Cilia Defects in Human CEP290 Ciliopathy Models

The photoreceptor outer segment is a highly specialized primary cilium that is essential for phototransduction and vision. Biallelic pathogenic variants in the cilia-associated gene CEP290 cause non-syndromic Leber congenital amaurosis 10 (LCA10) and syndromic diseases, where the retina is also affected. While RNA antisense oligonucleotides and gene editing are potential treatment options for the common deep intronic variant c.2991+1655A>G in CEP290, there is a need for variant-independent approaches that could be applied to a broader spectrum of ciliopathies. Here, we generated several distinct human models of CEP290-related retinal disease and investigated the effects of the flavonoid eupatilin as a potential treatment. Eupatilin improved cilium formation and length in CEP290 LCA10 patient-derived fibroblasts, in gene-edited CEP290 knockout (CEP290 KO) RPE1 cells, and in both CEP290 LCA10 and CEP290 KO iPSCs-derived retinal organoids. Furthermore, eupatilin reduced rhodopsin retention in the outer nuclear layer of CEP290 LCA10 retinal organoids. Eupatilin altered gene transcription in retinal organoids by modulating the expression of rhodopsin and by targeting cilia and synaptic plasticity pathways. This work sheds light on the mechanism of action of eupatilin and supports its potential as a variant-independent approach for CEP290-associated ciliopathies.

Association between the antioxidant properties of SESN proteins and anti-cancer therapies

Since the beginning of SESN protein development, they have attracted highly progressive attention due to their regulatory role in multiple signalling pathways. Through their antioxidant activity and autophagy regulation implication, they can function as powerful antioxidants to reduce oxidative stress in cells. SESN proteins received special attention in the field of regulation of reactive oxygen species level in the cell and its interplay with signalling pathways determining energy and nutrient homeostasis. Since perturbations in these pathways are implicated in cancer onset and development, SESNs might constitute potential novel therapeutic targets of broad interest. In this review, we discuss the impact of SESN proteins on anti-cancer therapy based on naturally occurring compounds and conventionally used drugs that influence oxidative stress and autophagy-induced cellular signalling pathways. The significant changes in reactive oxygen species level and nutrient status in cancer cells generate subsequent biological effect through the regulation of SESN-dependent pathways. Thus, SESN may serve as the key molecule for regulating anti-cancer drugs' induced cellular response.

Activation of Sestrin2 accelerates deep second-degree burn wound healing through PI3K/AKT pathway

Deep second-degree burns heal slowly, and promoting the healing process is a focus of clinical research. Sestrin2 is a stress-inducible protein with antioxidant and metabolic regulatory effects. However, its role during acute dermal and epidermal re-epithelialization in deep second-degree burns is unknown. In this study, we aimed to explore the role and molecular mechanism of sestrin2 in deep second-degree burns as a potential treatment target for burn wounds. To explore the effects of sestrin2 on burn wound healing, we established a deep second-degree burn mouse model. Then we detected the expression of sestrin2 by western blot and immunohistochemistry after obtaining the wound margin of full-thickness burned skin. The effects of sestrin2 on burn wound healing were explored in vivo and in vitro through interfering sestrin2 expression using siRNAs or the small molecule agonist of sestrin2, eupatilin. We also investigated the molecular mechanism of sestrin2 in promoting burn wound healing by western blot and CCK-8 assay. Our in vivo and in vitro deep second-degree burn wound healing model demonstrated that sestrin2 was promptly induced at murine skin wound edges. The small molecule agonist of sestrin2 accelerated the proliferation and migration of keratinocytes, as well as burn wound healing. Conversely, the healing of burn wounds was delayed in sestrin2-deficient mice and was accompanied by the secretion of inflammatory cytokines as well as the suppression of keratinocyte proliferation and migration. Mechanistically, sestrin2 promoted the phosphorylation of the PI3K/AKT pathway, and inhibition of PI3K/AKT pathway abrogated the promoting role of sestrin2 in keratinocyte proliferation and migration. Therefore, sestrin2 plays a critical role in activation of the PI3K/AKT pathway to promote keratinocyte proliferation and migration, as well as re-epithelialization in the process of deep second-degree burn wound repair.

Eupatilin improves cilia defects in human CEP290 ciliopathy models

The photoreceptor outer segment is a highly specialized primary cilium essential for phototransduction and vision. Biallelic pathogenic variants in the cilia-associated gene CEP290 cause non-syndromic Leber congenital amaurosis 10 (LCA10) and syndromic diseases, where the retina is also affected. While RNA antisense oligonucleotides and gene editing are potential treatment options for the common deep intronic variant c.2991+1655A>G in CEP290 , there is a need for variant-independent approaches that could be applied to a broader spectrum of ciliopathies. Here, we generated several distinct human models of CEP290 -related retinal disease and investigated the effects of the flavonoid eupatilin as a potential treatment. Eupatilin improved cilium formation and length in CEP290 LCA10 patient-derived fibroblasts, in gene-edited CEP290 knockout (CEP290 KO) RPE1 cells, and in both CEP290 LCA10 and CEP290 KO iPSCs-derived retinal organoids. Furthermore, eupatilin reduced rhodopsin retention in the outer nuclear layer of CEP290 LCA10 retinal organoids. Eupatilin altered gene transcription in retinal organoids, by modulating the expression of rhodopsin, and by targeting cilia and synaptic plasticity pathways. This work sheds light into the mechanism of action of eupatilin, and supports its potential as a variant-independent approach for CEP290 -associated ciliopathies.

Abstract Figure

A cross-talk between sestrins, chronic inflammation and cellular senescence governs the development of age-associated sarcopenia and obesity

The rapid increase in both the lifespan and proportion of older adults is accompanied by the unprecedented rise in age-associated chronic diseases, including sarcopenia and obesity. Aging is also manifested by increased susceptibility to multiple endogenous and exogenous stresses enabling such chronic conditions to develop. Among the main physiological regulators of cellular adaption to various stress stimuli, such as DNA damage, hypoxia, and oxidative stress, are sestrins (Sesns), a family of three evolutionarily conserved proteins, Sesn1, 2, and 3. Age-associated sarcopenia and obesity are characterized by two key processes: (i) accumulation of senescent cells in the skeletal muscle and adipose tissue and (ii) creation of a systemic, chronic, low-grade inflammation (SCLGI). Presumably, failed SCLGI resolution governs the development of these chronic conditions. Noteworthy, Sesns activate senolytics, which are agents that selectively eliminate senescent cells, as well as specialized pro-resolving mediators, which are factors that physiologically provide inflammation resolution. Sesns reveal clear beneficial effects in pre-clinical models of sarcopenia and obesity. Based on these observations, we propose a novel treatment strategy for age-associated sarcopenia and obesity, complementary to the conventional therapeutic modalities: Sesn activation, SCLGI resolution, and senescent cell elimination.

Sestrin2 as a Protective Shield against Cardiovascular Disease

A timely and adequate response to stress is inherently present in each cell and is important for maintaining the proper functioning of the cell in changing intracellular and extracellular environments. Disruptions in the functioning or coordination of defense mechanisms against cellular stress can reduce the tolerance of cells to stress and lead to the development of various pathologies. Aging also reduces the effectiveness of these defense mechanisms and results in the accumulation of cellular lesions leading to senescence or death of the cells. Endothelial cells and cardiomyocytes are particularly exposed to changing environments. Pathologies related to metabolism and dynamics of caloric intake, hemodynamics, and oxygenation, such as diabetes, hypertension, and atherosclerosis, can overwhelm endothelial cells and cardiomyocytes with cellular stress to produce cardiovascular disease. The ability to cope with stress depends on the expression of endogenous stress-inducible molecules. Sestrin2 (SESN2) is an evolutionary conserved stress-inducible cytoprotective protein whose expression is increased in response to and defend against different types of cellular stress. SESN2 fights back the stress by increasing the supply of antioxidants, temporarily holding the stressful anabolic reactions, and increasing autophagy while maintaining the growth factor and insulin signaling. If the stress and the damage are beyond repair, SESN2 can serve as a safety valve to signal apoptosis. The expression of SESN2 decreases with age and its levels are associated with cardiovascular disease and many age-related pathologies. Maintaining sufficient levels or activity of SESN2 can in principle prevent the cardiovascular system from aging and disease.

Sestrin2: multifaceted functions, molecular basis, and its implications in liver diseases

Sestrin2 (SESN2), a highly conserved stress-responsive protein, can be triggered by various noxious stimuli, such as hypoxia, DNA damage, oxidative stress, endoplasmic reticulum (ER) stress, and inflammation. Multiple transcription factors regulate SESN2 expression, including hypoxia-inducible factor 1 (HIF-1), p53, nuclear factor E2-related factor 2 (Nrf2), activating transcription factor 4 (ATF4), ATF6, etc. Upon induction, SESN2 generally leads to activation of adenosine monophosphate-activated protein kinase (AMPK) and inhibition of mechanistic target of rapamycin complex 1 (mTORC1). To maintain cellular homeostasis, SESN2 and its downstream molecules directly scavenge reactive oxygen species or indirectly influence the expression patterns of key genes associated with redox, macroautophagy, mitophagy, ER stress, apoptosis, protein synthesis, and inflammation. In liver diseases including acute liver injury, fatty liver diseases, hepatic fibrosis, and hepatocellular carcinoma (HCC), SESN2 is abnormally expressed and correlated with disease progression. In NAFLD, SESN2 helps with postponing disease progression through balancing glycolipid metabolism and macroautophagy (lipophagy), and rectifying oxidative damage and ER stress. During hepatic fibrosis, SESN2 represses HSCs activation and intrahepatic inflammation, hindering the occurrence and progress of fibrogenesis. However, the role of SESN2 in HCC is controversial due to its paradoxical pro-autophagic and anti-apoptotic effects. In conclusion, this review summarizes the biological functions of SESN2 in hypoxia, genotoxic stress, oxidative stress, ER stress, and inflammation, and specifically emphasizes the pathophysiological significance of SESN2 in liver diseases, aiming to providing a comprehensive understanding for SESN2 as a potential therapeutic target in liver diseases.

Tanshinone IIA Regulates Keap1/Nrf2 Signal Pathway by Activating Sestrin2 to Restrain Pulmonary Fibrosis

Tanshinone IIA (Tan-IIA) is a major component extracted from the traditional herbal medicine Danshen, which has shown antipulmonary fibrosis by suppress reactive oxygen species-mediated activation of myofibroblast. However, the exact mechanism of Tan-IIA against pulmonary fibrosis (PF) remains unclear. This work aimed to explore the underlying mechanism of the protective effects of Tan-IIA on PF. By using high-throughput RNA-Seq analysis, we have compared the genome-wide gene expression profiles and pathway enrichment of Tan-IIA-treated NIH-3T3 cells with or without transforming growth factor beta 1 (TGF-[Formula: see text]1) induction. In normal NIH-3T3 cells, Tan-IIA treatment up-regulated 181 differential expression genes (DEGs) and down-regulated 137 DEGs. In TGF-[Formula: see text]1-induced NIH-3T3 cells, Tan-IIA treatment up-regulated 709 DEGs and down-regulated 1075 DEGs, and these DEGs were enriched in extracellular matrix organization, collagen fibril organization, cell adhesion, ECM-receptor interaction, PI3K-Akt signaling pathway and P53 signaling pathway. Moreover, there were 207 co-expressed DEGs between Tan-IIA treatment vs. the Control and TGF-[Formula: see text]1 plus Tan-IIA treatment vs. TGF-[Formula: see text]1 alone treatment, some of which were related to anti-oxidative stress. In both normal and TGF-[Formula: see text]1-induced NIH-3T3 cells, protein-protein interaction network analysis indicated that Tan-IIA can regulate the expression of several common anti-oxidant genes including Heme oxygenase 1 (Ho-1, also known as Homx1), Sestrin2 (Sesn2), GCL modifier subunit (Gclm), GCL catalytic subunit (Gclc) and Sequestosome-1 (Sqstm1). Quantitative Real-time polymerase chain reaction analysis confirmed some DEGs specifically expressing on Tan-IIA treated cells, which provided new candidates for further functional studies of Tan-IIA. In both in vitro and in vivo PF models, the protein expression of Sesn2 was significantly enhanced by Tan-IIA treatment. Overexpression and knockdown experiments showed that Sesn2 is required for Tan-IIA against TGF-[Formula: see text]1-induced myofibroblast activation by reinforcing nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated anti-oxidant response via downregulation of kelch-like ECH-associated protein 1 (Keap1). These results suggest Tan-IIA inhibits myofibroblast activation by activating Sesn2-Nrf2 signaling pathway, and provide a new insight into the essential role of Sesn2 in PF.

Possible roles of sestrin2 in multiple sclerosis and its relationships with clinical outcomes

BACKGROUND

Characterized by demyelination, inflammation and axonal damage, multiple sclerosis (MS) is one of the most common disorders of central nervous system led by the immune system. There is an urgent and obvious need for biomarkers for the diagnosis and follow-up of MS.

OBJECTIVE

To investigate serum levels of sestrin2 (SESN2), a protein that responds to acute stress, in MS patients.

METHODS

A total of 85 participants, 40 patients diagnosed previously with relapsing-remitting MS and 45 healthy controls, were included. Serum SESN2 parameters were investigated in blood samples drawn from each participant in the patient and control groups.

RESULTS

SESN2 levels were significantly lower in MS patients than in controls (z: -3.06; p=0.002). In the ROC analysis of SESN2, the predictive level for MS was 2.36 ng/mL [sensitivity, 72.50%; specificity, 55.56%; p=0.002; area under the curve (AUC)=0.693]. For the cut-off value in both groups, SESN2 was an independent predictor for MS [Exp (B)=3.977, 95% confidence interval (95%CI) 1.507-10.494 and p=0.013].

CONCLUSIONS

The decreased expression of SESN2 may play a role in MS pathogenesis, and SESN2 could be used as a biomarker for MS and as immunotherapeutic agent to treat MS.

Target Sestrin2 to Rescue the Damaged Organ: Mechanistic Insight into Its Function

Sestrin2 is a stress-inducible metabolic regulator and a conserved antioxidant protein which has been implicated in the pathogenesis of several diseases. Sestrin2 can protect against atherosclerosis, heart failure, hypertension, myocardial infarction, stroke, spinal cord injury neurodegeneration, nonalcoholic fatty liver disease (NAFLD), liver fibrosis, acute kidney injury (AKI), chronic kidney disease (CKD), and pulmonary inflammation. Oxidative stress and cellular damage signals can alter the expression of Sestrin2 to compensate for organ damage. Different stress signals such as those mediated by P53, Nrf2/ARE, HIF-1α, NF-κB, JNK/c-Jun, and TGF-β/Smad signaling pathways can induce Sestrin2 expression. Subsequently, Sestrin2 activates Nrf2 and AMPK. Furthermore, Sestrin2 is a major negative regulator of mTORC1. Sestrin2 indirectly regulates the expression of several genes and reprograms intracellular signaling pathways to attenuate oxidative stress and modulate a large number of cellular events such as protein synthesis, cell energy homeostasis, mitochondrial biogenesis, autophagy, mitophagy, endoplasmic reticulum (ER) stress, apoptosis, fibrogenesis, and lipogenesis. Sestrin2 vigorously enhances M2 macrophage polarization, attenuates inflammation, and prevents cell death. These alterations in molecular and cellular levels improve the clinical presentation of several diseases. This review will shed light on the beneficial effects of Sestrin2 on several diseases with an emphasis on underlying pathophysiological effects.

Potential Roles of Sestrin2 in Alzheimer's Disease: Antioxidation, Autophagy Promotion, and Beyond

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disease. It presents with progressive memory loss, worsens cognitive functions to the point of disability, and causes heavy socioeconomic burdens to patients, their families, and society as a whole. The underlying pathogenic mechanisms of AD are complex and may involve excitotoxicity, excessive generation of reactive oxygen species (ROS), aberrant cell cycle reentry, impaired mitochondrial function, and DNA damage. Up to now, there is no effective treatment available for AD, and it is therefore urgent to develop an effective therapeutic regimen for this devastating disease. Sestrin2, belonging to the sestrin family, can counteract oxidative stress, reduce activity of the mammalian/mechanistic target of rapamycin (mTOR), and improve cell survival. It may therefore play a crucial role in neurodegenerative diseases like AD. However, only limited studies of sestrin2 and AD have been conducted up to now. In this article, we discuss current experimental evidence to demonstrate the potential roles of sestrin2 in treating neurodegenerative diseases, focusing specifically on AD. Strategies for augmenting sestrin2 expression may strengthen neurons, adapting them to stressful conditions through counteracting oxidative stress, and may also adjust the autophagy process, these two effects together conferring neuronal resistance in cases of AD.

Autophagy Modulators From Chinese Herbal Medicines: Mechanisms and Therapeutic Potentials for Asthma

Asthma has become a global health issue, suffering more than 300 million people in the world, which is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. Combination of inhaled corticosteroids (ICS) and long acting β-agonists (LABA) can relieve asthma symptoms and reduce the frequency of exacerbations, especially for patients with refractory asthma, but there are limited treatment options for people who do not gain control on combination ICS/LABA. The increase in ICS dose generally provides little additional benefit, and there is an increased risk of side effects. Therefore, therapeutic interventions integrating the use of different agents that focus on different targets are needed to overcome this set of diseases. Some findings suggest autophagy is closely correlated with the severity of asthma through eosinophilic inflammation, and its modulation may provide novel therapeutic approaches for severe allergic asthma. The chinese herbal medicine (CHM) have been demonstrated clinically as potent therapeutic interventions for asthma. Moreover some reports have found that the bioactive components isolated from CHM could modulate autophagy, and exhibit potent Anti-inflammatory activity. These findings have implied the potential for CHMs in asthma or allergic inflammation therapy via the modulation of autophagy. In this review, we discuss the basic pathomechanisms underpinning asthma, and the potential role of CHMs in treating asthma with modulating autophagy.

Study of the Mechanism by Which Curcumin Cooperates with Sestrin2 to Inhibit the Growth of Pancreatic Cancer

Background

Pancreatic carcinoma is a malignant tumor with a high fatality rate, and the increased resistance of pancreatic carcinoma to chemotherapy has become a difficult problem in clinical practice. Hence, it is imperative to develop an effective treatment for pancreatic cancer. Sestrins are a class of stress-induced proteins that have antioxidation functions, regulating cell growth and metabolism. Curcumin is a natural pigment isolated from turmeric. Several studies have also suggested that this molecule has multiple pharmacological effects, such as anti-inflammatory, antioxidant, and antitumor effects. However, there are insufficient studies on curcumin cooperating with the sestrin family to inhibit tumors, and the mechanism is still unclear. Our aim was to observe the potential anticancer effects of curcumin combined with the sestrin family on pancreatic carcinoma and probe its possible molecular mechanisms.

Methods

Lentiviral infection, real-time fluorescence quantitative PCR assays, Cell Counting Kit-8 assays, real-time cell analysis technology, colony formation assays, wound healing assays, Transwell invasion assays, protein extraction, and western blots (WBs) were used to evaluate the effect of curcumin combined with sestrin2 on the proliferation, invasion, and migration of pancreatic carcinoma cells.

Results

The results revealed that curcumin cooperated with sestrin2 to significantly suppress pancreatic cancer. In addition, we determined that sestrin2 cooperated with curcumin to inhibit pancreatic cancer by specifically targeting Nrf2/Keap1/HO-1/NQO-1.

Conclusion

These findings clarify that curcumin-mediated synergistic targeting of sestrin2 is a potentially valuable treatment for pancreatic cancer.

Eupatilin Impacts on the Progression of Colon Cancer by Mitochondria Dysfunction and Oxidative Stress

Colon cancer is one of the most frequently diagnosed cancer types. Some colon cancer cases resist standard anticancer drugs. Therefore, many studies have focused on developing therapeutic supplements using natural products with low side effects and broad physiological activity. Eupatilin is a flavonoid that is mainly extracted from artemisia and promotes apoptosis in numerous cancer types. However, since the current understanding of its physiological mechanisms on colon cancer cells is insufficient, we investigated how eupatilin affects the growth of two colon cancer cell lines, namely HCT116 and HT29. Our results showed that eupatilin inhibits cell viability and induces apoptosis accompanied by mitochondrial depolarization. It also induces oxidative stress in colon cancer cells and regulates the expression of proteins involved in the endoplasmic reticulum stress and autophagic process. Moreover, eupatilin may target the PI3K/AKT and mitogen-activated protein kinase (MAPK) signaling pathways in colon cancer cells. It also prevents colon cancer cell invasion. Furthermore, eupatilin has a synergistic effect with 5-fluorouracil (5-FU; a standard anticancer drug) on 5-FU-resistant HCT116 cells. These results suggest that eupatilin can be developed as an adjuvant to enhance traditional anticancer drugs in colon cancer.

Resveratrol protects against high glucose-induced oxidative damage in human lens epithelial cells by activating autophagy

In the pathogenesis of diabetic cataract, high glucose levels induce oxidative damage in human lens epithelial cells (HLECs). Resveratrol has been demonstrated to be a potent antioxidant in various disease conditions; however, limited information is available on its effects on oxidative damage associated with the pathogenesis of diabetic cataract in HLECs. The present study aimed to determine whether resveratrol prevents high glucose-induced oxidative damage to human lens epithelial cells by activating autophagy. In the present study, HLECs treated with high glucose were used as a cellular model of diabetic cataract and treated with resveratrol for 24 h. Flow cytometry was performed to detect the cellular reactive oxygen species (ROS) content. Autophagy marker protein levels were determined by western blotting. Immunofluorescence assay was performed to analyze in vitro microtubule-associated protein 1 light chain 3 β (LC3B) protein expression. Autophagosome formation in HLECs was observed using transmission electron microscopy. The results demonstrated that high glucose suppressed HLEC viability and proliferation rate compared with normal glucose levels (5 mM), which were significantly reversed by resveratrol treatment. High glucose also increased the ROS content compared with ROS content in normal HLECs, which was reduced following resveratrol treatment. Further experiments demonstrated that resveratrol significantly reversed the high glucose-decreased protein levels of LC3II and beclin-1 proteins and the high glucose-increased protein levels of LC3I and p62 in HLECs. In conclusion, resveratrol inhibited the high glucose-induced oxidative damage in HLECs by promoting autophagy through the activation of the p38 mitogen-activated protein kinase signaling pathway. These results provide a theoretical basis for the application of resveratrol in diabetic cataract prevention and treatment.

The potential role of sestrin 2 in liver regeneration

Liver regeneration is a remarkably complex phenomenon conserved across all vertebrates, enabling the restoration of lost liver mass in a matter of days. Unfortunately, extensive damage to the liver may compromise this process, often leading to the death of affected individuals. Ischemia/reperfusion injury (IRI) is a common source of damage preceding regeneration, often present during liver transplantation, resection, trauma, or hemorrhagic shock. Increased oxidative stress and mitochondrial dysfunction are key hallmarks of IRI, which can jeopardize the liver's ability to regenerate. Therefore, a better understanding of both liver regeneration and IRI is of important clinical significance. In the current review, we discuss the potential role of sestrin 2 (SESN2), a novel anti-aging protein, in liver regeneration and ischemia/reperfusion preceding regeneration. We highlight its beneficial role in protecting cells from mitochondrial dysfunction and oxidative stress as key aspects of its involvement in liver regeneration. Additionally, we describe how its ability to promote the expression of Nrf2 bears significant importance in this context. Finally, we focus on a potential novel link between SESN2, mitohormesis and ischemic preconditioning, which could explain some of the protective effects of preconditioning.

SESTRINs: Emerging Dynamic Stress-Sensors in Metabolic and Environmental Health

Proper timely management of various external and internal stresses is critical for metabolic and redox homeostasis in mammals. In particular, dysregulation of mechanistic target of rapamycin complex (mTORC) triggered from metabolic stress and accumulation of reactive oxygen species (ROS) generated from environmental and genotoxic stress are well-known culprits leading to chronic metabolic disease conditions in humans. Sestrins are one of the metabolic and environmental stress-responsive groups of proteins, which solely have the ability to regulate both mTORC activity and ROS levels in cells, tissues and organs. While Sestrins are originally reported as one of several p53 target genes, recent studies have further delineated the roles of this group of stress-sensing proteins in the regulation of insulin sensitivity, glucose and fat metabolism, and redox-function in metabolic disease and aging. In this review, we discuss recent studies that investigated and manipulated Sestrins-mediated stress signaling pathways in metabolic and environmental health. Sestrins as an emerging dynamic group of stress-sensor proteins are drawing a spotlight as a preventive or therapeutic mechanism in both metabolic stress-associated pathologies and aging processes at the same time.

Implications of flavonoids as potential modulators of cancer neovascularity

PURPOSE

The formation of new blood vessels from previous ones, angiogenesis, is critical in tissue repair, expansion or remodeling in physiological processes and in various pathologies including cancer. Despite that, the development of anti-angiogenic drugs has great potential as the treatment of cancer faces many problems such as development of the resistance to treatment or an improperly selected therapy approach. An evaluation of predictive markers in personalized medicine could significantly improve treatment outcomes in many patients.

METHODS

This comprehensive review emphasizes the anticancer potential of flavonoids mediated by their anti-angiogenic efficacy evaluated in current preclinical and clinical cancer research.

RESULTS AND CONCLUSION

Flavonoids are important groups of phytochemicals present in common diet. Flavonoids show significant anticancer effects. The anti-angiogenic effects of flavonoids are currently a widely discussed topic of preclinical cancer research. Flavonoids are able to regulate the process of tumor angiogenesis through modulation of signaling molecules such as VEGF, MMPs, ILs, HIF or others. However, the evaluation of the anti-angiogenic potential of flavonoids within the clinical studies is not frequently discussed and is still of significant scientific interest.

Sestrin 2 controls the cardiovascular aging process via an integrated network of signaling pathways

As an inevitable biological process, cardiovascular aging is the greatest risk factor for cardiovascular diseases (CVDs). Sestrin 2 (Sesn2), a stress-inducible and age-related protein associated with various stress conditions, plays a pivotal role in slowing this process. It acts as an anti-aging agent, mainly through its antioxidant enzymatic activity and regulation of antioxidant signaling pathways, as well as by activating adenosine monophosphate-activated protein kinase and inhibiting mammalian target of rapamycin complex 1. In this review, we first introduce the biochemical functions of Sesn2 in the cardiovascular aging process, and describe how Sesn2 expression is regulated under various stress conditions. Next, we emphasize the role of Sesn2 signal transduction in a series of age-related CVDs, including hypertension, myocardial ischemia and reperfusion, atherosclerosis, and heart failure, as well as provide potential mechanisms for the association of Sesn2 with CVDs. Finally, we present the potential therapeutic applications of Sesn2-directed therapy and future prospects.

Sestrin2 promotes angiogenesis to alleviate brain injury by activating Nrf2 through regulating the interaction between p62 and Keap1 following photothrombotic stroke in rats

AIMS

The lack of effective treatments for ischemic stroke is concerning. Here, we aimed to examine the protective effects of sestrin2 in ischemic stroke and determine the mechanism by which sestrin2 attenuates cerebral injuries.

MAIN METHODS

Ischemic stroke was induced in Sprague-Dawley rats using a photothrombotic ischemia (PTI) model. After sestrin2 was overexpressed or silenced, neurological deficits and brain infarction were evaluated. Cerebral angiogenesis and the expression of related proteins were examined by Western blotting and immunofluorescence. The interaction between p62 and Keap1 was measured by coimmunoprecipitation (CoIP) and an in situ proximity ligation assay (PLA).

KEY FINDINGS

The overexpression of sestrin2 was found to improve the neurological function of rats 10 days after PTI and to reduce the infarct volume and brain edema in rats 10 days after PTI. It was shown that upregulating sestrin2 enhanced the relative immunofluorescence intensity of CD34, CD31 and DCX. Sestrin2 overexpressionalso increased the number and total length of CD34 and CD31 positive vessels and the expression of nuclear and total Nrf2, HO-1, VEGF and p62. However, downregulating sestrin2 induced almost the opposite results. Furthermore, we demonstrated that sestrin2 increased the interaction between p62 and Keap1.

SIGNIFICANCE

Based on our data, sestrin2 may promote angiogenesis by activating the Nrf2 pathway through increasing the interaction between p62 and Keap1 via upregulating p62 expression.

Sestrin2 as a potential therapeutic target for cardiovascular diseases

Sestrin2 is a cysteine sulfinyl reductase that plays crucial roles in regulation of antioxidant actions. Sestrin2 provides cytoprotection against multiple stress conditions, including hypoxia, endoplasmic reticulum (ER) stress and oxidative stress. Recent research reveals that upregulation of Sestrin2 is induced by various transcription factors such as p53 and activator protein 1 (AP-1), which further promotes AMP-activated protein kinase (AMPK) activation and inhibits mammalian target of rapamycin protein kinase (mTOR) signaling. Sestrin2 triggers autophagy activity to reduce cellular reactive oxygen species (ROS) levels by promoting nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) activation and Kelch-like ECH-associated protein 1 (Keap1) degradation, which plays a pivotal role in homeostasis of metabolic regulation. Under hypoxia and ER stress conditions, elevated Sestrin2 expression maintains cellular homeostasis through regulation of antioxidant genes. Sestrin2 is responsible for diminishing cellular ROS accumulation through autophagy via AMPK activation, which displays cardioprotection effect in cardiovascular diseases. In this review, we summarize the recent understanding of molecular structure, biological roles and biochemical functions of Sestrin2, and discuss the roles and mechanisms of Sestrin2 in autophagy, hypoxia and ER stress. Understanding the precise functions and exact mechanism of Sestrin2 in cellular homeostasis will provide the evidence for future experimental research and aid in the development of novel therapeutic strategies for cardiovascular diseases.

Sestrin2 overexpression alleviates hydrogen peroxide-induced apoptosis and oxidative stress in retinal ganglion cells by enhancing Nrf2 activation via Keap1 downregulation

Oxidative stress-induced apoptosis of retinal ganglion cells (RGCs) contributes to the development and progression of glaucoma. Sestrin2 (Sesn2), a stress-inducible protein, has a potent antioxidant capacity that can provide cytoprotection against various noxious stimuli. However, whether Sesn2 is involved in protecting RGCs from oxidative stress remains unexplored. The purpose of this study was to evaluate the role of Sesn2 in regulating hydrogen peroxide (H₂O₂)-induced oxidative stress of RGCs. Here, we showed that Sesn2 expression was induced in RGCs following H₂O₂ exposure. Sesn2 depletion markedly exacerbated H₂O₂-induced apoptosis and reactive oxygen species (ROS) generation in RGCs. Notably, upregulation of Sesn2 significantly decreased H₂O₂-induced apoptosis and ROS generation. Moreover, Sesn2 overexpression increased the nuclear translocation of nuclear factor erythroid-derived 2-like 2 (Nrf2), elevated Nrf2/antioxidant response element (ARE)-mediated transcriptional activity and upregulated the expression of Nrf2 target genes in H₂O₂-stimulated RGCs. Interestingly, we found that Sesn2 promoted Nrf2/ARE activation through downregulation of kelch-like ECH-associated protein 1 (Keap1). Restoration of Keap1 or inhibition of Nrf2 significantly reversed the Sesn2-mediated protective effect in H₂O₂-stimulated RGCs. In conclusion, these results elucidated that Sesn2 confers a protective effect in RGCs against H₂O₂-induced oxidative stress by reinforcing Nrf2/ARE activation via downregulation of Keap1. Our study suggests that the Sesn2/Keap1/Nrf2 axis may play an important role in retinal degeneration in glaucoma.

Eupatilin Ameliorates Cerulein-Induced Pancreatitis Via Inhibition of the Protein Kinase D1 Signaling Pathway In Vitro

OBJECTIVE

The aim of this study was to investigate the effects of eupatilin on protein kinase D1 (PKD1) and nuclear factor kappa B (NF-κB) signaling pathways in cerulein-induced in vitro pancreatitis.

METHODS

We used collagenase digestion to isolate pancreatic acinar cells from male C57BL/6 mice. In vitro acute pancreatitis was induced by treatment with a supramaximal dose of cerulein. Eupatilin was pretreated before stimulation with cerulein.

RESULTS

Eupatilin significantly reduced cerulein-induced amylase release in pancreatic acini. Eupatilin treatment downregulated cerulein-induced expression of interleukin (IL)-1β, IL-6, and CC chemokine ligands 2 and 5, but it upregulated expression of IL-4 and IL-10. We demonstrated that eupatilin pretreatment attenuated cerulein-induced necrosis in isolated pancreatic acinar cells. This effect of eupatilin was confirmed by lactic dehydrogenase assay, fluorescence-activated cell sorting analysis, and cytopathologic analysis. Eupatilin inhibited cerulein-induced activation of PKD1/NF-κB and the nuclear translocation of NF-κB.

CONCLUSIONS

Our data demonstrated that eupatilin is a potential therapeutic candidate for the treatment of pancreatitis through its ability to reduce cellular necrosis and inflammatory responses by inhibition of the PKD1/NF-κB signaling pathway.

Eupatilin: a natural pharmacologically active flavone compound with its wide range applications

Eupatilin (5,7-dihydroxy-3',4',6-trimethoxyflavone) is a pharmacologically active flavone which has been isolated from a variety of medicinal plants. Eupatilin is known to possess various pharmacological properties such as anti-cancer, anti-oxidant, and anti-inflammatory. It is speculated that eupatilin could be subjected to structural optimization for the synthesis of derivative analogs to reinforce its efficacy, to minimize toxicity, and to optimize absorption profiles, which will ultimately lead towards potent drug candidates. Although, reported data acclaim multiple pharmacological activities of eupatilin but further experimentations on its molecular mechanism of action are yet mandatory to elucidate full spectrum of its pharmacological activities.

Sestrin2: Its Potential Role and Regulatory Mechanism in Host Immune Response in Diseases

Sestrin2 (SESN2), a highly evolutionarily conserved protein, is critically involved in cellular responses to various stresses. SESN2 has a protective effect on physiological and pathological states mainly via regulating oxidative stress, endoplasmic reticulum stress, autophagy, metabolism, and inflammation. In recent years, breakthrough investigations with regard to the regulation and signaling mechanisms of SESN2 have markedly deepened our understanding of its potential role as well as its significance in host response. However, the functions of SESN2 in the immune system and inflammation remain elusive. It has been documented that many immune cells positively express SESN2 and, in turn, that SESN2 might modulate cellular activities. This review incorporates recent progress and aims to provide novel insight into the protective role and regulatory pathway of SESN2, which acts as a potential biomarker and therapeutic target in the context of various diseases.

Sestrins as a Therapeutic Bridge between ROS and Autophagy in Cancer

The regulation of Reactive Oxygen Species (ROS) levels and the contribution therein from networks regulating cell metabolism, such as autophagy and the mTOR-dependent nutrient-sensing pathway, constitute major targets for selective therapeutic intervention against several types of tumors, due to their extensive rewiring in cancer cells as compared to healthy cells. Here, we discuss the sestrin family of proteins—homeostatic transducers of oxidative stress, and drivers of antioxidant and metabolic adaptation—as emerging targets for pharmacological intervention. These adaptive regulators lie at the intersection of those two priority nodes of interest in antitumor intervention—ROS control and the regulation of cell metabolism and autophagy—therefore, they hold the potential not only for the development of completely novel compounds, but also for leveraging on synergistic strategies with current options for tumor therapy and classification/stadiation to achieve personalized medicine.

Sesn3 deficiency promotes carcinogen-induced hepatocellular carcinoma via regulation of the hedgehog pathway

Sestrin 3 (Sesn3) belongs to a small protein family that has been implicated in multiple biological processes including anti-oxidative stress, anti-aging, cell signaling, and metabolic homeostasis. However, the role of Sesn3 in hepatocellular carcinoma (HCC) remains unclear. Here we generated a Sesn3 knockout mouse model and induced HCC development by a combination of a single dose of diethylnitrosamine and chronic feeding of a choline deficient-high fat diet. After 6 months of the dietary treatment, Sesn3 knockout mice developed more severe HCC with higher levels of alpha-fetoprotein, arginase 1, and cytokeratin 19, but also higher metastatic rates than wild-type mice. Histological analysis revealed elevated extracellular matrix and cancer stem cell markers including Acta2, Cd44, and Cd133. Signaling analysis showed activated IL6-Stat3 and Akt pathways. Biochemical and microscopic analyses uncovered a novel inhibitory regulation of Gli2, a downstream transcription factor of the hedgehog signaling, by Sesn3. Two of the Gli2-regulated genes - Pdgfrb and Cd44 were upregulated in the Sesn3-deficient liver tissue. In conclusion, our data suggest that Sesn3 plays a critical tumor suppressor role in the liver partly through the inhibition of the hedgehog signaling.

Sestrin2 Negatively Regulates Casein Synthesis through the SH3BP4-mTORC1 Pathway in Response to AA Depletion or Supplementation in Cow Mammary Epithelial Cells

Sestrin2 (SESN2) negatively regulates the mammalian target of rapamycin complex 1 (mTORC1) pathway and casein synthesis in response to amino acid (AA) depletion in cow mammary epithelial cells (CMECs); however, the underlying mechanism is unclear. In the current study, the regulation of SESN2 on AA-mediated β-casein (CSN2) synthesis in CMECs and its mechanism were investigated. Overexpression and silencing of SESN2 demonstrated that SESN2 negatively regulated AA-mediated expression of CSN2 and mTORC1 pathway. Co-immunoprecipitation analysis showed that SESN2 interacted with SH3 domain-binding protein 4 (SH3BP4). Overexpression and silencing of SH3BP4 demonstrated that SH3BP4 negatively regulated AA-mediated expression of CSN2 and mTORC1 pathway and that SESN2 negatively regulated expression of CSN2 and mTORC1 pathway through the SH3BP4 in the presence and absence of AA. The absence or presence of AA demonstrated that AA negatively regulated expression and nuclear localization of activating transcription factor 4 (ATF4). Overexpression and silencing of ATF4 demonstrated that AA negatively regulated SESN2 expression through ATF4. Together, these results indicate that SESN2 negatively regulates the mTORC1 pathway and subsequent CSN2 synthesis through the SH3BP4 in response to AA absence or presence in CMECs.

Diverse Functions of Autophagy in Liver Physiology and Liver Diseases

Autophagy is a catabolic process by which eukaryotic cells eliminate cytosolic materials through vacuole-mediated sequestration and subsequent delivery to lysosomes for degradation, thus maintaining cellular homeostasis and the integrity of organelles. Autophagy has emerged as playing a critical role in the regulation of liver physiology and the balancing of liver metabolism. Conversely, numerous recent studies have indicated that autophagy may disease-dependently participate in the pathogenesis of liver diseases, such as liver hepatitis, steatosis, fibrosis, cirrhosis, and hepatocellular carcinoma. This review summarizes the current knowledge on the functions of autophagy in hepatic metabolism and the contribution of autophagy to the pathophysiology of liver-related diseases. Moreover, the impacts of autophagy modulation on the amelioration of the development and progression of liver diseases are also discussed.

Sipjeondaebo-tang Alleviates Oxidative Stress-Mediated Liver Injury through Activation of the CaMKK2-AMPK Signaling Pathway

Sipjeondaebo-tang (SDT) is used frequently as a herbal prescription to treat deficiency syndromes in traditional Korean medicine. We investigated the hepatoprotective effects of SDT against oxidative stress and attempted to clarify the underlying molecular mechanisms. SDT pretreatment reduced arachidonic acid (AA) plus iron-mediated cytotoxicity in a concentration-dependent manner and prevented changes in apoptosis-related protein expression. In addition, SDT pretreatment significantly reduced glutathione depletion, hydrogen peroxide production, and mitochondrial dysfunction via treatment with AA plus iron. SDT increased the phosphorylation of AMP-activated protein kinase (AMPK) in accordance with the phosphorylation of Ca²⁺/calmodulin-dependent protein kinase kinase 2 (CaMKK2). Experiments using an AMPK chemical inhibitor (Compound C) or CaMKK2 chemical inhibitor (STO-609) suggested that the CaMKK2-AMPK signaling pathway contributes to SDT-mediated protection of mitochondria and cells. Moreover, administration of SDT for 4 consecutive days to mice significantly reduced the alanine aminotransferase and aspartate aminotransferase activities induced by carbon tetrachloride, and the numbers of degenerated hepatocytes, infiltrated inflammatory cells, nitrotyrosine-positive cells, and 4-hydroxynonenal-positive cells in liver tissue. Therefore, SDT protects hepatocytes from oxidative stress via CaMKK2-dependent AMPK activation and has the therapeutic potential to prevent or treat oxidative stress-related liver injury.

SESN2 negatively regulates cell proliferation and casein synthesis by inhibition the amino acid-mediated mTORC1 pathway in cow mammary epithelial cells

Amino acids (AA) are one of the key nutrients that regulate cell proliferation and casein synthesis in cow mammary epithelial cells (CMEC), but the mechanism of this regulation is not yet clear. In this study, the effect of SESN2 on AA-mediated cell proliferation and casein synthesis in CMEC was assessed. After 12 h of AA starvation, CMECs were cultured in the absence of all AA (AA-), in the presences of only essential AA (EAA+), or of all AA (AA+). Cell proliferation, casein expression, and activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway were increased; but SESN2 expression was decreased in response to increased EAA or AA supply. Overexpressing or inhibiting SESN2 demonstrated that cell proliferation, casein expression, and activation of the mTORC1 pathway were all controlled by SESN2 expression. Furthermore, the increase in cell proliferation, casein expression, and activation of the mTORC1 pathway in response to AA supply was inhibited by overexpressing SESN2, and those effects were reversed by inhibiting SESN2. These results indicate that SESN2 is an important inhibitor of mTORC1 in CMEC blocking AA-mediated cell proliferation and casein synthesis.

Epimedium koreanum Ameliorates Oxidative Stress-Mediated Liver Injury by Activating Nuclear Factor Erythroid 2-Related Factor 2

Oxidative stress induced by reactive oxygen species is the main cause of various liver diseases. This study investigated the hepatoprotective effect of Epimedium koreanum Nakai water extract (EKE) against arachidonic acid (AA)[Formula: see text][Formula: see text][Formula: see text]iron-mediated cytotoxicity in HepG2 cells and carbon tetrachloride (CCl₄-)-mediated acute liver injury in mice. Pretreatment with EKE (30 and 100[Formula: see text][Formula: see text]g/mL) significantly inhibited AA[Formula: see text][Formula: see text][Formula: see text]iron-mediated cytotoxicity in HepG2 cells by preventing changes in the expression of cleaved caspase-3 and poly(ADP-ribose) polymerase. EKE attenuated hydrogen peroxide production, glutathione depletion, and mitochondrial membrane dysfunction. EKE also increased the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), transactivated anti-oxidant response element harboring luciferase activity, and induced the expression of anti-oxidant genes. Furthermore, the cytoprotective effect of EKE against AA[Formula: see text][Formula: see text][Formula: see text]iron was blocked in Nrf2 knockout cells. Ultra-performance liquid chromatography analysis showed that EKE contained icariin, icaritin, and quercetin; icaritin and quercetin were both found to protect HepG2 cells from AA[Formula: see text][Formula: see text][Formula: see text]iron via Nrf2 activation. In a CCl₄-induced mouse model of liver injury, pretreatment with EKE (300[Formula: see text]mg/kg) for four consecutive days ameliorated CCl₄-mediated increases in serum aspartate aminotransferase activity, histological activity index, hepatic parenchyma degeneration, and inflammatory cell infiltration. EKE also decreased the number of nitrotyrosine-, 4-hydroxynonenal-, cleaved caspase-3-, and cleaved poly(ADP-ribose) polymerase-positive cells in hepatic tissues. These results suggest EKE is a promising candidate for the prevention or treatment of oxidative stress-related liver diseases via Nrf2 activation.

Activating transcription factor 6-dependent sestrin 2 induction ameliorates ER stress-mediated liver injury

Endoplasmic reticulum (ER) stress is characterized by an accumulation of misfolded proteins, and ER stress reduction is essential for maintaining tissue homeostasis. However, the molecular mechanisms that protect cells from ER stress are not completely understood. The present study investigated the role of sestrin 2 (SESN2) on ER stress and sought to elucidate the mechanism responsible for the hepatoprotective effect of SESN2 in vitro and in vivo. Treatment with tunicamycin (Tm) increased SESN2 protein and mRNA levels and reporter gene activity. Activating transcription factor 6 (ATF6) bound to unfolded protein response elements of SESN2 promoter, transactivated SESN2, and increased SESN2 protein expression. In addition, dominant negative mutant of ATF6α and siRNA against ATF6α blocked the ER stress-mediated SESN2 induction, whereas chemical inhibition of PERK or IRE1 did not affect SESN2 induction by Tm. Ectopic expression of SESN2 in HepG2 cells inhibited CHOP and GRP78 expressions by Tm. Moreover, SESN2 decreased the phosphorylations of JNK and p38 and PARP cleavage, and blocked the cytotoxic effect of excessive ER stress. In a Tm-induced liver injury model, adenoviral delivery of SESN2 in mice decreased serum ALT, AST and LDH activities and the mRNA levels of CHOP and GRP78 in hepatic tissues. Moreover, SESN2 reduced numbers of degenerating hepatocytes, and inhibited caspase 3 and PARP cleavages. These results suggest ATF6 is essential for ER stress-mediated SESN2 induction, and that SESN2 acts as a feedback regulator to protect liver from excess ER stress.