• Biomolecules & Therapeutics
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• v.31 no.3
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• pp.330-339
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• 2023

Liver kinase B1 (LKB1) is a crucial tumor suppressor involved in various cellular processes, including embryonic development, tumor initiation and progression, cell adhesion, apoptosis, and metabolism. However, the precise mechanisms underlying its functions remain elusive. In this study, we demonstrate that LKB1 interacts directly with malic enzyme 3 (ME3) through the N-terminus of the enzyme and identified the binding regions necessary for this interaction. The binding activity was confirmed to promote the expression of ME3 in an LKB1-dependent manner and was also shown to induce apoptosis activity. Furthermore, LKB1 and ME3 overexpression upregulated the expression of tumour suppressor proteins (p53 and p21) and downregulated the expression of antiapoptotic proteins (nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and B-cell lymphoma 2 (Bcl-2)). Additionally, LKB1 and ME3 enhanced the transcription of p21 and p53 and inhibited the transcription of NF-κB. Moreover, LKB1 and ME3 suppressed the phosphorylation of various components of the phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B signaling pathway. Overall, these results suggest that LKB1 promotes pro-apoptotic activities by inducing ME3 expression.

• Biomolecules & Therapeutics
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• v.31 no.4
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• pp.456-465
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• 2023

Cervical tumors represent a prevalent form of cancer affecting women worldwide; current treatment options involve surgery, radiotherapy, and chemotherapy. Angiogenesis, the process of new blood vessel formation, is a crucial factor in cervical tumor growth. The molecular mechanisms underlying the effects of the liver kinase B1 (LKB1/STK11) tumor suppressor protein on tumor angiogenesis have not been elucidated. Therefore, we investigated the role of LKB1 in cervical tumor angiogenesis both in vitro and in vivo in this study. Our results demonstrated that LKB1 inhibited cervical tumor angiogenesis by suppressing the expression of angiogenesis-related factors such as vascular endothelial growth factor (VEGF) and hypoxia inducible factor-1α. LKB1 directly affected both carcinoma and vascular endothelial cells, resulting in a significant reduction in tumor growth and angiogenesis. Furthermore, LKB1 was found to bind to VEGF receptor 2 (VEGFR-2) and target the VEGFR-2-mediated protein kinase B/mechanistic target of rapamycin signaling pathway in endothelial cells, thereby reducing cervical tumor growth and angiogenesis. Our study provides new insights into the molecular mechanisms underlying the anti-tumor and anti-angiogenic effects of LKB1 in cervical cancer. These findings will help develop new therapeutic strategies for cervical cancer.

• Nutrition Research and Practice
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• v.14 no.4
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• pp.309-321
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• 2020

BACKGROUND/OBJECTIVES: The present study aimed to evaluate the effects of folic acid supplementation in high-fructose-induced hepatic steatosis and clarify the underlying mechanism of folic acid supplementation. MATERIALS/METHODS: Male SD rats were fed control, 64% high-fructose diet, or 64% high-fructose diet with folic acid for eight weeks. Plasma glutamate-pyruvate transaminase, glutamate-oxaloacetate transaminase, lipid profiles, hepatic lipid content, S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) were measured. RESULTS: The HF diet significantly increased hepatic total lipid and triglyceride (TG) and decreased hepatic SAM, SAH, and SAM:SAH ratio. In rats fed a high fructose diet, folic acid supplementation significantly reduced hepatic TG, increased hepatic SAM, and alleviated hepatic steatosis. Moreover, folic acid supplementation in rats fed high fructose enhanced the levels of phosphorylated AMP-activated protein kinase (AMPK) and liver kinase B (LKB1) and inhibited phosphorylation of acetyl coenzyme A carboxylase (ACC) in the liver. CONCLUSIONS: These results suggest that the protective effect of folic acid supplementation in rats fed high fructose may include the activation of LKB1/AMPK/ACC and increased SAM in the liver, which inhibit hepatic lipogenesis, thus ameliorating hepatic steatosis. The present study may provide evidence for the beneficial effects of folic acid supplementation in the treatment of non-alcoholic fatty liver disease.

• Journal of Ginseng Research
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• v.41 no.3
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• pp.392-402
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• 2017

Background: Previously, we reported that Korean Red Ginseng inhibited liver fibrosis in mice and reduced the expressions of fibrogenic genes in hepatic stellate cells (HSCs). The present study was undertaken to identify the major ginsenoside responsible for reducing the numbers of HSCs and the underlying mechanism involved. Methods: Using LX-2 cells (a human immortalized HSC line) and primary activated HSCs, MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assays were conducted to examine the cytotoxic effects of ginsenosides. $H_2O_2$ productions, glutathione contents, lactate dehydrogenase activities, mitochondrial membrane permeabilities, apoptotic cell subpopulations, caspase-3/-7 activities, transferase dUTP nick end labeling (TUNEL) staining, and immunoblot analysis were performed to elucidate the molecular mechanism responsible for ginsenoside-mediated cytotoxicity. Involvement of the AMP-activated protein kinase (AMPK)-related signaling pathway was examined using a chemical inhibitor and small interfering RNA (siRNA) transfection. Results and conclusion: Of the 11 ginsenosides tested, 20S-protopanaxadiol (PPD) showed the most potent cytotoxic activity in both LX-2 cells and primary activated HSCs. Oxidative stress-mediated apoptosis induced by 20S-PPD was blocked by N-acetyl-$\text\tiny L$-cysteine pretreatment. In addition, 20S-PPD concentration-dependently increased the phosphorylation of AMPK, and compound C prevented 20S-PPD-induced cytotoxicity and mitochondrial dysfunction. Moreover, 20S-PPD increased the phosphorylation of liver kinase B1 (LKB1), an upstream kinase of AMPK. Likewise, transfection of LX-2 cells with LKB1 siRNA reduced the cytotoxic effect of 20S-PPD. Thus, 20S-PPD appears to induce HSC apoptosis by activating LKB1-AMPK and to be a therapeutic candidate for the prevention or treatment of liver fibrosis.

• Biomolecules & Therapeutics
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• v.29 no.6
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• pp.650-657
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• 2021

Metformin is an anti-diabetic drug and has anticancer effects on various cancers. Several studies have suggested that metformin reduces cell proliferation and stimulates cell-cycle arrest and apoptosis. However, the definitive molecular mechanism of metformin in the pathophysiological signaling in endometrial tumorigenesis and metastasis is not clearly understood. In this study, we examined the effects of metformin on the cell viability and apoptosis of human cervical HeLa and endometrial HEC-1-A and KLE cancer cells. Metformin suppressed cell growth in a dose-dependent manner and dramatically evoked apoptosis in HeLa cervical cancer cells, while apoptotic cell death and growth inhibition were not observed in endometrial (HEC-1-A, KLE) cell lines. Accordingly, the p27 and p21 promoter activities were enhanced while Bcl-2 and IL-6 activities were significantly reduced by metformin treatment. Metformin diminished the phosphorylation of mTOR, p70S6K and 4E-BP1 by accelerating adenosine monophosphate-activated kinase (AMPK) in HeLa cancer cells, but it did not affect other cell lines. To determine why the anti-proliferative effects are observed only in HeLa cells, we examined the expression level of liver kinase B1 (LKB1) since metformin and LKB1 share the same signalling system, and we found that the LKB1 gene is not expressed only in HeLa cancer cells. Consistently, the overexpression of LKB1 in HeLa cancer cells prevented metformin-triggered apoptosis while LKB1 knockdown significantly increased apoptosis in HEC-1-A and KLE cancer cells. Taken together, these findings indicate an underlying biological/physiological molecular function specifically for metformin-triggered apoptosis dependent on the presence of the LKB1 gene in tumorigenesis.

• The Korea Journal of Herbology
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• v.36 no.6
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• pp.39-46
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• 2021

Objectives : AMP-activated protein kinase (AMPK) is a key metabolic regulator that reduces lipogenesis. AMPK is mainly activated via phosphorylation of liver kinase B (LKB) 1 under energy stress. Here, we highlighted the anti-obesity effect and underlying mechanism of Coix lacryma-jobi var. mayuen Stapf sprout water extract (CSW) sprout extract in connection with the LKB1/AMPK signaling pathway. Methods : C57BL/6 mice (20~25 g) fed HFD to induce obesity and at the same time administered CSW 100 mg/kg (CSWL; (CSWL; CSW low concentration) or CSW 200 mg/kg (CSWH; CSW high concentration) or Garcinia extract (Garcinia) 200 mg/kg orally for 6 weeks. Body weight and food intake were measured at the same time each day. After 6 weeks of CSW administration, liver tissue and serum were obtained through an autopsy. After the end of the experiment, biochemical analysis (triglycerides (TG), total cholesterol (TC), HDL-cholesterol, and LDL-cholesterol) was performed on the serum. And then, protein levels related to TG and TC synthesis were measured through western blot analysis in liver tissue. Results : As a result, serum TG, TC, and LDL-cholesterol levels were significantly increased in the control group and significantly decreased in the CSW administration group. On the other hand, the HDL-cholesterol level was increased in the CSW-administered group. And as a result of Western blot analysis, CSW significantly increased the phosphorylation of LKB1 & AMPK, and remarkably decreased the expression of factors related to TG and TC synthesis. Conclusions : Our findings suggest that CSW influences the TG and TC synthesis to positively affect HFD-induced obesity in C57BL/6 mice.

• Herbal Formula Science
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• v.30 no.3
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• pp.155-163
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• 2022

Objectives : Lonicera japonica is known for anti-inflammation and antibiotic effect in Korean medicine. This study aimed for investigating the cytoprotective effect of Lonicera japonica extract (LJE) for HepG2 cells against arachidonic acid (AA)+iron-induced oxidative stress. Methods : The effect of LJE on cell viability was assessed by MTT assay. ROS assay was selected to assess antioxidant effect of LJE. To assess LJE's effect on mitochondrial function, flow cytometric analysis was operated. And immunoblot analysis was used to establish the underlying mechanism of LJE. Results : LJE protected HepG2 cells against AA+iron-induced oxidative stress by phosphorylation of liver kinase B1 and blocked the decline of procaspase 3. Also, LJE preserved the mitochondrial membrane permeability induced by AA+iron. Conclusion : LJE protected the hepatocyte from AA+iron-induced oxidative stress by activation of LKB1 by the preservation of mitochondrial functions.

• Journal of Ginseng Research
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• v.44 no.3
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• pp.386-398
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• 2020

Tissue fibrosis is an eventual pathologic change of numerous chronic illnesses, which is characterized by resident fibroblasts differentiation into myofibroblasts during inflammation, coupled with excessive extracellular matrix deposition in tissues, ultimately leading to failure of normal organ function. Now, there are many mechanistic insights into the pathogenesis of tissue fibrosis, which facilitate the discovery of effective antifibrotic drugs. Moreover, many chronic diseases remain a significant clinical unmet need. For the past five years, many research works have undoubtedly addressed the functional dependency of ginsenosides in different types of fibrosis and the successful remission in various animal models treated with ginsenosides. Caveolin-1, interleukin, thrombospondin-1 (TSP-1), liver X receptors (LXRs), Nrf2, microRNA-27b, PPARδ-STAT3, liver kinase B1 (LKB1)-AMPK, and TGF-β1/Smads are potential therapy targeting using ginsenosides. Ginsenosides can play a targeting role and suppress chronic inflammatory response, collagen deposition, and epitheliale-mesenchymal transition (EMT), as well as myofibroblast activation to attenuate fibrosis. In this report, our aim was to focus on the therapeutic prospects of ginsenosides in fibrosis-related human diseases making use of results acquired from various animal models. These findings should provide important therapeutic clues and strategies for the exploration of new drugs for fibrosis treatment.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.1
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• pp.20-26
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• 2016

Prunellae Spica, the herbaceous plant in the genus Prunella, is a traditional herbal medicine and has been reported to have diuretic, anti-bacterial and anti-oxidant effects. However, the mechanism of its action was not clearly identified. In the present study, we investigated the hepatoprotective effect of Prunellae Spica extract (PSE) against the damage of mitochondria and death in hepatocyte induced by oxidative stress. Treatment of arachidonic acid (AA)+iron significantly induced oxidative stress and apoptosis in the hepatocytes. However, PSE protected cells and inhibited apoptosis by altering the protein levels such as poly(ADP-ribose) polymerase and pro-caspase 3. Moreover, AA+iron induced reactive oxygen species production and mitochondrial dysfunction, and Both of them were inhibited by PSE treatment. PSE markedly activated AMP-activated protein kinase (AMPK), an important regulator in cell survival. Furthermore, this activation by PSE was mediated with liver kinase B1, a major upstream kinase that phosphorylates Thr 172 of AMPKα, and this activation was associated with its cell protection, as assessed by an experiment of a chemical inhibitor. In conclusion, this study demonstrate that PSE protects hepatocytes against oxidative stress as mediated with activation of LKB1-dependent AMPK pathway.

• Journal of Korean Medicine Rehabilitation
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• v.32 no.2
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• pp.19-36
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• 2022

Objectives This study is to investigate the effects and mechanisms of Imyo-san (IMS) on the obese mice model induced by high-fat diet. Methods Antioxidative capacity was measured by in vitro method. C57BL/6 mice were randomly assigned into 5 groups (n=7). Normal group was fed general diet (Normal). The other 4 groups were fed high fat diet (HFD) with water (Control), with Garcinia gummi-gutta (GG, Garcinia gummi-gutta 200 mg/kg), with low-dose IMS (IMSL, Imyo-san 0.54 g/kg) and with high-dose IMS (IMSH, Imyo-san 1.08 g/kg). Results IMS showed high radical scavenging activity. After 6 week experiment, body weight, food intake, food efficiency ratio (FER), epididymal fat and liver weight, triglyceride (TG), total cholesterol (TC), high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, very low density lipoprotein (VLDL) cholesterol, sterol regulatory element-binding protein-1 (SREBP-1), phospho-acetyl-CoA carboxylase (p-ACC), fatty acid synthase (FAS), stearoyl-CoA desaturase-1 (SCD-1), SREBP-2, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), phospho-liver kinase B1 (p-LKB1), phospho-AMP-activated protein kinase (p-AMPK), peroxisome proliferator-activated receptor 𝛼 (PPAR𝛼), peroxisome proliferator-activated receptor 𝛾 coactivator-1𝛼 (PGC-1𝛼), uncoupling protein-2 (UCP-2), carnitine palmitoyltransferase 1A (CPT-1A), and histology of liver and epididymal fat were measured and analysed. Body weight gain, FER, liver and epididymal fat weight of IMS groups were significantly decreased. There were significant improvements in blood lipids with less TG, TC, LDL-cholesterol, VLDL-cholesterol and more HDL-cholesterol. Proteins associated with lipid synthesis (SREBP-1, p-ACC, FAS, SCD-1) and cholesterol (SREBP-2, HMGCR) was improved. Factors regulating lipid synthesis and lipid catabolism (p-LKBI, p-AMPK, PPARα, PGC-1α, UCP-2, CPT-1A) were increased. In histological examinations, IMS group had smaller fat droplets than control group. All results increased depending on concentration. Conclusions It can be suggested that IMS has anti-obesity effects with improving lipid metabolism.