Luteolin induces apoptosis through endoplasmic reticulum stress and mitochondrial dysfunction in Neuro-2a mouse neuroblastoma cells

Epigallocatechin gallate and curcumin inhibit Bcl-2: a pharmacophore and docking based approach against cancer

The protein Bcl-2, well-known for its anti-apoptotic properties, has been implicated in cancer pathogenesis. Identifying the primary gene responsible for promoting improved cell survival and development has provided compelling evidence for preventing cellular death in the progression of malignancies. Numerous research studies have provided evidence that the abundance of Bcl-2 is higher in malignant cells, suggesting that suppressing Bcl-2 expression could be a viable therapeutic approach for cancer treatment. In this study, we acquired a compound collection using a database that includes constituents from Traditional Chinese Medicine (TCM). Initially, we established a pharmacophore model and utilized it to search the TCM database for potential compounds. Compounds with a fitness score exceeding 0.75 were selected for further analysis. The Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET) analysis identified six compounds with favorable therapeutic characteristics. The compounds that successfully passed the initial screening process based on the pharmacodynamic model were subjected to further evaluation. Extra-precision (XP) docking was employed to identify the compounds with the most favorable XP docking scores. Further analysis using the Molecular Mechanics Generalized Born Surface Area (MM-GBSA) method to calculate the overall free binding energy. The binding energy between the prospective ligand molecule and the target protein Bcl-2 was assessed by a 100 ns molecular dynamics simulation for curcumin and Epigallocatechin gallate (EGCG). The findings of this investigation demonstrate the identification of a molecular structure that effectively inhibits the functionality of the Bcl-2 when bound to the ligand EGCG. Consequently, this finding presents a novel avenue for the development of pharmaceuticals capable of effectively addressing both inflammatory and tumorous conditions.

Neuroprotective effects of flavonoids: endoplasmic reticulum as the target

The incidence of neurological disorders, particularly age-related neurodegenerative pathologies, exhibits an alarming upward trend, while current pharmacological interventions seldom achieve curative outcomes. Despite their diverse clinical presentations, neurological diseases often share a common pathological thread: the aberrant accumulation of misfolded proteins within the endoplasmic reticulum (ER). This phenomenon, known as ER stress, arises when the cell's intrinsic quality control mechanisms fail to cope with the protein-folding burden. Consequently, misfolded proteins accumulate in the ER lumen, triggering a cascade of cellular stress responses. Recognizing this challenge, researchers have intensified their efforts over the past two decades to explore natural compounds that could potentially slow or even reverse these devastating pathologies. Flavonoids constitute a vast and heterogeneous class of plant polyphenols, with over 10,000 identified from diverse natural sources such as wines, vegetables, medicinal plants, and organic products. Flavonoids are generally divided into six different subclasses: anthocyanidins, flavanones, flavones, flavonols, isoflavones, and flavonols. The diverse family of flavonoids, featuring a common phenolic ring backbone adorned with varying hydroxyl groups and additional modifications, exerts its antioxidant activity by inhibiting the formation of ROS, as evidenced by research. Also, studies suggest that polyphenols such as flavonoids can regulate ER stress through apoptosis and autophagy. By understanding these mechanisms, we can unlock the potential of flavonoids as novel therapeutic agents for neurodegenerative disorders. Therefore, this review critically examines the literature exploring the modulatory effects of flavonoids on various steps of the ER stress in neurological disorders.

Luteolin Protects Against 6-Hydoroxydopamine-Induced Cell Death via an Upregulation of HRD1 and SEL1L

Parkinson's Disease (PD) is caused by many factors and endoplasmic reticulum (ER) stress is considered as one of the responsible factors for it. ER stress induces the activation of the ubiquitin-proteasome system to degrade unfolded proteins and suppress cell death. The ubiquitin ligase 3-hydroxy-3-methylglutaryl-coenzyme A reductase degradation 1 (HRD1) and its stabilizing molecule, the suppressor/enhancer lin-12-like (SEL1L), can suppress the ER stress via the ubiquitin-proteasome system, and that HRD1 can also suppress cell death in familial and nonfamilial PD models. These findings indicate that HRD1 and SEL1L might be key proteins for the treatment of PD. Our study aimed to identify the compounds with the effects of upregulating the HRD1 expression and suppressing neuronal cell death in a 6-hydroxydopamine (6-OHDA)-induced cellular PD model. Our screening by the Drug Gene Budger, a drug repositioning tool, identified luteolin as a candidate compound for the desired modulation of the HRD1 expression. Subsequently, we confirmed that low concentrations of luteolin did not show cytotoxicity in SH-SY5Y cells, and used these low concentrations in the subsequent experiments. Next, we demonsrated that luteolin increased HRD1 and SEL1L mRNA levels and protein expressions. Furthermore, luteolin inhibited 6-OHDA-induced cell death and suppressed ER stress response caused by exposure to 6-OHDA. Finally, luteolin did not reppress 6-OHDA-induced cell death when expression of HRD1 or SEL1L was suppressed by RNA interference. These findings suggest that luteolin might be a novel therapeutic agent for PD due to its ability to suppress ER stress through the activation of HRD1 and SEL1L.

Potential Treatment Options for Neuroblastoma with Polyphenols through Anti-Proliferative and Apoptotic Mechanisms

Neuroblastoma (NB) is an extracranial tumor of the peripheral nervous system arising from neural crest cells. It is the most common malignancy in infants and the most common extracranial solid tumor in children. The current treatment for high-risk NB involves chemotherapy and surgical resection followed by high-dose chemotherapy with autologous stem-cell rescue and radiation treatment. However, those with high-risk NB are susceptible to relapse and the long-term side effects of standard chemotherapy. Polyphenols, including the sub-class of flavonoids, contain more than one aromatic ring with hydroxyl groups. The literature demonstrates their utility in inducing the apoptosis of neuroblastoma cells, mostly in vitro and some in vivo. This review explores the use of various polyphenols outlined in primary studies, underlines the pathways involved in apoptotic activity, and discusses the dosage and delivery of these polyphenols. Primary studies were obtained from multiple databases with search the terms “neuroblastoma”, “flavonoid”, and “apoptosis”. The in vitro studies showed that polyphenols exert an apoptotic effect on several NB cell lines. These polyphenols include apigenin, genistein, didymin, rutin, quercetin, curcumin, resveratrol, butein, bisphenols, and various plant extracts. The mechanisms of the therapeutic effects include calpain-dependent pathways, receptor-mediated apoptosis, and, notably, and most frequently, mitochondrial apoptosis pathways, including the mitochondrial proteins Bax and Bcl-2. Overall, polyphenols demonstrate potency in decreasing NB proliferation and inducing apoptosis, indicating significant potential for further in vivo research.

In vitro evaluation of dioscin and protodioscin against ER-positive and triple-negative breast cancer

Women's breast cancer is one of the most significant healthcare issues for the human race that demands a proactive strategy for a cure. In this study, the cytotoxic activity (MTT assay) of two natural steroidal compounds, protodioscin and dioscin, against two major subtypes of human breast cancer estrogen receptor-positive (ER-positive)/MCF-7 and triple-negative breast cancer (TNBC)/MDA-MB-468), was assessed. The clonogenic capacity was evaluated using the clonogenic assay. Oxidative stress was determined by measuring the formation of malondialdehyde and H2O2 and the assessment of total antioxidant enzyme activities (SOD, GPx, GR, and TrxR). Protodioscin and dioscin were highly cytotoxic against the tested cell lines (1.53 μM <IC50< 6 μM) with low cytotoxicity on normal cells (PBMC; IC50 ≥ 50 μM). Interestingly, these compounds were responsible for a substantial decrease in the clonogenic capacity of both cell lines. Moreover, dioscin was able to reduce the cell motility of the invasive breast cancer cells (MDA-MB-468). At the molecular level, the two treatments resulted in an increase of reactive oxygen species. Notably, both compounds were responsible for decreasing the enzymatic activities of glutathione reductase and thioredoxin reductase. On the basis of such considerations, protodioscin and dioscin may serve as promising natural compounds to treat TNBC and ER-positive breast cancer through the induction of oxidative stress.

Structural Characterization of a Pleurotus sajor-caju Polysaccharide and Its Neuroprotection Related to the Inhibition of Oxidative Stress

A novel polysaccharide PSP2-1 was isolated and purified from Pleurotus sajor-caju. The structural characterization data displayed that the molecular weight of PSP2-1 was 44.9 kDa, and PSP2-1 consisted of fucose, galactose, glucose, and mannose. The methylation results showed that the glycosidic bonds of PSP2-1 included T-Fuc, 1,6-Gal, T-Glc, 1,6-Glc, 1,3,6-Glc, 1,3-Man, 1,2,6-Man, and T-Man. Neuroprotective studies indicated that PSP2-1 significantly improved the cell viability of the H₂O₂-induced oxidatively damaged neuronal cell HT22, reduced the release of LDH, inhibited apoptosis and release of cytochrome c, and alleviated the decline of mitochondrial membrane potential and ROS accumulation. Furthermore, PSP2-1 decreased the phosphorylation levels of cleaved PARP and cleaved caspase-3, and increased the ratio of bcl-2/bax. Additionally, PSP2-1 could inhibit the phosphorylation of MAPK family members including JNK, p38, and Erk. Finally, animal experiments showed that PSP2-1 could improve the oxidative stress injury and the learning and memory ability of mice with aging induced by D-galactose. Our results confirmed that PSP2-1 significantly ameliorated the oxidative stress injury, inhibited the apoptosis in H₂O₂-induced neuronal cells via MAPK pathway, and also improved cognition in mice with aging induced by D-galactose. Our research gives the foundation for the functional food application of P. sajor-caju polysaccharides in the future.

Mucoadhesive nanoemulsion enhances brain bioavailability of luteolin after intranasal administration and induces apoptosis to sh-sy5y neuroblastoma cells

Neuroblastoma is the most frequently diagnosed extracranial solid tumor in children and accounts for 7% of all childhood malignancies and 15% cancer mortality in children. Luteolin (LUT) is recognized by its anticancer activity against several types of cancer. The aim of this study was to prepare chitosan-coated nanoemulsion containing luteolin (NECh-LUT), investigate its potential for brain delivery following intranasal administration, and to evaluate its cytotoxicity against neuroblastoma cells. NECh-LUT was developed by cavitation process and characterized for its size, surface charge, encapsulation efficiency, and mucoadhesion. The developed formulation presented size 68±1 nm, zeta potential +13±1 mV, and encapsulation efficiency of 85.5±0.3%. The NECh-LUT presented nearly 6-fold higher permeation through the nasal mucosa ex vivo and prolonged LUT release up to 72 h in vitro, following Baker-Lonsdale kinetic model. The pharmacokinetic evaluation of NECh-LUT revealed a 10-fold increase in drug half-life and a 4.4 times enhancement in LUT biodistribution in brain tissue after intranasal administration of single-dose. In addition, NECh-LUT inhibited the growth of neuroblastoma cells after 24, 48 and 72 h in concentrations starting from 2 µM. The NECh-LUT developed for intranasal administration proved to be a promising alternative for brain delivery of LUT, and a viable option for the treatment of neuroblastoma.

Compound C Inhibits Renca Renal Epithelial Carcinoma Growth in Syngeneic Mouse Models by Blocking Cell Cycle Progression, Adhesion and Invasion

Compound C (CompC), an inhibitor of AMP-activated protein kinase, reduces the viability of various renal carcinoma cells. The molecular mechanism underlying anti-proliferative effect was investigated by flow cytometry and western blot analysis in Renca cells. Its effect on the growth of Renca xenografts was also examined in a syngeneic BALB/c mouse model. Subsequent results demonstrated that CompC reduced platelet-derived growth factor receptor signaling pathways and increased ERK1/2 activation as well as reactive oxygen species (ROS) production. CompC also increased the level of active Wee1 tyrosine kinase (P-Ser⁶⁴²-Wee1) and the inactive form of Cdk1 (P-Tyr¹⁵-Cdk1) while reducing the level of active histone H3 (P-Ser¹⁰-H3). ROS-dependent ERK1/2 activation and sequential alterations in Wee1, Cdk1, and histone H3 might be responsible for the CompC-induced G2/M cell cycle arrest and cell viability reduction. In addition, CompC reduced the adhesion, migration, and invasion of Renca cells in the in vitro cell systems, and growth of Renca xenografts in the BALB/c mouse model. Taken together, the inhibition of in vivo tumor growth by CompC may be attributed to the blockage of cell cycle progression, adhesion, migration, and invasion of tumor cells. These findings suggest the therapeutic potential of CompC against tumor development and progression.

Therapeutic Potential of Phlorotannin-Rich Ecklonia cava Extract on Methylglyoxal-Induced Diabetic Nephropathy in In Vitro Model

Advanced glycation end-products (AGEs) play a vital role in the pathogenesis of diabetic complications. Methylglyoxal (MGO), one of the major precursors of AGEs, is a highly reactive dicarbonyl compound that plays an important role in the pathogenesis of diabetic nephropathy. This study was designed to evaluate the therapeutic potential of phlorotannin-rich Ecklonia cava extract (ECE) on MGO-induced diabetic nephropathy in in vitro models using mouse glomerular mesangial cells. ECE showed anti-glycation activity via breaking of AGEs-collagen cross-links and inhibition of AGEs formation and AGE-collagen cross-linking formation. The renoprotective effects were determined by assessing intracellular reactive oxygen species (ROS) and MGO accumulation, cell apoptosis, and the Nrf-2/ARE signaling pathway. MGO-induced renal damage, intracellular ROS production level, and MGO-protein adduct accumulation were significantly decreased by pretreating ECE. Moreover, ECE pretreatment exhibited preventive properties against MGO-induced dicarbonyl stress via activation of the Nrf2/ARE signaling pathway and reduction of RAGE protein expression in mouse glomerular mesangial cells. Collectively, these results indicated potential anti-glycation properties and prominent preventive effects of ECE against MGO-induced renal damage. Additionally, ECE may be utilized for the management of AGE-related diabetic nephropathy.

Early Aerobic Exercise Promotes Neurological Function Recovery of Rats after Cerebral Ischemia/Reperfusion by Upregulating the Expression of Heat Shock Protein A5

OBJECTIVE

The neuroprotective function of heat shock protein A5 (HSPA5) in ischemic stroke has been confirmed. This study aimed to investigate the effects of early aerobic exercise on neurological function recovery from cerebral ischemia/reperfusion and to determine whether these effects are associated with the expression level of HSPA5 in the ischemic penumbra.

METHODS

A total of 72 male Sprague-Dawley rats were randomly assigned to the ischemia and exercise group [middle cerebral artery occlusion (MCAO)-Ex, n=18], ischemia and sedentary group (MCAO-St, n=18), sham-surgery and exercise group (Sham-Ex, n=18), or sham-surgery and sedentary group (Sham-St, n=18). The MCAO-Ex and MCAO-St groups were subjected to MCAO for 60 min, whereas the Sham-Ex and Sham-St groups were subjected to an identical operation without MCAO. Rats in the MCAO-Ex and Sham-Ex groups then ran on a treadmill for 30 min once a day for 5 consecutive days. After reperfusion, the motor function of the rats was scored by the Bederson neurological function test, balance beam test, and screen test. Nissl staining was conducted to assess morphological and structural change of nerve cells in the ischemic penumbra. The reverse transcription-quantitative polymerase chain reaction was applied to detect the mRNA expression of HSPA5. Western blot analysis was conducted to determine the protein expression of HSPA5. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining was carried out in the ischemic penumbra after MCAO.

RESULTS

Rats receiving early treadmill exercise had lower Bederson neurological function, balance beam, and screen test scores on the 3rd, 7th, and 14th days after MCAO; in addition, more neurons survived in the ischemic penumbra after MCAO, and higher mRNA and protein expression of HSPA5 and fewer TUNEL-positive stained cells were observed.

CONCLUSION

Our study demonstrated that early aerobic exercise can improve neurological function recovery after ischemia/reperfusion. Furthermore, the increased level of HSPA5 in the ischemic penumbra might be one of the mechanisms of enhanced neurological function recovery.

ZC3H4 promotes pulmonary fibrosis via an ER stress-related positive feedback loop

BACKGROUND

Pulmonary fibrosis is a sequela of many pulmonary diseases, such as pneumoconiosis and idiopathic pulmonary fibrosis. The principal characteristics of pulmonary fibrosis comprise myofibroblast proliferation, alveolar damage and deposition of extracellular matrix components, which cause abnormal lung structure remodeling and an irreversible decline in lung function; however, the detailed mechanisms remain unclear. The current study focused on the role of ZC3H4, a new member of the zinc finger protein family, in SiO₂-induced pulmonary fibrosis.

METHODS

The expression of ZC3H4 and fibroblast activation markers (COL1A1, COL3A1 and ACTA1) was measured by western blotting and immunofluorescence staining after SiO₂ exposure (50 μg/cm²). The functional change in fibroblasts was studied with a scratch assay and a 3D migration assay. The CRISPR/Cas9 system was used to explore the regulatory mechanisms of ZC3H4 in pulmonary fibroblast cells.

RESULTS

The expression levels of ZC3H4 and sigmar1 (a key regulator of ER stress) were increased in pulmonary fibroblast cells and were associated with fibroblast activation, as indicated by the increase in COL1A1, COL3A1 and ACTA1, as well as the migration ability. SiO₂-enhanced fibroblast activation was attenuated by specific knockdown of ZC3H4 and inhibition of ER stress, demonstrating that ZC3H4 activated fibroblasts via the sigmar1/ER stress pathway. Interestingly, ER stress blockade also inhibited ZC3H4 expression, indicating the positive feedback regulatory mechanism of ER stress on ZC3H4.

CONCLUSIONS

Our results demonstrate that ZC3H4 and sigmar1 might act as novel therapeutic targets for silicosis, providing a reference for further pulmonary fibrosis research.

Healthy ageing and Mediterranean diet: A focus on hormetic phytochemicals

Mediterranean diet (MedDiet) is rich in fruits and vegetables associated with longevity and a reduced risk of several age-related diseases. It is demonstrated that phytochemicals in these plant products enhance the positive effects of MedDiet by acting on the inflammatory state and reducing oxidative stress. Evidence support that these natural compounds act as hormetins, triggering one or more adaptive stress-response pathways at low doses. Activated stress-response pathways increase the expression of cytoprotective proteins and multiple genes that act as lifespan regulators, essential for the ageing process. In these ways, the hormetic response by phytochemicals such as resveratrol, ferulic acid, and several others in MedDiet might enhance cells' ability to cope with more severe challenges, resist diseases, and promote longevity. This review discusses the role of MedDiet phytochemicals in healthy ageing and the prevention of age-related diseases.

Ishige okamurae Ameliorates Methylglyoxal-Induced Nephrotoxicity via Reducing Oxidative Stress, RAGE Protein Expression, and Modulating MAPK, Nrf2/ARE Signaling Pathway in Mouse Glomerular Mesangial Cells

Advanced glycation end-products (AGEs) such as methylglyoxal (MGO) play a vital role in the pathogenesis of nephropathy, a diabetic complication. In the present study, we evaluated the anti-glycation and renal protective properties of Ishige okamurae extract (IOE) against AGE-induced oxidative stress. HPLC analysis confirmed that bioactive phlorotannins such as diphlorethohydroxycarmalol and ishophloroglucin A are predominantly present in IOE. IOE showed strong anti-glycation activities via inhibition of AGE formation, inhibition of AGE-protein cross-linking, and breaking of AGE-protein cross-links. In addition, in vitro studies using mesangial cells demonstrated that IOE effectively suppressed intracellular reactive oxygen species production, intracellular MGO accumulation, and apoptotic cell death by MGO-induced oxidative stress, in addition to regulating the expression of proteins involved in the receptor for AGEs and nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response elements (ARE) signaling pathways. Therefore, IOE can serve as a natural therapeutic agent for the management of AGE-related nephropathy.

Effect of luteolin on apoptosis and vascular endothelial growth factor in human choroidal melanoma cells

AIM

To investigate the effects of luteolin on apoptosis, the cell cycle, and the expression and secretion of vascular endothelial growth factor (VEGF) in human choroidal melanoma cells (C918 and OCM-1).

METHODS

C918 and OCM-1 cells cultured in vitro were treated with various concentrations of luteolin (0, 5, 10, 15 µmol/L). Cell growth was observed with an inverted microscope, and cell cycle arrest was detected by propidium iodide (PI) staining using flow cytometry. Apoptosis was detected by Hoechst33342 staining, and apoptosis rate was determined by Annexin V-FITC/PI experiments using flow cytometry. The expression of apoptosis-related proteins Bcl-2, Bax and VEGF was analyzed using Western blots. The levels of VEGF secreted by the cells into the supernatant was analyzed using ELISA.

RESULTS

After treating with 5 to 15 µmol/L luteolin for 48h, the fusion degree of C918 and OCM-1 cells decreased, and more floating apoptotic cells appeared. Luteolin treatment increased the G0-G1 phase ratio of the C918 and OCM-1 cells, blocked cell cycle progression, and increased the apoptosis rate of the C918 and OCM-1 cells. Western blot showed that luteolin decreased the expression of Bcl-2 and VEGF in the C918 and OCM-1 cells and increased the expression of Bax protein. The ELISA results showed that 10 to 15 µmol/L luteolin decreased the cell secretion of VEGF.

CONCLUSION

Luteolin may induce apoptosis by regulating the levels of apoptosis-related proteins in C918 and OCM-1 cells. Luteolin can induce cell cycle arrest, decrease the expression of VEGF.

Bioavailability and Pharmaco-therapeutic Potential of Luteolin in Overcoming Alzheimer's Disease

Luteolin is a naturally occurring, yellow crystalline flavonoid found in numerous dietary supplements we frequently have in our meals. Studies in the last 2 decades have revealed its therapeutic potential to reduce the Alzheimer's disease (AD) symptoms in various in vitro and in vivo models. The anti-Alzheimer's potential of luteolin is attributed to its ability to suppress Aβ as well as tau aggregation or promote their disaggregation, down-regulate the expression of COX-2, NOS, MMP-9, TNF-α, interleukins and chemokines, reduce oxidative stress by scavenging ROS, modulate the activities of transcription factors CREB, cJun, Nrf-1, NF-κB, p38, p53, AP-1 and β-catenine and inhibiting the activities of various protein kinases. In several systems, luteolin has been described as a potent antioxidant and anti-inflammatory agent. In addition, we have also discussed about the bio-availability of the luteolin in the plasma. After being metabolized luteolin persists in plasma as glucuronides and sulphate-conjugates. Human clinical trials indicated no dose limiting toxicity when administered at a dose of 100 mg/day. Improvements in the formulations and drug delivery systems may further enhance the bioavailability and potency of luteolin. The current review describes in detail the data supporting these studies.

Isosamidin from Peucedanum japonicum Roots Prevents Methylglyoxal-Induced Glucotoxicity in Human Umbilical Vein Endothelial Cells via Suppression of ROS-Mediated Bax/Bcl-2

Methylglyoxal (MGO) is a highly reactive metabolite of glucose. Elevated levels of MGO induce the generation of reactive oxygen species (ROS) and cause cell death in endothelial cells. Vascular endothelial cell damage by ROS has been implicated in the progression of diabetic vascular complications, cardiovascular diseases, and atherosclerosis. In this study, the protective effect of isosamidin, isolated from Peucedanum japonicum roots, on MGO-induced apoptosis was investigated using human umbilical vein endothelial cells (HUVECs). Among the 20 compounds isolated from P. japonicum, isosamidin showed the highest effectiveness in inhibiting MGO-induced apoptosis of HUVECs. Pretreatment of HUVECs with isosamidin significantly prevented the generation of ROS and cell death induced by MGO. Isosamidin prevented MGO-induced apoptosis in HUVECs by downregulating the expression of Bax and upregulating the expression of Bcl-2. MGO treatment activated mitogen-activated protein kinases (MAPKs), such as p38, c-Jun N terminal kinase (JNK), and extracellular signal-regulated kinase (ERK). In contrast, pretreatment with isosamidin strongly inhibited the activation of p38 and JNK. Furthermore, isosamidin caused the breakdown of the crosslinks of the MGO-derived advanced glycation end products (AGEs). These findings suggest that isosamidin from P. japonicum may be used as a preventive agent against MGO-mediated endothelial dysfunction in diabetes. However, further study of the therapeutic potential of isosamidin on endothelial dysfunction needs to explored in vivo models.

Luteolin impairs hypoxia adaptation and progression in human breast and colon cancer cells

Hypoxia-inducible factors (HIFs) are the force which drives hypoxic cancer cells to a more aggressive and resistant phenotype in a number of solid tumors, including colorectal and breast cancer. Results from recent studies suggest a role for HIF-1 in immune evasion and cancer stem cell phenotype promotion, establishing HIF-1 as a potential therapeutic target. Thus, identifying new compounds that might inhibit HIF1 activity, or at least exert antiproliferative effects that are unaffected by HIF1-dependent adaptations, is an attractive goal for the management of hypoxic tumors. Here we show that the flavonoid luteolin exerts a significant cytotoxic effect on the colon cancer cell line HCT116 and the breast adenocarcinoma cell line MDA-MB231, by inducing both apoptotic and necrotic cell death, and that this effect is not impaired by HIF-1 activation. In these cells, luteolin also stimulates autophagy; however this seems to be part of a protective response, rather than contribute to the cytotoxic effect. Interestingly, luteolin induces a decrease in HIF-1 transcriptional activity. This is accompanied by a decrease in the levels of protein markers of stemness and invasion, and by a reduction of migratory capacity of the cells. Taken together, our results suggest that luteolin could be developed into a useful therapeutic agent aimed at hypoxic tumors.

Compound C Inhibits B16-F1 Tumor Growth in a Syngeneic Mouse Model Via the Blockage of Cell Cycle Progression and Angiogenesis

We recently observed that Compound C (CompC), a reversible inhibitor of AMP-activated protein kinase, reduced the cell viability of B16-F1 melanoma cells. To establish its molecular mechanism(s) of action, the cell cycle was examined by flow cytometry and the expression of cell cycle regulatory proteins and angiogenesis-related proteins were examined by western blot analysis. In addition, its effect on tumor growth was investigated using C57BL/6 syngeneic mice bearing B16-F1 xenografts. We found that CompC induced G2/M cell cycle arrest, which was associated with reduced levels of cell cycle regulatory proteins, such as phosphorylated pRB, cyclin-dependent protein kinases (Cdks), cyclins, and phosphorylated P-Ser¹⁰-histone H3, and increased levels of Cdk inhibitors, such as p21 and p53. We also found that CompC inhibits proliferation, migration, and tube formation of human umbilical vascular endothelial cells via the inhibition of vascular endothelial growth factor receptor-induced signaling pathways. As expected, CompC significantly reduced the tumor size of B16-F1 xenografts in the syngeneic mouse model. Inhibition of tumor growth may be attributed to reduced cell proliferation via cell cycle inhibition and in part to decreased angiogenesis in CompC-treated mice. These findings suggest the potential use of CompC against melanoma development and progression.

Carfilzomib enhances cisplatin-induced apoptosis in SK-N-BE(2)-M17 human neuroblastoma cells

Neuroblastoma is a solid malignant tumor of the sympathetic nervous system, which accounts for 8–10% of childhood cancers. Considering the overall high risk and poor prognosis associated with neuroblastoma, effective therapeutics should be developed to improve patient survival and quality of life. A recent study showed that a proteasome inhibitor, carfilzomib (CFZ), reduced cell viability of SK-N-BE(2)-M17 neuroblastoma cells. Therefore, we investigated the molecular mechanisms by which CFZ lower the cell viability of neuroblastoma cells. CFZ reduced cell viability via cell cycle arrest at G2/M and apoptosis, which involved caspase activation (caspases-8, 9, 4, and 3), endoplasmic reticulum stress, reactive oxygen species production, mitochondrial membrane potential loss, and autophagy in a dose- and time-dependent manner. The effect of CFZ was additive to that of cisplatin (Cis), a well-known chemotherapeutic drug, in terms of cell viability reduction, cell cycle arrest, and apoptosis. Importantly, the additive effect of CFZ was maintained in Cis-resistant neuroblastoma cells. These results suggest that CFZ can be used in combination therapy for patients with neuroblastoma to overcome the resistance and adverse side effects of Cis.

Alantolactone induces gastric cancer BGC-823 cell apoptosis by regulating reactive oxygen species generation and the AKT signaling pathway

Alantolactone (ALT), a natural sesquiterpene lactone, has been suggested to exert anti-cancer activities in various cancer cell lines. However, the effects and mechanisms of action of ALT in human gastric cancer remains to be elucidated. In the present study, the effects of ALT on BGC-823 cells were examined and the underlying molecular mechanisms associated with these effects were investigated. Cell viability was detected by using an MTT assay. Cell cycle, cell apoptosis and the level of reactive oxygen species (ROS) were assessed by flow cytometry, and the expression levels of proteins of interest were analyzed by western blot assay. The results demonstrated that ALT triggered apoptosis and induced G0/G1 phase arrest in a dose-dependent manner. Furthermore, the expression level of the anti-apoptosis protein Bcl-2 was downregulated, and expression of the pro-apoptosis proteins Bax and cleaved PARP were significantly upregulated. The cell cycle-associated proteins cyclin-dependent kinase inhibitor 1 and cyclin-dependent kinase inhibitor 1B were also increased, while cyclin D1 was deceased. In addition, ALT induced apoptosis via the inhibition of RAC-alpha serine/threonine-protein kinase (AKT) signaling and ROS generation, which was effectively inhibited by the ROS scavenger, N-acetyl cysteine. Therefore, the results from the present study indicated that the ROS-mediated inhibition of the AKT signaling pathway serves an important role in ALT-induced apoptosis in BGC-823 cells. In conclusion, the results demonstrated that ALT exerted significant anti-cancer effects against gastric cancer cells in vitro.

Luteolin, a flavonoid, as an anticancer agent: A review

Many food-derived phytochemicals and their derivatives represent a cornucopia of new anti-cancer compounds. Luteolin (3,4,5,7-tetrahydroxy flavone) is a flavonoid found in different plants such as vegetables, medicinal herbs, and fruits. It acts as an anticancer agent against various types of human malignancies such as lung, breast, glioblastoma, prostate, colon, and pancreatic cancers. It also blocks cancer development in vitro and in vivo by inhibition of proliferation of tumor cells, protection from carcinogenic stimuli, and activation of cell cycle arrest, and by inducing apoptosis through different signaling pathways. Luteolin can additionally reverse epithelial-mesenchymal transition (EMT) through a mechanism that involves cytoskeleton shrinkage, induction of the epithelial biomarker E-cadherin expression, and by down-regulation of the mesenchymal biomarkers N-cadherin, snail, and vimentin. Furthermore, luteolin increases levels of intracellular reactive oxygen species (ROS) by activation of lethal endoplasmic reticulum stress response and mitochondrial dysfunction in glioblastoma cells, and by activation of ER stress-associated proteins expressions, including phosphorylation of eIF2α, PERK, CHOP, ATF4, and cleaved-caspase 12. Accordingly, the present review article summarizes the progress of recent research on luteolin against several human cancers.

Alpha-naphthoflavone induces apoptosis through endoplasmic reticulum stress via c-Src-, ROS-, MAPKs-, and arylhydrocarbon receptor-dependent pathways in HT22 hippocampal neuronal cells

α-Naphthoflavone (αNF) is a prototype flavone, also known as a modulator of aryl hydrocarbon receptor (AhR). In the present study, we investigated the molecular mechanisms of αNF-induced cytotoxic effects in HT22 mouse hippocampal neuronal cells. αNF induced apoptotic cell death via activation of caspase-12 and -3 and increased expression of endoplasmic reticulum (ER) stress-associated proteins, including C/EBP homologous protein (CHOP). Inhibition of ER stress by treatment with the ER stress inhibitor, salubrinal, or by CHOP siRNA transfection reduced αNF-induced cell death. αNF activated mitogen-activated protein kinases (MAPKs), such as p38, JNK, and ERK, and inhibition of MAPKs reduced αNF-induced CHOP expression and cell death. αNF also induced accumulation of reactive oxygen species (ROS) and an antioxidant, N-acetylcysteine, reduced αNF-induced MAPK phosphorylation, CHOP expression, and cell death. Furthermore, αNF activated c-Src kinase, and inhibition of c-Src by a kinase inhibitor, SU6656, or siRNA transfection reduced αNF-induced ROS accumulation, MAPK activation, CHOP expression, and cell death. Inhibition of AhR by an AhR antagonist, CH223191, and siRNA transfection of AhR and AhR nuclear translocator reduced αNF-induced AhR-responsive luciferase activity, CHOP expression, and cell death. Finally, we found that inhibition of c-Src and MAPKs reduced αNF-induced transcriptional activity of AhR. Taken together, these findings suggest that αNF induces apoptosis through ER stress via c-Src-, ROS-, MAPKs-, and AhR-dependent pathways in HT22 cells.

Luteolin Induces Apoptosis and Autophagy in Mouse Macrophage ANA-1 Cells via the Bcl-2 Pathway

Plants rich in luteolin have been used as Chinese traditional medicines for inflammatory diseases, hypertension, and cancer. However, little is known about the effect of luteolin on the apoptosis or autophagy of the macrophages. In this study, mouse macrophage ANA-1 cells were incubated with different concentrations of luteolin. The viability of the cells was determined by an MTT assay, apoptosis was determined by flow cytometric analysis, the level of cell autophagy was observed by confocal microscopy, and the expression levels of apoptotic or autophagic and antiapoptotic or antiautophagic proteins were detected by Western blot analysis. The results showed that luteolin decreased the viability of ANA-1 cells and induced apoptosis and autophagy. Luteolin induced apoptosis accompanied by downregulation of the expression of Bcl-2 and upregulation of the expression of caspase 3 and caspase 8. And luteolin increased FITC-LC3 punctate fluorescence accompanied by the increased expression levels of LC3-I, ATG7, and ATG12, while it suppressed the expression level of Beclin-1. Luteolin treatment resulted in obvious activation of the p38, JNK, and Akt signaling pathways, which is important in modulating apoptosis and autophagy. Thus, we concluded that luteolin induced the apoptosis and autophagy of ANA-1 cells most likely by regulating the p38, JNK, and Akt pathways, inhibiting the activity of Bcl-2 and Beclin-1 and upregulating caspase 3 and caspase 8 expression. These results provide novel insights into a therapeutic strategy to prevent and possibly treat macrophage-related diseases through luteolin-induced apoptosis and autophagy.

Grape seed proanthocyanidins protect against streptozotocin‑induced diabetic nephropathy by attenuating endoplasmic reticulum stress‑induced apoptosis

Diabetic nephropathy (DN) is by far the most common cause of end-stage renal disease (ESRD) in industrial countries, accounting for ~45% of all new ESRD cases in the United States. Grape seed proanthocyanidin extracts (GSPE) are powerful antioxidants, with an antioxidant ability 50-fold greater than that of vitamin E and 20-fold greater than that of vitamin C. The present study investigated whether GSPE can protect against streptozotocin (STZ)-induced DN and aimed to elucidate a possible mechanism. Male Sprague Dawley rats were randomly divided into three groups: Control group (N), diabetes mellitus group (DM) injected with 40 mg/kg STZ, and the GSPE treatment group (intragastric administration of 250 mg/kg/day GSPE for 16 weeks after diabetes was induced in the rats). Blood and kidney samples were collected after treatment. The renal pathological changes were determined with periodic acid-Schiff (PAS) staining, while the protein expression levels of glucose-regulated protein 78 (GRP78), phosphorylated-extracellular signal-regulated kinase (p-ERK) and Caspase-12 were determined by western blotting and immunohistochemical staining. Apoptosis was determined with a terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Compared with the DM group, the GSPE group had no significant changes in the blood urea nitrogen (BUN) level and serum creatinine (Scr) level, but showed a significant decline in the renal index (RI) level and 24-h urinary albumin level (P<0.05). The histopathology results indicated very little pathological damage in the GSPE group. Compared with the DM group, the GSPE group had a significantly reduced number of TUNEL-positive cells (P<0.05), and the GSPE group had an obvious reduction in the protein expression of GRP78, p-ERK, and Caspase-12 (P<0.05). In this study, the results indicated that GSPE can protect renal function and attenuate endoplasmic reticulum stress-induced apoptosis via the Caspase-12 pathway in STZ-induced DN.

Luteolin and sorafenib combination kills human hepatocellular carcinoma cells through apoptosis potentiation and JNK activation

Sorafenib is a small-molecule multi-kinase inhibitor approved by FDA as an oral agent for the treatment of hepatocellular carcinoma (HCC) and renal cell carcinoma. However, unresponsiveness and acquired resistance are commonly observed, which hinder the clinical use of sorafenib. As combination therapy is a promising approach to improve its efficacy, we investigated if sorafenib and luteolin combination is effective in killing human HCC cells. Cell death was examined by lactate dehydrogenase (LDH) releasing assay. Apoptosis was detected by flow cytometric. The activation of apoptotic pathway and c-Jun N-terminal kinase (JNK) signaling pathway was measured by western blot. The results showed that sorafenib and luteolin combination synergistically induced cytotoxicity in HCC cells, which was accompanied by potentiation of apoptosis as demonstrated by increased apoptotic cell populations, caspase activation, and suppression of cell death by the pan-caspase inhibitor z-VAD-fmk. Furthermore, the combination of both agents enhanced expression of phosphorylated form of JNK, and the JNK inhibitor SP600125 effectively attenuated cell death induced by the combination treatment. Thus, sorafenib and luteolin combination synergistically kills HCC cells through JNK-mediated apoptosis, and luteolin may be an ideal candidate for increasing the activity of sorafenib in HCC therapy.

Selective Cytotoxicity of Luteolin and Kaempferol on Cancerous Hepatocytes Obtained from Rat Model of Hepatocellular Carcinoma: Involvement of ROS-Mediated Mitochondrial Targeting

To evaluate the cytotoxicity effects of luteolin (LUT) and kaempferol (KAE) via reactive oxygen species (ROS) mediated mitochondrial targeting on hepatocytes obtained from the liver of hepatocellular carcinoma (HCC) rats. In this study, HCC induced by diethylnitrosamine (DEN) and 2-acetylaminofluorene (2-AAF). In the following, rat liver hepatocytes and mitochondria were isolated and tested for every eventual apoptotic and anti-HCC effects of LUT and KAE. The results of MTT assay showed that LUT and KAE were able to induce selective cytotoxicity in hepatocytes of HCC group in a dose- and time-dependent manner. Treatment of mitochondria from hepatocytes of HCC group with LUT and KAE were accompanied by loss of mitochondrial membrane potential (MMP) and mitochondrial swelling and release of cytochrome c (P < 0.001) via reactive oxygen species (ROS) generation before cytotoxicity ensued. LUT and KAE also increased activation of caspase-3 (P < 0.001 and P < 0.01, respectively). Flow-cytometry analysis indicated that the mode of cell death induced by these flavonoids were mostly apoptosis. Importantly, LUT and KAE were nontoxic for healthy hepatocytes and mitochondria. Therefore, we suggest that LUT and KAE are a good candidate for the complementary therapeutic agent against HCC.

Toxicarioside N induces apoptosis in human gastric cancer SGC-7901 cell by activating the p38MAPK pathway

Natural plant compounds with potent proliferation inhibition and apoptosis induction properties have been screened as novel anticancer drugs. Toxicarioside N (Tox N) was isolated from the seeds of the tropical plant Antiaris toxicaria in Hainan province, China. To our knowledge, the effects that Tox N has on the apoptosis of SGC-7901 cells and its potential mechanism have never been investigated. In this study, we detected the anticancer activities of Tox N and explored the potential mechanism in the human gastrointestinal cancer cell line SGC-7901. Here, we found that Tox N inhibited SGC-7901 cell growth in a dose- and time-dependent manner and induced apoptosis in cells based on cell morphology and flow cytometry analyses. Additionally, the SGC-7901 cell treated with Tox N up-regulated the expression level of cleaved caspase-3/9 and PARP, increased the Bax/Bcl-2 ratio, and led to the release of cytochrome c into the cytoplasm. In addition, Tox N treatment led to the phosphorylation of p38MAPK. SB203580, a p38MAPK inhibitor, partially attenuated Tox N induced apoptosis by preventing the activation of caspase-3/9 and PARP. Our results indicated for the first time that Tox N can induce SGC-7901 cells apoptosis by activating the p38MAPK pathway.

Autophagy mediated by endoplasmic reticulum stress enhances the caffeine-induced apoptosis of hepatic stellate cells

Caffeine has been identified to have beneficial effects against chronic liver diseases, particularly liver fibrosis. Many studies have reported that caffeine ameliorates liver fibrosis by directly inducing hepatic stellate cell (HSC) apoptosis; however, the molecular mechanisms involved in this process remain unclear. The presents study aimed to detect the underlying mechanisms by which caffeine mediates HSC apoptosis and eliminates activated HSCs. For this purpose, the LX-2 cell line was applied in this study and the cells were exposed to various concentrations of caffeine for the indicated times. The effects of caffeine on cell viability and apoptosis were assessed by Cell Counting Kit-8 assay and flow cytometry, respectively. Autophagy and endoplasmic reticulum (ER) stress were explored by morphological assessment and western blotting. In the present study, caffeine was found to inhibit the viability and increase the apoptosis of the LX-2 cells in dose- and time-dependent manners. ER stress was stimulated by caffeine as demonstrated by increased levels of GRP78/BiP, CHOP and inositol-requiring enzyme 1 (IRE1)-α as well as many enlarged ERs detected by electron microscopy. Caffeine induced autophagy as shown by increased p62 and LC3II accumulation and the number of GFP/RFP-LC3 puncta and autophagosomes/autolysosomes. Moreover, IRE1-α knockdown decreased the level of autophagic flux, and inhibition of autophagy protected LX-2 cells from apoptotic death. In conclusion, our study showed that the caffeine-enhanced autophagic flux in HSCs was stimulated by ER stress via the IRE1-α signaling pathway, which further weakened HSC viability via the induction of apoptosis. These findings provide new insight into the mechanism of caffeine's anti-fibrotic effects.

MicroRNA Changes in Preconditioning-Induced Neuroprotection

Preconditioning is a paradigm in which sublethal stress-prior to a more injurious insult-induces protection against injury. In the central nervous system (CNS), preconditioning against ischemic stroke is induced by short durations of ischemia, brief seizures, exposure to anesthetics, and other stresses. Increasing evidence supports the contribution of microRNAs (miRNAs) to the pathogenesis of cerebral ischemia and ischemic tolerance induced by preconditioning. Studies investigating miRNA changes induced by preconditioning have to date identified 562 miRNAs that change expression levels after preconditioning, and 15% of these changes were reproduced in at least one additional study. Of miRNAs assessed as changed by preconditioning in more than one study, about 40% changed in the same direction in more than one study. Most of the studies to assess the role of specific miRNAs in the neuroprotective mechanism of preconditioning were performed in vitro, with fewer studies manipulating individual miRNAs in vivo. Thus, while many miRNAs change in response to preconditioning stimuli, the mechanisms underlying their effects are not well understood. The data does suggest that miRNAs may play significant roles in preconditioning-induced neuroprotection. This review focuses on the current state of knowledge of the possible role of miRNAs in preconditioning-induced cerebral protection.

Luteolin induces apoptosis by ROS/ER stress and mitochondrial dysfunction in gliomablastoma

OBJECTIVE

Luteolin, a common dietary flavonoid, induces apoptosis of many types of cancer cells. However, its role in glioblastoma and the potential mechanisms remain unknown. In this research, we studied the molecular mechanisms of the anti-cancer effect of luteolin in glioblastoma cancer cell lines.

METHODS

Both U251MG and U87MG human glioblastoma cell lines were tested. Cell growth was assessed by the cell counting kit-8. Cell apoptosis was detected with flow cytometry and caspase-3 immunofluorescence staining. The protein levels of caspase-3/Bax/Bcl-2 and p-PERK/p-eIF2α/ATF4/CHOP/caspase-12 pathway were analyzed using western blots. Reactive oxygen species generation was measured with DCFH-DA staining using flow cytometry. Mitochondrial membrane potential was tested with JC-1 staining. Anti-cancer effect in vivo was measured using tumor xenograft mode in nude mice.

RESULTS

Luteolin induced a lethal endoplasmic reticulum stress response and mitochondrial dysfunction in glioblastoma cells by increasing intracellular reactive oxygen species (ROS) levels. Luteolin induced expression of ER stress-associated proteins, including phosphorylation of PERK, eIF2α, ATF4, CHOP and cleaved-caspase 12. Inhibition of ROS production by anti-oxidant N-acetylcysteine could reverse luteolin-induced ER stress and mitochondrial pathways activation as well as apoptosis. What's more, we also showed the anticancer effect of luteolin in vivo.

CONCLUSIONS

Our results suggest that luteolin induces apoptosis through activating ER stress and mitochondrial dysfunction in glioblastoma cell lines and in vivo, which provides the anti-cancer candidate to treat glioblstoma.

9-Norbornyl-6-chloropurine (NCP) induces cell death through GSH depletion-associated ER stress and mitochondrial dysfunction

9-Norbornyl-6-chloropurine (NCP) is a representative of a series of antienteroviral bicycle derivatives with selective cytotoxicity towards leukemia cell lines. In this work we explored the mechanism of the antileukemic activity of NCP in T-cell lymphoblast cells (CCRF-CEM). Specifically, we searched for a potential link between its ability to induce cell death on the one hand and to modulate intracellular glutathione (GSH) that is necessary to its metabolic transformation via glutathione-S-transferase on the other hand. We have observed that GSH levels decreased rapidly in NCP-treated cells. Despite a complete regeneration following 24h of incubation with NCP, this profound drop in cellular GSH content triggered ER stress, ROS production and lipid peroxidation leading to the loss of mitochondrial membrane potential (MMP). These events induced concentration-dependent cell cycle arrest in G2/M phase and apoptosis. Both MMP loss and apoptosis were reversed by sulfhydryl-containing compounds (GSH, N-acetyl-l-cysteine). Furthermore, we have also shown that NCP-induced GSH decrease activated the Nrf2 pathway and its downstream targets

NAD(P)H

quinone oxidoreductase (NQO-1) and glutamate cysteine ligase modifier subunit (GCLm), thus explaining the fast restoration of GSH pool and ROS decrease. Importantly, we confirmed that the cell death-inducing properties of the compounds were co-dependent on their ability to diminish cellular GSH level by analyzing the relationships between the GSH-depleting potency and cytotoxicity in a series of other norbornylpurine analogs. Altogether, the results demonstrated that in CCRF-CEM cells NCP triggered apoptosis through GSH depletion-associated oxidative and ER stress and mitochondrial depolarization.

CSTMP induces apoptosis and mitochondrial dysfunction in human myeloma RPMI8226 cells via CHOP-dependent endoplasmic reticulum stress

BACKGROUND

The natural product tetramethylpyrazine (TMP) and resveratrol have a variety of biologic activities, including anti-cancer effects. However the pharmacological function of CSTMP (a newly designed and synthesized TMP and resveratrol derivative) in cancer have not been elucidated.

METHODS

In RPMI8226 cells, the cytotoxic effects and apoptosis were detected by MTT and Double staining for Annexin V-FITC and propidium iodide (PI). The protein and mRNA expression levels were detected by Real Time PCR and Western blot, respectively. The localization of cleaved caspase-12 was evaluated by immunofluorescent staining. The activation of caspase were measured by colorimetric assays and Western blot.

RESULTS

CSTMP showed significantly cytotoxic effects and induced apoptosis in RPMI8226 cells. Caspase activation, Cytochrome c release and Bax, Bcl-2 and Bcl-XL levels analyses demonstrated that the anti-cancer effect of CSTMP in RPMI8226 cells was mediated by promoting caspase- and mitochondria-dependent apoptosis. In addition, CSTMP induced the increased expression of endoplasmic reticulum (ER) stress related proteins (CHOP, GRP78, GRP94 and cleaved caspase-12) and the activation of multiple branches of ER stress transducers (PERK-eIF2α, IRE1α and ATF6). Moreover, knockdown of CHOP by siRNA markedly inhibited CSTMP-induced cytotoxic effects, caspases activity and mitochondrial dysfunction in RPMI8226 cells.

CONCLUSIONS

Our results indicated that CSTMP could induce apoptosis and mitochondrial dysfunction in RPMI8226 cells via CHOP-dependent ER stress.

Angiopoietin-1 attenuates angiotensin II-induced ER stress in glomerular endothelial cells via a Tie2 receptor/ERK1/2-p38 MAPK-dependent mechanism

Research has indicated that endoplasmic reticulum (ER) stress in endothelial cells affects vascular pathologies and induces cellular dysfunction and apoptosis. Angiopoietin1 (Angpt1) has been shown to have therapeutic potential in some vascular diseases, including chronic kidney disease. This study showed that Angpt1 is a powerful factor that attenuated ER stress-induced cellular dysfunction and apoptosis in glomerular endothelial cells (GEnCs). Furthermore, Angpt1 significantly decreased the angiotensin II (Ang II)-induced expression of the ER stress response proteins GRP78, GRP94, p-PERK and CHOP. These results suggest that the Angpt1-mediated cellular protection may occur downstream of the ER stress response. In addition, both specific inhibitors and siRNAs for Tie2 reversed these changes, implying the importance of Tie2 receptor activation in the signalling pathways that prevent ER stress. The protective effects of Angpt1 are related to the activation of two downstream signalling pathways, ERK1/2 and p38 MAPK. The inhibition of these pathways with specific inhibitors, PD98059 and SB203580, respectively, partially increased the expression of chaperones that assist in folding proteins in the ER and reduce the protective effects of Angpt1. In conclusion, Angpt1 attenuated ER stress-induced cellular dysfunction and apoptosis via the Tie2 receptor/ERK1/2-p38 MAPK pathways in GEnCs. This study may provide insights into a novel underlying mechanism and a strategy for alleviating ER stress-induced injury.

δ-Tocopherol prevents methylglyoxal-induced apoptosis by reducing ROS generation and inhibiting apoptotic signaling cascades in human umbilical vein endothelial cells

Methylglyoxal (MGO) is a highly reactive metabolite of glucose, which is known to cause damage and induce apoptosis in endothelial cells. Endothelial cell damage is implicated in the progression of diabetes-associated complications and atherosclerosis. Nuts are high in vitamin E. Consumption of nuts has been recommended for the prevention of cardiovascular disease. However, different nuts contain different forms of vitamin E, which can have different effects on endothelial cells. In this work, we investigated the protective effect of different isoforms of vitamin E on MGO-induced apoptosis in human umbilical vein endothelial cells (HUVECs). Among all forms of vitamin E, δ-tocopherol showed the highest effect on apoptosis of HUVECs. We also compared the anti-apoptotic activity of δ-tocopherol with that of α-tocopherol in MGO-treated HUVECs. Pretreatment with α- or δ-tocopherol significantly inhibited MGO-induced changes in cell morphology, cell death, and production of intracellular reactive oxygen species. δ-Tocopherol prevented MGO-induced apoptosis in HUVECs by increasing Bcl-2 expression and decreasing Bax expression. Interestingly, α-tocopherol also inhibited these factors but to a lesser extent than δ-tocopherol. MGO was found to activate mitogen-activated protein kinases (MAPKs). Compared to pretreatment with α-tocopherol, pretreatment with δ-tocopherol more strongly inhibited the activation of MAPKs, such as JNK and ERK1/2. These findings suggest that δ-tocopherol may be a more effective regulator of MGO-induced apoptosis than α-tocopherol.

Effects of Flavonoids from Potamogeton crispus L. on Proliferation, Migration, and Invasion of Human Ovarian Cancer Cells

In order to explore the efficient utilization of plant resources from constructed wetlands, the potential anti-metastatic effects of flavonoids from Potamogeton crispus L. were investigated in human ovarian cancer cells (ES-2). Two major flavonoids, luteolin-3'-O-β-D-glucopyranoside and flavone-6-C-β-D-glucopyranoside, were isolated from P. crispus and identified. The effects of these flavonoids on cell proliferation, cell morphology, cell cycle, apoptosis, and cell migration and invasion were then investigated. Furthermore, reverse transcriptase polymerase chain reaction assays and western blotting analysis were conducted to examine the expression level of mRNA and protein. Results indicated that Luteolin-3'-O-β-D-glucopyranoside inhibited ES-2 cell migration and invasion and suppressed the expression of two matrix metalloproteinases (MMPs), MMP-2 and MMP-9, and Flavone-6-C-β-D-glucopyranoside had no significant inhibitory effects on ES-2 cells. Thus, this study demonstrated the potential anti-metastatic properties of a P. crispus flavonoid, and provided a scientific approach for the screening of promising natural resources from constructed wetlands to identify useful products for use in the pharmaceutical and healthcare industries.

Anticancer potential of the histone deacetylase inhibitor-like effects of flavones, a subclass of polyphenolic compounds: a review

Cancer is characterized by the uncontrolled division of cells, followed by their invasion to other tissues. These kinds of cellular abnormalities arise as a result of the accumulation of genetic mutations or epigenetic alterations. Targeting genetic mutations by drugs is a conventional treatment approach. Nowadays, the development and use of epigenetic drugs are burgeoning, owing to the advancements in epigenetic research. The therapeutic intervention of cancer development by histone deacetylase inhibitors (HDACIs) holds promise for helping to control the disease, but their nonspecific functions impose certain side effects. Therefore, the search for more HDACIs becomes essential. Plentiful literature on the versatility of dietary components including flavones, a class of the flavonoid group, has already established these compounds to be better anticancer agents. The present review focuses on the significance of flavones with regard to their HDACI-mimicking effects as suggested by the recent evidences. The review also proposes an in-depth screening of flavones in future studies, in the hope that flavones may provide a better alternative to synthetic HDACIs.

Adaptive cellular stress pathways as therapeutic targets of dietary phytochemicals: focus on the nervous system

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phytochemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examplesof such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-κB, hypoxia-inducible factor 1α, peroxisome proliferator-activated receptor γ, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Translational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.

Chikusetsu saponin V attenuates MPP+-induced neurotoxicity in SH-SY5Y cells via regulation of Sirt1/Mn-SOD and GRP78/caspase-12 pathways

Studies have shown that saponins from Panax japonicus (SPJ) possess neuroprotective effects. However, whether Chikusetsu saponin V (CsV), the most abundant member of SPJ, can exert neuroprotective effects against 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced cytotoxicity is not known. In this study, we aimed to investigate the neuroprotective effects of CsV on MPP⁺-induced cytotoxicity in human neuroblastoma SH-SY5Y cells and explore its possible mechanisms. Our results show that CsV attenuates MPP⁺-induced cytotoxicity, inhibits ROS accumulation, and increases mitochondrial membrane potential dose-dependently. We also found that levels of Sirt1 protein and Mn-SOD mRNA significantly decreased in MPP⁺-treated group but were restored with CsV treatment in a dose-dependent manner. Furthermore, GRP78 protein and Caspase-12 mRNA levels were elevated by MPP⁺ exposure but reversed by CsV treatment. CsV inhibited the MPP⁺-induced downregulation of Bcl-2 and up-regulation of Bax in a dose-dependent manner and, thus, increased the ratio of Bcl-2/Bax. Overall, these results suggest that Sirt1/Mn-SOD and GRP78/Caspase-12 pathways might be involved in the CsV-mediated neuroprotective effects.