A novel Gymnema sylvestre extract protects pancreatic beta‐cells from cytokine‐induced apoptosis

Inflammatory cytokines such as interleukin‐1β, TNF‐α, and interferon‐γ are known to be involved in mediating β‐cells death in diabetes mellitus (DM). Thus, protecting from β‐cells death in patients with DM may be a useful target in alleviating symptoms of hyperglycemia. Traditional plant‐based remedies have been used to treat DM for many centuries and may play a role in protecting β‐cell from death. An example of these remedies is Gymnema sylvestre (GS) extract. In this study, we investigated the effect of this plant extract on β‐cells apoptosis. Om Santal Adivasi (OSA®) maintained cell membrane integrity in MIN6 cells and mouse islets. Om Santal Adivasi significantly protected MIN6 cells and mouse islets from cytokine‐induced apoptosis. In the presence of cytokines, OSA® significantly reduced the expression and activity of caspase‐3. The antiapoptotic effect of OSA® as shown by microarray analysis is largely mediated by activating pathways involved in cell survival (mainly casein kinase II pathway) and the free radical scavenger system (specifically superoxide dismutase and catalase). This study indicates that the GS isolate OSA® protects against cytokine‐induced apoptosis of β‐cells by increasing the expression of cell survival pathways and free radical scavenger system.     

Silibinin protects rat pancreatic β‐cell through up‐regulation of estrogen receptors' signaling against amylin‐ or Aβ1–42‐induced reactive oxygen species/reactive nitrogen species generation

Amylin and amyloid‐β (Aβ) were found to induce reactive oxygen species (ROS) and reactive nitrogen species (RNS) in rat pancreatic β‐cell line, INS‐1 cells, leading to cell death. In this study, we report on reciprocal relationship between the expression of estrogen receptors (ERs) α and β (ERα and ERβ) and generation of ROS/RNS in amylin/Aβ_1–42‐treated INS‐1 cells. That is, pharmacological activation of ERs in INS‐1 cells significantly decreases ROS/RNS generation, but blockage of ERs increases ROS/RNS generation. Silibinin is a natural polyphenolic flavonoid isolated from milk thistle with phytoestrogen activities, also known as silybin. Treatment with silibinin down‐regulated ROS/RNS production induced by treatment with amylin/Aβ_1–42 in the cells. Silencing ERs expression with siRNAs targeting ERs showed that the protective effect of silibinin was markedly weakened, indicating that silibinin protection is largely attributed to activation of ERs' signaling. The binding of silibinin to ERs implies that the protective effect of silibinin on amylin/Aβ_1–42‐treated INS‐1 cells owes to down‐regulation of ROS/RNS through the activation of ERs phosphorylation. Amylin and Aβ_1–42 cotreatment enhanced furthermore ROS/RNS generation and cytotoxicity through further down‐regulation of ERs phosphorylation, and this was reversed by silibinin. Silibinin also protects INS‐1 cells from amylin and Aβ_1–42 cotreatment. These results indicate that protective effect of silibinin is mediated by enhancement of ERs phosphorylation that depresses ROS/RNS generation in amylin/Aβ_1–42‐treated INS‐1 cells.     

Kaempferol protects HIT‐T15 pancreatic beta cells from 2‐deoxy‐D‐ribose‐induced oxidative damage

During the progression of Type 2 diabetes, glucose toxicity is likely to contribute importantly to progressive beta cell failure. Oxidative stress is an important aspect of glucose toxicity in pancreatic beta cells, and reducing sugars, such as 2‐deoxy‐D‐ribose (dRib), produce reactive oxygen species. Furthermore, many of the biological properties of flavonoids are likely to be related to their antioxidant and free‐radical scavenging abilities. Accordingly, in the present study, we investigated whether kaempferol (a flavonol) protects beta cells from dRib‐induced oxidative damage. HIT‐T15 cells were cultured with various concentrations of dRib for 24h. Cell survivals, amounts of reactive oxygen species (ROS) generated, apoptosis, and lipid peroxidation were measured. dRib was found to dose‐dependently reduce cell survival and to markedly increase intracellular ROS levels, apoptosis, and lipid peroxidation. However, kaempferol (10 µM) suppressed dRib (20 mM) induced intracellular ROS, apoptosis, and lipid peroxidation. So, we demonstrate that kaempferol reduces dRib‐mediated beta cell damage interfering with ROS metabolism and protective effects against lipid peroxidation. Our findings indicate that kaempferol protects HIT‐T15 cells from dRib‐induced associated oxidative damage. Copyright © 2009 John Wiley & Sons, Ltd.     

Genistein inhibits Aβ25–35‐induced SH‐SY5Y cell damage by modulating the expression of apoptosis‐related proteins and Ca2+ influx through ionotropic glutamate receptors

In this study, we investigated the protective effects of genistein against SH‐SY5Y cell damage induced by β‐amyloid 25–35 peptide (Aβ_25–35) and the underlying mechanisms. Aβ‐induced neuronal death, apoptosis, glutamate receptor subunit expression, Ca²⁺ ion concentration, amino acid transmitter concentration, and apoptosis‐related factor expression were evaluated to determine the effects of genistein on Aβ‐induced neuronal death and apoptosis. The results showed that genistein increased the survival of SH‐SY5Y cells and decreased the level of apoptosis induced by Aβ_25–35. In addition, genistein reversed the Aβ_25–35‐induced changes in amino acid transmitters, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptors, and N‐methyl‐d ‐aspartate (NMDA) receptor subunits in SH‐SY5Y cells. Aβ_25–35‐induced changes in Ca²⁺ and B‐cell lymphoma‐2 (Bcl‐2) and Bcl‐2‐associated X (Bax) protein and gene levels in cells were also reversed by genistein. Our data suggest that genistein protects against Aβ_25–35‐induced damage in SH‐SY5Y cells, possibly by regulating the expression of apoptosis‐related proteins and Ca²⁺ influx through ionotropic glutamate receptors.     

Pycnogenol Cytotoxicity in Pancreatic INS‐1E β cells Induced by Calcium Dysregulation

Natural standardized flavonoid extract from the bark of Pinus pinaster, Pycnogenol (Pyc), was recently found to decrease intensively the activity of sarcoplasmic reticulum Ca²⁺‐ATPase of rabbit skeletal muscle (SERCA1). On the basis of this inhibitory effect in a cell‐free system and similarities of SERCA1 to its other isoforms, proapoptotic properties of Pyc may be expected in cellular systems. Pycnogenol (40–100 μg/mL) induced a concentration‐dependent decrease of the viability of pancreatic INS‐1E β cells associated with induction of apoptosis. In addition, intracellular Ca²⁺ level increase was found along with reduction of protein expression level of SERCA2b and impairment of insulin secretion by β cells. These facts indicate that Pyc may induce apoptosis by impairment of calcium homeostasis. Copyright © 2017 John Wiley & Sons, Ltd.     

1,7‐Bis(4‐hydroxyphenyl)‐4‐hepten‐3‐one from Betula platyphylla induces apoptosis by suppressing autophagy flux and activating the p38 pathway in lung cancer cells

Betula platyphylla (BP) is frequently administered in the treatment of various human diseases, including cancers. This study was undertaken to investigate the pharmacological function of the active components in BP and the underlying mechanism of its chemotherapeutic effects in human lung cancer cells. We observed that BP extracts and 1,7‐bis(4‐hydroxyphenyl)‐4‐hepten‐3‐one (BE1), one of the components of BP, effectively decreased the cell viability of several lung cancer cell lines. BE1‐treated cells exhibited apoptosis induction and cell cycle arrest at the G2/M phase. Further examination demonstrated that BE1 treatment resulted in suppression of autophagy, as evidenced by increased protein expression levels of both LC3 II and p62/SQSTM1. Interestingly, the pharmacological induction of autophagy with rapamycin remarkably reduced the BE1‐induced apoptosis, indicating that apoptosis induced by BE1 was associated with autophagy inhibition. Our data also demonstrated that BE1 exposure activated the p38 pathway resulting in regulation of the pro‐apoptotic activity. Taken together, we believe that BE1 is a potential anticancer agent for human lung cancer, which exerts its effect by enhancing apoptosis via regulating autophagy and the p38 pathway.     

β‐Eudesmol Induces JNK‐Dependent Apoptosis through the Mitochondrial Pathway in HL60 Cells

β‐eudesmol, a natural sesquiterpenol present in a variety of Chinese herbs, is known to inhibit the proliferation of human tumor cells. However, the molecular mechanisms of the effect of β‐eudesmol on human tumor cells are unknown. In the present study, we report the cytotoxic effect of β‐eudesmol on the human leukemia HL60 cells and its molecular mechanisms. The cytotoxic effect of β‐eudesmol on HL60 cells was associated with apoptosis, which was characterized by the presence of DNA fragmentation. β‐eudesmol‐induced apoptosis was accompanied by cleavage of caspase‐3, caspase‐9, and poly (ADP‐ribose) polymerase; downregulation of Bcl‐2 expression; release of cytochrome c from mitochondria; and decrease in mitochondrial membrane potential (MMP). Activation of c‐Jun N‐terminal kinases (JNK) mitogen‐activated protein kinases was observed in β‐eudesmol‐treated HL60 cells, and the inhibitor of JNK blocked the β‐eudesmol‐induced apoptosis, downregulation of Bcl‐2, and the loss of MMP. These data suggest that β‐eudesmol induces apoptosis in HL60 cells via the mitochondrial apoptotic pathway, which is controlled through JNK signaling. Copyright © 2012 John Wiley & Sons, Ltd.     

Ferulate Protects the Epithelial Barrier by Maintaining Tight Junction Protein Expression and Preventing Apoptosis in Tert‐Butyl Hydroperoxide‐Induced Caco‐2 Cells

Epithelial barrier function is determined by both transcellular and paracellular permeability, the latter of which is mainly influenced by tight junctions (TJs) and apoptotic leaks within the epithelium. We investigated the protective effects of ferulate on epithelial barrier integrity by examining permeability, TJ protein expression, and apoptosis in Caco‐2 cells treated with tert‐butyl hydroperoxide (t‐BHP), a strong reactive species inducer. Caco‐2 cells pretreated with ferulate (5 or 15 μM) were exposed to t‐BHP (100 μM), and ferulate suppressed the t‐BHP‐mediated increases in reactive species and epithelial permeability in Caco‐2 cells. Moreover, ferulate inhibited epithelial cell leakage induced by t‐BHP, which was accompanied by decreased expression of the TJ proteins zonula occludens‐1 and occludin. In addition, pretreatment with ferulate markedly protected cells against t‐BHP‐induced apoptosis, as evidenced by decreased nuclear condensation, cytochrome c release, and caspase‐3 cleavage and an increased Bax/Bcl‐2 ratio. These results suggest that ferulate protects the epithelial barrier of Caco‐2 cells against oxidative stress, which results in increased epithelial permeability, decreased TJ protein expression, and increased apoptosis. The most significant finding of our study is the demonstration of protective, ferulate‐mediated antioxidant effects on barrier integrity, with a particular focus on intracellular molecular mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

Sanguisorbae Radix Protects Against 6‐Hydroxydopamine‐induced Neurotoxicity by Regulating NADPH Oxidase and NF‐E2‐related Factor‐2/Heme Oxygenase‐1 Expressions

6‐Hydroxydopamine (6‐OHDA) produces neuronal cell damage by generating reactive oxygen species (ROS). The major mechanisms of protection against ROS‐induced stress are inhibiting expression of ROS generating genes such as NADPH oxidase (NOX) and increasing expression of endogenous antioxidant genes such as heme oxygenase‐1 (HO‐1). This study investigated whether a standardized Sanguisorbae Radix extract (SRE), a medical herb commonly used in Asian traditional medicine, has a protective effect on 6‐OHDA‐induced cell toxicity by regulating ROS in SH‐SY5Y cells. SRE at 10 and 50 µg/mL significantly reduced 6‐OHDA‐induced cell damage dose dependently in the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay and by Hoechst 33342 staining. SRE increased the B‐cell lymphoma 2 (Bcl‐2)/Bcl‐2‐associated X ratio and decreased cytochrome C release and caspase‐3 activity. SRE also abolished 6‐OHDA‐induced ROS by inhibiting NOX expression and by inducing HO‐1 expression via NF‐E2‐related factor‐2 activation. Taken together, these results demonstrate that SRE has protective effects against 6‐OHDA‐induced cell death by regulating ROS in SH‐SY5Y cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Mulberrofuran G Protects Ischemic Injury‐induced Cell Death via Inhibition of NOX4‐mediated ROS Generation and ER Stress

The aim of this study was to investigate the neuroprotective effect of mulberrofuran G (MG) in in vitro and in vivo models of cerebral ischemia. MG was isolated from the root bark of Morus bombycis. MG inhibited nicotinamide adenine dinucleotide phosphate oxidase (NOX) enzyme activity and oxygen–glucose deprivation/reoxygenation (OGD/R)‐induced NOX4 protein expression in SH‐SY5Y cells. MG inhibited the expression of activated caspase‐3 and caspase‐9 and cleaved poly adenine dinucleotide phosphate‐ribose polymerase in OGD/R‐induced SH‐SY5Y cells. In addition, MG protected OGD/R‐induced neuronal cell death and inhibited OGD/R‐induced reactive oxygen species generation in SH‐SY5Y cells. In in vivo model, MG‐treated groups (0.2, 1, and 5 mg/kg) reduced the infarct volume in middle cerebral artery occlusion/reperfusion‐induced ischemic rats. The MG‐treated groups also reduced NOX4 protein expression in middle cerebral artery occlusion/reperfusion‐induced ischemic rats. Furthermore, protein expression of 78‐kDa glucose‐regulated protein/binding immunoglobulin protein, phosphorylated IRE1α, X‐box‐binding protein 1, and cytosine enhancer binding protein homologous protein, mediators of endoplasmic reticulum stress, were inhibited in MG‐treated groups. Taken together, MG showed protective effect in in vitro and in vivo models of cerebral ischemia through inhibition of NOX4‐mediated reactive oxygen species generation and endoplasmic reticulum stress. This finding will give an insight that inhibition of NOX enzyme activity and NOX4 protein expression could be a new potential therapeutic strategy for cerebral ischemia. Copyright © 2016 John Wiley & Sons, Ltd.     

Coriolus versicolor‐derived protein‐bound polysaccharides trigger the caspase‐independent cell death pathway in amelanotic but not melanotic melanoma cells

We have investigated the potential cell death mechanism promoted by Coriolus versicolor fungus‐derived protein‐bound polysaccharides (PBPs) in melanoma cells. Knowing that melanogenesis has the potential to affect the tumor behavior and melanoma therapy outcome, the cytotoxic effects of PBPs were evaluated in human SKMel‐188 melanoma cell line, whose phenotype, amelanotic versus pigmented, depends on the concentration of melanin precursors in the culture medium. Our results showed that inhibitory effect of PBPs (100 and 200 μg/ml) towards melanoma cells is inversely associated with the pigmentation level. This cytotoxicity induced in nonpigmented melanoma cells by PBPs was caspase‐independent; however, it was accompanied by an increased intracellular reactive oxygen species (ROS) generation. The ROS production was controlled by c‐Jun N‐terminal kinase (JNK) because SP600125, a JNK inhibitor, significantly reduced ROS generation and protected cells against PBPs‐induced death. We also found that PBPs‐induced lactate dehydrogenase release in amelanotic melanoma cells was abolished by co‐treatment with receptor‐interacting serine/threonine‐protein kinase 1 inhibitor, implying engagement of this kinase in PBPs‐induced death pathway. The results suggest that PBPs induce an alternative programmed cell death, regulated by receptor‐interacting protein‐1 and ROS and that this process is modified by melanin content in melanoma cells. These findings are remarkable when considering the use of commercially available Coriolus versicolor by patients who suffer from melanoma cancer.     

Epigallocatechin‐3‐gallate enhances differentiation of acute promyelocytic leukemia cells via inhibition of PML‐RARα and HDAC1

The use of all‐trans retinoic acid (ATRA) has dramatically improved the treatment and survival rate of patients with acute promyelocytic leukemia (APL). However, toxicity and resistance to this drug are major problems in the treatment of APL with ATRA. Earlier studies have suggested that the green tea polyphenol epigallocatechin gallate (EGCG) induces cell death in hematopoietic neoplasms without adversely affecting normal cells. In the present study, the potential therapeutic effect of EGCG in APL and the underlying molecular mechanisms were investigated. EGCG (100 μM) significantly inhibited proliferation and induced apoptosis in HL‐60 and NB4 cells. This effect was associated with decreased expressions of multidrug resistance proteins ABCB1, and ABCC1, whereas the expressions of pro‐apoptotic genes CASP3, CASP8, p21, and Bax/Bcl‐2 ratio were significantly increased. EGCG, at 25 μM concentration, induced differentiation of leukemic cells towards granulocytic pattern in a similar manner to that observed for ATRA (1 μM). Furthermore, EGCG suppressed the expression of clinical marker PML/RARα in NB4 cells and reduced the expression of HDAC1 in leukemic cells. In conclusion, the results suggested that EGCG can be considered as a potential treatment for APL.     

Genistein protects against amyloid‐beta‐induced toxicity in SH‐SY5Y cells by regulation of Akt and Tau phosphorylation

Alzheimer's disease is a neurodegenerative disorder characterized by extracellular deposition of amyloid‐β (Aβ) peptide and hyperphosphorylation of Tau protein, which ultimately leads to the formation of intracellular neurofibrillary tangles and cell death. Increasing evidence indicates that genistein, a soy isoflavone, has neuroprotective effects against Aβ‐induced toxicity. However, the molecular mechanisms involved in its neuroprotection are not well understood. In this study, we have established a neuronal damage model using retinoic‐acid differentiated SH‐SY5Y cells treated with different concentrations of Aβ_25–35 to investigate the effect of genistein against Aβ‐induced cell death and the possible involvement of protein kinase B (PKB, also termed Akt), glycogen synthase kinase 3β (GSK‐3β), and Tau as an underlying mechanism to this neuroprotection. Differentiated SH‐SY5Y cells were pre‐treated for 24 hr with genistein (1 and 10 nM) and exposed to Aβ_25–35 (25 μM), and we found that genistein partially inhibited Aβ induced cell death, primarily apoptosis. Furthermore, the protective effect of genistein was associated with the inhibition of Aβ‐induced Akt inactivation and Tau hyperphosphorylation. These findings reinforce the neuroprotective effects of genistein against Aβ toxicity and provide evidence that its mechanism may involve regulation of Akt and Tau proteins.     

Soy Isoflavone Glycitin (4'‐Hydroxy‐6‐Methoxyisoflavone‐7‐D‐Glucoside) Promotes Human Dermal Fibroblast Cell Proliferation and Migration via TGF‐β Signaling

Glycitin is a soy isoflavone that exhibits antioxidant, antiallergic, and anti‐osteoporosis activities. We investigated the effects of glycitin on dermal fibroblast proliferation and migration. Treatment of primary dermal fibroblasts with glycitin increased cell proliferation and migration. In addition, treatment with 20 μM glycitin for 24 h induced the synthesis of collagen type I and type III at both the mRNA and protein levels. Fibronectin was also increased by 20% after treatment. Matrix metalloproteinase‐1 collagenase was decreased in the media after 24‐h incubation with glycitin, and the synthesis of transforming growth factor‐beta (TGF‐β) mRNA increased approximately twofold in cells following glycitin treatment. Phosphorylation of Smad2 and Smad3 increased after 1 h of glycitin treatment, and phosphorylation continued for 24 h. Furthermore, the phosphorylated form of AKT was increased in glycitin‐treated cells after 3 h and remained higher for 24 h. Thus, glycitin treatment produces anti‐aging effects including increased total collagen in the culture media, decreased elastase, and decreased β‐galactosidase. Together, these results indicate that glycitin stimulates TGF‐β secretion, and the subsequent autocrine actions of TGF‐β induce proliferation of fibroblasts, ultimately protecting skin cells from aging and wrinkling. Copyright © 2015 John Wiley & Sons, Ltd.     

Upregulation of PPARγ by Aegle marmelos ameliorates insulin resistance and β-cell dysfunction in high fat diet fed-streptozotocin induced type 2 diabetic rats

The global epidemic of type 2 diabetes demands the rapid evaluation of new and accessible interventions. This study investigated whether Aegle marmelos fruit aqueous extract (AMF; 250, 500 and 1000 mg/kg) improves insulin resistance, dyslipidemia and β‐cell dysfunction in high fat diet fed‐streptozotocin (HFD‐STZ)‐induced diabetic rats by modulating peroxisome proliferator‐activated receptor‐γ (PPARγ) expression. The serum levels of glucose, insulin, homeostasis model assessment of insulin resistance (HOMA‐IR), homeostasis model assessment of β‐cell function (HOMA‐B), lipid profile, TNF‐α and IL‐6 were evaluated. Further, the TBARS level and SOD activity in pancreatic tissue and PPARγ protein expression in liver were assessed. In addition, histopathological and ultrastructural studies were performed to validate the effect of AMF on β‐cells. The HFD‐STZ treated rats showed a significant increase in the serum levels of glucose, insulin, HOMA‐IR, TNF‐α, IL‐6, dyslipidemia with a concomitant decrease in HOMA‐B and PPARγ expression. Treatment with AMF for 21 days in diabetic rats positively modulated the altered parameters in a dose‐dependent manner. Furthermore, AMF prevented inflammatory changes and β‐cell damage along with a reduction in mitochondrial and endoplasmic reticulum swelling. These findings suggest that the protective effect of AMF in type 2 diabetic rats is due to the preservation of β‐cell function and insulin‐sensitivity through increased PPARγ expression. Copyright © 2011 John Wiley & Sons, Ltd.     

Guarana (Paullinia cupana Mart.) Prevents β‐Amyloid Aggregation,Generation of Advanced Glycation‐end Products (AGEs), and Acrolein‐Induced Cytotoxicity on Human Neuronal‐Like Cells

Advanced glycation end‐products (AGEs) are considered potent molecules capable of promoting neuronal cell death and participating in the development of neurodegenerative disorders such as Alzheimer's disease (AD). Previous studies have shown that AGEs exacerbate β‐amyloid (Aβ) aggregation and AGE‐related cross‐links are also detected in senile plaques. Acrolein (ACR) is an α, β‐unsaturated aldehyde found in the environment and thermally processed foods, which can additionally be generated through endogenous metabolism. The role of ACR in AD is widely accepted in the literature. Guarana (Paullinia cupana Mart.) is popularly consumed by the population in Brazil, mainly for its stimulant activity. In the present study, we showed that guarana (10, 100, and 1000 µg/mL) is able to prevent protein glycation, β‐amyloid aggregation, in vitro methylglyoxal, glyoxal, and ACR (20 μM)‐induced toxicity on neuronal‐like cells (SH‐SY5Y). Since these are considered typical AD pathological hallmarks, we propose that guarana may deserve further research as a potential therapeutic agent in such a neurodegenerative disease. Copyright © 2014 John Wiley & Sons, Ltd.