Cyanidin suppresses neoplastic cell transformation by directly targeting phosphatidylinositol 3-kinase

Cyanidin, an anthocyanidin found in fruits and vegetables, has been reported to possess anti-cancer effects. However, there is no study on the chemopreventive effect of cyanidin against neoplastic cell transformation and its molecular mechanisms. In the present study, we compare the anti-carcinogenic effects of cyanidin and cyanidin-3-glucoside (C3G) and investigate their underlying mechanisms. The inhibitory effect of cyanidin on EGF-induced cell transformation was higher than those of C3G in JB6 P+ mouse epidermal (JB6 P+) cells. Both cyanidin and C3G showed dose-dependent radical scavenging activities. It is indicated that the divergent inhibitory effects of cyanidin and C3G are not due to their antioxidant activities. We found that cyanidin, but not C3G, inhibited the EGF-induced Akt/p70S6K phosphorylation. Moreover, cyanidin directly suppressed the activity of PI3K by binding to PI3K directly in an ATP-competitive manner, which indicates that PI3K is one of the molecular targets of cyanidin.     

Inhibitory effects of flavonoid glycosides isolated from the peel of Japanese persimmon (Diospyros kaki Fuyu) on antigen-stimulated degranulation in rat basophilic leukaemia RBL-2H3 cells

We found that two distinct flavonoid glycosides isolated from the peel of Japanese persimmon (Diospyros kaki Fuyu), isoquercitrin (Isq) and hyperin (Hyp), are capable of inhibiting antigen-stimulated degranulation in rat basophilic leukaemia RBL-2H3 cells. In order to elucidate the underlying mechanisms, we examined effects of Isq and Hyp on cellular responses induced by antigen stimulation. Treatment with both Isq and Hyp markedly inhibited antigen-stimulated elevation of intracellular free Ca²⁺ concentration and reactive oxygen species (ROS). Isq and Hyp did not affect NADPH oxidase (NOX) activity, but they possessed DPPH radical-scavenging activity similar to that of epigallocatechin gallate, a potent anti-oxidant, Finally, Isq and Hyp showed little or no effects on Ag-stimulated Syk activation or phosphorylation of signalling molecules. These results indicate that inhibition of antigen-stimulated degranulation by Isq and Hyp is mainly due to suppression of intracellular Ca²⁺ elevation, which is caused by direct scavenging of ROS that are generated by NOX. Our findings suggest that Isq and Hyp, isolated from the peel of persimmon, would be beneficial for alleviating symptoms of type I allergy.     

Biological evaluation and structural determinants of p38α mitogen-activated-protein kinase and c-Jun-N-terminal kinase 3 inhibition by flavonoids

A series of 42 naturally occurring flavonoids and one flavonoid glucuronide were tested for their ability to inhibit p38α mitogen-activated protein kinase (p38α) and c-Jun-N-terminal kinase 3 (JNK3). Potent inhibitors with IC(50) values in the low micromolar range were identified. Structure-activity relationships were evaluated and the most promising compounds were docked into the ATP binding site of these kinases. Among the different classes of flavonoids, the flavonol group showed better inhibition of p38α. Of this class, kaempferol-7,4'-dimethylether was a potent p38α inhibitor, displaying 13-fold selectivity for p38α over JNK3. The flavone compounds without a 6-methoxy group preferentially inhibited JNK3. The flavone glycoside, luteolin-7-O-glycoside, was identified as a potent inhibitor with the greatest selectivity toward JNK3. In contrast, the flavanol compounds displayed similar inhibitory activities toward both kinases.     

抗血小板溶栓素对局灶性脑缺血/再灌注大鼠脑损伤的作用观察

目的: 观察抗血小板溶栓素(anti-platelet thrombolysin,APT)对缺血性脑损伤的保护作用并初步探讨其作用机制。方法: SD大鼠,随机分为假手术组(Sham)、模型组(缺血再灌注组)、阳性组(依达拉奉注射液)、APT高、中、低组。双侧颈动脉结扎,建立脑缺血模型,测定大鼠脑含水量,HE染色观察脑组织病理改变;线栓法建立大鼠脑缺血/再灌注模型,进行行为学评分,酶联免疫法(ELISA)及免疫组化测定脑组织中Toll样受体4(TLR4)、c-Jun氨基末端激酶(JNK)、Bax蛋白含量。结果: 与模型组比较,APT高、中剂量组可明显改善缺血再灌注后大鼠神经功能障碍症状,降低脑水肿程度,改善缺血后脑组织的病理改变,明显降低缺血后脑组织中TLR4、JNK、Bax蛋白表达。结论: APT对缺血性脑损伤有较好的保护作用,其机制可能与抑制脑组织中TLR4/JNK/Bax信号通路表达,从而抑制细胞凋亡有关。     

ZnO nanoparticle-induced oxidative stress triggers apoptosis by activating JNK signaling pathway in cultured primary astrocytes

It has been documented in in vitro studies that zinc oxide nanoparticles (ZnO NPs) are capable of inducing oxidative stress, which plays a crucial role in ZnO NP-mediated apoptosis. However, the underlying molecular mechanism of apoptosis in neurocytes induced by ZnO NP exposure was not fully elucidated. In this study, we investigated the potential mechanisms of apoptosis provoked by ZnO NPs in cultured primary astrocytes by exploring the molecular signaling pathways triggered after ZnO NP exposure. ZnO NP exposure was found to reduce cell viability in MTT assays, increase lactate dehydrogenase (LDH) release, stimulate intracellular reactive oxygen species (ROS) generation, and elicit caspase-3 activation in a dose- and time-dependent manner. Apoptosis occurred after ZnO NP exposure as evidenced by nuclear condensation and poly(ADP-ribose) polymerase-1 (PARP) cleavage. A decrease in mitochondrial membrane potential (MMP) with a concomitant increase in the expression of Bax/Bcl-2 ratio suggested that the mitochondria also mediated the pathway involved in ZnO NP-induced apoptosis. In addition, exposure of the cultured cells to ZnO NPs led to phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), and p38 mitogen-activated protein kinase (p38 MAPK). Moreover, JNK inhibitor (SP600125) significantly reduced ZnO NP-induced cleaved PARP and cleaved caspase-3 expression, but not ERK inhibitor (U0126) or p38 MAPK inhibitor (SB203580), indicating that JNK signaling pathway is involved in ZnO NP-induced apoptosis in primary astrocytes.     

UVB-Stimulated TNFα Release from Human Melanocyte and Melanoma Cells Is Mediated by p38 MAPK

Ultraviolet (UV) radiation activates cell signaling pathways in melanocytes. As a result of altered signaling pathways and UV-induced cellular damage, melanocytes can undergo oncogenesis and develop into melanomas. In this study, we investigated the effect of UV-radiation on p38 MAPK (mitogen-activated protein kinase), JNK and NFκB pathways to determine which plays a major role in stimulating TNFα secretion in human HEM (melanocytes) and MM96L (melanoma) cells. MM96L cells exhibited 3.5-fold higher p38 activity than HEM cells at 5 min following UVA + B radiation and 1.6-fold higher JNK activity at 15–30 min following UVB+A radiation, while NFκB was minimally activated in both cells. Irradiated HEM cells had the greatest fold of TNFα secretion (UVB: 109-fold, UVA + B: 103-fold & UVB+A: 130-fold) when co-exposed to IL1α. The p38 inhibitor, SB202190, inhibited TNFα release by 93% from UVB-irradiated HEM cells. In the UVB-irradiated MM96L cells, both SB202190 and sulfasalazine (NFκB inhibitor) inhibited TNFα release by 52%. Although, anisomycin was a p38 MAPK activator, it inhibited TNFα release in UV-irradiated cells. This suggests that UV-mediated TNFα release may occur via different p38 pathway intermediates compared to those stimulated by anisomycin. As such, further studies into the functional role p38 MAPK plays in regulating TNFα release in UV-irradiated melanocyte-derived cells are warranted.     

JNK-Bcl-2/Bcl-xL-Bax/Bak Pathway Mediates the Crosstalk between Matrine-Induced Autophagy and Apoptosis via Interplay with Beclin 1

Autophagy is associated with drug resistance which has been a threat in chemotherapy of hepatocellular carcinoma (HCC). The interconnected molecular regulators between autophagy and apoptosis serve as switching points critical to the ultimate outcome of the cell. Our study was performed to investigate the crosstalk between autophagy and apoptosis in HCC after the treatment of matrine. Flow cytometry and TUNEL (terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling) assay were used to detect apoptosis in vitro and in vivo, respectively. Bax oligomerization and Cytochrome c release assay were performed. Immunoprecipitation and siRNA transfection were used to detect the interplay between Bcl-2/Bcl-xL,Bax, and Beclin 1. Our results showed that: (1) matrine not only activated caspase and PARP (poly ADP-ribose polymerase) cleavage, but also triggered autophagy as shown by the increased levels of LC3II, Beclin 1, and PI3KC3, and the decreased level of p62; (2) matrine treatment promoted the JNK-Bcl-2/Bcl-xL-Bax/Bak pathway; (3) Bax was oligomerized, the mitochondrial membrane potential altered, and Cytochrome c was released subsequently; (4) Bax interacts with Beclin 1 and inhibits autophagy, which may be a new crosstalk point; and (5) finally, we showed that matrine suppressed the growth of a MHCC97L xenograft in vivo for the first time. In conclusion, the JNK-Bcl-2/Bcl-xL-Bax/Bak pathway mediates the crosstalk between matrine-induced autophagy and apoptosis via interplay with Beclin 1.     

Kinase Signaling in Apoptosis Induced by Saturated Fatty Acids in Pancreatic β-Cells

Pancreatic β-cell failure and death is considered to be one of the main factors responsible for type 2 diabetes. It is caused by, in addition to hyperglycemia, chronic exposure to increased concentrations of fatty acids, mainly saturated fatty acids. Molecular mechanisms of apoptosis induction by saturated fatty acids in β-cells are not completely clear. It has been proposed that kinase signaling could be involved, particularly, c-Jun N-terminal kinase (JNK), protein kinase C (PKC), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase (ERK), and Akt kinases and their pathways. In this review, we discuss these kinases and their signaling pathways with respect to their possible role in apoptosis induction by saturated fatty acids in pancreatic β-cells.     

JNK在缺血后处理减轻再灌注损伤肺细胞凋亡中的作用

目的: 探讨C-Jun氨基末端激酶(JNK)在缺血后处理(IPO)减轻缺血/再灌注损伤大鼠肺细胞凋亡中的作用。方法: 雄性SD大鼠随机分成5组(n＝8),即对照组(C组)、肺缺血/再灌注组(I/R组)、肺缺血/再灌注+缺血后处理组(IPO组)、缺血后处理+溶剂对照组(PPCES溶液)(P组)、缺血后处理+SP600125组(SP组)。分别于再灌注 2 h 颈动脉取血、留取左肺组织,检测血清超氧化物歧化酶(SOD)、丙二醛(MDA)、髓过氧化物酶(MPO),检测肺组织湿/干重比(W/D)和总肺含水量(TLW);光电镜观察肺组织形态学结构改变,并进行肺组织损伤定量评估(IQA);原位末端标记法(TUNEL)检测肺细胞凋亡情况并计算凋亡指数(AI)。结果: 与C组相比,I/R组血清SOD活性显著降低,MDA含量、MPO活力显著升高(P均<0.01),肺组织W/D、TLW、IQA和AI均显著升高(P<0.05 或P<0.01),光镜电镜下肺组织结构发生明显损伤;IPO组、P组、SP组与I/R组相比,MDA含量、MPO活力显著降低,SOD活性升高(P<0.05 或P<0.01),肺组织W/D、TLW、IQA和AI均显著降低(P<0.05 或P<0.01),光镜电镜下肺组织结构损伤情况有所改善;P组与IPO组比较各项指标均无明显差异(P均>0.05);SP组与IPO组相比,MDA含量、MPO活力显著降低,SOD活性升高(P<0.05 或P<0.01),肺组织W/D、TLW、IQA和AI均显著降低(P<0.05或P<0.01),光镜电镜下肺组织结构未见明显损伤。结论: I/R导致大鼠肺组织过度氧化应激,激活JNK,肺内中性粒细胞聚集,导致肺组织结构严重破坏,细胞大量凋亡;IPO可以减轻氧化应激,抑制JNK通路的激活,从而改善其结构破坏和细胞凋亡。