Rattlesnake venom induces apoptosis by stimulating PC-PLC and upregulating the expression of integrin β4, P53 in vascular endothelial cells

Intracellular Zinc Trafficking during Crotalus atrox Venom Wound Development

In this study, we examined zinc trafficking in human umbilical vein endothelial cells (HUVEC) stimulated with Crotalus atrox (CA venom) snake venom. We utilized MTS cytotoxicity assays to monitor the cytotoxic range of CA venom. HUVEC monolayers stimulated with 10 µg/mL CA venom for 3 h displayed cellular retraction, which coincided with 53.0 ± 6.5 percent viability. In contrast, venom concentrations of 100 µg/mL produced a complete disruption of cellular adherence and viability decreased to 36.6 ± 1.0. The zinc probe Fluozin-3AM was used to detect intracellular zinc in non-stimulated controls, HUVEC stimulated with 10 µg/mL CA venom or HUVEC preincubated with TPEN for 2 h then stimulated with 10 µg/mL CA venom. Fluorescent intensity analysis returned values of 1434.3 ± 197.4 for CA venom demonstrating an increase of about two orders of magnitude in labile zinc compared to non-stimulated controls. Endothelial response to CA venom induced a 96.1 ± 3.0- and 4.4 ± 0.41-fold increase in metallothionein 1X (MT1X) and metallothionein 2A (MT2A) gene expression. Zinc chelation during CA venom stimulation significantly increased cell viability, suggesting that the maintenance of zinc homeostasis during envenomation injury improves cell survival.

Identification of New Small Molecules as Apoptosis Inhibitors in Vascular Endothelial Cells

Vascular endothelial cell (VEC) apoptosis is involved in the development of atherosclerosis and other cardiovascular diseases. We previously found that ethyl 1-(2-hydroxy-3-aroxypropyl)-3-aryl-1H-pyrazole -5-carboxylate derivatives (3a-o) play important roles in cell fate control. In this study, among the 15 compounds, we further screened 2 compounds, 3d and 3k, that suppressed VEC apoptosis induced by deprivation of serum and fibroblast growth factor 2. To clarify which chiral enantiomers of 3d and 3k functioned, we synthesized 3d-S and its enantiomer 3d-R, 3k-S, and its enantiomer 3k-R. Then, we investigated the apoptosis-inhibiting activity of the chiral compounds in VECs. Four small molecules, 3d-S, 3d-R, 3k-S, 3k-R, significantly elevated VEC viability and inhibited apoptosis. Furthermore, these small molecules could obviously decrease the level of integrin β4 that plays a key role in the regulation of VEC apoptosis. 3k-S and 3k-R increased Bcl-2/Bax ratio and reduced reactive oxygen species levels dramatically. Therefore, we provide new VEC apoptosis inhibitors. These compounds may be potential agents in the prevention of vascular diseases associated with VEC apoptosis.

Phosphorylation and nuclear translocation of integrin β4 induced by a chemical small molecule contribute to apoptosis in vascular endothelial cells

Integrin β4 and its Y-1494 phosphorylation play an important role in cell signaling. We found a small molecule, ethyl1-(3-(4-chlorophenoxy)-2-hydroxypropyl)-3-(4-chlorophenyl)-1H-pyrazole-5-carboxylate (ECPC), that could elevate the levels of KIT ligand (KITLG), interleukin 8 (IL-8), prostaglandin-endoperoxide synthase 2 (PTGS2) and activating transcription factor 3 (ATF3) and promote apoptosis in vascular endothelial cells (VECs) through integrin β4. We investigated the underlying mechanism of integrin β4 participating in this process. ECPC treatment increased the phosphorylation of Y-1494 in the integrin β4 cytoplasmic domain via a well-known receptor tyrosine kinase, fibroblast growth factor receptor 1 (FGFR1), and integrin β4 translocated from the cytoplasm to nucleus. With suppression of Y-1494 phosphorylation by FGF-2 or siRNA of FGFR1, ECPC failed to promote integrin β4 nuclear translocation and could not increase the expression of KITLG, IL-8, PTGS2 or ATF3. Y-1494 phosphorylation and nuclear translocation of integrin β4 may be important during ECPC-induced apoptosis in VECs.

Targeting phosphatidylcholine-specific phospholipase C for atherogenesis therapy

Atherosclerosis, a dynamic and progressive vascular disease arising from the combination of endothelial dysfunction and inflammation, is becoming a major killer in the 21st century. Accumulating evidence implicates phosphatidylcholine-specific phospholipase C (PC-PLC) in endothelial dysfunction and several inflammation processes. In addition, in a recent study, we demonstrated that PC-PLC contributed to the progression of atherosclerosis. Considering the important roles of PC-PLC in vascular endothelial cell dysfunction and its proinflammatory properties, we propose that a pharmacological blockade of PC-PLC represents a rational approach to atherosclerosis therapy.

Regulation of apoptosis and autophagy by sphingosylphosphorylcholine in vascular endothelial cells

Sphingosylphosphorylcholine (SPC), an important cardiovascular mediator derived from sphingomyelin that has atheroprotective effects via actions on vascular endothelial cells (VECs) at normal levels in vivo. However, the underlying mechanism is not well known. To clarify this question, we first investigated the effect of SPC on VEC apoptosis and autophagy induced by deprivation of serum and fibroblast growth factor 2 (FGF-2). SPC at 5-20 µM inhibited apoptosis and induced autophagy in vitro. To understand the underlying mechanism, we investigated the role of integrin β4 in SPC-induced autophagy in VECs. SPC significantly decreased the level of integrin β4, whereas overexpression of integrin β4 inhibited SPC-induced autophagy. Moreover, knockdown of integrin β4 promoted VEC autophagy. To understand the downstream factors of integrin β4 in this process, we observed the effects of SPC on phosphatidylcholine-specific phospholipase C (PC-PLC) activity and level of p53. PC-PLC activity and p53 level in cytoplasm was decreased during autophagy induced by SPC, and knockdown of integrin β4 inhibited the activity of PC-PLC and the cytoplasmic level of p53. SPC may promote autophagy via integrin β4. Moreover, PC-PLC and p53 may be the downstream factors of integrin β4 in autophagy of VECs deprived of serum and FGF-2.

Inhibitory effect of chinese propolis on phosphatidylcholine-specific phospholipase C activity in vascular endothelial cells

To understand the mechanisms underlying the anti-inflammatory action of Chinese propolis, we investigated its effect on the activity of phosphatidylcholine-specific phospholipase C (PC-PLC) that plays critical roles in control of vascular endothelial cell (VEC) function and inflammatory responses. Furthermore, p53 and reactive oxygen species (ROS) levels and mitochondrial membrane potential (Δψm) were investigated. Our data indicated that treatment of Chinese propolis 6.25 and 12.5 μg/ml for 12 hours increased VEC viability obviously. Exposure to Chinese propolis 6.25, 12.5, and 25 μg/ml for 6 and 12 hours significantly decreased PC-PLC activity and p53 level, and ROS levels were depressed by Chinese propolis 12.5 μg/ml and 25 μg/ml dramatically. The Δψm of VECs was not affected by Chinese propolis at low concentration but disrupted by the propolis at 25 μg/ml significantly, which indicated that Chinese propolis depressed PC-PLC activity and the levels of p53 and ROS in VECs but disrupted Δψm at a high concentration.

Modulation of vascular endothelial cell senescence by integrin β4

Increasing evidence has demonstrated that the senescence of vascular endothelial cells (VECs) has critical roles in the pathogenesis of vascular dysfunction. Finding important factors that regulate VEC senescence will help provide novel therapeutic strategies for vascular disorders. Previously, we found that integrin β4 was involved in VEC senescence. However, the mechanism underlying VEC senescence mediated by integrin β4 remains poorly understand. In this study, we used a mouse in vivo model and showed that the level of integrin β4 in the endothelium of mouse thoracic aorta was increased during natural aging and atherosclerosis. Furthermore, we found that H-ras, caveolin-1, and AP-1 were implicated in the senescent signal pathway mediated by integrin β4 in human umbilical vein ECs (HUVECs). Knockdown of integrin β4 could attenuate HUVEC senescent features, including increased interleukin-8 (IL-8) release and decreased endothelial nitric oxide synthase (eNOS) and NO levels and mitochondrial membrane potential in vitro. Our findings provide new clues illustrating the mechanism of VEC senescence. Integrin β4 might be a potential target for therapy in cardiovascular diseases.

Effect of Brazilian propolis on human umbilical vein endothelial cell apoptosis

Brazilian propolis has been widely studied in recent years. Considering the lack of data concerning the effects of Brazilian propolis on human umbilical vein endothelial cells (HUVECs), we examined the effects of ethanol-extracted Brazilian propolis (EEBP) at 12.5, 25 and 50 μg/ml on apoptosis of HUVECs deprived of basic fibroblast growth factor (FGF-2) and serum. A high concentration of the extract induced HUVEC apoptosis at 24h. Furthermore, we investigated the molecular mechanisms of HUVEC apoptosis induced by EEBP by testing the levels of integrin β4, p53, reactive oxygen species (ROS) and mitochondrial membrane potential. A low concentration of EEBP (12.5 μg/ml) could decrease the expression of integrin β4, p53 and ROS levels, whereas high concentrations (25 and 50 μg/ml) could increase the levels of integrin β4, p53 and ROS at 24h and depress mitochondrial membrane potential level at all times. Considering the doses and the results obtained in this study, Brazilian propolis at high concentrations may be an apoptosis-inducing agent associated with the signal pathway mediated by integrin β4, p53, ROS and mitochondrial membrane potential, thus, propolis should be used in safer levels for human health.

Lipopolysaccharide induces autophagy through BIRC2 in human umbilical vein endothelial cells

Lipopolysaccharide (LPS), as an important proinflammatory agent, targets the endothelium. However, almost all in vitro experiments of the effect of LPS on vascular endothelial cells (VECs) were performed under an artificially decreased concentration of serum that was not enough to maintain the cell growth for a long time. The mechanism underlying LPS action on VECs cultured in a nutrient-rich condition is not clear. To address this question and mimic the in vivo condition, we investigated the effect of LPS on VEC autophagy, which is involved in numerous physiological processes. The effect of LPS on microtubule-associated protein 1 light chain 3 (LC3) distribution, LC3-II accumulation and p62 degradation showed that LPS effectively induced autophagy in VECs cultured in the presence of 20% serum. To understand the mechanism by which LPS triggers the cell autophagy, we first investigated the effects of LPS on the expression of BIRC2 (cIAP1), a well-known apoptosis inhibitor, and on the kinase activity of mammalian target of rapamycin (mTOR) and nuclear translocation of p53. LPS increased BIRC2 expression in a dose- and time-dependent manner and elevated the intranuclear level of p53 but had no effect on the mTOR pathway when it triggered VEC autophagy. Furthermore, knockdown of BIRC2 by RNA interference inhibited the autophagy and the translocation of p53 to nuclei induced by LPS. These data suggest a novel role for BIRC2 in LPS-induced autophagy in VECs.

D609 Inhibits Progression of Preexisting Atheroma and Promotes Lesion Stability in Apolipoprotein E −/− Mice

Objective— Atherosclerosis is considered to be a chronic inflammatory disease. Previous research has demonstrated that phosphatidylcholine-specific phospholipase C (PC-PLC) plays critical roles in various inflammatory responses. However, the association between PC-PLC and atherosclerosis is undetermined. Therefore, we sought to investigate whether PC-PLC was implicated in atherosclerosis.

Methods and Results— Immunofluorescence analysis revealed an upregulation of PC-PLC in the aortic endothelium from apolipoprotein E-deficient (apoE −/− ) mice. PC-PLC level and activity were also increased in human umbilical vein endothelial cells in response to oxidized low-density lipoprotein treatment. Pharmacological blockade of PC-PLC by D609 inhibited the progression of preexisting atherosclerotic lesions in apoE −/− mice and changed the lesion composition into a more stable phenotype. Using a combination of pharmacological inhibition, polyclonal antibodies, confocal laser scanning microscopy and Western blotting, we demonstrated that PC-PLC was required for endothelial expression of lectin-like oxidized low-density lipoprotein receptor-1. In addition, D609 treatment significantly decreased the aortic endothelial expression of the vascular cell adhesion molecule-1 and the intercellular adhesion molecule-1. Furthermore, inhibition of PC-PLC in human umbilical vein endothelial cells reduced the oxidized low-density lipoprotein induced expression of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, and monocyte chemotactic protein-1.

Conclusion— Our data suggest that PC-PLC contributes to the progression of atherosclerosis.

Hepatic uptake and metabolism of phosphatidylcholine associated with high density lipoproteins

BACKGROUND

Phosphatidylcholine (PC) is the predominant phospholipid associated with high density lipoproteins (HDL). Although the hepatic uptake of cholesteryl esters from HDL is well characterized, much less is known about the fate of PC associated with HDL. Thus, we investigated the uptake and subsequent metabolism of HDL-PC in primary mouse hepatocytes.

METHODS AND RESULTS

The absence of scavenger receptor-BI resulted in a 30% decrease in cellular incorporation of [(3)H]PC whereas [(3)H]cholesteryl ether uptake was almost completely abolished. Although endocytosis is not involved in the uptake of cholesteryl esters from HDL, we demonstrate that HDL internalization accounts for 40% of HDL-PC uptake. Extracellular remodeling of HDL by secretory phospholipase A(2) significantly enhances HDL lipid uptake. HDL-PC taken up by hepatocytes is partially converted to triacylglycerols via PC-phospholipase C-mediated hydrolysis of PC and incorporation of diacylglycerol into triacylglycerol. The formation of triacylglycerol is independent of scavenger receptor-BI and occurs in extralysosomal compartments.

CONCLUSIONS AND GENERAL SIGNIFICANCE

These findings indicate that HDL-associated PC is incorporated into primary hepatocytes via a pathway that differs significantly from that of HDL-cholesteryl ester, and shows that HDL-PC is more than a framework molecule, as evidenced by its partial conversion to hepatic triacylglycerol.

Promotion of autophagy and inhibition of apoptosis by low concentrations of cadmium in vascular endothelial cells

Recent reports, highlighting the relationships of cadmium exposure and vascular diseases, indicated that vascular endothelial cell was the target of cadmium (Cd) toxicity. However, the underlying mechanisms have not been fully elucidated. In this study, we evaluated the internalization of Cd2+ into human umbilical vein endothelial cells (HUVECs) by a novel Cd2+-selective sensor suitable for living cells. Then, we detected apoptosis in the treated cells. Our results showed that Cd2+ at low concentrations (< 10 micromol/l) inhibited apoptosis induced by deprivation of serum and basic fibroblast growth factor (bFGF). To investigate the corresponding molecular mechanisms, we employed acridine orange staining and Western blotting of MAP1 LC3 to detect autophagy, and analyzed the levels of integrin beta4, caveolin-1 and activity of PC-PLC. Our results showed that low concentrations of Cd2+ promoted autophagy and depressed the levels of integrin beta4, caveolin-1 and PC-PLC activity. The data suggested that autophagy played a key role in Cd2+ induced endothelial dysfunction; integrin beta4, caveolin-1 and PC-PLC might be the targets of Cd2+ in vascular endothelial cells.

Both senescence and apoptosis induced by deprivation of growth factors were inhibited by a novel butyrolactone derivative through depressing integrin beta4 in vascular endothelial cells

Both senescence and apoptosis of vascular endothelial cells (VECs) are involved in the development of cardiovascular diseases, including atherosclerosis. To understand the association between senescence and apoptosis in vascular endothelial cells, the authors first explored whether senescence and apoptosis took place at the same time in human umbilical vein endothelial cells (HUVECs) deprived of the growth factors. Integrin beta4 is a key factor in HUVEC apoptosis, to know whether this integrin is implicated in VEC senescence, the authors checked the changes of integrin beta4 level during HUVEC aging. Then the authors investigated the effects of 3BDO (3-benzyl-5-((2-nitrophenoxy)methyl)-dihydrofuran-2(3H)-one) on the senescence induced by deprivation of serum and fibroblast growth factor (FGF)-2. The results showed that deprivation of growth factors not only induced apoptosis, but also triggered senescence in HUVECs. The authors found that the level of integrin beta 4 was increased markedly during HUVEC senescence. 3BDO (20 to 60 microg/mL) could inhibit both senescence and apoptosis and depress integrin beta 4 level. The data suggested that integrin beta4 might be a pivotal factor in the relationship between senescence and apoptosis.

Conversion of low density lipoprotein-associated phosphatidylcholine to triacylglycerol by primary hepatocytes

We have studied the uptake and metabolism of phosphatidylcholine (PC), the major phospholipid of low density lipoproteins (LDL), by cultures of primary hepatocytes. Strikingly, in the absence of the LDL receptor, PC incorporation into hepatocytes was inhibited by only 30%, whereas cholesteryl ether uptake was inhibited by 60-70%. On the other hand, scavenger receptor class B, type I, the other important receptor for LDL in the liver, was found to be responsible for the uptake of the remaining 30-40% of LDL-cholesteryl ether. PC uptake was, however, only partially inhibited (30%) in scavenger receptor class B, type I, knock-out hepatocytes. Once LDL-PC was taken up by hepatocytes, approximately 50% of LDL-[(3)H]oleate-PC was converted to triacylglycerol rather than degraded in lysosomes as occurs for LDL-derived cholesteryl esters. The remainder of the LDL-derived PC was not significantly metabolized to other products. Triacylglycerol synthesis from LDL-PC requires a PC-phospholipase C activity as demonstrated by inhibition with the phospholipase C inhibitor D609 or activation with rattlesnake venom. Small interfering RNA-mediated suppression of acyl-CoA:diacylglycerol acyltransferase 2 (DGAT2), but not DGAT1, decreased the acylation of the LDL-derived diacylglycerol. These findings show that PC in LDL particles is taken up not only by the classical receptors but also by additional mechanism(s) followed by metabolism that is completely different from the cholesteryl esters or apoB100, the other main components of LDL.

Knockdown of integrin beta4 in primary cultured mouse neurons blocks survival and induces apoptosis by elevating NADPH oxidase activity and reactive oxygen species level

Recently, the specific roles of integrin beta4 in the signaling networks that drive pathological angiogenesis and tumor progression have been revealed. Our previous study showed that integrin beta4 might be involved in neuron survival signal transduction. To further our study on the role of integrin beta4 in the survival and apoptosis of primary cultured mouse neurons, we inhibited the expression of integrin beta4 by its specific small interfering RNA. Viability of the cells remarkably declined, and neurons underwent apoptosis with down-regulation of integrin beta4. Next, we investigated the effect of siRNA-mediated down-regulation of integrin beta4 on the level of intracellular reactive oxygen species and the activities of NADPH oxidase and superoxide dismutase. The level of reactive oxygen species in the neurons was elevated significantly, the activities of manganese-dependent superoxide dismutase and copper/zinc-dependent superoxide dismutase were not altered, but the activity of NADPH oxidase was increased. Furthermore, inhibition of NADPH oxidase by its specific inhibitor dibenziodolium chloride attenuated the neuronal death induced by integrin beta4 knockdown. The data suggest that integrin beta4 is a key factor in neuron survival and apoptosis and indicate that this integrin subunit might perform its action through regulating NADPH oxidase and the level of reactive oxygen species in neuronal survival and apoptosis.

Novel morpholin-3-one derivatives induced apoptosis and elevated the level of P53 and Fas in A549 lung cancer cells

Previously, we found that nine kinds of new morpholin-3-one derivatives could inhibit the growth of A549 lung cancer cells in a dose-dependent manner, but how they performed their function remained unknown. In this paper, we studied the effects of the three more effective morpholin-3-one derivatives {4-(4-chlorophenyl)-6-((4-nitrophenoxy) methyl) morpholin-3-one (1); 6-(4-chlorophenoxy)-4-(4-methoxyphenyl) morpholin-3-one (2); and 6-((4-nitrophenoxy) methyl)-4-phenylmorpholin-3-one (3)} on the cell cycle distribution, apoptosis, and the level of P53 and Fas that are two kinds of important proteins in the regulation of A549 cell growth and apoptosis. According to the results of cell viability, we selected 40 microg/ml of morpholin-3-one derivatives as the most appropriate concentration for the following study. The results showed that the morpholin-3-one derivatives partly blocked the cells at G1 phase, induced apoptosis, and elevated the level of P53 and Fas proteins significantly. The effect of the morpholin-3-one derivates was associated with translocation of P53 and clustering of Fas. Our data suggested that the morpholin-3-one derivates might be promising tools for elucidating the molecular mechanism of lung cancer cell apoptosis and they will be very potential candidates for developing anti-cancer drugs.

Safrole oxide induces neuronal apoptosis through inhibition of integrin beta4/SOD activity and elevation of ROS/NADPH oxidase activity

Neuronal apoptosis is a very important event in the development of the central nervous system (CNS), but the underlying mechanisms remain to be elucidated. We have previously shown that safrole oxide, a small molecule, induces integrin beta4 expression and promotes apoptosis in vascular endothelial cells. In this study, the effects of safrole oxide on cell growth and apoptosis have been examined in primary cultures of mouse neurons. Safrole oxide was found to significantly inhibit neuronal cell growth and to induce apoptosis. The inhibitory and apoptotic activities of safrole oxide followed a dose- and time-dependent manner. Interestingly, the expression of integrin beta4 was significantly inhibited with safrole oxide treatment. Furthermore, safrole oxide dramatically increases the level of intracellular reactive oxygen species (ROS) and the activity of NADPH oxidase. Moreover, manganese-dependent superoxide dismutase (MnSOD) activity was decreased significantly with safrole oxide treatment. Our study thus demonstrates that safrole oxide induces neuronal apoptosis through integrin beta4, ROS, NADPH, and MnSOD.

Phosphatidylcholine-specific phospholipase C and ROS were involved in chicken blastodisc differentiation to vascular endothelial cells

To find the key factors that were involved in the survival and vascular endothelial differentiation of chick blatodisc induced by fibroblast growth factor 2 (FGF-2), we built a chick vasculogenesis model in vitro. Subsequently, the activities of phosphatidylcholine-specific phospholipase C (PC-PLC), including Ca(2+)-dependent and -independent PC-PLC, and the level of reactive oxygen species (ROS) were evaluated during the endothelial differentiation of chick blastodisc. The results showed that Ca(2+)-indepentent PC-PLC underwent a remarkable increase in 24 h (P < 0.01), then it decreased gradually with the cell differentiation, while the Ca(2+)-depentent PC-PLC was nearly not changed in the whole process. At the same time, ROS level dramatically decreased during the cell differentiation. To understand the role of PC-PLC and how it performs its function in the vascular endothelial differentiation induced by FGF-2, we suppressed PC-PLC activity by its specific inhibitor D609 (tricyclodecan-9-yl potassium xanthate) at 24 h during the cell differentiation. As a result, the cell differentiation could not progress and the intracellular level of ROS was elevated. The data suggested that PC-PLC and ROS were involved in chicken blastodisc differentiation to vascular endothelial cells. PC-PLC was an important factor in the blastodisc cell survival and differentiation, and it might perform its function associated with ROS.

D609 blocks cell survival and induces apoptosis in neural stem cells

In order to investigate the effects of tricyclodecane-9-yl-xanthogenate (D609) on the survival of neural stem cells (NSCs), which were isolated from rat forebrain, we treated the NSCs with D609 in the presence of basic fibroblast growth factor (bFGF). We found that when NSCs were exposed to 18.76-56.29 microM D609, the viability of the cells remarkably declined and apoptosis occurred. At the same time, the ROS level in NSCs was depressed. The data suggested that D609 was a powerful growth inhibitor and apoptosis inducer in NSCs.

Phosphatidylcholine-specific phospholipase C, p53 and ROS in the association of apoptosis and senescence in vascular endothelial cells

Previously, we found that phosphatidylcholine-specific phospholipase C (PC-PLC) participated in apoptosis signaling of vascular endothelial cells (VECs). Here, to explore whether PC-PLC is involved in the association of apoptosis and senescence in VECs, we analyzed p53 expression and intracellular reactive oxygen species (ROS) levels in young and senescent VECs before and after inhibiting PC-PLC activity. The results showed that suppressing PC-PLC inhibited apoptosis and the elevation of p53 expression induced by apoptosis in young cells, but not in senescent cells, and that inhibiting PC-PLC depressed intracellular ROS levels both in young and senescent cells. The data suggested that PC-PLC was involved in the association of apoptosis and senescence. Its function might be closely related to the level of p53 in VECs.

Suppressing Akt phosphorylation and activating Fas by safrole oxide inhibited angiogenesis and induced vascular endothelial cell apoptosis in the presence of fibroblast growth factor-2 and serum

At present, vascular endothelial cell (VEC) apoptosis induced by deprivation of fibroblast growth factor-2 (FGF-2) and serum has been well studied. But how to trigger VEC apoptosis in the presence of FGF-2 and serum is not well known. To address this question, in this study, the effects of safrole oxide on angiogenesis and VEC growth stimulated by FGF-2 were investigated. The results showed that safrole oxide inhibited angiogenesis and induced VEC apoptosis in the presence of FGF-2 and serum. To understand the possible mechanism of safrole oxide acting, we first examined the phosphorylation of Akt and the activity of nitric oxide synthase (NOS); secondly, we analyzed the expressions and distributions of Fas and P53; then we measured the activity of phosphatidylcholine specific phospholipase C (PC-PLC) in the VECs treated with and without safrole oxide. The results showed that this small molecule obviously suppressed Akt phosphorylation and the activity of NOS, and promoted the expressions of Fas and P53 markedly. Simultaneously, Fas protein clumped on cell membrane, instead of homogenously distributed. The activity of PC-PLC was not changed obviously. The data suggested that safrole oxide effectively inhibited angiogenesis and triggered VEC apoptosis in the presence of FGF-2 and serum, and it might perform its functions by suppressing Akt/NOS signal pathway, upregulating the expressions of Fas and P53 and modifying the distributing pattern of Fas in VEC. This finding provided a powerful chemical probe for promoting VEC apoptosis during angiogenesis stimulated by FGF-2.

Safrole oxide induces apoptosis by up-regulating Fas and FasL instead of integrin β4 in A549 human lung cancer cells

Previously, we found that 3,4-(methylenedioxy)-1-(2',3'-epoxypropyl)-benzene (safrole oxide) induced a typical apoptosis in A549 human lung cancer cells by activating caspase-3, -8, and -9. In this study, we further investigated which upstream pathways were activated by safrole oxide during the apoptosis. Immunofluorescence assay combined with laser scanning confocal microscopy revealed that both Fas and Fas ligand (FasL) were up-regulated by the small molecule. In addition, Fas protein distribution was altered, showing a clustering distribution instead of a homogeneous one. Subsequently, Western blot analysis confirmed the up-regulations of Fas and its membrane-binding form of FasL (m-FasL), as well as P53 protein. Conversely, safrole oxide hardly affected integrin beta4 subunit expression or distribution, which was reflected from the data obtained by immunofluorescence assay combined with laser scanning confocal microscopy. The results suggested that Fas/FasL pathway might be involved in safrole oxide-induced apoptosis of A549 cells, while integrin beta4 might be irrelevant to the apoptosis. Nevertheless, we first found the strong expression of integrin beta4 in A549 cells. The study first suggested that safrole oxide might be used as a small molecular promoter of Fas/FasL pathway to elicit apoptosis in A549 cells, which would lay the foundation for us to insight into the new strategies for lung cancer therapy.

Inhibition of PC-PLC blocked the survival of mouse neural cells by up-regulating the expression of integrin beta4 and Rb

In order to understand the survival signals of neural cells during the development of the central nervous system (CNS), we explored the role of phosphatidylcholine-specific phospholipase C (PC-PLC) in the survival of primary culture mouse neural cells (MNCs). We found that when the activity of PC-PLC in the neural cells was suppressed by its specific inhibitor, D609 (tricyclodecan-9-yl-xanthogenate), the cell survival was blocked, the viability of the cells remarkably declined. At the same time, the expressions of integrin beta4 and Rb protein were evidently elevated. We also examined the intracellular ROS (reactive oxygen species) levels after the cells were treated with D609. The result showed that the ROS level in neural cells was reduced. Our data suggested that PC-PLC had an important role in regulating neural cell survival, and PC-PLC might perform its function by upregulating the expressions of integrin beta4 and Rb protein. The changes of intracellular ROS level induced by D609 indicated that a modest level of ROS might be indispensable to neural cell survival.

Upregulating of Fas, integrin β4 and P53 and depressing of PC-PLC activity and ROS level in VEC apoptosis by safrole oxide

Previously, we found that safrole oxide could trigger vascular endothelial cell (VEC) apoptosis. In this study, to investigate its mechanism to induce apoptosis in VECs, the activities of nitric oxide synthetase and phosphatidylcholine specific phospholipase C, the level of reactive oxygen species and the expressions of Fas, integrin beta4 and P53 were analyzed. The data showed that safrole oxide induced apoptosis by increasing the expressions of Fas, integrin beta4 and P53, and depressing the activity of Ca(2+)-independent phosphatidylcholine-specific phospholipase C and intracellular reactive oxygen species levels in VECs.

Protection against amyloid beta-peptide (1–42)-induced loss of phospholipid asymmetry in synaptosomal membranes by tricyclodecan-9-xanthogenate (D609) and ferulic acid ethyl ester: Implications for Alzheimer's disease

Amyloid-beta (1-42) [Abeta (1-42)] deposition in the brain is a hallmark of Alzheimer's disease (AD) and has been shown to induce apoptosis and disrupt cellular ion homeostasis. Abeta (1-42) induces membrane lipid peroxidation, and 4-hydroxynonenal (HNE) and 2-propenal (acrolein) are the two reactive products of lipid peroxidation, which structurally modify proteins by covalent interaction and inhibit enzyme function. Phosphatidylserine (PS), an aminophospholipid, is sequestered in the inner leaflet of the plasma membrane in nonstimulated cells. An early signal of synaptosomal apoptosis is the loss of phospholipid asymmetry and the appearance of phosphatidylserine in the outer leaflet of the membrane. The ATP-requiring enzyme, flippase, maintains phospholipid asymmetry of PS. Here, we have investigated the inactivation of the transmembrane enzyme aminophospholipid-translocase (or flippase) by Abeta (1-42). Flippase activity depends on a critical cysteine residue, a putative site of covalent modification by the Abeta (1-42)-induced lipid peroxidation products, HNE or acrolein. The present study is aimed to investigate the protective effects of tricyclodecan-9-xanthogenate (D609) and ferulic acid ethyl ester (FAEE) on Abeta (1-42) induced modulation in phospholipid asymmetry in the synaptosomal membranes. Pretreatment of synaptosomes with D609 and FAEE significantly protected Abeta (1-42)-induced loss of phospholipid asymmetry in synaptosomal membranes. Our results suggest that D609 and FAEE exert protective effects against Abeta (1-42) induced apoptosis. The increase in intracellular Ca(2+) might not be the sole cause for the loss of flippase activity. Rather, other mechanisms that could modulate the function of flippase might be important in the modulation of phospholipid asymmetry. The results of this study are discussed with relevance to neuronal loss in the AD brain.