Involvement of calcium in 7beta -hydroxycholesterol and cholesterol-5beta,6beta -epoxide-induced apoptosis

Oxidized low-density lipoprotein (oxLDL) is believed to play a central role in the development of atherosclerosis. The induction of apoptosis in cells of the arterial wall is a critical event in the development of atheroma. 7beta-Hydroxycholesterol (7beta-OH) and cholesterol-5beta,6beta-epoxide (beta-epoxide) are components of oxLDL and have previously been shown to be potent inducers of apoptosis. The exact mechanism through which these oxysterols induce apoptosis remains to be fully elucidated. A perturbation of intracellular calcium homeostasis has been found to trigger apoptosis in many experimental systems. The aim of the present study was to determine the involvement of calcium signaling in 7beta-OH and beta-epoxide-induced apoptosis. To this end, the authors employed the calcium channel blockers verapamil and nifedipine and inhibitors of calpain activation, ALLM and ALLN. Verapamil protected against the decrease in viability induced by 7beta-OH whereas nifedipine had a protective effect in both 7beta-OH and beta-epoxide-treated cells, though these compounds did not restore viability to control levels. Verapamil, nifedipine, and ALLM prevented apoptosis induced by beta-epoxide. None of the compounds employed in the current study protected against 7beta-OH-induced apoptosis. Our results implicate calcium signaling in the apoptotic pathway induced by beta-epoxide and also highlight differences between apoptosis induced by 7beta-OH and beta-epoxide.     

Analgesic narcotic antagonists. 6. 7 beta, 8 beta-Methano- and 7 beta, 8 beta-epoxydihydrocodeinone

Reaction of codeinone (2) with CH2N2 in the presence of Pd(OAc)2 yielded mixtures of starting material and (2) and 7 beta, 8 beta-methanodihydrocodeinone (3). Initial resolution of this mixture was achieved via carbonyl reduction followed by chromatography to give pure 7 beta, 8 beta-methanodihydrocodeine (4), which was oxidized to 3. Reaction of the mixture containing 2 and 3 with mercaptoethanol and NaOH [2 leads to 8 beta-[(hydroxyethyl)thio]dihydrocodeinone (5)] allowed selective crystallization of 3. The beta configuration of the cyclopropane ring in 3 was established by cleavage with aqueous HCl to give the 8 beta-(chloromethyl) compound 6, followed by carbonyl reduction and dehalogenation to 8 beta-methyldihydrocodeine (8). Reaction of the N-(cycloalkylmethyl) derivatives (13 and 18) of 2 with CH2N2/Pd(OA)2 gave potential mixed agonist-antagonists and 14 and 19, which were purified by reduction-oxidation (14) or mercaptoethanol-base treatment (19). Compound 2, on oxidation with alkaline peroxide, gave the previously reported 7 beta, 8 beta-epoxydihydrocodeinone (22) as the hemimethanol ketal (21). Compound 3 was about ninefold more potent an agonist than dihydrocodeine, and the N-(cyclopropylmethyl)-7 beta, 8 beta-methano compound 19 had moderately potent mixed agonist-narcotic antagonist properties.     

Involvement of mitochondrial permeability transition pore opening in 7-xylosyl-10-deacetylpaclitaxel-induced apoptosis

7-Xylosyl-10-deacetylpaclitaxel is a natural hydrophilic paclitaxel derivative. It has long been used in Chinese clinics to treat cancer. In order to further explore the underlying intracellular target of 7-xylosyl-10-deacetylpaclitaxel towards the PC-3 cell line, the ultra-structural morphology of mitochondria, the intracellular Ca (2+), the intracellular ATP, the intracellular hydrogen peroxide and pro-apoptotic Bax and Bcl-2 protein expression were measured. Additionally, the changes of mitochondrial morphology and membrane potential ( ΔΨm) were analyzed by atomic force microscopy (AFM) and flow cytometry, respectively. Our results suggest that the intracellular target of 7-xylosyl-10-deacetylpaclitaxel may be the mitochondrial permeability transition pore (mPTP). To further evaluate this hypothesis, we assessed the effect of a specific mPTP inhibitor (cyclosporine A) on the toxic action of 7-xylosyl-10-deacetylpaclitaxel. The 7-xylosyl-10-deacetylpaclitaxel-induced decrease in mitochondrial inner transmembrane potential (ΔΨm) was abolished by the addition of cyclosporine A (CsA) in PC-3 cells, indicating that 7-xylosyl-10-deacetylpaclitaxel may target mPTP. Furthermore, treatment with 7-xylosyl-10-deacetylpaclitaxel increased ROS levels in PC-3 cells. This effect was counteracted by 10 μM cyclosporine A. These data indicate that oxidative damage is involved in mPTP.     

Role of Fas/Fas ligand-mediated apoptosis in murine contact hypersensitivity

Apoptosis plays an important role in immune responses, but little is known about its involvement in contact hypersensitivity (CH). In this study, we have investigated the role of Fas/Fas ligand (FasL)-mediated apoptosis in the pathogenesis of CH. Mice were sensitized by one topical application of 100 microl of 3% oxazolone to shaved skin of the abdomen. Six days later, CH was provoked by challenging both sides of sensitized mouse right ear with 15 microl of 1% oxazolone. Using a DNA ladder assay, we found that apoptosis was induced in the skin of oxazolone-sensitized mice 24-96 h after allergen challenge. Annexin V-fluorescein isothiocyanate (FITC)-propidium iodide (PI) apoptosis flow cytometric assay showed that early apoptotic CD4(+) T cells (annexin V-FITC(+)PI(-)), but not late apoptotic CD4(+) T cells (annexin V-FITC(+)PI(+)), increased in the inflamed skin of mice with CH. Moreover, the expressions of mRNAs for T helper (Th2) cytokine (interleukin (IL)-4), Th1 cytokine (interferon (IFN)-gamma) and proapoptotic molecules (Bax, Fas, FasL and IL-1beta-converting enzyme (ICE)/caspase-1) were significantly elevated in the oxazolone-sensitized mouse skin 6-72 h after allergen challenge. Dramatic increase in IL-10 mRNA was only observed in the sensitized mouse skin 6 and 12 h after allergen challenge. Furthermore, CH was significantly inhibited with decreased apoptosis and early apoptotic CD4(+) T cells in inflamed skin in Fas mutant lpr/lpr mice compared to wild-type mice, whereas there were no significant differences in IL-4, IFN-gamma, IL-10, Bax and ICE mRNAs in the inflamed skin of CH between lpr/lpr and wild-type mice. Our results thus suggest that Fas/FasL pathway partially contributes to apoptosis in murine CH and that Fas/FasL-mediated apoptosis plays a partial role in the development of CH. The contribution of Fas/FasL-mediated apoptosis to CH appears independent of Th1 and Th2 cytokines.     

Aldosterone antagonists. 1. Synthesis and activities of 6 beta,7 beta:15 beta,16 beta-dimethylene steroidal spirolactones

Several derivatives of the highly active aldosterone antagonists dihydrospirorenone (2) and spirorenone (3) were synthesized. The purpose of these efforts was to prepare compounds exhibiting reduced endocrinological properties with the same or better aldosterone antagonistic activity than that of spirorenone. The 1 alpha,2 alpha-methylene derivative 20 has a similar aldosterone antagonistic potency compared to that of spirorenone but does not show decreased endocrinological side effects. Other substituents as in compounds 4-11, 15-19, and 21 sharply decreased the aldosterone antagonistic activity of 2 or 3, respectively.     

Studies of the time-dependent inactivation of aromatase by 4beta,5beta-epoxy-6-one and 5beta,6beta-epoxy-4-one steroids under various conditions

The time-dependent inactivation of aromatase by epoxy analogs of the good aromatase inhibitors, androst-4-ene-6,17-dione (3) and androst-5-ene-4,17-dione (7), 4beta,5beta-epoxy and 5beta,6beta-epoxy compounds 10 and 13 and their 19-oxo derivatives 11 and 14, was examined in either the presence or absence of NADPH. The 4beta,5beta-epoxy-19-oxo steroid 11 along with the 19-methyl-5beta,6beta-epoxide 13 inactivated human placental aromatase in a mechanism-based manner, in the presence of NADPH, with rate constants for inactivation (k(inact)) of 0.133 min(-1) for steroid 11 and 0.100 min(-1) for steroid 13, whereas the two other steroids, 10 and 14, did not. On the other hand, none of four epoxides studied caused time-dependent inactivation of aromatase in an affinity-labeling manner in the absence of NADPH. These results are the first report showing that inhibitors 11 and 13 are suicide substrates having an epoxyketone structural feature.     

Involvement of 5-HT6 receptors in nigro-striatal function in rodents

1. 4-Amino-N-(2,4 bis-methylamino-pyrimidin-4-yl) benzene sulphonamide (Ro 04-6790) is a potent, selective and competitive antagonist for the 5-HT₆ receptor which can be detected in the cerebro-spinal fluid (CSF) of rats following intraperitoneal administration. Since 5-HT₆ receptor mRNA and 5-HT₆ receptor-like immunoreactivity have been shown to be present in the striatum, the purpose of the present study was to evaluate the effect of 5-HT₆ receptor antagonism on haloperidol- and SCH 23390-induced catalepsy in mice and on the turning behaviour of rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the medial forebrain bundle.
2. Ro 04-6790 (3, 10 and 30 mg kg⁻¹ i.p.) did not induce catalepsy and had no effect on catalepsy induced by either haloperidol or SCH 23390.
3. Ro 04-6790 (3, 10 and 30 mg kg⁻¹ i.p.) did not itself induce rotational behaviour in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the medial forebrain bundle nor did it affect the rotational behaviour induced by either L-Dopa or amphetamine.
4. 5-HT₆ receptor antagonism inhibited the rotational behaviour of 6-OHDA lesioned rats induced by treatment with the muscarinic antagonists scopolamine and atropine.
5. The data support earlier conclusions from experiments with antisense oligonucleotides that the 5-HT₆ receptor is involved in the control of acetylcholine neurotransmission in the rat brain.

     

Structures of isomers of ursodeoxycholic acid: 3 beta,7 alpha- and 3 beta,7 beta-dihydroxy-5 beta-cholan-24-oic acids]

Isomers of ursodeoxycholic acid, 3 beta,7 alpha- and 3 beta,7 beta-dihydroxy-5 beta-cholan-24-oic acids (3 beta 7 alpha U and 3 beta 7 beta U) crystallize in the orthorhombic space group P2(1)2(1)2(1) containing one molecule and in the monoclinic group P2(1) containing two independent molecules in an asymmetric unit. The cell dimensions are a = 28.032(17), b = 9.973(5), c = 8.049(6) A for 3 beta 7 alpha U, and a = 11.771(8), b = 27.999(12), c = 6.637(2) A, beta = 90.78(6) degrees for 3 beta 7 beta U, respectively. Both structures were solved by the direct method and refined to the residual values of 0.065 (3 beta 7 alpha U) and 0.059 (3 beta 7 beta U). The conformations of the D rings of each molecule are different from each other: 3 beta 7 alpha U intermediate, 3 beta 7 beta U (A and B) half-chair form. In the crystal, 3 beta 7 alpha U molecules are connected by a hydrogen bond extended nearly parallel to the bc plane and 3 beta 7 beta U molecules are connected by the helical hydrogen bond system or by the zigzag one parallel to the ac plane.     

Involvement of 5-hydroxytryptamine7 receptors in inhibition of porcine myometrial contractility by 5-hydroxytryptamine

1. 5-Hydroxytryptamine (5-HT; 1 nM–100 μM) concentration-dependently inhibited the amplitude and frequency of spontaneous contractions in longitudinal and circular muscles of the porcine myometrium. The circular muscle (EC₅₀; 68–84 nM) was more sensitive than the longitudinal muscle (EC₅₀; 1.3–1.44 μM) to 5-HT. To characterize the 5-HT receptor subtype responsible for inhibition of myometrial contractility, the effects of 5-HT receptor agonists on spontaneous contractions and of 5-HT receptor antagonists on inhibition by 5-HT were examined in circular muscle preparations.
2. Pretreatment with tetrodotoxin (1 μM), propranolol (1 μM), atropine (1 μM), guanethidine (10 μM) or L-NAME (100 μM) failed to change the inhibition by 5-HT, indicating that the inhibition was due to a direct action of 5-HT on the smooth muscle cells.
3. 5-CT, 5-MeOT and 8-OH-DPAT mimicked the inhibitory response of 5-HT, and the rank order of the potency was 5-CT>5-HT>5-MeOT>8-OH-DPAT. On the other hand, oxymethazoline, α-methyl-5-HT, 2-methyl-5-HT, cisapride, BIMU-1, BIMU-8, ergotamine and dihydroergotamine had almost no effect on spontaneous contractions, even at 10–100 μM.
4. Inhibition by 5-HT was not decreased by either pindolol (1 μM), ketanserin (1 μM), tropisetron (10 μM), MDL72222 (1 μM) or {"type":"entrez-nucleotide","attrs":{"text":"GR113808","term_id":"238362519","term_text":"GR113808"}}GR113808 (10 μM), but was antagonized by the following compounds in a competitive manner (with pA₂ values in parentheses): methiothepin (8.05), methysergide (7.92), metergoline (7.4), mianserin (7.08), clozapine (7.06) and spiperone (6.86).
5. Ro 20-1724 (20 μM) and rolipram (10 μM) significantly enhanced the inhibitory response of 5-HT, but neither zaprinast (10 μM) nor dipyridamole (10 μM) altered the response of 5-HT.
6. 5-HT (1 nM–1 μM) caused a concentration-dependent accumulation of intracellular cyclic AMP in the circular muscle.
7. From the present results, the 5-HT receptor, which is functionally correlated with the 5-HT₇ receptor, mediates the inhibitory effect of 5-HT on porcine myometrial contractility. This inhibitory response is probably due to an increase in intracellular cyclic AMP through the activation of adenylate cyclase that is positively coupled to 5-HT₇ receptors.

     

5,7-二甲氧基黄酮增强TRAIL诱导肝癌干细胞凋亡的研究

目的研究天然源性化合物5,7-二甲氧基黄酮(5,7-dimethoxyfl avone,5,7-DMF)是否具有增强肿瘤坏死因子相关凋亡诱导配体(TNF related apoptosis inducing ligand,TRAIL)诱导肝癌干细胞(liver cancer stem cells,LCSCs)凋亡的作用。方法采用干细胞条件培养基超低黏附板悬浮培养得到肝癌肿瘤球形成细胞;Western blot检测肿瘤干细胞标志物CD133、CD44和ALDH1蛋白表达状态;ELISA和Annexin V/PI染色流式细胞术检测肝癌球形成细胞凋亡率。结果第3代肿瘤球细胞的单个细胞成球的百分率(73.4%)相对第5代原代培养细胞的肿瘤球形成百分率(18.7%)显著提高,且其肿瘤球大小亦有差异。源自复发性肝细胞癌的第3代球细胞高表达肿瘤干细胞标志物CD133、CD44和Oct4。亚细胞毒性浓度5,7-DMF(1.0μmol·L-1)明显增强TRAIL(10.0 ng·m L-1)诱导LCSCs的凋亡作用。结论本研究证明,5,7-DMF具有增强TRAIL诱导LCSCs凋亡的作用。     

New dimensions in G protein signalling: G beta 5 and the RGS proteins

The beta gamma complex of G-proteins regulates effectors independently of the G alpha subunits, such that upon activation G proteins give may signal downstream along one or both pathways. The G beta 5 isoform exhibits much less homology with other G beta isoforms (approximately 50%) and is preferentially expressed in brain. The G beta 5 isoform exhibits novel properties in its activation of effector pathways such as MAPK, phospholipase C-beta, and adenylyl cyclase type II when compared to G beta 1. Recently specific native complexes between G beta 5 and the regulator of G protein signaling (RGS) protein-7 (RGS7) and between G beta 5L (a splice variant with a 42 amino acid N-terminal extension) and RGS9 have been isolated from different retinal fractions. Such findings are not accounted for by current models as only the G alpha subunits and not G beta had been previously implicated in RGS protein function. These recent novel observations further reinforce the view of G beta 5 as a unique and highly specialized G protein subunit.     

白藜芦醇通过激活p38-p53通路诱导人乳腺癌MCF-7细胞凋亡

本研究探讨了白藜芦醇(resveratrol,RSV)诱导人乳腺癌MCF-7细胞凋亡及其作用机制。以MTT法检测白藜芦醇对MCF-7的细胞毒性;应用Hoechst 33258染色观察细胞凋亡的形态学变化;采用流式细胞术检测细胞的凋亡率;以Western blotting检测相关蛋白的表达。结果表明,白藜芦醇可以时间和剂量依赖性地抑制MCF-7细胞的生长;60μmol.L-1白藜芦醇作用于MCF-7细胞48 h后可使细胞核皱缩、染色质凝聚,并形成明显的凋亡小体;白藜芦醇可以时间依赖性地诱导MCF-7细胞凋亡及p38和p53蛋白的活化。p38 MAPK抑制剂SB203580和p53抑制剂pifithrin-α可以显著降低白藜芦醇诱导的MCF-7细胞的生长抑制率和凋亡率;并且SB203580可以下调由白藜芦醇引起的p53的活化,而pifithrin-α对白藜芦醇引起p38的活化无影响。研究表明,白藜芦醇可以通过激活p38-p53信号通路诱导MCF-7细胞发生凋亡。     

Gas6 rescues cortical neurons from amyloid beta protein-induced apoptosis

Gas6, a product of the growth-arrest-specific gene 6, protects neurons from serum deprivation-induced apoptosis. Neuronal apoptosis is also caused by amyloid β protein (Aβ), whose accumulation in the brain is a characteristic feature of Alzheimer’s disease. Aβ induces Ca²⁺ influx via L-type voltage-dependent calcium channels (L-VSCCs), leading to its neurotoxicity. In the present study, we investigated effects of Gas6 on Aβ-induced cell death in primary cultures of rat cortical neurons. Aβ caused neuronal cell death in a concentration- and time-dependent manner. Gas6 significantly prevented neurons from Aβ-induced cell death. Gas6 ameliorated Aβ-induced apoptotic features such as the condensation of chromatin and the fragmentation of DNA. Prior to cell death, Aβ increased influx of Ca²⁺ into neurons through L-VSCCs. Gas6 significantly inhibited the Aβ-induced Ca²⁺ influx. The inhibitor of L-VSCCs also suppressed Aβ-induced neuronal cell death. The present cortical cultures contained few non-neuronal cells, indicating that Gas6 affected the survival of neurons directly, but not indirectly via non-neuronal cells. In conclusion, we demonstrate that Gas6 rescues cortical neurons from Aβ-induced apoptosis. Furthermore, the present study indicates that inhibition of L-VSCC contributes to the neuroprotective effect of Gas6.     

土槿皮乙酸B不通过Fas途径诱导人乳腺癌MCF-7细胞凋亡和M期周期阻滞

目的初探土槿皮乙酸B(PAB)诱导人乳腺癌MCF-7细胞凋亡和周期阻滞。方法MTT法测定PAB对MCF-7细胞的生长抑制情况;相差显微镜观察细胞形态变化;荧光显微镜观察经Hoechst33258染色的DNA变化;流式细胞仪检测用PI染色后MCF-7细胞的周期分布;免疫印迹实验检测相关蛋白的表达。结果PAB时间剂量依赖性的抑制MCF-7细胞生长。4μmol.L-1PAB在24h使DNA皱缩,在36和48h使DNA皱缩的细胞死亡。4μmol.L-1PAB时间依赖性的促进PARP〔poly-(ADP-ribose)polymerase〕的剪切。在36hPAB剂量依赖性的增加cdc2和核内cyclinB1的表达。Fas拮抗性抗体UB2不影响PAB诱导的凋亡,但Fas激动性抗体CH11促进PAB诱导的凋亡。并且UB2不影响PAB诱导的细胞周期阻滞,Fas激动性抗体CH11不影响G1和S期,但促进凋亡特征性的亚二倍体峰生成。结论4μmol.L-1的PAB通过凋亡方式可明显地抑制MCF-7细胞生长,并促进M期阻滞。Fas途径不参与PAB诱导的凋亡和周期阻滞。     

The renal action of spirorenone and other 6 beta,7 beta; 15 beta,16 beta-dimethylene-17-spirolactones, a new type of steroidal aldosterone antagonists

The aldosterone antagonistic activity in vivo and the affinity for mineralocorticoid receptors (MCR) in vitro of 3-(17 beta-hydroxy-6 beta,7 beta; 15 beta,16 beta-dimethylene-3-oxo-1, 4-androstadiene-17 alpha-yl) propionic acid gamma-lactone (spirorenone), a new aldosterone antagonist, and four of its derivatives were studied in comparison with spironolactone in rats. Spirorenone was 8.6 times as potent as spironolactone, but showed a lower affinity for the MCR than the standard. The C1/C2 saturated derivative (compound I) had 7.6 times the antialdosterone potency and 2 times the binding activity of spironolactone. The 17-spiroether derivative of spirorenone (compound II) showed a lower aldosterone antagonistic activity (1.7 the potency of spironolactone) as well as a lower affinity for the MCR (0.5 the affinity of spironolactone). The analogue with a 17 beta-hydroxyl group and a 17 alpha-hydroxypropyl side chain (compound III) possessed a very low binding capacity for MCR (1/10 of that of spironolactone) but still a 1.3 times higher antialdosterone activity than spironolactone. This result is probably due to a transformation of compound III to an active metabolite in vivo. Finally, the derivative with a reversed configuration of the 17-spirolactone ring (compound IV) had no biological activity in vivo and no affinity for the MCR. These results show that spirorenone or one of its active derivatives might lead to a new series of potent aldosterone antagonists.     

Nanomolar small molecule inhibitors for alphav(beta)6, alphav(beta)5, and alphav(beta)3 integrins

Integrin adhesion receptors frequently recognize a core amino acid sequence, Arg-Gly-Asp, in their target ligands. Inhibitors with the ability to inhibit one or a small subset of such RGD-dependent integrins have been invaluable in defining their biological function. Here, we have characterized low molecular weight inhibitors for their ability to specifically inhibit alphav(beta)6 integrin, a fibronectin/tenascin receptor. As of yet, no nonpeptidic inhibitor of alphav(beta)6 was known. New peptidomimetic and nonpeptidic compounds were examined in isolated integrin binding assays and in cell adhesion assays for their ability to block alphav(beta)6, alphav(beta)3, alphav(beta)5, and alphalIb(beta)3 integrins. The compounds are based on an aromatically substituted beta amino acid or glutaric acid derivative as an acidic center and an aminopyridyl or guanidyl residue as a basic mimetic. We found several classes of inhibitors with different selectivities, especially mono- or biselectivity on the alpha(v)-integrins alphav(beta)6 and alphav(beta)3, and nanomolar activity. Furthermore, nearly all compounds are inactive on alphaIIb(beta)3. Compound 11 is the first specific, peptidomimetic inhibitor of the alphav(beta)6 integrin receptor.     

The Fas signalling pathway and its role in the pathogenesis of cancer

Tumor cells frequently exhibit de novo expression of Fas ligand (FasL/CD95L). Coupled with resistance to Fas-mediated apoptosis, FasL expression enables many cancers to deliver a pre-emptive strike or 'counterattack' against the immune system. New studies also indicate that FasL expression on tumor cells could confer a double advantage to these cells by stimulating their own proliferation. However, pro-inflammatory effects of FasL have also been observed. New findings are beginning to reconcile the paradoxical effects of FasL, with the clinical significance of the Fas counterattack only beginning to emerge.