SD大鼠肺气肿模型的建立及全反式维甲酸干预作用探讨

目的观察不同浓度的全反式维甲酸(all-transretinoicacid,ATRA)对猪胰蛋白酶复制的大鼠肺气肿模型的治疗作用。方法建立猪胰蛋白酶(porcine pancreatic elastase,PPE)复制的大鼠肺气肿模型,将体重170~220 g的60只SD大鼠随机分为生理盐水对照组(N)、模型组(P)、小剂量ATRA治疗组(R1)、中剂量ATRA治疗组(R2)、大剂量AT-RA治疗组(R3)、棉籽油组(C)各10只。后5组向大鼠气管内滴注1U·g-1PPE,N组同样滴注等量生理盐水,饲养76d,治疗组和棉籽油组分别向大鼠腹腔内连续注入大、中、小剂量ATRA和棉籽油14 d。测量干预前后的大鼠肺体积,血气分析和病理形态学图像分析了解不同浓度ATRA对于PPE复制的大鼠肺气肿模型的治疗效果。结果R1、R2、R3组、P组、C组的大鼠肺体积明显大于N组(P<0.01),C组和P组的肺体积无差异,各治疗组的肺体积较P组有差异,各治疗组之间的肺体积无差异。肺泡形态学结果显示R1、R2、R3组、P组、C组与N组比较,每个视野内的肺泡数(Na)明显减少,平均肺泡面积(MAA)增大,平均内衬间隔(MLI)较大,差异有显著性(P<0.05);R1、R2组相对于P组Na增加,MAA减少,差异有统计学意义,但两组之间无差别;R3组、C组和P组的各指标无明显差别。血气分析结果P组、R1、R2、R3组和C组的二氧化碳分压(PaCO2)比N组升高,P组、C组和R3组的氧分压(PaO2)、氧饱和度(SaO2)值明显低于N组,R1、R2组的PaO2、SaO2值与N组无差异,与P组也无差异。结论中、低剂量组的ATRA对肺气肿模型的治疗在肺泡修复上明显效果,但肺功能的改善不明显;大剂量组ATRA治疗后效果不明显。     

Novel mutual prodrug of retinoic and butyric acids with enhanced anticancer activity

Acyloxylalkyl esters of retinoic acid and small carboxylic acids (C3-5) were evaluated for anticancer activity. The derivative of butyric acid (BA) and all-trans-retinoic acid (ATRA)-retinoyloxymethyl butyrate (RN1)-acting as a mutual prodrug was a more potent inducer of cancer cell differentiation and inhibitor of proliferation than the parent acids. ED50 of RN1 for differentiation induction in HL-60 was over 40-fold lower than that of ATRA. The differentiating activity of ATRA compared to that of the acyloxylalkyl esters derived from butyric (RN1), propionic (RN2), isobutyric (RN3), and pivalic (RN4) acids was found to be: RN1 > RN2 > RN3 > ATRA approximately RN4. This observation implies that the activity of the prodrugs depends on the specific acyl fragment attached to the retinoyl moiety, and the butyroyl fragment conferred the highest potency. The IC50 values for inhibition of Lewis lung (3LLD122) and pancreatic (PaCa2) carcinoma cell line colony formation elicited by RN1 were significantly higher than those of ATRA. In addition to its superiority over ATRA or BA as growth inhibitors of the above cell lines, RN1 was also able to overcome the resistance to ATRA in 3LLD122 cells.     

All-trans retinoic acid protects against arsenic-induced uterine toxicity in female Sprague-Dawley rats

Background and purpose

Arsenic exposure frequently leads to reproductive failures by disrupting the rat uterine histology, hormonal integrity and estrogen signaling components of the rat uterus, possibly by generating reactive oxygen species. All-trans retinoic acid (ATRA) was assessed as a prospective therapeutic agent for reversing reproductive disorders.

Experimental approach

Rats exposed to arsenic for 28 days were allowed to either recover naturally or were treated simultaneously with ATRA for 28 days or treatment continued up to 56 days. Hematoxylin-eosin double staining was used to evaluate changes in the uterine histology. Serum gonadotropins and estradiol were assayed by ELISA. Expression of the estrogen receptor (ERα), an estrogen responsive gene vascular endothelial growth factor (VEGF), and cell cycle regulatory proteins, cyclin D1 and CDK4, was assessed by RT-PCR, immunohistochemistry and western blot analysis.

Key results

ATRA ameliorated sodium arsenite-induced decrease in circulating estradiol and gonadotropin levels in a dose- and time-dependent manner, along with recovery of luminal epithelial cells and endometrial glands. Concomitant up regulation of ERα, VEGF, cyclin D1, CDK4 and Ki-67 was also observed to be more prominent for ATRA-treated rats as compared to the rats that were allowed to recover naturally for 56 days.

Conclusions and implications

Collectively, the results reveal that ATRA reverses arsenic-induced disruption of the circulating levels of gonadotropins and estradiol, and degeneration of luminal epithelial cells and endometrial glands of the rat uterus, indicating resumption of their functional status. Since structural and functional maintenance of the pubertal uterus is under the influence of estradiol, ATRA consequently up regulated the estrogen receptor and resumed cellular proliferation, possibly by an antioxidant therapeutic approach against arsenic toxicity.     

Participation of CYP2C8 in retinoic acid 4-hydroxylation in human hepatic microsomes.

Cytochromes P450 (CYPs) catalyze the 4-hydroxylation of all-trans-retinoic acid (ATRA), an agent used in the treatment of certain malignancies. Literature studies have implicated several CYPs in this reaction, but the relative importance of individual CYPs is unclear. Human microsomal CYPs that contribute to the activity were evaluated by correlation with activities of hepatic drug-metabolizing CYPs, the capacity of cDNA-derived CYPs to catalyze the reaction, and inhibition of the microsomal activity by chemicals. 4-HydroxyATRA formation in microsomes varied 7-fold (8.7 to 61 pmol/mg protein/min) and correlated partially with activities mediated by CYPs 3A, 2C, and 1A (p = 0.53 to 0.66). cDNA-derived CYPs 2C8, 2C9, and 3A4, but not 1A1 or 1A2, catalyzed ATRA 4-hydroxylation (2.53, 4.68, and 1.29 pmol/pmol CYP/hr). The Km for the reaction was 9 +/- 3 microM in hepatic microsomes (N = 3) and 6 microM in microsomes containing cDNA-derived CYP2C8; by comparison, Km values for the activity mediated by CYPs 2C9 and 3A4 were 100 and 74 microM, respectively. Inhibition of microsomal ATRA 4-hydroxylation was elicited by chemicals that interact with CYP2C8 (paclitaxel and diclofenac), but not those that interact with CYP2C9 (sulfaphenazole, tolbutamide, and torasemide). The CYP3A inhibitor troleandomycin and an anti-CYP3A IgG inhibited the activity slightly. Greater inhibition was produced by the less selective CYP3A inhibitors parathion, quinidine, and ketoconazole; CYP1A inhibitors were ineffective. These findings suggest that CYP2C8 is a major contributor to ATRA 4-hydroxylation in human liver and that 3A subfamily CYPs may be minor participants. Individual variation in CYP2C8 and 3A4 expression may influence ATRA pharmacokinetics and drug interactions during therapy.     

Addition of angiotensin II receptor antagonist to an ACE inhibitor in heart failure improves cardiovascular function by a bradykinin-mediated mechanism

Whether cardiovascular responses to bradykinin are augmented by additional treatment with angiotensin II receptor antagonism (ATRA) to angiotensin-converting enzyme inhibition (ACEI) in congestive heart failure (CHF) is unknown. To clarify the level and functional effects of endogenous bradykinin in CHF with combined ATRA and ACEI, 35 dogs were assigned to the following treatment protocols: 1). rapid ventricular pacing (240 bpm), 2). concomitant ATRA (TCV116, 1.5 mg x kg-1.day-1) and rapid pacing, 3). concomitant ACEI (enalapril 1.9 mg x kg-1.day-1) and rapid pacing, 4). concomitant combined ATRA (TCV116, 0.75 mg x kg-1.day-1) and ACEI (enalapril 0.95 mg x kg-1.day-1) and rapid pacing, and 5). sham-operated control. Plasma bradykinin levels were increased and B(2) receptors were synergistically upregulated in CHF groups treated with combined ATRA and ACEI compared with those treated with ATRA or ACEI alone. HOE-140 (0.3 mg/kg), a bradykinin B(2) receptor antagonist, produced an increase in total systemic resistance and a decrease in left ventricular contractility in CHF with combined therapy compared with either monotherapy. Thus, endogenous bradykinin partially contributes to the synergistic improvement of cardiovascular function in CHF with additional treatment with ATRA to ACEI.     

Arachidonic acid-mediated cooxidation of all-trans-retinoic acid in microsomal fractions from human liver

The quantitative importance of prostaglandin H synthase (PGHS)-mediated cooxidation of all-trans-retinoic acid (ATRA) was evaluated in human liver microsomes (n=17) in relation to CYP-dependent ATRA 4-hydroxylation. Observed rates of ATRA cooxidation (4.6 - 20 pmol mg protein(-1) min(-1)) and 4-hydroxylation (8.7 - 45 pmol mg protein(-1) min(-1)) were quantitatively similar and exhibited similar individual variation (4 and 5 fold, respectively). From kinetic studies cooxidation was an efficient process in human hepatic microsomes (V(max) K(m)(-1)=0.25) compared with NADPH- and NADH-mediated 4-hydroxylation by CYP (V(max) K(m)(-1)=0.14 and 0.02, respectively). The capacity of lipid hydroperoxide metabolites of arachidonic acid to mediate ATRA oxidation was established directly, but downstream products (D, E, F and I-series prostaglandins) were inactive. cDNA-expressed CYPs supported ATRA oxidation by lipid hydroperoxides. Whereas CYPs 2C8, 2C9 and 3A4, but not CYPs 1A2 or 2E1, were effective catalysts of the NADPH-mediated reaction, cooxidation supported by 15(S)-hydroperoxyeicosatetraenoic acid was mediated by all five CYPs. The cooxidation reaction in human hepatic microsomes was inhibited by the CYP inhibitor miconazole. These findings indicate that ATRA oxidation is quantitatively significant in human liver. Lipid hydroperoxides generated by intracellular enzymes such as prostaglandin synthase and lipoxygenases are sources of activated oxygen for CYP-mediated deactivation of ATRA to polar products.     

全反式维甲酸对肺气肿模型大鼠的干预作用

目的研究不同时间段给予全反式维甲酸(ATRA)对肺气肿模型大鼠的干预作用及其机制。方法60只SD大鼠随机分为6组:生理盐水组(N组)、模型组(P组)、棉籽油组(C组)、早期干预组(R1组)、中期干预组(R2组)和后期干预组(R3组),每组10只。N组大鼠气管滴注生理盐水1mL·kg-1,其余5组气管滴注5%木瓜蛋白酶1mL·kg-1建立肺气肿模型。R1、R2和R3组分别于造模后15～30d、30～45d和45～60d给予ATRA500μg·kg-1腹腔注射,C组给予棉籽油腹腔注射。观察各组支气管肺泡灌洗液(BALF)中血管内皮生长因子(VEGF)含量和细胞数,肺组织病理学改变及肺组织血管内皮生长因子受体2(VEGFR-2)、基质金属蛋白酶1(MMP-1)的表达水平。结果与N组比较,P组BALF中细胞总数明显升高(P<0.01),其中以巨噬细胞和中性粒细胞为主。R1、R2和R3组与P组比较细胞总数降低(P<0.01),此3组之间无显著差异。与N组比较,其余5组平均肺泡面积和内衬间隔增大,每个视野内肺泡数减少(P<0.01);与P组相比,R1、R2和R3组肺泡数增加、平均肺泡面积减小(P<0.01),以R1组最为明显。与N组相比,P组VEGF和VEGFR-2表达降低,MMP-1表达增高(P<0.01);与P组相比,R1、R2和R3组VEGF和VEGFR-2表达增高,MMP-1表达降低(P<0.05),R1、R2和R3组之间无显著差异。结论ATRA可以促进肺泡再生,早期干预效果较佳,这种作用可能与调节VEGF、VEGFR-2、MMP-1有关。     

维A酸对HL-60细胞端粒酶活性的影响

目的:探讨维A酸(ATRA)诱导HL-60细胞增殖过程中端粒酶活性的变化.方法:将不同浓度(10-6、10-7及10-8M)的ATRA处理体外培养的HL-60细胞,采用四甲基偶氮唑盐比色法(MTT)测定其细胞增殖情况,培养72 h时用TRAP-ELISA法检测端粒酶活性的变化.结果:维A酸呈时间-剂量依赖方式抑制HL-60细胞增殖,与对照组比较,实验组端粒酶活性均下降,其中10-6M及10-7M两组差异显著(P＜0.05,P＜0.01),而10-8M组无显著差异(P＞0.05).结论:维A酸能够抑制HL-60细胞增殖,该过程可能与其下调细胞端粒酶的活性有关.     

Evaluation of the pharmacokinetics of all-trans-retinoic acid (ATRA) in Wistar rats after intravenous administration of ATRA loaded into tributyrin submicron emulsion and its cellular activity on caco-2 and HepG2 cell lines

The pharmacokinetics of all-trans-retinoic acid (ATRA), an anti-cancer drug was highly variable due to its poor aqueous solubility. In this study, we investigated the pharmacokinetics of ATRA in male Wistar rats following intravenous administration of the ATRA loaded tributyrin emulsion. In vitro, the ATRA emulsion was proved binding to apolipoprotein(s). In vivo, the clearance of ATRA was significantly reduced by formulating into the tributyrin emulsion, leading to higher AUCs. Co-administration with 17alpha-ethynylestradiol, a compound known to upregulate the activity of low-density lipoprotein receptors in tissues, significantly increased the K(e), V, and CL of ATRA. The variation of plasma AUCs after administering the ATRA emulsion to the healthy rats was two times less than that after the ATRA solution. The IC(50) in ATRA of the ATRA emulsion for the Caco-2 carcinoma cells was 3.8 microg/mL lower than 6 microg/mL of the ATRA solution. The IC(50) of the emulsion for the HepG2 carcinoma cells was 2.8 microg/mL, while IC(50) was not achieved with the ATRA solution over the test concentration range. The finding indicated that the tributyrin emulsion could be used as a carrier for ATRA and enhances the drug effect by reducing the clearance and increasing the in vitro activity.     

Andrographolide inhibits growth of acute promyelocytic leukaemia cells by inducing retinoic acid receptor‐independent cell differentiation and apoptosis

Objectives The growth inhibiting potential of andrographolide was evaluated in three acute promyelocytic leukaemia cell line models (HL‐60, NB4 and all‐trans retinoic acid (ATRA)‐resistant NB4‐R2). Methods In elucidating the mechanisms of growth inhibition, a special emphasis was placed on assessing the induction of differentiation and apoptosis by andrographolide in the primary acute promyelocytic leukaemia NB4 cells. Key findings The compound was 2‐ and 3‐fold more active in inhibiting the growth of HL‐60 and NB4‐R2 cells compared with NB4 cells, respectively. At IC50 (concentration at which growth of 50% of the cells (compared with medium only treated control cells) is inhibited; 4.5 μM) the compound exhibited strong cell‐differentiating activity in NB4 cells, similar to ATRA (IC50 1.5 μM). In the presence of a pure retinoic acid receptor antagonist AGN193109, the growth inhibition of NB4 cells by ATRA was reversed, whereas the activity of andrographolide was not affected. This clearly suggested that andrographolide's cell differentiating activity to induce growth inhibition of NB4 cells most likely occurred via a retinoic acid receptor‐independent pathway. At higher concentration (2 × IC50), andrographolide was an efficient inducer of apoptosis in NB4 cells. Conclusions Taken together, these results suggest andrographolide and its derivatives, apparently with a novel cell differentiating mechanism and with ability to induce apoptosis, might be beneficial in the treatment of primary and ATRA‐resistant acute promyelocytic leukaemia.     

三氧化二砷治疗急性早幼粒细胞白血病疗效观察

目的 :观察三氧化二砷 (As2 O3)治疗急性早幼粒细胞白血病的完全缓解率、高白细胞发生率、肝功损害及融合基因转阴率 ,并与维甲酸 (ATRA )的治疗情况进行比较。方法 :随机分为两组 ,As2 O3组 17例 ,ATRA组 2 1例 ,分别选用 0 .1% As2 O310 m L/ d,静脉滴注 ;ATRA2 5 mg· m- 2 · d- 1 ,分 3次服用。分别观察两组的完全缓解率 (CR)、不良反应以及融合基因转阴率。结果 :As2 O3组 15 / 17例 (88.2 % )获 CR,获得 CR时间为 (2 8.1± 4 .6 ) d;ATRA组 19/2 1例 (90 .4 % )获 CR,获得 CR时间为 (39.4± 8.6 ) d,两组之间 CR无明显差别 ,但 As2 O3组获得 CR时间明显缩短。高白细胞发生率 As2 O3组 10 / 15例 (6 6 .7% ) ,ATRA组 18/ 19例 (94 .7% ) ,P<0 .0 5。肝功能异常 ,As2 O3组 11/ 17例(6 4 .7% ) ,ATRA组 13/ 19例 (6 8.4 % ) ,P>0 .0 5。所有患者治疗前 PML- RARα融合基因阳性。 As2 O3组 CR时 ,2 /14例 (14 % )转阴 ,ATRA组 2 / 19例 (10 .5 % )转阴 ,P<0 .0 5。CR后 1a,As2 O3组 5 / 8例 (6 2 .5 % )转阴 ,ATRA组 4 /11例 (36 .3% )转阴 ,P<0 .0 5。As2 O3组 15例获 CR者 ,无 1例复发。ATRA组 19例获 CR者 ,4例 (2 1% )复发。结论 :与 ATRA相比 As2 O3获得 CR时间缩短 ,高白细胞发生率低 ,CR及 CR     

Novel retinoic acid metabolism blocking agents endowed with multiple biological activities are efficient growth inhibitors of human breast and prostate cancer cells in vitro and a human breast tumor xenograft in nude mice

Novel retinoic acid metabolism blocking agents (RAMBAs) have been synthesized and characterized. The synthetic features include introduction of nucleophilic ligands at C-4 of all-trans-retinoic acid (ATRA) and 13-cis-retinoic acid, and modification of terminal carboxylic acid group. Most of our compounds are powerful inhibitors of hamster liver microsomal ATRA metabolism enzyme(s). The most potent compound is methyl (2E,4E,6E,8E)-9-(3-imidazolyl-2,6,6-trimethylcyclohex-1-enyl)-3,7-dimethylnona-2,4,6,8-tetraenoate (5) with an IC(50) value of 0.009 nM, which is 666,667 times more potent than the well-known RAMBA, liarozole (Liazal, IC(50) = 6000 nM). Quite unexpectedly, there was essentially no difference between the enzyme inhibitory activities of the two enantiomers of compound 5. In MCF-7 cell proliferation assays, the RAMBAs also enhance the ATRA-mediated antiproliferative activity in a concentration dependent manner. The novel atypical RAMBAs, in addition to being highly potent inhibitors of ATRA metabolism in microsomal preparations and in intact human cancer cells (MCF-7, T47D, and LNCaP), also exhibit multiple biological activities, including induction of apoptosis and differentiation, retinoic acid receptor binding, and potent antiproliferative activity on a number of human cancer cells. Following subcutaneous administration to mice bearing human breast MCF-7 tumor xenografts, 6 (VN/14-1, the free carboxylic acid of 5) was well-tolerated and caused significant tumor growth suppression ( approximately 85.2% vs control, p = 0.022). Our RAMBAs represent novel anticancer agents with unique multiple mechanisms of action. The most potent compounds are strong candidates for development as therapeutic agents for the treatment of a variety of cancers.     

Pretranslational up-regulation of the hepatic microsomal delta4-3-oxosteroid 5alpha-oxidoreductase in male rat liver by all-trans-retinoic acid.

Administration of all-trans-retinoic acid (ATRA; 60 mg/kg daily for 3 days) to male rats increased the rate of 5alpha-dihydrotestosterone (5alpha-DHT) formation from testosterone in microsomal fractions in vitro. The formation of androstane-3alpha,17beta-diol from testosterone was also increased because of the higher concentration of 5alpha-DHT produced in microsomal incubations. Northern analysis confirmed that the increased rate of 5alpha-DHT formation was due to the pretranslational up-regulation in delta4-3-oxosteroid 5alpha-oxidoreductase (EC 1.3.99.5) mRNA expression in ATRA-treated male rat liver. Thus, ATRA elicited in male rat liver a partial feminization of the expression of this enzyme, which normally exhibits a female-selective distribution in the rat. Subsequent experiments evaluated whether the administration of human chorionic gonadotropin or thyroxine to ATRA-treated male rats decreases 5alpha-reductase activity to that observed in untreated male rat liver. Although these treatments did not decrease 5alpha-reductase to untreated male levels, it was found that administration of ATRA to gonadectomized male rats produced complete feminization of the enzyme. Again, up-regulation was confirmed at the mRNA level. The activity of the male-specific cytochrome P450 2C11 (as reflected by microsomal testosterone 16alpha-hydroxylation activity) was correspondingly decreased by treatments that increased steroid 5alpha-reductase activity. Thus, gonadectomy in combination with ATRA administration effected a more pronounced decrease in 16alpha-hydroxylation activity than either treatment alone. These findings suggest that ATRA is a novel positive regulator of the 5alpha-reductase that in combination with the removal of circulating androgen, which normally suppresses 5alpha-reductase levels, feminizes the expression of this enzyme in rat liver.     

Differential expression of dendritic cell markers by all-trans retinoic acid on human acute promyelocytic leukemic cell line

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) for naive T cells and play an important role in cancer immunology. All-trans retinoic acid (ATRA) is known to be a differentiating agent in the treatment of acute promyelocytic leukemia (APL). In this study, we investigated whether ATRA can differentiate the retinoic acid (RA)-sensitive promyelocytic leukemic cell line, NB4, to DC-like cells and whether these differentiated cells can activate T cells. NB4 cells were differentiated to myeloid cells by 4, 6, and 8 days of ATRA treatment. NB4 cells up-regulated markers found in DCs, including HLA-DR, costimulatory molecules (CD80 and CD86), adhesion molecules (CD40), and chemokine receptors (CCR6) when cultured for 8 days in the presence of 1 microM ATRA. Upregulation of CD83 was also detected on the surface of ATRA-treated NB4 cells versus untreated cells. The addition of cytokines alone, such as GM-CSF or CD40 ligand, did not affect the expression of CD83 in untreated NB4 cells but they up-regulated CD83 in ATRA-treated cells. CD11b was coexpressed with CD80, CD83, and CD86 in ATRA-treated NB4 cells. In a functional assay, ATRA-treated NB4 cells stimulated T cell proliferation when challenged with Staphylococcus enterotoxin B. These results suggest that the differentiation of NB4 cells by ATRA causes the cells to express DC markers, and that ATRA-differentiated NB4 cells are able to present antigens to T cells.     

Antitumor activity of the retinoid-related molecules (E)-3-(4'-hydroxy-3'-adamantylbiphenyl-4-yl)acrylic acid (ST1926) and 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) in F9 teratocarcinoma: Role of retinoic acid receptor gamma and retinoid-independent pathways

The retinoid-related molecules (RRMs) ST1926 [(E)-3-(4'-hydroxy-3'-adamantylbiphenyl-4-yl)acrylic acid] and CD437 (6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid) are promising anticancer agents. We compared the retinoic acid receptor (RAR) trans-activating properties of the two RRMs and all-trans-retinoic acid (ATRA). ST1926 and CD437 are better RARgamma agonists than ATRA. We used three teratocarcinoma cell lines to evaluate the significance of RARgamma in the activity of RRMs: F9-wild type (WT); F9gamma-/-, lacking the RARgamma gene; F9gamma51, aF9gamma-/-derivative, complemented for the RARgamma deficit. Similar to ATRA, ST1926 and CD437 activate cytodifferentiation only in F9-WT cells. Unlike ATRA, ST1926 and CD437 arrest cells in the G2/M phase of the cell cycle and induce apoptosis in all F9 cell lines. Our data indicate that RARgamma and the classic retinoid pathway are not relevant for the antiproliferative and apoptotic activities of RRMs in vitro. Increases in cytosolic calcium are fundamental for apoptosis, in that intracellular calcium chelators abrogate the process. Comparison of the gene expression profiles associated with ST1926 and ATRA in F9-WT and F9gamma-/-indicates that the RRM activates a conspicuous nonretinoid response in addition to the classic and RAR-dependent pathway. The pattern of genes regulated by ST1926 selectively, in a RARgamma-independent manner, provides novel insights into the possible molecular determinants underlying the activity of RRMs in vitro. Furthermore, it suggests that RARgamma-dependent responses are relevant to the activity of RRMs in vivo. Indeed, the receptor hinders the antitumor activity in vivo, in that both syngeneic and immunosuppressed SCID mice bearing F9gamma-/- tumors have increased life spans after treatment with ST1926 and CD437 relative to their F9-WT counterparts.     

Stimulation of vitamin A(1) acid signaling by the HIV protease inhibitor indinavir

HIV protease inhibitors (PIs) are effective drugs for the treatment of AIDS. However, PI therapy is sometimes associated with side-effects including increased plasma lipids and altered body fat distribution, although fat redistribution may occur in some patients not treated with PIs. Overdosage with vitamin A(1) acid (all-trans-retinoic acid, ATRA) or its metabolites may cause similar changes in lipid metabolism. Moreover, the PI indinavir and retinoids have been associated with nail, skin, and hair defects, suggesting that indinavir and retinoids may exert their effects through similar molecular mechanisms. This hypothesis was tested by examining the effects of PIs on retinoid signaling in vitro. Mesenchymal stem cells (C3H10T1/2) were cultured in the presence of various PIs (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) and synthetic retinoids, and the metabolic response was assessed by measuring the activity of a retinoid-regulated protein, alkaline phosphatase (ALP). Of the PIs tested, only indinavir stimulated ATRA-dependent ALP activity and altered stem cell morphology; the effects of indinavir occurred in the presence of ATRA, but not in its absence. Moreover, indinavir increased the effects of ATRA on lipid accumulation during fat cell differentiation. AGN 193109 (4-[[5,6-dihydro-5, 5-dimethyl-8-(4-methylphenyl)-2-naphthalenyl]ethynyl]-benzoic acid), a retinoic acid receptor (RAR) antagonist, inhibited the synergistic effects of indinavir and ATRA, indicating that indinavir increases RAR signaling. However, indinavir did not potentiate ALP activity in the presence of the RAR agonist CH55 (3,5-di-tert-butylchalcone 4'-carboxylic acid). Unlike ATRA, CH55 does not bind to cytosolic retinoic acid binding protein (CRABP), suggesting that CRABP may regulate the effects of indinavir on RAR signaling. These observations support the proposal that altered retinoid signaling promotes some of the adverse reactions associated with indinavir therapy, such as altered lipid metabolism.     

All-trans-retinoic acid 4-hydroxylation in human liver microsomes: in vitro modulation by therapeuticretinoids

All- trans retinoic acid (ATRA) induces remission in patients with acute promyelocytic leukaemia. Other retinoids, including 9- cis - and 13- cis -retinoic acid (9- cis - and 13- cis -RA), are now being evaluated for their therapeutic potential. The elimination of ATRA is partially dependent on cytochrome P450 (P450)-mediated 4-hydroxylation, but the interaction of other retinoids with P450 has not yet been assessed. In the present study 9- cis - and 13- cis -RAs, as well as all- trans -retinol and three isomeric retinals were found to inhibit ATRA 4-hydroxylation in human hepatic microsomes, but the arotinoids acitretin and etretinate were not inhibitors. 9- cis - and 13- cis -RA were competitive inhibitors of ATRA 4-hydroxylation ( K _i: K _m ratios 3.5±0.8 and 6.3±0.5, respectively) suggesting that these retinoids are alternate, but inferior, substrates for the P450 enzyme(s) that mediate the activity. The biotransformation of therapeutic retinoids containing the β-ionone ring system is likely to involve the microsomal ATRA 4-hydroxylase P450.     

全反式维甲酸对高糖诱导肾小管上皮细胞增殖及凋亡的影响

摘要： 目的 探讨全反式维甲酸 （ATRA） 对高糖诱导人 HK-2 细胞增殖及凋亡的影响, 以期延缓糖尿病肾病（DN）。方法 体外培养 HK-2 细胞, 随机分为 6 组： 空白组 （未加任何刺激物）、 高糖组 （加 D-葡萄糖 30 mmol/L）、 高渗组 （加入甘露醇 24.5 mmol/L）、 低浓度 ATRA 组 （加入 ATRA 1×10-7 mol/L+D-葡萄糖 30 mmol/L）、 中浓度 ATRA 组（加入 ATRA 1×10-6 mol/L+D-葡萄糖 30 mmol/L）、 高浓度 ATRA 组 （加入 ATRA 1×10-5 mol/L+D-葡萄糖 30 mmol/L）。各组细胞培养 48 h。MTT 法检测各组细胞增殖情况, 流式细胞术检测各组细胞凋亡情况。结果 空白组与高渗组细胞光密度 （OD） 值和凋亡率差异无统计学意义。高糖组较空白组、 高渗组细胞增殖减少, 凋亡率增加; 低浓度、 中浓度、 高浓度 ATRA 组细胞增殖均较高糖组增加, 且低、 中及高浓度 ATRA 组依次增加, 凋亡率较高糖组减少, 且低、 中及高浓度 ATRA 组依次减少 （均 P＜0.05）。结论 ATRA 可促进高糖诱导的 HK-2 细胞增殖, 抑制其凋亡, 并与 ATRA 浓度可能具有一定的依赖性。