芒果苷作用于COX-2和5-LOX双靶点改善良性前列腺增生炎症

目的 研究芒果苷对良性前列腺增生(benign prostatic hyperplasia, BPH)炎症的治疗作用及其潜在的作用机制。方法 Western Blot和q-PCR技术检测大鼠前列腺组织中环氧合酶-2(cyclooxygenase-2,COX-2)、5-脂氧合酶(5-lipoxygenase, 5-LOX)在蛋白水平上和mRNA水平上的表达，并用计算机分子对接技术加以佐证。此外，对前列腺湿质量(prostate weight, PW)、前列腺指数(prostate index, PI)、前列腺组织学形态进行考察。结果 Western Blot和q-PCR结果表明，芒果苷可抑制大鼠前列腺组织中COX-2和5-LOX在蛋白水平和mRNA水平上的表达，分子对接技术结果表明芒果苷与COX-2和5-LOX受体模型均有结合能力。同时，PW、PI及组织病理学切片结果均表明芒果苷可明显改善BPH炎症。结论 芒果苷同时作用于COX-2和5-LOX双靶点，通过下调COX-2和5-LOX的表达，从而改善BPH炎症。     

芒果苷对慢性炎症大鼠外周血单核细胞髓样分化因子88表达的影响

目的探讨芒果苷对脂多糖诱导慢性炎症大鼠外周血单核细胞髓样分化因子88表达的调控作用。方法以间断尾静脉注射小剂量脂多糖(200μg.kg-1)建立慢性炎症大鼠模型,大鼠随机分为对照组、模型组、泼尼松(5 mg.kg-1.d-1)组与芒果苷高、中、低剂量(MGF-H、MGF-M、MGF-L,200、100、50 mg.kg-1.d-1)组,灌胃给药,共4周。第4周末分离外周血单核细胞并经磁珠分选纯化,分别以RT-PCR、流式细胞术检测单核细胞髓样分化因子88的表达水平。结果与模型组比较,MGFH组外周血单核细胞髓样分化因子88过表达被明显抑制,全血白细胞计数与血清超敏C反应蛋白水平明显降低。结论芒果苷可抑制脂多糖诱导慢性炎症大鼠外周血单核细胞髓样分化因子88的过表达,可能与其抗炎作用有关。     

环氧合酶-2和5-脂氧化酶双重抑制剂的研究进展

传统的非甾体抗炎药和选择性环氧合酶-2(COX-2)抑制剂在治疗炎症过程中引发胃肠道及肾脏不良反应,制约了其临床应用。COX-2和5-脂氧化酶(5-LOX)双重抑制剂同时抑制前列腺素(PGs)和炎症介质白三烯类(LTs)的生物合成,比单一的抑制剂抗炎效果好、安全性高,是一类有发展前景的新型非甾体抗炎药。笔者简要介绍COX-2/5-LOX双重抑制剂的研究进展,并讨论其作用机制及构效关系     

积雪草苷对脂多糖诱导大鼠发热的预防及对相关炎症因子的影响

目的探索积雪草苷的解热作用。方法雄性SD大鼠56只,随机平均分为正常组、模型组、溶媒对照组、对乙酰氨基酚组和积雪草苷3个剂量组。除正常组外,每只大鼠ip细菌脂多糖(LPS)100μg.kg-1制备大鼠发热模型,连续6h监测大鼠体温变化,6h后取血、肝脏和脑组织标本。积雪草苷3个剂量组造模前连续3dig积雪草苷(5,15和45mg.kg-1),每日1次;正常组和模型组给予等量生理盐水;溶媒对照组给予等量0.5%羧甲基纤维素钠;对乙酰氨基酚组于造模前30min一次性给予对乙酰氨基酚(50mg.kg-1,ip)。肝组织髓过氧化物酶(MPO)活性采用MPO试剂盒检测,肝脏组织血红素氧化酶1(HO-1)和脑组织环氧合酶2(COX-2)蛋白表达采用Western印迹方法测定,血浆前列腺素E2(PGE2)含量用酶联免疫法检测,HO-1活性用Morita法检测。结果注射LPS后,模型组出现3相热,最高升温幅度为2.01℃。积雪草苷5,15和45mg.kg-1组体温明显低于模型组,其中45mg.kg-1组与对乙酰氨基酚组相当。与模型组比较,3个积雪草苷剂量组发热后6h肝组织MPO活性、脑组织COX-2蛋白表达和血浆中PGE2的产生明显降低,肝组织HO-1活性和蛋白表达升高。结论积雪草苷具有预防发热作用,该作用可能与抑制COX-2/PGE2系统,并抑制炎症因子MPO活性、增强炎症保护因子HO-1的活性和表达有关。     

环氧合酶-2和5-脂氧化酶双重抑制剂的研究进展

传统的非甾体抗炎药和选择性环氧合酶-2(COX-2)抑制剂在治疗炎症过程中引发胃肠道及肾脏不良反应.制约了其临床应用. COX-2和5-脂氧化酶(5-LOX)双重抑制剂同时抑制前列腺素(PGs)和炎症介质白三烯类(LTs)的生物合成.比单一的抑制剂抗炎效果好、安全性高,是一类有发展前景的新型非甾体抗炎药.笔者简要介绍COX-2/5-LOX双重抑制剂的研究进展,并讨论其作用机制及构效关系.     

选择性环氧合酶-2抑制剂体外筛选模型的建立

目的:建立选择性环氧合酶-2(COX-2)抑制剂筛选模型。方法:以脂多糖(LPS)为刺激剂刺激大鼠腹腔巨噬细胞产生前列腺素E2(PGE2),采用放免法确定最佳刺激浓度和时间,以选择性COX-2抑制剂戊地昔布和达布非隆(darbufelone)为阳性对照药验证实验模型。结果:达布非隆和戊地昔布对COX-2和COX-1的半数抑制浓度(IC50)的比值分别为3．175×10-4和3．576×10-3。结论:本实验建立的COX-2抑制剂筛选模型比较灵敏,可靠,可用于选择性COX-2抑制剂的筛选。     

5-脂氧合酶和结直肠癌关系的研究进展

结直肠癌是我国最常见的胃肠道恶性肿瘤之一,发病率仅次于食管癌和胃癌,且发病率和病死率呈逐年升高趋势.花生四烯酸代谢通路在肿瘤的发生发展中起着重要作用.环氧合酶(cyclooxygenase,COX)及脂氧合酶(lipoxygenase,LOX)是催化体内花生四烯酸代谢通路的两个关键酶,花生四烯酸可通过环氧合酶(COX)通路代谢,主要生成血栓素A2(TXA2)、前列环素(PGI2)、前列腺素E2(PGE2)、前列腺素D2(PGD2)、前列腺素F2α(PGF2α),参与多种疾病的发生;亦可通过脂氧合酶(LOX)途径生成具有生物活性的多种物质,如炎症介质HD4等.大量实验证明,脂氧合酶代谢途径中的代谢产物在肿瘤中表达升高,其表达水平与肿瘤的分期、分级、转移、预后生存相关,其代谢途径通过影响细胞的增殖、凋亡、血管生成、细胞的侵袭和迁移等机制参与肿瘤的发生发展.使用脂氧合酶抑制剂(lipoxygenase inhibitors)特别是5-脂氧合酶抑制剂(5-lipoxygenase inhibitors)可预防及抑制肿瘤的发生、发展.     

环氧合酶／5-脂氧合酶双重抑制剂的研究进展

非甾体类抗炎药(NSAID)广泛用于各种炎症的治疗。长期使用经典的NSAID会产生严重的副作用,尤其是胃肠道副作用。为避免经典的NSAID的副作用,开发出了选择性COX-2抑制剂,但长期使用选择性COX-2抑制剂对心血管系统有副作用。COX/5-LOX双重抑制剂通过同时阻断炎症介质前列腺素和白三烯的形成,产生协同的抗炎作用,有望提高疗效,同时避免COX抑制剂引发的副作用。本文对COX/5-LOX双重抑制剂的抗炎镇痛作用机制,以及研究现状进行综述。     

薯蓣皂苷对胶原性关节炎模型大鼠环氧合酶2及NF-κB的抑制作用

目的研究薯蓣皂苷对大鼠胶原性关节炎(CIA)的治疗作用并探讨其可能的作用机制。方法第1天大鼠左后足底皮内注射胶原乳剂制备CIA模型,第7天加强注射。第12天ig给予薯蓣皂苷30,60和120mg·kg-1,吲哚美辛8mg·kg-1,连续14d。给药前和给药开始,每4d测量1次右后足跖肿胀程度;处死后光镜观察右后足组织形态变化;检测CIA大鼠脏器指数;Western印迹法检测踝关节滑膜组织中NF-κB p65亚基和环氧合酶2蛋白(COX-2)表达;放射免疫法检测足爪肿瘤坏死因子α(TNF-α)及前列腺素E2(PGE2)含量。结果与正常对照组相比,CIA模型大鼠右后足跖明显肿胀(P<0.01);病理切片发现明显增生和大量炎症细胞浸润;胸腺指数和脾指数明显增高(P<0.01);踝关节滑膜组织中NF-κB p65亚基和COX-2的水平显著升高(P<0.01);足爪TNF-α及PGE2含量亦显著增高(P<0.01)。与模型组相比,薯蓣皂苷60和120mg·kg-1治疗可抑制CIA大鼠的足趾肿胀,明显改善大鼠病变关节的病理组织结构,降低大鼠胸腺指数,显著降低NF-κB p65亚基和COX-2的水平(P<0.01),降低足爪TNF-α及PGE2含量(P<0.01),对关节炎大鼠有明显的治疗作用。结论薯蓣皂苷对CIA大鼠具有较强的抗炎作用,机制可能与抑制NF-κB p65亚基和COX-2的表达有关。     

加味三棱丸含药血清对子宫内膜异位症内膜细胞芳香化酶及环氧合酶-2的影响

目的:观察子宫肌瘤与子宫内膜异位症(内异症)患者在位内膜芳香化酶(aromatase)和环氧合酶-2(cyclooxygenase-2,COX-2)表达上的差异,探讨加味三棱丸(SLW)含药血清对内异症在位内膜芳香化酶、COX-2表达的影响.方法:Westernblot和RT-PCR方法分别检测子宫肌瘤组、给予SLW含药血清前后内异症组芳香化酶、COX-2蛋白和mRNA的表达,发光免疫分析法及放射免疫分析法分别检测上述各组细胞上清中雌二醇及前列腺素E2的含量.结果:以未给药的内异症内膜组为对照,子宫肌瘤组芳香化酶、COX-2 mRNA蛋白的表达,分泌雌二醇及前列腺素E2水平均明显低于对照组,差异有显著性(P<0.05).SLW 5.0,2.5 g·kgll·d-1组芳香化酶、COX-2蛋白和mRNA的表达低于对照组,差异有显著性或极显著性(P<0.05或P<0.01).SLW 1.25 g·kg-1·d-1组芳香化酶mRNA和蛋白、COX-2蛋白的表达也明显低于对照组(P<0.01),但COX-2 mRNA的表达与对照组比较差异无显著性(P0.05).SLW 5.0,2.5,1.25 g·kg-1·d-1组分泌的雌二醇和前列腺素E2水平明显低于对照组(P<0.05).结论:SLW可抑制子宫内膜异位症在位内膜细胞芳香化酶和COX-2的表达,从而降低局部雌激素及前列腺素E2的水平.     

苦参碱调控环氧化酶-2的表达及对大鼠膀胱癌抑制作用的初步研究

目的研究苦参碱(matrine)对膀胱癌形成和发展的抑制作用及其对大鼠膀胱环氧化酶-2(COX-2)表达的影响。方法采用N-丁基-N-(4-羟丁基)亚硝基胺(BBN)诱发大鼠膀胱癌,苦参碱50、100和200 mg.kg-1灌胃给药35周后,分别以病理和免疫组织化学法观察苦参碱抑制膀胱癌的作用和对膀胱组织COX-2蛋白表达的影响。结果苦参碱对BBN诱导的大鼠膀胱癌变率无影响(P>0.05),但可抑制膀胱癌的生长(P<0.05),并可抑制浸润性膀胱癌的发生率(P<0.05)。免疫组化结果显示,与BBN组比较,苦参碱各剂量组均可降低大鼠膀胱癌组织中COX-2蛋白的表达(P<0.05)。结论苦参碱对BBN诱导大鼠膀胱癌的发生无抑制作用,但对膀胱癌的生长和进展具有抑制作用,其机制与抑制大鼠膀胱组织中COX-2蛋白的表达有关。     

Vascular responses to leukotriene B4, C4 and D4 following FPL 55712, indomethacin, saralasin, phentolamine and verapamil in the conscious rat.

The pressor and vascular permeability effects of leukotrienes B4 (LTB4), C4 and D4 were investigated in conscious unrestrained rats. Leukotrienes C4 and D4 (3.2-51 nmol kg-1 i.v.) caused an acute dose-dependent elevation of the mean arterial pressure, which was maximal after 2 min and returned to control levels within 14 min. Heart rate was significantly reduced by the higher doses of LTC4 and LTD4. LTB4 (up to a dose of 51 nmol kg-1) was essentially inactive. These effects of LTC4 and LTD4 were abolished by FPL 55712, a putative antagonist of sulphidopeptide leukotrienes and by verapamil, a calcium channel blocker. Indomethacin, phentolamine or saralasin pretreatment failed to modify the pressor response to LTC4 and LTD4. LTC4 and LTD4 furthermore caused an increase in haematocrit values, which was significantly attenuated by FPL 55712, indomethacin and verapamil. The present findings show that the pressor effect of LTC4 and LTD4 is not related to prostanoid release and can be reversed by calcium channel blockade; whereas the effect on vascular permeability seems to require the presence of both cyclo-oxygenase product(s) and calcium.     

Dual inhibitors of cyclooxygenase and 5-lipoxygenase. A new avenue in anti-inflammatory therapy?

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a mainstay in the treatment of inflammatory disease and are among the most widely used drugs worldwide. They are anti-inflammatory, antipyretic, and analgesic and are prescribed as first choice for the treatment of rheumatic disorders and, in general, inflammation. The main limitation in using NSAIDs consists in their side-effects, including gastrointestinal ulcerogenic activity and bronchospasm. The mechanism of action of these drugs is attributed to the inhibition of cyclooxygenase (COX), and, consequently, the conversion of arachidonic acid into prostaglandins. It is hypothesized that the undesirable side-effects of NSAIDs are due to the inhibition of COX-1 (constitutive isoform), whereas the beneficial effects are related to the inhibition of COX-2 (inducible isoform). Arachidonic acid can also be converted to leukotrienes (LTs) by the action of 5-lipoxygenase (5-LOX). LTC(4,) LTD(4,) and LTE(4) are potent bronchoconstrictors, whereas LTB(4) is chemotactic for leukocytes and plays an important role in the development of gastrointestinal ulcers by contributing to the inflammatory process. Thus, developing dual inhibitor compounds that will simultaneously inhibit COX and 5-LOX could enhance their individual anti-inflammatory effects and reduce the undesirable side-effects associated with NSAIDs, especially of the gastrointestinal tract. The most promising COX/5-LOX inhibitor is ML3000 ([2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2,3-dihydro-1H-pyrrolizine-5-yl]-acetic acid), now in Phase III clinical trials. This new approach will certainly help to unravel the mechanisms at the root of the undesirable effects of NSAIDs and to develop safer NSAIDs.     

Stimulation of arachidonic acid metabolism and generation of thromboxane A2 by leukotrienes B4, C4 and D4 in guinea-pig lung in vitro.

1 Leukotriene C4 (LTC4), LTD4, slow-reacting substance of anaphylaxis (SRS-A) (from guinea-pig lung), bradykinin (Bk) and arachidonic acid (AA) release thromboxane A2 (TxA2) and prostaglandin-like materials from guinea-pig isolated perfused lungs. 2 Release of TxA2 induced by LTC4 and LTD4 is inhibited by a thromboxane synthetase inhibitor, imidazole (2.9 mM). 3 Mepacrine (200 microM), a phospholipase inhibitor, inhibits release of TxA2 and prostaglandin-like materials caused by SRS-A and Bk but not that due to exogenous AA 4 Leukotrienes B4, C4 and D4 are approximately equipotent in inducing dose-related contractions of guinea-pig parenchymal strips (GPPs). 5 Leukotriene-induced contractions of GPPs are greatly inhibited by imidazole (2.9 mM), carboxyheptylimidazole (24 microM) and mepacrine (400 microM). 6 FPL 55712 (1.9 microM), the SRS-A antagonist, blocks contractions of GPPs induced by LTC4 and LTD4 but not those due to LTB4 or Bk. 7 Tachyphylaxis to LTB4 occurs in GPPs but not to LTC4 or LTD4. 8 These results suggest that in guinea-pig lung in vitro, LTB4, LTC4 and LTD4 activate a phospholipase with subsequent generation of cyclo-oxygenase products of which TxA2 plays an important role.     

Responses of human skin to intradermal injection of leukotrienes C4, D4 and B4.

The ability of intradermally injected leukotrienes C4 (LTC4), LTD4 and LTB4 to produce inflammatory changes in human skin alone and in combination with prostaglandin E2 (PGE2) has been investigated. LTC4 and D4 (0.012-0.38 nmol) caused dose-related erythema and wealing. No evidence of synergism between PGE2 and LTC4 or LTD4 was detected, although only single dose combinations were studied. LTB4 (0.15-1.5 nmol) caused areas of induration which persisted for more than 4 h and which showed perivascular neutrophil infiltrates on histological examination. Only slight synergism between PGE2 and LTB4 was found. It was concluded that these pro-inflammatory properties of LTC4, LTD4 and LTB4 are consistent with their proposed roles as mediators of inflammation in the skin and other tissues.     

Leukotriene formation by human polymorphonuclear leukocytes from endogenous arachidonate. Physiological triggers and modulation by prostanoids

Human polymorphonuclear leukocytes (PMN) were isolated from freshly drawn venous blood by Dextran sedimentation and discontinuous Percoll gradient centrifugation. The effects of several putative triggers of the leukotriene formation such as C5a, PAF, FMLP, C3a, PMA, LTC4, LTD4, LTB4 or arachidonate were studied by RP-HPLC analysis. 280 nM C5a, 100 nM FMLP, 1 microM PAF or 20 microM arachidonate induced a marginal formation of 1.5-18 ng of LTB4 plus LTB4 metabolites/2 x 10(7) PMN. 560 nM C3a, 100 nM PMA, 1 microM LTC4, 1 microM LTD4 and 1 microM LTB4 each failed to induce any formation of 5-lipoxygenase products. Pretreatment of the cells with 40 microM ethylmercurithiosalicylate (merthiolate) enhanced the leukotriene formation by 100 nM FMLP about 40-fold, by 280 nM C3a about 120-fold and by 1 microM PAF about 14-fold. Merthiolate itself induced no leukotriene formation from human PMN and reduced the leukotriene formation by 20 microM arachidonate. The FMLP/merthiolate-induced activation of the PMN was concentration-dependent in respect to both FMLP and merthiolate. 1 microM LTC4, 1 microM LTD4 or 1 microM LTB4 also failed to trigger any LTB4 formation of merthiolate-treated PMN. 560 nM C3a or 100 nM PMA in combination with 40 microM merthiolate induced a slight formation of 28 ng and 10 ng of LTB4 plus LTB4 metabolites, respectively. The FMLP/merthiolate-induced leukotriene formation was modulated by prostanoids. PGE2, PGE1, PGD2 and 6-keto-PGE1 each evoked a concentration-dependent inhibition of the leukotriene formation with IC50 values of 0.07 microM, 0.18 microM, 0.27 microM and 6 microM respectively. In addition, significant inhibitory effects by PGI2, Iloprost (a carbacyclin analogue of prostacyclin), PGF2a or 6-keto-PGF1a were achieved; the corresponding IC50 values, however, amounted to 19-59 microM. Thus these compounds were about 500-fold less potent in comparison with PGE2 in inhibiting LTB4 formation by human PMN.     

Failure of the inhibition of rat gastric mucosal 5-lipoxygenase by novel acetohydroxamic acids to prevent ethanol-induced damage.

1. The role of leukotriene B4 (LTB4) and LTC4 as mediators of gastric mucosal damage following ethanol challenge in vivo has been investigated using two selective 5-lipoxygenase inhibitors, BW A4C and BW A137C. 2. Oral administration of ethanol to rats in vivo, induced macroscopic damage to the gastric mucosa and markedly increased the formation of the 5-lipoxygenase products, LTB4 and LTC4, from the mucosa ex vivo. 3. Pretreatment with the acetohydroxamic acids BW A4C and BW A137C (5-50 mg kg-1 p.o.) dose-dependently reduced ethanol-stimulated LTB4 and LTC4 formation by the gastric mucosa, with an ID50 of approximately 5 mg kg-1 p.o. 4. A single oral dose of BW A4C (20 mg kg-1) induced near-maximal inhibition of mucosal LTB4 formation within 30 min, which was well maintained for 5 h, whereas BW A137C (20 mg kg-1 p.o.) induced maximal inhibition between 30 and 60 min after administration, which then diminished over the subsequent 5 h. 5. The mucosal formation of the cyclo-oxygenase product, 6-keto-prostaglandin F1 alpha, which was unaltered following ethanol challenge, was not inhibited by the acetohydroxamic acids. Likewise, the small increase in mucosal thromboxane B2 formation following challenge was not inhibited by BW A4C. 6. Neither BW A4C nor BW A137C, at doses that almost completely inhibited the mucosal synthesis of LTB4 or LTC4, reduced the macroscopic gastric mucosal damage induced by ethanol. 7. Pretreatment with the lipoxygenase inhibitor BW 755C (5-50 mg kg-1 p.o.) did reduce mucosal damage, but there was a dissociation between the degree of protection and the inhibition of leukotriene biosynthesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of two benzimidazoles as proton pump inhibitors on water immersion stress-induced gastric ulcers in rats.

This study was designed to clarify effects of proton pump inhibitors, E-3810(2-([4-(3-methoxypropoxy)-3methylpyridine-2-yl]methyl- sulfinyl)-1H-benzimidazol sodium salt) and omeprazole (CAS 73590-58-6), on water immersion stress-induced gastric ulcers in relation to mucosal prostaglandins (PGs) and leukotrienes (LTs). Mucosal PGs were measured by high performance liquid chromatography (HPLC). In untreated rats, 4 kinds of PGs, i.e., 6-keto-PGF1 alpha, PGF2 alpha, PGE2 and PGD2 were detected in gastric mucosa, but no LTs were detected. Water immersion stress for 6 h caused severe hemorrhagic lesions in the fundic portion and, concomitantly, significant decreases in mucosal PG levels. On the other hand, LTC4 and LTD4 were detected after 6 h stress treatment, though LTB4 and LTE4 were not detected throughout the experiments. Peptide-LT (the sum of LTC4 and LTD4) levels were 23.5 +/- 3.2 ng/g tissue 6 h after water immersion stress. Administration of 20 mg/kg of E-3810 or 20 mg/kg of omeprazole mitigated gastric lesions and increases in the mucosal peptide-LT levels, but dit not improve the decrease in mucosal PGs.     

Species differences in release of arachidonate metabolites in response to inhaled diluted diesel exhaust

In life-span studies in CD-1 mice and F344/Crl rats, inhaled diluted diesel exhaust was highly fibrogenic in rats but not in mice. This was the case despite the higher lung burden, in mg soot/g lung, achieved in mice compared to rats. We tested the hypothesis that the greater fibrogenicity of the soot in rats was due in part to greater release of mediators of inflammation from alveolar cells in rats compared to mice. Female F344/rats and B6C3F1 mice were exposed for up to 17 days to diluted diesel exhaust containing 3.5 mg/m3 of soot. The lungs of control and soot-exposed animals were lavaged after 2, 12 or 17 days of exposure. The presence of leukotriene (LT)B4, LTC4, prostaglandin (PG)E2, PGF2 alpha and thromboxane (TX) B2 in the lavage fluids and LTB4 and PGF2 alpha in cultured lavage cell supernatants was determined. The total amount of each lavage fluid constituent was normalized to lung weight for species comparisons. Control rats had higher levels of TXB2 (16-fold), and LTB4 (6-fold) and PGE2 (2-fold) than control mice, but control mice had higher amounts of LTC4 (4-fold). Control rats and mice had approximately the same amounts of PGF2 alpha/g lung in bronchoalveolar lavage fluid (BALF). Rats exposed to diesel exhaust had increases in BALF PGF2 alpha and LTB4 that were highest after 2 days of exposure and decreased thereafter. Mice had lesser increases in both parameters. Rat cells recovered from lavage fluid released larger amounts of LTB4 into culture supernatants than mouse cells. The data were consistent with the hypothesis that soot-laden rat alveolar cells release greater quantities of mediators of inflammation than do the alveolar cells in mice.