Tachykinin dysfunction attenuates monocrotaline-induced pulmonary hypertension

We explored the dysfunction of tachykinins on monocrotaline (MCT)-induced pulmonary hypertension by using double-stranded preprotachykinin (ds PPT) RNA and neurokinin receptor (NK) antagonists. Here, we showed the possibility to attenuate the PPT gene expression by ds RNA, RNA interference (RNAi), in fully developed tissue of rats. We designed four groups (control, MCT, RNAi + MCT, and solvent + MCT) of experiments in series 1 and seven groups (control, MCT, MCT + CP-96345-3.4, MCT + CP-96345-10, MCT + CP-96344-10, MCT + SR-48968, and MCT + SR-48965) of experiments in series 2. Rats in the control groups received saline injection. MCT-treated rats received a single MCT injection (60 mg/kg sc). One day prior to MCT, bilateral nodose ganglia were microinjected with ds PPT RNA in rats of the RNAi + MCT group or with solvent in the solvent + MCT group. Beginning from 1 day post-MCT, MCT-treated rats received a daily injection of the NK(1) receptor antagonist, CP-96345 (3.4 or 10 mg/kg ip) or its inactive enantiomer CP-96344 (10 mg/kg ip). The NK(2) receptor antagonist SR-48968 (3 mg/kg ip) or its inactive enantiomer SR-48965 (3 mg/kg ip) was injected to MCT-treated rats every other day starting 1 day post-MCT. Functional study was carried out 2 weeks (series 1) or 3 weeks (series 2) after MCT. MCT induced right ventricular hypertrophy, as well as increases in pulmonary arterial pressure, PPT mRNA (nodose ganglia and lung tissue), and lung tissue substance P level. All of the above MCT-induced alterations were attenuated by either RNAi or NK receptor antagonists. We conclude that tachykinins play an important role in MCT-induced pulmonary hypertension.     

DA-8159, a potent cGMP phosphodiesterase inhibitor,attenuates monocrotaline-induced pulmonary hypertension in rats

In this study, we evaluated the effects of oral administration of DA-8159, a selective phosphodiesterase-5 inhibitor, on the development of pulmonary hypertension (PH) induced by monocrotaline (MCT). Rats were administered either MCT (60 mg/kg) or saline. MCT-treated rats were divided into three groups and received orally administered vehicle, or 1 mg/kg or 5 mg/kg of DA-8159, twice a day for twenty-one days. The MCT group demonstrated increased right ventricular weights, medial wall thickening in the pulmonary arteries, myocardial fibrosis and the level of plasma cyclic guanosine monophosphate (cGMP), along with decreased body weight gains. However, DA-8159 markedly and dose-dependently reduced the development of right ventricular hypertrophy and medial wall thickening. DA-8159 also amplified the increase in plasma cGMP level and significantly increased the level of lung cGMP, compared with the MCT group. Although the body weight gain was still lower from the saline-treated control group, DA-8159 demonstrated a significant increase in body weight gains, in both 1 mg/kg and 5 mg/kg groups, when compared with the MCT group. In myocardial morphology, MCT-induced myocardial fibrosis was markedly prevented by DA-8159. These results suggest that DA-8159 may be a useful oral treatment option for PH.     

2-Methoxyestradiol mediates the protective effects of estradiol in monocrotaline-induced pulmonary hypertension

When exposed to chronic hypoxia or toxin monocrotaline (MCT), female animals develop less severe pulmonary arterial hypertension (PH) compared to males; ovariectomy (OVX) exacerbates PH, and OVX animals treated with estradiol (E2) develop less severe disease. There is a line of evidence suggesting that cardiovascular protective effects of E2 are mediated by its major metabolite, 2-methoxyestradiol (2ME). Recently, we have shown that 2ME attenuates the development and retards the progression of MCT-induced pulmonary hypertension in male rats. We hypothesized that the protective effects of E2 in experimental PH are mediated by 2ME. Subsets of intact and OVX female rats were injected saline (Cont and OXV groups) or MCT (60 mg/kg; MCT and OVX-MCT groups) and some of OVX-MCT animals were treated with 2ME (10 microg/kg/h via osmotic minipumps; OVX-MCT+2ME). After 28 days, MCT caused PH, i.e., increased right ventricular peak systolic pressure (RVPSP) and right ventricle/left ventricle+septum (RV/LV+S) ratio, induced inflammatory response in the lungs and caused media hypertrophy (media thickness and % media index) and adventitia widening of small size pulmonary arteries. Ovariectomy exacerbated the disease, i.e., further increased RVPSP, and RV/LV+S ratio, and augmented vascular remodeling and inflammatory response. In diseased OVX rats, treatment with 2ME prevented the worsening of PH and attenuated the inflammatory response and vascular remodeling. No mortality was recorded in the OVX-MCT+2ME group vs. 10% and 36% mortality in the MCT and OVX-MCT group, respectively. This study suggests that 2-methoxyestradiol (a major non-estrogenic metabolite of E2) may mediate the protective effects of estradiol in MCT-induced PH, and warrants further evaluation of 2ME for treatment of PH.     

新型磷酸二酯酶5抑制剂CPD1对肺动脉高压大鼠血管收缩的影响

目的探讨新型磷酸二酯酶5抑制剂CPD1对肺动脉高压(pulmonary arterial hypertension,PAH)大鼠肺动脉和主动脉收缩效应的影响。方法一次性腹腔注射野百合碱(monocrotaline,MCT,50 mg·kg^-1),制备PAH大鼠模型,造模7 d后给予CPD1(10 mg·kg^-1·d^-1)灌胃治疗,持续14 d。通过血管环张力检测技术观察CPD1对MCT致PAH大鼠血管收缩效应的作用。结果成功制备PAH大鼠模型;CPD1治疗可显著降低PAH大鼠右心室收缩压和右心质量指数,改善肺小动脉内膜增生情况,抑制苯肾上腺素(phenylephrine,Phen)和内皮素-1(endothelin-1,ET-1)诱导的PAH大鼠肺动脉和主动脉的收缩效应,而对KCl诱导的血管收缩效应无影响。结论磷酸二酯酶5抑制剂CPD1干预能抑制PAH大鼠模型,其机制可能是CPD1抑制PAH大鼠非电压依赖性钙通道功能,引起血管收缩力降低、血管平滑肌增殖减弱和血管重塑减轻。     

野百合碱诱导的肺动脉高压大鼠肺血管5-HT转载体表达增强

目的　研究野百合碱诱导的大鼠肺动脉高压与5 HT转载体基因表达的关系。方法　应用MCT诱导的慢性肺动脉高压大鼠模型,建立离体动脉环5 HT浓度反应曲线;HE染色观察肺动脉构型重建,应用RT PCR检测大鼠肺动脉5 HT转载体mRNA表达。结果　MCT大鼠肺血管对5 HT收缩反应增强,肺肌型小动脉中膜增厚,MCT诱导的肺动脉高压大鼠肺血管5 HT转载体mRNA表达明显增多。5 HT转载体基因表达与肺肌型小动脉中膜增厚有明显相关性。结论　MCT诱导的肺动脉高压大鼠肺血管构型重建及5 HT引起收缩反应增强,伴有5 HT转载体mRNA表达增多;同时5 HT转载体mRNA表达与肺肌型小动脉中膜增厚有明显相关性,提示5 HT转载体可能在肺动脉高压中起重要作用。     

Modes of cell death in rat liver after monocrotaline exposure.

Monocrotaline (MCT) is a pyrrolizidine alkaloid (PA) plant toxin that produces sinusoidal endothelial cell (SEC) injury, hemorrhage, fibrin deposition, and coagulative hepatic parenchymal cell (HPC) oncosis in centrilobular regions of rat livers. Cells with apoptotic morphology have been observed in the livers of animals exposed to other PAs. Whether apoptosis occurs in the livers of MCT-treated animals and whether it is required for full manifestation of pathological changes is not known. To determine this, rats were treated with 300 mg MCT/kg, and apoptosis was detected by transmission electron microscopy and the TUNEL (TdT-mediated dUTP nick end labeling) assay. MCT produced significant apoptosis in the liver by 4 h after treatment. To determine if MCT kills cultured HPCs by apoptosis, HPCs were isolated from the livers of rats and exposed to MCT. MCT caused a concentration-dependent release of alanine aminotransferase (ALT), a marker of HPC injury. Furthermore, caspase 3 was activated and TUNEL staining increased in MCT-treated HPCs. MCT-induced TUNEL staining and release of ALT into the medium were completely prevented by the pancaspase inhibitors z-VAD.fmk and IDN-7314, suggesting that MCT kills cultured HPCs by apoptosis. To determine if caspase inhibition prevents MCT-induced apoptosis in the liver, rats were cotreated with MCT and IDN-7314. IDN-7314 reduced MCT-induced TUNEL staining in the liver and release of ALT into the plasma. Morphometric analysis confirmed that IDN-7314 reduced HPC oncosis in the liver by approximately 50%. Inasmuch as HPC hypoxia occurred in the livers of MCT-treated animals, upregulation of the hypoxia-regulated cell-death factor, BNIP3 (Bcl2/adenovirus EIB 19kD-interacting protein 3), was examined. BNIP3 was increased in the livers of mice treated 24 h earlier with MCT. Results from these studies show that MCT kills cultured HPCs by apoptosis but causes both oncosis and apoptosis in the liver in vivo. Furthermore, caspase inhibition reduces both apoptosis and HPC oncosis in the liver after MCT exposure.     

The relative estrogenic activity of technical toxaphene mixture and two individual congeners

Some studies have indicated that the injury induced by the hepato- and pneumotoxin monocrotaline (MCT) is in part mediated by oxidation. Because beta-carotene is a potent antioxidant, we hypothesized that it would protect the lung and liver parenchyma against MCT-induced injury. Twenty rats were assigned randomly to four groups. All rats were fed a standard AIN93G diet with or without beta-carotene. After 1 week on the purified diets, half of the rats fed the control (standard) diet and half of the rats fed the beta-carotene-supplemented diet were injected subcutaneously with 60 mg MCT/kg body weight or its vehicle (water). All rats were sacrificed at 4 weeks. Histological examination showed that beta-carotene alone did not affect lung or liver structure. On the other hand, lungs of MCT-treated rats had severe focal pneumonia, extensive deposition of collagen in the septa, marked inflammation of the small arteries and arterioles, and arterialization of the small venules. Livers of MCT-treated rats showed some fatty infiltration and diffuse hemorrhages, more prominent sometimes in the centrilobular area and sometimes in the periportal region. Concomitant treatment with beta-carotene protected the lung parenchyma from the inflammatory reaction and the septal fibrosis, but did not prevent cardiac right ventricular hypertrophy and only slightly reduced the thickening of the wall of small arteries and arterioles. Incidence of steatosis and hemorrhages was decreased in the liver. These results indicate that MCT-induced pulmonary vascular remodeling occurs in the absence of inflammatory cell infiltration. Furthermore, beta-carotene prevented inflammation and protected the lung and liver parenchyma of MCT-treated rats.     

Roles of endothelin ETA and ETB receptors in the pathogenesis of monocrotaline-induced pulmonary hypertension

The functional roles of endothelin ETA and ETB receptors in the development of monocrotaline (MCT)-induced pulmonary hypertension were investigated using MCT-treated rats in the absence or presence of a daily administration of A-192621, a selective ETB receptor antagonist, ABT-627, a selective ETA receptor antagonist, or a combination of both drugs. Four weeks after the injection of saline or MCT (60 mg/kg, s.c.), cardiac hypertrophy, right ventricular systolic pressure and morphologic changes of pulmonary arteries were evaluated. Compared with the control animals, MCT produced marked pulmonary hypertension associated with increases in right ventricular pressure and hypertrophy, and pulmonary arterial medial thickening. These MCT-induced alterations were markedly suppressed by daily treatment with ABT-627 for 4 weeks (10 mg/kg/d, twice daily), whereas treatment with A-192621 significantly aggravated the above MCT-induced pathologic changes. The blockade of both receptor subtypes by a combination of A-192621 and ABT-627 also significantly improved the MCT-induced pathologic changes, to the same extent as with ABT-627 administration. Thus, an exaggerated response to MCT during ETB receptor blockade also seems to be mediated by ETA receptor activation, thereby suggesting that ETA receptor-mediated action is exclusively contributive to the pathogenesis of MCT-induced pulmonary hypertension, although we cannot rule out a protective role of ETB receptor-mediated action.     

CPU0213, a non-selective ETA/ETB receptor antagonist, improves pulmonary arteriolar remodeling of monocrotaline-induced pulmonary hypertension in rats

1. The aim of the present study was to explore the effects of CPU0213, a dual endothelin ET(A)/ET(B) receptor antagonist, and nifedipine, a calcium antagonist, in relieving pulmonary hypertension (PH). Both endothelin receptor and calcium antagonists have been reported to be effective in alleviating the remodelling of pulmonary arteries induced by monocrotaline (MCT) in rats. 2. After an initial single dose of 60 mg/kg, s.c., MCT, CPU0213 was administered to rats at doses of 25, 50 or 100 mg/kg, p.o., for 28 days. In addition, nifedipine was administered to another group of rats at a dose of 10 mg/kg, p.o., for 28 days. The haemodynamics of the right ventricle, pulmonary vascular activity, remodelling of the pulmonary arterioles (< 150 microm) and biochemical changes were evaluated. 3. Right ventricular systolic pressure (RVSP), central venous pressure (CVP), the maximum rate of uprising pressure (dP/dT(max)) and the weight index of the right ventricle were significantly elevated in MCT-treated rats. In addition, increases in pulmonary endothelin-1, malonyldialdehyde (MDA) and hydroxyproline content and a reduction in superoxide dismutase activity was found after MCT treatment. The thickness and area of the pulmonary arterial wall were significantly increased in MCT-treated rats compared with control rats. At all three doses tested, CPU0213 ameliorated these changes in a dose-dependent manner and the effects were associated with a greater reduction in the remodelling of pulmonary arterioles. However, nifedipine was only partially effective in amelerioating biochemical and haemodynamic changes induced by MCT, significantly reducing RVSP, CVP, +dp/dt(max), tissue MDA, inducible nitric oxide synthase and hydroxyproline content, increasing -dp/dt(min) and having no effect on the other parameters investigated. In addition, nifedipine had no effect on remodelling of the arterial wall. 4. In conclusion, CPU0213 is more effective than nifedipine in suppressing the remodelling of pulmonary arterioles in PH induced by MCT treatment of rats. Furthermore, CPU0213 may have promise in treating PH secondary to connective tissue disease.     

Effects of a chronic exercise training protocol on oxidative stress and right ventricular hypertrophy in monocrotaline-treated rats

1. In the present study, we investigated the effects of exercise training on cardiac hypertrophy and oxidative stress in a monocrotaline (MCT)-induced cor pulmonale model. Male Wistar rats were assigned to one of three groups: sedentary control (SC); sedentary MCT (SM); or trained MCT (TM). 2. Right ventricular hypertrophy (RVH) was induced by a single injection of MCT (60 mg/kg, i.p.). Exercise training consisted of running on a treadmill (five times a week, during Weeks 3, 4 and 5). Systemic oxidative stress was evaluated in erythrocytes by chemiluminescence (CL) and the activity of the anti-oxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) was determined. 3. At Week 3, MCT-treated animals exhibited RVH, lung congestion, decreased SOD activity and increased CAT activity. Exercise training reduced MCT-induced RVH and increased GST activity. At Week 4, MCT-induced RVH was accompanied by an increase in CL and GST activity. However, in TM animals there was a decrease in CL and augmented SOD activity. At Week 5, there were no survivors in the SM group, whereas GST activity was elevated in TM rats compared with SC rats. There was no difference in GPx activity throughout the experimental protocol between the groups. 4. Taken together, our results indicate that exercise training is able to ameliorate RVH and improve survival, which is associated with a reduction in oxidative stress in MCT-treated rats.     

A urotensin II receptor antagonist,KR36676, decreases vascular remodeling and inflammation in experimental pulmonary hypertension

The pathophysiological implications of binding of urotensin II (U-II) to urotensin II receptor (UT) in pulmonary arterial hypertension (PAH) have been proposed recently. Besides high expression of U-II in experimental models and patients with PAH, U-II has been shown to increase proliferation of pulmonary vascular smooth muscle cells and inflammatory responses, which were critical for PAH pathophysiology. However, the direct role of the urotensinergic system in the pathogenesis of PAH is yet to be understood. The aim of the present study was to determine whether a novel UT antagonist, KR36676, attenuates the pathophysiological progression of PAH in an animal model of PAH. PAH was induced by a single subcutaneous injection of monocrotaline (MCT, 60 mg/kg) in rats. All the animals received KR36676 (30 mg/kg/day) or vehicle by oral gavage. Three weeks after MCT-injection, changes in hemodynamic parameters, extent of right ventricular hypertrophy, fibrosis and pulmonary vascular remodeling, and degree of protein expression were determined. Oral administration of KR36676 effectively decreased the MCT-induced increase in right ventricular systolic pressure, hypertrophy and fibrosis. Furthermore, wall thickness of pulmonary arterioles, proliferation of pulmonary vascular cells, and inflammatory response significantly decreased in the KR36676-treated group following MCT injection compared to that in the MCT-treated vehicle group. These preventive effects of KR36676 are mediated, at least in part, by suppression of ERK1/2 and NF-κB signaling pathways. The novel UT antagonist, KR36676, effectively prevented MCT-induced PAH progression and pulmonary vascular remodeling in rat model. Our findings support the therapeutic efficacy of UT antagonist in PAH prevention and elucidate the possible underlying mechanisms of action.     

间尼索地平对野百合碱诱导的肺动脉高压防治作用及其抗5-羟色胺—细胞外信号调节激酶通路的机制探讨

研究间尼索地平对野百合碱诱导的肺动脉高压的防治作用及其作用机制。大鼠单剂量皮下注射野百合碱(60 mg·kg^-1)制备肺动脉高压模型。导管法测定肺血流动力学指标；光镜观察肺小动脉结构的改变；同时测定血清中MDA及SOD的含量(活性)；免疫印迹法测定PCNA、ERK1和p-ERK的表达水平；免疫组化法观察5-HT和PCNA的表达。结果表明，与正常对照组相比，模型组大鼠的平均肺动脉压及右心指数明显增加；肺小动脉肌化程度加重；丙二醛含量显著升高，超氧化物歧化酶活性明显降低；PCNA和5-HT阳性细胞数目明显增加；PCNA蛋白表达及p-ERK/ERK1比率也显著增加，不同剂量间尼索地平在一定程度上逆转了上述变化。间尼索地平对野百合碱诱导的肺动脉高压表现出一定的保护作用。这一作用可能与其降低5-HT的表达，抑制ERK/MAPK信号通路有关。     

鲁斯可皂苷元对野百合碱诱导的肺动脉高压大鼠炎症反应的影响

目的研究鲁斯可皂苷元(ruscogenin,RUS)对野百合碱(monocrotaline,MCT)诱导的肺动脉高压(pulmonary arteryhypertension,PAH)大鼠炎症反应的影响。方法将36只清洁级SD大鼠随机分为对照(Control)组、MCT组、RUS+MCT(RUS)组(每组12只)。MCT组及RUS组大鼠给予MCT 60 mg.kg-1腹腔注射1次,第1～21天,RUS组每天给予RUS 0.4 mg.kg-1灌胃,Control组和MCT组给予相同量溶剂灌胃。第22天测量各组大鼠体重、平均肺动脉压(mPAP),HE染色观察肺小动脉血管壁病理变化,酶联免疫吸附法(ELISA)测定第各组大鼠外周血及肺组织炎症因子白细胞介素-1β(IL-1β)的含量,ED1+单核细胞免疫组化测定肺小动脉周围单核细胞的浸润。结果 RUS可抑制MCT诱导的大鼠mPAP升高、肺动脉壁(pulmonary aterial wallthickness,PAWT)增厚、肺动脉周围单核细胞浸润,降低大鼠外周血及肺组织IL-1β的水平。结论 RUS可能通过抑制肺血管炎症反应、降低肺动脉压及肺小动脉厚度防治肺动脉高压。     

2-Ethoxyestradiol is antimitogenic and attenuates monocrotaline-induced pulmonary hypertension and vascular remodeling

Our previous studies show that 2-methoxyestradiol, a non-estrogenic metabolite of estradiol (E2), attenuates the development and retards the progression of pulmonary hypertension (PH) in male rats, and in female rats prevents the exacerbation of PH and eliminates mortality due to ovariectomy. Recent studies suggest that 2-ethoxyestradiol (2-EE), a synthetic analog of 2-ME, is an even more potent antimitogen than 2-ME. The goals of this study were: 1) to compare the effects of E2, 2-ME and 2-EE on proliferation of human pulmonary artery endothelial (hPAEC) and smooth muscle cells (hPASMC) and lung fibroblasts (hLF); 2) to examine the effects of 2-ME, its metabolic precursor 2-hydroxyestradiol (2-HE) and 2-EE on isoproterenol (ISO)-induced cardiac hypertrophy in male rats; and 3) to investigate in male rats the effects of 2-EE (10 mug/kg/h via osmotic pump) on the development of monocrotaline (MCT; 60 mg/kg i.p.)-induced PH. E2 had biphasic effects on growth (stimulation at low and inhibition at high concentrations) in hPAEC and mild growth inhibitory effects in hPASMC and hLF (1-10 muM). In contrast, in all three pulmonary cell lines, 2-ME and 2-EE inhibited cell growth with 2-EE being ten times more potent than 2-ME. In ISO-induced cardiac hypertrophy, 2-ME, 2-HE and 2-EE similarly reduced (~-50%) left (LV) and right (RV) ventricular hypertrophy and fibrosis (hydroxyproline content). In animals with MCT-induced PH, treatment with 2-EE for 28 days significantly decreased the elevated RV peak systolic pressure and reduced RV/LV+septum weight ratio, strongly inhibited vascular remodeling (media hypertrophy and adventitia widening), markedly reduced inflammatory responses, and eliminated MCT-induced (63%) mortality. This study provides the first evidence that 2-ethoxyestradiol strongly inhibits vascular remodeling in PH and suggests that anti-proliferative agents, including synthetic analogs of estradiol metabolites may be protective in PH.     

Tetrandrine prevents monocrotaline-induced pulmonary hypertension in rats

In this study, the effects of chronic administration of tetrandrine (TET) on monocrotaline (MCT) induced pulmonary hypertension were investigated. The results showed that MCT induced marked pulmonary hypertension and right ventricular hypertrophy; TET 50 mg kg⁻¹ and 100 mg kg⁻¹ significantly decreased pulmonary artery pressure (Ppa, from 5.2 ± 0.48 kPa to 4.35 ± 0.69 kPa, P < 0.05 and to 3.79 ± 0.84 kPa, P < 0.05, respectively) without marked influence on systemic arterial pressure (Psa). TET restored right ventricular hypertrophy (right ventricular index significantly decreased from 0.41 to 0.37 and 0.32, respectively). Histological findings showed that TET restored MCT-induced lung tissues and vascular lesion and pulmonary arteries media hypertrophy. We conclude that chronic administration of TET does have selective effects on pulmonary hypertension produced by MCT. Drug Dev. Res. 39:158–160. © 1997 Wiley-Liss, Inc.     

Effects on cytokines and histology by treatment with the ACE inhibitor captopril and the antioxidant retinoic acid in the monocrotaline model of experimentally induced lung fibrosis

Monocrotaline (MCT), a pyrrolizidine alkaloid extracted from the shrub Crotalaria spectabilis, induces in the lungs of many mammalian species severe hypertension and fibrosis. Previous work with MCT-induced lung disease in rats has shown that some of the steps to progressive fibrosis can be interrupted or decreased by intervention with retinoic acid (RA) or with the angiotensin converting enzyme inhibitor, captopril. This report emphasizes the pathology and cytokines present in lungs of rats in the MCT model of hypertension and fibrosis in 8 treatment groups, six per group: (1) controls, not treated; (2) captopril; (3) RA; (4) combined captopril and RA. Groups 5-8 replicated groups 1-4 and also received MCT subcutaneously. Tissues were harvested at 28 days for histopathology and measurement of cytokines TGFbeta, TNFalpha, interleukin 6, and IFN_. TGFbeta was depressed at 28 days by MCT, an effect reversed by a combination of captopril and RA. RA influences production of an important Th1 cytokine, IFN_, and demonstrated the greatest limitation of MCT-induced TNFalpha. The MCT-induced lung pathology of vasculitis, interstitial pneumonia and fibrosis was limited by captopril. Smooth muscle actin was overexpressed in MCT treated animals receiving RA, an effect reduced with captopril. Overall, the study confirmed the existence of a protective effect for both captopril and RA from MCT-induced lung damage at 30 days. No synergistic or antagonistic activity was observed when the two drugs were administered together. Each of the drugs exerts different and particular effects on serum and tissue levels of various cytokines, suggesting that each drug is efficient at different points of attack in the control of lung fibrosis.     

Anticoagulants prevent monocrotaline-induced hepatic parenchymal cell injury but not endothelial cell injury in the rat

Monocrotaline (MCT) is a pyrrolizidine alkaloid plant toxin that produces hepatotoxicity in humans and animals. Human exposure to MCT occurs through consumption of contaminated grains and herbal medicines. Administration of MCT to rats stimulates activation of the coagulation system and fibrin deposition in the liver. Fibrin deposition occurs simultaneously with endothelial cell damage and prior to hepatic parenchymal cell injury. Accordingly, the hypothesis that activation of the coagulation system is required for MCT-induced liver injury was tested. Treatment of rats with either heparin or warfarin significantly reduced MCT-induced activation of the coagulation system and the increase in alanine aminotransferase activity in the plasma, a biomarker of hepatic parenchymal cell injury. Histopathological examination of liver sections revealed that heparin decreased parenchymal cell necrosis but did not affect central venular endothelial cell damage, congestion and dilation of the sinusoids, or hemorrhage in the liver. Morphometric analysis revealed that 28% of the area of livers from MCT-treated rats contained regions of coagulative necrosis, whereas less than 5% of the area of livers from rats treated with MCT and heparin contained these regions. By contrast, neither heparin nor warfarin prevented MCT-induced damage to endothelial cells in the liver as estimated by increased plasma hyaluronic acid concentration. These results suggest that activation of the coagulation system is required for MCT-induced parenchymal cell injury but not endothelial cell injury in the liver.     

Hypoxic pulmonary vasoconstriction and vascular contractility in monocrotaline-induced pulmonary arterial hypertensive rats

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by vascular remodeling of pulmonary arteries (PAs) and increased vascular resistance in the lung. Monocrotaline (MCT), a toxic alkaloid, is widely used for developing rat models of PAH caused by injury to pulmonary endothelial cells; however, characteristics of vascular functions in MCT-induced PAH vary and are not fully understood. Here, we investigated hypoxic pulmonary vasoconstriction (HPV) responses and effects of various vasoconstrictors with isolated/perfused lungs of MCT-induced PAH (PAH-MCT) rats. Using hematoxylin and eosin staining, we confirmed vascular remodeling (i.e., medial thickening of PA) and right ventricle hypertrophy in PAH-MCT rats. The basal pulmonary arterial pressure (PAP) and PAP increase by a raised flow rate (40 mL/min) were higher in the PAH-MCT than in the control rats. In addition, both high K⁺ (40 mM KCl)- and angiotensin II-induced PAP increases were higher in the PAH-MCT than in the control rats. Surprisingly, application of a nitric oxide synthase inhibitor, L-N^G-Nitroarginine methyl ester (L-NAME), induced a marked PAP increase in the PAH-MCT rats, suggesting that endothelial functions were recovered in the three-week PAH-MCT rats. In addition, the medial thickening of the PA was similar to that in chronic hypoxia-induced PAH (PAH-CH) rats. However, the HPV response (i.e., PAP increased by acute hypoxia) was not affected in the MCT rats, whereas HPV disappeared in the PAH-CH rats. These results showed that vascular contractility and HPV remain robust in the MCT-induced PAH rat model with vascular remodeling.     

氟伐他汀对野百合碱所致的大鼠肺血管重塑和右心室肥厚的影响

目的观察氟伐他汀对野百合碱(MCT)所致的大鼠肺血管重塑和右心室肥厚的影响。方法66只大鼠被随机分为3组:(1)M+F组(n=24):本组大鼠首先给予每日1次MCT(60mg/kg)皮下注射,连续2周,第3周至第6周末给予氟伐他汀(1mg/kg)灌胃,每日1次。(2)MCT组(n=24):实验前2周给予每日1次MCT(60mg/kg)皮下注射,第3周至第6周末给予与氟伐他汀等体积的0.9盐水灌胃;(3)Saline组(n=18):分别于实验前2周及第2周末至第6周末给予等体积的0.9盐水皮下注射和灌胃。MCT注射前记为第0周,实验共观察6周。分别于不同时间点观察大鼠肺组织形态学变化,并对平均肺动脉压(mPAP)、管壁厚度百分比(PWT)、右心室肥厚指数(RVHI)进行测定。结果MCT注射2周后,大鼠出现显著的肺血管重塑和右心室肥厚,MCT组大鼠在MCT停止注射后mPAP、PWT及RVHI进一步增高。而M+F组大鼠在给予连续4周氟伐他汀1mg/(kg.d)灌胃处理后,mPAP(23.3±3.2)mmHg及PWT(42.3±2.7)均较MCT组减轻。RVHI(0.32±0.02)亦较MCT组(0.54±0.03)显著降低,且与正常对照组(Saline组)比较无显著差异。结论氟伐他汀能有效减轻MCT诱导的大鼠肺血管重塑和右心室肥厚。