Vanadium exposure enhances lipid peroxidation in the kidney of rats and mice

Vanadium (V) as sodium orthovanadate induces an increase in lipid peroxidation in the kidneys after a single subcutaneous or intraperitoneal injection to rats or mice. The rate of malondialdehyde (MDA) formation, an index of lipid peroxidation, by kidney homogenates increased by more than 100% 1 h after injection. Chronic exposure of rats to vanadium sulfate, initially through maternal milk and later in the drinking water, resulted after 10 weeks in a significant increase in MDA formation by kidney but not by other tissues. In both acute and chronic studies in rats and mice, no significant increase in lipid peroxidation by V treatment was detected in brain, heart, lung, spleen, or liver. In mice, administration of ascorbate prior to acute exposure to V diminished both toxicity, i.e., respiratory depression and limb paralysis, and the formation of MDA in kidney.     

Regulatory mechanisms to control tissue alpha-tocopherol

To test the hypothesis that hepatic regulation of alpha-tocopherol metabolism would be sufficient to prevent overaccumulation of alpha-tocopherol in extrahepatic tissues and that administration of high doses of alpha-tocopherol would up-regulate extrahepatic xenobiotic pathways, rats received daily subcutaneous injections of either vehicle or 0.5, 1, 2, or 10 mg alpha-tocopherol/100 g body wt for 9 days. Liver alpha-tocopherol increased 15-fold in rats given 10 mg alpha-tocopherol/100 g body wt (mg/100 g) compared with controls. Hepatic alpha-tocopherol metabolites increased with increasing alpha-tocopherol doses, reaching 40-fold in rats given the highest dose. In rats injected with 10 mg/100 g, lung and duodenum alpha-tocopherol concentrations increased 3-fold, whereas alpha-tocopherol concentrations of other extrahepatic tissues increased 2-fold or less. With the exception of muscle, daily administration of less than 2 mg/100 g failed to increase alpha-tocopherol concentrations in extrahepatic tissues. Lung cytochrome P450 3A and 1A levels were unchanged by administration of alpha-tocopherol at any dose. In contrast, lung P-glycoprotein (MDR1) levels increased dose dependently and expression of this xenobiotic transport protein was correlated with lung alpha-tocopherol concentrations (R(2)=0.88, p<0.05). Increased lung MDR1 may provide protection from exposure to environmental toxins by increasing alveolar space alpha-tocopherol.     

Hydrogen sulfide protects rat lung from ischemia-reperfusion injury

Recent studies have indicated that hydrogen sulfide (H(2)S) is capable of modulating many physiological processes, which prompted us to investigate the potential of H(2)S as a lung protective agent. To explore changes in the generation of endogenous H(2)S and the role of H(2)S in the pathogenesis of pulmonary ischemia-reperfusion (I/R) injury in rats, we built an isolated rat lung I/R model. Lungs were subjected to 45 min ischemia followed by reperfusion (45 min) and were pretreated with H(2)S (50 micromol/l or 100 micromol/l) or an irreversible inhibitor of cystathionine-gamma-lyase (CSE), propargylglycine (PPG; 2 mmol/l). We examined indices of lung injury: lung histological change, perfusion flow rate, ratio of lung wet weight to dry weight (w/d), and lung compliance. H(2)S content and CSE protein expression in lung tissues were measured. Malondialdehyde (MDA) content, activities of superoxide dismutase (SOD) and catalase (CAT), and restraint of superoxide anion (O(2)(-)) production in lung tissues were measured to reflect oxidative stress. In the current study, we demonstrated that H(2)S content and CSE activity in lungs after I/R were significantly higher than those in the control group. Preperfusion with H(2)S attenuated the lung I/R injury while preperfusion with PPG aggravated the lung I/R injury. H(2)S preperfusion reduced I/R-induced MDA production and potentiated SOD and CAT activities and the restraint of O(2)(-) production in the lungs under I/R, which attenuated lung oxidative injury. These findings suggest that endogenous CSE/H(2)S pathway might be involved in the pathogenesis of lung I/R injury and that administration of H(2)S might be of clinical benefit in lung I/R injury.     

Increased vitamin E content in the lung after ozone exposure: a possible mobilization in response to oxidative stress

Vitamin E (vE) is a biological free radical scavenger capable of providing antioxidant protection depending upon its tissue content. In previous studies, we observed that vE increased significantly in rat lungs after oxidant exposure, and we postulated that vE may be mobilized to the lung from other body sites under oxidative stress. To test this hypothesis, we fed Long-Evans rats either a vE-supplemented or a vE-deficient diet, injected them intraperitoneally with 14C-labeled vE, and then exposed half of each group to 0.5 ppm ozone (O3) for 5 days. After exposure, we determined vE content and label retention in lungs, liver, kidney, heart, brain, plasma, and white adipose tissue. Tissue vE content of all tissues generally reflected the dietary level, but labeled vE retention in all tissues was inversely related to tissue content, possibly reflecting a saturation of existing vE receptor sites in supplemented rats. Following O3 exposure, lung vE content increased significantly in supplemented rats and decreased in deficient rats, but the decrease was not statistically significant, and vE content remained unchanged in all other tissues of both dietary groups. Retention of 14C-labeled vE increased in all tissues of O3-exposed rats of both dietary groups, except in vE-deficient adipose tissue and vE-supplemented brain, where it decreased, and plasma, where it did not change. The marked increases in lung vE content and labeled vE retention of O3-exposed vE-supplemented rats support our hypothesis that vE may be mobilized to the lung in response to oxidative stress, providing that the vitamin is sufficiently available in other body sites.     

Exhaled NO is reduced at an early stage of hypoxia-induced pulmonary hypertension in newborn piglets

Altered nitric oxide (NO) production could contribute to the pathogenesis of hypoxia-induced pulmonary hypertension. To determine whether parameters of lung NO are altered at an early stage of hypoxia-induced pulmonary hypertension, newborn piglets were exposed to room air (control, n = 21) or 10% O(2) (hypoxia, n = 19) for 3-4 days. Some lungs were isolated and perfused for measurement of exhaled NO output and the perfusate accumulation of nitrite and nitrate (NOx-), the stable metabolites of NO. Pulmonary arteries (20-600-microm diameter) and their accompanying airways were dissected from other lungs and incubated for NOx- determination. Abundances of the nitric oxide synthase (NOS) isoforms endothelial NOS and neural NOS were assessed in homogenates of PAs and airways. The perfusate NOx- accumulation was similar, whereas exhaled NO output was lower for isolated lungs of hypoxic, compared with control, piglets. The incubation solution NOx- did not differ between pulmonary arteries (PAs) of the two groups but was lower for airways of hypoxic, compared with control, piglets. Abundances of both eNOS and nNOS proteins were similar for PA homogenates from the two groups of piglets but were increased in airway homogenates of hypoxic compared with controls. The NO pathway is altered in airways, but not in PAs, at an early stage of hypoxia-induced pulmonary hypertension in newborn piglets.     

肺血管EDNO及其合酶在大鼠低氧性肺动脉高压形成中的作用

本研究观察了低氧对大鼠肺组织和血管内皮一氧化氮合酶（ＮＯＳ）活性及内皮衍生一氧化氮（ＥＤＮＯ）依赖性舒张反应的影响,以及ＮＯＳ抑制剂（Ｌ－ＮＡＭＥ）对常氧和低氧大鼠肺组织和血管内皮ＮＯＳ活性及颈、肺动脉血压（ＣＡＰｓ、ｍＰＡＰ）的作用。结果表明常氧大鼠肺泡内无肌性血管内皮未见ＮＯＳ活性,其肺血管床对ＥＤＮＯ依赖性舒血管物质ＢＫ没有反应,注射Ｌ－ＮＡＭＥ后大鼠ｍＰＡＰ略有降低,ＣＡＰｓ有所升高。低氧大鼠肺泡内无肌性血管内皮显示ＮＯＳ活性,对ＢＫ的ＥＤＮＯ依赖性舒张反应呈剂量依赖性增大,注射Ｌ－ＮＡＭＥ使低氧大鼠ｍＰＡＰ显著降低（Ｐ＜０．０１）,ＣＡＰｓ显著升高（Ｐ＜０．０５）。提示肺血管ＥＤＮＯ及其合酶在维持正常成年大鼠肺循环低压低阻中的生理作用值得进一步探讨;低氧引起肺血管内皮ｅｃＮＯＳ活性增加和ＥＤＮＯ生成增多可能起到限制肺动脉压过度升高的调制作用,也可能对肺血管内皮产生毒性作用,反而促进肺动脉高压的发生和发展。     

Hypoxia decreases proteins involved in epithelial electrolyte transport in A549 cells and rat lung

Fluid reabsorption from alveolar space is driven by active Na reabsorption via epithelial Na channels (ENaCs) and Na-K-ATPase. Both are inhibited by hypoxia. Here we tested whether hypoxia decreases Na transport by decreasing the number of copies of transporters in alveolar epithelial cells and in lungs of hypoxic rats. Membrane fractions were prepared from A549 cells exposed to hypoxia (3% O(2)) as well as from whole lung tissue and alveolar type II cells from rats exposed to hypoxia. Transport proteins were measured by Western blot analysis. In A549 cells, alpha(1)- and beta(1)-Na-K-ATPase, Na/K/2Cl cotransport, and ENaC proteins decreased during hypoxia. In whole lung tissue, alpha(1)-Na-K-ATPase and Na/K/2Cl cotransport decreased. alpha- and beta-ENaC mRNAs also decreased in hypoxic lungs. Similar results were seen in alveolar type II cells from hypoxic rats. These results indicate a slow decrease in the amount of Na-transporting proteins in alveolar epithelial cells during exposure to hypoxia that also occurs in vivo in lungs from hypoxic animals. The reduced number of transporters might account for the decreased transport activity and impaired edema clearance in hypoxic lungs.     

Selenium deficiency potentiates paraquat-induced lipid peroxidation in isolated perfused rat lung

Glutathione peroxidase (GSHPx), a seleno-enzyme, reduces lipid hydroperoxides while producing oxidized glutathione (GSSG), which can efflux from cells. To study the role of GSHPx in antioxidant defense, isolated lungs from selenium-deficient rats were perfused for 2 h with or without 1 mM paraquat. Perfusate GSSG was measured as an index of GSHPx activity, and malondialdehyde (MDA) as an index of lipid peroxidation. Selenium deficiency decreased lung GSHPx activity 75-80%. During perfusion control lungs showed GSSG efflux of 8.5 +/- 4.5 nmol/h and with paraquat 49.1 +/- 12.1 nmol/h. Selenium-deficient lungs with or without paraquat showed GSSG efflux of 16.4 +/- 5.3 and 13.7 +/- 8.9 nmol/h, respectively. MDA efflux occurred only in paraquat-perfused selenium-deficient lungs (7.8 +/- 2.7 nmol/h). Lung homogenates from this group had lower GSH + GSSG than the other three groups. These results indicate an inverse correlation between GSSG efflux and MDA accumulation from paraquat-perfused lungs and suggest that increased turnover of the GSHPx reaction protects paraquat-perfused lungs from lipid peroxidation.     

Decreased pulmonary vascular responsiveness in rats raised on an essential fatty acid deficient diet

Leukotriene C₄ is produced during hypoxic pulmonary vasoconstriction and leukotriene inhibitors preferentially inhibit the hypoxic pressor response in rats. If lipoxygenase products are important in hypoxic vasoconstriction, then an animal deficient in arachidonic acid should have a blunted hypoxic pressor response. We investigated if vascular responsiveness was decreased in vascular rings and isolated perfused lungs from rats raised on an essential fatty acid deficient diet (EFAD) compared to rats raised on a normal diet. Rats raised on the EFAD diet had decreased esterified plasma arachidonic acid and increased 5-, 8-, 11- eicosatrieonic acid compared to rats raised on the normal diet (control). Compared to the time matched responses in control isolated perfused lungs the pressor responses to angiotensin II and alveolar hypoxia were blunted in lungs from the arachidonate deficient rats. This decreased pulmonary vascular responsiveness was not affected by the addition of indomethacin or arachidonic acid to the lung perfusate. Similarly, the pulmonary artery rings from arichidonate deficient rats demonstrated decreased reactivity to norepinephrine compared to rings from control rats. In contrast, the tension increases to norepinephrine were greater in aortic rings from the arachidonate deficient rats compared to control. Stimulated lung tissue from the arachidonate deficient animals produced less slow reacting substance and platelet activating factor like material but the same amount of 6-keto-PGF_1α and TXB₂ compared to control lungs. Thus there is an associated between altered vascular responsiveness and impairment of stimulated production of slow reacting substance and platelet activating factor like materiali rat raised on an EFAD diet.     

Effects of coenzyme Q10 and alpha-tocopherol administration on their tissue levels in the mouse: elevation of mitochondrial alpha-tocopherol by coenzyme Q10.

Coenzyme Q (CoQ) was previously demonstrated in vitro to indirectly act as an antioxidant in respiring mitochondria by regenerating alpha-tocopherol from its phenoxyl radical. The objective of this study was to determine whether CoQ has a similar sparing effect on alpha-tocopherol in vivo. Mice were administered CoQ10 (123 mg/kg/day) alone, or alpha-tocopherol (200 mg/kg/day) alone, or both, for 13 weeks, after which the amounts of CoQ10, CoQ9 and alpha-tocopherol were determined by HPLC in the serum as well as homogenates and mitochondria of liver, kidney, heart, upper hindlimb skeletal muscle and brain. Administration of CoQ10 and alpha-tocopherol, alone or together, increased the corresponding levels of CoQ10 and alpha-tocopherol in the serum. Supplementation with CoQ10 also elevated the amounts of the predominant homologue CoQ9 in the serum and the mitochondria. A notable effect of CoQ10 intake was the enhancement of alpha-tocopherol in mitochondria. alpha-Tocopherol administration resulted in an elevation of alpha-tocopherol content in the homogenates of nearly all tissues and their mitochondria. Results of this study thus indicate that relatively long-term administration of CoQ10 or alpha-tocopherol can result in an elevation of their concentrations in the tissues of the mouse. More importantly, CoQ10 intake has a sparing effect on alpha-tocopherol in mitochondria in vivo.     

Differential responses of targeted lung redox enzymes to rat exposure to 60 or 85% oxygen

Rat exposure to 60% O(2) (hyper-60) or 85% O(2) (hyper-85) for 7 days confers susceptibility or tolerance, respectively, of the otherwise lethal effects of exposure to 100% O(2). The objective of this study was to determine whether activities of the antioxidant cytosolic enzyme NAD(P)H:quinone oxidoreductase 1 (NQO1) and mitochondrial complex III are differentially altered in hyper-60 and hyper-85 lungs. Duroquinone (DQ), an NQO1 substrate, or its hydroquinone (DQH(2)), a complex III substrate, was infused into the arterial inflow of isolated, perfused lungs, and the venous efflux rates of DQH(2) and DQ were measured. Based on inhibitor effects and kinetic modeling, capacities of NQO1-mediated DQ reduction (V(max1)) and complex III-mediated DQH(2) oxidation (V(max2)) increased by ～140 and ～180% in hyper-85 lungs, respectively, compared with rates in lungs of rats exposed to room air (normoxic). In hyper-60 lungs, V(max1) increased by ～80%, with no effect on V(max2). Additional studies revealed that mitochondrial complex I activity in hyper-60 and hyper-85 lung tissue homogenates was ～50% lower than in normoxic lung homogenates, whereas mitochondrial complex IV activity was ～90% higher in only hyper-85 lung tissue homogenates. Thus NQO1 activity increased in both hyper-60 and hyper-85 lungs, whereas complex III activity increased in hyper-85 lungs only. This increase, along with the increase in complex IV activity, may counter the effects the depression in complex I activity might have on tissue mitochondrial function and/or reactive oxygen species production and may be important to the tolerance of 100% O(2) observed in hyper-85 rats.     

五味子乙素对二氧化硅致大鼠肺损伤的保护作用

目的探讨五味子乙素（schisandrin B,Sch-B）对二氧化硅致大鼠肺损伤的保护作用。方法将64只大鼠随机分为对照组、染矽尘组、Sch-B干预组。非暴露气管法建立大鼠二氧化硅矽肺模型,灌胃给予Sch-B80 mg/kg/d。药后3、7、14和21 d,对照组、染矽尘组和Sch-B干预组分别随机安乐死4、6和6只大鼠,取其肺组织,测定肺系数;光镜观测其病理8切片;紫外分光光度计检测大鼠肺组织匀浆中羟脯氨酸（hydroxyproline,HYP）、丙二醛（malondialdehyde,MDA）、谷胱甘肽（glutathione,GSH）的含量变化。结果Sch-B对矽肺病理形态学有明显的改善作用,可以降低染矽大鼠的肺系数,降低肺组织匀浆中HYP和MDA含量,提高GSH含量,与染矽尘组比较,具有统计学差异（P〈0.05或P〈0.01）。结论Sch-B可以提高机体的抗氧化能力,对二氧化硅致大鼠肺损伤具有保护作用。     

Evalution of toxicity of abcisic acid and gibberellic acid in rats: 50 days drinking water study

In the present study, the influence of subchronic effects of two plant growth regulators (PGRs) [Abcisic acid (ABA) and Gibberellic acid (GA3)] on antioxidant defense systems [reduced glutathione (GSH), glutathione reductase (GR), superoxide dismutase (SOD), glutathione-S-transferase (GST) and catalase (CAT)] and lipid peroxidation level (malondialdehyde = MDA) in various tissues of the rat were investigated during treatment as a drinking water model. 75 ppm of ABA and GA3 in drinking water were continuously administered orally to rats (Sprague-Dawley albino) ad libitum for 50 days. The PGRs treatments caused different effects on the antioxidant defense systems and MDA content of dosed rats compared to controls. The lipid peroxidation end product MDA significantly increased in the lungs, heart and kidney of rats treated with GA3 without significant change in the spleen. ABA caused also a significant increase in MDA content in the spleen, lungs, heart and kidney. The GSH levels were significantly depleted in the spleen, lungs and stomach of rats treated with ABA without any change in the tissues of rats treated with GA3 except the kidney where it increased. Antioxidant enzyme activities such as SOD significantly increased in the lungs and stomach and decreased in the spleen and heart tissues of rats treated with GA3. Meanwhile, SOD significantly decreased in the spleen, heart and kidney and increased in the lungs of rats treated with ABA. While CAT activity significantly decreased in the lungs of rats treated with GA3, a significant increase occurred in the heart of rats treated with both PGRs. On the other hand, the ancillary enzyme GR activity in the tissues were either significantly depleted or not changed with PGRs treatment. The drug metabolizing enzyme GST activity significantly decreased in the lungs of rats treated with ABA but increased in the stomach of rats treated with both PGRs. As a conclusion, the rats resisted oxidative stress via the antioxidant mechanism. But the antioxidant mechanism could not prevent the increases in lipid peroxidation in rat's tissues. This data, along with changes, suggests that PGRs produced substantial systemic organ toxicity in the spleen, lungs, stomach, heart and kidney during a 50-day period of subchronic exposure.     

外源性apelin对大鼠慢性低氧性肺动脉高压的防治作用

目的:探讨外源性给予小分子活性肽apelin对大鼠慢性低氧性肺动脉高压和肺血管重构的作用及其机制。方法:采用常压低氧法建立SD大鼠低氧性肺动脉高压模型。实验分4组(n=10)对照组(NC)、低氧组(HH)、低氧+apelin低剂量组(5nmol/(kg.d)(LA)和低氧+apelin高剂量组(10nmol/(kg.d)(HA),HA组和LA组通过皮下埋植微量渗透泵持续给药。低氧4周后,测定平均肺动脉压(mPAP)、右心室与左心室加室间隔的重量比[RV/(LV+S)]、肺细小动脉管壁面积/管总面积(WA/TA)、管腔面积/管总面积(CA/TA)、中膜厚度(PAMT)以及肺组织超氧化物歧化酶(SOD)活性与丙二醛(MDA)含量。结果:①mPAP和RV/(LV+S):HH组较NC组高,HA组较HH组低;LA组mPAP较HH低,而RV/(LV+S)两组间无显著性差异。②WA/TA和PAMT:HH组较NC组高,HA组、LA组均较HH低。③CA/TA:HH组较NC组低,HA组、LA组均较HH高。④肺组织SOD含量:HH组较NC低,HA组、LA组均较HH高。⑤MDA含量:HH组较NC高,HA组、LA组均较HH低。结论:Apelin对低氧性肺动脉高压和肺血管重构的形成具有防治作用,这种作用可能与直接舒张肺血管作用及改善氧化应激有关。     

Decreased pulmonary vascular responsiveness in rats raised on an essential fatty acid deficient diet

Leukotriene C4 is produced during hypoxic pulmonary vasoconstriction and leukotriene inhibitors preferentially inhibit the hypoxic pressor response in rats. If lipoxygenase products are important in hypoxic vasoconstriction, then an animal deficient in arachidonic acid should have a blunted hypoxic pressor response. We investigated if vascular responsiveness was decreased in vascular rings and isolated perfused lungs from rats raised on an essential fatty acid deficient diet (EFAD) compared to rats raised on a normal diet. Rats raised on the EFAD diet had decreased esterified plasma arachidonic acid and increased 5-, 8-, 11-eicosatrienoic acid compared to rats raised on the normal diet (control). Compared to the time matched responses in control isolated perfused lungs the pressor responses to angiotensin II and alveolar hypoxia were blunted in lungs from the arachidonate deficient rats. This decreased pulmonary vascular responsiveness was not affected by the addition of indomethacin or arachidonic acid to the lung perfusate. Similarly, the pulmonary artery rings from arachidonate deficient rats demonstrated decreased reactivity to norepinephrine compared to rings from control rats. In contrast, the tension increases to norepinephrine were greater in aortic rings from the arachidonate deficient rats compared to control. Stimulated lung tissue from the arachidonate deficient animals produced less slow reacting substance and platelet activating factor like material but the same amount of 6-keto-PGF1 alpha and TXB2 compared to control lungs. Thus there is an association between altered vascular responsiveness and impairment of stimulated production of slow reacting substance and platelet activating factor like material in rats raised on an EFAD diet.     

Evalution of toxicity of abcisic acid and gibberellic acid in rats: 50 days drinking water study

In the present study, the influence of subchronic effects of two plant growth regulators (PGRs) [Abcisic acid (ABA) and Gibberellic acid (GA₃)] on antioxidant defense systems [reduced glutathione (GSH), glutathione reductase (GR), superoxide dismutase (SOD), glutathione-S-transferase (GST) and catalase (CAT)] and lipid peroxidation level (malondialdehyde = MDA) in various tissues of the rat were investigated during treatment as a drinking water model. 75 ppm of ABA and GA₃ in drinking water were continuously administered orally to rats (Sprague-Dawley albino) ad libitum for 50 days. The PGRs treatments caused different effects on the antioxidant defense systems and MDA content of dosed rats compared to controls. The lipid peroxidation end product MDA significantly increased in the lungs, heart and kidney of rats treated with GA₃ without significant change in the spleen. ABA caused also a significant increase in MDA content in the spleen, lungs, heart and kidney. The GSH levels were significantly depleted in the spleen, lungs and stomach of rats treated with ABA without any change in the tissues of rats treated with GA₃ except the kidney where it increased. Antioxidant enzyme activities such as SOD significantly increased in the lungs and stomach and decreased in the spleen and heart tissues of rats treated with GA₃. Meanwhile, SOD significantly decreased in the spleen, heart and kidney and increased in the lungs of rats treated with ABA. While CAT activity significantly decreased in the lungs of rats treated with GA₃, a significant increase occurred in the heart of rats treated with both PGRs. On the other hand, the ancillary enzyme GR activity in the tissues were either significantly depleted or not changed with PGRs treatment. The drug metabolizing enzyme GST activity significantly decreased in the lungs of rats treated with ABA but increased in the stomach of rats treated with both PGRs.

As a conclusion, the rats resisted oxidative stress via the antioxidant mechanism. But the antioxidant mechanism could not prevent the increases in lipid peroxidation in rat's tissues. This data, along with changes, suggests that PGRs produced substantial systemic organ toxicity in the spleen, lungs, stomach, heart and kidney during a 50-day period of subchronic exposure.