Ozone induces synthesis of systemic prostacyclin by cyclooxygenase-2 dependent mechanism in vivo

Under certain pathological conditions, e.g., infectious or neoplastic diseases, application of ozone exerts therapeutic effects. However, pharmacological mechanisms are not understood. Since an interaction with the arachidonic acid metabolism is suggested we investigated the effect of intraperitoneal insufflation of ozone on prostanoid system in vivo. Upon ozone application (4 mg/kg) to rats we observed an approximate 3-fold increase in excretion rate of 6-keto-prostaglandin (PG) F1α and of 2,3-dinor-6-keto-PG F1α, the measurable stable products of prostacyclin. In plasma and vessel tissue 6-keto-PG F1α concentration was also significantly increased. In contrast, excretion rates for PGE2 and thromboxane (TX) B2 did not change. F2-isoprostanes, regarded as endogenous indicators of oxidative stress, were also unaffected by ozone application. Oxygen insufflation used as control was without any effect on prostanoid levels. Ozone caused increase in 6-keto-PG F1α by arterial but not by venous vessel tissues with peak activity 6-9h following insufflation. The increase in PGI2 synthesis was dependent on cyclooxygenase (COX)-2 activity, demonstrated by its sensitivity towards COX-2 inhibition, and by enhanced COX-2 mRNA and protein expression in vessels. Ozone exerted no rise in excretion rate of prostacyclin metabolites in COX-2(-/-) but in COX-1(-/-) mice. Enzymatic activity and mRNA expression of vascular PGI2 synthase (PGIS) was unaffected by ozone treatment. In summary our study shows for the first time that ozone insufflation causes enhanced expression of COX-2 in the vessel system leading to exclusive elevation of systemic PGI2 levels. We assume that PGI2 stimulation may contribute to the beneficial effects of ozone treatment.     

Rofecoxib对肾间质纤维化大鼠TGF-及肾小管上皮细胞凋亡的影响

目的 探讨Rofecoxib对肾间质纤维化大鼠的肾脏保护机制。方法以UUO建立肾间质纤维化大鼠模型,随机分为假手术组、UUO组及Rofecoxib干预组,检测不同时间点肾脏COX-2、TGF-1及肾小管上皮细胞凋亡的表达。结果与假手术组相比,UUO组随着模型时间延长,TGF-β、COX-2蛋白表达明显增加,可检测到较多的凋亡细胞（P〈0．01）,用药组与UUO组平行相比TGF-β,、COX-2蛋白表达明显减少（P〈0．01）,凋亡细胞明显减少（P〈0．01）。结论特异性COX-2抑制剂Rofecoxib可能通过阻断UUO大鼠肾组织COX-2活性,下调TGF-的蛋白合成,减少肾小管细胞的过度凋亡,起到肾脏保护的作用。     

Honokiol up-regulates prostacyclin synthease protein expression and inhibits endothelial cell apoptosis

Honokiol is a bioactive compound extracted from the Chinese medicinal herb Magnolia officinalis. We recently demonstrated that honokiol inhibited arterial thrombosis through stimulation of prostacyclin (PGI2) generation and endothelial cell protection. The current study is designed to investigate its mechanism of stimulation of PGI2 generation and cell protection. 6-keto-PGF1alpha, the stable metabolite of PGI2, in the media of rat aortic endothelial cells was measured with radioimmunoassay kits. Indomethacin, an inhibitor of cyclooxygenase (COX) and tranylcypromine, a prostacyclin synthease inhibitor were used to ascertain the target enzyme affected by honokiol. Prostacyclin synthease protein levels in endothelial cells were determined by Western blot analysis using an anti-PGI2 synthease rabbit polyclonal antibody. Flow cytometry was used to quantify the apoptotic cells and spectrophotometry was used to test the caspase-3 activity. Honokiol (0.376-37.6 microM) increased the level of 6-keto-PGF1alpha in the media of normal endothelial cells. It counteracted the inhibitory effect of tranylcypromine on the PGI2 generation, but did not influence the effect of indomethacin; evidently, honokiol up-regulated the expression of prostacyclin synthease in the endothelial cells. These effects showed perfect concentration-dependent behavior. In addition, at lower concentration (0.376-3.76 microM), honokiol significantly decreased the percentage of apoptotic endothelial cells induced by oxidized low-density lipoprotein (ox-LDL) and significantly lowered the activity of caspase-3 stimulated by ox-LDL. A high dose of honokiol (37.6 microM), however, failed to influence either of them. In conclusion, honokiol augments PGI2 generation in normal endothelial cells; its effect on PGI2 generation attributes to up-regulation of prostacyclin synthease expression; its cell protection may be correlated with its inhibition on apoptosis of endothelial cells. These findings have partly revealed the molecular mechanism of honokiol on inhibiting arterial thrombosis.     

Berberine protects HK-2 cells from hypoxia/reoxygenation induced apoptosis via inhibiting SPHK1 expression

Renal ischemia reperfusion injury (RIRI) refers to the irreversible damage for renal function when blood perfusion is recovered after ischemia for an extended period, which is common in clinical surgeries and has been regarded as a major risk for acute renal failures (ARF) that is accompanied with unimaginably high morbidity and mortality. Hypoxia during ischemia followed by reoxygenation via reperfusion serves as a major event contributing to cell apoptosis, which has been widely accepted as the vital pathogenesis in RIRI. Preventing apoptosis in renal tubular epithelial cell has been considered as effective method for blocking RIRI. In this paper, we established a hypoxia/reoxygenation (H/R) injury model in human proximal tubular epithelial HK-2 cells. Here, we found increased SPHK1 levels in H/R injured HK-2 cells, which could be significantly down regulated after berberine treatment. Berberine has been reported to exert a protective effect on H/R-induced apoptosis of HK-2 cells. So, in our present study, we planned to investigate whether SPHK1 participated in the anti-apoptosis process of berberine in H/R injured HK-2 cells. Our study confirmed the protective effect of berberine against H/R-induced apoptosis in HK-2 cells through promoting cells viability, inhibiting cells apoptosis, and down-regulating p-P38, caspase-3, caspase-9 as well as SPHK1, while up regulating the ratio of Bcl-2/Bax. However, SPHK1 overexpression in HK-2 cells induced severe apoptosis, which can be significantly ameliorated with additional berberine treatment. We concluded that berberine could remarkably prevent H/R-induced apoptosis in HK-2 cells through down-regulating SPHK1 expression levels, and the mechanisms included the suppression of p38 MAPK activation and mitochondrial stress pathways.     

Organic solvent-induced proximal tubular cell apoptosis via caspase-9 activation

Long-term exposure to solvents is associated with apoptosis, which is implicated in the development and progression of tubulo-interstitial fibrosis and chronic renal failure. In our previous study, we demonstrated that toluene and p-xylene as the most commonly used organic solvents induced proximal tubular cells apoptosis. This study was conducted to assess the apoptotic pathway of toluene and p-xylene induced proximal tubular apoptosis. This was assessed by measuring the caspase-9 activity LLC-PK1 cells exposed to both compounds. A model of proximal tubular cell (LLC-PK1) cytotoxicity exposed to 1 mM of either p-xylene or toluene was compared to untreated control for caspase-9 activity and Bax/Bcl-2 protein level. Furthermore, DNA fragmentation in the presence of caspase-9 inhibitor (Z-LEHD-FMK) in a dose-dependent manner was assessed. Both compounds induced caspase-9 activity, which was accompanied by up-regulation of Bax, whereas Bcl-2 level did not change. DNA fragmentation induced by both solvents was inhibited by caspase-9 inhibitor in dose-dependent manner. This data suggest that p-xylene or toluene induces nephrotoxicity via mitochondrial caspase-9 pathway. This mechanism involves up-regulation of the apoptotic protein, Bax.     

Cyclooxygenase-2 inhibitors: a painful lesson

Non-steroidal anti-inflammatory drugs (NSAIDs) represent a clinically important class of agents. NSAIDs are commonly used in treatment of conditions such as headache, fever, inflammation and joint pain. Complications often arise from chronic use of NSAIDs. Gastrointestinal (GI) toxicity in the form of gastritis, peptic erosions and ulcerations and GI bleeds limit usage of NSAIDs. These toxicities are thought to be due to cyclooxygenase (COX)-1 blockade. COX-1 generates cytoprotective prostanoids such as prostaglandin (PG) E2 and prostacyclin (PGI2). COX-2 inhibitors, commonly referred to as coxibs, were developed to inhibit inflammatory prostanoids without interfering with production of COX-1 prostanoids. Concerns over cardiovascular safety, however, have evolved based on the concept of inhibition of COX-2-derived endothelial prostanoids without inhibition of platelet thromboxane A2, leading to increased cardiovascular risk. The Celecoxib Long-Term Arthritis Safety Study (CLASS) trial did not show a significant increase in cardiovascular risk for celecoxib (Celebrex), but results of the Vioxx Gastrointestinal Outcomes Research (VIGOR) study showed an increased cardiovascular risk with long-term daily usage of rofecoxib in patients with rheumatoid arthritis. The Adenomatous Poly Prevention on Vioxx (APPROVe) trial further evaluated cardiovascular effects of rofecoxib and recently led to removal of this drug from the marketplace. Coxibs affect renal function via blockade of normal COX-2 functions. COX-2 expression increases in high renin states and in response to a high-sodium diet or water deprivation. PGI2 and PGE2 are the most important renal prostanoids. PGI2 inhibition results in hyperkalemia. PGE2 inhibition results in sodium retention, which leads to hypertension, peripheral edema and potentially exacerbation of heart failure. This review article discusses beneficial and deleterious effects associated with prostanoids produced by COX-1 and COX-2 in various organs and how blockade of these products translates into clinical medicine.     

Prostacyclin analogues: prevention of cardiovascular diseases

Prostacyclin (PGI(2)) inhibits platelet aggregation and vasoconstriction. PGI(2) synthase (PGIS), a catalyst of PGI(2) formation from prostaglandin H2, is widely distributed and predominantly found in vascular endothelial and smooth muscle cells. Vane et al. first discovered PGI(2) in 1976, for which they received the Nobel Prize in medicine and physiology in 1982. However, the later discovery of nitric oxide (NO), which also resulted in a Nobel Prize for the scientists involved, led to less attention being focused on PGI(2). The reason for this is somewhat perplexing and may have been due to the lack of information on how to correctly use PGI(2). Current findings suggest that researchers concentrated too much effort on the therapeutic effects of PGI(2), while largely ignoring the potential for preventative effects. In addition, PGI(2) was shown to be effective against diseases in some studies but was without effect in others. The present paper contains a review of PGI(2) and PGIS, in addition to an examination of the relationship between PGIS gene mutations and cardiovascular diseases. PGI(2) analogues that can be used in the prevention of cardiovascular diseases are also discussed.     

超声心动图评价卡维地洛和依那普利对慢性心力衰竭大鼠心功能的影响

目的 本研究主要应用高频超声评价卡维地洛和依那普利对阿霉素诱导的慢性心力衰竭大鼠心脏结构和功能的影响.方法 大鼠分为4组(阿霉素组12只、阿霉素 卡维地洛组12只、阿霉素 依那普利组12只和对照组8只),腹腔注射及药物灌胃建立动物模型.超声心动图检测心功能,光镜观察心肌病理变化.结果 阿霉素组与对照组相比,左室舒张期末、收缩期末内径显著扩大(P＜0.01),射血分数及短轴缩短率显著降低(P＜0.01).卡维地洛和依那普利能明显改善这些异常.阿霉素组病理结果显示心肌细胞空泡变性、局部心肌细胞溶解、心肌纤维断裂以及间质水肿;卡维地洛组和依那普利组病变较轻,病理积分显著小于阿霉素组.结论 多普勒超声结果表明卡维地洛和依那普利能有效改善阿霉素心肌病大鼠心功能,与病理结果相一致.     

Hirudin improves renal interstitial fibrosis by reducing renal tubule injury and inflammation in unilateral ureteral obstruction (UUO) mice

Renal interstitial fibrosis (RIF) often occurs in many chronic kidney diseases (CKD). Hirudin now is applied to treat fibrosis in some organs. In this study, we verified the treatment effects of hirudin on RIF in vivo and in vitro with the underlying mechanism. The RIF in vivo was the unilateral ureteral obstruction (UUO) model and RIF in vitro was the renal tubular epithelial cells induced by TGF-β. The renal pathological changes and renal fibrosis were observed by hematoxylin and eosin (H&E) staining and Masson staining. The α-SMA in renal tissues was detected by immunohistochemistry. The inflammatory factors were analyzed by the ELISA assay. The cell apoptosis was observed by TUNEL assay. The related proteins of fibrosis, epithelial-mesenchymal transition (EMT) and apoptosis were assessed by western blot analysis. The experimental data demonstrated that hirudin decreased fibrosis, EMT, inflammation and cell apoptosis in renal tissues of UUO rats and TGF-β-induced renal tubular epithelial cells. Furthermore, hirudin also reduced the expression of collgen-I, FN, α-SMA, N-cad, slug, E-cad, IL-1β, IL-6 and TNF-α in mice serum and TGF-β-induced renal tubular epithelial cells. The apoptosis related proteins (pro-caspase3, pro-caspase9, bcl2 and bax) expression was also down-regulated in renal tissues of UUO rats. In conclusion, hirudin depressed the fibrosis in renal tissues and renal tubular epithelial cells by inhibiting the inflammation, regulating the related proteins of fibrosis and ETM and decreasing the apoptosis of renal tubular epithelial cells. These findings may offer an effective treatment method for RIF.     

Long-term leptin treatment exerts a pro-apoptotic effect on renal tubular cells via prostaglandin E2 augmentation

Adipokine leptin reportedly acts on the kidney in pathophysiological states. However, the influence of leptin on renal tubular epithelial cells is still unclear. Gentamicin, a widely used antibiotic for the treatment of bacterial infection, can cause nephrotoxicity. This study aims to investigate the influence of long-term leptin treatment on gentamicin-induced apoptosis in rat renal tubular cells (NRK-52E) and mice. We monitored apoptosis and molecular mechanisms using annexin V/ propidium iodide staining and small interfering RNA transfection. In NRK-52E cells, leptin reduced gentamicin-induced apoptosis at 24h, but significantly increased apoptosis at 48 h. Long-term treatment of leptin decreased Bcl-x(L) expression and increased caspase activity in gentamicin-treated NRK-52E cells. Leptin also increased the expression of cyclooxygenase-2 (COX-2) and its product, prostaglandin E(2) (PGE(2)), in a dose-dependent manner. The COX-2 inhibitor, NS398 (N-[2-(Cyclohexyloxy)-4- nitrophenyl]methanesulfonamide), blocked PGE(2) augmentation and the pro-apoptotic effects of leptin. The addition of PGE(2) recovered the pro-apoptotic effect of leptin in NS398-treated NRK-52E cells. In a mouse animal model, a 10 day leptin treatment significantly increased gentamicin-induced apoptotic cells in proximal tubules. NS398 treatment inhibited this in vivo pro-apoptotic effect of leptin. Results reveal that long-term elevation of leptin induces COX-2-mediated PGE(2) augmentation in renal tubular cells, and then increases these cells' susceptibility to gentamicin-induced apoptosis.     

环氧化酶-2参与丹参酮IIA改善脓毒症大鼠的心肌凋亡

目的: 探讨丹参酮IIA改善脓毒症大鼠心肌凋亡的作用及可能的机制——花生四烯酸环氧化酶-2途径。方法: 采用盲肠结扎穿孔术制备脓毒症大鼠模型(CLP),雄性Wistar大鼠随机分成4组:假手术组(Sham组),脓毒症组(CLP组),Tan IIA组和Celecoxib组,后两组于CLP后给予丹参酮IIA(Tan IIA)腹腔注射处理,Celecoxib组同时选用花生四烯酸环氧化酶-2的特异性抑制剂塞来昔布灌胃处理,分析治疗12 h后的心肌细胞的炎性氧化因子(TNF-α、IL -1β、MDA、SOD)含量、凋亡情况、心肌促凋亡基因(Bax、Fas、 P53和Caspase-3)和抑制凋亡基因(Bcl-2)的表达情况以及左心室心肌COX-2的mRNA、蛋白表达和活性水平。结果: 与Sham组相比,CLP组大鼠心肌细胞凋亡指数升高(P<0.05);COX-2的蛋白、mRNA表达水平增加、活性增强;Bax、fas、 P53及Caspase-3的蛋白和mRNA表达水平上升(P<0.05),Bcl-2的蛋白和mRNA表达水平下降(P<0.05);给予丹参酮ⅡA处理的脓毒症大鼠,上述指标均有显著改善(P<0.05);在丹参酮ⅡA处理的同时给予赛来昔布干预后,上述指标水平与仅用丹参酮ⅡA处理后相似(P>0.05)。结论: 丹参酮IIA对脓毒症大鼠心肌凋亡具有保护作用,可能通过花生四烯酸环氧化酶(COX-2)途径实现。     

Etiology of iodinated radiocontrast nephrotoxicity and its attenuation by beraprost

Radiocontrast nephropathy (RCN) is a major complication after radiographical examination with iodinated contrast media (CM). Although little is known about the mechanism of RCN, a direct toxic action on renal cells and/or decrease in renal blood flow are considered to be implicated in the pathogenesis of the disease/the condition, A large number of vasodilatory agents, including endothelin antagonists, adenosine antagonists, atrial natriuretic peptide, calcium channel blockers, dopamine, dopamine D1 receptor agonist fenoldopam, and prostaglandin E1 have been tried clinically to prevent RCN, however, most of them have failed. Although prophylactic effects of antioxidant N-acetylcysteine have recently been reported by several investigators, only hydration is a universally accepted protocol to prevent it. In our recent in vitro and in vivo study, we have elucidated that CM induced apoptosis of renal tubular cells through the reduction in Bcl-2 expression and the subsequent activation of caspase-9 and caspase-3. Moreover, we found that CM caused an increase in ceramide content in renal tubular cells, which leads to apoptosis by inhibiting the phosphorylation of Akt and cAMP responsive element binding protein (CREB) and the subsequent reduction in Bcl-2 expression. The inhibitor of ceramide synthase, fumonisin B1, reversed both the elevation of ceramide content and renal cell injury induced by CM. On the other hand, a prostacyclin analog beraprost prevented RCN in mice by the increase of endogenous cAMP and subsequent CREB phosphorylation resulted in enhancement of Bcl-2 expression. These findings suggest that ceramide synthesis inhibitor or beraprost is potentially useful for the prophylaxis of RCN.     

Effects of phospholipases A2 from Vipera russelli snake venom on blood pressure, plasma prostacyclin level and renin activity in rats

Vipera russelli venom contains several isoenzymes of phospholipase A2 (PLA2) which were isolated by column chromatography. The effects of PLA2 fractions on blood pressure, plasma prostacyclin level and renin activity were studied in normotensive and renal hypertensive rats. PLA2 fractions II-5, II-7, III-3 and III-6 (0.1 mg/kg) injected i.v. into rats decreased the arterial blood pressure. The hypotensive action of PLA2 fractions was not affected by heat treatment (70-80 degrees C, 30 min, pH 6.8). After indomethacin (30 mg/kg, i.v.), the hypotensive response to PLA2 was markedly reduced. Plasma prostacyclin (PGI2) and thromboxane A2 (TXA2) levels were measured by radioimmunoassays of their degradation products, 6-keto-PGF1 alpha and TXB2, respectively. PLA2 fractions (0.1 mg/kg) induced an increase in plasma PGI2 and TXA2 levels. There was a positive linear correlation between the PLA2-induced hypotensive effect and the ratio of increased 6-keto-PGF1 alpha to TXB2 (r = 0.83) in normotensive rats. In renal hypertensive rats, the increase in PGI2 level was larger than in normotensive rats. Plasma renin activity was also measured by the radioimmunoassay. Plasma renin activity was reduced by PLA2 fractions in renal hypertensive rats, but not in normotensive rats. These results suggest that the hypotensive effect of PLA2 fractions in normotensive rats may be partly due to the increase in plasma prostacyclin and thromboxane A2 levels. In addition to the larger increase in plasma PGI2 level, the reduction in plasma renin activity may also contribute to the greater hypotensive effect of PLA2 fractions in renal hypertensive rats.     

Prostacyclin, atherothrombosis, and cardiovascular disease

Prostacyclin (PGI(2)) is a major product of COX-2 catalyzed metabolism of arachidonic acid in the endothelium. Recent studies have demonstrated that PGI(2) protects against atherothrombosis. The prostacyclin receptor knockout mice exhibit increased atherosclerosis, enhanced thrombosis, and enhanced proliferative response to carotid vascular injury with increased intima to media ratios [1-3]. Moreover, the recent withdrawal of rofecoxib (Vioxx) due to increased cardiovascular events further supports the critical role of prostacyclin in inhibiting atherothrombosis in humans. Such studies have paralleled intense chemical biology studies to develop more stable prostacyclin analogues. Indeed a number of these analogues are currently being successfully used for the treatment of pulmonary hypertension. In this review we will summarize the current literature on some principles of prostacyclin analogue development, our current understanding of the receptor, and recent developments which implicate prostacyclin in atherothrombotic protection. More than 68 million Americans suffer from cardiovascular disease, which causes more deaths, disability and economic loss than any other group of diseases. Further clinical investigations of orally stable prostacyclin analogues for treatment of cardiovascular diseases other than pulmonary hypertension may now be warranted.     

金纳多对肾缺血/再灌注诱导的肾小管上皮细胞凋亡的影响

目的研究银杏叶提取物金纳多(Ginaton)注射液对大鼠肾脏缺血/再灌注(I/R)诱导的肾小管上皮细胞凋亡的保护作用及机制。方法采用双侧夹闭大鼠肾蒂缺血45min后再灌注20min、3、24h的方法制备动物模型。在预定时间点采用免疫印迹分析JNK及其底物c-Jun的激活和表达。TUNEL(原位末端标记法)及流式细胞术检测肾小管上皮细胞凋亡情况。结果肾脏缺血45min再灌注24h后肾小管上皮细胞凋亡明显增多,肾脏病理改变明显。肾脏缺血/再灌注20min时,JNK的磷酸化水平明显增加,缺血/再灌注3h,c-Jun的磷酸化水平明显增加。金纳多明显抑制了肾I/R诱导的JNK(vsI/R20min,P<0·05)和c-Jun(vsI/R3h,P<0·05)的磷酸化水平的增加。同时,金纳多明显减轻肾I/R诱导的肾小管上皮细胞凋亡(vsI/R24h,P<0·05),改善肾脏组织病理学改变。结论金纳多抑制肾I/R诱导的肾小管上皮细胞凋亡,保护缺血性肾损伤的作用,至少部分是通过抑制JNK通路的激活实现的。     

芪附汤对大鼠抗阿霉素心脏毒性作用的血清气相色谱-质谱代谢组学研究

目的 采用基于气相色谱-质谱（GC-MS）血清代谢组学技术研究芪附汤抗阿霉素心脏毒性的作用,并初步探讨其作用机制。方法 将24只大鼠分为正常组、阿霉素组和芪附汤治疗组,给予4周相应的干预治疗后,采集大鼠血清进行GC-MS分析,结合多变量和单变量统计分析,研究阿霉素诱导的心脏毒性损伤大鼠血清中内源性代谢物的变化,以及芪附汤对其的干预作用,寻找其抗阿霉素心脏毒性潜在的生物标志物,采用代谢通路分析鉴定芪附汤靶向代谢通路。结果 GC-MS血清代谢组学分析鉴定了17种阿霉素心脏毒性潜在生物标志物,芪附汤对其中10种代谢物具有显著的逆转作用,代谢通路分析表明,三羧酸循环、乙醛酸和二羧酸代谢（简称二羧酸代谢）、花生四烯酸代谢是芪附汤主要的靶向代谢通路。结论 芪附汤能够通过调节失衡的三羧酸循环、二羧酸代谢和花生四烯酸代谢而发挥抗阿霉素心脏毒性的作用。