Evidence for cigarette smoke-induced oxidative stress in the rat pancreas

Background/aims: Recent findings with a rodent model of cigarette smoke inhalation revealed a causal relationship between chronic exposure to cigarette smoke and the development of pancreatitis. The present study was conducted to ascertain whether cigarette smoke induces oxidative stress in the rat pancreas concurrently with inflammation.

Methodology: Rats (six per treatment group) were treated for 0, 3, 6, 9, or 12 weeks with cigarette smoke (0.7?mg/L). Pancreatic tissues were examined for histological and pathological alterations and serum for changes in interleukin-6 concentration. Pancreatic expression and localization of α-smooth muscle actin, transforming growth factor-β1, and collagen-1 were determined as measures of progressive inflammation/fibrosis. Pancreatic superoxide dismutase and glutathione peroxidase activities and malondialdehyde content were measured as indices of oxidative stress.

Results: Inflammatory cell infiltration and ductal hyperplasia were detected in pancreata after 12 weeks of treatment with cigarette smoke. The serum interleukin-6 concentration increased significantly and pancreatic glutathione peroxidase activity declined significantly after 12 weeks of treatment. No other significant changes were observed.

Conclusions: Pancreata of rats exposed chronically to cigarette smoke exhibit inflammation concurrently with suppression of glutathione peroxidase activity. These observations favor a role for oxidative stress in the induction of pancreatitis associated with chronic cigarette smoke inhalation.     

Nrf2 protects against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced oxidative injury and steatohepatitis

Previous studies demonstrate that Nrf2, a master regulator of antioxidative responses, is essential in mediating induction of many antioxidative enzymes by acute activation of the AhR. However, the role of Nrf2 in protecting against oxidative stress and DNA damage induced by sustained activation of the AhR remains unknown and was investigated herein. Tissue and blood samples were collected from wild-type (WT) and Nrf2-null mice 21 days after administration of a low-toxic dose (10 μg/kg ip) of TCDD. Only Nrf2-null mice lost body weight after TCDD treatment; however, blood levels of ALT were not markedly changed in either genotype, indicating a lack of extensive necrosis. Compared to livers of TCDD-treated WT mice, livers of TCDD-treated Nrf2-null mice had: 1) degenerated hepatocytes, lobular inflammation, marked fat accumulation, and higher mRNA expression of inflammatory and fibrotic genes; 2) depletion of glutathione, elevation in lipid peroxidation and marker of DNA damage; 3) attenuated induction of phase-II enzymes Nqo1, Gsta1/2, and Ugt2b35 mRNAs, but higher induction of cytoprotective Ho-1, Prdx1, Trxr1, Gclc, and Epxh1 mRNAs; 4) higher mRNA expression of Fgf21 and triglyceride-synthesis genes, but down-regulation of bile-acid-synthesis genes and cholesterol-efflux transporters; and 5) trend of induction/activation of c-jun and NF-kB. Additionally, TCDD-treated Nrf2-null mice had impaired adipogenesis in white adipose tissue. In conclusion, Nrf2 protects livers of mice against oxidative stress, DNA damage, and steatohepatitis induced by TCDD-mediated sustained activation of the AhR. The aggravated hepatosteatosis in TCDD-treated Nrf2-null mice is due to increased lipogenesis in liver and impaired lipogenesis in white adipose tissue.     

姜黄素对急性肺栓塞大鼠氧化损伤及血红素加氧酶-1表达的影响

目的观察姜黄素对急性肺栓塞大鼠氧化损伤的作用及对血红素加氧酶-1(HO-1)表达的影响。方法大鼠分为假手术组、模型组、姜黄素低、高剂量(50 mg/kg、150 mg/kg)组。制备急性自体血栓肺栓塞模型。进行血气分析。检测肺组织超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)活性、丙二醛(MDA)含量;HE染色观察肺组织病理改变;RT-PCR方法和Western blot法检测肺组织HO-1的表达。结果与模型组比较,姜黄素低、高剂量组可不同程度的升高PO2、PCO2水平,升高SOD、GSH-Px、CAT活性,降低MDA含量,减轻肺组织的氧化病理损伤。姜黄素低、高剂量组均能显著升高肺组织HO-1表达。结论姜黄素对急性肺栓塞大鼠有抗氧化损伤作用,并能上调肺组织HO-1表达。     

Eriodictyol-7-O-glucoside activates Nrf2 and protects against cerebral ischemic injury

Stroke is a complex disease that may involve oxidative stress-related pathways in its pathogenesis. The nuclear factor erythroid-2-related factor 2/antioxidant response element (Nrf2/ARE) pathway plays an important role in inducing phase II detoxifying enzymes and antioxidant proteins and thus has been considered a potential target for neuroprotection in stroke. The aim of the present study was to determine whether eriodictyol-7-O-glucoside (E7G), a novel Nrf2 activator, can protect against cerebral ischemic injury and to understand the role of the Nrf2/ARE pathway in neuroprotection. In primary cultured astrocytes, E7G increased the nuclear localization of Nrf2 and induced the expression of the Nrf2/ARE-dependent genes. Exposure of astrocytes to E7G provided protection against oxygen and glucose deprivation (OGD)-induced oxidative insult. The protective effect of E7G was abolished by RNA interference-mediated knockdown of Nrf2 expression. In vivo administration of E7G in a rat model of focal cerebral ischemia significantly reduced the amount of brain damage and ameliorated neurological deficits. These data demonstrate that activation of Nrf2/ARE signaling by E7G is directly associated with its neuroprotection against oxidative stress-induced ischemic injury and suggest that targeting the Nrf2/ARE pathway may be a promising approach for therapeutic intervention in stroke.     

草质素苷对香烟烟雾所致慢性阻塞性肺疾病大鼠治疗作用及主要作用机制研究

目的 探讨草质素苷对香烟烟雾所致慢性阻塞性肺疾病（COPD）大鼠治疗作用及主要作用机制。方法 将40只Wistar大鼠随机分为对照组、模型组和草质素苷低、高剂量（50、100 mg/kg）组,除对照组外,其余各组大鼠采用香烟烟熏法制备COPD模型,连续烟熏30 d,并于每日烟熏结束1 h后,对各组大鼠进行ig给药处理。末次给药后24 h,取大鼠左右侧肺组织,采用HE染色观察大鼠左侧部分肺组织病理学变化;取另一份左侧肺组织,制备组织匀浆,试剂盒法检测过氧化氢酶（CAT）、血红素加氧酶（HO-1）、8-羟基脱氧鸟苷（8-OHDG）及髓过氧化物酶（MPO）含量。取右侧肺组织,平均分为4份,采用免疫组化法观察其中嗜酸性粒细胞趋化因子（Eotaxin）、嗜酸性阳离子蛋白（ECP）、巨噬细胞炎性蛋白-1α（MIP-1α）及淀粉样蛋白A （SAA）炎性因子的阳性表达情况,并观察相对表达量。结果 HE染色结果显示,草质素苷低、高剂量组大鼠肺组织中肺泡间隔变薄及炎症细胞浸润等病理变化程度均不及模型组;与模型组比较,草质素苷低、高剂量组大鼠肺组织匀浆中CAT、HO-1含量均显著升高,8-OHDG、MPO含量则均显著降低（P<0.05）。免疫组化检测结果表明,草质素苷低、高剂量组大鼠Eotaxin、ECP、MIP-1α及SAA的阳性表达程度均不及模型组,且蛋白的相对表达量均明显降低（P<0.05）。结论 草质素苷对香烟烟雾所致COPD具有较好的保护作用,主要机制可能与其抗氧化及抗炎活性有关。     

Isorhamnetin protects against oxidative stress by activating Nrf2 and inducing the expression of its target genes

Isorhamentin is a 3′-O-methylated metabolite of quercetin, and has been reported to have anti-inflammatory and anti-proliferative effects. However, the effects of isorhamnetin on Nrf2 activation and on the expressions of its downstream genes in hepatocytes have not been elucidated. Here, we investigated whether isorhamnetin has the ability to activate Nrf2 and induce phase II antioxidant enzyme expression, and to determine the protective role of isorhamnetin on oxidative injury in hepatocytes. In HepG2 cells, isorhamnetin increased the nuclear translocation of Nrf2 in a dose- and time-dependent manner, and consistently, increased antioxidant response element (ARE) reporter gene activity and the protein levels of hemeoxygenase (HO-1) and of glutamate cysteine ligase (GCL), which resulted in intracellular GSH level increases. The specific role of Nrf2 in isorhamnetin-induced Nrf2 target gene expression was verified using an ARE-deletion mutant plasmid and Nrf2-knockout MEF cells. Deletion of the ARE in the promoter region of the sestrin2 gene, which is recently identified as the Nrf2 target gene by us, abolished the ability of isorhamnetin to increase luciferase activity. In addition, Nrf2 deficiency completely blocked the ability of isorhamnetin to induce HO-1 and GCL. Furthermore, isorhamnetin pretreatment blocked t-BHP-induced ROS production and reversed GSH depletion by t-BHP and consequently, due to reduced ROS levels, decreased t-BHP-induced cell death. In addition isorhamnetin increased ERK1/2, PKCδ and AMPK phosphorylation. Finally, we showed that Nrf2 deficiency blocked the ability of isorhamnetin to protect cells from injury induced by t-BHP. Taken together, our results demonstrate that isorhamnetin is efficacious in protecting hepatocytes against oxidative stress by Nrf2 activation and in inducing the expressions of its downstream genes.     

The natural compound 2,3,5,4′‐tetrahydroxystilbene‐2‐O‐β‐d glucoside protects against adriamycin‐induced nephropathy through activating the Nrf2‐Keap1 antioxidant pathway

2,3,5,4′‐Tetrahydroxystilbene‐2‐O‐β‐d ‐glucoside (THSG) is an active compound extracted from Polygonum multiflorum Thunb. This herb and radix Polygoni Multiflori preparata have been used to treat arteriosclerosis, hyperlipidemia, hypercholesterolemia, and diabetes for thousands of years. This study aimed to investigate the protective effects of THSG in an Adriamycin (AD)‐induced focal segmental glomerulosclerosis (FSGS) mouse model and the underlying mechanisms in an in vitro system. Mice were treated with THSG (2.5 and 10 mg/kg, oral gavage) for 24 consecutive days. On the third day, mice were intravenously given a single dose of AD (10 mg/kg). At the end of the experiment, plasma and kidney samples were harvested to evaluate the therapeutic effects of THSG. The potential mechanisms of THSG in protecting against AD‐induced cytotoxicity were examined using a real‐time polymerase chain reaction, immunoblots, lactate dehydrogenase assay, and a cellular oxidized‐thiol detection system in a mouse mesangial cell line. In this study, THSG showed concentration‐dependent protective effects in ameliorating the progression of AD‐induced FSGS. THSG suppressed albuminuria and hypercholesterolemia and reduced the status of lipid peroxidation in urine, plasma, and kidney tissue samples. Furthermore, THSG protected against podocyte damage, reduced renal fibrotic gene expressions, and alleviated the severity of glomerulosclerosis. Treatment of mouse mesangial cells with THSG induced nuclear factor erythroid‐derived 2‐like 2 (Nrf2) nuclear translocation, increased heme oxygenase‐1 and NAD(P)H:quinone oxidoreductase (NQO)‐1 gene expressions, and reduced cellular thiol oxidation and resistance to AD‐induced cytotoxicity. Silencing Nrf2 and its repressor protein, Kelch‐like ECH‐associated protein 1 (Keap1), abolished these protective effects of THSG. In conclusion, THSG can play a protective role in ameliorating the progression of FSGS in a mouse model through activation of the Nrf2‐Keap1 antioxidant pathway. Although a well‐designed therapeutic study is needed, THSG may be applied to manage chronic kidney disease.     

Taurine protects rat testes against NaAsO2-induced oxidative stress and apoptosis via mitochondrial dependent and independent pathways

Arsenic (As) is a well known toxicity inducer. Recent investigations, however, showed that it might have some therapeutic application in cancer treatment. These dual roles of arsenic have attracted a renewed research in organ pathophysiology. In this study, we report that As administration (in the form of NaAsO₂ at a dose of 10 mg/kg body weight for 2 days, orally) induces apoptosis in testicular tissue of the experimental rats by the activation of caspase-3 and reciprocal regulation of Bcl-2/Bad with the concomitant reduction of mitochondrial membrane potential and increased level of cytosolic cytochrome C. Arsenite has also been shown to induce activation of mitogen-activated protein kinases (MAPKs), Akt as well as NF-κB (p65) in testicular tissue. In addition, As significantly decreased testicular Δ⁵-3β-HSD and 17β-HSD activities and reduced the plasma testosterone level, testicular sperm count and sperm motility. Besides, arsenite exposure increased the levels of reactive oxygen species (ROS), serum TNF-α, As accumulation and lipid peroxidation and decreased the activities of the antioxidant enzymes and glutathione in the testicular tissue. Oral administration of taurine (at a dose of 100 mg/kg body weight for 5 days) was found to be effective in counteracting As-induced oxidative stress, attenuation of testicular damages and amelioration of apoptosis in testicular tissue by controlling the reciprocal regulation of Bcl-2/Bad, phospho-ERK1/2, phospho-p38, phospho-Akt and NF-κB. Taurine was also found to play similar beneficial role via mitochondrial dependent pathways in As-induced testicular damages leading to apoptotic cell death.     

穿心莲内酯磺化物雾化治疗急性加重期慢性阻塞性肺疾病的效果

目的观察穿心莲内酯磺化物雾化治疗急性加重期慢性阻塞性肺疾病(AECOPD)的临床效果。方法将96例急性加重期COPD患者随机分为干预组和对照组,各48例,治疗7 d后观察比较两组的生活质量评分、血气指标及第1秒用力呼气容积(FEV1)占预计值百分比百分值。结果干预组患者的生活质量评分明显优于对照组,差异有显著性(P<0.05)。治疗后血气分析各指标及FEV1占预计值百分比比较,干预组与对照组相比差异均有统计学意义(P<0.05)。结论穿心莲内酯磺化物雾化吸入治疗COPD急性加重期疗效较好,值得临床推广。     

Systemic perfluorohexane attenuates lung injury induced by lipopolysaccharide in rats: the role of heme oxygenase-1

Clinical trials with partial liquid ventilation demonstrate improvement in oxygenation, as well as some adverse side effects linked to the application of liquid perfluorocarbons (PFCs) during liquid ventilation. Thus, we examined the effects of systemic administration of PFC on acute lung injury (ALI) induced by lipopolysaccharide (LPS) and its effects on heme oxygenase-1 (HO-1), a compound that provides potent cytoprotection against lung injury.Rats were assigned to one of six groups (n = 8). Thirty minutes after they were challenged with LPS aerosol inhalation, perfluorohexane was given intraperitoneally every two hours. Ten hours after LPS inhalation, bronchoalveolar lavage fluid (BALF) and lung tissue were obtained for enzyme linked immunosorbent assay, histologic, and Western-blot analyses. The results showed that perfluorohexane significantly decreased the wet to dry weight ratio, malondialdehyde (MDA) production, and myeloperoxidase (MPO) activity in the lung tissue. Also, perfluorohexane reduced the total protein content and levels of tumor necrosis factor-α (TNF-α) but increased the levels of the anti-inflammatory cytokine interleukin-10 (IL-10) in the BALF, resulting in decreased pulmonary edema and the infiltration of neutrophils into the lung tissues of LPS-treated rats. Furthermore, perfluorohexane increased HO-1 protein production and stimulated HO-1 activity in the lung tissue. Pre-treatment with Zinc protoporphyrin IX, an inhibitor of HO-1, decreased the protective effects of perfluorohexane in rats.In summary, systemic perfluorohexane alleviates LPS-induced lung injury in rats, and HO-1 may be involved in the mechanism of this reduction.     

Eriodictyol-7-O-glucoside,a novel Nrf2 activator,confers protection against cisplatin-induced toxicity

Eriodictyol-7-O-glucoside, a flavonoid isolated from Dracocephalum rupestre, is among the most potent free radical scavenger. In the present study, we identified eriodictyol-7-O-glucoside as a novel nuclear factor E2-related factor 2 (Nrf2) activator using a high-throughput cellular screening method. This compound activated Nrf2 signaling pathway and was able to stabilize Nrf2 by delaying Nrf2 degradation, resulting in accumulation of Nrf2 protein and activation of the Nrf2-dependent protective response. Recent studies have suggested that activation of Nrf2 pathway would confer protection against cisplatin-induced toxicity. The protective role of eriodictyol-7-O-glucoside in cisplatin-induced toxicity was investigated in a human renal mesangial cell line, HRMC. Cotreatment of HRMC cells with eriodictyol-7-O-glucoside significantly improved cell survival under cisplatin exposure. These findings demonstrated the feasibility of using natural compounds targeting Nrf2 as a therapeutic approach to subvert the side effects of cisplatin in normal cells.     

Inhibition of microRNA-199a-5p ameliorates oxygen-glucose deprivation/reoxygenation-induced apoptosis and oxidative stress in HT22 neurons by targeting Brg1 to activate Nrf2/HO-1 signalling

MicroRNAs (miRNAs) have emerged as critical regulators of neuronal survival during cerebral ischaemia/reperfusion injury. Accumulating evidence has shown that miR-199a-5p plays a crucial role in regulating apoptosis and survival in various cell types. However, whether miR-199a is involved in regulating neuronal survival during cerebral ischaemia/reperfusion injury remains unknown. In this study, we aimed to explore the biological role of miR-199a-5p in regulating neuronal injury induced by oxygen-glucose deprivation/reoxygenation (OGD/R), an in vitro cellular model of cerebral ischaemia and reperfusion injury. We found that miR-199a-5p expression was significantly altered in neurons in response to OGD/R treatment. Overexpression of miR-199a-5p facilitated OGD/R-induced apoptosis and reactive oxygen species (ROS) production, whereas miR-199a-5p inhibition alleviated OGD/R-induced apoptosis and ROS production. Notably, our results identified Brahma-related gene 1 (Brg1) as a target gene of miR-199a-5p. Moreover, inhibition of miR-199a-5p promoted the activation of nuclear factor-erythroid-2-related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) signalling via targeting Brg1. However, silencing of Brg1 markedly reversed the miR-199a-5p inhibition-mediated neuroprotective effect. Taken together, our results suggest that downregulation of miR-199a-5p protects neurons from OGD/R-induced neuronal injury through upregulating Brg1 to activate Nrf2/HO-1 signalling. The miR-199a-5p/Brg1/Nrf2/HO-1 regulation axis may play an important role in regulating neuronal survival during cerebral ischaemic/reperfusion injury in vivo.     

ROS signaling, oxidative stress and Nrf2 in pancreatic beta-cell function

This review focuses on the emerging evidence that reactive oxygen species (ROS) derived from glucose metabolism, such as H₂O₂, act as metabolic signaling molecules for glucose-stimulated insulin secretion (GSIS) in pancreatic beta-cells. Particular emphasis is placed on the potential inhibitory role of endogenous antioxidants, which rise in response to oxidative stress, in glucose-triggered ROS and GSIS. We propose that cellular adaptive response to oxidative stress challenge, such as nuclear factor E2-related factor 2 (Nrf2)-mediated antioxidant induction, plays paradoxical roles in pancreatic beta-cell function. On the one hand, induction of antioxidant enzymes protects beta-cells from oxidative damage and possible cell death, thus minimizing oxidative damage-related impairment of insulin secretion. On the other hand, the induction of antioxidant enzymes by Nrf2 activation blunts glucose-triggered ROS signaling, thus resulting in reduced GSIS. These two premises are potentially relevant to impairment of beta-cells occurring in the late and early stage of Type 2 diabetes, respectively. In addition, we summarized our recent findings that persistent oxidative stress due to absence of uncoupling protein 2 activates cellular adaptive response which is associated with impaired pancreatic beta-cell function.     

血红素氧合酶-1对脂多糖诱导的急性心肌细胞损伤细胞内钙离子浓度的影响

目的研究HO-1对脂多糖刺激的心肌细胞内钙离子含量的影响。方法差速贴壁法培养乳鼠心肌细胞,分为对照组（C）,脂多糖LPS组（L）,LPS＋Hemin组（L＋H）,LPS＋ZnPP组（L＋Zn）,分别诱导或阻断HO-1的合成,并检测心肌细胞内钙离子含量。结果 LPS诱导心肌细胞钙离子含量升高,Hemin增加HO-1水平,降低细胞内钙离子水平,ZnPP降低HO-1水平,细胞内钙离子浓度进一步增加。结论 LPS刺激使心肌细胞内钙离子含量明显升高,HO-1可降低细胞内钙超载。