Disruption of cytochrome P4501A2 in mice leads to increased susceptibility to hyperoxic lung injury

Prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) augments neonatal hyperoxic lung injury: Role of cytochrome P450 (CYP)1A1, 1A2, and 1B1

Pregnant women exposed to polycyclic aromatic hydrocarbons (PAHs) are at increased risk for premature delivery. Premature infants often require supplemental oxygen, a known risk factor for bronchopulmonary dysplasia (BPD). Cytochrome P450 (CYP) enzymes have been implicated in hyperoxic lung injury. We hypothesize that prenatal PAH exposure exacerbates oxygen-mediated lung injury in neonatal mice, and that this effect is differentially altered in mice lacking the gene for (Cyp)1a1, 1a2, or 1b1. Timed pregnant wild type (WT) (C57BL/6J) mice were orally administered a PAH mixture of benzo[a]pyrene (BP) and benzo[b]fluoranthene (BbF) or the vehicle corn oil (CO) once daily on gestational days 16-19, and the dose response on postnatal lung injury was examined. In addition, timed pregnant mice with one of four genotypes, WT, Cyp1a1-null, Cyp1a2-null, and Cyp1b1-null, were treated orally with CO or PAH on gestational days 16-19 and exposed to hyperoxia or room air for 14 days. Lung injury was assessed on PND15 by radial alveolar count (RAC) and mean linear intercept (MLI) Gene expression of DNA repair genes in lung and liver were measured. Results showed that neonatal hyperoxic lung injury is augmented by prenatal PAH exposure in a dose-dependent manner. This effect was differentially altered in the Cyp-null mice, with Cyp1a2-null showing the greatest extent of lung injury. We concluded that newborn mice exposed to PAH in utero had more significant lung injury in response to hyperoxia than non-PAH exposed pups, and that CYP1A1 and CYP1A2 are protective against lung injury while CYP1B1 augments lung injury.

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Characterization of acute lung injury in the bleomycin rat model

The aim of this study was to describe and characterize the pathophysiological changes occurring during the early inflammatory phase (first 3 days) in the rat bleomycin model of lung injury preceding the development of fibrosis. Further, we wanted to understand the kinetics and factors contributing to bleomycin-induced acute lung injury (ALI) and provide a robust, reliable and reproducible framework of features of ALI readouts to assess effects of therapeutics on bleomycin-induced ALI in rats. We induced ALI in rats with intratracheal (i.t.) installation of bleomycin. The animals were sacrificed on predetermined time points, that is, Day 0, 1, 2, and 3 post the bleomycin challenge. We analyzed bronchoalveolar lavage fluid (BALF) and lung tissue to establish and assess relevant experimental features of ALI. We demonstrated that bleomycin induced key features of experimental ALI including a profound increase in neutrophils in BALF (50-60%), pulmonary edema, and lung pathology on Day 3 after challenge. Furthermore, we showed that TGF-β1, IL-1β, TNF-α, IL-6, CINC-1, TIMP-1, and WISP-1 were induced by studying their kinetic profile during the first 3 days after bleomycin injury consistent with their known role ALI. We also confirmed that detectable fibrogenesis occurs at the earliest on Day 3 after injury based on collagen content, along with changes in the TGF-β/Smad signaling pathway and increased expression of Galectin-3, Vimentin, and Fibronectin in lung homogenate. Our report presents robust features and contributing mediators/factors to the pathology of bleomycin-induced ALI in rats on Day 3. The kinetic data provide insights on the progression of ALI and a detailed understanding of early events before actual fibrosis development. This set of experimental endpoints is very appropriate and invaluable for efficacy testing of potential novel therapeutic treatments (single or combined) in ALI and understanding their mechanism of action.

The protective effect of natural medicines against excessive inflammation and oxidative stress in acute lung injury by regulating the Nrf2 signaling pathway

Acute lung injury (ALI) is a common critical disease of the respiratory system that progresses into acute respiratory distress syndrome (ARDS), with high mortality, mainly related to pulmonary oxidative stress imbalance and severe inflammation. However, there are no clear and effective treatment strategies at present. Nuclear factor erythroid 2-related factor 2(Nrf2) is a transcription factor that interacts with multiple signaling pathways and regulates the activity of multiple oxidases (NOX, NOS, XO, CYP) related to inflammation and apoptosis, and exhibits antioxidant and anti-inflammatory roles in ALI. Recently, several studies have reported that the active ingredients of natural medicines show protective effects on ALI via the Nrf2 signaling pathway. In addition, they are cheap, naturally available, and possess minimal toxicity, thereby having good clinical research and application value. Herein, we summarized various studies on the protective effects of natural pharmaceutical components such as polyphenols, flavonoids, terpenoids, alkaloids, and polysaccharides on ALI through the Nrf2 signaling pathway and demonstrated existing gaps as well as future perspectives.

The Aryl Hydrocarbon Receptor (AHR): A Novel Therapeutic Target for Pulmonary Diseases?

The aryl hydrocarbon receptor (AHR) is a cytoplasmic transcription factor that is well-known for regulating xenobiotic metabolism. Studies in knockout and transgenic mice indicate that the AHR plays a vital role in the development of liver and regulation of reproductive, cardiovascular, hematopoietic, and immune homeostasis. In this focused review on lung diseases associated with acute injury and alveolar development, we reviewed and summarized the current literature on the mechanistic role(s) and therapeutic potential of the AHR in acute lung injury, chronic obstructive pulmonary disease, and bronchopulmonary dysplasia (BPD). Pre-clinical studies indicate that endogenous AHR activation is necessary to protect neonatal and adult lungs against hyperoxia- and cigarette smoke-induced injury. Our goal is to provide insight into the high translational potential of the AHR in the meaningful management of infants and adults with these lung disorders that lack curative therapies.

Role of Human NADPH Quinone Oxidoreductase (NQO1) in Oxygen-Mediated Cellular Injury and Oxidative DNA Damage in Human Pulmonary Cells

Supplemental oxygen administration is frequently used in premature infants and adults with pulmonary insufficiency. NADPH quinone oxidoreductase (NQO1) protects cells from oxidative injury by decreasing reactive oxygen species (ROS). In this investigation, we tested the hypothesis that overexpression of NQO1 in BEAS-2B cells will mitigate cell injury and oxidative DNA damage caused by hyperoxia and that A-1221C single nucleotide polymorphism (SNP) in the NQO1 promoter would display altered susceptibility to hyperoxia-mediated toxicity. Using stable transfected BEAS-2B cells, we demonstrated that hyperoxia decreased cell viability in control cells (Ctr), but this effect was differentially mitigated in cells overexpressing NQO1 under the regulation of the CMV viral promoter, the wild-type NQO1 promoter (NQO1-NQO1), or the NQO1 promoter carrying the SNP. Interestingly, hyperoxia decreased the formation of bulky oxidative DNA adducts or 8-hydroxy-2′-deoxyguanosine (8-OHdG) in Ctr cells. qPCR studies showed that mRNA levels of CYP1A1 and NQO1 were inversely related to DNA adduct formation, suggesting the protective role of these enzymes against oxidative DNA injury. In SiRNA experiments entailing the NQO1-NQO1 promoter, hyperoxia caused decreased cell viability, and this effect was potentiated in cells treated with CYP1A1 siRNA. We also found that hyperoxia caused a marked induction of DNA repair genes DDB2 and XPC in Ctr cells, supporting the idea that hyperoxia in part caused attenuation of bulky oxidative DNA lesions by enhancing nucleotide excision repair (NER) pathways. In summary, our data support a protective role for human NQO1 against oxygen-mediated toxicity and oxidative DNA lesions in human pulmonary cells, and protection against toxicity was partially lost in SNP cells. Moreover, we also demonstrate a novel protective role for CYP1A1 in the attenuation of oxidative cells and DNA injury. Future studies on the mechanisms of attenuation of oxidative injury by NQO1 should help in developing novel approaches for the prevention/treatment of ARDS in humans.

Biomarkers and Mechanisms of Oxidative Stress-Last 20 Years of Research with an Emphasis on Kidney Damage and Renal Transplantation

Oxidative stress is an imbalance between pro- and antioxidants that adversely influences the organism in various mechanisms and on many levels. Oxidative damage occurring concomitantly in many cellular structures may cause a deterioration of function, including apoptosis and necrosis. The damage leaves a molecular “footprint”, which can be detected by specific methodology, using certain oxidative stress biomarkers. There is an intimate relationship between oxidative stress, inflammation, and functional impairment, resulting in various diseases affecting the entire human body. In the current narrative review, we strengthen the connection between oxidative stress mechanisms and their active compounds, emphasizing kidney damage and renal transplantation. An analysis of reactive oxygen species (ROS), antioxidants, products of peroxidation, and finally signaling pathways gives a lot of promising data that potentially will modify cell responses on many levels, including gene expression. Oxidative damage, stress, and ROS are still intensively exploited research subjects. We discuss compounds mentioned earlier as biomarkers of oxidative stress and present their role documented during the last 20 years of research. The following keywords and MeSH terms were used in the search: oxidative stress, kidney, transplantation, ischemia-reperfusion injury, IRI, biomarkers, peroxidation, and treatment.

Hyperoxia and Lungs: What We Have Learned From Animal Models

Although oxygen (O₂) is essential for aerobic life, it can also be an important source of cellular damage. Supra-physiological levels of O₂ determine toxicity due to exacerbated reactive oxygen species (ROS) production, impairing the homeostatic balance of several cellular processes. Furthermore, injured cells activate inflammation cascades, amplifying the tissue damage. The lung is the first (but not the only) organ affected by this condition. Critically ill patients are often exposed to several insults, such as mechanical ventilation, infections, hypo-perfusion, systemic inflammation, and drug toxicity. In this scenario, it is not easy to dissect the effect of oxygen toxicity. Translational investigations with animal models are essential to explore injuring stimuli in controlled experimental conditions, and are milestones in understanding pathological mechanisms and developing therapeutic strategies. Animal models can resemble what happens in critical care or anesthesia patients under mechanical ventilation and hyperoxia, but are also critical to explore the effect of O₂ on lung development and the role of hyperoxic damage on bronchopulmonary dysplasia. Here, we set out to review the hyperoxia effects on lung pathology, contributing to the field by describing and analyzing animal experimentation's main aspects and its implications on human lung diseases.

The role of cytochrome P450 (CYP) enzymes in hyperoxic lung injury

INTRODUCTION

Hyperoxic lung injury is a condition that can occur in patients in need of supplemental oxygen, such as premature infants with bronchopulmonary dysplasia or adults with acute respiratory distress syndrome. Cytochrome P450 (CYP) enzymes play critical roles in the metabolism of endogenous and exogenous compounds.

AREAS COVERED

Through their complex pathways, some subfamilies of these enzymes may contribute to or protect against hyperoxic lung injury. Oxidative stress from reactive oxygen species (ROS) production is most likely a major contributor of hyperoxic lung injury. CYP1A enzymes have been shown to protect against hyperoxic lung injury while CYP1B enzymes seem to contribute to it. CYP2J2 enzymes help protect against hyperoxic lung injury by triggering EET production, thereby, increasing antioxidant enzymes. The metabolism of arachidonic acid to ω-terminal hydroxyeicosatetraenoic acid (20-HETEs) by CYP4A and CYP4F enzymes could impact hyperoxic lung injury via the vasodilating effects of 20-HETE. CYP2E1 and CYP2A enzymes may contribute to the oxidative stress in the lungs caused by ethanol- and nicotine-metabolism, respectively.

EXPERT OPINION

Overall, the CYP enzymes, depending upon the isoform, play a contributory or protective role in hyperoxic lung injury, and are, therefore, ideal candidates for developing drugs that can treat oxygen-mediated lung injury.

Oxygen-mediated lung injury in mice lacking the gene for NRF2: Rescue with the cytochrome P4501A-inducer, beta-naphthoflavone (BNF), and differential sex-specific effects

BACKGROUND

Acute respiratory distress syndrome (ARDS) leads to progressive lung injury, which significantly impacts patient morbidity and mortality but may differ clinically between the sexes. Cytochrome P450 (CYP) 1A enzymes are protective against hyperoxic lung injury and may contribute to sex-dependent pathology. NRF2 is a critical transcriptional regulator of antioxidants and loss of NRF2 leads to severe hyperoxic lung injury and mortality in mice. NRF2 deficiencies and polymorphisms have been observed in patients with pulmonary diseases such as chronic obstructive pulmonary disease and severe asthma. No prior studies have evaluated whether there are sex-specific differences in oxygen-mediated lung injury in Nrf2^-/- mice and there are few rescue studies.

OBJECTIVE

To test the hypothesis that hyperoxia induces greater lung injury and inflammation in Nrf2^-/- mice compared to wild type (WT) that differs between sexes, and that this phenotype will be rescued by the administration of the cytochrome P450 (CYP) 1A inducer beta-naphthoflavone (BNF).

DESIGN/METHODS

Male and female 8-10-week-old WT or Nrf2^-/- C57BL/6 mice were pre-treated with BNF (40 mg/kg) or corn oil control and exposed to hyperoxia (95% O₂) for 68 h. Survival, pulmonary edema, neutrophil recruitment, and lung injury scores were evaluated. Gene expression of phase II detoxification enzymes, pulmonary cytokines, and Cyp1a1/2 was quantified. CYP1A1/2 protein expression and catalytic activities were also measured.

RESULTS

Hyperoxia exposure greatly reduced survival in Nrf2^-/- mice, particularly in females. BNF treatment improved survival by 182.8% in Nrf2^-/- females and by 41.4% in Nrf2^-/- males as well as in WT females by 85.7%. Females had greater pulmonary edema as measured by lung weight to body weight ratios but was attenuated in all groups except Nrf2^-/- females by BNF. Neutrophils doubled in Nrf2^-/- lungs compared to WT in hyperoxia but were decreased in BNF-treated females of both genotypes. Pulmonary cytokine gene expression including Il-6 and Tnf-α increased in hyperoxia especially in Nrf2^-/- mice and was unaffected by BNF. Pulmonary and hepatic Nqo1 gene expression w-as decreased in Nrf2^-/- mice and was largely unaffected by BNF; however pulmonary Ho-1 did not vary significantly between the genotypes and was decreased in WT animals treated with BNF. Activities and protein expression of pulmonary and hepatic CYP1A1/2 were induced via BNF across all groups. Although hepatic Cyp1a2 gene expression was higher in Nrf2^-/- males, the catalytic activity was higher in Nrf2^-/- females.

CONCLUSIONS

Hyperoxia augmented lung injury in Nrf2^-/- mice, and pre-treatment with BNF was protective against mortality and injury, eliminating the sex-dependent survival difference in both genotypes. Our results support the hypothesis that NRF2 protects mice against lung injury, and the fact that BNF rescues the lung injury phenotype in Nrf2^-/- mice suggests that augmented CYP1A expression by BNF may contribute to the beneficial effects. Further studies could lead to the development of BNF and other flavonoids for the prevention/treatment of hyperoxic lung injury, particularly in vulnerable patients with relative NRF2 deficiency, regardless of sex.

Hepatic transcriptomics analysis reveals that fructose intervention down-regulated xenobiotics-metabolising enzymes through aryl hydrocarbon receptor signalling suppression in C57BL/6N mice

For decades, fructose intake has been recognised as an environmental risk for metabolic syndromes and diseases. Here we comprehensively examined the effects of fructose intake on mice liver transcriptomes. Fructose-supplemented water (34 %; w/v) was fed to both male and female C57BL/6N mice at their free will for 6 weeks, followed by hepatic transcriptomics analysis. Based on our criteria, differentially expressed genes (DEG) were selected and subjected to further computational analyses to predict key pathways and upstream regulator(s). Subsequently, predicted genes and pathways from the transcriptomics dataset were validated via quantitative RT-PCR analyses. As a result, we identified eighty-nine down-regulated and eighty-eight up-regulated mRNA in fructose-fed mice livers. These DEG were subjected to bioinformatics analysis tools in which DEG were mainly enriched in xenobiotic metabolic processes; further, in the Ingenuity Pathway Analysis software, it was suggested that the aryl hydrocarbon receptor (AhR) is an upstream regulator governing overall changes, while fructose suppresses the AhR signalling pathway. In our quantitative RT-PCR validation, we confirmed that fructose suppressed AhR signalling through modulating expressions of transcription factor (AhR nuclear translocator; Arnt) and upstream regulators (Ncor2, and Rb1). Altogether, we demonstrated that ad libitum fructose intake suppresses the canonical AhR signalling pathway in C57BL/6N mice liver. Based on our current observations, further studies are warranted, especially with regard to the effects of co-exposure to fructose on (1) other types of carcinogens and (2) inflammation-inducing agents (or even diets such as a high-fat diet), to find implications of fructose-induced AhR suppression.

Molecular role of cytochrome P4501A enzymes inoxidative stress

Cytochrome P4501A (CYP1A) enzymes play important roles in xenobiotic and endobiotic metabolism. Due to uncoupling reactions during the enzymatic cycle, CYP1A enzymes can release reactive oxidative species (ROS) in the form of superoxide radical, hydrogen peroxide, hydroxyl radical etc. An imbalance between production of free radicals and the ability of antioxidants to detoxify the free radicals can lead to accumulation of ROS, which in turn can lead to oxidative stress. Oxidative stress can lead to inflammation and toxicity, which in turn can cause human diseases such as bronchopulmonary disease (BPD), ARDS, renal hypertension, etc. CYP1A enzymes, depending on the organ system, they either contribute or protect against oxidative injury. Thus, they have dual roles in regard to oxidative stress. This review presents an overview of the mechanistic relationship between CYP1A enzymes and oxidative stress in relation to various diseases in different organs (e.g., liver, lungs, heart, kidneys, and reproductive organs).

Mice Lacking the Cytochrome P450 1B1 Gene Are Less Susceptible to Hyperoxic Lung Injury Than Wild Type

Supplemental oxygen is a life-saving intervention administered to individuals suffering from respiratory distress, including adults with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Despite the clinical benefit, supplemental oxygen can create a hyperoxic environment that increases reactive oxygen species, oxidative stress, and lung injury. We have previously shown that cytochrome P450 (CYP)1A enzymes decrease susceptibility to hyperoxia-induced lung injury. In this investigation, we determined the role of CYP1B1 in hyperoxic lung injury in vivo. Eight- to ten-week old C57BL/6 wild type (WT) and Cyp1b1-/- mice were exposed to hyperoxia (>95% O2) for 24-72 h or maintained in room air (21% O2). Lung injury was assessed by histology and lung weight to body weight (LW/BW) ratios. Extent of inflammation was determined by assessing pulmonary neutrophil infiltration and cytokine levels. Lipid peroxidation markers were quantified by gas chromatography mass spectrometry, and oxidative DNA adducts were quantified by 32P-postlabeling as markers of oxidative stress. We found that Cyp1b1-/- mice displayed attenuation of lung weight and pulmonary edema, particularly after 48-72 h of hyperoxia compared with WT controls. Further, Cyp1b1-/- mice displayed decreased levels of pulmonary oxidative DNA adducts and pulmonary isofurans after 24 h of hyperoxia. Cyp1b1-/- mice also showed increased pulmonary CYP1A1 and 1A2 and mRNA expression. In summary, our results support the hypothesis that Cyp1b1-/- mice display decreased hyperoxic lung injury than wild type counterparts and that CYP1B1 may act as a pro-oxidant during hyperoxia exposure, contributing to increases in oxidative DNA damage and accumulation of lipid hydroperoxides.

The mechanism of Psoralen and Isopsoralen hepatotoxicity as revealed by hepatic gene expression profiling in SD rats

BACKGROUND

The main bioactive components of Fructus psoraleae, such as psoralen and isopsoralen, are known to be hepatotoxic. However, its underlying mechanism is to be elucidated.

METHODS

To address this, SD rats were randomly divided into control group, 60 mg/kg psoralen group and 60 mg/kg isopsoralen group. Blood was collected to detect serum biochemical indices. RNA was extracted from liver samples, and then, cDNA gene expression profiles were analysed.

RESULTS

Psoralen administration significantly up-regulated serum AST (aspartate aminotransferase) while addition of isopsoralen increased serum ALT (alanine aminotransferase), AST, TBA (total bile acid) and TG (total triglyceride) levels. A total of 172 differentially expressed genes (DEGs) were acquired between psoralen group and control group while 884 DEGs were screened between isopsoralen group and control group. Chemical Carcinogenesis and Metabolism of Xenobiotics by Cytochrome P450 were the two most significantly enriched pathways as revealed by DEGs. Liver was the most impacted organ, and endoplasmic reticulum was the most impacted organelle in subcellular level. Finally, some kinds of cancers and cytochrome p450 oxidoreductase deficiency were predicted. Taken together, psoralen and isopsoralen might cause hepatotoxicity mainly through cytochrome P450 metabolism of xenobiotics. Furthermore, Cyp1a1, Cyp1a2, Gstm1 and Akr7a3 worked as key genes in hepatotoxicity. Moreover, endoplasmic reticulum was the main target subcellular structure in hepatotoxicity induced by psoralen and isopsoralen.

Selection signature reveals genes associated with susceptibility loci affecting respiratory disease due to pleiotropic and hitchhiking effect in Chinese indigenous pigs

Objective

Porcine respiratory disease is one of the most important health problems causing significant economic losses. To understand the genetic basis for susceptibility to swine enzootic pneumonia (EP) in pigs, we detected 102,809 single nucleotide polymorphisms in a total of 249 individuals based on genome-wide sequencing data.

Methods

Genome comparison of susceptibility to swine EP in three pig breeds (Jinhua, Erhualian, and Meishan) with two western lines that are considered more resistant (Duroc and Landrace) using cross-population extended haplotype homozygosity and F-statistic (F_ST) statistical approaches identified 691 positively selected genes. Based on quantitative trait loci, gene ontology terms and literature search, we selected 14 candidate genes that have convincible biological functions associated with swine EP or human asthma.

Results

Most of these genes were tested by several methods including transcription analysis and candidate genes association study. Among these genes: cytochrome P450 1A1 and catenin beta 1 (CTNNB1) are involved in fertility; transforming growth factor beta receptor 3 plays a role in meat quality traits; Wnt family member 2, CTNNB1 and transcription factor 7 take part in adipogenesis and fat deposition simultaneously; plasminogen activator, urokinase receptor (completely linked to AXL receptor tyrosine kinase, r² = 1) plays an essential role in the successful ovulation of matured oocytes in pigs; colipase like 2 (strongly linked to SAM pointed domain containing ETS transcription factor, r² = 0.848) is involved in male fertility.

Conclusion

These adverse genes susceptible to swine EP may be selected while selecting for economic traits (especially reproduction traits) due to pleiotropic and hitchhiking effect of linked genes. Our study provided a completely new point of view to understand the genetic basis for susceptibility or resistance to swine EP in pigs thereby, provides insight for designing sustainable breed selection programs. Finally, the candidate genes are crucial due to their potential roles in respiratory diseases in a large number of species, including human.

Newborn Mice Lacking the Gene for Cyp1a1 Are More Susceptible to Oxygen-Mediated Lung Injury, and Are Rescued by Postnatal β-Naphthoflavone Administration: Implications for Bronchopulmonary Dysplasia in Premature Infants

Prolonged hyperoxia contributes to bronchopulmonary dysplasia (BPD) in preterm infants. β-Naphthoflavone (BNF) is a potent inducer of cytochrome P450 (CYP)1A enzymes, which have been implicated in hyperoxic injuries in adult mice. In this investigation, we tested the hypothesis that newborn mice lacking the Cyp1a1 gene would be more susceptible to hyperoxic lung injury than wild-type (WT) mice and that postnatal BNF treatment would rescue this phenotype by mechanisms involving CYP1A and/or NAD(P)H quinone oxidoreductase (NQO1) enzymes. Newborn WT or Cyp1a1-null mice were treated with BNF (10 mg/kg) or the vehicle corn oil (CO) i.p., from postnatal day (PND) 2 to 14 once every other day, while being maintained in room air or hyperoxia (85% O2) for 14 days. Both genotypes showed lung injury, inflammation, and alveolar simplification in hyperoxia, with Cyp1a1-null mice displaying increased susceptibility compared to WT mice. BNF treatment resulted in significant attenuation of lung injury and inflammation, with improved alveolarization in both WT and Cyp1a1-null mice. BNF exposed normoxic or hyperoxic WT mice showed increased expression of hepatic CYP1A1/1A2, pulmonary CYP1A1, and NQO1 expression at both mRNA and protein levels, compared with vehicle controls. However, BNF caused greater induction of hepatic CYP1A2 and pulmonary NQO1 enzymes in the Cyp1a1-null mice, suggesting that BNF protects against hyperoxic lung injury in WT and Cyp1a1-null mice through the induction of CYP1A and NQO1 enzymes. Further studies on the protective role of flavonoids against hyperoxic lung injury in newborns could lead to novel strategies for the prevention and/or treatment of BPD.

ROS Signaling in the Pathogenesis of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS)

The generation of reactive oxygen species (ROS) plays an important role for the maintenance of cellular processes and functions in the body. However, the excessive generation of oxygen radicals under pathological conditions such as acute lung injury (ALI) and its most severe form acute respiratory distress syndrome (ARDS) leads to increased endothelial permeability. Within this hallmark of ALI and ARDS, vascular microvessels lose their junctional integrity and show increased myosin contractions that promote the migration of polymorphonuclear leukocytes (PMNs) and the transition of solutes and fluids in the alveolar lumen. These processes all have a redox component, and this chapter focuses on the role played by ROS during the development of ALI/ARDS. We discuss the origins of ROS within the cell, cellular defense mechanisms against oxidative damage, the role of ROS in the development of endothelial permeability, and potential therapies targeted at oxidative stress.

Quercetin attenuates the hyperoxic lung injury in neonatal mice: Implications for Bronchopulmonary dysplasia (BPD)

Quercetin (QU) is one of the most common flavonoids that are present in a wide variety of fruits, vegetables, and beverages. This compound possesses potent anti-inflammatory and anti-oxidant properties. Supplemental oxygen is routinely administered to premature infants with pulmonary insufficiency. However, hyperoxia is one of the major risk factors for the development of bronchopulmonary dysplasia (BPD), which is also termed chronic lung disease in premature infants. Currently, no preventive approaches have been reported against BPD. The treatment of BPD is notably limited to oxygen administration, ventilatory support, and steroids. Since QU has been shown to be effective in reducing inflammation and oxidative stress in various disease models, we hypothesized that the postnatal QU treatment of newborn mice will protect against hyperoxic lung injury by the upregulation of the phase I (CYP1A/B) and/or phase II, NADPH quinone reductase enzymes. Newborn C57BL/6J mice within 24 h of birth with the nursing dams were exposed to either 21% O₂ (air) and/or 85% O₂ (hyperoxia) for 7 days. The mice were treated, intraperitoneally (i.p.) once every other day with quercetin, at a concentration of 20 mg/kg, or saline alone from postnatal day (PND) 2-6. The mice were sacrificed on day 7, and lung and liver tissues were collected. The expression levels of CYP1A1, CYP1B1, NQO1 proteins and mRNA as well as the levels of MDA-protein adducts were analyzed in lung and liver tissues. The findings indicated that QU attenuated hyperoxia-mediated lung injury by reducing inflammation and improving alveolarization with decreased number of neutrophil and macrophage infiltration. The attenuation of this lung injury correlated with the upregulation of CYP1A1/CYP1B1/NQO1 mRNA, proteins and the down regulation of NF-kB levels and MDA-protein adducts in lung and liver tissues. The present study demonstrated the potential therapeutic value of quercetin in the prevention and/or treatment of BPD.

ROLE OF CYTOCHROME P450S IN THE GENERATION AND METABOLISM OF REACTIVE OXYGEN SPECIES

The cytochrome P450 (CYP) enzymes are a diverse group of heme monooxygenases that, through the course of their reaction cycle, contribute to cellular reactive oxygen species (ROS). CYP enzymes play a crucial role in human physiology and are involved in drug and xenobiotic metabolism as well as biosynthesis of endogenous molecules and are expressed throughout the human body. However, during the course of the CYP catalytic cycle, ROS can be generated through uncoupling of the enzymatic cycle. ROS is known to modify endogenous molecules, included lipids, proteins, and nucleic acids, which can lead to cell damage and death and contribute to disease development. ROS has been implicated in a wide range of diseases and conditions, including cancer and ageing, but ROS also play a role in the normal physiological functions in the cell. Here, we discuss specific examples whereby ROS generated by CYPs contribute to or protect against various phenomena, such as hyperoxic lung injury, oxidative hepatic toxicity, formation of DNA adducts from lipid peroxidation products. We have also discussed the mechanistic roles of CYP enzymes belonging to various families, and their effect on cellular ROS production, in relation to normal cellular function as well as disease pathophysiology.

Birth delivery method affects expression of immune genes in lung and jejunum tissue of neonatal beef calves

Background

Caesarean section is a routine veterinary obstetrical procedure employed to alleviate dystocia in cattle. However, CS, particularly before the onset of labour, is known to negatively affect neonatal respiration and metabolic adaptation in humans, though there is little published information for cattle. The aim of this study was to investigate the effect of elective caesarean section (ECS) or normal trans-vaginal (TV) delivery, on lung and jejunal gene expression profiles of neonatal calves.

Results

Paternal half-sib Angus calves (gestation length 278 + 1.8 d) were delivered either transvaginally (TV; n = 8) or by elective caesarean section (ECS; n = 9) and immediately euthanized. Lung and jejunum epithelial tissue was isolated and snap frozen. Total RNA was extracted using Trizol reagent and reverse transcribed to generate cDNA. For lung tissue, primers were designed to target genes involved in immunity, surfactant production, cellular detoxification, membrane transport and mucin production. Primers for jejunum tissue were chosen to target mucin production, immunoglobulin uptake, cortisol reaction and membrane trafficking. Quantitative real-time PCR reactions were performed and data were statistically analysed using mixed models ANOVA. In lung tissue the expression of five genes were affected (p < 0.05) by delivery method. Four of these genes were present at lower (LAP, CYP1A1, SCN11α and SCN11β) and one (MUC5AC) at higher abundance in ECS compared with TV calves. In jejunal tissue, expression of TNFα, Il-1β and 1 l-6 was higher in ECS compared with TV calves.

Conclusions

This novel study shows that ECS delivery affects the expression of key genes involved in the efficiency of the pulmonary liquid to air transition at birth, and may lead to an increased inflammatory response in jejunal tissue, which could compromise colostral immunoglobulin absorption. These findings are important to our understanding of the viability and management of neonatal calves born through ECS.

β-Naphthoflavone treatment attenuates neonatal hyperoxic lung injury in wild type and Cyp1a2-knockout mice

Exposure to supraphysiological concentrations of oxygen (hyperoxia) leads to bronchopulmonary dysplasia (BPD), one of the most common pulmonary morbidities in preterm neonates, which is more prevalent in males than females. Beta-naphthoflavone (BNF) is protective against hyperoxic lung injury in adult and neonatal wild type (WT) mice and in and mice lacking Cyp1a1gene. In this investigation, we tested the hypothesis that BNF treatment will attenuate neonatal hyperoxic lung injury in WT and Cyp1a2-/- mice, and elucidated the effect of sex-specific differences. Newborn WT or Cyp1a2-/- mice were treated with BNF (10mg/kg) or the vehicle corn oil (CO) i.p., from postnatal day (PND) 2 to 8 once every other day, while being maintained in room air or hyperoxia (85% O2) for 14days. Hyperoxia exposure lead to alveolar simplification and arrest in angiogenesis in WT as well as Cyp1a2-/- mice No significant differences were seen between WT and Cyp1a2-/- mice. Cyp1a2-/- female mice had better preservation of pulmonary angiogenesis at PND15 compared to similarly exposed males. BNF treatment attenuated lung injury and inflammation in both genotypes, and this was accompanied by a significant induction of hepatic and pulmonary CYP1A1 in WT but not in Cyp1a2-/- mice. BNF treatment increased NADPH quinone oxidoreductase (NQO1) mRNA levels in Cyp1a2-/- mouse livers compared to WT mice. These results suggest that BNF is protective in neonatal mice exposed to hyperoxia independent of CYP1A2 and this may entail the protective effect of phase II enzymes like NQO1.

Hyperoxia-mediated transcriptional activation of cytochrome P4501A1 (CYP1A1) and decreased susceptibility to oxygen-mediated lung injury in newborn mice

Hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. In this study, we tested the hypothesis that newborn transgenic mice carrying the human CYP1A1-Luc promoter will display transcriptional activation of the human CYP1A1 promoter in vivo upon exposure to hyperoxia, and that these mice will be less susceptible to hyperoxic lung injury and alveolar simplification than similarly exposed wild type (WT) mice. Newborn WT (CD-1) or transgenic mice carrying a 13.2 kb human CYP1A1 promoter and the luciferase (Luc) reporter gene (CYP1A1-luc) were maintained in room air or exposed to hyperoxia (85% O₂) for 7-14 days. Hyperoxia exposure of CYP1A1-Luc mice for 7 and 14 days resulted in 4- and 30-fold increases, respectively, in hepatic Luc (CYP1A1) expression, compared to room air controls. In lung, hyperoxia caused a 2-fold induction of reporter Luc at 7 days, but the induction declined after 14 days. The newborn CYP1A1-Luc mice were less susceptible to lung injury and alveolar simplification than similarly exposed wild type (WT) CD-1 mice. Also, the CYP1A1-Luc mice showed increased levels of hepatic and pulmonary CYP1A1 expression and hepatic CYP1A2 activity after hyperoxia exposure. Hyperoxia also increased NADP(H) quinone reductase (NQO1) pulmonary gene expression in both CD-1 and CYP1A1-Luc mice at both time points, but this was more pronounced in the latter at 14 days. Our results support the hypothesis that hyperoxia activates the human CYP1A1 promoter in newborn mice, and that increased endogenous expression of CYP1A1 and NADP(H) quinone reductase (NQO1) contributes to the decreased susceptibilities to hyperoxic lung injury in the transgenic animals. This is the first report providing evidence of hyperoxia-mediated transcriptional activation of the human CYP1A1 promoter in newborn mice, and this in conjunction with decreased lung injury, suggests that these phenomena have important implications for BPD.

Role of Cytochrome P450 (CYP)1A in Hyperoxic Lung Injury: Analysis of the Transcriptome and Proteome

Hyperoxia contributes to lung injury in experimental animals and diseases such as acute respiratory distress syndrome in humans. Cytochrome P450 (CYP)1A enzymes are protective against hyperoxic lung injury (HLI). The molecular pathways and differences in gene expression that modulate these protective effects remain largely unknown. Our objective was to characterize genotype specific differences in the transcriptome and proteome of acute hyperoxic lung injury using the omics platforms: microarray and Reverse Phase Proteomic Array. Wild type (WT), Cyp1a1−/− and Cyp1a2−/− (8–10 wk, C57BL/6J background) mice were exposed to hyperoxia (FiO₂ > 0.95) for 48 hours. Comparison of transcriptome changes in hyperoxia-exposed animals (WT versus knock-out) identified 171 genes unique to Cyp1a1−/− and 119 unique to Cyp1a2−/− mice. Gene Set Enrichment Analysis revealed pathways including apoptosis, DNA repair and early estrogen response that were differentially regulated between WT, Cyp1a1−/− and Cyp1a2−/− mice. Candidate genes from these pathways were validated at the mRNA and protein level. Quantification of oxidative DNA adducts with ³²P-postlabeling also revealed genotype specific differences. These findings provide novel insights into mechanisms behind the differences in susceptibility of Cyp1a1−/− and Cyp1a2−/− mice to HLI and suggest novel pathways that need to be investigated as possible therapeutic targets for acute lung injury.

Leflunomide induces NAD(P)H quinone dehydrogenase 1 enzyme via the aryl hydrocarbon receptor in neonatal mice

Aryl hydrocarbon receptor (AhR) has been increasingly recognized to play a crucial role in normal physiological homeostasis. Additionally, disrupted AhR signaling leads to several pathological states in the lung and liver. AhR activation transcriptionally induces detoxifying enzymes such as cytochrome P450 (CYP) 1A and NAD(P)H quinone dehydrogenase 1 (NQO1). The toxicity profiles of the classical AhR ligands such as 3-methylcholanthrene and dioxins limit their use as a therapeutic agent in humans. Hence, there is a need to identify nontoxic AhR ligands to develop AhR as a clinically relevant druggable target. Recently, we demonstrated that leflunomide, a FDA approved drug, used to treat rheumatoid arthritis in humans, induces CYP1A enzymes in adult mice via the AhR. However, the mechanisms by which this drug induces NQO1 in vivo are unknown. Therefore, we tested the hypothesis that leflunomide will induce pulmonary and hepatic NQO1 enzyme in neonatal mice via AhR-dependent mechanism(s). Leflunomide elicited significant induction of pulmonary CYP1A1 and NQO1 expression in neonatal mice. Interestingly, the dose at which leflunomide increased NQO1 was significantly higher than that required to induce CYP1A1 enzyme. Likewise, it also enhanced hepatic CYP1A1, 1A2 and NQO1 expression in WT mice. In contrast, leflunomide failed to induce these enzymes in AhR-null mice. Our results indicate that leflunomide induces pulmonary and hepatic CYP1A and NQO1 enzymes via the AhR in neonatal mice. These findings have important implications to prevent and/or treat disorders such as bronchopulmonary dysplasia in human infants where AhR may play a crucial role in the disease pathogenesis.

Antioxidant Functions of the Aryl Hydrocarbon Receptor

The aryl hydrocarbon receptor (AhR) is a transcription factor belonging to the basic helix-loop-helix/PER-ARNT-SIM family. It is activated by a variety of ligands, such as environmental contaminants like polycyclic aromatic hydrocarbons or dioxins, but also by naturally occurring compounds and endogenous ligands. Binding of the ligand leads to dimerization of the AhR with aryl hydrocarbon receptor nuclear translocator (ARNT) and transcriptional activation of several xenobiotic phase I and phase II metabolizing enzymes. It is generally accepted that the toxic responses of polycyclic aromatic hydrocarbons, dioxins, and structurally related compounds are mediated by activation of the AhR. A multitude of studies indicate that the AhR operates beyond xenobiotic metabolism and exerts pleiotropic functions. Increasing evidence points to a protective role of the AhR against carcinogenesis and oxidative stress. Herein, I will highlight data demonstrating a causal role of the AhR in the antioxidant response and present novel findings on potential AhR-mediated antioxidative mechanisms.

The novelty of phytofurans, isofurans, dihomo-isofurans and neurofurans: Discovery, synthesis and potential application

Polyunsaturated fatty acids (PUFA) are oxidized in vivo under oxidative stress through free radical pathway and release cyclic oxygenated metabolites, which are commonly classified as isoprostanes and isofurans. The discovery of isoprostanes goes back twenty-five years compared to fifteen years for isofurans, and great many are discovered. The biosynthesis, the nomenclature, the chemical synthesis of furanoids from α-linolenic acid (ALA, C18:3 n-3), arachidonic acid (AA, C20:4 n-6), adrenic acid (AdA, 22:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3) as well as their identification and implication in biological systems are highlighted in this review.

Mechanistic role of cytochrome P450 (CYP)1B1 in oxygen-mediated toxicity in pulmonary cells: A novel target for prevention of hyperoxic lung injury

Supplemental oxygen, which is routinely administered to preterm infants with pulmonary insufficiency, contributes to bronchopulmonary dysplasia (BPD) in these infants. Hyperoxia also contributes to the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) in adults. The mechanisms of oxygen-mediated pulmonary toxicity are not completely understood. Recent studies have suggested an important role for cytochrome P450 (CYP)1A1/1A2 in the protection against hyperoxic lung injury. The role of CYP1B1 in oxygen-mediated pulmonary toxicity has not been studied. In this investigation, we tested the hypothesis that CYP1B1 plays a mechanistic role in oxygen toxicity in pulmonary cells in vitro. In human bronchial epithelial cell line BEAS-2B, hyperoxic treatment for 1-3 days led to decreased cell viability by about 50-80%. Hyperoxic cytotoxicity was accompanied by an increase in levels of reactive oxygen species (ROS) by up to 110%, and an increase of TUNEL-positive cells by up to 4.8-fold. Western blot analysis showed hyperoxia to significantly down-regulate CYP1B1 protein level. Also, there was a decrease of CYP1B1 mRNA by up to 38% and Cyp1b1 promoter activity by up to 65%. On the other hand, CYP1B1 siRNA appeared to rescue the cell viability under hyperoxia stress, and overexpression of CYP1B1 significantly attenuated hyperoxic cytotoxicity after 48 h of incubation. In immortalized lung endothelial cells derived from Cyp1b1-null and wild-type mice, hyperoxia increased caspase 3/7 activities in a time-dependent manner, but endothelial cells lacking the Cyp1b1 gene showed significantly decreased caspase 3/7 activities after 48 and 72 h of incubation, implying that CYP1B1 might promote apoptosis in wild type lung endothelial cells under hyperoxic stress. In conclusion, our results support the hypothesis that CYP1B1 plays a mechanistic role in pulmonary oxygen toxicity, and CYP1B1-mediated apoptosis could be one of the mechanisms of oxygen toxicity. Thus, CYP1B1 could be a novel target for preventative and/or therapeutic interventions against BPD in infants and ALI/ARDS in adults.

Mouse Models of Acute Respiratory Distress Syndrome: A Review of Analytical Approaches, Pathologic Features, and Common Measurements

Acute respiratory distress syndrome (ARDS) is a severe pulmonary reaction requiring hospitalization, which is incited by many causes, including bacterial and viral pneumonia as well as near drowning, aspiration of gastric contents, pancreatitis, intravenous drug use, and abdominal trauma. In humans, ARDS is very well defined by a list of clinical parameters. However, until recently no consensus was available regarding the criteria of ARDS that should be evident in an experimental animal model. This lack was rectified by a 2011 workshop report by the American Thoracic Society, which defined the main features proposed to delineate the presence of ARDS in laboratory animals. These should include histological changes in parenchymal tissue, altered integrity of the alveolar capillary barrier, inflammation, and abnormal pulmonary function. Murine ARDS models typically are defined by such features as pulmonary edema and leukocyte infiltration in cytological preparations of bronchoalveolar lavage fluid and/or lung sections. Common pathophysiological indicators of ARDS in mice include impaired pulmonary gas exchange and histological evidence of inflammatory infiltrates into the lung. Thus, morphological endpoints remain a vital component of data sets assembled from animal ARDS models.