Role Of Cytochrome P450 Monooxygenase Research Articles

Resistance of Anopheles gambiae s.s. against commonly used insecticides and implication of cytochrome P450 monooxygenase in resistance to pyrethroids in Lambaréné (Gabon)

BackgroundInsecticides are a crucial component of vector control. However, resistance constitute a threat on their efficacy and the gains obtained over the years through malaria vector control. In Gabon, little data on phenotypic insecticide resistance in Anopheles vectors are published, compromising the rational implementation of resistance management strategies. We assessed the susceptibility to pyrethroids, carbamates and organophosphates of Anopheles gambiae sensu lato (s.l.) and discuss the mechanisms involved in the pyrethroid resistance-phenotype.MethodsA. gambiae s.l. larvae were collected from breeding sites in Lambaréné. Emerging adults were used in WHO tube assays at an insecticide concentration that defines resistance (diagnostic concentration). Subsequently, deltamethrin and permethrin were used at 5x and 10x diagnostic concentrations and after preexposure with the cytochrome p450 (and glutathione S-transferase) inhibitor piperonyl butoxide (PBO). A subset of mosquitoes was typed by molecular methods and screened using Taqman assays for mutations conferring target site resistance at the Voltage-gated sodium channel 1014 (Vgsc-1014) locus and the acetylcholinesterase (Ace-1) gene.ResultsAll mosquitoes were A. gambiae sensu stricto (s.s.) and resistant to permethrin, deltamethrin and alphacypermethrin (mortality less than 98%). However, mosquitoes were susceptible to malathion but resistant to bendiocarb. The level of resistance was high for permethrin and at least moderate for deltamethrin. Pre-exposure to PBO significantly increased the mortality of resistant mosquitoes (P < 0.0001). They became fully susceptible to deltamethrin and permethrin-induced mortality increased 4-fold. The G119S Ace-1 resistance allele, which confers resistance to both organophosphates and carbamates, was not present. All sampled mosquitoes were either homozygous for the Vgsc-L1014F or heterozygous for Vgsc-L1014F/L1014S, a marker for resistance to pyrethroids and organochlorides.ConclusionThese findings demonstrate a role of cytochrome P450 monooxygenases in the pyrethroid-resistance of A. gambiae s.s. from Lambaréné. Combining PBO with pyrethroids, as done in second generation bednets, may be used to revert resistance. In addition, malathion could also be used in combination with pyrethroids-based methods for resistance management.

Effects of deltamethrin exposure on the cytochrome P450 monooxygenases of Aedes albopictus (Skuse) larvae from a dengue-endemic region of northern part of West Bengal, India.

Aedes albopictus is highly prevalent in the northern part of West Bengal and is considered to be responsible for the recent dengue outbreaks in this region. Control of this vector is largely relied on the use of synthetic pyrethroids, which can lead to the development of resistance. In the present study, larvae of three wild Ae. albopictus populations from the dengue-endemic regions were screened for deltamethrin resistance, and the role of cytochrome P450 monooxygenases (CYPs) was investigated in deltamethrin exposed and unexposed larvae. Two populations were incipient resistant, and one population was completely resistant against deltamethrin. Monooxygenase titration assay revealed the involvement of CYPs in deltamethrin resistance along with an induction effect of deltamethrin exposure. Gene expression studies revealed differential expression of five CYP6 family genes, CYP6A8, CYP6P12, CYP6A14, CYP6N3 and CYP6N6, with high constitutive expression of CYP6A8 and CYP6P12 in all the populations before and after deltamethrin exposure. From these findings, it was evident that CYPs play an important role in the development of deltamethrin resistance in the Ae. albopictus populations in this region.

Differential regulation of cytochrome P450 genes associated with biosynthesis and detoxification in bifenthrin-resistant populations of navel orangewom (Amyelois transitella)

Pyrethroid resistance was first reported in 2013 for the navel orangeworm, Amyelois transitella, but the genetic underpinnings of pyrethroid resistance are unknown. We investigated the role of cytochrome P450 monooxygenases (P450s) belonging to the CYP3 and CYP4 clans using colonies derived from individuals collected in 2016 from almond orchards in two counties. One colony (ALM) originated from an almond orchard in Madera County with no reported pyrethroid resistance and the second colony (R347) originated from the same Kern County orchard where pyrethroid resistance was first reported. We used high-throughput quantitative real-time PCR (qRT-PCR) analyses of 65 P450s in the CYP3 and CYP4 clans of A. transitella to identify P450s induced by bifenthrin and associated with pyrethroid resistance. Nine P450s were constitutively overexpressed in R347 compared to ALM, including CYP6AE54 (11.7-fold), belonging to a subfamily associated with metabolic pesticide detoxification in Lepidoptera and CYP4G89 (33-fold) belonging to a subfamily associated with cuticular hydrocarbon (CHC) synthesis and resistance via reduced pesticide penetrance. Cuticular hydrocarbons analysis revealed that R347 produced twice as many total CHCs in the egg and adult stages as ALM. Topical toxicity bioassays for R347 determined that egg mortality was reduced at low bifenthrin concentrations and larval mortality was reduced at high concentrations of bifenthrin compared to ALM. Our discovery of both changes in metabolism and production of CHCs for R347 have implications for the possible decreased efficacy of other classes of insecticide used to control this insect. The threat of widespread pyrethroid resistance combined with the potential for cross-resistance to develop through the mechanism of reduced penetrance warrants developing management strategies that facilitate insecticide passage across the cuticle.

More P450s Are Involved in Secondary Metabolite Biosynthesis in Streptomyces Compared to Bacillus, Cyanobacteria, and Mycobacterium.

Unraveling the role of cytochrome P450 monooxygenases (CYPs/P450s), heme-thiolate proteins present in living and non-living entities, in secondary metabolite synthesis is gaining momentum. In this direction, in this study, we analyzed the genomes of 203 Streptomyces species for P450s and unraveled their association with secondary metabolism. Our analyses revealed the presence of 5460 P450s, grouped into 253 families and 698 subfamilies. The CYP107 family was found to be conserved and highly populated in Streptomyces and Bacillus species, indicating its key role in the synthesis of secondary metabolites. Streptomyces species had a higher number of P450s than Bacillus and cyanobacterial species. The average number of secondary metabolite biosynthetic gene clusters (BGCs) and the number of P450s located in BGCs were higher in Streptomyces species than in Bacillus, mycobacterial, and cyanobacterial species, corroborating the superior capacity of Streptomyces species for generating diverse secondary metabolites. Functional analysis via data mining confirmed that many Streptomyces P450s are involved in the biosynthesis of secondary metabolites. This study was the first of its kind to conduct a comparative analysis of P450s in such a large number (203) of Streptomyces species, revealing the P450s’ association with secondary metabolite synthesis in Streptomyces species. Future studies should include the selection of Streptomyces species with a higher number of P450s and BGCs and explore the biotechnological value of secondary metabolites they produce.

Stress response and detoxification mechanisms involved in non‐target‐site herbicide resistance in sunflower

AbstractThe nature of non‐target‐site herbicide resistance (NTSR) to imidazolinone (IMI) in HA425 sunflower (Helianthus annuus L.) has not yet been fully characterized but could be related to xenobiotic metabolism. The objective of this study was to evaluate the role of cytochrome P450 monooxygenases (P450s) and other detoxification‐related proteins in NTSR in sunflower. Two sunflower inbred lines were used: HA 425, which is IMI resistant (Imisun), and HA 89, which is IMI susceptible. The growth response to the IMI herbicide imazethapyr in combination with the P450 inhibitors 1‐aminobenzotriazole (ABT) or piperonyl butoxide (PBO) was evaluated in 15‐d‐old sunflower plantlets. Roots were collected, and label‐free quantitation (LFQ) proteomic analysis was carried out to characterize the NTSR mechanisms involved in the IMI resistance trait in sunflower. The increased phytotoxicity of imazethapyr observed in the resistant line when ABT or PBO were present agrees with the hypothesis that NTSR mechanisms may contribute to herbicide resistance in sunflower. The herbicide treatment also led to changes in the levels of biotic and abiotic stress‐related proteins, glutathione S‐transferases, and cytochrome P450s, among others. Plant growth and root protein expression response to IMI herbicides in sunflower would be a combination of stress‐related and detoxification mechanisms. Understanding the basis of NTSR becomes helpful to exploit this trait in sunflower crop and to develop xenobiotic‐resistant, soil‐remediating cultivars.

Biodegradation of Bisphenol A by Sphingobium sp. YC-JY1 and the Essential Role of Cytochrome P450 Monooxygenase.

Bisphenol A (BPA) is a widespread pollutant threatening the ecosystem and human health. An effective BPA degrader YC-JY1 was isolated and identified as Sphingobium sp. The optimal temperature and pH for the degradation of BPA by strain YC-JY1 were 30 °C and 6.5, respectively. The biodegradation pathway was proposed based on the identification of the metabolites. The addition of cytochrome P450 (CYP) inhibitor 1-aminobenzotriazole significantly decreased the degradation of BPA by Sphingobium sp. YC-JY1. Escherichia coli BL21 (DE3) cells harboring pET28a-bisdAB achieved the ability to degrade BPA. The bisdB gene knockout strain YC-JY1ΔbisdB was unable to degrade BPA indicating that P450bisdB was an essential initiator of BPA metabolism in strain YC-JY1. For BPA polluted soil remediation, strain YC-JY1 considerably stimulated biodegradation of BPA associated with the soil microbial community. These results point out that strain YC-JY1 is a promising microbe for BPA removal and possesses great application potential.

Cytochrome P450 monooxygenases-mediated sex-differential spinosad resistance in house flies Musca domestica (Diptera: Muscidae)

Females developed notably higher resistance than males in a spinosad-resistant house fly strain, however, resistance factors responsible for this phenomenon are poorly understood. In this study, the potential role of cytochrome P450 monooxygenases involved in the sex-differential spinosad resistance in house flies was investigated, using a susceptible strain (SSS) and a spinosad resistant near-isogenic line (N-SRS). Combination of the synergism of spinosad by PBO and increased cytochrome P450 monooxygenase activity in the N-SRS strain implied that cytochrome P450 monooxygenases contributed to spinosad resistance in house flies. Transcriptional levels of eight P450 genes related to insecticide resistance in two genders of the SSS and N-SRS strain were separately evaluated by quantitative real-time PCR. Notably, compared with the corresponding gender of susceptible SSS house flies, CYP4G2 and CYP6A5v2 were overexpressed in resistant N-SRS females, while the expression of these two P450 genes was significantly decreased in resistant N-SRS males. Furthermore, by measuring the expression of CYP4G2 and CYP6A5v2 in female and male house fly populations with different spinosad resistance levels, which were generated from a series of genetic crosses, the genetic linkage between spinosad resistance and P450 gene expression was analyzed. It was found that with increased spinosad resistance, CYP4G2 and CYP6A5v2 were up-regulated in females, while both of them were down-regulated in males, and this suggested their involvement in the female-linked spinosad resistance of house flies. Taken together, our results provide valuable insight into the involvement of cytochrome P450 monooxygenases in the sex-differential spinosad resistance in house flies.

Bioremediation of triphenyl phosphate by Brevibacillus brevis: Degradation characteristics and role of cytochrome P450 monooxygenase

Triphenyl phosphate (TPHP) has been detected with increasing frequency in environmental samples, which has aroused great attention regarding its potential adverse effects. In this study, biodegradation of TPHP by Brevibacillus brevis was investigated. The results revealed that the highest degradation efficiency of 3μmol/L TPHP by B. brevis reached 92.1% at pH7 and 30°C. The major metabolites of TPHP, diphenyl phosphate and phenyl phosphate were detected within 5days of incubation with the maximum concentrations at 308.2 and 11.8nmol/L, respectively. The activities of superoxide dismutase and catalase along with malondialdehyde content also increased significantly, indicating that TPHP caused a severe oxidative stress on B. brevis. Meanwhile, the addition of cytochrome P450 (CYP) inhibitor piperonyl butoxide markedly decreased the degradation of TPHP by B. brevis. Further transcription studies using quantitative real-time RT-PCR confirmed that the expression of CYP gene in B. brevis were significantly down-regulated. These findings demonstrated the important role of CYP in the degradation of TPHP. To our best knowledge, this is the first report about the biodegradation of TPHP by B. brevis. Overall, this study provides new insights into the potential mechanisms of TPHP biodegradation by microorganisms.

Determination of the Baseline Susceptibility of European Populations of Cydia pomonella (Lepidoptera: Tortricidae) to Chlorantraniliprole and the Role of Cytochrome P450 Monooxygenases.

The codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), is the key pest on pome fruit and walnut orchards worldwide. Its resistance to available insecticides has been widely reported. Chlorantraniliprole is an anthranilic diamide that was introduced in European countries in 2008-2009 and acts by activating the insect's ryanodine receptors. The aims of this study were to determine the baseline susceptibility of European populations of C. pomonella to chlorantraniliprole, to establish the discriminant concentrations (DC) to check the possible development of resistance, and to know the role of cytochrome P450 monooxygenases (P450) in the possible susceptibility decrease of field populations to the insecticide. Ten field populations from Spain along with others were used to calculate the baseline response of larvae to chlorantraniliprole incorporated into the diet. A pooled probit line was calculated, and three DC were established: 0.3 mg a.i./kg (close to the LC50), 1.0 mg a.i./kg (close to the LC90), and 10 mg a.i./kg diets (threefold the LC99). The DC were used to test the susceptibility of 27 field populations from France, Germany, Hungary, Italy, and Spain. The corrected mortality observed in all cases ranged within the expected interval, even with Spanish populations that showed between 12.1 and 100.0% of individuals with high P450 activity. However, the mortality caused by the DC0.3 decreased as the mean P450 activity increased. Field populations resistant to other insecticides were susceptible to chlorantraniliprole. The determined baseline codling moth susceptibility is a valuable reference for tracking possible future alterations in the efficacy of the insecticide.

Role of Cytochrome P450 Monooxygenase in the Bioactivation of Aflatoxin B1

In a previous study, the gene EgP450 that encodes the proteins of 505 amino acids was isolated from oil palm. The recombinant protein EgP450 is bound to phenylurea-like herbicides which detoxify the substance. Aflatoxin B1 (AFB1), a mycotoxin produced by Aspergillus sp., is another toxic compound that is known to cause acute toxic effects and act as a hepatocarcinogenic agent. This study aimed to examine the role of EgP450 enzyme in mycotoxin bioactivation in human mesenchymal stem cells (hMSCs). Docking analysis showed that EgP450 is bound to the group of carcinogens, which includes AFB1, n-(2-fluorenyl) acetamide, n-n-butyl-n-butan-4-ol-nitrosamine, n-nitrosodiethylamine, n-nitrosodiethylamine and n-nitrosodimethylamine. An in vivo aflatoxin toxicity test on hMSCs and AFB1 induces the expression of Bmi-1 which is one of the markers for the development of cancer. The presence of EgP450 at 0.15 μg/mL could reduced the Bmi-1 expression in AFB1 induced cells. Moreover, this protein also showed some antioxidant activity. These results exhibited the enormous potential of EgP450 in the detoxification processes.

Contribution of non-target-site resistance in imidazolinone-resistant Imisun sunflower

ABSTRACT The first commercial herbicide-resistant trait in sunflower (Helianthus annuus L.) is known as ‘Imisun’. Imidazolinone resistance in Imisun cultivars has been reported to be genetically controlled by a major gene (known as Imr1 or Ahasl1-1) and modifier genes. Imr1 is an allelic variant of the Ahasl1 locus that codes for the acetohydroxyacid synthase, which is the target site of these herbicides. The mechanism of resistance endowed by modifier genes has not been characterized and it could be related to non-target-site resistance. The objective of this study was to evaluate the role of cytochrome P450 monooxygenases (P450s) in Imisun resistance. The response to imazapyr herbicide in combination with P450s inhibitor malathion was evaluated in 2 Imisun lines, IMI-1 and RHA426. Malathion reduced herbicide efficacy in both lines, but IMI-1 was affected in a greater extent. A significant reduction in plant growth in response to P450s inhibitors 1-aminobenzotriazole and piperonyl butoxide treatment was detected in the Imisun line HA425. The increased susceptibility to imazapyr after P450s-inhibitor treatment indicates that herbicide metabolism by P450s is a mechanism involved in Imisun resistance. These results also suggest the involvement of different P450s isozymes in endowing resistance to imazapyr in Imisun cultivars.

Role of Cytochrome P450 Monooxygenase in Carcinogen and Chemotherapeutic Drug Metabolism.

The purpose of this chapter is to provide insight into which human cytochromes P450 (CYPs) may be involved in metabolism of chemical carcinogens and anticancer drugs. A historical overview of this field and the development of literature using relevant animal models and expressed human CYPs have provided information about which specific CYPs may be involved in carcinogen metabolism. Definition of the biochemical properties of CYP activity came from several groups who studied the reaction stoichiometry of butter yellow and benzo[α]pyrene, including their role in induction of these enzyme systems. This chapter will list as much as is known about the human CYPs involved in carcinogen and anticancer drug metabolism, as well as summarize studies with rodent CYPs. A review of three major classes of anticancer drugs and their metabolism in humans is covered for cyclophosphamide, procarbazine, and anthracycline antibiotics, cancer chemotherapeutic compounds extensively metabolized by CYPs. The emerging information about human CYP gene polymorphisms as well as other enzymes involved in foreign compound metabolism provides considerable information about how these genetic variants affect carcinogen and anticancer drug metabolism. With information available from individual's genomic sequences, consideration of populations who may be at risk due to environmental exposure to carcinogens or how to optimize their cancer therapy regimens to enhance efficacy of the anticancer drugs appears to be an important field of study to benefit individuals in the future.

Overexpression of Cytochrome P450 CYP6B7 Mediated Pyrethroid Resistance in Indian Strains of the Cotton Bollworm, Helicoverpa Armigera (Hübner)

Abstract The role of cytochrome P450 monooxygenase in pyrethroid resistance was studied in different strains of the cotton bollworm, Helicoverpa armigera, from India. Filed collected strains of Nagpur and Delhi were compared to the laboratory reared population. The results showed a high resistance to deltamethrin, α-cypermethrin, and β-cyfluthrin. The results also showed that this resistance could be reduced by using piperonyl butoxide (PBO). The Nagpur and Delhi strains were found to have a 2.40 and 1.79 fold higher monooxygenase activity compared to a susceptible strain. A strong, positive correlation between monooxygenase activity and pyrethroid resistance was observed (r = 0.86 - 0.98). The relative expression of the housekeeping gene, EF-1α, and three P450 genes, was studied in the 5th instar larval midgut of the three strains. Out of the three P450 genes examined, expression of CYP6B7 mRNA was not detected in the midgut of the susceptible strain though it was highly expressed in the resistant strains. The midgut of the Nagpur strain had a 2.60 fold overexpression of CYP6B7 mRNA compared to the moderately resistant, Delhi strain. The mRNA of CYP4G8 and CYP6B2 were not overexpressed in either the Nagpur or Delhi strain. The results indicated that the elevated cytochrome P450 monooxygenase activity is associated with pyrethroid resistance in Indian strains of H. armigera, and CYP6B7 could be the P450 form responsible for pyrethroid resistance.

The role of cytochrome P450 monooxygenase in the different responses to fenoxaprop-P-ethyl in annual bluegrass (Poa annua L.) and short awned foxtail (Alopecurus aequalis Sobol.)

Herbicide resistance or tolerance in weeds mediated by cytochrome P450 monooxygenase is a considerable problem. However, cytochrome P450 mediated resistance or tolerance in weeds was less studied. Thus, in this work, the role of the cytochrome P450 monooxygenase in the different responses of Poa annua and Alopecurus aequalis to fenoxaprop-P-ethyl was studied. We found that the effect of fenoxaprop-P-ethyl could be synergized by piperonyl butoxide (PBO) in P. annua, but not by malathion. After being treated with fenoxaprop-P-ethyl (containing mefenpyr-diethyl), the contents of cytochrome P450 and cytochrome b5 in P. annua increased significantly compared to plants treated with mefenpyr-diethyl only or untreated plants. However, the increase was less in A. aequalis, which was susceptible to fenoxaprop-P-ethyl. The activities of ρ-nitroanisole O-demethylase (PNOD), ethoxyresorufin O-deethylase (EROD), ethoxycoumarin oxidase (ECOD) and NADPH-dependent cytochrome P450 reductase mediated by cytochrome P450 monooxygenase increased in P. annua after treatment with fenoxaprop-P-ethyl, especially the activities of ECOD and cytochrome P450 reductase. Besides this, cytochrome P450 monooxygenase activity toward fenoxaprop-P-ethyl in P. annua increased significantly compared to untreated or treated with mefenpyr-diethyl plants and treated or untreated A. aequalis. Cytochrome P450 monooxygenase may play an important role in the different responses to fenoxaprop-P-ethyl in P. annua and A. aequalis.

Evaluation of Cytochrome P&lt;SUB&gt;450&lt;/SUB&gt; Activity in Field Populations of &lt;I&gt;Cydia pomonella&lt;/I&gt; (Lepidoptera: Tortricidae) Resistant to Azinphosmethyl, Acetamiprid, and Thiacloprid

The Río Negro and Neuquén Valley is the most important apple and pear growing region in Argentina. Cydia pomonella L. (Lepidoptera: Tortricidae), the main fruit-tree pest is being controlled by azinphosmethyl (AzMe), acetamiprid (Acet), and thiacloprid (Thia) among other insecticides. The objective of this study was to evaluate the response of neonate larvae of codling moth to these three insecticides and on the role of cytochrome P450 monooxygenase in their toxicity. All field populations presented significantly lower mortality to a discriminating concentration (DC) of Acet and AzMe. In addition, 13 of the 14 populations showed significantly lower mortality to DC of Thia. Most of the field populations (71%) showed significantly higher 7-ethoxycoumarine O-deethylase activity compared with the laboratory-susceptible strain. While positive significant correlation (gamma = 0.59) was found between Thia and AzMe mortalities at the DC level, no significant correlations were detected between Acet and Thia (gamma = 0.35) or Acet and AzMe (gamma = 0.12). However, Acet and Thia mortalities were significantly correlated to the percentage of individuals exhibiting 7-ethoxy-coumarine O-deethylase activity activities higher than the mean upper 95% confidence limit of the susceptible strain (gamma = -0.52 and gamma = -0.63, respectively).

Transformation of the Recalcitrant Pharmaceutical Compound Carbamazepine by Pleurotus ostreatus: Role of Cytochrome P450 Monooxygenase and Manganese Peroxidase

Carbamazepine (CBZ) is an environmentally recalcitrant compound highly stable in soil and during wastewater treatment. In this study, we examined the mechanisms by which the white-rot fungus Pleurotus ostreatus metabolizes CBZ in liquid culture using a physiological approach. P. ostreatus PC9 was grown in media known to support different levels of a multiplicity of enzyme systems such as cytochrome P450 (CYP450) and manganese peroxidase (MnP). When both CYP450 and MnP systems were active, 99% of the added CBZ was eliminated from the solution and transformed to 10,11-epoxycarbamazepine. High removal of CBZ was also obtained when either MnP or CYP450 was active. When both CYP450 and MnP were inactivated, only 10 to 30% of the added CBZ was removed. In this latter system, removal of CBZ might be partially attributed to the activity of versatile peroxidase. P. ostreatus was able to eliminate CBZ in liquid culture even when CBZ was added at an environmentally relevant concentration (1 μg L(-1)). On the basis of our study, we suggest that two families of enzymes are involved in the oxidation of CBZ in liquid culture: MnP in a Mn(2+)-dependent or independent manner and CYP450. Our study also highlights the potential of using P. ostreatus for bioremediation systems.

The role of cytochrome P450 monooxygenases in microbial fatty acid metabolism

Cytochrome P450 monooxygenases (P450s) are a diverse collection of enzymes acting on various endogenous and xenobiotic molecules. Most of them catalyse hydroxylation reactions and one group of possible substrates are fatty acids and their related structures. In this minireview, the significance of P450s in microbial fatty acid conversion is described. Bacteria and yeasts possess various P450 systems involved in alkane and fatty acid degradation, and often several enzymes with different activities and specificities are retrieved in one organism. Furthermore, P450s take part in the formation of fatty acid-based secondary metabolites. Finally, there are a substantial number of microbial P450s displaying activity towards fatty acids, but to which no biological role could be assigned despite the often quite intense research.

Chemical Exposures: Not Immune to PFOS Effects?

Two recent studies have demonstrated that exposure to perfluorooctanyl sulfonate (PFOS) can alter mammalian immune system function. In one study, PFOS induced immunotoxicity in test animals at exposures analogous to those reported in the U.S. population, raising the possibility that “if humans and mice share similarities in their immune systems, then people today could be immunocompromised due to current PFOS exposure,” says Jennifer Keller, a research biologist at the National Institute of Standards and Technology’s Hollings Marine Laboratory. However, resolving this question will require carefully controlled epidemiologic studies that include relevant immune system and infectious disease end points. PFOS was removed from 3M’s Scotchgard™ stain repellent by the end of 2002, but the compound degrades slowly and is dispersed widely throughout the environment. Data from the National Health and Nutrition Examination Survey 2003–2004 documented that it was found in 99.9% of samples. Research slated for publication in the 1 July 2008 issue of Toxicological Sciences documents that production of the immunoglobulin M (IgM) antibody decreased in B6C3F1 mice exposed to PFOS. This suggests the immune response to pathogens may be suppressed and could result in increased disease susceptibility, says lead author Margie Peden-Adams, a research assistant professor at the Medical University of South Carolina. She says these effects occurred at serum PFOS levels (91.5 ppb in male mice) that were 14 times lower than the average blood concentrations of occupationally exposed humans and in the upper range of concentrations reported for the general population, making this the lowest reported lowest-observable-effect level for PFOS. She adds that suppression of IgM production in female mice occurred at dose concentrations 10 times higher than in males. The male mice’s natural killer (NK) cell population, an important part of the innate immune system for tumor and viral surveillance, was increased, but female NK cell function was not affected. Peden-Adams speculates that the increase could be a compensation for a decrease in the male mice’s populations of cytotoxic T cells, which also have functions related to killing tumor cells. Additional testing determined that the cause of the decreased IgM production is probably an issue with B cells, the cell type that differentiates into antibody-producing cells, she says. Another study, published 1 May 2008 in Toxicological Sciences by Deborah Keil, an associate professor of clinical laboratory sciences at the University of Nevada at Las Vegas, also linked a reduction in IgM antibody response to PFOS exposure. This study, which evaluated the immune systems of B6C3F1 mouse pups whose mothers were exposed to the compound during pregnancy, showed that NK cell function was decreased in male pups. Both studies document that PFOS targeted antibody production and that males appeared more sensitive than females to the effects of PFOS, Keil says. Peden-Adams says her group was quite surprised by their findings and that further research is needed to determine the effects’ mode of action in order to determine human risk. Her paper posits that sex differences in sensitivity may be related to levels of estrogen and testosterone, because these steroids are known to affect immune system function. “We know that PFOS does have some endocrine-disrupting activity,” she says, adding that some research suggests the chemical may be antiestrogenic. A third study using a different mouse strain found similar effects for perfluorooctanoic acid (PFOA). The study, published in the May 2008 issue of EHP by research biologist Robert Luebke of the U.S. Environmental Protection Agency National Health and Environmental Effects Research Laboratory, showed that adult female C57BL/6J mice exposed to higher concentrations of PFOA also exhibited a reduction in IgM production.

Mechanistic role of cytochrome P450 monooxygenases in oxidized low-density lipoprotein-induced vascular injury: therapy through LOX-1 receptor antagonism?

Oxidized low-density lipoprotein (oxLDL) is an important risk factor for vascular injury. Its role on coronary vasoconstriction remains speculative. Endothelial monooxygenases (cytochrome P450s [CYPs]) are regulators of vascular tonus through production of epoxy fatty acids. We investigated the effects of oxLDL on CYP monooxygenases in human arterial coronary endothelial cells and explanted healthy and atherosclerotic aortae. We found oxLDL to induce radical oxygen species production via the action of NADPH oxidase NOX4. Intracellular radical oxygen species production prompted reduced protein expression of the transcriptional regulator nuclear factor 1 (NF-1). We identified novel DNA binding sites for NF-1 in promoter regions of CYPs. DNA binding of NF-1 was confirmed by electromobility shift assays. OxLDL repressed DNA binding of NF-1 and diminished transcript level of CYP genes targeted by this factor. The production of endothelial-derived hyperpolarization factor, a key regulator of vascular tonus, was also reduced. Repression of CYP monooxygenases was reversed, and production of endothelial-derived hyperpolarization factor was normalized after treatment of endothelium with the lectin-like oxLDL receptor antagonist kappa-carrageenan or blocking of LOX-1 with a specific antibody. This suggests a mechanistic role of CYP monooxygenases in oxLDL-induced vascular injury. Therapy of endothelial dysfunction through LOX-1 receptor antagonism will be an interesting avenue to explore. The full text of this article is available online at http://www.circresaha.org.

Role of cytochrome P450 monooxygenases in hyperoxic pulmonary damage

Role of cytochrome P450 monooxygenases in hyperoxic pulmonary damage