Differential alterations in levels of hepatic microsomal cytochrome P450 isozymes following intracerebroventricular injection of bacterial lipopolysaccharide in rats

Eicosanoids derived from cytochrome P450 pathway of arachidonic acid and inflammatory shock

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Septic shock, the most common form of vasodilatory shock, is a subset of sepsis in which circulatory and cellular/metabolic abnormalities are severe enough to increase mortality. Inflammatory shock constitutes the hallmark of sepsis, but also a final common pathway of any form of severe long-term tissue hypoperfusion. The pathogenesis of inflammatory shock seems to be due to circulating substances released by pathogens (e.g., bacterial endotoxins) and host immuno-inflammatory responses (e.g., changes in the production of histamine, bradykinin, serotonin, nitric oxide [NO], reactive nitrogen and oxygen species, and arachidonic acid [AA]-derived eicosanoids mainly through NO synthase, cyclooxygenase, and cytochrome P450 [CYP] pathways, and proinflammatory cytokine formation). Therefore, refractory hypotension to vasoconstrictors with end-organ hypoperfusion is a life threatening feature of inflammatory shock. This review summarizes the current knowledge regarding the role of eicosanoids derived from CYP pathway of AA in animal models of inflammatory shock syndromes with an emphasis on septic shock in addition to potential therapeutic strategies targeting specific CYP isoforms responsible for proinflammatory/anti-inflammatory mediator production.

The Role of Cytochromes P450 in Infection

Cytochromes are expressed in many different tissues of the human body. They are found mostly in intestinal and hepatic tissues. Cytochromes P450 (CYPs) are enzymes that oxidize substances using iron and are able to metabolize a large variety of xenobiotic substances. CYP enzymes are linked to a wide array of reactions including and O-dealkylation, S-oxidation, epoxidation, and hydroxylation. The activity of the typical P450 cytochrome is influenced by a variety of factors, such as genus, environment, disease state, herbicide, alcohol, and herbal medications. However, diet seems to play a major role. The mechanisms of action of dietary chemicals, macro- and micronutrients on specific CYP isoenzymes have been extensively studied. Dietary modulation has effects upon the metabolism of xenobiotics. Cytochromes harbor intra- or interindividual and intra- or interethnic genetic polymorphisms. Bacteria were shown to express CYP-like genes. The tremendous metabolic activity of the microbiota is associated to its abundant pool of CYP enzymes, which catalyze phase I and II reactions in drug metabolism. Disease states, intestinal disturbances, aging, environmental toxic effects, chemical exposures or nutrition modulate the microbial metabolism of a drug before absorption. A plethora of effects exhibited by most of CYP enzymes can resemble those of proinflammatory cytokines and IFNs. Moreover, they are involved in the initiation and persistence of pathologic pain by directly activating sensory neurons and inflammatory cytokines.

Causes and Consequences of Variability in Drug Transporter Activity in Pediatric Drug Therapy

Drug transporters play a key role in mediating the uptake of endo- and exogenous substances into cells as well as their efflux. Therefore, variability in drug transporter activity can influence pharmaco- and toxicokinetics and be a determinant of drug safety and efficacy. In children, particularly in neonates and young infants, the contribution of tissue-specific drug transporters to drug absorption, distribution, and excretion may differ from that in adults. In this review 5 major factors and their interdependence that may influence drug transporter activity in children are discussed: developmental differences, genetic polymorphisms, pediatric comorbidities, interacting comedication, and environmental factors. Even if data are sparse, altered drug transporter activity due to those factors have been associated with clinically relevant differences in drug disposition, efficacy, and safety in pediatric patients. Single nucleotide polymorphisms in drug transporter-encoding genes were the most studied source of drug transporter variability in children. However, in the age group where drug transporter activity has been reported to differ from that in adults, namely neonates and young infants, hardly any studies have been performed. Longitudinal studies in this young population are required to investigate the age- and disease-dependent genotype-phenotype relationships and relevance of drug transporter drug-drug interactions. Physiologically based pharmacokinetic modeling approaches can integrate drug- and patient-specific parameters, including drug transporter ontogeny, and may further improve in silico predictions of pediatric-specific pharmacokinetics.

Listeriosis downregulates hepatic cytochrome P450 enzymes in sublethal murine infection

PURPOSE

Listeria monocytogenes (Lm) can cross the intestinal barrier in humans and then disseminates into different organs. Invasion of the liver occurs even in sublethal infections, however, knowledge of affected physiological processes is scarce. This study employed a sublethal murine infection model to investigate liver responses systematically by proteomics.

EXPERIMENTAL DESIGN

Liver samples from three stages of the sublethal infection covering the initial invasion, the peak of infection, and the clearance phase (1, 3, 9 days postinoculation) were analyzed in comparison to samples from noninfected mice. Apart from flow cytometry and RT-PCRs for immune status control, liver responses were analyzed by quantitative peptide sequencing (HPLC-Orbitrap Fusion) using 4-plex iTRAQ-labeling.

RESULTS

Accurate MS characterized about 3600 proteins and statistics revealed 15% of the hepatic proteome as regulated. Immunological data as well as protein regulation dynamics strongly indicate stage-specific hepatic responses in sublethal infections. Most notably, this study detected a comprehensive deregulation of drug metabolizing enzymes at all stages, including 25 components of the cytochrome P450 system.

CONCLUSIONS AND CLINICAL RELEVANCE

Sublethal Lm infection deregulates hepatic drug metabolizing pathways. This finding indicates the need to monitor drug administration along Lm infections, especially in all patients needing constant medication.

Drug disposition in pathophysiological conditions

Expression and activity of several key drug metabolizing enzymes (DMEs) and transporters are altered in various pathophysiological conditions, leading to altered drug metabolism and disposition. This can have profound impact on the pharmacotherapy of widely used clinically relevant medications in terms of safety and efficacy by causing inter-individual variabilities in drug responses. This review article highlights altered drug disposition in inflammation and infectious diseases, and commonly encountered disorders such as cancer, obesity/diabetes, fatty liver diseases, cardiovascular diseases and rheumatoid arthritis. Many of the clinically relevant drugs have a narrow therapeutic index. Thus any changes in the disposition of these drugs may lead to reduced efficacy and increased toxicity. The implications of changes in DMEs and transporters on the pharmacokinetics/pharmacodynamics of clinically-relevant medications are also discussed. Inflammation-mediated release of pro-inflammatory cytokines and activation of toll-like receptors (TLRs) are known to play a major role in down-regulation of DMEs and transporters. Although the mechanism by which this occurs is unclear, several studies have shown that inflammation-associated cell-signaling pathway and its interaction with basal transcription factors and nuclear receptors in regulation of DMEs and transporters play a significant role in altered drug metabolism. Altered regulation of DMEs and transporters in a multitude of disease states will contribute towards future development of powerful in vitro and in vivo tools in predicting the drug response and opt for better drug design and development. The goal is to facilitate a better understanding of the mechanistic details underlying the regulation of DMEs and transporters in pathophysiological conditions.

Global gene expression analysis of the mouse colonic mucosa treated with azoxymethane and dextran sodium sulfate

BACKGROUND

Chronic inflammation is well known to be a risk factor for colon cancer. Previously we established a novel mouse model of inflammation-related colon carcinogenesis, which is useful to examine the involvement of inflammation in colon carcinogenesis. To shed light on the alterations in global gene expression in the background of inflammation-related colon cancer and gain further insights into the molecular mechanisms underlying inflammation-related colon carcinogenesis, we conducted a comprehensive DNA microarray analysis using our model.

METHODS

Male ICR mice were given a single ip injection of azoxymethane (AOM, 10 mg/kg body weight), followed by the addition of 2% (w/v) dextran sodium sulfate (DSS) to their drinking water for 7 days, starting 1 week after the AOM injection. We performed DNA microarray analysis (Affymetrix GeneChip) on non-tumorous mucosa obtained from mice that received AOM/DSS, AOM alone, and DSS alone, and untreated mice at wks 5 and 10.

RESULTS

Markedly up-regulated genes in the colonic mucosa given AOM/DSS at wk 5 or 10 included Wnt inhibitory factor 1 (Wif1, 48.5-fold increase at wk 5 and 5.7-fold increase at wk 10) and plasminogen activator, tissue (Plat, 48.5-fold increase at wk 5), myelocytomatosis oncogene (Myc, 3.0-fold increase at wk 5), and phospholipase A2, group IIA (platelets, synovial fluid) (Plscr2, 8.0-fold increase at wk 10). The notable down-regulated genes in the colonic mucosa of mice treated with AOM/DSS were the peroxisome proliferator activated receptor binding protein (Pparbp, 0.06-fold decrease at wk 10) and the transforming growth factor, beta 3 (Tgfb3, 0.14-fold decrease at wk 10). The inflammation-related gene, peroxisome proliferator activated receptor gamma (Ppargamma 0.38-fold decrease at wk 5), was also down-regulated in the colonic mucosa of mice that received AOM/DSS.

CONCLUSION

This is the first report describing global gene expression analysis of an AOM/DSS-induced mouse colon carcinogenesis model, and our findings provide new insights into the mechanisms of inflammation-related colon carcinogenesis and the establishment of novel therapies and preventative strategies against carcinogenesis.

Regulation of drug metabolism and disposition during inflammation and infection

The expression and activity of cytochrome P450 (CYP) is altered during periods of infectious disease or when an inflammatory response is activated. Most of the major forms of CYP are affected in this manner and this leads to a decrease in the capacity of the liver and other organs to handle drugs, chemicals and some endogenous compounds. The loss in drug metabolism is predominantly an effect resulting from the production of cytokines and the modulation of the transcription factors that control the expression of specific CYP forms. In clinical medicine numerous examples have been reported indicating the occurrence of compromised drug clearance and changes to pharmacokinetics during disease states with an inflammatory component or during infections. For any drug that is metabolised by CYP and has a narrow therapeutic index, there is a significant risk in placing patients in a position where an infection or inflammatory response might lead to aberrant drug handling and an adverse drug response.

Impact of inflammation on the duodenal mRNA expression of CYP3A and P-glycoprotein in children with Crohn's disease

BACKGROUND AND AIMS

Crohn's disease (CD) is a chronic and invalidating inflammatory bowel disease of unknown etiology. The coordinated action of the cytochrome metabolizing subfamily CYP3A and the transport protein P-glycoprotein (P-gp) in the enterocyte results in a reduced bioavailability of drugs administered orally. Cytokines modulate the expression and functionality of CYP3A and P-gp. Although P-gp results are in disagreement between animal and Caco-2 cell studies, all authors report a decrease in CYP3A levels after exposure to proinflammatory agents. In humans, CYP3A and P-gp mRNA, protein, and functionality levels were higher in various tissues in patients with CD as compared with control groups. Our study's aim was to analyze the impact of systemic inflammation on the expression of CYP3A and P-gp in duodenal normal tissue.

MATERIALS AND METHODS

We compared CYP3A and P-gp mRNA expression in 19 noninflamed duodenal biopsies from children with CD with 19 normal biopsies. We used a real-time reverse-transcription-polymerase chain reaction technique.

RESULTS

There was a high variability in the expression of the 3 CYP3A isoforms and P-gp. CYP3A4, CYP3A5, and P-gp levels were significantly higher in the CD group than in the control group.

DISCUSSION AND CONCLUSIONS

CYP3A and P-gp are involved in the metabolism and transport of many drugs prescribed in CD including corticosteroids. Changes occurring in their duodenal and hepatic expression may explain important interindividual differences in the bioavailability and response to treatment. Further explorations considering protein and activity must be undertaken to understand how such changes affect drug absorption and bioavailability.

The signal transduction pathways involved in hepatic cytochrome P450 regulation in the rat during a lipopolysaccharide-induced model of central nervous system inflammation

It is well known that inflammatory and infectious conditions of the central nervous system (CNS) differentially regulate hepatic drug metabolism through changes in cytochrome P450 (P450); however, the pathways leading to this regulation remain unknown. We provide evidence delineating a signal transduction pathway for hepatic P450 gene expression down-regulation in an established rat model of CNS inflammation using lipopolysaccharide (LPS) injected (i.c.v.) directly into the lateral cerebral ventricle. Brain cytokine levels were elevated, and the expression of tumor necrosis factor alpha and inhibitor of kappaB alpha (IkappaBalpha) were increased in the liver following the i.c.v. administration of LPS, indicating the presence of an inflammatory response in the brain and liver. The expression of CYP2D1/5, CYP2B1/2, and CYP1A1 was down-regulated following CNS inflammation. The binding of several transcription factors [nuclear factor of the kappa enhancer in B cells (NF-kappaB), activator protein-1, cAMP response element binding protein, CCAAT-enhancer binding protein (C/EBP)] to responsive elements on P450 promoter regions was examined using electromobility shift assays. Binding of both NF-kappaB and C/EBP to the promoter regions of CYP2D5 and CYP2B1, respectively, was increased, indicating that they play an important role in the regulation of these two isoforms during inflammatory responses. Evidence is also provided suggesting that the rapid transfer of LPS from the CNS into the periphery likely accounts for the down-regulation of P450s in the liver.

Nitric oxide mediates an LPS-induced depression of cytochrome P450 (CYP1A) activity in astrocytes

During inflammatory responses in the brain, the expression of cytochrome P450 isoforms in the CNS are modulated and the capacity of the brain to metabolize drugs and to synthesize or degrade certain endogenous chemicals and drugs is diminished. While this response can be attributed in part, to the production and action of cytokines within the brain, it is also likely that other inflammatory mediators play an integral role. This paper investigates a potential role for nitric oxide (NO) in the loss of cytochrome P450 (CYP1A) in the brain during inflammation. Escherichia coli lipopolysaccharide (LPS), a commonly used proinflammatory endotoxin, was incubated with cultured rat astrocytes to provide a model of inflammation in the CNS. CYP1A activity was significantly decreased in cultured astrocytes incubated with LPS for 24 h. This loss in enzyme activity was accompanied by a substantial production of nitric oxide (NO) by these cells. Immunohistochemical examination demonstrated an upregulation of inducible nitric oxide synthase (iNOS) expression following the exposure of astrocytes to LPS. The addition of a selective iNOS blocker (1400W) caused a partial but significant reversal of the LPS-mediated loss in CYP1A. The incubation of astrocytes with the NO-generating compound (DETA NONOate) resulted in a loss of CYP1A. Taken together, these observations suggest that NO plays a pivotal role in the inflammation mediated loss in CYP1A activity in the brain.

beta-naphthoflavone induction of CYP1A in brain of juvenile lake trout (Salvelinus namaycush Walbaum)

Many environmental pollutants induce expression of the cytochrome P450 (CYP) 1A subfamily of genes. We integrated cellular and molecular biological techniques to examine the effects of beta-naphthoflavone (BNF) exposure in lake trout brain CYP1A distribution and dynamics. Over a 32-day time-course, real time quantitative reverse transcription polymerase chain reaction (Q-RT-PCR) results showed that CYP1A mRNA induction in response to BNF exposure occurred rapidly and continued to rise in the BNF-treated lake trout after 4 h, with a peak at or after 2 days. Messenger RNA levels fell after 4 days, and this trend continued after 16 days of exposure. In situ hybridization indicated that CYP1A mRNA was universally elevated in the brain of BNF-exposed fish and was mainly expressed in the endothelia and occasionally in the glial cells. CYP1A immunoreactivity was induced in the olfactory bulb and valvula cerebelli of BNF-treated fish. Other brain areas showed constitutive CYP1A immunoreactivity in both control and BNF-treated fish. Some BNF-treated fish contained multifocal hemorrhages in the brain tissue, and these fish had overall depressed CYP1A immunoreactivity in the brain. The relationship between transcriptional and translational effects of BNF exposure in the brain of juvenile lake trout is discussed.

Differential effects of traumatic brain injury on the cytochrome p450 system: a perspective into hepatic and renal drug metabolism

Traumatic brain injury is known to cause several secondary effects, one of which is altered drug clearance. Given the fact that patients who sustain TBI are subsequently treated with a variety of pharmacological agents for the purpose of either neuroprotection or physiological support, it is imperative to clarify changes in expression and/or activities of enzymes involved in clearing drugs. The mixed function oxidase system, which consists of cytochrome P450 and cytochrome P450 reductase, plays a vital role in phase I drug metabolism. This paper addresses the issue as to what extent TBI affects the levels and activity of various rat CYP450 subfamilies. Our results show that TBI induces tissue-specific and time-dependent alterations. Total hepatic CYP450 content showed a biphasic response with a decrease seen at 24 h followed by an increase at 2 weeks. CYP450 reductase, in contrast, showed an opposite temporal profile. Immunoblot analyses and marker substrate metabolism demonstrated a clear decrease in hepatic CYP1A levels while a significant increase in kidney was seen at both 24 h and 2 weeks. A dramatic induction of CYP3A was evident at 2 weeks in liver, while no changes were noticed in CYP2B or CYP2D subfamilies. CYP4F subfamily showed induction in kidney only. Collectively, the data reveal the differential effects of TBI on hepatic and renal drug metabolism.

Modulation of hepatic cytochrome P450 during Listeria monocytogenes infection of the brain

Hepatic cytochrome P450 enzymes can be modulated during systemic infections. Inflammatory responses in the brain have also been shown to cause a significant decrease in the levels and activities of important cytochrome P450 isoforms in the liver. We determined some of the effects of central nervous system (CNS) Listeria monocytogenes infection on hepatic cytochrome P450 systems in rats. Intracerebroventricular injection of L. monocytogenes resulted in a time-dependent modulation of CYP1A, CYP2B, and CYP3A activities in the liver. Total hepatic cytochrome P450 content was significantly lowered 48 h after administration of the bacterium, and hepatic CYP1A and CYP2B activities were significantly altered 48 and 72 h after infection, respectively, whereas CYP3A activity and protein content were depressed 72 h after the insult. Bacterial load in the brain increased dramatically over a 72-h period, but the number of bacteria cultured from liver over this time period was relatively small. Therefore, an infection largely confined to the CNS in the rat results in abnormal activity levels of certain hepatic cytochrome P450 enzymes crucial in drug metabolism. If such a response also occurs in humans, this has the potential to produce serious complications with drug and endogenous substrate metabolism in patients with an infectious disease involving the CNS.

The role of cytokines in the depression of CYP1A activity using cultured astrocytes as an in vitro model of inflammation in the central nervous system

The interaction and modulation of hepatic cytochrome P450 enzymes by infection and inflammation has been well described both in clinical settings and in animal models. Recent evidence found that inflammation in the central nervous system (CNS) leads to alterations in cytochrome P450 activity in both brain and liver. The bacterial endotoxin lipopolysaccharide (LPS) was used to induce an inflammatory response in cultured astrocytes as a model of CNS inflammation. This inflammatory response involves a range of immune mediators, such as acute phase cytokines, nitric oxide, prostanoid products, and reactive oxygen species. It is hypothesized that cytokines, released during inflammation, act to modulate the expression of specific isoforms of cytochrome P450 resulting in altered activity levels. High levels of the cytokines tumor necrosis factor-alpha and interleukin-1beta were released into culture medium after the addition of LPS to astrocyte cultures. When these same cytokines were added directly to the cultures, they also were able to modulate levels of CYP1A activity. The concurrent addition of dexamethasone to astrocytes blocked both the cytokine release and the alteration of CYP1A activity, thus supporting a role for these cytokines in this response. These results provide evidence suggesting an involvement of acute phase cytokines in mediating the LPS-induced depression of CYP1A activity in cultured astrocytes.

Role of cytokines in the lipopolysaccharide-evoked depression of cytochrome P450 in the brain and liver

A role for cytokines as mediators of the depression in cytochrome P450 activity in brain and liver during CNS inflammation is proposed. Lipopolysaccharide (LPS) was given directly into the lateral ventricle of the brain to mimic a localized CNS infection. CYP1A activity and protein in both brain and liver were depressed in response to this treatment. The administration of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interferon-gamma (IFN-gamma) directly into the lateral ventricle emulated the effects of LPS on CYP1A activity only in the brain. In contrast, these centrally administered cytokines did not produce a concomitant loss of CYP1A activity in the liver. Significant levels of several cytokines (TNF-alpha, IL-1beta, and IFN-gamma) were produced in the serum of animals following intracerebroventricular (i.c.v.) administration of LPS. This production of peripheral cytokines by LPS could not be mimicked by the i.c.v. injection of IL-1beta or TNF-alpha. These results suggest that induction of cytokines in the brain may play a direct role in the depression of CYP1A activity in the CNS following the administration of LPS into the lateral ventricle. The production of cytokines within the brain does not appear to participate in the signaling process in the brain that leads to the concomitant loss of CYP1A activity in the liver. The subsequent production of cytokines in peripheral tissues, however, does appear to play a role in the loss of cytochrome P450 in the liver.

Alteration of drug biotransformation and elimination during infection and inflammation

During infection or inflammation, the expression of cytochrome P450 and its dependent biotransformation pathways are modified. This results in a change in the capacity of the liver to handle drugs and in alterations in the production and elimination of endogenous substances throughout the body. The majority of the CYP isoforms are modified at pre-translational steps in protein synthesis, and, in most cases, cytokines are involved as mediators of the response. Recent information suggests that inflammatory responses that are localized to the CNS cause a loss of CYP within the brain. This is accompanied by a parallel down-regulation of CYP in peripheral organs that is mediated by a signaling pathway between the brain and periphery. This review covers the loss that occurs in the major mammalian CYP families in response to infection/inflammation and the mediator pathways that are key to this response.

Decrease in hepatic CYP2C11 mRNA and increase in heme oxygenase activity after intracerebroventricular injection of bacterial endotoxin

We previously reported (Arch. Toxcol. 1998, 72, 492-498) that the differential decrease in the levels of hepatic cytochrome P450 (CYP) isozymes in rats was observed 24 hr after intracerebroventricular (i.c.v.) injection of bacterial lipopolysaccharide (LPS) at the dose ineffective (0.1 microgram) when injected intraperitoneally (i.p.). Among CYP isozymes we examined, the male specific CYP isozyme, CYP2C11 was most severely affected by i.c.v. injection of LPS. In this study, we examined the gene expression of CYP2C11, the total P450 contents, the CYP2C11-dependent activity of imipramine N-demethylase (IMND) and protein of CYP2C11 10 hr after i.c.v. or i.p. injections of LPS. Intracerebroventricular injection of LPS significantly decreased the level of CYP2C11 mRNA (to 63% of saline i.c.v. control), the total P450 contents (to 70% of saline i.c.v. control), the IMND activity (to 74% of saline i.c.v. control), but not protein of CYP2C11 in rat liver. In contrast, i.p. injection of LPS at the same dose as i.c.v. did not significantly affect these parameters. Since CYP is a heme protein, we also measured the activity of heme oxygenase (HO) using the same rat liver microsomes. The HO activity was increased to 166% by i.c.v. injection of LPS and 135% by i.p. injection of LPS compared to corresponding saline control. It is suggested that i.c.v. injection of LPS down-regulates the expression of CYP2C11 at transcriptional level and that both the decrease in CYP2C11 mRNA and the increase in heme degradation may be involved in the decreased level of protein and activity of CYP2C11 by i.c.v. injection of LPS in rat liver.