The interleukin-2 receptor down-regulates the expression of cytochrome P450 in cultured rat hepatocytes

IL-2-mediated hepatotoxicity: knowledge gap identification based on the irAOP concept

Drug-induced hepatotoxicity constitutes a major reason for non-approval and post-marketing withdrawal of pharmaceuticals. In many cases, preclinical models lack predictive capacity for hepatic damage in humans. A vital concern is the integration of immune system effects in preclinical safety assessment. The immune-related Adverse Outcome Pathway (irAOP) approach, which is applied within the Immune Safety Avatar (imSAVAR) consortium, presents a novel method to understand and predict immune-mediated adverse events elicited by pharmaceuticals and thus targets this issue. It aims to dissect the molecular mechanisms involved and identify key players in drug-induced side effects. As irAOPs are still in their infancy, there is a need for a model irAOP to validate the suitability of this tool. For this purpose, we developed a hepatotoxicity-based model irAOP for recombinant human IL-2 (aldesleukin). Besides producing durable therapeutic responses against renal cell carcinoma and metastatic melanoma, the boosted immune activation upon IL-2 treatment elicits liver damage. The availability of extensive data regarding IL-2 allows both the generation of a comprehensive putative irAOP and to validate the predictability of the irAOP with clinical data. Moreover, IL-2, as one of the first cancer immunotherapeutics on the market, is a blueprint for various biological and novel treatment regimens that are under investigation today. This review provides a guideline for further irAOP-directed research in immune-mediated hepatotoxicity.

Evaluation of the potential herb-drug interaction between Bojungikki-tang and PD-L1 immunotherapy in a syngeneic mouse model

Atezolizumab (a PD-L1 inhibitor) has shown remarkable efficacy and tolerability in various cancer types. Despite its efficacy and safety, atezolizumab monotherapy has limitations, such as acquired resistance and adverse events. Bojungikki-tang (BJIKT) is an herbal decoction widely prescribed in Asian countries and used to treat cancer-related symptoms including fatigue, appetite loss, gastrointestinal disorders, and other side effects from cancer therapy. Due to its immunomodulatory effects, Bojungikki-tang has been investigated as a combined treatment with anticancer agents. We evaluated the potential drug-drug interaction (DDI) between Bojungikki-tang and the anti-PD-L1 antibody based on the Food and Drug Administration (FDA) guidelines. In the study, we conducted an in vivo drug-drug interaction study using a syngeneic mouse model of CMT-167 in C57BL/6. We then determined the antibody concentrations to evaluate the pharmacokinetic (PK) drug-drug interaction and measured variable biomarkers related to therapeutic efficacy and immune response. The pharmacodynamic (PD) drug-drug interaction study investigated changes in response between anti-PD-L1 antibody monotherapy and combination therapy. Using the pharmacokinetic and pharmacodynamic data, we conducted a statistical analysis to assess drug-drug interaction potential. In the presence of Bojungikki-tang, the pharmacokinetic characteristics of the anti-PD-L1 antibody were not changed. This study suggested that combination treatment with Bojungikki-tang and atezolizumab is a safe treatment option for non-small cell lung cancer. Clinical studies are warranted to confirm this finding.

Disease-drug and drug-drug interaction in COVID-19: Risk and assessment

COVID-19 is announced as a global pandemic in 2020. Its mortality and morbidity rate are rapidly increasing, with limited medications. The emergent outbreak of COVID-19 prompted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) keeps spreading. In this infection, a patient's immune response plays pivotal role in the pathogenesis. This inflammatory factor was shown by its mediators that, in severe cases, reach the cytokine at peaks. Hyperinflammatory state may sparks significant imbalances in transporters and drug metabolic machinery, and subsequent alteration of drug pharmacokinetics may result in unexpected therapeutic response. The present scenario has accounted for the requirement for therapeutic opportunities to relive and overcome this pandemic. Despite the diminishing developments of COVID-19, there is no drug still approved to have significant effects with no side effect on the treatment for COVID-19 patients. Based on the evidence, many antiviral and anti-inflammatory drugs have been authorized by the Food and Drug Administration (FDA) to treat the COVID-19 patients even though not knowing the possible drug-drug interactions (DDI). Remdesivir, favipiravir, and molnupiravir are deemed the most hopeful antiviral agents by improving infected patient’s health. Dexamethasone is the first known steroid medicine that saved the lives of seriously ill patients. Some oligopeptides and proteins have also been using. The current review summarizes medication updates to treat COVID-19 patients in an inflammatory state and their interaction with drug transporters and drug-metabolizing enzymes. It gives an opinion on the potential DDI that may permit the individualization of these drugs, thereby enhancing the safety and efficacy.

2020 FDA Drug-drug Interaction Guidance: A Comparison Analysis and Action Plan by Pharmaceutical Industrial Scientists

Background:

In January 2020, the US FDA published two final guidelines, one entitled “In vitro Drug Interaction Studies - Cytochrome P450 Enzyme- and Transporter-Mediated Drug Interactions Guidance for Industry” and the other entitled “Clinical Drug Interaction Studies - Cytochrome P450 Enzyme- and Transporter-Mediated Drug Interactions Guidance for Industry”. These were updated from the 2017 draft in vitro and clinical DDI guidance.

Methods:

This study is aimed to provide an analysis of the updates along with a comparison of the DDI guidelines published by the European Medicines Agency (EMA) and Japanese Pharmaceuticals and Medical Devices Agency (PMDA) along with the current literature.

Results:

The updates were provided in the final FDA DDI guidelines and explained the rationale of those changes based on the understanding from research and literature. Furthermore, a comparison among the FDA, EMA, and PMDA DDI guidelines are presented in Tables 1, 2 and 3.

Conclusion:

The new 2020 clinical DDI guidance from the FDA now has even higher harmonization with the guidance (or guidelines) from the EMA and PMDA. A comparison of DDI guidance from the FDA 2017, 2020, EMA, and PMDA on CYP and transporter based DDI, mathematical models, PBPK, and clinical evaluation of DDI is presented in this review.

Cytochrome P450-mediated drug interactions in COVID-19 patients: Current findings and possible mechanisms

At the end of 2019, the entire world has witnessed the birth of a new member of coronavirus family in Wuhan, China. Ever since, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has swiftly invaded every corner on the planet. By the end of April 2020, almost 3.5 million cases have been reported worldwide, with a death toll of about 250,000 deaths. It is currently well-recognized that patient’s immune response plays a pivotal role in the pathogenesis of Coronavirus Disease 2019 (COVID-19). This inflammatory element was evidenced by its elevated mediators that, in severe cases, reach their peak in a cytokine storm. Together with the reported markers of liver injury, such hyperinflammatory state may trigger significant derangements in hepatic cytochrome P450 metabolic machinery, and subsequent modulation of drug clearance that may result in unexpected therapeutic/toxic response. We hypothesize that COVID-19 patients are potentially vulnerable to a significant disease-drug interaction, and therefore, suitable dosing guidelines with therapeutic drug monitoring should be implemented to assure optimal clinical outcomes.

Therapeutic protein drug-drug interactions: navigating the knowledge gaps-highlights from the 2012 AAPS NBC Roundtable and IQ Consortium/FDA workshop

The investigation of therapeutic protein drug-drug interactions has proven to be challenging. In May 2012, a roundtable was held at the American Association of Pharmaceutical Scientists National Biotechnology Conference to discuss the challenges of preclinical assessment and in vitro to in vivo extrapolation of these interactions. Several weeks later, a 2-day workshop co-sponsored by the U.S. Food and Drug Administration and the International Consortium for Innovation and Quality in Pharmaceutical Development was held to facilitate better understanding of the current science, investigative approaches and knowledge gaps in this field. Both meetings focused primarily on drug interactions involving therapeutic proteins that are pro-inflammatory cytokines or cytokine modulators. In this meeting synopsis, we provide highlights from both meetings and summarize observations and recommendations that were developed to reflect the current state of the art thinking, including a four-step risk assessment that could be used to determine the need (or not) for a dedicated clinical pharmacokinetic interaction study.

Influence of chronic hepatitis C infection on cytochrome P450 3A4 activity using midazolam as an in vivo probe substrate

PURPOSE

Inflammation-related changes in pharmacokinetics have been described for a number of disease-states including cancer, infection, and autoimmune disorders. This study examined the impact of chronic hepatitis C infection (CHC) on the pharmacokinetics of the cytochrome P450 3A probe midazolam in patients without significant liver disease who were either treatment naïve or prior interferon null-responders.

METHODS

Data were pooled from three studies which compared the pharmacokinetics of oral midazolam in healthy volunteers (n = 107) and in treatment-naive patients (n = 35) and interferon-null responders (n = 24) with CHC but without significant liver disease. Oral midazolam was administered as a single 2 mg oral dose, followed by frequent pharmacokinetic sampling and determination of the pharmacokinetics of midazolam and its α-hydroxy metabolite. CYP3A activity was determined by the metabolic ratio (MR) of the AUC metabolite/AUC parent and compared across groups as the mean effect ratio (test/reference).

RESULTS

The midazolam MR was lower in treatment-naïve patients with CHC than in health volunteers with a mean effect ratio of 0.63 [90 % confidence interval (CI) 0.56-0.72]. The effect was more pronounced in null-responders, who demonstrated a mean MR effect ratio of 0.46 (90 % CI 0.39-0.53) compared to volunteers. The mean area under the concentration-time curve (AUCinf) for midazolam in healthy volunteers, naïve patients, and null-responders was 32.3 [coefficient of variation (CV%) 41], 36.5 (CV% 33.5), and 55.3 (CV% 36.9) ng.h/mL, respectively.

CONCLUSIONS

The results of this study demonstrate a reduction in CYP3A4 activity between healthy volunteers and patients with CHC, with interferon null-responders demonstrating the most substantial difference. These results may have implications for the pharmacotherapy of patients infected with CHC.

Regulation of hepatic cytochrome P450 expression in mice with intestinal or systemic infections of citrobacter rodentium

We reported previously that infection of C3H/HeOuJ (HeOu) mice with the murine intestinal pathogen Citrobacter rodentium caused a selective modulation of hepatic cytochrome P450 (P450) gene expression in the liver that was independent of the Toll-like receptor 4. However, HeOu mice are much more sensitive to the pathogenic effects of C. rodentium infection, and the P450 down-regulation was associated with significant morbidity in the animals. Here, we report that oral infection of C57BL/6 mice with C. rodentium, which produced only mild clinical signs and symptoms, produced very similar effects on hepatic P450 expression in this strain. As in HeOu mice, CYP4A mRNAs and proteins were among the most sensitive to down-regulation, whereas CYP4F18 was induced. CYP2D9 mRNA was also induced 8- to 9-fold in the C57BL/6 mice. The time course of P450 regulation followed that of colonic inflammation and bacterial colonization, peaking at 7 to 10 days after infection and returning to normal at 15 to 24 days as the infection resolved. These changes also correlated with the time course of significant elevations in the serum of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, as well as of interferon-gamma and IL-2, with serum levels of IL-6 being markedly higher than those of the other cytokines. Intraperitoneal administration of C. rodentium produced a rapid down-regulation of P450 enzymes that was quantitatively and qualitatively different from that of oral infection, although CYP2D9 was induced in both models, suggesting that the effects of oral infection on the liver are not due to bacterial translocation.

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.

Use of duplex PCR-CTPP methods for CYP2E1RsaI/IL-2 T-330G and IL-1B C-31T/TNF-A T-1031C polymorphisms

BACKGROUND

Two duplex polymerase chain reaction (PCR) with confronting two-pair primer (PCR-CTPP) methods were designed for cytochrome P450 (CYP) 2E1 RsaI and interleukin (IL-2) T-330G, and for IL-1B C-31T and tumor necrosis factor-alpha (TNF-A) T-1031C. The four polymorphisms are considered to be functional, and the three cytokines reportedly inhibit CYP2E1 expression. Many studies have reported associations between the above polymorphisms and risk of diseases including cancers and inflammatory diseases.

AIM

The main objective of this study was to examine the applicability of the established PCR conditions to a real situation.

PARTICIPANTS

Participants were female examinees aged from 35 to 85 years who attended health checks run by a local government in Japan.

RESULTS

The allele frequencies among 325 female health check examinees were 0.804 for CYP2E1 c1 allele, 0.668 for IL-2-330T allele, 0.554 for IL-1B-31T allele, and 0.822 for TNF-A-1031T allele. p-Values from a Hardy-Weinberg equilibrium test were 0.658, 0.955, 0.062, and 0.806, respectively.

DISCUSSION

Clear DNA bands observed with electrophoresis allowed us to genotype the four polymorphisms. The genotype frequencies were within the Hardy-Weinberg equilibrium test proportions, though the p-value for IL-1B C-31T was marginal.

CONCLUSIONS

Both duplex PCR-CTPP methods may be useful tools for studies on the association between these polymorphisms and disease risk.

Transcriptional regulation of the human hepatic CYP3A4: identification of a new distal enhancer region responsive to CCAAT/enhancer-binding protein beta isoforms (liver activating protein and liver inhibitory protein)

CCAAT/enhancer-binding proteins (C/EBPs) are key transcription factors involved in the constitutive expression of several cytochrome P450 genes in the liver. Their concentration and activity change in several pathophysiological conditions. For instance, during inflammation, released cytokines induce repressive C/EBPbeta-liver inhibitory protein (LIP), which antagonizes constitutive C/EBP transactivators [C/EBPalpha and C/EBPbeta-liver activating protein (LAP)], down-regulating genes such as CYP3A4. However, the mechanism by which hepatic C/EBP factors modulate transcription of the CYP3A4 gene is not known. To elucidate the mechanism of action, we cotransfected luciferase reporter vectors, containing 5'-flanking deletions of the CYP3A4 gene, along with expression vectors for C/EBPbeta-LAP, C/EBPbeta-LIP, and C/EBPalpha, in hepatic (HepG2) and nonhepatic (HeLa) cells. Analysis of the -3557 to -6954 base pair (bp) region demonstrated the existence of a 288-bp sequence at -5.95 kilobases (kb), which showed maximal response to C/EBPbeta-LAP ( approximately 30-fold increase in HepG2 cells). Coexpression of LAP with increasing amounts of LIP reduced the activating effect by approximately 70%. Site-directed mutagenesis of predicted C/EBPbeta binding sites demonstrated the presence of four functional C/EBPbeta-responsive motifs within this distal flanking region. Further experiments using chromatin immunoprecipitation proved the binding of endogenous C/EBPbeta to the -5.95-kilobase enhancer of the CYP3A4 gene in human hepatocytes. Expression of recombinant LAP and LIP by means of adenoviral vectors resulted in their binding to this region, which was followed by activation/repression of CYP3A4. Together, our results uncover a new distal enhancer site in the CYP3A4 gene where C/EBPbeta-LAP binds and activates transcription, whereas the truncated form, C/EBPbeta-LIP, antagonizes LAP activity and causes gene repression.

Kupffer cell-mediated IL-2 suppression of CYP3A activity in human hepatocytes

Interleukin (IL)-2 administration has been shown to decrease CYP3A enzyme activity in vivo. To determine whether IL-2 suppression of human hepatocyte CYP3A activity is direct or whether it is facilitated by the presence of Kupffer cells, primary human hepatocytes were cultured alone or cocultured with primary human Kupffer cells at physiologic hepatocyte/Kupffer cell ratios of 10:1 or 10:4. Using proinflammatory cytokines as positive controls, IL-1 (0.2-20 ng/ml) and IL-6 (2-200 ng/ml) exposure resulted in a 70 to 90% decrease in CYP3A activity after 72 h in hepatocyte cultures. In the hepatocyte/Kupffer cell cocultures, an 80% decrease in CYP3A activity was observed with IL-1 (2 ng/ml) or IL-6 (20 ng/ml), suggesting that direct suppressive effects of proinflammatory cytokines on hepatocyte CYP3A activity are not substantially altered by Kupffer cells. In contrast to the effects of these proinflammatory cytokines, no sustained suppression of CYP3A activity was observed with IL-2 (2-200 ng/ml) in hepatocyte cultures. However, in hepatocyte/Kupffer cell cocultures, a concentration-dependent 50 to 70% suppression of CYP3A activity was observed with IL-2 at 72 h. In summary, these data suggest that Kupffer cells are required to reconstitute the suppressive effects of IL-2 on CYP3A activity that are observed in vivo and that hepatocyte/Kupffer cell cocultures may provide a useful model for investigating mechanisms of CYP3A4 regulation by cytokines. Of particular relevance to certain hepatic diseases, these findings suggest potential mechanisms whereby cytokines released from infiltrating blood mononuclear cells might modulate intercellular signaling and controls on hepatocyte function by various cell types that reside in liver.

Subliminal Fas stimulation increases the hepatotoxicity of acetaminophen and bromobenzene in mice

The hepatotoxicity of several drugs is increased by mild viral infections. During such infections, death receptor ligands are expressed at low levels, and most parenchymal cells survive. We tested the hypothesis that subliminal death receptor stimulation may aggravate the hepatotoxicity of drugs, which are transformed by cytochrome P-450 cytochrome P-450 into glutathione-depleting reactive metabolites. Twenty-four-hour-fasted mice were pretreated with a subtoxic dose of the agonistic Jo2 anti-Fas antibody (1 microg per mouse) 3 hours before acetaminophen (500 mg/kg) or 1 hour before bromobenzene (400 mg/kg) administration. Administration of Jo2 alone increased hepatic inducible nitric oxide synthase nitric oxide synthase but did not modify serum alanine aminotransferase (ALT), hepatic adenosine triphosphate (ATP), glutathione (GSH), cytochrome P-450, cytosolic cytochrome c, caspase-3 activity or hepatic morphology. However, pretreating mice with Jo2 further decreased both hepatic GSH and ATP by 40% 4 hours after acetaminophen administration, and further increased serum ALT and the area of centrilobular necrosis at 24 hours. In mice pretreated with the Jo2 antibody before bromobenzene administration, hepatic GSH 4 hours after bromobenzene administration was 51% lower than in mice treated with bromobenzene alone, and serum ALT activity at 24 hours was 47-fold higher. In conclusion, administration of a subtoxic dose of an agonistic anti-Fas antibody before acetaminophen or bromobenzene increases metabolite-mediated GSH depletion and hepatotoxicity. Subliminal death receptor stimulation may be one mechanism whereby mild viral infections can increase drug-induced toxicity.

Downregulation of cytochromes P450 in growth-stimulated rat hepatocytes: role of c-Myc induction and impaired C/EBP binding to DNA

BACKGROUND/AIMS

Several cytochromes P450 (CYPs) are expressed in differentiated hepatocytes, but downregulated in growth-stimulated cells. We determined the signals involved in CYP downregulation by epidermal growth factor (EGF).

METHODS

Rat hepatocytes were cultured with or without diverse substances for 72 h and EGF for the last 48 h.

RESULTS

EGF increased c-myc mRNA and protein, and decreased CYP mRNAs and proteins; both effects were prevented by two agents blocking c-myc transcription (retinoic acid and DMSO) and two antisense c-myc oligomers. Despite unchanged CCAAT-enhancer binding protein alpha (C/EBPalpha) and increased C/EBPbeta levels, nuclear proteins of EGF-treated cells did not bind to a C/EBP DNA probe in a gel mobility shift assay. This binding was restored when cells were co-treated with both EGF and c-myc antisense oligomers (preventing c-Myc induction). The N-terminal c-Myc domain added to control nuclear extracts prevented C/EBP DNA binding. A monoclonal anti-c-Myc antibody co-immunoprecipitated c-Myc, C/EBPalpha and C/EBPbeta from nuclear extracts. In cells not treated with EGF, an antisense C/EBPalpha oligomer decreased CYP expression.

CONCLUSIONS

EGF overexpresses c-Myc, decreases C/EBP binding to DNA and downregulates CYPs. We suggest that c-Myc may form inactive complexes with C/EBPs, thus decreasing C/EBP-mediated CYP transactivation.

Effect of age and degree of immune activation on cytochrome P450 3A4 activity after influenza immunization

STUDY OBJECTIVE

To measure age- or sex-related changes in cytochrome P450 (CYP) activity secondary to influenza vaccination.

DESIGN

Open-label, single-dose study.

SETTING

General clinical research center at a university hospital.

SUBJECTS

Fifteen healthy volunteers aged 22-51 years.

INTERVENTION

Each subject was given an erythromycin breath test (ERMBT) to measure CYP3A4 activity before influenza immunization and again on day 7 after immunization. Blood was drawn before immunization and on day 28 after immunization to measure influenza antibody concentrations.

MEASUREMENTS AND MAIN RESULTS

Age of subject and change in ERMBT results after influenza immunization were correlated (correlation coefficient -0.624, p < 0.015). However, no correlations could be made between antibody concentrations after influenza immunization or change in antibody concentrations from baseline and age.

CONCLUSION

Decreases in CYP3A4 activity after influenza immunization are associated with increasing age. The decreases in CYP3A4 activity, however, are not associated with influenza antibody concentrations. This study bears repeating in an older cohort since the study sample did not include elderly individuals.

The effect of sepsis during parenteral nutrition on hepatic microsomal function in rats

STUDY OBJECTIVE

To investigate the effect of sepsis during parenteral nutrition on hepatic cytochrome P450 (CYP) activity in rats.

DESIGN

Prospective, randomized, controlled study.

SETTING

University-based animal research laboratory.

ANIMALS

Twenty adult male Sprague-Dawley rats.

INTERVENTION

The animals were cannulated intravenously and randomized to receive parenteral nutrition (PN), intravenous live Escherichia coli 4 x 10(8) colony-forming units/100 g body weight for 2 consecutive days with PN (PNEC), or chow (CH).

MEASUREMENTS AND MAIN RESULTS

Both PN alone and PNEC resulted in a progressive decline in hepatic CYP concentration compared with CH (0.53 +/- 0.10, 0.41 +/- 0.17, and 0.35 +/- 0.14 nmol/mg microsomal protein, respectively, p < 0.05). Parenteral nutrition alone was associated with a 57% decrease in isoenzyme ethoxycoumarin-O-deethylase activity (ECOD) compared with CH, but sepsis did not further decrease ECOD activity any more than PN alone (0.103 +/- 0.049, 0.044 +/- 0.018, and 0.050 +/- 0.020 nmol/mg microsomal protein/min, respectively, p < 0.05).

CONCLUSION

Hepatic CYP concentration declines with PN and is further decreased when compounded by sepsis. The disproportional decrease in ECOD activity relative to CYP concentration with PN is unchanged by sepsis, indicating a selective alteration in hepatic isoenzymes by PN.

Effect of hr-IL2 treatment on intestinal P-glycoprotein expression and activity in Caco-2 cells

Caco-2 cells were used to investigate the effect of human recombinant interleukin-2 (IL2) on intestinal P-glycoprotein (P-gp) transporter activity in-vitro. More specifically the efflux function of P-gp was studied by measuring the transepithelial transport of rhodamine-123, a fluorescent substrate of P-gp. Its transport was completely inhibited by two specific P-gp inhibitors, ciclosporin A and GG918, in our experiments. Conversely, these two specific P-gp inhibitors inhibited only 50% of transepithelial transport when [3H]vincristine was used as substrate. After Caco-2 cells were treated with 100 IU mL-1 (6.1 ng mL-1) IL2 for 24 h, a significant diminution (21%) of P-gp transporter function was observed with rhodamine-123 substrate. This effect was also confirmed after 48 and 72 h of exposure to IL2. However, for higher concentrations of IL2 (1000 and 5000 IU mL-1), diminution of P-gp function only occurred after a longer treatment period (48 h and more). The inhibitory effect of IL2 on P-gp activity was found to be independent of tight junction function as demonstrated by constant transepithelial electrical resistance (TEER) measurements for all experimental conditions encountered in this study (time and concentration of IL2 exposure). Furthermore, the MDR1 mRNA level was found to be strongly repressed in Caco-2 cells exposed with 1000 IU mL-1 IL2 for 72 h while the amount of MRP1 mRNA remained unchanged. In conclusion, acute incubation of Caco-2 cells with IL2 induced a decrease of P-gp transporter expression and activity.

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.

Hepatic drug metabolism and immunostimulation

When host defence mechanisms are stimulated there is a concomitant decrease in cytochrome P450 based drug biotransformation and elimination. This has resulted in a number of clinically important unwanted drug responses in patients with infections or inflammatory responses. The loss in cytochrome P450 is predominantly an effect at the level of the gene expression and the majority of enzyme forms examined to date are involved. Although the effect occurs predominantly in the liver it has been recently shown that inflammatory responses in the brain also cause a loss of the same enzyme forms in that organ. The loss of cytochrome P450 in the brain in response to localised inflammation is accompanied by a similar loss in the liver. The decrease of cytochrome P450 and its dependent drug biotransformation is of concern whenever drugs are used in patients with infections or disease states with an inflammatory component.

Oncostatin M: signal transduction and biological activity

Oncostatin M (OSM) is a multifunctional cytokine produced by activated T lymphocytes and monocytes that is structurally and functionally related to the subfamily of cytokines known as the IL-6-type cytokine family. OSM shares properties with all members of this family of cytokines, but is most closely related structurally and functionally to LIE OSM acts on a wide variety of cells and elicits diversified biological responses in vivo and in vitro which suggest potential roles in the regulation of gene activation, cell survival, proliferation and differentiation. OSM and LIF can bind to the same functional receptor complex (LIF-receptor beta and gp130 heteromultidimers) and thus mediate overlapping spectra of biological activities. There is a second specific beta receptor that binds OSM with high affinity and also involves the subunit gp130. The two receptors for OSM can be functionally different and be coupled to different signal transduction pathways. OSM-specific receptors are expressed in a wide variety of cell types and do not possess an intrinsic tyrosine kinase domain, but the JAK/STAT tyrosine kinase pathway mediates signal transduction.

Lipopolysaccharide evokes the modulation of brain cytochrome P4501A in the rat

The cytochrome P450 enzyme system is a multigene family of enzymes that is modulated in the liver during systemic inflammatory responses or during infection Several forms of the enzyme are expressed in discrete areas of the brain and likely play a critical role in the metabolism of drugs and endogenous chemicals in the central nervous system (CNS). Even though the brain responds to inflammation in a manner different from most tissues, we examined the possible modification of a major cytochrome P450 form (CYP1A) in the brain during inflammation confined to that organ. Total brain CYP1A activity, as measured by ethoxyresorufin dealkylase (EROD), was downregulated 24 and 48 h following the administration of a single dose of lipopolysaccharide (LPS). Regionally, a similar effect was determined in the cortex, hippocampus and the mid-brain but the activity in the cerebellum was unaffected. The examination of coronal brain sections using an antibody directed against CYP1A indicated that the enzyme was distributed in discrete cells of the hippocampus, thalamus and cortex and in the tanycytes surrounding the third ventricle. In each of these areas, the immunoreactivity was diminished in animals receiving LPS as compared to saline-treated animals. LPS also evoked the expression of the small molecular weight heat shock protein hsp27 throughout the brain indicating the development of an inflammatory response. These studies indicate that inflammation localized to the CNS causes an alteration in the levels and activity of a major cytochrome P450 form in the brain. This could have implications to the metabolism or activation of drugs and endogenous chemicals in the CNS during a disease state that features an inflammatory component.

Decrease in hepatic cytochrome P450 after interleukin-2 immunotherapy

Interleukin-2 (IL-2) has been shown to decrease cytochrome P450 (CYP) mRNAs and proteins in cultured rat hepatocytes, and IL-2 administration decreases CYPs in rats. Although high doses of IL-2 are administered to cancer patients, the effect on human CYPs has not yet been determined. Patients with hepatic metastases from colon or rectum carcinomas were randomly allocated to various daily doses of human recombinant IL-2 (from 0 to 12.10(6) units/m(2)). IL-2 was infused from day 7 to day 3 before hepatectomy and the conservation of a non-tumorous liver fragment in liquid nitrogen. Hepatic CYPs and monooxygenase activities were not significantly decreased in 5 patients receiving daily doses of 3 or 6 10(6) IL-2 units/m2, compared to 7 patients who did not receive IL-2. In contrast, in 6 patients receiving daily doses of 9 or 12 x 10(6) IL-2 units/m2, the mean values for immunoreactive CYP1A2, CYP2C, CYP2E1, and CYP3A4 were 37, 45, 60 and 39%, respectively, of those in controls; total CYP was significantly decreased by 34%, methoxyresorufin O-demethylation by 62%, and erythromycin N-demethylation by 50%. These observations suggest that high doses of IL-2 may decrease total CYP and monooxygenase activities in man.

Comparative effects of cytokines on constitutive and inducible expression of the gene encoding for the cytochrome P450 3A6 isoenzyme in cultured rabbit hepatocytes: consequences on progesterone 6beta-hydroxylation

Cultured rabbit hepatocytes were used to compare the relative activities of cytokines to inhibit the constitutive or rifampicin (RIF)-induced expression of the cytochrome P450 3A6 gene (CYP3A6). Human recombinant cytokines tested were interleukin-1beta (IL-1beta) (2 U/mL), interleukin-2 (IL-2) (5,000 U/mL) and interferon-gamma (IFN-gamma) (50 U/mL). Hepatocytes were cultured in the presence or absence of 25 microM RIF for 24 hr, with or without cytokines alone or in combination. All these cytokines inhibited RIF-induced P4503A6 expression without apparent cellular toxicity. By contrast, only IFN-gamma treatment provided a significant decrease (41%) in the constitutive P4503A6 protein level. Moreover, cytokines differed in their ability to repress RIF-dependent transcriptional induction of CYP3A6: IL-1beta and IL-2 were approximately equipotent, causing an almost 40-50% suppression of CYP3A6 mRNA and protein levels, whereas IFN-gamma exerted repressive effects only on P4503A6-related erythromycin N-demethylase activity and inducible protein expression. In fact, although strongly reducing P4503A6 protein content (an approximate 70% decrease), IFN-gamma did not exhibit any influence on CYP3A6 mRNAs with the exception of its association with interleukins. All these results suggest that IL-1beta and IL-2 mainly promote a transcriptional repression mechanism, given the absence of effect of these cytokines on the basal P4503A6 level, whereas IFN-gamma exerts a post-transcriptional suppressive action on both induced and constitutive P4503A6 expression. Consequently, P4503A6-dependent progesterone 6beta-hydroxylase activity also presented a cytokine-specific pattern of inhibition, with a much greater sensitivity than P4503A6 immunoreactive protein to IL-1beta and IL-2 + IFN-gamma treatments. Thus, this study underlines the significant impact of inflammation on steroid metabolism.

Steatohepatitis-inducing drugs cause mitochondrial dysfunction and lipid peroxidation in rat hepatocytes

BACKGROUND & AIMS

4,4'-Diethylaminoethoxyhexestrol (DEAEH), amiodarone, and perhexiline cause steatohepatitis in humans. The mechanisms of these effects are unknown for DEAEH and have not been completely elucidated for amiodarone and perhexiline. The aim of this study was to determine these mechanisms.

METHODS

Rat liver mitochondria, cultured rat hepatocytes, or rats were treated with these drugs, and the effects on mitochondrial respiration, beta-oxidation, reactive oxygen species formation, and lipid peroxidation were determined.

RESULTS

DEAEH accumulated in mitochondria and inhibited carnitine palmitoyl transferase I and acyl-coenzyme A dehydrogenases; it decreased beta-oxidation and caused lipid deposits in hepatocytes. DEAEH also inhibited mitochondrial respiration and decreased adenosine triphosphate (ATP) levels in hepatocytes. DEAEH, amiodarone, and perhexiline augmented the mitochondrial formation of reactive oxygen species and caused lipid peroxidation in rats.

CONCLUSIONS

Like amiodarone and perhexiline, DEAEH accumulates in mitochondria, where it inhibits both beta-oxidation (causing steatosis) and respiration. Inhibition of respiration decreases ATP and also increases the mitochondrial formation of reactive oxygen species. The latter oxidize fat deposits, causing lipid peroxidation. We suggest that ATP depletion and lipid peroxidation may cause cell death and that lipid peroxidation products may account, in part, for other steatohepatitis lesions.

Putrescine decreases cytochrome P450 3A4 levels during liver regeneration in the rat

BACKGROUND/AIMS

The mechanism by which many cytochrome P450 (CYP) isozymes decrease during liver regeneration is unclear. Peptides and growth factors are thought to be involved. Putrescine, the first polyamine synthesised by ornithine decarboxylase, peaks early following partial hepatectomy and is known to play an essential role in hepatic regeneration. Gamma amino butyric acid was reported as a physiologic inhibitor of ornithine decarboxylase. In this work we studied the possible involvement of putrescine in the CYP reduction during liver regeneration.

METHODS

Hepatectomised, putrescine-treated sham, and GABA-treated hepatectomised rats were used throughout. Total hepatic cytochrome P450, o-dealkylase activities (CYP1A1 and CYP2B1/2), nifedipine oxidase activity (CYP3A4), and Western blot assays of their respective apoproteins were analysed in liver microsomes. Putrescine levels in hepatic tissue were also measured.

RESULTS

Partial hepatectomy and putrescine treatment induced a significant diminution in total CYP (50% and 30% of sham-operated rats, respectively). Gamma amino butyric acid treatment prevented this decrease in partially hepatectomised rats. Nifedipine oxidase activity of partially hepatectomised and putrescine-treated rats significantly decreased to 43% and 60% of that in sham-operated rats, respectively. Again, gamma amino butyric acid prevented the diminution in partially hepatectomised rats. No significant changes were observed in o-dealkylase activities.

CONCLUSIONS

These results show that inducible CYP1A1 and CYP2B1/2, which are important in carcinogen metabolisation, are preserved after partial hepatectomy. However, constitutive CYP3A4, which represents 50% of total CYP and metabolises drugs like nifedipine, warfarin, acetaminophen, cyclosporin and FK-506, is reduced during liver regeneration. Our experiments suggest that endogenous putrescine is, at least, partly responsible for this decrease.

Risperidone dose and blood level variability: accumulation effects and interindividual and intraindividual variability in the nonresponder patient in the clinical practice setting

Risperidone blood levels were measured every 2 weeks after initiation of therapy in 24 refractory chronic schizophrenic patients referred to a locked, skilled nursing facility for long-term treatment. Blood levels were assessed on 285 occasions over a 1- to 16-month treatment program. Drug plasma level increases peaked by 2 months for risperidone at 334% and by 6 months for 9-hydroxy-risperidone at 104% over the baseline levels. Total blood levels (risperidone plus 9-hydroxy-risperidone) peaked at 111% increase at 6 months and then declined 8% per month to 12 months, stabilizing at a value 31% higher than the initial value. Significant dose to blood level interindividual variation was noted. Considerable blood level variation was evident in single blood level sample determinations. The results suggest the value of risperidone blood levels, consideration of reduction of initial recommended starting dosages, and a need to optimize risperidone dosage approaches individually to patients.

Antigenic targets in tienilic acid hepatitis. Both cytochrome P450 2C11 and 2C11-tienilic acid adducts are transported to the plasma membrane of rat hepatocytes and recognized by human sera

Patients with tienilic acid hepatitis exhibit autoantibodies that recognize unalkylated cytochrome P450 2C9 in humans but recognize 2C11 in rats. Our aim was to determine whether the immune reaction is also directed against neoantigens. Rats were treated with tienilic acid and hepatocytes were isolated. Immunoprecipitation, immunoblotting, and flow cytometry experiments were performed with an anti-tienilic acid or an anti-cytochrome P450 2C11 antibody. Cytochrome P450 2C11 was the main microsomal or plasma membrane protein that was alkylated by tienilic acid. Inhibitors of vesicular transport decreased flow cytometric recognition of both unalkylated and tienilic acid-alkylated cytochrome P450 2C11 on the plasma membrane of cultured hepatocytes. Tienilic acid hepatitis sera that were preadsorbed on microsomes from untreated rats (to remove autoantibodies), poorly recognized untreated hepatocytes in flow cytometry experiments, but better recognized tienilic acid-treated hepatocytes. This recognition was decreased by adsorption with tienilic acid or by preexposure to the anti-tienilic acid or the anti-cytochrome P450 2C11 antibody. We conclude that cytochrome P450 2C11 is alkylated by tienilic acid and follows a vesicular route to the plasma membrane. Tienilic acid hepatitis sera contain antibodies against this tienilic acid adduct, in addition to the previously described anticytochrome P450 autoantibodies.