Depression of liver drug metabolism and increase in plasma fibrinogen by interleukin 1 and tumor necrosis factor: a comparison with lymphotoxin and interferon

Circulating γ-Tocopherol Concentrations Are Inversely Associated with Antioxidant Exposures and Directly Associated with Systemic Oxidative Stress and Inflammation in Adults

Background

Although α- and γ-tocopherol are co-consumed antioxidants, circulating γ-tocopherol concentrations were paradoxically found to be inversely associated with total vitamin E intake and circulating α-tocopherol concentrations. There are limited data on this apparent paradox or on determinants of circulating γ-tocopherol concentrations.

Objective

To help clarify possible determinants of circulating γ-tocopherol concentrations, we investigated associations of circulating γ-tocopherol concentrations with various dietary and lifestyle factors and biomarkers of oxidative stress and inflammation.

Methods

We pooled cross-sectional data from 2 outpatient, adult, elective colonoscopy populations (pooled n = 419) on whom extensive dietary, lifestyle, and medical information was collected, and the following plasma concentrations were measured: α- and γ-tocopherol (via HPLC), F2-isoprostanes (FiPs; via gas chromatography-mass spectrometry), and high-sensitivity C-reactive protein (hsCRP; via latex-enhanced immunonephelometry). Multivariable general linear models were used to assess mean γ-tocopherol differences across quantiles of plasma antioxidant micronutrients, FiPs, and hsCRP; an oxidative balance score [OBS; a composite of anti- and pro-oxidant dietary and lifestyle exposures (a higher score indicates higher antioxidant relative to pro-oxidant exposures)]; and multiple dietary and lifestyle factors.

Results

Adjusted for serum total cholesterol, mean γ-tocopherol concentrations among those in the highest relative to the lowest tertiles of circulating α-tocopherol and β-carotene, the OBS, and total calcium and dietary fiber intakes were 31.0% (P < 0.0001), 29.0% (P < 0.0001), 27.6% (P = 0.0001), 29.7% (P < 0.0001), and 18.6% (P = 0.008) lower, respectively. For those in the highest relative to the lowest tertiles of circulating FiPs and hsCRP, mean γ-tocopherol concentrations were 50% (P < 0.0001) and 39.0% (P < 0.0001) higher, respectively.

Conclusions

These findings support the conclusion that circulating γ-tocopherol concentrations are inversely associated with antioxidant exposures and directly associated with systemic oxidative stress and inflammation in adults. Additional research on possible mechanisms underlying these findings and on whether circulating γ-tocopherol may serve as a biomarker of oxidative stress, inflammation, or both is needed.

Elimination of intravascular thrombi prevents early mortality and reduces gliosis in hyper-inflammatory experimental cerebral malaria

BACKGROUND

Cerebral malaria (CM) is the most lethal outcome of Plasmodium infection. There are clear correlations between expression of inflammatory cytokines, severe coagulopathies, and mortality in human CM. However, the mechanisms intertwining the coagulation and inflammation pathways, and their roles in CM, are only beginning to be understood. In mice with T cells deficient in the regulatory cytokine IL-10 (IL-10 KO), infection with Plasmodium chabaudi leads to a hyper-inflammatory response and lethal outcome that can be prevented by anti-TNF treatment. However, inflammatory T cells are adherent within the vasculature and not present in the brain parenchyma, suggesting a novel form of cerebral inflammation. We have previously documented behavioral dysfunction and microglial activation in infected IL-10 KO animals suggestive of neurological involvement driven by inflammation. In order to understand the relationship of intravascular inflammation to parenchymal dysfunction, we studied the congestion of vessels with leukocytes and fibrin(ogen) and the relationship of glial cell activation to congested vessels in the brains of P. chabaudi-infected IL-10 KO mice.

METHODS

Using immunofluorescence microscopy, we describe severe thrombotic congestion in these animals. We stained for immune cell surface markers (CD45, CD11b, CD4), fibrin(ogen), microglia (Iba-1), and astrocytes (GFAP) in the brain at the peak of behavioral symptoms. Finally, we investigated the roles of inflammatory cytokine tumor necrosis factor (TNF) and coagulation on the pathology observed using neutralizing antibodies and low-molecular weight heparin to inhibit both inflammation and coagulation, respectively.

RESULTS

Many blood vessels in the brain were congested with thrombi containing adherent leukocytes, including CD4 T cells and monocytes. Despite containment of the pathogen and leukocytes within the vasculature, activated microglia and astrocytes were prevalent in the parenchyma, particularly clustered near vessels with thrombi. Neutralization of TNF, or the coagulation cascade, significantly reduced both thrombus formation and gliosis in P. chabaudi-infected IL-10 KO mice.

CONCLUSIONS

These findings support the contribution of cytokines, coagulation, and leukocytes within the brain vasculature to neuropathology in malaria infection. Strikingly, localization of inflammatory leukocytes within intravascular clots suggests a mechanism for interaction between the two cascades by which cytokines drive local inflammation without considerable cellular infiltration into the brain parenchyma.

Regulation of cytochrome P450 4F11 by nuclear transcription factor-κB

Although the mechanisms that regulate CYP4F genes have been and are currently being studied in a number of laboratories, the specific mechanisms for the regulation of these genes are not yet fully understood. This study shows that nuclear factor κB of the light-chain-enhancer in activated B cells (NF-κB) can inhibit CYP4F11 expression in human liver carcinoma cell line (HepG2) as summarized below. Tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, has been shown to activate NF-κB signaling while also activating the c-Jun NH(2)-terminal kinase (JNK) signaling pathway. Other studies have reported that JNK signaling can up-regulate CYP4F11 expression. The results of this study demonstrate that in the presence of TNF-α and the specific NF-κB translocation inhibitor N-[3,5-bis(trifluoromethyl)phenyl]-5-chloro-2-hydroxybenzamide (IMD-0354), there is a greater increase in CYP4F11 expression than that elicited by TNF-α alone, indicating that NF-κB plays an inhibitory role. Moreover, NF-κB stimulation by overexpression of mitogen-activated protein kinase kinase kinase inhibited CYP4F11 promoter expression. CYP4F11 promoter inhibition can also be rescued in the presence of TNF-α when p65, a NF-κB protein, is knocked down. Thus, NF-κB signaling pathways negatively regulate the CYP4F11 gene.

Evaluation of biomarkers of inflammation in response to benzalkonium chloride on corneal and conjunctival epithelial cells

PURPOSE

Most eye drops contain preservatives; benzalkonium chloride (BAK) is most common. Recent data demonstrated BAK adding to toxicity. BAK is degraded into hydrogen peroxide (H(2)O(2)), which in even small amounts is known to be an irritant. Increased toxicity should cause localized inflammation with increased elaboration of inflammatory biomarkers. To evaluate the inflammation BAK causes to the ocular surface, enzyme linked immunosorbant assays (ELISAs) were utilized to quantify the levels of inflammatory biomarkers in response to BAK and/or H(2)O(2).

METHODS

Immortalized human conjunctival and corneal epithelial cells were exposed to: BAK (0.001%-0.1%), hydrogen peroxide (H(2)O(2)) (0.01%-0.1%), and cell media for 1 h. Cytokine quantification was performed via enzyme-linked immunosorbent assays [ELISAs]). Additional experimentation was performed in which testing solutions were replaced with media after 1 h and the resulting supernatants quantified after 24 h.

RESULTS

BAK induced significant amounts of interleukin (IL-) 1 and tumor necrosis factor (TNF), but only moderate amounts of C-reactive protein (CRP), IL- 10 and 12, and H(2)O(2). Lower concentrations of BAK induced proportionally less elaboration. Replacing the test solutions with media and providing 23 h for cytokine elaboration significantly increased TNF, but not IL-1. Lipopolysaccharide (LPS) positive controls induced substantial elaboration/release of both IL-1 and TNF as did in increasing the exposure to the full 24 h.

CONCLUSIONS

After 1 h of exposure, BAK increased quantities of all biomarkers. The biomarkers in decreasing order of induction/upregulation were: TNF > or = IL-1 > or = IL-12 > or = IL-10 > or = CRP. Even low concentrations caused some degree of inflammation. Replacing the testing solution with media and providing 23 h for cytokine elaboration, significantly increased the elaboration/release of TNF, but not IL-1, as compared to the 1-h BAK exposure. Whereas increasing the exposure to the full 24 h by not removing the testing solution at the 1-h time point significantly increased the elaboration/release of both IL-1 and TNF.

Elevated blood concentrations of calcineurin inhibitors during diarrheal episode in pediatric liver transplant recipients: involvement of the suppression of intestinal cytochrome P450 3A and P-glycoprotein

We encountered two cases of pediatric living-related liver transplant recipients who showed increases in blood concentration of cyclosporine or tacrolimus, a dual substrate for cytochrome P450 (CYP) 3A and P-glycoprotein (P-gp), during a diarrheal episode. To investigate the effect of intestinal inflammation on the metabolic and efflux pump activities, we conducted the experiments using the lipopolysaccharide (LPS)-induced intestinal damage model. Intestinal epithelial CYP3A activity was assessed by nifedipine oxidation using intestinal epithelial microsomes in rat. Drug efflux by P-gp was tested using digoxin flux with the excised intestine perfusion system in rats. Intraperitoneal injection of LPS (0.3 mg/kg) significantly reduced the intestinal epithelial CYP3A activity by 41% (p < 0.01). In the proximal jejunal segment of the rats treated with LPS, mucosal to serosal flux of digoxin was significantly enhanced compared to that of control (p < 0.05). Efflux of digoxin, which was taken up by intestinal epithelium, to mucosal perfusate was significantly blunted in the jejunum treated with LPS (p < 0.05), which indicates that the LPS treatment reduced the P-gp activity in rat small intestine. These findings suggest that the suppression of CYP3A and P-gp activities may be involved in the mechanism of elevated blood concentrations of cyclosporine and tacrolimus during enteritis-induced diarrhea. To prevent a drug-induced adverse effect, dose of a drug, which is a substrate of CYP3A or P-gp, should be reduced during such an episode.

Quinine distribution in mice withplasmodium berghei malaria

The disposition of a single 80 mg/kg injection of quinine base was compared in control and Plasmodium berghei-infected mice. Pharmacokinetic parameters were determined on repeated whole blood samples from caudal vein (experiment 1) and quinine distribution was evaluated in tissues and blood fractions from mice sacrificed two hours post dosing (experiment 2). Quinine concentrations were assessed by high performance liquid chromatography with fluorometric detection. Whole blood concentrations and AUC(0 - infinity) of quinine increased in a parasitaemia-dependent manner. Quinine blood clearance and peak blood concentrations of metabolites negatively correlated with the parasitaemia. The apparent distribution volume of quinine only decreased in severely ill mice. Quinine concentrations rise in a parasitaemia-dependent manner in homogenates of spleen, lungs and kidney and in erythrocyte pellets. The negative relationship, observed between the parasitaemia and the tissue-to-whole blood ratio for muscle, heart, liver and brain, contributes to the reduction of the blood distribution volume. Quinine uptake by muscle and heart was dependent on the free fraction of plasma quinine. The liver and brain concentrations of quinine were similar in control and infected mice. The tissue-to-plasma free fraction ratios decrease when the parasitaemia rises suggesting a restrictive uptake of quinine by these tissues. In conclusion. P. berghei malaria decreases both total clearance and apparent volume of distribution with a heterogeneous redistribution of quinine between the tissues.

Possible pathomechanism of autoimmune hepatitis

The hepatotropic viruses, measles, and herpesviruses as well as different drugs were repeatedly shown to act presumably as a trigger in patients with autoimmune hepatitis (AI-H). On the other hand, it is known that viral infections stimulate interferon production, which inactivates the cytochrome P-450 enzymes involved in the metabolism of several endogenous substances and exogenous environmental agents. Moreover, it was reported that several cytokines, including interferons, as well as transforming growth factor beta1 and human hepatocyte growth factor, which are abundantly produced and released in the body during infections, also downregulated expression of major cytochrome P-450 and/or other biotransformation enzymes. It seems that all these factors, in addition to individual immune response and the nature and amount of the neoantigen(s) produced, impair the equilibrium of bioactivation and detoxication pathways, thus leading to the development of AI-H in a genetically predisposed person continually exposed to harmful environmental factor(s). Possible increased/decreased density of lysine residues at position D-related human leukocyte antigen locus (DR)beta71 of the antigen-binding groove may affect the eventual steroid-sparing effect of this critical amino acid at the cellular level. In addition, some food additives, such as monosodium glutamate (MSG) and/or aspartame regularly consumed in excessive amounts, may eventually disturb the delicate balance between a positively charged amino acid residue at position DRbeta71 (lysine or arginine) and a negatively charged amino acid residue at position P4 on the antigenic peptide (glutamic acid or aspartic acid). This may favor formation of a salt bridge between these amino acid residues within the hypervariable region 3 on the alpha-helix of the DRbeta polypeptide and facilitate autoantigen presentation and CD4 T-helper cell activation. MSG and aspartate may also depress serum concentrations of growth hormone, which downregulate the activity of several cytochrome P-450 hepatic and other drug-metabolizing enzymes, thus increasing sensitivity to some environmental agents and possibly influencing efficacy of treatment regimens and final outcome of patients with type 1 AI-H.

Important role of prodromal viral infections responsible for inhibition of xenobiotic metabolizing enzymes in the pathomechanism of idiopathic Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis, and hepatotoxicity of the therapeutic doses of acetaminophen used in genetically predisposed persons

Upper respiratory tract febrile illnesses caused by various viruses, mycoplasma, chlamydia infections, and/or inflammatory diseases are usually observed a few days to a few (several) weeks before the onset of Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis (hepatotropic virus infections), or hepatotoxicity associated with therapeutic administration of acetaminophen in persons with varying degrees of deficits of important enzymatic activity. Activation of systemic host defense mechanisms by inflammatory component(s) results in depression of various induced and constitutive isoforms of cytochrome P-450 mixed-function oxidase system superfamily enzymes in the liver and most other tissues of the body. Because several cytochrome P-450 enzymes activities important for biotransformation of many endogenous and egzogenous substances show considerable variability between individuals, in some genetically predisposed persons, even the administration of therapeutic doses of a drug may result in serious clinical mishaps, if an important concomitant risk factor (eg, acute viral infection) is involved. Several inflammatory cytokines, such as interleukins, transforming growth factor beta1, human hepatocyte growth factor, and lymphotoxin, downregulate gene expression of major cytochrome P-450 enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity observed with a given cytokine varying for each P-450 studied, thus eventually leading to metabolite-mediated adverse drug reactions and immunometallic diseases which sometimes result in tissue injury beyond the site(s) where metabolic bioactivation takes place. On the other hand, it must be emphasized that inhibition of metabolism of several drugs, as well as influence on the concentration and/or ratio of various cytokines in inflamed tissues, may exert beneficial effects in patients with different diseases, thus opening new therapeutic possibilities. Clinically relevant interactions may be exemplified by the effects of some fluoroquinolone antibiotics, such as pefloxacin and ciprofloxacin, which probably have a steroid-sparing effect in some patients with frequently relapsing nephrotic syndrome, and an increased bioavailability of several drugs following concomitant intake with freshly pressed grapefruit juice, eventually caused by inhibition of their metabolism, mediated mainly by CYP3A and specifically inhibited by naturally occurring flavonoids.

Regulation of cytochromes P450 during inflammation and infection

Hepatic P450 activities are profoundly affected by various infectious and inflammatory stimuli, and this has clinical and toxicological consequences. Whereas the expression of most P450s in the liver is suppressed, some are induced. Many of the effects observed in vivo can be mimicked by pro-inflammatory cytokines and IFNs, and P450s are differentially regulated by these agents. Therefore, different cytokine profiles and concentrations in the vicinity of the hepatocyte in different models of inflammation may result in qualitatively and quantitatively different effects on populations of P450s. In addition to cytokines, glucocorticoids may have an important role in P450 regulation in stress conditions, including that caused by inflammatory stimuli. Although in many cases the decreases in activity are due primarily to a down-regulation of P450 gene transcription, it is likely that modulation of RNA and protein turnover, as well as enzyme inhibition, contributes to some of the observed effects. The mechanisms whereby these effects are produced may also vary with both the P450 under study and the time course of the effect. The complexity of the P450 response to inflammation and infection means that all of the above factors must be considered when trying to predict the effect of a given infectious or inflammatory condition on the clinical or toxic response of humans or animals to an administered drug or toxin. The question of whether the down-regulation of the hepatic P450 system to inflammation or infection is a homeostatic or pathological response cannot be answered at present. It is difficult to discern the physiological benefit of reducing hepatic P450 activities, unless it is to prevent the generation of reactive oxygen species generated by uncoupled catalytic turnover of the enzymes. On the other hand, as we proposed some years ago [64], the suppression of P450 may be due to the liver's need to utilize its transcriptional machinery and energy for the synthesis of APPs involved in the inflammatory response. In that case, one could ask why the organism has gone to the trouble of employing differential mechanisms for suppression of P450. One answer could be that the response evolved after the divergence of many of the P450 genes, necessitating the evolution of multiple redundant mechanisms for P450 suppression. In contrast to the down-regulation of P450s in the liver, the induction of several forms in this and other tissues suggests a more specific homeostatic role of these effects, e.g., in generation or catabolism of bioactive metabolites.

Differential effect of interleukin-1 alpha on rat hepatic cytochrome P450 monooxygenases

Administration of recombinant human interleukin-1 alpha to adult male rats caused a significant reduction in the levels of hepatic cytochrome P450 and P450 reductase activity at 24 h after the treatment. The mRNAs for cytochrome P450 1A2 and 2E1 were reduced more than 70% at 12 h after administration of interleukin-1 alpha and remained decreased even after 48 h. By contrast, cytochrome P450 2C11 mRNA was reduced only by 30% at 12 h after the treatment and returned to the control levels by 48 h, suggesting that interleukin-1 alpha has a differential effect on the expression of P450 mRNAs. Aniline hydroxylase, benzphetamine N-demethylase and 7-ethoxycoumarin O-deethylase activities were significantly decreased at 24 h after interleukin-1 alpha treatment. The proteins for cytochrome P450 1A2 and 2E1 were reduced by about 50% at 24 h after interleukin-1 alpha treatment.

Suppression of intestinal and hepatic cytochrome P4503A in murine Toxoplasma infection. Effects of N-acetylcysteine and N(G)-monomethyl-L-arginine on the hepatic suppression

1. Cytochrome P4503A (CYP3A) expression was studied in a murine model of infection. Mice were infected with a cystogenic strain of Toxoplasma gondii and microsomes were prepared for liver homogenates and jejunum villus tip enterocytes on day 10 postinfection. Total cytochrome P450 (CYP) and CYP3A were quantitated, and CYP3A activity was determined. 2. In the infected mouse, total CYP and CYP3A contents fell in the liver (-39 and - 49% respectively) and intestine (-43 and - 48 % respectively), as did the rate of metabolism of erythromycin (Ery) and cyclosporine A (CyA), two markers of CYP3A activity (-36 and -26% in the liver, -35 and -58% in the intestine). 3. To determine the mechanism(s) involved in the depression of hepatic CYP3A, infected mice were treated on day 7.5 post-infection with a monoclonal antibody raised against interferon-gamma (anti-IFN-gamma, or from days 7.5 to 10 post-infection with either N(G)-monomethyl-L-arginine (NMMA), an inhibitor of reactive nitrogen intermediates (RNI) production, or N-acetylcysteine (NAC), a reactive oxygen intermediates (ROI) scavenger. 4. Total CYP content was restored in the liver of infected mice treated with anti-IFN-gamma, but with marked interindividual variability. NAC treatment led to a recovery in the liver of total CYP content (+35 %), CYP3A content (total recovery), and the rates of Ery (+59%) and CyA (+87%) metabolism, whereas inconsistent results were obtained with NMMA. These results suggest that NAC, but probably not NMMA, partially protects hepatic CYP3A from Toxoplasma-mediated suppression in mouse.

Modulation of constitutive and inducible hepatic cytochrome(s) P-450 by interferon beta in mice

AIMS/METHODS

Interferon beta is used as a therapeutic agent, but its effects on the hepatic cytochrome P-450-dependent drug metabolizing system have not yet been characterized. We investigated the effect of interferon beta on cytochrome P-450 in mice.

RESULTS

Interferon beta (2 x 10(5) units/mouse) significantly reduced total hepatic cytochrome P-450 (20%) and the activity of NADPH cytochrome C reductase (12%) 24 h after administration; lower doses had no such effect. Various monooxygenase activities were slightly reduced, the one most affected being 7-ethoxycoumarin O-deethylase (29%). In phenobarbital-treated mice, interferon beta reduced the induction of total cytochrome P-450 (22%), the activities of pentoxyresorufin O-dealkylase (38%), benzyloxyresorufin O-dealkylase (30%), erythromycin N-demethylase (30%), 7-ethoxycoumarin O-deethylase (16%) and cytochrome P-450 2B1 (33%) and 3A (45%) proteins. In beta-naphthoflavone-treated mice, interferon beta lowered the induction of total cytochrome P-450 (18%), the activities of ethoxyresorufin O-deethylase (31%) and of 7-ethoxycoumarin O-deethylase (25%) and of cytochrome P-450 1A1 protein (31%).

CONCLUSIONS

Thus it appears that induced cytochrome(s) P-450 were susceptible to interferon beta, this effect not being influenced by the type of inducer. Since various members of the same cytochrome P-450 subfamilies catalyze oxidation of drugs in humans, our findings have potential significance as regards the fate of drugs or exogenous compounds given to patients receiving interferon beta.

The role of cytochrome P450 enzymes in hepatic and extrahepatic human drug toxicity

The human cytochrome P450 enzyme system metabolises a wide array of xenobiotics to pharmacologically inactive metabolites, and occasionally, to toxicologically active metabolites. Impairment of cytochrome P450 activity, which may be either genetic or environmental, may lead to toxicity caused by the parent compound itself. In practise, this usually only applies to drugs that have a narrow therapeutic index and when their clearance is critically dependent upon the fraction normally metabolised by that pathway. P450 enzymes may also convert the drug to a chemically reactive metabolite, which, if not detoxified, may lead to various forms of hepatic and extrahepatic toxicity, including cellular necrosis, hypersensitivity, teratogenicity, and carcinogenicity, depending on the site of formation and the relative stability of the metabolite, and the cellular macromolecule with which it reacts. Variation in the regulation and expression of the drug metabolising enzymes may play a key role in both interindividual variation in sensitivity to drug toxicity and tissue-specific damage. Avoidance of toxicity may be possible in rare instances by prediction of individual susceptibility or by designing new chemical entities that are metabolised by a range of enzymes (both cytochromes P450 and others) and do not undergo bioactivation.

Nitric oxide and intracellular heme

Figure 2 depicts a working hypothesis for these results. Activation of .NO synthesis results in nitrogen oxide-induced loss of protein-bound heme from CYP proteins, which remain relatively intact. This heme liberation results in a decrease in heme synthesis (decreased ALAS) and an increase in heme degradation (increased HO). In addition, .NO synthesis results in direct inhibition of ferrochelatase, which further contributes to inhibition of heme synthesis. There also appears to be a mechanism to repair or resynthesize CYP after .NO synthesis is inhibited. Finally, a result of this effect may be protection against cellular injury, since increased HO is an important response against cellular injury from a variety of insults.

Endotoxin administration to humans inhibits hepatic cytochrome P450-mediated drug metabolism

In experimental animals, injection of gram-negative endotoxin (LPS) decreases hepatic cytochrome P450-mediated drug metabolism. To evaluate this phenomenon in a human model of gram-negative sepsis, LPS was administered on two consecutive days to healthy male volunteers during which time a cocktail of antipyrine (AP-250 mg), hexobarbital (HB-500 mg), and theophylline (TH-150 mg) was ingested and the apparent oral clearance of each drug determined. Each subject had a control drug clearance study with saline injections. In the first experiment, six subjects received the drug cocktail 0.5 h after the first dose of LPS. In the second experiment, another six subjects received the drug cocktail 0.5 h after the second dose of LPS. In both experiments, LPS caused the expected physiologic responses of inflammation including fever with increases in serum concentrations of TNF alpha, IL-1 beta, IL-6, and acute phase reactants. In the first experiment, only minor decreases in clearances of the probe drugs were observed (7-12%). However in the second experiment, marked decreases in the clearances of AP (35, 95% CI 18-48%), HB (27, 95% CI 14-34%), and TH (22, 95% CI 12-32%) were seen. The decreases in AP clearance correlated with initial peak values of TNF alpha (r = 0.82) and IL-6 (r = 0.86). These data show that in humans the inflammatory response to even a very low dose of LPS significantly decreases hepatic cytochrome P450-mediated drug metabolism and this effect evolves over a 24-h period. It is likely that septic patients with much higher exposures to LPS have more profound inhibition of drug metabolism.

Factors involved in the down-regulation of cytochrome P450 during Listeria monocytogenes infection

The activation of host defense mechanisms has been shown to cause a depression in hepatic cytochrome P450-mediated metabolism in rodents and humans. In a previous study, it was demonstrated that the Gram-positive bacteria Listeria monocytogenes causes a down-regulation of hepatic cytochrome P450 and related substrate metabolism as a result of a pretranslational depression of apoprotein synthesis. The objectives of this study were to determine whether the effect of listeria on hepatocyte cytochrome P450 involves hepatic nonparenchymal cells and whether the hemolysin, secreted only by hemolytic forms of the bacteria, plays any part in mediating this effect. Total cytochrome P450 levels as well as ethoxyresorufin-O-dealkylase (EROD) and benzyloxyresorufin-O-dealkylase (BROD) activities were significantly reduced in hepatic microsomes isolated from mice infected in vivo for 48 h with 15U listeria, whereas the same dose of the avirulent non-hemolytic M3D strain had no effect. Listeria (15U) significantly depressed hepatocyte EROD and BROD activities after 24 h incubations with liver cell cultures containing hepatocytes and nonparenchymal cells, as the result of both a direct effect on the hepatocyte and an interaction of listeria with hepatic nonparenchymal cells. The M3D strain of listeria had no effect on cytochrome P-450-mediated metabolism in isolated cells, confirming that hemolysin is an essential component of the mechanism responsible for the down-regulation of cytochrome P450 during listeria infections.

Short report: interferon-alpha decreases 14C-aminopyrine breath test values in patients with chronic hepatitis C

OBJECTIVE

To investigate the effect of interferon-alpha on cytochrome P-450 dependent microsomal function.

METHODS

The 14C-aminopyrine breath test was performed before, during and after a standard dose of interferon-alpha (3,000,000 units three times per week) was administered for at least six months (nine patients with chronic hepatitis C).

RESULTS

Mean aminopyrine breath test values obtained during therapy were significantly lower than either pre- or post-treatment, the degree of reduction varying widely between individuals. Pre- and post-treatment aminopyrine breath test values did not differ significantly.

CONCLUSION

Interferon therapy is associated with a significant and transient inhibition of cytochrome P-450 activity, which should be taken into account when prescribing concurrent therapy with drugs metabolized by this pathway.

Clinical toxicity of the interferons

Since their initial description in 1957, the interferons (IFNs) have been increasingly used to treat a wide array of diseases. Acute adverse effects, i.e. 'flu-like' syndromes, hypo- or hypertension, tachycardia, headache, myalgias and gastrointestinal disorders, occur within the first hour or day after starting treatment. They are seldom treatment-limiting and are easily manageable. Sub-acute and chronic effects develop after several days, usually within 2 and 4 weeks of therapy. The most typical is neurological toxicity, including fatigue/asthenia, and behavioural and cognitive changes. Such symptoms may seriously impair quality of life and result in treatment discontinuation. Seizures have seldom been described. Other infrequent central nervous system adverse effects include vertigo, cramp and oculomotor nerve paralysis. Distal paraesthesias and peripheral neuropathy have been reported. IFN-associated autoimmunity is quite rare but a matter of concern. Biological or clinical manifestations usually require several months to become apparent. Autoantibodies have been shown to develop in most patients but have been inconsistently associated with clinical symptoms of systemic lupus erythematosus, rheumatoid-like arthritis and thyroiditis. Both hypo- and hyperthyroidism have been described but are usually reversible. Other infrequent autoimmune reactions include diabetes, pemphigus and worsening of multiple sclerosis. Although several patients present with a pre-existing autoimmune disorder, no predisposing factor has been clearly established. While hypotension and tachycardia are the most frequent acute cardiovascular complications, a few additional cases of cardiac arrhythmias and myocardial ischaemia have been reported after a short course or several weeks of treatment. These latter complications do not appear to be dose-dependent or age-related. Isolated cases of congestive heart failure have also been described. Mild proteinuria has been observed in 15 to 25% of patients, but acute renal toxicity is uncommon. A transient rise in serum aminotransferase levels is frequently noted during the first stage of therapy, especially in patients receiving the highest dosages. Direct hepatotoxicity is extremely rare. Autoimmune hepatitis, which is ill-diagnosed as chronic viral hepatitis, and de novo induction of autoimmune hepatitis, account for the majority of liver diseases. Haematotoxicity is relatively common but mild to moderate, and develops gradually during the first weeks of treatment. Neutropenia is the most common haematological toxicity, but is usually not dose-limiting and resolves rapidly upon drug discontinuation. Myelosuppression, autoimmune and immune allergic haemolytic anaemias and thrombocytopenias have seldom been described. Cutaneous adverse effects comprised nonspecific erythema and hair loss and, less frequently, vasculitis, local ulcerations at the site of injection and exacerbation of psoriasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of interferon-alpha monotherapy on hepatic drug metabolism in cancer patients

1. The influence of interferon-alpha (IFN alpha) on the clearances of theophylline (TH), antipyrine (AP) and hexobarbitone (HB) was studied in seven cancer patients given IFN alpha as their only treatment. In addition, IFN alpha effects on drug clearance were correlated with changes in serum inflammatory cytokines and acute phase proteins. 2. A 'baseline' study was performed by administering an oral drug 'cocktail' of TH (150 mg), AP (250 mg) and HB (250 mg) with saline injected simultaneously and again 24 h later. One week later, an 'acute' study was performed at the initiation of IFN alpha therapy, 3 x 10(6) units injected with the drug cocktail and again 24 h later. After 2 weeks of IFN alpha treatment three times per week, a 'chronic' study was performed with IFN alpha injected the day prior to, simultaneously with, as well as 24 h after the drug cocktail. 3. Plasma samples were collected over 48 h and the clearances of TH, AP and HB were estimated. Serum samples were collected at various times for the measurement of tumor necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6), C-reactive protein (C-RP) and alpha 1-acid glycoprotein (AGP). 4. IFN alpha caused a 33% decrease in the oral clearance of TH during the chronic study compared with baseline (P < or = 0.05). Although IFN alpha inhibited TH clearance by 16% during the acute study and AP clearance by 20-21% during both acute and chronic studies, these changes did not reach statistical significance. IFN alpha caused minimal changes in HB clearance. There were no chronic effects of IFN alpha on serum cytokines or acute phase proteins. 5. The findings confirm that the most commonly used dose of IFN alpha inhibits the hepatic clearance in humans of some but not all drugs and that this inhibition persists during IFN alpha therapy. Because inhibition was not associated with increases in serum cytokines or acute phase proteins, the mechanism by which IFN alpha inhibits cytochrome P450 activities in vivo does not appear to involve inflammatory mediators such as TNF. IL-1 or IL-6.

Cytokine induction of haem oxygenase mRNA in mouse liver. Interleukin 1 transcriptionally activates the haem oxygenase gene

Accumulation of the mRNA coding for haem oxygenase (HO, EC 1.14.99.3) was stimulated by treating mice with endotoxin (lipopolysaccharide, LPS; 20 micrograms/mouse intraperitoneally), suggesting that haem catabolism is a target of infection and inflammation in vivo. Therefore various cytokines, possible mediators for the biological responses to LPS, were administered intraperitoneally to mice, and the levels of HO mRNA were measured by Northern-blotting analysis using the rat HO cDNA as a probe [Shibahara, Müller, Taguchi and Yoshida (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 7865-7869]. Marked induction of HO mRNA was observed 2 h after administration of interleukin 1 (IL-1) (34-fold) and tumour necrosis factor (19.5-fold) (5 micrograms/mouse), whereas interleukin 6 (6.2 micrograms/mouse) was much less active (3.5-fold) and interleukin 2 (25 micrograms/mouse) and interferon-gamma (3 micrograms/mouse) were ineffective. HO mRNA induced by the cytokines of LPS accumulated rapidly (maximum at 1-2 h after administration), preceding the elevation of HO enzymic activity. Treatment of mice with IL-1 stimulated the transcription of the HO gene by 4-fold, as assessed by in vitro nuclear-run-on assay. These results indicate that enzymic haem catabolism in the liver is a process inducible in vivo by inflammatory cytokines, which up-regulate HO synthesis at the transcriptional level. Increased removal of haem might be part of the protective mechanisms elicited by the acute-phase response, possibly to reduce the pro-oxidant state of the cell.

Effects of interleukin-6 on cytochrome P450-dependent mixed-function oxidases in the rat

Intravenous treatment of male rats with recombinant human interleukin-6 (rhIL6) at 50, 100 and 200 micrograms/kg (corresponding to 4, 8 and 16 x 10(4) U/animal, respectively) reduced the activities of hepatic microsomal cytochrome P450-dependent monoxygenases to varying degrees. Ethylmorphine-N-demethylase activity fell to 53% of control values, an effect similar to that induced by 2.5 mg/kg Escherichia coli lipopolysaccharide (LPS). Ethoxycoumarin-O-deethylase activity was also sensitive to inhibition, whereas IL6 had little effect on the activities of other P450-dependent enzymes, including ethoxyresorufin-O-deethylase. Pentoxyresorufin dealkylase activity, which is representative of the cytochrome P450 IIB 1/2 subfamily, was unaffected by IL6 whereas LPS reduced it to 33.7% of control values. Another hepatocyte-related parameter, serum concentration of alpha 1-acid glycoprotein (AGP), was increased by up to 3.5-fold over baseline by IL6 and 10-fold by LPS. Recombinant human interleukin-1 beta (rhIL1 beta) (10 micrograms/kg, corresponding to 5 x 10(4) U/rat) and recombinant human tumor necrosis factor alpha (rhTNF) (150 micrograms/kg corresponding to 24 x 10(4) U/rat) were both as potent as LPS (2.5 mg/kg) in increasing serum AGP levels and reducing hepatic microsomal monoxygenase activities. IL6 did not potentiate the effects of rhIL1 beta. Hepatic microsomal glucuronyltransferase activities were little affected by LPS and unaffected by rhIL6. Finally, rhIL6 was more potent after i.p. injection than after i.v. or s.c. injection. These results suggest that the effects of LPS, TNF and IL1 on the mixed-function oxidase system in vivo may be due partly to an induction of IL6 in vivo. The different sensitivities of the enzymes to IL6 but not to IL1 or TNF may be due to the involvement of two distinct mechanisms.

O6-alkylguanine DNA alkyltransferase is induced by human recombinant interferon-alpha A/D in mouse liver

Treatment of C57Bl or BALB/C mice with human interferon-alpha A/D (HuIFN-alpha A/D) significantly increased hepatic levels of the DNA repair enzyme O6-alkylguanine DNA alkyltransferase (AT). The maximum induction was seen 24 h after a single dose of 50-100 micrograms/kg IFN-alpha A/D. No induction was observed in rat liver hepatocytes cultured in vitro. Liver AT was also induced by poly(I:C), which is a potent IFN inducer. By increasing AT levels, IFN could protect against the potentially mutagenic alkylation at guanine O6 position caused by some carcinogens. Moreover this finding suggests a link between immune response and the DNA repair system, possibly acting in concert to defend the body from potentially toxic compounds.

Interleukin-1, platelet derived growth factor, free radicals and monocyte aryl hydrocarbon hydroxylase activity in liver disease. Role of cell communication

Monocytes were isolated from blood of human origin and cultured in supplemented Leibovitz (L-15) medium for 24 hr. The medium was then decanted and filtered, and all subsequent tests were done on monocyte conditioned medium (MCM). The monocytes of patients with liver disease spontaneously secrete temperature-sensitive arylhydrocarbon hydroxylase (AHH) inhibitory factors detectable in the MCM. Anti-interleukin-1 antibody (IL-1Ab) reduced the AHH inhibitory activity of the MCM, suggesting that part of the AHH inhibitory activity was due to interleukin-1 (IL-1). Platelet derived growth factor did not affect AHH activity. Interleukin-1 beta was detectable in MCM but did not differ significantly between patients and normal volunteers. A time course experiment indicated that interleukin-1 beta inhibited hepatocyte AHH activity after only 2 hr of incubation. Catalase partially blocked the AHH inhibitory activity of MCM suggesting that activated oxygen intermediates are partially involved in the AHH inhibitory activity of the MCM. Simultaneous incubation of interleukin-1 beta and catalase did not prevent or augment the inhibitory action of IL-1 on AHH activity. IL-1 stimulates collagen synthesis and elevates serum procollagen type 3 peptide (P-III-P). Results indicated that serum P-III-P was elevated in blood sources producing temperature-sensitive AHH inhibitory factor.

Cytochrome P-450-dependent metabolism in alveolar type II epithelial cells: modulation by platelet-activating factor

Platelet-activating factor (PAF), an ether lipid mediator released from activated pulmonary phagocytes, was evaluated for its ability to affect cytochrome P-450-dependent activities in isolated rat alveolar type II cells. The data indicate that at non-toxic doses, PAF caused an increase in beta-naphthoflavone (BNF) inducible/alpha-naphthoflavone (ANF) sensitive ethoxyphenoxazone deethylase (EtOPx'ase) activity. At high concentrations of PAF, inhibition of both EtOPx'ase and metyrapone (MP) sensitive benzyloxyphenoxazone debenzylase (BzOPx'ase) activities and aggregation of type II cells were observed. The PAF analogs, lyso-PAF and enantio-PAF, exhibited actions similar to those observed with PAF. PAF-induced enhancement of EtOPx'ase activity required the presence of intact cells, whereas at high PAF concentrations decreased enzyme activities were observed in both intact cell and sonicated cell preparations. The data thus suggest that xenobiotic metabolism in alveolar type II cells can be modified by an inflammatory mediator, such as PAF, produced by alveolar phagocytes.

Effect of Plasmodium falciparum malaria infection on the plasma concentration of alpha 1-acid glycoprotein and the binding of quinine in Malawian children

1. We have measured plasma concentrations of alpha 1-acid glycoprotein (AGP) in 18 healthy children and 85 children with falciparum malaria in Malawi. In addition, we determined the degree of protein binding of quinine (QN) in the plasma of 52 of the patients and each of the healthy controls. 2. The mean plasma AGP concentration was higher in patients than in controls (P less than 0.0001) and remained elevated 3 weeks after complete resolution of malaria infection. 3. The mean unbound QN fraction was significantly less (P less than 0.00001) in patients with malaria (0.128 +/- 0.037) than in controls (0.193 +/- 0.051) and significantly higher (P = 0.02) in convalescence (0.153 +/- 0.067) than during acute illness. 4. There were highly significant negative correlations between plasma AGP concentration and the free QN fraction in spiked plasma samples (r = -0.534, P less than 0.0001, n = 93) and in clinical samples (r = -0.484, P less than 0.00001, n = 225). There was a significant positive correlation between plasma concentrations of AGP and another acute phase reactant, C reactive protein (P less than 0.001).

Effect of interleukin 6 on phenobarbital induction of cytochrome P-450IIB in cultured rat hepatocytes

Human recombinant interleukin 6 (rhIL-6) caused a dose dependent decrease in the phenobarbital induction of benzyloxyresorufin O-deethylase activity in cultured rat hepatocytes. Decreased enzymatic activity was associated with a decrease in the amount of immunoreactive P-450IIB1/2. rhIL-6 also prevented the PB-induced increase in the steady state level of P-450IIB mRNA. These results suggest that altered P-450 levels observed in vivo during the acute phase reaction may be due to interleukin 6.

Chlorpromazine protection against interleukin-1 and tumor necrosis factor-mediated activities in vivo

Interleukin (IL-1) and tumor necrosis factor (TNF) are thought to play a key role in septic shock and inflammation. We had previously shown that chlorpromazine (CPZ) has a protective effect in various models of endotoxic shock and IL-1 toxicity. We have tested the effect of CPZ on several activities of IL-1 in vivo. CPZ (4 mg/kg) inhibited increases in serum corticosterone, triglycerides and serum amyloid A (SAA). Chlorpromazine also antagonized these same effects when they were induced by endotoxin or TNF, suggesting that this activity could be implicated in the protective effect of CPZ in various models of endotoxic shock and IL-1 lethality.