The role of lymphocytes, macrophages and interferon in the depression of drug metabolism by dextran sulfate

Interactions between immune and biotransformation systems in fish: a review

In animals biotransformation and immune system are not totally independent, there are numerous functional interrelationships between these two systems. They are both implicated in the capacity of organisms to resist to a wide variety of environmental components such as viruses, bacteria and xenobiotics. It is known for a long time that the immune system functions as a physiologic system and interacts with all the other components of the organism including nervous or endocrine ones. In the same manner, the biotransformation system (especially the cytochrome P450 monooxygenases) is involved in the regulation of numerous hormone productions. In this way, many studies in mammals have revealed the possible interaction between immune and biotransformation systems. Among these interactions, the capacity of the activation of host defense mechanisms to down-regulate microsomal cytochrome P450 and the role of biotransformation system in the xenobiotic-mediated immunotoxicity have been underlined. Advances in the basic knowledge of fish immune and biotransformation systems should lead to a better understanding of the possible interactions between both systems and should improve fish health monitoring which is a crucial ecotoxicological goal.

Possible implication of macrophages in the regulation of cytochrome P450 activities in carp (Cyprinus carpio)

Macrophages play a key role in the regulation of cytochrome P450 activity induced by immunostimulants in mammals. We investigated the effects of immunostimulants (LPS, dextran sulfate and tilorone) on biotransformation and macrophage activities in carp. The major effect of LPS was its capacity to inhibit 3-MC-induced cytochrome P450 activities in the liver and head kidney. Basal phase I activities were reduced by tilorone and dextran sulfate in immune organs. Tilorone and dextran sulfate differently modulated total cytochrome P450 contents and P4501A activities suggesting differential sensitivity for P450 classes. In immune organs, tilorone and dextran sulfate inhibited basal EROD activity. Tilorone inhibited 3-MC-induced EROD activity whereas dextran sulfate enhanced this activity. LPS and dextran sulfate increased ROS production by macrophages and all the immunostimulants induced macrophage activating factor (MAF) production. This study demonstrates for the first time in fish the capacity of CYP-regulated immunostimulants to activate macrophages and provides initial insight into the capacity of macrophages to regulate CYP activity induced by immunostimulants in fish.

Modulation of drug-metabolizing systems by bacterial endotoxin in carp liver and immune organs

This report describes a study of the effects of bacterial endotoxin [lipopolysaccharide (LPS)] on cytochrome P450 levels and ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities in liver and two main immune organs of carp: spleen and head kidney. Also studied was the paucity of the carp drug-metabolizing system in an environment subject to pollution by a polycyclic aromatic hydrocarbon, 3-methylcholanthrene (3MC), when fish respond to an immune activation by lipopolysaccharide (LPS). In the presence of bacterial endotoxin the basal cytochrome P450 levels were decreased in liver and spleen. EROD activity was increased in liver and basal GST activity was increased in spleen. When fish were treated concomitantly with 3MC and LPS, a suppression of cytochrome P450 induction in liver and head kidney was observed. EROD activity induced by 3MC was not modified by administration of LPS. GST activity was suppressed by treatment with LPS and inducing agent in liver and head kidney. In the present study it was found that endotoxin can have profound and differential effects on fish basal biotransformation of drugs in the liver and immune organs. Also, the induction of biotransformation enzymes by 3MC was modified when fish responded to an immune stimulation.

The role of nitric oxide in hepatic metabolism

Nitric oxide (NO) may regulate hepatic metabolism directly by causing alterations in hepatocellular (hepatocyte and Kupffer cell) metabolism and function or indirectly as a result of its vasodilator properties. Its release from the endothelium can be elicited by numerous autacoids such as histamine, vasoactive intestinal peptide, adenosine, ATP, 5-HT, substance P, bradykinin, and calcitonin gene-related peptide. In addition, NO may be released from the hepatic vascular endothelium, platelets, nerve endings, mast cells, and Kupffer cells as a response to various stimuli such as endotoxemia, ischemia-reperfusion injury, and circulatory shock. It is synthesized by nitric oxide synthase (NOS), which has three distinguishable isoforms: NOS-1 (ncNOS), a constitutive isoform originally isolated from neuronal sources; NOS-2 (iNOS), an inducible isoform that may generate large quantities of NO and may be induced in a variety of cell types throughout the body by the action of inflammatory stimuli such as tumor necrosis factor and interleukin (IL)-1 and -6; and NOS-3 (ecNOS), a constitutive isoform originally located in endothelial cells. Another basis for differentiation between the constitutive and inducible enzymes is the requirement for calcium binding to calmodulin in the former. NO is vulnerable to a plethora of biologic reactions, the most important being those involving higher nitrogen oxides (NO2-), nitrosothiol, and nitrosyl iron-cysteine complexes, the products of which (for example, peroxynitrite), are believed to be highly cytotoxic. The ability of NO to react with iron complexes renders the cytochrome P450 series of microsomal enzymes natural targets for inhibition by NO. It is believed that this mechanism provides negative feedback control of NO synthesis. In addition, NO may regulate prostaglandin synthesis because the cyclooxygenases are other hem-containing enzymes. It may also be possible that NO-induced release of IL-1 inhibits cytochrome P450 production, which ultimately renders the liver less resistant to trauma. It is believed that Kupffer cells are the main source of NO during endotoxemic shock and that selective inhibition of this stimulation may have future beneficial therapeutic implications. NO release in small quantities may be beneficial because it has been shown to decrease tumor cell growth and levels of prostaglandin E2 and F2 alpha (proinflammatory products) and to increase protein synthesis and DNA-repair enzymes in isolated hepatocytes. NO may possess both cytoprotective and cytotoxic properties depending on the amount and the isoform of NOS by which it is produced. The mechanisms by which these properties are regulated are important in the maintenance of whole body homeostasis and remain to be elucidated.

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.

Depression of cytochrome P-450 in mouse liver induced by fractions from Nocardia opaca

We measured the liver cytochrome P-450 content of mice 24 h after they had been injected with the following immunoadjuvants: Nocardia opaca derivatives and peptidoglycans from several bacterial strains. The cell wall fraction was not active, the others diminished liver cytochrome P-450 levels. The dose-response activity varied with the bacterial origin of the peptidoglycans. These findings indicate that the toxicity and efficiency of immunochemotherapeutic protocols can be modified by altering drug metabolism.

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.

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.

Fibroproliferation in liver disease: role of monocyte factors

Fibroproliferation was measured as the uptake of [3H]thymidine into fibroblasts. Human fibroblasts were incubated with 200 microliters monocyte-conditioned medium, the 0.22 microns filtrate from cultured monocytes, in Dulbecco's modified Eagle medium supplemented with controlled process serum replacement 2, a fetal calf serum substitute with low mitogenic activity. Increasing the numbers of fibroblasts resulted in a parallel increase in thymidine uptake to a maximal level. Fibroblasts (2 x 10(3] were plated into microwell plates and incubated with monocyte-conditioned medium for 72 hr. At 16 hr before harvest, 1 muCi [3H]thymidine was added. Cells were harvested with phosphate-buffered saline and washed, and the filters were counted. Fibroblasts incubated with Dulbecco's modified Eagle medium and controlled process serum replacement 2 showed minimal thymidine uptake. Fibroblasts incubated with Dulbecco's modified Eagle medium plus monocyte-conditioned medium from monocytes stimulated with 10 micrograms/ml lipopolysaccharides showed a sixfold increase in thymidine uptake over fibroblasts in Dulbecco's modified Eagle medium and controlled process serum replacement 2 alone. Fibroblasts incubated with Dulbecco's modified Eagle medium plus monocyte-conditioned medium from monocytes of patients with liver disease (n = 20) showed a 10-fold elevation in thymidine uptake compared with Dulbecco's modified Eagle medium and controlled process serum replacement 2. Results indicated that preincubation of monocyte-conditioned medium with either anti-interleukin-1 beta (12.5 half-maximal units, 4 degrees C, 16 hr) or catalase (1,870 IU, 25 degrees C, 1 hr) did not alter the fibroproliferative activity of the monocyte-conditioned medium, suggesting that neither interleukin-1 beta nor activated oxygen intermediates were involved in fibroproliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

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 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.

Effect of Mycobacterium butyricum on the hepatic cytochrome P-450 system of the mouse: influence of anti-inflammatory drug

1. M. butyricum administration to rats induces arthritis and impairment in hepatic cytochrome P-450 activity. 2. This work was performed to verify if M. butyricum administrated to mice produces similar effects on cytochrome P-450 hepatic without involvement of articular lesions. 3. We also studied the role of arachidonate metabolites in the genesis and perpetuation of hepatic injury. 4. Intraperitoneal M. butyricum administration to mice increased sleeping time induced by pentobarbital and decreased both aminopyrine N-demethylase (AND) and aniline p-hydroxylase (APH) activities without producing articular inflammation. 5. Only preventative oral administration of indomethacin or dexamethasone during the week before M. butyricum injection avoided drug-metabolizing system alterations. 6. Our results suggest a possible link between arachidonate metabolites inhibited by indomethacin or dexamethasone and the genesis of cytochrome P-450 disfunction.

Protein A induced abrogation of cyclophosphamide toxicity is associated with concomitant potentiation of immune function of host

This report confirms our previous observation that protein A (PA) of Staphylococcus aureus Cowan I reduces the cyclophosphamide (Cy) induced toxicity. PA treated animals recover quickly from the toxic effects of Cy. We have exhaustively studied the role of specific and nonspecific immunity in the protection of the animals. It was observed that PA helped the animals in the accelerated regeneration of leukocytes of blood (p less than 0.001) and different lymphoid organs like thymus (p less than 0.001), spleen (p less than 0.01) and bone marrow (p less than 0.01). Increased number and function of macrophages was also observed in PA (p less than 0.001) and PA+Cy (p less than 0.001) groups. PA, on one hand enhanced the cell mediated immunity while suppressed the humoral immunity as was assessed by increase in delayed type hypersensitivity response (p less than 0.001) and decreased in plaque forming cells (p less than 0.001), EAC-rosettes (p less than 0.001), hemagglutination (p less than 0.001) and hemolysin titre (p less than 0.05). On the basis of above observations we propose that the immunomodulatory activity of PA helped the animals to remain alive in two ways- (1) by early generation of the cells depleted by the Cy thus helping animals to repair the damaged immune system and fast clearance of the toxic metabolites of Cy (2) by temporarily suppressing the cells responsible for humoral immunity which are more susceptible to Cy metabolites.

In vivo effects of immunostimulating lipopeptides on mouse liver microsomal cytochromes P-450 and on paracetamol-induced toxicity

Immunomodulating lipopeptides lauroyl-L-Ala-gamma-D-Glu-LL-A2pmNH2-Gly (RP 44.102) and lauroyl-L-Ala-gamma-D-Glu-LL-A2pmNH2 (RP 56.142) were found to protect mice against the hepatotoxicity of paracetamol, which is due to cytochrome P-450 dependent formation of toxic metabolites and radicals. In fact they decreased the amount of hepatic microsomal cytochrome P-450, and the level of CCl4-induced lipid peroxidation. In contrast lauroyl-L-Ala-gamma-D-Glu-DD-A2pmNH2 (RP 53.204), which only differs by the configuration of the two chiral carbons of A2pm (diaminopimelic acid) and is not an immunomodulating agent, failed to protect against poisoning by paracetamol and had no effect on the level of hepatic cytochrome P-450 or the microsomal CCl4-induced lipid peroxidation. This provides a clear connection between the immunostimulating properties of a compound and its effects on xenobiotic biotransformations.

Drug-metabolizing enzymes in rat, mouse, pig and human macrophages and the effect of phagocytic activation

Aryl hydrocarbon hydroxylase (AHH) activity mediated by cytochrome P-450 is present in pig hepatic microsomes [10 nmol.3 mg protein-1.hr-1]. AHH activity was detectable in both hepatocytes and Kupffer cells isolated from pig liver biopsy material. These cells were isolated from needle or wedge biopsy material by collagenase perfusion and incubation with collagenase at 37 degrees. The two cell types were separated from the resulting cell suspension as previously described for whole liver. Kupffer cells were enriched by adherence and were cultured for 24 hr prior to harvesting. Cells were harvested, and cell viability was determined. AHH activity was assayed in Kupffer cell and hepatocyte homogenates. Kupffer cell AHH activity was approximately one-eighth the level detected in hepatocytes. To determine whether this enzyme was present in other macrophages, monocytes were isolated from 10 ml of heparinized peripheral blood using Ficoll-Hypaque and were enriched by adherence. After 24 hr in culture, cell viability was assessed and monocytes were identified by by cytochemical staining. AHH activity was detectable in pig monocyte homogenates, and the AHH level was similar to that in pig Kupffer cells. AHH was also easily detectable in human monocytes. This macrophage AHH activity was compared with AHH activity in rat monocytes, mouse Kupffer cells and mouse peritoneal macrophages. Monocyte AHH was relatively stable in cell culture but decreased rapidly upon storage at -70 degrees. Macrophage AHH activity was depressed following phagocytic activation in vitro by latex beads with a concomitant increase in heme oxygenase activity.

Depression of peripheral blood monocyte aryl hydrocarbon hydroxylase activity in patients with liver disease: possible involvement of macrophage factors

Aryl hydrocarbon hydroxylase activity was detectable in cultured macrophage monolayers of peripheral blood monocyte origin. Peripheral blood monocytes were isolated from patients with biopsy-confirmed liver disease and healthy volunteers. Macrophage monolayers were prepared and incubated at 37 degrees C. After 24 hr, the aryl hydrocarbon hydroxylase activity and cellular protein concentration were assayed on cell homogenates. The monocyte aryl hydrocarbon hydroxylase activity in cultured macrophages from normal volunteers was 1.23 +/- 0.16 (n = 19). The aryl hydrocarbon hydroxylase activity in macrophage cultures from patients with biopsy-confirmed liver disease was 0.48 +/- 0.05 (n = 20). This represents a significant (61%) decrease in monocyte aryl hydrocarbon hydroxylase compared to controls. The 20 patients have established cirrhosis or early stage liver disease. The established cirrhosis group includes alpha 1-antitrypsin deficiency-associated cirrhosis; primary biliary cirrhosis; alcoholic (Laennec's) cirrhosis; cryptogenic cirrhosis, and hemochromatosis. Early stage liver disease is attributed to methotrexate (Stage III), early stage primary biliary cirrhosis and alpha 1-antitrypsin deficiency. Our results indicate that the depression in monocyte aryl hydrocarbon hydroxylase activity is greater in patients with established cirrhosis than early stage liver disease. Our results further suggest that cultured monocytes from patients with liver disease spontaneously release soluble factors into the culture medium. Incubation of this medium, containing macrophage factors, with isolated hepatocytes significantly depress hepatocyte aryl hydrocarbon hydroxylase activity compared to medium obtained from cultures of monocytes from normal volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)