Spectral EMG Changes in Cervical Dystonia Patients and the Influence of Botulinum Toxin Treatment.

Botulinum toxin (BoNT) injections in the dystonic muscles is the preferred treatment for Cervical Dystonia (CD), but the proper identification of the dystonic muscles remains a challenge. Previous studies showed decreased 8-14 Hz autospectral power in the electromyography (EMG) of splenius muscles in CD patients. Cumulative distribution functions (CDF's) of dystonic muscles showed increased CDF10 values, representing increased autospectral powers between 3 and 10 Hz, relative to power between 3 and 32 Hz. In this study, we evaluated both methods and investigated the effects of botulinum toxin. Intramuscular EMG recordings were obtained from the splenius, semispinalis, and sternocleidomastoid muscles during standardized isometric tasks in 4 BoNT-naïve CD patients, 12 BoNT-treated patients, and 8 healthy controls. BoNT-treated patients were measured 4-7 weeks after their last BoNT injections and again after 11-15 weeks. We found significantly decreased 8-14 Hz autospectral power in splenius muscles, but not in the semispinalis and sternocleidomastoid muscles of CD patients when compared to healthy controls. CDF10 analysis was superior in demonstrating subtle autospectral changes, and showed increased CDF10 values in all studied muscles of CD patients. These results did not change significantly after BoNT injections. Further studies are needed to investigate the origin of these autospectral changes in dystonia patients, and to assess their potential in muscle selection for BoNT treatment.

Dystonic neck muscles show a shift in relative autospectral power during isometric contractions.

OBJECTIVE: To identify effects of a deviant motor drive in the autospectral power of dystonic muscles during voluntary contraction in cervical dystonia patients. METHODS: Submaximal (20%) isometric head-neck tasks were performed with the head fixed, measuring surface EMG of the sternocleidomastoid, splenius capitis and semispinalis capitis in CD patients and controls. Autospectral power of muscle activity, and head forces was analyzed using cumulative distribution functions (CDF). A downward shift between the theta/low alpha-band (3-10Hz) and the high alpha/beta-band (10-30Hz) was detected using the CDF10, defined as the cumulative power from 3 to 10Hz relative to power from 3 to 30Hz. RESULTS: CDF10 was increased in dystonic muscles compared to controls and patient muscles unaffected by dystonia, due to a 3-10Hz power increase and a 10-30Hz decrease. CDF10 also increased in patient head forces. CONCLUSIONS: Submaximal isometric contractions with the head fixed provided a well-defined test condition minimizing effects of reflexive feedback and tremor. We associate shifts in autospectral power with prokinetic sensorimotor control. SIGNIFICANCE: Analysis of autospectral power in isometric tasks with the head fixed is a promising approach in research and diagnostics of cervical dystonia.

Improved identification of dystonic cervical muscles via abnormal muscle activity during isometric contractions.

BACKGROUND: The preferred treatment for cervical dystonia (CD) is injection of botulinum toxin in the dystonic muscles. Unfortunately, in the absence of reliable diagnostic methods it can be difficult to discriminate dystonic muscles from healthy muscles acting in compensation. We investigated if dystonic muscle activation patterns could be identified in cervical dystonia patients during a harmonized isometric contraction task. Furthermore, we investigated whether dystonia worsens at higher levels of voluntary contraction, which might further improve the identification of dystonic muscle activity. METHODS: An isometric device was used to investigate muscle activation during voluntary contraction tasks in 10 controls and 10 CD patients. Surface electromyography (EMG) of the sternocleidomastoidus, splenius capitis, and semispinalis capitis muscles was evaluated during a rest task and when performing submaximal (20%) and maximal voluntary contractions for eight head transversal force directions and for head twist. Two measures were developed to identify dystonic activation: 1) Muscle activity in the contraction direction in which the contribution of the muscle was lowest (Minimum EMG), and 2) the average muscle activity over all contraction directions (Total Mean EMG). RESULTS: Patients showed increased dystonic activity in the rest task and during submaximal contractions relative to controls, but not during maximal contractions. Increases in Minimum EMG indicated an inability of patients to deactivate dystonic muscles counteracting the task. Increases in Total Mean EMG indicated dystonic activity in all task directions. During maximal contractions these effects were absent in dystonic muscles. Dystonia is therefore found not to worsen at higher levels of isometric voluntary contraction. The activity of dystonic muscles modulated with different loading directions similar to controls. Using Minimum EMG 54% of the muscles clinically diagnosed as dystonic and 91% of non-dystonic muscles were predicted correctly. CONCLUSIONS: Dystonic muscle activity was found in cervical dystonia patients during submaximal contractions in all task directions using a harmonized isometric task, but no differences were found during maximal contractions. With some adaptation this method may prove useful to identify dystonic muscles.

EMG coherence and spectral analysis in cervical dystonia: discriminative tools to identify dystonic muscles?

OBJECTIVE: Botulinum toxin injections in the dystonic muscles are the preferred treatment for cervical dystonia (CD), but proper selection of the dystonic muscles remains a challenge. We investigated the use of EMG coherence and autospectral analysis as discriminative tools to identify dystonic muscles in CD patients. METHODS: We compared the occurrence of 8-14 Hz autospectral peaks and 4-7 Hz intermuscular coherences between 10 CD patients and 10 healthy controls. Secondly, we compared the muscles with significant 4-7 Hz coherences with the muscles that were selected clinically for botulinum toxin treatment. RESULTS: Autospectral peaks between 8 and 14 Hz were significantly more often absent in the splenius capitis (SPL) muscles of CD patients compared to controls (p<0.01). Contrary to previous findings, there was no significant difference in the occurrence of 4-7 Hz intermuscular coherences between patients and controls and the diagnostic accuracy of coherence analysis to identify the clinically dystonic muscles was low. CONCLUSION: Intermuscular EMG coherence analysis cannot reliably discriminate patients from controls. Autospectral changes in the SPL muscles are a more discriminative feature of CD. In patients, coherence analysis does not seem to be a reliable method to identify dystonic muscles. The clinical relevance and the origin of the autospectral changes need further study.

Cervical dystonia: improved treatment response to botulinum toxin after referral to a tertiary centre and the use of polymyography.

RATIONALE: Cervical dystonia is the most common form of (primary) dystonia. The first line of treatment for cervical dystonia is intramuscular injections with botulinum toxin. To optimise the response to botulinum toxin proper muscles selection is required. Pre-treatment polymyographic EMG in addition to clinical evaluation is hypothesised to be a good tool to improve muscle selection and treatment outcome. OBJECTIVE: To determine the efficacy of botulinum toxin treatment after adjacent polymyographic EMG in cervical dystonia patients referred to our tertiary referral centre with an unsatisfactory response to botulinum toxin treatment elsewhere. METHODS: We performed a retrospective analysis of 40 consecutive second opinion cervical dystonia patients. Standard polymyographic EMG was performed before treatment. We retrieved the Tsui scores and subjective evaluations from the first visit, after 12 weeks and after one year of treatment. In addition, we assessed the final outcome of treatment in our centre based on the records and asked the patients for their personal opinion about the effect of referral to our centre on their treatment response. RESULTS: After one year of treatment there was a significant improvement on both the Tsui scores (p < 0.01) and the subjective treatment evaluation (p < 0.001.) On their last visit 60% of the patients still continued treatment with a reasonable to good response. CONCLUSION: A substantial amount of CD patients with an unsatisfactory response to botulinum toxin improved after polymyography and subsequent treatment with botulinum toxin in a tertiary referral centre.

Design and pharmacological characterization of VUF14480, a covalent partial agonist that interacts with cysteine 98(3.36) of the human histamine H4 receptor.

BACKGROUND AND PURPOSE: The recently proposed binding mode of 2-aminopyrimidines to the human (h) histamine H4 receptor suggests that the 2-amino group of these ligands interacts with glutamic acid residue E182(5.46) in the transmembrane (TM) helix 5 of this receptor. Interestingly, substituents at the 2-position of this pyrimidine are also in close proximity to the cysteine residue C98(3.36) in TM3. We hypothesized that an ethenyl group at this position will form a covalent bond with C98(3.36) by functioning as a Michael acceptor. A covalent pyrimidine analogue will not only prove this proposed binding mode, but will also provide a valuable tool for H4 receptor research. EXPERIMENTAL APPROACH: We designed and synthesized VUF14480, and pharmacologically characterized this compound in hH4 receptor radioligand binding, G protein activation and ß-arrestin2 recruitment experiments. The ability of VUF14480 to act as a covalent binder was assessed both chemically and pharmacologically. KEY RESULTS: VUF14480 was shown to be a partial agonist of hH4 receptor-mediated G protein signalling and ß-arrestin2 recruitment. VUF14480 bound covalently to the hH4 receptor with submicromolar affinity. Serine substitution of C98(3.36) prevented this covalent interaction. CONCLUSION AND IMPLICATIONS: VUF14480 is thought to bind covalently to the hH4 receptor-C98(3.36) residue and partially induce hH4 receptor-mediated G protein activation and ß-arrestin2 recruitment. Moreover, these observations confirm our previously proposed binding mode of 2-aminopyrimidines. VUF14480 will be a useful tool to stabilize the receptor into an active confirmation and further investigate the structure of the active hH4 receptor.

Detailed analysis of biased histamine H4 receptor signalling by JNJ 7777120 analogues.

BACKGROUND AND PURPOSE: The histamine H4 receptor, originally thought to signal merely through Gαi proteins, has recently been shown to also recruit and signal via ß-arrestin2. Following the discovery that the reference antagonist indolecarboxamide JNJ 7777120 appears to be a partial agonist in ß-arrestin2 recruitment, we have identified additional biased hH4R ligands that preferentially couple to Gαi or ß-arrestin2 proteins. In this study, we explored ligand and receptor regions that are important for biased hH4R signalling. EXPERIMENTAL APPROACH: We evaluated a series of 48 indolecarboxamides with subtle structural differences for their ability to induce hH4R-mediated Gαi protein signalling or ß-arrestin2 recruitment. Subsequently, a Fingerprints for Ligands and Proteins three-dimensional quantitative structure-activity relationship analysis correlated intrinsic activity values with structural ligand requirements. Moreover, a hH4R homology model was used to identify receptor regions important for biased hH4R signalling. KEY RESULTS: One indolecarboxamide (75) with a nitro substituent on position R7 of the aromatic ring displayed an equal preference for the Gαi and ß-arrestin2 pathway and was classified as unbiased hH4R ligand. The other 47 indolecarboxamides were ß-arrestin2-biased agonists. Intrinsic activities of the unbiased as well as ß-arrestin2-biased indolecarboxamides to induce ß-arrestin2 recruitment could be correlated with different ligand features and hH4R regions. CONCLUSION AND IMPLICATIONS: Small structural modifications resulted in diverse intrinsic activities for unbiased (75) and ß-arrestin2-biased indolecarboxamides. Analysis of ligand and receptor features revealed efficacy hotspots responsible for biased-ß-arrestin2 recruitment. This knowledge is useful for the design of hH4R ligands with biased intrinsic activities and aids our understanding of the mechanism of H4R activation.

Muscle selection for treatment of cervical dystonia with botulinum toxin--a systematic review.

RATIONALE: Cervical dystonia, also called spasmodic torticollis, is the most common form of (primary) dystonia. Intramuscular injections with botulinum toxin are the first line of treatment for cervical dystonia. To optimise the treatment response to botulinum toxin correct muscles should be selected. Clinical evaluation is important for muscle selection but the value of additional tests to identify dystonic muscles remains unclear. OBJECTIVE: To evaluate all relevant literature regarding the best approach to select dystonic muscles for treatment with botulinum toxin. METHODS: We conducted a systematic review of studies that had investigated methods of selecting muscles for treatment with botulinum toxin. In addition, we compared all prospective botulinum toxin trials using either clinical evaluation or polymyographic electromyography for muscle selection. RESULTS: Forty relevant studies were included and polymyographic electromyography recordings were most often employed. In several studies, polymyographic electromyography revealed a different pattern of muscle involvement compared to that found during clinical evaluation. In one randomized controlled trial polymyographic electromyography significantly improved the outcome of botulinum toxin treatment. A limited number of studies used positron emission tomography -computed tomography imaging or frequency analysis of the electromyography signal to identify dystonic muscles but their effect on the outcome of treatment has never been studied. CONCLUSION: Polymyographic electromyography may improve the outcome of botulinum toxin treatment in cervical dystonia, but evidence is limited and larger studies are needed.

High-resolution metabolic profiling towards G protein-coupled receptors: rapid and comprehensive screening of histamine H4 receptor ligands.

In the past years we developed high-resolution screening platforms involving separation of bioactive mixtures and on-line or at-line bioassays for a wide variety of biological targets with parallel mass spectrometric detection and identification. In the current research, we make a major step forward in the development of at-line bioassays by implementation of radioligand receptor binding and functional cellular assays to evaluate bioactvity and selectivity. We demonstrate a new platform for high-resolution metabolic profiling of lead compounds for functional activity and selectivity toward the human histamine H(4) receptor (hH(4)R), a member of the large family of membrane-bound G protein-coupled receptors. In this platform analytical chemistry, cell biology and pharmacology are merged. The methodology is based on chromatographic separation of metabolic mixtures by HPLC coupled to high-resolution fractionation onto (multiple) microtiter well plates for complementary assaying. The methodology was used for efficient and rapid metabolic profiling of the drug clozapine and three selective hH(4)R lead compounds. With this new platform metabolites with undesired alterations in target selectivity profiles can be readily identified. Moreover, the parallel identification of metabolite structures, with accurate-mass measurements and MS/MS, allowed identification of liable metabolic 'hotspots' for further lead optimization and plays a central role in the workflow and in this study. The methodology can be easily adapted for use with other receptor screening formats. The efficient combination of pharmacological assays with analytical techniques by leveraging high-resolution at-line fractionation as a linking technology will allow implementation of comprehensive metabolic profiling in an early phase of the drug discovery process.

Genistein induces breast cancer-associated aromatase and stimulates estrogen-dependent tumor cell growth in in vitro breast cancer model.

In breast cancer, the interaction between estrogen-producing breast adipose fibroblasts (BAFs) and estrogen-dependent epithelial tumor cells is pivotal. Local estrogen production is catalyzed by aromatase, which is differentially regulated in disease-free and tumorigenic breast tissue. The use of aromatase inhibitors to block local estrogen production has proven effective in treatment of estrogen-dependent breast cancer. However, a major problem during breast cancer treatment is the sudden onset of menopause and many women seek for alternative medicines, such as the soy isoflavone genistein. In this study, we show that genistein can induce estrogen-dependent MCF-7 tumor cell growth and increase breast cancer-associated aromatase expression and activity in vitro. We have previously developed an in vitro breast cancer model where the positive feedback loop between primary BAFs and estrogen-dependent MCF-7 tumor cells is operational, thereby representing a more natural in vitro model for breast cancer. In this model, genistein could negate the growth inhibitory action of the aromatase inhibitor fadrozole at physiologically relevant concentrations. These data suggest that soy-based supplements might affect the efficacy of breast cancer treatment with aromatase inhibitors. Considering the high number of breast cancer patients using soy supplements to treat menopausal symptoms, the increasing risk for adverse interactions with breast cancer treatment is of major concern and should be considered with care.

Clearance and clearance inhibition of the HIV-1 protease inhibitors ritonavir and saquinavir in sandwich-cultured rat hepatocytes and rat microsomes.

The metabolism and active transport of ritonavir and saquinavir were studied using sandwich-cultured rat hepatoyctes and rat liver microsomes. For ritonavir four comparable metabolites were observed in the sandwich-culture and in microsomes. For saquinavir eight metabolites were observed in sandwich-culture and 14 different metabolites in microsomes. Ketoconazole did not affect the metabolism of ritonavir in sandwich-culture or microsomes and slightly inhibited the metabolism of saquinavir in sandwich-culture. This inhibition resulted in a different metabolite profile for saquinavir in microsomes. Ritonavir had a pronounced inhibiting effect on the metabolism of saquinavir and affected the hydroxylation of 6beta-testosterone negatively. In the active transport studies, cyclosporin A and PSC833 enhanced the metabolism of ritonavir, suggesting that ritonavir is normally excreted into the bile canaliculi. Verapamil, showed no effect on the metabolism of ritonavir. The intrinsic clearance was estimated at 1.65 and 67.5 microl/min/1 x 10(6) cells and the hepatic metabolism clearance at 0.017 and 6.83ml/min/SRW for ritonavir and saquinavir respectively. In conclusion, for saquinavir the metabolism rate and the amount of metabolites produced was higher than for ritonavir. Ritonavir had a strong inhibitory effect on the metabolism of saquinavir and seemed to be excreted into the bile.

Aromatase inhibition by synthetic lactones and flavonoids in human placental microsomes and breast fibroblasts--a comparative study.

Interference of exogenous chemicals with the aromatase enzyme can be useful as a tool to identify chemicals that could act either chemopreventive for hormone-dependent cancer or adverse endocrine disruptive. Aromatase is the key enzyme in the biosynthesis of steroids, as it converts androgens to estrogens. Certain flavonoids, plant derived chemicals, are known catalytic aromatase inhibitors. Various systems are in use to test aromatase inhibitory properties of compounds. Commonly used are microsomes derived from ovary or placental tissue characterized by high aromatase activity. To a lesser extent whole cell systems are used and specifically cell systems that are potential target tissue in breast cancer development. In this study aromatase inhibitory properties of fadrozole, 8-prenylnaringenin and a synthetic lactone (TM-7) were determined in human placental microsomes and in human primary breast fibroblasts. In addition, apigenin, chrysin, naringenin and two synthetic lactones (TM-8 and TM-9) were tested in human microsomes only. Comparison of the aromatase inhibitory potencies of these compounds between the two test systems showed that the measurement of aromatase inhibition in human placental microsomes is a good predictor of aromatase inhibition in human breast fibroblasts.

Interactions of polybrominated diphenyl ethers with the aryl hydrocarbon receptor pathway.

Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants that have been in use as additives in various consumer products. Structural similarities of PBDEs with other polyhalogenated aromatic hydrocarbons that show affinity for the aryl hydrocarbon receptor (AhR), such as some polychlorinated biphenyls, raised concerns about their possible dioxin-like properties. We studied the ability of environmentally relevant PBDEs (BDE-47, -99, -100, -153, -154, and -183) and the "planar" congener BDE-77 to bind and/or activate the AhR in stably transfected rodent hepatoma cell lines with an AhR-responsive enhanced green fluorescent protein (AhR-EGFP) reporter gene (H1G1.1c3 mouse and H4G1.1c2 rat hepatoma). 7-Ethoxyresorufin-O-deethylation (EROD) was used as a marker for CYP1A1 activity. Dose- and bromination-specific inhibition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced responses was measured by their ability to inhibit the induction of AhR-EGFP expression and EROD activity. Individual exposure to these PBDEs did not result in any increase in induction of AhR-EGFP or CYP1A1 activity. The lower brominated PBDEs showed the strongest inhibitory effect on TCDD-induced activities in both cell lines. While the highest brominated PBDE tested, BDE-183, inhibited EROD activity, it did not affect the induction of AhR-EGFP expression. Similar findings were observed after exposing stably transfected human hepatoma (xenobiotic response element [XRE]-HepG2) cells to these PBDEs, resulting in a small but statically significant agonistic effect on XRE-driven luciferase activity. Co-exposure with TCDD resulted again in antagonistic effects, confirming that the inhibitory effect of these PBDEs on TCDD-induced responses was not only due to direct interaction at receptor level but also at DNA-binding level. This antagonism was confirmed for BDE-99 in HepG2 cells transiently transfected with a Gal4-AhR construct and the corresponding Gal4-Luc reporter gene. In addition, a chromatin immunoprecipitation assay further confirmed that BDE-99 could bind to the AhR and activate the AhR nuclear translocation and dioxin responsive element (DRE) binding in the context of the CYP1A1 promoter. However, the transactivation function of the BDE-99-activated AhR seems to be very weak. These combined results suggest that PBDEs do bind but not activate the AhR-AhR nuclear translocator protein-XRE complex.

Metabolism-mediated Ochratoxin A genotoxicity in the single-cell gel electrophoresis (Comet) assay.

The mycotoxin Ochratoxin A (OTA) is a contaminant of food and feed commodities in many countries. Long-term exposure to OTA in humans has been associated with an increased incidence of a progressive nephropathy (BEN). Bio-activation of OTA has been implicated in the OTA-mediated toxicity, although inconsistent results have been reported. The aim of the present study was to investigate the genotoxic potency of OTA and its metabolites in NIH/3T3 cells stably expressing the human cytochrome P450 iso-enzymes CYP2C9 and CYP3A4, by using the single-cell gel electrophoresis (SCGE/Comet) assay, which detects single strand DNA breaks. The obtained results confirm the hypothesis that biotransformation processes mediate OTA toxicity, and differences in response were observed in CYP2C9-hOR and CYP3A4-hOR expressing cells, respectively. Results showed that biotransformation of OTA increased the genotoxicity. Measurement of reactive oxygen species (ROS) production showed that the OTA-induced ROS production corresponded to the OTA-induced genotoxicity in the used NIH/3T3 cell lines.

Endotoxin-induced liver damage in rats is minimized by beta 2-adrenoceptor stimulation.

OBJECTIVE AND DESIGN: To investigate the effects of beta(2)-adrenoceptor (beta(2)-AR) stimulation on endotoxin-induced liver damage and systemic cytokine levels in rats. SUBJECTS: Standard male Wistar rats. TREATMENT: A disease-model of lipopolysaccharide (LPS)-induced acute systemic inflammation was used. The beta(2)-selective AR agonist clenbuterol was administered before, during, and after LPS-challenge to investigate its effects on the acute inflammatory response and associated liver-failure. METHODS: The following parameters have been measured in plasma: TNF alpha, IL-1 beta, IL-6, IL-10, AST, ALT, and Bilirubin. Liver histological examination was performed to look for changes in tissue morphology. RESULTS: Administration of clenbuterol (p.o.) one hour before, or intravenous at the same time as LPS-challenge resulted in a marked reduction of plasma levels of TNF alpha, IL-1 beta, and IL-6. A change both in plasma-level and in time-concentration profile of the anti-inflammatory cytokine IL-10 was found. Clenbuterol minimized LPS-induced liver damage, as represented by significantly lowered concentrations of several parameters for liver-failure (AST, ALT, Bilirubin), and improved hepatic tissue morphology. Clenbuterol administration after LPS challenge failed to inhibit TNF alpha-release but reduced liver-damage. Simultaneous use of the beta(2)-AR antagonist propranolol augmented LPS-induced liver failure, suggesting a role of endogenous adrenoceptor-agonists in prevention of organ-failure during systemic inflammation. CONCLUSIONS: The results indicate that a selective beta(2)-AR agonist might be used as an additional therapeutic agent in the clinic for the treatment of (acute) systemic inflammatory disorders in order to reduce or prevent subsequent liver failure.

The role of oxidative stress in the ochratoxin A-mediated toxicity in proximal tubular cells.

Balkan endemic nephropathy (BEN), a disease characterized by progressive renal fibrosis in human patients, has been associated with exposure to ochratoxin A (OTA). This mycotoxin is a frequent contaminant of human and animal food products, and is toxic to all animal species tested. OTA predominantly affects the kidney and is known to accumulate in the proximal tubule (PT). The induction of oxidative stress is implicated in the toxicity of this mycotoxin. In the present study, primary rat PT cells and LLC-PK(1) cells, which express characteristics of the PT, were used to investigate the OTA-mediated oxidative stress response. OTA exposure of these cells resulted in a concentration-dependent elevation of reactive oxygen species (ROS) levels, depletion of cellular glutathione (GSH) levels and an increase in the formation of 8-oxoguanine. The OTA-induced ROS response was significantly reduced following treatment with alpha-tocopherol (TOCO). However, this chain-braking anti-oxidant did not reduce the cytotoxicity of OTA and was unable to prevent the depletion of total GSH levels in OTA-exposed cells. In contrast, pre-incubation of the cell with N-acetyl-L-cysteine (NAC) completely prevented the OTA-induced increase in ROS levels as well as the formation of 8-oxoguanine and completely protected against the cytotoxicity of OTA. In addition, NAC treatment also limited the GSH depletion in OTA-exposed PT- and LLC-PK(1) cells. From these data, we conclude that oxidative stress contributes to the tubular toxicity of OTA. Subsequently, cellular GSH levels play a pivotal role in limiting the short-term toxicity of this mycotoxin in renal tubular cells.

Differential effects of pentoxifylline on the hepatic inflammatory response in porcine liver cell cultures. Increase in inducible nitric oxide synthase expression.

Pentoxifylline (PTX) has been shown to exert hepatoprotective effects in various liver injury models. However, little information is available about the effect of PTX on the hepatic acute phase response. In the present study, the effect of PTX on a lipopolysaccharide (LPS)-induced acute phase response in primary porcine liver cell cultures was examined. During 72 hr of incubation with or without LPS, the ability of PTX to influence the secretion of tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), acute phase proteins, and nitric oxide (NO) was assessed. PTX completely inhibited LPS-induced TNF-alpha production and attenuated IL-6 only after 48 hr of incubation. In contrast, PTX potentiated NO production and the expression of inducible nitric oxide synthase (iNOS) in hepatocytes after stimulation with LPS. The increased expression of iNOS and concurrent production of NO was also observed when liver cell cultures were incubated with dibutyryl cyclic adenosine monophosphate. No effect of PTX on acute phase protein secretion was observed during 72 hr of incubation. The present results show that PTX differentially affects the endotoxin-induced inflammatory response in primary porcine liver cell cultures by suppressing TNF-alpha and IL-6 while potentiating NO production.

Characterization of cytochrome P450 isoenzymes in primary cultures of pig hepatocytes.

Despite the fact that pigs are increasingly used in pharmacological and toxicological studies, knowledge on the enzymes which metabolize xenobiotics, in particular cytochrome P450 (CYP) enzymes, in pigs is still very limited. Primary cultures of pig hepatocytes were used to characterize CYP enzymes. The characterization was performed at the level of enzymatic activities, apoprotein and mRNA analyses. Enzyme inducers investigated were beta-naphthoflavone (BNF), phenobarbital (PB), dexamethasone (DEX) and rifampicin (RIF). After 48hr of BNF treatment, CYP1A protein and mRNA levels were increased, and ethoxyresorufin O-deethylation and caffeine 3-demethylation were strongly induced. PB and RIF increased the levels of CYP3A apoprotein and mRNA, whereas BNF down-regulated CYP3A and related activities. PB and RIF treatment resulted in increased ethylmorphine N-demethylation and testosterone hydroxylation, which appears to be the result of CYP3A induction. Hybridization of pig RNA with a human CYP2C9 cDNA probe showed a PB and RIF inducible CYP, which was down-regulated by BNF. Similar inducing effects were observed for tolbutamide, a marker substrate for CYP2C. DEX was not a potent inducer, although some induction of CYP3A mRNA was observed. The present results indicate the absence of CYP2B and probably CYP2D enzymes and activities in pig liver. Despite some dissimilarities, the results indicate that pigs, apart from their very human-like physiology, might represent a more appropriate model species for oxidative drug metabolism in humans than rats.

A lipopolysaccharide-induced acute phase response in the pig is associated with a decrease in hepatic cytochrome P450-mediated drug metabolism.

Drug disposition, including hepatic drug metabolism, is markedly affected by infection, inflammation and other conditions that invoke the acute phase response. In the present study, an Escherichia coli lipopolysaccharide (LPS)-induced acute phase response model was developed in pigs. This model was used to study the effects of the acute phase response on drug disposition and hepatic drug metabolism in vivo and in microsomal preparations. The results obtained were compared with those from Actinobacillus pleuropneumoniae-infected pigs. Intermittent intravenous administration of LPS induced a mild acute phase response as evidenced by increased rectal body temperatures, anorexia and increased cytokine (TNF-alpha and IL-6) serum levels within 1-2 h after the first LPS injection. The acute phase response is associated with a pronounced decrease of antipyrine plasma clearance (control 8.5 +/- 0.8 vs. LPS 2.2 +/- 0.7 mL/min.kg). Furthermore, total cytochrome P450 content and microsomal cytochrome P450-dependent activities were significantly decreased after 24 h. The decrease in cytochrome P450 activities was accompanied by losses of cytochrome P4501A and P4503A apoproteins. The microsomal glucuronidation rate of 1-naphthol was not affected in LPS-treated pigs. Comparing the LPS model with our previous findings in the Actinobacillus pleuropneumoniae model showed a remarkable similarity with regard to the effects on hepatic drug metabolism.

Cytochrome P-450 complex formation in rat liver by the antibiotic tiamulin.

Tiamulin is a semisynthetic diterpene antibiotic frequently used in farm animals. The drug has been shown to produce clinically important--often lethal--interactions with other compounds. It has been suggested that this is caused by a selective inhibition of oxidative drug metabolism via the formation of a cytochrome P-450 metabolic intermediate complex. In the present study, rats were treated orally for 6 days with tiamulin at two different doses: 40 and 226 mg/kg of body weight. For comparison, another group received 300 mg of triacetyloleandomycin (TAO) per kg, which is equivalent to the 226-mg/kg tiamulin group. Subsequently, microsomal P-450 contents, P-450 enzyme activities, metabolic intermediate complex spectra, and P-450 apoprotein concentrations were assessed. In addition, effects on individual microsomal P-450 activities were studied in control microsomes at different tiamulin and substrate concentrations. In the rats treated with tiamulin, a dose-dependent complex formation as evidenced by its absorption spectrum and an increase in cytochrome P-4503A1/2 contents as assessed by Western blotting (immunoblotting) were found. The effects were comparable to those of TAO. Tiamulin induced microsomal P-450 content, testosterone 6 beta-hydroxylation rate, erythromycin N-demethylation rate, and the ethoxyresorufin O-deethylation activity. Other activities were not affected or decreased. When tiamulin was added to microsomes of control rats, the testosterone 6 beta-hydroxylation rate and the erythromycin N-demethylation were strongly inhibited. It is concluded that tiamulin is a potent and selective inducer-inhibitor of cytochrome P-450. Though not belonging to the macrolides, the compound produces an effect on P-450 similar to those of TAO and related compounds.