Weekly dosing with the platelet-derived growth factor receptor tyrosine kinase inhibitor SU9518 significantly inhibits arterial stenosis

The platelet-derived growth factor (PDGF) ligands and their receptors have been implicated as critical regulators of the formation of arterial lesions after tissue injury. SU9518 (3[5-(5-bromo-2-oxo-1,2-dihydroindol-3-ylidenemethyl)-2,4-dimethyl-1H-pyrrol-3-yl]propionic acid) is a novel synthetic indolinone that potently and selectively inhibits the cellular PDGF receptor kinase and PDGF receptor-induced cell proliferation. Inhibition of PDGF receptor phosphorylation in cell-based assays occurs within 5 minutes after drug exposure and persists for >6 hours after drug removal. The pharmacokinetics indicate plasma levels that exceeded the effective concentration required to inhibit the PDGF receptor in cells for up to 8 hours or 7 days after a single oral or subcutaneous administration, respectively. In the rat balloon arterial injury-induced stenosis model, once-daily oral or once-weekly subcutaneous administration of SU9518 reduced intimal thickening of the carotid artery (ratio of neointimal to medial area, 1.94+/-0.38 versus 1.03+/-0.29 [P<0.01] 2.21+/-0.32 versus 1.34+/-0.45 [P<0.01], respectively). These studies provide the rationale to evaluate PDGF receptor tyrosine kinase inhibitors, including inhibitors related to the indolinone, SU9518, for the treatment of arterial restenosis.

Role of calcineurin in angiotensin II-induced cardiac myocyte hypertrophy of rats

OBJECTIVE

The present study investigated the role of calcineurin in angiotensin II(AngII) -induced cardiac myocyte hypertrophy of rats.

METHOD

The primary cardiac myocytes were cultured under the standard conditions. The calcineurin activity in AngII-treated cardiomyocytes was tested by using PNPP; protein synethsis rate was assessed by 3H-leucine incorporation; atrial natriuretic factor(ANF) mRNA level was determined by Northern blot analysis. Cell viability was estimated by lactate dehydrogenase (LDH) levels in cultured medium and by dyed cell numbers.

RESULT

After stimulation of 10, 100 and 1 000 nmol/L of AngIi, calcineurin activities in the cardiomyocytes were increased by 13%, 57% (P < 0.05) and 228% (P < 0.01) respectively, compared with control group. Cyclosporin A(CsA), a specific inhibitor of calcineurin, markedly inhibited the calcineurin activity and decreased the 3H-leucine incorporation in AngII-treated cardiomyocytes in a dose-dependent manner. It was also found that CsA slightly reduced the mRNA level of ANF gene in AngII-stimulated cardiomyocytes.

CONCLUSION

During AngII-induced cardiac myocyte hypertrophy, calcineurin signal pathway is activated, and inhibition of the pathway can attenuate AngII-induced cardiac myocyte hypertrophy, which suggests that the calcineurin signal pathway may play an important role in AngII-induced myocardial hypertrophy of rats.

Primary culture of porcine pancreatic acinar cells

OBJECTIVE

To develop a method for the primary culture of porcine pancreatic acinar cells.

INTERVENTIONS

Dispersed pancreatic acinar cells available utilizing RPMI-1640 medium containing collagenase III. After purification, the isolated acinar cells were cultured in RPMI-1640 medium with the addition of 2.5% fetal bovine serum.

MAIN OUTCOME MEASURES

The morphological characteristics of acinar cells were described. (3)H-thymidine incorporation of acinar cells and the activity of amylase or lipase were determined during the culture process.

RESULTS

There were no remarkable morphological changes in the pancreatic acinar cells during the 20 days culture. The acini showed a tendency to gather but did not attach to the walls of the culture disks. A good (3)H-thymidine incorporation of acinar cells in the primary culture was maintained. The secretion of amylase or lipase from the acini decreased with the length of time of the culture.

DISCUSSION

The primary culture of acinar cells from a porcine pancreas which was carried out in this study maintained the normal morphology of the acinar cells and their ability to grow but not their secretion of amylase or lipase. The method would benefit by the further experiments on acini of porcine pancreas.

Externalization and internalization of cardiac endothelin receptors during different phases of sepsis in rat

OBJECTIVE

To study the redistribution of endothelin-1 (ET-1) receptors in two subcellular organelles, the sarcolemmal membrane and the light vesicle, of rat heart during the progression of sepsis.

METHODS

Sepsis was induced by cecal ligation and puncture (CLP). ET1 receptor was assayed by using [125I]-ET1 binding. Marker enzyme activities, protein yield, and dry-to-wet weight ratio of cardiac membranes were measured.

RESULTS

Septic rat heart exhibited two distinct phases: an initial hyperdynamic phase( 9h after CLP; early stage of sepsis) followed by a hypodynamic (18h after CLP, late stage of sepsis) phase. [125I]-ET1 binding study showed that during early stage of sepsis, the B(max) of ET1 receptors was increased by 30% in sarcolemma but decreased by 19% in light vesicles, while during late stage of sepsis, the B(max) was decreased by 24% in sarcolemma but increased by 38% in light vesicles. The total binding of sarcolemma and light vesicles was increased by 25% during early stage of sepsis but decreased by 17% during late stage of sepsis.

CONCLUSIONS

These data indicated that ET1 receptors in the rat heart were externalized from light vesicles to sarcolemmal membranes during early hyperdynamic phase while internalized from surface membranes to intracellular compartment during late hypodynamic phase of sepsis.

Enzyme kinetics of cytochrome P450-mediated reactions

The most common drug-drug interactions may be understood in terms of alterations of metabolism, associated primarily with changes in the activity of cytochrome P450 (CYP) enzymes. Kinetic parameters such as Km, Vmax, Ki and Ka, which describe metabolism-based drug interactions, are usually determined by appropriate kinetic models and may be used to predict the pharmacokinetic consequences of exposure to one or multiple drugs. According to classic Michaelis-Menten (M-M) kinetics, one binding site models can be employed to simply interpret inhibition (pure competitive, non-competitive and uncompetitive) or activation of the enzyme. However, some cytochromes P450, in particular CYP3A4, exhibit unusual kinetic characteristics. In this instance, the changes in apparent kinetic constants in the presence of inhibitor or activator or second substrate do not obey the rules of M-M kinetics, and the resulting kinetics are not straightforward and hamper mechanistic interpretation of the interaction in question. These unusual kinetics include substrate activation (autoactivation), substrate inhibition, partial inhibition, activation, differential kinetics and others. To address this problem, several kinetic models can be proposed, based upon the assumption that multiple substrate binding sites exist at the active site of a particular P450, and the resulting kinetic constants are, therefore, solved to adequately describe the observed interaction between multiple drugs. The following is an overview of some cytochrome P450-mediated classic and atypical enzyme kinetics, and the associated kinetic models. Applications of these kinetic models can provide some new insights into the mechanism of P450-mediated drug-drug interactions.

Patterns of cortical activity and memory performance in Alzheimer's disease

BACKGROUND

Declarative memory changes are the hallmark of Alzheimer's disease, although their functional neuroanatomy is not restricted to a single structure. Factor analysis provides statistical methods for evaluating patterns of cerebral changes in regional glucose uptake.

METHODS

Thirty-three Alzheimer's patients and 33 age- and gender-matched control subjects were studied with magnetic resonance imaging and positron emission tomography with [(18)F] deoxyglucose. During the tracer-uptake period, subjects performed a serial verbal learning task. Cortical activity was measured in 32 regions of interest, four in each lobe on both hemispheres.

RESULTS

Factor analysis with varimax rotation identified seven factors explaining 80% of the variance ("parietal cortex," "occipital cortex," "right temporo-prefrontal areas," "frontal cortex," "motor strip," "left temporal cortex," and "posterior temporal cortex"). Relative to control subjects, Alzheimer's patients showed significantly reduced values on the factors occipital cortex, right temporo-prefrontal areas, frontal cortex, and left temporal cortex. The factor temporo-prefrontal areas showed large differences between patients with good and poor performance, but little difference when control subjects were similarly divided.

CONCLUSIONS

Findings suggest that Alzheimer's disease is characterized by altered patterns of cortical activity, rather than deficits in a single location, and emphasize the importance of right temporo-prefrontal circuitry for understanding memory deficits.

Factors limiting contrast sensitivity in experimentally amblyopic macaque monkeys

Contrast detection is impaired in amblyopes. To understand the contrast processing deficit in amblyopia, we studied the effects of masking noise on contrast threshold in amblyopic macaque monkeys. Amblyopia developed as a result of either experimentally induced strabismus or anisometropia. We used random spatiotemporal broadband noise of varying contrast power to mask the detection of sinusoidal grating patches. We compared masking in the amblyopic and non-amblyopic eyes. From the masking functions, we calculated equivalent noise contrast (the noise power at which detection threshold was elevated by square root of 2) and signal-to-noise ratio (the ratio of threshold contrast to noise contrast at high noise power). The relation between contrast threshold and masking noise level was similar for amblyopic and non-amblyopic eyes. Although in most cases there was some elevation in equivalent noise for amblyopic compared to fellow eyes, signal-to-noise ratio showed greater variation with the extent of amblyopia. These results support the idea that the contrast detection deficit in amblyopia is a cortical deficit.

Exact solution of a stochastic directed sandpile model

We introduce and analytically solve a directed sandpile model with stochastic toppling rules. The model clearly belongs to a different universality class from its counterpart with deterministic toppling rules, previously solved by Dhar and Ramaswamy. The critical exponents are D(//)=7/4, tau=10/7 in two dimensions and D(//)=3/2, tau=4/3 in one dimension. The upper critical dimension of the model is three, at which the exponents apart from logarithmic corrections reach their mean-field values D(//)=2, tau=3/2.

Th type 1-stimulating activity of lung macrophages inhibits Th2-mediated allergic airway inflammation by an IFN-gamma-dependent mechanism

In the mucosal immune system, resident dendritic cells are specialized for priming Th2-polarized immunity, whereas the Ag-presenting activity of macrophages has been linked with the development of Th1 phenotype. As an immune switch toward Th1 can protect against Th2-mediated allergic response, this study investigated the capacity of lung macrophages to stimulate Th1 responses during the secondary exposure to inhaled allergen, thereby suppressing Th2-mediated allergic airway inflammation in a murine model of allergic asthma. Following airway macrophage depletion in OVA-sensitized mice, lung T cells defaulted to a phenotype that produced less Th1 (IFN-gamma) and more Th2 (IL-4 and IL-5) cytokines, leading to more severe airway hyperreactivity and inflammation after intranasal Ag challenge. After OVA pulsing and adoptive transfer, lung macrophages selectively promoted a Th1 response in Ag-sensitized recipients and did not induce pulmonary eosinophilia. By contrast, OVA pulsing and adoptive transfer of a lung cell preparation, consisting of dendritic cells, B cells, and macrophages, promoted a Th2 response with an associated inflammatory response that was suppressed when macrophages were present and pretreated with IFN-gamma, but exacerbated when macrophages were depleted before IFN-gamma treatment. In addition, Th1-promoting activity of lung macrophages was not related to the autocrine production of IL-12p40. These results suggest that the Th1-promoting APC activity may be an inherent property of the lung macrophage population, and may play an important role, upon stimulation by IFN-gamma, in antagonizing an ongoing Th2 immunity and Th2-dependent allergic responses.

[The effects of DiBaiRen decoction on the proliferation of human keratinocytes and its in vitro anti--oxidation role]

OBJECTIVE

To investigate the effects of DiBaiRen decoction on the proliferation of human keratinocytes and its in vitro anti -- oxidation role.

METHODS

Human keratinocytes were cultured in vitro in the media containing gradient diluted DiBaiRen decoction. The cell proliferation rates at different culture times were recorded. Cellular oxidation injury inflicted by superoxide anion and hydroxyl anion was produced by adding hypoxanthine -- xanthine oxidase and hydrogen peroxide to the culture media. MTT colorimetry was employed to determine cellular activity. The antagonistic effects of DiBaiRen decoction on cellular oxidation injury were analyzed.

RESULTS

In the case that DiBaiRen decoction was added to the culture in concentrations of 30 ml/L to 100 ml/L, there exhibited obvious accelerated proliferation of the keratinocytes, with evident shortening of the cell fusion time. In addition, the oxidation injury of cultured keratinocytes caused by hypoxanthine -- xanthine oxidase and hydrogen peroxide was ameliorated or eliminated by the addition of DiBaiRen decoction, and the effects were dose -- dependent.

CONCLUSION

DiBaiRen decoction might possess anti -- oxidation effects and could promote the in vitro proliferation of cultured human keratinocytes, and it might be beneficial in wound protection and epithelization.

The accumulation effect of lead on DNA damage in mice blood cells of three generations and the protection of selenium

The accumulation effect of lead on DNA damage and the protection of selenium against lead were studied in mice blood cells of three generations. The test animals were divided into four groups: controls, Pb group, Se group, Pb + Se group. Lead and Selenium were administered to mice in the drinking water. The concentrations of lead (in form of lead acetate) and selenium (in form of Kappa-selenocarrageenan) used in this paper were 1 microgram/ml and 0.25 microgram/ml respectively. The percentage of damaged cells (DNA comets) was examined and detected conveniently by the single-cell gel electrophoresis (comet) assay. Results showed that 1 microgram/ml lead did not damage the female mice blood cells of the first generation seriously. However, there was a significant damage effect in both sexes of the second and third generations, suggesting the accumulation effect of lead was very significant starting from the second generation. In addition, under normal physiological conditions, Kappa-Se did not appear to enhance the protective ability on DNA damage significantly, whereas under lead exposure conditions, administration of Kappa-Se displayed the occurrence of a good protection against lead intoxication which was started from the female mice of the second generation.

[Effect of qiongyugao on the action of DDP in inhibiting the division of GLC-82 cell strain in vitro]

OBJECTIVE

To observe the effect of Qiongyugao (QYG) on the action of DDP in inhibiting the division of GLC-82 cell strain in vitro.

METHODS

The method of serum pharmacology was used in observing the morphological change of the cancer cells. By accounting the number of the live cells of each day during 6 days respectively, the growth curve was drawn up. The effects of the three groups on the cancer cells apoptosis of GLC-82 cell strain were analysed by FACS. RESULLTS: The growth of the cancer cells in control group (normal saline) was much better than the other two groups; in chemical therapy group (DDP), the number of the live cells almost kept steady; the number of the live cells in combined group(DDP plus QYG) became even lower. QYG could enhance the action of DDP in inducing the apoptosis of GLC-82 cells strain remarkably.

CONCLUSION

QYG can enhance the effects of chemotherapy in inhibiting cancer cells division and inducing their apoptosis.

Heregulin regulates the actin cytoskeleton and promotes invasive properties in breast cancer cell lines

The metastatic process requires changes in tumor cell adhesion properties, cell motility and remodeling of the extracellular matrix. The erbB2 proto-oncogene is overexpressed in approximately 30% of breast cancers and is a major prognostic parameter when present in invasive disease. A ligand for the erbB2 receptor has not yet been identified but it can be activated by heterodimerization with heregulin (HRG)-stimulated erbB3 and erbB4 receptors. The HRGs are a family of polypeptide growth factors that have been shown to play a role in embryogenesis, tumor formation, growth and differentiation of breast cancer cells. The erbB3 and erbB4 receptors are involved in transregulation of erbB2 signaling. The work presented here suggests biological roles for HRG including regulation of the actin cytoskeleton and induction of motility and invasion in breast cancer cells. HRG-expressing breast cancer cell lines are characterized by low erbB receptor levels and a high invasive and metastatic index, while those which overexpress erbB2 demonstrate minimal invasive potential in vitro and are non-tumorigenic in vivo. Treatment of the highly tumorigenic and metastatic HRG-expressing breast cancer cell line MDA-MB-231 with an HRG-neutralizing antibody significantly inhibited proliferation in culture and motility in the Boyden chamber assay. Addition of exogenous HRG to non-invasive erbB2 overexpressing cells (SKBr-3) at low concentrations induced formation of pseudopodia, enhanced phagocytic activity and increased chemomigration and invasion in the Boyden chamber assay. The specificity of the chemomigration response to HRG is demonstrated by inhibition with the anti-HRG neutralizing antibody. These results suggest that either HRG can act as an autocrine or paracrine ligand to promote the invasive behavior of breast cancer cells in vitro or thus may enhance the metastatic process in vivo.

KAI1 protein is down-regulated during the progression of human breast cancer

The KAI1 gene was identified as a metastasis suppressor gene for human prostate cancer. Recently, we showed that KAI1 mRNA levels were higher in an immortal, normal-like breast epithelial cell line and nonmetastatic breast cancer cell lines but lower substantially in highly metastatic breast cancer cell lines. In this study, we examined KAI1 protein expression in breast cancer cell lines by Western blot and immunohistochemical study. KAI1 protein levels paralleled KAI1 mRNA levels and were inversely correlated with the metastatic potential of breast cancer cells. Furthermore, we examined KAI1 protein expression immunohistochemically in specimens from 81 patients with breast cancer and then correlated the findings with the clinical and histopathological parameters of the patients. High levels of KAI1 protein expression were found in normal breast tissues and noninvasive breast cancer (ductal carcinoma in situ). In contrast, KAI1 expression was reduced in most of the infiltrating breast tumors. We found that, in general, more malignant tumors demonstrated significantly lower KAI1 expression (P = 0.004). Additionally, among 29 specimens demonstrating multiple stages of malignancy within a single specimen, 23 demonstrated significant differences in KAI1 expression between benign breast tissue, ductal carcinoma in situ, and invasive carcinoma. The higher the incidence for malignancy within a given specimen, the lower the KAI1 expression (P < 0.001). These data suggest that in advanced breast cancer, KAI1 expression is down-regulated. Therefore, KAI1 may be a potentially useful indicator of human breast cancer progression.

Involvement of calcineurin in angiotensin II-induced cardiomyocyte hypertrophy and cardiac fibroblast hyperplasia of rats

A rapidly emerging body of literature implicates a pivotal role for the Ca2+-calmodulin-dependent phosphatase, calcineurin, as a cellular target for a variety of Ca2+-dependent signaling pathways culminating in cardiac hypertrophy. The aim of the present study was to test whether calcineurin is involved in the signal transduction of angiotensin II (AngII)-induced cardiac myocyte hypertrophy and fibroblast hyperplasia. Firstly, we observed that calcineurin activity was significantly increased in AngII-stimulated cardiac myocytes as well as fibroblasts, but was markedly inhibited by Losartan (50 micromol/l), H7 (50 micromol/l), and Fura-2/AM (5 micromol/l). It is indicated that AngII-induced activation of calcineurin is through an ATI receptor, may be dependent on the sustained increases of [Ca2+]i, and be regulated by protein kinase C. In a second experiment, we found that cyclosporin (0.1-10micromol/l), a specific inhibitor of calcineurin, decreased the protein synthesis rate in AngII-stimulated cardiomyocytes and the DNA synthesis rate in AngII-treated fibroblasts in a dose-dependent manner. In the latter experiment, calcineurin inhibition reduced the mRNA level of the atrial natriuretic factor gene. These results indicate that calcineurin is involved in the signal transduction of AngII-induced cardiomyocyte hypertrophy and fibroblast hyperplasia.

SU6668 is a potent antiangiogenic and antitumor agent that induces regression of established tumors

Vascular endothelial growth factor, fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) and their cognate receptor tyrosine kinases are strongly implicated in angiogenesis associated with solid tumors. Using rational drug design coupled with traditional screening technologies, we have discovered SU6668, a novel inhibitor of these receptors. Biochemical kinetic studies using isolated Flk-1, FGF receptor 1, and PDGF receptor beta kinases revealed that SU6668 has competitive inhibitory properties with respect to ATP. Cocrystallographic studies of SU6668 in the catalytic domain of FGF receptor 1 substantiated the adenine mimetic properties of its oxindole core. Molecular modeling of SU6668 in the ATP binding pockets of the FIk-1/KDR and PDGF receptor kinases provided insight to explain the relative potency and selectivity of SU6668 for these receptors. In cellular systems, SU6668 inhibited receptor tyrosine phosphorylation and mitogenesis after stimulation of cells by appropriate ligands. Oral or i.p. administration of SU6668 in athymic mice resulted in significant growth inhibition of a diverse panel of human tumor xenografts of glioma, melanoma, lung, colon, ovarian, and epidermoid origin. Furthermore, intravital multifluorescence videomicroscopy of C6 glioma xenografts in the dorsal skinfold chamber model revealed that SU6668 treatment suppressed tumor angiogenesis. Finally, SU6668 treatment induced striking regression of large established human tumor xenografts. Investigations of SU6668 activity in cancer patients are ongoing in Phase I clinical trials.

Binding of retinol induces changes in rat cellular retinol-binding protein II conformation and backbone dynamics

The structure and backbone dynamics of rat holo cellular retinol-binding protein II (holo-CRBP II) in solution has been determined by multidimensional NMR. The final structure ensemble was based on 3980 distance and 30 dihedral angle restraints, and was calculated using metric matrix distance geometry with pairwise Gaussian metrization followed by simulated annealing. The average RMS deviation of the backbone atoms for the final 25 structures relative to their mean coordinates is 0.85(+/-0.09) A. Comparison of the solution structure of holo-CRBP II with apo-CRBP II indicates that the protein undergoes conformational changes not previously observed in crystalline CRBP II, affecting residues 28-35 of the helix-turn-helix, residues 37-38 of the subsequent linker, as well as the beta-hairpin C-D, E-F and G-H loops. The bound retinol is completely buried inside the binding cavity and oriented as in the crystal structure. The order parameters derived from the (15)N T(1), T(2) and steady-state NOE parameters show that the backbone dynamics of holo-CRBP II is restricted throughout the polypeptide. The T(2) derived apparent backbone exchange rate and amide (1)H exchange rate both indicate that the microsecond to second timescale conformational exchange occurring in the portal region of the apo form has been suppressed in the holo form.

Identification of substituted 3-[(4,5,6, 7-tetrahydro-1H-indol-2-yl)methylene]-1,3-dihydroindol-2-ones as growth factor receptor inhibitors for VEGF-R2 (Flk-1/KDR), FGF-R1, and PDGF-Rbeta tyrosine kinases

A series of new 3-substituted indolin-2-ones containing a tetrahydroindole moiety was developed as specific inhibitors of receptor tyrosine kinases associated with VEGF-R, FGF-R, and PDGF-R growth factor receptors. These compounds were evaluated for their inhibitory properties toward VEGF-R2 (Flk-1/KDR), FGF-R1, PDGF-Rbeta, p60(c)()(-)()(Src)(), and EGF-R tyrosine kinases and their ability to inhibit growth factor-dependent cell proliferation. Structure-activity relationships of this new pharmacophore have been determined at the level of kinase inhibition. Compounds containing a propionic acid moiety at the C-3' position of the tetrahydroindole ring represented the most potent indolin-2-ones to inactivate the VEGF, FGF, and PDGF receptor kinases. The inhibitory activities of 9d against VEGF-R2 (Flk-1), 9h against FGF-R1, and 9b against PDGF-Rbeta were 4, 80, and 4 nM, respectively. However, all of these compounds were inactive when tested against the EGF-R tyrosine kinase. Compounds 9a and 9b represented the most potent inhibitors of these classes to inhibit both biochemical kinase and growth factor-dependent cell proliferation for these three targets. In addition, compound 9a was cocrystallized with the catalytic domain of FGF-R1 providing evidence to explain the structure-activity relationship results. This study has provided evidence to support the potential of these new tyrosine kinase inhibitors for the treatment of angiogenesis and other growth factor-related diseases including human cancers.

Simultaneous determination of urinary free cortisol and 6beta-hydroxycortisol by liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry and its application for estimating hepatic CYP3A induction

A reversed-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry (HPLC-APCI-MS-MS) assay was developed to simultaneously determine monkey urinary free cortisol (C) and 6beta-hydroxycortisol (6beta-OHC) in 8 min. Urine sample (0.5 ml) containing fludrocortisone acetate (F-C) as the internal standard was extracted with ethyl acetate for 5 min with an extraction efficiency of 90% and 75% for C and 6beta-OHC, respectively. A Perkin-Elmer Sciex API 3000 triple quadruple instrument was used for mass spectrometric detection and the column eluent was directed to a heated nebulizer probe. The assay was linear over the range 0.25-10 microM for each analyte. The intra- and inter-day relative standard deviation (RSD) over the entire concentration range for both analytes was less than 10%. Accuracy determined at three concentrations (0.8, 2.0 and 8.0 microM) ranged between 95.5 and 108%. The method described herein is suitable for the rapid and efficient measurement of 6beta-OHC/C ratio in Rhesus monkey urine following administration of known hepatic CYP3A inducers and can be used to estimate potential CYP3A induction by drug candidates in the process of early drug development.

Comparison of imidazole- and 2-methyl imidazole-containing farnesyl-protein transferase inhibitors: interaction with and metabolism by rat hepatic cytochrome P450s

Methylation at the 2-position of the imidazole ring of IBN (I), a 1, 5-substituted imidazole-containing compound, was carried out to minimize its inhibition of rat cytochrome P450 (CYP)3A activity. The resulting analog 2-MIBN (II) exhibited an inhibitory potency 70-fold weaker (K(i) = 25 microM) than that of I (K(i) = 0.3 microM) toward CYP3A, the major rat liver microsomal P450 isoform(s) for the metabolism of I and II by rat liver microsomes in the presence of NADPH. The structural modification did not switch the major metabolic pathways for I and II, but significantly decreased the affinity of II to the metabolizing enzyme(s) as reflected by the difference in their K(i) values for CYP3A. Enzyme kinetic studies also demonstrated that I had a lower apparent K(m) (0.3 microM) than than II (18 microM), but an apparent V(max) 14 times lower than II. This finding indicates that methylation at the imidazole ring reduced the affinity of the compound to CYP3A, but increased the catalytic capacity, turning I as a substrate of low K(m) value but low capacity into a compound of high K(m) but high capacity for the metabolism. Our results suggest the significance of substrate concentration in comparing the metabolic stability of compounds with different kinetic parameters. Although higher intrinsic clearance is implied for I when the substrate concentration is below or close to its K(m) value, higher metabolic rate was constantly seen with II over micromolar range. The different kinetic parameters of I and II may also explain the observation that no significant difference in pharmacokinetic behavior was seen after an i.v. administration of I and II to the rat.

[Effect of smoking on the guanylin in the injured lung of rats]

In order to survey the influence of smoking on the level of guanylin in lung tissue in rats, a method of passive smoking was used to set up chronic bronchitis model in rats. The content of guanylin was measured by radioimmunoassay. In the smoking group, remarkable pathological changes in the lung tissue were found. There was no significant difference in the contents of guanylin in the plasma of experimental rats, compared with the control(P < 0.05). But in the lung tissue, the difference was significant(P < 0.01).

Challenge of investigating biologically relevant functions of virulence factors in bacterial pathogens

Recent innovations have increased enormously the opportunities for investigating the molecular basis of bacterial pathogenicity, including the availability of whole-genome sequences, techniques for identifying key virulence genes, and the use of microarrays and proteomics. These methods should provide powerful tools for analysing the patterns of gene expression and function required for investigating host-microbe interactions in vivo. But, the challenge is exacting. Pathogenicity is a complex phenotype and the reductionist approach does not adequately address the eclectic and variable outcomes of host-microbe interactions, including evolutionary dynamics and ecological factors. There are difficulties in distinguishing bacterial 'virulence' factors from the many determinants that are permissive for pathogenicity, for example those promoting general fitness. A further practical problem for some of the major bacterial pathogens is that there are no satisfactory animal models or experimental assays that adequately reflect the infection under investigation. In this review, we give a personal perspective on the challenge of characterizing how bacterial pathogens behave in vivo and discuss some of the methods that might be most relevant for understanding the molecular basis of the diseases for which they are responsible. Despite the powerful genomic, molecular, cellular and structural technologies available to us, we are still struggling to come to grips with the question of 'What is a pathogen?'

Major role of human liver microsomal cytochrome P450 2C9 (CYP2C9) in the oxidative metabolism of celecoxib, a novel cyclooxygenase-II inhibitor

In vitro studies were conducted to identify the cytochromes P450 (CYP) involved in the oxidative metabolism of celecoxib. The hydroxylation of celecoxib conformed to monophasic Michaelis-Menten kinetics (mean +/- S.D., n = 4 livers, K(m) = 3.8 +/- 0.95 microM, V(max) = 0.70 +/- 0.45 nmol/min/mg protein) in the presence of human liver microsomes, although substrate inhibition was significant at higher celecoxib concentrations. The treatment of a panel of human liver microsomal samples (n = 16 subjects) with antibodies against CYP2C9 and CYP3A4 inhibited the formation of hydroxy celecoxib by 72 to 92% and 0 to 27%, respectively. The presence of both antibodies in the incubation suppressed the activity by 90 to 94%. In addition, the formation of hydroxy celecoxib significantly correlated with CYP2C9-selective tolbutamide methyl hydroxylation (r = 0.92, P <. 001) and CYP3A-selective testosterone 6beta-hydroxylation (r = 0.55, P <.02). In contrast, correlation with activities selective for other forms of CYP was weak (r </= 0.46). Chemical inhibition studies showed that ketoconazole (selective for CYP3A4) and sulfaphenazole (selective for CYP2C9) inhibited the formation of hydroxy celecoxib in a concentration-dependent manner, whereas potent inhibitors selective for other forms of CYP did not show any significant effect over a range of 1 to 10 microM. In agreement, cDNA-expressed CYP2C9 catalyzed the formation of hydroxy celecoxib with an apparent K(m) value (microM) and a V(max) value (pmol/min/pmol recombinant CYP) of 5.9 and 21.7, whereas a higher K(m) value (18.2) and a lower V(max) value (1.42) were obtained with rCYP3A4. It is concluded that methyl hydroxylation of celecoxib is primarily catalyzed by human liver microsomal CYP2C9, although CYP3A4 also plays a role.