Flavonoids are a class of dietary phytochemicals that modulate various biological activities. The effects of flavone and five hydroxylated derivatives on the methoxyresorufin O-demethylase activity ...catalyzed by cDNA-expressed human cytochromes P450 (CYP)1A1 and 1A2 were examined. Flavone was a less potent inhibitor of CYP1A1 (IC50 = 0.14 microM) than CYP1A2 (IC50 = 0.066 microM). Four hydroxylated flavone derivatives (3-hydroxy-, 5-hydroxy-, 7-hydroxy-, and 3,7-dihydroxyflavone) were also potent inhibitors of CYP1A1 (IC50 < 0.1 microM) and CYP1A2 (IC50 < 0.3 microM). For CYP1A1, 7-hydroxyflavone exhibited a competitive mode of inhibition, with a Ki value of 0.015 microM and 6-fold selectivity for CYP1A1 over CYP1A2. 3,5,7-Trihydroxyflavone (galangin) showed the highest potency toward CYP1A2. The inhibition by galangin of the methoxyresorufin O-demethylase activity of CYP1A2 was mixed-type, with a Ki value of 0.008 microM. Galangin showed 5-fold selectivity in its inhibition of CYP1A2 over CYP1A1. The results indicate that some flavonoids have high potencies and selectivities for inhibition of CYP1A isozymes. This may have important implications for cancer prevention, as well as other pharmacological and toxicological effects of these compounds.
BACKGROUND: Asthma death rates are rising, with the greatest rise and highest death rates in old age. A reduced cardiovascular response in the elderly may lead to the underestimation by physicians of ...the severity of acute asthma attacks. This would be compounded if elderly patients had reduced awareness of bronchoconstriction. METHODS: Methacholine provoked bronchoconstriction was compared in 34 elderly (17 asthmatic, 17 normal; age 60-83, mean 68 years) and 33 young subjects (16 asthmatic, 17 normal; 20-46, mean 30 years). None were smokers. All underwent inhaled methacholine challenge by the Newcastle dosimeter method, monitored by maximal expiratory flow-volume loops (MEFVL). The endpoints were a 35% fall in forced expiratory flow at 50% vital capacity or cumulative inhalation of 6.4 mg methacholine. The one second forced expiratory volume (FEV1) was derived from MEFVL. After challenge and before bronchodilatation subjects graded awareness of respiratory discomfort from 1 (no symptoms) to 4 (pronounced symptoms needing immediate treatment). RESULTS: Despite a greater fall in FEV1 in elderly asthmatic patients (mean (SE) 27.4% (2.2%)) than in young asthmatic patients (21.5% (1.7%)) elderly patients were less aware of bronchoconstriction (awareness score 2.00 (SE 0.15) than young patients (3.06 (0.11)). Similar differences in awareness score were seen between elderly normal subjects (1.53 (0.17)) and young normal subjects (2.76 (0.22)), despite no difference in degree of bronchoconstriction. CONCLUSIONS: Reduced awareness of moderate acute bronchoconstriction in old age may delay self referral in acute asthma and contribute to higher asthma mortality in the elderly.
Lymphocytes of normal elderly subjects and young asthmatics display dysfunctional β-adrenoceptors. If β-adrenoceptor dysfunction were found in senescent airways, it might help explain the ...pathogenesis of late onset asthma.
The bronchodilatory effects of albuterol after methacholine-provoked bronchoconstriction were compared in 17 healthy young (age 20 to 36 years) and 17 healthy elderly (age 60 to 76 years) volunteer subjects. Albuterol was inhaled via dosimeter (initially 7.8 μg, doubling every 7.5 min) with forced expiratory flow at 50% vital capacity (FEF50) measured prior to each dose. Albuterol sensitivity was expressed as the cumulative logarithm of the area under the FEF50 recovery curve (AUC); a greater AUC meant lower sensitivity. On another study day, spontaneous recovery from methacholine was assessed similarly.
There was no intergroup difference in spontaneous recovery. Despite lower methacholine doses provoking similar (35%) FEF50 falls in elderly subjects, albuterol AUC was greater in elderly subjects (6,552%·min·μg) than young subjects (3,922%·min μg; p=0.03). Multiple regression showed that AUC and age were related (p=0.02).
Airway β2-adrenoceptor responsiveness is diminished in old age, suggesting that airway βadrenoceptor dysfunction may be implicated in late-onset asthma. (CHEST 1995; 108:401-06)
The CD40 molecule, a member of the TNF receptor gene family, has been intensively studied with respect to regulation of B cell proliferation and survival. Although CD40 is also expressed on carcinoma ...cell lines, information concerning the biological function of CD40 on cells of epithelial origin is limited. In this study we detected constitutive CD40 on human breast carcinoma cell lines and an increase in CD40 expression following treatment with cytokines IL-1alpha and IFN-gamma. CD40 ligation was also found to increase MHC II expression in cells pretreated with IFN-gamma. In contrast to normal B cells, where CD40 signaling provides a potent survival signal, we observed that CD40 ligation in breast carcinoma cells results in growth inhibition and enhanced susceptibility to Fas-mediated apoptosis. Enhanced apoptosis appears to be attributable, at least in part, to an up-regulation of Fas expression caused by CD40 ligation. These results suggest a potentially important role for CD40 in breast tumor biology.
Management of drug therapy in the elderly Montamat, S C; Cusack, B J; Vestal, R E
The New England journal of medicine,
08/1989, Letnik:
321, Številka:
5
Journal Article
Oncostatin M (OSM), an IL-6 subtamily cytokine, inhibits proliteration and causes morphological changes in many tumor cell lines. GM-CSF, phorbol-12-myristate-13-acetate (PMA), and lipopolysaccharide ...(LPS) induce OSM expression. To investigate the mechanisms governing OSM promoter activity, we have cloned and partially sequenced an 8.5 kb fragment of human genomic DNA immediately 5′ of the OSM coding region and mapped the transcription start site. Transient transfection assays with a series of 5′ deletion plasmids demonstrated maximal reporter activity in U937 cells with a minimum 304 bp construct. The 5′-proximal region of the human OSM gene contains a C/EBP consensus element around −45 bp and several GC-rich regions around −60, each of which is responsible for basal promoter activity. Electrophoretic mobility shift assay coupled with supershift analysis confirmed the presence of a cis-acting binding site for activated STAT5 complexes following GM-CSF treatment. Furthermore, transient transfection studies demonstrated a loss of GM-CSF responsiveness in reporter constructs containing mutations within this STAT element. Our results establish that C/EBP and an as yet unidentified GC-rich binding transcription factor are responsible for basal OSM promoter activity, while GM-CSF-stimulated OSM expression is driven by activated STAT5 complexes binding to a cis-acting STAT element on the OSM promoter.
In this paper we describe a sterol-independent regulation of low density, lipoprotein receptor (LDLR) transcription by the cytokine oncostatin M (OM) in HepG2 cells. We show that OM-induced ...expression is independent of cholesterol regulation and occurs at the transcriptional level. To elucidate regulatory mechanism(s), we constructed a luciferase reporter system comprising either the native LDLR promoter including repeats 1, 2, and 3, or a synthetic promoter vector containing repeats 2+3 only, allowing us to directly examine OM effects on individual elements. Specific mutants in repeats 1, 2, and 3 were made to facilitate the mapping of the OM effect on the promoter. Wildtype and mutant constructs were assayed for cholesterol and OM regulation. The results show that mutation within the core SRE-1 element of repeat 2 totally abolished cholesterol regulation but had no effect on OM inducibility. More interesting, a mutation within repeat 1 reduced basal transcription activity to 10% of the native promoter, but OM induction was unaltered. However, the identical mutation engineered in repeat 3 significantly decreased OM induction of LDLR promoter activity. These results suggest a novel regulatory role for the repeat 3 element in LDLR transcription.
Modulation of the human polymorphonuclear leukocyte (PMN) respiratory burst by selective cyclic 3',5' adenosine monophosphate (cAMP) phosphodiesterase (PDE) inhibitors was studied with respect to PDE ...isozyme characteristics. Zaprinast, an inhibitor of a cyclic guanosine monophosphate (cGMP)-specific PDE (PDE I), at concentrations up to 100 mumol/L, had no significant effect on the respiratory burst. Milrinone and imazodan, inhibitors of cAMP-metabolizing, cGMP-sensitive PDE (PDE III), reduced the respiratory burst to 60% of control magnitude but only had significant effects when they were introduced at high (100 mumol/L) concentrations. In contrast, rolipram and RO 20-1724, inhibitors of a cAMP-metabolizing, cGMP-insensitive PDE (PDE IV), had significant effects at low concentrations (0.1 mumol/L) and caused marked reduction of the respiratory burst at higher concentrations (25% of control at 10 mumol/L). The selective PDE IV inhibitors significantly potentiated PMN inhibition by isoproterenol. Diethylaminoethyl (DEAE)-Sepharose chromatography demonstrated a predominant PDE isozyme with high affinity and selectivity for cAMP that was insensitive to cGMP and was completely inhibited by rolipram, a PDE IV inhibitor. These results are consistent with the conclusion that the PMN respiratory burst is inhibited by an elevation of cAMP induced by PDE IV inhibition.
Oncostatin M (OM) inhibits proliferation of H3922, a human breast cancer cell line derived from a ductal infiltrating carcinoma. We have found that treatment of H3922 cells with OM for 72 h lowers ...the steady-state level of c-myc mRNA to 16% of that seen in control cells. Our present study showed that down-regulation of c-myc mRNA levels was both dose and time dependent. Results from nuclear run-off analysis and mRNA stability studies established that a major component of the observed OM-induced down-regulation of c-myc mRNA occurs at the transcriptional level. OM treatment of H3922 cells reduced the abundance of actively transcribed c-myc mRNAs to approximately 25% of that observed in control cells. These data were supported by our finding that OM did not significantly affect the half-life of c-myc mRNA in actinomycin-treated H3922 cells. Taken together, these data demonstrate that the suppressive effect of OM on c-myc gene expression in H3922 cells occurs at the transcriptional level.
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