Cholera toxin induces prostaglandin synthesis via post-transcriptional activation of cyclooxygenase-2 in the rat jejunum. (73/1563)

The mechanisms of diarrhea in Asiatic cholera have been studied extensively. Cyclic AMP, 5-hydroxytryptamine, prostaglandins, and the function of neuronal structures have been implicated in the pathogenesis of cholera. To elucidate the role of the different isoforms (COX-1 and COX-2) of cyclooxygenase in cholera toxin (CT)-induced fluid secretion and intraluminal prostaglandin E(2) (PGE(2)) release in the rat jejunum in vivo, the effects of the COX-2 inhibitors NS-398 ([N-(2-cyclohexaloxy-4-nitrophenyl)methanesulfonamide]) and DFU [5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone], and of the COX-1 inhibitor SC-560, were studied. Net fluid transport was measured gravimetrically and PGE(2) by radioimmunoassay. COX-1 and COX-2 mRNA expression were determined by reverse transcription-polymerase chain reaction (RT-PCR) and COX-2 protein by Western blot analysis in mucosal scrapings. CT caused profuse net fluid secretion in all control rats. The COX-2 inhibitors NS-398 and DFU, but not the COX-1 inhibitor SC-560 or dexamethasone, dose-dependently inhibited CT-induced fluid secretion and PGE(2) release. RT-PCR showed expression of COX-1 and of COX-2 mRNA in control rats. CT did not induce an increase and dexamethasone did not reduce COX-2 mRNA, whereas lipopolysaccharide caused a marked induction of COX-2 mRNA, which was inhibited by dexamethasone. A weak band of COX-2 protein was observed in controls; however, CT enhanced COX-2 levels, which remained unaffected by dexamethasone. It can be assumed that post-transcriptional modulation is responsible for CT-induced increase in COX-2 protein. COX-1 does not seem to be involved. Therefore, PGE(2) produced by COX-2 seems to be responsible for the profuse fluid secretion induced by CT, and COX-2 appears to be a specific target for the treatment of Asiatic cholera.  (+info)

Pharmacokinetics of perlolyrine in rats by stable isotope dilution in conjunction with GC-MS. (74/1563)

AIM: To determine the pharmacokinetics of perlolyrine in rats. METHODS: The plasma concentration and pharmacokinetic parameters of perlolyrine were determined by gas chromatography-mass spectrometry (GC-MS) with selected ion (m/z 247 and m/z 248) and [2-(15) N] perlolyrine (m/z 248) as internal standard. RESULTS: The concentration-time profile of perlolyrine after ig perlolyrine 2 mg.kg-1 fitted a two-compartment open model in rats. The pharmacokinetic parameters were T1/2 alpha = 0.33 h, T1/2 beta = 4.52 h, T1/2 (ka) = 0.14 h, Tmax = 0.35 h, Cmax = 18.84 micrograms/L, K12 = 0.88 h-1, K21 = 0.42 h-1, K10 = 0.32 h-1, V/F = 109.22 L.kg-1, AUC = 112.68 micrograms.h.L-1. CONCLUSION: The method was constant, sensitive, and accurate. It provides a useful method for the determination of pharmacokinetics of perlolyrine which are important for clinical use of perlolyrine.  (+info)

1H NMR spectroscopic investigation of serum and urine in a case of acute tetrahydrofuran poisoning. (75/1563)

This article reports the investigation by 1H nuclear magnetic resonance (1H NMR) spectroscopy of biological fluids in a case of intentional poisoning with tetrahydrofuran (THF). Occupational exposures to this solvent are well documented, but acute poisoning cases are extremely rare, and the one presented here is the second known case of this kind. Urine and serum samples were collected. Without any pretreatment, the presence of THF was confirmed by characteristic resonances at 1.90 and 3.76 ppm; high lactate levels were also observed. The presence of gamma-hydroxybutyric acid (GHB) was noted. Quantitative analysis was performed by relative integration of peak areas. THF concentrations were 813 and 850 mg/L (11.3 and 11.8 mmol/L), and GHB concentrations 239 and 2,977 mg/L (2.3 and 28.6 mmol/L) in serum and urine, respectively. A gas chromatographic-mass spectrometric method confirmed 1H NMR observations. The origin of GHB detected in serum and urine is also discussed.  (+info)

Release of tumor necrosis factor-alpha and prostanoids in whole blood cultures after in vivo exposure to low-dose aspirin. (76/1563)

BACKGROUND: The preventive effect of low-dose aspirin in cardiovascular disease is generally attributed to its antiplatelet action caused by differential inhibition of platelet cyclooxygenase-1. However, there is evidence that aspirin also affects release of inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha). It is not known whether this is caused by direct action on the cytokine pathway or indirectly through cyclooxygenase inhibition and altered prostanoid synthesis, or both. METHODS: We assessed the capacity of lipopolysaccharide-activated leukocytes in whole blood cultures of eight healthy subjects following a single oral dose of 80 mg aspirin to release TNF-alpha, prostanoid E2 (PGE2) and prostanoid I2 (PGI2), and thromboxane A2 (TXA2). TNF-alpha and prostanoids were determined by enzyme-linked immunoassays. RESULTS: In seven subjects, TNF-alpha release in blood cultures decreased 24h after intake of aspirin. The effect of aspirin on prostanoid release was assessed in three individuals: PGE2 increased in all subjects, PGI2 increased in two and remained unchanged in one, and TXA2 was reduced in two and unchanged in one individual The presence of DFU, a specific inhibitor of cyclooxygenase 2, did not affect the reduction of TNF-alpha release by aspirin, but abolished prostanoid production in all three individuals. CONCLUSION: The capacity of activated leukocytes to release TNF-alpha is reduced by ingestion of low-dose aspirin, independent of changes in prostanoid biosynthesis.  (+info)

DNA-binding activity and cytotoxicity of the extended diphenylfuran bisamidines in breast cancer MCF-7 cells. (77/1563)

The DNA binding properties of three novel extended diphenylfuran bisamidines (1-3) possessing different dicationic terminal side chains were studied. The ultrafiltration assay showed that bisamidines 1-3 have significant affinity for DNA. The DNA-binding data for bisamidines 1-3 using homopolymers poly(dA-dT)- poly(dA-dT) and poly(dG-dC)- poly(dG-dC), indicated that these compounds show moderate specificity for AT base pairs. We studied the cytotoxicity effects of bisamidines 1-3, Hoechst 33258 and DAPI (4',6-diamidino-2-phenylindole) in cultured breast cancer MCF-7 cells. The bisamidines 1-3 showed comparable antitumour activity to Hoechst 33258, but were substantially more cytotoxic compared to DAPI. These data show that in broad terms the cytotoxic potency of bisamidines 1-3 in cultured breast cancer MCF-7 cells decreases with the size of the alkyl group substituent (cyclopropyl>isopropyl>cyclopentyl), in accord with their increases in DNA affinity, as shown by the binding constant values.  (+info)

Novel syntheses of murrayaquinone A and furostifoline through 4-oxygenated carbazoles by allene-mediated electrocyclic reactions starting from 2-chloroindole-3-carbaldehyde. (78/1563)

The formal total synthesis of murrayaquinone A (1) and the total synthesis of furostifoline (5) were completed by the construction of 4-oxygenated 3-methylcarbazoles 7 based on a new type of electrocyclic reaction through 2-alkenyl-3-allenylindole intermediates 8 derived from the 2-alkenyl-3-propargylindoles 9, starting from 2-chloroindole-3-carbaldehyde (11). The N,O-bisbenzyloxymethyl group of 16c and 22 underwent a Birch reduction followed by treatment with Triton B to produce the known 4-hydroxy-3-methylcarbazole (7a) and 4-hydroxy-3-methylfuro[3,2-a]carbazole (7b) as precursors of murrayaquinone A (1) and furostifoline (5), respectively. The trifluoromethanesulfonyloxy-3-methylfuro[3,2-alcarbazole (24), prepared from 7b, was subjected to reductive cleavage to provide furostifoline (5).  (+info)

Mycophenolate mofetil combined with a cyclooxygenase-2 inhibitor ameliorates murine lupus nephritis. (79/1563)

BACKGROUND: Approaches to the treatment of lupus nephritis include immunosuppressants associated with anti-inflammatory drugs, mainly steroids, which, however, cause major side effects. Mycophenolate mofetil (MMF) has been described as being less toxic than conventional immunosuppressants, and it was effective in preventing progressive nephritis in lupus mice. Our study evaluated the therapeutic effect of MMF in NZB/W F1 hybrid mice with established disease. We also examined the combination of MMF with a selective cyclooxygenase-2 (COX-2) inhibitor, DFU, based on previous findings of excessive renal production of COX-2-derived thromboxane A2 (TXA2) in lupus nephritis. METHODS: Four groups of NZB/W mice (N = 30 each group), starting at five months of age, were given daily by gavage the following: vehicle, MMF 60 mg/kg, DFU 3 mg/kg, or MMF + DFU. Fifteen mice for each group were used for the survival studies, and the remaining mice were sacrificed at nine months. RESULTS: MMF or DFU alone partially delayed the onset of proteinuria compared with vehicle. Combined therapy was significantly (P < 0.05) more effective than single drugs. Animal survival was partially ameliorated by MMF and significantly improved by the drug combination in comparison with the vehicle (P = 0.005) and DFU alone (P < 0.03). At nine months, serum blood urea nitrogen (BUN) levels were lower in all of the treated groups than in the vehicle group. Renal damage was also limited, but to a greater extent in mice given the combined therapy. In untreated mice, renal COX-2 mRNA expression was up-regulated, and generation of TXB(2), the stable breakdown product of TXA(2), increased. DFU prevented the abnormal renal TXB(2) production, confirming the COX-2 origin of this eicosanoid, whereas renal 6-keto-PGF(1 alpha) and prostaglandin E(2) (PGE(2)) were not affected substantially. CONCLUSIONS: These results offer a strong case for exploring the possibility that in humans MMF combined with COX-2 inhibitors has a role in the treatment options for lupus nephritis. This combined drug therapy may be at least as effective as steroids but without the obvious nephrotoxicity of the latter.  (+info)

Suppression of intestinal polyps in Msh2-deficient and non-Msh2-deficient multiple intestinal neoplasia mice by a specific cyclooxygenase-2 inhibitor and by a dual cyclooxygenase-1/2 inhibitor. (80/1563)

Epidemiological studies suggest that nonsteroidal anti-inflammatory agents decrease the risk of colorectal cancer. This is believed to be mediated, at least in part, by inhibition of cyclooxygenase (COX) activity. There are two COX isoenzymes, namely the constitutively expressed COX-1 and the inducible COX-2. COX-2 is overexpressed in adenomas and colorectal cancers, and COX-2-specific inhibitors have been shown to inhibit intestinal polyps in Apc(Delta716) mice more effectively than dual COX-1/COX-2 inhibitors such as sulindac. Various Apc knockout mice, including the multiple intestinal neoplasia (Min) mouse and the Apc(Delta716) mouse, are limited by their lack of large numbers of colonic adenomas and aberrant crypt foci, the putative precursors of large-bowel polyps and cancers. Our DNA mismatch-repair-deficient Min mouse model (Apc+/-Msh2-/-) has genetic features of both familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, and most importantly, rapidly develops numerous small- and large-bowel adenomas, as well as colonic aberrant crypt foci. The purpose of this study was to determine the effects of COX inhibitors on intestinal adenomas and colonic aberrant crypt foci in this accelerated polyposis, mismatch-repair-deficient Min mouse model, in addition to a standard Min mouse model. Weanling Apc+/-Msh2-/- and Min mice were fed diets containing no drug, sulindac, or a specific COX-2 inhibitor (MF-tricyclic). Apc+/-Msh2-/- and Min mice were sacrificed after 4 weeks and 5 months on diet, respectively. Apc+/-Msh2-/- mice treated with MF-tricyclic had significantly fewer small-bowel polyps (mean +/- SD, 178 +/- 29) compared with mice on sulindac (278 +/- 80), or control diet (341 +/- 43; P < 0.001). There was no difference in numbers of large-bowel polyps or aberrant crypt foci in mice in the three groups. MF-tricyclic was also effective in reducing both small- and large-bowel polyps in Min mice. Western analysis demonstrated COX-2 expression in both large- and small-bowel polyps from mice of both genotypes. This study demonstrates that a specific COX-2 inhibitor is effective in preventing small-bowel polyps in mismatch-repair-deficient Min mice and both small- and large-bowel polyps in standard Min mice. Therefore, specific COX-2 inhibitors may be useful as chemopreventive and therapeutic agents in humans at risk for colorectal neoplasia.  (+info)