Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RNA Aggregation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed2001

Cloricromene, a semi-synthetic coumarin derivative, inhibits tumor necrosis factor-alpha production at a pre-transcriptional level.

Cloricromene decreases myocardial infarct size after ischemic-reperfusion injury in vivo, and it has been suggested that this is due to inhibition of tumor necrosis factor-alpha (TNF-alpha). The purpose of this work was to characterize the mechanism of cloricromene-induced inhibition of TNF-alpha in rat macrophages. Cloricromene inhibited lipopolysaccharide-induced TNF-alpha release in a dose-dependent manner (IC(50)=5.9 +/- 0.8 microM). This was not due to cytotoxicity, as cloricromene was well tolerated up to 500 microM. Cloricromene inhibited lipopolysaccharide-induced expression of TNF-alpha mRNA, which suggests a pre-transcriptional effect. We then investigated the early signal transduction pathway triggered by lipopolysaccharide. The binding of lipopolysaccharide to its receptor CD14 activates protein kinase C and nuclear factor-kappaB (NF-kappaB). Cloricromene inhibited NF-kappaB activation in a dose-dependent manner, but affected protein kinase C translocation only slightly. We then established that cloricromene inhibited lipopolysaccharide-induced cellular oxidative activity, which is important for NF-kappaB activation. Our results show that cloricromene interferes with the early signal transduction pathway triggered by lipopolysaccharide.

Animals↗
PubMed1997

Influence of highly purified eicosapentaenoic acid ethyl ester on insulin resistance in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous non-insulin-dependent diabetes mellitus.

We investigated the effect of long-term administration of highly purified eicosapentaenoic acid ethyl ester (EPA-E), an n-3 polyunsaturated fatty acid derived from fish oil, in comparison to the effects of lard, olive oil, safflower oil, or distilled water as the control on the development of insulin resistance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of spontaneous non-insulin-dependent diabetes mellitus (NIDDM) with obesity. After 17 or 18 weeks of treatment, the glucose infusion rate (GIR) in the euglycemic insulin-glucose clamp test only showed a significant increase in EPA-E-treated rats compared with control rats given distilled water alone as the vehicle. The GIR in EPA-E-treated animals was approximately three times greater than in the controls. This is the first report to display the influence of various fatty acids on the development of insulin resistance in OLETF rats. We demonstrated that EPA-E prevents the onset of insulin resistance, whereas olive oil and safflower oil have no effect and lard exacerbates insulin resistance. Fatty acid analysis of phospholipids in skeletal muscle showed a significant increase of the C18:2, C20:5, and C22:5 components in EPA-E-treated rats and, conversely, a significant decrease in C20:4. In addition, EPA-E-treated rats showed a significant increase in GLUT4 mRNA in skeletal muscle when compared with control rats. Our results indicate that the beneficial effect of EPA-E on insulin resistance in OLETF rats is likely to be dependent on modification of the phospholipid components of the skeletal muscle membrane. These findings suggest that dietary fatty acids may play a key role in the development of insulin resistance in patients with NIDDM.

Animals↗
PubMed2001

The effect of jararhagin, a metalloproteinase from Bothrops jararaca venom, on pro-inflammatory cytokines released by murine peritoneal adherent cells.

The release of pro-inflammatory cytokines (IL-1beta, IL-6 and TNF-alpha) from murine peritoneal adherent cells (MPAC) was studied after exposure to jararhagin, a metalloproteinase/disintegrin isolated from Bothrops jararaca venom. MPACs were treated with LPS (lipopolysaccharide), jararhagin, or EDTA-inactivated jararhagin for up to 24h. Following incubation, the culture supernatant was assayed by ELISA for the presence of cytokines, while the cells were analysed for viability and cytokine mRNA expression. The cells exposed to native jararhagin released TNF-alpha and IL-1beta after 4 and 24h respectively. When MPACs were exposed to Jararhagin treated with EDTA, TNF-alpha and IL-1beta production was sustained throughout the culture period and IL-6 production was observed. TNF-alpha, IL-6 and IL-1beta mRNA were detected 4h after stimulation with either native or EDTA-treated jararhagin. Addition of jararhagin to LPS stimulated cells resulted in a dramatic decrease in the release of IL-6 and TNF-alpha. RT-PCR showed that this inhibition does not occur at the transcriptional level and further experiments showed that jararhagin degraded soluble cytokines by proteolytic activity. This study suggests that jararhagin induces TNF-alpha, IL-1beta and IL-6 expression, which may be rapidly degraded by its proteolytic activity.

Animals↗
PubMed1999

Effect of trilinolein on the activity and gene expression of superoxide dismutase in cultured rat brain astrocytes.

Cerebrovascular disease is one of the major causes of morbidity and mortality in recent. Oxygen free radicals produced during cerebral infarction increases the damage to neurons. Superoxide dismutase (SOD) is the endogenous antioxidant enzyme that can effectively scavenge superoxide radicals. Trilinolein is a lipophilic antioxidant purified from the herb of Panax pseudoginseng. In the cultured rat brain astrocytes (RBA), the activity of SOD (both Cu,Zn-SOD and Mn-SOD subtypes) was markedly increased by incubation with trilinolein at low concentration (0.1 microM) for 2 days. This stimulatory effect of trilinolein was not related to the incubating concentration. However, long-term (7 days) incubation with trilinolein at same concentration decreased the activity. Similar changes were also observed in the gene expression of SOD in RBA; short-term (2 days) incubation of RBA by 0.1 microM trilinolein increased the mRNA level that was lowered in RBA received a long-term incubation with 0.1 microM trilinolein. This result shows that trilinolein is an effective antioxidant to increase the activity of SOD in RBA which would be beneficial to neurons subjected to oxygen free radical damage. However, long-term medication of antioxidant shall be concerned.

Animals↗
PubMed2002

Rosmarinic acid, a major polyphenolic component of Perilla frutescens, reduces lipopolysaccharide (LPS)-induced liver injury in D-galactosamine (D-GalN)-sensitized mice.

The protective activity of rosmarinic acid from Perilla frutescens on liver injury induced by LPS in D-GalN-sensitized mice was examined. We also investigated the effects of antitumor necrosis factor-alpha antibody (anti-TNF), superoxide dismutase (SOD), and aminoguanidine (AG) on this model in order to elucidate the mechanism of rosmarinic acid protection. Perilla extract (PE) and rosmarinic acid (RA) treatments significantly reduced the elevation of plasma asparatate aminotransferase levels, as well as anti-TNF and SOD treatment, compared with controls, but this reduction was not seen in the AG group. These results were confirmed by histological examination using hematoxylin-eosin and in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Increases in tumor necrosis factor-alpha (TNF-alpha) mRNA expression in liver and in plasma TNF-alpha levels, which were observed in control mice, were not significantly reduced by PE or RA. PE and RA treatments also did not significantly diminish iNOS mRNA expression or plasma nitrate/nitrite levels. Nitrotyrosine and N(epsilon)-(hexanonyl)lysine (HEL) production, the residue of oxidative stress, was observed in livers from controls, but not in those mice pretreated with PE or RA. These results suggest that the liver protection of RA is due to the scavenging or reducing activities-superoxide or peroxynitirite rather than to inhibition of TNF-alpha production.

Alanine Transaminase↗
PubMed2003

Naftidrofuryl-driven regulation of endothelial ICAM-1 involves nitric oxide.

Naftidrofuryl is a selective inhibitor of the 5-HT2 receptor expressed on human endothelial cells. This drug has been used over the years to cope with cerebral or peripheral ischemic accidents; however, no clear mechanism of action of this molecule has been highlighted to explain its vascular effects. In the present work, we demonstrate that the involvement of nitric oxide can account for the effects of naftidrofuryl. Indeed, naftidrofuryl potently inhibited the TNF-alpha-triggered increase of intercellular adhesion molecule-1 (ICAM-1) expression as well as stress fiber formation in human umbilical vein endothelial cells (HUVEC). Moreover, naftidrofuryl induced the expression of type II nitric oxide synthase (NOS II) messenger and protein, leading to a noticeable increase in nitric oxide synthesis. Furthermore, using the specific NOS II inhibitor 1400W, we verified that the observed effects of naftidrofuryl were NOS II-dependent. The biology of nitric oxide accounts for the reduction of the vasospasm associated with stroke and the strong inhibition of platelet aggregation. In conclusion, our work provides evidence for the inhibition of leukocyte recruitment by downregulation of CD54/ICAM-1, an additional key factor to be dealt with during thrombotic accidents. Importantly, it also highlights a novel NOS II-dependent mechanism of action for naftidrofuryl.

Cells, Cultured↗
PubMed1999

4-trifluoromethyl derivatives of salicylate, triflusal and its main metabolite 2-hydroxy-4-trifluoromethylbenzoic acid, are potent inhibitors of nuclear factor kappaB activation.

1. The effect of two derivatives of salicylate, 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) and 2-acetoxy-4-trifluoromethylbenzoic acid (triflusal), on the activation of NF-kappaB elicited by tumour necrosis factor-alpha (TNF-alpha) on human umbilical vein endothelial cells (HUVEC) was tested. 2. The expression of the mRNA of vascular cell adhesion molecule-1 (VCAM-1) was studied as an example of a gene the expression of which is regulated by NF-kappaB. To extend these findings to other systems, the induction of nitric oxide synthase in rat adherent peritoneal macrophages was studied. 3. Both HTB and triflusal were more potent than aspirin or salicylate as inhibitors of the nuclear translocation of NF-kappaB. The calculation of the IC50 values showed approximately 2 mM for HTB, 4 mM for aspirin and >4 mM for salicylate. 4. Comparison of the potency of these compounds on VCAM-1 mRNA expression showed complete inhibition by both triflusal and HTB at a concentration of 4 mM whereas aspirin and salicylate produced only 36-43% inhibition at the same concentration. 5. Inhibition of NF-kappaB activation was also observed in rat peritoneal macrophages stimulated via their receptors for the Fc portion of the antibody molecule with IgG/ovalbumin immune complexes. This was accompanied by a dose-dependent inhibition of nitrite production by the L-arginine pathway via iNOS. IC50 values for this effect were 1.13+/-0.12 mM (triflusal), 1.84+/-0.34 (HTB), 6.08+/-1.53 mM (aspirin) and 9.16+/-1.9 mM (salicylate). 6. These data indicate that the incorporation of a 4-trifluoromethyl group to the salicylate molecule strongly enhances its inhibitory effect on NF-kappaB activation, VCAM-1 mRNA expression and iNOS induction, irrespective of the presence of the acetyl moiety involved in the inhibition of cyclo-oxygenase.

Animals↗
PubMed1997

Cilostazol, a cAMP phosphodiesterase inhibitor, attenuates the production of monocyte chemoattractant protein-1 in response to tumor necrosis factor-alpha in vascular endothelial cells.

The induction of monocyte chemoattractant protein-1 (MCP-1) in vascular endothelial cells is thought to be an initial event in the development of atherosclerotic lesions. Therefore, inhibition of MCP-1 production may exhibit some effects in preventing atherosclerosis. In the present study, we found that 10 microM cilostazol, a cAMP phosphodiesterase inhibitor, increased the intracellular cAMP content by a twenty-five times of the basal level and resulted in the reduction of basal MCP-1 release by 41% from 168 +/- 11 ng/24 hr/mg protein to 99 +/- 14 ng/24 hr/mg protein (P < 0.001) from cultured human umbilical vein endothelial cells. Furthermore, 10 microM cilostazol also significantly attenuated the dose-dependent increment of MCP-1 production by tumor necrosis factor-alpha. The inhibition was consistent with the reduction of MCP-1 mRNA level, possibly through reduced activation of transcription factor NF-kappa B level. Similarly, 1 mM dibutyryl cAMP inhibited MCP-1 production in endothelial cells. These data suggest that cilostazol inhibits MCP-1 production through increased intracellular cAMP levels and modulation of its expression in vascular endothelial cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1998

The effect of extracellular matrix proteins on porcine smooth muscle cell insulin-like growth factor (IGF) binding protein-5 synthesis and responsiveness to IGF-I.

The aim of this study was to determine if cultured porcine vascular smooth muscle cells (pSMCs) that had been maintained on different extracellular matrix proteins had an alteration in their expression of insulin-like growth factor binding protein-5 (IGFBP-5) and their responsiveness to insulin-like growth factor-I (IGF-I). When pSMCs were plated on fibronectin, they synthesized 6.0 +/- 1.2-fold more IGFBP-5 than did cells maintained on laminin and type IV collagen. IGF-I increased IGFBP-5 gene expression 3-fold in the cells plated on fibronectin. The addition of an RGD peptide and echistatin to pSMC cultures that had been plated on fibronectin inhibited IGFBP-5 mRNA expression. The addition of an antibody against alpha2beta1 integrin partially reversed the inhibitory effects of laminin and type IV collagen on IGFBP-5 expression. Cells maintained on fibronectin had a 5.0 +/- 1.1-fold greater DNA synthesis response to IGF-I compared with those maintained on laminin/type IV collagen, and echistatin significantly inhibited the DNA synthesis response of the fibronectin-maintained cells to IGF-I. The anti-alpha2beta1 antibody partially reversed the inhibitory effect of laminin and type IV collagen on IGF-I-stimulated DNA synthesis. The addition of IGFBP-5 to cultures plated on laminin and type IV collagen significantly increased their response to IGF-I. Atherosclerotic plaques from pig aorta contained abundant fibronectin and had increased IGFBP-5 mRNA (4.5 +/- 1.5-fold) compared with tissue from the normal vessel wall that had a low fibronectin content. These results indicate that fibronectin, laminin, and type IV collagen have major effects on IGFBP-5 expression and on IGF-I-stimulated pSMC responses and that these effects are mediated by their respective integrins.

Animals↗
PubMed2004

InsP3R-associated cGMP kinase substrate (IRAG) is essential for nitric oxide-induced inhibition of calcium signaling in human colonic smooth muscle.

Nitric oxide (NO)-mediated relaxation of colonic smooth muscle is crucial for the maintenance of human gut function. The molecular mechanisms of NO-dependent smooth muscle relaxation involve cyclic GMP-mediated inhibition of store-dependent calcium signaling. Recently, IRAG (inositol 1,4,5-trisphophate receptor-associated cGMP kinase substrate) has been characterized as a novel target molecule of cGMP-dependent protein kinase (cGKI) mediating NO-/cGMP-dependent inhibition of inositol 1,4,5-trisphosphate (InsP(3))-dependent calcium release in transfected COS cells. The aim of the present study was to characterize IRAG expression and its functional role in NO-dependent signaling in human colonic smooth muscle. Reverse transcriptase-PCR revealed IRAG mRNA expression in human colon, rectum, and cultured colonic smooth muscle cells. In cultured human colonic smooth muscle cells, bradykinin (BK) elicited InsP(3)-dependent calcium transients that were repeatable and independent of extracellular calcium. The NO donor sodium nitroprusside and the specific cGK activator 8-(4-chlorophenylthio)guanosine-3',5'-cyclic-monophosphate (8-pCPT-cGMP) significantly inhibited BK-induced increase in intracellular calcium. Cells transfected with antisense oligonucleotides raised against IRAG (IRAG-AS) showed strongly decreased IRAG protein expression. In these cells, sodium nitroprusside and 8-pCPT-cGMP both failed to modulate BK-induced calcium transients. Thus, endogenous IRAG appears to be essentially involved in the NO/cGK-dependent inhibition of InsP(3)-dependent Ca(2+)-signaling in colonic smooth muscle.

Animals↗
PubMed1961

A comparative electron microscopical study of RNA from different sources.

Electron micrographs of ribosomal RNA from Escherichia coli, microsomal RNA from calf, rat, and chick liver, Bacillus cereus RNA and E. coli soluble RNA are presented. Filaments of about 10 A in diameter could be observed in preparations obtained from aqueous solutions of high molecular weight RNA. When ammonium acetate solutions were used a tendency for coiling and aggregation was observed. E. coli soluble RNA appears as small, sometimes elongated particles the smallest diameter being of about 10 A.

Animals↗
PubMed1966

Some properties of DNA from phage-infected bacteria.

Replicating T5 or lambda phage DNA has been labeled by adding tritiated thymidine for short periods to cultures of phage-infected Escherichia coli before isolation of intracellular DNA. Two procedures are described for separating T5 replicating DNA from DNA of intracellular phage particles. Both T5 and lambda replicating DNA had the same bouyant density in cesium chloride as DNA from phage particles but sedimented faster when centrifuged in sucrose density gradients. The fast sedimentation did not appear to be caused by DNA protein or DNA-RNA complexes or by aggregation of DNA, but is probably due to DNA molecules of unusual structure. Experiments involving hydrodynamic shear and sucrose density gradient centrifugation at alkaline pH have suggested that with lambda the replicating form of DNA is a linear molecule considerably longer than the DNA molecules of lambda-phage particles. The constituent polynucleotide chains of lambda but not T5 replicating DNA also appear to be longer than those of phage DNA.

Centrifugation, Density Gradient↗
PubMed2005

NMPdb: Database of Nuclear Matrix Proteins.

The nuclear matrix (NM) is a structure resulting from the aggregation of proteins and RNA in the nucleus of eukaryotic cells; it is the 'sticky bit' that remains after aggressive DNAse digestion and salt extraction protocols. Owing to the important role of the NM in DNA replication, DNA transcription and RNA splicing, the expression pattern of NM proteins has become an important early indicator for numerous cancers/tumors. Recent descriptions of the NM structure distinguish between a network-like 'internal nuclear matrix' (INM) and a 'nuclear shell' that connects the INM to the inner and outer nuclear membranes. A cautious NM preparation protocol reveals a coat of proteins on top of the INM; these proteins are usually referred to as the 'nuclear matrix-associated proteins'. Here, we describe a new database (NMPdb at http://www.rostlab.org/db/NMPdb/) that currently contains details of 398 NM proteins. We collected these data through a semi-automated analysis of over 3000 scientific articles in PubMed. We could match these 398 proteins to 302 protein sequences in UniProt or GenBank. Our NMPdb repository annotates these links along with the following annotations: organism, cell type, PubMed identifier, sequence-based predictions of structural and functional features and for some entries the explicit sequence segment that is responsible for localization (nuclear matrix targeting signal).

Amino Acid Sequence↗
PubMed2006

Progestins overcome inhibition of platelet aggregation by endothelial cells by down-regulating endothelial NO synthase via glucocorticoid receptors.

Hormone replacement therapy with estroprogestin preparations is associated with an increased risk of venous and arterial thromboembolic events in postmenopausal women. This study examined whether progestins affect the formation of NO in endothelial cells, and, if so, to determine the underlying mechanism. Experiments were performed with human umbilical vein endothelial cells. Endothelial nitric oxide synthase (eNOS) expression was assessed by real-time polymerase chain reaction (PCR) and Western blot analysis, NO formation by electron spin resonance spectroscopy, nuclear translocation of the glucocorticoid receptor by immunofluorescence microscopy, and platelet aggregation by an aggregometer. Medroxyprogesterone acetate (MPA) and progesterone markedly decreased the eNOS mRNA and protein levels, whereas levonorgestrel and nomegestrol acetate had only small effects. This effect was associated with a decreased NO formation leading to a reduced ability of endothelial cells to prevent platelet aggregation and was prevented by knockdown of the glucocorticoid receptor using siRNA. MPA and progesterone, but not levonorgestrel and nomegestrol acetate, caused nuclear translocation of the glucocorticoid receptor. The present findings indicate that certain progestins, including MPA, reduce the antiaggregatory effect of endothelial cells by decreasing the expression of eNOS and the formation of NO in endothelial cells, an effect that is mediated via activation of glucocorticoid receptors.

Cells, Cultured↗
PubMed2002

PAF antagonist treatment reduces pro-inflammatory cytokine mRNA after spinal cord injury.

Platelet-activating factor (PAF) is a pro-inflammatory molecule which contributes to secondary damage after spinal cord injury (SCI). To test if PAF contributes to cytokine induction following SCI, female Long-Evans rats were pretreated with the PAF antagonist WEB 2170 prior to receiving a contusion injury at spinal cord level T10 using the NYU impactor. RNase protection assay (RPA) analysis revealed that IL-1alpha mRNA peaked at I h post-injury while IL-1beta and IL-6 mRNA levels were higher and peaked at 6 h.TNF-alpha mRNA was almost undetectable. All mRNA levels approached baseline by 24 h. Treatment with WEB 2170 (1 mg/kg, i.p.) 15 min prior to injury significantly decreased mRNA levels for all three cytokines at 6 h post-injury, but not at I h post-injury. These results demonstrate a role for PAF in proinflammatory cytokine induction after SCI.

Animals↗
PubMed2004

Platelet inhibition limits TGF-beta overexpression and matrix expansion after induction of anti-thy1 glomerulonephritis.

BACKGROUND: Although a role of platelets is well established in atherosclerosis, only little is known about their contribution to pathologic renal matrix expansion. The present study analyzes the effect of the platelet inhibitor clopidogrel on the early injury and subsequent repair phase of experimental anti-thy1 glomerulonephritis. METHODS: In male Sprague-Dawley rats, acute anti-thy1 glomerulonephritis was induced by intravenous injection of OX-7 antibody. In protocol 1 (injury), clopidogrel was given starting 5 days before antibody injection. One day after disease induction, parameters of mesangial cell injury (glomerular cell number, inducible NO synthesis, and macrophage infiltration) were analyzed. In protocol 2 (repair), clopidogrel treatment was started one day after antibody injection. On day 6, parameters of glomerular repair [glomerular matrix score, expression of transforming growth factor (TGF)-beta 1, fibronectin, and plasminogen activator inhibitor (PAI)-1] and thrombosis (aneurysm formation and fibrinogen deposition) were determined. In both protocols, an additional group of rats was treated with the angiotensin-converting enzyme (ACE) inhibitor enalapril. RESULTS: In the injury protocol, platelet inhibition did not affect mesangial cell lysis, glomerular NO production, and macrophage infiltration, while ACE inhibition was protective. In the repair protocol, clopidogrel significantly limited aneurysm formation and fibrinogen deposition, as well as glomerular matrix expansion, TGF-beta 1, fibronectin, and PAI-1 expression. In comparison, enalapril was less effective in preventing glomerular thrombosis, but was significantly superior to clopidogrel in limiting matrix protein expression and accumulation. CONCLUSION: The present study shows that platelets play a significant role in the sequence from mesangial cell injury to renal matrix expansion in anti-thy1 glomerulonephritis. The results, directly comparing renin-angiotensin-system and platelet inhibition, suggest that platelets contribute less than angiotensin II to TGF-beta overexpression and matrix accumulation in this model of acute glomerular wound repair.

Animals↗
PubMed2002

Nitric oxide-induced Cl- secretion in isolated rat colon is mediated by the release of thromboxane A2.

We have shown previously that thromboxane A2 (TXA2), which may be released by the anti-tumour drug irinotecan and by platelet-activating factor (PAF), causes Cl- secretion in the isolated rat colon. In the present study, the involvement of TXA2 in nitric oxide-induced Cl- secretion in isolated rat colon was investigated. In colonic mucosa set between Ussing chambers, the NO donor sodium nitroprusside (SNP; 100 microM) caused Cl- secretion, an effect that was almost completely inhibited by the NO scavenger carboxy-PTIO at 200 microM. The SNP-induced Cl- secretion was inhibited in a concentration-dependent manner by the TXA2 receptor antagonist ONO-3708 (IC50 = 2 microM) and the TX synthase inhibitor Y-20811 (IC50 = 0.4 microM). SNP significantly increased the release of TXA2 (measured as TXB2 release) from the mucosa. The SNP-induced increases in Cl- secretion and TXA2 release were blocked by a NO-sensitive guanylate cyclase inhibitor (ODQ). Dibutyryl cGMP (500 microM) also induced Cl- secretion, which was sensitive to ONO-3708 (10 microM) and Y-20811 (1 microM), and increased the release of TXA2 from the mucosa. PAF-induced (10 microM) Cl- secretion was inhibited by carboxy-PTIO (200 microM) and ODQ (10 microM), whereas irinotecan-induced (500 microM) Cl- secretion was not significantly inhibited by these drugs. A stable TXA2 analogue (STA2) but not SNP (100 microM) changed the membrane potential of epithelial cells in isolated colonic crypts under the whole-cell current-clamp condition. These results indicate that PAF elicits the NO-cGMP pathway and then stimulates the release of TXA2, which is a stimulant of colonic Cl- secretion. In contrast, the NO-cGMP pathway is not involved in the TXA2-mediated Cl- secretion induced by irinotecan.

Animals↗
PubMed2006

Autoinduction of MKC-963 [(R)-1-(1-cyclohexylethylamino)-4-phenylphthalazine] metabolism in healthy volunteers and its retrospective evaluation using primary human hepatocytes and cDNA-expressed enzymes.

MKC-963, (R)-1-(1-cyclohexylethylamino)-4-phenylphthalazine, a potent inhibitor of platelet aggregation, was synthesized and used in clinical trials in the 1990s. In the process of clinical study, it was found that urinary excretion ratios for 6beta-hydroxycortisol and free cortisol increased significantly in parallel with decreases in the plasma concentrations of MKC-963 after repeated oral administration of the compound to healthy volunteers. These findings suggested that MKC-963 caused autoinduction (defined as the ability of a drug to induce enzymes that enhance its own metabolism, resulting in dispositional tolerance) in humans, and clinical studies using the compound were stopped. This experience prompted us to reevaluate the effects of this compound on CYP3A4 using primary human hepatocytes and cDNA-expressed human cytochrome P450 (P450) enzymes to determine whether the autoinduction of MKC-963 metabolism in humans could have been predicted if these in vitro systems had been used for the evaluation of MKC-963 in the preclinical study. The results of in vitro study showed that MKC-963 increased CYP3A4 mRNA expression level and activity of testosterone 6beta-hydroxylation to extents similar to those observed with rifampicin in primary human hepatocytes. In addition, approximately 90% of the MKC-963 metabolism in human liver microsomes was estimated to be attributable to CYP3A4. These in vitro findings are in good agreement with the results of clinical study, suggesting that studies using human hepatocytes and cDNA-expressed human P450s are useful for assessing the autoinductive nature of compounds under development before starting clinical studies.

Administration, Oral↗