Biochemical pharmacology
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Biochemical pharmacology · Sep 2003
Protective role of heme oxygenase-1 induction in carbon tetrachloride-induced hepatotoxicity.
Reductive metabolism of carbon tetrachloride (CCl(4)) is thought to cause lipid peroxidation which results in hepatic injury. Heme oxygenase-1 (HO-1) (EC 1.14.99.3), the rate-limiting enzyme in heme catabolism, is known to be induced by oxidative stress and to confer protection against oxidative tissue injuries. In this study, we examined the role of HO-1 induction in a rat model of CCl(4)-induced acute liver injury. ⋯ Inhibition of HO activity by tin-mesoporphyrin (Sn-MP), which resulted in a sustained increase in microsomal free heme concentration, exacerbated liver injury, as judged by the sustained increase in serum ALT activity, extensive hepatocytes injuries, a more pronounced expression of hepatic TNF-alpha mRNA and an enhanced NF-kappa B activation. These findings indicate that induction of HO-1 is an adaptive response to CCl(4) treatment, and it may be critical in the recovery of hepatocytes from injury. Our findings also suggest that HO-1 induction may play an important role in conferring protection on hepatocytes from oxidative damage caused by free heme.
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Biochemical pharmacology · Jun 2003
Induction of G1 phase arrest in MCF human breast cancer cells by pentagalloylglucose through the down-regulation of CDK4 and CDK2 activities and up-regulation of the CDK inhibitors p27(Kip) and p21(Cip).
Pentagalloylglucose (5GG) is a potent and specific inhibitor of NADPH dehydrogenase or xanthine oxidase. In our previous study, we showed that 5GG was able to induce apoptosis in HL-60 cells in a time- and concentration-dependent manner via the activation of caspase-3. Recently, we found that 5GG was capable of perturbing the cell cycle of the human breast cancer cell line MCF-7. ⋯ The level of several G1 phase-related cyclins and cyclin-dependent kinases did not change in these cells during a 24-hr exposure to 5GG. However, the activity of cyclin E/CDK2 was decreased in a concentration- and time-dependent manner and the activity of cyclin D/CDK4 was inhibited when serum-starved synchronized cells were released from synchronization. p27(Kip) and p21(Cip), inhibitors of cyclin/CDK complexes in G1-phase, were gradually increased after 5GG treatment in a time-dependent manner and the induction of p21(Cip) was correlated with an increase in p53 levels. These results suggest that the suppression of cell-cycle progression in the G1 phase by 5GG was mediated in MCF-7 cells, at least in part, by either the inhibition of cyclin D/CDK4 and cyclin E/CDK2 activity or the induction of the CDK inhibitors p27(Kip) and p21(Cip).
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Biochemical pharmacology · May 2003
Novel selective and metabolically stable inhibitors of anandamide cellular uptake.
Novel aromatic analogues of N-oleoylethanolamine and N-arachidonoylethanolamine (anandamide, AEA) were synthesized and, based on the capability of similar compounds to interact with proteins of the endocannabinoid and endovanilloid signaling systems, were tested on: (i) cannabinoid CB(1) and CB(2) receptors; (ii) vanilloid VR1 receptors; (iii) anandamide cellular uptake (ACU); and (iv) the fatty acid amide hydrolase (FAAH). The (R)- and, particularly, the (S)-1'-(4-hydroxybenzyl) derivatives of N-oleoylethanolamine and AEA (OMDM-1, OMDM-2, OMDM-3, and OMDM-4) inhibited to a varied extent ACU in RBL-2H3 cells (K(i) ranging between 2.4 and 17.7 micro M), the oleoyl analogues (OMDM-1 and OMDM-2, K(i) 2.4 and 3.0 micro M, respectively) being 6- to 7-fold more potent than the arachidonoyl analogues (OMDM-3 and OMDM-4). ⋯ In conclusion, we report two novel potent and selective inhibitors of ACU (OMDM-1 and OMDM-2) and one "hybrid" agonist of CB(1) and VR1 receptors (OMDM-6). Unlike other compounds of the same type, OMDM-1, OMDM-2, and OMDM-6 were very stable to enzymatic hydrolysis by rat brain homogenates.
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Biochemical pharmacology · Jan 2003
The effects of cladribine and fludarabine on DNA methylation in K562 cells.
The effects of the antileukemic adenosine analogues, 2-chloro-2'-deoxyadenosine (cladribine) and 9-beta-D-arabinosyl-2-fluoroadenine (fludarabine), on DNA methylation were studied in a cell line K562. It was previously found that both drugs inactivated SAH hydrolase, an enzyme which participates in the "active methyl" cycle. The study examined the effects of these drugs on three aspects of DNA methylation: (i) activity of endogenous C-5 DNA methyltransferase; (ii) capacity of genomic DNA (gDNA) to accept methyl groups, transferred from S-adenosylmethionine by the bacterial methyltransferase, SssI; (iii) estimation of changes of methylated cytosine levels in gDNA, using methylation-dependent restriction analysis. ⋯ Inhibition of DNA methylation by fludarabine was observed mainly in CpG dinucleotide located within sequences sensitive to HpaII. The perturbation of DNA methylation was considered as a complex process. Our findings for cladribine and fludarabine should be regarded as an extra element of their antileukemic efficacy.
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Biochemical pharmacology · Jul 2002
GPI 6150, a PARP inhibitor, reduces the colon injury caused by dinitrobenzene sulfonic acid in the rat.
Poly (ADP-ribose) polymerase, a nuclear enzyme activated by DNA strand breaks, has been shown to play an important role in the pathogenesis of inflammatory bowel disease. Here we investigate the effects of 1,11b-dihydro-[2H]benzopyrano [4,3,2-de]isoquinolin-3-one (GPI 6150), a new poly (ADP-ribose) polymerase inhibitor, in animal models of experimental colitis. Colitis was induced in rats by intra-colonic instillation of dinitrobenzene sulfonic acid. ⋯ GPI 6150 also caused a substantial reduction of (i) the degree of colon injury, (ii) the rise in myeloperoxidase activity (mucosa), (iii) the increase in the tissue levels of malondialdehyde, (iv) the increase in staining (immunohistochemistry) for poly (ADP-ribose), as well as (v) the upregulation of ICAM-1 and P-selectin caused by dinitrobenzensulfonic acid in the colon. Thus, GPI 6150 reduces the degree of colitis caused by dinitrobenzensulfonic acid. We propose that GPI 6150 may be useful in the treatment of inflammatory bowel disease.