Biomedical subjects

J J Martinez-Irujo

Publications and source records attributed to J J Martinez-Irujo.

5 recordsLinked to original sources

PubMed2000

New antiherpetic 1,3-phenylene derivatives, inhibitors of the interaction of the HSV-1 origin binding protein (OBP) with DNA.

The synthesis of new 1,3-phenylene derivatives and their preliminary evaluation as antivirals (Herpes simplex 1, HSV-1) whose antiherpetic activity can be related with the inhibition of the interaction of the origin binding protein (OBP) with the DNA are presented. The new compounds are adjusted to a previously defined common structural model, consisting of a central aromatic system, which presents two side chains of different lengths in relative position 1, 3; these chains are made up of atomic groups characterized by the alternation of positive and negative centers, situating differently substituted rings, preferably aromatic, at the ends of both chains. Some of these derivatives, such as N,N''-(4-methoxy-1,3-phenylene)bis[N'-(4-nitrophenyl)urea] (2c) or (1,3-phenylene)bis[N-(p-tolyl)aminosulfonyl] (11b), show antiherpetic activity related to the proposed mechanism.

Animals↗

PubMed1999

Contribution of phosphodiesterase isoenzymes and cyclic nucleotide efflux to the regulation of cyclic GMP levels in aortic smooth muscle cells.

Involvement of phosphodiesterase isoenzymes (PDEs) in guanosine-3',5'-cyclic monophosphate (cGMP) hydrolysis was analyzed in aortic smooth muscle cells. Four families of PDEs were separated from pig aorta: PDE1 (calcium-calmodulin-activated), PDE3 (cGMP-inhibited), PDE4 (adenosine 3',5'-cyclic monophosphate [cAMP]-specific), and PDE5 (cGMP-specific). Within this PDE complement, PDE1 and PDE5 mostly contributed to the hydrolysis of cGMP both in the presence and absence of calcium-calmodulin. The role of these isoenzymes in cGMP degradation was analyzed in primary cultures of porcine aortic smooth muscle cells after stimulation with sodium nitroprusside (SNP) or atrial natriuretic factor (ANF). Pretreatment with 10 microM zaprinast, a concentration that selectively inhibits PDE5, did not potentiate the SNP- or ANF-induced rise of cGMP, questioning the widespread opinion that only PDE5 accounts for cGMP hydrolysis in this tissue. Further evidence came from experiments assessing the effect of zaprinast or 3-isobutyl-1-methylxanthine at concentrations inhibiting both type 1 and type 5 isoenzymes, in which this potentiation was clearly seen. Contribution of cGMP egression to the control of intracellular cGMP levels after SNP or ANF stimulation was also investigated. Shortly after guanylate cyclase activation, extracellular cGMP levels surpassed intracellular levels. However, comparison of the amounts of cGMP extruded to the extracellular medium with those degraded by PDEs leads to the conclusion that efflux is of relatively minor importance in regulating intracellular cGMP levels. In cells made tolerant to SNP, selective PDE5 inhibition synergistically increased intra- and extracellular cGMP amounts after SNP stimulation. These results indicate a previously undescribed greater relevance of PDE5 after tolerance development in aortic smooth muscle cells.

Animals↗

PubMed1998

Analysis of the combined effect of two linear inhibitors on a single enzyme.

Different methods for studying the concurrent effects of two linear inhibitors on a single enzyme have been published, including the fractional product of Webb, the Yonetani-Theorell plot or the method of Chou and Talalay. Recently the use of combination plots has also been advocated for this purpose. We have evaluated the applicability of these methods and found that most of them depend on assumptions about the mechanism of action of the inhibitors. If the mechanism of action is not completely understood, or if some assumptions about the mechanism are unfounded, the parameters obtained may be meaningless. Even if these assumptions are correct, the interaction can be advantageously measured using an alternative representation that does not require a knowledge of the inhibition constants and allows experimental data to be retrieved from the plot. In other cases it is the interpretation of the results rather than the validity of the method that is misleading. A common mistake is to take the exclusivity of the effects of two inhibitors as exclusivity of their binding. We show that this assumption is seldom justified. In any case, it is possible to decide whether the combination of two or more inhibitors is more effective than their individual use by means of isobolographic analysis, even when no information about their mechanism of action is available.

Adenosine Diphosphate↗

PubMed1997

Synergistic inhibition of HIV-1 reverse transcriptase by combinations of chain-terminating nucleotides.

Synergistic inhibition of HIV replication in cell culture has been reported for many combinations of reverse transcriptase inhibitors. However, the biochemical basis underlying this interaction is in most cases unknown. It has been previously shown that combinations of L-697,661 or U-90152s with AZT or ddC synergistically inhibit HIV-1 replication in cell culture. The combination of AZT with ddC is also favorable with respect to the inhibition of viral replication. However, the corresponding combinations showed no synergy in inhibiting enzyme activity when tested on conventional polymerase assays using homo- or heteropolymeric RNA and DNA as template. Data obtained suggest that amplification of the effect of chain terminators, a consequence of the high potential number of termination sites present on the template, override the synergistic effect expected for the combination of two independent nucleotide analogs. When a saturating amount of enzyme over template:primer was used, and a single site on the template was available for each chain terminator, the combination of AZTTP and ddCTP synergistically inhibited enzyme activity, whereas, as expected, the combination of AZTTP and ddTTP behaved as merely additive. Under similar conditions the combination of U-90152s and AZTTP was also synergistic. These results suggest that synergy found in antiviral assays with combinations having nucleosidic inhibitors is not related to the synergistic inhibition of reverse transcriptase and might be due to the presence in the viral population of virus strains with different sensitivity to the inhibitors.

Anti-HIV Agents↗

PubMed1996

A checkerboard method to evaluate interactions between drugs.

A method to evaluate interactions between biologically active agents is presented. Synergism, zero interaction, and antagonism were easily detected with the three-dimensional approach proposed herein. This method is compatible with a checkerboard design to diagnose the interaction between agents and obviate the need to test their mixtures in a fixed concentration ratio as proposed by Chou and Talalay. Dose-response curves for individual agents were obtained, and experimental data fitted to appropriate equations by nonlinear regression. If zero interaction was present, the predicted effect could be calculated for each combination using the classical isobole equation with any spreadsheet having a command to solve mathematical equations by iteration. This allowed the selection of appropriate concentrations for the combination of two or more agents. Interaction between agents could be assessed in two ways: by comparing experimental with expected effects, if zero interaction is present; or by analyzing the reduction or increase in total dose found as a consequence of the interaction. The applicability of both approaches is discussed and, for purposes of comparison with other methods, examples based on published data are analyzed and commented upon.

Alcohol Dehydrogenase↗