5 research outputs found
Direct intramyocardial plasmid vascular endothelial growth factor-A165gene therapy in patients with stable severe angina pectoris A randomized double-blind placebo-controlled study: The Euroinject One trial
ObjectivesIn the Euroinject One phase II randomized double-blind trial, therapeutic angiogenesis of percutaneous intramyocardial plasmid gene transfer of vascular endothelial growth factor (phVEGF-A165) on myocardial perfusion, left ventricular function, and clinical symptoms was assessed.BackgroundEvidence for safety and treatment efficacy have been presented in phase I therapeutic angiogenesis trials.MethodsEighty “no-option” patients with severe stable ischemic heart disease, Canadian Cardiovascular Society functional class 3 to 4, were assigned randomly to receive, via the NOGA-MyoStar system (Cordis Corp., Miami Lakes, Florida), either 0.5 mg of phVEGF-A165(n = 40) or placebo plasmid (n = 40) in the myocardial region showing stress-induced myocardial perfusion defects on 99mTc sestamibi/tetrofosmin single-photon emission computed tomography.ResultsNo differences among the groups were recorded at baseline with respect to clinical, perfusion, and wall motion characteristics. After three months, myocardial stress perfusion defects did not differ significantly between the VEGF gene transfer and placebo groups (38 ± 3% and 44 ± 2%, respectively). Similarly, semiquantitative analysis of the change in perfusion in the treated region of interest did not differ significantly between the two groups. Compared with placebo, VEGF gene transfer improved the local wall motion disturbances, assessed both by NOGA (p = 0.04) and contrast ventriculography (p = 0.03). Canadian Cardiovascular Society functional class classification of angina pectoris improved significantly in both groups but without difference between the groups. No phVEGF-A165-related adverse events were observed; however, NOGA procedure-related adverse events occurred in five patients.ConclusionsThe VEGF gene transfer did not significantly improve stress-induced myocardial perfusion abnormalities compared with placebo; however, improved regional wall motion, as assessed both by NOGA and by ventriculography, may indicate a favorable anti-ischemic effect. This result should encourage more studies within the field. Transient VEGF overexpression seems to be safe
Molecular pharmacology of amiodarone
MOLECULAR PHARMACOLOGY OF AMIODARONE
Amiodarone (Am) is a potent class III antiarrhythmic drug. Its use is
limited due to serious side effects and it was therefore used only when
other therapeutic interventions proved to be ineffective. The CAST study
in 1989, showing an increased mortality in patients treated with Class I
drugs, changed this scenario and resulted in an increased use of
amiodarone. The mechanism underlying the electrophysiological effects of
amiodarone remains uncertain. An intriguing possibility is that Am, as
indicated by earlier studies, exerts its action through antagonism of
thyroid hormone (T3). The actions of T3 are mediated through nuclear
receptors, the thyroid hormone receptors (ThR), which regulate gene
expression essential for the cellular integrity and the electrical
stability of the cardiomyocyte. In addition, the interaction between the
thyroid hormone- and the B-adrenergic signaling pathways is well known
and there is a possibility that the antiadrenergic effect of Am is
mediated through the T3 system.
AIMS OF THE STUDY:
1 ) To characterize the interaction between Am and ThR; to determine
whether other antiarrhytbmic drugs
have any specific affinity for the ThR.
2 ) To establish a suitable cell culture model for studies of the
molecular effects of Am on B-adrenergic
receptors (B-Ar).
3 ) To investigate the effects of Am and of cathecholamine stress on ThR
levels.
4 ) To characterize the antiadrenergic mechanism of Am.
5 ) To investigate if the prolongation of the repolarisation induced by
desethylamiodarone (DEA) is
dependent of gene expression and if levels of ThR subtypes are affected.
DEA is the major metabolite of
Am with similar pharmacodynamic profile.
CONCLUSIONS:
1 ) Am inhibits T3 binding to human ThR B,. Am acts as a non-competitive
inhibitor at low concentrations
(< 2 uLM) and as a competitive inhibitor at higher concentrations (2-8
uLM). Disopyramide, lignocaine,
propafenone, metoprolol, dl-sotalol and verapamil do not bind to human
ThR.
2 ) The AT- 1 cardiomyocytes were found to be a suitable cell model.
These cells express functional B
adrenergic receptors as measured with radioligand binding and cAMP
measurements Spontaneous
cytosolic Ca2+ transients present in the AT- 1 cardiomyocytes could be
modulated by sympathomimetic
drugs.
3 ) Thyroid hormone receptor mRNA levels in AT-1 cardiomyocytes are
modulated by both Am and
isoproterenol This observation demonstrates that Am exerts its effect on
cardiomyocytes at least in part
via the ThRs Together with previous observations of T3 action on B-Ar
levels, these findings suggest a
bi-directional regulation between the thyroid hormone and the
B-adrenergic systems.
4 ) In AT- I cardiomyocytes Am downregulates cell surface B-Ar and cAMP
generation without
affecting the affinity for the radioactive ligand to the receptor. The
downregulation of B-Ar was
reversed by T3. The protein synthesis inhibitor cycloheximide blocked the
Am induced down
regulation of B-Ar. Western blot analysis revealed a decreased expression
of B-Ar protein in Am
treated cells as compared to control. The house-keeping protein a-tubulin
remained unchanged.
These findings indicate a new antiadrenergic mechanism mediated through
gene expression.
5 ) In Langendorff perfused guinea pig hearts, the prolongation of
cardiac repolarisation induced by DEA
could be totally blocked by the protein synthesis inhibitor
cycloheximide. The action of DEA could be
reversed by T3 indicating an antagonism between DEA and T3. In DEA
treated hearts as compared to
control hearts, Western blot analysis revealed an increased expression of
ThR a, protein and a
decreased expression of ThR B, protein. The house-keeping protein
c~-tubulin remained unchanged.
These results suggest a new electrophysiologic mechanism dependent on
gene expression, probably by
modulation of ThR, rather than a direct effect on cell membrane receptors
or channels.
KEY WORDS: Amiodarone, thyroid hormone receptors, B-adrenergic receptors,
AT-1 cardiomyocytes, Western blot, solution hybridization, Fura-2,
Langendorff heart, mouse, guinea pi