Control of left ventricular mass by moxonidine involves reduced DNA synthesis and enhanced DNA fragmentation.
OBJECTIVE
Left ventricular hypertrophy (LVH) is a maladaptive process associated with increased cardiovascular risk. Regression of LVH is associated with reduced complications of hypertension. Moxonidine is an antihypertensive imidazoline compound that reduces blood pressure primarily by central inhibition of sympathetic outflow and by direct actions on the heart to release atrial natriuretic peptide, a vasodilator and an antihypertrophic cardiac hormone. This study investigated the effect of moxonidine on LVH and the mechanisms involved in this effect.


METHODS
Spontaneously hypertensive rats were treated with several doses of moxonidine (s.c.) over 4 weeks. Blood pressure and heart rate were continuously monitored by telemetry. Body weight and water and food intake were measured weekly. Measurements also included left ventricular mass, DNA content, synthesis, fragmentation, and apoptotic/anti-apoptotic pathway proteins.


RESULTS
The decrease in mean arterial pressure stabilized at approximately -10 mm Hg after 1 week of treatment and thereafter. Compared to vehicle-treated rats (100%), left ventricular mass was dose- and time-dependently reduced by treatment. This reduction remained significantly lower after normalizing to body weight. Moxonidine reduced left ventricular DNA content and inhibited DNA synthesis. DNA fragmentation transiently, but significantly increased at 1 week of moxonidine treatment and was paralleled by elevated active caspase-3 protein. The highest dose significantly decreased the apoptotic protein Bax and all doses stimulated anti-apoptotic Bcl-2 after 4 weeks of treatment.


CONCLUSIONS
These studies implicate the modulation of cardiac DNA dynamics in the control of left ventricular mass by moxonidine in a rat model of hypertension.
Laboratory of Cardiovascular Biochemistry, Centre Hospitalier de L'Université de Montréal Research Center, Campus Hotel-Dieu and Department of Medicine, Université de Montréal, Montréal, Quebec, Canada.
P-A
PA
Paquette
D
D
Duguay
R
R
El-Ayoubi
A
A
Menaouar
B
B
Danalache
J
J
Gutkowska
D
D
DeBlois
S
S
Mukaddam-Daher
D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects*; D053938:DNA Fragmentation / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D017379:Hypertrophy, Left Ventricular / Q000188:drug therapy* / Q000503:physiopathology; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D013686:Telemetry; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000187:drug effects / Q000378:metabolism
D000959:Antihypertensive Agents; D007093:Imidazoles; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D004247:DNA; C043482:moxonidine; D053148:Caspase 3