Caspase-dependent cell death mediates the early phase of aortic hypertrophy regression in losartan-treated spontaneously hypertensive rats.
Blockade of angiotensin type 1 (AT1) receptors induces smooth muscle cell (SMC) death and regression of aortic hypertrophy in spontaneously hypertensive rats (SHR). We postulated that SMC death and vascular remodeling in this model may be attenuated by z-Val-Ala-Asp(OMe)-CH2F (z-VAD-fmk), a tripeptide inhibitor of caspase enzymes mediating apoptosis. To determine the time course of SMC death and aortic remodeling, SHR were treated with losartan (30 mg/kg per day) for up to 9.5 days. Transient SMC apoptosis occurred in the aortic media with a peak around day 5 of treatment, with increases in the Bax to Bcl-2 protein ratio (>3-fold), in active caspase-3 (5.6-fold), in TUNEL-positive nuclei (19-fold), preceding by 24 hours the peak activation of capase-9 (3.8-fold), and significant reductions in SMC number (46%) and aortic cross-sectional area (8.5%) at 5.5 days. The decrease in total aortic DNA reached significance at 6.5 days (29%). Blood pressure reduction with losartan was progressive and reached significance at day 7 of treatment. Next, we examined the causal link between vascular apoptosis and remodeling. SHR received placebo or losartan (30 mg/kg per day) for 6 days. During the last 24 hours, a subgroup of losartan-treated rats received 3 IV injections of z-VAD-fmk (cumulative dose: 4.4 mg x kg(-1)). All other rats received the vehicle, DMSO. The 24-hour cotreatment with z-VAD-fmk effectively prevented losartan-induced caspase-3 activation and internucleosomal DNA fragmentation, as well as SMC depletion and the reductions in aortic mass and DNA content. Together, these data suggest that caspase-dependent SMC death mediates the early phase of vascular remodeling in response to AT1 receptor blockade in this model of hypertension.
Marchand
Eve-Lyne
EL
Department of Pharmacology, University of Montreal Hospital Research Center, 3840 St-Urbain St, Rm 7-132B, Montreal, Quebec H2W 1T8, Canada.
Der Sarkissian
Shant
S
Hamet
Pavel
P
deBlois
Denis
D
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001011:Aorta / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D017209:Apoptosis / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002452:Cell Count; D053938:DNA Fragmentation / Q000187:drug effects; D006973:Hypertension / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D006984:Hypertrophy; D020287:In Situ Nick-End Labeling; D019808:Losartan / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D012074:Remission Induction; D013997:Time Factors; D051028:bcl-2-Associated X Protein
D000590:Amino Acid Chloromethyl Ketones; D000959:Antihypertensive Agents; C494828:Bax protein, rat; D061945:Caspase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C505410:Casp3 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases; D019808:Losartan