Differential regulation of Akt, caspases and MAP kinases underlies smooth muscle cell apoptosis during aortic remodelling in SHR treated with amlodipine.
OBJECTIVE
The regression of aortic hypertrophy is initiated by a transient wave of smooth muscle cell (SMC) apoptosis in spontaneously hypertensive rats (SHR) treated with antihypertensive drugs, although the molecular pathways remain unclear.


METHODS
Enzymes involved in apoptosis regulation were examined daily during onset aortic remodelling in SHR treated with amlodipine (20 mg kg(-1) day(-1)).


RESULTS
Significant reduction of aortic SMC number occurred by day 3 of amlodipine, reaching -13% at 28 days, followed by a significant regression of medial hypertrophy by day 5, reaching -13% at 28 days. ISOL-positive (apoptotic) SMC nuclei increased by 4.6-fold between days 2 and 4, in temporal correlation with the activation of caspase-8 (2.7-fold) at day 2 only, caspase-3 at days 3 and 4 (1.7-fold) and caspase-9 at day 3 only (3.1-fold). Akt phosphorylation, a pro-survival pathway, was reduced prior to apoptosis at day 1 (-52%) and until day 3. During the first 6 days of amlodipine treatment, significant reduction in phosphorylation of mitogen-activated protein (MAP) kinases was transient for p38 (-46% at day 3 only) but continuous for ERK1/2 after 3 days (-40%), and for JNK after 4 days (>-50%).


CONCLUSIONS
Amlodipine inhibition of Akt occurred prior to and during SMC apoptosis induction, a process mediated by the early activation of caspase-8 followed by caspase-9 and -3 and associated with MAP kinase inhibition. These findings provide insights about the molecular pathways underlying SMC apoptosis leading to vascular remodelling during amlodipine treatment of hypertension.
Duguay
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Department of Pharmacology, University of Montreal, 2900 Edouard-Montpetit, Montreal, Quebec, Canada.
deBlois
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D017311:Amlodipine / Q000494:pharmacology*; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001011:Aorta / Q000187:drug effects / Q000503:physiopathology; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D053181:Caspase 8 / Q000187:drug effects / Q000378:metabolism; D053453:Caspase 9 / Q000187:drug effects / Q000378:metabolism; D006984:Hypertrophy / Q000188:drug therapy* / Q000503:physiopathology; D048031:JNK Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular; D032389:Myocytes, Smooth Muscle; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR
D000959:Antihypertensive Agents; D017311:Amlodipine; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9