Uupregulation of High Affinity Cyclic AMP Phosphodiesterase (PDE) Genes Following BALloon Catheter Deendothelialization (Bal) in Rat Aorta
Inhibitors of PDE 3 and/or PDE4 block smooth muscle cell (SMC) proliferation/migration in vitro and reduce restenosis. To evaluate chronic regulation of SMC PDEs, rats were subjected to BAL. At several times after BAL (30 min to 10days/10D), medial SMC were isolated from the thoracic aortae. Tissues were fractionated for total RNA (analyzed by Northern blots/ RNAase protection) or cytosolic protein (Western blots or low Km [100 nM] cAMP PDE activity). BAL-dependent increases in PDE4B mRNA were biphasic: 2.7-fold at 1hr, which declined by 24hr below control values, followed by 2-3-fold increases by 4-7D (p<0.05 vs controls, n=3-6). PDE4B and c-myc mRNAs were selectively superinduced in cycloheximide-treated rats. Despite modest changes in PDE3 mRNAs, both 80 and 120 kDa PDE3A proteins were detected and only the 80kDa increased 7D post-BAL (10-fold increase, p<0.05, n=6). PDE4B2 (80kDa) persistently increased 2.5-3-fold (p<0.05, n=4-6) from 24 hr to 10D post-BAL, while 2-fold increases in PDE4D3 (90kDa) and PDE4B1 (104kDa) were evident at 24hr or 7D, respectively. PDE activity increased 50-60% (p<0.05; n=4) at 24 hr and 7D after BAL. Thus PDE4B resembles an immediate-early gene. Selective induction of the PDE4 family is associated with 2 waves of SMC proliferation in vivo, the latter of which is also accompanied by induction of PDE3A/80kDa. Upregulation of specific SMC PDEs following angioplasty represents an important response to injury that may be a useful therapeutic target in vascular disease.