Posttranscriptional activation of BNP gene expression in response to increased left ventricular wall stress: role of calcineurin and PKC.
To study the molecular mechanisms for load-induced activation of BNP gene expression, increased wall stress was imposed on isolated isovolumetrically beating adult rat hearts by distension of a fluid filled balloon within the left ventricle. The wall stress for 2 h resulted in a 1.6-fold increase in the expression of BNP gene and a 2.0-fold increase of the c-fos gene. The inhibition of transcription by actinomycin D significantly decreased the baseline BNP mRNA levels but the wall stretch-induced increase of the gene expression remained unaffected. In contrast, the protein synthesis inhibitor cycloheximide increased baseline BNP mRNA levels and abolished the load-induced activation of gene expression. Furthermore, we studied the effects of protein kinase C (PKC), calcineurin and protein phosphatase 2A (PP2A) inhibition to characterize the role of intracellular pathways in the stretch-induced gene expression in the left ventricle. The expression of BNP and c-fos genes were not influenced by calcineurin, PP2A and PKC inhibition. In conclusion, we showed that the stretch-induced activation of BNP gene expression by increased left ventricular wall stress is independent of transcriptional mechanisms and dependent on protein synthesis. Moreover, our results suggest that the load-induced activation of BNP gene expression is independent of calcineurin, PKC and PP2A.
Tenhunen
Olli
O
Department of Pharmacology and Toxicology, Faculty of Medicine, Biocenter Oulu, University of Oulu, Finland.
Szokodi
István
I
Ruskoaho
Heikki
H
D000818:Animals; D019703:Calcineurin / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005786:Gene Expression Regulation; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D023421:Models, Animal; D020097:Natriuretic Peptide, Brain / Q000235:genetics*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D054648:Protein Phosphatase 2; D012323:RNA Processing, Post-Transcriptional; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D016277:Ventricular Function, Left / Q000502:physiology*
D020097:Natriuretic Peptide, Brain; D003609:Dactinomycin; D003513:Cycloheximide; D011493:Protein Kinase C; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2