title: Differential cardiotoxic/cardioprotective effects of beta-adrenergic receptor subtypes in myocytes and fibroblasts in doxorubicin cardiomyopathy.
abstract: beta-Adrenoceptor (beta-AR) subtypes act through different signaling pathways to regulate cardiac function and remodeling. Previous in vivo data show a markedly enhanced cardiotoxic response to doxorubicin in beta2-/- mice, which is rescued by the additional deletion of the beta1-AR. We determined whether this differential response was myocyte specific by examining the effects of doxorubicin in myocytes and fibroblasts from WT and beta1, beta2 and beta1/beta2-/- mice. Cells were exposed to doxorubicin at 1-50 microM and viability and apoptosis assessed at 6, 24 and 48 h. WT myocytes showed a time and dose-dependent decrease in viability (42% decrease at 1 microM after 24 h). beta2-/- Myocytes showed a greater decrease in viability vs. WT (20.8% less at 6 h; 14% less at 24 h, P<0.05); beta1-/- and beta1/beta2-/- myocytes showed enhanced survival (beta1-/- 11%; beta1/beta2-/- 18% greater than WT, P<0.05). TUNEL staining demonstrated a similar differential susceptibility (WT 26% apoptotic nuclei, beta2-/- 45.9%, beta1/beta2-/- 16.8%, P<0.05). beta2-/- Fibroblasts also showed enhanced toxicity. Pertussis toxin pretreatment of WT cells decreased survival similar to the beta2-/-, suggesting a role for Gi signaling. JNK was differentially activated in beta2-/- myocytes after doxorubicin and its inhibition increased cardiotoxicity. In conclusion, the differential cardioprotective/cardiotoxic effects mediated by beta1 vs. beta2-AR subtypes in knockout mice are recapitulated in myocytes isolated from these mice. beta2-ARs appear to play a cardioprotective role, whereas beta1-ARs a cardiotoxic role.
authors.affiliation: Department of Pediatrics, Stanford University, Stanford, CA 94305, USA.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Fajardo
authors.forename: Mingming
authors.initials: M
authors.lastname: Zhao
authors.forename: Jennifer
authors.initials: J
authors.lastname: Powers
authors.forename: Daniel
authors.initials: D
authors.lastname: Bernstein
mesh_terms: D000818:Animals; D009202:Cardiomyopathies / Q000139:chemically induced*; D002316:Cardiotonic Agents / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects* / Q000502:physiology; D007700:Kinetics; D051379:Mice; D020297:Mice, Congenic; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology; D018342:Receptors, Adrenergic, beta-1 / Q000235:genetics / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
chemical_list: D002316:Cardiotonic Agents; D017077:Culture Media, Conditioned; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D004317:Doxorubicin