title: NF-κB inhibition compromises cardiac fibroblast viability under hypoxia.
abstract: Cardiac fibroblasts are reported to be relatively resistant to stress stimuli compared to cardiac myocytes and fibroblasts of non-cardiac origin. However, the mechanisms that facilitate their survival under conditions of stress remain unclear. We explored the possibility that NF-κB protects cardiac fibroblasts from hypoxia-induced cell death. Further, we examined the expression of the antiapoptotic cIAP-2 and Bcl-2 in hypoxic cardiac fibroblasts, and their possible regulation by NF-κB. Phase contrast microscopy and propidium iodide staining revealed that cardiac fibroblasts are more resistant than pulmonary fibroblasts to hypoxia. Electrophoretic Mobility Shift Assay showed that hypoxia activates NF-κB in cardiac fibroblasts. Supershift assay indicated that the active NF-κB complex is a p65/p50 heterodimer. An I-κB-super-repressor was constructed that prevented NF-κB activation and compromised cell viability under hypoxic but not normoxic conditions. Similar results were obtained with Bay 11-7085, an inhibitor of NF-κB. Western blot analysis showed constitutive levels of Bcl-2 and hypoxic induction of cIAP-2 in these cells. NF-κB inhibition reduced cIAP-2 but not Bcl-2 levels in hypoxic cardiac fibroblasts. The results show for the first time that NF-κB is an important effector of survival in cardiac fibroblasts under hypoxic stress and that regulation of cIAP-2 expression may contribute to its pro-survival role.
authors.affiliation: Division of Cellular and Molecular Cardiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695011, India.
authors.forename: M
authors.initials: M
authors.lastname: Sangeetha
authors.forename: Malini S
authors.initials: MS
authors.lastname: Pillai
authors.forename: Linda
authors.initials: L
authors.lastname: Philip
authors.forename: Edward G
authors.initials: EG
authors.lastname: Lakatta
authors.forename: K
authors.initials: K
authors.lastname: Shivakumar
mesh_terms: D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000860:Hypoxia / Q000378:metabolism*; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D009570:Nitriles / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013450:Sulfones / Q000494:pharmacology
chemical_list: C416282:BAY 11-7085; D051034:Inhibitor of Apoptosis Proteins; D016328:NF-kappa B; D009570:Nitriles; D019253:Proto-Oncogene Proteins c-bcl-2; D013450:Sulfones; D053148:Caspase 3