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 anti- apoptotic 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 assayindicated 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.

Protective effect and mechanistic evaluation of linalool against acute myocardial ischemia and reperfusion injury in rats

“…Earlier studies have stated that the role of the activation of NF-kB which is connected with the phosphorylation of IkBa and transport of p65 from the nucleus. 26,27 In the present study, it was found that linalool was able to inhibit the phosphorylation of IkB-a together with reduction of NF-kB in myocardial tissues. Thus, it has been suggested that the protective effects of linalool could be attributed to the attenuation effect which might be because of the signals of the inammation via inhibition of the NF-kB activation.…”

The impact of hypoxia on cell death pathways

“…IAPs directly block the cleavage (and activation) of the caspases, thus inhibiting apoptosis [59]. Notably, c-IAP2 is up-regulated in hypoxia in an NF-κB-dependent manner [60].…”

Combined hypoxia and sodium nitrite pretreatment for cardiomyocyte protection in vitro

“…Using our model system we demonstrated that hypoxic pretreatment promoted the survival of CMs but not cardiac fibroblasts following H/R injury (Figures ). Cardiac fibroblasts are less sensitive to stress than CMs and are relatively resistant to pro‐apoptotic stimuli, including hypoxia, as seen here in the >2‐fold decrease in CM viability relative to the fibroblasts upon H/R injury. It is possible therefore that we did not observe an effect from hypoxic pretreatment on fibroblast viability because the hypoxic condition during the pretreatment period was of insufficient duration or severity to induce the initiation of prosurvival mechanisms in this cell type.…”