Dichotomous actions of NF-kappaB signaling pathways in heart.

Despite the substantial progress in heart research over the past two decades heart failure still remains a major cause of morbidity and mortality in North America and is reaching pandemic proportions worldwide. Though the underlying causes are varied, the functional loss of contractile myocytes through apoptosis, necrosis, and autophagy has emerged a central unifying theme to explain diminished cardiac performance in individuals with heart failure. At the molecular level, there has been considerable interest in understanding the signaling pathways that regulate cell death in the heart with specific interest in the extrinsic and intrinsic cell death pathways. The cellular factor nuclear factor-kappaB (NF-kappaB) is a key transcription factor involved in the regulation of a wide range of genes involved in cellular process including inflammation, immune cell maturation, cell proliferation, and, most recently, cell survival. NF-kappaB signaling is important for the normal cellular growth and is a major target of inflammatory cytokines. Several studies have highlighted a protective role of NF-kappaB in the heart under certain circumstances including hypoxic or ischemic myocardial injury. The diverse nature and involvement of NF-kappaB in regulation of vital cellular processes including cell survival notably in the post-mitotic heart has sparked considerable interest in understanding the signaling pathways involved in regulating NF-kappaB in the heart under normal and pathological conditions. However, whether NF-kappaB is adaptive, maladaptive or is a homeostatic response to cardiac injury may simply depend on the context and timing of its activation. In this forum we discuss NF-kappaB signaling pathways and therapeutic opportunities to modulate NF-kappaB activity in heart failure.