NF-kappaB action in sepsis: the innate immune system and the heart.

Sepsis is the clinical syndrome that results from a host's inflammatory response to infection via activation of the innate immune system. This response involves a complex network of inflammatory mediators that is self-reinforcing. When this immune response progresses uncontrollably, it can ultimately result in cardiovascular collapse and death. This complex inflammatory response is comprised of multiple mediators including cytokines such as TNF-alpha and IL-1beta, that are synthesized and secreted in response to signaling by receptors of the Toll-like receptor (TLR) family of pattern recognition receptors (PRR) that bind to pathogen associated molecules. A central downstream element of TLR-dependent signaling is the pleiotropic transcription factor NF-kappaB. NF-kappaB has been implicated in the regulation of multiple biological phenomena and disease states, including apoptosis, cell growth, stress response, innate immunity and septic shock. NF-kappaB-dependent genes are numerous and several have been implicated in the pathogenesis of sepsis and associated with cardiac dysfunction in sepsis. NF-kappaB activation occurs in multiple organs and cell types, and may be primarily protective in one tissue but injurious in another. Thus, a detailed understanding of the molecular basis of the pathophysiology of sepsis is needed in order to specifically block pro-inflammatory and pro-apoptotic signaling in the heart, while avoiding adverse effects in other organs.