[TNF alpha and heart failure]

Tumor necrosis factor alpha (TNF alpha) is a cytokine with proinflammatory properties which produces negative inotropic effects on the heart. It is produced in a variety of conditions such as septic shock, acute myocarditis, reperfusion injury, and congestive hear failure (CHF). This production is probably due to activation of immune elements localized in the heart or periphery, or both. TNF alpha acts by binding to two specific receptors: TNF-R1 and TNF-R2. These two proteins have different effects. TNF-R1 has cytotoxic and antiviral activity, induces fibroblast proliferation, and mediates apoptosis. TNF-R2 is involved in septic shock and in lymphocyte proliferation. They both have negative inotropic effect on the heart. It has been showed that these receptors are down-regulated in congestive heart failure, while their soluble forms (sTNF-R1 and sTNF-R2) increase with the severity of symptoms. However the significance of this increase is still unclear. The role of Fas, a receptor protein that induces apoptosis, is also examined. Fas and its ligand have homologies respectively with TNF alpha and TNF-R. Also the soluble form of Fas (sFas) increases in relation to heart failure and is related to soluble forms of the similar receptor family, therefore it is possible that the same stimuli lead the three receptors to act together. SFas, as well as sTNF receptors, may play an important role in CHF.