Thymosinβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin 4 (T4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for the T4 and/or its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by two successive enzymes meprin α and prolyl oligopeptidase (POP). We also discussed the possible mechanisms involved in the T4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, T4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, T4 and Ac-SDKP have anti-fibrotic and anti-inflammatory properties in the arteries, heart, lungs and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of T4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains, though promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.