Molecular signaling pathways in ischemia/reperfusion.

Ischemia and reperfusion (I/R) is an important pathologic phenomenon that has not been completely defined from the perspective of the molecular signaling pathways developed immediately at its inception to minutes and hours thereafter. From the practical point of view, we have divided I/R into 3 phases: phase I, which occurs seconds to minutes after the injury and is associated with changes dependent on the activation of phospholipases, intracellular calcium, eicosanoids, other lipid molecules, protein kinases, inducible nitric oxide synthase, and the expression of preformed adhesion molecules like P-selectin; phase II, which occurs minutes to hours after I/R injury and is associated with the active transcription of protein synthesis of molecules like inflammatory cytokines (mainly tumor necrosis factor-alpha and interleukin 1) starting their signaling downstream from the membrane into the cytoplasm where kinases will be activated and send signals to the nucleus for the activation of transcription factors and further continuing with the inflammatory event; and phase III, which occurs several hours to days after I/R and is associated with the appearance of molecular chronic mechanisms of protection like the presence of anti-inflammatory cytokines of the IL-10 type, late adhesion molecules, and other growth factors such as TGF-beta. This completes the whole molecular event related to I/R injury.