IMMUNOHISTOCHEMISTRY OF 4-HYDROXYNONENAL-PROTEIN CONJUGATES IN RAT LIVER AFTER ISCHEMIA-REPERFUSION INJURY

Oxidative stress (OS) is associated with various types of injury, in particular ischemia/reperfusion (I/R) injury. Lipid peroxidation is an important process in OS causing secondary tissue damage, hence, products of lipid peroxidation such as 4-hydroxynonenal (HNE) are considered as „second messengers of reactive oxigen species“. The aim of our study was to analyze the distribution of HNE-protein conjugates during I/R injury of rat liver. Immunohistochemistry (PAP method, DAB staining with hematoxyillin contrast staining) was applied using monoclonal antibodies against HNE-protein conjugates. The animals were anesthetized by ether and exposed to either complete or incomplete ischemia (closing either portal vein only or both portal vein and hepatic arthery) for 1 hour. Subsequently the animals were either sacrificed or were exposed to 10 minutes reperfusion before sacrifice. Complete ischemia without reperfusion was not associated with the formation of HNE-protein conjugates although it caused severe damage of liver tissue. Incomplete ischemia was manifested by less severe liver damage but aditionally by very veak and diffuse presence of HNE, which did not show any particular anatomical distribution. Reperfusion did not change the intensity of HNE immunopositivity markedly but it resulted in a change of the histological distribution, i.e. most of HNE-positive cells were found around cenral veins and in the portal space. The most intensive HNE-immunopositivity was found in case of complete ischemia followed by reperfusion, although, like in case of incomplete I/R, the damage of the liver structure was less obvious than in case of ischemia only. Thus, afer complete I/R multifocal HNE-positivity was noticed, mostly around the central veins, but only in hepatocytes and not in Kupffer cells. Ocassionally, bile ducts and blood vessels in the portal space were also positive. These findings indicate that reperfusion is not only important for the development of OS in the I/R damage, but it can promote recovery of the liver tissue damaged by ischemia (hypoxia). Since HNE is not only a toxic product of lipid peroxidation but also a growth modifying factor interfering with the activity of serum and tissue growth factors, the formation of HNE during liver I/R might influence also liver regeneration and lipid metabolism.