engleski

Immunohistochemistry of 4-hydroxynonenal -protein conjugates in rat liver after ischemia-reperfusion injury

Oxidative stress (OS) is the pathophysiological condition of excessive production of reactive oxygen species (ROS) 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, the end products of lipid peroxidation such as 4-hydroxynonenal (HNE) are considered as "second messengers of ROS". In case of liver damage (caused by toxic chemicals or partial hepatectomy) the activation of antioxidative capacities is considered as one of the major hepatoprotective mechanisms needed to achieve successful liver regeneration. The aim of our study was to analyze the distribution of HNE-protein conjugates during I/R injury of rat liver by immunohistochemistry (PAP method, DAB staining with hematoxyllin contrast staining) applying genuine monoclonal antibodies. 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 artery) for 1 hour. Afterwards, 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 alhough it caused severe damage of liver tissue. Incomplete ischemia was manifested by less severe liver damage but additionally by very weak 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 central 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, after complete I/R multifocal HNE-positivity was noticed, mostly around the central veins, but only in hepatocytes and not in Kooffer cells. Occasionally, 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 damage by ischemia (hypoxia). Since HNE is also known not only as a toxic lipid peroxidation product but as a growth modifying factor, interfering with the activity of serum and tissue growth factors, formation of HNE (as detected by protein conjugates during liver I/R) might influence also liver regeneration and lipid metabolism which will be further studied.

immunohistochemistry; oxidative stress; ischemia-reperfusion of liver

Rad je kao pozvano predavanje prezentiran i na skupu Meeting of the Italian Cooperative Group of the Liver, održanom 26.10.2000.g., Torino, Italija.