Efeitos da radiação ionizante X na expressão de MMP-9 enamorfologia do cerebelo de ratos

Abstract

The metalloproteinase-9 (MMP-9) is an enzyme that is present inthecentral and peripheral nervous system, acting on tissue remodeling, either in pathological conditions or during the process of morphogenesis. MMP-9 levelscanbeincreased in the CNS after some injury. However, little is knownabout theexpression of this metalloproteinase in CNS lesions, caused by cranial radiotherapy,which despite destroying neoplastic cells can reach adjacent healthytissues.Therefore, the aim of this study was to evaluate the expression of MMP-9andthecerebellum morphology of rats that received a single dose of Xradiationtothehead. For this, thirty male Wistar rats were divided into six groups: oneasacontrol and the others irradiated. The cerebellums were collected and evaluatedat4, 9, 14, 25 and 60 days after a single radiation dose of 15.75grays. Thecollected samples were submitted to immunohistochemistry for MMP-9, andFeulgen's histochemistry for morphologicalanalysis of the cerebellar cortexandthenuclei of Purkinje cells. The results ofimmunohistochemistry showed anincreaseinMMP-9 expression at 4, 9 and 14 days. MMP-9 was immunolocalizedinneuronextensions in the molecular layer and around Purkinje cells. Histological analyzesallowed to establish that changes in the cerebellar cortex occur after 4daysandare evident up to 60 days. In addition, it has been shown that the areaandthenumber of Purkinje cells are reduced after radiation. The optical densityanalysisshowed that the irradiated animals have a more condensed or fragmentedchromatin. We conclude that the damage caused by a dose of X radiationof 15.75Gy in the cephalic region of the rat, leads to an increase in the expressionofMMP-9, changes in the normal morphology of the cerebellar cortex, reductionofthe nuclear area and the number of Purkinje cells, as well as chromatincondensation.