Evaluation of MMP-9 and iNOS expressions in sheep with encephalitic listeriosis

Abstract

This study aimed to correlate Matrix Metalloproteinase-9 and iNOS expressions with the severity of histopathological findings in tissue samples taken from sheep with encephalitic listeriosis. Thus, the role of these molecules in the pathogenesis of the disease can be elucidated. After systemic necropsy, tissue samples of adult sheeps with meningoencephalitis were investigated by the culture, histopathological and immunohistochemical methods in the presence of Listeria spp. isolation from tissues was performed in accordance with the USDA-FSIS method with some modifications. Tissue samples were fixed in a 10% buffered formaldehyde solution. Following routine procedures, tissue sections at 5 µm were stained with Hematoxylin and Eosin, investigated under light microscope and photographed. Immunohistochemical staining was performed on the tissues using the avidin-biotin immune peroxidase complex method. Listeria spp. were obtained in 20 (83.3%) of 24 tissue samples with the presence of bright grey-black centred smooth colonies on Listeria Selective Agar and identified as Listeria monocytogenes through the phenotypically supportive tests. Liquefaction necrosis, purulent meningoencephalitis, perivascular cuffing, microabscesses and glial nodules were the most important histopathological findings. MMP-9 immunpositive reactions were observed in the cytoplasm of microglial cells and neurons in areas where inflammatory and necrotic areas are concentrated in medulla oblongata and pons. In perivascular cuffing areas, immune reactions in endothelial cells were detected. We detected iNOS positive reactions in the medulla oblangata and pons, especially in inflammatory cells in the microabscesses. Consequently, a positive correlation (p < 0.05) was found between MMP-9 expression and the severity of histopathological findings in sheep with encephalitic listeriosis. In addition, we found that iNOS expression increased in parallel with the increase in MMP-9 expression.