Abstract
Intracellular generation of nitric oxide (NO) and superoxide anion (SOA) can result in the formation of 3'-nitrotyrosine proteins (NTp). Nitrated proteins usually are associated with significant perturbation in protein function, apoptosis, autophagy, and cell death. We undertook the present study to establish the temporal dynamics of NTp generation in cytokeratin-18-positive epithelial cells (ETCs) of broiler chickens in response to infection with Eimeria acervulina. Duodenal tissue was harvested from noninfected (NOI) and infected (INF) broilers on days (d) 1, 3, 6, 7, and 10 postinfection (PI) and fixed, embedded, and sectioned for quantitative image analysis, immunohistochemistry with antibodies specific to NTp and the SOA-generating enzyme xanthine oxidase (XO). The pixel density characteristics for NTp and XO representative of ETCs demonstrated that NTp and XO increased in intestinal villi as early as d1 PI (P < 0.05 vs. NOI). Progressive increases in NTp were evident in ETCs through d6 PI. For XO, increases in cell content increased only through d3. On d6 and d7 PI, high levels of NTp were present in immune infiltrating cells (IIC) where no XO was detected. The increases in ETC NTp occurred in a defined pattern, significant by villus-to-crypt location for day of infection, initiating in the distal villus and progressing down into the crypts. Two NTp patterns were observed for ETCs: a high level associated with ETCs harboring parasites and a low-level increase in ETCs not containing Eimeria but in proximity to such. The data suggest that NTp and XO responses may mediate some of the processes through which ETCs respond to Eimeria to limit the extent of infection by this pathogen.