Interpretive Summary: Temporal pattern changes in duodenal protein tyrosine nitration events in response to Eimeria acervulina infection in chickens.
By: Jackie Walling
A recent article in the June 2018 Issue of the Journal of Animal Science was published by a laboratory focusing on protein tyrosine residue nitration in epithelial cells and their signal transduction processes during infection. This study was conducted to define the intestinal epithelial cells (ETC) nitration response to Eimeria acervulina in broiler chickens. E.acervulina is a parasitic coccidiosis targeting the duodenum resulting in poor nutrient absorption and growth. Though curable, this disease is detrimental in the production industry.
It is not known if low-level infections could be curtailed by acute pathogen control, but researchers suspect nitration of proteins indicate early signs in the nonimmune cell response of infection. Compounds such as superoxide anion (SOA) and nitric oxide (NO) respond intracellularly to pathogens combining to create nitrotyrosine proteins (NTp) commonly associated with disruption of protein function, apoptosis, autophagy, and cell death. To define the nitration response in intestinal ETCs by day and cell type (location), 40 male chicks were divided into treatment groups: Infected (INF) and Noninfected (NOI). Five sampling groups within each treatment group represented days 1, 3, 6, 7, and 10 post infection (PI). Sets of four chicks were sacrificed on each day. INF chicks were given E.acervulina USDA APU-culture by oral gavage and NOI chicks received water.
Biomarkers such as body weight gain were similar for both groups through day 3 and then declined for the duration of the experiment in INF. Plasma carotenoid concentration (nutrient intake and gut uptake) was lower in INF than NOI hitting the lowest on day 6. Plasma concentration for NOx was higher in INF than NOI throughout the period until day 10. Infection attacked duodenal structure as a function of time revealing a decrease in villus height, increase in diameter of villus at midpoint, a thinning of exterior thickness in epithelial layer, and an increase in crypt depth all reaching respective peaks of destruction on day 6 before resuming normalization by day 10.
Immunostaining and microscopy identified cell types affected and showed a biological response towards infection resulting in the sloughing of villus with a repopulation of enhanced crypt development. Considering the intestines are normally challenged by pathogens, NOI showed low levels of NTp at villi tips associated with enterocytes. NTp in INF were also detected in enterocytes with increasing intensity and more cells affected moving in a pattern from the distal villus, toward the crypts, and into the smooth muscle layers. Numbers peaked on day 6 before dwindling back to normal levels as infection subsided. Cell marker cytokeratin-18 was used to validate NTp having a principle association with epithelial/enterocyte cells and an increase in xanthine oxidase (XO generates SOA) was observed in correlation with infection.
It is thought E.acervulina is capable of preventing cells it has infected from undergoing apoptosis in order to survive in its host. Nitration results from the generation of reactive oxy-nitrogen species. When E.acervulina infection inhabits the body, it triggers pro-inflammatory signals which result in the generation of SOA and NO disturbing metabolic activities. XO production along with NTp may serve as mediators in limiting infection response in ETCs. Enterocytes themselves have the ability to signal nitration before infection and if their mechanisms can be understood, ways to induce faster gut restoration could be formulated stifling the escalation of E.acervulina immediately.
To read the full article, go to the Journal of Animal Science.