Location: Food and Feed Safety Research
Title: Protein tyrosine kinase and mitogen-activated protein kinase signalling pathways contribute to differences in heterophil-mediated innate immune responsiveness between two lines of broilers Authors
Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 2010
Publication Date: June 27, 2011
Citation: Swaggerty, C.L., He, L.H., Genovese, K.J., Pevzner, I.Y., Kogut, M.H. 2011. Protein tyrosine kinase and mitogen-activated protein kinase signaling pathways contribute to differences in heterophil-mediated innate immune responsiveness between two lines of broilers. Avian Pathology. 40:289-297. Interpretive Summary: Cellular functions are controlled by a highly complex network of events that initiate and direct various signaling cascades that are regulated, in large part, by the phosphorylation of protein tyrosine kinases (PTK) and the mitogen-activated protein kinase (MAPK) super-family of enzymes, which is composed of three separate pathways (the p38, JNK, and ERK pathways). Immune responses are determined by the events of these pathways, and different pathways will generate different types of immune responses. We wanted to know which set of pathways were associated with an effective innate immune response in chicken cells from birds that are more resistant to Salmonella infections. Cells were isolated from two lines of chickens [line A (more resistant) and line B (more susceptible)] and exposed to Salmonella in a test tube. The results showed that line A cells were characterized by increased PTK and p38 activity, while JNK activity was increased in the susceptible line B cells. This study provides valuable information on the specific signaling pathways associated with increased resistance which will allow us to identify lines of birds that are more likely to be resistant to food-borne pathogens, including Salmonella.
Technical Abstract: Protein tyrosine phosphorylation mediates signal transduction of cellular processes, with protein tyrosine kinases (PTKs) regulating virtually all signaling events. The mitogen-activated protein kinase (MAPK) super-family consists of three conserved pathways that convert receptor activation into cellular functions: extracellular response kinases (ERK), c-Jun N-terminal kinases (JNK), and p38. Previously conducted studies using two chicken lines (A and B) show line A heterophils are functionally more responsive and produce a differential cytokine/chemokine profile compared to line B, which also translates to increased resistance to bacterial challenges. Therefore, we hypothesize the differences between the lines result from distinctive signaling cascades that mediate heterophil function. Heterophils from lines A and B were isolated from day-old chickens, and total PTK, p38, JNK, ERK, and transcription factor (AP-1 and NF-'B) levels quantitated following interaction with Salmonella enteritidis (SE). Control and SE-treated heterophils from line A had greater (p=0.05) PTK phosphorylation compared to line B, with increased (p=0.05) activation of p38. Conversely, line B heterophils activated JNK (p=0.05). There were no differences in ERK between control and activated heterophils for either line. Defined signaling inhibitors were used to show specificity. AP-1 and NF-'B transcription factor families were also examined, and c-Jun and p50, respectively, were the only members different between the lines, and both were up-regulated in A compared to B. These data indicate increased responsiveness of line A heterophils is mediated largely by an increased ability to activate PTKs, the p38 MAPK pathway, and specific transcription factors, all of which directly affect the innate immune response.