Identification of neutrophil gelatinase‐associated lipocalin (NGAL) as a discriminatory marker of the hepatocyte‐secreted protein response to IL‐1β: a proteomic analysis

Publisher Website
Google Scholar
Abstract
The liver is the major source of proteins used throughout the body for various functions. Upon injury or infection, an acute phase response (APR) is initiated in the liver that is primarily mediated by inflammatory cytokines such as interleukin‐1β (IL‐1β) and interleukin‐6. Among others, the APR is characterized by an altered protein synthetic profile. We used two‐dimensional gel electrophoresis to study the dynamics of changes in protein synthesis in hepatocytes exposed to these inflammatory cytokines. Protein profiles were quantified using image analysis and further analyzed using multivariate statistical methods. Our results indicate that IL‐1β and IL‐6 each induces secreted protein responses with distinct dynamics and dose‐dependence. Parallel stimulation by IL‐1β and IL‐6 results in a protein pattern indistinguishable from the IL‐1β pattern, indicating a dominant effect of IL‐1β over IL‐6 at the doses tested. Multidimensional scaling (MDS) of correlation distances between protein secretion levels revealed two protein pairs that are robustly co‐secreted across the various cytokine stimulation conditions, suggesting shared regulatory pathways. Finally, we also used multivariate alternating conditional expectation (MACE) to identify transformation functions that discriminated the cytokine‐stimulated and untreated hepatocyte‐secreted protein profiles. Our analysis indicates that the expression of neutrophil gelatinase‐associated lipocalin (NGAL) was sufficient to discriminate between IL‐1β and IL‐6 stimulation. The combination of proteomics and multivariate analysis is expected to provide new information on the cellular regulatory networks involved in generating specific cellular responses.