Study of Role of Ribosomal Protein L13a in Resolving Inflammation

Inflammation is an obligatory attempt of the host immune system to protect the body against infection. However, unregulated synthesis of pro-inflammatory products can have detrimental effects. Though mechanisms which contribute to inflammation are well appreciated, those that resolve inflammation are poorly understood. Therefore, understanding the molecular basis of such pathways will provide an entirely novel approach to treat and prevent inflammatory diseases. Transcript-selective translational control can regulate the expression of a set of inflammatory genes. We have identified one such mechanism in a novel animal model which relies on the abrogation of ribosomal protein L13a-dependent translational silencing by creating macrophage-specific L13a-knockout mice where resolution of inflammation is severely compromised. We have used these knockout mice to study two different kinds of inflammation: LPS induced systemic inflammation and dextran sodium sulphate (DSS) induced experimental colitis. Upon LPS induced endotoxemia, these mice displayed high mortality rates and severe symptoms of inflammation such as infiltration of immune cells in the peritoneum and major organs leading to tissue destruction. These animals also exhibited high serum levels of TNF-╬▒, blood urea nitrogen (BUN), aspartate aminotransferase (AST) and several other markers of inflammation. Macrophages from these knockouts showed unregulated synthesis of several chemokines (e.g., CXCL13, CCL22, CCL8 and CCR3) and increased polysomal abundance of these mRNAs due to the abrogation of their translational silencing. Upon DSS induced colitis, these knockout mice demonstrated higher susceptibility to colitis displaying reduced survival, significant weight loss, enhanced rectal bleeding and diarrhea. Histopathology analysis of tissue sections from the knockouts showed disruption of epithelial crypts in the colon with infiltration of macrophages in colon and spleen sections. Additionally, elevated levels of several chemokines and cytokine