The role of Lysophosphatidylcholine acyltransferase-2 (LPCAT-2) in inflammatory responses
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Sepsis is the overwhelming inflammatory response to infection, especially bacterial infection and associated bacterial products. It has major healthcare impacts, affecting an estimated 19-30 million persons/year worldwide with a mortality of 30-70%. Despite intense research, no specific therapy has been established for sepsis and in addition to the high mortality, the associated economic costs are very high. For example, recent data shows that the annual cost of patients with sepsis is more than $20 billion in the USA, and £2.5 billion in the UK. Therefore, novel targets and new therapies for sepsis are required which will have an important impact on both mortality and economic benefits. Recent work has demonstrated that the phopsholipid modifying enzyme, LPCAT, has a role in the regulation of inflammatory responses to bacterial infections. However, the mechanism of action in this regard is not well understood. This project aimed to identify the role of LPCAT-2 in inflammatory response to infections. This project has utilized the RAW264.7 murine macrophage cell line as an experimental model and LPS or Pam3CSK4 as infectious stimuli to investigate the role of overexpressing LPCAT-2 as well as silencing the over-expressed LPCAT-2 using siRNA technique. RAW264.7 cells transiently or stably transfected with the LPCAT-2 gene were used to study the role of LPCAT-2 in the inflammatory responses of macrophages. LPCAT-2 was successfully over-expressed in RAW264.7 cells and the overexpression was successfully confirmed with real time polymerase chain reaction (RT-PCR) and western blotting. The overexpression of LPCAT-2 significantly upregulated the pro-inflammatory cytokines TNF-α and IL-6, at both gene expression, and protein level, while the anti-inflammatory cytokine, IL-10, was down regulated in these cells. Moreover, overexpression of LPCAT-2 significantly decreased the expression of TLR4, peroxisome proliferator-activated receptors –gamma (PPARγ) and CD206 (a marker of M2 macrophages) while it significantly increased CD14, TLR2, COX-2 and iNOS (M1 markers). LPCAT-2 gene expression was also increased when PPARγ was blocked with the selective (PPAR-γ) antagonist T0070907. Importantly, silencing the transiently over-expressed murine LPCAT-2 resulted in a significant reduction in TNF-alpha and a significant increase in IL-10 gene expression. Both the transient and stably transfected RAW264.7 cells have been used to study the role of LPCAT-2 in regulating inflammatory responses in macrophages. The results have significantly added to knowledge of the role of LPCAT-2 in the inflammatory response and will aid in the development of novel therapies for inflammatory conditions such as sepsis.