Analysis of expression of secreted phospholipases A2 in mouse tissues at protein and mRNA levels

Secreted phospholipases A2 (sPLA2) form a group of low-molecular weight enzymes that catalyze the hydrolysis of phospholipids. Some sPLA2s are likely to play a role in inflammation, cancer, and as antibacterial enzymes in innate immunity. We developed specific and sensitive time-resolved fluroimmunoassays (TR-FIA) for mouse group (G) IB, GIIA, GIID, GIIE, GIIF, GV and GX sPLA2s and measured their concentrations in mouse serum and tissues obtained from both Balb/c and C57BL/6J mice. We also analyzed the mRNA expression of the sPLA2s by quantitative real-time reverse transcriptase PCR (qPCR). In most tissues, the concentrations of sPLA2 proteins corresponded to the expression of sPLA2s at the mRNA level. With a few exceptions, the sPLA2 proteins were found in the gastrointestinal tract. The qPCR results showed that GIB sPLA2 is synthesized widely in the gastrointestinal tract, including esophagus and colon, in addition to stomach and pancreas. Our results also suggest that the loss of GIIA sPLA2 in the intestine of GIIA sPLA2-deficient C57BL/6J mice is not compensated by other sPLA2s under normal conditions. Outside the gastrointestinal tract, sPLA2s were expressed occasionally in a number of tissues. The TR-FIAs developed in the current study may serve as useful tools to measure the levels of sPLA2 proteins in mouse serum and tissues in various experimental settings.