Expression of members of the phospholipase A2 family of enzymes in human nasal mucosa

Phospholipase A(2) (PLA(2)) is a family of enzymes thought to play a key role in inflammation by releasing arachidonic acid for the synthesis of eicosanoids and lysophospholipid for the synthesis of platelet-activating factor. However, the precise contribution of different PLA(2) types to the formation of inflammatory lipid mediators in the upper airways is not known and the expression of different PLA(2) genes in the human nasal mucosa has not been examined. This study therefore investigated the occurrence of messenger ribonucleic acids (mRNAs) for different PLA2 forms (IB, IIA, IID, IIE, III, IVA, IVB, IVC, V, VI, VII, X, acid calcium-independent (aiPLA(2)), and calcium-independent membrane bound PLA(2), (iPLA(2)-2)) in the nasal mucosa of five healthy human subjects. Using reversed transcription-polymerase chain reaction (RT-PCR) techniques it was found that all these PLA(2) types except PLA(2) V were expressed in all subjects, whereas PLA(2) V was detected in only one individual on one single occasion. The relative abundance of the different PLA(2) transcripts were aiPLA(2)>X approximate to IVA > IIA approximate to IIE approximate to IVB approximate to VI > IB approximate to IID approximate to III approximate to IVC approximate to VII approximate to iPLA(2)-2. To further quantify the mRNA-expression of PLA(2) X, IVA and IIA, the samples were reanalysed with a quantitative PCR-technique utilizing competitive deoxyribonucleic acid (DNA) mimics as references. The amounts of PLA(2) X, IVA and IIA mRNA were then estimated to 0.9 +/-0.2, 1.1 +/-0.7, and 0.0025 +/-0.0021 amol (mean +/- SE), respectively, confirming the relative abundance of these PLA(2) transcripts and indicating that the recently, described PLA(2) X form is relatively strongly expressed. These findings demonstrate that a large number of PLA(2) types are expressed in the normal human nasal mucosa. Moreover. this investigation demonstrates, for the first time, the presence of the newly discovered phospholipase A(2) forms IID, IIE, Ill, IVB, IVC, X and calcium-independent membrane bound phospholipase A(2) in the human nasal mucosa and raises the possibility, that one or several of these may be involved in inflammatory reactions in the nose.