Phospholipase A2 (PLA2) is a superfamily of enzymes that play a key role in inflammation by releasing arachidonic acid for the synthesis of eicosanoids and lysophospholipid for the synthesis of platelet-activating factor (PAF). On the other hand, several members of the PLA2 family (VIIA, VIIB, VIIIA and VIIIB) are able to degrade PAF and are therefore potentially important anti-inflammatory enzymes. The precise roles of the different PLA2 enzymes in airway inflammation are not known and the gene expression of the different PLA2s in the human nasal mucosa has not previously been examined. Using reversed transcriptionpolymerase chain reaction (RT-PCR) techniques, this thesis investigated (i) the occurrence of mRNAs for different PLA2 types in the nasal mucosa of healthy subjects; (ii) the levels of different PLA2 mRNAs in the nasal mucosa of patients with seasonal allergic rhinitis (SAR) and healthy controls, and (iii) the effect of tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) on the gene expression of different PLA2s in human nasal (RPMI 2650) and bronchoepithelial (BEAS-2B) cells.
The relative abundances of the different PLA2 transcripts in normal human nasal mucosa were found to be X ≈ IVA > IIA ≈ IIE ≈ IVB ≈ VI > IB ≈ IID ≈ III ≈ IVC ≈ VII ≈ VIB. Notably, the mRNA levels of PLA2 VIIA (PAF acetylhydrolase I) were lower in SAR patients than controls during both the pollen season and the off-season for pollen. In both cell lines, TNF-α increased the expression of PLA2 IVA and IVC, while IFN-γ increased the expression of PLA2 IIA and IID. These findings demonstrate that a large number of PLA2 types are constitutively expressed in the normal human nasal mucosa, and they also demonstrate the presence of the newly discovered PLA2 types IID, IIE, IIF, III, IVB, IVC, VIB, X, XII, and XIII. Moreover, the findings indicate that TNF-α and IFN-γ cause increased gene expression of two novel cytosolic and secretory PLA2 types (IVC and IID, respectively) in human airway epithelial cells, suggesting that these PLA2 types may be involved in cytokine-mediated inflammation in the respiratory tract. The observation that PAF acetylhydrolase mRNA expression in the nasal mucosa is lower in SAR patients than in healthy subjects suggests the possibility that impaired ability to inactivate PAF might be of in1portance in SAR.
Linköping: Linköpings universitet , 2002. , 48 p.