Isoforms of secretory group two phospholipase A (sPLA2) in mouse ocular surface epithelia and lacrimal glands

To compare and contrast the distribution patterns of select secretory group two phospholipase A (sPLA2) isoforms in corneal epithelia (CN), conjunctival epithelia (CNJ), and lacrimal glands (LG) of BALB/c and C57BL/6 mice.

Gene expression of select sPLA2 isoforms was quantified via real-time reverse-transcription PCR (qRT(2)-PCR). Immunofluorescence assay (IFA) of the sPLA2-IIa, -V, and -X isoforms were used to confirm qRT(2)-PCR results. sPLA2-IIa function was confirmed via in vitro CN and CNJ culturing.

qRT(2)-PCR revealed that sPLA2 isoforms (pla2g5, 12a, and 12b), cPLA2 isoform (pla2g4a), iPLA2 isoform (pla2g6), and PLA2-receptor (pla2r1) were present in all tissues of both strains, whereas sPLA2 isoforms (pla2g1b, 2e, and 3) were absent. sPLA2 isoforms (pla2g2a, 2d, 2f, and 10) showed tissue- and strain-specific expression: 2a in BALB/c CNJ only; 2d at higher levels in CNJ than LG; and 2f and 10 in CN and CNJ, but absent in LG. Upon dry eye (DE) induction, pla2g2a, 2d, and 2f were upregulated in BALB/c CNJ, and 10 was absent from CN. Furthermore, BALB/c DE mice showed upregulation of pla2r1 in CN and CNJ and downregulation of 12a and 12b in LG. IFA of sPLA2-IIa, -V, and -X in DE CNJ confirmed the upregulation of pla2g2a, 5, and 10. Last, in vitro CN and CNJ culturing confirmed that sPLA2-IIa amplifies ocular surface inflammation in CNJ but not in CN.

sPLA2 isoforms exhibit differential expression patterns when comparing BALB/c with C57BL/6 mice; and DE with control BALB/c mice. These findings suggest that at least some sPLA2 isoforms must have significant roles in ocular surface physiology and inflammation.