Diverse regulation of retinal pigment epithelium phagocytosis of photoreceptor outer segments by calcium-independent phospholipase A₂, group VIA and secretory phospholipase A₂, group IB.
OBJECTIVE
To investigate the roles of the phospholipases A(2) (PLA(2)) subtypes, iPLA(2)-VIA and sPLA(2)-IB in retinal pigment epithelium (RPE) phagocytosis of photoreceptor outer segments (POS) and to explore a possible interaction between sPLA(2)-IB and iPLA(2)-VIA in the RPE.


METHODS
To explore the role of iPLA(2)-VIA in RPE phagocytosis of POS, experiments with iPLA(2)-VIA vector transfection, iPLA(2)-VIA(-/-) knockout (KO) mice, and iPLA(2)-VIA inhibition by bromoenol lactone (BEL) were done. Exogenous addition of sPLA(2)-IB was used to investigate the role of sPLA(2)-IB in RPE phagocytosis. A Luciferase Reporter Vector containing the iPLA(2)-VIA promoter was used to study the effects of sPLA(2)-IB on the iPLA(2)-VIA promoter.


RESULTS
ARPE-19 and primary mouse RPE cells transfected with iPLA(2)-VIA showed increased phagocytosis. Phagocytosis was reduced in primary mouse RPE inhibited with BEL and in RPE from KO mice. Exogenous addition of enzymatically active and inactive sPLA(2)-IB reduced phagocytosis in ARPE-19 and primary mouse RPE cells. Finally, sPLA(2)-IB did not seem to affect the iPLA(2)-VIA promoter.


CONCLUSIONS
The present study confirms the involvement of iPLA(2)-VIA in efficient RPE phagocytosis of POS, while exogenously added sPLA(2)-IB decreases phagocytosis regardless of enzymatic activity. No apparent interaction between iPLA(2)-VIA and sPLA(2)-IB was found.
Department of Neuroscience and Pharmacology, University of Copenhagen, Blegdamsvej, Copenhagen, Denmark.
Chen
C
Zhan
Jinmei
J
Wang
Miriam
M
Kolko
D000818:Animals; D002417:Cattle; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D017930:Genes, Reporter; D054500:Group IB Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D054522:Group VI Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000502:physiology*; D061251:Primary Cell Culture; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D055214:Retinal Photoreceptor Cell Outer Segment / Q000502:physiology*; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000201:enzymology*
D012333:RNA, Messenger; D054500:Group IB Phospholipases A2; D054522:Group VI Phospholipases A2; C516202:PLA2G1B protein, human; C516475:PLA2G6 protein, human; C516203:Pla2g1b protein, mouse; C516476:Pla2g6 protein, mouse