Diverse regulation of retinal pigment epithelium phagocytosis of photoreceptor outer segments by calcium-independent phospholipase A₂, group VIA and secretory phospholipase A₂, group IB

Curr Eye Res. 2012 Oct;37(10):930-40. doi: 10.3109/02713683.2012.691598. Epub 2012 Jun 8.

Abstract

Purpose: 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.

Conclusion: 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.

MeSH terms

  • Animals
  • Cattle
  • Cell Line
  • Cell Survival / physiology
  • Gene Expression Regulation, Enzymologic / physiology
  • Genes, Reporter
  • Group IB Phospholipases A2 / genetics
  • Group IB Phospholipases A2 / metabolism*
  • Group VI Phospholipases A2 / genetics
  • Group VI Phospholipases A2 / metabolism*
  • Humans
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Phagocytosis / physiology*
  • Primary Cell Culture
  • Promoter Regions, Genetic / physiology
  • RNA, Messenger / metabolism
  • Retinal Photoreceptor Cell Outer Segment / physiology*
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / enzymology*

Substances

  • RNA, Messenger
  • Group IB Phospholipases A2
  • Group VI Phospholipases A2
  • PLA2G1B protein, human
  • PLA2G6 protein, human
  • Pla2g1b protein, mouse
  • Pla2g6 protein, mouse