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Daniele LL, Caughey J, Volland S, Sharp RC, Dhingra A, Williams DS, Philp NJ, Boesze-Battaglia K. Peroxisome turnover and diurnal modulation of antioxidant activity in retinal pigment epithelia utilizes microtubule-associated protein 1 light chain 3B (LC3B). Am J Physiol Cell Physiol 2019; 317:C1194-C1204. [PMID: 31577510 DOI: 10.1152/ajpcell.00185.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The retinal pigment epithelium (RPE) supports the outer retina through essential roles in the retinoid cycle, nutrient supply, ion exchange, and waste removal. Each day the RPE removes the oldest ~10% of photoreceptor outer segment (OS) disk membranes through phagocytic uptake, which peaks following light onset. Impaired degradation of phagocytosed OS material by the RPE can lead to toxic accumulation of lipids, oxidative tissue damage, inflammation, and cell death. OSs are rich in very long chain fatty acids, which are preferentially catabolized in peroxisomes. Despite the importance of lipid degradation in RPE function, the regulation of peroxisome number and activity relative to diurnal OS ingestion is relatively unexplored. Using immunohistochemistry, immunoblot analysis, and catalase activity assays, we investigated peroxisome abundance and activity at 6 AM, 7 AM (light onset), 8 AM, and 3 PM, in wild-type (WT) mice and mice lacking microtubule-associated protein 1 light chain 3B (Lc3b), which have impaired phagosome degradation. We found that catalase activity, but not the amount of catalase protein, is 50% higher in the morning compared with 3 PM, in RPE of WT, but not Lc3b-/-, mice. Surprisingly, we found that peroxisome abundance was stable during the day in RPE of WT mice; however, numbers were elevated overall in Lc3b-/- mice, implicating LC3B in autophagic organelle turnover in RPE. Our data suggest that RPE peroxisome function is regulated in coordination with phagocytosis, possibly through direct enzyme regulation, and may serve to prepare RPE peroxisomes for daily surges in ingested lipid-rich OS.
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Affiliation(s)
- Lauren L Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jennifer Caughey
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Stefanie Volland
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, California.,Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Rachel C Sharp
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Anuradha Dhingra
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - David S Williams
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, California.,Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Nancy J Philp
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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