Senescence-induced alteration of circadian phagocytic activity of retinal pigment epithelium cell line ARPE-19

Renewal of retinal photoreceptor outer segments is conducted through daily shedding of distal photo-receptor outer segment tips and subsequent their phagocytosis by the adjacent retinal pigment epithelium (RPE) monolayer. Dysregulation of the diurnal clearance of photoreceptor outer segment tips has been implicated in age-related retinal degeneration, but it remains to be clarified how the circadian phagocytic activity of RPE cells is modulated by senescence. In this study, we used the human RPE cell line ARPE-19 to investigate whether hydrogen peroxide (H2O2)-induced senescence in ARPE-19 cells alters the circadian rhythm of their phagocytic activity. After synchronization of the cellular circadian clock by dexamethasone treatment, the phagocytic activity of normal ARPE-19 cells exhibited significant 24-h oscillation, but this oscillation was modulated by senescence. The phagocytic activity of senescent ARPE-19 cells increased constantly throughout the 24-h period, which still exhibited blunted circadian oscillation, accompanied by an alteration in the rhythmic expression of circadian clock genes and clock-controlled phagocytosis-related genes. The expression levels of REV-ERBa, a molecular component of the circadian clock, were constitutively increased in senescent ARPE-19 cells. Furthermore, pharmacological activation of REV-ERBa by its agonist SR9009 enhanced the phagocytic activity of normal ARPE-19 cells and increased the expression of clock-controlled phagocytosis-related genes. Our present findings extend to understand the role of circadian clock in the alteration of phagocytic activity in RPE during aging. Constitutive enhancement of phagocytic activity of senescent RPE may contribute to age-related retinal degeneration.(c) 2023 Elsevier Inc. All rights reserved.

Automated summary

Renewal of retinal photoreceptor outer segments involves shedding and phagocytosis, but senescence can modulate the circadian phagocytic activity of RPE cells. The phagocytic activity of senescent ARPE-19 cells increased constantly and exhibited altered circadian oscillation, accompanied by changes in the expression of circadian clock genes. Additionally, activation of the circadian clock component REV-ERBa enhanced the phagocytic activity of normal ARPE-19 cells and increased the expression of phagocytosis-related genes.