Decline in cellular clearance systems induces inflammasome signaling in human ARPE-19 cells

Area of Science:

• Ophthalmology
• Cell Biology
• Immunology

Background:

• Retinal pigment epithelium (RPE) is crucial for photoreceptor health.
• RPE degeneration is linked to age-related macular degeneration (AMD).
• Cellular aging involves protein aggregate accumulation, oxidative stress, and inflammation.

Purpose of the Study:

• Investigate the impact of impaired degradation systems on RPE cells.
• Determine the role of proteasomal and autophagic inhibition in RPE cell response.
• Elucidate the mechanisms linking degradation dysfunction to inflammation and AMD pathology.

Main Methods:

• Human ARPE-19 cells were treated with proteasome inhibitor MG-132 and autophagy inhibitor bafilomycin A1.
• Analyzed the release of cytokines IL-1β and IL-18.
• Assessed NLRP3 receptor and caspase-1 activation.
• Measured intracellular oxidative stress via 4-hydroxynonenal (HNE)-protein adducts.
• Investigated IL-8 production and its dependence on IL-1β and caspase-1.

Main Results:

• Inhibition of degradation pathways induced IL-1β release but not IL-18.
• Upregulation of NLRP3 receptor and activation of caspase-1 were observed.
• Increased intracellular protein aggregates and oxidative stress (elevated HNE-protein adducts) occurred.
• IL-8 was secreted, and low concentrations of IL-1β triggered significant IL-8 production.
• Caspase-1 inhibition attenuated IL-8 secretion.

Conclusions:

• Declining intracellular degradation systems in RPE cells lead to RPE dysfunction.
• This decline activates NLRP3 inflammasomes via elevated IL-1β production.
• The process involves increased protein aggregates, oxidative stress, and inflammatory cytokine release, potentially contributing to AMD pathogenesis.