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Exp Eye Res. 2018 May;170:29-39. doi: 10.1016/j.exer.2018.02.014. Epub 2018 Feb 16.

Distinct CD40L receptors mediate inflammasome activation and secretion of IL-1β and MCP-1 in cultured human retinal pigment epithelial cells.

Author information

1
Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, USA.
2
Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, USA. Electronic address: mgfield@umich.edu.
3
Department of Internal Medicine-Rheumatology, University of Michigan, Ann Arbor, MI, 48105, USA.

Abstract

CD40L signaling occurs in several diseases with inflammatory components, including ocular and retinal diseases. However, it has never been evaluated as a pathogenic mechanism in age-related macular degeneration (AMD) or as an inducer of inflammasome formation in any cell type. mRNA and protein levels of CD40, IL-1β, NALP1, NALP3, caspase-1, and caspase-5 were determined by RT-PCR, qPCR, and Western blot. CD40L receptor (CD40, α5β1, and CD11b) expression was determined by Western and immunofluorescent staining. IL-1β, IL-18, and MCP-1 secretions were determined by ELISA. NALP1 and NALP3 inflammasome formation were determined by Co-IP. Experiments were conducted on primary human retinal pigment epithelial (hRPE) cells from four different donors. Human umbilical vein endothelial (HUVEC) and monocytic leukemia (THP-1) cells demonstrated the general applicability of our findings. In hRPE cells, CD40L-induced NALP1 and NALP3 inflammasome activation, cleavage of caspase-1 and caspase-5, and IL-1β and IL-18 secretion. Interestingly, neutralizing CD11b and α5β1 antibodies, but not CD40, reduced CD40L-induced IL-1β secretion in hRPE cells. Similarly, CD40L treatment also induced HUVEC and THP-1 cells to secret IL-1β through CD11b and α5β1. Additionally, the CD40L-induced IL-1β secretion acted in an autocrine/paracrine manner to feed back and induce hRPE cells to secrete MCP-1. This study is the first to show that CD40L induces inflammasome activation in any cell type, including hRPE cells, and that this induction is through CD11b and α5β1 cell-surface receptors. These mechanisms likely play an important role in many retinal and non-retinal diseases and provide compelling drug targets that may help reduce pro-inflammatory processes.

KEYWORDS:

AMD; Age-related macular degeneration; CD40L; IL-1β; Inflammasome; MCP-1; RPE; Retinal pigment epithelium

PMID:
29454857
PMCID:
PMC5924621
[Available on 2019-05-01]
DOI:
10.1016/j.exer.2018.02.014
[Indexed for MEDLINE]

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