NLRP3 Upregulation in Retinal Pigment Epithelium in Age-Related Macular Degeneration

Int J Mol Sci. 2016 Jan 8;17(1):73. doi: 10.3390/ijms17010073.

Abstract

Inflammation and oxidative stress are involved in age-related macular degeneration (AMD) and possibly associated with an activation of neuronal apoptosis inhibitor protein/class II transcription activator of the Major Histocompatibility Complex (MHC)/heterokaryon incompatibility/telomerase-associated protein 1, leucine-rich repeat or nucleotide-binding domain, leucine-rich repeat-containing family, and pyrin domain-containing 3 (NLRP3) inflammasome. In the present study, we used a translational approach to address this hypothesis. In patients with AMD, we observed increased mRNA levels of NLRP3, pro-interleukin-1 beta (IL-1β) and pro-IL-18 in AMD lesions of the retinal pigment epithelium (RPE) and photoreceptor. In vitro, a similar increase was evoked by oxidative stress or lipopolysaccharide (LPS) stimulation in the adult retinal pigment epithelium (ARPE-19) cell line, and the increase was reduced in siRNA transfected cells to knockdown NLRP3. Ultrastructural studies of ARPE-19 cells showed a swelling of the cytoplasm, mitochondrial damage, and occurrence of autophagosome-like structures. NLRP3 positive dots were detected within autophagosome-like structures or in the extracellular space. Next, we used a mouse model of AMD, Ccl2/Cx3cr1 double knockout on rd8 background (DKO rd8) to ascertain the in vivo relevance. Ultrastructural studies of the RPE of these mice showed damaged mitochondria, autophagosome-like structures, and cytoplasmic vacuoles, which are reminiscent of the pathology seen in stressed ARPE-19 cells. The data suggest that the NLRP3 inflammasome may contribute in AMD pathogenesis.

Keywords: autophagy; inflammation; mitochondria; oxidative stress; retina.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Adult
  • Aged, 80 and over
  • Animals
  • Carrier Proteins / genetics*
  • Carrier Proteins / immunology
  • Cell Line
  • Cells, Cultured
  • Humans
  • Inflammasomes / genetics
  • Inflammasomes / immunology
  • Inflammation / genetics
  • Inflammation / immunology
  • Inflammation / pathology
  • Macula Lutea / immunology
  • Macula Lutea / metabolism
  • Macula Lutea / pathology
  • Macular Degeneration / genetics*
  • Macular Degeneration / immunology
  • Macular Degeneration / pathology*
  • Male
  • Mice, Inbred C57BL
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Oxidative Stress
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Retinal Pigment Epithelium / immunology
  • Retinal Pigment Epithelium / metabolism
  • Retinal Pigment Epithelium / pathology*
  • Up-Regulation*

Substances

  • Carrier Proteins
  • Inflammasomes
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • NLRP3 protein, human
  • RNA, Small Interfering