Connexin 30 expression and frequency of connexin heterogeneity in astrocyte gap junction plaques increase with age in the rat retina

PLoS One. 2013;8(3):e57038. doi: 10.1371/journal.pone.0057038. Epub 2013 Mar 14.

Abstract

We investigated age-associated changes in retinal astrocyte connexins (Cx) by assaying Cx numbers, plaque sizes, protein expression levels and heterogeneity of gap junctions utilizing six-marker immunohistochemistry (IHC). We compared Wistar rat retinal wholemounts in animals aged 3 (young adult), 9 (middle-aged) and 22 months (aged). We determined that retinal astrocytes have gap junctions composed of Cx26, -30, -43 and -45. Cx30 was consistently elevated at 22 months compared to younger ages both when associated with parenchymal astrocytes and vascular-associated astrocytes. Not only was the absolute number of Cx30 plaques significantly higher (P<0.05) but the size of the plaques was significantly larger at 22 months compared to younger ages (p<0.05). With age, Cx26 increased significantly initially, but returned to basal levels; whereas Cx43 expression remained low and stable with age. Evidence that astrocytes alter connexin compositions of gap junctions was demonstrated by the significant increase in the number of Cx26/Cx45 gap junctions with age. We also found gap junctions comprised of 1, 2, 3 or 4 Cx proteins suggesting that retinal astrocytes use various connexin protein combinations in their gap junctions during development and aging. These data provides new insight into the dynamic and extensive Cx network utilized by retinal astrocytes for communication within both the parenchyma and vasculature for the maintenance of normal retinal physiology with age. This characterisation of the changes in astrocytic gap junctional communication with age in the CNS is crucial to the understanding of physiological aging and age-related neurodegenerative diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Animals
  • Astrocytes / metabolism*
  • Connexin 30
  • Connexins / metabolism*
  • Gap Junctions / metabolism*
  • Immunohistochemistry
  • Rats
  • Retina / metabolism*

Substances

  • Connexin 30
  • Connexins
  • Gjb6 protein, rat

Grants and funding

This work was supported by grants to TC-L from the National Health and Medical Research Council of Australia (Nos. 1005730 and 571100), the Baxter Charitable Foundation, the Rebecca L. Cooper Medical Research Foundation (Sydney, Australia) and the Brian M. Kirby Foundation (Gift of Sight Initiative). HM was the recipient of a University of Sydney Medical Foundation/Blues and Research Scholarship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.