Aging and BDNF‐deficiency upregulates heat shock protein expression in mouse retina

Abstract

Purpose To examine heat shock protein (HSP) expression in retinas of mice that lack brain derived neurotrophic factor (BDNF+/‐) and their wild type littermates (WT) at young and old age. Methods Eyes from 2‐ and 22‐months old WT and BDNF+/‐ mice (The Jackson Laboratory, Bar Harbor, ME, USA) were used. HSP 27 kDa (HSP27), 60 kDa (HSP60) and 70 kDa (HSP70) protein levels in retina were determined by Western blotting. Paraffin‐embedded retinal sections were immunostained for HSPs to determine their localisation and abundance in various retinal layers. Results Western blot analysis of the whole retina showed a 2‐fold increase in HSP27 and HSP60, and a 1.5‐fold increase in HSP70 in aged WT mice as compared to young mice. The lack of BDNF significantly upregulated HSPs expression in retina. Thus, young BDNF+/‐ mice had similar expression levels of HSPs in retina as in old WT mice, whereas a further increase in HSPs expression was observed in aged BDNF+/‐ mice as compared to young BDNF+/‐ mice. Conclusion Aging is associated with an increased expression of HSPs in the mouse retina. The lack of BDNF induces similar expression of stress‐related proteins in retina already at young age as it is seen at old age under normal BDNF levels.