Semiquantitative analysis of protein expression in heated rat lens using shotgun proteomics

Previous studies have reported that a strong correlation between the estimated cumulative thermal exposure in the crystalline lens and the incidence of nuclear cataracts; however, the precise relationship between temperature and cataracts remains to be fully elucidated. In the present study, the shotgun liquid chromatography/mass spectroscopy-based global proteomic approach was applied to investigate cataract-inducing factors in lens cultured at normal (35.0°C) and slightly warmer (37.5°C) conditions. In the rat lens, 190 proteins (total) were identified. Of these, 48 proteins (25.3%) were found in lenses cultured at both 35.0°C and 37.5°C. Moreover, 85 proteins (44.7%) were unique to lenses cultured at 35.0°C, while 57 proteins (30.0%) were unique to lenses cultured at 37.5°C. Protein expression changes in rat lenses cultured at 37.5°C were examined using a label-free semiquantitative approach that uses spectral counting and Gene Ontology analysis. Filensin and vimentin protein expression, key factors in maintaining lens structure, were decreased. These findings may serve as a valuable indicator for elucidating the relationship between temperature and the onset of nuclear cataracts.