Protein oxidation seems to be linked to constitutive autophagy: a sex study

Abstract

Aim: Although constitutive autophagy is linked to redox state and participates in cell homeostasis, it is scarcely known if redox state, autophagy, and lysosomal function depend on sex, a factor that largely influences health and diseases. Therefore, we evaluated the existence of sex differences in redox state and constitutive autophagy in rat tissues.

Main methods: 7week old Sprague-Dawley rats were used to obtain organs. Malondialdehyde (MDA), and carbonylated proteins were measured by spectrophotometric methods for redox state assessment. The autophagy biomarkers Beclin-1, and microtubule-associated protein 1 light chain 3 (LC3), the mammalian target of rapamycin (mTOR; checkpoint in autophagic process), and the lysosomal associated membrane protein (LAMP-1; biomarker of lysosomes) were evaluated by Western blotting. Immunofluorescence analysis was also performed for LC3 and LAMP-1 colocalization.

Key findings: In the heart, Beclin-1, and LC3-II/LC3-I were higher in males than in females suggesting that the male heart has a major constitutive autophagy and this was linked with higher levels of carbonyl groups, indicating that protein oxidation could play a role. In the liver, it was found that LAMP-1 was higher in males and greatly colocalized with LC3 indicating a larger number of autophagolysosomes. None of the above parameters was significantly different in the kidneys of both sexes with the exception of MDA, which was significantly higher in females.

Significance: The above results suggest that sex differences exist in redox state and autophagy and they occur in an organ-specific way. Importantly, it seems that the protein oxidation is more linked with constitutive autophagy, at least in cardiac ventricles, in comparison with lipid peroxidation.

Keywords: Autophagy; Lysosomes; Protein carbonylation; Sex.