The effect of autophagy and mitochondrial fission on Harderian gland is greater than apoptosis in male hamsters during different photoperiods

Photoperiod is an important factor of mammalian seasonal rhythm. We studied the morphological differences in HG which is a vital photosensitive organ of male striped dwarf hamsters (Cricetulus barabensis), under different photoperiods (short photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and further investigated the molecular mechanisms related to these morphological differences. Results showed that body weight, carcass weight, and HG weight were lower in SP and LP. Protein expression of bax/bcl2 and Cytochrome C showed no significant differences, indicating that the level of apoptosis remained stable. Protein aggregation of LC3 and protein expression of LC3II/LC3I were higher in SP than. Furthermore, comparison of changes in the HG ultrastructure demonstrated autolysosome formation in the LP, which suggesting the lowest autophagy level in MP. Protein expression levels of ATP synthase and mitochondrial fission factor were highest in the MP, whereas citrate synthase, dynamin-related protein1, and fission1 remained unchanged in three groups. In summary, the significant up-regulation of autophagy under short and long photoperiod may be the main factor leading to the loss of HG weight and reduced mitochondrial energy supply.