Daily torpor in hamsters (Rodentia, Cricetinae)

et al. 2020

PLoS ONE

Photoperiod is an important factor of mammalian seasonal rhythm. Here, we studied morphological differences in the Harderian gland (HG), a vital photosensitive organ, in male striped dwarf hamsters (Cricetulus barabensis) under different photoperiods (short photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and investigated the underlying molecular mechanisms related to these morphological differences. Results showed that carcass weight and HG weight were lower under SP and LP conditions. There was an inverse correlation between blood melatonin levels and photoperiod in the order SP > MP > LP. Protein expression of hydroxyindole-O-methyltransferase (HIOMT), a MT synthesis-related enzyme, was highest in the SP group. Protein expression of bax/bcl2 showed no significant differences, indicating that the level of apoptosis remained stable. Protein expression of LC3II/LC3I was higher in the SP group than that in the MP group. Furthermore, comparison of changes in the HG ultrastructure demonstrated autolysosome formation in the LP, suggesting the lowest autophagy level in under MP. Furthermore, the protein expression levels of ATP synthase and mitochondrial fission factor were highest in the MP group, whereas citrate synthase, dynamin-related protein1, and fission1 remained unchanged in the three groups. The change trends of ATP synthase and citrate synthase activity were similar to that of protein expression among the three groups. In summary, the up-regulation of autophagy under SP and LP may be a primary factor leading to loss of HG weight and reduced mitochondrial energy supply capacity.

Section: Discussionmentioning

confidence: 99%

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

et al. 2020

PLoS ONE

“…On the one hand, it may be that exogenous injection of MT is not the same as simple photoperiod treatment. On the other hand, Syrian hamsters hibernate in winter (45), whereas striped dwarf hamsters display daily torpor (46). Therefore, the effects on these two hamsters differ under the short photoperiod of winter.…”

Section: Discussionmentioning

confidence: 98%

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

et al. 2020

Preprint

15Photoperiod is an important factor of mammalian seasonal rhythm. We studied the 16 morphological differences in HG which is a vital photosensitive organ of male striped 17 dwarf hamsters (Cricetulus barabensis), under different photoperiods (short 18 photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and further 19investigated the molecular mechanisms related to these morphological differences. 20Results showed that body weight, carcass weight, and HG weight were lower in SP and 21LP. Protein expression of bax/bcl2 and Cytochrome C showed no significant differences, 22indicating that the level of apoptosis remained stable. Protein aggregation of LC3 and 23 protein expression of LC3II/LC3I were higher in SP than. Furthermore, comparison of 24 changes in the HG ultrastructure demonstrated autolysosome formation in the LP, 25 which suggesting the lowest autophagy level in MP. Protein expression levels of ATP 26 synthase and mitochondrial fission factor were highest in the MP, whereas citrate 27 synthase, dynamin-related protein1, and fission1 remained unchanged in three groups. 28In summary, the significant up-regulation of autophagy under short and long 29 photoperiod may be the main factor leading to the loss of HG weight and reduced 30 mitochondrial energy supply. 31

“…On the one hand, it may be that exogenous injection of MT is not the same as simple photoperiod treatment. On the other hand, Syrian hamsters hibernate in winter (44), whereas striped dwarf hamsters display daily torpor (45). Therefore, the effects on these two hamsters differ under the short photoperiod of winter.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2020

Preprint

Background: Photoperiod is one of the important factors of mammalian seasonal rhythm. As an important photosensitive organ in addition to the eyes and pinecones, Harderian gland (HG) may respond to seasonal light cycle changes. Here, we studied the morphological differences in the HG of male striped dwarf hamsters (Cricetulus barabensis), a small mammal with annual rhythm under different photoperiods (short photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and further investigated the molecular mechanisms related to these morphological differences.Results: Results showed that body weight, carcass weight, and HG weight were lower in the SP and LP groups than that in MP group. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining showed that random DNA fragmentation was observed in all three groups. The protein expression of bax/bcl2 and cytochrome C all have no significant difference between three groups, indicated that the level of apoptosis remained stable. Protein aggregation and mRNA expression of LC3 as well as the protein expression of LC3II/LC3I in the SP group were higher than that in the MP group. P62 protein aggregates and protein expression were lower in long photoperiod than other two groups. These results suggested that autophagy level was the lowest in MP group. The protein expression of ATP synthase and mitochondrial fission factor showed highest in MD group, while citrate synthase, dynamin-related protein1, and fission1 remain unchanged during three groups. These indicate that the mitochondrion fission and energy function are slightly reduced in SD and LD groups.Conclusion: In summary, since the fact that there is no significant change in the level of apoptosis in HGs under different photoperiods, the significant up-regulation of autophagy level in the long and short photoperiod may be the main factor leading to the loss of HG weight as well as the reduced mitochondrial energy supply.