Novel ultrastructural findings on cardiac mitochondria of huddling Brandt's voles in mild cold environment

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2020-11, Vol.249, p.110766-110766, Article 110766
• Main Authors: Wang, Zhe, Xu, Jin-hui, Mou, Jun-jie, Kong, Xiao-tong, Zou, Jian-wen, Xue, Hui-liang, Wu, Ming, Xu, Lai-xiang
• Format: Article
• Language: English
• Subjects: Apoptosis; Heart; Huddling; Low temperature; Mitochondrial autophagy; Mitochondrial fission
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2020.110766

Reduced ambient temperature has a damaging effect on mammalian myocardium. Huddling as a cooperative behavior has evolved in social mammals as a strategy to maximize adaptation to environmental cooling. Here, we studied the effects of huddling behavior on mitochondrial morphology, number, and function in the myocardia of Brandt's voles (Lasiopodomys brandtii) under cool environmental temperatures (15 °C). Results showed (1) mitochondrial swelling and cristae disruption in the cool huddling group (CH) and cool separated group (CS). Compared to the control group (CON, 22 °C), damaged mitochondria in the cool huddling and separated groups reached >90%; however, total number of mitochondria in the CH group was similar to that in the CON group. (2) ATP synthase activity was lowest in the CS group, whereas citrate synthetase activity was maintained among the three treatment groups. (3) Bax/bcl2 protein expression in the CH and CS groups was higher than that in the CON group, whereas DNA fragmentation, nuclear number, and caspase3 activity showed no significant differences among the three groups. (4) The protein expression levels of dynamin-related protein1 and mitochondrial fission factor were highest in the CH group. (5) Both protein expression of PINK1 and phosphorylation ratio of Parkin showed the pattern CS > CH > CON. (6) Total number of mitochondria was higher in males than in females. In general, the increased mitochondrial fission level observed in huddling voles partially counteracted the decrease in myocardial mitochondria caused by the increase in autophagy. •A cool environment led to damage of myocardial mitochondria and reduction of mitochondrial number in voles, which could be partially alleviated by huddling behavior.•The increased mitochondrial fission level in huddling voles partly counteracted the decrease in myocardial mitochondria caused by the increase in autophagy.•Bax-induced mitochondrial structural damage and increased autophagy were identified as common mechanisms related to the reduction in myocardial mitochondria in voles under a cool environment, and the increase in mitochondrial fission may be one of the mechanisms used to alleviate the decrease in mitochondrial number.•Mitochondrial energy supply were higher in huddling voles than in separated voles, which may be an adaptive change caused by the collective overwintering behavior of socialized animals.