Effect of hyperthermia on cell viability, amino acid transfer, and milk protein synthesis in bovine mammary epithelial cells

Jia Zhou¹, Shungming Yue², Benchu Yue¹, Zhisheng Wang¹, Lizhi Wang¹, Quanhui Peng¹, Rui Hu¹, Bai Xue¹^,^*

¹Sichuan Agricultural University, Chengdu 611130, China.

²Sichuan Water Conservancy Vocation College, Chengdu 611845, China.

^*Corresponding Author: Bai Xue, Sichuan Agricultural University, Chengdu 611130, China. E-mail: xuebai@sicau.edu.cn.

© Copyright 2021 Korean Society of Animal Science and Technology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Sep 19, 2021; Revised: Nov 08, 2021; Accepted: Nov 16, 2021

Published Online: Dec 10, 2021

Abstract

The reduction of milk yield caused by heat stress in summer is the main condition restricting the economic benefits of dairy farms. To examine the impact of hyperthermia on bovine mammary epithelial (MAC-T) cells, we incubated the MAC-T cells at thermal-neutral (37°C, CON group) and hyperthermic (42°C, HS group) temperatures for 6 h. Subsequently, the cell viability and apoptotic rate of MAC-T cells, apoptosis-related genes expression, casein and amino acid transporter genes, and the expression of the apoptosis-related proteins were examined. Compared with the CON group, hyperthermia significantly decreased the cell viability (<italic>p</italic><0.05) and elevated the apoptotic rate (<italic>p</italic><0.05) of MAC-T cells. Moreover, the expression of <italic>HSP70</italic>, <italic>HSP90B1</italic>, <italic>BAX</italic>, <italic>Caspase-9,</italic> and <italic>Caspase-3</italic> genes was upregulated (<italic>p</italic><0.05). The expression of HSP70 and BAX (pro-apoptotic) proteins was upregulated (<italic>p</italic><0.05) while that of BCL2 (antiapoptotic) protein was downregulated (<italic>p</italic><0.05) by hyperthermia. Decreased mRNA expression of mTOR signaling pathway-related genes, amino acid transporter genes (<italic>SLC7A5</italic>, <italic>SLC38A3</italic>, <italic>SLC38A2</italic>, and<italic> SLC38A9</italic>), and casein genes (<italic>CSNS1</italic>, <italic>CSN2</italic>, and<italic> CSN3</italic>) was found in the HS group <italic>(p</italic><0.05) in contrast with the CON group. These findings illustrated that hyperthermia promoted cell apoptosis and reduced the transport of amino acids into cells, which inhibited the milk proteins synthesis in MAC-T cells.

Keywords: hyperthermia; heat stress; apoptosis; milk protein synthesis; amino acid transport