Graduate Student Literature Review: Potential use of HSP70 as an indicator of heat stress in dairy cows—A review*

Abstract

ABSTRACT: Heat stress (HS) poses significant challenges to the dairy industry, resulting in reduced milk production, impaired reproductive performance, and compromised animal welfare. Therefore, understanding the molecular mechanisms underlying cellular responses to HS is crucial for developing effective strategies to mitigate its adverse effects. Heat shock protein 70 (HSP70) has emerged as a potential player involved in cellular thermotolerance in dairy cows. This review provides a comprehensive overview of the role of HSP70 as a molecular chaperone in cellular thermotolerance in dairy cows under HS. HSP70 facilitates proper protein folding and prevents the aggregation of denatured proteins. By binding to misfolded proteins, it helps maintain protein homeostasis and prevents the accumulation of damaged proteins during HS. Additionally, HSP70 interacts with various regulatory proteins and signaling pathways, contributing to the cellular adaptive response to HS. The upregulation of HSP70 expression in response to HS is regulated by a complex network involving heat shock factors (HSF), heat shock element-binding proteins, and HSF co-chaperones. Therefore, HSP70 holds the potential to be a useful indicator of tissue stress due to its role in maintaining cellular balance and because it is released both inside and outside cells in response to stress. Traditional methods of measuring HSP70 in blood samples are labor intensive, and because the process is potentially stressful for the animals, this may subsequently affect the results. Therefore, measuring HSP expression in cow milk has shown promise as an easy, noninvasive, and accurate way to detect HS in dairy cows. Monitoring HSP70 levels in milk can be applied as a supplementary approach to identify HS or HS resistance of individual cows, select suitable animals, and guide targeted management strategies. However, despite the potential advantages of using HSP70 as a biomarker for monitoring HS on dairy cows, challenges remain in standardizing measurement protocols, establishing species-specific reference ranges, addressing interindividual variations, and determining the specificity of changes in HSP70 due to HS. Future research should focus on developing noninvasive techniques for HSP70 detection, with consideration of climatic conditions and unraveling the molecular interactions and regulatory networks involving HSP70.

Keywords

• animal welfare
• biomarker
• ELISA
• heat shock protein
• milk