# Proteomic Analysis of Differentially Expressed Plasma Exosome Proteins in Heat-Stressed Holstein cows

## TL;DR

This study identifies proteins in exosomes from heat-stressed cows that could serve as biomarkers for heat stress, offering insights into how cows respond to high temperatures.

## Contribution

The study reveals novel differentially expressed exosomal proteins and their roles in heat stress response pathways in Holstein cows.

## Key findings

- 28 upregulated and 18 downregulated proteins were identified in plasma exosomes from heat-stressed cows.
- Cytoskeletal, signaling, and coagulation proteins were significantly upregulated, while HP-25_1 was downregulated.
- Differentially expressed proteins were enriched in actin cytoskeleton regulation, endoplasmic reticulum stress, and PI3K-Akt signaling pathways.

## Abstract

Heat stress in dairy cows during summer reduces milk production and causes economic losses. Using proteomics, we analyzed plasma exosomes from heat-stressed (HS) and non-heat-stressed (Ctr) cows. Among 46 differentially expressed proteins, cytoskeletal, signaling, and coagulation protein groups were significantly upregulated, and HP-25_1 was downregulated, suggesting their utility as heat stress biomarkers in dairy cattle. Bioinformatic analyses found these differentially expressed proteins enriched in actin cytoskeleton regulation, endoplasmic reticulum stress, and PI3K-Akt signaling pathways. In summary, this work highlights plasma exosomes’ utility for heat stress and provides valuable insights into the molecular mechanisms of heat stress response.

Heat stress in dairy cows, caused by high temperature and humidity during summer, has led to significant declines in milk production and severe economic losses for farms. Exosomes—extracellular vesicles carrying bioactive molecules—are critical for intercellular communication and immunity but remain understudied in heat-stressed Holstein cows. In this study, we extracted exosomes from three heat-stressed (HS) cows and three non-heat-stressed (Ctr) cows and employed proteomics to analyze plasma exosomes. We identified a total of 28 upregulated and 18 downregulated proteins in the HS group compared to the control group. Notably, we observed a significant upregulation of key protein groups, including cytoskeletal regulators, signaling mediators, and coagulation factors, alongside the downregulation of HP-25_1. These differentially expressed proteins demonstrate strong potential as heat stress biomarkers. GO and KEGG analyses linked the differentially expressed proteins to actin cytoskeleton regulation and endoplasmic reticulum pathways. Additionally, protein–protein interaction (PPI) analysis revealed the PI3K-Akt signaling pathway as a central node in the cellular response to heat stress. These findings establish plasma exosomes as valuable biospecimens, provide valuable insights into the molecular mechanisms of heat stress response, and may contribute to the development of precision breeding strategies for enhanced thermal resilience in dairy herds.