# Targeted Regulation of HSP70 by the ARP2/3 Complex in Mammary Epithelial Cells and Its Impact on Host Cell Apoptosis

## TL;DR

This study explores how the ARP2/3 complex regulates HSP70 in mammary cells during inflammation, affecting cell death and offering a potential treatment target for mastitis.

## Contribution

The study reveals a novel functional relationship between ARPC3/ARPC4 and HSP70 in regulating apoptosis during mammary epithelial inflammation.

## Key findings

- ARPC3/ARPC4 and HSP70 are significantly upregulated during mammary epithelial cell inflammation.
- Inhibiting ARPC3/ARPC4 with CK666 increases HSP70 expression and reduces inflammation and apoptosis.
- Targeting ARPC3/ARPC4 to regulate HSP70 may serve as a therapeutic strategy for mastitis.

## Abstract

Mastitis is frequently triggered by the bacterial disruption of the epithelial cell barrier. The actin-related protein 2/3 complex (Arp2/3), a major endogenous protein involved in cytoskeletal regulation, plays a crucial role in preserving epithelial barrier integrity during inflammation; however, its specific role in mastitis progression remains unclear. This study aims to use lipopolysaccharide (LPS) to establish mammary alveolar cells-large T antigen cells (MAC-T is a bovine mammary epithelial cell line) and mouse models of mastitis, investigating the functional relationship between actin-related protein 2/3 complex subunits 3 (ARPC3) and 4 (ARPC4) and heat shock protein 70 (HSP70) during mammary epithelial cell inflammation and assessing its effects on apoptosis. Transcriptomic sequencing initially identified 48 differentially expressed genes associated with the bacterial invasion of epithelial cells and apoptosis. Further molecular biology analyses showed a significant upregulation of ARPC3/ARPC4 and HSP70 expression during inflammation, along with a marked increase in apoptosis rates. When ARPC3/ARPC4 was inhibited using CK666, HSP70 expression further increased compared to the LPS group, while inflammatory factors, apoptosis rates, and apoptosis-related protein expression were notably reduced. These findings indicate that targeting ARPC3/ARPC4 to regulate HSP70 can promote inflammation and apoptosis, highlighting its potential as a therapeutic target for mastitis.