The pathogenesis of many inflammatory diseases is associated with the uncontrolled
activation of nuclear factor kappa B (NF-κB) in macrophages. Previous studies have shown that in
various cell types, heat shock protein 70 (Hsp70) plays a crucial role in controlling NF-κB activity.
So far, little is known about the role of Hsp70 in canine inflammatory processes. In this study we
investigated the potential anti-inflammatory effects of Hsp70 in canine macrophages as well as the
mechanisms underlying these effects. To this end, a canine macrophage cell line was stressed with
arsenite, a chemical stressor, which upregulated Hsp70 expression as detected by flow cytometry and
qPCR. A gene-edited version of this macrophage cell line lacking inducible Hsp70 was generated using
CRISPR-Cas9 technology. To determine the effects of Hsp70 on macrophage inflammatory properties,
arsenite-stressed wild-type and Hsp70 knockout macrophages were exposed to lipopolysaccharide
(LPS), and the expression of the inflammatory cytokines IL-6, IL-1β and tumor necrosis factor-α
(TNF-α) and levels of phosphorylated NF-κB were determined by qPCR and Western Blotting,
respectively. Our results show that non-toxic concentrations of arsenite induced Hsp70 expression in
canine macrophages; Hsp70 upregulation significantly inhibited the LPS-induced expression of the
pro-inflammatory mediators TNF-α and IL-6, as well as NF-κB activation in canine macrophages.
Furthermore, the gene editing of inducible Hsp70 by CRISPR-Cas9-mediated gene editing neutralized
this inhibitory effect of cell stress on NF-κB activation and pro-inflammatory cytokine expression.
Collectively, our study reveals that Hsp70 may regulate inflammatory responses through NF-κB
activation and cytokine expression in canine macrophages.