Heat Shock Protein 70 Deficient Mice Exhibit Reduced Psoriasis-like Skin Inflammation

<b>Background/Objectives</b>: Psoriasis is a chronic, systemic, and multifactorial disease affecting approximately 1-2% of the Caucasian population. It is characterized by distinct histopathological features, including epidermal hyperplasia and infiltration of immune cells into the skin. Despite its high prevalence, the underlying mechanisms driving psoriasis remain incompletely understood. Heat shock proteins (HSPs), particularly HSP70, are known to play key roles in modulating immune responses and inflammation. Although previous studies have examined the involvement of HSPs in dermatological conditions such as psoriasis, current evidence remains inconclusive. In this study, we aimed to elucidate the role of <i>Hsp70</i> deficiency in the pathogenesis of psoriasis using an in vivo model. <b>Methods</b>: We used male mice that were either genetically normal (<i>Hsp70</i>+/+) or lacked the Hsp70 gene (<i>Hsp70</i>-/-) at 8-12 weeks of age. Psoriasis was induced by applying imiquimod cream daily for 7 days. At the end of this period mice were sacrificed and blood and tissue collected for further analysis. The severity of the psoriasis was evaluated daily using the PASI Score. <b>Results</b>: <i>Hsp70</i> depletion was accompanied by significantly decreased psoriatic-like skin inflammation, fewer histological abnormalities, and lower PASI scores. Flow cytometry analysis revealed a decrease in LY6C⁺ monocytes and an increase in LY6G⁺ neutrophils infiltration in <i>Hsp70</i>-deficient mice. In addition, HSP60 expression was lower in the absence of HSP70, while HSP90 expression was markedly elevated. <b>Conclusions</b>: These results point to a significant regulatory function of HSP70 in psoriatic inflammation and raise the possibility that it could be a therapeutic target.