Blockade of HSP70 Improves Vascular Function in a Mouse Model of Type 2 Diabetes

Type 2 diabetes (T2D) is a chronic disease that damages blood vessels and increases the risk of cardiovascular disease (CVD). Heat-shock protein 70 (HSP70), a family of chaperone proteins, has been recently reported as a key player in vascular reactivity that affects large blood vessels like the aorta. Hyperglycemia, a hallmark of diabetes, correlates with the severity of vascular damage and circulating HSP70 levels. In diabetes, blood vessels often show impaired contractility, contributing to vascular dysfunction. However, HSP70's specific role in T2D-related vascular contraction remains unclear. We hypothesized that blocking HSP70 would improve vascular function in a widely used diabetic mouse model (db/db). To test this, we measured both vascular intracellular and serum circulating HSP70 levels in control and diabetic male mice using immunofluorescence and Western blotting. We also examined the aorta's contractile response using a wire myograph system, which measured the force produced in response to phenylephrine (PE), both with and without VER155008, a pharmacological inhibitor that targets the ATPase domain of HSP70, and after removing extracellular calcium. Our findings show that intracellular HSP70 (iHSP70) levels were similar in control and diabetic groups, while circulating HSP70 (eHSP70) levels were higher in the serum of diabetic mice, altering the iHSP70/eHSP70 ratio. Even though VER155008 attenuated both phases of the contractile curve in the diabetic and control groups, enhanced vasoconstriction to PE was only observed in the tonic phase of the curve in the db/db group, which was prevented by iHSP70 inhibition. This effect involved calcium mobilization, as both the maximal and total contraction forces to PE were restored in groups treated with VER155008. Additionally, internal calcium levels in aortic rings treated with VER155008 decreased, as observed in force generation upon calcium reintroduction, which was further corroborated using a biochemical calcium assay. In conclusion, our study demonstrates that blocking HSP70 improves vascular reactivity in the hyperglycemic state of T2D by restoring proper vascular contraction.