Increased eHSP70-to-iHSP70 ratio disrupts vascular responses to calcium and activates the TLR4-MD2 complex in type 1 diabetes.

AIMS: Vascular dysfunction is a clinical hallmark of diabetes. While various pathways drive vascular alterations in diabetes, many gaps persist in understanding this process. Heat-shock protein 70 (HSP70) has a long-recognized role in diabetes, but the contributions of HSP70 to the diabetic vasculature remain largely unknown. MAIN METHODS: We determined the systemic and local (aorta) levels of HSP70 in control (CTL) and streptozotocin (STZ)-induced diabetic rats. Functional studies were conducted in a wire myograph in the presence or absence of a pharmacological inhibitor for HSP70 (VER155008). Calcium (Ca2+) dynamics was indirectly evaluated as a function of change in force development in vehicle and VER-treated vessels, as well as in the presence of inhibitors for voltage-dependent and -independent plasmalemmal Ca2+ channels. Furthermore, mimicking the extracellular diabetic environment, we exposed aortic rings to serum from CTL and STZ-induced animals, which contains higher levels of HSP70, as well as to purified recombinant HSP70. Then, we performed functional studies following the modulation of Toll-like receptor 4 (TLR4) and its co-adaptor MD2, which interact with HSP70. KEY FINDINGS: HSP70 plays a dual role in diabetes-induced vascular dysfunction: intracellular (i)HSP70 affects Ca2+ handling mechanisms, and extracellular (e)HSP70 modulates the TLR4-MD2 complex. SIGNIFICANCE: These newly discovered roles of HSP70 push forward the field of vascular biology and open research avenues for other diseased states associated with altered vascular responses.