Glypican 1 and syndecan 1 differently regulate noradrenergic hypertension development: Focus on IP3R and calcium

Background: Vascular dysfunction is a checkpoint to the development of hypertension. Heparan sulfate proteoglycans (HSPG) participate in nitric oxide (NO) and calcium signaling, key regulators of vascular function. The relationship between HSPG-mediated NO and calcium signaling and vascular dysfunction has not been explored. Likewise, the role of HSPG on the control of systemic blood arterial pressure is unknown. Herein, we sought to determine if the HSPG syndecan 1 and glypican 1 control systemic blood pressure and the progression of hypertension. Purpose: To determine the mechanisms whereby glypican 1 and syndecan 1 regulate vascular tone and contribute to the development of noradrenergic hypertension. Experimental approach and key results: By assessing systemic arterial blood pressure we observed that syndecan 1 (Sdc1^-/-) and glypican 1 (Gpc1^-/-) knockout mice show a similar phenotype of decreased systolic blood pressure that is presented in a striking manner in the Gpc1^-/- strain. Gpc1^-/- mice are also uniquely protected from a norepinephrine hypertensive challenge failing to become hypertensive. This phenotype was associated with impaired calcium-dependent vasoconstriction and altered expression of calcium-sensitive proteins including SERCA and calmodulin. In addition, Gpc1^-/- distinctively showed decreased IP₃R activity and increased calcium storage in the endoplasmic reticulum. Conclusions and implications: Glypican 1 is a trigger for the development of noradrenergic hypertension that acts via IP₃R- and calcium-dependent signaling pathways. Glypican 1 may be a potential target for the development of new therapies for resistant hypertension or conditions where norepinephrine levels are increased.