Sarcoplasmic Reticulum Calcium ATPase (SERCA) proteolysis by matrix metalloproteinase-2 contributes to vascular dysfunction in early hypertension.

AIMS: Hypertension is associated with an increased activity of matrix metalloproteinase (MMP)-2 in the vasculature, which, in turn, proteolyzes extra- and intracellular proteins that lead to vascular dysfunction. The activity of sarcoplasmic reticulum calcium ATPase (SERCA) is decreased in the aortas of hypertensive rats. Increased activity of MMP-2 proteolyzed SERCA in rat heart during ischemia and reperfusion injury, thus impairing cardiac function. Therefore, we examined whether increased activity of MMP-2 in early hypertension contributes to proteolyze SERCA in the aortas, thus leading to maladaptive vascular remodeling and dysfunction.

MAIN METHODS: Male Sprague-Dawley rats were submitted to two kidney-one clip (2K-1C) or Sham surgery and treated with doxycycline. Systolic blood pressure (SBP) was assessed by tail-cuff plethysmography. After 7 days, aortas were collected for zymography assays, western blot to SERCA, ATPase activity assay, vascular reactivity, Ki-67 immunofluorescence and hematoxylin/eosin stain.

KEY FINDINGS: SBP was increased in 2K-1C rats and doxycycline did not reduce it, but decreased MMP-2 activity and prevented SERCA proteolysis in aortas. Cross sectional area, media to lumen ratio and Ki-67 were all increased in the aortas of hypertensive rats and doxycycline decreased Ki-67. In 2K-1C rats, arterial relaxation to acetylcholine was impaired and doxycycline ameliorated it.

SIGNIFICANCE: doxycycline reduced MMP-2 activity in aortas of 2K-1C rats and prevented proteolysis of SERCA and its dysfunction, thus ameliorating hypertension-induced vascular dysfunction.