Aromatase inhibition increases blood pressure and markers of renal injury in female rats

Abstract

Aromatase is a monooxygenase that catalyzes the rate-limiting step of estrogen biosynthesis from androgens. Aromatase inhibitors are widely used for the treatment of patients with hormone receptor-positive breast cancer. However, the effects of aromatase inhibitors on cardiovascular and renal health in females are understudied. Given that estrogen is protective against cardiovascular and kidney diseases, we hypothesized that aromatase inhibition elevates blood pressure and induces kidney injury in female Sprague-Dawley rats. Twelve-week-old female rats were implanted with radiotelemetry transmitters to continuously monitor blood pressure. After baseline blood pressure recording, rats were randomly assigned to treatment with the aromatase inhibitor anastrozole (ASZ) or vehicle (Veh) in drinking water. Twenty days after treatment initiation, rats were shifted from a normal-salt (NS) diet to a high-salt (HS) diet for an additional 40 days. Rats were euthanized 60 days after treatment initiation. Body weight increased in both groups over the study period, but the increase was greater in the ASZ-treated group than in the Veh-treated group. Mean arterial pressure increased in ASZ-treated rats during the NS and HS diet phases but remained unchanged in Veh-treated rats. In addition, urinary excretion of albumin and kidney injury marker-1 and plasma urea were increased in response to aromatase inhibition. Furthermore, histological assessment revealed that ASZ treatment increased morphological evidence of renal tubular injury and proximal tubular brush border loss. In conclusion, chronic aromatase inhibition in vivo with ASZ increases blood pressure and markers of renal proximal tubular injury in female Sprague-Dawley rats, suggesting an important role for aromatization in the maintenance cardiovascular and renal health in females.NEW & NOTEWORTHY Aromatase enzyme catalyzes the rate-limiting step in estrogen biosynthesis. Aromatase inhibitors are clinically used for the treatment of patients with breast cancer; however, the impact of inhibiting aromatization on blood pressure and renal function is incompletely understood. The present findings demonstrate that systemic anastrozole treatment increases blood pressure and renal tubular injury markers in female rats fed a high-salt diet, suggesting an important role for aromatization in preserving cardiovascular and renal health in females.

Keywords: anastrozole; dietary sodium; estrogen; hypertension; proximal tubule.

Graphical abstract

Figure 1.

Experimental timeline. ASZ, anastrozole; SD, Sprague–Dawley.

Figure 2.

Aromatase inhibition increases body weight gain and decreases uterus weight in female rats. Body weight (A), uterus weight (B), and the relative uterus weight-to-body weight ratio (C) were measured in female Sprague–Dawley rats treated with anastrozole (ASZ) or vehicle (Veh) in drinking water throughout the normal-salt (NS) and high-salt (HS) diet periods. White and gray bars represent the NS and HS diet periods, respectively. Data are presented as means ± SE; n = 8 rats/group. Statistical comparisons were performed by repeated-measures two-way ANOVA with a Sidak’s post hoc test for multiple comparisons (A) and an unpaired t test (B and C). ANOVA results: P_interaction = 0.1268, P_ASZ = 0.0233, and P_diet <0.0001.

Figure 3.

Plasma sex hormonal levels in anastrozole (ASZ)-treated female rats. Plasma estrone (E₁; A), estradiol (E₂; B), testosterone (C), and the E₂-to-testosterone ratio (D) were measured in high-salt diet-fed female Sprague–Dawley rats treated with ASZ or vehicle (Veh) in drinking water for 60 days. Data are presented as means ± SE; n = 8 rats/group. Statistical comparisons were performed by an unpaired t test.

Figure 4.

Aromatase inhibition elevates blood pressure in female rats. Twenty-four-hour mean arterial pressure (A) and the change in mean arterial pressure from day 0 to day 60 (B) were measured in female Sprague–Dawley rats treated with anastrozole (ASZ) or vehicle (Veh) in drinking water throughout the normal-salt (NS) and high-salt (HS) diet periods. White and gray bars represent NS and HS diet periods, respectively. Data are presented as means ± SE; n = 8 rats/group. Statistical comparisons were performed by repeated-measures two-way ANOVA with a Sidak’s post hoc test for multiple comparisons (A) and an unpaired t test (B). ANOVA results: P_interaction = 0.0009, P_ASZ = 0.0615, and P_time < 0.0001.

Figure 5.

Aromatase inhibition increases albuminuria and plasma urea in high-salt (HS) diet-fed female rats. Urinary excretion of protein (A) and albumin (B) were measured in female Sprague–Dawley rats treated with anastrozole (ASZ) or vehicle (Veh) in drinking water throughout the normal-salt (NS) and HS diet periods. White and gray bars represent NS and HS diet periods, respectively. C: plasma urea was measured in HS diet-fed female Sprague–Dawley rats treated with ASZ or Veh in drinking water for 60 days. Data are presented as means ± SE; n = 8 rats/group. Statistical comparisons were performed by repeated-measures two-way ANOVA with a Sidak’s post hoc test for multiple comparisons (A and B) and an unpaired t test (C). ANOVA results: P_interaction = 0.4008, P_ASZ = 0.2727, and P_diet = 0.0292 for protein and P_interaction = 0.1709, P_ASZ = 0.2269, and P_diet = 0.0181 for albumin.

Figure 6.

Aromatase inhibition promotes renal cortical tubular injury in high-salt (HS) diet-fed female rats. A and B: urinary excretion of kidney injury molecule-1 (KIM-1; A) and nephrin (B) measured in HS diet-fed female Sprague–Dawley rats treated with anastrozole (ASZ) or vehicle (Veh) in drinking water. C and D: quantification of the extent of renal tubular injury in the cortical region (C) and calculated percentage of the tubular dilation and brush border loss within the renal cortex (D) in HS diet-fed female Sprague–Dawley rats treated with ASZ or Veh in drinking water. E and F, left: representative images of the proximal tubule and brush border integrity within the renal cortex of Veh-treated (E) and ASZ-treated (F) female Sprague–Dawley rats. Areas indicated by squares in D and E are shown at higher magnification on the right. Data are presented as means ± SE; n = 8 rats/group. Statistical comparisons were performed by repeated-measures two-way ANOVA with a Sidak’s post hoc test for multiple comparisons (A) and an unpaired t test (B and C). ANOVA results: P_interaction = 0.6982, P_ASZ = 0.0428, and P_time = 0.1661 for KIM-1 and P_interaction = 0.4316, P_ASZ = 0.9872, and P_time = 0.1242 for nephrin. Original magnification: ×20.