Dose-dependent toxic effects of high-dose estrogen on renal and cardiac injury in surgically postmenopausal mice

Abstract

Aims: We previously found that in mice with experimental myocardial infarction (MI), 17β-estradiol (E2) increased mortality and worsened cardiac remodeling and these deleterious effects were associated with renal enlargement and hydronephrosis in a dose-dependent manner. In the present study we questioned whether E2-induced renal damage predisposes to rather than results from its adverse effects on the heart.

Main methods: Ovariectomized (ovx) mice received either placebo (P) or E2 at 0.02 (E2-L, low dose), 0.42 (E2-M, moderate dose) or 4.2 μg/d (E2-H, high dose) for 8 weeks.

Key findings: E2-L partially restored uterine weight and plasma estrogen levels without affecting heart, lung and liver weight, hemodynamic parameters, or heart and kidney morphology and function. E2-M restored normal uterine weight, but this was accompanied by a significant increase in kidney weight, albuminuria, glomerular matrix formation and markers for oxidative stress. E2-H increased uterine weight 4.5-fold and resulted in higher plasma creatinine levels, severe albuminuria, renal tubular dilatation, tubulointerstitial injury, hydronephrosis, glomerulosclerosis and oxidative stress. E2-H also caused ascites, hepatomegaly and fluid retention in the uterine horns but had no significant effect on blood pressure or heart function.

Significance: Our data demonstrated that an excessive dose of E2 that raises uterine weight beyond physiological levels adversely affects the kidney even before it damages the heart. We believe estrogen dosage should be taken into account when considering hormonal replacement therapy, since inappropriate doses of E2 may damage not only the heart but also the kidney.

Figure 1

Dose-effect of 17β-estradiol (E2) replacement on plasma estrogen levels (A) and uterine weight corrected by body weight (UW/BW) (B) in ovariectomized (ovx) mice. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose(all doses given for 8 weeks).

Figure 2

Dose-effect of 17β-estradiol (E2) replacement on kidney weight corrected by body weight (KW/BW) (A), 24-hr urine volume (B), and 24-hr urinary albumin excretion (C) in ovariectomized (ovx) mice. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.

Figure 3

Dose-effect of 17β-estradiol (E2) replacement on plasma creatinine (A) and creatinine clearance (CrCl) (B) in ovariectomized (ovx) mice. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.

Figure 4

Dose-effect of 17β-estradiol (E2) replacement on renal tubule dilatation in ovariectomized (ovx) mice. Left panels: representative images showing E2-induced tubular dilatation (seen mostly with high-dose E2) (E). Right panel: number of mice exhibiting tubular dilatation in each treatment group. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.

Figure 5

Dose-effect of 17β-estradiol (E2) replacement on glomerulosclerosis in ovariectomized (ovx) mice. Left panels: representative images showing E2-induced increase in glomerular matrix (dark purple-stained area seen with periodic acid-Schiff staining). Right panel: quantitative analysis of E2-induced glomerulosclerosis. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.

Figure 6

Dose-effect of 17β-estradiol (E2) replacement on tubulointerstitial injury score. Left panels: representative images ofhigh -dose E2-induced tubulointerstitialinjury; A: dilated tubules combined with flattened epithelial cells, loss of the brush border, dead cells and/or cell fragments and casts in the lumen as well as increased distance between two neighboring tubules; B: interstitial fibrosis (picrosirius red staining); and C: renal calcium deposition (von Kassa staining, showing dark calcium crystals using a dark filed and polarized light). s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.

Figure 7

Dose-effect of 17β-estradiol (E2) replacement on Nox2 protein expression (A) and urinary 8-isoprostane excretion (B) in ovariectomized (ovx) mice. s-ovx: sham ovariectomy; pl: placebo; 0.02 μg/day: E2-low dose; 0.42 μg/day: E2-moderate dose; 4.2 μg/day: E2-high dose.