Selenium-Rich Diet Induces Myocardial Structural and Functional Abnormalities by Activating Caspase-9 and Caspase-3 in Gpx-1P198L-Overexpression Transgenic Mice

Abstract

BACKGROUND Selenium (Se) deficiency and supplementation result in multiple effects. GPx-1 (Pro198Leu) polymorphism is associated with Se deficiency. This study aimed to observe associations between Se-deficiency/supplement and GPx-1-198Leu overexpression in myocardial injuries. MATERIAL AND METHODS GPx-1P198L transgenic (Tg) mice and non-transgenic wild-type (WT) littermates were divided into Control (CON, 0.1-0.2 mg/kg), Se-deficiency (SD, <0.02 mg/kg), and Se-supplement (SS, 0.4 mg/kg) groups. Cardiac functions were observed with animal M-mode echocardiography. Se level was measured using 2,3-diamino Kenai fluorospectrophotometry. Total cardiac GPx activity was also measured. Myocardial histopathology was determined with HE and Masson's trichrome staining. Caspase-9 and caspase-3 were measured with Western blot analysis. RESULTS In WT Se-deficient mice, cardiac GPx activity was significantly decreased, and was not elevated by overexpression of GPx-1-198Leu gene. Increased GPx activity was observed in WT Se-supplemented mice and Tg Se-supplemented mice (much more). Se deficiency as well as supplementation resulted in cardiac systolic dysfunction, which was not affected by GPx-1-198Leu gene. Se deficiency led to myocardial fibrosis and pathological changes accompanied by increased activation of caspase-9 and caspase-3. Se supplementation significantly reduced pathological changes, as well as caspase-9 and caspase-3 levels in the presence of increased myocardial fibrosis. In Se-deficient mice, GPx-1-198Leu overexpression did not significantly decrease myocardial pathological injuries and fibrosis. In Se-supplemented Tg mice, myocardial fibrosis and caspase-9 level were increased, although pathological injuries and caspase-3 were similar to that in Se-supplemented WT mice. CONCLUSIONS Se deficiency as well as supplementation induced myocardial structural and functional abnormalities through activation of caspase-9 and caspase-3 in GPx-1P198L overexpression transgenic mice.

Figure 1

Effect of different diets on serum Se level in each group. (A) Effect on serum Se level. (B) Effect on cardiac GPx activity. WTCON – wild-type control mice, WTSD – wild-type Se-deficient mice, WTSS – wild-type Se-supplemented mice, TgCON – transgenic control mice, TgSD – transgenic Se-deficient mice, TgSS – transgenic Se-supplemented mice. * p<0.0001 vs. WTCON, WTSS, ^# p<0.0001 vs. TgCON, TgSS.

Figure 2

Effect of different diets on cardiac GPx activity in each group. WTCON – wild-type control mice, WTSD – wild-type Se-deficient mice, WTSS – wild-type Se-supplemented mice, TgCON – transgenic control mice, TgSD – transgenic Se-deficient mice, TgSS – transgenic Se-supplemented mice. * p<0.05 vs. WTCON, ** p<0.05 vs. WTCON, WTSD; ^& p<0.05 vs. TgCON, ^# p<0.05 pTgCON, TgSD, WTSS.

Figure 3

M-mode echocardiography of mice in each group. (A) Wild-type control mice. (B) Wild-type Se-deficient mice. (C) Wild-type Se-supplemented mice. (D) Transgenic control mice. (E) Transgenic Se-deficient mice. (F) Transgenic Se-supplemented mice.

Figure 4

Myocardial HE staining of mice in each group. (A) Wild-type control mice. (B) Wild-type Se-deficient mice. (C) Wild-type Se-supplemented mice. (D) Transgenic control mice. (E) Transgenic Se-deficient mice. (F) Transgenic Se-supplemented mice. Scar bar=100 μm.

Figure 5

Masson’s trichrome staining and statistical analysis of mice in each group. (A) Wild-type control mice. (B) Wild-type Se-deficient mice. (C) Wild-type Se-supplemented mice. (D) Transgenic control mice. (E) Transgenic Se-deficient mice. (F) Transgenic Se-supplemented mice. (G) Comparison of interstitial fibrosis of mice in each group. WTCON – wild-type control mice, WTSD – wild-type Se-deficient mice, WTSS – wild-type Se-supplemented mice, TgCON – transgenic control mice, TgSD – transgenic Se-deficient mice, TgSS – transgenic Se-supplemented mice. * P<0.05 vs. WTCON, ** P<0.05 vs. WTCON, TgSS, ^# P<0.05 vs. TgCON. Scar bar=100 μm.

Figure 6

Expression level of caspase-9 in each group. (A) Image results of caspase-9. (B) Relative expression level of caspase-9. W1 – wild-type control mice, W2 – wild-type Se-deficient mice, W3 – wild-type Se-supplemented mice, T1 – transgenic control mice, T2 – transgenic Se-deficient mice, T3 – transgenic Se-supplemented mice. * P<0.05 vs. W1; ** P<0.05 vs. W1, W2, ^& P<0.05 vs. W2, T1; ^# P<0.05 vs. W3, T1, T2.

Figure 7

Expression level of caspase-3 in each group. (A) Image results of caspase-9. (B) Relative expression level of caspase-3. W1 – wild-type control mice, W2 – wild-type Se-deficient mice, W3 – wild-type Se-supplemented mice, T1 – transgenic control mice, T2 – transgenic Se-deficient mice, T3 – transgenic Se-supplemented mice. * P<0.05 vs. W1, W3, ^# P<0.05 vs. T1, T3.