Atorvastatin Improves Ventricular Remodeling after Myocardial Infarction by Interfering with Collagen Metabolism

Abstract

Purpose: Therapeutic strategies that modulate ventricular remodeling can be useful after acute myocardial infarction (MI). In particular, statins may exert effects on molecular pathways involved in collagen metabolism. The aim of this study was to determine whether treatment with atorvastatin for 4 weeks would lead to changes in collagen metabolism and ventricular remodeling in a rat model of MI.

Methods: Male Wistar rats were used in this study. MI was induced in rats by ligation of the left anterior descending coronary artery (LAD). Animals were randomized into three groups, according to treatment: sham surgery without LAD ligation (sham group, n = 14), LAD ligation followed by 10mg atorvastatin/kg/day for 4 weeks (atorvastatin group, n = 24), or LAD ligation followed by saline solution for 4 weeks (control group, n = 27). After 4 weeks, hemodynamic characteristics were obtained by a pressure-volume catheter. Hearts were removed, and the left ventricles were subjected to histologic analysis of the extents of fibrosis and collagen deposition, as well as the myocyte cross-sectional area. Expression levels of mediators involved in collagen metabolism and inflammation were also assessed.

Results: End-diastolic volume, fibrotic content, and myocyte cross-sectional area were significantly reduced in the atorvastatin compared to the control group. Atorvastatin modulated expression levels of proteins related to collagen metabolism, including MMP1, TIMP1, COL I, PCPE, and SPARC, in remote infarct regions. Atorvastatin had anti-inflammatory effects, as indicated by lower expression levels of TLR4, IL-1, and NF-kB p50.

Conclusion: Treatment with atorvastatin for 4 weeks was able to attenuate ventricular dysfunction, fibrosis, and left ventricular hypertrophy after MI in rats, perhaps in part through effects on collagen metabolism and inflammation. Atorvastatin may be useful for limiting ventricular remodeling after myocardial ischemic events.

Fig 1. Histological Images Showing LVs of Animals in the Three Groups.

Sham (A and D), control (B and E), and atorvastatin groups (C and F). Sections were stained with Masson trichrome for fibrosis analysis (top) or Picro Sirius red for collagen analysis (bottom). Scale bars: 1000μm. Histograms show that the percentage of fibrosis in the LV was reduced after treatment with atorvastatin (white), without affecting the collagen content, compared to the control group (black). Sham group (gray) showed less collagen deposition compared to the atorvastatin and control groups. Data are expressed as the mean ± SD. *P<0.05 versus sham group, #P<0.05 versus control group.

Fig 2. Fibrosis and Collagen Levels in Remote Regions of the LV after MI.

Histogram shows that treatment with atorvastatin (white) did not reduce the deposition of fibrosis or collagen compared to the control group (black). Fibrosis content was reduced in animals from the sham group (gray) compared to animals subjected to MI (atorvastatin and control groups). Data are expressed as the mean ± SD. *P<0.05 versus sham group. Data are representative of 14 animals per group.

Fig 3. Myocyte Cross-sectional Areas in Remote Regions of LV Infarcts.

Images correspond to sham (A), control (B), and atorvastatin groups (C). Scale bars: 100μm. Sections were stained with H&E. Seventy cells were analyzed per plate (n = 14 animals per group). Data are expressed as the mean ± SD. *P<0.05 versus sham group, #P<0.05 versus control group.

Fig 4. Immunoblotting Results for Expression Levels of Proteins Related to Collagen Metabolism in Remote Regions of LV Infarcts.

Representative blots for expression levels of each studied protein. Bands corresponding to each protein (top) were normalized by Ponceau staining (red bands on bottom). Histograms show expression levels determined by densitometry. Data are expressed as the mean ± SD. *P<0.05 versus sham group; #P<0.05 versus control group. Data are representative of nine animals per group.

Fig 5. Immunoblotting Results for Expression Levels of Proteins Related to Inflammatory Processes in Remote Regions of LV Infarcts.

Representative blots for expression levels of studied proteins. Signs of bands corresponding to phosphorylated IκBα (top) were normalized by total IκBα expression (bottom). Signs of bands corresponding to Tenascin-C (TN-C), TLR2, and TLR4 (top) were normalized by Ponceau staining (red bands on bottom). Histograms show expression levels determined by densitometry. Data are expressed as the mean ± SD. *P<0.05 versus sham group, ^#P<0.05 versus control group. Data are representative of nine animals per group.

Fig 6. Quantitative PCR Results for mRNA Levels of Genes Related to Inflammatory Processes.

Expression levels were normalized using actin as a reference gene. Data are expressed as mean ± SD.*P<0.05 versus sham group, #P<0.05 versus control group. Data representative of 8 animals in each group.