Effects of Long-Term Intervention with Losartan, Aspirin and Atorvastatin on Vascular Remodeling in Juvenile Spontaneously Hypertensive Rats

Abstract

Hypertension in adolescents is associated with adverse cardiac and vascular events. In addition to lowering blood pressure, it is not clear whether pharmacological therapy in early life can improve vascular remodeling. This study aimed to evaluate the effects of long-term administration of losartan, aspirin, and atorvastatin on vascular remodeling in juvenile spontaneously hypertensive rats (SHRs). Losartan, aspirin, and atorvastatin were administered via gavage at doses of 20, 10, and 10 mg/kg/day, respectively, on SHRs aged 6-22 weeks. Paraffin sections of the blood vessels were stained with hematoxylin-eosin (H&E) and Sirius Red to evaluate the changes in the vascular structure and the accumulation of different types of collagen. The plasma levels of renin, angiotensin II (Ang II), aldosterone (ALD), endothelin-1 (ET-1), interleukin-6 (IL-6), and neutrophil elastase (NE) were determined using ELISA kits. After the 16-week treatment with losartan, aspirin, and atorvastatin, the wall thickness of the thoracic aorta and carotid artery decreased. The integrity of the elastic fibers in the tunica media was maintained in an orderly manner, and collagen deposition in the adventitia was retarded. The plasma levels of renin, ALD, ET-1, IL-6, and NE in the SHRs also decreased. These findings suggest that losartan, aspirin, and atorvastatin could improve vascular remodeling beyond their antihypertensive, anti-inflammatory, and lipid-lowering effects. Many aspects of the protection provided by pharmacological therapy are important for the prevention of cardiovascular diseases in adults and older adults.

Keywords: aspirin; atorvastatin; juvenile SHR; losartan; vascular remodeling.

Figure 1

The histological morphological changes in thoracic aorta in each group (22 weeks rats). (A) H&E stain in cross section of thoracic aortas. (scale bar = 300 μm); (B) magnified images of (A) (scale bar = 50 μm); (C) wall thickness (WT), wall-to-lumen ratio (WLR), inner diameter (ID) and number of VSMCs (VSMC) in tunica media, respectively. The data are presented as the mean ± SD. n = 6, ^## p < 0.01 vs. WKY; * p < 0.05, ** p < 0.01 vs. SHR-M.

Figure 2

The histological morphological changes in carotid aorta in each group (22 weeks rats). (A) H&E stain in cross section of carotid aortas. (scale bar = 200 μm); (B) magnified images of (A) (scale bar = 100 μm); (C) wall thickness (WT), wall-to-lumen ratio (WLR), inner diameter (ID), and number of VSMCs (VSMC) in tunica media, respectively. The data are presented as the mean ± SD. n = 6, ^## p < 0.01 vs. WKY; * p < 0.05, ** p < 0.01 vs. SHR-M.

Figure 3

Thoracic aortas (A,B) or carotid arteries (C,D) elastin by H&E stain under fluorescence microscope showed intense red autofluorescence (22 weeks rats). (B,D) are enlarged views of (A,C), respectively (A: scale bar = 300 μm; B: scale bar = 50 μm; C: scale bar = 200 μm; D: scale bar = 50 μm); (E) counts of link across elastin fiber layers in thoracic aortas; (F) counts of link across elastin fiber layers in carotid arteries. The data are presented as the mean ± SD. n = 6, ^## p < 0.01 vs. WKY; ** p < 0.01 vs. SHR-M.

Figure 4

The distribution of collagen fibers in cross sections of thoracic aortas (22 weeks rats). (A) Sirius Red stain of collagen fibers under optical microscope (scale bar = 300 μm); (B) magnified images of (A) (scale bar = 100 μm); (C) Sirius Red stain of collagen I and collagen III under polarized light microscopy, collagen I was bright red or strong orange–red, and collagen III was green (scale bar = 100 μm); (D) the percentage of collagen fibers in thoracic aortas. The data are presented as the mean ± SD. n = 6, ^# p < 0.05, vs. WKY.

Figure 5

The distribution of collagen in cross sections of carotid arteries (22 weeks rats). (A) Sirius Red stain of collagen under optical microscope (scale bar = 200 μm); (B) magnified images of (A) (scale bar = 100 μm); (C) Sirius Red stain of collagen I and collagen III under polarized light microscopy, collagen I was bright red or strong orange–red, and collagen III was green (scale bar = 100 μm); (D) the percentage of collagen fibers in carotid arteries. The data are presented as the mean ± SD. n = 6.

Figure 5

The distribution of collagen in cross sections of carotid arteries (22 weeks rats). (A) Sirius Red stain of collagen under optical microscope (scale bar = 200 μm); (B) magnified images of (A) (scale bar = 100 μm); (C) Sirius Red stain of collagen I and collagen III under polarized light microscopy, collagen I was bright red or strong orange–red, and collagen III was green (scale bar = 100 μm); (D) the percentage of collagen fibers in carotid arteries. The data are presented as the mean ± SD. n = 6.

Figure 6

Effects of losartan, aspirin, and atorvastatin on the plasma contents of renin (A), Ang II (B), and ALD (C) in 22 weeks rats. The data are presented as the mean ± SD. n = 6, ^## p < 0.01 vs. WKY; * p < 0.05, ** p < 0.01 vs. SHR-M.

Figure 7

Effects of losartan, aspirin, and atorvastatin on the plasma contents of ET-1 (A), NE (B), and IL-6 (C) in 22 weeks rats. The data are presented as the mean ± SD. n = 6, ^## p < 0.01 vs. control (WKY); * p < 0.05, ** p < 0.01 vs. SHR-M group.