Aerobic Exercise versus Electronic Cigarette in Vascular Aging Process: First Histological Insight

Abstract

Smoking is related to vascular aging. However, the hazardous effect of e-cigarette is often debatable, with limited studies available. In contrast, moderate-intensity aerobic exercise is well known to decrease aortic stiffness. We provide novel research to determine the effect of e-cigarette and aerobic moderate-intensity exercise on the aortic structure of Wistar rats. A total of 26 male Wistar rats (Rattus norvegicus) 8 weeks aged, 200-250 g b.w., were randomly divided into 4 groups, namely, K0 (normal rats), K1 (rats were given moderate-intensity aerobic exercise by animal treadmill 20 m/30 min), K2 (rats were given e-cigarette with 6 mg nicotine, 40% propylene glycol, and 60% vegetable glycerine 30 min for 5 days/week), and K3 (rats were given e-cigarette and moderate-intensity aerobic exercise). After exposure for 6 weeks, all animals were sacrificed to isolate the aorta for histopathological analysis with hematoxylin-eosin stain to evaluate the elastic fiber layer and intimal-medial thickness. The Verhoeff-Van Gieson staining was done for quantification elastic lamina fragmentation. Our study found that the e-cigarette group had the highest elastic lamina fragmentation among groups (8.14 ± 2.85). The exercise only group showed the lowest elastic lamina fragmentation (2.50 ± 1.87). Fragmentation in the e-cigarette and exercise group was higher than in the exercise only group (5.83 ± 0.753 vs. 2.50 ± 1.87, p = 0.002). There is a significant difference of NO serum between four groups. The result of post hoc analysis using LSD showed that there is a significant difference of NO serum between K0 and K2, K0 and K3, K1 and K2, and K1 and K3. Therefore, our research demonstrated that the most injury of aorta elastic lamina was in the group that was exposed to e-cigarette that leads to vascular aging while exercise is not yet proven to reverse this effect.

Figure 1

Elastic fiber layers. (a) Negative control (K0) with an average number of elastic fiber layers of 10.3. (b) Moderate-intensity aerobic physical exercise (K1) with an average number of elastic fiber layers of 9.5. (c) Exposure to electronic cigarettes (K2) with an average number of elastic fiber layers of 9.0. (d). The combination of exposure to electronic cigarettes and moderate-intensity aerobic physical exercise (K3) showed an average number of elastic fiber layers of 8.7 (H&E), 40x.

Figure 2

Tunica intima-media thickness. Average thickness of tunica intima-media (μm). (a) The control group (K0) with an average of 104.8 μm. (b) The moderate-intensity aerobic physical exercise group (K1) with an average of 95.6 μm. (c) The e-cigarette exposure group (K2) with an average of 104.2 μm. (d) The combination group of e-cigarette exposure and moderate-intensity aerobic physical exercise (K3) showed an average of 102.15 μm (H&E), 40x.

Figure 3

Elastic lamina fragmentation. (a) Negative control (K0) showed neatly arranged and dense elastic lamina with minimal fragmentation (red arrows). (b) Moderate-intensity aerobic physical exercise (K1) showed lower fragmentation than K0 (red arrows). (c) Exposure to e-cigarette (K2) showed increased elastic lamina fragmentation (red arrows). (d) Exposure to electronic cigarettes (K3) showed lower elastic lamina fragmentation (red arrows).

Figure 4

Immunohistochemistry CD68. The result of CD68 immunohistochemistry stains was found to be negative in all treatment groups (400x).

Figure 5

Correlation between NO serum and elastic lamina fragmentation. Scatter plot with fit line of elastic lamina fragmentation by NO serum showed negative correlation.