Effects of single-dose atorvastatin on interleukin-6, interferon gamma, and myocardial no-reflow in a rabbit model of acute myocardial infarction and reperfusion

Abstract

The mechanisms of statins relieving the no-reflow phenomenon and the effects of single-dose statins on it are not well known. This study sought to investigate the effects of inflammation on the no-reflow phenomenon in a rabbit model of acute myocardial infarction and reperfusion (AMI/R) and to evaluate the effects of single-dose atorvastatin on inflammation and myocardial no-reflow. Twenty-four New Zealand white male rabbits (5-6 months old) were randomized to three groups of eight: a sham-operated group, an AMI/R group, and an atorvastatin-treated group (10 mg/kg). Animals in the latter two groups were subjected to 4 h of coronary occlusion followed by 2 h of reperfusion. Serum levels of interleukin (IL)-6 were measured by enzyme-linked immunosorbent assay. The expression of interferon gamma (IFN-γ) in normal and infarcted (reflow and no-reflow) myocardial tissue was determined by immunohistochemical methods. The area of no-reflow and necrosis was evaluated pathologically. Levels of serum IL-6 were significantly lower in the atorvastatin group than in the AMI/R group (P<0.01). Expression of IFN-γ in infarcted reflow and no-reflow myocardial tissue was also significantly lower in the atorvastatin group than in the AMI/R group. The mean area of no-reflow [47.01% of ligation area (LA)] was significantly smaller in the atorvastatin group than in the AMI/R group (85.67% of LA; P<0.01). The necrosis area was also significantly smaller in the atorvastatin group (85.94% of LA) than in the AMI/R group (96.56% of LA; P<0.01). In a secondary analysis, rabbits in the atorvastatin and AMI/R groups were divided into two groups based on necrosis area (90% of LA): a small group (<90% of LA) and a large group (>90% of LA). There was no significant difference in the area of no-reflow between the small (61.40% of LA) and large groups (69.87% of LA; P>0.05). Single-dose atorvastatin protected against inflammation and myocardial no-reflow and reduced infarct size during AMI/R in rabbits. No-reflow was not dependent on the reduction of infarct size.

Figure 1. A, Comparison of ischemic area (ligation area) between two groups. B, Comparison of area of no-reflow and necrosis area between two groups. C, Comparison of area of no-reflow and necrosis area between small and large groups. AMI/R: acute myocardial infarction and reperfusion. *P<0.01, compared to AMI/R or small groups (one-way ANOVA followed by the Student-Newman-Keuls test and the Student t-test).

Figure 2. Ligation area, area of no-reflow and necrosis area after 4 h of occlusion and 2 h of reperfusion (pathological staining, 1×). The red areas show the ligation area, black areas show the area of no-reflow, and white areas show necrosis (see black arrows). AMI/R: acute myocardial infarction and reperfusion.

Figure 3. Effects of atorvastatin on serum interleukin-6 at different time points. *P<0.01, compared to acute myocardial infarction and reperfusion (AMI/R); ^#P<0.01, compared to baseline; ⁺P<0.01, compared to ischemia (4 h) (repeated measures ANOVA followed by the Student-Newman-Keuls test).

Figure 4. Expression of IFN-γ in different regions of the myocardium in the three groups after 4 h of occlusion and 2 h of reperfusion (IHC, DAB staining, 200×). Positive IFN-γ expression was seen in vascular endothelial cells (as shown by arrows). AMI/R: acute myocardial infarction and reperfusion.

Figure 5. Integral optical density (IOD) analysis of IFN-γ levels in myocardium of different regions in three groups. *P<0.01, compared to normal region; ^#P<0.01, compared to reflow region; ⁺P<0.01, compared to acute myocardial infarction and reperfusion (AMI/R) (one-way ANOVA followed by the Student-Newman-Keuls test).