Effect Of Interleukin-16 On Atherosclerosis And Its Mechanism

Objective To study influences of interleukin-16（IL-16）on atherosclerosis（AS）development and the underlying mechanisms,through analyzing the expression of IL-16in AS patients plaque,and the changes of plaque in apolipoprotein E deficient(ApoE^-/-)mice,which was treated with recombinant IL-16.Methods Analysis of the expression of interleukin-16 in serum and plaque tissue of AS patients:（1）The study subjects were collected during August 2015 to August 2016,in Department of Cardiology of the Affiliated Hospital of Jining Medical College.The case group included 30 AS patients,which were confirmed with concurrent coronary angiography.The healthy control group was composed of 29 individuals,from the hospital’s physical examination center at the same time,matched with the cases by age.The levels of IL-16 in peripheral blood were measured by enzyme-linked immunosorbent assay（ELISA）.The difference of the IL-16 levels between the two groups were compared.（2）Reverse transcription polymerase chain reaction was applied to detect the mRNA levels of IL-16 in peripheral blood mononuclear cells,and the differences between the two groups were compared.（3）AS plaque specimens were obtained from patients who accepted atherosclerotic carotid artery endometrial plaque exfoliation（CEA）.Immunohistochemical（histochemical）staining was performed to analyze IL-16expression in the AS plaque specimen.The study of IL-16 expression in AS mice model,and of the effect of recombinant IL-16 intervention on plaque development in AS mice:（1）20 Apo E^-/-mice were randomly divided into 2 groups,10 in each group.Atherosclerosis ApoE^-/-mice models were established by feeding high-fat diet（0.25%cholesterol and 15%cocoa butter）for 4weeks.The other group was fed for 4 weeks with normal diet.After 4 weeks,the mice in both groups were sacrificed.The pathological sections of the paraffin were prepared from the aortic root of the mouse.Immunohistochemical staining was performed to observe the formation and development of AS plaque and the expression level of IL-16.（2）Another20 ApoE^-/-AS mice models were also randomly divided into two groups,10 in each group.The treated group was injected with recombinant IL-16,once a week after high-fat feeding.The control group was injected GST protein with the same dose and same way with mice in treated group.After the mice were sacrificed,the pathological sections of the paraffin were prepared from the aortic roots of the mice.HE staining was performed to observe the changes of plaque size.CD3 immunohistochemical staining was used to analyze the effect of recombinant IL-16 on the stability of atherosclerotic plaque in AS mice.Results（1）The serum levels of IL-16 in peripheral blood of patients with AS were higher than that in healthy controls,which was analyzed by enzyme-linked immunosorbent assay（ELISA）.The difference between the two groups was statistically significant（P<0.05）.（2）Detection of IL-16 mRNA level in peripheral blood mononuclear cells in both groups,through RT-PCR,revealed that IL-16 mRNA levels in AS patients’peripheral blood were higher than that of healthy controls.The difference between the two groups was statistically significant（P<0.05）.（3）The result of immunohistochemistry showed that IL-16 expression was obvious in human AS plaques;（4）Higher expression level of IL-16was observed in AS plaques of ApoE^-/-mice model which was fed with high-fat food.（5）After intraperitoneal injection of IL-16 in AS mice modle,the area of aortic plaque shrinked which indicated increased AS plaque stability.Conclusion 1.Higher IL-16 levels were detected in peripheral blood of AS patients,and AS plaque tissue of mice modles.Few IL-16 expression was detected in the aortic roots of normal-fed ApoE^-/-mice.These results indicate that IL-16 aggregates in atherosclerotic disease.2.The comparison between AS mice intraperitoneally injected with recombinant IL-16and AS mice without IL-16 intervention showed that the aortic plaque area was reduced and that the stability of the plaque was increased,suggesting that IL-16 may play an protective role on AS.3.IL-16 could reduce local CD3⁺T cell content in AS plaque,suggesting that IL-16 might reduce the local inflammatory level of plaque and increase plaque stability,through decreasing T cell infiltration.