Effects And Mechanisms Of Tirofiban On Anatomic No Reflow And Ventricular Remodeling After Myocardial Ischemia/reperfusion In Rats

Objective: To investigate effects and mechanisms of tirofiban on anatomic noreflow and ventricular remodeling after acute myocardial ischemia reperfusion in rats.Methods: Male Wistar rats were randomized into sham operation group, control group and tirofiban treatment group.For acute experiments, Control group andtirofiban group were subjected ischemia for 90 minutes by ligation of coronary artery after thoracotomy and sequently reperfusion for 120 minutes to establish acute myocardial ischemia/reperfusion no reflow models. Sham operation group weren't underwent occlusion of coronary artery. All rats were sacrificed afterreperfusion for 120 minutes. Thioflavine S, Evans blue and Triphenyltetra zolium chloride (TTC) staining were performed to evaluate area of no refiow(ANR), infracted area(IA), risk area(RA) of heart; Activity of myeloperoxidase (MPO), total nitric oxide synthase (tNOS), inducible nitric oxide synthase (iNOS),endothelial nitric oxide synthase (eNOS) and content of nitric oxide (NO),malondialdehyde (MDA) in risk area of heart were detected by ultraviolet spectrophotometer. Immunohistochemistry was used to semi-quantitive analysize expression of nuclear factor-κBP65 (NF-κBP65) protein in myocyte and vessel.For chronic experiments, Rats of control group and tirofiban group were subjected ischernia for 90 minutes by ligation of coronary artery after thoracotomy and sequently persistent reperfusion. Sham operation group weren't underwent occlusionof coronary artery. On the 28th day after operation, hemodynamic parameters a nd cardiac function in all surviving rats were evaluated. Rats were sacrificed. Picrosirius red staining plus light microscopy was used to quantitive analysize thickness of left ventricular free wall in infracted region (left ventricular free wall for sham group, LVWT), septum (SPT) and ratio of SPT/LVWT, myocardial across area in septum (MAAS) and collagen volume fraction in non-infarcted and infracted region(left ventricular free wall for sham group).Results:1 After 120 minutes for reperfusion, a markedly reduced ANR and IA wereobserved in tirofiban group than in control group (34.36±6.04%vs.52.09±6.89%,P=0.001; 80.41±8.48%vs.90.13±5.72%, P＜0.042); there were no statistical differences in RA between the two groups(43.13±5.69% vs.39.98±3.75%, P=0.285).2 Compared with sham group, there were higher activity of MPO, iNOS andcontent of MDA, NO both in control and tirofiban group and statistical differences were received. Activity of eNOS was attenuated both in control and tirofiban group than in sham group whereas there were no statistical differences between tirofiban and sham group. There was elevated activity of tNOS both in control and tirofiban group compared with that in sham group even though no statistical differences were achieved between tirofiban and sham groups. Compared with control group, there were lower activity of MPO iNOS and content ofMDA NO in tirofiban (205.41±44.94U/g vs.384.11±40.68U/g, P＜0.001; 8.798±1.51U/mg vs. 11.45±2.52U/mg, P=0.027; 68.65±20.28nmol/g vs. 111.84±38.58nmol/g, P=0.01; 504.78±82.11μmol/g vs.744.49±137.54μmol/g, P=0.001), activity of eNOS were significantly enhanced in tirofiban than in control group (1.89±0.28U/mg vs.1.41±0.39U/mg, P=0.024), statistical differences were observed. Therewas depressed activity of tNOS in tirofiban group compared with that in control group whereas there were no differences between the two groups (P=0.092).3 Analysis of immunohistochemistry demonstrated that Positive index of NF- κB P65 in myocyte and vessel of risk region were significantly higher both incontrol and tirofiban group than in sham group and statistical differences werereceived; Compared with control group, lower PI of NF-κB P65 in myocyte and vessel were observed in tirofiban grouop(19.24±9.03% vs.34.32±9.56%, P=0.03; 17.63±7.22% vs.46.24±9.08%, P＜0.001). In all three groups, there were no statistical differences in PI of NF-κB P65 in myocyte of non-ischemic region(P＞0.05)4 After reperfusion for 28 days,compared with sham group, a reduced left ventricular wall thickness with an increased ratio of SPT/LVWT and MAAS wereobserved both in tirofiban and control group (P＜0.01); although SPT has anelevating tendency bothin control and tirofiban group and a more obvious tendency was observed in control group, there were no statistical differences in all three groups(P＞0.05). Compared with control group, there were a higher LVWT with a lower ratio of SPT/LVWT and MAAS in tirofiban group(1.78±0.27mm vs.1.36±0.28mm,P=0.014;1.47±0.49 vs.2.01±0.22, P＜0.001; 825.97±80.01μm²vs.1056.73±130.54μm², P=0.001).5 CVF in infracted region was higher both in control and tirofiban group compared with that of left ventricular free wall in sham group (P＜0.01). referred to CVF in non-infarcted region, no statistical differences were observed in a11 three groups(P＞0.05).. Compared with control group, CVF in infracted region were lower in tirofiban group (62.68±6.59% vs.80.63±9.07%,P＜0.001)..6 The haemodynamics analysis demonstrated that heart rate were of no statistical differences in all three groups(P＞0.01); Compared with sham group, there were lower systolic blood pressure(SBP),diastolic blood pressure(DBP),left ventricular systolic pressure(LVSP),±dp/dt_max and higher left ventricular end diastolic pressure(LVEDP) observed both in control and tirofiban group, the differences had statistical significance. Compared with control group, there were a hig her±dp/dt_max and a lower LVEDP in tirofiban group(7931.78±843.51 mmHg/s vs.6555.34±859.63mmHg/s,P=0.012; 6448.01±857.39mmHg/s vs.5253.87±638.19mmHg/s, P=0.014; 6.62±2.88mmHg vs.9.64±2.17mmHg,P=0.028).Statistical significance was not achieved although tirofiban group had a increasing tendency inSBP, DBP and LVSP (P＞0.05).Conclusions: Tirofiban can inhibit adhesion and infiltration of neutrophile in myocyte and vessel, improve function of vascular endothelium, reduce area of anatomic no reflow and infarcted area after ischemia/reperfusion in rats through aNF-κB-dependent mechanisms. In additionally, Tirofiban can inhibit ventricular remodeling after myocardial ischemia/reperfusion in rats and improve cardiac function through a mechanism that probably is associated with reducing area of no reflow and infarct after ischemia/reperfusion.