Blockage of Fibronectin 1 Ameliorates Myocardial Ischemia/Reperfusion Injury in Association with Activation of AMP-LKB1-AMPK Signaling Pathway

Abstract

Myocardial ischemia/reperfusion injury (I/RI) is closely associated with energy substrate metabolism. Fibronectin 1 (Fn1) was markedly elevated in the heart of I/R pigs and ischemic patients, but its role in myocardial I/RI is controversial and the precise mechanism involved remains elusive. Herein, we tested whether blockage of Fn1 with its inhibitor (fibronectin tetrapeptide, RGDS) would alleviate myocardial I/RI. Wild-type (WT) mice were administered with RGDS once 3 h before I/R operation and once at 24 or 48 h postreperfusion, and sacrificed at 24 or 72 h post-I/R, respectively. Cardiac function was evaluated by echocardiography. Myocardial infarction size, apoptosis, fibrosis, and inflammation were examined via histological staining. Uptake of glucose and fatty acids were detected by positron emission tomography (PET) and computer tomography (CT) with [18F]-2-fluoro-2-deoxy-D-glucose (FDG) and [18F]-fluoro-6-thia-heptadecanoic acid (FTHA), respectively. Our results showed that administration of RGDS to mice remarkably limited the I/R-induced myocardial infarct size, myocyte apoptosis, inflammation, oxidative stress, and fibrosis and improved cardiac contractile dysfunction. These protective effects were associated with upregulation of the AMP/ATP ratio and the activation of LKB1-AMPK signaling, which subsequently increased AS160-GLUT4-mediated glucose and fatty acid uptake, improved mitochondrial dynamic imbalance, and inactivated TGF-β and NF-κB signals in the I/R heart. In conclusion, the current study identified that blocking Fn1 protects against myocardial I/RI likely through activating the LKB1-AMPK-dependent signals and highlights that inhibition of Fn1 may be a novel therapeutic option for treating ischemic heart diseases.

Ursolic Acid Ameliorates Myocardial Ischaemia/Reperfusion Injury by Improving Mitochondrial Function via Immunoproteasome-PP2A-AMPK Signalling

“…Cardiac I/R injury was induced in male mice (20–23 g, n = 46) at 8–9 weeks old by occlusion of the proximal left anterior descending coronary artery (LAD) for 0.5 h followed by reperfusion for 24 h as described previously [ 20 , 21 ]. Sham mice ( n = 54) underwent the same operation procedure with no LAD artery ligation.…”

“…After 24 h of I/R or sham injury, all mice ( n = 6 per group) were anaesthetized using 1.5–2.0% isoflurane. Echocardiography was used to detect cardiac structure and left ventricular (LV) function with a Vevo 2100 Imaging System (Visual Sonics Inc., Toronto, ON, Canada) The parameters, including LV internal dimension at end-diastole (LVIDd) and end-systole (LVIDs), LV posterior wall at end-diastole (LVPWd) and end-systole (LVPWs), LV anterior wall at end-diastole (LVAWd) and end-systole (LVAWs), ejection fraction (EF%), and fractional shortening (FS%) for all mice were analysed as previously described [ 21 , 24 ]. All data used for the calculation of these parameters are provided in Supplementary Table S1 .…”

“…The infarct area is shown in red, the LV area at risk (AAR) is shown in white + red, and the nonischaemic region is shown in blue. Average percentage of total ischaemic areas = infarct area/LV area; percentage of AAR = (infarct + at-risk) area/LV area [ 21 ].…”

“…Ten milligrams of fresh cardiac tissues ( n = 6 per group) was resuspended in ATP lysis buffer (100 μL), homogenized, and centrifuged at 12,000× g for 5 min. Then, supernatants were added into ATP assay working solution (100 μL) for 5 min [ 21 , 31 ]. A spectrophotometer plate reader (Tecan, Spark model) was used to measure the fluorescence intensity, and all values were normalized to controls.…”

“…Equal amounts (1–2 μg) of total RNA and RT Enzyme mix (Takara) were used to synthesize cDNA. The mRNA expression of the target genes was analysed with a PCR thermocycler (Applied Biosystems) as previously described [ 21 ]. The data were normalized to GAPDH expression levels.…”