[Paeoniflorin improves myocardial injury via inhibition of Src/VE-cadherin pathway in septic rats]

Objective: To study the protective effect and mechanism of paeoniflorin (pae) on myocardial injury in septic rats. Methods: Sprague-Dawley (SD) rats were randomly divided into 4 groups with 10 rats in each group. Rats were intraperitoneally injected with 1.4 ml normal saline and 1.4 ml 5% dimethyl sulfoxide (DMSO)solution independently in control group and DMSO group. Rats were intraperitoneally injected with 1.4 ml normal saline and 1.4 ml pae independently, then with 0.1 ml lipopolysaccharide (LPS) 1 hour later in sepsis group and pae group. Enzyme linked immunosorbent assay (ELISA) was used to detect serum cardiac troponin I (cTnI) levels and myocardial tissue tumor necrosis factor alpha (TNFα), interleukin(IL)-6, IL-1β, chemokine (C-X-C motif) ligand 1 (CXCL1), chemokine (C-X-C motif) ligand 2 (CXCL2), vascular cell adhesion molecule 1 (VCAM-1) levels. Evans blue (EB) method was used to detect the EB content of myocardial tissue. HE staining method was used to observe the pathological changes, real-time quantitative polymerase chain reaction (RT-qPCR) to detect mRNA expression levels of the above molecules, and Western-blot to detect vascular endothelium-cadherin (VE-cadherin), phosphorylated p38 mitogen-activated protein kinase (P-p38MAPK), phosphorylated Src protein (P-Src), Ras-Related C3 Botulinum Toxin Substrate 1 (Rac1) levels. Results: Compared with control group, cTnI level and the EB content in sepsis group increased significantly, and the myocardial inflammatory cell infiltration was obvious. The cTnI level and EB content in pae group were significantly reduced, and myocardial inflammatory cell infiltration was reduced [cTnI: (227.7±15.9)pg/ml vs. (312.9±17.9)pg/ml;EB: (13.2±2.3)μg/g vs. (23.8±2.9)μg/g; P<0.05]. Compared with control group, the levels of TNFα, IL-6, IL-1β, CXCL1, CXCL2, and VCAM-1 in sepsis group were increased. Compared with sepsis group, the above-mentioned molecular levels of pae group were significantly decreased [TNFα: (63.39±9.55)pg/ml vs. (126.54±19.17)pg/ml ;IL-6: (64.03±8.82)pg/ml vs. (85.60±9.52)pg/ml;IL-1β: (69.52±9.23)pg/ml vs. (130.45±15.10)pg/ml;CXCL1: (2 600.19±379.54)pg/ml vs. (4 903.89±533.42)pg/ml;CXCL2: (93.71±10.83)pg/ml vs. (127.24±13.92)pg/ml;VCAM-1: (112.22±13.49)pg/ml vs. (149.32±15.65)pg/ml, both P<0.05]. RT-qPCR results showed that the mRNA expressions of TNFα, IL-6, IL-1β, CXCL1, CXCL2 and VCAM-1 in the sepsis group were increased compared with the control group; Compared with sepsis group, the IL-6 mRNA (1.271±0.139 vs. 1.920±0.191, P<0.05), IL-1βmRNA (1.180±0.130 vs. 1.817±0.191, P<0.05), VCAM-1 mRNA (1.088±0.144 vs. 1.460±0.166, P<0.05) expression decreased significantly in the pae group. Compared with control group, the levels of P-p38MAPK and P-Src in sepsis group increased, and the level of VE-cadherin decreased. Compared with sepsis group, the levels of p38MAPK and P-p38MAPK in pae group were significantly decreased, and the level of VE-cadherin was increased (p38MAPK/β-actin: 1.125±0.078 vs. 1.520±0.164; P-p38MAPK protein: 1.639±0.133 vs. 2.112±0.222; both P<0.05). Conclusion: Paeoniflorin could improve the permeability of cardiac microvascular endothelium in sepsis rats and inhibit the secretion and expression of inflammation-related proteins and genes, which might be related to the inhibition of Src/VE-cadherin pathway by paeoniflorin.