ABSTRACT
Total flavonoids of Dracocephalum moldavica L. (TFDM) is an effective component extracted and isolated from the traditional Uighur medicinal herb Cymbidium fragrans. Cymbidium fragrans has the effects of tonifying the heart and brain, promoting blood circulation and resolving blood stasis, and has been widely used in the treatment of cardiovascular and cerebrovascular diseases for a long time. The purpose of this study was to determine the effect of total flavonoids from Cymbidium fragrans on hypoxia/re-oxygenation (H/R) injury in H9c2 (rat cardiomyocytes) cells and its mechanism. A model (H/R) of hypoxia/re-oxygenation injury in H9c2 cells was established using hypoxia and glucose deprivation for 9 h combined with re-oxygenation and rehydration for 2 h to simulate myocardial ischemia-reperfusion injury. The effects of total flavonoids from Cymbidium fragrans on cell viability, markers of myocardial cell damage, oxidative stress levels, and reactive oxygen radical (ROS) content were investigated, Western blot was used to detect the expression of vascular endothelial growth factor B (VEGF-B) and adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway related proteins. The results showed that the total flavonoids of Cymbidium fragrans significantly increased the viability of myocardial cells after H/R injury, and decreased the content of lactate dehydrogenase (LDH) and creatine kinase isozyme (CK-MB) in the cell supernatant. It significantly reduced malondialdehyde (MDA), increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, and decreased intracellular ROS and nitric oxide (NO) content. Western blot analysis showed that the total flavonoids of Cymbidium fragrans decreased Bax levels in H9c2 cells damaged by H/R and increased Bcl-2 expression. Total flavones of Cymbidium fragrans upregulate VEGF-B/AMPK pathway related proteins VEGF-B, vascular endothelial growth factor receptor 1 (VEGFR-1), neuropilin 1 (NRP-1), peroxisome-proliferator-activated receptor γ coactivator-1α (PGC-1α), phosphorylated adenosine monophosphate activated protein (p-AMPK) and phospho mechanistic target of rapamycin (p-MTOR) levels. The above research results indicate that the total flavonoids of Cymbidium can significantly reduce the H/R injury of myocardial cells, which may be related to the upregulation of VEGF-B/AMPK pathway and inhibition of oxidative stress response.
ABSTRACT
Z-VAD-FMK was combined with hypoxia-reoxygenation (H/R) injury to establish a necroptosis model of H9c2 cells to mimic the pathological changes of myocardial ischemia reperfusion injury (MIRI) in vitro and to study the effect and mechanism of tilianin against myocardial ischemia-reperfusion injury. A cell counting kit-8 (CCK-8) was used to detect cell viability, and commercial kits were used to detect lactate dehydrogenase (LDH) and superoxide dismutase (SOD) in the cell culture supernatant. Hoechst 33342/PI immunofluorescence staining was used to detect cell death. DCFH-DA, BBcellProbeTMM61, and JC-1 probes were used to detect reactive oxygen species (ROS), mitochondrial permeability transition pore (mPTP), and mitochondrial membrane potential (MMP), respectively. An enzyme-linked immunosorbent assay (ELISA) method was used to detect the release of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6). The results show that the cell viability, SOD activity, and MMP of the model group induced by H/R injury decreased, as compared with control group, but the necroptosis rate, LDH level, and ROS release increased significantly. Furthermore, mPTP of the model group cells opened, and TNF-α, IL-1β, and IL-6 levels were significantly higher. Molecular docking modeling showed that tilianin can bind to calmodulin-dependent protein kinase II (CaMKII), and Western blot results showed that compared with control group, the expression levels of p-CaMKII and phospho-mixed lineage kinase domain-like protein increased in the model group, and tilianin could decrease the expression level of these proteins. The above results indicate that tilianin can protect H9c2 cells by inhibiting the phosphorylation of CaMKⅡ at threonine 287, protecting mitochondrial function, and inhibiting the opening of mPTP to prevent necroptosis. This study has value for research on new methods to treat H/R injury.