Enzastaurin cardiotoxicity: QT interval prolongation, negative inotropic responses and negative chronotropic action.

Several clinical trials observed that enzastaurin prolonged QT interval in cancer patients. However, the mechanism of enzastaurin-induced QT interval prolongation is unclear. Therefore, this study aimed to assess the effect and mechanism of enzastaurin on QT interval and cardiac function. The Langendorff and Ion-Optix MyoCam systems were used to assess the effects of enzastaurin on QT interval, cardiac systolic function and intracellular Ca2+ transient in guinea pig hearts and ventricular myocytes. The effects of enzastaurin on the rapid delayed rectifier (IKr), the slow delayed rectifier K+ current (IKs), transient outward potassium current (Ito), action potentials, Ryanodine Receptor 2 (RyR2) and the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) expression and activity in HEK 293 cell system and primary cardiomyocytes were investigated using whole-cell recording technique and western blotting. We found that enzastaurin significantly prolonged QT interval in guinea pig hearts and increased the action potential duration (APD) in guinea pig cardiomyocytes in a dose-dependent manner. Enzastaurin potently inhibited IKr by binding to the human Ether-à-go-go-Related gene (hERG) channel in both open and closed states, and hERG mutant channels, including S636A, S631A, and F656V attenuated the inhibitory effect of enzastaurin. Enzastaurin also moderately decreased IKs. Additionally, enzastaurin also induced negative chronotropic action. Moreover, enzastaurin impaired cardiac systolic function and reduced intracellular Ca2+ transient via inhibition of RyR2 phosphorylation. Taken together, we found that enzastaurin prolongs QT, reduces heart rate and impairs cardiac systolic function. Therefore, we recommend that electrocardiogram (ECG) and cardiac function should be continuously monitored when enzastaurin is administered to cancer patients.

4-(2-Butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid inhibits angiogenesis via modulation of vascular endothelial growth factor receptor 2 signaling pathway.

4-(2-Butyl-6,7-dichloro-2-cyclopentyl-indan-1-on-5-yl) oxobutyric acid (DCPIB), was discovered to be a potent and specific antagonist of volume-regulated anion channel that is closely linked to angiogenesis. However, the effect of DCPIB on angiogenesis remains unclear. Here, we found that DCPIB inhibited angiogenesis in the corneal suture and myocardial infarction in vivo model. In addition, DCPIB inhibited human umbilical vein endothelial cell migration, tube formation and proliferation in vitro. Moreover, DCPIB repressed the activation and expression of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream signaling pathway. Computer modeling further confirmed that DCPIB binds with high affinity to VEGFR2. Collectively, we present evidence supporting an antiangiogenic role of DCPIB by targeting VEGFR2 signaling pathway, which suggests that DCPIB is a valuable lead compound for the treatment of angiogenesis-related diseases.

Shikonin induces programmed death of fibroblast synovial cells in rheumatoid arthritis by inhibiting energy pathways.

Shikonin is the main component of the traditional Chinese medicine comfrey, which can inhibit the activity of PKM2 by regulating glycolysis and ATP production. Rheumatoid arthritis synovial cells (RA-FLSs) have been reported to increase glycolytic activity and have other similar hallmarks of metabolic activity. In this study, we investigated the effects of shikonin on glycolysis, mitochondrial function, and cell death in RA-FLSs. The results showed that shikonin induced apoptosis and autophagy in RA-FLSs by activating the production of reactive oxygen species (ROS) and inhibiting intracellular ATP levels, glycolysis-related proteins, and the PI3K-AKT-mTOR signaling pathway. Shikonin can significantly reduce the expression of apoptosis-related proteins, paw swelling in rat arthritic tissues, and the levels of inflammatory factors in peripheral blood, such as TNF-α, IL-6, IL-8, IL-10, IL-17A, and IL-1ß while showing less toxicity to the liver and kidney.

Matrine Reverses the Warburg Effect and Suppresses Colon Cancer Cell Growth via Negatively Regulating HIF-1α.

The Warburg effect is a peculiar feature of cancer's metabolism, which is an attractive therapeutic target that could aim tumor cells while sparing normal tissue. Matrine is an alkaloid extracted from the herb root of a traditional Chinese medicine, Sophora flavescens Ait. Matrine has been reported to have selective cytotoxicity toward cancer cells but with elusive mechanisms. Here, we reported that matrine was able to reverse the Warburg effect (inhibiting glucose uptake and lactate production) and suppress the growth of human colon cancer cells in vitro and in vivo. Mechanistically, we revealed that matrine significantly decreased the messenger RNA (mRNA) and protein expression of HIF-1α, a critical transcription factor in reprogramming cancer metabolism toward the Warburg effect. As a result, the expression levels of GLUT1, HK2, and LDHA, the downstream targets of HIF-1α in regulating glucose metabolism, were dramatically inhibited by matrine. Moreover, this inhibitory effect of matrine was significantly attenuated when HIF-1α was knocked down or exogenous overexpressed in colon cancer cells. Together, our results revealed that matrine inhibits colon cancer cell growth via suppression of HIF-1α expression and its downstream regulation of Warburg effect. Matrine could be further developed as an antitumor agent targeting the HIF-1α-mediated Warburg effect for colon cancer treatment.

The pro-apoptotic effects of TIPE2 on AA rat fibroblast-like synoviocytes via regulation of the DR5-caspase-NF-κB pathway in vitro.

TIPE2, also known as TNFAIP8L2, a member of the tumor necrosis factor-alpha-induced protein-8 (TNFAIP8) family, is known as an inhibitor in inflammation and cancer, and its overexpression induces cell death. We examined the role of TIPE2 with respect to adjuvant arthritis (AA)-associated pathogenesis by analyzing the TIPE2 regulation of death receptor (DR5)-mediated apoptosis in vitro. The results showed that TIPE2 was detected in normal fibroblast-like synoviocytes (FLSs), but scarcely observed in AA-FLSs. Therefore, recombinant MIGR1/TIPE2(+/+) and control MIGR1 lentivirus vectors were transfected to AA-FLSs, which were denoted as TIPE2(+/+)-FLSs and MIGR1-FLSs, respectively. Our results showed that TIPE2(+/+)-FLSs were highly susceptible to ZF1-mediated apoptosis, and ZF1 was our own purification of an anti-DR5 single chain variable fragment antibody. Under the presence of TIPE2, the expression of DR5 was significantly increased compared with that of the MIGR1-FLS group. In contrast, the level of phosphorylated nuclear factor-kappa B (pNF-κB) was lower in the TIPE2(+/+)-FLS group treated with ZF1, whereas the activity of caspase was higher. Moreover, the rate of apoptosis in the TIPE2(+/+)-FLS group, which was pretreated with caspase inhibitor Z-VAD-FMK, was significantly decreased. In contrast, the apoptosis occurrence in the MIGR1-FLS group increased significantly with the pretreatment of the NF-κB inhibitor Bay. These results indicated that TIPE2 increased the apoptosis of AA-FLSs by enhancing DR5 expression levels, thereby promoting the activation of caspase and inhibiting the activation of NF-κB in AA-FLSs. TIPE2 might potentially act as a therapeutic target for rheumatoid arthritis.