Inhibition of autophagy promoted sphingosylphosphorylcholine induced cell death in non-small cell lung cancer cells

Sphingosylphosphorylcholine ameliorates doxorubicin-induced cardiotoxicity in zebrafish and H9c2 cells by reducing excessive mitophagy and mitochondrial dysfunction

Doxorubicin (DOX, C₂₇H₂₉NO₁₁), is an anthracycline tumor chemotherapy drug, which has significant side effects on many organs including the heart. In recent years, mitochondrial dysfunction caused by DOX was identified as an important reason for cardiotoxic injury. Sphingosylphosphorylcholine (SPC) is essential for mitochondrial homeostasis in our previous report, however, its role in DOX-caused cardiomyopathy has remained elusive. Herein, DOX treated zebrafish embryos (90 μM) and adult fish (2.5 μM/g) were used to simulate DOX-induced cardiotoxic damage. Histopathological and ultrastructural observations showed that SPC (2.5 μM) significantly ameliorated DOX-induced pericardial edema, myocardial vacuolization and apoptosis. Furthermore, SPC (2.5 μM) can significantly inhibit DOX-induced apoptosis and promote cell proliferation in DOX treated H9c2 cells (1 μM), which is dependent on the restoration of mitochondrial homeostasis, including restored mitochondrial membrane potential, mitochondrial superoxide and ATP levels. We finally confirmed that SPC restored mitochondrial homeostasis through ameliorating DOX-induced excessive mitophagy. Mechanistically, SPC reduced calmodulin (CaM) levels and thus inhibiting Parkin activation and Parkin-dependent mitophagy. These results suggest that reducing the cardiotoxicity of chemotherapeutic drugs by targeting SPC may be a new solution to rescue chemotherapy injury.

Role of Sphingosylphosphorylcholine in Tumor and Tumor Microenvironment

Sphingosylphosphorylcholine (SPC) is a unique type of lysosphingolipid found in some diseases, and has been studied in cardiovascular, neurological, and inflammatory phenomena. In particular, SPC’s studies on cancer have been conducted mainly in terms of effects on cancer cells, and relatively little consideration has been given to aspects of tumor microenvironment. This review summarizes the effects of SPC on cancer and tumor microenvironment, and presents the results and prospects of modulators that regulate the various actions of SPC.

Novel effects of sphingosylphosphorylcholine on the apoptosis of breast cancer via autophagy/AKT/p38 and JNK signaling

Sphingosylphosphorylcholine (SPC), an important lipid mediator in blood, inhibits the proliferation and migration of various cancer cells. However, its effect as a cell-specific sphingolipid in breast cancer cells is still unknown. Here, we showed that SPC promoted autophagy and apoptosis in triple-negative breast cancer MDA-MB-231 cells. Autophagy worked as a negative regulator of apoptosis-induced by SPC. Mechanistically, SPC mediated apoptosis via activating c-Jun N-terminal kinase (JNK). Meanwhile, p38MAPK (p38) and protein kinase B (PKB or AKT) signaling pathways were also activated to inhibit apoptosis, suggesting that SPC could evoke multiple signaling pathways to modulate cell apoptosis. In addition, the crosstalk between autophagy, p38, AKT and JNK is that autophagy, p38, and AKT attenuated the JNK. AKT and p38 were in the downstream of autophagy, which is autophagy/AKT/p38 signaling evoked by SPC to antagonize JNK signaling and subsequent apoptosis. Although the pathways that antagonize apoptosis were evoked, the cells eventually reached apoptosis by SPC. Therefore, the combination with pharmacological autophagy inhibitors would be a more effective therapeutic strategy for eliminating breast cancer cells by SPC.

Activation of autophagy flux by metformin downregulates cellular FLICE-like inhibitory protein and enhances TRAIL- induced apoptosis

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily. TRAIL is regarded as one of the most promising anticancer agents, because it can destruct cancer cells without showing any toxicity to normal cells. Metformin is an anti-diabetic drug with anticancer activity by inhibiting tumor cell proliferation. In this study, we demonstrated that metformin could induce TRAIL-mediated apoptotic cell death in TRAIL-resistant human lung adenocarcinoma A549 cells. Pretreatment of metformindownregulation of c-FLIP and markedly enhanced TRAIL-induced tumor cell death by dose-dependent manner. Treatment with metformin resulted in slight increase in the accumulation of microtubule-associated protein light chain LC3-II and significantly decreased the p62 protein levels by dose-dependent manner indicated that metformin induced autophagy flux activation in the lung cancer cells. Inhibition of autophagy flux using a specific inhibitor and genetically modified ATG5 siRNA blocked the metformin-mediated enhancing effect of TRAIL. These data demonstrated that downregulation of c-FLIP by metformin enhanced TRAIL-induced tumor cell death via activating autophagy flux in TRAIL-resistant lung cancer cells and also suggest that metformin may be a successful combination therapeutic strategy with TRAIL in TRAIL-resistant cancer cells including lung adenocarcinoma cells.

Aspirin alleviates cardiac fibrosis in mice by inhibiting autophagy

Aspirin (ASA) is a cardioprotective drug with anti-cardiac fibrosis action in vivo. This study was aimed to clarify the anti-cardiac fibrosis action of ASA and the underlying mechanisms. Two heart injury models (injection of isoproterenol and ligation of the left anterior descending branch) were used in mice to induce cardiac fibrosis. The animals were treated with ASA (10 mg·kg^-1·d^-1, ig) for 21 and 14 d, respectively. ASA administration significantly improved cardiac function, and ameliorated heart damage and fibrosis in the mice. The mechanisms underlying ASA's anti-fibrotic effect were further analyzed in neonatal cardiac fibroblasts (CFs) exposed to hypoxia in vitro. ASA (0.5-5 mmol/L) dose-dependently inhibited the proliferation and Akt phosphorylation in the CFs. In addition, ASA significantly inhibited CF apoptosis, and decreased the levels of apoptosis markers (cleaved caspase 3 and Parp1), which might serve as a side effect of anti-fibrotic effect of ASA. Furthermore, ASA dose-dependently inhibited the autophagy in the CFs, as evidenced by the reduced levels of autophagy marker LC3-II. The autophagy inhibitor Pepstatin A (PepA) promoted the inhibitory effect of ASA on CF proliferation, whereas the autophagy inducer rapamycin rescued ASA-caused inhibition of CF proliferation, suggesting an autophagy-dependent anti-proliferative effect of ASA. Both p38 inhibitor SB203580 and ROS scavenger N-acetyl-cysteine (NAC) significantly decreased Akt phosphorylation in CFs in the basal and hypoxic situations, but they both significantly increased LC3-II levels in the CFs. Our results suggest that an autophagy- and p38/ROS-dependent pathway mediates the anti-cardiac fibrosis effect of ASA in CFs. As PepA and SB203580 did not affect ASA-caused inhibition of CF apoptosis, the drug combination will enhance ASA's therapeutic effects.

Polydatin regulates proliferation, apoptosis and autophagy in multiple myeloma cells through mTOR/p70s6k pathway

BACKGROUND

Polydatin (PD) plays an important role in suppressing platelet aggregation, reducing blood lipid, restoring microcirculation and protecting from myocardial ischemia/reperfusion injury and shock. In addition, PD possesses anticancer activity. However, the effect and the mechanism of PD in regulating multiple myeloma (MM) cell survival and death are still unknown.

METHODS

Cell proliferation and apoptosis of RPMI 8226 cells, respectively, were analyzed by cell counting kit8 (CCK-8) assay and flow cytometry. The levels of caspase-3, cleaved caspase-3, caspase-9, cleaved caspase-9, Bcl-2 and Bax were analyzed by Western blot. Autophagy induced by PD was investigated by detecting the levels of Beclin 1, Atg5, LC3I, LC3II, HSP70 and HSP27. The autophagy inhibitor 3-methyladenine (3-MA), mTOR/p70s6k inhibitor rapamycin, and mTOR activator MHY1485 were used to analyze the mechanism of cell proliferation, apoptosis and autophagy influenced by PD. The phosphorylations of mTOR and p70s6k were detected by Western blot.

RESULTS

A gradual decrease in cell proliferation of RPMI 8226 cells was observed with an increase in PD concentrations (P<0.05). PD also induced cell apoptosis and autophagy in a concentration-dependent manner. Both 3-MA and MHY1485 reversed the inhibitory effect of PD on cell proliferation and attenuated the positive effect of PD on cell apoptosis and autophagy. The phosphorylation of mTOR and p70s6k was significantly suppressed by PD (P<0.05). Furthermore, inhibition of the mTOR/p70s6k signaling pathway by rapamycin significantly induced autophagy and apoptosis and inhibited cell viability (P<0.05).

CONCLUSION

PD effectively suppressed cell proliferation and induced apoptosis and autophagy of MM cells via the mTOR/p70s6k signaling pathway in a concentration-dependent manner in vitro, indicating that PD could be a potential anticancer drug for MM therapy.

PP242 suppresses bladder cancer cell proliferation and migration through deactivating the mammalian target of rapamycin complex 2/AKT1 signaling pathway

While most cancer types are resistant to mammalian target of rapamycin complex 1 (mTORC1) inhibitor rapamycin, recent studies have identified mTORC2 as an important prospective therapeutic target for cancer. The present study assessed the effects of mTORC2 inhibitor PP242 on the proliferation and migration of bladder cancer cells by using Cell Counting Kit‑8, 5‑ethynyl‑2'‑deoxyuridine incorporation, wound healing and Transwell assays. Furthermore, the phosphorylation status of downstream signaling proteins of mTORC1 and mTORC2 was assessed using western blot analysis. The results demonstrated that PP242 concentration‑dependently inhibited the proliferation of bladder cancer cells. Simultaneously, the migration ability of bladder cancer cells was suppressed by PP242. In addition, PP242 markedly restrained the phosphorylation of AKT1 and mTORC2, while the phosphorylation status of S6K1 and mTORC1 was not affected. These results suggested that PP242 exerts potent inhibitory effects on bladder cancer cells by modulating the activity of the mTORC2/AKT1 pathway.

Increased Levels of Sphingosylphosphorylcholine (SPC) in Plasma of Metabolic Syndrome Patients

Recent developments in lipid mass spectrometry enable extensive lipid class and species analysis in metabolic disorders such as diabesity and metabolic syndrome. The minor plasma lipid class sphingosylphosphorylcholine (SPC) was identified as a ligand for lipid sensitive G-protein coupled receptors playing a key role in cell growth, differentiation, motility, calcium signaling, tissue remodeling, vascular diseases and cancer. However, information about its role in diabesity patients is sparse. In this study, we analyzed plasma lipid species in patients at risk for diabesity and the metabolic syndrome and compared them with healthy controls. Our data show that SPC is significantly increased in plasma samples from metabolic syndrome patients but not in plasma from patients at risk for diabesity. Detailed SPC species analysis showed that the observed increase is due to a significant increase in all detected SPC subspecies. Moreover, a strong positive correlation is observed between total SPC and individual SPC species with both body mass index and the acute phase low grade inflammation marker soluble CD163 (sCD163). Collectively, our study provides new information on SPC plasma levels in metabolic syndrome and suggests new avenues for investigation.

Inactivated Sendai virus induces apoptosis and autophagy via the PI3K/Akt/mTOR/p70S6K pathway in human non-small cell lung cancer cells

Inactivated Sendai virus (HVJ-E) has shown potential anticancer efficacy in various cancer cells. However, the ability of HVJ-E to regulate cancer cell survival and death remains largely unknown. In the present study we first found that HVJ-E exhibited cytotoxic effects in the non-small cell lung cancer cell (NSCLC) line A549 and cisplatin-resistant A549 cells (A549/DDP). The suppression of cell viability was due to both the activation of caspases and the JNK and p38 MAPK signaling pathways in A549 and A549/DDP human lung cancer cells. In addition, we demonstrated that HVJ-E could induce autophagy in NSCLC cells via the PI3K/Akt/mTOR/p70S6K signaling pathway for the first time. Inhibiting autophagy in A549/DDP cells and inducing autophagy in A549 cells enhanced HVJ-E-induced apoptosis. These findings provide a molecular basis of HVJ-E-mediated cell death and support the notion that combination treatment with autophagy modulators is an effective strategy to augment the cytotoxic effects of HVJ-E in NSCLC cells.