Acetyl-L-carnitine confers neuroprotection against lipopolysaccharide (LPS) -induced neuroinflammation by targeting TLR4/NFκB, autophagy, inflammation and oxidative stress

Acetyl-L-carnitine has been shown to exert neuroprotection against neurodegenerative diseases. The present study was performed to evaluate neuroprotection effects of acetyl-L-carnitine against lipopolysaccharide (LPS) -induced neuroinflammation and clarify possible mechanisms. A single dose (500 µg/kg) of LPS was intraperitoneally injected to rats to induce model. The animals were intraperitoneally treated with different doses of acetyl-L-carnitine (30, 60, and 100) for 6 days. Y-maze task, single-trial passive avoidance and novel object recognition tests were used to evaluate memory impairments. ELISA assay was used to evaluate the expression of TLR4/NFκB, autophagic and oxidative stress markers. Our result showed that intraperitoneal injection of LPS resulted in initiation of neuroinflammation by activation of TLR4/NFκB, suppression of autophagic markers such as LC3 II/ LC3 I ratio and becline-1, and excessive production of ROS and MDA. Intraperitoneal administration of acetyl-L-carnitine contributed to neuroprotection against LPS -induced neuroinflammation by suppression of TLR4/NFκB pathway, restoring activity of autophagy and inhibition of oxidative stress. Collectively, our findings show that acetyl-L-carnitine attenuated LPS-induced neuroinflammation by targeting TLR4/NFκB pathway, autophagy and oxidative stress.

The role of Beclin 1 in IR-induced crosstalk between autophagy and G2/M cell cycle arrest

OBJECTIVES

Beclin 1 is a well-established core mammalian autophagy protein. Autophagy has been demonstrated to play roles in cellular responses to DNA damage, such as cell cycle regulation and apoptosis. In the present study, we investigated the exact mechanism by which Beclin 1 acts as a bridge between autophagy and cell cycle, when cells are exposed to ionizing radiation (IR).

MATERIALS AND METHODS

Western blotting and coimmunoprecipitation were performed to investigate protein expression levels and interactions. Immunofluorescence was used to monitor the localization and distribution of the indicated proteins. The levels of apoptosis and cell cycle changes were evaluated by flow cytometry. Double thymidine deoxyribonucleoside (TdR) blocking was conducted to differentiate G2 from mitotic delay. In vitro kinase assays using ATM kinase were performed to elucidate the specific phosphorylation site in Beclin 1.

RESULTS

In this study, we show that Beclin 1 knockdown reduces IR-induced autophagy. IR enhanced Beclin 1/PIK3CIII complex activity as demonstrated by the results of coimmunoprecipitation and immunofluorescence assays. An investigation to assess the possible relationship between autophagy and G2/M arrest showed that, similar to the autophagy inhibitor 3MA, Beclin 1 knockdown delayed IR-induced G2/M arrest. Furthermore, the interactions between Beclin 1 and several G2/M checkpoint-related proteins, namely, PLK1 and CDC25C, were observed to increase. In addition, we observed that both 3MA and Beclin 1 inhibition decreased IR-induced apoptosis. Regarding the potential mechanism associated with this phenomenon, we showed that IR induced the interaction between Beclin 1 and Tip60 as well as their redistribution. Furthermore, we demonstrated that Beclin 1 T57 may be a targeted phosphorylation site for ATM.

CONCLUSIONS

In the present study, we demonstrate the crucial and intricate roles of Beclin 1 in IR-induced autophagy, G2/M cell cycle arrest, and apoptosis. Additionally, Tip60 and ATM were identified as important molecular regulators of Beclin 1. Our findings show the precise mechanism of crosstalk between IR-induced autophagy and G2/M cell cycle arrest.

Autophagy promotes the survival of dormant breast cancer cells and metastatic tumour recurrence

Cancer recurrence after initial diagnosis and treatment is a major cause of breast cancer (BC) mortality, which results from the metastatic outbreak of dormant tumour cells. Alterations in the tumour microenvironment can trigger signalling pathways in dormant cells leading to their proliferation. However, processes involved in the initial and the long-term survival of disseminated dormant BC cells remain largely unknown. Here we show that autophagy is a critical mechanism for the survival of disseminated dormant BC cells. Pharmacologic or genetic inhibition of autophagy in dormant BC cells results in significantly decreased cell survival and metastatic burden in mouse and human 3D in vitro and in vivo preclinical models of dormancy. In vivo experiments identify autophagy gene autophagy-related 7 (ATG7) to be essential for autophagy activation. Mechanistically, inhibition of the autophagic flux in dormant BC cells leads to the accumulation of damaged mitochondria and reactive oxygen species (ROS), resulting in cell apoptosis.

The mTOR Kinase Inhibitor CZ415 Inhibits Human Papillary Thyroid Carcinoma Cell Growth

BACKGROUND/AIM

Mammalian target of rapamycin (mTOR) plays an important role in papillary thyroid carcinoma (PTC) cell progression. CZ415 is a novel, highly-efficient and specific mTOR kinase inhibitor. The current study tested the potential anti-tumor activity of CZ415 in human PTC cells.

METHODS

The established (TPC-1 cell line) and primary human PTC cells were treated with CZ415. Cell survival and growth were tested by Cell Counting Kit-8 assay and BrdU ELISA assay, respectively. Cell apoptosis was tested by caspase-3/-9 activity assay, Hoechst-33342 staining assay and single-stranded DNA ELISA assay. Cell cycle progression was tested by propidium iodide-FACS assay. The mTOR signaling was tested by Western blotting assay and co-immunoprecipitation assay. The mouse xenograft tumor model was applied to study the effect of CZ415 in vivo.

RESULTS

In cultured human PTC cells, treatment with CZ415 at nM concentrations significantly inhibited cell survival and growth. CZ415 induced apoptosis activation and cell cycle arrest in human PTC cells. CZ415 disrupted assembling of mTORC1 (mTOR-Raptor association) and mTORC2 (mTOR-Rictor-GβL association) in TPC-1 cells, which led to de-phosphorylation of the mTORC1 substrates (S6K1 and 4E-BP1) and the mTORC2 substrate AKT (Ser-473). Further studies show that the autophagy inhibitor 3-methyladenine (3-MA) or Beclin-1 shRNA aggravated CZ415-induced cytotoxicity against PTC cells. In vivo, CZ415 oral administration inhibited TPC-1 xenograft tumor growth in mice.

CONCLUSION

Our results show that mTOR blockage by CZ415 inhibits PTC cell growth in vitro and in vivo.

Ghrelin protects adult rat hippocampal neural stem cells from excessive autophagy during oxygen-glucose deprivation

Ghrelin functions as a neuroprotective agent and saves neurons from various insults include ischemic injury. However, it remains to be elucidated whether ghrelin protects neuronal cells against ischemic injury-induced excessive autophagy. Autophagy is required for the maintenance of neural stem cell homeostasis. However, regarding autophagic cell death, it is commonly assumed that excessive autophagy leads to self-elimination of mammalian cells. The purpose of this study was to investigate the potential neuroprotection effects of ghrelin from excessive autophagy in adult rat hippocampal neural stem cells (NSCs). Oxygen-Glucose Deprivation (OGD) strongly induces autophagy in adult rat hippocampal NSCs. Ghrelin treatment inhibited OGD-induced cell death of adult rat hippocampal NSCs assessed by cell-counting-kit-8 assay. Ghrelin also suppressed OGD-induced excessive autophagy activity. The protective effect of ghrelin was accompanied by an increased expression levels of Bcl-2, p-62 and decreased expression level of LC3-II, Beclin-1 by Western blot. Furthermore, ghrelin reduced autophagosome formation and number of GFP-LC3 transfected puncta. In conclusion, our data suggest that ghrelin protects adult rat hippocampal NSCs from excessive autophagy in experimental stroke (oxygen-glucose deprivation) model. Regulating autophagic activity may be a potential optimizing target for promoting adult rat hippocampal NSCs based therapy for stroke.

Down-Regulation of Lncrna MALAT1 Attenuates Neuronal Cell Death Through Suppressing Beclin1-Dependent Autophagy by Regulating Mir-30a in Cerebral Ischemic Stroke

BACKGROUND/AIMS

LncRNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was reported to be highly expressed in an in vitro mimic of ischemic stroke conditions. However, the exact biological role of MALAT1 and its underlying mechanism in ischemic stroke remain to be elucidated.

METHODS

The roles of MALAT1 and miR-30a on cell death and infarct volume and autophagy were evaluated in experimental ischemic stroke. The relationships between miR-30a and MALAT1, Beclin1 were confirmed by luciferase reporter assay. The autophagy inhibitor 3-methyadenine (3-MA) was used to examine the impact of autophagy on ischemic injury.

RESULTS

We found that MALAT1, along with the levels of conversion from autophagy-related protein microtubule-associated protein light chain 3-I (LC3-I) to LC3-phosphatidylethanolamine conjugate (LC3-II), as well as Beclin1 were up-regulated and miR-30a was down-regulated in cerebral cortex neurons after oxygen-glucose deprivation (OGD) and mouse brain cortex after middle cerebral artery occlusion-reperfusion (MCAO). Down-regulation of MALAT1 suppressed ischemic injury and autophagy in vitro and in vivo. Furthermore, MALAT1 may serve as a molecular sponge for miR-30a and negatively regulate its expression. In addition, MALAT1 overturned the inhibitory effect of miR-30a on ischemic injury and autophagy in vitro and in vivo, which might be involved in the derepression of Beclin1, a direct target of miR-30a. Mechanistic analyses further revealed that autophagy inhibitor 3-methyadenine (3-MA) markedly suppressed OGD-induced neuronal cell death and MCAO-induced ischemic brain infarction.

CONCLUSION

Taken together, our study first revealed that down-regulation of MALAT1 attenuated neuronal cell death through suppressing Beclin1-dependent autophagy by regulating miR-30a expression in cerebral ischemic stroke. Besides, our study demonstrated a novel lncRNA-miRNA-mRNA regulatory network that is MALAT1-miR-30a-Beclin1 in ischemic stroke, contributing to a better understanding the pathogenesis and progression of ischemic stroke.

18α-Glycyrrhetinic acid lethality for neuroblastoma cells via de-regulating the Beclin-1/Bcl-2 complex and inducing apoptosis

18α-Glycyrrhetinic acid (18-GA) is a known gap-junction inhibitor with demonstrated anticancer effects. However, the different modes of cell cytotoxicity for 18-GA remain to be characterized. In this study, 18-GA reduced the expression of cell-cell interaction proteins (N- and VE-cadherin), and led to a dose-dependent increase in cytotoxicity of the neuroblastoma cells tested, but was less toxic toward actively dividing human embryonic kidney cells. We found that 18-GA could induce both autophagy and apoptosis. 18-GA mediated autophagy was due to accumulation of Atg5, Atg7 and LC3II and degradation of p62. Individual siRNAs against Atg5 and Atg7 prevented autophagy and resulted in a further loss of viability with 18-GA. In addition, combination of 18-GA with autophagy inhibitor chloroquine produced a more significant cell death. This implied a pro-survival function for autophagy induction with 18-GA. 18-GA also led to the destabilization of Bcl-2/Beclin-1 interaction and cleavage of Beclin-1, a protein known to play role in apoptosis and autophagy induction. Treatment of cells by a pan-caspase inhibitor or a caspase-3 siRNA prevented a large portion of 18-GA mediated cytotoxicity, demonstrating that caspase-dependent apoptosis induction was responsible for most of the observed cytotoxicity. In terms of signaling, 18-GA led to reduced phosphorylation of all three classes of MAP kinases. Taken together, 18-GA or its pathways may lead to more effective, targeted therapeutics against neuroblastoma.