Inhibition of PI3K/Akt/mTOR signaling by NDRG2 contributes to neuronal apoptosis and autophagy in ischemic stroke.

BACKGROUND: Astrocytic N-myc downstream-regulated gene 2 (NDRG2), a differentiation- and stress-associated molecule, has been involved in the cause of ischemic stroke (IS). However, its downstream effector in IS remains unclear. This study aimed to characterize expression of NDRG2 in IS patients and rats and to investigate the underlying mechanism. METHODS: The protein expression of NDRG2 and mammalian target of the rapamycin (mTOR) and the extent of mTOR phosphorylation in plasma of IS patients were detected by ELISA. An oxygen-glucose deprivation model was established in mouse neuronal cells CATH.a, followed by cell counting kit-8, flow cytometry, TUNEL, and western blot assays to examine cell viability, apoptosis and autophagy. Finally, the effect of NDRG2-mediated phosphatidylinositol 3-kinase/protein kinase-B/mTOR (PI3K/AKT/mTOR) pathway on neuronal apoptosis and autophagy was verified in rats treated with middle cerebral artery occlusion. RESULTS: NDRG2 was highly expressed in the plasma of IS patients, while the extent of mTOR phosphorylation was reduced in IS patients. NDRG2 blocked the PI3K/Akt/mTOR signaling through dephosphorylation. Depletion of NDRG2 suppressed apoptosis and autophagy in CATH.a cells, which was reversed by a dual inhibitor of PI3K and mTOR, BEZ235. In vivo experiments confirmed that NDRG2 promoted neuronal apoptosis and autophagy by dephosphorylating and blocking the PI3K/Akt/mTOR signaling. CONCLUSION: The present study has shown that NDRG2 impairs the PI3K/Akt/mTOR pathway via dephosphorylation to promote neuronal apoptosis and autophagy in IS. These findings provide potential targets for future clinical therapies for IS.

LncRNA KCNQ1OT1 attenuates osteoarthritic chondrocyte dysfunction via the miR-218-5p/PIK3C2A axis.

The occurrence of osteoarthritis is closely related to chondrocyte dysfunction caused by cellular inflammatory response and matrix degradation, which seriously affect the quality of life of patients. Therefore, this study aimed to investigate the role of potassium voltage-gated channel subfamily Q member 1 overlapping transcript 1 (KCNQ1OT1), a member of the lncRNA voltage-gated channel subfamily Q, in the development of osteoarthritis. In this study, RT-qPCR results showed that KCNQ1OT1 expression was downregulated in osteoarthritic chondrocytes compared with normal chondrocytes. In addition, upregulation of KCNQ1OT1 significantly enhanced the viability of osteoarthritic chondrocytes, inhibited cell apoptosis, and reduced the release of inflammatory cytokines and metal matrix enzymes. Next, bioinformatics analysis and luciferase reporter gene analysis predicted and validated the targeting relationship between KCNQ1OT1 and miR-218-5p. We found that the expression of miR-218-5p was significantly upregulated in osteoarthritic chondrocytes, and knockdown of miR-218-5p significantly enhanced the viability of osteoarthritic chondrocytes, inhibited apoptosis, and decreased the abundance of inflammatory cytokines and metal matrix enzymes. Furthermore, the targeting relationship between miR-218-5p and recombinant phosphoinositide-3-kinase class-2-alpha polypeptide (PIK3C2A) was identified, and overexpression of PIK3C2A enhanced cell viability, and reduced apoptosis and secretion of inflammatory factors. Finally, we found that miR-218-5p overexpression reversed the protective effect of overexpression of KCNQ1OT1 or PIK3C2A on osteoarthritic chondrocytes. In conclusion, our results demonstrated that KCNQ1OT1 upregulated PIK3C2A and activated the PI3K/AKT/mTOR pathway to reduce chondrocyte dysfunction by targeting miR-218-5p, providing new insights into the pathogenesis of osteoarthritis.

Knockdown of KLF5 suppresses hypoxia-induced resistance to cisplatin in NSCLC cells by regulating HIF-1α-dependent glycolysis through inactivation of the PI3K/Akt/mTOR pathway.

BACKGROUND: Hypoxia-mediated chemoresistance has been regarded as an important obstacle in the development of cancer treatment. Knockdown of krüppel-like factor 5 (KLF5) was reported to inhibit hypoxia-induced cell survival and promote cell apoptosis in non-small cell lung cancer (NSCLC) cells via direct regulation of hypoxia inducible factor-1α (HIF-1α) expression. However, the roles of KLF5 in the development of hypoxia-induced cisplatin (DDP) resistance and its underlying mechanism in NSCLC cells remain to be further elucidated. METHODS: Western blot was performed to determine the protein levels of KLF5, P-glycoprotein (P-gp) and HIF-1α in treated NSCLC cells. Cell survival was examined by MTT assay. The effect of KLF5 knockdown on hypoxia-induced glycolysis was assessed by measuring glucose consumption and lactate production. The effect of KLF5 knockdown on the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway was analyzed by western blot. RESULTS: Hypoxia upregulated the expression of KLF5 in NSCLC cells. KLF5 knockdown suppressed hypoxia-induced DDP resistance in NSCLC cells, as demonstrated by the increased cytotoxic effects of DDP and reduced P-gp expression in NSCLC cells in hypoxia. Moreover, KLF5 knockdown inhibited hypoxia-induced HIF-1α expression and glycolysis, and KLF5 knockdown suppressed hypoxia-induced DDP resistance by inhibiting HIF-1α-dependent glycolysis in NSCLC cells. Furthermore, KLF5 knockdown suppressed hypoxia-induced activation of the PI3K/Akt/mTOR pathway in NSCLC cells and KLF5 overexpression promoted hypoxia-induced DDP resistance in NSCLC cells through activation of the PI3K/Akt/mTOR pathway. CONCLUSIONS: KLF5 knockdown could suppress hypoxia-induced DDP resistance, and its mechanism may be due to the inhibition of HIF-1α-dependent glycolysis via inactivation of the PI3K/Akt/mTOR pathway.

Rotating magnetic field improves cognitive and memory impairments in APP/PS1 mice by activating autophagy and inhibiting the PI3K/AKT/mTOR signaling pathway.

Alzheimer's disease (AD) is a geriatric disorder that can be roughly classified into sporadic AD and hereditary AD. The latter is strongly associated with genetic factors, and its treatment poses greater challenges compared to sporadic AD. Rotating magnetic fields (RMF) is a non-invasive treatment known to have diverse biological effects, including the modulation of the central nervous system and aging. However, the impact of RMF on hereditary AD and its underlying mechanism remain unexplored. In this study, we exposed APP/PS1 mice to RMF (2 h/day, 0.2 T, 4 Hz) for a duration of 6 months. The results demonstrated that RMF treatment significantly ameliorated their cognitive and memory impairments, attenuated neuronal damage, and reduced amyloid deposition. Furthermore, RNA-sequencing analysis revealed a significant enrichment of autophagy-related genes and the PI3K/AKT-mTOR signaling pathway. Western blotting further confirmed that RMF activated autophagy and suppressed the phosphorylation of proteins associated with the PI3K/AKT/mTOR signaling pathway in APP/PS1 mice. These protective effects and the underlying mechanism were also observed in Aß25-35-exposed HT22 cells. Collectively, our findings indicate that RMF improves cognitive and memory dysfunction in APP/PS1 mice by activating autophagy and inhibiting the PI3K/AKT/mTOR signaling pathway, thus highlighting the potential of RMF as a clinical treatment for hereditary AD.

LHPP suppresses gastric cancer progression via the PI3K/AKT/mTOR signaling pathway.

Emerging evidence has revealed the anti-oncogenic role of LHPP in several malignancies. The current study aims to explore the underlying mechanism of LHPP in gastric cancer (GC). We used the TCGA and GEO databases to investigate the expression profile, prognostic value, and cellular function of LHPP in GC. LHPP expression pattern were further verified using clinical samples by immunohistochemistry and western blot analysis. Moreover, stable cancer cell lines with LHPP overexpression or knockdown were established. CCK-8 assay, colony formation assay, transwell assay, qRT-PCR, and western blot analysis were performed to uncover the underlying mechanism concerning LHPP during the progression of GC. The present study revealed that LHPP was down-regulated in GC cell lines and tissue samples at both mRNA and protein level. LHPP inhibited GC cells proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro. Mechanically, LHPP overexpression led to decreased level of PI3K/AKT/mTOR pathway phosphorylation, while LHPP depletion produced opposite results. Moreover, our data indicated that the enzymatic active site of LHPP is neither the cysteine residue at position 226 nor at position 53 in GC. Overall, our study demonstrated that LHPP function as a tumor suppressor gene in GC by regulating the PI3K/AKT/mTOR pathway.

Curcumin suppresses the progression of laryngeal squamous cell carcinoma through the upregulation of miR-145 and inhibition of the PI3K/Akt/mTOR pathway.

BACKGROUND: Curcumin is a polyphenol extracted from the rhizomes of Curcuma longa with extensive biological and pharmacological effects. The present study aimed to investigate the mechanisms of curcumin in laryngeal squamous cell carcinoma (LSCC). METHODS: Quantitative real-time reverse transcriptase-polymerase chain reaction was performed to detect the expressions of miR-145 in LSCC tissues and cells. The effects of miR-145 and curcumin on cell proliferation, apoptosis, cell cycle, migration and invasion were explored by MTT assay, flow cytometry analysis, Transwell migration and invasion assay, respectively. The effects of miR-145 combined with curcumin on the phosphoinositol 1,3 kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway were detected by Western blot analysis. RESULTS: miR-145 was significantly downregulated in LSCC tissues and cells. Curcumin administration upregulated miR-145 expression in LSCC cells in a dose-dependent manner. miR-145 overexpression and curcumin treatment both markedly suppressed cell proliferation, migration and invasion and induced cell cycle arrest and apoptosis in LSCC cells. Moreover, curcumin treatment reversed the enhanced effects on cell viability, migration and invasion and the inhibitory effects on apoptosis conferred by anti-miR-145 in LSCC cells. Curcumin treatment dramatically aggravated miR-145-induced inhibition of the PI3K/Akt/mTOR pathway and reversed anti-miR-145-mediated activation of the PI3K/Akt/mTOR pathway in LSCC cells. CONCLUSION: Curcumin suppressed LSCC progression through the upregulation of miR-145 and inhibition of the PI3K/Akt/mTOR pathway.