Blockage of Extracellular Signal-Regulated Kinase Exerts an Antitumor Effect via Regulating Energy Metabolism and Enhances the Efficacy of Autophagy Inhibitors by Regulating Transcription Factor EB Nuclear Translocation in Osteosarcoma

Accumulating evidence suggests that extracellular signal-regulated kinase (ERK) is a valuable target molecule for cancer. However, antitumor drugs targeting ERK are still in their clinical phase and no FDA-approved medications exist. In this study, we identified an ERK inhibitor (ERKi; Vx-11e) with potential antitumor activities, which was reflected by the inhibition in the survival and proliferation of Osteosarcoma (OS) cells. Mechanistically, the ERKi regulated autophagic flux by promoting the translocation of transcription factor EB (TFEB) in OS cells, thereby increasing the dependence of OS cells on autophagy and sensitivity to treatment with autophagy inhibitors in OS. Besides, we also found that the ERKi could regulate mitochondrial apoptosis through the ROS/mitochondria pathway and aerobic glycolysis in OS, which also increases the dependence of OS cells on autophagy to clear metabolites to a certain extent. These results may provide a reference for the clinically improved efficacy of ERKis in combination with autophagy inhibitors in the treatment of OS and indicate its potential as a therapeutic agent.

Up-regulation thioredoxin contributes to inhibite diabetic hearing impairment

Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycemia. An association between DM and hearing impairment has been widely discussed. It’s essential to find effective prevetion or diagnosis of diabetic hearing loss. Thioredoxin (Trx) is a small molecule protein (12kDa) and plays biological functions such as anti-apoptotic, transcriptional regulation. In this study, our aim is to clarify the protective effect of Trx on diabetic hearing loss to find the early potential therapeutic target of diabetic hearing impairment in clinic in the future. Trx transgenic(Tg) mice was used to induce diabetic model by intraperitoneal injected Streptozotocin (STZ) and with/without SF or PX12 treatment. Succinate Dehydrogenase (SDH) Staining was used to evaluate the loss of hair cells. The relative expression of related proteins and genes was detected by Western blot and qRT-PCR. In diabetic mice, the outer hair cells were lost significantly. However, the loss of hair cells was delayed over-expression Trx. Moreover, the expression of PGC-1α, bcl-2 and LC3 was increased in Tg(+)-DM mice compared with Tg(-)-DM mice. The expression of ASK1, Txnip, GRP78, CHOP and p62 was decreased in Tg(+)-DM mice compared with Tg(-)-DM mice. Taken together, up-regulation Trx can protect cochlear hair cell from damage in diabetes. The underlying mechanism may be related to regulate ER stress through ASK1 and mitochondria pathway or autophagy via Txnip.

Up-regulation thioredoxin contributes to inhibite diabetic hearing impairment

Background Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycemia. An association between DM and hearing impairment has been widely discussed. It’s essential to find effective prevetion or diagnosis of diabetic hearing loss. Thioredoxin (Trx) is a small molecule protein (12kDa) and plays biological functions such as anti-apoptotic, transcriptional regulation. In this study, our aim is to clarify the protective effect of Trx on diabetic hearing loss to find the early potential therapeutic target of diabetic hearing impairment in clinic in the future. Methods Trx transgenic(Tg) mice was used to induce diabetic model by intraperitoneal injected Streptozotocin (STZ) and with/without SF or PX12 treatment. Succinate Dehydrogenase (SDH) Staining was used to evaluate the loss of hair cells. The relative expression of related proteins and genes was detected by Western blot and qRT-PCR. Results In diabetic mice, the outer hair cells were lost significantly. However, the loss of hair cells was delayed over-expression Trx. Moreover, the expression of PGC-1α, bcl-2 and LC3 was increased in Tg(+)-DM mice compared with Tg(-)-DM mice. The expression of ASK1, Txnip, GRP78, CHOP and p62 was decreased in Tg(+)-DM mice compared with Tg(-)-DM mice. Conclusion Taken together, up-regulation Trx can protect cochlear hair cell from damage in diabetes. The underlying mechanism may be related to regulate ER stress through ASK1 and mitochondria pathway or autophagy via Txnip.

Purine Metabolism and Hematopoietic Stem and Progenitor Stem Cells Under Stress

Hematopoietic stem cells (HSCs) play a key role in the lifelong maintenance of hematopoiesis through self-renewal and multi-lineage differentiation. Adult HSCs reside within a specialized microenvironment of the bone marrow (BM), called "niche", in which they are maintained in a quiescent state in cell cycle. Most of HSCs within BM show quiescence under the hypoxic niche. Since the loss of HSC quiescence leads to the exhaustion or aging of stem cells through excess cell division, the regulation of quiescence in HSCs is essential for hematopoietic homeostasis. On the other hand, cellular metabolism has been suggested to play a critical role in many biological processes including the regulation of stem cell properties and functions. However, the metabolic condition and adaptation of stem cells remain largely unaddressed. First, we have analyzed HSC metabolism using metabolomics approaches. With step-wise differentiation of stem cells, the cell metabolism associated with each differentiation stage may be different. A feature of quiescent HSCs is their low baseline energy production; quiescent HSCs rely on glycolysis and exhibit low mitochondrial membrane potential (ΔΨm). Likewise, HSCs with a low ΔΨm show higher reconstitution activity in BM hematopoiesis, compared to cells with high ΔΨm. By contrast, upon stress hematopoiesis, HSCs actively divide and proliferate. However, the underlying mechanism for the initiation of HSC division still remains unclear. In order to elucidate the mechanism underlying the transition of cell cycle state in HSCs, we analyzed the change of mitochondria activity in HSCs after BM suppression induced by 5-fluoruracil (5-FU). Upon 5-FU treatment, cycling progenitors are depleted and then quiescent HSCs start to divide. We found that HSCs initiate cell division after exhibiting enhanced ΔΨm, as a result of increased intracellular Ca2+ level. We hypothesize that extracellular adenosine, derived from hematopoietic progenitors, inhibits the calcium influx and mitochondrial metabolism. While further activation of Ca2+-mitochondria pathway led to loss of the stem cell function after cell division, the appropriate suppression of intracellular Ca2+ level by nifedipine, a blocker of L-type voltage-gated Ca2+ channels, prolonged cell division interval in HSCs, and simultaneously achieved both cell division and HSC maintenance (self-renewal division). Thus, our results indicate that the adenosine-Ca2+-mitochondria pathway induces HSC division critically to determine HSC cell fate. Next, to examine the mitochondria oxidative metabolism and purinergic pathways, we introduced the study on a tumor suppressor, Folliculin (FLCN). Conditional deletion of FLCN in HSC compartment using the Mx1-Cre or Vav-iCre system disrupted HSC quiescence and BM homeostasis dependently on the lysosomal stress response induced by TFE3. Together all, we propose that the change in cellular metabolism involving mitochondria is crucial for HSC homeostasis in the stress settings. Disclosures No relevant conflicts of interest to declare.