Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health

Implication of Pyrethroid Neurotoxicity for Human Health: A Lesson from Animal Models

Pyrethroids, synthetic insecticides used in pest management, pose health risks, particularly neurotoxic effects, with studies linking exposure to a neurodegenerative disorder. This review examines the neurotoxic mechanisms of pyrethroids analyzing literature from animal model studies. It identifies critical targets for neurotoxicity, including ion channels, oxidative stress, inflammation, neuronal cell loss, and mitochondrial dysfunction. The review also discusses key therapeutic targets and signaling pathways relevant to Pyrethroids neurotoxicity management, including calcium, Wnt/β-catenin, mTOR, MAPK/Erk, PI3K/Akt, Nrf2, Nurr1, and PPARγ. Our findings demonstrate that pyrethroid exposure triggers multiple neurotoxic pathways that bear resemblance to the mechanisms underlying neurotoxicity. Oxidative stress and inflammation emerge as prominent factors that contribute to neuronal degeneration, alongside disrupted mitochondrial function. The investigation highlights the significance of ion channels as primary neurodegeneration targets while acknowledging the potential involvement of various other receptors and enzymes that may exacerbate neurological damage. Additionally, we elucidate how pyrethroids may interfere with therapeutic targets associated with neuronal dysfunction, potentially impairing treatment efficacy.Also, exposure to these chemicals can alter DNA methylation patterns and histone modifications, ultimately leading to changes in gene expression that may enhance susceptibility to neurological disorders. Pyrethroid neurotoxicity poses a significant public health risk, necessitating future research for protective strategies against pesticide-induced neurological disorders and understanding the interplay between neurodegenerative diseases, potentially leading to innovative therapeutic interventions.

Stanniocalcin 2 Regulates Autophagy and Ferroptosis in Mammary Epithelial Cells of Dairy Cows Through the Mechanistic Target of Rapamycin Complex 1 Pathway

BACKGROUND

Stanniocalcin 2 (STC2), a glycoprotein hormone, is extensively expressed in various organs and tissues, particularly in the mammary gland. STC2 plays a crucial role in enabling cells to adapt to stress conditions and avert apoptosis. The efficiency of milk production is closely linked to both the quantity and quality of mammary cells. Yet, there remains a dearth of research on the impact of STC2 on mammary cells' activity in dairy cows.

OBJECTIVES

The objective of this study was to investigate the effects of STC2 on the viability of mammary epithelial cells in dairy cows and to elucidate the underlying mechanisms.

METHODS

First, the Gene Expression Profiling and Interactive Analysis database was employed to perform survival analysis on STC2 expression in relation to prognosis using The Cancer Genome Atlas and GETx data. Subsequently, the basic physical and chemical properties, gene expression, and potential signaling pathways involved in the growth of dairy cow mammary epithelial cells were determined using STC2 knockdown.

RESULTS

STC2 knockdown significantly suppressed autophagy in mammary epithelial cells of dairy cows. Moreover, STC2 knockdown upregulated glutathione peroxidase 4 protein expression, elicited an elevation in lipid ROS concentrations, and inhibited the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway, consequently repressing downstream genes involved in lipid synthesis regulated by mTORC1 and ultimately inducing ferroptosis.

CONCLUSIONS

The findings of our study suggest that STC2 suppresses autophagy and ferroptosis through the activation of mTORC1. Mechanically, STC2 exerts an inhibitory effect on ferroptosis by activating antioxidative stress-related proteins, such as glutathione peroxidase 4, to suppress lipid ROS production and stimulating the mTORC1 signaling pathway to enhance the expression of genes associated with lipid synthesis.

Propionate promotes gluconeogenesis by regulating mechanistic target of rapamycin (mTOR) pathway in calf hepatocytes

Enhancing hepatic gluconeogenesis is one of the main modes of meeting the glucose requirement of dairy cows. This study attempted to determine whether the gluconeogenesis precursor propionate had an effect on the expression of the main genes involved in gluconeogenesis in calf hepatocytes and elucidate the associated mechanisms. Calf hepatocytes were obtained from 5 healthy calves (1 d old; 30 to 40 kg) and exposed to 0-, 1-, 2.5-, or 5-mM sodium propionate (NaP), which is known to promote the expression of genes involved in the gluconeogenesis pathway, including fructose 1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase. With regard to the underlying mechanism, propionate promoted the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, hepatocyte nuclear factor 4, and forkhead box O1 (transcription factors that regulate the expression of hepatic gluconeogenic genes) by promoting mammalian target of rapamycin complex 1 (mTORC1), but inhibiting mTORC2 activity (P < 0.01). We also established a model of palmitic acid (PA)-induced hepatic injury in calf hepatocytes and found that PA could inhibit the gluconeogenic capacity of calf hepatocytes by suppressing the expression of gluconeogenic genes, inhibiting mTORC1, and promoting the activity of mTORC2 (P < 0.01). In contrast, NaP provided protection to calf hepatocytes by counteracting the inhibitory effect of PA on the gluconeogenic capacity of calf hepatocytes (P < 0.05). Collectively, these findings indicate that NaP enhances the gluconeogenic capacity of calf hepatocytes by regulating the mTOR pathway activity. Thus, in addition to improving the glucose production potential, propionate may have therapeutic potential for the treatment of hepatic injury in dairy cows.

Role of the p38/AKT Pathway in the Promotion of Cell Proliferation by Serum Heat Inactivation

Serum is a common biomaterial in cell culture that provides nutrients and essential growth factors for cell growth. Serum heat inactivation is a common treatment method whose main purpose is to remove complement factors and viruses. As serum contains many heat-labile factors, heat inactivation may affect cell proliferation, migration, differentiation, and other functions. However, the specific mechanism of its effect on cell function has not been studied. Thus, we investigate the exact effects of heat-inactivated FBS on the viability of various cells and explore the possible molecular mechanisms. We treated HCT116, HT-29, and HepG2 cell lines with heat-inactivated (56 °C for 30 min) medium, DMEM, or fetal bovine serum (FBS) for different times (0, 10, 15, 30, 60, or 90 min); we found that heat-inactivated FBS significantly promoted the viability of these cells, whereas DMEM did not have this effect. Moreover, heat-inactivated FBS stimulated cells to produce a small amount of ROS and activated intracellular signaling pathways, mainly the p38/AKT signaling pathway. These results indicate that heat-inactivated FBS may regulate the p38/AKT signaling pathway by promoting the production of appropriate amounts of ROS, thereby regulating cell viability.

Changes of Signaling Pathways in Hypothalamic Neurons with Aging

The hypothalamus is an important regulator of autonomic and endocrine functions also involved in aging regulation. The aging process in the hypothalamus is accompanied by disturbed intracellular signaling including insulin/insulin-like growth factor-1 (IGF-1)/growth hormone (GH), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/protein kinase B (AKT)/the mammalian target of rapamycin (mTOR), mitogen activated protein kinase (MAPK), janus kinase (JAK)/signal transducer and activator of transcription (STAT), AMP-activated protein kinase (AMPK), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-ĸB), and nitric oxide (NO). In the current review, I have summarized the current understanding of the changes in the above-mentioned pathways in aging with a focus on hypothalamic alterations.

Butyrate dictates ferroptosis sensitivity through FFAR2-mTOR signaling

Evidence shows that short-chain fatty acids (SCFAs) play an important role in health maintenance and disease development. In particular, butyrate is known to induce apoptosis and autophagy. However, it remains largely unclear whether butyrate can regulate cell ferroptosis, and the mechanism by which has not been studied. In this study, we found that RAS-selective lethal compound 3 (RSL3)- and erastin-induced cell ferroptosis were enhanced by sodium butyrate (NaB). With regard to the underlying mechanism, our results showed that NaB promoted ferroptosis by inducing lipid ROS production via downregulating the expression of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4). Moreover, the FFAR2-AKT-NRF2 axis and FFAR2-mTORC1 axis accounts for the NaB-mediated downregulation of SLC7A11 and GPX4, respectively, in a cAMP-PKA-dependent manner. Functionally, we found that NaB can inhibit tumor growth and the inhibitory effect could be eliminated by administrating MHY1485 (mTORC1 activator) and Ferr-1 (ferroptosis inhibitor). Altogether, in vivo results suggest that NaB treatment is correlated to the mTOR-dependent ferroptosis and consequent tumor growth through xenografts and colitis-associated colorectal tumorigenesis, implicating the potential clinical applications of NaB for future colorectal cancer treatments. Based on all these findings, we have proposed a regulatory mechanism via which butyrate inhibits the mTOR pathway to control ferroptosis and consequent tumorigenesis.

Role of FLCN Phosphorylation in Insulin-Mediated mTORC1 Activation and Tumorigenesis

The amino acid-stimulated Rag GTPase pathway is one of the main pathways that regulate mechanistic target of rapamycin complex 1 (mTORC1) activation and function, but little is known about the effects of growth factors on Rag GTPase-mediated mTORC1 activation. Here, a highly conserved insulin-responsive phosphorylation site on folliculin (FLCN), Ser62, that is phosphorylates by AKT1 is identified and characterized. mTORC2-AKT1 is localized on lysosomes, and RagD-specific recruitment of mTORC2-AKT1 on lysosomes is identified as an essential step in insulin-AKT1-mediated FLCN phosphorylation. Additionally, FLCN phosphorylation inhibits the activity of RagC GTPase and is essential for insulin-induced mTORC1 activation. Functionally, phosphorylated FLCN promotes cell viability and induces autophagy, and also regulates in vivo tumor growth in an mTORC1-dependent manner. Its expression is also positively correlated with mTORC1 activity in colon cancer, clear cell renal cell carcinoma, and chordoma. These results indicate that FLCN is an important intermediate for cross-talk between the amino acid and growth factor pathways. Further, FLCN phosphorylation may be a promising therapeutic target for diseases characterized by mTORC1 dysregulation.

Trans-gnetin H isolated from the seeds of Paeonia species induces autophagy via inhibiting mTORC1 signalling through AMPK activation

Paeonia is a well-known species of ornamental plants, traditional Chinese medicines, and emerging oilseed crops. Apart from nutritional unsaturated fatty acids, the seeds of peonies are rich in stilbenes characterized by their wide-ranging health-promoting properties. Although the typical stilbene resveratrol has been widely reported for its multiple bioactivities, it remains uncertain whether the trimer of resveratrol trans-gnetin H has properties that regulate cancer cell viability, let alone the underlying mechanism. Autophagy regulated by trans-gnetin H was detected by western blotting, immunofluorescence, and quantitative real-time PCR. The effects of trans-gnetin H on apoptosis and proliferation were examined by flow cytometry, colony formation and Cell Counting Kit-8 assays. Trans-gnetin H significantly inhibits cancer cell viability through autophagy by suppressing the phosphorylation of TFEB and promoting its nuclear transport. Mechanistically, trans-gnetin H inhibits the activation and lysosome translocation of mTORC1 by inhibiting the activation of AMPK, indicating that AMPK is a checkpoint for mTORC1 inactivation induced by trans-gnetin H. Moreover, the binding of TSC2 to Rheb was markedly increased in response to trans-gnetin H stimulation. Similarly, trans-gnetin H inhibited the interaction between Raptor and RagC in an AMPK-dependent manner. More importantly, trans-gnetin H-mediated autophagy highly depends on the AMPK-mTORC1 axis. We propose a regulatory mechanism by which trans-gnetin H inhibits the activation of the mTORC1 pathway to control cell autophagy.

Suffruticosol C-Mediated Autophagy and Cell Cycle Arrest via Inhibition of mTORC1 Signaling

Paeonia species are well-known ornamental plants that are used in traditional Chinese medicines. The seeds of these species are rich in stilbenes, which have wide-ranging health-promoting effects. In particular, resveratrol, which is a common stilbene, is widely known for its anticancer properties. Suffruticosol C, which is a trimer of resveratrol, is the most dominant stilbene found in peony seeds. However, it is not clear whether suffruticosol C has cancer regulating properties. Therefore, in the present study, we aimed to determine the effect of suffruticosol C against various cancer cell lines. Our findings showed that suffruticosol C induces autophagy and cell cycle arrest instead of cell apoptosis and ferroptosis. Mechanistically, suffruticosol C regulates autophagy and cell cycle via inhibiting the mechanistic target of rapamycin complex 1 (mTORC1) signaling. Thus, our findings imply that suffruticosol C regulates cancer cell viability by inducing autophagy and cell cycle arrest via the inhibition of mTORC1 signaling.