Itaconate inhibits corticosterone-induced necroptosis and neuroinflammation via up-regulating menin in HT22 cells.

Corticosterone (CORT) damages hippocampal neurons as well as induces neuroinflammation. The tricarboxylic acid cycle metabolite itaconate has an anti-inflammatory role. Necroptosis is a form of programmed cell death, also known as inflammatory cell death. Menin is a multifunctional scaffold protein, which deficiency aggravates neuroinflammation. In this study, we explored whether itaconate inhibits CORT-induced neuroinflammation as well as necroptosis and further investigated the mediatory role of Menin in this protective effect of itaconate by using an exposure of CORT to HT22 cells (a hippocampal neuronal cell line). The viability of HT22 cells was examined by the cell counting kit 8 (CCK-8). The morphology of HT22 cells was observed by transmission electron microscope (TEM). The expressions of necroptosis-related proteins (p-RIP1/RIP1, p-RIP3/RIP3, and p-MLKL/MLKL) were evaluated by western blotting. The contents of inflammatory factors were detected by an enzyme-linked immunosorbent assay (ELISA) kit. Our results showed that CORT increases the contents of pro-inflammatory factors (IL-1ß, TNF-α) as well as decreases the contents of anti-inflammatory factors (IL-4, IL-10) in HT22 cells. We also found that CORT increases the expressions of necroptosis-related proteins (p-RIP1/RIP1, p-RIP3/RIP3, and p-MLKL/MLKL) and decreases the cell viability in HT22 cells, indicating that CORT induces necroptosis in HT22 cells. Itaconate improves CORT-induced neuroinflammation and necroptosis. Furthermore, itaconate upregulates the expression of Menin in CORT-exposed HT22 cells. Importantly, silencing Menin abolishes the antagonistic effect of itaconate on CORT-induced necroptosis and neuroinflammation. In brief, these results indicated that itaconate protects HT22 cells against CORT-induced neuroinflammation and necroptosis via upregulating Menin.

Isthmin: A multifunctional secretion protein.

Isthmin is a polypeptide secreted by adipocytes that was first detected in Xenopus gastrula embryos. Recent studies have focused on the biological functions of isthmin in growth and development, angiogenesis, and metabolism. Distinct spatiotemporal expression of isthmin-1 (ISM-1) was observed during growth and development. ISM-1 plays an important role in the occurrence and development of cancer by regulating cell proliferation, migration, angiogenesis, and immune microenvironments. Moreover, ISM-1, as a newly identified insulin-like adipokine, increases adipocyte glucose uptake and inhibits hepatic lipid synthesis. However, the biological function of ISM-1 remains largely unknown. In this review, we highlight the structure and physiological functions of isthmin and explore its application potential, contributing to a better understanding of its function and providing prevention and treatment strategies for various diseases.

Hydrogen sulfide antagonizes formaldehyde-induced ferroptosis via preventing ferritinophagy by upregulation of GDF11 in HT22 cells.

Formaldehyde (FA) has neurotoxic characteristics and causes neurodegenerative disease. Our previous study demonstrated the neuroprotective effects of hydrogen sulfide (H2S) on FA-induced neurotoxicity in HT22 cells. Emerging evidence have supported that ferroptosis is involved in FA-induced neurotoxicity. To understand the mechanism of the protection of H2S against FA-induced neurotoxicity, this study explored the regulatory effect of H2S on FA-induced ferroptosis and the underlying mechanisms. The researcher found that H2S (100, 200, and 400 µM, 30 min) reverses the ferroptosis induced by FA (100 µM, 24 h) in HT22 cells (a cell line of mouse hippocampal neurons), including decreases in free iron, reactive oxygen species (ROS), 4-hydroxy-2-trans-nominal (4-HNE), and malondialdehyde (MDA) contents, as well as an increase in glutathione (GSH) content. H2S (100, 200, and 400 µM, 30 min) also inhibited ferritinaphagy in FA-exposed HT22 cells, as evidenced by the downregulation of the ferritinophagy receptor nuclear receptor coactivator 4 (NCOA4) and microtubule-associated protein 1 light chain-3B (LC3B) as well as the upregulation of the main iron storage protein ferritin heavy chain 1 (FTH1) and p62. H2S (100, 200, and 400 µM, 30 min) also up-regulated the expression of growth differentiation factor-11 (GDF11) in FA-exposed HT22 cells. Furthermore, knockdown of GDF11 in HT22 cells cancelled the beneficial effects of H2S in FA-induced ferroptosis and ferritinaphagy. These data indicated that the protective mechanism underlying H2S-prevented neurotoxicity of FA is involved in alleviating FA-induced ferroptosis via inhibiting ferritinaphagy by upregulation of GDF11.

Improvement of autophagic flux mediates the protection of hydrogen sulfide against arecoline-elicited neurotoxicity in PC12 cells.

Arecoline, the most abundant alkaloid of the areca nut, induces toxicity to neurons. Hydrogen sulfide (H2S) is an endogenous gas with neuroprotective effects. We recently found that arecoline reduced endogenous H2S content in PC12 cells. In addition, exogenously administration of H2S alleviated the neurotoxicity of arecoline on PC12 cells. Increasing evidence has demonstrated the neuroprotective role of improvement of autophagic flux. Therefore, the aim of the present work is to explore whether improvement of autophagic flux mediates the protection of H2S against arecoline-caused neurotoxicity. Transmission electron microscope (TEM) for observation of ultrastructural morphology. Western blotting was used to detect protein expression of the related markers. Functional analysis contained LDH release assay, Hoechst 33,258 nuclear staining and flow cytometry were used to detect cytotoxicity and apoptosis. In the present work, we found that arecoline disrupted autophagy flux in PC12 cells as evidenced by accumulation of autophagic vacuoles, increase in LC3II/LC3I, and upregulation of p62 expression in PC12 cells. Notably, we found that sodium hydrosulfide (NaHS), the donor of H2S improved arecoline-blocked autophagy flux in PC12 cells. Furthermore, we found that blocking autophagic flux by chloroquine (CQ), the inhibitor of autophagy flux, antagonized the inhibitory role of NaHS in arecoline-induced cytotoxicity apoptosis and endoplasmic reticulum (ER) stress. In conclusion, H2S improves arecoline-caused disruption of autophagic flux to exert its protection against the neurotoxicity of arecoline.

PI3K/AKT pathway mediates the antidepressant- and anxiolytic-like roles of hydrogen sulfide in streptozotocin-induced diabetic rats via promoting hippocampal neurogenesis.

We have previously demonstrated that hydrogen sulfide (H2S), the third endogenous gasotransmitter, ameliorates the depression- and anxiety-like behaviors in diabetic rats, but the underlying mechanism remains unclear. The present was aimed to investigate whether the hippocampal phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway mediates H2S-ameliorated depression- and anxiety-like behaviors in diabetic rats by improving the hippocampal neurogenesis. The depression-like behaviors were examined by Tail suspension test (TST), the anxiety-like behaviors were examined by Elevated plus maze test (EPM), and the locomotor activity was detected by Open Field Test (OFT). The expressions of doublecortin (DCX), neuron-specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), p-AKT, and AKT in the hippocampus were determined by Western blot analysis. Results showed that NaHS, a donor of exogenous H2S, not only activated the hippocampal PI3K/AKT pathway, as evidenced by the increase of phosphorylated AKT, but also favorably reversed streptozotocin (STZ)-disturbed hippocampal neurogenesis, as evidenced by the increases in the expressions of DCX and NeuN as well as the decrease in the expression of GFAP in the hippocampus of STZ-induced diabetic rats. Furthermore, inhibited PI3K/AKT pathway by LY294002 significantly abolished H2S-exerted the improvement of hippocampal neurogenesis and the antidepressant- and anxiolytic-like effects in the STZ-induced diabetic rats. Taken together, these results uncover that the activation of hippocampal PI3K/AKT pathway plays an important role to restore hippocampal neurogenesis and subsequently to mediate the antidepressant- and anxiolytic-like roles of H2S in STZ-induced diabetic rats and enhance our understanding of the robustness of H2S as a therapeutic strategy for treatment of depression in diabetes mellitus.

Formaldehyde induces ferroptosis in hippocampal neuronal cells by upregulation of the Warburg effect.

The mechanisms underlying formaldehyde (FA)-induced neurotoxicity have not yet been fully clarified. Ferroptosis is a novel regulatory cell death and the Warburg effect is involved in regulating neural function. In this study, we investigated whether FA-induced neurotoxicity is implicated in neuronal ferroptosis and determined whether the Warburg effect mediates FA-induced neuronal ferroptosis. We found that FA (0.1, 0.5 and 1.0 mM, 6 h) induced cell death in HT22 cells (a cell line of mouse hippocampal neuron), as evidenced by a decrease in cell viability and an increase in cell mortality; enhanced oxidative stress, as evidenced by a decrease in glutathione (GSH) and increases in malondialdehyde (MDA), 4-Hydroxynonenal (4-HNE), as well as reactive oxygen species (ROS); increased the iron content; and upregulated the ferroptosis-associated genes, including Ptgs2 (prostaglandin-endoperoxide synthase 2), GLS2 (glutaminase 2), solute carrier family 1 member 5 (SLC1A5), and solute carrier family 38 member 1 (SLC38A1) in HT22 cells, indicating the inductive role of FA in the ferroptosis of HT22 cells. Meanwhile, we found that FA (0.1, 1, 10 µmol) decreased the cross-sectional of mitochondria, increased the level of lipid ROS and iron content in primary hippocampal cells. We showed that FA (0.1, 0.5 and 1.0 mM, 6 h) upregulated the Warburg effect in HT22 cells, as evidenced by up-regulations of pyruvate kinase M2 (PKM2), pyruvate dehydrogenase kinase 1(PDK-1), and lactate dehydrogenase (LDHA) proteins; down-regulation of pyruvate dehydrogenase (PDH); and an increase in lactate production. Also, we found that FA (0.1, 1, 10 µmol, 7 d) upregulated the Warburg effect in hippocampal tissue, as evidenced by up-regulations of PKM2, PDK-1, and LDHA proteins; down-regulation of PDH. Furthermore, the inhibition of the Warburg effect by dichloroacetate (DCA) protected HT22 cells against FA-induced ferroptosis and cell death. Collectively, these data indicated that FA induces ferroptosis in hippocampal neuronal cells by upregulation of the Warburg effect.

Hydrogen Sulfide Inhibits Homocysteine-Induced Neuronal Senescence by Up-Regulation of SIRT1.

Homocysteine (Hcy) accelerates neuronal senescence and induces age-related neurodegenerative diseases. Silence signal regulating factor 1 (SIRT1) prolongs lifespan and takes neuroprotective effects. We have previously demonstrated that hydrogen sulfide (H2S) prevents Hcy-induced apoptosis of neuronal cells and has neuroprotective effect. In the present work, we aimed to investigate whether H2S protects HT22 cells against Hcy-induced neuronal senescence and whether SIRT1 mediates this role of H2S. We found that Hcy induced cellular senescence in HT22 cells, as determined by ß-galactosidase staining, expressions of P16INK4a, P21CIPL, and trypan blue Staining, which are the markers of cellular senescence. However, sodium hydrosulfide (NaHS, the donor of H2S) significantly reversed Hcy-induced cellular senescence. Interestingly, NaHS not only up-regulated the expression of SIRT1 in HT22 cells but also reversed Hcy-downregulated the expression of SIRT1 in HT22 cells. Furthermore, we found that pretreatment with Sirtinol (an inhibitor of SIRT1) markedly reversed the protection of NaHS against Hcy-induced HT22 cells senescence and apoptosis. Our findings illustrated that H2S protects HT22 cells against Hcy-induced senescence by up-regulating SIRT1.

Hydrogen Sulfide Inhibits Formaldehyde-Induced Senescence in HT-22 Cells via Upregulation of Leptin Signaling.

It has been previously demonstrated that hydrogen sulfide (H2S) prevents formaldehyde (FA)-induced neurotoxicity. However, the exact mechanisms underlying this protection remain to be fully elucidated. Neuronal senescence is involved in FA-induced neurotoxicity. Leptin signaling has anti-aging function. The present work was to investigate the protection of H2S against FA-induced neuronal senescence and the mediatory role of leptin signaling. FA-exposed HT-22 cells were used as the vitro model of FA-induced neuronal senescence. The senescence-associated ß-galactosidase (SA-ß-Gal) positive cell was detected by ß-galactosidase staining. The expressions of P16INK4a, P21CIP1, leptin, and lepRb (leptin receptor) were measured by western blot. The proliferation, viability, and apoptosis of cells were evaluated by Trypan blue exclusion assay, Cell Counting Kit-8 (CCK-8) assay, and Flow cytometry analysis, respectively. We found that H2S suppressed FA-induced senescence, as evidenced by the decrease in SA-ß-Gal positive cells, the downregulations of P16INK4a and P21CIP1, as well as decrease in cell growth arrest, in HT-22 cells. Also, H2S upregulated the expressions of leptin and lepRb in FA-exposed HT-22 cells. Furthermore, leptin tA (a specific inhibitor of the leptin) abolished the protective effects of H2S on FA-induced senescence and neurotoxicity (as evidenced by the increase in cell viability and the decrease in cell apoptosis) in HT-22 cells. These results indicated that H2S prevents FA-induced neuronal senescence via upregulation of leptin signaling. Our findings offer a novel insight into the mechanisms underlying the protection of H2S against FA-induced neurotoxicity. FA upregulates the expressions of P16INK4a and P21CIP1 via inhibiting leptin signaling, which in turn induces senescence in HT-22 cells; H2S downregulates the expressions of P16INK4a and P21CIP1 via reversing FA-downregulated leptin signaling, which in turn prevents FA-induced senescence in HT-22 cells.

Hydrogen sulfide prevents homocysteine­induced endoplasmic reticulum stress in PC12 cells by upregulating SIRT­1.

It was previously confirmed that hydrogen sulfide (H2S) has a neuroprotective effect, preventing homocysteine­induced neurotoxicity. However, the exact molecular mechanisms underlying this protective effect remain to be fully elucidated. Endoplasmic reticulum (ER) stress contributes to homocysteine­induced neurotoxicity. Silent mating type information regulator 2 homolog 1 (SIRT­1) can attenuate ER stress, exerting its neuroprotective effect. Therefore, the present study aimed to investigate whether H2S protects PC12 cells against homocysteine­induced ER stress and whether SIRT­1 mediates this protective effect of H2S. Western blotting was used to detect the expression of SIRT­1, glucose­regulated protein 78 (GRP78), and cleaved caspase­12 in PC12 cells. It was observed that sodium hydrosulfide (NaHS), an exogenous H2S donor, significantly attenuated the homocysteine­induced ER stress responses, including increases in the protein expression levels of GRP78 and cleaved caspase­12. Simultaneously, NaHS upregulated the expression of SIRT­1 and reversed the homocysteine­induced downregulation of SIRT­1 in PC12 cells. Sirtinol, a specific inhibitor of SIRT­1, eliminated the protective effects of H2S in homocysteine­induced ER stress. These data indicated that H2S prevented homocysteine­induced ER stress via enhancing the expression of SIRT­1. These findings offer novel insight into the protective mechanisms of H2S against homocysteine­induced neurotoxicity.