Hydrogen sulfide-induced processing of the amyloid precursor protein in SH-SY5Y human neuroblastoma cells involves the PI3-K/Akt signaling pathway

Role of Hydrogen Sulfide in Oncological and Non-Oncological Disorders and Its Regulation by Non-Coding RNAs: A Comprehensive Review

Recently, myriad studies have defined the versatile abilities of gasotransmitters and their synthesizing enzymes to play a "Maestro" role in orchestrating several oncological and non-oncological circuits and, thus, nominated them as possible therapeutic targets. Although a significant amount of work has been conducted on the role of nitric oxide (NO) and carbon monoxide (CO) and their inter-relationship in the field of oncology, research about hydrogen sulfide (H2S) remains in its infancy. Recently, non-coding RNAs (ncRNAs) have been reported to play a dominating role in the regulation of the endogenous machinery system of H2S in several pathological contexts. A growing list of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are leading the way as upstream regulators for H2S biosynthesis in different mammalian cells during the development and progression of human diseases; therefore, their targeting can be of great therapeutic benefit. In the current review, the authors shed the light onto the biosynthetic pathways of H2S and their regulation by miRNAs and lncRNAs in various oncological and non-oncological disorders.

Hydrogen Sulfide (H2S) Signaling as a Protective Mechanism against Endogenous and Exogenous Neurotoxicants

In view of the significant role of H₂S in brain functioning, it is proposed that H₂S may also possess protective effects against adverse effects of neurotoxicants. Therefore, the objective of the present review is to discuss the neuroprotective effects of H₂S against toxicity of a wide spectrum of endogenous and exogenous agents involved in the pathogenesis of neurological diseases as etiological factors or key players in disease pathogenesis. Generally, the existing data demonstrate that H₂S possesses neuroprotective effects upon exposure to endogenous (amyloid β, glucose, and advanced-glycation end-products, homocysteine, lipopolysaccharide, and ammonia) and exogenous (alcohol, formaldehyde, acrylonitrile, metals, 6-hydroxydopamine, as well as 1-methyl-4-phenyl- 1,2,3,6- tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenyl pyridine ion (MPP)) neurotoxicants. On the one hand, neuroprotective effects are mediated by S-sulfhydration of key regulators of antioxidant (Sirt1, Nrf2) and inflammatory response (NF-κB), resulting in the modulation of the downstream signaling, such as SIRT1/TORC1/CREB/BDNF-TrkB, Nrf2/ARE/HO-1, or other pathways. On the other hand, H₂S appears to possess a direct detoxicative effect by binding endogenous (ROS, AGEs, Aβ) and exogenous (MeHg) neurotoxicants, thus reducing their toxicity. Moreover, the alteration of H₂S metabolism through the inhibition of H₂S-synthetizing enzymes in the brain (CBS, 3-MST) may be considered a significant mechanism of neurotoxicity. Taken together, the existing data indicate that the modulation of cerebral H₂S metabolism may be used as a neuroprotective strategy to counteract neurotoxicity of a wide spectrum of endogenous and exogenous neurotoxicants associated with neurodegeneration (Alzheimer's and Parkinson's disease), fetal alcohol syndrome, hepatic encephalopathy, environmental neurotoxicant exposure, etc. In this particular case, modulation of H₂S-synthetizing enzymes or the use of H₂S-releasing drugs should be considered as the potential tools, although the particular efficiency and safety of such interventions are to be addressed in further studies.

Naphthalimide derivatives as fluorescent probes for imaging endogenous gasotransmitters

Gasotransmitters have gained significant recognition attributed to their evident biological impacts, and is accepted as a promising and less-explored area with immense research scope. The three-member family comprising of nitric oxide, carbon monoxide and hydrogen sulphide as endogenous gaseous signaling molecules have been found to elicit a plethora of crucial biological functions, spawning a new research area. The sensing of these small molecules is vital to gain deeper insights into their functions, as they can act both as a friend or a foe in mammalian systems. The initial sections of the review present the physiological and pathophysiological roles of these endogenous gas transmitters and their synergistic interactions. Further, various detection approaches, especially the usage of fascinating features of 1,8-naphthalimide as fluorescent probe in the detection and monitoring of these small signaling molecules are highlighted. The current limitations and the future scope of improving the sensing of the three gasotransmitters are also discussed.

Emerging roles of cystathionine β-synthase in various forms of cancer

The expression of the reverse transsulfuration enzyme cystathionine-β-synthase (CBS) is markedly increased in many forms of cancer, including colorectal, ovarian, lung, breast and kidney, while in other cancers (liver cancer and glioma) it becomes downregulated. According to the clinical database data in high-CBS-expressor cancers (e.g. colon or ovarian cancer), high CBS expression typically predicts lower survival, while in the low-CBS-expressor cancers (e.g. liver cancer), low CBS expression is associated with lower survival. In the high-CBS expressing tumor cells, CBS, and its product hydrogen sulfide (H₂S) serves as a bioenergetic, proliferative, cytoprotective and stemness factor; it also supports angiogenesis and epithelial-to-mesenchymal transition in the cancer microenvironment. The current article reviews the various tumor-cell-supporting roles of the CBS/H₂S axis in high-CBS expressor cancers and overviews the anticancer effects of CBS silencing and pharmacological CBS inhibition in various cancer models in vitro and in vivo; it also outlines potential approaches for biomarker identification, to support future targeted cancer therapies based on pharmacological CBS inhibition.

Naphthalimide-based a highly selective two-photon fluorescent probe for imaging of hydrogen sulfide in living cells and inflamed tissue of mouse model

Hydrogen sulfide (H₂S) is a very important third endogenously generated gaseous signaling molecule and plays a key role in physiological and pathological regulation processes of living biosystems. Although a lot of H₂S fluorescent probes have been reported, the relationship between the physiology and pathology of H₂S in inflamed tissues remains unclear. Herein, by adopting a donor-π-acceptor (D-π-A)-structured naphthalimide derivative as the two-photon (TP) fluorophore and a 4-dinitrobenzene-ether (DNB) with a strong intramolecular charge transfer (ICT) effect as the recognition moiety, we reported a novel TP bioimaging probe NP-H₂S for H₂S with improved sensitivity. The NP-H₂S exhibits very low background fluorescence in the absence of H₂S, and a significant 258-fold fluorescence intensity enhancement was observed in the presence of H₂S, resulting in a high sensitivity and selectivity to H₂S in aqueous solutions with a detection limit of 18.8 nM observed. The probe also shows a wide linear response concentration range (0-10.0 μM) to H₂S with high selectivity. All these features are favorable for direct monitoring of H₂S in complex biological samples. It was then applied for direct TP imaging of H₂S in tissues of inflammation model with satisfactory sensitivity, indicating it has the latent capability in further biological applications for investigation of the interaction H₂S with inflammation.

Relaxin induces up-regulation of ADAM10 metalloprotease in RXFP1-expressing cells by PI3K/AKT signaling

ADAM10 metalloprotease is required for activation of Notch-1, a transmembrane receptor regulating cell differentiation, proliferation and apoptosis, whose intracellular proteolytic fragment NICD mediates some key cardiovascular effects of the hormone relaxin (RLX). This study demonstrates the involvement of ADAM10 and PI3K/Akt signaling in mediating RLX-induced Notch-1 activation. H9c2 cardiomyocytes and NIH3T3 fibroblasts were incubated with human RLX-2 (17 nmol/l, 24 h) in presence or absence of the PI3K or Akt inhibitors wortmannin (WT, 100 nmol/l) and triciribine (TCN, 1 μmol/l). Cyclohexanedione-inactivated RLX (iRLX) served as negative control. RLX significantly increased Akt phosphorylation, ADAM10 and NICD expression, which were abolished by WT or TCN and did not occur with iRLX. These findings highlight a new receptor-specific signal transduction pathway of RLX.

Identification of Circulating miR-125b as a Potential Biomarker of Alzheimer's Disease in APP/PS1 Transgenic Mouse

Alzheimer's disease (AD) is the most common form of dementia, characterized by progressive decline in cognitive abilities of the affected individuals. Biological markers are essential to identify individuals at early stages of the disease for timely therapeutic intervention. Currently, pathological biomarkers are detected either through cerebrospinal fluid analysis or brain imaging, or postmortem, all of which are expensive, invasive, or time consuming. Recently, some studies have shown that circulating miR-125b, miR-181c, miR-9, miR-191-5p, miR-26b-3p, and miR-28-3p may be biomarkers of AD. However, those potential biomarkers are not validated in an AD mouse model. In the current study, we found that circulating miR-125b, miR-9, and miR-191-5p are downregulated, and miR-28-3p is upregulated in an APP/PS1 transgenic mouse model of AD. Furthermore, the correlation analysis shows a positive correlation between the expression of miR-125b and cognitive function of the APP/PS1 transgenic mouse. Moreover, we also determined that the level of serum miR-125b, miR-9, and miR-191-5p were reversed in EGCG-treated APP/PS1 transgenic mouse models. Finally, the expression of miR-125b was significantly downregulated in EGCG-treated SH-SY5Y cells.

Hydrogen sulfide promotes autophagy of hepatocellular carcinoma cells through the PI3K/Akt/mTOR signaling pathway

Hydrogen sulfide (H₂S), in its gaseous form, plays an important role in tumor carcinogenesis. This study investigated the effects of H₂S on the cell biological functions of hepatocellular carcinoma (HCC). HCC cell lines, HepG2 and HLE, were treated with NaHS, a donor of H₂S, and rapamycin, a classic autophagy inducer, for different lengths of time. Western blotting, immunofluorescence, transmission electron microscopy (TEM), scratch assay, CCK-8 and flow cytometric analysis were carried out to examine the effects of H₂S on HCC autophagy, cell behavior and PI3K/Akt/mTOR signaling. Treatment with NaHS upregulated expression of LC3-II and Atg5, two autophagy-related proteins, in HepG2 and HLE cells. TEM revealed increased numbers of intracellular double-membrane vesicles in those cells treated with NaHS. Like rapamycin, NaHS also significantly inhibited expression of p-PI3K, p-Akt and mTOR proteins in HCC cells. Interestingly, the expression of LC3-II was further increased when the cells were treated with NaHS together with rapamycin. In addition, NaHS inhibited HCC cell migration, proliferation and cell division. These findings show that H₂S can induce HCC cell apoptosis. The biological function of the gasotransmitter H₂S in HCC cells was enhanced by the addition of rapamycin. Hydrogen sulfide influences multiple biological functions of HCC cells through inhibiting the PI3K/Akt/mTOR signaling pathway.

Thamnolia vermicularis extract improves learning ability in APP/PS1 transgenic mice by ameliorating both Aβ and Tau pathologies

Considering the complicated pathogenesis of Alzheimer's disease (AD), multi-targets have become a focus in the discovery of drugs for treatment of this disease. In the current work, we established a multi-target strategy for discovering active reagents capable of suppressing both Aβ level and Tau hyperphosphorylation from natural products, and found that the ethanol extract of Thamnolia vermicularis (THA) was able to improve learning ability in APP/PS1 transgenic mice by inhibiting both Aβ levels and Tau hyperphosphorylation. SH-SY5Y and CHO-APP/BACE1 cells and primary astrocytes were used in cell-based assays. APP/PS1 transgenic mice [B6C3-Tg(APPswe, PS1dE9)] were administered THA (300 mg·kg-1·d-1, ig) for 100 d. After the administration was completed, the learning ability of the mice was detected using a Morris water maze (MWM) assay; immunofluorescence staining, Congo red staining and Thioflavine S staining were used to detect the senile plaques in the brains of the mice. ELISA was used to evaluate Aβ and sAPPβ contents, and Western blotting and RT-PCR were used to investigate the relevant signaling pathway regulation in response to THA treatment. In SH-SY5Y cells, THΑ (1, 10, 20 μg/mL) significantly stimulated PI3K/AKT/mTOR and AMPK/raptor/mTOR signaling-mediated autophagy in the promotion of Aβ clearance as both a PI3K inhibitor and an AMPK indirect activator, and restrained Aβ production as a suppressor against PERK/eIF2α-mediated BACE1 expression. Additionally, THA functioned as a GSK3β inhibitor with an IC50 of 1.32±0.85 μg/mL, repressing Tau hyperphosphorylation. Similar effects on Aβ accumulation and Tau hyperphosphorylation were observed in APP/PS1 transgenic mice treated with THA. Furthermore, administration of THA effectively improved the learning ability of APP/PS1 transgenic mice, and markedly reduced the number of senile plaques in their hippocampus and cortex. The results highlight the potential of the natural product THA for the treatment of AD.

Hydrogen sulfide prevents Abeta-induced neuronal apoptosis by attenuating mitochondrial translocation of PTEN

Neuronal cell apoptosis is an important pathological change in Alzheimer's disease (AD). Hydrogen sulfide (H(2)S) is known to be a novel gaseous signaling molecule and a cytoprotectant in many diseases including AD. However, the molecular mechanism of the antiapoptosis activity of H(2)S in AD is not yet fully understood. The aim of the present study is to evaluate the inhibitory effects of H(2)S on Abeta (Aβ)-induced apoptosis and the molecular mechanisms underlying primary neuron cells. Our results showed that sodium hydrosulfide (NaHS), a donor of H(2)S, significantly ameliorated Aβ-induced cell apoptosis. NaHS also reversed the Aβ-induced translocation of the phosphatase and tensin homologs deleted on chromosome 10 (PTEN) from the cytosol to the mitochondria. Furthermore, H(2)S increased the level of p-AKT/AKT significantly. Interestingly, the antiapoptosis effects of H(2)S were blocked down by specific PI3K/AKT inhibitor wortmannin. In conclusion, these data indicate that H(2)S inhibits Aβ-induced neuronal apoptosis by attenuating mitochondrial translocation of PTEN and that activation of PI3K/AKT signaling pathway plays a critical role in H(2)S-mediated neuronal protection. Our findings provide a novel route into the molecular mechanisms of neuronal apoptosis in AD.