Hydrogen Sulfide Mediates Tumor Cell Resistance to Thioredoxin Inhibitor

Decreased levels of hydrogen sulfide in the hypothalamic paraventricular nucleus contribute to sympathetic hyperactivity induced by cerebral infarction

Paroxysmal sympathetic hyperactivity (PSH) is a common clinical feature secondary to ischemic stroke (IS), but its mechanism is poorly understood. We aimed to investigate the role of H2S in the pathogenesis of PSH. IS patients were divided into malignant (MCI) and non-malignant cerebral infarction (NMCI) group. IS in rats was induced by the right middle cerebral artery occlusion (MCAO). H2S donor (NaHS) or inhibitor (aminooxy-acetic acid, AOAA) were microinjected into the hypothalamic paraventricular nucleus (PVN). Compared with the NMCI group, patients in the MCI group showed PSH, including tachycardia, hypertension, and more plasma norepinephrine (NE) that was positively correlated with levels of creatine kinase, glutamate transaminase, and creatinine respectively. The 1-year survival rate of patients with high plasma NE levels was lower. The hypothalamus of rats with MCAO showed increased activity, especially in the PVN region. The levels of H2S in PVN of the rats with MCAO were reduced, while the blood pressure and renal sympathetic discharge were increased, which could be ameliorated by NaHS and exacerbated by AOAA. NaHS completely reduced the disulfide bond of NMDAR1 in PC12 cells. The inhibition of NMDAR by MK-801 microinjected in PVN of rats with MCAO also could lower blood pressure and renal sympathetic discharge. In conclusion, PSH may be associated with disease progression and survival in patients with IS. Decreased levels of H2S in PVN were involved in regulating sympathetic efferent activity after cerebral infarction. Our results might provide a new strategy and target for the prevention and treatment of PSH.

Efficient targeting of HIF-1α mediated by YC-1 and PX-12 encapsulated niosomes: potential application in colon cancer therapy

A number of molecular biofactors have been documented in pathogenesis and poor prognosis of colorectal cancer (CRC). Among them, the Hypoxia-Inducible Factor (HIF-1a) is frequently reported to become over-expressed, and its targeting could restrict and control a variety of essential hallmarks of CRC. Niosomes are innovative drug delivery vehicles with the encapsulating capacity for co-loading both hydrophilic and hydrophobic drugs at the same time. Also, they can enhance the local accumulation while minimizing the dose and side effects of drugs. YC-1 and PX-12 are two inhibitors of HIF-1a. The purpose of this work was to synthesize dual-loaded YC-1 and PX-12 niosomes to efficiently target HIF-1α in CRC, HT-29 cells. The niosomes were prepared by the thin-film hydration method, then the niosomal formulation of YC-1 and PX-12 (NIO/PX-YC) was developed and optimized by the central composition method (CCD) using the Box-Behnken design in terms of size, polydispersity index (PDI), entrapment efficiency (EE). Also, they are characterized by DLS, FESEM, and TEM microscopy, as well as FTIR spectroscopy. Additionally, entrapment efficiency, in vitro drug release kinetics, and stability were assessed. Cytotoxicity, apoptosis, and cell cycle studies were performed after the treatment of HT-29 cells with NIO/PX-YC. The expression of HIF-1αat both mRNA and protein levels were studied after NIO/PX-YC treatment. The prepared NIO/PX-YC showed a mean particle size of 185 nm with a zeta potential of about-7.10 mv and a spherical morphology. Also, PX-12 and YC-1 represented the entrapment efficiency of about %78 and %91, respectively, with a sustainable and controllable release. The greater effect of NIO/PX-YC than the free state of PX-YC on the cell survival rate, cell apoptosis, and HIF-1α gene/protein expression were detected (p < 0.05). In conclusion, dual loading of niosomes with YC-1 and PX-12 enhanced the effect of drugs on HIF-1α inhibition, thus boosting their anticancer effects.

Circulating Levels of Hydrogen Sulfide (H2S) in Patients with Age-Related Diseases: A Systematic Review and Meta-Analysis

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that promotes multiple biological effects in many organs and tissues. An imbalanced biosynthesis of H₂S has been observed in animal models of age-related pathological conditions. However, the results from human studies are inconsistent. We performed a systematic review with meta-analysis of studies searched in Medline, Embase, Scopus, and CENTRAL databases. We included observational studies on patients with age-related diseases showing levels of H₂S in blood, plasma, or serum. All the analyses were carried out with R software. 31 studies were included in the systematic review and 21 in the meta-analysis. The circulating levels of H₂S were significantly reduced in patients with progressive, chronic, and degenerative diseases compared with healthy people (standardized mean difference, SMD: -1.25; 95% confidence interval, CI: -1.98; -0.52). When we stratified results by type of disorder, we observed a significant reduction in circulating levels of H₂S in patients with vascular disease (e.g., hypertension) (SMD: -1.32; 95% CI: -2.43; -0.22) or kidney disease (SMD: -2.24; 95% CI: -4.40; -0.08) compared with the control group. These results could support the potential use of compounds targeting the "H₂S system" to slow down the progression of many diseases in the elderly.

Hydrogen sulfide protects Sertoli cells against toxicant Acrolein-induced cell injury

Acrolein (ACR), a highly toxic α,β-unsaturated aldehyde, is considered to be a common mediator behind the reproductive injury induced by various factors. However, the understanding of its reproductive toxicity and prevention in reproductive system is limited. Given that Sertoli cells provide the first-line defense against various toxicants and that dysfunction of Sertoli cell causes impaired spermatogenesis, we, therefore, examined ACR cytotoxicity in Sertoli cells and tested whether hydrogen sulfide (H₂S), a gaseous mediator with potent antioxidative actions, could have a protective effect. Exposure of Sertoli cells to ACR led to cell injury, as indicated by reactive oxygen species (ROS) generation, protein oxidation, P38 activation and ultimately cell death that was prevented by antioxidant N-acetylcysteine (NAC). Further studies revealed that ACR cytotoxicity on Sertoli cells was significantly exacerbated by the inhibition of H₂S-synthesizing enzyme cystathionine γ-lyase (CSE), while significantly suppressed by H₂S donor Sodium hydrosulfide (NaHS). It was also attenuated by Tanshinone IIA (Tan IIA), an active ingredient of Danshen that stimulated H₂S production in Sertoli cells. Apart from Sertoli cells, H₂S also protected the cultured germ cells from ACR-initiated cell death. Collectively, our study characterized H₂S as endogenous defensive mechanism against ACR in Sertoli cells and germ cells. This property of H₂S could be used to prevent and treat ACR-related reproductive injury.

The Combined Administration of Vitamin C and Copper Induces a Systemic Oxidative Stress and Kidney Injury

Vitamin C (ascorbic acid; AA) and copper (Cu²⁺) are well used supplements with many health-promoting actions. However, when they are used in combination, the Fenton reaction occurs, leading to the formation of highly reactive hydroxyl radicals. Given that kidney is vulnerable to many toxicants including free radicals, we speculated that the in vivo administration of AA plus Cu²⁺ may cause oxidative kidney injury. The purpose of this study was to address this possibility. Mice were administered with AA and Cu²⁺, alone or in combination, via oral gavage once a day for various periods. Changes in the systemic oxidative status, as well renal structure and functions, were examined. The administration of AA plus Cu²⁺ elevated protein oxidation in serum, intestine, bladder, and kidney, as evidenced by the increased sulfenic acid formation and decreased level of free sulfhydryl groups (-SH). The systemic oxidative stress induced by AA plus Cu²⁺ was associated with a significant loss of renal function and structure, as indicated by the increased blood urea nitrogen (BUN), creatinine and urinary proteins, as well as glomerular and tubular cell injury. These effects of AA and Cu²⁺ were only observed when used in combination, and could be entirely prevented by thiol antioxidant NAC. Further analysis using cultured renal tubular epithelial cells revealed that AA plus Cu²⁺ caused cellular protein oxidation and cell death, which could be abolished by NAC and catalase. Moreover, coincubation of AA and Cu²⁺ led to H₂O₂ production. Collectively, our study revealed that a combined administration of AA and Cu²⁺ resulted in systemic oxidative stress and renal cell injury. As health-promoting supplements, AA and Cu²⁺ should not be used together.

Site-Specific Activity-Based Protein Profiling Using Phosphonate Handles

Most drug molecules target proteins. Identification of the exact drug binding sites on these proteins is essential to understand and predict how drugs affect protein structure and function. To address this challenge, we developed a strategy that uses immobilized metal-affinity chromatography-enrichable phosphonate affinity tags, for efficient and selective enrichment of peptides bound to an activity-based probe, enabling the identification of the exact drug binding site. As a proof of concept, using this approach, termed PhosID-ABPP (activity-based protein profiling), over 500 unique binding sites were reproducibly identified of an alkynylated afatinib derivative (PF-06672131). As PhosID-ABPP is compatible with intact cell inhibitor treatment, we investigated the quantitative differences in approachable binding sites in intact cells and in lysates of the same cell line and observed and quantified substantial differences. Moreover, an alternative protease digestion approach was used to capture the previously reported binding site on the epidermal growth factor receptor, which turned out to remain elusive when using solely trypsin as protease. Overall, we find that PhosID-ABPP is highly complementary to biotin-based enrichment strategies in ABPP studies, with PhosID-ABPP providing the advantage of direct activity-based probe interaction site identification.

Hydrogen Sulfide Biology and Its Role in Cancer

Hydrogen sulfide (H2S) is an endogenous biologically active gas produced in mammalian tissues. It plays a very critical role in many pathophysiological processes in the body. It can be endogenously produced through many enzymes analogous to the cysteine family, while the exogenous source may involve inorganic sulfide salts. H2S has recently been well investigated with regard to the onset of various carcinogenic diseases such as lung, breast, ovaries, colon cancer, and neurodegenerative disorders. H2S is considered an oncogenic gas, and a potential therapeutic target for treating and diagnosing cancers, due to its role in mediating the development of tumorigenesis. Here in this review, an in-detail up-to-date explanation of the potential role of H2S in different malignancies has been reported. The study summarizes the synthesis of H2S, its roles, signaling routes, expressions, and H2S release in various malignancies. Considering the critical importance of this active biological molecule, we believe this review in this esteemed journal will highlight the oncogenic role of H2S in the scientific community.

The Role of the Thioredoxin Detoxification System in Cancer Progression and Resistance

The intracellular redox homeostasis is a dynamic balancing system between the levels of free radical species and antioxidant enzymes and small molecules at the core of cellular defense mechanisms. The thioredoxin (Trx) system is an important detoxification system regulating the redox milieu. This system is one of the key regulators of cells’ proliferative potential as well, through the reduction of key proteins. Increased oxidative stress characterizes highly proliferative, metabolically hyperactive cancer cells, which are forced to mobilize antioxidant enzymes to balance the increase in free radical concentration and prevent irreversible damage and cell death. Components of the Trx system are involved in high-rate proliferation and activation of pro-survival mechanisms in cancer cells, particularly those facing increased oxidative stress. This review addresses the importance of the targetable redox-regulating Trx system in tumor progression, as well as in detoxification and protection of cancer cells from oxidative stress and drug-induced cytotoxicity. It also discusses the cancer cells’ counteracting mechanisms to the Trx system inhibition and presents several inhibitors of the Trx system as prospective candidates for cytostatics’ adjuvants. This manuscript further emphasizes the importance of developing novel multitarget therapies encompassing the Trx system inhibition to overcome cancer treatment limitations.

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.

Therapeutic implication of carbon monoxide in drug resistant cancers

Drug resistance is the major obstacle that undermines effective cancer treatment. Recently, the application of gas signaling molecules, e.g., carbon monoxide (CO), in overcoming drug resistance has gained significant attention. Growing evidence showed that CO could inhibit mitochondria respiratory effect and glycolysis, two major ATP production pathways in cancer cells, and suppress angiogenesis and inhibit the activity of cystathionine β-synthase that is important in regulating cancer cells homeostasis, leading to synergistic effects when combined with cisplatin, doxorubicin, or phototherapy, etc. in certain resistant cancer cells. In the current review, we attempted to have a summary of these research conducted in the past decade using CO in treating drug resistant cancers, and have a detailed interpretation of the underlying mechanisms. The critical challenges will be discussed and potential solutions will also be provided. The information collected in this work will hopefully evoke more effects in using CO for the treatment of drug resistant cancers.

Hydrogen sulfide as a potent scavenger of toxicant acrolein

Acrolein (ACR) is a metabolic byproduct in vivo and a ubiquitous environmental toxicant. It is implicated in the initiation and development of many diseases through multiple mechanisms, including the induction of oxidative stress. Currently, our understanding of the body defense mechanism against ACR toxicity is still limited. Given that hydrogen sulfide (H₂S) has strong antioxidative actions and it shares several properties of ACR scavenger glutathione (GSH), we, therefore, tested whether H₂S could be involved in ACR detoxification. Taking advantage of two cell lines that produced different levels of endogenous H₂S, we found that the severity of ACR toxicity was reversely correlated with H₂S-producing ability. In further support of the role of H₂S, supplementing cells with exogenous H₂S increased cell resistance to ACR, whereas inhibition of endogenous H₂S sensitized cells to ACR. In vivo experiments showed that inhibition of endogenous H₂S with CSE inhibitor markedly increased mouse susceptibility to the toxicity of cyclophosphamide and ACR, as evidenced by the increased mortality and worsened organ injury. Further analysis revealed that H₂S directly reacted with ACR. It promoted ACR clearance and prevented ACR-initiated protein carbonylation. Collectively, this study characterized H₂S as a presently unrecognized endogenous scavenger of ACR and suggested that H₂S can be exploited to prevent and treat ACR-associated diseases.

Tanshinone IIA Stimulates Cystathionine γ-Lyase Expression and Protects Endothelial Cells from Oxidative Injury

Tanshinone IIA (Tan IIA), an active ingredient of Danshen, is a well-used drug to treat cardiovascular diseases. Currently, the mechanisms involved remain poorly understood. Given that many actions of Tan IIA could be similarly achieved by hydrogen sulfide (H2S), we speculated that Tan IIA might work through the induction of endogenous H2S. This study was to test this hypothesis. Exposure to endothelial cells to Tan IIA elevated H2S-synthesizing enzyme cystathionine γ-Lyase (CSE), associated with an increased level of endogenous H2S and free thiol activity. Further analysis revealed that this effect of Tan IIA was mediated by an estrogen receptor (ER) and cAMP signaling pathway. It stimulated VASP and CREB phosphorylation. Inhibition of ER or PKA abolished the CSE-elevating effect, whereas activation of ER or PKA mimicked the effect of Tan IIA. In an oxidative endothelial cell injury model, Tan IIA potently attenuated oxidative stress and inhibited cell death. In support of a role of endogenous H2S, inhibition of CSE aggerated oxidative cell injury. On the contrary, supplement of H2S attenuated cell injury. Collectively, our study characterized endogenous H2S as a novel mediator underlying the pharmacological actions of Tan IIA. Given the multifaceted functions of H2S, the H2S-stimulating property of Tan IIA could be exploited for treating many diseases.

Reductively modified albumin attenuates DSS-Induced mouse colitis through rebalancing systemic redox state

Albumin (Alb) is the most abundant plasma protein with multiple biological functions, including antioxidative property through its thiol activity. Given that inflammatory bowel disease is associated with a decreased level of Alb and an increased level of Alb oxidation, we asked whether Alb could have a therapeutic effect on colitis. Here we tested this possibility. Bovine serum albumin (BSA) was reductively modified with dithiothreitol (DTT) and administrated via gavage or intraperitoneal injection. Dextran sulfate sodium (DSS)-induced mice colitis was associated with massive oxidative stress, as indicated by the elevated sulfenic acid formation in blood, colon tissues, and feces. Treatment of mice with the reductively modified albumin (r-Alb) attenuated the oxidative stress and reduced local inflammation and tissue injury. These effects of r-Alb were only partially achieved by unmodified Alb and wholly lost after blocking the -SH groups with maleimide. In cultured colon epithelial cells, r-Alb prevented DSS- and H2O2-induced ROS elevation and barrier dysfunction, preceded by inhibition of sulfenic acid formation and P38 activation. Further analysis revealed that Alb was susceptible to H2O2-induced oxidation, and it detoxified H2O2 in a -SH group-dependent way. Moreover, Alb reacted with GSH/GSSG via thiol-disulfide exchange and reciprocally regulated the availability of -SH groups. Collectively, our study shows that r-Alb effectively attenuates DSS colitis via -SH group-mediated antioxidative action. Given that the oxidative stress underlies many life-threatening diseases, r-Alb, functioning as a potent antioxidant, could have a wide range of applications.

A Novel BODIPY Quaternary Ammonium Salt-Based Fluorescent Probe: Synthesis, Physical Properties, and Live-Cell Imaging

The development of biological fluorescent probes is of great significance to the field of cancer bio-imaging. However, most current probes within the bulky hydrophobic group have limited application in aqueous medium and restricted imaging under physiological conditions. Herein, we proposed two efficient molecules to study their physical properties and imaging work, and the absorption and fluorescence intensity were collected with varying ions attending in aqueous medium. We enhance the water solubility through the quaternization reaction and form a balance between hydrophilic and hydrophobicity with dipyrrome-theneboron difluoride (BODIPY) fluorophore. We introduced pyridine and dimethylaminopyridine (DMAP) by quaternization and connected the BODIPY fluorophore by ethylenediamine. The final synthesized probes have achieved ideal affinity with HeLa cells (human cervical carcinoma cell line) in live-cell imaging which could be observed by Confocal Microscope. The probes also have a good affinity with subcutaneous tumor cells in mice in in vivo imaging, which may make them candidates as oncology imaging probes.

Generating tumor-selective conditionally active biologic anti-CTLA4 antibodies via protein-associated chemical switches

Anticytotoxic T lymphocyte-associated protein 4 (CTLA4) antibodies have shown potent antitumor activity, but systemic immune activation leads to severe immune-related adverse events, limiting clinical usage. We developed novel, conditionally active biologic (CAB) anti-CTLA4 antibodies that are active only in the acidic tumor microenvironment. In healthy tissue, this binding is reversibly inhibited by a novel mechanism using physiological chemicals as protein-associated chemical switches (PaCS). No enzymes or potentially immunogenic covalent modifications to the antibody are required for activation in the tumor. The novel anti-CTLA4 antibodies show similar efficacy in animal models compared to an analog of a marketed anti-CTLA4 biologic, but have markedly reduced toxicity in nonhuman primates (in combination with an anti-PD1 checkpoint inhibitor), indicating a widened therapeutic index (TI). The PaCS encompass mechanisms that are applicable to a wide array of antibody formats (e.g., ADC, bispecifics) and antigens. Examples shown here include antibodies to EpCAM, Her2, Nectin4, CD73, and CD3. Existing antibodies can be engineered readily to be made sensitive to PaCS, and the inhibitory activity can be optimized for each antigen's varying expression level and tissue distribution. PaCS can modulate diverse physiological molecular interactions and are applicable to various pathologic conditions, enabling differential CAB antibody activities in normal versus disease microenvironments.