Gaseous mediator-based anti-inflammatory drugs

Chemistry of Hydrogen Sulfide-Pathological and Physiological Functions in Mammalian Cells

Hydrogen sulfide (H2S) was recognized as a gaseous signaling molecule, similar to nitric oxide (-NO) and carbon monoxide (CO). The aim of this review is to provide an overview of the formation of hydrogen sulfide (H2S) in the human body. H2S is synthesized by enzymatic processes involving cysteine and several enzymes, including cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), cysteine aminotransferase (CAT), 3-mercaptopyruvate sulfurtransferase (3MST) and D-amino acid oxidase (DAO). The physiological and pathological effects of hydrogen sulfide (H2S) on various systems in the human body have led to extensive research efforts to develop appropriate methods to deliver H2S under conditions that mimic physiological settings and respond to various stimuli. These functions span a wide spectrum, ranging from effects on the endocrine system and cellular lifespan to protection of liver and kidney function. The exact physiological and hazardous thresholds of hydrogen sulfide (H2S) in the human body are currently not well understood and need to be researched in depth. This article provides an overview of the physiological significance of H2S in the human body. It highlights the various sources of H2S production in different situations and examines existing techniques for detecting this gas.

ADT-OH synergistically enhanced the antitumor activity of celecoxib in human colorectal cancer cells

BACKGROUND

Colorectal cancer is one of the most prevalent cancers in the world, but the research on its prevention, early diagnosis and treatment is still a major challenge in clinical oncology. Thus, there is a pressing requirement to find effective strategies to improve the survival of colon cancer patients.

METHODS

Celecoxib has been accounted to be an effective antitumor drug, but may exhibit significant side effects. In recent studies, 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADT-OH), one of the most commonly used reagents for the synthesis of sustained-release H2 S donors, has also been reported to inhibit cancer progression by affecting processes such as cell cycle, angiogenesis, and apoptosis. Therefore, we evaluated the therapeutic effect of the combination of ADT-OH and celecoxib on colorectal cancer through in vitro and in vivo, hoping to achieve better therapeutic effect and reduce the effect of celecoxib on gastric injury through exogenous administration of H2 S.

RESULTS

Our results demonstrated that ADT-OH combined with celecoxib synergistically inhibited the proliferation and migration ability of human colorectal cancer HCT116 cells, altered cell cycle and cytoskeleton, increased intracellular reactive oxygen species (ROS), and promoted cell apoptosis. Noteworthy, in vivo studies also indicated the excellent antitumor therapeutic effect of the combination therapy without apparent toxicity.

CONCLUSIONS

In general, our results provide a reasonable combination strategy of low-dose ADT-OH and celecoxib in the preclinical application of colorectal cancer.

Gastroprotective effect methanol extract of Caesalpinia coriaria pods against indomethacin- and ethanol-induced gastric lesions in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Caesalpinia coriaria (Jacq.) Willd is widely used as a traditional medinal plant in Mexico for protective and healing purposes and the treatment of gastrointestinal diseases.

AIM OF THE STUDY

To investigate the gastroprotective effect of extract of Caesalpinia coriaria pods against ethanol-induced and indomethacin-induced gastric lesion models, its anti-inflammatory and antioxidative activities, and its main compounds through LC-MS analysis.

MATERIALS AND METHODS

Male Wistar rats were orally administered a methanol extract obtained from the pods of C. coriaria at doses of 10, 30, 100, and 300 mg/kg prior to inducing gastric lesions with ethanol or indomethacin. Gastric mucosal lesions were evaluated by macroscopic and histopathological alterations. Determination of prostaglandin E₂ (PGE₂), alpha tumor necrosis factor (TNF-α), leukotriene B₄ (LTB₄), nitrites/nitrates, superoxide dismutase (SOD), and H₂S gastric levels were investigated. Its main compounds of the active extract through LC-MS analysis.

RESULTS

Phenolic compounds were identified as major components of methanol extract. LC-MS analysis identified 15 constituents, and the significant compounds were gallic acid, 3-O-galloylquinic acid, digalloylglucose, tetragalloylglucose, valoneic acid dilactone, pentagalloylglucose, digalloylshikimic acid, and ellagic acid. Pretreatment with the extract at doses of 100 and 300 mg/kg significantly reduced gastric ulcer lesions in both models. Compared with the reference drugs (omeprazole or ranitidine, respectively), no significant difference was found (p < 0.05). The extract's gastroprotective effect was accompanied by significant decreases in leukocyte recruitment, and gastric levels of TNF-α and LTB₄ by two to fourfold (p < 0.05). Also, gastric levels of PGE₂ gastric levels were maintained and the antioxidant enzyme activities of SOD and nitrate/nitrite in the gastric tissue were improved (p < 0.05). The LC-MS analysis indicated the presence of hydrolyzable tannins (mainly gallic acid derivatives).

CONCLUSION

The results suggest that the gastroprotective effect of the methanol extract of C. coriaria pods occurs through anti-inflammatory, antioxidant, and NO modulation properties, and gallic acid derivatives may be the main possible compounds responsible for its actions.

H2S Donors and Their Use in Medicinal Chemistry

Hydrogen sulfide (H2S) is a ubiquitous gaseous signaling molecule that has an important role in many physiological and pathological processes in mammalian tissues, with the same importance as two others endogenous gasotransmitters such as NO (nitric oxide) and CO (carbon monoxide). Endogenous H2S is involved in a broad gamut of processes in mammalian tissues including inflammation, vascular tone, hypertension, gastric mucosal integrity, neuromodulation, and defense mechanisms against viral infections as well as SARS-CoV-2 infection. These results suggest that the modulation of H2S levels has a potential therapeutic value. Consequently, synthetic H2S-releasing agents represent not only important research tools, but also potent therapeutic agents. This review has been designed in order to summarize the currently available H2S donors; furthermore, herein we discuss their preparation, the H2S-releasing mechanisms, and their -biological applications.

Gaseous Mediators as a Key Molecular Targets for the Development of Gastrointestinal-Safe Anti-Inflammatory Pharmacology

Non-steroidal anti-inflammatory drugs (NSAIDs) represent one of the most widely used classes of drugs and play a pivotal role in the therapy of numerous inflammatory diseases. However, the adverse effects of these drugs, especially when applied chronically, frequently affect gastrointestinal (GI) tract, resulting in ulceration and bleeding, which constitutes a significant limitation in clinical practice. On the other hand, it has been recently discovered that gaseous mediators nitric oxide (NO), hydrogen sulfide (H₂S) and carbon monoxide (CO) contribute to many physiological processes in the GI tract, including the maintenance of GI mucosal barrier integrity. Therefore, based on the possible therapeutic properties of NO, H₂S and CO, a novel NSAIDs with ability to release one or more of those gaseous messengers have been synthesized. Until now, both preclinical and clinical studies have shown promising effects with respect to the anti-inflammatory potency as well as GI-safety of these novel NSAIDs. This review provides an overview of the gaseous mediators-based NSAIDs along with their mechanisms of action, with special emphasis on possible implications for GI mucosal defense mechanisms.

MOFs-Based Nitric Oxide Therapy for Tendon Regeneration

Tendon regeneration is still a great challenge due to its avascular structure and low self-renewal capability. The nitric oxide (NO) therapy emerges as a promising treatment for inducing the regeneration of injured tendon by angiogenesis. Here, in this study, a system that NO-loaded metal-organic frameworks (MOFs) encapsulated in polycaprolactone (PCL)/gelatin (Gel) aligned coaxial scaffolds (NMPGA) is designed and prepared for tendon repair. In this system, NO is able to be released in vitro at a slow and stable average speed of 1.67 nM h^-1 as long as 15 d without a burst release stage in the initial 48 h. Furthermore, NMPGA can not only improve the tubular formation capability of endothelial cells in vitro but also obviously increase the blood perfusion near the injured tendon in vivo, leading to accelerating the maturity of collagen and recovery of biomechanical strength of the regenerated tendon tissue. As a NO-loaded MOFs therapeutic system, NMPGA can promote tendon regeneration in a shorter healing period with better biomechanical properties in comparison with control group by angiogenesis. Therefore, this study not only provides a promising scaffold for tendon regeneration, but also paves a new way to develop a NO-based therapy for biomedical application in the future.

Hydrogen Sulfide in Pharmacotherapy, Beyond the Hydrogen Sulfide-Donors

Hydrogen sulfide (H₂S) is one of the important biological mediators involved in physiological and pathological processes in mammals. Recently developed H₂S donors show promising effects against several pathological processes in preclinical and early clinical studies. For example, H₂S donors have been found to be effective in the prevention of gastrointestinal ulcers during anti-inflammatory treatment. Notably, there are well-established medicines used for the treatment of a variety of diseases, whose chemical structure contains sulfur moieties and may release H₂S. Hence, the therapeutic effect of these drugs may be partly the result of the release of H₂S occurring during drug metabolism and/or the effect of these drugs on the production of endogenous hydrogen sulfide. In this work, we review data regarding sulfur drugs commonly used in clinical practice that can support the hypothesis about H₂S-dependent pharmacotherapeutic effects of these drugs.

Hydrogen Sulfide Affects Radical Formation in the Hippocampus of LPS Treated Rats and the Effect of Antipsychotics on Hydrogen Sulfide Forming Enzymes in Human Cell Lines

Objectives: Psychiatric disorders, such as schizophrenia and other neuroinflammatory diseases are accompanied by an increase in the oxidative stress and changes in the immune system and in the metabolic, hormonal and neurological components of the central nervous system (CNS). Hydrogen sulfide (H2S) is a gaseous molecule that is endogenously produced in the peripheral and central nervous system through cysteine by the following major H2S producing enzymes in the brain: cystathionine-γlyase (CSE), cystathionine ß-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST). The physiological effects of H2S are broad, with antioxidative properties being a major role in the body. The aims of our investigation were to analyze the central nervous antioxidant, metabolic and neuronal effects in the hippocampus of the rat after inflammatory peripheral lipopolysaccharide (LPS) treatment; and to examine the effects of antipsychotics on the expression of these enzymes in human cell lines. Material and Methods: Male Lewis rats (250 g) received an i.p. LPS injection (1 mg/kg) 24 h before microdialysis experiments. Conscious rats were infused via these probes (1.5 μl/min) with a radical scavenger 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) in Krebs-Ringer solution. Sodiumhydrogensulfide (NaHS, 10 μg/min) was infused after a 2- h baseline for 1 h. Corticosterone, glutamate, glucose and lactate were measured by Elisa. Reactive oxygen species (ROS) were detected by electron spin resonance spectroscopy (ESR). The impact of the antipsychotics haloperidol, clozapine, olanzapine and risperidone on the expression of genes encoding the key enzymes of H2S synthesis was studied at the human neuroblastoma SH-SY5Y and monocytic U-937 cell lines. The cells were incubated for 24 h with 30 μM antipsychotic following which mRNA levels were measured by polymerase chain reaction. Results: Microdialysate glucose and lactate levels dramatically increased in the hippocampus of LPS untreated rats by local application of NaHS. By contrast, in the LPS pretreated rats, there was no effect of NaHS infusion on glucose but a further significant increase in microdialysate lactate was found. It was LPS pretreatment alone that particularly enhanced lactate levels. There was a marked increase in hippocampal microdialysate glutamate levels after local NaHS infusion in LPS untreated animals. In LPS treated rats, no change was observed by NaHS, but LPS itself had the strongest effect on microdialysate glutamate levels. Microdialysate corticosterone levels were reduced by NaHS in both LPS pretreated and untreated rats. The formation of free radicals in the hippocampus significantly reduced in LPS pretreated rats, while in LPS untreated rats a significant increase was observed after NaHS infusion. In human SH-SY5Y and U-937 cells, all three major enzymes of H2S-Synthesis, namely cystathionine-γ-lyase, cystathione ß-synthase and 3-mercaptopyruvate sulfurtransferase, could be detected by PCR. The antipsychotics haloperidol, clozapine, olanzapine and risperidone affected all three enzymes in different ways; with haloperidol and risperidone showing major effects that led to reductions in CBS or CSE expression. Discussion: The local application of NaHS in the hippocampus of the rat strongly affected glucose, lactate and glutamate release. Contrastingly, in LPS pretreated rats, a decreased radical formation was the only effect found. H2S synthetizing enzymes may be involved in antipsychotic mechanisms, although no clear common mechanism could be found.

Hydrogen sulphide as a signalling molecule regulating physiopathological processes in gastrointestinal motility

The biology of H₂ S is a still developing area of research and several biological functions have been recently attributed to this gaseous molecule in many physiological systems, including the cardiovascular, urogenital, respiratory, digestive and central nervous system (CNS). H₂ S exerts anti-inflammatory effects and can be considered an endogenous mediator with potential effects on gastrointestinal motility. During the last few years, we have investigated the role of H₂ S as a regulator of gastrointestinal motility using both animal and human tissues. The aim of the present work is to review published data regarding the potential role of H₂ S as a signalling molecule regulating physiopathological processes in gastrointestinal motor function. H₂ S is endogenously produced by defined enzymic pathways in different cell types of the intestinal wall including neurons and smooth muscle. Inhibition of H₂ S biosynthesis increases motility and H₂ S donors cause smooth muscle relaxation and inhibition of propulsive motor patterns. Impaired H₂ S production has been described in animal models with gastrointestinal motor dysfunction. The mechanism(s) of action underlying these effects may include several ion channels, although no specific receptor has been identified. At this time, even though there is much experimental evidence for H₂ S as a modulator of gastrointestinal motility, we still do not have conclusive experimental evidence to definitively propose H₂ S as an inhibitory neurotransmitter in the gastrointestinal tract, causing nerve-mediated relaxation.

Properties of a flavonol-based photoCORM in aqueous buffered solutions: influence of metal ions, surfactants and proteins on visible light-induced CO release

A flavonol-based photoCORM exhibits reliable visible light-induced CO release in aqueous buffer environments containing constituents of relevance to biological environments.

Protective effects of exogenous and endogenous hydrogen sulfide in mast cell-mediated pruritus and cutaneous acute inflammation in mice

The recently described 'gasomediator' hydrogen sulfide (H₂S) has been involved in pain mechanisms, but its effect on pruritus, a sensory modality that similarly to pain acts as a protective mechanism, is poorly known and controversial. The effects of the slow-releasing (GYY4137) and spontaneous H₂S donors (Na₂S and Lawesson's reagent, LR) were evaluated in histamine and compound 48/80 (C48/80)-dependent dorsal skin pruritus and inflammation in male BALB/c mice. Animals were intradermally (i.d.) injected with C48/80 (3μg/site) or histamine (1μmol/site) alone or co-injected with Na₂S, LR or GYY4137 (within the 0.3-100nmol range). The involvement of endogenous H₂S and K_ATP channel-dependent mechanism were also evaluated. Pruritus was assessed by the number of scratching bouts, whilst skin inflammation was evaluated by the extravascular accumulation of intravenously injected ¹²⁵I-albumin (plasma extravasation) and myeloperoxidase (MPO) activity (neutrophil recruitment). Histamine or C48/80 significantly evoked itching behavior paralleled by plasma extravasation and increased MPO activity. Na₂S and LR significantly ameliorated histamine or C48/80-induced pruritus and inflammation, although these effects were less pronounced or absent with GYY4137. Inhibition of endogenous H₂S synthesis increased both Tyrode and C48/80-induced responses in the skin, whereas the blockade of K_ATP channels by glibenclamide did not. H₂S-releasing donors significantly attenuate C48/80-induced mast cell degranulation either in vivo or in vitro. We provide first evidences that H₂S donors confer protective effect against histamine-mediated acute pruritus and cutaneous inflammation. These effects can be mediated, at least in part, by stabilizing mast cells, known to contain multiple mediators and to be primary initiators of allergic processes, thus making of H₂S donors a potential alternative/complementary therapy for treating inflammatory allergic skin diseases and related pruritus.

Challenges to develop novel anti-inflammatory and analgesic drugs

Chronic inflammatory diseases and persistent pain of different origin represent common medical, social, and economic burden, and their pharmacotherapy is still an unresolved issue. Therefore, there is a great and urgent need to develop anti-inflammatory and analgesic agents with novel mechanisms of action, but it is a very challenging task. The main problem is the relatively large translational gap between the preclinical experimental data and the clinical results due to characteristics of the models, difficulties with the investigational techniques particularly for pain, as well as species differences in the mechanisms. We summarize here the current state-of-the-art medication and related ongoing strategies, and the novel targets with lead molecules under clinical development. The first members of the gold-standard categories, such as nonsteroidal anti-inflammatory drugs, glucocorticoids, and opioids, were introduced decades ago, and since then very few drugs with novel mechanisms of action have been successfully taken to the clinics despite considerable development efforts. Several biologics targeting different key molecules have provided breakthrough in some autoimmune/inflammatory diseases, but they are expensive, only parenterally available, their long-term side effects often limit their administration, and they do not effectively reduce pain. Some kinase inhibitors and phosphodiesterase-4 blockers have recently been introduced as new directions. There are in fact some promising novel approaches at different clinical stages of drug development focusing on transient receptor potential vanilloid 1/ankyrin 1 channel antagonism, inhibition of voltage-gated sodium/calcium channels, several enzymes (kinases, semicarbazide-sensitive amine oxidases, and matrix metalloproteinases), cytokines/chemokines, transcription factors, nerve growth factor, and modulation of several G protein-coupled receptors (cannabinoids, purinoceptors, and neuropeptides). WIREs Nanomed Nanobiotechnol 2017, 9:e1427. doi: 10.1002/wnan.1427 For further resources related to this article, please visit the WIREs website.

Patent highlights: December 2015-January 2016

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.