Treatment of Xerostomia with the Bile Secretion-Stimulating Drug Anethole Trithione: A Clinical Trial

H2S Donors with Cytoprotective Effects in Models of MI/R Injury and Chemotherapy-Induced Cardiotoxicity

Hydrogen sulfide (H2S) is an endogenous signaling molecule that greatly influences several important (patho)physiological processes related to cardiovascular health and disease, including vasodilation, angiogenesis, inflammation, and cellular redox homeostasis. Consequently, H2S supplementation is an emerging area of interest, especially for the treatment of cardiovascular-related diseases. To fully unlock the medicinal properties of hydrogen sulfide, however, the development and refinement of H2S releasing compounds (or donors) are required to augment its bioavailability and to better mimic its natural enzymatic production. Categorizing donors by the biological stimulus that triggers their H2S release, this review highlights the fundamental chemistry and releasing mechanisms of a range of H2S donors that have exhibited promising protective effects in models of myocardial ischemia-reperfusion (MI/R) injury and cancer chemotherapy-induced cardiotoxicity, specifically. Thus, in addition to serving as important investigative tools that further advance our knowledge and understanding of H2S chemical biology, the compounds highlighted in this review have the potential to serve as vital therapeutic agents for the treatment (or prevention) of various cardiomyopathies.

Progress and perspective on hydrogen sulfide donors and their biomedical applications

Following the discovery of nitric oxide (NO) and carbon monoxide (CO), hydrogen sulfide (H₂ S) has been identified as the third gasotransmitter in humans. Increasing evidence have shown that H₂ S is of preventive or therapeutic effects on diverse pathological complications. As a consequence, it is of great significance to develop suitable approaches of H₂ S-based therapeutics for biomedical applications. H₂ S-releasing agents (H₂ S donors) play important roles in exploring and understanding the physiological functions of H₂ S. More importantly, accumulating studies have validated the theranostic potential of H₂ S donors in extensive repertoires of in vitro and in vivo disease models. Thus, it is imperative to summarize and update the literatures in this field. In this review, first, the background of H₂ S on its chemical and biological aspects is concisely introduced. Second, the studies regarding the H₂ S-releasing compounds are categorized and described, and accordingly, their H₂ S-donating mechanisms, biological applications, and therapeutic values are also comprehensively delineated and discussed. Necessary comparisons between related H₂ S donors are presented, and the drawbacks of many typical H₂ S donors are analyzed and revealed. Finally, several critical challenges encountered in the development of multifunctional H₂ S donors are discussed, and the direction of their future development as well as their biomedical applications is proposed. We expect that this review will reach extensive audiences across multiple disciplines and promote the innovation of H₂ S biomedicine.

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.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

A Randomized, Double-Blind, Placebo-Controlled, Cross-Over Study to Evaluate the Efficacy of AqualiefTM Mucoadhesive Tablets in Head and Neck Cancer Patients Who Developed Radiation-Induced Xerostomia

Xerostomia, the subjective complaint of dry mouth, is caused by therapeutic interventions or diseases. Nowadays, radiotherapy (RT) in patients with head and neck cancer (HNC) stands out as one of the most important causes of xerostomia. Currently available therapies for the treatment of xerostomia are still less than optimal and xerostomia still represents an unmet clinical need. In this article, we present the results of a prospective clinical study with a new product, Aqualief^TM, in patients treated with curative RT with or without chemotherapy for HNC. Aqualief^TM is based on two main ingredients, carnosine and karkadé, which have acid buffering and antioxidant properties. The study was performed on 30 patients, with 4 of the patients being lost during the study period. Each patient received randomly one of the two treatments, Aqualief^TM or placebo, for 8 days. After a 10-day wash-out period, each patient received the other treatment for a further 8 days. The results show that Aqualief^TM stimulated salivation in these patients and reduced the pH drop that was observed in an equivalent placebo-treated population of patients. Moreover, no serious, treatment-related adverse events were observed. Aqualief^TM has shown positive results, although with limitations due to unsuccessful trial accrual. Therefore, it may be further investigated as a tool for the treatment of RT-related xerostomia.

Trends in H2S-Donors Chemistry and Their Effects in Cardiovascular Diseases

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter recently emerged as an important regulatory mediator of numerous human cell functions in health and in disease. In fact, much evidence has suggested that hydrogen sulfide plays a significant role in many physio-pathological processes, such as inflammation, oxidation, neurophysiology, ion channels regulation, cardiovascular protection, endocrine regulation, and tumor progression. Considering the plethora of physiological effects of this gasotransmitter, the protective role of H₂S donors in different disease models has been extensively studied. Based on the growing interest in H₂S-releasing compounds and their importance as tools for biological and pharmacological studies, this review is an exploration of currently available H₂S donors, classifying them by the H₂S-releasing-triggered mechanism and highlighting those potentially useful as promising drugs in the treatment of cardiovascular diseases.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

NRF2 pathway activation by KEAP1 inhibition attenuates the manifestation of aging phenotypes in salivary glands

Saliva plays an essential role in the maintenance of oral health. The oral cavity environment changes during aging mainly due to alterations in the secretion and composition of saliva. In particular, unstimulated basal salivary flow decreases with age. The functional decline of the salivary glands impairs chewing and swallowing abilities and often becomes one of the predispositions for aging-related disorders, including aspiration pneumonia. The KEAP1-NRF2 system plays a central role in the regulation of the oxidative stress response. NRF2 is a transcription factor that coordinately regulates cytoprotective genes, and KEAP1 is a negative regulator of NRF2. Although NRF2 activation has been suggested to be advantageous for the prevention of aging-related diseases, its role in the course of physiological aging is not well understood. To investigate the impact of NRF2 activation on salivary gland aging, we compared the submandibular glands of Keap1-knockdown (KD) (Keap1FA/FA) mice in which NRF2 is activated with those of wild-type mice. Young mice did not show any apparent differences between the two genotypes, whereas in old mice, clear differences were observed. Aged wild-type submandibular glands exhibited iron and collagen depositions, immune cell infiltration and increased DNA damage and apoptosis accompanied by elevated oxidative stress, which were all markedly attenuated in Keap1-KD mice, suggesting that NRF2 activation has antiaging effects on salivary glands. We propose that appropriate activation of NRF2 is effective for the maintenance of healthy salivary gland conditions and for the prevention of hyposalivation in the elderly.

The evolving landscape for cellular nitric oxide and hydrogen sulfide delivery systems: A new era of customized medications

Nitric oxide (NO) and hydrogen sulfide (H2S) are industrial toxins or pollutants; however, both are produced endogenously and have important biological roles in most mammalian tissues. The recognition that these gasotransmitters have a role in physiological and pathophysiological processes has presented opportunities to harness their intracellular effects either through inhibition of their production; or more commonly, through inducing their levels and or delivering them by various modalities. In this review article, we have focused on an array of NO and H2S donors, their hybrids with other established classes of drugs, and the various engineered delivery platforms such a fibers, polymers, nanoparticles, hydrogels, and others. In each case, we have reviewed the rationale for their development.

Synthesis, Characterization, and In Vivo Evaluation of Desmethyl Anethole Trithione Phosphate Prodrug for Ameliorating Cerebral Ischemia-Reperfusion Injury in Rats

Anethol trithione (ATT) has a wide range of physiological activities, but its use is limited due to its poor water solubility. To improve the solubility of ATT, we synthesized and characterized a novel phosphate prodrug (ATXP) relying on the availability of the hydroxy group in 5-(4-hydroxyphenyl)-3H-1,2-dithiole3-thione (ATX), which was transformed from ATT rapidly and extensively in vivo. Our results showed that ATXP significantly improved drug solubility. ATXP was rapidly converted to ATX and reached a maximum plasma concentration with a T _max of approximately 5 min after intravenous (iv) administration. Furthermore, after the oral administration of ATXP, the C _max was 3326.30 ± 566.50 ng/mL, which was approximately 5-fold greater than that of the parent drug form, indicating that ATXP has greater absorption than that of ATT. Additionally, the oral phosphate prodrug ATXP increased the ATX in the area under the plasma concentration vs time curves (AUC_0-t = 3927.40 ± 321.50 and AUC_0-∞ = 4579.0 ± 756.30), making its use in practical applications more meaningful. Finally, compared to the vehicle, ATXP was confirmed to maintain the bioactivity of the parent drug for a significant reduction in infarct volume 24 h after reperfusion. Based on these findings, the phosphate prodrug ATXP is a potentially useful water-soluble prodrug with improved pharmacokinetic properties.

The Benefits of Macromolecular/Supramolecular Approaches in Hydrogen Sulfide Delivery: A Review of Polymeric and Self-Assembled Hydrogen Sulfide Donors

Significance: Cell homeostasis and redox balance are regulated in part by hydrogen sulfide (H2S), a gaseous signaling molecule known as a gasotransmitter. Given its biological roles, H2S has promising therapeutic potential, but controlled delivery of this reactive and hazardous gas is challenging due to its promiscuity, rapid diffusivity, and toxicity at high doses. Macromolecular and supramolecular drug delivery systems are vital for the effective delivery of many active pharmaceutical ingredients, and H2S stands to benefit greatly from the tunable physical, chemical, and pharmacokinetic properties of polymeric and/or self-assembled drug delivery systems. Recent Advances: Several types of H2S-releasing macro- and supramolecular materials have been developed in the past 5 years, and the field is expanding quickly. Slow-releasing polymers, polymer assemblies, polymer nano- and microparticles, and self-assembled hydrogels have enabled triggered, sustained, and/or localized H2S delivery, and many of these materials are more potent in biological assays than analogous small-molecule H2S donors. Critical Issues: H2S plays a role in a number of (patho)physiological processes, including redox balance, ion channel regulation, modulation of inducible nitric oxide synthase, angiogenesis, blood pressure regulation, and more. Chemical tools designed to (i) deliver H2S to study these processes, and (ii) exploit H2S signaling pathways for treatment of diseases require control over the timing, rate, duration, and location of release. Future Directions: Development of new material approaches for H2S delivery that enable long-term, triggered, localized, and/or targeted delivery of the gas will enable greater understanding of this vital signaling molecule and eventually expedite its clinical application.

Mechanism of H2S Formation from the Metabolism of Anetholedithiolethione and Anetholedithiolone by Rat Liver Microsomes

The drug anetholedithiolethione (ADT) and its analogs have been extensively used as H₂S donors. However, the mechanism of H₂S formation from ADT under biologic conditions remains almost completely unknown. This article shows that only small amounts of H₂S are formed during incubation of ADT and of its metabolite anetholedithiolone (ADO) with rat liver cytosol or with rat liver microsomes (RLM) in the absence of NADPH, indicating that H₂S formation under these conditions is of hydrolytic origin only to a minor extent. By contrast, much greater amounts of H₂S are formed upon incubation of ADT and ADO with RLM in the presence of NADPH and dioxygen, with a concomitant formation of H₂S and para-methoxy-acetophenone (pMA). Moreover, H₂S and pMA formation under those conditions are greatly inhibited in the presence of N-benzyl-imidazole indicating the involvement of cytochrome P450-dependent monooxygenases. Mechanistic studies show the intermediate formation of the ADT-derived 1,2-dithiolium cation and of the ADO sulfoxide during microsomal metabolism of ADT and ADO, respectively. This article proposes the first detailed mechanisms for the formation of H₂S from microsomal metabolism of ADT and ADO in agreement with those data and with previously published data on the metabolism of compounds involving a C=S bond. Finally, this article shows for the first time that ADO is a better H₂S donor than ADT under those conditions. SIGNIFICANCE STATEMENT: Incubation of anetholedithiolethione (ADT) or its metabolite anetholedithiolone (ADO) in the presence of rat liver microsomes, NADPH, and O₂ leads to H₂S. This article shows for the first time that this H₂S formation involves several steps catalyzed by microsomal monooxygenases and that ADO is a better H₂S donor than ADT. We propose the first detailed mechanisms for the formation of H₂S from the microsomal metabolism of ADT and ADO.

An old medicine as a new drug to prevent mitochondrial complex I from producing oxygen radicals

Findings

Here, we demonstrate that OP2113 (5-(4-Methoxyphenyl)-3H-1,2-dithiole-3-thione, CAS 532-11-6), synthesized and used as a drug since 1696, does not act as an unspecific antioxidant molecule (i.e., as a radical scavenger) but unexpectedly decreases mitochondrial reactive oxygen species (ROS/H₂O₂) production by acting as a specific inhibitor of ROS production at the I_Q site of complex I of the mitochondrial respiratory chain. Studies performed on isolated rat heart mitochondria also showed that OP2113 does not affect oxidative phosphorylation driven by complex I or complex II substrates. We assessed the effect of OP2113 on an infarct model of ex vivo rat heart in which mitochondrial ROS production is highly involved and showed that OP2113 protects heart tissue as well as the recovery of heart contractile activity.

Conclusion / Significance

This work represents the first demonstration of a drug authorized for use in humans that can prevent mitochondria from producing ROS/H₂O₂. OP2113 therefore appears to be a member of the new class of mitochondrial ROS blockers (S1QELs) and could protect mitochondrial function in numerous diseases in which ROS-induced mitochondrial dysfunction occurs. These applications include but are not limited to aging, Parkinson’s and Alzheimer's diseases, cardiac atrial fibrillation, and ischemia-reperfusion injury.

A review of hydrogen sulfide (H2S) donors: Chemistry and potential therapeutic applications

Hydrogen sulfide (H2S) is a ubiquitous small gaseous signaling molecule, playing an important role in many physiological processes and joining nitric oxide and carbon monoxide in the group of signaling agents termed gasotransmitters. Endogenous concentrations of H2S are generally low, making it difficult to discern precise biological functions. As such, probing the physiological roles of H2S is aided by exogenous delivery of the gas in cell and animal studies. This need for an exogenous source of H2S provides a unique challenge for chemists to develop chemical tools that facilitate the study of H2S under biological conditions. Compounds that degrade in response to a specific trigger to release H2S, termed H2S donors, include a wide variety of functional groups and delivery systems, some of which mimic the tightly controlled endogenous production in response to specific, biologically relevant conditions. This review examines a variety of H2S donor systems classified by their H2S-releasing trigger as well as their H2S release profiles, byproducts, and potential therapeutic applications.

Dithiolethione compounds inhibit Akt signaling in human breast and lung cancer cells by increasing PP2A activity

The chemo-preventative effects of dithiolethione compounds are attributed to their activation of anti-oxidant response elements (ARE) by reacting with the Nrf2/Keap1 protein complex. In this study, we demonstrate anti-proliferative effects of the dithiolethione compound ACS-1 in human cancer cell lines (A549 and MDA-MB-231) by increasing the activity of the tumor suppressor PP2A. ACS-1 inhibited EGF-induced cellular proliferation in a concentration and time-dependent manner. Akt activation, as determined by serine-473 phosphorylation, was inhibited by ACS-1 in cells stimulated with either EGF or fibronectin. Furthermore, ACS-1 inhibited mTOR signaling and decreased c-myc protein levels. ACS-1 did not proximally alter EGFR or integrin signaling, but caused a concentration-dependent increase in PP2A activity. The effect of ACS-1 on Akt activation was not observed in the presence of the PP2A inhibitor okadaic acid. ACS-1 effects on PP2A activity were independent of ARE activation and cAMP formation. In addition to ACS-1, other dithiolethione compounds showed similar effects in reducing Akt activation, suggesting that this class of compounds may have other effects beyond chemoprevention.

Efficacy of a new oral lubricant solution in the management of psychotropic drug-induced xerostomia: a randomized controlled trial

OBJECTIVE

Xerostomia is a subjective sensation of mouth dryness often occurring as an unwanted effect of psychotropic drugs.

METHODS

The clinical efficacy and acceptability of a new oxygenated glycerol triester (OGT) oral spray (1 or 2 sprays up to 4 times daily) in the treatment of xerostomia was compared with those of a commercially available artificial saliva substitute (ASS [Saliveze]) in a 2-week, open-labeled, randomized, parallel-group study. Clinical assessment of xerostomia included evaluation of mouth dryness by means of a 10-cm-long visual analog scale, objective blinded assessment of the oral tissue condition by a dental hygienist by means of a 4-point ordinal scale, and subjective patient-based assessment of dry mouth symptoms by means of dichotomous responses to a questionnaire. [Day 14 - baseline] patient-based mouth dryness score was the primary end point.

RESULTS

Seventy-four patients (41 women and 33 men, 44 +/- 15 years) undergoing long-term psychotropic drug treatment were consecutively enrolled. At day 14, OGT resulted in better efficacy than ASS in mouth dryness score (mean difference, 1.2 +/- 0.4; P = 0.006), speech difficulties (mean difference, 1.2 +/- 0.4; P = 0.005), taste (mean difference, 1.1 +/- 0.4; P = 0.02), and overall mouth condition (mean difference, 1.4 +/- 0.9; P = 0.005). Taste of OGT was better than that of ASS (mean difference, 1.4 +/- 0.6; P = 0.04), as was OGT acceptability (mean difference, 1.4 +/- 0.9; P = 0.005).

CONCLUSION

Oxygenated glycerol triester lubricant oral spray was superior to a commercially available ASS in improving xerostomia and overall condition of the oral tissue.

Proposta de um método prático de sialometria

Introdução: A xerostomia é uma queixa subjetiva que pode ou não estar relacionada à diminuição da salivação. Deve, porém, ser sempre investigada, pois está freqüentemente associada a doenças sistêmicas, incluindo a síndrome de Sjögren. Apesar de não haver padrão universal que caracterize a hipossalivação, consideramos a sialometria importante para avaliação do tratamento, através da realização de exames seriados em um mesmo paciente. Analisando as técnicas de sialometria já descritas, optamos por adaptar e padronizar o método de Bolwig e Rafaelsen (1972) por considerá-lo o mais prático e fidedigno e visando à partir de então a sua utilização em larga escala. Objetivo: Avaliar os resultados de método submúltiplo de sialometria. Material e método: Foram avaliados 10 sujeitos, 5 sem sintomatologia de xerostomia que formam considerados compatíveis e 5 com xerostomia. Foram submetidos ao método de sialometria com algodão pré e pós estimulados. Os resultados foram comprovados. Resultados: Todos os pacientes apresentaram melhora da saliva mensurável pelo método pós-estimulado. Conclusões: O método utilizado se mostrou de fácil realização e fidedigno.

The excretion of cephem antibiotics into saliva is inversely associated with their plasma protein-binding activities

BACKGROUND

The excretion of medicated drugs into saliva may disturb the oral environment and antibiotic excretion into saliva appears to be regulated by many factors that have not been fully explored.

METHODS

Excretion of four cephem antibiotics into saliva was examined in healthy volunteers and rats, using high-performance liquid chromatography, and the relationship between excretion levels and plasma protein-binding activities of the antibiotics was investigated.

RESULTS

Following addition of 50 microgram/ml of each antibiotic to human plasma, protein binding rates (PBRs) of cefuzonam (CZON, molecular weight (MW): 535.58), cefotaxime (CTX, MW: 477.45), flomoxef (FMOX, MW: 518.45) and cefozopran (CZOP, MW: 551.99) were 87.8 +/- 1.2, 70.8 +/- 0.8, 36.2 +/- 0.5 and 8.3 +/- 0.3%, respectively. In rat plasma, PBRs of the four antibiotics were 94.0 +/- 0.5, 62.1 +/- 1.4, 54.0 +/- 0.8 and 6.0 +/- 0.8%, respectively. Similar PBRs were observed when the antibiotic concentration was increased to 100 and 200 microgram/ml. CZOP was most rapidly excreted into saliva and had the highest concentration in saliva among the tested antibiotics, while the plateau level of CZON was the lowest. The excreted levels of each antibiotic in saliva, when locally perfused through the rat facial artery, were inversely associated with each PBR. Similarly, the ratios of antibiotic concentration in saliva to rat plasma were almost constant for each antibiotic, revealing an inverse relationship with PBRs.

CONCLUSION

These results appear to indicate that low molecular weight antibiotics are excreted into saliva through passive diffusion, inversely relating to their PBRs, and that high concentrations of antibiotics in the saliva have the potential to change the oral ecological environment.