3H-1,2-dithiole-3-thione suppresses LPS-induced proinflammatory responses in macrophages: potential involvement of antioxidant induction, NF-κB, and Nrf2

Previously, we reported that 3H-1,2-dithiole-3-thione (D3T), an Nrf2 activator, acted as a potential chemoprotectant against lipopolysaccharide (LPS)-induced mortality in mice. In view of the critical involvement of macrophages in the pathogenesis of LPS-induced endotoxemia, in the present study, we investigated the protective effects of D3T on LPS-induced proinflammatory responses in cultured murine RAW 264.7 macrophage cell line and primary peritoneal macrophages and the potential involvement of antioxidant induction, NF-κB, and Nrf2. We showed that treatment with D3T resulted in increased levels of a series of antioxidants in RAW 264.7 cells in a concentration-dependent manner. These included the reduced form of glutathione, glutathione peroxidase, glutathione reductase, glutathione S-transferase, and NADPH:quinone oxidoreductase 1. Catalase was also potently induced by D3T which, however, did not show a concentration dependency. Concurrent with the ability to induce the above cellular antioxidants, D3T pretreatment of RAW 264.7 cells also led to a concentration-dependent suppression of LPS-induced interleukin-1beta (IL-1β) production and nitric oxide release. LPS-stimulated tumor necrosis factor-alpha (TNF-α) production was also suppressed by D3T, but to a much lesser extent. Using NF-κB reporter gene-expressing RAW 264.7 cells, we further showed that D3T pretreatment also suppressed LPS-induced NF-κB activation. To investigate the potential involvement of Nrf2, a chief regulator of cellular antioxidant genes, we used peritoneal macrophages isolated from Nrf2^+/+ and Nrf2^-/- mice. Our results showed that D3T pretreatment suppressed LPS-induced proinflammatory responses in Nrf2^+/+ macrophages, and this inhibitory effect of D3T was completely lost in Nrf2^-/- macrophages. Collectively, the results of the present study demonstrated that D3T acted as a potent suppressor of LPS-induced proinflammatory responses in macrophages. Antioxidant induction, NF-κB suppression, and Nrf2 activation appeared to contribute to the anti-proinflammatory activity of D3T in macrophages.

Synthesis, Molecular Docking Analysis and in Vitro Biological Evaluation of Some New Heterocyclic Scaffolds-Based Indole Moiety as Possible Antimicrobial Agents

In the present study, a general approach for the synthesis of 1-(1H-indol-3-yl)-3,3-dimercaptoprop-2-en-1-one (1) and 5-(1H-indol-3-yl)-3H-1,2-dithiole-3-thione (2) was performed. They are currently used as efficient precursors for the synthesis of some new compounds bearing five- and/or six-membered heterocyclic moieties, e.g., chromenol (3, 4), 3,4-dihydroquinoline (7, 8) and thiopyran (10, 12)-based indole core. In addition, molecular docking studies were achieved, which showed that all the newly synthesized compounds are interacting with the active site region of the target enzymes, the targets UDP-N-acetylmuramatel-alanine ligase (MurC), and human lanosterol14α-demethylase, through hydrogen bonds and pi-stacked interactions. Among these docked ligand molecules, the compound (9) was found to have the minimum binding energy (−11.5 and −8.5 Kcal/mol) as compared to the standard drug ampicillin (−8.0 and −8.1 Kcal/mol) against the target enzymes UDP-N-acetylmuramatel-alanine ligase (MurC), and Human lanosterol14α-demethylase, respectively. Subsequently, all new synthesized analogues were screened for their antibacterial activities against Gram-positive (Bacillus subtilis), and Gram-negative bacteria (Escherichia coli), as well as for antifungal activities against Candida albicans and Aspergillus flavus. The obtained data suggest that the compounds exhibited good to excellent activity against bacterial and fungi strains. The compound (E)-2-(6-(1H-indole-3-carbonyl)-5-thioxotetrahydrothieno [3,2-b]furan-2(3H)-ylidene)-3-(1H-indol-3-yl)-3-oxopropanedithioic acid (9) showed a high binding affinity as well as an excellent biological activity. Therefore, it could serve as the lead for further optimization and to arrive at potential antimicrobial agent.

Neuroprotective effects of disubstituted dithiolethione ACDT against manganese-induced toxicity in SH-SY5Y cells

Dithiolethiones are lipophilic, organosulfur compounds that activate the Nrf2 transcription factor causing an upregulation of various phase II antioxidant enzymes. A disubstituted dithiolethione 5-amino-3-thioxo-3H-(1,2) dithiole-4-carboxylic acid ethyl ester (ACDT) retains the functional pharmacophore while also containing modifiable functional groups. Neuroprotection against autoimmune encephalomyelitis in vivo and 6-hydroxy dopamine (a model for Parkinson's disease) in vitro have been previously reported with ACDT. Manganese (Mn) is a metal essential for metabolic processes at low concentrations. Overexposure and accumulation of Mn leads to a neurological condition called manganism which shares pathophysiological sequelae with parkinsonism. Here we hypothesized ACDT to be protective against manganese-induced cytotoxicity. SH-SY5Y human neuroblastoma cells exposed to 300 μM MnCl₂ displayed approximately 50% cell death, and a 24-h pretreatment with 75 μM ACDT significantly reversed this cytotoxicity. ACDT pretreatment was also found to increase total GSH levels (2.18-fold) and the protein levels of NADPH:quinone oxidoreductase-1 (NQO1) enzyme (6.33-fold), indicating an overall increase in the cells' antioxidant defense stores. A corresponding 2.32-fold reduction in the level of Mn-induced reactive oxygen species was also observed in cells pretreated with ACDT. While no changes were observed in the protein levels of apoptotic markers Bax and Bcl-2, pretreatment with 75 μM ACDT led to a 2.09-fold downregulation of ZIP14 import transporter, indicating a potential reduction in the cellular uptake of Mn as an additional neuroprotective mechanism. These effects did not extend to other transporters like the divalent metal transporter 1 (DMT1) or ferroportin. Collectively, ACDT showed substantial neuroprotection against Mn-induced cytotoxicity, opening a path for dithiolethiones as a potential novel therapeutic option against heavy metal neurotoxicity.

3H-1,2-Dithiole-3-Thione as a Potentially Novel Therapeutic Compound for Sepsis Intervention

Through the history of modern medicine, bioactive components in natural products have been either employed directly as medicines or used as prototypes for synthetic drug development. This brief Research Highlights paper considers 3H-1,2-dithiole-3-thione (D3T), a member of the 1,2-dithiole-3-thiones-compounds which may naturally occur in cruciferous vegetables. Among 1,2-dithiole-3-thiones, D3T is the most potent member with regard to the capacity of inducing tissue defenses against oxidative and inflammatory stress. Oxidative and inflammatory stress is a major pathophysiological process involved in numerous human disorders, including cancer, cardiovascular diseases, neurodegeneration, and sepsis, to name just a few. This article surveys recent major research findings on D3T as an inducer of tissue antioxidative and antiinflammatory defenses and as a potential therapeutic modality for sepsis intervention.

GPx4 in Bacterial Infection and Polymicrobial Sepsis: Involvement of Ferroptosis and Pyroptosis

While it is well known that bacterial infection is the predominant cause of sepsis, the molecular pathophysiology of this clinical syndrome remains ill-defined. In this Research Highlights article, we discuss the recent research findings regarding a protective role for glutathione peroxidase-4 (GPx4) in bacterial infection and polymicrobial sepsis via modulating ferroptosis and pyroptosis, two novel modes of regulated cell death. It is suggested that GPx4, being a requisite gateway to both ferroptosis and pyroptosis, may serve as a critical molecular target for developing effective drugs for controlling infection and sepsis.

Graphene Quantum Dots Protect against Copper Redox-Mediated Free Radical Generation and Cardiac Cell Injury

In this work, we investigated the effects of graphene quantum dots (GQDs) on copper redox-mediated free radical generation and cell injury. Using electron paramagnetic resonance (EPR) spectrometry in conjunction with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap, we found that GQDs at a concentration as low as 1 μg/ml significantly inhibited Cu(II)/H₂O₂-mediated hydroxyl radical formation. GQDs also blocked Cu(II)-catalyzed nucleophilic addition of H₂O to DMPO to form a DMPO-OH adduct in the absence of H₂O₂, suggesting a potential for GQDs to inhibit copper redox activity. Indeed, we observed that the presence of GQDs prevented H₂O₂-mediated reduction of Cu(II) to Cu(I) though GQDs themselves also caused the reduction of Cu(II) to Cu(I). To further investigate the effects of GQDs on copper redox activity, we employed the Cu(II)/hydroquinone system in which copper redox activity plays an essential role in the oxidation of hydroquinone to semiquinone radicals with consequent oxygen consumption. Using oxygen polarography as well as EPR spectrometry, we demonstrated that the presence of GQDs drastically blocked the oxygen consumption and semiquinone radical formation resulting from the reaction of Cu(II) and hydroquinone. These results suggested that GQDs suppressed free radical formation via inhibiting copper redox activity. Lastly, using cultured human cardiomyocytes, we demonstrated that the presence of GQDs also protected against Cu(II)/H₂O₂-mediated cardiac cell injury as indicated by morphological changes (e.g., cell shrinkage and degeneration). In conclusion, our work shows, for the first time, the potential for using GQDs to counteract copper redox-mediated biological damage.

Switching Selectivity of α-Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles

An operationally simple cascade protocol has been developed for the construction of 1,2- and 1,3-dithiole derivatives from α-enolic dithioesters. 1,2-Dithioles are achieved by the reaction of dithioesters with elemental sulfur in the presence of InCl₃ under solvent-free conditions. 1,3-Dithioles have been constructed via DABCO mediated self-coupling of dithioesters in open air enabling the formation of two new C-S bonds and one ring in a single operation in contiguous fashion. The reactions proceeded smoothly affording the desired sulfur-rich heterocycles in good to excellent yields, exhibiting gram-scale ability and broad functional group tolerance utilizing easy to handle cheap and easily available reagents. The probable mechanisms for the formation of 1,2- and 1,3-dithioles from α-enolic dithioesters have been suggested.

Phytochemical regulation of Fyn and AMPK signaling circuitry

During the past decades, phytochemical terpenoids, polyphenols, lignans, flavonoids, and alkaloids have been identified as antioxidative and cytoprotective agents. Adenosine monophosphate-activated protein kinase (AMPK) is a kinase that controls redox-state and oxidative stress in the cell, and serves as a key molecule regulating energy metabolism. Many phytochemicals directly or indirectly alter the AMPK pathway in distinct manners, exerting catabolic metabolism. Some of them are considered promising in the treatment of metabolic diseases such as type II diabetes, obesity, and hyperlipidemia. Another important kinase that regulates energy metabolism is Fyn kinase, a member of the Src family kinases that plays a role in various cellular responses such as insulin signaling, cell growth, oxidative stress and apoptosis. Phytochemical inhibition of Fyn leads to AMPK-mediated protection of the cell in association with increased antioxidative capacity and mitochondrial biogenesis. The kinases may work together to form a signaling circuitry for the homeostasis of energy conservation and expenditure, and may serve as targets of phytochemicals. This review is intended as a compilation of recent advancements in the pharmacological research of phytochemicals targeting Fyn and AMPK circuitry, providing information for the prevention and treatment of metabolic diseases and the accompanying tissue injuries.

Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent

Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by

NAD(P)H

quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16-F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16-F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ~80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16-F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells.

Synthesis and structure-activity relationships study of dithiolethiones as inducers of glutathione in the SH-SY5Y neuroblastoma cell line

Parkinson's disease is a neurodegenerative disorder that involves the degeneration of nigrostriatal dopaminergic neurons. Elevated levels of reactive oxygen species have been shown to deplete cellular levels of the ubiquitous antioxidant glutathione, leading to oxidative stress and eventual neuronal cell death. Dithiolethiones, a class of sulfur-containing heterocyclic molecules, have been shown to induce cellular production of glutathione in a variety of tissues, but have not been extensively evaluated in neurons. Herein, we report the synthesis and preliminary structure-activity relationships study of several substituted dithiolethiones. Three molecules were identified (D3T, CPDT, and 2d) that potently induced cellular glutathione in the SH-SY5Y neuroblastoma cell line. Furthermore, these compounds were found to provide neuroprotection in the 6-hydroxydopamine model of neurotoxicity. This study suggests that dithiolethione-mediated neuroprotection may have potential as a disease-modifying antiparkinsonian therapy.

Role of the renin-angiotensin-aldosterone system and the glutathione S-transferase Mu, Pi and Theta gene polymorphisms in cardiotoxicity after anthracycline chemotherapy for breast carcinoma

BACKGROUND

Anthracyclines are among the most active drugs against breast cancer, but can exert cardiotoxic effects eventually resulting in congestive heart failure (CHF). Identifying breast cancer patients at high risk of developing cardiotoxicity after anthracycline therapy would be of value in guiding the use of these agents.

AIMS

We determined whether polymorphisms in the renin-angiotensin-aldosterone system (RAAS) and in the glutathione S-transferase (GST) family of phase II detoxification enzymes might be useful predictors of left ventricular ejection fraction (LVEF) kinetics and risk of developing CHF. We sought correlations between the development of cardiotoxicity and gene polymorphisms in 48 patients with early breast cancer treated with adjuvant anthracycline chemotherapy.

METHODS

We analyzed the following polymorphisms: p.Met235Thr and p.Thr174Met in angiotensinogen (AGT), Ins/Del in angiotensin-converting enzyme (ACE), A1166C in angiotensin II type-1 receptor (AGTR1A), c.-344T>C in aldosterone synthase (CYP11B2), p.Ile105Val in GSTP1. Additionally, we analyzed the presence or absence of the GSTT1 and GSTP1 genes. A LVEF <50% was detected at least once during the 3 years of follow-up period in 13 out of 48 patients (27.1%).

CONCLUSION

RAAS gene polymorphisms were not significantly associated with the development of cardiotoxicity. GSTM1may be useful as a biomarker of higher risk of cardiotoxicity, as demonstrated in our cohort of patients (p=0.147).

Mitochondrial function in human neuroblastoma cells is up-regulated and protected by NQO1, a plasma membrane redox enzyme

Background

Recent findings suggest that NADH-dependent enzymes of the plasma membrane redox system (PMRS) play roles in the maintenance of cell bioenergetics and oxidative state. Neurons and tumor cells exhibit differential vulnerability to oxidative and metabolic stress, with important implications for the development of therapeutic interventions that promote either cell survival (neurons) or death (cancer cells).

Methods and Findings

Here we used human neuroblastoma cells with low or high levels of the PMRS enzyme NADH-quinone oxidoreductase 1 (NQO1) to investigate how the PMRS modulates mitochondrial functions and cell survival. Cells with elevated NQO1 levels exhibited higher levels of oxygen consumption and ATP production, and lower production of reactive oxygen species. Cells overexpressing NQO1 were more resistant to being damaged by the mitochondrial toxins rotenone and antimycin A, and exhibited less oxidative/nitrative damage and less apoptotic cell death. Cells with basal levels of NQO1 resulted in increased oxidative damage to proteins and cellular vulnerability to mitochondrial toxins. Thus, mitochondrial functions are enhanced and oxidative stress is reduced as a result of elevated PMRS activity, enabling cells to maintain redox homeostasis under conditions of metabolic and energetic stress.

Conclusion

These findings suggest that NQO1 is a potential target for the development of therapeutic agents for either preventing neuronal degeneration or promoting the death of neural tumor cells.

Downregulation of vitamin C transporter SVCT-2 in doxorubicin-induced cardiomyocyte injury

Vitamin C (Vit C) has been shown to be protective against doxorubicin (Dox)-induced cardiotoxicity. However, Vit C uptake into cardiomyocytes is poorly understood. Furthermore, whether the antioxidant enzyme reserve is enhanced by Vit C is also not known. The present study investigated an influence of Dox on Vit C transporters, expression of endogenous antioxidant reserve as well as enzymes, oxidative stress, and apoptosis in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were exposed to control (culture medium 199 alone), Dox (10 μM), Vit C (25 μM), and Vit C + Dox for 24 h. Vit C transporter expression and localization, oxidative stress, antioxidant enzymes, and apoptosis were studied. Expression and localization of sodium-dependent vitamin C transporter-2 (SVCT-2) in the sarcolemma was reduced by Dox, but Vit C supplementation was able to blunt this change. There was a decrease in the expression of antioxidant enzymes glutathione peroxidase (GPx), catalase, and Cu/Zn superoxide dismutase (SOD) due to Dox, but only GPx expression was completely prevented and Cu/Zn SOD was partially rescued by Vit C. Dox-induced decrease in antioxidant reserve and increase in oxidative stress were partially mitigated by Vit C. Dox-induced apoptosis was ameliorated by Vit C. It is suggested that cardioprotection offered by Vit C in Dox-induced cardiomyopathy may involve an upregulation of SVCT-2 transporter followed by a reduction in oxidative stress as well as blunting of cardiomyocyte injury.

Adiponectin: anti-inflammatory and cardioprotective effects

Adipose tissue is an endocrine organ that plays an essential role in regulating several metabolic functions through the secretion of biological mediators called "adipokines". Dysregulation of adipokines plays a crucial role in obesity-related diseases. Adiponectin (APN) is the most abundant adipokine accounting for the 0.01% of total serum protein, and is involved in a wide variety of physiological processes including energy metabolism, inflammation, and vascular physiology. APN plasma levels are reduced in individuals with obesity, type 2 diabetes and coronary artery disease, all traits with low-grade chronic inflammation. It is has been suggested that the absence of APN anti-inflammatory effects may be a contributing factor to this inflammation. APN inhibits the expression of tumor necrosis factor-α-induced endothelial adhesion molecules, macrophage-to-foam cell transformation, tumor necrosis factor-α expression in macrophages and adipose tissue, and smooth muscle cell proliferation. It also has anti-apoptotic and anti-oxidant effects, which play a role in its cardioprotective action. This review will focus on APN as an anti-inflammatory, anti-atherogenic and cardioprotective plasma protein.

Activation of the aryl hydrocarbon receptor by doxorubicin mediates cytoprotective effects in the heart

AIMS

Doxorubicin (DOX) is a highly effective chemotherapeutic agent; however, cumulative dose-dependent cardiotoxicity is a significant side effect of this therapy. Because DOX is a polyaromatic hydrocarbon, we hypothesized that it will be metabolized by the activation of the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that is involved in the metabolism of numerous xenobiotic agents. These studies were performed to determine whether DOX activates AhR and whether this activation modulates the toxicity of DOX in cardiomyocytes.

METHODS AND RESULTS

Treatment with DOX induced AhR migration to the nucleus, increased AhR binding with its co-factor, aryl hydrocarbon receptor nuclear translocator-1 (ARNT1), and increased the expression of AhR-regulated phase I (CYP1A1) and phase II (GSTA1) drug-metabolizing enzymes in both cardiomyocytes and in the intact heart. Knockdown of AhR in H9C2 cells abolished DOX-induced increases in CYP1A1 and GSTA1 expression. Similar results were obtained by treating adult rat ventricular myocytes with the AhR antagonist, CH-223191. Taken together, these findings indicate that DOX-induced upregulation of CYP1A1 and GSTA1 expression is AhR dependent. AhR null mice treated with 10 mg/kg DOX did not show any activation of CYP1A1 or GSTA1 expression. Moreover, lack of AhR in vivo resulted in a significant decrease in left ventricular function compared with wild-type animals, and increased p53 activation and apoptosis in the heart after treatment with DOX.

CONCLUSIONS

These findings indicate that AhR plays an important role in DOX metabolism by the heart and further demonstrate that AhR is cardioprotective against DOX-induced cardiotoxicity.