A tellurium-based small compound ameliorates tumor metastasis by downregulating heparanase expression.

Tellurium is a rare element, and ammonium trichloro (dioxoethylene-o,o') tellurate (AS101) is the most bioactive molecule among several synthetic tellurium compounds. AS101 was found to be immunomodulatory and can modulate types of cytokines. However, the effect of AS101 on tumor metastasis remains unclear. Heparanase, an endo-glucuronidase, cleaves heparin sulfate side chains of proteoglycans on the cell surface, further leading to the degradation of the extracellular matrix. Heparanase also releases angiogenic factors in the extracellular matrix, is overexpressed in tumor cells, and promotes tumor metastasis and angiogenesis. In this study, we investigated the effect of AS101 in 4T1 and CT26 cells, especially heparanase. Heparanase expression was downregulated in 4T1 and CT26 cells after treatment with AS101 in vitro. The protein level involved in the protein kinase-B/mammalian target of rapamycin (AKT/mTOR) signaling pathway also declined. Cell migration assays revealed the inhibitory effect of AS101 on migration. The results of this study indicate that AS101 inhibits tumor migration by downregulating heparanase through the AKT/mTOR signaling pathway and has positive effects in vivo.

Immunomodulator AS101 restores colistin susceptibility of clinical colistin-resistant Escherichia coli and Klebsiella pneumoniae in vitro and in vivo.

OBJECTIVES: Colistin (COL) was once considered to be the last line of defence against multidrug-resistant bacteria belonging to the family Enterobacteriaceae. Due to the misuse of COL, COL-resistant (COL-R) Enterobacteriaceae have emerged. To address this clinical issue and combat COL resistance, novel approaches are urgently needed. METHODS: In this study, the in vitro and in vivo antimicrobial and antibiofilm effects of the immunomodulator AS101 were investigated in combination with COL against COL-R Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae). RESULTS: Checkerboard assay, time-kill assay, and scanning electron microscopy confirmed the in vitro antimicrobial phenotype, whereas, crystal violet staining and multidimensional confocal laser scanning microscopy with live/dead staining confirmed the antibiofilm capability of the combination therapy. Moreover, the Galleria mellonella infection model and the mouse infection model indicated the high in vivo efficacy of the combination therapy. Additionally, cytotoxicity experiments performed using human kidney-derived HK-2 cells and haemolysis assays performed using human erythrocytes collectively demonstrated safety at effective combination concentrations. Furthermore, quantification of the expression of inflammatory cytokines via enzyme-linked immunosorbent assay confirmed the anti-inflammatory advantage of combination therapy. At the mechanistic level, changes in outer and inner membrane permeability and accumulation of ROS levels, which might be potential mechanisms for synergistic antimicrobial effects. CONCLUSIONS: This study found that AS101 can restore COL susceptibility in clinical COL-R E. coli and K. pneumoniae and also has synergistic antibiofilm and anti-inflammatory capabilities. This study provided a novel strategy to combat clinical infections caused by COL-R E. coli and K. pneumoniae.

AS101 regulates the Teff/Treg balance to alleviate rabbit autoimmune dacryoadenitis through modulating NFATc2.

Sjögren's syndrome (SS) dry eye can cause ocular surface inflammation and lacrimal gland (LG) damage, leading to discomfort and potential vision problems. The existing treatment options for SS dry eye are currently constrained. We investigated the possible therapeutic effect and the underlying mechanism of AS101 in autoimmune dry eye. AS101 was injected subconjunctivally into a rabbit model of autoimmune dacryoadenitis and its therapeutic effects were determined by evaluating clinical and histological scores. The expressions of effector T cells (Teff)/regulatory T cells (Treg)-related transcription factors and cytokines, inflammation mediators, and transcription factor NFATc2 were measured by quantitative real-time PCR and/or Western blot both in vivo and in vitro. Additionally, the role of NFATc2 in the immunomodulatory effects of AS101 on T cells was explored by co-culturing activated peripheral blood lymphocytes (PBLs) transfected with NFATc2 overexpression lentiviral plasmid with AS101. AS101 treatment potently ameliorated the clinical severity and reduced the inflammation of LG. Further investigation revealed that AS101 treatment led to decreased expression of Th1-related genes (T-bet and IFN-γ) and Th17-related genes (RORC, IL-17A, IL-17F, and GM-CSF) and increased expression of Treg-related gene Foxp3 in vivo and in vitro. Meanwhile, AS101 suppressed the expression of TNF-α, IL-1ß, IL-23, IL-6, MMP-2, and MMP-9. Mechanistically, AS101 downregulated the expression of NFATc2 in inflamed LGs. Overexpression of NFATc2 in activated PBLs partially blunted the effect of AS101 on Teff suppression and Treg promotion. In conclusion, AS101 is a potential regulator of Teff/Treg cell balance and could be an effective treatment agent for SS dry eye.

Unveiling the mechanism of activation of the Te(IV) prodrug AS101. New chemical insights towards a better understanding of its medicinal properties.

AS101 (Ammonium trichloro (dioxoethylene-O,O') tellurate) is an important hypervalent Te-based prodrug. Recently, we started a systematic investigation on AS101 with the aim to correlate its promising biological effects as a potent immunomodulator drug with multiple medicinal applications and its specific chemical properties. To date, a substantial agreement on the rapid conversion of the initial AS101 species into the corresponding TeOCl3- anion does exist, and this latter species is reputed as the pharmacologically active one. However, we realized that TeOCl3- could quickly undergo further steps of conversion in an aqueous medium, eventually producing the TeO2 species. Using a mixed experimental and theoretical investigation approach, we characterized the conversion process leading to TeO2 occurring both in pure water and in reference buffers at physiological-like pH. Our findings may offer a valuable "chemical tool" for a better description, interpretation -and optimization- of the mechanism of action of AS101 and Te-based compounds. This might be a starting point for improved AS101-based medicinal application.

Combination of AS101 and Mefloquine Inhibits Carbapenem-Resistant Pseudomonas aeruginosa in vitro and in vivo.

Background: In recent years, carbapenem-resistant Pseudomonas aeruginosa (CRPA) has spread around the world, leading to a high mortality and close attention of medical community. In this study, we aim to find a new strategy of treatment for CRPA infections. Methods: Eight strains of CRPA were collected, and PCR detected the multi-locus sequence typing (MLST). The antimicrobial susceptibility test was conducted using the VITEK@2 compact system. The minimum inhibitory concentration (MIC) for AS101 and mefloquine was determined using the broth dilution method. Antibacterial activity was tested in vitro and in vivo through the chessboard assay, time killing assay, and a mouse model. The mechanism of AS101 combined with mefloquine against CRPA was assessed through the biofilm formation inhibition assay, electron microscopy, and detection of reactive oxygen species (ROS). Results: The results demonstrated that all tested CRPA strains exhibited multidrug resistance. Moreover, our investigation revealed a substantial synergistic antibacterial effect of AS101-mefloquine in vitro. The assay for inhibiting biofilm formation indicated that AS101-mefloquine effectively suppressed the biofilm formation of CRPA-5 and CRPA-6. Furthermore, AS101-mefloquine were observed to disrupt the bacterial cell wall and enhance the permeability of the cell membrane. This effect was achieved by stimulating the production of ROS, which in turn hindered the growth of CRPA-3. To evaluate the therapeutic potential, a murine model of CRPA-3 peritoneal infection was established. Notably, AS101-mefloquine administration resulted in a significant reduction in bacterial load within the liver, kidney, and spleen of mice after 72 hours of treatment. Conclusion: The present study showed that the combination of AS101 and mefloquine yielded a notable synergistic bacteriostatic effect both in vitro and in vivo, suggesting a potential clinical application of this combination in the treatment of CRPA.

Potentials of organic tellurium-containing compound AS101 to overcome carbapenemase-producing Escherichia coli.

BACKGROUND: The issue of carbapenem-resistant Escherichia coli was aggravated yearly. The previous studies reported the varied but critical epidemiology of carbapenem-resistant E. coli among which the carbapenemase-producing strains were regarded as one of the most notorious issues. AS101, an organic tellurium-containing compound undergoing clinical trials, was revealed with antibacterial activities. However, little is known about the antibacterial effect of AS101 against carbapenemase-producing E. coli (CPEC). MATERIALS AND METHODS: The minimum inhibitory concentration (MIC) of AS101 against the 15 isolates was examined using a broth microdilution method. The scanning electron microscopy, pharmaceutical manipulations, reactive oxygen species level, and DNA fragmentation assay were carried out to investigate the antibacterial mechanism. The sepsis mouse model was employed to assess the in vivo treatment effect. RESULTS: The blaNDM (33.3%) was revealed as the dominant carbapenemase gene among the 15 CPEC isolates, followed by the blaKPC gene (26.7%). The MICs of AS101 against the 15 isolates ranged from 0.5 to 32 µg/ml, and 99.9% of bacterial eradication was observed at 8 h, 4 h, and 2 h for 1×, 2×, and 4 × MIC, respectively. The mechanistic investigations suggest that AS101 would enter the bacterial cell, and induce ROS generation, leading to DNA fragmentation. The in vivo study exhibited that AS101 possessed a steady treatment effect in a sepsis mouse model, with an up to 83.3% of survival rate. CONCLUSION: The in vitro activities, mechanisms, and in vivo study of AS101 against CPEC were unveiled. Our finding provided further evidence for the antibiotic development of AS101.

Screening of AS101 analog, organotellurolate (IV) compound 2 for its in vitro biocompatibility, anticancer, and antibacterial activities.

Organotellurium compounds are being well researched as potential candidates for their functional roles in therapeutic and clinical biology. Here, we report the in vitro anticancer and antibacterial activities of an AS101 analog, cyclic zwitterionic organotellurolate (IV) compound 2 [Te-{CH2CH(NH3+)COO}(Cl)3]. Different concentrations of compound 2 were exposed to fibroblast L929 and breast cancer MCF-7 cell lines to study its effect on cell viability. The fibroblast cells with good viability confirmed the biocompatibility, and compound 2 also was less hemolytic on RBCs. A cytotoxic effect on MCF-7 breast cancer cell line investigated compound 2 to be anti-cancerous with IC50 value of 2.86 ± 0.02 µg/mL. The apoptosis was confirmed through the cell cycle phase arrest of the organotellurolate (IV) compound 2. Examination of the antibacterial potency compound 2 was done based on the agar disk diffusion, minimum inhibitory concentration, and time-dependent assay for the Gram-positive Bacillus subtilis and Gram-negative Pseudomonas putida. For both bacterial strains, tests were performed with the concentration range of 3.9-500 µg/mL, and the minimum inhibition concentration value was found to be 125 µg/mL. The time-dependent assay suggested the bactericidal activity of organotellurolate (IV) compound, 2 against the bacterial strains.

In Vitro Evaluation of Tellurium-Based AS101 Compound against Neisseria gonorrhoeae Infectivity.

Neisseria gonorrhoeae (GC) is a obligate human pathogen responsible for gonorrhea, one of the most common sexually transmitted infections. The yearly increased multidrug resistance in GC has led to treatment failure clinically, suggesting an urgent need for novel therapy to combat this global health issue. AS101 [ammonium trichloro(dioxoethylene-O,O'-)tellurate], a tellurium-based compound previously used as an immunomodulatory agent, was found to have antimicrobial effects against Klebsiella pneumoniae via a high-throughput drug screening and showed antibacterial activity against Acinetobacter spp. This study aimed to evaluate the in vitro anti-gonococcal activity of AS101, including its antimicrobial activity, biofilm and infectivity inhibition, and potential underlying mechanisms. The agar-dilution-based MIC was used. The inhibition of GC microcolony formation and continual growth by AS101 was assessed by microscopy. The effect of AS101 on GC infectivity was evaluated by infecting endocervical ME180 and colorectal T84 epithelial cell lines. The mode of action was evaluated by a time-killing curve, transmission electron microscopy (TEM), and the level of reactive oxygen species (ROS). The MICs of MS11 and WHO GC isolates were both found to be 0.05 µg/mL. The biofilm formation, continual growth, and infectivity of two epithelial cell lines were significantly decreased with AS101 treatment. The time-kill curve, similar to that of azithromycin, suggested that AS101 is a bacteriostatic antimicrobial. However, TEM and ROS levels implied a mode of action different from that of azithromycin. Our findings highlighted the robust anti-gonococcal activities of AS101, which potentiates its use as a future antimicrobial for GC. IMPORTANCE Neisseria gonorrhoeae is an obligate human pathogen responsible for gonorrhea, one of the most common sexually transmitted infections. The yearly increased multidrug resistance in GC has led to treatment failure clinically, suggesting an urgent need for novel therapy to combat the global health issue. This study aimed to evaluate the in vitro anti-gonococcal activity of a previous immunomodulatory agent, AS101, and its underlying mechanisms. Here, we report that AS101 possesses remarkable anti-gonococcal activity. These findings supported further studies on in vivo experiments and formulations for the clinical application of AS101 as an anti-gonococcal agent.

Medicinal Hypervalent Tellurium Prodrugs Bearing Different Ligands: A Comparative Study of the Chemical Profiles of AS101 and Its Halido Replaced Analogues.

Ammonium trichloro (dioxoethylene-O,O') tellurate (AS101) is a potent immunomodulator prodrug that, in recent years, entered various clinical trials and was tested for a variety of potential therapeutic applications. It has been demonstrated that AS101 quickly activates in aqueous milieu, producing TeOCl3-, which likely represents the pharmacologically active species. Here we report on the study of the activation process of AS101 and of two its analogues. After the synthesis and characterization of AS101 and its derivatives, we have carried out a comparative study through a combined experimental and computational analysis. Based on the obtained results, we describe here, for the first time, the detailed reaction that AS101 and its bromido- and iodido-replaced analogues undergo in presence of water, allowing the conversion of the original molecule to the likely true pharmacophore. Interestingly, moving down in the halogens' group we observed a higher tendency to react, attributable to the ligands' effect. The chemical and mechanistic implications of these meaningful differences are discussed.

Synergistic Combination of AS101 and Azidothymidine against Clinical Isolates of Carbapenem-Resistant Klebsiella pneumoniae.

Owing to the over usage of carbapenems, carbapenem resistance has become a vital threat worldwide, and, thus, the World Health Organization announced the carbapenem-resistant Enterobacteriaceae (CRE) as the critical priority for antibiotic development in 2017. In the current situation, combination therapy would be one solution against CRE. Azidothymidine (AZT), a thymidine analog, has demonstrated its synergistically antibacterial activities with other antibiotics. The unexpected antimicrobial activity of the immunomodulator ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) has been reported against carbapenem-resistant Klebsiella pneumoniae (CRKP). Here, we sought to investigate the synergistic activity between AS101 and AZT against 12 CRKP clinical isolates. According to the gene detection results, the blaOXA-1 (7/12, 58.3%), blaDHA (7/12, 58.3%), and blaKPC (7/12, 58.3%) genes were the most prevalent ESBL, AmpC, and carbapenemase genes, respectively. The checkerboard analysis demonstrated the remarkable synergism between AS101 and AZT, with the observable decrease in the MIC value for two agents and the fractional inhibitory concentration (FIC) index ≤0.5 in all strains. Hence, the combination of AS101 and azidothymidine could be a potential treatment option against CRKP for drug development.

Evaluation of the Organotellurium Compound AS101 for Treating Colistin- and Carbapenem-Resistant Klebsiella pneumoniae.

Colistin- and carbapenem-resistant Enterobacteriaceae cases are increasing at alarming rates worldwide. Drug repurposing is receiving greater attention as an alternative approach in light of economic and technical barriers in antibiotics research. The immunomodulation agent ammonium trichloro(dioxoethylene-O,O'-)tellurate (AS101) was repurposed as an antimicrobial agent against colistin- and carbapenem-resistant Klebsiella pneumoniae (CRKP). 134 CRKP isolates were collected between 2012 and 2015 in Taiwan. The in vitro antibacterial activities of AS101 was observed through broth microdilution, time-kill assay, and electron microscopy. Pharmaceutical manipulation and RNA microarray were applied to investigate these antimicrobial mechanisms. Caenorhabditis elegans, a nematode animal model, and the Institute for Cancer Research (ICR) mouse model was employed for the evaluation of in vivo efficacy. The in vitro antibacterial results were found for AS101 against colistin- and CRKP isolates, with minimum inhibitory concentration (MIC) values ranging from <0.5 to 32 µg/mL. ROS-mediated antibacterial activity eliminated 99.9% of bacteria within 2-4 h. AS101 also extended the median survival time in a C. elegans animal model infected with a colistin-resistant CRKP isolate and rescued lethally infected animals in a separate mouse model of mono-bacterial sepsis by eliminating bacterial organ loads. These findings support the use of AS101 as an antimicrobial agent for addressing the colistin and carbapenem resistance crisis.

In Vitro and In Vivo Activity of AS101 against Carbapenem-Resistant Acinetobacter baumannii.

The increasing trend of carbapenem-resistant Acinetobacter baumannii (CRAB) worldwide has become a concern, limiting therapeutic alternatives and increasing morbidity and mortality rates. The immunomodulation agent ammonium trichloro (dioxoethylene-O,O'-) tellurate (AS101) was repurposed as an antimicrobial agent against CRAB. Between 2016 and 2018, 27 CRAB clinical isolates were collected in Taiwan. The in vitro antibacterial activities of AS101 were evaluated using broth microdilution, time-kill assay, reactive oxygen species (ROS) detection and electron microscopy. In vivo effectiveness was assessed using a sepsis mouse infection model. The MIC range of AS101 for 27 CRAB isolates was from 0.5 to 32 µg/mL, which is below its 50% cytotoxicity (approximately 150 µg/mL). Bactericidal activity was confirmed using a time-kill assay. The antibacterial mechanism of AS101 was the accumulation of the ROS and the disruption of the cell membrane, which, in turn, results in cell death. The carbapenemase-producing A. baumannii mouse sepsis model showed that AS101 was a better therapeutic effect than colistin. The mice survival rate after 120 h was 33% (4/12) in the colistin-treated group and 58% (7/12) in the high-dose AS101 (3.33 mg/kg/day) group. Furthermore, high-dose AS101 significantly decreased bacterial population in the liver, kidney and spleen (all p < 0.001). These findings support the concept that AS101 is an ideal candidate for further testing in future studies.

The tellurium-based immunomodulator, AS101 ameliorates adjuvant-induced arthritis in rats.

Despite undeniable improvement in the management of rheumatoid arthritis (RA), the discovery of more effective, less toxic and, ideally, less immune suppressive drugs are much needed. In the current study, we set to explore the potential anti-rheumatic activity of the non-toxic, tellurium-based immunomodulator, AS101 in an experimental animal model of RA. The effect of AS101 was assessed on adjuvant-induced arthritis (AIA) rats. Clinical signs of arthritis were assessed. Histopathological examination was used to assess inflammation, synovial changes and tissue lesions. Very late antigen-4 (VLA-4)+ cellular infiltration was detected using immunohistochemical staining. Enzyme-linked immunosorbent assay (ELISA) was used to measure circulating anti-cyclic citrullinated-peptide autoantibody (ACPA) and real-time polymerase chain reaction (PCR) was used to measure the in-vitro effect of AS101 on interleukin (IL)-6 and IL-1ß expression in activated primary human fibroblasts. Prophylactic treatment with intraperitoneal AS101 reduced clinical arthritis scores in AIA rats (P < 0·01). AS101 abrogated the migration of active chronic inflammatory immune cells, particularly VLA-4+ cells, into joint cartilage and synovium, reduced the extent of joint damage and preserved joint architecture. Compared to phosphate-buffered saline (PBS)-treated AIA rats, histopathological inflammatory scores were significantly reduced (P < 0·05). Furthermore, AS101 resulted in a marked reduction of circulating ACPA in comparison to PBS-treated rats (P < 0·05). Importantly, AS101 significantly reduced mRNA levels of proinflammatory mediators such as IL-6 (P < 0·05) and IL-1ß (P < 0·01) in activated primary human fibroblasts. Taken together, we report the first demonstration of the anti-rheumatic/inflammatory activity of AS101 in experimental RA model, thereby supporting an alternative early therapeutic intervention and identifying a promising agent for therapeutic intervention.

A Tellurium-Based Small Immunomodulatory Molecule Ameliorates Depression-Like Behavior in Two Distinct Rat Models.

Major depressive disorder (MDD) is a leading cause of morbidity, and the fourth leading cause of disease burden worldwide. While MDD is a treatable condition for many individuals, others suffer from treatment-resistant depression (TRD). Here, we suggest the immunomodulatory compound AS101 as novel therapeutic alternative. We previously showed in animal models that AS101 reduces anxiety-like behavior and elevates levels of the brain-derived neurotrophic factor (BDNF), a protein that has a key role in the pathophysiology of depression. To explore the potential antidepressant properties of AS101, we used the extensively characterized chronic mild stress (CMS) model, and the depressive rat line (DRL Finally, in Exp. 3 to attain insight into the mechanism we knocked down BDNF in the hippocampus, and demonstrated that the beneficial effect of AS101 was abrogated. Together with the previously established safety profile of AS101 in humans, these results may represent the first step towards the development of a novel treatment option for MDD and TRD.

Pre-conceptional maternal exposure to cyclophosphamide results in modifications of DNA methylation in F1 and F2 mouse oocytes: evidence for transgenerational effects.

Cyclophosphamide (CPM), an agent widely used in breast cancer therapy, has strong gonadotoxic effects. Female reproductive potential after therapy relies on ovulated oocytes deriving from primordial follicles surviving CPM toxic insult. In this study, we investigated in the mouse model whether pre-conceptional maternal exposure to CPM has epigenetic effects on offspring oocytes and if they are inherited. Adult female mice mated following CPM exposure, generated an offspring (F1) with delayed growth, normal fertility and altered methylation of three imprinted genes (H19, Igf2r and Peg3) in their oocytes. These alterations were present in oocytes generated by F2 mice. Pre-conceptional maternal exposure to fertoprotective agents AS101 and crocetin prior to CPM was not able to fully counteract alterations in offspring oocyte imprinting. For the first time, current study evidences that pre-conceptional CPM maternal exposure can affect the competence of offspring's oocytes and warns on possible long-term effects on the health of next generations.

AS101 ameliorates experimental autoimmune uveitis by regulating Th1 and Th17 responses and inducing Treg cells.

AS101 is an organotellurium compound with multifaceted immunoregulatory properties that is remarkable for its lack of toxicity. We tested the therapeutic effect of AS101 in experimental autoimmune uveitis (EAU), a model for human autoimmune uveitis. Unexpectedly, treatment with AS101 elicited Treg generation in vivo in otherwise unmanipulated mice. Mice immunized for EAU with the retinal antigen IRBP and treated with AS101 developed attenuated disease, as did AS101-treated recipients of retina-specific T cells activated in vitro. In both settings, eye-infiltrating effector T cells were decreased, whereas regulatory T (Treg) cells in the spleen were increased. Mechanistic studies in vitro revealed that AS101 restricted polarization of retina-specific T cells towards Th1 or Th17 lineage by repressing activation of their respective lineage-specific transcription factors and downstream signals. Retina-specific T cells polarized in vitro towards Th1 or Th17 in the presence of AS101 had impaired ability to induce EAU in naïve recipients. Finally, AS101 promoted differentiation of retina-specific T cells to Tregs in vitro independently of TGF-ß. We conclude that AS101 modulates autoimmune T cells by inhibiting acquisition and expression of effector function and by promoting Treg generation, and suggest that AS101 could be useful as a therapeutic approach for autoimmune uveitis.

AS101-Loaded PLGA-PEG Nanoparticles for Autoimmune Regulation and Chemosensitization.

The in vivo delivery of therapeutic nanoparticles (NPs) represents a potentially powerful tool that can significantly alter the biological effects of pharmaceutically active compounds. Here, we report on sensitization of tumors to chemotherapy by ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) encapsulated in NPs, termed AS101-NPs, developed as a composite with the biocompatible and biodegradable copolymer of poly(d,l-lactic-co-glycolic acid)-block-poly(ethylene glycol) (PLGA-b-PEG). AS101 is a potent immunomodulating agent (both in vitro and in vivo) currently undergoing phase II clinical trials for antitumor activity and sensitization of tumors to chemotherapy. Approaches that can control the pharmacokinetic parameters to regulate its clearance from the administered drug delivery system and minimize side effects are of prodigious importance. A strategy to synthesize AS101-NPs by nanoprecipitation is presented, along with their physical characterization. The influence of AS101 encapsulation on its properties was evaluated in vivo. The AS101-NPs demonstrated a significantly enhanced peritoneal macrophage count compared with AS101 administered in vivo at a conventional dosage in mouse models. Moreover, AS101 inhibited B16 melanoma lung metastasis in mice when given intraperitoneally, before or after tumor cell inoculation. A bell-shaped dose-response was observed. The frequency of AS101 administration appears to be an important factor for achieving an optimal antimetastatic effect.

Ammonium trichloro [1,2-ethanediolato-O,O']-tellurate cures experimental visceral leishmaniasis by redox modulation of Leishmania donovani trypanothione reductase and inhibiting host integrin linked PI3K/Akt pathway.

In an endeavor to search for affordable and safer therapeutics against debilitating visceral leishmaniasis, we examined antileishmanial potential of ammonium trichloro [1,2-ethanediolato-O,O']-tellurate (AS101); a tellurium based non toxic immunomodulator. AS101 showed significant in vitro efficacy against both Leishmania donovani promastigotes and amastigotes at sub-micromolar concentrations. AS101 could also completely eliminate organ parasite load from L. donovani infected Balb/c mice along with significant efficacy against infected hamsters (˃93% inhibition). Analyzing mechanistic details revealed that the double edged AS101 could directly induce apoptosis in promastigotes along with indirectly activating host by reversing T-cell anergy to protective Th1 mode, increased ROS generation and anti-leishmanial IgG production. AS101 could inhibit IL-10/STAT3 pathway in L. donovani infected macrophages via blocking α4ß7 integrin dependent PI3K/Akt signaling and activate host MAPKs and NF-κB for Th1 response. In silico docking and biochemical assays revealed AS101's affinity to form thiol bond with cysteine residues of trypanothione reductase in Leishmania promastigotes leading to its inactivation and inducing ROS-mediated apoptosis of the parasite via increased Ca2+ level, loss of ATP and mitochondrial membrane potential along with metacaspase activation. Our findings provide the first evidence for the mechanism of action of AS101 with excellent safety profile and suggest its promising therapeutic potential against experimental visceral leishmaniasis.

The Small Tellurium Compound AS101 Ameliorates Rat Crescentic Glomerulonephritis: Association with Inhibition of Macrophage Caspase-1 Activity via Very Late Antigen-4 Inactivation.

Crescentic glomerulonephritis (CGN) is the most aggressive form of GN and, if untreated, patients can progress to end-stage renal failure within weeks of presentation. The α4ß1 integrin very late antigen-4 (VLA-4) is an adhesion molecule of fundamental importance to the recruitment of leukocytes in inflammation. We addressed the role of VLA-4 in mediating progressive renal injury in a rat model of CGN using a small tellurium compound. AS101 [ammonium trichloro(dioxoethylene-o,o')tellurate]. This compound has been previously shown to uniquely inhibit VLA-4 activity by redox inactivation of adjacent thiols in the exofacial domain of VLA-4. The study shows that administration of AS101 either before or after glomerular basement membrane anti-serum injection ameliorates crescent formation or preserves renal function. This was associated with profound inhibition of critical inflammatory mediators, accompanied by decreased glomerular infiltration of macrophages. Mechanistic studies demonstrated vla-4 inactivation on glomerular macrophages both in vitro and in vivo as well as inhibition of caspase-1 activity. Importantly, this cysteine protease activity modification was dependent on VLA-4 inactivation and was associated with the anti-inflammatory activity of AS101. We propose that inactivation of macrophage VLA-4 by AS101 in vivo results in a decrease of inflammatory cytokines and chemokines produced in the glomeruli of diseased rats, resulting in decreased further macrophage recruitment and decreased extracellular matrix expansion. Thus, AS101, which is currently in clinical trials for other indications, might be beneficial for treatment of CGN.

The effect of the novel tellurium compound AS101 on autoimmune diseases.

Tellurium is a rare element, which has been regarded as a non-essential trace element despite its relative abundance in the human body. The chemistry of tellurium supports a plethora of activities, but its biochemistry is not clearly established to date. The small tellurium(IV) compound, ammonium trichloro (dioxoethylene-o,o')tellurate (AS101) developed and initially investigated by us, is currently being evaluated in Phase II clinical trials in psoriasis patients. AS101 is the first tellurium compound to be tested for clinical efficacy. This compound is a potent immunomodulator both in vitro and in vivo with a variety of potential therapeutic applications. The present review will focus on the immunomodulatory properties of AS101, and specifically, its effects in mitigating autoimmune diseases. AS101 has several activities that act on the immune system, including: 1) its ability to reduce IL-17 levels and to inhibit the function of Th17 cells; 2) its specific unique redox-modulating activities enabling the inhibition of specific leukocyte integrins such as α4ß1 and α4ß7, that are pivotal for diapedesis of macrophages and CD4(+) T inflammatory/auto-reactive cells into the autoimmune tissues; and 3) its ability to enhance the activity of regulatory T cells (Treg). These activities coupled with its excellent safety profile suggest that AS101 may be a promising candidate for the management of autoimmune diseases.