Monensin synergizes with chemotherapy in uveal melanoma through suppressing RhoA.

OBJECTIVE: Uveal melanoma (UM) is the common primary cancer of the eye and new treatments are needed. Substantial evidence has shown that an antibiotic monensin is an attractive candidate for the development of anti-cancer drug. In this study, we investigated the potential of repositioning monensin for the treatment of UM in the pre-clinical setting. MATERIALS AND METHODS: Cellular activity assays were performed using multiple cell lines representing UM models with different cellular origins and genetic profiling and normal cells as control. Combination studies were performed using Chou-Talalay method. Mechanism studies were performed using immunoblotting and ELISA. RESULTS: Monensin was effective against all tested UM cell lines and less effective against normal fibroblast cells. Monensin induced G0/G1 arrest and thus decreased S phase, leading to UM cell growth inhibition. It also inhibited migration and induced apoptosis in UM cells. In addition, the combination of monensin and dacarbazine was synergistic in targeting UM cells. Our mechanistic studies showed that monensin specifically decreased activity of RhoA without affecting other small GTPases, such as Ras and Rac1. Consistently, monensin decreased phosphorylation of downstream effectors of RhoA signaling, including ROCK, MYPT1 and MLC. Rescue studies using RhoA activator calpeptin showed that calpeptin significantly abolished the inhibitory effects of monensin on RhoA activity, proliferation, migration and survival, confirming that RhoA is the target of monensin in UM cells. CONCLUSIONS: Our study demonstrates that monensin is a potent inhibitor of UM and synergizes with chemotherapy, via suppressing RhoA activity and RhoA-mediated signaling. Our findings suggest that monensin may be a potential lead compound for further development into a drug for UM treatment.

Ionophore-mediated swelling of erythrocytes as a therapeutic mechanism in sickle cell disease.

Sickle cell disease (SCD) is characterized by sickle hemoglobin (HbS) which polymerizes under deoxygenated conditions to form a stiff, sickled erythrocyte. The dehydration of sickle erythrocytes increases intracellular HbS concentration and the propensity of erythrocyte sickling. Prevention of this mechanism may provide a target for potential SCD therapy investigation. Ionophores such as monensin can increase erythrocyte sodium permeability by facilitating its transmembrane transport, leading to osmotic swelling of the erythrocyte and decreased hemoglobin concentration. In this study, we treated 13 blood samples from patients with SCD with 10 nM of monensin ex vivo. We measured changes in cell volume and hemoglobin concentration in response to monensin treatment, and we perfused treated blood samples through a microfluidic device that permits quantification of blood flow under controlled hypoxia. Monensin treatment led to increases in cell volume and reductions in hemoglobin concentration in most blood samples, though the degree of response varied across samples. Monensin-treated samples also demonstrated reduced blood flow impairment under hypoxic conditions relative to untreated controls. Moreover, there was a significant correlation between the improvement in blood flow and the decrease in hemoglobin concentration. Thus, our results demonstrate that a reduction in intracellular HbS concentration by osmotic swelling improves blood flow under hypoxic conditions. Although the toxicity of monensin will likely prevent it from being a viable clinical treatment, these results suggest that osmotic swelling should be investigated further as a potential mechanism for SCD therapy.

Monensin inhibits glioblastoma angiogenesis via targeting multiple growth factor receptor signaling.

Glioblastoma is characterized by the extensive vascularization with poor prognosis. Targeting both tumor cell and angiogenesis may present an effective therapeutic strategy for glioblastoma. Monensin, a polyether ionophore antibiotic, has been recently recognized as promising anticancer drug candidate due to its potent and selective anti-tumor activities. However, little is known on the effects of monensin on tumor angiogenesis. In this work, we investigated the effects and underlying mechanisms of monensin on glioblastoma angiogenesis and growth. We show that monensin at nanomolar concentrations inhibits early stages of capillary network formation of glioblastoma endothelial cell. Monensin inhibited multiple endothelial cellular events, including migration, growth and survival, without affecting adhesion to Matrigel. We further demonstrate that monensin acts on endothelial cells via suppressing VEGFR- and EGFR-mediated signaling pathways. Monensin also inhibits proliferation and induces apoptosis in a panel of glioblastoma cells. However, monensin is more effective in targeting endothelial cells than tumor cells. Using glioblastoma growth xenograft mice model, we show that monensin at tolerable dose effectively inhibits glioblastoma growth. Of note, there is a significant decreased tumor vascularization from monensin-treated mice. Our work clearly demonstrates the anti-angiogenic activity of monensin and its ability in suppressing multiple tyrosine kinase receptor-mediated pathways. Our findings suggest that is a useful addition to the treatment armamentarium for glioblastoma.

Doxycycline, salinomycin, monensin and ivermectin repositioned as cancer drugs.

Chemotherapy is one of the standard methods for the treatment of malignant tumors. It aims to cause lethal damage to cellular structures, mainly DNA. Noteworthy, in recent years discoveries of novel anticancer agents from well-known antibiotics have opened up new treatment pathways for several cancer diseases. The aim of this review article is to describe new applications for the following antibiotics: doxycycline (DOX), salinomycin (SAL), monensin (MON) and ivermectin (IVR) as they are known to show anti-tumor activity, but have not yet been introduced into standard oncological therapy. To date, these agents have been used for the treatment of a broad-spectrum of bacterial and parasitic infectious diseases and are widely available, which is why they were selected. The data presented here clearly show that the antibiotics mentioned above should be recognised in the near future as novel agents able to eradicate cancer cells and cancer stem cells (CSCs) across several cancer types.

A preliminary study investigating effects of oral monensin sodium in an enteric Mycobacterium avium ssp. paratuberculosis infection model of calves.

Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of Johne's disease, an enteric infection of ruminants that causes significant economic burden for dairy and beef producers. Efforts to control MAP in endemic herds typically focus on herd management practices such as limiting exposure or early culling of infected animals and, occasionally, vaccination. The ionophore monensin sodium may have protective effects against MAP both in vivo and in vitro; however, this has not been thoroughly evaluated experimentally. Using a direct intestinal MAP challenge model, we have observed similarities regarding persistence of MAP in tissues and apparent resilience to infection compared with experimental oral infection or natural disease. Here we sought to investigate the effects of oral monensin supplementation in experimentally MAP-infected calves. We examined the persistence of MAP in the intestinal tissues, MAP-induced intestinal inflammation, fecal MAP shedding, and seroconversion using a commercial serologic assay. Monensin-supplemented MAP-infected calves demonstrated evidence for resilience to MAP infection earlier in this study compared with monensin-free MAP-infected calves. However, statistical modeling did not identify a significant effect of monensin on outcomes of infection, and more work is required to understand how monensin affects early tissue colonization of MAP in calves.

Repurposing Ionophores as novel antimicrobial agents for the treatment of bovine mastitis caused by Gram-positive pathogens.

Increasing reports of multidrug-resistant bacterial infections in animals has created a need for novel antimicrobial agents that do not promote cross-resistance to critically important antimicrobial classes used in human medicine. In response to the recent emergence of antimicrobial resistance in several bovine mastitis pathogens, in vitro antimicrobial susceptibility was determined for four polyether ionophores (lasalocid, monensin, narasin and salinomycin) against Staphylococcus spp. and Streptococcus spp. isolated from clinical cases. In addition, erythrocyte haemolysis and WST-1 cell proliferation assays were used to assess in vitro mammalian cell cytotoxicity and biofilm susceptibility testing was performed using the minimum biofilm eradication concentration (MBEC™) biofilm assay. Lasalocid, monensin, narasin and salinomycin exhibited bacteriostatic antimicrobial activity against all pathogens tested, including methicillin-resistant staphylococci, with MIC90 values <16 µg/ml. Narasin and monensin displayed the least toxicity against mammalian cell lines and all compounds significantly reduced viable cell numbers in a Staphylococcus aureus biofilm. Based on in vitro characterization, all four ionophores offer potentially novel treatments against bovine mastitis but in vivo studies will be essential to determine whether acceptable safety and efficacy is present following intramammary administration.

Metal chelators and neurotoxicity: lead, mercury, and arsenic.

This article reviews the clinical use of the metal chelators sodium 2,3-dimercapto-1-propanesulfonate (DMPS), meso-2,3-dimercaptosuccinic acid (DMSA), and calcium disodium edetate (CaEDTA, calcium EDTA) in overexposure and poisonings with salts of lead (Pb), mercury (Hg), and arsenic (As). DMSA has considerably lower toxicity than the classic heavy metal antagonist BAL (2,3-dimercaptopropanol) and is also less toxic than DMPS. Because of its adverse effects, CaEDTA should be replaced by DMSA as the antidote of choice in treating moderate Pb poisoning. Combination therapy with BAL and CaEDTA was previously recommended in cases of severe acute Pb poisoning with encephalopathy. We suggest that BAL in such cases acted as a shuttling Pb transporter from the intra- to the extracellular space. The present paper discusses if a combination of the extracellularly distributed DMSA with the ionophore, Monensin may provide a less toxic combination for Pb mobilization by increasing both the efflux of intracellularly deposited Pb and the urinary Pb excretion. Anyhow, oral therapy with DMSA should be continued with several intermittent courses. DMPS and DMSA are also promising antidotes in Hg poisoning, whereas DMPS seems to be a more efficient agent against As poisoning. However, new insight indicates that a combination of low-dosed BAL plus DMPS could be a preferred antidotal therapy to obtain mobilization of the intracerebral deposits into the circulation for subsequent rapid urinary excretion.

Economic value of ionophores and propylene glycol to prevent disease and treat ketosis in Canada.

A partial budget model was developed to evaluate the economic value of Rumensin Controlled Release Capsule (CRC) boluses when administered before calving to reduce disease and increase milk production. After accounting for disease incidences in a herd and the percentage by which Rumensin CRC can reduce them, and the increase in milk production attributable to administration of Rumensin CRC, the return on investment (ROI) per lactation was 4:1. Another partial budget model was developed to estimate the economic value of propylene glycol (PG) to treat ketosis when diagnosed by 3 different cow-side tests or when administered to all cows without using any cow-side testing. After accounting for the sensitivity and specificity of each test, ROI per lactation ranged from 2:1 to 4:1. The ROI was 2:1 when no cow-side testing was used. In conclusion, prevention of diseases that occur in the postpartum period and treatment of ketosis after calving yielded a positive ROI that varies based on disease incidence and method of diagnosis.

Valeur économique des ionophores et du propylèneglycol pour prévenir la maladie et traiter l'acétonémie au Canada. Un modèle de budget partiel a été développé pour évaluer la valeur économique des bolus de capsules à libération contrôlée (CLC) de Rumensin lors de l'administration avant le vêlage afin de réduire les maladies et d'accroître la production de lait. Après avoir tenu compte de l'incidence des maladies dans un troupeau et du pourcentage par lequel la CLC de Rumensin peut les réduire et de l'augmentation de la production de lait attribuable à l'administration de la CLC de Rumensin, le rendement du capital investi (RCI) par lactation était de 4:1. Un autre modèle de budget partiel a été développé pour estimer la valeur économique du propylèneglycol (PG) afin de traiter l'acétonémie lors du diagnostic par 3 tests différents pour les vaches ou lors de l'administration à toutes les vaches sans le recours à des tests auprès des vaches. Après avoir tenu compte de la sensibilité et de la spécificité de chaque test, le RCI par lactation s'échelonnait de 2:1 à 4:1. Le RCI était de 2:1 lorsqu'aucun test auprès des vaches n'était utilisé. En conclusion, la prévention des maladies qui se produit dans la période postpartum et le traitement de l'acétonémie après le vêlage a donné un RCI positif qui varie selon l'incidence de maladies et la méthode de diagnostic.(Traduit par Isabelle Vallières).

Comparison of the anticoccidial effect of granulated extract of Artemisia sieberi with monensin in experimental coccidiosis in broiler chickens.

Coccidiosis is the most important parasitic disease of the poultry production industry. Due to increasing resistance to conventional anticoccidial agents, it is necessary to find new anticoccidial compounds. Herbal compounds such as those from Artemisia species are promising weapons in this regard since preliminary studies have shown its anticoccidial effects. To compare the anticoccidial effect of a granulated extract of Artemisia sieberi (GEAS) versus monensin in experimental broiler coccidiosis, 120 one-day old Ross 308 broiler chickens were divided in four groups, each with three replicates (n=10). Group 1 was separated as an uninfected negative control and received no treatment. At 21days of age, groups 2, 3 and 4 were inoculated with a mixed suspension of 2×10(5) oocysts of Eimeria tenella, Eimeria maxima, Eimeria acervulina and Eimeria necatrix. Group 2 was maintained as an infected positive control and received no treatment while groups 3 and 4 received GEAS (5mg/kg feed), and monensin (110mg/kg feed) from the first day until 42days of age as a feed additive, respectively. Five days after inoculation, the number of oocycts per gram (OPG) of feces for 7 successive days was measured. Also, mean body weight (MBW), weight gain (WG), feed intake (FI) and feed conversion ratio (FCR) were determined weekly in all groups and replicates. The results showed that GEAS and monensin improved performance attributes (FI, MBW, WG, FCR) and significantly (P<0.05) decreased OPG in inoculated broiler chickens.

Investigation of the anticancer mechanism of monensin via apoptosis-related factors in SH-SY5Y neuroblastoma cells.

Monensin is an ionophore antibiotic that inhibits the growth of cancer cells. The aim of this study was to investigate the apoptosis-mediated anticarcinogenic effects of monensin in SH-SY5Y neuroblastoma cells. The effects of monensin on cell viability, invasion, migration, and colony formation were determined by XTT, matrigel-chamber, wound healing, and colony formation tests, respectively. The effects of monensin on apoptosis were determined by real-time polymerase chain reaction, TUNEL, Western blot, and Annexin V assay. We have shown that monensin suppresses neuroblastoma cell viability, invasion, migration, and colony formation. Moreover, we reported that monensin inhibits cell viability by triggering apoptosis of neuroblastoma cells. Monensin caused apoptosis by increasing caspase-3, 7, 8, and 9 expressions and decreasing Bax and Bcl-2 expressions in neuroblastoma cells. In Annexin V results, the rates of apoptotic cells were found to be 9.66 ± 0.01% (p < 0.001), 29.28 ± 0.88% (p < 0.01), and 62.55 ± 2.36% (p < 0.01) in the 8, 16, and 32 µM monensin groups, respectively. In TUNEL results, these values were, respectively; 35 ± 2% (p < 0.001), 34 ± 0.57% (p < 0.001), and 75 ± 2.51% (p < 0.001). Our results suggest that monensin may be a safe and effective therapeutic candidate for treating pediatric neuroblastoma.

Boosting intracellular sodium selectively kills hepatocarcinoma cells and induces hepatocellular carcinoma tumor shrinkage in mice.

Pharmacological treatments for advanced hepatocellular carcinoma (HCC) have a partial efficacy. Augmented Na+ content and water retention are observed in human cancers and offer unexplored targets for anticancer therapies. Na+ levels are evaluated upon treatments with the antibiotic cation ionophore Monensin by fluorimetry, ICP-MS, 23Na-MRI, NMR relaxometry, confocal or time-lapse analysis related to energy production, water fluxes and cell death, employing both murine and human HCC cell lines, primary murine hepatocytes, or HCC allografts in NSG mice. Na+ levels of HCC cells and tissue are 8-10 times higher than that of healthy hepatocytes and livers. Monensin further increases Na+ levels in HCC cells and in HCC allografts but not in primary hepatocytes and in normal hepatic and extrahepatic tissue. The Na+ increase is associated with energy depletion, mitochondrial Na+ load and inhibition of O2 consumption. The Na+ increase causes an enhancement of the intracellular water lifetime and death of HCC cells, and a regression and necrosis of allograft tumors, without affecting the proliferating activity of either HCCs or healthy tissues. These observations indicate that HCC cells are, unlike healthy cells, energetically incapable of compensating and surviving a pharmacologically induced Na+ load, highlighting Na+ homeostasis as druggable target for HCC therapy.

Forward genetic analysis of monensin and diclazuril resistance in Eimeria tenella.

Worldwide distributed coccidiosis is caused by infection of both Eimeria species and Cystoisospora in the host intestine and causes huge economic losses to the livestock industry, especially the poultry industry. The control of such diseases relies mainly on chemoprophylaxis with anticoccidials, which has led to a very common drug resistance in this field. However, the genetic mechanisms underlying resistance to many anticoccidial drugs remain unknown. In this study, strains of E. tenella resistant to 250 mg/kg monensin were generated and characterized. Forward genetic approaches based on pooled genome sequencing, including experimental evolution and linkage group selection, were used to locate candidate targets responsible for resistance to monensin and diclazuril in E. tenella. A total of 16 nonsynonymous mutants in protein-coding genes were identified in monensin-resistant strains, and two genomic regions with strong selection signals were also detected in diclazuril-resistant strains. Our study reveals the genetic characterization of the experimental evolution and linkage group selection in Eimeria species, and also provides important information that contributes to the understanding of the molecular mechanism of drug resistance in coccidia.

Effects of dietary supplementation with a herbal extract on the performance of broilers infected with a mixture of Eimeria species.

1. A herbal extract containing a blend of three essential oils, derived from oregano, laurel leaf and lavender, was investigated as a feed additive alternative to the conventional anticoccidial sodium monensin. 2. Broilers were infected with a mixture of Eimeria species or left uninfected. Both infected and uninfected broilers were provided with diets containing either herbal extract (HEX), monensin (MON) or without these supplements (CON). The HEX group had 50 mg herbal extract/kg diet and the MON group 100 mg monensin/kg diet. 3. All of the uninfected broilers exhibited higher body weight gain and better feed conversion when compared with their infected counterparts at d 28 and 42 of age. Both HEX and MON supplements caused significant improvements in performance in the infected broilers, but failed to have any effect on uninfected broilers. 4. Faecal oocyst output measured daily by sampling excreta, and expressed on a per bird basis, was lower in the HEX and MON groups than in the CON group. However, the herbal extract was not as effective as monensin in reducing oocyst excretion. Coccidial infection caused a significant increase in total intestinal length and caecal weight, but the dietary treatments did not influence these measurements. 5. These results indicate that providing a herbal extract in the diet was not as effective as monensin in protecting broilers exposed to a coccidial challenge.

Monensin Inhibits Anaplastic Thyroid Cancer via Disrupting Mitochondrial Respiration and AMPK/mTOR Signaling.

OBJECTIVE: The clinical management of anaplastic thyroid cancer (ATC) remains challenging, and novel treatment methods are needed. Monensin is a carboxyl polyether ionophore that potently inhibits the growth of various cancer types. Our current work investigates whether monensin has selective anti-ATC activity and systematically explores its underlying mechanisms. METHODS: Proliferation and apoptosis assays were performed using a panel of thyroid cancer cell lines. Mitochondrial biogenesis profiles, ATP levels, oxidative stress, AMPK, and mTOR were examined in these cells after monensin treatment. RESULTS: Monensin is effective in inhibiting proliferation and inducing apoptosis in a number of thyroid cancer cell lines. The results are consistent across cell lines of varying cellular origins and genetic mutations. Compared to other thyroid cancer cell types, ATC cell lines are the most sensitive to monensin. Of note, monensin used at our experimental concentration affects less of normal cells. Mechanistic studies reveal that monensin acts on ATC cells by disrupting mitochondrial function, inducing oxidative stress and damage, and AMPK activation-induced mTOR inhibition. We further show that mitochondrial respiration is a critical target for monensin in ATC cells. CONCLUSIONS: Our pre-clinical findings demonstrate the selective anti-ATC activities of monensin. This is supported by increasing evidence that monensin can be repurposed as a potential anti-cancer drug.

Anti-glioblastoma activity of monensin and its analogs in an organoid model of cancer.

Glioblastoma (GBM) remains the most frequently diagnosed primary malignant brain cancer in adults. Despite recent progress in understanding the biology of GBM, the clinical outcome for patients remains poor, with a median survival of approximately one year after diagnosis. One factor contributing to failure in clinical trials is the fact that traditional models used in GBM drug discovery poorly recapitulate patient tumors. Previous studies have shown that monensin (MON) analogs, namely esters and amides on C-26 were potent towards various types of cancer cell lines. In the present study we have investigated the activity of these molecules in GBM organoids, as well as in a host:tumor organoid model. Using a mini-ring cell viability assay we have identified seven analogs (IC50 = 91.5 ± 54.4-291.7 ± 68.8 nM) more potent than parent MON (IC50 = 612.6 ± 184.4 nM). Five of these compounds induced substantial DNA fragmentation in GBM organoids, suggestive of apoptotic cell death. The most active analog, compound 1, significantly reduced GBM cell migration, induced PARP degradation, diminished phosphorylation of STAT3, Akt and GSK3ß, increased É£H2AX signaling and upregulated expression of the autophagy associated marker LC3-II. To investigate the activity of MON and compound 1 in a tumor microenvironment, we developed human cerebral organoids (COs) from human induced pluripotent stem cells (iPSCs). The COs showed features of early developing brain such as multiple neural rosettes with a proliferative zone of neural stem cells (Nestin+), neurons (TUJ1 +), primitive ventricular system (SOX2 +/Ki67 +), intermediate zone (TBR2 +) and cortical plate (MAP2 +). In order to generate host:tumor organoids, we co-cultured RFP-labeled U87MG cells with fully formed COs. Compound 1 and MON reduced U87MG tumor size in the COs after four days of treatment and induced a significant reduction of PARP expression. These findings highlight the therapeutic potential of MON analogs towards GBM and support the application of organoid models in anti-cancer drug discovery.

Sodium bentonite and monensin under chronic aflatoxicosis in broiler chickens.

Clay feed additives have been increasingly incorporated into animal diets to prevent aflatoxicosis. Due to the nonselective nature of the binding interaction, many important components of the diets could also be made unavailable because of these feed additives. The anticoccidial monensin (MON) could also be sequestered by these clays. The use of sodium bentonite (Na-B) from a mine in the province of Mendoza, Argentina, was investigated as a sequestering agent to prevent the effects of 100 µg/kg of dietary aflatoxin B(1) (AFB(1)). In vitro studies demonstrated that the above Na-B was a good candidate to prevent aflatoxicosis. They also showed that MON competes with AFB(1) for the adsorption sites on the clay surface and effectively displaces the toxin when it is in low concentration. Even though the levels of MON in diets, approximately 55 mg/kg, are high enough to not be significantly changed as a consequence of the adsorption, they can further affect the ability of the clays to bind low levels of AFB(1). An in vivo experiment carried out with poultry showed that 100 µg/kg of AFB(1) does not significantly change productive or biochemical parameters. However, liver histopathology not only confirmed the ability of this particular Na-B to prevent aflatoxicosis but also the decrease of this capacity in the presence of 55 mg/kg of MON. This is the first report stressing this fact and further research should be performed to check if this behavior is a characteristic of the assayed Na-B or of this type of clay. On the other hand, the presence of MON should also be taken into account when assaying the potential AFB(1) binding ability of a given bentonite.

Forty years of monensin for the control of coccidiosis in poultry.

In July 1971, the polyether ionophorous antibiotic monensin was introduced in the United States for the control of coccidiosis in poultry. At that time, prospects for new anticoccidial agents were not good. Amprolium had enjoyed several years of use, but many other compounds had been abandoned as resistance to them developed. After the introduction of monensin, most commercial broilers were medicated with the drug and it is still widely used for this purpose today. Apart from in poultry, monensin is also used to control coccidiosis in game birds, sheep, and cattle. Indeed, more animals have been medicated with ionophores, such as monensin, for control of disease than any other medicinal agents in the history of veterinary medicine. In this review, we discuss the discovery, mode of action, and efficacy of monensin, together with matters of importance to the poultry industry such as commercial use, drug resistance, toxicity, pharmacology and residues, host immunity to coccidiosis, and effects in other avian species.

Identification of Potent and Safe Antiviral Therapeutic Candidates Against SARS-CoV-2.

COVID-19 pandemic has infected millions of people with mortality exceeding >1 million. There is an urgent need to find therapeutic agents that can help clear the virus to prevent severe disease and death. Identifying effective and safer drugs can provide more options to treat COVID-19 infections either alone or in combination. Here, we performed a high throughput screening of approximately 1,700 US FDA-approved compounds to identify novel therapeutic agents that can effectively inhibit replication of coronaviruses including SARS-CoV-2. Our two-step screen first used a human coronavirus strain OC43 to identify compounds with anti-coronaviral activities. The effective compounds were then screened for their effectiveness in inhibiting SARS-CoV-2. These screens have identified 20 anti-SARS-CoV-2 drugs including previously reported compounds such as hydroxychloroquine, amlodipine besylate, arbidol hydrochloride, tilorone 2HCl, dronedarone hydrochloride, mefloquine, and thioridazine hydrochloride. Five of the newly identified drugs had a safety index (cytotoxic/effective concentration) of >600, indicating a wide therapeutic window compared to hydroxychloroquine which had a safety index of 22 in similar experiments. Mechanistically, five of the effective compounds (fendiline HCl, monensin sodium salt, vortioxetine, sertraline HCl, and salifungin) were found to block SARS-CoV-2 S protein-mediated cell fusion. These FDA-approved compounds can provide much needed therapeutic options that we urgently need during the midst of the pandemic.

Golgi organization is regulated by proteasomal degradation.

The Golgi is a dynamic organelle whose correct assembly is crucial for cellular homeostasis. Perturbations in Golgi structure are associated with numerous disorders from neurodegeneration to cancer. However, whether and how dispersal of the Golgi apparatus is actively regulated under stress, and the consequences of Golgi dispersal, remain unknown. Here we demonstrate that 26S proteasomes are associated with the cytosolic surface of Golgi membranes to facilitate Golgi Apparatus-Related Degradation (GARD) and degradation of GM130 in response to Golgi stress. The degradation of GM130 is dependent on p97/VCP and 26S proteasomes, and required for Golgi dispersal. Finally, we show that perturbation of Golgi homeostasis induces cell death of multiple myeloma in vitro and in vivo, offering a therapeutic strategy for this malignancy. Taken together, this work reveals a mechanism of Golgi-localized proteasomal degradation, providing a functional link between proteostasis control and Golgi architecture, which may be critical in various secretion-related pathologies.

Monensin and the prevention of tryptophan-induced acute bovine pulmonary edema and emphysema.

3-Methylindole, a ruminal fermentation product of tryptophan, induces acute pulmonary edema and emphysema in cattle, and 3-methylindole is present in the ruminal fluid and blood of cows with a natually occurring form of this disease. Monensin, a polyether antibiotic and widely used feed additive for beef cattle, prevented tryptophan-induced acute bovine pulmonary edema and emphysema. Monensin acted by reducing the ruminal conversion of L-tryptophan to 3-methylindole both in vitro and in vivo. Lasalocid, also a polyether antibiotic, showed similar effects in vitro. These results provide a promising approach to prevention of this major respiratory disease of cattle.