monensin and Disease-Models--Animal

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.

Topics: Administration, Oral; Animals; Anti-Bacterial Agents; Cattle; Cattle Diseases; Disease Models, Animal; Feces; Male; Monensin; Mycobacterium avium subsp. paratuberculosis; Paratuberculosis

This study was designed to determine the susceptibility in vitro and infectivity of 1 field isolate of Mycobacterium avium sbsp paratuberculosis after exposure to monensin sodium and tilmicosin phosphate. Minimum inhibitory concentrations (0.39 microg monensin sodium/mL; 1.60 microg tilmicosin phosphate/mL) were determined in quintuplicate. Organisms were then incubated with 3 different concentrations of each medication for 3 different lengths of time, then washed and resuspended in sterile physiologic saline and injected intraperitoneally into mice that were genetically susceptible to infection. Mice were euthanatized 50 d later and the number of hepatic granulomas was used as the indicator of infectivity. Neither time of incubation nor concentration of medication had any effect on the infectivity of the organisms. Monensin sodium significantly reduced the number of hepatic granulomas in genetically susceptible mice while tilmicosin phosphate did not. Antimycobacterial activity of monensin sodium suggests that the role of monensin in the control of bovine paratuberculosis should be evaluated further.

Topics: Animals; Antitubercular Agents; Cattle; Cattle Diseases; Disease Models, Animal; Drug Resistance, Bacterial; Female; Macrolides; Mice; Mice, Inbred C57BL; Microbial Sensitivity Tests; Monensin; Mycobacterium avium subsp. paratuberculosis; Paratuberculosis; Tylosin

Asthma is a common respiratory disease associated with airway hyperresponsiveness (AHR), airway inflammation and mast cell (MC) accumulation in the lung. Monensin, an ionophoric antibiotic, has been shown to induce apoptosis of human MCs. The aim of this study was to define the effect of monensin on MC responses, e.g., antigen induced bronchoconstriction, and on asthmatic features in models of allergic asthma. Tracheal segments from house dust mite (HDM) extract sensitized guinea pigs were isolated and exposed to monensin, followed by histological staining to quantify MCs. Both guinea pig tracheal and human bronchi were used for pharmacological studies in tissue bath systems to investigate the monensin effect on tissue viability and antigen induced bronchoconstriction. Further, an HDM-induced guinea pig asthma model was utilized to investigate the effect of monensin on AHR and airway inflammation. Monensin decreased MC number, caused MC death, and blocked the HDM or anti-IgE induced bronchoconstriction in guinea pig and human airways. In the guinea pig asthma model, HDM-induced AHR, airway inflammation and MC hyperplasia could be inhibited by repeated administration of monensin. This study indicates that monensin is an effective tool to reduce MC number and MCs are crucial for the development of asthma-like features.

Topics: Allergens; Animals; Asthma; Disease Models, Animal; Guinea Pigs; Humans; Inflammation; Mast Cells; Monensin; Pyroglyphidae

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.

Topics: Animals; Apoptosis; Autoantigens; Cell Line, Tumor; Disease Models, Animal; Golgi Apparatus; HEK293 Cells; Humans; Intracellular Membranes; Ionophores; Membrane Proteins; Mice; Monensin; Multiple Myeloma; Proteasome Endopeptidase Complex; Proteolysis; Proteostasis; Ubiquitination; Valosin Containing Protein

Stress and anxiety disorders are risk factors for depression and these behaviors are modulated by corticotrophin-releasing factor receptor 1 (CRFR1) and serotonin receptor (5-HT(2)R). However, the potential behavioral and cellular interaction between these two receptors is unclear. We found that pre-administration of corticotrophin-releasing factor (CRF) into the prefrontal cortex of mice enhanced 5-HT(2)R-mediated anxiety behaviors in response to 2,5-dimethoxy-4-iodoamphetamine. In both heterologous cell cultures and mouse cortical neurons, activation of CRFR1 also enhanced 5-HT(2) receptor-mediated inositol phosphate formation. CRFR1-mediated increases in 5-HT(2)R signaling were dependent on receptor internalization and receptor recycling via rapid recycling endosomes, resulting in increased expression of 5-HT(2)R on the cell surface. Sensitization of 5-HT(2)R signaling by CRFR1 required intact PDZ domain-binding motifs at the end of the C-terminal tails of both receptor types. These data suggest a mechanism by which CRF, a peptide known to be released by stress, enhances anxiety-related behavior via sensitization of 5-HT(2)R signaling.

Topics: Amphetamines; Animals; Anxiety; Behavior, Animal; Biotinylation; Cells, Cultured; Corticotropin-Releasing Hormone; Cyclic AMP; Disease Models, Animal; Dose-Response Relationship, Drug; Embryo, Mammalian; Fluorobenzenes; Hormones; Humans; Inositol Phosphates; Ionophores; Male; Maze Learning; Mice; Monensin; Mutation; Neurons; Piperidines; Prefrontal Cortex; Rats; Reaction Time; Receptors, Corticotropin-Releasing Hormone; Receptors, Serotonin, 5-HT2; Serotonin; Serotonin 5-HT2 Receptor Agonists; Serotonin 5-HT2 Receptor Antagonists; Serotonin Agents; Signal Transduction; Transfection

A large animal with diminished cardiac function would be desirable for chronic testing of pathophysiologic responses to many human-sized devices and other therapies, especially if this model did not require prior surgical interventions or extensive technical skill and expense. Overdoses of monensin, widely used in the cattle industry as a growth promotant, are cardiotoxic, suggesting its possible use in creating cardiomyopathy. We gave a single oral dose of monensin (20 to 40 mg/kg) to 13 calves (55 to 90 kg) to produce diminished cardiac function. Hemodynamics and cardiac geometry were monitored for as long as 21 days postinduction. Within 3 days, there were signs of decreased cardiac function, as evidenced by a 10- to 20-mm Hg decrease in peak systolic blood pressure (P < 0.01 versus baseline) and a 2- to 9-mm Hg increase in central venous pressure (P < 0.01 versus baseline). There was a trend towards an increase in left ventricular end-systolic lumen diameter. Compared with those of similar-sized normal animals, stroke volume was 42% lower (P < 0.05), left atrial pressure was 67% higher (P < 0.01), and end-diastolic left ventricular pressure was 143% higher (P < 0.05). Histopathologic analysis showed extensive cardiomyocyte death. These results suggest that monensin could provide a simple, noninvasive, inexpensive, and likely irreversible means of producing clinically relevant diminished cardiac function in a human-sized animal model.

Topics: Administration, Oral; Animals; Cattle; Disease Models, Animal; Heart Diseases; Hemodynamics; Hypertrophy, Left Ventricular; Ionophores; Male; Monensin; Myocytes, Cardiac

Immunotoxins directed against human transferrin receptor have been evaluated in a nude mouse model of human malignant mesothelioma. Immunotoxins were constructed by linking ricin A chain to murine monoclonal antibodies reactive with the human transferrin receptor. A chain was obtained either by isolation from the parent toxin or by recombinant DNA techniques. These immunotoxins acted as potent in vitro cytotoxins against human malignant mesothelioma cells (H-MESO-1) (ID50, 2 X 10(-9) M). Cytotoxic potency and kinetics of cell kill were potentiated in vitro by the carboxylic ionophore monensin. For in vivo trials, nude mice were injected i.p. with 6-9 X 10(6) human malignant mesothelioma cells 24 h prior to the start of i.p. immunotoxin treatments. The survival of tumor-bearing mice was extended by 149-404%, representing a probable cell kill of 2-4 logs. Specificity of this antitransferrin receptor immunotoxin response was confirmed by the ineffectiveness of irrelevant control immunotoxins and blockade of specific immunotoxin action by excess free antibody. Monensin showed limited in vivo potentiation of immunotoxin effect, but a derivative formed by esterification of monensin with linoleic acid gave improved survival times over treatment with immunotoxin alone. Immunotoxins constructed with ricin A chain have significant tumoricidal activity in this model of regional antitumor therapy. These results may have direct relevance for treatment of i.p. malignancy in clinical settings.

Topics: Animals; Antineoplastic Agents; Cell Survival; Cytotoxicity, Immunologic; Disease Models, Animal; Humans; Immunotoxins; Injections, Intraperitoneal; Mesothelioma; Mice; Mice, Inbred BALB C; Mice, Nude; Monensin; Neoplasm Transplantation; Receptors, Transferrin; Ricin; Transplantation, Heterologous