Maduramicin induces apoptosis and necrosis, and blocks autophagic flux in myocardial H9c2 cells

Maduramicin ammonium impairs autophagic flux through activating AMPK-mediated eIF2α-ATF4 endoplasmic reticulum stress pathway in skeletal muscle

BACKGROUND

Maduramicin ammonium (MA), a widely used coccidiostat, has been reported to cause skeletal muscle degeneration in animals and even humans. In this study, we explore the underlying mechanism of its toxicity in skeletal muscle.

RESULTS

First, we observed that MA impaired autophagic flux which was evidenced by increased protein level of LC3-II and p62 in skeletal myoblast C2C12 and L6 cell lines and rectus femoris muscle tissues of rats and broilers. Then, we found that MA induced eIF2α phosphorylation and ATF4 expression in the cells and tissues. Co-treatment with ISRIB attenuated MA-induced LC3-II and p62 in C2C12 and L6 cells, suggesting that MA-induced eIF2α-ATF4 pathway contributed to impairment of autophagic flux in the cells. Lastly, we showed that MA activated AMPK signaling in skeletal muscle, since the phosphorylation of AMPK was increased by MA treatment in skeletal myoblast cell lines and muscle tissues. Furthermore, in AMPK downregulated C2C12 cells, MA-induced LC3-II, ATF4 and phosphorylation of eIF2α was reversed, supporting that AMPK was involved in the regulation of the eIF2α-ATF4 pathway and autophagic flux during MA exposure.

CONCLUSION

Our findings showed that MA impairs autophagic flux through activating the AMPK-induced eIF2α-ATF4 pathway in skeletal muscle. © 2024 Society of Chemical Industry.

The highly hazardous veterinary drug "maduramicin" and its toxicokinetics in rats

Background

Maduramicin (MAD) is an anticoccidial veterinary drug, but it frequently causes fatal poisonings in poultry, livestock, or humans. However, there is no specific antidote or guidance on first aid for MAD poisoning.

Aim

The aim of the present study is to evaluate the acute toxicity and toxicokinetics of MAD after oral exposure, so as to make a foundation for developing diagnostic and therapeutic protocols for human intoxication.

Methods

Five groups of rats (eight-to-nine-week-old male Wistar rats) were orally administered MAD via gavage at doses of 0, 4.64, 10.0, 21.5, or 46.4 mg/kg bw for only one time. The survival rates of the rats were observed over the following 14 days to assess acute toxicity. To evaluate the toxic effects of MAD, two doses (4.8 mg/kg bw and 10 mg/kg bw) were orally administered via gavage. Biochemical parameters including creatine kinase, lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, urea, creatinine, serum myoglobin, and urinary myoglobin were measured. Liver, kidney, heart, and hind limb skeletal muscle samples from severely poisoned rats were obtained for pathological examination. For toxicokinetic analysis, samples of serum, urine, and feces from the 4.8 mg/kg bw dose group were analyzed using high-performance liquid chromatography-tandem mass spectrometry.

Results

The LD50 of MAD in male Wistar rats was determined to be 6.81 mg/kg bw. In the 10 mg/kg bw group, elevated serum urea levels and increased myoglobin levels in both serum and urine indicated renal injury and potential muscle damage. Toxicokinetics in serum revealed that following oral administration of 4.8 mg/kg bw MAD, peak serum concentration of 59.8 ± 8.9 μg/L was achieved at 30.0 ± 13.9 h. MAD exhibited a slow elimination from the blood with an elimination half-life of 72.9 ± 36.8 h and a mean residence time of 79.6 ± 25.5 h. Additionally, fecal excretion of MAD was found to be greater than urinary excretion.

Conclusion

MAD is a highly toxic veterinary drug which requires careful handling. The primary effects of poisoning include kidney injury and suspected rhabdomyolysis. It is excreted very slowly after oral administration. Promoting toxin excretion in individuals poisoned by MAD could potentially serve as an effective treatment method until a specific antidote is identified.

Nanotherapeutics against malaria: A decade of advancements in experimental models

Malaria, caused by different species of protists of the genus Plasmodium, remains among the most common causes of death due to parasitic diseases worldwide, mainly for children aged under 5. One of the main obstacles to malaria eradication is the speed with which the pathogen evolves resistance to the drug schemes developed against it. For this reason, it remains urgent to find innovative therapeutic strategies offering sufficient specificity against the parasite to minimize resistance evolution and drug side effects. In this context, nanotechnology-based approaches are now being explored for their use as antimalarial drug delivery platforms due to the wide range of advantages and tuneable properties that they offer. However, major challenges remain to be addressed to provide a cost-efficient and targeted therapeutic strategy contributing to malaria eradication. The present work contains a systematic review of nanotechnology-based antimalarial drug delivery systems generated during the last 10 years. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

V-ATPase V0 subunit activation mediates maduramicin-induced methuosis through blocking endolysosomal trafficking in vitro and in vivo

Methuosis, a novel cell death phenotype, is characterized by accumulation of cytoplasmic vacuolization upon external stimulus. Methuosis plays a critical role in maduramicin-induced cardiotoxicity despite the underlying mechanism is largely unknown. Herein, we aimed to investigate the origin and intracellular trafficking of cytoplasmic vacuoles, as well as the molecular mechanism of methuosis caused by maduramicin (1 μg/mL) in myocardial cells. H9c2 cells and broiler chicken were used and were exposed to maduramicin at doses of 1 μg/mL in vitro and 5 ppm-30 ppm in vivo. Morphological observation and dextran-Alexa Fluor 488 tracer experiment showed that endosomal compartments swelling and excessive macropinocytosis contributed to madurdamcin-induced methuosis. Cell counting kit-8 assay and morphology indicated pharmacological inhibition of macropinocytosis largely prevent H9c2 cells from maduramicin-triggered methuosis. In addition, late endosomal marker Rab7 and lysosomal associated membrane protein 1 (LAMP1) increased in a time-dependent manner after maduramicin treatment, and the recycling endosome marker Rab11 and ADP-ribosylation factor 6 (Arf6) were decreased by maduramicin. Vacuolar-H⁺-ATPase (V-ATPase) was activated by maduramicin, and pharmacological inhibition and genetic knockdown V0 subunit of V-ATPase restore endosomal-lysosomal trafficking and prevent H9c2 cells methuosis. Animal experiment showed that severe cardiac injury included the increase of creatine kinase (CK) and creatine kinase-MB (CK-MB), and vacuolar degeneration resembled methuosis in vivo after maduramicin treatment. Taken together, these findings demonstrate that targeting the inhibition of V-ATPase V0 subunit will prevent myocardial cells methuosis by restoring endosomal-lysosomal trafficking.

Ionophore Toxicity in Animals: A Review of Clinical and Molecular Aspects

For many years, ionophores have been used to control coccidiosis in poultry. However, misuse of ionophores can cause toxicity with significant clinical symptoms. The most critical factors influencing ionophores' toxicity are administration dose, species, and animal age. Although clinical signs of ionophore intoxication are well studied, the toxicity mechanisms of the ionophores at the molecular level still are not fully elucidated. This review summarizes the studies focused on polyether ionophores toxicity mechanisms in animals at the clinical and molecular levels. Studies show that ionophore toxicity mainly affects myocardial and skeletal muscle cells. The molecular mechanism of the toxication could be explained by the inhibition of oxidative phosphorylation via dysregulation of ion concentration. Tiamulin-ionophore interaction and the synergetic effect of tiamulin in ionophore biotransformation are discussed. Furthermore, in recent years ionophores were candidates for reprofiling as antibacterial and anti-cancer drugs. Identifying ionophores' toxicity mechanisms at the cellular level will likely help develop novel therapies in veterinary and human medicine.

Undescribed polyether ionophores from Streptomyces cacaoi and their antibacterial and antiproliferative activities

Polyether ionophores represent a large group of naturally occurring compounds mainly produced by Streptomyces species. With previously proven varieties of bioactivity including antibacterial, antifungal, antiparasitic, antiviral and anti-tumor effects, the discovery of undescribed polyethers leading to development of efficient therapeutics has become important. As part of our research on polyether-rich Streptomyces cacaoi, we previously performed modification studies on fermentation conditions to induce synthesis of specialized metabolites. Here, we report four undescribed and nine known polyether compounds from S. cacaoi grown in optimized conditions. Antimicrobial activity assays revealed that four compounds, including the undescribed (6), showed strong inhibitory effects over both Bacillus subtilis and methicillin-resistant Staphylococcus aureus (MRSA) growth. Additionally, K41-A and its C15-demethoxy derivative exhibited significant cytotoxicity. These results signified that selectivity of C15-demethoxy K41-A towards cancer cells was higher than K41-A, which prompted us to conduct mechanistic experiments. These studies showed that this uninvestigated compound acts as a multitarget compound by inhibiting autophagic flux, inducing reactive oxygen species formation, abolishing proteasome activity, and stimulating ER stress. Consequently, the optimized fermentation conditions of S. cacaoi led to the isolation of undescribed and known polyethers displaying promising activities.

Liposomes for malaria management: the evolution from 1980 to 2020

Malaria is one of the most prevalent parasitic diseases and the foremost cause of morbidity in the tropical regions of the world. Strategies for the efficient management of this parasitic infection include adequate treatment with anti-malarial therapeutics and vaccination. However, the emergence and spread of resistant strains of malaria parasites to the majority of presently used anti-malarial medications, on the other hand, complicates malaria treatment. Other shortcomings of anti-malarial drugs include poor aqueous solubility, low permeability, poor bioavailability, and non-specific targeting of intracellular parasites, resulting in high dose requirements and toxic side effects. To address these limitations, liposome-based nanotechnology has been extensively explored as a new solution in malaria management. Liposome technology improves anti-malarial drug encapsulation, bioavailability, target delivery, and controlled release, resulting in increased effectiveness, reduced resistance progression, and fewer adverse effects. Furthermore, liposomes are exploited as immunological adjuvants and antigen carriers to boost the preventive effectiveness of malaria vaccine candidates. The present review discusses the findings from studies conducted over the last 40 years (1980-2020) using in vitro and in vivo settings to assess the prophylactic and curative anti-malarial potential of liposomes containing anti-malarial agents or antigens. This paper and the discussion herein provide a useful resource for further complementary investigations and may pave the way for the research and development of several available and affordable anti-malarial-based liposomes and liposomal malaria vaccines by allowing a thorough evaluation of liposomes developed to date for the management of malaria.

Maduramicin induces cardiotoxicity via Rac1 signaling-independent methuosis in H9c2 cells

Maduramicin frequently induces severe cardiotoxicity in target and nontarget animals in clinic. Apoptotic and non-apoptotic cell death mediate its cardiotoxicity; however, the underlying non-apoptotic cell death induced by maduramicin remains unclear. In current study, a recently described non-apoptotic cell death "methuosis" caused by maduramicin was defined in mammalian cells. Rat myocardial cell H9c2 was used as an in vitro model, showing excessively cytoplasmic vacuolization upon maduramicin (0.0625-5 μg/mL) exposure for 24 h. Maduramicin-induced reversible cytoplasmic vacuolization of H9c2 cells in a time- and concentration-dependent manner. The vacuoles induced by maduramicin were phase lucent with single membrane and were not derived from the swelling of organelles such as mitochondria, endoplasmic reticulum, lysosome, and Golgi apparatus. Furthermore, maduramicin-induced cytoplasmic vacuoles are generated from micropinocytosis, which was demonstrated by internalization of extracellular fluid-phase marker Dextran-Alexa Fluor 488 into H9c2 cells. Intriguingly, these cytoplasmic vacuoles acquired some characteristics of late endosomes and lysosomes rather than early endosomes and autophagosomes. Vacuolar H⁺ -ATPase inhibitor bafilomycin A1 efficiently prevented the generation of cytoplasmic vacuoles and decreased the cytotoxicity of H9c2 cells triggered by maduramicin. Mechanism studying indicated that maduramicin activated H-Ras-Rac1 signaling pathway at both mRNA and protein levels. However, the pharmacological inhibition and siRNA knockdown of Rac1 rescued maduramicin-induced cytotoxicity of H9c2 cells but did not alleviate cytoplasmic vacuolization. Based on these findings, maduramicin induces methuosis in H9c2 cells via Rac-1 signaling-independent seriously cytoplasmic vacuolization.

Maduramicin triggers methuosis-like cell death in primary chicken myocardial cells

Maduramicin frequently induces severe cardiotoxicity in broiler chickens as well as in humans who consume maduramicin accidentally. Apoptosis and non-apoptotic cell death occur concurrently in the process of maduramicin-induced cardiotoxicity; however, the underlying mechanism of non-apoptotic cell death is largely unknown. Here, we report the relationship between maduramicin-caused cytoplasmic vacuolization and methuosis-like cell death as well as the underlying mechanism in primary chicken myocardial cells. Maduramicin induced a significant increase of cytoplasmic vacuoles with a degree of cell specificity in primary chicken embryo fibroblasts and chicken hepatoma cells (LMH), along with a decrease of ATP and an increase of LDH. The accumulated vacuoles were partly derived from cellular endocytosis rather than the swelling of endoplasm reticulum, lysosomes, and mitochondria. Moreover, the broad-spectrum caspase inhibitor carbobenzoxy-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk) did not prevent maduramicin-induced cytoplasmic vacuolization. DNA ladder and cleavage of PARP were not observed in chicken myocardial cells during maduramicin exposure. Pretreatment with 3-methyladenine (3-MA) and cholorquine (CQ) of chicken myocardial cells did not attenuate cytoplasmic vacuolization and cytotoxicity, although LC3 and p62 were activated. Bafilomycin A1 almost completely prevented the generation of cytoplasmic vacuoles and significantly attenuated cytotoxicity induced by maduramicin, along with downregulation of K-Ras and upregulation of Rac1. Taken together, "methuosis" due to excessive cytoplasmic vacuolization mediates the cardiotoxicity of maduramicin. This provides new insights for understanding a nonclassical form of cell death in the field of drug-induced cytotoxicity.

Potential anti-inflammatory and anti-apoptotic effect of Coccinia grandis plant extract in LPS stimulated-THP-1 cells

Coccinia grandis (C. grandis) L is an Indian medicinal plant from the Cucurbitaceae family whose extracts possess anti-oxidant, anti-infective, and anti-inflammatory properties. The objective of the present study was to probe the potential immunomodulatory of C. grandis crude extract on different pathways in THP-1 cells as probed by changes in expression of several proteins. THP-1 cells were differentiated into macrophages after treatment with phorbol-12-myristate 13-acetate, followed by exposure to lipopolysaccharide (LPS) with or without 50 or 100 μg/ml of C. grandis extract. Treatment of the cells with the extract significantly downregulated the expression and release of pro-inflammatory cytokines (IL-6, IL-1β, CCL2, CCL22, CXCL10/IP-10, CX3CL1 and CXCL8/IL-8), proteins (ERK5, BAX, BCL2, Cyclin D, ERK1, NF-κB, P-IκBα,P- NF-κB and P-p38) and molecular signaling pathways (NF-κB, p38 MAPK, ERK1/2 and IL-6/JAK/STAT3 signaling cascades). This study is the first to highlight the ability of C. grandis extract to modulate several pathways, including proliferation, the expression of inflammatory cytokines, phagocytosis, migration properties and apoptosis, in human monocytic THP-1 cells.

Maduramicin inactivation of Akt impairs autophagic flux leading to accumulated autophagosomes-dependent apoptosis in skeletal myoblast cells

It has been clinically documented that maduramicin (Mad), a polyether ionophore antibiotic widely used in the control of coccidiosis in poultry worldwide, can elicit skeletal muscle degeneration, heart failure, and even death in animals and humans, if improperly used. Here, we show that Mad induced apoptosis dose-dependently, which was associated with impaired autophagic flux in skeletal myoblast (C2C12 and L6) cells. This is supported by the findings that Mad treatment resulted in increase of autophagosomes with a concomitant elevation of LC3-II and p62 in the cells. Also, Mad increased co-localization of mCherry and GFP tandem-tagged LC3 puncta in the cells, suggesting a blockage of autophagic flux. Furthermore, addition of chloroquine (CQ) strengthened the basic and Mad-enhanced LC3-II and p62 levels, autophagosome formation and cell apoptosis, whereas pretreatment with rapamycin alleviated the effects in the cells exposed to Mad. Moreover, we noticed that Mad treatment inactivated Akt dose-dependently. Inhibition of Akt with inhibitor X potentiated Mad-induced decrease in phosphorylated Akt, and increases in LC3-II and p62 levels, autophagosome formation and cell apoptosis, whereas ectopic expression of constitutively active Akt rendered resistance to these events. Collectively, these results indicate that Mad inactivation of Akt impairs autophagic flux leading to accumulated autophagosomes-dependent apoptosis in skeletal myoblast cells. Our findings suggest that manipulation of Akt activity to improve autophagic flux is a promising strategy against Mad-induced myotoxicity.

Maduramicin induces apoptosis through ROS-PP5-JNK pathway in skeletal myoblast cells and muscle tissue

Our previous work has shown that maduramicin, an effective coccidiostat used in the poultry production, executed its toxicity by inducing apoptosis of skeletal myoblasts. However, the underlying mechanism is not well understood. Here we show that maduramicin induced apoptosis of skeletal muscle cells by activating c-Jun N-terminal kinase (JNK) pathway in murine C2C12 and L6 myoblasts as well as skeletal muscle tissue. This is supported by the findings that inhibition of JNK with SP600125 or ectopic expression of dominant negative c-Jun attenuated maduramicin-induced apoptosis in C2C12 cells. Furthermore, we found that treatment with maduramicin reduced the cellular protein level of protein phosphatase 5 (PP5). Overexpression of PP5 substantially mitigated maduramicin-activated JNK and apoptosis. Moreover, we noticed that treatment with maduramicin elevated intracellular reactive oxygen species (ROS) level. Pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger and antioxidant, suppressed maduramicin-induced inhibition of PP5 and activation of JNK as well as apoptosis. The results indicate that maduramicin induction of ROS inhibits PP5, which results in activation of JNK cascade, leading to apoptosis of skeletal muscle cells. Our finding suggests that manipulation of ROS-PP5-JNK pathway may be a potential approach to prevent maduramicin-induced apoptotic cell death in skeletal muscle.

Long circulatory liposomal maduramicin inhibits the growth of Plasmodium falciparum blood stages in culture and cures murine models of experimental malaria

Malaria continues to be one of the deadliest infectious diseases and a global health menace. The emergence and spread of drug-resistant strains of malaria parasites have further made the process of disease management grimmer. Thus, there is an urgent need to identify promising antimalarial strategies that can target the blood stages as well as block parasite transmission. Maduramicin is one such ionophore selected out of a recent screen of gametocytocidal compounds that exhibit potent antiplasmodial activity. However, maduramicin's strong hydrophobic nature and associated toxicity restrict its application in chemotherapy. To alleviate this problem, we have developed a liposomal formulation loaded with the ionophore maduramicin for the treatment of chloroquine sensitive and resistant Plasmodium infections. Here, we show that maduramicin in PEGylated liposomal formulations displayed enhanced antiplasmodial activity in vitro compared to free maduramicin. Significantly, four consecutive doses of 1.5 mg kg-1 body weight of PEGylated maduramicin loaded lipid vesicles completely cured cerebral and chloroquine resistant murine models of malaria without any obvious toxic effects and suppressed the key inflammatory markers associated with the progression of the disease. PEGylated liposomal maduramicin also exhibited a prolonged plasma clearance rate, implying a greater chance of interaction and uptake by infected RBCs. Furthermore, we also provide evidence that the detrimental effect of liposomal maduramicin on parasite survival is mediated by increased ROS generation and subsequent perturbation of parasite mitochondrial membrane potential. This study presents the first report to demonstrate the potent antimalarial efficacy of maduramicin liposomes, a strategy that holds promise for the development of successful therapeutic intervention against malaria in humans.