Exploring the inhibitory potential of the antiarrhythmic drug amiodarone against Clostridioides difficile toxins TcdA and TcdB

Abstract

The intestinal pathogen Clostridioides difficile is the leading cause of antibiotic-associated diarrhea and pseudomembranous colitis in humans. The symptoms of C. difficile -associated diseases (CDADs) are directly associated with the pathogen’s toxins TcdA and TcdB, which enter host cells and inactivate Rho and/or Ras GTPases by glucosylation. Membrane cholesterol is crucial during the intoxication process of TcdA and TcdB, and likely involved during pore formation of both toxins in endosomal membranes, a key step after cellular uptake for the translocation of the glucosyltransferase domain of both toxins from endosomes into the host cell cytosol. The licensed drug amiodarone, a multichannel blocker commonly used in the treatment of cardiac dysrhythmias, is also capable of inhibiting endosomal acidification and, as shown recently, cholesterol biosynthesis. Thus, we were keen to investigate in vitro with cultured cells and human intestinal organoids, whether amiodarone preincubation protects from TcdA and/or TcdB intoxication. Amiodarone conferred protection against both toxins independently and in combination as well as against toxin variants from the clinically relevant, epidemic C. difficile strain NAP1/027. Further mechanistic studies suggested that amiodarone’s mode-of-inhibition involves also interference with the translocation pore of both toxins. Our study opens the possibility of repurposing the licensed drug amiodarone as a novel pan-variant antitoxin therapeutic in the context of CDADs.

New treatment approaches for Clostridioides difficile infections: alternatives to antibiotics and fecal microbiota transplantation

“…Recently, amiodarone, an antiarrhythmic drug blocking potassium, sodium, and calcium channels, was shown to be a potent inhibitor of TcdA and TcdB exotoxins. 165 In an elegant study, the authors demonstrated that amiodarone prevents glucosyltransferase domain release into the cytosol by insertion into and blockage of the toxins’ translocation pore. In vitro , the drug was active against the toxin variants from the clinically relevant epidemic C. difficile strain NAP1/027 at concentrations comparable to those reached in the plasma of patients treated for arrhythmia.…”

Trauma-toxicology: concepts, causes, complications

“…Therefore, the hypocholesterolemic drug simvastatin, which acts as an inhibitor of the HMG-CoA reductase, was found to be capable of inhibiting cell entry of TcdA/B by decreasing the cholesterol content in membranes of cultured cells (Papatheodorou et al 2019 ). Recently, it was shown that the antiarrhythmic drug amiodarone prevents intoxication of cells by TcdA/B (Schumacher et al 2023 ). Amiodarone’s main mode of inhibition likely involves interference with pore formation and translocation of both toxins.…”