The lantibiotic duramycin (Moli1901, Lancovutide) has been suggested as a drug of choice in the treatment for cystic fibrosis (CF). It has been proposed that duramycin may stimulate chloride secretion through Ca²(+) -activated Cl⁻ channels (CaCC). We investigated whether duramycin exhibited any effect on Cl⁻ efflux and intracellular Ca²(+) concentration ([Ca²(+)](i)) in CF and non-CF epithelial cells. Duramycin did stimulate Cl⁻ efflux from CF bronchial epithelial cells (CFBE) in a narrow concentration range (around 1 μM). However, 100 and 250 μM of duramycin inhibited Cl⁻ efflux from CFBE cells. An inhibitor of the CF transmembrane conductance regulator (CFTR(inh)₋₁₇₂) and a blocker of the capacitative Ca²(+) entry, gadolinium chloride, inhibited the duramycin-induced Cl⁻ efflux. No effect on Cl⁻ efflux was observed in non-CF human bronchial epithelial cells (16HBE), human airway submucosal gland cell line, human pancreatic epithelial cells, CF airway submucosal gland epithelial cells, and CF pancreatic cells. The [Ca²(+)](i) was increased by 3 μM duramycin in 16HBE cells, but decreased after 1, and 3 μM of duramycin in CFBE cells. The results suggest that the mechanism responsible for the stimulation of Cl⁻ efflux by duramycin is mainly related to unspecific changes of the cell membrane or its components rather than to effects on CaCC.

Background Coronavirus disease 2019 (COVID-19) spreading from Wuhan, Hubei province in China, is an expanding global pandemic with significant morbidity and mortality. Even though respiratory failure is the cardinal form of severe COVID-19, concomitant cardiac involvement is common. Myocarditis is a challenging diagnosis due to heterogeneity of clinical presentation, ranging from mild symptoms to fatal arrhythmia and cardiogenic shock (CS). The aetiology is often viral and endomyocardial biopsy (EMB) is the gold standard for definite myocarditis. However, the diagnosis is often made on medical history, clinical presentation, magnetic resonance imaging, and blood tests. Case summary We present a 43-year-old man with mixed connective tissue disease treated with hydroxychloroquine who rapidly developed CS 4 days from symptom onset with fever and cough, showing positive polymerase chain reaction nasopharyngeal swab for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. While computed tomography of the thorax was normal, high-sensitivity troponin T was elevated and electrocardiogram showed diffuse ST elevation and low voltage as signs of myocardial oedema. Echocardiography showed severe depression of left ventricular function. The myocardium recovered completely after a week with mechanical circulatory support (MCS). EMB was performed but could neither identify the virus in the cardiomyocytes, nor signs of inflammation. Still the most probable aetiology of CS in this case is myocarditis as a sole symptom of COVID-19. Discussion COVID-19 patients in need of hospitalization present commonly with respiratory manifestations. We present the first case of fulminant myocarditis rapidly progressing to CS in a COVID-19 patient without respiratory failure, successfully treated with inotropes and MCS.

It was investigated whether azithromycin (AZM) stimulates chloride (Cl-) efflux from cystic fibrosis (CF) and non-CF airway epithelial cells, possibly secondary to up-regulation of the multidrug resistance protein (MDR). CF and non-CF human airway epithelial cell lines (CFBE and 16HBE) were treated with 0.4, 4, and 40 microg/mL AZM for 4 days. Cl- efflux was explored in the presence or absence of specific inhibitors of CFTR and alternative Cl- channels. Six CF patients received AZM (500 mg daily) for 6 months. The percentage of predicted forced vital capacity (FVC%), forced expiratory volume (FEV1%), and the number of acute exacerbations were compared before and after treatment. Nasal biopsies were taken before and after treatment, and mRNA expression of MDR and CFTR was determined by in situ hybridization. A significant dose-dependent increase of Cl- efflux from CFBE cells (but not from 16HBE cells) was observed after AZM treatment. A CFTR inhibitor significantly reduced AZM-stimulated Cl- efflux from CFBE cells. A significant improvement in FEV1%, and fewer exacerbations were observed. AZM treatment did not affect mRNA expression of MDR and CFTR. The stimulation of Cl- efflux could be part of the explanation for the clinical improvement seen among the patients.