Proceedings of The Physiological Society

Mitochondria: Form and function (London, UK) (2017) Proc Physiol Soc 38, PC09

Poster Communications

Tetracycline antibiotics impair cardiac mitochondrial and contractile function

R. Wüst1, N. Held1, E. van Deel2, D. Kuster2, R. Houtkooper1

1. Amsterdam Medical Center, Amsterdam, Netherlands. 2. VU Medical Center, Amsterdam, Netherlands.

Tetracyclines antibiotics act through inhibiting bacterial protein translation. Given the bacterial ancestry of mitochondria, we tested the hypothesis that doxycycline reduces mitochondrial function, and results in cardiac contractile dysfunction. We cultured H9C2 cardiomyoblasts and adult rat cardiomyocytes (male, 250 g, n=3; anaesthetised with isoflurane) in the presence of doxycycline (0, 10 and 30 μg/ml, DOX0, DOX10 and DOX30 respectively). Ampicillin and carbenicillin (both 100 μg/ml) were used as control antibiotics. ANOVA was performed to assess differences between groups and values are presented as mean±stdev. The ratio between protein abundance of a mtDNA-encoded OXPHOS subunit (cytochrome c oxidase subunit I) and a nDNA-encoded OXPHOS subunit (Succinate DeHydrogenase A) was 39±5% lower in DOX30 compared to control (p=0.02), with intermediate values for DOX10, confirming a mitonuclear protein imbalance in doxycycline-treated H9C2 cells. Maximal uncoupled respiration was lower in DOX30 than control (136±22 vs. 272±25 pmol.μgDNA-1.min-1, p=0.01). Complex I respiration (-66±20%) was more affected compared to complex II respiration (-46±36%) in DOX30. Interestingly, also the protein content of the nuclear-encoded complex I subunit NDUFS3 was significantly reduced by ~50% in DOX10 and DOX30, indicative of a mitonuclear imbalance that goes beyond a reduced mitochondrial protein synthesis in doxycycline-treated H9C2 cells. TMRM-loaded mitochondria (200 nM) appeared fragmented and the content of mitochondrial fission-related Dynamin related protein 1 (DRP1) was 43±9% larger in DOX30 compared to DOX0. Cardiac contractility was assessed by Fura-2AM in electrically stimulated (at 0.5 Hz) adult rat cardiomyocytes kept in culture for 2 days. Diastolic calcium concentration was significantly higher in DOX10 (0.68±0.01) vs. DOX0 (0.64±0.01, p=0.01). No differences were observed in other parameters of the calcium transient. We conclude that tetracycline antibiotics impair mitochondrial function, particularly mitochondrial complex I respiration, cause fragmentation and result in diastolic dysfunction in adult cardiomyocytes. These results could have major implications for giving specific classes of antibiotics to patients at risk of developing cardiovascular dysfunction. Also, scientists should be aware of the potential confounding effects of certain classes of antibiotics (including streptomycin) on experimental results.

Where applicable, experiments conform with Society ethical requirements