Antibiotic Use and Abuse: a Threat to Mitochondria and Chloroplasts with Impact on Research, Health, and Environment

Insights & Perspectives Think again Antibiotic use and abuse: A threat to mitochondria and chloroplasts with impact on research, health, and environment Xu Wang1)†, Dongryeol Ryu1)†, Riekelt H. Houtkooper2)* and Johan Auwerx1)* Recently, several studies have demonstrated that tetracyclines, the antibiotics Introduction most intensively used in livestock and that are also widely applied in biomedical research, interrupt mitochondrial proteostasis and physiology in animals Mitochondria and chloroplasts are ranging from round worms, fruit flies, and mice to human cell lines. Importantly, unique and subcellular organelles that a plant chloroplasts, like their mitochondria, are also under certain conditions have evolved from endosymbiotic - proteobacteria and cyanobacteria-like vulnerable to these and other antibiotics that are leached into our environment. prokaryotes, respectively (Fig. 1A) [1, 2]. Together these endosymbiotic organelles are not only essential for cellular and This endosymbiotic origin also makes organismal homeostasis stricto sensu, but also have an important role to play in theseorganellesvulnerabletoantibiotics. the sustainability of our ecosystem as they maintain the delicate balance Mitochondria and chloroplasts retained between autotrophs and heterotrophs, which fix and utilize energy, respec- multiple copies of their own circular DNA (mtDNA and cpDNA), a vestige of the tively. Therefore, stricter policies on antibiotic usage are absolutely required as bacterial DNA, which encodes for only a their use in research confounds experimental outcomes, and their uncontrolled few polypeptides, tRNAs and rRNAs [1, 3, applications in medicine and agriculture pose a significant threat to a balanced 4]. Furthermore, both mitochondria and ecosystem and the well-being of these endosymbionts that are essential to chloroplasts have bacterial-type ribo- sustain health. somes that are distinct from the 80S ribosomes in the cytoplasm; for instance, Keywords: all chloroplasts contain 70S ribosomes, .antibiotics; chloroplasts; doxycycline; environmental pollution; mitochondria; whereas animal mitochondria have 55– 60S ribosomes and plant mitochondria mitochondrial unfolded protein response; tetracycline have 70–80S ribosomes, depending on the species [5, 6]. Mitochondria are biochemical hubs contributing to a diversity of cellular events such as energy homeostasis, calcium homeostasis, thermogenesis, DOI 10.1002/bies.201500071 steroidogenesis, detoxification, inflam- mation, oxidative stress, cell death, and 1) Laboratory of Integrative and Systems Abbreviations: Physiology, Ecole Polytechnique Fed erale de cpDNA, chloroplast DNA; ETC, electron transport so on [7–12]. One of the major and well- Lausanne, Lausanne, Switzerland chain; mtDNA, mitochondrial DNA; nDNA, nuclear characterized roles of mitochondria is 2) Laboratory Genetic Metabolic Diseases, DNA; ROS, reactive oxygen species; UPRmt, oxidative phosphorylation, the harvest- Academic Medical Center, Amsterdam, The mitochondrial unfolded protein response. ing of energy contained in nutrients into Netherlands † These authors contributed equally to this work. adenosine triphosphate (ATP), the major *Corresponding authors: energy currency molecule of life. The Riekelt Houtkooper majority of the mitochondrial proteins are E-mail: [email protected] Johan Auwerx encoded by nuclear DNA (nDNA) and E-mail: admin.auwerx@epfl.ch transcribed by the general transcriptional Bioessays 37: 1045–1053, ß 2015 The Authors. Bioessays published by WILEY Periodicals, Inc. This is an www.bioessays-journal.com 1045 open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. X. Wang et al. Insights & Perspectives..... reduced nicotinamide adenine dinucleo- tide phosphate (NADPH) through the ETC and photophosphorylation on the thylakoid membrane. Then in the dark reaction also known as the Calvin cycle, the energy is transferred into sugars following carbon fixation in the stroma. Photosynthesis is sensitive to environmental perturbations, which may inhibit plant growth and influence crop yield, Think again such as nutrient deficiency [26–29], high light intensity [30], and diverse biotic and abiotic stresses [31, 32]. In addition, impaired chloroplast translation can also significantly decrease chlorophyll con- tent and efficiency of photosynthesis [5]. Antibiotics are antimicrobial organic substances that are produced from natural microorganisms or through industrial synthesis [33]. Since the introduction of antibiotics for the treatment and prevention of bacterial infection Figure 1. Conceptual figure illustrating the general idea showing the targeted effect of about 7 decades ago, a wide variety of antibiotics. A: Antibiotics induce bacterial cell death meanwhile also interrupting the function antibiotics have been used in human of endosymbiotic organelles, mitochondria, and chloroplast, and generating a signal turning on the unfolded protein response pathways in eukaryotic cells. B: A schematic figure medicine as well as in agriculture for showing the targeted effect of tetracyclines on the Tet-On/Tet-Off system in nucleus and preventing or treating animal and plant their adverse collateral effects on mitochondrial translation. Other antibiotics, such as the bacterial infections [34]. In addition, amphenicols, also have similar effects on the mitochondria. Using antibiotics that impair antibiotics are also used as feed additives mitochondrial translation can induce a mitonuclear protein imbalance and lead to the for animals (mammals, birds, and fishes) mt mitochondrial unfolded protein response (UPR ) pathway. to promote their growth [33]. During the production and various application of such massive amount of antibiotics, they machinery into mRNAs that are trans- dynamics (fission/fusion), mitophagy, are released and can affect the environ- ported into cytosol where they are and the mitochondrial unfolded protein ment. Whereas the public and scientific translated into proteins by the cytoplas- response (UPRmt) [18–22]. Chronic over- community has been mostly focusing on mic ribosomes. These nuclear encoded load of these quality control pathways is the influence of overuse or misuse of and mitochondria-targeted proteins are a major cause for mitochondrial dysfunc- antibiotics on human health, there have imported in a co-translation manner, tion and contributes to the pathogenesis been relatively few studies on the impact folded, and assembled together with of mitochondrial diseases, ranging from of antibiotics on ecosystems, especially mtDNA-encoded polypeptides that are rare inherited mitochondrial diseases toa on the kingdom Plantae. Here, we translated by the specific translation palette of common age-related disorders summarize recent achievements show- machinery that resides in mitochondria that include metabolic diseases, neuro- ing adverse effects of antibiotics on [13–15]. Assembly of complexes and degeneration, and cancer [8, 9, 23]. mitochondria and chloroplast function, supercomplexes of the mitochondrial Chloroplasts are located in the cyto- which are off-site targets of several electron transport chain (ETC) hence plasm of plant leaf cells as well as in antibiotics. The ultimate goal of this requires a stoichiometric match between micro- and macroalgae. There are three review is to inform the reader about why nDNA-encoded and mtDNA-encoded key subcompartments in the chloro- judicious antibiotic usage is required to polypeptides [16]. An imbalance in the plasts, including the chloroplast enve- protect our health and the ecosystem. ratio between nuclear- and mitochon- lope, a double membrane, the stroma, drial-encoded proteins, termed the mito- and the thylakoid membranes, which nuclear protein imbalance, inflicts a form thylakoid vesicles [24]. Chloroplasts Elevated antibiotic proteotoxic and metabolic stress on the fulfill many essential functions in plant production increases mitochondria [17]. The exposure of cells, such as carbon assimilation mitochondria to many stressors of a through photosynthesis, nitrogen and potential of environmental proteotoxic, energetic, osmotic, and sulfur metabolism, and biosynthesis of release oxidative nature explains the existence amino acids, chlorophyll, and fatty of multiple quality control mechanisms acids [24]. Photosynthesis consist of light Due to the successful application of and adaptive pathways to maintain reactions and dark reactions [25]. In light antibiotics in human medicine and espe- proper mitochondrial function, such as reaction, the energy of light is trans- cially in agriculture, antibiotic produc- mitochondrial biogenesis, mitochondrial formed into chemical energy in ATP and tion has increased massively recently. 1046 Bioessays 37: 1045–1053, ß 2015 The Authors. Bioessays published by WILEY Periodicals, Inc. .....Insights & Perspectives X. Wang et al. From 2000 to 2010, human consumption to the data in 2009 [37]. More critically, trying to make antibiotics only available of antibiotics increased by 36%, primarily China produces and consumes the most onmedical orveterinaryprescription[39]. in developing countries [35]. According to antibiotics of all countries with an However, in 2012 there were still 8 Think again Food and Drug Administration (FDA) estimated 162 million kg of antibiotics million kg of antibiotics delivered to reports [36], in 2011, 3.3 million kg of being sold in China in 2013, of

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