Effects of aminoglycoside antibiotics on cholinergic autonomic nervous transmission

Prophylactic intravenous gentamicin with sedation-free cystoscopic injection of BoNT-A: No demonstrable adverse extravesical neuromuscular effects in a pilot safety study of 220 idiopathic overactive bladder patients

Objectives:

To determine whether administration of single dose prophylactic intravenous gentamicin prior to intravesical injection of botulinum toxin type A (BoNT-A) is associated with adverse extravesical neuromuscular effects in idiopathic overactive bladder syndrome.

Patients and methods:

A retrospective analysis of 220 consecutive idiopathic overactive bladder patients following sedation-free flexible cystoscopic injection of intravesical BoNT-A. All patients received a single dose of intravenous gentamicin (160 mg) followed by 100-200 IU of BoNT-A. They were followed up at intervals to determine whether they had experienced any adverse extravesical neuromuscular side effects.

Results:

None of our patients developed adverse extravesical neuromuscular side effects from intravesical botulinum injections with concomitant administration of intravenous gentamicin.

Conclusion:

Single dose intravenous gentamicin is safe to use as a prophylaxis for intravesical BoNT-A injections of 200 IU or below in idiopathic overactive bladder patients.

Level of evidence:

Not applicable.

Long-term effects of oxytetracycline exposure in zebrafish: A multi-level perspective

Oxytetracycline (OTC) is a broad-spectrum antibiotic widely used in livestock production. Like many other pharmaceuticals, OTC is not completely metabolized by the organism and thus, increasing amounts of the compound are being detected in the aquatic environment. The assessment of the environmental risk of pharmaceuticals is hindered by their very low concentrations and specific modes of action and thus relevant exposure scenarios and sensitive endpoints are needed. Thus, this work aimed to study the long-term effect of OTC exposure in zebrafish (at behavior and biochemical levels) and associated bacterial communities (fish gut and water bacterial communities). Results revealed that at behavioral level, boldness increase (manifested by increased exploratory behavior of a new environment) was observed in fish exposed to low OTC concentrations. Moreover, changes in fish swimming pattern were observed in light periods (increased stress response: hyperactivity and freezing) probably due to photo-sensibility conferred by OTC exposure. Effects at biochemical level suggest that long-term exposure to OTC interfere with cellular energy allocation mainly by reducing lipids levels and increasing energy consumption. Moreover, evidences of oxidative damage were also observed (reduced levels of TG, GST and CAT). The analysis of water and gut microbiome revealed changes in the structure and diversity of bacterial communities potentially leading to changes in communities' biological function. Some of the effects were observed at the lowest concentration tested, 0.1 μg/L which is a concentration already detected in the environment and thus clearly demonstrating the need of a serious ecotoxicological assessment of OTC effects on non-target organisms.

Oxytetracycline effects in specific biochemical pathways of detoxification, neurotransmission and energy production in Oncorhynchus mykiss

Oxytetracycline (OTC) is a tetracycline antibiotic, widely used in human and veterinary medicines, including in aquaculture. Given this use, OTC has been detected in different aquatic environments. Some recent works have demonstrated unintentional biological activity of OTC in non-target aquatic organisms. This study investigated the acute and chronic effects of OTC on the physiology of the fish species Oncorhynchus mykiss (rainbow trout), namely through the quantification of the activity of enzymes involved in different biochemical pathways, such as detoxification (phase II - glutathione S-transferases - GSTs, uridine-diphosphate-glucuronosyltransferases - UGTs), neurotransmission (acetylcholinesterase - AChE) and energy production (lactate dehydrogenase - LDH). The here-obtained data demonstrated the induction of GSTs activity in gills, and inhibition of AChE activity in eyes tissue, in chronically exposed organisms, as well as alterations in LDH activity following both exposures. Considering this set of results, we can infer that OTC exposure may have induced the glutathione pathway of detoxification in gills with the involvement of GSTs, or indirectly due to the metabolites that may have been produced. In turn, these metabolites may have interfered with the mechanism of neurotransmission, also causing physiological and biochemical disturbances in rainbow trout after OTC exposure, namely disturbances in energetic metabolism. In addition, it is important to stress that such occurrences took place at low, environmentally realistic levels of OTC, suggesting that organisms exposed in the wild may be putative targets of toxic effects by commonly used drugs such as antibiotics.

Ecotoxicological evaluation of gilthead seabream (Sparus aurata) exposed to the antibiotic oxytetracycline using a multibiomarker approach

Oxytetracycline (OTC) is an antibiotic widely used in human and veterinary medicines. Since the primary toxicity occurs mainly at molecular/biochemical levels, the study of different biological responses corresponds to a sensitive and crucial approach. The aim of the present study was to assess the toxic effects of OTC in gilthead seabream (Sparus aurata) through the use of multibiomarkers and elucidate about the possible toxicological mechanisms involved. S. aurata were acutely (96 h: 0.04-400 μg/L) and chronically (28 days: 0.0004-4 μg/L) exposed to OTC. Detoxification, antioxidant defense, lipid peroxidation, genotoxicity, neurotransmission and energy metabolism biomarkers were evaluated. OTC impaired the detoxification pathways and caused peroxidative damage and genotoxicity. The relevance of the here-obtained data is high, since significant effects were recorded for levels already reported to occur in the wild, meaning that environmentally-exposed marine organisms (including those cultured at fish farms) are not completely exempt of risks posed by OTC.

Acute effects of tetracycline exposure in the freshwater fish Gambusia holbrooki: antioxidant effects, neurotoxicity and histological alterations

A large body of evidence was compiled in the recent decades showing a noteworthy increase in the detection of pharmaceutical drugs in aquatic ecosystems. Due to its ubiquitous presence, chemical nature, and practical purpose, this type of contaminant can exert toxic effects in nontarget organisms. Exposure to pharmaceutical drugs can result in adaptive alterations, such as changes in tissues, or in key homeostatic mechanisms, such as antioxidant mechanisms, biochemical/physiological pathways, and cellular damage. These alterations can be monitored to determine the impact of these compounds on exposed aquatic organisms. Among pharmaceutical drugs in the environment, antibiotics are particularly important because they include a variety of substances widely used in medical and veterinary practice, livestock production, and aquaculture. This wide use constitutes a decisive factor contributing for their frequent detection in the aquatic environment. Tetracyclines are the individual antibiotic subclass with the second highest frequency of detection in environmental matrices. The characterization of the potential ecotoxicological effects of tetracycline is a much-required task; to attain this objective, the present study assessed the acute toxic effects of tetracycline in the freshwater fish species Gambusia holbrooki by the determination of histological changes in the gills and liver, changes in antioxidant defense [glutathione S-transferase (GST), catalase (CAT), and lipoperoxidative damage] as well as potential neurotoxicity (acetylcholinesterase activity). The obtained results suggest the existence of a cause-and-effect relationship between the exposure to tetracycline and histological alterations (more specifically in gills) and enzymatic activity (particularly the enzyme CAT in liver and GST in gills) indicating that this compound can exert a pro-oxidative activity.

Therapeutic targeting of CPT-11 induced diarrhea: a case for prophylaxis

CPT-11 (irinotecan), a DNA topoisomerase I inhibitor is one of the main treatments for colorectal cancer. The main dose limiting toxicities are neutropenia and late onset diarrhea. Though neutropenia is manageable, CPT-11 induced diarrhea is frequently severe, resulting in hospitalizations, dose reductions or omissions leading to ineffective treatment administration. Many potential agents have been tested in preclinical and clinical studies to prevent or ameliorate CPT-11 induced late onset diarrhea. It is predicted that prophylaxis of CPT-11 induced diarrhea will reduce sub-therapeutic dosing as well as hospitalizations and will eventually lead to dose escalations resulting in better response rates. This article reviews various experimental agents and strategies employed to prevent this debilitating toxicity. Covered topics include schedule/dose modification, intestinal alkalization, structural/chemical modification, genetic testing, anti-diarrheal therapies, transporter (ABCB1, ABCC2, BCRP2) inhibitors, enzyme (β-glucuronidase, UGT1A1, CYP3A4, carboxylesterase, COX-2) inducers and inhibitors, probiotics, antibiotics, adsorbing agents, cytokine and growth factor activators and inhibitors and other miscellaneous agents.

DO ANTIBIOTICS CONTRIBUTE TO POSTOPERATIVE ILEUS? CONTRACTILE RESPONSES OF ILEUM SMOOTH MUSCLE IN GUINEA PIGS TO LONG-TERM PARENTERAL CEFTRIAXONE AND AMPICILLIN

BACKGROUND

Antibiotics may impair small bowel smooth muscle contractility and contribute to postoperative ileus. The aim of this study was to compare the contractile responses of ileum smooth muscle to different agonists in guinea pigs treated with ceftriaxone (Rocephin; F. Hoffman-La Roche, Kaiseraugst, Switzerland) or ampicillin (Ampisina; Mustafa Nevzat Ilaç Sanayii AS, Istanbul, Turkey).

METHODS

Twenty-four adult guinea pigs were randomly divided into three groups. Whereas eight of these received ceftriaxone sodium (100 mg/kg per day, i.m.) for 10 days, another eight guinea pigs received ampicillin (50 mg/kg per day, i.m.) for 10 days and the remaining eight served as the control group receiving 1 mL distilled water during 10 days as placebo. By the end of 10 days, the animals were killed and their ilea were excised. Ileum segments were placed in an organ bath; concentration-response relationship for carbachol and histamine were obtained by adding the reagent cumulatively to the bath.

RESULTS

pD(2) values being the same, maximum contractile responses (E(max)) to carbachol and histamine were significantly reduced in the ceftriaxone sodium group compared with the control group. No significant differences in E(max) and pD(2) values to carbachol and histamine were observed between the ampicillin group and the control group.

CONCLUSION

These data indicate that whereas ceftriaxone may impair small bowel smooth muscle contractility, ampicillin does not. There are implications for the long-term use of parenteral antibiotics in the postoperative period.

Transforming growth factor alpha treatment alters intracellular calcium levels in hair cells and protects them from ototoxic damage in vitro

To determine if transforming growth factor alpha (TGF alpha) pretreatment protects hair cells from aminoglycoside induced injury by modifying their intracellular calcium concentration, we assayed hair cell calcium levels in organ of Corti explants both before and after aminoglycoside (i.e. neomycin, 10(-3) M) exposure either with or without growth factor pretreatment. After TGF alpha (500 ng/ml) treatment, the intracellular calcium level of hair cells showed a five-fold increase as compared to the levels observed in the hair cells of control cultures. After ototoxin exposure, calcium levels in hair cells of control explants showed an increase relative to their baseline levels, while in the presence of growth factors pretreatment, hair cells showed a relative reduction in calcium levels. Pretreatment of organ of Corti explants afforded significant protection of hair cell stereocilia bundle morphology from ototoxic damage when compared to explants exposed to ototoxin alone. This study correlates a rise in hair cell calcium levels with the otoprotection of hair cells by TGF alpha in organ of Corti explants.

Block of P/Q-type calcium channels by therapeutic concentrations of aminoglycoside antibiotics

Aminoglycoside antibiotics can cause neuromuscular block by inhibiting Ca2+ influx into motor nerve terminals. P/Q-type Ca2+ channels, which are formed by alpha 1A subunits, are mainly responsible for depolarization-dependent presynaptic Ca2+ entry in motor neurons. We therefore investigated the possibility that aminoglycosides function as P/Q-type channel blockers. They inhibited [125I]-omega-CTx-MVIIC binding to P/Q-type channels in guinea pig cerebellum membranes with nanomolar IC50 values (e.g., 8 nM for neomycin). Divalent cations decreased the apparent affinity of neomycin. Barium inward currents through alpha 1A subunits expressed in Xenopus oocytes were partially blocked by therapeutic concentrations of aminoglycosides. This explains that therapeutically relevant concentrations of these drugs decrease the reserve of neuromuscular transmission, which can lead to neuromuscular block. We conclude that micromolar concentrations of aminoglycosides block not only N-type but also P/Q-type channels in mammalian neurons.

Acute presynaptic inhibition by doxorubicin of negative chrono- and inotropic responses to parasympathetic nerve stimulation in isolated, blood-perfused dog atrium

The clinical use of doxorubicin, an anthracycline antineoplastic agent, is limited by its cardiotoxicity. Although several previous reports have shown neurotoxic effects of doxorubicin, there is little information about the acute effects of doxorubicin on the autonomic nerve functions in the heart. Accordingly, to evaluate the effects of doxorubicin on the cardiac responses to autonomic nerve activation, we studied the effects of doxorubicin on the negative chrono- and inotropic responses to intracardiac parasympathetic nerve stimulation and acetylcholine (ACh), and the positive chrono- and inotropic responses to norepinephrine (NE) in the isolated, blood-perfused dog atrium. Doxorubicin (0.01-3 mumol), injected into the sinus node artery of the isolated atrium, induced negative inotropic effects dose dependently and weak negative chronotropic effects. Doxorubicin inhibited the negative chrono- and inotropic responses to parasympathetic nerve stimulation dose dependently. However, doxorubicin affected neither the negative chrono- and inotropic responses to ACh nor the positive chrono- and inotropic responses to NE. These results indicate that doxorubicin interacts with neither muscarinic receptors nor beta-adrenoceptors and suggest that doxorubicin inhibits the negative cardiac responses to parasympathetic nerve activation due to the inhibition of ACh release from nerve varicosities in the heart.