New developments in aminoglycoside therapy and ototoxicity

Preliminary Analysis of Drug-Induced Ototoxicity in South Korea: Trends From a National Sample Dataset

BACKGROUND AND OBJECTIVES

Certain medications are associated with ototoxicity. This study assesses drug-induced ototoxicity in South Korea by analyzing the Korean national health data.

SUBJECTS AND METHODS

Hospital records of National Health Insurance members from 2009 to 2016 were reviewed. Data were compared between patients with and without hearing loss (HL). Individuals with HL were identified as having a primary diagnosis code for sensorineural HL or another type of HL in at least one outpatient or inpatient record according to the International Classification of Diseases-10.

RESULTS

The members in the HL group increased slightly from 0.8% to 1.0% relative to the total sample, compared with 99.2% to 99.0% among the controls. The proportion of males in the HL group ranged from 45.6% to 47.6%, compared with 48.4% to 48.8% among the controls. The proportion of those aged ≥65 years in the HL group increased from 34.1% to 41.4%, compared with 10.6% to 13.3% among the controls. Hypertension prevalence (24.7%-25.7%) in the HL group was higher than that in the control group (12%-12.6%). Diabetes prevalence in the HL group was 10.6%-12.3%, compared with 4.4%-5.9% among the controls. The use of proton pump inhibitor components increased, particularly esomeprazole magnesium trihydrate and rabeprazole sodium, whereas the usage of pantoprazole sodium sesquihydrate and revaprazan was high initially but declined subsequently. The usage of painkillers such as acetaminophen, loxoprofen sodium, and ibuprofen remained high, and antibiotics such as cephalosporins indicated the highest usage. However, the use of penicillin antibiotics such as amoxicillin decreased significantly. Anticancer agents showed relatively low usage compared with other drug categories, whereas antihistamines showed extremely high usage across all years, with a continual increase.

CONCLUSIONS

These correlations and the underlying mechanisms necessitate further investigation, as several medicines have been linked to an increased risk of HL.

Aminoglycoside heteroresistance in Enterobacter cloacae is driven by the cell envelope stress response

Enterobacter cloacae is a Gram-negative nosocomial pathogen of the ESKAPE (Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter spp.) priority group with increasing multi-drug resistance via the acquisition of resistance plasmids. However, E. cloacae can also display forms of antibiotic refractoriness, such as heteroresistance and tolerance. Here, we report that E. cloacae displays transient heteroresistance to aminoglycosides, which is accompanied with the formation of small colony variants (SCVs) with increased minimum inhibitor concentration (MIC) of gentamicin and other aminoglycosides used in the clinic, but not other antibiotic classes. To explore the underlying mechanisms, we performed RNA sequencing of heteroresistant bacteria, which revealed global gene expression changes and a signature of the CpxRA cell envelope stress response. Deletion of the cpxRA two-component system abrogated aminoglycoside heteroresistance and SCV formation, pointing to its indispensable role in these processes. The introduction of a constitutively active allele of cpxA led to high aminoglycoside MICs, consistent with cell envelope stress response driving these behaviors in E. cloacae. Cell envelope stress can be caused by environmental cues, including heavy metals. Indeed, bacterial exposure to copper increased gentamicin MIC in the wild-type but not in the ΔcpxRA mutant. Moreover, copper exposure also elevated the gentamicin MICs of clinical isolates from bloodstream infections, suggesting that CpxRA- and copper-dependent aminoglycoside resistance is broadly conserved in E. cloacae strains. Altogether, we establish that E. cloacae relies on transcriptional reprogramming via the envelope stress response pathway for transient resistance to a major class of frontline antibiotic.IMPORTANCEEnterobacter cloacae is a bacterium that belongs to the WHO high-priority group and an increasing threat worldwide due its multi-drug resistance. E. cloacae can also display heteroresistance, which has been linked to treatment failure. We report that E. cloacae shows heteroresistance to aminoglycoside antibiotics. These are important frontline microbicidal drugs used against Gram-negative bacterial infections; therefore, understanding how resistance develops among sensitive strains is important. We show that aminoglycoside resistance is driven by the activation of the cell envelope stress response and transcriptional reprogramming via the CpxRA two-component system. Furthermore, heterologous activation of envelope stress via copper, typically a heavy metal with antimicrobial actions, also increased aminoglycoside MICs of the E. cloacae type strain and clinical strains isolated from bloodstream infections. Our study suggests aminoglycoside recalcitrance in E. cloacae could be broadly conserved and cautions against the undesirable effects of copper.

Ivacaftor attenuates gentamicin-induced ototoxicity through the CFTR-Nrf2-HO1/NQO1 pathway

OBJECTIVES

Gentamicin is one of the most common ototoxic drugs that can lower patients' quality of life. Oxidative stress is a key factors inducing sensory hair cell death during gentamicin administration. So far, there are no effective drugs to prevent or treat gentamicin- induced hearing loss. A recent study found cystic fibrosis transmembrane conductance regulator (CFTR) as a new target to modulate cellular oxidative balance. The objective of this study was to estimate the effect of the CFTR activator ivacaftor on gentamicin-induced ototoxicity and determine its mechanism.

METHODS

The hair cell count was analyzed by Myosin 7a staining. Apoptosis was analyzed by TUNEL Apoptosis Kit. Cellular reactive oxygen species (ROS) level was detected by DCFH-DA probes. The Nrf2 related proteins expression levels were analyzed by western blot.

RESULTS

An in vitro cochlear explant model showed that gentamicin caused ROS accumulation in sensory hair cells and induced apoptosis, and this effect was alleviated by pretreatment with ivacaftor. Western blotting showed that ivacaftor administration markedly increased the protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO1), and NAD(P)H:quinone oxidoreductase 1 (NQO1). The protective effect of ivacaftor was abolished by the Nrf2 inhibitor ML385.

DISCUSSION

Our results indicate the protective role of the CFTR-Nrf2-HO1/NQO1 pathway in gentamicin-induced ototoxicity. Ivacaftor may be repositioned or repurposed towards aminoglycosides-induced hearing loss.

Predictive model for aminoglycoside induced ototoxicity

Background

Irreversible hearing loss is a well-known adverse effect of aminoglycosides, however, inability to accurately predict ototoxicity is a major limitation in clinical care. We addressed this limitation by developing a prediction model for aminoglycoside ototoxicity applicable to the general population.

Methods

We employed a prospective non-drug-resistant tuberculosis (TB), non-HIV/AIDS cohort of 153 adults on Streptomycin based anti-TB therapy. High frequency pure-tone audiometry was done at regular intervals throughout the study. Clinical and audiological predictors of ototoxicity were collated and ototoxic threshold shift from the baseline audiogram computed. The prediction model was developed with logistic regression method by examining multiple predictors of ototoxicity. Series of models were fitted sequentially; the best model was identified using Akaike Information Criterion and likelihood ratio test. Key variables in the final model were used to develop a logit model for ototoxicity prediction.

Results

Ototoxicity occurred in 35% of participants. Age, gender, weight, cumulative Streptomycin dosage, social class, baseline pure tone average (PTA) and prior hearing symptoms were explored as predictors. Multiple logistic regression showed that models with age, cumulative dosage and baseline PTA were best for predicting ototoxicity. Regression parameters for ototoxicity prediction showed that yearly age increment raised ototoxicity risk by 5% (AOR = 1.05; CI, 1.01-1.09), and a gram increase in cumulative dosage increased ototoxicity risk by 7% (AOR = 1.05; CI, 1.05-1.12) while a unit change in baseline log (PTA) was associated 254% higher risk of ototoxicity (AOR = 3.54, CI: 1.25, 10.01). Training and validation models had area under the receiver operating characteristic curve as 0.84 (CI, 0.76-0.92) and 0.79 (CI, 0.62-0.96) respectively, showing the model has discriminatory ability.

Conclusion

This model can predict aminoglycoside ototoxicity in the general population.

Re-telling the story of aminoglycoside ototoxicity: tales from sub-Saharan Africa

Background

Aminoglycosides, such as Streptomycin, are cheap, potent antibiotics widely used Sub-Saharan Africa. However, aminoglycosides are the commonest cause of ototoxicity. The limited prospective epidemiological studies on aminoglycoside ototoxicity from Sub-Saharan Africa motivated this study to provide epidemiological information on Streptomycin-induced ototoxicity, identify risk factors and predictors of ototoxicity.

Method

A longitudinal study of 153 adults receiving Streptomycin-based anti-tuberculous drugs was done. All participants underwent extended frequency audiometry and had normal hearing thresholds at baseline. Hearing thresholds were assessed weekly for 2 months, then monthly for the subsequent 6 months. Ototoxicity was determined using the ASHA criteria. Descriptive statistics were used to analyze socio-demographic variables. Ototoxicity incidence rate was calculated, and Kaplan-Meier estimate used to determine cumulative probability of ototoxicity. Chi-square test was done to determine parameters associated with ototoxicity and Cox regression models were used to choose the predictors of ototoxicity.

Results

Age of participants was 41.43 ± 12.66 years, with a male-to-female ratio of 1:0.6. Ototoxicity was found in 34.6% of the participants, giving an incidence of 17.26 per 1,000-person-week. The mean onset time to ototoxicity was 28.0 ± 0.47 weeks. By 28th week, risk of developing ototoxicity for respondents below 40 years of age was 0.29, and for those above 40 years was 0.77. At the end of the follow-up period, the overall probability of developing ototoxicity in the study population was 0.74. A significant difference in onset of ototoxicity was found between the age groups: the longest onset was seen in <40 years, followed by 40-49 years, and shortest onset in ≥50 years. Hazard of ototoxicity was significantly higher in participants aged ≥50 years compared to participants aged ≤40 years (HR = 3.76, 95% CI = 1.84-7.65). The probability of ototoxicity at 40 g, 60 g and 80 g cumulative dose of Streptomycin was 0.08, 0.43 and 2.34, respectively. Age and cumulative dose were significant predictors of ototoxicity.

Conclusion

The mean onset time to Streptomycin-induced ototoxicity was 28 weeks after commencement of therapy. Age and cumulative dose can reliably predict the onset of Streptomycin-induced ototoxicity. Medium to long term monitoring of hearing is advised for patients on aminoglycoside therapy.

A New Perspective to Interpret How the Vestibular Efferent System Correlates the Complexity of Routine Balance Maintenance with Management of Emergency Fall Prevention Strategies

Bipedalism is unique among mammals. Until modern times, a fall and resulting leg fracture could be fatal. Balance maintenance after a destabilizing event requires instantaneous decision making. The vestibular system plays an essential role in this process, initiating an emergency response. The afferent otolithic neural response is the first directionally oriented information to reach the cortex, and it can then be used to initiate an appropriate protective response. Some vestibular efferent axons feed directly into type I vestibular hair cells. This allows for rapid vestibular feedback via the striated organelle (STO), which has been largely ignored in most texts. We propose that this structure is essential in emergency fall prevention, and also that the system of sensory detection and resultant motor response works by having efferent movement information simultaneously transmitted to the maculae with the movement commands. This results in the otolithic membrane positioning itself precisely for the planned movement, and any error is due to an unexpected external cause. Error is fed back via the vestibular afferent system. The efferent system causes macular otolithic membrane movement through the STO, which occurs simultaneously with the initiating motor command. As a result, no vestibular afferent activity occurs unless an error must be dealt with.

Ototoxic and nephrotoxic drugs in neonatal intensive care units: results of a Spanish and Italian survey

Neonates face heightened susceptibility to drug toxicity, often exposed to off-label medications with dosages extrapolated from adult or pediatric studies. Premature infants in Neonatal Intensive Care Units (NICUs) are particularly at risk due to underdeveloped pharmacokinetics and exposure to multiple drugs. The study aimed to survey commonly used medications with a higher risk of ototoxicity and nephrotoxicity in Spanish and Italian neonatal units. A prospective cross-sectional study was conducted in Italian and Spanish neonatal units using a web-based survey with 43 questions. A modified Delphi method involved experts refining the survey through online consensus. Ethical approval was obtained, and responses were collected from January to July 2023. The survey covered various aspects, including drug-related ototoxic and nephrotoxic management, hearing screening, and therapeutic drug monitoring. Responses from 131 participants (35.9% from Spain and 64.1% from Italy) revealed awareness of drug toxicity risks. Varied practices were observed in hearing screening protocols, and a high prevalence of ototoxic and nephrotoxic drug use, including aminoglycosides (100%), vancomycin (70.2%), loop diuretics (63.4%), and ibuprofen (62.6%). Discrepancies existed in guideline availability and adherence, with differences between Italy and Spain in therapeutic drug monitoring practices.

CONCLUSIONS

The study underscores the need for clinical guidelines and uniform practices in managing ototoxic and nephrotoxic drugs in neonatal units. Awareness is high, but inconsistencies in practices indicate a necessity for standardization, including the implementation of therapeutic drug monitoring and the involvement of clinical pharmacologists. Addressing these issues is crucial for optimizing neonatal care in Southern Europe.

WHAT IS KNOWN

• Neonates in intensive care face a high risk of nephrotoxicity and ototoxicity from drugs like aminoglycosides, vancomycin, loop diuretics, and ibuprofen. • Therapeutic drug monitoring is key for managing these risks, optimizing dosing for efficacy and minimizing side effects.

WHAT IS NEW

• NICUs in Spain and Italy show high drug toxicity awareness but differ in ototoxic/nephrotoxic drug management. • Urgent need for standard guidelines and practices to address nephrotoxic risks from aminoglycosides, vancomycin, loop diuretics, and ibuprofen.

Role of Memantine in Limiting Cochleotoxicity in Rats

Οur aim was to test whether amikacin's well-known cochleotoxic effects could be suppressed, depending on whether an NMDA-antagonist (memantine) was administered simultaneously with or after amikacin treatment. Forty Wistar rats were used in this experiment. Ten rats acted as controls and received no medication (group A). Amikacin (200 mg/kg) was administered intraperitoneally (i.p.) once daily for 14 days to 10 animals in group B; amikacin (200 mg/kg) was administered concurrently with memantine (10 mg/kg, i.p., once daily) to the same 10 animals in group C. Group D was given intraperitoneal memantine (10 mg/kg, once daily) for 14 days following a 2-week amikacin treatment. The cochlear activity of the right ear was tested using DPOAE in conscious animals. All animals were sacrificed at the conclusion of the experiment and both cochleae were collected for histological and immunohistochemical analysis. All groups treated with amikacin showed decreased cochlear activity, as testified by decreased DPOAE-amplitudes compared to the pre-treatment state. In the rats of group B, the DPOAE reduction was more pronounced. On histologic exam, the cochlear structures of group C rats and, although to a lesser extent, group D rats showed less severe cochlea damage. Memantine plays a protective role, resulting in restoring partially cochlear structures when administered either simultaneously with or after completion of amikacin i.p. treatment in rats.

A Consolidated Understanding of the Contribution of Redox Dysregulation in the Development of Hearing Impairment

The etiology of hearing impairment is multifactorial, with contributions from both genetic and environmental factors. Although genetic studies have yielded valuable insights into the development and function of the auditory system, the contribution of gene products and their interaction with alternate environmental factors for the maintenance and development of auditory function requires further elaboration. In this review, we provide an overview of the current knowledge on the role of redox dysregulation as the converging factor between genetic and environmental factor-dependent development of hearing loss, with a focus on understanding the interaction of oxidative stress with the physical components of the peripheral auditory system in auditory disfunction. The potential involvement of molecular factors linked to auditory function in driving redox imbalance is an important promoter of the development of hearing loss over time.

Integrated Preparation of Hollow Lignin Nanoparticles as a Drug Carrier and Levulinic Acid from the Poplar Wood Prehydrolysis Liquor

Prehydrolysis liquid (PHL) from dissolving pulp and biorefinery industries is rich in saccharides and lignin, being considered as a potential source of value-added materials and platform molecules. This study proposed an environmentally friendly and simple method to prepare morphologically controllable hollow lignin nanoparticles (LNPs) and levulinic acid (LA) from PHL. In the first step, after hydrothermal treatment of PHL with p-toluenesulfonic acid (p-TsOH), lignin with a uniform molecular weight was obtained to prepare LNPs. The prepared LNPs have an obvious hollow structure, with an average size of 490-660 nm, and exhibit good stability during 30 days of storage. When the as-obtained LNPs were used as a sustained-release agent for amikacin sulfate, the encapsulation efficiency reached over 70% and the release efficiency within 40 h reached 69.2% in a pH 5.5 buffer. Subsequently, the remaining PHL that contains saccharides was directly used for LA production under the catalysis of p-TsOH. At 150 °C for 1.5 h, the LA yield reached 58.4% and remained at 56% after 5 cycles of p-TsOH. It is worth noting that only p-TsOH was used as a reactive reagent throughout the entire preparation process. Overall, this study provided a novel pathway for the integrated utilization of PHL and showed the immense potential of the preparation and application of LNPs.

Ototoxicity: a high risk to auditory function that needs to be monitored in drug development

Hearing loss constitutes a major global health concern impacting approximately 1.5 billion people worldwide. Its incidence is undergoing a substantial surge with some projecting that by 2050, a quarter of the global population will experience varying degrees of hearing deficiency. Environmental factors such as aging, exposure to loud noise, and the intake of ototoxic medications are implicated in the onset of acquired hearing loss. Ototoxicity resulting in inner ear damage is a leading cause of acquired hearing loss worldwide. This could be minimized or avoided by early testing of hearing functions in the preclinical phase of drug development. While the assessment of ototoxicity is well defined for drug candidates in the hearing field - required for drugs that are administered by the otic route and expected to reach the middle or inner ear during clinical use - ototoxicity testing is not required for all other therapeutic areas. Unfortunately, this has resulted in more than 200 ototoxic marketed medications. The aim of this publication is to raise awareness of drug-induced ototoxicity and to formulate some recommendations based on available guidelines and own experience. Ototoxicity testing programs should be adapted to the type of therapy, its indication (targeting the ear or part of other medications classes being potentially ototoxic), and the number of assets to test. For multiple molecules and/or multiple doses, screening options are available: in vitro (otic cell assays), ex vivo (cochlear explant), and in vivo (in zebrafish). In assessing the ototoxicity of a candidate drug, it is good practice to compare its ototoxicity to that of a well-known control drug of a similar class. Screening assays provide a streamlined and rapid method to know whether a drug is generally safe for inner ear structures. Mammalian animal models provide a more detailed characterization of drug ototoxicity, with a possibility to localize and quantify the damage using functional, behavioral, and morphological read-outs. Complementary histological measures are routinely conducted notably to quantify hair cells loss with cochleogram. Ototoxicity studies can be performed in rodents (mice, rats), guinea pigs and large species. However, in undertaking, or at the very least attempting, all preclinical investigations within the same species, is crucial. This encompasses starting with pharmacokinetics and pharmacology efficacy studies and extending through to toxicity studies. In life read-outs include Auditory Brainstem Response (ABR) and Distortion Product OtoAcoustic Emissions (DPOAE) measurements that assess the activity and integrity of sensory cells and the auditory nerve, reflecting sensorineural hearing loss. Accurate, reproducible, and high throughput ABR measures are fundamental to the quality and success of these preclinical trials. As in humans, in vivo otoscopic evaluations are routinely carried out to observe the tympanic membrane and auditory canal. This is often done to detect signs of inflammation. The cochlea is a tonotopic structure. Hair cell responsiveness is position and frequency dependent, with hair cells located close to the cochlea apex transducing low frequencies and those at the base transducing high frequencies. The cochleogram aims to quantify hair cells all along the cochlea and consequently determine hair cell loss related to specific frequencies. This measure is then correlated with the ABR & DPOAE results. Ototoxicity assessments evaluate the impact of drug candidates on the auditory and vestibular systems, de-risk hearing loss and balance disorders, define a safe dose, and optimize therapeutic benefits. These types of studies can be initiated during early development of a therapeutic solution, with ABR and otoscopic evaluations. Depending on the mechanism of action of the compound, studies can include DPOAE and cochleogram. Later in the development, a GLP (Good Laboratory Practice) ototoxicity study may be required based on otic related route of administration, target, or known potential otic toxicity.

Genetic Variations and Antibiotic-Related Adverse Events

Antibiotic-related adverse events are common in both adults and children, and knowledge of the factors that favor the development of antibiotic-related adverse events is essential to limit their occurrence and severity. Genetics can condition the development of antibiotic-related adverse events, and the screening of patients with supposed or demonstrated specific genetic mutations may reduce drug-related adverse events. This narrative review discusses which genetic variations may influence the risk of antibiotic-related adverse events and which conclusions can be applied to clinical practice. An analysis of the literature showed that defined associations between genetic variations and specific adverse events are very few and that, at the moment, none of them have led to the implementation of a systematic screening process for patients that must be treated with a given antibiotic in order to select those at risk of specific adverse events. On the other hand, in most of the cases, more than one variation is implicated in the determination of adverse events, and this can be a limitation in planning a systematic screening. Moreover, presently, the methods used to establish whether a patient carries a "dangerous" genetic mutation require too much time and waiting for the result of the test can be deleterious for those patients urgently requiring therapy. Further studies are needed to definitively confirm which genetic variations are responsible for an increased risk of a well-defined adverse event.

Protective role of pyrroloquinoline quinone against gentamicin induced cochlear hair cell ototoxicity

Gentamicin (GM) is one of the commonly used antibiotics in the aminoglycoside class but is ototoxic, which constantly impacts the quality of human life. Pyrroloquinoline quinone (PQQ) as a redox cofactor produced by bacteria was found in soil and foods that exert an antioxidant and redox modulator. It is well documented that the PQQ can alleviate inflammatory responses and cytotoxicity. However, our understanding of PQQ in ototoxicity remains unclear. We reported that PQQ could protect against GM-induced ototoxicity in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells in vitro. To evaluate reactive oxygen species (ROS) production and mitochondrial function, ROS and JC-1 staining, oxygen consumption rate (OCR), and extracellular acidification rate (ECAR) measurements in living cells, mitochondrial dynamics analysis was performed. GM-mediated damage was performed by reducing the production of ROS and inhibiting mitochondria biogenesis and dynamics. PQQ ameliorated the cellular oxidative stress and recovered mitochondrial membrane potential, facilitating the recovery of mitochondrial biogenesis and dynamics. Our in vitro findings improve our understanding of the GM-induced ototoxicity with therapeutic implications for PQQ.

Development of Chinese herbal medicine for sensorineural hearing loss

According to the World Health Organization's world report on hearing, nearly 2.5 billion people worldwide will suffer from hearing loss by 2050, which may contribute to a severe impact on individual life quality and national economies. Sensorineural hearing loss (SNHL) occurs commonly as a result of noise exposure, aging, and ototoxic drugs, and is pathologically characterized by the impairment of mechanosensory hair cells of the inner ear, which is mainly triggered by reactive oxygen species accumulation, inflammation, and mitochondrial dysfunction. Though recent advances have been made in understanding the ability of cochlear repair and regeneration, there are still no effective therapeutic drugs for SNHL. Chinese herbal medicine which is widely distributed and easily accessible in China has demonstrated a unique curative effect against SNHL with higher safety and lower cost compared with Western medicine. Herein we present trends in research for Chinese herbal medicine for the treatment of SNHL, and elucidate their molecular mechanisms of action, to pave the way for further research and development of novel effective drugs in this field.

Otoprotection against aminoglycoside- and cisplatin-induced ototoxicity focusing on the upstream drug uptake pathway

Aminoglycoside- and cisplatin-induced ototoxicity, which is a significant issue owing to the widespread use of these drugs in clinical practice, involves the entry of aminoglycosides and cisplatin into the endolymph and hair cells via specific channels or transporters, followed by reactive oxygen species (ROS) generation and hair cells apoptosis. Current strategies focalize primarily on interference with downstream ROS effects; however, recent evidence has demonstrated that inhibiting the uptake of aminoglycosides and cisplatin by hair cells is another promising strategy for tackling the upstream drug uptake pathway. With advances in structural biology, the conformations of certain aminoglycoside and cisplatin channels and transporters, such as the mechanoelectrical transduction channel and organic cation transporter-2, have been largely elucidated. These channels and transporters may become potential targets for the introduction of new otoprotective strategies. This review focuses on the strategies for inhibiting ototoxic drugs uptake by auditory hair cells and provides potential targets for recent developments in the field of otoprotection. Molecular dynamics (MD) simulations of these proteins could help identify the molecules that inhibit the uptake of aminoglycosides and cisplatin by hair cells. Integrating upstream drug uptake pathway targets and MD simulations may help dissect molecular mechanisms and develop novel otoprotective strategies for aminoglycoside- and cisplatin-induced ototoxicity.

Aminoglycosides: Single- or Multiple-daily Dosing? An Updated Qualitative Systematic Review of Randomized Trials on Toxicity and Efficacy

INTRODUCTION

Aminoglycosides are among the first-choice antibiotics for routine clinical use. However, dose-limiting factors such as ototoxicity and nephrotoxicity are considered as serious complications of aminoglycosides.

OBJECTIVE

In this systematic review, the main goal was to investigate the efficacy and incidence of nephrotoxicity and ototoxicity of once-daily dosing (ODD) and multiple daily dosing (MDD) regimens of aminoglycosides through available randomized controlled trials (RCTs).

METHODS

We performed a literature-based research in relevant databases, including EMBASE, MEDLINE, and SCOPUS published between 1987 and 2023 using the keywords "aminoglycosides", "pharmacokinetics", "ODD", "MDD", "once daily", "multiple daily", "dosing regimen", "nephrotoxicity", "ototoxicity", "efficacy", "safety", and "toxicity". As so told, the results of this article were limited to papers available in English. Our initial search yielded 1124 results. After a review of the titles and abstracts of the articles, 803 articles were excluded from this study because they did not address the toxicity and effectiveness of ODD versus MDD of aminoglycosides. A total number of 20 studies on gentamicin, tobramycin, netilmicin, and amikacin met the inclusion criteria for the efficacy of aminoglycosides and their role in ototoxicity and nephrotoxicity were included in this review. Studies recruited different age classes, and the age of relevant cohorts varied from only a few days to more than 70 years.

RESULTS

The most common clinical condition in the included studies was cystic fibrosis.

CONCLUSION

In most studies, there were no significant differences between the two regimens regarding ototoxicity. In addition, the ODD regimens were safer than MDD concerning nephrotoxicity.

6'-sialyllactose ameliorates the ototoxic effects of the aminoglycoside antibiotic neomycin in susceptible mice

Sialic acids are terminal sugars of the cellular glycocalyx and are highly abundant in the nervous tissue. Sialylation is sensed by the innate immune system and acts as an inhibitory immune checkpoint. Aminoglycoside antibiotics such as neomycin have been shown to activate tissue macrophages and induce ototoxicity. In this study, we investigated the systemic subcutaneous application of the human milk oligosaccharide 6'-sialyllactose (6SL) as a potential therapy for neomycin-induced ototoxicity in postnatal mice. Repeated systemic treatment of mice with 6SL ameliorated neomycin-induced hearing loss and attenuated neomycin-triggered macrophage activation in the cochlear spiral ganglion. In addition, 6SL reversed the neomycin-mediated increase in gene transcription of the pro-inflammatory cytokine interleukin-1β (Il-1b) and the apoptotic/inflammatory kinase Pik3cd in the inner ear. Interestingly, neomycin application also increased the transcription of desialylating enzyme neuraminidase 3 (Neu3) in the inner ear. In vitro, we confirmed that treatment with 6SL had anti-inflammatory, anti-phagocytic, and neuroprotective effects on cultured lipopolysaccharide-challenged human THP1-macrophages. Thus, our data demonstrated that treatment with 6SL has anti-inflammatory and protective effects against neomycin-mediated macrophage activation and ototoxicity.

Risk assessment of Enterococcus faecium, Klebsiella pneumoniae, and Pseudomonas aeruginosa in environmental water sources: Development of surrogate models for antibiotic resistance genes

The presence of Enterococcus faecium (E. faecium), Klebsiella pneumoniae (K. pneumoniae), Pseudomonas aeruginosa (P. aeruginosa), and the aminoglycoside resistance genes, aac(6')-Ib and aac(6')-aph(2″), was investigated in environmental water sources obtained from informal settlements in the Western Cape (South Africa). Using ethidium monoazide bromide quantitative polymerase chain reaction (EMA-qPCR) analysis, E. faecium, K. pneumoniae, and P. aeruginosa were detected in 88.9 %, 100 %, and 93.3 % of the samples (n = 45), respectively, with a significantly higher mean concentration recorded for K. pneumoniae (7.83 × 104 cells/100 mL) over the sampling period. The aac(6')-Ib gene was detected in 95.6 % (43/45) of the environmental water samples [mean concentration of 7.07 × 106 gene copies (GC)/100 mL], while the aac(6')-aph(2″) gene was detected in 100 % (n = 45) of the samples [mean concentration of 6.68 × 105 GC/100 mL]. Quantitative microbial risk assessment (QMRA) subsequently indicated that the risks posed by K. pneumoniae and P. aeruginosa were linked to intentional drinking, washing/bathing, cleaning of the home, and swimming, in the samples collected from the various sampling sites. Surrogate risk assessment models were then designed and applied for Gram-positive [aac(6')-aph(2″) gene] and Gram-negative [aac(6')-Ib gene] pathogens that may exhibit aminoglycoside resistance. The results indicated that only the Gram-negative pathogens posed a risk (>10-4) in all the samples for cleaning of the home and intentional drinking, as well as for washing laundry by hand, garden hosing, garden work, washing/bathing, accidental consumption, and swimming at the stream and marsh sites. Thus, while environmental waters may pose a health risk of exposure to pathogenic bacteria, the results obtained indicate that screening for antibiotic resistant genes, associated with multiple genera/species, could serve as a surrogate model for estimating risks with the target group under investigation.

The Relevance of Autophagy within Inner Ear in Baseline Conditions and Tinnitus-Related Syndromes

Tinnitus is the perception of noise in the absence of acoustic stimulation (phantom noise). In most patients suffering from chronic peripheral tinnitus, an alteration of outer hair cells (OHC) starting from the stereocilia (SC) occurs. This is common following ototoxic drugs, sound-induced ototoxicity, and acoustic degeneration. In all these conditions, altered coupling between the tectorial membrane (TM) and OHC SC is described. The present review analyzes the complex interactions involving OHC and TM. These need to be clarified to understand which mechanisms may underlie the onset of tinnitus and why the neuropathology of chronic degenerative tinnitus is similar, independent of early triggers. In fact, the fine neuropathology of tinnitus features altered mechanisms of mechanic-electrical transduction (MET) at the level of OHC SC. The appropriate coupling between OHC SC and TM strongly depends on autophagy. The involvement of autophagy may encompass degenerative and genetic tinnitus, as well as ototoxic drugs and acoustic trauma. Defective autophagy explains mitochondrial alterations and altered protein handling within OHC and TM. This is relevant for developing novel treatments that stimulate autophagy without carrying the burden of severe side effects. Specific phytochemicals, such as curcumin and berberin, acting as autophagy activators, may mitigate the neuropathology of tinnitus.

Aminoglycosides-Related Ototoxicity: Mechanisms, Risk Factors, and Prevention in Pediatric Patients

Aminoglycosides are broad-spectrum antibiotics largely used in children, but they have potential toxic side effects, including ototoxicity. Ototoxicity from aminoglycosides is permanent and is a consequence of its action on the inner ear cells via multiple mechanisms. Both uncontrollable risk factors and controllable risk factors are involved in the pathogenesis of aminoglycoside-related ototoxicity and, because of the irreversibility of ototoxicity, an important undertaking for preventing ototoxicity includes antibiotic stewardship to limit the use of aminoglycosides. Aminoglycosides are fundamental in the treatment of numerous infectious conditions at neonatal and pediatric age. In childhood, normal auditory function ensures adequate neurocognitive and social development. Hearing damage from aminoglycosides can therefore strongly affect the normal growth of the child. This review describes the molecular mechanisms of aminoglycoside-related ototoxicity and analyzes the risk factors and the potential otoprotective strategies in pediatric patients.

Age-related hearing loss and its potential drug candidates: a systematic review

BACKGROUND

Age-related hearing loss (ARHL) is one of the main illnesses afflicting the aged population and has a significant negative impact on society, economy, and health. However, there is presently no appropriate therapeutic treatment of ARHL due to the absence of comprehensive trials.

OBJECTIVES

The goal of this review is to systematically evaluate and analyze recent statistics on the pathologic classifications, risk factors, treatment strategies, and drug candidates of ARHL, including that from traditional Chinese medicine (TCM), to provide potential new approaches for preventing and treating ARHL.

METHODS

Literature related to ARHL was conducted in databases such as PubMed, WOS, China National Knowledge Infrastructure (CNKI), and Wanfang from the establishment of the database to Jan, 2023. The pathology, causal factor, pathophysiological mechanism, treatment strategy, and the drug candidate of ARHL were extracted and pooled for synthesis.

RESULTS

Many hypotheses about the etiology of ARHL are based on genetic and environmental elements. Most of the current research on the pathology of ARHL focuses on oxidative damage, mitochondrial dysfunction, inflammation, cochlear blood flow, ion homeostasis, etc. In TCM, herbs belonging to the kidney, lung, and liver meridians exhibit good hearing protection. Seven herbs belonging to the kidney meridian, 9 belonging to the lung meridian, and 4 belonging to the liver meridian were ultimately retrieved in this review, such as Polygonum multiflorum Thunb., Panax ginseng C.A. Mey, and Pueraria lobata (Willd.) Ohwi. Their active compounds, 2,3,4',5-Tetrahydroxystilbene-2-O-D-glucoside, ginsenoside Rb1, and puerarin, may act as the molecular substance for their anti-ARHL efficacy, and show anti-oxidative, neuroprotective, anti-inflammatory, anti-apoptotic, or mitochondrial protective effects.

CONCLUSION

Anti-oxidants, modulators of mitochondrial function, anti-inflammation agents, vasodilators, K+ channel openers, Ca2+ channel blockers, JNK inhibitors, and nerve growth factors/neurotrophic factors all contribute to hearing protection, and herbs are an important source of potential anti-ARHL drugs.

Off target toxicities and links with physicochemical properties of medicinal products, including antibiotics, oligonucleotides, lipid nanoparticles (with cationic and/or anionic charges). Data review suggests an emerging pattern

Toxicology is an essential part of any drug development plan. Circumnavigating the risk of failure because of a toxicity issue can be a challenge, and failure in late development is extremely costly. To identify potential risks, it requires more than just understanding the biological target. The toxicologist needs to consider a compound's structure, it's physicochemical properties (including the impact of the overall formulation), as well as the biological target (e.g., receptor interactions). Understanding the impact of the physicochemical properties can be used to predict potential toxicities in advance by incorporating key endpoints in early screening strategies and/or used to compare toxicity profiles across lead candidates. This review discussed the risks of off-target and/or non-specific toxicities that may be associated with the physicochemical properties of compounds, especially those carrying dominant positive or negative charges, including amphiphilic small molecules, peptides, oligonucleotides and lipids/liposomes/lipid nanoparticles. The latter of which are being seen more and more in drug development, including the recent Covid pandemic, where mRNA and lipid nanoparticle technology is playing more of a role in vaccine development. The translation between non-clinical and clinical data is also considered, questioning how a physicochemical driven toxicity may be more universal across species, which means that such toxicity may be reassuringly translatable between species and as such, this information may also be considered as a support to the 3 R's, particularly in the early screening stages of a drug development plan.

MRPL12-ANT3 interaction involves in acute kidney injury via regulating MPTP of tubular epithelial cells

Acute kidney injury (AKI) is a serious disease with no effective treatment. Abnormal opening of mitochondrial permeability transition pore (MPTP) is an important pathological process in ischemia reperfusion injury (IRI), the key factor of AKI. It is essential to elucidate MPTP regulation mechanism. Here, we identified mitochondrial ribosomal protein L7/L12 (MRPL12) specifically binds to adenosine nucleotide translocase 3 (ANT3) under normal physiological conditions, stabilizes MPTP and maintains mitochondrial membrane homeostasis in renal tubular epithelial cells (TECs). During AKI, MRPL12 expression was significantly decreased in TECs, and MRPL12-ANT3 interaction was reduced, leading to ANT3 conformation change, MPTP abnormal opening, and cell apoptosis. Importantly, MRPL12 overexpression protected TECs from MPTP abnormal opening and apoptosis during hypoxia/reoxygenation (H/R). Our results suggest MRPL12-ANT3 axis involves in AKI by regulating MPTP, and MRPL12 could be potential intervention target for treatment of AKI.

Immunotherapy and immunochemotherapy in combating visceral leishmaniasis

Visceral leishmaniasis (VL), a vector-borne disease, is caused by an obligate intramacrophage, kinetoplastid protozoan parasite of the genus Leishmania. Globally, VL is construed of diversity and complexity concerned with high fatality in tropics, subtropics, and Mediterranean regions with ~50,000-90,000 new cases annually. Factors such as the unavailability of licensed vaccine(s), insubstantial measures to control vectors, and unrestrained surge of drug-resistant parasites and HIV-VL co-infections lead to difficulty in VL treatment and control. Furthermore, VL treatment, which encompasses several problems including limited efficacy, emanation of drug-resistant parasites, exorbitant therapy, and exigency of hospitalization until the completion of treatment, further exacerbates disease severity. Therefore, there is an urgent need for the development of safe and efficacious therapies to control and eliminate this devastating disease. In such a scenario, biotherapy/immunotherapy against VL can become an alternative strategy with limited side effects and no or nominal chance of drug resistance. An extensive understanding of pathogenesis and immunological events that ensue during VL infection is vital for the development of immunotherapeutic strategies against VL. Immunotherapy alone or in combination with standard anti-leishmanial chemotherapeutic agents (immunochemotherapy) has shown better therapeutic outcomes in preclinical studies. This review extensively addresses VL treatment with an emphasis on immunotherapy or immunochemotherapeutic strategies to improve therapeutic outcomes as an alternative to conventional chemotherapy.

Colistin- and amikacin-loaded lipid-based drug delivery systems for resistant gram-negative lung and wound bacterial infections

Antimicrobial resistance (AMR) is a global health issue, which needs to be tackled without further delay. The World Health Organization(WHO) has classified three gram-negative bacteria, Pseudomonas aeruginosa, Klebsiella pneumonia and Acinetobacter baumannii, as the principal responsible for AMR, mainly causing difficult to treat nosocomial lung and wound infections. In this regard, the need for colistin and amikacin, the re-emerged antibiotics of choice for resistant gram-negative infections, will be examined as well as their associated toxicity. Thus, current but ineffective clinical strategies designed to prevent toxicity related to colistin and amikacin will be reported, highlighting the importance of lipid-based drug delivery systems (LBDDSs), such as liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs), as efficient delivery strategies for reducing antibiotic toxicity. This review reveals that colistin- and amikacin-NLCs are promising carriers with greater potential than liposomes and SLNs to safely tackle AMR, especially for lung and wound infections.

Recoding of Nonsense Mutation as a Pharmacological Strategy

Approximately 11% of genetic human diseases are caused by nonsense mutations that introduce a premature termination codon (PTC) into the coding sequence. The PTC results in the production of a potentially harmful shortened polypeptide and activation of a nonsense-mediated decay (NMD) pathway. The NMD pathway reduces the burden of unproductive protein synthesis by lowering the level of PTC mRNA. There is an endogenous rescue mechanism that produces a full-length protein from a PTC mRNA. Nonsense suppression therapies aim to increase readthrough, suppress NMD, or are a combination of both strategies. Therefore, treatment with translational readthrough-inducing drugs (TRIDs) and NMD inhibitors may increase the effectiveness of PTC suppression. Here we discuss the mechanism of PTC readthrough and the development of novel approaches to PTC suppression. We also discuss the toxicity and bioavailability of therapeutics used to stimulate PTC readthrough.

Otoprotective Effects of Fucoidan Reduce Cisplatin-Induced Ototoxicity in Mouse Cochlear UB/OC-2 Cells

Cisplatin is a widely used standard chemotherapy for various cancers. However, cisplatin treatment is associated with severe ototoxicity. Fucoidan is a complex sulfated polysaccharide mainly derived from brown seaweeds, and it shows multiple bioactivities such as antimicrobial, anti-inflammatory, anticancer, and antioxidant activities. Despite evidence of the antioxidant effects of fucoidan, research on its otoprotective effects remains limited. Therefore, the present study investigated the otoprotective effects of fucoidan in vitro using the mouse cochlear cell line UB/OC-2 to develop new strategies to attenuate cisplatin-induced ototoxicity. We quantified the cell membrane potential and analyzed regulators and cascade proteins in the apoptotic pathway. Mouse cochlear UB/OC-2 cells were pre-treated with fucoidan before cisplatin exposure. The effects on cochlear hair cell viability, mitochondrial function, and apoptosis-related proteins were determined via flow cytometry, Western blot analysis, and fluorescence staining. Fucoidan treatment reduced cisplatin-induced intracellular reactive oxygen species production, stabilized mitochondrial membrane potential, inhibited mitochondrial dysfunction, and successfully protected hair cells from apoptosis. Furthermore, fucoidan exerted antioxidant effects against oxidative stress by regulating the Nrf2 pathway. Therefore, we suggest that fucoidan may represent a potential therapeutic agent for developing a new otoprotective strategy.

Physicochemical properties of otic products for Canine Otitis Externa: comparative analysis of marketed products

BACKGROUND

Otitis externa is a commonly diagnosed dermatological disorder in canines. The pathogens primarily involved in canine otitis externa (COE) include Staphylococcus pseudintermedius, Pseudomonas aeruginosa, Proteus mirabilis, and Malassezia pachydermatis. As COE tends to be superficial, medications delivered topically are often effective and practical in managing the condition. As such, there is a wide variety of approved topical products currently available in the market. The efficacy of topical dosage forms can be dependent on various factors such as the pharmacology of active constituents and the physicochemical properties of the formulation, including pH, viscosity, spreadability, and bio-adhesion. Currently, there is a lack of published literature available on the optimal properties of topical COE products. In this study, we compared the physicochemical properties of nine commercially available otic veterinarian products in Australia used clinically to manage COE.

RESULTS

Based on our comparative analysis, the pH (6.26 ± 0.04) of an aqueous-based product was similar to a healthy dog's external auditory canal. Products containing polymers exhibited higher viscosity and bio-adhesion. Spreadability was inversely related to viscosity and Osurnia ® a product with high viscosity demonstrated the lowest spreadability. Aqueous-based otic products showed better syringebility whereas oil-based systems required higher force to expel the products. Variability in droplet size was noted. Derm Otic, Baytril Otic, and Aurizon Ear Drops had the lower standard deviation which indicates they would give a more consistent dose.

CONCLUSIONS

Findings from this work provide considerations for industry researchers or formulation scientists working in the area of otic dosage formulations.

Amphiphilic aminoglycosides: Modifications that revive old natural product antibiotics

Widely-used Streptomyces-derived antibacterial aminoglycosides have encountered challenges because of antibiotic resistance and toxicity. Today, they are largely relegated to medicinal topical applications. However, chemical modification to amphiphilic aminoglycosides can revive their efficacy against bacterial pathogens and expand their targets to other pathogenic microbes and disorders associated with hyperactive connexin hemichannels. For example, amphiphilic versions of neomycin and neamine are not subject to resistance and have expanded antibacterial spectra, and amphiphilic kanamycins are effective antifungals and have promising therapeutic uses as connexin hemichannel inhibitors. With further research and discoveries aimed at improved formulations and delivery, amphiphilic aminoglycosides may achieve new horizons in pharmacopeia and agriculture for Streptomyces aminoglycosides beyond just serving as topical antibacterials.

Downstream Alternate Start Site Allows N-Terminal Nonsense Variants to Escape NMD and Results in Functional Recovery by Readthrough and Modulator Combination

Genetic variants that introduce premature termination codons (PTCs) have remained difficult to therapeutically target due to lack of protein product. Nonsense mediated mRNA decay (NMD) targets PTC-bearing transcripts to reduce the potentially damaging effects of truncated proteins. Readthrough compounds have been tested on PTC-generating variants in attempt to permit translation through a premature stop. However, readthrough compounds have not proved efficacious in a clinical setting due to lack of stable mRNA. Here, we investigate N-terminal variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which have been shown to escape NMD, potentially through a mechanism of alternative translation initiation at downstream AUG codons. We hypothesized that N-terminal variants in CFTR that evade NMD will produce stable transcript, allowing CFTR function to be restored by a combination of readthrough and protein modulator therapy. We investigate this using two cell line models expressing CFTR-expression minigenes (EMG; HEK293s and CFBEs) and primary human nasal epithelial (NE) cells, and we test readthrough compounds G418 and ELX-02 in combination with CFTR protein modulators. HEK293 cells expressing the variants E60X and L88X generate CFTR-specific core glycosylated products that are consistent with downstream translation initiation. Mutation of downstream methionines at codons 150 and 152 does not result in changes in CFTR protein processing in cells expressing L88X-CFTR-EMG. However, mutation of methionine at 265 results in loss of detectable CFTR protein in cells expressing E60X, L88X, and Y122X CFTR-EMGs, indicating that downstream translation initiation is occurring at the AUG codon at position M265. In HEK293 stable cells harboring L88X, treatment with readthrough compounds alone allows for formation of full-length, but misfolded CFTR protein. Upon addition of protein modulators in combination with readthrough, we observe formation of mature, complex-glycosylated CFTR. In CFBE and NE cells, addition of readthrough ELX-02 and modulator therapy results in substantial recovery of CFTR function. Our work indicates that N-terminal variants generate stable CFTR transcript due to translation initiation at a downstream AUG codon. Thus, individuals with CF bearing 5′ nonsense variants that evade NMD are ideal candidates for treatment with clinically safe readthrough compounds and modulator therapy.

A scoping review of global aminoglycoside antibiotic overuse: A potential opportunity for primary ototoxicity prevention

BACKGROUND

Aminoglycosides are widely used, broad-spectrum antibiotics with significant potential for ototoxicity. Global efforts to prevent ototoxicity must account for aminoglycoside overuse and non-prescription use.

OBJECTIVES

The goals of this study were to a) estimate the prevalence of aminoglycoside overuse by synthesizing evidence on self-medication, over the counter (OTC) availability, and household antibiotic storage for later use, and to report the specific aminoglycosides used and the predictors of overuse, and b) leverage this information to comment on potential risk of ototoxicity.

METHODS

Two systematic search strings were conducted to extract peer-reviewed articles published from 2005 to 2020. The first focused on overuse of aminoglycoside antibiotics. The second focused on potentially ototoxic effects of aminoglycosides related to drug overuse.

RESULTS

A total of 26 articles were included (first search string: n = 21; second search string: n = 5). The prevalence of aminoglycoside self-medication was high and household storage and OTC availability of aminoglycosides was common. Gentamicin was the most commonly overused aminoglycoside. No studies provided information on antibiotic dosing or resultant toxicities, including ototoxicity.

CONCLUSIONS

The limited available evidence indicates that antibiotic overuse (self-medication, home storage, and non-prescription availability) is relatively common, especially in low resource settings, and that aminoglycoside antibiotics comprise a variable, but concerning, proportion of non-prescribed antibiotics. Additional evidence is needed to evaluate the relationship between these dispensing patterns and ototoxicity.

Translation termination codons in protein synthesis and disease

Fidelity of protein synthesis, a process shaped by several mechanisms involving specialized ribosome regions and external factors, ensures the precise reading of sense as well as stop codons (UGA, UAG, UAA), which are usually localized at the 3' of mRNA and drive the release of the polypeptide chain. However, either natural (NTCs) or premature (PTCs) termination codons, the latter arising from nucleotide changes, can undergo a recoding process named ribosome or translational readthrough, which insert specific amino acids (NTCs) or subset(s) depending on the stop codon type (PTCs). This process is particularly relevant for nonsense mutations, a relatively frequent cause of genetic disorders, which impair gene expression at different levels by potentially leading to mRNA degradation and/or synthesis of truncated proteins. As a matter of fact, many efforts have been made to develop efficient and safe readthrough-inducing compounds, which have been challenged in several models of human disease to provide with a therapy. In this view, the dissection of the molecular determinants shaping the outcome of readthrough, namely nucleotide and protein contexts as well as their interplay and impact on protein structure/function, is crucial to identify responsive nonsense mutations resulting in functional full-length proteins. The interpretation of experimental and mechanistic findings is also important to define a possibly clear picture of potential readthrough-favorable features useful to achieve rescue profiles compatible with therapeutic thresholds typical of each targeted disorder, which is of primary importance for the potential translatability of readthrough into a personalized and mutation-specific, and thus patient-oriented, therapeutic strategy.

Small molecule eRF3a degraders rescue CFTR nonsense mutations by promoting premature termination codon readthrough

The vast majority of people with cystic fibrosis (CF) are now eligible for CF transmembrane regulator (CFTR) modulator therapy. The remaining individuals with CF harbor premature termination codons (PTCs) or rare CFTR variants with limited treatment options. Although the clinical modulator response can be reliably predicted using primary airway epithelial cells, primary cells carrying rare CFTR variants are scarce. To overcome this obstacle, cell lines can be created by overexpression of mouse Bmi-1 and human TERT (hTERT). Using this approach, we developed 2 non-CF and 6 CF airway epithelial cell lines, 3 of which were homozygous for the W1282X PTC variant. The Bmi-1/hTERT cell lines recapitulated primary cell morphology and ion transport function. The 2 F508del-CFTR cell lines responded robustly to CFTR modulators, which was mirrored in the parent primary cells and in the cell donors’ clinical response. Cereblon E3 ligase modulators targeting eukaryotic release factor 3a (eRF3a) rescued W1282X-CFTR function to approximately 20% of WT levels and, when paired with G418, rescued G542X-CFTR function to approximately 50% of WT levels. Intriguingly, eRF3a degraders also diminished epithelial sodium channel (ENaC) function. These studies demonstrate that Bmi-1/hTERT cell lines faithfully mirrored primary cell responses to CFTR modulators and illustrate a therapeutic approach to rescue CFTR nonsense mutations.

Tigecycline and Gentamicin-Combined Treatment Enhances Renal Damage: Oxidative Stress, Inflammatory Reaction, and Apoptosis Interplay

Although the combination of antibiotics is generally well-tolerated, they may have nephrotoxic effects. This study investigated whether tigecycline (TG) and gentamicin (GM) co-administration could accelerate renal damage. Male Wistar rats were randomly divided into six experimental groups: the control, TG7 (tigecycline, 7 mg/kg), TG14 (tigecycline, 14 mg/kg), GM (gentamicin, 80 mg/kg), TG7+GM, and TG14+GM groups. The combination of TG and GM evoked renal damage seen by the disruption of kidney function tests. The perturbation of renal tissue was mainly confounded to the TG and GM-induced oxidative damage, which was exhibited by marked increases in renal MDA (malondialdehyde) along with a drastic reduction in GSH (reduced-glutathione) content and CAT (catalase) activity compared to their individual treatments. More obvious apoptotic events and inflammation were also revealed by elevating the annexin-V and interleukin-6 (IL-6) levels, aside from the upregulation of renal PCNA (proliferating cell nuclear antigen) expression in the TG and GM concurrent treatment. The principal component analysis indicated that creatinine, urea, annexin-V, IL-6, and MDA all played a role in discriminating the TG and GM combined toxicity. Oxidative stress, inflammatory response, and apoptosis were the key mechanisms involved in this potentiated toxicity.

Evaluation and comparison of antibiotic susceptibility profiles of Streptomyces spp. from clinical specimens revealed common and region-dependent resistance patterns

Notwithstanding the fact that streptomycetes are overlooked in clinical laboratories, studies describing their occurrence in disease and potential pathogenicity are emerging. Information on their species diversity in clinical specimens, aetiology and appropriate therapeutic treatment is scarce. We identified and evaluated the antibiotic susceptibility profile of 84 Streptomyces clinical isolates from the Czech Republic. In the absence of appropriate disk diffusion (DD) breakpoints for antibiotic susceptibility testing (AST) of Streptomyces spp., we determined DD breakpoints by correlation with the broth microdilution method and by the distribution of zone diameters among isolates. Correlation accuracy was high for 9 antibiotics, leading to the establishment of the most valid DD breakpoints for Streptomyces antibiotic susceptibility evaluation so far. Clinical strains belonged to 17 different phylotypes dominated by a cluster of strains sharing the same percentage of 16S rRNA gene sequence identity with more than one species (S. albidoflavus group, S. hydrogenans, S. resistomycificus, S. griseochromogenes; 70% of isolates). AST results showed that Streptomyces exhibited intrinsic resistance to penicillin, general susceptibility to amikacin, gentamycin, vancomycin and linezolid, and high percentage of susceptibility to tetracyclines and clarithromycin. For the remaining antibiotics, AST showed inter- and intra-species variations when compared to available literature (erythromycin, trimethoprim-sulfamethoxazole), indicating a region-dependent rather than species-specific patterns.

Elucidation of the mechanism of miR‑122‑5p in mediating FOXO3 injury and apoptosis of mouse cochlear hair cells induced by hydrogen peroxide

Unveiling the mechanism of miR-122-5p in the mediation of forkhead box O3 (FOXO3) in regards to cochlear hair cell damage provides an effective solution for the treatment of ear hearing disorders. An oxidative stress model using a mouse cochlear hair cell line (HEI-OC1) was established via hydrogen peroxide (H₂O₂). Then HEI-OC1 cells were transfected with miR-122-5p mimic, miR-122-5p inhibitor, and lentiviral vector FOXO3-WT/MUT. Cell viability and apoptosis rate were determined by MTT assay and flow cytometry. Reactive oxygen species (ROS) were observed by confocal laser scanning microscopy. Bcl-2, Bax, capase-3 and c-caspase-9 levels were quantified by western blot analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR). Enzyme-linked immunosorbent assay (ELISA) was used to detect superoxide dismutase (SOD) and malondialdehyde (MDA) levels, and flow cytometry was performed to measure the mitochondrial membrane potential levels. In the HEI-OC1 oxidative stress model after transfection, the miR-122-5p level was decreased, whereas the FOXO3 level was increased, Moreover, the increased FOXO3 level diminished the cell viability, but promoted cell apoptosis. Apart from this, the Bcl-2 level was downregulated, while levels of Bax, c-caspase-3, c-caspase-9, ROS and MDA were upregulated. Meanwhile, the mitochondrial membrane potential level was also elevated. Overexpression of miR-122-5p was able to partially offset the effects of FOXO3 in the H₂O₂-treated HEI-OC1 cells. Collectively, miR-122-5p restrained the decrease in HEI-OC1 cell viability and apoptosis induced by treatment with H₂O₂.

Aminoglycoside treatment alters hearing-related genes and depicts behavioral defects in Drosophila

The hearing organ of Drosophila is present within the second segment of antennae. The hearing organ of Drosophila (Johnston's organ [JO]) shares much structural, developmental, and functional similarity with the vertebrate hearing organ (Organ of Corti). JO is evolving as a potential model system to examine the hearing-associated defects in vertebrates. In the vertebrates, aminoglycosides like gentamicin, kanamycin, and neomycin have been known to cause defects in the hearing organ. However, a complete mechanism of toxicity is not known. Taking the evolutionary conservation into account the current study aims to test various concentrations of aminoglycoside on the model organism, Drosophila melanogaster. The current study uses the oral route to check the toxicity of various aminoglycosides at different concentrations (50, 100, 150, 200, and 250 μg ml^{- 1} ). In Drosophila, many foreign particles enter the body through the gut via food. The aminoglycoside treated third instar larvae show defective crawling and sound avoidance behavior. The adult flies release lower amounts of acetylcholine esterase and higher amounts of reactive oxygen species than control untreated animals, accompanied by defective climbing and aggressive behavior. All these behavioral defects are further confirmed by the altered expression level of hearing genes such as nompC, inactive, nanchung, pyrexia. All the behavioral and genetic defects are reported as a readout of aminoglycoside toxicity.

Tetrandrine Prevents Neomycin-Induced Ototoxicity by Promoting Steroid Biosynthesis

Aminoglycoside antibiotics are widely used for the treatment of serious acute infections, life-threatening sepsis, and tuberculosis, but all aminoglycosides cause side effects, especially irreversible ototoxicity. The mechanisms underlying the ototoxicity of aminoglycosides need further investigation, and there are no effective drugs in the clinic. Here we showed that tetrandrine (TET), a bioactive bisbenzylisoquinoline alkaloid derived from Stephania tetrandra, ameliorated neomycin-induced cochlear hair cell injury. In both in vitro and in vivo experiments we found that TET administration significantly improved auditory function and reduced hair cell damage after neomycin exposure. In addition, we observed that TET could significantly decrease oxidative stress and apoptosis in hair cells after neomycin exposure. Finally, RNA-seq analysis suggested that TET protected against neomycin-induced ototoxicity mainly by promoting steroid biosynthesis. Collectively, our results provide pharmacological evidence showing that TET may be a promising agent in preventing aminoglycosides-induced ototoxicity.

Medical Therapy of Hearing Impairment and Tinnitus with Chinese Medicine: An Overview

The current review gives a comprehensive overview of the recent development in Chinese medicine (CM) for treating several kinds of acquired nerve deafness and tinnitus, as well as links the traditional principle to well-established pharmacological mechanisms for future research. To date, about 24 herbal species and 40 related ingredients used in CM to treat hearing loss and tinnitus are reported for the treatment of endocochlear potential, endolymph growth, lowering toxic and provocative substance aggregation, inhibiting sensory cell death, and retaining sensory transfer. However, there are a few herbal species that can be used for medicinal purposes. Nevertheless, clinical studies have been hampered by a limited population sample, a deficiency of a suitable control research group, or contradictory results. Enhanced cochlear blood flow, antiinflammatory antioxidant, neuroprotective effects, and anti-apoptotic, as well as multi-target approach on different auditory sections of the inner ear, are all possible benefits of CM medications. There are numerous unknown natural products for aural ailment and tinnitus identified in CM that are expected to be examined in the future utilizing various aural ailment models and processes.

A longitudinal community-based ototoxicity monitoring programme and treatment effects for drug-resistant tuberculosis treatment, Western Cape

Background

South Africa has a high burden of drug-resistant tuberculosis (DRTB) and until recently, ototoxic aminoglycosides were predominant in treatment regimens. Community-based ototoxicity monitoring programmes (OMPs) have been implemented for early detection of hearing loss and increased patient access.

Objectives

A longitudinal study was conducted to describe the service delivery characteristics of a community-based OMP for DRTB patients facilitated by CHWs as well as observed ototoxic hearing loss in this population.

Method

A descriptive retrospective record review of longitudinal ototoxicity monitoring of 194 DRTB patients undergoing treatment at community-based clinics in the city of Cape Town between 2013 and 2017.

Results

Follow-up rates between consecutive monitoring assessments reached as high as 80.6% for patients assessed by CHWs. Few patients (14.2% – 32.6%) were assessed with the regularity (≥ 6 assessments) and frequency required for effective ototoxicity monitoring, with assessments conducted, on average, every 53.4–64.3 days. Following DRTB treatment, 51.5% of patients presented with a significant ototoxic shift meeting one or more of the American Speech-Language-Hearing Association (ASHA) criteria. Deterioration in hearing thresholds was bilateral and most pronounced at high frequencies (4 kHz – 8 kHz). The presence of pre-existing hearing loss, human immunodeficiency virus co-infection and a history of noise exposure were significant predictors of ototoxicity in patients.

Conclusion

DRTB treatment with kanamycin resulted in significant deterioration of hearing longitudinally, predominantly at high frequencies. With ongoing training and supportive supervision, CHWs can facilitate community-based ototoxicity monitoring of DRTB patients. Current protocols and guidelines may require reassessment for appropriate community-based ototoxicity monitoring.

Hippo/YAP signaling pathway protects against neomycin-induced hair cell damage in the mouse cochlea

The Hippo/Yes-associated protein (YAP) signaling pathway has been shown to be able to maintain organ size and homeostasis by regulating cell proliferation, differentiation, and apoptosis. The abuse of aminoglycosides is one of the main causes of sensorineural hearing loss (SSNHL). However, the role of the Hippo/YAP signaling pathway in cochlear hair cell (HC) damage protection in the auditory field is still unclear. In this study, we used the YAP agonist XMU-MP-1 (XMU) and the inhibitor Verteporfin (VP) to regulate the Hippo/YAP signaling pathway in vitro. We showed that YAP overexpression reduced neomycin-induced HC loss, while downregulated YAP expression increased HC vulnerability after neomycin exposure in vitro. We next found that activation of YAP expression inhibited C-Abl-mediated cell apoptosis, which led to reduced HC loss. Many previous studies have reported that the level of reactive oxygen species (ROS) is significantly increased in cochlear HCs after neomycin exposure. In our study, we also found that YAP overexpression significantly decreased ROS accumulation, while downregulation of YAP expression increased ROS accumulation. In summary, our results demonstrate that the Hippo/YAP signaling pathway plays an important role in reducing HC injury and maintaining auditory function after aminoglycoside exposure. YAP overexpression could protect against neomycin-induced HC loss by inhibiting C-Abl-mediated cell apoptosis and decreasing ROS accumulation, suggesting that YAP could be a novel therapeutic target for aminoglycosides-induced sensorineural hearing loss in the clinic.

Novel Application of Eupatilin for Effectively Attenuating Cisplatin-Induced Auditory Hair Cell Death via Mitochondrial Apoptosis Pathway

Eupatilin (5,7-dihydroxy-3′,4′,6-trimethoxyflavone) is a pharmacologically active flavone that has been isolated from a variety of medicinal plants and possesses a number of pharmacological properties. This study evaluates the antioxidant and antiapoptotic effects of eupatilin on cisplatin-induced ototoxicity using in vitro and in vivo models including HEI-OC1 cells, cochlear hair cells, and zebrafish. Employing a CCK8 assay and Annexin V-FITC/PI double staining, we found that eupatilin significantly alleviated cisplatin-induced apoptosis and increased hair cell viability. The level of reactive oxygen species (ROS) was evaluated by CellROX green and MitoSOX Red staining. The results showed that eupatilin possesses antioxidant activity. MitoTracker Red staining indicated that eupatilin remarkably decreased mitochondrial damage. Furthermore, we demonstrated that eupatilin protects hair cells from cisplatin-induced damage. Mechanistic studies in cisplatin-induced HEI-OC1 cells revealed that eupatilin promoted Bcl-2 expression, downregulated Bax expression, reversed the increase in caspase-3 and PARP activity, and reduced the expression of phosphorylated p38 and JNK. Our data suggest a novel role for eupatilin as a protective agent against ototoxic drug-induced hair cell apoptosis by inhibiting ROS generation and modulating mitochondrial-related apoptosis.

Bronchiectasis and inhaled tobramycin: A literature review

BACKGROUND

Inhaled antibiotics have been incorporated into contemporary European and British guidelines for bronchiectasis, yet no inhaled antibiotics have been approved in the United States or Europe for the treatment of bronchiectasis not related to cystic fibrosis. Pseudomonas aeruginosa infection is common in patients with bronchiectasis, contributing to a cycle of progressive inflammation, exacerbations, and airway remodelling.

OBJECTIVE

The aim of the current study was to identify and evaluate published studies of inhaled tobramycin solution or powder in patients with bronchiectasis and P. aeruginosa infection not associated with cystic fibrosis.

METHODS

A literature review was conducted utilising the PubMed and Cochrane databases. Studies published in the English language that reported safety and/or efficacy outcomes of inhaled tobramycin either alone or in combination with other antibiotics were included.

RESULTS

Seven clinical trials published between 1999 and 2021 were identified that met inclusion criteria. Inhaled tobramycin therapy was effective in reducing P. aeruginosa microbial density in the sputum of patients with bronchiectasis. Several studies demonstrated favourable impacts on hospitalisations, number and severity of exacerbations, and symptoms. Other studies were underpowered for these clinical outcomes or were exploratory in nature. Although tobramycin was generally well tolerated, some evidence of treatment-associated wheezing was reported.

CONCLUSIONS

In patients with bronchiectasis and chronic P. aeruginosa infection, inhaled tobramycin was effective in reducing the density of bacteria in sputum, which may be associated with additional clinical benefits. Definitive phase 3 trials of inhaled tobramycin in patients with bronchiectasis are indicated to determine clinical efficacy and long-term safety.

Analysis of potential protective effects of caffeic acid phenethyl ester against gentamicin ototoxicity: An experimental study

OBJECTIVES

In this study, it is aimed to investigate the potential protective effect of caffeic acid phenethyl ester (CAPE) on ototoxicity caused by gentamicin in a rat model.

MATERIALS AND METHODS

Thirty Wistar albino rats were divided into 3 groups. Group I was selected as the control group. Gentamicin was administered intraperitoneally in group II, gentamicin and CAPE in group III. Audiological assessment was performed by the distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) measurements before and after treatment of each group. At the end of the study all rats were decapitated, cochlea was removed and electron microscopic examination was performed.

RESULTS

In group II post-treatment DPOAE levels were found to be lower than pretreatment DPOAE levels (P<0.05). However, in group III, there is no significant difference between pre- and post-treatment DPOAE levels (P>0.05). Except for Group I, ABR thresholds increased after the procedure and this increase was statistically significant (P<0.0001). According to histological examination by transmission electron microscopy, CAPE has a cellular protective effect against gentamicin ototoxicity.

CONCLUSION

CAPE may ameliorate hearing deterioration caused by gentamicin ototoxicity and protect the cochlear cells from apoptosis due to the strong antioxidant effect.

Antioxidant Effect of Curcumin on the Prevention of Oxidative Damage to the Cochlea in an Ototoxic Rat Model Based on Malondialdehyde Expression

Introduction  Aminoglycoside, as an antimicrobial medication, also has side-effects on the inner ears, bringing about hearing disorders. Curcumin has been proven to be a strong scavenger against various reactive oxygen species (ROS), and the increase in ROS production is considered to play an important role in the process of hearing disorder. Objective  To prove that curcumin is an effective antioxidant to prevent cochlear damage based on malondialdehyde (MDA) expression. Methods  The present research used 32 Rattus norvegicus , of the Wistar lineage, randomly divided into 8 groups: negative control, ototoxic control (a single dose of 40 mg/ml of gentamicin via intratympanic injection), 2 groups submitted to ototoxic control + curcumin treatment (100 mg/kg, 200 mg/kg), 2 groups who iunderwent ototoxic control + curcumin treatment for 7 days, and two groups submitted to curcumin treatment as prevention for 3 days + ototoxic induction. Results  The results showed that the lowest dosage of curcumin (100 mg/kg) could decrease MDA expression on the cochlear fibroblastic wall of the ototoxic model; however using greater doses of curcumin (200 mg/kg) for 7 days would provide a better effect. Curcumin could also significantly decrease MDA expression when it was administered during the preototoxic exposure. Conclusion  Curcumin can be used as a therapy for ototoxic prevention based on the decrease in MDA expression.

Aminoglycoside- and glycopeptide-induced ototoxicity in children: a systematic review

Background

Ototoxicity has been reported after administration of aminoglycosides and glycopeptides.

Objectives

To identify available evidence for the occurrence and determinants of aminoglycoside- and glycopeptide-related ototoxicity in children.

Materials and methods

Systematic electronic literature searches that combined ototoxicity (hearing loss, tinnitus and/or vertigo) with intravenous aminoglycoside and/or glycopeptide administration in children were performed in PubMed, EMBASE and Cochrane Library databases. Studies with sample sizes of ≥50 children were included. The QUIPS tool and Cochrane criteria were used to assess the quality and risk of bias of included studies.

Results

Twenty-nine aminoglycoside-ototoxicity studies met the selection criteria (including 7 randomized controlled trials). Overall study quality was medium/low. The frequency of hearing loss within these studies ranged from 0%–57%, whereas the frequency of tinnitus and vertigo ranged between 0%–53% and 0%–79%, respectively. Two studies met the criteria on glycopeptide-induced ototoxicity and reported hearing loss frequencies of 54% and 55%. Hearing loss frequencies were higher in gentamicin-treated children compared to those treated with other aminoglycosides. In available studies aminoglycosides had most often been administered concomitantly with platinum agents, diuretics and other co-medication.

Conclusions

In children the reported occurrence of aminoglycoside/glycopeptide ototoxicity highly varies and seems to depend on the diagnosis, aminoglycoside subtype and use of co-administered medication. More research is needed to investigate the prevalence and determinants of aminoglycoside/glycopeptide ototoxicity. Our results indicate that age-dependent audiological examination may be considered for children frequently treated with aminoglycosides/glycopeptides especially if combined with other ototoxic medication.

Community-Based Ototoxicity Monitoring for Drug-Resistant Tuberculosis in South Africa: An Evaluation Study

In response to the drug-resistant tuberculosis (DRTB) ototoxicity burden in South Africa, ototoxicity monitoring has been decentralised, with community health workers (CHWs) acting as facilitators. This study describes a community-based ototoxicity monitoring programme (OMP) for patients with DRTB. Findings are compared to the recommended guidelines for ototoxicity monitoring, the OMP protocol and published studies. This was a retrospective study of longitudinal ototoxicity monitoring of 831 patients with DRTB, using data collected at community-based clinics in the City of Cape Town between 2013 and 2017. Approximately half (46.8%) of the patients had an initial assessment conducted in accordance with the OMP protocol recommendations, and follow-up rates (79.5%) were higher than those of a similar DRTB programme. However, patients in this study were not monitored within the timeframes or with the regularity recommended by the guidelines or the OMP protocol. Extended high-frequency pure-tone audiometry (27.5%) was underutilised by testers and data recording was inconsistent (e.g., 37.7% of patient gender was not recorded by testers). Community-based OMP using CHWs to facilitate monitoring showed improvement over previous hospital-based reports, with more accessible services and higher follow-up rates. However, to improve OMP outcomes, OMP managers should reassess current protocols and data recording practices.