N-Acetylcysteine in the prevention of ototoxicity

[Assessment of the risk of hearing loss in children with cystic fibrosis]

BACKGROUND

Cystic fibrosis (CF) is a severe hereditary disease with a multisystem lesion. Manifestations of CF include severe infectious purulent lesions of all parts of the respiratory tract, including purulent rhinosinusitis with nasal polyps. The involvement of the sinonasal region and the need for systemic use of ototoxic drugs (primarily aminoglycosides to treat resistant bacterial infection) potentially create a risk of both conductive and sensorineural hearing loss (SNHL). The available data on the epidemiology of hearing disorders in CF is contradictory. Currently, genetic determinants of the development of aminoglycoside SNHL have been identified.

MATERIAL AND METHODS

For 136 CF patients (75 girls, 61 boys) aged 3 to 17 (9.4±3.9) years were performed audiological examination: tympanometry, transient-evoked otoacoustic emission and the pure tone threshold audiometry (standard frequency range) (n=126). History of systemic therapy with aminoglycosides was evaluated for each patient. Sequencing of c.35delG mutations in the GJB2 gene (nuclear DNA) and A1555G in the 12S rRNA gene (mitochondrial DNA) was performed in 215 patients with cystic fibrosis (the group partially overlaps with the audiological group), and as a control - 106 children with bronchial asthma and 103 healthy children, their age ranged from 3 to 17 (8.8±3.8) years.

RESULTS

Audiological examination of CF children reveled a prevalence of conductive hearing loss comparable to the general population (2.4%). The frequency of SNHL was 1.6%, wich exceeds that of non-CF children. A genetic study revealed one case of heterozygous carriage of the c.35delG mutation in the GJB2 gene in a patient with bronchial asthma. In the group of patients with CF (n=215), mutations in the connexin 26 gene were not detected. No A1555G mutation was detected either in the group of patients with CF or in the control groups.

CONCLUSIONS

Children with CF are at risk for the development of sensorineural, but not conductive hearing loss. Routine total screening for A1555G and c.35delG mutations probably seems not to be recommended.

Antibacterial Efficacy of Liposomal Formulations Containing Tobramycin and N-Acetylcysteine against Tobramycin-Resistant Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii

The antibacterial activity and biofilm reduction capability of liposome formulations encapsulating tobramycin (TL), and Tobramycin-N-acetylcysteine (TNL) were tested against tobramycin-resistant strains of E. coli, K. pneumoniae and A. baumannii in the presence of several resistant genes. All antibacterial activity were assessed against tobramycin-resistant bacterial clinical isolate strains, which were fully characterized by whole-genome sequencing (WGS). All isolates acquired one or more of AMEs genes, efflux pump genes, OMP genes, and biofilm formation genes. TL formulation inhibited the growth of EC_089 and KP_002 isolates from 64 mg/L and 1024 mg/L to 8 mg/L. TNL formulation reduced the MIC of the same isolates to 16 mg/L. TNL formulation was the only effective formulation against all A. baumannii strains compared with TL and conventional tobramycin (in the plektonic environment). Biofilm reduction was significantly observed when TL and TNL formulations were used against E. coli and K. pneumoniae strains. TNL formulation reduced biofilm formation at a low concentration of 16 mg/L compared with TL and conventional tobramycin. In conclusion, TL and TNL formulations particularly need to be tested on animal models, where they may pave the way to considering drug delivery for the treatment of serious infectious diseases.

Effect of N-Acetylcysteine on hsCRP in Patients on Continues Ambulatory Peritoneal Dialysis: A Quasi-Experimental Study

Background: Inflammatory processes are proved in patients with chronic kidney disease (CKD) as one of the leading causes of mortality and morbidity. N-acetylcysteine (NAC) is known as an antioxidant drug with anti-inflammatory effects. Objectives: This study aimed to evaluate the effects of NAC on hsCRP in CKD patients on peritoneal dialysis. Methods: This quasi-experimental self-controlled study examined adult CKD patients on peritoneal dialysis referred to the peritoneal dialysis clinic. The participants were assigned into two groups (A: CRP of 5 - 15 mg/L and B: CRP < 5 mg/L), and both groups were treated with oral NAC 600mg twice a day for eight weeks. First, the hsCRP was measured before and after the intervention, and then all the collected data were analyzed. Results: Forty patients (n = 24 in the group A and n = 26 in the group B) participated in this study. NAC decreased the hsCRP level in both groups (P = 0.001 in the group A vs. P = 0.002 in group B); however, the decrease was more prominent in the group A (P = 0.013). The hsCRP decrease was more significant in women (P = 0.002) in general and women in the group B (P = 0.02) in particular. The hsCRP variation had a significant relationship with the underlying disease (P = 0.009). There was no significant correlation between the hsCRP variation with age (r = -0.173, P = 0.285) and the duration of dialysis. Conclusions: The administration of NAC (600 mg, twice a day for eight weeks) significantly decreased the level of hsCRP in patients on peritoneal dialysis, especially in those with CRP = 5 - 15 mh/L. The decrease has no relationship with age and duration of dialysis; however, it was more highlighted in women.

Increased oxidative stress, inflammation, and glutamate: Potential preventive and therapeutic targets for hearing disorders

Hearing disorders constitute one of the major health concerns in the USA. Decades of basic and clinical studies have identified numerous ototoxic agents and investigated their modes of action on the inner ear, utilizing tissue culture as well as animal and human models. Current preventive and therapeutic approaches are considered unsatisfactory. Therefore, additional modalities should be developed. Many studies suggest that increased levels of oxidative stress, chronic inflammation, and glutamate play an important role in the initiation and progression of damage to the inner ear leading to hearing impairments. To prevent these cellular deficits, antioxidants, anti-inflammatory agents, and antagonists of glutamate receptor have been used individually or in combination with limited success. It is essential, therefore, to simultaneously enhance the levels of antioxidant enzymes by activating the Nrf2 (a nuclear transcriptional factor) pathway, dietary and endogenous antioxidant compounds, and B12-vitamins in order to reduce the levels of oxidative stress, chronic inflammation, and glutamate at the same time. This review presents evidence to show that increased levels of these cellular metabolites, biochemical or factors are involved in the pathogenesis of cochlea leading to hearing impairments. It presents scientific rationale for the use of a mixture of micronutrients that may decrease the levels of oxidative damage, chronic inflammation, and glutamate at the same time. The benefits for using oral administration of proposed micronutrient mixture in humans are presented. Animal and limited human studies indirectly suggest that orally administered micronutrients can accumulate in the inner ear. Therefore, this route of administration may be useful in prevention, and in combination with standard care, in improved management of hearing problems following exposure to well-recognized and studied ototoxic agents, such as noise, cisplatin, aminoglycoside antibiotics, and advanced age.

Long-Term Protective Effect of N-Acetylcysteine against Amikacin-Induced Ototoxicity in End-Stage Renal Disease: A Randomized Trial

BACKGROUND

The aim of the study is to evaluate the long-term protective effect of N-acetylcysteine (NAC), an antioxidant agent, against aminoglycoside (AG)-induced ototoxicity.

METHODS

A total of 40 patients receiving continuous ambulatory peritoneal dialysis (CAPD) and having their first peritonitis attacks and planned to be treated with AGs were enrolled in the study. They were randomized into 2 groups: 1 group received additional NAC and the other did not. All patients underwent hearing tests with pure tone audiometry (PTA) after the diagnosis, at 1 month and 12 months and at the same time the tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels were measured.

RESULTS

Patients taking NAC had better hearing test results in both ears at 1 month except 2,000 Hz for the left ear, which wasn't significantly different between the 2 groups. Although patients taking NAC had generally better PTA results at 12 months, differences between the 2 groups were not statistically significant. Baseline IL-6 level was significantly higher in the NAC group than the control group. Both TNF-α and IL-6 levels at 1 month were significantly lower in the NAC group than in the control group. On the other hand, there was no significant difference between the 2 groups in terms of TNF-α and IL-6 levels at 12 months.

CONCLUSIONS

The results of the current study showed that NAC, a potent anti-inflamatory drug, may be otoprotective, but that the effect is not long-lasting.

Prevention of gentamicin ototoxicity with N-acetylcysteine and vitamin A

OBJECTIVE

To investigate the use of systemic N-acetylcysteine and vitamin A in the prevention of gentamicin ototoxicity in rats.

METHODS

Forty-two Wistar rats were divided into four groups according to treatment: intratympanic saline, intratympanic gentamicin, intraperitoneal vitamin A after intratympanic gentamicin, and intraperitoneal N-acetylcysteine after intratympanic gentamicin. Signal-to-noise ratio and distortion product otoacoustic emissions were evaluated in all groups.

RESULTS

N-acetylcysteine had a significant protective effect at 1.5, 2, 3, 4, 6 and 8 kHz, whilst vitamin A had a significant protective effect at 2, 3, 4 and 6 kHz, as determined by the distortion product otoacoustic emission measurements. According to the signal-to-noise measurements, N-acetylcysteine had a significant protective effect at 1.5, 2, 3, 4, 6 and 8 kHz, whilst vitamin A had a significant protective effect at 3, 6 and 8 kHz.

CONCLUSION

Gentamicin-induced hearing loss in rats may be prevented by the concomitant use of vitamin A and N-acetylcysteine. Specifically, N-acetylcysteine appeared to have a more protective effect than vitamin A for a greater range of noise frequencies.

Antioxidant micronutrient impact on hearing disorders: concept, rationale, and evidence

PURPOSE

Although auditory disorders are complex conditions, device-related modalities dominate current treatment. However, dysfunction from the central cortex to the inner ear apparatus is increasingly thought to be related to biochemical pathway abnormalities and to free radical-induced oxidative damage and chronic inflammation. Therefore, considering appropriate biologic therapy as an adjunct to standard care against these damaging factors may provide rational expansion of treatment options for otolaryngologists and audiologists.

METHODS

This review outlines the biologic concepts related to some auditory and vestibular conditions and details the current rationale for utilizing antioxidants for a spectrum of hearing disorders. The strategy is based on the authors' collective experience in antioxidant science and supported with published research, pilot animal data and preliminary clinical observations.

RESULTS

A comprehensive micronutrient approach was developed to exploit these pathways, and demonstrated safety and efficacy against oxidative damage and inflammation and clinically relevant neuroprotection. Cooperative research with Department of Defense institutions used prospective, randomized designs to show (1) reduction in oxidative damage measured in plasma and urine over six months, (2) protection against oxidative damage during 12 weeks of intense military training, (3) protection against inflammation after total body blast exposure (rodents), (4) strong neuroprotection against chemically-induced Parkinson's disease (rodents), (5) nerve VIII function improvement after concussive head injury in military personnel, and (6) tinnitus improvement in majority of patients after 90-day evaluation.

CONCLUSION

This systematic review of biologic strategies against hearing disorders combined with new animal and human observations may provide a rational basis for expanding current practice paradigms.

Effect of oral N-acetylcysteine treatment on plasma inflammatory and oxidative stress markers in peritoneal dialysis patients: a placebo-controlled study

BACKGROUND

Inflammation and oxidative stress (OS) are cardiovascular risk factors in patients with chronic kidney disease. N-acetylcysteine (NAC) is a thiol-containing antioxidant with anti-inflammatory properties and has been shown to reduce the number of cardiovascular events in hemodialysis patients.

METHODS

The current study aimed to determine the effect of oral NAC (2 x 600 mg/daily) on plasma levels of inflammatory and OS markers in peritoneal dialysis (PD) patients. We performed a placebo-controlled study over 8 weeks in 30 patients (40% males, age 52 +/- 13 years) on regular PD. Before the study was started, the patients were divided into 2 groups of 15 patients matched for age and gender. 22 patients completed the study (12 on NAC, 10 on placebo). Proinflammatory cytokines [high-sensitivity C-reactive protein, interleukin-6 (IL-6), tumor necrosis factor-alpha, and pentraxin 3] and markers of OS (pentosidine, advanced oxidation protein products, homocysteine, glutathione, asymmetric dimethylarginine, and free sulfhydryls) were measured before and after treatment with NAC.

RESULTS

Treatment with NAC for 8 weeks increased mean baseline plasma NAC levels from 2.6 to 24.8 mumol/L (p = 0.007). This intervention, which caused no side effects, significantly diminished IL-6 levels, from 9.4 (4.5 - 31) to 7.6 (4.9 - 13.5) pg/mL (p = 0.006), whereas no such changes were observed in the placebo group. NAC treatment did not significantly affect the other inflammatory and OS markers.

CONCLUSION

Short-term oral NAC treatment resulted in reduction of circulating IL-6, suggesting that such treatment could be a useful strategy in blunting the inflammatory response in PD patients.