4-hydroxy-2-nonenal and Hearing-Loss--Noise-Induced

Noise-induced hearing loss (NIHL) is a common inner ear disease but has complex pathological mechanisms, one of which is increased oxidative stress in the cochlea. The high-mobility group box 1 (HMGB1) protein acts as an inflammatory mediator and shows different activities with redox modifications linked to the generation of reactive oxygen species (ROS). We aimed to investigate whether manipulation of cochlear HMGB1 during noise exposure could prevent noise-induced oxidative stress and hearing loss. Sixty CBA/CaJ mice were divided into two groups. An intraperitoneal injection of anti-HMGB1 antibodies was administered to the experimental group; the control group was injected with saline. Thirty minutes later, all mice were subjected to white noise exposure. Subsequent cochlear damage, including auditory threshold shifts, hair cell loss, expression of cochlear HMGB1, and free radical activity, was then evaluated. The levels of HMGB1 and 4-hydroxynonenal (4-HNE), as respective markers of reactive nitrogen species (RNS) and ROS formation, showed slight increases on post-exposure day 1 and achieved their highest levels on post-exposure day 4. After noise exposure, the antibody-treated mice showed markedly less ROS formation and lower expression of NADPH oxidase 4 (NOX4), nitrotyrosine, inducible nitric oxide synthase (iNOS), and intercellular adhesion molecule-1 (ICAM-1) than the saline-treated control mice. A significant amelioration was also observed in the threshold shifts of the auditory brainstem response and the loss of outer hair cells in the antibody-treated versus the saline-treated mice. Our results suggest that inhibition of HMGB1 by neutralization with anti-HMGB1 antibodies prior to noise exposure effectively attenuated oxidative stress and subsequent inflammation. This procedure could therefore have potential as a therapy for NIHL.

Topics: Aldehydes; Animals; Antibodies, Neutralizing; Cells, Cultured; Cochlea; Disease Models, Animal; Hair Cells, Auditory; Hearing Loss, Noise-Induced; HMGB1 Protein; Inflammation; Mice, Inbred CBA; NADPH Oxidase 4; Nitric Oxide Synthase Type II; Oxidative Stress; Protective Agents; Reactive Oxygen Species; Recombinant Proteins; Up-Regulation

Intracochlear electrical stimulation (ES) generated by cochlear implants (CIs) is used to activate auditory nerves to restore hearing perception in deaf subjects and those with residual hearing who use electroacoustic stimulation (EAS) technology. Approximately 1/3 of EAS recipients experience loss of residual hearing a few months after ES activation, but the underlying mechanism is unknown. Clinical evidence indicates that the loss is related to the previous history of noise-induced hearing loss (NIHL). In this report, we investigated the impact of intracochlear ES on oxidative stress levels and synaptic counts in inner hair cells (IHCs) of the apical, middle and basal regions of guinea pigs with normal hearing (NH) and NIHL. Our results demonstrated that intracochlear ES with an intensity of 6 dB above the thresholds of electrically evoked compound action potentials (ECAPs) could induce the elevation of oxidative stress levels, resulting in a loss of IHC synapses near the electrodes in the basal and middle regions of the NH cochleae. Furthermore, the apical region of cochleae with NIHL were more susceptible to synaptic loss induced by relatively low-intensity ES than that of NH cochleae, resulting from the additional elevation of oxidative stress levels and the reduced antioxidant capability throughout the whole cochlea.

Topics: Action Potentials; Aldehydes; Animals; Antioxidants; Cochlea; Cochlear Implants; Electric Stimulation; Evoked Potentials, Auditory, Brain Stem; Fatty Acids, Unsaturated; Guinea Pigs; Hair Cells, Auditory, Inner; Hearing Loss, Noise-Induced; Hydroxy Acids; Isoindoles; Organoselenium Compounds; Oxidative Stress; Severity of Illness Index; Synapses; Tyrosine

It is well-known that outer hair cell (OHC) loss occurs in the cochlea of animal models of permanent hearing loss induced by intense noise exposure. Our earlier studies demonstrated the production of hydroxynonenal and peroxynitrite, as well as the disruption of gap junction-mediated intercellular communication (GJIC), in the cochlear spiral ligament prior to noise-induced sudden hearing loss. The goal of the present study was to evaluate the mechanism underlying cochlear OHC loss after sudden hearing loss induced by intense noise exposure. In organ of Corti explant cultures from mice, no significant OHC loss was observed after in vitro exposure to 4-hydroxynonenal (a product of lipid peroxidation), H

Topics: Acoustic Stimulation; Aldehydes; Animals; Cell Communication; Cochlea; Gap Junctions; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Hydrogen Peroxide; Male; Mice; Organ Culture Techniques; Spiral Ligament of Cochlea

Previous studies have convincingly argued that reactive oxygen species (ROS) contribute to the development of several major types of sensorineural hearing loss, such as noise-induced hearing loss (NIHL), drug-induced hearing loss, and age-related hearing loss. However, the underlying molecular mechanisms induced by ROS in these pathologies remain unclear. To resolve this issue, we established an in vivo model of ROS overproduction by generating a transgenic (TG) mouse line expressing the human NADPH oxidase 4 (NOX4, NOX4-TG mice), which is a constitutively active ROS-producing enzyme that does not require stimulation or an activator. Overproduction of ROS was detected at the cochlea of the inner ear in NOX4-TG mice, but they showed normal hearing function under baseline conditions. However, they demonstrated hearing function vulnerability, especially at high-frequency sounds, upon exposure to intense noise, which was accompanied by loss of cochlear outer hair cells (OHCs). The vulnerability to loss of hearing function and OHCs was rescued by treatment with the antioxidant Tempol. Additionally, we found increased protein levels of the heat-shock protein 47 (HSP47) in models using HEK293 cells, including H

Topics: Aldehydes; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cochlea; Disease Models, Animal; Evoked Potentials, Auditory, Brain Stem; Gene Expression Regulation; Hearing Loss, Noise-Induced; HEK293 Cells; HSP47 Heat-Shock Proteins; Humans; Immunoprecipitation; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; NADPH Oxidase 4; Reactive Oxygen Species; Transfection

Connexin 26 (cx26) plays an important role in the intercellular signaling and is related to K(+) metabolism in stria vascularis (SV). Reactive oxygen species (ROS) are negative regulators of cx26, reducing intercellular coupling in cochlea. ROS plays an important role in acoustic trauma. Radix astragali is a natural antioxidant that decreases impulse noise-induced hearing loss through its ability to inhibit ROS. The purpose of this study was to investigate if radix astragali has the potential to reduce the change of cx26 in SV from impulse noise. Guinea pigs in the experimental group were administered radix astragali intraperitoneally. Auditory thresholds were assessed by sound-evoked auditory brainstem response (ABR) at click and tone bursts of 8, 16 and 32 kHz, 24 h before and 72 h after exposure to impulse noise. 4-Hydroxynonenal, cx26 and KCNQ1 were determined immunohistochemically in SV. SV was analyzed by transmission electron microscopy. Radix astragali significantly reduced the ABR deficits and the SV damage, and decreased the shifts of the expression of cx26 and KCNQ1 in the SV. These results suggest that the beneficial effect of radix astragali on impulse noise-induced hearing loss may be also due to its ability to reduce the change of cx26 in SV.

Topics: Aldehydes; Animals; Astragalus propinquus; Auditory Threshold; Connexin 26; Connexins; Disease Models, Animal; Down-Regulation; Drugs, Chinese Herbal; Evoked Potentials, Auditory, Brain Stem; Guinea Pigs; Hearing Loss, Noise-Induced; Stria Vascularis

Reactive oxygen species play a dual role in mediating both cell stress and defense pathways. Here, we used pharmacological manipulations and siRNA silencing to investigate the relationship between autophagy and oxidative stress under conditions of noise-induced temporary, permanent, and severe permanent auditory threshold shifts (temporary threshold shift [TTS], permanent threshold shift [PTS], and severe PTS [sPTS], respectively) in adult CBA/J mice.. Levels of oxidative stress markers (4-hydroxynonenal [4-HNE] and 3-nitrotyrosine [3-NT]) increased in outer hair cells (OHCs) in a noise-dose-dependent manner, whereas levels of the autophagy marker microtubule-associated protein light chain 3 B (LC3B) were sharply elevated after TTS but rose only slightly in response to PTS and were unaltered by sPTS noise. Furthermore, green fluorescent protein (GFP) intensity increased in GFP-LC3 mice after TTS-noise exposure. Treatment with rapamycin, an autophagy activator, significantly increased LC3B expression, while diminishing 4-HNE and 3-NT levels, reducing noise-induced hair cell loss, and, subsequently, noise-induced hearing loss (NIHL). In contrast, treatment with either the autophagy inhibitor 3-methyladenine (3MA) or LC3B siRNA reduced LC3B expression, increased 3-NT and 4-HNE levels, and exacerbated TTS to PTS.. This study demonstrates a relationship between oxidative stress and autophagy in OHCs and reveals that autophagy is an intrinsic cellular process that protects against NIHL by attenuating oxidative stress.. The results suggest that the lower levels of oxidative stress incurred by TTS-noise exposure induce autophagy, which promotes OHC survival. However, excessive oxidative stress under sPTS-noise conditions overwhelms the beneficial potential of autophagy in OHCs and leads to OHC death and NIHL.

Topics: Acetylcysteine; Aldehydes; Animals; Antioxidants; Autophagy; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Male; Mice; Microtubule-Associated Proteins; Oxidative Stress; Sirolimus; Tyrosine

Noise-induced hearing loss is at least in part due to disruption of endocochlear potential, which is maintained by various K(+) transport apparatuses including Na(+), K(+)-ATPase and gap junction-mediated intercellular communication in the lateral wall structures. In this study, we examined the changes in the ion-trafficking-related proteins in the spiral ligament fibrocytes (SLFs) following in vivo acoustic overstimulation or in vitro exposure of cultured SLFs to 4-hydroxy-2-nonenal, which is a mediator of oxidative stress. Connexin (Cx)26 and Cx30 were ubiquitously expressed throughout the spiral ligament, whereas Na(+), K(+)-ATPase α1 was predominantly detected in the stria vascularis and spiral prominence (type 2 SLFs). One-hour exposure of mice to 8 kHz octave band noise at a 110 dB sound pressure level produced an immediate and prolonged decrease in the Cx26 expression level and in Na+, K(+)-ATPase activity, as well as a delayed decrease in Cx30 expression in the SLFs. The noise-induced hearing loss and decrease in the Cx26 protein level and Na(+), K(+)-ATPase activity were abolished by a systemic treatment with a free radical-scavenging agent, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, or with a nitric oxide synthase inhibitor, N(ω)-nitro-L-arginine methyl ester hydrochloride. In vitro exposure of SLFs in primary culture to 4-hydroxy-2-nonenal produced a decrease in the protein levels of Cx26 and Na(+), K(+)-ATPase α1, as well as Na(+), K(+)-ATPase activity, and also resulted in dysfunction of the intercellular communication between the SLFs. Taken together, our data suggest that disruption of the ion-trafficking system in the cochlear SLFs is caused by the decrease in Cxs level and Na(+), K(+)-ATPase activity, and at least in part involved in permanent hearing loss induced by intense noise. Oxidative stress-mediated products might contribute to the decrease in Cxs content and Na(+), K(+)-ATPase activity in the cochlear lateral wall structures.

Topics: Aldehydes; Animals; Cell Communication; Connexin 26; Connexin 30; Connexins; Free Radical Scavengers; Free Radicals; Gene Expression Regulation; Hearing Loss, Noise-Induced; Ion Transport; Male; Mice; Mice, Transgenic; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type I; Noise; Oxidative Stress; Piperidines; Primary Cell Culture; Signal Transduction; Sodium-Potassium-Exchanging ATPase; Spiral Ligament of Cochlea; Stria Vascularis

This study addresses the relationship between cochlear oxidative damage and auditory cortical injury in a rat model of repeated noise exposure. To test the effect of increased antioxidant defenses, a water-soluble coenzyme Q10 analog (Qter) was used. We analyzed auditory function, cochlear oxidative stress, morphological alterations in auditory cortices and cochlear structures, and levels of coenzymes Q9 and Q10 (CoQ9 and CoQ10, respectively) as indicators of endogenous antioxidant capability. We report three main results. First, hearing loss and damage in hair cells and spiral ganglion was determined by noise-induced oxidative stress. Second, the acoustic trauma altered dendritic morphology and decreased spine number of II-III and V-VI layer pyramidal neurons of auditory cortices. Third, the systemic administration of the water-soluble CoQ10 analog reduced oxidative-induced cochlear damage, hearing loss, and cortical dendritic injury. Furthermore, cochlear levels of CoQ9 and CoQ10 content increased. These findings indicate that antioxidant treatment restores auditory cortical neuronal morphology and hearing function by reducing the noise-induced redox imbalance in the cochlea and the deafferentation effects upstream the acoustic pathway.

Topics: Accessory Atrioventricular Bundle; Acoustic Stimulation; Aldehydes; Analysis of Variance; Animals; Antioxidants; Auditory Pathways; Brain Injuries; Cochlea; Disease Models, Animal; Ethidium; Evoked Potentials, Auditory, Brain Stem; Hair Cells, Auditory; Hearing Loss, Noise-Induced; Male; Oxidative Stress; Rats; Rats, Wistar; Silver Staining; Ubiquinone; Visual Cortex

The results suggest that the beneficial effect of astragaloside IV on impulse noise-induced hearing loss may be due to its ability to inhibit reactive oxygen species (ROS) and prevent apoptosis.. Astragaloside IV is the major active constituent of Astragalus membranaceus, which has been widely used for the treatment of diseases in China for its antioxidant properties. ROS and apoptosis are involved in damage induced by impulse noise trauma. We aimed to investigate if the beneficial effects of astragaloside IV on cochlea exposed to impulse noise are associated with the inhibition of ROS and the decrease in apoptosis.. 4-Hydroxynonenal (HNE) was used as the marker of ROS. Active-caspase-3 (cas-3) served as a marker for apoptosis. 4HNE and cas-3 were determined immunohistochemically. Guinea pigs in the experimental group were administered astragaloside IV intragastrically. Auditory thresholds were assessed by sound-evoked auditory brainstem response (ABR) 72 h before and after exposure to impulse noise.. The results showed that astragaloside IV significantly reduced ABR deficits, and decreased the expression of ROS and cas-3.

Topics: Aldehydes; Animals; Apoptosis; Caspase 3; Cell Death; Cochlea; Disease Models, Animal; Drugs, Chinese Herbal; Evoked Potentials, Auditory, Brain Stem; Follow-Up Studies; Guinea Pigs; Hearing Loss, Noise-Induced; Immunohistochemistry; Noise; Reactive Oxygen Species; Saponins; Treatment Outcome; Triterpenes

Noise-induced hearing loss (NIHL) is one of the most common forms of sensorineural hearing loss and a well-known contributor to presbycusis. Based on the generation of reactive oxygen species (ROS) in the pathogenesis of NIHL, augmentation of the antioxidative defense system is a major target for pharmacological prevention. In this study, we assessed whether administration of pravastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, which is a rate-limiting enzyme of cholesterol synthesis, before noise exposure protects against cochlear injury in BALB/c mice. Noise exposure produced both compound threshold shift (CTS) and permanent threshold shift (PTS) over 40 dB at 16 and 32 kHz. Pretreatment with pravastatin (25 mg/kg) for 5 days significantly decreased both CTS and PTS. Pravastatin also reduced hair cell death after noise exposure in the cochlea, which was identified by surface preparation and scanning electron microscopy (SEM). It also reduced the formation of noise-induced 4-hydroxynonenal (4-HNE), a byproduct of lipid peroxidation. Activation of Rac1, one of the subunits of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex, which is a major superoxide generator in the cell membrane, was inhibited by the administration of pravastatin. These findings suggest that pravastatin can protect against cochlear acoustic injury by lowering ROS generation via inhibition of the formation of the NADPH oxidase complex. This study will be helpful for the development of new therapeutic strategies for NIHL and other hearing loss-related diseases caused by ROS overproduction.

Topics: Aldehydes; Animals; Blotting, Western; Cholesterol; Cochlea; Evoked Potentials, Auditory, Brain Stem; Hair Cells, Auditory, Inner; Hearing Loss, Noise-Induced; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Immunohistochemistry; Lipid Peroxidation; Male; Mice; Mice, Inbred BALB C; Microscopy, Electron, Scanning; NADPH Oxidases; Pravastatin; Presbycusis; rac1 GTP-Binding Protein; Reactive Oxygen Species

Our results are in agreement with the general idea that natural antioxidants achieve their best cytoprotective capacity if given before and soon after the stressor.. We focused on ferulic acid (FA, 4-hydroxy 3-methoxycinnamic acid), a phenolic compound that is known to exhibit antioxidant properties. Our study was designed to evaluate the effectiveness of FA for different schedules of treatment to establish the 'therapeutic window' for FA protection.. Guinea pigs were exposed to acoustic trauma (6 kHz at 120 dB for 60 min) and received a total dose of 600 mg/kg of FA. Group I, noise control; group II, noise + FA (150 mg/kg) for 4 days starting 24 h post exposure; group III, noise + FA (60 mg/kg) 1 h before and 9 days post exposure; group IV, noise + FA (60 mg/kg) given 3 days before and 7 days post exposure; group V, noise + FA (150 mg/kg) 1 h before and 3 days post noise exposure. Auditory brainstem response (ABR) test and immunohistochemical and morphological studies were performed.. Group V had significantly decreased noise-induced hearing loss at day 21 from noise exposure. The improvement of auditory function by FA was paralleled by a significant reduction in oxidative stress marker. The other schedules of drug administration showed a minor degree of protection.

Topics: Aldehydes; Animals; Cell Count; Coumaric Acids; Drug Administration Schedule; Evoked Potentials, Auditory, Brain Stem; Free Radical Scavengers; Guinea Pigs; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Immunohistochemistry

The results suggest that melanin inhibits formation of reactive oxygen species (ROS) and prevents apoptosis in spiral ganglion cells (SGCs) of pigmented guinea pigs following impulse noise.. The stria vascularis of pigmented guinea pig cochlea contains melanocytes that produce melanin, which has a protective effect on noise-induced hair cell damage through its antioxidant property. ROS are involved in cochlear damage induced by impulse noise trauma. The purpose of the present study was to investigate the oxidative stress in SGCs of pigmented and albino guinea pigs after exposure to impulse noise.. Pigmented and albino guinea pigs were exposed to impulse noise. Auditory thresholds were assessed by sound-evoked auditory brainstem response (ABR) before impulse noise exposure and 72 h after impulse noise exposure. 4-Hydroxynonenal (HNE) was used as a histochemical marker of ROS formation, and active-caspase-3 (cas-3) served as a marker for apoptosis. 4-HNE and cas-3 were determined immunohistochemically. Hair cell damage was analyzed by scanning electron microscopy.. The rates of 4-HNE-positive and cas-3-positive SGCs in pigmented guinea pigs were much less than those for albino guinea pigs. Correspondingly, there was less hair cell damage and reduced ABR threshold shifts in pigmented guinea pigs.

Topics: Acoustic Stimulation; Aldehydes; Animals; Apoptosis; Brain Stem; Caspase 3; Evoked Potentials, Auditory, Brain Stem; Guinea Pigs; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Humans; Lipid Peroxidation; Melanins; Microscopy, Electron, Scanning; Oxidative Stress; Spiral Ganglion

This study analysed the acoustic and vestibular functional and morphological modifications in guinea pigs after acoustic trauma. Animals were exposed to noise (6 kHz, at 120 dB SPL for 60 minutes) and then auditory brainstem responses (ABR) and vestibuloocular reflex (VOR) were measured at 6 hours, 1 day, 3, 7, and 21 days after noise. Western blotting and immunostaining for 4-hydroxy-2-noneal (4-HNE) and vascular endothelial growth factor (VEGF) were performed in the cochlear and vestibular regions at 1 and 7 days after noise exposure. A significant decrease of VOR gain was observed on day 1 and the recovery was completed at day 21. ABR threshold values reached a level of 80 dB at day 1 after trauma reaching a value of about 50 dB SPL on day 21. 4-HNE expression, a marker of lipid peroxidation was strongly increased in the cochlea. In the vestibule, 4-HNE immunoreactivity was faint. However, VEGF was up-regulated both in the cochlea and vestibule. In conclusion, the expression of VEGF in both cochlear and vestibular structures suggests a reparative role with potentially therapeutic implications.

Topics: Aldehydes; Animals; Blotting, Western; Cochlea; Evoked Potentials, Auditory, Brain Stem; Guinea Pigs; Hearing Loss, Noise-Induced; Immunohistochemistry; Reflex, Vestibulo-Ocular; Time Factors; Vascular Endothelial Growth Factor A; Vestibule, Labyrinth

The results of this study indicate that coenzyme Q10 reduces cochlear oxidative stress induced by acoustic overstimulation.. We investigated the effects of coenzyme Q10 on noise-induced hearing loss in guinea pigs.. Animals received water-soluble coenzyme Q10 intraperitoneally 2 h before noise exposure. Seven days after noise exposure (130 dB sound pressure level for 3 h), the auditory brainstem response (ABR) threshold shift and cochlear hair cell damage were assessed.. We observed that the ABR threshold shift was significantly less in the coenzyme Q10 group than in the vehicle control group. In addition, the percentage of missing outer hair cells was lower in the coenzyme Q10 group than in the control group. Moreover, 2 days after administration of coenzyme Q10, increased antioxidative activity in the cochlea, as measured by analysis of hydroxy radical scavenging activity by electron spin resonance was observed.

Topics: Aldehydes; Animals; Antioxidants; Auditory Threshold; Electron Spin Resonance Spectroscopy; Evoked Potentials, Auditory, Brain Stem; Free Radical Scavengers; Guinea Pigs; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Hydroxyl Radical; Immunohistochemistry; Male; Ubiquinone

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are involved in sensory cell and neural death in the peripheral nervous system, including damage induced by noise trauma. Antioxidant administration prior to or concomitant with noise exposure can prevent auditory deficits, but the efficacy of a delayed treatment is not known. We have recently found continued reactive oxygen species/reactive nitrogen species formation in the ear for 7-10 days following noise exposure and reasoned that antioxidant intervention during this period should also reduce noise-induced hearing loss. Guinea-pigs were subjected to 4 kHz octave band noise at 120 decibels sound- pressure-level (dB SPL) for 5 hours and received treatment with ROS and RNS scavengers (salicylate and trolox) beginning 3 days prior, 1 hour, 1, 3, or 5 days after noise exposure. Auditory thresholds were assessed by sound-evoked auditory brainstem response at 4, 8, and 16 kHz, before and 10 days after noise exposure. Hair cell damage was analyzed by quantitative histology, and free radical activity was determined immunohistochemically via 4-hydroxynonenal and nitrotyrosine as markers of reactive oxygen species and reactive nitrogen species action. Delivered up to 3 days after noise exposure, salicylate and trolox significantly reduced auditory brainstem response deficits, reduced hair cell damage, and decreased reactive oxygen species and reactive nitrogen species formation. Earlier drug treatment was more effective than later treatment. Our results detail a window of opportunity for rescue from noise trauma, and provide evidence for both morphological and functional protection by delayed pharmacological intervention.

Topics: Aldehydes; Animals; Cochlea; Guinea Pigs; Hearing Loss, Noise-Induced; Immunohistochemistry; Male; Reactive Oxygen Species; Sound; Time Factors; Tyrosine