Purinergic Signaling and Cochlear Injury-Targeting the Immune System?

Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K+ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.

[The estimation of the efficacy of manual therapy included in the combined treatment of cochlear-vestibular disorders based on the results of computed stabilography].

The objective of the present study was to estimate the efficacy of the combined treatment of spondylogenic cochlear-vestibular disorders with the use of both medicamental and non-medicamental modalities. Computed static stabilometry was applied for diagnostics of postural disbalance and evaluation of the treatment outcomes. It was shown that the application of manual therapy for the management of 56 patients presenting with spondylogenic cochlear-vestibular disorders resulted in the decrease of tinnitus and the improvement of vestibular and cochlear functions.

[Cochleovestibular disorders: approaches to diagnostics and treatment].

The aim of this work was to evaluate the efficacy of introduction of milgamma and milgamma compositum in the treatment of 52 patients with cochleovestibular disorders of different etiology. Thirteen patients enrolled in the study received standard therapy and 39 others were given its combination with milgamma preparations. Combined therapy with milgamma and milgamma compositum ensured faster vestibular compensation including posturographic characteristics than the standard treatment (within 3-4 weeks compared with 5 weeks in controls). The results of the study give reason to recommend milgamma and milgamma compositum as neurotropic medicines in addition to standard therapy for the management of the patients presenting with cochleovestibular disorders for the acceleration of the vestibular compensation.

[Susac syndrome: study of five cases]. / Syndrome de Susac: étude de cinq cas.

INTRODUCTION: Susac syndrome is a rare microangiopathy, responsible for small cerebral, retinal and cochlear infarcts. The classic clinical triad includes multiple neurologic signs (from headaches to coma), retinal branch occlusions and sensorineural hearing loss. METHODS: We report a series of five patients with Susac syndrome followed in our department from 1997 to 2007. RESULTS: There were four women and one man (mean age at onset: 35.2 years). Clinical symptoms at onset were neurological (n=1), ophthalmological (n=1), auditory (n=1) and clinical triad (n=2). Neurologic symptoms included encephalopathy (n=2), headache (n=5), transient ischemic attacks (n=1). Brain MRI showed T2 lesions in the white and grey matter, corpus callosum and gadolinium-enhanced punctiform lesions. Cerebrospinal fluid contained an elevated protein level in three cases. Immunologic treatments (steroids [n=4], cylophosphamid [n=3], intravenous immunoglobulins [n=5]) associated with aspirin and/or oral anticoagulants, despite early relapses (n=2), led to dramatic clinical improvement (n=5). CONCLUSION: Due to its polymorphism the SS is difficult to diagnose when the clinical triad is lacking. In the absence of clinical trial and consensus treatment is empiric and based on supposed pathogenesis.

State-of-the-art methods in clinical intracochlear drug delivery.

PURPOSE OF REVIEW: Increasing awareness and prevalence of disorders in hearing and balance have placed emphasis on treatment strategies. With the rapid evolution in molecular, gene, and nanotechnology, alternate delivery methods have advanced intracochlear drug delivery. This review aims to raise awareness of recent developments in technologies to augment current clinical practices. RECENT FINDINGS: Intracochlear drug delivery research has expanded with the familiarity and accessibility to cochlear implantation. Various therapeutics are closely studied for both safety and efficacy as well as biologic effect. Agents including neurotrophins, antiapoptotics, cell therapy, gene therapy, and anti-inflammatory drugs are on the forefront of preclinical research. Cochlear implant electrode modification and drug administration at the time of implantation is a major focus of research. Improvements in study design have focused on overcoming barriers including elucidating the role of the blood-perilymph barrier. SUMMARY: Inner ear drug delivery methods include systemic, intratympanic, and intracochlear administration. Therapeutic technologies aim to overcome delivery barriers and to improve overall biologic effect while minimizing toxicity. Precision of drug application through intratympanic and intracochlear administration with minimal trauma is the future of inner ear drug development.

Remission of Recurrent Cochlear Hydrops Associated With Bromocriptine Treatment for Macroprolactinoma.

Objective Current recommendations for cochlear hydrops treatment include systemic glucocorticoids and diuretics. Cochlear cells express dopamine receptors, although their role is unknown in the pathophysiology of cochlear hydrops. Case Description We report the case of remission of recurrent right-sided cochlear hydrops in a young male patient treated with bromocriptine due to pituitary macroprolactinoma. Transient improvement was observed after oral steroid and diuretic treatment, but cochlear hydrops recurred until the dose of bromocriptine was increased to 10 mg daily. Conclusion Bromocriptine may stimulate dopamine receptors in cochlear cells with potential therapeutic role in patients with cochlear hydrops. There are no widely accepted and effective treatments for endolymphatic hydrops, and identifying potential new and efficacious therapeutics is of high relevance.

Innovative pharmaceutical approaches for the management of inner ear disorders.

The sense of hearing is essential for permitting human beings to interact with the environment, and its dysfunctions can strongly impact on the quality of life. In this context, the cochlea plays a fundamental role in the transformation of the airborne sound waves into electrical signals, which can be processed by the brain. However, several diseases and external stimuli (e.g., noise, drugs) can damage the sensorineural structures of cochlea, inducing progressive hearing dysfunctions until deafness. In clinical practice, the current pharmacological approaches to treat cochlear diseases are based on the almost exclusive use of systemic steroids. In the last decades, the efficacy of novel therapeutic molecules has been proven, taking advantage from a better comprehension of the pathological mechanisms underlying many cochlear diseases. In addition, the feasibility of intratympanic administration of drugs also permitted to overcome the pharmacokinetic limitations of the systemic drug administration, opening new frontiers in drug delivery to cochlea. Several innovative drug delivery systems, such as in situ gelling systems or nanocarriers, were designed, and their efficacy has been proven in vitro and in vivo in cochlear models. The current review aims to describe the art of state in the cochlear drug delivery, highlighting lights and shadows and discussing the most critical aspects still pending in the field.

Preclinical and clinical otoprotective applications of cell-penetrating peptide D-JNKI-1 (AM-111).

There is a growing interest in the auditory community to develop novel prophylactic and therapeutic drugs to prevent permanent sensorineural hearing loss following acute cochlear injury. The jun-N-terminal protein kinase (JNK) pathway plays a crucial role in acute sensory hearing loss. Blocking the JNK pathway using the cell-penetrating peptide D-JNKI-1 (AM-111/brimapitide) has shown promise as both a prophylactic and therapeutic agent for acute cochlear injury. A number of pre-clinical and clinical studies have determined the impact of D-JNKI-1 on acute sensorineural hearing loss. Given the inner-ear selective therapeutic profile, local route of administration, and ability to diffuse across cellular membranes rapidly using both active and passive transport makes D-JNK-1 a promising oto-protective drug. In this review article, we discuss the application of D-JNKI-1 in various auditory disorders as well as its pharmacological properties and distribution in the cochlea.

The effects of the glucocorticoid receptor antagonist RU486 and phospholipase A2 inhibitor quinacrine on acoustic injury of the mouse cochlea.

Glucocorticoids are used clinically for the treatment of acoustic injury. However, the protective mechanism of glucocorticoid in acoustic injury has not been completely clarified. Also, the effects of phospholipase A2 (PLA2) on acoustic injury have not been examined to the best of our knowledge. The purpose of the present study was to examine the effects of methylprednisolone, a glucocorticoid receptor inhibitor (RU486) and a phospholipase A2 inhibitor (quinacrine) on cochlear injury induced by acoustic overexposure. Seventy-eight mice were exposed to a 4kHz pure tone at 128dB SPL for 4h. The auditory brainstem response (ABR) was used to examine the hearing thresholds. Cochlear morphology was examined to estimate the outer hair cell loss induced by acoustic overexposure. Methylprednisolone and quinacrine significantly alleviated the hearing threshold shift and hair cell loss induced by acoustic overexposure. RU486 antagonized the protective effect of methylprednisolone. The present findings suggest firstly that glucocorticoids exert protective effects against acoustic injury; secondly, that the protective effect of methylprednisolone was exerted by binding glucocorticoid receptors, and finally that activation of PLA2 may be involved in acoustic injury.

Ginsenoside Rb1 protects against damage to the spiral ganglion cells after cochlear ischemia.

The effects of transient cochlear ischemia on spiral ganglion cells (SGCs) were studied in Mongolian gerbils. Ischemic insult was induced by occluding the bilateral vertebral arteries of gerbils for 15min. Seven days after ischemia, the percentage of SGCs decreased to 67.5% from the preischemic baseline in the basal turn. Evaluation with immunohistochemical staining showed TUNEL-positive reactions in the SGCs with fragmented nuclei. In addition, we investigated the protective effects of ginsenoside Rb1 (gRb1) against ischemic injury to SGCs. Seven days after ischemia, the auditory brainstem response threshold shift was significantly reduced and the percentage of SGCs decreased to 90.2% from the preischemic baseline in the basal turn in the gRb1-treated group. These findings suggest that gRb1 prevented hearing loss caused by ischemic injury to SGCs in Mongolian gerbils.

Cochlear protection by local insulin-like growth factor-1 application using biodegradable hydrogel.

OBJECTIVE: The aim of this experimental study was to examine the potential of local recombinant human insulin-like growth factor-1 (rhIGF-1) application through a biodegradable hydrogel for the treatment of cochleae. METHODS: A hydrogel immersed with rhIGF-1 was placed on the round window membrane of Sprague-Dawley rats while a hydrogel immersed with physiological saline was applied to control animals. On day 3 after drug application, the animals were exposed to white noise at 120 dB sound pressure level (SPL) for 2 hours. Cochlear function was monitored using measurements of auditory brain stem responses (ABRs) at frequencies of 8, 16, and 32 kHz. The temporal bones were collected 7 or 30 days after noise exposure and the loss of hair cells was quantitatively analyzed. RESULTS: Local rhIGF-1 treatment significantly reduced the elevation of ABR thresholds on days 7 and 30 after noise exposure. Histologic analysis revealed that local rhIGF-1 treatment significantly prohibited the loss of outer hair cells. CONCLUSIONS: These findings demonstrate that local IGF-1 application through the biodegradable hydrogel has the potential for protection of cochleae from noise trauma.

Cochlear preservation after meningitis: an animal model confirmation of adjunctive steroid therapy.

OBJECTIVE/HYPOTHESIS: The objective of the present study was to determine whether treating pneumococcal meningitis with a combined antibiotic and steroid regime will prevent cochlear damage, a common pneumococcal meningitis side effect. STUDY DESIGN: This was a prospective animal study. METHODS: Gerbils were randomly assigned to three experimental groups. Animals in group 1, the control animals, received intrathecal saline injections. Animals in groups 2 and 3 received intrathecal injections of Streptococcus pneumoniae to induce meningitis. Although group 2 solely was treated for 7 days with intraperitoneal penicillin injections (48,0000 units), group 3 received, in addition to the antibiotic for 4 days, 0.5 mg/kg intraperitoneal dexamethasone injections. Three months after the meningitis was induced, the animals' cochlear function was determined using auditory brainstem responses (ABRs). Fifteen frequencies were tested, five octaves at three steps per octave between 2 and 50 kHz. RESULTS: ABR thresholds were significantly elevated only in group 2. When compared with group 1, ABR thresholds were 19 dB higher (P<.05). Frequencies at the low-frequency end of the hearing range were affected more than the midfrequencies. Animals that received dexamethasone had 2-dB higher thresholds than the control group (P>.05). CONCLUSIONS: Dexamethasone therapy in conjunction with antibiotic therapy preserves cochlear function in cases of S. pneumoniae meningitis in the Mongolian gerbil model.

Response of cochlear blood flow to prostaglandin E1 applied topically to the round window.

CONCLUSIONS: The increase in cochlear blood flow (CBF) after administration of prostaglandin E1 (PGE1) to the round window depends on increased blood flow through the anterior inferior cerebellar artery (AICA). OBJECTIVES: To evaluate the response of CBF to PGE1 applied topically to the round window, and to investigate the origin of blood flow changes after this topical application. MATERIAL AND METHODS: The response of CBF to topically applied PGE1 was measured by placing the tip of a laser Doppler probe on the bony wall of the basal turn of the cochlea after the middle ear mucosa over the cochlea had been removed in guinea pigs and rats. In rats, the CBF response to PGE1 administration was investigated after occlusion of the AICA or stapedial artery. RESULTS: CBF increased following PGE1 administration in both guinea pigs and rats. In rats, CBF increased from 100% to 132%+/-10% (mean+/-SD) after the topical application of 0.5 microl of a 0.014% PGE1 solution. CBF decreased after occlusion of the AICA or stapedial artery but did not increase after PGE1 administration during occlusion of the AICA. The CBF response to PGE1 administration was similar before and after occlusion of the stapedial artery.

Triamcinolone acetonide protects auditory hair cells from 4-hydroxy-2,3-nonenal (HNE) ototoxicity in vitro.

CONCLUSION: Triamcinolone acetonide crystalline suspension (e.g. Volon A) was not ototoxic to the auditory hair cells present within organ of Corti explants and protected them from an ototoxic molecule, i.e. 4-hydroxy-2,3-nonenal (HNE), that is produced within the organ of Corti as a result of oxidative stress-induced damage. OBJECTIVES: To test the corticosteroid, triamcinolone acetonide, for ototoxicity and otoprotective capacity in organ of Corti explants. MATERIALS AND METHODS: Organ of Corti explants excised from 4-day-old rats were the test system, HNE was the ototoxin challenge. Hair cell integrity counts were performed with fluorescent microscopy on fixed explants stained with FITC-labeled phalloidin. Statistical significance was set at p<0.05. RESULTS: Triamcinolone acetonide did not affect hair cell integrity in the organ of Corti explants and it provided a high level of protection of hair cells against the ototoxic effects of a damaging level of HNE as determined by hair cell density counts.

A unique case of adolescent neuroborreliosis presenting with multiple cranial neuritis and cochlear inflammation on magnetic resonance imaging.

BACKGROUND: Lyme disease is the most common vector-borne disease in the United States and is caused by infection with the spirochete Borrelia burgdorferi. In children, neuroborreliosis usually presents as peripheral facial nerve palsy and lymphocytic meningitis and only rarely is associated with cranial polyneuritis. PATIENT DESCRIPTION: We present a 15-year-old with tinnitus, hearing loss, and facial nerve palsy in the setting of acute, severe right arm pain and a several week history of malaise and headache. Lumbar puncture was notable for lymphocytic pleocytosis. Serologic testing demonstrated positive Lyme antibody and a positive immunoglobulin M Western blot. Immunofluorescent assay of cerebrospinal fluid was also positive for anti-Lyme immunoglobulin M. Audiologic testing revealed mixed, right-sided hearing loss. Neuroimaging demonstrated cranial polyneuritis and right-sided cochlear inflammation. The patient was treated with parenteral ceftriaxone with resolution of his symptoms at close follow-up. DISCUSSION: Neuroborreliosis with radiculopathy, lymphocytic meningitis, and cranial polyneuritis is a rare presentation of pediatric Lyme disease. Additionally, cochlear inflammation along with cranial nerve VIII inflammation may contribute to hearing loss in patients with neuroborreliosis.

The role of acidic fibroblast growth factor in recovery of acoustic trauma.

We administered acidic fibroblast growth factor (aFGF) to the perilymph of the guinea pig cochlea after exposure to intense sound to investigate its effect on the process of recovery after acoustic trauma. We assessed auditory brain stem response (ABR) thresholds to evaluate cochlear function and observed the sensory epithelium using confocal laser-scanning microscopy. After noise exposure (120 dB SPL, 5 h), the ABR threshold showed an increase of approximately 50 dB SPL that recovered after 14 days. Cochlear function in aFGF treated ears recovered more quickly than that in control ears. These results suggest that aFGF may play an important role in cochlear recovery after acoustic injury.

Effects of immunosuppression on the development of cochlear disease in the MRL-Fas(lpr) mouse.

OBJECTIVES: The MRL-Fas(lpr) mouse, an animal that spontaneously develops multisystemic autoimmune disease, has been proposed as model of immune-mediated inner ear disease. Previous studies revealed that this mouse manifested elevated auditory brainstem response thresholds, hydropic degeneration of strial cells, and antibody deposition within strial capillaries. As the etiology of the observed strial disease may be immune, genetic, or uremic, a study was designed to attempt to delineate between these possible etiologic factors. STUDY DESIGN: Prospective, controlled animal study. METHODS: Dexamethasone, which is known to suppress autoantibody production and glomerulonephritis in these animals, was administered systemically on a daily basis to experimental animals, beginning at 6 weeks of age. Control animals received no treatment. Animals were allowed to age, with control animals predictably manifesting systemic disease at 20 weeks of age, at which point all animals were sacrificed. RESULTS: Animals receiving dexamethasone treatment manifested a significant reduction in serum immunoglobulin levels, lymphoid hyperplasia, and a significant improvement in the level of renal function. However, morphologic analysis revealed a persistence of strial disease despite the elimination of strial antibody deposition. CONCLUSION: The results of this experiment support the hypothesis that genetic mechanisms may be responsible for the observed strial disease. Further studies are under way to confirm these findings.

Otosyphilis: a diagnostic and therapeutic dilemma.

Traditional treatment of otosyphilis with penicillin and corticosteroids has achieved hearing improvement; however, selecting which patients with a positive fluorescent treponemal antibody absorption (FTA-ABS) test will benefit from treatment remains a problem. In order to study this problem, 18 patients with cochleovestibular dysfunction of unknown etiology and positive syphilis serology were treated with intravenous penicillin and corticosteroids. In addition, lumbar puncture and human immunodeficiency virus (HIV) testing were performed on all patients. Hearing improved in 5 (31%) of 16 patients, tinnitus decreased in 11 (85%) of 13, and vertigo improved in 6 (86%) of 7. Factors associated with hearing improvement were hearing loss present less than 5 years, fluctuating hearing, and age less than 60. Improvement was unrelated to the severity of the loss or previous therapy. All patients with cerebrospinal fluid abnormalities, including two patients with HIV disease, had subjective improvements. A diagnostic and treatment protocol is presented.