d-jnki-1 and Disease-Models--Animal

JNKs (c-Jun N- terminal kinases) are important transducing enzymes involved in many faces of cellular regulation such as gene expression, cell proliferation and programmed cell death. The activation of JNK pathway is critical for naturally occurring neuronal death during development as well as for pathological death of adult brain following different insults. In particular, JNKs play an important role in excitotoxicity and all related phenomena. Initial research concentrated on defining the components and organization of JNK signalling cascades, but more recent studies have begun to see JNK as the appropriate target for prevent cell loss. We used a specific JNK inhibitor, the cell permeable peptide D-JNKI1, to block JNK action in neuronal death following excitotoxicity in vitro and cerebral ischemia in vivo. Here we review our recent findings and we discuss the possibility of using D-JNKI1 as a therapeutic agent to prevent cell loss in the central nervous system.

Topics: Animals; Central Nervous System; Disease Models, Animal; Enzyme Inhibitors; Hippocampus; Humans; Ischemia; MAP Kinase Kinase 4; Mice; Nerve Degeneration; Neurodegenerative Diseases; Neurons; Peptides; Rats

Alzheimer's disease (AD) is characterized by accumulations of amyloid-β (Aβ42) and hyperphosphorylated tau proteins, associated with neuroinflammation, synaptic loss, and neuronal death. Several studies indicate that c-Jun N-terminal kinase (JNK) is implicated in the pathological features of AD. We have investigated in 5XFAD mice, the therapeutic effects of Brimapitide, a JNK-specific inhibitory peptide previously tested with higher concentrations in another AD model (TgCRND8). Three-month-old 5XFAD and wild-type littermate mice were treated by intravenous injections of low doses (10 mg/kg) of Brimapitide every 3 weeks, for 3 or 6 months (n = 6-9 per group). Cognitive deficits and brain lesions were assessed using Y-maze, fear-conditioning test, and histological and biochemical methods. Chronic treatment of Brimapitide for 3 months resulted in a reduction of Aβ plaque burden in the cortex of 5XFAD treated mice. After 6 months of treatment, cognitive deficits were reduced but also a significant reduction of cell death markers and the pro-inflammatory IL-1β cytokine in treated mice were detected. The Aβ plaque burden was not anymore modified by the 6 months of treatment. In addition to modulating cognition and amyloid plaque accumulation, depending on the treatment duration, Brimapitide seems experimentally to reduce neuronal stress in 5XFAD mice.

Topics: Alzheimer Disease; Animals; Brain; Cell Death; Cognition; Disease Models, Animal; Humans; Learning; Male; MAP Kinase Kinase 4; Mice, Transgenic; Neurons; Neuroprotective Agents; Nootropic Agents; Peptides; Plaque, Amyloid

Roux-en-Y gastric bypass (RYGB) reduces obesity-associated comorbidities and cardiovascular mortality. RYGB improves endothelial dysfunction, reducing c-Jun N-terminal kinase (JNK) vascular phosphorylation. JNK activation links obesity with insulin resistance and endothelial dysfunction. Herein, we examined whether JNK1 or JNK2 mediates obesity-induced endothelial dysfunction and if pharmacological JNK inhibition can mimic RYGB vascular benefits.. After 7 weeks of a high-fat high-cholesterol diet, obese rats underwent RYGB or sham surgery; sham-operated ad libitum-fed rats received, for 8 days, either the control peptide D-TAT or the JNK peptide inhibitor D-JNKi-1 (20 mg/kg per day subcutaneous). JNK peptide inhibitor D-JNKi-1 treatment improved endothelial vasorelaxation in response to insulin and glucagon-like peptide-1, as observed after RYGB. Obesity increased aortic phosphorylation of JNK2, but not of JNK1. RYGB and JNK peptide inhibitor D-JNKi-1 treatment blunted aortic JNK2 phosphorylation via activation of glucagon-like peptide-1-mediated signaling. The inhibitory phosphorylation of insulin receptor substrate-1 was reduced, whereas the protein kinase B/endothelial NO synthase pathway was increased and oxidative stress was decreased, resulting in improved vascular NO bioavailability.. Decreased aortic JNK2 phosphorylation after RYGB rapidly improves obesity-induced endothelial dysfunction. Pharmacological JNK inhibition mimics the endothelial protective effects of RYGB. These findings highlight the therapeutic potential of novel strategies targeting vascular JNK2 against the severe cardiovascular disease associated with obesity.

Topics: Animals; Cardiovascular Diseases; Disease Models, Animal; Endothelium, Vascular; Gastric Bypass; Injections, Subcutaneous; Male; Mitogen-Activated Protein Kinase 9; Neuroprotective Agents; Obesity; Oxidative Stress; Peptides; Phosphorylation; Rats; Rats, Wistar; Vasodilation

XG-102, a TAT-coupled dextrogyre peptide inhibiting the c-Jun N-terminal kinase, was shown efficient in the treatment of experimental uveitis. Preclinical studies are now performed to determine optimal XG-102 dose and route of administration in endotoxin-induced uveitis (EIU) in rats with the purpose of clinical study design.. EIU was induced in Lewis rats by lipopolysaccharides (LPS) injection. XG-102 was administered at the time of LPS challenge by intravenous (IV; 3.2, 35 or 355 μg/injection), intravitreal (IVT; 0.08, 0.2 or 2.2 μg/eye), or subconjunctival (SCJ; 0.2, 1.8 or 22 μg/eye) routes. Controls received either the vehicle (saline) or dexamethasone phosphate injections. Efficacy was assessed by clinical scoring, infiltrating cells count, and expression of inflammatory mediators [inducible nitric oxide synthase (iNOS), cytokine-induced neutrophil chemoattractant-1 (CINC-1)]. The effect of XG-102 on phosphorylation of c-Jun was evaluated by Western blot.. XG-102 demonstrated a dose-dependent anti-inflammatory effect in EIU after IV and SCJ administrations. Respective doses of 35 and 1.8 μg were efficient as compared with the vehicle-injected controls, but only the highest doses, respectively 355 and 22 μg, were as efficient as dexamethasone phosphate. After IVT injections, the anti-inflammatory effect of XG-102 was clinically evaluated similar to the corticoid's effect with all the tested doses. Regardless of the administration route, the lowest efficient doses of XG-102 significantly decreased the ration of phospho c-Jun/total c-Jun, reduced cells infiltration in the treated eyes, and significantly downregulated iNOS and CINC-1 expression in the retina.. These results confirm that XG-102 peptide has potential for treating intraocular inflammation. SCJ injection appears as a good compromise to provide a therapeutic effect while limiting side effects.

Topics: Animals; Anti-Inflammatory Agents; Chemokine CXCL1; Disease Models, Animal; Dose-Response Relationship, Drug; Down-Regulation; Female; Injections, Intraocular; Injections, Intravenous; Lipopolysaccharides; Nitric Oxide Synthase Type II; Peptides; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-jun; Random Allocation; Rats; Rats, Inbred Lew; Uveitis

Chronic ethanol (EtOH) abuse worsens pathophysiological derangements after hemorrhagic shock and resuscitation (H/R) that induce hepatic injury and strong inflammatory changes via JNK and NF-κB activation. Inhibiting JNK with a cell-penetrating, protease-resistant peptide D-JNKI-1 after H/R in mice with healthy livers ameliorated these effects. Here, we studied if JNK inhibition by D-JNKI-1 in chronically EtOH-fed mice after hemorrhagic shock prior to the onset of resuscitation also confers protection.. Male mice were fed a Lieber-DeCarli diet containing EtOH or an isocaloric control (ctrl) diet for 4 weeks. Animals were hemorrhaged for 90 min (32 ± 2 mm Hg) and randomly received either D-JNKI-1 (11 mg/kg, intraperitoneally, i. p.) or sterile saline as vehicle (veh) immediately before the onset of resuscitation. Sham animals underwent surgical procedures without H/R and were either D-JNKI-1 or veh treated. Two hours after resuscitation, blood samples and liver tissue were harvested.. H/R induced hepatic injury with increased systemic interleukin (IL)-6 levels, and enhanced local gene expression of NF-κB-controlled genes such as intercellular adhesion molecule (ICAM)-1 and matrix metallopeptidase (MMP)9. c-Jun and NF-κB phosphorylation were increased after H/R. These effects were further increased in EtOH-fed mice after H/R. D-JNKI-1 application inhibited the proinflammatory changes and reduced significantly hepatic injury after H/R in ctrl-fed mice. Moreover, D-JNKI-1 reduces in ctrl-fed mice the H/R-induced c-Jun and NF-κB phosphorylation. However, in chronically EtOH-fed mice, JNK inhibition did not prevent the H/R-induced hepatic damage and proinflammatory changes nor c-Jun and NF-κB phosphorylation after H/R.. These results indicate, that JNK inhibition is protective only in not pre-harmed liver after H/R. In contrast, the pronounced H/R-induced liver damage in mice being chronically fed with ethanol cannot be prevented by JNK inhibition after H/R and seems to be under the control of NF-κB.

Topics: Alcoholism; Animals; Disease Models, Animal; Ethanol; Gene Expression Regulation; Interleukin-6; Liver Diseases; Male; MAP Kinase Kinase 4; Mice, Inbred C57BL; NF-kappa B; Peptides; Phosphorylation; Resuscitation; Shock, Hemorrhagic; Tumor Necrosis Factor-alpha

Altered synaptic function is considered one of the first features of Alzheimer disease (AD). Currently, no treatment is available to prevent the dysfunction of excitatory synapses in AD. Identification of the key modulators of synaptopathy is of particular significance in the treatment of AD. We here characterized the pathways leading to synaptopathy in TgCRND8 mice and showed that c-Jun N-terminal kinase (JNK) is activated at the spine prior to the onset of cognitive impairment. The specific inhibition of JNK, with its specific inhibiting peptide D-JNKI1, prevented synaptic dysfunction in TgCRND8 mice. D-JNKI1 avoided both the loss of postsynaptic proteins and glutamate receptors from the postsynaptic density and the reduction in size of excitatory synapses, reverting their dysfunction. This set of data reveals that JNK is a key signaling pathway in AD synaptic injury and that its specific inhibition offers an innovative therapeutic strategy to prevent spine degeneration in AD.

Topics: Alzheimer Disease; Animals; Disease Models, Animal; Female; Humans; JNK Mitogen-Activated Protein Kinases; Male; Mice; Mice, Transgenic; Peptides; Signal Transduction; Synapses

Neonatal encephalopathy is associated with high mortality and life-long developmental consequences. Therapeutic options are very limited. We assessed the effects of D-JNKi, a small peptide c-Jun N-terminal kinase (JNK) MAP kinase inhibitor, on neuroinflammation, mitochondrial integrity and neuronal damage in a neonatal rat model of ischemic brain damage. Hypoxic-ischemic (HI) brain injury was induced in postnatal-day 7 rats by unilateral carotid artery occlusion and hypoxia, and was followed by intraperitoneal D-JNKi treatment. We demonstrate here for the first time that a single intraperitoneal injection with D-JNKi directly after HI strongly reduces neonatal brain damage by >85% with a therapeutic window of at least 6h. D-JNKi treatment also restored cognitive and motor function as analyzed at 9weeks post-insult. Neuroprotective D-JNKi treatment inhibited phosphorylation of nuclear c-Jun (P-c-Jun), and consequently reduced activity of the AP-1 transcription factor and production of cerebral cytokines/chemokines as determined at 3 and 24h post-HI. Inhibition of P-c-Jun by D-JNKi is thought to be mediated via inhibition of the upstream phosphorylation of cytosolic and nuclear JNK and/or by preventing the direct interaction of phosphorylated (P-)JNK with c-Jun. Surprisingly, however, HI did not induce a detectable increase in P-JNK in cytosol or nucleus. Notably, we show here for the first time that HI induces P-JNK only in the mitochondrial fraction, which was completely prevented by D-JNKi treatment. The hypothesis that mitochondrial JNK activation is key to HI brain injury was supported by data showing that treatment of rat pups with SabKIM1 peptide, a specific mitochondrial JNK inhibitor, is also neuroprotective. Inhibition of HI-induced mitochondrial JNK activation was associated with preservation of mitochondrial integrity as evidenced by prevention of ATP loss and inhibition of lipid peroxidation. The HI-induced increase in apoptotic markers (cytochrome c release and caspase 3 activation) as analyzed at 24h post-HI were also strongly reduced by D-JNKi and the mitochondrial anti-apoptotic proteins Bcl-2 and Bcl-xL were upregulated. Neuroprotection was lost after repeated 0+3h D-JNKi treatment which was associated with complete inhibition of the second peak of AP-1 activity and disability to upregulate mitochondrial Bcl-2 and Bcl-xL. We show here for the first time that D-JNKi treatment efficiently protects the neonatal brain against ischemic brain da

Topics: Animals; Animals, Newborn; Apoptosis; Blotting, Western; Brain Ischemia; Disease Models, Animal; Electrophoretic Mobility Shift Assay; Enzyme Inhibitors; Inflammation; MAP Kinase Kinase 4; Mitochondria; Neuroprotective Agents; Oxidative Stress; Peptides; Phosphorylation; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction

Kainic acid (KA) induced seizures provokes an extensive neuronal degeneration initiated by c-Jun N-terminal kinases (JNK) as central mediators of excitotoxicity. However, the actions of their individual isoforms in cellular organelles including mitochondria remain to be elucidated. Here, we have studied the activation of JNK1, JNK2 and JNK3 and their activators, mitogen-activated protein kinase kinase (MKK) 4/7, in brain mitochondria, cytosolic and nuclear fractions after KA seizures. In the mitochondrial fraction, KA significantly increased the presence of JNK1, JNK3 and MKK4 and stimulated their phosphorylation i.e. activation. The pro-apoptotic proteins, Bim and Bax were induced and, consequently, the ratio Bcl-2-Bax decreased. These changes were paralleled by the release of cytochrome c and cleavage of poly(ADP-ribose)-polymerase (PARP). The JNK peptide inhibitor, D-JNKI-1 (XG-102) reversed these pathological events in the mitochondria and almost completely abolished cytochrome c release and PARP cleavage. Importantly, JNK3, but not JNK1 or JNK2, was associated with Bim in mitochondria and D-JNKI-1 prevented the formation of this apoptotic complex. Apart from of the attenuation of c-Jun phosphorylation in the nucleus, D-JNKI-1 did not affect the level of JNK3 isoform in the nuclear and cytosolic fractions. These findings provide novel insights into the mode of action of individual JNK isoforms in cell organelles and points to the JNK3 pool in mitochondria as a target of the JNK inhibitor D-JNKI-1 to confer neuroprotection.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Brain; Cytochromes c; Disease Models, Animal; Hippocampus; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Signaling System; Mitochondria; Mitogen-Activated Protein Kinase Kinases; Peptides; Phosphorylation; Poly(ADP-ribose) Polymerases; Rats; Rats, Sprague-Dawley

Traumatic brain injury (TBI) is a major environmental risk factor for subsequent development of Alzheimer disease (AD). Pathological features that are common to AD and many tauopathies are neurofibrillary tangles (NFTs) and neuropil threads composed of hyperphosphorylated tau. Axonal accumulations of total and phospho-tau have been observed within hours to weeks, and intracytoplasmic NFTs have been documented years after severe TBI in humans. We previously reported that controlled cortical impact TBI accelerated tau pathology in young 3xTg-AD mice. Here, we used this TBI mouse model to investigate mechanisms responsible for increased tau phosphorylation and accumulation after brain trauma. We found that TBI resulted in abnormal axonal accumulation of several kinases that phosphorylate tau. Notably, c-Jun N-terminal kinase (JNK) was markedly activated in injured axons and colocalized with phospho-tau. We found that moderate reduction of JNK activity (40%) by a peptide inhibitor, D-JNKi1, was sufficient to reduce total and phospho-tau accumulations in axons of these mice with TBI. Longer-term studies will be required to determine whether reducing acute tau pathology proves beneficial in brain trauma.

Topics: Amyloid beta-Peptides; Animals; Brain Injuries; Cerebral Cortex; Disability Evaluation; Disease Models, Animal; Enzyme Inhibitors; Humans; JNK Mitogen-Activated Protein Kinases; Mice; Mice, Transgenic; Nerve Tissue Proteins; Peptides; Phosphorylation; Presenilin-1; Severity of Illness Index; tau Proteins; Tauopathies

Excitotoxicity and cerebral ischemia induce strong endocytosis in neurons, and we here investigate its functional role in neuroprotection by a functional transactivator of transcription (TAT)-peptide, the c-Jun N-terminal kinase (JNK) inhibitor D-JNKI1, against NMDA-excitotoxicity in vitro and neonatal ischemic stroke in P12 Sprague-Dawley rats. In both situations, the neuroprotective efficacy of D-JNKI1 was confirmed, but excessively high doses were counterproductive. Importantly, the induced endocytosis was necessary for neuroprotection, which required that the TAT-peptide be administered at a time when induced endocytosis was occurring. Uptake by other routes failed to protect, and even promoted cell death at high doses. Blocking the induced endocytosis of D-JNKI1 with heparin or with an excess of D-TAT-peptide eliminated the neuroprotection. We conclude that excitotoxicity-induced endocytosis is a basic property of stressed neurons that can target neuroprotective TAT-peptides into the neurons that need protection. Furthermore, it is the main mediator of neuroprotection by D-JNKI1. This may explain promising reports of strong neuroprotection by TAT-peptides without apparent side effects, and warns that the timing of peptide administration is crucial.

Topics: Analysis of Variance; Animals; Animals, Newborn; Cells, Cultured; Cerebral Cortex; Disease Models, Animal; Endocytosis; Excitatory Amino Acid Agonists; Infarction, Middle Cerebral Artery; JNK Mitogen-Activated Protein Kinases; L-Lactate Dehydrogenase; N-Methylaspartate; Neurons; Neuroprotective Agents; Peptides; Phosphopyruvate Hydratase; Rats; Rats, Sprague-Dawley; Transfection

To evaluate the effect of XG-102 (formerly D-JNKI1), a TAT-coupled dextrogyre peptide that selectively inhibits the c-Jun N-terminal kinase, in the treatment of endotoxin-induced uveitis (EIU).. EIU was induced in Lewis rats by LPS injection. XG-102 was administered at the time of LPS challenge. The ocular biodistribution of XG-102 was evaluated using immunodetection at 24 hours after either 20 microg/kg IV (IV) or 0.2 microg/injection intravitreous (IVT) administrations in healthy or uveitic eyes. The effect of XG-102 on EIU was evaluated using clinical scoring, infiltration cell quantification, inducible nitric oxide synthase (iNOS) expression and immunohistochemistry, and cytokines and chemokines kinetics at 6, 24, and 48 hours using multiplex analysis on ocular media. Control EIU eyes received vehicle injection IV or IVT. The effect of XG-102 on c-Jun phosphorylation in EIU was evaluated by Western blot in eye tissues.. After IVT injection, XG-102 was internalized in epithelial cells from iris/ciliary body and retina and in glial and microglial cells in both healthy and uveitic eyes. After IV injection, XG-102 was concentrated primarily in inflammatory cells of uveitic eyes. Using both routes of administration, XG-102 significantly inhibited clinical signs of EIU, intraocular cell infiltration, and iNOS expression together with reduced phosphorylation of c-Jun. The anti-inflammatory effect of XG-102 was mediated by iNOS, IFN-gamma, IL-2, and IL-13.. This is the first evidence that interfering with the JNK pathway can reduce intraocular inflammation. Local administration of XG-102, a clinically evaluated peptide, may have potential for treating uveitis.

Topics: Animals; Chemokines; Cytokines; Disease Models, Animal; Down-Regulation; Drug Combinations; Female; Glyceraldehyde-3-Phosphate Dehydrogenase (Phosphorylating); Injections, Intraocular; Injections, Intravenous; JNK Mitogen-Activated Protein Kinases; Lipopolysaccharides; Nitric Oxide Synthase Type II; Oils; Peptides; Phenols; Rats; Rats, Inbred Lew; Signal Transduction; Tissue Distribution; Uveitis; Vitreous Body

Activation of extracellular signal-regulated kinase (ERK) in spinal cord neurons could serve as a marker for sensitization of dorsal horn neurons in persistent pain. ERK is normally activated by high-threshold noxious stimuli. We investigated how low-threshold mechanical stimuli could activate ERK after complete Freund's adjuvant (CFA)-induced inflammation. Unilateral injection of CFA induced ipsilateral heat hyperalgesia and bilateral mechanical allodynia. CFA-induced ERK activation in ipsilateral dorsal horn neurons declined after 2 days. Interestingly, low-threshold mechanical stimulation given by light touch either on the inflamed paw or the contralateral non-inflamed paw dramatically increased ERK phosphorylation in the dorsal horn ipsilateral to touch stimulation. Notably, light touch induced ERK phosphorylation mainly in superficial neurons in laminae I-IIo. Intrathecal administration of the astroglial toxin L-α-aminoadipate on post-CFA day 2 reversed CFA-induced bilateral mechanical allodynia but not heat hyperalgesia. Furthermore, L-α-aminoadipate, the glial inhibitor fluorocitrate, and a peptide inhibitor of c-Jun N-terminal Kinase all reduced light touch-evoked ERK activation ipsilateral to touch. Collectively, these data suggest that (i) ERK can be activated in superficial dorsal horn neurons by low-threshold mechanical stimulation under pathological condition and (ii) ERK activation by light touch is associated with mechanical allodynia and requires an astrocyte network.

Topics: 2-Aminoadipic Acid; Analysis of Variance; Animals; Astrocytes; Citrates; Disease Models, Animal; Edema; Excitatory Amino Acid Antagonists; Extracellular Signal-Regulated MAP Kinases; Freund's Adjuvant; Functional Laterality; Hyperalgesia; Inflammation; Male; Mitogen-Activated Protein Kinase Kinases; Peptides; Physical Stimulation; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Signal Transduction; Spinal Cord; Touch

The c-Jun N-terminal kinase (JNK) signaling pathway plays a critical role in ischemic brain injury. The d-retro-inverso form of c-Jun N-terminal kinase-inhibitor (D-JNKI1), a cell-permeable inhibitor of JNK, powerfully reduces neuronal death induced by permanent and transient ischemia, even when administered 6 h after the ischemic insult, offering a clinically relevant window. We investigated the JNK molecular cascade activation in rat cerebral ischemia and the effects of D-JNKI1 on this cascade. c-Jun activation starts after 3 h after ischemia and peaks at 6 h in the ischemic core and in the penumbra at 1 h and at 6 h respectively. The 6 h c-Jun activation peak correlates well with that of P-JNK. We also examined the activation of the two direct JNK activators, MAP kinase kinase 4 (MKK4) and MAP kinase kinase 7 (MKK7). MKK4 showed the same time course as JNK in both core and penumbra, reaching peak activation at 6 h. MKK7 did not show any significant increase of phosphorylation in either core or penumbra. D-JNKI1 markedly prevented the increase of P-c-Jun in both core and penumbra and powerfully inhibited caspase-3 activation in the core. These results confirm that targeting the JNK cascade using the TAT cell-penetrating peptide offers a promising therapeutic approach for ischemia, raising hopes for human neuroprotection, and elucidates the molecular pathways leading to and following JNK activation.

Topics: Animals; Animals, Newborn; Caspase 3; Disease Models, Animal; Enzyme Activation; Infarction, Middle Cerebral Artery; JNK Mitogen-Activated Protein Kinases; Male; Peptides; Proto-Oncogene Proteins c-jun; Rats; Rats, Wistar; Signal Transduction; Time Factors

This study investigated the otoprotective properties of AM-111, an inhibitor of c-Jun N-terminal kinase-mediated apoptosis and inflammation.. A controlled, prospective animal study using a guinea pig model of acute labyrinthitis.. Acute labyrinthitis was generated by injection of antigen into the scala tympani of sensitized guinea pigs. Treatment groups received 100 microL of AM-111 at concentrations of 100 micromol/L, 10 micromol/L, and 1 micromol/L in a hyaluronic acid gel formulation delivered over the round window niche within 1 hour of antigen challenge. Cochlear function was monitored over 21 days with serial auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measurements followed by histologic analysis.. The ABR results on day 21 demonstrated that untreated control ears for acute labyrinthitis had a mean hearing loss (HL) of 68 +/- 12 dB. In contrast, ears treated with AM-111 (100 micromol/L) had a mean HL of 39 +/- 31 dB. These two groups were statistically different (one-way analysis of variance, P = .03). Secondary outcomes, including DPOAE shift, inner hair cell survival, inflammatory cell counts, and spiral ganglion density, were also statistically significant in favor of an otoprotective effect of AM-111. Lower doses of AM-111 did not produce a statistically significant reduction in HL over controls.. AM-111 delivered over the round window membrane in a 100 microL hyaluronic acid formulation at a 100 micromol/L concentration immediately after induction of acute labyrinthitis in the guinea pig cochlea protects hearing, reduces hair cell loss, and reduces the number of inflammatory cells at 21 days after treatment.

Topics: Animals; Apoptosis; Cell Count; Disease Models, Animal; Evoked Potentials, Auditory, Brain Stem; Female; Follow-Up Studies; Guinea Pigs; Hearing Loss; Labyrinthitis; Peptides; Prospective Studies; Spiral Ganglion; Treatment Outcome

Recent advances in molecular pharmacology of the cochlea have lead to a much better understanding of the physiology, and especially the pathophysiology, of the sensorineural structures of the organ of Corti. Knowledge of the intimate molecular mechanisms of cellular dysfunction is of considerable use in the development of new therapeutic strategies. Herein, we summarize the mechanisms of sensory hair cell death after various injuries. Based on these molecular mechanisms, we propose novel therapeutic strategies to restore hearing. In addition to permanent hearing loss, exposure to noise or ototoxic drugs also induces tinnitus. We thus review recent findings obtained from a behavioral model of tinnitus in rats. In addition to providing evidence for the site and mechanism of generation of tinnitus induced by salicylate, these results support the idea that targeting cochlear N-methyl-D-aspartate receptors may represent a promising therapeutic strategy for treating tinnitus.

Topics: Animals; Apoptosis; Disease Models, Animal; Hair Cells, Auditory; Hearing Loss; JNK Mitogen-Activated Protein Kinases; MAP Kinase Kinase 4; Mitogen-Activated Protein Kinase Kinases; Neuroprotective Agents; Peptides; Riluzole; Salicylates; Signal Transduction; Tinnitus

Hearing loss can be caused by a variety of insults, including acoustic trauma and exposure to ototoxins, that principally effect the viability of sensory hair cells via the MAP kinase (MAPK) cell death signaling pathway that incorporates c-Jun N-terminal kinase (JNK). We evaluated the otoprotective efficacy of D-JNKI-1, a cell permeable peptide that blocks the MAPK-JNK signal pathway. The experimental studies included organ cultures of neonatal mouse cochlea exposed to an ototoxic drug and cochleae of adult guinea pigs that were exposed to either an ototoxic drug or acoustic trauma. Results obtained from the organ of Corti explants demonstrated that the MAPK-JNK signal pathway is associated with injury and that blocking of this signal pathway prevented apoptosis in areas of aminoglycoside damage. Treatment of the neomycin-exposed organ of Corti explants with D-JNKI-1 completely prevented hair cell death initiated by this ototoxin. Results from in vivo studies showed that direct application of D-JNKI-1 into the scala tympani of the guinea pig cochlea prevented nearly all hair cell death and permanent hearing loss induced by neomycin ototoxicity. Local delivery of D-JNKI-1 also prevented acoustic trauma-induced permanent hearing loss in a dose-dependent manner. These results indicate that the MAPK-JNK signal pathway is involved in both ototoxicity and acoustic trauma-induced hair cell loss and permanent hearing loss. Blocking this signal pathway with D-JNKI-1 is of potential therapeutic value for long-term protection of both the morphological integrity and physiological function of the organ of Corti during times of oxidative stress.

Topics: Acoustic Stimulation; Aminoglycosides; Animals; Cell Death; Cells, Cultured; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Routes; Drug Evaluation, Preclinical; Enzyme Inhibitors; Guinea Pigs; Hair Cells, Auditory; Hearing Loss; Hearing Loss, Noise-Induced; Hearing Tests; In Vitro Techniques; JNK Mitogen-Activated Protein Kinases; Ligands; Mice; Mitogen-Activated Protein Kinases; Neuroprotective Agents; Organ of Corti; Peptides; Proto-Oncogene Proteins c-fos; Signal Transduction