Molecular mechanisms underlying cochlear degeneration in the tubby mouse and the therapeutic effect of sulforaphane

Probucol-bile acid based nanoparticles protect auditory cells from oxidative stress: an in vitro study

Aim: Excessive free radicals contribute to oxidative stress and mitochondrial dysfunction in sensorineural hearing loss (SNHL). The antioxidant probucol holds promise, but its limited bioavailability and inner ear barriers hinder effective SNHL treatment. Methodology: We addressed this by developing probucol-loaded nanoparticles with polymers and lithocholic acid and tested them on House Ear Institute-Organ of Corti cells. Results: Probucol-based nanoparticles effectively reduced oxidative stress-induced apoptosis, enhanced cellular viability, improved probucol uptake and promoted mitochondrial function. Additionally, they demonstrated the capacity to reduce reactive oxygen species through the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Conclusion: This innovative nanoparticle system holds the potential to prevent oxidative stress-related hearing impairment, providing an effective solution for SNHL.

Identifying key antioxidative stress factors regulating Nrf2 in the genioglossus with human umbilical cord mesenchymal stem-cell therapy

Intermittent hypoxia in patients with obstructive sleep apnea (OSA) hypopnea syndrome (OSAHS) is associated with pharyngeal cavity collapse during sleep. The effect of human umbilical cord mesenchymal stem cells (HUCMSCs) on OSA-induced oxidative damage in the genioglossus and whether nuclear factor erythroid 2-related factor 2 (Nrf2) or its upstream genes play a key role in this process remains unclear. This study aimed to identify the key factors responsible for oxidative damage during OSAHS through Nrf2 analysis and hypothesize the mechanism of HUCMSC therapy. We simulated OSA using an intermittent hypoxia model, observed the oxidative damage in the genioglossus and changes in Nrf2 expression during intermittent hypoxia, and administered HUCMSCs therapy. Nrf2 initially increased, then decreased, aggravating the oxidative damage in the genioglossus; Nrf2 protein content decreased during hypoxia. Using transcriptomics, we identified seven possible factors in HUCMSCs involved in ameliorating oxidative stress by Nrf2, of which DJ-1 and MEF2A, showing trends similar to Nrf2, were selected by polymerase chain reaction. HUCMSCs may reduce oxidative stress induced by intermittent hypoxia through Nrf2, and the possible upstream target genes in this process are MEF2A and DJ-1. Further studies are needed to verify these findings.

Distribution of ciliary adaptor proteins tubby and TULP3 in the organ of Corti

Tubby-like proteins are membrane-associated adaptors that mediate directional trafficking into primary cilia. In inner ear sensory epithelia, cilia-including the hair cell's kinocilium-play important roles as organizers of polarity, tissue architecture and cellular function. However, auditory dysfunction in tubby mutant mice was recently found to be related to a non-ciliary function of tubby, the organization of a protein complex in sensory hair bundles of auditory outer hair cells (OHCs). Targeting of signaling components into cilia in the cochlea might therefore rather rely on closely related tubby-like proteins (TULPs). In this study, we compared cellular and subcellular localization of tubby and TULP3 in the mouse inner ear sensory organs. Immunofluorescence microscopy confirmed the previously reported highly selective localization of tubby in the stereocilia tips of OHCs and revealed a previously unnoticed transient localization to kinocilia during early postnatal development. TULP3 was detected in the organ of Corti and vestibular sensory epithelium, where it displayed a complex spatiotemporal pattern. TULP3 localized to kinocilia of cochlear and vestibular hair cells in early postnatal development but disappeared subsequently before the onset of hearing. This pattern suggested a role in targeting ciliary components into kinocilia, possibly related to the developmental processes that shape the sensory epithelia. Concurrent with loss from kinocilia, pronounced TULP3 immunolabeling progressively appeared at microtubule bundles in non-sensory Pillar (PCs) and Deiters cells (DC). This subcellular localization may indicate a novel function of TULP proteins associated with the formation or regulation of microtubule-based cellular structures.

Biallelic Inactivating TUB Variants Cause Retinal Ciliopathy Impairing Biogenesis and the Structure of the Primary Cilium

Inherited retinal degeneration (IRD) represents a clinically variable and genetically heterogeneous group of disorders characterized by photoreceptor dysfunction. These diseases typically present with progressive severe vision loss and variable onset, ranging from birth to adulthood. Genomic sequencing has allowed to identify novel IRD-related genes, most of which encode proteins contributing to photoreceptor-cilia biogenesis and/or function. Despite these insights, knowledge gaps hamper a molecular diagnosis in one-third of IRD cases. By exome sequencing in a cohort of molecularly unsolved individuals with IRD, we identified a homozygous splice site variant affecting the transcript processing of TUB, encoding the first member of the Tubby family of bipartite transcription factors, in a sporadic case with retinal dystrophy. A truncating homozygous variant in this gene had previously been reported in a single family with three subjects sharing retinal dystrophy and obesity. The clinical assessment of the present patient documented a slightly increased body mass index and no changes in metabolic markers of obesity, but confirmed the occurrence of retinal detachment. In vitro studies using patient-derived fibroblasts showed the accelerated degradation of the encoded protein and aberrant cilium morphology and biogenesis. These findings definitely link impaired TUB function to retinal dystrophy and provide new data on the clinical characterization of this ultra-rare retinal ciliopathy.

New Target of Oxidative Stress Regulation in Cochleae: Alternative Splicing of the p62/Sqstm1 Gene

We investigated oxidative stress and antioxidant response in the p62/Sqstm1-Keap1-Nrf2 pathway in C57BL/6 mice cochleae during age-related hearing loss (ARHL) and noise-induced hearing loss (NIHL), and the function of full-length and variant p62 in the regulation of Nrf2 activation. Groups of young (2 months), old (13-14 months), control, and acoustic trauma (AT) mice were examined cochlear damage and oxidative stress as follows: auditory brainstem response and hair cell counts; malondialdehyde (MDA) levels measured by assay kit and 7,8-dihydro-8-oxoguanine (8-oxoG) detected by immunohistochemistry. Full-length and variant p62 were examined for expression in cochleae, hippocampus (HIP), and auditory cortex (AC) using immunoblotting. Keap1-Nrf2 pathway activation was based on immunoblotting of nuclear Nrf2 and quantitative real-time PCR of Nrf2 target genes HO-1/NQO-1. The oxidative function of full-length and variant p62 was examined in HEI-OC-1 cells by flow cytometry. The results showed hearing loss, and cochlear hair cell loss was associated with MDA accumulation and 8-oxoG expression during ARHL and NIHL. Nrf2 showed no obvious changes in nuclear protein. Expression levels mRNA for HO-1 and NQO1 were lower in old mice and mildly greater in AT Mice. The expression of p62 splicing variant lacking the Keap1-interacting region was greater than full-length p62 in cochleae. However, the expression of p62 splicing variant was lesser than full-length p62 in HIP and AC. For HEI-OC-1 cells, overexpression of full-length p62 decreased ROS levels induced by H₂O₂. Oxidative stress is closely related to ARHL and NIHL. Changing the ratio of full-length to variant p62 protein expression may be a new target to reduce the level of oxidative stress in cochleae.

The Nrf2 Pathway in Ischemic Stroke: A Review

Ischemic stroke, characterized by the sudden loss of blood flow in specific area(s) of the brain, is the leading cause of permanent disability and is among the leading causes of death worldwide. The only approved pharmacological treatment for acute ischemic stroke (intravenous thrombolysis with recombinant tissue plasminogen activator) has significant clinical limitations and does not consider the complex set of events taking place after the onset of ischemic stroke (ischemic cascade), which is characterized by significant pro-oxidative events. The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of a great number of antioxidant and/or defense proteins, has been pointed as a potential pharmacological target involved in the mitigation of deleterious oxidative events taking place at the ischemic cascade. This review summarizes studies concerning the protective role of Nrf2 in experimental models of ischemic stroke, emphasizing molecular events resulting from ischemic stroke that are, in parallel, modulated by Nrf2. Considering the acute nature of ischemic stroke, we discuss the challenges in using a putative pharmacological strategy (Nrf2 activator) that relies upon transcription, translation and metabolically active cells in treating ischemic stroke patients.

The Role of Nrf2 in Hearing Loss

Hearing loss is a major unresolved problem in the world, which has brought a heavy burden to society, economy, and families. Hair cell damage and loss mediated by oxidative stress are considered to be important causes of hearing loss. The nuclear factor erythroid 2–related factor 2 (Nrf2) is a major regulator of antioxidant capacity and is involved in the occurrence and development of a series of toxic and chronic diseases associated with oxidative stress. In recent years, studies on the correlation between hearing loss and Nrf2 target have continuously broadened our knowledge, and Nrf2 has become a new strategic target for the development and reuse of hearing protection drugs. This review summarized the correlation of Nrf2 in various types of hearing loss, and the role of drugs in hearing protection through Nrf2 from the literature.

Distinct roles of stereociliary links in the nonlinear sound processing and noise resistance of cochlear outer hair cells

Outer hair cells (OHCs) play an essential role in hearing by acting as a nonlinear amplifier which helps the cochlea detect sounds with high sensitivity and accuracy. This nonlinear sound processing generates distortion products, which can be measured as distortion-product otoacoustic emissions (DPOAEs). The OHC stereocilia that respond to sound vibrations are connected by three kinds of extracellular links: tip links that connect the taller stereocilia to shorter ones and convey force to the mechanoelectrical transduction channels, tectorial membrane-attachment crowns (TM-ACs) that connect the tallest stereocilia to one another and to the overlying TM, and horizontal top connectors (HTCs) that link adjacent stereocilia. While the tip links have been extensively studied, the roles that the other two types of links play in hearing are much less clear, largely because of a lack of suitable animal models. Here, while analyzing genetic combinations of tubby mice, we encountered models missing both HTCs and TM-ACs or HTCs alone. We found that the tubby mutation causes loss of both HTCs and TM-ACs due to a mislocalization of stereocilin, which results in OHC dysfunction leading to severe hearing loss. Intriguingly, the addition of the modifier allele modifier of tubby hearing 1 in tubby mice selectively rescues the TM-ACs but not the HTCs. Hearing is significantly rescued in these mice with robust DPOAE production, indicating an essential role of the TM-ACs but not the HTCs in normal OHC function. In contrast, the HTCs are required for the resistance of hearing to damage caused by noise stress.

Hidden cochlear impairments

Pure tone audiometry is a routine clinical examination used to identify hearing loss. A normal pure tone audiogram is usually taken as evidence of normal hearing. Auditory deficits detected in subjects with normal audiograms, such as poor sound discrimination and auditory perceptual disorders, are generally attributed to central problems. Does the pure tone audiogram truly reflect cochlear status? Recent evidence suggests that individuals with normal audiogram may still have reduced peripheral auditory responses but normal central responses, indicating that the pure tone audiometry may not detect some types of cochlear injuries. In the cochlea, the outer hair cells (OHCs), inner hair cells (IHCs), and the spiral ganglion neurons that synapse with IHCs are the 3 key cochlear components in transducing acoustical vibrations into the neural signals. This report reviews three types of cochlear damage identified in laboratory animals that may not lead to overt hearing loss. The first type of cochlear impairment, such as missing a certain proportion of IHCs without damage to OHCs, may reduce the cochlear output and elevate response threshold; however, the reduced peripheral auditory sensitivity may be restored along the auditory pathway via central gain enhancement. The second type of cochlear impairment, such as selective damage to the synapses of the high-threshold thin auditory nerve fibers (ANFs), reduces cochlear output at high stimulation levels with no effect on response threshold. In this case the reduced cochlear output may be compensated along the auditory pathway as well. The third type of cochlear impairment, such as missing a certain number of OHCs without damage to others, may not even affect cochlear function at all. These “hidden” cochlear impairments do not result in overt hearing loss, but they may increase the vulnerability of the cochlea to traumatic exposure and lead to disrupted central auditory processing.

Immunohistochemical localization of Nrf2 in the human cochlea

Oxidative stress plays an important role in several inner ear diseases and normal aging. Nuclear (erythroid-derived 2)-like 2, also known as Nrf2, is a transcription factor encoded by the NFE2L2 gene that controls the expression of genes necessary to reduce oxidative stress. There are no studies to the date on the localization of Nrf2 in the human inner ear in normal or pathological conditions. Therefore, we investigated the immunohistochemical localization of Nrf2 in the human cochlea and vestibule using formalin-fixed celloidin-embedded human temporal bone sections. Nrf2 immunoreactivity (IR) was found in the inner and outer hair cells and supporting cells of the organ of Corti throughout the cochlea. Nfr2-IR was also found in hair cells and supporting cells of the maculae and cristae vestibular sensory epithelia. Nrf2-IR was decreased in the organ of Corti of older age individuals. The immunolocalization of Nrf2 in both auditory and vestibular sensory epithelia suggest that this transcription factor may play a relevant role in protecting sensory hair cells from oxidative stress.

The therapeutic potential of sulforaphane on light-induced photoreceptor degeneration through antiapoptosis and antioxidant protection

Oxidative stress due to excessive light exposure can exacerbate a variety of human retinal diseases by accelerating photoreceptor cell death. The thioredoxin (Trx) system is considered to play a crucial role in reduction/oxidation (redox) regulation of signal transduction and in cell defense against oxidative stresses. Sulforaphane (SF) protects cells from oxidative damage through nuclear factor (erythroid-derived 2)-like 2 (Nrf2), which is responsible for multiple detoxification processes, including elevating the expression of Trx. This study sought to demonstrate whether SF increased Trx expression in retinal tissues in vivo and whether it could preserve the photoreceptors from degeneration induced by oxidative stress. Our data clearly showed that pretreatment with SF abated photoreceptor cell loss, in association with increased expression of Nrf2 and Trx, subsequently activating the Ras/Raf1/Erk signaling pathway and decreasing the expression of Bak1, Cyt-c release and the activity of caspase-3 in light-induced mouse retinas. These data suggested that the therapeutic potential of SF in retinal degeneration due to oxidative stress might partially involve anti-caspase and antioxidant protection mediated by Trx.

Sulforaphane exerts neuroprotective effects via suppression of the inflammatory response in a rat model of focal cerebral ischemia

Inflammatory damage plays an important role in cerebral ischemic pathogenesis and may represent a promising target for treatment. Sulforaphane exerts protective effects in a rat model of focal cerebral ischemia/reperfusion injury by alleviating brain edema. However, the possible mechanisms of sulforaphane after cerebral ischemia/reperfusion injury have not been fully elucidated. Therefore, in the present study, we investigated the effect of sulforaphane on inflammatory reaction and the potential molecular mechanisms in cerebral ischemia rats. We found that sulforaphane significantly attenuated the blood-brain barrier (BBB) disruption; decreased the levels of pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-1β; reduced the nitric oxide (NO) levels and inducible nitric oxide synthase (iNOS) activity; inhibited the expression of iNOS and cyclooxygenase-2 (COX-2). In addition, sulforaphane inhibits the expression of p-NF-κB p65 after focal cerebral ischemia-reperfusion injury. Taken together, our results suggest that sulforaphane suppresses the inflammatory response via inhibiting the NF-κB signaling pathway in a rat model of focal cerebral ischemia, and sulforaphane may be a potential therapeutic agent for the treatment of cerebral ischemia injury.

Sulforaphane enhances the activity of the Nrf2-ARE pathway and attenuates inflammation in OxyHb-induced rat vascular smooth muscle cells

AIM

A growing body of evidence indicates that the nuclear factor erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE) pathway plays a protective role in many physiological stress processes such as inflammatory damage, oxidative stress, and the accumulation of toxic metabolites, which are all involved in the cerebral vasospasm following subarachnoid hemorrhage (SAH). We hypothesized that the Nrf2-ARE pathway might have a protective role in cerebral vasospasm following SAH.

MATERIALS AND METHODS

In our study, we investigate whether the oxyhemoglobin (OxyHb) can induce the activation of the Nrf2-ARE pathway in vascular smooth muscle cells (VSMCs), and evaluate the modulatory effects of sulforaphane (SUL) on OxyHb-induced inflammation in VSMCs.

RESULTS

As a result, both the protein level and the mRNA level of the nuclear Nrf2 were significantly increased, while the mRNA levels of two Nrf2-regulated gene products, both heme oxygenase-1 and NAD(P)H: quinone oxidoreductase-1, were also up-regulated in VSMCs induced with OxyHb. A marked increase of inflammatory cytokines such as IL-1β, IL-6 and TNF-α release was observed at 48 h after cells were treated with OxyHb. SUL enhanced the activity of the Nrf2-ARE pathway and suppressed cytokine release.

CONCLUSIONS

Our results indicate that the Nrf2-ARE pathway was activated in OxyHb-induced VSMCs. SUL suppressed cytokine release via the activation of the Nrf2-ARE pathway in OxyHb-induced VSMCs.

Protective effect of sulphoraphane against oxidative stress mediated toxicity induced by CuO nanoparticles in mouse embryonic fibroblasts BALB 3T3

Despite the great interest in nanoparticles (NPs) safety, no comprehensive test paradigm has been developed. Oxidative stress has been implicated as an explanation behind the toxicity of NPs. It is reported that sulphoraphane (SFN) present in cruciferous vegetables like cauliflower and broccoli has potential to protect cells from oxidative damage and inflammation. However, protective role of SFN in nanotoxicity is not explored. We investigated the protective effect of SFN against the toxic response of copper oxide (CuO) NPs in mouse embryonic fibroblasts (BALB 3T3). Results showed that CuO NPs induced dose-dependent (5-15 µg/ml) cytotoxicity in BALB 3T3 cells demonstrated by MTT and lactate dehydrogenase (LDH) assays. CuO NPs were also found to induce oxidative stress in dose-dependent manner indicated by induction of reactive oxygen species (ROS) and lipid peroxidation (LPO) and depletion of glutathione and glutathione reductase. Co-treatment of BALB 3T3 cells with SFN (6 µM) significantly attenuated the cytotoxicity, ROS generation and oxidative stress caused by CuO NPs. Moreover, we found that co-treatment of another antioxidant N-acetyl-cysteine (NAC) (2 mM) also significantly attenuated glutathione depletion caused by CuO NPs but protection from the loss of cell viability due to CuO NPs exposure was not significant. We believe this is the first report showing that SFN significantly protected the BALB 3T3 cells from CuO NPs toxicity, which is mediated through generation of oxidants and depletion of antioxidants. Consequently, protective mechanism of SFN against CuO NPs toxicity was different from NAC that should be further investigated.

Sulphoraphane inhibited the expressions of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 through MyD88-dependent toll-like receptor-4 pathway in cultured endothelial cells

BACKGROUND AND AIMS

Chronic inflammation plays pivotal roles in both cancer and cardiovascular diseases. A large body of evidence suggests that high intake of cruciferous vegetables is closely related with low risk of these disorders. However, the underlying mechanisms of protection are not fully understood. The aim of this study is to test the protective effects of an isothiocyanate sulphoraphane on inflammatory injury and related regulation pathways in cultured endothelial cells.

METHODS AND RESULTS

The expressions of adhesion molecules were determined by TaqMan real-time polymerase chain reaction (PCR) and Western blot analysis. Nuclear factor-kappa B (NF-кB) translocation was detected by immunofluorescent hybridisation. Other proteins were measured by Western blot analysis. The results demonstrated that sulphoraphane significantly suppresses the expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 stimulated by lipopolysaccharide (LPS) both at the transcriptional and translational levels. In addition, sulphoraphane inhibited the translocation of NF-кB into the nucleus. Sulphoraphane decreased the phosphorylation of extra-cellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), while further blockade and activation using individually specific agents confirm that p38 MAPK and JNK are mainly involved. Interestingly, sulphoraphane down-regulated Toll-like receptor (TLR)-4, a receptor of LPS located on the membrane. In addition, MyD88, an effector downstream TLR-4 signal pathway was subsequently attenuated.

CONCLUSION

Taken all together, adhesion molecules are confirmed to be the novel targets of sulphoraphane in preventing inflammatory insult to endothelial cells. Sulphoraphane suppressed TLR-4 followed by MyD88 and downstream factors such as p38 MAPK and JNK, ultimately blocking NF-кB translocation and the subsequent expression of adhesion molecules. These data suggested a novel inflammatory pathway mediated by sulphoraphane.

Expression pattern of oxidative stress and antioxidant defense-related genes in the aging Fischer 344/NHsd rat cochlea

The biological mechanisms that give rise to age-related hearing loss (ARHL) are still poorly understood. However, there is growing recognition that oxidative stress may be an important factor. To address this issue, we measured the changes in the expression of cochlear oxidative stress and antioxidant defense-related genes in young (2 months old), middle-aged (12 months old), and old (21-25 months old) Fischer 344/NHsd (F344/NHsd) rats and compared gene expression changes with ARHL. A quantitative real-time reverse transcription polymerase chain reaction array revealed a significant age-related downregulation of only 1 gene, stearoyl-coenzyme A desaturase 1, and upregulation of 12 genes: 24-dehydrocholesterol reductase; aminoadipate-semialdehyde synthase; cytoglobin; dual oxidase 2; glutathione peroxidase 3; glutathione peroxidase 6; glutathione S-transferase, kappa 1; glutathione reductase; nicotinamide adenine dinucleotide phosphate (NAD(P)H) dehydrogenase, quinone 1; solute carrier Family 38, Member 5; thioredoxin interacting protein; and vimentin. Statistical analyses revealed significant correlations between gene expression and auditory function in 8 genes. Our results identified specific subsets of oxidative stress genes that appear to play an important role in ARHL in the Fischer 344/NHsd rat.

Sulforaphane suppresses vascular adhesion molecule-1 expression in TNF-α-stimulated mouse vascular smooth muscle cells: involvement of the MAPK, NF-κB and AP-1 signaling pathways

Atherosclerosis is a long-term inflammatory disease of the arterial wall. Increased expression of the cell adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) is associated with increased proliferation of vascular smooth muscle cells (VSMCs), leading to increased neointima or atherosclerotic lesion formation. Therefore, the functional inhibition of adhesion molecules could be a critical therapeutic target of inflammatory disease. In the present study, we investigate the effect of sulforaphane on the expression of VCAM-1 induced by TNF-α in cultured mouse vascular smooth muscle cell lines. Pretreatment of VSMCs for 2h with sulforaphane (1-5μg/ml) dose-dependently inhibited TNF-α-induced adhesion of THP-1 monocytic cells and protein expression of VCAM-1. Sulforaphane also suppressed TNF-α-induced production of intracellular reactive oxygen species (ROS) and activation of p38, ERK and JNK. Furthermore, sulforaphane inhibited NK-κB and AP-1 activation induced by TNF-α. Sulforaphane inhibited TNF-α-induced ΙκΒ kinase activation, subsequent degradation of ΙκΒα and nuclear translocation of p65 NF-κB and decreased c-Jun and c-Fos protein level. This study suggests that sulforaphane inhibits the adhesive capacity of VSMC and downregulates the TNF-α-mediated induction of VCAM-1 in VSMC by inhibiting the MAPK, NF-κB and AP-1 signaling pathways and intracellular ROS production. Thus, sulforaphane may have beneficial effects to suppress inflammation within the atherosclerotic lesion.

Protective role of Nrf2 in age-related hearing loss and gentamicin ototoxicity

Expression of antioxidant enzymes is regulated by transcription factor NF-E2-related factor (Nrf2) and induced by oxidative stress. Reactive oxygen species contribute to the formation of several types of cochlear injuries, including age-related hearing loss and gentamicin ototoxicity. In this study, we examined the roles of Nrf2 in age-related hearing loss and gentamicin ototoxicity by measuring auditory brainstem response thresholds in Nrf2-knockout mice. Although Nrf2-knockout mice maintained normal auditory thresholds at 3 months of age, their hearing ability was significantly more impaired than that of age-matched wild-type mice at 6 and 11 months of age. Additionally, the numbers of hair cells and spiral ganglion cells were remarkably reduced in Nrf2-knockout mice at 11 months of age. To examine the importance of Nrf2 in protecting against gentamicin-induced ototoxicity, 3-day-old mouse organ of Corti explants were cultured with gentamicin. Hair cell loss caused by gentamicin treatment was enhanced in the Nrf2-deficient tissues. Furthermore, the expressions of some Nrf2-target genes were activated by gentamicin treatment in wild-type mice but not in Nrf2-knockout mice. The present findings indicate that Nrf2 protects the inner ear against age-related hearing injuries and gentamicin ototoxicity by up-regulating antioxidant enzymes and detoxifying proteins.

Nanoceria extend photoreceptor cell lifespan in tubby mice by modulation of apoptosis/survival signaling pathways

Cerium oxide nanoparticles, nanoceria, are inorganic antioxidants that have catalytic activities which mimic those of the neuroprotective enzymes superoxide dismutase and catalase. We have previously shown that nanoceria preserve retinal morphology and prevent loss of retinal function in a rat light damage model. In this study, the homozygous tubby mutant mouse, which exhibits inherited early progressive cochlear and retinal degeneration, was used as a model to test the ability of nanoceria to slow the progression of retinal degeneration. Tubby mice were injected systemically, intracardially, with 20 μl of 1mM nanoceria in saline, at postnatal day 10 and subsequently at P20 and P30 whereas saline injected and uninjected wild type (or heterozygous tubby) served as injected and uninjected controls, respectively. Assays for retinal function, morphology and signaling pathway gene expression were performed on P34 mice. Our data demonstrate that nanoceria protect the retina by decreasing Reactive Oxygen Species (ROS), up-regulating the expression of neuroprotection-associated genes; down-regulating apoptosis signaling pathways and/or up-regulating survival signaling pathways to slow photoreceptor degeneration. These data suggest that nanoceria have significant potential as global agents for therapeutic treatment of inherited retinal degeneration and most types of ocular diseases.

Role of the Nrf2-ARE pathway in early brain injury after experimental subarachnoid hemorrhage

The nuclear factor erythroid 2-related factor 2 and antioxidant-response element (Nrf2-ARE) pathway is a key regulator for modulating inflammation and oxidative damage, which are involved in the pathogenesis of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Previous studies have demonstrated that Nrf2-ARE pathway play neural protective roles in traumatic brain injury, cerebral ischemia, and intracerebral hemorrhage models; however, it has not been investigated whether, and to what degree, the Nrf2-ARE pathway is induced by SAH, and the role of the Nrf2-ARE pathway in development of EBI following SAH remains unknown. Experiment 1 sought to investigate the time course of Nrf2-ARE activation in the cortex in the early stage of SAH. In experiment 2, we assessed the effect of sulforaphane (SUL; a specific Nrf2 activator) on regulation of the Nrf2-ARE pathway in the SAH model and evaluated the impact of SUL on EBI after SAH. The rat SAH model was used injection of 0.3 ml fresh arterial, nonheparinized blood into the prechiasmatic cistern over 20 sec. As a result, Nrf2 and its target gene product, heme oxygenase-1 (HO-1), were up-regulated in the cortex after SAH and peaked at 24 hr post-SAH. After intraperitoneal SUL administration, the elevated expression of Nrf2-ARE-related factors such as Nrf2, HO-1, NAD(P)H:quinone oxidoreductase 1 (NQO1), and glutathione S-transferase-α1 (GST-α1) was detected in the cortex at 48 hr following blood injection. In the SUL-treated group, early brain damage such as brain edema, blood-brain barrier (BBB) impairment, cortical apoptosis, and motor deficits was significantly ameliorated compared with vehicle-treated SAH rats. Our results suggest that the Nrf2-ARE pathway is activated in the brain after SAH, playing a beneficial role in EBI development, possibly through inhibiting cerebral oxidative stress by inducing antioxidant and detoxifying enzymes.

Electrophilic tuning of the chemoprotective natural product sulforaphane

Sulforaphane [1-isothiocyanato-4-(methylsulfinyl)butane], a naturally occurring isothiocyanate derived from cruciferous vegetables, is a highly potent inducer of phase 2 cytoprotective enzymes and can protect against electrophiles including carcinogens, oxidative stress, and inflammation. The mechanism of action of sulforaphane is believed to involve modifications of critical cysteine residues of Keap1, which lead to stabilization of Nrf2 to activate the antioxidant response element of phase 2 enzymes. However, the dithiocarbamate functional group formed by a reversible reaction between isothiocyanate of sulforaphane and sulfhydryl nucleophiles of Keap1 is kinetically labile, and such modification in intact cells has not yet been demonstrated. Here we designed sulforaphane analogs with replacement of the reactive isothiocyanate by the more gentle electrophilic sulfoxythiocarbamate group that also selectively targets cysteine residues in proteins but forms stable thiocarbamate adducts. Twenty-four sulfoxythiocarbamate analogs were synthesized that retain the structural features important for high potency in sulforaphane analogs: the sulfoxide or keto group and its appropriate distance to electrophilic functional group. Evaluation in various cell lines including hepatoma cells, retinal pigment epithelial cells, and keratinocytes as well as in mouse skin shows that these analogs maintain high potency and efficacy for phase 2 enzyme induction as well as the inhibitory effect on lipopolysaccharide-induced nitric oxide formation like sulforaphane. We further show in living cells that a sulfoxythiocarbamate analog can label Keap1 on several key cysteine residues as well as other cellular proteins offering new insights into the mechanism of chemoprotection.

Evaluation of the protective effects of PACAP with cell-specific markers in ischemia-induced retinal degeneration

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurotrophic and neuroprotective peptide that has been shown to exert protective effects in different neuronal injuries, such as traumatic brain injury, models of neurodegenerative diseases and cerebral ischemia. We have provided evidence that PACAP is neuroprotective in several models of retinal degeneration in vivo. In our previous studies we showed that PACAP treatment significantly ameliorated the damaging effects of permanent bilateral common carotid artery occlusion (BCCAO). In the present study cell-type-specific markers were used in the same models in order to further specify the protective effects of PACAP. In rats BCCAO led to severe degeneration of all retinal layers that was attenuated by PACAP (100 pmol) administered unilaterally immediately following BCCAO into the vitreous body of one eye. Retinas were processed for immunohistochemistry after 3 weeks. Immunolabeling was executed for vesicular glutamate transporter 1 (VGLUT 1), vesicular gamma-aminobutyric acid transporter (VGAT), protein kinase Calpha (PKCalpha), glial fibrillary acidic protein (GFAP) and calcium-binding proteins, such as calbindin, calretinin, parvalbumin. In BCCAO retinas, intensity of immunopositivity for all antisera was dramatically decreased, except in the case of GFAP. In PACAP-treated retinas, immunostaining was similar to that of the control animals. In summary, our study presented immunohistochemical identification of cell types sensitive to chronic retinal hypoperfusion and the protective effects of PACAP. This analysis revealed that the retinoprotective effects of PACAP are not phenotype-specific, but it rather influences general cytoprotective pathways irrespective of the neuronal subtypes in the retina subjected to chronic hypoperfusion.