Inhibition of Protein arginine methyltransferase 6 reduces reactive oxygen species production and attenuates aminoglycoside- and cisplatin-induced hair cell death

Metal-Phenolic Vehicles Potentiate Cycle-Cascade Activation of Pyroptosis and cGAS-STING Pathway for Tumor Immunotherapy

The treatment of triple-negative breast cancer (TNBC) faces challenges due to its limited immune response and weak tumor immunogenicity. A collaborative strategy involves combining the activation of pyroptosis and the stimulator of interferon genes (STING) pathway to enhance tumor immunogenicity and fortify the antitumor immune response, which may improve therapeutic outcomes in TNBC. In this study, we report the fabrication of a zinc-phenolic nanocapsule (RMP@Cap), which is loaded with mitoxantrone (MTO) and anti-PD-L1 antibodies (aPD-L1) and coated with erythrocyte membrane, for TNBC immunotherapy. The delivery of RMP@Cap can induce tumor cell pyroptosis and, therefore, trigger the release of mitochondrial DNA, which further combines with zinc agonists to intensify STING activation, resulting in a cascade amplification of the therapeutic effect on tumors. Additionally, the incorporation of aPD-L1 into the zinc-phenolic nanocapsule relieves the inhibitory effect of tumor cells on recruited cytotoxic T cells, thereby improving the tumor-killing capacity. Furthermore, the incorporation of a camouflaged erythrocyte membrane coating enables nanocapsules to achieve prolonged in vivo circulation, resulting in improved tumor accumulation for effective antitumor therapy. This study demonstrates a synergistic therapeutic modality involving pyroptosis, coupled with the simultaneous activation and cyclic amplification of the STING pathway in immunotherapy.

Pcolce2 overexpression promotes supporting cell reprogramming in the neonatal mouse cochlea

Hair cell (HC) damage is a leading cause of sensorineural hearing loss, and in mammals supporting cells (SCs) are unable to divide and regenerate HCs after birth spontaneously. Procollagen C-endopeptidase enhancer 2 (Pcolce2), which encodes a glycoprotein that acts as a functional procollagen C protease enhancer, was screened as a candidate regulator of SC plasticity in our previous study. In the current study, we used adeno-associated virus (AAV)-ie (a newly developed adeno-associated virus that targets SCs) to overexpress Pcolce2 in SCs. AAV-Pcolce2 facilitated SC re-entry into the cell cycle both in cultured cochlear organoids and in the postnatal cochlea. In the neomycin-damaged model, regenerated HCs were detected after overexpression of Pcolce2, and these were derived from SCs that had re-entered the cell cycle. These findings reveal that Pcolce2 may serve as a therapeutic target for the regeneration of HCs to treat hearing loss.

The Antioxidant Ergothioneine Alleviates Cisplatin-Induced Hearing Loss through the Nrf2 Pathway

Aims: Cisplatin (CDDP) is a commonly used chemotherapeutic agent for treating head and neck tumors. However, there is high incidence of ototoxicity in patients treated with CDDP, which may be caused by the excessive reactive oxygen species (ROS) generation in the inner ear. Many studies have demonstrated the strong antioxidant effects of ergothioneine (EGT). Therefore, we assumed that EGT could also attenuate cisplatin-induced hearing loss (CIHL) as well. However, the protective effect and mechanism of EGT on CIHL have not been elucidated as so far. In this study, we investigated whether EGT could treat CIHL and the mechanism. Results: In our study, we confirmed the protective effect of EGT on preventing CDDP-induced toxicity both in vitro and in vivo. The auditory brainstem response threshold shift in the EGT + CDDP treatment mice was 30 dB less than that in the CDDP treatment mice. EGT suppressed production of ROS and proapoptotic proteins both in tissue and cells. By silencing nuclear factor erythroid 2-related factor 2 (Nrf2), we confirmed that EGT protected against CIHL via the Nrf2 pathway. We also found that SLC22A4 (OCTN1), an important molecule involved in transporting EGT, was expressed in the cochlea. Innovation: Our results revealed the role of EGT in the prevention of CIHL by activating Nrf2/HO-1/NQO-1 pathway, and broadened a new perspective therapeutic target of EGT. Conclusion: EGT decreased ROS production and promoted the expression of antioxidative enzymes to maintain redox homeostasis in sensory hair cells. Overall, our results indicated that EGT may serve as a novel treatment drug to attenuate CIHL.

Nuciferine Protects Cochlear Hair Cells from Ferroptosis through Inhibiting NCOA4-Mediated Ferritinophagy

Cisplatin is a widely used antineoplastic drug for treating various types of cancers. However, it can cause severe side effects, such as bilateral and irreversible hearing loss, which significantly impacts quality of life. Ferroptosis, an iron-dependent form of programmed cell death, has been implicated in the pathogenesis of cisplatin-induced ototoxicity. Here, we investigated the effects of nuciferine, a natural active ingredient isolated from lotus species, on the ferroptosis of cochlear hair cells. Firstly, our results demonstrated that nuciferine can protect hair cells against RSL3-induced and cisplatin-induced damage. Secondly, nuciferine treatment reduced ferrous iron (Fe2+) overload in cochlear hair cells via inhibiting NCOA4-mediated ferritinophagy. Inhibition of ferritinophagy by knocking down Ncoa4 alleviated cisplatin-induced ototoxicity. Importantly, nuciferine treatment mitigated cochlear hair cell loss and damage to ribbon synapse, and improved mouse hearing function in an acute cisplatin-induced hearing loss model. Our findings highlight the role of NCOA4-mediated ferritinophagy in the pathogenesis of cisplatin-induced ototoxicity and provide evidence for nuciferine as a promising protective agent for treating cisplatin-induced hearing loss.

PRMT6 deficiency or inhibition alleviates neuropathic pain by decreasing glycolysis and inflammation in microglia

Microglia induced chronic inflammation is the critical pathology of Neuropathic pain (NP). Metabolic reprogramming of macrophage has been intensively reported in various chronic inflammation diseases. However, the metabolic reprogramming of microglia in chronic pain remains to be elusive. Here, we reported that immuno-metabolic markers (HIF-1α, PKM2, GLUT1 and lactate) were related with increased expression of PRMT6 in the ipsilateral spinal cord dorsal horn of the chronic construction injury (CCI) mice. PRMT6 deficiency or prophylactic and therapeutic intrathecal administration of PRMT6 inhibitor (EPZ020411) ameliorated CCI-induced NP, inflammation and glycolysis in the ipsilateral spinal cord dorsal horn. PRMT6 knockout or knockdown inhibited LPS-induced inflammation, proliferation and glycolysis in microglia cells. While PRMT6 overexpression exacerbated LPS-induced inflammation, proliferation and glycolysis in BV2 cells. Recent research revealed that PRMT6 could interact with and methylate HIF-1α, which increased HIF-1α protein stability. In sum, increased expression of PRMT6 exacerbates NP progress by increasing glycolysis and neuroinflammation through interacting with and stabilizing HIF-1α in a methyltransferase manner, which outlines novel pathological mechanism and drug target for NP.

A DNA-inspired injectable adhesive hydrogel with dual nitric oxide donors to promote angiogenesis for enhanced wound healing

Chronic diabetic wounds are a severe complication of diabetes, often leading to high treatment costs and high amputation rates. Numerous studies have revealed that nitric oxide (NO) therapy is a promising option because it favours wound revascularization. Here, base-paired injectable adhesive hydrogels (CAT) were prepared using adenine- and thymine-modified chitosan (CSA and CST). By further introducing S-nitrosoglutathione (GSNO) and binary l-arginine (bArg), we obtained a NO sustained-release hydrogel (CAT/bArg/GSON) that was more suitable for the treatment of chronic wounds. The results showed that the expression of HIF-1α and VEGF was upregulated in the CAT/bArg/GSON group, and improved blood vessel regeneration was observed, indicating an important role of NO. In addition, the research findings revealed that following treatment with the CAT/bArg/GSON hydrogel, the viability of Staphylococcus aureus and Escherichia coli decreased to 14 ± 2 % and 6 ± 1 %, respectively. Moreover, the wound microenvironment was improved, as evidenced by a 60 ± 1 % clearance of DPPH. In particular, histological examination and immunohistochemical staining results showed that wounds treated with CAT/bArg/GSNO exhibited denser neovascularization, faster epithelial tissue regeneration, and thicker collagen deposition. Overall, this study proposes an effective strategy to prepare injectable hydrogel dressings with dual NO donors. The functionality of CAT/bArg/GSON has been thoroughly demonstrated in research on chronic wound vascular regeneration, indicating that CAT/bArg/GSON could be a potential option for promoting chronic wound healing. STATEMENT OF SIGNIFICANCE: This article prepares a chitosan hydrogel utilizing the principle of complementary base pairing, which offers several advantages, including good adhesion, biocompatibility, and flow properties, making it a good material for wound dressings. Loaded GSNO and bArg can steadily release NO and l-arginine through the degradation of the gel. Then, the released l-arginine not only possesses antioxidant properties but can also continue to generate a small amount of NO under the action of NOS. This design achieves a sustained and stable supply of NO at the wound site, maximizing the angiogenesis-promoting and antibacterial effects of NO. More neovascularization and abundant collagen were observed in the regenerated tissues. This study provides an effective repair hydrogel material for diabetic wound.

Dual-drug controllable co-assembly nanosystem for targeted and synergistic treatment of hepatocellular carcinoma

The effectiveness of chemotherapeutic agents for hepatocellular carcinoma (HCC) is unsatisfactory because of tumor heterogeneity, multidrug resistance, and poor target accumulation. Therefore, multimodality-treatment with accurate drug delivery has become increasingly popular. Herein, a cell penetrating peptide-aptamer dual modified-nanocomposite (USILA NPs) was successfully constructed by coating a cell penetrating peptide and aptamer onto the surface of sorafenib (Sora), ursolic acid (UA) and indocyanine green (ICG) condensed nanodrug (USI NPs) via one-pot assembly for targeted and synergistic HCC treatment. USILA NPs showed higher cellular uptake and cytotoxicity in HepG2 and H22 cells, with a high expression of epithelial cell adhesion molecule (EpCAM). Furthermore, these NPs caused more significant mitochondrial membrane potential reduction and cell apoptosis. These NPs could selectively accumulate at the tumor site of H22 tumor-bearing mice and were detected with the help of ICG fluorescence; moreover, they retarded tumor growth better than monotherapy. Thus, USILA NPs can realize the targeted delivery of dual drugs and the integration of diagnosis and treatment. Moreover, the effects were more significant after co-administration of iRGD peptide, a tumor-penetrating peptide with better penetration promoting ability or programmed cell death ligand 1 (PD-L1) antibody for the reversal of the immunosuppressive state in the tumor microenvironment. The tumor inhibition rates of USILA NPs + iRGD peptide or USILA NPs + PD-L1 antibody with good therapeutic safety were 72.38 % and 67.91 % compared with control, respectively. Overall, this composite nanosystem could act as a promising targeted tool and provide an effective intervention strategy for enhanced HCC synergistic treatment.

Identification and experimental validation of ferroptosis-related gene lactotransferrin in age-related hearing loss

Objective

To reveal the relationship between ARHL and ferroptosis and screen ferroptosis-related genes (FRGs) in ARHL.

Methods

Bioinformatics were used to analyze the hub genes and molecular mechanism of ferroptosis in the aging cochleae. Senescence β-galactosidase staining, iron content detection, and micro malondialdehyde (MDA) assay kits were used to measure β-galactosidase activity, and expression of Fe2+ and MDA, respectively. Fluorescence microscope was used for immunofluorescence assay of hub genes. Western blot was used to verify the expression of hub genes in HEI-OC1 cells, cochlear explants, and cochleae of C57BL/6J mice. Data were expressed as mean ± SD of at least three independent experiments.

Results

The analysis of bioinformatics confirmed that lactotransferrin (LTF) is the hub gene and CEBPA-miR-130b-LTF network is the molecular mechanism for cochlear ferroptosis. Compared with the control group, the experiments proved that the indicators of ferroptosis, including Fe2+, MDA, and LTF were differentially expressed in aging HEI-OC1 cells, aging cochlear explants, and aging cochleae.

Conclusion

These results demonstrate that ferroptosis plays an important role in ARHL, and LTF is a potential therapeutic target for ARHL via regulating cochlear ferroptosis.

Cortisol Sensitizes Cochlear Hair Cells to Gentamicin Ototoxicity Via Endogenous Apoptotic Pathway

BACKGROUND

The widespread use of aminoglycosides is a prevalent cause of sensorineural hearing loss. Patients receiving aminoglycosides usually have elevated levels of circulating stress hormones due to disease or physiological stress; however, whether the stress hormone cortisol impacts aminoglycoside-mediated injury of cochlear hair cells has not been fully investigated.

METHODS

House Ear Institute-Organ of Corti 1 (HEI-OC1) cells with or without cortisol pretreatment were exposed to gentamicin, we investigated the effect of cortisol pretreatment on gentamicin ototoxicity by assessing cell viability. Molecular pathogenesis was explored by detecting apoptosis and oxidative stress. Meanwhile, by inhibiting glucocorticoid receptors (GR) and mineralocorticoid receptors (MR), the potential roles of receptor types in cortisol-mediated sensitization were evaluated.

RESULTS

Cortisol concentrations below 75 μmol/l did not affect cell viability. However, pretreatment with 50 μmol/l cortisol for 24 hours sensitized hair cells to gentamicin-induced apoptosis. Further mechanistic studies revealed that cortisol significantly increased hair cell apoptosis and oxidative stress, and altered apoptosis-related protein expressions induced by gentamicin. In addition, blockade of either GR or MR attenuated cortisol-induced hair cell sensitization to gentamicin toxicity.

CONCLUSION

Cortisol pretreatment increased mammalian hair cell susceptibility to gentamicin toxicity. Sensitization was related to the activation of the intrinsic apoptotic pathway and excessive generation of reactive oxygen species. Cortisol may exacerbate aminoglycoside ototoxicity.

Lysophosphatidic acid exerts protective effects on HEI-OC1 cells against cytotoxicity of cisplatin by decreasing apoptosis, excessive autophagy, and accumulation of ROS

Lysophosphatidic acid (LPA) is an active phospholipid signaling molecule that binds to six specific G protein-coupled receptors (LPA1-6) on the cell surface and exerts a variety of biological functions, including cell migration and proliferation, morphological changes, and anti-apoptosis. The earliest study from our group demonstrated that LPA treatment could restore cochlear F-actin depolymerization induced by noise exposure, reduce hair cell death, and thus protect hearing. However, whether LPA could protect against cisplatin-induced ototoxicity and which receptors play the major role remain unclear. To this end, we integrated the HEI-OC1 mouse cochlear hair cell line and zebrafish model, and found that cisplatin exposure induced a large amount of reactive oxygen species accumulation in HEI-OC1 cells, accompanied by mitochondrial damage, leading to apoptosis and autophagy. LPA treatment significantly attenuated autophagy and apoptosis in HEI-OC1 cells after cisplatin exposure. Further investigation revealed that all LPA receptors except LPA3 were expressed in HEI-OC1 cells, and the mRNA expression level of LPA1 receptor was significantly higher than that of other receptors. When LPA1 receptor was silenced, the protective effect of LPA was reduced and the proportion of apoptosis cells was increased, indicating that LPA-LPA1 plays an important role in protecting HEI-OC1 cells from cisplatin-induced apoptosis. In addition, the behavioral trajectory and in vivo fluorescence imaging results showed that cisplatin exposure caused zebrafish to move more actively, and the movement speed and distance were higher than those of the control and LPA groups, while LPA treatment reduced the movement behavior. Cisplatin caused hair cell death and loss in zebrafish lateral line, and LPA treatment significantly protected against hair cell death and loss. LPA has a protective effect on hair cells in vitro and in vivo against the cytotoxicity of cisplatin, and its mechanism may be related to reducing apoptosis, excessive autophagy and ROS accumulation.

FAM134B-induced endoplasmic reticulum (ER)-phagy exacerbates cisplatin-insulted hair cell apoptosis ：Possible relation to excessive ER stress

AIMS

FAM134B, the initial endoplasmic reticulum (ER)-phagy receptor identified, facilitates ER-phagy during ER stress. The malfunction of FAM134B has been demonstrated to have a crucial role in the pathological mechanisms of diverse human ailments. However, the role of FAM134B-mediated ER-phagy in ototoxicity, particularly in cisplatin-induced ototoxicity, remains unclear. The present study endeavors to investigate whether FAM134B is expressed in House Ear Institute-Organ of Corti 1 (HEI-OC1) and C57BL/6 murine cochlear hair cells (HCs), and to explore its potential function in cisplatin-mediated ototoxicity, with the aim of discovering new insights that can mitigate or forestall the irreversible adverse effect of cisplatin.

METHODS

Immunofluorescence (IF) staining was used to test the expression pattern of FAM134B, levels of C/EBP-homologous protein (CHOP), autophagy, and co-localization ratio of lysosomes and ER. Western blotting was employed to measure changes in expression levels of FAM134B, LC3B, ER stress-related proteins, LAMP1 and apoptotic mediators. Cell apoptosis was examined using transferase dUTP nick end labeling (TUNEL) assay and flow cytometry.

RESULTS

In the present investigation, it was observed that FAM134B exhibited a diffuse expression pattern in the cytoplasm and nuclei of control HEI-OC1 cells. Following cisplatin administration, FAM134B was found to accumulate and form distinct dots around the nuclei, concomitant with increased levels of ER-phagy, ER stress, unfolded protein response (UPR), and cell apoptosis. Additionally, knockdown of FAM134B resulted in reduced ER-phagy, mitigated ER stress and UPR, and decreased apoptotic activity in HEI-OC1 cells following cisplatin exposure.

CONCLUSIONS

Collectively, the findings of this study demonstrate that FAM134B-mediated ER-phagy enhances the susceptibility of HCs to ER stress and apoptosis in response to cisplatin-induced stress. This suggests a sequential progression of ER-phagy, ER stress and apoptosis following cisplatin stimulus, and implies the potential therapeutic benefit of inhibiting of FAM134B-mediated ER-phagy in the prevention of cisplatin-related ototoxicity.

Inhibition of histone methyltransferase PRMT5 attenuates cisplatin-induced hearing loss through the PI3K/Akt-mediated mitochondrial apoptotic pathway

This study aimed to evaluate the therapeutic potential of inhibiting protein arginine methyltransferase 5 (PRMT5) in cisplatin-induced hearing loss. The effects of PRMT5 inhibition on cisplatin-induced auditory injury were determined using immunohistochemistry, apoptosis assays, and auditory brainstem response. The mechanism of PRMT5 inhibition on hair cell survival was assessed using RNA-seq and Cleavage Under Targets and Tagment-quantitative polymerase chain reaction (CUT&Tag-qPCR) analyses in the HEI-OC1 cell line. Pharmacological inhibition of PRMT5 significantly alleviated cisplatin-induced damage to hair cells and spiral ganglion neurons in the cochlea and decreased apoptosis by protecting mitochondrial function and preventing the accumulation of reactive oxygen species. CUT&Tag-qPCR analysis demonstrated that inhibition of PRMT5 in HEI-OC1 cells reduced the accumulation of H4R3me2s/H3R8me2s marks at the promoter region of the Pik3ca gene, thus activating the expression of Pik3ca. These findings suggest that PRMT5 inhibitors have strong potential as agents against cisplatin-induced ototoxicity and can lay the foundation for further research on treatment strategies of hearing loss.

Metabolic Modulation of Intracellular Ammonia via Intravesical Instillation of Nanoporter-Encased Hydrogel Eradicates Bladder Carcinoma

Tumor protein 53 (TP53) mutation in bladder carcinoma (BC), upregulates the transcription of carbamoyl phosphate synthetase 1 (CPS1), to reduce intracellular ammonia toxicity. To leverage ammonia combating BC, here, an intravesically perfusable nanoporter-encased hydrogel system is reported. A biomimetic fusogenic liposomalized nanoporter (FLNP) that is decorated with urea transporter-B (UT-B) is first synthesized with protonated chitosan oligosaccharide for bladder tumor-targeted co-delivery of urease and small interfering RNA targeting CPS1 (siCPS1). Mussel-inspired hydrogel featured with dual functions of bio-adhesion and injectability is then fabricated as the reservoir for intravesical immobilization of FLNP. It is found that FLNP-mediated UT-B immobilization dramatically induces urea transportation into tumor cells, and co-delivery of urease and siCPS1 significantly boosts ammonia accumulation in tumor inducing cell apoptosis. Treatment with hybrid system exhibits superior anti-tumor effect in orthotopic bladder tumor mouse model and patient-derived xenograft model, respectively. Combined with high-protein diet, the production of urinary urea increases, leading to an augmented intracellular deposition of ammonia in BC cells, and ultimately an enhanced tumor inhibition. Together, the work establishes that cascade modulation of ammonia in tumor cells could induce tumor apoptosis and may be a practical strategy for eradication of TP53-mutated bladder cancer.

DJ-1 Protects Auditory Cells from Cisplatin-induced Ototoxicity via Regulating Apoptosis and Autophagy

AIMS

DJ-1, a multifunctional protein encoded by the Park7 gene, is tightly related to mitochondrial dysfunction, oxidative stress, protein aggregation, and autophagy regulation. The current study was designed to investigate whether DJ-1 is expressed in auditory cells and, if so, to explore the possible correlation between DJ-1 and cisplatin-induced ototoxicity in this type of cells.

METHODS

The location and dynamic expression of DJ-1 in mouse cochlea hair cells (HCs) and House Ear Institute-Organ of Corti 1 (HEI-OC1 cells) were detected by immunofluorescence, real-time PCR, and western blot. The apoptosis of auditory cells was assessed by TUNEL staining and flow cytometry. The levels of ROS were evaluated by MitoSox red staining. The expression of protein cleaved caspase-9, cleaved caspase-3, and LC3B was examined by immunofluorescence and western blot. The expressions of certain key factors relevant to apoptosis (Bcl-2 and Bax) and autophagy (Beclin1, p-JNK, and p-c-Jun) were determined by western blot. The dynamic alterations of those factors in response to DJ-1 knockdown in HEI-OC1 cells (DJ-1-KD) were measured by western blotting and MitoSox red staining.

RESULTS

The expression of DJ-1 was clearly shown in both HCs and HEI-OC1 cells and cisplatin led to the reduction of DJ-1 expression in a concentration and time-dependent manner. Meanwhile, cisplatin-induced apoptotic process was implemented by promoting reactive oxygen species (ROS) production and activating the mitochondrial pathway. Furthermore, DJ-1 explicitly participated in cisplatin-trigged cell damage by regulating autophagy.

CONCLUSIONS

Findings from this work clearly reveal, for the first time, that DJ-1 is expressed in the cochlea. Of particular importance, DJ-1 exerts its protective action against cisplatin-elicited injury on auditory cells via regulating apoptosis and autophagy, which provides a new strategy for the prevention of cisplatin-induced ototoxicity.

Isoginkgetin-loaded reactive oxygen species scavenging nanoparticles ameliorate intervertebral disc degeneration via enhancing autophagy in nucleus pulposus cells

Excessive reactive oxygen species (ROS) in nucleus pulposus cells (NPCs) promote extracellular matrix (ECM) degradation and cellular inflammatory responses by activating a variety of cellular pathways, ultimately inducing cell apoptosis and leading to the development of low back pain. Here, we designed and fabricated an isoginkgetin-loaded ROS-responsive delivery system (IGK@SeNP) based on diselenide block copolymers. Successfully encapsulated IGK was released intelligently and rapidly in a microenvironment with high ROS levels in degenerative disc. Controlled-release IGK not only efficiently scavenged ROS from the intervertebral disc together with diselenide block copolymers but also effectively enhanced autophagy in NPCs to inhibit ECM degradation and cell apoptosis, and showed significant therapeutic effects in the rat intervertebral disc degeneration (IDD) model. Overall, the synergistic effects of IGK@SeNP in ROS scavenging and autophagy enhancement endowed it with an attractive therapeutic strategy for IDD treatment.

A mycobacterial effector promotes ferroptosis-dependent pathogenicity and dissemination

Ferroptosis is a lipid peroxidation-driven and iron-dependent programmed cell death involved in multiple physical processes and various diseases. Emerging evidence suggests that several pathogens manipulate ferroptosis for their pathogenicity and dissemination, but the underlying molecular mechanisms remain elusive. Here, we identify that protein tyrosine phosphatase A (PtpA), an effector secreted by tuberculosis (TB)-causing pathogen Mycobacterium tuberculosis (Mtb), triggers ferroptosis to promote Mtb pathogenicity and dissemination. Mechanistically, PtpA, through its Cys11 site, interacts with host RanGDP to enter host cell nucleus. Then, the nuclear PtpA enhances asymmetric dimethylation of histone H3 arginine 2 (H3R2me2a) via targeting protein arginine methyltransferase 6 (PRMT6), thus inhibiting glutathione peroxidase 4 (GPX4) expression, eventually inducing ferroptosis to promote Mtb pathogenicity and dissemination. Taken together, our findings provide insights into molecular mechanisms of pathogen-induced ferroptosis, indicating a potential TB treatment via blocking Mtb PtpA-host PRMT6 interface to target GPX4-dependent ferroptosis.

Protective mechanism of ferulic acid against neomycin-induced ototoxicity in zebrafish

Ototoxicity refers to damage of sensory hair cells and functional hearing impairment following aminoglycosides exposure. Previously, we have determined that ferulic acid (FA) protected hair cells against serial concentrations of neomycin-induced ototoxic damage. The aim of the present study is to assess the mechanism and effects of FA on neomycin-induced hair cells loss and impact on mechanosensory-mediated behaviors alteration using transgenic zebrafish (pvalb3b: TagGFP). We first identified the optimal protective condition as pre/co-treatment method in early fish development. Pretreatment of the larvae with FA significantly protected against neomycin-induced hair cells loss through preventing neomycin passed through the cytoplasm of hair cells, and subsequently decreased reactive oxygen species production and TUNEL signals in 4 day post-fertilization (dpf) transgenic zebrafish larvae. Moreover, preservation of functional hair cells correlated directly with rescue of the altered swimming behavior, indicates FA pretreatment protects against neomycin ototoxic damage in 7-dpf transgenic zebrafish larvae. Together, our findings unravel the otoprotective role of FA as an effective agent against neomycin-induced ototoxic effects and offering the theoretical foundation for discovering novel candidates for hearing protection.

Chemometric Discrimination of Cichorium glandulosum Boiss. et Huet and Cichorium intybus L. via Their Metabolic Profiling, Antioxidative, and Hypoglycemic Activities

Cichorium glandulosum Boiss. et Huet (CG) and Cichorium intybus L. (CI) are widely used as the main raw material of functional food with hepatoprotective and hypoglycemic effects. Due to the lack of comparison on the chemical ingredients and efficacy, they were often used imprecisely and interchangeably. It is necessary to distinguish between them. With the plant metabolomics based on high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) and multivariate chemometric techniques, the chemical ingredients were characterized and 59 compounds between CG and CI were classified. As for antioxidative and hypoglycemic activities in vitro, CI extraction exhibited better antioxidant activity than CG, while CG extraction showed stronger hypoglycemic activity. Furthermore, a bivariate correlation between the chemical composition and efficacy of the extract was also analyzed, and three differentially strong correlation components between CI and CG were prepared, and the antioxidative and hypoglycemic efficacies were compared in vivo and different active phenotypes were obtained. Finally, we revealed chemical and biological differences between CG and CI, providing a basis for achieving better quality control and developing more effective functional foods.

PRMT6-CDC20 facilitates glioblastoma progression via the degradation of CDKN1B

PRMT6, a type I arginine methyltransferase, di-methylates the arginine residues of both histones and non-histones asymmetrically. Increasing evidence indicates that PRMT6 plays a tumor mediator involved in human malignancies. Here, we aim to uncover the essential role and underlying mechanisms of PRMT6 in promoting glioblastoma (GBM) proliferation. Investigation of PRMT6 expression in glioma tissues demonstrated that PRMT6 is overexpressed, and elevated expression of PRMT6 is negatively correlated with poor prognosis in glioma/GBM patients. Silencing PRMT6 inhibited GBM cell proliferation and induced cell cycle arrest at the G0/G1 phase, while overexpressing PRMT6 had opposite results. Further, we found that PRMT6 attenuates the protein stability of CDKN1B by promoting its degradation. Subsequent mechanistic investigations showed that PRMT6 maintains the transcription of CDC20 by activating histone methylation mark (H3R2me2a), and CDC20 interacts with and destabilizes CDKN1B. Rescue experimental results confirmed that PRMT6 promotes the ubiquitinated degradation of CDKN1B and cell proliferation via CDC20. We also verified that the PRMT6 inhibitor (EPZ020411) could attenuate the proliferative effect of GBM cells. Our findings illustrate that PRMT6, an epigenetic mediator, promotes CDC20 transcription via H3R2me2a to mediate the degradation of CDKN1B to facilitate GBM progression. Targeting PRMT6-CDC20-CDKN1B axis might be a promising therapeutic strategy for GBM.

Evaluation of Cardiovascular Toxicity of Folic Acid and 6S-5-Methyltetrahydrofolate-Calcium in Early Embryonic Development

Folic acid (FA) is a synthetic and highly stable version of folate, while 6S-5-methyltetrahydrofolate is the predominant form of dietary folate in circulation and is used as a crystalline form of calcium salt (MTHF-Ca). The current study aims to evaluate the toxicity and safety of FA and MTHF-Ca on embryonic development, with a focus on cardiovascular defects. We began to analyze the toxicity of FA and MTHF-Ca in zebrafish from four to seventy-two hours postfertilization and assessed the efficacy of FA and MTHF-Ca in a zebrafish angiogenesis model. We then analyzed the differently expressed genes in in vitro fertilized murine blastocysts cultured with FA and MTHF-Ca. By using gene-expression profiling, we identified a novel gene in mice that encodes an essential eukaryotic translation initiation factor (Eif1ad7). We further applied the morpholino-mediated gene-knockdown approach to explore whether the FA inhibition of this gene (eif1axb in zebrafish) caused cardiac development disorders, which we confirmed with qRT-PCR. We found that FA, but not MTHF-Ca, could inhibit angiogenesis in zebrafish and result in abnormal cardiovascular development, leading to embryonic death owing to the downregulation of eif1axb. MTHF-Ca, however, had no such cardiotoxicity, unlike FA. The current study thereby provides experimental evidence that FA, rather than MTHF-Ca, has cardiovascular toxicity in early embryonic development and suggests that excessive supplementation of FA in perinatal women may be related to the potential risk of cardiovascular disorders, such as congenital heart disease.

Mitochondria-Driven Dye Rearrangement That Enables Spatiotemporally Controlled Photomedicine

Reversibly controlling the dye arrangements in living systems has great potential to realize spatiotemporally controlled photomedicine. However, tuning or even maintaining a certain arrangement of dyes in a complex living environments is extremely challenging due to the interference of the various biological species. Herein, a conceptual supramolecular strategy to engineer a switchable photosensitizer (PS) via mitochondria-mediated dynamic interconversion between monomer and J-aggregation, enabling specific activation of the mitochondria-targeting photodynamic therapy (PDT) and hibernation after mitochondria damage is presented. The presented mitochondria-mediated "activate-then-hibernate" PS design enables a fascinating spatiotemporally controlled PDT in which spatially controlled mitochondrial-targeting enhances therapeutic efficacy and temporally controlled activation-then-hibernation averts off-target damage during PDT and tissue damage after clinical treatment, thus offering significant potential for biological research and clinical needs.

Potential therapeutic role of SIRT1 in age- related hearing loss

Age-related hearing loss (ARHL) is a major public health burden worldwide that profoundly affects the daily life of elderly people. Silent information regulator 1 (SIRT1 or Sirtuin1), known as a regulator of the cell cycle, the balance of oxidation/antioxidant and mitochondrial function, has been proven to have anti-aging and life-extending effects, and its possible connection with ARHL has received increasing attention in recent years. This paper provides an overview of research on the connection between SIRT1 and ARHL. Topics cover both the functions of SIRT1 and its important role in ARHL. This review concludes with a look at possible research directions for ARHL in the future.

Pitavastatin protects against neomycin-induced ototoxicity through inhibition of endoplasmic reticulum stress

Irreversible injury to inner ear hair cells induced by aminoglycoside antibiotics contributes to the formation of sensorineural hearing loss. Pitavastatin (PTV), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has been reported to exert neuroprotective effects. However, its role in aminoglycoside-induced hearing loss remains unknown. The objectives of this study were to investigate the beneficial effects, as well as the mechanism of action of PTV against neomycin-induced ototoxicity. We found that PTV remarkably reduced hair cell loss in mouse cochlear explants and promoted auditory HEI-OC1 cells survival after neomycin stimulation. We also observed that the auditory brainstem response threshold that was increased by neomycin was significantly reduced by pretreatment with PTV in mice. Furthermore, neomycin-induced endoplasmic reticulum stress in hair cells was attenuated by PTV treatment through inhibition of PERK/eIF2α/ATF4 signaling. Additionally, we found that PTV suppressed the RhoA/ROCK/JNK signal pathway, which was activated by neomycin stimulation in HEI-OC1 cells. Collectively, our results showed that PTV might serve as a promising therapeutic agent against aminoglycoside-induced ototoxicity.

Neomycin inhibits Megalocytivirus infection in fish by antagonizing the increase of intracellular reduced glutathione

Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the Megalocytivirus genus that infects a number of marine and freshwater fishes, causing huge economic losses in aquaculture. The ISKNV infection leads to increase of reducing power in cells. As the antibiotic neomycin can promote the production of reactive oxygen species (ROS) in animal cells, in the current study, the potential therapeutic effect of neomycin on ISKNV infection was explored. We showed that neomycin could decrease the reducing power in cultured MFF-1 cells and inhibit ISKNV infection by antagonizing the shift of the cellular redox balance toward reduction. In vivo experiments further demonstrated that neomycin treatment significantly suppresses ISKNV infection in mandarin fish. Expression of the major capsid protein (MCP) and the proportion of infected cells in tissues were down-regulated after neomycin treatment. Furthermore, neomycin showed complex effects on expression of a set of antiviral related genes of the host. Taking together, the current study suggested that the viral-induced redox imbalance in the infected cells could be used as a target for suppressing ISKNV infection. Neomycin can be potentially utilized for therapeutic treatment of Megalocytivirus diseases by antagonizing intracellular redox changes.

Cichoric Acid May Play a Role in Protecting Hair Cells from Ototoxic Drugs

Ototoxic hearing loss due to antibiotic medication including aminoglycosides and excess free radical production causes irreversible hair cell injury. Cichoric acid, a naturally occurring phenolic acid, has recently been found to exert anti-oxidative and anti-inflammatory properties through its free radical scavenging capacity. The present study aimed to investigate the protective effects of cichoric acid against neomycin-induced ototoxicity using transgenic zebrafish (pvalb3b: TagGFP). Our results indicated that cichoric acid in concentrations up to 5 μM did not affect zebrafish viability during the 2 h treatment period. Therefore, the otoprotective concentration of cichoric acid was identified as 5 μM under 2 h treatment by counting viable hair cells within the neuromasts of the anterior- and posterior-lateral lines in the study. Pretreatment of transgenic zebrafish with 5 μM of cichoric acid for 2 h significantly protected against neomycin-induced hair cell death. Protection mediated by cichoric acid was, however, lost over time. A terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and FM4-64 staining, respectively, provided in situ evidence that cichoric acid ameliorated apoptotic signals and mechanotransduction machinery impairment caused by neomycin. A fish locomotor test (distance move, velocity, and rotation frequency) assessing behavioral alteration after ototoxic damage revealed rescue due to cichoric acid pretreatment before neomycin exposure. These findings suggest that cichoric acid in 5 μM under 2 h treatment has antioxidant effects and can attenuate neomycin-induced hair cell death in neuromasts. Although cichoric acid offered otoprotection, there is only a small difference between pharmacological and toxic concentrations, and hence cichoric acid can be considered a rather prototypical compound for the development of safer otoprotective compounds.

Mitochondria-Targeted Mesoporous Organic Silica Nanoplatforms for Overcoming Cisplatin Resistance by Disturbing Mitochondrial Redox Homeostasis

Cisplatin (also known as DDP) resistance is one of the biggest challenges in the treatment of ovarian cancer. Recent studies have found that mitochondrion, as a potential target of DDP, participates in drug-related apoptosis and resistance. Overexpressed glutathione (GSH) in resistant cells is involved in protecting mitochondria from DDP or DDP-induced ROS. In this work, triphenylphosphonium (TPP) modified disulfide bond-rich (S-S) mesoporous organic silica nanoplatforms (DMON) were developed to deliver DDP (TPP-DMON@DDP) to mitochondria for overcoming DDP resistance. TPP supported the migration of nanoplatforms to the mitochondria, with consequent depletion of mitochondrial GSH by the S-S bond of DMON, leading to mitochondria in redox dyshomeostasis. These treated cells seemed more susceptible to the DDP released from the nanoplatforms. Significantly increased ROS production, mitochondrial damage, and apoptosis were observed in TPP-DMON@DDP-treated cells. Overall, interference of mitochondrial redox homeostasis provides a new opportunity for improving DDP cytotoxicity against resistant cells.

Tetrandrine Prevents Neomycin-Induced Ototoxicity by Promoting Steroid Biosynthesis

Aminoglycoside antibiotics are widely used for the treatment of serious acute infections, life-threatening sepsis, and tuberculosis, but all aminoglycosides cause side effects, especially irreversible ototoxicity. The mechanisms underlying the ototoxicity of aminoglycosides need further investigation, and there are no effective drugs in the clinic. Here we showed that tetrandrine (TET), a bioactive bisbenzylisoquinoline alkaloid derived from Stephania tetrandra, ameliorated neomycin-induced cochlear hair cell injury. In both in vitro and in vivo experiments we found that TET administration significantly improved auditory function and reduced hair cell damage after neomycin exposure. In addition, we observed that TET could significantly decrease oxidative stress and apoptosis in hair cells after neomycin exposure. Finally, RNA-seq analysis suggested that TET protected against neomycin-induced ototoxicity mainly by promoting steroid biosynthesis. Collectively, our results provide pharmacological evidence showing that TET may be a promising agent in preventing aminoglycosides-induced ototoxicity.

Heme Oxygenase-1 Protects Hair Cells From Gentamicin-Induced Death

Gentamicin ototoxicity can generate free radicals within the inner ear, leading to permanent damage to sensory hair cells (HCs) and eventually hearing loss. The following study examined the alterations of oxidative damage-related genes in the cochlea and important molecules responsible for oxidation following gentamicin injury in vitro. The RT² Profiler polymerase chain reaction (PCR) array was used to screen candidate targets for treatment to prevent hearing loss caused by gentamicin. We found that during gentamicin-induced death in HCs, Heme oxygenase-1 (HO-1) had a high fold change in the HCs of the cochlea. Moreover, the use of CoPPIX to induce HO-1 inhibited gentamicin-induced HC death, while HO-1 inhibitors ZnPPIX after CoPPIX reversed this process. Furthermore, the inhibitors of NF-E2-related factor-2 (Nrf2) reduced the expression of HO-1 and inhibited the protective effect of HO-1 after gentamicin, thus suggesting that the Nrf2/HO-1 axis might regulate gentamicin-associated ototoxicity. We further demonstrated that induction of HO-1 up-regulated the expression of Nrf2 in both cochlear and HEI-OC1 cells. In summary, these findings indicated that HO-1 protects HCs from gentamicin by up-regulating its expression in HCs and interacting with Nrf2 to inhibit reactive oxygen species (ROS).

Puerarin attenuates cisplatin-induced apoptosis of hair cells through the mitochondrial apoptotic pathway

Puerarin, one of the main components of Pueraria lobata, has been reported to possess a wide range of pharmacological activities, including anti-inflammatory, antioxidative and anti-apoptotic effects. However, the role of puerarin in ototoxic drug-induced hair cell injury has not been well characterized. This study explored whether puerarin protects against cisplatin-induced hair cell damage and its potential mechanisms. The viability of puerarin-treated HEI-OC1 cells was assessed by CCK8 assay. Reactive oxygen species (ROS) was estimated with flow cytometric analysis using Cellrox Green fluorescent probe. Apoptosis-related protein levels were detected by western blot analysis. Immunostaining of the organ of Corti was performed to determine mice cochlear hair cell survival. Our results showed that puerarin improved cell viability and suppressed apoptosis in the cisplatin-damaged HEI-OC1 cells and cochlear hair cells. Mechanistic studies revealed that puerarin attenuated mitochondrial apoptosis pathway by regulating apoptotic related proteins, such as Bax and cleaved caspase-3, and attenuated ROS accumulation after cisplatin damage. Moreover, puerarin was involved in regulating the Akt pathway in HEI-OC1 cells in response to cisplatin. Our results demonstrated that puerarin administration decreased the sensitivity to apoptosis dependent on the mitochondrial apoptotic pathway by reducing ROS generation, which could be used as a new protective agent against cisplatin-induced ototoxicity.

Overexpression of XIAP inhibits cisplatin-induced hair cell loss

Cisplatin is a platinum-containing drug with ototoxicity commonly used clinically and has significant efficacy against a variety of solid tumors. One of the most important mechanisms of ototoxicity is that cisplatin induces apoptosis of hair cells. According to relevant literature, X-linked inhibitor of apoptosis protein (XIAP, anti-apoptotic protein) could inhibit the apoptotic pathway. We hypothesized that this protein might protect cochlear hair cells from cisplatin-induced injury. To figure it out, we treated cochlea of normal mice with various concentrations of cisplatin to observe the response and morphology of hair cells and determine a reasonable concentration. Next, Western Blot and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) experiments were conducted to make an investigation about the expression of XIAP protein and mRNA. In addition, we constructed and identified XIAP overexpressing mice. Finally, we treated cochlear tissues of normal and overexpressing mice with cisplatin to investigate the cyto-protection of XIAP on hair cells, respectively. It was found that 50 μmol/L cisplatin resulted in significant loss and disorganization of hair cells, while simultaneously downregulating the protein and mRNA of XIAP. In XIAP overexpressing mice, the loss and disorganization of hair cells were significantly lessened. These results showed that XIAP can lessen cisplatin-induced hair cell loss and play a role in otoprotection.

The Protective Effect of Rutin against the Cisplatin-induced Cochlear Damage in vitro

Rutin is a natural flavonoid, with typical effects including interaction with enzymes and scavenging of free radicals. However, the role of rutin in the auditory system is still unclear. In the present study, we used neonatal organ of Corti explants in vitro to investigate the effects of rutin in cisplatin-induced ototoxicity. The TUNEL assay and the cleaved caspase-3 immunohistochemistry were used to detect the apoptosis of hair cell (HCs) in cochlear explants, and the MitoSox-Red staining was used to detect the difference in mitochondrial superoxide among different groups. Western blot was used to investigate the expression of genes. Confocal microscopy showed that after pretreatment with rutin, the accumulation of reactive oxygen species in HCs caused by cisplatin exposure was significantly reduced. Furthermore, the expression levels of p-P38 and p-JNK were significantly decreased, while ratio of p-AKT/AKT was significantly upregulated. Our study showed that rutin reduced cisplatin-induced HCs death in neonatal cochlear explants in vitro. The potential mechanism involved the alleviation of mitochondrial damage, the scavenging of reactive oxygen species (ROS), the suppression of MAPK signaling pathway, and the activation of PI3K/AKT signaling pathway. DATA AVAILABILITY STATEMENT: The datasets during and/or analyzed during the current study available from the corresponding author on reasonable request.

The pro-tumorigenic activity of p38γ overexpression in nasopharyngeal carcinoma

It is urgent to identify and validate biomarkers for early diagnosis and efficient treatment of nasopharyngeal carcinoma (NPC). Recent studies have proposed p38 gamma (p38γ) as a cyclin-dependent kinase (CDK)-like kinase that phosphorylates retinoblastoma (Rb) to promote cyclins expression and tumorigenesis. Here the Gene Expression Profiling Interactive Analysis (GEPIA) database and results from the local NPC tissues demonstrate that p38γ is significantly upregulated in NPC tissues, correlating with poor overall survival. Furthermore, p38γ mRNA and protein expression is elevated in established NPC cell lines (CNE-1 HONE-1 and CNE-2) and primary human NPC cells, but low expression detected in human nasal epithelial cells. In established and primary NPC cells, p38γ depletion, using the shRNA strategy or the CRISPR/Cas9 gene-editing method, largely inhibited cell growth, proliferation and migration, and induced significant apoptosis activation. Contrarily, ectopic p38γ overexpression exerted opposite activity and promoted NPC cell proliferation and migration. Retinoblastoma (Rb) phosphorylation and cyclin E1/A expression were decreased in NPC cells with p38γ silencing or knockout, but increased after p38γ overexpression. Moreover, mitochondrial subcellular p38γ localization was detected in NPC cells. Significantly, p38γ depletion disrupted mitochondrial functions, causing mitochondrial depolarization, reactive oxygen species production, oxidative injury and ATP depletion in NPC cells. In vivo, intratumoral injection of adeno-associated virus-packed p38γ shRNA potently inhibited primary human NPC xenograft growth in nude mice. In p38γ shRNA virus-injected NPC xenograft tissues, p38γ expression, Rb phosphorylation, cyclin E1/A expression and ATP levels were dramatically decreased. Taken together, we conclude that p38γ overexpression is required for NPC cell growth, acting as a promising therapeutic target of NPC.

Inhibiting DNA methylation alleviates cisplatin-induced hearing loss by decreasing oxidative stress-induced mitochondria-dependent apoptosis via the LRP1-PI3K/AKT pathway

Cisplatin-related ototoxicity is a critical side effect of chemotherapy and can lead to irreversible hearing loss. This study aimed to assess the potential effect of the DNA methyltransferase (DNMT) inhibitor RG108 on cisplatin-induced ototoxicity. Immunohistochemistry, apoptosis assay, and auditory brainstem response (ABR) were employed to determine the impacts of RG108 on cisplatin-induced injury in murine hair cells (HCs) and spiral ganglion neurons (SGNs). Rhodamine 123 and TMRM were utilized for mitochondrial membrane potential (MMP) assessment. Reactive oxygen species (ROS) amounts were evaluated by Cellrox green and Mitosox-red probes. Mitochondrial respiratory function evaluation was performed by determining oxygen consumption rates (OCRs). The results showed that RG108 can markedly reduce cisplatin induced damage in HCs and SGNs, and alleviate apoptotic rate by protecting mitochondrial function through preventing ROS accumulation. Furthermore, RG108 upregulated BCL-2 and downregulated APAF1, BAX, and BAD in HEI-OC1 cells, and triggered the PI3K/AKT pathway. Decreased expression of low-density lipoprotein receptor-related protein 1 (LRP1) and high methylation of the LRP1 promoter were observed after cisplatin treatment. RG108 treatment can increase LRP1 expression and decrease LRP1 promoter methylation. In conclusion, RG108 might represent a new potential agent for preventing hearing loss induced by cisplatin via activating the LRP1-PI3K/AKT pathway.

Inhibition of PRMT6 reduces neomycin-induced inner ear hair cell injury through the restraint of FoxG1 arginine methylation

OBJECTIVE

Hair cells in the inner ear have been demonstrated to be sensitive to the ototoxicity from some beneficial pharmaceutical drugs. This study aimed to explore the role of protein arginine methyltransferase 6 (PRMT6) in the process of neomycin-induced hearing loss and the underlying mechanism.

METHODS

The neomycin-induced hearing loss mouse model and hair cell injury in vitro model were established. We took advantage of the HEI-OC1 cell line to evaluate PRMT6 expression in neomycin-induced hair cells, and the effect of PRMT6 on mitochondrial function and FoxG1 arginine methylation. Apoptotic cells were assessed and apoptotic marker cleaved caspase-3 level was detected. Reactive oxygen species (ROS) level and mitochondrial membrane potential (MMP) were subsequently measured.

RESULT

The result showed that PRMT6 was significantly upregulated in neomycin-induced HEI-OC-1 cells, and PRMT6 silencing prevented MMP loss, reduced ROS production, as well as decreased cell apoptosis under neomycin treatment. Further results showed that FoxG1 was downregulated in neomycin-induced HEI-OC-1 cells, and PRMT6 promoted the FoxG1-mediated luciferase activity, while PRMT6 silencing reversed this effect. Mechanistic experiments revealed that PRMT6 silencing reduced the arginine methylation level of FoxG1 protein. In vivo, neomycin-induced upregulation of hearing thresholds and increased cell apoptosis, whereas PRMT6 inhibitor partly reversed these effects.

CONCLUSION

Our findings suggested that inhibition of PRMT6 reduced neomycin-induced inner ear hair cell injury through the restraint of FoxG1 arginine methylation.

Inhibition of KDM5A attenuates cisplatin-induced hearing loss via regulation of the MAPK/AKT pathway

The study aimed to investigate the potential role of lysine-specific demethylase 5A (KDM5A) in cisplatin-induced ototoxicity. The effect of the KDM5A inhibitor CPI-455 was assessed by apoptosis assay, immunofluorescence, flow cytometry, seahorse respirometry assay, and auditory brainstem response test. RNA sequencing, qRT-PCR, and CUT&Tag assays were used to explore the mechanism underlying CPI-455-induced protection. Our results demonstrated that the expression of KDM5A was increased in cisplatin-injured cochlear hair cells compared with controls. CPI-455 treatment markedly declined KDM5A and elevated H3K4 trimethylation levels in cisplatin-injured cochlear hair cells. Moreover, CPI-455 effectively prevented the death of hair cells and spiral ganglion neurons and increased the number of ribbon synapses in a cisplatin-induced ototoxicity mouse model both in vitro and in vivo. In HEI-OC1 cells, KDM5A knockdown reduced reactive oxygen species accumulation and improved mitochondrial membrane potential and oxidative phosphorylation under cisplatin-induced stress. Mechanistically, through transcriptomics and epigenomics analyses, a set of apoptosis-related genes, including Sos1, Sos2, and Map3k3, were regulated by CPI-455. Altogether, our findings indicate that inhibition of KDM5A may represent an effective epigenetic therapeutic target for preventing cisplatin-induced hearing loss.

The Ganglioside Monosialotetrahexosylganglioside Protects Auditory Hair Cells Against Neomycin-Induced Cytotoxicity Through Mitochondrial Antioxidation: An in vitro Study

Neomycin is a common ototoxic aminoglycoside antibiotic that causes sensory hearing disorders worldwide, and monosialotetrahexosylganglioside (GM1) is reported to have antioxidant effects that protect various cells. However, little is known about the effect of GM1 on neomycin-induced hair cell (HC) ototoxic damage and related mechanism. In this study, cochlear HC-like HEI-OC-1 cells along with whole-organ explant cultures were used to establish an in vitro neomycin-induced HC damage model, and then the apoptosis rate, the balance of oxidative and antioxidant gene expression, reactive oxygen species (ROS) levels and mitochondrial membrane potential (MMP) were measured. GM1 could maintain the balance of oxidative and antioxidant gene expression, inhibit the accumulation of ROS and proapoptotic gene expression, promoted antioxidant gene expression, and reduce apoptosis after neomycin exposure in HEI-OC-1 cells and cultured cochlear HCs. These results suggested that GM1 could reduce ROS aggregation, maintain mitochondrial function, and improve HC viability in the presence of neomycin, possibly through mitochondrial antioxidation. Hence, GM1 may have potential clinical value in protecting against aminoglycoside-induced HC injury.

Melatonin protects cochlear hair cells from nicotine-induced injury through inhibiting apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress

Hearing loss positively links with cigarette smoking. However, the involved mechanism and treatment strategies are largely unrevealed. This study aimed to investigate the damaging effect of nicotine on cochlear hair cells, reveal the underlying mechanism and evaluate the therapeutic effect of melatonin on nicotine-induced injury. The results showed that nicotine induced cytotoxicity of House Ear Institute-Organ of Corti 1 (HEI-OC1) cochlear hair cells in a dose-dependent manner (0, 2.5, 5, 10, 20, 40 and 80 μM). Functional investigations showed that nicotine (10 μM) stimulation dramatically promoted apoptosis, inflammatory response, oxidative stress and endoplasmic reticulum stress in HEI-OC1 cells. Moreover, melatonin treatment dose-dependently alleviated the nicotine-induced cytotoxicity in HEI-OC1 cells (0, 10 25, 50 and 100 μM). Further investigation showed that melatonin (100 μM) effectively attenuated the nicotine-induced apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress in HEI-OC1 cells. Collectively, we demonstrated that nicotine induced apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress of cochlear hair cells in an in vitro cell model. Melatonin showed protective effect on these aspects, suggesting that melatonin may be a potential agent for treating smoking-induced hearing loss.

Effect of Sodium Salicylate on Calcium Currents and Exocytosis in Cochlear Inner Hair Cells: Implications for Tinnitus Generation

Sodium salicylate is an anti-inflammatory medication with a side-effect of tinnitus. Here, we used mouse cochlear cultures to explore the effects of salicylate treatment on cochlear inner hair cells (IHCs). We found that IHCs showed significant damage after exposure to a high concentration of salicylate. Whole-cell patch clamp recordings showed that 1-5 mmol/L salicylate did not affect the exocytosis of IHCs, indicating that IHCs are not involved in tinnitus generation by enhancing their neuronal input. Instead, salicylate induced a larger peak amplitude, a more negative half-activation voltage, and a steeper slope factor of Ca²⁺ current. Using noise analysis of Ca²⁺ tail currents and qRT-PCR, we further found that salicylate increased the number of Ca²⁺ channels along with Ca_V1.3 expression. All these changes could act synergistically to enhance the Ca²⁺ influx into IHCs. Inhibition of intracellular Ca²⁺ overload significantly attenuated IHC death after 10 mmol/L salicylate treatment. These results implicate a cellular mechanism for tinnitus generation in the peripheral auditory system.

Protein arginine methylation: from enigmatic functions to therapeutic targeting

Protein arginine methyltransferases (PRMTs) are emerging as attractive therapeutic targets. PRMTs regulate transcription, splicing, RNA biology, the DNA damage response and cell metabolism; these fundamental processes are altered in many diseases. Mechanistically understanding how these enzymes fuel and sustain cancer cells, especially in specific metabolic contexts or in the presence of certain mutations, has provided the rationale for targeting them in oncology. Ongoing inhibitor development, facilitated by structural biology, has generated tool compounds for the majority of PRMTs and enabled clinical programmes for the most advanced oncology targets, PRMT1 and PRMT5. In-depth mechanistic investigations using genetic and chemical tools continue to delineate the roles of PRMTs in regulating immune cells and cancer cells, and cardiovascular and neuronal function, and determine which pathways involving PRMTs could be synergistically targeted in combination therapies for cancer. This research is enhancing our knowledge of the complex functions of arginine methylation, will guide future clinical development and could identify new clinical indications.

Targeting Epigenetic Regulators with Covalent Small-Molecule Inhibitors

Epigenetic regulation of gene expression plays a critical role in various physiological processes, and epigenetic dysregulation is implicated in a number of diseases, prominently including cancer. Epigenetic regulators have been validated as potential therapeutic targets, and significant progress has been made in the discovery and development of epigenetic-based inhibitors. However, successful epigenetic drug discovery is still facing challenges, including moderate selectivity, limited efficacy, and acquired drug resistance. Inspired by the advantages of covalent small-molecule inhibitors, targeted covalent inhibition has attracted increasing interest in epigenetic drug discovery. In this review, we comprehensively summarize the structure-based design and characterization of covalent inhibitors targeting epigenetic writers, readers, and erasers and highlight their potential benefits in enhancing selectivity across the enzyme family and improving in vivo efficacy. We also discuss the challenges and opportunities of covalent small-molecule inhibitors and hope to shed light on future epigenetic drug discovery.

Liproxstatin-1 Protects Hair Cell-Like HEI-OC1 Cells and Cochlear Hair Cells against Neomycin Ototoxicity

Ferroptosis is a recently discovered iron-dependent form of oxidative programmed cell death distinct from caspase-dependent apoptosis. In this study, we investigated the effect of ferroptosis in neomycin-induced hair cell loss by using selective ferroptosis inhibitor liproxstatin-1 (Lip-1). Cell viability was identified by CCK8 assay. The levels of reactive oxygen species (ROS) were determined by DCFH-DA and cellROX green staining. The mitochondrial membrane potential (ΔΨm) was evaluated by TMRM staining. Intracellular iron and lipid peroxides were detected with Mito-FerroGreen and Liperfluo probes. We found that ferroptosis can be induced in both HEI-OC1 cells and neonatal mouse cochlear explants, as evidenced by Mito-FerroGreen and Liperfluo staining. Further experiments showed that pretreatment with Lip-1 significantly alleviated neomycin-induced increased ROS generation and disruption in ΔΨm in the HEI-OC1 cells. In parallel, Lip-1 significantly attenuated neomycin-induced hair cell damage in neonatal mouse cochlear explants. Collectively, these results suggest a novel mechanism for neomycin-induced ototoxicity and suggest that ferroptosis inhibition may be a new clinical intervention to prevent hearing loss.

Histone Demethylase PHF8 Is Required for the Development of the Zebrafish Inner Ear and Posterior Lateral Line

Histone demethylase PHF8 is crucial for multiple developmental processes, and hence, the awareness of its function in developing auditory organs needs to be increased. Using in situ hybridization (ISH) labeling, the mRNA expression of PHF8 in the zebrafish lateral line system and otic vesicle was monitored. The knockdown of PHF8 by morpholino significantly disrupted the development of the posterior lateral line system, which impacted cell migration and decreased the number of lateral line neuromasts. The knockdown of PHF8 also resulted in severe malformation of the semicircular canal and otoliths in terms of size, quantity, and position during the inner ear development. The loss of function of PHF8 also induced a defective differentiation in sensory hair cells in both lateral line neuromasts and the inner ear. ISH analysis of embryos that lacked PHF8 showed alterations in the expression of many target genes of several signaling pathways concerning cell migration and deposition, including the Wnt and FGF pathways. In summary, the current findings established PHF8 as a novel epigenetic element in developing auditory organs, rendering it a potential candidate for hearing loss therapy.

Ferrostatin-1 protects auditory hair cells from cisplatin-induced ototoxicity in vitro and in vivo

Cisplatin is used in a wide variety of malignancies, but cisplatin-induced ototoxicity remains a major issue in clinical practice. Experimental evidence indicates that ferroptosis plays a key role in mediating the unwanted cytotoxicity effect caused by cisplatin. However, the role of ferroptosis in cisplatin-induced ototoxicity requires elucidation. Ferrostatin-1 (Fer-1) was identified as a potent inhibitor of ferroptosis and radical-trapping antioxidant with its ability to reduce the accumulation of lipid peroxides and chain-carrying peroxyl radicals. In the current study, we investigated the effects of Fer-1 in cisplatin-induced ototoxicity in in vitro, ex vivo, and in vivo models. We found, for the first time that Fer-1 efficiently alleviated cisplatin-induced cytotoxicity in HEI-OC1 cells via a concentration-dependent manner. Furthermore, Fer-1 mitigated cisplatin cytotoxicity in transgenic zebrafish sensory hair cells. In HEI-OC1 cells, Fer-1 pretreatment not only drastically reduced the generation of intracellular reactive oxygen species but also remarkably decreased lipid peroxidation levels induced by cisplatin. This was not only ascribed to the inhibition of 4-hydroxynonenal, the final product of lipid peroxides, but also to the promotion of glutathione peroxidase 4, the protein marker of ferroptosis. MitoTracker staining and transmission electron microscopy of mitochondrial morphology suggested that in HEI-OC1 cells, Fer-1 can effectively abrogate mitochondrial damage resulting from the interaction with cisplatin. In addition, Fer-1 pretreatment of cochlear explants substantially protected hair cells from cisplatin-induced damage. Therefore, our results demonstrated that ferroptosis might be involved in cisplatin ototoxicity. Fer-1 administration mitigated cisplatin-induced hair cell damage, further investigations are required to elucidate the molecular mechanisms of its otoprotective effect.

Inhibition of ferroptosis protects House Ear Institute-Organ of Corti 1 cells and cochlear hair cells from cisplatin-induced ototoxicity

Ferroptosis is a recently recognized form of non‐apoptotic cell death caused by an iron‐dependent accumulation of lipid hydroperoxides, which plays important roles in a wide spectrum of pathological conditions. The present study was aimed to investigate the impact of ferroptosis on cisplatin‐induced sensory hair cell damage. Cell viability was determined by Cell Counting Kit‐8 and lactase dehydrogenase assays. The reactive oxygen species (ROS) levels were evaluated by 2,7‐Dichlorodi‐hydrofluorescein diacetate (DCFH‐DA) and MitoSox‐Red staining. Mitochondrial membrane potential (MMP) was measured by tetramethylrhodamine methyl ester (TMRM) staining. Lipid peroxidation, intracellular and mitochondrial iron were detected by Liperfluo, C11‐BODIPY^581/591, FerroOrange and Mito‐FerroGreen, respectively. We found that cisplatin treatment not only markedly augmented ROS accumulation, decreased the MMP, but increased lipid peroxidation and iron accumulation in House Ear Institute‐Organ of Corti 1 (HEI‐OC1) cells. Of note, treatment with the specific ferroptosis inhibitor ferrostatin‐1 could effectively abrogate the cisplatin‐induced toxicity and subsequent cell death. Specifically, the improvement of mitochondrial functions is important mechanisms for protective action of ferroptosis inhibitor against cisplatin‐induced damages in HEI‐OC1 cells. Moreover, inhibition of ferroptosis significantly protected murine cochlear hair cells against cisplatin damage. In addition, treatment murine cochlear hair cells with ferroptosis inducer, RSL3, significantly exacerbated cisplatin‐induced damage, which could be alleviated by ROS inhibitor N‐acetyl‐L‐cysteine. Collectively, our study indicated that ferroptosis inhibition could alleviate the cisplatin‐induced ototoxicity via inactivation of lipid peroxide radical and improvement of mitochondrial function in hair cells.

Elevated Cellular Oxidative Stress in Circulating Immune Cells in Otherwise Healthy Young People Who Use Electronic Cigarettes in a Cross-Sectional Single-Center Study: Implications for Future Cardiovascular Risk

Background

Tobacco cigarettes (TCs) increase oxidative stress and inflammation, both instigators of atherosclerotic cardiac disease. It is unknown if electronic cigarettes (ECs) also increase immune cell oxidative stress. We hypothesized an ordered, “dose‐response” relationship, with tobacco‐product type as “dose” (lowest in nonsmokers, intermediate in EC vapers, and highest in TC smokers), and the “response” being cellular oxidative stress (COS) in immune cell subtypes, in otherwise, healthy young people.

Methods and Results

Using flow cytometry and fluorescent probes, COS was determined in immune cell subtypes in 33 otherwise healthy young people: nonsmokers (n=12), EC vapers (n=12), and TC smokers (n=9). Study groups had similar baseline characteristics, including age, sex, race, and education level. A dose‐response increase in proinflammatory monocytes and lymphocytes, and their COS content among the 3 study groups was found: lowest in nonsmokers, intermediate in EC vapers, and highest in TC smokers. These findings were most striking in CD14_dimCD16⁺ and CD14⁺⁺CD16⁺ proinflammatory monocytes and were reproduced with 2 independent fluorescent probes of COS.

Conclusions

These findings portend the development of premature cardiovascular disease in otherwise healthy young people who chronically vape ECs. On the other hand, that the COS is lower in EC vapers compared with TC smokers warrants additional investigation to determine if switching to ECs may form part of a harm‐reduction strategy.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03823885.

Advances in Inner Ear Therapeutics for Hearing Loss in Children

Purpose of review

Hearing loss is a common congenital sensory disorder with various underlying causes. Here, we review and focus on genetic, infectious, and ototoxic causes and recent advances in inner ear therapeutics.

Recent findings

While hearing aids and cochlear implantation are the mainstay of treatment for pediatric hearing loss, novel biological therapeutics are being explored. Recent preclinical studies report positive results in viral-mediated gene transfer techniques and surgical approaches to the inner ear for genetic hearing loss. Novel pharmacologic agents, on the other hand, show promising results in reducing aminoglycoside and cisplatin ototoxicity. Clinical trials are underway to evaluate the efficacy of antivirals for cytomegalovirus-related hearing loss, and its pathogenesis and other potential therapeutics are currently under investigation.

Summary

Individualized therapies for genetic and infectious causes of sensorineural hearing loss in animal models as well as pediatric patients show promising results, with their potential efficacy being active areas of research.