Sirtuin-3 Protects Cochlear Hair Cells Against Noise-Induced Damage via the Superoxide Dismutase 2/Reactive Oxygen Species Signaling Pathway

Tranylcypromine upregulates Sestrin 2 expression to ameliorate NLRP3-related noise-induced hearing loss

JOURNAL/nrgr/04.03/01300535-202505000-00030/figure1/v/2024-07-28T173839Z/r/image-tiff Noise-induced hearing loss is the primary non-genetic factor contributing to auditory dysfunction. However, there are currently no effective pharmacological interventions for patients with noise-induced hearing loss. Here, we present evidence suggesting that the lysine-specific demethylase 1 inhibitor-tranylcypromine is an otoprotective agent that could be used to treat noise-induced hearing loss, and elucidate its underlying regulatory mechanisms. We established a mouse model of permanent threshold shift hearing loss by exposing the mice to white broadband noise at a sound pressure level of 120 dB for 4 hours. We found that tranylcypromine treatment led to the upregulation of Sestrin2 (SESN2) and activation of the autophagy markers light chain 3B and lysosome-associated membrane glycoprotein 1 in the cochleae of mice treated with tranylcypromine. The noise exposure group treated with tranylcypromine showed significantly lower average auditory brainstem response hearing thresholds at click, 4, 8, and 16 kHz frequencies compared with the noise exposure group treated with saline. These findings indicate that tranylcypromine treatment resulted in increased SESN2, light chain 3B, and lysosome-associated membrane glycoprotein 1 expression after noise exposure, leading to a reduction in levels of 4-hydroxynonenal and cleaved caspase-3, thereby reducing noise-induced hair cell loss. Additionally, immunoblot analysis demonstrated that treatment with tranylcypromine upregulated SESN2 expression via the autophagy pathway. Tranylcypromine treatment also reduced the production of NOD-like receptor family pyrin domain-containing 3 (NLRP3) production. In conclusion, our results showed that tranylcypromine treatment ameliorated cochlear inflammation by promoting the expression of SESN2, which induced autophagy, thereby restricting NLRP3-related inflammasome signaling, alleviating cochlear hair cell loss, and protecting hearing function. These findings suggest that inhibiting lysine-specific demethylase 1 is a potential therapeutic strategy for preventing hair cell loss and noise-induced hearing loss.

The Carcinogenesis of the Human Scalp: An Immunometabolic-Centered View

The human scalp is a common site of skin cancer in humans, with nonmelanoma skin cancer being exceedingly common. In this review, two dermatologists with extensive experience in cutaneous oncology will discuss unique features of the epidemiology of cancer of the scalp. Clinical observations on these common skin cancers lead to insight into the pathogenesis and potential prevention and treatment of cutaneous scalp neoplasia. Our hypothesis is that the presence of hair protects against the development of skin cancer but not by serving as a physical shield but rather by providing continuous IL-17-biased immunosurveillance. The loss of hair allows for a release from immunosurveillance, resulting in the expansion of neoplastic cells towards skin cancer. Both hair follicles and metabolic changes in stroma allow for permissiveness for tumor promotion.

Protective effect and mechanism of lycium barbarum polysaccharide against UVB-induced skin photoaging

BACKGROUND

Cellular senescence can be categorized into two main types, including exogenous and endogenous aging. Photoaging, which is aging induced by ultraviolet (UV) radiation, significantly contributes to exogenous aging, accounting for approximately 80% of such cases. Superoxide Dismutase (SOD) is a class of antioxidant enzymes, with SOD2 being predominantly localized in the mitochondrial matrix. Ultraviolet radiation (UVR) inhibits SOD2 activity by acetylating the key lysine residues on SOD2. Sirtuin3 (SIRT3), the principal mitochondrial deacetylase, enhances the anti-oxidant capacity of SOD2 by deacetylating. Lycium barbarum polysaccharide (LBP) is the main bioactive component extracted from Lycium barbarum (LB). It has been reported to have numerous potential health benefits, such as anti-oxidation, anti-aging, anti-inflammatory and anti-apoptotic properties. Furthermore, LBP has been shown to regulate hepatic oxidative stress via the SIRT3-SOD2 pathway. The aim of this study was to construct a UVB-Stress-induced Premature Senescence (UVB-SIPS) model to investigate the protective effects and underlying mechanisms of LBP against UVB-induced skin photoaging.

METHODS

Irradiated with different UVB doses to select the suitable dose for constructing the UVB-SIPS model. Cell morphology was observed using a microscope. The proportion of senescent cells was assessed by senescence-associated β-galactosidase (SA-β-gal) staining. Cell viability was studied using the Cell Counting Kit-8 (CCK-8). Intracellular levels of reactive oxygen species (ROS) were observed using flow cytometry and an inverted fluorescence microscope. Expression of γ-H2AX was investigated using flow cytometry. Western blot (WB) was used to verify the expression of senescence-associated proteins (p21, p53, MMP-1, and MMP-3). Enzyme-Linked Immunosorbnent Assay (ELISA) was used to measure pro-inflammatory cytokines levels (IL-6, TNF-α). WB was also used to analyze the expression of SIRT3, SOD2, and Ac-SOD2, and a specific kit was employed to detect SOD2 activity.

RESULTS

Our results suggested that the UVB-SIPS group pre-treated with LBP exhibited a reduced proportion of cells positive for SA-β-gal staining, mitigated production of intracellular ROS, an amelioration in γ-H2AX expression, and down-regulated expression of senescence-associated proteins and pro-inflammatory cytokines as compared to the UVB-SIPS group. Moreover, in contrast to the control group, the UVB-SIPS group showed regulated SIRT3 expression and SOD activity, elevated Ac-SOD2 expression and an increased ratio of Ac-SOD2/SOD2. However, the UVB-SIPS group pre-treated with LBP showed an upregulation of SIRT3 expression and enhanced SOD activity, a reduction in AC-SOD2 expression, and a decreased ratio of AC-SOD2/SOD2, compared to the untreated UVB-SIPS group. Additionally, the photo-protective effect of LBP was diminished following treatment with 3-TYP, a SIRT3-specific inhibitor. This study suggested that LBP, a natural component, exhibits anti-oxidant and anti-photoaging properties, potentially mediated through the SIRT3-SOD2 pathway.

Reversible opening of the blood-labyrinth barrier by low-pressure pulsed ultrasound and microbubbles for the treatment of inner ear diseases

Systemic drug administration provides convenience and non-invasive benefits for preventing and treating inner ear diseases. However, the blood-labyrinth barrier (BLB) restricts the transport of drugs to inner ear tissues. Ultrasound can stimulate specific areas and penetrate tissues, with the potential to overcome physiological barriers. We present a novel strategy based on low-pressure pulsed ultrasound assisted by microbubbles (USMB) to transiently open the BLB and deliver therapeutics into the inner ear. A pulsed ultrasound device with adjustable pressure was established; the generated ultrasound was transmitted through the external auditory canal into the guinea pig's inner ear. We observed that the application of microbubbles allowed the use of safe and efficient ultrasound conditions to penetrate the BLB. We found that USMB-mediated BLB opening seemed to be associated with a reduced expression of the tight junction proteins zonula occludens-1 and occludin. Following intravenous administration, hydrophilic dexamethasone sodium phosphate (DSP), hydrophobic curcumin (CUR), as well as drug-loaded nanoparticles (Fe3O4@CUR NPs) could be efficiently delivered into the inner ear. We observed better drug accumulation in the perilymph of the inner ear, resulting in less drug (cisplatin)-induced ototoxicity. Furthermore, physiological, hematological, and histological studies showed that the modulation of the BLB by low-pressure USMB was a safe process without significant adverse effects. We conclude that USMB could become a promising strategy for the systematic delivery of therapeutics in the treatment of inner ear diseases.

Honokiol relieves hippocampal neuronal damage in Alzheimer's disease by activating the SIRT3-mediated mitochondrial autophagy

BACKGROUND

This work elucidated the effect of honokiol (HKL) on hippocampal neuronal mitochondrial function in Alzheimer's disease (AD).

METHODS

APP/PS1 mice were used as AD mice models and exposed to HKL and 3-TYP. Morris water maze experiment was performed to appraise cognitive performance of mice. Hippocampal Aβ+ plaque deposition and neuronal survival was evaluated by immunohistochemistry and Nissl staining. Hippocampal neurons were dissociated from C57BL/6 mouse embryos. Hippocampal neuronal AD model was constructed by Aβ oligomers induction and treated with HKL, CsA and 3-TYP. Neuronal viability and apoptosis were detected by cell counting kit-8 assay and TUNEL staining. mRFP-eGFP-LC3 assay, MitoSOX Red, dichlorodihydrofluorescein diacetate, and JC-1 staining were performed to monitor neuronal autophagosomes, mitochondrial reactive oxygen species (ROS), neuronal ROS, and mitochondrial membrane potential. Autophagy-related proteins were detected by Western blot.

RESULTS

In AD mice, HKL improved cognitive function, relieved hippocampal Aβ1-42 plaque deposition, promoted hippocampal neuron survival, and activated hippocampal SIRT3 expression and mitochondrial autophagy. These effects of HKL on AD mice were abolished by 3-TYP treatment. In hippocampal neuronal AD model, HKL increased neuronal activity, attenuated neuronal apoptosis and Aβ aggregation, activated SIRT3 and mitochondrial autophagy, reduced mitochondrial and neuronal ROS, and elevated mitochondrial membrane potential. CsA treatment and 3-TYP treatment abrogated the protection of HKL on hippocampal neuronal AD model. The promotion of mitochondrial autophagy by HKL in hippocampal neuronal AD model was counteracted by 3-TYP.

CONCLUSIONS

HKL activates SIRT3-mediated mitochondrial autophagy to mitigate hippocampal neuronal damage in AD. HKL may be effective in treating AD.

Oroxylin A suppress LL-37 generated rosacea-like skin inflammation through the modulation of SIRT3-SOD2-NF-κB signaling pathway

Rosacea is a long-term inflammatory skin disease associated with the dysfunction of vascular and immunological systems. Treatment options for rosacea are difficult to implement. Oroxylin A(OA), a traditional Chinese medicine, has anti-inflammation effects in a variety of inflammatory diseases. However, it is not known that whether OA exerts protective effects against LL-37-induced rosacea. In this study, bioinformatics analyses showed that the mechanisms of rosacea and the pharmacological targets of OA were highly overlapped. Subsequently, it was shown that the administration of OA resulted in a notable amelioration of rosacea-like skin lesions, as evidenced by a reduction in immune cell infiltration, modulation of cytokine production, and inhibition of angiogenesis. Plus, it was shown that OA effectively suppressed the generation of ROS generated by LL-37, as well as the subsequent activation of NF-κB signaling pathway. To explore further, we found that OA inhibited LL-37-induced ROS production via SIRT3-SOD2 signaling pathway in keratinocytes. Based on the aforementioned evidence, it can be inferred that OA exhibits a mitigating effect on the inflammatory response in rosacea by modulating the SIRT3-SOD2-NF-κB signaling pathway.

Early-Onset Hearing Loss in Mouse Models of Alzheimer's Disease and Increased DNA Damage in the Cochlea

There is considerable interest in whether sensory deficiency is associated with the development of Alzheimer's disease (AD). Notably, the relationship between hearing impairment and AD is of high relevance but still poorly understood. In this study, we found early-onset hearing loss in two AD mouse models, 3xTgAD and 3xTgAD/Polβ+/-. The 3xTgAD/Polβ+/- mouse is DNA repair deficient and has more humanized AD features than the 3xTgAD. Both AD mouse models showed increased auditory brainstem response (ABR) thresholds between 16 and 32 kHz at 4 weeks of age, much earlier than any AD cognitive and behavioral changes. The ABR thresholds were significantly higher in 3xTgAD/Polβ+/- mice than in 3xTgAD mice at 16 kHz, and distortion product otoacoustic emission signals were reduced, indicating that DNA damage may be a factor underlying early hearing impairment in AD. Poly ADP-ribosylation and protein expression levels of DNA damage markers increased significantly in the cochlea of the AD mice but not in the adjacent auditory cortex. Phosphoglycerate mutase 2 levels and the number of synaptic ribbons in the presynaptic zones of inner hair cells were decreased in the cochlea of the AD mice. Furthermore, the activity of sirtuin 3 was downregulated in the cochlea of these mice, indicative of impaired mitochondrial function. Taken together, these findings provide new insights into potential mechanisms for hearing dysfunction in AD and suggest that DNA damage in the cochlea might contribute to the development of early hearing loss in AD.

ROS-induced oxidative stress and mitochondrial dysfunction: a possible mechanism responsible for noise-induced ribbon synaptic damage

Evidence suggests that damage to the ribbon synapses (RS) may be the main cause of auditory dysfunction in noise-induced hearing loss (NIHL). Oxidative stress is implicated in the pathophysiology of synaptic damage. However, the relationship between oxidative stress and RS damage in NIHL remains unclear. To investigate the hypothesis that noise-induced oxidative stress is a key factor in synaptic damage within the inner ear, we conducted a study using mice subjected to single or repeated noise exposure (NE). We assessed auditory function using auditory brainstem response (ABR) test and examined cochlear morphology by immunofluorescence staining. The results showed that mice that experienced a single NE exhibited a threshold shift and recovered within two weeks. The ABR wave I latencies were prolonged, and the amplitudes decreased, suggesting RS dysfunction. These changes were also demonstrated by the loss of RS as evidenced by immunofluorescence staining. However, we observed threshold shifts that did not return to baseline levels following secondary NE. Additionally, ABR wave I latencies and amplitudes exhibited notable changes. Immunofluorescence staining indicated not only severe damage to RS but also loss of outer hair cells. We also noted decreased T-AOC, ATP, and mitochondrial membrane potential levels, alongside increased hydrogen peroxide concentrations post-NE. Furthermore, the expression levels of 4-HNE and 8-OHdG in the cochlea were notably elevated. Collectively, our findings suggest that the production of reactive oxygen species leads to oxidative damage in the cochlea. This mitochondrial dysfunction consequently contributes to the loss of RS, precipitating an early onset of NIHL.

D-galactose-induced mitochondrial oxidative damage and apoptosis in the cochlear stria vascularis of mice

BACKGROUND

Age-related hearing loss, known as presbycusis, is the result of auditory system degeneration. Numerous studies have suggested that reactive oxygen species (ROS) and mitochondrial oxidative damage play important roles in the occurrence and progression of aging. The D-galactose (D-gal)-induced aging model is well known and widely utilized in aging research. Our previous studies demonstrate that administration of D-gal causes mitochondrial oxidative damage and causes subsequent dysfunction in the cochlear ribbon synapses, which in turn leads to hearing changes and early stage presbycusis. Stria vascularis (SV) cells are vital for hearing function. However, it is unclear to what extent D-gal induces oxidative damage and apoptosis in the cochlear SV of mice. In addition, the source of the causative ROS in the cochlear SV has not been fully investigated.

METHODS

In this study, we investigated ROS generation in the cochlear SV of mice treated with D-gal. Hearing function was measured using the auditory brainstem response (ABR). Immunofluorescence was used to examine apoptosis and oxidative damage. Transmission electron microscopy was also used to investigate the mitochondrial ultrastructure. DNA fragmentation was determined using the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Mitochondrial membrane potential (MMP) and ATP were also measured.

RESULTS

We found that D-gal-treated mice exhibited a significant shift in the mean amplitude and latency of the ABR; a remarkable increase in the levels of NADPH oxidase (NOX-2), Uncoupling protein 2 (UCP2) and cleaved caspase-3 (c-Cas3) was observed, as well as an increase in the number of TUNEL-positive cells were observed in the SV of mice. Both the expression of the DNA oxidative damage biomarker 8-hydroxy-2-deoxyguanosine (8-OHdG) and a commonly occurring mitochondrial DNA deletion were markedly elevated in the SV of mice that had been treated with D-gal to induce aging. Conversely, the ATP level and MMP were significantly reduced in D-gal-induced aging mice. We also found alterations in the mitochondrial ultrastructure in the SV of aging mice, which include swollen and distorted mitochondrial shape, shortened and thickened microvilli, and the accumulation of lysosomes in the SV.

CONCLUSION

Our findings suggest that the impairment of cochlear SV during presbycusis may be caused by mitochondrial oxidative damage and subsequent apoptosis.

Apoptotic vesicles resist oxidative damage in noise-induced hearing loss through activation of FOXO3a-SOD2 pathway

BACKGROUND

Mesenchymal stem cell (MSC) transplantation is a promising therapeutic approach for noise-induced hearing loss (NIHL). As the indispensable role of apoptosis in MSC transplantation was raised, the benefits of MSC-derived apoptotic vesicles (apoVs) in several disease models have been proved. However, whether apoVs benefit in NIHL have not been studied yet.

METHODS

Female CBA/J mice and HEI-OC1 cells were used in this study. Flow cytometry, nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) were used to characterize apoVs. Proteomic analysis was used to identify function proteins in apoVs. Immunofluorescence was used to reveal distribution pattern. Auditory brainstem response (ABR) test was used to measure the effect of apoVs treatment. DCFH-DA staining and MitoSOX staining were used to indicate oxidative damage. Western-blot and qRT-PCR were used to study the signaling pathways.

RESULTS

We found that apoVs can be endocytosed by hair cells through systemic administration. Importantly, apoVs administration effectively attenuated NIHL and reduced hair cell loss by resisting oxidative damage in vivo. Further, apoVs application activated forkhead box o3 (FOXO3a)-mitochondrial superoxide dismutase 2(SOD2) pathway, which may relate to signal transduction and activators of transcription 3 (STAT3) in apoVs.

CONCLUSIONS

These findings uncovered the role of apoVs in preventing NIHL and resisting oxidative damage, indicating that apoVs is a promising way for inner ear delivery and a prospective cell-free therapy for NIHL.

Oroxylin A relieves intrauterine adhesion in mice through inhibiting macrophage pyroptosis via SIRT3-SOD2-ROS pathway

Intrauterine adhesion (IUA) is manifested by endometrial fibrosis and inflammation, which seriously affects female reproductive health. Macrophages are mainly inflammatory cells and have been reported to participate in the fibrosis of IUA. Oroxylin A (OA), a kind of flavonoid compounds, was showed to possess the inhibitory effects on inflammation and fibrosis. However, the role of OA in IUA remains unclear. In the present study, we found that OA effectively alleviated the level of inflammation and uterine fibrosis in IUA mice. OA also decreased the macrophage pyroptosis which increased in uteri of IUA mice. Pyroptosis is a programmed cell death accompanied by an inflammatory response. Moreover, OA repressed the mediators of pyroptosis including the expression of NOD-like receptor family pyrin domain containing 3 (NLRP3), caspase-1 and Gasdermin D (GSDMD) and the release of IL-1β, IL-18 and cleaved-caspase-1 in J774A.1 cells induced by LPS/ATP in vitro. Mechanistically, the alleviation of OA on uterine fibrosis is achieved by inhibiting macrophage pyroptosis via SIRT3-SOD2-ROS pathway. Our data indicate that OA may serve as an effective agent for the treatment of the endometrial fibrosis with IUA.

POLYDATIN AMELIORATES TRAUMATIC BRAIN INJURY-INDUCED SECONDARY BRAIN INJURY BY INHIBITING NLRP3-INDUCED NEUROINFLAMMATION ASSOCIATED WITH SOD2 ACETYLATION

ABSTRACT

Traumatic brain injury (TBI) is a kind of disease with high morbidity, mortality, and disability, and its pathogenesis is still unclear. Research shows that nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) activation in neurons and astrocytes is involved in neuroinflammatory cascades after TBI. What is more, polydatin (PD) has been shown to have a protective effect on TBI-induced neuroinflammation, but the mechanisms remain unclear. Here, we speculated that PD could alleviate TBI-induced neuroinflammatory damage through the superoxide dismutase (SOD2)-NLRP3 signal pathway, and SOD2 might regulate NLRP3 inflammasome activation. The model of lateral fluid percussion for in vivo and cell stretching injury for in vitro were established to mimic TBI. NLRP3 chemical inhibitor MCC950, SOD2 inhibitor 2-methoxyestradiol, and PD were administered immediately after TBI. As a result, the expression of SOD2 acetylation (SOD2 Ac-K122), NLRP3, and cleaved caspase-1 were increased after TBI both in vivo and in vitro , and using SOD2 inhibitor 2-methoxyestradiol significantly promoted SOD2 Ac-K122, NLRP3, and cleaved caspase-1 expression, as well as exacerbated mitochondrial ROS (mtROS) accumulation and mitochondrial membrane potential (MMP) collapse in PC12 cells. However, using NLRP3 inhibitor MCC950 significantly inhibited cleaved caspase-1 activation after TBI both in vivo and in vitro ; meanwhile, MCC950 inhibited mtROS accumulation and MMP collapse after TBI. More importantly, PD could inhibit the level of SOD2 Ac-K122, NLRP3, and cleaved caspase-1 and promote the expression of SOD2 after TBI both in vivo and in vitro. Polydatin also inhibited mtROS accumulation and MMP collapse after stretching injury. These results indicated that PD inhibited SOD2 acetylation to alleviate NLRP3 inflammasome activation, thus acting a protective role against TBI neuroinflammation.

AAV-ie-mediated UCP2 overexpression accelerates inner hair cell loss during aging in vivo

BACKGROUND

Uncoupling protein 2 (UCP2), activated by excessive reactive oxygen species (ROS) in vivo, has the dual effect of reducing ROS to protect against oxidative stress and reducing ATP production to regulate cellular metabolism. Both the UCP2 and ROS are increased in cochleae in age-related hearing loss (ARHL). However, the role of UCP2 in sensory hair cells in ARHL remains unclear.

METHODS

Male C57BL/6 J mice were randomly assigned to an 8-week-old group (Group 1), a 16-week-old group (Group 2), a 16-week-old + adeno-associated virus-inner ear (AAV-ie) group (Group 3), and a 16-week-old + AAV-ie-UCP2 group (Group 4). Mice aged 8 weeks were administrated with AAV-ie-GFP or AAV-ie-UCP2 via posterior semicircular canal injection. Eight weeks after this viral intervention, hearing thresholds and wave-I amplitudes were tested by auditory brainstem response (ABR). Subsequently, the cochlear basilar membrane was dissected for investigation. The number of hair cells and inner hair cell (IHC) synapses, the level of ROS, and the expression of AMP-activated protein kinase α (AMPKα), were assessed by immunofluorescence staining. In addition, mitochondrial function was determined, and the expression of AMPKα and UCP2 proteins was further evaluated using western blotting.

RESULTS

Mice with early-onset ARHL exhibited enhanced oxidative stress and loss of outer hair cells and IHC synapses, while UCP2 overexpression aggravated hearing loss and cochlear pathophysiological changes in mice. UCP2 overexpression resulted in a notable decrease in the number of IHCs and IHC synapses, caused ATP depletion and excessive ROS generation, increased AMPKα protein levels, and promoted IHC apoptosis, especially in the apical and middle turns of the cochlea.

CONCLUSION

Collectively, our data suggest that UCP2 overexpression may cause mitochondrial dysfunction via energy metabolism, which activates mitochondrion-dependent cellular apoptosis and leads to IHC loss, ultimately exacerbating ARHL.

Trimethylamine-N-Oxide Promotes Osteoclast Differentiation and Bone Loss via Activating ROS-Dependent NF-κB Signaling Pathway

Trimethylamine-N-oxide (TMAO), an important gut microbiota (GM)-derived metabolite, has been shown to be abnormally increased in osteoporosis. However, the role and underlying mechanism of TMAO in regulating bone loss during osteoporosis have not been fully investigated. In the current study, we found that 100–400 μM TMAO dose-dependently enhanced TRAP-positive osteoclasts, F-actin ring formation, and resorption area on bovine bone slices and up-regulated osteoclast-related gene expression (Calcr, Traf6, Dcstamp, Acp5, C-Fos, and NFATc1). Western blotting validated that TMAO not only activated NF-κB signaling pathway but also stimulated c-Fos and NFATc1 protein expression in a dose-dependent manner. Furthermore, BAY 11-7082, an NF-κB inhibitor, pretreatment markedly suppressed TRAP-positive osteoclast formation and osteoclast-related genes under TMAO treatment. BAY 11-7082 also inhibited p-p65/p65, c-Fos, and NFATc1 protein expression promoted by TMAO. Moreover, TMAO significantly increased ROS production, which was inhibited by N-acetylcysteine (NAC), an ROS antagonist. In addition, we proved that NAC pretreatment could inhibit TMAO-promoted NF-κB activation. NAC also suppressed TRAP-positive osteoclast formation, osteoclast-related gene expression, and protein expression of c-Fos and NFATc1 under TMAO treatment. In vivo studies showed significantly decreased bone mass and increased TRAP-positive osteoclasts in TMAO-treated C57BL/6 mice. Moreover, western-blotting and immunohistochemical staining showed that TMAO administration markedly stimulated NF-κB p65 expression. Additionally, TMAO administration significantly promoted the gene and protein expression of C-Fos and NFATc1. In conclusion, TMAO could promote osteoclast differentiation and induce bone loss in mice by activating the ROS-dependent NF-κB signaling pathway.

SIRT3 inhibitor 3-TYP exacerbates thioacetamide-induced hepatic injury in mice

The purpose of the study was to explore the effects of SIRT3 inhibitor 3-TYP on acute liver failure (ALF) in mice and its underlying mechanism. The mice were treated with thioacetamide (TAA, 300 mg/kg) for inducing ALF model. 3-TYP (50 mg/kg) was administered 2 h prior to TAA. The liver histological changes were measured by HE staining. Blood samples were collected for analysis of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). MDA and GSH were used to evaluate the oxidative stress of liver. The expression levels of inflammatory cytokines (TNF-α and IL-1β) were measured by ELISA and Western blotting. The cell type expression of IL-1β in liver tissue was detected by immunofluorescent staining. The expression of SIRT3, MnSOD, ALDH2, MAPK, NF-κB, Nrf2/HO-1, p-elF2α/CHOP, and cleaved caspase 3 was determined by Western blotting. TUNEL staining was performed to detect the apoptosis cells of liver tissues. 3-TYP exacerbated the liver injury of ALF mice. 3-TYP increased the inflammatory responses and activation of MAPK and NF-κB pathways. In addition, 3-TYP administration enhanced the damage of oxidative stress, endoplasmic reticulum stress, and promoted hepatocyte apoptosis in ALF mice. 3-TYP exacerbates thioacetamide-induced hepatic injury in mice. Activation of SIRT3 could be a promising target for the treatment of ALF.

SIRT3-mediated deacetylation protects inner hair cell synapses in a H2O2-induced oxidative stress model in vitro

Oxidative stress is considered a driving event in the damage to inner hair cell (IHC) synapses. Mitochondrial deacetylase Sirtuin 3 (SIRT3) is an important regulator of reactive oxygen species (ROS) production. However, the effect of SIRT3 on IHC synapses remains elusive. In this study, we treated cochlear basilar membrane (CBM) with hydrogen peroxide (H₂O₂) to establish an oxidative stress model in vitro. The H₂O₂-induced CBM exhibited decreased the number of IHC synapses with low levels of ATP and mitochondrial membrane potential. Additionally, H₂O₂-incuded CBM showed markedly reduced levels of forkhead box protein O 3a (FOXO3a), superoxide dismutase 2 (SOD2), and isocitrate dehydrogenase 2 (IDH2), thereby increasing ROS generation. SIRT3 overexpression via administrating nicotinamide riboside in the H₂O₂-induced CBM protected IHC synapses against oxidative stress and inhibited hair cell apoptosis. We further demonstrated that SIRT3 overexpression led to upregulation of IDH2, and hypoacetylation of several proteins, such as FOXO3a and SOD2, which in turn reduced the levels of ROS and improved mitochondrial function. Collectively, these findings reveal that SIRT3 may be a potential therapeutic approach for damaged IHC synapses induced by oxidative stress.

Advancements in prevention and intervention of sensorineural hearing loss

The inner ear is a complex and difficult organ to study, and sensorineural hearing loss (SNHL) is a multifactorial sensorineural disorder with characteristics of impaired speech discrimination, recognition, sound detection, and localization. Till now, SNHL is recognized as an incurable disease because the potential mechanisms underlying SNHL have not been elucidated. The risk of developing SNHL is no longer viewed as primarily due to environmental factors. Instead, SNHL seems to result from a complicated interplay of genetic and environmental factors affecting numerous fundamental cellular processes. The complexity of SNHL is presented as an inability to make an early diagnosis at the earliest stages of the disease and difficulties in the management of symptoms during the process. To date, there are no treatments that slow the neurodegenerative process. In this article, we review the recent advances about SHNL and discuss the complexities and challenges of prevention and intervention of SNHL.