Silencing Nrf2 attenuates chronic suppurative otitis media by inhibiting pro-inflammatory cytokine secretion through up-regulating TLR4

Icariin ameliorates the cuprizone-induced demyelination associated with antioxidation and anti-inflammation

The treatment of immunomodulation in multiple sclerosis (MS) can alleviate the severity and relapses. However, it cannot improve the neurological disability of patients due to a lack of myelin protection and regeneration. Therefore, remyelinating therapies may be one of the feasible strategies that can prevent axonal degeneration and restore neurological disability. Natural product icariin (ICA) is a flavonol compound extracted from epimedium flavonoids, which has neuroprotective effects in several models of neurological diseases. Here, we attempt to explore whether ICA has the potential to treat demyelination and its possible mechanisms of action using lipopolysaccharide-treated BV2 microglia, primary microglia, bone marrow-derived macrophages, and cuprizone-induced demyelination model. The indicators of oxidative stress and inflammatory response were evaluated using commercial kits. The results showed that ICA significantly reduced the levels of oxidative intermediates nitric oxide, hydrogen peroxide, malondialdehyde, and inflammatory cytokines TNF-α, IL-1β, and increased the levels of antioxidants superoxide dismutase, catalase, glutathione peroxidase, and anti-inflammatory cytokines IL-10 and TGF-β in vitro cell experiments. In vivo demyelination model, ICA significantly alleviated the behavioral abnormalities and enhanced the integrated optical density/mm2 of Black Gold II and myelin basic protein myelin staining, accompanied by the inhibition of oxidative stress/inflammatory response. Immunohistochemical staining showed that ICA significantly induced the expression of nuclear factor erythroid derived 2/heme oxygenase-1 (Nrf2/HO-1) and inhibited the expression of toll-like receptor 4/ nuclear factor kappa B (TLR4/NF-κB), which are two key signaling pathways in antioxidant and anti-inflammatory processes. Our results strongly suggest that ICA may be used as a potential agent to treat demyelination via regulating Nrf2/HO-1-mediated antioxidative stress and TLR4/NF-κB-mediated inflammatory responses.

The expression of Nrf2 and TLRs in ear effusion in children with different types of otitis media and their relationship with inflammatory factors

OBJECTIVE

This study aimed to analyze the differences in the expression of Toll-like receptors (TLRs) and nuclear factor erythroid 2-related factor 2 (Nrf2) in ear effusion in children with different types of otitis media (OM), to elaborate the relationship between the expression of TLRs and Nrf2 in ear effusion and the pathogenesis of OM, and to explore the relationship between the two indicators and pro-inflammatory cytokines in children with OM, thereby laying a scientific foundation for revealing the underlying molecular mechanisms of the progression of different types of OM.

METHODS

A total of 73 children with OM who were treated in our hospital from March 2019 to July 2021 were selected as the study subjects. By using the cross-sectional investigation method, participants were divided into three groups according to the different pathological types, including the secretory OM group (30 cases), the chronic suppurative OM group (27 cases), and the cystic lesional OM group (16 cases). The levels of Nrf2, TLR2, TLR4 and proinflammatory cytokines [interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), transforming growth factor-β 1(TGF-β1), procalcitonin (PCT) and interleukin-1β (IL-1β)] were detected in ear effusion of children with different types of OM. Linear regression was used to analyze the correlation between the Nrf2, TLR2 and TLR4 expression levels and pro-inflammatory cytokines in ear effusion.

RESULTS

The expression levels of TNF-α and PCT in the ear effusion of the children under 3 years old were significantly higher than that of the children between 3 and 5 years old and that of the children between 6 and 8 years old (all P < 0.001). The mRNA levels of Nrf2, TLR2 and TLR4 in the ear effusion of the children from the chronic suppurative OM group were higher than these from the secretory OM group (P < 0.001, P = 0.008 and P = 0.021). The mRNA levels of Nrf2, TLR2, and TLR4 in the ear effusion of the children from the cystic lesional OM group were higher than those from the chronic suppurative OM group (P < 0.001, P = 0.029 and P = 0.018). A prominent increase in the concentrations of IFN-γ, TNF-α, TGF-β1, PCT and IL-1β was found in the ear effusion of children from the chronic suppurative OM group compared to these from the secretory OM group (P = 0.021, P = 0.044, P = 0.048, P = 0.004 and P = 0.001). The concentrations of IFN-γ, TNF-α, TGF-β1, PCT and IL-1β in the ear effusion of the children from the cystic lesional OM group were markedly increased as compared with these from the chronic suppurative OM group (P < 0.001, P = 0.004, P = 0.003, P < 0.001 and P < 0.001). Nrf2, TLR2 and TLR4 were taken as independent variables, and inflammatory indexes, including IFN-γ, TNF-α, TGF-β1, PCT and IL-1β were used as dependent variables for the linear regression analysis. The results showed that Nrf2, TLR2 and TLR4 were positively correlated with the secretion levels of pro-inflammatory cytokines after adjusting for age, sex, course and the OM classification (all P < 0.05).

CONCLUSION

The expressions of Nrf2, TLR2 and TLR4 in the ear effusion of children with different types of OM gradually increased with the severity of the disease, these were significantly positively correlated with the pro-inflammatory cytokines of the children. Nrf2/TLR signaling pathway maintained chronic inflammation in OM, induced damage of middle ear tissue, and promoted the transition from acute OM to chronic OM.

Otitis media: Interactions between host and environment, immune and inflammatory responses

OBJECTIVE

To review and highlight progress in otitis media (OM) research in the areas of immunology, inflammation, environmental influences and host-pathogen responses from 2019 to 2023. Opportunities for innovative future research were also identified.

DATA SOURCES

PubMed database of the National Library of Medicine.

REVIEW METHODS

Key topics were assigned to each panel member for detailed review. Search of the literature was from June 2019 until February 2023. Draft reviews were collated, circulated, and discussed among panel members at the 22nd International Symposium on Recent Advances in Otitis Media in June 2023. The final manuscript was prepared and approved by all the panel members.

CONCLUSIONS

Important advances were identified in: environmental influences that enhance OM susceptibility; polymicrobial middle ear (ME) infections; the role of adaptive immunity defects in otitis-proneness; additional genes linked to OM; leukocyte contributions to OM pathogenesis and recovery; and novel interventions in OM based on host responses to infection. Innovative areas of research included: identification of novel bacterial genes and pathways important for OM persistence, bacterial adaptations and evolution that enhance chronicity; animal and human ME gene expression, including at the single-cell level; and Sars-CoV-2 infection of the ME and Eustachian tube.

Transcription Factor NRF2 in Shaping Myeloid Cell Differentiation and Function

NFE2-related factor 2 (NRF2) is a master transcription factor (TF) that coordinates key cellular homeostatic processes including antioxidative responses, autophagy, proteostasis, and metabolism. The emerging evidence underscores its significant role in modulating inflammatory and immune processes. This chapter delves into the role of NRF2 in myeloid cell differentiation and function and its implication in myeloid cell-driven diseases. In macrophages, NRF2 modulates cytokine production, phagocytosis, pathogen clearance, and metabolic adaptations. In dendritic cells (DCs), it affects maturation, cytokine production, and antigen presentation capabilities, while in neutrophils, NRF2 is involved in activation, migration, cytokine production, and NETosis. The discussion extends to how NRF2's regulatory actions pertain to a wide array of diseases, such as sepsis, various infectious diseases, cancer, wound healing, atherosclerosis, hemolytic conditions, pulmonary disorders, hemorrhagic events, and autoimmune diseases. The activation of NRF2 typically reduces inflammation, thereby modifying disease outcomes. This highlights the therapeutic potential of NRF2 modulation in treating myeloid cell-driven pathologies.

Nrf2 orchestrates transition from acute to chronic otitis media through inflammatory macrophages

Introduction

Acute and chronic otitis media (AOM and COM) are common middle ear infections that can lead to hearing loss and other complications. Recent research has shown that both macrophages and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway are involved in the immune response to and the resolution of otitis media. However, the specific effects of Nrf2 on macrophages in the transition of AOM to COM are not well understood, and a practical approach to prevent this transition by targeting Nrf2/macrophages has not been established.

Methods

In an AOM mouse model using lipopolysaccharide (LPS) injection into the middle ear, middle ear effusion (OME)-macrophages were isolated and analyzed for Nrf2 expression. M2-like polarization of macrophages was induced by Nrf2 activation and its effects on inflammatory resolution were studied by examining inflammatory neutrophils and macrophages, proinflammatory cytokines, and oxidative levels. The survival of human middle ear epithelial cells (HMMECs) co-cultured with Nrf2-modified macrophages was also evaluated. Furthermore, restoration of Nrf2 in macrophages with adeno-associated virus (AAV) vectors was performed to determine the effect on the transition of AOM to COM in experimental mice.

Results

Reduced Nrf2 in OME-macrophages during the recovery phase was associated with uncured AOM or its development into COM, demonstrated by persistent increases in inflammatory neutrophils and macrophages, proinflammatory cytokines, and oxidative levels. Nrf2 activation induced M2-like polarization of macrophages, which improved the survival of co-cultured HMMECs treated with LPS in vitro. Restoration of Nrf2 in OME-derived low-Nrf2-expressing macrophages with AAV vectors significantly inhibited the transition of AOM to COM in experimental mice.

Discussion

Nrf2 in macrophages plays a critical role in the immune response to and resolution of otitis media Restoration of Nrf2 expression in OME-macrophages could be a promising therapeutic approach to prevent the development of COM in AOM patients.

Regulation of innate immunity by Nrf2

The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) has been mainly investigated as a regulator of redox homeostasis. However, research over the past years has implicated Nrf2 as an important regulator of innate immunity. Here, we discuss the role of Nrf2 in the innate immune response, highlighting the interaction between Nrf2 and major components of the innate immune system. Indeed, Nrf2 has been shown to widely control the immune response by interacting directly or indirectly with important innate immune components, including the toll-like receptors-Nuclear factor kappa B (NF-kB) pathway, inflammasome signaling, and the type-I interferon response. This indicates an essential role for Nrf2 in diseases related to microbial infections, inflammation, and cancer. Yet, further studies are required to determine the exact mechanism underpinning the interactions between Nrf2 and innate immune players in order to allow a better understanding of these diseases and leverage new therapeutic strategies.

Immunomodulation as a Protective Strategy in Chronic Otitis Media

Introduction

Major features of the pathogenesis in otitis media, the most common disease in childhood, include hyperplasia of the middle ear mucosa and infiltration by leukocytes, both of which typically resolve upon bacterial clearance via apoptosis. Activation of innate immune receptors during the inflammatory process leads to the activation of intracellular transcription factors (such as NF-κB, AP-1), which regulate both the inflammatory response and tissue growth. We investigated these leading signaling pathways in otitis media using mouse models, human samples, and human middle ear epithelial cell (HMEEC) lines for therapeutic immunomodulation.

Methods

A stable otitis media model in wild-type mice and immunodeficient KO-mice, as well as human tissue samples from chronic otitis media, skin from the external auditory canal and middle ear mucosa removed from patients undergoing ear surgery, were studied. Gene and protein expression of innate immune signaling molecules were evaluated using microarray, qPCR and IHC. In situ apoptosis detection determined the apoptotic rate. The influence of bacterial infection on immunomodulating molecules (TNFα, MDP, Tri-DAP, SB203580, Cycloheximide) in HMEEC was evaluated. HMEEC cells were examined after bacterial stimulation/inhibition for gene expression and cellular growth.

Results

Persistent mucosal hyperplasia of the middle ear mucosa in chronic otitis media resulted from gene and protein expression of inflammatory and apoptotic genes, including NODs, TNFα, Casp3 and cleaved Casp3. In clinical chronic middle ear samples, these molecules were modulated after a specific stimulation. They also induced a hyposensitive response after bacterial/NOD-/TLR-pathway double stimulation of HMEEC cells in vitro. Hence, they might be suitable targets for immunological therapeutic approaches.

Conclusion

Uncontrolled middle ear mucosal hyperplasia is triggered by TLRs/NLRs immunoreceptor activation of downstream inflammatory and apoptotic molecules.

Long non-coding RNA NEAT1 contributes to lipopolysaccharide-induced inflammation and apoptosis of human middle ear epithelial cells via regulating the miR-301b-3p/TLR4 axis

Acute otitis media (AOM) is a common infectious disease in children that is accompanied by signs and symptoms of middle ear inflammation and infection. Previous studies have shown that the long non-coding (lnc)RNA nuclear-enriched abundant transcript 1(NEAT1) participates in various inflammatory conditions and plays an important regulatory role. The focus of the present study was the biological function of NEAT1 and underlying molecular mechanism in lipopolysaccharide (LPS)-induced human middle ear epithelial cells (HMEECs). The expression of NEAT1, miR-301b-3p and toll-like receptor 4 (TLR4) protein were determined by reverse transcription-quantitative PCR and western blot assays, respectively. Dual-luciferase reporter assay was performed to investigate the combination of miR-301b-3p and NEAT1 or TLR4. In addition, cell viability, apoptosis and the levels of pro-inflammatory factors (IL-1β, TNF-α and IL-6) were measured by Cell Counting Kit-8 assay, flow cytometry and ELISA, respectively. Cell viability was significantly decreased, whereas apoptosis and inflammation were increased in LPS-stimulated HMEECs. Functional analyses demonstrated that NEAT1 was upregulated following LPS treatment, whereas knockdown of NEAT1 significantly increased cell viability and alleviated apoptosis and inflammation. Mechanistically, NEAT1 directly bound to and negatively regulated miR-301b-3p expression, whereas miR-301b-3p inhibitors abolished the inhibitory effect of NEAT1 knockdown on cell apoptosis and inflammation. As a target of miR-301b-3p, TLR4 was regulated by NEAT1 and miR-301b-3p. TLR4 overexpression alleviated NEAT1 silencing-induced inflammatory suppression. Rescue experiments demonstrated that NEAT1 promoted TLR4 expression by inhibiting miR-301b-3p. Collectively, the results of the present study suggested that NEAT1 may attenuate LPS-induced inflammation and apoptosis in HMEECs by modulating the miR-301b-3p/TLR4 axis, and may provide a new therapeutic target for the clinical treatment of AOM.

Toll-Like Receptors: Expression and Roles in Otitis Media

Otitis media is mainly caused by upper respiratory tract infection and eustachian tube dysfunction. If external upper respiratory tract infection is not detected early in the middle ear, or an appropriate immune response does not occur, otitis media can become a chronic state or complications may occur. Therefore, given the important role of Toll-like receptors (TLRs) in the early response to external antigens, we surveyed the role of TLRs in otitis media. To summarize the role of TLR in otitis media, we reviewed articles on the expression of TLRs in acute otitis media (AOM), otitis media with effusion (OME), chronic otitis media (COM) with cholesteatoma, and COM without cholesteatoma. Many studies showed that TLRs 1–10 are expressed in AOM, OME, COM with cholesteatoma, and COM without cholesteatoma. TLR expression in the normal middle ear mucosa is absent or weak, but is increased in inflammatory fluid of AOM, effusion of OME, and granulation tissue and cholesteatoma of COM. In addition, TLRs show increased or decreased expression depending on the presence or absence of bacteria, recurrence of disease, tissue type, and repeated surgery. In conclusion, expression of TLRs is associated with otitis media. Inappropriate TLR expression, or delayed or absent induction, are associated with the occurrence, recurrence, chronicization, and complications of otitis media. Therefore, TLRs are very important in otitis media and closely related to its etiology.

Treatment with a neutrophil elastase inhibitor and ofloxacin reduces P. aeruginosa burden in a mouse model of chronic suppurative otitis media

Chronic suppurative otitis media (CSOM) is a widespread, debilitating problem with poorly understood immunology. Here, we assess the host response to middle ear infection over the course of a month post-infection in a mouse model of CSOM and in human subjects with the disease. Using multiparameter flow cytometry and a binomial generalized linear machine learning model, we identified Ly6G, a surface marker of mature neutrophils, as the most informative factor of host response driving disease in the CSOM mouse model. Consistent with this, neutrophils were the most abundant cell type in infected mice and Ly6G expression tracked with the course of infection. Moreover, neutrophil-specific immunomodulatory treatment using the neutrophil elastase inhibitor GW 311616A significantly reduces bacterial burden relative to ofloxacin-only treated animals in this model. The levels of dsDNA in middle ear effusion samples are elevated in both humans and mice with CSOM and decreased during treatment, suggesting that dsDNA may serve as a molecular biomarker of treatment response. Together these data strongly implicate neutrophils in the ineffective immune response to P. aeruginosa infection in CSOM and suggest that immunomodulatory strategies may benefit drug-tolerant infections for chronic biofilm-mediated disease.

The effect of probiotics on lipid profile & anthropometric indices in diabetic nephropathy; a systematic review and meta-analysis of clinical trials

Purpose

Recent trials have demonstrated the possible improvements in lipid profile & anthropometric indices after probiotics supplementation. We aimed to reanalyze the related literature to explore the efficacy of probiotics in Diabetic Nephropathy (DN) patients.

Methods

PubMed, Embase, Web of science, google scholar, Scopus, and Cochrane Library databases were systematically searched to find the related data on diabetic nephropathy population. All Randomized controlled trials (RCTs) that investigated the effect of probiotics on serum lipid markers (High-Density Lipoprotein [HDL], Triglyceride, Total Cholesterol, TC-to-HDL ratio, Low-Density Lipoprotein, Very Low-Density Lipoprotein) and anthropometric indices (Body Weight, Body Mass Index, waist-to-hip ratio) were included (PROSPERO No.CRD42020186189). Meta-analysis was performed using the random-effect model.

Results

Of 156 studies, seven were eligible for inclusion. Lipid biomarkers had a marginal reduction (except for HDL; WMD = 2.59 mg/dl; 95% CI = -0.28, 5.47; P = 0.077); whereas anthropometric indices increased in a non-significant manner.

Conclusion

There is limited evidence to support the efficacy of probiotics for the modulation of lipid profile and anthropometric indices in DN patients.

Graphical abstract

Probiotics did not beneficial effect on lipid profile & anthropometric markers in Diabetic Nephropathy; anyway, more trials should be conducted.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-021-00765-8.