Daphnetin inhibits proliferation and inflammatory response in human HaCaT keratinocytes and ameliorates imiquimod-induced psoriasis-like skin lesion in mice

Abstract Background Psoriasis is a common chronic inflammatory skin disease. Keratinocytes hyperproliferation and excessive inflammatory response contribute to psoriasis pathogenesis. The agents able to attenuate keratinocytes hyperproliferation and excessive inflammatory response are considered to be potentially useful for psoriasis treatment. Daphnetin exhibits broad bioactivities including anti-proliferation and anti-inflammatory. This study aims to evaluate the anti-psoriatic potential of daphnetin in vitro and in vivo, and explore underlying mechanisms. Methods HaCaT keratinocytes was stimulated with the mixture of IL-17A, IL-22, oncostatin M, IL-1α, and TNF-α (M5) to establish psoriatic keratinocyte model in vitro. Cell viability was measured using Cell Counting Kit-8 (CCK-8). Quantitative Real-Time PCR (qRT-PCR) was performed to measure the mRNA levels of hyperproliferative marker gene keratin 6 (KRT6), differentiation marker gene keratin 1 (KRT1) and inflammatory factors IL-1β, IL-6, IL-8, TNF-α, IL-23A and MCP-1. Western blotting was used to detect the protein levels of p65 and p-p65. Indirect immunofluorescence assay (IFA) was carried out to detect p65 nuclear translocation. Imiquimod (IMQ) was used to construct psoriasis-like mouse model. Psoriasis severity (erythema, scaling) was scored based on Psoriasis Area Severity Index (PASI). Hematoxylin and eosin (H&E) staining was performed to examine histological change in skin lesion. The expression of inflammatory factors including IL-6, TNF-α, IL-23A and IL-17A in skin lesion was measured by qRT-PCR. Results Daphnetin attenuated M5-induced hyperproliferation in HaCaT keratinocytes. M5 stimulation significantly upregulated mRNA levels of IL-1β, IL-6, IL-8, TNF-α, IL-23A and MCP-1. However, daphnetin treatment partially attenuated the upregulation of those inflammatory cytokines. Daphnetin was found to be able to inhibit p65 phosphorylation and nuclear translocation in HaCaT keratinocytes. In addition, daphnetin significantly ameliorate the severity of skin lesion (erythema, scaling and epidermal thickness, inflammatory cell infiltration) in IMQ-induced psoriasis-like mouse model. Daphnetin treatment attenuated IMQ-induced upregulation of inflammatory cytokines including IL-6, IL-23A and IL-17A in skin lesion of mice. Conclusions Daphnetin was able to attenuate proliferation and inflammatory response induced by M5 in HaCaT keratinocytes through suppression of NF-κB signaling pathway. Daphnetin could ameliorate the severity of skin lesion and improve inflammation status in IMQ-induced psoriasis-like mouse model. Daphnetin could be an attractive candidate for future development as an anti-psoriatic agent.

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Nerolidol Mitigates Colonic Inflammation: An Experimental Study Using both In Vivo and In Vitro Models

Nutrients ◽

10.3390/nu12072032 ◽

2020 ◽

Vol 12 (7) ◽

pp. 2032

Author(s):

Vishnu Raj ◽

Balaji Venkataraman ◽

Saeeda Almarzooqi ◽

Sanjana Chandran ◽

Shreesh K. Ojha ◽

...

Keyword(s):

Nuclear Translocation ◽

In Vitro Models ◽

Mrna Levels ◽

Colonic Inflammation ◽

Tnf Α ◽

Cox 2 ◽

Anti Inflammatory ◽

Ht 29

Nerolidol (NED) is a naturally occurring sesquiterpene alcohol present in various plants with potent anti-inflammatory effects. In the current study, we investigated NED as a putative anti-inflammatory compound in an experimental model of colonic inflammation. C57BL/6J male black mice (C57BL/6J) were administered 3% dextran sodium sulfate (DSS) in drinking water for 7 days to induce colitis. Six groups received either vehicle alone or DSS alone or DSS with oral NED (50, 100, and 150 mg/kg body weight/day by oral gavage) or DSS with sulfasalazine. Disease activity index (DAI), colonic histology, and biochemical parameters were measured. TNF-α-treated HT-29 cells were used as in vitro model of colonic inflammation to study NED (25 µM and 50 µM). NED significantly decreased the DAI and reduced the inflammation-associated changes in colon length as well as macroscopic and microscopic architecture of the colon. Changes in tissue Myeloperoxidase (MPO) concentrations, neutrophil and macrophage mRNA expression (CXCL2 and CCL2), and proinflammatory cytokine content (IL-1β, IL-6, and TNF-α) both at the protein and mRNA level were significantly reduced by NED. The increase in content of the proinflammatory enzymes, COX-2 and iNOS induced by DSS were also significantly inhibited by NED along with tissue nitrate levels. NED promoted Nrf2 nuclear translocation dose dependently. NED significantly increased antioxidant enzymes activity (Superoxide dismutase (SOD) and Catalase (CAT)), Hemeoxygenase-1 (HO-1), and SOD3 mRNA levels. NED treatment in TNF-α-challenged HT-29 cells significantly decreased proinflammatory chemokines (CXCL1, IL-8, CCL2) and COX-2 mRNA levels. NED supplementation attenuates colon inflammation through its potent antioxidant and anti-inflammatory activity both in in vivo and in vitro models of colonic inflammation.

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IL-33/ST2 axis promotes the inflammatory response of nasal mucosal epithelial cells through inducing the ERK1/2 pathway

Innate Immunity ◽

10.1177/1753425920918911 ◽

2020 ◽

Vol 26 (6) ◽

pp. 505-513

Author(s):

Yun-Qiu Li ◽

Yu Zhong ◽

Xu-Ping Xiao ◽

Dan-Dan Li ◽

Zheng Zhou ◽

...

Keyword(s):

Epithelial Cells ◽

Ar Model ◽

Inflammatory Factors ◽

Mrna Levels ◽

Model Group ◽

Protein Levels ◽

Tnf Α ◽

Der P1 ◽

The Relationship

Allergic rhinitis (AR) is a nasal mucosal inflammatory disease mediated by environmental allergens. At present, the relationship between the IL-33/ST2 axis, ERK1/2 pathway and AR progression needs further exploration. In our study, an AR model was constructed in vitro by treating HNEpC cells with Der p1. qRT-PCR was applied to assess the mRNA levels of IL-33, ST2, TNF-α, IL-6, and IL-8. Western blotting was used to measure the protein levels of IL-33, ST2, and the downstream proteins p-ERK1/2, ERK1/2, p-RSK, and RSK. IL-6, IL-8, IL-33, and TNF-α protein levels in cell supernatants were evaluated by ELISA. Flow cytometry was performed to check cell apoptosis of HNEpC in the presence or absence of Der p1. Our results indicate that the relative levels of IL-33, ST2, TNF-α, IL-6, and IL-8 were increased significantly in the AR model group. The above effects were notably reversed after transfection with shIL-33 or shST2. IL-33 stimulation further resulted in the increase in both ST2 and inflammation-associated cytokines, and these effects were restored after shST2 treatment. Also, the levels of inflammatory factors induced by IL-33 stimulation or ST2 overexpression were reversed after applying an ERK1/2 pathway blocker. In conclusion, IL-33/ST2 mediated inflammation of nasal mucosal epithelial cells by inducing the ERK1/2 pathway.

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Protective Effect of Uric Acid on ox-LDL-Induced HUVECs Injury via Keap1-Nrf2-ARE Pathway

Journal of Immunology Research ◽

10.1155/2021/5151168 ◽

2021 ◽

Vol 2021 ◽

pp. 1-19

Author(s):

Yajuan Lin ◽

Yunpeng Xie ◽

Zhujing Hao ◽

Hailian Bi ◽

Yang Liu ◽

...

Keyword(s):

Oxidative Stress ◽

Uric Acid ◽

Nuclear Translocation ◽

Density Lipoprotein ◽

Endothelial Damage ◽

The Body ◽

Inflammatory Factors ◽

Cell Phenotype ◽

Mrna Levels

Uric acid is an effective antioxidant. Oxidized low-density lipoprotein (ox-LDL) is derived from circulating LDL and promotes atherosclerosis. The Keap1-Nrf2-ARE pathway is a key body pathway involved in protection against internal and external oxidative damages. The role of uric acid on vascular endothelial function damaged by ox-LDL, and its effect on the Keap1-Nrf2-ARE pathway has not been fully explored. HUVECs were treated with different concentrations of uric acid and ox-LDL to explore the effect of uric acid in vitro. Cell phenotype was determined by cytometry and Western blot. Nuclear translocation of Nrf2 was determined by immunofluorescence. Coimmunoprecipitation was used to determine the level of Nrf2 ubiquitination. A microfluidic device was used to mimic the vascular environment in the body, and the level of mRNA levels of inflammatory factors was determined by RT-PCR. The findings of this study show that suitable uric acid can significantly reduce endothelial damage caused by ox-LDL, such as oxidative stress, inflammation, and increased adhesion. In addition, uric acid reduced Nrf2 ubiquitination and increased nuclear translocation of Nrf2 protein, thus activating the Keap1-Nrf2-ARE pathway and playing a protective role. Interestingly, the effects of UA were significantly inhibited by administration of Brusatol, an inhibitor of Nrf2. In summary, suitable concentrations of uric acid can alleviate the oxidative stress level of endothelial cells through Nrf2 nuclear translocation and further protect cells from damage.

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Aberrant MUC1 accumulation in salivary glands of Sjögren’s syndrome patients is reversed by TUDCA in vitro

Rheumatology ◽

10.1093/rheumatology/kez316 ◽

2019 ◽

Vol 59 (4) ◽

pp. 742-753 ◽

Cited By ~ 3

Author(s):

Isabel Castro ◽

Nicolás Albornoz ◽

Sergio Aguilera ◽

María-José Barrera ◽

Sergio González ◽

...

Keyword(s):

Er Stress ◽

Salivary Glands ◽

Nuclear Translocation ◽

Secretory Process ◽

Mrna Levels ◽

Mucin 1 ◽

Tnf Α ◽

Mucin Expression ◽

Ifn Γ

Abstract Objectives Xerostomia in SS patients has been associated with low quality and quantity of salivary mucins, which are fundamental for the hydration and protection of the oral mucosa. The aim of this study was to evaluate if cytokines induce aberrant mucin expression and whether tauroursodeoxycholic acid (TUDCA) is able to counteract such an anomaly. Methods Labial salivary glands from 16 SS patients and 15 control subjects, as well as 3D acini or human submandibular gland cells stimulated with TNF-α or IFN-γ and co-incubated with TUDCA, were analysed. mRNA and protein levels of Mucin 1 (MUC1) and MUC7 were determined by RT-qPCR and western blot, respectively. Co-immunoprecipitation and immunofluorescence assays for mucins and GRP78 [an endoplasmic reticulum (ER)-resident protein] were also performed. mRNA levels of RelA/p65 (nuclear factor-κB subunit), TNF-α, IL-1β, IL-6, SEL1L and EDEM1 were determined by RT-qPCR, and RelA/p65 localization was evaluated by immunofluorescence. Results MUC1 is overexpressed and accumulated in the ER of labial salivary gland from SS patients, while MUC7 accumulates throughout the cytoplasm of acinar cells; however, MUC1, but not MUC7, co-precipitated with GRP78. TUDCA diminished the overexpression and aberrant accumulation of MUC1 induced by TNF-α and IFN-γ, as well as the nuclear translocation of RelA/p65, together with the expression of inflammatory and ER stress markers in 3D acini. Conclusion Chronic inflammation alters the secretory process of MUC1, inducing ER stress and affecting the quality of saliva in SS patients. TUDCA showed anti-inflammatory properties decreasing aberrant MUC1 accumulation. Further studies are necessary to evaluate the potential therapeutic effect of TUDCA in restoring glandular homeostasis in SS patients.

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Procyanidin A1 Alleviates Inflammatory Response induced by LPS through NF-κB, MAPK, and Nrf2/HO-1 Pathways in RAW264.7 cells

Scientific Reports ◽

10.1038/s41598-019-51614-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 10

Author(s):

Shan Han ◽

Hongwei Gao ◽

Shaoru Chen ◽

Qinqin Wang ◽

Xinxing Li ◽

...

Keyword(s):

Inflammatory Response ◽

Molecular Mechanisms ◽

Nuclear Translocation ◽

Inflammatory Diseases ◽

Raw264.7 Cells ◽

Tnf Α ◽

Intracellular Ros ◽

Anti Inflammatory ◽

Cellular Thermal Shift Assay

Abstract Inflammation is a complex physiological process that poses a serious threat to people’s health. However, the potential molecular mechanisms of inflammation are still not clear. Moreover, there is lack of effective anti-inflammatory drugs that meet the clinical requirement. Procyanidin A1 (PCA1) is a monomer component isolated from Procyanidin and shows various pharmacological activities. This study further demonstrated the regulatory role of PCA1 on lipopolysaccharide (LPS)-stimulated inflammatory response and oxidative stress in RAW264.7 cells. Our data showed that PCA1 dramatically attenuated the production of pro-inflammatory cytokines such as NO, iNOS, IL-6, and TNF-α in RAW264.7 cells administrated with LPS. PCA1 blocked IκB-α degradation, inhibited IKKα/β and IκBα phosphorylation, and suppressed nuclear translocation of p65 in RAW264.7 cells induced by LPS. PCA1 also suppressed the phosphorylation of JNK1/2, p38, and ERK1/2 in LPS-stimulated RAW264.7 cells. In addition, PCA1 increased the expression of HO-1, reduced the expression of Keap1, and promoted Nrf2 into the nuclear in LPS-stimulated RAW264.7 cells. Cellular thermal shift assay indicated that PCA1 bond to TLR4. Meanwhile, PCA1 inhibited the production of intracellular ROS and alleviated the depletion of mitochondrial membrane potential in vitro. Collectively, our data indicated that PCA1 exhibited a significant anti-inflammatory effect, suggesting that it is a potential agent for the treatment of inflammatory diseases.

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Alantolactone Suppresses Proliferation and the Inflammatory Response in Human HaCaT Keratinocytes and Ameliorates Imiquimod-Induced Skin Lesions in a Psoriasis-Like Mouse Model

Life ◽

10.3390/life11070616 ◽

2021 ◽

Vol 11 (7) ◽

pp. 616

Author(s):

Wen-Ho Chuo ◽

Yu-Tang Tung ◽

Chao-Liang Wu ◽

Nicole Bracci ◽

Yu-Kang Chang ◽

...

Keyword(s):

Mouse Model ◽

Inflammatory Cytokines ◽

Skin Lesions ◽

Psoriatic Skin ◽

World Population ◽

Mrna Levels ◽

Hacat Keratinocytes ◽

Stat3 Phosphorylation ◽

New Findings ◽

Tnf Α

Psoriasis is an immune-mediated inflammatory disease that affects 2% to 3% of the world population. Alantolactone, a sesquiterpene lactone, was isolated from Inula helenium and Radix inulae and has several biological effects, including antifungal, anthelmintic, antimicrobial, anti-inflammatory, antitrypanosomal, and anticancer properties. This study aimed to evaluate the antipsoriatic potential of alantolactone in vitro and in vivo and to explore its underlying mechanisms. These results showed that alantolactone significantly attenuated IL-17A, IL-22, oncostatin M, IL-1α, and TNF-α (M5) cytokine-induced hyperproliferation in HaCaT keratinocytes. Moreover, M5 cytokines significantly upregulated the mRNA levels of TNF-α, IL-6, IL-1β, and IL-8. However, alantolactone attenuated the upregulation of these inflammatory cytokines. In addition, alantolactone was found to inhibit STAT3 phosphorylation and NF-κB p65 nuclear translocation in HaCaT keratinocytes. Furthermore, alantolactone treatment in mice significantly alleviated the severity of skin lesions (erythema, scaling and epidermal thickness, and inflammatory cell infiltration) and decreased the mRNA expression of inflammatory cytokines (e.g., TNF-α, IL-6, IL-1β, IL-8, IL-17A, and IL-23) in an IMQ-induced-like mouse model. Therefore, our new findings revealed that alantolactone alleviates psoriatic skin lesions by inhibiting inflammation, making it an attractive candidate for future development as an antipsoriatic agent.

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Comparative gene responses to collected ambient particles in vitro: endothelial responses

Physiological Genomics ◽

10.1152/physiolgenomics.00051.2011 ◽

2011 ◽

Vol 43 (15) ◽

pp. 917-929 ◽

Cited By ~ 29

Author(s):

Hnin H. Aung ◽

Michael W. Lame ◽

Kishorchandra Gohil ◽

Guochun He ◽

Michael S. Denison ◽

...

Keyword(s):

Particulate Matter ◽

Inflammatory Response ◽

Nuclear Translocation ◽

Cardiovascular Effects ◽

Urban Setting ◽

Cellular Stress Response ◽

Luciferase Reporter ◽

Target Cells ◽

Mrna Levels

Epidemiologic studies associate exposure to ambient particulate matter (APM) with increased cardiovascular mortality. Since both pulmonary inflammation and systemic circulation of ultrafine particles are hypothesized as initiating cardiovascular effects, we examined responses of potential target cells in vitro. Human aortic endothelial cells (HAEC) were exposed to 10 μg/ml fine and ultrafine APM collected in an urban setting in summer 2006 or winter 2007 in the San Joaquin Valley, California. RNA isolated after 3 h was analyzed with high-density oligonucleotide arrays. Summer APM treatment affected genes involved in xenobiotic and oxidoreductase activity, transcription factors, and inflammatory responses in HAEC, while winter APM had a robust xenobiotic but lesser inflammatory response. Real-time polymerase chain reaction analysis confirmed that particulate matter (PM)-treated HAEC increased mRNA levels of xenobiotic response enzymes CYP1A1, ALDH1A3, and TIPARP and cellular stress response transcription factor ATF3. Inflammatory response genes included E-selectin, PTGS2, CXCL-2 (MIP-2α), and CCL-2 (MCP-1). Multiplex protein assays showed secretion of IL-6 and MCP-1 by HAEC. Since induction of CYP1A1 is mediated through the ligand-activated aryl hydrocarbon receptor (AhR), we demonstrated APM induced AhR nuclear translocation by immunofluorescence and Western blotting and activation of the AhR response element using a luciferase reporter construct. Inhibitor studies suggest differential influences of polycyclic aromatic hydrocarbon signaling, ROS-mediated responses and endotoxin alter stress and proinflammatory endothelial cell responses. Our findings demonstrate gene responses correlated with current concepts that systemic inflammation drives cardiovascular effects of particulate air pollution. We also demonstrate a unique pattern of gene responses related to xenobiotic metabolism in PM-exposed HAEC.

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DAP Inhibits the TNF-α-Induced Inflammatory Response by Modulating the MAPK Signaling Pathway in Synovial Cells

10.21203/rs.3.rs-394300/v1 ◽

2021 ◽

Author(s):

Jieying Wang ◽

Nanzhen Kuang ◽

Mao zheng ◽

Chan Dai ◽

Huimin Deng ◽

...

Keyword(s):

Inflammatory Response ◽

Signaling Pathway ◽

Nuclear Translocation ◽

Mapk Signaling ◽

Mapk Signaling Pathway ◽

Inflammatory Factors ◽

Control Group ◽

Synovial Cells ◽

Tnf Α ◽

Model Control

Abstract Daphnetin(DAP) is extracted from Daphne odora var. marginata and contains coumarin compounds, which have a good anti-inflammatory analgesic effect. In this study, we investigated whether daphnetin can reduce the TNF-α-induced inflammatory response by inhibiting the MAPK signaling pathway in the synovial cells of CIA rats. A model of synovial cells was constructed using CIA rats induced by TNF-α. The expression of inflammatory cytokines in the synovial cells of CIA rats was observed by real-time PCR and ELISA. The expression and nuclear translocation of MAPK signaling pathway proteins were detected by Western blot and immunofluorescence assays. The results show that the mRNA and protein levels of IL-6, TGF-β, MMP-3 and MMP-13 were significantly lower than those in the culture supernatant of the model control group. The synovial cells of CIA rats induced by TNF-α exhibited decreased expression of p-p38, p-ERK1/2 and p-JNK in the nucleus. In conclusion, daphnetin can affect the activation of the MAPK signaling pathway and reduce the expression of inflammatory factors by inhibiting the MAPK signaling pathway, which plays a role in anti-rheumatic inflammation.

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Bullatine a Exerted Anti-Inflammatory Effects by Inhibiting JNK/ROS/NF-κB Pathway and Attenuates Systemic Inflammatory Response in LPS-Challenged Mice

10.21203/rs.3.rs-710437/v1 ◽

2021 ◽

Author(s):

Shuhan Liu ◽

Meichen Yan ◽

Yajin Liao ◽

Yong Cheng

Keyword(s):

Inflammatory Response ◽

Inflammatory Cytokines ◽

Nuclear Translocation ◽

Ros Generation ◽

Mrna Levels ◽

Iκb Kinase ◽

Inflammatory Mechanism ◽

Anti Inflammatory

Abstract Background: The genus Aconitum has rich pharmacological characteristics. Aconiti brachypodi Radix (Xue-shang-yi-zhi-hao) is a dried root of aconitum, which is considered to be analgesic and anti-inflammatory in modern medical and pharmaceutical clinical studies. Bullatine A (BA), a major active ingredient of this plant, has been reported for its significant anti-analgesic effect in previous studies. However, the role of BA in inflammation is unknown. In the current study, we aimed to explore the effect of BA on lipopolysaccharide (LPS)-induced inflammatory response both in vitro and in vivo and its potential anti-inflammatory mechanism.Materials and Methods: The anti-inflammatory effect of BA was evaluated in two different types of LPS-induced macrophages, including BV-2 microglial cells and immortalized murine bone marrow-derived macrophages (iBMDMs), and in acute inflammation mouse models induced by LPS. Immunofluorescence, flow cytometry, quantitative RT-PCR, western blot and Hematoxylin-Eosin staining were used to determine the anti-inflammatory properties of BA.Results: The results showed that BA significantly reduced the mRNA levels of several pro-inflammatory cytokines induced by LPS both in BV-2 cells and iBMDMs. Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in response to LPS were also decreased by BA. Further investigations indicated BA significantly blocked the phosphorylation of IκB kinase, degradation of the inhibitor IκBa and the nuclear translocation of nuclear factor-κB (NF-κB) p65. BA also reduced c-Jun N-terminal kinases (JNK) phosphorylation and ROS generation in iBMDMs activated with LPS, but had no effect on other mitogen-activated protein kinases (MAPKs) family proteins such as extracellular signal-regulated kinase (ERK) or p38. Furthermore, BA treatment alleviate liver and lung tissue damage, reduce inflammatory cell infiltration, and inhibit the expression of inflammatory cytokines in LPS-challenged mice.Conclusions: This study illustrated that BA has obvious anti-inflammatory effects both in vitro and in vivo, and its underlying anti-inflammatory mechanism may be via inactivating JNK/ROS/NF-κB pathway. Therefore, BA may have a certain therapeutic potential for inflammatory-related diseases.

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NOD1/RIP2 signalling enhances the microglia-driven inflammatory response and undergoes crosstalk with inflammatory cytokines to exacerbate brain damage following intracerebral haemorrhage in mice

Journal of Neuroinflammation ◽

10.1186/s12974-020-02015-9 ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

Miao Wang ◽

Xinchun Ye ◽

Jinxia Hu ◽

Qiuchen Zhao ◽

Bingchen Lv ◽

...

Keyword(s):

Inflammatory Response ◽

Brain Damage ◽

Microglial Activation ◽

Inflammatory Factors ◽

Primary Microglia ◽

Tnf Α ◽

Factor Α ◽

Necrosis Factor

Abstract Background Secondary brain damage caused by the innate immune response and subsequent proinflammatory factor production is a major factor contributing to the high mortality of intracerebral haemorrhage (ICH). Nucleotide-binding oligomerization domain 1 (NOD1)/receptor-interacting protein 2 (RIP2) signalling has been reported to participate in the innate immune response and inflammatory response. Therefore, we investigated the role of NOD1/RIP2 signalling in mice with collagenase-induced ICH and in cultured primary microglia challenged with hemin. Methods Adult male C57BL/6 mice were subjected to collagenase for induction of ICH model in vivo. Cultured primary microglia and BV2 microglial cells (microglial cell line) challenged with hemin aimed to simulate the ICH model in vitro. We first defined the expression of NOD1 and RIP2 in vivo and in vitro using an ICH model by western blotting. The effect of NOD1/RIP2 signalling on ICH-induced brain injury volume, neurological deficits, brain oedema, and microglial activation were assessed following intraventricular injection of either ML130 (a NOD1 inhibitor) or GSK583 (a RIP2 inhibitor). In addition, levels of JNK/P38 MAPK, IκBα, and inflammatory factors, including tumour necrosis factor-α (TNF-α), interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS) expression, were analysed in ICH-challenged brain and hemin-exposed cultured primary microglia by western blotting. Finally, we investigated whether the inflammatory factors could undergo crosstalk with NOD1 and RIP2. Results The levels of NOD1 and its adaptor RIP2 were significantly elevated in the brains of mice in response to ICH and in cultured primary microglia, BV2 cells challenged with hemin. Administration of either a NOD1 or RIP2 inhibitor in mice with ICH prevented microglial activation and neuroinflammation, followed by alleviation of ICH-induced brain damage. Interestingly, the inflammatory factors interleukin (IL)-1β and tumour necrosis factor-α (TNF-α), which were enhanced by NOD1/RIP2 signalling, were found to contribute to the NOD1 and RIP2 upregulation in our study. Conclusion NOD1/RIP2 signalling played an important role in the regulation of the inflammatory response during ICH. In addition, a vicious feedback cycle was observed between NOD1/RIP2 and IL-1β/TNF-α, which could to some extent result in sustained brain damage during ICH. Hence, our study highlights NOD1/RIP2 signalling as a potential therapeutic target to protect the brain against secondary brain damage during ICH.

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