Glycyrrhizin regulates rat TMJOA progression by inhibiting the HMGB1-RAGE/TLR4-NF-κB/AKT pathway

DDIT3 aggravates TMJOA cartilage degradation via Nrf2/HO-1/NLRP3-mediated autophagy

OBJECTIVE

DNA damage-inducible transcript 3 (DDIT3), as a downstream transcription factor of endoplasmic reticulum stress, is reported to regulate chondrogenic differentiation under physiological and pathological state. However, the specific involvement of DDIT3 in the degradation of condylar cartilage of temporomandibular joint osteoarthritis (TMJOA) is unclarified.

DESIGN

The expression patterns of DDIT3 in condylar cartilage from monosodium iodoacetate-induced TMJOA mice were examined to uncover the potential role of DDIT3 in TMJOA. The Ddit3 knockout (Ddit3-/-) mice and their wildtype littermates (Ddit3+/+) were used to clarify the effect of DDIT3 on cartilage degradation. Primary condylar chondrocytes and ATDC5 cells were applied to explore the mechanisms of DDIT3 on autophagy and extracellular matrix (ECM) degradation in chondrocytes. The autophagy inhibitor chloroquine (CQ) was used to determine the effect of DDIT3-inhibited autophagy in vivo.

RESULTS

DDIT3 were highly expressed in condylar cartilage from TMJOA mice. Ddit3 knockout alleviated condylar cartilage degradation and subchondral bone loss, compared with their wildtype littermates. In vitro study demonstrated that DDIT3 exacerbated ECM degradation in chondrocytes induced by TNF-α through inhibiting autophagy. The intraperitoneal injection of CQ further confirmed that Ddit3 knockout alleviated cartilage degradation in TMJOA through activating autophagy in vivo.

CONCLUSIONS

Our findings identified the crucial role of DDIT3-inhibited autophagy in condylar cartilage degradation during the development of TMJOA.

Chrysin mitigated neuropathic pain and peripheral sensitization in knee osteoarthritis rats by repressing the RAGE/PI3K/AKT pathway regulated by HMGB1

BACKGROUND

Knee osteoarthritis (KOA) is a chronic progressive osteoarthropathy. Chrysin's anti-KOA action has been demonstrated, however more research is needed to understand how chrysin contributes to KOA.

METHODS

LPS/ATP-induced macrophages transfected with or without HMGB1 overexpression underwent 5 μg/mL chrysin. The cell viability and macrophage pyroptosis were examined by cell counting kit-8 and flow cytometer. In vivo experiments, rats were injected with 1 mg monosodium iodoacetate by the infrapatellar ligament of the bilateral knee joint to induce KOA. The histological damage was analyzed by Safranin O/Fast Green staining and hematoxylin and eosin staining. The PWT, PWL and inflammatory factors were analyzed via Von-Frey filaments, thermal radiometer and ELISA. Immunofluorescence assay examined the expressions of CGRP and iNOS. The levels of HMGB1/RAGE-, NLRP3-, PI3K/AKT- and neuronal ion channel-related markers were examined by qPCR and western blot.

RESULTS

Chrysin alleviated macrophage pyroptosis by inhibiting HMGB1 and the repression of chrysin on HMGB1/RAGE pathway and ion channel activation was reversed by overexpressed HMGB1. HMGB1 facilitated neuronal ion channel activation through the RAGE/PI3K/AKT pathway. Chrysin could improve the pathological injury of knee joints in KOA rats. Chrysin suppressed the HMGB1-regulated RAGE/PI3K/AKT pathway, hence reducing KOA damage and peripheral sensitization.

CONCLUSION

Chrysin mitigated neuropathic pain and peripheral sensitization in KOA rats by repressing the RAGE/PI3K/AKT pathway modulated by HMGB1.

Alpha-ketoglutarate ameliorates age-related and surgery induced temporomandibular joint osteoarthritis via regulating IKK/NF-κB signaling

Recent studies have shed light on the important role of aging in the pathogenesis of joint degenerative diseases and the anti-aging effect of alpha-ketoglutarate (αKG). However, whether αKG has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. Here, we demonstrate that αKG administration improves condylar cartilage health of middle-aged/aged mice, and ameliorates pathological changes in a rat model of partial discectomy (PDE) induced TMJOA. In vitro, αKG reverses IL-1β-induced/H2O2-induced decrease of chondrogenic markers (Col2, Acan and Sox9), and inhibited IL-1β-induced/ H2O2-induced elevation of cartilage catabolic markers (ADAMTS5 and MMP13) in condylar chondrocytes. In addition, αKG downregulates senescence-associated (SA) hallmarks of aged chondrocytes, including the mRNA/protein level of SA genes (p16 and p53), markers of nuclear disorders (Lamin A/C) and SA-β-gal activities. Mechanically, αKG decreases the expressions of p-IKK and p-NF-κB, protecting TMJ from inflammation and senescence-related damage by regulating the NF-κB signaling. Collectively, our findings illuminate that αKG can ameliorate age-related TMJOA and PDE-induced TMJOA, maintain the homeostasis of cartilage matrix, and exert anti-aging effects in chondrocytes, with a promising therapeutic potential in TMJOA, especially age-related TMJOA.

The State-of-the-Art Antibacterial Activities of Glycyrrhizin: A Comprehensive Review

Licorice (Glycyrrhiza glabra) is a plant of the genus Glycyrrhiza in the family Fabaceae/Leguminosae and is a renowned natural herb with a long history of medicinal use dating back to ancient times. Glycyrrhizin (GLY), the main active component of licorice, serves as a widely utilized therapeutic agent in clinical practice. GLY exhibits diverse medicinal properties, including anti-inflammatory, antibacterial, antiviral, antitumor, immunomodulatory, intestinal environment maintenance, and liver protection effects. However, current research primarily emphasizes GLY's antiviral activity, while providing limited insight into its antibacterial properties. GLY demonstrates a broad spectrum of antibacterial activity via inhibiting the growth of bacteria by targeting bacterial enzymes, impacting cell membrane formation, and altering membrane permeability. Moreover, GLY can also bolster host immunity by activating pertinent immune pathways, thereby enhancing pathogen clearance. This paper reviews GLY's inhibitory mechanisms against various pathogenic bacteria-induced pathological changes, its role as a high-mobility group box 1 inhibitor in immune regulation, and its efficacy in combating diseases caused by pathogenic bacteria. Furthermore, combining GLY with other antibiotics reduces the minimum inhibitory concentration, potentially aiding in the clinical development of combination therapies against drug-resistant bacteria. Sources of information were searched using PubMed, Web of Science, Science Direct, and GreenMedical for the keywords "licorice", "Glycyrrhizin", "antibacterial", "anti-inflammatory", "HMGB1", and combinations thereof, mainly from articles published from 1979 to 2024, with no language restrictions. Screening was carried out by one author and supplemented by others. Papers with experimental flaws in their experimental design and papers that did not meet expectations (antifungal papers, etc.) were excluded.

miR-708-5p deficiency involves the degeneration of mandibular condylar chondrocytes via the TLR4/NF-κB pathway

OBJECTIVE

Ageing and aberrant biomechanical stimulation are two major risk factors for osteoarthritis (OA). One of the main characteristics of aged cartilage is cellular senescence. One of the main characteristics of osteoarthritic joints is cartilage degeneration. The cells in the temporomandibular joint (TMJ) cartilage are zonally arranged. The deep zone cells are differentiated from the superficial zone cells (SZCs). The purpose of the present study was to investigate whether degenerative shear stress (SS) stimulates the senescence programme in TMJ SZCs, and to determine which miRNA is involved in this process.

METHOD

SZCs were isolated from the TMJ condyles of 3-week-old rats and treated with continuous passaging or SS. RNA sequencing was conducted to identify miRNA(s) that overlap with those involved in the replication senescence process and the SS-induced degeneration programme. Unilateral anterior crossbite (UAC), which is TMJ-OA inducible, was applied to 2-month-old and 12-month-old mice for 3 weeks. The effect of TMJ local injection of agomiR-708-5p was evaluated histologically.

RESULTS

Both replication and SS treatment induced SZC senescence. miR-708-5p was identified. Knocking down miR-708-5p in SS-treated SZCs led to more severe senescence by alleviating the inhibitory impact of miR-708-5p on the TLR4/NF-κB pathway. miR-708-5p expression in mouse TMJ cartilage decreased with age. UAC induced more severe osteoarthritic cartilage lesions in 12-month-old mice than in 2-month-old mice. Injection of agomiR-708-5p suppressed UAC-induced osteoarthritic cartilage lesions.

CONCLUSIONS

Age-related miR-708-5p deficiency is involved in the mechanically stimulated OA process. Intra-articular administration of agomiR-708-5p is a promising new strategy for OA treatment.

Glutathione peroxidase 4 restrains temporomandibular joint osteoarthritis progression by inhibiting ferroptosis

There are few effective therapeutic strategies for temporomandibular joint osteoarthritis (TMJOA) due to the unclear pathology and mechanisms. We aimed to confirm the roles of GPX4 and ferroptosis in TMJOA progression. ELISA assay was hired to evaluate concentrations of ferroptosis-related markers. The qRT-PCR assay was hired to assess gene mRNA level. Western blot assay and immunohistochemistry were hired to verify the protein level. CCK-8 assay was hired to detect cell viability. Human fibroblast-like synoviocytes (FLSs) were cultured to confirm the effects of GPX4 and indicated inhibitors, and further verified the effects of GPX4 and ferroptosis inhibitors in TMJOA model rats. Markers of ferroptosis including 8-hidroxy-2-deoxyguanosine (8-OHdG) and iron were notably increased in TMJOA tissues and primary OA-FLSs. However, the activity of the antioxidant system including the glutathione peroxidase activity, glutathione (GSH) contents, and glutathione/oxidized glutathione (GSH/GSSG) ratio was notably inhibited in TMJOA tissues, and the primary OA-FLSs. Furthermore, the glutathione peroxidase 4 (GPX4) expression was down-regulated in TMJOA tissues and primary OA-FLSs. Animal and cell experiments have shown that ferroptosis inhibitors notably inhibited ferroptosis and promoted HLS survival as well as up-regulated GPX4 expression. Also, GPX4 knockdown promoted ferroptosis and GPX4 overexpression inhibited ferroptosis. GPX4 also positively regulated cell survival which was the opposite with ferroptosis. In conclusion, GPX4 and ferroptosis regulated the progression of TMJOA. Targeting ferroptosis might be an effective therapeutic strategy for TMJOA patients in the clinic.

TRIM52 knockdown inhibits proliferation, inflammatory responses and oxidative stress in IL-1β-induced synovial fibroblasts to alleviate temporomandibular joint osteoarthritis

To explore the mechanism of tripartite motif 52 (TRIM52) in the progression of temporomandibular joint osteoarthritis (TMJOA). Gene and protein expression were tested by quantitative real-time polymerase chain reaction and western blot, respectively. The levels of pro-inflammatory cytokines and oxidative stress factors were evaluated using enzyme-linked immunosorbent assay and biochemical kit, respectively. Cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays were carried out to assess cell proliferation. Immunofluorescence was used to detect the expression of CD68 and Vimentin in primary synovial fibroblasts (SFs). Haematoxylin and eosin staining and Safranin O/Fast green were used to evaluate the pathological damage of synovial and cartilage tissue in rats. TRIM52 was upregulated in the synovial tissue and SFs in patients with TMJOA. Interleukin (IL)-1β treatment upregulated TRIM52 expression in TMJOA SFs and normal SF (NSF), promoting cell proliferation, inflammatory response and oxidative stress in NSF, SFs. Silence of TRIM52 relieved the cell proliferation, inflammatory response and oxidative stress induced by IL-1β in SFs, while overexpression of TRIM52 enhanced IL-1β induction. Meanwhile, IL-1β induction activated toll-like receptor 4 (TLR4)/nuclear factor (NF)-κB pathway, which was augmented by upregulation of TRIM52 in NSF, and was attenuated by TRIM52 knockdown in SFs. Besides, pyrrolidinedithiocarbamic acid ameliorated IL-1β-induced proliferation and inflammatory response by inhibiting TLR4/NF-κB signalling. Meanwhile, TRIM52 knockdown inhibited cell proliferation, oxidative stress and inflammatory response in IL-1β-induced SFs through downregulation of TLR4. TRIM52 promoted cell proliferation, inflammatory response, and oxidative stress in IL-1β-induced SFs. The above functions were mediated by the activation of TLR4/NF- κB signal pathway.

Enhancing collagen based nanoemulgel for effective topical delivery of Aceclofenac and Citronellol oil: Formulation, optimization, in-vitro evaluation, and in-vivo osteoarthritis study with a focus on HMGB-1/RAGE/NF-κB pathway, Klotho, and miR-499a

The majority of conventional osteoarthritis (OA) treatments are based on molecular adjustment of certain signaling pathways associated with osteoarthritis (OA) pathogenesis, however there is a significant need to search for more effective and safe treatments. This study centers around formulating Aceclofenac (ACF) with high bioavailability in combination with Citronellol oil and collagen. The optimal concentrations of Citronellol oil/D-Limonene oil, Tween 80, and Transcutol HP were determined using a pseudoternary phase diagram. The formulated nanoemulsions were studied for thermophysical stability. Thermodynamically stable formula were analyzed for droplet size, zeta potential, and in-vitro permeation. Then, collagen based nanoemulsion were prepared to capitalize on its efficacy in reducing osteoarthritis side effects and characterized for nano size properties. Formulae F10 and F10C were chosen as optimum nanosize formula. Hense, they were prepared and characterized as nanoemulgel dosage form. The nanoemulgel formulae F10NEG1 and F10CNEG1 showed reasonable viscosity and spreadability, with complete drug release after 4 h. These formulae were chosen for further In vivo anti-OA study. Collagen based ACF/citronellol emugel were able to modulate HMGB-1/RAGE/NF-κB pathway, mitigating the production of inflammatory cytokine TNF-α. They were also able to modulate Klotho and miR-499, reducing serum CTXII and COMP, by reducing the cartilage destruction. Histological investigations validated the efficacy, safety, and superiority of Aceclofenac in combination with Citronellol oil and collagen (F10CNEG1) over solo the treated group (F10NEG1 and blank). Hence, the findings of the current work encourage the use of this promising combined formula in treatment of OA patients.

A patent review on HMGB1 inhibitors for the treatment of liver diseases

INTRODUCTION

HMGB1 is a non-histone chromatin protein released or secreted in response to tissue damage or infection. Extracellular HMGB1, as a crucial immunomodulatory factor, binds with several different receptors to innate inflammatory responses that aggravate acute and chronic liver diseases. The increased levels of HMGB1 have been reported in various liver diseases, highlighting that it represents a potential biomarker and druggable target for therapeutic development.

AREAS COVERED

This review summarizes the current knowledge on the structure, function, and interacting receptors of HMGB1 and its significance in multiple liver diseases. The latest patented and preclinical studies of HMGB1 inhibitors (antibodies, peptides, and small molecules) for liver diseases are summarized by using the keywords 'HMGB1,' 'HMGB1 antagonist, HMGB1-inhibitor,' 'liver disease' in Web of Science, Google Scholar, Google Patents, and PubMed databases in the year from 2017 to 2023.

EXPERT OPINIONS

In recent years, extensive research on HMGB1-dependent inflammatory signaling has discovered potent inhibitors of HMGB1 to reduce the severity of liver injury. Despite significant progress in the development of HMGB1 antagonists, few of them are approved for clinical treatment of liver-related diseases. Developing safe and effective specific inhibitors for different HMGB1 isoforms and their interaction with receptors is the focus of future research.

Glycyrrhizin alleviates radiation-induced lung injury by regulating the NLRP3 inflammasome through endoplasmic reticulum stress

Objective

Radiation pneumonitis (RP) is the major adverse response of radiation therapy for thoracic malignant tumors, and there is a lack of effective interventions. The aim of this study was to investigate the radioprotective effect of Glycyrrhizin (GL) on RP and its potential mechanism.

Method

The body weight and lung weight of mice were monitored. HE staining was used to observe lung injury, and the expression of endoplasmic reticulum (ER) stress biomarkers and the activation of NLRP3 inflammasome were determined by Western blotting and immunohistochemistry. Flow cytometry was performed to check MLE-12 apoptosis. ER stress activator, Tunicamycin (Tuni), was used to verify the potential mechanism of GL. A systemic pharmacology explored the potential targets and pathways of GL.

Results

In this study, the lungs of irradiated mice showed significant pneumonic changes. In vivo and in vitro assay, NLRP3 inflammasome was significantly activated, the expression of ER stress biomarkers was elevated, flow cytometry confirms increased apoptosis in irradiated MLE-12 cells. GL inhibits the activation of NLRP3 inflammasome and ER stress pathways. Furthermore, systemic pharmacology revealed that the radioprotective effect of GL may be related to the MAPK signaling pathway.

Conclusion

In the present study, the results indicated that GL may regulate NLRP3 inflammasome through ER stress, thus exerting irradiation-protective effects on RP, and the ER stress pathway may be a potential target for RP treatment.

Forsythoside B alleviates osteoarthritis through the HMGB1/TLR4/NF-κB and Keap1/Nrf2/HO-1 pathways

Osteoarthritis (OA) is a joint pain and dysfunction syndrome resulting from severe joint degeneration. Inflammation and degeneration of the articular cartilage are two main features of OA and have tight interactions during OA progression. Conventional treatment with nonsteroidal anti-inflammatory drugs has been widely utilized clinically, whereas the side effects have restricted their application. Forsythoside B has been found with anti-inflammatory effects and antiapoptosis in inflammatory diseases, whereas in OA it remains poorly understood. Interleukin (IL)-1β (10 ng/mL) was taken to induce an OA cell model on HC-A chondrocytes and an OA rat model was constructed for in vivo experiments. Forsythoside B was adopted to treat HC-A chondrocytes and OA rats. As shown by the data, Forsythoside B hampered IL-1β-elicited rat chondrocyte apoptosis, oxidative stress, and facilitated proliferation. The profiles of inflammatory factors, NOD-like receptor family pyrin domain containing 3 inflammasomes, Kelch-like epichlorohydrin-associated protein-1 (Keap1), and nuclear factor-κB (NF-κB) phosphorylation were suppressed by Forsythoside B, whereas the nuclear factor E2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels were promoted. Further, Forsythoside B mitigated cartilage damage and degeneration. Moreover, the oxidative stress and inflammation mediators in the cartilage tissue of OA rats were remarkably abated. Collectively, Forsythoside B hinders the NF-κB and Keap1/Nrf2/HO-1 pathways to curb IL-1β-elicited OA rat oxidative stress and inflammation both in vivo and ex vivo, ameliorating OA development. All over, this study provides an underlying strategy for treating OA, which might help the clinical treatment of OA patients.

THE ALARMIN EFFECT OF HMGB1/RIP3 ON TRANSFUSION-RELATED ACUTE LUNG INJURY VIA TLR4/NF-ΚB OR MAPK PATHWAY

ABSTRACT

Nonantibody-mediated transfusion-related acute lung injury (TRALI) may account for up to 25% of TRALI cases. This indicates the need for further research to understand the pathophysiological mechanisms involved beyond antibody mediation fully. During this research, a TRALI rat model was developed using the trauma-blood loss-massive transfusion method. The severity of pulmonary edema was checked via measurement of lung histopathological changes and the amount of Evans blue dye fluid and bronchoalveolar lavage fluid protein leakage. In addition, potential mechanisms of pathophysiological pathways and inflammation cascades were investigated in TRALI rats in vivo . The findings indicated that TRALI increased inflammatory cytokines and triggered elevated levels of high-mobility group box 1 (HMGB1)/receptor-interacting protein kinase 3 (RIP3), apoptosis protein, and mRNAs in the TM (TRALI model) group as opposed to the normal control. Furthermore, TRALI activated the toll-like receptor 4/nuclear factor kappa B and mitogen-activated protein kinase signaling pathways, which partially regulated the inflammatory response in the TRALI rats. A significant increase was observed in the inflammatory mediators HMGB1 and RIP3 during the early stages of TRALI, suggesting that these mediators could be used as diagnostic markers for TRALI. In addition, HMGB1 and RIP3 promoted the inflammatory response by stimulating the toll-like receptor 44/nuclear factor kappa B and mitogen-activated protein kinase signaling pathways in the lung tissue of rats. Identifying efficient agents from inflammatory mediators such as alarmin can be an innovative scheme for diagnosing and preventing TRALI. These findings give HMGB1 and RIP3 a strong theoretical and experimental foundation for clinical use.

Potential pathological and molecular mechanisms of temporomandibular joint osteoarthritis

Temporomandibular joint osteoarthritis (TMJ OA) is a progressive degenerative disease of the temporomandibular joint (TMJ). The unclear etiology and mechanisms of TMJ OA bring great difficulties to early diagnosis and effective treatment, causing enormous burdens to patients' life and social economics. In this narrative review, we summarized the main pathological changes of TMJ OA, including inflammatory responses, degeneration of extracellular matrix (ECM), abnormal cell biological behaviors (apoptosis, autophagy, and differentiation) in TMJ tissue, and aberrant angiogenesis. All pathological features are closely linked to each other, forming a vicious cycle in the process of TMJ OA, which results in prolonged disease duration and makes it difficult to cure. Various molecules and signaling pathways are involved in TMJ OA pathogenesis, including nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), extracellular regulated protein kinases (ERKs) and transforming growth factor (TGF)-β signaling pathways et al. One molecule or pathway can contribute to several pathological changes, and the crosstalk between different molecules and pathways can further lead to a complicated condition TMJ OA. TMJ OA has miscellaneous etiology, complex clinical status, depressed treatment results, and poor prognosis. Therefore, novel in-vivo and in-vitro models, novel medicine, materials, and approaches for therapeutic procedures might be helpful for further investigation of TMJ OA. Furthermore, the role of genetic factors in TMJ OA needs to be elucidated to establish more reasonable and effective clinical strategies for diagnosing and treating TMJ OA.

Transglutaminase 2 inhibitors attenuate osteoarthritic degeneration of TMJ-osteoarthritis by suppressing NF-κB activation

BACKGROUND

The temporomandibular joint osteoarthritis (TMJ-OA) is characterized by progressive cartilage degradation, subchondral bone erosion, and chronic pain, leading to articular damage and chewing dysfunction. Studies have shown that interleukin-1β (IL-1β) plays a critical role in the development of TMJ-OA. Transglutaminase 2 (TG2) has been identified as a marker of chondrocyte hypertrophy and IL-1β was able to increase TG2 expression in chondrocytes. Therefore, the aim of this study was to explore the ability of TG2 inhibitors to suppress TMJ-OA progression.

METHODS

Firstly, toluidine blue staining, cell counting kit-8 assay, immunocytofluorescent staining and western blot were used to investigate the anti-inflammatory effects of TG2 inhibitors in IL-1β-stimulated murine chondrocytes and the underlying mechanisms. Afterwards, micro-CT analysis, histological staining, immunohistochemical and immunohistofluorescent staining were used to evaluate the therapeutic efficacy of TG2 inhibitors in monosodium iodoacetate (MIA)-induced TMJ-OA in rats.

RESULTS

TG2 inhibitors suppressed the IL-1β-induced upregulation of COX-2, iNOS, MMP-13, and MMP-3 and reversed the IL-1β-induced proteoglycan loss in chondrocytes through inhibiting NF-κB activation. Consistently, the MIA-induced upregulation of MMP-13 and MMP-3, and loss of structural integrity of the articular cartilage and subchondral bone were markedly reversed by TG2 inhibitors via inhibiting NF-κB activation.

CONCLUSIONS

TG2 inhibitors demonstrated a potent therapeutic efficacy on cartilage and subchondral bone structures of TMJ-OA by reducing inflammation and cartilage degradation through suppressing NF-κB activation.

Keratinocyte TLR2 and TLR7 contribute to chronic itch through pruritic cytokines and chemokines in mice

Although neuronal Toll-like receptors (TLRs) (e.g., TLR2, TLR3, and TLR7) have been implicated in itch sensation, the roles of keratinocyte TLRs in chronic itch are elusive. Herein, we evaluated the roles of keratinocyte TLR2 and TLR7 in chronic itch under dry skin and psoriasis conditions, which was induced by either acetone-ether-water treatment or 5% imiquimod cream in mice, respectively. We found that TLR2 and TLR7 signaling were significantly upregulated in dry skin and psoriatic skin in mice. Chronic itch and epidermal hyperplasia induced by dry skin or psoriasis were comparably reduced in TLR2 and TLR7 knockout mice. In the dry skin model, the enhanced messenger RNA (mRNA) expression levels of pruritic CXCL1/2, IL-31, IL-33, ST2, IL-6, IL-17A, TNF-α, and IFN-γ were inhibited in TLR2^-/- mice, while CXCL2, IL-31, and IL-6 were inhibited in TLR7^-/- mice. In psoriasis model, the enhanced mRNA expression levels of pruritic CXCL1/2, IL-31, IL-33, ST2, IL-6, and TNF-α were inhibited in TLR2^-/- mice, while CXCL1/2, IL-31, IL-33, ST2, IL-6, IL-17A, and TNF-α were inhibited in TLR7^-/- mice. Incubation with Staphylococcus aureus (S. aureus) peptidoglycan (PGN-SA) (a TLR2 agonist), imiquimod (a TLR7 agonist), and miR142-3p (a putative TLR7 agonist) were sufficient to upregulate the expression of pruritic cytokines or chemokines in cultured keratinocyte HaCaT cells. Finally, pharmacological blockade of C-X-C Motif Chemokine Receptor 1/2 and high mobility group box protein 1 dose-dependently attenuated acute and chronic itch in mice. Together, these results indicate that keratinocyte TLR2 and TLR7 signaling pathways are distinctly involved in the pathogenesis of chronic itch.