Glycyrrhizin mitigates radiation-induced acute lung injury by inhibiting the HMGB1/TLR4 signalling pathway

Glycyrrhizin Protects Submandibular Gland Against Radiation Damage by Enhancing Antioxidant Defense and Preserving Mitochondrial Homeostasis

Aims: Radiotherapy inevitably causes radiation damage to the salivary glands (SGs) in patients with head and neck cancers (HNCs). Excessive reactive oxygen species (ROS) levels and imbalanced mitochondrial homeostasis are serious consequences of ionizing radiation in SGs; however, there are few mitochondria-targeting therapeutic approaches. Glycyrrhizin is the main extract of licorice root and exhibits antioxidant activity to relieve mitochondrial damage in certain oxidative stress conditions. Herein, the effects of glycyrrhizin on irradiated submandibular glands (SMGs) and the related mechanisms were investigated. Results: Glycyrrhizin reduced radiation damage in rat SMGs at both the cell and tissue levels, and promoted saliva secretion in irradiated SMGs. Glycyrrhizin significantly downregulated high-mobility group box-1 protein (HMGB1) and toll-like receptor 5 (TLR5). Moreover, glycyrrhizin significantly suppressed the increases in malondialdehyde and glutathione disulfide (GSSG) levels; elevated the activity of some critical antioxidants, including superoxide dismutase, catalase, glutathione peroxidase, and glutathione (GSH); and increased the GSH/GSSG ratio in irradiated cells. Importantly, glycyrrhizin effectively enhanced thioredoxin-2 levels and scavenged mitochondrial ROS, inhibited the decline in mitochondrial membrane potential, improved adenosine triphosphate synthesis, preserved the mitochondrial ultrastructure, activated the proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α)/nuclear respiratory factor 1/2 (NRF1/2)/mitochondrial transcription factor A (TFAM) signaling pathway, and inhibited mitochondria-related apoptosis in irradiated SMG cells and tissues. Innovation: Radiotherapy causes radiation sialadenitis in HNC patients. Our data suggest that glycyrrhizin could be a mitochondria-targeted antioxidant for the prevention of radiation damage in SGs. Conclusion: These findings demonstrate that glycyrrhizin protects SMGs from radiation damage by downregulating HMGB1/TLR5 signaling, maintaining intracellular redox balance, eliminating mitochondrial ROS, preserving mitochondrial homeostasis, and inhibiting apoptosis.

Urolithin A exerts a protective effect on lipopolysaccharide-induced acute lung injury by regulating HMGB1-mediated MAPK and NF-κB signaling pathways

Acute lung injury (ALI) is a severe inflammatory disorder that has a high morbidity and mortality rate. Urolithin A (UA) is reported to have anti-inflammatory and anti-oxidative effects in ALI. However, its molecular mechanisms in ALI remain to be explored. Mice and BEAS-2B cells were administrated with lipopolysaccharide (LPS) to mimic the ALI model in vivo and in vitro. Hematoxylin-eosin (HE) staining was used to detect the pathological injury of lung tissues. The levels of proinflammatory cytokines in bronchoalveolar lavage fluid (BALF) and culture supernatant and the levels of oxidative stress markers in lung tissues were measured using ELISA. DCFH-DA probe was used to assess the reactive oxygen species (ROS) level. TUNEL staining and flow cytometry were performed to determine cell apoptosis. The key targets and pathways were confirmed by immunohistochemistry (IHC) and western blot. UA suppressed the pathologic damage, wet/dry weight ratio, and total protein and inflammatory cells in BALF. UA decreased neutrophil infiltration and proinflammatory cytokines production. UA reduced the level of malondialdehyde (MDA) and increased the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in pulmonary tissues. UA also inhibited cell apoptosis in lung tissues by decreasing Bax expression and increasing Bcl-2 expression. In addition, UA suppressed LPS-induced inflammatory factor production, ROS level, and cell apoptosis in BEAS-2B. Importantly, UA decreased the expression of HMGB1 in LPS-treated mice and BEAS-2B cells. HMGB1 overexpression greatly abrogated the inhibition of UA on inflammation, ROS, and cell apoptosis in LPS-administrated BEAS-2B. Furthermore, UA treatment suppressed the phosphorylated levels of p38, JNK, ERK, and p65 in LPS-administrated mice and BEAS-2B cells. UA alleviated lung inflammation, oxidative stress, and apoptosis in ALI by targeting HMGB1 to inactivate the MAPK/NF-κB signaling, suggesting the potential of UA to treat ALI.

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.

DAMPs and radiation injury

The heightened risk of ionizing radiation exposure, stemming from radiation accidents and potential acts of terrorism, has spurred growing interests in devising effective countermeasures against radiation injury. High-dose ionizing radiation exposure triggers acute radiation syndrome (ARS), manifesting as hematopoietic, gastrointestinal, and neurovascular ARS. Hematopoietic ARS typically presents with neutropenia and thrombocytopenia, while gastrointestinal ARS results in intestinal mucosal injury, often culminating in lethal sepsis and gastrointestinal bleeding. This deleterious impact can be attributed to radiation-induced DNA damage and oxidative stress, leading to various forms of cell death, such as apoptosis, necrosis and ferroptosis. Damage-associated molecular patterns (DAMPs) are intrinsic molecules released by cells undergoing injury or in the process of dying, either through passive or active pathways. These molecules then interact with pattern recognition receptors, triggering inflammatory responses. Such a cascade of events ultimately results in further tissue and organ damage, contributing to the elevated mortality rate. Notably, infection and sepsis often develop in ARS cases, further increasing the release of DAMPs. Given that lethal sepsis stands as a major contributor to the mortality in ARS, DAMPs hold the potential to function as mediators, exacerbating radiation-induced organ injury and consequently worsening overall survival. This review describes the intricate mechanisms underlying radiation-induced release of DAMPs. Furthermore, it discusses the detrimental effects of DAMPs on the immune system and explores potential DAMP-targeting therapeutic strategies to alleviate radiation-induced injury.

Adipose-derived stem cells repair radiation-induced chronic lung injury via inhibiting TGF-β1/Smad 3 signaling pathway

To investigate the effect of adipose-derived stem cells (ASCs) transplantation on radiation-induced lung injury (RILI), Sprague-Dawley rats were divided into phosphate-buffered saline (PBS) group, ASCs group, Radiation + PBS group, and Radiation + ASCs group. Radiation + PBS and Radiation + ASCs groups received single dose of 30 Gy X-ray radiation to the right chest. The Radiation + PBS group received 1 mL PBS suspension and Radiation + ASCs group received 1 mL PBS suspension containing 1 × 107 CM-Dil-labeled ASCs. The right lung tissue was collected on Days 30, 90, and 180 after radiation. Hematoxylin-eosin and Masson staining were performed to observe the pathological changes and collagen fiber content in the lung tissue. Immunohistochemistry (IHC) and western blot (WB) were used to detect levels of fibrotic markers collagen I (Collal), fibronectin (FN), as well as transforming growth factor-β1 (TGF-β1), p-Smad 3, and Smad 3. Compared with the non-radiation groups, the radiation groups showed lymphocyte infiltration on Day 30 after irradiation and thickened incomplete alveolar walls, collagen deposition, and fibroplasia on Days 90 and 180. ASCs relieved these changes on Day 180 (Masson staining, P = 0.0022). Compared with Radiation + PBS group, on Day 180 after irradiation, the Radiation + ASCs group showed that ASCs could significantly decrease the expressions of fibrosis markers Collal (IHC: P = 0.0022; WB: P = 0.0087) and FN (IHC: P = 0.0152; WB: P = 0.026) and inhibit the expressions of TGF-β1 (IHC: P = 0.026; WB: P = 0.0152) and p-Smad 3 (IHC: P = 0.0043; WB: P = 0.0087) in radiation-induced injured lung tissue. These indicated that ASCs could relieve RILI by inhibiting TGF-β1/Smad 3 signaling pathway.

Immunomodulatory Macrophages Enable E-MNC Therapy for Radiation-Induced Salivary Gland Hypofunction

A newly developed therapy using effective-mononuclear cells (E-MNCs) is reportedly effective against radiation-damaged salivary glands (SGs) due to anti-inflammatory and revascularization effects. However, the cellular working mechanism of E-MNC therapy in SGs remains to be elucidated. In this study, E-MNCs were induced from peripheral blood mononuclear cells (PBMNCs) by culture for 5-7 days in medium supplemented with five specific recombinant proteins (5G-culture). We analyzed the anti-inflammatory characteristics of macrophage fraction of E-MNCs using a co-culture model with CD3/CD28-stimulated PBMNCs. To test therapeutic efficacy in vivo, either E-MNCs or E-MNCs depleted of CD11b-positive cells were transplanted intraglandularly into mice with radiation-damaged SGs. Following transplantation, SG function recovery and immunohistochemical analyses of harvested SGs were assessed to determine if CD11b-positive macrophages contributed to tissue regeneration. The results indicated that CD11b/CD206-positive (M2-like) macrophages were specifically induced in E-MNCs during 5G-culture, and Msr1- and galectin3-positive cells (immunomodulatory macrophages) were predominant. CD11b-positive fraction of E-MNCs significantly inhibited the expression of inflammation-related genes in CD3/CD28-stimulated PBMNCs. Transplanted E-MNCs exhibited a therapeutic effect on saliva secretion and reduced tissue fibrosis in radiation-damaged SGs, whereas E-MNCs depleted of CD11b-positive cells and radiated controls did not. Immunohistochemical analyses revealed HMGB1 phagocytosis and IGF1 secretion by CD11b/Msr1-positive macrophages from both transplanted E-MNCs and host M2-macrophages. Thus, the anti-inflammatory and tissue-regenerative effects observed in E-MNC therapy against radiation-damaged SGs can be partly explained by the immunomodulatory effect of M2-dominant macrophage fraction.

TLR4-A Pertinent Player in Radiation-Induced Heart Disease?

The heart is one of the organs that is sensitive to developing delayed adverse effects of ionizing radiation (IR) exposure. Radiation-induced heart disease (RIHD) occurs in cancer patients and cancer survivors, as a side effect of radiation therapy of the chest, with manifestation several years post-radiotherapy. Moreover, the continued threat of nuclear bombs or terrorist attacks puts deployed military service members at risk of exposure to total or partial body irradiation. Individuals who survive acute injury from IR will experience delayed adverse effects that include fibrosis and chronic dysfunction of organ systems such as the heart within months to years after radiation exposure. Toll-like receptor 4 (TLR4) is an innate immune receptor that is implicated in several cardiovascular diseases. Studies in preclinical models have established the role of TLR4 as a driver of inflammation and associated cardiac fibrosis and dysfunction using transgenic models. This review explores the relevance of the TLR4 signaling pathway in radiation-induced inflammation and oxidative stress in acute as well as late effects on the heart tissue and the potential for the development of TLR4 inhibitors as a therapeutic target to treat or alleviate RIHD.

Kainic acid induced hyperexcitability in thalamic reticular nucleus that initiates an inflammatory response through the HMGB1/TLR4 pathway

OBJECTIVE

To explore the relationship between the proinflammatory factor high-mobility group box 1 (HMGB1) and glutamatergic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the development of epilepsy.

METHODS

Thalamic reticular nucleus (TRN) slices were treated with kainic acid (KA) to simulate seizures. Action potentials and spontaneous inhibitory postsynaptic currents (sIPSCs) were recorded within TRN slices using whole-cell patch clamp techniques. The translocation of HMGB1 was detected by immunofluorescence. The HMGB1/TLR4 signaling pathway and its downstream inflammatory factors (IL-1β and NF-κB) were detected by RTPCR, Western blot and ELISA.

RESULTS

KA-evoked spikings were observed in TRN slices and blocked by perampanel. sIPSCs in the TRN were enhanced by KA and reduced by perampanel. The translocation of HMGB1 in the TRN was promoted by KA and inhibited by perampanel. The expression of the HMGB1/TLR4 signaling pathway was promoted by KA and suppressed by perampanel.

CONCLUSION

KA induced hyperexcitability activates the HMGB1/TLR4 pathway, which potentially leading to neuroinflammation in epilepsy.

Saponins: Research Progress and Their Potential Role in the Post-COVID-19 Pandemic Era

In the post-COVID-19 pandemic era, the new global situation and the limited therapeutic management of the disease make it necessary to take urgent measures in more effective therapies and drug development in order to counteract the negative global impacts caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its new infectious variants. In this context, plant-derived saponins-glycoside-type compounds constituted from a triterpene or steroidal aglycone and one or more sugar residues-may offer fewer side effects and promising beneficial pharmacological activities. This can then be used for the development of potential therapeutic agents against COVID-19, either as a therapy or as a complement to conventional pharmacological strategies for the treatment of the disease and its prevention. The main objective of this review was to examine the primary and current evidence in regard to the therapeutic potential of plant-derived saponins against the COVID-19 disease. Further, the aim was to also focus on those studies that highlight the potential use of saponins as a treatment against SARS-CoV-2. Saponins are antiviral agents that inhibit different pharmacological targets of the virus, as well as exhibit anti-inflammatory and antithrombotic activity in relieving symptoms and clinical complications related to the disease. In addition, saponins also possess immunostimulatory effects, which improve the efficacy and safety of vaccines for prolonging immunogenicity against SARS-CoV-2 and its infectious variants.

Lung Pneumonitis and Fibrosis in Cancer Therapy: A Review on Cellular and Molecular Mechanisms

Fibrosis and pneumonitis are the most important side effects of lung tissue following cancer therapy. Radiotherapy and chemotherapy by some drugs, such as bleomycin, can induce pneumonitis and fibrosis. Targeted therapy and immunotherapy also may induce pneumonitis and fibrosis to a lesser extent compared to chemotherapy and radiotherapy. Activation of lymphocytes by immunotherapy or infiltration of inflammatory cells such as macrophages, lymphocytes, neutrophils, and mast cells following chemo/radiation therapy can induce pneumonitis. Furthermore, the polarization of macrophages toward M2 cells and the release of anti-inflammatory cytokines stimulate fibrosis. Lung fibrosis and pneumonitis may also be potentiated by some other changes such as epithelial-mesenchymal transition (EMT), oxidative stress, reduction/oxidation (redox) responses, renin-angiotensin system, and the upregulation of some inflammatory mediators such as a nuclear factor of kappa B (NF-κB), inflammasome, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). Damages to the lung vascular system and the induction of hypoxia also can induce pulmonary injury following chemo/radiation therapy. This review explains various mechanisms of the induction of pneumonitis and lung fibrosis following cancer therapy. Furthermore, the targets and promising agents to mitigate lung fibrosis and pneumonitis will be discussed.

The Effect of PD-1 Inhibitor Combined with Irradiation on HMGB1-Associated Inflammatory Cytokines and Myocardial Injury

PURPOSE

To explore the effect of PD-1 inhibitors combined with irradiation on myocardial injury and the changes of HMGB1-associated inflammatory markers.

METHODS

Four groups of five mice were used, each groupformed by randomly dividing 20 mice (group A control; group B PD-1 inhibitors; group C Irradiation; group D PD-1 inhibitors+irradiation; n = 5 for each). The mice were treated with either PD-1 inhibitors or a 15 Gy dose of single heart irradiation, or both. Hematoxylin-eosin staining assessed the morphology and pathology of heart tissue; Masson staining assessed heart fibrosis; Tunel staining evaluated heart apoptosis; flow cytometry detected CD3+, CD4+, and CD8+ T lymphocytes in heart tissues; enzyme linked immunosorbent assay evaluated IL-1β, IL-6, and TNF-ɑ of heart tissue; Western blot and quantitative real-time PCR (qPCR) detected the expression of protein and mRNA of HMGB1, TLR-4, and NF-κB p65 respectively.

RESULTS

The degree of heart injury, collagen volume fraction (CVF) and apoptotic index (AI) in groups B, C, and D were higher than group A, but the differences between the CVF and AI of group A and group B were not statistical significance (P>0.05). Similarly, the absolute counts and relative percentage of CD3+ and CD8+ T lymphocytes and the concentrations of IL-1β, IL-6, and TNF-α in heart tissue with group D were significantly higher than the other groups (P<0.05). In addition, compared with group A, the expression of protein and mRNA of HMGB1 and NF-κB p65 in other groups were higher, and the differences between each group were statistically significant while TLR4 was not. In addition, interaction by PD-1 inhibitors and irradiation was found in inflammatory indicators, especially in the expression of the HMGB1 and CD8+ T lymphocytes.

CONCLUSION

PD-1 inhibitors can increase the expression of HMGB1-associated inflammatory cytokines and aggravate radiation-induced myocardial injury.

The role of HMGB1/RAGE/TLR4 signaling pathways in cigarette smoke-induced inflammation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common chronic respiratory disease with irreversible and continuous progression. It has become the fifth most burdensome disease and the third most deadly disease globally. Therefore, the prevention and treatment of COPD are urgent, and it is also important to clarify the pathogenesis of it. Smoking is the main and most common risk factor for COPD. Cigarette smoke (CS) can cause lung inflammation and other pathological mechanisms in the airways and lung tissue. Airway inflammation is one of the important mechanisms leading to the pathogenesis of COPD. Recent studies have shown that high mobility group box 1 (HMGB1) is involved in the occurrence and development of respiratory diseases, including COPD. HMGB1 is a typical damage-associated molecular pattern (DAMP) protein, which mainly exerts its activity by binding to the receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4) and further participate in the process of airway inflammation. Studies have shown that the abnormal expression of HMGB1, RAGE, and TLR4 are related to inflammation in COPD. Herein, we discuss the roles of HMGB1, RAGE, and TLR4 in CS/cigarette smoke extract-induced inflammation in COPD, providing a new target for the diagnosis, treatment and prevention of COPD.

Role of RAGE and its ligand HMGB1 in the development of COPD

Smoking is a well-established risk factor for chronic obstructive pulmonary disease (COPD). Chronic lung inflammation continues even after smoking cessation and leads to COPD progression. To date, anti-inflammatory therapies are ineffective in improving pulmonary function and COPD symptoms, and new molecular targets are urgently needed to deal with this challenge. The receptor for advanced glycation end-products (RAGE) was shown to be relevant in COPD pathogenesis, since it is both a genetic determinant of low lung function and a determinant of COPD susceptibility. Moreover, RAGE is involved in the physiological response to cigarette smoke exposure. Since innate and acquired immunity plays an essential role in the development of chronic inflammation and emphysema in COPD, here we summarized the roles of RAGE and its ligand HMGB1 in COPD immunity.

Predictive role of circulatory levels of high-mobility group box 1 for radiation pneumonitis in patients with non-small cell lung cancer treated with definitive thoracic radiotherapy

BACKGROUND

High-mobility group box 1 (HMGB1) is a pro-inflammatory protein associated with the pathophysiology of lung injury and lung tumorigenesis. Here, we investigated the predictive potential of serum HMGB1 levels for radiation pneumonitis in patients with lung cancer.

METHODS

This was a retrospective biomarker study of 73 patients with non-small cell lung cancer treated with definitive thoracic radiotherapy between August 2007 and January 2021. We measured HMGB1 levels in serum stored before treatment, and analyzed its association with the development of grade ≥ 2 or grade ≥ 3 radiation pneumonitis. Additionally, baseline characteristics affecting HMGB1 levels were identified.

RESULTS

Of the 73 patients, 21 (28.8%) and 6 (8.2%) patients experienced grade 2 and ≥ 3 radiation pneumonitis, respectively. Univariate and multivariate logistic regression analyses revealed that higher baseline levels of serum HMGB1 were significantly associated with a higher risk of grade ≥ 3, but not grade ≥ 2, radiation pneumonitis. The incidence of grade ≥ 3 radiation pneumonitis was higher in patients with HMGB1 levels ≥ 6.2 ng/mL than in those with levels < 6.2 ng/mL (25.0% vs. 3.5%, p = 0.019). Baseline serum levels of HMGB1 were independently and positively associated with gross tumor volume.

CONCLUSIONS

Higher serum HMGB1 levels were significantly associated with the risk of grade ≥ 3 radiation pneumonitis in patients with lung cancer, and therefore, HMGB1 could be a potential blood biomarker for predicting severe radiation pneumonitis.

Targeting HMGB1-NFκb Axis and miR-21 by Glycyrrhizin: Role in Amelioration of Corneal Injury in a Mouse Model of Alkali Burn

Corneal neovascularization (CNV) is a sight-threatening condition usually associated with various inflammatory settings including chemical injury. High mobility group box 1 (HMGB1) is identified as an inflammatory alarmin in diverse tissue damage. Here, we evaluate the expression of HMGB1 and the consequences of its inhibition through its selective inhibitor glycyrrhizin (GLY) in alkali burn-induced corneal inflammation and neovascularization. GLY effectively attenuated alkali burn-induced HMGB1 expression at both mRNA and protein levels. Furthermore, slit-lamp analysis, ink perfusion, H&amp;E staining, and CD31 histochemical staining showed that GLY relieved corneal neovascularization, while GLY attenuated VEGF expression via inhibiting HMGB1/NF-κB/HIF-1α signal pathway. In addition, GLY treatment decreased the cytokine expression of CCL2 and CXCL5, accompanied by the reduction of their receptors of CCR2 and CXCR2. GLY diminished the inflammatory cell infiltration of the cornea, as well as reduced the expression of IL-1β, IL-6, and TNF-α. Moreover, treatment with GLY reduced the degree of cornea opacity through inactivating extracellular HMGB1 function, which otherwise induces TGF-β1 release and myofibroblast differentiation. Furthermore, we found that GLY treatment attenuated the upregulation of miR-21 levels in alkali burned cornea; while inhibition of miR-21in keratocytes in vitro, significantly inhibited TGF-β1-induced myofibroblast differentiation. Collectively, our results suggested that targeting HMGB1-NFκb axis and miR-21 by GLY could introduce a therapeutic approach to counter CNV.

High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases

In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

Glycyrrhizic Acid against Mycoplasma gallisepticum-Induced Inflammation and Apoptosis Through Suppressing the MAPK Pathway in Chickens

Mycoplasma gallisepticum (MG) is the primary pathogen of chronic respiratory diseases (CRDs) in chickens. In poultry production, antibiotics are mostly used to prevent and control MG infection, but the drug resistance and residue problems caused by them cannot be ignored. Glycyrrhizic acid (GA) is derived from licorice, a herb traditionally used to treat various respiratory diseases. Our study results showed that GA significantly inhibited the mRNA and protein expression of pMGA1.2 and GapA in vitro and in vivo. Furthermore, the network pharmacology study revealed that GA most probably resisted MG infection through the MAPK signaling pathway. Our results demonstrated that GA inhibited MG-induced expression of MMP2/MMP9 and inflammatory factors through the p38 and JUN signaling pathways, but not the ERK pathway in vitro. Besides, histopathological sections showed that GA treatment obviously attenuated tracheal and lung damage caused by MG invasion. In conclusion, GA can inhibit MG-triggered inflammation and apoptosis by suppressing the expression of MMP2/MMP9 through the JNK and p38 pathways and inhibit the expression of virulence genes to resist MG. Our results suggest that GA might serve as one of the antibiotic alternatives to prevent MG infection.

The role of ferroptosis in acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a common disease with high morbidity and mortality, and its pathogenesis is believed to be related to oxidative stress, apoptosis, inflammation, and hypoxia. Ferroptosis is a type of nonapoptotic cell death characterized by iron-dependent lipid peroxide accumulation and is involved in many cellular physiological processes. Recent studies have confirmed that ferroptosis may be involved in the development of ALI. This review summarizes the most recent discoveries on the role of ferroptosis in ALI to provide new strategies for its prevention and treatment.

Crossed Pathways for Radiation-Induced and Immunotherapy-Related Lung Injury

Radiation-induced lung injury (RILI) is a form of radiation damage to normal lung tissue caused by radiotherapy (RT) for thoracic cancers, which is most commonly comprised of radiation pneumonitis (RP) and radiation pulmonary fibrosis (RPF). Moreover, with the widespread utilization of immunotherapies such as immune checkpoint inhibitors as first- and second-line treatments for various cancers, the incidence of immunotherapy-related lung injury (IRLI), a severe immune-related adverse event (irAE), has rapidly increased. To date, we know relatively little about the underlying mechanisms and signaling pathways of these complications. A better understanding of the signaling pathways may facilitate the prevention of lung injury and exploration of potential therapeutic targets. Therefore, this review provides an overview of the signaling pathways of RILI and IRLI and focuses on their crosstalk in diverse signaling pathways as well as on possible mechanisms of adverse events resulting from combined radiotherapy and immunotherapy. Furthermore, this review proposes potential therapeutic targets and avenues of further research based on signaling pathways. Many new studies on pyroptosis have renewed appreciation for the value and importance of pyroptosis in lung injury. Therefore, the authors posit that pyroptosis may be the common downstream pathway of RILI and IRLI; discussion is also conducted regarding further perspectives on pyroptosis as a crucial signaling pathway in lung injury treatment.

Scorpion bradykinin potentiating factor mitigates lung damage induced by γ-irradiation in rats: Insights on AngII/ACE/Ang(1-7) axis

The goal of this research is to study the mitigating impact of bradykinin potentiating factor (BPF) found in scorpion Androctonus bicolor venom on irradiation-induced lung damage as a new functional target for angiotensin-converting enzyme inhibitors (ACEIs). Male rats were exposed to 7 Gy of γ-radiation as a single dose, with a biweekly intraperitoneal injection of 1 μg/g BPF. Gamma irradiation not only boosted the ACE activity and angiotensin II (Ang II) level, in lung tissue but also significantly depressed the angiotensin (1-7) (Ang (1-7)) that, lead to lung toxicity through a significant elevation of pulmonary levels of CXC-chemokine receptor 4 (CXCR4), toll-like receptor 4 (TLR4), nitric oxide (NO) and lactate dehydrogenase (LDH) activity with a marked disruption in oxidative stress markers, via a reduction in the level of total thiol (tSH) and superoxide dismutase (SOD) activity associated with an elevation in protein carbonyl (PCO) contents. In addition, apoptotic consequences of gamma irradiation were evidenced by raising the levels of mitogen-activated protein kinase (MAPK), C-Jun N-Terminal Kinases (JNK), and cleaved caspase-3. BPF administration leads to ACE inhibition, consequently sustaining decreased Ang II alongside increased Ang (1-7) production. Those sensitive molecules reduce irradiated lung issues. In conclusion, BPF significantly diminished the biochemical and histopathological consequences of radiation through renin-angiotensin system (RAS) control and ACE suppression in the lung.

PIEZO1 Ion Channel Mediates Ionizing Radiation-Induced Pulmonary Endothelial Cell Ferroptosis via Ca2+/Calpain/VE-Cadherin Signaling

Pulmonary endothelial cell dysfunction plays an important role in ionizing radiation (IR)-induced lung injury. Whether pulmonary endothelial cell ferroptosis occurs after IR and what are the underlying mechanisms remain elusive. Here, we demonstrate that 15-Gy IR induced ferroptosis characterized by lethal accumulation of reactive oxygen species (ROS), lipid peroxidation, mitochondria shrinkage, and decreased glutathione peroxidase 4 (GPX4) and SLC7A11 expression in pulmonary endothelial cells. The phenomena could be mimicked by Yoda1, a specific activator of mechanosensitive calcium channel PIEZO1. PIEZO1 protein expression was upregulated by IR in vivo and in vitro. The increased PIEZO1 expression after IR was accompanied with increased calcium influx and increased calpain activity. The effects of radiation on lung endothelial cell ferroptosis was partly reversed by inhibition of PIEZO1 activity using the selective inhibitor GsMTx4 or inhibition of downstreaming Ca²⁺/calpain signaling using PD151746. Both IR and activation of PIEZO1 led to increased degradation of VE-cadherin, while PD151746 blocked these effects. VE-cadherin knockdown by specific siRNA causes ferroptosis-like phenomena with increased ROS and lipid peroxidation in the lung endothelial cells. Overexpression of VE-cadherin partly recused the ferroptosis caused by IR or PIEZO1 activation as supported by decreased ROS production, lipid peroxidation and mitochondria shrinkage compared to IR or PIEZO1 activation alone. In summary, our study reveals a previously unrecognized role of PIEZO1 in modulating ferroptosis, providing a new target for future mitigation of radiation-induced lung injury.

Glycyrrhizin ameliorating sterile inflammation induced by low-dose radiation exposure

Glycyrrhizin (GL) is a direct inhibitor of HMGB1 which acts as an alarmin when excreted into the extracellular space. High-dose radiation in radiotherapy induces collateral damage to the normal tissue, which can be mitigated by GL inhibiting HMGB1. The purpose of this study was to assess changes in HMGB1 and pro-inflammatory cytokines and to evaluate the protective effect of GL after low-dose radiation exposure. BALB/c mice were irradiated with 0.1 Gy (n = 10) and 1 Gy (n = 10) with GL being administered to half of the mice (n = 5, respectively) before irradiation. Blood and spleen samples were harvested and assessed for oxidative stress, HMGB1, pro-inflammatory cytokines, and cell viability. HMGB1 and pro-inflammatory cytokines increased and cell viability decreased after irradiation in a dose-dependent manner. Oxidative stress also increased after irradiation, but did not differ between 0.1 Gy and 1 Gy. With the pretreatment of GL, oxidative stress, HMGB1, and all of the pro-inflammatory cytokines decreased while cell viability was preserved. Our findings indicate that even low-dose radiation can induce sterile inflammation by increasing serum HMGB1 and pro-inflammatory cytokines and that GL can ameliorate the sterile inflammatory process by inhibiting HMGB1 to preserve cell viability.

Promising Biomarkers of Radiation-Induced Lung Injury: A Review

Radiation-induced lung injury (RILI) is one of the main dose-limiting side effects in patients with thoracic cancer during radiotherapy. No reliable predictors or accurate risk models are currently available in clinical practice. Severe radiation pneumonitis (RP) or pulmonary fibrosis (PF) will reduce the quality of life, even when the anti-tumor treatment is effective for patients. Thus, precise prediction and early diagnosis of lung toxicity are critical to overcome this longstanding problem. This review summarizes the primary mechanisms and preclinical animal models of RILI reported in recent decades, and analyzes the most promising biomarkers for the early detection of lung complications. In general, ideal integrated models considering individual genetic susceptibility, clinical background parameters, and biological variations are encouraged to be built up, and more prospective investigations are still required to disclose the molecular mechanisms of RILI as well as to discover valuable intervention strategies.

Herbal Active Ingredients: Potential for the Prevention and Treatment of Acute Lung Injury

Acute lung injury (ALI) is a life-threatening clinical syndrome with high morbidity and mortality. The main pathological features of ALI are increased alveolar-capillary membrane permeability, edema, uncontrolled migration of neutrophils to the lungs, and diffuse alveolar damage, resulting in acute hypoxemic respiratory failure. Glucocorticoids, aspirin, and other anti-inflammatory drugs are commonly used to treat ALI. Respiratory supports, such as a ventilator, are used to alleviate hypoxemia. Many treatment methods are available, but they cannot significantly ameliorate the quality of life of patients with ALI and reduce mortality rates. Herbal active ingredients, such as flavonoids, terpenoids, saponins, alkaloids, and quinonoids, exhibit advantages for ALI prevention and treatment, but the underlying mechanism needs further study. This paper summarizes the role of herbal active ingredients in anti-ALI therapy and progresses in the understanding of their mechanisms. The work also provides some references and insights for the discovery and development of novel drugs for ALI prevention and treatment.

The protective effects of granulocyte-macrophage colony-stimulating factor against radiation-induced lung injury

Background

Radiation-induced lung injury (RILI) is a common complication of thoracic cancer radiation therapy. Currently, there is no effective treatment for RILI. RILI is associated with chronic inflammation, this injury is perpetuated by the stimulation of chemokines and proinflammatory cytokines. Recent studies have demonstrated that granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a pivotal role in inflammation and fibrosis. This study aimed to investigate the protective effect of GM-CSF against the development of RILI in lung tissue.

Method

First, a single fraction of radiation at a dose of 16 Gy was targeted at the entire thorax of wild-type (WT) C57BL/6 mice and GM-CSF^–/– mice to induce RILI. Second, we detected the radioprotective effects of GM-CSF by measuring the inflammatory biomarkers and fibrosis alteration on radiated lung tissues. Furthermore, we investigated the potential mechanism of GM-CSF protective effects in RILI.

Results

The GM-CSF^–/– mice sustained more severe RILI than the WT mice. RILI was significantly alleviated by GM-CSF treatment. Intraperitoneally administered GM-CSF significantly inhibited inflammatory cytokine production and decreased epithelial-mesenchymal transition (EMT) in the RILI mouse model.

Conclusions

GM-CSF was shown to be an important modulator of RILI through regulating inflammatory cytokines, which provides a new strategy for the prevention and treatment of RILI.

TGF-β1-based CRISPR/Cas9 gene therapy attenuate Radiation-induced Lung Injury

BACKGROUND

Radiation-induced lung injury (RILI) is lacking effective therapeutic strategies. In this study, we conducted TGF-β1-based CRISPR/Cas9 gene therapy for RILI.

OBJECTIVES

Mouse lungs were irradiated with a single-dose of 20-Gy gamma rays followed by intravenous administration of Ad-CRISPR-TGF-β1 or Ad- CRISPR-Null.

METHODS

Haematoxylin and eosin staining, as well as Masson staining were performed to observe lung morphology. Albumin and IgM concentrations in bronchoalveolar lavage fluid were measured by ELISA. Cytokine levels were measured using ELISA and/or real-time PCR with terminal deoxynucleotidyl transferase mediated nick-end labelling.

RESULTS

Ad-CRISPR-TGFβ1 improved histopathological and biochemical markers of lung injury, reduced secretion and expression of inflammatory cytokines, and inhibited progression of fibrosis. Importantly, the SK1/S1P axis-which is known to play a key role via S1P1 in TGF-β1-dependent S1PR pattern remodelling-is responsible for promoting fibrosis.

CONCLUSION

Our results indicate novel insights for RILI therapy.

Role of HMGB1/TLR4 Axis in Ischemia/Reperfusion-Impaired Extracellular Glutamate Clearance in Primary Astrocytes

(1) Background: Abnormal accumulation of extracellular glutamate can occur as dysfunction of astrocytic glutamate transporters, which has been linked to ischemic brain injury. Excessive extracellular glutamate-induced abnormal excitotoxicity is the major cause of secondary neuronal damage after cerebral ischemia/reperfusion. However, the definite mechanism of impaired astrocytic glutamate reuptake remains unclear. (2) Methods: We investigated the mechanism of the HMGB1/TLR4 axis in extracellular glutamate clearance in primary astrocytes exposed to ischemia/reperfusion by using OGD/R (oxygen-glucose deprivation/reoxygenation) model. (3) Results: OGD/R insult activated the HMGB1/TLR4 axis for reducing the activity of glutamate clearance by inhibiting GLAST (glutamate aspartate transporter) expression in primary astrocytes. Interestingly, OGD/R-untreated astrocytes showed impairment of glutamate clearance after exposure to exogenous HMGB1 or conditioned medium from OGD/R-treated astrocytes culture. Inhibition of HMGB1 or TLR4 effectively prevented impaired glutamate clearance, which was induced by OGD/R, exogenous HMGB1, or conditioned medium from OGD/R-treated astrocytes. Furthermore, glycyrrhizic acid attenuated OGD/R-induced impairment of astrocytic glutamate clearance mediated by the HMGB1-TLR4 axis. (4) Conclusion: The HMGB1/TLR4 axis is a potential target for the treatment of post-ischemic excitotoxicity caused by GLAST dysfunction in astrocytes.

Glycyrrhizin potentially suppresses the inflammatory response in preeclampsia rat model

OBJECTIVE

The expression of high-mobility group box 1 (HMGB1) in trophoblasts is elevated, which contributes to the development of preeclampsia. Thus, this study aimed to investigate the effect of glycyrrhizin, a natural HMGB1 inhibitor, on the development of preeclampsia.

METHODS

Preeclampsia was induced in pregnant Lewis rats through oral administration of L-NAME (50 mg/kg/day) on gestational day (GD) 13-19. Glycyrrhizin (10, 30, or 60 mg/kg/day) was given by oral gavage on GD 10-19. Systolic blood pressure (SBP), diastolic blood pressure (DBP), 24-hour proteinuria, live pup birth ratio, pup weight, pup body length, and placental weight were measured. Also, the expression levels of inflammatory factors (TNF-α, iNOS, IL-1, and IL-6), HMGB1, and TLR4 in the placenta or in the serum were analyzed by enzyme-linked immunosorbent assay, RT-PCR, and Western blot analysis.

RESULTS

Glycyrrhizin significantly reduced the SBP, DBP, and 24-hour proteinuria on GD 16 and 20 in a dose-dependent manner and ameliorated the pregnancy outcomes in preeclampsia rats. The elevated inflammatory molecule levels were markedly decreased by glycyrrhizin not only in the serum but also in the placenta. Moreover, the upregulated HMGB1 and TLR4 expression levels were diminished by glycyrrhizin administration.

CONCLUSION

This study shows that glycyrrhizin could alleviate preeclampsia and the preeclampsia-associated inflammatory reaction, and this effect could be attributed to HMGB1 inhibition.

Myeloid cells in sensing of tissue damage

Myeloid cells are components of the innate immune system that represent the first line of defense. Tissue damage, associated with pathological conditions such as infection, cancer or autoimmunity, leads to the exposure of the intracellular content to the extracellular environment. Myeloid cells detect ligands exposed or released by dead cells through specific receptors that signal for a diversity of responses. Inflammatory responses triggered by myeloid cells after sensing tissue injury can contribute to resolution of the damage. The signaling response following dead-cell sensing by myeloid cells can contribute either to an inflammatory or a regulatory response. We review herein some representative examples of how myeloid cells react to the recognition of cell death during specific tissue damage contexts. A deep understanding of the cellular and molecular mechanisms underlying these processes would allow to improve therapeutical interventions in pathologies associated with tissue damage.

Glycyrrhizin: An alternative drug for the treatment of COVID-19 infection and the associated respiratory syndrome?

Safe and efficient drugs to combat the current COVID-19 pandemic are urgently needed. In this context, we have analyzed the anti-coronavirus potential of the natural product glycyrrhizic acid (GLR), a drug used to treat liver diseases (including viral hepatitis) and specific cutaneous inflammation (such as atopic dermatitis) in some countries. The properties of GLR and its primary active metabolite glycyrrhetinic acid are presented and discussed. GLR has shown activities against different viruses, including SARS-associated Human and animal coronaviruses. GLR is a non-hemolytic saponin and a potent immuno-active anti-inflammatory agent which displays both cytoplasmic and membrane effects. At the membrane level, GLR induces cholesterol-dependent disorganization of lipid rafts which are important for the entry of coronavirus into cells. At the intracellular and circulating levels, GLR can trap the high mobility group box 1 protein and thus blocks the alarmin functions of HMGB1. We used molecular docking to characterize further and discuss both the cholesterol- and HMG box-binding functions of GLR. The membrane and cytoplasmic effects of GLR, coupled with its long-established medical use as a relatively safe drug, make GLR a good candidate to be tested against the SARS-CoV-2 coronavirus, alone and in combination with other drugs. The rational supporting combinations with (hydroxy)chloroquine and tenofovir (two drugs active against SARS-CoV-2) is also discussed. Based on this analysis, we conclude that GLR should be further considered and rapidly evaluated for the treatment of patients with COVID-19.

S100A12 promotes inflammation and cell apoptosis in sepsis-induced ARDS via activation of NLRP3 inflammasome signaling

Sepsis is a multiple organ dysfunction elicited by the dysregulated host immune response to microbial infection. Acute respiratory distress syndrome (ARDS) is a serious and acute inflammatory lung injury resulting from sepsis and other severe diseases. The present study aims to investigate the role of S100A12, a pro-inflammatory factor, in the pathophysiologic mechanism underlying the process in sepsis-induced ARDS. In present study, Hematoxylin and Eosin (H&E) Staining was performed to observe pathological changes. Enzyme-Linked Immunosorbent Assay (ELISA) was employed to analyze the levels of inflammatory cytokines. Western blot, immunohistochemistry (IHC) staining and reverse-transcriptase quantitative real-time PCR (RT-qPCR) were performed to determine target gene and protein expression. TUNEL assay and flow cytometry were performed to assay cell apoptosis. We found that the levels of S100A12 and soluble receptor for advanced glycation end-products (sRAGE) are upregulated in the serum of patients with Sepsis-induced ARDS and sepsis mice. Furthermore, higher cell apoptosis rate was observed in lung tissue of sepsis mice. In addition, S100A12 resulted in excessive mucins and the secretion of inflammatory cytokines secretion, and promoted the expression of chemokines and cell adhesion molecules via activating nucleotide-binding oligomerization domain (Nod) -like receptor (NLR) P3 inflammasome pathway in NHBE cells. Finally, S100A12 increased oxidative stress status and cell apoptosis in NHBE cells. Generally, the present study provides evidence that S100A12 is closely related to pathogenesis of sepsis-induced ARDS. Hence, S100A12 may be a useful biomarker of pulmonary injuries for clinical diagnosis of sepsis-induced ARDS.

FK866 attenuates sepsis-induced acute lung injury through c-jun-N-terminal kinase (JNK)-dependent autophagy

AIMS

Increasing evidence indicates that FK866, a specific noncompetitive nicotinamide phosphoribosyl transferase inhibitor, exhibits a protective effect on acute lung injury (ALI). Autophagy plays a pivotal role in sepsis-induced ALI. However, the contribution of autophagy and the underlying mechanism by which FK866-confered lung protection remains elusive. Herein, we aimed to study whether FK866 could alleviate sepsis-induced ALI via the JNK-dependent autophagy.

MAIN METHODS

Male C57BL/6 mice were subjected to cecal ligation and puncture (CLP) to establish the polymicrobial sepsis mice model, and treated with FK866 (10 mg/kg) at 24, 12 and 0.5 h before the CLP procedure. The lung protective effects were measured by lung histopathology, tissue edema, vascular leakage, inflammation infiltration, autophagy-related protein expression and JNK activity. A549 cells were stimulated with LPS (1000 ng/ml) to generate the ALI cell model, and pretreated with FK866 or SP600125 for 30 min to measure the autophagy-related protein expression and JNK activity.

KEY FINDINGS

Our results demonstrated that FK866 reduced lung injury score, tissue edema, vascular leakage, and inflammatory infiltration, and upregulated autophagy. The protective effect of autophagy conferred by FK866 on ALI was further clarified by using 3-methyladenine (3MA) and rapamycin. Additionally, the activity of JNK was suppressed by FK866, and inhibition of JNK promoted autophagy and showed a benefit effect.

SIGNIFICANCE

Our study indicates that FK866 protects against sepsis-induced ALI by induction of JNK-dependent autophagy. This may provide new insights into the functional mechanism of NAMPT inhibition in sepsis-induced ALI.

Glycyrrhizin suppresses epithelial-mesenchymal transition by inhibiting high-mobility group box1 via the TGF-β1/Smad2/3 pathway in lung epithelial cells

Background

Epithelial-mesenchymal transition (EMT) plays an important role in fibrosis, chronic inflammation, tumor metastasis, etc. Glycyrrhizin, an active component extracted from licorice plant, has been reported to treat a variety of inflammatory reactions through inhibiting high-mobility group box1 (HMGB1), which has been suggested to be a significant mediator in EMT process. However, whether glycyrrhizin affects the EMT process or not remains unclear.

Methods

Human alveolar epithelial cell line A549 and normal human bronchial epithelial cell line BEAS-2B were treated with extrinsic TGF-β1 to induce EMT. Elisa was used to detect HMGB1 concentrations in cell supernatant. RNA interference and lentivirus infection experiments were performed to investigate the involvement of HMGB1 in EMT process. Cell Counting Kit-8 (CCK-8) was used to detect the viability of A549 and BEAS-2B cells treated with glycyrrhizin. Finally, the effects of glycyrrhizin on EMT changes, as well as the underlying mechanisms, were evaluated via Western blot, immunofluorescence and transwell assays.

Results

Our results showed that HMGB1 expression was increased by TGF-β1, and knockdown of HMGB1 expression reversed TGF-β1-induced EMT in A549 and BEAS-2B cells. Ectopic HMGB1 expression or TGF-β1 treatment caused a significant increase in HMGB1 release. Notably, we found that glycyrrhizin treatment effectively suppressed TGF-β1-induced EMT process by inhibiting HMGB1. Also, glycyrrhizin significantly inhibited the migration of both A549 and BEAS-2B cells promoted by TGF-β1. Mechanistically, HMGB1 overexpression could activate Smad2/3 signaling in A549 and BEAS-2B cells. Glycyrrhizin significantly blocked the phosphorylation of Smad2/3 stimulated either by TGF-β1 or by ectopic HMGB1 in A549 and BEAS-2B cells.

Conclusions

HMGB1 is a vital mediator of EMT changes induced by TGF-β1 in lung epithelial cells. Importantly, glycyrrhizin can effectively block Smad2/3 signaling pathway through inhibiting HMGB1, thereby suppressing the EMT progress.

Glycyrrhizin mitigates radiation-induced acute lung injury by inhibiting the HMGB1/TLR4 signalling pathway

Radiation‐induced lung injury (RILI) is the major complication of thoracic radiation therapy, and no effective treatment is available. This study explored the role of high‐mobility group box 1 (HMGB1) in acute RILI and the therapeutic effect of glycyrrhizin, an inhibitor of HMGB1, on RILI. C57BL/6 mice received a 20 Gy dose of X‐ray radiation to the whole thorax with or without administration of glycyrrhizin. Severe lung inflammation was present 12 weeks after irradiation, although only a mild change was noted at 2 weeks and could be alleviated by administration of glycyrrhizin. Glycyrrhizin decreased the plasma concentrations of HMGB1 and sRAGE as well as TNF‐α, IL‐1β and IL‐6 levels in the bronchoalveolar lavage fluid (BALF). The expression of RAGE was decreased while that of TLR4 was significantly increased at 12 weeks, but not 2 weeks, after irradiation in mouse lung tissue. In vitro, the expression of TLR4 increased in RAW 264.7 cells after conditioning with the supernatant from the irradiated MLE‐12 cells containing HMGB1 but showed no change when conditioned medium without HMGB1 was used. However, conditioned culture had no effect on RAGE expression in RAW 264.7 cells. Glycyrrhizin also inhibited the related downstream transcription factors of HMGB/TLR4, such as NF‐κB, JNK and ERK1/2, in lung tissue and RAW 264.7 cells when TLR4 was activated. In conclusion, the HMGB1/TLR4 pathway mediates RILI and can be mitigated by glycyrrhizin.