High mobility group box 1 induced human lung myofibroblasts differentiation and enhanced migration by activation of MMP-9

AMPK signaling inhibits the differentiation of myofibroblasts: impact on age-related tissue fibrosis and degeneration

Disruption of the extracellular matrix (ECM) and an accumulation of fibrotic lesions within tissues are two of the distinctive hallmarks of the aging process. Tissue fibroblasts are mesenchymal cells which display an impressive plasticity in the regulation of ECM integrity and thus on tissue homeostasis. Single-cell transcriptome studies have revealed that tissue fibroblasts exhibit a remarkable heterogeneity with aging and in age-related diseases. Excessive stress and inflammatory insults induce the differentiation of fibroblasts into myofibroblasts which are fusiform contractile cells and abundantly secrete the components of the ECM and proteolytic enzymes as well as many inflammatory mediators. Detrimental stresses can also induce the transdifferentiation of certain mesenchymal and myeloid cells into myofibroblasts. Interestingly, many age-related stresses, such as oxidative and endoplasmic reticulum stresses, ECM stiffness, inflammatory mediators, telomere shortening, and several alarmins from damaged cells are potent inducers of myofibroblast differentiation. Intriguingly, there is convincing evidence that the signaling pathways stimulated by the AMP-activated protein kinase (AMPK) are potent inhibitors of myofibroblast differentiation and accordingly AMPK signaling reduces fibrotic lesions within tissues, e.g., in age-related cardiac and pulmonary fibrosis. AMPK signaling is not only an important regulator of energy metabolism but it is also able to control cell fate determination and many functions of the immune system. It is known that AMPK signaling can delay the aging process via an integrated signaling network. AMPK signaling inhibits myofibroblast differentiation, e.g., by suppressing signaling through the TGF-β, NF-κB, STAT3, and YAP/TAZ pathways. It seems that AMPK signaling can alleviate age-related tissue fibrosis and degeneration by inhibiting the differentiation of myofibroblasts.

Ghost messages: cell death signals spread

Cell death is a mystery in various forms. Whichever type of cell death, this is always accompanied by active or passive molecules release. The recent years marked the renaissance of the study of these molecules showing they can signal to and communicate with recipient cells and regulate physio- or pathological events. This review summarizes the defined forms of messages cells could spread while dying, the effects of these signals on the target tissue/cells, and how these types of communications regulate physio- or pathological processes. By doing so, this review hopes to identify major unresolved questions in the field, formulate new hypothesis worthy of further investigation, and when possible, provide references for the search of novel diagnostic/therapeutics agents. Video abstract.

The Epithelial-Immune Crosstalk in Pulmonary Fibrosis

Interactions between the lung epithelium and the immune system involve a tight regulation to prevent inappropriate reactions and have been connected to several pulmonary diseases. Although the distal lung epithelium and local immunity have been implicated in the pathogenesis and disease course of idiopathic pulmonary fibrosis (IPF), consequences of their abnormal interplay remain less well known. Recent data suggests a two-way process, as illustrated by the influence of epithelial-derived periplakin on the immune landscape or the effect of macrophage-derived IL-17B on epithelial cells. Additionally, damage associated molecular patterns (DAMPs), released by damaged or dying (epithelial) cells, are augmented in IPF. Next to “sterile inflammation”, pathogen-associated molecular patterns (PAMPs) are increased in IPF and have been linked with lung fibrosis, while outer membrane vesicles from bacteria are able to influence epithelial-macrophage crosstalk. Finally, the advent of high-throughput technologies such as microbiome-sequencing has allowed for the identification of a disease-specific microbial environment. In this review, we propose to discuss how the interplays between the altered distal airway and alveolar epithelium, the lung microbiome and immune cells may shape a pro-fibrotic environment. More specifically, it will highlight DAMPs-PAMPs pathways and the specificities of the IPF lung microbiome while discussing recent elements suggesting abnormal mucosal immunity in pulmonary fibrosis.

High Mobility Group Box Chromosomal Protein-1 Induces Myofibroblast Differentiation and Extracellular Matrix Production via RAGE, p38, JNK and AP-1 Signaling Pathways in Nasal Fibroblasts

BACKGROUND

Chronic rhinosinusitis is involved in myofibroblast differentiation and extracellular matrix (ECM) accumulation. High mobility group box chromosomal protein 1 (HMGB-1) is known to stimulate lung fibroblast to produce ECM in lung fibrosis. The aim of this study was to investigate whether HMGB-1 induces myofibroblast differentiation and ECM production in nasal fibroblasts and to identify the signal pathway.

METHODS

Human nasal fibroblasts were cultured. After stimulation with HMGB-1, expressions of α-smooth muscle actin (α-SMA) and fibronectin were determined by real-time PCR and western blot. Total collagen was measured by Sircol assay. To investigate signal pathway, various signal inhibitors and RAGE siRNA were used.

RESULTS

HMGB-1 increased α-SMA and fibronectin in mRNA and protein levels. It also increased collagen production. RAGE siRNA inhibited HMGB-1-induced α-SMA and fibronectin, and production of collagen. Furthermore, the inhibitors of RAGE downstream molecules such as p38, JNK and AP-1 also blocked the HMGB-1-induced effects.

CONCLUSIONS

HMGB-1 induces myofibroblast differentiation and ECM production in nasal fibroblast, which is mediated by RAGE, p38, JNK and AP-1 signal pathway. These results suggest that HMGB-1 may play an important role in tissue remodeling during chronic rhinosinusitis progression.

Role of the Receptor for Advanced Glycation End Products in Heat Stress-Induced Endothelial Hyperpermeability in Acute Lung Injury

Objective

To study the role of the receptor for advanced glycation end products (RAGE) in endothelial barrier dysfunction induced by heat stress, to further explore the signal pathway by which RAGE contributes to heat-induced endothelia response, and thereby find a novel target for the clinical treatment of ALI (acute lung injury) induced by heatstroke.

Methods

This study established the animal model of heatstroke using RAGE knockout mice. We observed the role of RAGE in acute lung injury induced by heatstroke in mice by evaluating the leukocytes, neutrophils, and protein concentration in BALF (Bronchoalveolar lavage fluids), lung wet/dry ratio, histopathological changes, and the morphological ultrastructure of lung tissue and arterial blood gas analysis. To further study the mechanism, we established a heat stress model of HUVEC and concentrated on the role of RAGE and its signal pathway in the endothelial barrier dysfunction induced by heat stress, measuring Transendothelial electrical resistance (TEER) and western blot.

Results

RAGE played a key role in acute lung injury induced by heatstroke in mice. The mechanism C-Jun is located in the promoter region of the RAGE gene. C-Jun increased the RAGE protein expression while HSF1 suppressed RAGE protein expression. The overexpressed RAGE protein then increased HUVEC monolayer permeability by activating ERK and P38 MAPK under heat stress.

Conclusion

This study indicates the critical role of RAGE in heat stress-induced endothelial hyperpermeability in acute lung injury and suggests that RAGE could be a potential therapeutic target in protecting patients against acute lung injury induced by heatstroke.

The heterodimer S100A8/A9 is a potent therapeutic target for idiopathic pulmonary fibrosis

In patients with interstitial pneumonia, pulmonary fibrosis is an irreversible condition that can cause respiratory failure. Novel treatments for pulmonary fibrosis are necessary. Inflammation is thought to activate lung fibroblasts, resulting in pulmonary fibrosis. Of the known inflammatory molecules, we have focused on S100A8/A9 from the onset of inflammation to the subsequent progression of inflammation. Our findings confirmed the high expression of S100A8/A9 in specimens from patients with pulmonary fibrosis. An active role of S100A8/A9 was demonstrated not only in the proliferation of fibroblasts but also in the fibroblasts' differentiation to myofibroblasts (the active form of fibroblasts). S100A8/A9 also forced fibroblasts to upregulate the production of collagen. These effects were induced via the receptor of S100A8/A9, i.e., the receptor for advanced glycation end products (RAGE), on fibroblasts. The anti-S100A8/A9 neutralizing antibody inhibited the effects of S100A8/A9 on fibroblasts and suppressed the progression of fibrosis in bleomycin (BLM)-induced pulmonary fibrosis mouse model. Our findings strongly suggest a crucial role of S100A8/A9 in pulmonary fibrosis and the usefulness of S100A8/A9-targeting therapy for fibrosis interstitial pneumonia. HIGHLIGHTS: S100A8/A9 level is highly upregulated in the IPF patients' lungs as well as the blood. S100A8/A9 promotes not only the growth of fibroblasts but also differentiation to myofibroblasts. The cell surface RAGE acts as a crucial receptor to the extracellular S100A8/A9 in fibroblasts. The anti-S100A8/A9 antibody effectively suppresses the progression of IPF in a mouse model. In idiopathic pulmonary fibrosis (IPF), S100A8/A9, a heterodimer composed of S100A8 and S100A9 proteins, plays a crucial role in the onset of inflammation and the subsequent formation of a feed-forward inflammatory loop that promotes fibrosis. (1) The local, pronounced increase in S100A8/A9 in the injured inflammatory lung region-which is provided mainly by the activated neutrophils and macrophages-exerts strong inflammatory signals accompanied by dozens of inflammatory soluble factors including cytokines, chemokines, and growth factors that further act to produce and secrete S100A8/A9, eventually making a sustainable inflammatory circuit that supplies an indefinite presence of S100A8/A9 in the extracellular space with a mal-increased level. (2) The elevated S100A8/A9 compels fibroblasts to activate through receptor for advanced glycation end products (RAGE), one of the major S100A8/A9 receptors, resulting in the activation of NFκB, leading to fibroblast mal-events (e.g., elevated cell proliferation and transdifferentiation to myofibroblasts) that actively produce not only inflammatory cytokines but also collagen matrices. (3) Finally, the S100A8/A9-derived activation of lung fibroblasts under a chronic inflammation state leads to fibrosis events and constantly worsens fibrosis in the lung. Taken together, these findings suggest that the extracellular S100A8/A9 heterodimer protein is a novel mainstay soluble factor for IPF that exerts many functions as described above (1-3). Against this background, we herein applied the developed S100A8/A9 neutralizing antibody to prevent IPF. The IPF imitating lung fibrosis in an IPF mouse model was effectively blocked by treatment with the antibody, leading to enhanced survival. The developed S100A8/A9 antibody, as an innovative novel biologic, may help shed light on the difficulties encountered with IPF therapy in clinical settings.

Regeneration and repair in the healing lung

The lung achieves an efficient gas exchange between a complex non‐sterile atmosphere and the body via a delicate and extensive epithelial surface, with high efficiency because of elastic deformation allowing for an increase and decrease in volume during the process of breathing and because of an extensive vasculature which aids rapid gas diffusion. The lungs’ large surface area exposes the organ to a continual risk of damage from pathogens, toxins or irritants; however, lung damage can be rapidly healed via regenerative processes that restore its structure and function. In response to sustained and extensive damage, the lung is healed via a non‐regenerative process resulting in scar tissue which locally stiffens its structure, which over time leads to a serious loss of lung function and to increasing morbidities. This review discusses what is known about the factors which influence whether a lung is healed by regeneration or repair and what potential new therapeutic approaches may positively influence lung healing.

Alternatively activated macrophages are associated with the α2AP production that occurs with the development of dermal fibrosis : The role of alternatively activated macrophages on the development of fibrosis

Background

Fibrotic diseases are characterized by tissue overgrowth, hardening, and/or scarring because of the excessive production, deposition, and contraction of the extracellular matrix (ECM). However, the detailed mechanisms underlying these disorders remain unclear. It was recently reported that α2-antiplasmin (α2AP) is elevated in fibrotic tissue and that it is associated with the development of fibrosis. In the present study, we examined the mechanism underlying the production of α2AP on the development of fibrosis.

Methods

To clarify the mechanism underlying the production of α2AP on the development of fibrosis, we focused on high-mobility group box 1 (HMGB1), which is associated with the development of fibrosis. The mouse model of bleomycin-induced fibrosis was used to evaluate the production of α2AP on the development of fibrosis.

Results

We found that HMGB1 induced the production of α2AP through receptor for advanced glycation end products (RAGE) in fibroblasts. Next, we showed that macrophage reduction by a macrophage-depleting agent, clodronate, attenuated the progression of fibrosis and the production of α2AP and HMGB1 in the bleomycin-induced mice. We also showed that IL-4-stimulated alternatively activated macrophages induced the production of HMGB1, that IL-4-stimulated alternatively activated macrophage conditioned media (CM) induced pro-fibrotic changes and α2AP production, and that the inhibition of HMGB1 and RAGE attenuated these effects in fibroblasts. Furthermore, the blockade of IL-4 signaling by IL-4Rα neutralizing antibodies attenuated the progression of fibrosis and the production of α2AP and HMGB1 in the bleomycin-induced mice.

Conclusion

These findings suggest that alternatively activated macrophage-derived HMGB1 induced the production of α2AP through RAGE and that these effects are associated with the development of fibrosis. Our findings may provide a clinical strategy for managing fibrotic disorders.

Blockade of extracellular high-mobility group box 1 attenuates inflammation-mediated damage and haze grade in mice with corneal wounds

PURPOSE

To investigate the expression of extracellular high mobility group box 1 (HMGB1) and the effect of its inhibitor glycyrrhizin (GL) in corneal wound healing.

METHODS

We treated C57BL/6J mice with GL or PBS before and after establishing a corneal injury model. Fluorescein staining, Ki-67 expression, haze grade, and haematoxylin/eosin (H&E) staining were used to assess treatment efficacy. The expression of HMGB1, NF-κB-p65, the NLRP3 inflammasome, IL-1β, CCL2, CXCL2, TGF-β1, α-SMA, fibronectin, and collagen III and neutrophil influx were examined by immunohistochemical staining, western blot, and RT-qPCR at various time points after corneal injury.

RESULTS

After corneal injury, HMGB1 transferred from the nucleus to the cytoplasm and was passively released or actively secreted into the corneal stroma from epithelial cells and inflammatory cells; however, this increase was attenuated by GL treatment. Furthermore, GL indirectly attenuated the expression of IL-1β by directly inhibiting extracellular HMGB1 functions, which activated the NF-κB-p65/NLRP3/IL-1β signalling pathway. Moreover, application of GL alleviated the neutrophil infiltration that delays wound healing, accompanied by the downregulation of expression of the chemokines CCL2 and CXCL2. More interestingly, application of GL reduced the degree of haze grade through inactivating extracellular HMGB1 functions that induced TGF-β1 release and myofibroblast differentiation. In addition, fluorescein and H&E staining and Ki-67 levels suggest that GL promotes regeneration of corneal epithelium.

CONCLUSIONS

After corneal injury, extracellular HMGB1 can be an essential driver to trigger a neutrophil- and cytokine-mediated inflammatory injury amplification loop. The application of GL promotes the cornea to restore transparency and integrity, which may be related to the attenuation of extracellular HMGB1 levels and function.

S100A12 inhibits fibroblast migration via the receptor for advanced glycation end products and p38 MAPK signaling

The migration of lung fibroblasts plays a pivotal role in wound repair and fibrotic processes in the lung. Although the receptor for advanced glycation end products (RAGE) has been implicated in the pathogenesis of lung diseases, its role in lung fibroblast migration is unclear. The current study examined the effect of three different RAGE ligands, namely, high mobility group box 1 (HMGB1), S100A12, and N-epsilon-(carboxymethyl) lysine (CML), on human fibronectin-directed human fetal lung fibroblast (HFL-1) migration. HMGB1 augmented, whereas S100A12 inhibited, HFL-1 migration in a concentration-dependent manner. CML did not affect HFL-1 migration. The effect of HMGB1 was not through RAGE. However, the effect of S100A12 was mediated by RAGE, but not Toll-like receptor 4. S100A12 did not exert a chemoattractant effect, but inhibited HFL-1 chemotaxis and/or chemokinesis. Moreover, S100A12 mediated HFL-1 migration through p38 mitogen-activated protein kinase (MAPK) but not through nuclear factor-kappa B, protein kinase A, phosphatase and tensin homolog deleted on chromosome 10, or cyclooxygenase. In addition, western blot analysis showed that S100A12 augmented p38 MAPK activity in the presence of human fibronectin. In conclusion, S100A12 inhibits lung fibroblast migration via RAGE-p38 MAPK signaling. This pathway could represent a therapeutic target for pulmonary conditions characterized by abnormal tissue repair and remodeling.

Therapeutic Role of Recombinant Human Soluble Thrombomodulin for Acute Exacerbation of Idiopathic Pulmonary Fibrosis

Acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) is an acute respiratory worsening of unidentifiable cause that sometimes develops during the clinical course of IPF. Although the incidence of AE-IPF is not high, prognosis is poor. The pathogenesis of AE-IPF is not well understood; however, evidence suggests that coagulation abnormalities and inflammation are involved. Thrombomodulin is a transmembranous glycoprotein found on the cell surface of vascular endothelial cells. Thrombomodulin combines with thrombin, regulates coagulation/fibrinolysis balance, and has a pivotal role in suppressing excess inflammation through its inhibition of high-mobility group box 1 protein and the complement system. Thus, thrombomodulin might be effective in the treatment of AE-IPF, and we and other groups found that recombinant human soluble thrombomodulin improved survival in patients with AE-IPF. This review summarizes the existing evidence and considers the therapeutic role of thrombomodulin in AE-IPF.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Sirtuin 6 inhibits myofibroblast differentiation via inactivating transforming growth factor-β1/Smad2 and nuclear factor-κB signaling pathways in human fetal lung fibroblasts

Fibroblast-to-myofibroblast differentiation, which is characterized by increased expression of α-smooth muscle actin, is known to be involved in the pathogenesis of idiopathic pulmonary fibrosis. Sirtuin 6 (SIRT6), a member of the sirtuin family, has been proved to inhibit epithelial-to-mesenchymal transition during idiopathic pulmonary fibrosis. However, the function of SIRT6 in lung myofibroblast differentiation is still obscure. Transforming growth factor-β1 (TGF-β1) is one of the main factors that can powerfully promote myofibroblast differentiation. In the current study, we aimed to explore the role of SIRT6 in the cellular model of fibroblast-to-myofibroblast differentiation induced by TGF-β1 using human fetal lung fibroblasts (HFL1). We demonstrated that the SIRT6 protein level is upregulated by TGF-β1 in HFL1 cells. Overexpression of SIRT6 significantly suppresses TGF-β1-induced myofibroblast differentiation in HFL1 cells. Mechanistically, SIRT6 decreases phosphorylation and nuclear translocation of Smad2 under TGF-β1 stimulation. Nevertheless, mutant SIRT6 (H133Y) without histone deacetylase activity fails to inhibit phosphorylation and nuclear translocation of Smad2. Meanwhile, SIRT6 interacts with the nuclear factor-κB (NF-κB) subunit p65 and represses TGF-β1-induced NF-κB-dependent transcriptional activity, which is also dependent on its deacetylase activity. Overexpression of wild-type SIRT6 but not the H133Y mutant inhibits the expression of NF-κB-dependent genes including interleukin (IL)-1β, IL-6 and matrix metalloproteinase-9 (MMP-9) induced by TGF-β1, all of which have been demonstrated to promote myofibroblast differentiation. Collectively, our study reveals that SIRT6 prevents TGF-β1-induced lung myofibroblast differentiation through inhibiting TGF-β1/Smad2 and NF-κB signaling pathways.

Neurokinin 1 receptor promotes rat airway smooth muscle cell migration in asthmatic airway remodelling by enhancing tubulin expression

Background

Airway remodelling is a major contributor to hyper-responsiveness leading to chronic asthma; however, the underlying mechanisms remain unclear. This study aimed to investigate the effects of a neurokinin 1 receptor (NK1R) antagonist (WIN62577) on the migration of airway smooth muscle cells (ASMCs) and the expression of NK1R and alpha-tubulin in airway remodelling using young rats with asthma.

Methods

Sprague-Dawley rats were randomly divided into a control group and airway remodelling group. Rats in the model group were stimulated with ovalbumin for 8 weeks. Primary ASMCs were cultured and purified from all rats, and then treated with different doses of WIN62577. The expression of NK1R and α-tubulin in ASMCs was assessed using immunofluorescence, real-time quantitative polymerase chain reaction, and western blotting. Changes in ASMC migration were detected by a transwell chamber assay.

Results

The transwell assay showed that the number of migrating ASMCs in the asthmatic airway remodelling group was significantly greater than that in the control group (P<0.01), which was inhibited by WIN62577 in a dose-dependent manner, with peak inhibition detected at 10^-8 mol/L. The mRNA and protein expression levels of NK1R and α-tubulin were significantly higher in the asthmatic airway remodelling group than in the control group (P<0.05 and P<0.01, respectively), and were significantly decreased after treatment with WIN62577 (P<0.01 and P<0.05, respectively).

Conclusions

NK1R antagonists may suppress ASMC migration in a rat model of airway remodelling by inhibiting tubulin expression, indicating a new potential target for the treatment and control of chronic asthma.

Association of serum high-mobility group box protein 1 level with outcomes of acute exacerbation of idiopathic pulmonary fibrosis and fibrosing nonspecific interstitial pneumonia

BACKGROUND AND OBJECTIVE

High-mobility group box 1 (HMGB1) protein is important in acute lung injury. However, the role of HMGB-1 in acute exacerbation of fibrosing interstitial pneumonia (AE-FIP) has not been adequately studied.

METHODS

We prospectively measured serum HMGB1 level from disease onset to day 7 in 36 patients with AE-FIP6 patients had missing data because of early death (within 7 days). We then examined the association of HMGB1 level and outcome, and the associations of rhTM with HMGB1 level and outcome in 19 patients who were treated with rhTM (rhTM group) and 11 patients who were not (control group).

RESULTS

Data from 36 AE-FIP patients (mean age, 73.5±6.7years) were analyzed. Serum HMGB1 level was significantly higher in patients with AE-FIP than in those with stable idiopathic pulmonary fibrosis (16.4±13.5 vs 5.7±2.6 ng/ml, respectively; p = 0.003). HMGB1 was significantly lower on day 7 than at AE-FIP onset in survivors (6.5±4.8 vs 14.7±12.9 ng/ml, respectively; p = 0.02) but not in nonsurvivors (14.6±10.5 vs 9.2±4.8 ng/ml, respectively; p = 0.08). Although HMGB1 level at day 7 was significantly lower after rhTM treatment than at AE-FIP onset (8.4±6.1 vs 15.2±12.5 ng/ml, respectively; p = 0.02), it did not significantly decrease in patients receiving treatments other than rhTM (11.3±11.3 vs 8.3±5.3 ng/ml, respectively; p = 0.37). Three-month survival was 60.0% in the rhTM group and 36.4% in the control group (p = 0.449). In multivariate analysis, a decrease in HMGB1 was a significant independent predictor of 3-month survival (Odds ratio, 12.4; p = 0.007).

CONCLUSION

rhTM lowers serum HMGB1 level and may improve survival after AE-FIP. HMGB1 may be a promising therapeutic target for AE-FIP.

Endostatin Stimulates Proliferation and Migration of Myofibroblasts Isolated from Myocardial Infarction Model Rats

Myofibroblasts contribute to the healing of infarcted areas after myocardial infarction through proliferation, migration, and production of extracellular matrix (ECM). Expression of endostatin, a cleaved fragment of type XVIII collagen, increases in the heart tissue of an experimental myocardial infarction model. In the present study, we examined the effect of endostatin on the function of myofibroblasts derived from an infarcted area. The myocardial infarction model was created by ligating the left anterior descending artery in rats. Two weeks after the operation, α-smooth muscle actin (α-SMA)-positive myofibroblasts were isolated from the infarcted area. Endostatin significantly increased the proliferation and migration of myofibroblasts in vitro. On the other hand, endostatin had no effect on the production of type I collagen, a major ECM protein produced by myofibroblasts. Endostatin activated Akt and extracellular signal-regulated kinase (ERK), and the pharmacological inhibition of these signaling pathways suppressed the endostatin-induced proliferation and migration. A knockdown of the COL18A1 gene in the myocardial infarction model rats using small interference RNA (siRNA) worsened the cardiac function concomitant with wall thinning and decreased the α-SMA-positive myofibroblasts and scar formation compared with that of control siRNA-injected rats. In summary, we demonstrated for the first time that endostatin might be an important factor in the healing process after myocardial infarction through the activation of myofibroblasts.

Neuroprotective Effect of Curcumin Against Cerebral Ischemia-Reperfusion Via Mediating Autophagy and Inflammation

Curcumin, a polyphenolic compound extracted from Curcuma longa, has drawn attention for its effective bioactivities against ischemia-induced injury. This study aimed to evaluate the neuroprotective effect of curcumin and investigate the underlying mechanism that mediates autophagy and inflammation in an animal model of middle cerebral artery occlusion (MCAO) in rats. Curcumin was delivered to Sprague Dawley male rats at a dose of 200 mg/kg curcumin by intraperitoneal injection 30 min after ischemia-reperfusion (I/R). LY294002, a specific inhibitor of the PI3K/Akt/mTOR pathway, as well as anisomycin, an activator of TLR4/p38/MAPK, was administered by ventricle injection 30 min before MCAO. The same volume of saline was given as a control. Brain infarction and neurological function were determined 24 h post-MCAO. Immunoblotting and immunofluorescence were used to detect alterations in autophagy-relevant proteins Akt, p-Akt, mTOR, p-mTOR, LC3-II, and LC3-I, and inflammation-related proteins TLR4, p-38, p-p38, and IL-1 in the ipsilateral hemisphere. Cerebral I/R injury resulted in significant alterations of LC3-II/LC3-I, IL-1, TLR4, and p-p38. Curcumin in MCAO rats significantly improved brain damage and neurological function by upregulating p-Akt and p-mTOR and downregulating LC3-II/LC3-I, IL-1, TLR4, p-38, and p-p38. However, these protective effects against ischemia could be suppressed when LY294002 or anisomycin was included. Curcumin exerts neuroprotective effects by attenuating autophagic activities through mediating the PI3K/Akt/mTOR pathway, while also suppressing an inflammatory reaction by regulating the TLR4/p38/MAPK pathway. Furthermore, this study indicates that curcumin could be an effective therapy for patients afflicted with ischemia.

Roles of high-mobility group box 1 and thrombin in murine pulmonary fibrosis and the therapeutic potential of thrombomodulin

Cross talk between inflammation and coagulation plays important roles in acute or subacute progressive pulmonary fibrosis characterized by diffuse alveolar damage. Thrombomodulin is a physiological inhibitor of high-mobility group box 1 (HMGB1), and thrombin and may be effective for this condition. This study investigated the roles of HMGB1 and thrombin in the pathophysiology of bleomycin-induced pulmonary fibrosis and the efficacy of recombinant human soluble thrombomodulin (rhTM). Pulmonary fibrosis was induced in wild-type C57BL/6 mice by intratracheal instillation of bleomycin. We first assessed HMGB1, thrombin, transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA) levels in bronchoalveolar lavage fluid and lung tissue sections over time. Expression of HMGB1 and thrombin was elevated before that of TGF-β1 and α-SMA and remained high during the fibrotic phase after bleomycin instillation. We next examined whether in vitro stimulation with HMGB1 and thrombin induced expression of TGF-β1 and α-SMA in cultured alveolar macrophages and lung fibroblasts, respectively, by performing quantitative PCR, enzyme-linked immunosorbent assay, Western blot, and immunofluorescence analyses. HMGB1 and thrombin stimulation induced TGF-β1 production by alveolar macrophages, and thrombin stimulation also induced α-SMA expression in lung fibroblasts. Finally, we evaluated the effect of rhTM on bleomycin-induced pulmonary fibrosis. Compared with the vehicle control, both early and late-phase administration of rhTM suppressed the fibrotic process. Our results suggest that HMGB1 and thrombin were involved in the pathophysiology of pulmonary fibrosis via production of profibrotic proteins and that rhTM attenuated bleomycin-induced pulmonary fibrosis. rhTM may be a therapeutic option for acute or subacute pulmonary fibrosis.

Treponema pallidum flagellins stimulate MMP-9 and MMP-13 expression via TLR5 and MAPK/NF-κB signaling pathways in human epidermal keratinocytes

Syphilis is a chronic disease caused by Treponema pallidum and the pathogenesis is still unclear. T. pallidum infection induced inflammatory responses are involved in the immunopathological damage in skin and other tissues. Flagellin, the monomeric subunit of bacterial flagella, is a classic pathogen associated molecular patterns (PAMPs) that interacts to TLR5 and induces inflammatory responses. Keratinocytes, as immune sentinels recognize the PAMPs via TLRs, play an important role in skin innate immune response. Matrix metalloproteinases (MMPs) expressed by keratinocytes are involved in skin inflammatory responses and promoting pathogens invasion. In this study, we demonstrate that FlaB1, FlaB2 and FlaB3, the flagellins of T. pallidum, induced MMP-9 and MMP-13 production in human immortalized keratinocytes cell line HaCaT. Silencing of TLR5, but not TLR2 and TLR4 attenuated MMP-9 and MMP-13 expressions induced by T. pallidum flagellins. MMP-9 and MMP-13 expressions were also be abrogated by transfection with a dominant negative (DN) plasmid of MyD88. We also found that treatment of HaCaT cells with FlaB1, FlaB2 and FlaB3 activate the MAPK and NF-κB signaling pathways. Inhibited of ERK, JNK, p38 and NF-κB suppressed MMP-9 expression induced by the FlaB1. MMP-13 expression was found to be suppressed by pretreatment with inhibitors of ERK, JNK and NF-κB, but not p38. These findings demonstrate that T. pallidum flagellins (FlaB1, FlaB2 or FlaB3) can stimulate MMP-9 and MMP-13 expression through TLR5 and MAPK/NF-κB signaling pathways in human epidermal keratinocytes, which could contribute to the pathogenesis of T. pallidum infection.

LEF1-AS1, a long-noncoding RNA, promotes malignancy in glioblastoma

OBJECTIVES

The long-noncoding RNAs (lncRNAs) are identified as new crucial regulators of diverse cellular processes in glioblastoma (GBM) tissues. However, the expression pattern and biological function of lncRNAs remain largely unknown. Here, for the first time, the effects of lncRNA lymphoid enhancer-binding factor 1 antisense RNA 1 (LEF1-AS1) on GBM progression both in vitro and in vivo are investigated.

MATERIALS AND METHODS

Expression profiles of LEF1-AS1 in GBM specimens were investigated by bioinformatics analyses. LEF1-AS1 expression in GBM tissues was detected using a quantitative polymerase chain reaction. LEF1-AS1 expression was inhibited by transfecting the LEF1-AS1-specific small interfering RNAs (siRNAs) and stable cell lines established were inhibited by transfecting si-LEF1-AS1 viruses. The Cell Counting Kit-8, ethynyl deoxyuridine, and colony formation assay were used to examine proliferation function. The flow cytometry detected cell-cycle change and apoptosis. Migration effects were detected by a Transwell assay. The tumor xenografts and immunohistochemistry were performed to evaluate tumor growth in vivo.

RESULTS

In this study, LEF1-AS1 expression was found significantly upregulated in GBM specimens compared with normal tissues. The 5-year overall survival in GBM patients from The Cancer Genome Atlas with high expression of LEF1-AS1 was inferior to that with low expression. It was confirmed that expression of LEF1-AS1 was higher in GBM tissues than normal ones. Knockdown of LEF1-AS1 significantly inhibited the malignancy of GBM cells, including proliferation and invasion, and promoted cell apoptosis. The result of Western blot assays indicated that knockdown of LEF1-AS1-mediated tumor suppression in GBM cells may be via the reduction of ERK and Akt/mTOR signaling activities. Finally, the in vivo experiment also demonstrated that knockdown LEF1-AS1 inhibited the growth-promoting effect of LEF1-AS1 of U87 cells.

CONCLUSION

Our result indicated that lncRNA LEF1-AS1 acts as an oncogene in GBM and may be a pivotal target for this disease.

Maresin 1 inhibits transforming growth factor-β1-induced proliferation, migration and differentiation in human lung fibroblasts

The myofibroblast has been implicated to be an important pathogenic cell in all fibrotic diseases, through synthesis of excess extracellular matrix. Lung fibroblast migration, proliferation and differentiation into a myofibroblast-like cell type are regarded as important steps in the formation of lung fibrosis. In the present study, the effect of maresin 1 (MaR 1), a pro-resolving lipid mediator, on transforming growth factor (TGF)-β1-stimulated lung fibroblasts was investigated, and the underlying molecular mechanisms were examined. The results of the present study demonstrated that MaR 1 inhibited TGF-β1-induced proliferative and migratory ability, assessed using MTT and scratch wound healing assays. The TGF-β1-induced expression of α-smooth muscle actin (α-SMA) and collagen type I, the hallmarks of myofibroblast differentiation, was decreased by MaR 1 at the mRNA and protein levels, determined using the reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Immunofluorescence demonstrated that MaR 1 downregulated the TGF-β1-induced expression of α-SMA. In addition, phosphorylated mothers against decapentaplegic homolog 2/3 (Smad2/3) and extracellular signal-related kinases (ERK) 1/2 were upregulated in TGF-β1-induced lung fibroblasts, and these effects were attenuated by MaR 1 administration. In conclusion, the results of the present study demonstrated that MaR 1 inhibited the TGF-β1-induced proliferation, migration and differentiation of human lung fibroblasts. These observed effects may be mediated in part by decreased phosphorylation of Smad2/3 and ERK1/2 signaling pathways. Therefore, MaR 1 may be a potential therapeutic approach to lung fibrotic diseases.

HMGB1 promotes HLF-1 proliferation and ECM production through activating HIF1-α-regulated aerobic glycolysis

Aerobic glycolysis is a crucial event in fibroblast differentiation, and extracellular matrix (ECM) production in the progression of pulmonary fibrosis (PF). Abnormal high mobility group protein B1 (HMGB1) activation is involved in the pathogenesis of PF. However, whether aerobic glycolysis contributes to HMGB1-induced fibroblast proliferation and ECM production in PF has not yet been determined. In this study, we investigated the effects of HMGB1 on human embryonic lung fibroblast (HLF-1) proliferation, ECM production, and aerobic glycolysis. The lactate dehydrogenase inhibitor oxamic acid (OA), and PFKFB3 inhibitor 3PO were used to block certain crucial steps of aerobic glycolysis. As a result, we observed an increase of HMGB1 in bronchoalveolar lavage fluid (BALF) in bleomycin (BLM)-treated rats as compared to non-treated rats (control group). A concentration-dependent increase of HLF-1 proliferation and expression of α-SMA and α-collagen I were observed in the HMGB1 group, as well as increases of LDHA activation, glucose uptake levels, glycolytic rate, lactate level, and ATP production. OA and 3PO, or suppression of HIF1-α, blocked the effects of HMGB1. In summary, HMGB1 promotes fibroblast proliferation and ECM production though upregulating expression of HIF1-α to induce an increase of aerobic glycolysis.

Neogambogic acid prevents silica-induced fibrosis via inhibition of high-mobility group box 1 and MCP-1-induced protein 1

BACKGROUND

Silicosis is a systemic disease caused by inhaling silicon dioxide (SiO2); early stages are characterized by alveolar inflammation, and later stages are characterized by progressive lung fibrosis. Mounting evidence indicates that high-mobility group box 1 (HMGB1) is involved in pulmonary fibrosis. Whether neogambogic acid (NGA) inhibits macrophage and fibroblast activation induced by SiO2 by targeting HMGB1 remains unclear.

METHODS AND RESULTS

Experiments using cultured mouse macrophages (RAW264.7 cells) demonstrated that SiO2 treatment induces the expression of HMGB1 in a time- and dose-dependent manner via mitogen-activated protein kinases (MAPKs) and the phosphatidylinositol 3-kinase (PI3K)/Akt pathway; in turn, this expression causes macrophage apoptosis and fibroblast activation. Pretreating macrophages with NGA inhibited the HMGB1 expression induced by SiO2 and attenuated both macrophage apoptosis and fibroblast activation. Moreover, NGA directly inhibited MCP-1-induced protein 1 (MCPIP1) expression, as well as markers of fibroblast activation and migration induced by SiO2. Furthermore, the effects of NGA on macrophages and fibroblasts were confirmed in vivo by exposing mice to SiO2.

CONCLUSION

NGA can prevent SiO2-induced macrophage activation and apoptosis via HMGB1 inhibition and SiO2-induced fibrosis via the MCPIP1 pathway. Targeting HMGB1 and MCPIP1 with NGA could provide insights into the potential development of a therapeutic approach for alleviating the inflammation and fibrosis induced by SiO2.

Gartanin induces cell cycle arrest and autophagy and suppresses migration involving PI3K/Akt/mTOR and MAPK signalling pathway in human glioma cells

In central nervous system, glioma is the most common primary brain tumour. The diffuse migration and rapid proliferation are main obstacles for successful treatment. Gartanin, a natural xanthone of mangosteen, suppressed proliferation, migration and colony formation in a time- and concentration-dependent manner in T98G glioma cells but not in mouse normal neuronal HT22 cells. Gartanin, at low micromole, led to cell cycle arrest in G1 phase accompanied by inhibited expression level of G1 cell cycle regulatory proteins cyclin D1, while increased expression level of cyclin-dependent kinase inhibitor p27Kip1. In addition, the secretion and activity of matrix metalloproteinases 2/9 (MMP-2/-9) were significantly suppressed in T98G cells treated with gartanin, and it might result from modulating mitogen-activated protein kinases (MAPK) signalling pathway in T98G glioma cells. Moreover, gartanin significantly induced autophagy in T98G cells and increased GFP-LC3 punctate fluorescence accompanied by the increased expression level of Beclin 1 and LC3-II, while suppressed expression level of p62. Gartanin treatment resulted in obvious inhibition of PI3K/Akt/mTOR signalling pathway, which is important in modulating autophagy. Notably, gartanin-mediated anti-viability was significantly abrogated by autophagy inhibitors including 3-methyladenine (3-MA) and chloroquine (CQ). These results indicate that anti-proliferation effect of gartanin in T98G cells is most likely via cell cycle arrest modulated by autophagy, which is regulated by PI3K/Akt/mTOR signalling pathway, while anti-migration effect is most likely via suppression of MMP-2/-9 activity which is involved in MAPK signalling pathway.

Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension

Activation of the mammalian target of rapamycin complex 1 (mTORC1) subunit Raptor induces cell growth and is a downstream target of Akt. Elevated levels of aldosterone activate Akt, and, in pulmonary arterial hypertension (PAH), correlate with pulmonary arteriole thickening, which suggests that mTORC1 regulation by aldosterone may mediate adverse pulmonary vascular remodeling. We hypothesized that aldosterone-Raptor signaling induces abnormal pulmonary artery smooth muscle cell (PASMC) survival patterns to promote PAH. Remodeled pulmonary arterioles from SU-5416/hypoxia-PAH rats and monocrotaline-PAH rats with hyperaldosteronism expressed increased levels of the Raptor target, p70S6K, which provided a basis for investigating aldosterone-Raptor signaling in human PASMCs. Aldosterone (10(-9) to 10(-7) M) increased Akt/mTOR/Raptor to activate p70S6K and increase proliferation, viability, and apoptosis resistance in PASMCs. In PASMCs transfected with Raptor-small interfering RNA or treated with spironolactone/eplerenone, aldosterone or pulmonary arterial plasma from patients with PAH failed to increase p70S6K activation or to induce cell survival in vitro Optimal inhibition of pulmonary arteriole Raptor was achieved by treatment with Staramine-monomethoxy polyethylene glycol that was formulated with Raptor-small interfering RNA plus spironolactone in vivo, which decreased arteriole muscularization and pulmonary hypertension in 2 experimental animal models of PAH in vivo Up-regulation of mTORC1 by aldosterone is a critical pathobiologic mechanism that controls PASMC survival to promote hypertrophic vascular remodeling and PAH.-Aghamohammadzadeh, R., Zhang, Y.-Y., Stephens, T. E., Arons, E., Zaman, P., Polach, K. J., Matar, M., Yung, L.-M., Yu, P. B., Bowman, F. P., Opotowsky, A. R., Waxman, A. B., Loscalzo, J., Leopold, J. A., Maron, B. A. Up-regulation of the mammalian target of rapamycin complex 1 subunit Raptor by aldosterone induces abnormal pulmonary artery smooth muscle cell survival patterns to promote pulmonary arterial hypertension.

Mesenchymal-epithelial signalling in tumour microenvironment: role of high-mobility group Box 1

Glucose deprivation, hypoxia and acidosis are characteristic features of the central core of most solid tumours. Myofibroblasts are stromal cells present in many such solid tumours, including those of the colon, and are known to be involved in all stages of tumour progression. HMGB1 is a nuclear protein with an important role in nucleosome stabilisation and gene transcription; it is also released from immune cells and is involved in the inflammatory process. We report that the microenvironmental condition of glucose deprivation is responsible for the active release of HMGB1 from various types of cancer cell lines (HT-29, MCF-7 and A549) under normoxic conditions. Recombinant HMGB1 (10 ng/ml) triggered proliferation in myofibroblast cells via activation of PI3K and MEK1/2. Conditioned medium collected from glucose-deprived HT-29 colon cancer cells stimulated the migration and invasion of colonic myofibroblasts, and these processes were significantly inhibited by immunoneutralising antibodies to HMGB1, RAGE and TLR4, together with specific inhibitors of PI3K and MEK1/2. Our data suggest that HMGB1 released from cancer cells under glucose deprivation is involved in stimulating colonic myofibroblast migration and invasion and that this occurs through the activation of RAGE and TLR4, resulting in the activation of the MAPK and PI3K signalling pathways. Thus, HMGB1 might be released by cancer cells in areas of low glucose in solid tumours with the resulting activation of myofibroblasts and is a potential therapeutic target to inhibit solid tumour growth.

High mobility group box 1-induced epithelial mesenchymal transition in human airway epithelial cells

Epithelial–mesenchymal transition (EMT) is implicated in bronchial remodeling and loss of lung function in chronic inflammatory airway diseases. Previous studies showed the involvement of the high mobility group box 1 (HMGB1) protein in the pathology of chronic pulmonary inflammatory diseases. However, the role of HMGB1 in EMT of human airway epithelial cells is still unclear. In this study, we used RNA sequencing to show that HMGB1 treatment regulated EMT-related gene expression in human primary-airway epithelial cells. The top five upregulated genes were SNAI2, FGFBP1, VIM, SPARC (osteonectin), and SERPINE1, while the downregulated genes included OCLN, TJP1 (ZO-1), FZD7, CDH1 (E-cadherin), and LAMA5. We found that HMGB1 induced downregulation of E-cadherin and ZO-1, and upregulation of vimentin mRNA transcription and protein translation in a dose-dependent manner. Additionally, we observed that HMGB1 induced AKT phosphorylation, resulting in GSK3β inactivation, cytoplasmic accumulation, and nuclear translocation of β-catenin to induce EMT in human airway epithelial cells. Treatment with PI3K inhibitor (LY294006) and β-catenin shRNA reversed HMGB1-induced EMT. Moreover, HMGB1 induced expression of receptor for advanced glycation products (RAGE), but not that of Toll-like receptor (TLR) 2 or TLR4, and RAGE shRNA inhibited HMGB1-induced EMT in human airway epithelial cells. In conclusion, we found that HMGB1 induced EMT through RAGE and the PI3K/AKT/GSK3β/β-catenin signaling pathway.

Perineural expression of high-mobility group box-1 contributes to long-lasting mechanical hypersensitivity via matrix metalloprotease-9 up-regulation in mice with painful peripheral neuropathy

High-mobility group box-1 (HMGB1) has been shown to be critical in the modulation of nociceptive transduction following a peripheral neuropathy. However, the precise role of peripherally expressed HMGB1 in neuropathic pain has yet to be fully elaborated. Following a partial sciatic nerve ligation (PSNL) in mice, a persistent ipsilateral up-regulation of HMGB1 was observed from 3 to 21 days after PSNL, in paralleled with a robust ipsilateral hind paw mechanical hypersensitivity. Increased HMGB1 was detected in both infiltrating macrophages and proliferating Schwann cells in the ipsilateral nerve 14 days following PSNL. Repeated perineural treatment with anti-HMGB1 antibody significantly ameliorated PSNL-induced mechanical hypersensitivity. Several pronociceptive molecules, including matrix metalloprotease-9 (MMP-9), tumor necrosis factor-α, interleukin-1β (IL-1β), and cyclooxygenase-2, were up-regulated in injured sciatic nerve 14 days following PSNL. Repeated perineural treatment with an anti-HMGB1 antibody significantly suppressed expression of MMP-9, but not other pronociceptive molecules. Perineural treatment with a selective MMP-9 inhibitor ameliorated PSNL-induced mechanical hypersensitivity. The current findings demonstrate that the maintenance of the neuropathic state following an injured nerve is dependent on the up-regulation of HMGB1 and MMP-9. Thus, blocking HMGB1 function in sciatic nerve could be a potent therapeutic strategy for the treatment of neuropathic pain. Increased peripheral high-mobility group box-1 (HMGB1) is involved in the modulation of nociceptive transduction following a peripheral neuropathy. Following nerve injury in mice, increased HMGB1 is detected in both infiltrating macrophages and proliferating Schwann cells in the ipsilateral nerve. Repeated perineural treatment with anti-HMGB1 antibody significantly ameliorates nerve injury-induced mechanical hypersensitivity, and suppresses expression of matrix metalloprotease-9 (MMP-9). The findings demonstrate that the maintenance of the neuropathic state following an injury nerve is dependent on the up-regulation of HMGB1 and MMP-9.

Role of high-mobility group box 1 in methamphetamine-induced activation and migration of astrocytes

Background

Mounting evidence has indicated that high-mobility group box 1 (HMGB1) is involved in cell activation and migration. Our previous study demonstrated that methamphetamine mediates activation of astrocytes via sigma-1 receptor (σ-1R). However, the elements downstream of σ-1R in this process remain poorly understood. Thus, we examined the molecular mechanisms involved in astrocyte activation and migration induced by methamphetamine.

Methods

The expression of HMGB1, σ-1R, and glial fibrillary acidic protein (GFAP) was examined by western blot and immunofluorescent staining. The phosphorylation of cell signaling pathways was detected by western blot, and cell migration was examined using a wound-healing assay in rat C6 astroglia-like cells transfected with lentivirus containing red fluorescent protein (LV-RFP) as well as in primary human astrocytes. The role of HMGB1 in astrocyte activation and migration was validated using a siRNA approach.

Results

Exposure of C6 cells to methamphetamine increased the expression of HMGB1 via the activation of σ-1R, Src, ERK mitogen-activated protein kinase, and downstream NF-κB p65 pathways. Moreover, methamphetamine treatment resulted in increased cell activation and migration in C6 cells and primary human astrocytes. Knockdown of HMGB1 in astrocytes transfected with HMGB1 siRNA attenuated the increased cell activation and migration induced by methamphetamine, thereby implicating the role of HMGB1 in the activation and migration of C6 cells and primary human astrocytes.

Conclusions

This study demonstrated that methamphetamine-mediated activation and migration of astrocytes involved HMGB1 up-regulation through an autocrine mechanism. Targeting HMGB1 could provide insights into the development of a potential therapeutic approach for alleviation of cell activation and migration of astrocytes induced by methamphetamine.