High Mobility Group Box 1 Secretion Research Articles

HMGB1: A New Target for Ischemic Stroke and Hemorrhagic Transformation.

Stroke in China is distinguished by its high rates of morbidity, recurrence, disability, and mortality. The ultra-early administration of rtPA is essential for restoring perfusion in acute ischemic stroke, though it concurrently elevates the risk of hemorrhagic transformation. High-mobility group box 1 (HMGB1) emerges as a pivotal player in neuroinflammation after brain ischemia and ischemia-reperfusion. Released passively by necrotic cells and actively secreted, including direct secretion of HMGB1 into the extracellular space and packaging of HMGB1 into intracellular vesicles by immune cells, glial cells, platelets, and endothelial cells, HMGB1 represents a prototypical damage-associated molecular pattern (DAMP). It is intricately involved in the pathogenesis of atherosclerosis, thromboembolism, and detrimental inflammation during the early phases of ischemic stroke. Moreover, HMGB1 significantly contributes to neurovascular remodeling and functional recovery in later stages. Significantly, HMGB1 mediates hemorrhagic transformation by facilitating neuroinflammation, directly compromising the integrity of the blood-brain barrier, and enhancing MMP9 secretion through its interaction with rtPA. As a systemic inflammatory factor, HMGB1 is also implicated in post-stroke depression and an elevated risk of stroke-associated pneumonia. The role of HMGB1 extends to influencing the pathogenesis of ischemia by polarizing various subtypes of immune and glial cells. This includes mediating excitotoxicity due to excitatory amino acids, autophagy, MMP9 release, NET formation, and autocrine trophic pathways. Given its multifaceted role, HMGB1 is recognized as a crucial therapeutic target and prognostic marker for ischemic stroke and hemorrhagic transformation. In this review, we summarize the structure and redox properties, secretion and pathways, regulation of immune cell activity, the role of pathophysiological mechanisms in stroke, and hemorrhage transformation for HMGB1, which will pave the way for developing new neuroprotective drugs, reduction of post-stroke neuroinflammation, and expansion of thrombolysis time window.

Nuclear GAPDH in cortical microglia mediates cellular stress-induced cognitive inflexibility.

We report a mechanism that underlies stress-induced cognitive inflexibility at the molecular level. In a mouse model under subacute cellular stress in which deficits in rule shifting tasks were elicited, the nuclear glyceraldehyde dehydrogenase (N-GAPDH) cascade was activated specifically in microglia in the prelimbic cortex. The cognitive deficits were normalized with a pharmacological intervention with a compound (the RR compound) that selectively blocked the initiation of N-GAPDH cascade without affecting glycolytic activity. The normalization was also observed with a microglia-specific genetic intervention targeting the N-GAPDH cascade. At the mechanistic levels, the microglial secretion of High-Mobility Group Box (HMGB), which is known to bind with and regulate the NMDA-type glutamate receptors, was elevated. Consequently, the hyperactivation of the prelimbic layer 5 excitatory neurons, a neural substrate for cognitive inflexibility, was also observed. The upregulation of the microglial HMGB signaling and neuronal hyperactivation were normalized by the pharmacological and microglia-specific genetic interventions. Taken together, we show a pivotal role of cortical microglia and microglia-neuron interaction in stress-induced cognitive inflexibility. We underscore the N-GAPDH cascade in microglia, which causally mediates stress-induced cognitive alteration.

Hypochlorous acid derived from microglial myeloperoxidase could mediate high-mobility group box 1 release from neurons to amplify brain damage in cerebral ischemia–reperfusion injury

Myeloperoxidase (MPO) plays critical role in the pathology of cerebral ischemia–reperfusion (I/R) injury via producing hypochlorous acid (HOCl) and inducing oxidative modification of proteins. High-mobility group box 1 (HMGB1) oxidation, particularly disulfide HMGB1 formation, facilitates the secretion and release of HMGB1 and activates neuroinflammation, aggravating cerebral I/R injury. However, the cellular sources of MPO/HOCl in ischemic brain injury are unclear yet. Whether HOCl could promote HMGB1 secretion and release remains unknown. In the present study, we investigated the roles of microglia-derived MPO/HOCl in mediating HMGB1 translocation and secretion, and aggravating the brain damage and blood-brain barrier (BBB) disruption in cerebral I/R injury. In vitro, under the co-culture conditions with microglia BV cells but not the single culture conditions, oxygen–glucose deprivation/reoxygenation (OGD/R) significantly increased MPO/HOCl expression in PC12 cells. After the cells were exposed to OGD/R, MPO-containing exosomes derived from BV2 cells were released and transferred to PC12 cells, increasing MPO/HOCl in the PC12 cells. The HOCl promoted disulfide HMGB1 translocation and secretion and aggravated OGD/R-induced apoptosis. In vivo, SD rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus different periods of reperfusion. Increased MPO/HOCl production was observed at the reperfusion stage, accomplished with enlarged infarct volume, aggravated BBB disruption and neurological dysfunctions. Treatment of MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH) and HOCl scavenger taurine reversed those changes. HOCl was colocalized with cytoplasm transferred HMGB1, which was blocked by taurine in rat I/R-injured brain. We finally performed a clinical investigation and found that plasma HOCl concentration was positively correlated with infarct volume and neurological deficit scores in ischemic stroke patients. Taken together, we conclude that ischemia/hypoxia could activate microglia to release MPO-containing exosomes that transfer MPO to adjacent cells for HOCl production; Subsequently, the production of HOCl could mediate the translocation and secretion of disulfide HMGB1 that aggravates cerebral I/R injury. Furthermore, plasma HOCl level could be a novel biomarker for indexing brain damage in ischemic stroke patients.

Antiseptic Functions of CGK012 against HMGB1-Mediated Septic Responses.

High mobility group box 1 (HMGB1), a protein with important functions, has been recognized as a potential therapeutic target for the treatment of sepsis. One possible mechanism for this is that inhibiting HMGB1 secretion can exert antiseptic effects, which can restore the integrity of the vascular barrier. (7S)-(+)-cyclopentyl carbamic acid 8,8-dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (CGK012) is a newly synthesized pyranocoumarin compound that could function as a novel small-molecule inhibitor of the Wnt/β-catenin signaling pathway. However, no studies have yet determined the effects of CGK012 on sepsis. We investigated the potential of CGK012 to attenuate the excessive permeability induced by HMGB1 and enhance survival rates in a mouse model of sepsis with reduced HMGB1 levels following lipopolysaccharide (LPS) treatment. In both LPS-stimulated human endothelial cells and a mouse model exhibiting septic symptoms due to cecal ligation and puncture (CLP), we assessed proinflammatory protein levels and tissue damage biomarkers as indicators of reduced vascular permeability. CGK012 was applied after induction in human endothelial cells exposed to LPS and the CLP-induced mouse model of sepsis. CGK012 effectively mitigated excessive permeability and suppressed HMGB1 release, resulting in improved vascular stability, decreased mortality, and enhanced histological conditions in the mouse model of CLP-induced sepsis. In conclusion, our findings indicate that CGK012 treatment in mice with CLP-induced sepsis diminished HMGB1 release and increased the survival rate, suggesting its potential as a pharmaceutical intervention for sepsis.

The HMGB1-RAGE axis in nucleus accumbens facilitates cocaine-induced conditioned place preference via modulating microglial activation.

Repeated exposure to cocaine induces microglial activation. Cocaine exposure also induces a release of high mobility group box-1 (HMGB1) from neurons into the extracellular space in the nucleus accumbens (NAc). HMGB1 is an important late inflammatory mediator of microglial activation. However, whether the secretion of HMGB1 acts on microglia or contributes to cocaine addiction is largely unknown. Rats were trained by intraperitoneal cocaine administration and cocaine-induced conditioned place preference (CPP). Expression of HMGB1 was regulated by viral vectors. Activation of microglia was inhibited by minocycline. Interaction of HMGB1 and the receptor for advanced glycation end products (RAGE) was disrupted by peptide. Cocaine injection facilitated HMGB1 signaling, together with the delayed activation of microglia concurrently in the NAc. Furthermore, the inhibition of HMGB1 or microglia activation attenuated cocaine-induced CPP. Box A, a specific antagonist to interrupt the interaction of HMGB1 and RAGE, abolished the expression of cocaine reward memory. Meanwhile, the inhibition of HMGB1-RAGE interaction suppressed cocaine-induced microglial activation, as well as the consolidation of cocaine-induced memory. All above results suggest that the neural HMGB1 induces activation of microglia through RAGE, which contributes to the consolidation of cocaine reward memory. These findings offer HMGB1-RAGE axis as a new target for the treatment of drug addiction.

GLUT1 mediates the release of HMGB1 from airway epithelial cells in mixed granulocytic asthma

Asthma is quite heterogenous and can be categorized as eosinophilic, mixed granulocytic (presence of both eosinophils and neutrophils in the airways) and neutrophilic. Clinically, mixed granulocytic asthma (MGA) often tends to be severe and requires large doses of corticosteroids. High mobility group box 1 (HMGB1) is one of the epithelium-derived alarmins that contributes to type 2 inflammation and asthma. This study was aimed to investigate the role of glucose transporter 1 (GLUT1) in modulation of airway epithelial HMGB1 production in MGA. Induced sputum and bronchial biopsy specimens were obtained from healthy subjects and asthma patients. BALB/c mice, the airway epithelial cell line BEAS-2B, or primary human bronchial epithelial cells (HBECs) were immunized with allergens. Intracellular and extracellular HMGB1 were both detected. The role of GLUT1 was assessed by using a pharmacological antagonist BAY876. MGA patients have a significant higher sputum HMGB1 level than the health and subjects with other inflammatory phenotypes. Nuclear-to-cytoplasmic translocation of HMGB1 was also observed in the bronchial epithelia. Allergen exposure markedly induced GLUT1 expression in murine lungs and cultured epithelial cells. Pharmacological antagonism of GLUT1 with BAY876 dramatically decreased airway hyperresponsiveness, neutrophil and eosinophil accumulation, as well as type 2 inflammation in murine models of MGA. Besides, the allergen-induced up-regulation of HMGB1 was also partly recovered by BAY876, accompanied by inhibited secretion into the airway lumen. In vitro, treatment with BAY876 relieved the allergen-induced over-expression and secretion of HMGB1 in airway epithelia. Taken together, our data indicated that GLUT1 mediates bronchial epithelial HMGB1 release in MGA.

Ginseng (Panax ginseng) leaf extract modulates the expression of heme oxygenase-1 to attenuate osteoclast differentiation

Osteoporosis is an aging disease characterized by an imbalance between bone formation and resorption. However, drugs that inhibit bone resorption have various adverse effects. Ginseng (Panax ginseng), a prominent herbal medicine in East Asia for >2000 years, is renowned for its manifold beneficial properties, including antioxidant, anti-cancer, anti-diabetic, and anti-adipogenic activities. Despite its long history of use, the pharmacological functions of ginseng leaves are not yet fully comprehended. In this study, we evaluated the potential effects of ginseng leaf extract (GLE) on receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation in RAW264.7 macrophage cells. Tartrate-resistant acid phosphatase (TRAP) staining revealed that GLE had significant anti-osteoclastogenic activity. GLE significantly reduced mRNA levels of osteoclast differentiation markers including TRAP, nuclear factor of activated T cell cytoplasmic 1, and cathepsin K. It also suppressed the production of reactive oxygen species (ROS) and secretion of high mobility group box-1 (HMGB1) in RANKL-treated RAW264.7 cells. In addition, GLE upregulated dose- and time-dependently the expression of heme oxygenase-1 (HO-1), eventually suppressing ROS production and HMGB1 secretion. This effects of GLE were significantly reversed by Tin Protoporphyrin IX dichloride, an inhibitor of HO-1, and HO-1 shRNA, indicating that HO-1 potently inhibits RANKL-induced osteoclast differentiation by inhibiting ROS production and HMGB1 secretion. Taken together, these observations suggest that GLE could have therapeutic potential as a natural product-derived medicine for the treatment of bone disorders.

Inhibition of xanthine oxidase by allopurinol suppresses HMGB1 secretion and ameliorates experimental asthma

BackgroundExtracellular high mobility group box 1 (HMGB1) is a key mediator in driving allergic airway inflammation and contributes to asthma. Yet, mechanism of HMGB1 secretion in asthma is poorly defined. Pulmonary metabolic dysfunction is recently recognized as a driver of respiratory pathology. However, the altered metabolic signatures and the roles of metabolic to allergic airway inflammation remain unclear. MethodsMale C57BL/6 J mice were sensitized and challenged with toluene diisocyanate (TDI) to generate a chemically induced asthma model. Pulmonary untargeted metabolomics was employed. According to results, mice were orally administered allopurinol, a xanthine oxidase (XO) inhibitor. Human bronchial epithelial cells (16HBE) were stimulated by TDI-human serum albumin (HSA). ResultsWe identified the purine metabolism was the most enriched pathway in TDI-exposed lungs, corresponding to the increase of xanthine and uric acid, products of purine degradation mediated by XO. Inhibition of XO by allopurinol ameliorates TDI-induced oxidative stress and DNA damage, mixed granulocytic airway inflammation and Th1, Th2 and Th17 immunology as well as HMGB1 acetylation and secretion. Mechanistically, HMGB1 acetylation was caused by decreased activation of the NAD+-sirtuin 1 (SIRT1) axis triggered by hyperactivation of the DNA damage sensor poly (ADP-ribose)-polymerase 1 (PARP-1). This was rescued by allopurinol, PARP-1 inhibitor or supplementation with NAD+ precursor in a SIRT1-dependent manner. Meanwhile, allopurinol attenuated Nrf2 defect due to SIRT1 inactivation to help ROS scavenge. ConclusionsWe demonstrated a novel regulation of HMGB1 acetylation and secretion by purine metabolism that is critical for asthma onset. Allopurinol may have therapeutic potential in patients with asthma.

Starvation insult induces the translocation of high mobility group box 1 to cytosolic compartments in glioma.

High mobility group box 1 (HMGB1) is a highly conserved and ubiquitous nuclear protein in eukaryotic cells. In response to stress, it transfers from the nucleus to the cytoplasm and finally, to the extracellular matrix, participating in inflammation and carcinogenesis. Increased HMGB1 protein levels are frequently associated with the reduced survival of patients with glioma. HMGB1 plays contextual roles depending on its subcellular localization. However, the mechanisms underlying its subcellular localization and secretion remain unclear. In the present study, the subcellular localization and secretion of HMGB1 in starved glioma cells were investigated using immunofluorescence microscopy, enzyme‑linked immunosorbent assay, subcellular fractionation, western blotting and immunoelectron microscopy. The results demonstrated that starvation induced HMGB1 translocation from the nucleus to the cytoplasm and finally, to the extracellular milieu in glioma cells. HMGB1 was localized in the mitochondria, endoplasmic reticulum (ER), peroxisomes, autophagosomes, lysosomes, endosomes and the cytoskeleton. Immunoelectron microscopy confirmed that HMGB1 was present within or around cytosolic compartments. Subcellular fractionation further demonstrated that HMGB1 transferred to membrane‑bound compartments. In addition, HMGB1 was localized to specific contact areas between the ER and mitochondria, known as mitochondria‑associated membranes. On the whole, the results of the present study suggest that starvation induces HMGB1 secretion, which can be inhibited through the suppression of autophagy. Starvation insult induces HMGB1 translocation to the cytosolic compartments of glioma cells, and autophagy may be involved in the extracellular secretion of HMGB1 in starved glioma cells.

SFI Reduces the Nucleocytoplasmic Transportation of HMGB1 by Upregulating HDAC3 in LPS-induced RAW264.7 Cells

Shenfu injection (SFI) is widely used for treating endotoxin shock in China. In the present study, to investigate the anti-inflammatory effects of SFI and further explored the potential mechanism of HMGB1 nuclear translocation, we established a vitro cell model provoked by lipopolysaccharide (LPS), observed nucleocytoplasmic translocation of high mobility group box 1 (HMGB1) and the relationship between histone deacetylase 3 (HDAC3) and HMGB1 under SFI intervention. The results showed that SFI upregulated the transcription and expression of HDAC3 in RAW264.7 cells, inhibited the nuclear to cytoplasmic translocation of HMGB1 and its subsequent extracellular release, and depressed the secretion of HMGB1, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). However, targeted knockdown of HDAC3 induced an increase in HMGB1 translocation to the cytoplasm, and HMGB1 localization was not altered significantly following LPS stimulation. SFI failed to reverse the abnormal localization of HMGB1. These results suggested that SFI may inhibit LPS-induced HMGB1 nuclear translocation in RAW264.7 cells through upregulating HDAC3 expression, thereby inhibiting its downstream pathway and suppressing inflammatory response.

Cisplatin Dependent Secretion of Immunomodulatory High Mobility Group Box 1 (HMGB1) Protein from Lung Cancer Cells.

High mobility group box 1 (HMGB1) is secreted from activated immune cells, necrotic cells, and certain cancers. Previous studies have reported that different patterns of post-translational modification, particularly acetylation and oxidation, mediate HMGB1 release and confer distinct extracellular HMGB1 signaling activity. Here we report that cisplatin but not carboplatin induces secretion of HMGB1 from human A549 non-small cell lung cancer (NSCLC) cells. Cisplatin-mediated HMGB1 secretion was dose-dependent and was regulated by nuclear exportin 1 (XPO1) also known as chromosomal maintenance 1 (CRM1) rather than adenosine diphosphate (ADP)-ribosylation, acetylation, or oxidation. HMGB1, as well as lysine acetylation and cysteine disulfide oxidation of secreted HMGB1, were monitored by sensitive and specific assays using immunoprecipitation, stable isotope dilution, differential alkylation, and nano liquid chromatography parallel reaction monitoring/high-resolution mass spectrometry (nano-LC-PRM/HRMS). A major fraction of the HMGB1 secreted by low-dose cisplatin treatment of A549 NSCLC cells was found to be in the fully reduced form. In contrast, mainly oxidized forms of HMGB1 were secreted by dimethyl sulfoxide (DMSO)-mediated apoptosis. These findings suggest that inhibition of XPO1 could potentiate the anti-tumor activity of cisplatin by increasing the nuclear accumulation of HMGB1 protein, an inhibitor of cisplatin DNA-adduct repair. Furthermore, low-dose cisplatin therapy could modulate the immune response in NSCLC through the established chemokine activity of extracellular reduced HMGB1. This could potentially enhance the efficacy of subsequent immunotherapy treatment.

HMGB1, a potential regulator of tumor microenvironment in KSHV-infected endothelial cells.

High-mobility group box 1 (HMGB1) is a protein that binds to DNA and participates in various cellular processes, including DNA repair, transcription, and inflammation. It is also associated with cancer progression and therapeutic resistance. Despite its known role in promoting tumor growth and immune evasion in the tumor microenvironment, the contribution of HMGB1 to the development of Kaposi's sarcoma (KS) is not well understood. We investigated the effect of HMGB1 on KS pathogenesis using immortalized human endothelial cells infected with Kaposi's sarcoma-associated human herpes virus (KSHV). Our results showed that a higher amount of HMGB1 was detected in the supernatant of KSHV-infected cells compared to that of mock-infected cells, indicating that KSHV infection induced the secretion of HMGB1 in human endothelial cells. By generating HMGB1 knockout clones from immortalized human endothelial cells using CRISPR/Cas9, we elucidated the role of HMGB1 in KSHV-infected endothelial cells. Our findings indicate that the absence of HMGB1 did not induce lytic replication in KSHV-infected cells, but the cell viability of KSHV-infected cells was decreased in both 2D and 3D cultures. Through the antibody array for cytokines and growth factors, CXCL5, PDGF-AA, G-CSF, Emmprin, IL-17A, and VEGF were found to be suppressed in HMGB1 KO KSHV-infected cells compared to the KSHV-infected wild-type control. Mechanistically, phosphorylation of p38 would be associated with transcriptional regulation of CXCL5, PDGF-A and VEGF. These observations suggest that HMGB1 may play a critical role in KS pathogenesis by regulating cytokine and growth factor secretion and emphasize its potential as a therapeutic target for KS by modulating the tumor microenvironment.

PAG neuronal NMDARs activation mediated morphine-induced hyperalgesia by HMGB1-TLR4 dependent microglial inflammation

Morphine is one of the most effective and widely used analgesic drugs. However, chronic morphine use caused opioid-induced hyperalgesia (OIH). The development of OIH limits the use of morphine. The mechanisms of OIH are not fully understood. Toll-like receptor4 (TLR4) and glutamate receptors in the periaqueductal gray (PAG) are critical in OIH, however, the association between TLR4 and N-methyl-D-aspartate Receptors (NMDARs) activation in PAG remains unclear. Microglia activation, increased TLR4/p65 nuclear factor-kappa B (p65 NF-κB) and proinflammatory cytokines in microglia, and phosphorylation of NMDAR1 subunit (NR1) and NMDAR2B subunit (NR2B) in neurons were observed in PAG of OIH mice. Up-regulations of TLR4/p65 NF-κB and proinflammatory cytokines (IL-1β, IL-6, TNF-α) in BV2 cells were prevented by inhibiting and knocking down TLR4. By inhibiting myeloid differentiation factor 2 (MD2) and knocking down the High-mobility group box 1 (HMGB1), we found that morphine activated TLR4 by HMGB1 but not MD2. We co-cultured Neuro-2a (N2A) with BV2 microglial cell line and found that instead of directly phosphorylating NMDAR subunits, morphine increased the phosphorylation of NR1 and NR2B by inducing TLR4-mediated microglia inflammation. Knocking TLR4 out of PAG by Lentivirus-GFP-TLR4 shRNA reversed these changes and relieved OIH. Our findings suggested that the secretion of HMGB1 induced by morphine-activated TLR4 in microglia, and the proinflammatory factors released by activated microglia phosphorylated NR1 and NR2B of adjacent neurons, induced increased neuronal excitability. In conclusion, TLR4/NMDARs in PAG were involved in the development and maintenance of OIH and supported novel strategies for OIH treatment.

Knockdown of HMGB1 inhibits the crosstalk between oral squamous cell carcinoma cells and tumor-associated macrophages.

Tumor-associated macrophages (TAMs), the major component of the tumor microenvironment (TME), play distinctly different roles in different tumors. High mobility group box 1 (HMGB1), a nonhistone protein in the nucleus, can perform functions during inflammation and cancers. However, the role of HMGB1 in the crosstalk between oral squamous cell carcinoma (OSCC) cells and TAMs remains unclear. Here, we established a coculture system of TAMs and OSCC cells to explore the bidirectional effect and potential mechanism of HMGB1 in OSCC cell-TAM interactions. Our results showed that HMGB1 was significantly upregulated in OSCC tissues and positively associated with tumor progression, immune cell infiltration and macrophage polarization. Then, knocking down HMGB1 in OSCC cells inhibited the recruitment and polarization of cocultured TAMs. Moreover, the knockdown of HMGB1 in macrophages not only suppressed polarization, but also inhibited cocultured OSCC cell proliferation, migration and invasion in vitro and in vivo. Mechanistically, macrophages secreted higher levels of HMGB1 than OSCC cells, and dampening endogenous HMGB1 reduced HMGB1 secretion. Both OSCC cell-generated and macrophage-endogenous HMGB1 may regulate TAM polarization by promoting receptor TLR4 expression and NF-κB/p65 activation and enhancing IL-10/TGF-β expression. HMGB1 in OSCC cells may regulate macrophage recruitment via IL-6/STAT3. In addition, TAM-derived HMGB1 may affect aggressive phenotypes of cocultured OSCC cells by regulating the immunosuppressive microenvironment through the IL-6/STAT3/PD-L1 and IL-6/NF-κB/MMP-9 pathways. In conclusion, HMGB1 may regulate the crosstalk between OSCC cells and TAMs, including modulating macrophage polarization and attraction, enhancing cytokine secretion, and remodeling and creating an immunosuppressive TME to further affect OSCC progression.

Transcription and Secretion of Interleukin-1β and HMGB1 in Keratinocytes Exposed to Stimulations Mimicking Common Inflammatory Damages

Objective: Interleukin-1β (IL-1β) and high-mobility group box 1 (HMGB1) are widely known damage-associated molecular patterns (DAMPs). However, their expression and secretion in different skin diseases, especially in inflammatory skin disorders, remain to be further elucidated. This study was performed to explore and compare the transcriptional and secretory levels of IL-1β and HMGB1 in keratinocytes under 3 types of stimulation: ultraviolet B (UVB) irradiation; co-stimulation by tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) (simulation of T helper 1 cell inflammatory challenge); and psoriasis-like stimulation by M5, a mixture of 5 proinflammatory cytokines. Methods: We used quantitative reverse-transcription polymerase chain reaction to determine the transcription levels of IL-1β and HMGB1. Western blotting and enzyme-linked immunosorbent assay were used to detect the secretion levels of IL-1β and HMGB1. The results were statistically analyzed by t test. Results: A rapid transcriptional and secretory response of IL-1β from keratinocytes occurred in all 3 types of stimulation mimicking common inflammatory environments (P < 0.05). Transcription of HMGB1 was inhibited in all 3 types of stimulation (P < 0.05), but secretion was increased after exposure to UVB irradiation and co-stimulation by TNF-α and IFN-γ (P < 0.05). We observed no change in the secretion level of HMGB1 after treatment with M5 (P = 0.196). Conclusion: IL-1β is a critical cytokine for the immunomodulatory functions of keratinocytes in inflammatory responses. In this study, keratinocytes restrained transcription of HMGB1 when the secretion of HMGB1 was induced in certain stimulations (eg, by UVB exposure or stimulation by TNF-α and IFN-γ).

PARP1 Activation Induces HMGB1 Secretion Promoting Intestinal Inflammation in Mice and Human Intestinal Organoids.

Extracellular High-mobility group box 1 (HMGB1) contributes to the pathogenesis of inflammatory disorders, including inflammatory bowel diseases (IBD). Poly (ADP-ribose) polymerase 1 (PARP1) has been recently reported to promote HMGB1 acetylation and its secretion outside cells. In this study, the relationship between HMGB1 and PARP1 in controlling intestinal inflammation was explored. C57BL6/J wild type (WT) and PARP1-/- mice were treated with DSS to induce acute colitis, or with the DSS and PARP1 inhibitor, PJ34. Human intestinal organoids, which are originated from ulcerative colitis (UC) patients, were exposed to pro-inflammatory cytokines (INFγ + TNFα) to induce intestinal inflammation, or coexposed to cytokines and PJ34. Results show that PARP1-/- mice develop less severe colitis than WT mice, evidenced by a significant decrease in fecal and serum HMGB1, and, similarly, treating WT mice with PJ34 reduces the secreted HMGB1. The exposure of intestinal organoids to pro-inflammatory cytokines results in PARP1 activation and HMGB1 secretion; nevertheless, the co-exposure to PJ34, significantly reduces the release of HMGB1, improving inflammation and oxidative stress. Finally, HMGB1 release during inflammation is associated with its PARP1-induced PARylation in RAW264.7 cells. These findings offer novel evidence that PARP1 favors HMGB1 secretion in intestinal inflammation and suggest that impairing PARP1 might be a novel approach to manage IBD.

Gankyrin-mediated interaction between cancer cells and tumor-associated macrophages facilitates prostate cancer progression and androgen deprivation therapy resistance

ABSTRACT Increasing evidence reveals that the interaction between tumor cells and tumor-associated macrophages (TAMs) facilitates the progression of prostate cancer, but the related mechanisms remained unclear. This study determined how gankyrin, a component of the 19S regulatory complex of the 26S proteasome, regulates the progression and androgen deprivation therapy (ADT) resistance of prostate cancer through tumor cell–TAM interactions. In vitro functional experiments and in vivo subcutaneous tumor models were used to explore the biological role and molecular mechanisms of gankyrin in prostate cancer cell–TAM interactions. 234 prostate cancer patients were randomly divided into training and validation cohorts to examine the prognostic value of gankyrin through immunohistochemistry (IHC) and statistical analyses, and high gankyrin expression was correlated with poor prognosis. In addition, gankyrin facilitated the progression and ADT resistance of prostate cancer. Mechanistically, gankyrin recruited and upregulated non–POU-domain–containing octamer-binding protein (NONO) expression, resulting in increased androgen receptor (AR) expression. AR then bound to the high-mobility group box 1 (HMGB1) promoter to trigger HMGB1 transcription, expression, and secretion. Moreover, HMGB1 was found to promote the recruitment and activation of TAMs, which secrete IL-6 to reciprocally promote prostate cancer progression, ADT resistance and gankyrin expression via STAT3, resulting in formation of a gankyrin/NONO/AR/HMGB1/IL-6/STAT3 positive feedback loop. Furthermore, targeting the interaction between tumor cells and TAMs by blocking this loop inhibited ADT resistance in a tumor xenograft model. Taken together, the data show that gankyrin serves as a reliable prognostic indicator and therapeutic target for prostate cancer patients.

Upregulation of HMGB1 in tumor-associated macrophages induced by tumor cell-derived lactate further promotes colorectal cancer progression

BackgroundLactate accumulation leads to an acidic tumor microenvironment (TME), in turn promoting colorectal cancer (CRC) progression. Tumor-associated macrophages (TAMs) are the predominant cells in TME. This study aimed to reveal the regulation mechanism of CRC cell-derived lactate on TAMs and explore the mechanism underlying lactate accumulation-induced aggravation in CRC.MethodsCell growth and metastasis were evaluated by colony formation, Transwell, and wound healing assays. Western blot and RT-qPCR were applied to determine the protein and mRNA expression. Flow cytometry was used to analyze the polarization state and apoptotic rate of macrophages induced in THP-1 cells. The lactate in the cell supernatant was quantified using an ELISA kit. Immunofluorescence was performed to visualize the location of High Mobility Group Box 1 (HMGB1). H&E and Ki67 staining assays were used to assess tumorigenesis in nude mice bearing ectopic tumors.ResultsCell growth and metastasis were promoted in the hypoxic CRC cells. The hypoxic cell supernatant stimulated the M2-type polarization of macrophages. The lactate level increased in hypoxic cancer cells. However, the inhibition of lactate using 3-hydroxy-butyrate (3-OBA) reversed the effects of hypoxia. Also, macrophages showed no promoting effect on cancer cell growth and migration in the presence of 3-OBA. HMGB1 was secreted into the extracellular space of lactate-induced macrophages, further enhancing the malignant behaviors of cancer cells. ERK, EMT, and Wnt signaling pathways were activated in cancer cells due to HMGB1 upregulation.ConclusionsThe lactate metabolized by cancer cells stimulated M2 polarization and HMGB1 secretion by macrophages, aggravating the carcinogenic behaviors of cancer cells.

SARS-CoV-2 Infection Induces HMGB1 Secretion Through Post-Translational Modification and PANoptosis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection induces excessive pro-inflammatory cytokine release and cell death, leading to organ damage and mortality. High-mobility group box 1 (HMGB1) is one of the damage-associated molecular patterns that can be secreted by pro-inflammatory stimuli, including viral infections, and its excessive secretion levels are related to a variety of inflammatory diseases. Here, the aim of the study was to show that SARS-CoV-2 infection induced HMGB1 secretion via active and passive release. Active HMGB1 secretion was mediated by post-translational modifications, such as acetylation, phosphorylation, and oxidation in HEK293E/ACE2-C-GFP and Calu-3 cells during SARS-CoV-2 infection. Passive release of HMGB1 has been linked to various types of cell death; however, we demonstrated for the first time that PANoptosis, which integrates other cell death pathways, including pyroptosis, apoptosis, and necroptosis, is related to passive HMGB1 release during SARS-CoV-2 infection. In addition, cytoplasmic translocation and extracellular secretion or release of HMGB1 were confirmed via immunohistochemistry and immunofluorescence in the lung tissues of humans and angiotensin-converting enzyme 2-overexpressing mice infected with SARS-CoV-2.

Posttranslational S-nitrosylation modification regulates HMGB1 secretion and promotes its proinflammatory and neurodegenerative effects.

SUMMARYNuclear protein high-mobility group box 1 (HMGB1) can be actively secreted by activated immune cells and functions as a proinflammatory cytokine. Regulation of HMGB1 secretion is critical for treatment of HMGB1-mediated inflammation and related diseases. This study demonstrates that S-nitrosylation (SNO; the covalent binding of nitric oxide [NO] to cysteine thiols) by inducible nitric oxide synthase (iNOS)-derived NO at Cys106 is essential and sufficient for inflammation-elicited HMGB1 secretion. iNOS deletion or inhibition or Cys106Ser mutation prevents lipopolysaccharide (LPS)- and/or poly(I:C)-elicited HMGB1 secretion. NO donors induce SNO of HMGB1 and reproduce inflammogen-triggered HMGB1 secretion. SNO of HMGB1 promotes its proinflammatory and neurodegenerative effects. Intranigral HMGB1 injection induces chronic microglial activation, dopaminergic neurodegeneration, and locomotor deficits, the key features of Parkinson’s disease (PD), in wild-type, but not Mac1 (CD11b/CD18)-deficient, mice. This study indicates pivotal roles for SNO modification in HMGB1 secretion and HMGB1-Mac1 interaction for inflammatory neurodegeneration, identifying a mechanistic basis for PD development.