Ethyl pyruvate reduces organic dust-induced airway inflammation by targeting HMGB1-RAGE signaling

Targeting non-classical autophagy-dependent ferroptosis and the subsequent HMGB1/TfR1 feedback loop accounts for alleviating solar dermatitis by senkyunolide I

Given the substantial risks associated with ultraviolet B (UVB) radiation-induced solar dermatitis, enhancing current strategies to combat UVB regarding skin diseases is imperative. The cross-talk between ferroptosis and inflammation has been proven to be an essential factor in UVB-induced solar dermatitis, whereas detailed process of how their interaction contributes to this remains unclear. Therefore, further investigation of ferroptosis-mediated processes and identification of corresponding inhibitory approaches hold promise for repairing skin damage. Senkyunolide I (Sen I), a bioactive component mainly extracted from the traditional Chinese medicinal plants, Ligusticum chuanxiong Hort. and Angelica sinensis (Oliv.) Diels, has demonstrated efficacy in combating oxidative stress and inflammation. In this study, we utilized UVB-irradiated HaCaT cells as an in vitro model and C57BL/6J mice as an in vivo model of solar dermatitis. Our findings revealed the pivotal roles of autophagy and ferroptosis in inducing skin inflammation, particularly emphasizing the activation of ferroptosis through macroautophagy. Surprisingly, this mechanism operated independently of ferritinophagy, a classical autophagy-driven ferroptosis pathway. Instead, our results highlighted Transferrin Receptor 1 (TfR1), tightly controlled by autophagy, as a crucial mediator of ferroptosis execution and amplifier of subsequent lethal signals. Furthermore, extracellular High Mobility Group Box 1 protein (HMGB1), released following UVB-induced ferroptotic cells from activated autophagic flux, initiated a feedback loop with TfR1, propagating ferroptosis to neighboring cells and exacerbating damage. Remarkably, Sen I administration showed a significant protective effect against UVB damage in both in vitro and in vivo models by interrupting this cascade. Consequently, we have illuminated a novel therapeutic pathway post-UVB exposure and identified Sen I as a potent natural molecule that safeguarded against UVB-induced solar dermatitis by suppressing the autophagy-ferroptosis-HMGB1-TfR1 axis, highlighting a new frontier in photoprotection.

Effect of epithelial-specific MyD88 signaling pathway on airway inflammatory response to organic dust exposure

The Toll-like receptor (TLR) adaptor protein MyD88 is integral to airway inflammatory response to microbial-enriched organic dust extract (ODE) exposures. ODE-induced airway neutrophil influx and release of pro-inflammatory cytokines was essentially abrogated in global MyD88-deficient mice, yet these mice demonstrate an increase in airway epithelial cell mucin expression. To further elucidate the role of MyD88-dependent responses specific to lung airway epithelial cells in response to ODE in vivo, the surfactant protein C protein (SPC) Cre+ embryologic expressing airway epithelial cells floxed for MyD88 to disrupt MyD88 signaling were utilized. The inducible club cell secretory protein (CCSP) Cre+, MyD88 floxed, were also developed. Using an established protocol, mice were intranasally instilled with ODE or saline once or daily up to 3 weeks. Mice with MyD88-deficient SPC+ lung epithelial cells exhibited decreased neutrophil influx following ODE exposure once and repetitively for 1 week without modulation of classic pro-inflammatory mediators including tumor necrosis factor (TNF)-α, interleukin (IL)-6, and neutrophil chemoattractants. This protective response was lost after 3 weeks of repetitive exposure. ODE-induced Muc5ac mucin expression at 1 week was also reduced in MyD88-deficient SPC+ cells. Acute ODE-induced IL-33 was reduced in MyD88-deficient SPC+ cells whereas serum IgE levels were increased at one week. In contrast, mice with inducible MyD88-deficient CCSP+ airway epithelial cells demonstrated no significant difference in experimental indices following ODE exposure. Collectively, these findings suggest that MyD88-dependent signaling targeted to all airway epithelial cells plays an important role in mediating neutrophil influx and mucin production in response to acute organic dust exposures.

High mobility group box-1: a potential therapeutic target for allergic rhinitis

Allergic rhinitis (AR) is a prevalent chronic inflammatory disease of the nasal mucosa primarily characterized by symptoms, such as nasal itching, sneezing, runny nose, and nasal congestion. It has a high recurrence rate and low cure rate, with a lack of effective drugs for treatment. The current approach to management focuses on symptom control. High mobility group box-1 (HMGB1) is a highly conserved non-histone protein widely present in the nucleus of eukaryotes. It is recognized as a proinflammatory agent, and recent studies have demonstrated its close association with AR. Here, we will elaborate the role and mechanism of HMGB1 in AR, so as to reveal the potential value of HMGB1 in the occurrence and development of AR, and provide a new target for clinical research on the treatment of AR.

Biological impact of sequential exposures to allergens and ultrafine particle-rich combustion aerosol on human bronchial epithelial BEAS-2B cells at the air liquid interface

The prevalence of allergic diseases is constantly increasing since few decades. Anthropogenic ultrafine particles (UFPs) and allergenic aerosols is highly involved in this increase; however, the underlying cellular mechanisms are not yet understood. Studies observing these effects focused mainly on singular in vivo or in vitro exposures of single particle sources, while there is only limited evidence on their subsequent or combined effects. Our study aimed at evaluating the effect of subsequent exposures to allergy-related anthropogenic and biogenic aerosols on cellular mechanism exposed at air-liquid interface (ALI) conditions. Bronchial epithelial BEAS-2B cells were exposed to UFP-rich combustion aerosols for 2 h with or without allergen pre-exposure to birch pollen extract (BPE) or house dust mite extract (HDME). The physicochemical properties of the generated particles were characterized by state-of-the-art analytical instrumentation. We evaluated the cellular response in terms of cytotoxicity, oxidative stress, genotoxicity, and in-depth gene expression profiling. We observed that single exposures with UFP, BPE, and HDME cause genotoxicity. Exposure to UFP induced pro-inflammatory canonical pathways, shifting to a more xenobiotic-related response with longer preincubation time. With additional allergen exposure, the modulation of pro-inflammatory and xenobiotic signaling was more pronounced and appeared faster. Moreover, aryl hydrocarbon receptor (AhR) signaling activation showed to be an important feature of UFP toxicity, which was especially pronounced upon pre-exposure. In summary, we were able to demonstrate the importance of subsequent exposure studies to understand realistic exposure situations and to identify possible adjuvant allergic effects and the underlying molecular mechanisms.

HMGB1 is a Potential and Challenging Therapeutic Target for Parkinson's Disease

Parkinson's disease (PD) is one of the most common degenerative diseases of the human nervous system and has a wide range of serious impacts on human health and quality of life. Recently, research targeting high mobility group box 1 (HMGB1) in PD has emerged, and a variety of laboratory methods for inhibiting HMGB1 have achieved good results to a certain extent. However, given that HMGB1 undergoes a variety of intracellular modifications and three different forms of extracellular redox, the possible roles of these forms in PD are likely to be different. General inhibition of all forms of HMGB1 is obviously not ideal and has become one of the biggest obstacles in the clinical application of targeting HMGB1. In this review, pure mechanistic research of HMGB1 and in vivo research targeting HMGB1 were combined, the effects of HMGB1 on neurons and immune cell responses in PD are discussed in detail, and the problems that need to be focused on in the future are addressed.

Curcumin and capsaicin regulate apoptosis and alleviate intestinal inflammation induced by Clostridioides difficile in vitro

Background

The dramatic upsurge of Clostridioides difficile infection (CDI) by hypervirulent isolates along with the paucity of effective conventional treatment call for the development of new alternative medicines against CDI. The inhibitory effects of curcumin (CCM) and capsaicin (CAP) were investigated on the activity of toxigenic cell-free supernatants (Tox-S) of C. difficile RT 001, RT 126 and RT 084, and culture-filtrate of C. difficile ATCC 700057.

Methods

Cell viability of HT-29 cells exposed to varying concentrations of CCM, CAP, C. difficile Tox-S and culture-filtrate was assessed by MTT assay. Anti-inflammatory and anti-apoptotic effects of CCM and CAP were examined by treatment of HT-29 cells with C. difficile Tox-S and culture-filtrate. Expression of BCL-2, SMAD3, NF-κB, TGF-β and TNF-α genes in stimulated HT-29 cells was measured using RT-qPCR.

Results

C. difficile Tox-S significantly (P < 0.05) reduced the cell viability of HT-29 cells in comparison with untreated cells. Both CAP and CCM significantly (P < 0.05) downregulated the gene expression level of BCL-2, SMAD3, NF-κB and TNF-α in Tox-S treated HT-29 cells. Moreover, the gene expression of TGF-β decreased in Tox-S stimulated HT-29 cells by both CAP and CCM, although these reductions were not significantly different (P > 0.05).

Conclusion

The results of the present study highlighted that CCM and CAP can modulate the inflammatory response and apoptotic effects induced by Tox-S from different clinical C. difficile strains in vitro. Further studies are required to accurately explore the anti-toxin activity of natural components, and their probable adverse risks in clinical practice.

Transcriptomic and ultrastructural evidence indicate that anti-HMGB1 antibodies rescue organic dust-induced mitochondrial dysfunction

Exposure to organic dust (OD) in agriculture is known to cause respiratory symptoms including loss of lung function. OD exposure activates multiple signaling pathways since it contains a variety of microbial products and particulate matter. Previously, we have shown how OD exposure leads to the secretion of HMGB1 and HMGB1-RAGE signaling, and how this can be a possible therapeutic target to reduce inflammation. Cellular mitochondria are indispensable for homeostasis and are emerging targets to curtail inflammation. Recently, we have also observed that OD exposure induces mitochondrial dysfunction characterized by loss of structural integrity and deficits in bioenergetics. However, the role of HMGB1 in OD-induced mitochondrial dysfunction in human bronchial epithelial (NHBE) cells remains elusive. Therefore, we aimed to study whether decreased levels of intracellular HMGB1 or antibody-mediated neutralization of secreted HMGB1 would rescue mitochondrial dysfunction. Single and repeated ODE exposure showed an elongated mitochondrial network and cristolysis whereas HMGB1 neutralization or the lack thereof promotes mitochondrial biogenesis evidenced by increased mitochondrial fragmentation, increased DRP1 expression, decreased MFN2 expression, and increased PGC1α expression. Repeated 5-day ODE exposure significantly downregulated transcripts encoding mitochondrial respiration and metabolism (ATP synthase, NADUF, and UQCR) as well as glucose uptake. This was reversed by the antibody-mediated neutralization of HMGB1. Our results support our hypothesis that, in NHBE cells, neutralization of ODE-induced HMGB1 secretion rescues OD-induced mitochondrial dysfunction.

Nrf2 Activation Protects Against Organic Dust and Hydrogen Sulfide Exposure Induced Epithelial Barrier Loss and K. pneumoniae Invasion

Agriculture workers report various respiratory symptoms owing to occupational exposure to organic dust (OD) and various gases. Previously, we demonstrated that pre-exposure to hydrogen sulfide (H₂S) alters the host response to OD and induces oxidative stress. Nrf2 is a master-regulator of host antioxidant response and exposures to toxicants is known to reduce Nrf2 activity. The OD exposure-induced lung inflammation is known to increase susceptibility to a secondary microbial infection. We tested the hypothesis that repeated exposure to OD or H₂S leads to loss of Nrf2, loss of epithelial cell integrity and that activation of Nrf2 rescues this epithelial barrier dysfunction. Primary normal human bronchial epithelial (NHBE) cells or mouse precision cut-lung slices (PCLS) were treated with media, swine confinement facility organic dust extract (ODE) or H₂S or ODE+H₂S for one or five days. Cells were also pretreated with vehicle control (DMSO) or RTA-408, a Nrf2 activator. Acute exposure to H₂S and ODE+H₂S altered the cell morphology, decreased the viability as per the MTT assay, and reduced the Nrf2 expression as well as increased the keap1 levels in NHBE cells. Repeated exposure to ODE or H₂S or ODE+H₂S induced oxidative stress and cytokine production, decreased tight junction protein occludin and cytoskeletal protein ezrin expression, disrupted epithelial integrity and resulted in increased Klebsiella pneumoniae invasion. RTA-408 (pharmacological activator of Nrf2) activated Nrf2 by decreasing keap1 levels and reduced ODE+H₂S-induced changes including reversing loss of barrier integrity, inflammatory cytokine production and microbial invasion in PCLS but not in NHBE cell model. We conclude that Nrf2 activation has a partial protective function against ODE and H₂S.

Mitoapocynin Attenuates Organic Dust Exposure-Induced Neuroinflammation and Sensory-Motor Deficits in a Mouse Model

Increased incidences of neuro-inflammatory diseases in the mid-western United States of America (USA) have been linked to exposure to agriculture contaminants. Organic dust (OD) is a major contaminant in the animal production industry and is central to the respiratory symptoms in the exposed individuals. However, the exposure effects on the brain remain largely unknown. OD exposure is known to induce a pro-inflammatory phenotype in microglial cells. Further, blocking cytoplasmic NOX-2 using mitoapocynin (MA) partially curtail the OD exposure effects. Therefore, using a mouse model, we tested a hypothesis that inhaled OD induces neuroinflammation and sensory-motor deficits. Mice were administered with either saline, fluorescent lipopolysaccharides (LPSs), or OD extract intranasally daily for 5 days a week for 5 weeks. The saline or OD extract-exposed mice received either a vehicle or MA (3 mg/kg) orally for 3 days/week for 5 weeks. We quantified inflammatory changes in the upper respiratory tract and brain, assessed sensory-motor changes using rotarod, open-field, and olfactory test, and quantified neurochemicals in the brain. Inhaled fluorescent LPS (FL-LPS) was detected in the nasal turbinates and olfactory bulbs. OD extract exposure induced atrophy of the olfactory epithelium with reduction in the number of nerve bundles in the nasopharyngeal meatus, loss of cilia in the upper respiratory epithelium with an increase in the number of goblet cells, and increase in the thickness of the nasal epithelium. Interestingly, OD exposure increased the expression of HMGB1, 3- nitrotyrosine (NT), IBA1, glial fibrillary acidic protein (GFAP), hyperphosphorylated Tau (p-Tau), and terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL)-positive cells in the brain. Further, OD exposure decreased time to fall (rotarod), total distance traveled (open-field test), and olfactory ability (novel scent test). Oral MA partially rescued olfactory epithelial changes and gross congestion of the brain tissue. MA treatment also decreased the expression of HMGB1, 3-NT, IBA1, GFAP, and p-Tau, and significantly reversed exposure induced sensory-motor deficits. Neurochemical analysis provided an early indication of depressive behavior. Collectively, our results demonstrate that inhalation exposure to OD can cause sustained neuroinflammation and behavior deficits through lung-brain axis and that MA treatment can dampen the OD-induced inflammatory response at the level of lung and brain.

Anti-high-mobility group box-1 (HMGB1) mediates the apoptosis of alveolar epithelial cells (AEC) by receptor of advanced glycation end-products (RAGE)/c-Jun N-terminal kinase (JNK) pathway in the rats of crush injuries

Objectives

The lung injury is often secondary to severe trauma. In the model of crush syndrome, there may be secondary lung injury. We hypothesize that high-mobility group box 1 (HMGB1), released from muscle tissue, mediates the apoptosis of alveolar epithelial cells (AEC) via HMGB1/Receptor of advanced glycation end-products (RAGE)/c-Jun N-terminal kinase (JNK) pathway. The study aimed to investigate how HMGB1 mediated the apoptosis of AEC in the rat model.

Methods

Seventy-five SD male rats were randomly divided into five groups: CS, CS + vehicle, CS + Ethyl pyruvate (EP), CS + FPS-ZM1 group, and CS + SP600125 groups. When the rats CS model were completed after 24 h, the rats were sacrificed. We collected the serum and the whole lung tissues. Inflammatory cytokines were measured in serum samples. Western blot and RT-qPCR were used to quantify the protein and mRNA. Lastly, apoptotic cells were detected by TUNEL. We used SPSS 25.0 for statistical analyses.

Results

Nine rats died during the experiments. Dead rats were excluded from further analysis. Compared to the CS group, levels of HMGB1 and inflammatory cytokines in serum were downregulated in CS + EP, CS + FPS-ZM1, and CS + SP600125 groups. Western blot and RT-qPCR analysis revealed a significant downregulation of HMGB1, RAGE, and phosphorylated-JNK in CS + EP, CS + FPS-ZM1, and CS + SP600125 groups, compared with the CS groups, excluding total-JNK mRNA. Apoptosis of AEC was used TUNEL to assess. We found the TUNEL-positive cells were downregulated in CS + EP, CS + FPS-ZM1, and CS + SP600125 groups.

Conclusion

The remote lung injury begins early after crush injuries. The HMGB1/RAGE/JNK signaling axis is an attractive target to abrogate the apoptosis of AEC after crush injuries.

Prevention of IL-6 signaling ameliorates toluene diisocyanate-induced steroid-resistant asthma

BACKGROUND

Accumulating evidence indicated the crucial role for interleukin 6 (IL-6) signaling in the development of allergic asthma. Yet, the role of IL-6 signaling in toluene diisocyanate (TDI)-induced mixed granulocytic airway inflammation still remains unclear. Thus, the aims of this study were to dissect the role of IL-6 signaling and to evaluate the effect of tocilizumab on TDI-induced steroid-resistant asthma.

METHODS

TDI-induced asthma model was prepared and asthmatic mice were respectively given IL-6 monoclonal antibody, IL-6R monoclonal antibody (tocilizumab, 5 mg/kg, i.p. after each challenge) for therapeutic purposes or isotype IgG as control.

RESULTS

TDI exposure just elevated IL-6R expression in the infiltrated inflammatory cells around the airway, but increased glycoprotein 130 expression in the whole lung, especially in bronchial epithelium. Moreover, TDI inhalation increased airway hyperresponsiveness (AHR) to methacholine, coupled with mixed granulocytic inflammation, exaggerated epithelial denudation, airway smooth muscle thickening, goblet cell metaplasia, extensive submucosal collagen deposition, dysregulated Th2/Th17 responses, as well as innate immune responses and raised serum IgE. And almost all these responses except for raised serum IgE were markedly ameliorated by the administration of IL-6 neutralizing antibody or tocilizumab, but exhibited poor response to systemic steroid treatment. Also, TDI challenge induced nucleocytoplasm translocation of HMGB1 and promoted its release in the BALF, as well as elevated lung level of STAT3 phosphorylation, which were inhibited by anti-IL-6 and anti-IL-6R treatment.

CONCLUSIONS

Our data suggested that IL-6 monoclonal antibody and tocilizumab might effectively abrogate TDI-induced airway inflammation and remodeling, which could be used as a clinical potential therapy for patients with severe asthma.

Organic dust exposure induces stress response and mitochondrial dysfunction in monocytic cells

Exposure to airborne organic dust (OD), rich in microbial pathogen-associated molecular patterns (PAMPs), is shown to induce lung inflammation. A common manifestation in lung inflammation is altered mitochondrial structure and bioenergetics that regulate mitochondrial ROS (mROS) and feed a vicious cycle of mitochondrial dysfunction. The role of mitochondrial dysfunction in other airway diseases is well known. However, whether OD exposure induces mitochondrial dysfunction remains elusive. Therefore, we tested a hypothesis that organic dust extract (ODE) exposure induces mitochondrial stress using a human monocytic cell line (THP1). We examined whether co-exposure to ethyl pyruvate (EP) or mitoapocynin (MA) could rescue ODE exposure induced mitochondrial changes. Transmission electron micrographs showed significant differences in cellular and organelle morphology upon ODE exposure. ODE exposure with and without EP co-treatment increased the mtDNA leakage into the cytosol. Next, ODE exposure increased PINK1, Parkin, cytoplasmic cytochrome c levels, and reduced mitochondrial mass and cell viability, indicating mitophagy. MA treatment was partially protective by decreasing Parkin expression, mtDNA and cytochrome c release and increasing cell viability.

Ethyl Pyruvate as a Potential Defense Intervention against Cytokine Storm in COVID-19?

COVID-19 is a deadly pandemic and has resulted in a huge loss of money and life in the past few months. It is well known that the SARS-CoV-2 gene mutates relatively slowly as compared to other viruses but still may create hurdles in developing vaccines. Therefore, there is a need to develop alternative routes for its management and treatment of COVID-19. Based on the severity of viral infection in COVID-19 patients, critically ill patients (∼5%, with old age, and comorbidities) are at high risk of morbidities. The reason for this severity in such patients is attributed to "misleading cytokine storm", which produces ARDS and results in the deaths of critically ill patients. In this connection, ethyl pyruvate (EP) controls these cytokines/chemokines, is an anti-inflammatory agent, and possesses a protective effect on the lungs, brain, heart, and mitochondria against various injuries. Considering these facts, we propose that the site-selective EP formulations (especially aerosols) could be the ultimate adjuvant therapy for the regulation of misleading cytokine storm in severely affected COVID-19 patients and could reduce the mortalities.

Ambient hydrogen sulfide exposure increases the severity of influenza A virus infection in swine

Hydrogen sulfide (H₂S) is common in concentrated pig feed operations from the decomposition of manure. Ambient H₂S is a respiratory tract irritant and an environmental stressor for caretakers and pigs. Influenza A virus (IAV), a zoonotic pathogen, has caused prior pandemics. The effects of H₂S or IAV alone on the respiratory system have been investigated, but their interaction has not. We hypothesized that exposure to environmentally-relevant H₂S concentrations increases the pathogenicity of IAV infection in swine. Thirty-five, three-week old pigs of mixed sex were exposed to breathing air or H₂S via inhalation 6 hours daily for 12 days. After 7 days, pigs were inoculated with H3N2 IAV (or a placebo). Results showed that ambient H₂S increased the severity of respiratory distress and lung pathology. H₂S also suppressed IL-IL-1β, IL-6 and IL-8 cytokine response in BALF and increased viral loads and nasal shedding.

Organic dust-induced mitochondrial dysfunction could be targeted via cGAS-STING or cytoplasmic NOX-2 inhibition using microglial cells and brain slice culture models

Organic dust (OD) exposure in animal production industries poses serious respiratory and other health risks. OD consisting of microbial products and particulate matter and OD exposure-induced respiratory inflammation are under investigation. However, the effect of OD exposure on brain remains elusive. We show that OD exposure of microglial cells induces an inflammatory phenotype with the release of mitochondrial DNA (mt-DNA). Therefore, we tested a hypothesis that OD exposure-induced secreted mt-DNA signaling drives the inflammation. A mouse microglial cell line was treated with medium or organic dust extract (ODE, 1% v/v) along with either phosphate-buffered saline (PBS) or mitoapocynin (MA, 10 µmol). Microglia treated with control or anti-STING siRNA were exposed to medium or ODE. Mouse organotypic brain slice cultures (BSCs) were exposed to medium or ODE with or without MA. Various samples were processed to quantify mitochondrial reactive oxygen species (mt-ROS), mt-DNA, cytochrome c, TFAM, mitochondrial stress markers and mt-DNA-induced signaling via cGAS-STING and TLR9. Data were analyzed and a p value of ≤ 0.05 was considered significant. MA treatment decreased the ODE-induced mt-DNA release into the cytosol. ODE increased MFN1/2 and PINK1 but not DRP1 and MA treatment decreased the MFN2 expression. MA treatment decreased the ODE exposure-induced mt-DNA signaling via cGAS-STING and TLR9. Anti-STING siRNA decreased the ODE-induced increase in IRF3, IFN-β and IBA-1 expression. In BSCs, MA treatment decreased the ODE-induced TNF-α, IL-6 and MFN1. Therefore, OD exposure-induced mt-DNA signaling was curtailed through cytoplasmic NOX-2 inhibition or STING suppression to reduce brain microglial inflammatory response.

Pre-exposure to hydrogen sulfide modulates the innate inflammatory response to organic dust

Animal production units produce and store many contaminants on-site, including organic dust (OD) and hydrogen sulfide (H₂S). Workers in these settings report various respiratory disease symptoms. Both OD and H₂S have shown to induce lung inflammation. However, impact of co-exposure to both H₂S and OD has not been investigated. Therefore, we tested a hypothesis that pre-exposure to H₂S modulates the innate inflammatory response of the lungs to organic dust. In a mouse model of H₂S and organic dust extract (ODE) exposure, we assessed lung inflammation quantitatively. We exposed human airway epithelial and monocytic cells to medium or H₂S alone or H₂S followed by ODE and measured cell viability, oxidative stress, and other markers of inflammation. Exposure to 10 ppm H₂S followed by ODE increased the lavage fluid leukocytes. However, exposure to 10 ppm H₂S alone resulted in changes in tight junction proteins, an increase in mRNA levels of tlr2 and tlr4 as well as ncf1, ncf4, hif1α, and nrf2. H₂S alone or H₂S and ODE exposure decreased cell viability and increased reactive nitrogen species production. ODE exposure increased the transcripts of tlr2 and tlr4 in both in vitro and in vivo models, whereas increased nfkbp65 transcripts following exposure to ODE and H₂S was seen only in in vitro model. H₂S alone and H₂S followed by ODE exposure increased the levels of IL-1β. We conclude that pre-exposure to H₂S modulates lung innate inflammatory response to ODE.

HMGB1-Mediated Neuroinflammatory Responses in Brain Injuries: Potential Mechanisms and Therapeutic Opportunities

Brain injuries are devastating conditions, representing a global cause of mortality and morbidity, with no effective treatment to date. Increased evidence supports the role of neuroinflammation in driving several forms of brain injuries. High mobility group box 1 (HMGB1) protein is a pro-inflammatory-like cytokine with an initiator role in neuroinflammation that has been implicated in Traumatic brain injury (TBI) as well as in early brain injury (EBI) after subarachnoid hemorrhage (SAH). Herein, we discuss the implication of HMGB1-induced neuroinflammatory responses in these brain injuries, mediated through binding to the receptor for advanced glycation end products (RAGE), toll-like receptor4 (TLR4) and other inflammatory mediators. Moreover, we provide evidence on the biomarker potential of HMGB1 and the significance of its nucleocytoplasmic translocation during brain injuries along with the promising neuroprotective effects observed upon HMGB1 inhibition/neutralization in TBI and EBI induced by SAH. Overall, this review addresses the current advances on neuroinflammation driven by HMGB1 in brain injuries indicating a future treatment opportunity that may overcome current therapeutic gaps.

Cross talk between Hsp72, HMGB1 and RAGE/ERK1/2 signaling in the pathogenesis of bronchial asthma in obese patients

BACKGROUND

The incidence of obesity-related asthma has shown a remarkable increase.

OBJECTIVES

We aimed to explore the role of heat shock protein 72 (Hsp72) and receptor for advanced glycation end products (RAGE) axis with its downstream signaling in the pathogenesis of obesity-related asthma.

METHODS

We enrolled a total of 55 subjects and divided them into three groups. Groups I and II included healthy, normal weight (n = 15) and obese (n = 15) subjects, respectively. Twenty-five obese asthmatics (group III) were subdivided into group IIIa (10 patients with mild to moderate asthma) and group IIIb (15 patients with severe asthma). High mobility group box 1 (HMGB1), interleukin 8 (IL-8), monocyte chemoattractant protein 1 (MCP-1), extracellular signal-regulated protein kinases 1 and 2 (ERK1/2), and urinary Hsp72 were immunoassayed. Hydrogen peroxide (H₂O₂) and free fatty acids (FFAs) levels were photometrically measured. RAGE mRNA expression was relatively quantified by real-time PCR.

RESULTS

We found significant elevations of serum HMGB1, IL-8, MCP1, ERK1/2, FFAs, and H₂O₂ levels as well as urinary Hsp72 levels in obese subjects compared to healthy control. These were more evident in patients with severe asthma (group IIIb). Multivariate regression analysis identified Hsp72 and ERK1/2 as independent predictors of bronchial asthma severity. Receiver operating characteristic (ROC) curve analysis revealed that areas under the curve (AUC) for Hsp72 and ERK1/2 were 0.991 and 0.981, respectively, which denotes a strong predictive value for identifying the severity of bronchial asthma in obese patients.

CONCLUSION

The current study highlights the role of Hsp72 and HMGB1/RAGE/ERK1/2 signaling cascade in the pathogenesis of bronchial asthma and its link to obesity, which could be reflected on monitoring, severity grading, and management of this disease.

HMGB1-RAGE Signaling Plays a Role in Organic Dust-Induced Microglial Activation and Neuroinflammation

Occupational exposure to contaminants in agriculture and other industries is known to cause significant respiratory ailments. The effect of organic dust on lung inflammation and tissue remodeling has been actively investigated over many years but the adverse effect of organic dust-exposure on the central vital organ brain is beginning to emerge. Brain microglial cells are a major driver of neuroinflammation upon exposure to danger signals. Therefore, we tested a hypothesis that organic dust-exposure of microglial cells induces microglial cell activation and inflammation through HMGB1-RAGE signaling. Mouse microglial cells were exposed to organic dust extract showed a time-dependent increase in cytoplasmic translocation of high-mobility group box 1 (HMGB1) from the nucleus, increased expression of receptor for advanced glycation end products (RAGE) and activation of Iba1 as compared to control cells. Organic dust also induced reactive oxygen species generation, NF-κB activation, and proinflammatory cytokine release. To establish a functional relevance of HMGB1-RAGE activation in microglia-mediated neuroinflammation, we used both pharmacological and genetic approaches involving HMGB1 translocation inhibitor ethyl pyruvate (EP), anti-HMGB1 siRNA, and NOX-inhibitor mitoapocynin. Interestingly, EP effectively reduced HMGB1 nucleocytoplasmic translocation and RAGE expression along with reactive oxygen species (ROS) generation and TNF-α and IL-6 production but not NF-κB activation. HMGB1 knockdown by siRNA also reduced both ROS and reactive nitrogen species (RNS) and IL-6 levels but not TNF-α. NOX2 inhibitor mitoapocynin significantly reduced RNS levels. Collectively, our results demonstrate that organic dust activates HMGB1-RAGE signaling axis to induce a neuroinflammatory response in microglia and that attenuation of HMGB1-RAGE activation by EP and mitoapocynin treatments or genetic knockdown can dampen the neuroinflammation.