Potential role of high mobility group box 1 in viral infectious diseases

DAMP-ing IBD: Extinguish the Fire and Prevent Smoldering

In inflammatory bowel diseases (IBD), the most promising therapies targeting cytokines or immune cell trafficking demonstrate around 40% efficacy. As IBD is a multifactorial inflammation of the intestinal tract, a single-target approach is unlikely to solve this problem, necessitating an alternative strategy that addresses its variability. One approach often overlooked by the pharmaceutically driven therapeutic options is to address the impact of environmental factors. This is somewhat surprising considering that IBD is increasingly viewed as a condition heavily influenced by such factors, including diet, stress, and environmental pollution-often referred to as the "Western lifestyle". In IBD, intestinal responses result from a complex interplay among the genetic background of the patient, molecules, cells, and the local inflammatory microenvironment where danger- and microbe-associated molecular patterns (D/MAMPs) provide an adjuvant-rich environment. Through activating DAMP receptors, this array of pro-inflammatory factors can stimulate, for example, the NLRP3 inflammasome-a major amplifier of the inflammatory response in IBD, and various immune cells via non-specific bystander activation of myeloid cells (e.g., macrophages) and lymphocytes (e.g., tissue-resident memory T cells). Current single-target biological treatment approaches can dampen the immune response, but without reducing exposure to environmental factors of IBD, e.g., by changing diet (reducing ultra-processed foods), the adjuvant-rich landscape is never resolved and continues to drive intestinal mucosal dysregulation. Thus, such treatment approaches are not enough to put out the inflammatory fire. The resultant smoldering, low-grade inflammation diminishes physiological resilience of the intestinal (micro)environment, perpetuating the state of chronic disease. Therefore, our hypothesis posits that successful interventions for IBD must address the complexity of the disease by simultaneously targeting all modifiable aspects: innate immunity cytokines and microbiota, adaptive immunity cells and cytokines, and factors that relate to the (micro)environment. Thus the disease can be comprehensively treated across the nano-, meso-, and microscales, rather than with a focus on single targets. A broader perspective on IBD treatment that also includes options to adapt the DAMPing (micro)environment is warranted.

Serum High-Mobility Group Box 1 and Heme Oxygenase-1 as Biomarkers in COVID-19 Patients at Hospital Admission

The careful monitoring of patients with mild/moderate COVID-19 is of particular importance because of the rapid progression of complications associated with COVID-19. For prognostic reasons and for the economic management of health care resources, additional biomarkers need to be identified, and their monitoring can conceivably be performed in the early stages of the disease. In this retrospective cross-sectional study, we found that serum concentrations of high-mobility group box 1 (HMGB1) and heme oxygenase-1 (HO-1), at the time of hospital admission, could be useful biomarkers for COVID-19 management. The study included 160 randomly selected recovered patients with mild to moderate COVID-19 on admission. Compared with healthy controls, serum HMGB1 and HO-1 levels increased by 487.6 pg/mL versus 43.1 pg/mL and 1497.7 pg/mL versus 756.1 pg/mL, respectively. Serum HO-1 correlated significantly with serum HMGB1, oxidative stress parameters (malondialdehyde (MDA), the phosphatidylcholine/lysophosphatidylcholine ratio (PC/LPC), the ratio of reduced and oxidative glutathione (GSH/GSSG)), and anti-inflammatory acute phase proteins (ferritin, haptoglobin). Increased heme catabolism/hemolysis were not detected. We hypothesize that the increase in HO-1 in the early phase of COVID-19 disease is likely to have a survival benefit by providing protection against oxidative stress and inflammation, whereas the level of HMGB1 increase reflects the activity of the innate immune system and represents levels within which the disease can be kept under control.

HMGB1 is involved in viral replication and the inflammatory response in coxsackievirus A16-infected 16HBE cells via proteomic analysis and identification

Coxsackievirus A16 (CV-A16) is still an important pathogen that causes hand, foot and mouth disease (HFMD) in young children and infants worldwide. Previous studies indicated that CV-A16 infection is usually mild or self-limiting, but it was also found that CV-A16 infection can trigger severe neurological complications and even death. However, there are currently no vaccines or antiviral compounds available to either prevent or treat CV-A16 infection. Therefore, investigation of the virus‒host interaction and identification of host proteins that play a crucial regulatory role in the pathogenesis of CV-A16 infection may provide a novel strategy to develop antiviral drugs. Here, to increase our understanding of the interaction of CV-A16 with the host cell, we analyzed changes in the proteome of 16HBE cells in response to CV-A16 using tandem mass tag (TMT) in combination with LC‒MS/MS. There were 6615 proteins quantified, and 172 proteins showed a significant alteration during CV-A16 infection. These differentially regulated proteins were involved in fundamental biological processes and signaling pathways, including metabolic processes, cytokine‒cytokine receptor interactions, B-cell receptor signaling pathways, and neuroactive ligand‒receptor interactions. Further bioinformatics analysis revealed the characteristics of the protein domains and subcellular localization of these differentially expressed proteins. Then, to validate the proteomics data, 3 randomly selected proteins exhibited consistent changes in protein expression with the TMT results using Western blotting and immunofluorescence methods. Finally, among these differentially regulated proteins, we primarily focused on HMGB1 based on its potential effects on viral replication and virus infection-induced inflammatory responses. It was demonstrated that overexpression of HMGB1 could decrease viral replication and upregulate the release of inflammatory cytokines, but deletion of HMGB1 increased viral replication and downregulated the release of inflammatory cytokines. In conclusion, the results from this study have helped further elucidate the potential molecular pathogenesis of CV-A16 based on numerous protein changes and the functions of HMGB1 Found to be involved in the processes of viral replication and inflammatory response, which may facilitate the development of new antiviral therapies as well as innovative diagnostic methods.

Neutrophil Extracellular Traps and Their Possible Implications in Ocular Herpes Infection

Neutrophil extracellular traps (NETs) are net-like structures released from neutrophils. NETs predominantly contain cell-free deoxyribonucleic acid (DNA) decorated with histones and neutrophil granule proteins. Numerous extrinsic and intrinsic stimuli can induce the formation of NETs such as pathogens, cytokines, immune complexes, microcrystals, antibodies, and other physiological stimuli. The mechanism of NETosis induction can either be ROS-dependent or independent based on the catalase producing activity of the pathogen. NADPH is the source of ROS production, which in turn depends on the upregulation of Ca2+ production in the cytoplasm. ROS-independent induction of NETosis is regulated through toll-like receptors (TLRs). Besides capturing and eliminating pathogens, NETs also aggravate the inflammatory response and thus act as a double-edged sword. Currently, there are growing reports of NETosis induction during bacterial and fungal ocular infections leading to different pathologies, but there is no direct report suggesting its role during herpes simplex virus (HSV) infection. There are innumerable independent reports showing that the major effectors of NETosis are also directly affected by HSV infection, and thus, there is a strong possibility that HSV interacts with these facilitators that can either result in virally mediated modulation of NETosis or NETosis-mediated suppression of ocular HSV infection. This review focuses on the mechanism of NETs formation during different ocular pathologies, with its prime focus on highlighting their potential implications during HSV ocular infections and acting as prospective targets for the treatment of ocular diseases.

Association of the RAGE/RAGE-ligand axis with interstitial lung disease and its acute exacerbation

The receptor for advanced glycation end product (RAGE) is a transmembrane receptor highly expressed in type 1 pneumocytes of healthy lungs. RAGE is considered to play a homeostatic role in the lung, as RAGE knockout mice develop lung fibrosis as they age. In contrast, RAGE can bind numerous ligands, including high-mobility group box 1 (HMGB1). These interactions initiate pro-inflammatory signaling associated with the pathogenesis of lung injury and interstitial lung disease (ILD), including idiopathic pulmonary fibrosis (IPF). ILD is a broad category of diffuse parenchymal lung disease characterized by various extents of lung fibrosis and inflammation, and IPF is a common and progressive ILD of unknown cause. The prognosis of patients with IPF is poor, and acute exacerbation of IPF (AE-IPF) is one of the main causes of death. Recent reports indicate that acute exacerbations can occur in other ILDs (AE-ILD). Notably, ILD is frequently observed in patients with lung cancer, and AE-ILD after surgical procedures or the initiation of chemotherapy for concomitant lung cancer are clinically important due to their association with increased mortality. In this review, we summarize the associations of RAGE/soluble RAGE (sRAGE)/RAGE ligands with the pathogenesis and clinical course of ILD, including IPF and AE-IPF. Additionally, the potential use of sRAGE and RAGE ligands as predictive markers of AE-IPF and cancer treatment-triggered AE-ILD is also discussed.

Molecular Mechanisms in the Genesis of Seizures and Epilepsy Associated With Viral Infection

Seizures are a common presenting symptom during viral infections of the central nervous system (CNS) and can occur during the initial phase of infection ("early" or acute symptomatic seizures), after recovery ("late" or spontaneous seizures, indicating the development of acquired epilepsy), or both. The development of acute and delayed seizures may have shared as well as unique pathogenic mechanisms and prognostic implications. Based on an extensive review of the literature, we present an overview of viruses that are associated with early and late seizures in humans. We then describe potential pathophysiologic mechanisms underlying ictogenesis and epileptogenesis, including routes of neuroinvasion, viral control and clearance, systemic inflammation, alterations of the blood-brain barrier, neuroinflammation, and inflammation-induced molecular reorganization of synapses and neural circuits. We provide clinical and animal model findings to highlight commonalities and differences in these processes across various neurotropic or neuropathogenic viruses, including herpesviruses, SARS-CoV-2, flaviviruses, and picornaviruses. In addition, we extensively review the literature regarding Theiler's murine encephalomyelitis virus (TMEV). This picornavirus, although not pathogenic for humans, is possibly the best-characterized model for understanding the molecular mechanisms that drive seizures, epilepsy, and hippocampal damage during viral infection. An enhanced understanding of these mechanisms derived from the TMEV model may lead to novel therapeutic interventions that interfere with ictogenesis and epileptogenesis, even within non-infectious contexts.

Recent advances in glycyrrhizin metabolism, health benefits, clinical effects and drug delivery systems for efficacy improvement; a comprehensive review

BACKGROUND

Glycyrrhizin (GL) is a major active constituent of licorice root (Glycyrrhiza glabra) that is considered one of the oldest and most frequently employed botanicals in Chinese medicine and worldwide, with most effects attributed to its rich GL content. Structurally, GL a triterpene saponin that is widely used as a flavoring agent in foodstuffs and cosmetics, and also proposed for various clinical applications with a myriad of health benefits. Pharmacological and biological activities of GL include antiviral, anti-inflammatory, antioxidant, and anticancer activities (in vitro and in vivo). Currently, there is no comprehensive review on GL biological effects and its action mechanisms.

PURPOSE

This review summarizes GL pharmacological actions from a molecular biology perception, presented on its metabolism and side effects based on in vitro, in vitro and clinical studies. Moreover, the potential of GL as a nanomedicine delivery system is also summarized. The progress in drug delivery research using GL presented herein is expected to provide a theoretical basis for developing other novel drugs formulations.

METHODS

A systematic review was carried out in several electronic databases (Science Direct, SpringerLink, CNKI, PubMed, Web of Science, Elsevier, and Scopus), using the following key words: glycyrrhizin "AND" bioactivity "OR" clinic "OR" therapeutic "OR" drug delivery. This search included manuscripts published between 1989 and 2021.

RESULTS

126 researches were selected and summarized in this review. The analysis of these studies indicated that GL has antiviral activity against different viruses. Further, GL efficiently suppressed the respiratory manifestations associated with COVID-19 by reducing the expression of angiotensin converting enzyme 2 (ACE2) that employed by the virus as an entry point. Otherwise, GL was found to induce antioxidant, anti-inflammatory, immune-modulatory, and anticancer activity. Besides, diminution the particle size of GL to nanometer size significantly augments their action and biodistribution.

CONCLUSION

This article summarizes the pharmacological actions of GL. The potential of GL as a nanomedicine delivery system is also presented. Nevertheless, most studies reported provide no deep insight of GL health effects warranting for more future studies to elucidate its action mechanism and potential therapeutic benefits through preclinical and clinical trials.

High-mobility group box 1 (HMGB1) in COVID-19: extrapolation of dangerous liaisons

High-mobility group box 1 (HMGB1), a multifunctional nuclear protein, exists mainly within the nucleus of all mammal eukaryotic cells. It is actively secreted by the necrotic cells as a response to the inflammatory signaling pathway. HMGB1 binds to receptor ligands as RAGE, and TLR and becomes a pro-inflammatory cytokine with a robust capacity to trigger inflammatory response. It is a critical mediator of the pathogenesis of systemic inflammation in numerous inflammatory disorders. Release of HMGB1 is associated with different viral infections and strongly participates in the regulation of viral replication cycles. In COVID-19 era, high HMGB1 serum levels were observed in COVID-19 patients and linked with the disease severity, development of cytokine storm (CS), acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). SARS-CoV-2-induced cytolytic effect may encourage release of HMGB1 due to nuclear damage. Besides, HMGB1 activates release of pro-inflammatory cytokines from immune cells and up-regulation of angiotensin I-converting enzyme 2 (ACE2). Therefore, targeting of the HMGB1 pathway by anti-HMGB1 agents, such as heparin, resveratrol and metformin, may decrease COVID-19 severity. HMGB1 signaling pathway has noteworthy role in the pathogenesis of SARS-CoV-2 infections and linked with development of ALI and ARDS in COVID-19 patients. Different endogenous and exogenous agents may affect release and activation of HMGB1 pathway. Targeting of HMGB1-mediated TLR2/TLR4, RAGE and MAPK signaling, might be a new promising drug candidate against development of ALI and/or ARDS in severely affected COVID-19 patients.

Jing Si Herbal Drink as a prospective adjunctive therapy for COVID-19 treatment: Molecular evidence and mechanisms

Background

SARS-CoV-2 has led to a sharp increase in the number of hospitalizations and deaths from pneumonia and multiorgan disease worldwide; therefore, SARS-CoV-2 has become a global health problem. Supportive therapies remain the mainstay treatments against COVID-19, such as oxygen inhalation, antiviral drugs, and antibiotics. Traditional Chinese medicine (TCM) has been shown clinically to relieve the symptoms of COVID-19 infection, and TCMs can affect the pathogenesis of SARS-CoV-2 infection in vitro. Jing Si Herbal Drink (JSHD), an eight herb formula jointly developed by Tzu Chi University and Tzu Chi Hospital, has shown potential as an adjuvant treatment for COVID-19 infection. A randomized controlled trial (RCT) of JSHD as an adjuvant treatment in patients with COVID-19 infection is underway

Objectives

This article aims to explore the efficacy of the herbs in JSHD against COVID-19 infection from a mechanistic standpoint and provide a reference for the rational utilization of JSHD in the treatment of COVID-19.

Method

We compiled evidence of the herbs in JSHD to treat COVID-19 in vivo and in vitro.

Results

We described the efficacy and mechanism of action of the active ingredients in JSHD to treat COVID-19 based on experimental evidence. JSHD includes 5 antiviral herbs, 7 antioxidant herbs, and 7 anti-inflammatory herbs. In addition, 2 herbs inhibit the overactive immune system, 1 herb reduces cell apoptosis, and 1 herb possesses antithrombotic ability.

Conclusion

Although experimental data have confirmed that the ingredients in JSHD are effective against COVID-19, more rigorously designed studies are required to confirm the efficacy and safety of JSHD as a COVID-19 treatment.

Therapeutic potential of ginger against COVID-19: Is there enough evidence?

In addition to the respiratory system, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strikes other systems, including the digestive, circulatory, urogenital, and even the central nervous system, as its receptor angiotensin-converting enzyme 2 (ACE2) is expressed in various organs, such as lungs, intestine, heart, esophagus, kidneys, bladder, testis, liver, and brain. Different mechanisms, in particular, massive virus replication, extensive apoptosis and necrosis of the lung-related epithelial and endothelial cells, vascular leakage, hyper-inflammatory responses, overproduction of pro-inflammatory mediators, cytokine storm, oxidative stress, downregulation of ACE2, and impairment of the renin-angiotensin system contribute to the COVID-19 pathogenesis. Currently, COVID-19 is a global pandemic with no specific anti-viral treatment. The favorable capabilities of the ginger were indicated in patients suffering from osteoarthritis, neurodegenerative disorders, rheumatoid arthritis, type 2 diabetes, respiratory distress, liver diseases and primary dysmenorrheal. Ginger or its compounds exhibited strong anti-inflammatory and anti-oxidative influences in numerous animal models. This review provides evidence regarding the potential effects of ginger against SARS-CoV-2 infection and highlights its antiviral, anti-inflammatory, antioxidative, and immunomodulatory impacts in an attempt to consider this plant as an alternative therapeutic agent for COVID-19 treatment.

Potential effects of HMGB1 on viral replication and virus infection-induced inflammatory responses: A promising therapeutic target for virus infection-induced inflammatory diseases

Inflammatory responses, characterized by the overproduction of numerous proinflammatory mediators by immune cells, is essential to protect the host against invading pathogens. Excessive production of proinflammatory cytokines is a key pathogenic factor accounting for severe tissue injury and disease progression during the infection of multiple viruses, which are therefore termed as "cytokine storm". High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein released either over virus-infected cells or activated immune cells, may act as a proinflammatory cytokine with a robust capacity to potentiate inflammatory response and disease severity. Moreover, HMGB1 is a host factor that potentially participates in the regulation of viral replication cycles with complicated mechanisms. Currently, HMGB1 is regarded as a promising therapeutic target against virus infection. Here, we provide an overview of the updated studies on how HMGB1 is differentially manipulated by distinct viruses to regulate viral diseases.

Brain Microvascular Endothelial Cell-Derived HMGB1 Facilitates Monocyte Adhesion and Transmigration to Promote JEV Neuroinvasion

Infection with Japanese encephalitis virus (JEV) induces high morbidity and mortality, including potentially permanent neurological sequelae. However, the mechanisms by which viruses cross the blood-brain barrier (BBB) and invade into the central nervous system (CNS) remain unclear. Here, we show that extracellular HMGB1 facilitates immune cell transmigration. Furthermore, the migration of immune cells into the CNS dramatically increases during JEV infection which may enhance viral clearance, but paradoxically expedite the onset of Japanese encephalitis (JE). In this study, brain microvascular endothelial cells (BMECs) were utilized for the detection of HMGB1 release, and leucocyte, adhesion, and the integrity of the BBB in vitro. Genetically modified JEV-expressing EGFP (EGFP-JEV) and the BBB model were established to trace JEV-infected immune cell transmigration, which mimics the process of viral neuroinfection. We find that JEV causes HMGB1 release from BMECs while increasing adhesion molecules. Recombinant HMGB1 enhances leukocyte-endothelium adhesion, facilitating JEV-infected monocyte transmigration across endothelia. Thus, JEV successfully utilizes infected monocytes to spread into the brain, expanding inside of the brain, and leading to the acceleration of JE onset, which was facilitated by HMGB1. HMGB1-promoted monocyte transmigration may represent the mechanism of JEV neuroinvasion, revealing potential therapeutic targets.

Neuropathophysiology of coronavirus disease 2019: neuroinflammation and blood brain barrier disruption are critical pathophysiological processes that contribute to the clinical symptoms of SARS-CoV-2 infection

Coronavirus disease 2019 (COVID-19) is caused by the novel SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) first discovered in Wuhan, Hubei province, China in December 2019. SARS-CoV-2 has infected several millions of people, resulting in a huge socioeconomic cost and over 2.5 million deaths worldwide. Though the pathogenesis of COVID-19 is not fully understood, data have consistently shown that SARS-CoV-2 mainly affects the respiratory and gastrointestinal tracts. Nevertheless, accumulating evidence has implicated the central nervous system in the pathogenesis of SARS-CoV-2 infection. Unfortunately, however, the mechanisms of SARS-CoV-2 induced impairment of the central nervous system are not completely known. Here, we review the literature on possible neuropathogenic mechanisms of SARS-CoV-2 induced cerebral damage. The results suggest that downregulation of angiotensin converting enzyme 2 (ACE2) with increased activity of the transmembrane protease serine 2 (TMPRSS2) and cathepsin L in SARS-CoV-2 neuroinvasion may result in upregulation of proinflammatory mediators and reactive species that trigger neuroinflammatory response and blood brain barrier disruption. Furthermore, dysregulation of hormone and neurotransmitter signalling may constitute a fundamental mechanism involved in the neuropathogenic sequelae of SARS-CoV-2 infection. The viral RNA or antigenic peptides also activate or interact with molecular signalling pathways mediated by pattern recognition receptors (e.g., toll-like receptors), nuclear factor kappa B, Janus kinase/signal transducer and activator of transcription, complement cascades, and cell suicide molecules. Potential molecular targets and therapeutics of SARS-CoV-2 induced neurologic damage are also discussed.

Could Targeting HMGB1 be Useful for the Clinical Management of COVID-19 Infection?

Since the high mobility group box-1 (HMGB1) molecule had been recognized as a proinflammatory cytokine, which mediates endotoxin lethality of mice, there have been lots of papers about targeting the HMGB1 within the contexts of infection, inflammation, and cancer. The pathogenic impact of HMGB1 to the severe acute respiratory syndrome (SARS) and disease management with herbal formulations targeting this unique protein have already been proposed. However, the failure of the numerous current anti-viral therapies on the ongoing viral infections casts reappraisal of the possible interrelationships regarding the HMGB1 and SARS-CoV-2. COVID-19 pandemic due to the SARS-CoV-2 virus is a currently ongoing challenging global health crisis. There is still not any proven exact treatment of COVID-19 with high level of evidence. In this paper, we focused on the potential usage of external and/or inhalation preparation of antiviral/antibacterial herbal products capable of targeting HMGB1 for the clinical management candidates of the ongoing COVID-19 infection.

Exploring the Pivotal Immunomodulatory and Anti-Inflammatory Potentials of Glycyrrhizic and Glycyrrhetinic Acids

Licorice extract is a Chinese herbal medication most often used as a demulcent or elixir. The extract usually consists of many components but the key ingredients are glycyrrhizic (GL) and glycyrrhetinic acid (GA). GL and GA function as potent antioxidants, anti-inflammatory, antiviral, antitumor agents, and immuneregulators. GL and GA have potent activities against hepatitis A, B, and C viruses, human immunodeficiency virus type 1, vesicular stomatitis virus, herpes simplex virus, influenza A, severe acute respiratory syndrome-related coronavirus, respiratory syncytial virus, vaccinia virus, and arboviruses. Also, GA was observed to be of therapeutic valve in human enterovirus 71, which was recognized as the utmost regular virus responsible for hand, foot, and mouth disease. The anti-inflammatory mechanism of GL and GA is realized via cytokines like interferon-γ, tumor necrotizing factor-α, interleukin- (IL-) 1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, and IL-17. They also modulate anti-inflammatory mechanisms like intercellular cell adhesion molecule 1 and P-selectin, enzymes like inducible nitric oxide synthase (iNOS), and transcription factors such as nuclear factor-kappa B, signal transducer and activator of transcription- (STAT-) 3, and STAT-6. Furthermore, DCs treated with GL were capable of influencing T-cell differentiation toward Th1 subset. Moreover, GA is capable of blocking prostaglandin-E2 synthesis via blockade of cyclooxygenase- (COX-) 2 resulting in concurrent augmentation nitric oxide production through the enhancement of iNOS2 mRNA secretion in Leishmania-infected macrophages. GA is capable of inhibiting toll-like receptors as well as high-mobility group box 1.

SARS-CoV-2 and the possible connection to ERs, ACE2, and RAGE: Focus on susceptibility factors

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has provoked major stresses on the health-care systems of several countries, and caused the death of more than a quarter of a million people globally, mainly in the elderly population with preexisting pathologies. Previous studies with coronavirus (SARS-CoV) point to gender differences in infection and disease progression with increased susceptibility in male patients, indicating that estrogens may be associated with physiological protection against the coronavirus. Therefore, the objectives of this work are threefold. First, we aim to summarize the SARS-CoV-2 infection pathway and the roles both the virus and patient play in COVID-19 (Coronavirus disease 2019) progression, clinical symptomatology, and mortality. Second, we detail the effect estrogen has on viral infection and host infection response, including its role in both the regulation of key viral receptor expression and the mediation of inflammatory activity. Finally, we describe how ERs (estrogen receptors) and RAGE (receptor for advanced glycation end-products) play a critical role in metabolic pathways, which we envisage could maintain a close interplay with SARS-CoV and COVID-19 mortality rates, despite a current lack of research directly determining how. Taken together, we present the current state of the field regarding SARS-CoV-2 research and illuminate where research is needed to better define the role both estrogen and metabolic comorbidities have in the COVID-19 disease state, which can be key in screening potential therapeutic options as the search for effective treatments continue.

Severe COVID-19: NLRP3 Inflammasome Dysregulated

SARS-CoV-2 might directly activate NLRP3 inflammasome resulting in an endogenous adjuvant activity necessary to mount a proper adaptive immune response against the virus. Heterogeneous response of COVID-19 patients could be attributed to differences in not being able to properly downregulate NLRP3 inflammasome activation. This relates to the fitness of the immune system of the individual challenged by the virus. Patients with a reduced immune fitness can demonstrate a dysregulated NLRP3 inflammasome activity resulting in severe COVID-19 with tissue damage and a cytokine storm. We sketch the outlines of five possible scenarios for COVID-19 in medical practice and provide potential treatment options targeting dysregulated endogenous adjuvant activity in severe COVID-19 patients.

PCV2 Induces Reactive Oxygen Species To Promote Nucleocytoplasmic Translocation of the Viral DNA Binding Protein HMGB1 To Enhance Its Replication

Porcine circovirus type 2 (PCV2) is an important swine pathogen that causes significant economic losses to the pig industry. PCV2 interacts with host cellular factors to regulate its replication. High-mobility-group box 1 (HMGB1) protein, a major nonhistone protein in the nucleus, was recently discovered to participate in viral infections. Here, we demonstrate that nuclear HMGB1 negatively regulated PCV2 replication as shown by overexpression of HMGB1 or blockage of its nucleocytoplasmic translocation with ethyl pyruvate. The B box domain was essential in restricting PCV2 replication. Nuclear HMGB1 restricted PCV2 replication by sequestering the viral genome via binding to the Ori region. However, PCV2 infection induced translocation of HMGB1 from cell nuclei to the cytoplasmic compartment. Elevation of reactive oxygen species (ROS) induced by PCV2 infection was closely associated with cytosolic translocation of nuclear HMGB1. Treatment of PCV2-infected cells with ethyl pyruvate or N-acetylcysteine downregulated PCV2-induced ROS production, suppressed nucleocytoplasmic HMGB1 translocation, and decreased PCV2 replication. Collectively, these findings offer new insight into the mechanism of the PCV2 evasion strategy: PCV2 manages to escape restriction of its replication by nuclear HMGB1 by inducing ROS to trigger the nuclear-to-cytoplasmic translocation of HMGB1.IMPORTANCE Porcine circovirus type 2 (PCV2) is a small DNA virus that depends heavily on host cells for its infection. This study reports the close relationship between subcellular localization of host high-mobility-group box 1 (HMGB1) protein and viral replication during PCV2 infection. Restriction of PCV2 replication by nuclear HMGB1 is the early step of host defense at the host-pathogen interface. PCV2 then upregulates host reactive oxygen species (ROS) to prevent sequestration of its genome by expelling nuclear HMGB1 into the cytosol. It will be interesting to study if a similar evasion strategy is employed by other circoviruses such as beak and feather disease virus, recently discovered PCV3, and geminiviruses in plants. This study also provides insight into the justification and pharmacological basis of antioxidants as an adjunct therapy in PCV2 infection or possibly other diseases caused by the viruses that deploy the ROS-HMGB1 interaction favoring their replication.

Biomarkers of Cellular Stress Do Not Associate with sCD14 in Progressive HIV and SIV Infections in Vivo

Background

Microbial translocation occurs after damage to the structural and/or immunological barrier of the gastrointestinal (GI) tract into circulation. Microbial components that trans-locate from the lumen of the GI tract directly stimulate the immune system and contribute to inflammation. When microbial translocation becomes chronic, the inflammation has detrimental consequences. Given that microbial translocation is an important phenomenon in many diseases, defining biomarkers that reliably reflect microbial translocation is critical. Measurement of systemic microbial products is difficult since: 1) robust assays to measure microbial antigens simultaneously are lacking; 2) confounding factors influence assays used to detect microbial products; and 3) biological clearance mechanisms limit their detection in circulation. Thus, host proteins produced in response to microbial stimulation are used as surrogates for microbial translocation; however, many of these proteins are also produced in response to host proteins expressed by dying cells.

Methods

We measured plasma levels of biomarkers associated with GI tract damage, immune responses to microbial products, and cell-death in people living with HIV before and after antiretroviral administration, and in macaque nonhuman primates before and after SIV infection.

Results

Proteins secreted during cellular stress (receptor for advanced glycation endproducts-RAGE and high motility group box 1-HMGB1), which can induce sCD14 production in vitro and in vivo, do not associate with elevated levels of biomarkers associated with microbial translocation in progressively HIV-infected individuals and SIV-infected NHPs.

Conclusions

Bystander cell death and generalized inflammation do not contribute to elevated levels of sCD14 observed in HIV/SIV-infected individuals.

The novel immunomodulatory biologic LMWF5A for pharmacological attenuation of the "cytokine storm" in COVID-19 patients: a hypothesis

BACKGROUND

A common complication of viral pulmonary infections, such as in the ongoing COVID-19 pandemic, is a phenomenon described as a "cytokine storm". While poorly defined, this hyperinflammatory response results in diffuse alveolar damage. The low molecular weight fraction of commercial human serum albumin (LMWF5A), a novel biologic in development for osteoarthritis, demonstrates beneficial in vitro immunomodulatory effects complimentary to addressing inflammation, thus, we hypothesize that LMWF5A could improve the clinical outcomes of COVID-19 by attenuating hyperinflammation and the potential development of a cytokine storm.

PRESENTATION OF THE HYPOTHESIS

A variety of human in vitro immune models indicate that LMWF5A reduces the production of pro-inflammatory cytokines implicated in cytokine storm associated with COVID-19. Furthermore, evidence suggests LMWF5A also promotes the production of mediators required for resolving inflammation and enhances the barrier function of endothelial cultures.

TESTING THE HYPOTHESIS

A randomized controlled trial, to evaluate the safety and efficacy of nebulized LMWF5A in adults with Acute Respiratory Distress Syndrome (ARDS) secondary to COVID-19 infection, was developed and is currently under review by the Food and Drug Administration.

IMPLICATIONS OF HYPOTHESIS

If successful, this therapy may attenuate the cytokine storm observed in these patients and potentially reduce mortality, increase ventilation free days, improve oxygenation parameters and consequently lessen the burden on patients and the intensive care unit.

CONCLUSIONS

In conclusion, in vitro findings suggest that the immunomodulatory effects of LMWF5A make it a viable candidate for treating cytokine storm and restoring homeostasis to the immune response in COVID-19.

Glycyrrhetinic acid alleviates hepatic inflammation injury in viral hepatitis disease via a HMGB1-TLR4 signaling pathway

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Licorice defect in TCM recipes leads to the hepatotoxicity in administrated mice.

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GA inhibits viral hepatitis by suppressing HMGB1 release and cytokine activity.

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GA treatment effect on infected mice is similar with HMGB1 neutralizing antibody.

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HMGB1-TLR4 axis is involved in murine hepatic injury during MHV infection.

Various human disorders are cured by the use of licorice, a key ingredient of herbal remedies. Glycyrrhizic acid (GL), a triterpenoid glycoside, is the aqueous extract from licorice root. Glycyrrhetinic acid (GA) has been reported to be a major bioactive hydrolysis product of GL and has been regarded as an anti-inflammatory agent for the treatment of a variety of inflammatory diseases, including hepatitis. However, the mechanism by which GA inhibits viral hepatic inflammatory injury is not completely understood. In this study, we found that, by consecutively treating mice with a traditional herbal recipe, licorice plays an important role in the detoxification of mice. We also employed a murine hepatitis virus (MHV) infection model to illustrate that GA treatment inhibited activation of hepatic inflammatory responses by blocking high-mobility group box 1 (HMGB1) cytokine activity. Furthermore, decreased HMGB1 levels and downstream signaling triggered by injection of a neutralizing HMGB1 antibody or TLR4 gene deficiency, also significantly protected against MHV-induced severe hepatic injury. Thus, our findings characterize GA as a hepatoprotective therapy agent in hepatic infectious disease not only by suppressing HMGB1 release and blocking HMGB1 cytokine activity, but also via an underlying viral-induced HMGB1-TLR4 immunological regulation axis that occurs during the cytokine storm. The present study provides a new therapy strategy for the treatment of acute viral hepatitis in the clinical setting.

The hallmarks of COVID-19 disease

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a novel coronavirus that has caused a worldwide pandemic of the human respiratory illness COVID-19, resulting in a severe threat to public health and safety. Analysis of the genetic tree suggests that SARS-CoV-2 belongs to the same Betacoronavirus group as severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). Although the route for viral transmission remains a mystery, SARS-CoV-2 may have originated in an animal reservoir, likely that of bat. The clinical features of COVID-19, such as fever, cough, shortness of breath, and fatigue, are similar to those of many acute respiratory infections. There is currently no specific treatment for COVID-19, but antiviral therapy combined with supportive care is the main strategy. Here, we summarize recent progress in understanding the epidemiological, virological, and clinical characteristics of COVID-19 and discuss potential targets with existing drugs for the treatment of this emerging zoonotic disease.

Analysis of Circulating HMGB1 in Human Serum

As a ubiquitous nuclear protein, high-mobility group box 1 (HMGB1) is constitutively expressed and can be actively secreted by macrophages/monocytes, as well as passively released from damaged cells following pathological injuries. Studies indicate that HMGB1 functions as a mediator of infection- and injury-elicited inflammatory diseases. Although intracellular HMGB1 functions as a regulator of tumorigenesis, epigenetic anticancer agents or therapeutic γ-ray irradiation could also cause active secretion or passive release of HMGB1, enabling serum HMGB1 to serve as a biomarker for the diagnosis and therapy of various cancers. Here we describe a semiquantitative immune blotting method to measure HMGB1 in human serum, in comparison with a commercially available HMGB1 enzyme-linked immunosorbent assay (ELISA) technique.

Differential Pattern of Soluble Immune Markers in Asymptomatic Dengue, West Nile and Zika Virus Infections

Infections with dengue virus (DENV), West Nile virus (WNV) and Zika virus (ZIKV) usually present similar mild symptoms at early stages, and most infections (~80%) are asymptomatic. However, these infections may progress to severe disease with different clinical manifestations. In this study we attempted to identify unique characteristics for each infection at the presymptomatic/asymptomatic stage of infection and compared levels of soluble immune markers that have been shown to be altered during clinical course of these viral infections. Levels of soluble markers were determined by Luminex-based assays or by ELISA in plasma samples from asymptomatic blood donors who were reactive for RNA from DENV (n = 71), WNV (n = 52) or ZIKV (n = 44), and a control or non-infected (NI) group (n = 22). Results showed that even in the absence of symptoms, increased interleukin (IL) levels of IL-12, IL-17, IL-10, IL-5, CXCL9, E-Selectin and ST2/IL-1R4; and decreased levels of IL-13 and CD40 were found in all flavivirus group samples, compared to those from NI donors. DENV-infected donors demonstrated variation in expression of IL-1ra and IL-2; WNV-infected donors demonstrated variation in expression of IL-1ra, P-Selectin, IL-4 and IL-5; ZIKV-infected donors demonstrated variation in expression of IL-1ra, P-Selectin, IL-4, RANK-L, CD40L and C3a. The findings suggest that, even in the presymptomatic/asymptomatic phase of the infection, different immunomodulation profiles were associated with DENV, WNV and ZIKV infections.

Current Understanding of West Nile Virus Clinical Manifestations, Immune Responses, Neuroinvasion, and Immunotherapeutic Implications

West Nile virus (WNV) is the most common mosquito-borne virus in North America. WNV-associated neuroinvasive disease affects all ages, although elderly and immunocompromised individuals are particularly at risk. WNV neuroinvasive disease has killed over 2300 Americans since WNV entered into the United States in the New York City outbreak of 1999. Despite 20 years of intensive laboratory and clinical research, there are still no approved vaccines or antivirals available for human use. However, rapid progress has been made in both understanding the pathogenesis of WNV and treatment in clinical practices. This review summarizes our current understanding of WNV infection in terms of human clinical manifestations, host immune responses, neuroinvasion, and therapeutic interventions.

Phase I Trial of an ICAM-1-Targeted Immunotherapeutic-Coxsackievirus A21 (CVA21) as an Oncolytic Agent Against Non Muscle-Invasive Bladder Cancer

PURPOSE

The CANON [CAVATAK in NON-muscle-invasive bladder cancer (NMIBC)] study evaluated a novel ICAM-1-targeted immunotherapeutic-coxsackievirus A21 as a novel oncolytic agent against bladder cancer.

PATIENTS AND METHODS

Fifteen patients enrolled in this "window of opportunity" phase I study, exposing primary bladder cancers to CAVATAK prior to surgery. The first 9 patients received intravesical administration of monotherapy CAVATAK; in the second stage, 6 patients received CAVATAK with a subtherapeutic dose of mitomycin C, known to enhance expression of ICAM-1 on bladder cancer cells. The primary endpoint was to determine patient safety and maximum tolerated dose (MTD). Secondary endpoints were evidence of viral replication, induction of inflammatory cytokines, antitumor activity, and viral-induced changes in resected tissue.

RESULTS

Clinical activity of CAVATAK was demonstrated by induction of tumor inflammation and hemorrhage following either single or multiple administrations of CAVATAK in multiple patients, and a complete resolution of tumor in 1 patient. Whether used alone or in combination with mitomycin C, CAVATAK caused marked inflammatory changes within NMIBC tissue biopsies by upregulating IFN-inducible genes, including both immune checkpoint inhibitory genes (PD-L1 and LAG3) and Th1-associated chemokines, as well as the induction of the innate activator RIG-I, compared with bladder cancer tissue from untreated patients. No significant toxicities were reported in any patient, from either virus or combination therapy.

CONCLUSIONS

The acceptable safety profile of CAVATAK, proof of viral targeting, replication, and tumor cell death together with the virus-mediated increases in "immunological heat" within the tumor microenvironment all indicate that CAVATAK may be potentially considered as a novel therapeutic for NMIBC.

Lazarus Effect of High Dose Corticosteroids in a Patient With West Nile Virus Encephalitis: A Coincidence or a Clue?

West Nile virus (WNV) causes severe neuroinvasive disease in humans characterized by meningitis, encephalitis, and acute flaccid paralysis (poliomyelitis variant). In neuroinvasive disease, WNV infection of neurons resulting in neuronal loss is generally presumed to be the anatomical substrate for the high morbidity and mortality. However, on a molecular level, WNV infection also results in a significant upregulation of important proinflammatory molecules that have been reported to promote neuroinflammation and cytotoxicity. Currently, there is no specific treatment for the neurological complications of WNV infection. We present a 71-year-old woman who developed WNV infection that rapidly progressed to severe generalized weakness and encephalitis manifesting with bulbar signs (dysphagia, dysarthria) and persistent delirium and stupor. Consciousness remained impaired for 9 days and then she received a 5-day course of high-dose intravenous methylprednisolone (1,000 mg daily). After the first day, voluntary movement and spontaneous eye-opening increased and by the end of the second day, she was awake and responding to commands. Thereafter, she remained awake and responsive. Although the rapid improvement from stupor to wakefulness following treatment with an anti-inflammatory immunosuppressant could merely be coincidence, since these observations are of one patient, it may also provide a clue that in some cases of WNV neuroinvasive disease a post-infectious pro-inflammatory state, rather than neuronal loss, may also contribute to morbidity. Further clinical trials are warranted to determine if high dose corticosteroids and other drugs that can alter this neuro-inflammatory cascade may be potentially beneficial in the treatment of WNV neuroinvasive disease.

Adding a bio-response modifier and zinc oxide to piglet weaner diets influences immunological responses to weaning

The effect of zinc oxide (ZnO) and a Mycobacterium smegmatis-derived bio-response modifier (BRM) supplementation on blood neutrophil functions, high-mobility group box 1 (HMGB1) protein and pro-inflammatory cytokine responses was studied in early weanling piglets. In total, 45 piglets were placed in the following five groups: basal diet only (I), supplemented with ZnO (II), supplemented with BRM (III), supplemented with ZnO plus BRM (IV) in basal diet and basal diet without weaning from dam (V). The phagocytic activity, superoxide anion and myeloperoxidase production in blood neutrophils and the concentrations of HMGB1, TNF-α, IFN-γ and IL-1β in blood plasma were measured before and after weaning. The neutrophil functions were impaired and the concentrations of HMGB1, inflammatory cytokines, were elevated in piglets during the post-weaning period. The neutrophil functions were not improved until Day 7 of weaning (P > 0.05) and pronounced elevation (P < 0.05) in the concentration of pro-inflammatory cytokines and HMGB1 was observed until Days 14 and 21 respectively, in Groups II and III. The addition of BRM plus ZnO in basal diet improved superoxide anion and myeloperoxidase production on Day 2 (P < 0.05) and decreased the TNF-α and IFN-γ concentrations on Day 7 (P < 0.05), with no significant change in the level of IL-1β and HMGB1 in Group IV. Finally, it is concluded that addition of ZnO plus BRM in the diet induced the neutrophil functions and reduced the inflammatory cytokine response much earlier to stimulate innate immunity than did ZnO or BRM alone.

Role of Receptors for Advanced Glycation End Products and High-Mobility Group Box 1 in the Outcome of Human T Cell Lymphotropic Type 1 Infection

Human T cell lymphotropic type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic viral neuroinflammatory disease, which leads to damage of the central nervous system. Inflammatory responses and mediators are both involved in the pathogenesis of the disease and in determining its outcome. High-Mobility Group Box 1 (HMGB1) is a chromatin-associated nuclear protein acting as a signaling molecule in cells after binding to its receptors. Receptor for advanced glycation end products (RAGE) is a transmembrane multiligand receptor that binds to HMGB1. HMGB1-RAGE signaling has an important role in inflammatory and infectious diseases. Inhibition of HMGB1 activity reduces the inflammation in immune-associated diseases. In the present study, we examined the gene expressions and plasma levels of HMGB1 and its receptor RAGE in HAM/TSP patients, HTLV-1-infected asymptomatic carriers (ACs), and healthy controls. Peripheral blood mononuclear cells were collected from all the groups and complementary DNA (cDNA) was synthesized. HMGB-1 messenger RNA (mRNA) expression was quantified by real-time polymerase chain reaction (PCR) TaqMan method, and plasma levels of HMGB1 and soluble RAGE (sRAGE) were measured by enzyme-linked immunosorbent assay (ELISA). The mRNA expression of HMGB1 was the same among the groups (p > 0.05). No significant difference in the plasma levels of HMGB1 was observed between the groups (p > 0.05). The plasma levels of sRAGE were higher in ACs than HAM/TSP patients, and a significant difference was observed between the two groups (p < 0.001). Our results showed that sRAGE could play a potential role in the control of inflammatory response in HTLV-1 carriers through the inhibition of HMGB1 signaling and potentially could be used as an indicator for evaluation of HAM/TSP developing in HTLV-1-infected individuals.

Please stand by: how oncolytic viruses impact bystander cells

Oncolytic viruses (OVs) do more than simply infect and kill host cells. The accepted mechanism of action for OVs consists of a primary lytic phase and a subsequent antitumor and antiviral immune response. However, not all cells are subject to the direct effects of OV therapy, and it is becoming clear that OVs can also impact uninfected cells in the periphery. This review discusses the effects of OVs on uninfected neighboring cells, so-called bystander effects, and implications for OV therapies alone or in combination with other standard of care chemotherapy.

Expression profiling and microbial ligand binding analysis of high-mobility group box-1 (HMGB1) in turbot (Scophthalmus maximus L.)

High-mobility group box 1 (HMGB1), a highly conserved DNA-binding protein, was involved in nucleosome formation and transcriptional regulation, and could also act as an extracellular cytokine to trigger inflammation and immune responses. In this study, we identified a HMGB1 gene in turbot (Scophthalmus maximus L.). The full-length SaHMGB1 cDNA includes an open reading frame of 615 bp which encoded a 204 amino acid polypeptide with an estimated molecular mass of 23.19 kDa. SaHMGB1 was closely related to several fish HMGB1 and shared 74.4% overall identity with human. In addition, phylogenetic analyses revealed SaHMGB1 showed the closest relationship to Larimichthys crocea. Furthermore, QPCR analysis showed that SaHMGB1 was expressed in all examined tissues with abundant expression levels in brain, gill, intestine, and head kidney, and showed different expression patterns following different bacterial challenge. The significant quick regulation of SaHMGB1 in mucosal surfaces against infection suggest that HMGB1 might play critical roles in mucosal immunity against bacterial challenge. Finally, the in vitro binding assay showed that SaHMGB1 had strong binding ability to LPS, LTA, and PGN. Functional studies should further characterize HMGB1 function to understand the importance of the integrity of the mucosal barriers against infection, and to facilitate selection of the disease resistant family/strain in turbot.

High Mobility Group Box 1 Influences HSV1716 Spread and Acts as an Adjuvant to Chemotherapy

High Mobility Group Box 1 (HMGB1) is a multifunctional protein that plays various roles in the processes of inflammation, cancer, and other diseases. Many reports document abundant HMGB1 release following infection with oncolytic viruses (OVs). Further, other groups including previous reports from our laboratory highlight the synergistic effects of OVs with chemotherapy drugs. Here, we show that virus-free supernatants have varying cytotoxic potential, and HMGB1 is actively secreted by two established fibroblast cell lines (NIH 3T3 and 3T6-Swiss albino) following HSV1716 infection in vitro. Further, pharmacologic inhibition or genetic knock-down of HMGB1 reveals a role for HMGB1 in viral restriction, the ability to modulate bystander cell proliferation, and drug sensitivity in 3T6 cells. These data further support the multifactorial role of HMGB1, and suggest it could be a target for modulating the efficacy of oncolytic virus therapies alone or in combination with other frontline cancer treatments.

Endogenous DAMPs, Category I: Constitutively Expressed, Native Molecules (Cat. I DAMPs)

This chapter provides the reader with a collection of endogenous DAMPs in terms of constitutively expressed native molecules. The first class of this category refers to DAMPs, which are passively released from necrotic cells, and includes the most prominent subclasses of high mobility group box I and heat shock proteins. Further subclasses of DAMPs that are passively released from necrotic cells include S100 proteins, nucleic acids, histones, pro-forms of interleukin-1-family members, mitochondria-derived N-formylated peptides, F-actin, and heme. A particular subclass of these passively released DAMPs are molecules, which indirectly activate the inflammasome, including adenosine-5′-triphosphate, monosodium urate crystals, cholesterol crystals, some lipolytic species, and beta-amyloid. All these passively released DAMPs are characterized by their capability to promote necroinflammatory responses. The second class of this Category I refers to molecules, which are exposed on the surface of stressed cells. They include the subclass of phagocytosis-facilitating molecules such as calreticulin, as well as the subclass of MHC-I-related molecules such as MHC-I-related molecule A and B. These DAMPs are capable of inducing the activation of innate lymphoid cells and unconventional T cells. One of these DAMPs, the major histocompatibility complex I-related molecule A, is shown to act as a bona fide transplantation antigen. In sum, the endogenous constitutively expressed native molecules represent an impressive category of DAMPs with extraordinary properties, which play a critical role in the pathogenesis of many human diseases.

Alteration of serum high-mobility group protein 1 (HMGB1) levels in children with enterovirus 71-induced hand, foot, and mouth disease

Hand, foot, and mouth disease (HFMD) is a common pediatric disease caused by enterovirus infection. It typically presents as a fever along with flat, discolored spots and bumps on the hands, feet, and mouth. Compared with other viruses, enterovirus 71 (EV71)-induced HFMD is more prone to cause severe complications in children, such as brainstem encephalitis, cardiopulmonary disorders, and even death. More in-depth studies are still necessary to understand the characteristics of EV71-induced HFMD, although some related research has been reported so far. High-mobility group box 1 (HMGB1) is an inflammatory cytokine that can upregulate other inflammatory factors through its receptors, such as Toll-like receptors and the receptor for advanced glycation endproducts.We prospectively investigated the alteration of serum HMGB1, interleukin (IL)-6, and tumor necrosis factor (TNF)-α levels before and after treatment in 82 children with HFMD.We found that the serum HMGB1, IL-6, and TNF-α levels were significantly increased in EV71-induced HFMD, and that these changes were more serious in the severe and critical HMFD groups; however, there was no significant difference in the HMGB1 level between the normal control and mild HMFD groups. Moreover, the serum HMGB1 level was positively correlated with the alteration of serum IL-6 and TNF-α concentrations.These results suggest that HMGB1 is involved in the inflammatory pathogenesis of EV71-induced HFMD and that the serum level of HMGB1 could be applied as a clinical indicator for the severity of HFMD, and also a sign for the recovery prognosis of HFMD.

High Mobility Group Box-1 Protein and Outcomes in Critically Ill Surgical Patients Requiring Open Abdominal Management

Background. Previous studies assessing various cytokines in the critically ill/injured have been uninformative in terms of translating to clinical care management. Animal abdominal sepsis work suggests that enhanced intraperitoneal (IP) clearance of Damage-Associated Molecular Patterns (DAMPs) improves outcome. Thus measuring the responses of DAMPs offers alternate potential insights and a representative DAMP, High Mobility Group Box-1 protein (HMGB-1), was considered. While IP biomediators are being recognized in critical illness/trauma, HMGB-1 behaviour has not been examined in open abdomen (OA) management. Methods. A modified protocol for HMGB-1 detection was used to examine plasma/IP fluid samples from 44 critically ill/injured OA patients enrolled in a randomized controlled trial comparing two negative pressure peritoneal therapies (NPPT): Active NPPT (ANPPT) and Barker's Vacuum Pack NPPT (BVP). Samples were collected and analyzed at the time of laparotomy and at 24 and 48 hours after. Results. There were no statistically significant differences in survivor versus nonsurvivor HMGB-1 plasma or IP concentrations at baseline, 24 hours, or 48 hours. However, plasma HMGB-1 levels tended to increase continuously in the BVP cohort. Conclusions. HMGB-1 appeared to behave differently between NPPT cohorts. Further studies are needed to elucidate the relationship of HMGB-1 and outcomes in septic/injured patients.

Respiratory Syncytial Virus Infection Triggers Epithelial HMGB1 Release as a Damage-Associated Molecular Pattern Promoting a Monocytic Inflammatory Response

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in infant and elderly populations worldwide. Currently, there is no efficacious vaccine or therapy available for RSV infection. The molecular mechanisms underlying RSV-induced acute airway disease and associated long-term consequences remain largely unknown; however, experimental evidence suggests that the lung inflammatory response plays a fundamental role in the outcome of RSV infection. High-mobility group box 1 (HMGB1) is a nuclear protein that triggers inflammation when released from activated immune or necrotic cells and drives the pathogenesis of various infectious agents. Although HMGB1 has been implicated in many inflammatory diseases, its role in RSV-induced airway inflammation has not been investigated. This study investigates the molecular mechanism of action of extracellularly released HMGB1 in airway epithelial cells (A549 and small airway epithelial cells) to establish its role in RSV infection. Immunofluorescence microscopy and Western blotting results showed that RSV infection of human airway epithelial cells induced a significant release of HMGB1 as a result of translocation of HMGB1 from the cell nuclei to the cytoplasm and subsequent release into the extracellular space. Treating RSV-infected A549 cells with antioxidants significantly inhibited RSV-induced HMGB1 extracellular release. Studies using recombinant HMGB1 triggered immune responses by activating primary human monocytes. Finally, HMGB1 released by airway epithelial cells due to RSV infection appears to function as a paracrine factor priming epithelial cells and monocytes to inflammatory stimuli in the airways.

IMPORTANCE

RSV is a major cause of serious lower respiratory tract infections in young children and causes severe respiratory morbidity and mortality in the elderly. In addition, to date there is no effective treatment or vaccine available for RSV infection. The mechanisms responsible for RSV-induced acute airway disease and associated long-term consequences remain largely unknown. The oxidative stress response in the airways plays a major role in the pathogenesis of RSV. HMGB1 is a ubiquitous redox-sensitive multifunctional protein that serves as both a DNA regulatory protein and an extracellular cytokine signaling molecule that promotes airway inflammation as a damage-associated molecular pattern. This study investigated the mechanism of action of HMGB1 in RSV infection with the aim of identifying new inflammatory pathways at the molecular level that may be amenable to therapeutic interventions.

Neutrophil Extracellular Traps Go Viral

Neutrophils are the most numerous immune cells. Their importance as the first line of defense against bacterial and fungal pathogens is well described. In contrast, the role of neutrophils in controlling viral infections is less clear. Bacterial and fungal pathogens can stimulate neutrophils extracellular traps (NETs) in a process called NETosis. Although NETosis has previously been described as a special form of programmed cell death, there are forms of NET production that do not end with the demise of neutrophils. As an end result of NETosis, genomic DNA complexed with microbicidal proteins is expelled from neutrophils. These structures can kill pathogens or at least prevent their local spread within host tissue. On the other hand, disproportionate NET formation can cause local or systemic damage. Only recently, it was recognized that viruses can also induce NETosis. In this review, we discuss the mechanisms by which NETs are produced in the context of viral infection and how this may contribute to both antiviral immunity and immunopathology. Finally, we shed light on viral immune evasion mechanisms targeting NETs.

Alterations in oxidant/antioxidant balance, high-mobility group box 1 protein and acute phase response in cross-bred suckling piglets suffering from rotaviral enteritis

Rotaviral enteritis has emerged as a major cause of morbidity and mortality in piglets during their post-natal life. The present study was carried out to examine high-mobility group box 1 (HMGB1) protein, acute phase response and oxidative stress indices in the serum of suckling piglets suffering from enteritis with or without association of porcine group A rotavirus infection. The present investigation utilized 23 clinical cases with signs of acute enteritis and 12 more healthy piglets of a similar age group as control animals. Out of 23 enteritis cases, 12 cases were found to be positive for porcine group A rotavirus infection as confirmed by reverse transcription-polymerase chain reaction (RT-PCR) using specific primers for group A rotavirus, and the rest were found negative. The acute enteritis cases in piglets were associated with an elevated level of HMGB1 protein and serum haptoglobin and ceruloplasmin suggestive of an acute phase response. Among the oxidative stress indices, the concentrations of malondialdehyde (MDA) and nitric oxide (NO) in serum were significantly increased. A pronounced drop of total antioxidant capacity and the activity of antioxidant enzymes such as catalase and superoxide dismutase in the serum of piglets suffering from acute enteritis compared to healthy ones were also noticed. The alterations in HMGB1 protein, acute phase response and oxidative stress indices were more pronounced in cases with the involvement of porcine rotavirus as compared to rotavirus-negative cases. It is concluded that HMGB1 protein, markers of oxidative stress and acute phase proteins might play an important role in the aetiopathogenesis of porcine diarrhoea caused by rotavirus and might be true markers in diagnosing the conditions leading to the extension of the prompt and effective therapeutic care.

Molecular mechanism and therapeutic modulation of high mobility group box 1 release and action: an updated review

High mobility group box 1 (HMGB1) is an evolutionarily conserved protein, and is constitutively expressed in virtually all types of cells. Infection and injury converge on common inflammatory responses that are mediated by HMGB1 secreted from immunologically activated immune cells or passively released from pathologically damaged cells. Herein we review the emerging molecular mechanisms underlying the regulation of pathogen-associated molecular patterns (PAMPs)-induced HMGB1 secretion, and summarize many HMGB1-targeting therapeutic strategies for the treatment of infection- and injury-elicited inflammatory diseases. It may well be possible to develop strategies that specifically attenuate damage-associated molecular patterns (DAMPs)-mediated inflammatory responses without compromising the PAMPs-mediated innate immunity for the clinical management of infection- and injury-elicited inflammatory diseases.

Targeting HMGB1 in the treatment of sepsis

INTRODUCTION

Sepsis refers to the host's deleterious and non-resolving systemic inflammatory response to microbial infections and represents the leading cause of death in the intensive care unit. The pathogenesis of sepsis is complex, but partly mediated by a newly identified alarmin molecule, the high mobility group box 1 (HMGB1).

AREAS COVERED

Here we review the evidence that support extracellular HMGB1 as a late mediator of experimental sepsis with a wider therapeutic window and discuss the therapeutic potential of HMGB1-neutralizing antibodies and small molecule inhibitors (herbal components) in experimental sepsis.

EXPERT OPINION

It will be important to evaluate the efficacy of HMGB1-targeting strategies for the clinical management of human sepsis in the future.

Analysis of the released nuclear cytokine HMGB1 in human serum

A ubiquitous nuclear protein, the high-mobility group box 1 (HMGB1), is secreted by activated macrophages/monocytes and leaked passively from injured cells. HMGB1 functions as a mediator of infection- and injury-elicited inflammatory diseases. Here, we describe a semiquantitative immuno-blotting method to measure the released HMGB1 in human serum, in comparison with a commercially available HMGB1 ELISA technique.

High levels of circulating HMGB1 as a biomarker of acute liver failure in patients with viral hepatitis E

BACKGROUND

Viral hepatitis E clinically ranges between acute self-limiting hepatitis (AVH) and acute liver failure (ALF). The varied clinical course of the disease possibly thought to be immune-mediated. High-mobility group box 1 (HMGB1) is a non-histone chromosomal nuclear protein with recently discovered pro-inflammatory and immunomodulatory action. Its presence in abundance within hepatocytes is thought provoking in patients with hepatitis.

AIM

The present study was designed to elucidate the role of circulating HMGB1 and its gene expression in patients with viral hepatitis E.

METHODS

Blood samples were obtained from AVH (n = 38), ALF (n = 34) and healthy controls (HC, n = 30). The HMGB1 levels were estimated in serum by quantitative-micro-ELISA. Gene expression levels were studied in the patient's PBMCs by real-time PCR. Lymphocyte proliferation was estimated by colorimetric-MTT assay.

RESULTS

Mean circulating HMGB1 levels in HC, AVH and ALF patients were found to be 12.04 ± 2.23, 112.6 ± 13.33 and 225.3 ± 15.04 ng/ml respectively. The levels were significantly higher in ALF than AVH and HC (P < 0.0001). Moreover, 88.2% of ALF patients with >250 ng/ml of circulating HMGB1 had a fatal outcome. The gene expression of HMGB1 in the PBMCs of ALF and AVH patients were comparable. A positive correlation was observed between HMGB1 level and INR. A significantly low lymphocyte proliferation was observed in ALF patients (P = 0.008).

CONCLUSION

Massive necrosis of hepatocytes in ALF patients might predispose to excessive accumulation of extracellular HMGB1 leading to suppression of T-cell proliferation. Therefore, it is proposed that excessive circulating HMGB1 might play an important role in immunosuppression and fulminant course of the disease following HEV infection.

Two HMGB1 genes from grass carp Ctenopharyngodon idella mediate immune responses to viral/bacterial PAMPs and GCRV challenge

High mobility group box 1 (HMGB1) is a nuclear weapon in the immune arsenal and a master regulator of innate immunity, at the crossroads between innate and adaptive immunity. To clarify the immune characterizations of HMGB1 in fishes, two co-orthologs of HMGB1 (CiHMGB1a and CiHMGB1b) were identified in grass carp Ctenopharyngodon idella by local EST database searching and RACE techniques. mRNA expressions of the two HMGB1 genes are widespread in fifteen tissues investigated. The transcripts of CiHMGB1a and CiHMGB1b were significantly up-regulated and reached peak at 24h post GCRV challenge in spleen and head kidney tissues (P<0.05). The modulations are slow post-bacterial PAMP stimulations by contrast with those after viral PAMP or GCRV challenge. They are inhibited by bacterial PAMPs, but are enhanced by viral PAMP or virus. mRNA expression of CiHMGB1a is high and strongly modulated by nucleic acids and transcription of CiHMGB1b is low and mildly regulated by nucleic acids and capsids of GCRV. The over-expression vectors were constructed and transfected into C. idella kidney cell line to obtain stably expressing recombinant proteins. In HMGB1 over-expressed cells, mRNA expressions of IPS-1, MyD88 and Mx1 were down-regulated, whereas TRIF was found to be up-regulated and IFN-I showed no change in its expression. After GCRV challenge, the transcripts of IPS-1, MyD88 and Mx1 were up-regulated, while IFN-I showed down-regulation, and TRIF showed up-regulation after an initial phase of decline. The titer assay demonstrated no antiviral activity of HMGB1s. The results indicated mRNA expressions of HMGB1a and HMGB1b are enhanced by GCRV or viral PAMP, and are inhibited by bacterial PAMPs; HMGB1a and HMGB1b collaborate with each other and play important roles in modulating the innate immune responses, although without direct antiviral effect; the immune network triggered by HMGB1 work together in concert to maintain homeostasis.

High mobility group box chromosomal protein 1 in acute-on-chronic liver failure patients and mice with ConA-induced acute liver injury

High mobility group box chromosomal protein 1 (HMGB1) is an important proinflammatory molecule in many inflammatory disorders, but little is known about its role in acute-on-chronic liver failure (ACLF). Here, we investigated the relationship between the expression of HMGB1 and the disease onset and severity of ACLF patients and mice with acute liver injury/failure induced by concanavalin A (ConA). Peripheral blood mononuclear cells (PBMCs) and serum from ACLF patients were collected, and a mouse model of acute liver injury/failure was induced by ConA. HMGB1 mRNA expression in patient PBMCs or in murine livers and serum HMGB1 protein in ACLF patients and mice were assayed by RT-PCR and Western blotting, respectively. HMGB1 translocation in hepatocytes of ConA-treated mice was assessed by immunohistochemical staining. Up-regulated HMGB1 mRNA levels in PBMCs and accumulated protein in serum were both correlated with disease severity in ACLF patients. In the animal model, HMGB1 levels increased at 4 h and reached its peak value at 8-12 h after challenge with ConA, which suggests that HMGB1 is a relatively late proinflammatory cytokine compared with TNF-α. Translocation of HMGB1 from the nucleus to the cytoplasm in hepatocytes was correlated with the severity of liver injury in mice. While specific anti-HMGB1 antibodies and nicotine protected mice from acute liver injury/failure by reducing mortality and improving liver tissue injury, treatment with recombinant HMGB1 led to an increased mortality due to ConA challenge. Thus, the data from the present study suggest that HMGB1 plays a critical role in the systemic inflammation of ACLF and could be a potential therapeutic target in the treatment of ACLF.

Novel microRNAs encoded by duck enteritis virus

Duck enteritis virus (DEV) is an important herpesvirus pathogen associated with acute, highly contagious lethal disease in waterfowls. Using a deep sequencing approach on RNA from infected chicken embryo fibroblast cultures, we identified several novel DEV-encoded micro (mi)RNAs. Unlike most mardivirus-encoded miRNAs, DEV-encoded miRNAs mapped mostly to the unique long region of the genome. The precursors of DEV miR-D18 and miR-D19 overlapped with each other, suggesting similarities to miRNA-offset RNAs, although only the DEV-miR-D18-3p was functional in reporter assays. Identification of these novel miRNAs will add to the growing list of virus-encoded miRNAs enabling the exploration of their roles in pathogenesis.

Glycyrrhizin attenuates HMGB1-induced hepatocyte apoptosis by inhibiting the p38-dependent mitochondrial pathway

AIM: To examine how high-mobility group box 1 (HMGB1) regulates hepatocyte apoptosis and, furthermore, to determine whether glycyrrhizin (GL), a known HMGB1 inhibitor, prevents HMGB1-induced hepatocyte apoptosis.

METHODS: A human hepatocellular carcinoma cell line stably transfected with a bile acid transporter (Huh-BAT cells), were used in this study. Apoptosis was quantified using 4’,6-diamidino-2-phenylindole dihydrochloride staining and the APO Percentage apoptosis assay, and its signaling cascades were explored by immunoblot analysis. Kinase signaling was evaluated by immunoblotting and by using selective inhibitors. It is also tried to identify hepatocyte apoptosis affected by the HMGB1 inhibitor, GL.

RESULTS: HMGB1 increased cellular apoptosis in Huh-BAT cells. HMGB1 led to increased cytochrome c release from mitochondria into the cytosol, and induced the cleavage of procaspase 3. However, it did not affect the activation of caspase 8. HMGB1-induced caspase 3 activation was significantly attenuated by the p38 inhibitor SB203580. GL significantly attenuated HMGB1-induced hepatocyte apoptosis. GL also prevented HMGB1-induced cytochrome c release and p38 activation in Huh-BAT cells.

CONCLUSION: The present study demonstrated that HMGB1 promoted hepatocyte apoptosis through a p38-dependent mitochondrial pathway. In addition, GL had an anti-apoptotic effect on HMGB1-treated hepatocytes.