Folic acid derived-P5779 mimetics regulate DAMP-mediated inflammation through disruption of HMGB1:TLR4:MD-2 axes

A patent review on HMGB1 inhibitors for the treatment of liver diseases

INTRODUCTION

HMGB1 is a non-histone chromatin protein released or secreted in response to tissue damage or infection. Extracellular HMGB1, as a crucial immunomodulatory factor, binds with several different receptors to innate inflammatory responses that aggravate acute and chronic liver diseases. The increased levels of HMGB1 have been reported in various liver diseases, highlighting that it represents a potential biomarker and druggable target for therapeutic development.

AREAS COVERED

This review summarizes the current knowledge on the structure, function, and interacting receptors of HMGB1 and its significance in multiple liver diseases. The latest patented and preclinical studies of HMGB1 inhibitors (antibodies, peptides, and small molecules) for liver diseases are summarized by using the keywords 'HMGB1,' 'HMGB1 antagonist, HMGB1-inhibitor,' 'liver disease' in Web of Science, Google Scholar, Google Patents, and PubMed databases in the year from 2017 to 2023.

EXPERT OPINIONS

In recent years, extensive research on HMGB1-dependent inflammatory signaling has discovered potent inhibitors of HMGB1 to reduce the severity of liver injury. Despite significant progress in the development of HMGB1 antagonists, few of them are approved for clinical treatment of liver-related diseases. Developing safe and effective specific inhibitors for different HMGB1 isoforms and their interaction with receptors is the focus of future research.

Maternal Serum Folic Acid Levels and Onset of Kawasaki Disease in Offspring During Infancy

Importance

Kawasaki disease is an acute systemic vasculitis that primarily affects infants and young children. No reproducible risk factors have yet been identified, but a possible association between maternal folic acid supplementation and Kawasaki disease has been reported previously.

Objective

To investigate the associations of exposure to maternal serum folic acid levels and maternal folic acid supplementation with onset of Kawasaki disease during infancy among offspring.

Design, Setting, and Participants

This cohort study used data from the Japan Environment and Children's Study, a nationwide birth cohort, which has enrolled children since 2011. This study used the data set released in October 2019, and analysis was performed in January 2023.

Exposures

Maternal serum folic acid levels (≥10 ng/mL classified as exposed) during the second and third trimesters and the frequency of maternal folic acid supplementation during the first trimester and during the second and third trimesters of pregnancy (once a week or more was classified as exposed).

Main Outcomes and Measures

The primary outcome was onset of Kawasaki disease in offspring up to age 12 months. Odds ratios (ORs) for each exposure were estimated, and propensity score-adjusted logistic regression was conducted on the basis of the sets of variables.

Results

The study population comprised 87 702 children who were followed-up for 12 months. Of these, 336 children developed Kawasaki disease. Mothers who took folic acid supplements (31 275 mothers [35.7%]; mean [SD] age, 32 [5] years) had higher serum folic acid levels than those who did not take supplements. Higher maternal serum folic acid levels were associated with a significantly lower risk of Kawasaki disease in offspring than lower levels (folic acid ≥10 vs <10 ng/mL, 56 of 20 698 children [0.27%] vs 267 of 64 468 children [0.41%]; OR, 0.68; 95% CI, 0.50-0.92). Children whose mothers took folic acid supplementation during the first trimester had a lower prevalence of Kawasaki disease than children whose mothers did not take folic acid (131 of 39 098 children [0.34%] vs 203 of 48 053 children [0.42%]), although the difference was not statistically significant (OR, 0.83; 95% CI, 0.66-1.04). Supplementation during the second and third trimesters was associated with a significantly lower risk of Kawasaki disease compared with no supplementation (94 of 31 275 children [0.30%] vs 242 of 56 427 children [0.43%]; OR, 0.73; 95% CI, 0.57-0.94).

Conclusions and Relevance

In this cohort study, higher serum folic acid levels (≥10 ng/mL) and maternal folic acid supplementation more than once a week during the second and third trimesters were associated with reduced risk of Kawasaki disease in offspring during infancy.

Gut microbial metabolite hyodeoxycholic acid targets the TLR4/MD2 complex to attenuate inflammation and protect against sepsis

Sepsis, a critical condition resulting from the systemic inflammatory response to a severe microbial infection, represents a global public health challenge. However, effective treatment or intervention to prevent and combat sepsis is still lacking. Here, we report that hyodeoxycholic acid (HDCA) has excellent anti-inflammatory properties in sepsis. We discovered that the plasma concentration of HDCA was remarkably lower in patients with sepsis and negatively correlated with the severity of the disease. Similar changes in HDCA levels in plasma and cecal content samples were observed in a mouse model of sepsis, and these changes were associated with a reduced abundance of HDCA-producing strains. Interestingly, HDCA administration significantly decreased systemic inflammatory responses, prevented organ injury, and prolonged the survival of septic mice. We demonstrated that HDCA suppressed excessive activation of inflammatory macrophages by competitively blocking lipopolysaccharide binding to the Toll-like receptor 4 (TLR4) and myeloid differentiation factor 2 receptor complex, a unique mechanism that characterizes HDCA as an endogenous inhibitor of inflammatory signaling. Additionally, we verified these findings in TLR4 knockout mice. Our study highlights the potential value of HDCA as a therapeutic molecule for sepsis.

Binding energy analysis and molecular dynamic simulation studies of the designed orally active, non-toxic GABARAP modulators

Epilepsy is a severe neurological disorder that occurs when the communication between the neurons is disturbed. Gamma-amino butyric acid-associated protein (GABARAP) plays a key role in balancing Gamma-aminobutyric acid-A (GABA(A)) receptor functions of inhibiting the neurotransmission and controlling the seizure. In this study, we introduce the derivatives of the selected anti-epileptic drugs, namely Felbamate and Clobazam, by substituting different hydrophilic and hydrophobic groups at the specified positions. Molecular docking studies between the derivatives and GABARAP were carried out using PyRx software. The interacting residues were identified from LigPlot⁺. Drug-likeness, drug-related properties, and toxic endpoints of each derivative were analyzed using the SwissADME, Osiris property explorer, and ProTox-II servers. After analyzing the binding energy, drug-properties, and toxicity, the best five derivatives of Felbamate and Clobazam were selected. Molecular Dynamic simulation studies involving the target-ligand interaction were carried out for 100 nanoseconds using GROMACS 2018. The root mean square deviation, root mean square fluctuation, radius of gyration, Solvent accessible area, Energy plots and trajectories of the ten GABARAP complexes of the derivatives, and two GABARAP complexes of parent drugs were compared and critically analyzed. Among the five Felbamate derivatives, F7 formed the most stable complex with GABARAP. Among the five Clobazam derivatives, C27, C33 and C32 showed stable GABARAP interaction. In light of the above systematic computational analysis, we propose F7, C27, C33, and C32 as the potential anti-epileptic drug candidates for developing novel therapeutics. The substitution of hydrophobic groups at para position on benzene ring has promoted strong binding to GABARAP. Communicated by Ramaswamy H. Sarma.

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

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

Necrotic reshaping of the glioma microenvironment drives disease progression

Glioblastoma is the most common primary brain tumor and has a dismal prognosis. The development of central necrosis represents a tipping point in the evolution of these tumors that foreshadows aggressive expansion, swiftly leading to mortality. The onset of necrosis, severe hypoxia and associated radial glioma expansion correlates with dramatic tumor microenvironment (TME) alterations that accelerate tumor growth. In the past, most have concluded that hypoxia and necrosis must arise due to "cancer outgrowing its blood supply" when rapid tumor growth outpaces metabolic supply, leading to diffusion-limited hypoxia. However, growing evidence suggests that microscopic intravascular thrombosis driven by the neoplastic overexpression of pro-coagulants attenuates glioma blood supply (perfusion-limited hypoxia), leading to TME restructuring that includes breakdown of the blood-brain barrier, immunosuppressive immune cell accumulation, microvascular hyperproliferation, glioma stem cell enrichment and tumor cell migration outward. Cumulatively, these adaptations result in rapid tumor expansion, resistance to therapeutic interventions and clinical progression. To inform future translational investigations, the complex interplay among environmental cues and myriad cell types that contribute to this aggressive phenotype requires better understanding. This review focuses on contributions from intratumoral thrombosis, the effects of hypoxia and necrosis, the adaptive and innate immune responses, and the current state of targeted therapeutic interventions.

Platelet Toll-like Receptor 4–Related Innate Immunity Potentially Participates in Transfusion Reactions Independent of ABO Compatibility: An Ex Vivo Study

The role of platelet TLR4 in transfusion reactions remains unclear. This study analyzed platelet TLR4 and certain damage-associated molecular patterns (DAMPs) and evaluated how ABO compatibility affected TLR4 expression after a simulated ex vivo transfusion. A blood bank was the source of donor red blood cells. Blood from patients undergoing cardiac surgery was processed to generate a washed platelet suspension to which the donor blood was added in concentrations 1, 5, and 10% (v/v). Blood-mixing experiments were performed on four groups: a 0.9% saline control group (n = 31); a matched-blood-type mixing group (group M, n = 20); an uncross-matched ABO-specific mixing group (group S, n = 20); and an ABO-incompatible blood mixing group (group I, n = 20). TLR4 expression in the platelets was determined after blood mixing. We evaluated levels of TLR4-binding DAMPs (HMGB1, S100A8, S100A9, and SAA), lipopolysaccharide-binding protein, and endpoint proteins in the TLR4 signaling pathway. In the M, S, and I groups, 1, 5, and 10% blood mixtures significantly increased TLR4 expression (all p < 0.001) in a concentration-dependent manner. Groups M, S, and I were not discovered to have significantly differing TLR4 expression (p = 0.148). HMGB1, S100A8, and S100A9 levels were elevated in response to blood mixing, but SAA, lipopolysaccharide-binding protein, TNF-α, IL-1β, and IL-6 levels were not. Blood mixing may elicit innate immune responses by upregulating platelet TLR4 and DAMPs unassociated with ABO compatibility, suggesting that innate immunity through TLR4-mediated signaling may induce transfusion reactions.

Folic Acid Protects Melanocytes from Oxidative Stress via Activation of Nrf2 and Inhibition of HMGB1

Vitiligo is a cutaneous depigmentation disease due to loss of epidermal melanocytes. Accumulating evidence has indicated that oxidative stress plays a vital role in vitiligo via directly destructing melanocytes and triggering inflammatory response that ultimately undermines melanocytes. Folic acid (FA), an oxidized form of folate with high bioavailability, exhibits potent antioxidant properties and shows therapeutic potential in multiple oxidative stress-related diseases. However, whether FA safeguards melanocytes from oxidative damages remains unknown. In this study, we first found that FA relieved melanocytes from H₂O₂-induced abnormal growth and apoptosis. Furthermore, FA enhanced the activity of antioxidative enzymes and remarkably reduced intracellular ROS levels in melanocytes. Subsequently, FA effectively activated nuclear factor E2-related factor 2 (Nrf2) pathway, and Nrf2 knockdown blocked the protective effects of FA on H₂O₂-treated melanocytes. Additionally, FA inhibited the production of proinflammatory HMGB1 in melanocytes under oxidative stress. Taken together, our findings support the protective effects of FA on human melanocytes against oxidative injury via the activation of Nrf2 and the inhibition of HMGB1, thus indicating FA as a potential therapeutic agent for the treatment of vitiligo.

A Nonlethal Murine Flame Burn Model Leads to a Transient Reduction in Host Defenses and Enhanced Susceptibility to Lethal Pseudomonas aeruginosa Infection

Of the 486,000 burn injuries that required medical treatment in the United States in 2016, 40,000 people were hospitalized, with >3,000 fatalities. After burn injury, humans are at increased risk of sepsis and mortality from infections caused by Pseudomonas aeruginosa, an opportunistic pathogen. We hypothesize that systemic events were initiated from the burn that increased the host's susceptibility to P. aeruginosa. A nonlethal 10% total body surface area (TBSA), full-thickness flame burn was performed in CD-1 mice without and with subsequent P. aeruginosa (strain M2) infection. The 50% lethal dose for subcutaneous infection with P. aeruginosa M2 at the burn site immediately after the burn decreased by 6 log, with mortality occurring between 18 and 26 h, compared with P. aeruginosa-infected mice without burn injury. Bacteria in distal organs were detected by 18 h, concurrent with the onset of clinical symptoms. Serum proinflammatory cytokines (interleukin-6 [IL-6], IL-1β, gamma interferon, and tumor necrosis factor alpha) and the anti-inflammatory cytokine IL-10 were first detected at 12 h postburn with infection and continued to increase until death. Directly after burn alone, serum levels of HMGB1, a danger-associated molecular pattern and TLR4 agonist, transiently increased to 50 ng/ml before returning to 20 ng/ml. Burn with P. aeruginosa infection increased serum HMGB1 concentrations >10-fold (250 ng/ml) at the time of death. This HMGB1-rich serum stimulated TLR4-mediated NF-κB activation in a TLR4 reporter cell line. Treatment of infected burned mice with P5779, a peptide inhibitor of HMGB1, increased the mean survival from 23 to 42 h (P < 0.0001). We conclude that the high level of serum HMGB1, which preceded the increase in proinflammatory cytokines, is associated with postburn mortality.

Immunological mechanisms underlying sterile inflammation in the pathogenesis of atherosclerosis: potential sites for intervention

Introduction: Innate and adaptive immunity play a critical role in the underlying pathological mechanisms of atherosclerosis and potential target sites of sterile inflammation open opportunities to develop novel therapeutics. In response to oxidized LDL in the intimal layer, T cell subsets are recruited and activated at the site of atheroma to upregulate pro-atherogenic cytokines which exacerbate plaque formation instability.Areas covered: A systematic search of PubMed and the Web of Science was performed between January 2001- September 2020 and relevant articles in sterile inflammation and atherosclerosis were critically reviewed. The original information was collected on the interconnection between danger associated molecular patterns (DAMPs) as the mediators of sterile inflammation and the receptor complex of CD36-TLR4-TLR6 that primes and activates inflammasomes in the pathophysiology of atherosclerosis. Mediators of sterile inflammation are identified to target therapeutic strategies in the management of atherosclerosis.Expert opinion: Sterile inflammation via NLRP3 inflammasome is perpetuated by the activation of IL-1β and IL-18 and induction of pyroptosis resulting in the release of additional inflammatory cytokines and DAMPs. Challenges with current inhibitors of the NLRP3 inflammasome lie in the specificity, stability, and efficacy in targeting the NLRP3 inflammasome constituents without ameliorating upstream or downstream responses necessary for survival.

The role of RAGE in host pathology and crosstalk between RAGE and TLR4 in innate immune signal transduction pathways

Although the innate immune receptor protein, Receptor for Advanced Glycation End products (RAGE), has been extensively studied, there has been renewed interest in RAGE for its potential role in sepsis, along with a host of other inflammatory diseases of chronic, noninfectious origin. In contrast to other innate immune receptors, for example, Toll-like receptors (TLRs), that recognize ligands derived from pathogenic organisms that are collectively known as "pathogen-associated molecular patterns" (PAMPs) or host-derived "damage-associated molecular patterns" (DAMPs), RAGE has been shown to recognize a broad collection of DAMPs exclusively. Historically, these DAMPs have been shown to be pro-inflammatory in nature. Early studies indicated that the adaptor molecule, MyD88, might be important for this change. More recent studies have explored further the mechanisms underlying this inflammatory change. Overall, the newer results have shown that there is extensive crosstalk between RAGE and TLRs. The three canonical RAGE ligands, Advanced Glycation End products (AGEs), HMGB1, and S100 proteins, have all been shown to activate both TLRs and RAGE to varying degrees in order to induce inflammation in in vitro models. As with any field that delves deeply into innate signaling, obstacles of reagent purity may be a cause of some of the discrepancies in the literature, and we have found that commercial antibodies that have been widely used exhibit a high degree of nonspecificity. Nonetheless, the weight of published evidence has led us to speculate that RAGE may be physically interacting with TLRs on the cell surface to elicit inflammation via MyD88-dependent signaling.

Novel genes associated with folic acid-mediated metabolism in mouse: A bioinformatics study

Folic acid plays an essential role in the central nervous system and cancer. This study aimed to screen genes related to folic acid metabolism. Datasets (GSE80587, GSE65267 and GSE116299) correlated to folic acid were screened in the Gene Expression Omnibus. Weighed gene co-expression network analysis was performed to identify modules associated with sample traits of folic acid and organs (brain, prostate and kidney). Functional enrichment analysis was performed for the eigengenes in modules that were significantly correlated with sample traits. Accordingly, the hub genes and key nodes in the modules were identified using the protein interaction network. A total of 17,252 genes in three datasets were identified. One module, which included 97 genes that were highly correlated with sample traits (including folic acid treatment [cor = -0.57, P = 3e-04] and kidney [cor = -0.68, p = 4e-06]), was screened out. Hub genes, including tetratricopeptide repeat protein 38 (Ttc38) and miR-185, as well as those (including Sema3A, Insl3, Dll1, Msh4 and Snai1) associated with "neuropilin binding", "regulation of reproductive process" and "vitamin D metabolic process", were identified. Genes, including Ttc38, Sema3A, Insl3, Dll1, Msh4 and Snai1, were the novel factors that may be associated with the development of the kidneys and related to folic acid treatment.

High mobility group box 1 (HMGB1): a pivotal regulator of hematopoietic malignancies

High mobility group box 1 (HMGB1) is a nonhistone chromatin-associated protein that has been widely reported to play a pivotal role in the pathogenesis of hematopoietic malignancies. As a representative damage-associated molecular pattern (DAMP), HMGB1 normally exists inside cells but can be secreted into the extracellular environment through passive or active release. Extracellular HMGB1 binds with several different receptors and interactors to mediate the proliferation, differentiation, mobilization, and senescence of hematopoietic stem cells (HSCs). HMGB1 is also involved in the formation of the inflammatory bone marrow (BM) microenvironment by activating proinflammatory signaling pathways. Moreover, HMGB1-dependent autophagy induces chemotherapy resistance in leukemia and multiple myeloma. In this review, we systematically summarize the emerging roles of HMGB1 in carcinogenesis, progression, prognosis, and potential clinical applications in different hematopoietic malignancies. In summary, targeting the regulation of HMGB1 activity in HSCs and the BM microenvironment is highly beneficial in the diagnosis and treatment of various hematopoietic malignancies.

Targeting Inflammation Driven by HMGB1

High mobility group box 1 (HMGB1) is a highly conserved, nuclear protein present in all cell types. It is a multi-facet protein exerting functions both inside and outside of cells. Extracellular HMGB1 has been extensively studied for its prototypical alarmin functions activating innate immunity, after being actively released from cells or passively released upon cell death. TLR4 and RAGE operate as the main HMGB1 receptors. Disulfide HMGB1 activates the TLR4 complex by binding to MD-2. The binding site is separate from that of LPS and it is now feasible to specifically interrupt HMGB1/TLR4 activation without compromising protective LPS/TLR4-dependent functions. Another important therapeutic strategy is established on the administration of HMGB1 antagonists precluding RAGE-mediated endocytosis of HMGB1 and HMGB1-bound molecules capable of activating intracellular cognate receptors. Here we summarize the role of HMGB1 in inflammation, with a focus on recent findings on its mission as a damage-associated molecular pattern molecule and as a therapeutic target in inflammatory diseases. Recently generated HMGB1-specific inhibitors for treatment of inflammatory conditions are discussed.

Serum Nutrient Levels and Aging Effects on Periodontitis

Periodontal disease damages tissues as a result of dysregulated host responses against the chronic bacterial biofilm insult and approximately 50% of US adults >30 years old exhibit periodontitis. The association of five blood nutrients and periodontitis were evaluated due to our previous findings regarding a potential protective effect for these nutrients in periodontal disease derived from the US population sampled as part of the National Health and Nutrition Examination Survey (1999⁻2004). Data from over 15,000 subjects was analyzed for blood levels of cis-β-carotene, β-cryptoxanthin, folate, vitamin D, and vitamin E, linked with analysis of the presence and severity of periodontitis. Moderate/severe disease patients had lower cis-β-carotene levels across all racial/ethnic groups and these decreased levels in moderate/severe periodontitis were exacerbated with age. β-cryptoxanthin demonstrated lower levels in severe disease patients across the entire age range in all racial/ethnic groups. Folate differences were evident across the various age groups with consistently lower levels in periodontitis patients >30 years and most pronounced in females. Lower levels of vitamin D were consistently noted across the entire age range of patients with a greater difference seen in females with periodontitis. Finally, an analytical approach to identify interactions among these nutrients related to age and periodontitis showed interactions of vitamin D in females, and folate with race in the population. These findings suggest that improving specific nutrient intake leading to elevated blood levels of a combination of these protective factors may provide a novel strategy to affect the significant increase in periodontitis that occurs with aging.