Expatiating the molecular approaches of HMGB1 in diabetes mellitus: Highlighting signalling pathways via RAGE and TLRs

Oxidative High Mobility Group Box-1 Accelerates Mitochondrial Transfer from Mesenchymal Stem Cells to Colorectal Cancer Cells Providing Cancer Cell Stemness

Mitochondria are important organelles for cell metabolism and tissue survival. Their cell-to-cell transfer is important for the fate of recipient cells. Recently, bone marrow mesenchymal stem cells (BM-MSCs) have been reported to provide mitochondria to cancer cells and rescue mitochondrial dysfunction in cancer cells. However, the details of the mechanism have not yet been fully elucidated. In this study, we investigated the humoral factors inducing mitochondrial transfer (MT) and the mechanisms. BM-MSCs produced MT in colorectal cancer (CRC) cells damaged by 5-fluorouracil (5-FU), but were suppressed by the anti-high mobility group box-1 (HMGB1) antibody. BM-MSCs treated with oxidized HMGB1 had increased expression of MT-associated genes, whereas reduced HMGB1 did not. Inhibition of nuclear factor-κB, a downstream factor of HMGB1 signaling, significantly decreased MT-associated gene expression. CRC cells showed increased stemness and decreased 5-FU sensitivity in correlation with MT levels. In a mouse subcutaneous tumor model of CRC, 5-FU sensitivity decreased and stemness increased by the MT from host mouse BM-MSCs. These results suggest that oxidized HMGB1 induces MTs from MSCs to CRC cells and promotes cancer cell stemness. Targeting of oxidized HMGB1 may attenuate stemness of CRCs.

Targeting HMGB1 and Its Interaction with Receptors: Challenges and Future Directions

High mobility group box 1 (HMGB1) is a nonhistone chromatin protein predominantly located in the nucleus. However, under pathological conditions, HMGB1 can translocate from the nucleus to the cytoplasm and subsequently be released into the extracellular space through both active secretion and passive release mechanisms. The distinct cellular locations of HMGB1 facilitate its interaction with various endogenous and exogenous factors, allowing it to perform diverse functions across a range of diseases. This Perspective provides a comprehensive overview of the structure, release mechanisms, and multifaceted roles of HMGB1 in disease contexts. Furthermore, it introduces the development of both small molecule and macromolecule inhibitors targeting HMGB1 and its interaction with receptors. A detailed analysis of the predicted pockets is also presented, aiming to establish a foundation for the future design and development of HMGB1 inhibitors.

Human iPSC-based disease modeling studies identify a common mechanistic defect and potential therapies for AMD and related macular dystrophies

Age-related macular degeneration (AMD) and related macular dystrophies (MDs) primarily affect the retinal pigment epithelium (RPE) in the eye. A hallmark of AMD/MDs that drives later-stage pathologies is drusen. Drusen are sub-RPE lipid-protein-rich extracellular deposits, but how drusen forms and accumulates is not known. We utilized human induced pluripotent stem cell (iPSC)-derived RPE from patients with AMD and three distinct MDs to demonstrate that reduced activity of RPE-secreted matrix metalloproteinase 2 (MMP2) contributes to drusen in multiple maculopathies in a genotype-agnostic manner by instigating sterile inflammation and impaired lipid homeostasis via damage-associated molecular pattern molecule (DAMP)-mediated activation of receptor for advanced glycation end-products (RAGE) and increased secretory phospholipase 2-IIA (sPLA2-IIA) levels. Therapeutically, RPE-specific MMP2 supplementation, RAGE-antagonistic peptide, and a small molecule inhibitor of sPLA2-IIA ameliorated drusen accumulation in AMD/MD iPSC-RPE. Ultimately, this study defines a causal role of the MMP2-DAMP-RAGE-sPLA2-IIA axis in AMD/MDs.

High Mobility Group Box 1 (HMGB1): Molecular Signaling and Potential Therapeutic Strategies

High Mobility Group Box 1 (HMGB1) is a highly conserved non-histone chromatin-associated protein across species, primarily recognized for its regulatory impact on vital cellular processes, like autophagy, cell survival, and apoptosis. HMGB1 exhibits dual functionality based on its localization: both as a non-histone protein in the nucleus and as an inducer of inflammatory cytokines upon extracellular release. Pathophysiological insights reveal that HMGB1 plays a significant role in the onset and progression of a vast array of diseases, viz., atherosclerosis, kidney damage, cancer, and neurodegeneration. However, a clear mechanistic understanding of HMGB1 release, translocation, and associated signaling cascades in mediating such physiological dysfunctions remains obscure. This review presents a detailed outline of HMGB1 structure-function relationship and its regulatory role in disease onset and progression from a signaling perspective. This review also presents an insight into the status of HMGB1 druggability, potential limitations in understanding HMGB1 pathophysiology, and future perspective of studies that can be undertaken to address the existing scientific gap. Based on existing paradigm of various studies, HMGB1 is a critical regulator of inflammatory cascades and drives the onset and progression of a broad spectrum of dysfunctions. Studies focusing on HMGB1 druggability have enabled the development of biologics with potential clinical benefits. However, deeper understanding of post-translational modifications, redox states, translocation mechanisms, and mitochondrial interactions can potentially enable the development of better courses of therapy against HMGB1-mediated physiological dysfunctions.

Methylglyoxal: A Key Factor for Diabetic Retinopathy and Its Effects on Retinal Damage

Background: Diabetic retinopathy is the most common retinal vascular disease, affecting the retina's blood vessels and causing chronic inflammation, oxidative stress, and, ultimately, vision loss. Diabetes-induced elevated glucose levels increase glycolysis, the main methylglyoxal (MGO) formation pathway. MGO is a highly reactive dicarbonyl and the most rapid glycation compound to form endogenous advanced glycation end products (AGEs). MGO can act both intra- and extracellularly by glycating molecules and activating the receptor for AGEs (RAGE) pathway. Conclusions: This review summarizes the sources of MGO formation and its actions on various cell pathways in retinal cells such as oxidative stress, glycation, autophagy, ER stress, and mitochondrial dysfunction. Finally, the detoxification of MGO by glyoxalases is discussed.

High Mobility Group Box Protein (HMGB1): A Potential Therapeutic Target for Diabetic Encephalopathy

HMGB (high mobility group B) is one of the ubiquitous non-histone nuclear protein superfamilies that make up the HMG (high mobility group) protein group. HMGB1 is involved in a variety of physiological and pathological processes in the human body, including a structural role in the cell nucleus as well as replication, repair, DNA transcription, and assembly of nuclear proteins. It functions as a signaling regulator in the cytoplasm and a pro-inflammatory cytokine in the extracellular environment. Among several studies, HMGB1 protein is also emerging as a crucial factor involved in the development and progression of diabetic encephalopathy (DE) along with other factors such as hyperglycaemia-induced oxidative and nitrosative stress. Diabetes' chronic side effect is DE, which manifests as cognitive and psychoneurological dysfunction. The HMGB1 is released outside to the extracellular medium in diabetes condition through active or passive routes, where it functions as a damage-associated molecular pattern (DAMP) molecule to activate several signaling pathways by interacting with receptors for advanced glycosylation end-products (RAGE)/toll like receptors (TLR). HMGB1 reportedly activates inflammatory pathways, disrupts the blood-brain barrier, causes glutamate toxicity and oxidative stress, and promotes neuroinflammation, contributing to the development of cognitive impairment and neuronal damage which is suggestive of the involvement of HMGB1 in the enhancement of the diabetes-induced encephalopathic condition. Additionally, HMGB1 is reported to induce insulin resistance, further exacerbating the metabolic dysfunction associated with diabetes mellitus (DM). Thus, the present review explores the possible pathways associated with DM-induced hyperactivation of HMGB1 ultimately leading to DE.

Icariin attenuates vascular endothelial dysfunction by inhibiting inflammation through GPER/Sirt1/HMGB1 signaling pathway in type 1 diabetic rats

Icariin, a flavonoid glycoside, is extracted from Epimedium. This study aimed to investigate the vascular protective effects of icariin in type 1 diabetic rats by inhibiting high-mobility group box 1 (HMGB1)-related inflammation and exploring its potential mechanisms. The impact of icariin on vascular dysfunction was assessed in streptozotocin (STZ)-induced diabetic rats through vascular reactivity studies. Western blotting and immunofluorescence assays were performed to measure the expressions of target proteins. The release of HMGB1 and pro-inflammation cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The results revealed that icariin administration enhanced acetylcholine-induced vasodilation in the aortas of diabetic rats. It also notably reduced the release of pro-inflammatory cytokines, including interleukin-8 (IL-8), IL-6, IL-1β, and tumor necrosis factor-alpha (TNF-α) in diabetic rats and high glucose (HG)-induced human umbilical vein endothelial cells (HUVECs). The results also unveiled that the pro-inflammatory cytokines in the culture medium of HUVECs could be increased by rHMGB1. The increased release of HMGB1 and upregulated expressions of HMGB1-related inflammatory factors, including advanced glycation end products (RAGE), Toll-like receptor 4 (TLR4), and phosphorylated p65 (p-p65) in diabetic rats and HG-induced HUVECs, were remarkably suppressed by icariin. Notably, HMGB1 translocation from the nucleus to the cytoplasm in HUVECs under HG was inhibited by icariin. Meanwhile, icariin could activate G protein-coupled estrogen receptor (GPER) and sirt1. To explore the role of GPER and Sirt1 in the inhibitory effect of icariin on HMGB1 release and HMGB-induced inflammation, GPER inhibitor and Sirt1 inhibitor were used in this study. These inhibitors diminished the effects of icariin on HMGB1 release and HMGB1-induced inflammation. Specifically, the GPER inhibitor also negated the activation of Sirt1 by icariin. These findings suggest that icariin activates GPER and increases the expression of Sirt1, which in turn reduces HMGB1 translocation and release, thereby improving vascular endothelial function in type 1 diabetic rats by inhibiting inflammation.

Clinical significance of vascular endothelial growth factor and endothelin-1 in serum levels as novel indicators for predicting the progression of diabetic nephropathy

Objective: Early diagnosis and intervention of diabetic nephropathy (DN) is necessary to optimize therapy in order to delay the progression of diabetes. This research aimed to reveal the change of vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1) in patients with DN, and to assess possible correlations with glycated hemoglobin (HbAlc) values. Methods: The present study was a retrospective, single-center study conducted at a teaching hospital in the northeast China. A total of 120 patients were divided into proteinuria-positive group ( n = 40), the microalbuminuria group ( n = 40), and the high proteinuria group ( n = 40) according to the urinary albumin excretion rate (UAER), and 40 healthy volunteers were selected as the control group. The levels of VEGF, ET-1 and HbA1c were measured in all subjects and principal component analysis (PCA) was performed to classify and reveal correlations between VEGF, ET-1 and HbA1c. Results: Compared to the control group, a significant difference in the increase of HbA1c was detected in group I, II and III. A significant increase in the concentrations of serum VEGF and ET-1 was also observed. HbA1c in DN patients had proven to be positively correlated with VEGF (r = 0.7941; p < 0. 0001) and ET-1 (r = 0.8504; p < 0.0001) respectively. Conclusion: The elevated levels of VEGF and ET-1 in serum have been proposed as being able to supplement the additional information about the progression of DN. These data suggest that the decrease in endothelial function may be related to poor glycemic control.

Non-apoptotic programmed cell deaths in diabetic pulmonary dysfunction: the new side of advanced glycation end products

Diabetes mellitus (DM) is a chronic metabolic disorder that affects multiple organs and systems, including the pulmonary system. Pulmonary dysfunction in DM patients has been observed and studied for years, but the underlying mechanisms have not been fully understood. In addition to traditional mechanisms such as the production and accumulation of advanced glycation end products (AGEs), angiopathy, tissue glycation, oxidative stress, and systemic inflammation, recent studies have focused on programmed cell deaths (PCDs), especially the non-apoptotic ones, in diabetic pulmonary dysfunction. Non-apoptotic PCDs (NAPCDs) including autophagic cell death, necroptosis, pyroptosis, ferroptosis, and copper-induced cell death have been found to have certain correlations with diabetes and relevant complications. The AGE-AGE receptor (RAGE) axis not only plays an important role in the traditional pathogenesis of diabetes lung disease but also plays an important role in non-apoptotic cell death. In this review, we summarize novel studies about the roles of non-apoptotic PCDs in diabetic pulmonary dysfunction and focus on their interactions with the AGE-RAGE axis.

Endothelial cell dysfunction in cardiac disease: driver or consequence?

The vascular endothelium is a multifunctional cellular system which directly influences blood components and cells within the vessel wall in a given tissue. Importantly, this cellular interface undergoes critical phenotypic changes in response to various biochemical and hemodynamic stimuli, driving several developmental and pathophysiological processes. Multiple studies have indicated a central role of the endothelium in the initiation, progression, and clinical outcomes of cardiac disease. In this review we synthesize the current understanding of endothelial function and dysfunction as mediators of the cardiomyocyte phenotype in the setting of distinct cardiac pathologies; outline existing in vivo and in vitro models where key features of endothelial cell dysfunction can be recapitulated; and discuss future directions for development of endothelium-targeted therapeutics for cardiac diseases with limited existing treatment options.

The Redox Protein High-Mobility Group Box 1 in Cell Death and Cancer

Significance: As a redox-sensitive protein, high-mobility group box 1 (HMGB1) is implicated in regulating stress responses to oxidative damage and cell death, which are closely related to the pathology of inflammatory diseases, including cancer. Recent Advances: HMGB1 is a nonhistone nuclear protein that acts as a deoxyribonucleic acid chaperone to control chromosomal structure and function. HMGB1 can also be released into the extracellular space and function as a damage-associated molecular pattern protein during cell death, including during apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis, alkaliptosis, and cuproptosis. Once released, HMGB1 binds to membrane receptors to shape immune and metabolic responses. In addition to subcellular localization, the function and activity of HMGB1 also depend on its redox state and protein posttranslational modifications. Abnormal HMGB1 plays a dual role in tumorigenesis and anticancer therapy (e.g., chemotherapy, radiation therapy, and immunotherapy) depending on the tumor types and stages. Critical Issues: A comprehensive understanding of the role of HMGB1 in cellular redox homeostasis is important for deciphering normal cellular functions and pathological manifestations. In this review, we discuss compartmental-defined roles of HMGB1 in regulating cell death and cancer. Understanding these advances may help us develop potential HMGB1-targeting drugs or approaches to treat oxidative stress-related diseases or pathological conditions. Future Directions: Further studies are required to dissect the mechanism by which HMGB1 maintains redox homeostasis under different stress conditions. A multidisciplinary effort is also required to evaluate the potential applications of precisely targeting the HMGB1 pathway in human health and disease. Antioxid. Redox Signal. 39, 569-590.

LncRNA MEG3 aggravates adipocyte inflammation and insulin resistance by targeting IGF2BP2 to activate TLR4/NF-κB signaling pathway

Recently, emerging evidence has shown that LncRNA MEG3 is involved in adipocyte inflammation and insulin resistance progression, however, the specific mechanism of action remains unclear. In this study, we found that LncRNA MEG3 expression was increased in TNF-α stimulated 3T3-L1 mature adipocytes, and inflammatory factors IL-6 and MCP-1 secretion levels were increased, cell apoptosis and caspase3 activity was enhanced, ROS content was increased, and iNOS protein expression was increased. Moreover, TNF-α treatment attenuated glucose uptake, promoted triglyceride accumulation, inhibited GLUT4 protein expression at the plasma membrane, and reduced the phosphorylation levels of AMPK and ACC in the cells. Interestingly, we found that transfection of si-MEG3 reversed TNF-α caused inflammatory injury and insulin resistance of 3T3-L1 mature adipocytes. Next, we found that IGF2BP2 is an RNA binding protein of LncRNA MGE3 and transfection of si-IGF2BP2 reversed TNF-α caused inflammatory injury and insulin resistance in 3T3-L1 mature adipocytes, the same effects as transfection of si-MEG3. Mechanistically, LncRNA MGE3 was able to aggravate adipocyte inflammatory injury and dysregulation of insulin sensitivity by activating TLR4 pathway through upregulating the protein expression of IGF2BP2. In vivo findings showed that HFD mice with knockdown of MEG3 had reduced body weight, lower glucose concentrations and insulin levels in plasma, decreased inflammatory factors secretion, and reduced MEG3 and IGF2BP2 expression in epididymal adipose tissues and reduced fat accumulation in mice compared with HFD mice. Our results indicate that LncRNA MEG3 can aggravate chronic inflammation and insulin resistance in adipocytes by activating TLR4/NF-κB signaling pathway via targeting IGF2BP2.

Metformin Attenuates the Inflammatory Response via the Regulation of Synovial M1 Macrophage in Osteoarthritis

Osteoarthritis (OA), the most common chronic inflammatory joint disease, is characterized by progressive cartilage degeneration, subchondral bone sclerosis, synovitis, and osteophyte formation. Metformin, a hypoglycemic agent used in the treatment of type 2 diabetes, has been evidenced to have anti-inflammatory properties to treat OA. It hampers the M1 polarization of synovial sublining macrophages, which promotes synovitis and exacerbates OA, thus lessening cartilage loss. In this study, metformin prevented the pro-inflammatory cytokines secreted by M1 macrophages, suppressed the inflammatory response of chondrocytes cultured with conditional medium (CM) from M1 macrophages, and mitigated the migration of M1 macrophages induced by interleukin-1ß (IL-1ß)-treated chondrocytes in vitro. In the meantime, metformin reduced the invasion of M1 macrophages in synovial regions brought about by the destabilization of medial meniscus (DMM) surgery in mice, and alleviated cartilage degeneration. Mechanistically, metformin regulated PI3K/AKT and downstream pathways in M1 macrophages. Overall, we demonstrated the therapeutic potential of metformin targeting synovial M1 macrophages in OA.

The effect of a-Lipoic acid (ALA) on oxidative stress, inflammation, and apoptosis in high glucose-induced human corneal epithelial cells

PURPOSE

Oxidative stress and inflammation had been proved to play important role in the progression of diabetic keratopathy (DK). The excessive accumulation of AGEs and their bond to AGE receptor (RAGE) in corneas that cause the formation of oxygen radicals and the release of inflammatory cytokines, induce cell apoptosis. Our current study was aimed to evaluate the effect of ALA on AGEs accumulation as well as to study the molecular mechanism of ALA against AGE-RAGE axis mediated oxidative stress, apoptosis, and inflammation in HG-induced HCECs, so as to provide cytological basis for the treatment of DK.

METHODS

HCECs were cultured in a variety concentration of glucose medium (5.5, 10, 25, 30, 40, and 50 mM) for 48 h. The cell proliferation was evaluated by CCK-8 assay. Apoptosis was investigated with the Annexin V- fluorescein isothiocyanate (V-FITC)/PI kit, while, the apoptotic cells were determined by flow cytometer and TUNEL cells apoptosis Kit. According to the results of cell proliferation and cell apoptosis, 25 mM glucose medium was used in the following HG experiment. The effect of ALA on HG-induced HCECs was evaluated. The HCECs were treated with 5.5 mM glucose (normal glucose group, NG group), 5.5 mM glucose + 22.5 mM mannitol (osmotic pressure control group, OP group), 25 mM glucose (high glucose group, HG group) and 25 mM glucose + ALA (HG + ALA group) for 24 and 48 h. The accumulation of intracellular AGEs was detected by ELISA kit. The RAGE, catalase (CAT), superoxide dismutase 2 (SOD2), cleaved cysteine-aspartic acid protease-3 (Cleaved caspase-3), Toll-like receptors 4 (TLR4), Nod-like receptor protein 3 (NLRP3) inflammasome, interleukin 1 beta (IL-1 ß), and interleukin 18 (IL-18) were quantified by RT-PCR, Western blotting, and Immunofluorescence, respectively. Reactive oxygen species (ROS) production was evaluated by fluorescence microscope and fluorescence microplate reader.

RESULTS

When the glucose medium was higher than 25 mM, cell proliferation was significantly inhibited and apoptosis ratio was increased (P < 0.001). In HG environment, ALA treatment alleviated the inhibition of HCECs in a dose-dependent manner, 25 μM ALA was the minimum effective dose. ALA could significantly reduce the intracellular accumulation of AGEs (P < 0.001), activate protein and genes expression of CAT and SOD2 (P < 0.001), and therefore inhibited ROS-induced oxidative stress and cells apoptosis. Besides, ALA could effectively down-regulate the protein and gene level of RAGE, TLR4, NLRP3, IL-1B, IL-18 (P < 0.05), and therefore alleviated AGEs-RAGE-TLR4-NLRP3 pathway-induced inflammation in HG-induced HCECs.

CONCLUSION

Our study indicated that ALA could be a desired treatment for DK due to its potential capacity of reducing accumulation of advanced glycation end products (AGEs) and down-regulating AGE-RAGE axis-mediated oxidative stress, cell apoptosis, and inflammation in high glucose (HG)-induced human corneal epithelial cells (HCECs), which may provide cytological basis for therapeutic targets that are ultimately of clinical benefit.

RAGE Against the Glycation Machine in Synucleinopathies: Time to Explore New Questions

Oligomerization and aggregation of misfolded forms of α-synuclein are believed to be key molecular mechanisms in Parkinson's disease (PD) and other synucleinopathies, so extensive research has attempted to understand these processes. Among diverse post-translational modifications that impact α-synuclein aggregation, glycation may take place at several lysine sites and modify α-synuclein oligomerization, toxicity, and clearance. The receptor for advanced glycation end products (RAGE) is considered a key regulator of chronic neuroinflammation through microglial activation in response to advanced glycation end products, such as carboxy-ethyl-lysine, or carboxy-methyl-lysine. The presence of RAGE in the midbrain of PD patients has been reported in the last decades and this receptor was proposed to have a role in sustaining PD neuroinflammation. However, different PD animal models demonstrated that RAGE is preferentially expressed in neurons and astrocytes, while recent evidence demonstrated that fibrillar, non-glycated α-synuclein binds to RAGE. Here, we summarize the available data on α-synuclein glycation and RAGE in the context of PD, and discuss about the questions yet to be answered that may increase our understanding of the molecular bases of PD and synucleinopathies.

Research progress in inducing immunogenic cell death of tumor cells

Immunogenic cell death (ICD) is a regulated cell death (RCD) pathway. In response to physical and chemical signals, tumor cells activate specific signaling pathways that stimulate stress responses in the endoplasmic reticulum (ER) and expose damage-associated molecular patterns (DAMPs), which promote antitumor immune responses. As a result, the tumor microenvironment is altered, and many tumor cells are killed. The ICD response in tumor cells requires inducers. These inducers can be from different sources and contribute to the development of the ICD either indirectly or directly. The combination of ICD inducers with other tumor treatments further enhances the immune response in tumor cells, and more tumor cells are killed; however, it also produces side effects of varying severity. New induction methods based on nanotechnology improve the antitumor ability and significantly reduces side effects because they can target tumor cells precisely. In this review, we introduce the characteristics and mechanisms of ICD responses in tumor cells and the DAMPs associated with ICD responses, summarize the current methods of inducing ICD response in tumor cells in five distinct categories: chemical sources, physical sources, pathogenic sources, combination therapies, and innovative therapies. At the same time, we introduce the limitations of current ICD inducers and make a summary of the use of ICD responses in clinical trials. Finally, we provide an outlook on the future of ICD inducer development and provide some constructive suggestions.

Aggravated renal fibrosis is positively associated with the activation of HMGB1-TLR2/4 signaling in STZ-induced diabetic mice

Diabetic kidney dysfunction is closely associated with renal fibrosis. Although the suppression of fibrosis is crucial to attenuate kidney damage, the underlying mechanisms remain poorly understood. In this study, renal injury in diabetic mice was induced by the intraperitoneal injection of streptozotocin (100 or 150 mg/kg) for 2 consecutive days. In the model mice, remarkable renal injury was observed, manifested by albuminuria, swelling of kidneys, and histopathological characteristics. The renal fibrosis was obviously displayed with high-intensity staining of fibrin, type IV collagen (Col IV), and fibronectin. The levels of Col IV and transforming growth factor-β1 were significantly increased in diabetic mice kidneys. The aggravated fibrotic process was associated with the overexpression of HMGB1, TLR2/4, and p-NF-κB. Furthermore, a high expression of F4/80 and CD14 indicated that macrophage infiltration was involved in perpetuating inflammation and subsequent fibrosis in the kidneys of diabetic mice. The results demonstrate that the severity of renal fibrosis is positively associated with the activation of HMGB1/TLR2/4 signaling in diabetes.

Extracellular HMGB1 as Inflammatory Mediator in the Progression of Mycoplasma Gallisepticum Infection

High-mobility group box 1 (HMGB1), a member of damage-associated molecular patterns (DAMPs), is involved in the immune regulation of several infectious diseases. Mycoplasma gallisepticum (MG) infection is proved to cause an abnormal immune response, but the role of HMGB1 in MG-induced chronic respiratory disease (CRD) is unclear. In this study, we found that HMGB1 was released from the nucleus to the extracellular in macrophages upon infection with MG. Extracellular HMGB1 bound to TLR2 activating the NF-κB pathway triggering a severe inflammatory storm and promoting the progression of MG infection. More importantly, TLR4 could be activated by HMGB1 to trigger immune disorders after TLR2 was silenced. This disease process could be interrupted by ethyl pyruvate (EP) inhibition of HMGB1 release or glycyrrhizic acid (GA). Furthermore, treatment of MG-infected chickens with GA significantly alleviated immune organ damage. In conclusion, we demonstrate that HMGB1 is secreted extracellularly to form an inflammatory environment upon MG infection, triggering a further cellular inflammatory storm in a positive feedback approach. Blocking MG-induced HMGB1 release or suppression downstream of the HMGB1-TLR2/TLR4 axis may be a promising novel strategy for the treatment of CRD. Furthermore, this study may provide a theoretical reference for understanding non-LPS-activated TLR4 events.

HMGB1 signaling pathway in diabetes-related dementia: Blood-brain barrier breakdown, brain insulin resistance, and Aβ accumulation

Diabetes contributes to the onset of various diseases, including cancer and cardiovascular and neurodegenerative diseases. Recent studies have highlighted the similarities and relationship between diabetes and dementia as an important issue for treating diabetes-related cognitive deficits. Diabetes-related dementia exhibits several features, including blood-brain barrier disruption, brain insulin resistance, and Aβ over-accumulation. High-mobility group box1 (HMGB1) is a protein known to regulate gene transcription and cellular mechanisms by binding to DNA or chromatin via receptor for advanced glycation end-products (RAGE) and toll-like receptor 4 (TLR4). Recent studies have demonstrated that the interplay between HMGB1, RAGE, and TLR4 can impact both neuropathology and diabetic alterations. Herein, we review the recent research regarding the roles of HMGB1-RAGE-TLR4 axis in diabetes-related dementia from several perspectives and emphasize the importance of the influence of HMGB1 in diabetes-related dementia.

The RAGE/DIAPH1 Signaling Axis & Implications for the Pathogenesis of Diabetic Complications

Increasing evidence links the RAGE (receptor for advanced glycation end products)/DIAPH1 (Diaphanous 1) signaling axis to the pathogenesis of diabetic complications. RAGE is a multi-ligand receptor and through these ligand-receptor interactions, extensive maladaptive effects are exerted on cell types and tissues targeted for dysfunction in hyperglycemia observed in both type 1 and type 2 diabetes. Recent evidence indicates that RAGE ligands, acting as damage-associated molecular patterns molecules, or DAMPs, through RAGE may impact interferon signaling pathways, specifically through upregulation of IRF7 (interferon regulatory factor 7), thereby heralding and evoking pro-inflammatory effects on vulnerable tissues. Although successful targeting of RAGE in the clinical milieu has, to date, not been met with success, recent approaches to target RAGE intracellular signaling may hold promise to fill this critical gap. This review focuses on recent examples of highlights and updates to the pathobiology of RAGE and DIAPH1 in diabetic complications.

Interplay Among the Oral Microbiome, Oral Cavity Conditions, the Host Immune Response, Diabetes Mellitus, and Its Associated-Risk Factors-An Overview

This comprehensive review of the literature aimed to investigate the interplay between the oral microbiome, oral cavity conditions, and host immune response in Diabetes mellitus (DM). Moreover, this review also aimed to investigate how DM related risk factors, such as advanced age, hyperglycemia, hyperlipidemia, obesity, hypertension and polycystic ovary syndrome (PCOS), act in promoting or modifying specific mechanisms that could potentially perpetuate both altered systemic and oral conditions. We found that poorly controlled glycemic index may exert a negative effect on the immune system of affected individuals, leading to a deficient immune response or to an exacerbation of the inflammatory response exacerbating DM-related complications. Hyperglycemia induces alterations in the oral microbiome since poor glycemic control is associated with increased levels and frequencies of periodontal pathogens in the subgingival biofilm of individuals with DM. A bidirectional relationship between periodontal diseases and DM has been suggested: DM patients may have an exaggerated inflammatory response, poor repair and bone resorption that aggravates periodontal disease whereas the increased levels of systemic pro-inflammatory mediators found in individuals affected with periodontal disease exacerbates insulin resistance. SARS-CoV-2 infection may represent an aggravating factor for individuals with DM. Individuals with DM tend to have low salivary flow and a high prevalence of xerostomia, but the association between prevalence/experience of dental caries and DM is still unclear. DM has also been associated to the development of lesions in the oral mucosa, especially potentially malignant ones and those associated with fungal infections. Obesity plays an important role in the induction and progression of DM. Co-affected obese and DM individuals tend to present worse oral health conditions. A decrease in HDL and, an increase in triglycerides bloodstream levels seem to be associated with an increase on the load of periodontopathogens on oral cavity. Moreover, DM may increase the likelihood of halitosis. Prevalence of impaired taste perception and impaired smell recognition tend to be greater in DM patients. An important interplay among oral cavity microbiome, DM, obesity and hypertension has been proposed as the reduction of nitrate into nitrite, in addition to contribute to lowering of blood pressure, reduces oxidative stress and increases insulin secretion, being these effects desirable for the control of obesity and DM. Women with PCOS tend to present a distinct oral microbial composition and an elevated systemic response to selective members of this microbial community, but the association between oral microbiome, PCOS are DM is still unknown. The results of the studies presented in this review suggest the interplay among the oral microbiome, oral cavity conditions, host immune response and DM and some of the DM associated risk factors exist. DM individuals need to be encouraged and motivated for an adequate oral health care. In addition, these results show the importance of adopting multidisciplinary management of DM and of strengthening physicians-dentists relationship focusing on both systemic and on oral cavity conditions of DM patients.

Low Molecular Weight Heparin Improves the Inflammatory State of Acute Sinusitis Rats Through Inhibiting the TLR4-MyD88-NF-κB Signaling Pathway

Introduction: Low molecular weight heparin (LMWH), a natural sulfated glycosaminoglycan with an affinity for proangiogenic factors, is produced by chemical or enzymatic depolymerization of unfractionated heparin (UFH). Known for its anticoagulant effects, LMWH has recently been reported to have a strong anti-inflammatory effect on colitis, myocarditis, and airway inflammation. However, as a newly-developed drug, its anti-inflammatory mechanism in upper respiratory tract inflammation has not been well-studied.

Methods: SD rats were randomly divided into control and experimental groups. The experimental group was established by building an acute nasal sinusitis model with expansion sponges mixed with Streptococcus pneumoniae. Then the experimental group rats were subcutaneously injected with different concentrations of LMWH. After seven consecutive days of injection, some rats were sacrificed, and blood and nasal mucosa samples were taken to determine their inflammation status. The remaining acute sinusitis rats were randomly selected for a week of nasal irrigation with normal saline or saline mixed with different concentrations of LMWH. One week later, rats were sacrificed, and samples of blood and nasal mucosa were taken to determine the inflammation status.

Results: Rat nasal mucosa in the model group had obvious inflammation. The degree of nasal mucosa inflammation damage in the experimental group was lower than in the experimental control group, proving that LMWH has a protective effect on the nasal mucosa and that the effect correlates with dosage. Irrigation of the nose with saline mixed with LMWH can improve the anti-inflammatory effect. Protein related to the TLR4-MyD88-NF-κB signaling pathway was activated in the acute sinusitis rat model, and LMWH can significantly inhibit its expression.

Conclusion: This is the first report of the anti-inflammatory effect of LMWH in acute upper respiratory tract inflammation, together with an explanation of its anti-inflammatory mechanism. The findings contribute a theoretical basis for its potential anti-tumor effect.

Trimebutine suppresses Toll-like receptor 2/4/7/8/9 signaling pathways in macrophages

Because of the critical roles of Toll-like receptors (TLRs) and receptor for advanced glycation end-products (RAGE) in the pathophysiology of various acute and chronic inflammatory diseases, continuous efforts have been made to discover novel therapeutic inhibitors of TLRs and RAGE to treat inflammatory disorders. A recent study by our group has demonstrated that trimebutine, a spasmolytic drug, suppresses the high mobility group box 1‒RAGE signaling that is associated with triggering proinflammatory signaling pathways in macrophages. Our present work showed that trimebutine suppresses interleukin-6 (IL-6) production in lipopolysaccharide (LPS, a stimulant of TLR4)-stimulated macrophages of RAGE-knockout mice. In addition, trimebutine suppresses the LPS-induced production of various proinflammatory cytokines and chemokines in mouse macrophage-like RAW264.7 cells. Importantly, trimebutine suppresses IL-6 production induced by TLR2-and TLR7/8/9 stimulants. Furthermore, trimebutine greatly reduces mortality in a mouse model of LPS-induced sepsis. Studies exploring the action mechanism of trimebutine revealed that it inhibits the LPS-induced activation of IL-1 receptor-associated kinase 1 (IRAK1), and the subsequent activations of extracellular signal-related kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and nuclear factor-κB (NF-κB). These findings suggest that trimebutine exerts anti-inflammatory effects on TLR signaling by downregulating IRAK1‒ERK1/2‒JNK pathway and NF-κB activity, thereby indicating the therapeutic potential of trimebutine in inflammatory diseases. Therefore, trimebutine can be a novel anti-inflammatory drug-repositioning candidate and may provide an important scaffold for designing more effective dual anti-inflammatory drugs that target TLR/RAGE signaling.

Inflammatory Mechanisms Contributing to Endothelial Dysfunction

Maintenance of endothelial cell integrity is an important component of human health and disease since the endothelium can perform various functions including regulation of vascular tone, control of hemostasis and thrombosis, cellular adhesion, smooth muscle cell proliferation, and vascular inflammation. Endothelial dysfunction is encompassed by complex pathophysiology that is based on endothelial nitric oxide synthase uncoupling and endothelial activation following stimulation from various inflammatory mediators (molecular patterns, oxidized lipoproteins, cytokines). The downstream signaling via nuclear factor-κB leads to overexpression of adhesion molecules, selectins, and chemokines that facilitate leukocyte adhesion, rolling, and transmigration to the subendothelial space. Moreover, oscillatory shear stress leads to pro-inflammatory endothelial activation with increased monocyte adhesion and endothelial cell apoptosis, an effect that is dependent on multiple pathways and flow-sensitive microRNA regulation. Moreover, the role of neutrophil extracellular traps and NLRP3 inflammasome as inflammatory mechanisms contributing to endothelial dysfunction has recently been unveiled and is under further investigation. Consequently, and following their activation, injured endothelial cells release inflammatory mediators and enter a pro-thrombotic state through activation of coagulation pathways, downregulation of thrombomodulin, and an increase in platelet adhesion and aggregation owing to the action of von-Willebrand factor, ultimately promoting atherosclerosis progression.