Binding of S100 proteins to RAGE: an update

Single-cell RNA sequencing analysis of vestibular schwannoma reveals functionally distinct macrophage subsets

BACKGROUND

Vestibular schwannomas (VSs) remain a challenge due to their anatomical location and propensity to growth. Macrophages are present in VS but their roles in VS pathogenesis remains unknown.

OBJECTIVES

The objective was to assess phenotypic and functional profile of macrophages in VS with single-cell RNA sequencing (scRNAseq).

METHODS

scRNAseq was carried out in three VS samples to examine characteristics of macrophages in the tumour. RT-qPCR was carried out on 10 VS samples for CD14, CD68 and CD163 and a panel of macrophage-associated molecules.

RESULTS

scRNAseq revealed macrophages to be a major constituent of VS microenvironment with three distinct subclusters based on gene expression. The subclusters were also defined by expression of CD163, CD68 and IL-1β. AREG and PLAUR were expressed in the CD68+CD163+IL-1β+ subcluster, PLCG2 and NCKAP5 were expressed in CD68+CD163+IL-1β- subcluster and AUTS2 and SPP1 were expressed in the CD68+CD163-IL-1β+ subcluster. RT-qPCR showed expression of several macrophage markers in VS of which CD14, ALOX15, Interleukin-1β, INHBA and Colony Stimulating Factor-1R were found to have a high correlation with tumour volume.

CONCLUSIONS

Macrophages form an important component of VS stroma. scRNAseq reveals three distinct subsets of macrophages in the VS tissue which may have differing roles in the pathogenesis of VS.

Recognition of granulocyte-macrophage colony-stimulating factor by specific S100 proteins

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a pleiotropic myelopoietic growth factor and proinflammatory cytokine, clinically used for multiple indications and serving as a promising target for treatment of many disorders, including cancer, multiple sclerosis, rheumatoid arthritis, psoriasis, asthma, COVID-19. We have previously shown that dimeric Ca2+-bound forms of S100A6 and S100P proteins, members of the multifunctional S100 protein family, are specific to GM-CSF. To probe selectivity of these interactions, the affinity of recombinant human GM-CSF to dimeric Ca2+-loaded forms of 18 recombinant human S100 proteins was studied by surface plasmon resonance spectroscopy. Of them, only S100A4 protein specifically binds to GM-CSF with equilibrium dissociation constant, Kd, values of 0.3-2 μM, as confirmed by intrinsic fluorescence and chemical crosslinking data. Calcium removal prevents S100A4 binding to GM-CSF, whereas monomerization of S100A4/A6/P proteins disrupts S100A4/A6 interaction with GM-CSF and induces a slight decrease in S100P affinity for GM-CSF. Structural modelling indicates the presence in the GM-CSF molecule of a conserved S100A4/A6/P-binding site, consisting of the residues from its termini, helices I and III, some of which are involved in the interaction with GM-CSF receptors. The predicted involvement of the 'hinge' region and F89 residue of S100P in GM-CSF recognition was confirmed by mutagenesis. Examination of S100A4/A6/P ability to affect GM-CSF signaling showed that S100A4/A6 inhibit GM-CSF-induced suppression of viability of monocytic THP-1 cells. The ability of the S100 proteins to modulate GM-CSF activity is relevant to progression of various neoplasms and other diseases, according to bioinformatics analysis. The direct regulation of GM-CSF signaling by extracellular forms of the S100 proteins should be taken into account in the clinical use of GM-CSF and development of the therapeutic interventions targeting GM-CSF or its receptors.

S100A6 drives lymphatic metastasis of liver cancer via activation of the RAGE/NF-kB/VEGF-D pathway

Patients diagnosed with lymph node (LN) metastatic liver cancer face an exceedingly grim prognosis. In-depth analysis of LN metastatic patients' characteristics and tumor cells' interactions with human lymphatic endothelial cells (HLECs), can provide important biological and therapeutic insights. Here we identify at the single-cell level that S100A6 expression differs between primary tumor and their LN metastasis. Of particular significance, we uncovered the disparity in S100A6 expression between tumors and normal tissues is greater in intrahepatic cholangiocarcinoma (ICC) patients, frequently accompanied by LN metastases, than that in hepatocellular carcinoma (HCC), with rare occurrence of LN metastasis. Furthermore, in the infrequent instances of LN metastasis in HCC, heightened S100A6 expression was observed, suggesting a critical role of S100A6 in the process of LN metastasis. Subsequent experiments further uncovered that S100A6 secreted from tumor cells promotes lymphangiogenesis by upregulating the expression and secretion of vascular endothelial growth factor-D (VEGF-D) in HLECs through the RAGE/NF-kB/VEGF-D pathway while overexpression of S100A6 in tumor cells also augmented their migration and invasion. Taken together, these data reveal the dual effects of S100A6 in promoting LN metastasis in liver cancer, thus highlighting its potential as a promising therapeutic target.

S-100β level is closely associated with myocardial work in patients with acute ischemic stroke

BACKGROUND

The more severe the acute stroke is, the more serious myocardial damage is. This study aimed to determine the relationship between myocardial work and S100β, a quantitative biomarker of active cerebral lesions, in patients with acute ischemic stroke (AIS).

METHODS

A total of 63 patients with AIS were examined by myocardial work echocardiography, 4D echocardiography with the measurement of left ventricular (LV) myocardial work, volume and function within 24-48 h of symptom onset, respectively. Their plasma S100β was measured from a peripheral blood sample within 2-6 h of symptom onset.

RESULTS

Patients with elevated S-100β level had significantly increased ratios of peak early diastolic transmitral filling velocity to peak early diastolic lateral mitral annulus tissue velocity(E/e') and global longitudinal strain (GLS), and significantly reduced global work index(GWI) and global constructive work (GCW) compared with those with normal S-100β level (p < 0.05). S-100β positively correlated with E/e'(r = 0.878, p < 0.0001) and GLS (r = 0.511, p = 0.002) but negatively correlated with GWI(r = -0.409, p = 0.034) and GCW(r = -0.353, p = 0.041). S-100β showed an excellent ability to differentiate if a reduced GWI [cut-off value, 120.79 pg/mL; area under receiver operating characteristic curve (AUC), 1.000; sensitivity, 100%; specificity, 100%], GCW (cut-off value, 120.79 pg/mL;AUC,1.000; sensitivity,100%; specificity, 100%) and an increased E/e' (cut-off value, 91.1 pg/mL;AUC,0.913; sensitivity,80%; specificity, 100%) or not, but poor ability to differentiate if an increased GLS(cut-off value, 91.1 pg/mL; AUC,0.576; sensitivity,63.64%; specificity, 83.33%) or not.

CONCLUSION

S-100β level is closely associated with LV function. It is highly competent in determining an impaired myocardial work in patients with AIS.

Skin barrier-inflammatory pathway is a driver of the psoriasis-atopic dermatitis transition

As chronic inflammatory conditions driven by immune dysregulation are influenced by genetics and environment factors, psoriasis and atopic dermatitis (AD) have traditionally been considered to be distinct diseases characterized by different T cell responses. Psoriasis, associated with type 17 helper T (Th17)-mediated inflammation, presents as well-defined scaly plaques with minimal pruritus. AD, primarily linked to Th2-mediated inflammation, presents with poorly defined erythema, dry skin, and intense itching. However, psoriasis and AD may overlap or transition into one another spontaneously, independent of biological agent usage. Emerging evidence suggests that defects in skin barrier-related molecules interact with the polarization of T cells, which forms a skin barrier-inflammatory loop with them. This loop contributes to the chronicity of the primary disease or the transition between psoriasis and AD. This review aimed to elucidate the mechanisms underlying skin barrier defects in driving the overlap between psoriasis and AD. In this review, the importance of repairing the skin barrier was underscored, and the significance of tailoring biologic treatments based on individual immune status instead of solely adhering to the treatment guidelines for AD or psoriasis was emphasized.

Chemogenetics Modulation of Electroacupuncture Analgesia in Mice Spared Nerve Injury-Induced Neuropathic Pain through TRPV1 Signaling Pathway

Neuropathic pain, which is initiated by a malfunction of the somatosensory cortex system, elicits inflammation and simultaneously activates glial cells that initiate neuroinflammation. Electroacupuncture (EA) has been shown to have therapeutic effects for neuropathic pain, although with uncertain mechanisms. We suggest that EA can reliably cure neuropathic disease through anti-inflammation and transient receptor potential V1 (TRPV1) signaling pathways from the peripheral to the central nervous system. To explore this, we used EA to treat the mice spared nerve injury (SNI) model and explore the underlying molecular mechanisms through novel chemogenetics techniques. Both mechanical and thermal pain were found in SNI mice at four weeks (mechanical: 3.23 ± 0.29 g; thermal: 4.9 ± 0.14 s). Mechanical hyperalgesia was partially attenuated by 2 Hz EA (mechanical: 4.05 ± 0.19 g), and thermal hyperalgesia was fully reduced (thermal: 6.22 ± 0.26 s) but not with sham EA (mechanical: 3.13 ± 0.23 g; thermal: 4.58 ± 0.37 s), suggesting EA's specificity. In addition, animals with Trpv1 deletion showed partial mechanical hyperalgesia and no significant induction of thermal hyperalgesia in neuropathic pain mice (mechanical: 4.43 ± 0.26 g; thermal: 6.24 ± 0.09 s). Moreover, we found increased levels of inflammatory factors such as interleukin-1 beta (IL1-β), IL-3, IL-6, IL-12, IL-17, tumor necrosis factor alpha, and interferon gamma after SNI modeling, which decreased in the EA and Trpv1-/- groups rather than the sham group. Western blot and immunofluorescence analysis showed similar tendencies in the dorsal root ganglion, spinal cord dorsal horn, somatosensory cortex (SSC), and anterior cingulate cortex (ACC). In addition, a novel chemogenetics method was used to precisely inhibit SSC to ACC activity, which showed an analgesic effect through the TRPV1 pathway. In summary, our findings indicate a novel mechanism underlying neuropathic pain as a beneficial target for neuropathic pain.

Associations of circulating advanced glycation end products and their soluble receptors with cancer risk: A systematic review and meta-analysis of observational studies

Advanced glycation end products (AGE) in complex with their receptors (RAGE) cause a chronic inflammatory state in the body, which is the major mechanism in cancer development. This study aimed to conduct a systematic review and meta-analysis on the observational studies investigating the association between AGEs / sRAGE and cancer incidence. The PubMed, Scopus, and Web of Science databases were comprehensively searched to identify papers focused on the associations of sRAGE and AGEs with cancer incidence up to May 2023. Eight studies with a total of 7690 participants were included in the analysis to evaluate the association between circulating sRAGE and cancer incidence. The results indicated that circulating sRAGE (per 100 ng/L) had a significant inverse association with cancer incidence (RR 0.977; 95% CI 0.956, 0.999; p = 0.036; I 2 = 73.3%). The association between AGEs and cancer incidence was evaluated in 8 studies with a total of 3718 individuals. Serum concentrations of AGEs (per 100 µg/L) were not associated with the risk of cancer incidence (RR 0.988; 95% CI 0.974, 1.002; p = 0.08; I2 = 78.8%). Our findings revealed that a higher circulating sRAGE may have a protective effect against cancer incidence.

Blastocyst-Derived Lactic Acid May Regulate S100A6 Expression and Function in Mouse Decidualization via Stimulation of Uterine Epithelial Arachidonic Acid Secretion

(1) Background: Inflammatory responses are implicated in embryo implantation, decidualization, pregnancy maintenance and labor. Both embryo implantation and decidualization are essential to successful pregnancy in rodents and primates. S100A6 is involved in inflammation, tumor development, apoptosis and calcium homeostasis. S100A6 is strongly expressed in mouse decidua, but the underlying mechanisms of how S100A6 regulates implantation and decidualization are poorly defined. (2) Methods: Mouse endometrial stromal and epithelial cells are isolated from day 4 pseudopregnant mouse uteri. Both immunofluorescence and Western blotting are used to analyze the expression and localization of proteins. The molecular mechanism is verified in vitro by Western blotting and the quantitative polymerase chain reaction. (3) Results: From days 4 to 8 of pregnancy, S100A6 is specifically expressed in mouse subluminal stromal cells. Blastocyst-derived lactic acid induces AA secretion by activating the luminal epithelial p-cPLA2. The epithelial AA induces stromal S100A6 expression through the COX2/PGI2/PPAR δ pathway. Progesterone regulates S100A6 expression through the progesterone receptor (PR). S100A6/RAGE signaling can regulate decidualization via EGFR/ERK1/2 in vitro. (4) Conclusions: S100A6, as an inflammatory mediator, is important for mouse implantation and decidualization.

S100A8/A9 promotes endometrial fibrosis via regulating RAGE/JAK2/STAT3 signaling pathway

Intrauterine adhesion (IUA) is characterized by endometrial fibrosis. S100A8/A9 plays an important role in inflammation and fibroblast activation. However, the role of S100A8/A9 in IUA remains unclear. In this study, we collect normal and IUA endometrium to verify the expression of S100A8/A9. Human endometrial stromal cells (hEnSCs) are isolated to evaluate fibrosis progression after S100A8/A9 treatment. A porcine IUA model is established by electrocautery injury to confirm the therapeutic effect of menstrual blood-derived stromal cells (MenSCs) on IUA. Our study reveals increased S100A8/A9 expression in IUA endometrium. S100A8/A9 significantly enhances hEnSCs proliferation and upregulates fibrosis-related and inflammation-associated markers. Furthermore, S100A8/A9 induces hEnSCs fibrosis through the RAGE-JAK2-STAT3 pathway. Transplantation of MenSCs in a porcine IUA model notably enhances angiogenesis, mitigates endometrial fibrosis and downregulates S100A8/A9 expression. In summary, S100A8/A9 induces hEnSCs fibrosis via the RAGE-JAK2-STAT3 pathway, and MenSCs exhibit marked effects on endometrial restoration in the porcine IUA model.

S-100 and MATH-1 Protein Expressions Can Be Useful for the Prediction of Clinical Outcome in Neuroblastoma Patients

Neuroblastoma (NB) is the most frequent extracranial solid tumor of childhood, remarkable for its broad spectrum of clinical behavior. This diversity in behavior correlates closely with defined clinical and biological features and combinations of prognostic variables are used for risk-group assignment. S-100 proteins have roles in differentiation and were shown to be frequently dysregulated in NB. MATH-1 protein plays role in neuronal cell differentiation through development. However, up to date, there are no studies evaluating the relationship between MATH-1 and NB. Grb2-associated binding (Gab) proteins have roles in the regulation of cell growth and differentiation. Gab1 was reported to be related to poor survival of high-risk NB patients. The aim of this study was to investigate the relationship between differentiation-related S-100, MATH-1, and Gab1 proteins and risk group and/or stages of NB. A significant relation was found between S-100 and early stages of NB. This study also revealed a significant association between MATH-1 and low-risk groups. S-100 and MATH-1 were also shown to provide survival advantages among stages and risk groups. The findings of this study support the assumption that S-100 and MATH-1 can be potential prognostic biomarkers for staging and risk-group assignment of NB patients. These proteins can be useful tools for clinicians to guide through treatment options, especially for the evaluation of tumor differentiation.

Soluble receptor for advanced glycation end products (sRAGE) is associated with obesity rates: a systematic review and meta-analysis of cross-sectional study

BACKGROUND

Several studies have highlighted the possible positive effects of soluble receptor for advanced glycation end products (sRAGE) against obesity. However, due to their inconsistent results, this systematic review and meta-analysis aimed to quantitatively evaluate and critically review the results of studies evaluating the relationship between sRAGE with obesity among adult population.

METHODS

In the systematic search, the eligibility criteria were as follows: studies conducted with a cross-sectional design, included apparently healthy adults, adults with obesity, or obesity-related disorders, aged over 18 years, and evaluated the association between general or central obesity indices with sRAGE.

RESULTS

Our systematic search in electronic databases, including PubMed, Scopus, and Embase up to 26 October, 2023 yielded a total of 21,612 articles. After removing duplicates, screening the titles and abstracts, and reading the full texts, 13 manuscripts were included in the final meta-analysis. According to our results, those at the highest category of circulating sRAGE concentration with median values of 934.92 pg/ml of sRAGE, had 1.9 kg/m2 lower body mass index (BMI) (WMD: -1.927; CI: -2.868, -0.986; P < 0.001) compared with those at the lowest category of sRAGE concentration with median values of 481.88 pg/ml. Also, being at the highest sRAGE category with the median values of 1302.3 pg/ml sRAGE, was accompanied with near 6 cm lower waist circumference (WC) (WMD: -5.602; CI: -8.820, -2.383; P < 0.001 with 86.4% heterogeneity of I2) compared with those at the lowest category of sRAGE concentration with median values of 500.525 pg/ml. Individuals with obesity had significantly lower circulating sRAGE concentrations (WMD: -135.105; CI: -256.491, -13.72; P = 0.029; with 79.5% heterogeneity of I2). According to the subgrouping and meta-regression results, country and baseline BMI were possible heterogeneity sources. According to Begg's and Egger's tests and funnel plots results, there was no publication bias.

CONCLUSION

According to our results, higher circulating sRAGE concentrations was associated with lower BMI and WC among apparently healthy adults. Further randomized clinical trials are warranted for possible identification of causal associations.

The role of gut-brain axis in a rotenone-induced rat model of Parkinson's disease

Parkinson's disease (PD) is a widespread neurodegenerative condition affecting millions globally. This investigation centered on the gut-brain axis in a rotenone-induced PD rat model. Researchers monitored behavioral shifts, histological modifications, neurodegeneration, and inflammation markers throughout the rats' bodies. Results revealed that rotenone-treated rats displayed reduced exploration (p = 0.004) and motor coordination (p < 0.001), accompanied by decreased Nissl staining and increased alpha-synuclein immunoreactivity in the striatum (p = 0.009). Additionally, these rats exhibited weight loss (T3, mean = 291.9 ± 23.67; T19, mean = 317.5 ± 17.53; p < 0.05) and substantial intestinal histological alterations, such as shortened villi, crypt architecture loss, and inflammation. In various regions, researchers noted elevated immunoreactivity to ionized binding adapter molecule (IBA)-1 (p < 0.05) and reduced immunoreactivity to glial fibrillary acidic protein (p < 0.05) and S100B (p < 0.001), indicating altered glial cell activity. Overall, these findings imply that PD is influenced by gut-brain axis changes and may originate in the intestine, impacting bidirectional gut-brain communication.

Sex-Specific Genetic Determinants of Asthma-COPD Phenotype and COPD in Middle-Aged and Older Canadian Adults: An Analysis of CLSA Data

The etiology of sex differences in the risk of asthma-COPD phenotype and COPD is still not completely understood. Genetic and environmental risk factors are commonly believed to play an important role. This study aims to identify sex-specific genetic markers associated with asthma-COPD phenotype and COPD using the Canadian Longitudinal Study on Aging (CLSA) Baseline Comprehensive and Genomic data. There were a total of 1,415 COPD cases. Out of them, 504 asthma-COPD phenotype cases were identified. 20,524 participants without a diagnosis of asthma and COPD served as controls. We performed genome-wide SNP-by-sex interaction analysis. SNPs with an interaction p-value < 10^-5 were included in a sex-stratified multivariable logistic regression for asthma-COPD phenotype and COPD outcomes. 18 and 28 SNPs had a significant interaction term p-value < 10^-5 with sex in the regression analyses of asthma-COPD phenotype and COPD outcomes, respectively. Sex-stratified multivariable analysis of asthma-COPD phenotype showed that 7 SNPs in/near SMYD3, FHIT, ZNF608, RIMBP2, ZNF133, BPIFB1, and S100B loci were significant in males. Sex-stratified multivariable analysis of COPD showed that 8 SNPs in/near MAGI1, COX18, OSTC, ELOVL5, C7orf72 FGF14, and NKAIN4 were significant in males, and 4 SNPs in/near genes CAMTA1, SATB2, PDE10A, and LINC00908 were significant in females. An SNP in the ZPBP gene was associated with COPD in both males and females. Identification of sex-specific loci associated with asthma-COPD phenotype and COPD may offer valuable evidence toward a better understanding of the sex-specific differences in the pathophysiology of the diseases.

Effect of Proinflammatory S100A9 Protein on Migration and Proliferation of Microglial Cells

Alzheimer's disease (AD) is a multifactorial disease affecting aging population worldwide. Neuroinflammation became a focus of research as one of the major pathologic processes relating to the disease onset and progression. Proinflammatory S100A9 is the central culprit in the amyloid-neuroinflammatory cascade implicated in AD and other neurodegenerative diseases. We studied the effect of S100A9 on microglial BV-2 cell proliferation and migration. The responses of BV-2 cells to S100A9 stimulation were monitored in real-time using live cell microscopy, transcriptome sequencing, immunofluorescence staining, western blot analysis, and ELISA. We observed that a low dose of S100A9 promotes migration and proliferation of BV-2 cells. However, acute inflammatory condition (i.e., high S100A9 doses) causes diminished cell viability; it is uncovered that S100A9 activates TLR-4 and TLR-7 signaling pathways, leading to TNF-α and IL-6 expression, which affect BV-2 cell migration and proliferation in a concentration-dependent manner. Interestingly, the effects of S100A9 are not only inhibited by TNF-α and IL-6 antibodies. The addition of amyloid-β (Aβ) 1-40 peptide resumes the capacities of BV-2 cells to the level of low S100A9 concentrations. Based on these results, we conclude that in contrast to the beneficial effects of low S100A9 dose, high S100A9 concentration leads to impaired mobility and proliferation of immune cells, reflecting neurotoxicity at acute inflammatory conditions. However, the formation of Aβ plaques may be a natural mechanism that rescues cells from the proinflammatory and cytotoxic effects of S100A9, especially considering that inflammation is one of the primary causes of AD.

RAGE engagement by SARS-CoV-2 enables monocyte infection and underlies COVID-19 severity

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has fueled the COVID-19 pandemic with its enduring medical and socioeconomic challenges because of subsequent waves and long-term consequences of great concern. Here, we chart the molecular basis of COVID-19 pathogenesis by analyzing patients' immune responses at single-cell resolution across disease course and severity. This approach confirms cell subpopulation-specific dysregulation in COVID-19 across disease course and severity and identifies a severity-associated activation of the receptor for advanced glycation endproducts (RAGE) pathway in monocytes. In vitro THP1-based experiments indicate that monocytes bind the SARS-CoV-2 S1-receptor binding domain (RBD) via RAGE, pointing to RAGE-Spike interaction enabling monocyte infection. Thus, our results demonstrate that RAGE is a functional receptor of SARS-CoV-2 contributing to COVID-19 severity.

Anti-S100A4 antibody administration alleviates bronchial epithelial-mesenchymal transition in asthmatic mice

We elucidated the effect of S100A4 on airway remodeling by regulating airway inflammation and epithelial-mesenchymal transition (EMT) in mouse models of asthma. Asthmatic mouse models were established by sensitization and challenged with ovalbumin (OVA). Anti-S100A4 antibody or control IgG antibody was administered daily before the OVA challenge. After the last challenge, airway inflammation and airway hyperresponsiveness were measured; lung tissues and bronchoalveolar lavage fluid (BALF) were harvested. Lung tissue sections were stained and evaluated for pathological changes. Levels of inflammatory cytokines were measured using ELISA. Levels of S100A4 and EMT markers were determined via western blotting analysis. Human bronchial epithelial cells were stimulated with 100 mg/mL house dust mites (HDMs) to evaluate the effect of S100A4 downregulation on EMT in vitro. S100A4 was increased in lung tissues and BALF from asthmatic mice. The asthmatic mice presented airway hyperresponsiveness, airway inflammation, and airway remodeling. After anti-S100A4 antibody administration, pathophysiological signs, including airway hyperresponsiveness and increased infiltration of inflammatory cells, were attenuated. Additionally, anti-S100A4 administration downregulated vimentin and α-SMA expression and upregulated E-cadherin expression in OVA-challenged mice. S100A4 downregulation also inhibited EMT process in HDM-stimulated 16HBE cells. Anti-S100A4 antibody administration alters airway remodeling by preventing EMT in mouse models of asthma.

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

The Post-Translational Modifications of Human Salivary Peptides and Proteins Evidenced by Top-Down Platforms

In this review, we extensively describe the main post-translational modifications that give rise to the multiple proteoforms characterized to date in the human salivary proteome and their potential role. Most of the data reported were obtained by our group in over twenty-five years of research carried out on human saliva mainly by applying a top-down strategy. In the beginning, we describe the products generated by proteolytic cleavages, which can occur before and after secretion. In this section, the most relevant families of salivary proteins are also described. Next, we report the current information concerning the human salivary phospho-proteome and the limited news available on sulfo-proteomes. Three sections are dedicated to the description of glycation and enzymatic glycosylation. Citrullination and N- and C-terminal post-translational modifications (PTMs) and miscellaneous other modifications are described in the last two sections. Results highlighting the variation in the level of some proteoforms in local or systemic pathologies are also reviewed throughout the sections of the manuscript to underline the impact and relevance of this information for the development of new diagnostic biomarkers useful in clinical practice.

CD30 co-stimulation drives differentiation of protective T cells during Mycobacterium tuberculosis infection

Control of Mycobacterium tuberculosis (Mtb) infection requires generation of T cells that migrate to granulomas, complex immune structures surrounding sites of bacterial replication. Here we compared the gene expression profiles of T cells in pulmonary granulomas, bronchoalveolar lavage, and blood of Mtb-infected rhesus macaques to identify granuloma-enriched T cell genes. TNFRSF8/CD30 was among the top genes upregulated in both CD4 and CD8 T cells from granulomas. In mice, CD30 expression on CD4 T cells is required for survival of Mtb infection, and there is no major role for CD30 in protection by other cell types. Transcriptomic comparison of WT and CD30-/- CD4 T cells from the lungs of Mtb-infected mixed bone marrow chimeric mice showed that CD30 directly promotes CD4 T cell differentiation and the expression of multiple effector molecules. These results demonstrate that the CD30 co-stimulatory axis is highly upregulated on granuloma T cells and is critical for protective T cell responses against Mtb infection.

S100s and HMGB1 Crosstalk in Pancreatic Cancer Tumors

Pancreatic cancer remains a disease that is very difficult to treat. S100 proteins are small calcium binding proteins with diverse intra- and extracellular functions that modulate different aspects of tumorigenesis, including tumor growth and metastasis. High mobility group box 1 (HMGB1) protein is a multifaceted protein that also actively influences the development and progression of tumors. In this study, we investigate the possible correlations, at the transcript level, between S100s and HMGB1 in pancreatic cancer. For this purpose, we calculated Pearson's correlations between the transcript levels of 13 cancer-related S100 genes and HMGB1 in a cDNA array containing 19 pancreatic cancer tumor samples, and in 8 human pancreatic cancer cell lines. Statistically significant positive correlations were found in 5.5% (5 out of 91) and 37.4% (34 of 91) of the possible S100/S100 or S100/HMGB1 pairs in cells and tumors, respectively. Our data suggest that many S100 proteins crosstalk in pancreatic tumors either with other members of the S100 family, or with HMGB1. These newly observed interdependencies may be used to further the characterization of pancreatic tumors based on S100 and HMGB1 transcription profiles.

RAGE inhibitor TTP488 (Azeliragon) suppresses metastasis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic cancer subtype, which is generally untreatable once it metastasizes. We hypothesized that interfering with the Receptor for Advanced Glycation End-products (RAGE) signaling with the small molecule RAGE inhibitors (TTP488/Azeliragon and FPS-ZM1) would impair TNBC metastasis and impair fundamental mechanisms underlying tumor progression and metastasis. Both TTP488 and FPS-ZM1 impaired spontaneous and experimental metastasis of TNBC models, with TTP488 reducing metastasis to a greater degree than FPS-ZM1. Transcriptomic analysis of primary xenograft tumor and metastatic tissue revealed high concordance in gene and protein changes with both drugs, with TTP488 showing greater potency against metastatic driver pathways. Phenotypic validation of transcriptomic analysis by functional cell assays revealed that RAGE inhibition impaired TNBC cell adhesion to multiple extracellular matrix proteins (including collagens, laminins, and fibronectin), migration, and invasion. Neither RAGE inhibitor impaired cellular viability, proliferation, or cell cycle in vitro. Proteomic analysis of serum from tumor-bearing mice revealed RAGE inhibition affected metastatic driver mechanisms, including multiple cytokines and growth factors. Further mechanistic studies by phospho-proteomic analysis of tumors revealed RAGE inhibition led to decreased signaling through critical BC metastatic driver mechanisms, including Pyk2, STAT3, and Akt. These results show that TTP488 impairs metastasis of TNBC and further clarifies the signaling and cellular mechanisms through which RAGE mediates metastasis. Importantly, as TTP488 displays a favorable safety profile in human studies, our study provides the rationale for evaluating TTP488 in clinical trials to treat or prevent metastatic TNBC.

MRP8/14 Is a Molecular Signature Triggered by Dopamine in HIV Latent Myeloid Targets That Increases HIV Transcription and Distinguishes HIV+ Methamphetamine Users with Detectable CSF Viral Load and Brain Pathology

There is a significant overlap between HIV infection and substance-use disorders. Dopamine (DA) is the most abundantly upregulated neurotransmitter in methamphetamine abuse, with receptors (DRD1-5) that are expressed by neurons as well as by a large diversity of cell types, including innate immune cells that are the targets of HIV infection, making them responsive to the hyperdopaminergic environment that is characteristic of stimulant drugs. Therefore, the presence of high levels of dopamine may affect the pathogenesis of HIV, particularly in the brain. The stimulation of HIV latently infected U1 promonocytes with DA significantly increased viral p24 levels in the supernatant at 24 h, suggesting effects on activation and replication. Using selective agonists to different DRDs, we found that DRD1 played a major role in activating viral transcription, followed by DRD4, which increased p24 with a slower kinetic rate compared to DRD1. Transcriptome and systems biology analyses led to the identification of a cluster of genes responsive to DA, where S100A8 and S100A9 were most significantly correlated with the early increase in p24 levels following DA stimulation. Conversely, DA increased the expression of these genes' transcripts at the protein level, MRP8 and MRP14, respectively, which form a complex also known as calprotectin. Interestingly, MRP8/14 was able to stimulate HIV transcription in latent U1 cells, and this occurred via binding of the complex to the receptor for an advanced glycosylation end-product (RAGE). Using selective agonists, both DRD1 and DRD4 increased MRP8/14 on the surface, in the cytoplasm, as well as secreted in the supernatants. On the other hand, while DRD1/5 did not affect the expression of RAGE, DRD4 stimulation caused its downregulation, offering a mechanism for the delayed effect via DRD4 on the p24 increase. To cross-validate MRP8/14 as a DA signature with a biomarker value, we tested its expression in HIV+ Meth users' postmortem brain specimens and peripheral cells. MRP8/14+ cells were more frequently identified in mesolimbic areas such as the basal ganglia of HIV+ Meth+ cases compared to HIV+ non-Meth users or to controls. Likewise, MRP8/14+ CD11b+ monocytes were more frequent in HIV+ Meth users, particularly in specimens from participants with a detectable viral load in the CSF. Overall, our results suggest that the MRP8 and MRP14 complex may serve as a signature to distinguish subjects using addictive substances in the context of HIV, and that this may play a role in aggravating HIV pathology by promoting viral replication in people with HIV who use Meth.

Pathogenic role of S100 proteins in psoriasis

Psoriasis is a chronic inflammatory skin disease. The histopathological features of psoriasis include excessive proliferation of keratinocytes and infiltration of immune cells. The S100 proteins are a group of EF-hand Ca2+-binding proteins, including S100A2, -A7, -A8/A9, -A12, -A15, which expression levels are markedly upregulated in psoriatic skin. These proteins exert numerous functions such as serving as intracellular Ca2+ sensors, transduction of Ca2+ signaling, response to extracellular stimuli, energy metabolism, and regulating cell proliferation and apoptosis. Evidence shows a crucial role of S100 proteins in the development and progress of inflammatory diseases, including psoriasis. S100 proteins can possibly be used as potential therapeutic target and diagnostic biomarkers. This review focuses on the pathogenic role of S100 proteins in psoriasis.

RAGE pathways play an important role in regulation of organ fibrosis

Organ fibrosis is a pathological process of fibroblast activation and excessive deposition of extracellular matrix after persistent tissue injury and therefore is a common endpoint of many organ pathologies. Multiple cellular types and soluble mediators, including chemokines, cytokines and non-peptidic factors, are implicated in fibrogenesis and the remodeling of tissue architecture. The molecular basis of the fibrotic process is complex and consists of closely intertwined signaling networks. Research has strived for a better understanding of these pathological mechanisms to potentially reveal novel therapeutic targets for fibrotic diseases. In light of new knowledge, the receptor for advanced glycation end products (RAGE) emerged as an important candidate for the regulation of a wide variety of cellular functions related to fibrosis, including inflammation, cell proliferation, apoptosis, and angiogenesis. RAGE is a pattern recognition receptor that binds a broad range of ligands such as advanced glycation end products, high mobility group box-1, S-100 calcium-binding protein and amyloid beta protein. Although the link between RAGE and fibrosis has been established, the exact mechanisms need be investigated in further studies. The aim of this review is to collect all available information about the intricate function of RAGE and its signaling cascades in the pathogenesis of fibrotic diseases within different organs. In addition, to the major ligands and signaling pathways, we discuss potential strategies for targeting RAGE in fibrosis. We emphasize the functional links between RAGE, inflammation and fibrosis that may guide further studies and the development of improved therapeutic drugs.

Emerging markers of inflammation and oxidative stress as potential predictors of coronary artery disease

BACKGROUND AND AIMS

The multi-ligand receptor for advanced glycation end products (RAGE) and its ligands AGEs and S100/calgranulin proteins are important mediators of inflammation and oxidative stress whereas the soluble form of RAGE (sRAGE) by acting as a decoy and the antioxidant PARK7/DJ-1 exert antiatherogenic effects. We examined whether sRAGE and its ligands AGEs, S100A8/A9, S100B, S100A12 and DJ-1 are associated with the presence of angiographic coronary artery disease (CAD) in asymptomatic patients with and without diabetes.

METHODS AND RESULTS

Plasma levels of RAGE ligands, sRAGE and DJ-1 were determined in 50 patients with angiographically proven CAD and in 50 age-matched healthy controls. In the whole cohort, lower levels of sRAGE and higher levels of interleukin-6 (IL-6), the RAGE ligands S100B, S100A12 and the AGEs/sRAGE ratio were associated with CAD. In patients without diabetes (n = 72), lower levels of sRAGE and DJ-1 and higher levels of IL-6 and AGEs/sRAGE ratio were associated with CAD. In multivariable analysis, AGEs/sRAGE ratio was an independent predictor of CAD both in the whole cohort (p = 0.034, OR = 1.247, [95%CI: 1.024, 1.0519]) and in the subgroup of patients without diabetes (p = 0.021, OR = 1.363, 95%CI [1.048, 1.771]) on top of established cardiovascular risk factors.

CONCLUSION

Alterations in plasma RAGE axis inflammatory mediators are associated with atherosclerosis, and higher levels of AGEs/sRAGE ratio are independently associated with CAD in asymptomatic patients and may act as a novel biomarker for predicting CAD. DJ-1 emerges as promising marker of oxidative stress in CAD patients without diabetes, a finding that deserves further study.

Activation of immune signals during organ transplantation

The activation of host's innate and adaptive immune systems can lead to acute and chronic graft rejection, which seriously impacts graft survival. Thus, it is particularly significant to clarify the immune signals, which are critical to the initiation and maintenance of rejection generated after transplantation. The initiation of response to graft is dependent on sensing of danger and stranger molecules. The ischemia and reperfusion of grafts lead to cell stress or death, followed by releasing a variety of damage-associated molecular patterns (DAMPs), which are recognized by pattern recognition receptors (PRRs) of host immune cells to activate intracellular immune signals and induce sterile inflammation. In addition to DAMPs, the graft exposed to 'non-self' antigens (stranger molecules) are recognized by the host immune system, stimulating a more intense immune response and further aggravating the graft damage. The polymorphism of MHC genes between different individuals is the key for host or donor immune cells to identify heterologous 'non-self' components in allogeneic and xenogeneic organ transplantation. The recognition of 'non-self' antigen by immune cells mediates the activation of immune signals between donor and host, resulting in adaptive memory immunity and innate trained immunity to the graft, which poses a challenge to the long-term survival of the graft. This review focuses on innate and adaptive immune cells receptor recognition of damage-associated molecular patterns, alloantigens and xenoantigens, which is described as danger model and stranger model. In this review, we also discuss the innate trained immunity in organ transplantation.

Methylglyoxal-Modified Albumin Effects on Endothelial Arginase Enzyme and Vascular Function

Advanced glycation end products (AGEs) contribute significantly to vascular dysfunction (VD) in diabetes. Decreased nitric oxide (NO) is a hallmark in VD. In endothelial cells, NO is produced by endothelial NO synthase (eNOS) from L-arginine. Arginase competes with NOS for L-arginine to produce urea and ornithine, limiting NO production. Arginase upregulation was reported in hyperglycemia; however, AGEs' role in arginase regulation is unknown. Here, we investigated the effects of methylglyoxal-modified albumin (MGA) on arginase activity and protein expression in mouse aortic endothelial cells (MAEC) and on vascular function in mice aortas. Exposure of MAEC to MGA increased arginase activity, which was abrogated by MEK/ERK1/2 inhibitor, p38 MAPK inhibitor, and ABH (arginase inhibitor). Immunodetection of arginase revealed MGA-induced protein expression for arginase I. In aortic rings, MGA pretreatment impaired acetylcholine (ACh)-induced vasorelaxation, which was reversed by ABH. Intracellular NO detection by DAF-2DA revealed blunted ACh-induced NO production with MGA treatment that was reversed by ABH. In conclusion, AGEs increase arginase activity probably through the ERK1/2/p38 MAPK pathway due to increased arginase I expression. Furthermore, AGEs impair vascular function that can be reversed by arginase inhibition. Therefore, AGEs may be pivotal in arginase deleterious effects in diabetic VD, providing a novel therapeutic target.

Role of lymphoid lineage cells aberrantly expressing alarmins S100A8/A9 in determining the severity of COVID-19

BACKGROUND

Alarmins S100A8 and S100A9 are recognized as hallmarks of severe COVID-19 and are primarily produced in myeloid cells, such as monocytes and neutrophils. As single-cell RNA-sequencing (scRNA-seq) data from patients with COVID-19 revealed the expression of S100A8/A9 in lymphoid cells in patients with severe COVID-19.

OBJECTIVE

We investigated the characteristics of lymphoid cells expressing S100A8/A9 in COVID-19 patients.

METHODS

Publicly available scRNA-seq data from patients with mild (N = 12) or severe (N = 7) COVID-19 were reanalyzed. The data were further divided into the following two groups based on the time of sample collection (from infection-onset): within 6 days (early phase) and after 6 days (late phase). Differential expression and gene set enrichment analyses were performed between S100A8/A9^High and S100A8/A9^Low lymphoid cells. Finally, cell-cell interaction analysis was performed to investigate the role of lymphoid cells expressing high levels of S100A8/A9 in COVID-19.

RESULTS

S100A8/A9 overexpression was observed in lymphoid cells, including B cells, T cells, and NK cells, in patients with severe COVID-19 (compared to patients with mild COVID-19). Cells exhibiting strong interferon/cytokine responses were found to be associated with the severity of COVID-19. Furthermore, differences in S100A8/A9-TLR4/RAGE interactions were confirmed between patients with severe and mild disease.

CONCLUSIONS

Lymphoid cells overexpressing S100A8/A9 contribute to the dysregulation of the innate immune response in patients with severe COVID-19, specifically during the early phase of infection. This study fosters a better understanding of the hyper-induction of pro-inflammatory cytokine expression and the generation of a cytokine storm in response to COVID-19 infection.

Contributions of the receptor for advanced glycation end products axis activation in gastric cancer

Compelling shreds of evidence derived from both clinical and experimental research have demonstrated the crucial contribution of receptor for advanced glycation end products (RAGE) axis activation in the development of neoplasms, including gastric cancer (GC). This new actor in tumor biology plays an important role in the onset of a crucial and long-lasting inflammatory milieu, not only by supporting phenotypic changes favoring growth and dissemination of tumor cells, but also by functioning as a pattern-recognition receptor in the inflammatory response to Helicobacter pylori infection. In the present review, we aim to highlight how the overexpression and activation of the RAGE axis contributes to the proliferation and survival of GC cells as and their acquisition of more invasive phenotypes that promote dissemination and metastasis. Finally, the contribution of some single nucleotide polymorphisms in the RAGE gene as susceptibility or poor prognosis factors is also discussed.

Reversal of aging-associated increase in myelopoiesis and expression of alarmins by angiotensin-(1-7)

Aging is associated with chronic systemic inflammation largely due to increased myelopoiesis, which in turn increases risk for vascular disease. We have previously shown evidence for the therapeutic potential of Angiotensin-(1-7) (Ang-(1-7)) in reversing vasoreparative dysfunction in aging. This study tested the hypothesis that ischemic vascular repair in aging by Ang-(1-7) involves attenuation of myelopoietic potential in the bone marrow and decreased mobilization of inflammatory cells. Young or Old male mice of age 3-4 and 22-24 months, respectively, received Ang-(1-7) (1 µg/kg/min, s.c.) for four weeks. Myelopoiesis was evaluated in the bone marrow (BM) cells by carrying out the colony forming unit (CFU-GM) assay followed by flow cytometry of monocyte-macrophages. Expression of pro-myelopoietic factors and alarmins in the hematopoietic progenitor-enriched BM cells was evaluated. Hindlimb ischemia (HLI) was induced by femoral ligation, and mobilization of monocytes into the blood stream was determined. Blood flow recovery was monitored by Laser Doppler imaging and infiltration of inflammatory cells was evaluated by immunohistochemistry. BM cells from Old mice generated a higher number of monocytes (Ly6G-CD11b+Ly6Chi) and M1 macrophages (Ly6ChiF4/80+) compared to that of Young, which was reversed by Ang-(1-7). Gene expression of selected myelopoietic factors, alarmins (S100A8, S100A9, S100A14 and HMGb1) and the receptor for alarmins, RAGE, was higher in the Old hematopoietic progenitor-enriched BM cells compared to the Young. Increased expressions of these factors were decreased by Ang-(1-7). Ischemia-induced mobilization of monocytes was higher in Old mice with decreased blood flow recovery and increased infiltration of monocyte-macrophages compared to the Young, all of which were reversed by Ang-(1-7). Enhanced ischemic vascular repair by Ang-(1-7) in aging is largely by decreasing the generation and recruitment of inflammatory monocyte-macrophages to the areas of ischemic injury. This is associated with decreased alarmin signaling in the BM-hematopoietic progenitor cells.

Assessing the Immune Cell Subset and Genetic Mutations in Patients With Palindromic Rheumatism Seronegative for Rheumatoid Factor and Anti-Cyclic Citrullinated Peptide

OBJECTIVE

The etiology underlying cases of palindromic rheumatism (PR) not associated with other rheumatic diseases in patients who are seronegative for rheumatoid factor and anti-cyclic citrullinated peptide (seronegative PR) is unclear. We aimed to investigate the immune cells and genes involved.

METHODS

This was a single-center comparative study of 48 patients with seronegative PR and 48 healthy controls. Mass cytometry and RNA sequencing were used to identify distinct immune cell subsets in blood. Among the 48 seronegative PR patients, plasma samples from 40 patients were evaluated by enzyme-linked immunosorbent assay for cytokine levels, and peripheral blood samples from 25 patients were evaluated by flow cytometry for mononuclear cell subsets. Plasma samples from 21 patients were evaluated by real-time polymerase chain reaction for differential gene and protein expression, and samples from 3 patients were analyzed with whole-exome sequencing for gene mutations.

RESULTS

Immunophenotyping revealed a markedly increased frequency of CD14+CD11b+CD36+ and CD4+CD25-CD69+ cells in seronegative PR patients with active flares compared with healthy controls (P < 0.0001 for both cell subset comparisons). Gene enrichment analyses of RNA-sequencing data from sorted CD14+CD11b+CD36+ and CD4+CD25-CD69+ cells showed involvement of the inflammatory/stress response, phagocytosis, and regulation of apoptosis functional pathways. Up-regulated expression of CXCL16 and IL10RA was observed in monocytes from PR patients. Up-regulation of PFKFB3, DDIT4, and TGFB1, and down-regulation of PDIA6 were found in monocytes and lymphocytes from PR patients with active flares and PR patients in intercritical periods. Plasma levels of S100A8/A9 and interleukin-1β were elevated in PR patients. Whole-exome sequencing revealed novel polygenic mutations in HACL1, KDM5A, RASAL1, HAVCR2, PRDM9, MBOAT4, and JRKL.

CONCLUSION

In seronegative PR patients, we identified a distinct CD14+CD11b+CD36+ cell subset that can induce an inflammatory response under stress and exert antiinflammatory effects after phagocytosis of apoptotic cells, and a CD4+CD25-CD69+ T cell subset with pro- and antiinflammatory properties. Individuals with genetic mutations involving epigenetic modification, potentiation and resolution of stress-induced inflammation/apoptosis, and a dysregulated endoplasmic reticulum stress response could be predisposed to seronegative PR.

Toward an understanding of the conformational plasticity of S100A8 and S100A9 Ca2+-binding proteins

S100A8 and S100A9 are small, human, Ca²⁺-binding proteins with multiple intracellular and extracellular functions in signaling, regulation, and defense. The two proteins are not detected as monomers but form various noncovalent homo- or hetero-oligomers related to specific activities in human physiology. Because of their significant roles in numerous medical conditions, there has been intense research on the conformational properties of various S100A8 and S100A9 proteoforms as essential targets of drug discovery. NMR or crystal structures are currently available only for mutated or truncated protein complexes, mainly with bound metal ions, that may well reflect the proteins' properties outside cells but not in other biological contexts in which they perform. Here, we used structural mass spectrometry methods combined with molecular dynamics simulations to compare the conformations of wild-type full-length S100A8 and S100A9 subunits in biologically relevant homo- and hetero-dimers and in higher oligomers formed in the presence of calcium or zinc ions. We provide, first, rationales for their functional response to changing environmental conditions, by elucidating differences between proteoforms in flexible protein regions that may provide the plasticity of the binding sites for the multiple targets, and second, the key factors contributing to the variable stability of the oligomers. The described methods and a systematic view of the conformational properties of S100A8 and S100A9 complexes provide a basis for further research to characterize and modulate their functions for basic science and therapies.

Serum S100B Levels in Patients with Liver Cirrhosis and Hepatic Encephalopathy

Hepatic encephalopathy (HE) is one of the main complications of liver cirrhosis (LC) and is classified into minimal hepatic encephalopathy (MHE) and overt hepatic encephalopathy (overt HE). S100B is expressed mainly in astrocytes and other glial cells, and S100B has been reported to be associated with various neurological disorders. The present study aimed to investigate the diagnostic ability of serum S100B to discriminate the grade of HE and the parameters correlated with serum S100B levels. Additionally, we investigated whether serum S100B levels can be used to predict 1-year mortality in cirrhotic patients. In total, 95 cirrhotic patients were consecutively enrolled and divided into the following three groups: (i) without any types of HEs; (ii) with MHE; and (iii) with overt HE. The diagnosis of MHE was made by the Mini-Mental State Examination (MMSE) and Psychometric Hepatic Encephalopathy Score (PHES). Among the three groups, there were no significant differences in serum S100B levels regardless of HE severity. The clinical parameters correlated with serum S100B levels were age, serum bilirubin, and creatinine levels. The Model for End-Stage Liver Disease (MELD) score showed a significant positive correlation with serum S100B levels. The relationship between serum S100B levels and MELD score was maintained in 48 patients without any type of HE. Additionally, hyperammonemia, low cholesterol levels, and the combination of serum S100B levels ≥ 35 pg/mL with MELD score ≥ 13 were factors for predicting 1- year mortality. In conclusion, serum S100B level was not useful for differentiating the severity of HE. However, we found that serum S100B levels can be affected by age, serum bilirubin, and creatinine in cirrhotic patients and are associated with MELD scores. Additionally, serum S100B levels showed the possibility of predicting 1-year mortality in cirrhotic patients. These findings suggest that serum S100B levels may reflect liver dysfunction and prognosis in liver disease.

Advanced Glycation End-Products and Their Effects on Gut Health

Dietary advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed when reducing sugars are heated with proteins, amino acids, or lipids at high temperatures for a prolonged period. The presence and accumulation of AGEs in numerous cell types and tissues are known to be prevalent in the pathology of many diseases. Modern diets, which contain a high proportion of processed foods and therefore a high level of AGE, cause deleterious effects leading to a multitude of unregulated intracellular and extracellular signalling and inflammatory pathways. Currently, many studies focus on investigating the chemical and structural aspects of AGEs and how they affect the metabolism and the cardiovascular and renal systems. Studies have also shown that AGEs affect the digestive system. However, there is no complete picture of the implication of AGEs in this area. The gastrointestinal tract is not only the first and principal site for the digestion and absorption of dietary AGEs but also one of the most susceptible organs to AGEs, which may exert many local and systemic effects. In this review, we summarise the current evidence of the association between a high-AGE diet and poor health outcomes, with a special focus on the relationship between dietary AGEs and alterations in the gastrointestinal structure, modifications in enteric neurons, and microbiota reshaping.

Macrophage scavenger receptors: Tumor support and tumor inhibition

Tumor-associated macrophages (TAMs) are a heterogeneous population of myeloid cells that constitute up to 50% of the cell mass of human tumors. TAMs interact with the components of the tumor microenvironment (TME) by using scavenger receptors (SRs), a large superfamily of multifunctional receptors that recognize, internalize and transport to the endosomal/lysosomal pathway apoptotic cells, cytokines, matrix molecules, lipid modified lipoproteins and other unwanted-self ligands. In our review, we summarized state-of-the art for the role of macrophage scavenger receptors in tumor development and their significance as cancer biomarkers. In this review we focused on functional activity of TAM-expressing SRs in animal models and in patients, and summarized the data for different human cancer types about the prognostic significance of TAM-expressed SRs. We discussed the role of SRs in the regulation of cancer cell biology, cell-cell and cell-matrix interaction in TME, immune status in TME, angiogenesis, and intratumoral metabolism. Targeting of tumor-promoting SRs can be a promising therapeutic approach in anti-cancer therapy. In our review we provide evidence for both tumor supporting and tumor inhibiting functions of scavenger receptors expressed on TAMs. We focused on the key differences in the prognostic and functional roles of SRs that are specific for cancer types. We highlighted perspectives for inhibition of tumor-promoting SRs in anti-cancer therapy.

Time-Dependent Changes in the Biofluid Levels of Neural Injury Markers in Severe Traumatic Brain Injury Patients-Cerebrospinal Fluid and Cerebral Microdialysates: A Longitudinal Prospective Pilot Study

Monitoring protein biomarker levels in the cerebrospinal fluid (CSF) can help assess injury severity and outcome after traumatic brain injury (TBI). Determining injury-induced changes in the proteome of brain extracellular fluid (bECF) can more closely reflect changes in the brain parenchyma, but bECF is not routinely available. The aim of this pilot study was to compare time-dependent changes of S100 calcium-binding protein B (S100B), neuron-specific enolase (NSE), total Tau, and phosphorylated Tau (p-Tau) levels in matching CSF and bECF samples collected at 1, 3, and 5 days post-injury from severe TBI patients (n = 7; GCS 3-8) using microcapillary-based western analysis. We found that time-dependent changes in CSF and bECF levels were most pronounced for S100B and NSE, but there was substantial patient-to-patient variability. Importantly, the temporal pattern of biomarker changes in CSF and bECF samples showed similar trends. We also detected two different immunoreactive forms of S100B in both CSF and bECF samples, but the contribution of the different immunoreactive forms to total immunoreactivity varied from patient to patient and time point to time point. Our study is limited, but it illustrates the value of both quantitative and qualitative analysis of protein biomarkers and the importance of serial sampling for biofluid analysis after severe TBI.

S100A8 and S100A12 Proteins as Biomarkers of High Disease Activity in Patients with Rheumatoid Arthritis That Can Be Regulated by Epigenetic Drugs

Rheumatoid arthritis (RA) is an autoimmune chronic inflammatory disease that is still not well understood in terms of its pathogenesis and presents diagnostic and therapeutic challenges. Monocytes are key players in initiating and maintaining inflammation through the production of pro-inflammatory cytokines and S100 proteins in RA. This study aimed to test a specific DNA methylation inhibitor (RG108) and activator (budesonide) in the regulation of pro-inflammatory mediators-especially the S100 proteins. We also searched for new biomarkers of high disease activity in RA patients. RNA sequencing analysis of healthy controls (HCs) and RA monocytes was performed. Genes such as the S100 family, TNF, and IL-8 were validated by qRT-PCR following DNA-methylation-targeted drug treatment in a monocytic THP-1 cell line. The concentrations of the S100A8, S100A11, and S100A12 proteins in the sera and synovial fluids of RA patients were tested and correlated with clinical parameters. We demonstrated that RA monocytes had significantly increased levels of S100A8, S100A9, S100A11, S100A12, MYD88, JAK3, and IQGAP1 and decreased levels of IL10RA and TGIF1 transcripts. In addition, stimulation of THP-1 cells with budesonide statistically reduced the expression of the S100 family, IL-8, and TNF genes. In contrast, THP-1 cells treated with RG108 had increased levels of the S100 family and TNF genes. We also revealed a significant upregulation of S100A8, S100A11, and S100A12 in RA patients, especially in early RA compared to HC sera. In addition, protein levels of S100A8, S100A11, and S100A12 in RA synovial fluids compared to HC sera were significantly increased. Overall, our data suggest that the S100A8 and S100A12 proteins are strongly elevated during ongoing inflammation, so they could be used as a better biomarker of disease activity than CRP. Interestingly, epigenetic drugs can regulate these S100 proteins, suggesting their potential use in targeting RA inflammation.

The Anti-Cancer Activity of Pentamidine and Its Derivatives (WLC-4059) Is through Blocking the Interaction between S100A1 and RAGE V Domain

The S100A1 protein in humans is a calcium-binding protein. Upon Ca²⁺ binding to S100A1 EF-hand motifs, the conformation of S100A1 changes and promotes interactions with target proteins. RAGE consists of three domains: the cytoplasmic, transmembrane, and extracellular domains. The extracellular domain consists of C1, C2, and V domains. V domains are the primary receptors for the S100 protein. It was reported several years ago that S100A1 and RAGE V domains interact in a pathway involving S100A1-RAGE signaling, whereby S100A1 binds to the V domain, resulting in RAGE dimerization. The autophosphorylation of the cytoplasmic domain initiates a signaling cascade that regulates cell proliferation, cell growth, and tumor formation. In this study, we used pentamidine and a newly synthesized pentamidine analog (WLC-4059) to inhibit the S100A1-RAGE V interaction. ¹H-¹⁵N HSQC NMR titration was carried out to characterize the interaction between mS100A1 (mutant S100A1, C86S) and pentamidine analogs. We found that pentamidine analogs interact with S100A1 via ¹H-¹⁵N HSQC NMR spectroscopy. Based on the results, we utilized the HADDOCK program to generate structures of the mS100A1-WLC-4059 binary complex. Interestingly, the binary complex overlapped with the complex crystal structure of the mS100A1-RAGE-V domain, proving that WLC-4059 blocks interaction sites between S100A1 and RAGE-V. A WST-1 cell proliferation assay also supported these results. We conclude that pentamidine analogs could potentially enhance therapeutic approaches against cancers.

RAGE Inhibitors for Targeted Therapy of Cancer: A Comprehensive Review

The receptor for advanced glycation end products (RAGE) is a member of the immunoglobulin family that is overexpressed in several cancers. RAGE is highly expressed in the lung, and its expression increases proportionally at the site of inflammation. This receptor can bind a variety of ligands, including advanced glycation end products, high mobility group box 1, S100 proteins, adhesion molecules, complement components, advanced lipoxidation end products, lipopolysaccharides, and other molecules that mediate cellular responses related to acute and chronic inflammation. RAGE serves as an important node for the initiation and stimulation of cell stress and growth signaling mechanisms that promote carcinogenesis, tumor propagation, and metastatic potential. In this review, we discuss different aspects of RAGE and its prominent ligands implicated in cancer pathogenesis and describe current findings that provide insights into the significant role played by RAGE in cancer. Cancer development can be hindered by inhibiting the interaction of RAGE with its ligands, and this could provide an effective strategy for cancer treatment.

Liver-Derived S100A6 Propels β-Cell Dysfunction in NAFLD

Nonalcoholic fatty liver disease (NAFLD) is an independent predictor of systemic insulin resistance and type 2 diabetes mellitus (T2DM). However, converse correlates between excess liver fat content and β-cell function remain equivocal. Specifically, how the accumulation of liver fat consequent to the enhanced de novo lipogenesis (DNL) leads to pancreatic β-cell failure and eventually to T2DM is elusive. Here, we have identified that low-molecular-weight calcium-binding protein S100A6, or calcyclin, inhibits glucose-stimulated insulin secretion (GSIS) from β cells through activation of the receptor for the advanced glycation end products and diminution of mitochondrial respiration. Serum S100A6 level is elevated both in human patients with NAFLD and in a high-fat diet-induced mouse model of NAFLD. Although serum S100A6 levels are negatively associated with β-cell insulin secretory capacity in human patients, depletion of hepatic S100A6 improves GSIS and glycemia in mice, suggesting that S100A6 contributes to the pathophysiology of diabetes in NAFLD. Moreover, transcriptional induction of hepatic S100A6 is driven by the potent regulator of DNL, carbohydrate response element-binding protein (ChREBP), and ectopic expression of ChREBP in the liver suppresses GSIS in a S100A6-sensitive manner. Together, these data suggest elevated serum levels of S100A6 may serve as a biomarker in identifying patients with NAFLD with a heightened risk of developing β-cell dysfunction. Overall, our data implicate S100A6 as, to our knowledge, a hitherto unknown hepatokine to be activated by ChREBP and that participates in the hepato-pancreatic communication to impair insulin secretion and drive the development of T2DM in NAFLD.

Role of RAGE in the Pathogenesis of Neurological Disorders

This review reflects upon our own as well as other investigators' studies on the role of receptor for advanced glycation end-products (RAGE), bringing up the latest information on RAGE in physiology and pathology of the nervous system. Over the last ten years, major progress has been made in uncovering many of RAGE-ligand interactions and signaling pathways in nervous tissue; however, the translation of these discoveries into clinical practice has not come to fruition yet. This is likely, in part to be the result of our incomplete understanding of this crucial signaling pathway. Clinical trials examining the therapeutic efficacy of blocking RAGE-external ligand interactions by genetically engineered soluble RAGE or an endogenous RAGE antagonist, has not stood up to its promise; however, other trials with different blocking agents are being considered with hope for therapeutic success in diseases of the nervous system.

Interaction of RAGE with α-synuclein fibrils mediates inflammatory response of microglia

Microglia-mediated neuroinflammation and α-synuclein (α-syn) aggregation, both as pathological hallmarks of Parkinson's disease (PD), crosstalk to exacerbate degeneration of dopaminergic neurons and PD progression. However, the mechanism underlying their interaction is poorly understood, which obstructs effective therapeutic inhibition of α-syn-induced neuroinflammation. Here, we initiate from structure-based interaction predictions and find that receptor for advanced glycation end products (RAGE) serves as a receptor of α-syn fibrils on microglia. Results of nuclear magnetic resonance (NMR) spectroscopy and mutagenesis validate that the V domain of RAGE that contains an alkaline surface can bind with acidic C-terminal residues of α-syn. Furthermore, the binding of α-syn fibrils with RAGE induces neuroinflammation, which is blocked by both genetic depletion of RAGE and inhibitor FPS-ZM1. Our work shows the important role, as well as the structural mechanism, of RAGE in mediating the inflammatory response of microglia to α-syn fibrils, which may help to establish effective therapeutic strategies to alleviate α-syn-induced neuroinflammation and neuronal damage.

Role of RAGE and its ligand HMGB1 in the development of COPD

Smoking is a well-established risk factor for chronic obstructive pulmonary disease (COPD). Chronic lung inflammation continues even after smoking cessation and leads to COPD progression. To date, anti-inflammatory therapies are ineffective in improving pulmonary function and COPD symptoms, and new molecular targets are urgently needed to deal with this challenge. The receptor for advanced glycation end-products (RAGE) was shown to be relevant in COPD pathogenesis, since it is both a genetic determinant of low lung function and a determinant of COPD susceptibility. Moreover, RAGE is involved in the physiological response to cigarette smoke exposure. Since innate and acquired immunity plays an essential role in the development of chronic inflammation and emphysema in COPD, here we summarized the roles of RAGE and its ligand HMGB1 in COPD immunity.

Long COVID (PASC) Is Maintained by a Self-Sustaining Pro-Inflammatory TLR4/RAGE-Loop of S100A8/A9 > TLR4/RAGE Signalling, Inducing Chronic Expression of IL-1b, IL-6 and TNFa: Anti-Inflammatory Ezrin Peptides as Potential Therapy

Long COVID, also referred to as Post-Acute Sequelae of COVID (PASC), is probably triggered during SARS-CoV-2 infection and acute COVID-19 by SARS-CoV-2 Spike-protein binding and hyper-activating the cell-membrane expressed Receptor for Advance Glycation End-products (mRAGE) and Toll-Like Receptor 4 (TLR4). SARS-CoV-2 infects lung monocytes by Spike binding to mRAGE (not ACE2). During acute COVID-19, high levels of IL-6 hyper-stimulate S100A8/A9 expression and secretion. Although no viral protein nor mRNA can be detected in half of long COVID (PASC) patients, there is a significant elevation of serum levels of IL-1b, IL-6, TNFa, and S100A8/A9. It appears that a pathological pro-inflammatory feedback loop (the TLR4/RAGE-loop) is established during acute COVID-19, which is maintained by S100A8/A9 > RAGE/TLR4 chronic inflammatory signalling, even after SARS-CoV-2 has been cleared from the body. During long COVID/PASC, Ca2+-binding protein S100A8/A9 chronically stimulates TLR4/RAGE-signalling to induce chronic expression of IL-1b, IL-6 and TNFa. Secreted IL-6 binds to its IL-6R receptor on the surface of other cells and signals via STAT3 and C/EBPb for more S100A8/A9 expression. Secreted IL-1b binds to its receptor IL-1R on other cells, and signals via NFkB for more mRAGE and TLR4 expression. New S100A8/A9 can bind and activate cell-surface mRAGE and TLR4 to stimulate expression of more IL-1b, IL-6 and TNFa. This process establishes a pathogenic pro-inflammatory TLR4/RAGE-loop: IL-1b + IL-6 > IL-1R + IL-6R > TLR4/mRAGE + S100A8/A9 > IL-1b + IL-6, which generates multi-organ inflammation that persists in the blood vessels, the brain, the liver, the heart, the kidneys, the gut and the musculo-skeletal system, and is responsible for all the complex pathologies associated with long COVID/PASC. Chronic expression of IL-1, IL-6 and TNFa is critical for the maintenance of the TLR4/RAGE-loop and persistence of long COVID/PASC. Ezrin peptides are inhibitors of IL-1, IL-6, IL-8 and TNFa expression, so are now being investigated as potential therapy for long COVID/PASC. There is preliminary anecdotal evidence of symptomatic relief (not confirmed yet by formal clinical trials) from a few long COVID/PASC patient volunteers, after treatment with ezrin peptide therapy.

HMGB1 increases RAGE expression in vascular smooth muscle cells via ERK and p-38 MAPK-dependent pathways

The increased expression of receptors for advanced glycation end-product (RAGE) is known as a key player in the progression of vascular remodeling. However, the precise signal pathways regulating RAGE expression in vascular smooth muscle cells (VSMCs) in the injured vasculatures are unclear. Given the importance of mitogen-activated protein kinase (MAPK) signaling in cell proliferation, we investigated the importance of MAPK signaling in high-mobility group box 1 (HMGB1)-induced RAGE expression in VSMCs. In HMGB1 (100 ng/ml)-stimulated human VSMCs, the expression of RAGE mRNA and protein was increased in association with an increase in AGE-induced VSMC proliferation. The HMGB1-induced RAGE expression was attenuated in cells pretreated with inhibitors for ERK (PD98059, 10 μM) and p38 MAPK (SB203580, 10 μM) as well as in cells deficient in ERK and p38 MAPK using siRNAs, but not in cells deficient of JNK signaling. In cells stimulated with HMGB1, the phosphorylation of ERK, JNK, and p38 MAPK was increased. This increase in ERK and p38 MAPK phosphorylation was inhibited by p38 MAPK and ERK inhibitors, respectively, but not by JNK inhibitor. Moreover, AGE-induced VSMC proliferation in HMGB1-stimulated cells was attenuated in cells treated with ERK and p38 MAPK inhibitors. Taken together, our results indicate that ERK and p38 MAPK signaling are involved in RAGE expression in HMGB1-stimulated VSMCs. Thus, the ERK/p38 MAPK-RAGE signaling axis in VSMCs was suggested as a potential therapeutic target for vascular remodeling in the injured vasculatures.

Neurocognitive trajectory and proteomic signature of inherited risk for Alzheimer's disease

For Alzheimer's disease-a leading cause of dementia and global morbidity-improved identification of presymptomatic high-risk individuals and identification of new circulating biomarkers are key public health needs. Here, we tested the hypothesis that a polygenic predictor of risk for Alzheimer's disease would identify a subset of the population with increased risk of clinically diagnosed dementia, subclinical neurocognitive dysfunction, and a differing circulating proteomic profile. Using summary association statistics from a recent genome-wide association study, we first developed a polygenic predictor of Alzheimer's disease comprised of 7.1 million common DNA variants. We noted a 7.3-fold (95% CI 4.8 to 11.0; p < 0.001) gradient in risk across deciles of the score among 288,289 middle-aged participants of the UK Biobank study. In cross-sectional analyses stratified by age, minimal differences in risk of Alzheimer's disease and performance on a digit recall test were present according to polygenic score decile at age 50 years, but significant gradients emerged by age 65. Similarly, among 30,541 participants of the Mass General Brigham Biobank, we again noted no significant differences in Alzheimer's disease diagnosis at younger ages across deciles of the score, but for those over 65 years we noted an odds ratio of 2.0 (95% CI 1.3 to 3.2; p = 0.002) in the top versus bottom decile of the polygenic score. To understand the proteomic signature of inherited risk, we performed aptamer-based profiling in 636 blood donors (mean age 43 years) with very high or low polygenic scores. In addition to the well-known apolipoprotein E biomarker, this analysis identified 27 additional proteins, several of which have known roles related to disease pathogenesis. Differences in protein concentrations were consistent even among the youngest subset of blood donors (mean age 33 years). Of these 28 proteins, 7 of the 8 proteins with concentrations available were similarly associated with the polygenic score in participants of the Multi-Ethnic Study of Atherosclerosis. These data highlight the potential for a DNA-based score to identify high-risk individuals during the prolonged presymptomatic phase of Alzheimer's disease and to enable biomarker discovery based on profiling of young individuals in the extremes of the score distribution.

Decreased Monocyte HLA-DR Expression in Patients with Sepsis and Acute Kidney Injury

Background and objectives: Acute kidney injury (AKI) is common in critically ill patients, especially those with sepsis. Persistently low human leukocyte antigen (HLA)-DR expression in monocytes reflects the decreased function of antigen-presenting cells, contributing to poor outcomes in sepsis. This study aimed to establish an association between AKI and HLA-DR expression in monocytes of patients with sepsis. Materials and Methods: We detected HLA-DR expression in monocytes and measured plasma levels of S100A12, high-mobility group box 1 (HMGB1), advanced glycation end products (AGE), and soluble receptor for AGE (sRAGE) from septic patients and healthy controls. Results: HLA-DR expression in monocytes was decreased in patients with AKI than in those without AKI (29.8 ± 5.0% vs. 53.1 ± 5.8%, p = 0.005). Compared with AKI patients, the mean monocyte HLA-DR expression in patients with end-stage renal disease was increased without statistical significance. There were no differences in the AGE/sRAGE ratio and plasma levels of S100A12, HMGB1, AGE, and sRAGE between patients with and without AKI. Conclusions: Compared with septic patients without AKI, patients with AKI had significantly lower HLA-DR expression in monocytes. The role of hemodialysis in monocyte HLA-DR expression needs further studies to explore.

Biologically Active Fragment of the Receptor for Advanced Glycation End Products (RAGE) Is Able to Inhibit Oligomerization of the Beta-Amyloid

Abstract

It was found earlier that the synthetic fragment corresponding to the 60–76 sequence of the extracellular domain of the receptor for advanced glycation end products (RAGE) had a protective effect on animal and cellular models of Alzheimer’s disease. It was proposed that this effect was mediated via the interaction of the peptide with beta-amyloid (Aβ), which was one of the RAGE ligands, by inhibiting the formation of toxic Aβ oligomers. The aim of this study was an application of physicochemical methods to an investigation of the ability of the 60–76 peptide to prevent the Aβ40 oligomerization in solution in comparison with the nonprotective 65–76 truncated peptide. The dynamics of the formation of the Aβ40 fibrils in the presence of the peptides was evaluated using thioflavin T. The relative sizes of oligomers were determined by dynamic light scattering. The peptide binding to Aβ40 was examined by fluorescence titration. We demonstrated by the two methods that the peptide corresponding to the 60–76 sequence of RAGE considerably inhibited (by more than 90%) the formation of oligomers and fibrils of Aβ40 distinct from the 65–76 peptide. In addition, we found that the protective effect of the peptides and their ability to inhibit the Aβ40 oligomerization did not correlate with their binding to the monomeric/tetrameric Aβ40. We confirmed in vitro the hypothesis that the protective activity of the synthetic 60–76 fragment of RAGE was associated with its ability to inhibit the Aβ oligomerization.

Pathophysiology of RAGE in inflammatory diseases

The receptor for advanced glycation end products (RAGE) is a non-specific multi-ligand pattern recognition receptor capable of binding to a range of structurally diverse ligands, expressed on a variety of cell types, and performing different functions. The ligand-RAGE axis can trigger a range of signaling events that are associated with diabetes and its complications, neurological disorders, cancer, inflammation and other diseases. Since RAGE is involved in the pathophysiological processes of many diseases, targeting RAGE may be an effective strategy to block RAGE signaling.