The cytokine-serum amyloid A-chemokine network

G protein-coupled receptors and traditional Chinese medicine: new thinks for the development of traditional Chinese medicine

G protein-coupled receptors (GPCRs) widely exist in vivo and participate in many physiological processes, thus emerging as important targets for drug development. Approximately 30% of the Food and Drug Administration (FDA)-approved drugs target GPCRs. To date, the 'one disease, one target, one molecule' strategy no longer meets the demands of drug development. Meanwhile, small-molecule drugs account for 60% of FDA-approved drugs. Traditional Chinese medicine (TCM) has garnered widespread attention for its unique theoretical system and treatment methods. TCM involves multiple components, targets and pathways. Centered on GPCRs and TCM, this paper discusses the similarities and differences between TCM and GPCRs from the perspectives of syndrome of TCM, the consistency of TCM's multi-component and multi-target approaches and the potential of GPCRs and TCM in the development of novel drugs. A novel strategy, 'simultaneous screening of drugs and targets', was proposed and applied to the study of GPCRs. We combine GPCRs with TCM to facilitate the modernisation of TCM, provide valuable insights into the rational application of TCM and facilitate the research and development of novel drugs. This study offers theoretical support for the modernisation of TCM and introduces novel ideas for development of safe and effective drugs.

The potential role of serum amyloid A as biomarker of rheumatic diseases: a systematic review and meta-analysis

The identification of novel, robust biomarkers for the diagnosis of rheumatic diseases (RDs) and the presence of active disease might facilitate early treatment and the achievement of favourable long-term outcomes. We conducted a systematic review and meta-analysis of studies investigating the acute phase reactant, serum amyloid A (SAA), in RD patients and healthy controls to appraise its potential as diagnostic biomarker. We searched PubMed, Scopus, and Web of Science from inception to 10 April 2024 for relevant studies. We evaluated the risk of bias and the certainty of evidence using the JBI Critical Appraisal Checklist and GRADE, respectively (PROSPERO registration number: CRD42024537418). In 32 studies selected for analysis, SAA concentrations were significantly higher in RD patients compared to controls (SMD = 1.61, 95% CI 1.24-1.98, p < 0.001) and in RD patients with active disease compared to those in remission (SMD = 2.17, 95% CI 1.21-3.13, p < 0.001). Summary receiving characteristics curve analysis showed a good diagnostic accuracy of SAA for the presence of RDs (area under the curve = 0.81, 95% CI 0.78-0.84). The effect size of the differences in SAA concentrations between RD patients and controls was significantly associated with sex, body mass index, type of RD, and study country. Pending the conduct of prospective studies in different types of RDs, the results of this systematic review and meta-analysis suggest that SAA is a promising biomarker for the diagnosis of RDs and active disease.

Identification of a risk model for prognostic and therapeutic prediction in renal cell carcinoma based on infiltrating M0 cells

The tumor microenvironment (TME) comprises immune-infiltrating cells that are closely linked to tumor development. By screening and analyzing genes associated with tumor-infiltrating M0 cells, we developed a risk model to provide therapeutic and prognostic guidance in clear cell renal cell carcinoma (ccRCC). First, the infiltration abundance of each immune cell type and its correlation with patient prognosis were analyzed. After assessing the potential link between the depth of immune cell infiltration and prognosis, we screened the infiltrating M0 cells to establish a risk model centered on three key genes (TMEN174, LRRC19, and SAA1). The correlation analysis indicated a positive correlation between the risk score and various stages of the tumor immune cycle, including B-cell recruitment. Furthermore, the risk score was positively correlated with CD8 expression and several popular immune checkpoints (ICs) (TIGIT, CTLA4, CD274, LAG3, and PDCD1). Additionally, the high-risk group (HRG) had higher scores for tumor immune dysfunction and exclusion (TIDE) and exclusion than the low-risk group (LRG). Importantly, the risk score was negatively correlated with the immunotherapy-related pathway enrichment scores, and the LRG showed a greater therapeutic benefit than the HRG. Differences in sensitivity to targeted drugs between the HRG and LRG were analyzed. For commonly used targeted drugs in RCC, including axitinib, pazopanib, temsirolimus, and sunitinib, LRG had lower IC50 values, indicating increased sensitivity. Finally, immunohistochemistry results of 66 paraffin-embedded specimens indicated that SAA1 was strongly expressed in the tumor samples and was associated with tumor metastasis, stage, and grade. SAA1 was found to have a significant pro-tumorigenic effect by experimental validation. In summary, these data confirmed that tumor-infiltrating M0 cells play a key role in the prognosis and treatment of patients with ccRCC. This discovery offers new insights and directions for the prognostic prediction and treatment of ccRCC.

Association Between Serum Amyloid A Expression and Disease Control after Endoscopic Sinus Surgery in Patients With Chronic Rhinosinusitis With Nasal Polyps

OBJECTIVE

Our previous study revealed that serum amyloid A (SAA) levels in polyp tissues could serve as a biomarker for the prediction of corticosteroid insensitivity in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). However, their association with disease control status in the patients after endoscopic sinus surgery remains to be assessed.

METHODS

Polyp tissues and control uncinate process mucosa were collected from 48 patients with CRSwNP and 10 healthy control subjects. SAA expression was examined using immunohistochemistry and enzyme-linked immunosorbent assay. Receiver operating characteristic (ROC) curves were performed to determine the predictive value of SAA in nasal polyps. The clinical characteristics of 2 CRSwNP subtypes (SAAhigh and SAAlow) were evaluated.

RESULTS

The SAA expression levels in polyp tissues were significantly elevated both in non-eosinophilic and eosinophilic CRSwNP as compared to the healthy controls. In patients with CRSwNP, the tissue SAA level was significantly higher in the disease-controlled patients than those of the partly controlled and uncontrolled. ROC curve analysis revealed that a cut-off value of 114.9 ng/mL for the tissue SAA level predicted the patients with disease-controlled status with 93.33% sensitivity and 63.64% specificity (AUC = .8727, P < .001). Furthermore, The SAAhigh subgroup showed higher tissue eosinophil numbers and percentage of the disease-controlled patients compared to the SAAlow subgroup.

CONCLUSIONS

Our findings suggest that measurements of SAA in polyp tissues may provide useful information for evaluating CRSwNP conditions, especially identifying the CRSwNP patients with disease-controlled status after endoscopic sinus surgery.

Early life exposure to vitamin D deficiency impairs molecular mechanisms that regulate liver cholesterol biosynthesis, energy metabolism, inflammation, and detoxification

Introduction

Emerging data suggests liver disease may be initiated during development when there is high genome plasticity and the molecular pathways supporting liver function are being developed.

Methods

Here, we leveraged our Collaborative Cross mouse model of developmental vitamin D deficiency (DVD) to investigate the role of DVD in dysregulating the molecular mechanisms underlying liver disease. We defined the effects on the adult liver transcriptome and metabolome and examined the role of epigenetic dysregulation. Given that the parental origin of the genome (POG) influences response to DVD, we used our established POG model [POG1-(CC011xCC001)F1 and POG2-(CC001xCC011)F1] to identify interindividual differences.

Results

We found that DVD altered the adult liver transcriptome, primarily downregulating genes controlling liver development, response to injury/infection (detoxification & inflammation), cholesterol biosynthesis, and energy production. In concordance with these transcriptional changes, we found that DVD decreased liver cell membrane-associated lipids (including cholesterol) and pentose phosphate pathway metabolites. Each POG also exhibited distinct responses. POG1 exhibited almost 2X more differentially expressed genes (DEGs) with effects indicative of increased energy utilization. This included upregulation of lipid and amino acid metabolism genes and increased intermediate lipid and amino acid metabolites, increased energy cofactors, and decreased energy substrates. POG2 exhibited broader downregulation of cholesterol biosynthesis genes with a metabolomics profile indicative of decreased energy utilization. Although DVD primarily caused loss of liver DNA methylation for both POGs, only one epimutation was shared, and POG2 had 6.5X more differentially methylated genes. Differential methylation was detected at DEGs regulating developmental processes such as amino acid transport (POG1) and cell growth & differentiation (e.g., Wnt & cadherin signaling, POG2).

Conclusions

These findings implicate a novel role for maternal vitamin D in programming essential offspring liver functions that are dysregulated in liver disease. Importantly, impairment of these processes was not rescued by vitamin D treatment at weaning, suggesting these effects require preventative measures. Substantial differences in POG response to DVD demonstrate that the parental genomic context of exposure determines offspring susceptibility.

Major endothelial damage markers identified from hemadsorption filters derived from treated patients with septic shock - endoplasmic reticulum stress and bikunin may play a role

Introduction

In septic patients the damage of the endothelial barrier is decisive leading to circulatory septic shock with disseminated vascular coagulation, edema and multiorgan failure. Hemadsorption therapy leads to rapid resolution of clinical symptoms. We propose that the isolation of proteins adsorbed to hemadsorption devices contributes to the identification of mediators responsible for endothelial barrier dysfunction.

Material and methods

Plasma materials enriched to hemadsorption filters (CytoSorb®) after therapy of patients in septic shock were fractionated and functionally characterized for their effect on cell integrity, viability, proliferation and ROS formation by human endothelial cells. Fractions were further studied for their contents of oxidized nucleic acids as well as peptides and proteins by mass spectrometry.

Results

Individual fractions exhibited a strong effect on endothelial cell viability, the endothelial layer morphology, and ROS formation. Fractions with high amounts of DNA and oxidized DNA correlated with ROS formation in the target endothelium. In addition, defined proteins such as defensins (HNP-1), SAA1, CXCL7, and the peptide bikunin were linked to the strongest additive effects in endothelial damage.

Conclusion

Our results indicate that hemadsorption is efficient to transiently remove strong endothelial damage mediators from the blood of patients with septic shock, which explains a rapid clinical improvement of inflammation and endothelial function. The current work indicates that a combination of stressors leads to the most detrimental effects. Oxidized ssDNA, likely derived from mitochondria, SAA1, the chemokine CXCL7 and the human neutrophil peptide alpha-defensin 1 (HNP-1) were unique for their significant negative effect on endothelial cell viability. However, the strongest damage effect occurred, when, bikunin - cleaved off from alpha-1-microglobulin was present in high relative amounts (>65%) of protein contents in the most active fraction. Thus, a relevant combination of stressors appears to be removed by hemadsorption therapy which results in fulminant and rapid, though only transient, clinical restitution.

Predicting genetic risk factors for AA amyloidosis in Algerian patients with familial Mediterranean fever

Renal amyloid-associated (AA) amyloidosis is a harmful complication of familial Mediterranean fever (FMF). Its occurrence involves polymorphisms and mutations in the Serum Amyloid A1 (SAA1) and Mediterranean Fever (MEFV) genes, respectively. In Algeria, the association between SAA1 variants and FMF-related amyloidosis was not investigated, hence the aim of this case-control study. It included 60 healthy controls and 60 unrelated FMF patients (39 with amyloidosis, and 21 without amyloidosis). All were genotyped for the SAA1 alleles (SAA1.1, SAA1.5, and SAA1.3), and a subset of them for the - 13 C/T polymorphism by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Comparisons between genotype and allele frequencies were performed using Chi-square and Fisher tests. The SAA1.1/1.1 genotype was predominant in amyloid FMF patients, compared to non-amyloid FMF patients (p = 0.001) and controls (p < 0.0001). SAA1.1/1.5 was higher in non-amyloid patients (p = 0.0069) and in controls (p = 0.0082) than in patients with amyloidosis. Bivariate logistic regression revealed an increased risk of AA amyloidosis with three genotypes, SAA1.1/1.1 [odds ratio 7.589 (OR); 95% confidence interval (CI): 2.130-27.041] (p = 0.0018), SAA1.1/1.3 [OR 5.700; 95% CI: 1.435-22.644] (p = 0.0134), and M694I/M694I [OR 4.6; 95% CI: 1.400-15.117] (p = 0.0119). The SAA1.1/1.5 genotype [OR 0.152; 95% CI: 0.040-0.587] (p = 0.0062) was protective against amyloidosis. In all groups, the - 13 C/C genotype predominated, and was not related to renal complication [OR 0.88; 95% CI: 0.07-10.43] (p = 0.915). In conclusion, in contrast to the - 13 C/T polymorphism, the SAA1.1/1.1, SAA1.1/1.3 and M694I/M694I genotypes may increase the risk of developing renal AA amyloidosis in the Algerian population.

Crosstalk Between the Nervous System and Systemic Organs in Acute Brain Injury

Organ crosstalk is a complex biological communication between distal organs mediated via cellular, soluble, and neurohormonal actions, based on a two-way pathway. The communication between the central nervous system and peripheral organs involves nerves, endocrine, and immunity systems as well as the emotional and cognitive centers of the brain. Particularly, acute brain injury is complicated by neuroinflammation and neurodegeneration causing multiorgan inflammation, microbial dysbiosis, gastrointestinal dysfunction and dysmotility, liver dysfunction, acute kidney injury, and cardiac dysfunction. Organ crosstalk has become increasingly popular, although the information is still limited. The present narrative review provides an update on the crosstalk between the nervous system and systemic organs after acute brain injury. Future research might help to target this pathophysiological process, preventing the progression toward multiorgan dysfunction in critically ill patients with brain injury.

Proteomic profiling identifies SPP1 associated with rapidly progressive interstitial lung disease in anti-MDA5-positive dermatomyositis

BACKGROUND

Anti-melanoma differentiation-associated gene five antibody positive (MDA5+) dermatomyositis (DM) is significantly associated with rapidly progressive interstitial lung disease (RP-ILD). Early detection of RP-ILD remains a major challenge. This study aims to identify and validate prognostic factors for RP-ILD in MDA5+ DM patients.

METHODS

Plasma samples from 20 MDA5+ DM patients and 10 healthy controls (HC) were collected for proteomic analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The proteins of interest were validated in independent samples (20 HC, 20 MDA5+ DM with RP-ILD, and 20 non-RP-ILD patients) with enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 413 differentially expressed proteins (DEPs) were detected between the MDA5+ DM patients and HC. When comparing DEPs between RP-ILD and non-RP-ILD patients, 79 proteins were changed in RP-ILD patients, implicating acute inflammatory response, coagulation, and complement cascades. Six candidate biomarkers were confirmed with ELISA. Secreted phosphoprotein 1 (SPP1), serum amyloid A1 (SAA1), and Kininogen 1 (KNG1) concentrations were significantly elevated in RP-ILD patients than those in non-RP-ILD patients and HC. In the different clinical subgroups, SPP1 was particularly elevated in the high-risk RP-ILD subgroup of MDA5+ DM.

CONCLUSION

This study provides novel insights into the pathogenesis of RP-ILD development in MDA5+ DM and suggests the plasma protein SPP1 could serve as a potential blood biomarker for RP-ILD early warning.

Serum Amyloid A 4 as a Common Marker of Persistent Inflammation in Patients with Neovascular Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy

Background

Neovascular age-related macular degeneration (nAMD) and its subtype, polypoidal choroidal vasculopathy (PCV), are common choroidal vasculopathies. Although they share many common clinical manifestations and treatment strategies, a lack of comprehensive analysis of these conditions means that it is difficult for researchers to further explore the common pathomechanisms of nAMD and PCV. The aim of this study was to characterize aqueous humor (AH) proteome alterations and identify a novel biomarker related to both nAMD and PCV.

Methods

Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) was adopted to analyze the AH proteomes of nAMD, PCV and controls. The target protein was validated using the enzyme-linked immunosorbent assay (ELISA) and subjected to receiver operating characteristic (ROC) curve analysis.

Results

A total of 737 different proteins were identified in all the groups, of which 544 were quantifiable. The bioinformatics analysis suggested that immune response activation is the essential event in both nAMD and PCV. Serum amyloid A (SAA) 4 is closely associated with a number of chronic inflammatory diseases, and it was enriched as the hub protein. ROC analysis showed that SAA4 could distinguish both nAMD and PCV from the controls.

Conclusion

This comprehensive study provides insights into, and furthers our understanding of, the pathological mechanism of nAMD and PCV. Additionally, the SAA4 level alteration may serve as a common biomarker of nAMD and PCV.

Health concerns about possible long-term effects of legally marketed milk and dairy from animals with intramammary infections

Milk and dairy from animals with subclinical mastitis infections are marketable. Mastitis is detected with the somatic cell count (SCC). The EU regulation, among the stricter ones, limits an average of 400,000 somatic cells/ml in milk. Other countries have higher or no thresholds. This level suggests 40% of infected animals, and we indeed consume mastitic milk and dairy. A worldwide prevalence of dairy cattle and buffaloes with subclinical mastitis is estimated to range between 34 and 46%. The current food safety regulations account for mastitis pathogens, their toxins, and the risk of antimicrobial residues, but milk from animals with mastitis contains also compounds that derive from an immune response and inflammation process with biological function for the offspring. To the best of the current knowledge, it cannot be excluded that these compounds do not interfere with human homeostasis and that they do not contribute to redox or cytokine dysregulation that, in turn, could promote certain chronic diseases. These compounds include radicals, oxidation products, nitrosamines, and proinflammatory cytokines with nitrosamines being already recognized as probable carcinogens. Mastitis also alters the composition of caseins, plasmin, and plasminogen activators, which may be related to increased transformation into amyloid with similar characteristics as the fibrils associated with Alzheimer's disease. We should determine whether these bioactive compounds could, alone or in combination, represent any long-term risk to the consumer's health. Adapted regulations and concomitant subsidies for farmers are suggested, for sensing tools that reveal individual SCC and mastitis at milking. Frequent SCC determination is the prerequisite for any mastitis control program.

Catch of the Day: New Serum Amyloid A (SAA) Antibody Is a Valuable Tool to Study Fish Health in Salmonids

Serum amyloid A (SAA) proteins belong to a family of acute-phase reactants, playing an integral role in defending the organism from pathological damage. Despite a wealth of data on the regulation of SAA transcripts in teleosts, there is only limited information on these proteins' abundance in fish. The aim of this study is to characterise SAA protein levels in salmonids using a newly developed antibody specific to salmonid SAA. The salmonid SAA antibody detected SAA and accurately discriminated between stimulated and control specimens from rainbow trout macrophage cell line (RTS-11) in vitro, as well as rainbow trout challenged with Aeromonas salmonicida- or flagellin-stimulated Atlantic salmon in vivo. The presence of SAA protein was analysed in RTS-11 cell line supernatants, liver, and spleen samples using ELISA, immunoblotting, and immunohistochemistry. This study is the first to characterise SAA protein levels in salmonids in vivo and in vitro. The newly developed salmonid SAA antibody was able to discriminate between stimulated and unstimulated specimens, showing that it can be used to study the acute-phase response in salmonids with the potential to be further developed into assays to monitor and evaluate health in wild and farmed fish.

Clearance of defective muscle stem cells by senolytics restores myogenesis in myotonic dystrophy type 1

Muscle stem cells, the engine of muscle repair, are affected in myotonic dystrophy type 1 (DM1); however, the underlying molecular mechanism and the impact on the disease severity are still elusive. Here, we show using patients' samples that muscle stem cells/myoblasts exhibit signs of cellular senescence in vitro and in situ. Single cell RNAseq uncovers a subset of senescent myoblasts expressing high levels of genes related to the senescence-associated secretory phenotype (SASP). We show that the levels of interleukin-6, a prominent SASP cytokine, in the serum of DM1 patients correlate with muscle weakness and functional capacity limitations. Drug screening revealed that the senolytic BCL-XL inhibitor (A1155463) can specifically remove senescent DM1 myoblasts by inducing their apoptosis. Clearance of senescent cells reduced the expression of SASP, which rescued the proliferation and differentiation capacity of DM1 myoblasts in vitro and enhanced their engraftment following transplantation in vivo. Altogether, this study identifies the pathogenic mechanism associated with muscle stem cell defects in DM1 and opens a therapeutic avenue that targets these defective cells to restore myogenesis.

Serum amyloid A and metabolic disease: evidence for a critical role in chronic inflammatory conditions

Serum amyloid A (SAA) subtypes 1-3 are well-described acute phase reactants that are elevated in acute inflammatory conditions such as infection, tissue injury, and trauma, while SAA4 is constitutively expressed. SAA subtypes also have been implicated as playing roles in chronic metabolic diseases including obesity, diabetes, and cardiovascular disease, and possibly in autoimmune diseases such as systemic lupus erythematosis, rheumatoid arthritis, and inflammatory bowel disease. Distinctions between the expression kinetics of SAA in acute inflammatory responses and chronic disease states suggest the potential for differentiating SAA functions. Although circulating SAA levels can rise up to 1,000-fold during an acute inflammatory event, elevations are more modest (∼5-fold) in chronic metabolic conditions. The majority of acute-phase SAA derives from the liver, while in chronic inflammatory conditions SAA also derives from adipose tissue, the intestine, and elsewhere. In this review, roles for SAA subtypes in chronic metabolic disease states are contrasted to current knowledge about acute phase SAA. Investigations show distinct differences between SAA expression and function in human and animal models of metabolic disease, as well as sexual dimorphism of SAA subtype responses.

Serum amyloid protein A in inflammatory bowel disease: from bench to bedside

Inflammatory bowel diseases (IBD) is featured by gastrointestinal inflammation and a disease course with alternating recurrence and remission. The global burden caused by IBD has significantly boosted in recent years, necessitating treatment optimization. Serum amyloid A (SAA) is a class of 104 amino acid conservative acute-phase proteins, which is essential in immune-mediated inflammatory processes, like IBD. The SAA monomeric structure is composed of four α-helical regions and a C-terminal amorphous tail. Its disordered structure enables multiple bindings to different ligands and permits multiple functions. It has been proven that SAA has dual roles in the inflammatory process. SAA stimulates the pro-inflammatory cytokine expression and promotes the pathogenic differentiation of TH17 cells. In addition, SAA can remove toxic lipids produced during inflammatory responses and membrane debris from dead cells, redirect HDL, and recycle cholesterol for tissue repair. In IBD, SAA acts on gut epithelium barriers, induces T-cell differentiation, and promotes phagocytosis of Gram-negative bacteria. Owing to the tight connection between SAA and IBD, several clinical studies have taken SAA for a biomarker for diagnosis, assessing disease activity, and predicting prognosis in IBD. Furthermore, 5-MER peptide, a drug specifically targeting SAA, has shown anti-inflammatory effects in some SAA-dependent animal models, providing novel insights into the therapeutic targets of IBD.

Modulation of long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression in the liver of Beagle dogs by Toxocara canis infection

BACKGROUND

Long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) play crucial roles in regulating various physiological and pathological processes. However, the role of lncRNAs and mRNAs in mediating the liver response during Toxocara canis infection remains incompletely understood.

METHODS

In the present study, the expression profile of lncRNAs and mRNAs was investigated in the liver of Beagle dogs infected by T. canis using high-throughput RNA sequencing.

RESULTS

Compared with the control groups, 876 differentially expressed (DE) lncRNAs and 288 DEmRNAs were identified at 12 h post-infection (hpi), 906 DElncRNAs and 261 DEmRNAs were identified at 24 hpi, and 876 DElncRNAs and 302 DEmRNAs were identified at 36 days post-infection (dpi). A total of 16 DEmRNAs (e.g. dpp4, crp and gnas) were commonly identified at the three infection stages. Enrichment and co-localization analyses identified several pathways involved in immune and inflammatory responses during T. canis infection. Some novel DElncRNAs, such as LNC_015756, LNC_011050 and LNC_011052, were also associated with immune and inflammatory responses. Also, LNC_005105 and LNC_005401 were associated with the secretion of anti-inflammatory cytokines, which may play a role in the healing of liver pathology at the late stage of infection.

CONCLUSIONS

Our data provided new insight into the regulatory roles of lncRNAs and mRNAs in the pathogenesis of T. canis and improved our understanding of the contribution of lncRNAs and mRNAs to the immune and inflammatory response of the liver during T. canis infection.

Serum amyloid A—A potential therapeutic target for hyper-inflammatory syndrome associated with COVID-19

Serum amyloid-A (SAA) is associated with inflammatory disorders such as rheumatoid arthritis, Familial Mediterranean Fever, sarcoidosis, and vasculitis. There is accumulating evidence that SAA is a reliable biomarker for these autoinflammatory and rheumatic diseases and may contribute to their pathophysiology. Hyperinflammatory syndrome associated with COVID-19 is a complex interaction between infection and autoimmunity and elevation of SAA is strongly correlated with severity of the inflammation. In this review we highlight the involvement of SAA in these different inflammatory conditions, consider its potential role and discuss whether it could be a potential target for treatment of the hyperinflammatory state of COVID-19 with many potential advantages and fewer adverse effects. Additional studies linking SAA to the pathophysiology of COVID-19 hyper-inflammation and autoimmunity are needed to establish the causal relationship and the therapeutic potential of inhibitors of SAA activity.

Serum amyloid A regulates TLR2/4-mediated IFN-β signaling pathway against Marek's disease virus

Serum amyloid A (SAA), an acute response phase protein (APP), is crucial for the innate immune response during pathogenic microorganisms' invasion. Marek's disease virus (MDV) is a highly oncogenic alphaherpesvirus that activates multiple innate immune molecules, including SAA, in the host during infection. However, the pathway through which SAA participates in MDV-induced host innate immunity remains unknown. The present study aimed to elucidate the pathway through which SAA exerts its anti-MDV function. We observed that MDV infection in vivo and in vitro significantly elevated SAA expression. Furthermore, through SAA overexpression and knockdown experiments, we demonstrated that SAA could inhibit MDV replication. Subsequently, we found that SAA activated Toll-Like Receptor 2/4 (TLR2/4) -mediated Interferon Beta (IFN-β) promoter activity and IFN regulatory factor 7 (IRF7) promoter activity. During MDV infection, SAA enhanced TLR2/4-mediated IFN-β signal transduction and messenger RNAs (mRNAs) expression of type I IFN (IFN-I) and interferon-stimulated genes (ISGs). Finally, TLR2/4 inhibitor OxPAPC inhibits the anti-MDV activity of SAA. These results demonstrated that SAA inhibits MDV replication and enhancing TLR2/4-mediated IFN-β signal transduction to promote IFNs and ISGs expression. This finding is the first to demonstrate the signaling pathway by which SAA exerts its anti-MDV function. It also provides new insights into the control of oncogenic herpesviruses from the perspective of acute response phase proteins.

Serum amyloid A1 recruits neutrophils to the invasive front of T1 colorectal cancers

BACKGROUND AND AIM

The tumor microenvironment plays an essential role in the development and progression of colorectal cancer (CRC). We recently reported that crosstalk between CRC cells and tumor-associated macrophages (TAMs) via serum amyloid A1 (SAA1) promotes invasion by T1 CRCs. In the present study, we aimed to clarify the role of neutrophils in early CRCs.

METHODS

Immunohistochemical analysis of CD66b, chemokine CXC motif ligand 8 (CXCL8 or interleukin-8, IL-8) and matrix metalloproteinase-9 (MMP-9) was performed using primary T1 CRCs (n = 49). The HL-60 human promyelocytic leukemia cell line and THP-1 human monocytic leukemia cell line were used to obtain neutrophil-like and macrophage-like cells, respectively. Boyden chamber assays were used to analyze cell migration and invasion, and quantitative RT-PCR was used to analyze gene expression.

RESULTS

Immunohistochemical analysis revealed accumulation of neutrophils at the SAA1-positive invasive front of T1 CRCs. Experiments using HL-60 cells suggested that treatment with SAA1 induced neutrophil migration and expression of CXCL8 and MMP-9 in neutrophils and that neutrophils promote CRC cell migration and invasion. Immunohistochemistry confirmed accumulation of CXCL8- or MMP-9-positive neutrophils at the SAA1-positive invasive front of T1 CRCs. Moreover, co-culture experiments using CRC, THP-1 and HL-60 cells suggested that CRC cells activated by macrophages upregulate CXCL8 and MMP-9 in neutrophils.

CONCLUSIONS

Our results suggest that interplay between macrophages and CRC cells leads to recruitment of neutrophils to the invasive front of T1 CRCs and that SAA1 secreted by CRC cells activate neutrophils to promote invasion.

Evaluating the Utility of Proteomics for the Identification of Circulating Pharmacodynamic Biomarkers of IFNβ-1a Biologics

Proteomics has the potential to identify pharmacodynamic (PD) biomarkers for similarity assessment of proposed biosimilars without relying on clinical efficacy end points. In this study, with 36 healthy participants randomized to therapeutic doses of interferon-beta 1a products (IFNβ-1a) or pegylated-IFNβ-1a (pegIFNβ-1a) approved to treat multiple sclerosis or placebo, we evaluated the utility of a proteomic assay that profiles > 7,000 plasma proteins. IFNβ-1a and pegIFNβ-1a resulted in 248 and 528 differentially expressed protein analytes, respectively, between treatment and placebo groups over the time course. Thirty-one proteins were prioritized based on a maximal fold change ≥ 2 from baseline, baseline adjusted area under the effect curve (AUEC) and overlap between the 2 products. Of these, the majority had a significant AUEC compared with placebo in response to either product; 8 proteins showed > 4-fold maximal change from baseline. We identified previously reported candidates, beta-2microglobulin and interferon-induced GTP-binding protein (Mx1) with ~ 50% coefficient of variation (CV) for AUEC, and many new candidates (including I-TAC, C1QC, and IP-10) with CVs ranging from 26%-129%. Upstream regulator analysis of differentially expressed proteins predicted activation of IFNβ1 signaling as well as other cytokine, enzyme, and transcription signaling networks by both products. Although independent replication is required to confirm present results, our study demonstrates the utility of proteomics for the identification of individual and composite candidate PD biomarkers that may be leveraged to support clinical pharmacology studies for biosimilar approvals, especially when biologics have complex mechanisms of action or do not have previously characterized PD biomarkers.

The effect of FMT and vitamin C on immunity-related genes in antibiotic-induced dysbiosis in mice

Antibiotics are double-edged swords. Although antibiotics are used to inhibit pathogenic bacteria, they also run the risk of destroying some of the healthy bacteria in our bodies. We examined the effect of penicillin on the organism through a microarray dataset, after which 12 genes related to immuno-inflammatory pathways were selected by reading the literature and validated using neomycin and ampicillin. The expression of genes was measured using qRT-PCR. Several genes were significantly overexpressed in antibiotic-treated mice, including CD74 and SAA2 in intestinal tissues that remained extremely expressed after natural recovery. Moreover, transplantation of fecal microbiota from healthy mice to antibiotic-treated mice was made, where GZMB, CD3G, H2-AA, PSMB9, CD74, and SAA1 were greatly expressed; however, SAA2 was downregulated and normal expression was restored, and in liver tissue, SAA1, SAA2, SAA3 were extremely expressed. After the addition of vitamin C, which has positive effects in several aspects, to the fecal microbiota transplantation, in the intestinal tissues, the genes that were highly expressed after the fecal microbiota transplantation effectively reduced their expression, and the unaffected genes remained normally expressed, but the CD74 gene remained highly expressed. In liver tissues, normally expressed genes were not affected, but the expression of SAA1 was reduced and the expression of SAA3 was increased. In other words, fecal microbiota transplantation did not necessarily bring about a positive effect of gene expression restoration, but the addition of vitamin C effectively reduced the effects of fecal microbiota transplantation and regulated the balance of the immune system.

Sportomics method to assess acute phase proteins in Olympic level athletes using dried blood spots and multiplex assay

Sportomics is a subject-centered holistic method similar to metabolomics focusing on sports as the metabolic challenge. Dried blood spot is emerging as a technique due to its simplicity and reproducibility. In addition, mass spectrometry and integrative computational biology enhance our ability to understand exercise-induced modifications. We studied inflammatory blood proteins (Alpha-1-acid glycoprotein-A1AG1; Albumin; Cystatin C; C-reactive protein-CRP; Hemoglobin-HBA; Haptoglobin-HPT; Insulin-like growth factor 1; Lipopolysaccharide binding protein-LBP; Mannose-binding lectin-MBL2; Myeloperoxidase-PERM and Serum amyloid A1-SAA1), in 687 samples from 97 World-class and Olympic athletes across 16 sports in nine states. Data were analyzed with Spearman's rank-order correlation. Major correlations with CRP, LBP; MBL2; A1AG1, and SAA1 were found. The pairs CRP-SAA1 and CRP-LBP appeared with a robust positive correlation. Other pairs, LBP-SAA1; A1AG1-CRP; A1AG1-SAA1; A1AG1-MBL, and A1AG1-LBP, showed a broader correlation across the sports. The protein-protein interaction map revealed 1500 interactions with 44 core proteins, 30 of them linked to immune system processing. We propose that the inflammation follow-up in exercise can provide knowledge for internal cargo management in training, competition, recovery, doping control, and a deeper understanding of health and disease.

NLRP3 activation in neutrophils induces lethal autoinflammation, liver inflammation, and fibrosis

Sterile inflammation is a central element in liver diseases. The immune response following injurious stimuli involves hepatic infiltration of neutrophils and monocytes. Neutrophils are major effectors of liver inflammation, rapidly recruited to sites of inflammation, and can augment the recruitment of other leukocytes. The NLRP3 inflammasome has been increasingly implicated in severe liver inflammation, fibrosis, and cell death. In this study, the role of NLRP3 activation in neutrophils during liver inflammation and fibrosis was investigated. Mouse models with neutrophil-specific expression of mutant NLRP3 were developed. Mutant mice develop severe liver inflammation and lethal autoinflammation phenocopying mice with a systemic expression of mutant NLRP3. NLRP3 activation in neutrophils leads to a pro-inflammatory cytokine and chemokine profile in the liver, infiltration by neutrophils and macrophages, and an increase in cell death. Furthermore, mutant mice develop liver fibrosis associated with increased expression of pro-fibrogenic genes. Taken together, the present work demonstrates how neutrophils, driven by the NLRP3 inflammasome, coordinate other inflammatory myeloid cells in the liver, and propagate the inflammatory response in the context of inflammation-driven fibrosis.

The deciphering of the immune cells and marker signature in COVID-19 pathogenesis: An update

The precise interaction between the immune system and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical in deciphering the pathogenesis of coronavirus disease 2019 (COVID-19) and is also vital for developing novel therapeutic tools, including monoclonal antibodies, antivirals drugs, and vaccines. Viral infections need innate and adaptive immune reactions since the various immune components, such as neutrophils, macrophages, CD4⁺ T, CD8⁺ T, and B lymphocytes, play different roles in various infections. Consequently, the characterization of innate and adaptive immune reactions toward SARS-CoV-2 is crucial for defining the pathogenicity of COVID-19. In this study, we explain what is currently understood concerning the conventional immune reactions to SARS-CoV-2 infection to shed light on the protective and pathogenic role of immune response in this case. Also, in particular, we investigate the in-depth roles of other immune mediators, including neutrophil elastase, serum amyloid A, and syndecan, in the immunopathogenesis of COVID-19.

Liver Graft Proteomics Reveals Potential Incipient Mechanisms behind Early Renal Dysfunction after Liver Transplantation

Acute kidney injury (AKI) is frequent after liver transplantation (LT) and correlates with later development of chronic kidney disease. Its etiology is multifactorial and combines pre-, intra-, and postoperative factors. Additionally, the liver graft itself seems an important element in the development of AKI, yet the detailed mechanisms remain unclear. We hypothesized that grafts of LT recipients developing significant early AKI may show distinct proteomic alterations, and we set out to identify proteome differences between LT recipients developing moderate or severe AKI (n = 7) and LT recipients without early renal injury (n = 7). Liver biopsies obtained one hour after reperfusion were assessed histologically and using quantitative proteomics. Several cytokines and serum amyloid A2 (SAA2) were analyzed in serum samples obtained preoperatively, 2−4 h, and 20−24 h after graft reperfusion, respectively. LT induced mild histological alterations without significant differences between groups but uniformly altered liver function tests peaking on postoperative day 1, with a trend towards more severe alterations in patients developing AKI. Global quantitative proteomic analysis revealed 136 proteins differing significantly in their expression levels (p < 0.05, FC 20%): 80 proteins had higher and 56 had lower levels in the AKI group. Most of these proteins were related to immune and inflammatory responses, host defense, and neutrophil degranulation. No differences between the studied pro- and anti-inflammatory cytokines or SAA2 between groups were found at any moment. Our results suggest that grafts of LT patients who develop early AKI reveal a distinct proteome dominated by an early yet prominent activation of the innate immunity. These findings support the hypothesis that AKI after LT may be favored by certain graft characteristics.

Maternal siRNA silencing of placental SAA2 mitigates preterm birth following intrauterine inflammation

The placental inflammatory processes induced maternally result in preterm birth (PTB). Serum amyloid A (SAA) is a well-known biomarker of inflammation. The objective of this study was to investigate whether murine placental SAA isoforms (SAA1–4) participate in the mechanism of spontaneous PTB and whether maternal regulation of SAA production may serve as a therapeutic approach. During the gestation, all isoforms of SAA were detectable except SAA2. The mouse model of intrauterine inflammation was established using LPS infusion to the uterus. Following intrauterine inflammation, placental SAA2 increased significantly. Inhibition of Saa2, using siSaa2, markedly decreased PTB. The increased placental expression of pro-inflammatory cytokines Il1β, Il6, and Tnfα were downregulated by siSaa2 treatment. Maternal inhibition of Saa2 did not change the expression of Saa1–4 in the fetal brain. Explant inflammatory culture of placentas with siSaa2 showed similar results to our in vivo experiments. This study demonstrates the highly expressed placental SAA2 as a novel therapeutic target, and maternal administration of siRNA as a promising approach to alleviate PTB.

Association of Serum Interleukin-8 and Serum Amyloid A With Anxiety Symptoms in Patients With Cerebral Small Vessel Disease

Objective

Cerebral small vessel disease (CSVD) is a clinical syndrome caused by pathological changes in small vessels. Anxiety is a common symptom of CSVD. Previous studies have reported the association between inflammatory factors and anxiety in other diseases, but this association in patients with CSVD remains uncovered. Our study aimed to investigate whether serum inflammatory factors correlated with anxiety in patients with CSVD.

Methods

A total of 245 CSVD patients confirmed using brain magnetic resonance imaging (MRI) were recruited from December 2019 to December 2021. Hamilton Anxiety Rating Scale (HAMA) was used to assess the anxiety symptoms of CSVD patients. Patients with HAMA scores ≥7 were considered to have anxiety symptoms. The serum levels of interleukin-1β (IL-1β), IL-2R, IL-6, IL-8, IL-10, tumor necrosis factor-α (TNF-α), serum amyloid A (SAA), C-reactive protein (CRP), high-sensitivity C-reactive protein (hs-CRP) and erythrocyte sedimentation rate (ESR) were detected. We compared levels of inflammatory factors between the anxiety and non-anxiety groups. Logistic regression analyses examined the correlation between inflammatory factors and anxiety symptoms. We further performed a gender subgroup analysis to investigate whether this association differed by gender.

Results

In the fully adjusted multivariate logistic regression analysis model, we found that lower levels of IL-8 were linked to a higher risk of anxiety symptoms. Moreover, higher levels of SAA were linked to a lower risk of anxiety symptoms. Our study identified sex-specific effects, and the correlation between IL-8 and anxiety symptoms remained significant among males, while the correlation between SAA and anxiety symptoms remained significant among females.

Conclusions

In this study, we found a suggestive association between IL-8, SAA, and anxiety symptoms in CSVD participants. Furthermore, IL-8 and SAA may have a sex-specific relationship with anxiety symptoms.

Systematic analysis of inflammation and pain pathways in a mouse model of gout

Gout is a prevalent and painful inflammatory arthritis, and its global burden continues to rise. Intense pain induced by gout attacks is a major complication of gout. However, systematic studies of gout inflammation and pain are lacking. Using a monosodium urate (MSU) crystal-induced gout model, we performed genome-wide transcriptome analysis of the inflamed ankle joint, dorsal root ganglion (DRG), and spinal cord of gouty mice. Our results revealed important transcriptional changes, including highly elevated inflammation and broad activation of immune pathways in both the joint and the nervous system, in gouty mice. Integrated analysis showed that there was a remarkable overlap between our RNAseq and human genome-wide association study (GWAS) of gout; for example, the risk gene, stanniocalcin-1 (STC1) showed significant upregulation in all three tissues. Interestingly, when compared to the transcriptomes of human osteoarthritis (OA) and rheumatoid arthritis (RA) joint tissues, we identified significant upregulation of cAMP/cyclic nucleotide-mediated signaling shared between gouty mice and human OA with high knee pain, which may provide excellent drug targets to relieve gout pain. Furthermore, we investigated the common and distinct transcriptomic features of gouty, inflammatory pain, and neuropathic pain mouse models in their DRG and spinal cord tissues. Moreover, we discovered distinct sets of genes with significant differential alternative splicing or differential transcript usage in each tissue, which were largely not detected by conventional differential gene expression analysis approaches. Based on these results, our study provided a more accurate and comprehensive depiction of transcriptomic alterations related to gout inflammation and pain.

Acute phase protein response and changes in lipoprotein particle size in dogs with systemic inflammatory response syndrome

Background

Improved methodology to measure acute phase proteins and determination of lipoprotein particle‐size distribution (PSD) could be clinically useful in dogs with systemic inflammatory processes.

Objectives

Evaluate an immunoturbidometric assay for serum amyloid A (SAA) and lipoprotein PSD in dogs with sepsis, nonseptic systemic inflammation, and in healthy controls. Correlate dyslipidemic changes with SAA and C‐reactive protein (CRP) concentrations.

Animals

Twenty‐five dogs with sepsis, 15 dogs with nonseptic systemic inflammation, and 22 healthy controls.

Methods

Prospective, case‐control study. Variables included SAA, CRP, and electrophoretic subfractionation of high‐ and low‐density lipoproteins (HDL, LDL). Continuous variables were compared using ANOVA or Kruskal‐Wallis tests with linear regression or Spearman's rank correlation used to assess relationships between variables.

Results

Median SAA and CRP concentrations were greater in dogs with sepsis (SAA 460 mg/L, interquartile range [IQR] 886 mg/L; CRP 133.2 mg/L, IQR 91.6 mg/L) and nonseptic inflammation (SAA 201 mg/L, IQR 436 mg/L; CRP 91.1 mg/L, IQR 88.6 mg/L) compared to healthy dogs (SAA 0.0 mg/L, IQR 0.0 mg/L; CRP 4.9 mg/L, IQR 0.0 mg/L) P < .0001. A cutoff of >677.5 mg/L SAA was 43.2% sensitive and 92.3% specific for sepsis. Low‐density lipoprotein was higher in dogs with sepsis 29.6%, (mean, SD 14.6) compared to 14.4% (mean, SD 5.6) of all lipoproteins in healthy controls (P = .005). High‐density lipoprotein was not associated with CRP but was negatively correlated with SAA (r_s −0.47, P < .0001). Subfractions of LDL and HDL differed between groups (all P < .05).

Conclusions and Clinical Importance

Measurement of SAA using the immunoturbidometric assay evaluated in this study and lipoprotein PSD in dogs with inflammation might help distinguish septic from nonseptic causes of inflammation.

Acute-phase serum amyloid A for early detection of hepatocellular carcinoma in cirrhotic patients with low AFP level

Regular hepatocellular carcinoma (HCC) surveillance by ultrasonography in combination with the α-fetoprotein (AFP) examination is unsatisfactory in diagnostic sensitivity for early-stage HCC especially in cirrhotic patients. We conducted a prospective study in a tertiary medical center in Taiwan and consecutively collected serum samples from patients with chronic hepatitis, liver cirrhosis (LC), or HCC for new biomarker discovery. Overall, 166 patients were enrolled, including 40 hepatitis, 30 LC, and 96 HCC. Four acute-phase serum amyloid A (A-SAA) derived biomarkers including total A-SAA, A-SAA monomer and oligomer, and protein misfolding cyclic amplification (PMCA) signal were measured and compared between patients with and without HCC. A-SAA biomarkers significantly increased in the HCC group when compared to the hepatitis and LC groups, and generally increased in more advanced tumor stages. Among A-SAA biomarkers, the area under the receiver operator characteristic curves (AUROCs) for PMCA signal in discrimination of all-stage and early-stage HCC were 0.86 and 0.9 in cirrhotic patients, which is comparable to AFP. For cirrhotic patients with low AFP (< 7 ng/mL), PMCA signal maintained good capacity in prediction of early-stage HCC (AUROC: 0.94). Serum A-SAA and its prion-like property showed a potential to complement AFP in detection of early-stage HCC.

Association of Markers of Inflammation, the Kynurenine Pathway and B Vitamins with Age and Mortality, and a Signature of Inflammaging

BACKGROUND

Inflammation is a key feature of aging. We aimed to (i) investigate the association of 34 blood markers potentially involved in inflammatory processes with age and mortality and (ii) develop a signature of "inflammaging."

METHODS

Thirty-four blood markers relating to inflammation, B vitamin status, and the kynurenine pathway were measured in 976 participants in the Melbourne Collaborative Cohort Study at baseline (median age = 59 years) and follow-up (median age = 70 years). Associations with age and mortality were assessed using linear and Cox regression, respectively. A parsimonious signature of inflammaging was developed and its association with mortality was compared with 2 marker scores calculated across all markers associated with age and mortality, respectively.

RESULTS

The majority of markers (30/34) were associated with age, with stronger associations observed for neopterin, cystatin C, interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), several markers of the kynurenine pathway and derived indices KTR (kynurenine/tryptophan ratio), PAr index (ratio of 4-pyridoxic acid and the sum of pyridoxal 5'-phosphate and pyridoxal), and HK:XA (3-hydroxykynurenine/xanthurenic acid ratio). Many markers (17/34) showed an association with mortality, in particular IL-6, neopterin, C-reactive protein, quinolinic acid, PAr index, and KTR. The inflammaging signature included 10 markers and was strongly associated with mortality (hazard ratio [HR] per SD = 1.40, 95% CI: 1.24-1.57, p = 2 × 10-8), similar to scores based on all age-associated (HR = 1.38, 95% CI: 1.23-1.55, p = 4 × 10-8) and mortality-associated markers (HR = 1.43, 95% CI: 1.28-1.60, p = 1 × 10-10), respectively. Strong evidence of replication of the inflammaging signature association with mortality was found in the Hordaland Health Study.

CONCLUSION

Our study highlights the key role of the kynurenine pathway and vitamin B6 catabolism in aging, along with other well-established inflammation-related markers. A signature of inflammaging based on 10 markers was strongly associated with mortality.

Serum Amyloid A1 Exacerbates Hepatic Steatosis via TLR4 Mediated NF-κB Signaling Pathway

Objective

Chronic inflammatory response plays a prominent role in obesity-related nonalcoholic fatty liver disease (NAFLD). However, the intrahepatic triggering mechanism of inflammation remains obscure. This study aimed to elucidate the role of serum amyloid A1 (SAA1), an acute-phase response protein, in the obesity-induced hepatic inflammation and NAFLD.

Methods

Male mice were fed a high fat diet (HFD) for 16 weeks, and insulin resistance, hepatic steatosis, and inflammation in mice were monitored. Murine SAA1/2 was genetically manipulated to investigate the role of SAA1 in NAFLD.

Results

We found that SAA1 was increased in the NAFLD liver in both humans and mice. Knockout of SAA1/2 or knockdown of hepatic SAA1/2 promoted energy expenditure and alleviated HFD-induced metabolic disorder, hepatic steatosis, and inflammation. Endogenous overexpression of SAA1 in hepatocytes by adeno-associated virus 8 (AAV8) transfection aggravated overnutrition-associated gain of body weight, insulin resistance, hepatic lipid accumulation, and liver injury, which were markedly alleviated by knockout of murine toll-like receptor 4 (TLR4). Mechanistically, SAA1 directly bound with TLR4/myeloid differentiation 2 (MD2) to induce TLR4 internalization, leading to the activation of nuclear factor (NF)-κB signaling and production of both SAA1 and other inflammatory cytokines, including interleukin (IL)-6 and C–C chemokine ligand (CCL2) in hepatocytes. Administration of HFD mice with an AAV8-shRNA-SAA1/2 showed a therapeutic effect on hepatic inflammation and NAFLD progression.

Conclusions

These results demonstrate that SAA1 triggers hepatic steatosis and intrahepatic inflammatory response by forming a SAA1/TLR4/NF-κB/SAA1 feedforward regulatory circuit, which, in turn, leads to NAFLD progression. SAA1 may act as a potential target for the disease intervention.

•

SAA1/2 deficiency alleviates HFD-induced hepatic steatosis and inflammation in mice.

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SAA1 aggravating overnutrition-associated hepatic steatosis and inflammation is dependent on TLR4.

•

SAA1 directly binds to TLR4/MD2 to induce TLR4 internalization, leading to the activation of NF-κB signaling .

•

SAA1/TLR4/NF-κB/SAA1 positive feedback in hepatocytes may be a potential target for obesity associated NAFLD.

Immune Response to Persistent Staphyloccocus Aureus Periprosthetic Joint Infection in a Mouse Tibial Implant Model

Staphyloccocus aureus is one of the major pathogens in orthopedic periprosthetic joint infection (PJI), a devastating complication of total joint arthroplasty that often results in chronic and persistent infections that are refractory to antibiotics and require surgical interventions. Biofilm formation has been extensively investigated as a reason for persistent infection. The cellular composition, activation status, cytokine profile, and role of the immune response during persistent S. aureus PJI are incompletely understood. In this study, we used histology, multiparametric flow cytometry, and gene expression analysis to characterize the immune response in a clinically relevant orthopedic PJI model. We tested the hypothesis that persistent S. aureus infection induces feedback mechanisms that suppress immune cell activation, thereby affecting the course of infection. Surprisingly, persistent infection was characterized by strikingly high cytokine gene expression indicative of robust activation of multiple components of innate and adaptive immunity, along with ongoing severe neutrophil-dominated inflammation, in infected joint and bone tissues. Activation and expansion of draining lymph nodes and a bone marrow stress granulopoiesis reaction were also maintained during late phase infection. In parallel, feedback mechanisms involving T-cell inhibitory receptors and exhaustion markers, suppressive cytokines, and regulatory T cells were activated and associated with decreased T-cell proliferation and tissue infiltration during the persistent phase of infection. These results identify the cellular and molecular components of the mouse immune response to persistent S. aureus PJI and indicate that neutrophil infiltration, inflammatory cytokine responses, and ongoing lymph node and bone marrow reactions are insufficient to clear infection and that immune effector mechanisms are suppressed by feedback inhibitory pathways. These immune-suppressive mechanisms are associated with diminished T-cell proliferation and tissue infiltration and can be targeted as part of adjuvant immunotherapeutic strategies in combination with debridement of biofilm, antibiotics, and other therapeutic modalities to promote eradication of infection. © 2021 American Society for Bone and Mineral Research (ASBMR).

Role of Serum Amyloid A in Abdominal Aortic Aneurysm and Related Cardiovascular Diseases

Epidemiological data positively correlate plasma serum amyloid A (SAA) levels with cardiovascular disease severity and mortality. Studies by several investigators have indicated a causal role for SAA in the development of atherosclerosis in animal models. Suppression of SAA attenuates the development of angiotensin II (AngII)-induced abdominal aortic aneurysm (AAA) formation in mice. Thus, SAA is not just a marker for cardiovascular disease (CVD) development, but it is a key player. However, to consider SAA as a therapeutic target for these diseases, the pathway leading to its involvement needs to be understood. This review provides a brief description of the pathobiological significance of this enigmatic molecule. The purpose of this review is to summarize the data relevant to its role in the development of CVD, the pitfalls in SAA research, and unanswered questions in the field.

Hepatocyte-Specific Deletion of Yes-Associated Protein Improves Recovery From Acetaminophen-Induced Acute Liver Injury

Overdose of acetaminophen (APAP) is the major cause of acute liver failure (ALF) in the Western world with very limited treatment options. Previous studies from our groups and others have shown that timely activation of liver regeneration is a critical determinant of transplant-free survival of APAP-induced ALF patients. Here, we report that hepatocyte-specific deletion of Yes-associated protein (Yap), the downstream mediator of the Hippo Kinase signaling pathway results in faster recovery from APAP-induced acute liver injury. Initial studies performed with male C57BL/6J mice showed a rapid activation of Yap and its target genes within first 24 h after APAP administration. Treatment of hepatocyte-specific Yap knockout (Yap-KO) mice with 300 mg/kg APAP resulted in equal initial liver injury but a significantly accelerated recovery in Yap-KO mice. The recovery was accompanied by significantly rapid hepatocyte proliferation supported by faster activation of Wnt/β-catenin pathway. Furthermore, Yap-KO mice had significantly earlier and higher pro-regenerative inflammatory response following APAP overdose. Global gene expression analysis indicated that Yap-KO mice had a robust activation of transcription factors involved in response to endoplasmic reticulum stress (XBP1) and maintaining hepatocyte differentiation (HNF4α). In conclusion, these data indicate that inhibition of Yap in hepatocytes results in rapid recovery from APAP overdose due to an earlier activation of liver regeneration.

Fpr2/CXCL1/2 Controls Rapid Neutrophil Infiltration to Inhibit Streptococcus agalactiae Infection

Streptococcus agalactiae, also known as group B streptococcus (GBS), can cause pneumonia, meningitis, and bacteremia, making it a pathogen that can increase the risk of death in newborns and immunodeficient individuals. Neutrophils are the first barrier to a host's innate immune defense against these infections. Fpr2(Formyl peptide receptor 2) is an important chemotactic receptor of neutrophils, though its activation would cause pro- and anti-inflammatory effects. In this study, we found that mice without Fpr2 receptor were highly susceptible to GBS infections. These mice demonstrated decreased chemotaxis to neutrophils, decreased bactericidal ability of neutrophils, and high mortality. RNA-seq and Luminex assay indicated that Fpr2 activates key signal molecules downstream and produces chemokines CXCL1/2 to chemotaxis neutrophils. Like Fpr2-/-, CXCL1/2 or neutrophil depletion impairs host's ability to defend against GBS infection. Altogether, these data indicate that Fpr2 contributes to a host's ability to control GBS infection and that a lack of Fpr2 was associated with selective impairment during the production of chemokines CXCL1 and CXCL2 as well as neutrophil recruitment. Here, We clarified that Fpr2, as a chemotactic receptor, could not only directly chemotactic neutrophils, but also regulate the production of chemokines to control infection by chemotactic neutrophils.

Ratio of serum amyloid A to C-reactive protein is constant in the same patients but differs greatly between patients with inflammatory diseases

C-reactive protein (CRP) is commonly monitored to track the activity of inflammation and has become the gold standard in the management of all inflammatory diseases. Indeed, serum amyloid A (SAA) have seemed to correlate moderately with CRP, but the discrepancy of CRP and SAA levels has often been reported, especially in rheumatoid arthritis. Then, we examined CRP reflects a real magnitude of inflammation in patients with rheumatic and infectious inflammatory diseases. A total of 414 patients with infectious and non-infectious inflammatory diseases were enrolled. At initial visit, each patient underwent a clinical assessment and had also laboratory tests such as SAA and CRP. In each patient, we carried out a longitudinal analysis of CRP and SAA levels. We determined the inter-individual correlation between SAA and CRP and also clarified intra-individual changes of SAA/CRP ratio. SAA and CRP levels changed approximately linearly over time within individuals irrespective of rheumatic and infectious inflammatory diseases. However, SAA/CRP ratios differed dramatically between patients (from 0.117 to 50.8, median 5.71). In patients with high SAA/CRP ratio (>8.44), SAA is a better predictor of inflammation than CRP. In contrast, CRP is a better predictor in patients with low ratio (<3.52). Our results suggest that the SAA/CRP ratio differed greatly between individuals but was constant in intra-individuals. Low CRP levels could be accompanied by SAA levels predicting any degree of inflammation, implying that CRP is not reflecting a real magnitude of inflammation. To evaluate the real magnitude of inflammation, to access the SAA/CRP ratio in advance is essential.

Discrepancy Between SAA and CRP levels Linked to the Difference of SAA/CRP ratio in Early Rheumatoid Arthritis

OBJECTIVES

Indeed, serum amyloid A (SAA) and C-reactive protein (CRP) reportedly seem to have moderate correlation, but discrepancies between CRP and SAA levels have often been reported in patients with early rheumatoid arthritis (ERA). This study aimed to determine the reasons for this discrepancy.

METHODS

ERA patients (n = 206) were enrolled and treated with anti-RA drugs. Clinical features and disease activities were estimated. CRP and SAA levels were monitored, and the SAA/CRP ratio was compared. Correlations between CRP and SAA levels in individuals and between individuals, and disease activity scores were examined.

RESULTS

In a follow-up study, the SAA/CRP ratio remained almost constant over time in the same patients. However, SAA/CRP ratios differed widely between patients (0.233-106.3). In patients with high SAA/CRP ratio (>6.52), many (26.2%) had abnormal SAA values only. In patients with low SAA/CRP ratio (<6.52), not a few (6.8%) exhibited abnormal CRP values only.

CONCLUSIONS

The SAA/CRP ratio remained virtually constant in the same patients but differed dramatically between patients, which clarifies the discrepancy between CRP and SAA levels. CRP is the better marker in low-ratio patients, but not in high-ratio patients; the SAA/CRP ratio is critical for its interpretation.

A panel of urine-derived biomarkers to identify sepsis and distinguish it from systemic inflammatory response syndrome

Sepsis is a potentially fatal condition caused by infection. It is frequently difficult to distinguish sepsis from systemic inflammatory response syndrome (SIRS), often resulting in poor prognoses and the misuse of antibiotics. Hence, highly sensitive and specific biomarkers are needed to differentiate sepsis from SIRS. Urine samples were collected and segregated by group (a sepsis group, a SIRS group, and a healthy control group). iTRAQ was used to identify the differentially expressed proteins among the three groups. The identified proteins were measured by ELISA in urine samples. Finally, all the acquired data were analyzed in SPSS. C-reactive protein, leucine-rich alpha glycoprotein-1 and serum amyloid A (SAA) protein were differentially expressed among the three groups. The adjusted median concentrations of urinary C-reactive protein were 1337.6, 358.7, and 2.4 in the sepsis, SIRS, and healthy control groups, respectively. The urinary leucine-rich alpha glycoprotein-1 levels in these three groups were 1614.4, 644.5, and 13.6, respectively, and the levels of SAA were 6.3, 2.9, and 0.07, respectively. For all three of these measures, the sepsis group had higher levels than the SIRS group (P < 0.001), and the SIRS group had higher levels than the healthy control group. When combined, the three biomarkers had a sensitivity of 0.906 and a specificity of 0.896 in distinguishing sepsis from SIRS. Urinary C-reactive protein, urinary leucine-rich alpha glycoprotein-1 and urinary SAA have diagnostic value in cases of sepsis. This initial study suggests the possibility of improved differential diagnosis between sepsis and systemic inflammatory response syndrome; additional confirmation is necessary to corroborate the findings.

Fractionated Irradiation of Right Thorax Induces Abscopal Damage on Bone Marrow Cells via TNF-α and SAA

Radiation-induced abscopal effect (RIAE) outside of radiation field is becoming more attractive. However, the underlying mechanisms are still obscure. This work investigated the deleterious effect of thoracic irradiation (Th-IR) on distant bone marrow and associated signaling factors by irradiating the right thorax of mice with fractionated doses (8 Gy × 3). It was found that this localized Th-IR increased apoptosis of bone marrow cells and micronucleus formation of bone marrow polychromatic erythrocytes after irradiation. Tandem mass tagging (TMT) analysis and ELISA assay showed that the concentrations of TNF-α and serum amyloid A (SAA) in the mice were significantly increased after Th-IR. An immunohistochemistry assay revealed a robust increase in SAA expression in the liver rather than in the lungs after Th-IR. In vitro experiments demonstrated that TNF-α induced SAA expression in mouse hepatoma Hepa1-6 cells, and these two signaling factors induced DNA damage in bone marrow mesenchymal stem cells (BMSCs) by increasing reactive oxygen species (ROS). On the other hand, injection with TNF-α inhibitor before Th-IR reduced the secretion of SAA and attenuated the abscopal damage in bone marrow. ROS scavenger NAC could also mitigated Th-IR/SAA-induced bone marrow damage in mice. Our findings indicated that Th-IR triggered TNF-α release from lung, which further promoted SAA secretion from liver in a manner of cascade reaction. Consequently, these signaling factors resulted in induction of abscopal damage on bone marrow of mice.

Serum level of serum amyloid A1 protein in patients with acne vulgaris

INTRODUCTION

The serum amyloid A1 (SAA1) protein is involved in many pathological diseases. The increased secretion of SAA1 can maintain inflammatory conditions. Acne vulgaris (AV) is a chronic inflammatory disease of pilosebaceous glands and may be associated with systemic manifestations.

AIM OF THE WORK

This study aimed to evaluate the serum level of SAA1 in patients with AV.

SUBJECTS AND METHODS

120 participants were included in this study: 60 patients with AV and 60 apparently healthy volunteers as a control group. These participants were subjected to dermatological examination and assessments of lipid profile, fasting blood glucose (FBG), and serum SAA1.

RESULTS

Both serum SAA1 and FBG are significantly elevated in patients with AV than control (p < 0.0001 and p < 0.001, respectively). Furthermore, there are positive correlations between AV severity and SAA1 and FBG (p < 0.001 and p < 0.0001, respectively).

CONCLUSIONS

Serum amyloid A1 is increased in AV, and this elevation may play a role in the inflammatory milieu of AV.

MTADV 5-MER peptide suppresses chronic inflammations as well as autoimmune pathologies and unveils a new potential target-Serum Amyloid A

Despite the existence of potent anti-inflammatory biological drugs e.g., anti-TNF and anti IL-6 receptor antibodies, for treating chronic inflammatory and autoimmune diseases, these are costly and not specific. Cheaper oral available drugs remain an unmet need. Expression of the acute phase protein Serum Amyloid A (SAA) is dependent on release of pro-inflammatory cytokines IL-1, IL-6 and TNF-α during inflammation. Conversely, SAA induces pro-inflammatory cytokine secretion, including Th17, leading to a pathogenic vicious cycle and chronic inflammation. 5- MER peptide (5-MP) MTADV (methionine-threonine-alanine-aspartic acid-valine), also called Amilo-5MER, was originally derived from a sequence of a pro-inflammatory CD44 variant isolated from synovial fluid of a Rheumatoid Arthritis (RA) patient. This human peptide displays an efficient anti-inflammatory effects to ameliorate pathology and clinical symptoms in mouse models of RA, Inflammatory Bowel Disease (IBD) and Multiple Sclerosis (MS). Bioinformatics and qRT-PCR revealed that 5-MP, administrated to encephalomyelytic mice, up-regulates genes contributing to chronic inflammation resistance. Mass spectrometry of proteins that were pulled down from an RA synovial cell extract with biotinylated 5-MP, showed that it binds SAA. 5-MP disrupted SAA assembly, which is correlated with its pro-inflammatory activity. The peptide MTADV (but not scrambled TMVAD) significantly inhibited the release of pro-inflammatory cytokines IL-6 and IL-1β from SAA-activated human fibroblasts, THP-1 monocytes and peripheral blood mononuclear cells. 5-MP suppresses the pro-inflammatory IL-6 release from SAA-activated cells, but not from non-activated cells. 5-MP could not display therapeutic activity in rats, which are SAA deficient, but does inhibit inflammations in animal models of IBD and MS, both are SAA-dependent, as shown by others in SAA knockout mice. In conclusion, 5-MP suppresses chronic inflammation in animal models of RA, IBD and MS, which are SAA-dependent, but not in animal models, which are SAA-independent.

Activated macrophages promote invasion by early colorectal cancer via an interleukin 1β-serum amyloid A1 axis

Submucosal invasion and lymph node metastasis are important issues affecting treatment options for early colorectal cancer (CRC). In this study, we aimed to unravel the molecular mechanism underlying the invasiveness of early CRCs. We performed RNA‐sequencing (RNA‐seq) with poorly differentiated components (PORs) and their normal counterparts isolated from T1 CRC tissues and detected significant upregulation of serum amyloid A1 (SAA1) in PORs. Immunohistochemical analysis revealed that SAA1 was specifically expressed in PORs at the invasive front of T1b CRCs. Upregulation of SAA1 in CRC cells promoted cell migration and invasion. Coculture experiments using CRC cell lines and THP‐1 cells suggested that interleukin 1β (IL‐1β) produced by macrophages induces SAA1 expression in CRC cells. Induction of SAA1 and promotion of CRC cell migration and invasion by macrophages were inhibited by blocking IL‐1β. These findings were supported by immunohistochemical analysis of primary T1 CRCs showing accumulation of M1‐like/M2‐like macrophages at SAA1‐positive invasive front regions. Moreover, SAA1 produced by CRC cells stimulated upregulation of matrix metalloproteinase‐9 in macrophages. Our data suggest that tumor‐associated macrophages at the invasive front of early CRCs promote cancer cell migration and invasion through induction of SAA1 and that SAA1 may be a predictive biomarker and a useful therapeutic target.

Serum Amyloid A Promotes Inflammation-Associated Damage and Tumorigenesis in a Mouse Model of Colitis-Associated Cancer

BACKGROUND & AIMS

Identifying new approaches to lessen inflammation, as well as the associated malignant consequences, remains crucial to improving the lives and prognosis of patients diagnosed with inflammatory bowel diseases. Although it previously has been suggested as a suitable biomarker for monitoring disease activity in patients diagnosed with Crohn's disease, the role of the acute-phase protein serum amyloid A (SAA) in inflammatory bowel disease remains unclear. In this study, we aimed to assess the role of SAA in colitis-associated cancer.

METHODS

We established a model of colitis-associated cancer in wild-type and SAA double-knockout (Saa1/2-/-) mice by following the azoxymethane/dextran sulfate sodium protocol. Disease activity was monitored throughout the study while colon and tumor tissues were harvested for subsequent use in cytokine analyses, Western blot, and immunohistochemistry +experiments.

RESULTS

We observed attenuated disease activity in mice deficient for Saa1/2 as evidenced by decreased weight loss, increased stool consistency, decreased rectal bleeding, and decreased colitis-associated tissue damage. Macrophage infiltration, including CD206+ M2-like macrophages, also was attenuated in SAA knockout mice, while levels of interleukin 4, interleukin 10, and tumor necrosis factor-ɑ were decreased in the distal colon. Mice deficient for SAA also showed a decreased tumor burden, and tumors were found to have increased apoptotic activity coupled with decreased expression for markers of proliferation.

CONCLUSION

Based on these findings, we conclude that SAA has an active role in inflammatory bowel disease and that it could serve as a therapeutic target aimed at decreasing chronic inflammation and the associated risk of developing colitis-associated cancer.

Serum Amyloid A Proteins and Their Impact on Metastasis and Immune Biology in Cancer

Simple Summary

The liver responds to systemic inflammation and injury in a coordinated manner, called the acute phase response. While this normal physiological response aims to restore homeostasis, malignant transformation coopts this biology to increase the risk for metastasis, immune evasion, and therapeutic resistance. In this Review, we discuss the importance of acute phase response proteins in regulating cancer biology and treatment efficacy. We also consider potential strategies to intervene on acute phase biology as an approach to improve outcomes in cancer.

Abstract

Cancer triggers the systemic release of inflammatory molecules that support cancer cell metastasis and immune evasion. Notably, this biology shows striking similarity to an acute phase response that is coordinated by the liver. Consistent with this, a role for the liver in defining cancer biology is becoming increasingly appreciated. Understanding the mechanisms that link acute phase biology to metastasis and immune evasion in cancer may reveal vulnerable pathways and novel therapeutic targets. Herein, we discuss a link between acute phase biology and cancer with a focus on serum amyloid A proteins and their involvement in regulating the metastatic cascade and cancer immunobiology.

The turning away of serum amyloid A biological activities and receptor usage

Serum amyloid A (SAA) is an acute-phase protein (APP) to which multiple immunological functions have been attributed. Regardless, the true biological role of SAA remains poorly understood. SAA is remarkably conserved in mammalian evolution, thereby suggesting an important biological function. Since its discovery in the 1970s, the majority of researchers have investigated SAA using recombinant forms made available through bacterial expression. Nevertheless, recent studies indicate that these recombinant forms of SAA are unreliable. Indeed, commercial SAA variants have been shown to be contaminated with bacterial products including lipopolysaccharides and lipoproteins. As such, biological activities and receptor usage (TLR2, TLR4) revealed through the use of commercial SAA variants may not reflect the inherent nature of this APP. Within this review, we discuss the biological effects of SAA that have been demonstrated through more solid experimental approaches. SAA takes part in the innate immune response via the recruitment of leucocytes and executes, through pathogen recognition, antimicrobial activity. Knockout animal models implicate SAA in a range of functions, such as regulation of T-cell-mediated responses and monopoiesis. Moreover, through its structural motifs, not only does SAA function as an extracellular matrix protein, but it also binds extracellular matrix proteins. Finally, we here also provide an overview of definite SAA receptor-mediated functions and highlight those that are yet to be validated. The role of FPR2 in SAA-mediated leucocyte recruitment has been confirmed; nevertheless, SAA has been linked to a range of other receptors including CD36, SR-BI/II, RAGE and P2RX7.

Invited review: The influence of immune activation on transition cow health and performance-A critical evaluation of traditional dogmas

The progression from gestation into lactation represents the transition period, and it is accompanied by marked physiological, metabolic, and inflammatory adjustments. The entire lactation and a cow's opportunity to have an additional lactation are heavily dependent on how successfully she adapts during the periparturient period. Additionally, a disproportionate amount of health care and culling occurs early following parturition. Thus, lactation maladaptation has been a heavily researched area of dairy science for more than 50 yr. It was traditionally thought that excessive adipose tissue mobilization in large part dictated transition period success. Further, the magnitude of hypocalcemia has also been assumed to partly control whether a cow effectively navigates the first few months of lactation. The canon became that adipose tissue released nonesterified fatty acids (NEFA) and the resulting hepatic-derived ketones coupled with hypocalcemia lead to immune suppression, which is responsible for transition disorders (e.g., mastitis, metritis, retained placenta, poor fertility). In other words, the dogma evolved that these metabolites and hypocalcemia were causal to transition cow problems and that large efforts should be enlisted to prevent increased NEFA, hyperketonemia, and subclinical hypocalcemia. However, despite intensive academic and industry focus, the periparturient period remains a large hurdle to animal welfare, farm profitability, and dairy sustainability. Thus, it stands to reason that there are alternative explanations to periparturient failures. Recently, it has become firmly established that immune activation and the ipso facto inflammatory response are a normal component of transition cow biology. The origin of immune activation likely stems from the mammary gland, tissue trauma during parturition, and the gastrointestinal tract. If inflammation becomes pathological, it reduces feed intake and causes hypocalcemia. Our tenet is that immune system utilization of glucose and its induction of hypophagia are responsible for the extensive increase in NEFA and ketones, and this explains why they (and the severity of hypocalcemia) are correlated with poor health, production, and reproduction outcomes. In this review, we argue that changes in circulating NEFA, ketones, and calcium are simply reflective of either (1) normal homeorhetic adjustments that healthy, high-producing cows use to prioritize milk synthesis or (2) the consequence of immune activation and its sequelae.

Inflammation and Apolipoproteins Are Potential Biomarkers for Stratification of Cutaneous Melanoma Patients for Immunotherapy and Targeted Therapy

Malignant cutaneous melanoma is one of the most common cancers in young adults. During the last decade, targeted and immunotherapies have significantly increased the overall survival of patients with malignant cutaneous melanoma. Nevertheless, disease progression is common, and a lack of predictive biomarkers of patient response to therapy hinders individualized treatment strategies. To address this issue, we performed a longitudinal study using an unbiased proteomics approach to identify and quantify proteins in plasma both before and during treatment from 109 patients treated with either targeted or immunotherapy. Linear modeling and machine learning approaches identified 43 potential prognostic and predictive biomarkers. A reverse correlation between apolipoproteins and proteins related to inflammation was observed. In the immunotherapy group, patients with low pretreatment expression of apolipoproteins and high expression of inflammation markers had shorter progression-free survival. Similarly, increased expression of LDHB during treatment elicited a significant impact on response to immunotherapy. Overall, we identified potential common and treatment-specific biomarkers in malignant cutaneous melanoma, paving the way for clinical use of these biomarkers following validation on a larger cohort. SIGNIFICANCE: This study identifies a potential biomarker panel that could improve the selection of therapy for patients with cutaneous melanoma.

Serum amyloid A concentrations, COVID-19 severity and mortality: An updated systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

An excessive inflammatory response in patients with coronavirus disease 2019 (COVID-19) is associated with high disease severity and mortality. Specific acute phase reactants might be useful for risk stratification. A systematic review and meta-analysis was conducted of studies on serum amyloid A (SAA) in patients with COVID-19.

METHODS

The PubMed, Web of Science, and Scopus databases were searched, covering the period January 2020 to December 2020, for studies reporting SAA concentrations, COVID-19 severity, and survival status.

RESULTS

Nineteen studies involving 5617 COVID-19 patients were included in the meta-analysis. Pooled results showed that SAA concentrations were significantly higher in patients with severe disease and non-survivors (standard mean difference (SMD) 1.20, 95% confidence interval 0.91-1.49, P < 0.001). Extreme between-study heterogeneity was observed (I² = 92.4%, P < 0.001). In the sensitivity analysis, the effect size was not significantly affected when each study was removed in turn (range 1.10-1.29). The Begg test (P = 0.030), but not the Egger test (P = 0.385), revealed the presence of publication bias. Pooled SMD values were significantly and positively associated with sex (t = 2.20, P = 0.047) and aspartate aminotransferase (t = 3.44, P = 0.014).

CONCLUSIONS

SAA concentrations were significantly and positively associated with higher COVID-19 severity and mortality. This acute phase reactant might assist with risk stratification and monitoring in this group.

SAA1 regulates pro-labour mediators in term labour by activating YAP pathway

Term labour is associated with activation of inflammation which results in myometrial contractility, cervical ripening and decidual/membrane rupture. Serum amyloid A1 (SAA1) is an acute response protein, whose role and underlying regulatory mechanisms in human labour remain unknown. In this study, we found that the mRNA and protein expression of SAA1 in human myometrium at term was increased in labouring tissues compared to non-labouring tissues. In addition, the expression of SAA1 was significantly increased in human primary myometrial cells treated with the pro-inflammatory cytokines interleukin-1 beta (IL-1β) or tumour necrosis factor-alpha (TNF-α). Knockdown of SAA1 using siRNA (siSAA1) resulted in a significant reduction in the expression and secretion of pro-inflammatory cytokines (IL8, IL6), chemokines (CXCL5, CCL2), adhesion molecules (ICAM1, ICAM5) and contraction-associated factors (COX2, PGE2). Mechanistically, the effects of SAA1 were mediated through activation of the Yes-associated protein (YAP) pathway. There was a decrease in the protein expression of phosphorylated YAP (pYAP) after treatment of siSAA1-transfected human primary myometrial cells with IL-1β or TNF-α. Moreover, enhanced expression of YAP reversed the effect of siSAA1 on pro-labour mediators. In conclusion, these experiments demonstrated that SAA1 accelerates the inflammatory response associated with parturition by activating YAP pathway, which may be a novel understanding of the molecular mechanism of labour onset.