Serum Amyloid A Induces Inflammation, Proliferation and Cell Death in Activated Hepatic Stellate Cells. PLoS One. 2016;11:e0150893. [PMID: 26937641 PMCID: PMC4777566 DOI: 10.1371/journal.pone.0150893]

Multiomics blueprint of PANoptosis in deciphering immune characteristics and prognosis stratification of glioma patients

BACKGROUND

As the most prevalent primary brain tumor in adults, glioma accounts for the majority of all central nervous system malignant tumors. The concept of PANoptosis is a relatively new, underlining the interconnection and synergy among three distinct pathways: pyroptosis, apoptosis and necroptosis.

METHODS

We performed single-cell annotations of glioma cells and determined crucial signaling pathways through cell chat analysis. Using least absolute shrinkage and selection operator (LASSO) and Cox analyses, we identified a gene set with prognostic values. Our model was validated using independent external cohort. In addition, we employed single-sample gene set enrichment analysis and xCell analyses to describe the detailed profile of infiltrated immune cells and depicted the gene mutation landscape in the two groups.

RESULTS

We identified seven distinct cell clusters in glioma samples, including oligodendrocyte precursor cells (OPCs), myeloid cells, tumor cells, oligodendrocytes, astrocytes, vascular cells and neuronal cells. We found that myeloid cells showed the highest PANoptosis activity. An intense mutual cell communication pattern between the tumor cells and OPCs and oligodendrocytes was observed. Differentially expressed genes between the high-PANoptosis and low-PANoptosis cell groups were obtained, which were enriched to actin cytoskeleton, cell adhesion molecules and gamma R-mediated phagocytosis pathways. We determined a set of five genes of prognostic significance: SAA1, SLPI, DCX, S100A8 and TNR. The prognostic differences between the two groups in the internal and external sets were found to be statistically significant. We found a marked correlation between S100A8 and activated dendritic cell, macrophage, mast cell, myeloid derived suppressor cell and Treg infiltration. Moreover, we have observed a significant increase of PTEN mutation in the high risk (HR) group of glioma patients.

CONCLUSIONS

In the present study, we have constructed a prognostic model that is based on the PANoptosis, and we have demonstrated its significant efficacy in stratifying patients with glioma. This innovative prognostic model offers novel insights into precision immune treatments that could be used to combat this disease and improve patient outcomes, thereby providing a new avenue for personalized treatment options.

Interorgan communication with the liver: novel mechanisms and therapeutic targets

The liver is a multifunctional organ that plays crucial roles in numerous physiological processes, such as production of bile and proteins for blood plasma, regulation of blood levels of amino acids, processing of hemoglobin, clearance of metabolic waste, maintenance of glucose, etc. Therefore, the liver is essential for the homeostasis of organisms. With the development of research on the liver, there is growing concern about its effect on immune cells of innate and adaptive immunity. For example, the liver regulates the proliferation, differentiation, and effector functions of immune cells through various secreted proteins (also known as "hepatokines"). As a result, the liver is identified as an important regulator of the immune system. Furthermore, many diseases resulting from immune disorders are thought to be related to the dysfunction of the liver, including systemic lupus erythematosus, multiple sclerosis, and heart failure. Thus, the liver plays a role in remote immune regulation and is intricately linked with systemic immunity. This review provides a comprehensive overview of the liver remote regulation of the body's innate and adaptive immunity regarding to main areas: immune-related molecules secreted by the liver and the liver-resident cells. Additionally, we assessed the influence of the liver on various facets of systemic immune-related diseases, offering insights into the clinical application of target therapies for liver immune regulation, as well as future developmental trends.

SAA1 exacerbates pancreatic β-cell dysfunction through activation of NF-κB signaling in high-fat diet-induced type 2 diabetes mice

Insufficient decompensated insulin secretion and insulin resistance caused by pancreatic β-cell dysfunction are the pathological bases of type 2 diabetes mellitus (T2DM). Glucolipotoxicity in pancreatic β-cells is an important factor leading to their dysfunction, closely related to inflammatory signals, oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum stress (ERs). However, there may be other unproven regulatory mechanisms that govern pancreatic β-cell dysfunction. Therefore, further elucidation of the underlying mechanisms that lead to pancreatic β-cells dysfunction will provide a sufficient theoretical basis for the more effective prevention and treatment of T2DM. As a stress protein with pro-inflammatory properties, Serum Amyloid 1 (SAA1) promotes the progression of metabolic syndrome-related diseases by activating immune cells and damaging endothelial cells. In the development of T2DM, the activation of nuclear factor-kappa B (NF-κB) signaling aggravates pancreatic β-cells dysfunction under the stimulation of free fatty acids (FFAs), inflammatory factors, and chemokines. Moreover, the facilitating effect of SAA1 on the activation of the NF-κB signaling pathway has been demonstrated in other studies. In the present study, we demonstrated that SAA1 inhibits insulin secretion and promotes apoptotic molecular expression in pancreatic cells and islets and that NF-κB signaling inhibitors could reduce this effect of SAA1. SAA1 deficiency improved high-fat diet (HFD)-induced pancreatic β-cell dysfunction and decreased expression of NF-κB signaling molecules. Our findings suggested that HFD-induced SAA1 might exacerbate T2DM by enhancing pancreatic β-cell dysfunction; such a function of SAA1 might depend on NF-κB signaling activation.

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.

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.

Adipose lipolysis is important for ethanol to induce fatty liver in the National Institute on Alcohol Abuse and Alcoholism murine model of chronic and binge ethanol feeding

BACKGROUND AND AIMS

Alcohol-associated liver disease (ALD) pathologies include steatosis, inflammation, and injury, which may progress to fibrosis, cirrhosis, and cancer. The liver receives ~60% of fatty acids from adipose tissue triglyceride hydrolysis, but the role of this lipolytic pathway in ALD development has not been directly examined in any genetic animal models with selective inactivation of adipose lipolysis.

APPROACH AND RESULTS

Using adipose-specific comparative gene identification-58 (CGI-58) knockout (FAT-KO) mice, a model of impaired adipose lipolysis, we show that mice deficient in adipose lipolysis are almost completely protected against ethanol-induced hepatic steatosis and lipid peroxidation when subjected to the National Institute on Alcohol Abuse and Alcoholism chronic and binge ethanol feeding model. This is unlikely due to reduced lipid synthesis because this regimen of ethanol feeding down-regulated hepatic expression of lipogenic genes similarly in both genotypes. In the pair-fed group, FAT-KO relative to control mice displayed increased hepatocyte injury, neutrophil infiltration, and activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) in the liver; and none of these were exacerbated by ethanol feeding. Activation of STAT3 is associated with a marked increase in hepatic leptin receptor mRNA expression and adipose inflammatory cell infiltration.

CONCLUSIONS

Our findings establish a critical role of adipose lipolysis in driving hepatic steatosis and oxidative stress during ALD development.

Cytokimera GIL-11 rescued IL-6R deficient mice from partial hepatectomy-induced death by signaling via non-natural gp130:LIFR:IL-11R complexes

All except one cytokine of the Interleukin (IL-)6 family share glycoprotein (gp) 130 as the common β receptor chain. Whereas Interleukin (IL-)11 signal via the non-signaling IL-11 receptor (IL-11R) and gp130 homodimers, leukemia inhibitory factor (LIF) recruits gp130:LIF receptor (LIFR) heterodimers. Using IL-11 as a framework, we exchange the gp130-binding site III of IL-11 with the LIFR binding site III of LIF. The resulting synthetic cytokimera GIL-11 efficiently recruits the non-natural receptor signaling complex consisting of gp130, IL-11R and LIFR resulting in signal transduction and proliferation of factor-depending Ba/F3 cells. Besides LIF and IL-11, GIL-11 does not activate receptor complexes consisting of gp130:LIFR or gp130:IL-11R, respectively. Human GIL-11 shows cross-reactivity to mouse and rescued IL-6R^-/- mice following partial hepatectomy, demonstrating gp130:IL-11R:LIFR signaling efficiently induced liver regeneration. With the development of the cytokimera GIL-11, we devise the functional assembly of the non-natural cytokine receptor complex of gp130:IL-11R:LIFR.

cFOS expression in the prefrontal cortex correlates with altered cerebral metabolism in developing germ-free mice

Introduction

The microbiota plays a critical role in modulating various aspects of host physiology, particularly through the microbiota-gut-brain (MGB) axis. However, the mechanisms that transduce and affect gut-to-brain communication are still not well understood. Recent studies have demonstrated that dysbiosis of the microbiome is associated with anxiety and depressive symptoms, which are common complications of metabolic syndrome. Germ-free (GF) animal models offer a valuable tool for studying the causal effects of microbiota on the host.

Methods

We employed gene expression and nuclear magnetic resonance (NMR)-based metabolomic techniques to investigate the relationships between brain plasticity and immune gene expression, peripheral immunity, and cerebral and liver metabolism in GF and specific pathogen-free (SPF) mice.

Results

Our principal findings revealed that brain acetate (p = 0.012) was significantly reduced in GF relative to SPF mice, whereas glutamate (p = 0.0013), glutamine (p = 0.0006), and N-acetyl aspartate (p = 0.0046) metabolites were increased. Notably, cFOS mRNA expression, which was significantly decreased in the prefrontal cortex of GF mice relative to SPF mice (p = 0.044), correlated with the abundance of a number of key brain metabolites altered by the GF phenotype, including glutamate and glutamine.

Discussion

These results highlight the connection between the GF phenotype, altered brain metabolism, and immediate-early gene expression. The study provides insight into potential mechanisms by which microbiota can regulate neurotransmission through modulation of the host's brain and liver metabolome, which may have implications for stress-related psychiatric disorders such as anxiety.

"Theranekron: A Novel Anti-inflammatory Candidate for Acetic Acid-Induced Colonic Inflammation in Rats"

BACKGROUND

Inflammatory bowel disease (IBD) is characterized with chronic inflammation of gastrointestinal track. In the pathogenesis of IBD, inflammation is the main mechanism. Induction of inflammation triggers the oxidative stress that subsequently leading to apoptosis. Considering the all pathological mechanisms, many therapeutic agents have been used for IBD but because of serious side effects there is still a need for new therapeutic drugs. In this study, we aim to evaluate the possible protective effects of Theranekron (TH) on acetic acid (AA)- induced colonic damage and to describe the probable effect mechanisms of TH.

MATERIALS AND RESULTS

Fourty female adult Wistar albino rats were divided into 5 groups. Following 24 h fasting, colitis was induced by rectal instillation of AA. In TH group, a single dose of subcutaneous 0.2 ml TH was used. In treatment groups, 0.2 ml TH single dose or 100 mg/kg sulfasalazine (SS) for 7 days were used after colitis induction. Normal salin was used for all applications in control group. Histopathologically hemorrhage, edema and inflammatory reactions were seen in AA group. TH and SS decreased the severity of lesions. Nuclear factor kappa B, Serum amyloid A, C-reactive protein, Growth-related oncogene, and Osteopontin expressions were markedly increased in AA group and TH markedly reduced these expressions. In Western analysis, decreased NF-kB and caspase-3 levels were observed with TH. Oxidative markers did not changed significantly.

CONCLUSIONS

TH has a prominent anti-inflammatory effect on AA-induced colonic inflammation via NF-kB signaling whereas antiapoptic effects seem to be independent from this pathway.

Constitutive androstane receptor (CAR) mediates pyrene-induced mice liver inflammatory response with increased serum amyloid A proteins and Th17 cells

BACKGROUND AND PURPOSE

The constitutive androstane receptor (CAR), a known xenobiotic sensor, plays an important role in drug metabolism by regulating numerous genes. We previously reported that pyrene, an environmental pollutant, is a CAR activator and induces mouse hepatotoxicity via CAR. Here, we investigate the molecular mechanism of inflammatory response in pyrene-caused mice liver injury.

EXPERIMENTAL APPROACH

Effects of pyrene on the liver were investigated in wild-type and CAR knockout (KO) mice. Levels of pyrene and its metabolite were analyzed by high performance liquid chromatography (HPLC).

KEY RESULTS

Serum amyloid A proteins (SAAs) were dramatically induced in the liver and serum of pyrene-exposed wild-type mice. Interleukin 17 (IL-17)-producing helper T cells (Th17 cells) and IL-17 levels were significantly increased in the liver of pyrene-exposed wild-type mice. Hepatic mRNA levels of inflammatory cytokines including IL-1β, IL-6 and TNFα, and serum IL-6 levels were significantly elevated in pyrene-treated wild-type mice. However, the above induction was not observed in CAR KO mice.

CONCLUSION AND IMPLICATIONS

We demonstrate that CAR plays a crucial role in pyrene-caused mice liver inflammatory response with increased SAAs and Th17 cells. Our results suggest that serum SAAs may be a convenient biomarker for early diagnosis of liver inflammatory response caused by polycyclic aromatic hydrocarbons (PAHs) including pyrene. CAR and Th17 cells may be potential targets for novel therapeutic strategy for xenobiotic-induced liver inflammatory response.

Relationship of Troponin I with Neutrophil Lymphocyte Ratio and Serum Amyloid A in Acute Coronary Syndrome

Abstract Introduction: Acute coronary syndrome (ACS) is the leading cause of death in the world. Acute myocardial infarction can initiate an acute inflammatory process by inducing pro-inflammatory cytokines at the cellular level measured by NLR, at the biomolecular level characterized by SAA production in liver. The relationship of elevated troponin I levels as a marker of myocardial necrosis with NLR and SAA as inflammatory markers need further discussion. The purpose of this study was to determine the relationship between cardiac necrosis markers and inflammatory parameters in ACS. Methods: An analytic observational study with a cross-sectional approach was conducted from March to May 2019. This study involved 32 patients with ACS at the Emergency Department of Dr.Kariadi Hospital, with the onset of attacks of 4-6 hours which met the inclusion and exclusion criteria. Examination of troponin I level was done using the ELFA method, NLR value was measured using a hematology analyzer, and SAA level was measured using the ELISA method. Statistical test was done using Spearman correlation. Value of p < 0.05 was considered significant. Results: The median (min-max) of troponin I, NLR, and SAA values were 0.617 (0.001-40,000) μg/L, 4.92 (1.38-18.16) and 40.454 (5.879-66.059) μg/ml, respectively. The correlation of troponin I level with NLR and SAA were r=0.180, p=0.243 and r=0.655, p=0.000. Conclusions: There was a significant positive moderate relationship between troponin I level and SAA which could be used as a marker of acute inflammation in ACS, whereas cell inflammation marker of NLR did not provide a significant meaning. Keywords: ACS, NLR, SAA, troponin

IQGAP1-mediated mechanical signaling promotes the foreign body response to biomedical implants

The aim of this study was to further elucidate the molecular mechanisms that mediate pathologic foreign body response (FBR) to biomedical implants. The longevity of biomedical implants is limited by the FBR, which leads to implant failure and patient morbidity. Since the specific molecular mechanisms underlying fibrotic responses to biomedical implants have yet to be fully described, there are currently no targeted approaches to reduce pathologic FBR. We utilized proteomics analysis of human FBR samples to identify potential molecular targets for therapeutic inhibition of FBR. We then employed a murine model of FBR to further evaluate the role of this potential target. We performed histological and immunohistochemical analysis on the murine FBR capsule tissue, as well as single-cell RNA sequencing (scRNA-seq) on cells isolated from the capsules. We identified IQ motif containing GTPase activating protein 1 (IQGAP1) as the most promising of several targets, serving as a central molecular mediator in human and murine FBR compared to control subcutaneous tissue. IQGAP1-deficient mice displayed a significantly reduced FBR compared to wild-type mice as evidenced by lower levels of collagen deposition and maturity. Our scRNA-seq analysis revealed that decreasing IQGAP1 resulted in diminished transcription of mechanotransduction, inflammation, and fibrosis-related genes, which was confirmed on the protein level with immunofluorescent staining. The deficiency of IQGAP1 significantly attenuates FBR by deactivating downstream mechanotransduction signaling, inflammation, and fibrotic pathways. IQGAP1 may be a promising target for rational therapeutic design to mitigate pathologic FBR around biomedical implants.

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.

The Correlation between Serum Amyloid A, Mean Platelet Volume, and Creatine Kinase Myocardial B in Acute Coronary Syndrome

BACKGROUND: Atherosclerosis causes acute myocardial necrosis and inflammation characterized by increased mean platelet volume (MPV) and serum amyloid A (SAA). Creatine Kinase Myocardial Band (CKMB) is known as myocardial necrosis marker commonly used in daily practice to help diagnosing acute coronary syndrome. AIM: The purpose of this study was to determine the correlation between MPV, SAA, and CKMB in patients with acute coronary syndrome. METHODS: An analytic observational study with a cross-sectional approach was conducted from May to July 2019. This study involved 32 patients with ACS at the Emergency Department of Dr Kariadi Public Hospital. The inclusion criteria of this study were patients with chest pain, aged 30–75 years, and normal body temperature while the exclusion criteria were malignancy, undergoing chemotherapy/radiation, renal failure, hypertension, and liver disease. Examination of CKMB was done using the spectrophotometry method, MPV value was measured using a hematology analyzer, and SAA level was measured using the ELISA method. Statistical test was done using Spearman correlation. RESULTS: The median (min-max) of MPV and SAA values was 9.85 (2.78-11.7) fL and 40.454 (5.879–66.059) μg/ml, while the mean ± SD (min-max) value of CKMB was 115.47 ± 155.97 (10–608) U/L. The correlation coefficient between CKMB level with MPV and SAA levels were r = −0.244 (p = 0.179) and r = 0.442 (p = 0.011), respectively. CONCLUSION: There was a significant positive moderate correlation between CKMB and SAA levels which could be used as a marker of acute inflammation in ACS, whereas inflammatory marker of MPV did not have a significant correlation.

SAA1/TLR2 axis directs chemotactic migration of hepatic stellate cells responding to injury

Hepatic stellate cells (HSCs) are crucial for liver injury repair and cirrhosis. However, the mechanism of chemotactic recruitment of HSCs into injury loci is still largely unknown. Here, we demonstrate that serum amyloid A1 (SAA1) acts as a chemokine recruiting HSCs toward injury loci signaling via TLR2, a finding proven by gene manipulation studies in cell and mice models. The mechanistic investigations revealed that SAA1/TLR2 axis stimulates the Rac GTPases through PI3K-dependent pathways and induces phosphorylation of MLC (pSer19). Genetic deletion of TLR2 and pharmacological inhibition of PI3K diminished the phosphorylation of MLCpSer19 and migration of HSCs. In brief, SAA1 serves as a hepatic endogenous chemokine for the TLR2 receptor on HSCs, thereby initiating PI3K-dependent signaling and its effector, Rac GTPases, which consequently regulates actin filament remodeling and cell directional migration. Our findings provide novel targets for anti-fibrosis drug development.

•

SAA1 serves as a chemokine to guide migration of HSCs toward injury locus

•

TLR2 acts as a functional receptor for SAA1 in HSCs

•

SAA1/TLR2 axis-mediated migration of HSCs operates through PI3K/Rac1 signaling

•

SAA1/TLR2 axis provides a link for the cross talk between hepatocytes and HSCs

Efficacy of the Piperidine Nitroxide 4-MethoxyTEMPO in Ameliorating Serum Amyloid A-Mediated Vascular Inflammation

Intracellular redox imbalance in endothelial cells (EC) can lead to endothelial dysfunction, which underpins cardiovascular diseases (CVD). The acute phase serum amyloid A (SAA) elicits inflammation through stimulating production of reactive oxygen species (ROS). The cyclic nitroxide 4-MethoxyTEMPO (4-MetT) is a superoxide dismutase mimetic that suppresses oxidant formation and inflammation. The aim of this study was to investigate whether 4-MetT inhibits SAA-mediated activation of cultured primary human aortic EC (HAEC). Co-incubating cells with 4-MetT inhibited SAA-mediated increases in adhesion molecules (VCAM-1, ICAM-1, E-selectin, and JAM-C). Pre-treatment of cells with 4-MetT mitigated SAA-mediated increases in transcriptionally activated NF-κB-p65 and P120 Catenin (a stabilizer of Cadherin expression). Mitochondrial respiration and ROS generation (mtROS) were adversely affected by SAA with decreased respiratory reserve capacity, elevated maximal respiration and proton leakage all characteristic of SAA-treated HAEC. This altered respiration manifested as a loss of mitochondrial membrane potential (confirmed by a decrease in TMRM fluorescence), and increased mtROS production as assessed with MitoSox Red. These SAA-linked impacts on mitochondria were mitigated by 4-MetT resulting in restoration of HAEC nitric oxide bioavailability as confirmed by assessing cyclic guanosine monophosphate (cGMP) levels. Thus, 4-MetT ameliorates SAA-mediated endothelial dysfunction through normalising EC redox homeostasis. Subject to further validation in in vivo settings; these outcomes suggest its potential as a therapeutic in the setting of cardiovascular pathologies where elevated SAA and endothelial dysfunction is linked to enhanced CVD.

The liver metastatic niche: modelling the extracellular matrix in metastasis

Dissemination of malignant cells from primary tumours to metastatic sites is a key step in cancer progression. Disseminated tumour cells preferentially settle in specific target organs, and the success of such metastases depends on dynamic interactions between cancer cells and the microenvironments they encounter at secondary sites. Two emerging concepts concerning the biology of metastasis are that organ-specific microenvironments influence the fate of disseminated cancer cells, and that cancer cell-extracellular matrix interactions have important roles at all stages of the metastatic cascade. The extracellular matrix is the complex and dynamic non-cellular component of tissues that provides a physical scaffold and conveys essential adhesive and paracrine signals for a tissue's function. Here, we focus on how extracellular matrix dynamics contribute to liver metastases - a common and deadly event. We discuss how matrix components of the healthy and premetastatic liver support early seeding of disseminated cancer cells, and how the matrix derived from both cancer and liver contributes to the changes in niche composition as metastasis progresses. We also highlight the technical developments that are providing new insights into the stochastic, dynamic and multifaceted roles of the liver extracellular matrix in permitting and sustaining metastasis. An understanding of the contribution of the extracellular matrix to different stages of metastasis may well pave the way to targeted and effective therapies against metastatic disease.

Molecular regulation of autophagy in a pro-inflammatory tumour microenvironment: New insight into the role of serum amyloid A

Chronic inflammation, systemic or local, plays a vital role in tumour progression and metastasis. Dysregulation of key physiological processes such as autophagy elicit unfavourable immune responses to induce chronic inflammation. Cytokines, growth factors and acute phase proteins present in the tumour microenvironment regulate inflammatory responses and alter crosstalk between various signalling pathways involved in the progression of cancer. Serum amyloid A (SAA) is a key acute phase protein secreted by the liver during the acute phase response (APR) following infection or injury. However, cancer and cancer-associated cells produce SAA, which when present in high levels in the tumour microenvironment contributes to cancer initiation, progression and metastasis. SAA can activate several signalling pathways such as the PI3K and MAPK pathways, which are also known modulators of the intracellular degradation process, autophagy. Autophagy can be regarded as having a double edged sword effect in cancer. Its dysregulation can induce malignant transformation through metabolic stress which manifests as oxidative stress, endoplasmic reticulum (ER) stress and DNA damage. On the other hand, autophagy can promote cancer survival during metabolic stress, hypoxia and senescence. Autophagy has been utilised to promote the efficiency of chemotherapeutic agents and can either be inhibited or induced to improve treatment outcomes. This review aims to address the known mechanisms that regulate autophagy as well as illustrating the role of SAA in modulating these pathways and its clinical implications for cancer therapy.

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.

Inhibition of IRAK4 kinase activity improves ethanol-induced liver injury in mice

BACKGROUNDS & AIMS

Alcohol-related liver disease (ALD) is a major cause of chronic liver disease worldwide with limited therapeutic options. Interleukin-1 receptor associated kinase 4 (IRAK4), the master kinase of Toll-like receptor (TLR)/IL-1R-mediated signalling activation, is considered a novel therapeutic target in inflammatory diseases, but has not been investigated in the context of ALD.

METHODS

IRAK4 phosphorylation and IRAK1 protein were analysed in liver from alcohol-related hepatitis patients and healthy controls. IRAK4 kinase activity-inactive knock-in (Irak4 KI) mice and bone marrow chimeric mice were exposed to chronic ethanol-induced liver injury. IL-1β-induced IRAK4-mediated signalling and acute phase response were investigated in cultured hepatocytes. IRAK1/4 inhibitor was used to test the therapeutic potential for ethanol-induced liver injury in mice.

RESULTS

Increased IRAK4 phosphorylation and reduced IRAK1 protein were found in livers of patients with alcoholic hepatitis. In the chronic ethanol-induced liver injury mouse model, hepatic inflammation and hepatocellular damage were attenuated in Irak4 KI mice. IRAK4 kinase activity promotes expression of acute phase proteins in response to ethanol exposure, including C-reactive protein and serum amyloid A1 (SAA1). SAA1 and IL-1β synergistically exacerbate ethanol-induced cell death ex vivo. Pharmacological blockage of IRAK4 kinase abrogated ethanol-induced liver injury, inflammation, steatosis, as well as acute phase gene expression and protein production in mice.

CONCLUSIONS

Our data elucidate the critical role of IRAK4 kinase activity in the pathogenesis of ethanol-induced liver injury in mice and provide preclinical validation for use of an IRAK1/4 inhibitor as a new potential therapeutic strategy for the treatment of ALD.

LAY SUMMARY

Herein, we have identified the role of IRAK4 kinase activity in the development of alcohol-induced liver injury in mice. Hepatocyte-specific IRAK4 is associated with an acute phase response and release of proinflammatory cytokines/chemokines, which synergistically exacerbate alcohol-induced hepatocyte cell death ex vivo. Pharmacological inhibition of IRAK4 kinase activity effectively attenuates alcohol-induced liver injury in mice and could have therapeutic implications.

The impact of endotrophin on the progression of chronic liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and can lead to multiple complications, including non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. The fibrotic liver is characterized by the pathological accumulation of extracellular matrix (ECM) proteins. Type VI collagen alpha3 (Col6a3) is a biomarker of hepatic fibrosis, and its cleaved form, endotrophin (ETP), plays a critical role in adipose tissue dysfunction, insulin resistance, and breast cancer development. Here, we studied the effects of the Col6a3-derived peptide ETP on the progression of chronic liver diseases, such as NASH and liver cancer. We used a doxycycline (Dox)-inducible liver-specific ETP-overexpressing mouse model on a NAFLD-prone (liver-specific SREBP1a transgenic) background. For this, we evaluated the consequences of local ETP expression in the liver and its effect on hepatic inflammation, fibrosis, and insulin resistance. Accumulation of ETP in the liver induced hepatic inflammation and the development of fibrosis with associated insulin resistance. Surprisingly, ETP overexpression also led to the emergence of liver cancer within 10 months in the SREBP1a transgenic background. Our data revealed that ETP can act as a “second hit” during the progression of NAFLD and can play an important role in the development of NASH and hepatocellular carcinoma (HCC). These observations firmly link elevated levels of ETP to chronic liver disease.

Localized buildup in the liver of a collagen-derived cleavage fragment plays a critical role in accelerating the development of tissue scarring and liver cancer in mice. Using a transgenic mouse model of fatty liver disease, a team led by Philipp Scherer from the University of Texas Southwestern Medical Center, Dallas, USA, and Jiyoung Park of Ulsan National Institute of Science and Technology, South Korea, showed that liver-specific accumulation of a collagen fragment known as endotrophin leads to activation of inflammatory and fibrotic pathways. The mice subsequently develop metabolic dysfunction, insulin resistance and, with time, cancerous nodules in the liver. The findings suggest that endotrophin accumulation, when it occurs in liver tissue that already contains large depositions of fat, can overwhelm normal liver physiology and accelerate organ damage.

Serum amyloid A3 is required for caerulein-induced acute pancreatitis through induction of RIP3-dependent necroptosis

Serum amyloid A (SAA) is an early and sensitive biomarker of inflammatory diseases, but its role in acute pancreatitis (AP) is still unclear. Here, we used a caerulein-induced mouse model to investigate the role of SAA in AP and other related inflammatory responses. In our study, we found that the expression of a specific SAA isoform, SAA3, was significantly elevated in a caerulein-induced AP animal model. In addition, SAA3-knockout (Saa3^-/- ) mice showed lower serum levels of amylase and lipase, tissue damage and proinflammatory cytokine production in the pancreas compared with those of wild-type mice in response to caerulein administration. AP-associated acute lung injury was also significantly attenuated in Saa3^-/- mice. In our in vitro experiments, treatment with cholecystokinin and recombinant SAA3 significantly induced necroptosis and cytokine production. Moreover, we found that the regulatory effect of SAA3 on acinar cell necroptosis was through a receptor-interacting protein 3 (RIP3)-dependent manner. Collectively, our findings indicate that SAA3 is required for AP by inducing an RIP3-dependent necroptosis pathway in acinar cells and is a potential drug target for AP.

Cancer-associated adipocytes promote pancreatic cancer progression through SAA1 expression

Although pancreatic cancer often invades peripancreatic adipose tissue, little information is known about cancer-adipocyte interaction. We first investigated the ability of adipocytes to de-differentiate to cancer-associated adipocytes (CAAs) by co-culturing with pancreatic cancer cells. We then examined the effects of CAA-conditioned medium (CAA-CM) on the malignant characteristics of cancer cells, the mechanism underlying those effects, and their clinical relevance in pancreatic cancer. When 3T3-L1 adipocytes were co-cultured with pancreatic cancer cells (PANC-1) using the Transwell system, adipocytes lost their lipid droplets and changed morphologically to fibroblast-like cells (CAA). Adipocyte-specific marker mRNA levels significantly decreased but those of fibroblast-specific markers appeared, characteristic findings of CAA, as revealed by real-time PCR. When PANC-1 cells were cultured with CAA-CM, significantly higher migration/invasion capability, chemoresistance, and epithelial-mesenchymal transition (EMT) properties were observed compared with control cells. To investigate the mechanism underlying these effects, we performed microarray analysis of PANC-1 cells cultured with CAA-CM and found a 78.5-fold higher expression of SAA1 compared with control cells. When the SAA1 gene in PANC-1 cells was knocked down with SAA1 siRNA, migration/invasion capability, chemoresistance, and EMT properties were significantly attenuated compared with control cells. Immunohistochemical analysis on human pancreatic cancer tissues revealed positive SAA1 expression in 46/61 (75.4%). Overall survival in the SAA1-positive group was significantly shorter than in the SAA1-negative group (P = .013). In conclusion, we demonstrated that pancreatic cancer cells induced de-differentiation in adipocytes toward CAA, and that CAA promoted malignant characteristics of pancreatic cancer via SAA1 expression, suggesting that SAA1 is a novel therapeutic target in pancreatic cancer.

Biological Characterization of Commercial Recombinantly Expressed Immunomodulating Proteins Contaminated with Bacterial Products in the Year 2020: The SAA3 Case

The serum amyloid A (SAA) gene family is highly conserved and encodes acute phase proteins that are upregulated in response to inflammatory triggers. Over the years, a considerable amount of literature has been published attributing a wide range of biological effects to SAAs such as leukocyte recruitment, cytokine and chemokine expression and induction of matrix metalloproteinases. Furthermore, SAAs have also been linked to protumorigenic, proatherogenic and anti-inflammatory effects. Here, we investigated the biological effects conveyed by murine SAA3 (mu rSAA3) recombinantly expressed in Escherichia coli. We observed the upregulation of a number of chemokines including CCL2, CCL3, CXCL1, CXCL2, CXCL6 or CXCL8 following stimulation of monocytic, fibroblastoid and peritoneal cells with mu rSAA3. Furthermore, this SAA variant displayed potent in vivo recruitment of neutrophils through the activation of TLR4. However, a major problem associated with proteins derived from recombinant expression in bacteria is potential contamination with various bacterial products, such as lipopolysaccharide, lipoproteins and formylated peptides. This is of particular relevance in the case of SAA as there currently exists a discrepancy in biological activity between SAA derived from recombinant expression and that of an endogenous source, i.e. inflammatory plasma. Therefore, we subjected commercial recombinant mu rSAA3 to purification to homogeneity via reversed-phase high-performance liquid chromatography (RP-HPLC) and re-assessed its biological potential. RP-HPLC-purified mu rSAA3 did not induce chemokines and lacked in vivo neutrophil chemotactic activity, but retained the capacity to synergize with CXCL8 in the activation of neutrophils. In conclusion, experimental results obtained when using proteins recombinantly expressed in bacteria should always be interpreted with care.

Inflammatory networks cultivate cancer cell metastasis to the liver

The liver is the most frequent site of metastatic spread in malignancies that arise from the digestive system, including pancreatic ductal adenocarcinoma (PDAC). Metastasis to the liver is a major cause of morbidity and mortality in cancer patients, yet mechanisms that govern this process remain poorly understood. Until recently, liver tropism of metastasis was believed to be driven by mechanical factors that direct the passive flow of circulating cancer cells to the liver. However, emerging evidence now shows that liver metastasis is a dynamic process that is, at least in part, dependent on the formation of a "pro-metastatic niche". Key features of this niche are myeloid cells and fibrosis that support cancer cell colonization and growth. Inflammatory responses that are mounted early during primary tumor development are critical for the recruitment of myeloid cells and the deposition of extracellular matrix (ECM) proteins within the liver. Intriguingly, the inflammatory processes that direct the formation of a pro-metastatic niche share remarkable resemblance to mechanisms of liver injury and regeneration, suggesting that cancer co-opts physiological liver functions to support metastasis. Therefore, therapeutic strategies that target key elements of liver inflammation that form the basis of a pro-metastatic niche may lead to effective treatments for metastatic cancer.

Knockdown of miR-660 protects nucleus pulposus cells from TNF-a-induced apoptosis by targeting serum amyloid A1

Background

Intervertebral disc degeneration (IVDD) is a well-known cause of lower back pain, which is induced by multiple factors including increased apoptosis and decreased survival of nucleus pulposus cells. In this study, we evaluate the effect and potential mechanism of miR-660 on the nucleus pulposus cells apoptosis induced by TNF-α.

Methods

First, we collected tissue of nucleus pulposus from IVDD and healthy controls. General characteristic of the IVDD and healthy control was also collected. And, we also collected nucleus pulposus cells that stimulated by TNF-α or control. miRNA microarray was performed to identify the differentially expressed miRNAs. Apoptosis rate and miR-660 relative expression was measured after stimulated with different concentration of TNF-α to identify the optimal concentration of TNF-α. Second, we successfully constructed antigomiR-660 to block the miR-660 expression in nucleus pulposus cells and then stimulated with TNF-α (100 ng/ml, 12 h). The apoptosis rates and relative protein expression were then measured again. The target association between miR-660 and SAA1 was confirmed by dual-luciferase reporter.

Results

There was no significant difference between the age (IVDD: 39 ± 10 years, healthy controls: 36 ± 7 years), BMI and sex between IVDD and healthy controls. Microarray analysis found that miR-660 was significantly up-regulated in IVDD and TNF-α treated groups, which was further identified by PCR. We found that the rate of apoptosis and miR-660 expression increased with TNF-α concentration increased. Finally, TNF-a with 100 ng/ml was used for further experiment. Compared with TNF-α group, TNF-α + antigomiR-660 could significantly down-regulated the apoptosis rate and relative protein (c-Caspase3 and c-Caspase7). Dual-luciferase reporter revealed that miR-660 could directly binding to the SAA1 at 80–87 sites. Compared with TNF-α alone group, TNF-α + antigomiR-660 significantly up-regulated the SAA1 expression (P < 0.05).

Conclusion

These results indicated that knockdown of miR-660 protected the nucleus pulposus from apoptosis that induced TNF-α via up-regulation of SAA1. Further studies should focus on the role of miR-660 in protecting IVDD in vivo.

Expression and clinical significance of serum amyloid A and interleukin-6 in patients with acute exacerbation of chronic obstructive pulmonary disease

Expression and clinical significance of serum amyloid A (SAA) and interleukin-6 (IL-6) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) were investigated. Fifty-one patients with AECOPD (acute group, AG) and 51 patients with stable chronic obstructive pulmonary disease (stable group, SG) admitted to Qingdao Eighth People's Hospital were selected. The expression levels of SAA and IL-6 in peripheral blood of patients in the two groups were detected and compared before and after treatment. Pearson analysis was used in the correlation between SAA and IL-6 and Receiver operating characteristic (ROC) curve was employd to analyze the predictive value of SAA and IL-6 for AECOPD progression. Logistic regression analysis was used to analyze the risk factors of AECOPD patients. The expression levels of SAA and IL-6 of patients in AG were significantly higher than those in SG (P<0.05). Pearson analysis showed that SAA was positively correlated with IL-6 expression (P<0.05). ROC curve analysis showed that AUC predicted by SAA and IL-6 for AECOPD progress was 0.789 and 0.762 (P<0.05). Logistic regression analysis showed that SAA and IL-6 were prediction indexes of AECOPD progression. The levels of SAA and IL-6 were significantly increased during AECOPD and effectively predicted the progress of AECOPD and is a risk factor affecting AECOPD patients.

Serum amyloid A levels in patients with liver diseases

BACKGROUND

Serum amyloid A (SAA) is an acute phase protein mainly synthesized by the liver. SAA induces inflammatory phenotype and promotes cell proliferation in activated hepatic stellate cells, the major scar forming cells in the liver. However, few studies have reported on the serum levels of SAA in human liver disease and its clinical significance in various liver diseases.

AIM

To investigate the serum levels of SAA in patients with different liver diseases and analyze the factors associated with the alteration of SAA levels in chronic hepatitis B (CHB) patients.

METHODS

Two hundred and seventy-eight patients with different liver diseases and 117 healthy controls were included in this study. The patients included 205 with CHB, 22 with active autoimmune liver disease (AILD), 21 with nonalcoholic steatohepatitis (NASH), 14 with drug-induced liver injury (DILI), and 16 with pyogenic liver abscess. Serum levels of SAA and other clinical parameters were collected for the analysis of the factors associated with SAA level. Mann-Whitney U test was used to compare the serum SAA levels of patients with various liver diseases with those of healthy controls. Bonferroni test was applied for post hoc comparisons to control the probability of type 1 error (alpha = 0.05/6 = 0.008). For statistical tests of other variables, P < 0.05 was considered statistically significant. Statistically significant factors determined by single factor analysis were further analyzed by binary multivariate logistic regression analysis.

RESULTS

All patients with active liver diseases had higher serum SAA levels than healthy controls and the inactive CHB patients, with the highest SAA level found in patients with pyogenic liver abscess (398.4 ± 246.8 mg/L). Patients with active AILD (19.73 ± 24.81 mg/L) or DILI (8.036 ± 5.685 mg/L) showed higher SAA levels than those with active CHB (6.621 ± 6.776 mg/L) and NASH (6.624 ± 4.891 mg/L). Single (P < 0.001) and multivariate logistic regression analyses (P = 0.039) for the CHB patients suggested that patients with active CHB were associated with an SAA serum level higher than 6.4 mg/L. Serum levels of SAA and CRP (C-reactive protein) were positively correlated in patients with CHB (P < 0.001), pyogenic liver abscess (P = 0.045), and active AILD (P = 0.02). Serum levels of SAA (0.80-871.0 mg/L) had a broader fluctuation range than CRP (0.30-271.3 mg/L).

CONCLUSION

Serum level of SAA is a sensitive biomarker for inflammatory activity of pyogenic liver abscess. It may also be a weak marker reflecting milder inflammatory status in the liver of patients with CHB and other active liver diseases.

Cytokines and serum amyloid A in the pathogenesis of hepatitis C virus infection

Expression of the acute phase protein serum amyloid A (SAA) is dependent on the release of the pro-inflammatory cytokines IL-1, IL-6 and TNF-α during infection and inflammation. Hepatitis C virus (HCV) upregulates SAA-inducing cytokines. In line with this, a segment of chronically infected individuals display increased circulating levels of SAA. SAA has even been proposed to be a potential biomarker to evaluate treatment efficiency and the course of disease. SAA possesses antiviral activity against HCV via direct interaction with the viral particle, but might also divert infectivity through its function as an apolipoprotein. On the other hand, SAA shares inflammatory and angiogenic activity with chemotactic cytokines by activating the G protein-coupled receptor, formyl peptide receptor 2. These latter properties might promote chronic inflammation and hepatic injury. Indeed, up to 80 % of infected individuals develop chronic disease because they cannot completely clear the infection, due to diversion of the immune response. In this review, we summarize the interconnection between SAA and cytokines in the context of HCV infection and highlight the dual role SAA could play in this disease. Nevertheless, more research is needed to establish whether the balance between those opposing activities can be tilted in favor of the host defense.

Hepatocytes prepare the soil for liver metastasis

The liver is the most common organ site of cancer metastasis. Molecular determinants of this organotropism, though, are poorly understood. We recently showed that hepatocytes regulate the formation of a "pro-metastatic" niche in the liver via their release of serum amyloid proteins.

Silencing of SAA1 inhibits palmitate- or high-fat diet induced insulin resistance through suppression of the NF-κB pathway

Background

Obesity is one of the leading causes of insulin resistance. Accumulating reports have highlighted that serum amyloid A-1 (SAA1) is a potential candidate that is capable of attenuating insulin resistance. Hence, we conducted the current study with aims of investigating our proposed hypothesis that silencing SAA1 could inhibit the progression of obesity-induced insulin resistance through the NF-κB pathway.

Methods

Gene expression microarray analysis was initially performed to screen differentially expressed genes (DEGs) associated with obesity. Palmitate (PA)-induced insulin resistance Huh7 cell models and high-fat diet (HFD)-induced mouse models were established to elucidate the effect of SAA1/Saa1 on insulin resistance. The NF-κB pathway-related expression was subsequently determined through the application of reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis.

Results

Saa1 was identified as an obesity-related gene based on the microarray data of GSE39549. Saa1 was determined to be highly expressed in HFD-induced insulin resistance mouse models. PA-induced Huh7 cells, treated with silenced SAA1 or NF-κB pathway inhibition using BAY 11–7082, displayed a marked decrease in both Saa1 and SOCS3 as well as an elevation in 2DG, IRS1 and the extent of IRS1 phosphorylation. HFD mice treated with silenced Saa1 or inhibited NF-κB pathway exhibited improved fasting blood glucose (FBG) levels as well as fasting plasma insulin (FPI) levels, glucose tolerance and systemic insulin sensitivity. Saa1/SAA1 was determined to show a stimulatory effect on the transport of the NF-κBp65 protein from the cytoplasm to the nucleus both in vivo and in vitro, suggesting that Saa1/SAA1 could activate the NF-κB pathway.

Conclusion

Taken together, our key findings highlight a novel mechanism by which silencing of SAA1 hinders PA or HFD-induced insulin resistance through inhibition of the NF-κB pathway.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0075-4) contains supplementary material, which is available to authorized users.

Genetic Predisposition to Hepatocarcinogenesis in Inbred and Outbred Mouse Lines Selected for High or Low Inflammatory Response

AIRmax and AIRmin mouse strains phenotypically selected for high and low acute inflammatory responsiveness (AIR) are, respectively, susceptible or resistant to developing hepatocellular carcinoma (HCC) induced by the chemical carcinogens urethane and diethylnitrosamine (DEN). Early production of TNF-α, IL-1β, and IL-6 in the liver after DEN treatment correlated with tumor development in AIRmax mice. Transcriptome analysis of livers from untreated AIRmax and AIRmin mice showed specific gene expression profiles in each line, which might play a role in their differential susceptibility to HCC. Linkage analysis with SNP markers in F2 (AIRmax×AIRmin) intercross mice revealed two quantitative trait loci (QTL) in chromosomes 2 and 9, which are significantly associated with the number and progression of urethane-induced liver tumors. An independent linkage analysis with an intercross population from A/J and C57BL/6J inbred mice mapped regions in chromosomes 1 and 7 associated with the progression of urethane-induced liver tumors, evidencing the heterogeneity of HCC genetic control.

Adipose-Specific Lipin-1 Overexpression Renders Hepatic Ferroptosis and Exacerbates Alcoholic Steatohepatitis in Mice

Lipin-1 is a Mg²⁺-dependent phosphatidic acid phosphohydrolase involved in the generation of diacylglycerol during synthesis of phospholipids and triglycerides. Ethanol-mediated inhibitory effects on adipose-specific lipin-1 expression were associated with experimental steatohepatitis in rodents. In the present study, using an adipose-specific lipin-1 overexpression transgenic (Lpin1-Tg) mouse model, we tested a hypothesis that adipose-specific lipin-1 overexpression in mice might dampen ethanol-induced liver damage. Experimental alcoholic steatohepatitis was induced by pair-feeding ethanol to Lpin1-Tg and wild-type (WT) mice using the chronic-plus-binge ethanol feeding protocol. Unexpectedly, following the chronic-plus-binge ethanol challenge, Lpin1-Tg mice exhibited much more pronounced steatosis, exacerbated inflammation, augmented elevation of serum liver enzymes, hepatobiliary damage, and fibrogenic responses compared with the WT mice. Mechanistically, overexpression of adipose lipin-1 in mice facilitated the onset of hepatic ferroptosis, which is an iron-dependent form of cell death, and subsequently induced ferroptotic liver damage in mice under ethanol exposure. Concurrently, adipose lipin-1 overexpression induced defective adiponectin signaling pathways in ethanol-fed mice. Conclusion: We identified ferroptosis as a mechanism in mediating the detrimental effects of adipose-specific lipin-1 overexpression in mice under chronic-plus-binge ethanol exposure. Our present study sheds light on potential therapeutic approaches for the prevention and treatment of human alcoholic steatohepatitis.

Acute phase reactant serum amyloid A in inflammation and other diseases

Acute-phase reactant serum amyloid A (A-SAA) plays an important role in acute and chronic inflammation and is used in clinical laboratories as an indicator of inflammation. Although both A-SAA and C-reactive protein (CRP) are acute-phase proteins, the detection of A-SAA is more conclusive than the detection of CRP in patients with viral infections, severe acute pancreatitis, and rejection reactions to kidney transplants. A-SAA has greater clinical diagnostic value in patients who are immunosuppressed, patients with cystic fibrosis who are treated with corticoids, and preterm infants with late-onset sepsis. Nevertheless, for the assessment of the inflammation status and identification of viral infection in other pathologies, such as bacterial infections, the combinatorial use of A-SAA and other acute-phase proteins (APPs), such as CRP and procalcitonin (PCT), can provide more information and sensitivity than the use of any of these proteins alone, and the information generated is important in guiding antibiotic therapy. In addition, A-SAA-associated diseases and the diagnostic value of A-SAA are discussed. However, the relationship between different A-SAA isotypes and their human diseases are mostly derived from research laboratories with limited clinical samples. Thus, further clinical evaluations are necessary to confirm the clinical significance of each A-SAA isotype. Furthermore, the currently available A-SAA assays are based on polyclonal antibodies, which lack isotype specificity and are associated with many inflammatory diseases. Therefore, these assays are usually used in combination with other biomarkers in the clinic.

Extracellular matrix remodeling effects of serum amyloid A1 in the human amnion: Implications for fetal membrane rupture

PROBLEM

Rupture of fetal membranes is a crucial event at parturition, which is preceded by extensive extracellular matrix (ECM) remodeling. Our recent studies have demonstrated that the human fetal membranes are capable of de novo synthesis of serum amyloid A1 (SAA1), an acute phase protein, and the abundance of SAA1 in the amnion was increased at parturition. However, the exact role of SAA1 in human parturition remains to be established.

METHOD OF STUDY

The effects of SAA1 on the abundance of collagenases and lysyl oxidase, the enzyme that cross-links collagens, were investigated in culture primary human amnion fibroblasts and tissue explants with an aim to examine the involvement of SAA1 in the ECM remodeling in the amnion.

RESULTS

Serum amyloid A1 (SAA1) time- and dose-dependently increased the abundance of collagenases MMP-1, MMP-8, and MMP-13, while decreased the abundance of lysyl oxidase-like 1 (LOXL1). These effects of SAA1 were attenuated by siRNA-mediated knockdown of the Toll-like receptor (TLR) 4 and its antagonist CLI-095, but not by siRNA-mediated knockdown of TLR2. Furthermore, the inhibitors for NF-κB (JSH-23) and mitogen-activated protein kinases (MAPKs) p38 (SB203580) and JNK (SP600125) could also attenuate the effects of SAA1, while the inhibitor for MAPK ERK1/2 (PD 98059) could block the effects of SAA1 only on MMP-1, MMP-8, and LOXL1 but not on MMP-13.

CONCLUSION

These data highlight a possible role for SAA1 in ECM remodeling preceding membrane rupture by regulating the expression of collagenases MMP-1, MMP-8, MMP-13, and LOXL1 through TLR4-mediated activation of the NF-κB and MAPK pathways in amnion fibroblasts.

The ectoenzyme-side of matrix metalloproteinases (MMPs) makes inflammation by serum amyloid A (SAA) and chemokines go round

During an inflammatory response, a large number of distinct mediators appears in the affected tissues or in the blood circulation. These include acute phase proteins such as serum amyloid A (SAA), cytokines and chemokines and proteolytic enzymes. Although these molecules are generated within a cascade sequence in specific body compartments allowing for independent action, their co-appearance in space and time during acute or chronic inflammation points toward important mutual interactions. Pathogen-associated molecular patterns lead to fast induction of the pro-inflammatory endogenous pyrogens, which are evoking the acute phase response. Interleukin-1, tumor necrosis factor-α and interferons simultaneously trigger different cell types, including leukocytes, endothelial cells and fibroblasts for tissue-specific or systemic production of chemokines and matrix metalloproteinases (MMPs). In addition, SAA induces chemokines and both stimulate secretion of MMPs from multiple cell types. As a consequence, these mediators may cooperate to enhance the inflammatory response. Indeed, SAA synergizes with chemokines to increase chemoattraction of monocytes and granulocytes. On the other hand, MMPs post-translationally modify chemokines and SAA to reduce their activity. Indeed, MMPs internally cleave SAA with loss of its cytokine-inducing and direct chemotactic potential whilst retaining its capacity to synergize with chemokines in leukocyte migration. Finally, MMPs truncate chemokines at their NH₂- or COOH-terminal end, resulting in reduced or enhanced chemotactic activity. Therefore, the complex interactions between chemokines, SAA and MMPs either maintain or dampen the inflammatory response.

Saa3 is a key mediator of the protumorigenic properties of cancer-associated fibroblasts in pancreatic tumors

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the presence of abundant desmoplastic stroma primarily composed of cancer-associated fibroblasts (CAFs). It is generally accepted that CAFs stimulate tumor progression and might be implicated in drug resistance and immunosuppression. Here, we have compared the transcriptional profile of PDGFRα⁺ CAFs isolated from genetically engineered mouse PDAC tumors with that of normal pancreatic fibroblasts to identify genes potentially implicated in their protumorigenic properties. We report that the most differentially expressed gene, Saa3, a member of the serum amyloid A (SAA) apolipoprotein family, is a key mediator of the protumorigenic activity of PDGFRα⁺ CAFs. Whereas Saa3-competent CAFs stimulate the growth of tumor cells in an orthotopic model, Saa3-null CAFs inhibit tumor growth. Saa3 also plays a role in the cross talk between CAFs and tumor cells. Ablation of Saa3 in pancreatic tumor cells makes them insensitive to the inhibitory effect of Saa3-null CAFs. As a consequence, germline ablation of Saa3 does not prevent PDAC development in mice. The protumorigenic activity of Saa3 in CAFs is mediated by Mpp6, a member of the palmitoylated membrane protein subfamily of the peripheral membrane-associated guanylate kinases (MAGUK). Finally, we interrogated whether these observations could be translated to a human scenario. Indeed, SAA1, the ortholog of murine Saa3, is overexpressed in human CAFs. Moreover, high levels of SAA1 in the stromal component correlate with worse survival. These findings support the concept that selective inhibition of SAA1 in CAFs may provide potential therapeutic benefit to PDAC patients.

Serum amyloid a induces M2b-like macrophage polarization during liver inflammation

Hepatitis causes hepatic cell injury, regeneration and different levels of fibrogenesis, and severe liver fibrogenesis progresses into cirrhosis with liver dysfunction. Serum amyloid A (SAA) is an acute phase protein that is predominantly secreted by hepatocytes during early injury or infection. Nevertheless, the relationship of SAA and development of cirrhosis as well as the underlying molecular mechanisms is largely unknown. Here, we found that macrophages are the major SAA-binding cells in the injured liver. in vitro, macrophages treated with SAA exhibited high production of IL-10 but low production of IL-12, as features for M2 macrophages. Moreover, these polarized M2 macrophages by SAA also produced IL-1, IL-6 and TNFa, characteristics for an M2b subtype, rather than an alternative M2a or fibrogenic M2c subtype. In a mouse model of carbon tetrachloride (CCl4)-induced hepatic fibrogenesis/cirrhosis, anti-SAA sera were used to block the effects of SAA, resulting in increases in the severity of hepatic fibrosis, suggesting an overall anti-fibrogenic effect of SAA. Isolated macrophages from mouse liver showed that anti-SAA appeared to alter the polarization of macrophages from M2b to M2c, suggesting that SAA may induce M2b-like macrophage polarization during liver inflammation, which prevents the liver from fibrogenesis.

Hepatitis C virus-induced CCL5 secretion from macrophages activates hepatic stellate cells

Hepatitis C virus (HCV)-mediated chronic liver disease is a serious health problem around the world and often causes fibrosis/cirrhosis and hepatocellular carcinoma. The mechanism of liver disease progression during HCV infection is still unclear, although inflammation is believed to be an important player in disease pathogenesis. We previously reported that macrophages including Kupffer cells exposed to HCV induce proinflammatory cytokines. These secreted cytokines may activate hepatic stellate cells (HSCs) toward fibrosis. In this study, we examined crosstalk between macrophages and HSCs following HCV infection. Primary human HSCs and immortalized HSCs (LX2 cells) were incubated with conditioned medium derived from HCV-exposed human macrophages. Expression of inflammasome and fibrosis-related genes in these cells was examined, with increased expression of inflammatory (NLR family pyrin domain containing 3, interleukins 1β and 6, and cysteine-cysteine chemokine ligand 5 [CCL5]) and profibrogenic (transforming growth factor β1, collagen type 4 alpha 1, matrix metalloproteinase 2, and alpha-smooth muscle actin) markers. Further investigation suggested that CCL5, secreted from HCV-exposed macrophages, activates inflammasome and fibrosis markers in HSCs and that neutralizing antibody to CCL5 inhibited activation.

CONCLUSION

Together, our results demonstrate that human macrophages exposed to HCV induce CCL5 secretion, which plays a significant role in hepatic inflammation and fibrosis. (Hepatology 2017;66:746-757).

Vagus Nerve Attenuates Hepatocyte Apoptosis upon Ischemia-Reperfusion via α7 Nicotinic Acetylcholine Receptor on Kupffer Cells in Mice

BACKGROUND

Hepatic ischemia-reperfusion (HIR) injury is a complication of liver surgery. As much as 50% of hepatocytes undergo apoptosis within the first 24 h of reperfusion. The neurotransmitters of the vagus nerve can activate α7 nicotinic acetylcholine receptor (α7nAChR) on macrophages. The function of Kupffer cells (KCs) determines HIR injury. We hypothesize that the vagus nerve could attenuate HIR-induced hepatocyte apoptosis by activating α7nAChR on KCs.

METHODS

Hepatic vagotomized C57BL/6J mice, KC-eliminated C57BL/6J mice, and α7nAChR mice were used for HIR. Primary KCs and hepatocytes were subjected to hypoxia/reoxygenation (HR). Liver injury, hepatocyte apoptosis, reactive oxygen species (ROS) production, and soluble CD163 were measured.

RESULTS

Hepatic vagotomy and α7nAChR caused higher levels of alanine transaminase and liver caspase-3 and -8 activity by HIR. Activating α7nAChR attenuated these changes in wild-type but not in the α7nAChR mice. Furthermore, activating α7nAChR diminished hepatic injury and reduced liver apoptosis by HIR in vagotomized mice. In vitro, activating α7nAChR reduced apoptosis of hepatocytes cocultured with KCs that suffered HR. Similar to the effects by catalase, activating α7nAChR on KCs reduced ROS and H2O2 by HR. The supernatant from KCs, with α7nAChR activated or catalase treated, prevented hepatocyte apoptosis by HR. Finally, KC elimination reduced HIR-induced H2O2 production in mice. Activating α7nAChR significantly attenuated soluble CD163 both in mice by HIR (serum: 240 ± 34 vs. 446 ± 72; mean ± SD; n = 8; P < 0.01) and in KCs by HR (supernatant: 4.23 ± 0.06 vs. 5.60 ± 0.18; n = 3; P < 0.01).

CONCLUSIONS

The vagus nerve could minimize HIR-induced liver apoptosis through activating α7nAChR on KCs possibly by preventing their excessive ROS production.

Serum Amyloid A Induces a Vascular Smooth Muscle Cell Phenotype Switch through the p38 MAPK Signaling Pathway

Atherosclerosis is an important pathological condition which is accompanied by a vascular smooth muscle cell (VSMC) phenotype switch toward a synthetic phenotype. As an acute-phase protein, Serum Amyloid A (SAA) is thought to have a close relationship to atherosclerosis development. However, no study has investigated the direct effect of SAA on the VSMC phenotype switch, as well as the underlying mechanisms. The purpose of our study was to explore the effect of SAA on the VSMC phenotype switch and the potential mechanisms involved. In our study, we found that SAA induced the VSMC phenotype switch which reduced expression of the smooth muscle cell (SMC) marker and enhanced expression of the matrix synthesis related marker. The proliferative ability of VSMCs was also increased by SAA treatment. Furthermore, our research found that SAA activated the ERK1/2 and p38 MAPK signaling pathways. Finally, by applying the ERK1/2 and p38 inhibitors, U0126 and SB203580, we demonstrated that the SAA-induced VSMC phenotype switch was p38-dependent. Taken together, these results indicated that SAA may play an important role in promoting the VSMC phenotype switch through the p38 MAPK signaling pathway.

Induction of pro-inflammatory genes by serum amyloid A1 in human amnion fibroblasts

Serum amyloid A1 (SAA1) is an acute response protein, which is mainly produced by the liver, during infection. However, it remains unknown whether SAA1 can be produced in human fetal membranes where it is able to elicit events pertinent to labor initiation. We demonstrated that SAA1 was expressed in the fibroblasts and epithelium of the amnion and the trophoblasts of the chorion. Further study in human amnion fibroblasts showed that SAA1 production was augmented by interleukin-1β (IL-1β) and cortisol alone and synergistically, and SAA1 in turn induced the expression of IL-1β, interleukin-6 (IL-6), cyclooxygenase-2 (COX-2) and PGE2 production. These effects of SAA1 were mediated through activation of the NF-κB, p38 and ERK1/2 pathways via the toll-like receptor 4 (TLR4). Inhibition of TLR4 attenuated not only SAA1-induced activation of NF-κB, p38 and ERK1/2 but also increases in IL-1β, IL-6 and COX-2 expression. Moreover, SAA1 expression was increased in human amnion tissue following spontaneous labor. In conclusion, this study has demonstrated for the first time that SAA1 can be produced in human fetal membranes, which can be greatly induced in the presence of proinflammatory cytokines and glucocorticoids thereby producing effects associated with parturition.

iTRAQ-based quantitative proteomics reveals important host factors involved in the high pathogenicity of the H5N1 avian influenza virus in mice

We previously reported a pair of H5N1 avian influenza viruses which are genetically similar but differ greatly in their virulence in mice. A/Chicken/Jiangsu/k0402/2010 (CK10) is highly lethal to mice, whereas A/Goose/Jiangsu/k0403/2010 (GS10) is avirulent. In this study, to investigate the host factors that account for their virulence discrepancy, we compared the pathology and host proteome of the CK10- or GS10-infected mouse lung. Moderate lung injury was observed from CK10-infected animals as early as the first day of infection, and the pathology steadily progressed at later time point. However, only mild lesions were observed in GS10-infected mouse lung at the late infection stage. Using the quantitative iTRAQ coupled LC-MS/MS method, we first found that more significantly differentially expressed (DE) proteins were stimulated by GS10 compared with CK10. However, bio-function analysis of the DE proteins suggested that CK10 induced much stronger inflammatory response-related functions than GS10. Canonical pathway analysis also demonstrated that CK10 highly activated the "Acute Phase Response Signaling," which results in a wide range of biological activities in response to viral infection, including many inflammatory processes. Further in-depth analysis showed that CK10 exacerbated acute lung injury-associated responses, including inflammatory response, cell death, reactive oxygen species production and complement response. In addition, some of these identified proteins that associated with the lung injury were further confirmed to be regulated in vitro. Therefore, our findings suggest that the early increased lung injury-associated host response induced by CK10 may contribute to the lung pathology and the high virulence of this virus in mice.

Serum amyloid A, an acute phase protein, stimulates proliferative and proinflammatory responses of keratinocytes

OBJECTIVES

Serum amyloid A (SAA), an acute phase protein, is highly expressed in psoriatic lesions but its function is not fully understood. The aim of this study was to explore its role in activation of keratinocytes.

MATERIALS AND METHODS

Real-time PCR and immunofluorescence were performed to examine SAA expression in imiquimod (IMQ)-induced psoriasis-like mice. In vivo function of SAA was examined by treating psoriasis-like mice with SAA neutralising antibody. Cell viability was monitored using the CCK-8 assay. Real-time PCR was performed to determine expression of genes associated with differentiation and inflammation. Ki67⁺ percentage and immunological markers were analysed by flow cytometry. Involvement of formyl peptide receptor-like 1 (FPRL1) in SAA signal transduction was determined by RNA interference. Binding of SAA and FPRL1 was examined by co-immunoprecipitaion. Western blotting was conducted to assess phosphorylation of downstream signalling molecules.

RESULTS

SAA was highly expressed in skin lesions of IMQ-treated psoriasis-like mice and neutralising SAA attenuated epidermal hyperplasia and inflammation. SAA in vitro promoted keratinocyte proliferation and expression of immunological mediators, while inhibiting differentiation. Effects of SAA on keratinocyte proliferation and inflammation were mediated by FPRL1, as well as activation of the PI3K/Akt pathway.

CONCLUSIONS

These observations indicate that SAA/FPRL1 contributed to pathogenesis of psoriasis by promoting keratinocyte proliferation and inflammation, thus providing a potential therapeutic target for disease therapy.

Human hepatic stellate cells and inflammation: A regulated cytokine network balance

AIM

Uncertainty about the safety of cell therapy continues to be a major challenge to the medical community. Inflammation and the associated immune response represent a major safety concern hampering the development of long-term clinical therapy. In vivo interactions between the cell graft and the host immune system are mediated by functional environmental sensors and stressors that play significant roles in the immunobiology of the graft. Within this context, human liver stellate cells (HSC) demonstrated marked immunological plasticity that has main importance for future liver cell therapy application.

METHODS

By using qPCR technique, we established the cytokine gene expression profile of HSCs and investigated the effect of an inflammatory environment on the immunobiology of HSCs.

RESULTS AND DISCUSSION

HSCs present a specific immunological profile as demonstrated by the expression and modulation of major immunological cytokines. Under constitutive conditions, the cytokine pattern expressed by HSCs was characterized by the high expression of IL-6. Inflammation critically modulated the expression of major immunological cytokines. As evidenced by the induction of the expression of several inflammatory genes, HSCs acquire a pro-inflammatory profile that ultimately might have critical implications for their immunological shape.

CONCLUSION

These new observations have to be taken into account in any future liver cell therapy application based on the use of HSCs.

STAT3 Inhibition Suppresses Hepatic Stellate Cell Fibrogenesis: HJC0123, a Potential Therapeutic Agent for Liver Fibrosis

Hepatic Stellate Cells (HSCs) are the major source of the excessive extracellular matrix (ECM) production that replaces liver parenchyma with fibrous tissue during liver fibrosis. The signal transducer and activator of transcription 3 (STAT3) promotes HCSs survival, proliferation, and activation contributing to fibrogenesis. We have previously used a fragment-based drug design approach and have discovered a novel STAT3 inhibitor, HJC0123. Here, we explored the biological effects of HJC0123 on the fibrogenic properties of HSCs. HJC0123 treatment resulted in the inhibition of HSCs proliferation at submicromolar concentrations. HJC0123 reduced the phosphorylation, nuclear translocation, and transcriptional activity of STAT3. It decreased the expression of STAT3-regulated proteins, induced cell cycle arrest, promoted apoptosis and downregulated SOCS3. HJC0123 treatment inhibited HSCs activation and downregulated ECM protein fibronectin and type I collagen expression. In addition, HJC0123 increased IL-6 production and decreased TGF-β induced Smad2/3 phosphorylation. These results demonstrate that HJC0123 represents a novel STAT3 inhibitor that suppresses the fibrogenic properties of HSCs, suggesting its therapeutic potential in liver fibrosis.