Complement activation correlates with liver necrosis and fibrosis in chronic hepatitis C

Pathophysiological Mechanisms of Peritoneal Fibrosis and Peritoneal Membrane Dysfunction in Peritoneal Dialysis

The characteristic feature of chronic peritoneal damage in peritoneal dialysis (PD) is a decline in ultrafiltration capacity associated with pathological fibrosis and angiogenesis. The pathogenesis of peritoneal fibrosis is attributed to bioincompatible factors of PD fluid and peritonitis. Uremia is associated with peritoneal membrane inflammation that affects fibrosis, neoangiogenesis, and baseline peritoneal membrane function. Net ultrafiltration volume is affected by capillary surface area, vasculopathy, peritoneal fibrosis, and lymphangiogenesis. Many inflammatory cytokines induce fibrogenic growth factors, with crosstalk between macrophages and fibroblasts. Transforming growth factor (TGF)-β and vascular endothelial growth factor (VEGF)-A are the key mediators of fibrosis and angiogenesis, respectively. Bioincompatible factors of PD fluid upregulate TGF-β expression by mesothelial cells that contributes to the development of fibrosis. Angiogenesis and lymphangiogenesis can progress during fibrosis via TGF-β-VEGF-A/C pathways. Complement activation occurs in fungal peritonitis and progresses insidiously during PD. Analyses of the human peritoneal membrane have clarified the mechanisms by which encapsulating peritoneal sclerosis develops. Different effects of dialysates on the peritoneal membrane were also recognized, particularly in terms of vascular damage. Understanding the pathophysiologies of the peritoneal membrane will lead to preservation of peritoneal membrane function and improvements in technical survival, mortality, and quality of life for PD patients.

Blockade of C5aR1 alleviates liver inflammation and fibrosis in a mouse model of NASH by regulating TLR4 signaling and macrophage polarization

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is an advanced form of chronic fatty liver disease, which is a driver of hepatocellular carcinoma. However, the roles of the C5aR1 in the NASH remain poorly understood. Here, we aimed to investigate the functions and mechanisms of the C5aR1 on hepatic inflammation and fibrosis in murine NASH model.

METHODS

Mice were fed a normal chow diet with corn oil (ND + Oil), a Western diet with corn oil (WD + Oil) or a Western diet with carbon tetrachloride (WD + CCl4) for 12 weeks. The effects of the C5a-C5aR1 axis on the progression of NASH were analyzed and the underlying mechanisms were explored.

RESULTS

Complement factor C5a was elevated in NASH mice. C5 deficiency reduced hepatic lipid droplet accumulation in the NASH mice. The hepatic expression levels of TNFα, IL-1β and F4/80 were decreased in C5-deficient mice. C5 loss alleviated hepatic fibrosis and downregulated the expression levels of α-SMA and TGFβ1. C5aR1 deletion reduced inflammation and fibrosis in NASH mice. Transcriptional profiling of liver tissues and KEGG pathway analysis revealed that several pathways such as Toll-like receptor signaling, NFκB signaling, TNF signaling, and NOD-like receptor signaling pathway were enriched between C5aR1 deficiency and wild-type mice. Mechanistically, C5aR1 deletion decreased the expression of TLR4 and NLRP3, subsequently regulating macrophage polarization. Moreover, C5aR1 antagonist PMX-53 treatment mitigated the progression of NASH in mice.

CONCLUSIONS

Blockade of the C5a-C5aR1 axis reduces hepatic steatosis, inflammation, and fibrosis in NASH mice. Our data suggest that C5aR1 may be a potential target for drug development and therapeutic intervention of NASH.

The complement system testing in clinical laboratory

With the advancement in research in the field of the complement system, a more comprehensive understanding developed about the complement system's role in the life process of an organism. It is a system of innate immune surveillance. This system plays a pivotal role in host defense against pathogens, inflammation, B and T cell homeostasis. Complement system analysis has a significant advantage in the assessment of the immune system status, diagnosis and prognosis of diseases, and medication guidelines. Currently, complement system testing is neither yet widely used across all clinical laboratoriesnor are the testing protocols yet systematic. Based on the current research, it is suggested that the analysis of complement activator-activated complement activity and total complement activity would be comprehensively assessed to evaluate the complement system's immunological function, and combine of the detection of its components to establish a systematic protocol for the complement system testing in the clinical laboratory. This article reviews the complement system's physiological role, disease relevance and the current testing status in clinical laboratories. Further more, some suggestions have also been provided for the preparation of complement standards i.e., the standardized preparation process for complement standards seems to be a feasible option given the easy inactivation of complement.

Selective decrease in complement C2 hemolytic activity is a sensitive marker for cryoglobulinemia and active disease in hepatitis C patients

BACKGROUND

Some HCV patients present low/non-detected C2 hemolytic activity (C2h) without apparent consumption of other Complement components (selective low/non-detected C2h).

AIM

Characterization of the immunologic/clinical basis of this phenomenon.

METHODS

C2h, HCV-viral load, cryoglobulinemia and Complement components were determined in 726 HCV patients, with sequential C2h determination in 189 patients.

RESULTS

C2h was non-detected in 15.9%, low in 16.9% and normal in 67.2% subjects and showed temporal oscillation in 30.7% of patients. Samples with selective non-detected C2h presented lower C3/C4 than those with normal C2h, but still within the normal C3/C4 range. Selective non-detected C2h was associated with higher aspartate aminotransferase (AST) (p<0.001), alanine transferase (ALT) (p = 0.03) and APRI (Aspartate aminotransferase-to-Platelet Ratio Index) (p<0.001), lower serum albumin (p = 0.01) and platelet count (p = 0.012), more individuals at pre-treatment stage, with detectable HCV-RNA p<0.001), cryoglobulinemia (p<0.001) and with HCV genotype 3 (p = 0.003). Elevated ALT, HCV genotype 3, active disease and viral load were independent predictors of low/non-detected C2h. In vitro exposure of normal serum to exogenous HCV cryoglobulins caused dose-dependent decrease in C2h.

CONCLUSIONS

Selective C2h decrease is a sensitive marker of Complement activation in HCV patients and is associated with cryoglobulinemia, active disease, elevated ALT, higher viral load, and HCV genotype 3.

[Corneal wound healing-Pathophysiology and principles]

The cornea forms the anterior border of the eye and significantly contributes to a sharp optical image quality on the retina through its transparency, avascular nature and curvature. Because of its anatomical structure and as a barrier to the environment, the cornea is particularly exposed to various external factors, such as injuries and pathogens. A correct wound healing without the formation of light diverging scarring is therefore essential to preserve the integrity and function of the cornea. Misguided wound healing is of outstanding clinical relevance and can lead to corneal fibrogenesis. Corneal fibrosis results in scarring with a loss of optical transparency, which significantly reduces eyesight and can lead to blindness. Understanding the pathophysiological mechanisms of wound healing and fibrogenesis is of great importance for the diagnostics, treatment and evaluation of the subsequent healing process in order to prevent permanent damage as far as possible.

A model incorporating serum C3 complement levels may be useful for diagnosing biliary atresia in infants

INTRODUCTION

Correctly identifying patients with biliary atresia (BA), while avoiding invasive diagnostic methods is challenging. The purpose of this study was to determine the value of serum immune indicators for distinguishing BA from other causes of cholestasis in infants.

PATIENTS AND METHODS

The data of infants with a surgical/histological diagnosis of BA and those with other causes of cholestatic jaundice were retrospectively analyzed. Patients were divided into a BA group and a cholestasis control (CC) group. Biochemical parameters, major lymphocyte subsets, immunoglobin and C3 and C4 complement levels were compared between the groups.

RESULTS

A total of 129 infants with BA and 63 with other causes of cholestasis (CC control group) with a median age of 2.2 months were included in the analysis. The levels of CD3⁺ T cells, CD3⁺CD4⁺ T cells, and premature T cells and the levels of C3 and C4 were all significantly higher in the BA group compared to the CC group (all P<0.05). Pair-wise correlation analyses indicated that C3 and C4 had a significant positive correlation with γ-GT in the BA group, but not in the CC group. Five indices were found to be significantly associated with BA: stool color, globulin, γ-GT, C3 and C4. A model incorporating stool color, gamma-glutamyl transpeptidase level, and C3 level exhibited an area under the ROC curve (AUC) of 0.93, and a sensitivity of 93% and specificity of 83% for the diagnosis of BA.

CONCLUSIONS

Models incorporating serum C3 levels may be useful for accurately diagnosing BA in infants.

Molecular Crosstalk between the Hepatitis C Virus and the Extracellular Matrix in Liver Fibrogenesis and Early Carcinogenesis

Simple Summary

In the era of direct-acting antivirals against the hepatitis C virus (HCV), curing chronic hepatitis C has become a reality. However, while replicating chronically, HCV creates a peculiar state of inflammation and oxidative stress in the infected liver, which fuels DNA damage at the onset of HCV-induced hepatocellular carcinoma (HCC). This cancer, the second leading cause of death by cancer, remains of bad prognosis when diagnosed. This review aims to decipher how HCV durably alters elements of the extracellular matrix that compose the liver microenvironment, directly through its viral proteins or indirectly through the induction of cytokine secretion, thereby leading to liver fibrosis, cirrhosis, and, ultimately, HCC.

Abstract

Chronic infection by the hepatitis C virus (HCV) is a major cause of liver diseases, predisposing to fibrosis and hepatocellular carcinoma. Liver fibrosis is characterized by an overly abundant accumulation of components of the hepatic extracellular matrix, such as collagen and elastin, with consequences on the properties of this microenvironment and cancer initiation and growth. This review will provide an update on mechanistic concepts of HCV-related liver fibrosis/cirrhosis and early stages of carcinogenesis, with a dissection of the molecular details of the crosstalk during disease progression between hepatocytes, the extracellular matrix, and hepatic stellate cells.

Associations of ambient fine particulate matter and its constituents with serum complement C3 in a panel study of older adults in China

Epidemiological studies have demonstrated association between the total mass of fine particulate matter (PM_2.5) exposures and inflammation. There are few studies exploring the associations between PM_2.5 constituents and the biomarkers of inflammation in older adults and the underlying biological mechanisms are not exact. In this study, we examined the associations between PM_2.5 and its constituents (organic carbon (OC), elemental carbon (EC), total carbon (TC), polycyclic aromatic hydrocarbons (PAHs) and complement three factor (C3), an important biomarker of inflammation in a repeated panel of 175 older adults in Beijing, China. We have constructed three different linear mixed effect models (single-pollutant model, constituent-PM_2.5 joint model, and constituent-residual model) to evaluate the association of PM_2.5 and its constituents and complement C3, controlling for concentration of high sensitive C-reactive protein (hs-CRP), day of week, mean temperature, relative humidity, location and potential individual confounders. We found robust positive associations of OC, EC, TC, PAHs and PM_2.5 mass concentration with complement C3 at different lag patterns. The cumulative effects of pollutants increased across average of 2-5 days. Individuals aged 65 and above, or with diabetes, or BMI ≥30, or with no-cardiopathy, or with hypertension also exhibited positive associations between PM_2.5 and complement C3. The results revealed that short-term exposure to PM_2.5 and its constituents could result in a significant increase in serum level of complement C3. These findings suggested a possible involvement of complement C3 in the effect of PM_2.5 on inflammatory reaction.

Two sides of a coin: GG genotype of C7 provides protection against fibrosis severity while showing a higher risk for hepatocellular carcinoma in patients with hepatitis C

The complement system (CS) is a key element of immunity against pathogens but also seems to influence other events, such as tumorigenesis and tissue repair. Complement component 7 (C7) is a key component of the lytic pathway of CS, leading to the formation of the membrane attack complex (MAC). This study aimed to investigate the existence of the association of a polymorphism in the C7 gene, rs1063499, with hepatic fibrosis and the occurrence of hepatocellular carcinoma (HCC) in patients with hepatitis C. We analyzed 456 samples from patients with chronic hepatitis C. Real-time PCR was used for allelic discrimination. Patients were classified by their METAVIR score as F1 (n = 100), F2 (n = 83), F3 (n = 101) or F4 (n = 66); 106 patients were diagnosed with HCC. Patients carrying the G/G genotype of C7 had a lower chance of developing severe fibrosis in the recessive model (p = 0.042; OR: 0.65 95% CI 0.41-1.02). However, the G/G genotype frequency was higher in patients with HCC (P = 0.01; OR: 2.07 95% CI 1.20-3.53) and in those with larger tumors (p = 0.04). The G/G C7 genotype seems to be a protective factor against advanced fibrosis; however, it was associated with a higher risk of HCC and the occurrence of larger hepatic nodules, suggesting the involvement of C7 in the physiopathogenesis of HCC and fibrosis in patients with hepatitis C virus (HCV).

The Complement System and C1q in Chronic Hepatitis C Virus Infection and Mixed Cryoglobulinemia

The complement system bridges innate and adaptive immunity against microbial infections, with viral infection being a major trigger. Activation of the classical, alternative, and lectin pathways have been reported in chronic hepatitis C virus (HCV) infection and/or cryoglobulinemia. HCV infection leads to dysregulation of complement-mediated immune responses. Clinical and experimental evidence support involvement of complement in intra- and extrahepatic manifestations of HCV infection, such as liver fibrosis and type II cryoglobulinemia. In this review, we summarize studies that have investigated the interplay between HCV and the complement system to establish chronic infection and autoimmunity, as well as the association between HCV pathogenesis and abnormal complement profiles. Several unanswered questions are highlighted which suggest additional informative lines of investigation.

An integrative analysis of chemically-induced cirrhosis-associated hepatocarcinogenesis: Histological, biochemical and molecular features

This study aimed the integrative characterization of morphological, biochemical and molecular features of chemically-induced cirrhosis-associated hepatocarcinogenesis. Thus, male Wistar rats were submitted to a diethylnitrosamine (DEN)/thioacetamide (TAA)-induced model. Liver tissue was processed for global gene expression, histopathological and collagen evaluations; as well as immunohistochemical and oxidative stress analysis. Gene Ontology and functional analysis showed the upregulation of extracellular matrix deposition genes, such as collagen type I alpha 1 and 2 (Col1α1 and Col1α2) and tissue inhibitor of metalloproteinase 1 and 2 genes (Timp1 and Timp2). In agreement these findings, animals presented extensive liver cirrhosis with increased collagen deposition (Sirius red). Besides, the animals developed many glutathione S-transferase pi (GST-P)-positive preneoplastic lesions showing high cell proliferation (Ki-67), in keeping with the Gstp1 and Gstp2 increased gene expression. DEN/TAA-treated rats also showed the upregulation of tumorigenesis-related annexin A2 gene (Anxa2) and few neoplastic lesions (hepatocellular adenomas, carcinomas, and cholangiocarcinoma). In contrast, gene expression and activity of antioxidant enzymes were decreased (glutathione peroxidase, total glutathione-S-transferase, and catalase). The model featured remarkable similarities to human hepatocarcinogenesis. Our findings could bring up new molecular insights into cirrhosis-associated hepatocarcinogenesis, and provide a suitable animal model for the establishment of further diagnostic, preventive and therapeutic approaches.

Dectin-1 Regulates Hepatic Fibrosis and Hepatocarcinogenesis by Suppressing TLR4 Signaling Pathways

Dectin-1 is a C-type lectin receptor critical in anti-fungal immunity, but Dectin-1 has not been linked to regulation of sterile inflammation or oncogenesis. We found that Dectin-1 expression is upregulated in hepatic fibrosis and liver cancer. However, Dectin-1 deletion exacerbates liver fibro-inflammatory disease and accelerates hepatocarcinogenesis. Mechanistically, we found that Dectin-1 protects against chronic liver disease by suppressing TLR4 signaling in hepatic inflammatory and stellate cells. Accordingly, Dectin-1(-/-) mice exhibited augmented cytokine production and reduced survival in lipopolysaccharide (LPS)-mediated sepsis, whereas Dectin-1 activation was protective. We showed that Dectin-1 inhibits TLR4 signaling by mitigating TLR4 and CD14 expression, which are regulated by Dectin-1-dependent macrophage colony stimulating factor (M-CSF) expression. Our study suggests that Dectin-1 is an attractive target for experimental therapeutics in hepatic fibrosis and neoplastic transformation. More broadly, our work deciphers critical cross-talk between pattern recognition receptors and implicates a role for Dectin-1 in suppression of sterile inflammation, inflammation-induced oncogenesis, and LPS-mediated sepsis.

Complement activation is involved in the hepatic injury caused by high-dose exposure of mice to perfluorooctanoic acid

High-dose exposure of mice to perfluorooctanoate (PFOA) induces both hepatotoxicity and immunotoxicity. Here, we characterized the effects of 10-day dietary treatment with PFOA (0.002-0.02%, w/w) on the liver and complement system of male C57BL/6 mice. At all four doses, this compound caused hepatomegaly and reduced the serum level of triglycerides (an indicator for activation of the peroxisome proliferator-activated receptor-alpha (PPARα)). At the highest dose (0.02%, w/w), this hepatomegaly was associated with the hepatic injury, as reflected in increased activity of alanine aminotranferase (ALAT) in the serum, severe hepatocyte hypertrophy and hepatocellular necrosis. PFOA-induced hepatic injury was associated with in vivo activation of the complement system as indicated by (i) significant attenuation of the serum activities of both the classical and alternative pathways; (ii) a marked reduction in the serum level of the complement factor C3; and (iii) deposition of the complement factor C3 fragment (C3a) in the hepatic parenchyma. PFOA did not activate the alternative pathway of complement in vitro. At doses lower than 0.02%, PFOA induced hepatocyte hypertrophy without causing liver injury or activating complement. These results reveal substantial involvement of activation of complement in the pathogenesis of PFOA-induced hepatotoxicity.

The role of complement in the pathogenesis of renal ischemia-reperfusion injury and fibrosis

The complement system is a major component of innate immunity and has been commonly identified as a central element in host defense, clearance of immune complexes, and tissue homeostasis. After ischemia-reperfusion injury (IRI), the complement system is activated by endogenous ligands that trigger proteolytic cleavage of complement components via the classical, lectin and/or alternative pathway. The result is the formation of terminal complement components C3a, C5a, and the membrane attack complex (C5b-9 or MAC), all of which play pivotal roles in the amplification of the inflammatory response, chemotaxis, neutrophil/monocyte recruitment and activation, and direct tubular cell injury. However, recent evidence suggests that complement activity transcends innate host defense and there is increasing data suggesting complement as a regulator in processes such as allo-immunity, stem cell differentiation, tissue repair, and progression to fibrosis. In this review, we discuss recent advances addressing the role of complement as a regulator of IRI and renal fibrosis after organ donation for transplantation. We will also briefly discuss currently approved therapies that target complement activity in kidney ischemia-reperfusion and transplantation.

The role of complement in the pathogenesis of renal ischemia-reperfusion injury and fibrosis

The complement system is a major component of innate immunity and has been commonly identified as a central element in host defense, clearance of immune complexes, and tissue homeostasis. After ischemia-reperfusion injury (IRI), the complement system is activated by endogenous ligands that trigger proteolytic cleavage of complement components via the classical, lectin and/or alternative pathway. The result is the formation of terminal complement components C3a, C5a, and the membrane attack complex (C5b-9 or MAC), all of which play pivotal roles in the amplification of the inflammatory response, chemotaxis, neutrophil/monocyte recruitment and activation, and direct tubular cell injury. However, recent evidence suggests that complement activity transcends innate host defense and there is increasing data suggesting complement as a regulator in processes such as allo-immunity, stem cell differentiation, tissue repair, and progression to fibrosis. In this review, we discuss recent advances addressing the role of complement as a regulator of IRI and renal fibrosis after organ donation for transplantation. We will also briefly discuss currently approved therapies that target complement activity in kidney ischemia-reperfusion and transplantation.