The BAFFling problem of B cell-activating factor in nonalcoholic fatty liver disease

Role of B Lymphocytes in the Pathogenesis of NAFLD: A 2022 Update

Non-alcoholic fatty liver disease and its related complications are becoming one of the most important health problems globally. The liver functions as both a metabolic and an immune organ. The crosstalk between hepatocytes and intrahepatic immune cells plays a key role in coordinating a dual function of the liver in terms of the protection of the host from antigenic overload as a result of receiving nutrients and gut microbiota antigenic stimulation via facilitating immunologic tolerance. B cells are the most abundant lymphocytes in the liver. The crucial role of intrahepatic B cells in energy metabolism under different immune conditions is now emerging in the literature. The accumulating evidence has demonstrated that the antibodies and cytokines produced by B cells in the microenvironment play key and distinct roles in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Herein, we have aimed to consolidate and update the current knowledge about the pathophysiological roles of B cells as well as the underlying mechanisms in energy metabolism. Understanding how B cells can exacerbate and suppress liver damage by exploiting the antibodies and cytokines they produce will be of great importance for designing B-cell targeting therapies to treat various liver diseases.

TLR3\TLR7 as Differentially Expressed Markers Among Viral, Nonviral, and Autoimmune Diseases in Egyptian Patients

Toll-like receptors (TLRs) represent the immune link between the innate and the adaptive immune signals against various pathogens. This study aimed to evaluate the TLRs3 and 7 as immune-markers in differentiating between hepatitis C virus (HCV)-infected and -uninfected patients. Also, the use of the TLR3 and TLR7 as immune markers was compared with the prevalent bio and immune markers for autoimmune diseases in HCV-infected or -uninfected patients. The levels of GPT, GOT, B cell activated factors, tumor necrosis factor-alpha (TNF-α), and interleukin (IL)-10 were measured in plasma, while the levels of TLR3 and TLR7 were quantified in lysates of peripheral blood mononuclear cells from healthy donors, HCV-infected patients, nonalcoholic fatty liver (NAFL) patients without autoimmune diseases and with autoimmune diseases (HCV-infected patients with autoimmune diseases [HCV+auto], nonalcoholic fatty liver patients with autoimmune diseases [NAFL+auto]), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE) patients. The relative expression of TLR3, TLR7, TNF, and IL-10 in cell lysates was assessed against glyceraldehyde 3-phosphate dehydrogenase (GAPDH) by quantitative real time-polymerase chain reaction (qRT-PCR). Results showed that TLRs 3 and 7 levels were significantly higher in SLE, RA, HCV, HCV+auto, and the NAFL patients compared to the normal control. The cell lysates from SLE patients expressed TLR3 at relatively significantly higher mRNA levels compared to normal subjects or other patient groups. The NAFL+auto patients expressed TLR7 at relatively significantly high mRNA levels compared to normal subjects or other patients. The RA patients expressed TLR7 at relatively significantly higher mRNA levels when compared to HCV, HCV+auto, and NAFL+auto patients. Conclusions: At the protein level, TLR7 can differentiate between HCV and NAFL patients. In addition, both TLRs3 and 7 can serve as potent markers in differentiating between NAFL and NAFL+auto.

Noncanonical NF-κB Signaling Pathway in Liver Diseases

The noncanonical NF-κB signaling pathway is an important branch of NF-κB signaling. It is involved in regulating multiple important biological processes, including inflammation and host immune response. A central adaptor protein of the noncanonical NF-κB pathway is NF-κB-inducing kinase (NIK), which activates the downstream kinase IKKα to process p100 to p52, thereby forming the RelB/p52 heterodimer to initiate the expression of target genes. Currently, many specific inhibitors and monoclonal antibodies targeting or triggering this pathway are being developed and tested for various diseases, including cancers, autoimmune diseases, and virus infection. Given that aberrant activation of the noncanonical NF-κB pathway is frequently observed in various liver diseases, targeting this pathway may be a promising therapeutic strategy to alleviate liver inflammation. Moreover, activation of this pathway may contribute to the antiviral immune response and promote the clearance of persistent hepatotropic virus infection. Here, we review the role of the noncanonical NF-κB pathway in the occurrence and development of different liver diseases, and discuss the potency and application of modulating the noncanonical NF-κB pathway for treatment of these liver diseases.

B-Cell Activating Factor Enhances Hepatocyte-Driven Angiogenesis via B-Cell CLL/Lymphoma 10/Nuclear Factor-KappaB Signaling during Liver Regeneration

B-cell activating factor (BAFF) is found to be associated with the histological severity of nonalcoholic steatohepatitis (NASH). BAFF was also found to have a protective role in hepatic steatosis via down regulating the expression of steatogenesis genes and enhancing steatosis in hepatocytes through BAFF-R. However, the roles of BAFF during liver regeneration are not well defined. In this study, C57/B6 mice with 70% partial hepatectomy were used as a liver regeneration model. BAFF expression was determined by enzyme immunoassay, and anti-BAFF-neutralizing antibodies were administered to confirm the effects of BAFF on liver regeneration. Western blotting, immunohistochemistry, and florescence staining determined the expression of B-cell CCL/lymphoma 10 (BCL10). The angiogenesis promoting capability was evaluated after the transfection of cells with siRNA targeting BCL10 expression, and the role of NF-κB was assessed. The results revealed that the BAFF and BCL10 levels were upregulated after partial hepatectomy. Treatment with anti-BAFF-neutralizing antibodies caused death in mice that were subjected to 70% partial hepatectomy within 72 h. In vitro, recombinant BAFF protein did not enhance hepatocyte proliferation; however, transfection with BCL10 siRNA arrested hepatocytes at the G2/M phase. Interestingly, conditioned medium from BAFF-treated hepatocytes enhanced angiogenesis and endothelial cell proliferation. Moreover, Matrix metalloproteinase-9 (MMP-9), Fibroblast growth factor 4 (FGF4), and Interleukin-8 (IL-8) proteins were upregulated by BAFF through BCL10/NF-κB signaling. In mice that were treated with anti-BAFF-neutralizing antibodies, the microvessel density (MVD) of the remaining liver tissues and liver regeneration were both reduced. Taken together, our study demonstrated that an increased expression of BAFF and activation of BCL10/NF-κB signaling were involved in hepatocyte-driven angiogenesis and survival during liver regeneration.