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JHEP Reports : Innovation in Hepatology Apr 2024Hepatocellular necrosis is common in both acute and chronic liver injury and may evolve to fibrosis and liver failure. Injury leads to accumulation of necrotic cell...
BACKGROUND & AIMS
Hepatocellular necrosis is common in both acute and chronic liver injury and may evolve to fibrosis and liver failure. Injury leads to accumulation of necrotic cell debris in the liver, which drives persistent inflammation and poor recovery. This study investigated the role of natural antibodies (NAbs) in the clearance of necrotic cells in the injured liver, their impact on tissue regeneration and their potential as a therapy for acute liver injury.
METHODS
We used murine models of drug-induced liver injury and focal thermal injury in immunocompetent and antibody-deficient mice ( and IgMi). Intravital microscopy was used to investigate the role of NAbs in the phagocytosis of necrotic cells in the liver . Immunostainings were used to quantify the extent of liver necrosis (fibrin), antibody deposition (IgM and IgG) and cellular proliferation (Ki67).
RESULTS
Both IgM and IgG NAbs bound necrotic liver areas and opsonized multiple debris molecules released during hepatocellular necrosis such as DNA, histones, actin, phosphoinositides and mitochondrial cardiolipin, but not phosphatidylserine. and IgMi mice presented impaired recovery from liver injury, which was correlated to the sustained presence of necrotic debris in the tissue, prolonged inflammation and reduced hepatocellular proliferation. These defects were rescued by treating mice with NAbs after the induction of injury. Mechanistically, and , phagocytosis of necrotic debris was dependent on NAbs via Fcγ receptors and CD11b. Moreover, NAb-mediated phagocytosis of necrotic cell debris occurs in two waves, firstly driven by neutrophils and then by recruited monocytes. Importantly, supplementation of immunocompetent mice with NAbs also improved liver regeneration significantly, demonstrating the therapeutic potential of natural IgM and IgG.
CONCLUSION
NAbs drive the phagocytosis of necrotic cells in liver injury and promote liver regeneration and recovery.
IMPACT AND IMPLICATIONS
Treatment with natural antibodies after acute liver injury improved recovery by increasing the clearance of necrotic debris and by improving cellular proliferation in the liver. This preclinical study provides a basis for the development of an immunotherapy for patients with early-stage, reversible, liver injury that aims to prevent disease chronification into fibrosis and liver failure.
PubMed: 38481390
DOI: 10.1016/j.jhepr.2024.101013 -
Free Radical Biology & Medicine Apr 2024NADPH oxidase is a target of hyperglycemia in type 2 diabetes mellitus (T2DM), which causes dysregulation of enzyme. Alterations in regulation of NADPH oxidase activity...
NADPH oxidase is a target of hyperglycemia in type 2 diabetes mellitus (T2DM), which causes dysregulation of enzyme. Alterations in regulation of NADPH oxidase activity mediated receptor and non-receptor signaling in bone marrow granulocytes of mice with obesity-induced T2DM were studied. The animals fed high fat diet (516 kcal/100 g) for 16 weeks. NADPH oxidase-related generation of reactive species (RS) at normo- and hyperthermia was estimated using chemiluminescent analysis. The redox status of the cells was assessed by Redox Sensor Red CC-1. Baseline biochemical indicators in blood (glucose, cholesterol, HDL and LDL levels) were significant higher in T2DM mice versus controls. Using specific inhibitors, signaling mediated by formyl peptide receptors (FPRs) to NADPH oxidase was shown to involve PLC, PKC, cytochrome p450 in both control and T2DM groups and PLA2 in controls. In T2DM regulation of NADPH oxidase activity via mFpr1, a high-affinity receptors, occurred with a significant increase of the role of PKC isoforms and suppression of PLA2 participation. Significant differences between this regulation via mFpr2, low-affinity receptors, were not found. Non-receptor activation of NADPH oxidase with ionomycin (Ca ionophore) or phorbol ester (direct activator of PKC isoforms) did not revealed differences in the kinetic parameters between groups at 37 °C and 40 °C. When these agents were used together (synergistic effect), lower sensitivity of cells to ionophore was observed in T2DM at both temperatures. Redox status in responses to opsonized zymosan was higher in T2DM mice at 37 °C and similar to control levels at 40 °C. ROC-analysis identified Tmax, RS production and effect of opsonized zymosan as the most significant predictors for discriminating between groups. It was concluded that Ca-dependent/PKC-mediated regulation of NADPH oxidase activity was altered in BM granulocytes from diabetic mice.
Topics: Mice; Animals; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Zymosan; Granulocytes; NADPH Oxidases; Protein Isoforms; Ionophores; Phospholipases A2; Obesity; Reactive Oxygen Species
PubMed: 38479632
DOI: 10.1016/j.freeradbiomed.2024.03.006 -
International Journal of Molecular... Feb 2024Collectin-K1 (CL-K1) is a multifunctional C-type lectin that has been identified as playing a crucial role in innate immunity. It can bind to carbohydrates on pathogens,...
Collectin-K1 (CL-K1) is a multifunctional C-type lectin that has been identified as playing a crucial role in innate immunity. It can bind to carbohydrates on pathogens, leading to direct neutralization, agglutination, and/or opsonization, thereby inhibiting pathogenic infection. In this study, we investigated a homolog of CL-K1 (CL-K1) in Nile tilapia () and its role in promoting the clearance of the pathogen () and enhancing the antibacterial ability of the fish. Our analysis of bacterial load displayed that substantially reduced the amount of in tissues of the liver, spleen, anterior kidney, and brain in Nile tilapia. Furthermore, examination of tissue sections revealed that CL-K1 effectively alleviated tissue damage and inflammatory response in the liver, anterior kidney, spleen, and brain tissue of tilapia following infection. Additionally, 1 was found to decrease the expression of the pro-inflammatory factor and migration inhibitor , while increasing the expression of anti-inflammatory factor and chemokine in the spleen, anterior kidney, and brain tissues of tilapia. Moreover, statistical analysis of survival rates demonstrated that CL-K1 significantly improved the survival rate of tilapia after infection, with a survival rate of 90%. Collectively, our findings suggest that CL-K1 plays a vital role in the innate immune defense of resisting bacterial infection in Nile tilapia. It promotes the removal of bacterial pathogens from the host, inhibits pathogen proliferation in vivo, reduces damage to host tissues caused by pathogens, and improves the survival rate of the host.
Topics: Animals; Cichlids; Streptococcus agalactiae; Streptococcal Infections; Gene Expression Regulation; Amino Acid Sequence; Tilapia; Collectins
PubMed: 38473757
DOI: 10.3390/ijms25052508 -
Frontiers in Immunology 2024Single nucleotide variations (SNVs) are specific genetic variations that commonly occur in a population and often do not manifest phenotypically. However, depending on...
INTRODUCTION
Single nucleotide variations (SNVs) are specific genetic variations that commonly occur in a population and often do not manifest phenotypically. However, depending on their location and the type of nucleotide exchanged, an SNV can alter or inhibit the function of the gene in which it occurs. Immunoglobulin G (IgG) receptor genes have exhibited several polymorphisms, including rs1801274, which is found in the FcgRIIa gene. The replacement of A with T results in a Histidine (H) to Arginine (R) substitution, altering the affinity of the IgG receptor for IgG subtypes and C-reactive protein (CRP). In this study, we analyzed rs1801274 and its functional implications concerning L. Infantum uptake and cytokine production.
METHODS
We genotyped 201 individuals from an endemic area for visceral leishmaniasis to assess the presence of rs1801274 using Taqman probes for a candidate gene study. Additionally, we included seventy individuals from a non-endemic area for a functional study. Subsequently, we isolated and cultivated one-week adherent mononuclear cells (AMCs) derived from the peripheral blood of participants residing in the non-endemic region in the presence of L. infantum promastigotes, with and without antigen-specific IgG and/or CRP. We analyzed the rate of phagocytosis and the production of nitric oxide (NO), tumor necrosis factor (TNF)-a, interleukin (IL)-10, IL-12 p70, IL-1b, IL- 6, and IL-8 in the culture supernatants.
RESULTS AND DISCUSSION
In participants from the endemic region, the A/G (H/R isoform) heterozygous genotype was significantly associated with susceptibility to the disease. Furthermore, SNVs induced a change in the phagocytosis rate in an opsonin-dependent manner. Opsonization with IgG increased the production of IL-10, TNF-a, and IL-6 in AMCs with the H/R isoform, followed by a decrease in NO production. The results presented here suggest that the rs1801274 polymorphism is linked to a higher susceptibility to visceral leishmaniasis.
Topics: Humans; Leishmaniasis, Visceral; Leishmania infantum; Receptors, IgG; Interleukin-12; Tumor Necrosis Factor-alpha; Nucleotides; Protein Isoforms; Genetic Variation; Immunoglobulin G
PubMed: 38455048
DOI: 10.3389/fimmu.2024.1343602 -
Scandinavian Journal of Immunology Jan 2024Chlamydia trachomatis infections are an important sexually transmitted infection that can lead to inflammation, scarring and hydrosalpinx/infertility. However,...
Chlamydia trachomatis infections are an important sexually transmitted infection that can lead to inflammation, scarring and hydrosalpinx/infertility. However, infections are commonly clinically asymptomatic and do not receive treatment. The underlying cause of asymptomatic immunopathology remains unknown. Here, we demonstrate that IgG produced during male infection enhanced the incidence of immunopathology and infertility in females. Human endocervical cells expressing the neonatal Fc Receptor (FcRn) increased translocation of human IgG-opsonized C. trachomatis. Using total IgG purified from infected male mice, we opsonized C. muridarum and then infected female mice, mimicking sexual transmission. Following infection, IgG-opsonized Chlamydia was found to transcytose the epithelial barrier in the uterus, where it was phagocytosed by antigen-presenting cells (APCs) and trafficked to the draining lymph nodes. APCs then expanded both CD4 and CD8 T cell populations and caused significantly more infertility in female mice infected with non-opsonized Chlamydia. Enhanced phagocytosis of IgG-opsonized Chlamydia significantly increased pro-inflammatory signalling and T cell proliferation. As IgG is transcytosed by FcRn, we utilized FcRn mice and observed that shedding kinetics of Chlamydia were only affected in FcRn mice infected with IgG-opsonized Chlamydia. Depletion of CD8 T cells in FcRn mice lead to a significant reduction in the incidence of infertility. Taken together, these data demonstrate that IgG seroconversion during male infection can amplify female immunopathology, dependent on FcRn transcytosis, APC differentiation and enhanced CD8 T cell responses.
Topics: Humans; Female; Male; Animals; Mice; CD8-Positive T-Lymphocytes; Chlamydia; Immunoglobulin G; Infertility; Genitalia
PubMed: 38441219
DOI: 10.1111/sji.13331 -
The EMBO Journal Apr 2024Dysregulated immune responses contribute to the excessive and uncontrolled inflammation observed in severe COVID-19. However, how immunity to SARS-CoV-2 is induced and...
Dysregulated immune responses contribute to the excessive and uncontrolled inflammation observed in severe COVID-19. However, how immunity to SARS-CoV-2 is induced and regulated remains unclear. Here, we uncover the role of the complement system in the induction of innate and adaptive immunity to SARS-CoV-2. Complement rapidly opsonizes SARS-CoV-2 particles via the lectin pathway. Complement-opsonized SARS-CoV-2 efficiently induces type-I interferon and pro-inflammatory cytokine responses via activation of dendritic cells, which are inhibited by antibodies against the complement receptors (CR) 3 and 4. Serum from COVID-19 patients, or monoclonal antibodies against SARS-CoV-2, attenuate innate and adaptive immunity induced by complement-opsonized SARS-CoV-2. Blocking of CD32, the FcγRII antibody receptor of dendritic cells, restores complement-induced immunity. These results suggest that opsonization of SARS-CoV-2 by complement is involved in the induction of innate and adaptive immunity to SARS-CoV-2 in the acute phase of infection. Subsequent antibody responses limit inflammation and restore immune homeostasis. These findings suggest that dysregulation of the complement system and FcγRII signaling may contribute to severe COVID-19.
Topics: Humans; COVID-19; SARS-CoV-2; Antibodies, Viral; Complement System Proteins; Inflammation; Immunity, Innate
PubMed: 38418557
DOI: 10.1038/s44318-024-00061-0 -
MSphere Mar 2024Phage treatment has regained attention due to an increase in multiresistant bacteria. For phage therapy to be successful, phages must reach their target bacteria in...
Phage treatment has regained attention due to an increase in multiresistant bacteria. For phage therapy to be successful, phages must reach their target bacteria in sufficiently high numbers. Blood-borne phages are believed to be captured by macrophages in the liver and spleen. Since liver sinusoids also consist of specialized scavenger liver sinusoidal endothelial cells (LSECs) and Kupffer cells (KCs), this study investigated the contribution of both cell types in the elimination of phage K1Fg10b::gfp (K1F) in mice. Circulatory half-life, organ, and hepatocellular distribution of K1F were determined following intravenous administration. Internalization of K1F and effects of phage opsonization on uptake were explored using primary mouse and human LSEC and KC cultures. When inoculated with 10 virions, >95% of the total K1F load was eliminated from the blood within 20 min, and 94% of the total retrieved K1F was localized to the liver. Higher doses resulted in slower elimination, possibly reflecting temporary saturation of liver scavenging capacity. Phage DNA was detected in both cell types, with a KC:LSEC ratio of 12:1 per population following cell isolation. Opsonization with plasma proteins increased time-dependent cellular uptake in both LSECs and KCs . Internalized phages were rapidly transported along the endocytic pathway to lysosomal compartments. Reduced viability of intracellular K1F corroborated inactivation following endocytosis. This study is the first to identify phage distribution in the liver at the hepatocellular level, confirming clearance of K1F performed mostly by KCs with a significant uptake also in LSECs.IMPORTANCEFaced with the increasing amounts of bacteria with multidrug antimicrobial resistance, phage therapy has regained attention as a possible treatment option. The phage field has recently experienced an emergence in commercial interest as research has identified new and more efficient ways of identifying and matching phages against resistant superbugs. Currently, phages are unapproved drugs in most parts of the world. For phages to reach broad clinical use, they must be shown to be clinically safe and useful. The results presented herein contribute to increased knowledge about the pharmacokinetics of the T7-like phage K1F in the mammalian system. The cell types of the liver that are responsible for rapid phage blood clearance are identified. Our results highlight the need for more research about appropriate dose regimens when phage therapy is delivered intravenously and advise essential knowledge about cell systems that should be investigated further for detailed phage pharmacodynamics.
Topics: Mice; Humans; Animals; Bacteriophages; Endothelial Cells; Hepatocytes; Liver; Endocytosis; Mammals
PubMed: 38415633
DOI: 10.1128/msphere.00702-23 -
Frontiers in Immunology 2024Complement is an ancient and complex network of the immune system and, as such, it plays vital physiological roles, but it is also involved in numerous pathological... (Review)
Review
Complement is an ancient and complex network of the immune system and, as such, it plays vital physiological roles, but it is also involved in numerous pathological processes. The proper regulation of the complement system is important to allow its sufficient and targeted activity without deleterious side-effects. Factor H is a major complement regulator, and together with its splice variant factor H-like protein 1 and the five human factor H-related (FHR) proteins, they have been linked to various diseases. The role of factor H in inhibiting complement activation is well studied, but the function of the FHRs is less characterized. Current evidence supports the main role of the FHRs as enhancers of complement activation and opsonization, i.e., counter-balancing the inhibitory effect of factor H. FHRs emerge as soluble pattern recognition molecules and positive regulators of the complement system. In addition, factor H and some of the FHR proteins were shown to modulate the activity of immune cells, a non-canonical function outside the complement cascade. Recent efforts have intensified to study factor H and the FHRs and develop new tools for the distinction, quantification and functional characterization of members of this protein family. Here, we provide an update and overview on the versatile roles of factor H family proteins, what we know about their biological functions in healthy conditions and in diseases.
Topics: Humans; Complement Factor H; Complement System Proteins; Complement Activation
PubMed: 38410512
DOI: 10.3389/fimmu.2024.1135490 -
Frontiers in Immunology 2024Conformationally stabilized Env trimers have been developed as antigens for the induction of neutralizing antibodies against HIV-1. However, the non-glycosylated...
INTRODUCTION
Conformationally stabilized Env trimers have been developed as antigens for the induction of neutralizing antibodies against HIV-1. However, the non-glycosylated immunodominant base of these soluble antigens may compete with the neutralizing antibody response. This has prompted attempts to couple Env trimers to organic or inorganic nanoparticles with the base facing towards the carrier. Such a site-directed coupling could not only occlude the base of the trimer, but also enhance B cell activation by repetitive display.
METHODS
To explore the effect of an ordered display of HIV-1 Env on microspheres on the activation of Env-specific B cells we used Bind&Bite, a novel covalent coupling approach for conformationally sensitive antigens based on heterodimeric coiled-coil peptides. By engineering a trimeric HIV-1 Env protein with a basic 21-aa peptide (Peptide K) extension at the C-terminus, we were able to covalently biotinylate the antigen in a site-directed fashion using an acidic complementary peptide (Peptide E) bearing a reactive site and a biotin molecule. This allowed us to load our antigen onto streptavidin beads in an oriented manner.
RESULTS
Microspheres coated with HIV-1 Env through our Bind&Bite system showed i) enhanced binding by conformational anti-HIV Env broadly neutralizing antibodies (bNAbs), ii) reduced binding activity by antibodies directed towards the base of Env, iii) higher Env-specific B cell activation, and iv) were taken-up more efficiently after opsonization compared to beads presenting HIV-1 Env in an undirected orientation.
DISCUSSION
In comparison to site-directed biotinylation via the Avi-tag, Bind&Bite, offers greater flexibility with regard to alternative covalent protein modifications, allowing selective modification of multiple proteins via orthogonal coiled-coil peptide pairs. Thus, the Bind&Bite coupling approach via peptide K and peptide E described in this study offers a valuable tool for nanoparticle vaccine design where surface conjugation of correctly folded antigens is required.
Topics: Humans; HIV-1; HIV Antibodies; HIV Seropositivity; Antibodies, Neutralizing; Peptides; Phagocytosis
PubMed: 38390320
DOI: 10.3389/fimmu.2024.1344346 -
Journal of Colloid and Interface Science Jun 2024Peptide-based vaccines can trigger highly specific immune responses, although peptides alone are usually unable to confer strong humoral or cellular immunity....
Peptide-based vaccines can trigger highly specific immune responses, although peptides alone are usually unable to confer strong humoral or cellular immunity. Consequently, peptide antigens are administered with immunostimulatory adjuvants, but only a few are safe and effective for human use. To overcome this obstacle, herein a peptide antigen was lipidated to effectively anchor it to liposomes and emulsion. A peptide antigen B cell epitope from Group A Streptococcus M protein was conjugated to a universal T helper epitope, the pan DR-biding epitope (PADRE), alongside a lipidic moiety cholesterol. Compared to a free peptide antigen, the lipidated version (LP1) adopted a helical conformation and self-assembled into small nanoparticles. Surprisingly, LP1 alone induced the same or higher antibody titers than liposomes or emulsion-based formulations. In addition, antibodies produced by mice immunized with LP1 were more opsonic than those induced by administering the antigen with incomplete Freund's adjuvant. No side effects were observed in the immunized mice and no excessive inflammatory immune responses were detected. Overall, this study demonstrated how simple conjugation of cholesterol to a peptide antigen can produce a safe and efficacious vaccine against Group A Streptococcus - the leading cause of superficial infections and the bacteria responsible for deadly post-infection autoimmune disorders.
Topics: Mice; Humans; Animals; Adjuvants, Immunologic; Lipopeptides; Liposomes; Emulsions; Vaccines; Epitopes; Streptococcus
PubMed: 38387185
DOI: 10.1016/j.jcis.2024.02.134