RAMP1 in Kupffer cells is a critical regulator in immune-mediated hepatitis

Autonomic nervous system imbalance in diabetic mouse choroids

PURPOSE

We investigated neurohomeostasis and its possible underlying mechanisms in the choroids of diabetic mice.

METHODS

Streptozotocin-induced diabetic mice were used in this study. Choroidal nerve fiber alterations were observed via transmission electron microscopy (TEM). The levels of epinephrine and acetylcholine in the choroid were determined via ultra-high-performance liquid chromatography-tandem mass spectrometry. Tyrosine hydroxylase (TH), choline acetyl transferase (ChAT), and neuronal nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) levels were evaluated by western blot or quantitative real-time polymerase chain reaction. In addition, immunofluorescence staining were used to analyze the changes in key enzymes (TH, dopamine beta-hydroxylase (DβH), and CGRP) in the superior cervical sympathetic ganglia (SCG) and trigeminal ganglia (TG).

RESULTS

TEM revealed a loose myelin sheath around nerve fibers, axon atrophy, and cytoplasmic vacuoles in Schwann cells in diabetic choroids. Lower epinephrine levels were observed in diabetic mice. Although no difference was found in acetylcholine level, the epinephrine-to-acetylcholine ratio was greatly decreased. Decreased TH and increased ChAT, nNOS, VIP, NPY, and CGRP were found in diabetic choroids. Fewer TH-positive and DβH-positive neuronal cells were found in the SCGs of diabetic mice. More CGRP-positive and fewer TH-positive neuronal cells were observed in the TG of diabetic mice.

CONCLUSIONS

Altered markers of the sympathetic, parasympathetic and sensory systems were present in diabetic mouse choroids. An imbalanced choroidal nervous system might explain the initiation of choroidal neovascularization in diabetic patients.

Deletion of TP signaling in macrophages delays liver repair following APAP-induced liver injury by reducing accumulation of reparative macrophage and production of HGF

BACKGROUND

Acetaminophen (APAP)-induced liver injury is the most common cause of acute liver failure. Macrophages are key players in liver restoration following APAP-induced liver injury. Thromboxane A2 (TXA2) and its receptor, thromboxane prostanoid (TP) receptor, have been shown to be involved in tissue repair. However, whether TP signaling plays a role in liver repair after APAP hepatotoxicity by affecting macrophage function remains unclear.

METHODS

Male TP knockout (TP-/-) and C57BL/6 wild-type (WT) mice were treated with APAP (300 mg/kg). In addition, macrophage-specific TP-knockout (TP△mac) and control WT mice were treated with APAP. We explored changes in liver inflammation, liver repair, and macrophage accumulation in mice treated with APAP.

RESULTS

Compared with WT mice, TP-/- mice showed aggravated liver injury as indicated by increased levels of alanine transaminase (ALT) and necrotic area as well as delayed liver repair as indicated by decreased expression of proliferating cell nuclear antigen (PCNA). Macrophage deletion exacerbated APAP-induced liver injury and impaired liver repair. Transplantation of TP-deficient bone marrow (BM) cells to WT or TP-/- mice aggravated APAP hepatotoxicity with suppressed accumulation of macrophages, while transplantation of WT-BM cells to WT or TP-/- mice attenuated APAP-induced liver injury with accumulation of macrophages in the injured regions. Macrophage-specific TP-/- mice exacerbated liver injury and delayed liver repair, which was associated with increased pro-inflammatory macrophages and decreased reparative macrophages and hepatocyte growth factor (HGF) expression. In vitro, TP signaling facilitated macrophage polarization to a reparative phenotype. Transfer of cultured BM-derived macrophages from control mice to macrophage-specific TP-/- mice attenuated APAP-induced liver injury and promoted liver repair. HGF treatment mitigated APAP-induced inflammation and promoted liver repair after APAP-induced liver injury.

CONCLUSIONS

Deletion of TP signaling in macrophages delays liver repair following APAP-induced liver injury, which is associated with reduced accumulation of reparative macrophages and the hepatotrophic factor HGF. Specific activation of TP signaling in macrophages may be a potential therapeutic target for liver repair and regeneration after APAP hepatotoxicity.

Lack of RAMP1 Signaling Suppresses Liver Regeneration and Angiogenesis Following Partial Hepatectomy in Mice

BACKGROUND/AIM

The liver effectively restores both size and function following partial hepatectomy (PHx). Angiogenesis is crucial for the repair and regeneration of liver tissue post-PHx. Calcitonin gene-related peptide (CGRP) released from sensory nerves and its receptor-receptor activity-modifying protein 1 (RAMP1) are involved in angiogenesis. This study aimed to assess the role of RAMP1 signaling in angiogenesis during liver regeneration following PHx.

MATERIALS AND METHODS

RAMP1 deficient (RAMP1-/-) and wild-type (WT) mice were subjected to PHx.

RESULTS

RAMP1-/- mice demonstrated delayed liver regeneration, indicated by lower liver-to-body weight ratios compared to WT mice. This was associated with lower levels of Ki67+ hepatocytes and hepatic trophic growth factors. Additionally, RAMP1-/- mice exhibited lower levels of endothelial cell markers, including CD31, compared to WT mice. This reduction was associated with reduced levels of vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF receptor 3 (VEGFR3). In WT mice with PHx, the administration of a VEGFR3 inhibitor reduced the liver-to-body weight ratio, Ki67+ hepatocytes, and VEGF-C/VEGFR3 expression levels in the liver compared to those in the vehicle-treated group.

CONCLUSION

The deletion of RAMP1 signaling suppresses liver regeneration and angiogenesis through VEGFR3. Specific activation of RAMP1 signaling may represent a potential therapeutic strategy for liver regeneration following PHx.

Characteristics and risk factors for invasive fungal infection in hospitalized patients with acute-on-chronic hepatitis B liver failure: a retrospective cohort study from 2010 to 2023

BACKGROUND AND AIM

The global burden of invasive fungal infections (IFIs) is emerging in immunologic deficiency status from various disease. Patients with acute-on-chronic hepatitis B liver failure (ACHBLF) are prone to IFI and their conditions are commonly exacerbated by IFI. However, little is known about the characteristics and risk factors for IFI in hospitalized ACHBLF patients.

METHODS

A total of 243 hospitalized ACHBLF patients were retrospectively enrolled from January 2010 to July 2023. We performed restricted cubic spline analysis to determine the non-linear associations between independent variables and IFI. The risk factors for IFI were identified using logistic regression and the extreme gradient boosting (XGBoost) algorithm. The effect values of the risk factors were determined by the SHapley Additive exPlanations (SHAP) method.

RESULTS

There were 24 ACHBLF patients (9.84%) who developed IFI on average 17.5 (13.50, 23.00) days after admission. The serum creatinine level showed a non-linear association with the possibility of IFI. Multiple logistic regression revealed that length of hospitalization (OR = 1.05, 95% CI: 1.02-1.08, P = 0.002) and neutrophilic granulocyte percentage (OR = 1.04, 95% CI: 1.00-1.09, P = 0.042) were independent risk factors for IFI. The XGBoost algorithm showed that the use of antibiotics (SHAP value = 0.446), length of hospitalization (SHAP value = 0.406) and log (qHBV DNA) (SHAP value = 0.206) were the top three independent risk factors for IFI. Furthermore, interaction analysis revealed no multiplicative effects between the use of antibiotics and the use of glucocorticoids (P = 0.990).

CONCLUSION

IFI is a rare complication that leads to high mortality in hospitalized ACHBLF patients, and a high neutrophilic granulocyte percentage and length of hospitalization are independent risk factors for the occurrence of IFI.

From pain to tumor immunity: influence of peripheral sensory neurons in cancer

The nervous and immune systems are the primary sensory interfaces of the body, allowing it to recognize, process, and respond to various stimuli from both the external and internal environment. These systems work in concert through various mechanisms of neuro-immune crosstalk to detect threats, provide defense against pathogens, and maintain or restore homeostasis, but can also contribute to the development of diseases. Among peripheral sensory neurons (PSNs), nociceptive PSNs are of particular interest. They possess a remarkable capability to detect noxious stimuli in the periphery and transmit this information to the brain, resulting in the perception of pain and the activation of adaptive responses. Pain is an early symptom of cancer, often leading to its diagnosis, but it is also a major source of distress for patients as the disease progresses. In this review, we aim to provide an overview of the mechanisms within tumors that are likely to induce cancer pain, exploring a range of factors from etiological elements to cellular and molecular mediators. In addition to transmitting sensory information to the central nervous system, PSNs are also capable, when activated, to produce and release neuropeptides (e.g., CGRP and SP) from their peripheral terminals. These neuropeptides have been shown to modulate immunity in cases of inflammation, infection, and cancer. PSNs, often found within solid tumors, are likely to play a significant role in the tumor microenvironment, potentially influencing both tumor growth and anti-tumor immune responses. In this review, we discuss the current state of knowledge about the degree of sensory innervation in tumors. We also seek to understand whether and how PSNs may influence the tumor growth and associated anti-tumor immunity in different mouse models of cancer. Finally, we discuss the extent to which the tumor is able to influence the development and functions of the PSNs that innervate it.

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

Sensory Neurotransmitter Calcitonin Gene-Related Peptide Modulates Tumor Growth and Lymphocyte Infiltration in Oral Squamous Cell Carcinoma

Head and neck squamous cell carcinoma are highly innervated by peripheral sensory neurons. Local neurotransmitter release (e.g., calcitonin gene-related peptide (CGRP)) from sensory neurons innervating cancer is linked to tumorigenesis. CGRP-immunoreactive nerve presence comprised 9.53±1.9% of total nerve area across 11 HNSCC patients. A syngeneic tongue tumor transplant mouse model of oral cancer and a global Calca knockout mouse (CGRPKO ) are used to investigate the impact of CGRP signaling on tumor growth and the associated immune response in vivo. In tumor-bearing CGRPKO mice, there is a significant reduction in tumor size over time compared to wildtype mice using two different mouse oral cancer cell lines. Furthermore, tumor tissue from CGRPKO mice had a significant increase in tumor-infiltrating CD4+ T cells, cytotoxic CD8+ T cells, and NK1.1+ NK cells compared to wildtype. Fluorescent-activated cell sorting and real-time qPCR are used to confirm that CD4+ T cells are isolated from tumor-bearing wildtype mice containing a high expression of Ramp1 compared to sham mice. These data suggest that sensory neurotransmitter CGRP may modulate oral cancer progression via tumor immunosurveillance. Understanding the relationship between sensory neurons and cancer will aid in repurposing clinically available nervous system drugs for the treatment of cancer.

Pathophysiology of decompensated cirrhosis: Portal hypertension, circulatory dysfunction, inflammation, metabolism and mitochondrial dysfunction

Patients with acutely decompensated cirrhosis have a dismal prognosis and frequently progress to acute-on-chronic liver failure, which is characterised by hepatic and extrahepatic organ failure(s). The pathomechanisms involved in decompensation and disease progression are still not well understood, and as specific disease-modifying treatments do not exist, research to identify novel therapeutic targets is of the utmost importance. This review amalgamates the latest knowledge on disease mechanisms that lead to tissue injury and extrahepatic organ failure - such as systemic inflammation, mitochondrial dysfunction, oxidative stress and metabolic changes - and marries these with the classical paradigms of acute decompensation to form a single paradigm. With this detailed breakdown of pathomechanisms, we identify areas for future research. Novel disease-modifying strategies that break the vicious cycle are urgently required to improve patient outcomes.

Knockout of the Tachykinin Receptor 1 in the Mdr2-/- (Abcb4-/-) Mouse Model of Primary Sclerosing Cholangitis Reduces Biliary Damage and Liver Fibrosis

Activation of the substance P (SP)/neurokinin 1 receptor (NK1R) axis triggers biliary damage/senescence and liver fibrosis in bile duct ligated and Mdr2-/- (alias Abcb4-/-) mice through enhanced transforming growth factor-β1 (TGF-β1) biliary secretion. Recent evidence indicates a role for miR-31 (MIR31) in TGF-β1-induced liver fibrosis. We aimed to define the role of the SP/NK1R/TGF-β1/miR-31 axis in regulating biliary proliferation and liver fibrosis during cholestasis. Thus, we generated a novel model with double knockout of Mdr2-/- and NK1R-/ (alias Tacr1-/-) to further address the role of the SP/NK1R axis during chronic cholestasis. In vivo studies were performed in the following 12-week-old male mice: (i) NK1R-/-; (ii) Mdr2-/-; and (iii) NK1R-/-/Mdr2-/- (Tacr1-/-/Abcb4-/-) and their corresponding wild-type controls. Liver tissues and cholangiocytes were collected, and liver damage, changes in biliary mass/senescence, and inflammation as well as liver fibrosis were evaluated by both immunohistochemistry in liver sections and real-time PCR. miR-31 expression was measured by real-time PCR in isolated cholangiocytes. Decreased ductular reaction, liver fibrosis, biliary senescence, and biliary inflammation were observed in NK1R-/-/Mdr2-/- mice compared with Mdr2-/- mice. Elevated expression of miR-31 was observed in Mdr2-/- mice, which was reduced in NK1R-/-/Mdr2-/- mice. Targeting the SP/NK1R and/or miR-31 may be a potential approach in treating human cholangiopathies, including primary sclerosing cholangitis.

Inhibition of receptor activity-modifying protein 1 suppresses the development of endometriosis and the formation of blood and lymphatic vessels

Neuroimmune interactions are involved in the development of endometriosis. Here, we examined the role of a neuropeptide, calcitonin gene–related peptide (CGRP), and its receptor, receptor activity–modifying protein (RAMP) 1, in growth of endometrial tissues and the formation of blood and lymphatic vessels in a mouse ectopic endometrial transplantation model. Endometrial fragments from donor wild‐type (WT) mice transplanted into the peritoneal wall of recipient WT mice grew with increased density of blood and lymphatic vessels. When tissues from RAMP1‐deficient (RAMP1^−/−) mice were transplanted into RAMP1^−/− mice, implant growth and angiogenesis/lymphangiogenesis were decreased. CGRP was up‐regulated in dorsal root ganglia, and CGRP⁺ nerve fibres were distributed into the implants from the peritoneum. RAMP1 was co‐expressed with CD11b (macrophages) and S100A4 (fibroblasts), but did not co‐localize with blood vessel endothelial cell marker CD31 or lymphatic vessel endothelial hyaluronan receptor (LYVE)‐1. Cultured with CGRP, macrophages up‐regulated vascular endothelial growth factor (VEGF)‐A, VEGF‐C and VEGF‐D, whereas fibroblasts up‐regulated VEGF‐C, but not VEGF‐A or VEGF‐D, in a RAMP1‐dependent manner. CGRP receptor antagonist CGRP8‐37 inhibited growth of and angiogenesis/lymphangiogenesis within endometrial tissue implants. These results suggest that RAMP1 signalling is crucial for growth and angiogenesis/lymphangiogenesis in endometrial tissue. Blockade of RAMP1 is a potential tool for the treatment of endometriosis.

RAMP1 signaling in immune cells regulates inflammation-associated lymphangiogenesis

Calcitonin gene-related peptide (CGRP) regulates inflammation via signaling through receptor activity-modifying protein (RAMP) 1. Here, we investigated the role of RAMP1 signaling in growth of lymphatic vessels during inflammation. Lymphangiogenesis in the diaphragm of RAMP1-deficient (^-/-) mice or their wild-type (WT) counterparts was induced by repeated intraperitoneal injection of lipopolysaccharide (LPS). Compared with WT mice, LPS-induced lymphangiogenesis in RAMP1^-/- mice was suppressed. This was accompanied by the reduced expression of vascular endothelial growth factor (VEGF)-C and VEGF-D. The number of CD4⁺ cells in diaphragm tissue from WT mice was greater than RAMP1^-/- mice. Removing CD4⁺ cells attenuated lymphangiogenesis and expression of VEGF-C and VEGF-D. CD4⁺ cells isolated from RAMP1^-/- mice exhibited reduced expression of VEGF-C and VEGF-D. The number of CD11b⁺ cells from RAMP1^-/- mice was higher than WT mice and was associated with the upregulated expression of genes related to pro-inflammatory macrophage phenotype and downregulation of reparative macrophage phenotype-related expression. When fluorescein isothiocyanate (FITC)-dextran was injected into the peritoneal cavity, the amount of residual FITC-dextran in WT mice was lower than that in RAMP1^-/- mice. The present results suggest that RAMP1 signaling in immune cells plays a critical role in inflammation-related lymphangiogenesis; therefore, it represents a novel target for controlling lymphangiogenesis.

Crosstalk network among multiple inflammatory mediators in liver fibrosis

Liver fibrosis is the common pathological basis of all chronic liver diseases, and is the necessary stage for the progression of chronic liver disease to cirrhosis. As one of pathogenic factors, inflammation plays a predominant role in liver fibrosis via communication and interaction between inflammatory cells, cytokines, and the related signaling pathways. Damaged hepatocytes induce an increase in pro-inflammatory factors, thereby inducing the development of inflammation. In addition, it has been reported that inflammatory response related signaling pathway is the main signal transduction pathway for the development of liver fibrosis. The crosstalk regulatory network leads to hepatic stellate cell activation and proinflammatory cytokine production, which in turn initiate the fibrotic response. Compared with the past, the research on the pathogenesis of liver fibrosis has been greatly developed. However, the liver fibrosis mechanism is complex and many pathways involved need to be further studied. This review mainly focuses on the crosstalk regulatory network among inflammatory cells, cytokines, and the related signaling pathways in the pathogenesis of chronic inflammatory liver diseases. Moreover, we also summarize the recent studies on the mechanisms underlying liver fibrosis and clinical efforts on the targeted therapies against the fibrotic response.