The Mechanism of Interferon Refractoriness During Hepatitis C Virus Infection and Its Reversal with a Peroxisome Proliferator-Activated Receptor α Agonist

GAS6/TAM Axis as Therapeutic Target in Liver Diseases

TAM (TYRO3, AXL, and MERTK) protein tyrosine kinase membrane receptors and their vitamin K-dependent ligands GAS6 and protein S (PROS) are well-known players in tumor biology and autoimmune diseases. In contrast, TAM regulation of fibrogenesis and the inflammation mechanisms underlying metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and, ultimately, liver cancer has recently been revealed. GAS6 and PROS binding to phosphatidylserine exposed in outer membranes of apoptotic cells links TAMs, particularly MERTK, with hepatocellular damage. In addition, AXL and MERTK regulate the development of liver fibrosis and inflammation in chronic liver diseases. Acute hepatic injury is also mediated by the TAM system, as recent data regarding acetaminophen toxicity and acute-on-chronic liver failure have uncovered. Soluble TAM-related proteins, mainly released from activated macrophages and hepatic stellate cells after hepatic deterioration, are proposed as early serum markers for disease progression. In conclusion, the TAM system is becoming an interesting pharmacological target in liver pathology and a focus of future biomedical research in this field.

A perspective study of the possible impact of obeticholic acid against SARS-CoV-2 infection

The causative agent of CoV disease 2019 is a new coronavirus CoV type 2, affecting the respiratory tract with severe manifestations (SARS-CoV-2). Covid-19 is mainly symptomless, with slight indications in about 85% of the affected cases. Many efforts were done to face this pandemic by testing different drugs and agents to make treatment protocols in different countries. However, the use of these proposed drugs is associated with the development of adverse events. Remarkably, the successive development of SARS-CoV-2 variants which could affect persons even they were vaccinated, prerequisite wide search to find efficient and safe agents to face SARS-CoV-2 infection. Obeticholic acid (OCA), which has anti-inflammatory effects, may efficiently treat Covid-19. Thus, the goal of this perspective study is to focus on the possible medicinal effectiveness in managing Covid-19. OCA is a powerful farnesoid X receptor (FXR) agonist possessing marked antiviral and anti-inflammatory effects. FXR is dysregulated in Covid-19 resulting in hyper-inflammation with concurrent occurrence of hypercytokinemia. Interestingly, OCA inhibits the reaction between this virus and angiotensin-converting enzyme type 2 (ACE2) receptors. FXR agonists control the expression of ACE2 and the inflammatory signaling pathways in this respiratory syndrome, which weakens the effects of Covid-19 disease and accompanied complications. Taken together, FXR agonists like OCA may reveal both direct and indirect impacts in the modulation of immune reaction in SARS-CoV-2 conditions. It is highly recommended to perform many investigations regarding different phases of the discovery of new drugs.

Decoding the dynamics of multilayered stochastic antiviral IFN-I responses

Type I Interferon (IFN-I) responses were first recognized for their role in antiviral immunity, but it is now widely appreciated that IFN-Is have many immunomodulatory functions, influencing antitumor responses, autoimmune manifestations, and antimicrobial defenses. Given these pivotal roles, it may be surprising that multilayered stochastic events create highly heterogeneous, but tightly regulated, all-or-nothing cellular decisions. Recently, mathematical models have provided crucial insights into the stochastic nature of antiviral IFN-I responses, which we critically evaluate in this review. In this context, we emphasize the need for innovative single-cell technologies combined with mathematical models to further reveal, understand, and predict the complexity of the IFN-I system in physiological and pathological conditions that may be relevant to a plethora of diseases.

Enhancing Fatty Acid Catabolism of Macrophages Within Aberrant Breast Cancer Tumor Microenvironment Can Re-establish Antitumor Function

Triple-negative breast cancer (TNBC) remains an intractable challenge owing to its aggressive nature and lack of any known therapeutic targets. Macrophages play a crucial role in cancer promotion and poor prognosis within the tumor microenvironment (TME). The phagocytosis checkpoint in macrophages has broader implications for current cancer immunotherapeutic strategies. Here, we demonstrate the modulation in the antitumor activity of macrophages within the aberrant metabolic microenvironment of TNBC by metabolic intervention. The co-culture of macrophages with TNBC cell lines led to a decrease in both their phagocytic function and expression of interleukin (IL)-1β and inducible nitric oxide synthase (iNOS). The transcription of glycolysis and fatty acid (FA) catabolism-related factors was inhibited within the dysregulated tumor metabolic microenvironment. Enhancement of FA catabolism by treatment with the peroxisome proliferator-activated receptor-alpha (PPAR-α) agonist, fenofibrate (FF), could re-establish macrophages to gain their antineoplastic activity by activating the signal transducer and activator of transcription 1 (STAT1) signaling pathway and increasing ATP production by FA oxidation. The combination of fenofibrate and anti-CD47 therapy significantly inhibited tumor growth in a 4T1 tumor-bearing mouse model. In conclusion, the enhancement of FA catabolism of macrophages could re-establish them to resume antitumor activity in the TME. Anti-CD47 therapy combined with fenofibrate may serve as a novel and potential immunotherapeutic approach for the treatment of TNBC.

Possible Association of Elevated Plasma Levels of Growth Arrest-Specific Protein 6 and the Soluble Form of Tyrosine Kinase Receptor Axl with Low Hepatitis C Viral Load in Patients with Type 2 Diabetes Mellitus

This study aimed to investigate the plasma levels of Gas6 and soluble Axl (sAxl) in patients with chronic hepatitis C virus (HCV) infection with and without type 2 diabetes mellitus (T2DM). The study involved four groups; 50 patients with chronic HCV, 50 patients with T2DM, 50 patients with chronic HCV and T2DM, and 31 age- and sex-matched healthy controls. T2DM was diagnosed according to American Diabetes Association criteria, HCV antibodies were detected by enzyme-linked immunosorbent assays (ELISA) and confirmed by real-time-polymerase chain reaction. Plasma Gas6 and sAxl levels were assayed in all groups by ELISA. Significant low levels of GAS 6 in HCV/T2DM group versus HCV group were detected (7.92 ± 5.18 vs. 16.09 ± 7.36, respectively, p = 0.000), but higher than T2DM and control groups (p ≥ 0.05), although nonsignificant. HCV load was higher in the HCV group than the HCV/T2DM group (1,888,300 ± 5,595,070 vs. 1,417,900 ± 4,066,460 copies/mL, respectively, p = 0.632). Among HCV group, significant positive correlations were detected between Gas6 and sAxl levels with HCV viral load (r = 0.48, p = 0.000 and r = 0.43, p = 0.002, respectively), while among HCV/T2DM group, significant negative correlations were detected (r = -0.29, p = 0.04 and r = -0.34, p = 0.014, respectively). Significant negative correlations were detected between Gas6/sAxl levels and glycated hemoglobin (r = -0.36, p = 0.01 and r = -0.4, p = 0.003, respectively) in T2DM despite the positive correlations detected in HCV/T2DM (r = 0.27, p = 0.053 and r = 0.55, p = 0.000, respectively). In conclusion, Gas6/Axl system in combined HCV/T2DM diseases may affect the pathogenesis and can alter the biomarkers and complications of both diseases in a manner that differs from a solitary disease.

Defective monocyte oxidative burst predicts infection in alcoholic hepatitis and is associated with reduced expression of NADPH oxidase

OBJECTIVE

In order to explain the increased susceptibility to serious infection in alcoholic hepatitis, we evaluated monocyte phagocytosis, aberrations of associated signalling pathways and their reversibility, and whether phagocytic defects could predict subsequent infection.

DESIGN

Monocytes were identified from blood samples of 42 patients with severe alcoholic hepatitis using monoclonal antibody to CD14. Phagocytosis and monocyte oxidative burst (MOB) were measured ex vivo using flow cytometry, luminometry and bacterial killing assays. Defects were related to the subsequent development of infection. Intracellular signalling pathways were investigated using western blotting and PCR. Interferon-γ (IFN-γ) was evaluated for its therapeutic potential in reversing phagocytic defects. Paired longitudinal samples were used to evaluate the effect of in vivo prednisolone therapy.

RESULTS

MOB, production of superoxide and bacterial killing in response to Escherichia coli were markedly impaired in patients with alcoholic hepatitis. Pretreatment MOB predicted development of infection within two weeks with sensitivity and specificity that were superior to available clinical markers. Accordingly, defective MOB was associated with death at 28 and 90 days. Expression of the gp91 ^phox subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase was reduced in patients with alcoholic hepatitis demonstrating defective MOB. Monocytes were refractory to IFN-γ stimulation and showed high levels of a negative regulator of cytokine signalling, suppressor of cytokine signalling-1. MOB was unaffected by 7 days in vivo prednisolone therapy.

CONCLUSIONS

Monocyte oxidative burst and bacterial killing is impaired in alcoholic hepatitis while bacterial uptake by phagocytosis is preserved. Defective MOB is associated with reduced expression of NADPH oxidase in these patients and predicts the development of infection and death.

HELZ2 Is an IFN Effector Mediating Suppression of Dengue Virus

Flaviviral infections including dengue virus are an increasing clinical problem worldwide. Dengue infection triggers host production of the type 1 IFN, IFN alpha, one of the strongest and broadest acting antivirals known. However, dengue virus subverts host IFN signaling at early steps of IFN signal transduction. This subversion allows unbridled viral replication which subsequently triggers ongoing production of IFN which, again, is subverted. Identification of downstream IFN antiviral effectors will provide targets which could be activated to restore broad acting antiviral activity, stopping the signal to produce endogenous IFN at toxic levels. To this end, we performed a targeted functional genomic screen for IFN antiviral effector genes (IEGs), identifying 56 IEGs required for antiviral effects of IFN against fully infectious dengue virus. Dengue IEGs were enriched for genes encoding nuclear receptor interacting proteins, including HELZ2, MAP2K4, SLC27A2, HSP90AA1, and HSP90AB1. We focused on HELZ2 (Helicase With Zinc Finger 2), an IFN stimulated gene and IEG which encodes a promiscuous nuclear factor coactivator that exists in two isoforms. The two unique HELZ2 isoforms are both IFN responsive, contain ISRE elements, and gene products increase in the nucleus upon IFN stimulation. Chromatin immunoprecipitation-sequencing revealed that the HELZ2 complex interacts with triglyceride-regulator LMF1. Mass spectrometry revealed that HELZ2 knockdown cells are depleted of triglyceride subsets. We thus sought to determine whether HELZ2 interacts with a nuclear receptor known to regulate immune response and lipid metabolism, AHR, and identified HELZ2:AHR interactions via co-immunoprecipitation, found that AHR is a dengue IEG, and that an AHR ligand, FICZ, exhibits anti-dengue activity. Primary bone marrow derived macrophages from HELZ2 knockout mice, compared to wild type controls, exhibit enhanced dengue infectivity. Overall, these findings reveal that IFN antiviral response is mediated by HELZ2 transcriptional upregulation, enrichment of HELZ2 protein levels in the nucleus, and activation of a transcriptional program that appears to modulate intracellular lipid state. IEGs identified in this study may serve as both (1) potential targets for host directed antiviral design, downstream of the common flaviviral subversion point, as well as (2) possible biomarkers, whose variation, natural, or iatrogenic, could affect host response to viral infections.

Infections: A Possible Risk Factor for Type 2 Diabetes

Diabetes mellitus is one of the biggest challenges to human health globally, with an estimated 95% of the global diabetic population having type 2 diabetes. Classical causes for type 2 diabetes, such as genetics and obesity, do not account for the high incidence of the disease. Recent data suggest that infections may precipitate insulin resistance via multiple mechanisms, such as the proinflammatory cytokine response, the acute-phase response, and the alteration of the nutrient status. Even pathogen products, such as lipopolysaccharide and peptidoglycans, can be diabetogenic. Therefore, we argue that infections that are known to contribute to insulin resistance should be considered as risk factors for type 2 diabetes.

Analysis of TLR7, SOCS1 and ISG15 immune genes expression in the peripheral blood of responder and non-responder patients with chronic Hepatitis C

AIM

To evaluate the baseline expression of the immune genes in PBMCs of responder and non-responder patients with chronic Hepatitis C.

BACKGROUND

Although the contribution of peripheral blood mononuclear cell (PBMC) gene expression in treatment outcome of hepatitis C virus (HCV) infection is supposed, it has remained to be distinctly delineated. The baseline expression of the immune genes inside PBMCs may reflect the responsiveness status following IFN treatment.

METHODS

Totally, 22 chronic HCV encompasses 10 responders and 12 non-responsive cases enrolled randomly regarding medical records. The PBMCs from the peripheral blood samples were isolated and then incubated for 6 hours in the culture media. The baseline expression of TLR7, SOCS1 and ISG15 was measured by Real time PCR.

RESULTS

The gene expression pattern in PBMCs of both groups showed a similar trend. The expression of SOCS1 and TLR7 genes showed higher levels in non-responder group (P>0.05). The result of ISG15 showed a higher but non-significant expression in the responder group (P>0.05).

CONCLUSION

The similar pattern of TLR7, SOCS1 and ISG15 expression in the responder and non-responder patients indicated their poor discriminating and predictive value in PBMCs sample.

TAM receptor tyrosine kinase function and the immunopathology of liver disease

Tyro3, Axl, MERTK (TAM) receptor tyrosine kinases are implicated in the regulation of the innate immune response through clearance of apoptotic cellular debris and control of cytokine signaling cascades. As a result they are pivotal in regulating the inflammatory response to tissue injury. Within the liver, immune regulatory signaling is employed to prevent the overactivation of innate immunity in response to continual antigenic challenge from the gastrointestinal tract. In this review we appraise current understanding of the role of TAM receptor function in the regulation of both innate and adaptive immunity, with a focus on its impact upon hepatic inflammatory pathology.

Hepatitis C Virus Driven AXL Expression Suppresses the Hepatic Type I Interferon Response

Treatment of chronic hepatitis C virus (HCV) infection is evolving rapidly with the development of novel direct acting antivirals (DAAs), however viral clearance remains intimately linked to the hepatic innate immune system. Patients demonstrating a high baseline activation of interferon stimulated genes (ISGs), termed interferon refractoriness, are less likely to mount a strong antiviral response and achieve viral clearance when placed on treatment. As a result, suppressor of cytokine signalling (SOCS) 3 and other regulators of the IFN response have been identified as key candidates for the IFN refractory phenotype due to their regulatory role on the IFN response. AXL is a receptor tyrosine kinase that has been identified as a key regulator of interferon (IFN) signalling in myeloid cells of the immune system, but has not been examined in the context of chronic HCV infection. Here, we show that AXL is up-regulated following HCV infection, both in vitro and in vivo and is likely induced by type I/III IFNs and inflammatory signalling pathways. AXL inhibited type IFNα mediated ISG expression resulting in a decrease in its antiviral efficacy against HCV in vitro. Furthermore, patients possessing the favourable IFNL3 rs12979860 genotype associated with treatment response, showed lower AXL expression in the liver and a stronger induction of AXL in the blood, following their first dose of IFN. Together, these data suggest that elevated AXL expression in the liver may mediate an IFN-refractory phenotype characteristic of patients possessing the unfavourable rs12979860 genotype, which is associated with lower rates of viral clearance.