Low doses of the novel caspase-inhibitor GS-9450 leads to lower caspase-3 and -8 expression on peripheral CD4+ and CD8+ T-cells

Diagnostic performance of extrinsic apoptosis pathway in hepatitis C virus patients: apoptosis fibrosis crosstalk

BACKGROUND/AIM

Liver fibrosis assessment and evaluation of disease severity in hepatitis C virus (HCV) patients provides useful information for therapeutic decisions. Chronic HCV infection is associated with increased levels of peripheral T cell apoptosis. The aim was to study whether peripheral blood T lymphocyte apoptosis markers may contribute to clinical progression, and develop a simple index based on combination of apoptosis and routine biomarkers for accurate evaluation of fibrosis stages in HCV patients.

PATIENTS AND METHODS

Peripheral blood T lymphocytes were isolated from 72 patients with hepatitis C virus and 25 healthy control individuals. Serum samples were collected at time of liver biopsy. Liver fibrosis was tested in biopsies using the Metavair score system. Stepwise linear discriminate analysis and area under receiver-operating characteristic curves were utilized to produce a predictive score comprising significant apoptosis biomarkers.

RESULTS

A novel score named apoptosis fibrosis index (AFI) was created on the basis of a combination of CD8/Annexin, albumin and platelets. The multivariate discriminate analysis selected a score based on absolute values of the three biochemical markers; score = 5.8 + 0.008×CD8/Annexin-V (%) - 1.4×Albumin (g/dl) - 0.001×Platelet count (10/L), where 5.8 considered numerical constant. AFI produce an area under the curve of one for significant fibrosis, 0.80 for advanced fibrosis, and 0.889 for cirrhosis.

CONCLUSION

Apoptosis biomarkers in HCV patients were associated with liver fibrosis. AFI score, a novel noninvasive test, can be used easily for the prediction of liver fibrosis stage and may decrease the need for liver biopsy in hepatitis C virus Egyptian patients.

Relevance of the NLRP3 Inflammasome in the Pathogenesis of Chronic Liver Disease

Inflammation is a common characteristic of chronic liver disease (CLD). Inflammasomes are multiprotein complexes that can sense and recognize various exogenous and endogenous danger signals, eventually activating interleukin (IL)-1β and IL-18. The sensor component of the inflammasome system is a nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs). The NLRs family pyrin domain containing 3 (NLRP3) inflammasome has been involved in the initiation and progression of CLD. However, the molecular mechanisms by which it triggers liver inflammation and damage remain unclear. Here, we focus on recent advances on the potential role of NLRP3 inflammasome activation in the progression of CLD, including viral hepatitis, non-alcoholic steatohepatitis and alcoholic liver disease, and in particular, its ability to alleviate liver inflammation in animal models. Additionally, we also discuss various pharmacological inhibitors identifying the NLRP3 inflammasome signaling cascade as novel therapeutic targets in the treatment of CLD. In summary, this review summarizes the relevance of the NLRP3 inflammasome in the initiation and progression of CLD, and provides critical targets to suppress the development of CLD in clinical management.

Diagnosis and Management of Autoimmune Hepatitis: Current Status and Future Directions

Autoimmune hepatitis is characterized by autoantibodies, hypergammaglobulinemia, and interface hepatitis on histological examination. The features lack diagnostic specificity, and other diseases that may resemble autoimmune hepatitis must be excluded. The clinical presentation may be acute, acute severe (fulminant), or asymptomatic; conventional autoantibodies may be absent; centrilobular necrosis and bile duct changes may be present; and the disease may occur after liver transplantation or with features that suggest overlapping disorders. The diagnostic criteria have been codified, and diagnostic scoring systems can support clinical judgment. Nonstandard autoantibodies, including antibodies to actin, α-actinin, soluble liver antigen, perinuclear antineutrophil antigen, asialoglycoprotein receptor, and liver cytosol type 1, are tools that can support the diagnosis, especially in patients with atypical features. Prednisone or prednisolone in combination with azathioprine is the preferred treatment, and strategies using these medications in various doses can ameliorate treatment failure, incomplete response, drug intolerance, and relapse after drug withdrawal. Budesonide, mycophenolate mofetil, and calcineurin inhibitors can be considered in selected patients as frontline or salvage therapies. Molecular (recombinant proteins and monoclonal antibodies), cellular (adoptive transfer and antigenic manipulation), and pharmacological (antioxidants, antifibrotics, and antiapoptotic agents) interventions constitute future directions in management. The evolving knowledge of the pathogenic pathways and the advances in technology promise new management algorithms.

Dysfunctional HIV-specific CD8+ T cell proliferation is associated with increased caspase-8 activity and mediated by necroptosis

Decreased HIV-specific CD8(+) T cell proliferation is a hallmark of chronic infection, but the mechanisms of decline are unclear. We analyzed gene expression profiles from antigen-stimulated HIV-specific CD8(+) T cells from patients with controlled and uncontrolled infection and identified caspase-8 as a correlate of dysfunctional CD8(+) T cell proliferation. Caspase-8 activity was upregulated in HIV-specific CD8(+) T cells from progressors and correlated positively with disease progression and programmed cell death-1 (PD-1) expression, but negatively with proliferation. In addition, progressor cells displayed a decreased ability to upregulate membrane-associated caspase-8 activity and increased necrotic cell death following antigenic stimulation, implicating the programmed cell death pathway necroptosis. In vitro necroptosis blockade rescued HIV-specific CD8(+) T cell proliferation in progressors, as did silencing of necroptosis mediator RIPK3. Thus, chronic stimulation leading to upregulated caspase-8 activity contributes to dysfunctional HIV-specific CD8(+) T cell proliferation through activation of necroptosis and increased cell death.

Targeting apoptosis in autoimmune hepatitis

Apoptosis is the predominant mechanism of liver cell death in autoimmune hepatitis, and interventions that can modulate this activity are emerging. The aim of this review was to describe the apoptotic mechanisms, possible aberrations, and opportunities for intervention in autoimmune hepatitis. Studies cited in PubMed from 1972 to 2014 for autoimmune hepatitis, apoptosis in liver disease, apoptosis mechanisms, and apoptosis treatment were examined. Apoptosis is overactive in autoimmune hepatitis, and the principal pathway of cell death is receptor mediated. Surface death receptors are activated by extrinsic factors including liver-infiltrating cytotoxic T cells and the cytokine milieu. The executioner caspases 3 and 7 cleave nuclear deoxyribonucleic acid, and the release of apoptotic bodies can stimulate inflammatory, immune, and fibrotic responses. Changes in mitochondrial membrane permeability can be initiated by caspase 8, and an intrinsic pathway of apoptosis can complement the extrinsic pathway. Defects in the apoptosis of activated effector cells can prolong their survival and sustain the immune response. Caspase inhibitors have been used in diverse experimental and human diseases to retard apoptosis. Oligonucleotides that inhibit the signaling of toll-like receptors can limit the presentation of auto-antigens, and inhibitors of apoptosis that extend the survival of effector cells can be blocked by antisense oligonucleotides. Mechanisms that enhance the clearance of apoptotic bodies and affect key signaling pathways are also feasible. Interventions that influence the survival of liver and effector cells by altering their apoptosis are candidates for study in autoimmune hepatitis.

Complementary role of HCV and HIV in T-cell activation and exhaustion in HIV/HCV coinfection

Objectives

To investigate whether T-cell activation and exhaustion is linked to HCV- and HIV disease parameters in HIV/HCV infected individuals, we studied T-cell characteristics in HIV/HCV coinfected patients and controls.

Methods

14 HIV/HCV coinfected, 19 HCV monoinfected, 10 HIV monoinfected patients and 15 healthy controls were included in this cross-sectional study. Differences in expression of activation and exhaustion markers (HLA-DR, CD38, PD-1, Tim-3 and Fas) and phenotypic markers on CD4⁺ and CD8⁺ T-cells were analysed by flow cytometry and were related to HCV disease parameters (HCV-viremia, ALT and liver fibrosis).

Results

Frequencies of activated CD4⁺ and CD8⁺ T-cells were higher in HIV/HCV-coinfected compared to healthy controls and HCV or HIV mono-infected individuals. Coinfected patients also showed high expression of the exhaustion marker PD-1 and death receptor Fas. In contrast, the exhaustion marker Tim-3 was only elevated in HIV-monoinfected patients. T-cell activation and exhaustion were correlated with HCV-RNA, suggesting that viral antigen influences T-cell activation and exhaustion. Interestingly, increased percentages of effector CD8⁺ T-cells were found in patients with severe (F3–F4) liver fibrosis compared to those with no to minimal fibrosis (F0–F2).

Conclusions

HIV/HCV coinfected patients display a high level of T-cell activation and exhaustion in the peripheral blood. Our data suggest that T-cell activation and exhaustion are influenced by the level of HCV viremia. Furthermore, high percentages of cytotoxic/effector CD8⁺ T-cells are associated with liver fibrosis in both HCV monoinfected and HIV/HCV coinfected patients.

Inhibition of apoptosis in the management of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease in the developed world. The pathogenesis of NAFLD is multifactorial, involving obesity, insulin resistance, inflammation and oxidative stress. Accordingly, several treatments targeting these pathways have been evaluated in patients with NAFLD but have either shown limited efficacy or an unfavorable safety profile. On the other hand, increased hepatocyte apoptosis also appears to be implicated in the development and progression of NAFLD and recent pilot studies suggest that inhibition of apoptosis might represent a useful approach in this disease. However, several issues pertaining both to the efficacy and safety of this new class of agents remain unresolved and larger studies are required to clarify the role of this therapeutic modality in the management of NAFLD.

Radiation, inflammation, and immune responses in cancer

Chronic inflammation has emerged as one of the hallmarks of cancer. Inflammation also plays a pivotal role in modulating radiation responsiveness of tumors. As discussed in this review, ionizing radiation (IR) leads to activation of several transcription factors modulating the expression of numerous mediators in tumor cells and cells of the microenvironment promoting cancer development. Novel therapeutic approaches thus aim to interfere with the activity or expression of these factors, either in single-agent or combinatorial treatment or as supplements of the existing therapeutic concepts. Among them, NF-κB, STAT-3, and HIF-1 play a crucial role in radiation-induced inflammatory responses embedded in a complex inflammatory network. A great variety of classical or novel drugs including nutraceuticals such as plant phytochemicals have the capacity to interfere with the inflammatory network in cancer and are considered as putative radiosensitizers. Thus, targeting the inflammatory signaling pathways induced by IR offers the opportunity to improve the clinical outcome of radiation therapy by enhancing radiosensitivity and decreasing putative metabolic effects. Since inflammation and sex steroids also impact tumorigenesis, a therapeutic approach targeting glucocorticoid receptors and radiation-induced production of tumorigenic factors might be effective in sensitizing certain tumors to IR.

Apoptosis - an Ubiquitous T cell Immunomodulator

Apoptosis is a natural process where cells that are no longer required can be eliminated in a highly regulated, controlled manner. Apoptosis is important in maintaining the mammalian immune system and plays a significant role in immune response, positive and negative T cell selection, and cytotoxic death of target cells. When the apoptotic pathways are impaired or are not tightly regulated, autoimmune diseases, inflammatory diseases, viral and bacterial infections and cancers ensue. An imbalance in the anti-apoptotic and pro-apoptotic factors has been implicated in these diseases. Moreover, current therapies directed towards these diseases focus on the modulation of the apoptotic death pathways to regulate the immune response. In this review, we will focus on the process of T cell activation and apoptosis in autoimmune reactions, in response to tumor progression as well as in response to bacterial and viral infections.