Neutrophil Apoptosis in Neutropenic Patients With Hepatitis C Infection: Role of Caspases 3, 10, and GM-CSF

Neutrophils: Many Ways to Die

Neutrophils or polymorphonuclear leukocytes (PMN) are key participants in the innate immune response for their ability to execute different effector functions. These cells express a vast array of membrane receptors that allow them to recognize and eliminate infectious agents effectively and respond appropriately to microenvironmental stimuli that regulate neutrophil functions, such as activation, migration, generation of reactive oxygen species, formation of neutrophil extracellular traps, and mediator secretion, among others. Currently, it has been realized that activated neutrophils can accomplish their effector functions and simultaneously activate mechanisms of cell death in response to different intracellular or extracellular factors. Although several studies have revealed similarities between the mechanisms of cell death of neutrophils and other cell types, neutrophils have distinctive properties, such as a high production of reactive oxygen species (ROS) and nitrogen species (RNS), that are important for their effector function in infections and pathologies such as cancer, autoimmune diseases, and immunodeficiencies, influencing their cell death mechanisms. The present work offers a synthesis of the conditions and molecules implicated in the regulation and activation of the processes of neutrophil death: apoptosis, autophagy, pyroptosis, necroptosis, NETosis, and necrosis. This information allows to understand the duality encountered by PMNs upon activation. The effector functions are carried out to eliminate invading pathogens, but in several instances, these functions involve activation of signaling cascades that culminate in the death of the neutrophil. This process guarantees the correct elimination of pathogenic agents, damaged or senescent cells, and the timely resolution of the inflammation that is essential for the maintenance of homeostasis in the organism. In addition, they alert the organism when the immunological system is being deregulated, promoting the activation of other cells of the immune system, such as B and T lymphocytes, which produce cytokines that potentiate the microbicide functions.

Benign and Malignant Hematological Manifestations of Chronic Hepatitis C Virus Infection

Chronic hepatitis C virus (HCV) infection, that affects 3% of world's population, is associated with several hematological manifestations mainly benign cytopenias, coagulopathy and lymphoproliferative diseases. Immune or non-immune-mediated thrombocytopenia is a major challenge in chronic HCV infected patients especially in the setting of an advanced liver disease, with average prevalence of nearly 24%. Although several treatment modalities such as steroids, intravenous immunoglobulin, splenectomy and immunosuppresants have been tried with some success, their efficacy is not impressive and can result in an increase in viral load or other thrombotic complications. Even though a recent phase 2 study has shown promising role of a platelet growth factor, eltrombopag, in boosting platelets counts prior to antiviral treatment, its use in pre-operative setting had unexpected complications. Unlike thrombocytopenia, anemia and neutropenia are more frequently seen in treated patients and are often the result of antiviral therapy. HCV infection also pre-disposes to lymphoproliferative diseases, mainly non-Hodkings lymphomas, likely as a result of chronic antigenic stimulation and mutation of several genes involved in carcinogenesis. Understanding of the role of HCV infection in these conditions has therapeutic implications. Whereas antiviral therapy has shown therapeutic role in HCV-associated indolent lymphomas, monitoring of hepatic function and viral load is important in the management of diffuse large B-cell lymphoma in HCV-infected patients. Although our knowledge about the HCV infection and hematological manifestations has substantially grown in last few decades, further studies are important to advance our therapeutic approach.

Growth inhibitory effects and molecular mechanisms of crotoxin treatment in esophageal Eca-109 cells and transplanted tumors in nude mice

AIM

To investigate the antitumor actions of the Crotalus durissus neurotoxin (crotoxin) on human esophageal carcinoma (Eca-109) cells in vitro and transplanted esophageal Eca-109 tumors in nude mice.

METHODS

The growth-inhibitory effect was analyzed in Eca-109 cells using MTT assay. Cell morphology changes in nuclei were observed using Hoechst 33342 staining, while apoptosis and cell cycle distribution were examined by flow cytometry. RT-PCR was used to measure the Bcl-2, p15, and caspase-3 p17 gene expression levels. A tumor transplantation model was established by inoculation of Eca-109 cells were into female Balb/c nude mice. Crotoxin (25, 50, and 100 mg/kg) was subcutaneously injected into the transplanted tumors every 2 d for a total of 10 injections. Tumor size and weight were measured. Bcl-2, p15, and caspase-3 p17 protein expression in transplanted tumors was analyzed using Western blotting.

RESULTS

Crotoxin (25, 50, and 100 μg/mL) inhibited the growth of Eca-109 cells in a dose-dependent manner with inhibition rates of 22.9%, 35.8%, and 57.2%, respectively. Hoechst 33342 staining revealed apoptotic cells with pyknotic nuclear chromatin after crotoxin treatment. In Eca-109 cells, crotoxin induced apoptosis and G1 block, significantly upregulated the expression of p15 and caspase-3 p17 genes and downregulated the expression of Bcl-2 gene. Furthermore, crotoxin inhibited the growth of Eca-109 tumors in nude mice in a dose-dependent manner. Western blotting showed that crotoxin increased p15 and caspase-3 p17 protein levels and reduced Bcl-2 protein level in tumor specimens.

CONCLUSION

Crotoxin inhibits the growth of Eca-109 cells in vitro via apoptosis induction and G1 block. Local administration of crotoxin inhibits the growth of subcutaneously transplanted Eca-109 cells in nude mice, possibly via increasing p15 and caspase-3 p17 protein expression and reducing Bcl-2 protein expression.