Role of granulocyte macrophage colony stimulating factor in regeneration of the central nervous system

Role of the β Common (βc) Family of Cytokines in Health and Disease

The β common ([βc]/CD131) family of cytokines comprises granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-3, and IL-5, all of which use βc as their key signaling receptor subunit. This is a prototypic signaling subunit-sharing cytokine family that has unveiled many biological paradigms and structural principles applicable to the IL-2, IL-4, and IL-6 receptor families, all of which also share one or more signaling subunits. Originally identified for their functions in the hematopoietic system, the βc cytokines are now known to be truly pleiotropic, impacting on multiple cell types, organs, and biological systems, and thereby controlling the balance between health and disease. This review will focus on the emerging biological roles for the βc cytokines, our progress toward understanding the mechanisms of receptor assembly and signaling, and the application of this knowledge to develop exciting new therapeutic approaches against human disease.

Contrasting effect of the latency-reversing agents bryostatin-1 and JQ1 on astrocyte-mediated neuroinflammation and brain neutrophil invasion

Background

Despite effectiveness of the combined antiretroviral therapy, HIV-1 persists in long-lived latently infected cells. Consequently, new therapeutic approaches aimed at eliminating this latent reservoir are currently being developed. A “shock and kill” strategy using latency-reversing agents (LRA) to reactivate HIV-1 has been proposed. However, the impact of LRA on the central nervous system (CNS) remains elusive.

Methods

We used human fetal astrocytes and investigated the effects of several LRA on their functional and secretory activities. Astrocytes were infected with VSV-G-pseudotyped HIV-1 before treatment with various blood-brain barrier (BBB)-permeable LRA at subcytotoxic doses, which allow HIV-1 reactivation based on previous in vitro and clinical studies. Cells and supernatants were then used to evaluate effects of infection and LRA on (i) viability and metabolic activity of astrocytes using a colorimetric MTS assay; (ii) chemokines and proinflammatory cytokines secretion and gene expression by astrocytes using ELISA and RT-qPCR, respectively; (iii) expression of complement component 3 (C3), a proxy for astrogliosis, by RT-qPCR; (iv) glutamate uptake capacity by a fluorometric assay; and (v) modulation of neutrophil transmigration across an in vitro BBB model.

Results

We demonstrate that bryostatin-1 induces secretion of chemokines CCL2 and IL-8 and proinflammatory cytokines IL-6 and GM-CSF, whereas their production is repressed by JQ1. Bryostatin-1 also increases expression of complement component 3 and perturbs astrocyte glutamate homeostasis. Lastly, bryostatin-1 enhances transmigration of neutrophils across an in vitro blood-brain barrier model and induces formation of neutrophil extracellular traps.

Conclusions

These observations highlight the need to carefully assess the potential harmful effect to the CNS when selecting LRA for HIV-1 reactivation strategies.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1019-y) contains supplementary material, which is available to authorized users.

Glioblastoma-synthesized G-CSF and GM-CSF contribute to growth and immunosuppression: Potential therapeutic benefit from dapsone, fenofibrate, and ribavirin

Increased ratio of circulating neutrophils to lymphocytes is a common finding in glioblastoma and other cancers. Data reviewed establish that any damage to brain tissue tends to cause an increase in G-CSF and/or GM-CSF (G(M)-CSF) synthesized by the brain. Glioblastoma cells themselves also synthesize G(M)-CSF. G(M)-CSF synthesized by brain due to damage by a growing tumor and by the tumor itself stimulates bone marrow to shift hematopoiesis toward granulocytic lineages away from lymphocytic lineages. This shift is immunosuppressive and generates the relative lymphopenia characteristic of glioblastoma. Any trauma to brain-be it blunt, sharp, ischemic, infectious, cytotoxic, tumor encroachment, or radiation-increases brain synthesis of G(M)-CSF. G(M)-CSF are growth and motility enhancing factors for glioblastomas. High levels of G(M)-CSF contribute to the characteristic neutrophilia and lymphopenia of glioblastoma. Hematopoietic bone marrow becomes entrained with, directed by, and contributes to glioblastoma pathology. The antibiotic dapsone, the lipid-lowering agent fenofibrate, and the antiviral drug ribavirin are Food and Drug Administration- and European Medicines Agency-approved medicines that have potential to lower synthesis or effects of G(M)-CSF and thus deprive a glioblastoma of some of the growth promoting contributions of bone marrow and G(M)-CSF.