ABSTRACT
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.
Subject(s)
Adjuvants, Immunologic/toxicity , Astrocytes/drug effects , Azepines/toxicity , Brain/drug effects , Bryostatins/toxicity , Chemotaxis, Leukocyte/drug effects , Triazoles/toxicity , Brain/pathology , HIV-1/physiology , Humans , Inflammation/pathology , Neutrophils/drug effects , Virus Activation/drug effects , Virus Latency/drug effectsABSTRACT
Protein kinase C (PKC) isozymes play central roles in signal transduction on the cell surface and could serve as promising therapeutic targets of intractable diseases like cancer, Alzheimer's disease, and acquired immunodeficiency syndrome (AIDS). Although natural PKC ligands like phorbol esters, ingenol esters, and teleocidins have the potential to become therapeutic leads, most of them are potent tumor promoters in mouse skin. By contrast, bryostatin-1 (bryo-1) isolated from marine bryozoan is a potent PKC activator with little tumor-promoting activity. Numerous investigations have suggested bryo-1 to be a promising therapeutic candidate for the above intractable diseases. However, there is a supply problem of bryo-1 both from natural sources and by organic synthesis. Recent approaches on the synthesis of bryo-1 have focused on its simplification, without decreasing the ability to activate PKC isozymes, to develop new medicinal leads. Another approach is to use the skeleton of natural PKC ligands to develop bryo-1 surrogates. We have recently identified 10-methyl-aplog-1 (26), a simplified analog of tumor-promoting aplysiatoxin (ATX), as a possible therapeutic lead for cancer. This review summarizes recent investigations on the simplification of natural PKC ligands, bryo-1 and ATX, to develop potential medicinal leads.
Subject(s)
Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/pharmacology , Bryostatins/chemical synthesis , Bryostatins/pharmacology , Lyngbya Toxins/chemical synthesis , Lyngbya Toxins/pharmacology , Protein Kinase C/antagonists & inhibitors , Animals , Antineoplastic Agents/toxicity , Bryostatins/toxicity , Cell Proliferation/drug effects , Humans , Isoenzymes/antagonists & inhibitors , Isoenzymes/metabolism , Ligands , Lyngbya Toxins/toxicity , Protein Kinase C/metabolism , Structure-Activity RelationshipABSTRACT
BACKGROUND: Bryostatin-1, a highly oxygenated marine macrolide with a unique polyacetate backbone isolated from the marine animal Bugula neritina (Linnaeus), is now being developed as an anti-cancer drug for treating malignancy. In the present study, developmental toxicity of bryostatin-1 was evaluated in Sprague-Dawley rats. METHODS: Bryostatin-1 was intravenously administered to rats on gestation days 6-15 at 4.0, 8.0, and 16.0 microg/kg on a daily basis. Then the reproductive parameters were determined in animals, and fetuses were examined for external, visceral, and skeletal malformations. RESULTS: The total weight gains were significantly different in animals between the control group and 8.0 and 16.0 microg/kg bryostatin-1 groups during and after treatment. The resorption and death fetus rates were significantly different between the bryostatin-1 group (16 microg/kg) and the control group. The fetal weight and fetal crown-rump length in the bryostatin-1 groups were significantly lower than that in the control group. CONCLUSIONS: Our results indicated that maternal toxicity occurred when the dose of bryostatin-1 was at 8.0 microg/kg, embryotoxicity at 16.0 microg/kg, and fetotoxicity at 4.0 microg/kg; but bryostatin-1 showed no teratogenic effect in rats. In light of our findings, bryostatin-1 should be used with caution in pregnant women with cancer, if they would like to continue the pregnancy.
