Minocycline has anti-inflammatory effects and reduces cytotoxicity in an ex vivo spinal cord slice culture model of West Nile virus infection.

4 years ago

Minocycline has anti-inflammatory effects and reduces cytotoxicity in an ex vivo spinal cord slice culture model of West Nile virus infection.

Quick ED, Tyler KL, Clarke P, Seitz S

West Nile virus (WNV) is a neurotropic flavivirus that can cause significant neurological disease. Mouse models of WNV infection demonstrate that a pro-inflammatory environment is induced within the central nervous system (CNS) after WNV infection leading to entry of activated peripheral immune cells. We utilized ex vivo spinal cord slice cultures (SCSC) to demonstrate that anti-inflammatory mechanisms may also play a role in WNV-induced pathology and/or recovery. Microglia are a type of macrophage that function as resident CNS immune cells. Similar to mouse models, infection of SCSC with WNV induces the up-regulation of pro-inflammatory genes and proteins that are associated with microglial activation, including the microglia activation marker Iba1 and CC-motif chemokines CCL2, CCL3, and CCL5. This suggests that microglia assume a pro-inflammatory phenotype in response to WNV infection similar to the pro-inflammatory (M1) activation that can be displayed by other macrophages. We now show that the WNV-induced expression of these and other pro-inflammatory genes was significantly decreased in the presence of minocycline, which has anti-neuroinflammatory properties, including the ability to inhibit pro-inflammatory microglial responses. Minocycline also caused a significant increase in the expression of anti-inflammatory genes associated with alternative anti-inflammatory (M2) macrophage activation, including IL-4, IL-13, and FIZZ1. Minocycline-dependent alterations to M1/M2 gene expression were associated with a significant increase in survival of neurons, microglia, and astrocytes in WNV-infected slices and markedly decreased levels of iNOS. These results demonstrate that an anti-inflammatory environment induced by minocycline reduces viral cytotoxicity during WNV infection in ex vivo CNS tissue.IMPORTANCE West Nile virus (WNV) causes substantial morbidity and mortality, with no specific therapeutic treatments available. Antiviral inflammatory responses are a crucial component of WNV pathology, and understanding how they are regulated is important for tailoring effective treatments. Pro-inflammatory responses during WNV infection have been extensively studied, but anti-inflammatory responses (and their potential protective and reparative capabilities) following WNV infection have not been investigated. Minocycline induced the expression of genes associated with the anti-inflammatory (M2) activation of CNS macrophages (microglia) in WNV-infected SCSC whilst inhibiting the expression of genes associated with pro-inflammatory (M1) macrophage activation, and was protective for multiple CNS cell types indicating its potential use as a therapeutic reagent. This ex vivo culture system can uniquely address the ability of CNS parenchymal cells (neurons, astrocytes, microglia) to respond to minocycline and modulate the inflammatory environment and cytotoxicity in response to WNV infection without peripheral immune cell involvement.

Publisher URL: https://www.ncbi.nlm.nih.gov/pubmed/28878079

DOI: PubMed:28878079