Quick Eamon D, Seitz Scott, Clarke Penny, Tyler Kenneth L
Neuroscience Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
Department of Immunology and Microbiology, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
J Virol. 2017 Oct 27;91(22). doi: 10.1128/JVI.00569-17. Print 2017 Nov 15.
West Nile virus (WNV) is a neurotropic flavivirus that can cause significant neurological disease. Mouse models of WNV infection demonstrate that a proinflammatory environment is induced within the central nervous system (CNS) after WNV infection, leading to entry of activated peripheral immune cells. We utilized 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 upregulation of proinflammatory genes and proteins that are associated with microglial activation, including the microglial activation marker Iba1 and CC motif chemokines CCL2, CCL3, and CCL5. This suggests that microglia assume a proinflammatory phenotype in response to WNV infection similar to the proinflammatory (M1) activation that can be displayed by other macrophages. We now show that the WNV-induced expression of these and other proinflammatory genes was significantly decreased in the presence of minocycline, which has antineuroinflammatory properties, including the ability to inhibit proinflammatory microglial responses. Minocycline also caused a significant increase in the expression of anti-inflammatory genes associated with alternative anti-inflammatory (M2) macrophage activation, including interleukin 4 (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 inducible nitric oxide synthase (iNOS). These results demonstrate that an anti-inflammatory environment induced by minocycline reduces viral cytotoxicity during WNV infection in CNS tissue. 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. Proinflammatory 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 while inhibiting the expression of genes associated with proinflammatory (M1) macrophage activation and was protective for multiple CNS cell types, indicating its potential use as a therapeutic reagent. This culture system can uniquely address the ability of CNS parenchymal cells (neurons, astrocytes, and microglia) to respond to minocycline and to modulate the inflammatory environment and cytotoxicity in response to WNV infection without peripheral immune cell involvement.
西尼罗河病毒（WNV）是一种嗜神经性黄病毒，可引发严重的神经系统疾病。WNV感染的小鼠模型表明，WNV感染后中枢神经系统（CNS）内会诱导产生促炎环境，导致活化的外周免疫细胞进入。我们利用脊髓切片培养（SCSC）来证明抗炎机制可能也在WNV诱导的病理变化和/或恢复过程中发挥作用。小胶质细胞是一种巨噬细胞，作为中枢神经系统常驻免疫细胞发挥作用。与小鼠模型类似，用WNV感染SCSC会诱导与小胶质细胞活化相关的促炎基因和蛋白质上调，包括小胶质细胞活化标志物离子钙结合衔接分子1（Iba1）以及CC基序趋化因子CCL2、CCL3和CCL5。这表明小胶质细胞在WNV感染时呈现促炎表型，类似于其他巨噬细胞可表现出的促炎（M1）活化。我们现在表明，在具有抗神经炎症特性（包括抑制促炎性小胶质细胞反应能力）的米诺环素存在的情况下，WNV诱导的这些及其他促炎基因的表达显著降低。米诺环素还导致与替代性抗炎（M2）巨噬细胞活化相关的抗炎基因表达显著增加，包括白细胞介素4（IL - 4）、IL - 13和抵抗素样分子α（FIZZ1）。米诺环素对M1/M2基因表达的依赖性改变与WNV感染切片中神经元、小胶质细胞和星形胶质细胞存活率的显著提高以及诱导型一氧化氮合酶（iNOS）水平的显著降低相关。这些结果表明，米诺环素诱导的抗炎环境可降低CNS组织中WNV感染期间的病毒细胞毒性。西尼罗河病毒（WNV）会导致大量发病和死亡，目前尚无特效治疗方法。抗病毒炎症反应是WNV病理的关键组成部分，了解其调控方式对于制定有效治疗方案很重要。WNV感染期间的促炎反应已得到广泛研究，但WNV感染后的抗炎反应（及其潜在的保护和修复能力）尚未得到研究。米诺环素在WNV感染的SCSC中诱导与中枢神经系统巨噬细胞（小胶质细胞）抗炎（M2）活化相关的基因表达，同时抑制与促炎（M1）巨噬细胞活化相关的基因表达，并且对多种中枢神经系统细胞类型具有保护作用，表明其作为治疗试剂的潜在用途。这种培养系统能够独特地研究中枢神经系统实质细胞（神经元、星形胶质细胞和小胶质细胞）对米诺环素的反应能力，以及在无外周免疫细胞参与的情况下，调节炎症环境和对WNV感染的细胞毒性反应的能力。
