Inhibition of NADPH oxidase 2 enhances resistance to viral neuroinflammation by facilitating M1-polarization of macrophages at the extraneural tissues.

BACKGROUND: Macrophages play a pivotal role in the regulation of Japanese encephalitis (JE), a severe neuroinflammation in the central nervous system (CNS) following infection with JE virus (JEV). Macrophages are known for their heterogeneity, polarizing into M1 or M2 phenotypes in the context of various immunopathological diseases. A comprehensive understanding of macrophage polarization and its relevance to JE progression holds significant promise for advancing JE control and therapeutic strategies. METHODS: To elucidate the role of NADPH oxidase-derived reactive oxygen species (ROS) in JE progression, we assessed viral load, M1 macrophage accumulation, and cytokine production in WT and NADPH oxidase 2 (NOX2)-deficient mice using murine JE model. Additionally, we employed bone marrow (BM) cell-derived macrophages to delineate ROS-mediated regulation of macrophage polarization by ROS following JEV infection. RESULTS: NOX2-deficient mice exhibited increased resistance to JE progression rather than heightened susceptibility, driven by the regulation of macrophage polarization. These mice displayed reduced viral loads in peripheral lymphoid tissues and the CNS, along with diminished infiltration of inflammatory cells into the CNS, thereby resulting in attenuated neuroinflammation. Additionally, NOX2-deficient mice exhibited enhanced JEV-specific Th1 CD4 + and CD8 + T cell responses and increased accumulation of M1 macrophages producing IL-12p40 and iNOS in peripheral lymphoid and inflamed extraneural tissues. Mechanistic investigations revealed that NOX2-deficient macrophages displayed a more pronounced differentiation into M1 phenotypes in response to JEV infection, thereby leading to the suppression of viral replication. Importantly, the administration of H2O2 generated by NOX2 was shown to inhibit M1 macrophage polarization. Finally, oral administration of the ROS scavenger, butylated hydroxyanisole (BHA), bolstered resistance to JE progression and reduced viral loads in both extraneural tissues and the CNS, along with facilitated accumulation of M1 macrophages. CONCLUSION: In light of our results, it is suggested that ROS generated by NOX2 play a role in undermining the control of JEV replication within peripheral extraneural tissues, primarily by suppressing M1 macrophage polarization. Subsequently, this leads to an augmentation in the viral load invading the CNS, thereby facilitating JE progression. Hence, our findings ultimately underscore the significance of ROS-mediated macrophage polarization in the context of JE progression initiated JEV infection.

TLR3/TRIF pathway confers protection against herpes simplex encephalitis through NK cell activation mediated by a loop of type I IFN and IL-15 from epithelial and dendritic cells.

Autosomal recessive (AR) and dominant (AD) deficiencies of TLR3 and TRIF are believed to be crucial genetic causes of herpes simplex encephalitis (HSE), which is a fatal disease causing focal or global cerebral dysfunction following infection with herpes simplex virus type 1 (HSV-1). However, few studies have been conducted on the immunopathological networks of HSE in the context of TLR3 and TRIF defects at the cellular and molecular levels. In this work, we deciphered the crosstalk between type I IFN (IFN-I)-producing epithelial layer and IL-15-producing dendritic cells (DC) to activate NK cells for the protective role of TLR3/TRIF pathway in HSE progression after vaginal HSV-1 infection. TLR3- and TRIF-ablated mice showed enhanced susceptibility to HSE progression, along with high HSV-1 burden in vaginal tract, lymphoid tissues and CNS. The increased HSV-1 burden in TLR3- and TRIF-ablated mice did not correlate with increased infiltration of Ly-6C+ monocytes, but it was closely associated with impaired NK cell activation in vaginal tract. Furthermore, using delicate ex vivo experiments and bone marrow transplantation, TRIF deficiency in tissue-resident cells, such as epithelial cells in vaginal tract, was found to cause impaired NK cell activation by means of low IFN-I production, whereas IFN-I receptor in DC was required for NK cell activation via IL-15 production in response to IFN-I produced from epithelial layer. These results provide new information about IFN-I- and IL-15-mediated crosstalk between epithelial cells and DC at the primary infection site, which suppresses HSE progression in a TLR3- and TRIF-dependent manner.

T cell-intrinsic miR-155 is required for Th2 and Th17-biased responses in acute and chronic airway inflammation by targeting several different transcription factors.

Asthmatic airway inflammation is divided into two typical endotypes: Th2-mediated eosinophilic and Th1- or Th17-mediated neutrophilic airway inflammation. The miRNA miR-155 has well-documented roles in the regulation of adaptive T-cell responses and innate immunity. However, no specific cell-intrinsic role has yet been elucidated for miR-155 in T cells in the course of Th2-eosinophilic and Th17-neutrophilic airway inflammation using actual in vivo asthma models. Here, using conditional KO (miR155ΔCD4 cKO) mice that have the specific deficiency of miR-155 in T cells, we found that the specific deficiency of miR-155 in T cells resulted in fully suppressed Th2-type eosinophilic airway inflammation following acute allergen exposure, as well as greatly attenuated the Th17-type neutrophilic airway inflammation induced by repeated allergen exposure. Furthermore, miR-155 in T cells appeared to regulate the expression of several different target genes in the functional activation of CD4+ Th2 and Th17 cells. To be more precise, the deficiency of miR-155 in T cells enhanced the expression of c-Maf, SOCS1, Fosl2 and Jarid2 in the course of CD4+ Th2 cell activation, while C/EBPß was highly enhanced in CD4+ Th17 cell activation in the absence of miR-155 expression. Conclusively, our data revealed that miR-155 could promote Th2 and Th17-mediated airway inflammation via the regulation of several different target genes, depending on the context of asthmatic diseases. Therefore, these results provide valuable insights into actual understanding of specific cell-intrinsic role of miR-155 in eosinophilic and neutrophilic airway inflammation for the development of fine-tune therapeutic strategies.