Abstract

Aberrant or constitutive activation of nuclear factor kappa B (NF-κB) contributes to various human inflammatory diseases and malignancies via the upregulation of genes involved in cell proliferation, survival, angiogenesis, inflammation, and metastasis. Thus, inhibition of NF-κB signaling has potential for therapeutic applications in cancer and inflammatory diseases. We reported previously that Nei-like DNA glycosylase 2 (NEIL2), a mammalian DNA glycosylase, is involved in the preferential repair of oxidized DNA bases from the transcriptionally active sequences via the transcription-coupled base excision repair pathway. We have further shown that Neil2-null mice are highly sensitive to tumor necrosis factor α (TNFα)- and lipopolysaccharide-induced inflammation. Both TNFα and lipopolysaccharide are potent activators of NF-κB. However, the underlying mechanism of NEIL2's role in the NF-κB–mediated inflammation remains elusive. Here, we have documented a noncanonical function of NEIL2 and demonstrated that the expression of genes, such as Cxcl1, Cxcl2, Cxcl10, Il6, and Tnfα, involved in inflammation and immune cell migration was significantly higher in both mock- and TNFα-treated Neil2-null mice compared with that in the WT mice. NEIL2 blocks NF-κB's binding to target gene promoters by directly interacting with the Rel homology region of RelA and represses proinflammatory gene expression as determined by co-immunoprecipitation, chromatin immunoprecipitation, and electrophoretic mobility-shift assays. Remarkably, intrapulmonary administration of purified NEIL2 via a noninvasive nasal route significantly abrogated binding of NF-κB to cognate DNA, leading to decreased expression of proinflammatory genes and neutrophil recruitment in Neil2-null as well as WT mouse lungs. Our findings thus highlight the potential of NEIL2 as a biologic for inflammation-associated human diseases.

Highlights

  • The canonical nuclear factor kappa B (NF-κB) activation pathway, primarily in response to proinflammatory cytokines such as tumor necrosis factor α (TNFα), regulates the expression of various genes, including cytokines, chemokines, and cell adhesion molecules [21, 22]

  • In an effort to understand the role of Nei-like DNA glycosylase 2 (NEIL2) in modulating inflammatory gene expression, we induced systemic inflammation in Neil2-null (Neil2−/−) and WT (Neil2+/+) mice via intraperitoneal administration of a single dose of TNFα or phosphate buffered saline (PBS) as mock and conducted a multiplex Real-Time qPCR (RT-qPCR) analysis of 79 inflammation-associated genes (Fig. 1A)

  • TNFα-treated Neil2−/− lungs presented increased expression of genes involved in neutrophil trafficking (Cxcl1and Cxcl2), the Th1 response, natural killer cells, or monocyte trafficking (Cxcl10, Ccl3, and ccl2), as well as in the regulation of immune response, hematopoiesis, or inflammation (Tnfα, Il6, and IL1β) causing inflammation of lungs

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Summary

Introduction

The canonical NF-κB activation pathway, primarily in response to proinflammatory cytokines such as TNFα, regulates the expression of various genes, including cytokines, chemokines, and cell adhesion molecules [21, 22]. The basal level of Cxcl1, Cxcl2, Cxcl10, Il6, Tnfα, and ILβ expression in Neil2−/− mice lung was significantly higher compared with Neil2+/+ (Fig. 2A).

Results
Conclusion

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