LPS induces CD40 gene expression through the activation of NF-κB and STAT-1α in macrophages and microglia

Abstract

IntroductionCD40 is a member of the tumor necrosis factor receptor (TNFR) superfamily that is expressed by cells, including B cells, macrophages, microglia, dendritic cells, endothelial cells, and tumor cells. The interaction between CD40 and its cognate ligand, CD40L (CD154), is critical for a productive immune response. 1,2 Upregulation of various cell surface molecules, such as class II major histocompatibility complex, CD40, CD80, and CD86, occurs on CD40-CD154 contact, as well as the production of numerous cytokines and chemokines (interleukin 1 [IL-1], IL-6, IL-10, tumor necrosis factor ␣ [TNF-␣] and macrophage inflammatory protein 1 [MIP-1]) and cytotoxic radicals. 2 CD40 has been implicated in participating in many human diseases, particularly autoimmune diseases. 3,4 Blocking the interaction between CD40-CD154 with anti-CD154 or anti-CD40 antibody is beneficial in animal models of autoimmune diseases. 5 These findings illustrate the importance of CD40-CD154 interactions for homeostasis of immune responses. We have previously shown that macrophages and microglia, the endogenous macrophage of the brain, constitutively express CD40 at a low level, which is greatly enhanced by the cytokine interferon ␥ (IFN-␥). IFN-␥-induced CD40 expression involves IFN-␥-activated signal transducer and activator of transcription 1␣ (STAT-1␣) and nuclear factor-B (NF-B) activation through an autocrine response to IFN-␥-induced TNF-␣ production. [6][7][8][9] The immune response to microbial pathogens relies on both innate and acquired immunity. Innate immunity is determined by the interaction between potential pathogens and their cognate binding partners (receptors) on phagocytes, which is performed by a group of proteins, the Toll-like receptor (TLR) family. 10,11 At least 10 TLRs (TLR1-TLR10) recognize specific molecular patterns that are present in microbial components. Stimulation of different TLRs induces distinct patterns of gene expression, which not only leads to the activation of innate immunity but also instructs the development of antigen-specific acquired immunity. 12,13 The TLR family signals via shared downstream signaling molecules, including the adapter molecule myeloid differentiation primary-response protein 88 (MyD88), interleukin-1 receptor-associated protein kinases (IRAK1 and IRAK4), transforming growth factor ␤ (TGF-␤)-activated kinase (TAK1), TAK1-binding protein 1 (TAB1), TAB2, and tumor necrosis factor receptor-associated factor 6. 10,11 TAK1 is a member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, which is essential for IL-1, TNF-␣, and lipopolysaccharide (LPS)-induced activation of NF-B and MAPKs. 10 The NF-B family of transcription factors is composed of 5 members, p65 (Rel-A), Rel-B, c-Rel, p50, and p52, which function as homodimers and heterodimers. NF-B transcription factors are present in the cytoplasm in an inactive state, complexed with inhibitory IB proteins. The activation process is mediated by Supported by the National Institutes of Health (grants NS45290 and N...

SIGIRR modulates the inflammatory response in the brain

“…In addition to its ability to stimulate cytokine release, LPS upregulates expression of cell surface proteins, considered to be markers of microglial activation (Loane et al, 2007;Qin et al, 2005a). In this study, LPS is shown to increase expression of CD40, as well as another cell surface marker of microglial activation, ICAM-1, but the effect of LPS was several-fold greater in cells prepared from SIGIRR -/-mice.…”

NF-κB and STAT3 signaling pathways collaboratively link inflammation to cancer

“…NF-κB acts as a "rapid-acting" primary transcription factor to regulate many cellular responses. Many stimuli can induce NF-κB activity, such as tumor necrosis factor alpha (TNFα), interleukin 1-beta (IL-1β), bacterial lipopolysaccharides (LPS), ionizing radiation, reactive oxygen species (ROS), etc (Osborn et al, 1989;Basu et al, 1998;Kida et al, 2005;Qin et al, 2005). Most of the NF-κB activators induce the degradation of IκB protein via activation of the IκB kinase (IKK) complex (IKKα, IKKβ and IKKγ).…”

Inducible RasGEF1B circular RNA is a positive regulator of ICAM-1 in the TLR4/LPS pathway

“…19 To investigate if LPS-induced expression of mcircRasGEF1B is dependent on NF-kB, we blocked NF-kB activation by treating RAW246.7 cells with IKK inhibitor VII. 20 Treatment of RAW264.7 cells with increasing doses of IKK inhibitor VII significantly inhibited LPS-induced expression of CCL5, a known NF-kB target gene, mlinRasGEF1B and mcircRasGEF1B (Fig.…”