NADPH Oxidase 2 Interaction with TLR2 Is Required for Efficient Innate Immune Responses to Mycobacteria via Cathelicidin Expression

Abstract

Gp91phox/NADPH oxidase (NOX) 2 is the main catalytic component of NOX, which mediates the phagocytic killing of ingested pathogens via the production of reactive oxygen species (ROS). However, Mycobacterium tuberculosis (Mtb) is relatively resistant to the microbicidal effects of ROS. Thus, the exact roles of NOX2 in the innate immune control against Mtb infection are not fully resolved. In this study, we show that NOX2 is essential for TLR2-dependent inflammatory responses and 1,25-dihydroxyvitamin D3 (1,25D3)-mediated antimicrobial activity against Mtb via cathelicidin expression. NOX2-null macrophages prominently abrogated Mtb-induced ROS production and inflammatory signaling activation in a TLR2-dependent manner. Mtb triggered a physical association between NOX2 and TLR2. In addition, the knockdown of NOX2 inhibited 1,25D3-triggered antimicrobial activity against viable Mtb through the modulation of cathelicidin expression in human macrophages. Treatment of NOX2 knocked down cells with cathelicidin restored the 1,25D3-induced antimicrobial effect, suggesting that the NOX2-dependent induction of cathelicidin in macrophages is part of a defensive strategy against Mtb. Furthermore, cathelicidin expression was required for the Mtb-induced release of ROS and the production of proinflammatory cytokines/chemokines, indicating a positive circuit of inflammation in response to Mtb. Our data collectively demonstrate a novel regulatory mechanism for TLR2-dependent innate responses to Mtb involving crosstalk between NOX2 and TLR2 and the expression of cathelicidin.

Resveratrol Inhibits Inflammation Induced by Heat-Killed Listeria monocytogenes

“…Recent reports have shown that Mycobacterium stimulates TLR2 receptors, and that TLR2 interacts with Nox-2 to produce ROS. 25 However, our results showed that Nox-1 expression is strongly induced by HKLM, suggesting that Nox-1 plays an essential role in ROS production caused by TLR2. While resveratrol dramatically inhibited Nox-1 expression, ROS production only decreased partially, suggesting the presence of other ROS sources.…”

Combination of host susceptibility and Mycobacterium tuberculosis virulence define gene expression profile in the host

“…Cathelicidin is an antimicrobial peptide expressed in response to TLR2 stimuli and vitamin D treatment in a process also involving Gp91(phox)/NADPH oxidase (NOX2, Table 1 (IV)) [67]. Among vitamin D receptor (VDR)-regulated genes, cathelicidin plays a critical role during TB [68].…”

“…The role of vitamin D(3)-dependent gene expression in both WT and iNOS /-mice during TB has been established [67]. Cathelicidin is an antimicrobial peptide expressed in response to TLR2 stimuli and vitamin D treatment in a process also involving Gp91(phox)/NADPH oxidase (NOX2, Table 1 (IV)) [67].…”

TLR3-Triggered Reactive Oxygen Species Contribute to Inflammatory Responses by Activating Signal Transducer and Activator of Transcription-1

“…phox , TLR3, TRIF, and STAT1 knockout (KO) mice (on the C57BL/6 background), as described previously (16,18). Briefly, bone marrow cells from the femur and tibia were cultured for 4-5 d in DMEM (Life Technologies BRL) containing M-CSF (25 ng/ml), 4 mM glutamine, and 10% FBS.…”

“…phox /NADPH oxidase (NOX)2 plays an essential role in TLR2-dependent inflammatory responses and antimicrobial activity against mycobacteria (16). Additionally, TLR4-dependent ROS generation is essential for mammalian innate immunity by acting through the TRAF6/ASK1/ p38 axis (17).…”