Src kinase participates in LPS-induced activation of NADPH oxidase

Abstract

The production of superoxide from NADPH oxidase by macrophages in response to endotoxin (LPS) is an important innate immune response, yet it is not clear how LPS signals the activation of NADPH oxidase. The hypothesis is that LPS-induced src kinase and PI3 kinase (PI3K) facilitates the activation of p47 phox , the regulatory subunit of NADPH oxidase. In mouse macrophage RAW264.7 cells, inhibition of src tyrosine family kinases inhibited LPS-induced activation of NADPH oxidase, phosphorylation of p47phox, activation of PI3K and phosphorylation of the TLR4. Moreover, inhibition of LPS-induced increases in intracellular calcium blunted src kinase activation, PI3K association with TLR4, as well as PI3 kinase activation. These data suggest that both src kinase and PI3 kinase are involved in LPS-induced NADPH oxidase activation. Importantly, these data suggest that LPS-induced src kinase activation is critical for PI3 kinase activation as well as TLR4 phosphorylation and is dependent upon LPS-induced increase in intracellular calcium. These signaling events fill critical gaps in our understanding of LPS-induced free radical production as well as may potentially responsible for the mechanism of innate immune tolerance or desensitization caused by steroids or ethanol.

LPS induces pp60c-src-mediated tyrosine phosphorylation of Hsp90 in lung vascular endothelial cells and mouse lung

“…In particular, SNX-2122 has been reported to degrade both full-length HER2 and p95-HER2 and to downregulate HER2, AKT, and ERK signaling (7) and was in line with other studies that introduced LPS-induced pp60 Src activation in alveolar epithelial cells and macrophages (13,23,44). Src family tyrosine kinases (SFK) also play an important role in LPS-induced superoxide production and are responsible for the phosphorylation of the TLR4 in mouse RAW264 macrophages and in Chinese hamster ovary cells (8). In endothelial cells, pp60 src is activated in response to a variety of stimuli, including H 2 O 2 , estrogen, and shear stress and leads to activation of eNOS (15).…”

Diacylglycerol Kinases Terminate Diacylglycerol Signaling during the Respiratory Burst Leading to Heterogeneous Phagosomal NADPH Oxidase Activation

“…It is widely accepted that bacterial endotoxin can robustly prime phagocytes for superoxide production (19), although the underlying mechanism is still incompletely understood (20). We sought to determine whether this reflects increased production of superoxide by a constant number of phagosomes or an increased fraction of responding phagosomes.…”

Gut Microbiota, Bacterial Translocation, and Interactions with Diet: Pathophysiological Links between Major Depressive Disorder and Non-Communicable Medical Comorbidities

“…In addition, LPS can enhance the expression of inducible nitric oxide (NO) synthase, which triggers the formation of NO by macrophages through a process involving IFN-γ activation [53,59] . LPS also stimulates nicotinamide adenine dinucleotide phosphate-oxidase, which generates ROS and inflammatory markers, including superoxide, peroxide, cyclooxygenase-2 expression, and NF-κB activation [55,[60][61][62] . Mi-croglia, when activated by LPS, synthesize ROS, which initiate oxidative processes to proteins and may lead to proteolysis [63] .…”