Chemoattractant-induced phagocyte activation is an important mechanism of host defense. In phagocytes, induced activation of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase leads to robust production of reactive oxygen species (ROS), which is essential for the elimination of ingested bacteria and fungi. However, extracellular ROS production by phagocyte NADPH oxidase (also termed Nox2) can be harmful to the tissue and is a major cause of vascular injury in acute inflammation. This revised competing renewal application aims to understand how chemoattractant-induced neutrophil superoxide generation is regulated at the molecular and cellular levels. Building on the systems we developed and preliminary results obtained in the previous grant cycle, the application will focus on the critical roles for p47phox in the assembly of an NADPH oxidase. Experiments are proposed in 3 specific aims to challenge existing concept and identify novel regulatory mechanisms for NADPH oxidase activation.
Aim 1 will characterize Akt isoforms in chemoattractant-induced ROS production. In neutrophil research, Akt has been taken as one class of protein kinases functionally, but our preliminary study has led to an unexpected finding that the two major Akt isoforms in neutrophils play different roles in NADPH oxidase activation. Experiments are proposed to test the hypothesis that membrane translocation of an Akt isoform dictates its ability to mediate NADPH oxidase activation, and to examine whether the two Akt isoforms phosphorylates p47phox differently.
Aim 2 is based on our recent characterization of a mutant p47phox protein that mediates spontaneous superoxide production in the absence of physical interaction with p67phox. Experiments are designed to characterize a potentially novel mechanism for 47phox-mediated conformational change in cytochrome b558 that facilitates the assembly of a functional NADPH oxidase complex.
Aim 3 will investigate an important regulatory mechanism for p47phox-dependent oxidant production. We will examine the negative regulation of NADPH oxidase by MAP kinase phosphatase 5 (MKP5). Using in vivo and ex vivo approaches, we will investigate how MKP5 protects against LPS-induced vascular injury through suppression of neutrophil ROS production in a mouse model of vascular inflammation. Collectively, these studies are expected to provide novel insights into the activation and inactivation mechanisms of phagocyte NADPH oxidase, thereby facilitating therapeutic intervention of ROS-mediated tissue injury.
Phagocytes (a class of white blood cells that engulf bacteria and fungi) produce large amounts of reactive oxygen species that are toxic to bacteria and to host tissues. A balanced act of phagocyte activation is important for the maintenance of host defense capability and for minimizing unwanted tissue injury. The proposed studies will investigate how these cells are regulated by intrinsic mechanisms that prevent over-production of reactive oxygen species during acute inflammation, and how the machinery for oxidant production is assembled and activated when phagocytes are stimulated. Information derived from these studies is expected to have health benefit by reducing inflammatory tissue injury and the resulting failure of organ functions.
|Yan, Qian; Sun, Lei; Zhu, Ziyan et al. (2014) Jmjd3-mediated epigenetic regulation of inflammatory cytokine gene expression in serum amyloid A-stimulated macrophages. Cell Signal 26:1783-91|
|Chen, Mingjie; Zhou, Huibing; Cheng, Ni et al. (2014) Serum amyloid A1 isoforms display different efficacy at Toll-like receptor 2 and formyl peptide receptor 2. Immunobiology 219:916-23|
|He, Hui-Qiong; Troksa, Erica L; Caltabiano, Gianluigi et al. (2014) Structural determinants for the interaction of formyl peptide receptor 2 with peptide ligands. J Biol Chem 289:2295-306|
|Zhou, Jun-xian; Liao, Dan; Zhang, Shuo et al. (2014) Chemerin C9 peptide induces receptor internalization through a clathrin-independent pathway. Acta Pharmacol Sin 35:653-63|
|Hu, Yaogang; Cheng, Ni; Wu, Haifan et al. (2014) Design, synthesis and characterization of fMLF-mimicking AApeptides. Chembiochem 15:2420-6|
|Schepetkin, Igor A; Kirpotina, Liliya N; Khlebnikov, Andrei I et al. (2014) Antagonism of human formyl peptide receptor 1 (FPR1) by chromones and related isoflavones. Biochem Pharmacol 92:627-41|
|Sun, Lei; Zhu, Ziyan; Cheng, Ni et al. (2014) Serum amyloid A induces interleukin-33 expression through an IRF7-dependent pathway. Eur J Immunol 44:2153-64|
|Ye, Richard D (2014) STIM1 for stimulation of phagocyte NADPH oxidase. Blood 123:2129-30|
|Nie, Baoming; Cheng, Ni; Dinauer, Mary C et al. (2010) Characterization of P-Rex1 for its role in fMet-Leu-Phe-induced superoxide production in reconstituted COS(phox) cells. Cell Signal 22:770-82|
|Qian, Feng; Deng, Jing; Cheng, Ni et al. (2009) A non-redundant role for MKP5 in limiting ROS production and preventing LPS-induced vascular injury. EMBO J 28:2896-907|
Showing the most recent 10 out of 50 publications