PI3K-Akt/PKB signaling pathway in neutrophils and mononuclear cells exposed to N-nitrosodimethylamine

Abstract

Neutrophils (PMN) play diverse regulatory and effector functions in the immune system through the release of reactive nitrogen species, including nitric oxide (NO). The enzyme responsible for NO synthesis in PMN is inducible nitric oxide synthase (iNOS) that is regulated by various signaling pathways, e.g. PI3K-Akt/PKB, and transcription factors. N-Nitrosodimethylamine (NDMA), a xenobiotic widespread in the human environment, affects immune cells. The study objective here was to examine the role of the PI3K-Akt/PKB pathway in induction of NO synthesis (with involvement of iNOS) in human PMN, as well as in autologous mononuclear cells (PBMC), exposed to NDMA. Isolated cells were incubated for 2 h with a sublethal dose of NDMA and then the expression of several select proteins in the cell cytoplasmic and nuclear fractions were determined by Western blot analyses. The results indicated that NDMA enhanced expression of iNOS, phospho-PI3K, and phospho-IkBa in the cytoplasmic fraction of the PMN and PBMC. The nuclear fraction of these cells also had a higher NF-kB expression. Moreover, in PMN, NDMA caused an increased expression of phospho-Akt (T308), phospho-Akt (S473), and phospho-IKKab in the cytoplasm, and c-Jun and FosB in the nuclear fraction. Blocking of PI3K caused a decrease in expression of all these proteins in NDMAexposed PMN. However, inhibition of PI3K led to a drop in expression of iNOS, phospho-PI3K, and phospho-IkBa in the cytoplasm, and in NF-kB in the nuclear fraction, of PBMC. The results of these studies indicated to us that NDMA activates the PI3K-Akt/PKB pathway in human PMN and that this, in turn, contributes to the activation of transcription factors NF-kB, c-Jun, and FosB involved in NO production (through modulation of iNOS expression).

Inhibition of neuroinflammation in BV2 microglia by the biflavonoid kolaviron is dependent on the Nrf2/ARE antioxidant protective mechanism

“…LPS is known to trigger NF-B activation through TLR4 signalling. However, studies have shown that dimethyl nitrosamine could be activating the PI3K-Akt/PKB pathway inimmune cells, which then contributes to the activation of NF-B [29].…”

Carcinogenesis: Failure of resolution of inflammation?

“…Carcinogens can stimulate cancer via the production of critical pro-inflammatory, pro-angiogenic and pro-tumorigenic cytokines/transcription factors, including TNF-α, IL-6, and NF-κB, as well as proto-oncogenes (e.g., c-Myc) ( Chen, Yan, & Ye, 1998 ; George, Tsuchishima, & Tsutsumi, 2019 ). Moreover, carcinogens may impair the host protective immune response via immunotoxicity, including increased apoptosis of leukocytes and reactive oxygen species ( Iwaniuk, Jablonska, Jablonski, Ratajczak-Wrona, & Garley, 2015 ; Jablonski, Jablonska, & Chojnowski, 2001 ; Jablonski, Jablonska, & Leonik, 2011 ; Nowak, Ratajczak-Wrona, Garley, & Jablonska, 2018 ; Ratajczak-Wrona et al, 2014 ). Impaired resolution of inflammation can lead to many human diseases including cancer ( Gartung et al, 2019 ; Panigrahy et al, 2019 ; Serhan & Levy, 2018 ; Sulciner et al, 2018 ).…”

E3 ubiquitin ligase NKLAM positively regulates macrophage inducible nitric oxide synthase expression

“…One such mechanism is the generation of nitric oxide (NO) from L-arginine via the expression and activation of inducible nitric oxide synthase (iNOS; NOS2). iNOS is a dimeric protein that is expressed in several immune cells including macrophages, dendritic cells, and neutrophils (Cruz, et al, 2001, Ratajczak-Wrona, et al, 2013). The production of NO by iNOS in response to infection is a critical defense mechanism.…”