Activation of oxidative stress-responsive signaling pathways in early splenotoxic response of aniline

Abstract

Aniline exposure causes toxicity to the spleen, which leads to a variety of sarcomas, and fibrosis appears to be an important preneoplastic lesion. However, early molecular mechanisms in anilineinduced toxicity to the spleen are not known. Previously, we have shown that aniline exposure results in iron overload and induction of oxidative stress in the spleen, which can cause transcriptional upregulation of fibrogenic/inflammatory cytokines via activation of oxidative stress (OS)-responsive signaling pathways. To test this mechanism, male SD rats were treated with aniline (1 mmol/kg/day via gavage) for 7 days, an experimental condition that precedes the appearance of fibrosis. Significant increases in both NF-κB and AP-1 binding activity was observed in the nuclear extracts of splenocytes from aniline-treated rats as determined by ELISAs, and supported by Western blot data showing increases in p-IκBα, p-p65 and p-c-Jun. To understand the upstream signaling events which could account for the activation of NF-κB and AP-1, phosphorylation patterns of IκB kinases (IKKα and IKKβ) and mitogen-activated protein kinases (MAPKs) were pursued. Our data showed remarkable increases in both p-IKKα and p-IKKβ in the splenocytes from aniline-treated rats, suggesting their role in the phosphorylation of both IκBα and p65 subunits. Furthermore, aniline exposure led to activation of all three classes of MAPKs, as evident from increased phosphorylation of extracellularsignal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK1/2) and p38 MAPKs, which could potentially contribute to the observed activation of both AP-1 and NF-κB. Activation of upstream signaling molecules was also associated with simultaneous increases in gene transcription of cytokines IL-1, IL-6 and TNF-α. The observed sequence of events following aniline exposure could initiate a fibrogenic and/or tumorigenic response in the spleen.

RETRACTED: Mancozeb-induced genotoxicity and apoptosis in cultured human lymphocytes

“…This suggested that NF-κB promotes cell apoptosis through the FasL dependent pathway in in vitro mancozeb exposed CHLs. ROS are also key mediators in signaling pathways such as the NF-κB pathway (Wang et al, 2008) and it is also reported that oxidative stress enhanced NF-κB activation.…”

Enhanced expression of cyclins and cyclin-dependent kinases in aniline-induced cell proliferation in rat spleen

“…Splenomegaly is one of the earliest characteristic feature of aniline-induced splenotoxic responses preceding fibrosis and sarcomas (Weinberger et al, 1985; Bus and Popp, 1987; Khan et al, 1997, 1999a; Wang et al, 2005). As evidenced from previous studies, splenomegaly and splenotoxicity were associated with increased red pulp cellularity, increases in macrophages and fibroblasts, and such changes as iron overload, oxidative stress and activation of redox-sensitive transcription factors (Khan et al, 1997, 1999a, 1999b, 2003a, 2006; Wang et al, 2005, 2008). However, molecular mechanisms leading to aniline-induced cellular proliferation in the spleen remain largely unknown.…”

“…This study was, therefore, focused on evaluating the cellular proliferation and expression of cell cycle proteins, especially G1 phase cyclins and CDKs in an experimental condition preceding a tumorigenic response, but known to induce iron overload and oxidative stress in the spleen (Khan et al, 1999a, 1999b; Wang et al, 2008) following aniline insult.…”

Aniline-induced nitrosative stress in rat spleen: Proteomic identification of nitrated proteins

“…Real-time PCR was performed essentially as described earlier (Wang et al, 2005, 2008, 2010; Ma et al, 2008). First-strand cDNA was prepared from total RNA by using the SuperScript first-strand synthesis kit (Invitrogen, Carlsbad, CA) as per the manufacturer's instructions.…”