Iron Release and Oxidative DNA Damage in Splenic Toxicity of Aniline

Abstract

Mechanisms by which aniline produces selective toxicity to the spleen are not well understood. Previously, studies showed that aniline exposure induces lipid peroxidation and protein oxidation in the spleen. The present study was aimed to determine the release of free iron and oxidative DNA damage in the spleen following aniline exposure. To achieve this, male SD rats were orally administered 1 mmol/kg/d aniline for 7 d, while controls received the vehicle only. Total splenic iron content showed a significant increase of 200% in the aniline-treated rats, whereas free iron (low-molecular-weight chelatable iron) showed a marked increase of 375% in comparison to controls. Oxidative DNA damage, measured in terms of 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels, showed a remarkable increase of 83% in the aniline-treated rats. These results suggest an association between release of free iron and oxidative DNA damage, which could lead to mutagenic and/or carcinogenic responses in the spleen.

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

“…Therefore, it is critical to delineate the early molecular events in the spleen, which could potentially lead to splenic fibrosis and/or fibrosarcoma. Using an experimental condition known to generate oxidative stress and that precedes splenic fibrosis (Khan et al, 1997a(Khan et al, , 2003bWu et al, 2005), this study provides evidence that repeated-dose aniline exposure leads to activation of NF-κB and AP-1, causes phosphorylation of upstream critical signaling proteins [IKKα/β and MAPKs (ERK1/2, JNK1/2 and p38)], and results in the upregulation of pro-inflammatory and pro-fibrogenic cytokines in the spleen. These early molecular events could ultimately lead to splenic fibrosis and/or fibrosarcomas.…”

“…The choice of aniline dose was based on our earlier short-term studies that showed iron overload, and significant increases in lipid peroxidation, protein oxidation and DNA damage (oxidative stress) in the spleen (Khan et al, 1997a(Khan et al, , 2003bWu et al, 2005). Twenty four hours following the last dose, the animals were euthanized under nembutal (sodium pentobarbital) anesthesia and spleens were aseptically removed immediately, blotted, and weighed and then used for various analyses.…”

“…Iron overload in the spleen is one of the most consistent and striking consequences of aniline exposure (Khan et al, 1993(Khan et al, , 1995(Khan et al, , 1997a(Khan et al, , 1999aWu et al, 2005). In fact, aniline-induced splenic toxicity could be largely attributed to iron overload (increases in both total and free iron) as iron-induced oxidative and nitrosative stress in the spleen causes increased lipid peroxidation, protein oxidation, DNA oxidation and nitrotyrosine formation (Khan et al, 1997a(Khan et al, , 1997b(Khan et al, , 1999a(Khan et al, , 2003b(Khan et al, , 2003cWu et al, 2005).…”

“…In fact, aniline-induced splenic toxicity could be largely attributed to iron overload (increases in both total and free iron) as iron-induced oxidative and nitrosative stress in the spleen causes increased lipid peroxidation, protein oxidation, DNA oxidation and nitrotyrosine formation (Khan et al, 1997a(Khan et al, , 1997b(Khan et al, , 1999a(Khan et al, , 2003b(Khan et al, , 2003cWu et al, 2005). Earlier subchronic aniline exposure studies (related to fibrogenic response in the spleen) have also shown activation of redoxsensitive transcription factors (TFs) nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) in the spleen (Wang et al, 2005;Khan et al, 2006).…”

“…Specifically, in rats exposed to aniline under an experimental condition which precedes fibrogenic response but known to cause oxidative stress in the spleen (Khan et al, 1997a(Khan et al, , 1997bWu et al, 2005), we have evaluated phosphorylation of IKK (α and β) and MAPKs (ERK 1/2, JNK 1/2, and p38), activation of NF-κB and AP-1, and gene expression of cytokines (IL-1α, IL-6 and TNF-α) in the spleen.…”