Oxidative Stress in the Splenotoxicity of Aniline

Abstract

Aniline-induced splenic toxicity is characterized by hemorrhage, capsular hyperplasia, fibrosis, and a variety of sarcomas in rats. Early biochemical events responsible for the observed effects are not known. To understand the mechanism(s) of aniline-induced splenic toxicity, single and multiple (four and seven) doses of 1 mmol/kg of aniline hydrochloride(AH) were given in rats. Apart from changes in the hematological parameters, these studies demonstrated that AH could induce lipid peroxidation and protein oxidation in the spleen, and significant increases were observed at four doses. Subsequently, a dose-response study of AH was performed. Male SD rats were given four doses each (one dose/ day) of 0.25, 0.5, 1, and 2 mmol/kg of AH in water by gavage, while controls received water only. Animals were euthanized 24 hr following the last dose and tissues obtained. Spleen weight increased by 32 and 80% at 1 and 2 mmol/kg doses, respectively. Splenic lipid peroxidation showed dose-dependent increases of 24, 32, and 43% at 0.5, 1, and 2 mmol/kg, respectively. Protein oxidation in the spleen, quantitated by carbonyl content per milligram protein, showed 10, 28, and 27% increases at 0.5, 1, and 2 mmol/ kg, respectively. Iron content in the spleen also showed dose-dependent increases of 72, 172, and 325% at 0.5, 1, and 2 mmol/kg, respectively. Dose-related histopathologic expansion of splenic red pulp was characterized by increasing vascular congestion (most pronounced at 2 mmol/kg), increased red pulp cellularity, erythrophagocytosis, and cellular fragmentation at 1 and 2 mmol/kg; iron deposition in red pulp also increased dramatically with dose. These studies establish that aniline induces lipid peroxidation and protein oxidation in the spleen and suggest that oxidative stress plays a role in the splenic toxicity of aniline, e 1997 society of Toxicology.

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

“…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.…”

“…The toxicity is manifested by splenomegaly (Khan et al, 1997a(Khan et al, , 1999aCiccoli et al, 1999), elevated erythropoietic activity (Jenkins et al, 1972;Bus and Popp, 1987;Pauluhn, 2004), hyperpigmentation, hyperplasia, fibrosis (Bus and Popp, 1987;Khan et al, 1999aKhan et al, , 1999bKhan et al, , 2003a, and a variety of primary sarcomas after chronic exposure in rats (Goodman et al, 1984;Weinberger et al, 1985;Bus and Popp, 1987). Among various pathophysiological manifestations, fibrosis appears to be an important initiating preneoplastic lesion of the spleen (Khan et al, 1993(Khan et al, , 1995(Khan et al, , 1999a.…”

“…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.…”