Abstract
The present work evaluated the effect of flaxseed oil (FO) against toxicity induced by cadmium chloride (CdCl2) in the mouse liver and kidney. Male Swiss albino mice were treated with CdCl2 (4.5 mg/kg, intraperitoneally) with or without FO at three concentrations (4, 8, 12 mL/kg, orally) for two consecutive weeks. To analyze the effects of FO, we used the following techniques: (1) histopathological examination; (2) comet assay; (3) RT-PCR gene expression analysis of tumor necrosis factor (TNF-α) and tumor suppressor protein (p53); and (4) immunohistochemical analysis of caspase-9 protein expression. The gas chromatography-mass spectrometry results showed that FO had a high content of unsaturated fatty acids including, oleic acid, linolenic acid, and linoleic acid. Oral supplementation with FO (12 mL/kg) resulted in a normal histological appearance without alteration in the DNA integrity and gene expression of TNF-α, p53, and caspase-9 in liver and kidney tissues. As expected, CdCl2 remarkably induced loss of histological integrity, increased DNA comet formation, increased TNF-α and p53 mRNA expression levels and increased the immunoreactivity of caspase-9 expression. When FO was given before administration of CdCl2, these histopathological defects were reversed; necrosis, degeneration, inflammatory cell infiltration, hemorrhage, Kupffer cells, and pyknotic cells were all reduced. These histological improvements induced by FO were accompanied by reduced DNA breakage, downregulated mRNA expression of TNF-α and p53, and downregulated immunohistochemical expression of caspase-9 protein. In conclusion, FO and its constituents may act as signaling molecules and modify the expression of genes involved in proinflammatory cytokine production (TNF-α), cell cycle arrest (p53), and apoptosis (caspase-9), thereby improving biological activities and health.
Key Points
The beneficial effects of flax oil (FO) and its constituents have been studied in in vivo and in vitro systems. FO reduced cell proliferation in several human cancers and reduced tumor growth in an ectopic cervical cancer mouse model. Although the prophylactic activity of FO has been demonstrated, its protective mechanism is complex and still incompletely understood. Thus, the present investigation was planned to explore the protective mechanism by which FO counteracts the toxic effect of CdCl2 in the mouse liver and kidney. Two-weeks of repeated oral treatment with FO successfully prevented hepatic and renal histological deformities induced by CdCl2 in a concentration-dependent manner. These findings imply that FO can block the inflammatory process and oxidative stress, which are responsible for CdCl2-induced toxicity. These observations support the down-regulation of TNF-α mRNA expression observed in the present work and are also in agreement with previous studies.
The present study showed a pronounced reduction in the percentage of DNA in the comet tail induced by CdCl2 in the mouse liver tissues upon FO administration. These data indicate that FO can interfere with CdCl2 before it induces DNA strand breaks. This may occur through several mechanisms: (1) FO scavenges free radicals to terminate the formation of hydroperoxides, (2) FO chelates transition metals to suppress the generation of radical formation or decompose lipid peroxides; or (3) FO reduces the interaction of CdCl2 with lipid bilayers, thus preserving the integrity of the cell membrane. Co-supplementation with FO in the present study markedly downregulated the expression of TNF-α, p53, and caspase-9 in the three co-treated groups compared to the CdCl2 only group. These results imply that unsaturated fatty acids can alter the composition of the phospholipids of the cell membrane and can act as precursors of signaling molecules and ligands of nuclear receptors. They can stabilize the mitochondrial membrane, preventing cytochrome c release, caspase activation, and ROS formation. findings suggest that FO may alleviate CdCl2-induced histopathological deformities in the liver and kidney through the following actions: (1) reduction of the percentage DNA breaks in liver and kidney tissues; (2) downregulation of hepatic mRNA expression of TNF-α, and p53; and (3) downregulation of caspase-9 expression using immunohistochemical staining.