Iron overload decreases the protective effect of tumour necrosis factor-alpha on rat hepatocytes exposed to oxidative stress

Attenuation of senescence-induced oxidative exacerbations in aged rat brain by (-)-epigallocatechin-3-gallate

Aging is a complex biological phenomenon which involves free radicals and oxidative stress. Brain is more susceptible and vulnerable to oxidative damage due to its high-polyunsaturated fatty acid content and high rate of aerobic metabolism. Since the antioxidant defense system is diminished during aging, antioxidant supplementation might be a protective strategy against age-associated oxidative damage. The present study evaluates the antioxidant potential of (-)-epigallocatechin-3-gallate (EGCG), a major polyphenol present in green tea against age-associated oxidative damage in rat brain. Male albino rats of Wistar strain were used in the study. Group I (young) and Group II (aged) rats received saline alone orally for 30 days. Group III (young) and Group IV (aged) rats received EGCG (2mg/kg body weight/day) orally for 30 days. Antioxidant status and oxidative damage were assessed. EGCG brought about an augmentation in the activities of enzymic antioxidants like superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and improved the non-enzymic antioxidants like tocopherol, ascorbic acid and glutathione. EGCG ameliorated the malondialdehyde and protein carbonyl levels. Thus, EGCG has emerged out as a good antioxidant neutraceutical and a neuroprotective agent in alleviating the age-associated oxidative damage in aged rat brain.

Regulatory effects of tumor necrosis factor-alpha and interleukin-6 on HAMP expression in iron loaded rat hepatocytes

BACKGROUND/AIMS

To study the effect of iron and proinflammatory cytokines on the expression of HAMP and other iron regulatory genes in primary rat hepatocytes.

METHODS

Primary hepatocytes from rats fed a control or iron-enriched diet were plated on extracellular matrix and incubated with inflammatory stimuli in the presence or absence of serum. Cells were also incubated with desferrioxamine or ferric ammonium citrate. mRNA levels were determined by Real-Time PCR.

RESULTS

Hepatocytes from control rats increased their HAMP expression during culturing, whereas the opposite was seen in hepatocytes from carbonyl-iron loaded animals. In the presence of serum, tumor necrosis factor-alpha, lipopolysaccharide and interleukin-6 increased HAMP expression in hepatocytes from both control and iron-loaded rats. Under serum-free conditions only tumor necrosis factor-alpha increased HAMP mRNA levels. Desferrioxamine and ferric ammonium citrate decreased HAMP gene expression. Tumor necrosis factor-alpha significantly increased mRNA levels of TfR2 and decreased those of DMT1 and IREG1.

CONCLUSIONS

HAMP expression differs in cultured as compared with freshly isolated hepatocytes, and decreases in iron-loaded hepatocytes in serum free-media, suggesting that additional serum factors influence HAMP expression. Tumor necrosis factor-alpha regulates the mRNA levels of HAMP, IREG1, DMT1 and TfR2 in cultured hepatocytes from both iron-loaded and control animals.

Iron, oxidative stress, and disease risk

Based on epidemiologic evidence citing excess iron as a risk factor for many diseases, and oxidative stress as an underlying cause for those diseases, iron-induced oxidative stress has recently gained attention. Although iron can participate in oxidative reactions to generate free radicals under in vitro conditions, its involvement in vivo in the cause or progression of diseases is questionable.