Possible activation of NRF2 by Vitamin E/Curcumin against altered thyroid hormone induced oxidative stress via NFĸB/AKT/mTOR/KEAP1 signalling in rat heart.

Oxidative stress is implicated in both hypo- and hyper-thyroid conditions. In the present study an attempt has been made to elucidate possible interaction between vitamin E or/and curcumin (two established antioxidants) with active portion (redox signaling intervening region) of nuclear factor erythroid 2-related factor 2 (NRF2) as a mechanism to alleviate oxidative stress in rat heart under altered thyroid states. Fifty Wistar strain rats were divided into two clusters (Cluster A: hypothyroidism; Cluster B: hyperthyroidism). The hypo- (0.05% (w/v) propylthiouracil in drinking water) and hyper- (0.0012% (w/v) T4 in drinking water) thyroid rats in both clusters were supplemented orally with antioxidants (vitamin E or/and curcumin) for 30 days. Interactive least count difference and principal component analyses indicated increase in lipid peroxidation, reduced glutathione level, alteration in the activities and protein expression of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase under altered thyroid states. However, the expression of stress survival molecules; nuclear factor κB (NFκB) and the serine-threonine kinase B (Akt), in hyper-thyroidism only points towards different mechanisms responsible for either condition. Co-administration of vitamin E and curcumin showed better result in attenuating expression of mammalian target for rapamycin (mTOR), restoration of total protein content and biological activity of Ca2+ ATPase in hyperthyroid rats, whereas, their individual treatment showed partial restoration. Since NRF2 is responsible for activation of antioxidant response element and subsequent expression of antioxidant enzymes, possible interactions of both vitamin E or/and curcumin with the antioxidant enzymes, NRF2 and its regulator Kelch ECH associating protein (KEAP1) were studied in silico. For the first time, a modeled active portion of the zipped protein NRF2 indicated its interaction with both vitamin E and curcumin. Further, curcumin and vitamin E complex showed in silico interaction with KEAP1. Reduction of oxidative stress by curcumin and/or vitamin E may be due to modulation of NRF2 and KEAP1 function in rat heart under altered thyroid states.

Supplementation of T3 recovers hypothyroid rat liver cells from oxidatively damaged inner mitochondrial membrane leading to apoptosis.

Hypothyroidism is a growing medical concern. There are conflicting reports regarding the mechanism of oxidative stress in hypothyroidism. Mitochondrial oxidative stress is pivotal to thyroid dysfunction. The present study aimed to delineate the effects of hepatic inner mitochondrial membrane dysfunction as a consequence of 6-n-propyl-2-thiouracil-induced hypothyroidism in rats. Increased oxidative stress predominance in the submitochondrial particles (SMP) and altered antioxidant defenses in the mitochondrial matrix fraction correlated with hepatocyte apoptosis. In order to check whether the effects caused by hypothyroidism are reversed by T3, the above parameters were evaluated in a subset of T3-treated hypothyroid rats. Complex I activity was inhibited in hypothyroid SMP, whereas T3 supplementation upregulated electron transport chain complexes. Higher mitochondrial H2O2 levels in hypothyroidism due to reduced matrix GPx activity culminated in severe oxidative damage to membrane lipids. SMP and matrix proteins were stabilised in hypothyroidism but exhibited increased carbonylation after T3 administration. Glutathione content was higher in both. Hepatocyte apoptosis was evident in hypothyroid liver sections; T3 administration, on the other hand, exerted antiapoptotic and proproliferative effects. Hence, thyroid hormone level critically regulates functional integrity of hepatic mitochondria; hypothyroidism injures mitochondrial membrane lipids leading to hepatocyte apoptosis, which is substantially recovered upon T3 supplementation.

Expression of hepatic antioxidant genes in l-thyroxine-induced hyperthyroid rats: regulation by vitamin E and curcumin.

Earlier we have demonstrated that oral supplementation of vitamin E and curcumin alleviates hyperthyroidism-induced oxidative stress and distorted histoarchitecture in rat liver [5]. To delineate the underlying mechanism of protection, the present study was undertaken to investigate the regulatory role of vitamin E and curcumin on antioxidant gene (AOG) expression in hyperthyroid rat liver. Adult male rats were rendered hyperthyroid by administration of 0.0012% l-thyroxine in their drinking water, while vitamin E (200mg/kg body weight) and curcumin (30mg/kg body weight) were supplemented orally for 30 days. l-Thyroxine-induced hyperthyroidism decreased the transcript levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx1) and glutathione reductase (GR) in liver. Alleviated message levels of SOD and CAT were noticed following simultaneous administration of curcumin and vitamin E to hyperthyroid rats. Moreover vitamin E or curcumin treatment ameliorated GPx1 and GR mRNA levels. Translated products of AOGs showed differential expression in the liver of hyperthyroid rats, where Cu/Zn SOD (SOD1), CAT and GR were decreased in contrast to Mn SOD (SOD2) and GPx1. Vitamin E administration was able to alleviate SOD1, CAT and GR translated products while only CAT protein was restored to normal level by curcumin. Co-administration of both antioxidants normalized GPx1 protein expression. Interestingly decreased activities of cytosolic CAT and GPx1 were alleviated following vitamin E and curcumin administration. Increased mitochondrial SOD1 and decreased GR activities were also normalized by antioxidant treatment. Above findings suggest that administration of vitamin E and curcumin may alleviate the hepatic AOG expression in hyperthyroid rats.

Supplementation of curcumin and vitamin E enhances oxidative stress, but restores hepatic histoarchitecture in hypothyroid rats.

AIMS: In the present study, the effects of vitamin E and curcumin on hepatic dysfunction, mitochondrial oxygen consumption as well as hyperlipidemia in hypothyroid rats are reported. MAIN METHODS: Adult male rats were rendered hypothyroid by administration of 0.05% 6-n-propyl-2-thiouracil (PTU) in their drinking water, while vitamin E (200 mg/kg body weight) and curcumin (30 mg/kg body weight) were supplemented orally for 30 days. KEY FINDINGS: Hypothyroidism-induced elevation in serum aspartate aminotransferase activity was found to decline in vitamin E and curcumin treated rats. Nevertheless, distorted histoarchitecture revealed in hypothyroid rat liver was alleviated to normal by vitamin E and curcumin treatment. Regulation of hypothyroidism induced decrease in complexes I and II mediated mitochondrial respiration by vitamin E and curcumin was found to be different. Administration of curcumin to hypothyroid rats alleviates the decreased state 4 respiration and increased respiratory control ratio (RCR) level in complex I mediated mitochondrial oxygen consumption, whereas complex II mediated respiration was not influenced by exogenous antioxidants. Although, increase in serum concentration of total cholesterol was not modified by exogenous antioxidants, increased level of non-high-density lipoprotein cholesterol (non-HDL-C) in serum of hypothyroid rats was further enhanced by vitamin E and curcumin. Moreover, a significant elevation in mitochondrial lipid peroxidation and protein carbonylation was noticed in hypothyroid groups treated with vitamin E and curcumin. SIGNIFICANCE: The present study suggests that supplementation of curcumin and vitamin E enhances oxidative stress parameters and hyperlipidemia; nevertheless, it protects hypothyroid-induced altered rectal temperature, serum transaminase activity and hepatic histoarchitecture.