Gene expression and alterations of antioxidant enzymes in spleen of rats exposed to fluoride

BACKGROUND

Fluorosis is a slow and progressive process causing metabolic, functional and structural damages affecting many tissues particularly musculoskeletal, dental systems, kidney, liver and brain. It can be rapidly absorbed by passive diffusion through the stomach, small intestine, mouth and skin. Endemic fluorosis is connected to the high concentration of fluoride in drinking water. The present study aimed to evaluate the toxic effects of sodium fluoride (NaF) on splenic activity at the biochemical and molecular level.

MATERIALS AND METHODS

Wistar albino rats were randomly assigned to three groups. The control rats were given 1 ml deionized water orally for 40 days. Groups II and III were administered 300 and 600 mg NaF/kg b.w. /day for the same period. Animals were sacrificed under ether anaesthesia. The spleen tissue was excised and used for biochemical and real-time PCR analysis. The level of fluoride, malondialdehyde (MDA), reduced glutathione (GSH) and activities of different antioxidant enzymes such as cytosolic copper/zinc superoxide dismutase (Cu/Zn SOD), glutathione peroxidase (GPx) and catalase (CAT) were determined. The analysis of gene expression of Cu/Zn SOD, GPx and CAT in spleen was done using Real-time PCR.

RESULTS

The levels of fluoride and MDA were significantly (P < 0.0001) increased where as GSH content decreased significantly (P < 0.0001) in the spleen of fluoridated rats. The activities of antioxidant enzymes viz; Cu/Zn SOD, GPx and CAT declined significantly (P < 0.0001) compared to the control. Pearson's bivariate correlation and simple linear regression analysis exhibited strong positive correlation between levels of splenic tissue fluoride and MDA(r = 0.985) while negative correlations existed in GSH (r = -0.907) as well as activities of Cu/Zn SOD (r = -0.982), GPx (r = -0.966), and CAT (r = -0.935). The gene expression of Cu/Zn SOD, GPx and CAT were significantly (P < 0.0001) reduced in fluorotic rats.

CONCLUSION

It is concluded that fluoride intoxication leads to the development of oxidative stress and damaging the cellular metabolism resulting in the declined ability of free radical scavengers along with increased level of MDA and decreased expression level of antioxidant genes which helps to understand the possible mechanism of fluoride-induced toxicity at the molecular level.

Molecular Mechanism of Changes in Gene Expression of Cytosolic Cu/Zn SOD, Lipid Peroxidation and Hepatic Function Impairments during Experimental Fluorosis

Background: Long term intake of high amount of fluoride leads to fluorosis causing metabolic, functional and structural damages affecting many tissues and organs including dental and skeletal manifestations. The liver is the most susceptible organ to fluoride toxicity because of its active and major role in digestion and detoxification. Aim: The present study aims to elucidate the effects of sodium fluoride on hepatic function biomarkers, lipid peroxidation and gene expression of Cu/Zn SOD in albino rats. Materials and Methods: Wistar albino rats were randomly assigned to three groups. The control rats were given 1 ml deionized water orally for 40 days. Groups II and III were administered 300 and 600 mg NaF/kg b.w. /day for the same period. Animals were sacrificed under anaesthesia, liver tissue was excised and used for biochemical and molecular analysis. The level of fluoride and lipid peroxidation (MDA) as well as reduced glutathione (GSH) content was determined. The activities of cytosolic copper/zinc superoxide dismutase (Cu/Zn SOD), aminotransferases (ALT and AST), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) in the hepatic tissue were determined. The analysis of gene expression of Cu/Zn SOD in the liver was determined using Real-time PCR. Results: The results revealed significantly (P<0.0001) higher concentration of fluoride and MDA in the liver of rats exposed to fluoride when compared to control. The GSH content reduced significantly (P<0.0001) in fluorotic rats. The activities of hepatic function biomarkers viz; ALT, AST, LDH and ALP elevated significantly (P<0.0001) compared to the control. An elevation of 108.60% (ALP), 121.45% (AST), 33.77% (LDH) and least 24.40% (ALT) was found in rats treated with 300 mg/L fluoride and maximum elevation of 226.20% (ALP), 211.52% (AST), 57.75% (LDH) and least 56.79% (ALT) was registered in rats exposed to 600 mg/L fluoride in drinking water. The activity of cytosolic Cu/Zn SOD decreased significantly (P<0.0001) in fluorotic rats. Pearson’s bivariate correlation and simple linear regression analysis exhibited strong positive correlation between level of hepatic tissue fluoride and activities of ALT (Pearson r= 0.85), AST (Pearson r= 0.94), LDH (Pearson r= 0.89), ALP (Pearson r= 0.86) and in MDA (Pearson r=0.984) while negative correlations existed between levels of fluoride and GSH (Pearson r=-0.93) as well as activity of Cu/Zn SOD (Pearson r= -0.99). The gene expression of cytosolic Cu/Zn SOD was significantly (P<0.0001) reduced in fluorotic rats. Conclusion: The present study revealed that fluoride declined the antioxidant activity of hepatic Cu/Zn SOD at biochemical as well as molecular level which leads to oxidative stress and tissue damage. This further affirms by increased activities of hepatic function biomarkers in correlation with high fluoride level during experimental fluorosis.

Therapeutic Effect of Curcumin on Scanning Electron Microscopy of Rat Adrenal Gland in Experimental Fluorosis

Aim: The present study was designed to investigate the therapeutic role of Curcumin against fluoride induced toxicity on adrenal gland of rats by using scanning electron microscopy (SEM). Methodology: Wistar albino rats were divided randomly into six groups The group I was administered with 1 ml of deionized water/kg b.w./day orally for 40 days. The Groups II and III were given 300 and 600 mg of NaF/kg b.w./day for the same period, respectively. The group IV was given 200 mg/kg b.w. of Curcumin for 20 days. The Groups V and VI were treated with 300 and 600 mg of NaF/kg b.w./day for 40 days respectively were post-treated with 200 mg of Curcumin for next 20 days. The animals were excised and adrenal tissue was taken out and processed for SEM. Results: The results revealed that rats exposed to 300 mg/kg b.w./day of NaF showed rough edges, numerous microvilli and damaged surface with crystal depositions. Also, numerous granules were distributed all over the surface. The rats treated with 600 mg/kg b.w./day of NaF showed decellularized adrenal tissue along with network of collagen fibres. Moreover, adrenal gland surface displayed abrasions and distorted cuboidal cells. The filopodia were prominent on the surface and wall of cavity possessed rough outline. After post-treatment with Curcumin, fluoridated adrenal gland of rats showed normal structure, reappearance of cuboidal cells on the surface as well as less number of microvilli and filopodia. Conclusion: The post-treatment with Curcumin possess therapeutic potential against NaF induced toxicity in adrenal gland of rats.