Ameliorative role of antioxidant supplementation on sodium-arsenite induced adverse effects on the developing rat cerebellum

Abstract

Background: Arsenic is an environmental contaminant of global concern. Consumption of ground water contaminated with inorganic arsenic (iAs) continues to be the major source of its exposure. The developing nervous system is especially vulnerable to environmental insults due to its higher rate of oxygen consumption and provision of weaker antioxidant (AOX) machinery.

Objective: Since oxidative stress has been reported as one of the major factors underlying iAs induced toxicity, the aim of the present study is to study the effect of two AOXs i.e., Alpha Lipoic Acid (ALA) and Curcumin (Cur) in developing cerebellum of rats exposed to arsenic during postnatal period.

Materials and methods: The study was carried out on mother reared neonatal rat pups grouped as normal (Ia) and sham (vehicle) controls (Ib,c,d), while the experimental groups IIa/ IIb received sodium arsenite (NaAsO2) [(1.5/2.5 mg/kg body weight (bw)] alone or along with ALA (70 mg/kg bw)- IIIa/ IIIb or along with Cur (150 mg/kg bw)- IVa/ IVb. Behavioural, biochemical and immunohistochemical procedures were carried out to understand the underlying mechanisms.

Results: The observations indicated deficits in locomotor function, accumulation of iAs, increased levels of oxidative stress markers along with downregulation of the expression of proteins closely associated with synaptic functioning (Synaptophysin and Postsynaptic density protein95) in the cerebellum of iAs treated animals. Substantial recovery in all these parameters was observed in AOX co-treated groups.

Conclusion: Our results support the potential of ALA and Cur in amelioration of iAs induced developmental neurotoxicity. ALA and Cur can be proposed as dietary adjuvants amongst populations inhabiting areas with high iAs contamination as a safe and cost effective antidotes.

Keywords: PSD95; alpha lipoic acid; curcumin; synaptophysin.

Fig. 1

Grouping of animals based on the exposure pattern.

Fig. 2

Time spent on the rotating rod (rota-rod apparatus) by the control (I) and the experimental (IIa, b; IIIa, b; IVa, b) animals on day 1 (PND 20), 2 (PND 21) & 3 (PND 22) of trial. Significant at p < 0.05 values × compared to I, @ compared to IIa and # compared to IIb respectively. Note: Improved performance was evidenced by increased time spent by the animals receiving antioxidants (ALA or Cur) with NaAsO₂ on the rotating rod.

Fig. 3

Cerebellar iAs levels (μg/g tissue) in the control (I) and the experimental (IIa, b; IIIa, b; IVa, b) animals. Values are Mean ± SD. Significant at p < 0.05 levels × compared to I, @ compared to IIa, # compared to IIb & ˆ compared to IIIb respectively. Note: Significant decrease in iAs levels of antioxidant co-treated groups (IIIa, b; IVa, b) as compared to iAs alone (IIa, b) treated animals.

Fig. 4

Levels of GSH (A) and MDA (B) in cerebellum of control (I) and experimental (IIa, b; IIIa, b; IVa, b) groups. Values are Mean ± SD. Significant at p < 0.05 levels × compared to I, @ & # compared to IIa & IIb respectively. Note: Significant recovery in GSH & MDA levels in the antioxidant co-treated groups.

Fig. 5

Immuno-histochemical localization of Syp (→) in cerebellar cortical layers (ML, PCL & GL) of control (A) & experimental (B, C, D, E, F, G) groups (40X). Note: Decreased Syp immunoreactivity in B (IIa) & C (IIb) as compared to group A (I), D (IIIa), E (IIIb), F (IVa) & G (IVb).

Fig. 6

(A) Immunoblots of Syp (cerebellum) of control (I) & the experimental (IIa, b; IIIa, b; IVa, b) animals along with loading control (β actin). (B) Bar diagram showing fold change in Syp expression in the experimental (IIa, b; IIIa, b; IVa, b) vs control group. Values are Mean ± SD. Significant at p < 0.05 levels × compared to I, @ & # compared to IIa & IIb respectively.

Fig. 7

Immuno-histochemical localization of PSD95 (→) in ML, GCL & areas intervening between PCs of cerebellar cortex from control (A) & experimental (B, C, D, E, F, G) groups (40X). Note: Decrease in the cerebellar PSD95 immunoreactivity in B (IIa) & C (IIb) as compared to group A (I), D (IIIa), E (IIIb), F (IVa) & G (IVb).

Fig. 8

(A) Immunoblots of PSD95 (cerebellum) of control (I) & the experimental (IIa, b; IIIa, b; IVa, b) animals along with loading control (GAPDH). (B) Bar diagram showing fold change in PSD95 expression in the experimental (IIa, b; IIIa, b; IVa, b) vs control group. Values are Mean ± SD. Significant at p < 0.05 levels × compared to I, @ & # compared to IIa & IIb respectively.