Abstract:
Manganese (Mn) is essential for many biological functions as well as the development and functioning of the central nervous system. But a high level of Mn in the brain may cause central nervous system dysfunction known as manganism. This study was designed to evaluate the neuroprotective effect of Curcuma longa and Curcuma zedoaria on manganese-induced functional alterations in rat brain. Male Wistar rats were administered with 100 mg/kg body weight Mn (i.p.) and co-treated with 200 mg/kg and 400 mg/kg ethanol extracts of the rhizomes of Curcuma longa and Curcuma zedoaria (p.o.) for 8 consecutive days. After the period of treatment, neurobehavioural assessments of animals were performed followed by biochemical and histopathological evaluations in discrete brain regions. The results showed that there was motor impairment and reduction of locomotor activity in Mn-exposed rat. Also, the superoxide dismutase activity, catalase activity and reduced glutathione level were reduced while lipid peroxidation level was increased in the cortical, striatal and hippocampal regions of the brain by Mn administration. Furthermore, exposure to Mn caused elevation of the pro-inflammatory indices (xanthine oxidase activity, myeloperoxidase activity and nitric oxide) and increased LDH activity while Na+ K+ ATPase activity was reduced. The histopathological evaluation revealed neuronal degeneration, gliosis, distorted cerebral histo-architecture with pyknotic changes. The decreased performance of rats in the open field test and hang wire test in 100 mg/kg Mn-treated animals was reversed by 92.6 % and 95.6 % respectively, in 200 mg/kg Curcuma longa treated rats and by 25 % and 62.5 % respectively, in 200 mg/kg Curcuma zedoaria treated rats, compared with the Mn-toxified group (p<0.0001). Treatment with Curcuma longa and Curcuma zedoaria extracts also ameliorated Mn-induced oxidative damage in the brain regions, mediated the suppression of the pro-inflammatory indices and lactate dehydrogenase activity, and caused the reduction of Na+ K+ ATPase activity.
The histopathological evaluation shows that Curcuma longa and Curcuma zedoaria extracts reversed the neuronal degeneration and distorted cerebral histoarchitecture observed in Mn-toxified rats. Conclusively, Curcuma longa and Curcuma zedoaria abated manganese-induced toxicity in the cortical, striatal and hippocampal regions of the rat brain indicating that Curcuma longa and Curcuma zedoaria are potential neuroprotective agents against manganese-induced neurotoxicity where Curcuma longa shows superior protection
