In the present study, the antioxidant and neuroprotective potential of MS was studied against BCAO-induced oxidative stress in mice. Experimental models of stroke have been developed in animals in an attempt to mimic the events of human cerebral ischemia. It is well documented that transient global cerebral ischemia results in neurological abnormality. Therefore, global cerebral ischemia of short duration followed by reperfusion has been employed in the present study.
EGb761, a patented extract from the leaves of the Ginkgo biloba
, is a scientifically proven natural product widely used to treat cerebral ischemic disorder and neurological disorder [13
]. EGb761 was used as a reference to examine the neuroprotective abilities of MS in mice from I/R injury. The present investigations revealed that MS exhibited neuroprotective activity similar to that shown by EGb761. Pre-treatment with MS markedly reduced the infarct size induced by BCAO and produced significant protection against neuronal damage (), in harmony with other studies [51
TBARS, GSH, SOD and T-SH were estimated as an index to assess the severity of oxidative damage in the brain tissue, and also the effect of MS on the reversal of the damage produced by BCAO. All these parameters were markedly reversed and restored to near normal levels in the groups pre-treated with MS.
Free radicals are well investigated in the development of I/R-induced cerebral injury [53
]. ROS produces malondialdehyde (MDA), an end product of lipid peroxidation (LPO). MDA reacts with TBA and is, thus, estimated as TBARS [55
]. Therefore, MDA was estimated using TBARS assay to estimate extent of ROS. During ischemia, XD undergoes irreversible proteolytic conversion to XO, producing O•−2
in the presence of oxygen [53
does not directly induce LPO but can react with NO•
to form cytotoxic ONOO−
]. In addition, it is well documented that XO is an important prerequisite factor in the process of O•−2
generation in acute post-ischemic reperfusion injury [5
]. Such finding is in harmony with our results where a significant rise in % XO was found in mouse brain after I/R insult. The production of O•−2
paralleled the rise in % XO activity where a significant increase in O•−2
generation resulted in untreated control group compared to the sham group. In the current study, the elevated % XO activity of the untreated control group was effectively counteracted by administration of MS. Moreover, it also significantly hampered O•−2
burst to about half the value of the untreated control group. One proposed mechanism underlying this protective effect of MS, in the model used in the present investigations, could be through its antioxidant properties, restoring endogenous antioxidant levels and, therefore, detoxifying free radicals.
The overproduction of free radicals can be detoxified by endogenous antioxidants causing their cellular stores to be depleted [58
]. Glutathione is considered a central component in the antioxidant defenses of cells. It acts both to directly detoxify ROS and as a substrate for various peroxidases [59
]. Moreover, it is well evidenced that SOD activity in serum is reduced in stroke patients, and replacement of antioxidant activity could be beneficial in the acute treatment of cerebral ischemia [60
]. Similarly, fall in T-SH reflects the consumption of tissue thiols. As such, fall in GSH during cerebral reperfusion injury is well reported [61
]. Sulfhydryl compounds are considered important endogenous antioxidants. They have role in maintenance of cellular proteins and lipids in their functional states [62
]. Pre-treatment with MS significantly elevated GSH, SOD and prevented fall in T-SH in control groups.
Hippocampal neurons, which are involved in the regulation of short-term memory, are highly susceptible to I/R-induced injury [63
]. Therefore, elevated plus maze has been employed in present study to evaluate impairment of short-term memory as a result of cerebral I/R. Cerebral ischemia is documented to impair sensory motor ability [64
] and thus inclined beam walking test has been used in the present study to investigate the effect of cerebral I/R on motor performance.
In conclusion, the present findings suggest a potential role of MS in cerebral stroke, and the findings are important in view of the fact that stroke is at present the second leading cause of death worldwide [65
]. The mechanisms by which MS normalized the cerebral damage and stress, and prevented impairment of short-term memory and motor incoordination, is probably the antioxidant property of the drug which was evaluated in vitro
, to direct scavenged free radical generated against a stable radical DPPH and O•−2
radical generated in PMS-NADH systems, and its inhibitory effects on XD/XO conversion and resultant O•−2
production. Further studies are warranted to pursue the interesting lead emerging from the present results to exploit the full therapeutic potential of MS in cerebrovascular diseases.