Effect of Bromelain on BDNF level and memory deficit following intra-medial forebrain bundle 6-OHDA injection in rat model of Parkinsonism

Introduction: Episodic memory is a complex cognitive process that allows the encoding, storage and retrieval of unique events associated with the context in which they occurred. The memory function is however affected in Parkinson’s disease (PD) and this is quite associated with the functional loss of brain derived neurotrophic factor (BDNF) which is highly expressed within the brain. This study therefore addressed the question of whether prior/post bromelain treatment was able to show an effect on the memory function and BDNF level in 6-OHDA injected rat model of Parkinsonism. Methods: Male Sprague-Dawley rats were injected stereotaxically with the neurotoxin 6- OHDA. The anti-inflammatory agent, bromelain (40 mg/kg i.p) was used to treat a subset of the rats prior to or 24 hr post 6-OHDA lesion. Discrimination index in the neurotoxin injected rats was assessed using the novel object recognition test. The levels of BDNF in the plasma, PFC and hippocampus were measured using enzyme-linked immunosorbent assay. Results: 6-OHDA injection resulted in marked reduction in the discrimination index which was prevented by the treatment with bromelain prior to the lesion. The plasma level of BDNF was increased by the 6-OHDA injection and bromelain treatment, pre- and post 6-OHDA injection decreased the plasma level of BDNF in the neurotoxin injected rats. Meanwhile, a significant increase in cortical BDNF was observed with post-injection bromelain treatment. Conclusion: The plasma level of BDNF increased in the 6-OHDA rat model of PD. BDNF levels in plasma may represent an important early marker of brain damage and memory deficit. Bromelain treatment reversed the neurotoxininduced increase in plasma BDNF levels and memory deficit, suggesting that early treatment with bromelain might be useful in the prevention of memory loss in patients with PD.