NEUROPROTECTIVE POTENTIALS OF THE ETHANOL EXTRACT OF Adenopus breviflorus (Benth) FRUIT IN SWISS MICE AND WISTAR RATS

Abstract

Neuroinflammation is a well-characterised feature of neurodegenerative diseases affecting individuals’ movement, memory and speech. The use of synthetic drugs to improve cognition and motor functions caused by inflammation in neurodegenerative diseases has been associated with adverse effects. Tropical fruits offer therapeutic approaches in mitigating inflammation peripherally and centrally. Adenopus breviflorus fruit used as anticonvulsant and pain reliever in folkloric medicine has not been fully evaluated for its neuroprotective activity. This study was designed to investigate the neuroprotective potentials of ethanol extract of Adenopus breviflorus (EEAB) fruit in Swiss mice and Wistar rats. Ripe fruits of Adenopus breviflorus were authenticated at Forest Herbarium Ibadan (FHI: 112244), air-dried and extracted with 70% ethanol to obtain EEAB. In the anti-nociceptive study, 30 male Swiss mice (25-30g) were divided into six groups (n=5): control (distilled water, 10mL/kg), EEAB (25, 50, 100, 200mg/kg) and indomethacin (10mg/kg). Anti- nociceptive activity was evaluated 1hour after by Acetic Acid-induced writhing Test (AAT). In the inflammation study, 30 male Wistar rats (150-180g), were divided into six groups (n=5): normal-saline (10mL/kg), carrageenan (1%, s.c.), EEAB (50, 100, 200mg/kg) and indomethacin (5mg/kg). Air-pouch was induced in the animals for six days after which animals in groups 3-6 were challenged with carrageenan for 24hours. Exudates from the air-pouch were evaluated for Total Leukocyte Counts (TLC) and neutrophils using standard techniques while Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-6 were determined by ELISA. In the lipopolysaccharide-induced neuroinflammation model, 20 male Wistar rats (150-200g) were divided into four groups (n=5): normal saline (10mL/kg), lipopolysaccharide (250μg/kg, i.p.), EEAB (200mg/kg) and donepezil (0.5mg/kg i.p.). Memory function was assessed using Y-maze Tests (YMT). The Prefrontal Cortex (PFC), striatum and hippocampus were evaluated for inflammatory cytokines (TNF-α and Interleukin-6), neuronal morphology using Nissl and Golgi stains, and neuronal immunohistochemistry for expression of Amyloid-beta (Aβ) and Nuclear Factor kappa-B (NF-κB). Data were analysed using descriptive statistics and ANOVA at α0.05. vi The EEAB (100, 200mg/kg) significantly reduced writhing in AAT (27.83±8.89, 22.17±3.31) compared with control (46.67±4.03). The EEAB (100, 200mg/kg) relative to carrageenan-control significantly reduced TLC and neutrophil count. A significant reduction in TNF-α (337.20±29.29, 174.40±29.22 vs 521.80±35.02pg/ml exudate) and Interleukin-6 (289.90±26.48, 272.0±15.94 vs 392.10±17.69pg/ml exudate) of EEAB (100, 200mg/kg) compared with carrageenan-control was observed in the inflammation study. The EEAB (200mg/kg) significantly increased percentage alternations (69.72±2.56) in YMT relative to lipopolysaccharide-alone (55.63±2.82). The EEAB (200mg/kg) relative to lipopolysaccharide-alone significantly reduced TNF-α (pg/mg protein) in striatum (2.42±0.06 vs 3.19±0.12), and hippocampus (1.96±0.04 vs 2.32±0.10); and Interleukin-6 (pg/mg protein) in striatum (2.62±0.11 vs 3.71±0.33) alone. Neuronal morphology and dendritic arborization were preserved by EEAB (200mg/kg). The EEAB (200 mg/kg) relative to lipopolysaccharide-alone significantly decreased expressions of Aβ in the PFC (5.92±0.33 vs 15.46±0.77), and hippocampus (13.51±0.53 vs 17.19±1.44); and NF-κB in the PFC (8.61±1.03 vs 20.73±1.08), striatum (7.52±1.00 vs 18.84±0.77), and hippocampus (1.70±1.35 vs 14.08±1.13). Adenopus breviflorus fruit exhibited neuroprotective activities through repression of pro- inflammatory cytokines, amyloid beta and nuclear factor kappa-B in Swiss mice and Wistar rats.