NEUROBEHAVIOURAL AND BIOCHEMICAL EVIDENCE OF ANTIDEPRESSANT ACTIVITY OF TROXERUTIN IN MICE

Abstract

Depression is a debilitating neurological illness characterised by behavioural and neurochemical changes. Conventional antidepressants have poor efficacy, serious side effects and primarily target monoaminergic systems, whereas, there is involvement of neuroinflammation, necessitating newer antidepressants. Troxerutin, a bioflavonoid has been reported to have beneficial antidepressant and anti-inflammatory potentials; however, its mechanism is not fully elucidated. This study was designed to elucidate the antidepressant activity and underlying molecular mechanisms of troxerutin in Swiss mice. Troxerutin antidepressant activity was evaluated in 140 mice. In the acute study, 50 mice were used for Tail Suspension Test (TST) and Forced Swim Test (FST). Animals in each test were assigned into five treatment groups (n=5): distilled water (10 mL/kg), troxerutin (10, 20, 40 mg/kg) and imipramine (25mg/kg), respectively and their duration of immobility was measured 30 minutes after treatment. In the chronic studies, 90 mice were used in three experimental models: Chronic Unpredictable Mild Stress (CUMS), lipopolysaccharide (LPS), and Reserpine-induced Depression (RID). Animals were assigned into six treatment groups (n=5): distilled water (10mL/kg) naive, distilled water (10mL/kg) negative control, troxerutin (10, 20, 40 mg/kg) and imipramine (25mg/kg) respectively. Animals in CUMS, LPS or RID were exposed to stressors for 14 days (CUMS), single dose LPS (0.83mg/kg) after 7 days treatment, and reserpine (0.5mg/kg, daily) for seven days, respectively except for naïve group. The animals were subjected to behavioural assessment: Sucrose Preference Test (SPT), and Y-Maze in CUMS, Novelty Suppressed Feeding (NSF) in LPS, Splash Test in RID. Brain samples were collected for biochemical and histological analysis. In CUMS and LPS, the concentration of BDNF,CREB, MAPKs, corticosterone, TNF-α, IL-6, serotonin, norepinephrine, and dopamine were measured by ELISA and the levels of GSH, malondialdehyde, SOD, and nitrite were measured by spectrophotometry. In RID samples, concentrations of BDNF, CREB, serotonin, norepinephrine, and dopamine were measured. Histology assessment of prefrontal cortex and hippocampus was done by H&E staining for CUMS, and immunohistochemistry staining for iNOS in LPS model. Data were analysed using ANOVA at α0.05. Troxerutin significantly reduced immobility period in TST and FST. In chronic models, troxerutin reversed behavioural deficits compared to negative controls in SPT (75.40±3.38, 74.04±3.10, 75.76±1.62 vs 38.26±5.02%), Y-Maze (76.20±2.28, 75.40±1.03, 77.20±1.42 vs 45.20±1.31%), NSF (101.4±6.99, 100±3.06, 99.6±7.03 vs 216±4.94 sec), and Splash Test (100.6±3.01, 99.20±3.89, 100.6±3.25 vs 32.00±3.01). Troxerutin increased BDNF (184.2±1.47, 185.6±1.42, 190.0±0.50 vs 161.8±2.44pg/mL), MAPKs (2304±117.2, 2279±9.657, 2416±19.94 vs 1778±24.36pg/mL), CREB (15.97±0.60, 16.02±0.58, 17.86±1.35 vs 11.65±0.26ng/mL). Troxerutin also increased serotonin, norepinephrine and dopamine levels, but decreased corticosterone, TNF-α, and IL-6 in CUMS. Similar results were obtained with LPS and RID. Troxerutin compared to negative control increased GSH (0.626±0.02, 0.670±0.03, 0.668±0.03 vs 0.258±0.05µmol/g), SOD (4.90±0.21, 5.08±0.36,5.74±0.31 vs 2.44±0.27U/mg) but reduced nitrite (36.00±4.89, 31.60±4.99, 32.00±5.09 vs 76.00±9.69µg/ml),MDA (3.60±0.74, 3.60±0.24, 3.20±0.20 vs 8.60±0.24nmol/mg) in CUMS, and the same pattern was observed in LPS. Also, troxerutin increased neuronal density in CUMS and decreased iNOS expression in LPS. Troxerutin demonstrated antidepressant-like effect in mice by reversing neurobehavioural deficits in depression via inhibition of neuroinflammatory markers, modulation of oxidative stress, and up-regulation of monoaminergic neurotransmitters, and neurotrophic factors.