Targeting Toll-like Receptor 4/Nuclear Factor-κB and Nrf2/Heme Oxygenase-1 Crosstalk via Trimetazidine Alleviates Lipopolysaccharide-Induced Depressive-like Behaviors in Mice

Abstract

Depression is a global psychiatric illness that imposes a substantial economic burden. Unfortunately, traditional antidepressants induce many side effects which limit patient compliance thus, exploring alternative therapies with fewer adverse effects became urgent. This study aimed to investigate the effect of trimetazidine (TMZ); a well-known anti-ischemic drug in lipopolysaccharide (LPS) mouse model of depression focusing on its ability to regulate toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) as well as nuclear factor erythroid 2 related factor 2 (Nrf2)/ heme oxygenase-1 (HO-1) signaling pathways. Male Swiss albino mice were injected with LPS (500 µg/kg, i.p) every other day alone or parallel with oral doses of either escitalopram (Esc) (10 mg/kg/day) or TMZ (20 mg/kg/day) for 14 days. Treatment with TMZ attenuated LPS-induced animals' despair with reduced immobility time inforced swimming test. TMZ also diminished LPS- induced neuro-inflammation via inhibition of TLR4/NF-κB pathway contrary to Nrf2/HO-1 cascade activation with consequent increase in reduced glutathione (GSH) and HO-1 levels whereas the pro-inflammatory cytokines; tumor necrosis factor-α (TNF-α) and interleukin (IL)-1β were evidently reduced. Besides, TMZ replenished brain serotonin levels via serotonin transporter (SERT) inhibition. Thus, TMZ hindered LPS-induced neuro-inflammation, oxidative stress, serotonin deficiency besides its anti-apoptotic effect which was reflected by decreased caspase-3 level. Neuroprotective effects of TMZ were confirmed by the histological photomicrographs which showed prominent neuronal survival. Here we showed that TMZ is an affluent nominee for depression management via targeting TLR4/NF-κB and Nrf2/HO-1 pathways. Future research addressing TMZ-antidepressant activity in humans is mandatory to enroll it as a novel therapeutic strategy for depression.

Keywords: Depression; Lipopolysaccharide; Mice; NF-κB; Nrf2; Trimetazidine.

Fig. 1

Representation of the experimental design. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram, OFT open field test, FST forced swimming test

Fig. 2

Trimetazidine alleviated LPS-induced behavioral changes in forced swimming and open field tests. (A) Immobility time, (B) Ambulation frequency, and (C) Rearing frequency. Data were expressed as mean ± SD (n = 15) using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram

Fig. 3

Trimetazidine alleviated LPS-induced hippocampal histopathological changes in mice. Representative H&E photomicrographs of all experimental groups (n = 3); Control, TMZ, LPS, LPS + Esc, and LPS + TMZ groups. Magnifications: × 400. Black arrows indicate intact neurons while red arrows represent degenerated ones. Arrowheads show reactive glial cells infiltrate. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram

Fig. 4

Trimetazidine enhanced hippocampal neuronal survival in LPS-injected mice. Illustrative toluidine blue-stained photomicrographs of all experimental groups; Control, TMZ, LPS, LPS + Esc, and LPS + TMZ groups. Magnifications: × 400. Black arrows represent intact neurons while red arrows show degenerated ones. A bar chart showing the mean count of intact neurons in each group; where each bar with a vertical line illustrating the mean ± SD (n = 6), using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram

Fig. 5

Trimetazidine mitigated LPS-induced alterations in the hippocampal (A) TLR4 gene expression and (B) NF-κBp65 content. Data were expressed as mean ± SD (n = 6), using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram. TLR4 Toll-like receptor-4, NF-κB nuclear factor-kappa B

Fig. 6

Trimetazidine reduced LPS-induced alterations in the hippocampal contents of (A) TNF-α, (B) IL-1β, (C) Caspase-3, (D) Nrf2, (E) HO-1, and (F) GSH. Data were expressed as mean ± SD (n = 6), using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram, TNF-α tumor necrosis factor-α, IL-1β interleukin-1β, Nrf2 nuclear factor erythroid 2–related factor 2, HO-1 heme oxygenase-1, GSH reduced glutathione

Fig. 7

Trimetazidine diminished LPS-induced changes in the hippocampal SERT gene expression. Data were expressed as mean ± SD (n = 6) using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram, SERT serotonin transporter

Fig. 8

Trimetazidine attenuated LPS-induced changes in the hippocampal contents of (A) MMP-9 and (B) Claudin-5. Data were expressed as mean ± SD (n = 6) using one-way ANOVA followed by Tukey's post-hoc test, P < 0.05. LPS lipopolysaccharide, TMZ Trimetazidine, Esc escitalopram, MMP-9 matrix metallopeptidase 9