Involvement of Anti-Inflammatory and Stress Oxidative Markers in the Antidepressant-like Activity of Aloysia citriodora and Verbascoside on Mice with Bacterial Lipopolysaccharide- (LPS-) Induced Depression

Abstract

Aloysia citriodora Palau is popularly used to treat nervous disorders. Experimental evidence has indicated that verbascoside (VBS) isolated from A. citriodora has pharmacological potential. In this study, we evaluated the antidepressant-like effects of a hydroalcoholic extract of A. citriodora (HEAc) and VBS against lipopolysaccharide- (LPS-) induced depressive-like behavior in mice. In the pretreatment protocol (performed to evaluate the preventive potential), mice were pretreated with HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg) before the administration of LPS. In the posttreatment protocol (performed to evaluate the therapeutic potential), mice were initially administered LPS and were subsequently given HEAc (3, 30, or 300 mg/kg) or VBS (30 mg/kg). In both treatments, the mice were submitted to an open-field test and tail suspension test (TST) at 6 and 24 h after LPS administration. The posttreatment evaluation revealed that HEAc (30 or 300 mg/kg) and VBS produced an antidepressant-like effect, as indicated by a reduction in the time spent with no movement in the TST. Moreover, HEAc (30 or 300 mg/kg) was found to reduce interleukin-6 (IL-6) levels and N-acetyl-glycosaminidase activity in the hippocampus, increase glutathione (GSH) levels in the hippocampus and cortex, and enhance IL-10 in the cortex and, at a dose of 300 mg/kg, reduced myeloperoxidase activity in the cortex. Contrastingly, no comparable effects were detected in mice subjected to the pretreatment protocol. Administration of VBS similarly reduced the levels of IL-6 in the hippocampus and increased GSH levels in the cortex. Our observations indicate that both HEAc and VBS show promising antidepressant-like potential, which could be attributed to their beneficial effects in reducing neuroinflammatory processes and antioxidant effects in the central nervous system.

Figure 1

The timeline of the experimental design of the pretreatment (a) and posttreatment (b) stages in the evaluation of the antidepressant-like activity of the hydroalcoholic extract of A citriodora (HEAc) and verbascoside. Note: lipopolysaccharide (LPS; 600 μg/kg, i.p). N (naive); Veh (vehicle, water); HEAc (Aloysia citriodora hydroalcoholic extract: 3, 30, or 300 mg/kg); VBS (verbascoside, 30 mg/kg); Flu (fluoxetine 30 mg/kg). OFT: open-field test; TST: tail suspension test.

Figure 2

Chemical structure of verbascoside.

Figure 3

Behavioral effects of HEAc and verbascoside in mice in the pretreatment experiment. Note: pretreatment experiment: treatments administered (gavage) 1 h before exposure to bacterial lipopolysaccharide (LPS; 600 μg/kg, i.p). N (naive); Veh (vehicle, water); HEAc (Aloysia citriodora hydroalcoholic extract 3, 30, or 300 mg/kg); VBS (verbascoside, 30 mg/kg); Flu (fluoxetine 30 mg/kg). A–H: values are expressed as mean ± SEM (n = 8). ANOVA (one way), post hoc Tukey. ^∗p < 0.05, ^∗∗p < 0.001, and ^∗∗∗p < 0.001 compared to the naive group.

Figure 4

Antidepressant-like effects of HEAc and verbascoside (VBS) in the pretreatment experiment. Tail suspension test (TST) at 24 h after exposure to LPS. Note: pretreatment experiment: treatments administered (gavage) 1 h before exposure to bacterial lipopolysaccharide (LPS; 600 μg/kg, i.p). N (naive); Veh (vehicle, water); HEAc (Aloysia citriodora hydroalcoholic extract 3, 30, or 300 mg/kg); VBS (verbascoside, 30 mg/kg); Flu (fluoxetine 30 mg/kg). Values are expressed as mean ± SEM (n = 8). ANOVA (one way), post hoc Tukey. ^∗p < 0.05 compared to the naive group.

Figure 5

Intensity of sickness behavior of HEAc and verbascoside (VBS) in the therapeutic experiment. Note: N (naive); Veh (vehicle, water), hydroalcoholic extract of Aloysia citriodora (HEAc: 3, 30, or 300 mg/kg, po), VBS (verbascoside 30 mg/kg, po), Flu (fluoxetine 30 mg/kg), PS (Per se group, HEAc). Values are expressed as mean ± SEM (n = 8 mice/group). ANOVA (one way), post hoc Tukey. ^∗p < 0.05 and ^∗∗∗p < 0.001 compared to the naive group. ^##p < 0.01 and ^###p < 0.001 compared to the Veh group.

Figure 6

Behavioral effects of HEAc and verbascoside in mice in the posttreatment experiment. Note: posttreatment experiment: treatments administered (gavage) 5 h after exposure to bacterial lipopolysaccharide (LPS; 600 μg/kg, i.p). N (naive); Veh (vehicle, water); HEAc (Aloysia citriodora hydroalcoholic extract 3, 30, or 300 mg/kg); VBS (verbascoside, 30 mg/kg); Flu (fluoxetine 30 mg/kg), PS (per se group, HEAc). A–H: values are expressed as mean ± SEM (n = 8). ANOVA (one way), post hoc Tukey. ^∗p < 0.05, ^∗∗p < 0.001, and ^∗∗∗p < 0.001 compared to the naive group. ^#p < 0.05, ^##p < 0.001, and ^###p < 0.001 compared to the Veh group.

Figure 7

Antidepressant-like effects of HEAc and verbascoside (VBS) in the posttreatment experiment. Tail suspension test (TST) at 24 h after exposure to LPS. Note: posttreatment experiment: treatments administered (gavage) 5 h after exposure to bacterial lipopolysaccharide (LPS; 600 μg/kg, i.p). N (naive); Veh (vehicle, water); HEAc (Aloysia citriodora hydroalcoholic extract 3, 30, or 300 mg/kg); VBS (verbascoside, 30 mg/kg); Flu (fluoxetine 30 mg/kg), PS (per se group, HEAc). Values are expressed as mean ± SEM (n = 8). ANOVA (one way), post hoc Tukey. ^∗p < 0.05 and ^∗∗p < 0.05 compared to the naive group. ^#p < 0.05, ^##p < 0.001, and ^###p < 0.001 compared to the Veh group.

Figure 8

Effects of HEAc and VBS on the inflammatory markers MPO, NAG, and IL-6 in the hippocampus of mice evaluated in the posttreatment experiment of antidepressant-like activity. Note: N (naive); Veh (vehicle, water); Flu (fluoxetine 30 mg/kg); HEAc (Aloysia citriodora hydroalcoholic extract 30 or 300 mg/kg); VBS (verbascoside, 30 mg/kg). Values are expressed as mean ± SEM (n = 8). ANOVA (one way), post hoc Tukey. ^∗∗p < 0.01 and ^∗∗∗p < 0.001 compared to the naive group. ^##p < 0.01 and ^###p < 0.001 compared to the Veh group.

Figure 9

Effects of HEAc and VBS on the markers MPO, NAG, IL-6, and IL-10 in the cortex of mice evaluated in the posttreatment experiment of antidepressant-like activity.