Therapeutic potential of a rhein-loaded self-nano-emulsifying drug delivery system in ameliorating LPS-induced depression: mechanistic insights and behavioral outcomes

Abstract

Depression is a multifaceted disorder caused by neuroinflammation, which is mainly demarcated by a significant increase in proinflammatory cytokines, including interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Conventional treatments for depression typically focus on neurotransmitter theories and may lead to several undesirable side effects. Therefore, it is essential to identify innovative active compounds of herbal origin that can target proinflammatory cytokines to reduce neuroinflammation while minimizing side effects. Rhein has demonstrated considerable therapeutic efficacy in various neurological conditions; however, its mechanistic insights regarding antidepressant effects remain unclear. An in silico study of rhein against the putative target enzyme of depression showed prominent binding with neuroinflammatory proteins 1ALU, 2AZ5, and 5R88, achieving docking scores -5.84 kcal/mol, -5.23 kcal/mol, and -5.243 kcal/mol, respectively. However, the poor absorption of rhein limited its therapeutic efficacy. To address this issue, a rhein-loaded self-nano-emulsifying drug delivery system (R-SNEDDS) was developed and evaluated for its therapeutic effects in preventing a lipopolysaccharide-induced depression model in rats. The study found that intraperitoneal administration of R-SNEDDS (at doses of 50 mg/kg and 100 mg/kg rhein, i.p.) and duloxetine (as a positive control at 20 mg/kg) over three consecutive days reversed unusual depressive behaviors. Notably, the R-SNEDDS (100 mg/kg rhein, i.p.) significantly reduced levels of the proinflammatory cytokines IL-1β (30.91 ± 0.906), IL-6 (133.9 ± 2.232), and TNF-α (26.93 ± 1.807) compared to the lipopolysaccharide-induced group. These findings demonstrate that R-SNEDDS possesses anti-neuroinflammatory properties and could be promising for depression therapy.

Keywords: cytokines; depression; lipopolysaccharides; neuroinflammation; rhein; self-nano-emulsified drug delivery system.

FIGURE 1

1ALU, 2AZ5, and 5R88 proteins and rhein ligands.

FIGURE 2

Schematic representation of experimental protocol.

FIGURE 3

3D and 2D docked complexes of the selected phytochemical-derived natural compounds rhein with IL-6 (1A, 1B) and reference compounds with IL-6 (1C, 1D). Rhein with TNF-α (2A, 2B) and reference compounds with TNF-α (2C, 2D). Rhein with IL-6 (3A, 3B) and reference compounds with IL-1β (3C, 3D). In two-dimensional structures: H-bond formation (violet), hydrophobic interaction (green), polar residue (blue), negative residue (red), glycine (gray), and salt bridge (red and blue).

FIGURE 4

Effects of treatments on immobility time in the tail suspension test in LPS-induced depression in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; #p < 0.05; ###p < 0.001 compared to the LPS group.

FIGURE 5

Effects of treatments on immobility time in the forced swim test in LPS-induced depression in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; ###p < 0.001 compared to the LPS group.

FIGURE 6

Effects of treatments on (A) crossing and (B) rearing in the open-field test in LPS-induced depression in rats. Results are shown as mean ± SEM (n = 05).

FIGURE 7

Effects of treatments on sucrose (1% w/v) consumption in an LPS-induced depression model in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; ###p < 0.001 compared to the LPS group.

FIGURE 8

Effects of treatments on IL-1β levels in the brain in an LPS-induced depression model in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; ###p < 0.001 compared to the LPS group.

FIGURE 9

Effects of treatments on interleukin-6 levels in the brain in an LPS-induced depression model in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; ###p < 0.001 compared to the LPS group.

FIGURE 10

Effects of treatments on TNF-α levels in the brain in an LPS-induced depression model in rats. Results are shown as mean ± SEM (n = 05). ***p < 0.001 compared to the control group; ##p < 0.01, ###p < 0.001 compared to the LPS group.

FIGURE 11

CA3 of the hippocampus of the saline. (a) LPS; (b) LPS + SNEDDS; (c) LPS + Dulo; (d) LPS + R-SNEDSS; 50 mg/kg, i.p.; and (e) LPS + R-SNEDSS; 100 mg/kg, i.p. (f) Groups show three layers; the polymorphic (PO), the pyramidal (P), and the molecular (M). Note the changes in the pyramidal layer thickness. H&E staining. (×400). Dulo: duloxetine.

FIGURE 12

Dentate gyrus of the hippocampus of the saline. (a) LPS; (b) LPS + SNEDDS; (c) LPS + Dulo; (d) LPS + R-SNEDSS; 50 mg/kg, i.p.; and (e) LPS + R-SNEDSS; 100 mg/kg, i.p. (f) Groups show molecular (ML), granular cell (GCL), and pleomorphic layers (PL). Note the intactness of the granular cell layer and neuronal degeneration. H&E staining. (×400). Dulo: duloxetine.