Objective: To study the role of Kukoamine B (KB) in inhibiting the inflammatory response of small intestine in septic mice and its molecular mechanisms.
Methods: Twenty-four male ICR mice were randomly divided into control group, model group, and KB intervention group (each, n = 8). Sepsis model was reproduced by intra-peritoneal injection of 20 mg/kg lipopolysaccharide (LPS), while equivalent normal saline was given in control group, and 20 μg/kg KB was injected through caudal vein 4 hours after LPS challenge in KB intervention group. The blood/tissue samples (jejunum and ileum) were harvested 8 hours after LPS injection. The levels of plasma LPS, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were measured. The pathological changes in small intestine tissues were observed under light microscope, while the levels of inflammatory cytokines TNF-α and IL-1β in the tissue homogenates (jejunum and ileum) were assessed by enzyme linked immunosorbent assay (ELISA). The activity of myeloperoxidase (MPO) was measured by colorimetry. The expression of intercellular adhesion molecule-1 (ICAM-1) was determined by immunohistochemistry. The expressions of inducible nitric oxide synthase (iNOS) mRNA was assayed by reverse transcription-polymerase chain reaction (RT-PCR). The activation of nuclear factor-Κβ (NF-Κβ) was determined by Western Blot.
Results: The mice in model group were found to have an increase in microvascular permeability, interstitial edema, and infiltration of white blood cells, and the levels of LPS, TNF-α and IL-1β in their plasma, with an increase in concentrations of TNF-α and IL-1β, activity of MPO, positive expression of ICAM-1, expression of iNOS mRNA and NF-ΚB protein in small intestine (jejunum and ileum). Compared with model group, in mice with KB intervention, microvascular permeability, interstitial edema, and infiltration of white blood cells were reduced significantly, while the levels of LPS, TNF-α and IL-1β in plasma, the concentration of TNF-α and IL-1β, the activity of MPO, the positive expression of ICAM-1, the expression of iNOS mRNA and NF-ΚB protein in small intestine (jejunum and ileum) were significantly decreased [plasma LPS (kEU/L): 654.09±28.13 vs. 1 155.65±47.15, TNF-α (ng/L): 12.75±0.47 vs. 30.61±0.71, IL-1β (ng/L): 53.06±5.32 vs. 64.47±2.61; jejunum TNF-α (ng/L): 43.27±1.20 vs. 64.82±2.09, IL-1β (ng/L): 326.38±14.47 vs. 535.22±13.48, MPO (U/g): 0.14±0.01 vs. 0.32±0.02, iNOS mRNA (2(-ΔΔCt)): 2.39±0.13 vs. 10.80±0.22, NF-ΚB protein (gray value): 0.687±0.062 vs. 1.404±0.046; ileum TNF-α (ng/L): 62.75±3.92 vs. 104.24±2.82, IL-1β(ng/L): 408.06±1.70 vs. 521.97±1.16, MPO (U/g): 0.36±0.08 vs. 0.66±0.05, iNOS mRNA (2(-ΔΔCt)): 1.65±0.11 vs. 3.59±0.29, NF-ΚB protein (gray value): 0.830±0.114 vs. 1.609±0.051, all P <0.05].
Conclusions: KB can combine with LPS and inhibit LPS/Toll-like receptor 4 (TLR4) signaling pathway, thereby significantly inhibit the inflammatory response and protect the function of the small intestine in LPS-induced septic mice.