[Effect of miR-155-5p regulating the TLR4/MAPK/NF-κB pathway on inflammatory response, coronary artery lesion and immune function in mice with Kawasaki disease].

OBJECTIVES: To investigate the effect of miR-155-5p regulation of the TLR4/MAPK/NF-κB pathway on inflammatory response, coronary artery lesion, and immune function in mice with Kawasaki disease (KD).

METHODS: Sixty male BALB/C mice were randomly assigned to six groups (n=10 each): healthy, KD, miR-155-5p agomir, agomir-negative control (agomir-NC), miR-155-5p antagomir, and antagomir-negative control (antagomir-NC). KD models were established by intraperitoneal injection of Lactobacillus casei cell wall extract in all groups except the healthy group. Levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were measured by ELISA. Flow cytometry was used to determine the proportions of CD3+, CD4+, and CD8+ T lymphocyte subsets and the CD4+/CD8+ ratio. Coronary artery diameter was assessed by high-frequency ultrasound, and histopathological changes were observed by hematoxylin-eosin staining. Endothelial cell apoptosis in coronary tissue was detected with TUNEL staining. Expression levels of nuclear factor kappa-B (NF-κB) p65, phosphorylated NF-κB p65 (p-NF-κB p65), Toll-like receptor 4 (TLR4), and p38 mitogen-activated protein kinase (MAPK) proteins were analyzed by Western blot.

RESULTS: Compared with the healthy group, the KD group showed coronary arterial wall thickening, endothelial shedding, extensive inflammatory cell infiltration, disordered smooth muscle layer arrangement, vascular dilation, and lumen stenosis. The miR-155-5p agomir group exhibited aggravated coronary inflammation, wall thickening, and lumen stenosis versus the KD group, whereas the miR-155-5p antagomir group showed attenuated inflammation and wall thickening, improved smooth muscle arrangement, and reduced stenosis. The KD group demonstrated increased IL-6, IL-1β, TNF-α, CD4+ T cell percentage, CD4+/CD8+ ratio, coronary artery diameter, endothelial apoptosis rate, and p-NF-κB p65, TLR4, and p38 MAPK protein expression compared to the healthy group (all P<0.05), with decreased CD3+ and CD8+ T cell percentages (P<0.05). No significant differences were observed among the KD, agomir-NC, and antagomir-NC groups. Compared with the KD group, the miR-155-5p agomir group showed further increased inflammatory cytokines (IL-6, IL-1β, and TNF-α), CD4+ T cell percentage, CD4+/CD8+ ratio, coronary diameter, endothelial apoptosis, and protein expression of p-NF-κB p65, TLR4, and p38 MAPK, while reduced CD3+ and CD8+ T cell percentages (all P<0.05). Conversely, the miR-155-5p antagomir group showed significant reductions in inflammatory cytokines, protein expression of p-NF-κB p65, TLR4, and p38 MAPK, CD4+ T cell percentage, CD4+/CD8+ ratio, coronary artery diameter, and endothelial apoptosis, as well as significant increases in CD3+ and CD8+ T cell percentages (all P<0.05).

CONCLUSIONS: Overexpression of miR-155-5p exacerbates inflammatory response, coronary artery lesions, endothelial cell apoptosis, and immune dysfunction in KD, potentially through modulation of the TLR4/MAPK/NF-κB pathway. Inhibition of miR-155-5p may reverse these pathological changes.