Magnolol Reduces Atopic Dermatitis-like Symptoms in BALB/c Mice

Abstract

In traditional Korean medicines, Magnolia officinalis is commonly included for the remedy of atopic dermatitis, and magnolol is a major constituent of Magnolia officinalis. Its pharmacological effects include anti-inflammatory, hepatoprotective, and antioxidant effects. Using BALB/c mice repeatedly exposed to 1-chloro-2,4-dinitrobenzene (DNCB), magnolol was evaluated in atopic dermatitis-like lesions. Administration of magnolol (10 mg/kg, intraperitoneal injection) markedly relieved the skin lesion severity including cracking, edema, erythema, and excoriation, and significantly inhibited the increase in IgE levels in the peripheral blood. A DNCB-induced increase in mast cell accumulation in atopic dermatitis skin lesions was reversed by magnolol administration, as well as a rise in expression levels of pro-inflammatory Th2/Th17/Th1 cytokines' (IL-4, IL-13, IL-17A, IFN-γ, IL-12A, TARC, IL-8, and IL-6) mRNAs in the lymph nodes and skin (n = 5 per group). In lymph nodes, magnolol reversed DNCB's increase in CD4⁺RORγt⁺ Th17 cell fraction and decrease in CD4⁺FoxP3⁺ regulatory T cell fraction. The results also showed that magnolol suppressed T cell differentiation into Th17 and Th2 cells, but not Th1 cells. Magnolol suppresses atopic dermatitis-like responses in the lymph nodes and skin, suggesting that it may be feasible to use it as a treatment for atopic dermatitis through its suppression of Th2/Th17 differentiation.

Keywords: Magnolia officinalis; anti-atopy; atopic dermatitis; atopy; dermatitis; magnolia; magnolol.

Figure 1

Effect of magnolol on 1-chloro-2, 4-dinitrobenzene [DNCB]-induced atopic dermatitis in ears of mice. (A) Photographs of the ears. (B) H&E staining. (C) Histogram of ear thickness. (D) Chemical structure of magnolol. *** p < 0.001 vs. the vehicle-treated group, ### p < 0.001, ## p < 0.01 vs. the DNCB-treated group. A magnification of ×200 was used.

Figure 2

Effect of magnolol on the levels of serum immunoglobulin E. An ELISA was used to measure serum IgE levels. *** p < 0.001 vs. the vehicle-treated group, ### p < 0.001, # p < 0.05 vs. the DNCB-treated group.

Figure 3

Magnolol reduces mast cell count in the ears. (A) Toluidine blue O staining of ear sections. Red arrows indicate mast cells. (B) Histogram of counts of mast cells (n = 5). *** p < 0.001 vs. the vehicle-treated group, ### p < 0.001 vs. the DNCB-treated group. ×200 magnification.

Figure 4

Effect of magnolol on the expression levels of pro-inflammatory cytokines mRNAs in the ears. (A) IL-4, (B) IL-13, (C) IL-17A, (D) IFN-γ, (E) IL-12A, (F) TARC, (G) IL-8, and (H) IL-6 mRNA expression levels in skin tissues (n = 5). *** p < 0.001, ** p < 0.01, * p < 0.05 vs. the vehicle-treated group, ### p < 0.001, ## p < 0.01, # p < 0.05 vs. the DNCB-treated group.

Figure 5

Effect of magnolol on immune responses induced by DNCB in lymph nodes. (A) Sizes of cervical lymph nodes. (B) Lymph node weight (n = 5). *** p < 0.001 vs. the vehicle-treated group, ### p < 0.001 vs. the DNCB-treated group.

Figure 6

Suppressive effect of magnolol on the proportion of CD4⁺RORγt⁺ Th17 cells and CD4⁺FoxP3⁺ Treg cells in lymph nodes. (A) Dot plots of CD4⁺RORγt⁺ Th17 cells. (B) Dot plots of CD4⁺FoxP3⁺ Treg cells. (C) Percentage of CD4⁺RORγt⁺ Th17 cells. (D) Percentage of CD4⁺FoxP3⁺ Treg cells (n = 5). Double-positive cells are shown in the red-lined boxes. ** p < 0.01 vs. the vehicle-treated group, ### p < 0.001, ## p < 0.01, # p < 0.05 vs. the DNCB-treated group.

Figure 7

Effect of magnolol on the expression levels of pro-inflammatory cytokines mRNAs in lymph nodes. (A) IL-4, (B) IL-13, (C) IL-17A, and (D) IFN-γ mRNA expression levels in the lymph node tissues (n = 5). *** p < 0.001, ** p < 0.01, * p < 0.05 vs. the vehicle-treated group, ## p < 0.01, # p < 0.05 vs. the DNCB-treated group.

Figure 8

Suppressive effect of magnolol on T cell differentiation into Th17/Th1/Th2 cells. CD4⁺ T cells isolated from splenocytes were cultured in each differentiation media for Th17, Th1, or Th2 cells for 5 days in plates precoated with antibody to mouse CD3. (A,C,E) Flow cytometry results for (A) Th17 differentiation, (C) Th1 differentiation, and (E) Th2 differentiation. (B,D,F). Histograms of the cell percentage of (B) CD4⁺IL-17A⁺ cell population, (D) CD4⁺IFN-γ⁺ cell population, and (F) CD4⁺IL-4⁺ cell population (n = 5). Double-positive cells are shown as the red-lined boxes. *** p < 0.001 vs. the vehicle-treated group, ### p < 0.001, # p < 0.05 vs. the differentiation media-treated group.