Experimental anti-allergic and immunomodulatory effects of vernonia amygdalina-derived biomaterials, vernodalin and its leaf extracts

Abstract

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disorder with a relatively high prevalence in children in developed countries. In this study, we (1) explored the immunomodulatory and (2) compared the anti-allergic effects of Vernodalin isolated from Vernonia amygdalina (VAM) leaf and VAM leaf extracts in NC/Nga mice. In the first experiment, AD-like disease was induced using 2,4,6-trinitrochlorobenzene (TNCB); the hapten was applied on mice rostral and ear's dorsal areas after disrupting skin barrier with the use of SDS solution. After AD induction, 36 NC/Nga mice that developed moderate to severe skin lesions were divided into 6 pretreatment groups of 6 animals: 1 μg/mL Vernodalin, 10 μg/mL Vernodalin, 100 μg/mL Vernodalin, 1,000 μg/mL VAM extracts, 1,000 μg/mL VAM extracts, and PBS-treated vehicle group. Skin samples were collected after 14 days of treatment; immunofluorescence and qRT-PCR assays were performed to determine changes in filaggrin (FLG) production and FLGmRNA and IL-33mRNA expressions, respectively. In the second experiment, 18 NC/Nga mice with Dermatophagoides pteronyssinus extract (DPE)-induced AD-like disease were divided into 3 treatment groups to test the curative effects of the experimental agents: 100 μg/mL Vernodalin, 10 μg/mL VAM extracts, and PBS-treated vehicle group as control. Pretreatment with VAM extracts and Vernodalin caused an increase in FLGmRNA expression levels and a reduction of IL-33mRNA expression in mice (vs. control group). Furthermore, Vernodalin and VAM extracts significantly reduced the dermatitis score (vs. control) in regard to ear skin lesions. Findings from this study confirm the anti-allergic effects of VAM-derived bioactive compound, Vernodalin, and the plant extracts.