Crude leaf extracts of Piperaceae species downmodulate inflammatory responses by human monocytes

<div><p>In this study, we aimed to evaluate the immunomodulatory effects of crude leaf extracts from <i>Piper gaudichaudianum</i> Kunth, <i>P</i>. <i>arboreum</i> Aub., <i>P</i>. <i>umbellata</i> L., <i>P</i>. <i>fuligineum</i> Kunth, and <i>Peperomia obtusifolia</i> A. Dietr. on an <i>in vitro</i> model of inflammatory response. The crude extracts were previously obtained by maceration of the leaves. The half-maximal inhibitory concentration was determined by the MTT assay using human peripheral blood mononuclear cells. Human monocytes were simultaneously challenged with each crude extract and lipopolysaccharide (LPS), the major component of the outer membrane of Gram-negative bacteria, to induce a strong inflammatory response. After 24 h of incubation, cell-free supernatants were used for evaluating the mediators involved in inflammation: H₂O₂, TNF-α, IL-8, IL-6, IL-1β, IL-10, IL-12, FGF-b, and TGF-β1. We also compared the results with the effects of ketoprofen, a well-known anti-inflammatory drug. The <i>P</i>. <i>gaudichaudianum</i> crude extract downmodulated the production of H₂O₂, IL-1β, IL-6, IL-8, and TGF-β1 by LPS-stimulated monocytes; <i>P</i>. <i>arboreum</i>, IL-1β, IL-6, IL-8, and TNF-α; <i>P</i>. <i>umbellata</i> and <i>P</i>. <i>fuligineum</i>, H₂O₂, IL-1β, IL-6, IL-8, IL-10, and TNF-α; and <i>P</i>. <i>obtusifolia</i>, H₂O₂, IL-6, IL-8, IL-10, and TNF-α. In general, the crude leaf extracts amplified the anti-inflammatory response when compared with ketoprofen, particularly reducing the production of IL-8, a mediator involved in neutrophil recruitment during tissue damage. Thus, the crude leaf extracts of <i>P</i>. <i>gaudichaudianum</i>, <i>P</i>. <i>arboreum</i>, <i>P</i>. <i>umbellata</i>, <i>P</i>. <i>fuligineum</i>, and <i>Peperomia obtusifolia</i> elicited an anti-inflammatory response against LPS-challenged monocytes. These findings show the anti-inflammatory properties of these crude leaf extracts and offer new perspectives for their use in the treatment of inflammatory diseases.</p>