West African Sorghum bicolor leaf sheaths have anti-inflammatory and immune-modulating properties in vitro

Abstract

The impact of chronic inflammatory conditions on immune function is substantial, and the simultaneous application of anti-inflammatory and immune modulating modalities has potential for reducing inflammation-induced immune suppression. Sorghum-based foods, teas, beers, and extracts are used in traditional medicine, placing an importance on obtaining an increased understanding of the biological effects of sorghum. This study examined selected anti-inflammatory and immune-modulating properties in vitro of Jobelyn™, containing the polyphenol-rich leaf sheaths from a West African variant of Sorghum bicolor (SBLS). Freshly isolated primary human polymorphonuclear (PMN) and mononuclear cell subsets were used to test selected cellular functions in the absence versus presence of aqueous and ethanol extracts of SBLS. Both aqueous and nonaqueous compounds contributed to reduced reactive oxygen species formation by inflammatory PMN cells, and reduced the migration of these cells in response to the inflammatory chemoattractant leukotriene B4. Distinct effects were seen on lymphocyte and monocyte subsets in cultures of peripheral blood mononuclear cells. The aqueous extract of SBLS triggered robust upregulation of the CD69 activation marker on CD3- CD56+ natural killer (NK) cells, whereas the ethanol extract of SBLS triggered similar upregulation of CD69 on CD3+ CD56+ NKT cells, CD3+ T lymphocytes, and monocytes. This was accompanied by many-fold increases in the chemokines RANTES/CCL5, Mip-1α/CCL3, and MIP-1β/CCL4. Both aqueous and nonaqueous compounds contribute to anti-inflammatory effects, combined with multiple effects on immune cell activation status. These observations may help suggest mechanisms of action that contribute to the traditional use of sorghum-based products, beverages, and extracts for immune support.

Figures

FIG. 1.

Cellular antioxidant protection from oxidative damage. Aqueous and ethanol extractions of the Sorghum bicolor leaf sheaths (SBLS) were compared in the cellular antioxidant protection using erythrocytes (CAP-e) assay at a dose of 270 mg/L. The level of ethanol in the cellular CAP-e assay was below 0.2%. Levels of ethanol below 2% do not affect the CAP-e assay, so the amount of ethanol in the test was considered negligible. The ethanol extract provided better protection than the aqueous extract, but both fractions were able to provide significant protection of intracellular oxidative damage when comparing levels of cellular damage between cultures with and without SBLS extract (*P<.05).

FIG. 2.

Formation of reactive oxygen species (ROS) in polymorphonuclear (PMN) cells. Freshly isolated primary human PMN cells were either untreated or pretreated with serial dilutions of SBLS aqueous or ethanol extracts, then cultured under conditions of oxidative stress to provoke intracellular ROS formation. All test conditions were performed in quadruplicate. The data are shown as mean±SD and represent one of three separate experiments using cells from three different donors (*P<.05).

FIG. 3.

Migration of PMN cells toward the inflammatory chemoattractant leukotriene B4 (LTB4). Freshly isolated primary human PMN cells were either untreated or pretreated with serial dilutions of SBLS aqueous or ethanol extracts, then added to the top chambers of trans-well migration plates. LTB4 was added to the bottom chambers, except in negative control wells. All test conditions were performed in quadruplicate. The data are shown as mean±SD and represent one of three separate experiments using cells from three different donors (*P<.05).

FIG. 4.

Expression of the CD69 activation marker on CD3− CD56+ natural killer (NK) cells. Peripheral blood mononuclear cells (PBMC) were cultured for 18 h in the absence (baseline) or presence of either an aqueous extraction or an ethanol extraction from SBLS. The aqueous extract triggered a significant, dose-dependent increase in expression of the CD69 activation marker on NK cells. For data points where CD69 expression on treated cell cultures was significantly higher than on untreated cells (baseline, 4.36±0.43), this is indicated (*P<.05). Conditions were assayed in triplicate, and the results shown are mean±SD values from a representative of three separate experiments using PBMC from three different donors.

FIG. 5.

Expression of the CD69 activation marker on CD3+ CD56+ natural killer T (NKT) cells. PBMC were cultured for 18 h in the absence (baseline) or presence of either an aqueous extraction or an ethanol extraction from SBLS. The aqueous extract triggered a mild, but significant increase in expression of the CD69 activation marker on NKT cells. The ethanol fraction triggered a robust, dose-dependent increase in the CD69 expression on NKT cells. For data points where CD69 expression on treated cell cultures was significantly higher than on untreated cells (baseline, 4.05±0.17), this is indicated (*P<.05). Conditions were assayed in triplicate, and the results shown are mean±SD values from a representative of three separate experiments using cells from three different donors.

FIG. 6.

Expression of the CD69 activation marker on CD3+ T cells. PBMC were cultured for 18 h in the absence (baseline, 1.34±0.01) or presence of either an aqueous extraction or an ethanol extraction from SBLS. The ethanol extract triggered a significant, dose-dependent increase in expression of the CD69 activation marker on T cells. Conditions were assayed in triplicate, and the results shown are mean±SD values from a representative of three separate experiments using cells from three different donors.

FIG. 7.

Expression of the CD69 activation marker on monocytes. PBMC were cultured for 18 h in the absence (baseline, 11.56±0.30) or presence of either an aqueous extraction or an ethanol extraction from SBLS. The aqueous extract had a minor, but significant effect on monocytes. In contrast, the ethanol extract triggered a significant, dose-dependent increase in expression of the CD69 activation marker on monocytes. Conditions were assayed in triplicate, and the results shown are mean±SD values from a representative of three separate experiments using cells from three different donors.