Human Genome Screen to Identify the Genetic Basis of the Anti-inflammatory Effects ofBoswelliain Microvascular Endothelial Cells

Abstract

Inflammatory disorders represent a substantial health problem. Medicinal plants belonging to the Burseraceae family, including Boswellia, are especially known for their anti-inflammatory properties. The gum resin of Boswellia serrata contains boswellic acids, which inhibit leukotriene biosynthesis. A series of chronic inflammatory diseases are perpetuated by leukotrienes. Although Boswellia extract has proven to be anti-inflammatory in clinical trials, the underlying mechanisms remain to be characterized. TNFα represents one of the most widely recognized mediators of inflammation. One mechanism by which TNFα causes inflammation is by potently inducing the expression of adhesion molecules such as VCAM-1. We sought to test the genetic basis of the antiinflammatory effects of BE (standardized Boswellia extract, 5-Loxin^®) in a system of TNFα-induced gene expression in human microvascular endothelial cells. We conducted the first whole genome screen for TNFα- inducible genes in human microvascular cells (HMEC). Acutely, TNFα induced 522 genes and downregulated 141 genes in nine out of nine pairwise comparisons. Of the 522 genes induced by TNFα in HMEC, 113 genes were clearly sensitive to BE treatment. Such genes directly related to inflammation, cell adhesion, and proteolysis. The robust BE-sensitive candidate genes were then subjected to further processing for the identification of BE-sensitive signaling pathways. The use of resources such as GenMAPP, KEGG, and gene ontology led to the recognition of the primary BE-sensitive TNFα-inducible pathways. BE prevented the TNFα-induced expression of matrix metalloproteinases. BE also prevented the inducible expression of mediators of apoptosis. Most strikingly, however, TNFα-inducible expression of VCAM-1 and ICAM-1 were observed to be sensitive to BE. Realtime PCR studies showed that while TNFα potently induced VCAM-1 gene expression, BE completely prevented it. This result confirmed our microarray findings and built a compelling case for the anti-inflammatory property of BE. In an in vivo model of carrageenan-induced rat paw inflammation, we observed a significant antiinflammatory property of BE consistent with our in vitro findings. These findings warrant further research aimed at identifying the signaling mechanisms by which BE exerts its anti-inflammatory effects.