Coupling of boswellic acid-induced Ca2+ mobilisation and MAPK activation to lipid metabolism and peroxide formation in human leucocytes

摘要

We have previously shown that 11-keto boswellic acids (11-keto-BAs), the active principles of Boswellia serrata gum resins, activate p38 MAPK and p42/44MAPK and stimulate Ca2+ mobilisation in human polymorphonuclear leucocytes (PMNL).In this study, we attempted to connect the activation of MAPK and mobilisation of Ca2+ to functional responses of PMNL, including the formation of reactive oxygen species (ROS), release of arachidonic acid (AA), and leukotriene (LT) biosynthesis.We found that, in PMNL, 11-keto-BAs stimulate the formation of ROS and cause release of AA as well as its transformation to LTs via 5-lipoxygenase.Based on inhibitor studies, 11-keto-BA-induced ROS formation is Ca2+-dependent and is mediated by NADPH oxidase involving PI 3-K and p42/44MAPK signalling pathways. Also, the release of AA depends on Ca2+ and p42/44MAPK, whereas the pathways stimulating 5-LO are not readily apparent.Pertussis toxin, which inactivates Gi/0 protein subunits, prevents MAPK activation and Ca2+ mobilisation induced by 11-keto-BAs, implying the involvement of a Gi/0 protein in BA signalling.Expanding studies on differentiated haematopoietic cell lines (HL60, Mono Mac 6, BL41-E-95-A) demonstrate that the ability of BAs to activate MAPK and to mobilise Ca2+ may depend on the cell type or the differentiation status.In summary, we conclude that BAs act via Gi/0 protein(s) stimulating signalling pathways that control functional leucocyte responses, in a similar way as chemoattractants, that is, N-formyl-methionyl-leucyl-phenylalanine or platelet-activating factor.