Suppressive Effects of Coumarin Derivatives from Angelica Hirsutiflora on Human Neutrophil Functions

Neutrophils play a pivotal role in the defense of the human body against infections. However, overwhelming activation of neutrophils is known to elicit tissue damage. Human neutrophils are known to play important roles in the pathogenesis of various diseases such as ischemic heart disease, acute myocardial infarction, sepsis, chronic obstructive pulmonary disease, and asthma. In response to diverse stimuli, activated neutrophils secrete a series of cytotoxins, such as the superoxide anion, granule proteases, and bioactive lipids. Suppression of the extensive or inappropriate activation of neutrophils using drugs has been proposed as a way to ameliorate these inflammatory diseases. Despite this, there are only a few currently available agents that directly modulate neutrophil proinflammatory responses in clinical practice. Therefore, the research and development of new generation anti-inflammatory drugs continue as important targets. Angelica genus (Umbelliferae) has traditionally been used as the medicine and health food considered alleviating several disorders. Angelica plants exhibit diverse ranges of pharmacological effects, such as antimicrobial activity, anti-platelet aggregation, antioxidant, and anti-inflammatory effects. Angelica hirsutiflora is an endemic species and a folk medicine in Taiwan. This plant is traditional used to treat inflammatory diseases. However, the anti-inflammatory effects and active ingredients of Angelica hirsutiflora in human neutrophils are still unknown. In searching for suitable new anti-inflammatory agents from natural sources, a cellular model in isolated human neutrophils will be established to elucidate the anti-inflammatory functions of Angelica hirsutiflora in this project. In the meantime, we will explore the novel mechanism of the potential candidates and evaluate their potentials as the lead compounds for the drug development in this field. In the preliminary experiments, three active coumarins, osthol, auraptenol, and imperatorin, from Angelica hirsutiflora showed potent and specific inhibition of superoxide anion generation in formyl-L-methionyl-L-leucyl-L-phenylalanine-activated human neutrophils with IC50 values of 7.81±2.47 nM, 0.48±0.09 μM, and 0.17±0.02 μM, respectively. These inhibitory effects were not due to cytotoxicity because culturing with these compounds did not cause lactate dehydrogenase release. Moreover, osthol and imperatorin displayed no superoxide-scavenging ability, and they failed to alter subcellular NADPH oxidase activity. Significantly, our preliminary results suggest that osthol and imperatorin are cAMP-elevating agents in human neutrophils. Certainly, the mechanisms of action of these compounds will be further investigated in this project. On the basis of these preliminary findings, we therefore propose a three-year project to conduct studies in the following aspects: (i) to examine the pharmacological effects of osthol, auraptenol, and imperatorin on respiratory burst, degranulation, and migration in human neutrophils; (ii) to investigate the respective roles of cAMP, cGMP, calcium, PI3K, and MAPK signal transduction pathways in mediating the effects of osthol, auraptenol, and imperatorin. These studies will provide new insight into the pharmacological functions of these three coumurins, and support the hypothesis that osthol, auraptenol, and imperatorin may have the potential to protect against the progression of inflammatory diseases. Also, our results will support the beneficial use of this plant by traditional medicine.

Project ID:PC9907-0083
External Project ID:NSC99-2320-B182-006-MY3