APOPTOTIC ACTIVITY OF BOSWELLIA CARTERII EXTRACT ON HUMAN NEUTROPHILS.

Abstract

Neutrophil activation is required for the initiation of the defence mechanisms which include phagocytosis. Paradoxically, neutrophils also represent one of the main mediators of tissue injury in various human diseases. The resolution of inflammation requires getting rid of excess inflammatory cells through natural cell death and phagocyte clearance. Frankincense, an oleogum resin of different species of the genus Boswellia (Burseraceae), has long been used in eastern countries' traditional medicine to alleviate pain and inflammation. Although it was demonstrated that boswellic acids are potent activators of polymorphonuclear cells, little is known about the effects of the total extract on the human phagocytes’ apoptosis.

We here undertake a characterization of the Boswellia carteri resin extract (BCE) effects on human neutrophils activity and viability in vitro. Oxidative burst after stimulation with BCE was evaluated by reduction of nitroblue tetrazolium (NBT) colorimetric method for superoxide anion radical in the the presence of different compounds (N-ethyl maleimide, diltiazem, chelerythrine and wortmannin). Neutrophils viability was assessed by MTT. Flow analyses were performed with propidium iodide (PI) and annexin V-FITC.

Our results show that BCE induces the release reactive species of oxygen in human neutrophils in a dose dependent manner. The superoxide anion radical is principally produced via NADPH oxidase since inhibitors of the enzyme may prevent it. Ca⁺² depletion reduce the magnitude of activation and PKC and PI3-K are also apparently involved in the process. The BCE has also cytotoxic activity revealed by the MTT assay. This effect seems to be produced by an apoptotic process as shown by the exclusion of the dye propidium iodide and the annexin V-FITC binding.

The capacity of the Boswellia carterii extract to accelerate the cellular death by an apoptotic process suggest that either the extract or its active compounds could have applications for the resolution of some inflammatory conditions.