ENDOTHELIN-1 STIMULATES MONOCYTES IN-VITRO TO RELEASE CHEMOTACTIC ACTIVITY IDENTIFIED AS INTERLEUKIN-8 AND MONOCYTE CHEMOTACTIC PROTEIN-1

In the present study we examined whether endothelin-1 stimulation of human monocytes causes release of chemotactic factors. It was found that monocytes released neutrophil- and monocyte-chemotactic activity in a dose- and time-dependent manner in response to ET-1. ET-1 did not show any chemotactic activity by itself. NCA was detected in monocyte supernatants in response to ET-1 (0.01 - 100 nM) after 1, 4, 8 and 24 h stimulation. MCA was detected only after 24 h stimulation with ET-I (0.1 - 100 nM). Preincubation of the monocyte cultures with the lipoxygenase inhibitors nordihydroguaiaretic acid (10(-4) M) or diethylcarbamazine (10(-9) M) completely abolished the appearance of NCA and MCA. NCA was neutralized by > 75% using a polyclonal antibody against human interleukin-8. The ET-1 induced release of IL-8 was confirmed by IL-8 ELISA. A monoclonal antibody against human monocyte chemotactic protein-1 neutralized MCA by > 80%. It is concluded that ET-1 stimulation of monocytes in vitro causes release of neutrophil- and monocyte-chemotactic activity identified as IL-8 and MCP-1 respectively. An intact lipoxygenase pathway is crucial for this effect of ET-1 to occur.