[Calcitonin gene-related peptide induces chemokine interleukine-8 synthesis in human monocytes]

To study the effect of calcitonin gene-related peptide (CGRP) on the function of immune cells.

Human monocytes were cultured with calcitonin gene-related peptide in vitro and activated with lipopolysaccharide (LPS). The IL-8 level in the supernatant was measured with ELISA and the IL-8 mRNA expression in monocytes was observed by reverse transcription polymerase chain reaction (RT-PCR). The chemotactic activity of monocytes to neutrophils and lymphocytes was analyzed with micro-chemotacxis chamber. Chemotactic index (CI) was calculated by the formula: number of monocytes migrating to the underside of membrane in the LPS + CGRP group/number of monocytes migrating to the underside of membrane in the control group. CGRP receptor antagonist CGRP8 - 37 was added into the culture to study the effect of CGRP. Blank control and cultures of monocytes with LPS or with CGRP only were used as controls.

The level of IL-8 protein in the supernatant of the LPS + CGRP group was 1 120 pg/ml +/- 14.80 pg/ml, significantly higher than those in other groups (670 pg/ml +/- 15.10 pg/ml in LPS + CGRP + CGRP8 - 37 group). The expression of IL-8 mRNA in the LPS + CGRP group was the highest (IL-8/beta-actin = 1.845 +/- 0.587), IL-8/beta-actin in the LPS + CGRP + CGRP8 - 37 group was1.339 +/- 0.434. The chemotactic activities of the monocytes to neutrophils and lymphocytes were enhanced in the LPS + CGRP group (CI = 3.78 +/- 0.08 to neutrophils and CI = 3.4 +/- 0.27 to lymphocytes). The CI values were 1.15 +/- 0.31 and 1.21 +/- 0.06 respectively in the LPS + CGRP + CGRP 8 - 37 group.

CGRP in the peripheral nerve ending induces monocytes to synthetize and secret chemotactic factor IL-8 and enhance the chemotactic activity of monocytes, thus promoting the directional migration and aggregation of neutrophils and lymphocytes to foci of inflammation.