Purpose: To investigate the effects of triptolide (TP) on the proliferation of monocytes/macrophages, secretion of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor-C (VEGF-C) in mildly acid microenvironment.

Methods: Human monocytes/macrophage system (THP-1 strains) was cultured under acid (pH 6.6 and pH 6.8) microenvironment and normal microenvironment (pH 7.2) containing different concentrations of TP (5, 10, 20 and 50 µg/mL) for 24, 48 and 72 h. The number of monocytes/macrophages under the varying conditions was subsequently determined by methyl thiazolyl tetrazolium (MTT) assay. The supernatants were collected after 24-h culture, and the content of VEGF and VEGF-C in each supernatant measured by enzyme-linked immunosorbent assay (ELISA).

Results: The proliferation of monocytes/macrophages to some extent enhanced in mildly acid microenvironment. The content of VEGF and VEGF-C declined gradually with increasing TP concentration at the same pH value, and reached a minimum at 50 ug/mL and pH 6.6.

Conclusion: In mildly acid microenvironment, TP promotes the proliferation of monocytes/macrophages to some extent and can reduce their ability to secrete tumor growth promoting factors.