Background

Macrophages seem to play an important role in the development of glomerulosclerosis. In both human and experimental animal models of focal glomerulosclerosis (FSGS), infiltration of macrophages in the mesangium has been considered key in the development of FSGS.

Methods

In the present study, we evaluated the effect of vasoactive agents on the migration of monocytes across a filter in a modified Boyden chamber as well as across a cultured glomerular endothelial cell layer (in vitro model of glomerular mesangium). Both light as well as scanning electron microscopic studies were performed. We evaluated the effect of vasoactive agents including histamine, prostaglandin (PG) E2, angiotensin II, endothelin-1, platelet-activating factor, and interleukin-1 (IL) on the migration of monocytes/macrophages across an endothelial cell layer as well as a gelatin-coated filter. In addition, we evaluated the effect of cyclic adenosine 3', 5'cyclic monophosphate (cAMP) and PGE2 on vasoactive-induced migration of monocytes.

Results

Histamine increased (P< 0.003) the migration of monocytes across the filter. This effect of histamine was dose-dependent. Histamine at concentrations of 10 (-8) to 10 (-5) mol/L induced optimal migration across the filter (control, 16.6+/-1.1 vs histamine, 10 (-8) mol/L, 40.9+/-0.9 monocytes/high power field). Cimetidine, an H2 receptor blocker, attenuated (P< 0.001) the effect of histamine on the migration of monocytes. PGE2 inhibited the migration of monocytes in a dose-dependent manner. Histamine increased (P< 0.001) the passage of monocytes across the glomerular endothelial cell layer (control, 1012+/-37 vs 1711+/-163 cpm/well). Histamine also increased the migration of murine macrophages across the glomerular endothelial cell layer. PGE2 inhibited the migration of monocytes across the endothelial cell layer under basal as well as histamine-stimulated states. Dibutyryl cyclic (DBc) AMP also attenuated the migration of monocytes under basal as well as histamine-stimulated states. Both PGE2 and DBcAMP also attenuated the IL-1 beta-stimulated migration of monocytes. Angiotensin II, endothelin-1, and platelet-activating factor did not modulate the migration of monocytes.

Conclusions

Vasoactive agents directly modulate the transmigration of monocytes. The present in vitro study provides a basis for a hypothesis that vasoactive agents may also be modulating the migration of monocytes across the glomerular endothelial cell layer (into the mesangium).