The Functional Role of Rho and Rho-Associated Coiled-Coil Forming Protein Kinase in Eotaxin Signaling of Eosinophils

Abstract

The CC chemokine eotaxin plays a pivotal role in local accumulation of eosinophils. Very little is known about the eotaxin signaling in eosinophils except the activation of the mitogen-activated protein (MAP) kinase family. The p21 G protein Rho and its substrate Rho-associated coiled-coil forming protein kinase (ROCK) regulate the formation of stress fibers and focal adhesions. In the present study, we studied the functional relevance of Rho and ROCK in eosinophils using the ROCK inhibitor (Y-27632) and exoenzyme C3, a specific Rho inhibitor. Eotaxin stimulates activation of Rho A and ROCK II in eosinophils. Exoenzyme C3 almost completely inhibited the ROCK activity, indicating that ROCK is downstream of Rho. We then examined the role of Rho and ROCK in eosinophil chemotaxis. The eotaxin-induced eosinophil chemotaxis was significantly inhibited by exoenzyme C3 or Y-27632. Because extracellular signal-regulated kinase (ERK)1/2 and p38 MAP kinases are activated by eotaxin and are critical for eosinophil chemotaxis, we investigated whether Rho and ROCK are upstream of these MAP kinases. C3 partially inhibited eotaxin-induced phosphorylation of ERK1/2 but not p38. In contrast, neither ERK1/2 nor p38 phosphorylation was abrogated by Y-27632. Both C3 and Y-27632 reduced reactive oxygen species production from eosinophils. We conclude that both Rho and ROCK are important for eosinophil chemotaxis and reactive oxygen species production. There is a dichotomy of downstream signaling pathways of Rho, namely, Rho-ROCK and Rho-ERK pathways. Taken together, eosinophil chemotaxis is regulated by multiple signaling pathways that involve at least ROCK, ERK, and p38 MAP kinase.

Simvastatin Inhibits Airway Hyperreactivity

“…Simvastatin can induce eosinophilic apoptosis in an MA-dependent fashion (29), while Ras regulates eosinophil chemotaxis and survival (30). Furthermore, the observed simvastatin inhibition of airway eosinophilia ( Figure 1B) could also be due to broader systemic effects on T cells with subsequent inhibition of eosinophilic chemotaxis and transmigration (31,32). Statins also modulate monocyte-macrophage function and inflammatory responses (33,34), consistent with our finding of reduced BALF macrophage counts ( Figure 1D).…”

CCL11 and GM-CSF Differentially Use the Rho GTPase Pathway to Regulate Motility of Human Eosinophils in a Three-Dimensional Microenvironment

“…Furthermore, previous studies show that the Rho pathway is involved in eosinophil migration in vitro (22,41) including tail retraction (22) and the migratory response to CCL11 (41). However, studies on MDCK and HeLa cells show that Rho/ ROCK activity in the tail of migrating cells is context-dependent, as cells migrating at low density on collagen-coated glass coverslips showed high Rho activity in the tail, but cells migrating in a monolayer did not (42).…”

2-Arachidonoylglycerol Induces the Migration of HL-60 Cells Differentiated into Macrophage-like Cells and Human Peripheral Blood Monocytes through the Cannabinoid CB2 Receptor-dependent Mechanism

“…4). The inhibition of cell migration by Y-27632 (1-100 M) (41,42), PD98059 (10 -20 M) (43)(44)(45), and SB203580 (10 -50 M) (42,46) has already been reported for several types of cells stimulated with various chemoattractants, although there are conflicting results as to the inhibition by PD98059 (42,46). The relationship between Rho kinase and p38 MAP kinase, as well as MEK, is known to be complicated.…”