Israel Medical Association Journal

Background: Interleukin-8 is a prototypical inflammatory chemokine that induces leukocyte migration to inflammatory sites. Leukocyte recruitment in response to gradients of this chemokine is attenuated at advanced stages of inflammation to prevent damage to surrounding healthy tissues. Our published studies suggest that over-phosphorylation of focal adhesion kinase in migration-desensitizing conditions is involved in cessation of cell motility. This over-phosphorylation of FAK[1] was induced by IL-8[2] only when the receptor transmitting the chemokine signals was CXCR2, and not CXCR1, indicating that the two IL-8 receptors diverge in their signaling properties.

Objectives: To analyze the regulation of FAK in CXCR2-expressing hematopoietic cells under conditions of migratory desensitization, focusing on the roles played by adhesion-related components in this process.

Methods: Under conditions of migratory desensitization, we determined IL-8-induced cell spreading and FAK localization following disruption of actin filaments, and evaluated the role of integrins in FAK phosphorylation.

Results: The disturbance of intact activity of actin filaments resulted in inhibition of cell spreading and modification of FAK intracellular localization upon IL-8 stimulation. Also, adhesion-dependent pre-stimulation of integrins was required for IL-8-induced FAK phosphorylation.
Conclusions: Intact actin filaments and integrins are required for optimal IL-8-induced FAK phosphorylation in conditions of migratory desensitization. These observations suggest that lack of adequate activity/regulation of adhesion-related components may give rise to FAK activities that are not appropriately controlled, possibly leading to pathological conditions that are associated with perturbed leukocyte migration phenotypes

Chemokines and their receptors play regulatory roles in inflammatory reactions. Lipoprotein(a) is an atherogenic lipoprotein, however the mechanisms of its actions are not defined. Our interest in chemokines and their receptors was stimulated by the finding that incubation of Lp(a)[1] with human umbilical vein endothelial cells produced a conditioned medium that was chemotactic for human monocytes. Since infiltration of monocytes into the vessel wall is an early lesion in atherosclerosis, this finding provided a novel mechanism to explain the relationship between Lp(a) and atherosclerosis. The chemoattractant produced by HUVEC[2] was identified as CCL1/I-309, a CC chemokine previously reported to be secreted by stimulated monocytes/macrophages and T lymphocytes. CCR8, the CCL1 receptor, was identified on endothelial cells, and CCL1 was found to be a chemoattractant for these cells. Most recently we demonstrated functional CCR8 on human vascular smooth muscle cells and found that the Lp(a)-HUVEC conditioned medium is a chemoattractant for these cells. CCL1 increased metalloproteinase-2 production by HUVEC, an activity that enables these cells to remodel the vascular matrix. These studies suggest that CCR8 may play an important role in arterial wall pathology.

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[1] Lp(a) = lipoprotein(a)

[2] HUVEC = human umbilical vein endothelial cells

Background: Cell-mediated immunity is impaired in uremia. Cell-matrix interactions of immune cells such as CD4+T lymphocytes with extracellular matrix are an important requirement for an intact immune response. The adherence of CD4+T cells of healthy subjects (normal T cells) to ECM components is inhibited in the presence of uremic serum. Such decreased adhesive capacity is also found in T cells of dialysis patients. Various chemokines and cytokines affect the attachment of CD4+T cells to ECM.

Objective: To evaluate chemokine (MIP-1β and RANTES) and tumor necrosis factor α-induced adhesion of CD4+T cells to ECM in a uremic milieu.

Methods: We examined adhesion of normal CD4+T cells (resting and activated) to intact ECM in response to soluble or bound chemokines (MIP-1β and RANTES) and to TNF-α following incubation in uremic versus normal serum. Thereafter, we evaluated the adhesion of resting CD4+T cells from dialysis patients in a similar fashion and compared it to that obtained from a healthy control group.

Results: Addition of uremic serum diminished soluble and anchored chemokine-induced attachment of normal resting and activated CD4+T cells to ECM compared to a normal milieu (a peak response of 10–11% vs. 24–29% for soluble chemokines, P<0.001; 12–13% vs. 37–39% for bound chemokines on resting cells, P<0.01; and 18–20% vs. 45–47% for bound chemokines on activated cells, P<0.02). The same pattern of response was noted following stimulation with immobilized TNF-α (7 vs. 12% for resting cells, P<0.05; 17 vs. 51% for activated cells, P<0.01).  Adherence of dialysis patients’ cells to ECM following stimulation with both bound chemokines was reduced compared to control T cells (15–17% vs. 25–32%, P<0.0000). In contrast, adherence following stimulation by TNF-α was of equal magnitude.

Conclusions: Abnormal adhesive capacity of T lymphocytes to ECM in uremia may, in part, be related to a diminished response to MIP-1β, RANTES and TNF-α. However, whereas reduced adhesion to chemokines was present in both normal CD4+T cells in a uremic environment and in dialysis patients’ T cells, TNF-α-induced adhesion was found to be inhibited only in normal cells in a uremic milieu.

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ECM = extracellular matrix

TNF-α = tumor necrosis factor-a