Protective Roles of the Fractalkine/CX3CL1-CX3CR1 Interactions in Alkali-Induced Corneal Neovascularization through Enhanced Antiangiogenic Factor Expression

Abstract

Macrophage infiltration is observed during the course of corneal neovascularization. We examined corneal neovascularization process after alkali injury in mice deficient in fractalkine receptor/CX3CR1, which is expressed by macrophages. The mRNA expression of CX3CR1 and its ligand CX3CL1/fractalkine was augmented together in the corneas after alkali injury. Compared with WT mice, CX3CR1‐deficient (KO) mice exhibited enhanced corneal neovascularization 2 weeks after injury, as evidenced by enlarged CD31‐positive areas. Concomitantly, the infiltration of F4/80‐positive macrophages but not Gr‐1‐positive neutrophils was significantly attenuated in KO mice comparing with WT mice. The intraocular mRNA expression of angiogenic factor, vascular endothelial factor, was enhanced to similar extents in WT and KO after the injury. In contrast, the mRNA expression of anti‐angiogenic factors, a disintegrin and metalloprotease with thrombospondin (ADAMTS)‐1 and thrombospondin (TSP)‐1 was enhanced in wild‐type mice but the enhancement was attenuated in KO mice. A double immunofluorescence analysis demonstrated that F4/80‐positive cells also expressed CX3CR1 and ADAMTS‐1, TSP‐1 and ADAMTS‐1 were detected in CX3CR1‐positive cells. CX3CL1 enhanced the ADAMTS‐1 and TSP‐1 expression by peritoneal macrophages. Moreover, topical application of CX3CL1 inhibited corneal neovascularization at 2 weeks, together with enhanced intraocular ADAMTS‐1 and TSP‐1 expression. Thus, these observations indicate that intraocular infiltrating CX3CR1‐positive macrophages can dampen alkali‐induced corneal neovascularization by producing anti‐angiogenic factors, such as ADAMTS‐1 and TSPs.

Fractalkine and its receptor, CX3CR1, promote hypertensive interstitial fibrosis in the kidney

“…The male CX3CR1-deficient mice were on an outbred C57BL/6 genetic background (n48 generations), and were used at 30 weeks of age. 9,10 Five mice were used in each experiment. All animal experiments were performed at the Institute for Experimental Animals (Kanazawa University Advanced Science Research Center, Kanazawa, Japan), complied with the standards set out in the Guidelines for the Care and Use of Laboratory Animals of Kanazawa University, and were approved by the Committee on Animal Experimentation of Kanazawa University.…”

“…8 Recently, pathophysiological roles of the fractalkine-CX3CR1 axis were noted in the bactericidal host defense during septic peritonitis 9 and corneal neovascularization. 10 Additionally, fractalkine/CX3CL1 was reported to be involved in the progression of human glomerulopathy, including crescentic glomerulonephritis. 11 Collectively, these data suggest that the fractalkine-CX3CR1 axis may promote tissue injury through immune competent cell infiltration and fibrogenesis.…”

Protective effects of matrix metalloproteinase-12 following corneal injury

“…1C). Since macrophages are a major source of MMP12, it is interesting that the high expression levels of Mmp12 noted at 2 and 6 days after injury corresponded with time points of high macrophage recruitment (Lu et al, 2008;Nakao et al, 2005). Since resident macrophages are normally present in the cornea (Brissette-Storkus et al, 2002), we determined their ability to express Mmp12.…”

Opposite Roles of CCR2 and CX3CR1 Macrophages in Alkali-Induced Corneal Neovascularization

“…6 Although there is considerable evidence that macrophages are proangiogenic, [7][8][9][10][11] recent studies suggest that macrophages may be antiangiogenic. 12,13 Furthermore, the dichotomy of monocytes/ macrophages has been proposed based on their expression levels of CCR2 and CX3CR1. [14][15][16][17][18] We recently revealed that infiltrating CX3CR1-positive macrophages were protective for alkali-induced corneal neovascularization through antiangiogenic molecule expression.…”