Blockade of CCR2 Ameliorates Progressive Fibrosis in Kidney

Kiyoki Kitagawa

Takashi Wada

Kengo Furuichi

Hiroyuki Hashimoto

Kouji Matsushima+2 authors

From the Department of Gastroenterology and Nephrology,^{Graduate School of Medical Science, the Division of Blood Purification}^{and the Department of Molecular Oncology,}^{Cancer Research Institute, and the Institute for Experimental Animals,}^{Kanazawa University, Kanazawa, Japan; Sanwa Kagaku Kenkyusho Company, Limited,}^{Inabe, Japan; the Second Department of Pathology,}^{Kumamoto University School of Medicine, Kumamoto, Japan; the Department of Molecular Preventive Medicine,}^{Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and the Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology,}^{University of Texas, Austin, Texas}

Accepted 2004 Mar 30.

Abstract

Fibrosis is a hallmark of progressive organ diseases. Monocyte chemoattractant protein (MCP)-1, also termed as macrophage chemotactic and activating factor (MCAF/CCL2) and its receptor, CCR2 are presumed to contribute to progressive fibrosis. However, the therapeutic efficacy of MCP-1/CCR2 blockade in progressive fibrosis remains to be investigated. We hypothesized that blockade of CCR2 may lead to the improvement of fibrosis. To achieve this goal, we investigated renal interstitial fibrosis induced by a unilateral ureteral obstruction in CCR2 gene-targeted mice and mice treated with propagermanium or RS-504393, CCR2 inhibitors. Cell infiltrations, most of which were F4/80-positive, were reduced in CCR2 knockout mice. In addition, dual staining revealed that CCR2-positive cells were mainly F4/80-positive macrophages. Importantly, CCR2 blockade reduced renal interstitial fibrosis relative to wild-type mice. Concomitantly, renal transcripts and protein of MCP-1, transforming growth factor-β, and type I collagen were decreased in CCR2-null mice. Further, this CCR2-dependent loop for renal fibrosis was confirmed by treatment with CCR2 antagonists in a unilateral ureteral obstruction model. These findings suggest that the therapeutic strategy of blocking CCR2 may prove beneficial for progressive fibrosis via the decrease in infiltration and activation of macrophages in the diseased kidneys.

Abstract

Fibrosis is characteristic in progressive diseases, resulting in organ failure. Monocyte chemoattractant protein (MCP)-1 (also termed as monocyte chemotactic and activating factor/CCL2) is presumed to be a key molecule in chemotaxis and activation of macrophages.¹ MCP-1 has been implicated in a variety of renal diseases, including progressive renal damage such as chronic rejection of renal transplantation, lupus nephritis, IgA nephropathy, crescentic glomerulonephritis, and diabetic nephropathy in human and experimental models.^2–9 CCR2, a cognate receptor of MCP-1 expressed mainly on monocytes, has been reported to be involved in human crescentic glomerulonephritis and experimental models of progressive renal disease.^10,11 In addition to inducing tissue infiltration and activation of macrophages, MCP-1 expression and the consequent accumulation of CCR2-positive cells are considered to be closely related to pulmonary fibrosis.¹² Thus, the strategy of blocking MCP-1/CCR2 interaction might be effective in preventing macrophage-induced tissue damage. Supporting this notion, neutralization of MCP-1 has been reported to reduce macrophage infiltration and progressive kidney damage.^5,8,9,13

Newly developed antagonists against chemokine receptors are now available. For example, propagermanium is an organic germanium compound with a chemical structure of [(O_1/2)₃GeCH₂CH₂CO₂H]_n, which shows potent anti-inflammatory activity in various inflammatory experimental models,^14,15 and has been used as a therapeutic agent in chronic hepatitis type B. A recent study revealed that propagermanium inhibited the MCP-1-induced migration of monocytes via glycosylphosphatidylinositol-anchored protein associated with CCR2.¹⁶ In addition, RS-504393 also has the capacity to inhibit MCP-1-induced chemotaxis and ischemia-reperfusion injury in kidneys, where MCP-1 plays a role.¹⁷ However, whether the blockade of CCR2 might be effective for the treatment of renal interstitial fibrosis has not been fully examined.

In this study, we hypothesized that the blockade of CCR2 might be therapeutically beneficial for progressive fibrosis. To achieve this goal, we evaluated renal interstitial fibrosis induced by unilateral ureteral obstruction (UUO), a well-known renal fibrosis model,^18,19 in CCR2 gene-targeted mice and mice treated with propagermanium or RS-504393. We report here that the blockade of CCR2 represents a beneficial therapeutic approach for progressive fibrosis in kidney.

Acknowledgments

We thank Dr. Joost J. Oppenheim (National Cancer Institute-Frederick Cancer Research and Development Center-FCRDC) for his critical review of the manuscript and Dr. Toshikazu Kondo (Wakayama Medical University, Wakayama, Japan) for his advice in a dual staining.

Acknowledgments

Footnotes

Address reprint requests Dr. Takashi Wada, Division of Blood Purification and Department of Gastroenterology and Nephrology, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8641, Japan. .pj.ca.u-awazanak.m.fdem@adawt :liam-E

Supported in part by a grant-in-aids from the Ministry of Health, Labor, and Welfare of Japan; and the Ministry of Education, Science, Sports, and Culture in Japan (no. 14571019 to T.W.).

Footnotes