CXCR3 Is Involved in Tubulointerstitial Injury in Human Glomerulonephritis

Abstract

Chemokines are members of a family of chemotactic cytokines.¹ As the first chemoattractants specific for subsets of inflammatory cells, chemokines revolutionized our understanding of mononuclear cell recruitment, inflammatory processes, and microenvironment formation.^2–4 The importance of chemokines during renal inflammation has been described in various studies that have demonstrated expression of chemokines, infiltration of tissue by chemokine receptor-bearing cells, and the therapeutic impact of chemokine receptor antagonists.^5,6

The chemokine receptor CXCR3 signals in response to the chemokines CXCL9/monokine induced by γ-interferon (Mig), CXCL10/γ-interferon-inducible protein-10 (IP-10), and CXCL11/interferon-inducible T cell-α chemoattractant (I-TAC), which can be released by renal cells.^1,5 For example, CXCL10/IP-10 can be expressed by mesangial cells, endothelial cells, and interstitial cells after stimulation with proinflammatory cytokines (especially γ-interferon) or lipopolysacharide in vitro.⁵ Migration of activated peripheral blood lymphocytes toward supernatants derived from cultured tubular epithelial cells was inhibited to a significant extent through blockade of CXCR3.⁷

Expression of the receptor CXCR3 has been demonstrated on circulating T cells with a strong induction of CXCR3 after T cell activation. The receptor has also been described on B cells and natural killer cells.^8,9In vitro studies indicate that CXCR3 is predominantly expressed by T helper cells type 1 (Th1).¹⁰ Several studies support that CXCR3 and its corresponding ligands play a pivotal role during inflammatory diseases and allograft rejection. The diseases include inflammatory bowel disease, inflammatory skin diseases, multiple sclerosis, and periodontal disease.^11–14 The potential role of CXCR3 in allograft pathology has been demonstrated for liver, heart, and lung allografts, both in animal models as well as in human allografts.^15–19

We previously studied the expression of the chemokine receptor CCR5 in human kidney biopsies which is also mainly expressed by T cells. In these studies, the number of CCR5-positive interstitial infiltrating cells increased in patients with impaired renal function.²⁰ CCR5-positive T cells may play a role in chronic transplant nephropathy as patients deficient in CCR5 have an improved long-term allograft survival.²¹

The available data on the potential role of CXCR3-positive cells in renal diseases are still scarce. CXCR3 expression has previously been studied using the anti-human CXCR3 monoclonal antibody 49801.111 (R&D Systems, Minneapolis, MN) on cryostat sections of renal biopsies from patients with IgA nephropathy, membranoproliferative glomerulonephritis, and rapidly progressive glomerulonephritis.²² Expression was described on vascular smooth muscle cells, mesangial cells, and infiltrating mononuclear cells.²² Using the same antibody, CXCR3 immunohistochemistry staining on frozen sections from developing kidneys was described in ureteric buds, comma, and S-shaped bodies, on endothelial cells, and vascular smooth muscle cells including the developing mesangium.²³

Very recently, a splice variant of CXCR3 has been described by Lasagni et al.²⁴ This CXCR3-B variant is present on endothelial cells, and ligand binding results in antiproliferative effects rather than proproliferative effects as in the case of classical CXCR3 (now referred to as CXCR3-A). Interestingly the monoclonal antibody 49801.111 also recognizes the variant CXCR3-B in FACS analysis.²⁴

To further define the role of CXCR3-positive cells in human glomerulonephritis, we tested two monoclonal antibodies on formalin-fixed, paraffin-embedded tissues (49801.111, R&D Systems, Minneapolis, MN, and 1C6, BD Biosciences Pharmingen, Heidelberg, Germany). Only one turned out to be suitable (1C6, BD Biosciences Pharmingen), on formalin-fixed, paraffin-embedded renal biopsies. The number of CXCR3-positive cells was correlated with histological and clinical data, as well as with the number of CCR5-positive cells. Furthermore, expression of CXCR3 mRNA and its ligands was studied in microdissected tubulointerstitial areas from renal biopsies by real time RT-PCR. Finally, we evaluated the expression of CXCR3 and functional responses to the ligands by mesangial cells in culture. We report that the main CXCR3 expression in human glomerulonephritis is on interstitial infiltrating T cells, the number of which correlates inversely with renal function and histopathology, indicating that CXCR3-positive T cells seem to play an important role in the progression of glomerular diseases.

IgA, IgA nephropathy; SLE, lupus nephritis; MPGN, membranoproliferative glomerulonephritis; age, years, range; hematuria and leukozyturia, cases with >10 cells/μl/cases with available data.

IgA, IgA nephropathy; SLE, lupus nephritis; MPGN, membranoproliferative glomerulonephritis.

sr, Spearman correlation coefficient, nonparametric correlation; 95%, confidence interval; % globally sclerosed, percentage of globally sclerosed glomeruli; % chronic TI damage, percentage involved in chronic tubulointerstitial injury.

Acknowledgments

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