JAK3-STAT pathway blocking benefits in experimental lupus nephritis

Abstract

Background: Lupus nephritis (LN) is a complex chronic autoimmune disease of unknown etiology characterized by loss of tolerance against several self-antigens. Cytokines are known to be central players in LN pathogenesis. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is one important pathway that mediates signal transduction of several cytokines. In this study, we examined the pathogenic role of this pathway and how CP-690,550 treatment influences LN outcome.

Methods: Six-month-old NZB/NZWF1 mice were divided into two different treatment groups: (1) control animals given vehicle treatment, cyclophosphamide, and mycophenolate mofetil treatment as positive controls of the therapy and (2) mice treated with CP-690,550, a JAK3 inhibitor. Mice were treated for 12 weeks. We evaluated renal function, anti-double-stranded DNA (anti-dsDNA) antibody, renal histology changes, kidney complement and immunoglobulin G (IgG) deposits, T-cell and macrophage infiltration, kidney inflammatory gene expression, and circulating cytokine changes.

Results: CP-690,550 treatment significantly reduced proteinuria and improved renal function and histological lesions of the kidney. Compared with vehicle-treated animals, those undergoing CP-690,550 treatment showed significantly diminished anti-dsDNA antibody and complement component C3 and IgG deposition in glomeruli. We also observed a significant reduction of T-cell and macrophage infiltration. Kidney gene expression revealed a reduction in inflammatory cytokines and complement and related macrophage-attracting genes. Circulating inflammatory cytokines were also reduced with treatment.

Conclusions: On the basis of our results, we conclude that the JAK-STAT pathway is implicated in the progression of renal inflammation in NZB/WF1 mice and that targeting JAK3 with CP-690,550 is effective in slowing down the course of experimental LN. Thus, CP-690,550 could become a new therapeutic tool in LN and other autoimmune diseases.

Keywords: Autoimmunity; Glomerulonephritis; JAK3 inhibitor; Kidney infiltrate; Lupus nephritis.

Fig. 1

a Proteinuria and b albuminuria. Twenty-four-hour proteinuria increased progressively in PBS-treated mice (n = 14) to levels of heavy proteinuria. Treatment with cyclophosphamide (CYP; n = 14), mycophenolate mofetil (MMF; n = 8), and CP-690,550 (CP; n = 8) induced a progressive reduction of proteinuria almost to physiological levels. *p < 0.05 vs control

Fig. 2

Anti-double-stranded (anti-dsDNA) antibodies. Anti-dsDNA antibodies increased progressively in PBS-treated control mice. CP-690,550 (CP) treatment reduced this production more effectively than cyclophosphamide (CYP) or mycophenolate mofetil (MMF) treatment. *p < 0.05 vs control

Fig. 3

Renal histopathology. a Cyclophosphamide (CYP), mycophenolate mofetil (MMF), and CP-690,550 (CP) treatment reduced the elementary histological lesions of lupus nephritis (LN). b Representative photomicrograph of renal histology for each group (×200 original magnification, hematoxylin and eosin stain). Data are expressed as mean ± SEM. ^a p < 0.05 vs control

Fig. 4

Immunofluorescence analysis of renal immunoglobulin G (IgG) and complement component 3 (C3) deposits. Deposits of renal C3 (a) and IgG (b) were quantified with confocal microscopy, and the results were expressed as mean fluorescence intensity (MFI). All treatments reduced glomerular deposits. c Representative photomicrographs of C3 deposits (×630 original magnification) for each group. d Representative photomicrographs of IgG deposits (×630 original magnification) for each group. Data are expressed as mean ± SEM. *p < 0.05 vs control. CP CP-690,550; CYP cyclophosphamide; MMF mycophenolate mofetil

Fig. 5

Macrophages and T-cell kidney infiltrate. a Kidney macrophages and b T-cell infiltration were quantified. All treatment clearly reduced renal infiltration. Representative photomicrographs (×200 original magnification) of (c) macrophage and (d) T-cell infiltration for each group. Data are expressed as mean ± SEM. ^a p < 0.05 vs control. CP CP-690,550; CYP cyclophosphamide; MMF mycophenolate mofetil

Fig. 6

Systemic circulating inflammatory cytokines. Lupus nephritis promoted overexpression of proinflammatory cytokines in serum. Treatment with cyclophosphamide (CYP), mycophenolate mofetil (MMF), and CP-690,550 (CP) reduced their levels. Data are expressed as mean ± SEM. *p < 0.05 vs control. IFN interferon, IL interleukin, MCP monocyte chemoattractant protein, TNF tumor necrosis factor