DC-SIGN expression on podocytes and its role in inflammatory immune response of lupus nephritis

Abstract

Podocytes, the main target of immune complex, participate actively in the development of glomerular injury as immune cells. Dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) is an innate immune molecular that has an immune recognition function, and is involved in mediation of cell adhesion and immunoregulation. Here we explored the expression of DC-SIGN on podocytes and its role in immune and inflammatory responses in lupus nephritis (LN). Expression of DC-SIGN and immunoglobulin (Ig)G1 was observed in glomeruli of LN patients. DC-SIGN was co-expressed with nephrin on podocytes. Accompanied by increased proteinuria of LN mice, DC-SIGN and IgG1 expressions were observed in the glomeruli from 20 weeks, and the renal function deteriorated up to 24 weeks. Mice with anti-DC-SIGN antibody showed reduced proteinuria and remission of renal function. After the podocytes were stimulated by serum of LN mice in vitro, the expression of DC-SIGN, major histocompatibility complex (MHC) class II and CD80 was up-regulated, stimulation of T cell proliferation was enhanced and the interferon (IFN)-γ/interleukin (IL)-4 ratio increased. However, anti-DC-SIGN antibody treatment reversed these events. These results suggested that podocytes in LN can exert DC-like function through their expression of DC-SIGN, which may be involved in immune and inflammatory responses of renal tissues. However, blockage of DC-SIGN can inhibit immune functions of podocytes, which may have preventive and therapeutic effects.

Keywords: DC-SIGN; immunoregulation; lupus nephritis; podocytes.

Figure 1

Dendritic cell‐specific intercellular adhesion molecule‐3‐grabbing non‐integrin (DC‐SIGN) and IgG1 expression in renal tissues of different classes of lupus nephritis (LN) patients. (a) Immunohistochemistry of DC‐SIGN in renal tissues of LN patients (final magnification ×400). (b) Immunofluorescence of immunoglobulin (Ig)G1 in renal tissues of LN patients (final magnification ×200). (c) Double‐labelling with nephrin and DC‐SIGN in renal tissues of LN patients (final magnification ×400).

Figure 2

Pathology of renal tissues in mice. Periodic acid‐Schiff (PAS) staining of renal tissues and corresponding quantification (final magnification ×400). Renal tissues of Murphy Roths Large/lymphoproliferation (MRL/lpr) mice in the experimental group were harvested at 16, 20, 24 and 28 weeks of age. Renal tissues of mice in intervention group were harvested at 28 weeks.

Figure 3

Dendritic cell‐specific intercellular adhesion molecule‐3‐grabbing non‐integrin (DC‐SIGN) expression in mice renal tissues. (a) Immunohistochemistry of DC‐SIGN in mice and corresponding quantification (final magnification ×400). Renal tissues of Murphy Roths Large/lymphoproliferation (MRL/lpr) mice in experimental group were harvested at 16, 20, 24, and 28 weeks of age. Renal tissues of mice in intervention group were harvested at 28 weeks. (b) Integrated optical density (IOD) analysis of DC‐SIGN expression in renal tissues. *P < 0·05.

Figure 4

Immunoglobulin (Ig)G1 expression in mouse renal tissues. (a) Immunohistochemistry of IgG1 in mice and corresponding quantification (final magnification ×400). Renal tissues of Murphy Roths Large/lymphoproliferation (MRL/lpr) mice in experimental group were harvested at 16, 20, 24 and 28 weeks of age. Renal tissues of mice in intervention group were harvested at 28 weeks. (b) Integrated optical density (IOD) analysis of IgG1 expression in renal tissues. **P < 0·01.

Figure 5

Dendritic cell‐specific intercellular adhesion molecule‐3‐grabbing non‐integrin (DC‐SIGN), major histocompatibility complex (MHC) class II and CD80 expression on mouse podocytes. (a) Mouse podocytes were harvested after serum stimulation for 24 and 48 h. DC‐SIGN, MHC class II and CD80 expression of podocytes were detected by flow cytometry. (b) DC‐SIGN expression of mouse podocytes was detected by Western blotting. **P < 0·01.

Figure 6

Immunological function of mouse podocytes after stimulation with serum of Murphy Roths Large/lymphoproliferation (MRL/lpr) mice. (a) Ability of podocytes to stimulate T cell proliferation. (b) Ability of podocytes to stimulate T cells secreting T helper type 1 (Th1) and Th2 cytokines. Interferon (IFN)‐γ and interleukin (IL)‐4 expression in supernatant of co‐culture of podocytes and T cells were detected by enzyme‐linked immunosorbent assay (ELISA). **P < 0·01.