High Expression of Galectin-3 in Patients with IgG4-Related Disease: A Proteomic Approach

Abstract

Objectives Immunoglobulin G4-related disease (IgG4-RD) is a multiorgan condition manifesting itself in different forms. This study aimed to investigate protein expression profiles and to find the possible biomarker for IgG4-RD by liquid chromatography mass spectrometry (LC-MS) using tissue sections in IgG4-RD patients. Methods Protein expression profiles in five IgG4-related pancreatitis and three normal pancreatic samples were compared using LC-MS and were validated by quantitative real-time PCR (qRT-PCR), immunoblotting, and immunohistochemistry. ELISA was employed in the serum of 20 patients with systemic IgG4-RD before and during steroid treatment. Results LC-MS indicated that the levels of 17 proteins were significantly higher and 12 others were significantly lower in IgG4-related pancreatitis patients compared to controls. Among these proteins, galectin-3 levels were 13-fold higher in IgG4-related pancreatitis (P < 0.01). These results were confirmed by immunoblotting and qRT-PCR. The average number of galectin-3 + cells in various organs of IgG4-RD patients, including salivary glands, lungs, and lymph nodes, was higher than in controls. Galectin-3 was detectable in macrophages, dendritic cells, and stromal myofibroblast-like cells, but not in lymphocytes by immunofluorescence staining. Serum galectin-3 levels were higher in patients with IgG4-RD compared with healthy donors and remained high during steroid therapy. Conclusion Galectin-3 was overexpressed in IgG4-RD and the levels were indirectly related to clinical activity.

Identification of galectin-3 as an autoantigen in patients with IgG4-related disease

“…This work further characterized galectin-3 expression in many affected tissues in patients with IgG 4 -RD, including the lymph nodes, lung, salivary gland, pancreas, kidney, aorta, retroperitoneum, and bile ducts. 25 Interestingly, diseased lymph nodes were found to have the greatest number of galectin-3-positive cells per high-power field compared with all other organs studied, and this was also approximately 8-fold greater than the number of positive cells observed in normal lymph nodes. These data, in conjunction with our observations that IgG 4 anti-galectin-3 autoantibodies correlate with both increased plasma levels of galectin-3 and lymph node involvement, support the notion that protein overexpression can sometimes contribute to autoantibody formation.…”

“…26 Proteomic analysis of pancreatic tissue from patients with IgG 4 -RD revealed that tissue galectin-3 was among the proteins with the highest level of differential expression, with a 13-fold higher level in diseased compared with healthy pancreata. 25 Immunofluorescence-based analyses of tissues from patients with IgG 4 -RD demonstrated that a diverse collection of both stromal and immune cells express galectin-3, including macrophages, dendritic cells, and myofibroblasts. 25 In addition, interstitial staining for galectin-3 is consistent with the fact that this protein has both secreted and intracellular forms.…”

“…25 Immunofluorescence-based analyses of tissues from patients with IgG 4 -RD demonstrated that a diverse collection of both stromal and immune cells express galectin-3, including macrophages, dendritic cells, and myofibroblasts. 25 In addition, interstitial staining for galectin-3 is consistent with the fact that this protein has both secreted and intracellular forms. This work further characterized galectin-3 expression in many affected tissues in patients with IgG 4 -RD, including the lymph nodes, lung, salivary gland, pancreas, kidney, aorta, retroperitoneum, and bile ducts.…”

“…24 Recently, by using an unbiased quantitative proteomic approach, pancreata of patients with IgG 4 -RD were compared with those of control subjects. 25 Galectin-3 was observed as one of the highest differentially expressed proteins in pancreata of patients with IgG 4 -RD, which is present at a 13-fold higher amount compared with control subjects. 25 To support this idea, we quantified circulating galectin-3 levels in a subset of the IgG 4 -RD cohort compared with control subjects.…”

“…25 Galectin-3 was observed as one of the highest differentially expressed proteins in pancreata of patients with IgG 4 -RD, which is present at a 13-fold higher amount compared with control subjects. 25 To support this idea, we quantified circulating galectin-3 levels in a subset of the IgG 4 -RD cohort compared with control subjects. Using a cutoff value of 10.25 ng/mL based on systemic sclerosis literature, in which this cutoff value was an independent predictor of all-cause mortality, 26 we found that 15.5% of subjects in the IgG 4 -RD cohort had increased plasma galectin-3 levels (Fig 7, A) in contrast to systemic sclerosis, in which 41% of patients have circulating levels greater than this value.…”