Differences in clinical features of immunoglobulin G4-related disease between older and younger patients

The Contribution of the Interleukin-4-Induced Epithelial Cell Senescence to Glandular Fibrosis in IgG4-Related Sialadenitis

OBJECTIVE

Immunoglobulin G4-related sialadenitis (IgG4-RS) is a chronic fibro-inflammatory disease characterized by glandular fibrosis and hyposalivation. Here we aimed to explore the role of cellular senescence in the pathogenesis of IgG4-RS-related fibrosis.

METHODS

The expression of senescence markers and proinflammatory cytokines in the submandibular glands (SMGs) of IgG4-RS patients (n = 18) and controls (n = 14) was determined by proteomics, real-time polymerase chain reaction (PCR), western blot, and immunohistochemistry. After interleukin-4 (IL-4) treatment, high-throughput RNA-sequencing was performed to identify the differentially expressed genes in SMG-C6 cells. A glandular fibrosis model was established by the intraglandular injection of IL-4 into mouse SMGs (n = 8 per group).

RESULTS

Salivary acinar and ductal epithelial cells underwent senescence in IgG4-RS patients, as indicated by the elevated activity of senescence-associated β-galactosidase, lipofuscin accumulation, enhanced expression of senescence markers (p53 and p16^INK4A ), and upregulation of senescence-associated secretory phenotype factors. Moreover, there was a significant increase in IL-4 levels in SMGs of IgG4-RS patients, which positively correlated with p16^INK4A expression and the fibrosis score. Incubation with IL-4 exacerbated salivary epithelial cell senescence by increasing the expression of p16^INK4A through ROS-p38 mitogen-activated protein kinase (MAPK) pathway. The supernatant collected from IL-4-induced senescent SMG-C6 cells enhanced fibroblast activation and matrix protein production. Furthermore, injecting IL-4 promoted fibrosis and senescence phenotypes in the SMGs in vivo.

CONCLUSION

The cellular senescence induced by IL-4 through the ROS-p38 MAPK-p16^INK4A pathway promoted fibrogenesis during IgG4-RS. Our data suggest that cellular senescence could serve as a novel therapeutic target for treating IgG4-RS.

Differences in clinical characteristics of IgG4-related disease across age groups: a prospective study of 737 patients

OBJECTIVE

The aim of this study was to compare the clinical characteristics of IgG4-related disease (IgG4-RD) among different age groups.

METHODS

We conducted a prospective study of 737 patients who were newly diagnosed with IgG4-RD and compared detailed demographic features, organ involvements, laboratory tests, treatments and outcomes across age groups. The patients were divided into five groups according to their age at diagnosis: ≤39, 40-49, 50-59, 60-69 and ≥70 years. The clinical characteristics of paediatric patients were also described.

RESULTS

Sex ratio, disease duration, allergy history and clinical symptoms were significantly different across age groups. Besides, the proportions of superficial organ involvement (lacrimal gland and sinus) decreased with age, while the proportions of internal organ involvement (pancreas, biliary tract, retroperitoneal tissue, lung and prostate) increased with age, which was more prominent in male patients. Mikulicz's disease was the most common manifestation (70%) in paediatric IgG4-RD patients. Multiple Cox analysis identified that age ≤56 years at diagnosis was an independent risk factor of relapse.

CONCLUSION

We revealed the impact of age on clinical characteristics of IgG4-RD, which indicated that different management might be required among different age groups.