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The relationship between complement C3 expression and the MUC5B genotype in pulmonary fibrosis

Tsukasa Okamoto1, Susan K Mathai1, Corinne E Hennessy1

  • 1Department of Medicine, University of Colorado , Aurora, Colorado.

American Journal of Physiology. Lung Cellular and Molecular Physiology
|March 23, 2018
PubMed

Insights

The MUC5B promoter variant, a key risk factor for idiopathic pulmonary fibrosis (IPF), is linked to increased complement component 3 (C3) expression. C3-deficient mice showed protection against lung injury, suggesting complement

Area of Science:

  • Pulmonology and Immunology
  • Genetic Epidemiology
  • Host Defense Mechanisms

Background:

  • The MUC5B promoter variant (rs35705950) is the leading genetic risk factor for idiopathic pulmonary fibrosis (IPF).
  • The roles of MUC5B and the complement system in lung host defense are established, but their interplay in IPF remains unclear.
  • Previous research suggests a controversial role for the complement system in IPF pathogenesis.

Purpose of the Study:

  • To investigate the association between complement component 3 (C3) and MUC5B in patients with IPF.
  • To evaluate the relationship between C3 and MUC5B in a mouse model of bleomycin-induced lung injury.
  • To explore the potential contribution of the complement system to IPF development.

Main Methods:

  • Quantified C3 gene expression in whole lung tissue from 300 IPF patients and 175 healthy controls.
  • Analyzed C3 expression in relation to IPF MUC5B promoter genotypes (TT, GT, GG) and microscopic honeycombing.
  • Assessed lung injury and Muc5b expression in C3-deficient and wild-type mice following bleomycin exposure.

Main Results:

  • C3 expression was significantly elevated in IPF lungs compared to controls (1.40-fold increase, P < 0.0001).
  • IPF patients with the highest-risk MUC5B genotype (TT) exhibited greater C3 expression compared to other genotypes (1.59-1.66-fold increase, P < 0.05).
  • C3 expression was higher in IPF lungs without honeycombing than in those with honeycombing (1.40-fold increase, P < 0.01).
  • Bleomycin increased Muc5b in mice, but C3-deficient mice displayed reduced bleomycin-induced lung injury.

Conclusions:

  • The common MUC5B promoter variant is associated with increased C3 expression in IPF.
  • The complement system, specifically C3, may play a role in the pathogenesis of IPF.
  • Targeting the complement system could be a potential therapeutic strategy for IPF.
Keywords:
MUC5Bcomplement component 3host defenseidiopathic pulmonary fibrosis

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