PROJECT SUMMARY
Idiopathic pulmonary fibrosis (IPF) is a devastating, progressive aging-associated disease characterized by
scarred lung tissue containing excessive extracellular matrix (ECM). Changes in the oxidative (redox)
environment have long been known to accompany IPF, yet the mechanisms whereby redox perturbations affect
IPF pathogenesis remain incompletely understood. Our laboratory has discovered that a specific type of protein
oxidation, termed protein glutathionylation, is increased in the lungs of IPF patients and inversely correlates with
lung function. Importantly, the activity of glutaredoxin (GLRX), an enzyme that reverses protein glutathionylation,
was strongly decreased in IPF patient lungs. New studies from our laboratory showed that collagen 1A1 (COL1),
a major component of the fibrotic ECM, is a target for glutathionylation (COL1-SSG) that is increased in IPF.
Glutathionylation of COL1-SSG in the C-terminal pro-domain caused partial resistance to degradation by multiple
collagenases. We also discovered that COL1-SSG is a potent activator of fibroblasts and causes oxidative
signals that promote further glutathionylation. Collagens are the most abundant proteins produced in the ER and
are challenging to properly assemble and process, requiring oxidative processes. Collagen has its own
autophagy system consisting of calnexin (CANX) and FAM134B to remove aberrantly processed collagen via
ER-linked autophagy. Autophagy is decreased in aging, and both CANX and FAM134B are decreased in lungs
from IPF patients. These collective observations led us to hypothesize that in the aging lung, increases in ER
oxidation and diminished collagen autophagy result in the secretion of COL1-SSG to promote the progression
of pulmonary fibrosis by the activation myofibroblasts via a self-propagating stimulus that can be diminished by
GLRX. In Specific Aim 1 we will address whether the activity of protein disulfide isomerase A3 which is important
in the oxidative folding of COL1, and attendant increases in ER oxidoreductin 1-derived hydrogen peroxide
contribute to COL1-SSG and the increases in age-associated persistent fibrosis. In Specific Aim 2 we will
examine whether COL1-SSG is secreted by fibroblasts from fibrotic lung and whether this is linked to alterations
in ER redox stress and collagen autophagy. In Specific Aim 3 we will elucidate whether GLRX status affects
COL1-SSG, myofibroblast activation and age-associated lung fibrosis. Completion of these proposed studies
that utilize a combination of targeted knockout models in aged mice and isolated (myo)fibroblasts from patients
with IPF will provide novel insights into the mechanisms by which ECM dysregulation via oxidation (specifically
glutathionylation) affects COL1 stiffness and promotes the progression of pulmonary fibrosis. Completion of the
workplan will begin to unravel the potential role of aberrant collagen autophagy in IPF. Finally, completion of the
proposed studies will also further elucidate the mechanisms of action whereby GLRX exerts anti-fibrotic activity
and identify the potential improved anti-fibrotic action of a newly created oxidation-resistant version of GLRX.