Collagen Oxidation, Myofibroblast Activation and Age-Associated Pulmonary Fibrosis

PROJECT SUMMARY Idiopathic pulmonary fibrosis (IPF) is a devastating, progressive 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.