Human lung fibroblast-to-myofibroblast transformation is not driven by an LDH5-dependent metabolic shift towards aerobic glycolysis

Eva Schruf,
Victoria Schroeder,
Christian A. Kuttruff,
Sabine Weigle,
Martin Krell,
Maryke Benz,
Tom Bretschneider,
Alexander Holweg,
Michael Schuler,
Manfred Frick,
Paul Nicklin,
James P. Garnett†Email author View ORCID ID profile and
Mirko C. Sobotta†Email author

†Contributed equally

Respiratory Research201920:87

https://doi.org/10.1186/s12931-019-1058-2

Received: 4 February 2019
Accepted: 24 April 2019
Published: 9 May 2019

Abstract

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal respiratory disease characterized by aberrant fibroblast activation and progressive fibrotic remodelling of the lungs. Though the exact pathophysiological mechanisms of IPF remain unknown, TGF-β1 is thought to act as a main driver of the disease by mediating fibroblast-to-myofibroblast transformation (FMT). Recent reports have indicated that a metabolic shift towards aerobic glycolysis takes place during FMT and that metabolic shifts can directly influence aberrant cell function. This has led to the hypothesis that inhibition of lactate dehydrogenase 5 (LDH5), an enzyme responsible for converting pyruvate into lactate, could constitute a therapeutic concept for IPF.

Methods

In this study, we investigated the potential link between aerobic glycolysis and FMT using a potent LDH5 inhibitor (Compound 408, Genentech). Seahorse analysis was performed to determine the effect of Compound 408 on TGF-β1-driven glycolysis in WI-38 fibroblasts. TGF-β1-mediated FMT was measured by quantifying α-smooth muscle actin (α-SMA) and fibronectin in primary human lung fibroblasts following treatment with Compound 408. Lactate and pyruvate levels in the cell culture supernatant were assessed by LC-MS/MS. In addition to pharmacological LDH5 inhibition, the effect of siRNA-mediated knockdown of LDHA and LDHB on FMT was examined.

Results

We show that treatment of lung fibroblasts with Compound 408 efficiently inhibits LDH5 and attenuates the TGF-β1-mediated metabolic shift towards aerobic glycolysis. Additionally, we demonstrate that LDH5 inhibition has no significant effect on TGF-β1-mediated FMT in primary human lung fibroblasts by analysing α-SMA fibre formation and fibronectin expression.

Conclusions

Our data strongly suggest that while LDH5 inhibition can prevent metabolic shifts in fibroblasts, it has no influence on FMT and therefore glycolytic dysregulation is unlikely to be the sole driver of FMT.