Title:L-Ala-L-Gln Suppresses Hypoxic Phenotype and Fibrogenic Activity of
Rat Perineurial Fibroblasts
Volume: 22
Issue: 5
Author(s): Nilabh Ghosh, Catherine Bregere, Pia Bustos and Raphael Guzman*
Affiliation:
- Department of Biomedicine, University Hospital Basel, Basel, Switzerland
- Department of Neurosurgery, University
Hospital Basel, Basel, Switzerland
Keywords:
Peripheral nerve fibrosis, peripheral nerve injury, hypoxia, HIF-1α, L-Ala-L-Gln, collagen, fibroblasts, extracellular matrix.
Abstract:
Background: Twenty million Americans suffer from peripheral nerve injury (PNI) and
approximately $150 billion is spent annually in the United States for the treatment of nerve injuries.
Moreover, 50,000 cases of PNI repairs are performed annually in the United States, with even less
than 42% experiencing satisfactory sensory recovery. Available therapies control painful symptoms
but do not treat axonal degeneration or neuronal cell death. Peripheral nerve fibrosis (PNF) associated
with chronic inflammation, perineural adhesions, and scarring is often reported in patients with
nerve injury. Unfortunately, post-surgical adhesions and fibrosis often lead to aberrated wound healing
and impairment of nerve functions. Various treatment strategies have been attempted, including
the use of grafts and biomaterials; however, few appear promising.
Objective: L-Alanyl-L-Glutamine (L-Ala-L-Gln) was reported to protect the lung from sepsisinduced
injury and play an immunomodulatory role in stress and fibrosis. This study aimed to examine
the potential anti-fibrotic effects of L-Ala-L-Gln in an in vitro model of neural fibrosis.
Methods: Primary fibroblasts isolated from rat sciatic nerve were exposed to chronic (48 h) and episodic
(2 h) hypoxic conditions. Cultures were then treated for 48 h with various concentrations of
L-Ala-L-Gln (0, 1, 10, and 100 mM). The expression of hypoxic and pro-fibrotic markers in the different
culture conditions was assessed by immunocytochemistry and western blot analyses. Quantitative
phosphor-proteomic profiling was performed to investigate mechanistically the impact of L-Ala-
L-Gln on collagen biosynthesis and hypoxia-driven tissue fibrosis in vitro.
Results: In protein expression assays, L-Ala-L-Gln significantly reduced markers related to the cellular
response to hypoxia, in particular HIF-1 signaling. L-Ala-L-Gln also significantly reduced the
expression of pro-fibrotic and cell-adhesion-inducing factors. Phospho-proteomic data indicated that
L-Ala-L-Gln modulates several pro-fibrotic factors and associated pathways.
Conclusion: Altogether, our data demonstrate that L-Ala-L-Gln efficiently suppresses hypoxiamediated
fibrotic processes at different concentrations in rat primary fibroblasts. Thus, L-Ala-L-Gln
presents a high potential therapeutic value as an antifibrotic pharmaceutical agent for the treatment
of neural fibrosis.
