Amlexanox enhances premature termination codon read-through in COL7A1 and expression of full length type VII collagen: potential therapy for recessive dystrophic epidermolysis bullosa

摘要

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare monogenic blistering disorder caused by lack of functional type VII collagen, leading to skin fragility and subsequent trauma-induced separation of the epidermis from the underlying dermis. 46% of RDEB patients harbor at least one premature termination codon (PTC) mutation in COL7A1 and previous studies have shown that aminoglycosides are able to overcome RDEB PTC mutations by inducing “read-through” and incorporation of an amino acid at the PTC site. However, aminoglycoside toxicity will likely prevent widespread clinical application. Here the FDA-approved drug amlexanox was tested for its ability to read-through PTC mutations in RDEB patient derived cells. Eight of 12 different PTC alleles responded to treatment and produced full length protein, in some cases over 50% relative to normal controls. Read-through type VII collagen was readily detectable in cell culture media and also localized to the dermal-epidermal junction in organotypic skin culture. Amlexanox increased COL7A1 transcript and the phosphorylation of UPF-1, an RNA helicase associated with nonsense mediated mRNA decay (NMD), suggesting that amlexanox inhibits NMD in RDEB patient cells that read-through. This pre-clinical study demonstrates the potential of re-purposing amlexanox for treatment of RDEB patients harboring PTC mutation in COL7A1.