Findings from an investigative study revealed that elevated oxidative stress levels in both mice and humans with Pompe disease impaired the ability of enzyme replacement therapy (ERT) using recombinant human acid alpha-glucosidase (rhGAA) to correct the causative enzyme deficiency. Correction of oxidative stress using antioxidants in addition to ERT in both mouse and human models improved GAA enzyme activity.
This study highlights the clinical relevance of therapeutically targeting secondary cellular abnormalities contributing to disease pathology. The authors stated that this study showed that “factors related to recipient tissues, in addition to the intrinsic properties of the recombinant enzyme, influence the response to enzyme replacement therapy.” Therefore, “manipulation of secondary abnormalities may represent a strategy to improve the efficacy of therapies for this disorder,” they added.
Investigators collected myoblast and fibroblast tissue samples from humans with Pompe disease from the Telethon BioBank, Milan, and the Department of Translational Medical Sciences, Naples, both in Italy.
They purchased a knock-out mouse model and prepared it using an insertion of neo into the GAA gene exon 6 to simulate PD in the mice. In vivo experimentation included ERT treatment of the mice, with half receiving the antioxidant idebenone (IDE) and half receiving the antioxidant N-acetylcysteine (NAC). Researchers also studied the effects of other antioxidants, including edaravone (EDA) and resveratrol (RESV).
The investigators performed in-depth molecular analyses on tissues from both mice and humans with PD, utilizing methods such as immunofluorescence analyses, electron microscopy, differential scanning fluorimetry, and fluorescence activated cell sorting analyses.
The researchers assayed GAA enzyme activity using the fluorogenic substrate, 4-methylumbelliferyl-alpha-D glucopyranoside, and performed western blot analyses of cellular extracts. The investigators analyzed oxidative stress levels using 2′,7′-dichloro-dihydrofluorescein (DCFDA), lipid peroxidation using the thiobarbituric acid-reactive substances (TBARS) assay, and intracellular glutathione activity levels using 5,5′-dithiobis-2-nitrobenzoic acid (DTNB).
The researchers measured glycogen concentrations within tissue lysosomes by calculating the amount of glucose released following digestion of these tissues with Aspergillus niger amyloglucosidase. The amounts of glycogen (broken down into glucose) stored within the tissues comparatively indicated the efficacy of ERT with and without antioxidant supplementation.
The authors suggested future research topics, including clarification on mechanisms by which antioxidants improve ERT and long-term preclinical trials determining the efficacy of combination treatment using ERT with antioxidants.
Tarallo A, Damiano C, Strollo S, et al. Correction of oxidative stress enhances enzyme replacement therapy in Pompe disease. EMBO Mol Med. Published online October 4, 2021. doi:10.15252/emmm.202114434