Chloroquine may induce endothelial injury through lysosomal dysfunction and oxidative stress.

COVID-19 is a pandemic with no end in sight. There is only one approved antiviral agent but global stocks are deemed insufficient. Despite in vitro antiviral activity, clinical trials of chloroquine and hydroxychloroquine were disappointing, and they may even impair outcomes. Chloroquine causes zebroid deposits reminiscent of Fabry disease (α-galactosidase A deficiency) and endothelial cells are key targets of COVID-19. We have explored the effect of chloroquine on cultured endothelial cells and its modulation by recombinant α-galactosidase A (agalsidase). Following dose-response studies, 0.5 µg/mL chloroquine was added to cultured human endothelial cells. Neutral red and Lysotracker were used to assess lysosomes. Cytotoxicity was evaluated by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) - MTT assay and cell stress by assessing reactive oxygen species (ROS) and nitric oxide (NO). In endothelial cells, chloroquine induced dose-dependent cytotoxicity at in vitro test concentrations for COVID-19 therapy. At a sublethal concentration, chloroquine significantly induced the accumulation of acid organelles (P < 0.05), increased ROS levels, and decreased NO production (P < 0.05). These adverse effects of chloroquine on endothelial cell biology were decreased by agalsidase-ß (P < 0.05). Chloroquine-induced endothelial cell cytotoxicity and stress is attenuated by agalsidase-ß treatment. This suggests that endothelial cell injury may contribute to the failure of chloroquine as therapy for COVID-19 and may be at least in part related to causing dysfunction of the lysosomal enzyme α-galactosidase A.

Reduced alpha-Gal A enzyme activity in Fabry fibroblast cells and Fabry mice tissues induced by serum from antibody positive patients with Fabry disease.

Fabry disease is a progressive, life-threatening lysosomal storage disorder which is characterized by deficient activity of the lysosomal enzyme alpha-galactosidase A. Studies have demonstrated that both enzyme preparations currently available for treatment of Fabry disease (i.e., agalsidase beta and agalsidase alpha) elicit immune responses in the majority of patients which negatively influences the reduction of urinary globotriaosylceramide concentration. In the current study, agalsidase beta antibodies were found to be associated with inhibition of alpha-Gal A enzyme activity in cultured Fabry fibroblast and tissues from Fabry mice. However, the negative effect of antibody formation could be overcome by increasing the dose of enzyme administered to mice. In conclusion, antibody titers and the dose of enzyme influenced alpha-Gal A enzyme activities in vivo. Further studies are required to investigate to what extend antibody formation impacts on therapeutic responses in antibody positive Fabry patients receiving enzyme replacement therapy and if negative effects can be overcome by adjusting the dose of enzyme.