Effect of genistein and coenzyme Q10 in oxidative damage and mitochondrial membrane potential in an attenuated type II mucopolysaccharidosis cellular model

Mucopolysaccharidosis type II (MPS II) is an inborn error of the metabolism resulting from several possible mutations in the gene coding for iduronate-2-sulfatase (IDS), which leads to a great clinical heterogeneity presented by these patients. Many studies demonstrate the involvement of oxidative stress in the pathogenesis of inborn errors of metabolism, and mitochondrial dysfunction and oxidative stress can be related since most of reactive oxygen species come from mitochondria. Cellular models have been used to study different diseases and are useful in biochemical research to investigate them in a new promising way. The aim of this study is to develop a heterozygous cellular model for MPS II and analyze parameters of oxidative stress and mitochondrial dysfunction and investigate the in vitro effect of genistein and coenzyme Q10 on these parameters for a better understanding of the pathophysiology of this disease. The HP18 cells (heterozygous c.261_266del6/c.259_261del3) showed almost null results in the activity of the IDS enzyme and presented accumulation of glycosaminoglycans (GAGs), allowing the characterization of this knockout cellular model by MPS II gene editing. An increase in the production of reactive species was demonstrated (p < .05 compared with WT vehicle group) and genistein at concentrations of 25 and 50 µm decreased in vitro its production (p < .05 compared with HP18 vehicle group), but there was no effect of coenzyme Q10 in this parameter. There was a tendency for lysosomal pH change in HP18 cells in comparison to WT group and none of the antioxidants tested demonstrated any effect on this parameter. There was no increase in the activity of the antioxidant enzymes superoxide dismutase and catalase and oxidative damage to DNA in HP18 cells in comparison to WT group and neither genistein nor coenzyme q10 had any effect on these parameters. Regarding mitochondrial membrane potential, genistein induced mitochondrial depolarization in both concentrations tested (p < .05 compared with HP18 vehicle group and compared with WT vehicle group) and incubation with coenzyme Q10 demonstrated no effect on this parameter. In conclusion, it is hypothesized that our cellular model could be compared with a milder MPS II phenotype, given that the accumulation of GAGs in lysosomes is not as expressive as another cellular model for MPS II presented in the literature. Therefore, it is reasonable to expect that there is no mitochondrial depolarization and no DNA damage, since there is less lysosomal impairment, as well as less redox imbalance.

Clearance of heparan sulfate in the brain prevents neurodegeneration and neurocognitive impairment in MPS II mice

Mucopolysaccharidosis II (MPS II), a lysosomal storage disease caused by mutations in iduronate-2-sulfatase (IDS), is characterized by a wide variety of somatic and neurologic symptoms. The currently approved intravenous enzyme replacement therapy with recombinant IDS (idursulfase) is ineffective for CNS manifestations due to its inability to cross the blood-brain barrier (BBB). Here, we demonstrate that the clearance of heparan sulfate (HS) deposited in the brain by a BBB-penetrable antibody-enzyme fusion protein prevents neurodegeneration and neurocognitive dysfunctions in MPS II mice. The fusion protein pabinafusp alfa was chronically administered intravenously to MPS II mice. The drug reduced HS and attenuated histopathological changes in the brain, as well as in peripheral tissues. The loss of spatial learning abilities was completely suppressed by pabinafusp alfa, but not by idursulfase, indicating an association between HS deposition in the brain, neurodegeneration, and CNS manifestations in these mice. Furthermore, HS concentrations in the brain and reduction thereof by pabinafusp alpha correlated with those in the cerebrospinal fluid (CSF). Thus, repeated intravenous administration of pabinafusp alfa to MPS II mice decreased HS deposition in the brain, leading to prevention of neurodegeneration and maintenance of neurocognitive function, which may be predicted from HS concentrations in CSF.

Characterization of Fluid Biomarkers Reveals Lysosome Dysfunction and Neurodegeneration in Neuronopathic MPS II Patients

Mucopolysaccharidosis type II is a lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS) and characterized by the accumulation of the primary storage substrate, glycosaminoglycans (GAGs). Understanding central nervous system (CNS) pathophysiology in neuronopathic MPS II (nMPS II) has been hindered by the lack of CNS biomarkers. Characterization of fluid biomarkers has been largely focused on evaluating GAGs in cerebrospinal fluid (CSF) and the periphery; however, GAG levels alone do not accurately reflect the broad cellular dysfunction in the brains of MPS II patients. We utilized a preclinical mouse model of MPS II, treated with a brain penetrant form of IDS (ETV:IDS) to establish the relationship between markers of primary storage and downstream pathway biomarkers in the brain and CSF. We extended the characterization of pathway and neurodegeneration biomarkers to nMPS II patient samples. In addition to the accumulation of CSF GAGs, nMPS II patients show elevated levels of lysosomal lipids, neurofilament light chain, and other biomarkers of neuronal damage and degeneration. Furthermore, we find that these biomarkers of downstream pathology are tightly correlated with heparan sulfate. Exploration of the responsiveness of not only CSF GAGs but also pathway and disease-relevant biomarkers during drug development will be crucial for monitoring disease progression, and the development of effective therapies for nMPS II.

The efficacy of intracerebroventricular idursulfase-beta enzyme replacement therapy in mucopolysaccharidosis II murine model: heparan sulfate in cerebrospinal fluid as a clinical biomarker of neuropathology

Mucopolysaccharidosis II (MPS II) is caused by a deficiency of iduronate-2-sulfatase that results in accumulation of glycosaminoglycans (GAG), including heparan sulfate (HS), which is considered to contribute to neuropathology. We examined the efficacy of intracerebroventricular (ICV) enzyme replacement therapy (ERT) of idursulfase-beta (IDS-β) and evaluated the usefulness of HS as a biomarker for neuropathology in MPS II mice. We first examined the efficacy of three different doses (3, 10, and 30 μg) of single ICV injections of IDS-β in MPS II mice. After the single-injection study, its long-term efficacy was elucidated with 30 μg of IDS-β ICV injections repeated every 4 weeks for 24 weeks. The efficacy was assessed by the HS content in the cerebrospinal fluid (CSF) and the brain of the animals along with histologic examinations and behavioral tests. In the single-injection study, the 30 μg of IDS-β ICV injection showed significant reductions of HS content in brain and CSF that were maintained for 28 days. Furthermore, HS content in CSF was significantly correlated with HS content in brain. In the long-term repeated-injection study, the HS content in the brain and CSF was also significantly reduced and correlated. The histologic examinations showed a reduction in lysosomal storage. A significant improvement in memory/learning function was observed in open-field and fear-conditioning tests. ICV ERT with 30 μg of IDS-β produced significant improvements in biochemical, histological, and functional parameters in MPS II mice. Furthermore, we demonstrate for the first time that the HS in the CSF had significant positive correlation with brain tissue HS and GAG levels, suggesting HS in CSF as a useful clinical biomarker for neuropathology.

Effects of idursulfase enzyme replacement therapy for Mucopolysaccharidosis type II when started in early infancy: comparison in two siblings

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder that is progressive and involves multiple organs and tissues. While enzyme replacement therapy (ERT) with idursulfase has been shown to improve many somatic features of the disease, some such as dysostosis multiplex and cardiac valve disease appear irreversible once established, and little is known about the preventative effects of ERT in pre-symptomatic patients. We report on two siblings with severe MPS II caused by an inversion mutation with recombination breakpoints located within the IDS gene and its adjacent pseudogene, IDS-2. The siblings initiated treatment with idursulfase at 3.0 years (older brother) and 4 months (younger brother) of age, and we compared their outcomes following 2 years of treatment. At the start of treatment, the older brother showed typical features of MPS II, including intellectual disability. After 34 months of ERT, his somatic disease was stable or improved, but he continued to decline cognitively. By comparison, after 32 months of ERT his younger brother remained free from most of the somatic features that had already appeared in his brother at the same age, manifesting only exudative otitis media. Skeletal X-rays revealed characteristic signs of dysostosis multiplex in the older brother at the initiation of treatment that were unchanged two years later, whereas the younger brother showed only slight findings of dysostosis multiplex throughout the treatment period. The younger brother's developmental quotient trended downward over time to just below the normal range. These findings suggest that pre-symptomatic initiation of ERT may prevent or attenuate progression of the somatic features of MPS II. Follow-up in a larger number of patients is required to confirm the additive long-term benefits of ERT in pre-symptomatic patients.

Effects of enzyme replacement therapy on growth in patients with mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked, recessive, lysosomal storage disorder caused by deficiency of iduronate-2-sulfatase. It has multisystemic involvement, with manifestations in the brain, upper respiratory tract, heart, abdomen, joints and bones. Bone involvement leads to decreased growth velocity and short stature in nearly all patients. A therapeutic option for patients with MPS II is enzyme replacement therapy (ERT) with idursulfase (Elaprase®). We compared annual growth rates before and during ERT in 18 patients from Mainz, Germany, and Manchester, UK. Group 1 included nine patients who started ERT before 10 years of age; group 2 contained nine patients aged more than 10 years at the start of ERT. All patients had received weekly or biweekly ERT or placebo for 1 year, followed by ERT for more than 3 years. For patients in group 1, the mean (± SD) height increase was 14.6 ± 5.5 cm during 3 years of ERT. Only one patient in this group (who was below the 3rd percentile when starting ERT) deviated from the normal growth curve over this time. Patients in group 2 had a mean height increase of 8.1 ± 1.7 cm after 3 years of ERT compared with an increase of 1 cm in the year before ERT. ERT seems to have a positive influence on growth in patients with MPS II. Most benefit is seen in patients beginning ERT before the age of 10 years. This supports the recommendation that ERT should be started as early as possible in patients with MPS II.