Alterations of Plasmatic Biomarkers of Neurodegeneration in Mucopolysaccharidosis Type II Patients Under Enzyme Replacement Therapy

Mucopolysaccharidosis type II (MPS II) is a disorder caused by a deficient activity of iduronate-2-sulfatase, a lysosomal enzyme responsible for degrading glycosaminoglycans (GAGs). The abnormal storage of GAGs within lysosomes disrupts cellular homeostasis and leads to a severe symptomatology. Patients present neuropsychiatric impairment characterized by mental retardation and impaired cognition. The aim of this study was to quantify four neurodegeneration biomarkers in plasma: brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF-AA), neural cell adhesion molecule (NCAM) and cathepsin-D, as well as to identify possible correlations with urinary GAGs in seven patients undergoing treatment with ERT (Elaprase® 0.5 mg/kg of body weight). Patients with both severe and attenuated forms of MPS II showed signs of neurodegeneration in neuroimaging exams. Patients have a decrease in BDNF and PDGF-AA concentrations, and an increase in NCAM level compared to controls. No alterations in cathepsin-D concentration were seen. GAGs levels were higher in patients than in controls, but no significant correlations between GAGs and biomarkers were observed. These results evidence that patients have neurodegeneration and that monitoring these biomarkers might be useful for assessing this process. To this date, this is the first work to analyze these plasmatic markers of neurodegeneration in patients.

Increased cytokine levels induced by high phenylalanine concentrations in late diagnosis PKU patients compared to early diagnosis: Anti-inflammatory effect of L-carnitine

Phenylketonuria (PKU) was the first genetic disease to have an effective therapy, which consists of phenylalanine intake restriction. However, there are patients who do not adhere to treatment and/or are not submitted to neonatal screening. PKU patients present L-carnitine (L-car) deficiency, compound that has demonstrated an antioxidant and anti-inflammatory role in metabolic diseases. This study evaluated the effect caused by exposure time to high Phe levels in PKU patients at early and late diagnosis, through pro- and anti-inflammatory cytokines, as well as the L-car effect in patients under treatment. It was observed that there was a decrease in phenylalanine levels in treated patients compared to patients at diagnosis, and an increase in L-car levels in the patients under treatment. Inverse correlation between Phe versus L-car and nitrate plus nitrite versus L-car in PKU patients was also showed. We found increased proinflammatory cytokines levels: interleukin (IL)-1β, interferons (IFN)-gamma, IL-2, tumor necrosis factor (TNF)-alpha, IL-8 and IL-6 in the patients at late diagnosis compared to controls, and IL-8 in the patients at early diagnosis and treatment compared to controls. Increased IL-2, TNF-alpha, IL-6 levels in the patients at late diagnosis compared to early diagnosis were shown, and reduced IL-6 levels in the treated patients compared to patients at late diagnosis. Moreover, it verified a negative correlation between IFN-gamma and L-car in treated patients. Otherwise, it was observed that there were increased IL-4 levels in the patients at late diagnosis compared to early diagnosis, and reduction in treated patients compared to late diagnosed patients. In urine, there was an increase in 8-isoprostane levels in the patients at diagnosis compared to controls and a decrease in oxidized guanine species in the treated patients compared to the diagnosed patients. Our results demonstrate for the first time in literature that time exposure to high Phe concentrations generates a proinflammatory status, especially in PKU patients with late diagnosis. A pro-oxidant status was verified in not treated PKU patients. Our results demonstrate the importance of early diagnosis and prompt start of treatment, in addition to the importance of L-car supplementation, which can improve cellular defense against inflammation and oxidative damage in PKU patients.

L-carnitine protects DNA oxidative damage induced by phenylalanine and its keto acid derivatives in neural cells: a possible pathomechanism and adjuvant therapy for brain injury in phenylketonuria

Although phenylalanine (Phe) is known to be neurotoxic in phenylketonuria (PKU), its exact pathogenetic mechanisms of brain damage are still poorly known. Furthermore, much less is known about the role of the Phe derivatives phenylacetic (PAA), phenyllactic (PLA) and phenylpyruvic (PPA) acids that also accumulate in this this disorder on PKU neuropathology. Previous in vitro and in vivo studies have shown that Phe elicits oxidative stress in brain of rodents and that this deleterious process also occurs in peripheral tissues of phenylketonuric patients. In the present study, we investigated whether Phe and its derivatives PAA, PLA and PPA separately or in combination could induce reactive oxygen species (ROS) formation and provoke DNA damage in C6 glial cells. We also tested the role of L-carnitine (L-car), which has been recently considered an antioxidant agent and easily cross the blood brain barrier on the alterations of C6 redox status provoked by Phe and its metabolites. We first observed that cell viability was not changed by Phe and its metabolites. Furthermore, Phe, PAA, PLA and PPA, at concentrations found in plasma of PKU patients, provoked marked DNA damage in the glial cells separately and when combined. Of note, these effects were totally prevented (Phe, PAA and PPA) or attenuated (PLA) by L-car pre-treatment. In addition, a potent ROS formation also induced by Phe and PAA, whereas only moderate increases of ROS were caused by PPA and PLA. Pre-treatment with L-car also prevented Phe- and PAA-induced ROS generation, but not that provoked by PLA and PPA. Thus, our data show that Phe and its major metabolites accumulated in PKU provoke extensive DNA damage in glial cells probably by ROS formation and that L-car may potentially represent an adjuvant therapeutic agent in PKU treatment.