**5. Expression of GBA and other lysosomal enzyme in animal models of Parkinson's disease**

The majority of sporadic PD cases result from interaction between genes and environment but the age remains the greatest risk factor. The first evidence of a genetic involvement in PD manifestations was the identification of three missense mutations on the α-synuclein gene, SNCA. These mutations (A30P, E46K, A53T) segregate with the disease in unrelated families and caused PD with high penetrance (Polymeropoulos et al., 1997; Kruger et al., 1998; Zarranz et al., 2004). Afterward duplication and triplication of the SNCA gene has been shown to cause PD, suggesting that high level expression of α-synuclein may also be pathogenic (Singleton et al., 2003; Ibanez et al., 2004). The degree of overexpression was found to correlate with the degree of severity of the pathology. The effects of point mutation and duplication-triplication of SNCA gene have been investigated using transgenic technology and viral infection and different mouse models were created. All PD animal models are based on the concept that parkinsonian signs are linked to dopaminergic nigral cell loss and even if they show many of the symptoms of the disease they don't display all the complexity of the neurological pathology. A lot of mouse line expressing wild-type or

Role of Lysosomal Enzymes in Parkinson's Disease: Lesson from Gaucher's Disease 471

and cortico-striatal. The chemical model show a profound involvement of the brain's areas and this is, probably, a consequence of the 6-hydroxydopamine treatment, infact the neurotoxins destroied selectively and rapidly catecholaminergic neurons whereas the PD pathogenensis in human and in the mouse model follows a progressive course over decades. The results obtained in this rat model might explain the reduction on alpha-mannosidase, beta-glucosidase, and beta-mannosidse activities observed in the CSF od PD patients

**6. CSF lysosomal enzyme activities as possible marker of synucleinopathies**  Recently it became evident that accumulation of unwanted and misfolded protein play a central role in the PD pathogenesis. An involvement of the lysosomal system has been postulated. Lysosomal activity decreased over the lifespan and a lysosomal malfunction has been linked with cronic neurodegenerative disorders (Terman, 2006; Pan et al., 2008). This assumption has been confirmed by the selective inhibition of lysosomal enzyme in different cellular models that leads to protein aggregation, synaptic loss and neuronal death (Felbor et al., 2002; Bendiske & Bahr, 2003). Furthermore, in experimental system, has been noted that α-synuclein aggregation leads to inhibition of lysosomal functions, triggering a vicious cycle (Bennett et al., 2005; Cuervo et al., 2004). On the basis of these evidences was performed a comparative analysis of the activity of β−glucocerebrosidase (EC 3.2.1.45), αmannosidase (EC 3.2.1.24), β-mannosidase (EC 3.2.1.25), β-hexosaminidase (EC 3.2.1.52) and β-galactosidase (EC 3.2.1.23) in cerebrospinal fluid (CSF) of Parkinson's disease (PD) subjects and age matched controls first (Balducci et al., 2007), and then in Dementia with Lewy bodies (DLB), Alzheimer's disease (AD) and Frontotemporal Dementia (FTD) patients as well as in age matched controls (Parnetti et al., 2009). The framekork is different in the different neurodegenerative diseases, in PD patients a reduced activity of βglucocerebrosidase, β-mannosidase and α-mannosidase was found, whereas βgalactosidase and β-hexosaminidase remain unchanged. In DLB patients, all the enzymes tested showed a decrease activity with β−glucocerebrosidase with the lower value. In FTD patients, only α-mannosidase activity was lower than controls, while the other enzymes showed unchanged acticities. α-mannosidase and β-hexosaminidase are the only two

The data suggest a significant involvement of the ensosomal-lysosomal system in the neurodegenerative diseases examined. Moreover, the different pattern of lysosomal activity can reflect the diverse implication of the lysosomal apparatous in the distinct neurodegenerative pathologies. It has also been hypotized that ameliorate the activity of the lysosomal system can be a possible therapeutic strategy for these disorders characterized by misfolding and aggregation of wild-type or mutant protein in the cytoplas of neuronal cells

Clinical and genetic studies suggest that mutations in the glucocerebrosidase gene are an important risk factor for the development of parkinsonism and related didorders. While Gaucher disease is an autosomal inherited disorder, patients with parkinson's disease can be Gaucher heterozygotes or homozygotes. The involvment of the lysosomal system in

(Balducci et al., 2007).

(Lee et al., 2004).

**7. Conclusion** 

enzyme that showed reduced activity in AD patients.

mutant α-synuclein (Masliah et al., 2000; Lee et al., 2002; Richfield et al., 2002) was found to lead to the develp of granular deposits, but none of these results in the involvment of dopaminergic nerve cellsof the substantia nigra. Previous data demonstrated that truncated α-synuclein (1-120) was aboundantly presents in Lewy bodies extracts (Tofaris et al., 2003).

There are two different animal models of Parkinson's disease: the first one is a mouse model that express a truncated human α-synuclein (1-120) under the rat tyrosine hydroxylase promoter on a mouse α-synuclein null background (Tofaris et al., 2006). In this mouse model (TG Syn 120) were found pathological inclusions in substantia nigra and olfactory bulb, a reduction in dopamine levels in the striatum and in spontaneous locomotion and a better response to amphetamine. C-terminally truncated α-synuclein aggregates more quickly than full-lenght protein and has been found in Lewy bodies in human patients. The second one is a rat model (6OH-DA) with the lesion of the ascending nigrostriatal dopamine pathway due to 6-hydroxydopamine injection in the unilateral substantia nigra (Rozas et al., 1997; Picconi et al., 2003). These rats displayed some feautures of parkinsonian pathology. This rat model has been initially used to understand the behavioral functions of the basal ganglia, and to evaluate the brain's ability to compensate for specific neurochemical depletions. Now this model is use has strument to understand the mechanisms of PD pathology and as an experimental basis to develop new antiparkinsonian drugs and treatment strategies, or surgical approaches (Rozas et al., 1997). To deepen the involvement of lysosomal enzyme in Parkinson's disease, a comparative analysis of the activity of βglucocerebrosidase (EC 3.2.1.45), α-mannosidase (EC 3.2.1.24), β-mannosidase (EC 3.2.1.25), β-hexosaminidase (EC 3.2.1.52) and β-galactosidase (EC 3.2.1.23) have been performed in different brain sections of the two animal's model.

In particular lysosomal enzymatic activities were determined in cerebellum, cortex and brain-stem. The obtained results show a different expression in these sections of central nervous system of TG Syn 120 mouse model compared to control mice, with a decreased activity of all the enzymes in brain-stem, and an increased activity in the cerebellum. In the cortex all the enzymatic activities remain invariated.


Table 2. Lysosomal enzyme specific activities (μmol min-1/mg total protein x 1000) in, cerebellum, cortico-striatal and brain-stem of control and 6OH-DA rats. Mean ± SD are given. \*p<0.05 versus control.

A more pronunced differences in lysosomal enzyme expressions were observed in 6OH-DA rats (table 2). A clear reduction of enzyme activities were found in brain-stem, cerebellum and cortico-striatal. The chemical model show a profound involvement of the brain's areas and this is, probably, a consequence of the 6-hydroxydopamine treatment, infact the neurotoxins destroied selectively and rapidly catecholaminergic neurons whereas the PD pathogenensis in human and in the mouse model follows a progressive course over decades. The results obtained in this rat model might explain the reduction on alpha-mannosidase, beta-glucosidase, and beta-mannosidse activities observed in the CSF od PD patients (Balducci et al., 2007).
