Anna Oczkowska

Molecular basis of familial and sporadic Alzheimer's disease.

Alzheimers disease (AD) is a multifactorial disease with genetic (70%) and environmental (30%) causes. Among the genetic factors are genes associated with a family history of the disease (familial AD, FAD) and sporadic AD (SAD). The genes: APP (amyloid precursor protein), PSEN1 (Presenilin 1) and PSEN2 (Presenilin 2) are responsible for the presence of FAD. The APOE gene is responsible for the sporadic form of the disease. Other molecular factors related to the immunological cause (TREM2) of the disease are a disorder of the lipid (ABCA1, ABCA7) or biothiol (MTHFD1) metabolism and of the transport of metabolites (BIN1). Currently, it is believed that APOE is a risk factor for both SAD and late-onset FAD. The pathomechanism of AD is most commonly explained as based on the amyloid cascade theory. This theory is related to the FAD, although there are reports indicating the probability of its occurrence in the SAD. It seems that the excessive deposition of β-amyloid (Aβ) peptides and intracellular neurofibrillary tangles of tau protein hyperphosphorylated forms contribute to the damage of both DNA and RNA. Furthermore, it is believed that RNA-interference can affect both the level of pathological proteins (Aβ, tau protein) and the onset and progress of AD. It seems that a complete understanding of both FAD and SAD pathogenesis may contribute to the search for earlier clinical diagnosis and to an understanding of later occurrence of the disease, which may help modify its course and affect more effective therapy of this incurable neurological disease.

Polymorphism of the COMT, MAO, DAT, NET and 5-HTT Genes, and Biogenic Amines in Parkinson's Disease.

Epinephrine (E) and sympathetic nerve stimulation were described by Thomas Renton Elliott in 1905 for the first time. Dopamine (DA), norepinephrine (NE), E, and serotonin (5-HT) belong to the classic biogenic amines (or monoamines). Parkinson’s disease (PD) is among the diseases in which it has been established that catecholamines may account for the neurodegeneration of central and peripheral catecholamine neural systems. PD is a chronic and progressive neurological disorder characterized by resting tremor, rigidity, and bradykinesia, affecting 2% of individuals above the age of 65 years. This disorder is a result of degeneration of DA-producing neurons of the substantia nigra and a significant loss of noradrenergic neurons in the locus coeruleus. In PD and other related neurodegerative diseases, catecholamines play the role of endogenous neurotoxins. Catechol-O-methyltransferase (COMT) and/or monoamine oxidase (MAO) catalyze the metabolism of monoamines. However, the monoamine transporters for DA, NE, and 5-HT namely DAT, NET, and SERT, respectively regulate the monoamine concentration. The metabolism of catecholamines and 5-HT involves common factors. Monoamine transporters represent targets for many pharmacological agents that affect brain function, including psychostimulators and antidepressants. In PD, polymorphisms of the COMT, MAO, DAT, NET, and 5- HTT genes may change the levels of biogenic amines and their metabolic products. The currently available therapies for PD improve the symptoms but do not halt the progression of the disease. The most effective treatment for PD patients is therapy with L-dopa. Combined therapy for PD involves a DA agonist and decarboxylase, MAOs and COMT inhibitors, and is the current optimal form of PD treatment maintaining monoamine balance.

Mutations in PRKN and SNCA Genes Important for the Progress of Parkinson's Disease.

Although Parkinson’s disease (PD) was first described almost 200 years ago, it remains an incurable disease with a cause that is not fully understood. Nowadays it is known that disturbances in the structure of pathological proteins in PD can be caused by more than environmental and genetic factors. Despite numerous debates and controversies in the literature about the role of mutations in the SNCA and PRKN genes in the pathogenesis of PD, it is evident that these genes play a key role in maintaining dopamine (DA) neuronal homeostasis and that the dysfunction of this homeostasis is relevant to both familial (FPD) and sporadic (SPD) PD with different onset. In recent years, the importance of alphasynuclein (ASN) in the process of neurodegeneration and neuroprotective function of the Parkin is becoming better understood. Moreover, there have been an increasing number of recent reports indicating the importance of the interaction between these proteins and their encoding genes. Among others interactions, it is suggested that even heterozygous substitution in the PRKN gene in the presence of the variants +2/+2 or +2/+3 of NACP-Rep1 in the SNCA promoter, may increase the risk of PD manifestation, which is probably due to ineffective elimination of over-expressed ASN by the mutated Parkin protein. Finally, it seems that genetic testing may be an important part of diagnostics in patients with PD and may improve the prognostic process in the course of PD. However, only full knowledge of the mechanism of the interaction between the genes associated with the pathogenesis of PD is likely to help explain the currently unknown pathways of selective damage to dopaminergic neurons in the course of PD.

Mutations of PARK Genes and Alpha-Synuclein and Parkin Concentrations in Parkinson’s Disease

Parkinson’s disease (PD) is a chronic and progressive neurological disorder characterized by resting tremor, rigidity, and bradykinesia, affecting at least 2% of individuals above the age of 65 years. Parkinson’s disease is a result of degeneration of the dopamine-producing neurons of the substantia nigra. Available therapies in PD will only improve the symptoms but not halt progression of disease. The most effective treatment for PD patients is thera‐ py with L-3,4-dihydroxy-phenylalanine (L-dopa) [Olanow, 2008].

Analysis of PRKN Variants and Clinical Features in Polish Patients with Parkinson’s Disease

The etiology of Parkinson’s disease (PD) is still unclear, but mutations in PRKN have provided some biological insights. The role of PRKN mutations and other genetic variation in determining the clinical features of PD remains unresolved. The aim of the study was to analyze PRKN mutations in PD and controls in the Polish population and to try to correlate between the presence of genetic variants and clinical features. We screened for PRKN mutations in 90 PD patients and 113 controls and evaluated clinical features in these patients. We showed that in the Polish population 4% of PD patients had PRKN mutations (single or with additional polymorphism) while single heterozygous polymorphisms (S167N, E310D, D394N) of PRKN were present in 21% of sporadic PD. Moreover, 5% PD patients had more than one PRKN change (polymorphisms and mutations). Detected PRKN variants moderately correlated with PD course and response to L-dopa. It also showed that other PARK genes (SNCA, HTRA2, SPR) mutations probably may additionally influence PD risk and clinical features. PRKN variants are relatively common in our Polish series of patients with PD. Analysis of the PRKN gene may be useful in determining clinical phenotype, and helping with diagnostic and prognostic procedures in the future.

Genetic variants in diseases of the extrapyramidal system.

Knowledge on the genetics of movement disorders has advanced significantly in recent years. It is now recognized that disorders of the basal ganglia have genetic basis and it is suggested that molecular genetic data will provide clues to the pathophysiology of normal and abnormal motor control. Progress in molecular genetic studies, leading to the detection of genetic mutations and loci, has contributed to the understanding of mechanisms of neurodegeneration and has helped clarify the pathogenesis of some neurodegenerative diseases. Molecular studies have also found application in the diagnosis of neurodegenerative diseases, increasing the range of genetic counseling and enabling a more accurate diagno-sis. It seems that understanding pathogenic processes and the significant role of genetics has led to many experiments that may in the future will result in more effective treatment of such diseases as Parkinson’s or Huntington’s. Currently used molecular diagnostics based on DNA analysis can identify 9 neurodegenerative diseases, including spinal cerebellar ataxia inherited in an autosomal dominant manner, dentate-rubro-pallido-luysian atrophy, Friedreich’s disease, ataxia with ocu-lomotorapraxia, Huntingtons disease, dystonia type 1, Wilson’s disease, and some cases of Parkinsons disease.

Mutations of TP53 C708T and C748A, oxidative DNA damage, and p53 and OGG1 protein levels in peripheral lymphocytes of the people with Alzheimer's disease

Background: We have previously reported an increased susceptibility to cell death of lymphocytes obtained from patients with Alzheimer’s disease (AD) when exposed to oxidative stress induced by hydrogen peroxide (H2O2). Herewe investigated whether the susceptibility to H 2 O 2 -induced death was related to the degree of dementia severity. Methods: Lymphocytes were extracted from peripheral blood from 25 AD patients (9 mildmoderate, CDR 1-2; 6 severe, CDR 3) and 10 healthy controls (all 60 years old) and exposed to H 2 O 2 for 20hrs in the presence or absence of 5 mM 3-aminobenzamide (3-ABA), a PARP-1 inhibitoror to staurosporine, an apoptosis inducer. Cell death was evaluated by flow cytometry and propidium iodide (PI) staining, whereby viable (PI-negative), apoptotic (PI-positive, hypodiploid) and necrotic (PI-positive diploid) cells were distinguished. Results: The dose response curve of lymphocyte viability in the presence of H2O2 was shifted to the left in AD patients compared to healthy controls, with severe dementia showing the highest vulnerability to H 2 O 2 and those with mild to moderate dementia showing intermediate values; i.e. treatment with 50 mM H 2 O 2 (around LD50) for 20 hrs induced death of 68.1% of lymphocytes from patients with severe dementia, 51.1% of those with mild to moderate dementia, and 34.6% of healthy control lymphocytes. The greater susceptibility to death was due to an increase mostly of apoptosis. Staurosporine, an apoptosis inducer, at concentrations between 0.6 6mM provoked death to a similar extent in the three groups of patients. As previously shown, H 2 O 2 -induced death was significantly reduced by PARP inhibition, whereby the extent of protection was less significant in lymphocytes from patients with severe dementia. Conclusions: We confirm our previous results showing that lymphocytes from AD patients are more susceptible to H2O2-induced death, whereby extent of death observed correlated with dementia severity. Moreover, increased susceptibility to death observed for AD lymphocytes was specific for oxidative damage, since no differences between groups were detectable with staurosporine, a kinase inhibitor. These results suggest that measurement of lymphocyte death induced by H 2 O 2 might be exploited to serve as a non-invasive biological marker of the severity of Alzheimer’s disease.

Pulsatility index in carotid arteries is increased in levothyroxine-treated Hashimoto disease.

The aim of this case-control study was to evaluate carotid hemodynamic variables and traditional cardiovascular risk factors in women with Hashimoto thyroiditis (HT). The study group consisted of 31 females with HT on levothyroxine (L-T4) and 26 euthyroid women with HT without L-T4 matched for age and body mass index (BMI) as controls. Carotid intima-media thickness (CIMT), carotid extra-media thickness (CEMT), and pulsatility indexes in common carotid artery (PI CCA) and in internal carotid artery (PI ICA) were measured. BMI, waist circumference, lipid profile, fasting glucose and insulin levels, and parameters of thyroid function [TSH, free thyroxine (FT4) and antithyroperoxidase antibodies (TPOAbs)] were assessed. The study and the control groups did not differ in age, BMI, waist circumference, lipid profile, fasting glucose, and insulin levels. Results are expressed as median (IQR). Treated HT group had higher FT4 levels than nontreated [17.13 (5.11) pmol/l vs. 14.7 (2.27) pmol/l; p=0.0011] and similar TSH [1.64 (2.08) IU/ml vs. 2.07 (3.14) IU/ml; p=0.5915]. PI CCA and PI ICA were higher in the study group than in controls (p=0.0224 and p=0.0477, respectively). The difference remained statistically significant for PI ICA and PI CCA after adjustment for other variables (coefficient=0.09487; standard error=0.04438; p=0.037 and coefficient=0.1786; standard error=0.0870; p=0.0449, respectively). CIMT and CEMT were similar in both groups (p=0.8746 and p=0.0712, respectively). Women with HT on L-T4 replacement therapy have increased PI in common and internal carotid arteries than nontreated euthyroid HT patients. Therefore, it seems that hypothyroidism, but not autoimmune thyroiditis per se, influences arterial stiffness.