Anterograde and Retrograde Propagation of Inoculated Human Tau Fibrils and Tau Oligomers in a Non-Transgenic Rat Tauopathy Model

The tauopathy of Alzheimer's disease (AD) is first observed in the brainstem and entorhinal cortex, spreading trans-synaptically along specific pathways to other brain regions with recognizable patterns. Tau propagation occurs retrogradely and anterogradely (trans-synaptically) along a given pathway and through exosomes and microglial cells. Some aspects of in vivo tau spreading have been replicated in transgenic mice models expressing a mutated human MAPT (tau) gene and in wild-type mice. In this study, we aimed to characterize the propagation of different forms of tau species in non-transgenic 3-4 months old wild-type rats after a single unilateral injection of human tau oligomers and tau fibrils into the medial entorhinal cortex (mEC). We determined whether different variants of the inoculated human tau protein, tau fibrils, and tau oligomers, would induce similar neurofibrillary changes and propagate in an AD-related pattern, and how tau-related pathological changes would correlate with presumed cognitive impairment. We injected human tau fibrils and tau oligomers stereotaxically into the mEC and examined the distribution of tau-related changes at 3 days and 4, 8, and 11 months post-injection using antibodies AT8 and MC1, which reveal early phosphorylation and aberrant conformation of tau, respectively, HT7, anti-synaptophysin, and the Gallyas silver staining method. Human tau oligomers and tau fibrils exhibited some similarities and some differences in their ability to seed and propagate tau-related changes. Both human tau fibrils and tau oligomers rapidly propagated from the mEC anterogradely into the hippocampus and various parts of the neocortex. However, using a human tau-specific HT7 antibody, 3 days post-injection we found inoculated human tau oligomers in the red nucleus, primary motor, and primary somatosensory cortex, a finding not seen in animals inoculated with human tau fibrils. In animals inoculated with human tau fibrils, 3 days post-injection the HT7 antibody showed fibrils in the pontine reticular nucleus, a finding explained only by uptake of human tau fibrils by incoming presynaptic fibers to the mEC and retrograde transport of inoculated human tau fibrils to the brainstem. Rats inoculated with human tau fibrils showed as early as 4 months after inoculation a spread of phosphorylated tau protein at the AT8 epitopes throughout the brain, dramatically faster propagation of neurofibrillary changes than with human tau oligomers. The overall severity of tau protein changes 4, 8, and 11 months after inoculation of human tau oligomers and tau fibrils correlated well with spatial working memory and cognition impairments, as measured by the T-maze spontaneous alternation, novel object recognition, and object location tests. We concluded that this non-trangenic rat model of tauopathy, especially when using human tau fibrils, demonstrates rapidly developing pathologic alterations in neurons, synapses, and identifiable pathways together with cognitive and behavioral changes, through the anterograde and retrograde spreading of neurofibrillary degeneration. Therefore, it represents a promising model for future experimental studies of primary and secondary tauopathies, especially AD.

Prostate cancer in elderly Croatian men: 5-HT genetic polymorphisms and the influence of androgen deprivation therapy on osteopenia--a pilot study

BACKGROUND

The aim of this study was to determine the relationship between body mass index, biochemical parameters, and 5-hydroxytryptamine (5-HT) genetic polymorphisms and prostate dysfunction in an elderly general male population.

RESULTS

One hundred and seventeen elderly male subjects [60 men without symptoms of prostate hyperplasia, 42 men with untreated benign prostatic hyperplasia (BPH), and 15 men with prostate cancer (PCa)] treated with finasteride or flutamide were included. Multiple comparisons showed significant difference in age, T-score, concentration of phosphorus, calcium, C-reactive protein, and prostate-specific antigen (PSA) between the groups. T-score was the lowest and phosphorus concentration was the highest in the PCa group. Highest PSA, proteins, calcium, and Hekal's formula score were found in the BPH group. Patients with PCa were more frequent GG+GA carriers of 5-HT1B 1997A/G gene polymorphism (p=0.035). Univariate regression analysis showed association of PCa-treated subjects with age (p=0.010) and 5-HT1B genetic polymorphism (p=0.018). Antiandrogen therapy affects T-score (p=0.017), serum phosphorus (p=0.008), glucose (p=0.036), and total proteins (p=0.050). Multivariate-stepwise logistic regression analysis showed the significant association of treated PCa with age (p=0.028) and inorganic phosphorus (p=0.005), and a marginal association with ultrasonographic T-score (p=0.052).

CONCLUSIONS

Antiandrogen therapy might induce bone mineral loss in elderly PCa patients. Preliminary data imply that the genetic variants of the 5-HT1B receptor might be associated with PCa.

Serum lipid levels in patients with Alzheimer's disease

The role of lipids in the aetiology and progress of Alzheimer's disease (AD) is still unclear High lipid levels could be one of the risk factors for AD, but no association or even protective effects of high cholesterol levels in the development of the AD were also found. The aim of the study was to determine serum levels of total cholesterol, high-density-lipoprotein cholesterol (HDL-C), low-density-lipoprotein cholesterol (LDL-C) and triglycerides (TG) in female patients with AD and in healthy elderly controls. The 50 patients met the diagnostic criteria of probable AD according to the NINDS-ADRDA and DSM-IV criteria. Cognitive impairment was evaluated using the Mini Mental State Examination (MMSE). Patients were subdivided into two groups of 19 patients in the middle (MMSE 10-19) and 31 patients in the late (MMSE 0-9) phase ofAD. Psychotic and non-psychotic features, evaluated by means of Neuropsychiatric Inventory, were presented in 13 and 37patients with AD, respectively. Control group consisted of 58 subjects without cognitive impairment (MMSE >27) and with lipid levels within normal range. Serum lipid levels were determined by the enzymatic colour tests and by the enzymatic clearance assay. Significantly lower lipid levels were found in patients with AD, than in controls. Patients in the late phase of AD had significantly lower entire lipid profile than controls and significantly lower cholesterol and LDL-C levels than patients in the middle stage ofAD. There was no difference in lipid levels between patients with and without psychotic features. The significant positive correlations were found between MMSE scores and cholesterol, LDL-C levels and age in all AD patients. The results support the presumption that lipid profile might be connected with the aetiology and progress of AD and showed the association between low serum cholesterol and LDL-C levels and cognitive decline in patients with AD. Further studies are needed to confirm the relationship between lipid levels and cognition, and to validate the lipid profile as a biological marker for the progress of AD.

No association between histamine N-methyltransferase functional polymorphism Thr105Ile and Alzheimer's disease

Several abnormalities, including lower histamine levels in brain, elevated serum histamine and degeneration of histaminergic neurons in tuberomammillary nucleus, were described in the histaminergic system of patients with Alzheimer's disease (AD). Histamine is a central neurotransmitter with several functions in brain including regulation of memory, cognition, locomotion, and is degraded in part by histamine N-methyltransferase (HNMT). A common Thr105Ile polymorphism within HNMT gene results in decreased enzyme activity. The Thr105Ile polymorphism was associated with Parkinson's disease, essential tremor, attention-deficit hyperactivity disorder (ADHD), asthma and alcoholism, thus we tested possible association of HNMT functional polymorphism with AD. We have tested 256 AD cases and 1190 healthy controls of Croatian origin. Thr105Ile polymorphism was determined by TaqMan RT-PCR Genotyping Assay and EcoRV digestion. Prevalence of functional HNMT polymorphism among all tested groups was similar and frequency of less active Ile105 variant was 11.5% among AD patients and 13.4% for healthy controls (p=0.26, X(2)=1.25). Our results indicate lack of the association of HNMT Thr105Ile functional polymorphism with Alzheimer's disease.

Platelet serotonin and monoamine oxidase in Alzheimer's disease with psychotic features

Post mortem brain studies indicate that alterations in serotonergic and catecholaminergic systems might be associated with Alzheimer's disease (AD). The aim of the study was to determine serotonin (5-HT) levels and monoamine oxidase type B (MAO-B) activity in platelets of psychotic and non-psychotic patients with AD, established according to the NINCDS-ADRDA and DSM-IV-TR criteria. Cognitive impairment and psychotic features were evaluated using Mini Mental Status Examination and Neuropsychiatric Inventory. Platelet 5-HT concentration and MAO-B activity were determined spectrofluorimetrically in 116 (51 male, 65 female) healthy subjects and 70 psychotic (10 male, 60 female) and 151 non-psychotic (32 male, 119 female) patients. Psychotic and non-psychotic female and psychotic male patients had significantly lower platelet 5-HT concentration than corresponding sex matched control subjects. Platelet MAO-B activity was significantly increased in both male and female non-psychotic patients compared to the sex matched controls. Non-psychotic female patients had significantly higher platelet MAO-B activity than psychotic female patients. Our data suggest that platelet MAO-B activity, but not platelet 5-HT concentration, could differentiate between psychotic and non-psychotic subtypes of AD.

Dopamine beta-hydroxylase (DBH) activity and -1021C/T polymorphism of DBH gene in combat-related post-traumatic stress disorder

The roles of dopamine (DA) and norepinephrine (NE) in posttraumatic stress disorder (PTSD) are unclear. The aim of the study was to determine plasma dopamine beta-hydroxylase (DBH) activity and DBH-1021C/T gene polymorphism in combat veterans with (N = 133) or without (N = 34) chronic PTSD. Similar frequencies in genotype or allele distribution were found between veterans with or without PTSD. War veterans with PTSD had lower DBH activity, associated with the DBH-1021C/T variant in DBH genes, than veterans without PTSD. A significantly lower plasma DBH activity was found in combat veterans with PTSD carrying the CC genotype as compared to veterans without PTSD carrying the corresponding genotype. Since both groups were exposed to the same trauma, it is possible that a pre-existing trait difference in regulation of NE function contributed to a differential vulnerability to develop PTSD, or that the regulation of DBH expression was different in response to trauma. The results suggest that that genotype-controlled measurement of plasma DBH activity might be used as a potential biological marker of the response to trauma, and that further studies of DBH and other loci related to DA and NA in PTSD are warranted.

Platelet serotonin concentration in alcoholic subjects

Serotonin (5-hydroxytryptamine, 5-HT) is assumed to play a role in the pathophysiology of different psychiatric disorders including alcoholism. Since platelets and central serotonergic synaptosomes share similar pharmacodynamics of 5-HT, this study determined platelet 5-HT concentration in 148 male and 42 female drug-free subjects with alcohol dependency, according to the DSM-IV criteria, and in sex-and age-matched controls. Male and female alcoholics had significantly lower platelet 5-HT concentration than 110 male and 123 female healthy controls. Sex differences, i.e. higher platelet 5-HT concentration in men than in women, were found both in healthy and alcoholic subjects. Platelet 5-HT concentration differed significantly in male and female alcoholic subjects with or without different psychiatric comorbidities. Platelet 5-HT concentration was higher in male alcoholics with comorbid posttraumatic stress disorder (PTSD) than in male alcoholics with comorbid anxious-depressive disorder, or depression, or male alcoholics without any psychiatric comorbidities. Comorbid depression in female alcoholics slightly elevated platelet 5-HT levels but these values were still reduced compared to values in healthy women. Smoking status did not affect platelet 5-HT concentration either in healthy or in alcoholic subjects. The data from our study show sex differences, and reduced platelet 5-HT values, regardless of the nicotine dependence, in the large groups of male and female alcoholic subjects. Among male alcoholics the presence of comorbid PTSD partly normalized the decreased platelet 5-HT values. The results of the present study support the hypothesis that alterations in 5-HT system might be related to alcoholism.

Long-term sertraline treatment and peripheral biochemical markers in female depressed patients

Serotonergic system is implicated in the pathogenesis of depression. Peripheral biochemical markers, platelet serotonin (5-HT) and platelet monoamine oxidase (MAO) activity were determined spectrofluorimetrically at baseline and after 4 and 24 weeks of sertraline (a selective serotonin reuptake inhibitor (SSRI)) treatment in 15 female nonsuicidal, nonpsychotic patients with major depression and compared with 15 drug-free healthy women. The aim of the study was to determine the effects of 4 and 24 weeks of sertraline treatment on platelet 5-HT concentration and platelet MAO activity in depressed patients subdivided according to the treatment response into remitters, responders and nonresponders after 4 and 24 weeks of sertraline treatment based on the 70%, 50-69% and <49% reductions in baseline Montgomery-Asperg Depression Rating Scale (MADRS) scores, respectively. Platelet 5-HT concentration was significantly lower in all depressed patients at baseline than in healthy subjects. Among patients, platelet 5-HT concentration or platelet MAO activity did not differ before treatment. There was no significant correlation between MADRS scores and peripheral biochemical markers. The limitation of the study was in a small number of patients, but its advantage was in a long-term (24 weeks) follow-up of both patients and healthy controls. Our results show that long-term sertraline treatment induced remission and response in 87% patients, decreased platelet 5-HT concentration after 4 and 24 weeks of treatment and decreased platelet MAO activity after 24 weeks and suggest that pretreatment values of platelet 5-HT and platelet MAO might not predict therapeutic outcome to sertraline treatment in female depressed patients.