Neurofibrillary tangles of Alzheimer disease share antigenic determinants with the axonal microtubule-associated protein tau (?)

Astrocytic uptake of neuronal corpses promotes cell-to-cell spreading of tau pathology

Tau deposits in astrocytes are frequently found in Alzheimer's disease (AD) and other tauopathies. Since astrocytes do not express tau, the inclusions have been suggested to be of neuronal origin. However, the mechanisms behind their appearance and their relevance for disease progression remain unknown. Here we demonstrate, using a battery of experimental techniques that human astrocytes serve as an intermediator, promoting cell-to-cell spreading of pathological tau. Human astrocytes engulf and process, but fail to fully degrade dead neurons with tau pathology, as well as synthetic tau fibrils and tau aggregates isolated from AD brain tissue. Instead, the pathogenic tau is spread to nearby cells via secretion and tunneling nanotube mediated transfer. By performing co-culture experiments we could show that tau-containing astrocytes induce tau pathology in healthy human neurons directly. Furthermore, our results from a FRET based seeding assay, demonstrated that the tau proteoforms secreted by astrocytes have an exceptional seeding capacity, compared to the original tau species engulfed by the cells. Taken together, our study establishes a central role for astrocytes in mediating tau pathology, which could be of relevance for identifying novel treatment targets for AD and other tauopathies.

Prevalence of affective disorders and dementia in inflammatory polyarthropathies

Comorbid disorders are common in psychiatric diseases and understanding the risk of secondary diseases can aid successful clinical treatment. The objective of this study was to compare the frequency of comorbid dementia, affective disorders, and inflammatory polyarthropathies. Healthcare data obtained via the German Hospital Fees Act from two independent databases with more than 7.4 million cases were analyzed to compare the prevalence of comorbid disorders. Comorbid inflammatory polyarthropathy was observed in 2.27% of patients diagnosed with affective disorders and 1.35% of patients with dementia (p < 0.001). Among patients with a primary diagnosis of inflammatory polyarthropathy, 1.27% of patients were diagnosed with dementia, whereas 4.55% of age-matched patients without inflammatory polyarthropathies had comorbid dementia (p < 0.001). The opposite effect was demonstrated for affective disorders, as 5.77% of patients with a primary diagnosis of inflammatory polyarthropathy also had comorbid affective disorders, while 4.87% of age-matched patients without inflammatory polyarthropathy had an accompanying affective disease (p < 0.001). These findings show an association between the occurrence of inflammatory polyarthropathies, dementia, and affective disorders. This correlation might improve diagnosis and treatment for patients with comorbidities. Moreover, further exploration of the molecular pathophysiology underlying these relationships could be relevant for the development of novel treatment options.

Female Sex Hormones and Cardiac Pressure Overload Independently Contribute to the Cardiogenic Dementia Profile in Yucatan Miniature Swine

Post-menopausal women with heart failure (HF) frequently exhibit cardiogenic dementia. Using a pre-clinical swine model of post-menopausal HF, we recently demonstrated that experimental menopause (ovariectomy; OVX) and HF (6-month cardiac pressure overload/aortic banding; AB) independently altered cerebral vasomotor control and together impaired cognitive function. The purpose of this study was to examine the prefrontal cortex and hippocampus tissues from these animals to assess whether OVX and HF are associated with neurologic alterations that may contribute to cardiogenic dementia. We hypothesized that OVX and HF would independently alter neuronal cell signaling in swine with post-menopausal cardiogenic dementia. Immunoblot analyses revealed OVX was associated with reduced estrogen receptor-α in both brain regions and HF tended to exacerbate OVX-induced deficits in the hippocampus. Further, OVX was associated with a reduction in the ratio of phosphorylated:total Akt and ERK in the hippocampus as well as decreased total Akt and synaptophysin in the prefrontal cortex. In contrast, HF was associated with a trend toward reduced phosphorylated:total ERK in the prefrontal cortex. In addition, HF was associated with decreased β-amyloid (1-38) in the prefrontal cortex and increased β-amyloid (1-38) in the hippocampus. Regional brain lipid analysis revealed OVX tended to increase total, saturated, and monounsaturated fatty acid content in the prefrontal cortex, with the greatest magnitude of change occurring in the AB-OVX group. The data from this study suggest that OVX and HF are independently associated with regional-specific neurologic changes in the brain that contribute to the cardiogenic dementia profile in this model. This pre-clinical swine model may be a useful tool for better understanding post-menopausal cardiogenic dementia pathology and developing novel therapies.