We describe two new transgenic mouse lines for studying pathological changes of Tau protein related to Alzheimer's disease. They are based on the regulatable expression of the four-repeat domain of human Tau carrying the FTDP17 (frontotemporal dementia and parkinsonism linked to chromosome 17) mutation ⌬K280 (Tau RD /⌬K280), or the ⌬K280 plus two proline mutations in the hexapeptide motifs (Tau RD /⌬K280/I277P/I308P). The ⌬K280 mutation accelerates aggregation ("proaggregation mutant"), whereas the proline mutations inhibit Tau aggregation in vitro and in cell models ("antiaggregation mutant"). The inducible transgene expression was driven by the forebrain-specific CaMKII␣ (calcium/calmodulin-dependent protein kinase II␣) promoter. The proaggregation mutant leads to Tau aggregates and tangles as early as 2-3 months after gene expression, even at low expression (70% of endogenous mouse Tau). The antiaggregation mutant does not aggregate even after 22 months of gene expression. Both mutants show missorting of Tau in the somatodendritic compartment and hyperphosphorylation in the repeat domain [KXGS motifs, targets of the kinase MARK (microtubule affinity regulating kinase)]. This indicates that these changes are related to Tau expression rather than aggregation. The proaggregation mutant causes astrogliosis, loss of synapses and neurons from 5 months of gene expression onward, arguing that Tau toxicity is related to aggregation. Remarkably, the human proaggregation mutant Tau RD coaggregates with mouse Tau, coupled with missorting and hyperphosphorylation at multiple sites. When expression of proaggregation Tau RD is switched off, soluble and aggregated exogenous Tau RD disappears within 1.5 months. However, tangles of mouse Tau, hyperphosphorylation, and missorting remain, suggesting an extended lifetime of aggregated wild-type Tau once a pathological conformation and aggregation is induced by a proaggregation Tau species.

Neurofibrillary lesions are characteristic for a group of human diseases, named tauopathies, which are characterized by prominent intracellular accumulations of abnormal filaments formed by the microtubule-associated protein Tau. The tauopathies are accompanied by abnormal changes in Tau protein, including pathological conformation, somatodendritic mislocalization, hyperphosphorylation, and aggregation, whose interdependence is not well understood. To address these issues we have created transgenic mouse lines in which different variants of full-length Tau are expressed in a regulatable fashion, allowing one to switch the expression on and off at defined time points. The Tau variants differ by small mutations in the hexapeptide motifs that control the ability of Tau to adopt a ␤-structure conformation and hence to aggregate. The "pro-aggregation" mutant ⌬K280, derived from one of the mutations observed in frontotemporal dementias, aggregates avidly in vitro, whereas the "anti-aggregation" mutant ⌬K280/PP cannot aggregate because of two ␤-breaking prolines. In the transgenic mice, the pro-aggregation Tau induces a pathological conformation and pre-tangle aggregation, even at low expression levels, the antiaggregation mutant does not. This illustrates that abnormal aggregation is primarily controlled by the molecular structure of Tau in vitro and in the organism. Both variants of Tau become mislocalized and hyperphosphorylated independently of aggregation, suggesting that localization and phosphorylation are mainly a consequence of increased concentration. These pathological changes are reversible when the expression of Tau is switched off. The pro-aggregation Tau causes a strong reduction in spine synapses.

Amyloid-b, a peptide derived from the precursor protein APP, accumulates in the brain and contributes to the neuropathology of Alzheimer's disease. Increased generation of amyloid-b might be caused by axonal transport inhibition, via increased dwell time of APP vesicles and thereby higher probability of APP cleavage by secretase enzymes residing on the same vesicles. We tested this hypothesis using a neuronal cell culture model of inhibited axonal transport and by imaging vesicular transport of fluorescently tagged APP and b-secretase (BACE1). Microtubule-associated tau protein blocks vesicle traffic by inhibiting the access of motor proteins to the microtubule tracks. In neurons co-transfected with CFP-tau, APP-YFP traffic into distal neurites was strongly reduced. However, this did not increase amyloid-b levels. In singly transfected axons, APP-YFP was transported in large tubules and vesicles moving very fast (on average 3 mm/s) and with high fluxes in the anterograde direction (on average 8.4 vesicles/min). By contrast, BACE1-CFP movement was in smaller tubules and vesicles that were almost 2· slower (on average 1.6 mm/s) with~18· lower fluxes (on average 0.5 vesicles/min). Two-colour microscopy of co-transfected axons confirmed that the two proteins were sorted into distinct carriers. The results do not support the above hypothesis. Instead, they indicate that APP is transported on vesicles distinct from the secretase components and that amyloid-b is not generated in transit when transport is blocked by tau.

Abstract:The review will discuss in detail the effects of polyphenols on breast cancer, including both the advantages and disadvantages of the applications of these natural compounds. First, we focus on the characterization of the main classes of polyphenols and then on in vitro and in vivo experiments carried out in breast cancer models. Since the therapeutic effects of the administration of a single type of polyphenol might be limited because of the reduced bioavailability of these drugs, investigations on combination of several polyphenols or polyphenols with conventional therapy will also be discussed. In addition, we present recent data focusing on clinical trials with polyphenols and new approaches with nanoparticles in breast cancer. Besides the clinical and translational findings this review systematically summarizes our current knowledge about the molecular mechanisms of anti-cancer effects of polyphenols, which are related to apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways and epigenetic mechanisms. At the same time the effects of polyphenols on primary tumor, metastasis and angiogenesis in breast cancer are discussed. The increasing enthusiasm regarding the combination of polyphenols and conventional therapy in breast cancer might lead to additional efforts to motivate further research in this field.

Colorectal cancer is one of the leading causes of death, and the third most diagnosed type of cancer, worldwide. It is most common amongst men and women over 50 years old. Risk factors include smoking, alcohol, diet, physical inactivity, genetics, alterations in gut microbiota, and associated pathologies (diabetes, obesity, chronic inflammatory bowel diseases). This review will discuss, in detail, the chemopreventive properties of some dietary compounds (phenolic compounds, carotenoids, iridoids, nitrogen compounds, organosulfur compounds, phytosterols, essential oil compounds, polyunsaturated fatty acids and dietary fiber) against colorectal cancer. We present recent data, focusing on in vitro, laboratory animals and clinical trials with the previously mentioned compounds. The chemopreventive properties of the dietary compounds involve multiple molecular and biochemical mechanisms of action, such as inhibition of cell growth, inhibition of tumor initiation, inhibition of adhesion, migration and angiogenesis, apoptosis, interaction with gut microbiota, regulation of cellular signal transduction pathways and xenobiotic metabolizing enzymes, etc. Moreover, this review will also focus on the natural dietary compounds’ bioavailability, their synergistic protective effect, as well as the association with conventional therapy. Dietary natural compounds play a major role in colorectal chemoprevention and continuous research in this field is needed.