Affiliations: [a] International Centre of Biodynamics, Bucharest, Romania | [b] Laboratory of Molecular Medicine, ‘Victor Babeş’ National Institute of Pathology, Bucharest, Romania | [c] Department of Cellular and Molecular Medicine, School of Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania | [d] Department of Neurology, Colentina Clinical Hospital – CDPC, School of Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania
Correspondence:
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Correspondence to: Bogdan O. Popescu, Department of Neurology, Colentina Clinical Hospital – CDPC, School of Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, 19-21 şos. ştefan cel Mare, 020125 Bucharest 2, Romania. Tel.: +40 744 35 34 33; Fax: +40 21 318 06 29; E-mail: bopopescu@spitalulcolentina.ro; Eugen Gheorghiu, International Centre of Biodynamics, 1 B Intrarea Portocalelor, 060101 Bucharest 6, Romania. Tel.: +40 722 34 52 29; Fax: +40 21 310 43 61; E-mail: egheorghiu@biodyn.ro.
Note: [1] These authors contributed equally to this work.
Abstract: Recently, the blood-brain barrier (BBB) has been pointed to as an active player in neurodegenerative disorders, albeit the actual succession of pathogenic events remains to be elucidated. Amyloid-β (Aβ) is an important pathogenic player in Alzheimer's disease, and it is cleared from the brain partly by transportation across the BBB. In this work we asked the question whether Aβ-induced alteration of tight junction (TJ) protein expression is a result of the complex in situ microenvironment of the BBB or if it can be replicated in an externalized environment, such as an in vitro epithelial barrier, where barrier property changes can be investigated without confounding factors. Therefore, we treated barrier forming MDCKI and II epithelial cells with Aβ42 and investigated TJ occludin and claudin-2 protein levels and cellular distribution through western blot and immunofluorescence. To assess barrier function, we measured transepithelial resistance (TEER) and studied cell polarity through atomic force microscopy (AFM). We found that Aβ42 cell treatment increased occludin expression and decreased claudin-2 expression. With TEER, an increase in paracellular resistance was noted, which started at 10 hours and peaked at 20 hours of Aβ42 treatment. AFM analysis demonstrated an associated morphological alteration of the cell monolayer. In conclusion, we demonstrated that Aβ42 is able to modify TJ protein expression and to functionally alter barrier properties in vitro and that this effect is not conditioned by other pathogenic Alzheimer's disease events taking place in the complex brain microenvironment.
