Commentary: “Age-Associated Physiological and Pathological Changes at the Blood-Brain Barrier: A Review” Erdő F * Faculty of Information Technology and Bionics, Pazmany Peter Catholic University, Budapest, Hungary * Corresponding author: Erdő F, Faculty of Information Technology and Bionics, Pazmany Peter Catholic University, Prater u. 50/a, 1083 Budapest, Hungary, Tel: +36-1- 886-4790; Fax: +36-1-886-4724; E-mail: erdo.franciska@itk.ppke.hu Received date: February 08, 2017; Accepted date: February 21, 2017; Published date: February 28, 2017 Copyright: © 2017 Erdő F. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction Tis review article published by JCBFM in January 2017 gives an overview of the recent literature on the alterations of the Blood Brain Barrier (BBB) during normal and pathological process of aging. In the introductory section of the paper the role of blood brain barrier in the maintenance of brain homeostasis and the main cellular and molecular elements of this system are presented. Te most important cellular constituents are the classical three cell type of endothelial cells, astrocytes and perycites. However, in the last decade a close connection and complex interactions were revealed with additional cell types of neurovascular unit, like neurons and microglial cells, and further cellular elements were also included in the terminology of BBB in the scientifc literature as supportive cells in displaying the blood- brain barrier function. Having a closer view at the molecular level of BBB, we can see that the tight junctional and adherens junctional proteins [1] and also the diferent membrane transporter proteins [2] play an important role in the protection of the brain against the continuous changes in the concentrations of plasma constituents, harmful xenobiotic and microbial components originating from the circulation. During embryonic development the permeability and the paracellular transport through the brain capillary endothelial cell layer change dramatically [3]. Transendothelial Electrical Resistance (TEER) has been used to study ion permeability in many epithelia [4-7], and in cerebral blood vessels [8-11], and is a measure of both the cellular and paracellular ion transport. Electrical resistance of pial vessels in 17-20 day fetuses is 300 Ω cm 2 , lower than the 2000 Ω cm 2 typical for tight blood vessels [8], but considerably higher than the 2 Ω cm 2 observed in leaky mesenteric blood vessels [5], or the 20-30 Ω cm 2 as in muscle vessels and choroid plexus epithelium [4]. Tere is an acute increase in resistance of cerebral microvasculature to 1200 Ω cm 2 in 21 day fetuses, and there is no remarkable further increase in resistance afer birth. Te increase in electrical resistance and the onset of brain interstitial ion regulation occur immediately prior to birth over a relatively short period of time [3]. Te mean electrical resistance across the wall of blood vessels on the pial surface of the brain in 28-33 day old rats is about 1500 Ω cm 2 . Te in situ determination of TEER values can be performed in newborn and young adult rats but seems to be technically challenging in aged animals. In vitro studies in endothelial cell cultures show similar permeability data to the in vivo observations for newborn and adult individuals [12], but the investigation of cells from aged animals is still missing. Te morphological observations of brain microvasculature have shown that the capillary wall thickness is increased in humans [13], the number of endothelial cells, mitochondria and tight junction protein expression are decreased in association with aging [14,15]. Tickness of basal lamina, the number and size of astrocyte endfeet, glial fbrillary acidic protein expression, collagen IV and argin concentrations increase with age. Microglia turns to an amoeboid phenotype and produces pro-infammatory cytokines while the number of perycites is decreased in aged subjects [16-18]. In the second part of the paper the diferent neurodegenerative diseases are analyzed and presented in connection with the age- dependent changes in the blood-brain barrier function. Te most important neurodegenerative disorders like Alzheimer’s disease, multiple sclerosis, Parkinson’s disease and pharmacoresistant epilepsy and their pathomechanisms are summarized together with the neurodegenerative processes (gene defects, oxidative stress, protein misfolding and accumulation, cell death) in the supplementary fle. Alzheimer’s Disease Alteration of the BBB plays an important role in pathology of Alzheimer's disease. BBB breakdown is an early event in the aging human brain that begins in the hippocampus and may contribute to cognitive impairment. Tight junction proteins include occludin and claudins. Occludin is vulnerable to being attacked by Matrix Metalloproteinases (MMPs) and MMPs seem to have implications in Alzheimer’s disease. Te membrane transporters at the BBB and defected elimination mechanisms playing a role in the formation of Amyloid β plaques in the brain parenchyma in Alzheimer’s’ patients are shown in details. Te processes in the astrocytes and pericytes involved in this neurodegenerative disorder are also summarized [19]. Multiple Sclerosis Formation of multiple sclerosis focal lesions follows the extravasation of activated leukocytes from blood through the BBB into the central nervous system (CNS). Once the activated leukocytes enter the CNS environment, they propagate massive destruction to fnally result in the loss of both the myelin/oligodendrocyte complex and neurodegeneration. Also, the activated leukocytes locally release infammatory cytokines and chemokines leading to focal immune activation of the brain endothelial cells, and loss of the normal functioning of the BBB. Tight junctions, MMPs and transporters are also involved in multiple sclerosis; their role is presented in an article [20]. Parkinson’s Disease Using histologic markers of serum protein, iron, and erythrocyte extravasation, a signifcantly increased permeability of the BBB in a part of the caudate putamen of Parkinson’s disease patients has been shown. As in Alzheimer’s disease and multiple sclerosis, MMPs seem , Clin Exp Pharmacol 2017, 7:2 DOI: 10.4172/2161-1459.1000230 Commentary Open Access Clin Exp Pharmacol, an open access journal ISSN: 2161-1459 Volume 7 • Issue 2 • 1000230 Erdő Journal of Clinical and Experimental Pharmacology J o u r n a l o f C l i n i c a l & E x p e r i m e n t a l P h a r m a c o l o g y ISSN: 2161-1459