The role of aquaporin-4 in the blood–brain barrier development and integrity: Studies in animal and cell culture models

Nicchia, Grazia Paola; Nico, Beatrice; Camassa, Laura M. A.; Mola, Maria Grazia; Loh, Nellie Y.; Dermietzel, Rolf; Spray, David C.; Svelto, María; Frigeri, Antonio

doi:10.1016/j.neuroscience.2004.07.055

Cited by 195 publications

(137 citation statements)

References 56 publications

Supporting

Mentioning

123

Contrasting

Unclassified

Order By: Relevance

“…48 Glial DAPs, laminin and agrin in mdx mice B Nico et al AQP4 controls BBB functioning and integrity, because its expression parallels BBB development and is altered after BBB damage. 7,49 AQP4 expression on the perivascular processes of astrocytes is correlated to the ability of astrocytes to remove K þ excess from the extracellular clefts by active and passive uptake and K þ flux. 13,50 Nagelhus et al 9 demonstrated that Müller cells showed higher AQP4 content in the astrocytic endfoot and that the distribution of AQP4 was coupled with the K þ channel protein Kir 4.1.…”

Section: Discussionmentioning

confidence: 99%

Glial dystrophin-associated proteins, laminin and agrin, are downregulated in the brain of mdx mouse

Nico

Tamma

Annese

et al. 2010

Laboratory Investigation

View full text Add to dashboard Cite

In this study, we investigated the involvement of dystrophin-associated proteins (DAPs) and their relationship with the perivascular basement membrane in the brains of mdx mice and controls at the age of 2 months. We analyzed (1) the expression of glial DAPs a-b-dystroglycan (DG), a-syntrophin, aquaporin-4 (AQP4) water channel, Kir 4.1 and dystrophin isoform (Dp71) by immunocytochemistry, laser confocal microscopy, immunogold electron microscopy, immunoblotting and RT-PCR; (2) the ultrastructure of the basement membrane and expression of laminin and agrin; and (3) the dual immunofluorescence colocalization of AQP4/a-b-DG, and of Kir 4.1/agrin. The following results were observed in mdx brain as compared with controls: (1) a significant reduction in protein content and mRNA expression of DAPs; (2) ultrastructurally, a thickened and discontinuous appearance of the basement membrane and a significant reduction in laminin and agrin; and (3) a molecular rearrangment of a-b-DG, coupled with a parallel loss of agrin and Kir 4.1 on basement membrane and glial endfeet. These data indicate that in mdx brain the deficiency in dystrophin and dystrophin isoform (Dp71) is coupled with a reduction of DAP components, coupled with an altered anchoring to the basement membrane. The blood-brain barrier (BBB) controls the selective exchanges between blood and neuropil by specific molecular and structural features of its vascular and perivascular components, including endothelial cells, pericytes, glial endfeet and basement membrane. 1-3 Glial cells have a key role in the control of BBB development and integrity. They express in a polarized way, on their perivascular endfeet, carrier membranes and channel proteins, including aquaporin-4 (AQP4) water channel and potassium channel Kir 4.1, which are responsible for the water flow rate and spatial K þ buffering control. [4][5][6][7][8][9] In the retina, AQP4 colocalizes with Kir 4.1, 9-11 suggesting a tight cooperation between the water flux and K þ siphoning generated by neuronal activity at the BBB interfaces. Moreover, AQP4 and Kir 4.1 rearrangement has been described in BBB alterations, coupled with cytotoxic edema and K þ -delayed buffering capacity. 12,13 AQP4 has a crucial role in the regulation of the interactions occurring between endothelial and glial cells and between glial cells and the extracellular matrix components. AQP4 is a component of the orthogonal aggregate particles (OAPs), demonstrated by freeze fracturing on the ependimoglial membrane and perivascular glial endfeet, 14 the development of which occurs in parallel with AQP4 glial endfeet expression and BBB maturation. 7 Moreover, OAPs contain AQP4 associated with Kir 4.1 12 and their polarized distribution on the glial endfeet seems to be dependent by the presence of the perivascular basement membrane. 15 AQP4 controls BBB functioning, modifying

show abstract

Section: Discussionmentioning

confidence: 99%

Glial dystrophin-associated proteins, laminin and agrin, are downregulated in the brain of mdx mouse

Nico

Tamma

Annese

et al. 2010

Laboratory Investigation

View full text Add to dashboard Cite

show abstract

“…After 12 h, the beads were stirred continuously (20 rpm) for 4 -6 days before experiments. The astrocytes in primary culture were identified by immunostaining for glial fibrillary acidic protein (GFAP) and aquaporin-4, the major water channel expressed in brain perivas-cular astrocyte processes (30). Freshly isolated astrocytes identified by immunostaining for GFAP and aquaporin-4 account for Ͼ90% of the vessel-free astrocyte-enriched fraction of brain parenchyma purified by consecutive filtration through 300-, 60-and 20-m nylon mesh filters.…”

Section: Methodsmentioning

confidence: 99%

Glutamate-induced calcium signals stimulate CO production in piglet astrocytes

Tcheranova

Basuroy

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

Glutamate-stimulated, astrocyte-derived carbon monoxide (CO) causes cerebral arteriole dilation by activating smooth muscle cell large-conductance Ca 2ϩ -activated K ϩ channels. Here, we examined the hypothesis that glutamate activates heme oxygenase (HO)-2 and CO production via the intracellular Ca 2ϩ concentration ([Ca 2ϩ ]i)/ Ca 2ϩ -calmodulin signaling pathway in newborn pig astrocytes. The major findings are: 1) glutamate stimulated Ca 2ϩ transients and increased steady-state [Ca 2ϩ ]i in cerebral cortical astrocytes in primary culture, 2) in astrocytes permeabilized with ionomycin, elevation of [Ca 2ϩ ]i concentration-dependently increased CO production, 3) glutamate did not affect CO production at any [Ca 2ϩ ]i when the [Ca 2ϩ ]i was held constant, 4) thapsigargin, a sarco/endoplasmic reticulum Ca 2ϩ -ATPase blocker, decreased basal CO production and blocked glutamate-induced increases in CO, and 5) calmidazolium, a calmodulin inhibitor, blocked CO production induced by glutamate and by [Ca 2ϩ ]i elevation. Taken together, our data are consistent with the hypothesis that glutamate elevates [Ca 2ϩ ]i in astrocytes, leading to Ca 2ϩ -and calmodulin-dependent HO-2 activation, and CO production. cerebral circulation; heme oxygenase; calmodulin; gasotransmitter; neurovascular coupling IN THE NEUROVASCULAR UNIT, astrocytes act as intermediaries between neurons and arterioles to regulate vascular tone in response to neuronal activity. Release of glutamate from presynaptic neurons increases blood flow to match metabolic demands; such coupling is called functional hyperemia. Functional hyperemia has been investigated extensively, and many astrocyte-derived vasoactive mediators, including ADP (40, 41), ATP (34, 36), epoxyeicosatrienoic acids (1-3), K ϩ (11, 13, 33), and prostacyclin (42), appear to be involved, depending on experimental models. We have shown that carbon monoxide (CO) is another critical regulator of cerebrovascular tone in newborn piglets (19,24,26,31,39).CO dilates newborn pig pial arterioles (22,25). CO causes vasodilation by stimulating Ca 2ϩ sparks and large-conductance Ca 2ϩ -activated K ϩ (BK Ca ) channels and by increasing effective coupling between Ca 2ϩ sparks and BK Ca channels in arterial smooth muscle cells (17,18,25,38). Physiologically, CO is produced by heme oxygenase (HO)-catabolized breakdown of heme to CO, iron, and biliverdin (27). Of three HO isoforms, only HO-2 is expressed under basal conditions in newborn piglet brain (31, 32). In piglets, endogenous HO-2 can produce sufficient CO to induce cerebral arteriole dilation (23).Our previous studies in piglets demonstrated that glutamate stimulates astrocytic CO production in primary-cultured astrocytes and in vivo (24,26,31). We also demonstrated that astrocytes release CO and astrocyte-derived CO causes glutamate-induced pial arteriolar dilation in vivo (24), supporting a regulatory role for astrocytic CO in neurovascular coupling in the newborn brain. Indeed, in brain slices from newborn piglets, we demonstrated that glut...

show abstract

“…Astrocytes were grown in 75-ml flasks for 10 -14 days, changing the media twice a week and replated to 12-well plates and grown in astrocyte media for 4 -6 days to confluence. The astrocytes were identified by immunostaining for glial fibrillary acidic protein (GFAP) and aquaporin-4, the major water channel expressed in brain perivascular astrocyte processes (41). Such staining indicates these procedures produce pure astrocyte cultures.…”

Section: Methodsmentioning

confidence: 99%

Contributions of astrocytes and CO to pial arteriolar dilation to glutamate in newborn pigs

Leffler

Parfenova²,

Fedinec

et al. 2006

American Journal of Physiology-Heart and Circulatory Physiology

106

View full text Add to dashboard Cite

Astrocytes can act as intermediaries between neurons and cerebral arterioles to regulate vascular tone in response to neuronal activity. Release of glutamate from presynaptic neurons increases blood flow to match metabolic demands. CO is a gasotransmitter that can be related to neural function and blood flow regulation in the brain. The present study addresses the hypothesis that glutamatergic stimulation promotes perivascular astrocyte CO production and pial arteriolar dilation in the newborn brain. Experiments used anesthetized newborn pigs with closed cranial windows, piglet astrocytes, and cerebrovascular endothelial cells in primary culture and immunocytochemical visualization of astrocytic markers. Pial arterioles and arteries of newborn pigs are ensheathed by astrocytes visualized by glial fibrillary acidic protein staining. Treatment (2 h) of astrocytes in culture with L-2-␣-aminoadipic acid (L-AAA), followed by 14 h in toxin free medium, dose-dependently increased cell detachment, suggesting injury. Conversely, 16 h of continuous exposure to L-AAA caused no decrease in endothelial cell attachment. In vivo, topical L-AAA (2 mM, 5 h) disrupted the cortical glia limitans histologically. Such treatment also eliminated pial arteriolar dilation to the astrocytedependent dilator ADP and to glutamate but not to isoproterenol or CO. Glutamate stimulated CO production by the brain surface that also was abolished following L-AAA. In contrast, tetrodotoxin blocked dilation to N-methyl-D-aspartate but not to glutamate, isoproterenol, or CO or the glutamate-induced increase in CO. The concurrent loss of CO production and pial arteriolar dilation to glutamate following astrocyte injury suggests astrocytes may employ CO as a gasotransmitter for glutamatergic cerebrovascular dilation. glia limitans; cerebrovascular circulation; gasotransmitter; glia toxin IN THE CEREBROVASCULAR circulation, signals to vascular smooth muscle can come from endothelium, nerves, astrocytes, or pericytes, which interact to form a neurovascular unit (15). L-Glutamic acid (glutamate) is the principal excitatory neurotransmitter in the central nervous system (38). It is a dilator of cerebral arterioles in vivo (8, 12), although direct effects of glutamate on the vascular smooth muscle are uncertain. Release of glutamate from presynaptic neurons dilates cerebral arterioles, causing blood flow to increase to match metabolic demands (37).Astrocytes are the most abundant cell type in the higher mammalian brain. They function as intermediaries between neurons and cerebral arterioles in regulation of cerebral vascular tone in response to neuronal activity, thereby adjusting cerebral blood flow to metabolism (15,25). Whether astrocytes are involved in dilation in response to glutamate released at excitatory synapses and the nature of astrocyte-derived vasodilator(s) employed remain uncertain.The gas CO is produced physiologically by catabolism of heme to CO, iron, and biliverdin (36). This reaction is catalyzed by heme oxygenase (HO) with oxidation of...

show abstract

The role of aquaporin-4 in the blood–brain barrier development and integrity: Studies in animal and cell culture models

Cited by 195 publications

References 56 publications

Glial dystrophin-associated proteins, laminin and agrin, are downregulated in the brain of mdx mouse

Glial dystrophin-associated proteins, laminin and agrin, are downregulated in the brain of mdx mouse

Glutamate-induced calcium signals stimulate CO production in piglet astrocytes

Contributions of astrocytes and CO to pial arteriolar dilation to glutamate in newborn pigs

Contact Info

Product

Resources

About