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Rapedius M, Obergrussberger A, Humphries ESA, Scholz S, Rinke-Weiss I, Goetze TA, Brinkwirth N, Rotordam MG, Strassmaier T, Randolph A, Friis S, Liutkute A, Seibertz F, Voigt N, Fertig N. There is no F in APC: Using physiological fluoride-free solutions for high throughput automated patch clamp experiments. Front Mol Neurosci 2022; 15:982316. [PMID: 36072300 PMCID: PMC9443850 DOI: 10.3389/fnmol.2022.982316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 07/26/2022] [Indexed: 11/13/2022] Open
Abstract
Fluoride has been used in the internal recording solution for manual and automated patch clamp experiments for decades because it helps to improve the seal resistance and promotes longer lasting recordings. In manual patch clamp, fluoride has been used to record voltage-gated Na (NaV) channels where seal resistance and access resistance are critical for good voltage control. In automated patch clamp, suction is applied from underneath the patch clamp chip to attract a cell to the hole and obtain a good seal. Since the patch clamp aperture cannot be moved to improve the seal like the patch clamp pipette in manual patch clamp, automated patch clamp manufacturers use internal fluoride to improve the success rate for obtaining GΩ seals. However, internal fluoride can affect voltage-dependence of activation and inactivation, as well as affecting internal second messenger systems and therefore, it is desirable to have the option to perform experiments using physiological, fluoride-free internal solution. We have developed an approach for high throughput fluoride-free recordings on a 384-well based automated patch clamp system with success rates >40% for GΩ seals. We demonstrate this method using hERG expressed in HEK cells, as well as NaV1.5, NaV1.7, and KCa3.1 expressed in CHO cells. We describe the advantages and disadvantages of using fluoride and provide examples of where fluoride can be used, where caution should be exerted and where fluoride-free solutions provide an advantage over fluoride-containing solutions.
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Affiliation(s)
- Markus Rapedius
- Nanion Technologies GmbH, Munich, Germany
- *Correspondence: Markus Rapedius,
| | | | | | | | | | | | | | | | | | | | | | - Aiste Liutkute
- Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
- German Center for Cardiovascular Research, Partner Site Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells”, University of Göttingen, Göttingen, Germany
| | - Fitzwilliam Seibertz
- Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
- German Center for Cardiovascular Research, Partner Site Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells”, University of Göttingen, Göttingen, Germany
| | - Niels Voigt
- Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
- German Center for Cardiovascular Research, Partner Site Göttingen, Göttingen, Germany
- Cluster of Excellence “Multiscale Bioimaging: From Molecular Machines to Networks of Excitable Cells”, University of Göttingen, Göttingen, Germany
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Activation of non-classical NMDA receptors by glycine impairs barrier function of brain endothelial cells. Cell Mol Life Sci 2022; 79:479. [PMID: 35951110 PMCID: PMC9372018 DOI: 10.1007/s00018-022-04502-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/04/2022] [Accepted: 07/16/2022] [Indexed: 12/24/2022]
Abstract
Blood–brain barrier (BBB) integrity is necessary to maintain homeostasis of the central nervous system (CNS). NMDA receptor (NMDAR) function and expression have been implicated in BBB integrity. However, as evidenced in neuroinflammatory conditions, BBB disruption contributes to immune cell infiltration and propagation of inflammatory pathways. Currently, our understanding of the pathophysiological role of NMDAR signaling on endothelial cells remains incomplete. Thus, we investigated NMDAR function on primary mouse brain microvascular endothelial cells (MBMECs). We detected glycine-responsive NMDAR channels, composed of functional GluN1, GluN2A and GluN3A subunits. Importantly, application of glycine alone, but not glutamate, was sufficient to induce NMDAR-mediated currents and an increase in intracellular Ca2+ concentrations. Functionally, glycine-mediated NMDAR activation leads to loss of BBB integrity and changes in actin distribution. Treatment of oocytes that express NMDARs composed of different subunits, with GluN1 and GluN3A binding site inhibitors, resulted in abrogation of NMDAR signaling as measured by two-electrode voltage clamp (TEVC). This effect was only detected in the presence of the GluN2A subunits, suggesting the latter as prerequisite for pharmacological modulation of NMDARs on brain endothelial cells. Taken together, our findings argue for a novel role of glycine as NMDAR ligand on endothelial cells shaping BBB integrity.
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