Modulation of network activity and induction of homeostatic synaptic plasticity by enzymatic removal of heparan sulfates

Abstract

Heparan sulfates (HSs) are complex and highly active molecules that are required for synaptogenesis and long-term potentiation. A deficit in HSs leads to autistic phenotype in mice. Here, we investigated the long-term effect of heparinase I, which digests highly sulfated HSs, on the spontaneous bioelectrical activity of neuronal networks in developing primary hippocampal cultures. We found that chronic heparinase treatment led to a significant reduction of the mean firing rate of neurons, particularly during the period of maximal neuronal activity. Furthermore, firing pattern in heparinasetreated cultures often appeared as epileptiform bursts, with long periods of inactivity between them. These changes in network activity were accompanied by an increase in the frequency and amplitude of miniature postsynaptic excitatory currents, which could be described by a linear up-scaling of current amplitudes. Biochemically, we observed an upregulation in the expression of the glutamate receptor subunit GluA1, but not GluA2, and a strong increase in autophosphorylation of a and b Ca 2þ /calmodulin-dependent protein kinase II (CaMKII), without changes in the levels of kinase expression. These data suggest that a deficit in HSs triggers homeostatic synaptic plasticity and drastically affects functional maturation of neural network.

Heparin/heparan sulfates bind to and modulate neuronal L-type (Cav1.2) voltage-dependent Ca2+ channels

“…Hippocampal cells were dissociated from embryonic mice (on embryonic day 18) and plated with a high initial density of approximately 3000 cells/mm 2 on 6-well microelectrode arrays (Multi Channel Systems GmbH, Germany) pre-treated with polyethyleneimine (Sigma P3143) and laminin (Sigma L2020), as previously described (Korotchenko et al, 2014).…”

“…using neurons derived from the same culture preparations) to APV and diltiazem groups. A subset of control and heparinase data have been analysed previously (Korotchenko et al, 2014).…”

“…To analyze the neural network activity, we recorded spontaneous bursting activity for 15 min. All of the signal analyses and statistics were performed using custom made software Spycode (Matlab®) (Bologna et al, 2010), as described elsewhere (Korotchenko et al, 2014). Briefly, the detection of bursts was based on the detection of peak in inter-spike interval histogram.…”

An Advanced 3D Printed Design of the Hybrid Infusion-Multielectrode Recording System for Local Field Potential and Single Unit Acquisition and Intrabrain Drug Delivery in Freely Moving Mice

“…The improved HIME system can be used for experiments involving injection of extracellular proteases, such as matrix metalloproteinase MMP-9 [2] or enzymes that digest particular glycans, such as endoneuraminidase (EndoNF) for polysialic acid [3], chondroitinase ABC for chondroitin sulfates [4] and heparinase for heparan sulfates [5]. The functions of these and other carbohydrates carried by cell adhesion and extracellular matrix molecules have been mostly studied in vitro [6,7], and we anticipate that our HIME system will facilitate translation of in vitro insights into mechanistic in vivo studies.…”

Brain circuitry outside the synaptic cleft

“…Morawski et al [3] present their recent evidence that tenascin-R promotes assembly of the perineuronal nets through the clustering of aggrecan and demonstrate that it is possible to compensate a genetic deficiency in an ECM molecule by pharmacological intervention. In another experimental research paper, Korotchenko et al [4] report that the enzymatic removal of heparan sulfatescarried by a number of extracellular matrix (ECM) molecules-induces homeostatic synaptic plasticity and epileptiform network activity. A research study by Klueva et al [5] proposes that a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor mobility on aspiny neurons, in contrast to pyramidal cells, depends on intracellular Ca 2þ signalling rather than on the local ECM.…”