Collagen VI: Role in synaptic transmission and seizure-related excitability

Collagen VI (Col-VI) is an extracellular matrix protein primarily known for its bridging role in connective tissues that has been suggested to play a neuroprotective role. In the present study we report increased mRNA and protein expression of Col-VI in the hippocampus and cortex at a late stage of epileptogenesis in a post-status epilepticus (SE) model of epilepsy and in brain tissue from patients with epilepsy. We further present a novel finding that exposure of mouse hippocampal slices to Col-VI augments paired-pulse facilitation in Schaffer collateral-CA1 excitatory synapses indicating decreased release probability of glutamate. In line with this finding, lack of Col-VI expression in the knock-out mice show paired-pulse depression in these synapses, suggesting increased release probability of glutamate. In addition, we observed dynamic changes in Col-VI blood plasma levels in rats after Kainate-induced SE, and increased levels of Col-VI mRNA and protein in autopsy or postmortem brain of humans suffering from epilepsy. Thus, our data indicate that elevated levels of ColVI following seizures leads to attenuated glutamatergic transmission, ultimately resulting in less overall network excitability. Presumably, increased Col-VI may act as part of endogenous compensatory mechanism against enhanced excitability during epileptogenic processes in the hippocampus, and could be further investigated as a potential functional biomarker of epileptogenesis, and/or a novel target for therapeutic intervention.