Functional adaptation of presynaptic chemokine receptors in EAE mouse central nervous system

Abstract

In cortical synaptosomes of Experimental Autoimmune Encephalomyelitis (EAE) mice at the early stage of disease (13 days post immunization, d.p.i.), the Regulated upon Activation Normal T cell Expressed and Secreted (RANTES, CCL5)-mediated control of [3H]D-aspartate ([3H]D-ASP) exocytosis elicited by a mild depolarizing stimulus (12 mM KCl) shifted from inhibition to facilitation. By using selective antagonists for the chemokine receptor (CCR) 1, 3, and 5 subtypes, we found that the pharmacological profile of the receptor(s) accounting for CCL5-mediated effect was unaltered when compared to control. Inasmuch, CCR protein expression was unaltered. This studies was not extended at 21 d.p.i. since, at this stage, CCL5 failed to affect [3H]D-ASP exocytosis. At 13 d.p.i., the expression of CCR proteins was largely conserved when compared to control. In spinal cord synaptosomes of EAE mice at 21 d.p.i., when presynaptic defects became evident, the [3H]D-ASP exocytosis elicited by 15 mM KCl was significantly increased when compared to control and it was significantly potentiated by 1 nM CCL5. The antagonist pharmacological profile and the western blot analysis of the CCR proteins unveiled that the receptor repertoire involved was unmodified. Differently from controls, however, the CCR1 antagonist BX513 efficiently inhibited on its own [3H]D-ASP exocytosis suggesting that this receptor could have adopted an active conformation. Altogether, our observations favor the use of CCR antagonists to the cure of neurological symptoms in patients suffering from demyelinating syndrome.

Presynaptic, release‐regulating mGlu2‐preferring and mGlu3‐preferring autoreceptors in CNS: pharmacological profiles and functional roles in demyelinating disease

“…The KCl‐evoked [ 3 H]‐ d ‐Asp overflow was dramatically reduced from synaptosomes isolated from the cortex of EAE mice at the early stage of disease (13 d.p.i. ), but it was significantly increased from nerve terminals isolated from the spinal cord of EAE mice at the acute stage of disease (21 d.p.i., Table , but see Di Prisco et al , ).…”

“…Depending on the animal model used and the brain region under study, opposite modifications of glutamate release capability were observed in selected CNS regions, indicating that glutamate impairment in MS is a complex event. In particular, increased glutamate release was detected in the spinal cord of EAE rats (Sulkowski et al , ) and mice (Di Prisco et al ., ) as well as in striatal and spinal cord nerve terminals of EAE mice (Centonze et al , ; Marte et al , ; Di Prisco et al , ), while reduced glutamate release was observed in cortical nerve endings of both mice and rats suffering from EAE (Vilcaes et al , ; Di Prisco et al , ). As for glutamate receptors, previous studies have shown that both mGlu 1/5 and mGlu 4 receptors are suitable targets of drugs for ameliorating MS symptoms (Besong et al , ; Fazio et al , , Fallarino et al , ).…”

“…As already stated, mGlu 2/3 receptor‐mediated functions mainly rely on the inhibition of the AC/cAMP pathway (Nicoletti et al ., ). Interestingly, in EAE mice, this enzymatic pathway was significantly hampered in cortical nerve endings, but not in spinal cord terminals, where, on the contrary, it was even potentiated (Di Prisco et al , ). These enzymatic impairments might be responsible for the loss of efficacy of LY379268 in the cortex and could also explain the gain in efficacy of LY379268 in controlling glutamate exocytosis from spinal cord terminals of EAE mice.…”

CCL5–Glutamate Cross-Talk in Astrocyte-Neuron Communication in Multiple Sclerosis

“…However, depending on the animal model used and the brain region under study, opposite modifications of glutamate release efficiency were observed, consistent with the view that, in demyelinating disorders, impaired glutamate transmission at active synapses is a complex event. Increased glutamate release was detected in the spinal cord of EAE rats ( 123 , 124 ) as well as in striatal and spinal cord nerve terminals of EAE mice ( 72 , 88 , 124 – 126 ), while reduced glutamate release was observed in cortical and hippocampal nerve endings of both mice and rats suffering from EAE disease ( 72 , 88 , 100 , 126 , 127 ). As to glutamate receptors, both metabotropic and ionotropic glutamate receptors (namely mGlu1/5 and mGlu4, mGlu2/3 receptors, and NMDA and AMPA receptors) control glutamate release ( 83 , 109 , 113 , 115 , 116 , 128 , 129 ).…”

“…The existence of CCR1, CCR3, and CCR5 receptor proteins in neurons was then confirmed by other groups ( 20 , 78 – 81 ), despite some discrepancies concerning their exact location (in the soma, on axonal processes and/or in nerve terminals). As to this aspect, a relevant finding was that CCR1, CCR3, and CCR5 receptor proteins exist in both human and rodent cortical nerve endings, as well as in rodent spinal cord terminals, i.e., in those parts of neuron where transmitter exocytosis occurs ( 66 , 71 , 72 ).…”