Muscarinic receptor subtypes as potential targets to modulate oligodendrocyte progenitor survival, proliferation, and differentiation

Abstract

Acetylcholine (ACh) is a major neurotransmitter but also an important signaling molecule in neuron-glia interactions. Expression of ACh receptors has been reported in several glial cell populations, including oligodendrocytes (OLs). Nonetheless, the characterization of muscarinic receptors in these cells, as well as the description of the cholinergic effects at different stages of OL development, is still incomplete. In this study, we characterized the pattern of expression of muscarinic receptor subtypes in primary cultures of rat oligodendrocyte progenitor cells (OPC) and mature OLs, at both mRNA and protein levels. We found that muscarinic receptor expression is developmentally regulated. M1, M3, and M4 receptors were the main subtypes expressed in OPC, whereas all receptor subtypes were expressed at low levels in mature OLs. Exposure of OPC to muscarine enhanced cell proliferation, an effect mainly due to M1, M3, and M4 receptor subtypes as demonstrated by pharmacological competition with selective antagonists. Conversely, M2 receptor activation impaired OPC survival. In line with the mitogenic activity, muscarinic receptor activation increased the expression of platelet derived growth factor receptor α. Muscarine stimulation increased CX32 and myelin basic protein expression, left unaffected that of myelin proteolipid protein (PLP), and decreased member of the family of epidermal growth factor receptor (EGFR) ErbB3/ErbB4 receptor expression indicating a predominant role of muscarinic receptors in OPC. These findings suggest that ACh may contribute to the maintenance of an immature proliferating progenitor pool and impair the progression toward mature stage. This hypothesis is further supported by increased expression of Notch-1 in OL on muscarinic activation.

M2 muscarinic receptors inhibit cell proliferation in human glioblastoma cell lines

“…To confirm the involvement of M2 receptor subtype in the inhibition of cell growth, the M2 antagonist gallamine was used at the concentration (1 μM) comparable with that of its inhibition constant (Ki) reported for rat OLs (see De Angelis et al, 2012). As indicated in Fig.…”

“…To confirm the involvement of M2 receptor subtype, 15 × 10 4 cells were plated on 35 mm dishes and maintained for 72 h either in the absence of M2 agonist, or in the presence of arecaidine 100 μM or in the presence of arecaidine 100 μM plus 1 μM of M2 antagonist gallamine (see De Angelis et al, 2012).…”

M2 muscarinic receptors inhibit cell proliferation and migration in urothelial bladder cancer cells

“…Schwann cells, oligodendrocytes and glioblastoma cells). 28,[36][37][38] In the light of the above findings and given that the expression of M2 receptors is associated with the urothelial tumor grade in vivo, we aimed to investigate the effects of the M2 agonist Arecaidine on the T24 cell line.…”

Glial Cell Plasticity During Development and Myelinopathies

“…However, its success for accelerating remyelination following a demyelinating insult in mice (Mei et al, 2014) is likely due to its anticholinergic effects of antagonizing M1/M3 muscarinic acetylcholine receptors (Harlow et al, 2015). Oligodendrocytes have been shown to express M1 -M4 muscarinic receptor subtypes; however, OPCs demonstrate greater expression of M3, M1 and M4 subtypes whereas in mature oligodendrocytes, the expression of M1, M3 and M4 subtypes is down-regulated (De Angelis et al, 2012). Thus, oligodendrocyte differentiation is inhibited when muscarinic receptors are activated (De Angelis et al, 2012;Harlow et al, 2015).…”

“…Oligodendrocytes have been shown to express M1 -M4 muscarinic receptor subtypes; however, OPCs demonstrate greater expression of M3, M1 and M4 subtypes whereas in mature oligodendrocytes, the expression of M1, M3 and M4 subtypes is down-regulated (De Angelis et al, 2012). Thus, oligodendrocyte differentiation is inhibited when muscarinic receptors are activated (De Angelis et al, 2012;Harlow et al, 2015). Because of this, enhanced remyelination by antimuscarinic drugs like clemastine is proposed to occur by impacting oligodendrocyte differentiation directly (Kremer et al, 2015).…”