Investigation of Cuprizone-Induced Demyelination in mGFAP-Driven Conditional Transient Receptor Potential Ankyrin 1 (TRPA1) Receptor Knockout Mice

Abstract

Transient receptor potential ankyrin 1 (TRPA1) receptors are non-selective cation channels responsive to a variety of exogenous irritants and endogenous stimuli including products of oxidative stress. It is mainly expressed by primary sensory neurons; however, expression of TRPA1 by astrocytes and oligodendrocytes has recently been detected in the mouse brain. Genetic deletion of TRPA1 was shown to attenuate cuprizone-induced oligodendrocyte apoptosis and myelin loss in mice.In the present study we aimed at investigating mGFAP-Cre conditional TRPA1 knockout mice in the cuprizone model. These animals were generated by crossbreeding GFAP-Cre +/− and floxed TRPA1 (TRPA1 Fl/Fl ) mice. Cuprizone was administered for 6 weeks and demyelination was followed by magnetic resonance imaging (MRI). At the end of the treatment, demyelination and glial activation was also investigated by histological methods. The results of the MRI showed that demyelination was milder at weeks 3 and 4 in both homozygous (GFAP-Cre +/− TRPA1 Fl/Fl ) and heterozygous (GFAP-Cre +/− TRPA1 Fl/− ) conditional knockout animals compared to Cre −/− control mice. However, by week 6 of the treatment the difference was not detectable by either MRI or histological methods. In conclusion, TRPA1 receptors on astrocytes may transiently contribute to the demyelination induced by cuprizone, however, expression and function of TRPA1 receptors by other cells in the brain (oligodendrocytes, microglia, neurons) warrant further investigation.Cells 2020, 9, 81 2 of 13 and oxidized lipid molecules [1][2][3]. Apart from being a nocisensor for exogenous irritant compounds, it has been suggested to work as a sensor for oxidative stress [4]. Originally described to be localized on a subgroup of nociceptive primary afferent neurons [5,6], it was later revealed that TRPA1 is also expressed at lower levels by various non-neuronal cells including keratinocytes, endothelial cells and cells of the gastrointestinal mucosa [1-3,7]. More importantly, several studies have supported the presence of TRPA1 receptors in the brain on astrocytes [8][9][10], as well as oligodendrocytes [11]. A recent cell-specific transcriptome analysis of the mouse cortex revealed low level expression of TRPA1 on neurons, astrocytes, oligodendrocytes and microglia, as well [12].In astrocytes, TRPA1 receptors were implicated in both physiological and pathophysiological processes. Astrocyte TRPA1 receptors were shown to regulate resting Ca 2+ levels and modulate GABA-ergic inhibitory transmission by reducing GABA transport [8]. TRPA1 receptors on astrocytes were also suggested to play a role in long-term potentiation in the mouse hippocampus [9]. Since reactive astrocytes can contribute to the progression of neuroinflammation in neurodegenerative diseases [13,14], several workgroups, including ours, had started to investigate the role of TRPA1 in animal models of neurodegenerative diseases. Our previous study aimed at examining the role of TRPA1 in the cuprizone-induced demyelination model in mice. Cuprizone...

Transient Receptor Potential Ankyrin-1 (TRPA1) Block Protects against Loss of White Matter Function during Ischaemia in the Mouse Optic Nerve

“…The presence of TRPA1 in glial cells is a new concept, but the evidence for functional TRPA1 in both astrocytes [4,21] and OLs is growing [2,[22][23][24][25], reviewed in [26]. In astrocytes and OLs, TRPA1 activation and inhibition raises and decreases basal intracellular Ca 2+ (and Mg 2+ ) concentrations, respectively [2,21] (Figure 1e).…”

Presence of TRPA1 Modifies CD4+/CD8+ T Lymphocyte Ratio and Activation

“…Emerging evidence indicates that TRPA1 is a molecular ionotropic receptor mediator [1] of the neuro-immuno-epithelial interface network [2][3][4] in the lung [5], skin [6] and gut [3,7,8] acting as a "pro-inflammatory hub" [9][10][11]. Absence, dysfunction or inhibition of TRPA1 has been shown to decrease inflammation-related symptoms of psoriasis [6,12,13], rheumatoid arthritis [14], actinic keratosis [15], atopic dermatitis [16][17][18], multiple sclerosis [19][20][21][22][23][24], and its function has been proposed to contribute to a variety of interrelated sensory and inflammatory processes such as inflammatory hyperalgesia [25,26], colitis [7,27], airway inflammation [28,29] and even oxidative stress storm syndromes in COVID-19 [30,31].…”

The role of the astrocytic and microglial aryl hydrocarbon receptor in CNS demyelination

“…In the present study, mice lacking AhR in GFAP-positive astrocytes displayed no change in cuprizoneinduced pathology after 6 weeks of toxic demyelination. This is in accordance with findings by Kriszta et al who investigated mGFAP-driven conditional deletion of the TRPA1 receptors, which are non-selective cation channels controlling resting Ca 2+ levels and inhibitory synapses (Kriszta et al 2019;Shigetomi et al 2011). While no significant differences could be observed after 6 weeks, they detected significantly less demyelination between the 3 rd and 5 th week of cuprizone treatment.…”