Downregulation of CD73/A2AR-Mediated Adenosine Signaling as a Potential Mechanism of Neuroprotective Effects of Theta-Burst Transcranial Magnetic Stimulation in Acute Experimental Autoimmune Encephalomyelitis

Abstract

Multiple sclerosis (MS) is a chronic neurodegenerative disease caused by autoimmune-mediated inflammation in the central nervous system. Purinergic signaling is critically involved in MS-associated neuroinflammation and its most widely applied animal model—experimental autoimmune encephalomyelitis (EAE). A promising but poorly understood approach in the treatment of MS is repetitive transcranial magnetic stimulation. In the present study, we aimed to investigate the effect of continuous theta-burst stimulation (CTBS), applied over frontal cranial bone, on the adenosine-mediated signaling system in EAE, particularly on CD73/A2AR/A1R in the context of neuroinflammatory activation of glial cells. EAE was induced in two-month-old female DA rats and in the disease peak treated with CTBS protocol for ten consecutive days. Lumbosacral spinal cord was analyzed immunohistochemically for adenosine-mediated signaling components and pro- and anti-inflammatory factors. We found downregulated IL-1β and NF- κB-ir and upregulated IL-10 pointing towards a reduction in the neuroinflammatory process in EAE animals after CTBS treatment. Furthermore, CTBS attenuated EAE-induced glial eN/CD73 expression and activity, while inducing a shift in A2AR expression from glia to neurons, contrary to EAE, where tight coupling of eN/CD73 and A2AR on glial cells is observed. Finally, increased glial A1R expression following CTBS supports anti-inflammatory adenosine actions and potentially contributes to the overall neuroprotective effect observed in EAE animals after CTBS treatment.

Intermittent Theta Burst Stimulation Ameliorates Cognitive Deficit and Attenuates Neuroinflammation via PI3K/Akt/mTOR Signaling Pathway in Alzheimer’s-Like Disease Model

“…Attenuated neuronal death following iTBS was accompanied by a reduction in pro-inflammatory factors and an increase in anti-inflammatory factors. Anti-inflammatory effects of rTMS have been demonstrated in neurological disorders and animal models ( Aftanas et al, 2018 ; Hong et al, 2020 ; Clarke et al, 2021 ; Dragić et al, 2021c ). Furthermore, rTMS was found to inhibit the polarization of astrocytes toward neurotoxic (A1-like) phenotype ( Hong et al, 2020 ), which are also present in TMT-induced neurodegeneration ( Dragić et al, 2021a , b ).…”

Expression of functionally distinct ecto‐5′‐nucleotidase/CD73 glycovariants in reactive astrocytes in experimental autoimmune encephalomyelitis and neuroinflammatory conditions in vitro

“…Several studies conducted in experimental autoimmune encephalomyelitis (EAE) have demonstrated significant upregulation of eN/CD73 in spinal cord astrocytes (Dragić et al, 2021; Lavrnja et al, 2009) and the appearance of an alternative eN/CD73 variant(s) during the symptomatic phase of the disease (Jakovljevic et al, 2017; Lavrnja et al, 2015). Since eN/CD73 has no structural isoforms in rat, the variants that are identical at the protein, mRNA, and cDNA levels must represent glycoforms that differ in their carbohydrate content.…”

“…Within 15–20 years, the disease takes a progressive course with worsening neurological symptoms due to irreversible demyelination and axonal loss. Markedly lower autoimmune cell recruitment during the progressive phase of MS and the profound activation of microglia suggest a crucial contribution of resident glial cells to irreparable neurodegeneration in diffuse areas of the brain and spinal cord (Keegan & Noseworthy, 2002; Dragic et al, 2021). In active MS lesions, microglial cells lose their homeostatic signature (Zrzavy et al, 2017), assume an amoeboid form, and release proinflammatory mediators, including tumor necrosis factor‐α (TNF‐α), interleukin (IL)‐1β, IL‐6, interferon (IFN)‐γ, and NO, which damage brain tissue.…”

Clinical application of transcranial magnetic stimulation in multiple sclerosis

“…Researchers showed that cTBS acting on the EAE model (animal model of MS as mentioned earlier) can downregulate the pro-inflammatory mediator interleukin-1β (IL-1β) and upregulate the anti-inflammatory cytokine interleukin-10 (IL-10), thus playing an anti-inflammatory role. At the same time, cTBS can effectively improve the changes of adenosine signal transduction and weaken the reaction state of microglia and astrocytes in the EAE model, showing a strong potential for protection and repair in the treatment of the model ( 39 ). What is more, inflammatory injury in patients with MS can lead to abnormal cortical plasticity.…”