Neuroprotective effects of ex vivo-expanded regulatory T cells on trimethyltin-induced neurodegeneration in mice

Abstract

Background Trimethyltin (TMT) is a potent neurotoxicant that leads to hippocampal neurodegeneration. Regulatory T cells (Tregs) play an important role in maintaining the immune balance in the central nervous system (CNS), but their activities are impaired in neurodegenerative diseases. In this study, we aimed to determine whether adoptive transfer of Tregs, as a living drug, ameliorates hippocampal neurodegeneration in TMT-intoxicated mice. Methods CD4+CD25+ Tregs were expanded in vitro and adoptively transferred to TMT-treated mice. First, we explored the effects of Tregs on behavioral deficits using the Morris water maze and elevated plus maze tests. Biomarkers related to memory formation, such as cAMP response element-binding protein (CREB), protein kinase C (PKC), neuronal nuclear protein (NeuN), nerve growth factor (NGF), and ionized calcium binding adaptor molecule 1 (Iba1) in the hippocampus were examined by immunohistochemistry after killing the mouse. To investigate the neuroinflammatory responses, the polarization status of microglia was examined in vivo and in vitro using real-time reverse transcription polymerase chain reaction (rtPCR) and Enzyme-linked immunosorbent assay (ELISA). Additionally, the inhibitory effects of Tregs on TMT-induced microglial activation were examined using time-lapse live imaging in vitro with an activation-specific fluorescence probe, CDr20. Results Adoptive transfer of Tregs improved spatial learning and memory functions and reduced anxiety in TMT-intoxicated mice. Additionally, adoptive transfer of Tregs reduced neuronal loss and recovered the expression of neurogenesis enhancing molecules in the hippocampi of TMT-intoxicated mice. In particular, Tregs inhibited microglial activation and pro-inflammatory cytokine release in the hippocampi of TMT-intoxicated mice. The inhibitory effects of TMT were also confirmed via in vitro live time-lapse imaging in a Treg/microglia co-culture system. Conclusions These data suggest that adoptive transfer of Tregs ameliorates disease progression in TMT-induced neurodegeneration by promoting neurogenesis and modulating microglial activation and polarization.

Blocking Microglial Proliferation by CSF-1R Inhibitor Does Not Alter the Neuroprotective Effects of Adoptive Regulatory T Cells in 3xTg Alzheimer’s Disease Mice

“…Nevertheless, several challenges remain, such as the suppressive mechanism of adoptively transferred Tregs [26,27]. In previous studies, we revealed the therapeutic effects of Tregs were accompanied by microglial modulation in AD-and TMT-induced neuroinflammation models [11,14]. In the follow-up study, we sought to explore the interaction between adoptively transferred Tregs and microglia.…”

“…Aβ-specific Tregs were produced as previously described [14]. The purity of the isolated cells was analyzed using flow cytometry (Figure 2A).…”

“…Tregs protect against brain damage by limiting neuroinflammation, but their suppressive effect is dysregulated in CNS disorders [9,10]. Therefore, adoptive Treg therapy has been attempted in neurodegenerative animal models, including models of AD, Parkinson's disease (PD), atrophic lateral sclerosis, and trimethyltin (TMT)-induced neurodegeneration [11][12][13][14]. Indeed, Treg therapy has shown neuroprotective effects accompanied by inhibition of M1 microglial activation in these neurodegenerative diseases.…”

Peripheral MC1R Activation Modulates Immune Responses and is Neuroprotective in a Mouse Model of Parkinson’s Disease

“…In this study we found elevated levels of Tregs in response to NDP-MSH in MPTP + LPS treated mice. Tregs-mediated neuroprotection is reportedly a result of increased neurotrophins, reduced proinflammatory molecules, cytokines, and oxidative stress, and induced apoptosis in the M1 state of microglia (Park et al 2022 ; Gendelman and Appel 2011 ). Upon depletion of these cells, NDP-MSH neither abrogated microglia activation nor showed protective dopaminergic neuroprotection in the MPTP + LPS model of PD.…”

Peripheral MC1R activation modulates immune responses and is neuroprotective in a mouse model of Parkinson's disease

“…In this study we found elevated levels of Tregs in response to NDP-MSH in MPTP+LPS treated mice. Tregs-mediated neuroprotection is reportedly a result of increased neurotrophins, reduced proin ammatory molecules, cytokines, and oxidative stress, and induced apoptosis in the M1 state of microglia (72,73). Upon depletion of these cells, NDP-MSH neither abrogated microglia activation nor showed protective dopaminergic neuroprotection in the MPTP+LPS model of PD.…”