No abstract

Inflammation and oxidative stress play critical roles in PD. Moreover, T cell-mediated immunity regulates innate immunity to control or exacerbate neuroinflammation. We have previously shown in the MPTP mouse model that adoptive transfer of effector T cells (Teffs) which recognize nitrated α-synuclein (N-α-syn) as non-self exacerbates microglial-mediated neuroinflammation with amplified dopaminergic neurodegeneration. The specific mechanisms by which these Teffs modulate neurodegeneration remain enigmatic. However, increasing evidence suggests neurotoxic inflammatory activities have a profound effect on the pathogenesis of PD. Herein, we report on the generation and long-term culture of a N-α-syn specific CD4+ Teff line that induces increased production of reactive nitrogen species from microglia and also intensifies the loss of tyrosine hydroxylase+ (TH+) neurons of MPTP-intoxicated mice. Flow cytometric analysis showed the Teffs line exhibited very distinct expression of CD3 and CD4 cell surface markers and intracellular IL-17a cytokine, suggestive of characteristics consistent with a Th17 cell. Co-culture of the Teffs with a dopaminergic cell line significantly increased cell death of dopaminergic cells in comparison to controls. Lastly, adoptive transfer of the Teffs line to MPTP-intoxicated mice increased the loss of TH+ neurons. Together, these results support the notion that Teffs may play a pivotal role in the progression of neurodegeneration in PD. Further investigation of the mechanisms behind the exacerbation of neurodegeneration caused by Teffs has the potential to advance therapeutic strategies that target neurotoxic mechanisms to attenuate neuroinflammation and ameliorate neuronal loss in PD.

We have previously shown in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model that T cell-mediated immunity regulates innate immunity to exacerbate neuroinflammation. Effector T cells that recognize nitrated α-synuclein (N-α-syn) as non-self, increase reactive myeloid microglia and inflammatory mediators with prolonged progression and increased dopaminergic neurodegeneration within the substantia nigra (SN) of MPTP treated mice. This study focuses on the generation of an N-α-syn specific CD4+ T cell line with the ability to increase release of reactive nitrogen species (RNS) from myeloid lineage cells and also intensify the loss of tyrosine hydroxylase (TH) expressing dopaminergic neurons within the SN of MPTP intoxicated mice. Flow cytometric analysis showed the T cell line exhibited very distinct expression of CD3, CD4 and IL-17a, moderate staining for CD146, yet very little expression of CD8 and FoxP3. Co-culture of the T cells with N-α-syn and BV-2 cells increased RNS production of BV-2 cells by 150% compared to controls. Lastly, adoptive transfer of the T cell line to MPTP intoxicated mice exacerbated the loss of TH+ dopaminergic neurons by 63% compared to controls. Together, these results support the notion that effector T cells specific for N-α-syn increase oxidative stress as measured by RNS release from reactive myeloid microglia, increase the loss of TH+ neurons, and thus may play a pivotal role in the tempo and progression of Parkinson’s disease.