In this project, we identified differential genes co-expressed by intestinal and CD4+ T cells in PD patients. We classified miRNAs and their regulated mRNAs and concluded that hsa-miR-3180-3p-regulated CBX8, TP73, BICDL1, GPSM1 are involved in affecting T cell survival; hsa-miR-20a-3p-regulated PEG10, TPM2, NECTIN4, OTUD1, NEK9, PGM3, POU2AF1, MAP1B, ASNS, RAPH1, PLXND1 are involved in influencing T cell differentiation and infiltration; hsa-miR-1281-regulated JPT2, MPZ, SLC43A2, SIGLEC9, NCKAP1, ZNF556 are involved in affecting T cell infiltration; hsa-miR-574-5p-regulated RPH3A, EFNB1, TBC1D16, SEMA6C, CRISPLD2, GPR37L1, FOSL1, ADAT2 are involved in affecting T cell viability and differentiation.
T cell activation and infiltration are crucial for the development of neurodegenerative diseases such as Parkinson's disease. It has been shown that overexpression of α-synuclein in vivo induces elevated expression of major histocompatibility complex II (MHCII) and increased proliferation of CD4+ T cells. This suggests that α-synuclein may act as an antigen to elicit an immune response. However, increasing monomeric α-synuclein expression alone does not induce the immune response, and experiments have shown that the immune response acts only on aggregated α-synuclein. When α-synuclein interacted with microglia and migrated to the lysosome, α-synuclein alone did not activate microglia or elicit an inflammatory response, and CD4+ T cells had to be added to α-synuclein-treated microglia to elicit a strong immune response, suggesting that α-synuclein triggers the immune response The involvement of CD4+ T cells is crucial in the process of the α-synuclein-triggered immune response[2]. In our results, has-miR-3180-3p-regulated CBX8 is involved in cellular communication and immune response regulation and affects CD4+ T cell depletion[7]; has-miR-3180-3p-regulated GPSM1, which encodes the activator of G-protein signalling 3 (AGS3), regulates G-protein signalling in the immune system and thus regulates the activation process of T cells[8]; has-miR-20a-3p-regulated aberrant expression of PEG10 increased T cell size and promoted T cell proliferation and infiltration[9]; has-miR-20a-3p-regulated TPM2 was significantly and negatively correlated with the degree of CD8+ T cell infiltration[10]; the mutation of PGM3 which regulated by hsa-miR-20a-3p have recently been shown to lead to disorders of glycosylation, lymphopenia and impairment in T cell proliferation[11]; has-miR-1281-regulated NCKAP1 is significantly associated with the level of T cell infiltration[12]. The above mRNAs are involved in T-cell activation and infiltration, and changes in the expression of these mRNAs produced under miRNA regulation may lead to impaired T-cell activation and reduced infiltration, which may eventually lead to an immune response by T cells absent of α-synuclein-activated microglia, and the inability of microglia to clear α-synuclein-expressing neurons in a timely manner. This may lead to the spread of α-synuclein, with undesirable consequences; alternatively, altered mRNA expression may also lead to excessive activation and infiltration of T cells, resulting in an excessive immune response by microglia, clearing healthy neurons and advancing the pathogenesis of Parkinson's disease.
Different differentiation outcomes of T cells play a crucial role in the development of neurodegenerative diseases such as Parkinson's disease. For example, when CD4+ T cells differentiate into TH1 and TH17 cells will cause damage to dopaminergic neuronal cells, whereas differentiation into TH2 and Treg cells protects neurons. hsa-miR-20a-3p-regulated OTUD1 is a deubiquitinase that drives (Notch1770-ICD) NICD signaling, the signal could promote Th17 and Th1 cell differentiation and function[13]. Signalling (Sema) 4A is a transmembrane glycoprotein; Sema4A has a key role in regulating Th1 and Th2 differentiation. PlexinD1, regulated by hsa-miR-20a-3p, is a receptor for Sema4A, and PlexinD1 induces differentiation of T cell into TH1 cell while reducing differentiation into Th2 and Th17, and Sema4A- PlexinD1 signalling acts as a negative regulator of Th1 differentiation but is also a key mediator of Th2 and Th17 differentiation, suggesting that dysregulation of this axis may be implicated in the pathogenesis of CD4+ T cell-mediated disease[14]. Has-miR-574-5p-regulated EFNB1 is highly expressed in Th1, and Th17 cells, and T cells expressing EFNB1 are highly expressed in multiple sclerosis (MS) lesions found in immune cell infiltration. It has been shown that EFNB1 expression is associated with Th-cell differentiation and migration to sites of inflammation[15]. Aberrant expression of these mRNAs leads to differentiating CD4+ T cells into TH1 and TH17. It has been reported that M1-type microglia may act on TH1 and TH17 cells and activated TH1 and TH17 cells in turn, keep microglia M1-type through IFN-γ production, M1-type microglia release NO and O2, and these oxidative stress (OS) compounds damage dopaminergic neurons, M1-type microglia also release inflammatory factors (e.g. INF-α and IL-1β) that exacerbate inflammatory responses[3]. These mRNAs, which regulate the differentiation of T cells to TH1 and TH17, are abundantly expressed, exacerbating the neuroinflammatory response of M1 microglia and advancing the pathogenesis of neurodegenerative diseases such as Parkinson's disease.
In addition, has-miR-20a-3p-regulated Pou2af1 mutations lead to impaired T cells, such as impairment in cytokine production and T follicular helper (Tfh) differentiation[16]. Has-miR-20a-3p-regulated MAP1B upregulation leads to a lower proportion of plasma cells, CD8+ T cells and T cell follicular helper cells, suggesting that MAP1B may be involved in regulating T cell differentiation[17]. It has been reported that asparagine synthetase (Asns), whose expression peaks in effector T cells, may determine the outcome of T cell differentiation, leading to a decrease in the differentiation of TH2 and Treg cells[18]. In contrast, in the MPTP-induced PD immunoprotective model, firstly, TH2 and Treg cells release IL-4, IL-10 and TGF-β to maintain microglia in a neuroprotective M2 phenotype, and secondly, Treg cells inhibit microglial activation and release of ROS induced by misfolded α-synuclein. TH2 and Treg cells may also protect neurons through cell contact mechanisms or the release of neurotrophic factors such as BDNF. The damaged neurons themselves also have mechanisms that may cause M2 microglia to emerge or release chemokines to recruit more TH2 and Treg cells[3]. The expression of these mRNAs, which regulate the differentiation of T cells to TH2 and Treg cells, may be reduced when the above mRNAs are regulated by miRNAs, making microglia unable to maintain the M2 phenotype and with reduced neuroprotective capacity. the different differentiation outcomes of T cells have significant implications for neurodegenerative diseases, and therefore these mRNAs regulating T cell differentiation have great clinical potential as key targets for the treatment of diseases. great clinical potential.
We believe that biological processes such as activation and differentiation of T cells in the gut are closely related to the intestinal flora, that the intestinal flora can maintain a delicate balance between pro-inflammatory and anti-inflammatory mechanisms, and that specific members of the community can enhance the production of anti-inflammatory Treg or pro-inflammatory T helper cells 17 (TH17). In addition to the intestinal flora itself, its metabolites also influence the activation, differentiation and other important biological processes of T cells in the intestine. The metabolic by-products of the flora can be sensed by immune system cells and affect the balance between pro-inflammatory and anti-inflammatory cells. It has been reported that short-chain fatty acid (SCFA) butyrate produced by symbiotic microorganisms during starch fermentation in the mouse intestine promotes the extracellular production of Treg cells. In addition to butyrate, peripheral nascent Treg cell production was also enhanced by propionate, another microbial source of SCFA. These results suggest that flora metabolites mediate communication between the symbiotic microbiota and the immune system, affecting the balance between pro-inflammatory and anti-inflammatory mechanisms. However, evidence for specific factors triggering intestinal T-cell activation and differentiation remains to be explored[19].
Finally, our analysis focuses on constructing a network between miRNA and mRNA of intestinal CD4+T cells in PD and further refines the molecular targets of T cell activation, differentiation and other effects to point the way to mechanistic studies for T cell-mediated progression of Parkinson's disease.