The Dual Immunoregulatory function of Nlrp12 in T Cell-Mediated Immune Response: Lessons from Experimental Autoimmune Encephalomyelitis

Abstract

Although the etiology of multiple sclerosis (MS) remains enigmatic, the role of T cells is unquestionably central in this pathology. Immune cells respond to pathogens and danger signals via pattern-recognition receptors (PRR). Several reports implicate Nlrp12, an intracellular PRR, in the development of a mouse MS-like disease, called Experimental Autoimmune Encephalomyelitis (EAE). In this study, we used induced and spontaneous models of EAE, as well as in vitro T cell assays, to test the hypothesis that Nlrp12 inhibits Th1 response and prevents T-cell mediated autoimmunity. We found that Nlrp12 plays a protective role in induced EAE by reducing IFNγ/IL-4 ratio in lymph nodes, whereas it potentiates the development of spontaneous EAE (spEAE) in 2D2 T cell receptor (TCR) transgenic mice. Looking into the mechanism of Nlrp12 activity in T cell response, we found that it inhibits T cell proliferation and suppresses Th1 response by reducing IFNγ and IL-2 production. Following TCR activation, Nlrp12 inhibits Akt and NF-κB phosphorylation, while it has no effect on S6 phosphorylation in the mTOR pathway. In conclusion, we propose a model that can explain the dual immunoregulatory function of Nlrp12 in EAE. We also propose a model explaining the molecular mechanism of Nlrp12-dependent regulation of T cell response.

Aged hind-limb clasping experimental autoimmune encephalomyelitis models aspects of the neurodegenerative process seen in multiple sclerosis

“…It has been previously reported that 2D2 + mice develop spontaneous EAE with low incidence (0 to 20%) when housed under SPF conditions (16,(23)(24)(25)(26). We observed EAE incidence to be higher in our 2D2 + colony, with ∼25% of mice developing classic EAE signs including tail and hind-limb paralysis (Table 1).…”

NLRX1 Enhances Glutamate Uptake and Inhibits Glutamate Release by Astrocytes

“…To measure the total protein expression of glutamate transporters, intracellular staining was performed (protocol modified from Gharagozloo et al 2018 and Schwarz et al 2013) [58,59]. WT and Nlrx1 -/- astrocytes were washed with phosphate-buffered saline (PBS), fixed, permeabilized, and blocked with 5% dFBS in washing buffer.…”

NLRX1 inhibits the early stages of CNS inflammation and prevents the onset of spontaneous autoimmunity

“…CNS tissue was digested with 2.5 mg/mL collagenase D (Roche Diagnostics, Indianapolis, IN, 11088866001) and 1 mg/mL DNase I (Sigma-Aldrich, St. Louis, MO, 11284932001) and filtered through a 70-μm nylon sieve as described previously [12]. Mononuclear cells were isolated by percoll (Sigma-Aldrich, St. Louis, MO) centrifugation.…”

“…T-cell proliferation was quantified using 3 H-thymidine incorporation assay and Ki67 intranuclear staining following fixation and permeabilization using Foxp3/Transcription Factor staining kit (eBioscience, San Diego, CA, 00-5523-00). Intracellular staining of cytokines was performed as previously described [12]. Sample acquisition was performed with Beckman Coulter CytoFlex and data were analyzed using CytExpert 2 software (Beckman Coulter).…”

“…NLRs regulate both innate and adaptive immune responses [4]. In the context of neuroinflammation, some NLRs such as the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing 1 (NLRP1) and NLRP3 promote the development of experimental autoimmune encephalomyelitis (EAE), a mouse model of MS [9,10], whereas anti-inflammatory NLRs such as nucleotide-binding, leucine-rich repeat containing X1 (NLRX1) and NLRP12 inhibit CNS inflammation [11,12]. NLRX1 is a recently characterized member of the NLR family that is ubiquitously expressed and uniquely localized to the mitochondria.…”