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Muramyl Dipeptide Administration Delays Alzheimer’s Disease Physiopathology via NOD2 Receptors

ABSTRACT: Alzheimer’s disease (AD) is the most common form of dementia in the world. The prevalence is steadily increasing due to an aging population and the lack of effective treatments. However, modulation of innate immune cells is a new therapeutic avenue, which is quite effective at delaying disease onset and improving cognitive decline. Methods: We studied the effect of the NOD2 receptor ligand muramyl dipeptide (MDP) on the modulation of the innate immune cells, namely patrolling monocytes and microglia. We administrated MDP once a week for 3 months in an APPswe/PS1 mouse model in both sexes. We started the treatment at 3 months before plaque formation and evaluated its effects at 6 months. Results: We showed that the MDP injections delay cognitive decline in both sexes via different mechanisms and protect the blood brain barrier (BBB). In males, MDP triggers the sink effect from the BBB, leading to a diminution in the amyloid load in the brain. This phenomenon is underlined by the increased expression of phagocytosis markers such as TREM2, CD68, and LAMP2 and a higher expression of ABCB1 and LRP1 at the BBB level. The beneficial effect seems more restricted to the brain in females treated with MDP, where microglia surround amyloid plaques and prevent the spreading of amyloid peptides. This phenomenon is also associated with an increase in TREM2 expression. Interestingly, both treated groups showed an increase in Arg-1 expression compared to controls, suggesting that MDP modulates the inflammatory response. Conclusion: These results indicate that stimulation of the NOD2 receptor in innate immune cells is a promising therapeutic avenue with potential different mechanisms between males and females.

SUBMITTER: Piec P

PROVIDER: S-EPMC9321587 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We have begun to approach gd T cells more as prospective innate cells than as conventional T cells. Recent results indicated that purified gd T cells are primed directly in response to pathogen associated molecular patterns (PAMPs) to better respond to secondary signals and increase expression of chemokine and activation-related genes. In microarray and real time PCR analyses of RNA derived from bovine and human gd T cells, transcripts encoding Nod2 were repeatedly amplified. Nod2 is the intracellular receptor for muramyl dipeptide (MDP), a subunit of PGN, functions in regulating innate activities, and was thought to be expressed primarily in APCs. Given our repeated detection of Nod2 transcripts in gd T cells, the specific direct response of gd T cells to MDP was analyzed by microarray, real time PCR, proteome array and in a functional priming assay. The results indicate a subtle activation in response to MDP akin to priming, and suggest a unique mechanism for differential gene expression. Experiment Overall Design: PBLs from calf 129 were stained with GD3.8 directly conjugated to FITC, washed, and sorted on a Vantage SE cell sorter (BD Immunocytometry Systems) as previously described. PBLs from calves 150 and 151 were stained with GD3.8, and anti-Mouse IgG magnetic beads and sorted with MACS magnetic bead system (Miltenyi Biotec) as previously described to a purity of >98%. Sorted cells were rested overnight, stimulated for 4 hours then lysed in Buffer RLT and genomic DNA sheared using Qiashredder columns then frozen at -80oC. RNA was extracted following the manufacturerâs protocol for RNeasy (Qiagen) column purification, assessed on a Bioanalyzer 2100 (Agilent Technologies), and amplified using the Affymetrix One-cycle protocol with approximately 1.7micrograms of total RNA as described in the GeneChipÂ® Expression Analysis Technical Manual (June 2004). Hybridizations to GenechipÂ® Bovine Genome Arrays (Affymetrix) were performed with 15 mg biotin labeled cRNA. Washing and staining was performed in the GeneChipÂ® Fluidics Station 450 using the Midi_euk2v3 protocol. Chip scans were performed on the Affymetrix GeneChipÂ® Scanner 3000. GeneChipÂ® Operating Software (GCOS v.1.1, Affymetrix) 19;20 was used for data collection.

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Muramyl Dipeptide Administration Delays Alzheimer’s Disease Physiopathology via NOD2 Receptors

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