Transgenic rice seeds expressing altered peptide ligands against the M3 muscarinic acetylcholine receptor suppress experimental sialadenitis-like Sjögren’s syndrome

Abstract

Objective: We previously reported that Rag1^−/− mice inoculated with splenocytes from M3 muscarinic acetylcholine receptor (M3R) knockout mice immunized with an M3R peptide mixture developed sialadenitis-like Sjögren’s syndrome (M3R-induced sialadenitis [MIS]). We also found that intravenous administration of altered peptide ligand (APL) of N-terminal 1 (N1), which is one of the T-cell epitopes of M3R, suppressed MIS. In this study, we aimed to evaluate the suppressive ability and its mechanisms of rice seeds expressing N1-APL7 against MIS.

Methods: Rice seeds expressing N1 and N1-APL7 were orally administered to MIS mice for 2 weeks. The changes in saliva flow and sialadenitis (salivary gland inflammation) were analyzed. The M3R-specific T-cell response in the spleen and the expression of regulatory molecules in the cervical lymph nodes and mesenteric lymph nodes were also analyzed.

Results: Oral administration of N1-APL7-expressing rice seeds significantly recovered reduction in saliva flow and suppressed sialadenitis when compared with treatment with nontransgenic rice seeds and N1 rice seeds. IFNγ production from M3R-reactive T cells tended to decline in the N1-APL7 rice-treated group as compared with those in the other groups. In the N1-APL7 rice-treated group, the mRNA expression levels of Foxp3 in the cervical-lymph-node CD4⁺ T cells were higher than those in the other groups.

Conclusion: Oral administration of N1-APL7-expressing rice suppressed MIS via suppression of M3R-specific IFNγ and IL-17 production and via enhancement of regulatory molecule expression.

Key messages

• We generated N1-peptide- or N1-APL7-expressing rice seeds. Oral administration of N1-APL7-expressing rice seeds significantly recovered the reduction of saliva flow and suppressed sialadenitis via the suppression of M3R specific IFNγ and IL-17 production and via enhancement of regulatory T (Treg) cells.

Keywords:

• Altered peptide ligands
• autoimmune disease
• M3 muscarinic acetylcholine receptor
• rice seeds
• Sjögren’s syndrome

Acknowledgements

We thank F. Miyamasu of the Medical English Communications Center, University of Tsukuba, for her critical review of the manuscript.

Conflict of interest

None.