微生物・細胞内共生現象の解明とその破綻に起因する日和見感染発症機構の解析

2020 Fiscal Year Research-status Report

• Project/Area Number: 19K10088
• Research Institution: Hiroshima University
• Principal Investigator: 高橋 一郎 広島大学, 医系科学研究科(歯), 教授 (20206791)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 微生物・細胞内共生 / macrophage / S. maltophilia / smlt2713 / IL-10 / 粘膜免疫

Outline of Annual Research Achievements

Interactions between the microbiota and the mucosal immune system are absolutely important in shaping mucosal immune responses. It is becoming clear that specific microbes influence specific lymphoid and non-lymphoid populations, for example commensal bacteria survive within dendritic cells in Peyer’s patches and enhance mucosal IgA responses. We showed that Stenotrophomonas maltophilia is constitutively present in vivo in colonic lamina propria macrophages but not in lymphoid-tissue resident macrophages. Clinically isolated S. maltophilia enter bone marrow-derived macrophages (BMDMs) in vitro and persistent colonization increases mitochondrial respiration and IL-10 production. Colonization by S. maltophilia is impaired by IL-10 deficiency. The bacteria secrete a 25-KDa protein encoded by smlt2713. Expression of smlt2713 in BMDMs induces IL-10 production. Bacteria deficient in smlt2713 show reduced colonization and IL-10 production. In vivo, pre-transfer of smlt2713-transduced BMDMs protects against chronic enterocolitis. This year we noticed mTOR-HIF1-alpha mediated metabolic re-programing of macrophages by smlt2713 should be important for the persistent colonization of S. maltophilia within colonic macrophages.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

This year we evaluated how smlt2713 modulates/alters the metabolic/nutritional demand of colonic macrophages for the persistent colonization by S. maltophilia at the molecular levels. From the in vitro study, we observed that (1) increase of cytosol phosphorylated mTOR/nuclear HIF1-alpha expression within smlt2713 exposed BMDMs. We further observed by utilizing Seahorse flux analyzer that (2) moderate reduction of aerobic glucose oxidation dependent mitochondrial OCR in smlt2713 exposed BMDM, (3) severe reduction of FAO dependent mitochondrial OCR in smlt2713 exposed BMDM, and (4) increase of aerobic glycolysis (lactate production dependent ECAR) in smlt2713 exposed BMDM. In addition, flow cytometric analysis showed slight increase of cytosol lipid droplet (TAG accumulation) in smlt2713 exposed BMDM. From these results, we speculate that while host macrophage is more likely to utilize carbohydrate for energy source, S. maltophilia are likely to utilize host derived lipid for their symbiotic co-habitation.

Strategy for Future Research Activity

We should do the following experiments 2021.
1. How S. maltophilia utilize host derived lipid for their long-term persistent colonization.
2. How HIF1-alpha reduces mitochondrial FAO, we will focus on CPT-1 alpha, a rate limiting component of mitochondrial FAO, and eventually leading to lipid accumulation within BMDMs.
3. How smlt2713-mTOR-HIF1-alpha signal modulates BMDM mitochondria function for the persistent symbiotic colonization by S. maltophilia.
4. Finally, we will integrate these metabolic reprograming function of smlt2713 into the in vivo bacterial infection model by utilizing LPS induced steatotic hepatitis.

Causes of Carryover

令和2年度の物品費の予算執行の結果、2055円の繰越金が生じてしまったが、この端数金額は令和3年度の物品費として執行する。