Fig. 5

SCFA-dependent GPR43 signaling confers GI GVHD protection through the ERK–NLRP3 pathway. B6 WT and Gpr43^−/− mice received BMT from syngeneic or allogeneic donors. a Representative immunoblots and densitometric analysis of cleaved caspase 1 and cleaved IL-18 normalized to the presence of β-actin in IECs (CD326⁺) from allogeneic recipients 14 days after BMT (n = 4–5 each, two-tailed Mann–Whitney U test). b Serum IL-18 levels at day 7 and 14 after BMT (n = 4 WT, n = 5 Gpr43^−/−, two-tailed unpaired t-test). c Representative immunoblots and densitometric analysis of cleaved caspase 1 and cleaved IL-18 at day 14 after BMT in IECs (CD326⁺) from allogeneic recipients. Mice were treated with vehicle or propionate (15 mg kg⁻¹ per day) from day 0 (n = 4 WT, n = 3 Gpr43^−/−, two-tailed Mann–Whitney U test). d Serum IL-18 levels from allogeneic recipients treated with vehicle or propionate (15 mg kg⁻¹ per day) at day 7 and 14 after BMT (n = 5 WT each, n = 4 Gpr43^−/− each, two-tailed unpaired t-test). e Immunohistochemical staining of IL-18 in colon sections from WT B6 and Gpr43^−/− recipients 14 days after BMT treated with vehicle or propionate (15 mg kg⁻¹ per day) from day 0 (n = 3–5 each). f IL-22 levels in serum, homogenized tissues from syngeneic and allogeneic recipients at day 14 after BMT (n = 6 WT syn, n = 4 Gpr43^−/− syn, n = 5 WT allo, n = 10 Gpr43^−/− allo, two-tailed unpaired t-test). g WT B6 and Gpr43^−/− mice received oral administrations of vehicle or propionate (15 mg kg⁻¹ per day) for 3 days. Representative immunoblots and densitometric analysis of phosphorylated ERK normalized to total ERK in IECs (CD326⁺) after treatment (n = 4 WT each, n = 3 Gpr43^−/− each, two-tailed Mann–Whitney U test). h Colon explants from WT B6 mice were pretreated with U0126 (10 μM) for 30 min. Then tissues were primed with LPS (0.1 μg per ml) for 2 h and activated with butyrate or propionate (1 mM) for 2 h. Supernatants were assayed for IL-18 by ELISA (n = 3 each, two-tailed unpaired t-test). Data are representative of two to three experiments. *P < 0.05, **P < 0.01, ***P < 0.001, error bars show the mean ± s.e.m.