Anti-inflammatory properties of the short-chain fatty acids acetate and propionate: a study with relevance to inflammatory bowel disease

Abstract

Aim: To compare the anti-inflammatory properties of butyrate with two other SCFAs, namely acetate and propionate, which have less well-documented effects on inflammation.

Methods: The effect of SCFAs on cytokine release from human neutrophils was studied with ELISA. SCFA-dependent modulation of NF-kappaB reporter activity was assessed in the human colon adenocarcinoma cell line, Colo320DM. Finally, the effect of SCFAs on gene expression and cytokine release, measured with RT-PCR and ELISA, respectively, was studied in mouse colon organ cultures established from colitic mice.

Results: Acetate, propionate and butyrate at 30 mmol/L decreased LPS-stimulated TNFalpha release from neutrophils, without affecting IL-8 protein release. All SCFAs dose dependently inhibited NF-kappaB reporter activity in Colo320DM cells. Propionate dose-dependently suppressed IL-6 mRNA and protein release from colon organ cultures and comparative studies revealed that propionate and butyrate at 30 mmol/L caused a strong inhibition of immune-related gene expression, whereas acetate was less effective. A similar inhibition was achieved with the proteasome inhibitor MG-132, but not the p38 MAPK inhibitor SB203580. All SCFAs decreased IL-6 protein release from organ cultures.

Conclusion: In the present study propionate and butyrate were equipotent, whereas acetate was less effective, at suppressing NF-kappaB reporter activity, immune-related gene expression and cytokine release in vitro. Our findings suggest that propionate and acetate, in addition to butyrate, could be useful in the treatment of inflammatory disorders, including IBD.

Figures

Figure 1

Effects of Short-Chain Fatty Acids on LPS-stimulated TNFα and IL-8 release, and lactate dehydrogenase (LDH) activity in conditioned medium from neutrophil cultures. Cells were exposed to LPS (1 μg/mL) concomitant with acetate, propionate or butyrate (all 30 mmol/L) for 6 h followed by analysis of TNFα (upper panel, bars) and IL-8 (lower panel) protein levels and LDH activity (upper panel, diamonds). n.d: not detectable. mean ± SEM (n = 3), aP < 0.05, bP < 0.01.

Figure 2

Effects of Short-Chain Fatty Acids on TNFα-induced NF-κB reporter activity in Colo320DM cells. Cells were exposed to TNFα (10 ng/mL) along with acetate (diamonds), propionate (open squares) or butyrate (closed squares) for 24 h. Data is presented as the mean % inhibition of NF-κB activity after normalization to Renilla Luciferase (n = 3).

Figure 3

Dose-dependent effects of propionate in organ cultures from inflamed mouse colon. Dextran sulphate sodium (DSS) was used to induce colonic inflammation. Upper panel: IL-6 mRNA expression (data is shown as changes relative to the expression value obtained in non-inflamed organ cultures). Lower panel: IL-6 protein levels (bars) and lactate dehydrogenase (LDH) activity (diamonds) in culture medium. Organ cultures were exposed to various concentrations of propionate for 24 h. Mean ± SEM (n = 4), aP < 0.05, bP < 0.01.

Figure 4

Transcriptional profiling of gene expression in Short-Chain Fatty Acid-treated organ cultures. Dextran sulphate sodium (DSS) was used to induce colonic inflammation. (A) Organ cultures were incubated with acetate, propionate or butyrate (all 30 mmol/L) for 24 h followed by analysis of IL-1α, IL-6 and iNOS mRNA levels. Data was normalized to GAPDH mRNA levels and presented as fold change relative to control levels. Mean ± SEM (n = 4). (B) Heat map representation of gene expression changes induced by MG-132, SB203580 (both 10 μmol/L); acetate, propionate and butyrate (all 30 mmol/L). Data was normalized to GAPDH and expressed as the ratio between treatment and control. control (co), acetate (ac), propionate (pr), butyrate (bu), MG-132 (MG), SB203580 (SB).

Figure 5

Effects of Short-Chain Fatty Acids on IL-6 release and lactate dehydrogenase (LDH) activity in organ cultures from inflamed mouse colon. Dextran sulphate sodium (DSS) was used to induce colonic inflammation. Organ cultures were exposed to acetate, propionate or butyrate (all 30 mmol/L) for 24 h followed by analysis of IL-6 level (bars) and LDH activity (diamonds) in culture medium. Mean ± SEM (n = 4), bP < 0.01.