Anti-inflammatory effects of enzyme-treated asparagus extract and its constituents in hepatocytes

Abstract

Background: Asparagus (Asparagus officinalis L.) is one of the most ancient vegetables, and it is rich in asparagine. Enzyme-treated asparagus extract (ETAS™; Amino Up Chemical Co., Ltd., Sapporo, Japan) is the final product of enzyme-treatment of asparagus stems and subsequent extraction. Two constituents were purified from ETAS and identified: 5-hydroxymethyl-2-furfural (HMF), an abundant constituent, and (S)-asfural, a novel constituent, which is a derivative of HMF. ETAS has been reported to increase the expression of heat shock proteins (HSPs), which are essential for the repair or removal of defective proteins. The expression of Hsp family genes is regulated by the transcription factor heat shock factor 1 (HSF1). It is unknown whether ETAS and its constituents elicit anti-inflammatory effects, such as the suppression of nitric oxide (NO), an inflammatory mediator synthesized by inducible nitric oxide synthase (iNOS) in interleukin (IL)-1β-treated hepatocytes.Objective: To examine the anti-inflammatory effects of ETAS, we treated rat hepatocytes with ETAS, or its constituents (S)-asfural or HMF, and IL-1β and then analyzed the expression of the iNOS gene and other genes involved in inflammation.Methods: Primary cultured rat hepatocytes were prepared by collagenase perfusion. ETAS, (S)-asfural, or HMF was added to the medium with IL-1β and incubated at 37 °C. When necessary, an inhibitor of HSF1 was added. NO in the medium was measured by the Griess method, and the half-maximal inhibitory concentration (IC50) values were determined. To analyze the mRNA expression, a reverse transcription-quantitative polymerase chain reaction was performed. Antibody arrays were used to determine the levels of cytokines and chemokines in the medium.Results: ETAS suppressed NO production in IL-1β-treated hepatocytes without causing cytotoxicity. ETAS decreased the levels of both iNOS mRNA and the antisense transcript, whereas it increased the levels of Hsf1 mRNA and Hsp70 mRNA. ETAS also suppressed the production of pro-inflammatory cytokines and chemokines in hepatocytes. When (S)-asfural and HMF were added to the medium, they suppressed NO production and iNOS gene expression. The IC50 value of (S)-asfural was approximately 3-fold lower than that of HMF. In contrast, (S)-asfural increased the levels of Hsf1 mRNA. Interestingly, the KRIBB11, an inhibitor of HSF1, reduced the expression of the iNOS gene. When both (S)-asfural and KRIBB11 were added, the level of iNOS mRNA was lower than when (S)-asfural alone was added.Conclusion: ETAS and its constituents (S)-asfural and HMF suppressed NO production and the expression of pro-inflammatory cytokines and chemokines, thus showing anti-inflammatory effects. Our data suggest the possibility that the increased HSF1 level is involved in suppression of NO by ETAS and its constituents, although HSF1 is essential for the expression of the iNOS gene.Keywords: nitric oxide, inducible nitric oxide synthase, inflammation, heat shock factor, asparagus

Anti‐Inflammatory Effect of ETAS®50 by Inhibiting Nuclear Factor‐κB p65 Nuclear Import in Ultraviolet‐B‐Irradiated Normal Human Dermal Fibroblasts

“…Another group showed that ETAS 50 contains 5-hydroxymethyl-2-furfural and its unique derivative asfural, which is not present in raw asparagus [ 22 ]; these compounds exert anti-inflammatory effects on IL-1 β -induced iNOS production in rat primary hepatocytes [ 39 ]. The previous study showed that the anti-inflammatory effects of ETAS 50 and its compounds were mediated by their ability to induce heat shock protein 70 production [ 39 ]. However, we did not observe these effects in this study (unpublished data).…”

ETAS®50 Attenuates Ultraviolet‐B‐Induced Interleukin‐6 Expression by Suppressing Akt Phosphorylation in Normal Human Dermal Fibroblasts

“…In addition to our present finding, we also recently reported that ETAS 50 markedly suppressed UV-B irradiation-induced IL-1 β transactivation in NHDFs by inhibiting nuclear translocation of the NF- κ B p65 subunit [ 19 ]. Moreover, a recent study has shown that ETAS 50 attenuated IL-1 β -induced iNOS expression in rat primary hepatocytes [ 31 ]. Therefore, ETAS 50 has the potential to prevent proinflammatory responses induced directly by UV-B irradiation and indirectly by cytokines such as IL-1 β and IL-6 that are produced by UV-B-irradiated skin fibroblasts.…”

Enzyme-Treated Asparagus Extract Attenuates Hydrogen Peroxide-Induced Matrix Metalloproteinase-9 Expression in Murine Skin Fibroblast L929 Cells

“…These results suggest that ETAS modulates the JNK-AP-1 signaling pathway without affecting redox reactions in L929 cells. ETAS contains a unique 5-hydroxymethyl-2-furfural and its derivative asfural [16], which are not contained in raw asparagus [3]. Therefore, it is conceivable that such unique products derived from the enzymatic reactions utilized in ETAS production mediate its suppressive effects on intracellular signaling.…”