Some tumours respond favourably to tumour necrosis factor-alpha (TNF-alpha). Despite this preferential sensitivity, resistance to TNF-alpha remains a clinical problem and more interest is now being focused on finding compounds that induce apoptosis through other pathways. Sodium butyrate (NaBt) has anti-tumour effects on colon cancer cells, inhibiting cell growth and promoting differentiation and apoptosis. In this study we investigated whether NaBt induced apoptosis in the human colon cancer cell line HT-29 and examined the intracellular mechanisms involved. Pre-incubation of cells with NaBt significantly increased apoptosis as measured by fluorescence activated cell sorter analysis and mitochondrial membrane potential determination. This effect could be blocked with the caspase inhibitors, z-VAD-fmk (pan-caspase inhibitor), z-DEVD-fmk (caspase-3 inhibitor) and z-LEHD-fmk (caspase-9 inhibitor), but not with z-IETD-fmk (caspase-8 inhibitor). Enhancement of caspase-3 and caspase-9 activities suggests that NaBt induces apoptosis via mitochondrial pathways not involving TNF-alpha.

ContributorsZG and YL made substantial contributions to the study concept and design. LW was in charge of the manuscript draft. XL, CH, SY and DL took responsibility for obtaining written consent from patients, obtaining ethical approval, collecting samples, and confirming data accuracy. LW and ZG participated in drafting the manuscript, and revising it on the basis of reviewers' comments. LW made substantial contributions to data acquisition, analysis, and interpretation. Declaration of interestsWe declare no competing interests. Data sharingWith the permission of the corresponding authors, we can provide participant data without names and identifiers, but not the study protocol, statistical analysis plan, or informed consent form. Data can be provided after the Article is published. Once the data can be made public, the research team will provide an email address for communication. The corresponding authors have the right to decide whether to share the data or not based on the research objectives and plan provided.All rights reserved. No reuse allowed without permission. author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

These results demonstrate that magnolol can block the proliferation of VSMCs through inhibition of intracellular ROS production and Ras-MEK-ERK1/2 pathways. Magnolol, therefore, has a potential application in preventing atherosclerosis and restenosis.