title: Sodium butyrate induces DRP1-mediated mitochondrial fusion and apoptosis in human colorectal cancer cells.
abstract: Sodium butyrate (NaBt) is the byproduct of anaerobic microbial fermentation inside the gastro-intestinal tract that could reach up to 20mM, and has been shown to inhibit the growth of various cancers. Herein, we evaluated its effect on mitochondrial fusion and associated induction of apoptosis in colorectal cancer cells (CRC). NaBt treatment at physiological (1-5mM) concentrations for 12 and 24h decreased the cell viability and induced G2-M phase cell cycle arrest in HCT116 (12h) and SW480 human CRC cells. This cell cycle arrest was associated with mitochondria-mediated apoptosis accompanied by a decrease in survivin and Bcl-2 expression, and generation of reactive oxygen species (ROS). Furthermore, NaBt treatment resulted in a significant decrease in the mitochondrial mass which is an indicator of mitochondrial fusion. Level of dynamin-related protein 1 (DRP1), a key regulator of mitochondrial fission and fusion where its up-regulation correlates with fission, was found to be decreased in CRC cells. Further, at early treatment time, DRP1 down-regulation was noticed in mitochondria which later became drastically reduced in both mitochondria as well as cytosol. DRP1 is activated by cyclin B1-CDK1 complex by its ser616 phosphorylation in which both cyclin B1-CDK1 complex and phospho-DRP1 (ser616) were strongly reduced by NaBt treatment. DRP1 was observed to be regulated by apoptosis as pan-caspase inhibitor showing rescue from NaBt-induced apoptosis also caused the reversal of DRP1 to the normal level as in control proliferating cells. Together, these findings suggest that NaBt can modulate mitochondrial fission and fusion by regulating the level of DRP1 and induce cell cycle arrest and apoptosis in human CRC cells.
authors.affiliation: School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India.
authors.forename: Dhanir
authors.initials: D
authors.lastname: Tailor
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, USA; University of Pittsburgh Cancer Institute, Pittsburgh, USA.
authors.forename: Eun-Ryeong
authors.initials: ER
authors.lastname: Hahm
authors.affiliation: School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India; University of Pittsburgh Cancer Institute, Pittsburgh, USA.
authors.forename: Raosaheb K
authors.initials: RK
authors.lastname: Kale
authors.affiliation: Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, USA; University of Pittsburgh Cancer Institute, Pittsburgh, USA.
authors.forename: Shivendra V
authors.initials: SV
authors.lastname: Singh
authors.affiliation: School of Life Sciences, Central University of Gujarat, Gandhinagar, Gujarat, India; Cancer and Radiation Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India. Electronic address: rana_singh@mail.jnu.ac.in.
authors.forename: Rana P
authors.initials: RP
authors.lastname: Singh
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D020148:Butyric Acid / Q000008:administration & dosage / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors*; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors*; D063154:Mitochondrial Dynamics / Q000187:drug effects*; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D020148:Butyric Acid; D020558:GTP Phosphohydrolases; C110768:DNM1L protein, human; D034281:Dynamins
keywords: Apoptosis; Colon cancer; DRP1; Mitochondrial fusion; Sodium butyrate