Browsing by Author "Byrne, Frances L."

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    Identification of a novel mitochondrial uncoupler that does not depolarize the plasma membrane
    Kenwood, Brandon M.; Weaver, Janelle L.; Bajwa, Amandeep; Poon, Ivan K.; Byrne, Frances L.; Murrow, Beverley A.; Calderone, Joseph A.; Huang, Liping; Divakaruni, Ajit S.; Tomsig, Jose L.; Okabe, Kohki; Lo, Ryan H.; Coleman, G. Cameron; Columbus, Linda; Yan, Zhen; Saucerman, Jeffrey J.; Smith, Jeffrey S.; Holmes, Jeffrey W.; Lynch, Kevin R.; Ravichandran, Kodi S.; Uchiyama, Seiichi; Santos, Webster L.; Rogers, George W.; Okusa, Mark D.; Bayliss, Douglas A.; Hoehn, Kyle L. (Elsevier, 2013)
    Dysregulation of oxidative phosphorylation is associated with increased mitochondrial reactive oxygen species production and some of the most prevalent human diseases including obesity, cancer, diabetes, neurodegeneration, and heart disease. Chemical 'mitochondrial uncouplers' are lipophilic weak acids that transport protons into the mitochondrial matrix via a pathway that is independent of ATP synthase, thereby uncoupling nutrient oxidation from ATP production. Mitochondrial uncouplers also lessen the proton motive force across the mitochondrial inner membrane and thereby increase the rate of mitochondrial respiration while decreasing production of reactive oxygen species. Thus, mitochondrial uncouplers are valuable chemical tools that enable the measurement of maximal mitochondrial respiration and they have been used therapeutically to decrease mitochondrial reactive oxygen species production. However, the most widely used protonophore uncouplers such as carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) and 2,4-dinitrophenol have off-target activity at other membranes that lead to a range of undesired effects including plasma membrane depolarization, mitochondrial inhibition, and cytotoxicity. These unwanted properties interfere with the measurement of mitochondrial function and result in a narrow therapeutic index that limits their usefulness in the clinic. To identify new mitochondrial uncouplers that lack off-target activity at the plasma membrane we screened a small molecule chemical library. Herein we report the identification and validation of a novel mitochondrial protonophore uncoupler (2-fluorophenyl){6-[(2-fluorophenyl)amino](1,2,5-oxadiazolo[3,4-e]pyrazin-5-yl)}amine, named BAM15, that does not depolarize the plasma membrane. Compared to FCCP, an uncoupler of equal potency, BAM15 treatment of cultured cells stimulates a higher maximum rate of mitochondrial respiration and is less cytotoxic. Furthermore, BAM15 is bioactive in vivo and dose-dependently protects mice from acute renal ischemic-reperfusion injury. From a technical standpoint, BAM15 represents an effective new tool that allows the study of mitochondrial function in the absence of off-target effects that can confound data interpretation. From a therapeutic perspective, BAM15-mediated protection from ischemia-reperfusion injury and its reduced toxicity will hopefully reignite interest in pharmacological uncoupling for the treatment of the myriad of diseases that are associated with altered mitochondrial function.
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    Mitochondrial uncoupler BAM15 reverses diet-induced obesity and insulin resistance in mice
    Alexopoulos, Stephanie J.; Chen, Sing-Young; Brandon, Amanda E.; Salamoun, Joseph M.; Byrne, Frances L.; Garcia, Christopher J.; Beretta, Martina; Olzomer, Ellen M.; Shah, Divya P.; Philp, Ashleigh M.; Hargett, Stefan R.; Lawrence, Robert T.; Lee, Brendan; Sligar, James; Carrive, Pascal; Tucker, Simon P.; Philp, Andrew; Lackner, Carolin; Turner, Nigel; Cooney, Gregory J.; Santos, Webster L.; Hoehn, Kyle L. (Nature Research, 2020-05-14)
    Obesity is a health problem affecting more than 40% of US adults and 13% of the global population. Anti-obesity treatments including diet, exercise, surgery and pharmacotherapies have so far failed to reverse obesity incidence. Herein, we target obesity with a pharmacotherapeutic approach that decreases caloric efficiency by mitochondrial uncoupling. We show that a recently identified mitochondrial uncoupler BAM15 is orally bioavailable, increases nutrient oxidation, and decreases body fat mass without altering food intake, lean body mass, body temperature, or biochemical and haematological markers of toxicity. BAM15 decreases hepatic fat, decreases inflammatory lipids, and has strong antioxidant effects. Hyperinsulinemic-euglycemic clamp studies show that BAM15 improves insulin sensitivity in multiple tissue types. Collectively, these data demonstrate that pharmacologic mitochondrial uncoupling with BAM15 has powerful anti-obesity and insulin sensitizing effects without compromising lean mass or affecting food intake.
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    Phenotypic screen for oxygen consumption rate identifies an anti-cancer naphthoquinone that induces mitochondrial oxidative stress
    Byrne, Frances L.; Olzomer, Ellen M.; Marriott, Gabriella R.; Quek, Lake-Ee; Katen, Alice; Su, Jacky; Nelson, Marin E.; Hart-Smith, Gene; Larance, Mark; Sebesfi, Veronica F.; Cuff, Jeff; Martyn, Gabriella E.; Childress, Elizabeth; Alexopoulos, Stephanie J.; Poon, Ivan K.; Faux, Maree C.; Burgess, Antony W.; Reid, Glen; McCarroll, Joshua A.; Santos, Webster L.; Quinlan, Kate G. R.; Turner, Nigel; Fazakerley, Daniel J.; Kumar, Naresh; Hoehn, Kyle L. (2020-01)
    A hallmark of cancer cells is their ability to reprogram nutrient metabolism. Thus, disruption to this phenotype is a potential avenue for anti-cancer therapy. Herein we used a phenotypic chemical library screening approach to identify molecules that disrupted nutrient metabolism (by increasing cellular oxygen consumption rate) and were toxic to cancer cells. From this screen we discovered a 1,4-Naphthoquinone (referred to as BH10) that is toxic to a broad range of cancer cell types. BH10 has improved cancer-selective toxicity compared to doxorubicin, 17-AAG, vitamin K3, and other known anti-cancer quinones. BH10 increases glucose oxidation via both mitochondrial and pentose phosphate pathways, decreases glycolysis, lowers GSH:GSSG and NAPDH/NAPD(+) ratios exclusively in cancer cells, and induces necrosis. BH10 targets mitochondrial redox defence as evidenced by increased mitochondrial peroxiredoxin 3 oxidation and decreased mitochondrial aconitase activity, without changes in markers of cytosolic or nuclear damage. Over-expression of mitochondria-targeted catalase protects cells from BH10-mediated toxicity, while the thioredoxin reductase inhibitor auranofin synergistically enhances BH10-induced peroxiredoxin 3 oxidation and cytotoxicity. Overall, BH10 represents a 1,4-Naphthoquinone with an improved cancer-selective cytotoxicity profile via its mitochondrial specificity.
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    Targeting negative energy balance with calorie restriction and mitochondrial uncoupling in db/db mice
    Chen, Sing -Young; Beretta, Martina; Olzomer, Ellen M.; Shah, Divya P.; Wong, Derek Y. H.; Alexopoulos, Stephanie J.; Aleksovska, Isabella; Salamoun, Joseph M.; Garcia, Christopher J.; Cochran, Blake J.; Rye, Kerry-Anne; Smith, Greg C.; Byrne, Frances L.; Morris, Margaret J.; Santos, Webster L.; Cantley, James; Hoehn, Kyle L. (Elsevier, 2023-01)
    Objective: Calorie restriction is a first-line treatment for overweight individuals with metabolic impairments. However, few patients can adhere to long-term calorie restriction. An alternative approach to calorie restriction that also causes negative energy balance is mitochondrial uncoupling, which decreases the amount of energy that can be extracted from food. Herein we compare the metabolic effects of calorie restriction with the mitochondrial uncoupler BAM15 in the db/db mouse model of severe hyperglycemia, obesity, hypertriglyceridemia, and fatty liver. Methods: Male db/db mice were treated with w50% calorie restriction, BAM15 at two doses of 0.1% and 0.2% (w/w) admixed in diet, or 0.2% BAM15 with time-restricted feeding from 5 weeks of age. Mice were metabolically phenotyped over 4 weeks with assessment of key readouts including body weight, glucose tolerance, and liver steatosis. At termination, liver tissues were analysed by metabolomics and qPCR. Results: Calorie restriction and high-dose 0.2% BAM15 decreased body weight to a similar extent, but mice treated with BAM15 had far better improvement in glucose control. High-dose BAM15 treatment completely normalized fasting glucose and glucose tolerance to levels similar to lean db/+ control mice. Low-dose 0.1% BAM15 did not affect body mass but partially improved glucose tolerance to a similar degree as 50% calorie restriction. Both calorie restriction and high-dose BAM15 significantly improved hyperglucagonemia and liver and serum triglyceride levels. Combining high-dose BAM15 with time-restricted feeding to match the time that calorie restricted mice were fed resulted in the best metabolic phenotype most similar to lean db/+ controls. BAM15-mediated improvements in glucose control were associated with decreased glucagon levels and decreased expression of enzymes involved in hepatic gluconeogenesis. Conclusions: BAM15 and calorie restriction treatments improved most metabolic disease phenotypes in db/db mice. However, mice fed BAM15 had superior effects on glucose control compared to the calorie restricted group that consumed half as much food. Submaximal dosing with BAM15 demonstrated that its beneficial effects on glucose control are independent of weight loss. These data highlight the potential for mitochondrial uncoupler pharmacotherapies in the treatment of metabolic disease. (c) 2023 The Author(s). Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).