Measurement of autophagic flux in humans: an optimized method for blood samples
Creators: name: Bensalem, Julien
name: Hattersley, Kathryn J.
name: Hein, Leanne K.
name: Teong, Xiao Tong
name: Carosi, Julian M.
name: Hassiotis, Sofia
name: Grose, Randall H.
name: Fourrier, Célia
name: Heilbronn, Leonie K.
name: Sargeant, Timothy J.
Publisher: name: Taylor & Francis
Year: 2020
Subjects: subject: Biophysics
subject: Biochemistry
subject: Medicine
subject: Microbiology
subject: FOS: Biological sciences
subject: Cell Biology
subject: Genetics
subject: Molecular Biology
subject: Physiology
subject: Pharmacology
subject: Biotechnology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: Immunology
subject: FOS: Clinical medicine
subject: 69999 Biological Sciences not elsewhere classified
subject: Cancer
subject: Hematology
subject: 110309 Infectious Diseases
subject: FOS: Health sciences

description: Autophagic flux is a critical cellular process that is vastly under-appreciated in terms of its importance to human health. Preclinical studies have demonstrated that reductions in autophagic flux cause cancer and exacerbate chronic diseases, including heart disease and the pathological hallmarks of dementia. Autophagic flux can be increased by targeting nutrition-related biochemical signaling. To date, translation of this knowledge has been hampered because there has been no way to directly measure autophagic flux in humans. In this study we detail a method whereby human macroautophagic/autophagic flux can be directly measured from human blood samples. We show that whole blood samples can be treated with the lysosomal inhibitor chloroquine, and peripheral blood mononuclear cells isolated from these samples could be used to measure autophagic machinery protein LC3B-II. Blocking of autophagic flux in cells while still in whole blood represents an important advance because it preserves genetic, nutritional, and signaling parameters inherent to the individual. We show this method was reproducible and defined LC3B-II as the best protein to measure autophagic flux in these cells. Finally, we show that this method is relevant to assess intra-individual variation induced by an intervention by manipulating nutrition signaling with an <i>ex vivo</i> treatment of whole blood that comprised leucine and insulin. Significantly, this method will enable the identification of factors that alter autophagic flux in humans, and better aid their translation in the clinic. With further research, it could also be used as a novel biomarker for risk of age-related chronic disease. <b>Abbreviations:</b> AMPK: AMP-activated protein kinase; ACTB: actin beta; ATG5: autophagy related 5; BAF: bafilomycin A<sub>1</sub>; CQ: chloroquine; DMSO: dimethyl sulfoxide; DPBS: Dulbecco’s phosphate-buffered saline; EDTA: ethylenediaminetetraacetic acid; KO: knockout; MAP1LC3A/LC3A: microtubule associated protein 1 light chain 3 alpha; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAP1LC3C/LC3C: microtubule associated protein 1 light chain 3 gamma; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; PBMCs: peripheral blood mononuclear cells; PMNs: polymorphonuclear cells; RPMI: Roswell Park Memorial Institute; SQSTM1: sequestosome 1; TBST: Tris-buffered saline containing 0.1% (v:v) Tween 20; TEM: transmission electron microscopy.