Macrophage Migration Inhibitory Factor Deficiency Augments Doxorubicin‐Induced Cardiomyopathy

Abstract

BackgroundRecent evidence has depicted a role of macrophage migration inhibitory factor (MIF) in cardiac homeostasis under pathological conditions. This study was designed to evaluate the role of MIF in doxorubicin‐induced cardiomyopathy and the underlying mechanism involved with a focus on autophagy.Methods and ResultsWild‐type (WT) and MIF knockout (MIF−/−) mice were given saline or doxorubicin (20 mg/kg cumulative, i.p.). A cohort of WT and MIF−/− mice was given rapamycin (6 mg/kg, i.p.) with or without bafilomycin A1 (BafA1, 3 μmol/kg per day, i.p.) for 1 week prior to doxorubicin challenge. To consolidate a role for MIF in the maintenance of cardiac homeostasis following doxorubicin challenge, recombinant mouse MIF (rmMIF) was given to MIF−/− mice challenged with or without doxorubicin. Echocardiographic, cardiomyocyte function, and intracellular Ca2+ handling were evaluated. Autophagy and apoptosis were examined. Mitochondrial morphology and function were examined using transmission electron microscopy, JC‐1 staining, MitoSOX Red fluorescence, and mitochondrial respiration complex assay. DHE staining was used to evaluate reactive oxygen species (ROS) generation. MIF knockout exacerbated doxorubicin‐induced mortality and cardiomyopathy (compromised fractional shortening, cardiomyocyte and mitochondrial function, apoptosis, and ROS generation). These detrimental effects of doxorubicin were accompanied by defective autophagolysosome formation, the effect of which was exacerbated by MIF knockout. Rapamycin pretreatment rescued doxorubicin‐induced cardiomyopathy in WT and MIF−/− mice. Blocking autophagolysosome formation using BafA1 negated the cardioprotective effect of rapamycin and rmMIF.ConclusionsOur data suggest that MIF serves as an indispensable cardioprotective factor against doxorubicin‐induced cardiomyopathy with an underlying mechanism through facilitating autophagolysosome formation.

DIDS Reduces Ischemia/Reperfusion-Induced Myocardial Injury in Rats

“…Briefly, 10 μm frozen heart sections were fixed with ice acetone for 10 min, and loaded with 5 μM DHE for 1 h at 37°C in a humidified container in the dark. Fluorescence was captured using a laser scanning confocal microscope [29]. …”

Role of autophagy in metabolic syndrome-associated heart disease

“…Both micro- and macroautophagy sequestrate and degrade large structures in either a selective or non-selective manner. Macroautophagy, hereafter referred to as autophagy, is the one that is extensively studied and the best understood [12, 19, 20, 35]. According to the selectivity of the target cargo for degradation, autophagy can be further specified into mitophagy (mitochondria), ribophagy (ribosomes), pexophagy (peroxisomes), lipophagy (lipids), and reticulopathy (endoplasmic reticulum) to denote specific target for autophagy [19, 37].…”

“…Traditional methods to evaluate autophagy status include measuring the expression of Atg proteins including Beclin1, LC3B II or the ratio LC3B II/LC3B I, or using microscopy to monitor the number of autophagosomes. However, an increase in the number of autophagosomes does not necessarily reflect the activation of autophagy [12, 20, 45]. On one hand, the increase of autophagosomes might indicate that the autophagy is activated [35, 42].…”

“…On one hand, the increase of autophagosomes might indicate that the autophagy is activated [35, 42]. On the other hand, it could be the result of decreased degradation by lysosomes [12, 20, 46]. Therefore, the concept of ‘autophagic flux’ is introduced to better reflect the dynamic process of autophagy (Scheme 1) [47].…”

“…It is widely accepted that basal autophagy possesses an indispensible role in the maintenance of cardiac geometry and function under physiological conditions [15-17]. However, cardiac autophagy is susceptible to various cardiovascular insults such as ischemia-reperfusion injury [18], pressure overload [19], and certain cardiotoxic drugs including doxorubicin [20]. Interestingly, accumulating evidence suggests that disturbed autophagy is involved in the onset and development of cardiac injuries in metabolic syndrome [11, 12, 21, 22].…”