trans-Fatty acids facilitate DNA damage-induced apoptosis through the mitochondrial JNK-Sab-ROS positive feedback loop

Abstract

trans-fatty acids (tfAs) are unsaturated fatty acids that contain one or more carbon-carbon double bonds in trans configuration. Epidemiological evidence has linked TFA consumption with various disorders, including cardiovascular diseases. However, the underlying pathological mechanisms are largely unknown. Here, we show a novel toxic mechanism of TFAs triggered by DNA damage. We found that elaidic acid (EA) and linoelaidic acid, major TFAs produced during industrial food manufacturing (so-called as industrial TFAs), but not their corresponding cis isomers, facilitated apoptosis induced by doxorubicin. Consistently, EA enhanced UV-induced embryonic lethality in C. elegans worms. The pro-apoptotic action of EA was blocked by knocking down Sab, a c-Jun N-terminal kinase (JNK)interacting protein localizing at mitochondrial outer membrane, which mediates mutual amplification of mitochondrial reactive oxygen species (ROS) generation and JNK activation. EA enhanced doxorubicin-induced mitochondrial ROS generation and JNK activation, both of which were suppressed by Sab knockdown and pharmacological inhibition of either mitochondrial ROS generation, JNK, or Src-homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) as a Sab-associated protein. These results demonstrate that in response to DNA damage, TFAs drive the mitochondrial JNK-Sab-ROS positive feedback loop and ultimately apoptosis, which may provide insight into the common pathogenetic mechanisms of diverse TFA-related disorders. trans-Fatty acids (TFAs) are defined as unsaturated fatty acids containing one or more carbon-carbon double bonds in trans configuration. TFAs, such as elaidic acid (EA, C18:1 t9) and linoelaidic acid (LEA, C18:2 t9,t12), so-called as industrial TFAs, are produced during the food manufacturing processes, mainly through partial hydrogenation of vegetable and fish oils that contain cis isomers of TFAs, hereafter referred to as cis-fatty acids (CFAs) 1. On the other hand, TFAs such as trans-vaccenic acid (TVA, C18:1 t11), so-called as ruminant TFAs, are produced via enzymatic isomerization of CFAs by ruminal microbes in cows and sheep, and are present in dairy products and meat 1. Compelling epidemiological evidence has shown that the intake of TFAs, particularly industrial TFAs, increases the risk of various disorders, such as systemic inflammation, metabolic syndrome, neurodegenerative disorders, and cardiovascular diseases (CVDs) 2-5. However, few studies have focused on the mechanisms of action of TFAs, and the molecular mechanisms underlying TFA-related disorders remain to be elucidated. Among TFA-related disorders, TFAs have been most highly linked with atherosclerosis, one of the major cause of CVDs, and the underlying mechanisms have been explained by their deleterious effects on vascular endothelial functions and lipoprotein regulation 3,6-10. Importantly, we have recently revealed a novel toxic function of TFAs as an enhancer of inflammatory signaling and cell death induced by extracellular ATP, one of the damage-assoc...

Effect of <i>trans</i>-Octadecenoic Acid Positional Isomers on Tumor Necrosis Factor-α Secretion in RAW264.7 Cells

“…However, previous studies have reported the cytotoxic effect of trans-9-C18:1 and trans-11-C18:1 depending on conditions such as high concentration of TFA, cell type, and with/without stimulation. For instance, when RAW264.7 cells were stimulated with 200 μM of trans-9-C18:1 in the presence of the DNA-damaging agent doxorubicin, the cell viability was significantly decreased as compared to oleic acid cis-9-C18:1 16,17 . Montakhab and Dousti investigated the viability of RAW264.7 cells treated with 1,000-5,000 μM of trans-9-C18:1, which was found to reduce cell viability to less than 75 at concentrations higher than 2,000 μM 15 .…”

“…Hirata et al revealed the toxic function of TFAs as enhancers of pro-inflammatory signaling and apoptosis induced by doxorubicin. They showed that trans-9-C18:1, trans-11-C18:1, and linoelaidic acid, but not their corresponding cis-isomers, dramatically enhanced the apoptosis of RAW264.7 cells 16,17 . These are very important findings to elucidate the effects of TFAs on disease development.…”

Elaidic Acid Potentiates Extracellular ATP-Induced Apoptosis <i>via</i> the P2X₇-ROS-ASK1-p38 Axis in Microglial Cell Lines

“…BV2 and MG6 cell lines were originally immortalized by virusmediated transduction of rapidly accelerated fibrosarcoma (v-raf)/v-myc and c-myc, respectively. 17,18) v-Raf-transduced BV2 might have higher potency for CaMKII activation than MG6 without v-Raf, since CaMKII and Raf-mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK)-ERK MAPK pathway have been reported to interact each other, and thereby promote activation in a cooperative fasion. 34) Regarding the TFA amount in human bodies, plasma concentration of EA is approx.…”

“…Cell Culture BV2 and MG6 cells 17,18) were obtained from ATC C and RIKEN, respectively, and cultured in Dulbecco's Modified Eagle Medium (Nacalai Tesque, Kyoto, Japan) containing 10% heat-inactivated fetal bovine serum (Sigma) and 1% penicillin-streptomycin solution (Nacalai Tesque) in 5% CO 2 at 37 °C.…”

TAK1 Mediates ROS Generation Triggered by the Specific Cephalosporins through Noncanonical Mechanisms

“…Mitochondria were isolated as described previously [ 41 ]. Cells were washed twice with ice-cold PBS and were lysed by using a glass Dounce homogenizer in homogenization buffer [20 mM Hepes (pH 7.9), 0.22 M mannitol, 0.08 M sucrose, and 1% protease inhibitor cocktails (Nacalai Tesque)].…”