Fatty acid-binding proteins (FABPs) bind and internalize long-chain fatty acids, controlling lipid dynamics. Recent studies have proposed the involvement of FABPs, particularly FABP7, in lipid droplet (LD) formation in glioma, but the physiological significance of LDs is poorly understood. In this study, we sought to examine the role of FABP7 in primary mouse astrocytes, focusing on its protective effect against reactive oxygen species (ROS) stress. In FABP7 knockout (KO) astrocytes, ROS induction significantly decreased LD accumulation, elevated ROS toxicity, and impaired thioredoxin (TRX) but not peroxiredoxin 1 (PRX1) signalling compared to ROS induction in wild-type astrocytes. Consequently, activation of apoptosis signalling molecules, including p38 mitogen-activated protein kinase (MAPK) and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), and increased expression of cleaved caspase 3 were observed in FABP7 KO astrocytes under ROS stress. N-acetyl L-cysteine (NAC) application successfully rescued the ROS toxicity in FABP7 KO astrocytes. Furthermore, FABP7 overexpression in U87 human glioma cell line revealed higher LD accumulation and higher antioxidant defence enzyme (TRX, TRX reductase 1 [TRXRD1]) expression than mock transfection and protected against apoptosis signalling (p38 MAPK, SAPK/JNK and cleaved caspase 3) activation. Taken together, these data suggest that FABP7 protects astrocytes from ROS toxicity through LD formation, providing new insights linking FABP7, lipid homeostasis, and neuropsychiatric/neurodegenerative disorders, including Alzheimer’s disease and schizophrenia.
Fatty acid-binding protein 7 Astrocytes Lipid droplet Thioredoxin U87
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This research was supported mainly by grants from JSPS KAKENHI (16H05116 and 18K19723 to Y.O.) and in part by grants from the Project of Translational and Clinical Research Core Centers from AMED (grant no. JP17dm0107071) of Japan and the Tokyo Biochemical Research Foundation to Y.O.
Compliance with Ethical Standards
All experimental procedures involving mice were approved by the Institute of Laboratory Animals of Tohoku University Graduate School of Medicine and carried out according to the Guidelines for Animal Experimentation of the Tohoku University Graduate School of Medicine and according to the laws and notification requirements of Japanese governments.
Conflict of Interest
The authors declare that they have no conflict of interest.
Effect of ROS stress on astrocyte cell morphology. Morphology of primary astrocytes after confluency and maintained in conditioned medium (either in glucose or glucose-deprived medium) for 3 days in (a) normoxic (20% O2) and (b) hypoxic (1% O2) conditions. Scale bar 100 μm. (PNG 260 kb)
ROS generation under ROS stress in FABP7 KO astrocytes. (a) Mitochondrial ROS production was detected using MitoSox red staining (red) of live astrocytes under ROS stress, while MitoTracker (green) was used as a mitochondrial marker. The nucleus was counterstained with Hoechst 33342, and the cells were washed and mounted to be microphotographed under a fluorescence microscope. (b) Mitochondrial ROS production from astrocytes measured with MitoSox (mitochondrial superoxide indicator) after 24, 48 and 72 h of incubation with conditioned medium. The fluorescence was measured at Ex510 nm and Em580 nm. The data presented are the mean ± SEM of triplicate experiments using astrocytes derived from different mouse brain specimens. *p < 0.05 versus the respective WT control. The data are presented here as % change over the WT control. (PNG 1634 kb)
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