Browsing by Subject "Lipotoxicity"
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Item Open Access Identification of differentially expressed microRNAs during lipotoxic endoplasmic reticulum stress in RAW264.7 macrophages(Turkish Biochemistry Society, 2016-06) Nadir, M.; Tufanlı, Ö.; Erbay, E.; Atalay, A.Objective: Increased fatty acids in the circulation and their accumulation in non-adipose tissues play a significant role in the development of obesity related metabolic and inflammatory disorders such as insulin resistance, diabetes and atherosclerosis. While fat tissue has the ability to store excess fatty acids, uptake of excess fatty acids to other tissues burdens intracellular metabolic organelles such as mitochondria and endoplasmic reticulum (ER), leading to stress response and lipotoxic cell death. Unfolded protein response (UPR) is a key adaptation of the ER to stress. It is still not completely clear how lipids engage the UPR and how UPR manages both the adaptive and destructive consequences under its control. Increasing evidence point to the importance of miRNA regulation of the UPR as well as UPR’s role in miRNA biogenesis. In order to understand how lipids engage the UPR, we set forth to identify microRNAs regulated by lipotoxic ER stress in macrophages. Methods: We stressed the mouse macrophage cell line (RAW 264.7) with a saturated fatty acid, 500μM palmitate, reflecting the levels found in the circulation of obese patients. We analyzed the microRNAome profiles of this cell line using QRT-PCR based miScript miRNA PCR array which contained all known mouse microRNAs in miRBase release16 and performed pathway analysis for potential targets. Results: 227 microRNAs showed altered expression levels; 43 microRNAs above 2 fold difference and 13 microRNAs 3-24 fold difference. Pathway analysis enriched the target mRNAs of these lipotoxic ER stress associated miRNAs. Conclusion: When exposed to high concentrations of saturated fatty acids that can induce ER stress, macrophages display a dynamic range of changes in their microRNAome profiles. Our findings reflect the consequences of lipotoxic stress on circulating monocytes and tissue-associated macrophages in obesity. Further studies are needed to deliniate which UPR arm is reponsible for the microRNA changes reported here.Item Open Access Targeting IRE1 with small molecules counteracts progression of atherosclerosis(National Academy of Sciences, 2017-01) Tufanli, O.; Akillilar, P. T.; Acosta-Alvear, D.; Kocaturk, B.; Onat, U. I.; Hamid, S. M.; Çimen, I.; Walter, P.; Weber, C.; Erbay, E.Metaflammation, an atypical, metabolically induced, chronic lowgrade inflammation, plays an important role in the development of obesity, diabetes, and atherosclerosis. An important primer for metaflammation is the persistent metabolic overloading of the endoplasmic reticulum (ER), leading to its functional impairment. Activation of the unfolded protein response (UPR), a homeostatic regulatory network that responds to ER stress, is a hallmark of all stages of atherosclerotic plaque formation. The most conserved ERresident UPR regulator, the kinase/endoribonuclease inositol-requiring enzyme 1 (IRE1), is activated in lipid-laden macrophages that infiltrate the atherosclerotic lesions. Using RNA sequencing in macrophages, we discovered that IRE1 regulates the expression of many proatherogenic genes, including several important cytokines and chemokines. We show that IRE1 inhibitors uncouple lipid-induced ER stress from inflammasome activation in both mouse and human macrophages. In vivo, these IRE1 inhibitors led to a significant decrease in hyperlipidemia-induced IL-1β and IL-18 production, lowered T-helper type-1 immune responses, and reduced atherosclerotic plaque size without altering the plasma lipid profiles in apolipoprotein E-deficient mice. These results show that pharmacologic modulation of IRE1 counteracts metaflammation and alleviates atherosclerosis.