Browsing by Author "Shimada, K."
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Open Access Chlamydia pneumoniae hijacks a host autoregulatory IL-1β loop to drive foam cell formation and accelerate atherosclerosis(Cell Press, 2018) Tumurkhuu, G.; Dagvadorj, J.; Porritt, R. A.; Crother, T. R.; Shimada, K.; Tarling, E. J.; Erbay, E.; Arditi, M.; Chen, S.Pathogen burden accelerates atherosclerosis, but the mechanisms remain unresolved. Activation of the NLRP3 inflammasome is linked to atherogenesis. Here we investigated whether Chlamydia pneumoniae (C.pn) infection engages NLRP3 in promoting atherosclerosis. C.pn potentiated hyperlipidemia-induced inflammasome activity in cultured macrophages and in foam cells in atherosclerotic lesions of Ldlr−/− mice. C.pn-induced acceleration of atherosclerosis was significantly dependent on NLRP3 and caspase-1. We discovered that C.pn-induced extracellular IL-1β triggers a negative feedback loop to inhibit GPR109a and ABCA1 expression and cholesterol efflux, leading to accumulation of intracellular cholesterol and foam cell formation. Gpr109a and Abca1 were both upregulated in plaque lesions in Nlrp3−/− mice in both hyperlipidemic and C.pn infection models. Mature IL-1β and cholesterol may compete for access to the ABCA1 transporter to be exported from macrophages. C.pn exploits this metabolic-immune crosstalk, which can be modulated by NLRP3 inhibitors to alleviate atherosclerosis. Infections can accelerate atherosclerosis, but the mechanisms remain unresolved. Tumurkhuu et al. show that C.pn infection-induced IL-1β institutes negative feedback to inhibit Gpr109a, ABCA1 expression, and cholesterol efflux, leading to accumulation of intracellular cholesterol. Mature IL-1β can use ABCA1 for secretion from macrophages to the detriment of cholesterol efflux.Item Open Access Intercepting the lipid-induced integrated stress response reduces atherosclerosis(Elsevier, 2019) Onat, Umut I.; Yıldırım, Aslı D.; Tufanlı, Özlem; Çimen, İsmail; Kocatürk, Begüm; Veli, Zehra; Hamid, S.; Shimada, K.; Chen, S.; Sin, J.; Shah, P.; Gottlieb, R.; Arditi, M.; Erbay, EbruBackground Eukaryotic cells can respond to diverse stimuli by converging at serine-51 phosphorylation on eukaryotic initiation factor 2 alpha (eIF2α) and activate the integrated stress response (ISR). This is a key step in translational control and must be tightly regulated; however, persistent eIF2α phosphorylation is observed in mouse and human atheroma. Objectives Potent ISR inhibitors that modulate neurodegenerative disorders have been identified. Here, the authors evaluated the potential benefits of intercepting ISR in a chronic metabolic and inflammatory disease, atherosclerosis. Methods The authors investigated ISR’s role in lipid-induced inflammasome activation and atherogenesis by taking advantage of 3 different small molecules and the ATP-analog sensitive kinase allele technology to intercept ISR at multiple molecular nodes. Results The results show lipid-activated eIF2α signaling induces a mitochondrial protease, Lon protease 1 (LONP1), that degrades phosphatase and tensin-induced putative kinase 1 and blocks Parkin-mediated mitophagy, resulting in greater mitochondrial oxidative stress, inflammasome activation, and interleukin-1β secretion in macrophages. Furthermore, ISR inhibitors suppress hyperlipidemia-induced inflammasome activation and inflammation, and reduce atherosclerosis. Conclusions These results reveal endoplasmic reticulum controls mitochondrial clearance by activating eIF2α-LONP1 signaling, contributing to an amplified oxidative stress response that triggers robust inflammasome activation and interleukin-1β secretion by dietary fats. These findings underscore the intricate exchange of information and coordination of both organelles’ responses to lipids is important for metabolic health. Modulation of ISR to alleviate organelle stress can prevent inflammasome activation by dietary fats and may be a strategy to reduce lipid-induced inflammation and atherosclerosis.