Rapamycin Causes Upregulation of Autophagy and Impairs Islets Function Both In Vitro and In Vivo

Tanemura, Masahiro; Ohmura, Yoshiaki; Deguchi, Takashi; Machida, Tomohiko; Tsukamoto, Rosângela; Wada, Hiroshi; Kobayashi, Shogo; Marubashi, Shigeru; Eguchi, Hidetoshi; Ito, Toshifumi; Nagano, Hiroaki; Mori, Masaki; Doki, Yuichiro

doi:10.1111/j.1600-6143.2011.03771.x

Cited by 95 publications

(76 citation statements)

References 55 publications

(80 reference statements)

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“…However, such protection required either continuous treatment for several days (48), weeks (43), or a combined treatment of rapamycin and IL-2/anti-IL-2 mAb complexes (29). The dose of rapamycin and the length of treatment should be considered carefully because higher doses and/or repeated treatments of rapamycin have been shown to have detrimental effects in vivo (49)(50)(51)(52).…”

Section: Discussionmentioning

confidence: 99%

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

Manirarora

Wei

2015

The Journal of Immunology

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Regulatory T cells (Treg) play a crucial role in the maintenance of self-tolerance. In this study, we sought to expand Ag-specific Tregs in vivo and investigate whether the expanded Tregs can prevent or delay the development of type 1 diabetes (T1D) in the NOD mouse model. NOD mice were treated with a combination of IL-2/anti–IL-2 Ab complex, islet Ag peptide, and rapamycin. After the combined treatment, CD4+CD25+Foxp3+ Tregs were significantly expanded in vivo, they expressed classical Treg markers, exerted enhanced suppressive functions in vitro, and protected against spontaneous development of T1D in NOD mice. Moreover, treated mice were almost completely protected from the adoptively transferred, aggressive form of T1D caused by in vitro–activated cytotoxic islet Ag-specific CD8 T cells. Protection from T1D was transferrable by Tregs and could be attributed to reduced islet infiltration of immune cells as well as the skewing of the immune response toward a Th2 cytokine profile. This new method of peripheral immune regulation could potentially contribute to development of novel immunotherapeutic strategies to prevent the development of T1D or to promote tolerance to islet transplants without using immunosuppressive drugs for long terms.

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Section: Discussionmentioning

confidence: 99%

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

Manirarora

Wei

2015

The Journal of Immunology

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“…In our study, we highlight the importance of specifically targeting one arm of these autophagic processeslipid degradation. Also, there is some prior support for autophagy as a (short-term) negative regulator of beta cell responses, in that activation of autophagy by rapamycin resulted in decreased insulin secretion [48].…”

Section: Discussionmentioning

confidence: 99%

Lysosomal acid lipase and lipophagy are constitutive negative regulators of glucose-stimulated insulin secretion from pancreatic beta cells

et al. 2013

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Aims/hypothesis Lipolytic breakdown of endogenous lipid pools in pancreatic beta cells contributes to glucosestimulated insulin secretion (GSIS) and is thought to be mediated by acute activation of neutral lipases in the amplification pathway. Recently it has been shown in other cell types that endogenous lipid can be metabolised by autophagy, and this lipophagy is catalysed by lysosomal acid lipase (LAL). This study aimed to elucidate a role for LAL and lipophagy in pancreatic beta cells. Methods We employed pharmacological and/or genetic inhibition of autophagy and LAL in MIN6 cells and primary islets. Insulin secretion following inhibition was measured using RIA. Lipid accumulation was assessed by MS and confocal microscopy (to visualise lipid droplets) and autophagic flux was analysed by western blot. Results Insulin secretion was increased following chronic (≥8 h) inhibition of LAL. This was more pronounced with glucose than with non-nutrient stimuli and was accompanied by augmentation of neutral lipid species. Similarly, following inhibition of autophagy in MIN6 cells, the number of lipid droplets was increased and GSIS was potentiated. Inhibition of LAL or autophagy in primary islets also increased insulin secretion. This augmentation of GSIS following LAL or autophagy inhibition was dependent on the acute activation of neutral lipases. Conclusions/interpretation Our data suggest that lysosomal lipid degradation, using LAL and potentially lipophagy, contributes to neutral lipid turnover in beta cells. It also serves as a constitutive negative regulator of GSIS by depletion of substrate for the non-lysosomal neutral lipases that are activated acutely by glucose.

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“…Moreover, prolonging autophagy with rapamycin causes radioresistant cancer cells to enter senescence and inhibits the growth of cancer cells in a xenograft model (97). Furthermore, through the use of in vivo reporter systems, rapamycin treatment has been shown to induce autophagy in both the nervous system and pancreatic β cells of mice (98,99). Although further studies are necessary to determine whether the beneficial effects seen in these model systems can be attributed to increased autophagy, these studies demonstrate that rapamycin or rapalogs can induce autophagy in vitro and in vivo.…”

Section: R E V I E W S E R I E S : a U T O P H A G Ymentioning

confidence: 99%

mTOR: a pharmacologic target for autophagy regulation

Kim¹,

Guan²

2015

J. Clin. Invest.

1,560

1,141

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Overview of mTOR signaling pathwayNutrients, growth factors, and cellular energy levels are key determinants of cell growth and proliferation. mTOR, a serine/threonine kinase, is a master regulator of cellular metabolism and promotes cell growth in response to environmental cues. Deregulation of mTOR signaling has been implicated in many human diseases, including diabetes, neurodegenerative diseases, and cancer (1). mTOR forms two distinct signaling complexes, mTOR complex 1 (mTORC1) and mTORC2, by binding with multiple companion proteins (Figure 1). mLST8, DEPTOR, and the Tti1/ Tel2 complex exist in both mTORC1 and mTORC2 (2-5). On the other hand, RAPTOR and PRAS40 are specific to mTORC1 (6-11) whereas RICTOR, mSin1, and PROCTOR1/2 are specific to mTORC2 (10,(12)(13)(14)(15)(16). The two kinase complexes have specific substrate preferences and therefore elicit distinct downstream signaling events to modulate cellular function.One of the well-established roles of mTORC1 is to promote anabolic cellular metabolism to supply the necessary building blocks for cell growth and proliferation. mTORC1 integrates various stimuli and signaling networks to stimulate synthesis of protein, lipid, and nucleotides and block catabolic processes such as autophagy at the post-translational and transcriptional levels (reviewed in refs. 17, 18). The tuberous sclerosis (TSC) tumor suppressor complex (TSC1/TSC2) is arguably the most important upstream negative regulator of mTORC1. Genetic mutations in hamartin or tuberin (encoding TSC1 and TSC2, respectively) cause tumor development in various tissues such as angiofibromas, angiomyolipomas, lymphangioleiomyomatosis, and renal cell carcinoma. Loss-of-function mutations in either TSC1 or TSC2 lead to constitutive mTORC1 activation, which contributes to uncontrolled growth and underlies the TSC disease (19). These findings provide the scientific basis of using mTORC1 inhibitors for the treatment of TSC and related diseases such as cancer.A well-established upstream regulator of mTORC1 is the growth factor/PI3K/AKT signaling pathway. Growth factors such as insulin and IGF activate their cognate receptors (receptor tyrosine kinases [RTKs]) and subsequently activate the PI3K/ AKT signaling axis. Activated AKT directly phosphorylates and thereby inhibits TSC1/2, a GTPase-activating protein (GAP) for the Ras homolog enriched in brain (Rheb) GTPase (19-23). The AKT-dependent phosphorylation results in dissociation of TSC1/2 from lysosome, where Rheb is localized, promoting Rheb activation (24). Since GTP-bound Rheb is a potent mTORC1 activator, inhibition of TSC1/2 by AKT-dependent phosphorylation results in mTORC1 activation (25,26). Additionally, AKT directly phosphorylates and inhibits PRAS40, an mTORC1 component that negatively regulates the complex's kinase activity, leading to mTORC1 activation (8-11). Furthermore, the activated RTK also stimulates the Ras/Erk/p90 ribosomal S6 kinase 1 (RSK1) signaling axis, which directly phosphorylates TSC2 to inactivate its GAP activity (27,28). In co...

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Rapamycin Causes Upregulation of Autophagy and Impairs Islets Function Both In Vitro and In Vivo

Cited by 95 publications

References 55 publications

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

Lysosomal acid lipase and lipophagy are constitutive negative regulators of glucose-stimulated insulin secretion from pancreatic beta cells

mTOR: a pharmacologic target for autophagy regulation

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