The TSC-mTOR signaling pathway regulates the innate inflammatory response

mTOR Inhibitor Therapy and Metabolic Consequences: Where Do We Stand?

mTOR (mechanistic target of rapamycin) protein kinase acts as a central integrator of nutrient signaling pathways. Besides the immunosuppressive role after solid organ transplantations or in the treatment of some cancers, another promising role of mTOR inhibitor as an antiaging therapeutic has emerged in the recent years. Acute or intermittent rapamycin treatment has some resemblance to calorie restriction in metabolic effects such as an increased insulin sensitivity. However, the chronic inhibition of mTOR by macrolide rapamycin or other rapalogs has been associated with glucose intolerance and insulin resistance and may even provoke type II diabetes. These metabolic adverse effects limit the use of mTOR inhibitors. Metformin is a widely used drug for the treatment of type 2 diabetes which activates AMP-activated protein kinase (AMPK), acting as calorie restriction mimetic. In addition to the glucose-lowering effect resulting from the decreased hepatic glucose production and increased glucose utilization, metformin induces fatty acid oxidations. Here, we review the recent advances in our understanding of the metabolic consequences regarding glucose metabolism induced by mTOR inhibitors and compare them to the metabolic profile provoked by metformin use. We further suggest metformin use concurrent with rapalogs in order to pharmacologically address the impaired glucose metabolism and prevent the development of new-onset diabetes mellitus after solid organ transplantations induced by the chronic rapalog treatment.

Selenium deficiency impaired immune function of the immune organs in young grass carp (Ctenopharyngodon idella)

This study aimed to investigate the effects of dietary selenium on resistance to skin haemorrhages and lesions and on immune function as well as the underlying mechanisms of those effects in the head kidney, spleen and skin of young grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp with initial body weight (226.48 ± 0.68 g) were randomly divided into six groups and fed six separate diets with graded dietary levels of selenium (0.025, 0.216, 0.387, 0.579, 0.795 and 1.049 mg/kg diet) for 80 days. After the feeding period, an immunization trial was performed by infection with Aeromonas hydrophila for 14 days. The results showed that, compared with the optimal selenium level, (1) selenium deficiency impaired the production of antibacterial compounds and immunoglobulins and down-regulated the transcript abundances of antimicrobial peptides and selenoproteins; (2) selenium deficiency aggravated inflammatory responses in part by up-regulating pro-inflammatory cytokines and down-regulating anti-inflammatory cytokines mRNA levels, which were partially related to [IKKα, β, γ/IκBα/NF-κB] signalling and [TOR/(S6K1, 4E-BP1)] signalling, respectively. Interestingly, selenium deficiency had no effect on the expression of TGF-β2, IL-4/13B, IL-10, IL-12p35, IL-15 (skin only) or 4E-BP2 in the head kidney, spleen and skin of young grass carp. Finally, based on the percent weight gain (PWG), the morbidity of skin haemorrhages and lesions, the ACP activity in the head kidney and the lysozyme activity in spleen, the optimal dietary selenium requirements for young grass carp were estimated to be 0.546-0.604 mg/kg diet. In summary, selenium deficiency decreased the growth performance and impaired the immune function in the head kidney, spleen and skin of young grass carp.

Production of interleukin-1β related to mammalian target of rapamycin/Toll-like receptor 4 signaling pathway during Aspergillus fumigatus infection of the mouse cornea

AIM

To elucidate the effect of rapamycin on regulating the production of interleukin (IL)-1β in Aspergillus fumigatus (A. fumigatus)-induced keratitis and to verify whether the expression of IL-1β in A. fumigatus keratitis is associated with the mammalian target of rapamycin (mTOR)/Toll-like receptor 4 (TLR4) signaling pathway.

METHODS

Fungal keratitis mouse models of susceptible C57BL/6 mice were established using A. fumigatus. The mice were subsequently treated with rapamycin. The protein levels of p-mTOR, TLR4, and IL-1β in normal and infected corneal tissue were measured by Western blot. The TLR4 and IL-1β mRNA levels were determined by real-time polymerase chain reaction (PCR).

RESULTS

In C57BL/6 mice, rapamycin treatment decreased the clinical scores and production of the pro-inflammatory cytokine, IL-1β. The expression of TLR4, stimulated by A. fumigatus, was reduced as well when the mTOR signaling pathway was suppressed by rapamycin.

CONCLUSION

Rapamycin is beneficial for the outcome of fungal keratitis and has an inhibitory effect expression of the inflammatory cytokine IL-1β. The inhibitory effect on IL-1β expression can be associated with the mTOR/TLR4 signaling pathway in A. fumigatus infection in mice.

mTORC2 Signaling Selectively Regulates the Generation and Function of Tissue-Resident Peritoneal Macrophages

Tissue-resident macrophages play critical roles in sentinel and homeostatic functions as well as in promoting inflammation and immunity. It has become clear that the generation of these cells is highly dependent upon tissue-specific cues derived from the microenvironment that, in turn, regulate unique differentiation programs. Recently, a role for GATA6 has emerged in the differentiation programming of resident peritoneal macrophages. We identify a critical role for mTOR in integrating cues from the tissue microenvironment in regulating differentiation and metabolic reprogramming. Specifically, inhibition of mTORC2 leads to enhanced GATA6 expression in a FOXO1 dependent fashion. Functionally, inhibition of mTORC2 promotes peritoneal resident macrophage generation in the resolution phase during zymosan-induced peritonitis. Also, mTORC2-deficient peritoneal resident macrophages displayed increased functionality and metabolic reprogramming. Notably, mTORC2 activation distinguishes tissue-resident macrophage proliferation and differentiation from that of M2 macrophages. Overall, our data implicate a selective role for mTORC2 in the differentiation of tissue-resident macrophages.

Combination of dual mTORC1/2 inhibition and immune-checkpoint blockade potentiates anti-tumour immunity

mTOR inhibition can promote or inhibit immune responses in a context dependent manner, but whether this will represent a net benefit or be contraindicated in the context of immunooncology therapies is less understood. Here, we report that the mTORC1/2 dual kinase inhibitor vistusertib (AZD2014) potentiates anti-tumour immunity in combination with anti-CTLA-4 (αCTLA-4), αPD-1 or αPD-L1 immune checkpoint blockade. Combination of vistusertib and immune checkpoint blocking antibodies led to tumour growth inhibition and improved survival of MC-38 or CT-26 pre-clinical syngeneic tumour models, whereas monotherapies were less effective. Underlying these combinatorial effects, vistusertib/immune checkpoint combinations reduced the occurrence of exhausted phenotype tumour infiltrating lymphocytes (TILs), whilst increasing frequencies of activated Th1 polarized T-cells in tumours. Vistusertib alone was shown to promote a Th1 polarizing proinflammatory cytokine profile by innate primary immune cells. Moreover, vistusertib directly enhanced activation of effector T-cell and survival, an effect that was critically dependent on inhibitor dose. Therefore, these data highlight direct, tumour-relevant immune potentiating benefits of mTOR inhibition that complement immune checkpoint blockade. Together, these data provide a clear rationale to investigate such combinations in the clinic.

A hyaluronan-based nanosystem enables combined anti-inflammation of mTOR gene silencing and pharmacotherapy

Accompanied by overproduction of oxidants and reduction of pH, inflammation is closely related to many diseases such as cancer, atherosclerosis, and asthma. Besides chemotherapeutic agents, the potential regulative role of autophagy in inflammation is being actively investigated. RNA interference (RNAi)-based gene therapy is widely explored for clinical therapy but seriously restricted by lack of suitable carriers. In this study, we synthesized a hyaluronan-based ROS-sensitive polymer which was expected to release loaded chemical drugs in inflammatory environment and further developed a stable and nontoxic co-delivery nanosystem of siRNA targeting autophagy suppressive gene and chemotherapeutic agents. The in vitro transfection study of this nanosystem revealed improved intracellular accumulation of siRNA and excellent gene silencing efficacy comparable to that of conventional cationic liposome. Moreover, the mRNA expression of inflammatory cytokines was remarkably decreased by our nanosystem. Considering its biocompatibility, transfection efficacy, and anti-inflammatory capability, this co-delivery nanosystem proclaimed to be a promising combined therapeutic strategy for enhanced anti-inflammatory therapy.

Piperine potentiates curcumin-mediated repression of mTORC1 signaling in human intestinal epithelial cells: implications for the inhibition of protein synthesis and TNFα signaling

Persistent activation of the mechanistic target of rapamycin complex 1 (mTORC1) is linked to sustained inflammation and progression of colorectal cancer. Widely available dietary phenolics, curcumin and piperine are purported to have antiinflammatory and anticarcinogenic activities through yet-to-be-delineated multitarget mechanisms. Piperine is also known to increase the bioavailability of dietary components, including curcumin. The objective of the study was to determine whether curcumin and piperine have individual and combined effects in the setting of gut inflammation by regulating mTORC1 in human intestinal epithelial cells. Results show that curcumin repressed (a) mTORC1 activity (measured as changes in the phosphorylation state of p70 ribosomal protein S6 kinase B1 and 40S ribosomal protein S6) in a dose-dependent manner (2.5-20 μM, P<.007) and (b) synthesis of nascent proteins. Piperine inhibited mTORC1 activity albeit at comparatively higher concentrations than curcumin. The combination of curcumin + piperine further repressed mTORC1 signaling (P<.02). Mechanistically, curcumin may repress mTORC1 by preventing TSC2 degradation, the conserved inhibitor of mTORC1. Results also show that a functional mTORC1 was required for the transcription of TNFα as Raptor knockdown abrogated TNFα gene expression. Curcumin, piperine and their combination inhibited TNFα gene expression at baseline but failed to do so under conditions of mTORC1 hyperactivation. TNF∝-induced cyclooxygenase-2 expression was repressed by curcumin or curcumin + piperine at baseline and high mTORC1 levels. We conclude that curcumin and piperine, either alone or in combination, have the potential to down-regulate mTORC1 signaling in the intestinal epithelium with implications for tumorigenesis and inflammation.

Rapamycin regulates macrophage activation by inhibiting NLRP3 inflammasome-p38 MAPK-NFκB pathways in autophagy- and p62-dependent manners

Excessive and prolonged activation of macrophages underlies many inflammatory and autoimmune diseases. To regulate activation and maintain homeostasis, macrophages have multiple intrinsic mechanisms, one of which is modulation through autophagy. Here we demonstrate that autophagy induction by rapamycin suppressed the production of IL-1β and IL-18 in lipopolysaccharide- and adenosine triphosphate-activated macrophages at the post-transcriptional level by eliminating mitochondrial ROS (mtROS) and pro-IL1β in a p62/SQSTM1-dependent manner. In addition, rapamycin activated Nrf2 through up-regulation of p62/SQSTM1, which further contributed to the reduction of mtROS. Reduced IL-1β subsequently diminished the activation of p38 MAPK-NFκB pathways, leading to transcriptional down-regulation of IL-6, IL-8, MCP-1, and IκBα in rapamycin-treated macrophages. Therefore, our results suggest that rapamycin negatively regulates macrophage activation by restricting a feedback loop of NLRP3 inflammasome-p38 MAPK-NFκB pathways in autophagy- and p62/SQSTM1-dependent manners.

Lysosomal Protein Lamtor1 Controls Innate Immune Responses via Nuclear Translocation of Transcription Factor EB

Amino acid metabolism plays important roles in innate immune cells, including macrophages. Recently, we reported that a lysosomal adaptor protein, Lamtor1, which serves as the scaffold for amino acid-activated mechanistic target of rapamycin complex 1 (mTORC1), is critical for the polarization of M2 macrophages. However, little is known about how Lamtor1 affects the inflammatory responses that are triggered by the stimuli for TLRs. In this article, we show that Lamtor1 controls innate immune responses by regulating the phosphorylation and nuclear translocation of transcription factor EB (TFEB), which has been known as the master regulator for lysosome and autophagosome biogenesis. Furthermore, we show that nuclear translocation of TFEB occurs in alveolar macrophages of myeloid-specific Lamtor1 conditional knockout mice and that these mice are hypersensitive to intratracheal administration of LPS and bleomycin. Our observation clarified that the amino acid-sensing pathway consisting of Lamtor1, mTORC1, and TFEB is involved in the regulation of innate immune responses.

SALL1 functions as a tumor suppressor in breast cancer by regulating cancer cell senescence and metastasis through the NuRD complex

Background

SALL1 is a multi-zinc finger transcription factor that regulates organogenesis and stem cell development, but the role of SALL1 in tumor biology and tumorigenesis remains largely unknown.

Methods

We analyzed SALL1 expression levels in human and murine breast cancer cells as well as cancer tissues from different types of breast cancer patients. Using both in vitro co-culture system and in vivo breast tumor models, we investigated how SALL1 expression in breast cancer cells affects tumor cell growth and proliferation, metastasis, and cell fate. Using the gain-of function and loss-of-function strategies, we dissected the molecular mechanism responsible for SALL1 tumor suppressor functions.

Results

We demonstrated that SALL1 functions as a tumor suppressor in breast cancer, which is significantly down-regulated in the basal like breast cancer and in estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor 2 (HER2) triple negative breast cancer patients. SALL1 expression in human and murine breast cancer cells inhibited cancer cell growth and proliferation, metastasis, and promoted cell cycle arrest. Knockdown of SALL1 in breast cancer cells promoted cancer cell growth, proliferation, and colony formation. Our studies revealed that tumor suppression was mediated by recruitment of the Nucleosome Remodeling and Deacetylase (NuRD) complex by SALL1, which promoted cancer cell senescence. We further demonstrated that the mechanism of inhibition of breast cancer cell growth and invasion by SALL1-NuRD depends on the p38 MAPK, ERK1/2, and mTOR signaling pathways.

Conclusion

Our studies indicate that the developmental control gene SALL1 plays a critical role in tumor suppression by recruiting the NuRD complex and thereby inducing cell senescence in breast cancer cells.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0824-y) contains supplementary material, which is available to authorized users.

Acute Dietary Restriction Acts via TOR, PP2A, and Myc Signaling to Boost Innate Immunity in Drosophila

Dietary restriction promotes health and longevity across taxa through mechanisms that are largely unknown. Here, we show that acute yeast restriction significantly improves the ability of adult female Drosophila melanogaster to resist pathogenic bacterial infections through an immune pathway involving downregulation of target of rapamycin (TOR) signaling, which stabilizes the transcription factor Myc by increasing the steady-state level of its phosphorylated forms through decreased activity of protein phosphatase 2A. Upregulation of Myc through genetic and pharmacological means mimicked the effects of yeast restriction in fully fed flies, identifying Myc as a pro-immune molecule. Short-term dietary or pharmacological interventions that modulate TOR-PP2A-Myc signaling may provide an effective method to enhance immunity in vulnerable human populations.

mTOR co-targeting strategies for head and neck cancer therapy

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy worldwide. There is an urgent need to develop effective therapeutic approaches to prevent and treat HNSCC. Recent deep sequencing of the HNSCC genomic landscape revealed a multiplicity and diversity of genetic alterations in this malignancy. Although a large variety of specific molecules were found altered in each individual tumor, they all participate in only a handful of driver signaling pathways. Among them, the PI3K/mTOR pathway is the most frequently activated, which plays a central role in cancer initiation and progression. In turn, targeting of mTOR may represent a precision therapeutic approach for HNSCC. Indeed, mTOR inhibition exerts potent anti-tumor activity in HNSCC experimental systems, and mTOR targeting clinical trials show encouraging results. However, advanced HNSCC patients may exhibit unpredictable drug resistance, and the analysis of its molecular basis suggests that co-targeting strategies may provide a more effective option. In addition, although counterintuitive, emerging evidence suggests that mTOR inhibition may enhance the anti-tumor immune response. These new findings raise the possibility that the combination of mTOR inhibitors and immune oncology agents may provide novel precision therapeutic options for HNSCC.

Lysosomal acid lipase in mesenchymal stem cell stimulation of tumor growth and metastasis

Bone marrow mesenchymal stem cells (MSCs) are an important participant in the tumor microenvironment, in which they promote tumor growth and progression. Here we report for the first time that depletion of lysosomal acid lipase (LAL) in MSCs impairs their abilities to stimulate tumor growth and metastasis both in allogeneic and syngeneic mouse models. Reduced cell viability was observed in LAL-deficient (lal^−/−) MSCs, which was a result of both increased apoptosis and decreased proliferation due to cell cycle arrest. The synthesis and secretion of cytokines and chemokines that are known to mediate MSCs' tumor-stimulating and immunosuppressive effects, i.e., IL-6, MCP-1 and IL-10, were down-regulated in lal^−/− MSCs. When tumor cells were treated with the conditioned medium from lal^−/− MSCs, decreased proliferation was observed, accompanied by reduced activation of oncogenic intracellular signaling molecules in tumor cells. Co-injection of lal^−/− MSCs and B16 melanoma cells into wild type mice not only induced CD8⁺ cytotoxic T cells, but also decreased accumulation of tumor-promoting Ly6G⁺CD11b⁺ myeloid-derived suppressor cells (MDSCs), which may synergistically contribute to the impairment of tumor progression. Furthermore, lal^−/− MSCs showed impaired differentiation towards tumor-associated fibroblasts. In addition, MDSCs facilitated MSC proliferation, which was mediated by MDSC-secreted cytokines and chemokines. Our results indicate that LAL plays a critical role in regulating MSCs' ability to stimulate tumor growth and metastasis, which provides a mechanistic basis for targeting LAL in MSCs to reduce the risk of cancer metastasis.

Targeted delivery of microRNA 146b mimic to hepatocytes by lactosylated PDMAEMA nanoparticles for the treatment of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide, and precision therapeutic will be a benefit for the NAFLD regression. In this study, we observed low microRNA 146 b (miR-146 b) expression in NAFLD mice model induced by methionine-choline-deficient diet (MCD) compared with control group. Furthermore, miR-146b^-/- mice induced MCD exhibited severe liver steatosis and hepatitis. A bio-distribution study showed that novel Lactosylated PDMAEMA nanoparticles effectively targeted hepatocytes Lac-PDMAEMA. We coupled miR-146b mimic with Lac-PDMAEMA and then were administrated to NAFLD mice model, which could obviously alleviate the hepatic steatosis. Lac-PDMAEMA effectively delivered miR-146b mimic to hepatocytes with a ∼8-fold upregulation of miR-146b mimic targeting MyD88 and IRAK1, and in turn suppressed the expression of PPARγ. Meanwhile, TNF-α and IL-6 mRNA levels were decreased after administration of Lac-PDMAEMA/miR-146b mimic. So, we made a conclusion that targeted delivering miR-146b mimic to the hepatocytes by, coupling Lac-PDMAEMA nanoparticles could effectively alleviate the hepatic steatosis in NAFLD mice, which maybe bring a new and effective way to intervene and therapy the NAFLD.

REDD-1 aggravates endotoxin-induced inflammation via atypical NF-κB activation

Regulated in development and DNA damage responses 1 (REDD-1), an inhibitor of mammalian target of rapamycin (mTOR), is induced by various cell stressors, including LPS, a major player in the pathogenesis of endotoxemic shock. However, the pathologic role of REDD-1 in endotoxemia is largely unknown. We found that LPS increased REDD-1 expression, nuclear transcription factor-κB (NF-κB) activation, and inflammation and that these responses were suppressed by REDD-1 knockdown and in REDD-1^+/- macrophages. REDD-1 overexpression stimulated NF-κB-dependent inflammation without additional LPS stimulation. REDD-1-induced NF-κB activation was independent of 2 classic IKK-dependent NF-κB pathways and the mTOR signaling pathway; however, REDD-1, particularly its C-terminal region (178-229), interacted with and sequestered IκBα, to elicit atypical NF-κB activation during the delayed and persistent phases of inflammation after stimulation. Moreover, REDD-1 knockdown mitigated vascular inflammation and permeability in endotoxemic mice, resulting in decreases in immune cell infiltration, systemic inflammation, caspase-3 activation, apoptosis, and consequent mortality. We further confirmed the inflammatory and cytotoxic effects of REDD-1 in endotoxemic REDD-1^+/- mice. Our data support the likelihood that REDD-1 exacerbates endotoxemic inflammation via atypical NF-κB activation by sequestering IκBα.-Lee, D.-K., Kim, J.-H., Kim, J., Choi, S., Park, M., Park, W., Kim, S., Lee, K.-S., Kim, T., Jung, J., Choi, Y. K., Ha, K.-S., Won, M.-H., Billiar, T. R., Kwon, Y.-G., Kim, Y.-M. REDD-1 aggravates endotoxin-induced inflammation via atypical NF-κB activation.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

Methionine hydroxy analogue supplementation modulates gill immunological and barrier health status of grass carp (Ctenopharyngodon idella)

This study was conducted to investigate the effects of methionine hydroxy analogue (MHA) on the physical barrier and immune defence in the gill of young grass carp (Ctenopharyngodon idella). A total 630 young grass carp with an average initial weight of 259.70 ± 0.47 g were fed graded levels of MHA (0, 2.4, 4.4, 6.4, 8.5 and 10.5 g/kg diet) and one DL-methionine (DLM) group (6.4 g/kg diet) for 8 weeks. After feeding trial, 15 fish from each treatment were challenged with Flavobacterium columnare. Compared to the basal diet, optimal MHA improved cellular structure integrity of gill via repressing death receptor and mitochondria pathways induced apoptosis, which might be related to the down-regulation of c-Jun-N-terminal kinase mRNA levels (P < .05). Simultaneously, optimal MHA supplementation improved cellular structure integrity of gill via elevating glutathione contents, antioxidant enzymes activities and corresponding isoforms mRNA levels to attenuate oxidative damage, which might be to the up-regulation of NF-E2-related factor 2 mRNA levels and down-regulation of Kelch-like ECH-associating protein 1a mRNA levels (P < .05). Besides, optimal MHA improved intercellular structure integrity of immune organs via up-regulating the mRNA levels of intercellular tight junctions-related genes, which might be owing to the down-regulation of myosin light chain kinase (MLCK) mRNA levels (P < .05). Summarily, MHA could improve the physical barrier of fish gill. In addition, optimal MHA supplementation increased lysozyme (LZ) and acid phosphatase (ACP) activities, complement 3 (C3), C4 and immunoglobulin M contents and up-regulated mRNA levels of liver-expressed antimicrobial peptide 2, hepcidin and β-defensin, suggesting that MHA could enhance antimicrobial ability of fish gill. Meanwhile, optimal MHA supplementation enhanced the immune defence of gill via down-regulating pro-inflammatory cytokines mRNA levels and up-regulated anti-inflammatory cytokines mRNA levels, which might be attributed to the down-regulation of nuclear factor κB p65, c-Rel, IκB kinase β, p38 mitogen activated protein kinase, eIF4E-binding protein1 (4E-BP1) and 4E-BP2 mRNA levels and up-regulation of inhibitor of κBα, ribosomal protein S6 kinase 1 and target of rapamycin mRNA levels (P < .05). In conclusion, the positive effect of MHA on gill health is associated with the improvement of the defence against apoptosis, antioxidant status, tight junctions and immune defence of fish gill. Meanwhile, MHA was superior to DLM on improving the physical barrier of fish gill. For the direction to healthy breeding of young grass carp, the optimal MHA supplementation levels on the premise of 4.01 g/kg methionine basal were estimated by quadratic regression curve, such as 5.49, 6.17 and 6.02 g/kg diet bases on the defence against gill-rot, malondialdehyde content and LZ activity in the gill, respectively.

Emerging Perspectives on mTOR Inhibitor-Associated Pneumonitis in Breast Cancer

Substantial improvements in the early detection and treatment of breast cancer have led to improvements in survival, but breast cancer remains a significant cause of morbidity and mortality in women. In 2012, the mammalian target of rapamycin (mTOR) inhibitor everolimus was approved by the U.S. Food and Drug Administration for the treatment of advanced breast cancer in patients resistant to endocrine therapy. Although everolimus is generally well tolerated, mTOR inhibitor-associated pneumonitis is one of the most common adverse drug events leading to treatment discontinuation. To date, the underlying pathophysiology of this toxicity is unclear, and this uncertainty may hinder the optimization of management strategies. However, experiences from breast cancer and renal cell carcinoma clinical trials indicate that mTOR inhibitor-associated pneumonitis can be effectively managed by early detection, accurate diagnosis, and prompt intervention that generally involves everolimus dose reductions, interruptions, or discontinuation. Management can be achieved by a multidisciplinary approach that involves the collaborative efforts of nurses, oncologists, radiologists, infectious disease specialists, pulmonologists, clinical pharmacists, and pathologists. Comprehensive education must be provided to all health care professionals involved in managing patients receiving everolimus therapy. Although general recommendations on the management of mTOR inhibitor-associated pneumonitis have been published, there is a lack of consensus on the optimal management of this potentially serious complication. This article provides an overview of mTOR inhibitor-associated pneumonitis, with a focus on the detection, accurate diagnosis, and optimal management of this class-related complication of mTOR inhibitor therapy.

IMPLICATIONS FOR PRACTICE

This article summarizes the pathogenesis, clinical presentation, incidence, detection, and optimal management of everolimus-related noninfectious pneumonitis in breast cancer. In particular, this article provides a detailed overview of the important aspects of the detection, accurate diagnosis, and appropriate management of mammalian target of rapamycin inhibitor-associated pneumonitis. In addition, this article emphasizes that effective management of this adverse drug event in patients with breast cancer will require a multidisciplinary approach and collaboration among various health care professionals.

Mammalian Target of Rapamycin Inhibition in Trypanosoma cruzi-Infected Macrophages Leads to an Intracellular Profile That Is Detrimental for Infection

The causative agent of Chagas’ disease, Trypanosoma cruzi, affects approximately 10 million people living mainly in Latin America, with macrophages being one of the first cellular actors confronting the invasion during T. cruzi infection and their function depending on their proper activation and polarization into distinct M1 and M2 subtypes. Macrophage polarization is thought to be regulated not only by cytokines and growth factors but also by environmental signals. The metabolic checkpoint kinase mammalian target of rapamycin (mTOR)-mediated sensing of environmental and metabolic cues influences macrophage polarization in a complex and as of yet incompletely understood manner. Here, we studied the role of the mTOR pathway in macrophages during T. cruzi infection. We demonstrated that the parasite activated mTOR, which was beneficial for its replication since inhibition of mTOR in macrophages by different inhibitors decreased parasite replication. Moreover, in rapamycin pretreated and infected macrophages, we observed a decreased arginase activity and expression, reduced IL-10 and increased interleukin-12 production, compared to control infected macrophages treated with DMSO. Surprisingly, we also found a reduced iNOS activity and expression in these macrophages. Therefore, we investigated possible alternative mechanisms involved in controlling parasite replication in rapamycin pretreated and infected macrophages. Although, cytoplasmic ROS and the enzyme indoleamine 2, 3-dioxygenase (IDO) were not involved, we observed a significant increase in IL-6, TNF-α, and IL-1β production. Taking into account that IL-1β is produced by activation of the cytoplasmic receptor NLRP3, which is one of the main components of the inflammasome, we evaluated NLRP3 expression during mTOR inhibition and T. cruzi infection. We observed that rapamycin-pretreated and infected macrophages showed a significant increase in NLRP3 expression and produced higher levels of mitochondrial ROS (mtROS) compared with control cells. Moreover, inhibition of mtROS production partially reversed the effect of rapamycin on parasite replication, with there being a significant increase in parasite load in rapamycin pretreated and infected macrophages from NLRP3 KO mice compared to wild-type control cells. Our findings strongly suggest that mTOR inhibition during T. cruzi infection induces NLRP3 inflammasome activation and mtROS production, resulting in an inflammatory-like macrophage profile that controls T. cruzi replication.

Inhibition of LPS-induced inflammatory mediators by 3-hydroxyanthranilic acid in macrophages through suppression of PI3K/NF-κB signaling pathways

Many tryptophan metabolites have immunomodulatory effects on various immune cells. 3-Hydroxyanthranilic Acid (3-HAA) is a tryptophan metabolite reported to have anti-inflammatory activity. The mechanism of this activity is unclear. The present study examined the immunomodulatory effects and molecular mechanisms of 3-HAA on macrophages. Pretreatment of 3-HAA (0.1-10 μg mL(-1)) for 2 h markedly inhibited NO and cytokine production in LPS-stimulated Raw 264.7 cells. Moreover, translocation and activation of NF-κB by LPS in the nucleus were abrogated through the prevention of IκB degradation by 3-HAA treatment. 3-HAA significantly suppressed LPS-induced PI3K/Akt/mTOR activation, whereas MAPKs were not affected by 3-HAA treatment. Furthermore, the inhibition of mTOR by 3-HAA resulted in decreased production of inflammatory mediators and NF-κB activity. Similar results were also observed in primary peritoneal macrophages. Furthermore, 3-HAA modulated macrophage polarization. Collectively, the results suggest that 3-HAA has an immunomodulatory effect that may result from inhibition of PI3K/Akt/mTOR and NF-κB activation, thereby decreasing the production of pro-inflammatory mediators.

MTOR signaling is essential for the development of thymic epithelial cells and the induction of central immune tolerance

Thymic epithelial cells (TECs) are critical for the establishment and maintenance of appropriate microenvironment for the positive and negative selection of thymocytes and the induction of central immune tolerance. Yet, little about the molecular regulatory network on TEC development and function is understood. Here, we demonstrate that MTOR (mechanistic target of rapamycin [serine/threonine kinase]) is essential for proper development and functional maturation of TECs. Pharmacological inhibition of MTOR activity by rapamycin (RPM) causes severe thymic atrophy and reduction of TECs. TEC-specific deletion of Mtor causes the severe reduction of mTECs, the blockage of thymocyte differentiation and output, the reduced generation of thymic regulatory T (Treg) cells and the impaired expression of tissue-restricted antigens (TRAs) including Fabp2, Ins1, Tff3 and Chrna1 molecules. Importantly, specific deletion of Mtor in TECs causes autoimmune diseases characterized by enhanced tissue immune cell infiltration and the presence of autoreactive antibodies. Mechanistically, Mtor deletion causes overdegradation of CTNNB1/Beta-Catenin due to excessive autophagy and the attenuation of WNT (wingless-type MMTV integration site family) signaling in TECs. Selective inhibition of autophagy significantly rescued the poor mTEC development caused by Mtor deficiency. Altogether, MTOR is essential for TEC development and maturation by regulating proliferation and WNT signaling activity through autophagy. The present study also implies that long-term usage of RPM might increase the risk of autoimmunity by impairing TEC maturation and function.

mTOR drives cerebral blood flow and memory deficits in LDLR-/- mice modeling atherosclerosis and vascular cognitive impairment

We recently showed that mTOR attenuation blocks progression and abrogates established cognitive deficits in Alzheimer's disease (AD) mouse models. These outcomes were associated with the restoration of cerebral blood flow (CBF) and brain vascular density (BVD) resulting from relief of mTOR inhibition of NO release. Recent reports suggested a role of mTOR in atherosclerosis. Because mTOR drives aging and vascular dysfunction is a universal feature of aging, we hypothesized that mTOR may contribute to brain vascular and cognitive dysfunction associated with atherosclerosis. We measured CBF, BVD, cognitive function, markers of inflammation, and parameters of cardiovascular disease in LDLR-/- mice fed maintenance or high-fat diet ± rapamycin. Cardiovascular pathologies were proportional to severity of brain vascular dysfunction. Aortic atheromas were reduced, CBF and BVD were restored, and cognitive dysfunction was attenuated potentially through reduction in systemic and brain inflammation following chronic mTOR attenuation. Our studies suggest that mTOR regulates vascular integrity and function and that mTOR attenuation may restore neurovascular function and cardiovascular health. Together with our previous studies in AD models, our data suggest mTOR-driven vascular damage may be a mechanism shared by age-associated neurological diseases. Therefore, mTOR attenuation may have promise for treatment of cognitive impairment in atherosclerosis.

mTOR inhibition improves the immunomodulatory properties of human bone marrow mesenchymal stem cells by inducing COX-2 and PGE2

Background

Bone marrow mesenchymal stem cells (MSCs) are promising candidates for the treatment of various inflammatory disorders due to their profound immunomodulatory properties. However, the immunosuppressive capacity of MSCs needs activation by an inflammatory microenvironment, which may negatively impact the therapeutic effect because of increased immunogenicity. Here we explore the role of mammalian target of rapamycin (mTOR) signaling on the immunosuppressive capacity of MSCs, and its impact on immunogenicity in the inflammatory microenvironment.

Methods

Human bone marrow MSCs were cocultured with activated human peripheral blood mononuclear cells, CD4⁺ T cells, and mouse splenocytes to evaluate the immunosuppressive function. Immunosuppressive factors were assessed by quantitative real-time polymerase chain reaction (PCR), Western blot, and enzyme-linked immunosorbent assay (ELISA). The expression of major histocompatibility complex (MHC) was detected by flow cytometry. Short hairpin (sh)RNA was used to downregulate tuberous sclerosis complex (TSC)2, TSC1, and cyclooxygenase (COX)-2 in MSCs.

Results

Inhibition of mTOR signaling using rapamycin enhanced the immunosuppressive functions of MSCs, while prolonged exposure to rapamycin did not. The enhancement of the immunosuppressive function was independent of the inflammatory microenvironment, and occurred mainly through the upregulation of COX-2 and prostaglandin-E₂ (PGE₂) expression. Furthermore, mTOR inhibition did not impact the immunogenicity of MSCs. However, the upregulated expression of MHC class II molecules by interferon (IFN)-γ was attenuated by mTOR inhibition, whereas TSC2 knockdown had the opposite effect.

Conclusions

These results reveal that the mTOR signaling pathway regulates MSC immunobiology, and short-term exposure to rapamycin could be a novel approach to improve the MSC-based therapeutic effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0744-6) contains supplementary material, which is available to authorized users.

Therapeutic potency of mTOR signaling pharmacological inhibitors in the treatment of proinflammatory diseases, current status, and perspectives

Mammalian target of rapamycin (mTOR) signaling pathway controls cell energy metabolism. There is an interplay between mTOR and proinflammatory signaling pathways, supporting the role of the pathway in the pathogenesis of inflammatory diseases. Inhibition of mTOR signaling using specific pharmacological inhibitors could offer therapeutic promise in several inflammatory-associated diseases. In this review, we summarize recent findings on the regulatory effects of mTOR signaling on inflammation and the therapeutic potency of mTOR pharmacological inhibitors in the treatment of inflammatory diseases including cancer, neurodegenerative diseases, atherosclerosis, sepsis, and rheumatoid arthritis for a better understanding and hence a better management of these diseases.

Leucine alters immunoglobulin a secretion and inflammatory cytokine expression induced by lipopolysaccharide via the nuclear factor-κB pathway in intestine of chicken embryos

The mammalian target of rapamycin (mTOR) has been shown to be involved in lipopolysaccharide (LPS)-induced immune responses in many mammal cells. Here, we suggest that the mTOR pathway is involved in the intestinal inflammatory responses evoked by LPS treatment in chicken embryos. The intestinal tissue from Specific pathogen free chick embryos was cultured in the presence of LPS for 2 h. Secretory immunoglobulin A (sIgA) concentrations, messenger RNA (mRNA) expression of cytokines, and protein levels of nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK), mTOR and p70 ribosomal S6 kinase (p70S6K) were determined. The results showed that LPS treatment increased sIgA concentrations in a dose-dependent manner. The mRNA levels of interleukine (IL)-6, IL-8, IL-10, tumor necrosis factor-α and Toll-like receptor (TLR) 4 were upregulated by LPS treatment (P<0.05). Lipopolysaccharide increased the phosphorylation of Jun N-terminal kinase (JNK), p38 MAPK and NF-κB (P<0.05) while decreasing the phosphorylation level of mTOR (P<0.05). Supplementation of leucine at doses of 10, 20 and 40 mM dose-dependently decreased sIgA production. Leucine supplementation at 40 mM restored the phosphorylation level of mTOR and p70S6K while suppressing the phosphorylation levels of NF-κB (P<0.05) and partially down-regulating the phosphorylation of p38 MAPK and JNK. The transcription of IL-6 was significantly decreased by leucine supplementation. These results suggested that leucine could alleviate LPS-induced inflammatory responses by down-regulating NF-κB signaling pathway and evoking mTOR/p70S6K signaling pathway, which may involve in the regulation of the intestinal immune system in chicken embryos.

mTORC1-mediated downregulation of COX2 restrains tumor growth caused by TSC2 deficiency

Tuberous sclerosis complex (TSC), caused by loss-of-function mutations in the TSC1 or TSC2 gene, is characterized by benign tumor formation in multiple organs. Hyperactivation of mammalian target of rapamycin complex 1 (mTORC1) is the primary alteration underlying TSC tumors. By analyzing Tsc2-null mouse embryonic fibroblasts (MEFs) and rat uterine leiomyoma-derived Tsc2-null ELT3 cells, we detected evidence for the involvement of cyclooxygenase 2 (COX2) as a downstream target of mTORC1 in the development of TSC tumors. We showed that loss of TSC2 led to decreased COX2 expression through activation of an mTORC1/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Overexpression of COX2 promoted proliferation and tumoral growth of Tsc2-null cells. COX2 knockdown inhibited the proliferation of the control cells. COX2 enhanced Tsc2-null cell growth through upregulation of interleukin-6 (IL-6). In addition, rapamycin in combination with celecoxib, a COX2 inhibitor, strongly inhibited Tsc2-deficient cell growth. We conclude that downregulation of COX2 exerts a protective effect against hyperactivated mTORC1-mediated tumorigenesis caused by the loss of TSC2, and the combination of rapamycin and celecoxib may be an effective new approach to treating TSC.

New insights into the role of dietary spermine on inflammation, immune function and related-signalling molecules in the thymus and spleen of piglets

This study aimed to determine the effects of dietary spermine supplementation on the inflammatory response and immune function of the thymus and spleen in piglets. Eighty suckling piglets were randomly assigned to receive adequate nutrients supplemented with spermine (0.4 mmol/kg body weight) or restricted nutrient intake supplemented with normal saline for 7 h or 3, 6 and 9 days in pairs. Regardless of treatment time, spermine supplementation decreased (p < 0.05, compared with the controls) the following: (1) tumour necrosis factor α (TNF-α), interleukin (IL)-1β, 2 and 6, and interferon (IFN)-γ levels in serum; (2) gene expression of cluster of differentiation 8 and integrin beta-2 in the thymus and spleen and the lymphocyte function-associated antigen 1 in the thymus; (3) mRNA levels of TNF-α, IL 1β, 2, 6, and 12, IFN-γ and inducible nitric oxide synthase in the thymus and spleen, as well as IL-8 in the spleen; and (4) eukaryotic IF4E-binding protein 1, Janus kinase 2, signal transducer and activator of transcription 3, and nuclear factor-kappa B P65 gene transcriptions in the thymus and spleen. By contrast, spermine supplementation increased (p < 0.05) the following: (1) immunoglobulin M, IL-10, and transforming growth factor β1 gene expression, as well as (2) relative mRNA levels of mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase 1 in the thymus and spleen. These effects were also observed upon prolonged spermine administration (p < 0.05). In summary, dietary spermine supplementation can alleviate inflammatory response, enhance the immune function and regulate the gene expression of signalling molecules related to inflammation.

Phosphoproteomics of cAMP signaling of Bordetella adenylate cyclase toxin in mouse dendritic cells

The adenylate cyclase toxin (CyaA) of the whooping cough agent Bordetella pertussis subverts immune functions of host myeloid cells expressing the αMβ2 integrin (CD11b/CD18, CR3 or Mac-1). CyaA delivers into cytosol of cells an extremely catalytically active adenylyl cyclase enzyme, which disrupts the innate and adaptive immune functions of phagocytes through unregulated production of the key signaling molecule cAMP. We have used phosphoproteomics to analyze cAMP signaling of CyaA in murine bone marrow-derived dendritic cells. CyaA action resulted in alterations of phosphorylation state of a number of proteins that regulate actin cytoskeleton homeostasis, including Mena, Talin-1 and VASP. CyaA action repressed mTOR signaling through activation of mTORC1 inhibitors TSC2 and PRAS40 and altered phosphorylation of multiple chromatin remodelers, including the class II histone deacetylase HDAC5. CyaA toxin action further elicited inhibitory phosphorylation of SIK family kinases involved in modulation of immune response and provoked dephosphorylation of the transcriptional coactivator CRTC3, indicating that CyaA-promoted nuclear translocation of CRTC3 may account for CyaA-induced IL-10 production. These findings document the complexity of subversive physiological manipulation of myeloid phagocytes by the CyaA toxin, serving in immune evasion of the pertussis agent.

mTOR intersects antibody-inducing signals from TACI in marginal zone B cells

Mechanistic target of rapamycin (mTOR) enhances immunity in addition to orchestrating metabolism. Here we show that mTOR coordinates immunometabolic reconfiguration of marginal zone (MZ) B cells, a pre-activated lymphocyte subset that mounts antibody responses to T-cell-independent antigens through a Toll-like receptor (TLR)-amplified pathway involving transmembrane activator and CAML interactor (TACI). This receptor interacts with mTOR via the TLR adapter MyD88. The resulting mTOR activation instigates MZ B-cell proliferation, immunoglobulin G (IgG) class switching, and plasmablast differentiation through a rapamycin-sensitive pathway that integrates metabolic and antibody-inducing transcription programs, including NF-κB. Disruption of TACI-mTOR interaction by rapamycin, truncation of the MyD88-binding domain of TACI, or B-cell-conditional mTOR deficiency interrupts TACI signaling via NF-κB and cooperation with TLRs, thereby hampering IgG production to T-cell-independent antigens but not B-cell survival. Thus, mTOR drives innate-like antibody responses by linking proximal TACI signaling events with distal immunometabolic transcription programs.

Molecular Mechanisms Modulating the Phenotype of Macrophages and Microglia

Macrophages and microglia play crucial roles during central nervous system development, homeostasis and acute events such as infection or injury. The diverse functions of tissue macrophages and microglia are mirrored by equally diverse phenotypes. A model of inflammatory/M1 versus a resolution phase/M2 macrophages has been widely used. However, the complexity of macrophage function can only be achieved by the existence of varied, plastic and tridimensional macrophage phenotypes. Understanding how tissue macrophages integrate environmental signals via molecular programs to define pathogen/injury inflammatory responses provides an opportunity to better understand the multilayered nature of macrophages, as well as target and modulate cellular programs to control excessive inflammation. This is particularly important in MS and other neuroinflammatory diseases, where chronic inflammatory macrophage and microglial responses may contribute to pathology. Here, we perform a comprehensive review of our current understanding of how molecular pathways modulate tissue macrophage phenotype, covering both classic pathways and the emerging role of microRNAs, receptor-tyrosine kinases and metabolism in macrophage phenotype. In addition, we discuss pathway parallels in microglia, novel markers helpful in the identification of peripheral macrophages versus microglia and markers linked to their phenotype.

Dietary pyridoxine deficiency reduced growth performance and impaired intestinal immune function associated with TOR and NF-κB signalling of young grass carp (Ctenopharyngodon idella)

The objective of this study was to evaluate the effects of dietary pyridoxine (PN) deficiency on growth performance, intestinal immune function and the potential regulation mechanisms in young grass carp (Ctenopharyngodon idella). Fish were fed six diets containing graded levels of PN (0.12-7.48 mg/kg) for 70 days. After that, a challenge test was conducted by infection of Aeromonas hydrophila for 14 days. The results showed that compared with the optimal PN level, PN deficiency: (1) reduced the production of innate immune components such as lysozyme (LZ), acid phosphatase (ACP), complements and antimicrobial peptides and adaptive immune components such as immunoglobulins in three intestinal segments of young grass carp (P < 0.05); (2) down-regulated the mRNA levels of anti-inflammatory cytokines such as transforming growth factor β (TGF-β), interleukin 4/13A (IL-4/13A) (rather than IL-4/13B), IL-10 and IL-11 partly relating to target of rapamycin (TOR) signalling [TOR/ribosomal protein S6 kinases 1 (S6K1) and eIF4E-binding proteins (4E-BP)] in three intestinal segments of young grass carp; (3) up-regulated the mRNA levels of pro-inflammatory cytokines such as tumour necrosis factor α (TNF-α) [not in the proximal intestine (PI) and distal intestine (DI)], IL-1β, IL-6, IL-8, IL-12p35, IL-12p40, IL-15 and IL-17D [(rather than interferon γ2 (IFN-γ2)] partly relating to nuclear factor kappa B (NF-κB) signalling [IκB kinase β (IKKβ) and IKKγ/inhibitor of κBα (IκBα)/NF-κB (p65 and c-Rel)] in three intestinal segments of young grass carp. These results suggest that PN deficiency could impair the intestinal immune function, and the potential regulation mechanisms were partly associated with TOR and NF-κB signalling pathways. In addition, based on percent weight gain (PWG), the ability against enteritis and LZ activity, the dietary PN requirements for young grass carp were estimated to be 4.43, 4.75 and 5.07 mg/kg diet, respectively.

Effects of dietary hawthorn extract on growth performance, immune responses, growth- and immune-related genes expression of juvenile golden pompano (Trachinotus ovatus) and its susceptibility to Vibrio harveyi infection

The present study was conducted to investigate the effects of dietary hawthorn extract (HTE) supplementation on growth performance, immune responses, hepatic antioxidant abilities, growth- and immune-related and heat shock protein genes expression and resistance to the pathogen Vibrio harveyi in Trachinotus ovatus. A basal diet supplemented with HTE at 0 (Diet 1), 0.50 (Diet 2), 1.00 (Diet 3), 2.00 (Diet 4), 4.00 (Diet 5) and 10.00 (Diet 6) g kg^-1 were fed to golden pompano for 8 weeks. The highest final body weight, weight gain rate, specific growth rate, feed efficiency ratio and protein efficiency rate were observed in fish fed Diet 2 (P < 0.05). Dietary HTE significantly increased plasma complement 3, complement 4 and immunoglobulin M content (P < 0.05). Hepatic antioxidant enzymes (SOD, T-AOC, CAT, GPx, GR) significantly increased (P < 0.05), whereas MDA content decreased first and then increased in fish fed HTE supplement. After challenge with Vibrio harveyi, significant higher post-challenge survival was observed in fish fed Diet 2 and Diet 3 than the control group (P < 0.05). Transcription levels of growth-related genes (IGF-I and IGF-II) were significantly up-regulated in fish fed HTE supplement (P < 0.05), whereas HSP70 and HSP90 mRNA levels were significantly down-regulated (P < 0.05). With respect to immune-related genes, such as tumour necrosis factor-alpha (TNF-α), interleukin-8 (IL-8) and inhibitor protein κBα (IκB-α), upregulation was observed in the liver of fish fed with the diet supplemented with HTE. In contrast, the expression of antioxidant enzyme genes (CAT, GPx, MnSOD and Keap1) and cytokines (IL-10, TGF-β1 and TOR) was downregulated. These results indicated that golden pompano fed a diet supplemented with 0.50 g kg^-1 HTE could significantly promote growth performance and growth-related genes expression, strengthen immunity, and improve hepatic antioxidative abilities and resistance to Vibrio harveyi infection.

Structure-Function Relationships Underlying the Capacity of Bordetella Adenylate Cyclase Toxin to Disarm Host Phagocytes

Bordetellae, pathogenic to mammals, produce an immunomodulatory adenylate cyclase toxin-hemolysin (CyaA, ACT or AC-Hly) that enables them to overcome the innate immune defense of the host. CyaA subverts host phagocytic cells by an orchestrated action of its functional domains, where an extremely catalytically active adenylyl cyclase enzyme is delivered into phagocyte cytosol by a pore-forming repeat-in-toxin (RTX) cytolysin moiety. By targeting sentinel cells expressing the complement receptor 3, known as the CD11b/CD18 (α_Mβ₂) integrin, CyaA compromises the bactericidal functions of host phagocytes and supports infection of host airways by Bordetellae. Here, we review the state of knowledge on structural and functional aspects of CyaA toxin action, placing particular emphasis on signaling mechanisms by which the toxin-produced 3',5'-cyclic adenosine monophosphate (cAMP) subverts the physiology of phagocytic cells.

Aloperine Protects Mice against DSS-Induced Colitis by PP2A-Mediated PI3K/Akt/mTOR Signaling Suppression

Colitis is a major form of inflammatory bowel disease which involved mucosal immune dysfunction. Aloperine is an alkaloid isolated from the shrub Sophora alopecuroides L. and has been recognized as an effective treatment for inflammatory and allergic diseases. The present study aimed to examine the molecular mechanisms underlying aloperine-mediated colitis protection. We found that aloperine treatment improved colitis induced by dextran sodium sulfate (DSS) based on body weight, disease activity index, colonic length, and spleen index. Aloperine also effectively attenuated DSS-induced intestinal inflammation based on the pathological score and myeloperoxidase expression and activity in colon tissues. In addition, aloperine regulated T-cell proportions and promoted Foxp3 expression in the spleens and mesenteric lymph nodes of DSS-induced colitis mice and in the spleens of the Foxp3^GFP mice. Aloperine inhibited Jurkat and mouse naïve T-cell apoptosis. Furthermore, aloperine inhibited PI3K/Akt/mTOR signaling and upregulated PP2A expression in the DSS-induced colitis mice and in Jurkat cells, but LB-100 (PP2A inhibitor) resulted in an elevated Akt activity in Jurkat cells, activated T-cells, and human splenic mononuclear cells. Aloperine inhibited T-cell and lymphocyte proliferation, but LB-100 reverse these effects. In conclusion, aloperine regulates inflammatory responses in colitis by inhibiting the PI3K/Akt/mTOR signaling in a PP2A-dependent manner.

MenTORing Immunity: mTOR Signaling in the Development and Function of Tissue-Resident Immune Cells

Tissue-resident immune cells must balance survival in peripheral tissues with the capacity to respond rapidly upon infection or tissue damage, and in turn couple these responses with intrinsic metabolic control and conditions in the tissue microenvironment. The serine/threonine kinase mammalian/mechanistic target of rapamycin (mTOR) is a central integrator of extracellular and intracellular growth signals and cellular metabolism and plays important roles in both innate and adaptive immune responses. This review discusses the function of mTOR signaling in the differentiation and function of tissue-resident immune cells, with focus on the role of mTOR as a metabolic sensor and its impact on metabolic regulation in innate and adaptive immune cells. We also discuss the impact of metabolic constraints in tissues on immune homeostasis and disease, and how manipulating mTOR activity with drugs such as rapamycin can modulate immunity in these contexts.

Critical role of mammalian target of rapamycin for IL-10 dendritic cell induction by a flagellin A conjugate in preventing allergic sensitization

BACKGROUND

Fusion proteins incorporating the Toll-like receptor 5 ligand flagellin are currently undergoing clinical trials as vaccine candidates for many diseases.

OBJECTIVE

We studied the mechanisms of immune modulation by a flagellin:allergen fusion protein containing the Toll-like receptor 5 ligand flagellin A from Listeria monocytogenes and the birch pollen allergen Bet v 1 (recombinant flagellin A [rFlaA]:Betv1).

METHODS

BALB/c mice were vaccinated with rFlaA:Betv1 in an experimental Bet v 1 sensitization model. Myeloid dendritic cells (mDCs) were differentiated from mouse bone marrow, and PBMCs were isolated from subjects with birch pollen allergy. Cells were stimulated with equimolar amounts of rFlaA, rBet v 1, rFlaA plus rBet v 1, or the rFlaA:Betv1 conjugate and analyzed for cell activation, cytokine secretion, and metabolic state.

RESULTS

rFlaA:Betv1 displayed strong immune-modulating properties both in vivo and in vitro, as characterized by secretion of both proinflammatory and anti-inflammatory cytokines from murine mDCs and PBMCs from patients with birch allergy. rFlaA:Betv1 suppressed T_H2 responses from Bet v 1-specific CD4⁺ T cells and prevented allergic sensitization in a mouse allergy model. Aggregation of rFlaA:Betv1 resulted in stronger protein uptake accompanied by an increased resistance to microsomal digestion. Remarkably, rFlaA:Betv1 induced activation of mammalian target of rapamycin, which increased the metabolic activity of the stimulated mDCs. rFlaA:Betv1-mediated IL-10 secretion, but not proinflammatory cytokine secretion, was inhibited by rapamycin in mDCs.

CONCLUSION

These results provide evidence that mammalian target of rapamycin is a key player involved in prevention of T_H2 responses by flagellin A conjugate vaccines.

Autophagy: The spotlight for cellular stress responses

Autophagy is an essential cellular mechanism which plays "housekeeping" role in normal physiological processes including removing of long lived, aggregated and misfolded proteins, clearing damaged organelles, growth regulation and aging. Autophagy is also involved in a variety of biological functions like development, cellular differentiation, defense against pathogens and nutritional starvation. The integration of autophagy into these biological functions and other stress responses is determined by the transcriptional factors that undertake the regulatory mechanism. This review discusses the machinery of autophagy, the molecular web that connects autophagy to various stress responses like inflammation, hypoxia, ER stress, and various other pathologic conditions. Defects in autophagy regulation play a central role in number of diseases, including neurodegenerative diseases, cancer, pathogen infection and metabolic diseases. Similarly, inhibiting autophagy would contribute in the treatment of cancer. However, understanding the biology of autophagy regulation requires pharmacologically active compounds which modulate the autophagy process. Inducers of autophagy are currently receiving considerable attention as autophagy upregulation may be a therapeutic benefit for certain neurodegenerative diseases (via removal of protein aggregates) while the inhibitors are being investigated for the treatment of cancers. Both induction and inhibition of autophagy have been proven to be beneficial in the treatment of cancer. This dual role of autophagy in cancers is now getting uncovered by the advancement in the research findings and development of effective autophagy modulators.

Space-type radiation induces multimodal responses in the mouse gut microbiome and metabolome

BACKGROUND

Space travel is associated with continuous low dose rate exposure to high linear energy transfer (LET) radiation. Pathophysiological manifestations after low dose radiation exposure are strongly influenced by non-cytocidal radiation effects, including changes in the microbiome and host gene expression. Although the importance of the gut microbiome in the maintenance of human health is well established, little is known about the role of radiation in altering the microbiome during deep-space travel.

RESULTS

Using a mouse model for exposure to high LET radiation, we observed substantial changes in the composition and functional potential of the gut microbiome. These were accompanied by changes in the abundance of multiple metabolites, which were related to the enzymatic activity of the predicted metagenome by means of metabolic network modeling. There was a complex dynamic in microbial and metabolic composition at different radiation doses, suggestive of transient, dose-dependent interactions between microbial ecology and signals from the host's cellular damage repair processes. The observed radiation-induced changes in microbiota diversity and composition were analyzed at the functional level. A constitutive change in activity was found for several pathways dominated by microbiome-specific enzymatic reactions like carbohydrate digestion and absorption and lipopolysaccharide biosynthesis, while the activity in other radiation-responsive pathways like phosphatidylinositol signaling could be linked to dose-dependent changes in the abundance of specific taxa.

CONCLUSIONS

The implication of microbiome-mediated pathophysiology after low dose ionizing radiation may be an unappreciated biologic hazard of space travel and deserves experimental validation. This study provides a conceptual and analytical basis of further investigations to increase our understanding of the chronic effects of space radiation on human health, and points to potential new targets for intervention in adverse radiation effects.

Akt Signaling Pathway in Macrophage Activation and M1/M2 Polarization

Macrophages become activated initiating innate immune responses. Depending on the signals, macrophages obtain an array of activation phenotypes, described by the broad terms of M1 or M2 phenotype. The PI3K/Akt/mTOR pathway mediates signals from multiple receptors including insulin receptors, pathogen-associated molecular pattern receptors, cytokine receptors, adipokine receptors, and hormones. As a result, the Akt pathway converges inflammatory and metabolic signals to regulate macrophage responses modulating their activation phenotype. Akt is a family of three serine-threonine kinases, Akt1, Akt2, and Akt3. Generation of mice lacking individual Akt, PI3K, or mTOR isoforms and utilization of RNA interference technology have revealed that Akt signaling pathway components have distinct and isoform-specific roles in macrophage biology and inflammatory disease regulation, by controlling inflammatory cytokines, miRNAs, and functions including phagocytosis, autophagy, and cell metabolism. Herein, we review the current knowledge on the role of the Akt signaling pathway in macrophages, focusing on M1/M2 polarization and highlighting Akt isoform-specific functions.

mTOR regulates metabolic adaptation of APCs in the lung and controls the outcome of allergic inflammation

Antigen-presenting cells (APCs) occupy diverse anatomical tissues, but their tissue-restricted homeostasis remains poorly understood. Here, working with mouse models of inflammation, we found that mechanistic target of rapamycin (mTOR)-dependent metabolic adaptation was required at discrete locations. mTOR was dispensable for dendritic cell (DC) homeostasis in secondary lymphoid tissues but necessary to regulate cellular metabolism and accumulation of CD103⁺ DCs and alveolar macrophages in lung. Moreover, while numbers of mTOR-deficient lung CD11b⁺ DCs were not changed, they were metabolically reprogrammed to skew allergic inflammation from eosinophilic T helper cell 2 (T_H2) to neutrophilic T_H17 polarity. The mechanism for this change was independent of translational control but dependent on inflammatory DCs, which produced interleukin-23 and increased fatty acid oxidation. mTOR therefore mediates metabolic adaptation of APCs in distinct tissues, influencing the immunological character of allergic inflammation.

Knockdown of miR-155 protects microglia against LPS-induced inflammatory injury via targeting RACK1: a novel research for intracranial infection

Background

Intracranial infection, one of the complications of traumatic brain injury, is usually associated with inflammation. Several microRNAs (miRNAs), including miR-155, have been reported to be critical modulators in peripheral and central nervous system inflammation. In this study, we investigated the role of miR-155 in lipopolysaccharide (LPS)-induced inflammatory injury in mouse microglia BV2 cells.

Results

The expression level of miR-155 was significantly up-regulated after LPS stimulation in BV2 cells. LPS administration decreased BV2 cell viability, promoted apoptosis and increased the release of pro-inflammatory cytokines; while miR-155 knockdown rescued BV2 cell from LPS-induced injury. RACK1 was a directly target of miR-155. Interestingly, miR-155 knockdown did not attenuate LPS-induced inflammatory injury when RACK1 was knocked down. The mechanistic study indicated that miR-155 knockdown deactivated MAPK/NF-κB and mTOR signaling pathways under LPS-treated conditions.

Conclusions

Knockdown of miR-155 protected mouse microglia BV2 cells from LPS-induced inflammatory injury via targeting RACK1 and deactivating MAPK/NF-κB and mTOR signaling pathways.

Colonic Crohn Disease After Cardiac Transplantation: Case Report and Literature Review

Inflammatory bowel disease (IBD) after solid organ transplantation is rare. We report new-onset Crohn’s disease successfully treated with anti-tnfα therapy in a cardiac transplantation recipient. Our case highlights the importance of including IBD in the differential of chronic diarrhea despite significant immunosuppression and suggests that anti-tnf alpha therapy is effective in post-transplant IBD.

Fasting metabolism modulates the interleukin-12/interleukin-10 cytokine axis

A crucial role of cell metabolism in immune cell differentiation and function has been recently established. Growing evidence indicates that metabolic processes impact both, innate and adaptive immunity. Since a down-stream integrator of metabolic alterations, mammalian target of rapamycin (mTOR), is responsible for controlling the balance between pro-inflammatory interleukin (IL)-12 and anti-inflammatory IL-10, we investigated the effect of upstream interference using metabolic modulators on the production of pro- and anti-inflammatory cytokines. Cytokine release and protein expression in human and murine myeloid cells was assessed after toll-like receptor (TLR)-activation and glucose-deprivation or co-treatment with 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) activators. Additionally, the impact of metabolic interference was analysed in an in-vivo mouse model. Glucose-deprivation by 2-deoxy-D-glucose (2-DG) increased the production of IL-12p40 and IL-23p19 in monocytes, but dose-dependently inhibited the release of anti-inflammatory IL-10. Similar effects have been observed using pharmacological AMPK activation. Consistently, an inhibition of the tuberous sclerosis complex-mTOR pathway was observed. In line with our in vitro observations, glycolysis inhibition with 2-DG showed significantly reduced bacterial burden in a Th2-prone Listeria monocytogenes mouse infection model. In conclusion, we showed that fasting metabolism modulates the IL-12/IL-10 cytokine balance, establishing novel targets for metabolism-based immune-modulation.

Vibrio vulnificus induces mTOR activation and inflammatory responses in macrophages

Vibrio vulnificus (V. vulnificus), a Gram-negative marine bacterium, can cause life-threatening primary septicemia, especially in patients with liver diseases. How V. vulnificus affects the liver and how it acts on macrophages are not well understood. In this report, we demonstrated that V. vulnificus infection causes a strong inflammatory response, marked expansion of liver-resident macrophages, and liver damage in mice. We demonstrated further that V. vulnificus activates mTOR in macrophages and inhibition of mTOR differentially regulates V. vulnificus induced inflammatory responses, suggesting the possibility of targeting mTOR as a strategy to modulate V. vulnificus induced inflammatory responses.