Rapamycin specifically interferes with GM-CSF signaling in human dendritic cells, leading to apoptosis via increased p27KIP1 expression

Intravesical instillation-based mTOR-STAT3 dual targeting for bladder cancer treatment

BACKGROUND

Recent intravesical administration of adenoviral vectors, either as a single injection or in combination with immune checkpoint inhibitors, exemplified by cretostimogene grenadenorepvec and nadofaragene firadenovec, has demonstrated remarkable efficacy in clinical trials for non-muscle invasive bladder cancer. Despite their ability to induce an enhanced immune reaction within the lesion, the intracellular survival signaling of cancer cells has not been thoroughly addressed.

METHODS

An analysis of the prognostic data revealed a high probability of therapeutic efficacy with simultaneous inhibition of mTOR and STAT3. Considering the challenges of limited pharmaco-accessibility to the bladder due to its pathophysiological structure and the partially undruggable nature of target molecules, we designed a dual siRNA system targeting both mRNAs. Subsequently, this dual siRNA system was encoded into the adenovirus 5/3 (Ad 5/3) to enhance in vivo delivery efficiency.

RESULTS

Gene-targeting efficacy was assessed using cells isolated from xenografted tumors using a single-cell analysis system. Our strategy demonstrated a balanced downregulation of mTOR and STAT3 at the single-cell resolution, both in vitro and in vivo. This approach reduced tumor growth in bladder cancer xenograft and orthotopic animal experiments. In addition, increased infiltration of CD8+ T cells was observed in a humanized mouse model. We provided helpful and safe tissue distribution data for intravesical therapy of siRNAs coding adenoviruses.

CONCLUSIONS

The bi-specific siRNA strategy, encapsulated in an adenovirus, could be a promising tool to augment cancer treatment efficacy and overcome conventional therapy limitations associated with "undruggability." Hence, we propose that dual targeting of mTOR and STAT3 is an advantageous strategy for intravesical therapy using adenoviruses.

Cancer immunometabolism: advent, challenges, and perspective

For decades, great strides have been made in the field of immunometabolism. A plethora of evidence ranging from basic mechanisms to clinical transformation has gradually embarked on immunometabolism to the center stage of innate and adaptive immunomodulation. Given this, we focus on changes in immunometabolism, a converging series of biochemical events that alters immune cell function, propose the immune roles played by diversified metabolic derivatives and enzymes, emphasize the key metabolism-related checkpoints in distinct immune cell types, and discuss the ongoing and upcoming realities of clinical treatment. It is expected that future research will reduce the current limitations of immunotherapy and provide a positive hand in immune responses to exert a broader therapeutic role.

The Influence of Metabolism on Immune Response: A Journey to Understand Immunometabolism in the Context of Viral Infection

In recent years, the emergence of the concept of immunometabolism has shed light on the pivotal role that cellular metabolism plays in both the activation of immune cells and the development of immune programs. The antiviral response, a widely distributed defense mechanism used by infected cells, serves to not only control infections but also to attenuate their deleterious effects. The exploration of the role of metabolism in orchestrating the antiviral response represents a burgeoning area of research, especially considering the escalating incidence of viral outbreaks coupled with the increasing prevalence of metabolic diseases. Here, we present a review of current knowledge regarding immunometabolism and the antiviral response during viral infections. Initially, we delve into the concept of immunometabolism by examining its application in the field of cancer-a domain that has long spearheaded inquiries into this fascinating intersection of disciplines. Subsequently, we explore examples of immune cells whose activation is intricately regulated by metabolic processes. Progressing with a systematic and cellular approach, our aim is to unravel the potential role of metabolism in antiviral defense, placing significant emphasis on the innate and canonical interferon response.

An optimized cocktail of small molecule inhibitors promotes the maturation of dendritic cells in GM-CSF mouse bone marrow culture

Dendritic cells (DCs) are the most potent antigen-presenting cells, playing an essential role in the pathogen and tumor recognition, and anti-tumor immunity, and linking both the innate and adaptive immunity. The monocyte-derived DCs generated by ex vivo culture, have been used for cancer immunotherapy to eliminate tumor; however, the clinical efficacies are not sufficient, and further improvement is essential. In this study, we established a method to generate DCs using small molecule compounds for cancer immunotherapy. We observed an increase in the percentage of CD11c+I-A/I-Ehigh cells, representing DCs, by adding four small molecular inhibitors: Y27632, PD0325901, PD173074, and PD98059 (abbreviated as YPPP), in mouse bone marrow (BM) culture with granulocyte-macrophage colony stimulating factor (GM-CSF). BM-derived DCs cultured with YPPP (YPPP-DCs) showed high responsiveness to lipopolysaccharide stimulation, resulting in increased interleukin (IL) -12 production and enhanced proliferation activity when co-cultured with naïve T cells compared with the vehicle control. RNA-seq analysis revealed an upregulation of peroxisome proliferator - activated receptor (PPAR) γ associated genes increased in YPPP-DCs. In tumor models treated with anti-programmed death (PD) -1 therapies, mice injected intratumorally with YPPP-DCs as a DCs vaccine exhibited reduced tumor growth and increased survival. These findings suggested that our method would be useful for the induction of DCs that efficiently activate effector T cells for cancer immunotherapy.

Metabolic regulation of dendritic cell activation and immune function during inflammation

Dendritic cells (DCs) are antigen-presenting cells that bridge innate and adaptive immune responses. Multiple cell types, including DCs, rely on cellular metabolism to determine their fate. DCs substantially alter cellular metabolic pathways during activation, such as oxidative phosphorylation, glycolysis, fatty acid and amino acid metabolism, which have crucial implications for their functionality. In this review, we summarize and discuss recent progress in DC metabolic studies, focusing on how metabolic reprogramming influences DC activation and functionality and the potential metabolic differences among DC subsets. Improving the understanding of the relationship between DC biology and metabolic regulation may provide promising therapeutic targets for immune-mediated inflammatory diseases.

How to improve results after DCD (donation after circulation death)

The shortage of organs for transplantation has led health professionals to look for alternative sources of donors. One of the avenues concerns donors who have died after circulatory arrest. This is a special situation because the organs from these donors are exposed to warm ischaemia-reperfusion lesions that are unavoidable during the journey of the organs from the donor to the moment of transplantation in the recipient. We will address and discuss the key issues from the perspective of team organization, legislation and its evolution, and the ethical framework. In a second part, the avenues to improve the quality of organs will be presented following the itinerary of the organs between the donor and the recipient. The important moments from the point of view of therapeutic strategy will be put into perspective. New connections between key players involved in pathophysiological mechanisms and implications for innate immunity and injury processes are among the avenues to explore. Technological developments to improve the quality of organs from these recipients will be analyzed, such as perfusion techniques with new modalities of temperatures and oxygenation. New molecules are being investigated for their potential role in protecting these organs and an analysis of potential prospects will be proposed. Finally, the important perspectives that seem to be favored will be discussed in order to reposition the use of deceased donors after circulatory arrest. The use of these organs has become a routine procedure and improving their quality and providing the means for their evaluation is absolutely inevitable.

Phosphonate-Modified Cellulose Nanocrystals Potentiate the Th1 Polarising Capacity of Monocyte-Derived Dendritic Cells via GABA-B Receptor

Purpose

Phosphonates, like 3-AminoPropylphosphonic Acid (ApA), possess a great potential for the therapy of bone tumours, and their delivery via cellulose nanocrystals (CNCs) seems a promising approach for their increased efficacy in target tissues. However, the immunological effects of CNC-phosphonates have not been investigated thoroughly. The main aim was to examine how the modification of CNCs with phosphonate affects their immunomodulatory properties in human cells.

Methods

Wood-based native (n) CNCs were modified via oxidation (ox-CNCs) and subsequent conjugation with ApA (ApA-CNCs). CNCs were characterised by atomic force microscopy (AFM) and nanoindentation. Cytotoxicity and immunomodulatory potential of CNCs were investigated in cultures of human peripheral blood mononuclear cells (PBMCs) and monocyte-derived dendritic cells (MoDCs)/T cells co-cultures by monitoring phenotype, cytokines production, allostimulatory and Th/Treg polarisation capacity.

Results

AFM showed an increase in CNCs' thickens, elasticity modulus and hardness during the modification with ApA. When applied at non-toxic doses, nCNCs showed a tolerogenic potential upon internalisation by MoDCs, as judged by their increased capacity to up-regulate tolerogenic markers and induce regulatory T cells (Treg), especially when present during the differentiation of MoDCs. In contrast, ox- and ApA-CNCs induced oxidative stress and autophagy in MoDCs, which correlated with their stimulatory effect on the maturation of MoDCs, but also inhibition of MoDCs differentiation. ApA-CNC-treated MoDCs displayed the highest allostimulatory and Th1/CTL polarising activity in co-cultures with T cells. These effects of ApA-CNCs were mediated via GABA-B receptor-induced lowering of cAMP levels in MoDCs, and they could be blocked by GABA-B receptor inhibitor. Moreover, the Th1 polarising and allostimulatory capacity of MoDCs differentiated with ApA-CNC were largely preserved upon the maturation of MoDCs, whereas nCNC- and ox-CNC-differentiated MoDCs displayed an increased tolerogenic potential.

Conclusion

The delivery of ApA via CNCs induces potent DC-mediated Th1 polarisation, which could be beneficial in their potential application in tumour therapy.

Plant-Growth-Promoting Potential of PGPE Isolated from Dactylis glomerata L

Plant-growth-promoting endophytes (PGPE) are a kind of beneficial microorganisms which could inhabit plant tissues to antagonize certain plant pathogens and promote the host plant’s growth and development. At present, many studies have confirmed the mutualistic effect of endophytes with plants, but there are few systematic studies on beneficial roles between endophytes and Dactylis glomerata, especially on the PGPE characteristics of the forage and environmental restoration plant. This study aimed to isolate PGPE from D. glomerata, evaluate their effects on plant growth, and ultimately acquire desirable microbial inoculants for agricultural use. First, endophytes were isolated from D. glomerata by plant re-inoculation experiment, and identified by morphological and molecular analyses. Fixation medium and methods were carried out to assess the nitrogen fixation ability of the strains. Then, the ability to dissolve phosphorus was determined by the Olsen and silicate medium methods; secretory IAA was measured by Salkowski colorimetric method; and the inhibitive effects on phytopathogen were observed by confrontation culture. Twenty-one strains were isolated from four varieties of D. glomerata, among which 14 strains with plant-growth-promoting characteristics were obtained by re-inoculation experiments, including seven endophytic bacteria and seven endophytic fungi. Further evaluation of three selected strains with the most significant PGP attributes were performed by using the pot re-inoculation experiment which revealed that TG2-B derived from Myroides odoratimimus was the most effective plant-growth-promoting agent due to its ability to produce high levels of IAA; the strain Bacillus cereus exhibited the most robust ability in dissolving inorganic phosphorus; and Trichoderma harzianum manifested a conspicuously antagonistic effect against a variety of plant pathogens. For the first time, this study reports the identification of D. glomerata endophytes that were able to promote plant growth and have a considerable antagonistic effects on plant pathogens, which could be considered as microbial inoculants for using in improving crop production and plant disease control.

Dendritic Cells: Versatile Players in Renal Transplantation

Dendritic cells (DCs) induce and regulate adaptive immunity through migrating and maturing in the kidney. In this procedure, they can adopt different phenotypes—rejection-associated DCs promote acute or chronic injury renal grafts while tolerogenic DCs suppress the overwhelmed inflammation preventing damage to renal functionality. All the subsets interact with effector T cells and regulatory T cells (Tregs) stimulated by the ischemia–reperfusion procedure, although the classification corresponding to different effects remains controversial. Thus, in this review, we discuss the origin, maturation, and pathological effects of DCs in the kidney. Then we summarize the roles of divergent DCs in renal transplantation: taking both positive and negative stages in ischemia–reperfusion injury (IRI), switching phenotypes to induce acute or chronic rejection, and orchestrating surface markers for allograft tolerance via alterations in metabolism. In conclusion, we prospect that multidimensional transcriptomic analysis will revolute researches on renal transplantation by addressing the elusive mononuclear phagocyte classification and providing a holistic view of DC ontogeny and subpopulations.

Effect of AKT1 (p. E17K) Hotspot Mutation on Malignant Tumorigenesis and Prognosis

The substitution of the seventeenth amino acid glutamate by lysine in the homologous structural domain of the Akt1 gene pleckstrin is a somatic cellular mutation found in breast, colorectal, and ovarian cancers, named p. Glu17Lys or E17K. In recent years, a growing number of studies have suggested that this mutation may play a unique role in the development of tumors. In this review article, we describe how AKT1(E17K) mutations stimulate downstream signals that cause cells to emerge transformed; we explore the differential regulation and function of E17K in different physiological and pathological settings; and we also describe the phenomenon that E17K impedes tumor growth by interfering with growth-promoting and chemotherapy-resistant AKT1^lowQCC generation, an intriguing finding that mutants may prolong tumor patient survival by activating feedback mechanisms and disrupting transcription. This review is intended to provide a better understanding of the role of AKT1(E17K) in cancer and to inform the development of AKT1(E17K)-based antitumor strategies.

Tolerogenic Dendritic Cells: The Pearl of Immunotherapy in Organ Transplantation

Over a half century, organ transplantation has become an effective method for the treatment of end-stage visceral diseases. Although the application of immunosuppressants (IS) minimizes the rate of allograft rejection, the common use of IS bring many adverse effects to transplant patients. Moreover, true transplant tolerance is very rare in clinical practice. Dendritic cells (DCs) are thought to be the most potent antigen-presenting cells, which makes a bridge between innate and adaptive immunity. Among their subsets, a small portion of DCs with immunoregulatory function was known as tolerogenic DC (Tol-DC). Previous reports demonstrated the ability of adoptively transferred Tol-DC to approach transplant tolerance in animal models. In this study, we summarized the properties, ex vivo generation, metabolism, and clinical attempts of Tol-DC. Tol-DC is expected to become a substitute for IS to enable patients to achieve immune tolerance in the future.

Control of GM-CSF-Dependent Dendritic Cell Differentiation and Maturation by DEF6 and SWAP-70

Although GM-CSF has been widely used in dendritic cell (DC) research, the mechanisms, factors, and signals regulating steady-state differentiation and maturation of GM-CSF-dependent DCs are insufficiently known. We found that the absence, individually or combined, of the related proteins DEF6 and SWAP-70 strongly enhances differentiation of murine GM-CSF-derived DCs. Contrasting SWAP-70, control through DEF6 does not depend on RHOA activation. DEF6 deficiency leads to expression of the DC-specific transcription factor ZBTB46 and prolonged STAT5 activation in GM-CSF cultures. SWAP-70 and DEF6-mediated restriction of DC differentiation converges mechanistically at the NF-κB pathway. DEF6 acts at early stages of DC differentiation in CD115^-cKIT⁺ myeloid DC progenitors, whereas SWAP-70 acts subsequently. SWAP-70 and DEF6 regulate steady-state DC cytokine expression as well as in vivo accumulation in lymphatic tissue of migratory DCs. Our studies thus elucidate previously unknown roles of two closely related factors with distinct and complementary activities in DC differentiation and steady-state DC function.

Effects of Antirejection Drugs on Innate Immune Cells After Kidney Transplantation

Over the last decades, our understanding of adaptive immune responses to solid organ transplantation increased considerably and allowed development of immunosuppressive drugs targeting key alloreactive T cells mechanism. As a result, rates of acute rejection dropped and short-term graft survival improved significantly. However, long-term outcomes are still disappointing. Recently, increasing evidence supports that innate immune responses plays roles in allograft rejection and represents a valuable target to further improve long-term allograft survival. Innate immune cells are activated by molecules with stereotypical motifs produced during injury (i.e., damage-associated molecular patterns, DAMPS) or infection (i.e., pathogen-associated molecular patterns, PAMPs). Activated innate immune cells can exert direct pro- and anti-inflammatory effects, while also priming adaptive immune responses. These cells are activated after transplantation by multiple stimuli, including ischemia-reperfusion injury, rejection, and infections. Data from animal models of graft rejection, show that inhibition of innate immunity promotes development of tolerance. Therefore, understanding mechanisms of innate immunity is important to improve graft outcomes. This review discusses effects of currently used immunosuppressive agents on innate immune responses in kidney transplantation.

Metabolic Control of Dendritic Cell Functions: Digesting Information

Dendritic cells (DCs) control innate and adaptive immunity by patrolling tissues to gather antigens and danger signals derived from microbes and tissue. Subsequently, DCs integrate those environmental cues, orchestrate immunity or tolerance, and regulate tissue homeostasis. Recent advances in the field of immunometabolism highlight the notion that immune cells markedly alter cellular metabolic pathways during differentiation or upon activation, which has important implications on their functionality. Previous studies showed that active oxidative phosphorylation in mitochondria is associated with immature or tolerogenic DCs, while increased glycolysis upon pathogen sensing can promote immunogenic DC functions. However, new results in the last years suggest that regulation of DC metabolism in steady state, after immunogenic activation and during tolerance in different pathophysiological settings, may be more complex. Moreover, ontogenically distinct DC subsets show different functional specializations to control T cell responses. It is, thus, relevant how metabolism influences DC differentiation and plasticity, and what potential metabolic differences exist among DC subsets. Better understanding of the emerging connection between metabolic adaptions and functional DC specification will likely allow the development of therapeutic strategies to manipulate immune responses.

Metabolic Regulation of Dendritic Cell Differentiation

Dendritic cells (DCs) are important antigen-presenting cells (APCs) that play essential roles in bridging innate and adaptive immune responses. Differentiation stages of DC subsets from bone marrow progenitor cells have been well-defined during the past decades. Features that distinguish DC progenitor cells from each differentiation stages, related signaling pathways and transcription factors that are crucial for DC lineage commitment have been well-elucidated in numerous studies. Recently, growing evidence are showing that cellular metabolism, as one of the most fundamental process of cells, has essential role in the modulation of immune system. There have been multiple reports and reviews that focus on the metabolic modulations on DC functions, however little attention had been paid to the metabolic regulation of DC development and differentiation. In recent years, increasing evidence suggests that metabolic regulations also exert significant impact on DC differentiation, as well as on the homeostasis of tissue resident DCs. The focus of this review is to summarize the findings from recent studies on the metabolic regulation of DC differentiation and to discuss the impacts of the three major aspects of metabolism on the processes of DC development and differentiation, namely the changes in metabolic pathways, the molecular signaling pathways that modulate cell metabolism, and the effects of metabolites and nutrients. The aim of this review is to draw attentions to this important and exciting research field where the effects of metabolic process and their regulation in DC differentiation need to be further explored.

Regulation of Dendritic Cell Immune Function and Metabolism by Cellular Nutrient Sensor Mammalian Target of Rapamycin (mTOR)

Dendritic cell (DC) activation is characterized by an acute increase in glucose metabolic flux that is required to fuel the high anabolic rates associated with DC activation. Inhibition of glycolysis significantly attenuates most aspects of DC immune effector function including antigen presentation, inflammatory cytokine production, and T cell stimulatory capacity. The cellular nutrient sensor mammalian/mechanistic Target of Rapamycin (mTOR) is an important upstream regulator of glycolytic metabolism and plays a central role in coordinating DC metabolic changes and immune responses. Because mTOR signaling can be activated by a variety of immunological stimuli, including signaling through the Toll-like Receptor (TLR) family of receptors, mTOR is involved in orchestrating many aspects of the DC metabolic response to microbial stimuli. It has become increasingly clear that mTOR's role in promoting or attenuating inflammatory processes in DCs is highly context-dependent and varies according to specific cellular subsets and the immunological conditions being studied. This review will address key aspects of the complex role of mTOR in regulating DC metabolism and effector function.

Harnessing the Induction of CD8+ T-Cell Responses Through Metabolic Regulation by Pathogen-Recognition-Receptor Triggering in Antigen Presenting Cells

Cytotoxic CD8⁺ T-cells are key players of the immune responses against viruses. During the priming of a CD8⁺ T-cell response, the activation of a naïve T-cell by a professional antigen presenting cell (APC) involves the induction of various intracellular and metabolic pathways. The modulation of these pathways at the level of APCs or T-cells offers great potential to enhance the induction of robust effector cells and the generation of long-lived memory cells. On the one hand, signaling through pathogen recognition receptors (PRRs) expressed by APCs can greatly influence T-cell priming, and the potential of several PRR ligands as adjuvants are being studied. On the other hand, the engagement of several metabolic processes, at play in APCs and T-cells upon stimulation, implies that modulating cellular metabolism can impact on priming efficacy. Here, we review recent efforts to understand the interplay between PRR mediated signaling and metabolic pathway modulation in this context, through three examples: interplay between TLR4 and fatty acid metabolism, between TLR9 and IDO, and between STING and autophagy. These initial works highlight the potential for harnessing the induction of antiviral CD8⁺ T-cell responses using synergistic modulation of metabolic and PRR pathways.

Differential Gene Expression Analysis of Bovine Macrophages after Exposure to the Penicillium Mycotoxins Citrinin and/or Ochratoxin A

Mycotoxins produced by fungal species commonly contaminate livestock feedstuffs, jeopardizing their health and diminishing production. Citrinin (CIT) and ochratoxin A (OTA) are mycotoxins produced by Penicillium spp. and commonly co-occur. Both CIT and OTA can modulate immune response by inhibiting cell proliferation and differentiation, altering cell metabolism, and triggering programmed cell death. The objective of this study was to determine the effects of sublethal exposure (i.e., the concentration that inhibited cell proliferation by 25% (IC₂₅)) to CIT, OTA or CIT + OTA on the bovine macrophage transcriptome. Gene expression was determined using the Affymetrix Bovine Genome Array. After 6 h of exposure to CIT, OTA or CIT + OTA, the number of differentially expressed genes (DEG), respectively, was as follows: 1471 genes (822 up-regulated, 649 down-regulated), 5094 genes (2611 up-regulated, 2483 down-regulated) and 7624 genes (3984 up-regulated, 3640 down-regulated). Of these, 179 genes (88 up-regulated, 91 down-regulated) were commonly expressed between treatments. After 24 h of exposure to CIT, OTA or CIT + OTA the number of DEG, respectively, was as follows: 3230 genes (1631 up-regulated, 1599 down-regulated), 8558 genes (4167 up-regulated, 4391 down-regulated), and 10,927 genes (6284 up-regulated, 4643 down-regulated). Of these, 770 genes (247 up-regulated, 523 down-regulated) were commonly expressed between treatments. The categorization of common biological functions and pathway analysis suggests that the IC₂₅ of both CIT and OTA, or their combination, induces cellular oxidative stress, a slowing of cell cycle progression, and apoptosis. Collectively, these effects contribute to inhibiting bovine macrophage proliferation.

Genome-Wide Analyses of MicroRNA Profiling in Interleukin-27 Treated Monocyte-Derived Human Dendritic Cells Using Deep Sequencing: A Pilot Study

MicroRNAs (miRNAs) regulate gene expression and thereby influence cell fate and function. Recent studies suggest that an abundant class of miRNAs play important roles in immune cells, such as T cells, natural killer (NK) cells, B cells, and dendritic cells (DCs). Interleukin (IL)-27 is a member of the IL-12 family of cytokines with broad anti-viral effects. It is a potent inhibitor of HIV-1 infection in CD4+ T cells and macrophages, as well as monocyte-derived immature dendritic cells (iDCs). This pilot study compared miRNA profiles between iDCs and IL-27-treated iDCs (27DCs) using deep sequencing methods and identified 46 known miRNAs that were significantly differentially expressed in 27DCs: 36 were upregulated and 10 downregulated by IL-27. Many of the potential target genes of these miRNAs are involved in IL-27 associated pathways, such as JAK/STAT, MAPKs, and PI3K and several were also previously reported to be involved in the regulation of human DC function. This study found that these miRNAs also potentially target several viral genomes and therefore may have antiviral effects. Four of these differential miRNAs (miR-99a-5p, miR-222-3p, miR-138-5p, and miR-125b-5p) were validated using quantitative reverse transcription PCR (RT-qPCR). Twenty-two novel miRNAs were discovered from deep sequencing and confirmed using RT-qPCR. This study furthers the understanding of the role of IL-27 in immunity and lays a foundation for future characterization of the role of specific miRNAs in DCs.

miR-155 effectively induces apoptosis in K562 Philadelphia positive cell line through upregulation of p27kip1

Introduction: Chronic myelogenous leukemia (CML) is a myeloproliferative disorder caused by the Philadelphia chromosome translocation, at (9; 22), which results in BCR-ABL fusion tyrosine kinase oncoprotein. This fusion induces down-regulation of miR-155. Upregulation of miR-155 can influence cell fate via the effect on p27kip1 and apoptosis. The aim of this study was to induce apoptosis in K562 CML cell line by overexpression of miR-155.

Methods: The K562 cell line was transfected with pLenti-III-pre mir155-GFP constructs through electroporation. Then, overexpression of miR-155 as well as the expression level of p27kip1 and c-Myc was analyzed by quantitative PCR (qPCR). The level of p27 (Kip1) protein expression was measured by Western blot and the Annexin V method was carried out to investigate apoptosis.

Results: Flow cytometric analysis results of K562 cells transfected with pLenti-III-pre mir155-GFP construct showed a significant increase in cell apoptosis. Gene expression and protein level of p27kip1 were upregulated. However, there was no change in c-Myc expression profile.

Conclusion: miR-155 could be a promising approach to aid in the treatment of CML. However, further studies are required in this respect.

Propolis modulates miRNAs involved in TLR-4 pathway, NF-κB activation, cytokine production and in the bactericidal activity of human dendritic cells

Objectives

Dendritic cells (DCs) are antigen-presenting cells, essential for recognition and presentation of pathogens to T cells. Propolis, a resinous material produced by bees from various plants, exhibits numerous biological properties, highlighting its immunomodulatory action. Here, we assayed the effects of propolis on the maturation and function of human DCs.

Methods

DCs were generated from human monocytes and incubated with propolis and LPS. NF-κB and cytokines production were determined by ELISA. microRNA's expression was analysed by RT-qPCR and cell markers detection by flow cytometry. Colony-forming units were obtained to assess the bactericidal activity of propolis-treated DCs.

Key findings

Propolis activated DCs in the presence of LPS, inducing NF-kB, TNF-α, IL-6 and IL-10 production. The inhibition of hsa-miR-148a and hsa-miR-148b abolished the inhibitory effects on HLA-DR and pro-inflammatory cytokines. The increased expression of hsa-miR-155 may be correlated to the increase in TLR-4 and CD86 expression, maintaining LPS-induced expression of HLA-DR and CD40. Such parameters may be involved in the increased bactericidal activity of DCs against Streptococcus mutans.

Conclusion

Propolis modulated the maturation and function of DCs and may be useful in the initial steps of the immune response, providing a novel approach to the development of DC-based strategies and for the discovery of new immunomodulators.

Caspases uncouple p27(Kip1) from cell cycle regulated degradation and abolish its ability to stimulate cell migration and invasion

In addition to their role in programmed cell death, caspases exert non-lethal functions in diverse developmental processes including cell differentiation or tissue remodeling. Terminal cell cycle exit and differentiation can be promoted by increased level of the CDK inhibitor p27^Kip1. Activated caspases cause proteolytic processing of p27, and we identified a novel caspase cleavage site in human p27 that removes a C-terminal fragment of 22 amino acids from the CDK inhibitor, including a phosphodegron. Thereby, caspases protect the inhibitor from SCF-Skp2-mediated degradation in S, G2 and M phases of the cell cycle. As a consequence, p27 becomes stabilized and remains an efficient nuclear inhibitor of cell cycle progression. Besides controlling cyclin/CDK kinase activity, p27 also regulates cytoskeletal dynamics, cell motility and cell invasion. Following processing by caspases, p27 fails to bind to RhoA and to inhibit its activation, and thereby abolishes the ability of p27 to stimulate cell migration and invasion. We propose that the stabilization of the CDK inhibitor and elimination of RhoA-induced cytoskeletal remodeling upon caspase processing could contribute to cell cycle exit and cytoskeletal remodeling during non-lethal caspase controlled differentiation processes.

Validation of p27KIP1 expression levels as a candidate predictive biomarker of response to rapalogs in patient-derived breast tumor xenografts

Blockade of mammalian target of rapamycin (mTOR) is a promising area in breast cancer therapy. However, in clinical trials, objective response rate with mTOR inhibitor monotherapy in breast cancer was modest. Biomarker studies designed to identify the responders of rapalogs are of increasing interest. We validated p27KIP1 expression levels as a candidate predictive biomarker of response to rapalogs. We also analyzed the correlation between rapamycin activity and p27KIP1 expression in the primary breast cancer cells and the patient-derived breast tumor xenograft models. The cells isolated from the breast tumor tissues expressing high levels of p27KIP1 were sensitive to rapamycin, whereas the cells from the tissues expressing low levels of p27KIP1 exhibited resistance to rapamycin. The correlation between p27KIP1 expression and rapamycin antitumor activity was also observed in the patient-derived breast tumor xenograft models. Moreover, we also found rapamycin significantly decreased phosphorylated p70S6K1 and phosphorylated 4EBP1 in both samples. It seemed that the different sensitivity of tumor cells to rapamycin did not owe to its different potency against mTOR activity. We further propose p27KIP1 expression level may be also a candidate predictive biomarker of rapalogs for breast cancer therapy, which requires additional clinical validation.

Dendritic cell metabolism

The past 15 years have seen enormous advances in our understanding of the receptor and signalling systems that allow dendritic cells (DCs) to respond to pathogens or other danger signals and initiate innate and adaptive immune responses. We are now beginning to appreciate that many of these pathways not only stimulate changes in the expression of genes that control DC immune functions, but also affect metabolic pathways, thereby integrating the cellular requirements of the activation process. In this Review, we focus on this relatively new area of research and attempt to describe an integrated view of DC immunometabolism.

Mechanistic target of rapamycin inhibition extends cellular lifespan in dendritic cells by preserving mitochondrial function

TLR-mediated activation of dendritic cells (DCs) is associated with a metabolic transition in which mitochondrial oxidative phosphorylation is inhibited by endogenously synthesized NO and the cells become committed to glucose and aerobic glycolysis for survival. We show that inhibition of mechanistic target of rapamycin (mTOR) extends the lifespan of TLR-activated DCs by inhibiting the induction of NO production, thereby allowing the cells to continue to use their mitochondria to generate ATP, and allowing them the flexibility to use fatty acids or glucose as nutrients to fuel core metabolism. These data provide novel mechanistic insights into how mTOR modulates DC metabolism and cellular longevity following TLR activation and provide an explanation for previous findings that mTOR inhibition enhances the efficacy of DCs in autologous vaccination.

Rapamycin unbalances the polarization of human macrophages to M1

Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied. To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by lipopolysaccharide plus interferon-γ or interleukin-4 (IL-4), respectively. The presence of RAPA (10 ng/ml) induced macrophage apoptosis in M2 but not in M1. Beyond the impact on survival in M2, RAPA reduced CXCR4, CD206 and CD209 expression and stem cell growth factor-β, CCL18 and CCL13 release. In contrast, in M1 RAPA increased CD86 and CCR7 expression and IL-6, tumour necrosis factor-α and IL-1β release but reduced CD206 and CD209 expression and IL-10, vascular endothelial growth factor and CCL18 release. In view of the in vitro data, we examined the in vivo effect of RAPA monotherapy (0·1 mg/kg/day) in 12 patients who were treated for at least 1 month before islet transplant. Cytokine release by Toll-like receptor 4-stimulated peripheral blood mononuclear cells showed a clear shift to an M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1. These results suggest a role of mammalian target of rapamycin (mTOR) into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.

Knockdown of mTOR by lentivirus‑mediated RNA interference suppresses atherosclerosis and stabilizes plaques via a decrease of macrophages by autophagy in apolipoprotein E‑deficient mice

Atherosclerotic plaque destabilization and rupture leads to acute coronary syndromes which cause serious damage to human health worldwide. However, there is currently a lack of efficient therapeutic methods. Mammalian target of rapamycin (mTOR) has been suggested to be involved in the development of atherosclerotic plaques and serves as a therapeutic target. The present study was performed to determine whether RNA interference (RNAi) of mTOR in vivo by LV‑mediated small hairpin RNA (shRNA) was capable of inhibiting the progression of atherosclerotic plaques. LV‑mediated shRNA against mTOR (LV‑shmTOR) was designed and obtained. Male apolipoprotein E‑deficient mice were fed a high‑fat diet and a constrictive collar was placed around the right carotid arteries of these mice to induce plaque formation. Eight weeks after surgery, mice were randomly divided into the mTOR RNA interference (LV‑shmTOR) group, receiving treatment with LV‑mTOR‑shRNA; the LV‑shCON group, receiving treatment with LV‑non‑specific‑shRNA; and the control group, receiving treatment with phosphate‑buffered saline. Following transfection, the mice were sacrificed to evaluate the effects of mTOR expression silencing on atherosclerosis. Transfection of LV‑mTOR‑shRNA markedly inhibited the mRNA and protein expression levels. Knockdown of mTOR ameliorated dysregulated blood lipid metabolism and stabilized aortic atherosclerotic plaques by decreasing the plaque area and increasing the fibrous cap and cap‑to‑core ratio. Furthermore, macrophages were decreased by silencing mTOR in atherosclerotic plaques. In addition, western blot analysis revealed that the knockdown of mTOR increased autophagy‑related protein 13 (Atg13) dephosphorylation and light chain 3‑I/light chain 3‑II (LC3‑I/LC3‑II) ratios, both of which were associated with a high activity of autophagy, suggesting an increase of autophagy in atherosclerotic plaques. Moreover, genes including matrix metalloproteinase 2, monocyte chemoattractant protein 1 and tissue factor, which promote plaque instability, were downregulated by silencing mTOR. These results demonstrate that LV‑mediated mTOR silencing by RNAi treatment induces macrophage autophagy and is a potential strategy for the treatment of atherosclerotic plaques.

Clinical activity and safety of combination therapy with temsirolimus and bevacizumab for advanced melanoma: a phase II trial (CTEP 7190/Mel47)

PURPOSE

A CTEP-sponsored phase II trial was conducted to evaluate safety and clinical activity of combination therapy with CCI-779 (temsirolimus) and bevacizumab in patients with advanced melanoma.

EXPERIMENTAL DESIGN

Patients with unresectable stage III to IV melanoma were treated intravenously with temsirolimus 25 mg weekly and bevacizumab 10 mg every 2 weeks. Adverse events were recorded using CTCAE v3.0. Tumor response was assessed by Response Evaluation Criteria in Solid Tumors and overall survival was recorded. Correlative studies measured protein kinases and histology of tumor biopsies and immune function in peripheral blood.

RESULTS

Seventeen patients were treated. Most patients tolerated treatment well, but 2 had grade 4 lymphopenia and 1 developed reversible grade 2 leukoencephalopathy. Best clinical response was partial response (PR) in 3 patients [17.7%, 90% confidence interval (CI) 5, 0-39.6], stable disease at 8 weeks (SD) in 9 patients, progressive disease (PD) in 4 patients, and not evaluable in 1 patient. Maximal response duration for PR was 35 months. Ten evaluable patients had BRAF(WT) tumors, among whom 3 had PRs, 5 had SD, and 2 had PD. Correlative studies of tumor biopsies revealed decreased phospho-S6K (d2 and d23 vs. d1, P < 0.001), and decreased mitotic rate (Ki67(+)) among melanoma cells by d23 (P = 0.007). Effects on immune functions were mixed, with decreased alloreactive T-cell responses and decreased circulating CD4(+)FoxP3(+) cells.

CONCLUSION

These data provide preliminary evidence for clinical activity of combination therapy with temsirolimus and bevacizumab, which may be greater in patients with BRAF(wt) melanoma. Mixed effects on immunologic function also support combination with immune therapies.

Langerhans cell homeostasis in mice is dependent on mTORC1 but not mTORC2 function

The PI3K/Akt/mTOR pathway has emerged as a critical regulator of dendritic cell (DC) development and function. The kinase mTOR is found in 2 distinct complexes, mTORC1 and mTORC2. In this study, we show that mTORC1 but not mTORC2 is required for epidermal Langerhans cell (LC) homeostasis. Although the initial seeding of the epidermis with LCs is not affected, the lack of mTORC1 activity in DCs by conditional deletion of Raptor leads to a progressive loss of LCs in the skin of mice. Ablation of mTORC2 function by deletion of Rictor results in a modest reduction of LCs in skin draining lymph nodes. In young mice Raptor-deficient LCs show an increased tendency to leave the skin, leading to a higher frequency of migratory DCs in skin draining lymph nodes, indicating that the loss of LCs results from enhanced migration. LCs lacking Raptor are smaller and display reduced expression of Langerin, E-cadherin, β-catenin, and CCR7 but unchanged levels of MHC-II, ruling out enhanced spontaneous maturation. Ki-67 and annexin V stainings revealed a faster turnover rate and increased apoptosis of Raptor-deficient LCs, which might additionally affect the preservation of the LC network. Taken together our results show that the homeostasis of LCs strictly depends on mTORC1.

p27(Kip1) negatively regulates the magnitude and persistence of CD4 T cell memory

Much is known about the differentiation of naive T cells into distinct lineages of effector cells, but the molecular mechanisms underlying the generation and maintenance of CD4 T cell memory are poorly characterized. Our studies ascribe a novel role for the cell cycle regulator p27(Kip1) as a prominent negative regulator of the establishment and long-term maintenance of Th1 CD4 T cell memory. We demonstrate that p27(Kip1) might restrict the differentiation and survival of memory precursors by increasing the T-bet/Bcl-6 ratio in effector CD4 T cells. By promoting apoptosis and contraction of effector CD4 T cells by mechanisms that are at least in part T cell intrinsic, p27(Kip1) markedly limits the abundance of memory CD4 T cells. Furthermore, we causally link p27(Kip1)-dependent apoptosis to the decay of CD4 T cell memory, possibly by repressing the expression of γ-chain receptors and the downstream effector of the Wnt/β-catenin signaling pathway, Tcf-1. We extend these findings by showing that the antagonistic effects of p27(Kip1) on CD4 T cell memory require its cyclin-dependent kinase-binding domain. Collectively, these findings provide key insights into the mechanisms underlying the governance of peripheral CD4 T cell homeostasis and identify p27(Kip1) as a target to enhance vaccine-induced CD4 T cell memory.

Immunoregulatory properties of rapamycin-conditioned monocyte-derived dendritic cells and their role in transplantation

In efforts to minimize the chronic administration of immunosuppression (IS) drugs in transplantation and autoimmune disease, various cell-based tolerogenic therapies, including the use of regulatory or tolerogenic dendritic cells (tolDC) have been developed. These DC-based therapies aim to harness the inherent immunoregulatory potential of these professional antigen-presenting cells. In this short review, we describe both the demonstrated tolerogenic properties, and current limitations of rapamycin-conditioned DC (RAPA-DC). RAPA-DC are generated through inhibition of the integrative kinase mammalian target of rapamycin (mTOR) by the immunosuppressive macrolide rapamycin during propagation of monocyte-derived DC. Consistent with the characteristics of tolDC, murine RAPA-DC display resistance to phenotypic maturation induced by pro-inflammatory stimuli; exhibit the ability to migrate to secondary lymphoid tissue (important for 'cross-presentation' of antigen to T cells), and enrich for naturally-occurring CD4+ regulatory T cells. In rodent models, delivery of recipient-derived RAPA-DC pulsed with donor antigen prior to organ transplantation can prolong allogeneic heart-graft survival indefinitely, especially when combined with a short course of IS. These encouraging data support ongoing efforts to develop RAPA-DC for clinical testing. When compared to murine RAPA-DC however, human RAPA-DC have proven only partially resistant to maturation triggered by pro-inflammatory cytokines, and display heterogeneity in their impact on effector T-cell expansion and function. In total, the evidence suggests the need for more in-depth studies to better understand the mechanisms by which mTOR controls human DC function. These studies may facilitate the development of RAPA-DC therapy alone or together with agents that preserve/enhance their tolerogenic properties as clinical immunoregulatory vectors.

Inhibition of mechanistic target of rapamycin promotes dendritic cell activation and enhances therapeutic autologous vaccination in mice

Dendritic cells (DCs) are potent inducers of T cell immunity, and autologous DC vaccination holds promise for the treatment of cancers and chronic infectious diseases. In practice, however, therapeutic vaccines of this type have had mixed success. In this article, we show that brief exposure to inhibitors of mechanistic target of rapamycin (mTOR) in DCs during the period that they are responding to TLR agonists makes them particularly potent activators of naive CD8+ T cells and able to enhance control of B16 melanoma in a therapeutic autologous vaccination model in the mouse. The improved performance of DCs in which mTOR has been inhibited is correlated with an extended life span after activation and prolonged, increased expression of costimulatory molecules. Therapeutic autologous vaccination with DCs treated with TLR agonists plus the mTOR inhibitor rapamycin results in improved generation of Ag-specific CD8+ T cells in vivo and improved antitumor immunity compared with that observed with DCs treated with TLR agonists alone. These findings define mTOR as a molecular target for augmenting DC survival and activation, and document a novel pharmacologic approach for enhancing the efficacy of therapeutic autologous DC vaccination.

Defining the role of sirolimus in the management of graft-versus-host disease: from prophylaxis to treatment

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Measures developed that have significantly reduced GVHD were also frequently associated with an increased risk of relapse. GVHD and graft-versus-tumor (GVT) effects are tightly linked, and balance between both reactions is difficult to achieve. To have an impact on the outcome and quality of life after HSCT, improvements in current strategies to prevent and treat GVHD while preserving the GVT effect are clearly needed. Sirolimus (rapamycin) is a lipophilic macrocytic lactone with immunosuppressive, antitumor, and antiviral properties. Because of its multiple modes of activities, it is being increasingly used in the management of GVHD. This review aims to summarize its mechanisms of action and potential advantages over other immunosuppressors and to analyze the most relevant studies investigating its role in both prevention and treatment of GVHD.

Regulation of dendritic cell development by GM-CSF: molecular control and implications for immune homeostasis and therapy

Dendritic cells (DCs) represent a small and heterogeneous fraction of the hematopoietic system, specialized in antigen capture, processing, and presentation. The different DC subsets act as sentinels throughout the body and perform a key role in the induction of immunogenic as well as tolerogenic immune responses. Because of their limited lifespan, continuous replenishment of DC is required. Whereas the importance of GM-CSF in regulating DC homeostasis has long been underestimated, this cytokine is currently considered a critical factor for DC development under both steady-state and inflammatory conditions. Regulation of cellular actions by GM-CSF depends on the activation of intracellular signaling modules, including JAK/STAT, MAPK, PI3K, and canonical NF-κB. By directing the activity of transcription factors and other cellular effector proteins, these pathways influence differentiation, survival and/or proliferation of uncommitted hematopoietic progenitors, and DC subset–specific precursors, thereby contributing to specific aspects of DC subset development. The specific intracellular events resulting from GM-CSF–induced signaling provide a molecular explanation for GM-CSF–dependent subset distribution as well as clues to the specific characteristics and functions of GM-CSF–differentiated DCs compared with DCs generated by fms-related tyrosine kinase 3 ligand. This knowledge can be used to identify therapeutic targets to improve GM-CSF–dependent DC-based strategies to regulate immunity.

Rapamycin combined with allogenic immature dendritic cells selectively expands CD4+CD25+Foxp3+ regulatory T cells in rats

BACKGROUND

Dendritic cells (DCs) can initiate the expansion of regulatory T cells (Tregs), which play an indispensable role in inducing transplantation tolerance. Some studies have investigated the effect of the immunosuppressant rapamycin (Rapa) on Tregs in vitro. However, the in vivo effect of Rapa combined with immature DCs (iDCs) on Tregs is unknown. This study was undertaken to determine whether allogenic iDCs combined with a short course of Rapa have the ability to selectively expand the CD4+CD25+Foxp3+ Tregs in a rat model.

METHODS

Brown Norway rats were injected intravenously with 2X10(6) Lewis iDCs followed by 1 mg/kg per day Rapa intraperitoneally for 7 consecutive days. On day 8, the levels of CD4+CD25+Foxp3+ Treg cells in peripheral blood and spleen cells were analyzed by flow cytometry. IL-2, IL-4, TGF-beta1, and IFN-gamma levels in serum were assessed by ELISA. The experimental animals were divided into four groups: control, Rapa-treated, iDC-treated, and combination-treated.

RESULTS

CD4+CD25+Foxp3+ Tregs comprised 7%-8% of CD4+ T cells in control rats. Rapa combined with iDCs enhanced this percentage in the peripheral blood and spleen. However, the levels of Tregs did not significantly change after treatment with Rapa or iDCs alone. The levels of CD4+CD25-Foxp3+ T cells and CD4+CD25+Foxp3- T cells in CD4+ T cells did not significantly change in the combined group. The TGF-beta1 level in serum from the combined group increased significantly compared with the other groups.

CONCLUSIONS

A significantly higher percentage of CD4+ CD25+ Foxp3+ Tregs was found in rats treated with allogenic iDCs and a short course of Rapa, along with an increase in the TGF-beta1 level in serum. This improved protocol may be a promising therapeutic strategy to increase Tregs, which are beneficial to the induction of peritransplant tolerance.

Rapamycin combined with donor immature dendritic cells promotes liver allograft survival in association with CD4(+) CD25(+) Foxp3(+) regulatory T cell expansion

AIM

  To determine whether donor immature dendritic cells (imDCs) combined with a short postoperative course of rapamycin (Rapa) has the ability to expand the CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells and prolong liver allograft survival.

METHODS

  Orthotopic liver transplantation (OLT) was performed from Lewis rats to Brown Norway recipients. Three days before transplantation, animals were injected intravenously with 2 × 10(6) donor bone marrow-derived imDCs. Recipient rats (the combined treated group) also received Rapa for 7 d after liver transplantation. Additional groups received either imDCs alone, Rapa alone, or saline alone. Every six recipients from each group were killed at 14 days, 28 days after OLT. The changes of CD4(+) CD25(+) Foxp3(+) Treg cells in peripheral blood and spleen, histological changes of liver grafts, and serum cytokine levels were investigated. The other six recipients were left in each group to observe the animal survival.

RESULTS

  Donor imDCs followed by a short postoperative course of Rapa induced long-term allograft survival. The percentage of CD4(+) CD25(+) Foxp3(+) Treg cells in CD4(+) T cells in the combination treatment group were significantly higher compared with the acute rejection group. Moreover, within the CD4(+) CD25(+) T cell population the combination treatment recipients maintained a higher incidence of Foxp3(+) T cells compared with the other groups. Despite the lower serum levels of interleukin (IL)-2, IL-12, and interferon-γ in the combined treated group, the cytokine levels in the combined treated group at 7 days after OLT was nearly twice that at 3 days after OLT but decreased significantly compared with the other groups at 28 days after OLT. Serum IL-10 level in the combined treated group was higher than the other groups.

CONCLUSIONS

  A single imDC infusion followed by a short postoperative course of Rapa prolongs liver allograft survival and enhances the expansion of Treg cells. This optimal protocol may be a promising administration protocol for the peritransplant tolerance induction.

Intracellular glutathione redox status in human dendritic cells regulates IL-27 production and T-cell polarization

BACKGROUND

Glutathione redox status, changes in intracellular reduced (GSH) or oxidized (GSSG) glutathione, plays a significant role in various aspects of cellular function. In this study, we examined whether intracellular glutathione redox status in human dendritic cells (DCs) regulates the polarization of Th1/Th2 balance.

METHODS

Human monocyte-derived DCs (MD-DCs) treated with glutathione reduced form ethyl ester (GSH-OEt) or L-buthionine-(S,R)-sulfoximine (BSO) were stimulated by lipopolysaccharide (LPS), and the levels of polarization cytokines were measured. Next, DCs matured by LPS or thymic stromal lymphopoietin (TSLP) were cocultured with allogeneic CD4(+) naive T cells and Th1/Th2 balance was evaluated by cytokine production from the primed T cells.

RESULTS

Monocyte-derived DCs exposed to GSH-OEt and BSO had increased and decreased intracellular GSH contents, respectively. Lipopolysaccharide-induced interleukin (IL)-27 production was enhanced by GSH-OEt and suppressed by BSO, but neither GSH-OEt nor BSO affected the expression of HLA-DR, CD80, CD83, or CD86. Mature GSH-OEt-treated MD-DCs enhanced interferon (IFN)-γ production from CD4(+) T cells compared with nontreated MD-DCs, and small interfering RNA (siRNA) against IL-27 suppressed the effect of GSH-OEt on IFN-γ production. Additionally, although human myeloid DCs activated by TSLP (TSLP-DCs) prime naïve CD4(+) T cells to differentiate into Th2 cells, treatment of TSLP-DCs with GSH-OEt reduced IL-13 production and enhanced IFN-γ production by CD4(+) T cells. Interleukin-27 siRNA attenuated the inhibitory effect of GSH-OEt on Th2 polarization.

CONCLUSION

Our results reveal that Th1 and Th2 responses are controlled by intracellular glutathione redox status in DCs through IL-27 production.

Dendritic cells in cord blood transplantation: a review

Dendritic cells (DCs) are a heterogeneous population of antigen-presenting cells derived from hematopoietic progenitors that bridge the transition between the innate and adaptive immune responses, while maintaining self-tolerance and Th1/Th2 homeostasis, by priming other cells in either an immunogenic or tolerogenic direction. Through their role in both innate and adaptive immunity, DCs play a major part in transplant engraftment and rejection and in graft-versus-host disease (GvHD). Preferentially tolerogenic or immunogenic DC subtypes offer targets for immunotherapy, to optimize transplant success rates and prolong disease-free and overall survival. Cord blood DCs are immature and preferentially tolerogenic, due to maternal-fetal tolerance, leading to better graft acceptance and immune reconstitution and explaining the lower incidence and severity of GvHD in CB transplantation, despite donor-host mismatching. Manipulation of DC maturation and cell loading with tumor-antigens can direct antitumor immunity and target minimal residual disease, as demonstrated for acute myeloid leukemia, optimizing the graft-versus-leukemia effect.

Inhibition of mTOR blocks the anti-inflammatory effects of glucocorticoids in myeloid immune cells

A central role for the mammalian target of rapamycin (mTOR) in innate immunity has been recently defined by its ability to limit proinflammatory mediators. Although glucocorticoids (GCs) exert potent anti-inflammatory effects in innate immune cells, it is currently unknown whether the mTOR pathway interferes with GC signaling. Here we show that inhibition of mTOR with rapamycin or Torin1 prevented the anti-inflammatory potency of GC both in human monocytes and myeloid dendritic cells. GCs could not suppress nuclear factor-κB and JNK activation, the expression of proinflammatory cytokines, and the promotion of Th1 responses when mTOR was inhibited. Interestingly, long-term activation of monocytes with lipopolysaccharide enhanced the expression of TSC2, the principle negative regulator of mTOR, whereas dexamethasone blocked TSC2 expression and reestablished mTOR activation. Renal transplant patients receiving rapamycin but not those receiving calcineurin inhibitors displayed a state of innate immune cell hyper-responsiveness despite the concurrent use of GC. Finally, mTOR inhibition was able to override the healing phenotype of dexamethasone in a murine lipopolysaccharide shock model. Collectively, these data identify a novel link between the glucocorticoid receptor and mTOR in innate immune cells, which is of considerable clinical importance in a variety of disorders, including allogeneic transplantation, autoimmune diseases, and cancer.

Single-cell phospho-specific flow cytometric analysis demonstrates biochemical and functional heterogeneity in human hematopoietic stem and progenitor compartments

The low frequency of hematopoietic stem and progenitor cells (HSPCs) in human BM has precluded analysis of the direct biochemical effects elicited by cytokines in these populations, and their functional consequences. Here, single-cell phospho-specific flow cytometry was used to define the signaling networks active in 5 previously defined human HSPC subsets. This analysis revealed that the currently defined HSC compartment is composed of biochemically distinct subsets with the ability to respond rapidly and directly in vitro to a broader array of cytokines than previously appreciated, including G-CSF. The G-CSF response was physiologically relevant-driving cell-cycle entry and increased proliferation in a subset of single cells within the HSC compartment. The heterogeneity in the single-cell signaling and proliferation responses prompted subfractionation of the adult BM HSC compartment by expression of CD114 (G-CSF receptor). Xenotransplantation assays revealed that HSC activity is significantly enriched in the CD114(neg/lo) compartment, and almost completely absent in the CD114(pos) subfraction. The single-cell analyses used here can be adapted for further refinement of HSPC surface immunophenotypes, and for examining the direct regulatory effects of other factors on the homeostasis of stem and progenitor populations in normal or diseased states.

miR-221 and miR-155 regulate human dendritic cell development, apoptosis, and IL-12 production through targeting of p27kip1, KPC1, and SOCS-1

Dendritic cells (DCs) are potent antigen-presenting cells derived from hematopoietic progenitor cells and circulating monocytes. To investigate the role of microRNAs (miRNAs) during DC differentiation, maturation, and function, we profiled miRNA expression in human monocytes, immature DCs (imDCs), and mature DCs (mDCs). Stage-specific, differential expression of 27 miRNAs was found during monocyte differentiation into imDCs and mDCs. Among them, decreased miR-221 and increased miR-155 expression correlated with p27(kip1) accumulation in DCs. Silencing of miR-221 or overexpressing of miR-155 in DCs resulted in p27(kip1) protein increase and DC apoptosis. Moreover, mDCs from miR-155(-/-) mice were less apoptotic than those from wild-type mice. Silencing of miR-155 expression had little effect on DC maturation but reduced IL-12p70 production, whereas miR-155 overexpression in mDCs enhanced IL-12p70 production. Kip1 ubiquitination-promoting complex 1, suppressor of cytokine signaling 1, and CD115 (M-CSFR) were functional targets of miR-155. Furthermore, we provide evidence that miR-155 indirectly regulated p27(kip1) protein level by targeting Kip1 ubiquitination-promoting complex 1. Thus, our study uncovered miRNA signatures during monocyte differentiation into DCs and the new regulatory role of miR-221 and miR-155 in DC apoptosis and IL-12p70 production.

Down-regulation of granulocyte-macrophage colony-stimulating factor by 3C-like proteinase in transfected A549 human lung carcinoma cells

Background

Severe Acute Respiratory Syndrome (SARS) is a severe respiratory illness caused by a novel virus, the SARS coronavirus (SARS-CoV). 3C-like protease (3CL^pro) of SARS-CoV plays a role in processing viral polypeptide precursors and is responsible of viral maturation. However, the function of 3CL^pro in host cells remains unknown. This study investigated how the 3CL^pro affected the secretion of cytokines in the gene-transfected cells.

Results

From immunofluorescence microscopy, the localization of c-myc tagged 3CL^pro was detected both in the cytoplasm and nucleus of transfected A549 cells. Expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) was significantly decreased in 3CL^pro-transfected cells by both RT-PCR and ELISA, but without changes in other cytokines, i.e., IL-1β, IL-6, IL-8, IL12p40, TNF-α, and TGF-β. Furthermore, the protein levels of NF-kB decreased in 3CL^pro-transfected A549 cells when compared to EGFP transfected cells.

Conclusions

Our results suggest that the 3CL^pro may suppress expression of GM-CSF in transfected A549 cells through down-regulation of NF-kB production.

A versatile role of mammalian target of rapamycin in human dendritic cell function and differentiation

The mammalian target of rapamycin (mTOR) regulates cell growth and survival and exists as rapamycin-sensitive mTOR complex (mTORC) 1 and as rapamycin-insensitive mTORC2. Although mTOR is a well-known regulator of diverse immune cells, its detailed role in human dendritic cell (DC) function and differentiation is only incompletely understood. In this study, we demonstrate divergent roles of mTOR during activation and differentiation of myeloid DCs (mDCs) and monocyte-derived DCs (moDCs). Inhibition of mTORC1 in mDCs activated with TLR-dependent or -independent stimuli increased proinflammatory cytokines and NF-κB, whereas IL-10 and STAT3 were blocked. Rapamycin regulated the costimulatory/surface molecules CD86, programmed death ligand-1, and CD25 on mDCs and significantly increased the T cell allostimulatory potential of mDCs. In contrast, rapamycin suppressed immunostimulatory molecules and the allostimulatory potential of LPS-stimulated moDCs by an inability to augment NF-κB signaling. In differentiating moDCs, the PI3K/Akt-dependent mTOR pathway was constitutively activated by GM-CSF to induce DC differentiation in an mTORC1-dependent manner. Inhibition of mTORC1 or mTORC1/2 during moDC differentiation decreased moDC survival and markedly hampered its immunostimulatory phenotype. Analyzing the fate of DCs in vivo, we found that kidney transplant patients treated with rapamycin displayed an increased immunostimulatory potential of mDCs compared with patients treated with calcineurin inhibitors. Furthermore, rapamycin did not interfere with mDC differentiation in these patients. Collectively, mTOR exerts divergent immunoregulatory functions during DC activation and differentiation depending on the DC type that lead to opposing T cell responses, which might be of clinical importance in transplantation, cancer, and also for novel vaccination strategies.