Pbx-regulating-protein 1 (Prep1) as a novel transcription factor linking immune system function and metabolism.

Prep1 is a transcription factor which plays an important role in organogenesis, in the regulation of energy homeostasis and metabolism. In particular, Prep1 has been recently demonstrated to inhibit insulin signaling, inducing insulin-resistance and contributing to steatohepatitis. Since accumulating evidence has shown that metabolic disorders are associated with immune system dysregulation, in this thesis we have characterized the role of Prep1 in the control of immune system function. We found a decreased secretion of pro-inflammatory cytokines/chemokines and enhanced anti-inflammatory cytokines release in the sera of Prep1-hypomorphic heterozygous mice (Prep1i/+), which express 55-57% of Prep1 protein. In addition, Prep1 deficiency significantly inhibited T cells proliferation and activation. These effects were associated with an impaired mTOR pathway activation, cell growth arrest and an altered metabolic profile of CD4+ T cells. On the other hand, regulatory T cells (Treg) from Prep1i/+ mice displayed higher proliferative capacity and increased suppressive activity, which determined in vivo protection of Prep1i/+ mice from high fat diet-induced metabolic alterations and hepatic inflammation. These observations unmask a previously unknown role of Prep1 in the regulation of adaptive immune response and provide a rationale for further investigating Prep1 as a possible target for immune-mediate metabolic disorders

The Proteomic Landscape of Human Ex Vivo Regulatory and Conventional T Cells Reveals Specific Metabolic Requirements

Human CD4(+)CD25(hi)Foxp3(+)CD127(-) Treg and CD4(+)CD25(-)Foxp3(-) Tconv cell functions are governed by their metabolic requirements. Here we report a comprehensive comparative analysis between ex vivo human Treg and Tconv cells that comprises analyses of the proteomic networks in subcellular compartments. We identified a dominant proteomic signature at the metabolic level that primarily impacted the highly-tuned balance between glucose and fatty-acid oxidation in the two cell types. Ex vivo Treg cells were highly glycolytic while Tconv cells used predominantly fatty-acid oxidation (FAO). When cultured in vitro, Treg cells engaged both glycolysis and FAO to proliferate, while Tconv cell proliferation mainly relied on glucose metabolism. Our unbiased proteomic analysis provides a molecular picture of the impact of metabolism on ex vivo human Treg versus Tconv cell functions that might be relevant for therapeutic manipulations of these cells

Fatty acid metabolism complements glycolysis in th selective regulatory t cell expansion during tumor growth

The tumor microenvironment restrains conventional T cell (Tconv) activation while facilitating the expansion of Tregs. Here we showed that Tregs’ advantage in the tumor milieu relies on supplemental energetic routes involving lipid metabolism. In murine models, tumor-infiltrating Tregs displayed intracellular lipid accumulation, which was attributable to an increased rate of fatty acid (FA) synthesis. Since the relative advantage in glucose uptake may fuel FA synthesis in intratumoral Tregs, we demonstrated that both glycolytic and oxidative metabolism contribute to Tregs’ expansion. We corroborated our data in human tumors showing that Tregs displayed a gene signature oriented toward glycolysis and lipid synthesis. Our data support a model in which signals from the tumor microenvironment induce a circuitry of glycolysis, FA synthesis, and oxidation that confers a preferential proliferative advantage to Tregs, whose targeting might represent a strategy for cancer treatment

Effects of Long-Term Citrate Treatment in the PC3 Prostate Cancer Cell Line

Acute administration of a high level of extracellular citrate displays an anti-proliferative effect on both in vitro and in vivo models. However, the long-term effect of citrate treatment has not been investigated yet. Here, we address this question in PC3 cells, a prostate-cancer-derived cell line. Acute administration of high levels of extracellular citrate impaired cell adhesion and inhibited the proliferation of PC3 cells, but surviving cells adapted to grow in the chronic presence of 20 mM citrate. Citrate-resistant PC3 cells are significantly less glycolytic than control cells. Moreover, they overexpress short-form, citrate-insensitive phosphofructokinase 1 (PFK1) together with full-length PFK1. In addition, they show traits of mesenchymal-epithelial transition: an increase in E-cadherin and a decrease in vimentin. In comparison with PC3 cells, citrate-resistant cells display morphological changes that involve both microtubule and microfilament organization. This was accompanied by changes in homeostasis and the organization of intracellular organelles. Thus, the mitochondrial network appears fragmented, the Golgi complex is scattered, and the lysosomal compartment is enlarged. Interestingly, citrate-resistant cells produce less total ROS but accumulate more mitochondrial ROS than control cells. Consistently, in citrate-resistant cells, the autophagic pathway is upregulated, possibly sustaining their survival. In conclusion, chronic administration of citrate might select resistant cells, which could jeopardize the benefits of citrate anticancer treatment

Convergent effects of resveratrol and PYK2 on prostate cells

Resveratrol, a dietary polyphenol, is under consideration as chemopreventive and chemotherapeutic agent for several diseases, including cancer. However, its mechanisms of action and its effects on non-tumor cells, fundamental to understand its real efficacy as chemopreventive agent, remain largely unknown. Proline-rich tyrosine kinase 2 (PYK2), a non-receptor tyrosine kinase acting as signaling mediator of different stimuli, behaves as tumor-suppressor in prostate. Since, PYK2 and RSV share several fields of interaction, including oxidative stress, we have investigated their functional relationship in human non-transformed prostate EPN cells and in their tumor-prone counterpart EPN-PKM, expressing a PYK2 dead-kinase mutant. We show that RSV has a strong biological activity in both cell lines, decreasing ROS production, inducing morphological changes and reversible growth arrest, and activating autophagy but not apoptosis. Interestingly, the PYK2 mutant increases basal ROS and autophagy levels, and modulates the intensity of RSV effects. In particular, the anti-oxidant effect of RSV is more potent in EPN than in EPN-PKM, whereas its anti-proliferative and pro-autophagic effects are more significant in EPN-PKM. Consistently, PYK2 depletion by RNAi replicates the effects of the PKM mutant. Taken together, our results reveal that PYK2 and RSV act on common cellular pathways and suggest that RSV effects on prostate cells may depend on mutational-state or expression levels of PYK2 that emerges as a possible mediator of RSV mechanisms of action. Moreover, the observation that resveratrol effects are reversible and not associated to apoptosis in tumor-prone EPN-PKM cells suggests caution for its use in humans

IFNβ enhances mesenchymal stromal (Stem) cells immunomodulatory function through STAT1-3 activation and mTOR-associated promotion of glucose metabolism

Abstract Administration of mesenchymal stem cells (MSC) ameliorate experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS), at both clinical and neuropathological levels. The therapeutic properties of MSC in EAE are mainly mediated by the modulation of pathogenic immune response, but other neurotropic effects, including decreased demyelination and axonal loss as well as promotion of tissue repair, play also a role. Properly controlled phase II clinical trials to explore the potential of MSC transplantation as a treatment for MS are underway. Interferon beta (IFNβ) is an approved treatment for relapsing-remitting and secondary progressive MS. Here, we explored the possibility that IFNβ might influence the therapeutic potential of MSC, in view of possible synergistic effects as add-on therapy. IFNβ enhanced the immunomodulatory functions of MSC and induced the expression of secretory leukocyte protease inhibitor (Slpi) and hepatocyte growth factor (Hgf), two soluble mediators involved in immune and regenerative functions of MSC. At molecular level, IFNβ induced a rapid and transient phosphorylation of STAT1 and STAT3, the transcription factors responsible for Slpi and Hgf induction. Concomitantly, IFNβ dynamically affected the activity of mTOR, a key checkpoint in the control of metabolic pathways. Indeed, the impairment of mTOR activity observed early upon exposure to IFNβ, was followed by a long-lasting induction of mTOR signaling, that was associated with an increased glycolytic capacity in MSC. When induced to switch their energetic metabolism towards glycolysis, MSC showed an improved ability to control T-cell proliferation. These results suggest that modifications of MSC energetic metabolism induced by IFNβ may contribute to promote MSC immunomodulatory function and support a role for metabolic pathways in the therapeutic function of MSC. Altogether, these findings support the idea of a combined treatment for MS, in which the immunomodulatory and possibly regenerative activity of MSC could be enhanced by the administration of IFNβ

Identification of a highly suppressive Treg subset associated to immunotherapy response

Background Cancer immunotherapy has shown surprising efficacy in several types of advanced and incurable tumors, particularly, malignant melanoma. There are several immunotherapeutic strategies aimed at enhancing immunological defenses against tumor. Among these, monoclonal antibodies against the so-called “immune checkpoint inhibitors”, that counteract tumor-induced immune-disarming pathways, have shown the best outcomes. Regulatory T lymphocytes or Tregs are a subset of lymphocytes involved in immune-surveillance and maintenance of self-tolerance. Tumor often exploits Tregs to allow tolerance to its own antigens and avoid immune system attack. Tregs are usually increased in melanoma patients. It is noticeable that Tregs is a heterogeneous population with respect to their immunosuppressive capability. Lymphocytes are particularly rich in FKBP51 (FKBP5 gene), an immunophilin better known as the intracellular receptor for FK506 and rapamycin. Melanoma aberrantly expresses this immunophilin, which supports cancer resistance and invasion. Recently, our group has shown that melanoma interaction with immune cells, through PD-L1/PD1, bidirectionally generated the splicing of FKBP5 gene inducing a lower molecular weight form of FKBP51, termed FKBP51s, in both melanoma and lymphocyte. A study performed on PBMC of 64 patients with advanced melanoma (stage III/IV) showed that FKBP51s marks a Treg subset which was correlated, as an independent variable, to anti-CTLA4 (ipilimumab) response. More precisely, a low frequency of Treg FKBP51spos (1.2 and 0.04 and < 0.8%. After a transient increase registered following the first administration, the count decreased to 0.3+0.2% in responder patients. Interestingly, a patient with count = 0.72% developed autoimmune side effects that led to therapy discontinuation. Resolution of side effects was accompanied by an increase in Treg FKBP51s+ value to 9.9%; thenafter, anti-PD1 re-administration produced a successful and objective response. In vitro iTreg generation suggested that FKBP51s was induced in Treg CD25high, Ki67high and p70S6khigh , corresponding to a highly metabolically active profile associated with strong suppressive capability. Conclusion Our data reinforce the hypothesis that melanoma patients that benefit from immune checkpoint targeted therapy are recognizable by an expansion of a Treg subset which plays a central role in de-activation of stimulatory co-signalling pathways, in support of tumor immune evasion. Such a Treg subset is marked by FKBP51s, a splicing protein isoform generated by triggering of surface antigens (PD-L1, PD1) that are abundantly expressed on highly suppressive Tregs

Metformin restores the mitochondrial network and reverses mitochondrial dysfunction in Down syndrome cells

Alterations in mitochondrial activity and morphology have been demonstrated in human cells and tissues from individuals with Down syndrome (DS), as well as in DS mouse models. An impaired activity of the transcriptional coactivator PGC-1a/PPARGC1A due to the overexpression of chromosome 21 genes, such as NRIP1/RIP140, has emerged as an underlying cause of mitochondrial dysfunction in DS. We tested the hypothesis that the activation of the PGC-1α pathway might indeed reverse this mitochondrial dysfunction. To this end, we investigated the effects of metformin, a PGC-1α-activating drug, on mitochondrial morphology and function in DS foetal fibroblasts. Metformin induced both the expression of PGC-1α and an augmentation of its activity, as demonstrated by the increased expression of target genes, strongly promoting mitochondrial biogenesis. Furthermore, metformin enhanced oxygen consumption, ATP production, and overall mitochondrial activity. Most interestingly, this treatment reversed the fragmentation of mitochondria observed in DS and induced the formation of a mitochondrial network with a branched and elongated tubular morphology. Concomitantly, cristae remodelling occurred and the alterations observed by electron microscopy were significantly reduced. We finally demonstrated that the expression of genes of the fission/fusion machinery, namely OPA1 and MFN2, was reduced in trisomic cells and increased by metformin treatment. These results indicate that metformin promotes the formation of a mitochondrial network and corrects the mitochondrial dysfunction in DS cells. We speculate that alterations in the mitochondrial dynamics can be relevant in the pathogenesis of DS and that metformin can efficiently counteract these alterations, thus exerting protective effects against DS-associated pathologies