The recruitment and activation of phosphatidylinositol 4-phosphate 5-kinases α critically regulate CD28-dependent signaling responses

CD28 costimulatory receptor is a crucial determinant of the outcome of T lymphocyte activation. The engagement of CD28 by its natural ligands, B7.1/CD80 or B7.2/CD86, expressed on the surface of professional APC, lowers T cell receptor (TCR) activation threshold, thus leading to the enhancement of early signalling events necessary for efficient cytokine production, cell cycle progression, survival and regulation of T cells effector responses. CD28 is also able to act as a unique signalling receptor and to deliver TCR-independent autonomous signals, which account for its critical role in the regulation of pro-inflammatory cytokine/chemokine production and T cell survival. Most of the CD28-dependent signalling functions are initiated by the recruitment and activation of class IA phosphatidylinositol 3-kinase (PI3K), The intracytoplasmic domain of CD28 contains a N-terminal YMNM motif that following phosphorylation binds the p85 subunit of phosphatidylinositol 3-kinase (PI3K). Once activated, PI3K catalyzes the conversion of phosphatidylinositol 4,5-biphosphate (PIP2) to phosphatidylinositol 3,4,5-triphosphate (PIP3) and generates the docking sites for key signalling proteins. PIP2 plays a critical role in the regulation of both cytoskeleton dynamics and second messenger generation. Indeed, PIP2 is the common source for two major distinct signalling cascades involving PI3K and PLCγ1 that often colocalize in the same signalling complexes competing for the common pool of substrate. Consequently, PIP2 levels decrease following receptor activation, thus suggesting that stimulation of PIP2 synthesis may be an essential regulatory step to sustain the activation of both PI3K and PLCγ1 following CD28 engagement. The main biosynthetic pathway of PIP2 involves phosphorylation of phosphatidylinositol 4-monophosphate (PI4P) at the D5 position of the inositol ring by PIP5K. Three PIP5K isoforms (α, β and γ) have been identified. Several data obtained in different cell systems evidenced differential subcellular localizations of each isoform. PIP5Kα, for instance, is localized at the plasma membrane, where it guarantees the local availability of PIP2. Here we show that CD28 stimulation by both B7.1/CD80 or agonistic Abs induces the recruitment and activation of PIP5Kα in human primary CD4+ T lymphocytes. This event leads to the neo-synthesis of PIP2 that is consumed by CD28-activated PI3K. By either small interference RNA (siRNA)-driven cell silencing or overexpressing a kinase dead mutant, we evidenced that PIP5Kα activation is required for both CD28 autonomous signals regulating IL-8 gene expression as well as for CD28/TCR-induced Ca2+ mobilization, NF-AT nuclear translocation and IL-2 gene transcription. Our findings identify PIP5Kα as a critical mediator of CD28-dependent responses

CD28 individual signaling up-regulates IL-22 expression and IL-22-mediated effector functions in human T lymphocytes

IL‐22 is a member of the IL‐10 cytokine family involved in host protection against extracellular pathogens, by promoting epithelial cell regeneration and barrier functions. Dysregulation of IL‐22 production has also frequently been observed in acute respiratory distress syndrome (ARDS) and several chronic inflammatory and autoimmune diseases. We have previously described that human CD28, a crucial co‐stimulatory receptor necessary for full T cell activation, is also able to act as a TCR independent signalling receptor and to induce the expression of IL‐17A and inflammatory cytokines related to Th17 cells, which together with Th22 cells represent the main cellular source of IL‐22. Here we characterized the role of CD28 autonomous signalling in regulating IL‐22 expression in human CD4+ T cells. We show that CD28 stimulation in the absence of TCR strongly up‐regulates IL‐22 gene expression and secretion. As recently observed for IL‐17A, we also found that CD28‐mediated regulation of IL‐22 transcription requires the cooperative activities of both IL‐6‐activated STAT3 and RelA/NF‐κ transcription factors. CD28‐mediated IL‐22 production also promotes the barrier functions of epithelial cells by inducing mucin and metalloproteases expression. Finally, by using specific inhibitory drugs, we also identified CD28‐associated class 1A phosphatidylinositol 3‐kinase (PI3K) as a pivotal mediator of CD28‐mediated IL‐22 expression and IL‐ 22‐dependent epithelial cell barrier functions

CD28 autonomous signaling orchestrates IL-22 expression and IL-22-regulated epithelial barrier functions in human T lymphocytes

IL-22 is a member of the IL-10 cytokine family involved in host protection against extracellular pathogens, by promoting epithelial cell regeneration and barrier functions. Dysregulation of IL-22 production has also frequently been observed in acute respiratory distress syndrome (ARDS) and several chronic inflammatory and autoimmune diseases. We have previously described that human CD28, a crucial co-stimulatory receptor necessary for full T cell activation, is also able to act as a TCR independent signaling receptor and to induce the expression of IL-17A and inflammatory cytokines related to Th17 cells, which together with Th22 cells represent the main cellular source of IL-22. Here we characterized the role of CD28 autonomous signaling in regulating IL-22 expression in human CD4+ T cells. We show that CD28 stimulation in the absence of TCR strongly up-regulates IL-22 gene expression and secretion. As recently observed for IL-17A, we also found that CD28-mediated regulation of IL-22 transcription requires the cooperative activities of both IL-6-activated STAT3 and RelA/NF-κB transcription factors. CD28-mediated IL-22 production also promotes the barrier functions of epithelial cells by inducing mucin and metalloproteases expression. Finally, by using specific inhibitory drugs, we also identified CD28-associated class 1A phosphatidylinositol 3-kinase (PI3K) as a pivotal mediator of CD28-mediated IL-22 expression and IL-22–dependent epithelial cell barrier functions

Staphylococcal enterotoxin B (SEB) activates TCR- and CD28-mediated inflammatory signals in the absence of MHC class II molecules

The inflammatory activity of staphylococcal enterotoxin B (SEB) relies on its capacity to trigger polyclonal T‐cell activation by binding both T‐cell receptor (TCR) and costimulatory receptor CD28 on T cells and MHC class II and B7 molecules on antigen presenting cells (APC). Previous studies highlighted that SEB may bind TCR and CD28 molecules independently of MHC class II, yet the relative contribution of these interactions to the pro‐inflammatory function of SEB remained unclear. Here, we show that binding to MHC class II is dispensable for the inflammatory activity of SEB, whereas binding to TCR, CD28 and B7 molecules is pivotal, in both human primary T cells and Jurkat T cell lines. In particular, our finding is that binding of SEB to B7 molecules suffices to trigger both TCR‐ and CD28‐mediated inflammatory signalling. We also provide evidence that, by strengthening the interaction between CD28 and B7, SEB favours the recruitment of the TCR into the immunological synapse, thus inducing lethal inflammatory signallin

The Risk of Toxicities from Trastuzumab, Alone or in Combination, in an Elderly Breast Cancer Population

Abstract Background: Breast cancer in the elderly is associated with high recurrence and death rates, due mostly to undertreatment. Human epidermal growth factor receptor type 2 (HER2) overexpression is infrequent in older patients. Trastuzumab- based chemotherapy is often withheld from elderly patients because of its cardiotoxicity. Patients and Methods: Medical records of consecutive HER2-positive breast cancer patients aged 65 70 years old treated between 2005 and 2010 in the participating centers were retrospectively reviewed. All patients underwent multidimensional geriatric assessment (MGA). Results: Among 59 patients identified, 51 patients were evaluable (median age 76 years). The rate of any adverse event was 20% (10/51). The most relevant cardiac adverse event consisted of symptomatic congestive heart failure (CHF; n = 1, 2%) followed by asymptomatic decreases of left ventricular ejection fraction (LVEF; n = 6, 12%). Other toxicities included moderate hypersensitivity reactions during trastuzumab infusions (n = 3, 6%). Hypertension, obesity, prior anthracyclines exposure and concurrent chemotherapy were associated with a higher incidence of toxic events. Previous radiotherapy, concurrent endocrine therapy and different trastuzumab-based regimens did not seem to influence toxicity. Conclusions: Our data suggest that trastuzumab has a good safety profile in nonfrail women aged 70 years and older. These favorable findings may be related to a limited number of anthracycline pretreatments, patient selection and a close cardiologic monitoring

Polymerogenic neuroserpin causes mitochondrial alterations and activates NFκB but not the UPR in a neuronal model of neurodegeneration FENIB

The neurodegenerative condition FENIB (familiar encephalopathy with neuroserpin inclusion bodies) is caused by heterozygous expression of polymerogenic mutant neuroserpin (NS), with polymer deposition within the endoplasmic reticulum (ER) of neurons. We generated transgenic neural progenitor cells (NPCs) from mouse fetal cerebral cortex stably expressing either the control protein GFP or human wild type, polymerogenic G392E or truncated (delta) NS. This cellular model makes it possible to study the toxicity of polymerogenic NS in the appropriated cell type by in vitro differentiation to neurons. Our previous work showed that expression of G392E NS in differentiated NPCs induced an adaptive response through the upregulation of several genes involved in the defence against oxidative stress, and that pharmacological reduction of the antioxidant defences by drug treatments rendered G392E NS neurons more susceptible to apoptosis than control neurons. In this study, we assessed mitochondrial distribution and found a higher percentage of perinuclear localisation in G392E NS neurons, particularly in those containing polymers, a phenotype that was enhanced by glutathione chelation and rescued by antioxidant molecules. Mitochondrial membrane potential and contact sites between mitochondria and the ER were reduced in neurons expressing the G392E mutation. These alterations were associated with a pattern of ER stress that involved the ER overload response but not the unfolded protein response. Our results suggest that intracellular accumulation of NS polymers affects the interaction between the ER and mitochondria, causing mitochondrial alterations that contribute to the neuronal degeneration seen in FENIB patients

Perturbed nonlocal fourth order equations of Kirchhoff type with Navier boundary conditions

Abstract We investigate the existence of multiple solutions for perturbed nonlocal fourth-order equations of Kirchhoff type under Navier boundary conditions. We give some new criteria for guaranteeing that the perturbed fourth-order equations of Kirchhoff type have at least three weak solutions by using a variational method and some critical point theorems due to Ricceri. We extend and improve some recent results. Finally, by presenting two examples, we ensure the applicability of our results

Multiple solutions for a class of perturbed second-order differential equations with impulses

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