Differential regulation of cytokine production by PI3Kdelta in human monocytes upon acute and chronic inflammatory conditions

The role of phosphoinositide 3-kinases in immune-inflammatory responses: potential therapeutic targets for abdominal aortic aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) includes inflammatory responses, matrix metalloproteinases (MMPs) degradation, VSMC apoptosis, oxidative stress, and angiogenesis, among which the inflammatory response plays a key role. At present, surgery is the only curing treatment, and no effective drug can delay AAA progression in clinical practice. Therefore, searching for a signaling pathway related to the immune-inflammatory response is an essential direction for developing drugs targeting AAA. Recent studies have confirmed that the PI3K family plays an important role in many inflammatory diseases and is involved in regulating various cellular functions, especially in the immune-inflammatory response. This review focuses on the role of each isoform of PI3K in each stage of AAA immune-inflammatory response, making available explorations for a deeper understanding of the mechanism of inflammation and immune response during the formation and development of AAA.

Pharmacodynamic Monitoring of Tacrolimus-Based Immunosuppression in CD14+ Monocytes After Kidney Transplantation

BACKGROUND

Monocytes significantly contribute to ischemia-reperfusion injury and allograft rejection after kidney transplantation. However, the knowledge about the effects of immunosuppressive drugs on monocyte activation is limited. Conventional pharmacokinetic methods for immunosuppressive drug monitoring are not cell type-specific. In this study, phosphorylation of 3 signaling proteins was measured to determine the pharmacodynamic effects of immunosuppression on monocyte activation in kidney transplant patients.

METHODS

Blood samples from 20 kidney transplant recipients were monitored before and during the first year after transplantation. All patients received induction therapy with basiliximab, followed by tacrolimus (TAC), mycophenolate mofetil, and prednisolone maintenance therapy. TAC whole-blood predose concentrations were determined using an antibody-conjugated magnetic immunoassay. Samples were stimulated with phorbol 12-myristate 13-acetate (PMA)/ionomycin, and phosphorylation of p38MAPK, ERK, and Akt in CD14 monocytes was quantified by phospho-specific flow cytometry.

RESULTS

Phosphorylation of p38MAPK and Akt in monocytes of immunosuppressed recipients was lower after 360 days compared with before transplantation in the unstimulated samples [mean reduction in median fluorescence intensity 36%; range -28% to 77% for p-p38MAPK and 20%; range -22% to 53% for p-Akt; P < 0.05]. P-ERK was only decreased at day 4 after transplantation (mean inhibition 23%; range -52% to 73%; P < 0.05). At day 4, when the highest whole-blood predose TAC concentrations were measured, p-p38MAPK and p-Akt, but not p-ERK, correlated inversely with TAC (rs = -0.65; P = 0.01 and rs = -0.58; P = 0.03, respectively).

CONCLUSIONS

Immunosuppressive drug combination therapy partially inhibits monocyte activation pathways after kidney transplantation. This inhibition can be determined by phospho-specific flow cytometry, which enables the assessment of the pharmacodynamic effects of immunosuppressive drugs in a cell type-specific manner.

A phase 2 study of idelalisib plus rituximab in treatment-naïve older patients with chronic lymphocytic leukemia

Idelalisib is a first-in-class oral inhibitor of PI3Kδ that has shown substantial activity in patients with relapsed/refractory chronic lymphocytic leukemia (CLL). To evaluate idelalisib as initial therapy, 64 treatment-naïve older patients with CLL or small lymphocytic leukemia (median age, 71 years; range, 65-90) were treated with rituximab 375 mg/m(2) weekly ×8 and idelalisib 150 mg twice daily continuously for 48 weeks. Patients completing 48 weeks without progression could continue to receive idelalisib on an extension study. The median time on treatment was 22.4 months (range, 0.8-45.8+). The overall response rate (ORR) was 97%, including 19% complete responses. The ORR was 100% in patients with del(17p)/TP53 mutations and 97% in those with unmutated IGHV. Progression-free survival was 83% at 36 months. The most frequent (>30%) adverse events (any grade) were diarrhea (including colitis) (64%), rash (58%), pyrexia (42%), nausea (38%), chills (36%), cough (33%), and fatigue (31%). Elevated alanine transaminase/aspartate transaminase was seen in 67% of patients (23% grade ≥3). The combination of idelalisib and rituximab was highly active, resulting in durable disease control in treatment-naïve older patients with CLL. These results support the further development of idelalisib as initial treatment of CLL. This study is registered at ClinicalTrials.gov as #NCT01203930.

PI3kα and STAT1 Interplay Regulates Human Mesenchymal Stem Cell Immune Polarization

The immunomodulatory capacity of mesenchymal stem cells (MSCs) is critical for their use in therapeutic applications. MSC response to specific inflammatory cues allows them to switch between a proinflammatory (MSC1) or anti-inflammatory (MSC2) phenotype. Regulatory mechanisms controlling this switch remain to be defined. One characteristic feature of MSC2 is their ability to respond to IFNγ with induction of indoleamine 2,3-dioxygenase (IDO), representing the key immunoregulatory molecule released by human MSC. Here, we show that STAT1 and PI3Kα pathways interplay regulates IFNγ-induced IDO production in MSC. Chemical phosphoinositide 3-kinase (PI3K) pan-inhibition, PI3Kα-specific inhibition or shRNA knockdown diminished IFNγ-induced IDO production. This effect involved PI3Kα-mediated upregulation of STAT1 protein levels and phosphorylation at Ser727. Overexpression of STAT1 or of a constitutively active PI3Kα mutant failed to induce basal IDO production, but shifted MSC into an MSC2-like phenotype by strongly enhancing IDO production in response to IFNγ as compared to controls. STAT1 overexpression strongly enhanced MSC-mediated T-cell suppression. The same effect could be induced using short-term pretreatment of MSC with a chemical inhibitor of the counter player of PI3K, phosphatase and tensin homolog. Finally, downregulation of STAT1 abrogated the immunosuppressive capacity of MSC. Our results for the first time identify critical upstream signals for the induced production of IDO in MSCs that could be manipulated therapeutically to enhance their immunosuppressive phenotype.

Metabolomics--a novel window into inflammatory disease

Inflammation is an important component of normal responses to infection and injury. However, chronic activation of the immune system, due to aberrant responses to normal stimuli, can lead to the establishment of a persistent inflammatory state. Such inflammatory conditions are often debilitating, and are associated with a number of important co-morbidities including cardiovascular disease. Resting non-proliferative tissues have distinctive metabolic activities and requirements, which differ considerably from those in infiltrating immune cells, which are undergoing proliferation and differentiation. Immune responses in tissues may therefore be modulated by the relative abundance of substrates in the inflamed site. In turn immune cell activity can feed back and affect metabolic behaviour of the tissues, as most clearly demonstrated in cachexia - the loss of cellular mass driven by tumour necrosis factor-alpha (TNF-α) a key mediator of the inflammatory response. Here we discuss the potential for metabolomic analysis to clarify the interactions between inflammation and metabolic changes underlying many diseases. We suggest that an increased understanding of the interaction between inflammation and cellular metabolism, energy substrate use, tissue breakdown markers, the microbiome and drug metabolites, may provide novel insight into the regulation of inflammatory diseases.

IFNβ and glatiramer acetate trigger different signaling pathways to regulate the IL-1 system in multiple sclerosis

Imbalance in cytokine homeostasis plays an important part in the pathogenesis of various chronic inflammatory diseases. In multiple sclerosis (MS), the pro-inflammatory cytokine interleukin-1β (IL-1β) is present in the central nervous system, being expressed mainly in infiltrating macrophages and microglial cells. IL-1β activity is inhibited by the secreted form of IL-1 receptor antagonist (sIL-1Ra) whose production is increased in patients' blood and induced in human monocytes by IFNβ and glatiramer acetate (GA)-both immunomodulators displaying similar therapeutic efficacy in MS. Because intracellular pathways are currently considered as potential therapeutic targets, identification of specific kinases used by both immunomodulators might lead to more specific therapeutic targeting. We addressed the question of intracellular pathways used by IFNβ and GA to induce sIL-1Ra in human monocytes in two recent studies. This addendum to these studies aims at discussing common pathways and different elements used by IFNβ and GA to induce sIL-1Ra in human monocytes. This pinpoints PI3Kδ activation as a requirement to induce sIL-1Ra production downstream monocyte stimulation by either IFNβ or GA. However, the immunomodulators differentially use MEK/ERK pathway to induce sIL-1Ra production in human monocytes. Together, our current studies suggest that PI3Kδ and MEK2 might represent new targets in MS therapy.

Glatiramer acetate triggers PI3Kδ/Akt and MEK/ERK pathways to induce IL-1 receptor antagonist in human monocytes

Glatiramer acetate (GA), an immunomodulator used in multiple sclerosis (MS) therapy, induces the production of secreted IL-1 receptor antagonist (sIL-1Ra), a natural inhibitor of IL-1β, in human monocytes, and in turn enhances sIL-1Ra circulating levels in MS patients. GA is a mixture of peptides with random Glu, Lys, Ala, and Tyr sequences of high polarity and hydrophilic nature that is unlikely to cross the blood-brain barrier. In contrast, sIL-1Ra crosses the blood-brain barrier and, in turn, may mediate GA anti-inflammatory activities within the CNS by counteracting IL-1β activities. Here we identify intracellular signaling pathways induced by GA that control sIL-1Ra expression in human monocytes. By using kinase knockdown and specific inhibitors, we demonstrate that GA induces sIL-1Ra production via the activation of PI3Kδ, Akt, MEK1/2, and ERK1/2, demonstrating that both PI3Kδ/Akt and MEK/ERK pathways rule sIL-1Ra expression in human monocytes. The pathways act in parallel upstream glycogen synthase kinase-3α/β (GSK3α/β), the knockdown of which enhances sIL-1Ra production. Together, our findings demonstrate the existence of signal transduction triggered by GA, further highlighting the mechanisms of action of this drug in MS.

Overcoming reduced glucocorticoid sensitivity in airway disease: molecular mechanisms and therapeutic approaches

There is a considerable and growing unmet medical need in respiratory disease concerning effective anti-inflammatory therapies for conditions such as severe asthma, chronic obstructive pulmonary disease and cystic fibrosis. These diseases share a predominant characteristic of an enhanced and uncontrolled inflammatory response in the lungs, which contributes to disease progression, hospitalization and mortality. These diseases are poorly controlled by current anti-inflammatory therapies including glucocorticoids, which are otherwise effective in many other inflammatory conditions or in milder disease such as asthma. The exact cause of this apparent impairment of glucocorticoid function remains largely unclear; however, recent studies have now implicated a number of possible mechanisms. Central among these is an elevation of the oxidant burden in the lungs and the resulting reduction in the activity of histone deacetylase (HDAC)-2. This contributes to both the enhancement of proinflammatory mediator expression and the impaired ability of the glucocorticoid receptor (GR)-alpha to repress proinflammatory gene expression. The oxidant-mediated reduction in HDAC-2 activity is, in part, a result of an elevation in the phosphoinositol 3-kinase (PI3K) delta/Akt signalling pathway. Blockade of the PI3Kdelta pathway restores glucocortiocoid function in both in vitro and in vivo models, and in primary cells from disease. In addition, inhibition of the PI3Kdelta and PI3Kgamma isoforms is anti-inflammatory in both innate and adaptive immune responses. Consequently, selective inhibition of this pathway may provide a therapeutic strategy both as a novel anti-inflammatory and in combination therapy with glucocorticoids to restore their function. However, a number of other oxidant-related and -unrelated mechanisms, including altered kinase signalling and expression of the dominant negative GRbeta, may also play a role in the development of glucocorticoid insensitivity. Further elucidation of these mechanisms and pathways will enable novel therapeutic targeting for alternative anti-inflammatory drugs or combination therapies providing restoration for the anti-inflammatory action of glucocorticoids.

A role for phosphoinositol 3-kinase delta in the impairment of glucocorticoid responsiveness in patients with chronic obstructive pulmonary disease

BACKGROUND

Glucocorticoid function is markedly impaired in the lungs of patients with chronic obstructive pulmonary disease (COPD). This reduction in glucocorticoid sensitivity might be due to an oxidant-mediated increase in phosphoinositol 3-kinase (PI3K) delta signaling.

OBJECTIVE

We sought to determine the role of PI3Kdelta in the reduced glucocorticoid responsiveness in patients with COPD.

METHODS

Peripheral lung tissue was obtained from 24 patients with COPD, 20 age-matched smokers with normal lung function, and 13 nonsmokers. Peripheral blood monocytes were isolated from 9 patients with COPD and 7 age-matched smokers with normal lung function and from healthy volunteers.

RESULTS

The expressions of PI3Kdelta and Akt phosphorylation were increased in macrophages from patients with COPD compared with those from control groups of age-matched smokers and nonsmokers. In vitro oxidative stress induced phosphorylation of Akt in monocytes and macrophages, which was abolished by means of selective inhibition of PI3Kdelta but not PI3Kgamma. Dexamethasone was less effective at repressing LPS-induced GM-CSF and CXC motif chemokine 8 release in blood monocytes from patients with COPD compared with age-matched smokers. This reduced sensitivity was reversed by inhibition of PI3Kdelta but not PI3Kgamma.

CONCLUSION

PI3Kdelta expression and signaling is increased in the lungs of patients with COPD. Selective inhibition of PI3Kdelta might restore glucocorticoid function in patients with COPD and might therefore present a potential therapeutic target.

Blockade of T cell contact-activation of human monocytes by high-density lipoproteins reveals a new pattern of cytokine and inflammatory genes

BACKGROUND

Cellular contact with stimulated T cells is a potent inducer of cytokine production in human monocytes and is likely to play a substantial part in chronic/sterile inflammatory diseases. High-density lipoproteins (HDL) specifically inhibit the production of pro-inflammatory cytokines induced by T cell contact.

METHODOLOGY/PRINCIPAL FINDINGS

To further elucidate the pro-inflammatory functions of cellular contact with stimulated T cells and its inhibition by HDL, we carried out multiplex and microarray analyses. Multiplex analysis of monocyte supernatant revealed that 12 out of 27 cytokines were induced upon contact with stimulated T cells, which cytokines included IL-1Ra, G-CSF, GM-CSF, IFNgamma, CCL2, CCL5, TNF, IL-1beta, IL-6, IL-8, CCL3, and CCL4, but only the latter six were inhibited by HDL. Microarray analysis showed that 437 out of 54,675 probe sets were enhanced in monocytes activated by contact with stimulated T cells, 164 probe sets (i.e., 38%) being inhibited by HDL. These results were validated by qPCR. Interestingly, the cytokines induced by T cell contact in monocytes comprised IL-1beta, IL-6 but not IL-12, suggesting that this mechanism might favor Th17 polarization, which emphasizes the relevance of this mechanism to chronic inflammatory diseases and highlights the contrast with acute inflammatory conditions that usually involve lipopolysaccharides (LPS). In addition, the expression of miR-155 and production of prostaglandin E(2)-both involved in inflammatory response-were triggered by T cell contact and inhibited in the presence of HDL.

CONCLUSIONS/SIGNIFICANCE

These results leave no doubt as to the pro-inflammatory nature of T cell contact-activation of human monocytes and the anti-inflammatory functions of HDL.

Cytokines in chronic rheumatic diseases: is everything lack of homeostatic balance?

Biological systems have powerful inbuilt mechanisms of control intended to maintain homeostasis. Cytokines are no exception to this rule, and imbalance in cytokine activities may lead to inflammation with subsequent tissue and organ damage, altered function, and death. Balance is achieved through multiple, not mutually exclusive, mechanisms including the simultaneous production of agonist and antagonistic cytokines, expression of soluble receptors or membrane-bound nonsignaling receptors, priming and/or reprogramming of signaling, and uncoupling of ligand/receptor pairing from signal transduction. Insight into cytokine balance is leading to novel therapeutic approaches particularly in autoimmune conditions, which are intimately linked to a dysregulated cytokine production.