Moraxella catarrhalis evades neutrophil oxidative stress responses providing a safer niche for nontypeable Haemophilus influenzae

Moraxella catarrhalis and nontypeable Haemophilus influenzae (NTHi) are pathogenic bacteria frequently associated with exacerbation of chronic obstructive pulmonary disease (COPD), whose hallmark is inflammatory oxidative stress. Neutrophils produce reactive oxygen species (ROS) which can boost antimicrobial response by promoting neutrophil extracellular traps (NET) and autophagy. Here, we showed that M. catarrhalis induces less ROS and NET production in differentiated HL-60 cells compared to NTHi. It is also able to actively interfere with these responses in chemically activated cells in a phagocytosis and opsonin-independent and contact-dependent manner, possibly by engaging host immunosuppressive receptors. M. catarrhalis subverts the autophagic pathway of the phagocytic cells and survives intracellularly. It also promotes the survival of NTHi which is otherwise susceptible to the host antimicrobial arsenal. In-depth understanding of the immune evasion strategies exploited by these two human pathogens could suggest medical interventions to tackle COPD and potentially other diseases in which they co-exist

Idiopathic recurrent pericarditis refractory to colchicine treatment can reveal tumor necrosis factor receptor-associated periodic syndrome

Recurrences develop in up to 20-50% of patients with acute pericarditis. Although different causes of recurrent pericarditis have been identified, the etiology remains obscure in most cases which are therefore labelled as idiopathic. Autoinflammatory syndromes include familial Mediterranean fever (FMF), due to mutations in the MEFV gene, and tumor necrosis factor receptor-associated periodic syndrome (TRAPS), due to mutations in the TNFRSF1A gene. Recurrent pericarditis is a common feature of both conditions, but it rarely occurs alone. Colchicine is the standard treatment for FMF, while patients with TRAPS do not respond to colchicine therapy, but are responsive to corticosteroids. Based on the proven efficacy of colchicine in preventing polyserositis in FMF, colchicine has been proposed for the treatment of recurrent pericarditis and is able to decrease the recurrence rate. Our aim was to investigate the possible involvement of TNFRSF1A mutations in a group of patients with idiopathic recurrent pericarditis who were refractory to colchicine treatment. Thirty consecutive patients (17 males, 13 females) diagnosed with idiopathic recurrent pericarditis, who were characterized by a poor response to colchicine treatment, were enrolled in the study. Mutations of the TNFRSF1A gene were searched for by amplifying, using polymerase chain reaction (PCR), genomic DNA, and direct sequencing. TNFRSF1A mutations were found in 4 of the 30 patients. None of these 4 patients had a family history of recurrent inflammatory syndromes or history of pericarditis. One of the 4 patients had a novel heterozygous deletion (Delta Y103-R104) and three patients carried a heterozygous low-penetrance R92Q mutation. Our data suggest that TRAPS should be kept in mind in the differential diagnosis of recurrent pericarditis, and mutation analysis of the TNFRSF1A gene should be considered, in addition to MEFV analysis, in patients of Mediterranean origin. A poor response to colchicine treatment and/or a steroid-dependence may be the clue to investigate TNFRSF1A mutations in patients with idiopathic recurrent pericarditis

Anthrax Edema Toxin Modulates PKA- and CREB-Dependent Signaling in Two Phases

Background: Anthrax edema toxin (EdTx) is an adenylate cyclase which operates in the perinuclear region of host cells. However, the action of EdTx is poorly understood, especially at molecular level. The ability of EdTx to modulate cAMPdependent signaling was studied in Jurkat T cells and was compared with that of other cAMP-rising agents: Bordetella pertussis adenylate cyclase toxin, cholera toxin and forskolin. Methodology/Principal Findings: EdTx caused a prolonged increase of the intracellular cAMP concentration. This led to nuclear translocation of the cAMP-dependent protein kinase (PKA) catalytic subunit, phosphorylation of cAMP response element binding protein (CREB) and expression of a reporter gene under control of the cAMP response element. Neither p90 ribosomal S6 kinase nor mitogen- and stress-activated kinase, which mediate CREB phosphorylation during T cell activation, were involved. The duration of phospho-CREB binding to chromatin correlated with the spatio-temporal rise of cAMP levels. Strikingly, EdTx pre-treated T cells were unresponsive to other stimuli involving CREB phosphorylation such as addition of forskolin or T cell receptor cross-linking. Conclusions/Significance: We concluded that, in a first intoxication phase, EdTx induces PKA-dependent signaling, which culminates in CREB phosphorylation and activation of gene transcription. Subsequently CREB phosphorylation is impaired and therefore T cells are not able to respond to cues involving CREB. The present data functionally link the perinuclea

Molecular mechanisms underlying suppression of lymphocyte responses by nonsteroidal antiinflammatory drugs

Initially identified and further developed as inhibitors of cyclooxygenases, nonsteroidal antiinflammatory drugs (NSAIDs) have been more recently shown to bind to and act as agonists of the peroxisome proliferator-activated receptor family of transcription factors. Here we summarize the current knowledge on the functions of the principal targets of NSAIDs and review their role in T and B lymphocytes, with a focus on the molecular mechanisms underlying the effects of NSAIDs on lymphocyte development, activation, differentiation and death

The adenylate cyclase toxins of Bacillus anthracis and Bordetella pertussis promote Th2 cell development by shaping T cell antigen receptor signaling.

The adjuvanticity of bacterial adenylate cyclase toxins has been ascribed to their capacity, largely mediated by cAMP, to modulate APC activation, resulting in the expression of Th2-driving cytokines. On the other hand, cAMP has been demonstrated to induce a Th2 bias when present during T cell priming, suggesting that bacterial cAMP elevating toxins may directly affect the Th1/Th2 balance. Here we have investigated the effects on human CD4(+) T cell differentiation of two adenylate cyclase toxins, Bacillus anthracis edema toxin (ET) and Bordetella pertussis CyaA, which differ in structure, mode of cell entry, and subcellular localization. We show that low concentrations of ET and CyaA, but not of their genetically detoxified adenylate cyclase defective counterparts, potently promote Th2 cell differentiation by inducing expression of the master Th2 transcription factors, c-maf and GATA-3. We also present evidence that the Th2-polarizing concentrations of ET and CyaA selectively inhibit TCR-dependent activation of Akt1, which is required for Th1 cell differentiation, while enhancing the activation of two TCR-signaling mediators, Vav1 and p38, implicated in Th2 cell differentiation. This is at variance from the immunosuppressive toxin concentrations, which interfere with the earliest step in TCR signaling, activation of the tyrosine kinase Lck, resulting in impaired CD3zeta phosphorylation and inhibition of TCR coupling to ZAP-70 and Erk activation. These results demonstrate that, notwithstanding their differences in their intracellular localization, which result in focalized cAMP production, both toxins directly affect the Th1/Th2 balance by interfering with the same steps in TCR signaling, and suggest that their adjuvanticity is likely to result from their combined effects on APC and CD4(+) T cells. Furthermore, our results strongly support the key role of cAMP in the adjuvanticity of these toxins

ERKs are the point of divergence of PKA and PKC activation by PTHrP in human skin fibroblasts.

Parathyroid hormone-related peptide (PTHrP) receptors, coupled to trimeric G proteins, operate in most target cells through at least three different transduction routes: Galpha s-mediated stimulation of adenylylcyclase (AC), Galpha q-mediated activation of phospholipase Cbeta (PLC) and mitogen-activated protein kinase (MAPK) activation. In this study we investigated the relative role of different pathways in human skin fibroblast proliferation. Using chemical inhibitors and activators of signal transduction, we demonstrated that: (i) AC/cAMP and PLC/1,4,5 inositol triphosphate/diacylglycerol second-messenger systems are simultaneously activated following PTHrP binding to its receptors; (ii) the mitogenic response to PTHrP derives from a balance between two counteracting pathways--an activating route mediated by protein kinase C (PKC) and an inhibitory route mediated by protein kinase A (PKA); (iii) PTHrP mitogenic effects are largely dependent on MAPKs, whose activity can be modulated by both PKA and PKC. Our results indicate that MAPKs are common targets of both transduction routes and, at the same time, their point of divergence in mediating PTHrP dual and opposite mitogenic effects