Abstract
Aims
It remains unclear whether surgical or transcatheter mitral valve repair for secondary mitral regurgitation (MR) in patients with non-ischaemic cardiomyopathy reverse the underlying ...left ventricular (LV) pathophysiology. We hypothesized that mitral valve repair improves LV systolic function and forward flow and induces LV reverse remodelling in this group of patients.
Methods and results
Seventy-six patients (65 ± 14 years old, 43% male) with non-ischaemic cardiomyopathy and moderate to severe chronic secondary MR treated successfully with transcatheter or surgical mitral valve repair were evaluated. Transthoracic echocardiography was performed at baseline, discharge and 6 months post-repair. After mitral valve repair, LVEF, and LV global longitudinal strain (GLS) corrected for LV end-diastolic volume remained unchanged over time (P = 0.90 and P = 0.96, respectively). In contrast, LV forward flow increased significantly over time (stroke volume index: from 20 ± 7 to 29 ± 8 and 26 ± 8 mL/m2, P < 0.001; cardiac index: from 1.50 ± 0.44 to 2.36 ± 0.60 and 2.01 ± 0.48 L/min/m2, P < 0.001). In addition, LV end-diastolic and end-systolic volume index significantly reduced over time (from 87 ± 42 to 70 ± 33 and 75 ± 39 mL/m2, P < 0.001; and from 60 ± 35 to 50 ± 30 and 53 ± 36 mL/m2, P = 0.004, respectively). These changes were independent of the type of repair.
Conclusion
Surgical and transcatheter mitral valve repair for secondary MR in patients with non-ischaemic dilated cardiomyopathy improved LV forward flow and induced LV reverse remodelling but did not change LV systolic function.
Protein kinase C-thetas (PKC-thetas) translocates to the center of the immunological synapse, but the underlying mechanism and its importance in T cell activation are unknown. Here we found that the ...V3 domain of PKC-thetas was necessary and sufficient for localization to the immunological synapse mediated by association with the coreceptor CD28 and dependent on the kinase Lck. We identified a conserved proline-rich motif in V3 required for association with CD28 and immunological synapse localization. We found association with CD28 to be essential for PKC-thetas-mediated downstream signaling and the differentiation of T helper type 2 cells (T(H)2 cells) and interleukin 17-producing helper T cells (T(H)17 cells) but not of T helper type 1 cells (T(H)1 cells). Ectopic expression of V3 sequestered PKC-thetas from the immunological synapse and interfered with its functions. Our results identify a unique mode of CD28 signaling, establish a molecular basis for the immunological synapse localization of PKC-thetas and indicate V3-based 'decoys' may be therapeutic modalities for T cell-mediated inflammatory diseases.
Protein kinase C-θ (PKC-θ) translocates to the center of the immunological synapse, but the underlying mechanism and its importance in T cell activation are unknown. We found that the PKC-θ V3 domain ...is necessary and sufficient for IS localization mediated by Lck-dependent association with CD28. We identified a conserved proline-rich motif in V3 required for CD28 association and IS localization. CD28 association was essential for PKC-θ-mediated downstream signaling and T
H
2 and T
H
17, but not T
H
1, differentiation. Ectopic V3 expression sequestered PKC-θ from the IS and interfered with its functions. These results identify a unique mode of CD28 signaling, establish a molecular basis for the IS localization of PKC-θ, and implicate V3-based “decoys” as therapeutic modalities for T cell-mediated inflammatory diseases.
Regulatory T (Treg) cells, which maintain immune homeostasis and self-tolerance, form an immunological synapse (IS) with antigen-presenting cells (APCs). However, signaling events at the Treg cell IS ...remain unknown. Here we show that the kinase PKC-η associated with CTLA-4 and was recruited to the Treg cell IS. PKC-η-deficient Treg cells displayed defective suppressive activity, including suppression of tumor immunity but not of autoimmune colitis. Phosphoproteomic and biochemical analysis revealed an association between CTLA-4-PKC-η and the GIT2-αPIX-PAK complex, an IS-localized focal adhesion complex. Defective activation of this complex in PKC-η-deficient Treg cells was associated with reduced depletion of CD86 from APCs by Treg cells. These results reveal a CTLA-4-PKC-η signaling axis required for contact-dependent suppression and implicate this pathway as a potential cancer immunotherapy target.
In Enterobacteriaceae, beta-lactam antibiotic resistance involves murein recycling intermediates. Murein recycling is a complex process with discrete steps taking place in the periplasm and the ...cytoplasm. The AmpG permease is critical to this process as it transports N-acetylglucosamine anhydrous N-acetylmuramyl peptides across the inner membrane. In Pseudomonadaceae, this intrinsic mechanism remains to be elucidated. Since the mechanism involves two cellular compartments, the characterization of transporters is crucial to establish the link. Pseudomonas aeruginosa PAO1 has two ampG paralogs, PA4218 (ampP) and PA4393 (ampG). Topology analysis using beta-galactosidase and alkaline phosphatase fusions indicates ampP and ampG encode proteins which possess 10 and 14 transmembrane helices, respectively, that could potentially transport substrates. Both ampP and ampG are required for maximum expression of beta-lactamase, but complementation and kinetic experiments suggest they act independently to play different roles. Mutation of ampG affects resistance to a subset of beta-lactam antibiotics. Low-levels of beta-lactamase induction occur independently of either ampP or ampG. Both ampG and ampP are the second members of two independent two-gene operons. Analysis of the ampG and ampP operon expression using beta-galactosidase transcriptional fusions showed that in PAO1, ampG operon expression is beta-lactam and ampR-independent, while ampP operon expression is beta-lactam and ampR-dependent. beta-lactam-dependent expression of the ampP operon and independent expression of the ampG operon is also dependent upon ampP. In P. aeruginosa, beta-lactamase induction occurs in at least three ways, induction at low beta-lactam concentrations by an as yet uncharacterized pathway, at intermediate concentrations by an ampP and ampG dependent pathway, and at high concentrations where although both ampP and ampG play a role, ampG may be of greater importance. Both ampP and ampG are required for maximum induction. Similar to ampC, ampP expression is inducible in an ampR-dependent manner. Importantly, ampP expression is autoregulated and ampP also regulates expression of ampG. Both AmpG and AmpP have topologies consistent with functions in transport. Together, these data suggest that the mechanism of beta-lactam resistance of P. aeruginosa is distinct from well characterized systems in Enterobacteriaceae and involves a highly complicated interaction between these putative permeases and known Amp proteins.
Cell population density-dependent regulation of gene expression is an important determinant of bacterial pathogenesis. Staphylococci have two quorum-sensing (QS) systems. The accessory gene regulator ...(agr) is genus specific and uses a post-translationally modified peptide as an autoinducing signal. In the pathogens Staphylococcus aureus and Staphylococcus epidermidis, agr controls the expression of a series of toxins and virulence factors and the interaction with the innate immune system. However, the role of agr during infection is controversial. A possible second QS system of staphylococci, luxS, is found in a variety of Gram-positive and Gram-negative bacteria. Importantly, unlike many QS systems described in Gram-negative bacteria, agr and luxS of staphylococci reduce rather than induce biofilm formation and virulence during biofilm-associated infection. agr enhances biofilm detachment by up-regulation of the expression of detergent-like peptides, whereas luxS reduces cell-to-cell adhesion by down-regulating expression of biofilm exopolysaccharide. Significant QS activity in staphylococci is observed for actively growing cells at a high cell density, such as during the initial stages of an infection and under optimal environmental conditions. In contrast, the metabolically quiescent biofilm mode of growth appears to be characterized by an overall low activity of the staphylococcal QS systems. It remains to be shown whether QS control in staphylococci represents a promising target for the development of novel antibacterial agents.
Development of β-lactam resistance, production of alginate and modulation of virulence factor expression that alters host immune responses are the hallmarks of chronic Pseudomonas aeruginosa ...infection in cystic fibrosis patients. In this study, we propose that a co-regulatory network exists between these mechanisms. We compared the promoter activities of ampR, algT/U, lasR, lasI, rhlR, rhlI and lasA genes, representing the β-lactam antibiotic resistance master regulatory gene, the alginate switch operon, the las and rhl quorum-sensing (QS) genes, and the LasA staphylolytic protease, respectively. Four isogenic P. aeruginosa strains, the prototypic Alg(-) PAO1, Alg(-) PAOampR, the mucoid Alg(+) PAOmucA22 (Alg(+) PDO300) and Alg(+) PAOmucA22ampR (Alg(+) PDOampR) were used. We found that in the presence of AmpR regulator and β-lactam antibiotic, the extracytoplasmic function sigma factor AlgT/U positively regulated P(ampR), whereas AmpR negatively regulated P(algT/U). On the basis of this finding we suggest the presence of a negative feedback loop to limit algT/U expression. In addition, the functional AlgT/U caused a significant decrease in the expression of QS genes, whereas loss of ampR only resulted in increased P(lasI) and P(lasR) transcription. The upregulation of the las QS system is likely to be responsible for the increased lasA promoter and the LasA protease activities in Alg(-) PAOampR and Alg(+) PDOampR. The enhanced expression of virulence factors in the ampR strains correlated with a higher rate of Caenorhabditis elegans paralysis. Hence, this study shows that the loss of ampR results in increased virulence, and is indicative of the existence of a co-regulatory network between β-lactam resistance, alginate production, QS and virulence factor production, with AmpR playing a central role.
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