The proximal extension of acute type A aortic dissection is associated with ascending aortic wall degeneration.

Background: Aortic root involvement during acute type A aortic dissection (ATAAD) may depend on ascending aortic wall degeneration. Surgical decision-making for extended resection of the aortic root is clinically made without histopathology. The aim of the study was to investigate whether the degree of degeneration of the ascending aortic wall found in patients with ATAAD is associated with the aortic root involvement. Methods: Collectively, 141 consecutive patients undergoing ATAAD surgery at Tampere University Heart Hospital were investigated. The ascending aortic wall resected in surgery was processed for 11 different variables that describe medial and adventitial degeneration. In addition, atherosclerosis and inflammation were separately evaluated. Patients undergoing aortic root replacement were compared with those with supracoronary reconstruction of the ascending aorta with/without aortic valve surgery (root-sparing surgery) during a mean 4.9-year follow-up. Results: Aortic root replacement together with the ascending aortic replacement was performed in 39% of the patients (n=55). The mean age for all patients was 65 years [standard deviation (SD 13)]. Many patients with aortic root replacement had moderate to severe aortic valve regurgitation (85.5%). Most of the patients with aortic root-sparing surgery included a supracoronary tube prosthesis (89.5%), while nine patients also had aortic valve replacement. The degree of mucoid extracellular matrix accumulation was more prominent in patients with aortic root replacement compared to patients with root-sparing surgery (2.1 SD 0.4 vs. 1.9 SD 0.4, P=0.04, respectively). During follow-up, there were 52 deaths among patients (log rank P=0.79). Conclusions: Histopathology of the ascending aorta during ATAAD reveals distinctive aortic wall degeneration in patients with aortic root involvement vs. not. The degree of mucoid extracellular matrix accumulation assessed postoperatively is associated with the choice of surgical procedure in many patients.

Aortic elastic fiber degeneration during acute type a aortic dissection and reverse aortic remodeling.

BACKGROUND: Progression of proximal or distal aortic dilatation is defined as reverse aortic remodeling after surgery for acute type A aortic dissection (ATAAD) that may be dependent on aortic wall degeneration. METHODS: We investigated whether aortic wall degeneration is associated with reverse aortic remodeling leading to aortic reoperation after surgery for ATAAD. Altogether, 141 consecutive patients undergoing surgery for ATAAD at Tampere were evaluated. The resected ascending aortic wall at surgery was processed for 42 degenerative, atherosclerotic and inflammatory histological variables. Patients undergoing aortic reoperations (Redos) were compared with those without aortic reoperations (Controls) during a mean 4.9-year follow-up. RESULTS: Redos were younger than Controls (56 and 66 years, respectively, P < 0.001), and had less frequently previous cardiac surgery prior to ATAAD. Initial surgery encompassed replacement of the ascending aorta in the majority. There were 21 Redos in which one patient died during follow-up as compared with 51 deaths in Controls (log Rank P = 0.002). Histology of the aortic wall revealed increased elastic fiber fragmentation, loss, and disorganization in Redos as compared with Controls (2.1 ± 0.5 vs. 1.9 ± 0.5, Point score unit (PSU), P = 0.043 and 1.7 ± 0.8 vs. 1.2 ± 0.8, PSU, P = 0.016, respectively). Moderate atherosclerosis occurred less often in Redos vs. Controls (9.5% vs. 33%, PSU, P = 0.037, respectively). CONCLUSIONS: According to this exploratory study, histopathology reveals distinctive aortic wall degeneration during ATAAD. Reverse aortic remodeling after ATAAD is associated with the presence of ascending aortic wall elastic fiber fragmentation, loss and disorganization during ATAAD.

Oversulfated chondroitin sulfate binds to chemokines and inhibits stromal cell-derived factor-1 mediated signaling in activated T cells.

Oversulfated chondroitin sulfate (OSCS), a member of the glycosaminoglycan (GAG) family, was a contaminant in heparin that was linked to the 2008 heparin adverse events in the US. Because of its highly negative charge, OSCS can interact with many components of the contact and immune systems. We have previously demonstrated that OSCS inhibited the complement classical pathway by binding C1 inhibitor and potentiating its interaction with C1s. In the present study, by using surface plasmon resonance, we found OSCS interacts with T cell chemokines that can impact adaptive immunity. The binding of OSCS to stromal cell-derived factor-1 (SDF-1) chemokines, SDF-1α and SDF-1ß, caused a significant change in the secondary structures of these chemokines as detected by far-ultraviolet circular dichroism spectra analysis. Functionally, OSCS binding profoundly inhibited SDF-1-induced calcium mobilization and T cell chemotaxis. Imaging flow cytometry revealed T cell morphological changes mediated by SDF-1α were completely blocked by OSCS. We conclude that the OSCS, a past contaminant in heparin, has broad interactions with the components of the human immune system beyond the contact and complement systems, and that may explain, in part, prior OSCS-related adverse events, while suggesting potentially useful therapeutic applications for related GAGs in the control of inflammation.

Oversulfated chondroitin sulfate inhibits the complement classical pathway by potentiating C1 inhibitor.

Oversulfated chondroitin sulfate (OSCS) has become the subject of multidisciplinary investigation as a non-traditional contaminant in the heparin therapeutic preparations that were linked to severe adverse events. In this study, it was found that OSCS inhibited complement fixation on bacteria and bacterial lysis mediated by the complement classical pathway. The inhibition of complement by OSCS is not due to interference with antibody/antigen interaction or due to consumption of C3 associated with FXII-dependent contact system activation. However, OSCS complement inhibition is dependent on C1 inhibitor (C1inh) since the depletion of C1inh from either normal or FXII-deficient complement plasma prevents OSCS inhibition of complement activity. Surface plasmon resonance measurements revealed that immobilized C1inhibitor bound greater than 5-fold more C1s in the presence of OSCS than in presence of heparin. Although heparin can also inhibit complement, OSCS and OSCS contaminated heparin are more potent inhibitors of complement. Furthermore, polysulfated glycosaminoglycan (PSGAG), an anti-inflammatory veterinary medicine with a similar structure to OSCS, also inhibited complement in the plasma of dogs and farm animals. This study provides a new insight that in addition to the FXII-dependent activation of contact system, oversulfated and polysulfated chondroitin-sulfate can inhibit complement activity by potentiating the classical complement pathway regulator C1inh. This effect on C1inh may play a role in inhibiting inflammation as well as impacting bacterial clearance.

Complement C1 esterase inhibitor levels linked to infections and contaminated heparin-associated adverse events.

Activation of kinin-kallikrein and complement pathways by oversulfated-chondroitin-sulfate (OSCS) has been linked with recent heparin-associated adverse clinical events. Given the fact that the majority of patients who received contaminated heparin did not experience an adverse event, it is of particular importance to determine the circumstances that increase the risk of a clinical reaction. In this study, we demonstrated by both the addition and affinity depletion of C1inh from normal human plasma, that the level of C1inh in the plasma has a great impact on the OSCS-induced kallikrein activity and its kinetics. OSCS-induced kallikrein activity was dramatically increased after C1inh was depleted, while the addition of C1inh completely attenuated kallikrein activity. In addition, actual clinical infection can lead to increased C1inh levels. Plasma from patients with sepsis had higher average levels of functional C1inh and decreased OSCS-induced kallikrein activity. Lastly, descriptive data on adverse event reports suggest cases likely to be associated with contaminated heparin are inversely correlated with infection. Our data suggest that low C1inh levels can be a risk factor and high levels can be protective. The identification of risk factors for contact system-mediated adverse events may allow for patient screening and clinical development of prophylaxis and treatments.

Anthrax lethal toxin has direct and potent inhibitory effects on B cell proliferation and immunoglobulin production.

Protective host immune responses to anthrax infection in humans and animal models are characterized by the development of neutralizing Abs against the receptor-binding anthrax protective Ag (PA), which, together with the lethal factor (LF) protease, composes anthrax lethal toxin (LT). We now report that B cells, in turn, are targets for LT. Anthrax PA directly binds primary B cells, resulting in the LF-dependent cleavage of the MAPK kinases (MAPKKs) and disrupted signaling to downstream MAPK targets. Although not directly lethal to B cells, anthrax LT treatment causes severe B cell dysfunction, greatly reducing proliferative responses to IL-4-, anti-IgM-, and/or anti-CD40 stimulation. Moreover, B cells treated with anthrax LT in vitro or isolated from mice treated with anthrax LT in vivo have a markedly diminished capacity to proliferate and produce IgM in response to TLR-2 and TLR-4 ligands. The suppressive effects of anthrax LT on B cell function occur at picomolar concentrations in vitro and at sublethal doses in vivo. These results indicate that anthrax LT directly inhibits the function of B cells in vitro and in vivo, revealing a potential mechanism through which the pathogen could bypass protective immune responses.

Peptide immunization excludes antigen-specific T cells from splenic lymphoid compartments.

Using adoptive transfer of TCR-transgenic T cells, we examined the homing of transgenic T cells to splenic compartments in situ. After systemic immunization with peptide or protein antigen, the location of clonotypic T cells, cytokine production, cell surface markers, and apoptosis were assessed. There were distinct differences in the splenic homing of CD4(+) TCR-transgenic T cells in mice immunized with peptide as compared to mice immunized with whole-protein antigen. T cells in peptide-immunized mice were found almost exclusively in the splenic red pulp, but not in the T and B cell zones (white pulp), while the majority of T cells immunized with whole protein were found in the white pulp. Many more Fas ligand-expressing and apoptotic cells were present after peptide immunization than after whole-protein immunization. Localization of IL-4-, IL-2- and IFN-gamma-producing cells to the lymphocyte-containing splenic white pulp was only observed with whole-protein immunization. The unique homing and increased apoptosis of immune cells post peptide immunization may help explain the ineffectiveness of many peptide vaccines. Linkage of the same peptide epitope to a carrier protein increased white pulp T cell localization and decreased apoptosis, suggesting a strategy to enhance peptide vaccine responses.

Organ-specific cytokine polarization induced by adoptive transfer of transgenic T cells.

There are two distinct phenotypes of T cell cytokine responses that lead to different effector functions and different outcomes in disease processes. Although evidence suggests a possible role of the local microenvironment in the differentiation or localization of T cells with these phenotypes, there are no examples of divergent T cell cytokine phenotypes with the same Ag specificity concurrently existing in different tissue compartments. Using a CD8(+) T cell adoptive transfer model for graft-vs-host disease, we demonstrate that a potent type 2 cytokine response develops in the spleen while a potent type 1 cytokine response simultaneously develops in the testis. These experiments demonstrate for the first time that cytokine production can be oppositely polarized in different organs of the same individual. This may have important implications for organ-specific pathology in infection or autoimmunity: infections or autoimmune diseases that affect multiple organs may have heterogeneity in tissue cytokine responses that is not revealed in systemic lymphocyte cytokine responses. Therefore, attempts to modulate the immune response phenotype may ameliorate pathology in one organ while exacerbating pathology in another.

CD43 polarization in unprimed T cells can be dissociated from raft coalescence by inhibition of HMG CoA reductase.

Movement of T-lymphocyte cell surface CD43 is associated with both antigen activation of T-cell clones and chemokine induction of T-lymphocyte motility. Here, we demonstrate that CD43 movement away from the site of T-cell receptor ligation occurs in unprimed CD4(+) T cells as well as T-cell clones. The T-cell receptor (TCR)-dependent movement of CD43 in unprimed T cells is associated with a polarized morphology and CD43 accumulation at the uropods of the cells, unlike that reported for primed T cells. The polarization of CD43 has a requirement for Src kinases and occurs in conjunction with lipid raft coalescence. Thymocytes and T-cell hybridomas, cells that have altered responses to TCR activation and lack lipid raft coalescence, do not polarize CD43 as readily as unprimed T cells. The movement of CD43 depends on the cholesterol biosynthetic pathway enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. Blockade of this enzyme can specifically prevent CD43 redistribution without affecting cell shape polarization. The likely mechanism of this alteration in CD43 redistribution is through decreased protein prenylation because the cholesterol-dependent lipid rafts still coalesce on activation. These findings suggest that the polarization of cell shape, lipid raft coalescence, and CD43 redistribution on T-cell activation have signaling pathway distinctions. Dissecting out the relationships between various stages of molecular redistribution and lymphocyte activation may facilitate fine-tuning of immunologic responses.

A dominant negative mutant beta 2-microglobulin blocks the extracellular folding of a major histocompatibility complex class I heavy chain.

The major histocompatibility complex class I (MHC1) molecule plays a crucial role in cytotoxic lymphocyte function. beta 2-Microglobulin (beta 2m) has been demonstrated to be both a structural component of the MHC1 complex and a chaperone-like molecule for MHC1 folding. beta 2m binding to an isolated alpha 3 domain of MHC1 heavy chain at micromolar concentrations has been shown to accurately model the biochemistry and thermodynamics of beta 2m-driven MHC1 folding. These results suggested a model in which the chaperone-like role of beta 2m is dependent on initial binding to the alpha 3 domain interface of MHC1 with beta 2m. Such a model predicts that a mutant beta 2m molecule with an intact MHC1 alpha 3 domain interaction but a defective MHC1 alpha 1 alpha 2 domain interaction would block beta2m-driven folding of MHC1. In this study we generated such a beta 2m mutant and demonstrated that it blocks MHC1 folding by normal beta 2m at the expected micromolar concentrations. Our data support an initial interaction of beta 2m with the MHC1 alpha 3 domain in MHC1 folding. In addition, the dominant negative mutant beta 2m can block T-cell functional responses to antigenic peptide and MHC1.