STING Agonist Mitigates Experimental Autoimmune Encephalomyelitis by Stimulating Type I IFN-Dependent and -Independent Immune-Regulatory Pathways

The cGAS-cyclic GMP-AMP (cGAMP)-stimulator of IFN genes (STING) pathway induces a powerful type I IFN (IFN-I) response and is a prime candidate for augmenting immunity in cancer immunotherapy and vaccines. IFN-I also has immune-regulatory functions manifested in several autoimmune diseases and is a first-line therapy for relapsing-remitting multiple sclerosis. However, it is only moderately effective and can induce adverse effects and neutralizing Abs in recipients. Targeting cGAMP in autoimmunity is unexplored and represents a challenge because of the intracellular location of its receptor, STING. We used microparticle (MP)-encapsulated cGAMP to increase cellular delivery, achieve dose sparing, and reduce potential toxicity. In the C57BL/6 experimental allergic encephalomyelitis (EAE) model, cGAMP encapsulated in MPs (cGAMP MPs) administered therapeutically protected mice from EAE in a STING-dependent fashion, whereas soluble cGAMP was ineffective. Protection was also observed in a relapsing-remitting model. Importantly, cGAMP MPs protected against EAE at the peak of disease and were more effective than rIFN-β. Mechanistically, cGAMP MPs showed both IFN-I-dependent and -independent immunosuppressive effects. Furthermore, it induced the immunosuppressive cytokine IL-27 without requiring IFN-I. This augmented IL-10 expression through activated ERK and CREB. IL-27 and subsequent IL-10 were the most important cytokines to mitigate autoreactivity. Critically, cGAMP MPs promoted IFN-I as well as the immunoregulatory cytokines IL-27 and IL-10 in PBMCs from relapsing-remitting multiple sclerosis patients. Collectively, this study reveals a previously unappreciated immune-regulatory effect of cGAMP that can be harnessed to restrain T cell autoreactivity.

Multi-omics analyses of radiation survivors identify radioprotective microbes and metabolites

Ionizing radiation causes acute radiation syndrome, which leads to hematopoietic, gastrointestinal, and cerebrovascular injuries. We investigated a population of mice that recovered from high-dose radiation to live normal life spans. These "elite-survivors" harbored distinct gut microbiota that developed after radiation and protected against radiation-induced damage and death in both germ-free and conventionally housed recipients. Elevated abundances of members of the bacterial taxa Lachnospiraceae and Enterococcaceae were associated with postradiation restoration of hematopoiesis and gastrointestinal repair. These bacteria were also found to be more abundant in leukemia patients undergoing radiotherapy, who also displayed milder gastrointestinal dysfunction. In our study in mice, metabolomics revealed increased fecal concentrations of microbially derived propionate and tryptophan metabolites in elite-survivors. The administration of these metabolites caused long-term radioprotection, mitigation of hematopoietic and gastrointestinal syndromes, and a reduction in proinflammatory responses.

TRAF3IP3 negatively regulates cytosolic RNA induced anti-viral signaling by promoting TBK1 K48 ubiquitination

Innate immunity to nucleic acids forms the backbone for anti-viral immunity and several inflammatory diseases. Upon sensing cytosolic viral RNA, retinoic acid-inducible gene-I-like receptors (RLRs) interact with the mitochondrial antiviral signaling protein (MAVS) and activate TANK-binding kinase 1 (TBK1) to induce type I interferon (IFN-I). TRAF3-interacting protein 3 (TRAF3IP3, T3JAM) is essential for T and B cell development. It is also well-expressed by myeloid cells, where its role is unknown. Here we report that TRAF3IP3 suppresses cytosolic poly(I:C), 5'ppp-dsRNA, and vesicular stomatitis virus (VSV) triggers IFN-I expression in overexpression systems and Traf3ip3-/- primary myeloid cells. The mechanism of action is through the interaction of TRAF3IP3 with endogenous TRAF3 and TBK1. This leads to the degradative K48 ubiquitination of TBK1 via its K372 residue in a DTX4-dependent fashion. Mice with myeloid-specific gene deletion of Traf3ip3 have increased RNA virus-triggered IFN-I production and reduced susceptibility to virus. These results identify a function of TRAF3IP3 in the regulation of the host response to cytosolic viral RNA in myeloid cells.

Platelet-activating factor (PAF) mediates NLRP3-NEK7 inflammasome induction independently of PAFR

Platelet-activating factor (PAF) can drive pathophysiological inflammation, but the mechanism remains incompletely understood. Here, Deng et al. report that PAF activates the canonical NLRP3 inflammasome independently of its receptor PAFR.

The role of lipids in inflammasome activation remains underappreciated. The phospholipid, platelet-activating factor (PAF), exerts multiple physiological functions by binding to a G protein–coupled seven-transmembrane receptor (PAFR). PAF is associated with a number of inflammatory disorders, yet the molecular mechanism underlying its proinflammatory function remains to be fully elucidated. We show that multiple PAF isoforms and PAF-like lipids can activate the inflammasome, resulting in IL-1β and IL-18 maturation. This is dependent on NLRP3, ASC, caspase-1, and NEK7, but not on NLRC4, NLRP1, NLRP6, AIM2, caspase-11, or GSDMD. Inflammasome activation by PAF also requires potassium efflux and calcium influx but not lysosomal cathepsin or mitochondrial reactive oxygen species. PAF exacerbates peritonitis partly through inflammasome activation, but PAFR is dispensable for PAF-induced inflammasome activation in vivo or in vitro. These findings reveal that PAF represents a damage-associated signal that activates the canonical inflammasome independently of PAFR and provides an explanation for the ineffectiveness of PAFR antagonist in blocking PAF-mediated inflammation in the clinic.

Viral DNA Binding to NLRC3, an Inhibitory Nucleic Acid Sensor, Unleashes STING, a Cyclic Dinucleotide Receptor that Activates Type I Interferon

Immune suppression is a crucial component of immunoregulation and a subgroup of nucleotide-binding domain (NBD), leucine-rich repeat (LRR)-containing proteins (NLRs) attenuate innate immunity. How this inhibitory function is controlled is unknown. A key question is whether microbial ligands can regulate this inhibition. NLRC3 is a negative regulator that attenuates type I interferon (IFN-I) response by sequestering and attenuating stimulator of interferon genes (STING) activation. Here, we report that NLRC3 binds viral DNA and other nucleic acids through its LRR domain. DNA binding to NLRC3 increases its ATPase activity, and ATP-binding by NLRC3 diminishes its interaction with STING, thus licensing an IFN-I response. This work uncovers a mechanism wherein viral nucleic acid binding releases an inhibitory innate receptor from its target.

TRAF3IP3 negatively regulates type I interferon signaling by suppressing TBK1

Type I interferon (IFN) signaling is important for antiviral and autoimmune response, and it is subjected to tight control, however molecular mechanisms to tune down these pathways is incompletely understood. Upon sensing cytosolic viral RNA, retinoic acid-induced gene I (RIG-I) and melanoma-differentiation-associated gene 5 (MDA5) interact with mitochondrial antiviral signaling protein (MAVS) and activate TANK binding kinase 1 (TBK1) to induce IFNs. A golgi-associated factor, TRAF3-interacting protein 3 (TRAF3IP3), has been found to be crucial for thymocyte development and T regulatory cell functions. However its role in myeloid cells has not been explored. We find that the overexpression of TRAF3IP3 suppressed cytosolic poly(I:C), 5’ ppp-dsRNA, and vesicular stomatitis virus (VSV) triggered IFN production, whereas deficiency of Traf3ip3 potentiated viral RNA triggered IFN production. In support of the in vitro data, Traf3ip3-deficient mice were infected with VSV and found to exhibit enhanced susceptibility to VSV challenge. Mechanistically, TRAF3IP3 interacted with TBK1 and targeted TBK1 for ubiquitination and degradation. These results uncovered a previously unrecognized role of TRAF3IP3 in the regulation of RNA induced IFN pathway.

Transthoracic Echocardiography: Impact on Diagnosis and Management in Tertiary Care Intensive Care Units

The purpose of this study was to evaluate the utility of transthoracic echocardiography (TTE) in an intensive care unit by determining its impact on diagnosis and management. Over a six-month time period, we performed a prospective observational study on all patients admitted to either the medical or the surgical intensive care unit. Structured interviews were conducted with referring physicians before and after the TTE to determine the referring physicians’ pre-TTE diagnosis, reasons for requesting the TTE, and whether the TTE resulted in a change in diagnosis and/or management. A total of 135 TTE examinations were done in 126 patients. The referring physicians deemed that clinical information was inadequate to make a definitive diagnosis and management plan in 36/135 (27%) of the requests. In 99/135 (73%) studies, physicians indicated that there was probably sufficient clinical information to formulate a diagnosis and management plan, but ordered a TTE to corroborate their clinical findings. Overall, a change in diagnosis occurred in 39/135 (29%) of studies, and a change in management in 55/135 (41%) of studies. Diagnosis was changed in 19/99 (19%) studies with adequate clinical data, and in 20/36 (56%) studies with inadequate clinical data (P<0.001). Management was changed in 34/99 (34%) of studies with adequate clinical data and in 21/36 (58%) of studies with inadequate clinical data (P=0.017). Of the 62 management changes, 57/62 (92%) changes were minor, and 5/62 (8%) were major. In conclusion we have found that TTE frequently resulted in a change in the diagnosis and management.

The Inhibitory Innate Immune Sensor NLRP12 Maintains a Threshold against Obesity by Regulating Gut Microbiota Homeostasis

In addition to high-fat diet (HFD) and inactivity, inflammation and microbiota composition contribute to obesity. Inhibitory immune receptors, such as NLRP12, dampen inflammation and are important for resolving inflammation, but their role in obesity is unknown. We show that obesity in humans correlates with reduced expression of adipose tissue NLRP12. Similarly, Nlrp12-/- mice show increased weight gain, adipose deposition, blood glucose, NF-κB/MAPK activation, and M1-macrophage polarization. Additionally, NLRP12 is required to mitigate HFD-induced inflammasome activation. Co-housing with wild-type animals, antibiotic treatment, or germ-free condition was sufficient to restrain inflammation, obesity, and insulin tolerance in Nlrp12-/- mice, implicating the microbiota. HFD-fed Nlrp12-/- mice display dysbiosis marked by increased obesity-associated Erysipelotrichaceae, but reduced Lachnospiraceae family and the associated enzymes required for short-chain fatty acid (SCFA) synthesis. Lachnospiraceae or SCFA administration attenuates obesity, inflammation, and dysbiosis. These findings reveal that Nlrp12 reduces HFD-induced obesity by maintaining beneficial microbiota.

Platelet activating factor as a novel danger signal for activation of NLRP3 inflammasome

Platelet activating factor (PAF) is a biologically active phospholipid that promotes pathophysiological inflammation through binding to a unique G-protein-coupled seven transmembrane receptor (PAFR). Increased PAF level has been correlated with a number of inflammatory disorders, yet the molecular mechanism underlying the pro-inflammatory function of PAF remains incompletely elucidated. Here we showed PAF activates canonical NLRP3 inflammasome, resulting in ASC oligomerization, caspase-1 processing, and IL-1β and IL-18 maturation. PAF-induced IL-1β maturation is abrogated in macrophage from Nlrp3−/−, Asc−/−, Caspase-1−/− mice, but not Nlrc4−/−, Nlrp1−/−, Aim2−/−, Caspase-11−/− mice. In addition, NEK7, a new component of the NLRP3 inflammasome, is also essential for PAF induced IL-1β maturation. PAF activation of the NLRP3 inflammasome is dependent on calcium influx, potassium efflux, but independent of lysosome cathepsin, mitochondrial reactive oxygen species (ROS), and necroptosis. Surprisingly, PAFR is not essential for PAF induced NLRP3 inflammasome activation. Physiologically, PAF induced shock is protected in NLRP3 inflammasome component deficient mice. Together, our findings reveal a new PAFR independent pathway for detecting PAF which represents an unprecedented danger signaling function of PAF, and provide new insight for understanding the pathogenesis of PAF-mediated inflammatory disorders.

CCR2+ Inflammatory Dendritic Cells and Translocation of Antigen by Type III Secretion Are Required for the Exceptionally Large CD8+ T Cell Response to the Protective YopE69-77 Epitope during Yersinia Infection

During Yersinia pseudotuberculosis infection of C57BL/6 mice, an exceptionally large CD8⁺ T cell response to a protective epitope in the type III secretion system effector YopE is produced. At the peak of the response, up to 50% of splenic CD8⁺ T cells recognize the epitope YopE_69-77. The features of the interaction between pathogen and host that result in this large CD8⁺ T cell response are unknown. Here, we used Y. pseudotuberculosis strains defective for production, secretion and/or translocation of YopE to infect wild-type or mutant mice deficient in specific dendritic cells (DCs). Bacterial colonization of organs and translocation of YopE into spleen cells was measured, and flow cytometry and tetramer staining were used to characterize the cellular immune response. We show that the splenic YopE_69-77-specific CD8⁺ T cells generated during the large response are polyclonal and are produced by a “translocation-dependent” pathway that requires injection of YopE into host cell cytosol. Additionally, a smaller YopE_69-77-specific CD8⁺ T cell response (~10% of the large expansion) can be generated in a “translocation-independent” pathway in which CD8α⁺ DCs cross present secreted YopE. CCR2-expressing inflammatory DCs were required for the large YopE_69-77-specific CD8⁺ T cell expansion because this response was significantly reduced in Ccr2^-/- mice, YopE was translocated into inflammatory DCs in vivo, inflammatory DCs purified from infected spleens activated YopE_69-77-specific CD8⁺ T cells ex vivo and promoted the expansion of YopE_69-77-specific CD8⁺ T cells in infected Ccr2^-/- mice after adoptive transfer. A requirement for inflammatory DCs in producing a protective CD8⁺ T cell response to a bacterial antigen has not previously been demonstrated. Therefore, the production of YopE_69-77-specific CD8⁺ T cells by inflammatory DCs that are injected with YopE during Y. pseudotuberculosis infection represents a novel mechanism for generating a massive and protective adaptive immune response.

Dendritic cells (DCs) direct host protective adaptive immune responses during infection. How different subpopulations of DCs contribute to the formation of antigen-specific CD8⁺ T cells is incompletely understood. Infection of C57BL/6 mice with the bacterial pathogen Yersinia pseudotuberculosis results in the production of an exceptionally large CD8⁺ T cell response to an epitope in the type III secretion system effector YopE. Here, we show that this large CD8⁺ T cell response requires translocation of YopE into inflammatory DCs, which express CCR2 and accumulate in infected tissues. In contrast, when mice are infected with a Y. pseudotuberculosis strain that can secrete but not translocate YopE, a smaller response is seen, and under these conditions the generation of YopE-specific CD8⁺ T cell requires CD8α⁺ DCs. Our results indicate that distinct DC subsets participate in constructing the CD8⁺ T cell response to secreted, versus translocated, YopE. Furthermore our data indicate that inflammatory DCs are a driving force behind the massive CD8⁺ T cell response to a protective epitope in a bacterial virulence factor that is translocated into host cells.

Persistent salmonellosis causes pancreatitis in a murine model of infection

Pancreatitis, a known risk factor for the development of pancreatic ductal adenocarcinoma, is a serious, widespread medical condition usually caused by alcohol abuse or gallstone-mediated ductal obstruction. However, many cases of pancreatitis are of an unknown etiology. Pancreatitis has been linked to bacterial infection, but causality has yet to be established. Here, we found that persistent infection of mice with the bacterial pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) was sufficient to induce pancreatitis reminiscent of the human disease. Specifically, we found that pancreatitis induced by persistent S. Typhimurium infection was characterized by a loss of pancreatic acinar cells, acinar-to-ductal metaplasia, fibrosis and accumulation of inflammatory cells, including CD11b+ F4/80+, CD11b+ Ly6Cint Ly6G+ and CD11b+ Ly6Chi Ly6G- cells. Furthermore, we found that S. Typhimurium colonized and persisted in the pancreas, associated with pancreatic acinar cells in vivo, and could invade cultured pancreatic acinar cells in vitro. Thus, persistent infection of mice with S. Typhimurium may serve as a useful model for the study of pancreatitis as it relates to bacterial infection. Increased knowledge of how pathogenic bacteria can cause pancreatitis will provide a more integrated picture of the etiology of the disease and could lead to the development of new therapeutic approaches for treatment and prevention of pancreatitis and pancreatic ductal adenocarcinoma.

[Antigen analysis of Trichomonas vaginalis trophozoite by SDS-PAGE and two-dimensional gel electrophoresis]

OBJECTIVE

To analyze soluble antigens of Trichomonas vaginalis.

METHODS

Soluble antigens of the parasite from a patient suffering from trichomonad vaginitis were analyzed by SDS-PAGE, immunoblotting and two-dimensional gel electrophoresis.

RESULTS

A total of 26 distinct protein bands were demonstrated by using 10% resolution gel. Nine of them were main bands, eight with MWs 15-62 kDa, one with MW 97 kDa. By immunoblotting the specific anti-T. vaginalis antibodies raised in rabbit recognized 24 protein bands with 8 main bands in them. Two-dimensional gel electrophoresis revealed up to 43 individual trichomonad polypeptide spots, among which, 9 were main ones. The pI and MWs of these spots were 3.65-5.84 and 27-->100 kDa respectively.

CONCLUSION

Eight protein bands out of 26 soluble antigen bands of the parasite showed high immunogenicity. There were 9 main polypeptide spots in 43 polypeptide spots of the parasite.

Effects of Matrine on proliferation and differentiation in K-562 cells

We investigated the effects of Matrine on proliferation by trypan blue exclusion and differentiation by benzidine staining positive cells in K-562 cells, assayed the telomerase activity using PCR-ELISA assay, analyzed cell cycle by fluorescence-activated cell sorter analysis of the DNA content, and also determined the gene expression level of c-myc, N-ras and p53 by northern blot and dot blot analysis. The results showed that with the addition of 0.1 mg/ml Matrine, cell growth was inhibited significantly by 4 days, benizidine-positive cells rose from 1% to 2% in control cells to 15% in treated cells on day 5; treatment of K-562 cells with 0.1 mg/ml Matrine for 5 days resulted in a marked inhibition in telomerase activity, in a manner that correlated with the extent of differentiation; after exposure to Matrine for 72 h, 64.6% cells were arrested in the G1-phase of the cell cycle, the fraction of cells in S-phase had decreased from 56.9% in control cells to 24.4% in differentiated cells, and the levels of N-ras and p53 mRNA were remarkably increased for 24 and 48 h, respectively, c-myc mRNA expression level declined for 24 h and was inhibited significantly for 48 h. Our study confirmed that Matrine plays a significant effect on the inhibition of proliferation cells and inducing differentiation in K-562 cells.

Prospective multicenter study of pregnancy outcomes in women with heart disease

BACKGROUND

The maternal and neonatal risks associated with pregnancy in women with heart disease receiving comprehensive prenatal care have not been well defined.

METHODS AND RESULTS

We prospectively enrolled 562 consecutive pregnant women with heart disease and determined the outcomes of 599 pregnancies not ending in miscarriage. Pulmonary edema, arrhythmia, stroke, or cardiac death complicated 13% of pregnancies. Prior cardiac events or arrhythmia, poor functional class or cyanosis, left heart obstruction, and left ventricular systolic dysfunction independently predicted maternal cardiac complications; the cardiac event rate can be predicted using a risk index incorporating these predictors. Neonatal complications (20% of pregnancies) were associated with poor functional class or cyanosis, left heart obstruction, anticoagulation, smoking, and multiple gestations.

CONCLUSIONS

Pregnancy in women with heart disease is associated with significant cardiac and neonatal complications, despite state-of-the-art obstetric and cardiac care. Maternal cardiac risk can be predicted with the use of a risk index.

Tissue Doppler imaging consistently detects myocardial abnormalities in patients with hypertrophic cardiomyopathy and provides a novel means for an early diagnosis before and independently of hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH), the clinical hallmark of familial hypertrophic cardiomyopathy (FHCM), is absent in a significant number of subjects with causal mutations. In transgenic rabbits that fully recapitulate the FHCM phenotype, reduced myocardial tissue Doppler (TD) velocities accurately identified the mutant rabbits, even in the absence of LVH. We tested whether humans with FHCM also consistently showed reduced myocardial TD velocities, irrespective of LVH.

METHODS AND RESULTS

We performed 2D and Doppler echocardiography and TD imaging in 30 subjects with FHCM, 13 subjects who were positive for various mutations but did not have LVH, and 30 age- and sex-matched controls (all adults; 77% women). LV wall thickness and mass were significantly greater in FHCM subjects (P<0.01 versus those without LVH and controls). There were no significant differences in 2D echocardiographic, mitral, and pulmonary venous flow indices between mutation-positives without LVH and controls. In contrast, systolic and early diastolic TD velocities were significantly lower in both mutation-positives without LVH and in FHCM patients than in controls (P<0.001). Reduced TD velocities had a sensitivity of 100% and a specificity of 93% for identifying mutation-positives without LVH.

CONCLUSIONS

Myocardial contraction and relaxation velocities, detected by TD imaging, are reduced in FHCM, including in those without LVH. Before and independently of LVH, TD imaging is an accurate and sensitive method for identifying subjects who are positive for FHCM mutations.

Aortic valve area discrepancy by Gorlin equation and Doppler echocardiography continuity equation: relationship to flow in patients with valvular aortic stenosis

BACKGROUND

In vitro studies have shown a discrepancy between aortic valve area (AVA) measurements derived invasively by Gorlin equation (Gorlin AVA) and noninvasively by Doppler echocardiography (Doppler-echo) continuity equation (Doppler AVA) during low flow states.

OBJECTIVE

To assess whether a flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting in patients with isolated valvular aortic stenosis.

PATIENTS AND METHODS

Seventy-five consecutive patients with isolated valvular aortic stenosis, who had AVA determined both invasively by Gorlin equation and noninvasively by Doppler-echo continuity equation, were retrospectively reviewed.

RESULTS

Gorlin AVA and Doppler AVA correlated (r=0.68) over the narrow AVA range (Gorlin AVA 0.30 to 1.22 cm2); however, Doppler AVA was systematically larger than Gorlin AVA (0.80+/-0.21 versus 0.70+/-0.23 cm2, AVA difference = 0.10+/-0.17 cm2, P<0.0001). The AVA difference was inversely related to invasive cardiac index (r=-0.51) and was significantly greater at low flow states (cardiac index less than 2.5 L/min/m2) than at normal flow states (cardiac index 2.5 L/min/m2 or more) (0.16+/-0.15 versus -0.03+/-0.15 cm2, P<0.0001). Independent predictors of the AVA difference were the difference between Doppler-echo and invasive cardiac output (P<0.0001); the difference between Doppler-echo and invasive mean transvalvular pressure gradient (P=0.0002); and the average cardiac output (Doppler-echo plus invasive cardiac output/2, P=0.001) at the time of the hemodynamic assessments. The AVA difference was not related to average pressure gradient, average AVA or patient characteristics.

CONCLUSIONS

A flow-related discrepancy between Gorlin AVA and Doppler AVA occurs in the clinical setting of patients with isolated valvular aortic stenosis. This discrepancy should be considered when assessing aortic stenosis severity during low flow states, where Gorlin AVA may be significantly smaller than Doppler AVA.

Accelerated wound healing in mice with a disruption of the thrombospondin 2 gene

Mice that lack the extracellular matrix protein thrombospondin 2 have, among several abnormalities, an increase in vascular density, abnormal collagen fibrils, and dermal fibroblasts that are defective in adhesion. These findings suggested that responses involving these processes, such as wound healing, might be altered. To investigate the healing process, excisional wounds were made with the aid of a biopsy punch. Such wounds, observed over a 14 d period, appeared to heal at an accelerated rate and with less scarring in thrombospondin 2-null mice. Histologic analysis of thrombospondin 2-null wound sites revealed the presence of an irregularly organized and highly vascularized granulation tissue. In addition, thrombospondin 2-null wounds retained a higher total cellular content, than control wounds. No differences in wound re-epithelization rates were observed, but thrombospondin 2-null epithelia formed rete pegs and were thicker than control epithelia. By immunohistochemistry, we detected elevated levels and an irregular deposition pattern for fibronectin in thrombospondin 2-null wounds, observations that correlated with the abnormal collagen organization in the granulation tissue. Immunostaining for thrombospondin 2 in control wounds showed that the protein is present in both early and late wounds, in a scattered cell-associated pattern or widely distributed cell- and matrix-associated pattern, respectively. Our results suggest that thrombospondin 2 plays a crucial part in the organization and vascularization of the granulation tissue during healing, possibly by modulating fibroblast-matrix interactions in early wounds and regulating the extent of angiogenesis in late wounds.

A prospective transesophageal echocardiographic study to assess a new type of left atrial spontaneous contrast at rest and during respiratory manoeuvres

BACKGROUND

Recent observations suggest that a spontaneous echocardiographic contrast with fast motion (FEC) mimicking intravenous contrast can be seen in the left atrium in the absence of intravenous contrast injection.

OBJECTIVE

To assess the incidence of FEC and to evaluate the differentiating features between FEC and injected saline contrast.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary referral centre.

PATIENTS AND METHODS

Transesophageal echocardiography was performed in 91 consecutive patients with a mean age of 58+/-15 years. Patients with mechanical valves and congenital heart disease were excluded. Images of the right atrium, left atrium and pulmonary veins were obtained in the absence of an intravenous catheter during quiet respiration, cough and the Valsalva manoeuvre. The same procedure was repeated during injection with agitated saline after venous cannulation.

RESULTS

In the absence of intravenous cannulation, FEC was detected in eight patients (9%) during quiet respiration, 36 patients (40%) during cough and 55 patients (60%) during the Valsalva manoeuvre. During the Valsalva manoeuvre, FEC was detected in the right atrium in 41 patients (45%) and in the left atrium in 33 patients (36%) (P=0.15). FEC was not related to a history of embolic event, left atrial smoke or patent foramen ovale. Intra- and interobserver agreements in the detection of FEC were 96% and 90%, respectively.

CONCLUSIONS

FEC can be observed frequently in the left atrium during cough or the Valsalva manoeuvre, and awareness of FEC is important to avoid the erroneous diagnosis of patent foramen ovale.

What is the real clinical utility of echocardiography? A prospective observational study

This was a prospective, structured interview to evaluate physician expectations of echocardiography and the subsequent impact on patient care. The setting involved requests for echocardiograms in patients admitted to a tertiary care teaching hospital. Measurements included assessment of the diagnostic and therapeutic implications of echocardiography perceived by the physicians and subsequently reported and confirmed by blinded chart review. From January to May 1997, 542 echocardiograms were performed on 500 inpatients (age 62 +/- 17 years; 56% men). Referring physicians were mainly house staff (83%) and from medical services. The main indications were evaluation of left ventricular function (54%) or valve function (16%). At the time of the request, 89% of physicians believed that echocardiography was needed to guide future investigations or treatment, although in 24% of cases, physicians could not provide details of such. A reported change in treatment occurred in 57% and was validated by chart review in 38%. Changes occurred more frequently in patients in the intensive care unit versus those not in the intensive care unit (54% vs 37%, P =.02) but were similar between attending physicians and house staff (frequency of change 41% vs 39%, P = not significant) and between those with and those without previous echocardiograms (38% vs 39%, P = not significant). The utility of the echocardiogram to influence treatment decisions in hospitalized patients is high, especially in critically ill patients. However, this impact is less than is anticipated at the time of the initial request. Further studies involving more select populations of patients are required.

Long-term benzodiazepine users--characteristics, views and effectiveness of benzodiazepine reduction information leaflet

OBJECTIVE

The authors looked at the clinical characteristics of long-term benzodiazepine users and how they viewed their use of benzodiazepine. We also examined the effectiveness of a self-help leaflet on reducing benzodiazepine use.

METHOD

One hundred and nine long-term benzodiazepine users (daily use for more than 1 year) were assessed. Their perceived beneficial and undesirable effects of benzodiazepine and intention to reduce benzodiazepine use were studied and their history of benzodiazepine use was obtained. Psychiatric diagnosis and medical history were reviewed. A self-help leaflet was provided to 56 users whose anxiety symptoms were assessed to have been under control. We re-examined these 56 users 3 months later on their use of benzodiazepine and anxiety levels.

RESULTS

The 109 long-term benzodiazepine users used a therapeutic dose of benzodiazepine (median: 10 mg diazepam equivalent) regularly for a median of 9 years (range: 1-40). Most of the users found benzodiazepine helpful and only 11% of them reported undesirable side effects. Half of the 109 subjects refused to reduce the dosage. Most of the subjects still experienced significant anxiety despite the use of benzodiazepine. Fourteen of the 56 subjects provided with a self-help leaflet were able to reduce a median of 2.5 mg of diazepam equivalent when re-examined after 3 months.

CONCLUSION

The results are compared with previous studies in Western societies and are discussed in the light of clinical management of patients with anxiety disorders.

Low dose dobutamine echocardiography in the assessment of contractile reserve to predict the outcome of valve replacement for chronic aortic regurgitation

BACKGROUND

When to perform surgery for aortic regurgitation is a difficult clinical decision. Occult left ventricular (LV) dysfunction may be present in patients with minimal or no symptoms, and in some patients LV dysfunction may persist after valvular replacement.

OBJECTIVES

To examine the role of preoperative low dose dobutamine echocardiography (LDDE) in predicting postoperative outcome in patients who had aortic valve replacement for aortic regurgitation.

PATIENTS AND METHODS

The study group comprised 16 patients (15 men, aged 48 +/- 15 years) undergoing elective surgery for aortic regurgitation. Preoperative echocardiograms were obtained in the resting state and during dobutamine infusion at 7.5 micrograms/kg/min. Complete recovery was defined by normalization of LV size and function, and the absence of symptoms at the six-month follow-up visit. Patients with complete recovery (group 1) and without complete recovery (group 2) were compared in relation to their echocardiographic parameters at rest and during LDDE.

RESULTS

Of 16 patients in the study, nine were in group 1 and seven were in group 2. Age, functional class and LV end-diastolic dimensions were similar between the two groups. Group 1 patients had a smaller preoperative LV end-systolic dimension index (22.4 +/- 3.3 versus 29.9 +/- 5.9 mm/m2, P < 0.05) and a higher preoperative ejection fraction (53 +/- 8% versus 37 +/- 13%, P < 0.01). Dobutamine infusion augmented the difference in ventricular size and function between patients in group 1 and those in group 2 (LV end-systolic dimension index 18.9 +/- 3.9 mm/m2 versus 28.8 +/- 7.1 mm/m2, P < 0.01; ejection fraction 61 +/- 7% versus 41 +/- 12%, P < 0.01).

CONCLUSIONS

Dobutamine accentuates differences in ventricular size and function between those with and without subsequent complete recovery following valve surgery. Because preoperative ejection fraction during LDDE is highly predictive of postoperative ejection fraction, LDDE may have a role in predicting the clinical outcome of patients following aortic valve replacement for aortic regurgitation.

Management of patients with mild aortic stenosis undergoing coronary artery bypass grafting

BACKGROUND

The management of mild aortic stenosis during coronary artery bypass grafting remains controversial.

METHODS

We reviewed the medical records of consecutive patients between January 1, 1977, and December 31, 1994, to identify 51 patients with mild aortic stenosis who underwent isolated coronary artery bypass grafting (group A), and 19 patients with mild aortic stenosis who underwent combined coronary artery bypass grafting and aortic valve replacement (group B). Patients with more than moderate aortic regurgitation were excluded. Preoperative angiograms were reviewed to assess the severity of calcification and restricted mobility of the aortic cusps.

RESULTS

In group A there were 11 deaths and 8 subsequent aortic valve replacements; in group B there were 5 deaths and 3 prosthetic valve-related complications. There was no difference in event-free survival between the two groups after adjusting for the difference in age. Among group A patients, the initial transvalvular gradient (p = 0.0005) and aortic valvular calcification (p = 0.06) identified patients who demonstrated progression to severe aortic stenosis during follow-up.

CONCLUSIONS

Our data suggest that routine aortic valve replacement during coronary artery bypass grafting in patients with mild aortic stenosis is not indicated, but concomitant aortic valve replacement may be appropriate in patients with higher transvalvular gradients and calcified valves.

Feasibility and complications of single-plane and biplane versus multiplane transesophageal imaging: a review of 2947 consecutive studies

OBJECTIVE

To analyze and compare the incidence of procedural complications and failure of intubation with various sizes of probes used in transesophageal echocardiography.

DESIGN

Retrospective chart review.

SETTING

A Canadian, tertiary care hospital.

PATIENTS

A total of 2947 consecutive transesophageal echocardiographic patient examinations between January 1992 and March 1996 at the University of Ottawa Heart Institute, Ottawa, Ontario.

RESULTS

The multiplane probe (MP) was used in 1274 studies, biplane (BP) in 1642 and single plane (SP) in 31. Data for BP and SP were combined because of their similar size. Complications or failed intubation occurred in 86 studies (2.9%). There were 53 complications (1.8%) and 40 failed intubations (1.4%). Seven patients (0.3%) had both. Complications were death in one, tracheal intubation or bronchospasm in nine, bleeding in nine, angina in two, pulmonary edema in two, superficial thrombophlebitis in two, supraventricular tachycardia in one and minor adverse events in 27. Complications were unrelated to the choice of probe (MP 2%, BP and SP 1.7%, not significant). Failure of intubation (40 cases) was more common with MP than with BP and SP (2.3% versus 0.7%, P = 0.0003, OR 3.5, 95% CI 1.7 to 7.5). The main reasons for failure were cervical spondylosis in 16 patients and hypersensitive pharynx despite topical anesthesia and sedation in 13 patients. Of 21 cases of failed MP intubation, 16 (76%) were subsequently successful with BP.

CONCLUSIONS

Serious complications with transesophageal echocardiography, although infrequent, do occur. The MP carries a 3.5-fold increased risk of failed intubation. In the majority of failures, successful intubation can be achieved with a smaller probe.

Genomic organization and characterization of a three-gene rat adult beta-globin haplotype

The isolation and detailed characterization of a three-beta-globin gene (GloB) haplotype in the Sprague-Dawley (S-D) rat is described. An enriched library, lambda SDHelib, was screened with a human GloB probe, humbg44, and from which a beta minor gene, Rathbbz, was isolated, sequenced and characterized. A S-D rat GloB-specific probe, Ratbgze12, derived from the Rathbbz gene, was then used to screen a S-D rat genomic library, lambda SDglib. The clone T1510 was isolated and identified to include the entire Rathbbz gene and part of another GloB gene, Rathbby, which was 5' upstream from Rathbbz. Chromosomal walking upstream using the riboprobe, rnaT71, led to the isolation of an overlapping clone, Ta49, which was shown to include two full-length GloB genes; the most 5' was Rathbbx followed by Rathbby. Sequence data suggests that Rathbbx is a beta major gene, whereas Rathbby is a hybrid gene of Rathbbx and Rathbbz. Genomic hybridization confirmed this particular three-gene haplotype in the S-D rat. This haplotype, a1, may be the prototype of the GloB cluster in rat.

Identification of cis- and trans-acting factors regulating the expression of the human insulin receptor gene

The functional organization of the human insulin receptor (hIR) promoter was analyzed by deletion mutagenesis and protein-DNA interaction studies. A series of deletion mutants was expressed transiently in two human hepatocytes, HepG2 and PLC. The results revealed that the promoter region between -692 and -345 is essential for efficient transcription of the hIR gene. Multiple trans-acting factors were identified by band shift and footprinting analyses. Sp1 binds to a cluster of GC boxes and two GGGAGG hexamers locating at -637 to -594. Adjacent to GC boxes, there are two regions, from -550 to -530 and from -522 to -503, which bind to two novel factors, IRNF-I and IRNF-II. These two factors are distributed differentially in different cell lines. Linker scanning mutations on GC, GA boxes, or the IRNF-I binding site significantly decreased the transcriptional activity, indicating that IRNF-I and Sp1 are important for hIR promoter activity. In addition, we demonstrated that glucocorticoid-dependent transcriptional induction of hIR mRNA in vivo is conferred by a glucocorticoid response element in the hIR promoter. Taken together, these results imply that transcription of the human insulin receptor gene is regulated by multiple protein-DNA interactions occurring within the defined promoter region.

A simplified and improved method for the efficient double-stranded sequencing of mini-prep plasmid DNA

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Molecular characterization of beta-globin gene mutations in patients with beta-thalassaemia intermedia in south China

We have studied the spectrum of mutations producting beta-thalassaemia intermedia in South China. The methods of mutation detection include oligonucleotide analysis, polymerase chain reaction amplification of the beta-globin gene and direct genomic sequencing. The mutations have been identified in 22 beta-globin genes from the patients in 11 unrelated families. Seven different mutations have been identified and the A to G substitution in the TATA box of the beta-globin gene accounts for 42% of these mutant beta-globin genes. Most patients have a beta(+) thalassaemia and one copy of the TATA box mutation. In two patients with beta(0) thalassaemia intermedia the mild phenotype may be explained in one by the presence of the - + - + + 5' beta-globin gene cluster haplotype which contains the Xmn I site -158 nt to the G gamma-globin gene or in the other by the number of alpha-globin genes present.

Chemical modification of hemoglobin in intact whole cells: morphological studies by scanning electron microscope

1. Whole blood was incubated in physiological conditions with a variety of modifiers capable of modifying hemoglobin. Some of these compounds have been considered as therapeutic agents for certain hemoglobinopathies such as sickle-cell disease. 2. The extent of modification on hemoglobin was estimated by electrophoresis and the red-cell morphology by scanning electron microscope. 3. Results indicated that carbamyl phosphate, aspirin and glutaryl-salicylamide had no observable effect, whereas cross-linkers in general produced drastic changes in red-cell morphology. 4. Dibromoaspirin, a very effective acetylating agent, produced abnormalities even in concentrations as low as 1 mM.

Analysis of globin gene structure in patients with beta thalassemia by restriction endonuclease mapping

Twenty-six DNA samples from individuals either heterozygous or homozygous for beta thalassemia were analyzed by restriction endonuclease digestion, agarose gel electrophoresis, and Southern blot analysis to define DNA fragments containing portions or all of the beta globin gene. A total of twenty-seven genes affected by a beta thalassemia mutation and twenty-seven genes affected by a beta thalassemia mutation and twenty-two normal beta globin genes were examined in Italian, Greek, or Asian individuals. With all four restriction endonucleases used, the fragments generated from DNA of thalassemic individuals were identical to those found in DNA from normal. Thus, gross rearrangement or deletion within the genomic region containing the beta globin gene is not characteristic of mutations which cause a thalassemia. A third patient homozygous for pancellular hereditary persistence of fetal hemoglobin was shown to have complete deletion of the delta and beta globin genes.

Chemical cross-linking of hemoglobin H. A possible approach to introduce cooperativity and modification of its oxygen transport properties

Native and reconstituted hemoglobin H molecules were cross-linked with glutaraldehyde at pH values close to the physiological. The Schiff base adducts were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis before and after reduction with sodium borohydride. The major component had a molecular weight of about 31 000 which corresponded to the dimeric species of the beta subunit. In contrast to the native protein, which has very high oxygen affinity and no heme-heme interaction or 2,3-diphosphoglyceric acid effect, the modified hemoglobin H molecules showed cooperative oxygen binding, decreased oxygen affinity and a noticeable 2,3-diphosphoglyceric acid effect.

Acylation of hemoglobin by glutarylsalicylamide and its effect on oxygen transport properties

Hemoglobin A was modified in vitro with 0.02-0.03 M glutarylsalicylamide for two hours at pH 7.2 and 37 degrees C. The extent of modification was about 30-50%, as estimated by visual comparison after electrophoretic separation. A substantial decrease in oxygen affinity of modified hemoglobin solutions was observed. Similar results were also obtained for dilute cell suspensions of washed red blood cells and whole blood after GSM modification. Other properties such as cooperativity, Bohr effect and 2,3-DPG dependence remained essentially unchanged. Athough the site(s) of modification have not been determined, it is unlikely that they would involve any amino acid residue contributing to the above allosteric properties.

Glycosylation of hemoglobin S by reducing sugars and its effect on gelation

The binding of various reducing mono- and disaccharides to hemoglobin S has been measured both before and after treatment of the sugar-protein adducts with NaBH4. Incubation of 0.3 M solutions of D-glucose, D-galactose, D-maltose, and lactose, with 2% hemoglobin for 2 h at 37 degrees C, pH 7.2, leads to the incorporation of 1.1, 1.8, 1.8, and 3.3 mol of sugar, respectively, into 1 mol of hemoglobin tetramer (either A or S). Exposure of these aldose-protein adducts to NaBH4 for an additional hour at 10 degrees C increases the binding to 2.0, 3.3, 2.5, and 4.1 mol per mol tetramer, as would be expected if Schiff base linkages were involved in this protein modification reaction. The data suggest a stereochemical requirement for enhanced binding. The dependence of the pre-reduction binding of glucose on the sugar concentration, and on the oxygenation state of hemoglobin has also been examined. Glycosylation of hemoglobin significantly increases the minimum gelling concentration of the deoxy conformation, as measured by sedimentation equilibrium ultracentrifugation. Of the sugar derivatives of hemoglobin S examined by this method, those modified by D-galactose or lactose have minimum gelling concentrations (in the absence of 2,3-diphosphoglycerate) which are comparable to, or greater than, that of fully carbamylated hemoglobinS.

Acetylation of sickle cell hemoglobin by aspirin

Incubation of HbS (or HbA) with aspirin leads to incorporation of acetyl groups into the protein. Incorporation was followed by the use of aspirin labeled with (14)C in the acetyl group. The acetylated hemoglobins show an increase in oxygen affinity compared to the parent proteins. If acetylation also occurs in vivo, administration of aspirin might ameliorate the severity of sickle cell disease.