The guanylate kinase domain of the beta-subunit of voltage-gated calcium channels suffices to modulate gating

Inactivation of voltage-gated calcium channels is crucial for the spatiotemporal coordination of calcium signals and prevention of toxic calcium buildup. Only one member of the highly conserved family of calcium channel β-subunits—Ca_Vβ—inhibits inactivation. This unique property has been attributed to short variable regions of the protein; however, here we report that this inhibition actually is conferred by a conserved guanylate kinase (GK) domain and, moreover, that this domain alone recapitulates Ca_Vβ-mediated modulation of channel activation. We expressed and refolded the GK domain of Ca_Vβ_2a, the unique variant that inhibits inactivation, and of Ca_Vβ_1b, an isoform that facilitates it. The refolded domains of both Ca_Vβ variants were found to inhibit inactivation of Ca_V2.3 channels expressed in Xenopus laevis oocytes. These findings suggest that the GK domain endows calcium channels with a brake restraining voltage-dependent inactivation, and thus facilitation of inactivation by full-length Ca_Vβ requires additional structural determinants to antagonize the GK effect. We found that Ca_Vβ can switch the inactivation phenotype conferred to Ca_V2.3 from slow to fast after posttranslational modifications during channel biogenesis. Our findings provide a framework within which to understand the modulation of inactivation and a new functional map of Ca_Vβ in which the GK domain regulates channel gating and the other conserved domain (Src homology 3) may couple calcium channels to other signaling pathways.     

Evaluation of interleukin-6 and its soluble receptor components sIL-6R and sgp130 as markers of inflammation in inflammatory bowel diseases

Purpose

Interleukin-6 (IL-6) production and signalling are increased in the inflamed mucosa in inflammatory bowel diseases (IBD). As published serum levels of IL-6 and its soluble receptors sIL-6R and sgp130 in IBD are from small cohorts and partly contradictory, we systematically evaluated IL-6, sIL-6R and sgp130 levels as markers of disease activity in Crohn’s disease (CD) and ulcerative colitis (UC).

Methods

Consecutive adult outpatients with confirmed CD or UC were included, and their disease activity and medication were monitored. Serum from 212 CD patients (815 measurements) and 166 UC patients (514 measurements) was analysed, and 100 age-matched healthy blood donors were used as controls.

Results

IL-6 serum levels were significantly elevated in active versus inactive CD and UC, also compared with healthy controls. However, only a fraction of IBD patients showed increased serum IL-6. IL-6 levels ranged up to 32.7 ng/mL in active CD (>?5000-fold higher than in controls), but also up to 6.9 ng/mL in inactive CD. Increases in active UC (up to 195 pg/mL) and inactive UC (up to 27 pg/mL) were less pronounced. Associations between IL-6 serum levels and C-reactive protein concentrations as well as leukocyte and thrombocyte counts were observed. Median sIL-6R and sgp130 levels were only increased by up to 15%, which was considered of no diagnostic significance.

Conclusions

Only a minority of IBD patients shows elevated IL-6 serum levels. However, in these patients, IL-6 is strongly associated with disease activity. Its soluble receptors sIL-6R and sgp130 do not appear useful as biomarkers in IBD.

     

Diagnostic yield of bronchoscopy with bronchoalveolar lavage in febrile patients with hematologic malignancies and pulmonary infiltrates

Infectious complications are a major cause of morbidity and mortality in immunosuppressed patients. Febrile patients with hematologic malignancies and pulmonary infiltrates have high mortality rates, especially if mechanical ventilation is required. The diagnostic value of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) in these patients is controversial. We retrospectively analyzed the microbiological results of BAL samples obtained during 249 FOB examinations from 199 febrile patients with hematologic malignancies and pulmonary infiltrates (underlying diseases: acute leukemia 103 patients, lymphoma 84 patients, other malignancies 12 patients). Two hundred forty-six examinations could be evaluated. Seventy-three out of 246 BAL samples were sterile; 55 samples showed microbiological findings classified as contamination or colonization. One hundred eighteen samples showed positive microbiological results of bacteria and/or fungi classified as causative pathogens. Thereof, in 70 samples, only bacterial pathogens were detectable (Gram-positive, 35; Gram-negative, 30; mixed Gram-positive and Gram-negative, 5). Thirteen samples showed both fungi and bacterial pathogens. In 33 samples, only fungi were detectable, thereof, in 15 samples Aspergillus species, in 16 samples Candida species, and in 2 both. In two samples, a viral pathogen could be detected. Three nonlethal complications (bleeding, arrhythmia) occurred that required early termination of FOB. In 94 (38.2%) patient episodes, antibiotic treatment was modified as a result of microbiological findings in BAL samples. Our results show that FOB with BAL is a valuable diagnostic tool with low complication rates in high-risk febrile patients with hematologic malignancies and pulmonary infiltrates, contributing crucial results for the individual case, and also improving epidemiologic knowledge.     

Rest and exercise hemodynamic effects of sequential alpha-1-adrenoceptor (trimazosin) and beta-adrenoceptor (propranolol) antagonism in essential hypertension

The efficacy of acute beta blockade in essential hypertension is limited by reflex vasoconstriction. The aim of this study was to determine whether the latter response was modified by prior selective alpha-1-adrenoceptor blockade. A single-blind, within-patient, placebo-controlled evaluation of the immediate hemodynamic effects of sequential alpha-1 (trimazosin)- and beta (propranolol)-adrenoceptor blockade was undertaken in 10 men (34 to 58 years) with previously untreated essential hypertension. The study commenced with a 4-minute control period of constant-load (600 to 900 kpm/min) upright bicycle exercise, and measurements were made before (control) and 30 minutes after intravenous trimazosin (2 mg/kg) and exercise was then repeated; measurements at rest were again made 4 minutes after intravenous propranolol (0.2 mg/kg) before a final exercise period. Trimazosin at rest reduced systolic and diastolic arterial pressure and systemic vascular resistance without change in heart rate, cardiac output, or left ventricular (LV) filling pressure. During upright bicycle exercise the reductions in blood pressure were sustained without change in their rest-to-exercise increments. Other circulatory variables did not differ from control values. At rest the addition of propranolol further reduced systolic arterial pressure. Heart rate and cardiac output fell and systemic vascular resistance increased to its pretreatment control value. During exercise the changes at rest were sustained and the rest-to-exercise increments in blood pressure, heart rate, and cardiac output were reduced. LV filling pressure was significantly increased. In conclusion, alpha-1-adrenoceptor blockade modified the adverse effects of acute beta blockade at rest but not during exercise.     

Budget impact analysis on the introduction of a guideline based hepatitis B and C screening into a routine check-up in the German primary care setting

Objectives: Systematic screening for chronic hepatitis B and C does not yet exist in Germany. Therefore, the implementation of a screening approach within a preventive medical examination performed by primary care physicians (‘Check-Up 35+’) was evaluated in a recent prospective multicenter study. The present analysis estimates the financial consequences for the statutory health insurance by budget impact analysis.

Materials and methods: A Markov cohort model was developed consisting of 21 health states. Four different screening scenarios derived from the previous multicenter study were compared to usual care, a strategy without screening for hepatitis. Actual cost data for Germany were calculated and systematic literature searches for all input parameters were performed.

Results: The base case results in incremental costs for the screening strategies compared to no hepatitis screening of 165–227 € per patient in a 20-year horizon. Two main parameters influence the financial consequences: (A) detection and treatment increase the costs in the beginning. (B) Screening avoids hepatitis induced end-stage liver disease. The initial higher costs exceed the later savings. Sensitivity analyses demonstrate a strong impact of medication costs for the treatment of additionally detected hepatitis infections on the outcome. This finding is robust to sensitivity analysis.

Conclusions: The screening strategy proposed here implies additional costs for the statutory health insurance, however, a decision regarding its usefulness must consider criteria other than cost. For example, the high burden of disease due to liver cirrhosis and liver carcinoma should be considered. Therefore, an additional cost-effectiveness-analysis should be conducted.