Phospholipase A(2) is involved in thapsigargin-induced sodium influx in human lymphocytes

Previously, we reported that emptying of intracellular Ca(2+) pools with endoplasmatic Ca(2+)-ATP-ase inhibitor thapsigargin leads to the Na(+) influx in human lymphocytes (M. Tepel et al., 1994, J. Biol. Chem. 269, 26239-26242). In the present study we examined the mechanism underlying the thapsigargin-induced Na(+) entry. We found that the thapsigargin-induced increase in Na(+) concentration was effectively inhibited by three structurally unrelated phospholipase A(2) (PLA(2)) inhibitors, p-bromophenacyl bromide, 3-(4-octadecyl)-benzoylacrylic acid (OBAA), and bromoenol lactone (BEL). The thapsigargin-induced Na(+) influx could be mimicked by PLA(2) exogenously added to the lymphocyte suspension. In addition, thapsigargin stimulated formation of arachidonic acid (AA), the physiological PLA(2) product. AA induced Na(+) entry in a time- and concentration-dependent fashion. Both, thapsigargin-induced Na(+) influx and AA liberation were completely inhibited in the presence of tyrosine kinase inhibitor genistein but not in the absence of extracellular Ca(2+). Collectively, these data show that thapsigargin-induced Na(+) entry is associated with tyrosine kinase-dependent stimulation of PLA(2).

Involvement of CD28 cosignalling in the T cell-mediated suppression of the IgG antibody response against the TI-2 antigen alpha(1-->3) dextran

The humoral immune response against alpha(1-->3) dextran (Dex) in BALB/c mice is characterized by the formation of predominantly IgM antibodies bearing the J558 idiotype. IgG antibodies do not appear in euthymic mice. In athymic animals, however, the response proceeds to a vigorous IgG production. In euthymic mice formation of IgG is suppressed by J558 idiotype specific regulatory T cells recognizing in association with I-Ed and in cognate T/B interaction the V(H) CDR3 derived peptide of the J558 idiotype. Only B-2 lymphocytes produce IgG whereas B-1 cells do not participate in the production of this Ig class. Using novel synthetic all alpha(1-->3)-D-gluco configured tetrasaccharide the Dex-specific B cells can for the first time be analyzed in FACS. In experiments using this newly designed low molecular Dex no signs of B cell apoptosis can be found. This demonstrates a true silencing of persisting Bgamma memory cells as previously suggested by adoptive transfer experiments. In this suppression a further involvement of CD28 and B7-1 interaction can be demonstrated which delivers a necessary costimulatory suppression signal in addition to the cognate TCR/peptide-I-Ed interaction between J558 specific T cells and J558 idiotype bearing B cells.

Na(+)/Ca(2+) exchange inhibitors modulate thapsigargin-induced Ca(2+) and Na(+) influx in human lymphocytes

Thapsigargin has been shown the elevate intracellular Na(+) concentration in human lymphocytes, but mechanisms underlying thapsigargin-induced Na(+) entry are little understood. In the present study we investigated thapsigargin-induced changes in cytosolic free Na(+) and Ca(2+) concentration in human lymphocytes after inhibition of the Na(+)/Ca(2+) exchange with two structurally unrelated compounds, dimethylthiourea ad bepridil. The intracellular Na(+) increase induced by 5 microM thapsigargin was significantly enhanced in the presence of 5 mM dimethylthiourea or 40 microM bepridil. In contrast, both compounds significantly decreased the thapsigargin-induced intracellular Ca(2+) elevation. No effect of dimethylthiourea or bepridil on thapsigargin-induced Ca(2+) influx was observed in the absence of extracellular Na(+). These observations are consistent with the hypothesis that thapsigargin stimulates Na(+)/Ca(2+ )exchange in human lymphocytes. However, Na(+)/Ca(2+) exchange does not mediate Na(+) influx in human lymphocytes.

Diurnal variation of leukocyte counts affects the indirect estimation of reference intervals

It has been observed that the estimation of reference intervals of leukocytes in whole venous blood leads to higher upper reference limits (uRLs) with indirect methods than has been reported in the literature determined by direct approaches. This phenomenon was reinvestigated with a newer, more advanced indirect method, and could be confirmed. Furthermore, a diurnal variation was observed with lower values during the morning and higher values in the late afternoon and at night. This observation can explain why indirect approaches using samples collected during 24 h lead to higher uRLs than direct methods applied on samples collected presumably in the morning.

Single- and Multimarker Genome-Wide Scans Evidence Novel Genetic Risk Modifiers for Venous Thromboembolism

Previous genome-wide association studies (GWASs) have established several susceptibility genes for venous thromboembolism (VTE) and suggested many others. However, a large proportion of the genetic variance in VTE remains unexplained. Here, we report genome-wide single- and multimarker as well as gene-level associations with VTE in 964 cases and 899 healthy controls of European ancestry. We report 19 loci at the genome-wide level of association (p ≤ 5 × 10^-8). Our results add to the strong support for the association of genetic variants in F5, NME7, ABO, and FGA with VTE, and identify several loci that have not been previously associated with VTE. Altogether, our novel findings suggest that 20 susceptibility genes for VTE were newly discovered by our study. These genes may impact the production and prothrombotic functions of platelets, endothelial cells, and white and red blood cells. Moreover, the majority of these genes have been previously associated with cardiovascular diseases and/or risk factors for VTE. Future studies are warranted to validate our findings and to investigate the shared genetic architecture with susceptibility factors for other cardiovascular diseases impacting VTE risk.

Role of prothrombin 19911 A>G polymorphism, blood group and male gender in patients with venous thromboembolism: Results of a German cohort study

The role of the A>G polymorphism at position 19911 in the prothrombin gene (factor [F] 2 at rs3136516) as a risk factor for venous thromboembolism [VTE] is still unclear. To evaluate the presence of the F2 polymorphism in VTE patients compared to healthy blood donors and to adjust the results for common inherited thrombophilias [IT], age at onset and blood group [BG], and to calculate the risk of VTE recurrence. We investigated 1012 Caucasian patients with a diagnosis of VTE for the presence of the F2 rs3136516 polymorphism and compared these with 902 healthy blood donors. Odds ratios [OR] together with their 95% confidence intervals were calculated adjusted for F5 at rs6025, F2 at rs1799963, blood group, age and gender. In addition, we evaluated the risk of recurrent VTE during patient follow-up calculating hazard ratios [HR] together with their 95% CI. Compared with the AA wildtype, the F2 GG and AG genotypes (rs3136516) were associated with VTE (OR 1.48 and 1.45). The OR in F5 carriers compared to controls was 5.68 and 2.38 in patients with F2 (rs1799963). BG "non-O" was significantly more often diagnosed in patients compared to BG "O" (OR 2.74). VTE recurrence more often occurred in males (HR 2.3) and in carriers with combined thrombophilia (HR 2.11). Noteworthy, the rs3136516 polymorphism alone was not associated significantly with recurrence. In Caucasian patients with VTE the F2 GG/GA genotypes (rs3136516) were moderate risk factors for VTE. Recurrence was associated with male gender and combined thrombophilia.

High-density lipoproteins inhibit fibrinogen binding on adenosine diphosphate-activated monocytes

High levels of fibrinogen and low levels of high-density lipoprotein (HDL) cholesterol were reported to be risk factors for coronary heart disease. CD11b/CD18, a fibrinogen-binding protein, is expressed on the surface of monocytes, which play a crucial role in the formation of atherosclerotic lesions. In the present study, we investigate the effects of antibodies against CD11b and CD18, as well as HDL3 and low-density lipoprotein (LDL) cholesterol on fibrinogen binding on monocytes. We find that binding of fibrinogen on monocytes activated with adenosine diphosphate (ADP) was reduced to 66.0+/-8.3% (mean +/- SD) in the presence of anti-CD11b antibodies (12.5 microg/ml; P < or = 0.02) and to 54.5+/-4.9% in the presence of anti-CD18 antibodies (20 microg/ml; P < or = 0.01), respectively. Fibrinogen binding on Cytochalasin-B-activated monocytes was reduced to 79.8+/-6.0% in the presence of anti-CD18 (20 microg/ml; P < or = 0.05). Incubation of ADP-activated monocytes with HDL3 (0.5 g/l) led to a lowering of fibrinogen binding to 65.0+/-6.6% (P < or = 0.05). No effect of HDL3 on fibrinogen binding was seen on Cytochalasin-B-activated monocytes. A slight, non-significant stimulatory effect of LDL on fibrinogen binding on ADP-activated but not on Cytochalasin-B-activated monocytes was additionally observed. Neither incubation with HDL3 or with LDL had a significant influence on ADP-activated cellular binding of anti-CD11b or anti-CD18 antibodies. The inhibition of fibrinogen binding on monocytes in the presence of HDL3 is a major new finding of this study. Since inhibition of fibrinogen binding in the presence of HDL might impair both monocyte recruitment to the arterial wall and foam cells formation, our findings suggests a novel mechanism by which HDL may prevent development of arteriosclerosis.

B-cell-responses to vaccination with BNT162b2 and mRNA-1273 six months after second dose

Objectives

To examine the state of B-cell immunity 6 months after the second vaccination against SARS-CoV-2 in comparison to the state observed 2 weeks after vaccination.

Methods

Sera of 439 participants, whose immune responses to two doses of an mRNA-based vaccine (BNT162b2 or mRNA-1273) were previously characterized, was examined for anti-S1 IgG and IgA, anti-NCP IgG and neutralizing antibodies (nAb), and antinuclear antibodies (ANA).

Results

Levels of all examined markers decreased significantly from 2 weeks to 6 months after second vaccination (anti-S1 IgG: 3744 ± 2571.4 vs. 253 ± 144 binding antibody units (BAU)/mL; anti-S1 IgA: 12 ± 0 vs. 1.98 ± 1.75 optical density (OD) ratio; nAb: 100% ± 0% vs. 82% ± 19.3%), the vast majority of participants retaining reactive levels of anti-S1 IgG (436/439) and anti-S1 IgA (334/439) at 6 months. Immune responses were stronger for mRNA-1273 compared with BNT162b2 (anti-S1 IgG: 429 ± 289 vs. 243 ± 143 BAU/mL; anti-S1 IgA: 5.38 ± 3.91 vs. 1.89 ± 1.53 OD ratio; nAb: 90.5% ± 12.6% vs. 81% ± 19.3%). There was no meaningful influence of sex and age on the examined markers. There was a strong correlation between anti-S1 IgG and the surrogate neutralization assay (rho = 0.91, p <0.0001), but not for for IgA and the surrogate neutralization assay (rho = 0.52, p <0.0001). There was a ceiling effect for the association between anti-S1 IgG titres and the inhibition of binding between S1 and ACE2. ANA prevalence was unchanged from 2 weeks to 6 months after the second vaccination (87/498 vs. 77/435), as were the median ANA titres (1:160 vs. 1:160).

Discussion

Although the clinical consequences of decreasing anti-SARS-CoV-2 antibody titres cannot be estimated with certainty, a lowered degree of clinical protection against SARS-CoV-2 is possible. Persistently stronger responses to mRNA-1273 suggest that it might confer greater protection than BNT162b2, even 6 months after the second vaccination. Neither examined vaccinations induced ANA within the examined time frame.

Analysis of SARS-CoV-2 reverse transcription-quantitative polymerase chain reaction cycle threshold values vis-à-vis anti-SARS-CoV-2 antibodies from a high incidence region

Objectives

To examine the relationship between antibody status and cycle threshold (Ct) values, the prognostic value of the latter for COVID-19 patients, and the inter-assay comparability of SARS-CoV-2 Ct values.

Methods

In 347 COVID-19 inpatients, SARS-CoV-2 Ct values (via reverse transcription-quantitative polymerase chain reaction) on admission were compared between 2 assays and correlated with the antibody response (in the course of the disease), the clinical course and the time since onset of symptoms.

Results

Ct values for 2 of 3 target genes showed significant differences between the 2 assays used (P=0.012 and P<0.0001). Ct values were significantly higher for antibody positive patients (P<0.0001) and positively correlated with the amount of time since onset of symptoms (R: 0.332–0.363; P<0.001). Patients with fatal outcomes showed higher viral loads than survivors (P<0.0001).

Conclusions

Ct values depend strongly on assay used and target gene examined and should not be used as quantitative values to guide therapeutic or diagnostic decisions. The inverse association between antibody status and viral load suggests that antibodies contribute to the elimination of the virus, independent of the outcome, which is influenced by the viral load on admission and might depend more strongly on other parts of the immune response.

Age- and sex-dependent reference intervals for uric acid estimated by the truncated minimum chi-square (TMC) approach, a new indirect method

Background

Although the concentration of uric acid in serum or plasma is known to depend on sex and age and is subject to diurnal variation, the influence of these covariates on the reference interval (RI) is often neglected. Consequently, the values in the literature vary considerably. Therefore, we reinvestigated the reference limits and their dependence on covariates.

Methods

A new indirect approach was applied which derives a continuous function between age and RIs avoiding the usual “jumps” between various age groups.

Results

It is confirmed that the uric acid concentration in women is lower than in men. The RIs increase with age, in women more than in men. Between 80 and 90 years of age, the upper RI limit (RL) approximately reaches the same level in both sexes. Because the uric acid concentration may indicate renal insufficiency, the concentrations of creatinine and cystatin C were also measured. Both measurands showed the same behaviour as uric acid. Therefore, the age and sex dependency should be considered if the uric acid concentration is used as an indicator for hyperuricaemia (e.g. caused by gout or other metabolic diseases). Furthermore, a diurnal variation was observed.

Conclusions

Due to the variations of various covariates (age, sex, daytime, analytical systems), it is recommended that each laboratory should estimate its own RIs.

High density lipoproteins induce cell cycle entry in vascular smooth muscle cells via mitogen activated protein kinase-dependent pathway

In this study we found that HDL acts as a potent and specific mitogen in vascular smooth muscle cells (VSMC) by stimulating entry into S-phase and DNA synthesis in a time- and concentration-dependent manner, induction of cyclins D1, E, and A, as well as activation of cyclin D-dependent kinases as inferred from phosphorylation of the retinoblastoma protein (pRb). Moreover, HDL induced activation of the mitogen-activated protein kinase pathway including Raf-, MEK-1, and ERK1/2, as well as the expression of proto-oncogen c-fos, which is controlled by ERK1/2. PD98059, an inhibitor of MEK-1 blocked the mitogenic activity of HDL and cyclin D1 expression. HDL-induced VSMC proliferation, cell cycle progression, cyclin D1 expression, and activation of the Raf-1/MEK-1/ERK1/2 cascade were blocked by preincubation of cells with pertussis toxin indicating involvement of trimeric G-protein. By contrast, none of these responses was inhibited by the protein kinase C inhibitor, GF109203X. The mitogenic effects of native HDL were not mimicked by apo A-I, reconstituted HDL containing apo A-I, or cholesterol-containing liposomes. In conclusion, HDL possesses an intrinsic property to induce G-protein- and MAP-kinase-dependent proliferation and cell cycle progression in VSMC. The strong and specific mitogenic effect of HDL should be taken into account, when therapeutic strategies to elevate the plasma level of these lipoproteins are developed.

Cross-Sectional and Longitudinal Construct Validity of the Generic KINDL-A(dult)B(rief) Questionnaire in Adults with Thrombophilia or with Hereditary and Acquired Bleeding Disorders

BACKGROUND/AIMS

The newly adapted generic KINDL-A(dult)B(rief) questionnaire showed satisfactory cross-sectional psychometric properties in adults with bleeding disorders or thrombophilia. This investigation aimed to evaluate its cross-sectional and longitudinal construct validity.

METHODS

After ethical committee approval and written informed consent, 335 patients (mean age 51.8 ± 16.6 years, 60% women) with either predominant thrombophilia (n = 260) or predominant bleeding disorders (n = 75) participated. At baseline, patients answered the KINDL-AB, the MOS 36-item Short-Form Health Survey (SF-36), and the EQ-5D-3L. A subgroup of 117 patients repeated the questionnaire after a median follow-up of 2.6 years (range: 0.4-3.5). A priori hypotheses were evaluated regarding convergent correlations between KINDL-AB overall well-being and specific subscales, EQ-5D-3L index values (EQ-IV), EQ-5D visual analog scale (EQ-VAS), and SF-36 subscales.

RESULTS

Contrary to hypothesis, baseline correlations between the KINDL-AB and EQ-IV/EQ-VAS were all moderate while, as hypothesized, several KINDL-AB subscales and SF-36 subscales correlated strongly. At follow-up, no significant changes in all three instruments occurred. Correlations between instruments over the follow-up were mostly moderate and partially strong. Contrary to hypothesis but consistent with no significant changes in health-related quality of life, convergent correlations between changes in KINDL-AB overall well-being, physical and psychological well-being, and EQ-IV/EQ-VAS were all weak.

CONCLUSIONS

While repeated measures of KINDL-AB showed moderate to strong correlations, changes in KINDL-AB overall well-being and subscales correlated more weakly than expected with changes involving two established instruments of generic health status.