The HLA locus contains novel foetal susceptibility alleles for congenital heart block with significant paternal influence.

OBJECTIVE: The main aim of this study was to identify foetal susceptibility genes on chromosome six for Ro/SSA autoantibody-mediated congenital heart block. SUBJECTS AND DESIGN: Single nucleotide polymorphism (SNP) genotyping of individuals in the Swedish Congenital Heart Block (CHB) study population was performed. Low-resolution HLA-A, -Cw and -DRB1 allele typing was carried out in 86 families comprising 339 individuals (86 Ro/SSA autoantibody-positive mothers, 71 fathers, 87 CHB index cases and 95 unaffected siblings). RESULTS: A case-control comparison between index cases and population-based out-of-study controls (n = 1710) revealed association of CHB with 15 SNPs in the 6p21.3 MHC locus at a chromosome-wide significance of P < 2.59 × 10(-6) (OR 2.21-3.12). In a family-based analysis of association of SNP markers as well as distinct MHC class I and II alleles with CHB, HLA-DRB1*04 and HLA-Cw*05 variants were significantly more frequently transmitted to affected individuals (P < 0.03 and P < 0.05, respectively), whilst HLA-DRB1*13 and HLA-Cw*06 variants were significantly less often transmitted to affected children (P < 0.04 and P < 0.03). We further observed marked association of increased paternal (but not maternal) HLA-DRB1*04 transmission to affected offspring (P < 0.02). CONCLUSIONS: HLA-DRB1*04 and HLA-Cw*05 were identified as novel foetal HLA allele variants that confer susceptibility to CHB in response to Ro/SSA autoantibody exposure, whilst DRB1*13 and Cw*06 emerged as protective alleles. Additionally, we demonstrated a paternal contribution to foetal susceptibility to CHB for the first time.

RAGE is the major receptor for the proinflammatory activity of HMGB1 in rodent macrophages.

Abstract High-mobility group box chromosomal protein 1 (HMGB1) is a protein with both intranuclear functions and extracellular cytokine-like effects. In this report, we study possible candidate receptors for HMGB1 on macrophages (Mphi) and define pathways activated by HMGB1 binding. Bone marrow Mphi were prepared from Dark Agouti (DA) rats and stimulated in vitro with HMGB1. The kinetics of tumour necrosis factor (TNF) production, NO production, activation of p38 mitogen-activated protein kinase (MAPK), p44/42 MAPK- and SAPK/JNK-signalling pathways, nuclear translocation of nuclear factor kappa B (NF-kappaB) and HMGB1-induced upregulation of major histocompatibility complex (MHC) class II and CD86 were analysed. Mphi from interleukin (IL)-1 receptor type I-/-, Toll-like receptor 2 (TLR2-/-) and RAGE-/- mice were used to investigate the role of these receptors in HMGB1 signalling. HMGB1 induced TNF and NO production by Mphi, phosphorylation of all investigated MAP kinase pathways and NF-kappaB translocation, and expression of MHC class II was increased. Mphi from RAGE-/- mice produced significantly lower amounts of TNF, IL-1beta and IL-6, while IL-1RI-/- and TLR2-/- Mphi produced cytokine levels comparable with wildtype controls in response to HMGB1 stimulation. We conclude that HMGB1 has the potential to induce a proinflammatory phenotype in Mphi, with RAGE as the major activation-inducing receptor.

Synaptically triggered action potentials begin as a depolarizing ramp in rat hippocampal neurones in vitro.

1. During just-suprathreshold synaptic activation of CA1 pyramidal cells in rat hippocampal slices in vitro the action potential begins as a slow depolarizing ramp, superimposed on the underlying EPSP and forming an integral part of the action potential. We call this ramp a synaptic prepotential (SyPP). 2. In order to examine the SyPP, a procedure for subtraction of the underlying EPSP was necessary. Because action potentials were only elicited by a subset of EPSPs with larger than average amplitude, a subtraction of the mean subthreshold EPSP would not give valid results. Instead, an EPSP to be subtracted was selected from an assemblage of subthreshold EPSPs, so that its amplitude matched the initial part of the spike-generating EPSP. 3. Virtually all action potentials started with a SyPP. Using an amplitude criterion of 1 S.D. of the mean of the matching subthreshold EPSPs, just-suprathreshold EPSPs gave prepotentials in 72-100% of all action potentials from fifteen randomly selected cells. With a criterion of 2 S.D.S, the frequency of occurrence ranged from 36 to 100%. 4. With a constant stimulus strength, there was a certain variability of the spike latencies. Shorter latency spikes had steeper, but smaller SyPPs than later spikes, suggesting that the slope of SyPP influenced the timing of the cell discharge. 5. The SyPP was best fitted by a single, exponentially rising curve, and was both smaller and slower than the large amplitude action potential. Its amplitude was 1-6 mV and the time constant 1-5 ms, which was 10-50 times slower than that of the upstroke of the action potential. 6. A properly timed hyperpolarizing current pulse could block the large amplitude action potential, thereby unmasking the SyPP as an initial depolarizing ramp. 7. The SyPP was more sensitive than the large amplitude action potential to intracellular injection of QX-314, a lidocaine derivative. At the concentrations used (10 or 30 mM) no detectable changes were seen in the large amplitude action potential. 8. Droplet application of a specific N-methyl-D-aspartate receptor antagonist, DL-2-amino-5-phosphonovaleric acid (1 mM), reduced both the EPSP and the firing probability, but did not change the SyPP. 9. The SyPP amplitude and time course depended upon the membrane potential at which the cell was activated. Depolarization enhanced and prolonged the SyPP, while hyperpolarization gave opposite effects. In part, the depolarization-induced amplitude increase could be attributed to membrane accommodation. 10. Antidromically evoked action potentials never started with a prepotential.(ABSTRACT TRUNCATED AT 400 WORDS)