No abstract

As the increase of choline, creatine and myo-inositol are usually interpreted to indicate glial activation and macrophage infiltration in chronic inflammation and slow virus infections of the brain the present data endorse the hypothesis, that HCV infection may induce neuroinflammation and brain dysfunction. The concomitant increase of NN and the negative correlation to the extent of fatigue suggest a cerebral compensatory process after HCV infection.

The pathogenesis of spontaneous abortion is complex, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene C677T and A1298C polymorphisms are commonly associated with defects in folate dependent homocysteine metabolism and have been implicated as risk factors for recurrent embryo loss in early pregnancy. In the present study we have determined the prevalence of combined MTHFR C677T and A1298C polymorphisms in DNA samples from spontaneously aborted embryos (foetal death between sixth and twentieth week after conception) and adult controls using solid-phase minisequencing technique. There was a significant odds ratio of 14.2 (95% CI 1.78-113) in spontaneously aborted embryos comparing the prevalence of one or more 677T and 1298C alleles vs the wild type combined genotype (677CC/1298AA), indicating that the MTHFR polymorphisms may have a major impact on foetal survival. Combined 677CT/1298CC, 677TT/1298AC or 677TT/1298CC genotypes, which contain three or four mutant alleles, were not detected in any of the groups, suggesting complete linkage disequilibrium between the two polymorphisms. The present finding of high prevalence of mutated MTHFR genotypes in spontaneously aborted embryos emphasises the potential protective role of periconceptional folic acid supplementation.

Depressed cardiac Ca cycling by the sarcoplasmic reticulum (SR) has been associated with attenuated contractility, which can progress to heart failure. The histidine-rich Ca-binding protein (HRC) is an SR component that binds to triadin and may affect Ca release through the ryanodine receptor. HRC overexpression in transgenic mouse hearts was associated with decreased rates of SR Ca uptake and delayed relaxation, which progressed to hypertrophy with aging. The present study shows that HRC may mediate part of its regulatory effects by binding directly to sarco(endo)plasmic reticulum Ca-ATPase type 2 (SERCA2) in cardiac muscle, which is confirmed by coimmunostaining observed under confocal microscopy. This interaction involves the histidine- and glutamic acid-rich domain of HRC (320-460 aa) and the part of the NH(2)-terminal cation transporter domain of SERCA2 (74-90 aa) that projects into the SR lumen. The SERCA2-binding domain is upstream from the triadin-binding region in human HRC (609-699 aa). Specific binding between HRC and SERCA was verified by coimmunoprecipitation and pull-down assays using human and mouse cardiac homogenates and by blot overlays using glutathione S-transferase and maltose-binding protein recombinant proteins. Importantly, increases in Ca concentration were associated with a significant reduction of HRC binding to SERCA2, whereas they had opposite effects on the HRC-triadin interaction in cardiac homogenates. Collectively, our data suggest that HRC may play a key role in the regulation of SR Ca cycling through its direct interactions with SERCA2 and triadin, mediating a fine cross talk between SR Ca uptake and release in the heart.

Cardiac contractility is regulated through the activity of various key Ca(2+)-handling proteins. The sarco(endo)plasmic reticulum (SR) Ca(2+) transport ATPase (SERCA2a) and its inhibitor phospholamban (PLN) control the uptake of Ca(2+) by SR membranes during relaxation. Recently, the antiapoptotic HS-1-associated protein X-1 (HAX-1) was identified as a binding partner of PLN, and this interaction was postulated to regulate cell apoptosis. In the current study, we determined that HAX-1 can also bind to SERCA2. Deletion mapping analysis demonstrated that amino acid residues 575-594 of SERCA2's nucleotide binding domain are required for its interaction with the C-terminal domain of HAX-1, containing amino acids 203-245. In transiently cotransfected human embryonic kidney 293 cells, recombinant SERCA2 was specifically targeted to the ER, whereas HAX-1 selectively concentrated at mitochondria. On triple transfections with PLN, however, HAX-1 massively translocated to the ER membranes, where it codistributed with PLN and SERCA2. Overexpression of SERCA2 abrogated the protective effects of HAX-1 on cell survival, after hypoxia/reoxygenation or thapsigargin treatment. Importantly, HAX-1 overexpression was associated with down-regulation of SERCA2 expression levels, resulting in significant reduction of apparent ER Ca(2+) levels. These findings suggest that HAX-1 may promote cell survival through modulation of SERCA2 protein levels and thus ER Ca(2+) stores.