The matrilin-3 VWA1 domain modulates interleukin-6 release from primary human chondrocytes.

OBJECTIVE: We previously demonstrated the ability of matrilin-3 to modulate the gene expression profile of primary human chondrocytes (PHCs) toward a state favoring cartilage catabolism. The structure within matrilin-3 responsible for the induction of these catabolic genes is unknown. Here, we investigated the potential of matrilin-3 (MATN3) and truncated matrilin-3 proteins, in both monomeric and oligomeric form, to stimulate interleukin (IL)-6 release in PHCs. METHODS: We expressed full-length matrilin-3 oligomers, matrilin-3 von Willebrand factor A (VWA) domain oligomers, matrilin-3 four epidermal growth factor (EGF) domain oligomers, matrilin-3 monomers without oligomerization domains, matrilin-3 VWA domain monomers, and matrilin-3 4EGF monomers. We then incubated PHCs in the absence or presence of full-length matrilin-3 or one of the truncated matrilin-3 proteins and finally determined the release of IL-6 in cell-culture supernatants. RESULTS: The addition of full-length matrilin-3 oligomers, matrilin-3 VWA domain oligomers, and, less pronounced, matrilin-3 monomers without oligomerization domains, and matrilin-3 4EGF-oligomers to the cell-culture medium led to a significant induction of IL-6 in PHCs. DISCUSSION: Based on recombinant expression of different matrilin-3 domains in both monomeric and oligomeric form, this work demonstrated that the VWA1 domain of matrilin-3 is primarily responsible for the induction of IL-6 release and that the oligomerization of the VWA1 domain markedly promotes its activity.

Increased inorganic phosphate induces human endothelial cell apoptosis in vitro.

Chronic kidney disease with hyperphosphatemia is associated with accelerated atherosclerosis and endothelial dysfunction. However, the contribution of high serum phosphate levels to endothelial injury is incompletely understood. The aim of this work was to evaluate the responses of endothelial cells to elevated levels of extracellular phosphate in vitro. High phosphate in concentrations similar to those observed in uremia-associated hyperphosphatemia (>2.5 mM) induced apoptosis in two endothelial cell lines (EAhy926 cells and GM-7373 cells). This effect was enhanced when cells were incubated for 24 h in the presence of 2.8 mM calcium instead of 1.8 mM. By treating cells with 0.5 or 1.0 mM phosphonoformic acid, an inhibitor of the phosphate transporter, death was completely prevented. The process of phosphate-induced apoptosis was further characterized by increased oxidative stress, as detected by increased ROS generation and disruption of the mitochondrial membrane potential at approximately 2 h after treatment, followed by caspase activation. These findings show that hyperphosphatemia causes endothelial cell apoptosis, a process that impairs endothelial integrity. Endothelial cell injury induced by high phosphate concentrations may be an initial event leading to vascular complications in patients with chronic kidney disease.

17beta-estradiol increases volume, apical surface and elasticity of human endothelium mediated by Na+/H+ exchange.

OBJECTIVE: 17beta-estradiol is known to delay the onset of atherosclerosis in women but cellular mechanisms are still unclear. Estrogens bind to specific receptors and initiate a signaling cascade that involves the activation of plasma membrane Na(+)/H(+) exchange. We hypothesized that estrogens interfere with ion transport across the plasma membrane and thus control endothelial structure and function. Therefore, we investigated the effects of the sex steroids 17beta-estradiol, progesterone, and testosterone on volume, apical surface and elasticity in human endothelium. METHODS: The atomic force microscope was used as an imaging tool and as an elasticity sensor. We applied the antiestrogen tamoxifen, the Na(+)/H(+) exchange blocker cariporide and the epithelial Na(+)channel blocker amiloride to elucidate the role of transmembrane ion transport in hormone-treated human umbilical vein endothelial cells (HUVEC). RESULTS: Incubation with 17beta-estradiol for 72 h led to a dose-dependent increase of endothelial cell volume (41%), apical cell surface (22%), and cell elasticity (53%) as compared to non-17beta-estradiol treated controls. Block of the 17beta-estradiol receptor by tamoxifen and of plasma membrane Na(+)/H(+) exchange by cariporide prevented the hormone-induced changes. Progesterone and testosterone were ineffective. CONCLUSIONS: 17beta-estradiol increases HUVEC water content and HUVEC elasticity mediated by activated estrogen receptors. The estrogen response depends on the activation of plasma membrane Na(+)/H(+) exchange. The increase in endothelial cell elasticity could be one of the vasoprotective mechanisms postulated for 17beta-estradiol.

Endothelial cell swelling by aldosterone.

There is accumulating evidence that mineralocorticoids not only act on kidney but also on the cardiovascular system. We investigated the response of human umbilical venous endothelial cells (HUVECs) to aldosterone at a time scale of 20 minutes in absence and presence of the aldosterone antagonist spironolactone or other transport inhibitors. We applied atomic force microscopy (AFM), which measures cell volume and volume shifts between cytosol and cell nucleus. We observed an immediate cell volume increase (about 10%) approximately 1 min after addition of aldosterone (0.1 micromol/l), approaching a maximum (about 18%) 10 min after aldosterone treatment. Cell volume returned to normal 20 min after hormone exposure. Spironolactone (1 micromol/l) or amiloride (1 micromol/l) prevented the late aldosterone-induced volume changes but not the immediate change observed 1 min after hormone exposure. AFM revealed nuclear swelling 5 min after aldosterone addition, followed by nuclear shrinkage 15 min later. The Na(+)/H(+) exchange blocker cariporide (10 micromol/l) was ineffective. We conclude: (i). Aldosterone induces immediate (1 min) swelling independently of plasma membrane Na(+) channels and intracellular mineralocorticoid receptors followed by late mineralocorticoid receptor- and Na(+)-channel-dependent swelling. (ii). Intracellular macromolecule shifts cause the changes in cell volume. (iii). Both amiloride and spironolactone may be useful for medical applications to prevent aldosterone-induced vasculopathies.

Impact of estradiol blood concentrations on skin capillary Laser Doppler flow in premenopausal women.

OBJECTIVE AND METHOD: Estradiols are known to prevent cardiovascular diseases, but the underlying mechanisms remain unclear. We assessed the finger skin capillary blood flow in 20 premenopausal women with oral contraception noninvasively by Laser Doppler flowmetry (LDF). Blood flow was registered both under basal conditions and after 2 min of arterial occlusion. Furthermore, the combination with a beat-to-beat online finger blood pressure monitor allowed the calculation of the regional peripheral resistance (RPR). All measurements were performed in the menstrual phase. LDF and RPR were correlated to the estradiol whole blood levels. RESULTS: Both baseline (r(2)=0.826; P<0.01) and vasodilation (r(2)=0.747; P<0.01) blood flux were significantly correlated to the corresponding estradiol concentrations. A multiple stepwise regression analysis (with age, height, weight, duration of oral contraception, nicotine pack years and estradiol levels in the equation) showed positive correlations between estradiol levels and (a) baseline (P<0.05) or (b) vasodilation (P<0.05) Laser Doppler flux or (c) time to reach the peak flux (r(2)=0.31; P<0.05). Furthermore, the minimal local vascular resistance was negatively correlated to the estradiol levels (r(2)=0.45; P<0.05). CONCLUSION: The study provides evidence that both the baseline and the vasodilation capillary blood flux in women in the menstrual phase depend on the estradiol whole blood levels. Furthermore, the local vascular resistance shows a negative correlation to the hormonal state. Functional or structural alterations of the microvasculature may therefore contribute to the estradiol-associated cardiovascular protection.

[Taurodontism in patients with sex chromosome anomalies]. / Zum Taurodontismus bei Geschlechtschromosomenanomalien.

Out of a population of 61 patients with sex chromosome aberrations we could examine 25 patients with Klinefelter's syndrome and one female patient with triple X syndrome for taurodontism. Taurodontic molars were found in 6 out of 25 patients with Klinefelter's syndrome and in the patient with triple X syndrome.