Atherosclerosis in SLE: a potential role for serum parathormone levels

Objective

A link between bone metabolism and cardiovascular (CV) disease has been suggested mainly in the general population. In the current study we explored whether altered bone metabolism influence CV risk in patients with SLE.

Methods

In 138 consecutive patients with SLE, atherosclerosis was assessed by the presence of plaque and/or arterial wall thickening in carotid/femoral arteries by ultrasound. Bone mineral density (BMD) levels and hip/spinal cord fractures together with classical CV disease and osteoporosis risk factors including serum 25(OH) vitamin D₃ and parathormone (PTH) levels were recorded in all patients. Serum osteoprotegerin (OPG) and receptor activator of nuclear factor kappa-Β ligand were quantitated by commercial ELISA. Statistical analysis included both univariate and multivariate models.

Results

Abnormal PTH serum concentrations (>65 pg/mL)—but not 25(OH) vitamin D₃ serum levels—were identified as a risk factor for both plaque formation and arterial wall thickening in patients with SLE (ORs (95% CIs): 8.2 (1.8 to 37.4) and 3.9 (1.3 to 11.8), respectively). This association remained significant following adjustment for vitamin D₃ levels and classical CV risk factors. Moreover, an independent association between osteoporosis with plaque formation and arterial wall thickening was detected following adjustment for total steroid dose, premature menopause and disease duration (ORs (95% CIs): 5.3 (1.1 to 26.2) and 3.5 (1.1 to 11.4), respectively). An inverse correlation between femoral neck BMD values and intima–medial thickness scores was also observed (r: −0.42, p=0.008).

Conclusions

These findings further strengthen the concept of shared pathophysiological mechanisms between atherogenesis and altered bone metabolism in autoimmune populations, revealing heightened PTH levels as a potential marker for atherosclerosis among patients with SLE.

The electron conduction of photosynthetic protein complexes embedded in a membrane

The conductivity of two photosynthetic protein-pigment complexes, a light harvesting 2 complex and a reaction center, was measured with an atomic force microscope capable of performing electrical measurements. Current-voltage measurements were performed on complexes embedded in their natural environment. Embedding the complexes in lipid bilayers made it possible to discuss the different conduction behaviors of the two complexes in light of their atomic structure.

Gonadotrophin regulation of production of tissue inhibitor of metalloproteinases-1 by luteinized human granulosa cells: a potential mechanism for luteal rescue

Human granulosa cells were maintained in culture with extracellular matrix in the presence or absence of human chorionic gonadotrophin (HCG) using a defined culture medium. Such cultures are maintained by gonadotrophin in a manner suggesting that features of 'luteal rescue' may be occurring in vitro. Western analysis of culture medium demonstrated that the granulosa cells produced tissue inhibitor of metalloproteinases (TIMP)-1 but not TIMP-2. The presence of TIMP-1 in cultured cells was also detected immunocytochemically. Immunoassay of TIMP-1 output revealed that HCG exposure for 7 days caused a 2-fold increase in TIMP-1 production versus control reaching maximum at approximately 1 ng HCG/ml. The sensitivity of this response to HCG was similar to that observed for stimulation of progesterone production. Delayed addition of HCG, from day 4 of culture, elicited increases in TIMP-1 which were evident within 24 hours, and were not explained by changes in cell replication or survival. Removal of HCG from cultures previously luteinized with HCG for 6 days resulted in a fall in TIMP-1 production. Thus TIMP-1 production by luteinized granulosa cells in culture is gonadotrophin dependent. We speculate that prolonged cellular function associated with 'luteal rescue' may result from increased extracellular matrix stability mediated by up-regulation of TIMP-1 production.

Suppression of matrix metalloproteinase production by hCG in cultures of human luteinized granulosa cells as a model for gonadotrophin-induced luteal rescue

Granulosa cells were isolated from follicular aspirates collected at ovum recovery for in vitro fertilization. Cells were cultured in a defined medium on artificial extracellular matrix (Matrigel) in the presence or absence of hCG as a model for corpus luteum function. Release of cells from this culture system is reduced by hCG and this effect may be mediated through an inhibition of extracellular matrix degradation. Using zymography and western blot analysis, we confirm the identity of matrix metalloproteinases-2 and -9 in culture media. Matrix metalloproteinase-9 was the predominant gelatinase in freshly prepared granulosa cells and in culture media, and also represented a major metalloproteinase component in homogenates of early and mid-luteal phase samples of corpora lutea. Quantitative analysis of matrix metalloproteinases in culture media, obtained throughout the 14 day culture period and expressed per microgram of DNA, showed that matrix metalloproteinase-2, undetectable on day 2, rose throughout the culture period and that this rise was significantly inhibited by hCG. In contrast, matrix metalloproteinase-9 was clearly detectable on day 2 and remained relatively constant throughout much of the culture (day 2 to day 12) in the presence of gonadotrophin. Significantly increased production of matrix metalloproteinase-9 (day 6 to day 12) was evident in the absence of hCG. Our results provide further evidence for the hypothesis that the rescue of the corpus luteum in early pregnancy involves the maintenance of cellular function through the stabilization of the extracellular matrix.

Effect of gonadotrophin on cell and matrix retention and expression of metalloproteinases and their inhibitor in cultured human granulosa cells modelling corpus luteum function

Granulosa cells were prepared from follicular aspirates obtained at oocyte collection for in-vitro fertilization (IVF) and maintained in culture. Substantial loss of cells from the culture surface occurred in the absence of gonadotrophin when cells were maintained on a thin layer of extracellular matrix (ECM) using a defined, serum-free medium. This cell loss was clearly and significantly reduced in the presence of human chorionic gonadotrophin (HCG) by days 4-6 of culture, and occurred in conjunction with loss of ECM. Analysis of culture medium by zymography using gelatin as substrate demonstrated the presence of metalloproteinases (MMP), MMP-9 (gelatinase B) appearing as the predominant band. Measurement of overall gelatinase activity in culture media revealed a progressive fall in gelatinase expressed on a per cell basis in media from HCG-treated cultures and this was less marked in controls. This suppression of gelatinase activity was consistent with an observed increase in production of tissue inhibitor of metalloproteinase-1 (TIMP-1) by HCG-treated cells, which was significant by days 6-8 of culture. We speculate that stabilization of the ECM may be an important aspect of HCG action in the corpus luteum.

Biochemical, histochemical and cell biological investigations on the actions of mistletoe lectins I, II and III with human breast cancer cell lines

Cytotoxicity of the mistletoe lectins I, II and III towards six human breast cancer cell lines was assessed using the Mossman assay. In addition, binding of the three mistletoe lectins to the separated membrane glycoproteins of these cell lines, the binding and uptake of these lectins into the cells in tissue culture and the binding of the lectins to histological preparations of these cell lines were analysed. The results indicate that there are quantitative differences concerning the toxicity of these three lectins towards the different cell lines. Furthermore, the lectin binding pattern in the cell lines differed. In Western blots, several membrane glycoproteins were labelled by the lectins. Our results indicate subtle differences between the three lectins with regard to the parameters mentioned above; however, the toxicity of all three lectins from mistletoe is so similar that they all seem suitable for the construction of immunotoxins.