Circulating P-, L- and E-selectins in pseudoxanthoma elasticum patients

Weighted mutual information analysis substantially improves domain-based functional network models

Motivation: Functional protein–protein interaction (PPI) networks elucidate molecular pathways underlying complex phenotypes, including those of human diseases. Extrapolation of domain–domain interactions (DDIs) from known PPIs is a major domain-based method for inferring functional PPI networks. However, the protein domain is a functional unit of the protein. Therefore, we should be able to effectively infer functional interactions between proteins based on the co-occurrence of domains.

Results: Here, we present a method for inferring accurate functional PPIs based on the similarity of domain composition between proteins by weighted mutual information (MI) that assigned different weights to the domains based on their genome-wide frequencies. Weighted MI outperforms other domain-based network inference methods and is highly predictive for pathways as well as phenotypes. A genome-scale human functional network determined by our method reveals numerous communities that are significantly associated with known pathways and diseases. Domain-based functional networks may, therefore, have potential applications in mapping domain-to-pathway or domain-to-phenotype associations.

Availability and Implementation: Source code for calculating weighted mutual information based on the domain profile matrix is available from www.netbiolab.org/w/WMI.

Contact:Insuklee@yonsei.ac.kr

Supplementary information:Supplementary data are available at Bioinformatics online.

Chronic kidney disease results in deficiency of ABCC6, the novel inhibitor of vascular calcification

BACKGROUND

Chronic kidney disease (CKD) is associated with arterial medial calcification which plays a major role in the pathogenesis of cardiovascular disease in this population. Several factors are known to promote soft tissue and accelerated arterial calcification in CKD including systemic inflammation, altered calcium and phosphate homeostasis, hypertension, and deficiency of endogenous calcification inhibitors. The ABCC6 transporter (ATP-binding cassette subfamily C number 6), also known as multidrug resistance-associated protein 6 (MRP6), is highly expressed in the liver and kidney. Mutation of ABCC6 results in pseudoxanthoma elasticum, an inherited disorder characterized by arterial and soft tissue calcification. Given the prevalence of arterial medial calcification in CKD, the present study was undertaken to test the hypothesis that CKD may lead to acquired ABCC6 deficiency.

METHODS

CKD was induced via 5/6 nephrectomy in male Sprague-Dawley rats and by adenine-containing diet to cause chronic interstitial nephropathy in female DBA/2J mice. Sham-operated rats and mice fed regular diet served as controls. Liver and kidney tissues were harvested and processed for ABCC6 protein and mRNA analysis.

RESULTS

ABCC6 protein levels were significantly reduced in the liver and kidney tissues from CKD rats and mice. However, ABCC6 mRNA levels were unchanged, pointing to post-transcriptional or post-translational mechanisms for the observed ABCC6 deficiency. Additionally, plasma levels of the calcification inhibitor fetuin-A were significantly decreased in CKD animals compared to controls.

CONCLUSIONS

CKD results in acquired ABCC6 transporter deficiency. To our knowledge this abnormality has not been previously reported and may contribute to CKD-associated vascular and soft tissue calcification.

Fibroblast involvement in soft connective tissue calcification

Soft connective tissue calcification is not a passive process, but the consequence of metabolic changes of local mesenchymal cells that, depending on both genetic and environmental factors, alter the balance between pro- and anti-calcifying pathways. While the role of smooth muscle cells and pericytes in ectopic calcifications has been widely investigated, the involvement of fibroblasts is still elusive. Fibroblasts isolated from the dermis of pseudoxanthoma elasticum (PXE) patients and of patients exhibiting PXE-like clinical and histopathological findings offer an attractive model to investigate the mechanisms leading to the precipitation of mineral deposits within elastic fibers and to explore the influence of the genetic background and of the extracellular environment on fibroblast-associated calcifications, thus improving the knowledge on the role of mesenchymal cells on pathologic mineralization.

The vascular phenotype in Pseudoxanthoma elasticum and related disorders: contribution of a genetic disease to the understanding of vascular calcification

Vascular calcification is a complex and dynamic process occurring in various physiological conditions such as aging and exercise or in acquired metabolic disorders like diabetes or chronic renal insufficiency. Arterial calcifications are also observed in several genetic diseases revealing the important role of unbalanced or defective anti- or pro-calcifying factors. Pseudoxanthoma elasticum (PXE) is an inherited disease (OMIM 264800) characterized by elastic fiber fragmentation and calcification in various soft conjunctive tissues including the skin, eyes, and arterial media. The PXE disease results from mutations in the ABCC6 gene, encoding an ATP-binding cassette transporter primarily expressed in the liver, kidneys suggesting that it is a prototypic metabolic soft-tissue calcifying disease of genetic origin. The clinical expression of the PXE arterial disease is characterized by an increased risk for coronary (myocardial infarction), cerebral (aneurysm and stroke), and lower limb peripheral artery disease. However, the structural and functional changes in the arterial wall induced by PXE are still unexplained. The use of a recombinant mouse model inactivated for the Abcc6 gene is an important tool for the understanding of the PXE pathophysiology although the vascular impact in this model remains limited to date. Overlapping of the PXE phenotype with other inherited calcifying diseases could bring important informations to our comprehension of the PXE disease.

Selectins and Associated Adhesion Proteins in Inflammatory disorders

Inflammation is defined as the normal response of living tissue to injury or infection. It is important to emphasize two components of this definition. First, that inflammation is a normal response and, as such, is expected to occur when tissue is damaged. Infact, if injured tissue does not exhibit signs of inflammation this would be considered abnormal and wounds and infections would never heal without inflammation. Secondly, inflammation occurs in living tissue, hence there is need for an adequate blood supply to the tissues in order to exhibit an inflammatory response. The inflammatory response may be triggered by mechanical injury, chemical toxins, and invasion by microorganisms, and hypersensitivity reactions. Three major events occur during the inflammatory response: the blood supply to the affected area is increased substantially, capillary permeability is increased, and leucocytes migrate from the capillary vessels into the surrounding interstitial spaces to the site of inflammation or injury. The inflammatory response represents a complex biological and biochemical process involving cells of the immune system and a plethora of biological mediators. Cell-to-cell communication molecules such as cytokines play an extremely important role in mediating the process of inflammation. Inflammation and platelet activation are critical phenomena in the setting of acute coronary syndromes. An extensive exposition of this complex phenomenon is beyond the scope of this article (Rankin 2004).

Expression and clinical significance of hepaCAM and VEGF in urothelial carcinoma

PURPOSE

Investigate the expression of hepatocyte cell adhesion molecule (hepaCAM) and vascular endothelial growth factor (VEGF) mRNA in 55 cases of urothelial carcinoma to examine the potential relationship between hepaCAM and VEGF in urothelial carcinoma.

METHODS

Expression of hepaCAM and VEGF gene was determined by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) in 55 paired urothelial carcinoma specimens. T24 cells stably expressing hepaCAM gene were established by Lipofectamine 2000. RT-PCR and western blot analysis were used to detect gene and protein expression of hepaCAM and VEGF before and after transfection. MTT test was used to detect the effect of hepaCAM gene on the cell proliferation.

RESULTS

RT-PCR showed that hepaCAM expression level was significantly lower, and VEGF was significantly higher in urothelial carcinoma tissues than in adjacent tissues (P < 0.05, P < 0.05). hepaCAM and VEGF were strongly correlated with tumor stage (P < 0.05, P < 0.05). Spearman correlation analysis showed lower hepaCAM level was associated with higher VEGF level (r = -0.277 P = 0.041). Experiments with T24 cells in vitro demonstrated the expression of VEGF mRNA and protein were significantly decreased after transfection of hepaCAM gene (P < 0.05, P < 0.05). Expression of hepaCAM resulted in a significant inhibition of T24 cells proliferation (P < 0.05).

CONCLUSION

There is a close relationship between hepaCAM and VEGF in urothelial carcinoma. hepaCAM may be defined as a new target for diagnosis and anticancer therapy.

Elevated serum levels of intercellular adhesion molecule ICAM-1 in Pseudoxanthoma elasticum

BACKGROUND

Pseudoxanthoma elasticum (PXE, OMIM 177850 and 264800) is a rare heritable disorder predominantly affecting the skin, the eyes and the vascular system. The disease is caused by mutations in the ABCC6 gene and is characterized by calcification and extracellular matrix remodeling, including alterations of the vessel walls. Here, we investigated the cell adhesion molecules ICAM-1 in PXE patients.

METHODS

Soluble ICAM-1 was determined in 58 non-consanguineous PXE patients by quantitative sandwich enzyme immunoassay. The allelic frequencies of the ICAM-1 variant p.K469E were analyzed in patients and age- and sex-matched controls.

RESULTS

Soluble ICAM-1 levels were significantly elevated in male and female PXE patients (p<0.02 and p<0.001, respectively). In addition, the ICAM-1 concentration correlated with the ABCC6 gene status of the PXE patients. The ICAM variant p.K469E genotypes were not different in PXE patients and age- and sex-matched controls.

CONCLUSIONS

Our data show for the first time increased ICAM-1 concentrations in PXE patients, potentially due to the chronic oxidative stress and elevated protease activity followed by extracellular matrix remodeling which have been previously observed in PXE patients.