Recent advances on the regulation of bacterial biofilm formation by herbal medicines.

Biofilm formation is a fundamental part of life cycles of bacteria which affects various aspects of bacterial-host interactions including the development of drug resistance and chronic infections. In clinical settings, biofilm-related infections are becoming increasingly difficult to treat due to tolerance to antibiotics. Bacterial biofilm formation is regulated by different external and internal factors, among which quorum sensing (QS) signals and nucleotide-based second messengers play important roles. In recent years, different kinds of anti-biofilm agents have been discovered, among which are the Chinese herbal medicines (CHMs). CHMs or traditional Chinese medicines have long been utilized to combat various diseases around the world and many of them have the ability to inhibit, impair or decrease bacterial biofilm formation either through regulation of bacterial QS system or nucleotide-based second messengers. In this review, we describe the research progresses of different chemical classes of CHMs on the regulation of bacterial biofilm formation. Though the molecular mechanisms on the regulation of bacterial biofilm formation by CHMs have not been fully understood and there are still a lot of work that need to be performed, these studies contribute to the development of effective biofilm inhibitors and will provide a novel treatment strategy to control biofilm-related infections.

Precision Medicine for Heritable Skin Diseases-The Paradigm of Epidermolysis Bullosa.

The 2016 JID Beijing Workshop, held in the context of the 5th National Congress of Investigative Dermatology of the Chinese Society of Dermatology, had the thematic focus on "Precision Medicine in Dermatology." This theme was extremely timely, yet forward-looking, due to the fact that precision medicine is one of the fastest growing paradigms of contemporary medicine (Box 1).

Premature termination codon read-through in the ABCC6 gene: potential treatment for pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder manifesting with ectopic connective tissue mineralization, caused by mutations in the ABCC6 gene, with ~35% of all mutations being premature termination mutations. In this study, we investigated the therapeutic potential of the nonsense codon read-through-inducing drug, PTC124, in treating PXE. The ability of this drug to facilitate read-through of nonsense mutations was examined in HEK293 cells transfected with human ABCC6 expression constructs harboring seven different PXE-associated nonsense mutations, and was evaluated by immunofluorescence and In-Cell ELISA. Our data demonstrated that PTC124 did not exhibit cytotoxicity in concentrations up to 20 µg ml(-1), and the facilitated read-through varied not only with dose but also with sequence context. Considering the redundancy of the genetic code, it was postulated that in case of the most common recurrent nonsense mutation, p.R1141X, the read-through may result in substitution of the arginine 1,141 by glycine, tryptophan, or cysteine. Their potential pathogenicity was tested in a recently developed zebrafish messenger RNA (mRNA) rescue assay, and demonstrated that all three mRNA transcripts were able to rescue abcc6a morpholino-induced phenotype of zebrafish. Thus, our results suggest that read-through of nonsense mutations in ABCC6 by PTC124 may have potential for pharmacologic treatment of PXE.

Overexpression of fetuin-a counteracts ectopic mineralization in a mouse model of pseudoxanthoma elasticum (abcc6(-/-)).

The pathologic hallmark of pseudoxanthoma elasticum (PXE) is ectopic mineralization of soft connective tissues. Recent studies have suggested that PXE is a metabolic disease, and perturbations in a number of circulatory factors have been postulated. One of them is fetuin-A, a 60-kDa glycoprotein synthesized in the liver and secreted into blood. Observations in targeted mutant mice (Ahsg(-/-)) and in cell culture model systems have shown that fetuin-A is a powerful anti-mineralization factor in circulation, and the serum levels of fetuin-A in patients with PXE as well as in a mouse model of PXE (Abcc6(-/-)) have been shown to be reduced by up to 30%. In this study, we tested the hypothesis that overexpression of fetuin-A in Abcc6(-/-) mice counteracts the ectopic mineralization. Delivery of an expression construct containing full-length mouse fetuin-A complementary DNA (cDNA), linked to a His-tag, to the liver of these mice resulted in elevated serum levels of this protein. As a consequence, soft tissue mineralization, which is a characteristic of Abcc6(-/-) mice, was reduced by approximately 70% at 12 weeks of age, but the effect was transient when examined 4 weeks later. The results suggest that normalization of serum fetuin-A, either through gene therapy approaches or by direct protein delivery to the circulation, may offer strategies for treating PXE and perhaps other heritable disorders of soft tissue mineralization.

Elevated dietary magnesium prevents connective tissue mineralization in a mouse model of pseudoxanthoma elasticum (Abcc6(-/-)).

Pseudoxanthoma elasticum (PXE) is an autosomal recessive multisystem disorder characterized by ectopic connective tissue mineralization, with clinical manifestations primarily in the skin, eyes, and cardiovascular system. There is considerable, both intra- and interfamilial, variability in the spectrum of phenotypic presentation. Previous studies have suggested that mineral content of the diet may modify the severity of the clinical phenotype in PXE. In this study, we utilized a targeted mutant mouse (Abcc6(-/-)) as a model system for PXE. We examined the effects of changes in dietary phosphate and magnesium on the mineralization process using calcification of the connective tissue capsule surrounding the vibrissae as an early phenotypic biomarker. Mice placed on custom-designed diets either high or low in phosphate did not show changes in mineralization, which was similar to that noted in Abcc6(-/-) mice on control diet. However, mice placed on diet enriched in magnesium (fivefold) showed no evidence of connective tissue mineralization in this mouse model of PXE. The inhibitory capacity of magnesium was confirmed in a cell-based mineralization assay system in vitro. Collectively, our observations suggest that assessment of dietary magnesium in patients with PXE may be warranted.

Pseudoxanthoma elasticum: oxidative stress and antioxidant diet in a mouse model (Abcc6-/-).

Pseudoxanthoma elasticum (PXE), a multisystem disorder characterized by ectopic mineralization of soft connective tissues, is caused by mutations in the ABCC6 gene. The pathomechanistic details of the mineralization process are largely unknown, but oxidative stress has been suggested to play a role. In this study, we tested Abcc6(-/-) mice, which serve as a model of PXE, for markers of the oxidative stress in the liver and serum. The total antioxidant capacity as well as markers of protein oxidation and lipid peroxidation suggested the presence of chronic oxidative stress. Feeding these mice for 5 months with a diet supplemented with antioxidants (vitamins C and E, selenium, and N-acetylcysteine) countered the oxidative stress but did not modify the ectopic mineralization process. These results suggest that the Abcc6(-/-) mice suffer from chronic oxidative stress but this does not contribute to connective tissue mineralization, the hallmark of PXE.

Ectopic mineralization of connective tissue in Abcc6-/- mice: effects of dietary modifications and a phosphate binder--a preliminary study.

Pseudoxanthoma elasticum (PXE), a heritable multisystem disorder, is caused by mutations in the ABCC6 gene. We have developed a murine model for PXE by targeted inactivation of the corresponding mouse gene. A feature of this mouse model is ectopic mineralization of connective tissue capsule surrounding the bulb of vibrissae. This study was designed to investigate the effect of dietary sevelamer hydrochloride (Renagel), a phosphate binder, and specific mineral modifications on ectopic mineralization of connective tissue in Abcc6-/- mice. Three groups were fed a specific diet: (i) a standard rodent diet, (ii) a standard rodent diet supplemented with sevelamer hydrochloride, and (iii) a custom experimental diet with specific mineral modifications (high phosphorus, low calcium and low magnesium). The degree of mineralization was determined in hematoxylin-eosin-stained sections using computerized morphometric analysis and by chemical assays to measure the calcium and phosphorus content of the vibrissae. The results indicated increased mineralization in the Abcc6-/- mice fed a standard diet or a diet with mineral modifications as compared with control mice fed a standard diet. However, feeding Abcc6-/- mice with diet supplemented with sevelamer hydrochloride did not improve mineralization, in comparison to mice fed with normal diet. Collectively, these results suggest that the mineralization process in PXE may be exacerbated by changes in mineral intake. The role of dietary minerals, and phosphorus in particular, as well as that of phosphate binders, in ectopic mineralization of PXE, merits further investigation.