Environmental epigenetics: prospects for studying epigenetic mediation of exposure–response relationships

Changes in epigenetic marks such as DNA methylation and histone acetylation are associated with a broad range of disease traits, including cancer, asthma, metabolic disorders, and various reproductive conditions. It seems plausible that changes in epigenetic state may be induced by environmental exposures such as malnutrition, tobacco smoke, air pollutants, metals, organic chemicals, other sources of oxidative stress, and the microbiome, particularly if the exposure occurs during key periods of development. Thus, epigenetic changes could represent an important pathway by which environmental factors influence disease risks, both within individuals and across generations. We discuss some of the challenges in studying epigenetic mediation of pathogenesis and describe some unique opportunities for exploring these phenomena.     

Hepatic protein kinase C: translocation stimulated by prolactin and partial hepatectomy

Prolactin stimulates a hepatotrophic response similar to that caused by phorbol esters or partial hepatectomy in rats. Since phorbol esters, which activate protein kinase C, mimic prolactin action in liver, the relationship between prolactin administration and subsequent hepatic protein kinase C translocation was assessed. Prolactin administration rapidly stimulated a 4-fold elevation of membrane protein kinase C activity. The effect of prolactin on hepatic protein kinase C was specific for lactogenic hormones but could be duplicated by phorbol esters. Further, an increase in serum prolactin was demonstrated subsequent to partial hepatectomy and preceding hepatic protein kinase C translocation. Therefore, translocation of hepatic protein kinase C appears important for hepatic proliferation in response to prolactin administration and to partial hepatectomy.     

Stem cells are units of natural selection in a colonial ascidian

Stem cells are highly conserved biological units of development and regeneration. Here we formally demonstrate that stem cell lineages are also legitimate units of natural selection. In a colonial ascidian, Botryllus schlosseri, vascular fusion between genetically distinct individuals results in cellular parasitism of somatic tissues, gametes, or both. We show that genetic hierarchies of somatic and gametic parasitism following fusion can be replicated by transplanting cells between colonies. We prospectively isolate a population of multipotent, self-renewing stem cells that retain their competitive phenotype upon transplantation. Their single-cell contribution to either somatic or germline fates, but not to both, is consistent with separate lineages of somatic and germline stem cells or pluripotent stem cells that differentiate according to the niche in which they land. Since fusion is restricted to individuals that share a fusion/histocompatibility allele, these data suggest that histocompatibility genes in Botryllus evolved to protect the body from parasitic stem cells usurping asexual or sexual inheritance.     

Potent pyrimidinetrione-based inhibitors of MMP-13 with enhanced selectivity over MMP-14

Through the use of computational modeling, a series of pyrimidinetrione-based inhibitors of MMP-13 was designed based on a lead inhibitor identified through file screening. Incorporation of a biaryl ether moiety at the C-5 position of the pyrimidinetrione ring resulted in a dramatic enhancement of MMP-13 potency. Protein crystallography revealed that this moiety binds in the S(1)(') pocket of the enzyme. Optimization of the C-4 substituent of the terminal aromatic ring led to incorporation of selectivity versus MMP-14 (MT-1 MMP). Structure activity relationships of the biaryl ether substituent are presented as is pharmacokinetic data for a compound that meets our in vitro potency and selectivity goals.     

Carotid artery stenting: update

"Extracranial carotid artery stenosis is responsible for approximately 20-30% of ischemic strokes. Traditionally, carotid artery stenosis has been treated with carotid endarterectomy. However, the low periprocedural complication rate and the mid term durability of carotid artery stenting has made it a competitive alternative treatment strategy. This update reviews the technical aspects of carotid artery stenting, clinical data supporting carotid artery stenting-particularly in high risk patients, and the complications associated with carotid artery stenting."     

Rat epidermal keratinocytes as an organotypic model for examining the role of Cx43 and Cx26 in skin differentiation

In order to characterize connexin expression and regulation in the epidermis, we have characterized a rat epidermal keratinocyte (REK) cell line that is phenotypically similar to basal keratinocytes in that they have the ability to differentiate into organotypic epidermis consisting of a basal cell layer, 2-3 suprabasal cell layers, and a cornified layer. RT-PCR revealed that REK cells express mRNA for Cx26, Cx31, Cx31.1, Cx37, and Cx43, which mimics the reported connexin profile for rat tissue. In addition, we report the expression of Cx30, Cx30.3, Cx40, and Cx45 in rat keratinocytes, highlighting the complexity of the connexin complement in rat epidermis. Furthermore, 3-dimensional analysis of organotypic skin revealed that Cx26 and Cx43 are exquisitely regulated during the differentiation process. The life-cycle of these connexins including their expression, transport, assembly into gap junctions, internalization, and degradation are elegantly depicted in organotypic epidermis as keratinocytes proceed from differentiation to programmed cell death.     

Cyclodextrin-polyethylenimine conjugates for targeted in vitro gene delivery

Many human gene therapies will require cell-specific targeting. Though recombinant viruses are much more efficient than nonviral vectors, the latter, especially polymers, have the advantage of being targetable via conjugation of cell-specific ligands, including sugars, peptides, and antibodies, which can be covalently attached to the polymer using a variety of chemistries. Cyclodextrin, which forms inclusion complexes with small hydrophobic molecules, has been incorporated into a gene-delivery polymer and may provide a facile and versatile attachment site for targeting ligands. Polyethylenimine (PEI) was derivatized with beta-cyclodextrin on approximately 10% of the polymer's amines (termed CD-PEI). Human insulin was also derivatized with a hydrophobic palmitate group (pal-HI), which could anchor the protein to CD-PEI/DNA polyplexes. CD-PEI was essentially nontoxic to HEK293 cells at concentrations optimal for gene delivery and mediated nearly 4-fold higher gene expression than unmodified PEI, which is relatively toxic to these cells. More importantly, addition of the pal-HI to CD-PEI enhanced gene expression by more than an order of magnitude compared to unmodified PEI, either with or without the pal-HI. Because of the relative ease with which CD-binding moieties may be attached to various types of ligands, CD-PEI may be a generally useful material for testing novel cell-specific targeting compounds.     

Expression of estrogen receptor beta in prostate carcinoma cells inhibits invasion and proliferation and triggers apoptosis

The involvement of estrogen receptor beta (ERbeta) in prostate carcinogenesis has been hypothesized. Several reports have shown that ERbeta expression was decreased when prostate cells undergo neoplastic transformation, suggesting that it could play a tumor-suppressor role. By restoring ERbeta expression in prostatic carcinoma cells by adenoviral delivery, we aimed to test this hypothesis. We observed that ERbeta strongly inhibited the invasiveness and the growth of these cells. In addition, ERbeta cells were undergoing apoptosis, as shown by quantification of Bax, poly(ADP-ribose) polymerase and caspase-3 expression. Our data suggest that ERbeta acts as a tumor-suppressor by its anti-proliferative, anti-invasive and pro-apoptotic properties.