Project description:The botanical genus <i>Digitalis</i> is equal parts colorful, toxic, and medicinal, and its bioactive compounds have a long history of therapeutic use. However, with an extremely narrow therapeutic range, even trace amounts of <i>Digitalis</i> can cause adverse effects. Using chemical methods, the United States Food and Drug Administration traced a 1997 case of <i>Digitalis</i> toxicity to a shipment of <i>Plantago</i> (a common ingredient in dietary supplements marketed to improve digestion) contaminated with <i>Digitalis lanata</i>. With increased accessibility to next generation sequencing technology, here we ask whether this case could have been cracked rapidly using shallow genome sequencing strategies (e.g., genome skims). Using a modified implementation of the Site Identification from Short Read Sequences (SISRS) bioinformatics pipeline with whole-genome sequence data, we generated over 2 M genus-level single nucleotide polymorphisms in addition to species-informative single nucleotide polymorphisms. We simulated dietary supplement contamination by spiking low quantities (0-10%) of <i>Digitalis</i> whole-genome sequence data into a background of commonly used ingredients in products marketed for "digestive cleansing" and reliably detected Digitalis at the genus level while also discriminating between <i>Digitalis</i> species. This work serves as a roadmap for the development of novel DNA-based assays to quickly and reliably detect the presence of toxic species such as <i>Digitalis</i> in food products or dietary supplements using genomic methods and highlights the power of harnessing the entire genome to identify botanical species.
Project description:Digitalis drugs are selective inhibitors of the plasma membrane Na+/K+-ATPase. There are many studies on molecular mechanisms of digitalis interaction with purified pig kidney enzyme, with the tacit assumption that it is a good model of human kidney enzyme. However, previous studies on crude or recombinant human kidney enzymes are limited, and have not resulted in consistent findings on their digitalis sensitivities. Hence, we prepared comparably purified enzymes from human and pig kidneys and determined inhibitory constants of digoxin, ouabain, ouabagenin, bufalin, and marinobufagenin (MBG) on enzyme activity under optimal turnover conditions. We found that each compound had the same potency against the two enzymes, indicating that (i) the pig enzyme is an appropriate model of the human enzyme, and (ii) prior discrepant findings on human kidney enzymes were either due to structural differences between the natural and recombinant enzymes or because potencies were determined using binding constants of digitalis for enzymes under nonphysiological conditions. In conjunction with previous findings, our newly determined inhibitory constants of digitalis compounds for human kidney enzymes indicate that (i) of the compounds that have long been advocated to be endogenous hormones, only bufalin and MBG may act as such at kidney tubules, and (ii) beneficial effects of digoxin, the only digitalis with extensive clinical use, does not involve its inhibitory effect on renal tubular Na+/K+-ATPase.
Project description:<h4>Background</h4>Gastrointestinal cancers are characterized by a male predominance, suggesting a role of sex hormones. We hypothesized that digitalis medication, due to its estrogenic properties, decreases the risk of male-predominated gastrointestinal cancers.<h4>Results</h4>Long -term digitalis use (?2 years) was followed by decreased risk for several gastrointestinal cancers, but associations were statistically significant only for liver cancer (hazard ratio [HR]=0.40, 95% confidence interval (CI) 0.16-0.98). Short-term (<1 year) use was associated with an increased risk of esophageal squamous cell carcinoma (HR=1.79, 95% CI 1.01-3.17), colorectal cancer (HR=1.72, 95% CI 1.57-1.89), gallbladder cancer (HR=1.93, 95% CI 1.04-3.59), and pancreatic cancer (HR=1.33, 95% CI 1.00-1.76), but no such increase was found among long-term users.<h4>Methods</h4>We performed a nationwide population-based cohort study in Sweden. Participants included 156,385 individuals using digitalis and a reference group of 551,933 users of organic nitrates between 2005 and 2013, who were identified in the Swedish Prescribed Drug Register. New diagnoses of gastrointestinal cancers were identified from the Swedish Cancer Register. Hazard ratios of gastrointestinal cancers in digitalis users compared to users of organic nitrates were calculated from Cox proportional hazards regression with adjustment for sex, age, municipality of residence and comorbidity.<h4>Conclusions</h4>This study suggests a decreased risk of male-predominated gastrointestinal cancers, particularly of liver cancer, in long-term users of digitalis. Short-term use may be associated with an increased risk of esophageal squamous cell carcinoma, colorectal cancer, gallbladder cancer, and pancreatic cancer.The use of digitalis as preventive or therapeutic agents remains to be fully evaluated.
Project description:BACKGROUND:Invertebrate biominerals are characterized by their extraordinary functionality and physical properties, such as strength, stiffness and toughness that by far exceed those of the pure mineral component of such composites. This is attributed to the organic matrix, secreted by specialized cells, which pervades and envelops the mineral crystals. Despite the obvious importance of the protein fraction of the organic matrix, only few in-depth proteomic studies have been performed due to the lack of comprehensive protein sequence databases. The recent public release of the gastropod Lottia gigantea genome sequence and the associated protein sequence database provides for the first time the opportunity to do a state-of-the-art proteomic in-depth analysis of the organic matrix of a mollusc shell. RESULTS:Using three different sodium hypochlorite washing protocols before shell demineralization, a total of 569 proteins were identified in Lottia gigantea shell matrix. Of these, 311 were assembled in a consensus proteome comprising identifications contained in all proteomes irrespective of shell cleaning procedure. Some of these proteins were similar in amino acid sequence, amino acid composition, or domain structure to proteins identified previously in different bivalve or gastropod shells, such as BMSP, dermatopontin, nacrein, perlustrin, perlucin, or Pif. In addition there were dozens of previously uncharacterized proteins, many containing repeated short linear motifs or homorepeats. Such proteins may play a role in shell matrix construction or control of mineralization processes. CONCLUSIONS:The organic matrix of Lottia gigantea shells is a complex mixture of proteins comprising possible homologs of some previously characterized mollusc shell proteins, but also many novel proteins with a possible function in biomineralization as framework building blocks or as regulatory components. We hope that this data set, the most comprehensive available at present, will provide a platform for the further exploration of biomineralization processes in molluscs.
Project description:There are four isoforms of the alpha subunit (alpha1-4) and three isoforms of the beta subunit (beta1-3) of Na,K-ATPase, with distinct tissue-specific distribution and physiological functions. alpha2 is thought to play a key role in cardiac and smooth muscle contraction and be an important target of cardiac glycosides. An alpha2-selective cardiac glycoside could provide important insights into physiological and pharmacological properties of alpha2. The isoform selectivity of a large number of cardiac glycosides has been assessed utilizing alpha1beta1, alpha2beta1, and alpha3beta1 isoforms of human Na,K-ATPase expressed in Pichia pastoris and the purified detergent-soluble isoform proteins. Binding affinities of the digitalis glycosides, digoxin, beta-methyl digoxin, and digitoxin show moderate but highly significant selectivity (up to 4-fold) for alpha2/alpha3 over alpha1 (K(D) alpha1 > alpha2 = alpha3). By contrast, ouabain shows moderate selectivity ( approximately 2.5-fold) for alpha1 over alpha2 (K(D) alpha1 <or= alpha3 < alpha2). Binding affinities for the three isoforms of digoxigenin, digitoxigenin, and all other aglycones tested are indistinguishable (K(D) alpha1 = alpha3 = alpha2), showing that the sugar determines isoform selectivity. Selectivity patterns for inhibition of Na,K-ATPase activity of the purified isoform proteins are consistent with binding selectivities, modified somewhat by different affinities of K(+) ions for antagonizing cardiac glycoside binding on the three isoforms. The mechanistic insight on the role of the sugars is strongly supported by a recent structure of Na,K-ATPase with bound ouabain, which implies that aglycones of cardiac glycosides cannot discriminate between isoforms. In conclusion, several digitalis glycosides, but not ouabain, are moderately alpha2-selective. This supports a major role of alpha2 in cardiac contraction and cardiotonic effects of digitalis glycosides.