The Th2 cell-dependent inflammatory response is a central component of asthma, and the ways in which it is regulated is a critical question. The cysteinyl leukotrienes (cys-LTs) are 5-lipoxygenase pathway products implicated in asthma, in particular, by their function as smooth muscle constrictors of airways and microvasculature. To elucidate additional roles for cys-LTs in the pathobiology of pulmonary inflammation, we used an OVA sensitization and challenge protocol with mice lacking leukotriene C4 synthase (LTC4S), the terminal enzyme for cys-LT generation. Ag-induced pulmonary inflammation, characterized by eosinophil infiltration, goblet cell hyperplasia with mucus hypersecretion, and accumulation and activation of intraepithelial mast cells was markedly reduced in LTC4Snull mice. Furthermore, Ag-specific IgE and IgG1 in serum, Th2 cell cytokine mRNA expression in the lung, and airway hyperresponsiveness to methacholine were significantly reduced in LTC4Snull mice compared with wild-type controls. Finally, the number of parabronchial lymph node cells from sensitized LTC4Snull mice and their capacity to generate Th2 cell cytokines ex vivo after restimulation with Ag were also significantly reduced. In contrast, delayed-type cutaneous hypersensitivity, a prototypic Th1 cell-dependent response, was intact in LTC4Snull mice. These findings provide direct evidence of a role for cys-LTs in regulating the initiation and/or amplification of Th2 cell-dependent pulmonary inflammation.

BackgroundAnthocyanins are a class of brightly colored, glycosylated flavonoid pigments that imbue their flower and fruit host tissues with hues of predominantly red, orange, purple, and blue. Although all anthocyanins exhibit pH-responsive photochemical changes, distinct structural decorations on the core anthocyanin skeleton also cause dramatic color shifts, in addition to improved stabilities and unique pharmacological properties. In this work, we report for the first time the extension of the reconstituted plant anthocyanin pathway from (+)-catechin to O-methylated anthocyanins in a microbial production system, an effort which requires simultaneous co-option of the endogenous metabolites UDP-glucose and S-adenosyl-l-methionine (SAM or AdoMet).ResultsAnthocyanin O-methyltransferase (AOMT) orthologs from various plant sources were co-expressed in Escherichia coli with Petunia hybrida anthocyanidin synthase (PhANS) and Arabidopsis thaliana anthocyanidin 3-O-glucosyltransferase (At3GT). Vitis vinifera AOMT (VvAOMT1) and fragrant cyclamen ‘Kaori-no-mai’ AOMT (CkmOMT2) were found to be the most effective AOMTs for production of the 3′-O-methylated product peonidin 3-O-glucoside (P3G), attaining the highest titers at 2.4 and 2.7 mg/L, respectively. Following modulation of plasmid copy number and optimization of VvAOMT1 and CkmOMT2 expression conditions, production was further improved to 23 mg/L using VvAOMT1. Finally, CRISPRi was utilized to silence the transcriptional repressor MetJ in order to deregulate the methionine biosynthetic pathway and improve SAM availability for O-methylation of cyanidin 3-O-glucoside (C3G), the biosynthetic precursor to P3G. MetJ repression led to a final titer of 51 mg/L (56 mg/L upon scale-up to shake flask), representing a twofold improvement over the non-targeting CRISPRi control strain and 21-fold improvement overall.ConclusionsAn E. coli strain was engineered for production of the specialty anthocyanin P3G using the abundant and comparatively inexpensive flavonol precursor, (+)-catechin. Furthermore, dCas9-mediated transcriptional repression of metJ alleviated a limiting SAM pool size, enhancing titers of the methylated anthocyanin product. While microbial production of P3G and other O-methylated anthocyanin pigments will likely be valuable to the food industry as natural food and beverage colorants, we expect that the strain constructed here will also prove useful to the ornamental plant industry as a platform for evaluating putative anthocyanin O-methyltransferases in pursuit of bespoke flower pigment compositions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0623-3) contains supplementary material, which is available to authorized users.

Robust gene circuit construction requires use of promoters exhibiting low crosstalk. Orthogonal promoters have been engineered utilizing an assortment of natural and synthetic transcription factors, but design of large orthogonal promoter-repressor sets is complicated, labor-intensive, and often results in unanticipated crosstalk. The specificity and ease of targeting the RNA-guided DNA-binding protein dCas9 to any 20 bp user-defined DNA sequence makes it a promising candidate for orthogonal promoter regulation. Here, we rapidly construct orthogonal variants of the classic T7-lac promoter using site-directed mutagenesis, generating a panel of inducible hybrid promoters regulated by both LacI and dCas9. Remarkably, orthogonality is mediated by only two to three nucleotide mismatches in a narrow window of the RNA:DNA hybrid, neighboring the protospacer adjacent motif. We demonstrate that, contrary to many reports, one PAM-proximal mismatch is insufficient to abolish dCas9-mediated repression, and we show for the first time that mismatch tolerance is a function of target copy number. Finally, these promoters were incorporated into the branched violacein biosynthetic pathway as dCas9-dependent switches capable of throttling and selectively redirecting carbon flux in Escherichia coli. We anticipate this strategy is relevant for any promoter and will be adopted for many applications at the interface of synthetic biology and metabolic engineering.

Normal erectile physiology is heavily dependent on a delicate balance between the effects of endogenous vasoconstricting and vasorelaxing hormones on the tone of the corporal smooth muscle. Recent studies indicate that endothelin-1 (ET-1) is present and physiologically active in the human corpora. The primary goal of the present investigation was to further define the role of ET-1 in corporal physiology and to ascertain whether it might play a role in augmenting corporal tone in vivo, as reported in other vascular tissues. Thus, we conducted pharmacological studies of ET-1-induced steady-state contractions in isolated human corporal smooth muscle strips to determine if there were any detectable age- or diabetes-related alterations in ET-1-induced contractions. For statistical analysis, the patient population was divided into 2 age groups, A (< or = 59 years of age; = 11 patients) and B (> or = 60 years of age; n = 7 patients), and further subdivided into 2 diagnostic categories, diabetic (n = 7 patients) and nondiabetic (n = 11 patients). Construction of cumulative concentration response curves (CRCs) for ET-1-induced contractions revealed characteristically slow onset and long-lasting responses. Endothelin-1 CRC data were computer fit to the logistic equation to derive Emax (calculated maximal response), pEC50 (negative logarithm of the concentration that elicits one-half of the calculated maximal response) and slope factor (n) values. Two-factor analysis of variance revealed no detectable age- or diabetes-related alterations, nor any age-diabetes interaction in any of the logistic parameters. Furthermore, logistic analysis of ET-1 CRC data on 14 isolated corporal tissue strips derived from 3 potent patients with documented spontaneous erections revealed no differences in ET-1 contractility from that observed for patients with organic erectile dysfunction. Importantly, despite an apparent absence of age- or diabetes-related alterations in ET-1-induced steady-state contractions, preliminary studies demonstrated that coadministration of the alpha 1-adrenergic agonist phenylephrine and ET-1 produce much greater contractile responses than those observed in the presence of phenylephrine (PE) alone. Moreover, the magnitude of the augmentation was precisely that predicted by a model for simple additivity of agonist effects. Such observations suggest that the physiological relevance of ET-1 to corporal physiology may be related to its ability to augment the contractile responses of other vasomodulators present in the human corpora, in particular, perhaps modulating the contractile responses to sympathetic activity.