L-Phenylalanine ammonia-lyase (PAL) is the first enzyme in the biosynthesis of phenylpropanoid-derived plant compounds such as flavonoids, coumarins and the cell wall polymer lignin. The cell walls of grasses possess higher proportions of syringyl (S)-rich lignins and high levels of esterified coumaric acid compared with those of dicotyledonous plants, and PAL from grasses can also possess tyrosine ammonia-lyase (TAL) activity, the reason for which has remained unclear. Using phylogenetic, transcriptomic and in vitro biochemical analyses, we identified a single homotetrameric bifunctional ammonia-lyase (PTAL) among eight BdPAL enzymes in the model grass species Brachypodium distachyon. (13)C isotope labelling experiments along with BdPTAL1-downregulation in transgenic plants showed that the TAL activity of BdPTAL1 can provide nearly half of the total lignin deposited in Brachypodium, with a preference for S-lignin and wall-bound coumarate biosynthesis, indicating that PTAL function is linked to the characteristic features of grass cell walls. Furthermore, isotope dilution experiments suggest that the pathways to lignin from L-phenylalanine and L-tyrosine are distinct beyond the formation of 4-coumarate, supporting the organization of lignin synthesis enzymes in one or more metabolons.

The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions barrels of crude oil into the Gulf of Mexico. Photoinduced toxicity following coexposure to ultraviolet (UV) radiation is one mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Mahi-mahi (Coryphaena hippurus), an important fishery resource, have positively buoyant, transparent eggs. These characteristics may result in mahi-mahi embryos being at particular risk from photoinduced toxicity. The goal of this study was to determine whether exposure to ultraviolet radiation as natural sunlight enhances the toxicity of crude oil to embryonic mahi-mahi. Mahi-mahi embryos were exposed to several dilutions of water accommodated fractions (WAF) from slick oil collected during the 2010 spill and gradations of natural sunlight in a fully factorial design. Here, we report that coexposure to natural sunlight and WAF significantly reduced percent hatch in mahi-mahi embryos. Effect concentrations of PAH in WAF were within the range of surface PAH concentrations reported in the Gulf of Mexico during the Deepwater Horizon spill. These data suggest that laboratory toxicity tests that do not include UV may underestimate the toxicity of oil spills to early lifestage fish species.

N-Acylethanolamines (NAE) are fatty acid derivatives, some of which function as endocannabinoids in mammals. NAE metabolism involves common (phosphatidylethanolamines, PEs) and uncommon (N-acylphosphatidylethanolamines, NAPEs) membrane phospholipids. Here we have identified and quantified more than a hundred metabolites in the NAE/endocannabinoid pathway in mouse brain and heart tissues, including many previously unreported molecular species of NAPE. We found that brain tissue of mice lacking fatty acid amide hydrolase (FAAH −/−) had elevated PE and NAPE molecular species in addition to elevated NAEs suggesting that FAAH activity participates in the overall regulation of this pathway. This perturbation of the NAE pathway in brain was not observed in heart tissue of FAAH −/− mice indicating that metabolic regulation of the NAE pathway differs in these two organs and the metabolic enzymes that catabolize NAEs are most likely differentially distributed and / or regulated. Targeted lipidomics analysis, like that presented here, will continue to provide important insights into cellular lipid signaling networks.

Human pharmaceuticals are routinely being detected in the environment, and there is growing concern about whether these drugs could elicit effects on aquatic organisms. Regulatory paradigms have shifted accordingly, with a greater emphasis on chronic toxicity data compared with acute data. The Organisation for Economic Co-operation and Development 210 Early Life Stage Test has been proposed as a good measure of the potential for pharmaceuticals to elicit chronic toxicity. To begin building a data set regarding the early life-stage toxicity of pharmaceuticals to fish, fathead minnows (FHM) were exposed to amiodarone, carbamazepine, clozapine, dexamethasone, fenofibrate, ibuprofen, norethindrone, or verapamil. Survival and growth were used to assess chronic toxicity in FHM at 28 days posthatch. Exposure of FHM to carbamazepine, fenofibrate, and ibuprofen resulted in no significant adverse effects at the concentrations tested. FHM survival was not impacted by verapamil exposure; however, growth was significantly decreased at 600 μg/L. Dexamethasone-exposed FHM showed a significant decrease in survival at a concentration of 577 μg/L; however, growth was not impacted at the concentration tested. Norethindrone exposure resulted in a significant decrease in survival and dry weight at 14.8 and 0.74 μg/L, respectively. Exposure to amiodarone and clozapine resulted in a significant decrease in survival and a significant increase in growth at concentrations of 1020 and 30.8 μg/L, respectively. Although the effect levels derived in this study are greater then concentrations observed in the environment, these data suggest that synthetic progestins may require additional research.

In mammals, the endocannabinoid signaling pathway provides protective cellular responses to ischemia. Previous work demonstrated increases in long-chain N-acylethanolamines (NAE) in ischemia and suggested a protective role for NAE. Here, a targeted lipidomics approach was used to study comprehensive changes in the molecular composition and quantity of NAE metabolites in a rat model of controlled brain ischemia. Changes of NAE, its precursors, N-acylphosphatidylethanolamines (NAPE), major and minor phospholipids, and free fatty acids (FFA) were quantified in response to ischemia. The effect of intraperitoneal injection of N-palmitoylethanolamine (NAE 16:0) prior to ischemia on NAE metabolite and phospholipid profiles was measured. While ischemia, in general, resulted in elevated levels of N-acyl 16:0 and18:0 NAE, NAPE, and FFA species, pretreatment with NAE 16:0 reduced infarct volume, neurological behavioral deficits in rats, and FFA content in ischemic tissues. Pretreatment with NAE 16:0 did not affect the profiles of other NAE metabolites. These studies demonstrate the utility of a targeted lipidomics approach to measure complex and concomitant metabolic changes in response to ischemia. They suggest that the neuroprotective effects of exogenous NAE 16:0 and the reduction in inflammatory damage may be mediated by factors other than gross changes in brain NAE levels, such as modulation of transcriptional responses.