Effects of reactive oxygen species on the biosynthesis of 12 (S)-hydroxyeicosatetraenoic acid in mouse epidermal homogenate

Nature-inspired total synthesis of (-)-fusarisetin A

A concise, protecting group-free total synthesis of (-)-fusarisetin A (1) was efficiently achieved in nine steps from commercially available (S)-(-)-citronellal. The synthetic approach was inspired by our proposed biosynthesis of 1. Key transformations of our strategy include a facile construction of the decalin moiety that is produced via a stereoselective IMDA reaction and a one-pot TEMPO-induced radical cyclization/aminolysis that forms the C ring of 1. Our route is amenable to analogue synthesis for biological evaluation.

Fusarisetin A: Scalable Total Synthesis and Related Studies

Fusarisetin A (1) is a recently isolated natural product that displays an unprecedented chemical motif and remarkable bioactivities as a potent cancer migration inhibitor. We describe here our studies leading to an efficient and scalable total synthesis of 1. Essential to the strategy was the development of a new route for the formation of a trans-decalin moiety of this compound and the application of an oxidative radical cyclization (ORC) reaction that produces fusarisetin A (1) from equisetin (2) via a bio-inspired process. TEMPO-induced and metal/O(2)-promoted ORC reactions were evaluated. Biological screening in vitro confirms the reported potency of (+)-1. Importantly, ex vivo studies show that this compound is able to inhibit different types of cell migration. Moreover, the C(5) epimer of (+)-1 was also identified as a potent cancer migration inhibitor, while (-)-1 and 2 were found to be significantly less potent. The optimized synthesis is applicable on gram scale and provides a solid platform for analogue synthesis and methodical biological study.

Regulatory regions responsive to oxidative stress in the promoter of the human DNA glycosylase gene NEIL2

Reactive oxygen species (ROS) generated endogenously or from exogenous sources produce mutagenic DNA lesions. If not repaired, these lesions could lead to genomic instability and, potentially, to cancer development. NEIL2 (EC 4.2.99.18), a mammalian base excision repair (BER) protein and ortholog of the bacterial Fpg/Nei, excises oxidized DNA lesions from bubble or single-stranded structures, suggesting its involvement in transcription-coupled DNA repair. Perturbation in NEIL2 expression may, therefore, significantly impact BER capacity and promote genomic instability. To characterize the genetic and environmental factors regulating NEIL2 gene expression, we mapped the human NEIL2 transcriptional start site and partially characterized the promoter region of the gene using a luciferase reporter assay. We identified a strong positive regulatory region from nucleotide -206 to +90 and found that expression from this region was contingent on its being isolated from an adjacent strong negative regulatory region located downstream (+49 to +710 bp), suggesting that NEIL2 transcription is influenced by both these regions. We also found that oxidative stress, induced by glucose oxidase treatment, reduced the positive regulatory region expression levels, suggesting that ROS may play a significant role in regulating NEIL2 transcription. In an initial attempt to characterize the underlying mechanisms, we used in silico analysis to identify putative cis-acting binding sites for ROS-responsive transcription factors within this region and then used site-directed mutagenesis to investigate their role. A single-base change in the region encompassing nucleotides -206 to +90 abolished the effect of oxidative stress that was observed in the absence of the mutation. Our study is the first to provide an initial partial characterization of the NEIL2 promoter and opens the door for future research aimed at understanding the role of genetic and environmental factors in regulating NEIL2 expression.

Acute aspirin treatment abolishes, whereas acute ibuprofen treatment enhances morphine-induced cardioprotection: role of 12-lipoxygenase

Patients suffering an acute myocardial infarction routinely receive morphine and nonsteroidal anti-inflammatory drugs (NSAIDs) alone or in combination. However, the importance of the dose, timing, or the combined administration of both on infarct size reduction has not been assessed. Additionally, it is not known whether morphine or NSAIDs require 12-lipoxygenase (12-LO) to mediate infarct size reduction as found previously for ischemic preconditioning. Male Sprague-Dawley rats were subjected to 30 min of ischemia and 2 h of reperfusion, followed by infarct size assessment (mean +/- S.E.M.%, **P < 0.01). Morphine (0.3 mg/kg), ibuprofen (3 mg/kg), but not aspirin (3 mg/kg) reduced infarct size when administered 5 min before reperfusion compared with vehicle (42.3 +/- 1.5**, 40.8 +/- 2.8**, 60.7 +/- 2.3 versus 59.1 +/- 1.7%, respectively); however, none of these agents reduced infarct size when administered 10 s after reperfusion. Ibuprofen (3 mg/kg) administered with morphine (0.3 mg/kg) reduced infarct size (43.7 +/- 1.3%**), whereas aspirin (1 and 3 mg/kg) abolished morphine-induced infarct size reduction. Morphine (0.2 mg/kg) and ibuprofen (0.6 mg/kg) given at doses not effective individually reduced infarct size when given together (59.0 +/- 1.4, 57.6 +/- 2.8, and 43.9 +/- 1.6%**, respectively). Morphine- and ibuprofen-induced infarct size reduction was abolished by the 12-LO inhibitor baicalein (3 mg/kg) and mimicked by the 12-LO metabolite 12-(S)-hydroxyeicosa-5Z,8Z,10Z,14Z-tetraenoic acid (45.2 +/- 2.5%**). These data suggest that morphine and ibuprofen reduce infarct size individually or at subthreshold doses in combination by 12-LO when administered 5 min before reperfusion. Furthermore, acute aspirin administration has a detrimental interaction with morphine that abrogates morphine-induced infarct size reduction.

Changes in the fatty acid composition and hydroxyproline content in rat lung in relation to collagen synthesis after paraquat administration

OBJECTIVES

Effect of paraquat on the fatty acid composition (weight percentage) of rat lung was studied with particular reference to the change of hydroxyproline content in the course of paraquat-induced dysfunction and subsequent repair.

METHODS

Eight-week-old male Wistar rats were administered paraquat at 20 mg/kg body weight subcutaneously, and the wet weight, hydroxyproline content and fatty acid composition of lungs of each group rats were analyzed at 2, 7, 14 or 28 days after treatment, respectively.

RESULTS

The percentage of palmitic acid (C16:0), arachidonic acid (C20:4) and docosahexaenoic acid (C22:6) significantly increased, and the percentage of oleic acid (C18:1) and the ratio of monounsaturated fatty acids/saturated fatty acids (M/S) significantly decreased comparing to control on day 28 after paraquat administration. The time-course of each fatty acid was observed for 28 days after paraquat administration. M/S ratio decreased after paraquat administration up to the 28th day, but the polyunsaturated fatty acids/saturated fatty acids (P/S) ratio decreased during the first 7 days, followed by a increase, and then reached higher level than the 0 day control at the 28th day. Hydroxyproline also increased between the 14th and the 28th days. Eicosapentaenoic acid (C20:5) had once increased during the first 2 days and decreased gradually, while C20:4 maintained high level in this period. C22:6 increased after paraquat administration and maintained high level up to the 28th day. This result indicated that desaturation and elongation in n-3 series fatty acids were accelerated after paraquat treatment, and consequently C20:5 was rapidly converted into C22:6 and decreased.

CONCLUSIONS

Paraquat might cause elevation of unsaturated fatty acids, espe- cially C20:4 but not C20:5 by the stimulation of the fatty acid desaturase system, and could consequently stimulate local collagen synthesis by C20:4 metabolites in the healing stage.

Lichen metabolites. 1. Inhibitory action against leukotriene B4 biosynthesis by a non-redox mechanism

Of several lichen metabolites isolated from Parmelia nepalensis and Parmelia tinctorum, the didepsides atranorin (4) and diffractaic acid (5), as well as (+)-protolichesterinic acid (7), inhibited LTB4 biosynthesis in polymorphonuclear leukocytes. Ethyl hematommate (3) and (+)-usnic acid (1) were only weak inhibitors, while methyl beta-orcinolcarboxylate (2) and gyrophoric acid (6) were inactive at concentrations up to 60 microM. Redox properties of the compounds were evaluated in terms of inhibition of nonenzymatic lipid peroxidation in model membranes, reactivity against the stable free radical 2,2-diphenyl-1-picrylhydrazyl, and deoxyribose degradation as a measure of hydroxyl-radical generation. The results revealed that lichen metabolites neither acted as antioxidants against the peroxidation process in model membranes nor did they scavenge or produce free radicals, suggesting that the inhibitory effects on LTB4 biosynthesis was due to specific enzyme interaction rather than a nonspecific redox mechanism.