Biosynthesis of the Sesquiterpenoid Malfilanol D in Aspergillus ustus Implies Alkyl and Hydride Migrations during the Bicyclo[5.4.0]undecane Skeleton Formation.

The great variety and fascinating complexity of terpenoid skeletons are achieved through different cyclizations catalyzed by terpene cyclases. Here, we report a sesquiterpene cyclase (MfdS) from Aspergillus ustus for the formation of malfilanol D, a member of the group of biochemically less investigated sesquiterpenes with a bicyclo[5.4.0]undecane skeleton. Feeding 13C-labeled acetates in Aspergillus nidulans with the mfdS sequence provides evidence for a C-1 to C-10 cyclization with subsequent 1,2-alkyl and 1,2-hydride shifts in the formation of the 6/7-fused rings.

Retinal vascular morphological characteristics in diabetic retinopathy: an artificial intelligence study using a transfer learning system to analyze ultra-wide field images.

AIM: To investigate the morphological characteristics of retinal vessels in patients with different severity of diabetic retinopathy (DR) and in patients with or without diabetic macular edema (DME). METHODS: The 239 eyes of DR patients and 100 eyes of healthy individuals were recruited for the study. The severity of DR patients was graded as mild, moderate and severe non-proliferative diabetic retinopathy (NPDR) according to the international clinical diabetic retinopathy (ICDR) disease severity scale classification, and retinal vascular morphology was quantitatively analyzed in ultra-wide field images using RU-net and transfer learning methods. The presence of DME was determined by optical coherence tomography (OCT), and differences in vascular morphological characteristics were compared between patients with and without DME. RESULTS: Retinal vessel segmentation using RU-net and transfer learning system had an accuracy of 99% and a Dice metric of 0.76. Compared with the healthy group, the DR group had smaller vessel angles (33.68±3.01 vs 37.78±1.60), smaller fractal dimension (Df) values (1.33±0.05 vs 1.41±0.03), less vessel density (1.12±0.44 vs 2.09±0.36) and fewer vascular branches (206.1±88.8 vs 396.5±91.3), all P<0.001. As the severity of DR increased, Df values decreased, P=0.031. No significant difference between the DME and non-DME groups were observed in vascular morphological characteristics. CONCLUSION: In this study, an artificial intelligence retinal vessel segmentation system is used with 99% accuracy, thus providing with relatively satisfactory performance in the evaluation of quantitative vascular morphology. DR patients have a tendency of vascular occlusion and dropout. The presence of DME does not compromise the integral retinal vascular pattern.

Formation of the Fungal Indole Alkaloid Speradine F Implies Multiple Nonenzymatic Oxidation Steps.

The highly oxygenated indole alkaloid speradine F (4) with a 6/5/6/5/5/5 hexacyclic skeleton was isolated from a culture of Penicillium palitans, together with its precursors ß-cyclopiazonic acid (ß-CPA, 5) and cyclopiazonic acid (CPA, 1). Gene deletion and heterologous expression led to the identification of the responsible five-gene spe cluster for the speradine skeleton formation. Precursor supply experiments proved that 1 was enzymatically converted, via 2-oxoCPA (2), to speradine A (3), which subsequently undergoes multistep nonenzymatic hydroxylations to 4.

Biosynthesis of Viridicatol in Penicillium palitans Implies a Cytochrome P450-Mediated meta Hydroxylation at a Monoalkylated Benzene Ring.

Cyclopenol (1) and viridicatol (6) with m-hydroxyl groups were isolated from a culture of Penicillium palitans. Genome mining and heterologous expression in Aspergillus nidulans led to the identification of their biosynthetic gene cluster and the cytochrome P450 enzyme VdoD responsible for the meta hydroxylation. Precursor feeding experiments into vdoD transformant proved the conversion of cyclopenin (2) to 1, which then undergoes a spontaneous or VdoA-catalyzed rearrangement to 6. A direct conversion of viridicatin (5) to 6 by VdoD was not detected.

New triterpenoids from Staphylea bumalda flower buds and their neuroprotective activity against H2O2-induced injury in vitro.

Four new acylated triterpene glycosides with aliphatic chains (4-7) as well as five known triterpenoids were isolated from the flower buds of Staphylea bumalda with bioassay guidance. Their structures were determined on the basis of spectral techniques, including IR, 1D and 2D NMR, and HR-APCI-MS. Most compounds (except 8) were isolated from S. bumalda for the first time. Additionally, the neuroprotective effects of 1 and 4-9 on suckling rat primary cultured hippocampal neurons against H2O2-induced injury were evaluated in vitro. The four new triterpenoids (4-7) showed neuroprotective effects, which increased the cell viability to over 74% at different concentrations, which was higher than the negative control (59%), while compounds 1 and 8-9 exhibited cytotoxic activity.

Characterization of E2F3a function in HepG2 liver cancer cells.

E2F3a is a transcription factor that has been shown to be overexpressed in liver cancer tissues. To characterize the function of E2F3a in hepatocellular carcinoma (HCC), effects of ectopic overexpression of E2F3a on cell cycle, apoptosis, and gene expression of HepG2 cells were studied. E2F3a significantly enhances the apoptotic rate of HepG2 cells by 33% but only has minor effects on cell proliferation. By using microarray analyses, we identified 162 target genes (160 upregulated and 2 downregulated) of the E2F3a. Differential expression of 11 genes was further confirmed by real-time PCR. Eight of these 11 genes, including XAF1, CEACAM1, STAT1, ATF3, TNFSF10, KLF6, CLDN1, and TAP1, were confirmed to be upregulated by more than twofold. Functional enrichments of differentially expressed genes retrieved 21 apoptosis-related genes and 32 transcriptional regulation-related genes. These results suggest that E2F3a induces apoptosis in HepG2 cells and plays important roles in regulating transcription. Finally, positive correlation was found between E2F3a and CEACAM1 mRNA levels in clinically well-differentiated human HCC specimens.