4-Hydroxy Pyridones from Heterologous Expression and Cultivation of the Native Host.

4-Hydroxy pyridones are a class of fungi-derived polyketide-nonribosomal peptide products featuring a core of 4-hydroxy-2-pyridone which have a wide range of biological activities. Genome mining of in-house strains using polyketide synthase-nonribosomal peptide synthase as a query identified an endophyte Tolypocladium sp. 49Y, which possesses a potential 4-hydroxy pyridone biosynthetic gene cluster. Heterologous expression in Aspergillus oryzae NSAR1 revealed that this gene cluster is functional and able to produce a rare type of 4-hydroxy pyridones called tolypyridones (compounds 3 and 4). Tolypocladium sp. 49Y was grown in a variety of media which led to the isolation of six 4-hydroxy pyridones (5-10) and one pyrrolidone (11) from a rice culture, and compounds 3 and 9 showed antifungal activity. These latter compounds are different from those obtained by heterologous expression. This study shows that both heterologous expression and cultivation of the native host are complementary approaches to discover new natural products.

Protein ubiquitination in postsynaptic densities after transient cerebral ischemia.

The mechanisms underlying neurologic deficits and delayed neuronal death after ischemia are not fully understood. In the present study, we report that transient cerebral ischemia induces accumulation of ubiquitinated proteins (ubi-proteins) in postsynaptic densities (PSDs). By immunoelectron microscopy, we demonstrated that ubi-proteins were highly accumulated in PSD structures after ischemia. On Western blots, ubi-proteins were markedly increased in purified PSDs at 30 minutes of reperfusion, and the increase persisted until cell death in the CA1 region after ischemia. In the resistant DG area, however, the changes were transient and significantly less pronounced. Deposition of ubi-proteins in PSDs after ischemia correlates well with PSD structural damage in the CA1 region as viewed by electron microscopy. These results suggest that the ubiquitin-proteasome system fails to repair and remove damaged proteins in PSDs. The changes may demolish synaptic neurotransmission, contribute to neurologic deficits, and eventually lead to delayed neuronal death after transient cerebral ischemia.

The effect of salvianolic acid B combined with laminar shear stress on TNF-alpha-stimulated adhesion molecule expression in human aortic endothelial cells.

The study was conducted to investigate the effect of Salvianolic acid B (Sal B) on TNF-alpha-stimulated adhesion molecule expression i.e. vascular adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1) and E-selectin in human aortic endothelial cells (HAECs) under laminar shear stress (LSS) condition. Exposure of HAECs to LSS (12 dynes/cm(2) for 6 h decreased the TNF-alpha-induced protein expression of adhesion molecules i.e. VCAM-1, ICAM-1 and E-selectin. Pre-treatment of HAECs with Sal B (10 microg/ml) then exposed to LSS (12 dynes/cm(2)) for 6 h significantly inhibited VCAM-1, ICAM-1 and E-selectin expression stimulated by TNF-alpha. Moreover, combined Sal B and LSS treatment inhibited the adhesiveness of monocytic U937 cells to TNF-alpha-stimulated HAECs. We further examined the molecular mechanisms and found that the combination of Sal B and LSS treatment dramatically inhibited TNF-alpha-induced NF-kappaB activation evidenced by IkappaBalpha degradation and p65 nuclear translocation in HAECs. This study provides the first biomechanopharmacological evidence that Sal B has a combination effect with LSS to reduce the expression of three adhesion molecules, leading to reduced monocyte adhesion to HAECs, at least in part, by inhibiting the NF-kappaB signaling pathway. Data from this study thus support the potential clinical application of Sal B in vascular inflammatory diseases.

Salvianolic acid B inhibits hydrogen peroxide-induced endothelial cell apoptosis through regulating PI3K/Akt signaling.

BACKGROUND: Salvianolic acid B (Sal B) is one of the most bioactive components of Salvia miltiorrhiza, a traditional Chinese herbal medicine that has been commonly used for prevention and treatment of cerebrovascular disorders. However, the mechanism responsible for such protective effects remains largely unknown. It has been considered that cerebral endothelium apoptosis caused by reactive oxygen species including hydrogen peroxide (H(2)O(2)) is implicated in the pathogenesis of cerebrovascular disorders. METHODOLOGY AND PRINCIPAL FINDINGS: By examining the effect of Sal B on H(2)O(2)-induced apoptosis in rat cerebral microvascular endothelial cells (rCMECs), we found that Sal B pretreatment significantly attenuated H(2)O(2)-induced apoptosis in rCMECs. We next examined the signaling cascade(s) involved in Sal B-mediated anti-apoptotic effects. We showed that H(2)O(2) induces rCMECs apoptosis mainly through the PI3K/ERK pathway, since a PI3K inhibitor (LY294002) blocked ERK activation caused by H(2)O(2 )and a specific inhibitor of MEK (U0126) protected cells from apoptosis. On the other hand, blockage of the PI3K/Akt pathway abrogated the protective effect conferred by Sal B and potentated H(2)O(2)-induced apoptosis, suggesting that Sal B prevents H(2)O(2)-induced apoptosis predominantly through the PI3K/Akt (upstream of ERK) pathway. SIGNIFICANCE: Our findings provide the first evidence that H(2)O(2) induces rCMECs apoptosis via the PI3K/MEK/ERK pathway and that Sal B protects rCMECs against H(2)O(2)-induced apoptosis through the PI3K/Akt/Raf/MEK/ERK pathway.