ATM-CHK2-Beclin 1 axis promotes autophagy to maintain ROS homeostasis under oxidative stress.

The homeostatic link between oxidative stress and autophagy plays an important role in cellular responses to a wide variety of physiological and pathological conditions. However, the regulatory pathway and outcomes remain incompletely understood. Here, we show that reactive oxygen species (ROS) function as signaling molecules that regulate autophagy through ataxia-telangiectasia mutated (ATM) and cell cycle checkpoint kinase 2 (CHK2), a DNA damage response (DDR) pathway activated during metabolic and hypoxic stress. We report that CHK2 binds to and phosphorylates Beclin 1 at Ser90/Ser93, thereby impairing Beclin 1-Bcl-2 autophagy-regulatory complex formation in a ROS-dependent fashion. We further demonstrate that CHK2-mediated autophagy has an unexpected role in reducing ROS levels via the removal of damaged mitochondria, which is required for cell survival under stress conditions. Finally, CHK2-/- mice display aggravated infarct phenotypes and reduced Beclin 1 p-Ser90/Ser93 in a cerebral stroke model, suggesting an in vivo role of CHK2-induced autophagy in cell survival. Taken together, these results indicate that the ROS-ATM-CHK2-Beclin 1-autophagy axis serves as a physiological adaptation pathway that protects cells exposed to pathological conditions from stress-induced tissue damage.

Triterpenoids and steroids from the fruits of Melia toosendan and their cytotoxic effects on two human cancer cell lines.

Ten new triterpenoids, named meliasenins I-R (1-10), one new steroid (11), and 11 related known compounds (12-22) were isolated from fruits of Melia toosendan. The structures of the new compounds were established on the basis of spectroscopic methods, including 2D NMR techniques and mass spectrometry. The relative configuration of 1, (20R*,23E)-25-hydroperoxyeupha-7,23-diene-3ß,16ß-diol (meliasenin I), was confirmed by single-crystal X-ray diffraction analysis. All isolated triterpenoids (1-10, 12-15) and two steroids (11, 20) were tested for their cytotoxicity against U20S human osteosarcoma and MCF-7 human breast cancer cells using the MTT assay, and some of them were significantly cytotoxic (IC(50) <10 µg/mL). The insecticidal properties of compounds 1-15 and 20 were also briefly evaluated.

HIF-1α transgenic bone marrow cells can promote tissue repair in cases of corticosteroid-induced osteonecrosis of the femoral head in rabbits.

Although corticosteroid-induced osteonecrosis of the femoral head (ONFH) is common, the treatment for it remains limited and largely ineffective. We examined whether implantation of hypoxia inducible factor-1α (HIF-1α) transgenic bone marrow cells (BMCs) can promote the repair of the necrotic area of corticosteroid-induced ONFH. In this study, we confirmed that HIF-1α gene transfection could enhance mRNA expression of osteogenic genes in BMCs in vitro. Alkaline phosphatase activity assay and alizarin red-S staining indicated HIF-1α transgenic BMCs had enhanced osteogenic differentiation capacity in vitro. Furthermore, enzyme linked immunosorbent assay (ELISA) for VEGF revealed HIF-1α transgenic BMCs secreted more VEGF as compared to normal BMCs. An experimental rabbit model of early-stage corticosteroid-induced ONFH was established and used for an evaluation of cytotherapy. Transplantation of HIF-1α transgenic BMCs dramatically improved the bone regeneration of the necrotic area of the femoral head. The number and volume of blood vessel were significantly increased in the necrotic area of the femoral head compared to the control groups. These results support HIF-1α transgenic BMCs have enhanced osteogenic and angiogenic activity in vitro and in vivo. Transplantation of HIF-1α transgenic BMCs can potentially promote the repair of the necrotic area of corticosteroid-induced ONFH.

Fomentarols A-D, sterols from the polypore macrofungus Fomes fomentarius.

Four (1-4) hitherto unknown and seven (5-11) known ergostane-type sterols were isolated from the EtOH extract of the dried fruiting bodies of the polypore macrofungus Fomes fomentarius. On the basis of spectroscopic analysis, the structures of polyhydroxylated sterols 1-4 were elucidated to be (22E,24R)-3ß,5α,6ß,14α-tetrahydroxyergosta-7,9(11),22-triene (fomentarol A, 1), (22E,24R)-3ß,5ß,6α,7α-tetrahydroxy-8α,9α-dihydroergosta-14,22-diene (fomentarol B, 2), (22E,24R)-3ß,5α-dihydroxy-6ß-ethoxyergosta-7,22-diene (fomentarol C, 3), and (22E,24S)-3ß,25-dihydroxy-15α-O-ß-D-glucopyranosylergosta-7,22-dien-6-one (fomentarol D, 4), respectively. Rings A/B and B/C are in turn cis-fused in compound 2, which is uncommon in natural ergostane-type sterols. The potential biogenetic relationship of 2 and other ergostane-type sterols isolated from F. fomentarius was briefly discussed. Moderate cytotoxic effects of the isolated sterols against a small panel of human cancer cell lines were also established.

Gynostemosides A-E, megastigmane glycosides from Gynostemma pentaphyllum.

Megastigmane glycosides (1-5) together with seven (6-12) related known compounds were isolated from the whole plants of Gynostemma pentaphyllum. The structures were elucidated by means of spectroscopic methods, including 2D NMR, HR-ESIMS, and circular dichroism (CD), as well as chemical transformations to be (3R,4R,5S,6S,7E)-3,4,6-trihydroxymegastigmane-7-en-9-one-3-O-beta-D-glucopyranoside (gynostemoside A, 1), (3S,4S,5R,6R,7E,9R)-3,4,6,9-tetrahydroxymegastigmane-7-en-3-O-beta-D-glucopyranoside (gynostemoside B, 2), (3S,4S,5S,6S,7E,9R)-3,4,9-trihydroxymegastigmane-7-en-9-O-beta-D-glucopyranoside (gynostemoside C, 3), (3S,4S,5S,6S,7E,9R)-3,4,9-trihydroxymegastigmane-7-en-3-O-beta-D-glucopyranoside (gynostemoside D, 4), and (3S,4S,5S,6S,7E,9R)-3,4,9-trihydroxymegastigmane-7-en-4-O-beta-D-glucopyranoside (gynostemoside E, 5), respectively.