The disruption of brain microtubules in vitro by the phospholipase inhibitor p-bromophenacyl bromide

Concise synthesis and biological evaluation of 2-Aroyl-5-amino benzo[b]thiophene derivatives as a novel class of potent antimitotic agents

The biological importance of microtubules make them an interesting target for the synthesis of antitumor agents. The 2-(3',4',5'-trimethoxybenzoyl)-5-aminobenzo[b]thiophene moiety was identified as a novel scaffold for the preparation of potent inhibitors of microtubule polymerization acting through the colchicine site of tubulin. The position of the methoxy group on the benzo[b]thiophene was important for maximal antiproliferative activity. Structure-activity relationship analysis established that the best activities were obtained with amino and methoxy groups placed at the C-5 and C-7 positions, respectively. Compounds 3c-e showed more potent inhibition of tubulin polymerization than combretastatin A-4 and strong binding to the colchicine site. These compounds also demonstrated substantial antiproliferative activity, with IC50 values ranging from 2.6 to 18 nM in a variety of cancer cell lines. Importantly, compound 3c (50 mg/kg), significantly inhibited the growth of the human osteosarcoma MNNG/HOS xenograft in nude mice.

Synthesis and biological evaluation of 2-(3',4',5'-trimethoxybenzoyl)-3-N,N-dimethylamino benzo[b]furan derivatives as inhibitors of tubulin polymerization

Molecules that target microtubules have an important role in the treatment of cancer. A new class of inhibitors of tubulin polymerization based on the 2-(3,4,5-trimethoxybenzoyl)-2-dimethylamino-benzo[b]furan molecular skeleton was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. The most promising compound in this series was 2-(3,4,5-trimethoxybenzoyl)-3-dimethylamino-6-methoxy-benzo[b]furan, which inhibits cancer cell growth at nanomolar concentrations and interacts strongly with tubulin by binding to the colchicine site.

Involvement of axonal phospholipase A2 activity in the outgrowth of adult mouse sensory axons in vitro

The effect on axonal outgrowth of inhibition of phospholipase A2 activity was studied in a recently developed in vitro model, where dorsal root ganglia with attached spinal roots and nerve stumps from young adult mice were cultured in an extracellular matrix material (Matrigel). The phospholipase A2 inhibitors 4-bromophenacyl bromide and oleyloxyethyl phosphorylcholine dose-dependently reduced axonal outgrowth from the sciatic nerve stump. A similar inhibitory effect was seen when only the cut nerve end was exposed to the inhibitors in a compartmental culture system. The local effect of phospholipase A2 inhibition was further investigated on axons established in culture, using time-lapse recording. Exposure to phospholipase A2 inhibitors caused the retraction of filopodia extensions and a reduction in growth cone motility within a few minutes. After removal of inhibition, normal growth cone motility and axonal growth were regained. Nerve cell bodies and axons, in contrast to Schwann cells, showed immunoreactivity after staining with an antiserum against secretory phospholipase A2, and elevated levels of the enzyme could be detected after culture for 24 h. The immunoreactive protein was of approximately 170,000 molecular weight (phospholipase A2-170) as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. The localization of phospholipase A2-170 in axons growing into the Matrigel was also demonstrated by use of a whole-mount technique. The results of this study show the importance of continuous phospholipase A2 activity for growth cone motility and axonal outgrowth in the mammalian peripheral nerve, and suggest the involvement of an axonally localized enzyme.

N-Ras induces alterations in Golgi complex architecture and in constitutive protein transport

Aberrant glycosylation of proteins and lipids is a common feature of many tumor cell types, and is often accompanied by alterations in membrane traffic and an anomalous localization of Golgi-resident proteins and glycans. These observations suggest that the Golgi complex is a key organelle for at least some of the functional changes associated with malignant transformation. To gain insight into this possibility, we have analyzed changes in the structure and function of the Golgi complex induced by the conditional expression of the transforming N-Ras(K61) mutant in the NRK cell line. A remarkable and specific effect associated with this N-Ras-induced transformation was a conspicuous rearrangement of the Golgi complex into a collapsed morphology. Ultrastructural and stereological analyses demonstrated that the Golgi complex was extensively fragmented. The collapse of the Golgi complex was also accompanied by a disruption of the actin cytoskeleton. Functionally, N-Ras-transformed KT8 cells showed an increase in the constitutive protein transport from the trans-Golgi network to the cell surface, and did not induce the appearance of aberrant cell surface glycans. The Golgi complex collapse, the actin disassembly, and the increased constitutive secretion were all partially inhibited by the phospholipase A2 inhibitor 4-bromophenylacyl bromide. The results thus suggest the involvement of the actin cytoskeleton in the shape of the Golgi complex, and intracellular phospholipase A2 in its architecture and secretory function.

Rapid regulation of neurite outgrowth and retraction by phospholipase A2-derived arachidonic acid and its metabolites

Arachidonic acid and lipoxygenase metabolites have been proposed to act as retrograde synaptic messengers and as early mediators of neuronal injury, but few studies have analyzed their roles in controlling neurite behavior within a time window of minutes to hours. Phospholipase A2 inhibitors (BPB, ONO-RS-082, quinacrine and AACOCF3) and the lipoxygenase inhibitor AA861 delayed the initial outgrowth of NG108-15 cell neurites on laminin. Inhibitors of diacylglycerol lipase (RHC 80267), cyclooxygenase (indomethacin) and free radicals (N-acetyl cysteine and vitamin E) did not produce similar effects. Phospholipase A2 and lipoxygenase inhibitors also prevented acute neurite retraction in response to lysophosphatidic acid and eight other agents tested, and decreased F-actin staining at cell margins. Conversely, exogenous arachidonic acid (1 microM) enhanced the responses of neurites in outgrowth and retraction assays. Phospholipase A2 and lipoxygenase pathways appear to have a general role in maintaining the ability of neurites to respond rapidly to external stimuli, possibly via regulating the ability of the cytoskeleton to remodel.