Phosphodiesterase-5 is a therapeutic target for peripheral neuropathy in diabetic mice

Peripheral neuropathy is a common and major complication of diabetes, the underlying mechanisms of which are not fully understood. Using a mouse model of type II diabetes, the present study investigated the role of phosphodiesterase-5 (PDE5) in peripheral neuropathy. BKS.Cg-m+/+Leprdb/J (db/db) mice were treated with sildenafil, a specific inhibitor of PDE5, at doses of 2 and 10 mg/kg or saline. Levels of PDE5 and morphometric parameters in sciatic nerve tissue as well as the motor and sensory function were measured in these mice. In diabetic mice, PDE5 expression in sciatic nerve tissue was significantly upregulated, whereas the myelin sheath thickness, myelin basic protein (MBP), and subcutaneous nerve fibers were significantly reduced. Treatment with sildenafil significantly improved neurological function, assayed by motor and sensory conducting velocities and thermal and mechanical noxious stimuli, concomitantly with increases in myelin sheath thickness, MBP levels, and subcutaneous nerve fibers. In vitro, hyperglycemia upregulated PDE5 in Schwann cells and reduced Schwann cell proliferation, migration, and expression of brain-derived neurotrophic factor (BDNF). Blockage of PDE5 with sildenafil increased cyclic guanosine monophosphate (cGMP) and completely abolished the effect of hyperglycemia on Schwann cells. Sildenafil upregulated cGMP-dependent protein kinase G I (PKGI), whereas inhibition of PKGI with a PKG inhibitor, KT5823, suppressed the inhibitory effect of sildenafil on Schwann cells. These data indicate that hyperglycemia substantially upregulates PDE5 expression and that the cGMP/PKG signaling pathway activated by sildenafil mediates the beneficial effects of sildenafil on diabetic peripheral neuropathy.

Silica subsurface amine effect on the chemical stability and chromatographic properties of end-capped immobilized artificial membrane surfaces

The silica surface of immobilized artificial membranes containing phosphatidylcholine (IAM.PC) has approximately two aminopropyl groups per immobilized phosphatidylcholine molecule. Primary amines near the silica subsurface adsorb biomolecules and also decrease the chemical stability of IAM.PC surfaces. Consequently, subsurface amines were end-capped by several methods including silylating reagents, acetyl analogues, glycidol, methyl glycolate, short-chain anhydrides (3-6 carbons/anhydride chain), and long-chain anhydrides (10-12 carbons/anhydride chain). All end-capping reactions resulted in loss of the initially immobilized phosphatidylcholine molecule. However, the amount of PC loss during end capping was very low (for alkyl anhydride end-capping reactions) to very high (for silylation end-capping reactions). After end capping, IAM.PC showed increased chemical stability compared to non end-capped IAM.PC surfaces. The chemical stability of IAM packing material was monitored by phospholipid leaching from IAM surfaces exposed to organic and aqueous solvents using thin-layer chromatography, 1H NMR spectroscopy, infrared spectroscopy, and mass spectrometry. IAM.PC packing material end capped with long-chain anhydrides exhibited the greatest chemical stability, i.e., little or no detectable phospholipid leaching when challenged with aqueous and/or organic solvents. The chromatography of acidic and basic compounds on end-capped and non-end-capped IAM.PC surfaces was studied. Compared to non-end-capped IAM.PC HPLC columns, the chromatographic retention times of acidic compounds (deoxynucleotides) decreased after end capping. In contrast, the retention times of basic compounds (amphetamine analogues) increased on end-capped IAM.PC HPLC columns relative to non-end-capped IAM.PC HPLC columns. This indicates that these solutes have access to the silica subsurface amines during chromatography.

Preliminary evaluation of manassantin A, a potential neuroleptic agent from Saururus cernuus

Manassantin A (MNS-A), a novel dineolignan isolated from Saururus cernuus was evaluated for its central depressant effects. Intraperitoneal (IP) administration of MNS-A to mice at nontoxic doses caused a decrease in spontaneous motor activity and inhibition of amphetamine-induced stereotypy, with an ED50 of 0.21 +/- 0.02 mg/kg for its antiamphetamine activity. Doses of MNS-A up to the LD50 did not produce catalepsy and ptosis as were observed with haloperidol used as a reference drug. The compound caused a dose-dependent hypothermia, while haloperidol was not very effective in this test. Potentiation of pentobarbital-sleeping time was observed to be of comparable degree with both drugs. In spite of the higher toxicity (acute LD50 5.4 +/- 0.2 mg/kg, IP) than that shown by haloperidol, the somewhat selective neuroleptic profile of MNS-A makes it an interesting candidate for more detailed studies.

Antibiotic principle of Eupatorium capillifolium

Ethanolic extracts of Eupatorium capillifolium (Lam) Small showed activity against Bacillus subtilis grown in a chemically defined medium but not in a complex natural medium. The active principle was isolated as a colorless crystalline solid. A study of its properties and mass spectral fragmentation pattern showed that it was costic acid, a sesquiterpenic acid previously isolated from Costus root oil. The observed inactivity of costic acid against B. subtilis in a complex medium was shown to be due to the presence in the medium of glutamic acid, which is capable of reversing 90% of the activity of costic acid.