Inhibitory Effects of Secondary Metabolites from the Lichen Stereocaulon evolutum on Protein Tyrosine Phosphatase 1B.

Protein tyrosine phosphatase 1B plays a significant role in type 2 diabetes mellitus and other diseases and is therefore considered a new drug target. Within this study, an acetone extract from the lichen Stereocaulon evolutum was identified to possess strong protein tyrosine phosphatase 1B inhibition in a cell-free assay (IC50 of 11.8 µg/mL). Fractionation of this bioactive extract led to the isolation of seven known molecules belonging to the depsidones and the related diphenylethers and one new natural product, i.e., 3-butyl-3,7-dihydroxy-5-methoxy-1(3H)-isobenzofurane. The isolated compounds were evaluated for their inhibition of protein tyrosine phosphatase 1B. Two depsidones, lobaric acid and norlobaric acid, and the diphenylether anhydrosakisacaulon A potently inhibited protein tyrosine phosphatase 1B with IC50 values of 12.9, 15.1, and 16.1 µM, respectively, which is in the range of the protein tyrosine phosphatase 1B inhibitory activity of the positive control ursolic acid (IC50 of 14.4 µM). Molecular simulations performed on the eight compounds showed that i) a contact between the molecule and the four main regions of the protein is required for inhibitory activity, ii) the relative rigidity of the depsidones lobaric acid and norlobaric acid and the reactivity related to hydrogen bond donors or acceptors, which interact with protein tyrosine phosphatase 1B key amino acids, are involved in the bioactivity on protein tyrosine phosphatase 1B, iii) the cycle opening observed for diphenylethers decreased the inhibition, except for anhydrosakisacaulon A where its double bond on C-8 offsets this loss of activity, iv) the function present at C-8 is a determinant for the inhibitory effect on protein tyrosine phosphatase 1B, and v) the more hydrogen bonds with Arg221 there are, the more anchorage is favored.

Lobarin from the Sumatran lichen, Stereocaulon halei.

The diphenyl ether, lobarin (1) (syn. lobariol carboxylic acid) related to lobaric acid was isolated for the first time as a natural product along with five known compounds from Stereocaulon halei, a fruticose lichen collected in Indonesia. The structure of lobarin was elucidated by spectroscopic data analysis and its most stable conformers were determined by molecular mechanic dynamic calculations. A marked superoxide anion scavenging was found for compound 1 while no cytotoxicity on the B16 murine melanoma and HaCaT human keratinocyte cell lines was observed.

Disconnecting surgical treatment of hypothalamic hamartoma in children and adults with refractory epilepsy and proposal of a new classification.

A series of 17 patients aged from 9 months to 32 years with refractory epilepsy due to hypothalamic hamartoma were treated by total removal (one case) and disconnection (16 cases) between 1997 and 2002. The mean age at seizure onset was 16 months. Sixteen patients had gelastic seizures, 14 had partial seizures and three had generalized tonic-clonic seizures. The mean seizure frequency was 21 per day. Four patients had borderline intelligence quotient and the others were mentally retarded. Five patients presented with precocious puberty, one with acromegaly, and four suffered from obesity. Brain magnetic resonance imaging, performed at least twice in each patient, showed the hamartoma as a stable homogeneous interpeduncular mass implanted either on the mammilary tubercle or on the wall of the third ventricle with variable extension to the bottom. Ictal single photon emission computed tomography, performed in four patients, showed hyperperfusion within the hamartoma in two patients. Twenty-five operations were performed in the 17 patients. The first patient underwent total removal of the hamartoma, whereas the following 16 patients underwent disconnection through open surgery (14 procedures) and/or endoscopy (9 procedures). Eight patients became seizure-free, one patient had only brief gelastic seizures, and eight patients were dramatically improved with a mean follow up of 18.6 months (8 days to 43 months). Surgery was safe in all but two patients: the first patient had transient hemiplegia and the third cranial nerve paresis, and the other developed hemiplegia due to ischemia of the middle cerebral artery territory. The quality of life, and behavior and school performance were greatly improved in most patients. Our series illustrates the feasibility and relative safety of disconnection surgery for hypothalamic hamartomas with seizure relief in 53% of patients and dramatic improvement in the others. Surgical observations led us to propose a new anatomical classification according to the anatomical relationship between the hamartoma and the adjacent hypothalamus and third ventricle. Endoscopic disconnection seems to be a very safe way to treat hamartomas in intraventricular locations.

Persistence of ictal activity after functional hemispherectomy in Rasmussen syndrome.

A 15-year-old girl with a 3-year history of Rasmussen syndrome (RS) underwent left functional hemispherectomy by central disconnection. Clinical seizures then ceased. Five months postoperatively, ictal EEG discharges were associated with focal hyperperfusion on SPECT within the disconnected hypoperfused left hemisphere, suggesting that the basic mechanisms of RS may continue, only to remit later. EEG and SPECT may complement studies of these in seizure-free surgically treated patients in whom clinical follow-up may be unrevealing.

Hypothalamic hamartoma with refractory epilepsy: surgical procedures and results in 18 patients.

AIM: To study the surgical procedures and results on seizures, in 18 patients with refractory epilepsy due to hypothalamic hamartoma. PATIENTS AND METHODS: Eighteen patients aged from 9 months to 32 years underwent surgery between 1997 and 2002. The mean age at seizure onset was 15.5 months. Seventeen patients had gelastic seizures, 14 had partial seizures, two had infantile spasms, 10 had tonic or atonic seizures and three had generalized seizures. The mean seizure frequency was 21 per day. Four patients had borderline intellectual disability and the others were mentally retarded. Five patients had precocious puberty, one had acromegaly and four suffered from obesity. Brain MRI, performed at least twice in each patient showed the hamartoma as a stable, homogeneous interpeduncular mass implanted either on the mammillary tubercle or on the wall of the third ventricle, with variable extension to the bottom. Ictal SPECT, performed in four patients, showed hyperperfusion within the hamartoma in two. SURGICAL PROCEDURE: Twenty-six operations were performed in 18 patients. The first patient underwent a total removal of the hamartoma, whereas the following patients underwent a disconnection, either through open surgery (14 patients) or endoscopy (10 patients). RESULTS: Regarding the seizure outcome with a mean follow up of three years four months (one year to 4.5 years), nine patients are seizure-free, one patient has only brief gelastic seizures and eight are dramatically improved. Surgery was uncomplicated in all but two patients: one had transitory hemiplegia and paresis of the third cranial nerve, the other presented with hemiplegia due to ischemia of the middle cerebral artery territory. The quality of life, behavior and school performance were greatly improved in most of the patients. CONCLUSION: Our series illustrates the feasibility and relative safety of disconnecting surgery of hypothalamic hamartomas, with seizure relief in 50% and a dramatic improvement in the others. Endoscopic disconnection seems to be a very safe way to treat the intra-ventricular part of hamartomas.