Evidence of a net release of tissue-type plasminogen activator across the human cerebral vasculature

We have earlier described models for measuring local net release rates of tissue-type plasminogen activator (t-PA) in vivo across skeletal, coronary, pulmonary, and splanchnic vascular beds. Aim of the present study was to investigate whether there is a net release of t-PA across the human cerebral vascular bed and whether an acute regulated release can be induced by sympathoadrenal activation. Fourteen male subjects undergoing elective coronary artery bypass grafting were investigated prior to surgery and during sternotomy-induced sympathoadrenal activation. Blood samples were obtained simultaneously from the radial artery and the jugular bulb. Blood flow velocity in the middle cerebral artery (V(MCA)) was determined by transcranial Doppler. Cerebral net release of t-PA was calculated as the arterio-venous concentration gradient times V(MCA). Prior to surgery there was a significant cerebral net release of t-PA (131 and 42 ng/min for t-PA antigen and activity, respectively). The release was significantly induced by sternotomy (to 271 and 80 ng/min, respectively). No significant cerebral net release of plasminogen activator inhibitor type 1 (PAI-1) was detected throughout the experiment. The results show that there is a basal net release of t-PA across the human cerebral vascular bed and that sympathoadrenal activation induces a local regulated release of t-PA.     

Tumor-infiltrating lymphocytes and interleukin-2: dose and schedules of administration in the treatment of metastatic cancer

PURPOSE: The potential for therapeutic use of tumor-infiltrating lymphocytes (TIL), as adoptive cellular therapy has been touted for many years with some encouraging reports in patients with metastatic melanoma. MATERIALS AND METHODS: We previously described methodologies for TIL production and phenotypic characterization of TIL generated in our laboratory between 1991 and 1995 in semipermeable bags and between 1996 and 2000 in bioreactors. Patients treated in the earlier era were to have received a hybrid bolus and a 12-hour continuous infusion of interleukin (IL)-2 (total, 48 MIU), while in the latter era 4 days of interferon- alpha preceded the TIL and IL-2; which was given by a hybrid schedule that included bolus and 72- hour continuous IL-2 (total, 96 MIU). There were 55 patients, including 23 patients with melanoma, 9 patients with renal cell carcinoma, and 8 patients with colorectal cancer. There was only 1 objective tumor response, which was noted in a patient with renal cell carcinoma. The 55 patients who received these products were grouped in cohorts by treatment era, quantity of TIL received, amount of IL-2 intended, and different combinations of TIL and IL-2. RESULTS: There was no difference in survival by production method (treatment era), or amount of IL-2 given with TIL, but 33 patients who received an intermediate or higher dose of TIL (mean = 54.4 x 10(9)) had a median survival of 11.8 months, compared to 6.4 months for 22 patients who received 1 low-dose TIL (mean = 6.48 x 10(9)) (p = 0.059, log rank test). The objective response rate in this heterogeneous group of patients was not encouraging. The data suggest there may be a dose/benefit relationship between the total number of TIL infused and survival.     

Metformin rapidly increases insulin receptor activation in human liver and signals preferentially through insulin-receptor substrate-2

Metformin decreases endogenous glucose production by the liver. Few studies have examined the effect of metformin on the insulin-signaling pathway in liver models, and none have presented data on the effect in normal human liver. Huh7 human hepatoma cells and primary human hepatocytes were used. Insulin receptor (IR) and IR substrates (IRS)-1 and -2 were assessed by immunoprecipitation and immunoblot. Normal human liver was used to assay IR kinase activity (IR-KA). Tyrphostin AG1024 was used to inhibit IR-KA and examine effects on deoxyglucose uptake. Metformin (1 micro g/ml) increased IR tyrosine phosphorylation by 78% (P = 0.0007) in 30 min in human hepatocytes and Huh7 cells and increased IRS-2 but not IRS-1 activation, and the downstream increase in deoxyglucose uptake was mediated via increased translocation of GLUT-1 to the plasma membrane. Metformin did not augment maximal or submaximal insulin-stimulated IR activation. Metformin increased basal IR-KA by 150% (P = 0.0001). AG1024 inhibited metformin-induced IR-beta phosphorylation in a concentration-dependent manner and abolished metformin-induced 2-deoxyglucose uptake. This study demonstrates that the mechanism of action of metformin in liver involves IR activation, followed by selective IRS-2 activation, and increased glucose uptake via increased GLUT-1 translocation. The effect of metformin was completely blocked by an IR inhibitor.     

Glutathione-S-transferase pi expression and activity is increased in colonic neoplasia

Glutathione-S-transferase (GST) isoenzymes are involved in the conjugation of glutathione to electrophilic carcinogens. Recent studies have shown increased levels and activities of GST in different tumors suggesting their role in carcinogen detoxification. This study compared GST activity levels and GST-pi protein expression in paired samples of colorectal cancer, adenoma and adjacent normal mucosa from a total of thirteen patients. GST was isolated from human colorectal specimens and assayed spectrophotometrically; Western immunoblot analysis was used to quantify GST-pi levels. GST activity was greater in both colorectal cancer and adenomas than in adjacent normal colonic tissue, although statistical significance was achieved only when comparing colorectal cancer to normal tissue. Based on these observations, we conclude that increased GST activity may be a useful marker of colonic neoplasia.     

Pairing elevation of [cyclic GMP] with inhibition of PKA produces long-term depression of glutamate release from isolated rat hippocampal presynaptic terminals

Data suggest both presynaptic and postsynaptic changes contribute to activity-dependent long-term synaptic plasticity. We have shown that pairing elevation of intracellular [cyclic GMP], using the type V phosphodiesterase inhibitor zaprinast, with inhibition of cyclic AMP-dependent protein kinase (PKA), is sufficient to elicit chemical long-term depression (CLTD) of synaptic transmission at Schaffer collateral-CA1 and mossy fibre-CA3 synapses in rat hippocampus. CLTD does not require synaptic activity, and selective postsynaptic drug injections do not affect it, suggesting it is presynaptically induced and expressed. To directly evaluate this hypothesis, we tested whether CLTD of transmitter release can be expressed in isolated presynaptic nerve terminals. Presynaptic nerve terminals (synaptosomes) were isolated from rat hippocampi by Percoll density gradient centrifugation. Synaptosomes were loaded with [3H]glutamate, and basal and depolarisation-induced release of [3H]glutamate measured in control medium versus medium containing zaprinast (20 microm) plus or minus the PKA inhibitor H-89 (10 microm). Zaprinast produced a significant decrease in basal [3H]glutamate release. However, only combining zaprinast with H-89 significantly depressed K+-evoked [3H]glutamate release. After a 20-min drug washout, basal release returned to normal in all conditions, but K+-evoked [3H]glutamate release was persistently reduced only by the combination of zaprinast plus H-89. Long-term reduction of [3H]glutamate release from synaptosomes was completely prevented by the PKG inhibitor KT5823 (5 microm). These data demonstrate the existence of a presynaptic, cyclic GMP-PKG dependent cascade capable of expressing LTD of glutamate release from isolated hippocampal nerve terminals.     

Rapid genotyping of haemostatic gene polymorphisms using the 5' nuclease assay

Hemostatic gene polymorphisms have been shown to be associated with arterial and venous thrombotic disease. To date these polymorphisms have mainly been detected by labor-intensive conventional gel based methods. Aim of the present study was to design and optimize high throughput 5' nuclease assays for the detection of a set of 10 single-nucleotide polymorphisms (SNP) in genes of importance for hemostasis: plasminogen activator inhibitor type 1 -675 4G>5G, thrombin activatable fibrinolysis inhibitor Ala147Thr and 1,542C>G, beta-fibrinogen -455G>A, von Willebrand factor -1,051A>G, factor VII Arg353Gln, factor XIII Val34Leu, prothrombin 20,210G>A, tissue factor pathway inhibitor -287T>C, and methylenetetrahydrofolate reductase 1,298A>C. Specificity of each genotyping assay was confirmed by sequence-based typing and reproducibility was evaluated by repeated genotyping. The genotyping protocols presented here may serve as a valuable tool for clinical researchers interested in exploring associations between these SNPs and thrombotic disease.     

Transport of Lipophilic Drug Molecules in a New Mucus-Secreting Cell Culture Model Based on HT29-MTX Cells

Purpose. A new mucus-secreting in vitro drug absorption model based on monolayers of goblet-cell like sub-clones of the human colon carcinoma cell line HT29 obtained by methotrexate (MTX) treatment was investigated. Methods. Twelve sub-clones were isolated and characterized by light microscopy (LM), transelectron microscopy (TEM), confocal laser scanning microscopy (CLSM), transepithelial electrical resistance (TEER) and the transport of a paracellular marker FITC-Dextran (Mw 4400) (FD-4). Results. Significant differences of microscopical appearance, TEER-values and permeability of FD-4 between the sub-clones were evident. However, two of them, namely MTX-D1 and MTX-E12, formed tight confluent monolayers with a thick mucus-layer on the apical surface. They were used to compare the apparent permeability coefficient (P_app) of a series of lipophilic drugs, which should be affected by the mucus-layer, namely barbiturates (barbituric acid, barbital, phenobarbital, methylphenobarbital and heptabarbital) and testosterone, as a reference, to mucus-free Caco-2 cells. The permeability of drugs with a partition coefficient (log P) > 1 was decreased in the mucus-producing cell lines. Testosterone, the most lipophilic compound, showed a decrease of up to 43%. Conclusions. We demonstrated that the mucus layer is a significant barrier to drug absorption for lipophilic drugs. In conclusion, our model may serve as a suitable in-vitro cell culture model to study the influence of the mucus layer on drug diffusion.