New developments in the use of peptide gonadotropin-releasing hormone antagonists versus agonists

Gonadotropin-releasing hormone (GnRH) stimulates the pituitary secretion of both luteinising hormone (LH) and follicle-stimulating hormone (FSH), and thus controls the hormonal and reproductive functions of the gonads. The blockade of the effects of GnRH may be sought for a variety of reasons; for example, to control premature LH surges and to reduce the cancellation rate with the aim of improving the pregnancy rate per treatment cycle or in the treatment of sex hormone-dependent disorders. Selective blockade of LH/FSH secretion and subsequent chemical castration have previously been achieved by desensitising the pituitary to continuously administered GnRH or by giving long-acting GnRH agonists. GnRH analogues are indicated for clinical situations in which the suppression of endogenous gonadotropins (precocious puberty, contraception and controlled ovarian hyperstimulation) or sexual steroids (endometriosis, prostate hyperplasia, cancer and uterine fibroids) is desired. The immediate suppression of the pituitary that is achieved by GnRH antagonists without an initial stimulatory effect is the main advantage of these compounds over the agonists. GnRH antagonists have been developed for clinical use with acceptable pharmacokinetic, safety and commercial profiles. In assisted reproduction, these compounds seem to be as effective as established therapy, but with shorter treatment times, less use of gonadotropic hormones, improved patient acceptance, and fewer follicles and oocytes. All of the current indications for GnRH agonist desensitisation may prove to be indications for a GnRH antagonist, including endometriosis, leiomyoma and breast cancer in women, benign prostatic hypertrophy and prostatic carcinoma in men, and central precocious puberty in children. However, the best clinical evidence has been in assisted reproduction and prostate cancer.     

RNA interference-based gene silencing in mice: the development of a novel therapeutical strategy

RNAi (RNA interference) was originally detected in Caenorhabditis elegans as biological response to exogenous double-stranded RNA (dsRNA), which induces very effective sequence-specific silencing of gene expression. Further investigations revealed that RNAi can occur in many eukaryotic species. Increasing understanding of the biochemical components of RNAi indicates the existence of a conserved machinery for dsRNA-induced gene silencing that acts in two steps. In the first step, an RNase III family nuclease called Dicer processes the dsRNA to small interfering RNAs (siRNAs) 21-23 nt in length. These siRNAs enter a multimeric nuclease complex that identifies target mRNAs through their homology to siRNAs and induce destruction of the corresponding mRNAs. Since RNAi has become an excellent strategy for gene silencing, it is tempting to apply this technology to 'knock-down' gene expression in living animals. The generation of transgenic mice from embryonic stem cells expressing small hairpin RNAs (shRNAs) has provided evidence for in vivo application of RNAi. Furthermore, different experimental strategies have been developed to analyze the influence of chemically synthesized siRNAs and of vector-based shRNAs on the expression of different transgenes and endogenous genes in vivo. Recent studies describe the in vivo delivery of siRNAs to inhibit transgene expression in certain organs of adult mice, predominately murine liver. Strategies for the inhibition of cellular proliferation by systemic treatment of tumor-bearing animals with siRNAs are beginning to emerge. They are of utmost interest for systemic diseases such as cancer. In addition, several groups have shown that RNAi can also be used to block the infectivity or suppress the replication of different RNA viruses relevant to human diseases including human immunodeficiency virus-1 (HIV-1) and hepatitis C virus (HCV). In summary, multiple lines of evidence indicate that RNAi seems to become a powerful tool for the fight against undesirable gene expression in human diseases.     

Multiparameter analysis of a screen for progesterone receptor ligands: comparing fluorescence lifetime and fluorescence polarization measurements

Direct measurement of the fluorescence lifetime (FLT) of a fluorescent label is an emerging method for high-throughput screening. Changes in the fluorescence lifetime can be correlated to changes in the non-radiative relaxation pathway(s) for the excited state of the label. These pathways can be environmentally sensitive, such as when a labeled analyte is free in solution versus bound to a receptor. Because lifetime is an intrinsic property of a fluorophore, it is not concentration dependent, and therefore has advantages similar to those of ratiometric fluorescent techniques such as fluorescence resonance energy transfer or fluorescence polarization. We have applied the FLT measurement technique to a screen of a small compound library in order to identify compounds that bind to the progesterone receptor, and compared the results to those obtained by performing the assay in fluorescence polarization mode. Each readout modality showed excellent Z'; values, with the FLT readout performing slightly better in this respect. Interfering compounds could be rapidly identified for either assay format by comparing the results between the two formats.     

Different antioxidative potencies of dihydropyridine calcium channel modulators in various models

There is evidence that dihydropyridine calcium antagonists (DHP) play a beneficial role during the development of atherosclerosis. Since antioxidative properties of this substance class may be important, we investigated the antioxidative potency of the DHP prototype calcium channel antagonist nifedipine, the long acting calcium channel antagonist lacidipine, the DHP calcium channel agonist Bay K 8644 and the bulky DHP derivate Bay O 5572 (negligible effects on L-type calcium channels) in three different models. Additionally, we examined the potential correlation between lipophilic and antioxidative properties. In an in vitro model, Bay K 8644 was significantly more effective in scavenging superoxide anions (hypoxanthine/xanthine-oxidase-assay) than lacidipine, Bay O 5572 or nifedipine (micro- to millimolar concentration range). Addition of artificial membrane preparations (dimyristoylphosphatidylcholine) to mimic a physiological environment resulted in an enhanced antioxidative effect, with lacidipine being the most effective DHP to quench radicals (low micromolar concentration range). Thirdly, in a more physiological model of hyperglycemia (30 mmol/l) induced release of reactive oxygen species (ROS) from native endothelial cells of porcine coronary arteries, we showed that nifedipine was a significantly more potent antioxidant (therapeutical nanomolar concentration range) than the other DHP. Calculation of the lipophilicity of the four substances (lacidipine>Bay O 5572>Bay K 8644>nifedipine) showed a positive correlation between the antioxidative potency and the lipophilicity in the model with the artificial membranes but not in the other models. We conclude that it seems necessary to access antioxidative properties of substances in physiological models in which we could demonstrate that nifedipine exhibits ROS-quenching properties in a therapeutic concentration range.     

Effects of a metabotropic glutamate<Subscript>2/3</Subscript> receptor agonist (LY544344/LY354740) on panic anxiety induced by cholecystokinin tetrapeptide in healthy humans: preliminary results

Rationale Preclinical findings have repeatedly shown an anxiolytic-like action of agonists at metabotropic glutamate receptors type II, such as LY354740.Objective We aimed to investigate the effect of LY544344, the prodrug of LY354740, upon experimental panic anxiety in humans.Methods Twelve healthy human volunteers were treated orally with 80 mg bid LY544344 for 1 week in a randomized placebo-controlled cross-over study before 50 g cholecystokinin tetrapeptide (CCK-4) was injected intravenously. We assessed CCK-induced panic and anxiety symptoms and measured stress hormone release.Results While no significant treatment effect emerged in the entire sample, a significant reduction of the number of CCK-4-induced panic symptoms and of CCK-4-induced subjective anxiety ratings was detected after removing two subjects who did not show decreased CCK-4-elicited adrenocorticotropin (ACTH) release after LY544344 compared to placebo treatment.Conclusions Further studies are needed to clarify the potential of LY544344 as a new anxiolytic or antipanic drug.     

Class I antiarrhythmics inhibit Na<Superscript>+</Superscript> absorption and Cl<Superscript>−</Superscript> secretion in rabbit descending colon epithelium

To clarify the mechanism of the diarrhea associated with the clinical use of antiarrhythmic drugs we assessed the effects of these agents on transepithelial Na+ absorption and Cl- secretion, on basolateral K+ conductance, and on the properties of single basolateral K+ channels of rabbit colon epithelium. Quinidine and propafenone, both at 10 microM, inhibited Na+ absorption by 27 and 38% respectively, compared with 50% with 5 mM Ba2+. The other tested class I antiarrhythmics disopyramide, mexiletine, lidocaine, and flecainide decreased Na+ current by 9-13%. Procainamide and the class III antiarrhythmics N-acetylprocainamide, sotalol, ibutilide, and amiodarone were no or were very weak inhibitors of Na+ absorption. Cl- secretion, stimulated with the adenosine analogue NECA (5'-N-ethylcarboxamide-adenosine), was reduced by 54% with quinidine and by 29% with propafenone compared with 100% with Ba2+. Mexiletine, lidocaine, and flecainide inhibited Cl- secretion by 10-23%, whereas the class III antiarrhythmics were no or were weak inhibitors. Those antiarrhythmics that inhibited Na+ and Cl- transport also reduced basolateral K+ conductance, determined in amphotericin B permeabilized epithelia. The activity of the high-conductance, Ca2+-activated, voltage-dependent K+ (BK(Ca)) channel, which is primarily responsible for basolateral K+ recycling during Na+ absorption, was inhibited by 10-30 microM quinidine or propafenone in the form of a rapidly dissociating block. Mexiletine and flecainide inhibited the single channel conductance at higher concentrations; disopyramide, lidocaine, and procainamide were ineffective. In conclusion, the present evidence suggests that the diarrhea caused by class I antiarrhythmic drugs such as quinidine and propafenone is a result of a reduction in basolateral K+ conductance and inhibition of BK(Ca) channels, thereby impeding transepithelial Na+ and water absorption.     

Microarray versus conventional prediction of lymph node metastasis in colorectal carcinoma

BACKGROUND: The authors investigated whether microarray-based gene expression analysis of primary tumor biopsy material could be used to predict lymph node status in patients with colorectal carcinoma (CRC). Lymphatic metastasis strongly determines treatment algorithms in CRC. Currently, postoperative histology results are needed to determine lymph node status. Reliable preoperative information would be useful to advance treatment strategies. METHODS: In specimens from 66 patients with CRC from the Erlangen Registry of Colorectal Cancer, 41 shock-frozen samples of International Union Against Cancer (UICC) Stage I-II CRC and 25 samples of UICC Stage III CRC were microdissected manually, RNA was isolated, and gene chips (HG-U133A; Affymetrix) were hybridized. Prediction rates for lymphatic metastasis were calculated using conventional clinicopathologic parameters, gene expression data, and a combination of both. Prediction error, specificity, and sensitivity were analyzed using six different statistical classifiers. RESULTS: Analysis of conventional parameters produced a positive prediction rate that ranged between 53% and 61%, sensitivity of 42%, and specificity of 72%. Microarray prediction rates were between 62% and 67% for lymphatic metastasis. Specificity was between 76% and 83%, and sensitivity was between 38% and 48%, depending on the statistical procedure. The conventional estimates were improved by 9-12% when array data were added. CONCLUSIONS: Current data show that the prediction of lymphatic metastasis can be improved by gene expression profiling of the primary tumor biopsy, alone or in combination with conventional parameters. Gene expression profiling may become valuable increasingly in planning treatment for patients with CRC.     

Risk factors for the intermediate outcome of morbid obesity after laparoscopically placed adjustable gastric banding

BACKGROUND: The overall long-term results of medical treatment for morbid obesity are poor. Surgery is the only treatment option to obtain long-term weight reduction. Analysis of risk factors for treatment success of laparoscopically placed gastric banding (LGB) has not been available until now. METHODS: Prospective study with 99 patients with LGB between January 1997 and July 2003. The parameters assessed as risk factors included onset of obesity, feeling of postprandial satiety, and initial body mass index (BMI). RESULTS: Median follow-up was 36 months (3 to 72). Independent prognostic factors of excess body weight reduction (>25%) were for the first postoperative year: onset of obesity as an adolescent (relative risk [RR] 0.21), an initial BMI <45 kg/m(2) (RR 4.76), and a BMI between 45.1 and 50 kg/m(2) (RR 3.23). After the second year, independent prognostic factors were as follows: feeling of postprandial satiety (RR 5.26) and an initial BMI <45 kg/m(2) (RR 3.03). CONCLUSION: LGB is suitable to achieve intermediate weight reduction in patients with morbid obesity. To obtain the best results, patients should be treated before they achieve a BMI >45 kg/m(2). Additionally a postprandial feeling of satiety after LGB is mandatory for good long-term results.     

Posterior stabilisation of a malignant cervico-thoracic vertebral bone defect

Oesophageal cancer is frequently complicated by malignant fistulae. Necrosis of the tumour following radiotherapy or chemotherapy may lead to the development of fistulae between the oesophagus and adjacent tissues and organs. We report the expansion of an extra-luminal oesophageal cancer after resection, invading the cervico-thoracic spine, fortunately without neurological deficit, and leading to instability and formation of a malignant fistula linking the tracheo-bronchial tree to the subarachnoidal space. To prevent imminent paraplegia and to alleviate severe pain, we rigidly stabilised the spine at the cervico-thoracic junction using an angle-stable system through a single posterior approach. Further postoperative follow-up revealed no signs of neurological deterioration. Cervico-thoracic stability was preserved until the patient died nearly five months postoperatively. This case shows that posterior stabilisation and decompression may be a palliative option for patients with imminent paraplegia and severe pain due to advanced tumour infiltration of the cervico-thoracic spine.