Industry forum: Progress in pursuit of therapeutic A2A antagonists: The adenosine A2A receptor selective antagonist KW6002: Research and development toward a novel nondopaminergic therapy for Parkinson's disease

Research and development of the adenosine A2A receptor selective antagonist KW6002 have focused on developing a novel nondopaminergic therapy for Parkinson's disease (PD). Salient pharmacologic features of KW6002 were investigated in several animal models of PD. In rodent and primate models, KW6002 provides symptomatic relief from parkinsonian motor deficits without provoking dyskinesia or exacerbating existing dyskinesias. The major target neurons of the A2A receptor antagonist were identified as GABAergic striatopallidal medium spiny neurons. A possible mechanism of A2A receptor antagonist action in PD has been proposed based on the involvement of striatal and pallidal presynaptic A2A receptors in the "dual" modulation of GABAergic synaptic transmission. Experiments with dopamine D2 receptor knockout mice showed that A2A receptors can function and anti-PD activities of A2A antagonists can occur independent of the dopaminergic system. Clinical studies of KW6002 in patients with advanced PD with L-dopa-related motor complications yielded promising results with regard to motor symptom relief without motor side effects. The development of KW6002 represents the first time that a concept gleaned from A2A biologic research has been applied successfully to "proof of concept" clinical studies. The selective A2A antagonist should provide a novel nondopaminergic approach to PD therapy.

The Ca(2+)-ATPase of the scallop sarcoplasmic reticulum is of a cold-adapted type

At 0 to 20 degrees C, the Ca(2+)-ATPase activity of the scallop sarcoplasmic reticulum (SR) was observed to be 7-60% of the peak activity at 30 degrees C, while the ATPase activity of the rabbit SR was 0-7% of its peak at 55 degrees C. The relative rabbit ATPase activity (0.7-7.0%) at 7-20 degrees C became higher (6-15 times) and lower (1/4-1/2), respectively, by the solubilization of the rabbit ATPase with a detergent, dodecyloctaethylenglycol monoether, and by the reconstitution of the ATPase with asolectin (soybean lecithin). No activity at 0 degrees C remained irrespective of these treatments. The relative scallop ATPase activity at 0-20 degrees C was, however, scarcely affected by such solubilization and reconstitution. In contrast to the rabbit ATPase, the scallop ATPase seems to be capable of operating independently without the help of the membrane lipid at low temperature.

Intraoperative location of small gastrointestinal cancers with a handheld gamma probe

The location of a small lesion must be precisely identified during laparoscopic surgery. A gamma probe that is usually used for navigating sentinel lymph nodes was evaluated for its usefulness in locating small gastrointestinal lesions (14 gastric and 10 colonic). A total of 2 mCi of a Tc(99m)-labeled rhenium colloid was injected endoscopically around a tumor 16 h prior to surgery. During operation, the abdominal cavity was scanned using a handheld gamma probe (Navigator GPS, Tyco HealthCare, Norwalk, CT, USA). In all cases, the injection site was identified as the highest spot in the abdominal cavity, with 2585 counts per second on average (range, 910-8800 counts per second). The highest count in a lymph node was 637 per second on average. The gamma probe is a useful tool for identifying small gastrointestinal lesions during open and laparoscopic operations.

Paroxetine as a 5-HT neuroendocrine probe

RATIONALE

Acute administration of 40 mg paroxetine (a selective serotonin reuptake inhibitor) reportedly increases plasma cortisol in human subjects. This suggests that paroxetine may be a useful tool to probe brain serotonin function.

OBJECTIVE

To investigate a dose-response relationship for paroxetine administration, and to determine whether a lower dose of paroxetine is sufficient to increase plasma ACTH and cortisol.

METHODS

Twenty subjects were tested on three occasions in a double-blind, cross-over design receiving: (a) placebo, (b) paroxetine 20 mg and (c) paroxetine 40 mg administered orally at 8.00 a.m. In addition, five of the 20 subjects received paroxetine 20 mg plus cyproheptadine (a 5-HT(2) receptor antagonist) 4 mg and four subjects were given paroxetine 40 mg plus cyproheptadine 4 mg in an open manner. Plasma ACTH and cortisol levels were measured prior to administration and every hour for 6 h thereafter.

RESULTS

Paroxetine, particularly 20 mg rather than 40 mg, significantly increased plasma ACTH and cortisol. Paroxetine 40 mg but not 20 mg caused significantly more nausea than the placebo. Cyproheptadine attenuated ACTH and cortisol responses to 20 mg but not to 40 mg paroxetine.

CONCLUSIONS

Low-dose (20 mg) paroxetine has greater potential utility than larger doses as a neuroendocrine challenge test. The endocrine responses to paroxetine are probably mediated at least partially by 5-HT(2A/2C) receptors.

Allelic association of the neuronal nitric oxide synthase (NOS1) gene with schizophrenia

Nitric oxide (NO) has been identified as a widespread and multifunctional biological messenger molecule in the central nervous system (CNS), with possible roles in neurotransmission, neurosecretion, synaptic plasticity, and tissue injury in many neurological disorders, including schizophrenia. Neuronal NO is widely produced in the brain from L-arginine catalyzed by neuronal NO synthase (NOS1). We therefore hypothesized that the NOS1 gene may play a role in the pathophysiology of schizophrenia. In the present study, we examined the genetic association between a novel single nucleotide polymorphism (SNP: a C-->T transition located 276 base pairs downstream from the translation termination site) of the human NOS1 gene, which is located in chromosome 12q24, and schizophrenia (215 Japanese patients with schizophrenia and 182 healthy controls). The allele frequencies of the polymorphism in exon 29 of the NOS1 gene differed significantly between patients with schizophrenia and controls (chi(2) = 20.10, df = 1, P = 0.000007; relative risk = 1.92; 95% confidence interval = 1.44-2.55). Our results suggest that the NOS1 gene polymorphism may confer increased susceptibility to schizophrenia.

[Gastric cancer: an unusual presentation]

We want to introduce the case of an 18 year old male patient who consulted us because of proctorrhage, straining and rectal tenesmus. Diagnosis was rectal tumor which pathological anatomy revealed an adenocarcinoma of cells in seal ring shape, suggesting a probable gastric origin. The high endoscopy evidenced multiple polyps, less than a centimeter wide found in the cardiac orifice, body and antrum, with the same histology. All these findings were confirmed during the exploratory laparotomy. We thought it was interesting to report this case because of the clinical presentation, unusual in this type of gastric cancer.

Noninvolvement of hypertriglyceridemia and hyperleptinemia in blood pressure increases induced by dietary lard in rats

We investigated whether hypertriglyceridemia and hyperleptinemia are involved in the development of increases in blood pressure induced by dietary lard. Rats received either chow alone or chow in which 50% of the energy content was from substituted lard. Each group was divided into two groups according to whether the diet included bezafibrate or not. In another series of experiments, rats were fed either chow alone or chow in which 50% of the energy content was from substituted lard, safflower oil, or sucrose. Systolic blood pressure (SBP) was measured every week during each 7-week feeding period. A steady-state plasma glucose method was used to determine insulin sensitivity after lard substitution with or without bezafibrate. After the 7-week feeding period, the plasma levels of glucose, immunoreactive insulin, triglyceride and leptin were measured. In rats fed with a high lard diet, SBP, plasma levels of immunoreactive insulin, triglyceride, leptin and steady-state plasma glucose concentrations significantly increased, compared with levels of these substances in controls. Bezafibrate treatment completely reversed these effects. In rats fed with a high safflower oil or a high sucrose diet, no significant change was seen in SBP and plasma immunoreactive insulin levels. However, the plasma triglyceride levels were increased by dietary lard or sucrose. Moreover, the plasma leptin level was also increased by dietary lard and safflower oil. Neither dietary hypertriglyceridemia nor hyperleptinemia were involved in the development of increases in blood pressure induced by dietary lard.

Plasma levels of catecholamine metabolites predict the response to sulpiride or fluvoxamine in major depression

We investigated the relationships between the changes in plasma catecholamine metabolites obtained from depressed patients before and after administration of sulpiride, a benzamide compound, or fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), and between clinical responses to treatment with each of these drugs. Responders to sulpiride had significantly lower plasma homovanillic acid (pHVA) levels before administration of sulpiride than did non-responders or controls (responders: 4.5 +/- 3.1 ng/ml, non-responders: 11.1 +/- 5.9 ng/ml, controls: 10.9 +/- 5.3 ng/ml). Positive relationships were observed between changes in pHVA levels and improvement rates in the 17-item Hamilton Depression Rating Scale (Ham-D). In contrast, responders to fluvoxamine had significantly higher plasma free 3-methoxy-4-hydroxyphenylglycol (pMHPG) levels before administration of fluvoxamine than did non-responders or controls (responders: 8.5 +/- 1.8 ng/ml, non-responders: 5.9 +/- 2.I ng/ml, controls: 5.2 +/- 2.9 ng/ml). Negative relationships were observed between changes in pMHPG levels and improvement rates in Ham-D. These results suggest that lower pretreatment pHVA levels and higher pretreatment levels of pMHPG might be predictors of response to sulpiride and fluvoxamine, respectively, and that sulpiride might produce a functional increase in the dopaminergic system, resulting in improvement in some depressive symptoms; fluvoxamine, on the other hand, might produce a functional decrease in the noradrenergic system via serotonergic neurons, resulting in improvement of those symptoms.

Characteristic patterns of circadian variation in plasma catecholamine levels, blood pressure and heart rate variability in Type 2 diabetic patients

AIMS

To investigate whether Type 2 diabetic patients exhibit characteristic patterns of circadian variation in plasma levels of catecholamines, blood pressure (BP) and heart rate variability (HRV).

METHODS

Ten Type 2 diabetic and eight control in-patients were studied. Blood for catecholamine measurement was collected every 4 h, and non-invasive ambulatory BP and heart rate were monitored throughout the day. HRV was determined using frequency domain methods.

RESULTS

Diabetic patients showed a different pattern of circadian variation in BP and HRV from that of controls, the diurnal-nocturnal differences (D-N) being significantly smaller. The mean 24-h HRV levels were reduced in diabetic subjects. The mean 24-h plasma noradrenaline level of 1.36 +/- 0.12 nmol/l in diabetic patients was significantly lower than the 2.03 +/- 0.20 nmol/l in controls (P < 0.01). In contrast, no significant difference in adrenaline levels was observed. The mean 24-h plasma noradrenaline level demonstrated a significant positive correlation with D-N in systolic BP (r = 0.49, P = 0.0153).

CONCLUSIONS

The present study demonstrated distinctive patterns of circadian variation in plasma noradrenaline level, BP and HRV in Type 2 diabetic patients, associated with an abnormal circadian pattern of sympathovagal modulation.

Tumor cells as the origin of elevated serum alpha1,3fucosyltransferase in association with malignancy

We have previously reported that the elevated activities of serum alpha 1,3fucosyltransferase reverted to normal levels after curative removal of the tumors. To determine the origin of elevated serum alpha 1,3fucosyltransferase, blood samples were obtained from both the drainage vein and the artery in patients with different stages of colorectal cancer at surgery. The enzyme levels in all samples from the drainage vein were found to be higher than the levels in the artery that fed the tumor. Hence, the origin of elevated alpha1,3fucosyltransferase in serum was thought to be the tumor rather than the liver that is the normal source of serum alpha1,3fucosyltransferase. When serum samples not only from colorectal cancer patients but also from patients with gastric, liver, lung, pancreas, bladder and esophagus cancer were treated with anti-FUTVI antibody, the measured activities of alpha1,3fucosyltransferase were markedly reduced. Further, secretion of alpha1,3fucosyltransferase from human colorectal carcinoma cells was also detected in the culture medium by Western immuno-blot analysis with anti-FUTVI antibody.

The effect of cigarette smoking on soluble adhesion molecules in middle-aged patients with Type 2 diabetes mellitus

AIMS

To investigate the effect of smoking on soluble adhesion molecules in middle-aged diabetic patients.

METHODS

One hundred out-patients with Type 2 diabetes and 100 age- and sex-matched non-diabetic subjects without clinical macrovascular disease were selected. Soluble serum levels of adhesion molecules were analysed using enzyme immunoassay. Carotid atherosclerosis was assessed using an ultrasound system.

RESULTS

When compared with non-diabetic subjects, soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), and sE-selectin were found at significantly high levels in diabetic patients and significantly higher levels of sICAM-1, sE-selectin, and sP-selectin were observed in current smokers than never-smokers among diabetic or non-diabetic subjects, respectively. The combined, but not enhanced, effects of diabetes mellitus and smoking were observed in sICAM-1 and sE-selectin levels. Additionally, levels of sICAM-1 (P < 0.05) and sE-selectin (P < 0.01), but not sP-selectin, were high in ex-smokers when compared with never-smokers among diabetic patients. Diabetic smokers were also found to have marked carotid atherosclerosis, which was related to increased levels of sICAM-1.

CONCLUSIONS

Our present study shows that levels of adhesion molecules were higher in diabetic smokers than diabetic non-smokers or non-diabetic smokers, and that cessation after chronic smoking did not restore the levels of sICAM-1 and sE-selectin, though sP-selectin levels were restored. These data suggest a possible mechanism for accelerated atherosclerosis induced by smoking in patients with diabetes.

Dual phases of functional change in norepinephrine transporter in cultured bovine adrenal medullary cells by long-term treatment with clozapine

The effects of long-term treatment with clozapine, a prototype of atypical antipsychotic drugs, on the functional activity, synthesis and mRNA of norepinephrine (NE) transporter were examined in bovine adrenal medullary cells in culture. Treatment of cells with clozapine at 0.1-3.0 microM concentrations produced dual phases of changes in [(3)H]NE uptake, i.e. the first phase showed a decrease in [(3)H]NE uptake at 2-48 h, and the following phase showed an increase in uptake at 72-168 h. Treatment with clozapine for 6 h decreased V(max) to 40% of the control without changing the K(m) value for [(3)H]NE uptake. However, treatment with clozapine for 96 h increased V(max) by 56% over the control without a change in K(m). Scatchard plot analysis of [(3)H]desipramine (DMI) binding to membranes isolated from cells treated with clozapine for 6 h revealed a decrease in B(max) without any change in K(d); in contrast, treatment with clozapine for 96 h caused an increase in B(max) without any change in K(d). Both actinomycin D and cycloheximide, which are inhibitors of protein synthesis, suppressed the clozapine (96 h)-induced increase in [(3)H]NE uptake. Treatment of cells with clozapine for 12-96 h increased the level of NE transporter mRNA in a concentration-dependent manner (0.3-3.0 microM). These findings suggest that treatment of cells with clozapine results in the down-regulation and subsequent up-regulation of NE transporter. The latter change may be caused by the synthesis of new proteins of NE transporter via an increase in its mRNA.

Association between three functional polymorphisms of dopamine D2 receptor gene and tardive dyskinesia in schizophrenia

The dopamine D2 receptor (DRD2) gene is considered one of the candidate genes contributing to the development of tardive dyskinesia (TD). In the present study, we investigated the genetic association between three functional polymorphisms (Ser311Cys, -141C Ins/Del and TaqI A) in the DRD2 gene and TD (200 patients with schizophrenia: 44 with TD and 156 without TD). No significant difference in the allelic and genotypic distribution between patients with TD and those without TD was observed. However, we found a slightly significant association between the -141C Ins/Del polymorphism and the total Abnormal Involuntary Movement Scale (AIMS) score (P = 0.037). The significant association between the -141C Ins/Del polymorphism and the total AIMS score did not remain after the regression analysis was taken into account (P = 0.14). Our results suggest that that three functional polymorphisms in DRD2 may not play a major role in the occurrence of TD.

Ocular absorption behavior of palmitoyl tilisolol, an amphiphilic prodrug of tilisolol, for ocular drug delivery

The objective of this study was to examine the ocular absorption behavior of an amphiphilic prodrug after instillation onto the cornea of rabbits. A micellar solution of O-palmitoyl tilisolol (PalTL), an amphiphilic prodrug, was prepared. After instillation of tilisolol (TL) and PalTL, the drug concentrations in the tear fluid, cornea, aqueous humor, iris-ciliary body, vitreous body, and blood were measured. In addition, in situ ocular absorption behavior was also evaluated. After instillation of TL, the concentration of TL in the tear fluid quickly decreased. After instillation of PalTL, prolonged retention and high concentrations of PalTL in tear fluid and the cornea were observed. In addition, more prolonged retention of the TL concentration after instillation of PalTL than after instillation of TL was observed in the cornea, aqueous humor, and iris-ciliary body. In situ experiments demonstrated that PalTL was mainly absorbed by the corneal route and the improvement effects of PalTL under in vivo conditions was due to an enhanced transit time of PalTL in ocular tissues. PalTL, an amphiphilic prodrug, exhibited increased retention in the precorneal area compared with the parent drug, TL, resulted in improved ocular absorption of the parent drug.

Characteristics of fluvoxamine-induced nausea

We investigated the association between fluvoxamine and nausea from various viewpoints. The incidence of nausea induced by fluvoxamine was 29% (12/41). Plasma 5-hydroxyindoleacetic acid (p5-HIAA) levels after fluvoxamine administration were significantly higher in patients with nausea (6.6+/-3.4 ng/ml) than in those without nausea (3.5+/-2.7 ng/ml). On the other hand, no significant differences were found between patients with and patients without nausea in terms of sex, age, initial and maximum dosages of fluvoxamine and its plasma concentrations, and clinical response to fluvoxamine. However, the incidence of nausea in patients who were initially administered fluvoxamine at under 50 mg/day was significantly lower than in those who were started at above 50 mg/day. In addition, mosapride, a member of the benzamide family, was effective in alleviating fluvoxamine-induced nausea. These results suggest that fluvoxamine-induced nausea is associated with hyperactivity in serotonergic neurons.

Possible relationship between combined plasma concentrations of risperidone plus 9-hydroxyrisperidone and extrapyramidal symptoms. Preliminary study

We investigated the relationships between extrapyramidal symptoms (EPS) induced by risperidone, the dosage of risperidone and the combined plasma concentrations of risperidone plus its active metabolite, 9-hydroxyrisperidone, in 20 schizophrenic patients. There was a positive correlation between the scores on the Simpson and Angus Scale and both the dosage of risperidone and the sum of the plasma levels of risperidone and 9-hydroxyrisperidone. These results suggest that EPS induced by risperidone increase in conjunction with both the dosage of risperidone and the total plasma concentrations of the parent compound and its active metabolite.

17 beta-Hydroxysteroid dehydrogenase type 2 expression and enzyme activity in the human gastrointestinal tract

The 17 beta-hydroxysteroid dehydrogenases (17 beta HSDs) play an important role in the regulation of intracellular levels of biologically active sex steroid hormones in various human tissues. To date, eight distinctive 17 beta HSD enzymes have been cloned and characterized in humans. Among these isoenzymes, 17 beta HSD type 2 (17 beta HSD2) catalyses the conversion of testosterone into androstenedione and/or oestradiol into oestrone in various tissues, and it has thus been suggested to be involved in the biological inactivation of these sex steroids. The human gastrointestinal tract and liver are considered as the principle sites of inactivation and metabolism of various forms of orally administered sex steroids. We therefore examined 17 beta HSD2 expression and activity in human adult non-pathological gastrointestinal tract in order to clarify further the biological significance of this enzyme. A total of 80 specimens (40 from males and 40 from females) of normal oesophageal, stomach, duodenal, ileal, colonic and rectal tissues were examined for immunohistochemistry. Altogether, 17 tissue specimens were used for enzyme assay, and eight for RNA analysis. 17 beta HSD2 activity was detected in the stomach, duodenum, ileum, colon and rectum. 17 beta HSD2 mRNA was most abundant in the small intestine. 17 beta HSD2 immunoreactivity was localized almost exclusively to the absorptive epithelium, which may be involved in the inactivation of excessive endogenous and exogenous active sex steroids. Results from the present study thus suggest that the human gastrointestinal tract is an important sex steroid metabolizing organ in humans.

Association of plasma free-3-methoxy-4-hydroxyphenyl (ethylene)glycol, natural killer cell activity and delirium in postoperative patients

We measured and compared levels of plasma free 3-methoxy-4-hydroxyphenyl (ethylene)glycol (pMHPG), a major metabolite of noradrenaline, and natural killer (NK) cell activity in 26 patients prior to their undergoing an operation for cardiovascular diseases; 11 of whom expressed delirium and 15 who did not. In conclusion, we found that pMHPG levels before an operation were higher in patients with postoperative delirium than in the patients without, while NK cell activity showed no difference between the two groups. It is possible that hyperactivity of noradrenargic neurons is connected with the development of postoperative delirium. Furthermore, we considered that measurement of pMHPG level before operation might be a useful tool to predict the occurrence of postoperative delirium.