Phase I randomized, double-blind pilot study of micronized resveratrol (SRT501) in patients with hepatic metastases--safety, pharmacokinetics, and pharmacodynamics

The phytochemical resveratrol has undergone extensive preclinical investigation for its putative cancer chemopreventive properties. Low systemic availability of the parent compound due to rapid and extensive metabolism may confound its usefulness as a potential agent to prevent malignancies in organs remote from the site of absorption. Micronization allows increased drug absorption, thus increasing availability. Here we describe a pilot study of SRT501, micronized resveratrol, given as 5.0 g daily for 14 days, to patients with colorectal cancer and hepatic metastases scheduled to undergo hepatectomy. The purpose of the study was to assess the safety, pharmacokinetics, and pharmacodynamics of the formulation. SRT501 was found to be well tolerated. Mean plasma resveratrol levels following a single dose of SRT501 administration were 1,942 ± 1,422 ng/mL, exceeding those published for equivalent doses of nonmicronized resveratrol by 3.6-fold. Resveratrol was detectable in hepatic tissue following SRT501 administration (up to 2,287 ng/g). Cleaved caspase-3, a marker of apoptosis, significantly increased by 39% in malignant hepatic tissue following SRT501 treatment compared with tissue from the placebo-treated patients. SRT501 warrants further clinical exploration to assess its potential clinical utility.

Effect of the proteasome inhibitor MLN519 on the expression of inflammatory molecules following middle cerebral artery occlusion and reperfusion in the rat

Anti-inflammatory treatment with the proteasome inhibitor MLN519 has been previously reported to be neuroprotective against ischemic brain injury in rats. These effects have been related to inhibition of the transcription factor NF-kappaB, which is activated through ubiquitin-proteasomal degradation. The aim of this study was to evaluate the effects of MLN519 to alter the expression of several inflammatory genes under the control of NF-kappaB. Male Sprague-Dawley rats underwent middle cerebral artery occlusion (MCAo) followed by vehicle or MLN519 (1.0 g/kg, i.v.) treatment immediately after reperfusion of blood to the brain at 2h. Gene expression was evaluated 3-72 h post-MCAo. The most striking effects of intravenous treatment with MLN519 were associated with reductions in ICAM-1 expression at 3 h followed by reductions in E-selectin (12-72 h). Less dramatic reductions were observed in IL-1Beta (3-24 h) and TNF-Alpha (24 h) with no apparent effects on IL-6 and VCAM-1 mRNA levels. Immunohistochemical analysis revealed that the genes most dramatically affected by MLN519 had highest expression in endothelial cells and leukocytes (E-selectin, ICAM-1),indicating that these cell types may be the primary targets of intravenously delivered MLN519 treatment.

Early clinical experience with the novel proteasome inhibitor PS-519

AIMS

The main objective of this study was to investigate the safety, tolerability and pharmacodynamics of the novel proteasome inhibitor PS-519 in young male volunteers. Many pro-inflammatory mediators such as cytokines and cell adhesion molecules that are responsible for the development of the cerebral infarct are under the control of the transcription factor Nuclear Factor kappa-B (NF-kappaB). The activity of NF-kappaB is itself tightly regulated through the multicatalytic enzyme known as the proteasome. PS-519 is a novel and highly selective small molecule that inhibits the proteasome. An ex vivo assay of 20S proteasome activity allows monitoring of the drug effect in blood. PS-519 is protective in multiple animal models of cerebral ischaemia over a range of doses that achieve 20S inhibition of 40%-80%.

METHODS

PS-519 has been administered to healthy male volunteers as single and repeated doses up to 1.6 mg m(-2). It was given as an intravenous bolus over 20-30 s in a double blind, randomized, placebo-controlled phase I study, examining vital signs, safety, tolerability and blood 20S proteasome inhibition.

RESULTS

Thirty-nine subjects received single doses of 0.012 mg m-2-1.6 mg m(-2) and 28 subjects received doses of 0.5 mg m(-2)-1.6 mg m(-2) on three consecutive days. The drug was well tolerated. There was no clear treatment-emergent symptom or abnormality of laboratory tests. Proteasome inhibition in blood samples as measured by 20S assay achieved the intended maximum target level of 70-80% with 1.6 mg m(-2), and was reproducible with repeated dosing.

CONCLUSIONS

This study has demonstrated that proteasome inhibition is well tolerated by healthy subjects at levels that are maximally neuroprotective in experimental conditions. Further clinical evaluation appears justified.

The risk to the United Kingdom population of zinc cadmium sulfide dispersion by the Ministry of Defence during the "cold war"

OBJECTIVES

To estimate exposures to cadmium (Cd) received by the United Kingdom population as a result of the dispersion of zinc Cd sulfide (ZnCdS) by the Ministry of Defence between 1953 and 1964, as a simulator of biological warfare agents.

METHODS

A retrospective risk assessment study was carried out on the United Kingdom population during the period 1953-64. This determined land and air dispersion of ZnCdS over most of the United Kingdom, inhalation exposure of the United Kingdom population, soil contamination, and risks to personnel operating equipment that dispersed ZnCdS.

RESULTS

About 4600 kg ZnCdS were dispersed from aircraft and ships, at times when the prevailing winds would allow large areas of the country to be covered. Cadmium released from 44 long range trials for which data are available, and extrapolated to a total of 76 trials to allow for trials with incomplete information, is about 1.2% of the estimated total release of Cd into the atmosphere over the same period. "Worst case" estimates are 10 microg Cd inhaled over 8 years, equivalent to Cd inhaled in an urban environment in 12100 days, or from smoking 100 cigarettes. A further 250 kg ZnCdS was dispersed from the land based sites, but significant soil contamination occurred only in limited areas, which were and have remained uninhabited. Of the four personnel involved in the dispersion procedures (who were probably exposed to much higher concentrations of Cd than people on the ground), none are suspected of having related illnesses.

CONCLUSION

Exposure to Cd from dissemination of ZnCdS during the "cold war" should not have resulted in adverse health effects in the United Kingdom population.

Postischemic (6-Hour) treatment with recombinant human tissue plasminogen activator and proteasome inhibitor PS-519 reduces infarction in a rat model of embolic focal cerebral ischemia

BACKGROUND AND PURPOSE

The proteasome inhibitor PS-519 blocks activation of nuclear factor-kappaB, a major mediator of inflammation. We tested the hypothesis that combination treatment of recombinant human tissue plasminogen activator (rhtPA) and PS-519 extends the therapeutic window for treatment of stroke with rhtPA without increasing incidence of hemorrhagic transformation.

METHODS

The middle cerebral artery (MCA) of male Wistar rats (n=56) was occluded by an embolus. After embolization, animals were randomly divided into the following groups: PS-519 treatment groups: PS-519 was given at 2, 4, or 6 hours after MCA occlusion; rhtPA treatment groups: rhtPA was given at 2 or 4 hours after MCA occlusion; combination treatment groups: PS-519 and rhtPA were given at 2, 4, or 6 hours after MCA occlusion; control group: the same volume of saline was given at 2 hours after MCA occlusion.

RESULTS

Administration of PS-519 alone at 2 or 4 hours, but not 6 hours, significantly (P<0.05) reduced infarct volume and improved neurological recovery compared with the control group. Administration of rhtPA alone at 2 hours, but not 4 hours, significantly (P<0.05) reduced infarct volume and improved neurological recovery compared with the control group. Furthermore, combination treatment with rhtPA and PS-519 even at 6 hours significantly (P<0.05) reduced infarct volume, improved neurological recovery, and did not increase the incidence of hemorrhagic transformation compared with the control group or the group treated with PS-519 alone.

CONCLUSIONS

Our data suggest that combination treatment with PS-519 and rhtPA extends the neuroprotective effect to at least 6 hours after embolization.

The proteasome: a new target for novel drug therapies

The proteasome is an enzyme present in all cells, from yeast to human, and has a central role in the proteolytic degradation of the vast majority of intracellular proteins. Among the key proteins modulated by the proteasome are those involved in controlling inflammatory processes, cell cycle regulation, and gene expression. As such, agents that inhibit the proteasome have been shown to be active in numerous animal models of inflammation and cancer Two proteasome inhibitors are under clinical evaluation. PS-519 is being studied for the treatment of reperfusion injury that occurs following cerebral ischemia and myocardial infarction. The other, PS-341, has recently entered multiple phase 2 clinical trials for the treatment of multiple myeloma, chronic lymphocytic leukemia, and a variety of solid tumors. The proteasome may have an important role in the evolution of HIV-related disorders including AIDS and inflammatory disorders. Therapeutic strategies using proteasome inhibitors for the treatment of these conditions have now entered preclinical development.

Enhanced chemosensitivity to CPT-11 with proteasome inhibitor PS-341: implications for systemic nuclear factor-kappaB inhibition

Inducible activation of nuclear factor-kappaB (NF-kappaB) inhibits the apoptotic response to chemotherapy and irradiation. Activation of NF-kappaB via phosphorylation of an inhibitor protein IkappaB leads to degradation of IkappaB through the ubiquitin-proteasome pathway. We hypothesized that inactivation of proteasome function will inhibit inducible NF-kappaB activation, thereby increasing levels of apoptosis in response to chemotherapy and enhancing antitumor effects. To assess the effects of proteasome inhibition on chemotherapy response, human colorectal cancer cells were pretreated with the dipeptide boronic acid analogue PS-341 (1 microM) prior to exposure to SN-38, the active metabolite of the topoisomerase I inhibitor, CPT-11. Inducible activation of NF-kappaB and growth response were evaluated in vitro and in vivo. Effects on p53, p21, p27 and apoptosis were determined. Pretreatment with PS-341 inhibited activation of NF-kappaB induced by SN-38 and resulted in a significantly higher level of growth inhibition (64-75%) compared with treatment with PS-341 alone (20-30%) or SN-38 alone (24-47%; P < 0.002). Combination therapy resulted in a 94% decrease in tumor size compared with the control group and significantly improved tumoricidal response to treatment compared with all treatment groups (P = 0.02). The level of apoptosis was 80-90% in the treatment group that received combination treatment compared with treatment with single agent alone (10%). Proteasome inhibition blocks chemotherapy-induced NF-kappaB activation, leading to a dramatic augmentation of chemosensitivity and enhanced apoptosis. Combining proteasome inhibition with chemotherapy has significant potential to overcome the high incidence of chemotherapy resistance. Clinical studies are currently in development to evaluate the role of proteasome inhibition as an important adjuvant to systemic chemotherapy.

26S proteasome inhibition induces apoptosis and limits growth of human pancreatic cancer

The 26S proteasome degrades proteins that regulate transcription factor activation, cell cycle progression, and apoptosis. In cancer, this may allow for uncontrolled cell division, promoting tumor growth, and spread. We examined whether selective inhibition of the 26S proteasome with PS-341, a dipeptide boronic acid analogue, would block proliferation and induce apoptosis in human pancreatic cancer. Proteasome inhibition significantly blocked mitogen (FCS) induced proliferation of BxPC3 human pancreatic cancer cells in vitro, while arresting cell cycle progression and inducing apoptosis by 24 h. Accumulation of p21(Cip1-Waf-1), a cyclin dependent kinase (CDK) inhibitor normally degraded by the 26S proteasome, occurred by 3 h and correlated with cell cycle arrest. When BxPC3 pancreatic cancer xenografts were established in athymic nu/nu mice, weekly administration of 1 mg/kg PS-341 significantly inhibited tumor growth. Both cellular apoptosis and p21(Cip1-Waf-1) protein levels were increased in PS-341 treated xenografts. Inhibition of tumor xenograft growth was greatest (89%) when PS-341 was combined with the tumoricidal agent CPT-11. Combined CPT-11/PS-341 therapy, but not single agent therapy, yielded highly apoptotic tumors, significantly inhibited tumor cell proliferation, and blocked NF-kappaB activation indicating this systemic therapy was effective at the cancer cell level. 26S proteasome inhibition may represent a new therapeutic approach against this highly resistant and lethal malignancy.

The proteasome inhibitor PS-341 inhibits growth, induces apoptosis, and overcomes drug resistance in human multiple myeloma cells

Human multiple myeloma (MM) is a presently incurable hematological malignancy, and novel biologically based therapies are urgently needed. Proteasome inhibitors represent a novel potential anticancer therapy. In this study, we demonstrate that the proteasome inhibitor PS-341 directly inhibits proliferation and induces apoptosis of human MM cell lines and freshly isolated patient MM cells; inhibits mitogen-activated protein kinase growth signaling in MM cells; induces apoptosis despite induction of p21 and p27 in both p53 wild-type and p53 mutant MM cells; overcomes drug resistance; adds to the anti-MM activity of dexamethasone; and overcomes the resistance to apoptosis in MM cells conferred by interleukin-6. PS-341 also inhibits the paracrine growth of human MM cells by decreasing their adherence to bone marrow stromal cells (BMSCs) and related nuclear factor kappaB-dependent induction of interleukin-6 secretion in BMSCs, as well as inhibiting proliferation and growth signaling of residual adherent MM cells. These data, therefore, demonstrate that PS-341 both acts directly on MM cells and alters cellular interactions and cytokine secretion in the BM millieu to inhibit tumor cell growth, induce apoptosis, and overcome drug resistance. Given the acceptable animal and human toxicity profile of PS-341, these studies provide the framework for clinical evaluation of PS-341 to improve outcome for patients with this universally fatal hematological malignancy.

Proteasome inhibition: a new strategy in cancer treatment

The ubiquitin proteasome pathway is a highly conserved intracellular pathway for the degradation of proteins. Many of the short-lived regulatory proteins which govern cell division, growth, activation, signaling and transcription are substrates that are temporally degraded by the proteasome. In recent years, new and selective inhibitors of the proteasome have been employed in cell culture systems to examine the anti-tumor potential of these agents. This review covers the chemistry of selected proteasome inhibitors, possible mechanisms of action in cell culture and the in vivo examination of proteasome inhibitors in murine and human xenograft tumor models in mice. One inhibitor, PS-341, has recently entered Phase I clinical trials in cancer patients with advanced disease to further test the potential of this approach.

Proteasome inhibitor PS519 reduces infarction and attenuates leukocyte infiltration in a rat model of focal cerebral ischemia

BACKGROUND AND PURPOSE

Reperfusion brain injury after cerebral ischemia is associated with a developing inflammatory response at the site of infarction. Proteasome inhibitors block nuclear factor-kappaB activation and provide anti-inflammatory effects in several animal models of peripheral inflammation. We tested the novel proteasome inhibitor PS519 in a rat model of transient focal ischemia to establish its pharmacodynamics as a neuroprotection treatment and related effects on leukocyte infiltration.

METHODS

Rats were subjected to 2 hours of focal cerebral ischemia by means of the filament method of middle cerebral artery occlusion (MCAo). After either 22 or 70 hours of reperfusion, infarct size was measured and neurological function, electroencephalographic (EEG) activity, and/or neutrophil and macrophage infiltration was quantified. PS519 was administered in a single intravenous bolus at 2 hours after MCAo. In addition, the therapeutic window for PS519 was estimated by delaying treatment for 4 or 6 hours after MCAo.

RESULTS

Dose-response analysis of infarct volume at 24 hours revealed that PS519 neuroprotection approached 60%, and clinical evaluations showed significant improvements in neurological function and EEG activity. Neutrophil infiltration at 24 hours was also significantly decreased in cortical and striatal infarcted tissue of PS519-treated rats. Delaying the PS519 treatment up to 4 hours continued to result in significant neuroprotection. In the 72-hour injury model, infarction was reduced 40% by PS519, and significant improvements in neurological function and EEG recovery were again measured. Considerable reductions in both neutrophil and macrophage infiltration were evident.

CONCLUSIONS

PS519 mitigates infarction and improves neurological recovery in brain-injured rats, an effect in part caused by a reduction in the leukocyte inflammatory response.

Proteasome inhibition: a new strategy in cancer treatment

The ubiquitin proteasome pathway is a highly conserved intracellular pathway for the degradation of proteins. Many of the short-lived regulatory proteins which govern cell division, growth, activation, signaling and transcription are substrates that are temporally degraded by the proteasome. In recent years, new and selective inhibitors of the proteasome have been employed in cell culture systems to examine the anti-tumor potential of these agents. This review covers the chemistry of selected proteasome inhibitors, possible mechanisms of action in cell culture and the in vivo examination of proteasome inhibitors in murine and human xenograft tumor models in mice. One inhibitor, PS-341, has recently entered Phase I clinical trials in cancer patients with advanced disease to further test the potential of this approach.

Proteasome inhibition measurements: clinical application

BACKGROUND

PS-341, a selective inhibitor of the proteasome, currently is under evaluation as an anticancer agent in multiple phase I clinical trials. In animal-model studies, PS-341 was rapidly removed from the vascular compartment and distributed widely, quickly approaching the limits of detection. An accurate pharmacodynamic assay has been developed as an alternative or complement to pharmacokinetic measurements.

METHODS

Fluorogenic kinetic assays for both the chymotryptic and tryptic activities of the proteasome have been optimized for both whole blood and blood cells. Using the ratio of these activities and the catalytic mechanism of the proteasome, we developed a novel method of calculating percentage of inhibition, using two structurally unrelated inhibitors (PS-341 and lactacystin).

RESULTS

This ratio method was demonstrated to be sensitive (detection limit of 13% inhibition with 10 microgram of cell lysate), specific to the proteasome (PS-341 provides >98% inhibition), accurate (112% analyte recovery), and precise (0% +/- 5% inhibition at 0 nmol/L PS-341 and 74.5% +/- 1.7% inhibition at 200 nmol/L PS-341). Using these assays, we found that both erythrocytes and leukocytes contain proteasome at 3 micromol/L. Pharmacodynamic results for PS-341 obtained from the whole-blood ratio method were comparable to those using leukocytes determined by another method.

CONCLUSIONS

The described assay provides a reliable method for studying the pharmacodynamics of proteasome inhibitors and is now in use in concurrent phase I clinical trials with PS-341.

Treatment of established relapsing experimental autoimmune encephalomyelitis with the proteasome inhibitor PS-519

PLP139-151-induced relapsing experimental autoimmune encephalomyelitis (R-EAE) in SJL mice is a Th1-mediated autoimmune demyelinating disease model for multiple sclerosis (MS) in which the primary disease relapse is mediated by T cells specific for the endogenous PLP178-191 epitope. This complex inflammatory process requires the co-ordinated expression of a wide variety of immune-related genes active at a variety of stages of the autoimmune process which are regulated, in part, by the transcription factor nuclear factor (NF)-kappaB which is activated via the ubiquitin-proteasome pathway. We asked if in vivo administration of a selective inhibitor of the ubiquitin-proteasome pathway, PS-519, which downregulates activation of NF-kappaB, could downregulate ongoing R-EAE. Administration of PS-519 during the remission phase, following acute clinical disease was effective in significantly reducing the incidence of clinical relapses, CNS histopathology, and T cell responses to both the initiating and relapse-associated PLP epitopes. The inhibition of clinical disease was dependent upon continuous administration of PS-519 in that recovery of T cell function and onset of disease relapses developed within 10-14 days of drug withdrawal. The data suggest that targeting the ubiquitin proteasome pathway, in particular NF-kappaB, may offer a novel and efficacious approach for the treatment of progressive autoimmune diseases, including MS.

A new model of cancer cachexia: contribution of the ubiquitin-proteasome pathway

A new model of cachexia is described in which muscle protein metabolism related to the ubiquitin-proteasome pathway was investigated. Cloning of the colon-26 tumor produced a cell line, termed R-1, which induced cytokine (noninterleukin-1beta, interleukin-6 and tumor necrosis factor-alpha)-independent cachexia. Implantation of R-1 cells in mice elicited significant (20-30%) weight loss and decreased blood glucose by 70%, and adipose tissue levels declined by 95% and muscle weights decreased by 20-25%. Food intake was unaffected. The decrease in muscle weight reflected a decline in insoluble, but not soluble, muscle protein that was associated with a significant increase in net protein degradation. The rate of ubiquitin conjugation of proteins was significantly elevated in muscles of cachectic mice. Furthermore, the proteasome inhibitor lactacystin blocked the increase in protein breakdown but had no significant effect on proteolysis. Several markers of the ubiquitin-proteasome pathway, E2(14k) mRNA and E2(14k) protein and ubiquitin-protein conjugates, were not elevated. Future investigations with this new model should gain further insights into the mechanisms of cachexia and provide a background to evaluate novel and more efficacious therapies.

Proteasome inhibition: A novel mechanism to combat asthma

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) is a critical transcription factor required for the regulation of many genes involved in inflammatory responses to noxious stimuli. On activation, NF-kappaB induces the transcription of numerous proinflammatory cytokines, enzymes, and cellular adhesion molecules. Blockade of the proteasome with selective inhibitors attenuates the effects of NF-kappaB, leading to suppression of the inflammatory response.

OBJECTIVE

We sought to determine whether proteasome inhibitors would be active in a model of asthma.

METHODS

The mouse delayed-type hypersensitivity model was used to screen a panel of compounds for in vivo activity. The proteasome inhibitor, PS-519, was shown to be the most active in this model and was selected for further development. Allergen-induced pulmonary eosinophilia in Brown Norway rats was used subsequently to determine anti-inflammatory activity in an animal model.

RESULTS

Direct administration of PS-519 into the lungs significantly reduced leukocyte numbers, particularly the selective increase in eosinophils. Because steroids are the mainstay anti-inflammatory therapy in asthma, and data is available to suggest their possible interaction to suppress the activation of NF-kappaB, rats were also treated by inhalation with combinations of a steroid and the proteasome inhibitor. In both the delayed-type hypersensitivity and the animal eosinophil model, low doses of proteasome inhibitors were shown to be effective when given with low doses of steroids.

CONCLUSION

Taken together, the present data suggest that proteasome inhibition may represent a novel strategy for the treatment of inflammatory lung diseases such as asthma.

Proteasome inhibitors: a novel class of potent and effective antitumor agents

The ubiquitin-proteasome pathway plays a critical role in the regulated degradation of proteins involved in cell cycle control and tumor growth. Dysregulating the degradation of such proteins should have profound effects on tumor growth and cause cells to undergo apoptosis. To test this hypothesis, we developed a novel series of proteasome inhibitors, exemplified by PS-341, which we describe here. As determined by the National Cancer Institute in vitro screen, PS-341 has substantial cytotoxicity against a broad range of human tumor cells, including prostate cancer cell lines. The PC-3 prostate cell line was, therefore, chosen to further examine the antitumor activity of PS-341. In vitro, PS-341 elicits proteasome inhibition, leading to an increase in the intracellular levels of specific proteins, including the cyclin-dependent kinase inhibitor, p21. Moreover, exposure of such cells to PS-341 caused them to accumulate in the G2-M phase of the cell cycle and subsequently undergo apoptosis, as indicated by nuclear condensation and poly(ADP-ribose) polymerase cleavage. Following weekly i.v. treatment of PS-341 to mice bearing the PC-3 tumor, a significant decrease (60%) in tumor burden was observed in vivo. Direct injection of PS-341 into the tumor also caused a substantial (70%) decrease in tumor volume with 40% of the drug-treated mice having no detectable tumors at the end of the study. Studies also revealed that i.v. administration of PS-341 resulted in a rapid and widespread distribution of PS-341, with highest levels identified in the liver and gastrointestinal tract and lowest levels in the skin and muscle. Modest levels were found in the prostate, whereas there was no apparent penetration of the central nervous system. An assay to follow the biological activity of the PS-341 was established and used to determine temporal drug activity as well as its ability to penetrate tissues. As such, PS-341 was shown to penetrate PC-3 tumors and inhibit intracellular proteasome activity 1.0 h after i.v. dosing. These data illustrate that PS-341 not only reaches its biological target but has a direct effect on its biochemical target, the proteasome. Importantly, the data show that inhibition of this target site by PS-341 results in reduced tumor growth in murine tumor models. Together, the results highlight that the proteasome is a novel biochemical target and that inhibitors such as PS-341 represent a unique class of antitumor agents. PS-341 is currently under clinical evaluation for advanced cancers.

Inhibition of NF-kappa B activation in vitro and in vivo: role of 26S proteasome

It is becoming increasingly apparent that NF-kappa B plays a critical role in regulating the inflammatory response. Data obtained from studies in our laboratories demonstrate that the proteasome plays an important role in the inflammatory cascade by regulating the activation of NF-kappa B. Indeed, the availability of selective and orally active proteasome inhibitors should prove useful in delineating the roles of the proteasome and NF-kappa B in other pathophysiological conditions such as cancer and heart disease.

Role of the proteasome and NF-kappaB in streptococcal cell wall-induced polyarthritis

The transcription factor NF-kappaB activates a number of genes whose protein products are proinflammatory. In quiescent cells, NF-kappaB exists in a latent form and is activated via a signal-dependent proteolytic mechanism in which the inhibitory protein IkappaB is degraded by the ubiquitin-proteasome pathway. Consequently, inhibition of the proteasome suppresses activation of NF-kappaB. This suppression should therefore decrease transcription of many genes encoding proinflammatory proteins and should ultimately have an anti-inflammatory effect. To this end, a series of peptide boronic acid inhibitors of the proteasome, exemplified herein by PS-341, were developed. The proteasome is the large multimeric protease that catalyzes the final proteolytic step of the ubiquitin-proteasome pathway. PS-341, a potent, competitive inhibitor of the proteasome, readily entered cells and inhibited the activation of NF-kappaB and the subsequent transcription of genes that are regulated by NF-kappaB. Significantly, PS-341 displayed similar effects in vivo. Oral administration of PS-341 had anti-inflammatory effects in a model of Streptococcal cell wall-induced polyarthritis and liver inflammation in rats. The attenuation of inflammation in this model was associated with an inhibition of IkappaBalpha degradation and NF-kappaB-dependent gene expression. These experiments clearly demonstrate that the ubiquitin-proteasome pathway and NF-kappaB play important roles in regulating chronic inflammation and that, as predicted, proteasome inhibition has an anti-inflammatory effect.

Cerebrovascular effects of the bradykinin analog RMP-7 in normal and irradiated dog brain

The effects of an intravenous (i.v.) injection of the bradykinin analog RMP-7 (100 ng/kg) were assessed in normal dogs and dogs with focal, radiation-induced brain lesions. A dose of 20 Gy was delivered to a point 0.75 cm from a removable interstitial 125I source; parameters relating to blood flow and permeability were quantified using computed tomography 2-8 weeks after irradiation. Blood flow-related endpoints included regional cerebral blood flow (rCBF), mean transit time of blood and vascular volume, while endpoints related to permeability included blood-to-brain transfer constant (Ki), brain-to-blood transfer constant and plasma volume. In unirradiated brain, an i.v. bolus of RMP-7 administered through the left cephalic vein induced a rapid and transient hypotension and a statistically significant increase in vascular volume; no alterations in any parameter related to permeability were observed. After irradiation, changes in rCBF after RMP-7 depended upon time after exposure, effects presumably due to changing morphology in the irradiated tissues. In the radiation lesions, significant increases in Ki were observed 5 minutes after injection of RMP-7, but those increases were not related to time after irradiation or alteration in blood flow-related parameters. Our results showed that RMP-7 selectively increased permeability in already damaged vasculature without affecting the extent or volume of radiation-induced vasogenic edema. These data suggest that RMP-7 may provide an effective means to enhance the delivery of compounds to an already compromised brain while not exacerbating the potential adverse effects of pre-existing vasogenic edema.

Telomere length in myelodysplastic syndromes

We have studied telomere length in the bone marrow cells or the granulocyte and lymphocyte cell fractions of 54 patients with myelodysplastic syndromes (MDS) by Southern blot hybridization using the (TTAGGG)4 probe. The average telomere length expressed as the peak telomere repeat array (TRA) in the peripheral blood, or bone marrow samples obtained from a group of 21 healthy age-matched controls (26-89 years old, mean age 55), ranged between 7.5 and 9.5 kb (mean peak TRA 8.6 kb). Twenty-four patients with refractory anemia (RA) were studied; 10/24 (42%) had telomere reduction (<7.5 kb) relative to age-matched controls and the mean peak TRA was 7.5 kb (range 4.0-9.0 kb). Eleven patients with RA with excess blasts (RAEB) were studied; 5/11 (45%) had reduced telomeres relative to age-matched controls and the mean peak TRA was 7.1 kb (range 5.0-9.0 kb). Eighteen patients with MDS in transformation to AML, comprising 15 with RAEB in transformation (RAEBt) and 3 with CMML in transformation (CMMLt), were also studied. Thirteen of eighteen patients (72%) had telomere reduction relative to age-matched controls and the mean peak TRA was 6.1 kb (range 3.5-9.0 kb). Thirty-six patients included in the study had either a normal karyotype or a simple karyotype (1 karyotypic change) and 20/36 (55%) of these had telomere reduction and the mean peak TRA was 7.1 kb (range 4.3-9.0 kb); 8 patients had a complex karyotype (3 or more karyotypic changes) and 5/8 (62%) of these had telomere reduction and the mean peak TRA was 6.1 kb (range 3.5-9.0 kb). We conclude, firstly that there is heterogeneity of telomere length in MDS and that this is observed throughout the spectrum of FAB-subtypes. Secondly, these data show that a marked reduction in telomere length in MDS if often associated with leukemic transformation and with the presence of complex karyotypic abnormalities.

Controlled modulation of BBB permeability using the bradykinin agonist, RMP-7

Previous studies have shown that the bradykinin agonist, RMP-7, can safely permeabilize the blood brain barrier (BBB) by activation of constitutive B2 receptors on endothelial cells. The paper describes a series of studies using quantitative autoradiography and intracarotid infusions of RMP-7 to further elucidate the effect on BBB permeability. Because earlier studies also demonstrated that even greater effects of RMP-7 were observed in the BBB associated with brain tumors, animal models were employed so that comparisons could be made between the effects of RMP-7 within tumor, brain tissue proximal to tumor, and brain tissue distal from tumor. In the first study, the effect of RMP-7 on enhancing the BBB permeation of three compounds of different physical characteristics was directly compared ([14C]carboplatin, small, hydrophilic; [14C]dextran, large, hydrophilic; [14C]BCNU, small, lipophilic). RMP-7 increased permeability of the vascular barriers to both hydrophilic compounds, carboplatin and dextran. While the effects of RMP-7 were observed on nontumor BBB, the greatest and most consistent effects were observed on the blood brain tumor barrier. This was true for both carboplatin and dextran, with progressively less effect seen as the distance from tumor boundary increased. This topographic effect was more pronounced with the larger molecular weight compound, dextran. No effect of RMP-7 was seen in permeabilizing the BBB or the blood brain tumor barrier for the lipophilic drug, BCNU. In a second study, the generality of RMP-7's effects was established by demonstrating similar increases in permeability to carboplatin in both inbred (Fischer 344) and outbred (Wistar) rat strains, implanted with varying tumor cell lines. Finally, several additional studies were performed to gain greater insight into the dynamics involved with eventual restoration of the BBB following RMP-7 administration. In one series, it was demonstrated that the BBB begins to close nearly immediately upon withdrawal of RMP-7, with complete restoration occurring within minutes. In another series, tachyphylaxis or desensitization resulting from continuous RMP-7 infusion was studied. These studies demonstrated that 60 min of continuous RMP-7 infusion resulted in complete, spontaneous restoration of the barrier to both carboplatin and dextran. Moreover, the desensitization appears to be linked to the initial activation of the receptors in a way which suggests that obligatory desensitization may exist as part of a more complete response. These data are discussed as they relate to practical issues to enhance delivery of drugs across the BBB, as well as more fundamental issues involving the function of the BBB and its interaction with the brain.

Unlocking the blood-brain barrier: a role for RMP-7 in brain tumor therapy

The effect and mechanism of the blood-brain barrier-permeabilizing agent, RMP-7, was investigated in a series of studies employing a rat RG2 glioma model. Changes in uptake of carboplatin into brain tumor and various nontumor brain tissue regions was determined using a sophisticated image analysis system. This system permitted quantitative autoradiography to be analyzed simultaneously with overlayed histological images from the same coronal brain section. A wide range of intracarotid doses of RMP-7 (0.01 to 9.0 micrograms/kg) was shown to significantly increase the permeability of carboplatin into tumor tissue and surrounding brain tissue (up to twofold) in a dose-dependent manner. Additionally, substantially greater permeability effects were seen in the tumor compared to healthy brain. Moreover, a clear topographic profile was observed in nontumor brain tissue, with progressively less uptake observed with increasing distance from the tumor. The fact that RMP-7 increased the uptake of carboplatin into ipsilateral brain tissue outside the tumor mass has potential implications for treating human glioma patients, for it is commonly recognized that tumor cells typically migrate from the tumor mass into surrounding brain tissue thereby escaping conventional attempts to destroy the malignant cells. To help elucidate the mechanism of RMP-7's permeability effects, the uptake of carboplatin was also determined under conditions where either the bradykinin B2 receptor antagonist, HOE140, or the B1 antagonist, [desArg10]HOE140, was coadministered with RMP-7. Results indicate that RMP-7's effects are mediated specifically through bradykinin B2 receptors. Furthermore, neither bradykinin antagonist alone affected the uptake of carboplatin into the leaky tumor region, suggesting that abnormal elevations in endogenous bradykinin activity are not likely responsible for the characteristic leaky nature of the tumor vascular barrier. The combined results from these studies therefore offer new insight into the characteristics of the vascular barriers in normal and tumor brain tissue and further elucidate the novel permeability effects of RMP-7. Together, they support its potential use as an adjunctive therapy for the selective delivery of chemotherapeutic drugs to brain tumors and possibly other neurodegenerative conditions.

Intravenous RMP-7 selectively increases uptake of carboplatin into rat brain tumors

Rats implanted with RG-2 gliomas were administered i.v. RMP-7 and [14C]carboplatin. Changes in the permeability of the blood-brain barrier to carboplatin were determined using quantitative autoradiography. i.v. infusions of RMP-7 induced an increase in the permeability of the vascular barrier within the tumor to carboplatin. Additionally, permeability of brain tissue proximal to, but clearly outside the tumor mass, was also increased. Progressively less uptake of [14C]carboplatin was observed as distance from the tumor border increased. The increases in permeability induced by RMP-7 occurred in a dose-related fashion. No increase in carboplatin level was observed in several nonbrain tissues, including sciatic nerve, retina, heart, lung, liver, kidney, and spleen. Finally, the permeabilizing effects of RMP-7 were shown to occur independent of histaminergic or hypotensive mechanisms. These data provide additional insight into the permeabilizing effects and mechanism of RMP-7 and offer additional support for the therapeutic utility of this novel compound as an adjunctive treatment for human gliomas.

Lack of evidence for neutrophil participation during infarct formation following focal cerebral ischemia in the rat

The involvement of neutrophils in the pathogenesis of cerebral ischemic injury in two rat models of focal ischemia was investigated. In Experiment I, a model of focal ischemia with partial reperfusion was used. Although significant and discrete ischemic damage within the neocortex was nearly maximal at 12 h postocclusion, no elevation in neutrophils was seen at this time point. Even after 21 h postocclusion, only a subtle increase in neutrophils within the ischemic tissue was observed. To further investigate the possible role of neutrophils in cerebral ischemia, the effect of cyclophosphamide-induced neutropenia was investigated (Experiment II). While a marked reduction (>98%) in systemic neutrophils was achieved in advance of and during the ischemic challenge, no reduction in the volume of ischemic damage was observed. In Experiment III, variations in the rat model of focal ischemia were made to produce a larger area of ischemic damage, as well as to permit complete reperfusion of blood to the affected cortex. While more neutrophils were seen in this variation of the model, very few were observed (< 1 per field) prior to the time that maximal ischemic damage had already occurred. Together, these experiments revealed that substantial brain necrosis occurred prior to the appearance of neutrophils, under conditions of partial, as well as complete, reperfusion. Moreover, at the time points when elevations in neutrophils were observed, no further increase in volume of ischemic damage was noted. Finally, pharmacologic removal of neutrophils prior to ischemia did not alter the size of the ischemic region. These data therefore fail to support the hypothesis that neutrophils play a general and essential role in infarct formation following focal brain ischemia and argue that further studies are required to more clearly elucidate the conditions under which neutrophils might participate in ischemic pathogenesis.

RMP-7, a bradykinin agonist, increases permeability of blood-ocular barriers in the guinea pig

PURPOSE

To determine if the bradykinin agonist, RMP-7, could increase the ocular tissue concentration of agents that normally have limited access across the blood-ocular barriers. The extracellular space marker, sucrose, and the anti-viral drug, ganciclovir, were tested.

METHODS

Using the perfused eye method in guinea pigs, RMP-7 (1 microgram/kg over 5 minutes) or saline were administered intraarterially into the ocular circulation before either radiolabeled sucrose or ganciclovir (0.4 to 0.6 microCi/ml per minute). At time intervals ranging from 0.25 minute to 10 minutes, perfused eyes were removed, and the radioactivity within various compartments was measured using liquid scintillography.

RESULTS

Pretreatment with RMP-7 significantly increased uptake of both sucrose (up to 4.5-fold) and ganciclovir (up to 2-fold) into the guinea pig retina and lens. Smaller and less consistent effects were observed in other eye compartments.

CONCLUSIONS

This report demonstrates that RMP-7 enhances the permeability of blood-ocular barriers, and it provides the first pharmacologic evidence for a means to enhance the concentration of ganciclovir into the retina. Thus, these data support the concept that RMP-7 may prove to be a useful adjunct for enhanced delivery of therapeutics to the eye under conditions in which ocular barriers limit treatment.

Calpain as a novel target for treating acute neurodegenerative disorders

Calpains are cytosolic, neutral proteases that normally exist in an inactive or quiescent state. They require higher than normal levels of calcium for activation which, once accomplished, lead to irreversible proteolysis of numerous cytoskeletal, membrane-associated and regulatory proteins. Because of these characteristics, calpain is gaining attention as a potentially important pathogenic variable in ischemic neuronal death. This manuscript explores this hypothesis by briefly reviewing current support for the role played by calpain in ischemic neurodegeneration, and then discussing a series of recently published studies which: 1. offer further evidence for the hypothesis, and 2. provide direct support for the idea that selective inhibition of calpain can greatly limit the neuronal damage that would normally occur following both global as well as focal brain ischemia. Thus, the data reviewed in this manuscript support the ideas that unregulated activation and proteolysis of intraneuronal calpain plays a significant role in the brain damage that occurs following an ischemic event and that delivering selective and membrane permeant calpain inhibitors to ischemic tissue may provide a powerfully effective therapeutic means of limiting neuronal damage.

Calpain inhibitor AK295 protects neurons from focal brain ischemia. Effects of postocclusion intra-arterial administration

BACKGROUND AND PURPOSE

This research was performed to determine whether a selective inhibitor of the calcium-dependent protease, calpain, could reduce ischemia-associated brain damage when peripherally administered after a vascular occlusion.

METHODS

A variation of the rat middle cerebral artery occlusion model was used. A range of doses of AK295 (a novel calpain inhibitor synthesized for this purpose) was continuously infused through the internal carotid artery, beginning 1.25 hours from the initiation of the occlusion. Rats were killed at 21 hours, and the infarct volume was quantified.

RESULTS

Postocclusion (1.25-hour) infusion of the calpain inhibitor AK295 elicited a dose-dependent neuroprotective effect after focal ischemia. The highest dose tested (3 mg/kg per hour) afforded the maximum effect, illustrated by a 32% reduction in infarct volume 21 hours after the ischemia (vehicle, 81.7 +/- 4.7 mm3; AK295, 54.9 +/- 6.9 mm3; P < .007).

CONCLUSIONS

These data provide the first evidence that a peripherally administered calpain inhibitor can protect against ischemic brain damage. They offer further support for an important role of calpain proteolysis in the brain degeneration associated with cerebral ischemic events and suggest that selective calpain inhibitors provide a rational, novel, and viable means of treating such neurodegenerative problems.

Increased sensitivity to the antinociceptive activity of (+/-)-baclofen in an animal model of chronic neuropathic, but not chronic inflammatory hyperalgesia

Modulation of sensory afferent inputs to the spinal cord by GABA appears to be an important physiological mechanism and may provide an antinociceptive control system. In the present study we have evaluated the antinociceptive activity of the GABAB receptor agonist, (+/-)-baclofen, in rats with unilateral chronic inflammatory or neuropathic hyperalgesia. (+/-)-Baclofen was antinociceptive in untreated control animals and both animal models. In the neuropathic model the sensitivity to (+/-)-baclofen was significantly increased by 3-fold in the ipsilateral limb. By contrast, in animals with chronic inflammation no difference in sensitivity between ipsilateral and contralateral limbs to (+/-)-baclofen was observed. Receptor autoradiographic analysis in spinal cord sections revealed no increase in the density of GABAB receptor binding sites and no change in receptor affinity in the neuropathic model.

Postischemic administration of AK275, a calpain inhibitor, provides substantial protection against focal ischemic brain damage

Experiments were conducted to determine whether a potent, reversible calpain inhibitor could reduce the cortical ischemic brain damage associated with focal ischemia in the rat. AK275 (Z-Leu-Abu-CONH-CH2CH3), the active isomer of the diastereomeric mixture, CX275, was employed in conjunction with a novel method of perfusing drug directly onto the infarcted cortical surface. This protocol reduced or eliminated numerous, nonspecific pharmacokinetic, hemodynamic, and other potentially confounding variables that might complicate interpretation of any drug effect. Focal ischemia was induced using a variation of the middle cerebral artery occlusion method. These studies demonstrated a reliable and robust neuroprotective effect of AK275 over the concentration range of 10 to 200 microM (perfused supracortically at 4 microliters/h for 21 h). Moreover, a 75% reduction in infarct volume was observed when initiation of drug treatment was delayed for 3 h postocclusion. Our data further support an important role of calpain in ischemia-induced neuropathology and suggest that calpain inhibitors may provide a unique and potentially powerful means of treating stroke and other ischemic brain incidents.

Acute and chronic behavioural sequelae resulting from intrastriatal injection of an NMDA agonist

Unilateral and bilateral injections of cis-2,4-methanoglutamate, a potent and selective NMDA agonist, were made into the striatum of rats. Unilateral injections elicited MK-801-sensitive dose-related increases in contralateral turning, beginning 10-15 min after injection. Bilateral injections elicited typical seizure-like behaviours commencing approximately 80 min postinjection. Forty-eight hours after unilateral injection, and presumably after lesion development, no spontaneous preference for turning was seen. Upon challenge with apomorphine (1 mg/kg SC), ipsilateral turning lasting approximately 60 min was seen. Correlates are drawn between this model and some of the features of Huntington's disease.

Pre treatment with MK-801, a non-competitive NMDA antagonist, prevents development of mechanical hyperalgesia in a rat model of chronic neuropathy, but not in a model of chronic inflammation

In the rat, loose ligation of the sciatic nerve results in behavioural signs of hyperalgesia reminiscent of neuropathy in man. A further rat model, of chronic inflammatory hyperalgesia, is produced by intraplantar administration of Freund's complete adjuvant (FCA). We report here that preemptive administration of a non-competitive antagonist of the glutamate N-methyl-D-aspartate (NMDA) receptor, MK-801 (0.3 mg kg-1, s.c.) 30 min prior to and twice daily for a further 8 days following loose ligation of the sciatic nerve, blocks the development of mechanical hyperalgesia measured 27 days later. In contrast, MK-801 administration using the same dosing regimen did not significantly inhibit the hyperalgesia apparent 15 days following i.pl. administration of FCA. Our results suggest that the mechanisms responsible for the development of mechanical hyperalgesia associated with chronic nerve injury and chronic inflammation differ.

Interactive region and volume growing for segmenting volumes in MR and CT images

In radiation treatment planning it is necessary to mark out selected parts of CT or MR images which are clinically relevant before designing the treatment plan. This process is usually done manually with a mouse, and for a typical data set of some 40 slices it can be a time-consuming and tedious process. We report on a system for interactive region and volume growing that assists the clinical user in outlining relevant volumes. The algorithm detects regions of interest grown from a seed selected interactively by a user. The regions consist of connected areas or volumes having similar pixel intensity values. Threshold parameters for controlling the algorithm can be set interactively, or may be determined automatically from a sample region. Region growth can be successively extended into adjacent slices so building up a three-dimensional (3D volume. Direct 3D volume growth from a seed voxel is also possible. The algorithm has been integrated into one of the pilot systems developed as part of COVIRA, project A2003 in the EC's AIM programme.

Pre-emptive administration of clonidine prevents development of hyperalgesia to mechanical stimuli in a model of mononeuropathy in the rat

Traumatic nerve injury in man can often result in the development of neuropathy. An animal model of neuropathic hyperalgesia is produced by loose ligation of the sciatic nerve in the rat. We have examined the effect of pre-emptive treatment with a number of drugs on the development of hyperalgesia in this model. Animals received clonidine (1 mg.kg-1, s.c.), morphine (5 mg.kg-1, s.c.), (+/-)-baclofen (40 mg.kg-1, s.c.), carbamazepine (50 mg.kg-1, s.c.) or vehicle (4 ml.kg-1, s.c.) 30 min prior to loose ligation or sham-operation. Morphine- and clonidine-treated animals were administered a second dose of drug 6h following surgery. Twenty-six or twenty-nine days following surgery, the ipsilateral (ipsi.) and contralateral (contra.) paw withdrawal thresholds were determined using an Algesymeter. In vehicle-treated animals the ipsilateral paw withdrawal threshold (118 +/- 7 g) was significantly lower (P < 0.0001, paired t-test) than the contralateral (195 +/- 7 g). In contrast, in animals pre-treated with clonidine no significant difference between ipsilateral (200 +/- 9 g) and contralateral (191 +/- 7 g) paw withdrawal thresholds was detected. Morphine pre-treatment was less effective in preventing development of hyperalgesia; however, whilst the ipsilateral (146 +/- 18 g) paw withdrawal threshold tended to be lower than the contralateral (183 +/- 8 g), this was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine D1 and D2 receptor interactions in the MPTP-treated marmoset

In a modified MPTP model of Parkinson's disease in the marmoset, both L-DOPA and the dopamine D2 agonist quinpirole were found to exhibit anti-bradykinetic activity. Both the dopamine D1 agonist SKF38393 and the D1 antagonist SCH23390 reduced the anti-bradykinetic action of L-DOPA and quinpirole. These results are discussed with respect to partial agonist activity of SKF38393 and the possibility that other dopamine receptors may be required for anti-Parkinsonian drug activity.

Behavioral response of rats with cortical lesions to cholinomimetics

This study examined the performance of cortically lesioned rats and their response to cholinomimetic agents in passive avoidance and water maze tasks. Lesions encompassing mainly the frontal and parietal cortices produce a deficit in a 5-day passive avoidance retention test. This deficit was attenuated by the intraperitoneal (IP) administration of muscarinic agonists or an anticholinesterase. In the Morris water maze task, lesioned vehicle-treated animals showed greater escape latency times when compared to their sham counterparts. Cholinomimetics, injected daily during acquisition, improved mean escape latency time on days 3 and 4 of testing. The performance of the various groups in a cued version of the water task did not differ. This work demonstrates that performance deficits arising from neocortical loss can be attenuated by cholinergic drugs.

Modulation of the rat mesolimbic dopamine pathway by neurokinins

The locomotor activity (LMA) response induced after infusion of selective neurokinin (NK) agonists into the cell body (A10) and a terminal region of the mesolimbic pathway of the rat was investigated. Infusion of the NK1 receptor-selective agonist, GR73632, into the ventral tegmental area (VTA: A10) or the nucleus accumbens (NAS) significantly and dose-dependently increased basal LMA. Agonists selective for the NK2 and NK3 receptors, GR64349 and senktide respectively, had no effect on LMA after intra-NAS infusion. The LMA induced by GR73632 is mediated via dopamine (DA) since the response was abolished by haloperidol. From these studies it would appear that the elevated LMA reported previously after VTA or NAS administration of substance P probably occurs via NK1 receptors. Such data supports the notion that endogenous NKs are likely to be important in modulating the mesolimbic DA pathway and, as a consequence, compounds which antagonise their effects could be useful for the treatment of disorders associated with this system. However, simultaneous infusion of the NK1 agonists, +/- CP-96,345 and its analogue CPQ, into the VTA did not attenuate the LMA induced after intra-VTA infusion of GR73632. Co-infusion of the NK1 antagonist CPQ, but not +/- CP-96,345, attenuated the LMA response induced by GR73632 in the NAS. The apparent poor susceptibility of these responses to blockade by the recently developed non-peptide NK1 antagonists was unexpected but may reflect their poor affinity for the rat variant of the NK1 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioural consequences following infusion of selective neurokinin agonists into the median raphe nucleus of the rat

The locomotor activity induced after infusion of selective neurokinin (NK) agonists into the median raphé nucleus of rats was investigated. In photocell cages, the NK-2-agonist, GR64349, and the NK-3 agonist, senktide, both increased motor activity in a dose-dependent manner. However, the NK-1 agonist, GR73632, had little effect over a range of doses. In the open field, the motor effect of all three NK agonists was identical to that observed in the photocell cages. In addition, senktide induced straub-tail, hind-limb splaying and various oral movements. Such effects were not noted with the other two agonists. These results suggest that activation of NK-2 or NK-3 receptors by the neurokinins, in the median raphe nucleus of the rat, leads to an increase in locomotor activity.

Neurokinin agonists differentially affect A9 and A10 dopamine cells in the rat

The effect of selective neurokinin (NK) receptor agonists on the activity of A9 and A10 dopamine cells was assessed using extracellular recording. A higher proportion of A10 cells which were administered the NK1 receptor agonist GR73632 or the NK3 receptor agonist senktide showed an effect, whereas the NK2 receptor agonist GR64349 did not discriminate as clearly between the two cell groups. The most frequently encountered response in all cases was an increase in firing rate.

Role of NK-2 receptors in the antidipsogenic activity of neurokinins in the mouse

1. The receptors involved in the anti-dipsogenic activity of neurokinin (NK) agonists were investigated in water-deprived mice. 2. Intracerebral administration of agonists selective at all three NK receptors (NK-1, NK-2, NK-3) caused inhibition of drinking in this model. However, only the NK-2 receptor agonist, GR64349, inhibited drinking without producing other behavioural effects. Both NK-1 (GR73632) and NK-3 (senktide) agonists induced a variety of behavioural effects which appeared to compete with the drinking response. 3. The inhibitory effect on drinking observed after central injection of the NK-2 agonist, GR64349, was attenuated by co-administration of the NK-2 antagonist, L-659,877, but not by the NK-1 antagonist, GR82334. 4. These results illustrate that the antidipsogenic activity of the NKs, in mice, is mediated via NK-2 receptors.

Behavioural and biochemical responses following activation of midbrain dopamine pathways by receptor selective neurokinin agonists

Preferential activation of mesolimbic and nigro-striatal dopamine (DA) pathways by receptor-selective and peptidase-resistant neurokinin (NK) agonists is reported. The DA cell body region of the mesolimbic pathway appears to be activated by NK agonists selective for NK-1 and NK-3 receptors whereas the DA cell bodies in the substantia nigra are under an excitatory NK-2 receptor-mediated influence. Stimulation of the mesolimbic DA pathway by NK-1 (Ava[L-Pro9,N-Me-Leu10]SP (7-11) [GR73632]) or NK-3 (Senktide) agonists increase locomotor activity. Additional studies showed that this elevated motor response observed after intra-VTA infusion of GR73632 was accompanied by a corresponding increase in DA turnover in the terminal fields of this pathway. Similarly, unilateral activation of the nigro-striatal DA pathway by NK-2 selective agonists (Ava (D-Pro9) SP (7-11) [GR51667] or [Lys3,Gly8,R-Lac-Leu9]NKA (3-10) [GR64349]) elicit contralateral rotational activity and an increase in DA turnover in the ipsilateral striatum. The rotational response was attenuated by prior administration of an NK-2 antagonist (cyclo (Gln, Trp, Phe, Gly, Leu, Met)] L-659877]) into the nigra. Peripheral injection of haloperidol, a DA antagonist, also blocked the NK-2 agonist induced rotations.

Procedure for assessing the behavioral effects of novel anti-parkinsonian drugs in normal and MPTP-treated marmosets following central microinfusions

Comparison between drug effects in MPTP- and non-MPTP-treated marmosets following intracerebroventricular (ICV) and intraputamen administration are given in the present report. Both side-effect profiles and the ability to reverse MPTP-induced hypokinesia were assessed using a variety of dopamine receptor agonists (quinpirole, PHNO, ADTN), cholinergic antagonists (scopolamine, secoverine, himbacine), a glutamate receptor antagonist (MK801) and a 5-HT receptor agonist (8-OH-DPAT). Our results show that direct infusion of agents into the putamen or via the ICV route can reverse parkinsonian-like symptoms in marmosets. Furthermore, chronic implantation of cannulae into the putamen or ventricles of nonhuman primates can be useful in assessing the therapeutic activity of agents that do not readily cross the blood-brain barrier.

Two distinct monoclonal antibodies raised against mouse beta nerve growth factor. Generation of bi-specific anti-nerve growth factor anti-horseradish peroxidase antibodies for use in a homogeneous enzyme immunoassay

Two hybridomas producing monoclonal antibodies against mouse beta nerve growth factor (NGF) were obtained from the fusion of hyperimmune splenocytes from rats immunized with polymerized beta-NGF and Sp2/0.Ag mouse myeloma cells. The monoclonal antibodies coded IgG 24 and 30 produced and secreted by the hybrid cells are both of the IgG2a subclass. Both monoclonal antibodies are capable of recognizing native NGF coated on microassay plates as well as the denatured factor on Western blots. However, only IgG 30 has been found to block NGF-induced process outgrowth from the rat pheochromocytoma cell line (PC12) as well as NGF-induced increase in choline acetyltransferase activity in rat primary septal cell cultures. In addition, only IgG 30 was able to detect immunocytochemically NGF-immunoreactive sites in fixed tissue. And, finally, IgG 24 could not compete for IgG 30 binding to immobilized native NGF. Consequently, it appears that these antibodies are recognizing different epitopes on the NGF molecule. Neither monoclonal antibody displayed any crossreactivity with serum albumin, aprotinin, epidermal growth factor or insulin. A hybrid-hybridoma producing bi-specific anti-NGF anti-horseradish peroxidase (HRP) monoclonal antibodies was generated from the fusion of an azaguanine resistant anti-HRP hybridoma, coded RAP2.Ag and the anti-NGF IgG 30 hybridoma treated with emetine. The potential merits of using these bi-specific antibodies in combination with their mono-specific anti-NGF parent in a homogeneous sandwich immunoassay for the quantitation of NGF are discussed.