Matrix Metalloproteinases

Drugs & Aging - Matrix metalloproteinases (MMPs), or matrixins, are a family of zinc endopeptidases that play a key role in both physiological and pathological tissue degradation. Normally,...     

An electrophysiological correlate of protein kinase C isozyme distribution in cultured cerebellar neurons.

Protein kinase C (PKC) is a family of at least seven closely related molecules (isozymes) that vary in terms of their requirements for activation and their distribution among cells of the brain. A striking example of this differential distribution is seen in the cerebellum, where Purkinje cells express PKC-I, an isozyme that is strongly activated by both phorbol ester (PE), and low doses of cis-unsaturated fatty acid (c-UFA), while granule cells predominantly express PKC-II, an isozyme that is strongly activated by PE but not c-UFA. Both Purkinje and granule cells have large, easily recorded voltage-gated K currents. These currents are attenuated by PKC activators in several other varieties of neuron. We hypothesized that the effects of these two PKC activators would be predicted by the distribution of the relevant PKC isozyme, and that the delayed outward rectifier current, IK, would be attenuated by both PE and c-UFA in Purkinje cells, but only by PE in granule cells. This hypothesis was confirmed in perforated-patch recordings. The attenuation produced by both activators could be blocked by application of a specific PKC inhibitor, RO-31-8220, and could not be mimicked by inert forms of PE or c-UFA. To our knowledge, this study represents the first report of an electrophysiological correlate of PKC isozyme distribution.     

Diagnosis in Prader-Willi syndrome.

Thirty one patients with the putative diagnosis of Prader-Willi syndrome were reassessed clinically and by DNA analysis. Eleven patients were judged not to have Prader-Willi syndrome and 20 to have the condition. This was confirmed by DNA analysis in all but one case. The diagnosis of Prader-Willi syndrome, especially in early infancy, should be made with caution unless confirmed by molecular genetic studies.     

Early and late results of coronary artery bypass after failed angioplasty. Actuarial analysis of late cardiac events and comparison with initially successful angioplasty

We reviewed the results of early (less than 24 hours) coronary artery bypass after unsuccessful percutaneous coronary artery angioplasty in 146 patients treated between October 1979 and July 1986. Overall operative mortality was 2.7%, and risk was significantly increased among patients with hemodynamic instability and new occlusion or further narrowing of the dilated vessel (3.8 versus 0%, p less than 0.05). Actuarial analysis was used to compute the rates of cardiac events during the follow-up interval, and event rates were also estimated in a comparison group of 776 patients who had successful first-time PTCA during the same time period. At a follow-up interval of 5 years, the cumulative risks of recurrence of angina and need for an additional procedure (bypass or angioplasty) were significantly (p less than 0.05) lower for patients who had undergone bypass than for those who had successful angioplasty (angina 21% versus 56%, PTCA 2% versus 21%, CAB 6% versus 16%). Cumulative risks of myocardial infarction and death were 4% versus 9% and 6% versus 9% in the two groups. The differences between late outcomes in the bypass and angioplasty groups persisted when patients were stratified into cohorts with single-vessel and multivessel disease, and the highest late event rate occurred in patients in the angioplasty group who had incomplete revascularization. The difference in late events after bypass or angioplasty was greatest during the first year. These late data should be considered when the mode of revascularization (bypass or angioplasty) is selected for symptomatic patients, especially those with multivessel disease.     

The pharmacology of GR203040, a novel, potent and selective non-peptide tachykinin NK1 receptor antagonist.

1. The in vitro and in vivo pharmacology of GR203040 ((2S, 3S)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), a novel, highly potent and selective non-peptide tachykinin NK1 receptor antagonist, was investigated in the present study. 2. GR203040 potently inhibited [3H]-substance P binding to human NK1 receptors expressed in Chinese hamster ovary (CHO) and U373 MG astrocytoma cells, and NK1 receptors in ferret and gerbil cortex (pKi values of 10.3, 10.5, 10.1 and 10.1 respectively). GR203040 had lower affinity at rat NK1 receptors (pKi = 8.6) and little affinity for human NK2 receptors (pKi < 5.0) in CHO cells and NK3 receptors in guinea-pig cortex (pKi < 6.0). With the exception of the histamine H1 receptor (pIC50 = 7.5). GR203040 had little affinity (pIC50 < 6.0) at all non-NK1 receptors and ion channels examined. Furthermore, GR203040 produced only weak inhibition of Na+ currents in SH-SY5Y neuroblastoma and superior cervical ganglion cells (pIC50 values < 4.0). GR203040 produced only weak antagonism of Ca(2+)-evoked contractions of rat isolated portal vein (pKn = 4.1). The enantiomer of GR203040, GR205608 (2R, 3R)-2-methoxy-5-tetrazol-1-yl-benzyl-(2-phenyl-piperidin-3-y l)-amine), had 10,000 fold lower affinity at the human NK1 receptor expressed in CHO cells (pKi = 6.3). 3. In gerbil ex vivo binding experiments, GR203040 produced a dose-dependent inhibition of the binding of [3H]-substance P to cerebral cortical membranes (ED50 = 15 micrograms kg-1 s.c. and 0.42 mg kg-1 p.o.). At 10 micrograms kg-1 s.c., the inhibition of [3H]-substance P binding was maintained for > 6 h. In the rat, GR203040 was less potent (ED50 = 15.4 mg kg-1 s.c.) probably reflecting, at least in part, its lower affinity at the rat NK1 receptor. 4. In guinea-pig isolated ileum and dog isolated middle cerebral and basilar arteries, GR203040 produced a rightward displacement of the concentration-effect curves to substance P methyl ester (SPOMe) with suppression of the maximum agonist response (apparent pKB values of 11.9, 11.2 and 11.1 respectively). 5. In anaesthetized rabbits, GR203040 antagonized reductions in carotid arterial vascular resistance evoked by SPOMe, injected via the lingual artery (DR10 (i.e. the dose producing a dose-ratio of 10) = 1.1 micrograms kg-1, i.v.). At a dose 20 fold greater than its DR10 value (i.e. 22 micrograms kg-1, i.v.), significant antagonism was evident more than 2 h after GR203040 administration. 6. In anaesthetized rats, GR203040 (3 and 10 mg kg-1, i.v.) produced a dose-dependent inhibition of plasma protein extravasation in dura mater, conjunctiva, eyelid and lip in response to electrical stimulation of the trigeminal ganglion. 7. It is concluded that GR203040 is one of the most potent and selective NK1 receptor antagonists yet described, and as such, has considerable potential as a pharmacological tool to characterize the physiological and pathological roles of substance P and NK1 receptors. GR203040 may also have potential as a novel therapeutic agent for the treatment of conditions such as migraine, emesis and pain.     

Cardiovascular effects of 5-HT1A receptor agonists injected into the dorsal raphe nucleus of conscious rats

The aim of this study was to investigate the cardiovascular effects of the 5-HT1A receptor agonists, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), flesinoxan and 5-carboxamidotryptamine (5-CT) following injection into the dorsal raphe nucleus of conscious rats. 8-OH-DPAT (0.5-2.5 micrograms), hypotension, bradycardia and flat body posture. In contrast, injection of 8-OH-DPAT (0.5 microgram) into the median raphe nucleus caused no cardiovascular changes or flat body posture. (-)Pindolol (0.5 microgram dorsal raphe nucleus) had little effect on cardiovascular parameters, but significantly attenuated the cardiovascular effects of 8-OH-DPAT (0.5 microgram dorsal raphe nucleus). N-Methylatropine (1 mg/kg i.v.) antagonised the cardiovascular effects of 8-OH-DPAT (0.5 microgram dorsal raphe nucleus), suggesting these were vagally mediated. Both pretreatments also appeared to reduce 8-OH-DPAT-induced flat body posture. The results suggest that 8-OH-DPAT activates 5-HT1A receptors in the dorsal raphe nucleus to cause hypotension and bradycardia.     

Novel 1,2,4-oxadiazoles and 1,2,4-thiadiazoles as dual 5-lipoxygenase and cyclooxygenase inhibitors.

A series of 1,2,4-oxadiazoles and 1,2,4-thiadiazoles containing a 2,6-di-tert-butylphenol substituent were prepared and evaluated as dual inhibitors of 5-lipoxygenase and cyclooxygenase in rat basophilic leukemia (RBL-1) cells. Several of these compounds show oral efficacy in the rat carrageenan footpad edema (CFE) and mycobacterium footpad edema (MFE) antiinflammatory models, without concomitant gastric ulceration. Structure-activity relationships are discussed. The best compounds (ID40 values in MFE of 3-8 mg/kg po) contain guanidine-derived substituents on the heterocyclic ring.     

2,6-Diamino-N-([1-(1-oxotridecyl)-2-piperidinyl] methyl)hexanamide (NPC 15437): a novel inhibitor of protein kinase C interacting at the regulatory domain.

NPC 15437 is a prototype member of a new class of synthetically derived protein kinase C (PKC) inhibitors. PKC activity and binding of phorbol ester to the enzyme were inhibited by NPC 15437, with IC50 values of 19 +/- 2 microM and 23 +/- 4 microM, respectively. No inhibition of cAMP-dependent or calcium/calmodulin-dependent protein kinases was observed at concentrations of NPC 15437 up to 300 microM. To investigate the mechanism by which NPC 15437 exerts its effects, a kinetic analysis of the inhibition with respect to three activators of the enzyme, phosphatidylserine, calcium, and phorbol ester, was performed. NPC 15437 was a competitive inhibitor of the activation of PKC by phorbol ester (Ki = 5 +/- 3 microM). Stimulation of PKC alpha by phosphatidylserine was competitively inhibited by NPC 15437 (Ki = 12 +/- 4 microM). The inhibition was mixed with respect to activation by calcium. These results suggest that NPC 15437 is a selective inhibitor of PKC, interacting at the regulatory region of the enzyme. NPC 15437 inhibited PKC in intact cells, dose-dependently antagonizing the phorbol ester-induced phosphorylation of a 47-kDa protein in human platelets.     

Differential effects of octreotide on motor responses to nicotine in rats.

We tested the hypothesis that brain somatostatin levels modify two motor behaviors evoked by ICV infusions of nicotine. Unrestrained, awake rats were given fixed-concentration infusions of nicotine until the prostration/immobility (PI) syndrome and convulsions were produced. Infusion duration ranged from 0.9 to 1.2 min for the PI syndrome and 2.5 to 4.9 min for the convulsions. Octreotide, a stable somatostatin analog (4.5 micrograms, ICV), significantly raised the threshold for nicotine convulsions 1.0 and 5.5 h after pretreatment but not at 24 or 48 h. Cysteamine, a somatostatin releaser and depletor (0.35-0.75 mg/rat, ICV), also caused a dose-dependent increase in seizure threshold. Similarities in the response to octreotide and cysteamine suggest that depression of nicotine convulsions by cysteamine may be mediated by release of endogenous somatostatin. Neither octreotide nor cysteamine altered the threshold for the PI syndrome. These results support the view that one motor behavior evoked by nicotine is subject to control by somatostatin whereas another is not.