Inhibition of kidney potassium channels by fluoxetine: In vivo and in vitro studies.

In vitro studies have demonstrated that fluoxetine, a commonly used antidepressant drug, can modulate the activity of K+ channels. In the present study, we investigated the in vivo effect of acute and sub-chronic treatment of rats with fluoxetine on K+ renal transport. Furthermore, OK cells, a kidney epithelial cell line, were used in order to evaluate the in vitro effect of fluoxetine on K+ currents. In the sub-chronic study, fluoxetine was administrated daily (10 mg/kg, p.o.) for 15 days to male adult Wistar rats. In the acute study, rats were given increasing doses of fluoxetine (1, 3, 10, 30 and 50 mg/kg, p.o.) for 24 h. Results from the sub-chronic study show that urinary K+ content (in mmol/L) was markedly reduced in the fluoxetine-treated animals (fluoxetine: 83 ± 9; control: 131 ± 10; P < 0.001). K+ fractional renal excretion (in %) was also significantly lower in the fluoxetine group (fluoxetine: 6 ± 1; control: 13 ± 2; P < 0.001). No significant changes was observed in creatinine clearance and on renal tubular Na+ ,K+ -ATPase activity. Results obtained from the acute study demonstrate that, after a 24-h administration, fluoxetine produced a dose-dependent decrease in urinary K+ , with an ED50 (in mg/kg) of 4.2 (2.8; 5.5) and a maximal effect of 62% reduction. In vitro, fluoxetine produced a concentration-dependent inhibition of K+ currents in OK cells, with an EC50 of 107 (84.8; 129.5) µM. In conclusion, fluoxetine produces a marked reduction on urinary K+ excretion; this effect constitutes an in vivo evidence for the inhibitory action of fluoxetine on kidney epithelial K+ channels.

Cannabis induced psychosis: A systematic review on the role of genetic polymorphisms.

OBJECTIVE: Cannabis sativa is a recreational drug commonly consumed in Europe and is getting popularity for both recreational and therapeutic use. In some individuals, the use of cannabis leads to psychotic disorders. This systematic review summarizes the current evidence linking genetic polymorphisms and inter-individual susceptibility to psychosis induced by cannabis. METHOD: Studies published from 2005 to 2020 were identified through Medline using PubMed, Web of Science and Scopus database and searches were conducted according to PRISMA guidelines. Initial search was performed with terms: "cannabis induced psychosis" AND "genetics". RESULTS: From the initial group of 108 papers, 18 studies met our inclusion criteria. Many of the findings revealed associations with genetic polymorphisms modulations of genes involved directly (COMT, DRD2 and DAT) or indirectly (AKT1) to dopamine pathways. The most consistent finding was with COMT rs4680, where the presence of the Val allele was associated with a higher risk for cannabis-induced psychosis. This higher susceptibility was also reported for AKT1 (rs2494732) with the CC genotype. Of note, the only genome-wide association study identified a significant signal close to the cholinergic receptor muscarinic 3 represented by rs115455482 and rs74722579 predisposing to cannabis-induced hallucinations and remarkably no dopaminergic target was found. CONCLUSION: Actual evidence supports the role of dopamine in cannabis induced psychosis. However, most of genetic polymorphism studies have as a starting point the pre-existing dopaminergic theoretical basis for psychosis. This alerts to the importance of more broad genetic studies. Integrate genetic results into biological systems may enhance our knowledge of cannabis induced psychosis and could help in the prevention and treatment of these patients.

Effects of lithium use on the white matter of patients with bipolar disorder - a systematic review.

BACKGROUND: Several studies revealed changes in the microstructure of white matter in bipolar disorder patients. Lithium has been reported as having neuroprotective effects. However, its effect on the white matter remains unclear. This systematic review aims to identify the existing clinical evidence of lithium's effect on the white matter from bipolar disorder patients. METHODS: PRISMA guidelines were followed for a systematic literature review to assess the effect of lithium on the white matter of patients with bipolar disorder. From a total of 204 studies screened, 16 were included in the final systematic review. The quality assessment of the included records was assessed by the Newcastle-Ottawa scale. RESULTS: Most studies included (13 out of 16) evaluated diffusion tensor imaging measures to assess white matter integrity. Of these, eleven reported a positive effect of lithium on the integrity of white matter of bipolar disorder patients. Two reported no effect. Two studies evaluated white matter volume. The first reported that lithium attenuates the reduction of white matter volume over time, and the second reported significantly smaller white matter volume in non-lithium-using patients. The last evaluated ventricular brain ratio and reported that patients treated with lithium did not have a significantly greater ventricular size than their normal control counterparts. CONCLUSIONS: Lithium appears to positively influence the evolution of the white matter abnormalities described in bipolar disorder patients. Should this information be confirmed in future research, and given its important mood stabilizer effect, it could further reinforce the use of lithium in the treatment of bipolar disorder.

Targeting cannabinoid receptor 2 (CB2) limits collagen production-An in vitro study in a primary culture of human fibroblasts.

Previous studies showed that cannabinoid 2 (CB2) receptor is involved in skin inflammation, fibrogenesis and re-epithelialization in mice, indicating that this receptor may be implicated in wound healing. Thus, topical use of cannabinoids may have a role in local fibrotic and wound healing diseases such as scars or keloids. We investigate the effect of the CB2 selective receptor agonist (6aR,10aR)-3-(1,1-Dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran (JWH133) and the CB2 selective receptor antagonist (6-Iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl)(4-methoxyphenyl)-methanone (AM630), on primary cultures of human fibroblasts. Primary cultures of adult human fibroblasts were obtained from abdominal human skin samples. Fibroblasts pretreated with JWH133 and/or AM630 were stimulated with TGF-ß (10 ng/ml). Fibroblast activation into myofibroblasts was quantified by the expression of alpha-smooth muscle actin (α-SMA) using Immunocytochemistry and Western Blot assays. Collagen content was quantified with the Sirius red staining assay. Upon human fibroblasts stimulation with TGF-ß, a significant increase on α-SMA and CB2 receptor expression was observed. In these cells, JWH133 decreased α-SMA expression and collagen content. However, this effect was not observed in resting human fibroblasts. AM630 decreased α-SMA expression and collagen content in both resting and activated fibroblasts. This effect was time- and concentration-dependent with an IC50 value of 11 µM. The CB2 receptor appears to be involved in fibroblast repair during skin wound healing in humans, as TGF-ß increases CB2 receptor expression and JWH133 produces an anti-fibrotic effect in human fibroblasts. AM630 also showed an anti-fibrotic effect hypothesizing that other cannabinoid receptors, such as TRPV, may be involved in this response.

Effectiveness of multimodal interventions focused on smoking cessation in patients with schizophrenia: A systematic review.

BACKGROUND: Smoking is a significant risk factor for mortality and morbidity among patients with schizophrenia. OBJECTIVE: To clarify the effectiveness of multimodal smoking cessation interventions in adult smokers diagnosed with schizophrenia. METHODS: A systematic review was conducted according to PRISMA guidelines. Relevant electronic databases were searched for clinical trials that combined pharmacological and non-pharmacological smoking cessation interventions for patients with schizophrenia, published up to October 2020. Primary outcomes were smoking abstinence and smoking reduction. Secondary outcomes consisted in psychiatric symptoms. RESULTS: A final sample of nine articles was obtained from a total of 208 studies. All studies reported higher biochemically validated smoking reduction rates after treatment. However, the majority of the studies reported low smoking abstinence rates, which progressively decreased over time. Multimodal interventions did not worsen psychiatric symptoms. CONCLUSION: Evidence suggests that multimodal smoking cessation interventions for individuals diagnosed with schizophrenia should be recommended by clinicians, as they showed to be effective in reducing smoking without worsening psychiatric symptoms. Further studies are needed to understand how interventions can become more effective in helping patients achieve long-term smoking abstinence.

AM251, a cannabinoid receptor 1 antagonist, prevents human fibroblasts differentiation and collagen deposition induced by TGF-ß - An in vitro study.

Previous studies showed that cannabinoid 1 receptor (CB1) is linked with skin fibrosis and scar tissue formation in mice. Therefore, the topical use of cannabinoids may have a role in the prevention or treatment of local fibrotic and wound healing diseases as hypertrophic scars or keloids. In this study, we asked whether CB1 activation or inactivation would change fibroblast differentiation into myofibroblast and collagen deposition in skin human fibroblast. Primary cultures of adult human fibroblasts were obtained from abdominal human skin. Cells were stimulated with transforming growth factor-beta (TGF-ß, 10ng/ml) and treated with a CB1 selective agonist (arachidonyl-2-chloroethylamide, ACEA 1 µM) and an antagonist (AM251 1, 5 and 10 µM). Alpha-smooth muscle actin (α-SMA) was quantified using Immunocytochemistry and Western Blot. Collagen was quantified with Sirius Red staining assay. Significance was assessed by One-way ANOVA. P < 0.05 was considered significant. TGF-ß significantly increases α-SMA expression. ACEA 1 µM significantly increases collagen deposition but does not change α-SMA expression. AM251 10 µM added in the absence and the presence of ACEA reduces α-SMA expression and collagen content in TGF-ß treated cells. AM251 shows a concentration-dependent effect over collagen deposition with a pIC50 of 5.5 (4.6-6.4). TGF-ß significantly increases CB1 receptor expression. CB1 inactivation with AM251 prevents fibroblasts differentiation and collagen deposition, induced by TGF-ß in human fibroblasts. The outcome supports that CB1 is a molecular target for wound healing disorders and in vivo and pre-clinical studies should be implemented to clarify this premise.

A new role for anandamide: defective link between the systemic and skin endocannabinoid systems in hypertrophic human wound healing.

The use of cannabinoids to treat fibrotic skin diseases is an emergent issue. Therefore, we aimed to evaluate systemic and skin endocannabinoid responses in the wound-healing process in humans. A prospective study was performed in 50 patients who underwent body-contouring surgery. Anandamide (N-arachidonoylethanolamine, AEA), 2-arachidonoylglycerol (2-AG), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) were quantified using LC-MS/MS. Ten (20%) patients developed hypertrophic (HT) scars. No significant changes were observed between the normal (N) scar and HT scar groups in terms of plasma and skin endocannabinoids. Nevertheless, a positive correlation between plasma and skin AEA concentrations was found in the N group (r = 0.38, p = 0.015), which was absent in the HT group. Moreover, the AEA concentration was significantly lower in HT scar tissue than in normal scar tissue (0.77 ± 0.12 ng/g vs 1.15 ± 0.15 ng/g, p < 0.001). Interestingly, in all patients, the surgical intervention produced a time-dependent effect with a U shape for AEA, PEA and OEA plasma concentrations. In contrast, 2-AG plasma concentrations increased 5 days after surgery and were reduced and stabilized 3 months later. These results suggest crosstalk between systemic and local skin endocannabinoid systems during human wound healing. AEA appears to be the most likely candidate for this link, which is deficient in patients with HT scars.

Cutaneous endocannabinoid system: Does it have a role on skin wound healing bearing fibrosis?

INTRODUCTION: Recently, the endocannabinoid system has been identified in skin and it has been linked with the formation of skin fibrosis and wound healing. We aimed to find and analyse reported data on compounds acting in the endocannabinoid system with significant effect in skin fibrosis. METHODS: A literature search on PUBMED was conducted for studies published in English until February 2020 on cannabinoids and skin fibrosis. The initial search was performed with terms: "cannabinoid" AND "skin". This search retrieved 296 publications from which 18 directly related to skin fibrosis or wound healing process were included in this review. RESULTS: CB1 receptor inactivation and CB2 receptor activation show anti-fibrotic effects on cellular and animal experimental models of cutaneous fibrosis. CB2 receptor activation also promotes re-epithelization. Other cannabinoid related receptors, like adenosine A2A receptors and PPAR-γ, are also involved. Their activation lead to a pro-fibrotic and anti-fibrotic effect, respectively. CONCLUSION: Several molecular drug targets for endocannabinoid system were identified in skin. It may be a promising approach for the treatment of excessive skin fibrosis disorders.

Probiotics and prebiotics: focus on psychiatric disorders - a systematic review.

CONTEXT: The gut-brain axis and microbial dysbiosis may play a role in psychiatric diseases. In this view, the gut microbiota has been considered a potential therapeutic target using probiotics and prebiotics. OBJECTIVE: This systematic review aims to find the existing clinical evidence that may justify the use of probiotics or prebiotics in psychiatric patients. DATA SOURCES: PRISMA guidelines were followed for a systematic literature review of randomized controlled trials that assessed the effect of prebiotics or probiotics in patients diagnosed with a classified psychiatric disorder. DATA EXTRACTION: From a total of 212 studies screened, 11 were included in the final systematic review. Quality assessment of the included trials was assessed by the Jadad scale. RESULTS: Probiotics seem to offer some benefit in major depressive disorder and Alzheimer's disease. One study showed that probiotics reduced rehospitalization in patients with acute mania. In autism spectrum disorders, the results were controversial; however a single study found that early administration of probiotics showed a preventive role. No benefits were found for patients with schizophrenia. In most studies, no major adverse effects were reported. CONCLUSIONS: Although recent findings in specific psychiatric disorders are encouraging, the use of prebiotics and probiotics in clinical practice stills lacks sufficiently robust evidence.

Dimethyltryptamine: Endogenous Role and Therapeutic Potential.

N, N-dimethyltryptamine (DMT) is an indole alkaloid produced by a number of plants and animals, including humans. Its psychoactive effects were first described in 1956 by Stephen Szára, but have been exploited for centuries by South American indigenous populations in the form of ayahuasca. In the present review, we assess the state of the art regarding a putative role for endogenous DMT and potential clinical applications of ayahuasca and DMT. A review assessing the pharmacological profile of DMT and its clinical effects in humans was performed using the PubMed data base until 5 August 2018 with the words: ayahuasca and N,N-dimethyltryptamine. While the role of endogenous DMT remains unclear, ayahuasca has promising results in anxiety, depression and substance dependence. Since ayahuasca has a good safety profile, it is crucial to conduct further research aimed at developing new treatments for psychiatric disorders.

Hypertrophic Scars: Are Vitamins and Inflammatory Biomarkers Related with the Pathophysiology of Wound Healing?

BACKGROUND: Hypertrophic scars are a consequence of wound healing. OBJECTIVE: The objective of the present study is to evaluate vitamin D and inflammatory biomarker plasma levels during wound healing. METHODS: A prospective study was performed in patients (n = 63) submitted to body contouring surgery. Blood samples were collected before (t 0) and 5 days after surgery (t 5). Blood cell count, protein inflammatory biomarkers, and circulating plasma levels of 25(OH)D, vitamin A and vitamin E were quantified. Six months after surgery, scars were evaluated and classified as normal or hypertrophic. RESULTS: At the end of the study, 73% of the patients developed a normal scar (control group, n = 46) and 27% of the patients presented hypertrophic scars (HT group, n = 17). The patients in the HT group presented higher eosinophil (0.145 × 109 /L vs. 0.104 × 109 /L, p = 0.028) and basophil count (0.031 × 109 /L vs. 0.22 × 109 /L, p = 0.049) and C-reactive protein levels (6.12 mg/L vs. 2.30 mg/L, p = 0.015) in t 0 than the patients in the control group. At t 5, the patients in the HT group showed a decrease in neutrophil (3.144 × 109/L vs. 4.03 × 109/L, p = 0.031) and an increase in basophil (0.024 × 109/L vs. 0.015 × 109/L, p = 0.005) and lymphocyte count (1.836 × 109 /L vs. 1.557 × 109/L; p = 0.028). Before surgery, vitamin D plasma levels were found to be decreased by almost 50% (23.52 ng/mL vs. 15.46 ng/mL, p = 0.031) in the patients who developed hypertrophic scars. Thirty-one percent of the patients submitted to bariatric surgery had more hypertrophic scars, versus 24% of the patients with no previous bariatric surgery. CONCLUSION: There is a different systemic inflammatory profile response in the patients during the formation of hypertrophic scars. Vitamin D plasma levels are marked reduced in these patients. Considering the powerful anti-inflammatory effect of vitamin D, these findings could be related.

Effects of raftilose on serum biochemistry and liver morphology in rats fed with normal or high-fat diet.

Non-alcoholic fatty liver disease is the leading cause of chronic liver injury in developed countries. Oligofructose (OFS) is a prebiotic with proven benefits for health. The aim of the study is to evaluate the effect of 10% OFS on hepatic morphology and lipid metabolism in Wistar Kyoto rats submitted to normal diet (ND) or high-fat diet (FD). Animals were treated for 7 weeks. Lipid profile and serum alkaline phosphatase (ALP) activity were measured and liver histology evaluated at the end of the study. Ten percent OFS reduced triglyceride (TAG) levels when added to any of the diet regimens; 10% OFS decreased plasmatic urea in ND and plasmatic and urinary urea levels in FD; ND + 10% OFS treated rats showed lower ALP activity than controls. FD increased ALP activity, an effect not reversed by OFS. Animals submitted to FD have microscopic hepatic changes: marked steatosis with disarranged centrilobular zone structure; enlarged sinusoids; enlarged mitochondria and an increase in number and volume of adiposomes. Supplementation with 10% OFS in FD reversed those effects. In conclusion, 10% OFS supplementation prevented deleterious effects of FD such as alterations on lipid profile (TAG elevation) and hepatic morphologic changes. OFS decreased ALP activity in animals subjected to ND, which may have contributed to the differences on lipid metabolism.

Influence of dietary supplementation with dextrin or oligofructose on the hepatic redox balance in rats.

We assessed the impact of oligofructose (OFS) and dextrin (DEX) as diet supplements on hepatic redox state. Rats were fed either a 10% OFS or a 10% DEX supplemented diet for 9 wk. In the DEX diet group, the levels of hepatic protein carbonylation were decreased by 63%. Total glutathione and reduced glutathione (GSH) contents were reduced in the OFS and DEX diet groups by around 20%. DEX supplementation significantly reduced oxidized glutathione (GSSG) levels resulting in a 33% increase in the GSH/GSSG ratio. The activity of the hepatic antioxidant enzymes was not changed by either OFS or DEX supplementation. OFS supplementation caused a decrease in serum levels of triglycerides (36%), cholesterol (24%), HDL (16%) and LDL (17%). DEX supplementation only reduced triglycerides (32%) and urea (22%). Both diets increased serum levels of acetate by fivefold and propionate by twofold, but DEX diet decreased butyrate levels by 75%. Due to their different composition/structure these two dietary fibers affected metabolism in different ways. Diet supplementation with 10% DEX can potentially improve host health, by protecting the liver from protein carbonylation and by improving GSH/GSSG ratio and diet supplementation with 10% OFS can improve the lipid profile.

α2-Adrenoceptor-mediated inhibition of catecholamine release from the adrenal medulla of spontaneously hypertensive rats is preserved in the early stages of hypertension.

In this study, we evaluated the effect of α(2) -adrenoceptor activation on catecholamine release from the adrenal medulla of pre-hypertensive (6-week-old) and hypertensive (16-week-old) spontaneously hypertensive rats (SHR) and of age-matched normotensive control Wistar Kyoto (WKY) rats. Catecholamine overflow from isolated adrenal medullae was evoked by the nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP) in the absence and presence of the α(2) -adrenoceptor agonist medetomidine (MED). The spontaneous outflow of adrenaline was similar between age-matched SHR and WKY rats. However, the spontaneous outflow of noradrenaline was significantly lower in SHR compared with age-matched WKY rats. DMPP (0.1-3 mM) increased the outflow of noradrenaline and adrenaline in a concentration-dependent manner. The E(max) values for adrenaline overflow were similar between strains, but the E(max) values for noradrenaline overflow were significantly lower in SHR. The EC(50) values for noradrenaline and adrenaline overflow were significantly higher in SHR compared with age-matched WKY rats. MED (0.1-300 nM) reduced the DMPP-evoked overflow (DMPP 500 µM) of noradrenaline and adrenaline in a concentration-dependent manner and was capable of totally inhibiting this effect. The inhibitory action of MED was similar between age-matched SHR and WKY rats. In the adrenals, the α(2A)- and α(2B)-adrenoceptor subtypes had the highest mRNA expression levels; the α(2C)-adrenoceptor subtype had the lowest mRNA expression levels. The mRNA levels for the three subtypes were similar between strains. In conclusion, in SHR during the development of hypertension, adrenal α(2) -adrenoceptor inhibitory function is conserved, accompanied by reduced noradrenaline release and unchanged adrenaline release.

Decreased tyrosine hydroxylase activity in the adrenals of spontaneously hypertensive rats.

Higher activity of the peripheral sympathetic nervous system, accompanied by higher tyrosine hydroxylase activity is frequently and consistently reported in human essential hypertension as well as in animal models of hypertension. However, results obtained in the adrenals, particularly in young animals before the development of hypertension, are scarce and controversial. In the present study tyrosine hydroxylase activity and catecholamine content in the adrenals of spontaneously hypertensive rats and of age-matched control Wistar Kyoto rats were evaluated before, during and after the development of hypertension (5, 12 and 22-week-old animals). Results show that both tyrosine hydroxylase activity and total amine content in the adrenals of spontaneously hypertensive rats were significantly reduced (35% reduction) at all studied ages. Determination of the kinetic parameters for tyrosine hydroxylase in the adrenals of 5 week-old spontaneously hypertensive rats revealed a 38% reduction in V(max) values (13.4 versus 21.3 nmol L-DOPA/mg prot/h in age-matched controls) accompanied by lower levels of expression of both tyrosine hydroxylase total protein and phosphoSer40 observed by Western-Blot. In contrast, norepinephrine content in both plasma and tail artery were significantly higher in the spontaneously hypertensive strain. In conclusion, contrary to the higher peripheral sympathetic activity, tyrosine hydroxylase activity and catecholamine content in the adrenals of spontaneously hypertensive rats are markedly reduced before, during and after the development of hypertension. End product, long-term feedback inhibition by the high norepinephrine plasma levels could be responsible for this reduction, establishing yet another regulatory mechanism of tyrosine hydroxylase operating in adrenal cromaffin cells.

Synthesis, biological evaluation, and molecular modeling studies of a novel, peripherally selective inhibitor of catechol-O-methyltransferase.

A novel series of potent, peripherally selective, and long-acting inhibitors of catechol-O-methyltransferase (COMT) has been synthesized. The introduction and nature of heteroatom-containing substituents to the side-chain of the nitrocatechol pharmacophore was found to have a profound effect on both peripheral selectivity and duration of COMT inhibition in the mouse. This approach led to the discovery of 1-(3,4-dihydroxy-5-nitrophenyl)-3-[4-[3-(trifluoromethyl)phenyl]-1-piperazinyl]-1-propanone hydrochloride 35 (BIA 3-335), which was found to possess a superior inhibitory profile in vivo over both the nonselective inhibitor tolcapone 1 and the peripherally selective but short-acting entacapone 2. In this model, 35 retained 75% inhibition of peripheral COMT at 6 h after oral administration, yet significantly, only a minor reduction of central (cerebral) COMT activity was observed. Molecular modeling techniques were applied to review the analysis of the ternary enzyme-inhibitor complex previously determined by X-ray crystallography and to provide a deeper understanding of the structure-activity relationships within this novel series. Furthermore, a computational approach was applied in an effort to elucidate the particular structural factors relevant to the poor blood-brain permeability of 35. In conclusion, the improved biological properties herein reported reveal 35 as a candidate for clinical studies as an adjunct to L-DOPA therapy for Parkinson's disease.

Catechol-O-methyltransferase inhibition in erythrocytes and liver by BIA 3-202 (1-[3,4-dibydroxy-5-nitrophenyl]-2-phenyl-ethanone).

The present study evaluated the relationship between the degree of catechol-O-methyltransferase (COMT) inhibition in erythrocytes and liver by BIA 3-202 (1-[3,4-dihydroxy-5-nitrophenyl]-2-phenyl-ethanone) and determined its effects upon the O-methylation of L-DOPA in rats orally treated with L-DOPA plus benserazide. The soluble form of COMT (S-COMT) in erythrocytes was endowed with the same affinity as liver S-COMT for the substrate adrenaline. BIA 3-202 inhibited erythrocytes and liver S-COMT with ED50's of 1.9 (0.7, 3.1) and 1.9 (0.5, 3.2) (95% confidence limits) mg kg(-1), respectively. BIA 3-202 reduced the L-DOPA-induced rise of 3-O-methyl-L-DOPA in the peripheral circulation, striatal dialysate levels and striatum, and increased dopamine striatal levels. In BIA 3-202-treated rats the increase in L-DOPA in peripheral blood and striatal dialysates was significantly greater than in vehicle-treated rats. It is concluded that S-COMT activity in erythrocytes may provide important information on the pharmacodynamic profile of COMT inhibitors. The novel COMT inhibitor BIA 3-202 is a potent COMT inhibitor that enhances the availability of L-DOPA to the brain by reducing its O-methylation, which may prove beneficial in patients with Parkinson's disease treated with L-DOPA.

Regulation of Cl- secretion by alpha2-adrenergic receptors in mouse colonic epithelium.

Previous studies have shown that alpha2 adrenoceptor (alpha2AR) agonists inhibit electrolyte secretion in colonic epithelia, but little is known about the molecular mechanisms involved in this process. In this study we examined the effect of alpha2AR activation on transepithelial anion secretion across isolated murine colonic epithelium. We found that alpha2AR agonists, UK 14,304, clonidine and medetomidine were potent inhibitors of anion secretion, especially in the proximal colon. Short circuit current measurements (Isc) in colonic epithelia from normal and cystic fibrosis (CF) mice showed that alpha2AR agonists inhibited basal cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- secretion but had no effect on CFTR activation by cAMP-dependent phosphorylation. Apical administration of an ionophore, nystatin (90 microg ml-1), was used to investigate the effect of UK 14,304 on basolateral K+ transport. The Na+-K+-ATPase current, measured as ouabain-sensitive current in the absence of ion gradients, was unaltered by pretreatment of the tissue with UK 14,304 (1 microM). In the presence of a basolaterally directed K+ gradient, UK 14,304 significantly reduced nystatin-activated Isc indicating that activation of alpha2ARs inhibits basolateral K+ channels. Studies with selective K+ channel inhibitors and openers showed that alpha2AR agonists inhibited KATP channels that were tonically active in mouse colonic epithelia. RT-PCR and pharmacological studies suggested that these channels could be similar to vascular smooth muscle KATP channels comprising Kir6.1/SUR2B or Kir6.2/SUR2B subunits. Inhibition of anion secretion by alpha2AR agonists required activation of pertussis toxin-sensitive Gi/o proteins, but did not involve classical second messengers, such as cAMP or Ca2+. In summary, alpha2ARs inhibit anion secretion in colonic epithelia by acting on basolateral KATP channels, through a process that does not involve classical second messengers.

Synthesis of 1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone and derivatives as potent and long-acting peripheral inhibitors of catechol-O-methyltransferase.

A homologous series of novel nitro-catechol structures (7a-7e) were synthesized and tested as inhibitors of the enzyme catechol-O-methyltransferase (COMT). Increasing chain length was found to have significant impact on both brain penetration and duration of COMT inhibition in the rat. Of this series, compound 7b (1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone) was found to exhibit the most potent and selective inhibition of peripheral COMT, with an inhibition profile more similar to entacapone 2 than tolcapone 1 (an equipotent peripheral and central inhibitor) but with much improved duration of action (7b, 70% inhibition and 2, 25% inhibition at 9 h after administration). The effects of structural modifications to 7b on COMT inhibitory profile were investigated, and it is concluded that the carbonyl group and preferably unsubstituted aromatic ring are essential features to maintain prolonged peripheral COMT inhibition. The introduction of the alpha-methylene group, the major structural difference between 7b and 1, would appear responsible for the observed enhancement in selectivity of peripheral COMT inhibition of 7b, which has more limited access to the brain than 1.