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We investigated the pharmacological actions of a slow-releasing H2S donor, GYY 4137; a substrate for the biosynthesis of H2S, L-cysteine and its precursor, N-acetylcysteine on potassium (K+; 50 mM)-evoked [3H]D-aspartate release from bovine isolated retinae using the Superfusion Method. GYY 4137 (10 nM-10 µM), L-cysteine (100 nM-10 µM) and N-acetylcysteine (10 µM-1 mM) elicited a concentration-dependent decrease in K+-evoked [3H]D-aspartate release from isolated bovine retinae without affecting basal tritium efflux. At equimolar concentration of 10 µM, the rank order of activity was as follows: L-cysteine > GYY 4137 > N-acetylcysteine. A dual inhibitor of the biosynthetic enzymes for H2S, cystathionine ß-synthase (CBS) and cystathionine γ-lyase (CSE), amino-oxyacetic acid (AOA; 3 mM) reversed the inhibitory responses caused by GYY 4137, L-cysteine and N-acetylcysteine on K+-evoked [3H]D-aspartate release. Glibenclamide (300 µM), an inhibitor of KATP channels blocked the inhibitory action of GYY 4137 and L-cysteine but not that elicited by N-acetylcysteine on K+-induced [3H]D-aspartate release. The inhibitory effect of GYY 4137 and L-cysteine on K+-evoked [3H]D-aspartate release was reversed by the non-specific inhibitor of nitric oxide synthase (NOS), L-NAME (300 µM). Furthermore, a specific inhibitor of inducible NOS (iNOS), aminoguanidine (10 µM) blocked the inhibitory action of L-cysteine on K+-evoked [3H]D-aspartate release. We conclude that both donors and substrates for H2S production can inhibit amino acid neurotransmission in bovine isolated retinae, an effect that is dependent, at least in part, upon the intramural biosynthesis of this gas, and on the activity of KATP channels and NO synthase.
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Ácido Aspártico/metabolismo , Cisteína/metabolismo , Sulfeto de Hidrogênio/farmacologia , Retina/efeitos dos fármacos , Animais , Bovinos , Ácido D-Aspártico/metabolismo , Hidrogênio/metabolismo , Sulfeto de Hidrogênio/metabolismo , Retina/metabolismo , Sulfetos/metabolismoRESUMO
In the present study, we investigated the effect of three different sources of hydrogen sulfide (H2S) on sympathetic neurotransmission from isolated superfused bovine iris-ciliary bodies. The three agents under consideration were: ACS67, a hybrid of latanoprost and a H2S-donating moiety; L-cysteine, a substrate for endogenous production of H2S and GYY 4137, a slow donor of H2S. We also examined the contribution of prostaglandins to the pharmacological actions of the H2S donors on release of [(3)H]-norepinephrine ([(3)H]NE) triggered by electrical field stimulation. ACS67, L-cysteine and GYY 4137 caused a concentration-dependent inhibition of electrically-evoked [(3)H]NE release from isolated bovine iris-ciliary bodies without affecting basal [(3)H]NE efflux. The cyclooxygenase inhibitor, flurbiprofen enhanced the inhibitory action of ACS67 and L-cysteine on stimulated [(3)H]NE release. Both aminooxyacetic acid, an inhibitor of cystathionine-ß-synthase and glibenclamide, a KATP channel blocker reversed the inhibition of evoked NE release induced by the H2S donors. We conclude that H2S donors can inhibit sympathetic neurotransmission from isolated bovine iris-ciliary bodies, an effect partially dependent on the in situ production of H2S and prostanoids, and is mediated by an action on KATP channels.
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Sulfeto de Hidrogênio/metabolismo , Sistema Nervoso Simpático/efeitos dos fármacos , Úvea/efeitos dos fármacos , Animais , Bovinos , Corpo Ciliar/efeitos dos fármacos , Corpo Ciliar/metabolismo , Cisteína/farmacologia , Estimulação Elétrica , Técnicas In Vitro , Morfolinas/farmacologia , Norepinefrina/metabolismo , Compostos Organotiofosforados/farmacologia , Prostaglandinas/metabolismo , Prostaglandinas F Sintéticas/farmacologia , Sistema Nervoso Simpático/fisiologia , Transmissão Sináptica , Ácido Tióctico/análogos & derivados , Ácido Tióctico/farmacologia , Úvea/fisiologiaRESUMO
In the present study, we investigate the inhibitory effect of novel H2S donors, AP67 and AP72 on isolated bovine posterior ciliary arteries (PCAs) under conditions of tone induced by an adrenoceptor agonist. Furthermore, we examined the possible mechanisms underlying the AP67- and AP72-induced relaxations. Isolated bovine PCA were set up for measurement of isometric tension in organ baths containing oxygenated Krebs solution. The relaxant action of H2S donors was studied on phenylephrine-induced tone in the absence or presence of enzyme inhibitors for the following pathways: cyclooxygenase (COX); H2S; nitric oxide and the ATP-sensitive K(+) (KATP) channel. The H2S donors, NaSH (1 nM - 10 µM), AP67 (1 nM - 10 µM) and AP72 (10 nM - 1 µM) elicited a concentration-dependent relaxation of phenylephrine-induced tone in isolated bovine PCA. While the COX inhibitor, flurbiprofen (3 µM) blocked significantly (p < 0.05) the inhibitory response elicited by AP67, it had no effect on relaxations induced by NaSH and AP72. Both aminooxyacetic acid (30 µM) and propargylglycine (1 mM), enzyme inhibitors of H2S biosynthesis caused significant (p < 0.05) rightward shifts in the concentration-response curve to AP67 and AP72. Furthermore, the KATP channel antagonist, glibenclamide (300 µM) and the NO synthase inhibitor, l-NAME (100 µM) significantly attenuated (p < 0.05) the relaxation effect induced by AP67 and AP72 on PCA. We conclude that H2S donors can relax pre-contracted isolated bovine PCA, an effect dependent on endogenous production of H2S. The inhibitory action of only AP67 on pre-contracted PCA may involve the production of inhibitory endogenous prostanoids. Furthermore, the observed inhibitory action of H2S donors on PCA may depend on the endogenous biosynthesis of NO and by an action of KATP channels.
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Artérias Ciliares/fisiologia , Sulfeto de Hidrogênio/metabolismo , Músculo Liso Vascular/fisiologia , Compostos Organofosforados/farmacologia , Piperidinas/farmacologia , Pirrolidinas/farmacologia , Agonistas de Receptores Adrenérgicos alfa 1/farmacologia , Animais , Bovinos , Artérias Ciliares/efeitos dos fármacos , Cistationina beta-Sintase/antagonistas & inibidores , Cistationina beta-Sintase/metabolismo , Cistationina gama-Liase/antagonistas & inibidores , Cistationina gama-Liase/metabolismo , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/farmacologia , Contração Isométrica/fisiologia , Canais KATP/metabolismo , Relaxamento Muscular/efeitos dos fármacos , Óxido Nítrico/metabolismo , Fenilefrina/farmacologia , Design de Software , Vasoconstritores/farmacologiaRESUMO
We have evidence that F2-isoprostanes (F2-IsoPs) regulate the release of excitatory neurotransmitters in isolated bovine retina. Although 5-F3-IsoPs are generated in mammals, in vivo, their pharmacological actions on neurotransmitter release remain unknown. In this study, we investigated the effect of 5-epi-5-F3t-IsoP on K(+)-evoked [(3)H]D-aspartate release in isolated bovine retina using the superfusion method. Furthermore, we examined the role of arachidonic acid metabolites in the regulation of the neurotransmitter release by this novel IsoP. In the concentration range, 0.01 nM-0.1 µM, 5-epi-5-F3t-IsoP inhibited K(+)-evoked [(3)H]D-aspartate release in a concentration-dependent manner, achieving a maximum inhibition of 46.9 % at 0.1 µM (IC30 = 1 nM). The prostanoid receptor antagonists, AH 6809 (EP1-3/DP; 10 µM), SC 51322 (EP1; 10 µM) and SC 19220 (EP1; 1 µM) partially reversed 5-epi-5-F3t-IsoP-mediated inhibition of K(+)-induced [(3)H]D-aspartate release. Pretreatment of retinal tissues with the cyclooxygenase (COX) inhibitor, flurbiprofen (3 µM) unmasked a biphasic action of 5-epi-5-F3t-IsoP that was inhibitory at lower (0.1-10 pM) and stimulatory at higher concentrations (≥0.1 nM). The prostanoid pathway antagonists, BAY-u3405 (10 µM; TP/DP-receptors), SQ 29548 (10 µM; TP-receptor) and ozagrel (10 µM; Tx-synthase inhibitor) abolished the stimulatory action of the 5-epi-5-F3t-IsoP (0.1 µM) on neurotransmitter release. In conclusion, 5-epi-5-F3t-IsoP attenuates K(+)-induced [(3)H]D-aspartate release in a concentration-dependent manner by mechanisms that are partially dependent on activation of pre-junctional prostanoid EP1-receptors. Moreover, blockade of the COX-pathway unmasks a biphasic action for 5-epi-5-F3t-IsoP that is inhibitory at low concentrations and stimulatory at higher concentrations. Products of the thromboxane synthase pathway may partially account for the stimulatory action of this F3-IsoP on isolated bovine retina.
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Ácido Aspártico/metabolismo , Isoprostanos/metabolismo , Retina/metabolismo , Animais , BovinosRESUMO
In the original publication [...].
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BACKGROUND: Novel oral polio vaccine type 2 (nOPV2) has been used to interrupt circulating vaccine-derived poliovirus type 2 outbreaks following its WHO emergency use listing. This study reports data on the safety and immunogenicity of nOPV2 over two rounds of a campaign in The Gambia. METHODS: This observational cohort study collected baseline symptoms (vomiting, diarrhoea, irritability, reduced feeding, and reduced activity) and axillary temperature from children aged 6 weeks to 59 months in The Gambia before a series of two rounds of a nOPV2 campaign that took place on Nov 20-26, 2021, and March 19-22, 2022. Serum and stool samples were collected from a subset of the participants. The same symptoms were re-assessed during the week following each dose of nOPV2. Stool samples were collected on days 7 and 28, and serum was collected on day 28 following each dose. Adverse events, including adverse events of special interest, were documented for 28 days after each campaign round. Serum neutralising antibodies were measured by microneutralisation assay, and stool poliovirus excretion was measured by real-time RT-PCR. FINDINGS: Of the 5635 children eligible for the study, 5504 (97·7%) received at least one dose of nOPV2. There was no increase in axillary temperature or in any of the baseline symptoms following either rounds of the campaigns. There were no adverse events of special interest and no other safety signals of concern. Poliovirus type 2 seroconversion rates were 70% (95% CI 62 to 78; 87 of 124 children) following one dose of nOPV2 and 91% (85 to 95; 113 of 124 children) following two doses. Poliovirus excretion on day 7 was lower after the second round (162 of 459 samples; 35·3%, 95% CI 31·1 to 39·8) than after the first round (292 of 658 samples; 44·4%, 40·6 to 48·2) of the campaign (difference -9·1%; 95% CI -14·8 to -3·3), showing the induction of mucosal immunity. INTERPRETATION: In a campaign in west Africa, nOPV2 was well tolerated and safe. High rates of seroconversion and evidence of mucosal immunity support the licensure and WHO prequalification of this vaccine. FUNDING: Bill & Melinda Gates Foundation.
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Poliomielite , Poliovirus , Humanos , Anticorpos Antivirais , Gâmbia/epidemiologia , Esquemas de Imunização , Imunogenicidade da Vacina , Poliomielite/prevenção & controle , Vacina Antipólio de Vírus Inativado , Vacina Antipólio Oral , Lactente , Pré-EscolarRESUMO
Hydrogen sulfide (H2S), a colorless gas characterized by its pungent odor of rotten eggs has been reported to elicit relaxation effects on basal and pre-contracted non-ocular smooth muscles of several mammalian species. In the present study, we investigated the pharmacological actions of a H2S donor, GYY4137 on isolated bovine posterior ciliary artery after contraction with the adrenergic receptor agonist, phenylephrine. Furthermore, we studied the underlying mechanism of inhibitory action of GYY4137 on the posterior ciliary arteries. Isolated bovine posterior ciliary arteries were mounted in oxygenated organ baths and changes in isometric tension were measured with a Grass FT03 transducer connected to a recorder using a Grass Polyview Software. The relaxant actions of GYY4137 on phenylephrine pre-contracted arteries were observed in the absence and presence of an inhibitor of cyclo-oxygenase, flurbiprofen. Furthermore, the inhibitory effects of GYY4137 were studied in the absence or presence of inhibitors/activators of biosynthetic enzymes for H2S and nitric oxide production, as well as specific ion channel blockers. In the concentration range, 100 nM to 100 µM, GYY4137 elicited a concentration-dependant relaxation of phenylephrine-induced tone in isolated posterior ciliary arteries, with IC50 value of 13.4 ± 1.9 µM (n = 6). The cyclo-oxygenase inhibitor, flurbiprofen, significantly (p < 0.01) enhanced the relaxation induced by GYY4137 yielding IC50 value of 0.13 ± 0.08 µM (n = 6). Both the inhibitors of cystathionine ß-synthase (aminooxyacetic acid, AOAA, 30 µM) and cystathionine γ-lyase (propargylglycine, PAG, 1 mM) caused significant (p < 0.05) rightward shifts in the concentration-response curve to GYY4137. Furthermore, the KATP channel antagonist, glibenclamide (100 µM) significantly (p < 0.01) attenuated the relaxant action induced by GYY4137 on bovine ciliary artery. Conversely, the activator of cystathionine ß-synthase, SAM (100 µM) and an inhibitor of nitric oxide synthase, L-NAME (100 µM) had no significant effect on relaxations induced by GYY4137. We conclude that the inhibitory action of GYY4137 on isolated bovine ciliary artery is dependent upon the endogenous production of both prostanoids and H2S. Furthermore, the observed vascular smooth muscle relaxation induced by GYY4137 is mediated, at least in part, by KATP channels.
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Artérias Ciliares/fisiologia , Sulfeto de Hidrogênio/metabolismo , Morfolinas/farmacologia , Compostos Organotiofosforados/farmacologia , Fenilefrina/farmacologia , Vasodilatação/efeitos dos fármacos , Animais , Bovinos , Artérias Ciliares/efeitos dos fármacos , Preparações de Ação Retardada , Vasoconstritores/farmacologiaRESUMO
Hydrogen sulfide (H(2)S), a colorless gas with the pungent odor of rotten eggs has been reported to produce pharmacological actions in ocular and non-ocular tissues. We have evidence that H(2)S, using sodium hydrosulfide (NaHS) and sodium sulfide (Na(2)S) as donors can increase cyclic AMP (cAMP) production in neural retina. In the present study, we investigated the mechanism of action of H(2)S on cyclic nucleotide production in rat retinal pigment epithelial cells (RPE-J). Cultured RPE-J cells were incubated for 30 min in culture medium containing the cyclic nucleotide phosphodiesterase (PDE) inhibitor, IBMX (2 mM). Cells were exposed to varying concentrations of NaHS, the H(2)S substrate (L-cysteine), cyclooxygenase (COX) inhibitors or the diterpene activator of adenylate cyclase, forskolin in the presence or absence of H(2)S biosynthetic enzymes or the ATP-sensitive potassium (K(ATP)) channel antagonist, glibenclamide. Following drug-treatment at different time intervals, cell homogenates were prepared for cAMP assay using a well established methodology. In RPE-J cells, NaHS (10 nM-1 µM) produced a time-dependent increase in cAMP concentrations over basal levels which reached a maximum at 20 min. At this time point, both NaHS (1 nM-100 µM) and L-cysteine (1 nM-10 µM) produced a concentration-dependent significant (p<0.05) increase in cAMP concentrations over basal level. The effects of NaHS on cAMP levels in RPE-J cells was enhanced significantly (p<0.01) in the presence of the COX inhibitors, indomethacin and flurbiprofen. In RPE-J cells, the effects caused by forskolin (10 µM) on cAMP production were potentiated by addition of low concentrations of NaHS. Both the inhibitor of cystathionine ß-synthase (CBS), aminooxyacetic acid (AOA, 1 mM) and the inhibitor of cystathionine γ-lyase (CSE), proparglyglycine (PAG, 1mM) significantly attenuated the increased effect of L-cysteine on cAMP production. The K(ATP) channel antagonist, glibenclamide (100 µM) caused inhibition of NaHS induced-increase of cAMP formation in RPE-J cells. We conclude that, H(2)S (using H(2)S donor and substrate) can increase cAMP production in RPE-J cells, and removal of the apparent inhibitory effect of prostaglandins unmasks an excitatory activity of H(2)S on cAMP. Effects elicited by the H(2)S substrate on cAMP formation are dependent on biosynthesis of H(2)S catalyzed by the biosynthetic enzymes, CBS and CSE. In addition to the adenylyl cylcase pathway, K(ATP) channels are involved in mediating the observed effects of the H(2)S on cAMP production.
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AMP Cíclico/biossíntese , Sulfeto de Hidrogênio/farmacologia , Epitélio Pigmentado da Retina/efeitos dos fármacos , Alcinos/farmacologia , Ácido Amino-Oxiacético/farmacologia , Animais , Células Cultivadas , Inibidores de Ciclo-Oxigenase/farmacologia , Cistationina beta-Sintase/fisiologia , Cistationina gama-Liase/fisiologia , Cisteína/farmacologia , Relação Dose-Resposta a Droga , Ativação Enzimática , Glicina/análogos & derivados , Glicina/farmacologia , Canais KATP/metabolismo , Prostaglandinas/metabolismo , Ratos , Epitélio Pigmentado da Retina/metabolismo , Sulfetos/farmacologiaRESUMO
We have evidence that 15-F2-isoprostanes (15-F2-IsoPs) regulate excitatory neurotransmitter release in ocular tissues. Although 5-F2-IsoPs are abundantly produced in mammals, their pharmacological actions on neurotransmitter release remain unknown. In the present study, we compared the effect of the 5-F2-IsoP epimer pair, 5-F(2t)-IsoP (C5-OH in ß-position) and 5-epi-5-F(2t)-IsoP (C5-OH in α-position), on Kâº-evoked [³H]D-aspartate release in isolated bovine retina. We further examined the role of prostanoid receptors on the inhibitory action of 5-epi-5-F(2t)-IsoP on [³H]D-aspartate overflow. Isolated bovine retina were prepared for studies of Kâº-evoked release of [³H]D-aspartate using the superfusion method. 5-epi-5-F(2t)-IsoP (0.01 nM to 1 µM), attenuated Kâº-evoked [³H]D-aspartate release in a concentration-dependent manner, with the inhibitory effect of 26.9% (P < 0.001; IC25 = 0.2 µM) being achieved at 1 µM concentration. Its 5-(S)-OH-epimer, 5-F(2t)-IsoP (0.1 nM-1 µM), exhibited an inhibitory biphasic action, yielding a maximal response of 35.7% (P < 0.001) at 10 nM concentration of the drug (IC25 value of 3 nM). Although the prostanoid-receptor antagonists, AH 6809 (10 µM; EP1â3/DP) and BAY-u3405 (10 µM; DP/Tx) exhibited no effect on 5-epi-5-F(2t)-IsoP (10 nM-1 µM)-mediated inhibition, SC-19220 (1 µM; EP1) completely reversed 5-epi-5-F(2t)-IsoP (0.1 µM and 1 µM)-induced attenuation of Kâº-evoked [³H]D-aspartate release. Similarly, both SC-51322 (10 µM; EP1 and AH 23848 (1 µM; EP4) reversed the inhibitory action elicited by 5-epi-5-F(2t)-IsoP (0.1 µM) on the neurotransmitter release. We conclude that the 5-F2-IsoP epimer pair, 5-F(2t)-IsoP and 5-epi-5-F(2t)-IsoP, attenuate Kâº-induced [³H]D-aspartate release in isolated bovine retina presumably via prostanoid receptor dependent mechanisms. The trans-orientation of the allylic hydroxyl group at position C5 accounts for the apparent biphasic response exhibited by 5-F(2t)-IsoP on excitatory neurotransmitter release.
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Ácido D-Aspártico/metabolismo , F2-Isoprostanos/metabolismo , Retina/metabolismo , Animais , Bovinos , Técnicas In Vitro , TrítioRESUMO
Hydrogen sulfide (H(2)S) is a novel gasotransmitter with physiological and pathological functions in vascular homeostasis, cardiovascular system and central nervous system. In the present study, we determined the endogenous levels of H(2)S in various tissues of the bovine eye. We also examined the basal levels of H(2)S in response to donors (sodium hydrosulfide, NaHS and sodium sulfide, Na(2)S), substrate (L: -cysteine), inhibitors (propargylglycine, PAG and aminooxyacetic acid, AOA) and activator (S-adenosyl-L: -methionine, SAM) of this gas in the bovine retina. H(2)S was measured using a well established spectrophotometric method. The highest concentration of endogenous H(2)S was detected in cornea (19 ± 2.85 nmoles/mg protein, n = 6) and retina (17 ± 2.1 nmoles/mg protein, n = 6). Interestingly, H(2)S was not present in vitreous humor. The inhibitors of CSE and CBS; PAG (1 mM) and AOA (1 mM), significantly attenuated the production of H(2)S in the bovine retina by 56.8 and 42%, respectively. On the other hand the activator of CBS; SAM (100 µM), H(2)S donors; NaHS (1 µM) and Na(2)S (100 µM), significantly increased endogenous levels of H(2)S in bovine retina. L: -cysteine (10-300 µM) produced a significant (P < 0.05) concentration-dependent increase in H(2)S levels reaching a maximal at 300 µM. We conclude that H(2)S is endogenously produced in various tissues of the isolated bovine eye. Moreover, endogenous levels of H(2)S are enhanced in the presence of substrate (L: -cysteine), an activator of CBS (SAM) and H(2)S donors but are blocked by inhibitors of enzymes that synthesize this gas in neural retina.
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Olho/anatomia & histologia , Olho/metabolismo , Sulfeto de Hidrogênio/metabolismo , Animais , Bovinos , Cistationina beta-Sintase/metabolismo , Cistationina gama-Liase/metabolismo , Cisteína/farmacologia , Olho/efeitos dos fármacos , Neurotransmissores/metabolismo , Retina/efeitos dos fármacos , Retina/metabolismoRESUMO
INTRODUCTION: In 2011, member states of the World Health Organization (WHO) Africa Regional Office (AFRO) resolved to eliminate Measles by 2020. Our study aims to assess The Gambia's progress towards the set AFRO measles elimination target and highlight surveillance and immunisation gaps to better inform future measles prevention strategies. MATERIAL AND METHODS: A retrospective review of measles surveillance data for the period 2011-2019, was extracted from The Gambia case-based measles surveillance database. WHO-UNICEF national coverage estimates were used for estimating national level MCV coverage. Measles post campaign coverage survey coverage estimates were used to estimate national measles campaign coverage. RESULTS: One hundred and twenty-five of the 863 reported suspected cases were laboratory confirmed as measles cases. More than half (53.6%) of the confirmed cases have unknown vaccination status, 24% of cases were vaccinated, 52.8% of cases occurred among males, and 72.8% cases were among urban residents. The incidence of measles cases per million population was lowest (0) in 2011-2012 and highest in 2015 and 2016 (31 and 23 respectively). The indicator for surveillance sensitivity was met in all years except in 2016 and 2019. Children aged 5-9 years (Incidence Rate Ratio-IRR = 0.6) and residents of Central River region (IRR = 0.21) had lower measles risk whilst unvaccinated (Adjusted IRR = 5.95) and those with unknown vaccination status (IRR 2.21) had higher measles risk. Vaccine effectiveness was 89.5%. CONCLUSION: The Gambia's quest to attain measles elimination status by 2020 has registered significant success but it is unlikely that all target indicators will be met. Vaccination has been very effective in preventing cases. There is variation in measles risk by health region, and it will be important to take it into account when designing prevention and control strategies. The quality of case investigations should be improved to enhance the quality of surveillance for decision making.
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Programas de Imunização , Vacina contra Sarampo/uso terapêutico , Sarampo/epidemiologia , Cobertura Vacinal , Adolescente , Adulto , Criança , Pré-Escolar , Erradicação de Doenças , Feminino , Gâmbia/epidemiologia , Humanos , Incidência , Lactente , Recém-Nascido , Masculino , Sarampo/prevenção & controle , Vigilância da População , Estudos RetrospectivosRESUMO
Hydrogen sulfide (H(2)S) has been reported to exert pharmacological effects on neural and non-neural tissues from several mammalian species. In the present study, we examined the role of the intracellular messenger, cyclic AMP in retinal response to H(2)S donors, sodium hydrosulfide (NaHS) and sodium sulfide (Na(2)S) in cows and pigs. Isolated bovine and porcine neural retinae were incubated in oxygenated Krebs buffer solution prior to exposure to varying concentrations of NaHS, Na(2)S or the diterpene activator of adenylate cyclase, forskolin. After incubation at different time intervals, tissue homogenates were prepared for cyclic AMP assay using a well established methodology. In isolated bovine and porcine retinae, the combination of both phosphodiesterase inhibitor, IBMX (2 mM) and forskolin (10 microM) produced a synergistic increase (P < 0.001) in cyclic AMP concentrations over basal levels. NaHS (10 nM-100 microM) produced a time-dependent increase in cyclic AMP concentrations over basal levels which reached a maximum at 20 min in both bovine and porcine retinae. At this time point, both NaHS and Na(2)S (10 nM-100 microM) caused a significant (P < 0.05) dose-dependent increase in cyclic AMP levels in bovine and porcine retinae. For instance, NaHS (100 nM) elicited a four-fold and three-fold increase in cyclic AMP concentrations in bovine and porcine retinae respectively whilst higher concentrations of Na(2)S (100 microM) produced a much lesser effect in both species. In bovine and porcine retinae, the effects caused by forskolin (10 microM) on cyclic AMP production were not potentiated by addition of low or high concentrations of both NaHS and Na(2)S. We conclude that H(2)S donors can increase cyclic AMP production in isolated neural retinae from cows and pigs. Bovine retina appears to be more sensitive to the stimulatory effect of H(2)S donors on cyclic nucleotide production than its porcine counterpart indicating that species differences exist in the magnitude of this response. Furthermore, effects produced by forskolin on cyclic AMP formation were not additive with those elicited by H(2)S donors suggesting that these agents may share a common mechanism in their action on the adenylyl cyclase pathway.
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Poluentes Atmosféricos/toxicidade , AMP Cíclico/biossíntese , Sulfeto de Hidrogênio/toxicidade , Neurônios/metabolismo , Retina/metabolismo , 1-Metil-3-Isobutilxantina/farmacologia , 3',5'-AMP Cíclico Fosfodiesterases/antagonistas & inibidores , 3',5'-AMP Cíclico Fosfodiesterases/metabolismo , Adenilil Ciclases/metabolismo , Animais , Bovinos , Colforsina/farmacologia , Técnicas In Vitro , Neurônios/efeitos dos fármacos , Inibidores de Fosfodiesterase/farmacologia , Retina/efeitos dos fármacos , Sulfetos/farmacologia , SuínosRESUMO
Cataracts, one of the leading causes of preventable blindness worldwide, refers to lens degradation that is characterized by clouding, with consequent blurry vision. As life expectancies improve, the number of people affected with cataracts is predicted to increase worldwide, especially in low-income nations with limited access to surgery. Although cataract surgery is considered safe, it is associated with some complications such as retinal detachment, warranting a search for cheap, pharmacological alternatives to the management of this ocular disease. The lens is richly endowed with a complex system of non-enzymatic and enzymatic antioxidants which scavenge reactive oxygen species to preserve lens proteins. Depletion and/or failure in this primary antioxidant defense system contributes to the damage observed in lenticular molecules and their repair mechanisms, ultimately causing cataracts. Several attempts have been made to counteract experimentally induced cataract using in vitro, ex vivo, and in vivo techniques. The majority of the anti-cataract compounds tested, including plant extracts and naturally-occurring compounds, lies in their antioxidant and/or free radical scavenging and/or anti-inflammatory propensity. In addition to providing an overview of the pathophysiology of cataracts, this review focuses on the role of various categories of natural and synthetic compounds on experimentally-induced cataracts.
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Screening homes is an effective way of reducing house entry by mosquitoes. Here, we assess how important blocking the eaves is for reducing house entry by anopheline and culicine mosquitoes for houses that have screened doors and no windows. Twelve houses, with two screened doors and no windows, in which a single adult male slept, were included in a simple crossover design. In the first period, six houses were randomly selected and had the eaves blocked using a mixture of rubble and mortar; the other six were left with open eaves. Mosquitoes were sampled using CDC light traps from each house twice a week for 4 wk. Mosquito control activities and the number and type of domestic animals within the compound was recorded on each sampling occasion. Before beginning the second sampling period, homes with blocked eaves had them opened, and those with open eaves had them closed. Mosquitoes were then sampled from each house for a further 4 wk. When houses had their eaves closed, a three-fold reduction in Anopheles gambiae s.l. Giles caught indoors was observed. However, there was no reduction in total culicine numbers observed. This study demonstrates that the eaves are the major route by which An. gambiae enters houses. By contrast, culicine mosquitoes enter largely through doors and windows. Sealing the eave gap is an important method for reducing malaria transmission in homes where doors and windows are screened.
Assuntos
Aedes/fisiologia , Anopheles/fisiologia , Comportamento Animal , Culex/fisiologia , Habitação , Controle de Mosquitos/métodos , AnimaisRESUMO
PURPOSE: To standardize a new method for assessing cataractogenesis in isolated cultured bovine lenses using L-cysteine as the standard anti-cataract agent. METHODS: Intact bovine lenses were cultured in DMEM with L-cysteine in presence or absence of hydrogen peroxide (H2O2). Lens opacity (transmittance) was determined using a plate reader. Lens homogenate glutathione (GSH) and superoxide dismutase (SOD) contents were measured using enzyme immunoassays kits. RESULTS: DMEM-cultured lenses exhibited a time-dependent loss in transmittance (230-710â¯nm) up to 120â¯h, achieving the highest reduction of 38.6⯱â¯0.09% at 420â¯nm (pâ¯<â¯.001;nâ¯=â¯12). Compared to untreated lenses (time in hours [t]â¯=â¯0), L-cysteine (10-6â¯M and 10-5â¯M) significantly (pâ¯<â¯.001;nâ¯=â¯6) increased time-dependent transmittance (420â¯nm) by 31.6⯱â¯0.17% and 28.0⯱â¯0.07%(tâ¯=â¯120), respectively. When compared to DMEM-cultured lenses (tâ¯=â¯0), H2O2 (10â¯mM, 50â¯mM and 100â¯mM) significantly (pâ¯<â¯.001;nâ¯=â¯12) reduced transmittance by 57.8⯱â¯0.1, 57.4⯱â¯0.04 and 87.7⯱â¯0.6%(tâ¯=â¯120), respectively. Moreover, L-cysteine significantly (pâ¯<â¯.001;nâ¯=â¯6) attenuated H2O2 (50â¯mM)-induced decrease in transmittance by 12.5⯱â¯0.05%(10-6â¯M), 13.0⯱â¯0.09%(10-5â¯M), 14.5⯱â¯0.08%(10-4â¯M) and 8.6⯱â¯0.11%(10-3â¯M)(tâ¯=â¯120), respectively. When compared to untreated lenses (tâ¯=â¯0), the time-dependent decrease (pâ¯<â¯.001;nâ¯=â¯5) in lenticular total GSH content and total SOD activity of 46.1⯱â¯0.06% and 42.0⯱â¯1.65% (tâ¯=â¯120) was attenuated (pâ¯<â¯.001;nâ¯=â¯5) by L-cysteine (10-6â¯M) by 76.6⯱â¯0.06% and 7.4⯱â¯1.98%, respectively. Similarly, the H2O2(50â¯mM)-induced decline (pâ¯<â¯.001; nâ¯=â¯5) in total GSH content and SOD activity of 82.6⯱â¯0.08% and 86.6⯱â¯0.66% (tâ¯=â¯120) was attenuated by L-cysteine (10-4â¯M) by 74.7⯱â¯1.05% and 161.1⯱â¯4.9%, respectively. CONCLUSION: Measurement of spectral transmission coupled with assessment of the activity of antioxidant enzymes in bovine cultured lens can provide a useful tool in studies of cataracts in an animal model of this disease.
Assuntos
Catarata/patologia , Cristalino/patologia , Animais , Antioxidantes/metabolismo , Catarata/induzido quimicamente , Catarata/metabolismo , Bovinos , Cisteína/metabolismo , Glutationa/metabolismo , Peróxido de Hidrogênio/metabolismo , Peróxido de Hidrogênio/farmacologia , Cristalino/efeitos dos fármacos , Cristalino/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Padrões de Referência , Superóxido Dismutase/metabolismoRESUMO
Hydrogen sulfide (H2S) is a gaseous transmitter with well-known biological actions in a wide variety of tissues and organs. The potential involvement of this gas in physiological and pathological processes in the eye has led to several in vitro, ex vivo, and in vivo studies to understand its pharmacological role in some mammalian species. Evidence from literature demonstrates that 4 enzymes responsible for the biosynthesis of this gas (cystathionine ß-synthase, CBS; cystathionine γ-lyase, CSE; 3-mercaptopyruvate sulfurtransferase, 3MST; and d-amino acid oxidase) are present in the cornea, iris, ciliary body, lens, and retina. Studies of the pharmacological actions of H2S (using several compounds as fast- and slow-releasing gas donors) on anterior uveal tissues reveal an effect on sympathetic neurotransmission and the ability of the gas to relax precontracted iris and ocular vascular smooth muscles, responses that were blocked by inhibitors of CSE, CBS, and KATP channels. In the retina, there is evidence that H2S can inhibit excitatory amino acid neurotransmission and can also protect this tissue from a wide variety of insults. Furthermore, exogenous application of H2S-releasing compounds was reported to increase aqueous humor outflow facility in an ex vivo model of the porcine ocular anterior segment and lowered intraocular pressure (IOP) in both normotensive and glaucomatous rabbits. Taken together, the finding that H2S-releasing compounds can lower IOP and can serve a neuroprotective role in the retina suggests that H2S prodrugs could be used as tools or therapeutic agents in diseases such as glaucoma.
Assuntos
Humor Aquoso/efeitos dos fármacos , Glaucoma/tratamento farmacológico , Sulfeto de Hidrogênio/farmacologia , Soluções Oftálmicas/farmacologia , Animais , Humor Aquoso/metabolismo , Glaucoma/metabolismo , Humanos , Sulfeto de Hidrogênio/química , Sulfeto de Hidrogênio/metabolismo , Soluções Oftálmicas/química , Soluções Oftálmicas/metabolismoRESUMO
PURPOSE: To study the pharmacological profile of the serotonin (5-hydroxytryptamine [5-HT]) receptor subtype mediating contractions in bovine isolated ciliary muscles. METHODS: Ciliary muscle strips were isolated from bovine eyeballs and mounted in organ baths containing aerated (95% O2, 5% CO2) Krebs buffer solution maintained at 37°C. Each muscle strip was attached at 1 end to a Grass Force-displacement Transducer connected to a Polyview Computer System for recording changes in isometric tension. After an equilibration period, ciliary muscle strips were exposed to selective agonists and antagonists of 5-HT receptors. RESULTS: Both selective and nonselective agonists for 5-HT produced concentration-dependent contractions of isolated ciliary muscles with the following rank order of potency: BW723C86>α-methyl-5-HT>MK-212>>8-hydroxy-DPAT>quipazine>R-DOI>>5-HT>>tryptamine. The selective 5-HT2 receptor antagonists, M-100907 (5-HT2A), RS-127445 (5-HT2B), and RS-102221 (5-HT2C), produced noncompetitive inhibition of the contractile effects of selective agonists yielding antagonist potency (pKB) values of 251 ± 27.2 nM (n = 4), 52.5 ± 6.3 nM (n = 4), and 79.4 ± 9.5 nM (n = 4), respectively. CONCLUSION: On the basis of the profile of activity of selective agonists and antagonists, we conclude that the 5-HT2B and 5-HT2C receptor subtypes appear to be the predominant serotonin receptors that mediate the contractile action of this amine in bovine isolated ciliary muscles.
Assuntos
Corpo Ciliar/efeitos dos fármacos , Pressão Intraocular/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Receptor 5-HT2B de Serotonina/metabolismo , Receptor 5-HT2C de Serotonina/metabolismo , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologia , Animais , Bovinos , Corpo Ciliar/metabolismoRESUMO
PURPOSE: To determine the serotonergic (5HT) receptor subtype mediating the contraction of bovine posterior ciliary arteries (BPCAs) in vitro. METHODS: Longitudinal isometric tension was measured in BPCA strips (4-5 mm) mounted in 25 mL organ baths containing oxygenated Krebs solution at 37°C. Cumulative contractile concentration-response (C-R) curves were generated for various 5-HT agonists to assess their potencies and maximal degrees of contraction. Multiple agonist C-R curves were also constructed in the presence and absence of receptor-selective antagonists to determine antagonist potencies using Schild plots. RESULTS: Selective and nonselective agonists for 5-HT receptors elicited concentration-dependent contractile responses in BPCAs with the following rank order of potency: MK-212 > BW723C86 > α-methyl-5-HT >5-methoxy-α-5-methyl-5-HT >> R-DO1 > >5-HT >> cabergoline >> 5-methoxy-dimethyl-tryptamine >> 2-methyl-5-HT >> tryptamine. Interestingly, both 8-OH-DPAT (5HT1A agonist) and quipazine (5HT3 agonist) did not elicit contractions in BPCAs. The contractions produced by BW723C86 (5-HT2B agonist) were antagonized by 5-HT receptor blockers, RS-127445 (5-HT2B antagonist), and M-100907 (5-HT2A antagonist), yielding antagonist pA2 values of 7.5 ± 0.12 (n = 4) and 6.2 ± 0.17 (n = 4), respectively. Furthermore, contractions elicited by MK-212 (5-HT2C agonist) was blocked by RS-102221 (5-HT2C antagonist), although noncompetitively. CONCLUSIONS: On the basis of the pharmacological profile of selective agonists and antagonists, we conclude that serotonin-induced contractions of the BPCA are mediated primarily by a combination of 5HT2C and/or 5HT2B receptors. It appears that 5-HT1A and 5-HT3 receptors are not involved in the contractile action of BPCAs to serotonin.
Assuntos
Artérias Ciliares/efeitos dos fármacos , Contração Muscular/efeitos dos fármacos , Artéria Oftálmica/efeitos dos fármacos , Antagonistas da Serotonina/farmacologia , Animais , Velocidade do Fluxo Sanguíneo , Pressão Sanguínea/efeitos dos fármacos , Bovinos , Relação Dose-Resposta a Droga , Receptores de Serotonina/metabolismoRESUMO
Excitotoxicity occurs in neurons due to the accumulation of excitatory amino acids such as glutamate in the synaptic and extrasynaptic locations. In the retina, excessive glutamate concentrations trigger a neurotoxic cascade involving several mechanisms, including the elevation of intracellular calcium (Ca2+) and the activation of α-amino-3-hydroxy 5-methyl-4-iso-xazole-propionic acid/kainate (AMPA/KA) and N-methyl-d-aspartate (NMDA) receptors leading to retinal degeneration. Both ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGluRs) are present in the mammalian retina. Indeed, due to the abundant expression of GluRs, the mammalian retina is highly susceptible to excitotoxic neurodegeneration. Excitotoxicity has been postulated to present a common downstream mechanism for several stimuli, including hypoglycemia, hypoxia, ischemia, and chronic neurodegenerative diseases. Experimental approaches to the study of neuroprotection in the retina have utilized insults that trigger hypoxia, hypoglycemia, or excitotoxicity. Using these experimental approaches, the neuroprotective potential of GluR agents, including the NMDA receptor modulators (MK801, ifenprodil, memantine); AMPA/KA receptor antagonist (CNQX); Group II and III mGluR agonists (LY354740, quisqualate); and Ca2+-channel blockers (diltiazem, lomerizine, verapamil, ω-conotoxin), and others (pituitary adenylate cyclase activating polypeptide, neuropeptide Y, acetylcholine receptor agonists) have been elucidated. In addition to corroborating the exocytotic role of excitatory amino acids in retinal degeneration, these studies affirm that multiple mechanism/s contribute to the prevention of damage caused by excitotoxicity in the retina. Therefore, it is feasible that several pathways are involved in protecting the retina from toxic insults in ocular neurodegenerative conditions such as glaucoma and retinal ischemia. Furthermore, these experimental models are viable tools for evaluating therapeutic candidates in ocular neuropathies.
Assuntos
Aminoácidos Excitatórios/metabolismo , Fármacos Neuroprotetores/farmacologia , Soluções Oftálmicas/farmacologia , Retina/efeitos dos fármacos , Animais , Glaucoma/tratamento farmacológico , Glaucoma/metabolismo , Humanos , Retina/metabolismo , Doenças Retinianas/tratamento farmacológico , Doenças Retinianas/metabolismoRESUMO
PURPOSE: To investigate the pharmacological actions of hydrogen sulfide (H2S)-releasing compounds l-cysteine and sodium hydrosulfide (NaHS) on aqueous humor (AH) outflow facility in porcine ocular anterior segment. METHODS: Porcine ocular anterior segments were perfused with Dulbecco's modified Eagle's medium at a constant pressure of 7.35 mmHg. After stable outflow baseline, explants were exposed to NaHS or l-cysteine. The increase in outflow generated by the H2S-releasing compounds was measured in the absence and presence of inhibitor of H2S biosynthesis (aminooxyacetic acid; AOAA), blocker of KATP channels (glibenclamide), and inhibitor of adenylyl cyclase (SQ 22536). Hematoxylin and eosin (H&E) staining was used to assess trabecular meshwork (TM) morphology. RESULTS: l-cysteine elicited a concentration-dependent increase in AH outflow facility, reaching maximal effect at 100 nM (150.6% ± 17.2% of basal level). This increase in outflow induced by l-cysteine was significantly (P < 0.001) antagonized by AOAA (30 µM) and glibenclamide (100 µM). AOAA and glibenclamide had no significant action on baseline outflow, whereas SQ 22536 (100 µM) increased outflow for only an hour. In addition, NaHS produced a concentration-dependent increase in AH outflow, with a maximal effect at 10 µM (151.4% ± 22.9% of basal level). Likewise, the increase in outflow caused by NaHS was significantly (P < 0.04) blocked by glibenclamide and SQ 22536. H&E staining revealed that l-cysteine or NaHS did not alter TM conformation. CONCLUSION: H2S-releasing compounds can increase outflow facility in porcine ocular anterior segment. The stimulatory action of these compounds on outflow is mediated, in part by endogenously produced H2S, KATP channels, and adenylyl cyclase.