Anopheles gambiae eicosanoids modulate Plasmodium berghei survival from oocyst to salivary gland invasion

Eicosanoids affect the immunity of several pathogen/insect models, but their role on the Anopheles gambiae response to Plasmodium is still unknown. Plasmodium berghei-infected mosquitoes were injected with an eicosanoid biosynthesis inhibitor, indomethacin (IN), or a substrate, arachidonic acid (AA), at day 7 or day 12 post-infection (p.i.). Salivary gland invasion was evaluated by sporozoite counts at day 21 p.i. IN promoted infection upon sporozoite release from oocysts, but inhibited infection when sporozoites were still maturing within the oocysts, as observed by a reduction in the number of sporozoites reaching the salivary glands. AA treatment had the opposite effect. We show for the first time that An. gambiae can modulate parasite survival through eicosanoids by exerting an antagonistic or agonistic effect on the parasite, depending on its stage of development.

Arachidonic acid affects biofilm formation and PGE2 level in Candida albicans and non-albicans species in presence of subinhibitory concentration of fluconazole and terbinafine

Candida albicans utilizes arachidonic acid (AA) released during the course of infection (Candidiasis) from phospholipids of infected host cell membranes and synthesizes extracellular prostaglandin(s) which play an important role in hyphae formation and host cell damage. C. albicans biofilms secrete significantly more prostaglandin(s) and evidence suggests that Candida biofilms have dramatically reduced susceptibility to majority of antifungal drugs. AA influences the saturation level of lipids and fluidity of yeast cell membranes. Therefore the aim of this study was to evaluate the effect of AA alone or in combination with antifungal agents on biofilm formation and production of prostaglandin (PGE2) in C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, and C. albicans amphotericin B resistant strain (AmBR). Maximum biofilm formation was found to be in the case of C. albicans compared to C. non-albicans species. However, among the non-albicans species C. tropicalis exhibited highest biofilm formation. Treatment with AA in combination with subinhibitory concentrations of fluconazole and terbinafine separately exhibited significant (p < 0.05) reduction in biofilm formation against C. glabrata, C. parapsilosis, C. tropicalis and AmBR as compared to their individual effect. Further, these two antifungal agents in combination with AA caused an increase in production of prostaglandin from fungal cell itself which was significant (p < 0.05) in case of all the strains tested.

Producción de prostaciclina en arteria radial de diabéticos: comparación con la vena safena y arteria mamaria interna y su relevancia en el pronóstico de estos bypass coronarios / Prostacyclin production in internal mammary ano radial arteries and saphenous veins of diabetic and non diabetic subjects

Background: Myocardial revascularization surgery has used several vessels as coronary grafts including internal mammary and radial arteries which have a better prognosis than saphenous vein. Their long-term patency has been associated with the reléase of endothelium vasodilator and anti-aggregating producís such as prostacyclin. Diabetes induces endothelial dysfunction and a high number of diabetics require revascularization. Aim: To assess the capacity to synthesize prostacyclin of different vessels from diabetics. Material and methods: Internal mammary and radial arteries and saphenous veins obtained from 10 diabetic and 10 non diabetic patients subjected to coronary artery bypass surgery were studied. The capacity to synthesize prostacyclin was assessed in these vessels measuríng its hydrolysis product, the 6-keto-PGFla by radioimmunoassay. Results: Internal mammary arteries and saphenous veins from diabetics synthesized a lower amount of prostacyclin than those from non-diabetics. The radial artery produced similar amounts of prostacyclin in both groups. This response was associated with an increase of the conversión of the precursor arachidonic acid to prostacyclin. The saturating concentrations of this acid required to achieve the maximal stimulation were higher in the radial artery (20 µM) than in the internal mammary artery and saphenous vein (10 µM), suggesting that the enzymatic activity of the radial artery was not affected by diabetes. Conclusions: The radial artery appears as the best replacement vessel for coronary surgery in diabetics. Its favorable biochemical profile and potential lower long-term occlusion rate may be relevant for a better prognosis of myocardial revascularization in these patients.

Isolation of syringaldehyde from Mikania laevigata medicinal extract and its influence on the fatty acid profile of mice / Extrato medicinal de Mikania laevigata: influência no perfil de ácidos graxos em camundongos e isolamento de siringaldeído por CLAE semipreparativa

The Mikania genus is widely known as "guaco" and is used to treat fever, rheumatism, flu and respiratory diseases. Our previous work evidenced the synergism among M. laevigata extract components to produce desirable effects, and included the coumarin precursor, o-coumaric acid as marker. Many Mikania species are producers of ent-kaurene diterpenes which presented antiespasmodic and relaxant activities on smooth muscle. Seeking to standardize the guaco extract, which is registered in the Brazilian Pharmacopoea, this paper deals with the determination of kaurenoic acid through LC-PDA and the isolation through LC of syringaldehyde. Kaurenoic acid was not found in the extract, and syringaldehyde is one of the major compounds of pharmacopoeal extract, together with coumarin and o-coumaric acid. Samples from the lung and liver of Balb-C isogenic allergic pneumonitis bearing mice, treated with the same extract, were analyzed through GC-FID, and the fatty acid content was determined and analyzed. The results obtained by measuring the arachidonic acid (ARA) and docosahexaenoic acid (DHA) in the liver and lung of treated animals demonstrated that the fatty acid composition is distinct in both tissues, and that in the liver, only the DHA was altered as a result of the treatments. DHA is absent in the lung and in both organs, no significant difference in ARA production was observed. The aqueous extract, coumarin and o-coumaric acid stimulated DHA synthesis in the liver (p < 0.05).

O gênero Mikania é popularmente conhecido como "guaco" e é utilizado para tratar febre, reumatismo, resfriados e afecções respiratórias. Em trabalho prévio demonstramos sinergismo entre os componentes do extrato de M. laevigata para produzir os efeitos farmacológicos esperados, incluindo a cumarina e seu precursor ácido o-cumárico como marcadores. Muitas espécies de Mikania são produtoras de diterpenos ent-caurenos que apresentam atividade antispasmódica e relaxante da musculatura lisa. Buscando a padronização do extrato medicinal de guaco (preparado segundo a farmacopéia brasileira 1ª edição), este trabalho visou determinar a presença de ácido caurenóico através de CLAE-DAD e isolou siringaldeído através de CLAE semipreparativa, sendo que o primeiro não foi encontrado no extrato e o siringaldeído é um dos seus componentes majoritários. Camundongos isogênicos Balb-C portadores de pneumonite alérgica foram tratados com este extrato, e amostras de pulmão e fígado foram analisadas por CG-DIC quanto ao seu conteúdo de ácidos graxos. A quantidade de ácido araquidônico (ARA) e de ácido docosahexaenóico (DHA) encontrada demonstrou que a composição é distinta em ambos tecidos, e apenas a concentração de DHA hepático foi alterado em função do tratamento, o qual não foi encontrado no pulmão. Não foi detectada diferença significativa na produção de ARA. Tanto o extrato aquoso, quanto a cumarina e o ácido o-cumárico, estimularam a síntese de DHA no fígado (p < 0.05).

Arachidonic acid is a chemoattractant for Dictyostelium discoideum cells.

Cyclic AMP (cAMP)is a natural chemoattractant of the social amoeba Dictyostelium discoideum. It is detected by cell surface cAMP receptors. Besides a signalling cascade involving phosphatidylinositol 3,4,5-trisphosphate (PIP3), Ca2+ signalling has been shown to have a major role in chemotaxis. Previously, we have shown that arachidonic acid (AA) induces an increase in the cytosolic Ca2+ concentration by causing the release of Ca2+ from intracellular stores and activating influx of extracellular Ca2+. Here we report that AA is a chemoattractant for D. discoideum cells differentiated for 8-9 h. Motility towards a glass capillary filled with an AA solution was dose-dependent and qualitatively comparable to cAMP-induced chemotaxis. Ca2+ played an important role in AA chemotaxis of wild-type Ax2 as ethyleneglycol-bis(b-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA) added to the extracellular buffer strongly inhibited motility. In the HM1049 mutant whose iplA gene encoding a putative Ins(1,4,5)P3 -receptor had been knocked out, chemotaxis was only slightly affected by EGTA. Chemotaxis in the presence of extracellular Ca2+ was similar in both strains. Unlike cAMP, addition of AA to a cell suspension did not change cAMP or cGMP levels. A model for AA chemotaxis based on the findings in this and previous work is presented.

Angiotensin II-induced renal vasodilation mediated by cytochrome P-450 arachidonic acid metabolites

Activation of AT2 angiotensin II receptor release cytochrome P-450 arachidonic acid metabolites [CYP-AA]. The presence of the AT2 receptor and its ability to mediate renal vasodilation through CYP-AA metabolites were evaluated. Vascular response to angiotensin II in the isolated perfused kidney of the rat was evaluated in the absence and presence of angiotensin II AT1 and AT2 receptor blockers. Blockade of the AT1 receptor unmasked a vasodilatory response that was inhibited by AT2 receptor blockade and AA metabolism. The findings indicate that blockade of the AT1 angiotensin II receptor, activation of AT2 receptors, releases CYP-AA metabolites that induce renal vasodilation

Mechanism of cAMP-induced H(+)-efflux of Dictyostelium cells: a role for fatty acids.

Aggregating Dictyostelium cells release protons when stimulated with cAMP. To find out whether the protons are generated by acidic vesicles or in the cytosol, we permeabilized the cells and found that this did not alter the cAMP-response. Proton efflux in intact cells was inhibited by preincubation with the V-type H(+) ATPase inhibitor concanamycin A and with the plasma membrane H(+) ATPase blocker miconazole. Surprisingly, miconazole also inhibited efflux in permeabilized cells, indicating that this type of H(+) ATPase is present on intracellular vesicles as well. Vesicular acidification was inhibited by miconazole and by concanamycin A, suggesting that the acidic vesicles contain both V-type and P-type H(+) ATPases. Moreover, concanamycin A and miconazole acted in concert, both in intact cells and in vesicles. The mechanism of cAMP-induced Ca2(+)-fluxes involves phospholipase A2 activity. Fatty acids circumvent the plasma membrane and stimulate vesicular Ca2(+)-efflux. Here we show that arachidonic acid elicited H(+)-efflux not only from intact cells but also from acidic vesicles. The target of regulation by arachidonic acid seemed to be the vesicular Ca2(+)-release channel.

Membrane stretch increases the activity of Ca(2+)-activated K+ channels in rabbit coronary vascular smooth muscles

It has been proposed that Ca(2+)-activated K+ channels play an essential role in maintaining vascular tone during stretch of blood vessel. However, the underlying mechanism of stretch-induced change of Ca(2+)-activated K+ channel activities are still unknown. The present experiment was designed to investigate the effect of membrane stretch on these channels whose activity was measured from rabbit coronary smooth muscle cells using a patch clamp technique. Ca(2+)-activated K+ channel were identified by their Ca2+ and voltage dependencies and its large conductances as in other preparations. Perfusion of cells with a hypotonic solution, which mimics stretching the cell membrane by making a cell swelling, produced an increase in channel activity in cell-attached patch mode. The similar increase was observed when negative pressure was applied into the patch pipette for stretching the cell membrane within a patch area. In inside-out patch, stretch still increased channel activity even under the conditions which exclude the possible involvement of secondary messengers, or of transmembrane Ca2+ influx via stretch-activated cation channels. Pretreatment of arachidonic acid or albumin showed no effect on stretch-induced channel activation, excluding the possibility of fatty acids mediated channel activation during membrane stretch. These results indicate that the stretch may directly increase the activity of Ca(2+)-activated K+ channels in our experimental condition.

Fatty acids and the immune system

Os ácidos graxos têm diversos efeitos sobre as respostas imune e inflamatória, agindo como mediadores intracelulares e intercelulares. Os ácidos graxos poliinsaturados (PUFA) da família ômega 3 têm efeito supressor, inibindo a proliferação de linfócitos, a produção de anticorpos e citocinas, a expressão de moléculas de adesão, a atividade de células citotóxicas e causando morte celular. Os PUFA ômega 6 têm efeitos tanto inibitórios como estimulatórios. O mais estudado destes é o ácido araquidônico, que pode ser oxidado a eicosanóides, como prostaglandinas, leucotrienos e tromboxanas, todos eles potentes mediadores da inflamação. Apesar disso, muitos dos efeitos dos PUFA sobre os sistemas imune e inflamatório são independentes da geração de eicosanóides e podem ser devidos, pelo menos em parte, a alterações no metabolismo de glicose e glutamina...

Canales iónicos en células no excitables / Ion channels in non excitable cells

Several distinct types of voltage-gated and second-messenger-operated K+, Ca2+, Na+ and Cl- channels exist in electrically non excitable cells such as those of the hematopoietic lineage. In these cells ion channels mediate cellular functions involving intraceiiuiar biochemical responses, rather than rapid electrical signaling. The presence of the channels is required for several basic functions, such as activation, secretion of lymphokines, mitogenesis, the regulation of cell volume and the mechanisms of resistance to chemotherapeutic agents. Here IN we review the patch-clamp method for studying many characteristics of these ionic channels, particularly in blood cells.

Inibidores da agregacao plaquetaria induzida pelo PAF-acether / Inhibitor of the platelets aggregation induced by the PAF-acether

O efeito do PAF-acether foi avaliado em plaquetas humanas de individuos adultos clinicamente saudaveis atraves de estudos em plasma rico em plaquetas (PRP) com inibidores plaquetarios "in vitro"(AAS, NDHA e CP/CPK) e "ex-vivo" (AAS). O PAF-acether induziu agregacao dose dependente em concentracoes de 5x10-9M a 5x10-7M, com dose limite ou threshold em 9x10-8M. Os resultados obtidos demonstraram que a fase primaria de agregacao e independente da formacao de metabolicos de acido araquidonico e liberacao de ADP endogeno visto que, com excessao do BN 52021, os demais inibidores nao influenciaram nessa fase. Por outro lado, a fase secundaria de agregacao irreversivel envolve interrelacao entre os mediadores ADP e Acido Araquidonico dependentes preferencialmente da formacao de metabolicos do acido araquidonico via ciclo-oxigenase.