Hydrogen sulfide-induced dual vascular effect involves arachidonic acid cascade in rat mesenteric arterial bed.

Hydrogen sulfide (H(2)S), a novel gaseous transmitter, is considered a physiological regulator of vascular homeostasis. Recent evidence suggests H(2)S as an endothelium-hyperpolarizing factor (EDHF) candidate. To address this issue, we evaluated the vascular effect of sodium hydrogen sulfide (NaHS), an H(2)S donor, on the rat mesenteric arterial bed. NaHS concentration-response curve was performed on preconstricted mesenteric arterial bed. To assess the contribution of EDHF, we performed a pharmacologic dissection using indomethacin, N(G)-nitro-L-arginine methyl ester (L-NAME), or apamin and charybdotoxin as cyclooxygenase, nitric-oxide synthase, and calcium-dependent potassium channel inhibitors, respectively. In another set of experiments, we used 4-(4-octadecylphenyl)-4-oxobutenoic acid, baicalein, or proadifen as phospholipase A(2) (PLA(2)), lipoxygenase, and cytochrome P450 inhibitors, respectively. Finally, an immunofluorescence study was performed to support the involvement of PLA(2) in mesenteric artery challenged by NaHS. NaHS promoted a dual vascular effect (i.e., vasoconstriction and vasodilation). L-NAME or baicalein administration affected neither NaHS-mediated vasodilation nor vasoconstriction, whereas apamin and charybdotoxin significantly inhibited NaHS-induced relaxation. Pretreatment with PLA(2) inhibitor abolished both the contracting and the relaxant effect, whereas P450 cytochrome blocker significantly reduced NaHS-mediated relaxation. The immunofluorescence study showed that NaHS caused a migration of cytosolic PLA(2) close to the nucleus, which implicates activation of this enzyme. Our data indicate that H(2)S could activate PLA(2), which in turn releases arachidonic acid leading, initially, to vasoconstriction followed by vasodilation mediated by cytochrome P450-derived metabolites. Because EDHF has been presumed to be a cytochrome P450 derivative of the arachidonic acid, our results suggest that H(2)S acts through EHDF release

Crucial role of androgen receptor in vascular H2S biosynthesis induced by testosterone.

BACKGROUND AND PURPOSE: Hydrogen sulphide (H2S) is a gaseous mediator strongly involved in cardiovascular homeostasis, where it provokes vasodilation. Having previously shown that H2S contributes to testosterone (T) induced vasorelaxation, here we aim to uncover the mechanisms underlying this effect. EXPERIMENTAL APPROACH: H2S biosynthesis was evaluated in rat isolated aorta rings following androgen receptor (AR) stimulation. Co-immunoprecipitation and surface plasmon resonance analysis have been performed to investigate mechanisms involved in AR activation. KEY RESULTS: H2S biosynthesis is associated to activation of AR by testosterone or androgen agonist mesterolone and blocked by AR antagonist nilutamide. This event is linked to AR-multicomplex-derived heath shock protein 90 (hsp90), since its specific inhibitor geldanamycin strongly reduced T-induced H2S production. Neither progesterone nor 17-β-oestradiol actions did account for H2S release. Furthermore, we found that cystathionine gamma lyase (CSE), the main vascular H2S-synthesizing enzyme, is physically associated to AR/hsp90 complex and the generation of such a ternary system represents a key event leading to CSE activation. Finally, H2S levels in human blood collected from male healthy volunteers were higher than those observed in female samples. CONCLUSIONS AND IMPLICATIONS: Here, we demonstrated that selective activation of the AR is essential for H2S biosynthesis within vascular tissue and this event is based on formation of a ternary complex among CSE, AR and hsp90. This novel molecular mechanism operating in vascular district, corroborated by higher H2S level in males, suggested that L-cysteine/CSE/H2S pathway may be preferentially activated in males leading to a gender-related H2S biosynthesis

Peripheral relaxant activity of apomorphine and of a D1 selective receptor agonist on human corpus cavernosum strips

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Endogenous Urotensin II Selectively Modulates Erectile Function through eNOS

Urotensin II (U-II) is a cyclic peptide originally isolated from the neurosecretory system of the teleost fish and subsequently found in other species, including man. U-II was identified as the natural ligand of a G-protein coupled receptor, namely UT receptor. U-II and UT receptor are expressed in a variety of peripheral organs and especially in cardiovascular tissue. Recent evidence indicates the involvement of U-II/UT pathway in penile function in human, but the molecular mechanism is still unclear. On these bases the aim of this study is to investigate the mechanism(s) of U-II-induced relaxation in human corpus cavernosum and its relationship with L-arginine/Nitric oxide (NO) pathway.Human corpus cavernosum tissue was obtained following in male-to-female transsexuals undergoing surgical procedure for sex reassignment. Quantitative RT-PCR clearly demonstrated the U-II expression in human corpus cavernosum. U-II (0.1 nM-10 µM) challenge in human corpus cavernosum induced a significant increase in NO production as revealed by fluorometric analysis. NO generation was coupled to a marked increase in the ratio eNOS phosphorilated/eNOS as determined by western blot analysis. A functional study in human corpus cavernosum strips was performed to asses eNOS involvement in U-II-induced relaxation by using a pharmacological modulation. Pre-treatment with both wortmannin or geldanamycinin (inhibitors of eNOS phosphorylation and heath shock protein 90 recruitment, respectively) significantly reduced U-II-induced relaxation (0.1 nM-10 µM) in human corpus cavernosum strips. Finally, a co-immunoprecipitation study demonstrated that UT receptor and eNOS co-immunoprecipitate following U-II challenge of human corpus cavernosum tissue.U-II is endogenously synthesized and locally released in human corpus cavernosum. U-II elicited penile erection through eNOS activation. Thus, U-II/UT pathway may represent a novel therapeutical target in erectile dysfunction

Expression of Cystathionine β-synthase and Cystathionine γ-lyase in Human Pregnant Myometrium and Their Roles in the Control of Uterine Contractility

BACKGROUND: Human uterus undergoes distinct molecular and functional changes during pregnancy and parturition. Hydrogen sulfide (H(2)S) has recently been shown to play a key role in the control of smooth muscle tension. The role of endogenous H(2)S produced locally in the control of uterine contractility during labour is unknown. METHODOLOGY/PRINCIPAL FINDINGS: Human myometrium biopsies were obtained from pregnant women undergoing cesarean section at term. Immunohistochemistry analysis showed that cystathionine-γ-lyase (CSE) and cystathionine-β-synthetase (CBS), the principle enzymes responsible for H(2)S generation, were mainly localized to smooth muscle cells of human pregnant myometrium. The mRNA and protein expression of CBS as well as H(2)S production rate were down-regulated in labouring tissues compared to nonlabouring tissues. Cumulative administration of L-cysteine (10(-7)-10(-2) mol/L), a precursor of H(2)S, caused a dose-dependent decrease in the amplitude of spontaneous contractions in nonlabouring and labouring myometrium strips. L-cysteine at high concentration (10(-3) mol/L) increased the frequency of spontaneous contractions and induced tonic contraction. These effects of L-cysteine were blocked by the inhibitors of CBS and CSE. Pre-treatment of myometrium strips with glibenclamide, an inhibitor of ATP-sensitive potassium (K(ATP)) channels, abolished the inhibitory effect of L-cysteine on spontaneous contraction amplitude. The effects of L-cysteine on the amplitude of spontaneous contractions and baseline muscle tone were less potent in labouring tissues than that in nonlabouring strips. CONCLUSION/SIGNIFICANCE: H(2)S generated by CSE and CBS locally exerts dual effects on the contractility of pregnant myometrium. Expression of H(2)S synthetic enzymes is down-regulated during labour, suggesting that H(2)S is one of the factors involved in the transition of pregnant uterus from quiescence to contractile state after onset of parturition

Corticosteroids for severe sepsis: an evidence-based guide for physicians

Septic shock is characterized by uncontrolled systemic inflammation that contributes to the progression of organ failures and eventually death. There is now ample evidence that the inability of the host to mount an appropriate hypothalamic-pituitary and adrenal axis response plays a major in overwhelming systemic inflammation during infections. Proinflammatory mediators released in the inflamed sites oppose to the anti-inflammatory response, an effect that may be reversed by exogenous corticosteroids. With sepsis, via nongenomic and genomic effects, corticosteroids restore cardiovascular homeostasis, terminate systemic and tissue inflammation, restore organ function, and prevent death. These effects of corticosteroids have been consistently found in animal studies and in most recent frequentist and Bayesian meta-analyses. Corticosteroids should be initiated only in patients with sepsis who require 0.5 μg/kg per minute or more of norepinephrine and should be continued for 5 to 7 days except in patients with poor hemodynamic response after 2 days of corticosteroids and with a cortisol increment of more than 250 nmol/L after a standard adrenocorticotropin hormone (ACTH) test. Hydrocortisone should be given at a daily dose of 200 mg and preferably combined to enteral fludrocortisone at a dose of 50 μg. Blood glucose levels should be kept below 150 mg/dL

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

AimAmazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types.LocationAmazonia.TaxonAngiosperms (Magnoliids; Monocots; Eudicots).MethodsData for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran's eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny.ResultsIn the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R2 = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R2 = 28%). A greater number of lineages were significant indicators of geographic regions than forest types.Main ConclusionNumerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions

Geography and ecology shape the phylogenetic composition of Amazonian tree communities

Aim: Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location: Amazonia. Taxon: Angiosperms (Magnoliids; Monocots; Eudicots). Methods: Data for the abundance of 5082 tree species in 1989 plots were combined with a mega-phylogeny. We applied evolutionary ordination to assess how phylogenetic composition varies across Amazonia. We used variation partitioning and Moran\u27s eigenvector maps (MEM) to test and quantify the separate and joint contributions of spatial and environmental variables to explain the phylogenetic composition of plots. We tested the indicator value of lineages for geographic regions and edaphic forest types and mapped associations onto the phylogeny. Results: In the terra firme and várzea forest types, the phylogenetic composition varies by geographic region, but the igapó and white-sand forest types retain a unique evolutionary signature regardless of region. Overall, we find that soil chemistry, climate and topography explain 24% of the variation in phylogenetic composition, with 79% of that variation being spatially structured (R$^{2}$ = 19% overall for combined spatial/environmental effects). The phylogenetic composition also shows substantial spatial patterns not related to the environmental variables we quantified (R$^{2}$ = 28%). A greater number of lineages were significant indicators of geographic regions than forest types. Main Conclusion: Numerous tree lineages, including some ancient ones (>66 Ma), show strong associations with geographic regions and edaphic forest types of Amazonia. This shows that specialization in specific edaphic environments has played a long-standing role in the evolutionary assembly of Amazonian forests. Furthermore, many lineages, even those that have dispersed across Amazonia, dominate within a specific region, likely because of phylogenetically conserved niches for environmental conditions that are prevalent within regions