Has the Rio Doce "time bomb" been defused? Using a weight-of-evidence approach to determine sediment quality.

The Fundão mine tailings dam rupture of 2015, in the Rio Doce basin, Brazil, resulted in the deposition of tailings downstream of the dam. It has yet to be determined if metals associated with the tailings have contributed toxicity to organisms, burying a time bomb that could be ticking. Currently the data on toxicity to benthic and aquatic organisms have not been assessed sufficiently to allow an informed assessment using an approach based on weight-of-evidence. This study was conducted to ascertain if sediments at "hot spots" that received Fundão tailings reflected elevated concentrations of metals and if these concentrations were sufficient to result in toxicity to freshwater organisms. The lines-of-evidence considered included assessing metals concentrations in relation to sediment quality criteria, establishing biogeochemical characterizations, completing an evaluation of potential metal release upon resuspension to provide information on bioavailability, and identifying acute and chronic toxicity effects using sensitive native species for waters (water flea, Daphnia similis) and sediments (burrowing midge larvae, Chironomus sancticaroli). Only porewater concentrations of iron and manganese exceeded Brazilian surface water criteria, whereas most trace elements exhibited no enrichment or elevated environmental indexes. The concentrations of bioavailable metals were assessed to be low, and metal concentrations did not increase in the overlying water upon resuspension; rather, they decreased through time. Toxicity testing in resuspended waters and bulk sediments resulted in no acute or chronic toxicity to either benthic or aquatic species. The low metal bioavailability and absence of toxicity of the tailings-enriched sediments was attributed to the strong binding and rapid removal of potentially toxic metal ions caused by oxyhydroxides and particles in the presence of iron-rich particulates. The findings of these sediment hot-spot studies indicate the Fundão dam release of tailings more than six years ago is not causing the current release of toxic concentrations of metals into the freshwaters of the Rio Doce. Integr Environ Assess Manag 2024;20:148-158. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Metal Toxicity During Short-Term Sediment Resuspension and Redeposition in a Tropical Reservoir.

Billings Complex is the largest water-storage reservoir in São Paulo, Brazil, and has been contaminated since the 1960s. Periodically, Billings sediments are subjected to currents causing resuspension and subsequent release of metals. A short-term (4-h) resuspension was simulated using sediment flux exposure chambers (SeFECs) to better understand the fate, bioavailability, and transport of iron (Fe), manganese (Mn), and zinc (Zn) during these events, as well as possible organism toxicity. Daphnia magna and Hyalella azteca were exposed during the 4-h resuspension, and were monitored after exposure for survival, growth, and reproduction. Resuspension rapidly deoxygenated the overlying water, decreased the pH, and resulted in elevated dissolved Zn above the US Environmental Protection Agency's (2002) criteria for acute toxicity (120 µg L-1 ). However, Zn was scavenged (after 20 h) from solution as new sorption sites formed. Dissolved Mn increased during and after resuspension, with maximum values at 20 h post exposure. An initial release of Fe occurred, likely associated with oxidation of acid-volatile sulfides, but decreased after 1 h of resuspension. The Fe decrease is likely due to precipitation as oxyhydroxides. No acute toxicity was observed during resuspension; however, mortality of D. magna and H. azteca occurred during the postexposure period. Daphnia magna also exhibited chronic toxicity, with decreased neonate production after exposure. This sublethal effect could lead to decreased zooplankton populations over a longer period in the reservoir. Environ Toxicol Chem 2019;38:1476-1485. © 2019 SETAC.

Hybrid inhalable microparticles for dual controlled release of levofloxacin and DNase: physicochemical characterization and in vivo targeted delivery to the lungs.

Current medical treatments against recurrent pulmonary infections caused by Pseudomonas aeruginosa, such as cystic fibrosis (CF) disorder, involve the administration of inhalable antibiotics. The main challenge is, however, the eradication of microbial biofilms immersed in dense mucus that requires high and recurrent antibiotic doses. Accordingly, the development of novel drug delivery systems capable of providing local and controlled drug release in the lungs is a key factor to improve the therapeutic outcome of such therapeutic molecules. Inhalable hybrid carriers were prepared by co-precipitation of CaCO3 in the presence of alginate and the resulting microparticles were treated with alginate lyase (AL) in order to modify their porosity and enhance the drug loading. The hybrid microparticles were loaded with DNase (mucolytic agent) and levofloxacin (LV, wide-spectrum antibiotic) in the range of 20-40% for LV and 28-67% for DNase, depending on the AL treatment. In vitro studies demonstrated that microparticles were able to control the DNase release for 24 h, while 30-50% of LV was released in 3 days. The morphological characterization was performed by optical, fluorescence and scanning electron microscopies, showing a narrow size distribution (5 µm). FTIR, XRD, DSC and nitrogen adsorption isotherm studies revealed the presence of the drugs in a non-crystalline state. A microcidal effect of microparticles was found on P. aeruginosa in agar plates and corroborated by Live/Dead kit and TEM observations. Finally, to study whether the microparticles improved the localization of LV in the lungs, in vivo studies were performed by pulmonary administration of microparticles to healthy mice via nebulization and dry powder inhalation, followed by the quantification of LV in lung tissue. The results showed that microparticles loaded with LV delivered the antibiotic at least 3 times more efficiently than free LV. The developed system opens the gateway to new drug delivery systems that may provide enhanced therapeutic solutions against bacterial infections and in particular as a potential tool in CF pathology.

Effect of synthetic steroids on GABAA receptor binding in rat brain.

Neuroactive steroids, like allopregnanolone (A) and pregnanolone (P), bind to specifics sites on the GABAA receptor complex and modulate receptor function. They are capable to inhibit or stimulate the binding of GABAA receptor-specific ligands, like t-butyl-bicyclophosphorothionate, flunitrazepam and muscimol. We have previously characterized a set of oxygen-bridged synthetic steroids (SS) analogs to A or P using synaptosomes. Considering that the subunit composition of the GABAA receptor throughout the central nervous system affects the magnitude of the modulation of the GABAA receptor by NAS, we evaluated the action of two selected SS, in brain sections containing the cerebral cortex (CC) and hippocampus (HC) using quantitative receptor autoradiography. Both SS affected the binding of the three ligands in a similar way to A and P, with some differences on certain CC layers according to the ligand used. One of the SS, the 3α-hydroxy-6,19-epoxypregn-4-ene-20-one (compound 5), behaved similarly to the natural neuroactive steroids. However, significant differences with compound 5 were observed on the HC CA2 region, making it steroid suitable for a specific action. Those differences may be related to structural conformation of the SS and the subunits' composition present on the receptor complex.

Molecular mechanism of activation and nuclear translocation of the mineralocorticoid receptor upon binding of pregnanesteroids.

The mineralocorticoid receptor (MR) is primarily localized in the cytoplasm of the cell in the absence of ligand. The first step in the genomic-dependent mechanism of action of mineralocorticoids is the binding of steroid to the MR, which in turn triggers MR nuclear translocation. The regulation of hormone-binding to MR is complex and involves a multifactorial mechanism, making it difficult to determine the optimal structure of a steroid for activating the MR and promoting its nuclear translocation. Here we review the structure-activity relationship for several pregnanesteroids that possess various functional groups, and suggest that a flat conformation of the ligand rather than the presence of particular chemical groups is a critical parameter for the final biological effect in vivo. We also discuss how the MR undergoes differential conformational changes according to the nature of the bound ligand, which in turn affects the dynein-dependent retrograde rate of movement for the steroid/receptor complex.

Preparation and cytotoxicity toward cancer cells of mono(arylimino) derivatives of beta-lapachone.

A regio- and stereospecific synthesis of monoarylimino o-quinones derived from beta-lapachone (1) was achieved by treatment of the quinone with a slight excess of an arylamine in the presence of an excess of triethylamine/titanium tetrachloride 4:1. Imine formation occurred exclusively at position 6, giving the Z diastereomer, as determined by single-crystal X-ray analysis. In vitro tests for cytotoxicity in 55 human cancer cell cultures showed a substantial loss in activity for the p-nitrophenylimine (5), whereas the phenylimine (2), p-methylphenylimine (3), and p-methoxyphenylimine (4) retained (or bettered) most of the cytotoxicity and selectivity of the parent quinone. Preliminary in vivo testing in hollow fiber assays against a standard panel of 12 human tumor cell lines showed that although beta-lapachone failed, compounds 2 and 3 had good scores with net cell kills.

Withanolides from Salpichroa origanifolia.

Five new withanolides, 5 alpha,6 alpha:22,26:24,25-triepoxy-16 alpha,26-dihydroxy-18(13-->17)-abeo-ergosta-2,13-dien-1-one (salpichrolide N, 1), 5 alpha,6 alpha:22,26:24,25-triepoxi-15 alpha,26-dihydroxyergosta-2,16-dien-1-one (salpichrolide L, 2), 5 alpha,6 alpha:22,26-diepoxi-24,25,26-trihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide M, 3a), 5 alpha,6 alpha:22,25:22,26-triepoxy-24-hydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide J, 4), and 5 alpha,6 alpha:22,26-diepoxy-22,24,25-trihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide K, 5), were isolated from the leaves of Salpichroa origanifolia and characterized by a combination of spectroscopic (1D and 2D NMR, MS) and chemical methods.

Withanolides from Vassobia lorentzii.

Eight new withanolides were isolated from the aerial parts of Vassobia lorentzii and characterized by spectroscopic methods and with the aid of molecular modeling. The compounds were identified as (17S,20R,22R)-5beta,6beta:18,20-diepoxy-18-hydro xy-1-oxowitha-2,5, 24-trienolide (1); (17S,20R,22R)-18,20-epoxy-4beta, 18-dihydroxy-1-oxowitha-2,5,24-trienolide (2); (17S,18R,20R, 22R)-4beta-hydroxy-18,20-epoxy-18-methoxy-1-oxowitha-2,5, 24-trienolide (3); (17S,18S,20R,22R)-4beta-hydroxy-18, 20-epoxy-18-methoxy-1-oxowitha-2,5,24-trienolide (4); (17S,20R, 22R)-4beta-hydroxy-18,20-epoxy-1,18-dioxowitha-2,5,24-tri enolide (5); (17S,18R,20R,22R)-18,20-epoxy-18-methoxy-1,4-dioxowitha++ +-2,5, 24-trienolide (6); (17S,18S,20R,22R)-18,20-epoxy-18-methoxy-1, 4-dioxowitha-2,5,24-trienolide (7); and (17S,20R,22R)-5beta, 6beta-epoxy-4beta,18,20-trihydroxy-1-oxowitha-2,24-die nolide (8). Compounds 1 and 2 were obtained as epimeric mixtures at C-18.

Antifeedant activity of withanolides from Salpichroa origanifolia on Musca domestica.

The antifeedant effect of several salpichrolides on larvae of Musca domestica was investigated. Three naturally occurring compounds, salpichrolide A (1), salpichrolide C (2), and salpichrolide G (3), previously isolated from Salpichroa origanifolia, and two known (4, 6) and three new (5, 7, 8) synthetic analogues were tested. The maximal effect on development was observed for salpichrolide A (1), while salpichrolide G (3) was the most toxic. The content of the salpichrolides in S. origanifolia was monitored by HPLC during plant development, reaching a maximum during summer.

Mechanism of action of the potent sodium-retaining steroid 11, 19-oxidoprogesterone.

We have demonstrated previously that a planar conformation of the molecular frame is required for steroids to acquire optimal sodium-retaining activity and binding properties to the mineralocorticoid receptor (MR). One of the most active sodium-retaining compounds tested in those studies was 11, 19-oxidoprogesterone. Despite its biological potency, the relative affinity of 11,19-oxidoprogesterone for the MR is 5-fold lower than that of 21-deoxycorticosterone and 10-fold lower than aldosterone. Such a discrepancy may be assigned to uncommon biopharmacological properties of this synthetic steroid or an unusual molecular mechanism of action. In this work, we studied the biopharmacological and mechanistic features of 11,19-oxidoprogesterone. We show that both the pharmacokinetic properties of 11,19-oxidoprogesterone and its ability to transform and translocate the MR into the nucleus are undistinguishable from aldosterone. However, the capability of the serine/threonine phosphatase inhibitor tautomycin to impair nuclear translocation of the aldosterone-MR complex is not observed for the 11,19-oxidoprogesterone-MR complex. In addition, the binding properties of both steroids are differentially affected by modification of crucial lysyl residues of the MR. Kinetic studies performed on the aldosterone-MR complex in the presence of low concentrations of oxidopregnane suggest that 11,19-oxidoprogesterone may bind to the MR in a different binding site from the aldosterone binding pocket. Consistent with this postulate, a biologically inactive dose of 0.6 ng of oxidopregnane is able to potentiate the mineralocorticoid effect of a suboptimal dose of aldosterone.

Synthesis and GABA(A) receptor activity of 6-oxa-analogs of neurosteroids.

The 6-oxasteroids 3alpha-hydroxy-6-oxa-5alpha-pregnan-20-one (3) and 3alpha-hydroxy-6-oxa-5beta-pregnan-20-one (4) were obtained from pregnenolone acetate via the corresponding (5alpha or 5beta) 3beta, 20beta-diacetoxy-6-oxa-pregnane. Both steroids showed ca. 100-fold reduced potency for modulating [(3)H]flunitrazepam, [(3)H]muscimol or [(35)S]TBPS binding to the GABA(A) receptor when compared to their natural carbon analogs 3alpha-hydroxy-5alpha-pregnan-20-one (1) and 3alpha-hydroxy-5beta-pregnan-20-one (2).

Sesquiterpene lactone variability in Parthenium hysterophorus L.

A population of Parthenium hysterophorus collected in Salta Argentina afforded two ambrosanolides, 2beta-hydroxycoronopilin and 1alpha,2beta,4beta-trihydroxypseudoguaian-6beta,12-olide, as well as five known others. Plants of the fructification from those transplanted from the Puna Argentina at 1200 m over the sea level produced hymenin.

The glucocorticoid properties of the synthetic steroid pregna-1,4-diene-11beta-ol-3,20-dione (deltaHOP) are not entirely correlated with the steroid binding to the glucocorticoid receptor.

The natural steroid 11beta-hydroxyprogesterone is not only a modulator of 11beta-hydroxy-steroid dehydrogenase activity, but also an efficient inducer of tyrosine aminotransferase activity in hepatocytes. In contrast with the low affinity for the mineralocorticoid receptor. 11beta-hydroxyprogesterone binds well to both the glucocorticoid receptor and the carrier protein transcortin. It is accepted that the introduction of a 1:ene double bond into 3-keto 4:ene steroids increases the glucocorticoid potency, so that 3-keto-1,4:diene steroids show improved chemical stability and are more potent glucocorticoids than their respective 4:ene analogs. The steroid pregna-1,4-diene-11beta-ol-3,20-dione (deltaHOP) had previously been described as an anti-inflamatory compound and an inhibitor of macromolecular biosynthesis in thymocytes and lymphocytes. In such studies, deltaHOP also exhibited some particular glucocorticoid properties which made it attractive as a tool for the study of the mechanism of action of glucocorticoids. In the present paper we show that deltaHOP possesses some classical biological actions of glucocorticoids such as deposition of glycogen in rat liver, induction of TAT activity in hepatocytes, and inhibition of the uptake of leucine and thymidine by thymocytes. It also exhibits minimal sodium-retaining properties. Consistent with these biological effects, deltaHOP shows a 70 times lower relative binding affinity for the mineralocortioid receptor than aldosterone, but a reasonable affinity for the glucocorticoid receptor, and is as efficient as dexamethasone in dissociating the 90 kDa heat shock protein from the glucocorticoid receptor heterocomplex. However, the inhibition of the uptake of amino acids and nucleotides observed in the presence of deltaHOP is not efficiently blocked when thymocytes are coincubated in the presence of steroids with known antiglucocorticoid activity. deltaHOP is similarly inefficient in inducing chloramphenicol-acetyl transferase activity in cells transfected with a plasmid that possesses two canonical glucocorticoid-responsive elements. Unlike most glucocorticoids, deltaHOP does not induce the fragmentation of DNA in a regular pattern characteristic of apoptosis and it does not reduce thymus weight. This unusual dissociation of glucocorticoid parameters makes deltaHOP a useful tool to discriminate between mechanisms of action by which steroids can exert their biological effects.

Influence of calf serum on glucocorticoid-responses of certain progesterone derivatives.

UNLABELLED: The following in vitro glucocorticoid (GC) parameters of progesterone (P), 1-ene progesterone (deltaP), 11beta-hydroxyprogesterone (HOP), 11beta-1-ene progesterone (deltaHOP) and dexamethasone (Dexa) were assayed in the presence or absence of bovine calf serum (BCS): binding to thymus cytosol, dissociation of the glucocorticoid receptor (GR)-heat shock protein 90 (hsp90) complex (diss.), tyrosine aminotransferase (TAT) induction in hepatocytes and the inhibition of 3H-uridine and 35S-methionine uptake by thymocytes. Without BCS, steroids were in most cases active in this general order: Dex > deltaHOP > HOP > deltaP > P. BCS abolished all activities in P and deltaP, but left them unaltered in all other steroids, except diss. in HOP, which diminished intermediately. Binding of P, deltaP, HOP and deltaHOP to GR and CBG paralleled their in vivo activating effects on glycogen deposition. CONCLUSIONS: in this steroid series, BCS, but not CBG, inhibits GC responses of P and deltaP. 11-Beta hydroxylation frees those molecules from the inhibitory effects of BCS.

New Hydroxylated Withanolides from Salpichroa origanifolia

From the leaves of Salpichroa origanifolia three new withanolides, (20S,22R,24S,25S,26R)-5alpha,6alpha:22,26:24,25-triepoxy-15,26-dihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide G, 1), (20S,22R,24S,25R)-5alpha,6alpha:22,26-diepoxy-24,25,26-trihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17-tetraen-1-one (salpichrolide H, 2), and (20S,22R,25S)-5alpha,6alpha:22,26-diepoxy-25,26-dihydroxy-17(13-->18)-abeo-ergosta-2,13,15,17,23-pentaen-1-one (salpichrolide I, 3), were isolated and characterized by spectroscopic methods and with the aid of molecular modeling. The latter two compounds were obtained as an epimeric mixture at C-26.

21-Hydroxy-6,19-oxidoprogesterone: a novel synthetic steroid with specific antiglucocorticoid properties in the rat.

In the rat, the conformationally highly bent steroid 21-hydroxy-6, 19-oxidoprogesterone efficiently displaces [3H]corticosterone from thymus-glucocorticoid receptors and blocks type II receptors in kidney cytosols but competes with neither [3H]aldosterone for kidney-mineralocorticoid receptors nor [3H]progesterone for uterus-progesterone receptors. It evokes Na+ retention only at very high doses (approximately 100 microg/100 g of rat weight) and is unable to induce tyrosine aminotransferase or to increase glycogen deposits in rat liver. When coincubated with corticosterone or dexamethasone, 2.5 microM 21OH-6OP inhibits 80% of tyrosine aminotransferase induction. It may therefore be used experimentally as an antiglucocorticoid virtually lacking mineralocorticoid or glucocorticoid properties as well as affinity for mineralocorticoid or progesterone receptors.

Features of the shuttle pair 11 beta-hydroxyprogesterone-11-ketoprogesterone.

11 beta-hydroxyprogesterone (HOP) and 11-ketoprogesterone (KP) are reversible components of a shuttle pair whose interconversion in rat liver is catalyzed by isoform-1 of 11 beta-hydroxysteroid dehydrogenase. Kidneys also produce this interconversion. The present study was carried out to investigate the shuttle pair and its components in the rat. As in corticosterone/11-dehydrocorticosterone, oxidation is more effective at an alkaline pH, while reduction prevails at a neutral pH. Moreover, both reactions are inhibited by the detergent 3-[(3-cholamido propyl)-dimethylammonio]-1-propane-sulphonate (CHAPS). However, at variance with the 11-ketosteroids cortisone (E) and 11-dehydrocorticosterone (A) thought to be "inactive," KP has slight direct Na(+)-retaining properties, and it, as well as HOP, induces glucocorticoids (11 beta-hydroxycorticoids) to retain sodium. 11-ketoprogesterone exhibits 17 times better affinity for native type 1 mineralocorticoid receptor than HOP and a 3-fold affinity for partially purified (transcortin free) mineralocorticoid receptor. However, KP, in contrast to HOP, binds only weakly to transcortin, not at all to glucocorticoid receptor, and requires reduction at C11 for tyrosine aminotransferase (TAT) induction.

Synthesis of oxido-bridged analogs of 18-hydroxyprogesterone.

18-Hydroxy-6,19-oxidoprogesterone and 18-hydroxy-11, 19-oxidoprogesterone were synthesized from readily available materials. The functionalization of C-18 was accomplished with phenyliodosodiacetate/iodine, whereas that of C-19 was carried out with the mercuric oxide/iodine system, both under irradiation with visible light. For 18-hydroxy-11,19-oxidoprogesterone, C-19 was functionalized before C-18, whereas the reverse order had to be used for the 6,19-oxido derivative.

Sodium-retaining activity of some natural and synthetic 21-deoxysteroids.

The effect of progesterone and six other C21-deoxysteroids on renal sodium retention by male adrenalectomized rats was compared with the effect exerted by the natural corticoids aldosterone, 11-deoxycorticosterone, and corticosterone. Steroids were active in the following order: aldosterone > 11,19-oxidoprogesterone > 5 alpha H-3,20-pregnanedione > or = 5 beta H-3,20-pregnanedione > progesterone = 11-ketoprogesterone > 6,19-oxidoprogesterone = 11-keto-6,19-oxidoprogesterone > or = corticosterone. All C21-deoxysteroids, except 11,19-oxidoprogesterone, exhibited parabolic log dose-response functions, indicating an effect that opposes renal sodium retention at high doses. 11,19-Oxidoprogesterone and the natural corticoids exhibited normal, exponential, log dose-response curves. Diverse geometric parameters related to molecular planarity were calculated and their correlation with biopharmacological properties was attempted. The best linear regression was obtained for correlation of the concavity of log dose-response parabolas (second-order coefficients) of C21-deoxysteroids with the C3 = O/ring D angle of these molecules. A good linear regression could also be obtained for correlation of the affinity of C21-deoxysteroids, except 11,19-oxidoprogesterone, for purified type I mineralocorticoid receptors with those angles. The latter correlation deteriorated upon incorporation of the affinity data for the three natural corticoids, due to similar affinities of these hormones for type I mineralocorticoid receptors, but could be restored when the binding data for the unpurified, corticosterone-binding globulin-containing stage of the receptors were considered. In vivo binding data followed the same trend as that for unpurified receptors.

Synthesis of 21-hydroxy-11,19-oxidopregn-4-ene-3,20-dione and 21-hydroxy-6,19-oxidopregn-4-ene-3,20-dione.

The 21-hydroxy analogues of 11,19-oxidoprogesterone and 6,19-oxidoprogesterone have been synthesized from readily available materials. Hydroxylation at C-21 was effected with iodosobenzene (from phenyliodosodiacetate and methanolic potassium hydroxide) on a 20-ketopregnane. For the 11,19-oxido derivative, the hydroxylation was carried out on a precursor containing the oxido-bridge. This approach was not adequate for the 6,19-oxido steroid due to the very low yields encountered; hence in the latter case the order of introduction of the C-21 functionality and the oxido-bridge was reversed.