Photochemical Release of Hydropersulfides.

Hydropersulfides (RSSH) have received significant interest in the field of redox biology because of their intriguing biochemical properties. However, because RSSH are inherently unstable, their study is challenging, and as a result, the details of their physiological roles remain ill-defined. Herein, we report strategies to release RSSH utilizing photoremovable protecting groups. RSSH protection with the well-established p-hydroxyphenacyl (pHP) photoprotecting group resulted in inefficient RSSH photorelease along with complex chemistry. Therefore, an alternative precursor was examined in which a self-immolative linker was inserted between the pHP group and RSSH, providing nearly quantitative RSSH release following photolysis at 365 nm. Inspired by these results, we also synthesized an analogous precursor derivatized with 7-diethylaminocoumarin (DEACM), a visible light-cleavable photoprotecting group. Photolysis of this precursor at 420 nm led to efficient RSSH release, and in vitro experiments demonstrated intracellular RSSH delivery in breast cancer MCF-7 cells.

Electrospray ionization mass spectrometry ion suppression/enhancement caused by column bleed for three mixed-mode reversed-phase/anion-exchange high-performance liquid chromatography columns.

RATIONALE: Mixed-mode reversed-phase/anion exchange liquid chromatography is useful for separations of mixtures containing anions (e.g. ionized acids). However, when using this form of liquid chromatography with mass spectrometry detection, the bleed of amine-containing hydrolysis products from the columns may cause ion suppression or enhancement. METHODS: Using electrospray ionization tandem quadrupole mass spectrometry detection, we determined the ion suppression or enhancement caused by column bleed for three mixed-mode reversed-phase/weak anion-exchange columns containing stationary phases that differ in chemical structure. Two of the stationary phases are based on silica particles, while the third uses ethylene-bridged hybrid organic/inorganic particles, which have improved hydrolytic stability. Mixtures of acidic and basic analytes were combined with the chromatography flow postcolumn, both with and without a column, and their mass spectrometry ion signal responses (peak areas) were determined. The ratio of signal response with and without a column is the matrix factor. Positive ion electrospray measurements were carried out using 0.1% formic acid (pH ~ 2.7) as a mobile phase additive, and 10mM ammonium formate (pH ~ 6.4) was used for negative ion electrospray detection. RESULTS: The matrix factors under both positive and negative ionization modes were closest to 1 (0.74-1.16) for the hybrid particle-based columns, showing minimal ion suppression or enhancement. In contrast, the silica-based columns gave matrix factors ranging from 0.04 to 1.86, indicating high levels of ion suppression or enhancement. These results may be explained by the differences in the structures of the stationary phases, which affect the relative amounts of hydrolysis products that elute from the columns. CONCLUSIONS: The low levels of mass spectrometry ion suppression or enhancement caused by column bleed from the hybrid particle-based columns should allow for accurate quantitative mass spectrometric detection combined with mixed-mode reversed-phase/weak anion-exchange chromatography.

Alkylamine-Substituted Perthiocarbamates: Dual Precursors to Hydropersulfide and Carbonyl Sulfide with Cardioprotective Actions.

The recent discovery of hydropersulfides (RSSH) in mammalian systems suggests their potential roles in cell signaling. However, the exploration of RSSH biological significance is challenging due to their instability under physiological conditions. Herein, we report the preparation, RSSH-releasing properties, and cytoprotective nature of alkylamine-substituted perthiocarbamates. Triggered by a base-sensitive, self-immolative moiety, these precursors show efficient RSSH release and also demonstrate the ability to generate carbonyl sulfide (COS) in the presence of thiols. Using this dually reactive alkylamine-substituted perthiocarbamate platform, the generation of both RSSH and COS is tunable with respect to half-life, pH, and availability of thiols. Importantly, these precursors exhibit cytoprotective effects against hydrogen peroxide-mediated toxicity in H9c2 cells and cardioprotective effects against myocardial ischemic/reperfusion injury, indicating their potential application as new RSSH- and/or COS-releasing therapeutics.

Hydropersulfides (RSSH) attenuate doxorubicin-induced cardiotoxicity while boosting its anticancer action.

Cardiotoxicity is a frequent and often lethal complication of doxorubicin (DOX)-based chemotherapy. Here, we report that hydropersulfides (RSSH) are the most effective reactive sulfur species in conferring protection against DOX-induced toxicity in H9c2 cardiac cells. Mechanistically, RSSH supplementation alleviates the DOX-evoked surge in reactive oxygen species (ROS), activating nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent pathways, thus boosting endogenous antioxidant defenses. Simultaneously, RSSH turns on peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a master regulator of mitochondrial function, while decreasing caspase-3 activity to inhibit apoptosis. Of note, we find that RSSH potentiate anticancer DOX effects in three different cancer cell lines, with evidence that suggests this occurs via induction of reductive stress. Indeed, cancer cells already exhibit much higher basal hydrogen sulfide (H2S), sulfane sulfur, and reducing equivalents compared to cardiac cells. Thus, RSSH may represent a new promising avenue to fend off DOX-induced cardiotoxicity while boosting its anticancer effects.

Feasibility of depth profiling of animal tissue by ultrashort pulse laser ablation.

Experiments were performed to examine the feasibility of mass spectrometry (MS) depth profiling of animal tissue by ~75 fs, 800 nm laser pulses to expose underlying layers of tissue for subsequent MS analysis. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) was used to analyze phospholipids and proteins from both intact bovine eye lens tissue and tissue ablated by ultrashort laser pulses. Laser desorption postionization mass spectrometry (LDPI-MS) with 10.5 eV single photon ionization was also used to analyze cholesterol and other small molecules in the tissue before and after laser ablation. Scanning electron microscopy was applied to examine the ablation patterns in the tissue and estimate the depth of the ablation craters. Ultrashort pulse laser ablation was found to be able to remove a layer of several tens of micrometers from the surface of eye lens tissue while leaving the underlying tissue relatively undamaged for subsequent MS analysis. MS analysis of cholesterol, phospholipids, peptides, and various unidentified species did not reveal any chemical damage caused by ultrashort pulse laser ablation for analytes smaller than ~6 kDa. However, a drop in intensity of larger protein ions was detected by MALDI-MS following laser ablation. An additional advantage was that ablated tissue displayed up to an order of magnitude higher signal intensities than intact tissue when subsequently analyzed by MS. These results support the use of ultrashort pulse laser ablation in combination with MS analysis to permit depth profiling of animal tissue.

Quantification of antibiotic in biofilm-inhibiting multilayers by 7.87 eV laser desorption postionization MS imaging.

The potential of laser desorption postionization mass spectrometry (LDPI-MS) imaging for small molecule quantification is demonstrated here. The N-methylpiperazine acetamide (MPA) of ampicillin was adsorbed into polyelectrolyte multilayer surface coatings composed of chitosan and alginate, both high molecular weight biopolymers. These MPA-ampicillin spiked multilayers were then shown to inhibit the growth of Enterococcus faecalis biofilms that play a role in early stage infection of implanted medical devices. Finally, LDPI-MS imaging using 7.87 eV single-photon ionization was found to detect MPA-ampicillin within the multilayers before and after biofilm growth with limits of quantification and detection of 0.6 and 0.3 nmol, respectively. The capabilities of LDPI-MS imaging for small molecule quantification are compared to those of MALDI-MS. Furthermore, these results indicate that 7.87 eV LDPI-MS imaging should be applicable to quantification of a range of small molecular species on a variety of complex organic and biological surfaces. Finally, while MS imaging for quantification was demonstrated here using LDPI, it is a generally useful strategy that can be applied to other methods.

Hydropersulfides (RSSH) Outperform Post-Conditioning and Other Reactive Sulfur Species in Limiting Ischemia-Reperfusion Injury in the Isolated Mouse Heart.

Hydrogen sulfide (H2S) exhibits protective effects in cardiovascular disease such as myocardial ischemia/reperfusion (I/R) injury, cardiac hypertrophy, and atherosclerosis. Despite these findings, its mechanism of action remains elusive. Recent studies suggest that H2S can modulate protein activity through redox-based post-translational modifications of protein cysteine residues forming hydropersulfides (RSSH). Furthermore, emerging evidence indicates that reactive sulfur species, including RSSH and polysulfides, exhibit cardioprotective action. However, it is not clear yet whether there are any pharmacological differences in the use of H2S vs. RSSH and/or polysulfides. This study aims to examine the differing cardioprotective effects of distinct reactive sulfur species (RSS) such as H2S, RSSH, and dialkyl trisulfides (RSSSR) compared with canonical ischemic post-conditioning in the context of a Langendorff ex-vivo myocardial I/R injury model. For the first time, a side-by-side study has revealed that exogenous RSSH donation is a superior approach to maintain post-ischemic function and limit infarct size when compared with other RSS and mechanical post-conditioning. Our results also suggest that RSSH preserves mitochondrial respiration in H9c2 cardiomyocytes exposed to hypoxia-reoxygenation via inhibition of oxidative phosphorylation while preserving cell viability.

Brominated tyrosine and polyelectrolyte multilayer analysis by laser desorption vacuum ultraviolet postionization and secondary ion mass spectrometry.

The small molecular analyte 3,5-dibromotyrosine (Br(2)Y) and chitosan-alginate polyelectrolyte multilayers (PEM) with and without adsorbed Br(2)Y were analyzed by laser desorption postionization-mass spectrometry (LDPI-MS). LDPI-MS using a 7.87 eV laser and tunable 8-12.5 eV synchrotron vacuum ultraviolet (VUV) radiation found that desorption of clusters from Br(2)Y films allowed detection by ≤8 eV single photon ionization. Thermal desorption and electronic structure calculations determined the ionization energy of Br(2)Y to be ~8.3 ± 0.1 eV and further indicated that the lower ionization energies of clusters permitted their detection at ≤8 eV photon energies. However, single photon ionization could only detect Br(2)Y adsorbed within PEMs when using either higher photon energies or matrix addition to the sample. All samples were also analyzed by 25 keV Bi(3)(+) secondary ion mass spectrometry (SIMS), with the negative ion spectra showing strong parent ion signal which complemented that observed by LDPI-MS. However, the negative ion SIMS appeared strongly dependent on the high electron affinity of this specific analyte and the analyte's condensed phase environment.

Alkylsulfenyl thiocarbonates: precursors to hydropersulfides potently attenuate oxidative stress.

The recent discovery of the prevalence of hydropersulfides (RSSH) species in biological systems suggests their potential roles in cell regulatory processes. However, the reactive and transient nature of RSSH makes their study difficult, and dependent on the use of donor molecules. Herein, we report alkylsulfenyl thiocarbonates as a new class of RSSH precursors that efficiently release RSSH under physiologically relevant conditions. RSSH release kinetics from these precursors are tunable through electronic modification of the thiocarbonate carbonyl group's electrophilicity. In addition, these precursors also react with thiols to release RSSH with a minor amount of carbonyl sulfide (COS). Importantly, RSSH generation by these precursors protects against oxidative stress in H9c2 cardiac myoblasts. Furthermore, we demonstrate the ability of these precursors to increase intracellular RSSH levels.

Inhibition of Bacterial Gene Transcription with an RpoN-Based Stapled Peptide.

In response to environmental and other stresses, the σ54 subunit of bacterial RNA polymerase (RNAP) controls expression of several genes that play a significant role in the virulence of both plant and animal pathogens. Recruitment of σ54 to RNAP initiates promoter-specific transcription via the double-stranded DNA denaturation mechanism of the cofactor. The RpoN box, a recognition helix found in the C-terminal region of σ54, has been identified as the component necessary for major groove insertion at the -24 position of the promoter. We employed the hydrocarbon stapled peptide methodology to design and synthesize stapled σ54 peptides capable of penetrating Gram-negative bacteria, binding the σ54 promoter, and blocking the interaction between endogenous σ54 and its target DNA sequence, thereby reducing transcription and activation of σ54 response genes.

Malaria imported into the United Kingdom in 1996.

Virtually all malaria infections seen in the United Kingdom (UK) in recent years have been contracted overseas and imported into the UK, apart from two cases in 1976 due to imported infected mosquitoes and occasional cases of congenital or of transfusion

Late dropouts from group psychotherapy.

In five outpatient groups totalling 42 patients, over one-third of the patients quit group treatment between six and twelve months. Interviews suggest that efforts at development of greater intimacy precipitated leaving. In two groups this created a wave effect, with further quitting of two or three additional patients. Therapists' lack of awareness of potential for late dropping out may have contributed to this.

Trends in imported childhood malaria in the UK: 1999-2003.

OBJECTIVE: To describe the epidemiology of imported malaria in children in the UK. METHODS: Surveillance data on children with imported malaria, collected through an enhanced surveillance network set up by the Malaria Reference Laboratory (London, UK), diagnosed between January 1999 and December 2003 were analysed. RESULTS: Over the 5-year study period, 9238 cases were reported to the Malaria Reference Laboratory, and children accounted for 1456 (14.8%) cases. The number of imported paediatric malaria cases fell from 326 in 1999 to 241 in 2003. Malarial infection occurred in children of all ages and the number of patients increased gradually with age. Visiting family and relatives was the most common reason for travel (59.5%), with only 7.2% travelling to an area endemic to malaria on holiday. Most infections (88.4%) were acquired in Africa, and mainly in Nigeria (49.7%). Plasmodium falciparum was responsible for 81.7% of all cases, followed by P. vivax (11.1%). The number of both P. falciparum and P. vivax cases fell gradually from 262 and 45 cases in 1999 to 196 and 20 cases in 2003, respectively. Malaria prophylaxis was taken by 39% of 500 children with malaria who had travelled to a country endemic to malaria. The proportion of children with malaria who had taken malaria prophylaxis decreased steadily from 53% in 1999 to 29% in 2003. Two (0.14%) children died compared with 62 (0.76%) adults over the 5-year study period (p = 0.007). CONCLUSIONS: Although the incidence of malaria has started to decline, a considerable number of children are still diagnosed with malaria in the UK. In addition, the proportion of children with malaria who had taken malaria prophylaxis is falling. Although it is reassuring to note the low mortality, there is an urgent need to improve preventive measures among families travelling to high-risk countries.

Rational selection of structurally diverse natural product scaffolds with favorable ADME properties for drug discovery.

Natural product analogs are significant sources for therapeutic agents. To capitalize efficiently on the effective features of naturally occurring substances, a natural product-based library production platform has been devised at Aurigene for drug lead discovery. This approach combines the attractive biological and physicochemical properties of natural product scaffolds, provided by eons of natural selection, with the chemical diversity available from parallel synthetic methods. Virtual property analysis, using computational methods described here, guides the selection of a set of natural product scaffolds that are both structurally diverse and likely to have favorable pharmacokinetic properties. The experimental characterization of several in vitro ADME properties of twenty of these scaffolds, and of a small set of designed congeners based upon one scaffold, is also described. These data confirm that most of the scaffolds and the designed library members have properties favorable to their utilization for creating libraries of lead-like molecules.

Malaria imported into the United Kingdom in 1992 and 1993.

A total of 1,629 cases of malaria were reported in the United Kingdom in 1992, and 1,922 cases in 1993, fewer than the peak of 2,332 reached in 1991. Of the 3,551 cases of malaria reported during 1992 and 1993, 74 were reported from Scotland, 45 from Wales, and 13 from Northern Ireland. Fourteen people died of falciparum malaria in the two years, 12 of whom contracted the disease in Africa and two in India. Preventive measures were inadequately followed by 12 of the 14 patients who died, eight of whom took no prophylaxis at all, and diagnosis was delayed in the other two. Over a third of the malaria cases were immigrants from endemic areas who had settled in the United Kingdom and who travelled to visit friends and relations. This was the commonest reason for travel given by cases, and correlates with a marked rise in falciparum malaria in settled immigrants from West Africa.

Malaria in Britain: 1977-86.

The incidence of malaria in Britain as reported to the Malaria Reference Laboratory during the past decade has increased by 51%, from 1529 to 2309 cases, and infection with Plasmodium falciparum has increased from one fifth to one third of all cases. The case fatality rate for P falciparum infections declined from 2.7% to 0.5%. Of the 67 persons who died, 54 were of British origin, nine of Asian descent, and four African. Sixteen had taken chemoprophylaxis; of these, nine had taken pyrimethamine alone. The pattern of infection shows that resident ethnic minority groups, temporary residents from west Africa, and tourists who visit Kenya are particularly at high risk. The calculated attack rates suggest that men, children, and young adults are at greater risk of malaria than women and older people. Rates are highest in immigrants who have settled in Britain who visit relatives: 316 and 331 per 100,000 for Africa and Asia respectively, 120 and 39 in tourists to those same regions, and 228 and 38 in business travellers to those regions.

Malaria prophylaxis: survey of the response of British travellers to prophylactic advice.

A cohort study was conducted to determine the compliance of travellers with chemoprophylactic advice given over the telephone by the malaria reference advisory service. Travellers who visited their general practitioner first for advice about malaria prophylaxis were often advised to consult a specialist service themselves. Compliance fell in travellers who were given complicated information and those who received conflicting advice when they contacted other advisory services. After returning to Britain 48% of the travellers reported that they were fully compliant with prophylactic advice; over a third of the travellers studied did not maintain prophylaxis on their return.

Malaria imported into the United Kingdom 1989 and 1990.

Imported malaria cases reported to the Malaria Reference Laboratory as occurring in the United Kingdom have remained at around 2,000 cases annually for the past seven years. However, there has been a steady increase in falciparum malaria which now accounts for 52% of the cases, with mixed infections that include P. falciparum providing another 2% of the 4083 cases reported in the two years 1989-90. Compared with 1986, there has been a substantial increase in P. falciparum of African origin and a fall in Asian P. vivax. Eight people died. Except for one case who had had a previous splenectomy, either the fatal cases had taken no prophylaxis or diagnosis was very late, usually on a mistaken assumption that the patient had influenza. The future is likely to see continuing preponderance of P. falciparum infections, with an increasing problem of multiple drug resistance.