Mercury binding to proteins disclosed by ESI MS experiments: The case of three organomercurials

Solution interactions of three organomercury compounds, i.e., methylmercury chloride, thimerosal and phenylmercury acetate, with a group of biochemically relevant proteins, namely cytochrome c (Cyt c), ribonuclease A (RNase A), carbonic anhydrase I (hCA I), superoxide dismutase (SOD), and serum albumin (HSA), were investigated using an established ESI MS approach. Temporal analysis of sample aliquots provided insight into the binding kinetics, while comparative analysis of the obtained mass spectra disclosed adduct formation of each mercurial with the tested proteins and the relative abundance of the species. The three organomercurials bind, exclusively and tightly, to free cysteine residues as no binding was observed in the case of proteins lacking such groups. hCA I, SOD and HSA formed distinct mercury adducts, preserving the Hg bound alkyl/aryl ligands; yet, the three organomercurials displayed significant differences in reactivity in relation to their chemical structure. The investigation was then extended to analyze the reactions with the C-terminal dodecapeptide of the enzyme human thioredoxin reductase, which contains a characteristic selenol-thiol moiety: tight Hg binding was observed. Notably, this peptide was able to remove effectively and completely the alkyl/aryl ligands of the three tested organomercurials; this behavior may be relevant to the detoxification mechanism of organomercurials in mammals. Finally, a competition experiment was carried out to establish whether protein bound mercury centers may be displaced by other competing metals. Interestingly, and quite unexpectedly, we observed that a protein bound mercury fragment may be partially displaced from its coordination site in hCA I by the medicinal gold compound auranofin.

On the mechanism of action of arsenoplatins: arsenoplatin-1 binding to a B-DNA dodecamer

The reaction of Pt-based anticancer agents with arsenic trioxide affords robust complexes known as arsenoplatins. The prototype of this family of anticancer compounds is arsenoplatin-1 (AP-1) that contains an As(OH)2 fragment linked to a Pt(II) moiety derived from cisplatin. Crystallographic and spectrometric studies of AP-1 binding to a B-DNA double helix dodecamer are presented here, in comparison with cisplatin and transplatin. Results reveal that AP-1, cisplatin and transplatin react differently with the DNA model system. Notably, in the AP-1/DNA systems, the Pt-As bond can break down with time and As-containing fragments can be released. These results have implications for the understanding of the mechanism of action of arsenoplatins.

Cytotoxic Pt(II) complexes containing alizarin: a selective carrier for DNA metalation

Many efforts have been made in the last few decades to selectively transport antitumor agents to their potential target sites with the aim to improve efficacy and selectivity. Indeed, this aspect could greatly improve the beneficial effects of a specific anticancer agent especially in the case of orphan tumors like the triple negative breast cancer. A possible strategy relies on utilizing a protective leaving group like alizarin as the Pt(II) ligand to reduce the deactivation processes of the pharmacophore enacted by Pt resistant cancer cells. In this study a new series of neutral mixed-ligand Pt(II) complexes bearing alizarin and a variety of diamine ligands were synthesized and spectroscopically characterized by FT-IR, NMR and UV-Vis analyses. Three Pt(II) compounds, i.e., 2b, 6b and 7b, emerging as different both in terms of structural properties and cytotoxic effects (not effective, 10.49 ± 1.21 μM and 24.5 ± 1.5 μM, respectively), were chosen for a deeper investigation of the ability of alizarin to work as a selective carrier. The study comprises the in vitro cytotoxicity evaluation against triple negative breast cancer cell lines and ESI-MS interaction studies relative to the reaction of the selected Pt(II) complexes with model proteins and DNA fragments, mimicking potential biological targets. The results allow us to suggest the use of complex 6b as a prospective anticancer agent worthy of further investigations.

Reactions of Medicinal Gold Compounds with Cathepsin B Explored through Electrospray Mass Spectrometry Measurements

Medicinal gold compounds, a novel class of potential anticancer drugs, are believed to produce their pharmacological effects mainly through direct gold binding to protein targets at the level of solvent exposed cysteine (or selenocysteine) residues. We have explored therein the reactions of a panel of seven representative gold compounds with the cysteine protease cathepsin B according to an established ESI MS approach. Detailed information on the mode of protein binding of these gold compounds is gained; notably, quite distinct patterns of cathepsin B metalation have emerged from these studies. It is shown that panel gold compounds interact preferentially, often exclusively, with the free cysteine located in the active site of the enzyme.

The effects of two cytotoxic gold(i) carbene compounds on the metabolism of A2780 ovarian cancer cells: mechanistic inferences through NMR analysis

NMR metabolomics is a powerful tool to characterise the changes in cancer cell metabolism elicited by anticancer drugs. Here, the large metabolic alterations produced by two cytotoxic gold carbene compounds in A2780 ovarian cancer cells are described and discussed in comparison to auranofin, in the frame of the available mechanistic knowledge.

Protein Metalation by Medicinal Gold Compounds: Identification of the Main Features of the Metalation Process through ESI MS Experiments

Gold compounds form a new class of promising anticancer agents with innovative modes of action. It is generally believed that anticancer gold compounds, at variance with clinically established platinum drugs, preferentially target proteins rather than nucleic acids. The reactions of several gold compounds with a few model proteins have been systematically explored in recent years through ESI MS measurements to reveal adduct formation and identify the main features of those reactions. Here, we focus our attention on a group of five gold compounds of remarkable medicinal interest, i.e., Auranofin, Au(NHC)Cl, [Au(NHC)₂]PF₆, Aubipyc, and Auoxo6, and on their reactions with four different biomolecular targets, i.e., the proteins HEWL, hCA I, HSA and the C-terminal dodecapeptide of the enzyme thioredoxin reductase. Complete ESI MS data are available for those reactions due to previous experimental work conducted in our laboratory. From the comparative analysis of the ESI MS reaction profiles, some characteristic trends in the metallodrug-protein reactivity may be identified as detailed below. The main features are described and analyzed in this review. Overall, all these observations are broadly consistent with the concept that cytotoxic gold drugs preferentially target cancer cell proteins, with a remarkable selectivity for the cysteine and selenocysteine proteome. These interactions typically result in severe damage to cancer cell metabolism and profound alterations in the redox state, leading to eventual cancer cell death.

Dirhodium tetraacetate binding to a B-DNA double helical dodecamer probed by X-ray crystallography and mass spectrometry

The reaction of the cytotoxic compound dirhodium tetraacetate with a B-DNA double helical dodecamer was studied by X-ray crystallography and mass spectrometry. The structure of the dirhodium/DNA adduct reveals a dimetallic center binding to an adenine via axial coordination. Complementary information has been gained through ESI MS measurements. Comparison between the present data and those previously obtained for cisplatin indicates that the two metallodrugs react with this DNA dodecamer in a significantly different fashion.

Large Protein Assemblies for High-Relaxivity Contrast Agents: The Case of Gadolinium-Labeled Asparaginase

Biologics are emerging as the most important class of drugs and are used to treat a large variety of pathologies. Most of biologics are proteins administered in large amounts, either by intramuscular injection or by intravenous infusion. Asparaginase is a large tetrameric protein assembly, currently used against acute lymphoblastic leukemia. Here, a gadolinium(III)-DOTA derivative has been conjugated to asparaginase, and its relaxation properties have been investigated to assess its efficiency as a possible theranostic agent. The field-dependent ¹H longitudinal relaxation measurements of water solutions of gadolinium(III)-labeled asparaginase indicate a very large increase in the relaxivity of this paramagnetic protein complex with respect to small gadolinium chelates, opening up the possibility of its use as an MRI contrast agent.

Gold-Based Metal Drugs as Inhibitors of Coronavirus Proteins: The Inhibition of SARS-CoV-2 Main Protease by Auranofin and Its Analogs

Gold compounds have a long tradition in medicine and offer many opportunities for new therapeutic applications. Herein, we evaluated the lead compound Auranofin and five related gold(I) complexes as possible inhibitors of SARS-CoV-2 Main Protease (SARS-CoV-2 Mpro), a validated drug target for the COVID-19 disease. The investigational panel of gold compounds included Auranofin; three halido analogues, i.e., Au(PEt3)Cl, Au(PEt3)Br, and Au(PEt3)I; and two gold carbene complexes, i.e., Au(NHC)Cl and [Au(NHC)2]PF6. Notably, all these gold compounds, with the only exception of [Au(NHC)2]PF6, turned out to be potent inhibitors of the catalytic activity of SARS-CoV-2 Mpro: the measured Ki values were in the range 2.1-0.4 μM. The reactions of the various gold compounds with SARS-CoV-2 Mpro were subsequently investigated through electrospray ionization (ESI) mass spectrometry (MS) upon a careful optimization of the experimental conditions; the ESI MS spectra provided clear evidence for the formation of tight metallodrug-protein adducts and for the coordination of well defined gold-containing fragments to the SARS-CoV-2 Mpro, again with the only exception of [Au(NHC)2]PF6, The metal-protein stoichiometry was unambiguously determined for the resulting species. The crystal structures of the metallodrug- Mpro adducts were solved in the case of Au(PEt3)Br and Au(NHC)Cl. These crystal structures show that gold coordination occurs at the level of catalytic Cys 145 in the case of Au(NHC)Cl and at the level of both Cys 145 and Cys 156 for Au(PEt3)Br. Tight coordination of gold atoms to functionally relevant cysteine residues is believed to represent the true molecular basis of strong enzyme inhibition.

Systemic sclerosis therapy with iloprost: a prospective observational study of 30 patients treated for a median of 3 years

Iloprost is useful in the short-term treatment of severe Raynaud's phenomenon and ischaemic ulcers in patients with systemic sclerosis (SSc), but its long-term effects are largely unknown. The aim of this study was to report long-term outcome (median follow-up 36 months) in a prospective observational study of a cohort of 30 consecutive patients with SSc who received iloprost therapy with maintenance infusions every 3 weeks after an initial cycle of 5 consecutive days. At the end of the observation, compared to the pretreatment point, we observed complete healing of digital ulcers in 19/21 patients (90%), a decrease of the Raynaud's phenomenon visual analogue score from 10/10 (25th-75th percentile 7-10) to 5/10 (4-6.75) ( P <0.001) and, in patients with diffuse cutaneous involvement, of the modified Rodnan skin thickness score from 25.5 (16.5-31.5) to 16 (13.5-20) ( P = 0.02), minimal improvement of the Health Assessment Questionnaire from 0.87 (0.68-1.37) to 0.75 (0.62-1.25), which was neither statistically nor clinically significant. The forced vital capacity was not significantly changed, but the diffusion capacity corrected for the alveolar volume decreased from 71% (54-76.7) of the expected value to 62% (51.5-71) ( P = 0.02). In one patient with limited SSc a positive effect on pulmonary hypertension was observed. Six patients, after a median of 25 months of treatment and healing of digital ulcers, discontinued the therapy; after a median of 10 months ulcers did not recur in five of these six. Other reasons for discontinuation were: tolerability (1), disease progression (normotensive renal crisis: 1), and death due to intracranial haemorrhage (1). This same patient had previously suffered a central retinal vein thrombosis. In conclusion, long-term therapy with iloprost in patients with SSc has a durable effectiveness on ischaemic ulcers and Raynaud's phenomenon, but it is not possible to conclude that the natural history of the disease was modified.

[Competitive new generation myorelaxants in pediatric neuroanesthesia]

Two groups of 50 children were included in a study to examine the use of atracurium and vecuronium. In both groups, newborns and infants showed a shorter onset time and a longer clinical duration of the first dose of the neuromuscular blocking drug. The duration of subsequent doses in the various age groups was not significantly different. Atracurium and vecuronium both have a short recovery index, good cardiovascular stability and do not interfere with ICP. The Authors emphasise the importance of monitoring the use of neuromuscular blocking drugs.

[Anesthesia in the diagnostic stages of cerebral arteriovenous malformations in children under 3 years of age]

From 1974 through 1989, 36 patients with arteriovenous malformations were treated in the neuroradiological unit of the Santobono Children's Hospital, in Naples, 7 of these patients were younger than 3 years of age. During such a time-span, dramatic improvements in diagnostic work-up were jelded by introduction of CT-scan and MRI; better angiographic techniques, progress in anaesthesia drugs, equipment and procedures and more rational surgical modalities. Anaesthesia must be tailored in each patient with special consideration of the clinical and neurological conditions of the patients as well of the neuroradiological procedure, specifically, with minimal side effects on cardiovascular and respiratory functions as well on intracranial pressure. The present paper discuss of equipment for cardiovascular assistance and drugs to be employed in the various steps of the diagnostic work-up of such patients.

[Peroperative recovery in surgery of arteriovenous malformations in children under the age of 3 years]

From 1974 through 1989, 36 patients with arteriovenous malformations were studied in the neurosurgical department of the Santobono Children's Hospital in Naples; 7 of these patients were younger than three years of age: 5 underwent surgery. The remaining 2 patients presented, respectively, an aneurysm of the vein of Galen and an arteriovenous malformation of the brain stem. Improvements in surgical and anesthesiological techniques allow to treat lesions considered as not amenable to surgery until recent years, with minimal occurrence of preoperative and postoperative complication and a significant amelioration of prognosis.

Interrelations of cardiac and arterial vascular wall hypertrophy in essential hypertension

Structural vascular changes in the calf arteries and left ventricular mass were measured in 52 essential hypertensive patients (WHO I and II, 35 men and 17 women, age range 21-63 years). Left ventricular mass was measured on M-mode echocardiographic tracings. Structural vascular changes were evaluated indirectly by studying the minimal vascular resistance, calculated from mean arterial pressure and maximal (post-ischaemic) blood flow, measured by venous occlusion plethysmography. A statistically significant correlation between left ventricular mass and minimal vascular resistance was observed (r = 0.33, P < 0.05). The low correlation suggested that structural changes in the heart and in the systemic arteries did not develop simultaneously. In the subgroup of patients with minimal vascular resistance in the normal range, left ventricular hypertrophy was found in 15 out of 30 patients (50% of cases) whereas, in the subgroup of patients with high minimal vascular resistance, absence of left ventricular hypertrophy was found in six out of 22 patients (27% of cases). These results suggest that left ventricular hypertrophy more often precedes arterial structural changes in the calves.