Resveratrol-nitric oxide donor hybrid effect on priapism in sickle cell and nitric oxide-deficient mouse

Background

Children and adult with sickle cell disease (SCD) display priapism associated with low nitric oxide (NO) bioavailability and oxidative stress in penis.

Aim

This study aimed to evaluate the effects of hybrid compound RVT-FxMe, derived from resveratrol bearing a NO-donor subunit, on two murine model that display priapism phenotype, SCD transgenic mice and endothelial NO synthase gene-deficient (eNOS^-/-) mice.

Methods

Wild-type, SCD, and eNOS^-/- mice were treated with RVT-FxMe (25 mg/kg/d, 2 weeks).

Outcomes

Hematological parameters, concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP), as well as to electrical field stimulation (EFS), were obtained in mice corpus cavernosum strips.

Results

Corpus cavernosum relaxations to SNP and EFS were increased in eNOS^-/- group, which were normalized by RVT-FxMe treatment. SCD mice exhibited an excessive CC relaxant response induced by ACh, EFS and SNP RVT-FxMe treatment did not change the increased relaxant responses to ACh, EFS and SNP in corpus cavernosum from SCD group.

Clinical translation

Excess of plasma hemoglobin in SCD may interfere in pharmacological activity of NO donors compounds.

Strength/Limitations

While mechanistic data with promising potential is showed, the current study is not without limitations. RVT-FxMe effects in the mid- and long-term warrant complementary studies.

Conclusion

Treatment with RVT-FxMe reversed the enhanced NO-cGMP-mediated CC relaxations in eNOS^-/- mice, but not in SCD mice; it is likely that excess of plasma hemoglobin in SCD mice act to inactivate NO before it reaches soluble guanylyl cyclase, avoiding restoration of NO bioavailability in penis.

COVID-19: The question of genetic diversity and therapeutic intervention approaches

Coronavirus disease 2019 (COVID-19), caused by the Severe Acute Respiratory Syndrome Coronavirus type 2 (SARS-CoV-2), is the largest pandemic in modern history with very high infection rates and considerable mortality. The disease, which emerged in China's Wuhan province, had its first reported case on December 29, 2019, and spread rapidly worldwide. On March 11, 2020, the World Health Organization (WHO) declared the COVID-19 outbreak a pandemic and global health emergency. Since the outbreak, efforts to develop COVID-19 vaccines, engineer new drugs, and evaluate existing ones for drug repurposing have been intensively undertaken to find ways to control this pandemic. COVID-19 therapeutic strategies aim to impair molecular pathways involved in the virus entrance and replication or interfere in the patients' overreaction and immunopathology. Moreover, nanotechnology could be an approach to boost the activity of new drugs. Several COVID-19 vaccine candidates have received emergency-use or full authorization in one or more countries, and others are being developed and tested. This review assesses the different strategies currently proposed to control COVID-19 and the issues or limitations imposed on some approaches by the human and viral genetic variability.

Design, synthesis and biological evaluation of N-oxide derivatives with potent in vivo antileishmanial activity

Leishmaniasis is a neglected disease that affects 12 million people living mainly in developing countries. Herein, 24 new N-oxide-containing compounds were synthesized followed by in vitro and in vivo evaluation of their antileishmanial activity. Compound 4f, a furoxan derivative, was particularly remarkable in this regard, with EC₅₀ value of 3.6 μM against L. infantum amastigote forms and CC₅₀ value superior to 500 μM against murine peritoneal macrophages. In vitro studies suggested that 4f may act by a dual effect, by releasing nitric oxide after biotransformation and by inhibiting cysteine protease CPB (IC₅₀: 4.5 μM). In vivo studies using an acute model of infection showed that compound 4f at 7.7 mg/Kg reduced ~90% of parasite burden in the liver and spleen of L. infantum-infected BALB/c mice. Altogether, these outcomes highlight furoxan 4f as a promising compound for further evaluation as an antileishmanial agent.

Can natural products improve skin photoprotection?

Abstract Due to increased UV radiation on the Earth’s surface, caused by depletion of the stratospheric ozone, people have become more susceptible to different types of skin damage, such as erythema, sunburns, and cancer; this is especially of concern in tropical countries. Thus, efforts to improve awareness as well as the use of sunscreen are increasing worldwide. However, synthetic UV filters have been associated with deleterious effects such as photosensitization. Natural products have been used by ancient cultures for several purposes, including protecting the skin from the sun. However, there is still doubt today whether photoprotection is a real phenomenom or whether it is simply tanning of the skin. Plants have self-protective mechanisms and produce secondary metabolites that can protect themselves from UV radiation. Yet, can phytochemical compounds protect human skin? This review discusses the paradoxical effect of chemical UV filters and the influence of phytochemicals in in vitro and in vivo tests of photoprotection.

Peptide prodrugs for the treatment of CNS disorders: a perspective for new drugs

The treatment of central nervous system (CNS) diseases is a major challenge. The presence of the barrier intended to protect the brain from unwanted molecules also impairs the efficacy of CNS-targeted drugs. The discovery of drug targets for CNS diseases opens a door for the selective treatment of these diseases. However, the physicochemical properties of drugs, including their hydrophilic properties and their peripheral metabolism, as well as the blood-brain barrier, can adversely affect the therapeutic potential of CNS-targeted drugs. Although peptides are often metabolized by enzymes, they are of particular interest for the treatment of CNS diseases or as carriers to deliver drugs to the brain. In this review, we discuss the use of peptides as potential prodrugs for the treatment of CNS diseases.

Evaluation of antimalarial activity and toxicity of a new primaquine prodrug

Plasmodium vivax is the most prevalent of the five species causing malaria in humans. The current available treatment for P. vivax malaria is limited and unsatisfactory due to at least two drawbacks: the undesirable side effects of primaquine (PQ) and drug resistance to chloroquine. Phenylalanine-alanine-PQ (Phe-Ala-PQ) is a PQ prodrug with a more favorable pharmacokinetic profile compared to PQ. The toxicity of this prodrug was evaluated in in vitro assays using a human hepatoma cell line (HepG2), a monkey kidney cell line (BGM), and human red blood cells deficient in the enzyme glucose-6-phosphate-dehydrogenase (G6PD). In addition, in vivo toxicity assays were performed with rats that received multiple doses of Phe-Ala-PQ to evaluate biochemical, hematological, and histopathological parameters. The activity was assessed by the inhibition of the sporogonic cycle using a chicken malaria parasite. Phe-Ala-PQ blocked malaria transmission in Aedes mosquitoes. When compared with PQ, it was less cytotoxic to BGM and HepG2 cells and caused less hemolysis of G6PD-deficient red blood cells at similar concentrations. The prodrug caused less alteration in the biochemical parameters than did PQ. Histopathological analysis of the liver and kidney did show differences between the control and Phe-Ala-PQ-treated groups, but they were not statistically significant. Taken together, the results highlight the prodrug as a novel lead compound candidate for the treatment of P. vivax malaria and as a blocker of malaria transmission.

Pharmacological evaluation and preliminary pharmacokinetics studies of a new diclofenac prodrug without gastric ulceration effect

Long-term nonsteroidal anti-inflammatory drugs (NSAIDs) therapy has been associated with several adverse effects such as gastric ulceration and cardiovascular events. Among the molecular modifications strategies, the prodrug approach is a useful tool to discover new safe NSAIDs. The 1-(2,6-dichlorophenyl)indolin-2-one is a diclofenac prodrug which demonstrated relevant anti-inflammatory properties without gastro ulceration effect. In addition, the prodrug decreases PGE(2) levels, COX-2 expression and cellular influx into peritoneal cavity induced by carrageenan treatment. Preliminary pharmacokinetic studies have shown in vivo bioconversion of prodrug to diclofenac. This prodrug is a new nonulcerogenic NSAID useful to treat inflammatory events by long-term therapy.

In vitro and in vivo evaluation of a primaquine prodrug without red blood cell membrane destabilization property

Primaquine is an important therapeutic resource for malaria treatment and it has wide activity against several pathogens. The haematotoxicity of primaquine is the major problem for its therapeutic application. This effect is aggravated by repeated use at high doses and by the wide fluctuation of plasma levels after administration. The primaquine prodrug (Phe-Ala-PQ) was planned in order to modify the pharmacokinetics and toxicity of primaquine. The in vitro conversion of Phe-Ala-PQ to primaquine, and the primaquine pharmacokinetics were evaluated in four groups of rats: two groups that received a single dose of Phe-Ala-PQ, one by intravenous and the other by gavage route, and two other groups that received primaquine diphosphate, by intravenous and gavage routes. In addition, the erythrocyte osmotic fragility was compared in two groups of rats that received multiple doses of primaquine diphosphate or Phe-Ala-PQ, as a parameter of haematotoxicity. The in vitro conversion of Phe-Ala-PQ to primaquine by plasma enzyme action was observed. The pharmacokinetic profile of primaquine from Phe-Ala-PQ was more favourable due to the lower fluctuation of plasma concentrations. Haematotoxicity was not evidenced in the prodrug administration. The results reinforce the need for further studies with this prodrug, promising an alternative in the therapeutic use of primaquine.

A prodrug approach to improve the physico-chemical properties and decrease the genotoxicity of nitro compounds

In therapeutics research, the nitro compounds are part of an important group of drugs with multiple pharmacological activities. However, in drug design, the inclusion of a nitro group in a molecule changes the physico-chemical and electronic properties and is associated with increased mutagenicity and carcinogenicity. In addition, several studies have related the relationship between the antimicrobial and/or anti-protozoal activity and the mutagenic effect to reduction of the nitro group. This work reviews the toxicity of nitro compounds and shows how the use of prodrugs can increase the biological activity and decrease the genotoxicity of nitro compounds, without any modification in nitro reduction behavior, but rather by physico-chemical improvement. Examples are given of metronidazole and nitrofurazone prodrugs.

Advances in sickle cell disease treatment: from drug discovery until the patient monitoring

Sickle cell disease (SCD) is one of the most prevalent hematological diseases in the world. Despite the immense progress in molecular knowledge about SCD in last years few therapeutical sources are currently available. Nowadays the treatment is performed mainly with drugs such as hydroxyurea or other fetal hemoglobin inducers and chelating agents. This review summarizes current knowledge about the treatment and the advancements in drug design in order to discover more effective and safe drugs. Patient monitoring methods in SCD are also discussed.