In vitro Effect of Harmine Alkaloid and Its N-Methyl Derivatives Against Toxoplasma gondii.

Toxoplasmosis is one of the most prevalent and neglected zoonotic global diseases caused by Toxoplasma gondii. The current pharmacological treatments show clinical limitations, and therefore, the search for new drugs is an urgent need in order to eradicate this infection. Due to their intrinsic biological activities, ß-carboline (ßC) alkaloids might represent a good alternative that deserves further investigations. In this context, the in vitro anti-T. gondii activity of three ßCs, harmine (1), 2-methyl-harminium (2), and 9-methyl-harmine (3), was evaluated herein. Briefly, the three alkaloids exerted direct effects on the parasite invasion and/or replication capability. Replication rates of intracellular treated tachyzoites were also affected in a dose-dependent manner, at noncytotoxic concentrations for host cells. Additionally, cell cycle analysis revealed that both methyl-derivatives 2 and 3 induce parasite arrest in S/M phases. Compound 3 showed the highest irreversible parasite growth inhibition, with a half maximal inhibitory concentration (IC50) value of 1.8 ± 0.2 µM and a selectivity index (SI) of 17.2 at 4 days post infection. Due to high replication rates, tachyzoites are frequently subjected to DNA double-strand breaks (DSBs). This highly toxic lesion triggers a series of DNA damage response reactions, starting with a kinase cascade that phosphorylates a large number of substrates, including the histone H2A.X to lead the early DSB marker γH2A.X. Western blot studies showed that basal expression of γH2A.X was reduced in the presence of 3. Interestingly, the typical increase in γH2A.X levels produced by camptothecin (CPT), a drug that generates DSB, was not observed when CPT was co-administered with 3. These findings suggest that 3 might disrupt Toxoplasma DNA damage response.

DNA damage induced by bare and loaded microporous coordination polymers from their ground and electronic excited states.

We report on interactions of cell free double-stranded DNA (dsDNA) with a selected subgroup of Microporous Coordination Polymers (MCPs). In particular, we have studied the influence of different metal ion constituents and chemically modified linkers using a set of five benzene carboxylate-based MCPs. Our results suggest that the DNA moiety can be structurally modified in two different ways: by direct MCPs-dsDNA interaction and/or through photosensitized processes. The extent of the observed damage was found to be strongly dependent on the charge density of the material. The potential use of the MCPs tested as inert carriers of photosensitizers was demonstrated by analyzing the interaction between dsDNA and harmine-loaded Cr-based materials, both in the absence of light and upon UVA irradiation.

Comment on "Binding of alkaloid harmalol to DNA: photophysical and calorimetric approach".

The present manuscript is a comment on the article entitled "Binding of alkaloid harmalol to DNA: Photophysical and calorimetric approach" by Sarita Sarkar and Kakali Bhadra (2014) [1]. In their article, the authors reported the chemical structure as well as the absorption spectra of harmalol at different pH. On the bases of the previous publications and our own present results, the assignment of the number of the acid-base species and the corresponding pKa values, as well as the chemical structure for each species are erroneous. These facts have strong effect on the conclusions reached by the authors, in terms of the interaction with DNA.

Toxoplasma gondii Hsp90: potential roles in essential cellular processes of the parasite.

Hsp90 is a widely distributed and highly conserved molecular chaperone that is ubiquitously expressed throughout nature, being one of the most abundant proteins within non-stressed cells. This chaperone is up-regulated following stressful events and has been involved in many cellular processes. In Toxoplasma gondii, Hsp90 could be linked with many essential processes of the parasite such as host cell invasion, replication and tachyzoite-bradyzoite interconversion. A Protein-Protein Interaction (PPI) network approach of TgHsp90 has allowed inferring how these processes may be altered. In addition, data mining of T. gondii phosphoproteome and acetylome has allowed the generation of the phosphorylation and acetylation map of TgHsp90. This review focuses on the potential roles of TgHsp90 in parasite biology and the analysis of experimental data in comparison with its counterparts in yeast and humans.

In vitro evaluation of ß-carboline alkaloids as potential anti-Toxoplasma agents.

BACKGROUND: Toxoplasmosis is a worldwide infection caused by the protozoan parasite Toxoplasma gondii, which causes chorioretinitis and neurological defects in congenitally infected newborns or immunodeficient patients. The efficacy of the current treatment is limited, primarily by serious host toxicity. In recent years, research has focused on the development of new drugs against T. gondii. ß-Carbolines (ßCs), such as harmane, norharmane and harmine, are a group of naturally occurring alkaloids that show microbicidal activity. In this work, harmane, norharmane and harmine were tested against T. gondii. FINDINGS: The treatment of extracellular tachyzoites with harmane, norharmane and harmine showed a 2.5 to 3.5-fold decrease in the invasion rates at doses of 40 µM (harmane and harmine) and 2.5 µM (norharmane) compared with the untreated parasites. Furthermore, an effect on the replication rate could also be observed with a decrease of 1 (harmane) and 2 (norharmane and harmine) division rounds at doses of 5 to 12.5 µM. In addition, the treated parasites presented either delayed or no monolayer lysis compared with the untreated parasites. CONCLUSIONS: The three ßC alkaloids studied (norharmane, harmane and harmine) exhibit anti-T. gondii effects as evidenced by the partial inhibition of parasite invasion and replication. A dose-response effect was observed at a relatively low drug concentration (< 40 µM), at which no cytotoxic effect was observed on the host cell line (Vero).