Ningalins, Pyrrole-Bearing Metabolites Isolated from Didemnum spp. Synthesis and MDR-Reversion Activity in Cancer Therapy.

Multi-Drug Resistance (MDR) is one of the most frequent problems observed in the course of cancer chemotherapy. Cells under treatment, tend to develop survival mechanisms to drug-action thus generating drug-resistance. One of the most important mechanism to get it is the over expression of P-gp glycoprotein, which acts as an efflux-pump releasing the drug outside of the cancer cell. A strategy for a succesfull treatment consists in the co-administration of one compound that acts against P-gp and another which acts against the cell during chemotherapy. Ningalins are pyrrole-containing naturally occurring compounds isolated mainly from the marine tunicate Didemnum spp and also they are some of the top reversing agents in MDR treatment acting on P-gp. Considering the relevance displayed for some of these isolated alkaloids or their core as a drug for co-administration in cancer therapy, all the total synthesis described to date for the members of ningalins family are reviewed herein.

Secretion of the siderophore rhizoferrin is regulated by the cAMP-PKA pathway and is involved in the virulence of Mucor lusitanicus.

Mucormycosis is a fungal infection caused by Mucorales, with a high mortality rate. However, only a few virulence factors have been described in these organisms. This study showed that deletion of rfs, which encodes the enzyme for the biosynthesis of rhizoferrin, a siderophore, in Mucor lusitanicus, led to a lower virulence in diabetic mice and nematodes. Upregulation of rfs correlated with the increased toxicity of the cell-free supernatants of the culture broth (SS) obtained under growing conditions that favor oxidative metabolism, such as low glucose levels or the presence of H2O2 in the culture, suggesting that oxidative metabolism enhances virulence through rhizoferrin production. Meanwhile, growing M. lusitanicus in the presence of potassium cyanide, N-acetylcysteine, a higher concentration of glucose, or exogenous cAMP, or the deletion of the gene encoding the regulatory subunit of PKA (pkaR1), correlated with a decrease in the toxicity of SS, downregulation of rfs, and reduction in rhizoferrin production. These observations indicate the involvement of the cAMP-PKA pathway in the regulation of rhizoferrin production and virulence in M. lusitanicus. Moreover, rfs upregulation was observed upon macrophage interaction or during infection with spores in mice, suggesting a pivotal role of rfs in M. lusitanicus infection.

Novel 2-aryl-4-aryloxyquinoline-based fungistatics for Mucor circinelloides. Biological evaluation of activity, QSAR and docking study.

Zygomycetes are ubiquitous saprophytes in natural environments which transform organic matter. Some zygomycetes of gender Mucor have attracted interest in health sector. Due to its ability as opportunistic microorganisms infecting immuno-compromised people and to the few available pharmacological treatments, the mucormycosis is receiving worldwide attention. Concerning to the pharmacological treatments, some triazole-based compounds such as fluconazole are extensively used. Nevertheless, we focused in the quinolines since they are broadly used models for the design and development of new synthetic antifungal agents. In this study, the fungistatic activity on M. circinelloides of various 2-aryl-4-aryloxyquinoline-based compounds was discovered, and in some cases, it resulted better than reference compound fluconazole. These quinoline derivatives were synthesized via the Csp2-O bond formation using diaryliodonium(III) salts chemistry. A QSAR study was carried out to quantitatively correlate the chemical structure of the tested compounds with their biological activity. Also, a docking study to identify a plausible action target of our more active quinolines was carried out. The results highlighted an increased activity with the fluorine- and nitro-containing derivatives. In light of the few mucormycosis pharmacological treatments, herein we present some non-described molecules with excellent in vitro activities and potential use in the mucormycosis treatment.

Arf-like proteins (Arl1 and Arl2) are involved in mitochondrial homeostasis in Mucor circinelloides.

Mucor circinelloides is an opportunistic dimorphic pathogen, with the dimorphic process controlled in parts by fermentative and oxidative metabolisms, which lead to yeast or mycelial growth, respectively. Dimorphic transition is important for pathogenesis since the mycelium represents the virulent morphology. We previously reported that the deletion of arl1 or arl2 stimulate anaerobic germination in M. circinelloides, suggesting an augmented fermentative metabolism. In the present study, we demonstrate that the heterokaryon Δarl1(+)(-) and homokaryon Δarl2 strains contain low number of mitochondria, which possibly results in a dysfunctional oxidative metabolism, marked by a low oxygen consumption in glucose and poor growth in glycerol as the unique carbon source. This dysfunction is compensated for by an increase in the glycolysis and fermentation in aerobic conditions, demonstrating growth kinetics similar to that in the wild-type strain. Moreover, as a consequence a high fermentative activity, the Δarl1(+)(-) and Δarl2 strains possibly increased the yeast cell growth during low oxygen concentrations in presence of glucose. To the best of our knowledge, this is the first study to demonstrate the control of members of Arf family on the mitochondrial population in a Mucor species.

The Neurospora crassa chr-1 gene is up-regulated by chromate and its encoded CHR-1 protein causes chromate sensitivity and chromium accumulation.

The ChrA membrane protein belongs to the CHR superfamily of chromate ion transporters, which includes homologues from bacteria, archaea and eukaryotes. Bacterial ChrA homologues confer chromate resistance by exporting chromate ions from the cell's cytoplasm. The Neurospora crassa strain 74-A chr-1 gene encodes a putative CHR-1 protein of 507 amino acid residues, which belongs to the CHR superfamily. RT-PCR assays showed that expression of the chr-1 gene was up-regulated by chromate exposure of N. crassa cultures. Introduction in N. crassa of sense and antisense fragments of the chr-1 gene, as part of a silencing module within the pSilent-1 vector, produced transformants with a phenotype of resistance to chromate and diminished accumulation of chromium, as compared with the control strain containing only the vector. A chromate-resistance phenotype was also observed in N crassa strains deleted in the genomic chr-1 gene, thus confirming that the absence of CHR-1 protein confers chromate resistance to the fungus. The cDNA from N. crassa chr-1 gene (Ncchr-1) was cloned into the pYES2 vector under the control of a GAL promoter and the resulting recombinant plasmid was transferred to the yeast Saccharomyces cerevisiae. Galactose-induced S. cerevisiae transformants expressing Ncchr-1 were more sensitive to chromate and accumulated 2.5 times more chromium than the induced strain containing only the vector. Excess sulfate, a chromate analog, was unable to protect S. cerevisiae chr-1 transformants from chromate toxicity. These data indicate that the N. crassa CHR-1 protein functions as a transporter that takes up chromate; it also appears that this transport occurs in a sulfate-independent fashion. This is the first report assigning a role as a chromate transporter to a nonbacterial CHR protein.