Effects of cytochalasin E on Paracoccidioides brasiliensis

AIMS

To determine the effects of cytochalasin E, isolated from the extremophile fungus Aspergillus felis, on the cells of Paracoccidioides brasiliensis Pb18.

METHODS AND RESULTS

Cytochalasin E showed a minimal inhibitory concentration of 3·6 μmol l^-1 and minimum fungicidal concentration of 7·2 μmol l^-1 on P. brasiliensis by in vitro microdilution and IC₅₀ >964·0 μmol l^-1 on murine macrophages. Its selectivity index (>263) indicated that this compound has selectivity for fungal cells. Morphological alterations were determined by optical and fluorescence microscopy, as well as scanning and transmission electron microscopy. Cytochalasin E affected P. brasiliensis bud-forming pseudohyphae, cell morphology, cell walls and cell membranes; caused the release of cellular material; and resulted in the production of reactive oxygen species. In murine macrophages, it affected cytoskeletal actin and inhibited phagocytosis.

CONCLUSION

Cytochalasin E may be useful as an antifungal prototype against P. brasiliensis and in studies on phagocytosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Paracoccidioides spp. are the etiological agents of paracoccidioidomycosis (PCM). Treatment is prolonged to control the clinical manifestations and prevent relapse. The study on the effects of cytochalasin E in P. brasiliensis is important because it can be used as a prototype for new antifungal drugs and consequently, broadens the treatment options for PCM.

The cytosolic sensor STING is required for intestinal homeostasis and control of inflammation

STING (stimulator of interferon genes) is a cytosolic sensor for cyclic dinucleotides and also an adaptor molecule for intracellular DNA receptors. Although STING has important functions in the host defense against pathogens and in autoimmune diseases, its physiological relevance in intestinal homeostasis is largely unknown. In this study, we show that STING^-/- mice presented defective protective mechanisms of intestinal mucosa, including decreased number of goblet cells, diminished mucus production, and lower levels of secretory IgA, when compared with wild-type (WT) mice. Fecal content and microbiota DNA could activate STING, indicating a role of this molecule in gut. Microbiota composition was altered in STING^-/- mice toward a more inflammatory profile, evidencing a reduction in the Allobacolum and Bifidobacterium groups along with increase in Disulfovibrio bacteria. Absence of STING lead to decrease in induced intraepithelial lymphocytes (IEL) and to increase in group 1 innate lymphoid cell (ILC1) as well as ILC3 frequencies and decrease in ILC2 in the colon. Development and function of Foxp3+ and LAP+ regulatory T cells were also compromised in STING^-/- mice. Moreover, these mice were highly susceptible to dextran sodium sulfate-induced colitis, T-cell-induced colitis, and enteric Salmonella typhimurium infection when compared with WT animals. Therefore, our results identify an important role of STING in maintaining gut homeostasis and also a protective effect in controlling gut inflammation.

The hemicholinium-3 sensitive high affinity choline transporter is internalized by clathrin-mediated endocytosis and is present in endosomes and synaptic vesicles

Synthesis of acetylcholine depends on the plasma membrane uptake of choline by a high affinity choline transporter (CHT1). Choline uptake is regulated by nerve impulses and trafficking of an intracellular pool of CHT1 to the plasma membrane may be important for this regulation. We have generated a hemagglutinin (HA) epitope tagged CHT1 to investigate the organelles involved with intracellular trafficking of this protein. Expression of CHT1-HA in HEK 293 cells establishes Na+-dependent, hemicholinium-3 sensitive high-affinity choline transport activity. Confocal microscopy reveals that CHT1-HA is found predominantly in intracellular organelles in three different cell lines. Importantly, CHT1-HA seems to be continuously cycling between the plasma membrane and endocytic organelles via a constitutive clathrin-mediated endocytic pathway. In a neuronal cell line, CHT1-HA colocalizes with the early endocytic marker green fluorescent protein (GFP)-Rab 5 and with two markers of synaptic-like vesicles, VAMP-myc and GFP-VAChT, suggesting that in cultured cells CHT1 is present mainly in organelles of endocytic origin. Subcellular fractionation and immunoisolation of organelles from rat brain indicate that CHT1 is present in synaptic vesicles. We propose that intracellular CHT1 can be recruited during stimulation to increase choline uptake in nerve terminals.

Phylogeography of the human mitochondrial haplogroup L3e: a snapshot of African prehistory and Atlantic slave trade

The mtDNA haplogroup L3e, which is identified by the restriction site +2349 MboI within the Afro-Eurasian superhaplogroup L3 (-3592 HpaI), is omnipresent in Africa but virtually absent in Eurasia (except for neighbouring areas with limited genetic exchange). L3e was hitherto poorly characterised in terms of HVS-I motifs, as the ancestral HVS-I type of L3e cannot be distinguished from the putative HVS-I ancestor of the entire L3 (differing from the CRS by a transition at np 16223). An MboI screening at np 2349 of a large number of Brazilian and Caribbean mtDNAs (encompassing numerous mtDNAs of African ancestry), now reveals that L3e is subdivided into four principal clades, each characterised by a single mutation in HVS-I, with additional support coming from HVS-II and partial RFLP analysis. The apparently oldest of these clades (transition at np 16327) occurs mainly in central Africa and was probably carried to southern Africa with the Bantu expansion(s). The most frequent clade (transition at np 16320) testifies to a pronounced expansion event in the mid-Holocene and seems to be prominent in many Bantu groups from all of Africa. In contrast, one clade (transition at np 16264) is essentially restricted to Atlantic western Africa (including Cabo Verde). We propose a tentative L3e phylogeny that is based on 197 HVS-I sequences. We conclude that haplogroup L3e originated in central or eastern Africa about 46,000 (+/-14,000) years ago, and was a hitchhiker of much later dispersal and local expansion events, with the rise of food production and iron smelting. Enforced migration of African slaves to the Americas translocated L3e mitochondria, the descendants of which in Brazil and the Caribbean still reflect their different regional African ancestries.

Multiple geographic sources of region V 9-bp deletion haplotypes in Brazilians

We investigated 245 white Brazilians for the presence of the 9-bp deletion in the intergenic COII/tRNALys region of the mitochondrial DNA (mtDNA) and found the deletion in 21 individuals (8.6% of the sample). Because white Brazilians are believed to be predominantly of European descent and this marker is rare in Europe, we established the geographic origin of these 21 mtDNA sequences by sequencing the hypervariable segment I of the mtDNA control region and by performing an RFLP analysis. Only 1 European mtDNA lineage was identified. On the other hand, 16 of the individuals had matrilineages of Amerindian origin and 4 had African mtDNA haplotypes. These results demonstrate that in the formation of the present-day white Brazilian population there was a significant contribution of Amerindian and African matrilineages. Although these data initially appear surprising, they agree well with the historical records of Brazilian colonization.

Identification in Portugal and Brazil of a mtDNA lineage containing a 9-bp triplication of the intergenic COII/tRNALys region

Although the deletion of one of the 9-bp repeats in region V of mitochondrial DNA is very common in Asians, Asian-derived populations and Africans, the triplication of the 9-bp segment was described only a few times, mostly on individuals from Asian origin. Here, we report for the first time the presence of the 9-bp triplication in Europeans. The triplication was initially found in one Brazilian individual. Sequencing of the hypervariable segments I (HVSI) and II (HVS2) of the control region and RFLP analysis of the coding region classified the mtDNA as belonging to the European haplogroup H. Since white Brazilians are predominantly of Portuguese descent, we screened 96 unrelated Northern Portuguese for the 9-bp triplication and found its presence in two of them (2.1%). One of these had an mtDNA haplotype identical to that of the Brazilian individual, while the other differed in a single base change in HVS2. The fact that the 9-bp triplication has reached polymorphic frequencies in Northern Portugal and that it has apparently differentiated into at least two lineages defined by the mutuation in HVS2 suggests that it probably occurred a long time ago.