Antiprotozoal potential of Vismia species (Hypericaceae), medicinal plants used to fight cutaneous leishmaniasis

ETHNOPHARMACOLOGICAL RELEVANCE

Species of Vismia (Hypericaceae), known in Brazil as "lacre", are commonly used in traditional Amazonian medicine for the treatment of skin lesions, including those caused by Leishmania infection.

AIM OF THE STUDY

Hexane extracts from the leaves of Vismia cayennensis, V. gracilis, V. sandwithii and V. guianensis, as well as from the fruits of the latter, in addition to the anthraquinones vismiaquinone, physcion and chrysophanol isolated from these species were explored for their anti-promastigote and anti-amastigote activity on Leishmania amazonensis.

MATERIALS AND METHODS

Extracts were prepared by static maceration with n-hexane. The compounds, isolated by chromatographic techniques, were identified by spectroscopic methods (1H and 13C NMR). Promastigotes of L.amazonensis were incubated with hexane extracts (1-50 μg/mL) or anthraquinones (1-50 μM) and the parasite survival analyzed. The action of compounds on reactive oxygen species (ROS) production, mitochondrial membrane potential, and membrane integrity of promastigotes were evaluated by flow cytometer, and the cytotoxicity on mammalian cells using MTT assay. Furthermore, the activity of compounds against amastigotes and nitric oxide production were also investigated.

RESULTS

Vismiaquinone and physcion were obtained from the leaves of V. guianensis. Physcion, as well as chrysophanol, were isolated from V. sandwithii. Vismia cayennensis and V. gracilis also showed vismiaquinone, compound detected in lower quantity in the fruits of V. guianensis. All extracts were active against the parasite, corroborating the popular use. The greatest activity against promastigotes was achieved with V. guianensis extract (IC50 4.3 μg/mL), precisely the most used Vismia species for treating cutaneous leishmaniasis. Vismiaquinone and physcion exhibited relevant activity with IC50 12.6 and 2.6 μM, respectively. Moreover, all extracts and anthraquinones tested induced ROS production, mitochondrial dysfunction, membrane disruption and were able to kill intracellular amastigote forms, being worthy of further in vivo studies as potential antileishmanial drugs.

CONCLUSIONS

The overall data achieved in the current investigation scientifically validate the traditional use of Vismia species, mainly V. guianensis, as an anti-Leishmania agent. Furthermore, the promising results presented here indicate species of Vismia as potentially useful resources of Brazilian flora for the discovery of therapeutic solutions for neglected diseases.

Excess of body weight is associated with accelerated T-cell senescence in hospitalized COVID-19 patients

BACKGROUND

Several risk factors have been involved in the poor clinical progression of coronavirus disease-19 (COVID-19), including ageing, and obesity. SARS-CoV-2 may compromise lung function through cell damage and paracrine inflammation; and obesity has been associated with premature immunosenescence, microbial translocation, and dysfunctional innate immune responses leading to poor immune response against a range of viruses and bacterial infections. Here, we have comprehensively characterized the immunosenescence, microbial translocation, and immune dysregulation established in hospitalized COVID-19 patients with different degrees of body weight.

RESULTS

Hospitalised COVID-19 patients with overweight and obesity had similarly higher plasma LPS and sCD14 levels than controls (all p < 0.01). Patients with obesity had higher leptin levels than controls. Obesity and overweight patients had similarly higher expansions of classical monocytes and immature natural killer (NK) cells (CD56+CD16-) than controls. In contrast, reduced proportions of intermediate monocytes, mature NK cells (CD56+CD16+), and NKT were found in both groups of patients than controls. As expected, COVID-19 patients had a robust expansion of plasmablasts, contrasting to lower proportions of major T-cell subsets (CD4 + and CD8+) than controls. Concerning T-cell activation, overweight and obese patients had lower proportions of CD4+CD38+ cells than controls. Contrasting changes were reported in CD25+CD127low/neg regulatory T cells, with increased and decreased proportions found in CD4+ and CD8+ T cells, respectively. There were similar proportions of T cells expressing checkpoint inhibitors across all groups. We also investigated distinct stages of T-cell differentiation (early, intermediate, and late-differentiated - TEMRA). The intermediate-differentiated CD4 + T cells and TEMRA cells (CD4+ and CD8+) were expanded in patients compared to controls. Senescent T cells can also express NK receptors (NKG2A/D), and patients had a robust expansion of CD8+CD57+NKG2A+ cells than controls. Unbiased immune profiling further confirmed the expansions of senescent T cells in COVID-19.

CONCLUSIONS

These findings suggest that dysregulated immune cells, microbial translocation, and T-cell senescence may partially explain the increased vulnerability to COVID-19 in subjects with excess of body weight.

Vitamin C supplementation has no effect on American bullfrog's immune response

American bullfrog (Lithobates catesbeianus) is the only species raised in Brazilian commercial frog farms, and the intensive culture of these animals has gained great popularity in Brazil over the past several years. Stress is one of the major obstacles in frog culture. To minimise this problem, the aim of the present study was to investigate the role of added vitamin C in the diet of American bullfrogs as an antistress factor through the assessment of plasma corticosterone, leucocyte levels and macrophage activation in animals raised in confinement. The experimental design was entirely randomised, with six treatments (supplementation of 0, 250, 500, 750, 1000 and 2000 mg of vitamin C/kg of feed) and four replications. The plasma corticosterone level, leucocyte level and macrophage activation were evaluated. It was concluded that vitamin C had no influence on the evaluated parameters due to the possible adaptation of the animals to life in captivity (domestication). The results of this research indicate that farmers should not increase the levels of vitamin C in commercial feeds because this would only enhance production costs.

Proteomic inventory of myocardial proteins from patients with chronic Chagas' cardiomyopathy

Chronic Chagas' disease cardiomyopathy (CCC) is an often fatal outcome of Trypanosoma cruzi infection, with a poorer prognosis than other cardiomyopathies. CCC is refractory to heart failure treatments, and is the major indication of heart transplantation in Latin America. A diffuse myocarditis, plus intense myocardial hypertrophy, damage and fibrosis, in the presence of very few T. cruzi forms, are the histopathological hallmarks of CCC. To gain a better understanding of the pathophysiology of CCC, we analyzed the protein profile in the affected CCC myocardium. Homogenates from left ventricular myocardial samples of end-stage CCC hearts explanted during heart transplantation were subjected to two-dimensional electrophoresis with Coomassie blue staining; protein identification was performed by MALDI-ToF mass spectrometry and peptide mass fingerprinting. The identification of selected proteins was confirmed by immunoblotting. We demonstrated that 246 proteins matched in gels from two CCC patients. They corresponded to 112 distinct proteins. Along with structural/contractile and metabolism proteins, we also identified proteins involved in apoptosis (caspase 8, caspase 2), immune system (T cell receptor ss chain, granzyme A, HLA class I) and stress processes (heat shock proteins, superoxide dismutases, and other oxidative stress proteins). Proteins involved in cell signaling and transcriptional factors were also identified. The identification of caspases and oxidative stress proteins suggests the occurrence of active apoptosis and significant oxidative stress in CCC myocardium. These results generated an inventory of myocardial proteins in CCC that should contribute to the generation of hypothesis-driven experiments designed on the basis of the classes of proteins identified here.

Proteomic inventory of myocardial proteins from patients with chronic Chagas' cardiomyopathy

Chronic Chagas' disease cardiomyopathy (CCC) is an often fatal outcome of Trypanosoma cruzi infection, with a poorer prognosis than other cardiomyopathies. CCC is refractory to heart failure treatments, and is the major indication of heart transplantation in Latin America. A diffuse myocarditis, plus intense myocardial hypertrophy, damage and fibrosis, in the presence of very few T. cruzi forms, are the histopathological hallmarks of CCC. To gain a better understanding of the pathophysiology of CCC, we analyzed the protein profile in the affected CCC myocardium. Homogenates from left ventricular myocardial samples of end-stage CCC hearts explanted during heart transplantation were subjected to two-dimensional electrophoresis with Coomassie blue staining; protein identification was performed by MALDI-ToF mass spectrometry and peptide mass fingerprinting. The identification of selected proteins was confirmed by immunoblotting. We demonstrated that 246 proteins matched in gels from two CCC patients. They corresponded to 112 distinct proteins. Along with structural/contractile and metabolism proteins, we also identified proteins involved in apoptosis (caspase 8, caspase 2), immune system (T cell receptor ss chain, granzyme A, HLA class I) and stress processes (heat shock proteins, superoxide dismutases, and other oxidative stress proteins). Proteins involved in cell signaling and transcriptional factors were also identified. The identification of caspases and oxidative stress proteins suggests the occurrence of active apoptosis and significant oxidative stress in CCC myocardium. These results generated an inventory of myocardial proteins in CCC that should contribute to the generation of hypothesis-driven experiments designed on the basis of the classes of proteins identified here.

DNA damage by 3,6-dihydropyrazine-2,5-dipropanoic acid, the cyclic dimerization product of 5-aminolevulinic acid

5-Aminolevulinic acid (ALA) is a heme precursor that accumulates in lead poisoning and inborn porphyrias. It has been shown to produce reactive oxygen species upon metal-catalyzed aerobic oxidation and to cause oxidative damage to proteins, liposomes, DNA, and subcellular structures. Studies have also shown that ALA may condense to yield the cyclic product 3,6-dihydropyrazine-2,5-dipropanoic acid (DHPY). Here we propose that DHPY could be involved in DNA damage in the presence of high concentrations of ALA. Exposure of plasmid pUC19 DNA to low concentrations of DHPY (2-10 microM) in the presence of 0.1 mM Cu2+ ions causes DNA strand breaks, as demonstrated by agarose gel electrophoresis. It was also shown that in the presence of Cu2+ ions DHPY is able to increase the oxidation of monomeric 2'-deoxyguanosine to form 8-oxo-7,8-dihydro-2'-deoxyguanosine as inferred from high performance liquid chromatography measurements using electrochemical detection. Addition of a metal chelator (bathocuproine, 0.5 mM), the DNA compacting polyamines spermidine (1 mM) and spermine (1 mM) or antioxidant enzymes such as superoxide dismutase (10 microg/ml) and catalase (20 pg/ml) protect the DNA against these damages. The data presented here are discussed with respect to the increased frequency of liver cancer in patients with acute intermittent porphyria.

Non-coherent visible and infrared radiation increase survival to UV (254 nm) in Escherichia coli K12

Interactions between visible or infrared (IR) and ultraviolet (UV, 254 nm) radiation have been studied in E. coli. Pre-illumination with non-coherent monochromatic 446, 466, 570 and 685 nm radiation, as well as with polychromatic red and IR radiation at room temperature, leads to increased cell survival after a subsequent irradiation with UV light. In the thermic range of the spectrum (red and IR), IR but not red light pre-treatment is able to increase cell survival to a subsequent lethal heat (51 degrees C) challenge, suggesting that increased UV survival may be due to IR-induced heat-shock response. On the other hand, visible-light-induced resistance may be due to a different mechanism, possibly involved with unknown bacterial light receptors.

DNA damage by 5-aminolevulinic and 4,5-dioxovaleric acids in the presence of ferritin

Cellular accumulation of 5-aminolevulinic acid (ALA), the first specific intermediate of heme biosynthesis, is correlated in liver biopsy samples of acute intermittent porphyria affected patients with an increase in the occurrence of hepatic cancers and the formation of ferritin deposits in hepatocytes. 5-Aminolevulinic acid is able to undergo enolization and to be subsequently oxidized in a reaction catalyzed by iron complexes yielding 4,5-dioxovaleric acid (DOVA). The released superoxide radical (O(*-)(2)) is involved in the formation of reactive hydroxyl radical ((*)OH) or related species arising from a Fenton-type reaction mediated by Fe(II) and Cu(I). This leads to DNA oxidation. The metal catalyzed oxidation of ALA may be exalted by the O(*-)(2) and enoyl radical-mediated release of Fe(II) ions from ferritin. We report here the potentiating effect of ferritin on the ALA-mediated cleavage of plasmid DNA and the enhancement of the formation of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo). Plasmid pBR322 was incubated with ALA and varying amounts of purified ferritin. DNA damage was assessed by gel electrophoresis analysis of the open and the linear forms of the plasmid from the native supercoiled structure. Addition of either the DNA compacting polyamine spermidine or the metal chelator ethylenediaminetetraacetic acid (EDTA) inhibited the damage. It was also shown that ALA in the presence of ferritin is able to increase the oxidation of the guanine moiety of monomeric 2'-deoxyguanosine (dGuo) and calf thymus DNA (CTDNA) to form 8-oxodGuo as inferred from high performance liquid chromatography (HPLC) measurements using electrochemical detection. The formation of the adduct dGuo-DOVA was detected in CTDNA upon incubation with ALA and ferritin. In a subsequent investigation, the aldehyde DOVA was also able to induces strand breaks in pBR322 DNA.

Death Kinetics of Lactobacillus bulgaricus in a Spray Drying Process

Survival of Lactobacillus bulgaricus during spray drying was studied at various outlet air temperatures. During spray drying the logarithmic survival ratio decreased with increased outlet air temperature with first-order kinetics; the pseudo-z value for Lactobacillus bulgaricus was 17.3°C. Plots of the death-rate constant for Lactobacillus bulgaricus versus reciprocal outlet temperature during spray drying in skim milk show a curve with two different activation energies (E_a). The calculated E_a values were 33.47 kJ/mol above 70°C and 85.77 kJ/mol below 70°C. Thermodynamic quantities for spray drying of Lactobacillus bulgaricus are also presented. Results show that the relationship between the entropy of activation and the enthalpy of activation for both spray drying and heating in liquid medium is linear, with all the data for drying falling in the range of a negative entropy.