Saulo L. da Silva

Stem cells and calcium signaling.

The increasing interest in stem cell research is linked to the promise of developing treatments for many lifethreatening, debilitating diseases, and for cell replacement therapies. However, performing these therapeutic innovations with safety will only be possible when an accurate knowledge about the molecular signals that promote the desired cell fate is reached. Among these signals are transient changes in intracellular Ca(2+) concentration [Ca(2+)](i). Acting as an intracellular messenger, Ca(2+) has a key role in cell signaling pathways in various differentiation stages of stem cells. The aim of this chapter is to present a broad overview of various moments in which Ca(2+)-mediated signaling is essential for the maintenance of stem cells and for promoting their development and differentiation, also focusing on their therapeutic potential.

Antitumoral activity of snake venom proteins: new trends in cancer therapy

For more than half a century, cytotoxic agents have been investigated as a possible treatment for cancer. Research on animal venoms has revealed their high toxicity on tissues and cell cultures, both normal and tumoral. Snake venoms show the highest cytotoxic potential, since ophidian accidents cause a large amount of tissue damage, suggesting a promising utilization of these venoms or their components as antitumoral agents. Over the last few years, we have studied the effects of snake venoms and their isolated enzymes on tumor cell cultures. Some in vivo assays showed antineoplastic activity against induced tumors in mice. In human beings, both the crude venom and isolated enzymes revealed antitumor activities in preliminary assays, with measurable clinical responses in the advanced treatment phase. These enzymes include metalloproteases (MP), disintegrins, L-amino acid oxidases (LAAOs), C-type lectins, and phospholipases A2 (PLA2s). Their mechanisms of action include direct toxic action (PLA2s), free radical generation (LAAOs), apoptosis induction (PLA2s, MP, and LAAOs), and antiangiogenesis (disintegrins and lectins). Higher cytotoxic and cytostatic activities upon tumor cells than normal cells suggest the possibility for clinical applications. Further studies should be conducted to ensure the efficacy and safety of different snake venom compounds for cancer drug development.

Snake Venom L-Amino Acid Oxidases: Trends in Pharmacology and Biochemistry

L-amino acid oxidases are enzymes found in several organisms, including venoms of snakes, where they contribute to the toxicity of ophidian envenomation. Their toxicity is primarily due to enzymatic activity, but other mechanisms have been proposed recently which require further investigation. L-amino acid oxidases exert biological and pharmacological effects, including actions on platelet aggregation and the induction of apoptosis, hemorrhage, and cytotoxicity. These proteins present a high biotechnological potential for the development of antimicrobial, antitumor, and antiprotozoan agents. This review provides an overview of the biochemical properties and pharmacological effects of snake venom L-amino acid oxidases, their structure/activity relationship, and supposed mechanisms of action described so far.

Cytotoxic evaluation of essential oil from Zanthoxylum rhoifolium Lam. leaves

Zanthoxylum rhoifolium Lam is a plant popularly used as antimicrobial, for malaria and inflammatory treatment. The essential oil of Z. rhoifolium was extracted and its cytotoxic effects against HeLa (human cervical carcinoma), A-549 (human lung carcinoma), HT-29 (human colon adenocarcinoma), Vero (monkey kidney) cell lines and mice macrophages were evaluated. Some of the terpenes of its essential oil (s-caryophyllene, a-humulene, a -pinene, myrcene and linalool) were also tested to verify their possible influence in the oil cytotoxic activity. The results obtained permitted to confirm that the essential oil is cytotoxic against tumoral cells (CD50 = 82.3, 90.7 and 113.6 µg/ml for A-549, HeLa e HT-29 cell lines, respectively), while it did not show cytotoxicity against non-tumoral cells (Vero and mice macrophages). Thus, the essential oil from Z. rhoifolium leaves seems to present a possible therapeuthic role due to its selective cytotoxic activity against tumoral cell lines.

Characterization of bergenin in Endopleura uchi bark and its anti-inflammatory activity

Endopleura uchi (Huber) Cuatrec. is an Amazon species traditionally used for the treatment of inflammations and female disorders. Pure bergenin was isolated from the methanolic extract of bark of E. uchi, firstly by using liquid-liquid partition chromatography followed by column chromatography over Sephadex LH-20 and then silica gel 60 flash chromatography. The structure of bergenin was identified on the basis of its NMR spectra. The in vitro anti-inflammatory activity was determined by the measurement of the inhibitory concentration (IC) of bergenin against three key enzymes: COX-1, COX-2 (cyclooxygenases) and phospholipase A2 (PLA2). These enzymes were selected because they are important targets for the discovery of new anti-inflammatory drugs associated with the biosynthesis of prostaglandins. The IC50 of bergenin for phopholipase A2 was determined as 156.6 µmol L-1 and bergenin was not considered active as compared to the positive control, tioetheramide PC. Bergenin did not inhibit COX-1 as well (IC50 = 107.2 µmol L-1). However, bergenin selectively inhibited COX-2 (IC50 = 1.2 µmol L-1). Because of the use of E. uchi in traditional medicine, bergenin was quantified in teas prepared as prescribed in traditional medicine by RP-HPLC as being 3% in the bark of E. uchi. The inhibitory activity towards COX-2 is important, since selective inhibitors of COX-2 have been clinically validated as anti-inflammatory therapeutics due to their enhanced gastrointestinal safety.

Biological and biochemical characterization of new basic phospholipase A2 BmTX-I isolated from Bothrops moojeni snake venom☆

BmTX-I, an Asp49 phospholipase A(2), was purified from Bothrops moojeni venom after only one chromatographic step using reverse-phase HPLC on mu-Bondapak C-18 column. A molecular mass of 14238.71Da was determined by MALDI-TOF mass spectrometry. Amino acid analysis showed a high content of hydrophobic and basic amino acids as well as 14 half-cysteine residues. The BmTX-I PLA(2) had a sequence of 121 residues of amino acids: DLWQFNKMIK KEVGKLPFPF YGAYGCYCGW GGRGEKPKDG TDRCCFVHDC CYKKLTGCPK WDDRYSYSWK DITIVCGEDL PCEEICECDR AAAVCFYENL GTYNKKYMKH LKPCKKADYP C and pI value 7.84, and showed a high degree of homology with basic Asp49 PLA(2) myotoxins from other Bothrops venoms. BmTX-I presented PLA(2) activity in the presence of a synthetic substrate and showed a minimum sigmoidal behavior, reaching its maximal activity at pH 8.0 and 35-45 degrees C. Maximum PLA(2) activity required Ca(2+) and in the presence of Mg(2+), Cd(2+) and Mn(2+) it was reduced in presence or absence of Ca(2+). Crotapotin from Crotalus durissus colillineatus rattlesnake venom has significantly inhibited (P<0.05) the enzymatic activity of BmTX-I. In vitro, the whole venom and BmTX-I caused a blockade of the neuromuscular transmission in young chick biventer cervicis preparations in a similar way to other bothrops species. In mice, BmTX-I and the whole venom-induced myonecrosis and a systemic interleukin-6 response upon intramuscular injection. Edema-forming activity was also analyzed through injection of the venom and the purified BmTX-I into the subplantar region of the right footpad. Since BmTX-I exert a strong proinflammatory effect; the enzymatic phospholipids hydrolysis might be relevant for these phenomena.

Genome-wide association analysis of feed intake and residual feed intake in Nellore cattle

BackgroundFeed intake plays an important economic role in beef cattle, and is related with feed efficiency, weight gain and carcass traits. However, the phenotypes collected for dry matter intake and feed efficiency are scarce when compared with other measures such as weight gain and carcass traits. The use of genomic information can improve the power of inference of studies on these measures, identifying genomic regions that affect these phenotypes. This work performed the genome-wide association study (GWAS) for dry matter intake (DMI) and residual feed intake (RFI) of 720 Nellore cattle (Bos taurus indicus).ResultsIn general, no genomic region extremely associated with both phenotypic traits was observed, as expected for the variables that have their regulation controlled by many genes. Three SNPs surpassed the threshold for the Bonferroni multiple test for DMI and two SNPs for RFI. These markers are located on chromosomes 4, 8, 14 and 21 in regions near genes regulating appetite and ion transport and close to important QTL as previously reported to RFI and DMI, thus corroborating the literature that points these two processes as important in the physiological regulation of intake and feed efficiency.ConclusionsThis study showed the first GWAS of DMI to identify genomic regions associated with feed intake and efficiency in Nellore cattle. Some genes and QTLs previously described for DMI and RFI, in other subspecies (Bos taurus taurus), that influences these phenotypes are confirmed in this study.

Enzymatic and structural characterization of a basic phospholipase A2 from the sea anemone Condylactis gigantea

This work aimed at the isolation and structural/functional characterization of a phospholipase A(2) (CgPLA(2)) from the extract of the anemone Condylactis gigantea. CgPLA(2) was isolated with a high purity level through three chromatographic steps, showing pI 8.6 and molecular weights of 14,500 and 29,000 for the monomer and dimer, respectively. CgPLA(2) showed a high catalytic activity upon fluorescent phospholipids inducing no direct hemolytic activity. This enzyme, which is Ca(2+)-dependent, showed a lower stability against temperature and pH variations when compared with snake venom enzymes. The enzymatic activity was significantly reduced or completely abolished after chemical modification of CgPLA(2) with BPB. Its cDNA was then obtained, with 357 base pairs which codified for a mature protein of 119 amino acid residues. A comparative analysis of the primary structure of CgPLA(2) revealed 84%, 61%, 43% and 42% similarity to the PLA(2)s from Adamsia carciniopados, Nematostella vectensis, Vipera russelli russelli and Bothrops jararacussu, respectively.

Isolation and expression of a hypotensive and anti-platelet acidic phospholipase A2 from Bothrops moojeni snake venom

Phospholipases A(2) are important components of snake venoms, the basic isoforms have been more extensively studied than the acidic groups, maybe due to their higher toxicity. Trying to better understand the role of the acidic isoforms on the envenomation process, an acidic phospholipase A(2) was purified from Bothrops moojeni snake venom through two chromatographic steps (BmooPLA(2)). The enzyme showed a relative molecular mass of 13,601Da, pI 5.2, high phospholipase activity, bactericidal effect, moderate cytotoxic activity and was able to inhibit platelet aggregation. Moreover, BmooPLA(2) induced moderate in vivo edema and hypotensive effect. The 414bp cDNA encoding the BmooPLA(2) was cloned and expressed in Escherichia coli. The recombinant BmooPLA(2) showed phospholipase and inhibitory activities on platelet aggregation similar to those of the native protein. A comparative study between BmooPLA(2), the acidic (BthA-I) and basic (BthTX-II) PLA(2) from B. jararacussu venom showed that the effects of BmooPLA(2) and BthA-I-PLA(2) are similar. BmooPLA(2) is the first isolated and characterized non-myotoxic PLA(2) from B. moojeni snake venom. The recombinant PLA(2) can substitute the native toxin in studies aiming its biotechnological application in order to help the preservation of this endangered species. These data along with the preliminary structural studies here reported will provide a better understanding of this important class of proteins.

Genotoxic effect of Bothrops snake venoms and isolated toxins on human lymphocyte DNA.

In the present study, micronucleus with cytokinesis blocking and comet assays were used to evaluate the genotoxic potential of Bothrops jararacussu, Bothrops atrox, Bothrops moojeni, Bothrops alternatus (Rhinocerophis alternatus) and Bothrops brazili snake venoms, and also of some isolated toxins (MjTX-I, BthTX-I and II myotoxins, BjussuMP-II metalloprotease, and BatxLAAO l-amino acid oxidase) on human lymphocytes. Significant DNA damages were observed, indicating genotoxic potential after exposure of the lymphocytes to the toxins BthTX-I, II and BatxLAAO compared to untreated and Cisplatin-treated controls, which were able to induce greater formation of micronuclei. B. brazili, B. jararacussu and B. atrox crude venoms also presented genotoxic potential, and the latter two induced DNA breakage 5 times more often than in normal environmental conditions (control without treatment). B. jararacussu venom and its isolated toxins, as well as an LAAO from B. atrox, were able to cause lymphocyte DNA breakage in the comet test with more than 85% damage levels. The DNA damage evaluation allows a widening of the toxic-pharmacological characterization of snake venoms and their toxins and also contributes to the understanding of the mechanisms of action of these molecules in several human pathologies.