Leishmania donovani: thionins, plant antimicrobial peptides with leishmanicidal activity.

The leishmanicidal activity of plant antibiotic peptides (PAPs) from the principal families, such wheat thionins, a barley lipid transfer protein and potato defensins and snakins were tested in vitro against Leishmania donovani. Only thionins and defensins were active against this human pathogen at a low micromolar range of concentrations. Thionins resulted as the most active peptides tested until now. They collapsed ionic and pH gradients across the parasite plasma membrane together with a rapid depletion of intracellular ATP without affecting mitochondrial potential. Hence the lethal effect of thionins was mostly associated to permeabilization of the plasma membrane leading to an immediate death of the parasite. The present work is the first evidence for leishmanicidal activity in plant peptides. Future prospects for their development as new antiparasite agents on human diseases are considered.

Biliopancreatic diversion in a renal transplant patient.

Surgery is usually the only solution to modify the evolution of morbid obesity and resolve the associated co-morbidities. There is very little written regarding malabsorptive surgery and transplantation. A 48-year-old male with hypertension, hyperuricemia and obesity underwent renal transplantation in 1994 for renal amyloidosis. He was maintained on oral immunosuppressive cyclosporine. The patient developed uncontrollable hypertension, hyperlipemia, hyperglycemia and increasing weight to a BMI of 44. Thus, in December 2004, he underwent biliopancreatic diversion (BPD). After 18 months follow-up, he has lost 85% of his excess weight, and his hypertension, hyperglycemia and hyperlipemia are markedly improved. Renal function was not modified, nor were the levels of cyclosporine. He has had no complications derived from the BPD, and has a better quality of life.

A minimalist design approach to antimicrobial agents based on a thionin template.

Numerous studies have been devoted to the stabilization of secondary structure elements to improve receptor-ligand recognition. We report a novel application of this principle to create new antimicrobial agents using the highly folded thionin from Pyrularia puberaas a template. Non-native disulfide bonds have been used to induce two short linear segments of the protein into an amphipathic helix. The resulting 13- and 9-residue peptides are significantly more active than their linear counterparts and have an activity similar to that of native thionin.

Effects of weight loss after biliopancreatic diversion on metabolism and cardiovascular profile.

BACKGROUND: Obesity is associated with increased prevalence of cardiovascular risk factors. Biliopancreatic diversion (BPD) for morbid obesity has been reported to produce anemia and malnutrition in short-term follow-up. The aim of our study was to analyze the effect of weight reduction on cardiovascular profile, renal function and nutritional status. METHODS: 35 morbidly obese patients underwent BPD. We analyzed the presence of cardiovascular risk factors, renal status, proteinuria and nutritional status before and 1 year after BPD. RESULTS: Excess weight loss was 67% at 1 year after BPD. All cardiovascular risk factors (hypertension, diabetes, hyperlipidemia) improved during follow-up. We could not find any relevant signs of malnutrition in the patients. Microalbuminuria decreased and proteinuria disappeared after weight loss. We observed less urinary calcium and citrate excretion, with an increase in oxaluria, but these changes did not increase the incidence of renal stones. CONCLUSIONS: BPD was followed by improved cardiovascular profile and a lower pro-inflammatory state. BPD did not produce significant malnutrition, anemia or renal stone disease.

Structural dissection of a highly knotted peptide reveals minimal motif with antimicrobial activity.

The increasing occurrence of bacterial resistance to antibiotics is driving a renewed interest on antimicrobial peptides, in the hope that understanding the structural features responsible for their activity will provide leads into new anti-infective drug candidates. Most chemical studies in this field have focused on linear peptides of various eukaryotic origins, rather than on structures with complex folding patterns found also in nature. We have undertaken the structural dissection of a highly knotted, cysteine-rich plant thionin, with the aim of defining a minimal, synthetically accessible, structure that preserves the bioactive properties of the parent peptide. Using efficient strategies for directed disulfide bond formation, we have prepared a substantially simplified (45% size reduction) version with undiminished antimicrobial activity against a representative panel of pathogens. Analysis by circular dichroism shows that the downsized peptide preserves the central double alpha-helix of the parent form as an essential bioactive motif. Membrane permeability and surface plasmon resonance studies confirm that the mechanism of action remains unchanged.

The Erwinia chrysanthemi phoP-phoQ operon plays an important role in growth at low pH, virulence and bacterial survival in plant tissue.

We have studied the role of acidic pH as a barrier for the colonization of the plant apoplast by Erwinia chrysanthemi. A minitransposon containing a promoterless reporter gene, gus, was used for random mutagenesis of the bacterial genome. An acid-sensitive mutant, named BT119, was isolated and had the following differential features with respect to the wild-type strain: (i) inability to grow at pH

Synthetic and structural studies on Pyrularia pubera thionin: a single-residue mutation enhances activity against Gram-negative bacteria.

The thionin from Pyrularia pubera (Pp-TH), a 47-residue peptide with four internal disulfide bonds, was efficiently produced by chemical synthesis. Its antimicrobial activity in vitro against several representative pathogens (EC(50)=0.3-3.0 microM) was identical to that of natural Pp-TH. This peptide has a unique Asp(32) instead of the consensus Arg found in other thionins of the same family. In order to evaluate the effect of this mutation, the Arg(32) analogue (Pp-TH(D32R)) was also synthesized and showed a significant increase in antibiotic activity against several Gram-negative bacteria, whereas it retained the same activity against other pathogens. The overall structure of Pp-TH(D32R) was maintained, though a slight decrease in the helical content of the peptide was observed.

Natural variability in the Arabidopsis response to infection with Erwinia carotovora subsp. carotovora.

The natural variation in the response of Arabidopsis thaliana (L.) Heynh. to Erwinia carotovora subsp. carotovora has been studied in seven ecotypes and two mutants. The susceptibility of all the plant types was investigated by (i) macroscopic symptoms, (ii) fluorescence microscopy using green fluorescent protein (GFP) and (iii) bacterial growth in planta. Although all the plants were susceptible to the bacterium, there was no correlation in the degree of infection as ascertained by the three methods. The induction, upon infection, of several genes known to be involved in defense was analyzed by RNA blot hybridization. The patterns of expression of these genes differed according to the genotype. These results suggest that both salicylic and jasmonic acid play a role in the response of Arabidopsis to this bacterium.

Snakin-2, an antimicrobial peptide from potato whose gene is locally induced by wounding and responds to pathogen infection.

The peptide snakin-2 (StSN2) has been isolated from potato (Solanum tuberosum cv Jaerla) tubers and found to be active (EC(50) = 1-20 microM) against fungal and bacterial plant pathogens. It causes a rapid aggregation of both Gram-positive and Gram-negative bacteria. The corresponding StSN2 cDNA encodes a signal sequence followed by a 15-residue acidic sequence that precedes the mature StSN2 peptide, which is basic (isoelectric point = 9.16) and 66 amino acid residues long (molecular weight of 7,025). The StSN2 gene is developmentally expressed in tubers, stems, flowers, shoot apex, and leaves, but not in roots, or stolons, and is locally up-regulated by wounding and by abscisic acid treatment. Expression of this gene is also up-regulated after infection of potato tubers with the compatible fungus Botritys cinerea and down-regulated by the virulent bacteria Ralstonia solanacearum and Erwinia chrysanthemi. These observations are congruent with the hypothesis that the StSN2 is a component of both constitutive and inducible defense barriers.