RESUMO
Antimicrobial peptides (AMPs) are produced by the stimulated humoral immune system. Most mature AMPs contain less than 50 amino acid residues. Some of them are generated from proproteins upon microbial challenges. Here, we report the antimicrobial activities of a proline-rich proprotein, named SlLebocin1 (SlLeb1), from the tobacco cutworm Spodoptera litura. SlLebocin1 cDNA contains a 477-bp open reading frame (ORF). It is mainly expressed in hemocytes and the midgut in naïve larvae. The transcript level was significantly induced in hemocytes but repressed in the midgut and fat body by bacterial challenges. The proprotein contains 158 amino acids with 3 RXXR motifs that are characteristic of some Lepidopteral lebocin proproteins. Four peptides corresponding to the predicted processed fragments were synthesized chemically, and their antimicrobial activities against two Gram-negative and two Gram-positive bacterial strains were analyzed. The peptides showed differential antimicrobial activities. For Escherichia coli and Bacillus subtilis, only the C-terminal fragment (124-158) showed strong inhibitory effects. For Staphylococcus aureus, all peptides showed partial inhibitions. None of them inhibited Serratia marcescens. Bacterial morphologies were examined by the scanning electron microscopy and confocal laser scanning microscopy. The antimicrobial peptides either disrupted cellular membrane or inhibited cell division and caused elongated/enlarged morphologies. The results may provide ideas for designing novel antibiotics.
Assuntos
Peptídeos Catiônicos Antimicrobianos/genética , Proteínas de Insetos/genética , Domínios Proteicos Ricos em Prolina/genética , Precursores de Proteínas/genética , Spodoptera/genética , Sequência de Aminoácidos , Animais , Peptídeos Catiônicos Antimicrobianos/classificação , Peptídeos Catiônicos Antimicrobianos/farmacologia , Sequência de Bases , Sistema Digestório/metabolismo , Escherichia coli/efeitos dos fármacos , Escherichia coli/ultraestrutura , Perfilação da Expressão Gênica , Hemócitos/metabolismo , Proteínas de Insetos/classificação , Proteínas de Insetos/farmacologia , Larva/genética , Microscopia Eletrônica de Varredura , Filogenia , Precursores de Proteínas/classificação , Precursores de Proteínas/farmacologia , Homologia de Sequência de Aminoácidos , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/ultraestruturaRESUMO
The major ingredients of grassleaf sweetflag rhizome are ß-asarone and eugenol, which can cross the blood-brain barrier and protect neurons. This study aimed to observe the neuroprotective effects and mechanisms of ß-asarone and eugenol, components of the Chinese herb grassleaf sweetflag rhizome, on PC12 cells. First, PC12 cells were cultured with different concentrations (between 1 × 10(-10) M and 1 × 10(-5) M) of ß-asarone and eugenol. Survival rates of PC12 cells were not significantly affected. Second, PC12 cells incubated with amyloid-beta42, which reduced cell survival, were cultured under the same conditions (1 × 10(-6) M ß-asarone and eugenol). The survival rates of PC12 cells significantly increased, while expression levels of the mRNAs for the pro-apoptotic protein Bax decreased, and those for the anti-apoptotic protein Bcl mRNA increased. In addition, the combination of ß-asarone with eugenol achieved better results than either component alone. Our experimental findings indicate that both ß-asarone and eugenol protect PC12 cells through inhibiting apoptosis, and that the combination of the two is better than either alone.
