McLTP1 (Morinda citrifolia LIPID TRANSFER PROTEIN 1): efeito antimicrobiano in vitro e atividade protetora sobre a sepse induzida em camundongos

Abstract

Microbial resistance is a major public health problem of this century, that has led to increased concern of severe sepsis cases in intensive care units. Due to the nonspecific therapy and the absence of drugs approved for sepsis treatment, new therapeutic approaches has been demanded. Among these approaches, plant antimicrobial peptides have emerged as promising molecules with a potential therapeutic intervention in human health. Recently, our research group isolated a lipid transfer protein type 1 (McLTP1 - UniProt Accession Number: C0HJH5) from Morinda citrifolia L. seeds (noni). This study aimed to evaluate the antibacterial and antifungal potential of McLTP1 against species of clinical concern and investigate its protective effect in mice subjected to sepsis. McLTP1 was isolated from noni seeds crude extract by protein fractionation with trichloroacetic acid 2.5% and ultrafiltration in 30 kDa membrane. McLTP1 antimicrobial properties were evaluated in vitro against planktonic cells and biofilm of Candida spp., gram-positive and gram-negative bacteria species in 96-well plates. In addition, it was evaluated the effect of McLTP1 on bacterial virulence factors and its modulatory properties on clinical antimicrobial drugs. Sepsis in mice was induced by cecal ligation and puncture model, being evaluated the survival rate, body weight and fresh organ weights, haematological parameters and antipyretic effect in animals treated intraperitoneally and orally with McLTP1 (8 mg/kg). Although McLTP1 was not able to inhibit Candida spp. biofilm formation, McLTP1 antifungal activity was observed through growth inhibition of Candida parapsilosis planktonic cells at 25 μg/mL (52.72%; p < 0.05), and through the potentiation effect of amphotericin B (0.06 μg/mL; 28.6% inhibition C. parapsilosis growth) when in the cotreatment with McLTP1 (50 μg/mL; 88.1 % inhibition). Regarding to the antibacterial activity, McLTP1 did not inhibit gram-negative bacteria planktonic cells growth, exhibiting effect only against gram-positive bacteria of Staphylococcus genus, being observed inhibitions on planktonic cells ranging from 18.7% (0.78 μg/mL, p < 0.05) to 98.8% (800 μg/mL; p <0.05) and against biofilms from 34.5% (12.5 μg/mL; p < 0.05) to 73.6% (400 μg/mL). McLTP1 reduced the activity of bacterial virulence factors such as catalase and coagulase, and acted in synergism with the antibiotic oxacillin. In prophylactic and therapeutic treatments at a dose of 8 mg/kg by intraperitoneal and oral route, McLTP1 increased the survival of animals with sepsis, showing antipyretic effect within the first hours after sepsis induction. Moreover, McLTP1 significantly reduced leukocytosis condition observed to the animals of vehicle group with sepsis. In conclusion, McLTP1 showed promising antimicrobial properties and protective effects on animals with sepsis, a new activity for this class of proteins, configured as a therapeutic potential candidate to this syndrome.