RESUMO
Melittin exhibits high antibacterial potency against drug-resistant bacteria. However, the clinical utility of melittin is limited by its serious hemolytic activity. Thus, the need for developing novel melittin analogues with high antimicrobial activity and low hemolytic activity has grown. We designed, synthesized, and evaluated 20 novel melittin analogues with varying hydrophobic, polar or positively charged amino acids. The results showed that 8 compounds had antimicrobial activity (MIC: 1-4 μg·mL-1) against gram-positive pathogens equal to or better than that of melittin, and 16 compounds had low hemolytic activity (HC50 ≥ 11.9 μg·mL-1). Compounds 13 (MIC: 2-4 μg·mL-1) and 15 (MIC: 1-2 μg·mL-1) showed equal or better antimicrobial activity against both susceptible and resistant strains of Staphylococcus aureus and Enterococcus faecium compared to melittin (MIC: 4 μg·mL-1). Compound 13 (HC50: 24.0 ± 4.3 μg·mL-1) displayed noticeably decreased hemolytic activity compared to melittin (HC50: 5.3 ± 0.4 μg·mL-1). This work established a base for further study on the structure-activity relationships and structure-toxicity relationships of melittin.
RESUMO
Objective To evaluate the effect of α-melanocyte stimulating hormone (α-MSH) and its novel analogue STY39 on the production of tissue factor pathway inhibitor (TFPI) in mice with endotoxemia.Methods Female BALB/c mice were randomly divided into eight groups with 9 mice in each group.Endotoxemia was reproduced by intraperitoneal injection of lipopolysaccharide (LPS,25 μg/kg) and D-galactosamine (D-Gal,100 mg/kg).The animals of the control group were given phosphate buffered solution (PBS) instead.In the experimental groups,the mice were injected intraperitoneally with 2.5 mg/kg α-MSH or STY39 at 1,2 or 3 hours following LPS injection.The orbital blood was collected at different time points,and tissues of lung,liver,and kidney were collected 8 hours after the administration of LPS.The plasma TFPI levels were determined by enzyme linked immunosorbent assay (ELISA),and the expression of TFPI mRNA in different tissues was determined with reverse transcription-polymerase chain reaction (RT-PCR).Results The plasma TFPI levels (μg/L) began to increase (11.84 ± 1.55) in the endotoxemia mice 4 hours after LPS challenge and reached the peak (23.49 ± 1.12) at 8 hours.α-MSH or STY39 treatment at 1,2 or 3 hours after LPS challenge could significantly increase the TFPI content,with the best drug effect at 1 hour after LPS challenge (the blood was collected 8 hours after LPS challenge,α-MSH group:58.79 ± 2.67 vs.28.49 ± 1.69,STY39 group:71.08 ± 2.13 vs.28.49 ± 1.69,both P＜0.01),and the effect of STY39 was better than that of α-MSH (P＜0.01).A small amount of TFPI mRNA expression was observed in each tissue of the healthy mice.After LPS challenge,TFPI mRNA expression was increased in all the tissues,especially in the lung,liver and kidney.α-MSH or STY39treatment at 1 hour after LPS challenge could significantly up-regulate the expression of TFPI mRNA in the lung and liver (A value,α-MSH in lung:51.10 ±2.89 vs.32.43 ±2.51,STY39 in lung:72.11 ±3.48 vs.32.43 ±2.51;α-MSH in liver:43.21 ± 2.12 vs.29.29 ± 2.06,STY39 in liver:66.82 ± 1.76 vs.29.29 ± 2.06,both P＜0.01).The treatment with STY39 at 1 hour after LPS challenge could significantly up-regulate the expression of TFPI mRNA in the kidney (A value:45.21 ± 1.80 vs.30.44 ± 2.23,P＜0.01),but the treatment with α-MSH had no obvious effect (A value:24.61 ± 1.98 vs.30.44 ± 2.23,P＞0.05).The enhancing effect of early administration of STY39 on TTPI mRNA expression in the lung,liver and kidney tissues of endotoxemia mice was more powerful than that of α-MSH (all P＜0.01).Conclusion The early administration of α-MSH or STY39 may up-regulate TFPI production in the mice with endotoxemia,and the effect of STY39 is superior to α-MSH.