Purification, toxicity, and antiendotoxin activity of polymyxin B nonapeptide

Abstract

Polymyxin B, a relatively toxic antibiotic, has potent endotoxin-neutralizing properties that may be beneficial as adjunctive therapy in gram-negative sepsis. Polymyxin B nonapeptide (deacylated polymyxin B) is devoid of antibiotic activity but retains the capacity to disorganize the outer membrane of gram-negative bacteria. To evaluate the potential therapeutic usefulness of this derivative, we produced purified polymyxin B nonapeptide, tested its in vivo toxicity in animals, and evaluated its in vitro antiendotoxin activity. Effectiveness as an antiendotoxin agent was assessed by examining the ability of polymyxin B nonapeptide to block the enhanced release of toxic oxygen radicals induced by lipopolysaccharide in human neutrophils (priming). In vivo, at doses of 1.5 and 3.0 mg/kg, polymyxin B nonapeptide did not exhibit the neuromuscular blocking, neurotoxic, or nephrotoxic effects that were observed with polymyxin B sulfate. Both polymyxin B and polymyxin B nonapeptide inhibited lipopolysaccharide-induced neutrophil priming in a concentration-dependent manner, but the parent compound, polymyxin B, was 63 times more effective on a weight basis. The inhibitory activity of both compounds, however, diminished rapidly when they were added after the start of the lipopolysaccharide-neutrophil incubation. We conclude that polymyxin B nonapeptide is less toxic than polymyxin B and, at the doses tested, lacks the neurotoxicity and nephrotoxicity of the parent compound. Polymyxin B nonapeptide retains the antiendotoxin activity of polymyxin B but is much less potent. The findings suggest that these compounds block an early step in the neutrophil priming process, possibly lipopolysaccharide attachment to or insertion into the neutrophil membrane.

Nitric oxide synthase responsible for l‐arginine‐induced relaxation of rat aortic rings in vitro may be an inducible type

“…Polymyxin B, that binds to lipopolysaccharide and neutralizes its activity (Weinberg et al, 1978;Danner et al, 1989), has been reported to prevent spontaneous reduction of phenylephrine-induced tone possibly due to induction by lipopolysaccharide of an NO synthase (Rees et al, 1990a). Similarly, in the present experiments, polymyxin B also prevented development of L-arginine-induced relaxation, suggesting the possible induction of an NO synthase by lipopolysaccharide contamination of the Krebs solution which has been noted (Rees et al, 1990a).…”

Lipopeptides as anti-infectives: a practical perspective

“…In particular, removal of the fatty acid chain by proteolytic cleavage with ficin or related enzymes resulted in deacylated nonapeptides [65], with less acute toxicity than their parent polymyxins along with a reduced antibacterial activity [66][67][68]. Despite lacking bactericidal activity themselves, these polymyxin nonapeptides (PMBN) can damage the outermost cell wall structure of Gram-negative bacteria, greatly increasing its permeability to hydrophobic antibiotics, which may facilitate combinatorial use with other antibiotics to treat specific infections [69][70][71][72][73][74][75].…”

Amplification of Vacuole-targeting Fungicidal Activity of Antibacterial Antibiotic Polymyxin B by Allicin, an Allyl Sulfur Compound from Garlic

“…The supernatants obtained after cell removal by centrifugation were assayed for PMB content by HPLC using a reversephase C 18 column (4.7 by 250 mm; YMC-Pack ODS-AM, YMC Inc.). Elution was carried out by increasing the content of acetonitrile from 0 to 100% in a mobile phase of 0.15% trifluoroacetic acid in H 2 O over 30 minutes at a flow rate of 1.0 ml/minute, and PMB was detected at an absorbance at 215 nm [23].…”