Eur J Clin Microbiol Infect Dis. 2015 Jan;34(1):197-204.

Functional synergy of a-helical antimicrobial peptides and traditional antibiotics against Gram-negative and Gram-positive bacteria.

Qi Feng1, 2, 3, Yibing Huang1, 2, 3, Mingxia Chen4, Guirong Li1, 2, 3, Yuxin Chen1, 2, 3

  1. Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, 2699 Qianjin St, Jilin University, Changchun, China,130012
  2. National Engineering Laboratory for AIDS Vaccine, 2699 Qianjin St, Jilin University, Changchun, China,130012
  3. School of Life Sciences, 2699 Qianjin St, Jilin University, Changchun, China
  4. Changchun ProteLight Pharmaceutical & Biotechnology Co., Ltd, Changchun, China

Yuxin Chen , Email: chen_yuxin@jlu.edu.cn

 

Abstract:

 In this study, the antimicrobial activities that were based on the synergistic effects of traditional antibiotics (imipenem, cefepime, levofloxacin hydrochloride and vancomycin) and antimicrobial peptides (AMPs; PL-5, PL-31, PL-32, PL-18, PL-29 and PL-26), alone or in combination, against three Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae and Staphylococcus epidermidis) and three Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumonia) were investigated. In addition, the antimicrobial activity that was based on the synergistic effects of levofloxacin hydrochloride and PL-5 against Staphylococcus aureus, in vivo, was explored in a mouse infection model. Traditional antibiotics and antimicrobial peptides showed significant synergistic effects on the antibacterial activities against the different Gram-positive and Gram-negative bacteria in vitro. A strong synergistic effect in the PL-5 and levofloxacin hydrochloride combination against Staphylococcus aureus was observed in the mouse infection model in vivo. The mechanism of synergistic action was due to the different targets of antimicrobial peptides and traditional antibiotics. The combination of antimicrobial peptides and traditional antibiotics can dramatically enhance antimicrobial activity and may help prevent or delay the emergence of antibiotic resistance. Thus, this combination therapy could be a promising approach to treat bacterial infections, particularly mixed infections and multi-antibiotic resistant infections in the clinics.

PMID:25169965


Supplement:

Due to the abuse of traditional antibiotics, the problem of antibacterial resistance continuously emerging and superbugs have become a serious threat of human health. According to the data of Centers for Disease Control and Prevention (CDC) of USA, In USA, at least 2 million people become infected with bacteria each year that are resistant to antibiotics and at least 23,000 people die each year as a direct result of these infections. According to the report of World Health Organization (WHO), in 2013, there were about 480,000 new cases of multidrug-resistant tuberculosis (MDR-TB). Extensively drug-resistant tuberculosis (XDR-TB) has been identified in 100 countries and a high percentage of hospital-acquired infections are caused by highly resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant Gram-negative bacteria. Thus, development of new antibiotics or new treatment strategies is urgent.

What is antimicrobial resistance? According to the report of WHO, antimicrobial resistance is the resistance of microorganisms (bacteria, fungi, viruses, parasites, etc.) to the antimicrobial drugs, such as antibiotics, antifungals, antivirals, and antimalarials that were originally effective for treatment of infections caused by them. As we know, traditional antibiotics generally target a particular physiological process of bacteria, such as cell wall synthesis, DNA replication etc [1]. Bacteria can become resistant to antibiotics through several ways. For example, some bacteria can “neutralize” an antibiotic by modifying it and making it harmless. Others can pump an antibiotic back outside of the bacteria. In addition, some bacteria can change their outer structure and prevent antibiotics from attaching and killing the bacteria. Thus, the traditional antibiotics eventually become inefficient, and many standard medical treatments fail or turn into very high risk procedures without effective anti-infective treatment, resulting in death and disability of individuals.

Combination therapy is a therapy that uses more than one medication or modality to treat a single disease. Compared to the monotherapy, combination therapy has several advantages such as a broad spectrum of coverage, the theoretical possibility of minimizing antimicrobial resistance, the reduction of toxic side effects and the synergistic interaction between the two drugs. Many studies have shown that when two or more traditional antibiotics are co-administered to treat an infection, the therapeutic effects were significantly improved. Several types of traditional antibiotic combinations, such as the combination of a cell wall-active agent with an aminoglycosidic aminocyclitol, a β-lactam with an aminoglycoside, a β-lactamase inhibitor with a β-lactam and the combination of agents that inhibit sequential steps in a metabolic pathway, have been used in clinical practices and frequently show strong synergism. Thus, combination therapy has been extensively used to treat infectious disease.

Antimicrobial peptides (host defense peptides, AMPs) are widely distributed in almost all species including mammals, plants, birds, amphibians, fishes, insects, and microbes. AMPs are highly effective and play a key role in innate immune systems against pathogens including bacteria, viruses, parasites, fungi, and even cancer cells. Although the exact mechanism of AMPs is not clear, it is believed that the interactions between AMPs and the cell membrane including the electrostatic interaction and the hydrophobic interaction are the key step leading to cell lysis and bacteria death. Compared to the traditional antibiotics, AMPs exhibited several unique characteristics, such as the ability to quickly eradicate target cells, a wide range of activity against serious antibiotic-resistant pathogens in the clinic and the relative difficulty in selecting resistant mutants in vitro [2, 3]. Hence, AMPs have become promising molecules for novel antibiotics agents. Till date, more than 2400 AMPs have been found, refer to the website: http://aps.unmc.edu/AP/main.php. However, the development of peptide-based drugs also has several obstacles need to overcome such as the systemic toxicity, poor pharmacokinetics, and high-costs.

Based on the above reason, we focus on the development of new antibiotics or new treatment strategies to treat infection. Firstly, study on the relationship of structure and activity of AMPs, screening optimal AMPs and improvement the specificity of AMPs against bacteria and other pathogens by de novo design and modification. Secondary, we focus on the combination therapy of AMPs and other traditional drugs, such as antibiotics in vitro and in vivo. The synergistic effects of traditional antibiotics (imipenem, cefepime, levofloxacin hydrochloride and vancomycin) and antimicrobial peptides (PL-5, PL-31, PL-32, PL-18, PL-29 and PL-26) against three Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae and Staphylococcus epidermidis) and three Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumonia) have been investigated and the results also indicated that the combination of AMPs and traditional antibiotics was a method that could be used against antibiotic resistant pathogens due to a dual mode of action against the cell membranes and the cytoplasmic targets [4]. All results indicated that the combination therapy have significant potential for antimicrobial applications in clinical practice. Peptides and traditional antibiotics in combination therapy may become a new treatment strategy.

In summary, antimicrobial resistance is not a new problem but one that is becoming more dangerous. Thus, the development of new antibiotics or new treatment strategies is urgent. On one hand, using de novo design approach, more AMPs have been developed as novel antibiotics agents, although the development of peptide therapeutics has numerous challenges need to overcome; on the other hand, the application of combination therapy of AMPs and traditional antibiotics may be very potent to reduce the emerge rate of multi-drug resistant. We believe that these methods will bring the gospel to the health of the human.

 

References:

[1] H.C. Neu, The crisis in antibiotic resistance, Science, 257 (1992) 1064-1073.

[2] Y. Huang, Q. Feng, Q. Yan, X. Hao, Y. Chen, Alpha-helical cationic anticancer peptides: a promising candidate for novel anticancer drugs, Mini Rev Med Chem, 15 (2015) 73-81.

[3] Y. Huang, J. Huang, Y. Chen, Alpha-helical cationic antimicrobial peptides: relationships of structure and function, Protein Cell, 1 (2010) 143-152.

[4] Q. Feng, Y. Huang, M. Chen, G. Li, Y. Chen, Functional synergy of alpha-helical antimicrobial peptides and traditional antibiotics against Gram-negative and Gram-positive bacteria in vitro and in vivo, Eur J Clin Microbiol Infect Dis, 34 (2015) 197-204.

 

Acknowledgements: This work was supported by the National Natural Science Foundation of China (No. 81373445, Y. X. C. and No. 21442001, Y.B.H), the Natural Science Foundation of Jilin Province (No. 20140101042JC, Y. B. H. and No.20150101189JC,Y.X.C)

 

yuxin chen fig1Contact:

Yuxin Chen, PhD

Porfessor of Biochemistry and Molecular Biology

Key Lab for Molecular Enzymology and Engineering of the Ministry of Education

School of Life Sciences

Jilin University, China

E-mail: chen_yuxin@jlu.edu.cn

 

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