Khaled Hani

Dermaseptins and Magainins: Antimicrobial Peptides from Frogs' Skin—New Sources for a Promising Spermicides Microbicides—A Mini Review

Sexually transmitted infections (STIs) and human immunodeficiency virus (HIV), the causative agents of acquired immunodeficiency syndrome (AIDS), are two great concerns in the reproductive health of women. Thus, the challenge is to find products with a double activity, on the one hand having antimicrobial/antiviral properties with a role in the reduction of STI, and on the other hand having spermicidal action to be used as a contraceptive. In the absence of an effective microbicide along with the disadvantages of the most commonly used spermicidal contraceptive worldwide, nonoxynol-9, new emphasis has been focused on the development of more potential intravaginal microbicidal agents. Topical microbicides spermicides would ideally provide a female-controlled method of self-protection against HIV as well as preventing pregnancies. Nonoxynol-9, the only recommended microbicide spermicide, damages cervicovaginal epithelium because of its membrane-disruptive properties. Clearly, there is an urgent need to identify new compounds with dual potential microbicidal properties; antimicrobial peptides should be candidates for such investigations. Dermaseptins and magainins are two classes of cationic, amphipathic α-helical peptides that have been identified in the skin extracts of frogs Phyllomedusa sauvagei and Xenopus laevis. Regarding their contraceptive activities and their effect against various STI-causing pathogens, we believe that these two peptides are appropriate candidates in the evaluation of newer and safer microbicides spermicides in the future.

In vitro antiviral activity of dermaseptin S(4) and derivatives from amphibian skin against herpes simplex virus type 2.

Herpes simplex virus (HSV) infections have become a public health problem worldwide. The emergence of acyclovir‐resistant viral strains and the failure of vaccination to prevent herpetic infections have prompted the search for new antiviral drugs. Accordingly, the present study was undertaken to synthesize chemically and evaluate Dermaseptin S4 (S4), an anti‐microbial peptide derived from amphibian skin, and its derivatives in terms of anti‐herpetic activity. The effects of biochemical modifications on their antimicrobial potential were also investigated. The peptides were incubated together with HSV‐2 on target cells under various conditions, and the antiviral effects were examined via a cell metabolic labeling method. The findings revealed that DS4 derivatives elicited concentration‐dependent antiviral activity at micromole concentrations. The biochemical modifications of S4 allowed for the reduction of peptide cytotoxicity without altering antiviral activity. Dermaseptins were added at different times during the viral cycle to investigate the mode of antiviral action. At the highest non‐cytotoxic concentrations, most of the tested derivatives were noted to exhibit high antiviral activity particularly when pre‐incubated with free herpes viruses prior to infection. Among these peptides, K4K20S4 exhibited the highest antiviral activity against HSV‐2 sensitive and resistant strains. Interestingly, the antiviral activity of K4K20S4 was effective on both acyclovir‐resistant and ‐sensitive viruses. The findings indicate that K4K20S4 can be considered a promising candidate for future application as a therapeutic virucidal agent for the treatment of herpes viruses. J. Med. Virol. 85:272–281, 2013.

In vitro activity of dermaseptin S4 derivatives against genital infections pathogens

OBJECTIVES Sexually transmitted infections present a great risk to the reproductive health of women. Therefore, female-controlled vaginal products directed toward disease prevention are needed urgently. In the present study, efforts were made to evaluate the antimicrobial potency of dermaseptin DS4, an antimicrobial peptide derived from frog skin. To assess the structure-activity relationship between the native DS4 and their derivatives, a set of chemically modified peptides was synthesized and evaluated. METHODS Different strains of bacteria and fungi were used to detect the antimicrobial activity of the new compounds. HeLa cultures were used to determine the safety of compounds towards their toxicity. RESULTS All DS4 derivatives elicited concentration-dependent antimicrobial activity at micrograms concentrations (MIC values: 4 microg/mL-l mg/mL). K4S4(1-28) and K4S4(1-16)a were the most active peptides whereas S4(6-28) was the less one. The order was K4S4(1-28)>K4S4(1-16)a>S4a>S4>S4(6-28). In cytotoxicity assay, some compounds were found to be significantly safer than current antibiotics. Our data also show that increasing the number of positive charges of the peptide resulted in a reduced cytotoxicity without affecting the antimicrobial effect. CONCLUSIONS This study indicates that dermaseptins are antimicrobial molecules that deserve to be tested as topical microbicide with useful associated activities that can add to their prophylaxis, safety and effectiveness.

Bilateral renal infarction following atrial fibrillation and thromboembolism and presenting as acute abdominal pain: a case report

IntroductionRenal infarct is rare and often misdiagnosed because the symptoms are misleading. The mechanisms are various, mainly thrombotic and embolic.Case presentationIn this review, we report the case of a 61-year-old Tunisian woman presented to the emergency unit with a 4-hour history of abdominal pain diffused at both flanks, ultrasounds was performed to remove a surgical emergency, showed a peri-renal fluid collection with heterogeneous parenchyma.We followed by a CT scan, which confirmed the diagnosis of renal infarct. The patient was treated by heparin at a curative dose, and the outcome was favorable.ConclusionDiagnosis is difficult and should be considered in patients with inexplicable flank or abdominal pain and with risk factors to this disease. Our purpose is to raise clinician’s awareness for this condition so that they will be more likely to diagnose it. This will facilitate prompt diagnosis and treatment.A review of the literature was performed and the case is discussed in the context of the current knowledge of this condition.

In Vitro Activities of Dermaseptins K4S4 and K4K20S4 against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa Planktonic Growth and Biofilm Formation

ABSTRACT The rising number of infections caused by biofilm formation and the difficulties associated with their treatment by conventional antimicrobial therapies have led to an intensive search for novel antibiofilm agents. Dermaseptins are antimicrobial peptides with a number of attractive properties that might offer alternative therapies against resistant microorganisms. In this study, we synthesized a set of dermaseptin-derived peptides and evaluated their activities against Gram-positive and Gram-negative bacterial biofilm formation. All dermaseptin-derived peptides demonstrated concentration-dependent antibiofilm activities at microgram concentrations, and their activities were dependent on the nature of the peptides, with the highest levels of activity being exhibited by highly charged molecules. Fluorescent binding and confocal microscopy demonstrated that dermaseptin K4S4, a substituted derivative of the native molecule S4, significantly decreased the viability of planktonic and surface-attached bacteria and stopped biofilm formation under dynamic flow conditions. Cytotoxicity assays with HeLa cells showed that some of the tested peptides were less cytotoxic than current antibiotics. Overall, these findings indicate that dermaseptin derivatives might constitute new lead structures for the development of potent antibiofilm agents.

Dermaseptin S4 derivative K4K20S4: A potential candidate for development of a new microbicide contraceptive agent – an in vitro study

ABSTRACT Background and objectives Sexually transmitted infections (STIs) and unplanned pregnancies have serious effects on the reproductive health of women. The present study was undertaken with a view to develop an effective means of prevention. The microbicidal and contraceptive potential of cationic peptides from frogs skin, namely, dermaseptin S4 and its derivatives were investigated in vitro. Study design Different bacterial and fungal strains were resorted to for determining the antimicrobial activity of the new compounds. The spermicidal activities of the latter were assessed using normal human semen samples, and their toxic effects were identified in a HeLa culture. Results All S4 derivatives elicited concentration-dependent spermicidal and antimicrobial activities at microgram concentrations. The highest levels recorded for both types of activity were displayed by K4K20S4, and the lowest levels were exhibited by D4D20S4 and S4(5–28). Cytotoxicity assays revealed that some of these compounds were significantly safer than nonoxynol-9 (N-9). Conclusions The ability of these peptides to instantaneously kill human sperm and STI pathogens at low concentrations indicates that their application as active ingredients in vaginal contraceptive preparations could induce considerably better effects than N-9.

Antiviral and antifungal activity of some dermaseptin S4 analogues

Dermaseptins are peptides found in skin secretions of Phyllomedusinae frogs. These peptides exert lytic action on various microorganisms, and do not have a considerable haemolytic effect apart from dermaseptin S4 (DS-S4) that presents a potent cytotoxic effect. This investigation was an attempt to synthesize several biochemically modified, shorter bioactive analogues of DRS-S4, and to improve its biological profile with respect to that of the parent peptide. Peptides were synthesized and then tested on fungi ( Cryptococcus neoformans and Aspergillus fumigatus ) and viruses (HSV-1). Our results show that the N-terminus is necessary for the antifungal activity of peptide, but antiviral effect is determined by C-terminal domain and/or entire peptide sequence. Key words: Antimicrobial peptides, dermaseptin, structure-activity relationship, peptide synthesis.

Dermaseptins as potential antirabies compounds

Over the last 20 years, natural peptides playing a key role in defense mechanisms and innate immunity have been isolated from unicellular organisms. Amphibian skin secretes dermaseptins, 24-34 amino acids in length that have a wide antimicrobial spectrum incorporating yeast, fungi, protozoa, bacteria and enveloped viruses. The anti-rabies virus (RABV) activity of dermaseptins S3 (30aa) and S4 (28aa) from Phyllomedusa sauvagei has been investigated, and further dissected its molecular basis by comparing punctual mutation or deletion of S4 analogues. The results showed that: (1) S4 is more active than S3 against RABV infection, 89% versus 38% inhibition at 7.5 μM; (2) the 5 NH2-aa of S4 are crucial for its inhibitory potential (S46-28 lost any inhibition) but the COOH terminus stabilizes the inhibitory potential (S41-16 showed only 23% inhibition at 7.5 μM); (3) there is a correlation between viral inhibition and dermaseptin cytotoxicity, which remains however moderated for BSR cells (≤12% at 10 μM). A single mutation in position 4 (S4M4K) slightly reduced cytotoxicity while keeping its antiviral activity, 97% at 7.5 μM. S4 and S4M4K showed an antiviral activity in vitro when provided 1 h after infection. In vivo experiments in mice by intramuscular injection of non-toxic doses of dermaseptin S4M4K 1 h post-infection by a lethal dose of RABV at the same site allowed more than 50% improvement in mice survival. This study highlights the potential interest of dermaseptins as non-expansive alternatives to rabies immunoglobulins for the treatment of rabies that continues to claim about 60,000 human lives per year worldwide, almost exclusively in developing countries.