Efficacy of the bee-venom antimicrobial peptide Osmin against sensitive and carbapenem-resistant Klebsiella pneumoniae strains.

The emergence of multidrug-resistant (MDR) Klebsiella pneumoniae strains causes severe problems in the treatment of bacterial infections owing to limited treatment options. Especially, carbapenem-resistant Klebsiella pneumoniae (CRKP) is rapidly spreading worldwide and is emerging as a new cause of drug-resistant healthcare-associated infections. CRKP also has been announced by the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) as one of the most pressing antibiotic resistance threats. Antimicrobial peptides (AMPs) are drawing considerable attention as ideal antibiotic alternative candidates to combat MDR bacterial infections. In a previous study, Osmin is composed of 17 amino acids and is isolated from solitary bee (Osmia rufa) venom. Herein, we evaluated the potential of Osmin to be used against drug-resistant K. pneumoniae as an alternative to conventional antibiotics. Osmin exhibited significant antimicrobial and anti-biofilm activity and lower toxicity than melittin, a well-known bee venom peptide. Additionally, we confirmed that it possesses a bactericidal mechanism that rapidly destroys bacterial membranes. Osmin was relatively more stable than melittin under the influence of various environmental factors and unlike conventional antibiotics, it exhibited a low bacterial resistance risk. During in vivo tests, Osmin reduced bacterial growth and the expression of pro-inflammatory cytokines and fibrosis-related genes in mice with CRKP-induced sepsis. Overall, our results indicate a high potential for Osmin to be used as a valuable therapeutic agent against drug-resistant K. pneumoniae infections.

Neuroprotective Effects of Melittin Against Cerebral Ischemia and Inflammatory Injury via Upregulation of MCPIP1 to Suppress NF-κB Activation In Vivo and In Vitro.

Melittin, a principal constituent of honeybee venom, exhibits diverse biological effects, encompassing anti-inflammatory capabilities and neuroprotective actions against an array of neurological diseases. In this study, we probed the prospective protective influence of melittin on cerebral ischemia, focusing on its anti-inflammatory activity. Mechanistically, we explored whether monocyte chemotactic protein-induced protein 1 (MCPIP1, also known as ZC3H12A), a recently identified zinc-finger protein, played a role in melittin-mediated anti-inflammation and neuroprotection. Male C57/BL6 mice were subjected to distal middle cerebral artery occlusion to create a focal cerebral cortical ischemia model, with melittin administered intraperitoneally. We evaluated motor functions, brain infarct volume, cerebral blood flow, and inflammatory marker levels within brain tissue, employing quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assays, and western blotting. In vitro, an immortalized BV-2 microglia culture was stimulated with lipopolysaccharide (LPS) to establish an inflammatory cell model. Post-melittin exposure, cell viability, and cytokine expression were examined. MCPIP1 was silenced using siRNA in LPS-induced BV-2 cells, with the ensuing nuclear translocation of nuclear factor-κB assessed through cellular immunofluorescence. In vivo, melittin enhanced motor functions, diminished infarction, fostered blood flow restoration in ischemic brain regions, and markedly inhibited the expression of inflammatory cytokines (interleukin-1ß, interleukin-6, tumor necrosis factor-α, and nuclear factor-κB). In vitro, melittin augmented MCPIP1 expression in LPS-induced BV-2 cells and ameliorated inflammation-induced cell death. The neuroprotective effect conferred by melittin was attenuated upon MCPIP1 knockdown. Our findings establish that melittin-induced tolerance to ischemic injury is intrinsically linked with its anti-inflammatory capacity. Moreover, MCPIP1 is, at the very least, partially implicated in this process.

Melittin alleviates sepsis-induced acute kidney injury by promoting GPX4 expression to inhibit ferroptosis.

OBJECTIVES: Melittin, the main component of bee venom, is a natural anti-inflammatory substance, in addition to its ability to fight cancer, antiviral, and useful in diabetes treatment. This study seeks to determine whether melittin can protect renal tissue from sepsis-induced damage by preventing ferroptosis and explore the protective mechanism. METHODS: In this study, we investigated the specific protective mechanism of melittin against sepsis-induced renal injury by screening renal injury indicators and ferroptosis -related molecules and markers in animal and cellular models of sepsis. RESULTS: Our results showed that treatment with melittin attenuated the pathological changes in mice with lipopolysaccharide-induced acute kidney injury. Additionally, we found that melittin attenuated ferroptosis in kidney tissue by enhancing GPX4 expression, which ultimately led to the reduction of kidney tissue injury. Furthermore, we observed that melittin enhanced NRF2 nuclear translocation, which consequently upregulated GPX4 expression. our findings suggest that melittin may be a potential therapeutic agent for the treatment of sepsis-associated acute kidney injury by inhibiting ferroptosis through the GPX4/NRF2 pathway. CONCLUSIONS: Our study reveals the protective mechanism of melittin in septic kidney injury and provides a new therapeutic direction for Sepsis-AKI.

Recent advances in melittin-based nanoparticles for antitumor treatment: from mechanisms to targeted delivery strategies.

As a naturally occurring cytolytic peptide, melittin (MLT) not only exhibits a potent direct tumor cell-killing effect but also possesses various immunomodulatory functions. MLT shows minimal chances for developing resistance and has been recognized as a promising broad-spectrum antitumor drug because of this unique dual mechanism of action. However, MLT still displays obvious toxic side effects during treatment, such as nonspecific cytolytic activity, hemolytic toxicity, coagulation disorders, and allergic reactions, seriously hampering its broad clinical applications. With thorough research on antitumor mechanisms and the rapid development of nanotechnology, significant effort has been devoted to shielding against toxicity and achieving tumor-directed drug delivery to improve the therapeutic efficacy of MLT. Herein, we mainly summarize the potential antitumor mechanisms of MLT and recent progress in the targeted delivery strategies for tumor therapy, such as passive targeting, active targeting and stimulus-responsive targeting. Additionally, we also highlight the prospects and challenges of realizing the full potential of MLT in the field of tumor therapy. By exploring the antitumor molecular mechanisms and delivery strategies of MLT, this comprehensive review may inspire new ideas for tumor multimechanism synergistic therapy.

Exploring potential network pharmacology-and molecular docking-based mechanism of melittin in treating rheumatoid arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a type of difficult-to-cure arthralgia with a worldwide prevalence. It severely affects people's living standards. For a long time, bee venom has been used to treat RA and has shown good results. Melittin is the main active component of bee venom used for RA treatment, but the molecular mechanism of melittin in RA treatments remains unclear. METHODS: Potential melittin and RA targets were obtained from relevant databases, and common targets of melittin and RA were screened. The STRING database was used to build the PPI network and screen the core targets after visualization. The core targets were enriched by Gene Ontology functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway. Finally, the binding of melittin to target proteins was evaluated through simulated molecular docking, which verified the reliability of the prediction results of network pharmacology. RESULTS: In total, 138 melittin targets and 5795 RA targets were obtained from relevant databases, and 90 common targets were obtained through intersection. Eighteen core targets, such as STAT3, AKT1, tumor necrosis factor, and JUN, were screened out. Enrichment analysis results suggested that melittin plays an anti-RA role mainly through tumor necrosis factor, interleukin-17, toll-like receptors, and advanced glycation end products-RAGE signaling pathways, and pathogenic bacterial infection. Molecular docking results suggested that melittin has good docking activity with core target proteins. CONCLUSION: RA treatment with melittin is the result of a multi-target and multi-pathway interaction. This study offers a theoretical basis and scientific evidence for further exploring melittin in RA therapy.

An Updated Review Summarizing the Anticancer Efficacy of Melittin from Bee Venom in Several Models of Human Cancers.

Apitherapy (using bee products) has gained broad recognition in cancer therapeutics globally. Honeybee venom has a broad range of biological potential, and its utilization is rapidly emerging in apitherapy. Bee products have significant potential to strengthen the immune system and improve human health. Thus, this review is targeted toward recapitulating the chemo-preventive potential of melittin (MEL), which constitutes a substantial portion of honeybee venom. Honeybee venom (apitoxin) is produced in the venom gland of the honeybee abdomen, and adult bees utilize it as a primary colony defense mechanism. Apitoxin comprises numerous biologically active compounds, including peptides, enzymes, amines, amino acids, phospholipids, minerals, carbohydrates, and volatile components. We are mainly focused on exploring the potential of melittin (a peptide component) of bee venom that has shown promising potential in the treatment of several human cancers, including breast, stomach, lung, prostate, ovary, kidney, colon, gastric, esophageal, cervical cancers, melanoma, osteosarcoma, and hepatocellular carcinoma. This review has summarized all potential studies related to the anticancerous efficacy of melittin (apitoxin), its formulations, conjugates, and nano-formulations against several human carcinomas, which would further pave the way for future researchers in developing potent drugs for cancer management.

Beneficial Effect of Bee Venom and Its Major Components on Facial Nerve Injury Induced in Mice.

Peripheral nerve injury (PNI) is a health problem that affects many people worldwide. This study is the first to evaluate the potential effect of bee venom (BV) and its major components in a model of PNI in the mouse. For that, the BV used in this study was analyzed using UHPLC. All animals underwent a distal section-suture of facial nerve branches, and they were randomly divided into five groups. Group 1: injured facial nerve branches without any treatment. Group 2: the facial nerve branches were injured, and the normal saline was injected similarly as in the BV-treated group. Group 3: injured facial nerve branches with local injections of BV solution. Group 4: injured facial nerve branches with local injections of a mixture of PLA2 and melittin. Group 5: injured facial nerve branches with local injection of betamethasone. The treatment was performed three times a week for 4 weeks. The animals were submitted to functional analysis (observation of whisker movement and quantification of nasal deviation). The vibrissae muscle re-innervation was evaluated by retrograde labeling of facial motoneurons in all experimental groups. UHPLC data showed 76.90 ± 0.13%, 11.73 ± 0.13%, and 2.01 ± 0.01%, respectively, for melittin, phospholipase A2, and apamin in the studied BV sample. The obtained results showed that BV treatment was more potent than the mixture of PLA2 and melittin or betamethasone in behavioral recovery. The whisker movement occurred faster in BV-treated mice than in the other groups, with a complete disappearance of nasal deviation two weeks after surgery. Morphologically, a normal fluorogold labeling of the facial motoneurons was restored 4 weeks after surgery in the BV-treated group, but no such restoration was ever observed in other groups. Our findings indicate the potential of the use of BV injections to enhance appropriate functional and neuronal outcomes after PNI.

Enhanced Therapeutic Effect of Optimized Melittin-dKLA, a Peptide Agent Targeting M2-like Tumor-Associated Macrophages in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is characterized by a high possibility of metastasis. M2-like tumor-associated macrophages (TAMs) are the main components of the tumor microenvironment (TME) and play a key role in TNBC metastasis. Therefore, TAMs may be a potential target for reducing TNBC metastasis. Melittin-dKLA, a peptide composed of fused melittin and pro-apoptotic peptide d(KLAKLAK)2 (dKLA), showed a potent therapeutic effect against cancers by depleting TAMs. However, melittin has a strong adverse hemolytic effect. Hence, we attempted to improve the therapeutic potential of melittin-dKLA by reducing toxicity and increasing stability. Nine truncated melittin fragments were synthesized and examined. Of the nine peptides, the melittin-dKLA8-26 showed the best binding properties to M2 macrophages and discriminated M0/M1/M2. All fragments, except melittin, lost their hemolytic effects. To increase the stability of the peptide, melittin-dKLA8-26 fragment was conjugated with PEGylation at the amino terminus and was named PEG-melittin-dKLA8-26. This final drug candidate was assessed in vivo in a murine TNBC model and showed superior effects on tumor growth, survival rates, and lung metastasis compared with the previously used melittin-dKLA. Taken together, our study showed that the novel PEG-melittin-dKLA8-26 possesses potential as a new drug for treating TNBC and TNBC-mediated metastasis by targeting TAMs.

Melittin induces ferroptosis and ER stress-CHOP-mediated apoptosis in A549 cells.

Melittin is a natural polypeptide present in bee venom, with significant anti-tumor activity. Melittin has been reported to induce cell death in lung carcinoma cell line A549 cells, suggesting an excellent potential for treating lung cancer. However, the core mechanism underlying melittin-induced cell death in A549 cells remains unclear. This work reports that melittin induces reactive oxygen species (ROS) burst, upregulates intracellular Fe2+ levels, disrupts the glutathione-glutathione peroxidase 4 antioxidant system, and increases lipid peroxide accumulation, eventually inducing cell death, indicating that ferroptosis may be involved in the antitumor effects of melittin in A549 cells. Furthermore, A549 cells treated with the ferroptosis inhibitors ferrostatin-1 and deferoxamine demonstrated that these inhibitors could reverse the cell death induced by melittin, further confirming that melittin induces A549 cell death via ferroptosis. Furthermore, the results also illustrated that melittin activated the endoplasmic reticulum (ER) stress-CHOP (C/EBP homologous protein) apoptotic signal, closely associated with high-level intracellular ROS. The ER stress inhibitor, 4-Phenylbutyric acid, was used to confirm that ER stress-CHOP apoptotic signaling is another molecular mechanism of melittin-induced A549 cell death. Thus, our results demonstrate that ferroptosis and ER stress-CHOP signaling are key molecular mechanisms of melittin-induced cell death in lung cancer.KEY POLICY HIGHLIGHTSMelittin upregulates intracellular Fe2+ levels, leading to the accumulation of lipid peroxides in A549 cells.Melittin disrupts the glutathione-glutathione peroxidase 4 antioxidant system in A549 cells.Melittin induces activation of endoplasmic reticulum stress-C/EBP homologous protein apoptosis signal.Ferroptosis and ER stress are the core molecular mechanisms underlying melittin-induced cell death in A549 cells.

Therapeutic Effect of Bee Venom and Melittin on Skin Infection Caused by Streptococcus pyogenes.

Streptococcus pyogenes (S. pyogenes) bacteria cause almost all primary skin infections in humans. Bee venom (BV) and melittin (Mel) have multiple effects, including antibacterial and anti-inflammatory activities. This study aims to demonstrate their effects on bacterial mouse skin infection using S. pyogenes. The dorsal skin was tape-stripped, then S. pyogenes was topically applied. BV or Mel were topically applied to the lesion. The tissues were stained with hematoxylin and eosin, while immunohistochemical staining was performed with anti-neutrophil. S. pyogenes-infected skin revealed increased epidermal and dermal layers, but it was reduced in the BV and Mel groups. Finding increased neutrophils in the mice infected with S. pyogenes, but the BV and Mel mice showed decreased expression. These results suggest that BV and Mel treatments could reduce the inflammatory reactions and help improve lesions induced by S. pyogenes skin infection. This study provides additional assessment of the potential therapeutic effects of BV and Mel in managing skin infection caused by S. pyogenes, further suggesting that it could be a candidate for developing novel treatment alternative for streptococcal skin infections.

Anticancer Activity of Bee Venom Components against Breast Cancer.

While the survival rate has increased due to treatments for breast cancer, the quality of life has decreased because of the side effects of chemotherapy. Various toxins are being developed as alternative breast cancer treatments, and bee venom is drawing attention as one of them. We analyzed the effect of bee venom and its components on breast cancer cells and reviewed the mechanism underlying the anticancer effects of bee venom. Data up to March 2022 were searched from PubMed, EMBASE, OASIS, KISS, and Science Direct online databases, and studies that met the inclusion criteria were reviewed. Among 612 studies, 11 were selected for this research. Diverse drugs were administered, including crude bee venom, melittin, phospholipase A2, and their complexes. All drugs reduced the number of breast cancer cells in proportion to the dose and time. The mechanisms of anticancer effects included cytotoxicity, apoptosis, cell targeting, gene expression regulation, and cell lysis. Summarily, bee venom and its components exert anticancer effects on human breast cancer cells. Depending on the mechanisms of anticancer effects, side effects are expected to be reduced by using various vehicles. Bee venom and its components have the potential to prevent and treat breast cancer in the future.

Enhanced healing efficacy of an optimized gabapentin-melittin nanoconjugate gel-loaded formulation in excised wounds of diabetic rats.

The present study aimed to design and optimize, a nanoconjugate of gabapentin (GPN)-melittin (MLT) and to evaluate its healing activity in rat diabetic wounds. To explore the wound healing potency of GPN-MLT nanoconjugate, an in vivo study was carried out. Diabetic rats were subjected to excision wounds and received daily topical treatment with conventional formulations of GPN, MLT, GPN-MLT nanoconjugate and a marketed formula. The outcome of the in vivo study showed an expedited wound contraction in GPN-MLT-treated animals. This was confirmed histologically. The nanoconjugate formula exhibited antioxidant activities as evidenced by preventing malondialdehyde (MDA) accumulation and superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzymatic exhaustion. Further, the nanoconjugate showed superior anti-inflammatory activity as it inhibited the expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). This is in addition to enhancement of proliferation as indicated by increased expression of transforming growth factor-ß (TGF- ß), vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor receptor-ß (PDGFRB). Also, nanoconjugate enhanced hydroxyproline concentration and mRNA expression of collagen type 1 alpha 1 (Col 1A1). In conclusion, a GPN-MLT nanoconjugate was optimized with respect to particle size. Analysis of pharmacokinetic attributes showed the mean particle size of optimized nanoconjugate as 156.9 nm. The nanoconjugate exhibited potent wound healing activities in diabetic rats. This, at least partly, involve enhanced antioxidant, anti-inflammatory, proliferative and pro-collagen activities. This may help to develop novel formulae that could accelerate wound healing in diabetes.

Evaluation of the therapeutic effect of melittin peptide on the ulcerative colitis mouse model.

BACKGROUND: Ulcerative colitis (UC) is considered one of the most prevalent inflammatory bowel diseases (IBDs). However, due to the lack of satisfying efficacy of conventional therapies and their side effects, there is still a need for more efficient therapeutic agents. Melittin is a small peptide derived from bee venom, which shows potent anti-inflammatory activity. The present investigation aimed to assess the anti-inflammatory effect of melittin peptide alone and in co-therapy with sulfasalazine as a standard therapy on dextran sulfate sodium (DSS)-induced colitis models. MATERIAL AND METHODS: We used DSS to induce UC in C57BL/6 male mice. We investigated the effect of melittin peptide alone and in combination with sulfasalazine on improving the clinical symptoms among DSS-induced colitis models. Finally, we employed histological investigation to show the therapeutic effect of melittin on attenuating the pathological damage of colon tissue caused due to DSS-induced inflammation in colitis models. RESULTS: Our findings demonstrated that melittin peptide alone and in combination with sulfasalazine dramatically cured the clinical UC. Moreover, we observed that this peptide almost eliminated the histological damage of colon tissue in colitis, while significantly reducing the inflammation in colon tissue. Meanwhile, our results demonstrated that this peptide had an antioxidant effect through the disruption of the oxidant/antioxidant balance. CONCLUSION: All these findings suggest that melittin peptide has an anti-inflammatory effect and can probably be considered a novel therapeutic agent for UC. Furthermore, our results demonstrated that this peptide can enhance the therapeutic effects of conventional therapy while attenuating the adverse effects of conventional agents.

Gramicidin S and melittin: potential anti-viral therapeutic peptides to treat SARS-CoV-2 infection.

The COVID19 pandemic has led to multipronged approaches for treatment of the disease. Since de novo discovery of drugs is time consuming, repurposing of molecules is now considered as one of the alternative strategies to treat COVID19. Antibacterial peptides are being recognized as attractive candidates for repurposing to treat viral infections. In this study, we describe the anti-SARS-CoV-2 activity of the well-studied antibacterial peptides gramicidin S and melittin obtained from Bacillus brevis and bee venom respectively. The EC50 values for gramicidin S and melittin were 1.571 µg and 0.656 µg respectively based on in vitro antiviral assay. Significant decrease in the viral load as compared to the untreated group with no/very less cytotoxicity was observed. Both the peptides treated to the SARS-CoV-2 infected Vero cells showed viral clearance from 12 h onwards with a maximal viral clearance after 24 h post infection. Proteomics analysis indicated that more than 250 proteins were differentially regulated in the gramicidin S and melittin treated SARS-CoV-2 infected Vero cells against control SARS-CoV-2 infected Vero cells after 24 and 48 h post infection. The identified proteins were found to be associated in the metabolic and mRNA processing of the Vero cells post-treatment and infection. Both these peptides could be attractive candidates for repurposing to treat SARS-CoV-2 infection.

Therapeutic Effect of Melittin-dKLA Targeting Tumor-Associated Macrophages in Melanoma.

Melanoma is an immunogenic tumor and a serious type of skin cancer. Tumor-associated macrophages (TAMs) express an M2-like phenotype and are involved in all stages of melanomagenesis; it is hence a promising target for cancer immunotherapy. We herein investigated whether melittin-dKLA inhibits the growth of melanoma by inducing apoptosis of M2-like macrophages. For the in vitro study, a conditioned medium of macrophages was prepared from M0, M1, or M2-differentiated THP-1 cells with and without melittin-dKLA. The affinity of melittin for M2 macrophages was studied with FITC (fluorescein isothiocyanate)-conjugated melittin. For the in vivo study, murine melanoma cells were inoculated subcutaneously in the right flank of mice, melittin-dKLA was intraperitoneally injected at 200 nmol/kg every three days, and flow cytometry analysis of TAMs was performed. Since melittin binds preferentially to M2-like macrophages, melittin-dKLA induced more caspase 3 expression and cell death in M2 macrophages compared with M0 and M1 macrophages and melanoma cells. Melittin-dKLA significantly inhibited the proliferation and migration of M2 macrophages, resulting in a decrease in melanoma tumor growth in vivo. The CD206+ M2-like TAMs were reduced, while the CD86+ M1-like TAMs were not affected. Melittin-dKLA is therapeutically effective against melanoma by inducing the apoptosis of M2-like TAMs.

The bee venom active compound melittin protects against bicuculline-induced seizures and hippocampal astrocyte activation in rats.

Epilepsy is a chronic neuropathology characterized by an abnormal hyperactivity of neurons that generate recurrent, spontaneous, paradoxical and synchronized nerve impulses, leading or not to seizures. This neurological disorder affects around 70 million individuals worldwide. Pharmacoresistance is observed in about 30% of the patients and long-term use of antiepileptics may induce serious side effects. Thus, there is an interest in the study of the therapeutic potential of bioactive substances isolated from natural products in the treatment of epilepsy. Arthropod venoms contain neurotoxins that have high affinity for molecular structures in the neural tissue such as receptors, transporters and ion channels both in glial and neuronal membranes. This study evaluated the potential neuroprotective effect of melittin (MEL), an active compound of bee venom, in the bicuculline-induced seizure model (BIC) in rats. Male Wistar rats (3 months, 250-300 g) were submitted to surgery for the implantation of a unilateral cannula in the lateral ventricle. After the recovery period, rats received a microinjection of saline solution or MEL (0.1 mg per animal). Firstly, rats were evaluated in the open field (20 min) and in the elevated plus maze (5 min) tests after received microinjection of saline or MEL. After, 30 min later animals received BIC (100 mg/ml) or saline, and their behaviors were analyzed for 20 min in the open field according to a seizure scale. At the end, rats were euthanized, brains collected and processed to glial fibrillary acidic protein (GFAP) immunohistochemistry evaluation. No changes were observed in MEL-treated rats in the open field and elevated plus maze. However, 90% of MEL-treated animals were protected against seizures induced by BIC. There was an increase in the latency for the onset of seizures, accompanied by a reduction of GFAP-immunoreactivity cells in the dentate gyrus and CA1. Thus, our study suggests that MEL has an anticonvulsant potential, and further studies are needed to elucidate the mechanisms involved in this action.

Bottlebrush Polymer-Conjugated Melittin Exhibits Enhanced Antitumor Activity and Better Safety Profile.

Despite potency against a variety of cancers in preclinical systems, melittin (MEL), a major peptide in bee venom, exhibits non-specific toxicity, severe hemolytic activity, and poor pharmacological properties. Therefore, its advancement in the clinical translation system has been limited to early-stage trials. Herein, we report a biohybrid involving a bottlebrush-architectured poly(ethylene glycol) (PEG) and MEL. Termed pacMEL, the conjugate consists of a high-density PEG arrangement, which provides MEL with steric inhibition against protein access, while the high molecular weight of pacMEL substantially enhances plasma pharmacokinetics with a ∼10-fold increase in the area under the curve (AUC∞) compared to free MEL. pacMEL also significantly reduces hepatic damage and unwanted innate immune response and all but eliminated hemolytic activities of MEL. Importantly, pacMEL passively accumulates at subcutaneously inoculated tumor sites and exhibits stronger tumor-suppressive activity than molecular MEL. Collectively, pacMEL makes MEL a safer and more appealing drug candidate.

Molecular characterization of the anticancer properties associated with bee venom and its components in glioblastoma multiforme.

Glioblastoma multiforme (GBM) is a frequent form of malignant glioma. Strategic therapeutic approaches to treat this type of brain tumor currently involves a combination of surgery, radiotherapy and chemotherapy. Nevertheless, survival of GBM patients remains in the 12-15 months range following diagnosis. Development of novel therapeutic approaches for this malignancy is therefore of utmost importance. Interestingly, bee venom and its components have shown promising anti-cancer activities in various types of cancer even though information pertaining to GBMs have been limited. The current work was thus undertaken to better characterize the anti-cancer properties of bee venom and its components in Hs683, T98G and U373 human glioma cells. MTT-based cell viability assays revealed IC50 values of 7.12, 15.35 and 7.60 µg/mL for cell lines Hs683, T98G and U373 treated with bee venom, respectively. Furthermore, melittin treatment of these cell lines resulted in IC50 values of 7.77, 31.53 and 12.34 µg/mL, respectively. Cell viability assessment by flow cytometry analysis confirmed signs of late apoptosis and necrosis after only 1 h of treatment with either bee venom or melittin in all three cell lines. Immunoblotting-based quantification of apoptotic markers demonstrated increased expression of Bak and Bax, while Caspsase-3 levels were significantly lower when compared to control cells. Quantification by qRT-PCR showed increased expression levels of long non-coding RNAs RP11-838N2.4 and XIST in glioma cells treated with either bee venom or melittin. Overall, this study provides preliminary insight on molecular mechanisms via which bee venom and its main components can impact viability of glioma cells and warrants further investigation of its anticancer potential in gliomas.

In vitro and in vivo toxicity and antibacterial efficacy of melittin against clinical extensively drug-resistant bacteria.

BACKGROUND: Melittin is one of the most studied antimicrobial peptides, and several in vitro experiments have demonstrated its antibacterial efficacy. However, there is evidence showing melittin has non-promising effects such as cytotoxicity and hemolysis. Therefore, concerns about unwanted collateral toxicity of melittin lie ahead in the path toward its clinical development. With these considerations, the present study aimed to fill the gap between in vitro and in vivo studies. METHODS: In the first step, in vitro toxicity profile of melittin was assessed using cytotoxicity and hemolysis tests. Next, a maximum intraperitoneal (i.p.) sub-lethal dose was determined using BALB/c mice. Besides toxicity, antimicrobial efficacy of melittin against extensively drug-resistant (XDR) Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus (MRSA), and KPC-producing Klebsiella pneumonia (KPC-KP) pathogens were tested using both in vitro and in vivo methods. RESULTS: Melittin showed extensive hemolysis (HD50 = 0.44 µg/mL), and cytotoxicity (IC50 = 6.45 µg/mL) activities with i.p. LD50 value of 4.98 mg/kg in BALB/c mice. In vitro antimicrobial evaluation showed melittin MIC range from 8 to 32 µg/mL for the studied pathogens. Treatment of infected mice with repeated sub-lethal doses of melittin (2.4 mg/kg) displayed no beneficial effect on their survival and peritoneal bacterial loads. CONCLUSIONS: These results indicate that melittin at its safe dose could not exhibit antimicrobial activity, which hinders its application in clinical practice.