Human Intestinal Defensin 5 Ameliorates the Sensitization of Colonic Cancer Cells to 5-Fluorouracil

BACKGROUND AND AIM

The increasing dilemma of multidrug-resistant cancer cells in response to currently available chemotherapeutic drugs and their associated side effect(s), calls for the investigation of alternative anticancer advances and molecules. Therefore, the present study aimed to elucidate the combinatorial potential against colon cancer of human defensin 5 in combination with 5-fluorouracil (5-FU), and against 5-FU resistant colon tumor cells.

METHODS

The in vivo combinatorial potential of HD-5 with 5-FU was elucidated in terms of tumor morphometrics, apoptosis assay, surface morphology histology of the colon(s), and transcriptional alterations. Changes in membrane dynamics with mucin expression were evaluated by fluorescence microscopy and histochemistry. The in vitro activity of the peptide/drug conjunction was explored by phase contrast microscopy, MTT, LDH assay, and AO/EtBr staining. Chemoresistance to 5-FU was determined by phase contrast microscopy, MTT assay, annexin V-FITC/PI flow cytometry, and MDR-1, Bak, and Bax expression.

RESULTS

In vivo decreases in tumor parameters, with a marked increase in apoptosis and neutrophil infiltrations indicated restoration of normal architecture with improved mucin content in the treated colons. This happened with substantial changes in key molecular markers of the intrinsic apoptotic cascade. Membrane dynamics revealed that peptides and chemotherapeutic drugs could bind to cancerous cells by taking advantage of altered levels of membrane fluidity.

CONCLUSION

Peptide treatment of drug-resistant Caco-2 cells promotes enhanced 5-FU uptake, in contrast to when cells were treated with 5-FU alone. Hence, HD-5 as an adjunct to 5-FU, exhibited strong cancer cell killing even against 5-FU-resistant tumorigenic cells.

Strategic Approaches to Improvise Peptide Drugs as Next Generation Therapeutics

In recent years, the occurrence of a wide variety of drug-resistant diseases has led to an increase in interest in alternate therapies. Peptide-based drugs as an alternate therapy hold researchers' attention in various therapeutic fields such as neurology, dermatology, oncology, metabolic diseases, etc. Previously, they had been overlooked by pharmaceutical companies due to certain limitations such as proteolytic degradation, poor membrane permeability, low oral bioavailability, shorter half-life, and poor target specificity. Over the last two decades, these limitations have been countered by introducing various modification strategies such as backbone and side-chain modifications, amino acid substitution, etc. which improve their functionality. This has led to a substantial interest of researchers and pharmaceutical companies, moving the next generation of these therapeutics from fundamental research to the market. Various chemical and computational approaches are aiding the production of more stable and long-lasting peptides guiding the formulation of novel and advanced therapeutic agents. However, there is not a single article that talks about various peptide design approaches i.e., in-silico and in-vitro along with their applications and strategies to improve their efficacy. In this review, we try to bring different aspects of peptide-based therapeutics under one article with a clear focus to cover the missing links in the literature. This review draws emphasis on various in-silico approaches and modification-based peptide design strategies. It also highlights the recent progress made in peptide delivery methods important for their enhanced clinical efficacy. The article would provide a bird's-eye view to researchers aiming to develop peptides with therapeutic applications.

Graphical Abstract

Organogel mediated co-delivery of nisin and 5-fluorouracil: a synergistic approach against skin cancer

AIM

The present study aimed to develop topical combinatorial therapy of nisin and 5-fluorouracil in a single nanosized formulation against skin cancer.

METHODS

Nisin and 5-fluorouracil were encapsulated in an organogel system (NF-OG) and investigated for morphology, physicochemical properties, cytotoxicity, encapsulation and release. NF-OG was evaluated against DMBA/TPA murine skin cancer in terms of tumour statistics, histoarchitecture, TUNEL and M1/M2 macrophages.

RESULTS

The optimised NF-OG formulation exhibited particle size of 185.1 ± 11.24 nm, zeta potential of -7.93 ± 0.60 mV, offered substantial drug loading and temporal release. NF-OG therapy led to improved cytotoxicity of nisin and 5-FU against B16-F10 cells, significant decrease in tumour volume (84.983 mm³) in treated group as compared to untreated group (490.482 mm³) accompanied by restoration of histoarchitecture and repolarization of macrophages.

CONCLUSION

The study yielded a promising delivery system exhibiting potent anticancer activity and forms the bases for further applications in clinical settings.

Potential of 1-(1-napthylmethyl)-piperazine, an efflux pump inhibitor against cadmium-induced multidrug resistance in Salmonella enterica serovar Typhi as an adjunct to antibiotics

This study was focused on elucidating inhibition of antibiotic efflux mechanism of cadmium adapted (CdA) Salmonella Typhi Ty2 cells. Herein, upregulated expression of efflux genes (acrB, tolC) and their regulators (soxS, marA) was observed in CdA Ty2 cells by qRT-PCR. The pathogen further elevated the expression of these genes even in the presence of three efflux pump inhibitors (EPIs), i.e., Phe-Arg-β-naphthylamide, 1-(1-naphthyl-methyl)piperazine, and 5-hydroxy-2-methyl-1,4-naphthoquinone, perhaps by sensing the pressure of the latter in addition to cadmium stress. Interaction of different EPIs with efflux pumps of CdA Ty2 cells was confirmed using ethidium bromide (EtBr) accumulation and efflux assay. All the EPIs could cause retention of EtBr which was indicated by increased fluorescence units. Considering this potential of EPIs, retention of antibiotics was evaluated in CdA Ty2 cells wherein EPIs were used in combination with selected antibiotics (instead of EtBr). A decrease in the effective concentration of antibiotics was observed. This was further validated using the clinical isolates. The data revealed the efficiency of EPIs as they could inhibit the efflux potential of even the overexpressed efflux pumps. Thus, combination of EPI(s)-antibiotics may be exploited in future as one of the strategies for combating metal induced antibiotic resistance.

Doxorubicin-Loaded Mixed Micelles for the Effective Management of Skin Carcinoma: In Vivo Anti-Tumor Activity and Biodistribution Studies

Skin cancer is an alarming concern due to increased radiation and chemical exposure. Doxorubicin is a drug prescribed for various cancers by parenteral route. Apart from the pharmaceutical challenge of being a biopharmaceutical classification system (BCS) Class III drug, the side effects of doxorubicin are also a great concern. With an aim to enhance its safety and bioavailability, a phospholipid-based micellar system was developed. The developed nanometric and symmetric carriers not only offered substantial drug loading, but also offered a temporal drug release for longer durations. The pH-dependent drug release assured the spatial delivery at the target site, without loss of drug in the systemic circulation. The cancer cell toxicity studies along with the in vivo anti-tumor studies established the superior efficacy of the developed system. The blood profile studies and the biochemical estimations confirmed the safety of the developed nanocarriers. Lesser amount of drug was available for the microsomal degradation, as inferred by the biodistribution studies. The findings provide a proof of concept for the safer and effective doxorubicin delivery employing simple excipients like phospholipids for the management of skin cancer.

Nisin loaded carbopol gel against Pseudomonas aeruginosa infected third-degree burns: A therapeutic intervention

The emergence of multidrug resistant strains of Pseudomonas aeruginosa necessitates the exploration of novel therapeutic intervention (s). The present study aimed to develop a nisin loaded carbopol gel formulation (NLCG) and explore its therapeutic efficacy against P. aeruginosa infected burn wounds. The formulation was prepared using Carbopol 940 as a polymer and characterized in terms of its appearance, stability, pH, rheology, spreadability, release, and permeation profiles. Disc diffusion assay and field emission scanning electron microscopy were carried out to establish in vitro antibacterial activity while the in vitro cytotoxicity was evaluated by hemolytic and trypan blue exclusion assay. Furthermore, in vivo efficacy was investigated by developing P. aeruginosa infected third-degree murine burn wound model followed by evaluation of parameters like bacterial loads, skin restoration, histopathological architecture, levels of hydroxyproline, myeloperoxidase and cytokines. Our studies yielded a stable formulation with pH, viscosity and drug release flux values as 6.5 ± 0.02, 382.4 p and 160.55 ± 3.64 μg h^-1  cm^-2 , respectively. Approximately, 84.02 ± 1.63% of nisin was found to permeate into murine skin, further, affirmed by confocal microscopic observations. Interestingly, no in vitro cytotoxicity of NLCG (to erythrocytes and/or to peritoneal macrophages) could be observed. The log units decrease (s) in CFUs of Pseudomonas in skin were found to be 1.5137, 4.2257, 6.456 after 12, 24 and 72 h of topical gel therapy, respectively. Percentage wound closure, tensile strength, histological, and scanning electron microscopic studies further provided a healing evidence with skin showing restoration of the epithelium. The gel therapy also led to a significant modulation (p ≤ 0.05) in hydroxyproline content, myeloperoxidase levels, and serum levels of IL-1, IL-10, and TNF-α. Our formulation revealed anti-Pseudomonas, wound healing, and immunomodulatory efficacy of NLCG. Further investigations are warranted to determine the underlying mechanism (s) of these displayed antibacterial and immunomodulatory effects.

Antimicrobial peptides against colorectal cancer-a focused review

Despite recent advances in the treatment of colorectal cancer (CRC), low patient survival rate due to emergence of drug resistant cancer cells, metastasis and multiple deleterious side effects of chemotherapy, is a cause of public concern globally. To negate these clinical conundrums, search for effective and harmless novel molecular entities for the treatment of CRC is an urgent necessity. Since antimicrobial peptides (AMPs) are part of innate immunity of living beings, it is quite imperative to look for essential attributes of these peptides which may contribute to their effectiveness against carcinogenesis. Once identified, those characteristics can be suitably modified using several synthetic and computational techniques to further enhance their selectivity and pharmacokinetic profiles. Hence, this review analyses scientific reports describing the antiproliferative action of AMPs derived from several sources, particularly focusing on various colon cancer in vitro/in vivo investigations. On perusal of the literature, it appears that AMPs based therapeutics would definitely find special place in CRC therapy in future either alone or as an adjunct to chemotherapy provided some necessary alterations are made in their natural structures to make them more compatible with modern clinical practice. In this context, further in-depth research is warranted in adequate in vivo models.

Anticancer potential of human intestinal defensin 5 against 1, 2-dimethylhydrazine dihydrochloride induced colon cancer: A therapeutic approach

The escalating predicament of multidrug resistant cancer cells and associated side effects of conventional chemotherapy necessitates the exploration of alternative anticancer therapies. The present study evaluated anticancer therapeutic potential of human defensin 5 (HD-5) against colon cancer. The in vivo anticancer efficacy of HD-5 against 1,2-dimethylhydrazine (DMH) induced colon cancer was elucidated in terms of tumor biostatistics, number of aberrant crypt foci (ACF), in situ apoptosis assay,changes in morphological as well as histological architecture of colon(s). The direct interaction of peptide was investigated by incubating peptide with normal and/or cancerous colonocytes followed by phase contrast, Hoechst 3342 and AO/PI staining as well as confocal microscopy. Changes in membrane dynamics were evaluated by MC 540 and N-NBD-PE staining. In vivo decrease(s) in tumor parameters, number of aberrant crypt foci along with marked increase in the rate of apoptosis was observed.H&E staining revealed neutrophils infiltration and restoration of normal architecture in treated colon(s) which was consistent with scanning electron microscopic observations. Furthermore, non-membranolytic mechanism was found to be acquired by peptide as it could traverse cell membrane gaining access to nucleus and cytoplasm thereby disintegrating cellular architecture. MC 540 and NBD-PE staining revealed that peptide could bind to cancerous cells by taking advantage of altered fluidity levels. Our results indicated that HD-5 exhibited strong cancer cell killing and does not affect normal host cells. The peptide can be exploited as promising option to combat developing menace of colon cancer and/or can at least be used as an adjunct to present day chemotherapies.

Exploration of docetaxel palmitate and its solid lipid nanoparticles as a novel option for alleviating the rising concern of multi-drug resistance

Docetaxel (DTX), a widely prescribed anticancer agent, is now associated with increased instances of multidrug resistance. Also, being a problematic BCS class IV drug, it poses challenges for the formulators. Henceforth, it was envisioned to synthesize an analogue of DTX with a biocompatible lipid, i.e., palmitic acid. The in-silico studies (molecular docking and simulation) inferred lesser binding of docetaxel palmitate (DTX-PL) with P-gp vis-à-vis DTX and paclitaxel, indicating it to be a poor substrate for P-gp efflux. Solid lipid nanoparticles (SLNs) of the conjugate were prepared using various lipids, viz. palmitic acid, stearic acid, cetyl palmitate and glyceryl monostearate. The characterization studies for the nanocarrier were performed for the surface charge, drug payload, micromeritics, release pattern of drug and surface morphology. From the cytotoxicity assays on resistant MCF-7 cells, it was established that the new analogue offered substantially decreased IC₅₀ to that of DTX. Further, apoptosis assay also corroborated the results obtained in IC₅₀ determination wherein, SA-SLNs showed the highest apoptotic index than free DTX. The conjugate not only enhanced the solubility but also offered lower plasma protein binding and improved pharmacokinetic and pharmacodynamic effect for DTX loaded SA-SLNs in apt animal models, and lower affinity to P-gp efflux. The studies provide preliminary evidence and a ray of hope for a better candidate in its nano version for safer and effective cancer chemotherapy.

Advanced Approaches of Bioactive Peptide Molecules and Protein Drug Delivery Systems

Despite the fact that protein and peptide therapeutics are widely employed in the treatment of various diseases, their delivery is posing an unembellished challenge to the scientists. It was discovered that delivery of these therapeutic systems through oral route is easy with high patient compliance. However, proteolytic degradation and absorption through the mucosal epithelium are the barriers in this route. These issues can be minimized by the use of enzyme inhibitors, absorption enhancers, different carrier systems or either by direct modification. In the process of investigation, it was found that transdermal route is not posing any challenges of enzymatic degradation, but, still absorption is the limitation as the outer layer of skin acts as a barrier. To suppress the effect of the barrier and increase the rate of the absorption, various advanced technologies were developed, namely, microneedle technology, iontophoresis, electroporation, sonophoresis and biochemical enhancement. Indeed, even these molecules are targeted to the cells with the use of cell-penetrating peptides. In this review, delivery of the peptide and protein therapeutics using oral, transdermal and other routes is discussed in detail.

Augmented antibiotic resistance associated with cadmium induced alterations in Salmonella enterica serovar Typhi

In view of the reports on co-selection of metal and antibiotic resistance, recently we have reported that increased cadmium accumulation in Salmonella Typhi Ty2 leads to increased antibiotic resistance. In continuation, the present study was carried to substantiate this association in clinical isolates. Interestingly, the levels of cadmium were found to be more in the clinical isolates which co-related with their antibiotic sensitivity/resistance pattern. On cadmium accumulation, antibiotic(s) sensitive isolates were rendered resistant and the resistant isolates were rendered more resistant as per their minimum inhibitory concentration(s). Further, after subjecting the pathogen to cadmium accumulation, alterations occurring in the cells were assessed. Transgenerational cadmium exposure led to changes in growth response, morphology, proteome, elevated antioxidants other than SOD, increased biofilm formation, decreased intracellular macrophage killing coupled with upregulation of genes encoding metallothionein and metal transporters. Thus, these results indicate that cadmium, if acquired from the environment, being non-degradable can exert a long-lasting selective pressure on Salmonella in the host which may display antibiotic resistance later on, as a result of co-selection. Therefore, appropriate strategies need to be developed to inhibit such an enduring pressure of heavy metals, as these represent one of the factors for the emerging antibiotic resistance in pathogens.

Management of Staphylococcus Mediated Systemic Infection by Enhancing the Resurging Activity of Co-trimoxazole in Presence of Cryptdin-2

Resurgence of sensitivity of the antibiotics, to which the pathogen had developed resistance in the past, requires special attention for strengthening the reservoir of antimicrobial compounds. Reports in the recent past have suggested that co-trimoxazole (COT) has regained its activity against methicillin resistant Staphylococcus aureus (MRSA). The present study exploited the use of COT in the presence of an antimicrobial peptide (AMP), cryptdin-2 (a murine Paneth cell alpha defensin), in order to reduce the selective pressure of the antibiotic on the pathogen. In vitro antibacterial activity and in vivo efficacy of the combination was ascertained against MRSA induced systemic infection using a murine model. Observations of the present study might help in restoring the regained activity of conventional antibiotics, such as COT, when used in combination with novel antimicrobial molecules like AMPs. This might prove as a viable strategy to eliminate the chances of re-occurrence of resistance due to their multi-prong targeting and synergistically combating infections caused by these resistant pathogens.

Effect of L. plantarum cell-free extract and co-trimoxazole against Salmonella Typhimurium: a possible adjunct therapy

Background

Frequent and indiscriminate use of antibiotics has led to the development of multi-drug resistant bacterial strains. It necessitates the exploitation of alternative therapeutic strategies. In order to reduce the dose of antibiotic required and to decrease the associated side effects, the present study was aimed at evaluating the synergism, if any, between a conventional antibiotic, co-trimoxazole (CTZ)) and cell free supernatant (CFS) of a probiotic (L. plantarum) against S. Typhimurium NCTC 74. This antimicrobial combination was selected on the basis of antibiotic susceptibility pattern of Salmonella and L. plantarum.

Methods

The synergy was evaluated in terms of size of zone of inhibition, fractional inhibitory concentration index, time-kill assay (in-vitro) as well as macrophage functions (ex-vivo).

Results

The concentration producing the same or higher antibacterial effect (size of zone of inhibition) was reduced to half when both the agents were used in combination with respect to the concentrations required when used separately. CTZ and CFS exhibited synergetic activity against Salmonella by checkerboard microtitre test and the time-kill test. Ex-vivo studies demonstrated a significantly higher intracellular killing of bacteria by macrophages treated with CFS (80 AU/ml) + (CTZ) (2 μg/ml) as compared to when treated with both separately at higher concentrations. Significant reduction in the extent of lipid peroxidation and nitrite levels generated by macrophages in presence of CFS and CTZ, in conjunction, further substantiated the synergistic efficacy of the combination.

Conclusions

The antimicrobial efficacy of this combination indicates that it may serve as the basis in developing alternative strategies to combat Salmonella infections.

Experimental cysticercosis and the intrahepatic venous systems in Rattus norvegicus

During the present investigation, alterations in the intrahepatic venous and portal systems in Rattus norvegicus infected with 250, 500, and 1000 Taenia taeniaeformis eggs were studied. The corrosion cast technique was employed, which provides an extrinsic opportunity for study of the three-dimensional orientation of the vascular architecture. Both of the venous trees were found to be affected, though the portal damage was more extensive. Maximal damage was inferred at 40 days post-infection, when the normal regularity of ramification was lost. Concisely, cysticercosis induced severe changes in the intrahepatic vascular systems, which were found to have gradually recovered at the later stages of infection.