Polyethylene glycol (PEG) as a broad applicability marker for LC-MS/MS-based biodistribution analysis of nanomedicines.

Polyethylene glycol (PEG) conjugation (PEGylation) is a well-established strategy to improve the pharmacokinetic and biocompatibility properties of a wide variety of nanomedicines and therapeutic peptides and proteins. This broad use makes PEG an attractive 'allround' candidate marker for the biodistribution of such PEGylated compounds. This paper presents the development of a novel strategy for PEG quantification in biological matrices. The methodology is based on sample hydrolysis which both decomposes the sample matrix and degrades PEGylated analytes to specific molecular fragments more suitable for detection by LC-MS/MS. Method versatility was demonstrated by applying it to a wide variety of PEGylated compounds, including polymeric poly(ethylbutyl cyanoacrylate) (PEBCA) nanoparticles, lipidic nanoparticles (Doxil®, LipImage 815™ and lipid nanoparticles for nucleic acid delivery) and the antibody Cimzia®. Method applicability was assessed by analyzing plasma and tissue samples from a comprehensive drug biodistribution study in rats, of both PEBCA and LipImage 815™ nanoparticles. The results demonstrated the method's utility for biodistribution studies on PEG. Importantly, by using the method described herein in tandem with quantification of nanoparticle payloads, we showed that this approach can provide detailed understanding of various critical aspects of the in vivo behavior of PEGylated nanomedicines, such as drug release and particle stability. Together, the presented results demonstrate the novel method as a robust, versatile and generic approach for biodistribution analysis of PEGylated therapeutics.

Quality assessment of LNP-RNA therapeutics with orthogonal analytical techniques.

The availability of analytical methods for the characterization of lipid nanoparticles (LNPs) for in-vivo intracellular delivery of nucleic acids is critical for the fast development of innovative RNA therapies. In this study, analytical protocols to measure (i) chemical composition, (ii) drug loading, (iii) particle size, concentration, and stability as well as (iv) structure and morphology were evaluated and compared based on a comprehensive characterization strategy linking key physical and chemical properties to in-vitro efficacy and toxicity. Furthermore, the measurement protocols were assessed either by testing the reproducibility and robustness of the same technique in different laboratories, or by a correlative approach, comparing measurement results of the same attribute with orthogonal techniques. The characterization strategy and the analytical measurements described here will have an important role during formulation development and in determining robust quality attributes ultimately supporting the quality assessment of these innovative RNA therapeutics.

Development of quantitative assay for simultaneous measurement of purine metabolites and creatinine in biobanked urine by liquid chromatography-tandem mass spectrometry.

Purine metabolism is essential for all known living creatures, including humans in whom elevated serum concentration of purine break-down product uric acid (UA) is probably an independent risk factor for mortality, type 2 diabetes and cardiovascular events. An automated multiplex assay that measures several purine metabolites could therefore prove useful in many areas of medical, veterinary and biological research. The aim of the present work was to develop a sensitive LC-MS/MS method for simultaneous quantitation of xanthine, hypoxanthine, UA, allantoin, and creatinine in biobanked urine samples. This article describes details and performance of the new method studied in 55 samples of human urine. Archival sample preparation and effect of storage conditions on stability of the analytes are addressed. The intra-day and inter-day coefficients of variation were small for all the analytes, not exceeding 1% and 10%, respectively. Measurements of UA and creatinine in biobanked urine showed good agreement with values obtained using routine enzymatic assays on fresh urine. Spearman's correlation coefficients were 0.869 (p < .001) for creatinine and 0.964 (p < .001) for UA. Conclusion: the newly developed LC-MS/MS method allows reliable quantitative assessment of xanthine, hypoxanthine, allantoin, UA and creatinine. The proposed pre-analytical processing makes the method suitable for both fresh and biobanked urine stored frozen at -80 °C for at least 5.5 years.

Mucosal Metabolomic Profiling and Pathway Analysis Reveal the Metabolic Signature of Ulcerative Colitis.

The onset of ulcerative colitis (UC) is characterized by a dysregulated mucosal immune response triggered by several genetic and environmental factors in the context of host-microbe interaction. This complexity makes UC ideal for metabolomic studies to unravel the disease pathobiology and to improve the patient stratification strategies. This study aims to explore the mucosal metabolomic profile in UC patients, and to define the UC metabolic signature. Treatment- naïve UC patients (n = 18), UC patients in deep remission (n = 10), and healthy volunteers (n = 14) were recruited. Mucosa biopsies were collected during colonoscopies. Metabolomic analysis was performed by combined gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). In total, 177 metabolites from 50 metabolic pathways were identified. The most prominent metabolome changes among the study groups were in lysophosphatidylcholine, acyl carnitine, and amino acid profiles. Several pathways were found perturbed according to the integrated pathway analysis. These pathways ranged from amino acid metabolism (such as tryptophan metabolism) to fatty acid metabolism, namely linoleic and butyrate. These metabolic changes during UC reflect the homeostatic disturbance in the gut, and highlight the importance of system biology approaches to identify key drivers of pathogenesis which prerequisite personalized medicine.

Antimicrobial activity of amphipathic α,α-disubstituted ß-amino amide derivatives against ESBL - CARBA producing multi-resistant bacteria; effect of halogenation, lipophilicity and cationic character.

The rapid emergence and spread of multi-resistant bacteria have created an urgent need for new antimicrobial agents. We report here a series of amphipathic α,α-disubstituted ß-amino amide derivatives with activity against 30 multi-resistant clinical isolates of Gram-positive and Gram-negative bacteria, including isolates with extended spectrum ß-lactamase - carbapenemase (ESBL-CARBA) production. A variety of halogenated aromatic side-chains were investigated to improve antimicrobial potency and minimize formation of Phase I metabolites. Net positive charge and cationic character of the derivatives had an important effect on toxicity against human cell lines. The most potent and selective derivative was the diguanidine derivative 4e with 3,5-di-brominated benzylic side-chains. Derivative 4e displayed minimum inhibitory concentrations (MIC) of 0.25-8 µg/mL against Gram-positive and Gram-negative reference strains, and 2-32 µg/mL against multi-resistant clinical isolates. Derivative 4e showed also low toxicity against human red blood cells (EC50 > 200 µg/mL), human hepatocyte carcinoma cells (HepG2: EC50 > 64 µg/mL), and human lung fibroblast cells (MRC-5: EC50 > 64 µg/mL). The broad-spectrum antimicrobial activity and low toxicity of diguanylated derivatives such as 4e make them attractive as lead compounds for development of novel antimicrobial drugs.

Lipidomics in Ulcerative Colitis Reveal Alteration in Mucosal Lipid Composition Associated With the Disease State.

BACKGROUND: The onset of ulcerative colitis (UC) is associated with alterations in lipid metabolism and a disruption of the balance between pro- and anti-inflammatory molecules. Only a few studies describe the mucosal lipid biosignatures during active UC. Moreover, the dynamics of lipid metabolism in the remission state is poorly defined. Therefore, this study aims to characterize mucosal lipid profiles in treatment-naïve UC patients and deep remission UC patients compared with healthy subjects. METHODS: Treatment-naïve UC patients (n = 21), UC patients in deep remission (n = 12), and healthy volunteers (n = 14) were recruited. The state of deep remission was defined by histological and immunological remission defined by a normalized TNF-α gene expression. Mucosa biopsies were collected by colonoscopy. Lipid analysis was performed by means of ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS-MS). In total, 220 lipids from 11 lipid classes were identified. RESULTS: The relative concentration of 122 and 36 lipids was altered in UC treatment-naïve patients and UC remission patients, respectively, compared with healthy controls. The highest number of significant variations was in the phosphatidylcholine (PC), ceramide (Cer), and sphingomyelin (SM) composition. Multivariate analysis revealed discrimination among the study groups based on the lipid profile. Furthermore, changes in phosphatidylethanolamine(38:3), Cer(d18:1/24:0), and Cer(d18:1/24:2) were most distinctive between the groups. CONCLUSION: This study revealed a discriminant mucosal lipid composition pattern between treatment-naïve UC patients, deep remission UC patients, and healthy controls. We report several distinctive lipids, which might be involved in the inflammatory response in UC, and could reflect the disease state.

Lys-C/Trypsin Tandem-Digestion Protocol for Gel-Free Proteomic Analysis of Colon Biopsies.

The protocol presented was specifically optimized for in-depth analysis of the human colon mucosa proteome. After cell lysis in a sodium deoxycholate/urea buffer, a tandem digestion with Lys-C and trypsin was performed. Prior to LC-MS/MS analysis, peptides were TMT-labeled and fractionated by high pH reversed-phase spin columns. This protocol is a powerful, reproducible, sample-saving, and cost-effective option when an in-depth quantitative proteome analysis is desired.

Ulcerative colitis: functional analysis of the in-depth proteome.

BACKGROUND: Ulcerative colitis (UC) is one major form of inflammatory bowel disease. The cause and the pathophysiology of the disease are not fully understood and we therefor aim in this study to identify important pathophysiological features in UC from proteomics data. METHODS: Colon mucosa biopsies from inflamed tissue of untreated UC patients at diagnosis and from healthy controls were obtained during colonoscopy. Quantitative protein data was acquired by bottom-up proteomics and furthermore processed with MaxQuant. The quantitative proteome data was analyzed with Perseus and enrichment data was analyzed by ClueGO for Cytoscape. RESULTS: The generated proteome dataset is to-date the deepest from colon mucosa biopsies with 8562 identified proteins whereof 6818 were quantified in > 70% of the samples. We report abundance differences between UC and healthy controls and the respective p values for all quantified proteins in the supporting information. From this data set enrichment analysis revealed decreased protein abundances in UC for metallothioneins, PPAR-inducible proteins, fibrillar collagens and proteins involved in bile acid transport as well as metabolic functions of nutrients, energy, steroids, xenobiotics and carbonate. On the other hand increased abundances were enriched in immune response and protein processing in the endoplasmic reticulum, e.g. unfolded protein response and signal peptidase complex proteins. CONCLUSIONS: This explorative study describes the most affected functions in UC tissue. Our results complemented previous findings substantially. Decreased abundances of signal peptidase complex proteins in UC are a new discovery.

A Quantitative Analysis of Colonic Mucosal Oxylipins and Endocannabinoids in Treatment-Naïve and Deep Remission Ulcerative Colitis Patients and the Potential Link With Cytokine Gene Expression.

BACKGROUND: The bioactive metabolites of omega 3 and omega 6 polyunsaturated fatty acids (ω-3 and ω-6) are known as oxylipins and endocannabinoids (eCBs). These lipid metabolites are involved in prompting and resolving the inflammatory response that leads to the onset of inflammatory bowel disease (IBD). This study aims to quantify these bioactive lipids in the colonic mucosa and to evaluate the potential link to cytokine gene expression during inflammatory events in ulcerative colitis (UC). METHODS: Colon biopsies were taken from 15 treatment-naïve UC patients, 5 deep remission UC patients, and 10 healthy controls. Thirty-five oxylipins and 11 eCBs were quantified by means of ultra-high-performance liquid chromatography coupled with tandem mass spectrometry. Levels of mRNA for 10 cytokines were measured by reverse transcription polymerase chain reaction. RESULTS: Levels of ω-6-related oxylipins were significantly elevated in treatment-naïve patients with respect to controls, whereas the levels of ω-3 eCBs were lower. 15S-Hydroxy-eicosatrienoic acid (15S-HETrE) was significantly upregulated in UC deep remission patients compared with controls. All investigated cytokines had significantly higher mRNA levels in the inflamed mucosa of treatment-naïve UC patients. Cytokine gene expression was positively correlated with several ω-6 arachidonic acid-related oxylipins, whereas negative correlation was found with lipoxin, prostacyclin, and the eCBs. CONCLUSIONS: Increased levels of ω-6-related oxylipins and decreased levels of ω-3-related eCBs are associated with the debut of UC. This highlights the altered balance between pro- and anti-inflammatory lipid mediators in IBD and suggests potential targets for intervention.

Starvation induces rapid degradation of selective autophagy receptors by endosomal microautophagy.

It is not clear to what extent starvation-induced autophagy affects the proteome on a global scale and whether it is selective. In this study, we report based on quantitative proteomics that cells during the first 4 h of acute starvation elicit lysosomal degradation of up to 2-3% of the proteome. The most significant changes are caused by an immediate autophagic response elicited by shortage of amino acids but executed independently of mechanistic target of rapamycin and macroautophagy. Intriguingly, the autophagy receptors p62/SQSTM1, NBR1, TAX1BP1, NDP52, and NCOA4 are among the most efficiently degraded substrates. Already 1 h after induction of starvation, they are rapidly degraded by a process that selectively delivers autophagy receptors to vesicles inside late endosomes/multivesicular bodies depending on the endosomal sorting complex required for transport III (ESCRT-III). Our data support a model in which amino acid deprivation elicits endocytosis of specific membrane receptors, induction of macroautophagy, and rapid degradation of autophagy receptors by endosomal microautophagy.

Straightforward Protocol for Gel-Free Proteomic Analysis of Adipose Tissue.

After conducting systematic and quantitative comparisons of different sample preparation techniques regarding their capability to efficiently and reproducibly recover proteins from biopsies, we present here our superior protocol for extracting proteins from low amounts of adipose tissue. Adipose tissue as a matrix in bottom-up proteomics is challenging due to the extremely high lipid content.The lysis buffer utilized contains the detergent sodium deoxycholate, which does not impair the activity of trypsin and therefore enables direct digestion without detergent removal steps. The resulting workflow is time saving, cost efficient, easy to perform, and it can also be applied to other hydrophobic samples.

The Proteome of Ulcerative Colitis in Colon Biopsies from Adults - Optimized Sample Preparation and Comparison with Healthy Controls.

PURPOSE: The purpose of the study was to optimize the sample preparation and to further use an improved sample preparation to identify proteome differences between inflamed ulcerative colitis tissue from untreated adults and healthy controls. EXPERIMENTAL DESIGN: To optimize the sample preparation, we studied the effect of adding different detergents to a urea containing lysis buffer for a Lys-C/trypsin tandem digestion. With the optimized method, we prepared clinical samples from six ulcerative colitis patients and six healthy controls and analysed them by LC-MS/MS. We examined the acquired data to identify differences between the states. RESULTS: We improved the protein extraction and protein identification number by utilizing a urea and sodium deoxycholate containing buffer. Comparing ulcerative colitis and healthy tissue, we found 168 of 2366 identified proteins differently abundant. Inflammatory proteins are higher abundant in ulcerative colitis, proteins related to anion-transport and mucus production are lower abundant. A high proportion of S100 proteins is differently abundant, notably with both up-regulated and down-regulated proteins. CONCLUSION AND CLINICAL RELEVANCE: The optimized sample preparation method will improve future proteomic studies on colon mucosa. The observed protein abundance changes and their enrichment in various groups improve our understanding of ulcerative colitis on protein level.

Proteomics of hydrophobic samples: Fast, robust and low-cost workflows for clinical approaches.

In a comparative study, we investigated the influence of nine sample preparation workflows and seven different lysis buffers for qualitative and quantitative analysis of the human adipose tissue proteome. Adipose tissue is not just a fat depot but also an endocrine organ, which cross-talks with other tissue types and organs throughout the body, like liver, muscle, pancreas, and brain. Its secreted molecules have an influence on the nervous, immune, and vascular system, thus adipose tissue plays an important role in the regulation of whole-body homeostasis. Proteomic analysis of adipose tissue is challenging due to the extremely high lipid content and a variety of different cell types included. We investigated the influence of different detergents to the lysis buffer and compared commonly used methods like protein precipitation and filter-aided sample preparation (FASP) with workflows involving acid labile or precipitable surfactants. The results indicate that a sodium deoxycholate (SDC) based workflow had the highest efficiency and reproducibility for quantitative proteomic analysis. In total 2564 proteins from the adipose tissue of a single person were identified.

The Presumed Polyomavirus Viroporin VP4 of Simian Virus 40 or Human BK Polyomavirus Is Not Required for Viral Progeny Release.

The minor capsid protein of human BK polyomavirus (BKPyV), VP2, and its N-terminally truncated form, VP3, are both important for viral entry. The closely related simian virus 40 (SV40) reportedly produces an additional truncated form of VP2/3, denoted VP4, apparently functioning as a viroporin promoting progeny release. The VP4 open reading frame is conserved in some polyomaviruses, including BKPyV. In this study, we investigated the role of VP4 in BKPyV replication. By transfecting viral genomes into primary human renal proximal tubule epithelial cells, we demonstrated that unaltered BKPyV and mutants with start codon substitutions in VP4 (VP2M229I and VP2M229A) abolishing putative VP4 production were released at the same level to supernatants. However, during infection studies, VP2M229I and VP2M229A exhibited 90% and 65% reduced infectivity, respectively, indicating that isoleucine substitution inadvertently disrupted VP2/3 function to the detriment of viral entry, while inhibition of VP4 production during late infection was well tolerated. Unexpectedly, and similarly to BKPyV, wild-type SV40 and the corresponding VP4 start codon mutants (VP2M228I and VP2M228A) transfected into monkey kidney cell lines were also released at equal levels. Upon infection, only the VP2M228I mutant exhibited reduced infectivity, a 43% reduction, which also subsequently led to delayed host cell lysis. Mass spectrometry analysis of nuclear extracts from SV40-infected cells failed to identify VP4. Our results suggest that neither BKPyV nor SV40 require VP4 for progeny release. Moreover, our results reveal an important role in viral entry for the amino acid in VP2/VP3 unavoidably changed by VP4 start codon mutagenesis. IMPORTANCE: Almost a decade ago, SV40 was reported to produce a late nonstructural protein, VP4, which forms pores in the nuclear membrane, facilitating progeny release. By performing transfection studies with unaltered BKPyV and SV40 and their respective VP4-deficient mutants, we found that VP4 is dispensable for progeny release, contrary to the original findings. However, infection studies demonstrated a counterintuitive reduction of infectivity of certain VP4-deficient mutants. In addition to the isoleucine-substituted SV40 mutant of the original study, we included alanine-substituted VP4-deficient mutants of BKPyV (VP2M229A) and SV40 (VP2M228A). These revealed that the reduction in infectivity was not caused by a lack of VP4 but rather depended on the identity of the single amino acid substituted within VP2/3 for VP4 start codon mutagenesis. Hopefully, our results will correct the longstanding misconception of VP4's role during infection and stimulate continued work on unraveling the mechanism for release of polyomavirus progeny.

General Approach To Determine Disulfide Connectivity in Cysteine-Rich Peptides by Sequential Alkylation on Solid Phase and Mass Spectrometry.

Within the field of bioprospecting, disulfide-rich peptides are a promising group of compounds that has the potential to produce important leads for new pharmaceuticals. The disulfide bridges stabilize the tertiary structure of the peptides and often make them superior drug candidates to linear peptides. However, determination of disulfide connectivity in peptides with many disulfide bridges has proven to be laborious and general methods are lacking. This study presents a general approach for structure elucidation of disulfide-rich peptides. The method features sequential reduction and alkylation of a peptide on solid phase combined with sequencing of the fully alkylated peptide by tandem mass spectrometry. Subsequently, the disulfide connectivity is assigned on the basis of the determined alkylation pattern. The presented method is especially suitable for peptides that are prone to disulfide scrambling or are unstable in solution with partly reduced bridges. Additionally, the use of small amounts of peptide in the lowest nmol range makes the method ideal for structure elucidation of unknown peptides from the bioprospecting process. This study successfully demonstrates the new method for seven different peptides with two to four disulfide bridges. Two peptides with previous contradicting publications, µ-conotoxin KIIA and hepcidin-25, are included, and their disulfide connectivity is confirmed in accordance with the latest published results.

ß-CD-dextran polymer for efficient sequestration of cholesterol from phospholipid bilayers: Mechanistic and safe-toxicity investigations.

The aim of this work was to investigate the suitability of ß-cyclodextrin-dextran (BCD-dextran) polymer as cholesterol sequestering agent in vitro. For this purpose, BCD-dextran-cholesterol complexation was studied by phase solubility studies as well as with a specifically designed in vitro model based on giant unilamellar vesicles (GUVs) to evaluate the ability of this polymer to sequestrate cholesterol from phospholipid bilayers. Cholesterol-sequestering ability of BCD-dextran was also investigated on different cell lines relevant for the hematopoietic system and results were correlated to cells toxicity. BCD-dextran polymer was capable of extracting significant amount of cholesterol from phospholipid bilayers and to a higher extent in comparison to available ß-cyclodextrins (BCDs). The ability of BCD-dextran in sequestering cholesterol resulted also very high on cell lines relevant for the hematopoietic system. Moreover, BCD-dextran resulted less toxic on cell cultures due to higher selectivity in sequestering cholesterol in comparison to MBCD (that sequestrated also significant amounts of cholesteryl esters). In conclusion, BCD-dextran resulted an extremely efficient cholesterol-sequestering agent and BCD-dextran resulted more selective to cholesterol extraction in comparison to other BCDs (therefore of lower cytotoxicity). This phenomenon might play a key role to develop an efficient treatment for hypercholesterolemia based on cholesterol segregation.

New applications of phospholipid vesicle-based permeation assay: permeation model mimicking skin barrier.

The phospholipid vesicle-based permeation assay (PVPA), based on a tight barrier composed of liposomes mimicking cells, is providing an opportunity to predict passive drug permeability through biological membranes. Although it was originally developed to mimic the intestinal epithelia, this study focuses on its potential as a simple and affordable skin model for transdermal permeation of drug candidates and evaluation of various drugs and formulations at an early development stage. The changes induced in lipid composition of the lipid-based barriers to better mimic the in vivo stratum corneum lipid composition required optimization of liposomal properties and manufacturing conditions applied in barrier formation. The preparation conditions could be modified to prepare lipid-based barriers of different degrees of leakiness, potentially representing different degree of intact and compromised skin. The different PVPA models developed in this study appeared to be able to distinguish between drugs with different degrees of lipophilicity and penetration potential. Moreover, the PVPA can be produced in controlled and reproducible manner with different degree of leakiness. The model could therefore be applied in both pharmaceutical and cosmeceuticals manufacturing and also has the potential to provide deeper insight on safety of nanodelivery systems administered onto the skin.

Adenylylation, MS, and proteomics--Introducing a "new" modification to bottom-up proteomics.

Although the addition of a 5'-adenosine phosphodiester group to proteins, called adenylylation, has been known for decades, the possibility that adenylylation could be a molecular switch in cellular signaling pathways has emerged recently. The distinct mass shift upon adenylation of threonine or tyrosine residues renders it a good target for MS detection and identification; however, the fragmentation of adenylylated peptides derived from proteolytic digestion of adenylylated proteins has not yet been systematically investigated. Here, we demonstrate that adenylylated peptides show loss of parts of the adenosine monophosphate (AMP) upon different fragmentation techniques. As expected, causing the least fragmentation of the AMP group, electron transfer dissociation yields less complicated spectra. In contrast, CID and higher energy collision (HCD) fragmentation caused AMP to fragment, generating characteristic ions that could be utilized in the specific identification of adenylylated peptides. The characteristic ions and losses upon CID and higher energy collision fragmentation from the AMP group turned out to be highly dependent on which amino acid was adenylylated, with different reporter ions for adenylylated threonine and tyrosine. We also investigated how adenylylation is best incorporated into search engines, exemplified by Mascot and showed that it is possible to identify adenylylation by search engines.

Anticancer activity of small amphipathic ß²,²-amino acid derivatives.

We report the anticancer activity from screening of a series of synthetic ß(2,2)-amino acid derivatives that were prepared to confirm the pharmacophore model of short cationic antimicrobial peptides with high anti-Staphylococcal activity. The most potent derivatives against human Burkitt's lymphoma (Ramos) cells displayed IC(50) values below 8 µM, and low toxicity against human red blood cells (EC(50) > 200 µM). A more than 5-fold preference for Ramos cancer cells compared to human lung fibroblasts (MRC-5 cells) was also obtained for the most promising ß(2,2)-amino acid derivative 3-amino-N-(2-aminoethyl)-2,2-bis(naphthalen-2-ylmethyl)propanamide (5c). Screening of 5c at the National Cancer Institute (NCI, USA) confirmed its anticancer potency and revealed a very broad range of anticancer activity with IC(50) values of 0.32-3.89 µM against 59 different cancer cell lines. Highest potency was obtained against the colon cancer cell lines, a non-small cell lung cancer, a melanoma, and three leukemia cell lines included in the NCI screening panel. The reported ß(2,2)-amino acid derivatives constitute a promising new class of anticancer agents based on their high anticancer potency, ease of synthesis, mode-of-action, and optimized pharmacokinetic properties compared to much larger antimicrobial peptides.

Anticancer mechanisms of action of two small amphipathic ß(2,2)-amino acid derivatives derived from antimicrobial peptides.

We have recently discovered that small antimicrobial ß(2,2)-amino acid derivatives (Mw<500) also display activity against cancer cells. To explore their drug potential, we have presently investigated the mechanisms of action of two derivatives BAA-1 (IC(50) 8.1µg/ml) and BAA-2 (IC(50) 3.8µg/ml) on Ramos human Burkitt's lymphoma cells. Studies using annexin-V-FITC/propidium iodide staining and flow cytometry revealed essential mechanistic differences, which was confirmed by screening for active caspases, investigation of mitochondrial membrane potential, and electron microscopy studies. Our results indicated that BAA-1 killed Ramos cells by destabilizing the cell membrane, whereas BAA-2 caused apoptosis by the mitochondrial-mediated pathway.