Integrin Ligands with α/β-Hybrid Peptide Structure: Design, Bioactivity, and Conformational Aspects

Non-invasively differentiate non-alcoholic steatohepatitis by visualizing hepatic integrin αvβ3 expression with a targeted molecular imaging modality

BACKGROUND

Non-invasive methods to diagnose non-alcoholic steatohepatitis (NASH), an inflammatory subtype of non-alcoholic fatty liver disease (NAFLD), are currently unavailable.

AIM

To develop an integrin αvβ3-targeted molecular imaging modality to differentiate NASH.

METHODS

Integrin αvβ3 expression was assessed in Human LO2 hepatocytes Scultured with palmitic and oleic acids (FFA). Hepatic integrin αvβ3 expression was analyzed in rabbits fed a high-fat diet (HFD) and in rats fed a high-fat, high-carbohydrate diet (HFCD). After synthesis, cyclic arginine-glycine-aspartic acid peptide (cRGD) was labeled with gadolinium (Gd) and used as a contrast agent in magnetic resonance imaging (MRI) performed on mice fed with HFCD.

RESULTS

Integrin αvβ3 was markedly expressed on FFA-cultured hepatocytes, unlike the control hepatocytes. Hepatic integrin αvβ3 expression significantly increased in both HFD-fed rabbits and HFCD-fed rats as simple fatty liver (FL) progressed to steatohepatitis. The distribution of integrin αvβ3 in the liver of NASH cases largely overlapped with albumin-positive staining areas. In comparison to mice with simple FL, the relative liver MRI-T1 signal value at 60 minutes post-injection of Gd-labeled cRGD was significantly increased in mice with steatohepatitis (P < 0.05), showing a positive correlation with the NAFLD activity score (r = 0.945; P < 0.01). Hepatic integrin αvβ3 expression was significantly upregulated during NASH development, with hepatocytes being the primary cells expressing integrin αvβ3.

CONCLUSION

After using Gd-labeled cRGD as a tracer, NASH was successfully distinguished by visualizing hepatic integrin αvβ3 expression with MRI.

Characterization and preparation of food-derived peptides on improving osteoporosis: A review

Osteoporosis is a systemic bone disease characterized by reduced bone mass and deterioration of the microstructure of bone tissue, leading to an increased risk of fragility fractures and affecting human health worldwide. Food-derived peptides are widely used in functional foods due to their low toxicity, ease of digestion and absorption, and potential to improve osteoporosis. This review summarized and discussed methods of diagnosing osteoporosis, treatment approaches, specific peptides as alternatives to conventional drugs, and the laboratory preparation and identification methods of peptides. It was found that peptides interacting with RGD (arginine-glycine-aspartic acid)-binding active sites in integrin could alleviate osteoporosis, analyzed the interaction sites between these osteogenic peptides and integrin, and further discussed their effects on improving osteoporosis. These may provide new insights for rapid screening of osteogenic peptides, and provide a theoretical basis for their application in bone materials and functional foods.

A Versatile Microfluidic Platform for Extravasation Studies Based on DNA Origami-Cell Interactions

The adhesion of circulating tumor cells (CTCs) to the endothelial lumen and their extravasation to surrounding tissues are crucial in the seeding of metastases and remain the most complex events of the metastatic cascade to study. Integrins expressed on CTCs are major regulators of the extravasation process. This knowledge is primarily derived from animal models and biomimetic systems based on artificial endothelial layers, but these methods have ethical or technical limitations. We present a versatile microfluidic device to study cancer cell extravasation that mimics the endothelial barrier by using a porous membrane functionalized with DNA origami nanostructures (DONs) that display nanoscale patterns of adhesion peptides to circulating cancer cells. The device simulates physiological flow conditions and allows direct visualization of cell transmigration through microchannel pores using 3D confocal imaging. Using this system, we studied integrin-specific adhesion in the absence of other adhesive events. Specifically, we show that the transmigration ability of the metastatic cancer cell line MDA-MB-231 is influenced by the type, distance, and density of adhesion peptides present on the DONs. Furthermore, studies with mixed ligand systems indicate that integrins binding to RGD (arginine-glycine-aspartic acid) and IDS (isoleucine-aspartic acid-serine) did not synergistically enhance the extravasation process of MDA-MB-231 cells.

A Review of Advances in Molecular Imaging of Rheumatoid Arthritis: From In Vitro to Clinic Applications Using Radiolabeled Targeting Vectors with Technetium-99m

Rheumatoid arthritis (RA) is a systemic autoimmune disorder caused by inflammation of cartilaginous diarthrodial joints that destroys joints and cartilage, resulting in synovitis and pannus formation. Timely detection and effective management of RA are pivotal for mitigating inflammatory arthritis consequences, potentially influencing disease progression. Nuclear medicine using radiolabeled targeted vectors presents a promising avenue for RA diagnosis and response to treatment assessment. Radiopharmaceutical such as technetium-99m (99mTc), combined with single photon emission computed tomography (SPECT) combined with CT (SPECT/CT), introduces a more refined diagnostic approach, enhancing accuracy through precise anatomical localization, representing a notable advancement in hybrid molecular imaging for RA evaluation. This comprehensive review discusses existing research, encompassing in vitro, in vivo, and clinical studies to explore the application of 99mTc radiolabeled targeting vectors with SPECT imaging for RA diagnosis. The purpose of this review is to highlight the potential of this strategy to enhance patient outcomes by improving the early detection and management of RA.

Conjecturing about Small-Molecule Agonists and Antagonists of α4β1 Integrin: From Mechanistic Insight to Potential Therapeutic Applications

Integrins are heterodimeric cell-surface receptors that regulate cell-cell adhesion and cellular functions through bidirectional signaling. On the other hand, anomalous trafficking of integrins is also implicated in severe pathologies as cancer, thrombosis, inflammation, allergies, and multiple sclerosis. For this reason, they are attractive candidates as drug targets. However, despite promising preclinical data, several anti-integrin drugs failed in late-stage clinical trials for chronic indications, with paradoxical side effects. One possible reason is that, at low concentration, ligands proposed as antagonists may also act as partial agonists. Hence, the comprehension of the specific structural features for ligands' agonism or antagonism is currently of the utmost interest. For α4β1 integrin, the situation is particularly obscure because neither the crystallographic nor the cryo-EM structures are known. In addition, very few potent and selective agonists are available for investigating the mechanism at the basis of the receptor activation. In this account, we discuss the physiological role of α4β1 integrin and the related pathologies, and review the few agonists. Finally, we speculate on plausible models to explain agonism vs. antagonism by comparison with RGD-binding integrins and by analysis of computational simulations performed with homology or hybrid receptor structures.

Dual-targeting peptides@PMO, a mimetic to the pro-apoptotic protein Smac/DIABLO for selective activation of apoptosis in cancer cells

The refractoriness of tumor cells to apoptosis represents the main mechanism of resistance to chemotherapy. Smac/DIABLO mimetics proved to be effective in overcoming cancer-acquired resistance to apoptosis as a consequence of overexpression of the anti-apoptotic proteins XIAP, cIAP1, and cIAP2. In this work, we describe a dual-targeting peptide capable of selectively activating apoptosis in cancer cells. The complex consists of a fluorescent periodic mesoporous organosilica nanoparticle that carries the short sequences of Smac/DIABLO bound to the αvβ3-integrin ligand. The dual-targeting peptide @PMO shows significantly higher toxicity in αvβ3-positive HeLa cells with respect to αvβ3-negative Ht29 cells. @PMO exhibited synergistic effects in combination with oxaliplatin in a panel of αvβ3-positive cancer cells, while its toxicity is overcome by XIAP overexpression or integrin β3 silencing. The successful uptake of the molecule by αvβ3-positive cells makes @PMO promising for the re-sensitization to apoptosis of many cancer types.

Design, Pharmacological Characterization, and Molecular Docking of Minimalist Peptidomimetic Antagonists of α4β1 Integrin

Integrin receptors mediate cell-cell interactions via the recognition of cell-adhesion glycoproteins, as well as via the interactions of cells with proteins of the extracellular matrix, and upon activation they transduce signals bi-directionally across the cell membrane. In the case of injury, infection, or inflammation, integrins of β₂ and α₄ families participate in the recruitment of leukocytes, a multi-step process initiated by the capturing of rolling leukocytes and terminated by their extravasation. In particular, α₄β₁ integrin is deeply involved in leukocyte firm adhesion preceding extravasation. Besides its well-known role in inflammatory diseases, α₄β₁ integrin is also involved in cancer, being expressed in various tumors and showing an important role in cancer formation and spreading. Hence, targeting this integrin represents an opportunity for the treatment of inflammatory disorders, some autoimmune diseases, and cancer. In this context, taking inspiration from the recognition motives of α₄β₁ integrin with its natural ligands FN and VCAM-1, we designed minimalist α/β hybrid peptide ligands, with our approach being associated with a retro strategy. These modifications are expected to improve the compounds' stability and bioavailability. As it turned out, some of the ligands were found to be antagonists, being able to inhibit the adhesion of integrin-expressing cells to plates coated with the natural ligands without inducing any conformational switch and any activation of intracellular signaling pathways. An original model structure of the receptor was generated using protein-protein docking to evaluate the bioactive conformations of the antagonists via molecular docking. Since the experimental structure of α₄β₁ integrin is still unknown, the simulations might also shed light on the interactions between the receptor and its native protein ligands.

Design and Pharmacological Characterization of α4β1 Integrin Cyclopeptide Agonists: Computational Investigation of Ligand Determinants for Agonism versus Antagonism

α₄β₁ integrin is a cell adhesion receptor deeply involved in the migration and accumulation of leukocytes. Therefore, integrin antagonists that inhibit leukocytes recruitment are currently regarded as a therapeutic opportunity for the treatment of inflammatory disorder, including leukocyte-related autoimmune diseases. Recently, it has been suggested that integrin agonists capable to prevent the release of adherent leukocytes might serve as therapeutic agents as well. However, very few α₄β₁ integrin agonists have been discovered so far, thus precluding the investigation of their potential therapeutic efficacy. In this perspective, we synthesized cyclopeptides containing the LDV recognition motif found in the native ligand fibronectin. This approach led to the discovery of potent agonists capable to increase the adhesion of α₄ integrin-expressing cells. Conformational and quantum mechanics computations predicted distinct ligand-receptor interactions for antagonists or agonists, plausibly referable to receptor inhibition or activation.

Molecular Modeling Insights into the Structure and Behavior of Integrins: A Review

Integrins are heterodimeric glycoproteins crucial to the physiology and pathology of many biological functions. As adhesion molecules, they mediate immune cell trafficking, migration, and immunological synapse formation during inflammation and cancer. The recognition of the vital roles of integrins in various diseases revealed their therapeutic potential. Despite the great effort in the last thirty years, up to now, only seven integrin-based drugs have entered the market. Recent progress in deciphering integrin functions, signaling, and interactions with ligands, along with advancement in rational drug design strategies, provide an opportunity to exploit their therapeutic potential and discover novel agents. This review will discuss the molecular modeling methods used in determining integrins' dynamic properties and in providing information toward understanding their properties and function at the atomic level. Then, we will survey the relevant contributions and the current understanding of integrin structure, activation, the binding of essential ligands, and the role of molecular modeling methods in the rational design of antagonists. We will emphasize the role played by molecular modeling methods in progress in these areas and the designing of integrin antagonists.

Identification and validation of a novel prognostic model of inflammation-related gene signature of lung adenocarcinoma

Previous literatures have suggested the importance of inflammatory response during lung adenocarcinoma (LUAD) development. This study aimed at exploring the inflammation-related genes and developing a prognostic signature for predicting the prognosis of LUAD. Survival‑associated inflammation-related genes were identified by univariate Cox regression analysis in the dataset of The Cancer Genome Atlas (TCGA). The least absolute shrinkage and selection operator (LASSO) penalized Cox regression model was used to derive a risk signature which is significantly negatively correlated with OS and divide samples into high-, medium- and low-risk group. Univariate and multivariate Cox analyses suggested that the level of risk group was an independent prognostic factor of the overall survival (OS). Time-dependent receiver operating characteristic (ROC) curve indicated the AUC of 1-, 3- and 5-years of the risk signature was 0.715, 0.719, 0.699 respectively. A prognostic nomogram was constructed by integrating risk group and clinical features. The independent dataset GSE30219 of Gene Expression Omnibus (GEO) was used for verification. We further explored the differences among risk groups in Gene set enrichment analysis (GSEA), tumor mutation and tumor microenvironment. Furthermore, Single Sample Gene Set Enrichment Analysis (ssGSEA) and the results of Cell-type Identification By Estimating Relative Subsets Of RNA Transcripts (CIBERSORT) suggested the status of immune cell infiltration was highly associated with risk groups. We demonstrated the prediction effect of CTLA-4 and PD-1/PD-L1 inhibitors in the low-risk group was better than that in the high-risk group using two methods of immune score include immunophenoscore from The Cancer Immunome Atlas (TCIA) and TIDE score from Tumor Immune Dysfunction and Exclusion (TIDE). In addition, partial targeted drugs and chemotherapy drugs for lung cancer had higher drug sensitivity in the high-risk group. Our findings provide a foundation for future research targeting inflammation-related genes to predictive prognosis and some reference significance for the selection of immunotherapy and drug regimen for lung adenocarcinoma.

Novel ITGB2 Mutation Is Responsible for a Severe Form of Leucocyte Adhesion Deficiency Type 1

Leukocyte adhesion deficiency type 1 (LAD1) is a rare autosomal recessive hereditary disorder characterized by recurrent infections, impaired pus formation, delayed wound healing, omphalitis, and delayed separation of the umbilical cord as hallmark features of the disease. It results from mutations in the integrin β2 subunit gene ITGB2, which encodes the integrin beta chain-2 protein CD18. In this study, we aimed to investigate the case of a five-month-old boy who presented with a clinical phenotype and flow cytometry results suggesting LAD1 disease. Sanger sequencing of all exons and intron boundaries of ITGB2 identified a novel in-frame deletion in exon 7 (ITGB2 c.844_846delAAC, p.Asn282del) in the patient. The p.Asn282del mutation was heterozygous in the child's parents, whereas it was absent in the 96 control individuals from North Africa. This variant was evaluated by two in silico mutation analysis tools, PROVEAN and MutationTaster, which predicted that the mutation was likely to be pathogenic. In addition, molecular modeling with the YASARA View software suggested that this novel mutation may affect the structure of integrin beta-2 and, subsequently, its interaction with integrin alpha-X. In summary, we report a novel pathogenic mutation p.Asn282del associated with LAD1 that expands the mutation diversity of ITGB2 and suggest the combination of flow cytometry and ITGB2 sequencing as a first-line diagnostic approach for LAD disease.

Design of α/β-Hybrid Peptide Ligands of α4β1 Integrin Equipped with a Linkable Side Chain for Chemoselective Biofunctionalization of Microstructured Materials

Arg-Gly-Asp (RGD)-binding integrins, e.g., αvβ3, αvβ1, αvβ5 integrins, are currently regarded as privileged targets for the delivery of diagnostic and theranostic agents, especially in cancer treatment. In contrast, scarce attention has been paid so far to the diagnostic opportunities promised by integrins that recognize other peptide motifs. In particular, α4β1 integrin is involved in inflammatory, allergic, and autoimmune diseases, therefore, it represents an interesting therapeutic target. Aiming at obtaining simple, highly stable ligands of α4β1 integrin, we designed hybrid α/β peptidomimetics carrying linkable side chains for the expedient functionalization of biomaterials, nano- and microparticles. We identified the prototypic ligands MPUPA-(R)-isoAsp(NHPr)-Gly-OH (12) and MPUPA-Dap(Ac)-Gly-OH (13) (MPUPA, methylphenylureaphenylacetic acid; Dap, 2,3-diamino propionic acid). Modification of 12 and 13 by introduction of flexible linkers at isoAsp or Dap gave 49 and 50, respectively, which allowed for coating with monolayers (ML) of flat zeolite crystals. The resulting peptide–zeolite MLs were able to capture selectively α4β1 integrin-expressing cells. In perspective, the α4β1 integrin ligands identified in this study can find applications for preparing biofunctionalized surfaces and diagnostic devices to control the progression of α4β1 integrin-correlated diseases.

New 4-Aminoproline-Based Small Molecule Cyclopeptidomimetics as Potential Modulators of α4β1 Integrin

Integrin α₄β₁ belongs to the leukocyte integrin family and represents a therapeutic target of relevant interest given its primary role in mediating inflammation, autoimmune pathologies and cancer-related diseases. The focus of the present work is the design, synthesis and characterization of new peptidomimetic compounds that are potentially able to recognize α₄β₁ integrin and interfere with its function. To this aim, a collection of seven new cyclic peptidomimetics possessing both a 4-aminoproline (Amp) core scaffold grafted onto key α₄β₁-recognizing sequences and the (2-methylphenyl)ureido-phenylacetyl (MPUPA) appendage, was designed, with the support of molecular modeling studies. The new compounds were synthesized through SPPS procedures followed by in-solution cyclization maneuvers. The biological evaluation of the new cyclic ligands in cell adhesion assays on Jurkat cells revealed promising submicromolar agonist activity in one compound, namely, the c[Amp(MPUPA)Val-Asp-Leu] cyclopeptide. Further investigations will be necessary to complete the characterization of this class of compounds.

LncRNA EWSAT1 Regulates the Tumorigenesis of NSCLC as a ceRNA by Modulating miR-330-5p/ITGA5 Axis

The aim of the study is to investigate how lncRNA EWSAT1 regulates the tumorigenesis of non-small cell lung cancer (NSCLC) as a ceRNA by modulating miR-330-5p/ITGA5 axis. qRT-PCR was conducted to evaluate the expression of EWSAT1 in NSCLC tissue. Then, A549 cells were selected and divided into Blank shScramble, shEWSAT1, miR-330-5p inhibitor, shEWSAT1 + miR-330-5p inhibitor, and siITGA5 and miR-330-5p inhibitor + siITGA5 groups. Besides, a series of in-vitro experiments were carried out to determine the changes in cell proliferation, apoptosis, invasion, and migration in each group. In addition, xenograft models were also constructed on nude mice to detect the tumor volume and weight, and the expression of Ki67 and apoptosis in xenograft tumor were evaluated. In NSCLC tissue and cell, EWSAT1 was upregulated significantly, demonstrating a correlation with tumor diameter, differentiation, lymph node metastasis, and TNM stage. Dual luciferase reporter gene assay confirmed targeting relationships among miR-330-5p, EWSAT1, and ITGA5. In comparison with the Blank group, the number of cell clones in the shEWSAT1 group and siITGA5 decreased, with declined invasion and migration but increased apoptotic rate. Meanwhile, ITGA5, MMP-2, and MMP-9 were downregulated with upregulated cleaved caspase-3. However, the changes above were totally reversed in the miR-330-5p inhibitor group, and miR-330-5p inhibitor transfection abolished the effect of shEWSAT1. In addition, subcutaneous xenotransplantation showed that the tumor growth in shEWSAT1 group retarded significantly, with downregulation of Ki67 and increase apoptotic rate. Silencing EWSAT1 could inhibit the expression of ITGA5 via upregulating miR-330-5p, thus, resulting in the inhibition of NSCLC cell growth.

Integrin-Targeting Peptides for the Design of Functional Cell-Responsive Biomaterials

Integrins are a family of cell surface receptors crucial to fundamental cellular functions such as adhesion, signaling, and viability, deeply involved in a variety of diseases, including the initiation and progression of cancer, of coronary, inflammatory, or autoimmune diseases. The natural ligands of integrins are glycoproteins expressed on the cell surface or proteins of the extracellular matrix. For this reason, short peptides or peptidomimetic sequences that reproduce the integrin-binding motives have attracted much attention as potential drugs. When challenged in clinical trials, these peptides/peptidomimetics let to contrasting and disappointing results. In the search for alternative utilizations, the integrin peptide ligands have been conjugated onto nanoparticles, materials, or drugs and drug carrier systems, for specific recognition or delivery of drugs to cells overexpressing the targeted integrins. Recent research in peptidic integrin ligands is exploring new opportunities, in particular for the design of nanostructured, micro-fabricated, cell-responsive, stimuli-responsive, smart materials.

DPP-4 Cleaves α/β-Peptide Bonds: Substrate Specificity and Half-Lives

The incorporation of β-amino acids into a peptide sequence has gained particular attention as β- and α/β-peptides have shown remarkable proteolytic stability, even after a single homologation at the scissile bond. Several peptidases have been shown to cleave such bonds with high specificity but at a much slower rate compared to α-peptide bonds. In this study, a series of analogs of dipeptidyl peptidase-4 (DPP-4) substrate inhibitors were synthesized in order to investigate whether β-amino acid homologation at the scissile bond could be a valid approach to improving peptide stability towards DPP-4 degradation. DPP-4 cleaved the α/β-peptide bond after the N-terminal penultimate Pro with a broad specificity and retained full activity regardless of the β³ -amino acid side chain and peptide length. Significantly improved half-lives were observed for β³ Ile-containing peptides. Replacing the penultimate Pro with a conformationally constrained Pro mimetic led to proteolytic resistance. DPP-4 cleavage of α/β-peptide bonds with a broad promiscuity represents a new insight into the stability of peptide analogs containing β-amino acids as such analogs were thought to be stable towards enzymatic degradation.

Shedding New Light on The Role of ανβ3 and α5β1 Integrins in Rheumatoid Arthritis

ανβ3 and α5β1 are essential glycoproteins involved in the pathogenesis of rheumatoid arthritis (RA). Understanding of the role these integrins play in disease have been analyzed via description of cells-expressing ανβ3 and α5β1 and their mediators to trigger inflammation. ανβ3 and α5β1 facilitate cells-ECM and cell-cell communication, producing pro-inflammatory factors. Pro-inflammatory factors are essential for the building of undesirable new blood vessels termed angiogenesis which can further lead to destruction of bones and joints. Despite many attempts to target these glycoproteins, there are still some problems, therefore, there is still interest in understanding the synergistic role these integrins play in the pathogenesis of RA. The purpose of this review is to gain insights into the biological effects of ανβ3 and α5β1 in synovial tissues that are relevant to pathogenesis and therapy of RA.

Expression of integrin α-6 is associated with multi drug resistance and prognosis in ovarian cancer

Ovarian cancer is a serious threat to women's health. Multidrug resistance is a major cause of post-treatment relapse, metastasis, and even mortality. This characteristic severely restricts the survival of patients with ovarian cancer. Integrin α-6 (ITGA6) is a member of the adhesion molecule family that conducts signals through interactions between the extracellular domain and the matrix, serving important roles in cell adhesion-mediated drug resistance, which is considered to have a critical function in ovarian cancer drug resistance. The association between ITGA6 and ovarian cancer multidrug resistance has been investigated only rarely, to the best of our knowledge. Using RT-qPCR and immunohistochemistry, it was identified that ITGA6 is a central drug resistance gene, and that its expression was upregulated in cisplatin-resistant SKOV3 (SKOV3/DDP2), cisplatin-resistant A2780 (A2780/DDP) cells, and in 54 cases of drug-resistant tissues, as compared with in the controls. Furthermore, bioinformatics and text mining performed by Coremine Medical (http://www.coremine.com/medical/#search) confirmed that ITGA6 was significantly associated with ovarian cancer and drug resistance. Additionally, the high expression of ITGA6 is associated with a poor outcome. The present study provides the basis for further understanding the role of ITGA6 in the regulation of drug resistance in ovarian cancer, and demonstrates that it could be a potential marker for the prognosis of ovarian cancer.

Receptor expression by JEG-3 trophoblast cells in the presence of placenta secreted factors

Preeclampsia still remains one of the most severe pregnancy complications and is an actual problem in the obstetrics practice. At present, the joint impact of cytokines and other placenta secreted factors on trophoblast cell functional activity during preeclampsia complicated pregnancy remains unclear. The aim of the study is to estimate the surface receptors expression by trophoblast cells in the presence of placenta secreted factors during physiological pregnancy and at preeclampsia. Trophoblast cells of the JEG-3 line were incubated in the presence of supernatants obtained by cultivation of placentas from women with physiological pregnancy and with preeclampsia. Surface receptors expression by trophoblast cells was estimated by FACS Canto II flow cytometer. It was established that in the third trimester both under normal and pathological conditions, the placenta secreted factors impact on the cytokine receptor expression by trophoblast differs while the trophoblast response capacity to the migration and proliferation stimulating and inhibiting signals remains stable. JEG-3 line cells enhanced the expression of CD186, CD140a, Integrin β6, VE-cadherin, CD29, and CD140a in the case of incubation in the presence of placenta supernatants from the third-trimester pregnancy complicated with preeclampsia compared to incubation in the presence of placenta supernatants form the third trimester of physiological pregnancy.

A dimeric bicyclic RGD ligand displays enhanced integrin binding affinity and strong biological effects on U-373 MG glioblastoma cells

A C₂-symmetric dimeric bicyclic integrin ligand, bearing two RGD motifs, displays enhanced biological effects compared to monovalent RGD analogues.

Initial osteoblast adhesion and subsequent differentiation on zirconia surfaces are regulated by integrins and heparin-sensitive molecule

Purpose

It is well known that zirconia materials have good biocompatibility; however, little is known regarding the mechanism by which cells attach to these materials. The purpose of this study is to elucidate the mechanism of cell attachment.

Materials and methods

In this study, we examined the surface characteristics of ceria-stabilized zirconia/alumina nanocomposite (NANOZR), yttria-stabilized zirconia (Y-TZP) and commercially pure titanium (CpTi), and we evaluated the initial response of osteoblast-like cells to them with different inhibitors.

Results

Under the same polishing treatment, the three materials, NANOZR, Y-TZP and CpTi, show similar surface wettability but different surface roughness. Osteoblasts could adhere to the surface of all three materials, and spindle shapes were clearer in serum-containing media compared to PBS and serum-free culture media, suggesting that serum-contained proteins are helpful for the initial cell adhesion and spreading. Cell adhesion and proliferation were disrupted in the presence of EDTA. RGD-peptide interfered with cell proliferation by affecting cell protrusion and stress fibers. Monoclonal antibody against non-RGD type integrin α₂β₁ enhanced proliferation in Y-TZP, CpTi and culture dish but not in NANOZR. Cell proliferation on NANOZR was specifically inhibited in the presence of heparin. Furthermore, under heparin administration, spindle shape formation was maintained but actin cytoskeleton was disrupted, resulting in loose cellular spreading.

Conclusion

These results suggest that RGD type integrins and heparin-sensitive protein in coordination regulate cell morphology and proliferation on NANOZR, through the regulation of cell polarity and stress fiber formation, respectively.

DS-70, a novel and potent α4 integrin antagonist, is an effective treatment for experimental allergic conjunctivitis in guinea pigs

BACKGROUND AND PURPOSE

Allergic conjunctivitis is an eye inflammation that involves the infiltration of immune cells into the conjunctiva via cell surface-adhesion receptors, such as integrin α₄ β₁ . These receptors interact with adhesion molecules expressed on the conjunctival endothelium and may be a target to treat this disease. We synthesized DS-70, a novel α/β-peptidomimetic α₄ integrin antagonist, to prevent the conjunctival infiltration of immune cells and clinical symptoms in a model of allergic conjunctivitis.

EXPERIMENTAL APPROACH

In vitro, DS-70 was pharmacologically characterized using a scintillation proximity procedure to measure its affinity for α₄ β₁ integrin, and its effect on cell adhesion mediated by different integrins was also evaluated. The effects of DS-70 on vascular cell adhesion molecule-1 (VCAM-1)-mediated degranulation of a human mast cell line and an eosinophilic cell line, which both express α₄ β₁ , and on VCAM-1-mediated phosphorylation of ERK 1/2 in Jurkat E6.1 cells were investigated. Effects of DS-70 administered in the conjunctival fornix of ovalbumin-sensitized guinea pigs were evaluated.

KEY RESULTS

DS-70 bound to integrin α₄ β₁ with nanomolar affinity, prevented the adhesion of α₄ integrin-expressing cells, antagonized VCAM-1-mediated degranulation of mast cells and eosinophils and ERK 1/2 phosphorylation. Only 20% was degraded after an 8 h incubation with serum. DS-70 dose-dependently reduced the clinical symptoms of allergic conjunctivitis, conjunctival α₄ integrin expression and conjunctival levels of chemokines and cytokines in ovalbumin-sensitized guinea pigs.

CONCLUSIONS AND IMPLICATIONS

These findings highlight the role of α₄ integrin in allergic conjunctivitis and suggest that DS-70 is a potential treatment for this condition.

A critical assessment of force field accuracy against NMR data for cyclic peptides containing β-amino acids

Hybrid cyclic α/β-peptides, in which one or more β-amino acids are incorporated into the backbone, are gaining increasing interest as potential therapeutics, thanks to their ability to achieve enhanced binding affinities for a biological target through pre-organization in solution. The in silico prediction of their three dimensional structure through strategies such as MD simulations would substantially advance the rational design process. However, whether the molecular mechanics force fields are accurate in sampling highly constrained cyclopeptides containing β-amino acids remains to be verified. Here, we present a systematic assessment of the ability of 8 widely used force fields to reproduce 79 NMR observables (including chemical shifts and 3J scalar couplings) on five cyclic α/β-peptides that contain the integrin recognition motif isoDGR. Most of the investigated force fields, which include force fields from AMBER, OPLS, CHARMM and GROMOS families, display very good agreement with experimental 3J(HN,Hα), suggesting that MD simulations could be an appropriate tool in the rational design of therapeutic cyclic α-peptides. However, for NMR observables directly related to β-amino acids, we observed a poor agreement with experiments and a remarkable dependence of our evaluation on the choice of Karplus parameters. The force field weaknesses herein unveiled might constitute a source of inspiration for further force field optimization.

Selective detection of α4β1 integrin (VLA-4)-expressing cells using peptide-functionalized nanostructured materials mimicking endothelial surfaces adjacent to inflammatory sites

Persistent accumulation of immune cells mediated by α4β1 integrin (VLA-4) is a hallmark of the inflammatory diseases and of chronic inflammation observed in the affected tissues of autoimmune diseases. Aiming at exploring new methods for monitoring the course of the inflammatory processes, we designed the first peptide-functionalized nanostructured devices capable to mimic the high-density multivalency binding between the α4β1 integrin-expressing cells and the ligands overexpressed on the endothelial surfaces, in the proximity of the sites of inflammation. Specifically, we describe the first examples of monolayers constituted by dye-loaded zeolite L crystals, coated with α4β1 integrin peptide ligands, and we analyze the adhesion of model Jurkat cells in comparison to non-α4β1 integrin-expressing cells. In particular, the peptidomimetic diphenylurea-Leu-Asp-Val-diamine allows significant and selective detection of α4β1 integrin-expressing Jurkat cells, after very rapid incubation time, supporting the possible implementation in a diagnostic device capable to detect the desired cells from biological fluids, obtainable from patients in a noninvasive way.

Can Integrin Agonists Have Cards to Play against Cancer? A Literature Survey of Small Molecules Integrin Activators

The ability of integrins to activate and integrate intracellular communication illustrates the potential of these receptors to serve as functional distribution hubs in a bi-directional signal transfer outside-in and inside-out of the cells. Tight regulation of the integrin signaling is paramount for normal physiological functions such as migration, proliferation, and differentiation, and misregulated integrin activity could be associated with several pathological conditions. Because of the important roles of integrins and their ligands in biological development, immune responses, leukocyte traffic, haemostasis, and cancer, their potential as therapeutic tools is now widely recognized. Nowadays extensive efforts have been made to discover and develop small molecule ligands as integrin antagonists, whereas less attention has been payed to agonists. In recent years, it has been recognized that integrin agonists could open up novel opportunities for therapeutics, which gain benefits to increase rather than decrease integrin-dependent adhesion and transductional events. For instance, a significant factor in chemo-resistance in melanoma is a loss of integrin-mediated adhesion; in this case, stimulation of integrin signaling by agonists significantly improved the response to chemotherapy. In this review, we overview results about small molecules which revealed an activating action on some integrins, especially those involved in cancer, and examine from a medicinal chemistry point of view, their structure and behavior.

Self-assembled dehydropeptide nano carriers for delivery of ornidazole and curcumin

In the recent studies, it has been demonstrated that incorporation of unnatural amino acid, α,β-dehydrophenylalanine, in small peptides results in stable self-assembled nanostructures with different sizes and shapes. Here, we have replaced the natural amino acid, phenylalanine, from our earlier reported work on self-assembled peptide, Boc-Pro-Phe-Gly-OMe, with a constrained dehydro amino acid, α,β-dehydrophenylalanine, to study its influence on self-assembled nanostructures. Dehydrotripeptide, Boc-Pro-ΔPhe-Gly-OMe, self-assembled into nanostructures in aqueous solutions and formed hydrophobic matrix with improved encapsulation efficiency of hydrophobic molecules. The hydrodynamic size of peptide nanostructures from DLS study was found to be ∼257nm. The morphology and size of the loaded nanoparticles were also determined by TEM. To improve aqueous dispersibility the projected nanostructures for efficient use in drug delivery, self-assembled dehydropeptide nano carriers were further stabilized with Vitamin-E-TPGS. The final complex drug nanoparticles provided controlled drug release. These findings demonstrated that incorporation of constrained dehydro amino acids in peptides have the potential to construct stable nanostructures for development of nano materials with controlled drug release.

STROBE-compliant integrin through focal adhesion involve in cancer stem cell and multidrug resistance of ovarian cancer

Cancer stem cells (CSCs) are considered to be the root of carcinoma relapse and drug resistance in ovarian cancer. Hunting for the potential CSC genes and explain their functions would be a feasible strategy to meet the challenge of the drug resistance in ovarian cancer. In this study, we performed bioinformatic approaches such as biochip data extraction and pathway enrichment analyses to elucidate the mechanism of the CSC genes in regulation of drug resistance. Potential key genes, integrins, were identified to be related to CSC in addition to their associations with drug resistance and prognosis in ovarian cancer. A total of 36 ovarian CSC genes involved in regulation of drug resistance were summarized, and potential drug resistance-related CSC genes were identified based on 3 independent microarrays retrieved from the Gene Expression Omnibus (GEO) Profiles. Pathway enrichment of CSC genes associated with drug resistance in ovarian cancer indicated that focal adhesion signaling might play important roles in CSC genes-mediated drug resistance. Integrins are members of the adhesion molecules family, and integrin subunit alpha 1, integrin subunit alpha 5, and integrin subunit alpha 6 (ITGA6) were identified as central CSC genes and their expression in side population cells, cisplatin-resistant SKOV3 (SKOV3/DDP2) cells, and cisplatin-resistant A2780 (A2780/DDP) cells were dysregulated as measured by real-time quantitative polymerase chain reaction. The high expression of ITGA6 in 287 ovarian cancer patients of TCGA cohort was significantly associated with poorer progression-free survival. This study provide the basis for further understanding of CSC genes in regulation of drug resistance in ovarian cancer, and integrins could be a potential biomarker for prognosis of ovarian cancer.

Integrin-Targeting Fluorescent Proteins: Exploration of RGD Insertion Sites

The potential of the fluorescent protein scaffold to control peptide sequence functionality is illustrated by an exploration of fluorescent proteins as novel probes for targeting integrins. A library of fluorescent mCitrine proteins with RGD motifs incorporated at several positions in loops within the protein main chain was generated and characterized. Amino acid mutations to RGD as well as RGD insertions were evaluated: both led to constructs with typical mCitrine fluorescent properties. Screening experiments against four human integrin receptors revealed two strong‐binding constructs and two selective integrin binders. The effect of the site of RGD incorporation illustrates the importance of the protein scaffold on RGD sequence functionality, leading to fluorescent protein constructs with the potential for selective integrin targeting.

Modern tools for the chemical ligation and synthesis of modified peptides and proteins

The ability to improve nature's capacity by introducing modification of biological interest in proteins and peptides (P&P) is one of the modern challenges in synthetic chemistry. Due to the unfavorable pharmacokinetic properties, many native P&P are of little use as therapeutic agents. Today, few methods for the preparation of modified proteins are available. Initially introduced to realize the ligation between two standard peptidic sequences, and hence to afford native proteins, the modern chemical methodologies, in other words native chemical ligation, expressed ligation, Staudinger ligation, auxiliary mediated ligation, aldehyde capture, etc., can be virtually utilized to ligate a variety of peptidomimetic partners, allowing a systematic access to modified, unnatural large P&P.