Cyclic RGD peptides target human trabecular meshwork cells while ameliorating connective tissue growth factor-induced fibrosis

Role of integrins in the development of fibrosis in the trabecular meshwork

Primary open angle glaucoma (POAG) is a progressive and chronic disease exhibiting many of the features of fibrosis. The extracellular matrix (ECM) in the trabecular meshwork (TM) undergoes extensive remodeling and enhanced rigidity, resembling fibrotic changes. In addition, there are changes associated with myofibroblast activation and cell contractility that further drives tissue fibrosis and stiffening. This review discusses what is known about the integrins in the TM and their involvement in fibrotic processes.

Light-initiated 1,3-dipolar cycloaddition between dehydroalanines and tetrazoles: application to late-stage peptide and protein modifications

As an easily introduced noncoded amino acid with unique electrophilicity distinct from the 20 natural amino acids, dehydroalanine (Dha) is not only a precise protein post-translational modification (PTM) insertion tool, but also a promising multifunctional labelling site for peptides and proteins. However, achieving a balance between the reaction rate and mild reaction conditions has been a major challenge in developing novel Dha-modified strategies. Rapid, efficient, and mild Dha modification strategies are highly desired. Additionally, catalyst-free photocontrollable reactions for Dha-containing peptide and protein modification have yet to be developed. Here, we report a photoinitiated 1,3-dipolar cycloaddition reaction between Dha and 2,5-diaryl tetrazoles. Under low-power UV lamp irradiation, this reaction is completed within minutes without catalysis, resulting in a fluorescent pyrazoline-modified peptide or protein with excellent chemoselectivity for Dha residues. Notably, this reaction exhibits complete site-specificity in the modification of thiostrepton, a natural antimicrobial peptide containing multiple Dha residues (Dha3, Dha16, and Dha17), within 20 minutes in high yields. This is currently the fastest reaction for modifying the Dha residue in thiostrepton with clear site-specificity towards Dha16. This photoinitiated reaction also provides a chemoselective strategy for precise functionalization of proteins. Additionally, the rapidity and efficiency of the reaction minimize UV light damage to the biological reaction system. Combined with fluorogenic properties, this photo-controllable methodology can be applied to live cell imaging, further broadening the application scope of the Dha modification methodology.

Glaucoma: Novel antifibrotic therapeutics for the trabecular meshwork

Glaucoma is a chronic and progressive neurodegenerative disease characterized by the loss of retinal ganglion cells and visual field defects, and currently affects around 1% of the world's population. Elevated intraocular pressure (IOP) is the best-known modifiable risk factor and a key therapeutic target in hypertensive glaucoma. The trabecular meshwork (TM) is the main site of aqueous humor outflow resistance and therefore a critical regulator of IOP. Fibrosis, a reparative process characterized by the excessive deposition of extracellular matrix components and contractile myofibroblasts, can impair TM function and contribute to the pathogenesis of primary open-angle glaucoma (POAG) as well as the failure of minimally invasive glaucoma surgery (MIGS) devices. This paper provides a detailed overview of the current anti-fibrotic therapeutics targeting the TM in glaucoma, along with their anti-fibrotic mechanisms, efficacy as well as the current research progress from pre-clinical to clinical studies.

Human CD47-Derived Cyclic Peptides Enhance Engulfment of mAb-Targeted Melanoma by Primary Macrophages

CD47 on healthy cells, cancer cells, and even engineered particles can inhibit phagocytic clearance by binding SIRPα on macrophages. To mimic and modulate this interaction with peptides that could be used as soluble antagonists or potentially as bioconjugates to surfaces, we made cyclic "nano-Self" peptides based on the key interaction loop of human CD47. Melanoma cells were studied as a standard preclinical cancer model and were antibody-opsonized to adhere to and activate engulfment by primary mouse macrophages. Phagocytosis in the presence of soluble peptides showed cyclic > wildtype > scrambled activity, with the same trend observed with human cells. Opsonized cells that were not engulfed adhered tightly to macrophages, with opposite trends to phagocytosis. Peptide activity is nonetheless higher in human versus mouse assays, consistent with species differences in CD47-SIRPα. Small peptides thus function as soluble antagonists of a major macrophage checkpoint.

Pathogenesis of glaucoma: Extracellular matrix dysfunction in the trabecular meshwork-A review

The trabecular meshwork regulates aqueous humour outflow from the anterior chamber of the eye. It does this by establishing a tunable outflow resistance, defined by the interplay between cells and their extracellular matrix (ECM) milieu, and the molecular interactions between ECM proteins. During normal tissue homeostasis, the ECM is remodelled and trabecular cell behaviour is modified, permitting increased aqueous fluid outflow to maintain intraocular pressure (IOP) within a relatively narrow physiological pressure. Dysfunction in the normal homeostatic process leads to increased outflow resistance and elevated IOP, which is a primary risk factor for glaucoma. This review delineates some of the changes in the ECM that lead to gross as well as some more subtle changes in the structure and function of the ECM, and their impact on trabecular cell behaviour. These changes are discussed in the context of outflow resistance and glaucoma.

Targeting RGD-binding integrins as an integrative therapy for diabetic retinopathy and neovascular age-related macular degeneration

Integrins are a class of transmembrane receptors that are involved in a wide range of biological functions. Dysregulation of integrins has been implicated in many pathological processes and consequently, they are attractive therapeutic targets. In the ophthalmology arena, there is extensive evidence suggesting that integrins play an important role in diabetic retinopathy (DR), age-related macular degeneration (AMD), glaucoma, dry eye disease and retinal vein occlusion. For example, there is extensive evidence that arginyl-glycyl-aspartic acid (Arg-Gly-Asp; RGD)-binding integrins are involved in key disease hallmarks of DR and neovascular AMD (nvAMD), specifically inflammation, vascular leakage, angiogenesis and fibrosis. Based on such evidence, drugs that engage integrin-linked pathways have received attention for their potential to block all these vision-threatening pathways. This review focuses on the pathophysiological role that RGD-binding integrins can have in complex multifactorial retinal disorders like DR, diabetic macular edema (DME) and nvAMD, which are leading causes of blindness in developed countries. Special emphasis will be given on how RGD-binding integrins can modulate the intricate molecular pathways and regulate the underlying pathological mechanisms. For instance, the interplay between integrins and key molecular players such as growth factors, cytokines and enzymes will be summarized. In addition, recent clinical advances linked to targeting RGD-binding integrins in the context of DME and nvAMD will be discussed alongside future potential for limiting progression of these diseases.

Peptidomimetics Therapeutics for Retinal Disease

Ocular disorders originating in the retina can result in a partial or total loss of vision, making drug delivery to the retina of vital importance. However, effectively delivering drugs to the retina remains a challenge for ophthalmologists due to various anatomical and physicochemical barriers in the eye. This review introduces diverse administration routes and the accordant pharmacokinetic profiles of ocular drugs to aid in the development of safe and efficient drug delivery systems to the retina with a focus on peptidomimetics as a growing class of retinal drugs, which have great therapeutic potential and a high degree of specificity. We also discuss the pharmacokinetic profiles of small molecule drugs due to their structural similarity to small peptidomimetics. Lastly, various formulation strategies are suggested to overcome pharmacokinetic hurdles such as solubility, retention time, enzymatic degradation, tissue targeting, and membrane permeability. This knowledge can be used to help design ocular delivery platforms for peptidomimetics, not only for the treatment of various retinal diseases, but also for the selection of potential peptidomimetic drug targets.

Self-Assembled Dual-Targeted Epirubicin-Hybrid Polydopamine Nanoparticles for Combined Chemo-Photothermal Therapy of Triple-Negative Breast Cancer

PURPOSE

Folic acid and cyclic arginylglycylaspartic acid peptides were introduced to the surface of negatively charged lipid-coated hybrid polydopamine-cysteine cores for the delivery of epirubicin (EPI) (E/PCF-NPs). The combined chemo-photothermal therapy using E/PCF-NPs for triple-negative breast cancer was evaluated.

MATERIALS AND METHODS

The temperature elevation and thermal toxicity of nanoparticles were studied. The morphology and properties of E/PCF-NPs were characterized by transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. Physicochemical properties, including particle size, zeta potential, drug loading, entrapment efficiency (EE%), stability and in vitro release, were determined. The cell viability, reactive oxygen species (ROS) levels, ratios of oxidized nicotinamide adenine dinucleotide to its reduced form (NAD+/NADH), apoptosis assays, and cellular uptake of E/PCF-NPs were determined on 4T1 cells. Pharmacokinetic studies and tissue distributions were performed and detected by an ultra-high performance liquid chromatography/mass spectrometry system. The antitumor effects of E/PCF-NPs under near-infrared (NIR) laser irradiation were also evaluated.

RESULTS

The sphere-like morphology of E/PCF-NPs showed a high EE%, uniform size of 106.7 nm, remarkable stability, and highly improved cytotoxicity under NIR laser, when compared to that of photothermal treatment alone. In vitro release of EPI from E/PCF-NPs was pH sensitive, and a greater response was achieved under NIR laser irradiation. Compared to chemotherapy or photothermal treatment alone, the combined treatment in vitro significantly inhibited the survival rate of 4T1 cells to 17.7%, induced ROS generation, and reduced NAD+/NADH significantly. Treatment with E/PCF-NPs under irradiation induced 4T1 cell apoptosis in approximately 93.6% cells. In vitro cellular uptake of E/PCF-NPs was time-dependent. The long-circulating and higher tumor accumulation of E/PCF-NPs resulted in complete ablation of breast tumor tissue through the enhanced photothermal effect by NIR laser irradiation-mediated cell apoptosis.

CONCLUSION

E/PCF-NPs show enhanced anti-cancer effects due to synergistic effects of chemotherapy with photothermal therapy and may be potential therapeutic agents for cancer treatment.

Causative glaucoma treatment: promising targets and delivery systems

Glaucoma is one of the most common causes of blindness worldwide. Elevated intraocular pressure (IOP) is the major modifiable risk factor of the disease. Conventional therapy suffers from poor compliance, low bioavailability, and the lack of causative treatment options. To improve therapeutic success, it is crucial to identify major mediators of pathological changes associated with elevated IOP and to intervene at the molecular level. Here, we discuss relevant key functions of transforming growth factor-β2 (TGF-β2), connective tissue growth factor (CTGF), integrins, Rho-associated kinase (ROCK), and nitric oxide (NO) with regard to the onset of glaucoma, highlighting new drug delivery approaches for causative treatment.

Ligand Density and Linker Length are Critical Factors for Multivalent Nanoparticle-Receptor Interactions

Although there are a large number of studies available for the evaluation of the therapeutic efficacy of targeted polymeric nanoparticles, little is known about the critical attributes that can further influence their uptake into target cells. In this study, varying cRGD ligand densities (0-100% surface functionalization) were combined with different poly(ethylene glycol) (PEG) spacer lengths (2/3.5/5 kDa), and the specific receptor binding of targeted core-shell structured poly(lactic- co-glycolic acid)/poly(lactic acid)-PEG nanoparticles was evaluated using α_vβ₃ integrin-overexpressing U87MG glioblastoma cells. Nanoparticles with 100% surface functionalization and short PEG2k linkers displayed a high propensity to form colloidal clusters, allowing for the cooperative binding to integrin receptors on the cellular membrane. In contrast, the high flexibility of longer PEG chains enhanced the chance of ligand entanglement and shrouding, decreasing the number of ligand-receptor binding events. As a result, the combination of short PEG2k linkers and a high cRGD surface modification synergistically increased the uptake of nanoparticles into target cells. Even though to date, the nanoparticle size and its degree of functionalization are considered to be the major determinants for controlling the uptake efficiency of targeted colloids, these results strongly suggest that the role of the linker length should be carefully taken into consideration for the design of targeted drug delivery formulations to maximize the therapeutic efficacy and minimize adverse side effects.

CTGF/VEGFA-activated Fibroblasts Promote Tumor Migration Through Micro-environmental Modulation

Fibroblast activation is associated with tumor progression and implicated in metastasis, but the initial triggering signals required to kick-start this process remain largely unknown. Because small cancerous lesions share limited physical contact with neighboring fibroblasts, we reasoned the first tumor-derived signal for fibroblast activation should be secreted and diffusible. By pulsed metabolic labeling and click-chemistry based affinity enrichment, we sieved through the ductal carcinoma secretome for potential fibroblast activators. Using immuno-depletion/supplementation assays on various secreted factors, we pinpointed that tumor-secreted CTGF/VEGFA alone is sufficient to activate paired mammary fibroblasts from the same patient via ROCK1 and JunB signaling. Fibroblasts activated in this manner are distinct in morphology, growth, and adopt a highly tumor-like secretion profile, which in turn promotes tumor migration by counteracting oxidative and lactate stress. These findings reveal a profound division-of-labor between normal and cancer cells under the directive of the latter, and allude to potential metastatic prevention through inhibiting local fibroblast activation.

The many faces of the trabecular meshwork cell

With the combined purpose of facilitating useful vision over a lifetime, a number of ocular cells have evolved specialized features not found elsewhere in the body. The trabecular meshwork (TM) cell at the irido-corneal angle, which is a key regulator of intraocular pressure, is no exception. Examination of cells in culture isolated from the human TM has shown that they are unique in many ways, displaying characteristic features of several different cell types. Thus, these neural crest derived cells display expression patterns and behaviors typical of endothelia, fibroblasts, smooth muscle and macrophages, owing to the multiple roles and two distinct environments where they operate to maintain intraocular pressure homeostasis. In most individuals, TM cells function normally over a lifetime in the face of persistent stressors, including phagocytic, oxidative, mechanical and metabolic stress. Study of TM cells isolated from ocular hypertensive eyes has shown a compromised ability to perform their daily duties. This review highlights the many responsibilities of the TM cell and its challenges, progress in our understanding of TM biology over the past 30 years, as well as discusses unanswered questions about TM dysfunction that results in IOP dysregulation and glaucoma.