Matrix metalloproteases: underutilized targets for drug delivery

Unveiling Novel Drug Targets and Emerging Therapies for Rheumatoid Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disease, that causes joint damage, deformities, and decreased functionality. In addition, RA can also impact organs like the skin, lungs, eyes, and blood vessels. This autoimmune condition arises when the immune system erroneously targets the joint synovial membrane, resulting in synovitis, pannus formation, and cartilage damage. RA treatment is often holistic, integrating medication, physical therapy, and lifestyle modifications. Its main objective is to achieve remission or low disease activity by utilizing a "treat-to-target" approach that optimizes drug usage and dose adjustments based on clinical response and disease activity markers. The primary RA treatment uses disease-modifying antirheumatic drugs (DMARDs) that help to interrupt the inflammatory process. When there is an inadequate response, a combination of biologicals and DMARDs is recommended. Biological therapies target inflammatory pathways and have shown promising results in managing RA symptoms. Close monitoring for adverse effects and disease progression is critical to ensure optimal treatment outcomes. A deeper understanding of the pathways and mechanisms will allow new treatment strategies that minimize adverse effects and maintain quality of life. This review discusses the potential targets that can be used for designing and implementing precision medicine in RA treatment, spotlighting the latest breakthroughs in biologics, JAK inhibitors, IL-6 receptor antagonists, TNF blockers, and disease-modifying noncoding RNAs.

Enzyme-responsive design combined with photodynamic therapy for cancer treatment

Photodynamic therapy (PDT) is a noninvasive cancer treatment that has garnered significant attention in recent years. However, its application is still hampered by certain limitations, such as the hydrophobicity and low targeting of photosensitizers (PSs) and the hypoxia of the tumor microenvironment. Nevertheless, the fusion of enzyme-responsive drugs with PDT offers novel solutions to overcome these challenges. Utilizing the attributes of enzyme-responsive drugs, PDT can deliver PSs to the target site and selectively release them, thereby enhancing therapeutic outcomes. In this review, we spotlight recent advances in enzyme-responsive materials for cancer treatment and primarily delineate their application in combination with PDT.

Delving into Matrix Metalloproteinase-1 (MMP-1) and its Significance in Periodontal Diseases

Matrix metalloproteinase-1 (MMP-1) plays a pivotal role in the pathogenesis of periodontal diseases, particularly periodontitis, by virtue of its collagenolytic activity targeting collagen type I, the primary component of periodontal tissues. This review abstract elucidates the intricate involvement of MMP-1 in periodontal tissue homeostasis and its dysregulation in disease states. Elevated MMP-1 levels, observed in gingival tissues and crevicular fluid of individuals with periodontitis, correlate with the degradation of collagen fibers within the periodontium. This degradation contributes to the detachment of teeth from surrounding tissues and exacerbates alveolar bone resorption, hallmark features of periodontal breakdown. Therapeutically, targeting MMP-1 activity emerges as a promising strategy, prompting ongoing research into MMP inhibitors and host modulation therapies. Understanding MMP-1's nuanced role in periodontal diseases paves the way for personalized treatment approaches and holds promise in reshaping periodontal disease management for improved patient outcomes and periodontal health.

Effects of Nanomaterials on Synthesis and Degradation of the Extracellular Matrix

Extracellular matrix (ECM) remodeling is accompanied by the continuous synthesis and degradation of the ECM components. This dynamic process plays an important role in guiding cell adhesion, migration, proliferation, and differentiation, as well as in tissue development, body repair, and maintenance of homeostasis. Nanomaterials, due to their photoelectric and catalytic properties and special structure, have garnered much attention in biomedical fields for use in processes such as tissue engineering and disease treatment. Nanomaterials can reshape the cell microenvironment by changing the synthesis and degradation of ECM-related proteins, thereby indirectly changing the behavior of the surrounding cells. This review focuses on the regulatory role of nanomaterials in the process of cell synthesis of different ECM-related proteins and extracellular protease. We discuss influencing factors and possible related mechanisms of nanomaterials in ECM remodeling, which may provide different insights into the design and development of nanomaterials for the treatment of ECM disorder-related diseases.

Hydrogel-Based Growth Factor Delivery Platforms: Strategies and Recent Advances

Growth factors play a crucial role in regulating a broad variety of biological processes and are regarded as powerful therapeutic agents in tissue engineering and regenerative medicine in the past decades. However, their application is limited by their short half-lives and potential side effects in physiological environments. Hydrogels are identified as having the promising potential to prolong the half-lives of growth factors and mitigate their adverse effects by restricting them within the matrix to reduce their rapid proteolysis, burst release, and unwanted diffusion. This review discusses recent progress in the development of growth factor-containing hydrogels for various biomedical applications, including wound healing, brain tissue repair, cartilage and bone regeneration, and spinal cord injury repair. In addition, the review introduces strategies for optimizing growth factor release including affinity-based delivery, carrier-assisted delivery, stimuli-responsive delivery, spatial structure-based delivery, and cellular system-based delivery. Finally, the review presents current limitations and future research directions for growth factor-delivering hydrogels.

Current Advances in Stimuli-Responsive Hydrogels as Smart Drug Delivery Carriers

In recent years, significant advancements in the field of advanced materials and hydrogel engineering have enabled the design and fabrication of smart hydrogels and nanogels that exhibit sensitivity to specific signals or pathological conditions, leading to a wide range of applications in drug delivery and disease treatment. This comprehensive review aims to provide an in-depth analysis of the stimuli-responsive principles exhibited by smart hydrogels in response to various triggers, such as pH levels, temperature fluctuations, light exposure, redox conditions, or the presence of specific biomolecules. The functionality and performance characteristics of these hydrogels are highly influenced by both their constituent components and fabrication processes. Key design principles, their applications in disease treatments, challenges, and future prospects were also discussed. Overall, this review aims to contribute to the current understanding of gel-based drug delivery systems and stimulate further research in this rapidly evolving field.

Developments on the Smart Hydrogel-Based Drug Delivery System for Oral Tumor Therapy

At present, an oral tumor is usually treated by surgery combined with preoperative or postoperative radiotherapies and chemotherapies. However, traditional chemotherapies frequently result in substantial toxic side effects, including bone marrow suppression, malfunction of the liver and kidneys, and neurotoxicity. As a new local drug delivery system, the smart drug delivery system based on hydrogel can control drug release in time and space, and effectively alleviate or avoid these problems. Environmentally responsive hydrogels for smart drug delivery could be triggered by temperature, photoelectricity, enzyme, and pH. An overview of the most recent research on smart hydrogels and their controlled-release drug delivery systems for the treatment of oral cancer is given in this review. It is anticipated that the local drug release method and environment-responsive benefits of smart hydrogels will offer a novel technique for the low-toxicity and highly effective treatment of oral malignancy.

Matrix Metalloproteinases in Dental and Periodontal Tissues and Their Current Inhibitors: Developmental, Degradational and Pathological Aspects

Objectives: This review article aims to describe some of the roles of Matrix metalloproteinases (MMPs) in enamel, dentine, dental caries, hybrid layer degradation, pulp and periodontal tissues, throwing light on their current inhibitors. The article addresses the potential of MMPs to serve as biomarkers with diagnostic and therapeutic value. Design: The sections of this review discuss MMPs’ involvement in developmental, remodeling, degradational and turnover aspects of dental and periodontal tissues as well as their signals in the pathogenesis, progress of different lesions and wound healing of these tissues. The literature was searched for original research articles, review articles and theses. The literature search was conducted in PubMed and MEDLINE for articles published in the last 20 years. Results: 119 published papers, two textbooks and two doctoral theses were selected for preparing the current review. Conclusions: MMPs are significant proteases, of evident contribution in dental and periapical tissue development, health and disease processes, with promising potential for use as diagnostic and prognostic disease biomarkers. Continuing understanding of their role in pathogenesis and progress of different dental, periapical and periodontal lesions, as well as in dentine-pulp wound healing could be a keystone to future diagnostic and therapeutic regimens.

Enzyme-Responsive Hydrogels as Potential Drug Delivery Systems-State of Knowledge and Future Prospects

Fast advances in polymer science have provided new hydrogels for applications in drug delivery. Among modern drug formulations, polymeric type stimuli-responsive hydrogels (SRHs), also called smart hydrogels, deserve special attention as they revealed to be a promising tool useful for a variety of pharmaceutical and biomedical applications. In fact, the basic feature of these systems is the ability to change their mechanical properties, swelling ability, hydrophilicity, or bioactive molecules permeability, which are influenced by various stimuli, particularly enzymes. Indeed, among a great number of SHRs, enzyme-responsive hydrogels (ERHs) gain much interest as they possess several potential biomedical applications (e.g., in controlled release, drug delivery, etc.). Such a new type of SHRs directly respond to many different enzymes even under mild conditions. Therefore, they show either reversible or irreversible enzyme-induced changes both in chemical and physical properties. This article reviews the state-of-the art in ERHs designed for controlled drug delivery systems (DDSs). Principal enzymes used for biomedical hydrogel preparation were presented and different ERHs were further characterized focusing mainly on glucose oxidase-, β-galactosidase- and metalloproteinases-based catalyzed reactions. Additionally, strategies employed to produce ERHs were described. The current state of knowledge and the discussion were made on successful applications and prospects for further development of effective methods used to obtain ERH as DDSs.

Hydrogels and Hydrogel Nanocomposites: Enhancing Healthcare through Human and Environmental Treatment

Humans are constantly exposed to exogenous chemicals throughout their life, which can lead to a multitude of negative health impacts. Advanced materials can play a key role in preventing or mitigating these impacts through a wide variety of applications. The tunable properties of hydrogels and hydrogel nanocomposites (e.g., swelling behavior, biocompatibility, stimuli responsiveness, functionality, etc.) have deemed them ideal platforms for removal of environmental contaminants, detoxification, and reduction of body burden from exogenous chemical exposures for prevention of disease initiation, and advanced treatment of chronic diseases, including cancer, diabetes, and cardiovascular disease. In this review, three main junctures where the use of hydrogel and hydrogel nanocomposite materials can intervene to positively impact human health are highlighted: 1) preventing exposures to environmental contaminants, 2) prophylactic treatments to prevent chronic disease initiation, and 3) treating chronic diseases after they have developed.

HSP90 as a regulator of extracellular matrix dynamics

The extracellular matrix (ECM) is a dynamic and organised extracellular network assembled from proteins and carbohydrates exported from the cell. The ECM is critical for multicellular life, providing spatial and temporal cellular cues to maintain tissue homeostasis. Consequently, ECM production must be carefully balanced with turnover to ensure homeostasis; ECM dysfunction culminates in disease. Hsp90 is a molecular chaperone central to protein homeostasis, including in the ECM. Intracellular and extracellular Hsp90 isoforms collaborate to regulate the levels and status of proteins in the ECM via multiple mechanisms. In so doing, Hsp90 regulates ECM dynamics, and changes in Hsp90 levels or activity support the development of ECM-related diseases, like cancer and fibrosis. Consequently, Hsp90 levels may have prognostic value, while inhibition of Hsp90 may have therapeutic potential in conditions characterised by ECM dysfunction.

Causal contributors to tissue stiffness and clinical relevance in urology

Mechanomedicine is an emerging field focused on characterizing mechanical changes in cells and tissues coupled with a specific disease. Understanding the mechanical cues that drive disease progression, and whether tissue stiffening can precede disease development, is crucial in order to define new mechanical biomarkers to improve and develop diagnostic and prognostic tools. Classically known stromal regulators, such as fibroblasts, and more recently acknowledged factors such as the microbiome and extracellular vesicles, play a crucial role in modifications to the stroma and extracellular matrix (ECM). These modifications ultimately lead to an alteration of the mechanical properties (stiffness) of the tissue, contributing to disease onset and progression. We describe here classic and emerging mediators of ECM remodeling, and discuss state-of-the-art studies characterizing mechanical fingerprints of urological diseases, showing a general trend between increased tissue stiffness and severity of disease. Finally, we point to the clinical potential of tissue stiffness as a diagnostic and prognostic factor in the urological field, as well as a possible target for new innovative drugs.

Advancements in folate receptor targeting for anti-cancer therapy: A small molecule-drug conjugate approach

Targeted delivery combined with controlled release of drugs has a crucial role in future of personalized medicine. The majority of cancer drugs are intended to interfere with one or more cellular events. Anticancer agents can also be toxic to healthy cells, as healthy cells may also need to proliferate and avoid apoptosis. The focus of this review covers the principles, advantages, drawbacks and summarize criteria that must be met for design of small molecule-drug conjugates (SMDCs) to achieve the desired therapeutic potency with minimal toxicity. SMDCs are composed of a targeting ligand, a releasable bridge, a spacer, and a therapeutic payload. We summarize the criteria for the effective design that influences the selection of tumor specific receptor and optimum elements in the design of SMDCs. We also discuss the criteria for selecting the optimal therapeutic drug payload, spacer and linker. The linker chemistries and cleavage strategies are also discussed. Finally, we review the folate receptor targeting SMDCs that are in preclinical development and in clinical trials.

Enzyme-Triggered Disassembly of Polymeric Micelles by Controlled Depolymerization via Cascade Cyclization for Anticancer Drug Delivery

The high activity of specific enzymes in cancer has been utilized in cancer diagnosis, as well as tumor-targeted drug delivery. NAD(P)H:quinone oxidoreductase-1 (NQO1), an overexpressed enzyme in certain tumor types, maintains homeostasis and inhibits oxidative stress caused by elevated reactive oxygen species (ROS) in tumor cells. The activity of NQO1 in lung and liver cancer cells is increased compared to that in normal cells. Interestingly, NQO1 reacts with trimethyl-locked quinone propionic acid (QPA) and produces a lactone-based group via intramolecular cyclization. Toward this objective, we synthesized an amphiphilic block copolymer (QPA-P) composed of NQO1 enzyme-triggered depolymerizable QPA-locked polycaprolactone (PCL) and poly(ethylene glycol) (PEG) as hydrophobic and hydrophilic constituents, respectively. This QPA-P formed self-assembled micelles in aqueous conditions. It was observed that NQO1 catalyzed the depolymerization of QPA-locked PCL via a cascade two-step cyclization process, which eventually induced the dissociation of micellar structure and triggered the release of loaded drugs at the target cancer cells. Compared to the control group, the NQO1-responsive micelle showed NQO1-triggered intracellular drug release and enhanced anticancer effects. These results indicate that the NQO1-responsive polymeric micelles present a promising potential for improving therapeutic efficacy of an anticancer drug delivery system.

Outline of gelatinase inhibitors as anti-cancer agents: A patent mini-review for 2010-present

Matrix metalloproteinases (MMPs) are involved in several pathological and physiological functions. Gelatinases (MMP-2 and -9) have significant attention as therapeutic targets against cancer. Gelatinase inhibitors have demonstrated their effectiveness in several diseases including cancer. However, it is quite a challenging task to develop inhibitors as a therapeutic agent. This review summarizes the patent dedicated to the medicinal chemistry of gelatinase inhibitor reported over last decades. We examine the patent being pursued for gelatinase inhibitor development to highlight the key issues. The main aim is to provide the scientific community with an overview of the patented gelatinase inhibitors to allow further development. During early 2000s, some MMP inhibitors failed to pass the clinical trials. Hence, the lessons learned from early evidence and recent knowledge in that field will rejuvenate the development of selective inhibitors. Various studies and patents have continued in the recent years to expand knowledge. Continuously, our research team has been involved in the design of potent and selective gelatinase inhibitors for the past few years. This study is a part of our efforts. This study may be beneficial in the design and development of better gelatinase inhibitors in the future.

Tuneable peptide cross-linked nanogels for enzyme-triggered protein delivery

Many diseases are associated with the dysregulated activity of enzymes, such as matrix metalloproteinases (MMPs). This dysregulation can be leveraged in drug delivery to achieve disease- or site-specific cargo release. Self-assembled polymeric nanoparticles are versatile drug carrier materials due to the accessible diversity of polymer chemistry. However, efficient loading of sensitive cargo, such as proteins, and introducing functional enzyme-responsive behaviour remain challenging. Herein, peptide-crosslinked, temperature-sensitive nanogels for protein delivery were designed to respond to MMP-7, which is overexpressed in many pathologies including cancer and inflammatory diseases. The incorporation of N-cyclopropylacrylamide (NCPAM) into N-isopropylacrylamide (NIPAM)-based copolymers enabled us to tune the polymer lower critical solution temperature from 33 to 44 °C, allowing the encapsulation of protein cargo and nanogel-crosslinking at slightly elevated temperatures. This approach resulted in nanogels that were held together by MMP-sensitive peptides for enzyme-specific protein delivery. We employed a combination of cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), small angle neutron scattering (SANS), and fluorescence correlation spectroscopy (FCS) to precisely decipher the morphology, self-assembly mechanism, enzyme-responsiveness, and model protein loading/release properties of our nanogel platform. Simple variation of the peptide linker sequence and combining multiple different crosslinkers will enable us to adjust our platform to target specific diseases in the future.

Advances in Therapeutic Targeting of Cancer Stem Cells within the Tumor Microenvironment: An Updated Review

Despite great strides being achieved in improving cancer patients' outcomes through better therapies and combinatorial treatment, several hurdles still remain due to therapy resistance, cancer recurrence and metastasis. Drug resistance culminating in relapse continues to be associated with fatal disease. The cancer stem cell theory posits that tumors are driven by specialized cancer cells called cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells known to be resistant to therapy and cause metastasis. Whilst the debate on whether CSCs are the origins of the primary tumor rages on, CSCs have been further characterized in many cancers with data illustrating that CSCs display great abilities to self-renew, resist therapies due to enhanced epithelial to mesenchymal (EMT) properties, enhanced expression of ATP-binding cassette (ABC) membrane transporters, activation of several survival signaling pathways and increased immune evasion as well as DNA repair mechanisms. CSCs also display great heterogeneity with the consequential lack of specific CSC markers presenting a great challenge to their targeting. In this updated review we revisit CSCs within the tumor microenvironment (TME) and present novel treatment strategies targeting CSCs. These promising strategies include targeting CSCs-specific properties using small molecule inhibitors, immunotherapy, microRNA mediated inhibitors, epigenetic methods as well as targeting CSC niche-microenvironmental factors and differentiation. Lastly, we present recent clinical trials undertaken to try to turn the tide against cancer by targeting CSC-associated drug resistance and metastasis.

Smart Hydrogels - Synthetic Stimuli-Responsive Antitumor Drug Release Systems

Among modern drug formulations, stimuli-responsive hydrogels also called "smart hydrogels" deserve a special attention. The basic feature of this system is the ability to change their mechanical properties, swelling ability, hydrophilicity, bioactive molecules permeability, etc., influenced by various stimuli, such as temperature, pH, electromagnetic radiation, magnetic field and biological factors. Therefore, stimuli-responsive matrices can be potentially used in tissue engineering, cell cultures and technology of innovative drug delivery systems (DDSs), releasing the active substances under the control of internal or external stimuli. Moreover, smart hydrogels can be used as injectable DDSs, due to gel-sol transition connected with in situ cross-linking process. Innovative smart hydrogel DDSs can be utilized as matrices for targeted therapy, which enhances the effectiveness of tumor chemotherapy and subsequently limits systemic toxicity. External stimulus sensitivity allows remote control over the drug release profile and gel formation. On the other hand, internal factors provide drg accumulation in tumor tissue and reduce the concentration of active drug form in healthy tissue. In this report, we summarise the basic knowledge and chemical strategies for the synthetic smart hydrogel DDSs applied in antitumor therapy.

Inhibiting Matrix Metalloproteinase-2 Activation by Perturbing Protein-Protein Interactions Using a Cyclic Peptide

We report on a cyclic peptide that inhibits matrix metalloproteinase-2 (MMP2) activation with a low-nM-level potency. This inhibitor specifically binds to the D₅₇₀-A₅₈₃ epitope on proMMP2 and interferes with the protein-protein interaction (PPI) between proMMP2 and tissue inhibitor of metalloproteinases-2 (TIMP2), thereby preventing the TIMP2-assisted proMMP2 activation process. We developed this cyclic peptide inhibitor through an epitope-targeted library screening process and validated its binding to proMMP2. Using a human melanoma cell line, we demonstrated the cyclic peptide's ability to modulate cellular MMP2 activities and inhibit cell migration. These results provide the first successful example of targeting the PPI between proMMP2 and TIMP2, confirming the feasibility of an MMP2 inhibition strategy that has been sought after for 2 decades.

Targeting Inhibition of Foxp3 by MMP2/9 Sensitive Short Peptide Linked P60 Fusion Protein 6(P60-MMPs) to Enhance Antitumor Immunity

Regulatory T-cells (Tregs) play an important role in tumor immunosuppressive network, thus Tregs-targeted strategy is expected to enhance antitumor immunity and improve the effect of immunotherapy. Short peptide P60 can bind to the forkhead box protein P3 (Foxp3), a crucial transcriptional regulator for the development and inhibitory function of Tregs, and inhibit Foxp3 nuclear translocation in Tregs. However, its treatment effect in cancer is limited due to nonspecificity. Therefore, realizing the specific delivery of P60 in tumor microenvironment will greatly facilitate its Treg-suppressing effect for tumor therapeutics. Herein, utilizing the unique matrix metallase protease 2/9 (MMP2/9) overexpressing feature in tumor tissues, a fusion protein 6(P60-MMPs) containing six segments of P60 linked by MMP2/9-sensitive peptides is constructed for antitumor targeting immunotherapy. The fusion protein 6(P60-MMPs) specifically degrades into short peptide P60 in tumor, and then binds to Foxp3 to inhibit Foxp3 nuclear translocation in Tregs, thus impairing Tregs' activity. This fusion protein efficiently inhibits murine breast cancer 4T1 transplanted tumor growth and decreases lung metastasis through down-regulating tumor-infiltrated Tregs and up-regulating CD8⁺ T cells in tumor tissue. The study develops a Treg-targeted anticancer fusion protein with effective therapeutic activity, suggesting its potential in clinical translation.

Novel octapeptide-DTX prodrugs targeting MMP-7 as effective agents for the treatment of colorectal cancer with lower systemic toxicity

Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer death around the world. The current treatments of CRC exhibited high occurrence rate of side effects. Docetaxel (DTX), an important drug widely used in cancer chemotherapy, showed serious toxicity in CRC. Reducing toxicity of DTX could be a feasible and promising way to achieve the new indication of DTX for CRC. In this study, a series of MMP-7 activated octapeptide-DTX/4FDT prodrugs (6a-10a and 6b-10b) were designed and synthesized based on the features of MMP-7 which is highly expressed in CRC and could specially recognize octapeptides with specific sequences. Among them, 9a and 9b, both possessing an octapeptide Gly-Pro-Gln-Gly-Ile-Ala-Met-Gln moiety, were the most potent prodrugs. Compounds 9a and 9b were also tested their release rate in HCT116 cell culture fluids and tumor homogenate along with in vivo anti-CRC activity and systemic toxicity. Since 9a showed better anti-CRC activity and lower systemic toxicity than 9b in CRC tumor bearing mice, it was further evaluated for its acute toxicity, pharmacokinetics and tissue distribution in comparison with its parent drug DTX. These results revealed that 9a possessed good systemic stability, rapid release rate in CRC and reduced systemic toxicity, while retaining similar anti-CRC activity to its parent drug DTX. Thus, 9a, an MMP-7 polypeptide prodrug of DTX, has been identified as a promising candidate for the treatment of CRC.

Molecular Mechanisms of Complement System Proteins and Matrix Metalloproteinases in the Pathogenesis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disorder affecting predominantly the older people above the age of 50 years in which the macular region of the retina deteriorates, resulting in the loss of central vision. The key factors associated with the pathogenesis of AMD are age, smoking, dietary, and genetic risk factors. There are few associated and plausible genes involved in AMD pathogenesis. Common genetic variants (with a minor allele frequency of >5% in the population) near the complement genes explain 40-60% of the heritability of AMD. The complement system is a group of proteins that work together to destroy foreign invaders, trigger inflammation, and remove debris from cells and tissues. Genetic changes in and around several complement system genes, including the CFH, contribute to the formation of drusen and progression of AMD. Similarly, Matrix metalloproteinases (MMPs) that are normally involved in tissue remodeling also play a critical role in the pathogenesis of AMD. MMPs are involved in the degradation of cell debris and lipid deposits beneath retina but with age their functions get affected and result in the drusen formation, succeeding to macular degeneration. In this review, AMD pathology, existing knowledge about the normal and pathological role of complement system proteins and MMPs in the eye is reviewed. The scattered data of complement system proteins, MMPs, drusenogenesis, and lipofusogenesis have been gathered and discussed in detail. This might add new dimensions to the understanding of molecular mechanisms of AMD pathophysiology and might help in finding new therapeutic options for AMD.

Myocardial-Infarction-Responsive Smart Hydrogels Targeting Matrix Metalloproteinase for On-Demand Growth Factor Delivery

Although in situ restoration of blood supply to the infarction region and attenuating pre-existing extracellular matrix degradation remain potential therapeutic approaches for myocardial infarction (MI), local delivery of therapeutics has been limited by low accumulation (inefficacy) and unnecessary diffusion (toxicity). Here, a dual functional MI-responsive hydrogel is fabricated for on-demand drug delivery to promote angiogenesis and inhibit cardiac remodeling by targeting upregulated matrix metalloproteinase-2/9 (MMP-2/9) after MI. A glutathione (GSH)-modified collagen hydrogel (collagen-GSH) is prepared by conjugating collagen amine groups with GSH sulfhydryl groups and the recombinant protein GST-TIMP-bFGF (bFGF: basic fibroblast growth factor) by fusing bFGF with glutathione-S-transferase (GST) and MMP-2/9 cleavable peptide PLGLAG (TIMP). Specific binding between GST and GSH significantly improves the amount of GST-TIMP-bFGF loaded in collagen-GSH hydrogel. The TIMP peptide enclosed between GST and bFGF responds to MMPs for on-demand release during MI. Additionally, the TIMP peptide is a competitive substrate of MMPs that inhibits the excessive degradation of cardiac matrix by MMPs after MI. GST-TIMP-bFGF/collagen-GSH hydrogels promote the recovery of MI rats by enhancing vascularization and ameliorating myocardium remodeling. The results suggest that on-demand growth factor delivery by synchronously controlling binding and responsive release to promote angiogenesis and attenuate cardiac remodeling might be promising for the treatment of ischemic heart disease.

The Rebirth of Matrix Metalloproteinase Inhibitors: Moving Beyond the Dogma

The pursuit of matrix metalloproteinase (MMP) inhibitors began in earnest over three decades ago. Initial clinical trials were disappointing, resulting in a negative view of MMPs as therapeutic targets. As a better understanding of MMP biology and inhibitor pharmacokinetic properties emerged, it became clear that initial MMP inhibitor clinical trials were held prematurely. Further complicating matters were problematic conclusions drawn from animal model studies. The most recent generation of MMP inhibitors have desirable selectivities and improved pharmacokinetics, resulting in improved toxicity profiles. Application of selective MMP inhibitors led to the conclusion that MMP-2, MMP-9, MMP-13, and MT1-MMP are not involved in musculoskeletal syndrome, a common side effect observed with broad spectrum MMP inhibitors. Specific activities within a single MMP can now be inhibited. Better definition of the roles of MMPs in immunological responses and inflammation will help inform clinic trials, and multiple studies indicate that modulating MMP activity can improve immunotherapy. There is a U.S. Food and Drug Administration (FDA)-approved MMP inhibitor for periodontal disease, and several MMP inhibitors are in clinic trials, targeting a variety of maladies including gastric cancer, diabetic foot ulcers, and multiple sclerosis. It is clearly time to move on from the dogma of viewing MMP inhibition as intractable.

Quantitative Multiplex Substrate Profiling of Peptidases by Mass Spectrometry

Proteolysis is an integral component of life and has been implicated in many disease processes. To improve our understanding of peptidase function, it is imperative to develop tools to uncover substrate specificity and cleavage efficiency. Here, we combine the quantitative power of tandem mass tags (TMTs) with an established peptide cleavage assay to yield quantitative Multiplex Substrate Profiling by Mass Spectrometry (qMSP-MS). This assay was validated with papain, a well-characterized cysteine peptidase, to generate cleavage efficiency values for hydrolysis of 275 unique peptide bonds in parallel. To demonstrate the breath of this assay, we show that qMSP-MS can uncover the substrate specificity of minimally characterized intramembrane rhomboid peptidases, as well as define hundreds of proteolytic activities in complex biological samples, including secretions from lung cancer cell lines. Importantly, our qMSP-MS library uses synthetic peptides whose termini are unmodified, allowing us to characterize not only endo- but also exo-peptidase activity. Each cleaved peptide sequence can be ranked by turnover rate, and the amino acid sequence of the best substrates can be used for designing fluorescent reporter substrates. Discovery of peptide substrates that are selectively cleaved by peptidases which are active at the site of disease highlights the potential for qMSP-MS to guide the development of peptidase-activating drugs for cancer and infectious disease.

Enhanced nanoparticle delivery exploiting tumour-responsive formulations

Nanoparticles can be used as drug carriers, contrast agents and radiosensitisers for the treatment of cancer. Nanoparticles can either passively accumulate within tumour sites, or be conjugated with targeting ligands to actively enable tumour deposition. With respect to passive accumulation, particles < 150 nm accumulate with higher efficiency within the tumour microenvironment, a consequence of the enhanced permeability and retention effect. Despite these favourable properties, clinical translation of nano-therapeutics is inhibited due to poor in vivo stability, biodistribution and target cell internalisation. Nano-therapeutics can be modified to exploit features of the tumour microenvironment such as elevated hypoxia, increased pH and a compromised extracellular matrix. This is in contrast to cytotoxic chemotherapies which generally do not exploit the characteristic pathological features of the tumour microenvironment, and as such are prone to debilitating systemic toxicities. This review examines strategies for tumour microenvironment targeting to improve nanoparticle delivery, with particular focus on the delivery of nucleic acids and gold nanoparticles. Evidence for key research areas and future technologies are presented and critically evaluated. Among the most promising technologies are the development of next-generation cell penetrating peptides and the incorporation of micro-environment responsive stealth molecules.

Matrix remodeling in chronic lung diseases

Multicellular organisms synthesize and renew components of their subcellular and scaffolding proteins, collectively known as the extracellular matrix molecules (ECMs). In the lung, ECMs maintain tensile strength, elasticity, and dictate the specialized function of multiple cell lineages. These functions are critical in lung homeostatic processes including cellular migration and proliferation during morphogenesis or in response to repair. Alterations in lung ECMs that expose cells to new cryptic fragments, generated in response to endogenous proteinases or exogenous toxins, are associated with the development of several common respiratory diseases. How lung ECMs provide or relay vital signals to epithelial and mesenchymal cells has shed new light on development and progression of several common chronic respiratory diseases. This review will consider how ECMs regulate lung homeostasis and their reorganization under pathological conditions that can modulate the inflammatory diseases asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Better understanding of changes in the distribution of lung ECM could provide novel therapeutic approaches to treat chronic lung diseases.

Enzyme-responsive Drug Delivery Systems

One major challenge in the pharmaceutical industry is how to deliver drugs locally and specifically to a target area. One way to accomplish this is to develop drug delivery vehicles that respond to biomarkers or other cues that are indicative of a disease state. Over the past several years, enzymes have become key targets for bio-recognition due to their role in both healthy and diseased tissues. This has led to the development of drug delivery vehicles that release their cargo via either carrier degradation, shape change, or bond cleavage due to enzymes over-expressed at the disease site. This chapter will focus on the use of both oxidoreductases and hydrolases as triggers for enzyme-responsive drug delivery systems.

Toxicological profile and safety pharmacology of a single dose of fibroblast activation protein-α-based doxorubicin prodrug: in-vitro and in-vivo evaluation

Fibroblast activation protein-α (FAPα) is a promising tumor-associated target expressed by reactive stromal fibroblasts in tumor tissue. FAPα has a postprolyl peptidase activity and can specifically cleave N-terminal benzyloxycarbonyl (Z)-blocked peptides, such as the substrate Z-Gly-Pro-AMC. Doxorubicin (DOX) is an effective antitumor drug, but its application is greatly limited by toxic adverse effects owing to poor tumor selectivity. Based on these facts, we previously designed a FAPα-targeting prodrug of doxorubicin (FTPD) which can be selectively hydrolyzed by FAPα. FTPD can retain potent antitumor efficacy and has favorable tumor targeting. The present study aimed to further evaluate the toxicological profile and the safety pharmacological property of FTPD in vitro and in vivo. The cytotoxicity assay showed that FTPD displayed markedly lower cytotoxicity to 3T3 cells and HEK-293 cells compared with DOX. In the short-term toxicity study, mice treated with 25 mg/kg of FTPD showed no obvious change in the appearance and general behavior, and no case of mortality was observed within 14 days. Unlike DOX, FTPD exhibited reduced toxicity to heart, liver, kidney, spleen as well as peripheral white blood cells in mice. Moreover, open file test and general pharmacology study were also conducted correspondingly in mice and beagle dogs. It was found that FTPD may not produce significant pharmacological effects on spontaneous locomotor activity and cardiovascular-respiratory system except for a transient decreasing in systolic blood pressure. Taken together, the results of this work suggest that FTPD has more favorable toxicological profile and better drug safety compared with its parent drug DOX.

Antitumoral and antimetastatic activity of Maitake D-Fraction in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is associated with poor prognosis, high local recurrence rate and high rate of metastasis compared with other breast cancer subtypes. In addition, TNBC lacks a targeted therapy. This scenario highlights the need for novel compounds with high potential for TNBC treatment. In this regard, natural products are important sources of anticancer drugs. D-Fraction, a proteoglucan extracted from the edible and medicinal mushroom Grifola frondosa (Maitake), is a dietary supplement that has been shown to exert both immunostimulatory and immune-independent antitumoral effects on some cancer types. However, its antitumoral potential in TNBC is unknown. Therefore, we employed TNBC cells to investigate if D-Fraction is able to attenuate their aggressive phenotype. We found that D-Fraction decreases MDA-MB-231 cell viability through apoptosis induction and reduces their metastatic potential. D-Fraction increases cell-cell adhesion by increasing E-cadherin protein levels and β-catenin membrane localization, and increases cell-substrate adhesion. D-Fraction also decreases cell motility by affecting actin cytoskeleton rearrangements, and proteolytic activity of MMP-2 and MMP-9. Furthermore, D-Fraction decreases the invasive capacity of MDA-MB-231 cells. In concordance, D-Fraction retards tumor growth and reduces lung metastases in a xenograft model. Altogether, these results suggest the potential therapeutic role of D-Fraction in aggressive TNBC.

Application of Bld-1-Embedded Elastin-Like Polypeptides in Tumor Targeting

Expression of various molecules on the surface of cancer cells compared to normal cells creates a platform for the generation of various drug vehicles for targeted therapy. Multiple interactions between ligands and their receptors mediated by targeting peptide-modified polymer could enable simultaneous delivery of a drug selectively to target tumor cells, thus limiting side effects resulting from non-specific drug delivery. In this study, we synthesized a novel tumor targeting system by using two key elements: (1) Bld-1 peptide (SNRDARRC), a recently reported bladder tumor targeting peptide identified by using a phage-displayed peptide library, and (2) ELP, a thermally responsive polypeptide. B5V60 containing five Bld-1 peptides and non-targeted ELP77 with a thermal phase-transition over 37 °C were analyzed to determine their bioactivities. Further studies confirmed the superior binding ability of B5V60 to bladder tumor cells and the cellular accumulation of B5V60 in cancer cells was dependent on the expression level of sialyl-Tn antigen (STn), a tumor-associated carbohydrate antigen. Additionally, B5V60 displayed excellent localization in bladder tumor xenograft mice after intravenous injection and was strictly confined to sialyl-Tn antigen-overexpressing tumor tissue. Thus, our newly designed B5V60 showed high potential as a novel carrier for STn-specific targeted cancer therapy or other therapeutic applications.

Glial scars are permeable to the neurotoxic environment of chronic stroke infarcts

Following stroke, the damaged tissue undergoes liquefactive necrosis, a stage of infarct resolution that lasts for months although the exact length of time is currently unknown. One method of repair involves reactive astrocytes and microglia forming a glial scar to compartmentalize the area of liquefactive necrosis from the rest of the brain. The formation of the glial scar is a critical component of the healing response to stroke, as well as other central nervous system (CNS) injuries. The goal of this study was to evaluate the toxicity of the extracellular fluid present in areas of liquefactive necrosis and determine how effectively it is segregated from the remainder of the brain. To accomplish this goal, we used a mouse model of stroke in conjunction with an extracellular fluid toxicity assay, fluorescent and electron microscopy, immunostaining, tracer injections into the infarct, and multiplex immunoassays. We confirmed that the extracellular fluid present in areas of liquefactive necrosis following stroke is toxic to primary cortical and hippocampal neurons for at least 7 weeks following stroke, and discovered that although glial scars are robust physical and endocytic barriers, they are nevertheless permeable. We found that molecules present in the area of liquefactive necrosis can leak across the glial scar and are removed by a combination of paravascular clearance and microglial endocytosis in the adjacent tissue. Despite these mechanisms, there is delayed atrophy, cytotoxic edema, and neuron loss in regions adjacent to the infarct for weeks following stroke. These findings suggest that one mechanism of neurodegeneration following stroke is the failure of glial scars to impermeably segregate areas of liquefactive necrosis from surviving brain tissue.

The development of activatable lytic peptides for targeting triple negative breast cancer

Cytolytic peptides are an emerging class of promising cancer therapeutics shown to overcome drug resistance. They eliminate cancer cells via disruption of the phospholipid bilayer of cell membranes, a mechanism that differentiates it from traditional treatments. However, applications of lytic peptides via systematic administration are hampered by nonspecific toxicity. Here, we describe activatable, masked lytic peptides that are conjugated with anionic peptides via a cleavable linker sensitive to matrix metalloproteinases (Ac-w-βA-e₈-XPLG*LAG-klUklUkklUklUk-NH₂; lower case letters in the sequences represent D-amino-acids, U=Aib, α-aminoisobutyric acid, *cleavage site). The peptides were activated upon being introduced into the triple negative breast cancer cell line MDA-MB-231, which overexpresses secreted matrix metalloproteinases, to selectively cleave the peptide linker. Our results indicate that the activatable design could be applied to improve the targeting ability of lytic peptides.

Protease-Sensitive Nanomaterials for Cancer Therapeutics and Imaging

Many diseases can be characterized by the abnormal activity exhibited by various biomolecules, the targeting of which can provide therapeutic and diagnostic utility. Recent trends in medicine and nanotechnology have prompted the development of protease-sensitive nanomaterials systems for therapeutic, diagnostic, and theranostic applications. These systems can act specifically in response to the target enzyme and its associated disease conditions, thus enabling personalized treatment and improved prognosis. In this Review, we discuss recent advancements in the development of protease-responsive materials for imaging and drug delivery and analyze several representative systems to illustrate their key design principles.

Stressor-driven extracellular acidosis as tumor inducer via aberrant enzyme activation: A review on the mechanisms and possible prophylaxis

When the extracellular pH of human body vacillates in either direction, tissue homeostasis is compromised. Fluctuations in acidity have been linked to a wide variety of pathological conditions, including bone loss, cancer, allergies, and auto-immune diseases. Stress conditions affect oxygen tension, and the resultant hypoxia modulates the expression and/or activity of membrane-tethered transporters/pumps, transcription factors, enzymes and intercellular junctions. These modifications provoke erratic gene expression, aberrant tissue remodeling and oncogenesis. While the physiological optimization of pH in tissues is practically challenging, it is at least theoretically achievable and can be considered as a possible therapy to resolve a broad array of diseases.

Rationalized Computer-Aided Design of Matrix-Metalloprotease-Selective Prodrugs

Matrix metalloproteinases (MMPs) are central to cancer development and metastasis. They are highly active in the tumor environment and absent or inactive in normal tissues; therefore they represent viable targets for cancer drug discovery. In this study we evaluated in silico docking to develop MMP-subtype-selective tumor-activated prodrugs. Proof of principle for this therapeutic approach was demonstrated in vitro against an aggressive human glioma model, with involvement of MMPs confirmed using pharmacological inhibition.

Matrix-metalloproteinases as targets for controlled delivery in cancer: An analysis of upregulation and expression

While commonly known for degradation of the extracellular matrix, matrix metalloproteinases (MMPs) exhibit broad potential for use in targeting of bioactive and imaging agents in cancer treatment. MMPs are upregulated at all stages of expression in cancers. A comprehensive analysis of published literature on expression of all MMP subtypes at the genetic, protein, and activity levels in normal and diseased tissues indicate targeting applicability in a variety of cancers. This expression significantly increases at advanced cancer stages, providing an improved opportunity for controlled release in higher-stage patients. Since MMPs are integral at every stage of metastasis, MMP roles in cancer are discussed with a focus on MMP distribution and mobility within cells and tumors for cancer targeting applications. Several strategies for MMP utilization in targeting - such as matrix degradation, MMP cleavage, MMP binding, and MMP-induced environmental changes - are addressed.

Rotaxane probes for protease detection by 129Xe hyperCEST NMR

We report on the design and implementation of a cucurbit[6]uril rotaxane probe for the detection of matrix metalloproteases by Xe hyperCEST NMR.

Localized delivery of carbon monoxide

The heme oxygenase (HO)/carbon monoxide (CO) system is a physiological feedback loop orchestrating various cell-protective effects in response to cellular stress. The therapeutic use of CO is impeded by safety challenges as a result of high CO-Hemoglobin formation following non-targeted, systemic administration jeopardizing successful CO therapies as of this biological barrier. Another caveat is the use of CO-Releasing Molecules containing toxicologically critical transition metals. An emerging number of local delivery approaches addressing these issues have recently been introduced and provide exciting new starting points for translating the fascinating preclinical potential of CO into a clinical setting. This review will discuss these approaches and link to future delivery strategies aiming at establishing CO as a safe and effective medication of tomorrow.

Biocomputing nanoplatforms as therapeutics and diagnostics

Biocomputing nanoplatforms are designed to detect and integrate single or multiple inputs under defined algorithms, such as Boolean logic gates, and generate functionally useful outputs, such as delivery of therapeutics or release of optically detectable signals. Using sensing modules composed of small molecules, polymers, nucleic acids, or proteins/peptides, nanoplatforms have been programmed to detect and process extrinsic stimuli, such as magnetic fields or light, or intrinsic stimuli, such as nucleic acids, enzymes, or pH. Stimulus detection can be transduced by the nanomaterial via three different mechanisms: system assembly, system disassembly, or system transformation. The increasingly sophisticated suite of biocomputing nanoplatforms may be invaluable for a multitude of applications, including medical diagnostics, biomedical imaging, environmental monitoring, and delivery of therapeutics to target cell populations.

Robust Therapeutic Efficacy of Matrix Metalloproteinase-2-Cleavable Fas-1-RGD Peptide Complex in Chronic Inflammatory Arthritis

Objective

Therapeutic agents that are transformable via introducing cleavable linkage by locally enriched MMP-2 within inflamed synovium would enhance therapeutic efficacy on chronic inflammatory arthritis. Transforming growth factor-β-inducible gene-h3 (βig-h3), which consists of four fas-1 domains and an Arg-Gly-Asp (RGD) motif, intensifies inflammatory processes by facilitating adhesion and migration of fibroblast-like synoviocyte in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to investigate whether a MMP-2-cleavable peptide complex consisting of a fas-1 domain and an RGD peptide blocks the interaction between βig-h3 and resident cells and leads to the amelioration of inflammatory arthritis.

Methods

We designed βig-h3-derivatives, including the fourth fas-1 domain truncated for H1 and H2 sequences of mouse (MFK00) and MMP-2-cleavable peptide complex (MFK902). MMP-2 selectivity was examined by treatment with a series of proteases. MFK902 efficacy was determined by the adhesion and migration assay with NIH3T3 cells in vitro and collagen-induced arthritis (CIA) model using male DBA/1J mice in vivo. The mice were treated intraperitoneally with MFK902 at different dosages.

Results

MFK902 was specifically cleaved by active MMP-2 in a concentration-dependent manner, and βig-h3-mediated adhesion and migration were more effectively inhibited by MFK902, compared with RGD or MFK00 peptides. The arthritis activity of murine CIA, measured by clinical arthritis index and incidence of arthritic paws, was significantly ameliorated after treatment with all dosages of MFK902 (1, 10, and 30 mg/kg). MFK902 ameliorated histopathologic deterioration and reduced the expression of inflammatory mediators simultaneously with improvement of clinical features. In addition, a favorable safety profile of MFK902 was demonstrated in vivo.

Conclusion

The present study revealed that MMP-2-cleavable peptide complex based on βig-h3 structure is a potent and safe therapeutic agent for chronic inflammatory arthritis, thus providing reliable evidence for a MMP-2-cleavable mechanism as a tissue-targeted strategy for treatment of RA.

Matrix metalloproteinases-2/9-sensitive peptide-conjugated polymer micelles for site-specific release of drugs and enhancing tumor accumulation: preparation and in vitro and in vivo evaluation

Since elevated expression of matrix metalloproteinase (MMP)-2 and MMP-9 is commonly observed in several malignant tumors, MMPs have been widely reported as key factors in the design of drug delivery systems. Several strategies have been proposed to develop MMPs-responsive nanoparticles to deliver chemotherapeutics to malignant solid tumors. A stimuli-responsive drug delivery system, which could be cleaved by MMPs, was proposed in this study. By inserting an MMP-2/9 cleavable oligopeptide GPVGLIGK-NH₂ (GK8) as spacer between α-tocopherol succinate (α-TOS) and methoxy-polyethylene glycol molecular weight (MW 2000 Da) activated by N-hydroxysuccinimide (mPEG2K-NHS), mPEG2K-GK8-α-TOS (TGK) was synthesized as the primary ingredient for MMP-2/9-sensitive micelles composed of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) and TGK (n:n =40:60, TGK micelles). mPEG2K-α-TOS (T2K) was similarly synthesized as nonsensitive control. The TGK micelles showed better stability than nonsensitive micelles composed of TPGS and T2K (n:n =40:60, T2K micelles) owing to the inserted peptide. Fluorescence resonance energy transfer results indicated that TGK micelles could be successfully cleaved by MMP-2/9. Effective drug release was demonstrated in the presence of collagenase type IV, a mixture of MMP-2 and MMP-9. Compared with nonsensitive micelles, docetaxel (DTX)-loaded TGK micelles showed a fold higher cellular uptake in HT1080 cells. While the half-maximal inhibitory concentration (IC₅₀) of TGK and T2K micelles were similar (P>0.05) in MCF-7 cells (MMP-2/9 underexpression), the IC₅₀ values of the aforementioned micelles were 0.064±0.006 and 0.122±0.009 μg/mL, respectively, in HT1080 cells (MMP-2/9 overexpression). The MMP-2/9-sensitive micelles also demonstrated desired tumor targeting and accumulation ability in vivo. The results of in vivo antitumor effect evaluation indicate that TGK micelles are potent against solid tumors while maintaining minimum systemic toxicity compared with T2K micelles and DTX.