A senolysis-based theragnostic prodrug strategy towards chronic renal failure

Drug Delivery Strategies for Age-Related Diseases

Drug delivery systems (DDSs) enable the controlled release of drugs in the body. DDSs have attracted increasing attention for the treatment of various disorders, including cancer, inflammatory diseases, and age-related diseases. With recent advancements in our understanding of the molecular mechanisms of aging, new target molecules and drug delivery carriers for age-related diseases have been reported. In this review, we will summarize the recent research on DDSs for age-related diseases and identify DDS strategies in the treatment of age-related diseases.

Combining rejuvenation interventions in rodents: a milestone in biomedical gerontology whose time has come

INTRODUCTION

Longevity research has matured to the point where significantly postponing age-related decline in physical and mental function is now achievable in the laboratory and foreseeable in the clinic. The most promising strategies involve rejuvenation, i.e. reducing biological age, not merely slowing its progression.

AREAS COVERED

We discuss therapeutic strategies for rejuvenation and results achieved thus far, with a focus on in vivo studies. We discuss the implications of interventions which act on mean or maximum lifespan and those showing effects in accelerated disease models. While the focus is on work conducted in mice, we also highlight notable insights in the field from studies in other model organisms.

EXPERT OPINION

Rejuvenation was originally proposed as easier than slowing aging because it targets initially inert changes to tissue structure and composition, rather than trying to disentangle processes that both create aging damage and maintain life. While recent studies support this hypothesis, a true test requires a panel of rejuvenation interventions targeting multiple damage categories simultaneously. Considerations of cost, profitability, and academic significance have dampened enthusiasm for such work, but it is vital. Now is the time for the field to take this key step toward the medical control of aging.

Quinone Methide Based Self-Immobilizing Molecular Fluorescent Probes for In Situ Imaging of Enzymes

Enzymes play important roles not only in normal physiological processes but in the development of many diseases. In situ imaging of enzymes with high-resolution in living systems would helpful for clinical diagnosis and treatment. However, many molecular fluorescent probes suffer from the drawback of diffusing away from the reaction site of enzymes even out of the cells, losing the in situ information and resulting in poor imaging resolution. Quinone methide (QM) based self-immobilizing probes allow the fluorescent signal to be immobilized near the target for an extended period without deactivating the target enzymes, ensuring that it will provide amplified signals and in situ information of the target with high resolution. In this review, we summarized the recent progress of QM-based self-immobilizing probes including their design strategies, working mechanisms, classifications and applications in in situ enzyme imaging. This review calls for the development of more activatable QM-based probe with the advantages of high stability in the absence of the target but very high labeling efficiency after activation.

Selective Elimination of Senescent Cancer Cells by Galacto-Modified PROTACs

Although the selective and effective clearance of senescent cancer cells can improve cancer treatment, their development is confronted by many challenges. As part of efforts designed to overcome these problems, prodrugs, whose design is based on senescence-associated β-galactosidase (SA-β-gal), have been developed to selectively eliminate senescent cells. However, chemotherapies relying on targeted molecular inhibitors as senolytic drugs can induce drug resistance. In the current investigation, we devised a new strategy for selective degradation of target proteins in senescent cancer cells that utilizes a prodrug composed of the SA-β-gal substrate galactose (galacto) and the proteolysis-targeting chimeras (PROTACs) as senolytic agents. Prodrugs Gal-ARV-771 and Gal-MS99 were found to display senolytic indexes higher than those of ARV-771 and MS99. Significantly, results of in vivo studies utilizing a human lung A549 xenograft mouse model demonstrated that concomitant treatment with etoposide and Gal-ARV-771 leads to a significant inhibition of tumor growth without eliciting significant toxicity.

Design and preparation of NMN nanoparticles based on protein-marine polysaccharide with increased NAD+ level in D-galactose induced aging mice model

Nicotinamide mononucleotide (NMN) is being investigated for its ability to address the decline in NAD+ level during aging. This study aimed to construct a delivery system based on ovalbumin and fucoidan nanoparticles to ameliorate the bioaccessibility of NMN by increasing NAD+ level in aging mouse model. The NMN-loaded ovalbumin and fucoidan nanoparticles (OFNPs) were about 177 nm formed by the interplay of hydrogen bonds between ovalbumin and fucoidan. Compared with free NMN, NMN-loaded OFNPs intervention could obviously improve the antioxidant enzyme activity of senescent cell induced by D-galactose. The NMN-loaded OFNPs treatment could ameliorate the loss of weight and organ index induced by senescence, and maintain the water content for the aging mice. The Morris maze test indicated that hitting blind side frequency and escape time of NMN-loaded OFNPs group decreased by 13% and 35% compared with that of free NMN group. Furthermore, the NMN-loaded OFNPs significantly alleviated the age-related oxidative stress and increased the generation of NAD+ 1.34 times by improving the bioaccessibility of NMN. Our data in this study supplied a strategy to enhance the bioavailability of NMN in senescence treatment.

Theranostic Fluorescent Probes

The ability to gain spatiotemporal information, and in some cases achieve spatiotemporal control, in the context of drug delivery makes theranostic fluorescent probes an attractive and intensely investigated research topic. This interest is reflected in the steep rise in publications on the topic that have appeared over the past decade. Theranostic fluorescent probes, in their various incarnations, generally comprise a fluorophore linked to a masked drug, in which the drug is released as the result of certain stimuli, with both intrinsic and extrinsic stimuli being reported. This release is then signaled by the emergence of a fluorescent signal. Importantly, the use of appropriate fluorophores has enabled not only this emerging fluorescence as a spatiotemporal marker for drug delivery but also has provided modalities useful in photodynamic, photothermal, and sonodynamic therapeutic applications. In this review we highlight recent work on theranostic fluorescent probes with a particular focus on probes that are activated in tumor microenvironments. We also summarize efforts to develop probes for other applications, such as neurodegenerative diseases and antibacterials. This review celebrates the diversity of designs reported to date, from discrete small-molecule systems to nanomaterials. Our aim is to provide insights into the potential clinical impact of this still-emerging research direction.

Senolysis Enabled by Senescent Cell-Sensitive Bioorthogonal Tetrazine Ligation

Although the clearance of senescent cells has been proven to slow down the aging process and promote anti-cancer chemotherapy, the development of senolytics remains challenging. Herein, we report a senolytic strategy enabled by senescent cell-sensitive bioorthogonal tetrazine ligation. Our design is based on linking dihydrotetrazine (Tz) to a galactose (Gal) moiety that serves both as a recognition moiety for senescence-associated β-galactosidase and a caging group for the control of tetrazine activity. Gal-Tz enables efficient click-release of a fluorescent hemicyanine and doxorubicin from a trans-cyclooctene-caged prodrug to detect and eliminate senescent HeLa and A549 cells over non-senescent counterparts with a 16.44 senolytic index. Furthermore, we leverage the strategy for the selective activation and delivery of proteolysis-targeting chimeras (PROTACs) as senolytics. PROTAC prodrug TCO-ARV-771 can be selectively activated by Gal-Tz and delivered into senescent HeLa and A549 cells to induce the degradation of bromodomain-containing protein 4. Senolytic PROTACs may offer an efficient way for intervention on cell senescence thanks to their unique capacity to degrade target proteins in a sub-stoichiometric and catalytic fashion. The results of this study establish the bioorthogonal tetrazine ligation approach as a viable strategy for selective removal of senescent cells.

Targeting Senescent Cells as Therapy for CKD

Senescent cells accumulate in the kidney with aging, after acute and chronic injuries, and are present in increased numbers in deteriorating kidney transplants. Senescent cells have undergone permanent cell cycle arrest and release many proinflammatory cytokines/chemokines and profibrotic factors: the senescence-associated secretory phenotype. Recent work from several groups including our own has shown that senescent cells play a causative role in progression of kidney disease. Experimental evidence also indicates that targeting senescent cells has potential to alter the renal regenerative response, reducing progressive fibrosis and improving functional recovery after injury. Research and clinical interest is focused on understanding how accumulating chronic senescent cells link acute injury to progressive fibrosis, dysfunction, and mortality in human CKD. In this review, we outline current protocols for the identification of how senescent cells are identified in vitro and in vivo . We discuss the proposed mechanisms of actions of first-generation senolytic and senomorphic agents, such as ABT-263 (navitoclax) which targets the BCL2 family of survival factors, and senomorphic agents such as metformin which targets aspects of the senescence-associated secretory phenotype. We also review that emerging technologies, such as nanocarriers, are now being developed to have safer delivery systems for senolytics, greater specificity, fewer off-target effects, and less toxicity. Other methods of senescent cell elimination being developed target various immune evasion tactics displayed by these cells. By understanding the role of senescence in kidney homeostasis and disease, developing new, targeted compounds and the tools to allow their efficacy to be charted noninvasively, it should become possible for senolytic treatments to move from the bench to bedside.

Fidelity-oriented fluorescence imaging probes for beta-galactosidase: From accurate diagnosis to precise treatment

Beta-galactosidase (β-gal), a typical glycosidase catalyzing the hydrolysis of glycosidic bonds, is regarded as a vital biomarker for cell senescence and cancer occurrence. Given the advantages of high spatiotemporal resolution, high sensitivity, non-invasiveness, and being free of ionizing radiations, fluorescent imaging technology provides an excellent choice for in vivo imaging of β-gal. In this review, we detail the representative biotech advances of fluorescence imaging probes for β-gal bearing diverse fidelity-oriented improvements to elucidate their future potential in preclinical research and clinical application. Next, we propose the comprehensive design strategies of imaging probes for β-gal with respect of high fidelity. Considering the systematic implementation approaches, a range of high-fidelity imaging-guided theragnostic are adopted for the individual β-gal-associated biological scenarios. Finally, current challenges and future trends are proposed to promote the next development of imaging agents for individual and specific application scenarios.

Design and application of prodrug fluorescent probes for the detection of ovarian cancer cells and release of anticancer drug

Ovarian cancer is a gynecologic malignancy with high mortality. The main reason is that it is detected at an advanced stage due to a lack of early diagnosis and treatment. Therefore, it is of great interest to develop a chemical tool that can visualize ovarian cancer cells in real-time and eliminate them. Unfortunately, probes that can simultaneously monitor both modes of action for the diagnosis and treatment of ovarian cancer have not been developed. Here, we designed a novel prodrug fluorescent probe (YW-OAc) that not only visually tracks cancer cells but also enables the on-demand delivery of chemotherapeutic agents. By β-Gal-mediated glycosidic bond hydrolysis, the fluorescent signal changed from blue to green (signal 1), enabling visual tracking of ovarian cancer cells. Subsequently, the identified cancer cells were subjected to precise light irradiation to induce anticancer drug release accompanied by a fluorescence transition from green to blue (signal 2), enabling real-time information on drug release. Thus, the prodrug fluorescent probe YW-OAc provides comprehensive two-step monitoring during cancer cell recognition and clearance. Notably, YW-OAc exhibited high affinity (K_m = 3.74 μM), high selectivity, and low detection limit for β-Gal (0.0035 U/mL). We also demonstrated that YW-OAc can visually trace endogenous β-Gal in different cells and exhibit high phototoxicity in ovarian cancer cells. We hope that the prodrug fluorescent probe YW-OAc, can be used as an effective tool for biomedical diagnosis and treatment.