Selective Nanoparticle Targeting of the Renal Tubules

Renal Nano-drug delivery for acute kidney Injury: Current status and future perspectives

Acute kidney injury (AKI) causes considerable morbidity and mortality, particularly in the case of post-cardiac infarction or kidney transplantation; however, the site-specific accumulation of small molecule reno-protective agents for AKI has often proved ineffective due to dynamic fluid and solute excretion and non-selectivity, which impedes therapeutic efficacy. This article reviews the current status and future trajectories of renal nanomedicine research for AKI management from pharmacological and clinical perspectives, with a particular focus on appraising nanosized drug carrier (NDC) use for the delivery of reno-protective agents of different pharmacological classes and the effectiveness of NDCs in improving renal tissue targeting selectivity and efficacy of said agents. This review reveals the critical shift in the role of the small molecule reno-protective agents in AKI pharmacotherapy - from prophylaxis to treatment - when using NDCs for delivery to the kidney. We also highlight the need to identify the accumulation sites of NDCs carrying reno-protective agents in renal tissues during in vivo assessments and detail the less-explored pharmacological classes of reno-protective agents whose efficacies may be improved via NDC-based delivery. We conclude the paper by outlining the challenges and future perspectives of NDC-based reno-protective agent delivery for better clinical management of AKI.

Kidney-Targeted Redox Scavenger Therapy Prevents Cisplatin-Induced Acute Kidney Injury

Cisplatin-induced acute kidney injury (CI-AKI) is a significant co-morbidity of chemotherapeutic regimens. While this condition is associated with substantially lower survival and increased economic burden, there is no pharmacological agent to effectively treat CI-AKI. The disease is hallmarked by acute tubular necrosis of the proximal tubular epithelial cells primarily due to increased oxidative stress. We investigated a drug delivery strategy to improve the pharmacokinetics of an approved therapy that does not normally demonstrate appreciable efficacy in CI-AKI, as a preventive intervention. In prior work, we developed a kidney-selective mesoscale nanoparticle (MNP) that targets the renal proximal tubular epithelium. Here, we found that the nanoparticles target the kidneys in a mouse model of CI-AKI with significant damage. We evaluated MNPs loaded with the reactive oxygen species scavenger edaravone, currently used to treat stroke and ALS. We found a marked and significant therapeutic benefit with edaravone-loaded MNPs, including improved renal function, which we demonstrated was likely due to a decrease in tubular epithelial cell damage and death imparted by the specific delivery of edaravone. The results suggest that renal-selective edaravone delivery holds potential for the prevention of acute kidney injury among patients undergoing cisplatin-based chemotherapy.

Preferential siRNA delivery to injured kidneys for combination treatment of acute kidney injury

Acute kidney injury (AKI) is characterized by a sudden loss of renal function and is associated with high morbidity and mortality. Tumor suppressor p53 and chemokine receptor CXCR4 were both implicated in the AKI pathology. Here, we report on the development and evaluation of polymeric CXCR4 antagonist (PCX) siRNA carrier for selective delivery to injured kidneys in AKI. Our results show that PCX/siRNA nanoparticles (polyplexes) provide protection against cisplatin injury to tubule cells in vitro when both CXCR4 and p53 are inhibited. The polyplexes selectively accumulate and are retained in the injured kidneys in cisplatin and bilateral ischemia reperfusion injury models of AKI. Treating AKI with the combined CXCR4 inhibition and p53 gene silencing with the PCX/sip53 polyplexes improves kidney function and decreases renal damage. Overall, our results suggest that the PCX/sip53 polyplexes have a significant potential to enhance renal accumulation in AKI and deliver therapeutic siRNA.

A Kidney-Targeted Nanoparticle to Augment Renal Lymphatic Density Decreases Blood Pressure in Hypertensive Mice

Chronic interstitial inflammation and renal infiltration of activated immune cells play an integral role in hypertension. Lymphatics regulate inflammation through clearance of immune cells and excess interstitial fluid. Previously, we demonstrated increasing renal lymphangiogenesis prevents hypertension in mice. We hypothesized that targeted nanoparticle delivery of vascular endothelial growth factor-C (VEGF-C) to the kidney would induce renal lymphangiogenesis, lowering blood pressure in hypertensive mice. A kidney-targeting nanoparticle was loaded with a VEGF receptor-3-specific form of VEGF-C and injected into mice with angiotensin II-induced hypertension or LNAME-induced hypertension every 3 days. Nanoparticle-treated mice exhibited increased renal lymphatic vessel density and width compared to hypertensive mice injected with VEGF-C alone. Nanoparticle-treated mice exhibited decreased systolic blood pressure, decreased pro-inflammatory renal immune cells, and increased urinary fractional excretion of sodium. Our findings demonstrate that pharmacologically expanding renal lymphatics decreases blood pressure and is associated with favorable alterations in renal immune cells and increased sodium excretion.

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

Gypenoside XLIX loaded nanoparticles targeting therapy for renal fibrosis and its mechanism

Renal fibrosis is the main pathological feature of the occurrence and development of chronic nephropathy. At present, there is no effective treatment, except for renal transplantation and dialysis. Previous studies have shown that nano-preparations can be used as a therapeutic tool to target organs. In this study, we studied the therapeutic effect and mechanism of Chinese medicine monomer Gypenoside (Gyp) XLIX on renal fibrosis and explored the targeting and therapeutic effects of polylactic acid-co-glycoside (PLGA)-Gyp XLIX nanoparticles in unilateral ureteral occlusion (UUO) kidney. Gyp XLIX and PLGA-Gyp XLIX nanoparticles were used to treat UUO mice and Human renal tubular epithelial (HK2) cells stimulated by transforming growth factor-β (TGF-β). Histopathological and molecular biological techniques were used to detect the expression of type I collagen and alpha-smooth muscle actin (α-SMA). To investigate the in vivo targeting of PLGA nanoparticles, they were loaded with 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide and injected into UUO mice. We evaluated the effect of Gyp XLIX nanoparticles on TGF-β/Smad3 pathway, a central driver for renal fibrosis in Smad-deficient HK2 cells. Fluorescence imaging showed that the PLGA nanoparticles around 120 nm could be targeted to the UUO kidney. Compared with Gyp XLIX, PLGA-Gyp XLIX nanoparticles could effectively inhibit renal fibrosis and reduce collagen deposition and reduce renal tubular necrosis. Gyp XLIX decreased the phosphorylation of Smad3, but could not further reduce the levels of type I collagen and α-SMA in Smad-deficient cells. This study opens a promising way for targeted drug treatment of renal fibrosis.

Therapeutic potential of pro-resolving mediators in diabetic kidney disease

Renal microvascular disease associated with diabetes [Diabetic kidney disease - DKD] is the leading cause of chronic kidney disease. In DKD, glomerular basement membrane thickening, mesangial expansion, endothelial dysfunction, podocyte cell loss and renal tubule injury contribute to progressive glomerulosclerosis and tubulointerstitial fibrosis. Chronic inflammation is recognized as a major pathogenic mechanism for DKD, with resident and circulating immune cells interacting with local kidney cell populations to provoke an inflammatory response. The onset of inflammation is driven by the release of well described proinflammatory mediators, and this is typically followed by a resolution phase. Inflammation resolution is achieved through the bioactions of endogenous specialized pro-resolving lipid mediators (SPMs). As our understanding of SPMs advances 'resolution pharmacology' based approaches using these molecules are being explored in DKD.

Constructing a passive targeting and long retention therapeutic nanoplatform based on water-soluble, non-toxic and highly-stable core-shell poly(amino acid) nanocomplexes

Drug delivery nanoplatforms have been applied in bioimaging, medical diagnosis, drug delivery and medical therapy. However, insolubility, toxicity, instability, nonspecific targeting and short retention of many hydrophobic drugs limit their extensive applications. Herein, we have constructed a passive targeting and long retention therapeutic nanoplatform of core-shell gefitinib/poly (ethylene glycol)-polytyrosine nanocomplexes (Gef-PY NCs). The Gef-PY NCs have good water-solubility, non-toxicity (correspond to 1/10 dosage of effective gefitinib (hydrochloride) (Gef·HCl) (normal drug administration and slow-release) and high stability (120 days, 80% drug retention at 4 or 25 °C). The core-shell Gef-PY NCs present unexpected kidney targeting and drug slow-release capacity (ca. 72 h). The good water-solubility, non-toxicity and high stability of Gef-PY NCs effectively solve the bottleneck question that Gef-based therapy could be used only in intraperitoneal injection due to its insolubility and severe toxicity. Such excellent properties (e.g., water-solubility, non-toxicity, high stability, kidney targeting and long retention) of Gef-PY NCs create their prominent anti-fibrosis capabilities, such as decreasing approximately 40% tubulointerstitial fibrosis area and 68% expression of collagen I within 7 days. This therapeutic efficacy is well-matched with that of 10 times the dosage of toxic Gef·HCl. It is very hopeful that Gef-PY NCs could realize clinical applications and such a strategy offers an effective route to design high-efficiency treatments for kidney- and tumor-related diseases.

Stiffness of targeted layer-by-layer nanoparticles impacts elimination half-life, tumor accumulation, and tumor penetration

Nanoparticle (NP) stiffness has been shown to significantly impact circulation time and biodistribution in anticancer drug delivery. In particular, the relationship between particle stiffness and tumor accumulation and penetration in vivo is an important phenomenon to consider in optimizing NP-mediated tumor delivery. Layer-by-layer (LbL) NPs represent a promising class of multifunctional nanoscale drug delivery carriers. However, there has been no demonstration of the versatility of LbL systems in coating systems with different stiffnesses, and little is known about the potential role of LbL NP stiffness in modulating in vivo particle trafficking, although NP modulus has been recently studied for its impact on pharmacokinetics. LbL nanotechnology enables NPs to be functionalized with uniform coatings possessing molecular tumor-targeting properties, independent of the NP core stiffness. Here, we report that the stiffness of LbL NPs is directly influenced by the mechanical properties of its underlying liposomal core, enabling the modulation and optimization of LbL NP stiffness while preserving LbL NP outer layer tumor-targeting and stealth properties. We demonstrate that the stiffness of LbL NPs has a direct impact on NP pharmacokinetics, organ and tumor accumulation, and tumor penetration-with compliant LbL NPs having longer elimination half-life, higher tumor accumulation, and higher tumor penetration. Our findings underscore the importance of NP stiffness as a design parameter in enhancing the delivery of LbL NP formulations.

Atypical Renal Clearance of Nanoparticles Larger Than the Kidney Filtration Threshold

In recent years, several publications reported that nanoparticles larger than the kidney filtration threshold were found intact in the urine after being injected into laboratory mice. This theoretically should not be possible, as it is widely known that the kidneys prevent molecules larger than 6–8 nm from escaping into the urine. This is interesting because it implies that some nanoparticles can overcome the size limit for renal clearance. What kinds of nanoparticles can “bypass” the glomerular filtration barrier and cross into the urine? What physical and chemical characteristics are essential for nanoparticles to have this ability? And what are the biomolecular and cellular mechanisms that are involved? This review attempts to answer those questions and summarize known reports of renal-clearable large nanoparticles.

Non-invasive molecular imaging of kidney diseases

In nephrology, differential diagnosis or assessment of disease activity largely relies on the analysis of glomerular filtration rate, urinary sediment, proteinuria and tissue obtained through invasive kidney biopsies. However, currently available non-invasive functional parameters, and most serum and urine biomarkers, cannot capture intrarenal molecular disease processes specifically. Moreover, although histopathological analyses of kidney biopsy samples enable the visualization of pathological morphological and molecular alterations, they only provide information about a small part of the kidney and do not allow longitudinal monitoring. These limitations not only hinder understanding of the dynamics of specific disease processes in the kidney, but also limit the targeting of treatments to active phases of disease and the development of novel targeted therapies. Molecular imaging enables non-invasive and quantitative assessment of physiological or pathological processes by combining imaging technologies with specific molecular probes. Here, we discuss current preclinical and clinical molecular imaging approaches in nephrology. Non-invasive visualization of the kidneys through molecular imaging can be used to detect and longitudinally monitor disease activity and can therefore provide companion diagnostics to guide clinical trials, as well as the safe and effective use of drugs.

Eleutheroside B-loaded poly (lactic-co-glycolic acid) nanoparticles protect against renal fibrosis via Smad3-dependent mechanism

Although renal fibrosis is a common complication of chronic kidney disease (CKD), effective options for its treatment are currently limited. In this study, we evaluated the renal protective effect and possible mechanism of eleutheroside B. In order to solve the allergic reactions, side effects, and low oral bioavailability of eleutheroside B, we successfully prepared PLGA (poly [lactic-co-glycolic acid])-eleutheroside B nanoparticles (NPs) with the diameter of about 128 nm. In vitro and in vivo results showed that eleutheroside B could inhibit expression levels of α-smooth muscle actin (α-SMA) and collagen I. Molecular docking results showed that eleutheroside B bound to Smad3 and significantly decreased the expression of phospho-Smad3 (p-Smad3). Silencing Smad3 reversed the fibrotic protective effect of eleutheroside B in HK2 cells. Furthermore, small animal imaging showed that NPs can selectively accumulate in the UUO kidneys of mice, and retention time reached as long as 7 days. In conclusion, our results suggested that eleutheroside B is a potential drug to protect renal fibrosis and PLGA-eleutheroside B NPs could facilitate specific targeted therapy for renal fibrosis.

Nanotechnology, Nanomedicine, and the Kidney

The kidneys are vital organs performing several essential functions. Their primary function is the filtration of blood and the removal of metabolic waste products as well as fluid homeostasis. Renal filtration is the main pathway for drug removal, highlighting the importance of this organ to the growing field of nanomedicine. The kidneys (i) have a key role in the transport and clearance of nanoparticles (NPs), (ii) are exposed to potential NPs’ toxicity, and (iii) are the targets of diseases that nanomedicine can study, detect, and treat. In this review, we aim to summarize the latest research on kidney-nanoparticle interaction. We first give a brief overview of the kidney’s anatomy and renal filtration, describe how nanoparticle characteristics influence their renal clearance, and the approaches taken to image and treat the kidney, including drug delivery and tissue engineering. Finally, we discuss the future and some of the challenges faced by nanomedicine.

Recent advances in nanotherapeutics for the treatment and prevention of acute kidney injury

Acute kidney injury (AKI) is a serious kidney disease without specific medications currently except for expensive dialysis treatment. Some potential drugs are limited due to their high hydrophobicity, poor in vivo stability, low bioavailability and possible adverse effects. Besides, kidney-targeted drugs are not common and small molecules are cleared too quickly to achieve effective drug concentrations in injured kidneys. These problems limit the development of pharmacological therapy for AKI. Nanotherapeutics based on nanotechnology have been proved to be an emerging and promising treatment strategy for AKI, which may solve the pharmacological therapy dilemma. More and more nanotherapeutics with different physicochemical properties are developed to efficiently deliver drugs, increase accumulation and control release of drugs in injury kidneys and also directly as effective antioxidants. Here, we discuss the recent nanotherapeutics applied in the treatment and prevention of AKI with improved effectiveness and few side effects.

Formoterol PLGA-PEG Nanoparticles Induce Mitochondrial Biogenesis in Renal Proximal Tubules

Formoterol is a long-acting β₂ agonist (LABA). Agonism of the β₂-adrenergic receptor by formoterol is known to stimulate mitochondrial biogenesis (MB) in renal proximal tubules and recover kidney function. However, formoterol has a number of cardiovascular side effects that limits its usage. The goal of this study was to design and develop an intravenous biodegradable and biocompatible polymeric nanoparticle delivery system that targets formoterol to the kidney. Poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) nanoparticles containing encapsulated formoterol were synthesized by a modified single-emulsion solvent evaporation technique resulting in nanoparticles with a median hydrodynamic diameter of 442 + 17 nm. Using primary cell cultures of rabbit renal proximal tubular cells (RPTCs), free formoterol, encapsulated formoterol polymeric nanoparticles, and drug-free polymeric nanoparticles were biocompatible and not cytotoxic over a wide concentration range. In healthy male mice, polymeric nanoparticles were shown to localize in tubules of the renal cortex and improved the renal localization of encapsulated formoterol compared to the free formoterol. At a lower total formoterol dose, the nanoparticle localization resulted in increased expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), the master regulator of MB, and increased electron transport chain proteins, markers of MB. This was confirmed by direct visual quantification of mitochondria and occurred with both free formoterol and the encapsulated formoterol polymeric nanoparticles. At the same time, localization of nanoparticles to the kidneys resulted in reduced induction of MB markers in the heart. These new nanoparticles effectively target formoterol to the kidney and successfully produce MB in the kidney.

Targeted Drug Delivery Systems for Kidney Diseases

Kidney diseases have gradually become a global health burden. Along with the development of nanotechnology, many hybrids or nanomaterials have been utilized to promote treatment efficiency with negligible side effects. These therapeutic agents have been successfully applied in many fields. In particular, some efforts have also been made to ameliorate the treatment of kidney diseases through targeted delivery nanomaterials. Though most of the delivery systems have not yet been transmitted into clinical use or even still at an early stage, they have shown great potential in carrying immunosuppressants like tacrolimus and triptolide, antioxidants, or siRNAs. Excitingly, some of them have achieved significant treatment effectiveness and reduced systemic side effect in kidney disease animal models. Here, we have reviewed the recent advances and presented nanotherapeutic devices designed for kidney targeted delivery.

Improving kidney targeting: The influence of nanoparticle physicochemical properties on kidney interactions

Kidney-targeted nanoparticles have become of recent interest due to their potential to deliver drugs directly to diseased tissue, decrease off-target adverse effects, and increase overall tolerability to patients with chronic kidney disease that require lifelong drug exposure. Given the physicochemical properties of nanoparticles can drastically affect their ability to extravasate past cellular and biological barriers and access the kidneys, we surveyed the literature from the past decade and analyzed how nanoparticle size, charge, shape, and material density affects passage and interaction with the kidneys. Specifically, we found that nanoparticle size impacted the mechanism of nanoparticle entry into the kidneys such as glomerular filtration or tubular secretion. In addition, we found charge, aspect ratio, and material density influences nanoparticle renal retention and provide insights for designing nanoparticles for passive kidney targeting. Finally, we conclude by highlighting active targeting strategies that bolster kidney retention and discuss the clinical status of nanomedicine for kidney diseases.

Targeted drug delivery strategies for precision medicines

Progress in the field of precision medicine has changed the landscape of cancer therapy. Precision medicine is propelled by technologies that enable molecular profiling, genomic analysis, and optimized drug design to tailor treatments for individual patients. Although precision medicines have resulted in some clinical successes, the use of many potential therapeutics has been hindered by pharmacological issues, including toxicities and drug resistance. Drug delivery materials and approaches have now advanced to a point where they can enable the modulation of a drug's pharmacological parameters without compromising the desired effect on molecular targets. Specifically, they can modulate a drug's pharmacokinetics, stability, absorption, and exposure to tumours and healthy tissues, and facilitate the administration of synergistic drug combinations. This Review highlights recent progress in precision therapeutics and drug delivery, and identifies opportunities for strategies to improve the therapeutic index of cancer drugs, and consequently, clinical outcomes.

Stem/progenitor cell in kidney: characteristics, homing, coordination, and maintenance

Renal failure has a high prevalence and is becoming a public health problem worldwide. However, the renal replacement therapies such as dialysis are not yet satisfactory for its multiple complications. While stem/progenitor cell-mediated tissue repair and regenerative medicine show there is light at the end of tunnel. Hence, a better understanding of the characteristics of stem/progenitor cells in kidney and their homing capacity would greatly promote the development of stem cell research and therapy in the kidney field and open a new route to explore new strategies of kidney protection. In this review, we generally summarize the main stem/progenitor cells derived from kidney in situ or originating from the circulation, especially bone marrow. We also elaborate on the kidney-specific microenvironment that allows stem/progenitor cell growth and chemotaxis, and comment on their interaction. Finally, we highlight potential strategies for improving the therapeutic effects of stem/progenitor cell-based therapy. Our review provides important clues to better understand and control the growth of stem cells in kidneys and develop new therapeutic strategies.

Nanomedicine in the treatment of diabetic nephropathy

Globally, diabetic nephropathy (DN) is the foremost cause of end-stage renal disease. With the incidence of diabetes increasing day by day, DN's occurrence is expected to surge to pandemic proportions. Current available therapeutic interventions associated with DN emphasize blood pressure, glycemia and lipid control while ignoring DN's progression mechanism at a molecular level. This review sheds light on the molecular insights involved in DN to help understand the initiation and progression pattern. Further, we summarize novel strategies with reported applications in developing a nanomedicine-based platform for DN-targeted drug delivery to improve drug efficacy and safety.

Harnessing nanotechnology to expand the toolbox of chemical biology

Although nanotechnology often addresses biomedical needs, nanoscale tools can also facilitate broad biological discovery. Nanoscale delivery, imaging, biosensing, and bioreactor technologies may address unmet questions at the interface between chemistry and biology. Currently, many chemical biologists do not include nanomaterials in their toolbox, and few investigators develop nanomaterials in the context of chemical tools to answer biological questions. We reason that the two fields are ripe with opportunity for greater synergy. Nanotechnologies can expand the utility of chemical tools in the hands of chemical biologists, for example, through controlled delivery of reactive and/or toxic compounds or signal-binding events of small molecules in living systems. Conversely, chemical biologists can work with nanotechnologists to address challenging biological questions that are inaccessible to both communities. This Perspective aims to introduce the chemical biology community to nanotechnologies that may expand their methodologies while inspiring nanotechnologists to address questions relevant to chemical biology.

A ROS-scavenging multifunctional nanoparticle for combinational therapy of diabetic nephropathy

Although synergistic therapy for diabetes mellitus has displayed significant promise for the effective treatment of diabetic nephropathy (DN), developing a simple and effective strategy to construct multifunctional nanoparticles is still a huge challenge. Moreover, the complicated pathological mechanism of DN involves various pathway dysfunctions that limit the effectiveness of a single therapeutic approach. Herein, hollow mesoporous silica nanocomposite (HMSN) particles doped with trace cerium oxide that exhibit renoprotective activity have been designed, which not only have the ability to prevent ROS-associated DN pathogenesis but also have high drug loading capacity. Interestingly, the metformin (MET) loaded multifunctional nanoparticles (MET-HMSN-CeO2) with a special size exhibited significantly increased kidney accumulation over free MET. Moreover, the cyclic conversion between Ce3+ and Ce4+ of mixed-valence ceria in our system provides the possibility for long-term ROS-scavenging activity to achieve the antioxidative effect. Then, we investigated the renoprotective effect of these nanoparticles on the streptozotocin (STZ)-induced renal injury rat model and high-glucose induced NRK-52E cell damage model. As a result, our findings demonstrated that the nanoparticles could alleviate the DN symptoms by mitigating oxidative stress, suppressing cellular apoptosis and protecting renal injury both in vitro and in vivo. The kidney deficits of DN are significantly improved after treatment with MET-HMSN-CeO2. Overall, our studies indicated that the MET-HMSN-CeO2 multifunctional nanoparticles would be a promising therapeutic candidate for DN.

Selective Trafficking of Light Chain-Conjugated Nanoparticles to the Kidney and Renal Cell Carcinoma

Specific delivery platforms for drugs to the kidney and diagnostic agents to renal cell carcinoma (RCC) constitute urgent but unfulfilled clinical needs. To address these challenges, we engineered nanocarriers that interact selectively for the first time with proximal tubule epithelial cells (PTECs) in the kidney and with RCC through the interplay between lambda light chains (LCs) attached to PEGylated polylactic-co-glycolic acid (PLGA) nanoparticles and the membrane protein megalin. Systemic administration of these light chain-conjugated nanoparticles (LC-NPs) to mice resulted in their specific retention by megalin-expressing PTECs for seven days. Repetitive dosing of LC-NPs demonstrated no renal toxicity. LC-NPs also localized selectively to megalin-expressing RCC tumors in mice. Moreover, we confirmed that both the primary tumor and lymph node metastases of human RCC express megalin, reinforcing the potential of LC-NPs for clinical use. Thus, LC-NPs can contribute potentially to improving the management of both non-oncologic and oncologic renal disorders.

Renal proximal tubular NEMO plays a critical role in ischemic acute kidney injury

We determined that renal proximal tubular (PT) NF-κB essential modulator (NEMO) plays a direct and critical role in ischemic acute kidney injury (AKI) using mice lacking renal PT NEMO and by targeted renal PT NEMO inhibition with mesoscale nanoparticle-encapsulated NEMO binding peptide (NBP MNP). We subjected renal PT NEMO-deficient mice, WT mice, and C57BL/6 mice to sham surgery or 30 minutes of renal ischemia and reperfusion (IR). C57BL/6 mice received NBP MNP or empty MNP before renal IR injury. Mice treated with NBP MNP and mice deficient in renal PT NEMO were protected against ischemic AKI, having decreased renal tubular necrosis, inflammation, and apoptosis compared with control MNP-treated or WT mice, respectively. Recombinant peptidylarginine deiminase type 4 (rPAD4) targeted kidney PT NEMO to exacerbate ischemic AKI in that exogenous rPAD4 exacerbated renal IR injury in WT mice but not in renal PT NEMO-deficient mice. Furthermore, rPAD4 upregulated proinflammatory cytokine mRNA and NF-κB activation in freshly isolated renal proximal tubules from WT mice but not from PT NEMO-deficient mice. Taken together, our studies suggest that renal PT NEMO plays a critical role in ischemic AKI by promoting renal tubular inflammation, apoptosis, and necrosis.

Understanding the in vivo Fate of Advanced Materials by Imaging

Engineered materials are ubiquitous in biomedical applications ranging from systemic drug delivery systems to orthopedic implants, and their actions unfold across multiple time- and length-scales. The efficacy and safety of biologics, nanomaterials, and macroscopic implants are all dictated by the same general principles of pharmacology as apply to small molecule drugs, comprising how the body affects materials (pharmacokinetics, PK) and conversely how materials affect the body (pharmacodynamics, PD). Imaging technologies play an increasingly insightful role in monitoring both of these processes, often simultaneously: translational macroscopic imaging modalities such as MRI and PET/CT offer whole-body quantitation of biodistribution and structural or molecular response, while ex vivo approaches and optical imaging via in vivo (intravital) microscopy reveal behaviors at subcellular resolution. In this review, the authors survey developments in imaging the in situ behavior of systemically and locally administered materials, with a particular focus on using microscopy to understand transport, target engagement, and downstream host responses at a single-cell level. The themes of microenvironmental influence, controlled drug release, on-target molecular action, and immune response, especially as mediated by macrophages and other myeloid cells are examined. Finally, the future directions of how new imaging technologies may propel efficient clinical translation of next-generation therapeutics and medical devices are proposed.

Current Drug Nano-targeting Strategies for Improvement in the Diagnosis and Treatment of Prevalent Pathologies such as Cardiovascular and Renal Diseases

BACKGROUND

The kidney and cardiovascular system are closely related to each other during the modulation of the cardiovascular homeostasis. However, the search for new alternatives for the treatment and diagnosis of cardiovascular diseases does not take into account this relationship, so their evaluation results and the advantages offered by their global and integrative analysis are wasted. For example, a variety of receptors that are overexpressed in both pathologies is large enough to allow expansion in the search for new molecular targets and ligands. Nanotechnology offers pharmacological targeting strategies to kidney, heart, and blood vessels for overcoming one of the essential restrictions of traditional cardiovascular therapies the ones related to their unspecific pharmacodynamics distribution in these critical organs.

RECENT FINDINGS

Drug or contrast agent nano-targeting for treatment or diagnosis of atherosclerosis, thrombosis, renal cancer or fibrosis, glomerulonephritis, among other renal, cardiac and blood vessels pathologies would allow an increase in their efficacy and a reduction of their side effects. Such effects are possible because, through pharmacological targeting, the drug is mainly found at the desired site. Review Purpose: In this mini-review, active, passive, and physical targeting strategies of several nanocarriers that have been assessed and proposed for the treatment and diagnosis of different cardiovascular diseases, are being addressed.

Nanoparticle delivery in vivo: A fresh look from intravital imaging

Nanomedicine has proven promising in preclinical studies. However, only few formulations have been successfully translated to clinical use. A thorough understanding of how nanoparticles interact with cells in vivo is essential to accelerate the clinical translation of nanomedicine. Intravital imaging is a crucial tool to reveal the mechanisms of nanoparticle transport in vivo, allowing for the development of new strategies for nanomaterial design. Here, we first review the most recent progress in using intravital imaging to answer fundamental questions about nanoparticle delivery in vivo. We then elaborate on how nanoparticles interact with different cell types and how such interactions determine the fate of nanoparticles in vivo. Lastly, we discuss ways in which the use of intravital imaging can be expanded in the future to facilitate the clinical translation of nanomedicine.

Nanoparticles exhibit greater accumulation in kidney glomeruli during experimental glomerular kidney disease

Loss and dysfunction of glomerular podocytes result in increased macromolecule permeability through the glomerular filtration barrier and nephrotic syndrome. Current therapies can induce and maintain disease remission, but cause serious and chronic complications. Nanoparticle drug carriers could mitigate these side effects by delivering drugs to the kidneys more efficiently than free drug through tailoring of carrier properties. An important extrinsic factor of nanoparticle biodistribution is local pathophysiology, which may drive greater nanoparticle deposition in certain tissues. Here, we hypothesized that a "leakier" filtration barrier during glomerular kidney disease would increase nanoparticle distribution into the kidneys. We examined the effect of nanoparticle size and disease state on kidney accumulation in male BALB/c mice. The effect of size was tested using a panel of fluorescent polystyrene nanoparticles of size 20-200 nm, due to the relevance of this size range for drug delivery applications.Experimental focal segmental glomerulosclerosis was induced using an anti-podocyte antibody that causes abrupt podocyte depletion. Nanoparticles were modified with carboxymethyl-terminated poly(ethylene glycol) for stability and biocompatibility. After intravenous injection, fluorescence from nanoparticles of size 20 and 100 nm, but not 200 nm, was observed in kidney glomeruli and peritubular capillaries. During conditions of experimental focal segmental glomerulosclerosis, the number of fluorescent nanoparticle punctae in kidney glomeruli increased by 1.9-fold for 20 and 100 nm nanoparticles compared to normal conditions. These findings underscore the importance of understanding and leveraging kidney pathophysiology in engineering new, targeted drug carriers that accumulate more in diseased glomeruli to treat glomerular kidney disease.

Advances in kidney-targeted drug delivery systems

The management and treatment of kidney diseases currently have caused a huge global burden. Although the application of nanotechnology for the therapy of kidney diseases is still at an early stages, it has profound potential of development. More and more nano-based drug delivery systems provide novel solutions for the treatment of kidney diseases. This article summarizes the physiological and anatomical properties of the kidney and the biological and physicochemical characters of drug delivery systems, which affects the ability of drug to target the kidney, and highlights the prospects, opportunities, and challenges of nanotechnology in the therapy of kidney diseases.

Nanotechnology as a Platform for the Development of Injectable Parenteral Formulations: A Comprehensive Review of the Know-Hows and State of the Art

Within recent decades, the development of nanotechnology has made a significant contribution to the progress of various fields of study, including the domains of medical and pharmaceutical sciences. A substantially transformed arena within the context of the latter is the development and production of various injectable parenteral formulations. Indeed, recent decades have witnessed a rapid growth of the marketed and pipeline nanotechnology-based injectable products, which is a testimony to the remarkability of the aforementioned contribution. Adjunct to the ability of nanomaterials to deliver the incorporated payloads to many different targets of interest, nanotechnology has substantially assisted to the development of many further facets of the art. Such contributions include the enhancement of the drug solubility, development of long-acting locally and systemically injectable formulations, tuning the onset of the drug’s release through the endowment of sensitivity to various internal or external stimuli, as well as adjuvancy and immune activation, which is a desirable component for injectable vaccines and immunotherapeutic formulations. The current work seeks to provide a comprehensive review of all the abovementioned contributions, along with the most recent advances made within each domain. Furthermore, recent developments within the domains of passive and active targeting will be briefly debated.

Neutrophil membrane-enveloped nanoparticles for the amelioration of renal ischemia-reperfusion injury in mice

Ischemia-reperfusion (I/R) injury initiates and exacerbates a series of oxidative and inflammatory events, and causes high morbidity and mortality. Despite the progress made with recent clinical use of anti-malarial drugs, the response rate of I/R injury treatment remains unsatisfactory. Here, we showed a neutrophil membrane-enveloped Coenzyme Q (N-NP_CoQ10) nanoparticle strategy for I/R injury treatment. We validated the physicochemical and biological reproducibility of the nanoparticles and tested the protective effects of N-NP_CoQ10 in oxygen-glucose deprivation/reperfusion model and renal I/R injury mouse model. N-NP_CoQ10 nanoparticles administration exhibited synergistic protective effect against I/R injury, which significantly reduced oxidative damage in vitro and in vivo, inhibited renal cell apoptosis, attenuated inflammatory response in renal I/R injury model, and finally improved renal function of I/R injury mice. The N-NP_CoQ10 nanoparticles administration provides an efficient way to deliver anti-oxidant that suppresses oxidative damages and neutralize proinflammatory cytokines during renal I/R injury, which might be a potential strategy for renal acute kidney injury treatment. STATEMENT OF SIGNIFICANCE: The neutrophil membrane-enveloped Coenzyme Q nanoparticles (N-NP_CoQ10) provides an efficient way to protect oxidative, inflammatory, and apoptotic reaction in renal I/R injury, which might be a potential strategy for renal acute kidney injury treatment.

Proliferative signaling by ERBB proteins and RAF/MEK/ERK effectors in polycystic kidney disease

A primary pathological feature of polycystic kidney disease (PKD) is the hyperproliferation of epithelial cells in renal tubules, resulting in formation of fluid-filled cysts. The proliferative aspects of the two major forms of PKD-autosomal dominant PKD (ADPKD), which arises from mutations in the polycystins PKD1 and PKD2, and autosomal recessive PKD (ARPKD), which arises from mutations in PKHD1-has encouraged investigation into protein components of the core cell proliferative machinery as potential drivers of PKD pathogenesis. In this review, we examine the role of signaling by ERBB proteins and their effectors, with a primary focus on ADPKD. The ERBB family of receptor tyrosine kinases (EGFR/ERBB1, HER2/ERBB2, ERBB3, and ERBB4) are activated by extracellular ligands, inducing multiple pro-growth signaling cascades; among these, activation of signaling through the RAS GTPase, and the RAF, MEK1/2, and ERK1/2 kinases enhance cell proliferation and restrict apoptosis during renal tubuloepithelial cyst formation. Characteristics of PKD include overexpression and mislocalization of the ERBB receptors and ligands, leading to enhanced activation and increased activity of downstream signaling proteins. The altered regulation of ERBBs and their effectors in PKD is influenced by enhanced activity of SRC kinase, which is promoted by the loss of cytoplasmic Ca2+ and an increase in cAMP-dependent PKA kinase activity that stimulates CFTR, driving the secretory phenotype of ADPKD. We discuss the interplay between ERBB/SRC signaling, and polycystins and their depending signaling, with emphasis on thes changes that affect cell proliferation in cyst expansion, as well as the inflammation-associated fibrogenesis, which characterizes progressive disease. We summarize the current progress of preclinical and clinical trials directed at inhibiting this signaling axis, and discuss potential future strategies that may be productive for controlling PKD.

Selective nanoparticle-mediated targeting of renal tubular Toll-like receptor 9 attenuates ischemic acute kidney injury

We developed an innovative therapy for ischemic acute kidney injury with discerning kidney-targeted delivery of a selective Toll-like receptor 9 (TLR9) antagonist in mice subjected to renal ischemia reperfusion injury. Our previous studies showed that mice deficient in renal proximal tubular TLR9 were protected against renal ischemia reperfusion injury demonstrating a critical role for renal proximal tubular TLR9 in generating ischemic acute kidney injury. Herein, we used 300-400 nm polymer-based mesoscale nanoparticles that localize to the renal tubules after intravenous injection. Mice were subjected to sham surgery or 30 minutes renal ischemia and reperfusion injury after receiving mesoscale nanoparticles encapsulated with a selective TLR9 antagonist (unmethylated CpG oligonucleotide ODN2088) or mesoscale nanoparticles encapsulating a negative control oligonucleotide. Mice treated with the encapsulated TLR9 antagonist either six hours before renal ischemia, at the time of reperfusion or 1.5 hours after reperfusion were protected against ischemic acute kidney injury. The ODN2088-encapsulated nanoparticles attenuated renal tubular necrosis, inflammation, decreased proinflammatory cytokine synthesis. neutrophil and macrophage infiltration and apoptosis, decreased DNA fragmentation and caspase 3/8 activation when compared to the negative control nanoparticle treated mice. Taken together, our studies further suggest that renal proximal tubular TLR9 activation exacerbates ischemic acute kidney injury by promoting renal tubular inflammation, apoptosis and necrosis after ischemia reperfusion. Thus, our studies suggest a potential promising therapy for ischemic acute kidney injury with selective kidney tubular targeting of TLR9 using mesoscale nanoparticle-based drug delivery.

Recent advances in nanotechnology-based drug delivery systems for the kidney

The application of nanotechnology in medicine has the potential to make a great impact on human health, ranging from prevention to diagnosis and treatment of disease. The kidneys are the main organ of the human urinary system, responsible for filtering the blood, and concentrating metabolic waste into urine by means of the renal glomerulus. The glomerular filtration apparatus presents a barrier against therapeutic agents based on charge and/or molecular size. Therefore, drug delivery to the kidneys faces significant difficulties resulting in treatment failure in several renal disorders. Accordingly, different strategies have recently being explored for enhancing the delivery of therapeutic agents across the filtration barrier of the glomerulus. Nanosystems with different physicochemical properties, including size, shape, surface, charge, and possessing biological features such as high cellular internalization, low cytotoxicity, controllable pharmacokinetics and biodistribution, have shown promising results for renal therapy. Different types of nanoparticles (NPs) have been used to deliver drugs to the kidney. In this review, we discuss nanotechnology-based drug delivery approaches for acute kidney injury, chronic kidney disease, renal fibrosis, renovascular hypertension and kidney cancer.

Understanding molecular upsets in diabetic nephropathy to identify novel targets and treatment opportunities

Diabetes and related complications are becoming a global encumbrance. Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD). The available therapeutic modalities related to DN do not treat DN at the molecular level, proposing further amendments in the management of DN based on the pathogenesis of DN. This manuscript discusses the concept and applications of nanomedicine for the treatment of DN that can improve renal targeting, retention and localization. This review also highlights the current issues related to targeting DN, challenges and allied opportunities toward the development of next-generation drugs and treatments for the management of DN.

Sirtuin 5 Regulates Proximal Tubule Fatty Acid Oxidation to Protect against AKI

BACKGROUND

The primary site of damage during AKI, proximal tubular epithelial cells, are highly metabolically active, relying on fatty acids to meet their energy demands. These cells are rich in mitochondria and peroxisomes, the two organelles that mediate fatty acid oxidation. Emerging evidence shows that both fatty acid pathways are regulated by reversible posttranslational modifications, particularly by lysine acylation. Sirtuin 5 (Sirt5), which localizes to both mitochondria and peroxisomes, reverses post-translational lysine acylation on several enzymes involved in fatty acid oxidation. However, the role of the Sirt5 in regulating kidney energy metabolism has yet to be determined.

METHODS

We subjected male Sirt5-deficient mice (either +/- or -/-) and wild-type controls, as well as isolated proximal tubule cells, to two different AKI models (ischemia-induced or cisplatin-induced AKI). We assessed kidney function and injury with standard techniques and measured fatty acid oxidation by the catabolism of 14C-labeled palmitate to 14CO2.

RESULTS

Sirt5 was highly expressed in proximal tubular epithelial cells. At baseline, Sirt5 knockout (Sirt5-/- ) mice had modestly decreased mitochondrial function but significantly increased fatty acid oxidation, which was localized to the peroxisome. Although no overt kidney phenotype was observed in Sirt5-/- mice, Sirt5-/- mice had significantly improved kidney function and less tissue damage compared with controls after either ischemia-induced or cisplatin-induced AKI. This coincided with higher peroxisomal fatty acid oxidation compared with mitochondria fatty acid oxidation in the Sirt5-/- proximal tubular epithelial cells.

CONCLUSIONS

Our findings indicate that Sirt5 regulates the balance of mitochondrial versus peroxisomal fatty acid oxidation in proximal tubular epithelial cells to protect against injury in AKI. This novel mechanism might be leveraged for developing AKI therapies.

Intravital microscopy reveals a novel mechanism of nanoparticles excretion in kidney

Developing nanocarriers that accumulate in targeted organs and are harmlessly eliminated still remains a big challenge. Nanoparticles (NP) biodistribution is governed by their size, composition, surface charge and coverage. The current thinking in bionanotechnology is that renal clearance is limited by glomerular basement membrane pore size (≈6 nm), although there is a growing evidence that NP exceeding the threshold can also be excreted with urine. Here we compare biodistribution of PEGylated 140 nm iron oxide cubes and clusters with a special focus on renal accumulation and excretion. Atomic emission spectroscopy, fluorescent microscopy and magnetic resonance imaging revealed rapid and transient accumulation of magnetic NP in kidney. Using intravital microscopy we tracked in real time NP translocation from peritubular capillaries to basal compartment of tubular cells and subsequent excretion to the lumen within 60 min after systemic administration. Transmission electron microscopy revealed persistence of intact full-sized NP in urine 2 h post injection. The results suggest that translocation through peritubular endothelium to tubular epithelial cells is an alternative mechanism of renal clearance enabling excretion of NP above glomerular cut-off size.

Kidney nanotoxicity studied in human renal proximal tubule epithelial cell line TH1

Progressive expansion of nanomaterials in our everyday life raises concerns about their safety for human health. Although kidneys are the primary organs of xenobiotic elimination, little attention has been paid to the kidneys in terms of nanotoxicological studies up to now. Here we investigate the cytotoxic and genotoxic potential of four solid-core uncoated inorganic nanoparticles (TiO₂NPs, SiO₂NPs, Fe₃O₄NPs and AuNPs) using the human renal proximal tubule epithelial TH1 cells. To mimic the in vivo conditions more realistic, TH1 cells were exposed in vitro to inorganic NPs under static as well as dynamic conditions for 3 h and 24 h. The medium throughput alkaline comet assay (12 minigels per slide) was employed to evaluate the impact of these NPs on genome integrity and their capacity to produce oxidative lesions to DNA. The accumulation and localization of studied inorganic NPs inside the cells was monitored by transmission electron microscopy (TEM) and the efficacy of internalization of particular NPs was determined by atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). From all the tested NPs, only Fe₃O₄NPs induced a slight cytotoxicity in TH1 cells exposed to high concentrations (>700 μg/ml) for 24 h. On the other hand, the inorganic NPs did not increase significantly the level of DNA strand breaks or oxidative DNA damage regardless of the treatment mode (static vs. dynamic conditions). Interestingly, substantial differences were observed in the internalized amount of inorganic NPs in TH1 cells exposed to equivalent (2.2 μg/ml) concentration. Fe₃O₄NPs were most efficiently taken up while the lowest quantity of particles was determined in TiO₂NPs-treated cells. As the particle size and shape of individual inorganic NPs in culture medium was nearly identical, it is reasonable to suppose that the chemical composition may contribute to the differences in the efficacy of NPs uptake.