Noninvasive ROS imaging and drug delivery monitoring in the tumor microenvironment.

Reactive oxygen species (ROS) that are overproduced in certain tumors can be considered an indicator of oxidative stress levels in the tissue. Here, we report a magnetic resonance imaging (MRI)-based probe capable of detecting ROS levels in the tumor microenvironment (TME) using ROS-responsive manganese ion (Mn2+)-chelated, biotinylated bilirubin nanoparticles (Mn@bt-BRNPs). These nanoparticles are disrupted in the presence of ROS, resulting in the release of free Mn2+, which induces T1-weighted MRI signal enhancement. Mn@BRNPs show more rapid and greater MRI signal enhancement in high ROS-producing A549 lung carcinoma cells compared with low ROS-producing DU145 prostate cancer cells. A pseudo three-compartment model devised for the ROS-reactive MRI probe enables mapping of the distribution and concentration of ROS within the tumor. Furthermore, doxorubicin-loaded, cancer-targeting ligand biotin-conjugated Dox/Mn@bt-BRNPs show considerable accumulation in A549 tumors and also effectively inhibit tumor growth without causing body weight loss, suggesting their usefulness as a new theranostic agent. Collectively, these findings suggest that Mn@bt-BRNPs could be used as an imaging probe capable of detecting ROS levels and monitoring drug delivery in the TME with potential applicability to other inflammatory diseases.

Longitudinal Magnetic Resonance Imaging with ROS-Responsive Bilirubin Nanoparticles Enables Monitoring of Nonalcoholic Steatohepatitis Progression to Cirrhosis.

Despite the vital importance of monitoring the progression of nonalcoholic fatty liver disease (NAFLD) and its progressive form, nonalcoholic steatohepatitis (NASH), an efficient imaging modality that is readily available at hospitals is currently lacking. Here, a new magnetic-resonance-imaging (MRI)-based imaging modality is presented that allows for efficient and longitudinal monitoring of NAFLD and NASH progression. The imaging modality uses manganese-ion (Mn2+)-chelated bilirubin nanoparticles (Mn@BRNPs) as a reactive-oxygen-species (ROS)-responsive MRI imaging probe. Longitudinal T1-weighted MR imaging of NASH model mice is performed after injecting Mn@BRNPs intravenously. The MR signal enhancement in the liver relative to muscle gradually increases up to 8 weeks of NASH progression, but decreases significantly as NASH progresses to the cirrhosis-like stage at weeks 10 and 12. A new dual input pseudo-three-compartment model is developed to provide information on NASH stage with a single MRI scan. It is also demonstrated that the ROS-responsive Mn@BRNPs can be used to monitor the efficacy of potential anti-NASH drugs with conventional MRI. The findings suggest that the ROS-responsive Mn@BRNPs have the potential to serve as an efficient MRI contrast for monitoring NASH progression and its transition to the cirrhosis-like stage.

Glycocalyx-Mimicking Nanoparticles with Differential Organ Selectivity for Drug Delivery and Therapy.

Organ-selective drug delivery is expected to maximize the efficacy of various therapeutic modalities while minimizing their systemic toxicity. Lipid nanoparticles and polymersomes can direct the organ-selective delivery of mRNAs or gene editing machineries, but their delivery is limited to mostly liver, spleen, and lung. A platform that enables delivery to these and other target organs is urgently needed. Here, a library of glycocalyx-mimicking nanoparticles (GlyNPs) comprising five randomly combined sugar moieties is generated, and direct in vivo library screening is used to identify GlyNPs with preferential biodistribution in liver, spleen, lung, kidneys, heart, and brain. Each organ-targeting GlyNP hit show cellular tropism within the organ. Liver, kidney, and spleen-targeting GlyNP hits equipped with therapeutics effectively can alleviate the symptoms of acetaminophen-induced liver injury, cisplatin-induced kidney injury, and immune thrombocytopenia in mice, respectively. Furthermore, the differential organ targeting of GlyNP hits is influenced not by the protein corona but by the sugar moieties displayed on their surface. It is envisioned that the GlyNP-based platform may enable the organ- and cell-targeted delivery of therapeutic cargoes.

Bilirubin Nanomedicine Rescues Intestinal Barrier Destruction and Restores Mucosal Immunity in Colitis.

Inflammatory bowel disease (IBD) manifests as intestinal barrier destruction, mucosal immunity dysregulation, and disrupted gut microbiome homeostasis. Conventional anti-inflammatory medications for IBD therapy partially alleviate symptoms but are unable to restore normal barrier and immune function. Here, we report a nanomedicine comprising bilirubin (BR)-attached low-molecular-weight, water-soluble chitosan nanoparticles (LMWC-BRNPs), that promotes restoration of the intestinal barrier, mucosal immunity, and the gut microbiome, thereby exerting robust therapeutic efficacy. In a mouse model of dextran sulfate sodium salt (DSS)-induced colitis, orally administered LMWC-BRNPs were retained in the GI tract much longer than other nonmucoadhesive BRNPs owing to the mucoadhesiveness of LMWC via electrostatic interaction. Treatment with LMWC-BRNPs led to considerable recovery of the damaged intestinal barrier compared with the current IBD medication, 5-aminosalicylic acid (5-ASA). Orally administered LMWC-BRNPs were taken up by pro-inflammatory macrophages and inhibited their activity. They also concurrently increased the population of regulatory T cells, thereby leading to the recovery of dysregulated mucosal immunity. An analysis of the gut microbiome revealed that LMWC-BRNPs treatment significantly attenuated the increase Turicibacter, an inflammation-related microorganism, resulting in protection of gut microbiome homeostasis. Taken together, our findings indicate that LMWC-BRNPs restored normal functions of the intestine and have high potential for use as a nanomedicine for IBD therapy.

The Combination of Sinusoidal Perfusion Enhancement and Apoptosis Inhibition by Riociguat Plus a Galactose-PEGylated Bilirubin Multiplexing Nanomedicine Ameliorates Liver Fibrosis Progression.

Chronic liver injury and continuous wound healing lead to extracellular matrix (ECM) deposition and liver fibrosis. The elevated production of reactive oxygen species (ROS) in the liver leads to the apoptosis of hepatocytes and the activation of hepatic stellate cells (HSCs). In the current study, we describe a combination strategy of sinusoidal perfusion enhancement and apoptosis inhibition enabled by riociguat together with a tailor-designed galactose-PEGylated bilirubin nanomedicine (Sel@GBRNPs). Riociguat enhanced sinusoidal perfusion and decreased the associated ROS accumulation and inflammatory state of the fibrotic liver. Concurrently, hepatocyte-targeting galactose-PEGylated bilirubin scavenged excessive ROS and released encapsulated selonsertib. The released selonsertib inhibited apoptosis signal-regulating kinase 1 (ASK1) phosphorylation to alleviate apoptosis in hepatocytes. The combined effects on ROS and hepatocyte apoptosis attenuated the stimulation of HSC activation and ECM deposition in a mouse model of liver fibrosis. This work provides a novel strategy for liver fibrosis treatment based on sinusoidal perfusion enhancement and apoptosis inhibition.

Indirect bilirubin impairs invasion of osteosarcoma cells via inhibiting the PI3K/AKT/MMP-2 signaling pathway by suppressing intracellular ROS.

Background: Osteosarcoma is most prevalently found primary malignant bone tumors, with primary metastatic patients accounting for approximately 25% of all osteosarcoma patients, yet their 5-year OS remains below 30%. Bilirubin plays a key role in oxidative stress-associated events, including malignancies, making the regulation of its serum levels a potential anti-tumor strategy. Herein, we investigated the association of osteosarcoma prognosis with serum levels of TBIL, IBIL and DBIL, and further explored the mechanisms by which bilirubin affects tumor invasion and migration. Methods: ROC curve was plotted to assess survival conditions based on the determined optimal cut-off values and the AUC. Then, Kaplan-Meier curves, along with Cox proportional hazards model, was applied for survival analysis. Inhibitory function of IBIL on the malignant properties of osteosarcoma cells was examined using the qRT-PCR, transwell assays, western blotting, and flow cytometry. Results: We found that, versus osteosarcoma patients with pre-operative higher IBIL (>8.9 µmol/L), those with low IBIL (≤8.9 µmol/L) had shorter OS and PFS. As indicated by the Cox proportional hazards model, pre-operative IBIL functioned as an independent prognostic factor for OS and PFS in total and gender-stratified osteosarcoma patients (P < 0.05 for all). In vitro experiments further confirmed that IBIL inhibits PI3K/AKT phosphorylation and downregulates MMP-2 expression via reducing intracellular ROS, thereby decreasing the invasion of osteosarcoma cells. Conclusions: IBIL may serve as an independent prognostic predictor for osteosarcoma patients. IBIL impairs invasion of osteosarcoma cells through repressing the PI3K/AKT/MMP-2 pathway by suppressing intracellular ROS, thus inhibiting its metastatic potential.

Co-delivery of photosensitizer and diclofenac through sequentially responsive bilirubin nanocarriers for combating hypoxic tumors.

Considering that photodynamic therapy (PDT)-induced oxygen consumption and microvascular damage could exacerbate hypoxia to drive more glycolysis and angiogenesis, a novel approach to potentiate PDT and overcome the resistances of hypoxia is avidly needed. Herein, morpholine-modified PEGylated bilirubin was proposed to co-deliver chlorin e6, a photosensitizer, and diclofenac (Dc). In acidic milieu, the presence of morpholine could enable the nanocarriers to selectively accumulate in tumor cells, while PDT-generated reactive oxidative species (ROS) resulted in the collapse of bilirubin nanoparticles and rapid release of Dc. Combining with Dc showed a higher rate of apoptosis over PDT alone and simultaneously triggered a domino effect, including blocking the activity and expression of lactate dehydrogenase A (LDHA), interfering with lactate secretion, suppressing the activation of various angiogenic factors and thus obviating hypoxia-induced resistance-glycolysis and angiogenesis. In addition, inhibition of hypoxia-inducible factor-1α (HIF-1α) by Dc alleviated hypoxia-induced resistance. This study offered a sequentially responsive platform to achieve sufficient tumor enrichment, on-demand drug release and superior anti-tumor outcomes in vitro and in vivo.

Novel preparation of bilirubin-encapsulated pluronic F-127 nanoparticles as a potential biomaterial for wound healing.

Cutaneous wounds deteriorate the health of patients and liable for high economic loss. Previous studies showed promising wound healing potentials of bilirubin, however, this macromolecule constrained with poor water solubility and skin penetration. In this study, Pluronic F-127, a non-ionic copolymer surfactant, was used for the encapsulation of the wound healing agent the bilirubin. With this strategy, spherical shaped bilirubin nanoparticles of ∼100-150 nm with zeta potential ranging from -13.43 ± 0.56 to -17.53 ± 0.43 mV were obtained. Topical applications of bilirubin nanoparticle (0.3%) on cutaneous wounds of rats showed promising wound healing in comparison with other topical treatments. This topical nano-formulation also modulates the cytokine and growth factor responses in the treated group. On day 7 of healing, bilirubin nanoparticles treatment significantly reduced TNF-α and increased IL-10 levels with increased VEGF and TGF-ß1 expressions. Simultaneously, prominent pro-healing activities could be observed histopathologically. These include increased blood vessels, reduced inflammatory cells, more myofibroblasts, increased deposition of collagen fibres, and early re-epithelialization. The changes were prominent in bilirubin nanoparticles (0.3%) treated group indicating better granulation tissue, quality of healing and wound maturity. In conclusion, the proposed new encapsulated bilirubin nanoparticles strategy significantly improved wound healing by modulation of cytokines and growth factors response in comparison with native bulk bilirubin. These observations support its potential as a novel biomaterial for wound healing in the future.

Bilirubin Nanoparticles Protect Against Cardiac Ischemia/Reperfusion Injury in Mice.

Background Ischemia/reperfusion (I/R) injury causes overproduction of reactive oxygen species, which are the major culprits of oxidative stress that leads to inflammation, apoptosis, myocardial damage, and dysfunction. Bilirubin acts as a potent endogenous antioxidant that is capable of scavenging various reactive oxygen species. We have previously generated bilirubin nanoparticles (BRNPs) consisting of polyethylene glycol-conjugated bilirubin. In this study, we examined the therapeutic effects of BRNPs on myocardial I/R injury in mice. Methods and Results In vivo imaging using fluorophore encapsulated BRNPs showed BRNPs preferentially targeted to the site of I/R injury in the heart. Cardiac I/R surgery was performed by first ligating the left anterior descending coronary artery. After 45 minutes, reperfusion was achieved by releasing the ligation. BRNPs were administered intraperitoneally at 5 minutes before and 24 hours after reperfusion. Mice that received BRNPs showed significant improvements in their cardiac output, assessed by echocardiogram and pressure volume loop measurements, compared with the ones that received vehicle treatment. BRNPs treatment also significantly reduced the myocardial infarct size in mice that underwent cardiac I/R, compared with the vehicle-treatment group. In addition, BRNPs effectively suppressed reactive oxygen species and proinflammatory factor levels, as well as the amount of cardiac apoptosis. Conclusions Taken together, BRNPs could exert their therapeutic effects on cardiac I/R injury through attenuation of oxidative stress, apoptosis, and inflammation, providing a novel therapeutic modality for myocardial I/R injury.

A bilirubin-derived nanomedicine attenuates the pathological cascade of pulmonary fibrosis.

Pulmonary fibrosis is an irreparable and life-threatening disease with only limited therapeutic options. The recent outbreak of COVID-19 has caused a sharp rise in the incidence of pulmonary fibrosis owing to SARS-CoV-2 infection-mediated acute respiratory distress syndrome (ARDS). The considerable oxidative damage caused by locally infiltrated immune cells plays a crucial role in ARDS, suggesting the potential use of antioxidative therapeutics. Here, we report the therapeutic potential of nanoparticles derived from the endogenous antioxidant and anti-inflammatory bile acid, bilirubin (BRNPs), in treating pulmonary fibrosis in a bleomycin-induced mouse model of the disease. Our results demonstrate that BRNPs can effectively reduce clinical signs in mice, as shown by histological, disease index evaluations, and detection of biomarkers. Our findings suggest that BRNPs, with their potent antioxidant and anti-inflammatory effects, long blood circulation half-life, and preferential accumulation at the inflamed site, are potentially a viable clinical option for preventing Covid-19 infection-associated pulmonary fibrosis.

Bilirubin nanomedicine ameliorates the progression of experimental autoimmune encephalomyelitis by modulating dendritic cells.

Although the cause of multiple sclerosis (MS) is unclear, an autoimmune attack on myelin-based coating layers of nerve cells in the brain and spinal cord is the main feature of the disease, highlighting modulation of the immune response to myelin as a feasible therapeutic approach. Here, we report the potential of bilirubin nanoparticles (BRNPs) based on the endogenous antioxidant and anti-inflammatory agent, bilirubin, as a therapeutic nanomedicine for MS. In a mouse model of experimental autoimmune encephalomyelitis (EAE), multiple intravenous injections of BRNPs significantly delayed disease onset and suppressed disease progression and severity as well as disease incidence rate without systemic immunosuppression. Following intravenous injection, BRNPs accumulated more extensively and were retained longer in secondary lymphoid organs of EAE-induced mice compared with non-immunized control mice, including in inguinal lymph nodes (iLNs) and spleens, where antigen presenting cells (APCs) activated by the myelin antigen are abundant. Studies of the underlying mechanism of action further revealed that BRNPs negatively regulated the differentiation of naïve CD4+ T cells into T helper 17 (Th17) cells by inhibiting maturation of APCs through scavenging of reactive oxygen species (ROS) overproduced in both dendritic cells (DCs) and macrophages upon antigen uptake. These findings indicate that BRNPs have the potential to be used as a new therapeutic nanomedicine for treatment of various CD4+ T cell-associated autoimmune diseases.

Glutathione-Responsive Gold Nanoparticles as Computed Tomography Contrast Agents for Hepatic Diseases.

Glutathione (GSH) is produced at high levels in the normal liver, but its production is considerably reduced under certain pathological conditions. Accordingly, an imaging probe capable of visualizing the altered GSH level in the liver would be a useful tool for monitoring hepatic functions or diseases. Here, we report a gold nanoparticle (AuNP)-based computed tomography (CT) contrast agent that undergoes a change in colloidal stability in response to GSH levels, resulting in differential CT signal intensity between normal (higher intensity) and pathological (lower intensity) livers, enabling imaging of hepatic function. This GSH-responsive CT contrast agent, prepared by coating AuNPs with PEGylated bilirubin (PEG-BR), shows serum stability and high sensitivity to GSH. The resulting poly(ethylene glycol) (PEG)-BR@AuNPs preferentially accumulate in the normal liver, as evidenced by strongly enhanced CT intensity, but fail to do so in a GSH-depleted mouse model, where the CT signal in the liver was substantially decreased. In addition, injection of PEG-BR@AuNPs caused a greater reduction in CT signals in the liver in a drug-induced acute liver failure model than in healthy normal mice. These findings suggest that GSH-responsive PEG-BR@AuNPs have the potential to be used as a CT contrast agent to detect various hepatic function-related diseases and liver-metastasized tumors.

Bilirubin as a metabolic hormone: the physiological relevance of low levels.

Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.

Bilirubin nanomedicine alleviates psoriatic skin inflammation by reducing oxidative stress and suppressing pathogenic signaling.

Psoriasis is a prevalent chronic inflammatory skin disease characterized by thickening of the epidermis accompanied by lesional erythema, scaling, and induration as a result of abnormal proliferation of keratinocytes. During the development of psoriasis, levels of intracellular reactive oxygen species (ROS) within psoriatic lesions are elevated, activating a pro-inflammatory signaling cascade. Here, we evaluated the therapeutic efficacy and mode of action of bilirubin nanoparticles (BRNPs), based on the potent, endogenous antioxidant bilirubin, in a preclinical psoriasis model. We found that topical treatment of psoriatic lesions with BRNPs effectively attenuated upregulation of intracellular ROS levels within keratinocytes and ameliorated the symptoms of psoriasis. A subsequent mechanistic study showed that preventing oxidative stress in activated keratinocytes suppressed the secretion of inflammatory mediators and recruitment of immune cells. Subsequent expression of the antigen-presenting cell (APC) maturation markers, class II major histocompatibility complex (MHC class II), cluster of differentiation (CD) 80 and CD86, was significantly decreased, resulting in a reduction in the differentiation of naïve CD4+ T cells into interleukin (IL)-17-producing T-helper (Th) 17 cells. Unlike the commercial corticosteroid drug, clobetasol propionate (CLQ), BRNPs, composed of the endogenous antioxidant bilirubin and the approved polymer polyethylene glycol (PEG), did not exert systemic cytotoxicity. Collectively, these findings highlight the potential of BRNPs as a novel nanomedicine for ameliorating psoriasis-like skin inflammation through topical treatment and suggest that their use could be further expanded to treat other chronic skin inflammation diseases, including atopic dermatitis.

PEGylated Bilirubin-coated Iron Oxide Nanoparticles as a Biosensor for Magnetic Relaxation Switching-based ROS Detection in Whole Blood.

Rationale: Magnetic relaxation switching (MRSw) induced by target-triggered aggregation or dissociation of superparamagnetic iron oxide nanoparticles (SPIONs) have been utilized for detection of diverse biomarkers. However, an MRSw-based biosensor for reactive oxygen species (ROS) has never been documented. Methods: To this end, we constructed a biosensor for ROS detection based on PEGylated bilirubin (PEG-BR)-coated SPIONs (PEG-BR@SPIONs) that were prepared by simple sonication via ligand exchange. In addition, near infra-red (NIR) fluorescent dye was loaded onto PEG-BR@SPIONs as a secondary option for fluorescence-based ROS detection. Results: PEG-BR@SPIONs showed high colloidal stability under physiological conditions, but upon exposure to the model ROS, NaOCl, in vitro, they aggregated, causing a decrease in signal intensity in T2-weighted MR images. Furthermore, ROS-responsive PEG-BR@SPIONs were taken up by lipopolysaccharide (LPS)-activated macrophages to a much greater extent than ROS-unresponsive control nanoparticles (PEG-DSPE@SPIONs). In a sepsis-mimetic clinical setting, PEG-BR@SPIONs were able to directly detect the concentrations of ROS in whole blood samples through a clear change in T2 MR signals and a 'turn-on' signal of fluorescence. Conclusions: These findings suggest that PEG-BR@SPIONs have the potential as a new type of dual mode (MRSw-based and fluorescence-based) biosensors for ROS detection and could be used to diagnose many diseases associated with ROS overproduction.

Biotinylated Bilirubin Nanoparticles as a Tumor Microenvironment-Responsive Drug Delivery System for Targeted Cancer Therapy.

The tumor microenvironment (TME) plays a crucial role in tumorigenesis and cancer cell metastasis. Accordingly, a drug-delivery system (DDS) that is capable of targeting tumor and releasing drugs in response to TME-associated stimuli should lead to potent antitumor efficacy. Here, a cancer targeting, reactive oxygen species (ROS)-responsive drug delivery vehicle as an example of a TME-targeting DDS is reported. Tumor targeting is achieved using biotin as a ligand for "biotin transporter"-overexpressing malignant tumors, and bilirubin-based nanoparticles (BRNPs) are used as a drug-delivery carrier that enables ROS-responsive drug release. Doxorubicin-loaded, biotinylated BRNPs (Dox@bt-BRNPs) with size of ≈100 nm are prepared by a one-step self-assembly process. Dox@bt-BRNPs exhibit accelerated Dox-release behavior in response to ROS and show specific binding as well as anticancer activity against biotin transporter-overexpressing HeLa cells in vitro. bt-BRNPs labeled with cypate, near-infrared dye, show much greater accumulation at tumor sites in HeLa tumor-bearing mice than BRNPs lacking the biotin ligand. Finally, intravenous injection of Dox@bt-BRNPs into HeLa tumor-bearing mice results in greater antitumor efficacy compared with free Dox, bt-BRNPs only, and Dox@BRNPs without causing any appreciable body weight loss. Collectively, these findings suggest that bt-BRNPs hold potential as a new TME-responsive DDS for effectively treating various tumors.

Black Pigment Gallstone Inspired Platinum-Chelated Bilirubin Nanoparticles for Combined Photoacoustic Imaging and Photothermal Therapy of Cancers.

Bilirubin (BR), a bile pigment that exerts potent antioxidant and anti-inflammatory effects, is also a major constituent of black pigment gallstones found in bile ducts under certain pathological conditions. Inspired by the intrinsic metal-chelating power of BR found in gallstones, herein we report a cisplatin-chelated BR-based nanoparticle (cisPt@BRNP) for use as a new photonic nanomedicine for combined photoacoustic imaging and photothermal therapy of cancers. The cisPt@BRNPs were prepared by simply mixing cisplatin with BRNPs, yielding ca. 150-nm-size NPs. Upon near-IR laser irradiation at 808 nm, cisPt@BRNPs generated considerable heat and induced clear death of cancer cells in vitro. Following intravenous injection into human colon cancer-bearing mice, cisPt@BRNPs allowed effective tumor visualization by photoacoustic imaging and remarkable antitumor efficacy by photothermal therapy, suggesting their potential for use as a new photonic nanomedicine for cancer therapy.

Bilirubin nanoparticles ameliorate allergic lung inflammation in a mouse model of asthma.

Although asthma, a chronic inflammatory airway disease, is relatively well-managed by inhaled corticosteroids, the side effects associated with the long-term use of these agents precipitate the need for alternative therapeutic options based on differing modes of action. Bilirubin, a potent endogenous antioxidant, and anti-inflammatory molecule have been shown to ameliorate asthmatic symptoms; however, its clinical translation has been limited owing to its water insolubility and associated potential toxicity. Here we report the first application of bilirubin-based nanoparticles (BRNPs) as a nanomedicine for the treatment of allergic lung inflammatory disease. BRNPs were prepared directly from self-assembly of PEGylated bilirubin in aqueous solution and had a hydrodynamic diameter of ∼100 nm. Because allergen-specific type 2 T-helper (Th2) cells play a key role in the pathogenesis and progression of allergic asthma, the effects of BRNPs on Th2 immune responses were investigated both in vivo and in vitro. BRNPs after intravenous injection (i.v.) showed much higher serum concentration and a longer circulation time of bilirubin than the intraperitoneal injection (i.p.) of BRNPs or unconjugated bilirubin (UCB). The anti-asthmatic effects of BRNPs were assessed in a mouse model of allergen-induced asthma. Compared with UCB, treatment with BRNPs suppressed the symptoms of experimental allergic asthma and dramatically ameliorated Th2-related allergic lung inflammation. Consistent with these results, BRNPs caused a reduction of Th2 cell populations and the expression of related cytokines by antibody-stimulated CD4+ T cells in vitro. Therefore, our results establish BRNPs as an important immunomodulatory agent that may be useful as a therapeutic for allergic lung inflammatory disease and other immune-mediated disorders.

PEGylated bilirubin nanoparticle as an anti-oxidative and anti-inflammatory demulcent in pancreatic islet xenotransplantation.

Transplanted islets suffer hypoxic stress, which leads to nonspecific inflammation. This is the major cause of islet graft failure during the early stage of intrahepatic islet transplantation. Although bilirubin has shown potent anti-oxidative and anti-inflammatory functions, its clinical applications have been limited due to its insolubility and short half-life. To overcome this problem, novel amphiphilic bilirubin nanoparticles are designed. Hydrophilic poly(ethylene glycol) (PEG) is conjugated to the hydrophobic bilirubin molecule. Then, the PEG-bilirubin conjugates form nanoparticles via self-assembly, i.e., so-called to BRNPs. BRNPs can protect islet cells not only from chemically induced oxidative stress by scavenging reactive oxygen species molecules, but also from activated macrophages by suppressing cytokine release. Importantly, in vivo experiments demonstrate that BRNP treatment can dramatically and significantly prolong islet graft survival compared to bilirubin treatment. In addition, immunohistochemical analysis shows BRNPs have potent anti-oxidative and anti-inflammatory capabilities. Collectively, novel BRNPs can be a new potent remedy for successful islet transplantation.