Quantum dots for quantitative imaging: from single molecules to tissue.

Since their introduction to biological imaging, quantum dots (QDs) have progressed from a little known, but attractive, technology to one that has gained broad application in many areas of biology. The versatile properties of these fluorescent nanoparticles have allowed investigators to conduct biological studies with extended spatiotemporal capabilities that were previously not possible. In this review, we focus on QD applications that provide enhanced quantitative information concerning protein dynamics and localization, including single particle tracking and immunohistochemistry, and finish by examining the prospects of upcoming applications, such as correlative light and electron microscopy and super-resolution. Advances in single molecule imaging, including multi-color and three-dimensional QD tracking, have provided new insights into the mechanisms of cell signaling and protein trafficking. New forms of QD tracking in vivo have allowed the observation of biological processes at molecular level resolution in the physiological context of the whole animal. Further methodological development of multiplexed QD-based immunohistochemistry assays should enable more quantitative analysis of key proteins in tissue samples. These advances highlight the unique quantitative data sets that QDs can provide to further our understanding of biological and disease processes.

The population pharmacokinetics of R- and S-warfarin: effect of genetic and clinical factors.

BACKGROUND: Warfarin is a drug with a narrow therapeutic index and large interindividual variability in daily dosing requirements. Patients commencing warfarin treatment are at risk of bleeding due to excessive anticoagulation caused by overdosing. The interindividual variability in dose requirements is influenced by a number of factors, including polymorphisms in genes mediating warfarin pharmacology, co-medication, age, sex, body size and diet. AIMS: To develop population pharmacokinetic models of both R- and S-warfarin using clinical and genetic factors and to identify the covariates which influence the interindividual variability in the pharmacokinetic parameters of clearance and volume of distribution in patients on long-term warfarin therapy. METHODS: Patients commencing warfarin therapy were followed up for 26 weeks. Plasma warfarin enantiomer concentrations were determined in 306 patients for S-warfarin and in 309 patients for R-warfarin at 1, 8 and 26 weeks. Patients were also genotyped for CYP2C9 variants (CYP2C9*1,*2 and *3), two single-nucleotide polymorphisms (SNPs) in CYP1A2, one SNP in CYP3A4 and six SNPs in CYP2C19. A base pharmacokinetic model was developed using NONMEM software to determine the warfarin clearance and volume of distribution. The model was extended to include covariates that influenced the between-subject variability. RESULTS: Bodyweight, age, sex and CYP2C9 genotype significantly influenced S-warfarin clearance. The S-warfarin clearance was estimated to be 0.144 l h⁻¹ (95% confidence interval 0.131, 0.157) in a 70 kg woman aged 69.8 years with the wild-type CYP2C9 genotype, and the volume of distribution was 16.6 l (95% confidence interval 13.5, 19.7). Bodyweight and age, along with the SNPs rs3814637 (in CYP2C19) and rs2242480 (in CYP3A4), significantly influenced R-warfarin clearance. The R-warfarin clearance was estimated to be 0.125 l h⁻¹ (95% confidence interval 0.115, 0.135) in a 70 kg individual aged 69.8 years with the wild-type CYP2C19 and CYP3A4 genotypes, and the volume of distribution was 10.9 l (95% confidence interval 8.63, 13.2). CONCLUSIONS: Our analysis, based on exposure rather than dose, provides quantitative estimates of the clinical and genetic factors impacting on the clearance of both the S- and R-enantiomers of warfarin, which can be used in developing improved dosing algorithms.

C3a mediates epithelial-to-mesenchymal transition in proteinuric nephropathy.

Tubulointerstitial inflammation and progressive fibrosis are common pathways that lead to kidney failure in proteinuric nephropathies. Activation of the complement system has been implicated in the development of tubulointerstitial injury in clinical and animal studies, but the mechanism by which complement induces kidney injury is not fully understood. Here, we studied the effect of complement on the phenotype of tubular epithelial cells. Tubular epithelial cells exposed to serum proteins adopted phenotypic and functional characteristics of mesenchymal cells. Expression of E-cadherin protein decreased and expression of both alpha-smooth muscle actin protein and collagen I mRNA increased. Exposure of the cells to the complement anaphylotoxin C3a induced similar features. Treating with a C3a receptor (C3aR) antagonist prevented both C3a- and serum-induced epithelial-to-mesenchymal transition. In the adriamycin-induced proteinuria model, C3aR-deficient mice demonstrated less injury, preserved renal function, and improved survival compared with wild-type mice. Furthermore, the kidneys of C3aR-deficient mice had significantly less interstitial collagen I and alpha-smooth muscle actin. In summary, the complement anaphylotoxin C3a is an important mediator of glomerular and tubulointerstitial injury and can induce tubular epithelial-to-mesenchymal transition.

Variability of PD-L1 expression in mastocytosis.

Mastocytosis is a rare disease with heterogeneous clinical manifestations and few effective therapies. Programmed death-1 (PD-1) and its ligands (PD-L1 and PD-L2) protect tissues from immune-mediated damage and permit tumors to evade immune destruction. Therapeutic antibodies against PD-1 and PD-L1 are effective in the treatment of a variety of neoplasms. In the present study, we sought to systematically analyze expression of PD-1 and PD-L1 in a large number of patients with mastocytosis using immunohistochemistry and multiplex fluorescence staining. PD-L1 showed membrane staining of neoplastic mast cells (MCs) in 77% of systemic mastocytosis (SM) cases including 3 of 3 patients with MC leukemia, 2 of 2 with aggressive SM, 1 of 2 with smoldering SM, 3 of 4 with indolent SM, and 9 of 12 with SM with an associated hematologic neoplasm (SM component only). Ninety-two percent (23 of 25) of cutaneous mastocytosis (CM) cases and 1 of 2 with myelomastocytic leukemia expressed PD-L1, with no expression found in 15 healthy/reactive marrows, 18 myelodysplastic syndromes (MDSs), 16 myeloproliferative neoplasms (MPNs), 5 MDS/MPNs, and 3 monoclonal MC activation syndromes. Variable PD-L1 expression was observed between and within samples, with PD-L1 staining of MCs ranging from 10% to 100% (mean, 50%). PD-1 dimly stained 4 of 27 CM cases (15%), with no expression in SM or other neoplasms tested; PD-1 staining of MCs ranged from 20% to 50% (mean, 27%). These results provide support for the expression of PD-L1 in SM and CM, and PD-1 expression in CM. These data support the exploration of agents with anti-PD-L1 activity in patients with advanced mastocytosis.