Abstract 4024: NAMPT inhibitor decreases NAMPT capture by an antibody directed against the 5-phosphoribosyl-1-pyrophosphate-binding loop: Rationale for an NAMPT occupancy assay

Nicotinamide phosphoribosyl transferase (NAMPT) catalyzes the rate-limiting step of nicotinamide adenine dinucleotide (NAD) biosynthesis. As NAMPT inhibitors (NAMPTi) have been shown to be substrates of NAMPT, binding of NAMPTi to NAMPT results in the NAMPTi-phosphoribose adduct (RP) that binds tightly and strongly inhibits the NAMPT enzyme. Structural analyses performed in this study unveiled the proximity of the NAMPTi-RP complex to the phosphoribosyl diphosphate (PRPP)-binding loop within the NAMPT catalytic site. The PRPP-binding loop of NAMPT is subject to conformational flexibility. The PRPP-binding loop domain is oriented to the outer side of the NAMPT dimer and can potentially serve as an antigen-binding site for antibodies. Interestingly, we show that the NAMPTi-RP adduct bound to NAMPT decreases NAMPT capture by an antibody that is directed against the c-terminal 5-phosphoribosyl-1-pyrophosphate-binding loop in NAMPT. This finding was then used to explore cellular NAMPT occupancy. The NAMPTi-RP complex displays a sustained, cellular NAMPT occupancy that correlates with the inhibition of NAMPT activity. Moreover, a good correlation between NAMPT occupancy, NAD decrease, and NAMPTi efficacy was observed in-vivo in a NCI-H82 small cell lung cancer (SCLC) xenograft model. NAMPT-occupancy assay can be used in clinical settings to better define the optimal dose levels and dose regimen for effective NAMPT inhibition.

Citation Format: Maysoun Shomali, Sandrine Hilairet, Marianne Duhamel, Frederico Nardi, Thomas Bertrand, Geraldine Penarier, Laurent Debussche, Monsif Bouaboula. NAMPT inhibitor decreases NAMPT capture by an antibody directed against the 5-phosphoribosyl-1-pyrophosphate-binding loop: Rationale for an NAMPT occupancy assay [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4024.

Silica-Coated Nanoparticles with a Core of Zinc, l-Arginine, and a Peptide Designed for Oral Delivery

Nanoparticle constructs for oral peptide delivery at a minimum must protect and present the peptide at the small intestinal epithelium in order to achieve oral bioavailability. In a reproducible, scalable, surfactant-free process, a core was formed with insulin in ratios with two established excipients and stabilizers, zinc chloride and l-arginine. Cross-linking was achieved with silica, which formed an outer shell. The process was reproducible across several batches, and physicochemical characterization of a single batch was confirmed in two independent laboratories. The silica-coated nanoparticles (SiNPs) entrapped insulin with high entrapment efficiency, preserved its structure, and released it at a pH value present in the small intestine. The SiNP delivered insulin to the circulation and reduced plasma glucose in a rat jejunal instillation model. The delivery mechanism required residual l-arginine in the particle to act as a permeation enhancer for SiNP-released insulin in the jejunum. The synthetic process was varied in terms of ratios of zinc chloride and l-arginine in the core to entrap the glucagon-like peptide 1 analogue, exenatide, and bovine serum albumin. SiNP-delivered exenatide was also bioactive in mice to some extent following oral gavage. The process is the basis for a platform for oral peptide and protein delivery.

Utility of a Mouse Model of Osteoarthritis to Demonstrate Cartilage Protection by IFNγ-Primed Equine Mesenchymal Stem Cells

Objective

Mesenchymal stem cells isolated from adipose tissue (ASC) have been shown to influence the course of osteoarthritis (OA) in different animal models and are promising in veterinary medicine for horses involved in competitive sport. The aim of this study was to characterize equine ASCs (eASCs) and investigate the role of interferon-gamma (IFNγ)-priming on their therapeutic effect in a murine model of OA, which could be relevant to equine OA.

Methods

ASC were isolated from subcutaneous fat. Expression of specific markers was tested by cytometry and RT-qPCR. Differentiation potential was evaluated by histology and RT-qPCR. For functional assays, naïve or IFNγ-primed eASCs were cocultured with peripheral blood mononuclear cells or articular cartilage explants. Finally, the therapeutic effect of eASCs was tested in the model of collagenase-induced OA (CIOA) in mice.

Results

The immunosuppressive function of eASCs on equine T cell proliferation and their chondroprotective effect on equine cartilage explants were demonstrated in vitro. Both cartilage degradation and T cell activation were reduced by naïve and IFNγ-primed eASCs, but IFNγ-priming enhanced these functions. In CIOA, intra-articular injection of eASCs prevented articular cartilage from degradation and IFNγ-primed eASCs were more potent than naïve cells. This effect was related to the modulation of eASC secretome by IFNγ-priming.

Conclusion

IFNγ-priming of eASCs potentiated their antiproliferative and chondroprotective functions. We demonstrated that the immunocompetent mouse model of CIOA was relevant to test the therapeutic efficacy of xenogeneic eASCs for OA and confirmed that IFNγ-primed eASCs may have a therapeutic value for musculoskeletal diseases in veterinary medicine.

Development of an equine groove model to induce metacarpophalangeal osteoarthritis: a pilot study on 6 horses

The aim of this work was to develop an equine metacarpophalangeal joint model that induces osteoarthritis that is not primarily mediated by instability or inflammation. The study involved six Standardbred horses. Standardized cartilage surface damage or “grooves” were created arthroscopically on the distal dorsal aspect of the lateral and medial metacarpal condyles of a randomly chosen limb. The contralateral limb was sham operated. After 2 weeks of stall rest, horses were trotted 30 minutes every other day for 8 weeks, then evaluated for lameness and radiographed. Synovial fluid was analyzed for cytology and biomarkers. At 10 weeks post-surgery, horses were euthanized for macroscopic and histologic joint evaluation. Arthroscopic grooving allowed precise and identical damage to the cartilage of all animals. Under the controlled exercise regime, this osteoarthritis groove model displayed significant radiographic, macroscopic, and microscopic degenerative and reactive changes. Histology demonstrated consistent surgically induced grooves limited to non-calcified cartilage and accompanied by secondary adjacent cartilage lesions, chondrocyte necrosis, chondrocyte clusters, cartilage matrix softening, fissuring, mild subchondral bone inflammation, edema, and osteoblastic margination. Synovial fluid biochemistry and cytology demonstrated significantly elevated total protein without an increase in prostaglandin E2, neutrophils, or chondrocytes. This equine metacarpophalangeal groove model demonstrated that standardized non-calcified cartilage damage accompanied by exercise triggered altered osteochondral morphology and cartilage degeneration with minimal or inefficient repair and little inflammatory response. This model, if validated, would allow for assessment of disease processes and the effects of therapy.

Morphological behaviour and metabolic capacity of cryopreserved human primary hepatocytes cultivated in a perfused multiwell device

1. The quantitative prediction of the pharmacokinetic parameters of a drug from data obtained using human in vitro systems remains a significant challenge i.e. prediction of metabolic clearance in humans and estimation of the relative contribution of enzymes involved in the clearance. This has become particularly problematic for low turnover compounds. 2. Having human hepatocytes with stable cellular function over several days that adequately mimic the complexity of the physiological environment would be a major advance. Thus, we evaluated human hepatocytes, maintained in culture during 7 days in the microfluidic LiverChip™ system, in terms of morphological appearance, relative mRNA expression of phase I and II enzymes and transporters as a function of time, and metabolic capacity using probe substrates. 3. The results showed that mRNA levels of the major genes for enzymes involved in drug metabolism were well-maintained over a 7-day period of culture. Furthermore, after 4 days of culture, in the Liverchip™ device, human hepatocytes exhibited higher or similar CYPs activities compared to 1 day of culture in 2D-static conditions. 4. The functional data were supported by light/electron microscopies and immunohistochemistry showing viable tissue structure and well-differentiated human hepatocytes: presence of cell junctions, glycogen storage, and bile canaliculi.

The expression of peripheral benzodiazepine receptors in human skin: the relationship with epidermal cell differentiation

The peripheral benzodiazepine receptor (PBR) is a protein of mitochondrial outer membranes utilizing porphyrins as endogenous ligands. PBR is part of a heteromeric receptor complex involved in the formation of mitochondrial permeability transition pores and in the early events of apoptosis. PBR may function as an oxygen-dependent signal generator; recent data indicate that these receptors may preserve the mitochondria of haematopoietic cell lines from damage caused by oxygen radicals. To identify PBRs in human skin, we used a specific monoclonal antibody directed against the C-terminus fragment of the human receptor. PBR immunoreactivity was found in keratinocytes, Langerhans cells, hair follicles and dermal vascular endothelial cells. Interestingly, confocal microscopic examination of skin sections revealed that PBR expression was strongly upregulated in the superficial differentiated layers of the epidermis. Ultrastructurally, PBRs were distributed throughout the cytoplasm but were selectively expressed on the mitochondrial membranes of epidermal cells. The elevated level of PBRs in the spinous layer was not associated with an increased number of mitochondria nor with an increased amount of mRNA as assessed by in situ hybridization on microautoradiographed skin sections. The present work provides, for the first time, evidence of PBR immunoreactivity in human skin. This mitochondrial receptor may modulate apoptosis in the epidermis; its increased expression in differentiated epidermal layers may represent a novel mechanism of natural skin protection against free radical damage generated by ultraviolet exposure.