Metabolic activation stimulates acid secretion and expression of matrix degrading proteases in human osteoblasts

Quantum Dot/TiO2 Nanocomposite-Based Photoelectrochemical Sensor for Enhanced H2O2 Detection Applied for Cell Monitoring and Visualization

This work exploits the possibility of using CdSe/ZnS quantum dot (QD)-electrodes to monitor the metabolism of living cells based on photoelectrochemical (PEC) measurements. To realize that, the PEC setup is improved with respect to an enhanced photocurrent signal, better stability, and an increased signal-to-noise ratio, but also for a better biocompatibility of the sensor surface on which cells have been grown. To achieve this, a QD-TiO2 heterojunction is introduced with the help of atomic layer deposition (ALD). The heterojunction reduces the charge carrier recombination inside the semiconductor nanoparticles and improves the drift behavior. The PEC performance is carefully analyzed by adjusting the TiO2 thickness and combining this strategy with multilayer immobilizations of QDs. The optimal thickness of this coating is ≈5 nm; here, photocurrent generation can be enhanced significantly (e.g., for a single QD layer electrode by more than one order of magnitude at 0 V vs Ag/AgCl). The resulting optimized electrode is used for hydrogen peroxide (H2O2) sensing with a good sensitivity down to µmolar concentrations, reusability, stability, response rate, and repeatability. Finally, the sensing system is applied to monitor the activity of cells directly grown on top of the electrode surface.

Therapeutic applications of mesenchymal/medicinal stem/signaling cells preconditioned with external factors: Are there more efficient approaches to utilize their regenerative potential?

Mesenchymal/medicinal stem/signaling cells (MSCs) have emerged as a promising treatment option for various disorders. However, the donor's age, advanced stage of disease, and prolonged in vitro expansion often diminish the innate regenerative potential of MSCs. Besides that, the absence of MSCs' comprehensive "pre-admission testing" can result in the injection of cells with reduced viability and function, which may negatively affect the overall outcome of MSC-based therapies. It is, therefore, essential to develop effective strategies to improve the impaired biological performance of MSCs. This review focuses on the comprehensive characterization of various methods of external MSCs stimulation (hypoxia, heat shock, caloric restriction, acidosis, 3D culture, and application of extracellular matrix) that augment their medicinal potential. To emphasize the significance of MSCs priming, we summarize the effects of individual and combined preconditioning approaches, highlighting their impact on MSCs' response to either physiological or pathological conditions. We further investigate the synergic action of exogenous factors to maximize MSCs' therapeutic potential. Not to omit the field of tissue engineering, the application of pretreated MSCs seeded on scaffolds is discussed as well.

Efficacy and safety of JAK inhibitors in rheumatoid arthritis: update for the practising clinician

Janus kinase (JAK) inhibitors, including tofacitinib, baricitinib, upadacitinib and filgotinib, are increasingly used in the treatment of rheumatoid arthritis (RA). There has been debate about their safety, particularly following the issuance of guidance by regulatory agencies advising caution in their use in certain patients. The registrational clinical trials and registry data of JAK inhibitors did not identify a difference in the risk of major adverse cardiovascular events (MACEs), venous thromboembolism, malignancies or infections (other than herpes zoster) with a JAK inhibitor versus a biologic DMARD. In the ORAL Surveillance trial, which enrolled patients >50 years of age with ≥1 cardiovascular risk factor, tofacitinib was statistically inferior to TNF inhibitors for the occurrence of MACEs and malignancy. Further post hoc analysis of the data revealed that an age of ≥65 years, a high baseline cardiovascular risk, a history of smoking, sustained inflammation, disease activity and suboptimal treatment of cardiovascular comorbidities all increase the risk of these outcomes. The guidance issued by regulatory agencies should be carefully considered to ensure appropriate and safe treatment of patients with RA without undertreatment of patients who might benefit from JAK inhibitor, as well as biologic, treatment. As always, the risks associated with the use of these agents, treatment goals, costs and patient preferences should be discussed with the patient.

Tofacitinib for the treatment of psoriasis

INTRODUCTION

The identification of a number of psoriasis-susceptibility genes and a better understanding of the pathogenesis of the intracellular metabolic pathways, have generated new perspectives on psoriasis treatment, in particular new compounds that inhibit certain intracellular proteins involved in the immune response. In contrast to biologic agents, these compounds block intracellular targets such as transcriptional factors or enzymes.

AREAS COVERED

Tofacitinib is a small molecule that acts as a reversible, competitive inhibitor of ATP in the ATP binding site of JAK proteins, determining their inactivation, thus prevents the downstream activation of the STAT proteins, which are then unable to up-regulate the pro-inflammatory genes implicated in psoriasis. The authors present an overview of Phases I - III clinical trials of tofacitinib for psoriasis based on peer-reviewed literature.

EXPERT OPINION

In clinical practice, it is important to assess the response of psoriasis to tofacitinib and identify possible clinical, genetic, and immune biomarkers to predict the response. Comorbidities associated with psoriasis, in particular metabolic syndrome and obesity, are also an important aspect of using tofacitinib in clinical practice. There are some evidences that a drug such as tofacitinib could be used to improve not only psoriasis, but also some of its important comorbidities.

The Role of Biological and Small Molecule Therapy in the Management of Psoriatic Arthritis

The therapy of psoriatic arthritis (PsA) has blossomed in the past decade. Inhibition of tumor necrosis factor (TNF) has been at the fore of this approach and has paved the way for the investigation of many other potential pro-inflammatory and signaling pathways. Most of the initial studies of TNF inhibitors in PsA have been conducted in specific populations, largely focusing on those with established, peripheral joint disease. That said, in excess of 10 years’ worth of real world clinical experience has led to increased confidence in the wider use of these agents. We are now faced with an exciting time of discovery of many new molecules; these not only include new, large protein biological agents, but also smaller synthetic chemical molecules, many of which can be administered orally. Those currently under development are discussed within this article. Whilst there is scarce data about their real world efficacy and safety profile, it is evident that the therapeutic armamentarium for treating PsA will greatly increase in the foreseeable future and this is anticipated to improve patient outcomes.

Aminopeptidase activity profile in cultured human osteoblasts

Aminopeptidases (APs) are enzymes involved in a wide variety of biological processes and present in a variety of different cell populations. The authors studied these enzymes in primary cultured human osteoblasts in order to establish an activity profile and thereby contribute to knowledge of bone tissue. The authors used 13 different substrates (N-terminal amino acids) and a fluorimetric assay to examine AP activity associated with the membranes of cultured osteoblasts. The authors demonstrated activity > 10 pmol/min/10(4) cells when glycine, alanine, leucine, arginine, phenylalanine, methionine, and lysine were used as substrates. The activity was markedly lower (<1.6 pmol/min/10(4) cells) when the other N-terminal amino acids were used. Puromycin and bestatin inhibited AP activity, though not completely, when we used AlaNA or LeuNA as substrates. Further studies are warranted to determine the role of these enzymes in bone tissue physiology.

Transcriptome and proteome analysis of osteocytes treated with nitrogen-containing bisphosphonates

We combined high-throughput screening of differential mRNAs with mass spectrometric characterization of proteins obtained from osteocytes untreated and treated with Risedronate. Microarray analysis revealed, upon treatment, a marked upregulation of messengers encoding zinc-proteins. MS analysis identified 84 proteins in the osteocytes proteome map. Risedronate affected the expression of 10 proteins, associated with cytoskeleton, stress-response and metabolism. Data validated using gel imaging in combination with the GLaD post digestion isotopic labeling method provide the molecular basis for understanding the role of bisphosphonates as antiapoptotic drugs for osteocytes.

Human osteoblasts produce cathepsin K

Healthy bone is a rigid yet living tissue that undergoes continuous remodeling. Osteoclasts resorb bone in the remodeling cycle. They secrete H(+)-ions and proteinases to dissolve bone mineral and degrade organic bone matrix, respectively. One of the main collagenolytic proteinase in osteoclasts is cathepsin K, a member of papain family cysteine proteinases. Recently, it has been shown that osteoblasts may contribute to organic matrix remodeling. We therefore investigated their ability to produce cathepsin K for this action. Trabecular bone samples were collected from patients operated due to a fracture of the femoral neck. Part of the bone was decalcified and the rest was used for cell isolation. Sections from the decalcified bone were immunostained with antibodies against cathepsin K. Isolated cells were characterized for their ability to form mineralized matrix and subsequently analyzed for their cathepsin K production by Western blotting and quantitative RT-PCR. Osteoblasts, bone lining cells and some osteocytes in situ showed cathepsin K immunoreactivity and osteoblast-like cells in vitro produced cathepsin K mRNA and released both 42 kDa pro- and 27 kDa processed cathepsin K to culture media. Osteoblastic cathepsin K may thus contribute to collagenous matrix maintenance and recycling of improperly processed collagen I. Whether osteoblastic cathepsin K synthesis has consequences in diseases characterized by abnormal bone matrix turnover remains to be investigated.

Bone as an ion exchange organ: evidence for instantaneous cell-dependent calcium efflux from bone not due to resorption

The current study tests the hypothesis that basal level and minute-by-minute correction of plasma Ca2+ by outward and inward Ca2+ fluxes from and into an exchangeable ionic pool in bone is controlled by an active partition system without contributions from the bone remodeling system. Direct real-time measurements of Ca2+ fluxes were made using the scanning ion-selective electrode technique (SIET) on living bones maintained ex vivo in physiological conditions. SIET three-dimensional measurements of the local Ca2+ concentration gradient (10 microm spatial resolution) were performed on metatarsal bones of weanling mice after drilling a 100-mum hole through the cortex to expose the internal bone extracellular fluid (BECF) to the bathing solution, whose composition mimicked the extracellular fluid (ECF). Influxes of Ca2+ towards the center of the cortical hole (15.1+/-4.2 pmol cm-2 s-1) were found in the ECF and were reversed to effluxes (7.4+/-2.9 pmol cm-2 s-1) when calcium was depleted from the ECF, mimicking a plasma demand. The reversal from influx to efflux and vice versa was immediate and fluxes in both directions were steady throughout the experimental time (>or=2 h, n=14). Only the efflux was nullified within 10 min by the addition of 10 mM/L Na-Cyanide (n=7), demonstrating its cell dependence. The timeframes of the exchanges and the stability of the Ca2+ fluxes over time suggest the existence of an exchangeable calcium pool in bone. The calcium efflux dependency on viable cells suggests that an active partition system might play a central role in the short-term error correction of plasma calcium without the contribution of bone remodeling.