Prostaglandin E2 receptor type 2-selective agonist prevents the degeneration of articular cartilage in rabbit knees with traumatic instability

Introduction

Osteoarthritis (OA) is a common cause of disability in older adults. We have previously reported that an agonist for subtypes EP2 of the prostaglandin E2 receptor (an EP2 agonist) promotes the regeneration of chondral and osteochondral defects. The purpose of the current study is to analyze the effect of this agonist on articular cartilage in a model of traumatic degeneration.

Methods

The model of traumatic degeneration was established through transection of the anterior cruciate ligament and partial resection of the medial meniscus of the rabbits. Rabbits were divided into 5 groups; G-S (sham operation), G-C (no further treatment), G-0, G-80, and G-400 (single intra-articular administration of gelatin hydrogel containing 0, 80, and 400 μg of the specific EP2 agonist, ONO-8815Ly, respectively). Degeneration of the articular cartilage was evaluated at 2 or 12 weeks after the operation.

Results

ONO-8815Ly prevented cartilage degeneration at 2 weeks, which was associated with the inhibition of matrix metalloproteinase-13 (MMP-13) expression. The effect of ONO-8815Ly failed to last, and no effects were observed at 12 weeks after the operation.

Conclusions

Stimulation of prostaglandin E2 (PGE2) via EP2 prevents degeneration of the articular cartilage during the early stages. With a system to deliver it long term, the EP2 agonist could be a new therapeutic tool for OA.     

Localized cysteine sulfenic acid formation by vascular endothelial growth factor: role in endothelial cell migration and angiogenesis

Reactive oxygen species (ROS) are important mediators for VEGF receptor 2 (VEGFR2) signalling involved in angiogenesis. The initial product of Cys oxidation, cysteine sulfenic acid (Cys-OH), is a key intermediate in redox signal transduction; however, its role in VEGF signalling is unknown. We have previously demonstrated IQGAP1 as a VEGFR2 binding scaffold protein involved in ROS-dependent EC migration and post-ischemic angiogenesis. Using a biotin-labelled Cys-OH trapping reagent, we show that VEGF increases protein-Cys-OH formation at the lamellipodial leading edge where it co-localizes with NADPH oxidase and IQGAP1 in migrating ECs, which is prevented by IQGAP1 siRNA or trapping of Cys-OH with dimedone. VEGF increases IQGAP1-Cys-OH formation, which is prevented by N-acetyl cysteine or dimedone, which inhibits VEGF-induced EC migration and capillary network formation. In vivo, hindlimb ischemia in mice increases Cys-OH formation in small vessels and IQGAP1 in ischemic tissues. In summary, VEGF stimulates localized formation of Cys-OH-IQGAP1 at the leading edge, thereby promoting directional EC migration, which may contribute to post-natal angiogenesis in vivo. Thus, targeting Cys-oxidized proteins at specific compartments may be the potential therapeutic strategy for various angiogenesis-dependent diseases.     

Learning shapes spontaneous activity itinerating over memorized states

Learning is a process that helps create neural dynamical systems so that an appropriate output pattern is generated for a given input. Often, such a memory is considered to be included in one of the attractors in neural dynamical systems, depending on the initial neural state specified by an input. Neither neural activities observed in the absence of inputs nor changes caused in the neural activity when an input is provided were studied extensively in the past. However, recent experimental studies have reported existence of structured spontaneous neural activity and its changes when an input is provided. With this background, we propose that memory recall occurs when the spontaneous neural activity changes to an appropriate output activity upon the application of an input, and this phenomenon is known as bifurcation in the dynamical systems theory. We introduce a reinforcement-learning-based layered neural network model with two synaptic time scales; in this network, I/O relations are successively memorized when the difference between the time scales is appropriate. After the learning process is complete, the neural dynamics are shaped so that it changes appropriately with each input. As the number of memorized patterns is increased, the generated spontaneous neural activity after learning shows itineration over the previously learned output patterns. This theoretical finding also shows remarkable agreement with recent experimental reports, where spontaneous neural activity in the visual cortex without stimuli itinerate over evoked patterns by previously applied signals. Our results suggest that itinerant spontaneous activity can be a natural outcome of successive learning of several patterns, and it facilitates bifurcation of the network when an input is provided.     

18F-labeled flavones for in vivo imaging of β-amyloid plaques in Alzheimer’s brains

In vivo imaging of β-amyloid (Aβ) aggregates in the brain may lead to early detection of Alzheimer’s disease (AD) and monitoring of the progression and effectiveness of treatment. The purpose of this study was to develop novel ¹⁸F-labeled amyloid-imaging probes based on flavones as a core structure. Fluoropegylated (FPEG) flavone derivatives were designed and synthesized. The affinity of the derivatives for Aβ aggregates varied from 5 to 321 nM. In brain sections of AD model mice, FPEG flavones with the dimethylamino group intensely stained β-amyloid plaques. In biodistrubution experiments using normal mice, they displayed high uptake in the brain ranging from 2.9 to 4.2%ID/g at 2 min postinjection. The radioactivity washed out from the brain rapidly (1.3–2.0%ID/g at 30 min), which is highly desirable for β-amyloid imaging agents. FPEG flavones may be potential PET imaging agents for β-amyloid plaques in Alzheimer’s brains.     

Distribution of a novel protein AgK114 expression in the normal tissues of adult mice: dual expression of AgK114 and growth hormone in anterior pituitary cells

The novel antigen K114 (AgK114) has been previously identified in normal hamster skin, and its expression has been up-regulated accompanying tissue damages of the skin, although there is no information on its biological functions. To determine the physiological role of AgK114, we prepared anti-mouse AgK114 monoclonal antibody and studied its tissue distribution in healthy adult mice by immunocytochemistry. A widespread and unique expression of AgK114 peptide was found in the selected organs of various systems (hair follicle cells and sebaceous gland of skin, ciliated epithelial cells of trachea and bronchial tube, striated portion of submandibular gland, distal convoluted tubule cells of kidney, ciliated epithelial cells of oviduct, medulla of adrenal gland and anterior lobe of pituitary gland). Interestingly, dual expression of AgK114 peptide and growth hormone in somatotrophs was found in anterior lobe of pituitary gland by double immunocytochemistry. AgK114 peptide was expressed widely in many regionally well-defined cellular systems in various peripheral tissues, suggesting that AgK114 peptide may have some roles of physiological functions in these organs. The data from our current study have provided a rationale for further studies of functional roles of AgK114 peptide in a variety of organs or tissues under physiological conditions.     

The molecular scaffold Gab2 is a crucial component of RANK signaling and osteoclastogenesis

Morphogenesis and remodeling of bone involve synthesis of bone matrix by osteoblasts and coordinate resorption of bone by osteoclasts. Defective bone remodeling caused by altered osteoclast activity underlies a multitude of osteopenic disorders. Receptor activator of NF-kappaB (RANK) and its ligand RANKL have been identified as essential factors involved in osteoclast development and bone remodeling, but their mechanism and interacting factors have not been fully characterized. Here we report that the molecular adapter Grb-2-associated binder-2 (Gab2) associates with RANK and mediates RANK-induced activation of NF-kappaB, Akt and Jnk. Inactivation of the gene encoding Gab2 in mice results in osteopetrosis and decreased bone resorption as a result of defective osteoclast differentiation. We also show that Gab2 has a crucial role in the differentiation of human progenitor cells into osteoclasts. We have thus identified a new, key regulatory scaffold molecule, Gab2, that controls select RANK signaling pathways and is essential for osteoclastogenesis and bone homeostasis.     

OCA4: evidence for a founder effect for the p.D157N mutation of the MATP gene in Japanese and Korean

Oculocutaneous albinism type 4 (OCA4) was identified as a rare form of human OCA among a group of autosomal recessive hypopigmentary disorders. Little is known about the prevailing distribution of patients of OCA4 with mutations of the MATP gene, although one Turkish, five German, one Korean, and 18 Japanese patients have been reported so far. The p.D157N mutation was previously reported to be the most frequent (0.389; 14/36) in Japanese patients and was also found in a Korean patient. On the other hand, this mutation has not been found in Turkish and German patients. We therefore investigated haplotypes of the patients who have the p.D157N mutation. The results showed that OCA4 is prevalent in East Asia including Japan and Korea likely as a result of a founder effect for the p.D157N mutation. Furthermore, it is suspected that the p.D157N mutation might have occurred on an ancestral chromosome after the divergence of Orientals and Caucasians.