Inhibition of Basal and Stimulated Release of Endothelin-1 from Guinea Pig Tracheal Epithelial Cells in Culture by Beta 2-adrenoceptor Agonists and Cyclic AMP Enhancers

The effects of cyclic AMP-related compounds and beta adrenoceptor agonists on the basal and lipopolysaccharide (LPS)-stimulated release of endothelin-1 (ET-1) from guinea-pig tracheal epithelial cells (GPTEpCs) in culture were studied. Forskolin (a potent activator of adenylyl cyclase), 8-bromo-cyclic AMP (a cyclic AMP analogue), salbutamol and salmeterol (two beta 2-adrenoceptor agonists), were used to increase cyclic AMP levels. Cultured GPTEpCs released ET-1 continuously over a 24 h incubation period. The values reached 1,938 ± 122 pg/mg of total cell proteins after 24 h. LPS (10 μg/ml) significantly stimulated the release of ET-1 by 1.6- to 1.8-fold, up to 1,262 ± 56 pg/mg total cell proteins after an 8 h incubation period. Compound 8-bromo-cyclic AMP (10⁻⁵, 10⁻⁴ and 10⁻³ M) reduced the basal release of ET-1 from GPTEpCs by up to 31% (P < 0.01) and the LPS stimulated release by up to 42% (P < 0.05), after an 8 h incubation period. Forskolin (10⁻⁶, 10⁻⁵ and 10⁻⁴ M) also inhibited the basal release of ET-1 by up to 28% (P < 0.05) and LPS-stimulated release of ET-1 by up to 50% (P < 0.05), after an 8 h incubation period. At the concentration of 10⁻⁵ M, forskolin increased cyclic AMP levels in GPTEpCs by 17-fold (P < 0.001) in the medium, 15 min after the beginning of the incubation. Salbutamol (10⁻⁸ to 10⁻⁶ M) had no effect on the basal production and release of ET-1 after 8 h. Conversely, this short acting beta 2-adrenoceptor agonist significantly reduced LPS-mediated increase of ET-1 production by up to 55% (P < 0.05) after an 8 h incubation period. Salmeterol (10⁻⁹ M to 10⁻⁵ M) inhibited basal and LPS-stimulated production and release of ET-1 after an 8 h incubation period (between 44 and 51%, P < 0.01). Both salbutamol and salmeterol (10⁻⁶ M) increase cyclic AMP levels by five- and twofold, respectively (P < 0.05). In summary, these observations indicate that beta 2-adrenoceptor agonists or cyclic AMP enhancers can modulate both basal and more markedly, the enhanced production of ET-1 from LPS-activated guinea pig airway EpCs. In addition, these compounds increase cyclic AMP levels in the cells. It is suggested that there is a correlation between cyclic AMP increase and inhibition of ET-1 release by guinea pig airway EpCs. Since ET-1 production was shown to be elevated in asthmatic subjects and in patients suffering from other inflammatory lung disorders, the inhibition of its production by beta adrenoceptor agonists, such as salbutamol and salmeterol, could be added to their therapeutical benefits.     

脑震荡大鼠海马CA1区P-CREB的表达

目的观察磷酸化CREB（p-CREB）在脑震荡大鼠海马区的表达。方法在多聚甲醛固定的海马脑薄片上，用免疫组化法观察p-CREB在海马CA1区的表达。结果p-CREB在脑震荡大鼠海马结构CA1区的表达，1～72h增多（P〈0．05），7d后降至正常。结论p-CREB在脑震荡大鼠海马内伤后早期表达增多，P-CREB可能具有神经保护因子的作用。     

The genome of Bacillus coahuilensis reveals adaptations essential for survival in the relic of an ancient marine environment

The Cuatro Ciénegas Basin (CCB) in the central part of the Chihuahan desert (Coahuila, Mexico) hosts a wide diversity of microorganisms contained within springs thought to be geomorphological relics of an ancient sea. A major question remaining to be answered is whether bacteria from CCB are ancient marine bacteria that adapted to an oligotrophic system poor in NaCl, rich in sulfates, and with extremely low phosphorus levels (<0.3 μM). Here, we report the complete genome sequence of Bacillus coahuilensis, a sporulating bacterium isolated from the water column of a desiccation lagoon in CCB. At 3.35 Megabases this is the smallest genome sequenced to date of a Bacillus species and provides insights into the origin, evolution, and adaptation of B. coahuilensis to the CCB environment. We propose that the size and complexity of the B. coahuilensis genome reflects the adaptation of an ancient marine bacterium to a novel environment, providing support to a “marine isolation origin hypothesis” that is consistent with the geology of CCB. This genomic adaptation includes the acquisition through horizontal gene transfer of genes involved in phosphorous utilization efficiency and adaptation to high-light environments. The B. coahuilensis genome sequence also revealed important ecological features of the bacterial community in CCB and offers opportunities for a unique glimpse of a microbe-dominated world last seen in the Precambrian.     

Development of cyclic peptides with potent in vivo osteogenic activity through RaPID-based affinity maturation

Osteoporosis is caused by a disequilibrium between bone resorption and bone formation. Therapeutics for osteoporosis can be divided into antiresorptives that suppress bone resorption and anabolics which increase bone formation. Currently, the only anabolic treatment options are parathyroid hormone mimetics or an anti-sclerostin monoclonal antibody. With the current global increases in demographics at risk for osteoporosis, development of therapeutics that elicit anabolic activity through alternative mechanisms is imperative. Blockade of the PlexinB1 and Semaphorin4D interaction on osteoblasts has been shown to be a promising mechanism to increase bone formation. Here we report the discovery of cyclic peptides by a novel RaPID (Random nonstandard Peptides Integrated Discovery) system-based affinity maturation methodology that generated the peptide PB1m6A9 which binds with high affinity to both human and mouse PlexinB1. The chemically dimerized peptide, PB1d6A9, showed potent inhibition of PlexinB1 signaling in mouse primary osteoblast cultures, resulting in significant enhancement of bone formation even compared to non-Semaphorin4D–treated controls. This high anabolic activity was also observed in vivo when the lipidated PB1d6A9 (PB1d6A9-Pal) was intravenously administered once weekly to ovariectomized mice, leading to complete rescue of bone loss. The potent osteogenic properties of this peptide shows great promise as an addition to the current anabolic treatment options for bone diseases such as osteoporosis.

Osteoporosis is a common cause of bone fracture in the elderly, costing billions globally due to fractures leading to long-term disability and subsequent exit from the working population (1, 2). Several treatment options are available for osteoporosis which can be divided into antiresorptives and anabolics ranging from orally dosed small molecules to injectable peptides and biologics (2, 3). Antiresorptive and anabolic agents differ in that antiresorptives inhibit or reduce bone resorption, thereby suppressing bone remodeling, whereas anabolics enhance the rate of bone formation while allowing continued resorption and remodeling of bone tissue. Although both treatments result in increased bone mass, resorption and remodeling are key to the microstructural integrity of bone, and emerging evidence points toward anabolics being more effective in reducing fracture (4–6). Currently, the only anabolics in the clinic are the parathyroid hormone and parathyroid hormone-related peptide mimetics (teriparatide and abaloparatide, respectively) and the sclerostin inhibitor monoclonal antibody (romosozumab). Teriparatide and abaloparatide both cannot be administered over 24 mo in a patient’s lifetime due to the risk for developing osteosarcomas, and romosozumab treatment is recommended for 12 mo due to waning efficacy beyond this duration (7, 8). Therefore, with the ever increasing global median age and associated osteoporosis cases, the development of additional anabolic treatment options are of high importance.Bone resorption and bone formation are regulated through communications between osteoclasts and osteoblasts, respectively (9). Among the paracrine factors involved in this process, axon guidance molecules, such as Semaphorin4D (Sema4D) and Semaphorin3A, mediate the regulation of bone cell differentiation. Sema4D, which is expressed and secreted by mature osteoclasts, inhibits osteoblast differentiation through its receptor PlexinB1 (PlxnB1) expressed on osteoblast surfaces. Binding of Sema4D to PlxnB1 leads to the inhibition of the activation of insulin receptor substrate-1 which is downstream of insulin-like growth factor-1 signaling. In addition, Sema4D controls the spatial distribution of bone-forming osteoblasts through PlxnB1-RhoA signaling (10). Mice with genetic deletion of Sema4D or PlxnB1 as well as mice expressing a dominant-negative form of RhoA in osteoblasts exhibit a high bone mass phenotype due to increased bone formation (11). These findings suggest that inhibiting PlxnB1-Sema4D signaling would lead to a bone anabolic effect through enhancement of osteoblastic differentiation while keeping osteoblasts away from osteoclasts to enable efficient osteoclastic bone resorption.We have previously reported a macrocyclic peptide discovery campaign to identify binding sites on PlxnB1 that inhibit its interaction with Sema4D by means of messenger RNA (mRNA) display in combination with genetic code reprogramming, referred to as the RaPID (Random nonstandard Peptides Integrated Discovery) system (12). We successfully identified a 16-mer thioether-macrocyclic peptide, PB1m6, capable of binding human PlxnB1 (hPlxnB1) with single-digit nanomolar-binding affinity and inhibiting its interaction with Sema4D (13). X-ray structural analysis of cocrystals of PB1m6 and hPlxnB1 revealed that PB1m6 is a negative allosteric modulator of the hPlxnB1-Sema4D interaction by binding a cleft distal to the Sema4D-binding interface of hPlxnB1 while still able to inhibit the hPlxnB1-Sema4D interaction. However, PB1m6 was shown to be selective toward hPlxnB1 over mouse PlxnB1 (mPlxnB1) displaying no detectable affinity (dissociation constant (K_D) over 1 µM) regardless of having 88% sequence identity in the N-terminal sema domains of hPlxnB1 and mPlxnB1. Modeling efforts based on the three-dimensional (3D) structure to rationally increase the species cross-reactivity were unsuccessful in our hands. This high selectivity is often observed with RaPID-derived macrocyclic peptides and is generally considered beneficial (13–18). However, in this instance, the high selectivity of PB1m6 hinders its ability to validate the inhibitory mechanism in mouse models. In this study, we used a fragmented saturation mutagenesis approach to create an mRNA library of PB1m6 analogs to be utilized in a RaPID selection campaign against mouse PlxnB1. After five iterative rounds of selection, we discovered a PB1m6 analog, referred to as PB1m6A9, exhibiting enhanced cross-reactivity with 44 nM K_D against mouse PlxnB1 and which, remarkably, also showed 10-fold stronger binding affinity against human PlxnB1 (0.28 nM K_D). To further improve apparent affinity and inhibitory activity, a homodimer of PB1m6A9 was chemically synthesized (PB1d6A9), and it was shown to exhibit potent mPlxnB1-Sema4D inhibitory activity in mouse primary osteoblasts as well as enhanced osteogenesis even when compared to cells not treated with Sema4D. Moreover, once-weekly intravenous (i.v.) administration of palmitoylated PB1d6A9 (PB1d6A9-Pal) in a mouse model of postmenopausal osteoporosis showed significant enhancement of bone formation compared to both vehicle and sham-operated (Sham) control mice. This work presents the facile development of a novel bone anabolic modality which shows promise as an addition to the current repertoire of anabolic agents used to address osteoporosis.     

Nitroglycerin rebound associated with vascular, rather than platelet, hypersensitivity

OBJECTIVES

The purpose of this study was to determine whether acute withdrawal of nitroglycerin (NTG) during hemodynamic tolerance is associated with platelet hypersensitivity.

BACKGROUND

Nitroglycerin is an effective antianginal medication but its use is limited by the development of tolerance and rebound. We have previously demonstrated a sustained inhibition of platelet function during continued use of NTG, but whether cessation of NTG is associated with an increase in platelet function that may contribute to rebound is unknown.

METHODS

Normal porcine aortic media were exposed to flowing arterial blood from pigs (n = 8) treated continuously with NTG patches (Nitrodur 0.8 mg/h) for 48 h. Platelet function, blood pressure and the responses to angiotensin II infusion were evaluated before, during and after NTG treatment.

RESULTS

Mean arterial pressure fell by 15% after 3 h of treatment compared with control, returned to baseline by 48 h and increased significantly 2 h after drug removal. Autologous ⁵¹Cr-labelled platelet deposition on the aortic media was reduced by 30% after 48 h of continuous NTG administration compared with baseline (p = 0.02) and remained decreased 2 h after cessation of NTG therapy. Platelet aggregation to thrombin decreased in parallel to the decrease in platelet deposition. Blood pressure increase after intravenous injection of 10 μg of angiotensin II was blunted during treatment with NTG but increased significantly 2 h after cessation of nitrate therapy when compared with baseline.

CONCLUSIONS

Supersensitivity of the vessel wall to vasoconstrictors such as angiotensin 11, but not platelet hyperactivity, may contribute to the rebound phenomenon after acute nitrate withdrawal.     

A critical appraisal of studies on cyclic fatigue resistance of engine‐driven endodontic instruments

The endodontic literature contains a plethora of studies on static and dynamic cyclic fatigue resistance tests performed on a large array of rotary or reciprocating nickel–titanium endodontic instruments. It was the aim of this review to summarize the currently available evidence to point out the different outcomes from static versus dynamic tests and to assess whether cyclic fatigue tests provide useful data and information for clinical practice. An electronic literature research in the database PubMed was performed using appropriate search terms, and the titles and abstract were screened for relevance. Language was restricted to English. The review reveals marked differences between the results obtained in static and dynamic tests, and also, the results for the same instruments assessed either under static or dynamic experimental conditions are widely inconsistent. Between the lowest and the highest value for one and the same pathfinding instrument was a factor of about 123 when cyclic fatigue was assessed either under static or dynamic experimental conditions. Moreover, standard deviations of up to 30% have been reported. Environmental temperature has a 500% impact on the lifetime of instruments. In conclusion, fatigue resistance tests conducted under room temperature should be regarded as having little meaning and the scientific and clinical benefits of fatigue resistance tests are very limited. These data should be provided by the manufacturer of the instruments.