Extracellular superoxide dismutase is important for hippocampal neurogenesis and preservation of cognitive functions after irradiation

Cranial irradiation is widely used in cancer therapy, but it often causes cognitive defects in cancer survivors. Oxidative stress is considered a major cause of tissue injury from irradiation. However, in an earlier study mice deficient in the antioxidant enzyme extracellular superoxide dismutase (EC-SOD KO) showed reduced sensitivity to radiation-induced defects in hippocampal functions. To further dissect the role of EC-SOD in neurogenesis and in response to irradiation, we generated a bigenic EC-SOD mouse model (OE mice) that expressed high levels of EC-SOD in mature neurons in an otherwise EC-SOD–deficient environment. EC-SOD deficiency was associated with reduced progenitor cell proliferation in the subgranular zone of dentate gyrus in KO and OE mice. However, high levels of EC-SOD in the granule cell layer supported normal maturation of newborn neurons in OE mice. Following irradiation, wild-type mice showed reduced hippocampal neurogenesis, reduced dendritic spine densities, and defects in cognitive functions. OE and KO mice, on the other hand, were largely unaffected, and the mice performed normally in neurocognitive tests. Although the resulting hippocampal-related functions were similar in OE and KO mice following cranial irradiation, molecular analyses suggested that they may be governed by different mechanisms: whereas neurotrophic factors may influence radiation responses in OE mice, dendritic maintenance may be important in the KO environment. Taken together, our data suggest that EC-SOD plays an important role in all stages of hippocampal neurogenesis and its associated cognitive functions, and that high-level EC-SOD may provide protection against irradiation-related defects in hippocampal functions.Cranial irradiation is widely used as a treatment modality for patients with primary or metastatic brain tumors (1–3), and is also used as a prophylactic treatment to prevent metastases of high-risk tumors to the nervous system (4). Although effective, cranial irradiation is associated with various complications or side effects in cancer survivors (1–3). One of the severe complications is neurocognitive impairment, which can include defects in executive functions and learning and memory (3). Neurocognitive impairments occur in both adults and children and are generally associated with higher doses and younger age (3). The pathogenesis of radiation-induced neurocognitive impairment is not completely understood, but recent studies suggest that suppressed hippocampal neurogenesis (5, 6), increased hippocampal neuronal apoptosis (7, 8), and reduced growth hormone secretion (9, 10) may be involved.The production of reactive oxygen species (ROS) is considered a major cause of radiation-induced tissue damage (11). Ionizing irradiation not only results in the acute generation of short-lived ROS, it also results in a persistent state of oxidative stress that extends up to several months or even years after irradiation (12, 13). Accordingly, animal and cell models with altered antioxidant capacities have been used to investigate the biochemical pathways involved in radiation-induced tissue and cell injuries, and experimental antioxidant-based therapies have been designed to protect normal tissues during radiation treatments (14).Hippocampal neurogenesis is important for hippocampal-dependent functions of learning and memory and the process is exquisitely sensitive to suppression by various stressors, including radiation and oxidative stress (5, 6, 15). To determine if altered redox balance in the hippocampal microenvironment affects hippocampal neurogenesis and the associated functions of learning and memory, we used a knockout mouse model (KO) deficient in the extracellular antioxidant enzyme, EC-superoxide dismutase (EC-SOD), in an earlier study with cranial irradiation (13, 16). When examined at 3–4 mo of age, EC-SOD deficiency was associated with a significant suppression of baseline neurogenesis and impaired hippocampal-dependent cognitive functions (13, 16). Unexpectedly, EC-SOD deficiency also rendered the process less sensitive to radiation-induced changes. The underlining mechanism for this paradoxical finding was not clear, but preliminary studies ruled out up-regulation of major antioxidant enzymes (13). The results suggested that the interaction between redox balance and irradiation and their effects on hippocampal functions can be complex, and understanding how these elements work in concert may be a key to identifying strategies for radioprotection.To manipulate redox balance in the hippocampus, we generated a mouse model with inducible EC-SOD transgenes (17). In the current study, we combined the inducible transgenes with EC-SOD KO and generated a bigenic mouse model, designated as the overexpressor (OE), with high levels of EC-SOD expressed only in Ca/calmodulin-dependent protein kinase- (CaMKII) positive neurons in an otherwise EC-SOD–deficient environment (17). Hippocampal neurogenesis generates new granule cells that are functionally integrated into the hippocampal network (18). Because granule cells are CaMKII-positive neurons and are the principal excitatory neurons in the dentate gyrus, the manipulation leads to an estimated four- to fivefold increase in EC-SOD activity in the hippocampal formation in OE mice (17). The OE mice were used to investigate the effects of altered EC-SOD levels at different stages of hippocampal neurogenesis and the functional consequences of learning and memory. Comparison between WT, OE, and KO mice revealed the importance of EC-SOD in progenitor cell proliferation, dendritic development, and long-term survival of newborn neurons. The study results also suggested that maintenance of the dendritic system following cranial irradiation was important for preservation of neurocognitive functions.     

Increased treatment persistence and its determinants in women with osteoporosis with prior fracture compared to those without fracture

Summary

The purpose of this study is to analyze treatment persistence in patients with osteoporosis after fracture diagnosis in German primary care practices. We found that pain increased treatment persistence. One key next step is to demonstrate whether or not this pain is related to fracture.

Introduction

To analyze treatment persistence in patients with osteoporosis after fracture diagnosis in German primary care practices.

Methods

This study included postmenopausal women with osteoporosis aged between 40 and 90 years from 1188 general and 175 orthopedist practices in Germany. Treatment started between 2004 and 2013. The primary outcome measure was treatment persistence within 12 months after therapy initiation. Discontinuation of treatment was defined as a period of at least 90 days without therapy. Persistence analyses were carried out using Kaplan-Meier curves and log-rank tests, and the analyses of the impact of fracture on discontinuation risk were based on Cox regression models (with and without adjustment for pain medications).

Results

Thirteen thousand nine hundred seventy-five subjects (mean age?=?74.8 years) were included in the group with fracture before therapy initiation and 18,138 (mean age?=?72.7 years) in the group without fracture. Within 12 months after treatment initiation, therapy persistence increased with the delay between osteoporosis diagnosis and therapy initiation, rising from 40.7 % when the delay was lower than or equal to 12 months to 44.3 % when it exceeded 36 months (p value <0.0001). Fracture only decreased the risk of treatment discontinuation when the model was not adjusted for pain medications (HR?=?0.95, 95 % CI 0.93–0.98, p value <0.0001).

Conclusions

Pain increased treatment persistence in women with osteoporosis and fracture. Further studies are needed to better understand factors influencing persistence.

     

The effects of low-level laser irradiation on breast tumor in mice and the expression of Let-7a,miR-155, miR-21, miR125, and miR376b

Low-level laser therapy (LLLT) is a form of photon therapy which can be a non-invasive therapeutic procedure in cancer therapy using low-intensity light in the range of 450–800 nm. One of the main functional features of laser therapy is the photobiostimulation effects of low-level lasers on various biological systems including altering DNA synthesis and modifying gene expression, and stopping cellular proliferation. This study investigated the effects of LLLT on mice mammary tumor and the expression of Let-7a, miR155, miR21, miR125, and miR376b in the plasma and tumor samples. Sixteen mice were equally divided into four groups including control, and blue, green, and red lasers at wavelengths of 405, 532, and 632 nm, respectively. Weber Medical Applied Laser irradiation was carried out with a low power of 1–3 mW and a series of 10 treatments at three times a week after tumor establishment. Tumor volume was weekly measured by a digital vernier caliper, and qRT-PCR assays were performed to accomplish the study. Depending on the number of groups and the p value of the Kolmogorov-Smirnov test of normality, a t test, a one-way ANOVA, or a non-parametric test was used for data analyses, and p?<?0.05 was considered to be statistically significant. The average tumor volume was significantly less in the treated blue group than the control group on at days 21, 28, and 35 after cancerous cell injection. Our data also showed an increase of Let-7a and miR125a expression and a decrease of miR155, miR21, and miR376b expression after LLLT with the blue laser both the plasma and tumor samples compared to other groups. It seems that the non-invasive nature of laser bio-stimulation can make LLLT an attractive alternative therapeutic tool.     

Dielectric properties of porcine cerebrospinal tissues at microwave frequencies: in vivo, in vitro and systematic variation with age

The dielectric properties of pig cerebrospinal tissues were measured in vivo and in vitro, in the frequency range of 50 MHz-20 GHz. The total combined measurement uncertainty was calculated at each frequency point and is reported over representative frequency regions. Comparisons were made for each tissue between the two sets of data and with the literature of the past decade. The in vitro study was extended to include tissue from pigs weighing approximately 10, 50 and 250 kg to re-visit the question of the variation of dielectric properties with age. White matter and spinal chord showed significant variation as function of animal age, no age-related variations were recorded for grey matter.     

The application of tissue-engineered preputial matrix and fibrin sealant for urethral reconstruction in rabbit model

Background

To introduce the role of fibrin sealant and preputial acellular matrix (PAM) as a new source of inert collagen matrix for urethral reconstruction.

Methods

A ventral urethral segmental defect was created in 24 male rabbits divided into four groups. In group 1 (G1), urethrotomy was closed in layers. In group 2 (G2), closure was followed by applying fibrin sealant. In groups 3 (G3) and 4 (G4), urethroplasty was performed with a patch graft of PAM, and in G4, fibrin sealant was also applied. Serial urethrography was performed before and after the operation. Then, the animals were euthanized, and their urethra was excised 1, 3, and 9 months postoperatively for further electron microscopic examination, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) technique, and immunohistochemical (IHC) staining with CD34, CD31, desmin, SMA, and α-actin.

Results

In G1 and G2, the fistula repair failed in all the time points. In G3 and G4, serial urethrography confirmed the maintenance of a wide urethral caliber without signs of strictures or extravasations. Satisfactory vascularity was observed in G3 and G4 during the whole study, which was more significant in G4 after 9 months of follow-up. The presence of a complete transitional cell layer was confirmed over the graft in G3 and G4 in all time points. IHC staining confirmed the effectiveness of fistula repair in G3 and G4, 3 months postoperatively.

Conclusion

This rabbit model showed that PAM combined with fibrin sealant may herald a reliable option for repairing segmental urethral defects.     

Improved cardioprotection using a novel stepwise ischemic preconditioning protocol in rabbit heart

Background

The current commonly used cardiac ischemic preconditioning (IPC) protocol, involving three 5-min cycles of ischemia–reperfusion (I/R), may not be clinically beneficial because of its acutely deleterious effects on hemodynamics. This study attempted to assess the effects of a novel stepwise IPC scheme on cardiac function, infarct size, and arrhythmogenesis in a rabbit model of prolonged I/R.

Methods

Anesthetized open-chest rabbits were subjected to 60-min occlusion of a proximal branch of the left coronary artery followed by 180-min reperfusion. Animals were divided into five groups (n = 6 each): (1) control group (no IPC); (2) 2-min IPC group (three cycles of 2-min IPC); (3) 5-min IPC group (three cycles of 5-min IPC); (4) 10-min IPC group (three cycles of 10-min IPC); and (5) stepwise IPC group (2-, 5-, and 10-min I/R).

Results

Compared with control group, 2-, 5-, and 10-min IPC decreased arrhythmia score by 16%, 67%, and 33%, respectively. Remarkably, stepwise IPC resulted in a 78% reduction of arrhythmias. Stepwise IPC also produced the least ventricular infarct size when compared with 2-, 5-, and 10-min IPC groups (16.4% versus 39.3%, 28.1%, and 38.5%, P < 0.05).

Conclusions

These results suggest that stepwise IPC has better cardioprotective effects against prolonged I/R injury and may serve as an acceptable approach to clinical revascularization procedures on the heart, including catheter-based and surgical approaches.     

Effect of aromatase inhibition on serum levels of sclerostin and dickkopf-1, bone turnover markers and bone mineral density in women with breast cancer

Purpose

While their negative impact on bone health is well established, the effects of aromatase inhibition (AI) on Wnt inhibitors and osteoprotegerin (OPG) are unknown. The aim of the study was to investigate the effects of AI on serum levels of sclerostin, DKK-1 and OPG, as well as their associations with PINP and CTX as markers of bone turnover and bone mineral density (BMD) assessed by DXA.

Methods

We conducted a prospective longitudinal analysis of 70 postmenopausal women with hormone receptor-positive early breast cancer (BC) treated with anastrozole. All measurements were performed at baseline, 12 and 24 months of treatment. We measured the association of the investigated variables with circulating bone turnover markers, as well as with the BMD.

Results

After 24 months of AI therapy, sclerostin and OPG concentrations increased from 29.5 pmol/l (SD = 15.1) and 6.8 pmol/l (SD = 2.2) at baseline to 43.2 pmol/l (SD = 20.6) (p < 0.001) and 7.4 pmol/l (SD = 2.2) (p = 0.028), respectively. DKK-1 levels decreased from 34.3 pmol/l (SD = 13.5) at baseline to 29.7 pmol/l (SD = 12.3) at the 24-month visit (p = 0.005). Sclerostin levels significantly correlated with PTH, OPG and BMD of the lumbar spine, while DKK-1 correlated with the BMD of the femoral neck and of the total hip.

Conclusions

The observed increase in sclerostin levels indicates a central role of osteocytes in bone turnover in women with BC.