Exacerbated glial response in the aged mouse hippocampus following controlled cortical impact injury

Old age is associated with enhanced susceptibility to and poor recovery from brain injury. An exacerbated microglial and astrocyte response to brain injury might be involved in poor outcomes observed in the elderly. The present study was therefore designed to quantitate the expression of markers of microglia and astrocyte activation using real-time RT-PCR, immunoblot and immunohistochemical analysis in aging brain in response to brain injury. We examined the hippocampus, a region that undergoes secondary neuron death, in aged (21–24 months) and adult (5–6 months) mice following controlled cortical impact (CCI) injury to the sensorimotor cortex. Basal mRNA expression of CD11b and Iba1, markers of activated microglia, was higher in aged hippocampus as compared to the adult. The mRNA expression of microglial markers increased and reached maximum 3 days post-injury in both adult and aged mice, but was higher in the aged mice at all time points studied, and in the aged mice the return to baseline levels was delayed. Basal mRNA expression of GFAP and S100B, markers of activated astrocytes, was higher in aged mice. Both markers increased and reached maximum 7 days post-injury. The mRNA expression of astrocyte markers returned to near basal levels rapidly after injury in the adult mice, whereas again in the aged mice return to baseline was delayed. Immunochemical analysis using Iba1 and GFAP antibodies indicated accentuated glial responses in the aged hippocampus after injury. The pronounced and prolonged activation of microglia and astrocytes in hippocampus may contribute to worse cognitive outcomes in the elderly following TBI.     

Investigation of bladder dose and volume factors influencing late urinary toxicity after external beam radiotherapy for prostate cancer

BACKGROUND: We sought to identify the bladder dose-volume factors associated with an increased risk of late urinary toxicity among prostate cancer patients treated with radiotherapy. METHODS AND MATERIALS: This retrospective analysis included data from 128 prostate cancer patients treated on protocol with 2 Gy/fraction to 46 Gy followed by a boost to 78 Gy. The endpoint for this analysis was Grade 1 or greater late genitourinary (GU) toxicity occurring within two years of treatment. The Lyman-Kutcher-Burman, mean dose, threshold dose, and hottest volume models were fitted to the toxicity data using the maximum likelihood method. RESULTS: Model fits based on dose-volume histograms tended to fit the toxicity data better than models based on dose-wall histograms. The hottest volume (hotspot) model was found to be the best-fitting model investigated. The best fit was for the hottest 2.9% of bladder (95% CI, 1.1-6.8%). This model has an area under the receiver operating characteristic curve of 0.74. The hotspot model separated the patients into clinically meaningful subgroups with approximately 25% of the patients who received <78 Gy to the hottest 2.9% of bladder had GU toxicity at eight years compared with approximately 50% when the dose was > or =78 Gy (p = 0.002). CONCLUSION: This provides the first evidence supporting that bladder "hotspots" are related to GU toxicity within two years after external beam radiotherapy for prostate cancer. Confirming data are needed from other investigators. Particular attention should be given to hotspots higher than 78 Gy in bladder in radiation treatment planning.     

Effects of electrical stimulation in C2C12 muscle constructs

Electrical stimulation affects the deposition of extracellular matrices and cellular differentiation. Type I collagen is one of the most abundant extracellular matrix proteins; however, not much is known about the effects of electrical stimulation on collagen type I deposition in C2C12 cells. Thus, we studied the effects of electrical voltage and stimulation frequency in 3D cultured C2C12 muscle cells in terms of metabolic activity, type I collagen deposition and cell morphology. Electrically excitable C2C12 muscle cells were seeded in collagen scaffolds and stimulated with rectangular signals of voltage (2, 5, 7 V) and frequency (1, 2 Hz), using parallel carbon electrodes spaced 1 cm apart. Metabolic activity was quantified by the glucose:lactate concentration ratio in the medium. Apoptotic activity was assessed by TUNEL staining and changes in collagen deposition were identified by immunohistology. The ultrastructure of the tissue was examined by TEM. Glucose and lactate analysis indicated that all groups had similar metabolic activity. TUNEL stain showed no significant difference in apoptotic damage induced by electrical stimulation compared to the control. Samples stimulated at 2 Hz exhibited reduced collagen deposition compared to the control and 1 Hz stimulated samples. Muscle-protein marker desmin was highly expressed in constructs stimulated with 1 Hz/5 V sample. TEM revealed that the stimulated samples developed highly organized sarcomeres, which coincided with improved contractile properties in the 1 Hz/5 V- and 2 Hz/5 V-stimulated groups. Our data implicate that a specific electrical frequency may modulate type I collagen accumulation and a specific voltage may affect the differentiation of muscle sarcomeres in excitable cells.     

Masked Hypertension and Elevated Nighttime Blood Pressure in CKD: Prevalence and Association with Target Organ Damage

Background and objectives

Masked hypertension and elevated nighttime BP are associated with increased risk of hypertensive target organ damage and adverse cardiovascular and renal outcomes in patients with normal kidney function. The significance of masked hypertension for these risks in patients with CKD is less well defined. The objective of this study was to evaluate the association between masked hypertension and kidney function and markers of cardiovascular target organ damage, and to determine whether this relationship was consistent among those with and without elevated nighttime BP.

Design, setting, participants, & measurements

This was a cross-sectional study. We performed 24-hour ambulatory BP in 1492 men and women with CKD enrolled in the Chronic Renal Insufficiency Cohort Study. We categorized participants into controlled BP, white-coat, masked, and sustained hypertension on the basis of clinic and 24-hour ambulatory BP. We obtained echocardiograms and measured pulse wave velocity in 1278 and 1394 participants, respectively.

Results

The percentages of participants with controlled BP, white-coat, masked, and sustained hypertension were 49.3%, 4.1%, 27.8%, and 18.8%, respectively. Compared with controlled BP, masked hypertension independently associated with low eGFR (−3.2 ml/min per 1.73 m²; 95% confidence interval, −5.5 to −0.9), higher proteinuria (+0.9 unit higher in log₂ urine protein; 95% confidence interval, 0.7 to 1.1), and higher left ventricular mass index (+2.52 g/m^2.7; 95% confidence interval, 0.9 to 4.1), and pulse wave velocity (+0.92 m/s; 95% confidence interval, 0.5 to 1.3). Participants with masked hypertension had lower eGFR only in the presence of elevated nighttime BP (−3.6 ml/min per 1.73 m²; 95% confidence interval, −6.1 to −1.1; versus −1.4 ml/min per 1.73 m²; 95% confidence interval, −6.9 to 4.0, among those with nighttime BP <120/70 mmHg; P value for interaction with nighttime systolic BP 0.002).

Conclusions

Masked hypertension is common in patients with CKD and associated with lower eGFR, proteinuria, and cardiovascular target organ damage. In patients with CKD, ambulatory BP characterizes the relationship between BP and target organ damage better than BP measured in the clinic alone.     

Natriuretic Peptides in Chronic Kidney Disease

Background and objectives: B-type natriuretic peptide (BNP) and amino-terminal pro-B-type natriuretic peptide (NT-proBNP) are biomarkers of cardiovascular disease that is common in patients with chronic kidney disease (CKD). Conflicting data on the influence of glomerular filtration rate (GFR) on BNP and NT-proBNP levels in CKD may stem from failure to account fully for the effects of coexistent cardiac disease, dysfunction, and volume overload.Design, setting, participants, & measurements: Prospective head-to-head comparison of plasma BNP and NT-proBNP in ambulatory euvolemic CKD patients with normal LV ejection fraction and no manifest cardiac or vascular disease. GFR was estimated by the Modification of Diet in Renal Disease formula, BNP and NT-proBNP measured using Abbott AxSYM and Roche Elecsys assays, respectively, and cardiac morphology and function assessed by transthoracic echocardiography.Results: In 142 patients (42% female) of mean age 60 ± 11 yr, mean left ventricular ejection fraction was 71% ± 6%, GFR 38 ± 14 ml/min per 1.73 m², and median BNP and NT-proBNP level 59 and 311 pg/ml, respectively. Multivariate predictors of NT-proBNP level were GFR, β-blocker usage, LV mass index, and hemoglobin level. Plasma BNP was independently predicted by LV mass index and β-blocker usage but not GFR. In the 74 patients without diastolic dysfunction, there was a significant rise in NT-proBNP but not BNP as GFR declined.Conclusions: Unlike NT-proBNP, plasma BNP level is relatively independent of GFR. BNP may therefore be the more appropriate biomarker to screen for cardiac dysfunction in CKD.Patients with chronic kidney disease (CKD) are at increased risk of cardiovascular disease. Natriuretic peptides (NPs), biomarkers of myocardial dysfunction (1), offer the potential for early detection and risk stratification of cardiac disease, as evident in emergency department (2) and community (3,4) settings. This screening utility could be extended to CKD patients asymptomatic of cardiovascular disease.However, the precise influence of CKD on circulating levels of B-type natriuretic peptide (BNP) and amino-terminal pro-B-type natriuretic peptide (NT-proBNP), the two commonly used NPs in clinical practice, continues to be debated. Dependence of plasma BNP on glomerular filtration rate (GFR) has been reported among patients with and without heart failure (HF) (5,6), but this relationship may not be independent of cardiac or volume-related factors (7,8). The data on NT-proBNP in renal dysfunction are more concordant but were derived from populations that included patients with myocardial infarction, reduced left ventricular (LV) ejection fraction (LVEF), or HF (9,10). Indeed, most studies examining the impact of renal dysfunction on NPs uniformly included such patients (5,6,8–10). Recent Doppler myocardial imaging studies have shown that even HF patients with normal LVEF have reduced LV contractility compared with controls (11,12).To limit confounding by cardiac dysfunction or volume overload, we prospectively constituted a clinically euvolemic CKD cohort without symptoms or history of cardiac disease and normal LVEF and regional function. We measured circulating levels of both NPs, hypothesizing that, in these patients, BNP can be shown to be relatively independent of GFR compared with NT-proBNP if cardiac and loading factors can be comprehensively accounted for.     

L‐type calcium channel blocker ameliorates diabetic encephalopathy by modulating dysregulated calcium homeostasis

Diabetic encephalopathy is a complication of diabetes characterized by impaired cognitive functions. The objective of the present study was to examine the beneficial effect of the calcium channel blocker, nimodipine, on diabetes‐induced cognitive deficits and altered calcium homeostasis in the cerebral cortex. Diabetes was induced in mice by intraperitoneal injection of streptozotocin (40 mg/kg body wt) for 5 days. Nimodipine (10 mg/kg body weight) was administered intraperitoneally to the animals every 48 hr for 8 weeks. A significant impairment in spatial learning and memory was observed in diabetic animals, which was reversed by nimodipine treatment. Diabetic animals showed increased CaV1.2 mRNA and protein expression, which might be responsible for enhanced synaptosomal calcium uptake. Nimodipine treatment was found to lower CaV1.2 mRNA, protein expression, and calcium uptake. Mitochondrial Ca²⁺ uptake was reduced in diabetic brains, which was reversed with nimodipine treatment. Plasma membrane and sarcoplasmic reticulum Ca²⁺‐ATPase activity was found to be significantly decreased in diabetic animals, whereas nimodipine supplementation restored the activity of both Ca²⁺‐ATPases nearly to control values. Nimodipine treatment was shown to normalize intracellular free Ca²⁺ levels in diabetic animals. Nimodipine was shown to attenuate increased calpain activity measured in terms of hydrolysis of fluorogenic substrate and αII‐spectrin degradation. Nimodipine supplementation also reduced reactive oxygen species production and lipid peroxidation in diabetic animals. The data suggests that L‐type calcium channel blocker is beneficial in preventing cognitive deficits associated with diabetic encephalopathy through modulation of dysregulated calcium homeostasis. © 2014 Wiley Periodicals, Inc.