Citations

Previous studies using microdissected nephron segments reported that the exclusive site of renal 25-hydroxyvitamin D3-24-hydroxylase (24OHase) activity is the renal proximal convoluted tubule (PCT). We now report the presence of 24OHase mRNA, protein, and activity in cells that are devoid of markers of proximal tubules but express characteristics highly specific for the distal tubule. 24OHase mRNA was undetectable in vehicle-treated mouse distal convoluted tubule (DCT) cells but was markedly induced when DCT cells were treated with 1,25 dihydroxyvitamin D3[1,25(OH)2D3]. 24OHase protein and activity were also identified in DCT cells by Western blot analysis and HPLC, respectively. 8-Bromo-cAMP (1 mM) or parathyroid hormone [PTH-(1—34); 10 nM] was found to potentiate the effect of 1,25(OH)2D3on 24OHase mRNA. The stimulatory effect of cAMP or PTH on 24OHase expression in DCT cells suggests differential regulation of 24OHase expression in the PCT and DCT. In the presence of cAMP and 1,25(OH)2D3, a four- to sixfold induction in vitamin D receptor (VDR) mRNA was observed. VDR protein, as determined by Western blot analysis, was also enhanced in the presence of cAMP. Transient transfection analysis in DCT cells with rat 24OHase promoter deletion constructs demonstrated that cAMP enhanced 1,25(OH)2D3-induced 24OHase transcription but this enhancement was not mediated by cAMP response elements (CREs) in the 24OHase promoter. We conclude that 1) although the PCT is the major site of localization of 24OHase, 24OHase mRNA and activity can also be localized in the distal nephron; 2) both PTH and cAMP modulate the induction of 24OHase expression by 1,25(OH)2D3in DCT cells in a manner different from that reported in the PCT; and 3) in DCT cells, upregulation of VDR levels by cAMP, and not an effect on CREs in the 24OHase promoter, is one mechanism involved in the cAMP-mediated modulation of 24OHase transcription.

Lewis, Michael I., Thomas J. Lorusso, Wen-Zhi Zhan, and Gary C. Sieck. Interactive effects of denervation and malnutrition on diaphragm structure and function. J. Appl. Physiol. 81(5): 2165–2172, 1996.—The purpose of this study was to examine the interactive effects of unilateral denervation (DN) and prolonged malnutrition (MN) on the structure and function of the diaphragm muscle (Dia). Four groups of rats were studied: control (Con), MN, DN, and DN-MN. MN began 2 wk after DN and lasted 4 wk. In both the DN and DN-MN groups, the relative loss in Dia weight exceeded the relative change in body weight. Compared with the Con group, Dia specific force was reduced by ∼40% in both the DN and DN-MN groups but was unaffected in the MN group. Dia fatigue resistance improved in all experimental groups but to a greater extent in the DN and DN-MN groups. In both the DN and DN-MN groups, ∼50% of Dia fibers were classified as type IIc, whereas fiber type proportions did not change in the MN group. In the DN group, only type IIb/x fibers atrophied, whereas all fiber types atrophied in the MN and DN-MN groups. We conclude that in the DN-MN group the reduction in specific force combined with the reduction in total cross-sectional area of the muscle significantly curtails Dia force-generating capacity.

Sieck, Gary C., Louise E. Wilson, Bruce D. Johnson, and Wen-Zhi Zhan. Hypothyroidism alters diaphragm muscle development. J. Appl. Physiol. 81(5): 1965–1972, 1996.—The impact of hypothyroidism (Hyp) on myosin heavy chain (MHC) isoform expression, maximum specific force (Po), fatigability, and maximum unloaded shortening velocity ( Vo) was determined in the rat diaphragm muscle (Dia) at 0, 7, 14, 21, and 28 days of age. Hyp was induced by treating pregnant rats with 6- n-propyl-2-thiouracil (0.05% in drinking water) beginning at gestational day 10 and was confirmed by reduced plasma levels of 3,5,3′-triiodothyronine and thyroxine. MHC isoforms were separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and analyzed by densitometry. Isometric Poand fatigue resistance of the Dia were measured in vitro at 26°C, and Vowas determined at 15°C with the slack test. Compared with control muscles, expression of MHC-slow was higher and expression of adult fast MHC isoforms was lower in Hyp Dia at all ages. The neonatal isoform of MHC continued to be expressed in the Hyp Dia until day 28. At each age, Poand fatigability were reduced and Vowas slower in the Hyp Dia. We conclude that Hyp-induced alterations in MHC isoform expression do not fully predict the changes in Dia contractile properties.

Discogenic low back pain (DLBP) is extremely common and costly. Effective treatments are lacking due to DLBP's unknown pathogenesis. Currently, there are no in vivo mouse models of DLBP, which restricts research in this field. The aim of this study was to establish a reliable DLBP model in mouse that captures the pathological changes in the disc and allows longitudinal pain testing. The model was generated by puncturing the mouse lumbar discs (L4/5, L5/6, and L6/S1) and removing the nucleus pulposus using a microscalpel under the microscope. Histology, molecular pathways, and pain‐related behaviors were examined. Over 12 weeks post‐surgery, animals displayed the mechanical, heat, and cold hyperalgesia along with decreased burrowing and rearing. Histology showed progressive disc degeneration with loss of disc height, nucleus pulposus reduction, proteoglycan depletion, and annular fibrotic disorganization. Immunohistochemistry revealed a substantial increase in inflammatory mediators at 2 and 4 weeks. Nerve growth factor was upregulated from 2 weeks to the end of the experiment. Nerve fiber ingrowth was induced in the injured discs after 4 weeks. Disc‐puncture also produced an upregulation of neuropeptides in dorsal root ganglia neurons and an activation of glial cells in the spinal cord dorsal horn. These findings indicate that the cellular and structural changes in discs, as well as peripheral and central nervous system plasticity, paralleled persistent, and robust behavioral pain responses. Therefore, this mouse DLBP model could be used to investigate mechanisms underlying discogenic pain, thereby facilitating effective drug screening and development of treatments for DLBP.

Background— Diabetes mellitus (DM) adversely affects morbidity and mortality for cardiovascular diseases and procedures. Data evaluating the outcomes of transcatheter aortic valve replacement (TAVR) in diabetic patients are limited by small sample size and contradictory results. We aimed to establish the magnitude of risk and the incremental influence of insulin dependency by examining short- and long-term adverse outcomes according to DM status and therapy in the world’s largest TAVR registry. Methods and Results— We analyzed data from the Society of Thoracic Surgeons/American College of Cardiology Transcatheter Valve Therapy Registry. In-hospital mortality, 30-day mortality, and 1-year mortality after TAVR in patients with and without DM were evaluated using multivariate modeling. Among 47 643 patients treated with TAVR from November 2011 through September 2015 at 394 US hospitals, there were 17 849 (37.5%) patients with DM. Overall, 6600 of the diabetic patients were insulin treated (IT). Thirty-day mortality was 5.0% in patients with DM (6.1% in IT DM and 4.4% in non-IT DM; P <0.001) versus 5.9% in patients without DM ( P <0.001). Overall, 1-year mortality was 21.8% in patients with DM (24.8% in IT DM and 20.1% in non-IT DM; P <0.001) versus 21.2% in patients without DM ( P =0.274). In a multivariable model, DM was associated with increased 1-year mortality (hazard ratio, 1.30; 95% confidence interval, 1.13–1.49; P <0.001). Subgroup multivariable analysis showed stronger mortality association in IT diabetics (hazard ratio, 1.57; 95% confidence interval, 1.28–1.91; P <0.001) than in non-IT diabetics (hazard ratio, 1.17; 95% confidence interval, 1.00–1.38; P =0.052). Conclusions— Our data establish the magnitude of short- and long-term risk conferred by DM and the incremental risk conferred by insulin dependency in the performance of TAVR. Clinical Trial Registration— URL: https://www.clinicaltrials.gov . Unique identifier: NCT01737528.

Background and Purpose— White matter (WM) ischemic injury, a major neuropathological feature of cerebral small vessel diseases, is an important cause of vascular cognitive impairment in later life. The pathogenesis of demyelination after WM ischemic damage are often accompanied by microglial activation. Fingolimod (FTY720) was approved for the treatment of multiple sclerosis for its immunosuppression property. In this study, we evaluated the neuroprotective potential of FTY720 in a WM ischemia model. Methods— Chronic WM ischemic injury model was induced by bilateral carotid artery stenosis. Cognitive function, WM integrity, microglial activation, and potential pathway involved in microglial polarization were assessed after bilateral carotid artery stenosis. Results— Disruption of WM integrity was characterized by demyelination in the corpus callosum and disorganization of Ranvier nodes using Luxol fast blue staining, immunofluorescence staining, and electron microscopy. In addition, radial maze test demonstrated that working memory performance was decreased at 1-month post–bilateral carotid artery stenosis–induced injury. Interestingly, FTY720 could reduce cognitive decline and ameliorate the disruption of WM integrity. Mechanistically, cerebral hypoperfusion induced microglial activation, production of associated proinflammatory cytokines, and priming of microglial polarization toward the M1 phenotype, whereas FTY720 attenuated microglia-mediated neuroinflammation after WM ischemia and promoted oligodendrocytogenesis by shifting microglia toward M2 polarization. FTY720’s effect on microglial M2 polarization was largely suppressed by selective signal transducer and activator of transcription 3 (STAT3) blockade in vitro, revealing that FTY720-enabled shift of microglia from M1 to M2 polarization state was possibly mediated by STAT3 signaling. Conclusions— Our study suggested that FTY720 might be a potential therapeutic drug targeting brain inflammation by skewing microglia toward M2 polarization after chronic cerebral hypoperfusion.

Abstract Purpose: Glioblastoma is an aggressive and molecularly heterogeneous cancer with few effective treatment options. We hypothesized that next-generation sequencing can be used to guide treatment recommendations within a clinically acceptable time frame following surgery for patients with recurrent glioblastoma. Experimental Design: We conducted a prospective genomics-informed feasibility trial in adults with recurrent and progressive glioblastoma. Following surgical resection, genome-wide tumor/normal exome sequencing and tumor RNA sequencing were performed to identify molecular targets for potential matched therapy. A multidisciplinary molecular tumor board issued treatment recommendations based on the genomic results, blood–brain barrier penetration of the indicated therapies, drug–drug interactions, and drug safety profiles. Feasibility of generating genomics-informed treatment recommendations within 35 days of surgery was assessed. Results: Of the 20 patients enrolled in the study, 16 patients had sufficient tumor tissue for analysis. Exome sequencing was completed for all patients, and RNA sequencing was completed for 14 patients. Treatment recommendations were provided within the study's feasibility time frame for 15 of 16 (94%) patients. Seven patients received treatment based on the tumor board recommendations. Two patients reached 12-month progression-free survival, both adhering to treatments based on the molecular profiling results. One patient remained on treatment and progression free 21 months after surgery, 3 times longer than the patient's previous time to progression. Analysis of matched nonenhancing tissue from 12 patients revealed overlapping as well as novel putatively actionable genomic alterations. Conclusions: Use of genome-wide molecular profiling is feasible and can be informative for guiding real-time, central nervous system–penetrant, genomics-informed treatment recommendations for patients with recurrent glioblastoma. Clin Cancer Res; 24(2); 295–305. ©2017 AACR. See related commentary by Wick and Kessler, p. 256

AbstractAimMuscle wasting is one of the factors most strongly predicting mortality and morbidity in critically ill intensive care unit (ICU). This muscle wasting affects both limb and respiratory muscles, but the understanding of underlying mechanisms and muscle‐specific differences remains incomplete. This study aimed at investigating the temporal expression and phosphorylation of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway in muscle wasting associated with the ICU condition to characterize the JAK/STAT proteins and the related changes leading or responding to their activation during exposure to the ICU condition.MethodsA novel experimental ICU model allowing long‐term exposure to the ICU condition, immobilization and mechanical ventilation, was used in this study. Rats were pharmacologically paralysed by post‐synaptic neuromuscular blockade and mechanically ventilated for durations varying between 6 hours and 14 days to study muscle‐specific differences in the temporal activation of the JAK/STAT pathway in plantaris, intercostal and diaphragm muscles.ResultsThe JAK2/STAT3 pathway was significantly activated irrespective of muscle, but muscle‐specific differences were observed in the temporal activation pattern between plantaris, intercostal and diaphragm muscles.ConclusionThe JAK2/STAT3 pathway was differentially activated in plantaris, intercostal and diaphragm muscles in response to the ICU condition. Thus, JAK2/STAT3 inhibitors may provide an attractive pharmacological intervention strategy in immobilized ICU patients, but further experimental studies are required in the study of muscle‐specific effects on muscle mass and function in response to both short‐ and long‐term exposure to the ICU condition prior to the translation into clinical research and practice.