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Recent documents in eScholarship@UMMS
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The unconventional myosin CRINKLED and its mammalian orthologue MYO7A regulate caspases in their signalling roles

Wed, 12/07/2016 - 4:29pm

Caspases provide vital links in non-apoptotic regulatory networks controlling inflammation, compensatory proliferation, morphology and cell migration. How caspases are activated under non-apoptotic conditions and process a selective set of substrates without killing the cell remain enigmatic. Here we find that the Drosophila unconventional myosin CRINKLED (CK) selectively interacts with the initiator caspase DRONC and regulates some of its non-apoptotic functions. Loss of CK in the arista, border cells or proneural clusters of the wing imaginal discs affects DRONC-dependent patterning. Our data indicate that CK acts as substrate adaptor, recruiting SHAGGY46/GSK3-beta to DRONC, thereby facilitating caspase-mediated cleavage and localized modulation of kinase activity. Similarly, the mammalian CK counterpart, MYO7A, binds to and impinges on CASPASE-8, revealing a new regulatory axis affecting receptor interacting protein kinase-1 (RIPK1) > CASPASE-8 signalling. Together, our results expose a conserved role for unconventional myosins in transducing caspase-dependent regulation of kinases, allowing them to take part in specific signalling events.

Spontaneous coronary artery dissection in a patient with autosomal dominant polycystic kidney disease: a case report

Wed, 12/07/2016 - 4:29pm

BACKGROUND: Spontaneous coronary artery dissection is an uncommon syndrome. Its prevalence among patients with polycystic kidney disease is very rare, with no previously reported involvement of the right posterior descending coronary artery.

CASE PRESENTATION: We describe the case of a middle-aged Caucasian woman with polycystic kidney disease who presented with a non-ST elevation myocardial infarction. Cardiac catheterization revealed a dissection of her right posterior descending coronary artery. She was treated with dual antiplatelet therapy and had a favorable outcome.

CONCLUSION: We report a rare and interesting case of spontaneous coronary artery dissection of the right posterior descending coronary artery in a patient with polycystic kidney disease. It is important to consider spontaneous coronary artery dissection in the differential diagnosis of patients with polycystic kidney disease who present with an acute coronary syndrome.

Integrative analyses reveal a long noncoding RNA-mediated sponge regulatory network in prostate cancer

Wed, 12/07/2016 - 4:27pm

Mounting evidence suggests that long noncoding RNAs (lncRNAs) can function as microRNA sponges and compete for microRNA binding to protein-coding transcripts. However, the prevalence, functional significance and targets of lncRNA-mediated sponge regulation of cancer are mostly unknown. Here we identify a lncRNA-mediated sponge regulatory network that affects the expression of many protein-coding prostate cancer driver genes, by integrating analysis of sequence features and gene expression profiles of both lncRNAs and protein-coding genes in tumours. We confirm the tumour-suppressive function of two lncRNAs (TUG1 and CTB-89H12.4) and their regulation of PTEN expression in prostate cancer. Surprisingly, one of the two lncRNAs, TUG1, was previously known for its function in polycomb repressive complex 2 (PRC2)-mediated transcriptional regulation, suggesting its sub-cellular localization-dependent function. Our findings not only suggest an important role of lncRNA-mediated sponge regulation in cancer, but also underscore the critical influence of cytoplasmic localization on the efficacy of a sponge lncRNA.

Risk Factors for Nonplatelet Thromboxane Generation After Coronary Artery Bypass Graft Surgery

Wed, 12/07/2016 - 4:27pm

BACKGROUND: Persistent thromboxane (TX) generation while receiving aspirin therapy is associated with an increased risk of cardiovascular events. The Reduction in Graft Occlusion Rates (RIGOR) study found that aspirin-insensitive TXA2 generation, indicated by elevated urine 11-dehydro-TXB2 (UTXB2) 6 months after coronary artery bypass graft surgery, was a potent risk factor for vein graft thrombosis and originated predominantly from nonplatelet sources. Our goal was to identify risks factors for nonplatelet TXA2 generation.

METHODS AND RESULTS: Multivariable modeling was performed by using clinical and laboratory variables obtained from 260 RIGOR subjects with verified aspirin-mediated inhibition of platelet TXA2 generation. The strongest variable associated with UTXB2 6 months after surgery, accounting for 47.2% of the modeled effect, was urine 8-iso-prostaglandin (PG)F2alpha, an arachidonic acid metabolite generated nonenzymatically by oxidative stress (standardized coefficient 0.442, P < 0.001). Age, sex, race, lipid therapy, creatinine, left ventricular ejection fraction, and aspirin dose were also significantly associated with UTXB2 (P < 0.03), although they accounted for only 4.8% to 10.2% of the modeled effect. Urine 8-iso-PGF2alpha correlated with risk of vein graft occlusion (odds ratio 1.67, P=0.001) but was not independent of UTXB2. In vitro studies revealed that endothelial cells generate TXA2 in response to oxidative stress and direct exposure to 8-iso-PGF2alpha.

CONCLUSIONS: Oxidative stress-induced formation of 8-iso-PGF2alpha is strongly associated with nonplatelet thromboxane formation and early vein graft thrombosis after coronary artery bypass graft surgery. The endothelium is potentially an important source of oxidative stress-induced thromboxane generation. These findings suggest therapies that reduce oxidative stress could be useful in reducing cardiovascular risks associated with aspirin-insensitive thromboxane generation.

NEMO Prevents RIP Kinase 1-Mediated Epithelial Cell Death and Chronic Intestinal Inflammation by NF-kappaB-Dependent and -Independent Functions

Wed, 12/07/2016 - 4:26pm

Intestinal epithelial cells (IECs) regulate gut immune homeostasis, and impaired epithelial responses are implicated in the pathogenesis of inflammatory bowel diseases (IBD). IEC-specific ablation of nuclear factor kappaB (NF-kappaB) essential modulator (NEMO) caused Paneth cell apoptosis and impaired antimicrobial factor expression in the ileum, as well as colonocyte apoptosis and microbiota-driven chronic inflammation in the colon. Combined RelA, c-Rel, and RelB deficiency in IECs caused Paneth cell apoptosis but not colitis, suggesting that NEMO prevents colon inflammation by NF-kappaB-independent functions. Inhibition of receptor-interacting protein kinase 1 (RIPK1) kinase activity or combined deficiency of Fas-associated via death domain protein (FADD) and RIPK3 prevented epithelial cell death, Paneth cell loss, and colitis development in mice with epithelial NEMO deficiency. Therefore, NEMO prevents intestinal inflammation by inhibiting RIPK1 kinase activity-mediated IEC death, suggesting that RIPK1 inhibitors could be effective in the treatment of colitis in patients with NEMO mutations and possibly in IBD.

A Delphi process to address medication appropriateness for older persons with multiple chronic conditions

Wed, 12/07/2016 - 4:25pm

BACKGROUND: Frameworks exist to evaluate the appropriateness of medication regimens for older patients with multiple medical conditions (MCCs). Less is known about how to translate the concepts of the frameworks into specific strategies to identify and remediate inappropriate regimens.

METHODS: Modified Delphi method involving iterative rounds of input from panel members. Panelists (n = 9) represented the disciplines of nursing, medicine and pharmacy. Included among the physicians were two geriatricians, one general internist, one family practitioner, one cardiologist and two nephrologists. They participated in 3 rounds of web-based anonymous surveys.

RESULTS: The panel reached consensus on a set of markers to identify problems with medication regimens, including patient/caregiver report of non-adherence, medication complexity, cognitive impairment, medications identified by expert opinion as inappropriate for older persons, excessively tight blood sugar and blood pressure control among persons with diabetes mellitus, patient/caregiver report of adverse medication effects or medications not achieving desired outcomes, and total number of medications. The panel also reached consensus on approaches to address these problems, including endorsement of strategies to discontinue medications with known benefit if necessary because of problems with feasibility or lack of alignment with patient goals.

CONCLUSIONS: The results of the Delphi process provide the basis for an algorithm to improve medication regimens among older persons with MCCs. The algorithm will require assessment not only of medications and diagnoses but also cognition and social support, and it will support discontinuation of medications both when risks outweigh benefits and when regimens are not feasible or do not align with goals.

Apontic regulates somatic stem cell numbers in Drosophila testes

Wed, 12/07/2016 - 4:24pm

BACKGROUND: Microenvironments called niches maintain resident stem cell populations by balancing self-renewal with differentiation, but the genetic regulation of this process is unclear. The niche of the Drosophila testis is well-characterized and genetically tractable, making it ideal for investigating the molecular regulation of stem cell biology. The JAK/STAT pathway, activated by signals from a niche component called the hub, maintains both germline and somatic stem cells.

RESULTS: This study investigated the molecular regulation of the JAK/STAT pathway in the stem cells of the Drosophila testis. We determined that the transcriptional regulator Apontic (Apt) acts in the somatic (cyst) stem cells (CySCs) to balance differentiation and maintenance. We found Apt functions as a negative feedback inhibitor of STAT activity, which enables cyst cell maturation. Simultaneous loss of the STAT regulators apt and Socs36E, or the Stat92E-targeting microRNA miR-279, expanded the somatic stem cell-like population.

CONCLUSIONS: Genetic analysis revealed that a conserved genetic regulatory network limits JAK/STAT activity in the somatic stem cells of Drosophila testis. In these cells, we determined JAK/STAT signaling promotes apt expression. Then, Apt functions through Socs36E and miR-279 to attenuate pathway activation, which is required for timely CySC differentiation. We propose that Apt acts as a core component of a STAT-regulatory circuit to prevent stem cell overpopulation and allow stem cell maturation.

Does the Mutant CAG Expansion in Huntingtin mRNA Interfere with Exonucleolytic Cleavage of its First Exon

Wed, 12/07/2016 - 4:24pm

BACKGROUND: Silencing mutant huntingtin mRNA by RNA interference (RNAi) is a therapeutic strategy for Huntington's disease. RNAi induces specific endonucleolytic cleavage of the target HTT mRNA, followed by exonucleolytic processing of the cleaved mRNA fragments.

OBJECTIVES: We investigated the clearance of huntingtin mRNA cleavage products following RNAi, to find if particular huntingtin mRNA sequences persist. We especially wanted to find out if the expanded CAG increased production of a toxic mRNA species by impeding degradation of human mutant huntingtin exon 1 mRNA.

METHODS: Mice expressing the human mutant HTT transgene with 128 CAG repeats (YAC128 mice) were injected in the striatum with self-complementary AAV9 vectors carrying a miRNA targeting exon 48 of huntingtin mRNA (scAAV-U6-miRNA-HTT-GFP). Transgenic huntingtin mRNA levels were measured in striatal lysates after two weeks. For qPCR, we used species specific primer-probe combinations that together spanned 6 positions along the open reading frame and untranslated regions of the human huntingtin mRNA. Knockdown was also measured in the liver following tail vein injection.

RESULTS: Two weeks after intrastriatal administration of scAAV9-U6-miRNA-HTT-GFP, we measured transgenic mutant huntingtin in striatum using probes targeting six different sites along the huntingtin mRNA. Real time PCR showed a reduction of 29% to 36% in human HTT. There was no significant difference in knockdown measured at any of the six sites, including exon 1. In liver, we observed a more pronounced HTT mRNA knockdown of 70% to 76% relative to the untreated mice, and there were also no significant differences among sites.

CONCLUSIONS: Our results demonstrate that degradation is equally distributed across the human mutant huntingtin mRNA following RNAi-induced cleavage.

Total Elbow Arthroplasty in the United States: Evaluation of Cost, Patient Demographics, and Complication Rates

Wed, 12/07/2016 - 4:23pm

Total elbow arthroplasty (TEA) is utilized in the treatment of rheumatoid and post-traumatic elbow arthritis. TEA is a relatively low volume surgery in comparison to other types of arthroplasty and therefore little is known about current surgical utilization, patient demographics and complication rates in the United States. The purpose of our study is to evaluate the current practice trends and associated in-patient complications of TEA at academic centers in the United States. We queried the University Health Systems Consortium administrative database from 2007 to 2011 for patients who underwent an elective TEA. A descriptive analysis of demographics was performed which included patient age, sex, race, and insurance status. We also evaluated the following patient clinical benchmarks: hospital length of stay (LOS), hospital direct cost, in-hospital mortality, complications, and 30-day readmission rates. Our cohort consisted of 3146 adult patients (36.5% male and 63.5% female) with an average age of 58 years who underwent a total elbow arthroplasty (159 academic medical centers) in the United States. The racial demographics included 2334 (74%) Caucasian, 285 (9%) black, 236 (7.5%) Hispanic, 16 (0.5%) Asian, and 283 (9%) other patients. The mean LOS was 4.2+/-5 days and the mean total direct cost for the hospital was 16,300+/-4000 US Dollars per case. The overall inpatient complication rate was 3.1% and included mortality < 1%, DVT (0.8%), re-operation (0.5%), and infection (0.4%). The 30-day readmission rate was 4.4%. TEA is a relatively uncommon surgery in comparison to other forms of arthroplasty but is associated with low in-patient and 30-day perioperative complication rate. Additionally, the 30-day readmission rate and overall hospital costs are comparable to the traditional total hip and knee arthroplasty surgeries.