γ-Secretase-Regulated Mechanisms Similar to Notch Signaling May Play a Role in Signaling Events, Including APP Signaling, Which Leads to Alzheimer's Disease

Although gamma-secretase was first identified as a protease that cleaves amyloid precursor protein (APP) within the transmembrane domain, thus producing A beta peptides that are thought to be pathogenic in Alzheimer's disease (AD), its physiological functions have not been fully elucidated. In the canonical Notch signaling pathway, intramembrane cleavage by gamma-secretase serves to release an intracellular domain of Notch that shows activity in the nucleus through binding to transcription factors. Many type 1 transmembrane proteins, including Notch, Delta, and APP, have recently been shown to be substrates for gamma-secretase, and their intracellular domains are released from the cell membrane following cleavage by gamma-secretase. The common enzyme gamma-secretase modulates proteolysis and the turnover of possible signaling molecules, which has led to the attractive hypothesis that mechanisms similar to Notch signaling contribute widely to proteolysis-regulated signaling pathways. APP is also likely to have a signaling mechanism, although the physiological functions of APP have not been elucidated. Indeed, we have shown that the intracellular domain of APP alters gene expression and induces neuron-specific apoptosis. These results suggest that APP signaling responds to the onset of AD. Here, we review the possibility of gamma-secretase-regulated signaling, including APP signaling, which leads to AD.ArticleCELLULAR AND MOLECULAR NEUROBIOLOGY. 31(6):887-900 (2011)journal articl

TLR3 signaling is either protective or pathogenic for the development of Theiler's virus-induced demyelinating disease depending on the time of viral infection

Background: We have previously shown that toll-like receptor 3 (TLR3)-mediated signaling plays an important role in the induction of innate cytokine responses to Theiler\u27s murine encephalomyelitis virus (TMEV) infection. In addition, cytokine levels produced after TMEV infection are significantly higher in the glial cells of susceptible SJL mice compared to those of resistant C57BL/6 mice. However, it is not known whether TLR3-mediated signaling plays a protective or pathogenic role in the development of demyelinating disease. Methods: SJL/J and B6; 129S-Tlr3(tm1Flv)/J (TLR3KO-B6) mice, and TLR3KO-SJL mice that TLR3KO-B6 mice were backcrossed to SJL/J mice for 6 generations were infected with Theiler\u27s murine encephalomyelitis virus (2 x 10(5) PFU) with or without treatment with 50 mu g of poly IC. Cytokine production and immune responses in the CNS and periphery of infected mice were analyzed. Results: We investigated the role of TLR3-mediated signaling in the protection and pathogenesis of TMEV-induced demyelinating disease. TLR3KO-B6 mice did not develop demyelinating disease although they displayed elevated viral loads in the CNS. However, TLR3KO-SJL mice displayed increased viral loads and cellular infiltration in the CNS, accompanied by exacerbated development of demyelinating disease, compared to the normal littermate mice. Late, but not early, anti-viral CD4(+) and CD8(+) T cell responses in the CNS were compromised in TLR3KO-SJL mice. However, activation of TLR3 with poly IC prior to viral infection also exacerbated disease development, whereas such activation after viral infection restrained disease development. Activation of TLR3 signaling prior to viral infection hindered the induction of protective IFN-gamma-producing CD4(+) and CD8(+) T cell populations. In contrast, activation of these signals after viral infection improved the induction of IFN-gamma-producing CD4(+) and CD8(+) T cells. In addition, poly IC-pretreated mice displayed elevated PDL-1 and regulatory FoxP3(+) CD4+ T cells in the CNS, while poly IC-post-treated mice expressed reduced levels of PDL-1 and FoxP3(+) CD4(+) T cells. Conclusions: These results suggest that TLR3-mediated signaling during viral infection protects against demyelinating disease by reducing the viral load and modulating immune responses. In contrast, premature activation of TLR3 signal transduction prior to viral infection leads to pathogenesis via over-activation of the pathogenic immune response

Safety and tissue yield for percutaneous native kidney biopsy according to practitioner and ultrasound technique

BACKGROUND: Although percutaneous renal biopsy remains an essential tool in the diagnosis and treatment of renal diseases, in recent times the traditional procedure of nephrologists has been performed by non-nephrologists rather than nephrologists at many institutions. The present study assessed the safety and adequacy of tissue yield during percutaneous renal biopsy according to practitioners and techniques based on ultrasound. METHODS: This study included 658 native renal biopsies performed from 2005 to 2010 at a single centre. The biopsies were performed by nephrologists or expert ultrasound radiologists using the ultrasound-marked blind or real-time ultrasound-guided techniques. RESULTS: A total of 271 ultrasound-marked blind biopsies were performed by nephrologists, 170 real-time ultrasound-guided biopsies were performed by nephrologists, and 217 real-time ultrasound-guided biopsies were performed by radiologists during the study period. No differences in post-biopsy complications such as haematoma, need for transfusion and intervention, gross haematuria, pain, or infection were observed among groups. Glomerular numbers of renal specimens from biopsies performed by nephrologists without reference to any technique were higher than those obtained from real-time ultrasound-guided biopsies performed by expert ultrasound radiologists. CONCLUSIONS: Percutaneous renal biopsy performed by nephrologists was not inferior to that performed by expert ultrasound radiologists as related to specimen yield and post-biopsy complications

Immunoadsorption Therapy for Patients with Dilated Cardiomyopathy and Heart Failure

Several autoantibodies directed against cardiac cellular proteins including G-protein-linked receptors, contractile proteins and mitochondrial proteins, have been identified in patients with dilated cardiomyopathy (DCM). Among these autoantibodies, anti-β1-adrenoreceptor (AR) antibodies have long been discussed in terms of their pathogenetic role in DCM. Anti-β1-AR antibody-positive patients with DCM showed significant deterioration of NYHA functional class as well as reduced cardiac function compared to those in autoantibody-negative patients. Various studies with a limited number of patients indicate that the use of immunoadsorption to eliminate immunoglobulin G (IgG) significantly improves cardiac performance and clinical status in heart failure patients. Since removal of autoantibodies of the IgG3 subclass induces hemodynamic improvement and an increase in the left ventricular ejection fraction, antibodies belonging to IgG3 such as anti-β1-AR antibodies might play an important role in reducing cardiac function in patients with DCM. According to a recent report, however, the effect of hemodynamic improvement by immunoadsorption threapy was similar among patients who were positive and negative for anti-β1-AR antibodies, indicating that the beneficial effects of immunoadsorption might be not directly associated with the selective elimination of the β1-AR autoantibodies. Immunoadsorption therapy is a new therapeutic option for patients with DCM and heart failure, but further investigations are required to elucidate the specific antigens of cardiac autoantibodies responsible for the hemodynamic effects

Sirolimus-eluting stent is superior to paclitaxel-eluting stent for coronary intervention in patients with renal insufficiency: Long-term clinical outcomes

Background: Renal insufficiency (RI) is an independent risk factor for the adverse cardiovascular events. Long-term clinical outcome of percutaneous coronary intervention (PCI) in patients with RI is unknown especially in the era of first generation drug-eluting stents (DES). This study aims at comparing clinical outcomes between sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES) based on large scaled registry.Methods: Patients who underwent PCI with DES from January 2004 to December 2009 in the Catholic University of Korea-PCI (COACT) registry were prospectively enrolled. A group of 1,033 patients with RI, defined as estimated glomerular filtration rate under 60 mL/min, were analyzed. Major adverse cardiac events (MACE), including all-cause death, non-fatal myocardial infarction (MI), target lesion revascularization (TLR), and target vessel revascularization (TVR) according to the type of stents were compared.Results: Median follow-up period was 810 days (interquartile range: from 361 to 1,354 days). A group of 612 (59.2%) patients were treated with SES and 421 (40.8%) patients were treated with PES. The PES vs. SES group had significantly higher rate of MACE (35.9% vs. 28.3%, p = 0.01). In multivariate Cox hazard regression analysis, PES vs. SES group had significantly higher rate of MACE (adjusted hazard ratio [AHR] 1.29, 95% confidence interval [CI] 1.02–1.64, p = 0.033), particularly pronounced by all-cause death (AHR 1.34, 95% CI 1.008–1.770; p = 0.044). In further analysis with propensity score matching, overall findings were consistent.Conclusions: In patients with RI, PCI using PES provides poorer clinical outcomes than SES in terms of MACE and all-cause death

Decreased Angiotensin II -Stimulated Aldosterone Production, but Normal Inositol Phosphate Response in Adrenal Glomerulosa Cells from Streptozotocin-Induced Diabetic Rats: Role of lnsulin

Streptozotocin(SlZ)-induced diabetic rats develop hyporeninemic hypoaldosteronism during the progression of diabetes mellitus. However,the nature and mechanism of aldosterone deficiency in diabetic rats still remain unclear and acute effects of insulin on aldosterone production in-vitro are not known. We evaluated the responses of aldosterone production to angiotensin 11 (AlI), potassium (K+), AClH and insulin in adrenal glomerulosa cells prepared from SlZ-induced diabetic rats with and without insulin treatment 2 weeks after diabetes induction. We also measured inositol phosphate<IP) levels in All-stimulated glomerulosa cells labeled with [3HI myoinositol using standardized anion exchange chromatography. Plasma renin activity and aldosterone level were not different among control rats,untreated and insulin-treated diabetic rats. Basal aldosterone production was similar in cells from the three groups. Cells from untreated diabetic rats showed a significant decrease in the maximal All (to-8M)-stimuiated aldosterone production and a tendency to be low in the maximal K+(8.7 mM)-stimulated aldosterone production, compared with control rats (3.2±2.2 \IS 7.7±2.4, P (0.05 and 4.8±1.8 \IS 8.0±3.2 ng/105 cells/hr, 0.05 (P (0.1, respectively). In contrast, there were no differences in All- and K+-stimulated aldosterone production between control and insulin-treated diabetic rats. AClH (to-8M), however, caused a similar effect on aldosterone production and insulin (I mU /ml for 1 hour) did not alter either basal or agonists-stimulated aldosterone production in cells from the three groups. All (to-8M)-induced IP formation among the three groups was similar and did not change with the addition of insulin u mU / ml), These results indicate that reduced response to All in the early phase of SlZ-induced diabetes in rats may be due to the zona glomerulosa dysfunction secondary to chronic lack of insulin and the main defect responsible for altered All effects may be located at some step(s) mediating All action downstream from IP formation