407 research outputs found
High Throughput Screening for Small Molecule Therapy for Gaucher Disease Using Patient Tissue as the Source of Mutant Glucocerebrosidase
Gaucher disease (GD), the most common lysosomal storage disorder, results from the inherited deficiency of the lysosomal enzyme glucocerebrosidase (GCase). Previously, wildtype GCase was used for high throughput screening (HTS) of large collections of compounds to identify small molecule chaperones that could be developed as new therapies for GD. However, the compounds identified from HTS usually showed reduced potency later in confirmatory cell-based assays. An alternate strategy is to perform HTS on mutant enzyme to identify different lead compounds, including those enhancing mutant enzyme activities. We developed a new screening assay using enzyme extract prepared from the spleen of a patient with Gaucher disease with genotype N370S/N370S. In tissue extracts, GCase is in a more native physiological environment, and is present with the native activator saposin C and other potential cofactors. Using this assay, we screened a library of 250,000 compounds and identified novel modulators of mutant GCase including 14 new lead inhibitors and 30 lead activators. The activities of some of the primary hits were confirmed in subsequent cell-based assays using patient-derived fibroblasts. These results suggest that primary screening assays using enzyme extracted from tissues is an alternative approach to identify high quality, physiologically relevant lead compounds for drug development
Effects of urodilatin on natriuresis in cirrhosis patients with sodium retention
BACKGROUND: Sodium retention and ascites are serious clinical problems in cirrhosis. Urodilatin (URO) is a peptide with paracrine effects in decreasing sodium reabsorption in the distal nephron. Our aim was to investigate the renal potency of synthetic URO on urine sodium excretion in cirrhosis patients with sodium retention and ascites. METHODS: Seven cirrhosis patients with diuretics-resistant sodium retention received a short-term (90 min) infusion of URO in a single-blind, placebo-controlled cross-over study. In the basal state after rehydration the patients had urine sodium excretion < 50 mmol/24 h. RESULTS: URO transiently increased urine sodium excretion from 22 ± 16 μmol/min (mean ± SD) to 78 ± 41 μmol/min (P < 0.05) and there was no effect of placebo (29 ± 14 to 44 ± 32). The increase of URO's second messenger after the receptor, cGMP, was normal. URO had no effect on urine flow or on blood pressure. Most of the patients had highly elevated plasma levels of renin, angiotensin II and aldosterone and URO did not change these. CONCLUSION: The short-term low-dose URO infusion increased the sodium excretion of the patients. The increase was small but systematic and potentially clinically important for such patients. The small response contrasts the preserved responsiveness of the URO receptors. The markedly activated systemic pressor hormones in cirrhosis evidently antagonized the local tubular effects of URO
Diagnostic role of new Doppler index in assessment of renal artery stenosis
BACKGROUND: Renal artery stenosis (RAS) is one of the main causes of secondary systemic arterial hypertension. Several non-invasive diagnostic methods for RAS have been used in hypertensive patients, such as color Doppler ultrasound (US). The aim of this study was to assess the sensitivity and specificity of a new renal Doppler US direct-method parameter: the renal-renal ratio (RRR), and compare with the sensitivity and specificity of direct-method conventional parameters: renal peak systolic velocity (RPSV) and renal aortic ratio (RAR), for the diagnosis of severe RAS. METHODS: Our study group included 34 patients with severe arterial hypertension (21 males and 13 females), mean age 54 (± 8.92) years old consecutively evaluated by renal color Doppler ultrasound (US) for significant RAS diagnosis. All of them underwent digital subtraction arteriography (DSA). RAS was significant if a diameter reduction > 50% was found. The parameters measured were: RPSV, RAR and RRR. The RRR was defined as the ratio between RPSV at the proximal or mid segment of the renal artery and RPSV measured at the distal segment of the renal artery. The sensitivity and specificity cutoff for the new RRR was calculated and compared with the sensitivity and specificity of RPSV and RAR. RESULTS: The accuracy of the direct method parameters for significant RAS were: RPSV >200 cm/s with 97% sensitivity, 72% specificity, 81% positive predictive value and 95% negative predictive value; RAR >3 with 77% sensitivity, 90% specificity, 90% positive predictive value and 76% negative predictive value. The optimal sensitivity and specificity cutoff for the new RRR was >2.7 with 97% sensitivity (p < 0.004) and 96% specificity (p < 0.02), with 97% positive predictive value and 97% negative predictive value. CONCLUSION: The new RRR has improved specificity compared with the direct method conventional parameters (RPSV >200cm/s and RAR >3). Both RRR and RPSV show better sensitivity than RAR for the RAS diagnosis
In Vivo and Ex Vivo Evaluation of L-Type Calcium Channel Blockers on Acid β-Glucosidase in Gaucher Disease Mouse Models
Gaucher disease is a lysosomal storage disease caused by mutations in acid β-glucosidase (GCase) leading to defective hydrolysis and accumulation of its substrates. Two L-type calcium channel (LTCC) blockers—verapamil and diltiazem—have been reported to modulate endoplasmic reticulum (ER) folding, trafficking, and activity of GCase in human Gaucher disease fibroblasts. Similarly, these LTCC blockers were tested with cultured skin fibroblasts from homozygous point-mutated GCase mice (V394L, D409H, D409V, and N370S) with the effect of enhancing of GCase activity. Correspondingly, diltiazem increased GCase protein and facilitated GCase trafficking to the lysosomes of these cells. The in vivo effects of diltiazem on GCase were evaluated in mice homozygous wild-type (WT), V394L and D409H. In D409H homozygotes diltiazem (10 mg/kg/d via drinking water or 50–200 mg/kg/d intraperitoneally) had minor effects on increasing GCase activity in brain and liver (1.2-fold). Diltiazem treatment (10 mg/kg/d) had essentially no effect on WT and V394L GCase protein or activity levels (<1.2-fold) in liver. These results show that LTCC blockers had the ex vivo effects of increasing GCase activity and protein in the mouse fibroblasts, but these effects did not translate into similar changes in vivo even at very high drug doses
Role of Toll-Like Receptor (TLR) 2 in Experimental Bacillus cereus Endophthalmitis
Bacillus cereus causes a uniquely rapid and blinding intraocular infection, endophthalmitis. B. cereus replicates in the eye, synthesizes numerous toxins, and incites explosive intraocular inflammation. The mechanisms involved in the rapid and explosive intraocular immune response have not been addressed. Because Toll-like receptors (TLRs) are integral to the initial recognition of organisms during infection, we hypothesized that the uniquely explosive immune response observed during B. cereus endophthalmitis is directly influenced by the presence of TLR2, a known Gram-positive pathogen recognition receptor. To address this hypothesis, we compared the courses of experimental B. cereus endophthalmitis in wild type C57BL/6J mice to that of age-matched homozygous TLR2-/- mice. Output parameters included analysis of bacterial growth, inflammatory cell (PMN) infiltration, cytokine/chemokine kinetics, retinal function testing, and histology, with N≥4 eyes/assay/time point/mouse strain. B. cereus grew at similar rates to108 CFU/eye by 12 h, regardless of the mouse strain. Retinal function was preserved to a greater degree in infected TLR2-/- eyes compared to that of infected wild type eyes, but infected eyes of both mouse strains lost significant function. Retinal architecture was preserved in infected TLR2-/- eyes, with limited retinal and vitreal cellular infiltration compared to that of infected wild type eyes. Ocular myeloperoxidase activities corroborated these results. In general, TNFα, IFNγ, IL6, and KC were detected in greater concentrations in infected wild type eyes than in infected TLR2-/- eyes. The absence of TLR2 resulted in decreased intraocular proinflammatory cytokine/chemokine levels and altered recruitment of inflammatory cells into the eye, resulting in less intraocular inflammation and preservation of retinal architecture, and a slightly greater degree of retinal function. These results demonstrate TLR2 is an important component of the initial ocular response to B. cereus endophthalmitis
Behavioral and Immune Responses to Infection Require Gαq- RhoA Signaling in C. elegans
Following pathogen infection the hosts' nervous and immune systems react with coordinated responses to the danger. A key question is how the neuronal and immune responses to pathogens are coordinated, are there common signaling pathways used by both responses? Using C. elegans we show that infection by pathogenic strains of M. nematophilum, but not exposure to avirulent strains, triggers behavioral and immune responses both of which require a conserved Gαq-RhoGEF Trio-Rho signaling pathway. Upon infection signaling by the Gαq pathway within cholinergic motorneurons is necessary and sufficient to increase release of the neurotransmitter acetylcholine and increase locomotion rates and these behavioral changes result in C. elegans leaving lawns of M. nematophilum. In the immune response to infection signaling by the Gαq pathway within rectal epithelial cells is necessary and sufficient to cause changes in cell morphology resulting in tail swelling that limits the infection. These Gαq mediated behavioral and immune responses to infection are separate, act in a cell autonomous fashion and activation of this pathway in the appropriate cells can trigger these responses in the absence of infection. Within the rectal epithelium the Gαq signaling pathway cooperates with a Ras signaling pathway to activate a Raf-ERK-MAPK pathway to trigger the cell morphology changes, whereas in motorneurons Gαq signaling triggers behavioral responses independent of Ras signaling. Thus, a conserved Gαq pathway cooperates with cell specific factors in the nervous and immune systems to produce appropriate responses to pathogen. Thus, our data suggests that ligands for Gq coupled receptors are likely to be part of the signals generated in response to M. nematophilum infection
The impact of single and pairwise Toll-like receptor activation on neuroinflammation and neurodegeneration
Background Toll-like receptors (TLRs) enable innate immune cells to respond to
pathogen- and host-derived molecules. The central nervous system (CNS)
exhibits most of the TLRs identified with predominant expression in microglia,
the major immune cells of the brain. Although individual TLRs have been shown
to contribute to CNS disorders, the consequences of multiple activated TLRs on
the brain are unclear. We therefore systematically investigated and compared
the impact of sole and pairwise TLR activation on CNS inflammation and injury.
Methods Selected TLRs expressed in microglia and neurons were stimulated with
their specific TLR ligands in varying combinations. Cell cultures were then
analyzed by immunocytochemistry, FlowCytomix, and ELISA. To determine neuronal
injury and neuroinflammation in vivo, C57BL/6J mice were injected
intrathecally with TLR agonists. Subsequently, brain sections were analyzed by
quantitative real-time PCR and immunohistochemistry. Results Simultaneous
stimulation of TLR4 plus TLR2, TLR4 plus TLR9, and TLR2 plus TLR9 in microglia
by their respective specific ligands results in an increased inflammatory
response compared to activation of the respective single TLR in vitro. In
contrast, additional activation of TLR7 suppresses the inflammatory response
mediated by the respective ligands for TLR2, TLR4, or TLR9 up to 24 h,
indicating that specific combinations of activated TLRs individually modulate
the inflammatory response. Accordingly, the composition of the inflammatory
response pattern generated by microglia varies depending on the identity and
combination of the activated TLRs engaged. Likewise, neuronal injury occurs in
response to activation of only selected TLRs and TLR combinations in vitro.
Activation of TLR2, TLR4, TLR7, and TLR9 in the brain by intrathecal injection
of the respective TLR ligand into C57BL/6J mice leads to specific expression
patterns of distinct TLR mRNAs in the brain and causes influx of leukocytes
and inflammatory mediators into the cerebrospinal fluid to a variable extent.
Also, the intensity of the inflammatory response and neurodegenerative effects
differs according to the respective activated TLR and TLR combinations used in
vivo. Conclusions Sole and pairwise activation of TLRs modifies the pattern
and extent of inflammation and neurodegeneration in the CNS, thereby enabling
innate immunity to take account of the CNS diseases’ diversity
Maternal TLR4 and NOD2 Gene Variants, Pro-Inflammatory Phenotype and Susceptibility to Early-Onset Preeclampsia and HELLP Syndrome
Background: Altered maternal inflammatory responses play a role in the development of preeclampsia and the hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome. We examined whether allelic variants of the innate immune receptors toli-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain (NOD2), that impair the inflammatory response to endotexin are related to preeclampsia and HELLP syndrome. Methods and Finding: We determined five common mutations in TLR4 (D299G and T399I and NOD2 (R70W, G908R and L1007fs) in 340 primiparous women with a histo
Somatic diversification of variable lymphocyte receptors in the agnathan sea lamprey
Although jawless vertebrates are apparently capable of adaptive immune responses, they have not been found to possess the recombinatorial antigen receptors shared by all jawed vertebrates. Our search for the phylogenetic roots of adaptive immunity in the lamprey has instead identified a new type of variable lymphocyte receptors (VLRs) composed of highly diverse leucine-rich repeats (LRR) sandwiched between amino- and carboxy-terminal LRRs. An invariant stalk region tethers the VLRs to the cell surface by means of a glycosyl-phosphatidyl-inositol anchor. To generate rearranged VLR genes of the diversity necessary for an anticipatory immune system, the single lamprey VLR locus contains a large bank of diverse LRR cassettes, available for insertion into an incomplete germline VLR gene. Individual lymphocytes express a uniquely rearranged VLR gene in monoallelic fashion. Different evolutionary strategies were thus used to generate highly diverse lymphocyte receptors through rearrangement of LRR modules in agnathans ( jawless fish) and of immunoglobulin gene segments in gnathostomes ( jawed vertebrates).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62870/1/nature02740.pd
Free energies of binding of R- and S-propranolol to wild-type and F483A mutant cytochrome P450 2D6 from molecular dynamics simulations
Detailed molecular dynamics (MD) simulations have been performed to reproduce and rationalize the experimental finding that the F483A mutant of CYP2D6 has lower affinity for R-propranolol than for S-propranolol. Wild-type (WT) CYP2D6 does not show this stereospecificity. Four different approaches to calculate the free energy differences have been investigated and were compared to the experimental binding data. From the differences between calculations based on forward and backward processes and the closure of thermodynamic cycles, it was clear that not all simulations converged sufficiently. The approach that calculates the free energies of exchanging R-propranolol with S-propranolol in the F483A mutant relative to the exchange free energy in WT CYP2D6 accurately reproduced the experimental binding data. Careful inspection of the end-points of the MD simulations involved in this approach, allowed for a molecular interpretation of the observed differences
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