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Biomedical subjects

Mai Nguyen

Publications and source records attributed to Mai Nguyen.

At least 19 recordsLinked to original sources

MAPL regulates gasdermin-mediated release of mtDNA from lysosomes to drive pyroptotic cell death.

Mitochondrial control of cell death is of central importance to disease mechanisms from cancer to neurodegeneration. Mitochondrial anchored protein ligase (MAPL) is an outer mitochondrial membrane small ubiquitin-like modifier ligase that is a key determinant of cell survival, yet how MAPL controls the fate of this process remains unclear. Combining genome-wide functional genetic screening and cell biological approaches, we found that MAPL induces pyroptosis through an inflammatory pathway involving mitochondria and lysosomes. MAPL overexpression promotes mitochondrial DNA trafficking in mitochondrial-derived vesicles to lysosomes, which are permeabilized in a process requiring gasdermin pores. This triggers the release of mtDNA into the cytosol, activating the DNA sensor cGAS, required for cell death. Additionally, multiple Parkinson's disease-related genes, including VPS35 and LRRK2, also regulate MAPL-induced pyroptosis. Notably, depletion of MAPL, LRRK2 or VPS35 inhibited inflammatory cell death in primary macrophages, placing MAPL and the mitochondria-lysosome pathway at the nexus of immune signalling and cell death.

Lysosomes↗

Peripheral Macular Endothelial Dystrophy: Clinical, Histopathologic, Genetic and Functional Characterization.

OBJECTIVE: To report a CHST6-associated corneal endothelial dystrophy. DESIGN: Prospective observational case series. PARTICIPANTS: Thirty-five individuals from seven families, including 13 affected individuals exhibiting corneal epithelial and stromal edema, peripheral posterior corneal macular opacities, and endothelial guttae, as well as 22 unaffected family members. METHODS: Whole-exome sequencing was performed in 3 families and Sanger sequencing of CHST6 was performed in all individuals. Histological examination of Descemet membrane (DM) excised at the time of endothelial keratoplasty was performed for three probands. Serum keratan sulfate (KS) levels were measured in members of six families. Functional analysis of identified mutations was performed using CHST6 promoter containing CHST6 expression vector in human keratocytes (HK) and corneal endothelial cells (HCEnC). MAIN OUTCOME MEASURES: Clinical phenotype; genetic analysis; functional analysis of identified CHST6 mutations; serum KS levels; histologic examinations of DM. RESULTS: All affected individuals demonstrated peripheral macular opacities at the level of DM. Visually significant corneal edema in affected individuals was successfully managed by endothelial keratoplasty. Genetic analysis demonstrated a rare CHST6 promoter mutation (c.-690G>C) in the homozygous state in affected individuals from three families and in the compound heterozygous state with a CHST6 coding mutation (p.R211Q, p.Y268C or p.P280L) in affected individuals from the other four families. In silico analysis predicted c.-690G>C to be a regulatory variant, located at the RNA polymerase II binding site. Functional analysis in vitro demonstrated that c.-690G>C leads to increased KS sulfation in the corneal endothelium and DM, with no change of KS sulfation in keratocytes. Histologic examination of DM from affected individuals revealed elevated levels of sulfated and non-sulfated KS in DM and endothelium, consistent with the functional analysis. Minimum changes in serum sulfated KS levels were observed in affected individuals. CONCLUSIONS: We suggest the name Peripheral macular endothelial dystrophy (PMED) to describe this dystrophy that is characterized by peripheral posterior corneal macular opacities and endothelial dysfunction without stromal haze or opacities. Given that both PMED and macular corneal dystrophy are associated with promoter and coding region mutations in CHST6, we propose that they be categorized as CHST6-associated corneal dystrophies.

Humans↗

LC-MS/MS method for simultaneous determination of viramidine and ribavirin levels in monkey red blood cells.

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous determinations of total viramidine (viramidine, viramidine monophosphate, viramidine diphosphate, and viramidine triphosphate) and total ribavirin (ribavirin, ribavirin monophosphate, ribavirin diphosphate, and ribavirin triphosphate) in monkey red blood cells (RBC). The method involves the addition of internal standards and perchloric acid, conversion of viramidine or ribavirin phosphorylated metabolites to viramidine or ribavirin, purification with an aminopropyl (NH(2)) solid phase extraction (SPE) cartridge, and LC-MS/MS analysis. The MS/MS is selected to monitor m/z 245-->113, 250-->113, 244-->112, and 249-->112 for ribavirin, [(13)C]ribavirin, viramidine, and [(13)C]viramidine, respectively, using positive electrospray ionization. The calibration curves are linear over a concentration range of 100-10,000 ng/mL (0.412-41.2 microM) with a lower limit of quantification (LLOQ) of 100 ng/mL for both compounds. Mean inter-assay recoveries for ribavirin are 101%, 98.9%, and 96.0%, with coefficient of variance (%CV) values between 1.95 and 4.50% for 100, 1000, and 10,000 ng/mL quality control (QC) samples, respectively. Mean inter-assay recoveries for viramidine are 96.3%, 101%, and 102%, with coefficient of variation (%CV) values between 3.61 and 7.22%, for 100, 1000, and 10,000 ng/mL QC samples, respectively. Over-curve dilution QC at 400 microg/mL (1639 microM) for both viramidine and ribavirin are used to ensure the dilution accuracy (25 X dilutions) for monkey samples. The method has been used to simultaneously determine the total concentrations of ribavirin and viramidine in monkey RBC following 5, 15, and 36 weeks dosing of viramidine or ribavirin (60 mg/kg). The concentrations of total ribavirin following ribavirin dosing are 1242 microM at week 5, 1257 microM at week 15, and 1146 microM at week 36. The concentrations of total ribavirin following viramidine dosing are 634 microM at week 5, 716 microM at week 15, and 683 microM at week 36. Only small amounts of viramidine are detected in RBC following viramidine dosing, 7.80 microM at week 5, 6.63 microM at week 15, and 10.4 microM at week 36. The results suggest that ribavirin levels in RBC were at steady state at week 5 of ribavirin or viramidine dosing. At steady state, ribavirin levels in RBC are approximately 2x after ribavirin dosing than viramidine dosing. The relatively small percentage of viramidine in RBC suggests that viramidine either poorly penetrated into RBC or was extensively converted to ribavirin following entry into RBC.

Animals↗

Evaluation of the thermal stability of Gardasil.

The thermostability of GARDASIL (Merck & Co., Inc, Whitehouse Station, NJ, USA), a developmental vaccine against human papillomavirus (HPV), was evaluated using an enzyme immunoassay, referred to as the in vitro relative potency (IVRP) assay and differential scanning calorimetry (DSC). Gardasil samples were stored at temperatures ranging from 4 to 42 degrees C and tested for IVRP at various time points. Extrapolation of the IVRP results indicates GARDASIL is extremely stable. The half-life of the vaccine is estimated to be 130 months or longer at temperatures up to 25 degrees C. At 37 degrees C, the half-life is predicted to be 18 months and at 42 degrees C, the half-life is predicted to be approximately three months. Differential scanning calorimetry (DSC) analysis was used to evaluate the process of protein denaturation during a rapid temperature increase (as opposed to long-term storage at a specific temperature). Differences were seen among the DSC profiles of the four HPV types tested. This indicates that small differences in the amino acid structure can have a significant effect on the intermolecular contacts that stabilize the L1 proteins and the VLP assembly. For the Gardasil samples evaluated here, DSC results demonstrated the relative overall structural stability of the VLPs, but were not predictive of the excellent long-term stability observed with the IVRP assay.

Calorimetry, Differential Scanning↗

Astrocytic changes in the hippocampus and functional recovery after cerebral ischemia are facilitated by rehabilitation training.

In this study we examined whether astrocytic and basic fibroblast growth factor changes after cerebral ischemia can be influenced by rehabilitation training and if these changes are associated with functional improvement. After receiving either ischemia or sham surgery, male adult Wistar rats were assigned to one of two rehabilitation training group: complex environment housing (EC) or paired housing as controls (CON). Rats were tested in the water maze after 14 days of rehabilitation training. Results showed increased expression of reactive astrocytes (GFAP) in all ischemic animals and in the sham EC rats with a significant overall increased seen in the ischemia EC housed animals. The pattern of basic fibroblast growth factor (FGF-2) expression seen was somewhat similar to that of GFAP. Behavioral data showed that even though all animals learned to perform the water maze task over time, the ischemia CON rats took longer to learn the task while all the ischemia EC animals performed as well as the sham groups. Regression analysis showed that increased GFAP was able to explain some of the variances in the behavioral parameters in the water maze of the ischemia EC rats suggesting that the activation of astrocytes in this group probably mediated enhanced functional recovery. Lastly, it is possible that the favorable effect of astrocyte activation after cerebral ischemia was mediated by FGF-2.

Analysis of Variance↗

BAP31 and its caspase cleavage product regulate cell surface expression of tetraspanins and integrin-mediated cell survival.

BAP31, a resident integral protein of the endoplasmic reticulum membrane, regulates the export of other integral membrane proteins to the downstream secretory pathway. Here we show that cell surface expression of the tetraspanins CD9 and CD81 is compromised in mouse cells from which the Bap31 gene has been deleted. CD9 and CD81 facilitate the function of multiprotein complexes at the plasma membrane, including integrins. Of note, BAP31 does not appear to influence the egress of alpha5beta1 or alpha(v)beta3 integrins to the cell surface, but in Bap31-null mouse cells, these integrins are not able to maintain cellular adhesion to the extracellular matrix in the presence of reduced serum. Consequently, Bap31-null cells are sensitive to serum starvation-induced apoptosis. Reconstitution of wild-type BAP31 into these Bap31-null cells restores integrin-mediated cell attachment and cell survival after serum stress, whereas interference with the functions of CD9, alpha5beta1, or alpha(v)beta3 by antagonizing antibodies makes BAP31 cells act similar to Bap31-null cells in these respects. Finally, in human KB epithelial cells protected from apoptosis by BCL-2, the caspase-8 cleavage product, p20 BAP31, inhibits egress of tetraspanin and integrin-mediated cell attachment. Thus, p20 BAP31 can operate upstream of BCL-2 in living cells to influence cell surface properties due to its effects on protein egress from the endoplasmic reticulum.

Animals↗

A sensitive and specific method for the determination of total ribavirin in monkey liver by high-performance liquid chromatography with tandem mass spectrometry.

A sensitive and specific method using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of total ribavirin in monkey liver is developed and validated. In this method, ribavirin and its phosphorylated metabolites are extracted with perchloric acid. The metabolites are converted to ribavirin using acid phosphatase and further purified using a NH2 solid-phase extraction (SPE) cartridge prior to LC-MS/MS analysis. [13C]Ribavirin is added with the extraction solution as an internal standard to obtain better accuracy and precision of the analysis. The MS/MS was selected to monitor 245-->113 and 250-->113 transitions using positive electrospray ionization for ribavirin and [(13)C]ribavirin. The calibration curve is linear over a concentration of 1.0-100 microg/g with a limit of quantitation (LOQ) of 1.0 microg/g. Mean inter-assay accuracy for QC at 1.0, 10 and 100 microg/g are 108, 99.7 and 99.7%, respectively. Mean inter-assay precision (CV) for QC at 1.0, 10 and 100 microg/g are 5.34, 5.24 and 4.59%, respectively. Extractability of total ribavirin from liver has been confirmed with liver obtained from monkey dosed with [14C]ribavirin. The method has been proven to be useful in the determination of total ribavirin concentration in liver from monkeys in mass balance study (10 mg/kg) and in 28 days toxicology study (300 mg/kg/day). It is also used to determine the total ribavirin concentration in human livers from hepatitis C patients received dose of 600 mg ribavirin twice daily.

Animals↗

Intraocular microsporidiosis due to Encephalitozoon cuniculi in a patient with idiopathic CD4+ T-lymphocytopenia.

Encephalitozoon cuniculi was documented to cause disseminated microsporidial infection including an iris tumor and endophthalmitis in an adolescent with idiopathic CD4+ T-lymphocytopenia. The diagnosis was established by microscopic, serologic and molecular methods. E. cuniculi (rabbit strain) was identified from the iris tumor, as well as from urine, conjunctival, corneal, and nasal swabs. Treatment with oral albendazole led to rapid improvement. This case raises the possibility of disseminated microsporidial infection in the context of idiopathic CD4+ T-lymphocytopenia and possibly advanced human immunodeficiency virus (HIV) infection, and above all the possibility of intraocular infection with E. cuniculi in humans.

AIDS-Related Opportunistic Infections↗

Tumor metastasis but not tumor growth is dependent on Src-mediated vascular permeability.

Vascular endothelial growth factor (VEGF)-induced vascular permeability (VP) is a hallmark of tumor growth and metastasis. Previous studies have shown a requirement for Src kinase in VEGF-mediated VP and signaling in blood vessels. In this study, we have examined the effect of Src-mediated reduced VP on tumor growth and metastasis. The growth and spontaneous metastasis of VEGF-expressing tumor cells were determined in Src-knockout (src(-/-)) or control mice (src(+/+) or src(+/-)). In comparison to control mice, src-null mice had a significant reduction in tumor-induced VP as well as a subsequent reduction in spontaneous metastasis. In contrast, primary tumor weight and vascular density were unchanged between src-null and control mice. Consistent with a role for Src in the extravasation of tumor cells from the circulation, direct intravenous injection of lung carcinoma cells resulted in a more than 2-fold reduction in lung tumor burden in src-null mice compared to control mice. The comparison of the results from the experimental metastasis and the spontaneous metastasis models suggests that there are defects in VP in the primary site of Src-deficient mice and that there may be an essential role for Src and Src-mediated VP in tumor metastasis to the lung.

Animals↗

Evaluation of SET--a new device for the measurement of pain perception in comparison to standard measures of diabetic neuropathy.

BACKGROUND: Early detection of sensory impairment and loss of protective pain sensation is of major importance for the prevention of neuropathic foot ulceration. The aim of our study was to evaluate a new handheld device (SET, a prototype developed by Dr. W. Henniges, Zülpich, Germany) for measurement of pain perception, in comparison with established methods for diagnosis of diabetic neuropathy. METHODS: Sixty-one patients with diabetes mellitus (13 type 1, 48 type 2; 42 men, 19 women; mean +/- SD age 61.6 +/- 11.6 years) received measurement of pain perception threshold using the new SET device and a measurement of light touch sensation, temperature sensation, and vibration sensation by the use of standard clinical devices. In addition, warm, cold, heat pain and vibration perception thresholds were determined by the use of a computer-based peltier thermode and a vibration stimulator (TSA 2001, Medoc, Ramat Yishai, Israel). RESULTS: Using the new SET device, patients with sensory impairment showed significantly elevated pain perception thresholds at the dorsum of the foot (P < 0.001), while only a trend towards higher measurements could be observed at the plantar aspect of the foot. A significant correlation could be observed between plantar and dorsal measuring sites (r = 0.78, P < 0.0001) and between both feet (r = 0.85, P < 0.0001). Compared with other qualities of sensory dysfunction, pain perception measurement with the SET device provided the highest sensitivity (pain = 0.82; vibration = 0.61; temperature = 0.42; light touch = 0.11). CONCLUSIONS: Measurement of pain perception threshold using the SET device is an easy and reliable method for identifying patients with impaired small nerve fiber function.

Cold Temperature↗

Regulation of apoptosis by endoplasmic reticulum pathways.

Apoptotic programmed cell death pathways are activated by a diverse array of cell extrinsic and intrinsic signals, most of which are ultimately coupled to the activation of effector caspases. In many instances, this involves an obligate propagation through mitochondria, causing egress of critical proapoptotic regulators to the cytosol. Central to the regulation of the mitochondrial checkpoint is a complex three-way interplay between members of the BCL-2 family, which are comprised of an antiapoptotic subgroup including BCL-2 itself, and the proapoptotic BAX,BAK and BH3-domain-only subgroups. Constituents of all three of these BCL-2 classes, however, also converge on the endoplasmic reticulum (ER), an organelle whose critical contributions to apoptosis is only now becoming apparent. In addition to propagating death-inducing stress signals itself, the ER also contributes in a fundamental way to Fas-mediated apoptosis and to p53-dependent pathways resulting from DNA damage and oncogene expression. Mobilization of ER calcium stores can initiate the activation of cytoplasmic death pathways as well as sensitize mitochondria to direct proapoptotic stimuli. Additionally, the existence of BCL-2-regulated initiator procaspase activation complexes at the ER membrane has also been described. Here, we review the potential underlying mechanisms involved in these events and discuss pathways for ER-mitochondrial crosstalk pertinent to a number of cell death stimuli.

Amyloid beta-Protein Precursor↗

Uncleaved BAP31 in association with A4 protein at the endoplasmic reticulum is an inhibitor of Fas-initiated release of cytochrome c from mitochondria.

BAP31 is a polytopic integral protein of the endoplasmic reticulum membrane and, like BID, is a preferred substrate of caspase-8. Upon Fas/CD95 stimulation, BAP31 is cleaved within its cytosolic domain, generating proapoptotic p20 BAP31. In human KB epithelial cells expressing the caspase-resistant mutant crBAP31, Fas stimulation resulted in cleavage of BID and insertion of BAX into mitochondrial membrane, but subsequent oligomerization of BAX and BAK, egress of cytochrome c to the cytosol, and apoptosis were impaired. Bap31-null mouse cells expressing crBAP31 cannot generate the endogenous p20 BAP31 cleavage product, yet crBAP31 conferred resistance to cellular condensation and cytochrome c release in response to activation of ectopic FKBPcasp8 by FK1012z. Full-length BAP31, therefore, is a direct inhibitor of these caspase-8-initiated events, acting independently of its ability to sequester p20, with which it interacts. Employing a novel split ubiquitin yeast two-hybrid screen for BAP31-interacting membrane proteins, the putative ion channel protein of the endoplasmic reticulum, A4, was detected and identified as a constitutive binding partner of BAP31 in human cells. Ectopic A4 that was introduced into A4-deficient cells cooperated with crBAP31 to resist Fas-induced egress of cytochrome c from mitochondria and cytoplasmic apoptosis.

Adenosine Triphosphatases↗

The resident endoplasmic reticulum protein, BAP31, associates with gamma-actin and myosin B heavy chain.

BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulum whose cytosolic domain contains two caspase recognition sites that are preferentially cleaved by initiator caspases, such as caspase-8. Recently, we reported that the caspase-resistant BAP31 inhibited Fas-mediated apoptotic membrane fragmentation and the release of cytochrome c from mitochondria in KB epithelial cells (Nguyen M., Breckenridge G., Ducret A & Shore G. (2000) Mol. Cell. Biol.20, 6731-6740). We describe here the characterization by capillary liquid chromatography microelectrospray tandem MS of a BAP31 immunocomplex isolated from a HepG2 cell lysate in the absence of a death signal. We show that BAP31 specifically associates with nonmuscle myosin heavy chain B and nonmuscle gamma-actin, two components of the cytoskeleton actomyosin complex. Collectively, these data confirm that BAP31, in addition to its potential role as a chaperone, may play a fundamental role in the structural organization of the cytoplasm. Here we also show that Fas stimulation of apoptosis releases BAP31 associations with these motor proteins, a step that may contribute to extranuclear events, such as membrane remodelling, during the execution phase of apoptosis.

Actins↗

Marked (24-fold) elevation of peritoneal cavity drainage fluid vascular endothelial growth factor after successful "patch, drain, and wait" approach for extensive midgut necrosis in a newborn.

In a current publications, it has been suggested that hypoxia-triggered "good angiogenesis" involving hypoxic up-regulation of vascular endothelial growth factor (VEGF) molecules, genes, and receptors is likely responsible in a major way for the remarkable gut and patient salvage experience associated with use of the "patch, drain, and wait" (PD&W) surgical approach to perforated necrotizing enterocolitis and midgut volvulus (MGV) with extensive ischemia/necrosis. We report a case in which extensive ischemia/necrosis in a newborn with gastroschisis (likely MGV-induced) was managed successfully by PD&W with an associated marked (24-fold) elevation of VEGF in drainage fluid at 7 days post-initiation of PD&W.

Body Fluids↗

The procaspase-8 isoform, procaspase-8L, recruited to the BAP31 complex at the endoplasmic reticulum.

BAP31 is an integral protein of the endoplasmic reticulum membrane and a substrate of caspase-8. Here, we describe the procaspase-8 isoform, procaspase-8L, which is ubiquitously expressed and selectively recruited to the BAP31 complex in response to apoptotic signaling by E1A. Procaspase-8L is characterized by the N-terminal extension (Nex) domain, which extends procaspase-8/a at the N terminus and is required for selective association of procaspase-8L with the BAP31 complex. Gene deletion identified BAP31 and related BAP29 as required for processing of procaspase-8L in response to E1A, by a FADD-independent mechanism that was blocked by BCL-2. Further, Bap29,31 deletion, as well as a Nex-domain dominant-negative mutant, curtailed the activation of downstream caspases (IETDase and DEVDase) and cell death in response to E1A. Preferential recruitment of procaspase-8L by the BAP31 complex at the endoplasmic reticulum suggests an additional pathway for regulating initiator caspase-8 during apoptosis.

Adenovirus E1A Proteins↗

Curcumin exerts multiple suppressive effects on human breast carcinoma cells.

In our study, we present experimental evidence suggesting that curcumin exerts multiple different suppressive effects on human breast carcinoma cells in vitro. Our experiments demonstrate that curcumin's antiproliferative effects are estrogen dependent in ER (estrogen receptor)-positive MCF-7 cells, being more pronounced in estrogen-containing media and in the presence of exogenous 17-beta estradiol. Curcumin inhibits the expression of ER downstream genes including pS2 and TGF-beta (transforming growth factor) in ER-positive MCF-7 cells, and this inhibition is also dependent on the presence of estrogen. Curcumin also decreases ERE (estrogen responsive element)-CAT activities induced by 17-beta estradiol. In addition, we demonstrate that curcumin exerts strong anti-invasive effects in vitro that are not estrogen dependent in the ER-negative MDA-MB-231 breast cancer cells. These anti-invasive effects appear to be mediated through the downregulation of MMP-2 (matrix metalloproteinase) and the upregulation of TIMP-1 (tissue inhibitor of metalloproteinase), 2 common effector molecules that have been implicated in regulating tumor cell invasion. Our study also demonstrates that curcumin inhibits the transcript levels of 2 major angiogenesis factors VEGF (vascular endothelial growth factor) and b-FGF (basic fibroblast growth factor) mainly in ER-negative MDA-MB-231 cells.

Antineoplastic Agents↗

Identification of a novel endothelial-derived gene EG-1.

The identification of novel endothelial-derived genes is important in the study of angiogenesis, and may have potential uses in cancer diagnosis and treatment. We performed SSH (suppression subtractive hybridization) on control HUVECs (human umbilical vein endothelial cells) versus HUVECs exposed to tumor-conditioned media. We found that a novel cDNA (GenBank Accession No. AF358829) is differentially expressed in endothelial cells on Northern analysis, and named it endothelial-derived gene-1 (EG-1). This gene product is predicted to encode a 178-aa, 19.5-kDa protein, and is localized to chromosome 4. It has some homology to a mouse cDNA (94%) and a Drosophila cDNA (31%). On Northern analysis, endothelial cells express two EG-1 RNA species (1.2 and 2.4 kb). The expression of either transcripts is upregulated by endothelial cells when exposed to tumor conditioned media. This phenomenon is observed only under sparse conditions (50% confluency). Transcripts are present abundantly in highly vascular tissues such as placenta, testis, and liver. Interestingly, both Northern analysis and in situ hybridization studies show that this gene is expressed in other cell types as well, predominantly the epithelial type. Breast cancer, prostate cancer, and colon cancer cells show elevated expression of the higher 2.4-kb RNA form. Our data suggest that EG-1 is associated with a stimulated state in endothelial and epithelial cells, and may have a role in tumor angiogenesis.

Amino Acid Sequence↗

Angiogenic factors and bladder cancer.

Angiogenesis is required for the growth as well as expansion of a solid tumor. It has been reported that tumor angiogenesis may be triggered after an increase in the level of angiogenic factors and a concomitant decrease in the level of angiogenic inhibitors. Of all potential pro-angiogenic mediators of bladder cancer, VEGF and bFGF appear to be most relevant in terms of physiology. To date, it appears that the angiogenic factors and inhibitors may play an important role in the diagnosis and prognosis of bladder cancer.

Angiogenesis Inducing Agents↗