Identification of a novel aspartic protease (Asp 2) as beta-secretase

The Alzheimer's disease beta-amyloid peptide (Abeta) is produced by excision from the type 1 integral membrane glycoprotein amyloid precursor protein (APP) by the sequential actions of beta- and then gamma-secretases. Here we report that Asp 2, a novel transmembrane aspartic protease, has the key activities expected of beta-secretase. Transient expression of Asp 2 in cells expressing APP causes an increase in the secretion of the N-terminal fragment of APP and an increase in the cell-associated C-terminal beta-secretase APP fragment. Mutation of either of the putative catalytic aspartyl residues in Asp 2 abrogates the production of the fragments characteristic of cleavage at the beta-secretase site. The enzyme is present in normal and Alzheimer's disease (AD) brain and is also found in cell lines known to produce Abeta. Asp 2 localizes to the Golgi/endoplasmic reticulum in transfected cells and shows clear colocalization with APP in cells stably expressing the 751-amino-acid isoform of APP.

Compartmentalization of beta-secretase (Asp2) into low-buoyant density, noncaveolar lipid rafts

Recent epidemiological studies show a reduced prevalence of Alzheimer's disease (AD) in patients treated with inhibitors of cholesterol biosynthesis. Moreover, the cholesterol-transport protein, apolipoprotein E4, and elevated cholesterol are important risk factors for AD. Additionally, in vitro and in vivo studies show that intracellular cholesterol levels can modulate the processing of amyloid precursor protein (APP) to beta-amyloid, the major constituent of senile plaques. Cholesterol plays a crucial role in maintaining lipid rafts in a functional state. Lipid rafts are cholesterol-enriched membrane microdomains implicated in signal transduction, protein trafficking, and proteolytic processing. Since APP, beta-amyloid, and the putative gamma-secretase, presenilin-1 (PS-1), have all been found in lipid rafts, we hypothesized that the recently identified beta-secretase, Asp2 (BACE1), might also be present in rafts. Here, we report that recombinant Asp2 expressed in three distinct cell lines is raft associated. Using both detergent and nondetergent methods, Asp2 protein and activity were found in a light membrane raft fraction that also contained other components of the amyloidogenic pathway. Immunoisolation of caveolin-containing vesicles indicated that Asp2 was present in a unique raft population distinct from caveolae. Finally, depletion of raft cholesterol abrogated association of Asp2 with the light membrane fraction. These observations are consistent with the raft localization of APP processing and suggest that the partitioning of Asp2 into lipid rafts may underlie the cholesterol sensitivity of beta-amyloid production.

Brain responses to changes in bladder volume and urge to void in healthy men

Knowledge of how changes in bladder volume and the urge to void affect brain activity is important for understanding brain mechanisms that control urinary continence and micturition. This study used PET to evaluate brain activity associated with different levels of passive bladder filling and the urge to void. Eleven healthy male subjects (three left- and eight right-handed) aged 19-54 years were catheterized and the bladder filled retrogradely per urethra. Twelve PET scans were obtained during two repetitions of each of six bladder volumes, with the subjects rating their perception of urge to void prior to and after each scan. Increased brain activity related to increasing bladder volume was seen in the periaqueductal grey matter (PAG), in the midline pons, in the mid-cingulate cortex and bilaterally in the frontal lobe area. Increased brain activity relating to decreased urge to void was seen in a different portion of the cingulate cortex, in premotor cortex and in the hypothalamus. Both activation patterns were predominantly bilaterally symmetric and none of the effects could be attributed to the presence of the catheter. However, in some subjects, mostly those reporting intrusive sensations from the urethral catheter, there was a discrepancy between filling volume and urge so that they reported high urge with low volumes. As this 'mismatch' decreased, activation increased bilaterally in the somatosensory cortex. Our findings support the hypothesis that the PAG receives information about bladder fullness and relays this information to areas involved in the control of bladder storage. Our results also show that the network of brain regions involved in modulating the perception of the urge to void is distinct from that associated with the appreciation of bladder fullness.

Cleavage of Alzheimer's amyloid precursor protein by alpha-secretase occurs at the surface of neuronal cells

The amyloid precursor protein (APP) is proteolytically processed predominantly by alpha-secretase to release the ectodomain (sAPPalpha). In this study, we have addressed the cellular location of the constitutive alpha-secretase cleavage of endogenous APP in a neuronal cell line. Incubation of the neuroblastoma cell line IMR32 at 20 degrees C prevented the secretion into the medium of soluble wild-type APP cleaved by alpha-secretase as revealed by both immunoelectrophoretic blot analysis with a site-specific antibody and immunoprecipitation following metabolic labeling of the cells. No sAPPalpha was detected in the cell lysates following incubation of the cells at 20 degrees C, indicating that alpha-secretase does not cleave APP in the secretory pathway prior to or within the trans-Golgi network. Parallel studies using an antibody that recognizes specifically the neoepitope revealed on soluble APP cleaved by beta-secretase indicated that this enzyme was acting intracellularly. alpha-Secretase is a zinc metalloproteinase susceptible to inhibition by hydroxamate-based compounds such as batimastat [Parvathy, S., et al. (1998) Biochemistry 37, 1680-1685]. Incubation of the cells with a cell-impermeant, biotinylated hydroxamate inhibitor inhibited the release of sAPPalpha by >92%, indicating that alpha-secretase is cleaving APP almost exclusively at the cell surface. The observation that alpha-secretase cleaves APP at the cell surface, while beta-secretase can act earlier in the secretory pathway within the neuronal cell line indicates that there must be strict control mechanisms in place to ensure that APP is normally cleaved primarily by alpha-secretase in the nonamyloidogenic pathway to produce the neuroprotective sAPPalpha.

ASP1 (BACE2) cleaves the amyloid precursor protein at the beta-secretase site

Sequential proteolytic processing of the Amyloid Precursor Protein (APP) by beta- and gamma-secretases generates the 4-kDa amyloid (A beta) peptide, a key component of the amyloid plaques seen in Alzheimer's disease (AD). We and others have recently reported the identification and characterisation of an aspartic proteinase, Asp2 (BACE), as beta-secretase. Here we describe the characterization of a second highly related aspartic proteinase, Asp1 as a second beta-secretase candidate. Asp1 is expressed in brain as detected at the mRNA level and at the protein level. Transient expression of Asp1 in APP-expressing cells results in an increase in the level of beta-secretase-derived soluble APP and the corresponding carboxy-terminal fragment. Paradoxically there is a decrease in the level of soluble A beta secreted from the cells. Asp1 colocalizes with APP in the Golgi/endoplasmic reticulum compartments of cultured cells. Asp1, when expressed as an Fc fusion protein (Asp1-Fc), has the N-terminal sequence ALEP..., indicating that it has lost the prodomain. Asp1-Fc exhibits beta-secretase activity by cleaving both wild-type and Swedish variant (KM/NL) APP peptides at the beta-secretase site.

Alzheimer's amyloid precursor protein alpha-secretase is inhibited by hydroxamic acid-based zinc metalloprotease inhibitors: similarities to the angiotensin converting enzyme secretase

The 4 kDa beta-amyloid peptide that forms the amyloid fibrils in the brain parenchyma of Alzheimer's disease patients is derived from the larger integral membrane protein, the amyloid precursor protein. In the nonamyloidogenic pathway, alpha-secretase cleaves the amyloid precursor protein within the beta-amyloid domain, releasing an extracellular portion and thereby preventing deposition of the intact amyloidogenic peptide. The release of the amyloid precursor protein from both SH-SY5Y and IMR-32 neuronal cells by alpha-secretase was blocked by batimastat and other related synthetic hydroxamic acid-based zinc metalloprotease inhibitors, but not by the structurally unrelated zinc metalloprotease inhibitors enalaprilat and phosphoramidon. Batimastat inhibited the release of the amyloid precursor protein from both cell lines with an I50 value of 3 microM. Removal of the thienothiomethyl substituent adjacent to the hydroxamic acid moiety or the substitution of the P2' substituent decreased the inhibitory potency of batimastat toward alpha-secretase. In the SH-SY5Y cells, both the basal and the carbachol-stimulated release of the amyloid precursor protein were blocked by batimastat. In contrast, neither the level of full-length amyloid precursor protein nor its cleavage by beta-secretase were inhibited by any of the zinc metalloprotease inhibitors examined. In transfected IMR-32 cells, the release of both the amyloid precursor protein and angiotensin converting enzyme was inhibited by batimastat, marimastat, and BB2116 with I50 values in the low micromolar range, while batimastat and BB2116 inhibited the release of both proteins from HUVECs. The profile of inhibition of alpha-secretase by batimastat and structurally related compounds is identical with that observed with the angiotensin converting enzyme secretase suggesting that the two are closely related zinc metalloproteases.

Physiologic skin changes during pregnancy: a study of 140 cases

BACKGROUND

The endocrine, metabolic, and immunologic changes during pregnancy give rise to a number of physiologic cutaneous changes.

OBJECTIVE

We evaluated 140 pregnant women to determine the pattern of pregnancy-induced physiologic skin changes in our community.

RESULTS

The various changes observed include: increased pigmentation (90.7%), striae (77.1%), edema (48.5), melasma (46.4%), vascular changes (34.2%), and others.

CONCLUSIONS

Pigmentary changes were the most common finding, whereas the incidence of vascular changes was quite low (p < 0.01).

Characterization of the glycosylation profiles of Alzheimer's beta -secretase protein Asp-2 expressed in a variety of cell lines

Amyloid 39-42 beta -peptides are the main components of amyloid plaques found in the brain of Alzheimer's disease patients. Amyloid 39-42 beta-peptide is formed from amyloid precursor protein by the sequential action of beta- and gamma-secretases. Asp-2 is a transmembrane aspartic protease expressed in the brain, shown to have beta-secretase activity. Mature Asp-2 has four N-glycosylation sites. In this report we have characterized the carbohydrate structures in this glycoprotein expressed in three different cell lines, namely Chinese hamster ovary, CV-1 origin of SV40, and baculovirus-infected SF9 cells. Biantennary and triantennary oligosaccharides of the "complex" type were released from glycoprotein expressed in the mammalian cells, whereas mannose-rich glycans were identified from glycoprotein synthesized in the baculovirus-infected cells. Site-directed mutagenesis of the asparagine residues at amino acid positions 153, 172, 223, and 354 demonstrate that the protease activity of Asp-2 is dependent on its glycosylation.

Water turbidity sensing using a smartphone

Smartphone based platform turbidimeter measuring turbidity in drinking and different environmental water bodies.

A critical review on relationship of CeO2-based photocatalyst towards mechanistic degradation of organic pollutant

Nanostructured photocatalysts commonly offered opportunities to solve issues scrutinized with the environmental challenges caused by steep population growth and rapid urbanization. This photocatalyst is a controllable characteristic, which can provide humans with a clean and sustainable ecosystem. Over the last decades, one of the current thriving research focuses on visible-light-driven CeO₂-based photocatalysts due to their superior characteristics, including unique fluorite-type structure, rigid framework, and facile reducing oxidizing properties of cerium's tetravalent (Ce⁴⁺) and trivalent (Ce³⁺) valence states. Notwithstanding, owing to its inherent wide energy gap, the solar energy utilization efficiency is low, which limits its application in wastewater treatment. Numerous modifications of CeO₂ have been employed to enhance photodegradation performances, such as metals and non-metals doping, adding support materials, and coupling with another semiconductor. Besides, all these doping will form a different heterojunction and show a different way of electron-hole migration. Compared to conventional heterojunction, advanced heterojunction types such as p-n heterojunction, Z-scheme, Schottky junction, and surface plasmon resonance effect exhibit superior performance for degradation owing to their excellent charge carrier separation, and the reaction occurs at a relatively higher redox potential. This review attends to providing deep insights on heterojunction mechanisms and the latest progress on photodegradation of various contaminants in wastewater using CeO₂-based photocatalysts. Hence, making the CeO₂ photocatalyst more foresee and promising to further development and research.

Characterization of detergent-insoluble complexes containing the familial Alzheimer's disease-associated presenilins

Many cases of early-onset familial Alzheimer's disease have been linked to mutations within two genes encoding the proteins presenilin-1 and presenilin-2. The presenilins are 48-56-kDa proteins that can be proteolytically cleaved to generate an N-terminal fragment (approximately 25-35 kDa) and a C-terminal fragment (approximately 17-20 kDa). The N- and C-terminal fragments of presenilin-1, but not full-length presenilin-1, were readily detected in both human and mouse cerebral cortex and in neuronal and glioma cell lines. In contrast, presenilin-2 was detected almost exclusively in cerebral cortex as the full-length molecule with a molecular mass of 56 kDa. The association of the presenilins with detergent-insoluble, low-density membrane microdomains, following the isolation of these structures from cerebral cortex by solubilization in Triton X-100 and subsequent sucrose density gradient centrifugation, was also examined. A minor fraction (10%) of both the N- and C-terminal fragments of presenilin-1 was associated with the detergent-insoluble, low-density membrane microdomains, whereas a considerably larger proportion of full-length presenilin-2 was present in the same membrane microdomains. In addition, a significant proportion of full-length presenilin-2 was present in a high-density, detergent-insoluble cytoskeletal pellet enriched in beta-actin. The presence of the presenilins in detergent-insoluble, low-density membrane microdomains indicates a possible role for these specialized regions of the membrane in the lateral separation of Alzheimer's disease-associated proteins within the lipid bilayer and/or in the distinct functions of these proteins.

Nitric oxide synthase activity and mRNA expression in chicken macrophages

The activity of inducible nitric oxide synthase (iNOS) enzyme was quantified in chicken macrophages. Macrophages from Cornell K-strain (B15B15), GB1 (B13B13), and GB2 (B6B6) chickens and a transformed cell line (MQ-NCSU) were incubated with or without varying concentrations of bacterial lipopolysaccharide (LPS). The culture supernatants were tested for the presence of nitrite. Macrophages from either source produced minimal nitrite (< 4.4 microM/1 x 10(6) cells) levels without LPS stimulation. However, nitrite levels produced by K-strain (42 microM) and MQ-NCSU (41 microM) macrophages were higher (P < 0.05) than those produced by the GB1 (14 microM) and GB2 (14 microM) per 1 x 10(6) macrophages with optimum LPS concentration range of 50 ng to 1 microgram/mL. The addition of an L-arginine analog, NGMMLA, at a concentration of 200 microM completely abolished nitrite production. The addition of 10% vol/vol lymphokines exhibited an additive effect on nitrite production in conjunction with LPS. The increased nitrite production by the K-strain and MQ-NCSU macrophages corresponded to an increased expression of iNOS mRNA as compared to the mRNA produced by GB1 and GB2 macrophages. The iNOS mRNA kinetics study revealed that mRNA levels peaked between 6 to 12 h. The cells from avian lymphoid lineage failed to produce any detectable iNOS activity. These studies showed that macrophages from varying sources differ in NOS activity and implied that genetic background may dictate the extent of arginine-mediated contribution in various biological and immunological functions.

An open clinical pilot study of the efficacy and safety of oral terbinafine in dry non-inflammatory tinea capitis

Ten patients with dry non-inflammatory tinea capitis were evaluated in a pilot study which ran from September 1989 to February 1990. Each patient was given oral terbinafine for 6 weeks; each was followed up 2 weeks later. Eight (80%) were completely cured, one (10%) was mycologically cured and showed minimal signs and symptoms, and another (10%) showed improvement (negative mycology, but persistent clinical signs and symptoms). No topical or systemic side-effects were noted. Terbinafine appears to be an effective and safe antifungal agent in the treatment of non-inflammatory tinea capitis.

Staphylococcus aureus re-colonization in atopic dermatitis: beyond the skin

Patients with atopic dermatitis (AD) are often heavily colonized by Staphylococcus aureus, which adversely affects eczema severity. Strategies to control S. aureus in AD include antibiotic and or antiseptics. However long-term efficacy is unclear. In this study we consider extra-cutaneous factors that may cause S. aureus re-colonization in adult AD. Twenty-one patients with AD were recruited and were assessed for: duration of AD, use of topical or oral antibiotic within the preceding 3 months, the number of hospital admissions during the preceding year and current treatment. The types of topical treatments used, vehicle, container and the expiry dates were also recorded. The severity of AD was assessed by SCORAD index. Microbiological assessment for S. aureus carriage from affected skin, anterior nares, emollient and topical steroid was undertaken using culture, Staphaurex test and antibiotic resistance. Of the patients 86% had S. aureus colonization. The median SCORAD score were greater in those colonized with S. aureus (P = 0.02) and those with contaminated treatments (P = 0.05). Prior antibiotic treatment, prior hospital admission and nasal carriage did not influence the median SCORAD. Three extra-cutaneous mechanisms by which S. aureus can re-colonize the skin were identified: antibiotic resistance, nasal carriage and treatment contamination.

Survey of artemisinin production by diverse Artemisia species in northern Pakistan

Background

Artemisinin is the current drug of choice for treatment of malaria and a number of other diseases. It is obtained from the annual herb, Artemisia annua and some microbial sources by genetic engineering. There is a great concern that the artemisinin production at current rate will not meet the increasing demand by the pharmaceutical industry, so looking for additional sources is imperative.

Methods

In current study, artemisinin concentration was analysed and compared in the flowers, leaves, roots and stems of Artemisia annua and 14 other Artemisia species including two varieties each for Artemisia roxburghiana and Artemisia dracunculus using high performance liquid chromatography (HPLC).

Results

The highest artemisinin concentration was detected in the leaves (0.44 ± 0.03%) and flowers (0.42 ± 0.03%) of A. annua, followed by the flowers (0.34 ± .02%) of A. bushriences and leaves (0.27 ± 0%) of A. dracunculus var dracunculus. The average concentration of artemisinin varied in the order of flowers > leaves > stems > roots.

Conclusion

This study identifies twelve novel plant sources of artemisinin, which may be helpful for pharmaceutical production of artemisinin. This is the first report of quantitative comparison of artemisinin among a large number of Artemisia species.

The wound healing and antibacterial potential of triple-component nanocomposite (chitosan-silver-sericin) films loaded with moxifloxacin

AIM

The current study reports the development and evaluation of chitosan-sericin-silver nanocomposite (CSSN) films without and with moxifloxacin (Mox).

METHODOLOGY

The film preparation method involved the in-situ synthesis of silver nanoparticles within the chitosan-sericin colloidal composite followed by preparation into a film by solvent casting technique. In-situ formation and the particle size analysis of the silver nanoparticles was performed via UV-Visible and zeta-size spectrometer. The prepared films were tested for swelling ratio, contents uniformity, in-vitro Mox release, and permeation analysis. The morphological (SEM), elemental (EDX), spectral (FT-IR), structural (XRD), and thermal (TGA and DSC) properties of the composites were also inspected. The antibacterial activity of the CSSN films was performed against seven pathogenic bacterial strains including five ATCC and two clinical strains. The potential wound healing activity of the composite films was evaluated on burn wound model induced in Sprague Dawley male rats.

RESULTS

The prepared films displayed good swelling profile with a sustained in-vitro Mox release and permeation profile; attaining maximum of 78.57% (CSSM3) release and 55.05% (CSSM1) permeation (CSSM1) in 24 h. The prepared films, particularly the Mox-loaded CSSN films displayed a promising antibacterial activity against all the tested strains with the activity being highest against MRSA (clinical isolates). The prepared films indicated a remarkable wound healing applications with successful fibrosis, collagen reorganization, neovascularization, and mild epidermal regeneration after 7 days of treatment with no silver ions detection in animal's blood.

CONCLUSION

The obtained findings strongly suggest the use of the prepared novel composite dressing for wound care applications.

The expression and regulation of inducible nitric oxide synthase gene differ in macrophages from chickens of different genetic background

It has been previously reported that lipopolysaccharide (LPS)-stimulated macrophages from Cornell K-Strain chickens (B15B15) and a transformed cell line, MQ-NCSU, (broiler origin) produced significantly higher levels of inducible nitric oxide synthase (iNOS) mRNA than macrophages isolated from GBI (B13B13) and GB2 (B6B6) chickens. The purpose of this study was to determine the basis of such differential iNOS gene expression and to study the relationship of high or low expression of iNOS mRNA with iNOS enzyme activity in macrophages from GB2 (low iNOS mRNA expresser), K-strain and MQ-NCSU (high iNOS mRNA expressers). The enzyme activity in lysates from LPS-stimulated macrophages was lower in GB2 (range: 23 to 41 microM, P < 0.05) as compared with the K-strain and MQ-NCSU macrophages that exhibited intermediate (range: 27 to 59 microM) and the highest (range: 144 to 217 microM) activity, respectively. Total RNA collected from LPS-treated macrophages at various time-points post-actinomycin D treatment revealed comparable iNOS mRNA levels in MQ-NCSU, GB2, and K-strain macrophages, suggesting that post-transcriptional regulation mechanism(s) do not account for the difference in iNOS mRNA expression. To determine if differences in the transcription rate are the basis of the differential iNOS gene expression, macrophages were stimulated with or without LPS and nuclei-isolated. Inducible NOS mRNA probes were generated and hybridized with immobilized iNOS cDNA (reverse Northern blot). The resulting lumigraph yielded enhanced transcriptional activity from K-strain and MQ-NCSU macrophages whereas this activity was lower in GB2 macrophages. Therefore, these studies suggest that the previously reported genetically-based difference in iNOS mRNA expression further translates into differences in iNOS enzyme activity, and that the iNOS gene in chickens is transcriptionally regulated.

Onychomycosis in Lahore, Pakistan

BACKGROUND

Onychomycosis, a common nail disorder, is caused by yeasts, dermatophytes, and nondermatophyte molds. These fungi give rise to diverse clinical presentations. The present study aimed to isolate the causative pathogens and to determine the various clinical patterns of onychomycosis in the population in Lahore, Pakistan.

PATIENTS

In 100 clinically suspected cases, the diagnosis was confirmed by mycologic culture. Different clinical patterns were noted and correlated with causative pathogens.

RESULTS

Seventy-two women (mean age, 32.6 +/- 14.8 years) and 28 men (mean age, 40.6 +/- 15.8 years) were studied. Fingernails were involved in 50%, toenails in 23%, and both fingernails and toenails in 27% of patients. The various clinical types noted were distolateral subungual onychomycosis (47%), candidal onychomycosis (36%), total dystrophic onychomycosis (12%), superficial white onychomycosis (3%), and proximal subungual onychomycosis (2%). Candida was the most common pathogen (46%), followed by dermatophytes (43%) (Trichophyton rubrum (31%), T. violaceum (5%), T. mentagrophytes (4%), T. tonsurans (2%), and Epidermophyton floccosum (1%) and nondermatophyte molds (11%) (Fusarium (4%), Scopulariopsis brevicaulis (2%), Aspergillus (2%), Acremonium (1%), Scytalidium dimidiatum (1%), and Alternaria (1%).

CONCLUSIONS

Onychomycosis is more common in women of 20-40 years of age. Distolateral subungual onychomycosis and candidal onychomycosis are the most common clinical presentations, and Candida and T. rubrum are the major pathogens in Pakistan.

Canalicular infection caused by Actinomyces

We present 7 cases of canalicular involvement with Actinomyces collected over a 5-year period. All patients had involvement of one canaliculus, upper or lower, with lacrimal drainage patent to syringing. Curettings obtained by incising the involved canaliculi yielded Actinomyces species (5 cases) and Arachnia propionica (2 cases), typically in association with a mixed bacterial growth. Our results show that these patients often remain undiagnosed for months or even years, and are treated inappropriately for their recurrent symptoms. Despite sensitivity of Actinomyces to a broad spectrum of antibiotics, medical therapy alone does not eradicate the disease, and surgical evacuation of all concretions is essential to achieve a cure.

A double-blind, randomized, comparative trial of itraconazole versus terbinafine for 2 weeks in tinea capitis

In this randomized, double-blind study, the efficacy and safety of oral itraconazole (n = 28) and terbinafine (n = 27), each given for 2 weeks, was compared in patients with tinea capitis. Trichophyton violaceum was the major pathogen in both groups (82.1% and 88.9%, respectively). The final evaluation at week 12 showed a cure rate of 85.7% and 77.8%, respectively (P > 0.05). Adverse events noted were mild and did not warrant discontinuation of therapy.