Silencing of sigma-1 receptor induces cell death in human lens cells

Sigma receptors have no known homology with other receptor systems, have no known natural ligands, but appear to play a critical role in a large diversity of cell functions. In the absence of a conventional pharmacology, siRNA technology provides a direct means of elucidating the major cell signaling pathways influenced by this receptor system. The non-transformed human lens cell line FHL124 was found to express the sigma-1 receptor (Sig-1R) and was employed for these studies. 72 h of transfection with either of the two siRNA directed against the sigma-1 receptor reduced messenger RNA and protein levels by over 70 and 60% respectively. Subsequent incubation for 96 h in culture medium (EMEM) supplemented with 5% serum gave a partial recovery of message, but there was no significant increase in protein. LDH leakage assays showed that significant cell death occurred during this time with an increased expression of caspase-3. Thrombin (10 nM) drives the growth of lens cells with a concomitant increase in ERK and Akt phosphorylation. These increases were inhibited in the cells where knockdown had occurred but not in cells exposed to scrambled siRNA. This study establishes a central role for Sig-1R in cell survival and death.

A focus on the human lens in vitro

The lens is a unique organ in that it is avascular and non-innervated, obtaining all nutrients from the aqueous and vitreous humours that bathe the lens. All lenses attempt to achieve the same goal, namely to maintain transparency and focus light on to the retina. However, the mechanisms by which these processes are maintained, or disrupted leading to a loss of transparency, are likely to differ in some cases between animals and humans. To allow comparison to take place, human in vitro models have been developed, ranging from whole organ culture to the generation of human lens cell lines. All have their merits and limitations, but as a whole, they permit extensive studies of lens cell behaviour and function to be carried out. Together, these in vitro methods allow the biological events of the lens to be further understood. Moreover, they could help identify the mechanisms that give rise to cataract and posterior capsule opacification, a problem that occurs following surgery, providing therapeutic targets for their prevention.

Nucleolar localization of potato leafroll virus capsid proteins

Potato leafroll virus (PLRV) encodes two capsid proteins, major protein (CP) and minor protein (P5), an extended version of the CP produced by occasional translational 'readthrough' of the CP gene. Immunogold electron microscopy showed that PLRV CP is located in the cytoplasm and also localized in the nucleus, preferentially targeting the nucleolus. The nucleolar localization of PLRV CP was also confirmed when it was expressed as a fusion with green fluorescent protein (GFP) via an Agrobacterium vector. Mutational analysis identified a particular sequence within PLRV CP involved in nucleolar targeting [the nucleolar localization signal (NoLS)]. Minor protein P5 also contains the same NoLS, and was targeted to the nucleolus when it was expressed as a fusion with GFP from Agrobacterium. However, P5-GFP lost its nucleolar localization in the presence of replicating PLRV.

Divergent mechanisms of cis 9, trans 11 ‐ and trans 10 , cis 12 ‐ conjugated linoleic acid affecting insulin resistance and inflammation in apolipoprotein E knockout mice: a proteomics approach

Conjugated linoleic acids (CLA) affect atherogenesis, but mechanisms are not well understood. We explored how two isomers of CLA, cis9, trans11-CLA and trans10, cis12-CLA, affected lipid and glucose metabolism, as well as hepatic protein expression, in apolipoprotein E knockout mice. After 12 wk of intervention, plasma triglyceride, NEFA, and glucose concentrations were significantly higher in the trans10, cis12-CLA group, whereas plasma triglyceride, NEFA, glucose, and insulin concentrations were significantly lower in the cis9, trans11-CLA group, compared with control mice consuming linoleic acid. Proteomics identified significant up- or down-regulation of 113 liver cytosolic proteins by either CLA isomer. Principal component analysis revealed that the treatment effect of cis9, trans11-CLA was mainly explained by the up-regulation of different posttranslational forms of heat shock protein 70 kD. In contrast, the treatment effect of trans10, cis12-CLA was mainly explained by up-regulation of key enzymes in the gluconeogenic, beta-oxidation, and ketogenesic pathways. Correlation analysis again emphasized the divergent effects of both CLA isomers on different pathways, but also revealed a linkage between insulin resistance and increased levels of hepatic serotransferrin. Thus, our systems biology approach provided novel insights into the mechanisms by which individual CLA isomers differentially affect pathways related to atherogenesis, such as insulin resistance and inflammation.

Growth factor receptor signalling in human lens cells: role of the calcium store

In the human lens, stimulation of tyrosine-kinase coupled growth factor receptors such as epidermal growth factor receptor (EGFR) can induce calcium release from endoplasmic reticulum (ER) stores. The present study investigated the impact of calcium store inactivation on EGFR signalling, cell growth and death in a well-characterised human lens cell line (FHL124). FHL124 cells were routinely cultured in Eagle's minimum essential medium (EMEM) supplemented with 10% foetal calf serum (FCS) and seeded on 24-well plates (DNA and protein synthesis), tissue culture dishes (growth assay, western immunoblot), and glass coverslips (immunocytochemistry). DNA and protein synthesis rates were quantified by measuring the incorporation of (3)H-thymidine and (35)S-methionine into FHL124 cells in serum-free EMEM or EMEM supplemented with thapsigargin (Tg) (100 nM and 1 microM). Longer-term growth was assessed by quantifying the increase in area over time of a circular patch of seeded cells. EGFR was identified using anti-EGFR mouse monoclonal antibody and visualised by fluorescence microscopy with ALEXA 488 conjugated secondary antibody. Programmed cell death was determined by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay method. Activation of the mitogen-activated protein kinase (MAPK) signalling protein extracellular signal-regulated kinase (ERK) and the cell cycle proteins CDK2 and P27(kip1) were detected by western immunoblot techniques. Inactivation by > or =100 nM Tg inhibited both protein and DNA synthesis although the effect on the latter was greatest. The cell cycle activator CDK2 was reduced by Tg, while the inhibitor P27(kip1) was increased along with the percentage of apoptotic cells. A single, maximal epidermal growth factor (EGF) (10 ng ml(-1)) exposure induced receptor internalization and increased ERK phosphorylation. Both internalisation and ERK activation were unaffected by the presence of Tg. However, reduced internalisation and ERK activation followed repeated EGF applications in the presence of Tg. Additionally, ERK activation by submaximal EGF concentrations was reduced by store depletion. An intact endoplasmic reticulum calcium store therefore plays a significant role in human lens cell survival and growth.

Potentiation of ATP-induced Ca2+ mobilisation in human retinal pigment epithelial cells

Interaction of signalling pathways directs the functional output of many cells. This study investigated the consequences of activating adenosine and adrenergic receptors on ATP-induced Ca2+ responses in human retinal pigment epithelial (RPE) cells. Intracellular Ca2+ concentration ([Ca2+]i) of human RPE cells in primary culture was monitored using Fura-2. Cyclic adenosine monophosphate (cAMP) concentration was measured using an enzyme-linked immunosorbent assay. Both ATP and UTP (10 microM) increased [Ca2+]i in human RPE cells. Adenosine (10 nM-10 microM) had no effect on resting [Ca2+]i, but potentiated a sub-threshold response to ATP (100 nM) when ATP was added in the presence of adenosine. The potentiation occurred with other G-protein receptor agonists such as acetylcholine. Potentiation persisted in Ca-free medium, but was blocked by prior application of thapsigargin. The A1 and A2 adenosine receptor antagonists, DPCPX and MRS1706 (100 nM) respectively, inhibited potentiation in 76+/-7 and 23+/-12% of cells, respectively, but the A3 antagonist MRS1191 had no effect. Conversely, agents that activate the cAMP pathway, including isoproterenol (10 microM), forskolin (10 microM), and the protein kinase A (PKA) activator Sp-cBIMPS (1 microM), potentiated the ATP-induced response in the RPE cells. Agents that are known to inhibit the production of cAMP in other systems also caused potentiation, including clonidine (10 microM) and the Gi-activator mastoparan (10 microM). Under resting conditions, cAMP concentration in RPE cells was 7.1+/-0.5 pmol mg(-1) protein. Isoproterenol (10 microM) and forskolin (10 microM) increased levels to 104.6+/-5.2 and 113.7+/-4.2 pmol mg(-1) protein, respectively, while adenosine, clonidine, and mastoparan (all 10 microM) had no significant effect on cAMP levels. These data indicate that whilst activation of A1 and A2 adenosine receptors and alpha2 and beta adrenergic receptors does not influence basal Ca2+ levels, stimulation of these receptors can potentiate Ca2+ signalling by cAMP dependent and independent mechanisms in human RPE cells.

Sigma receptor antagonists inhibit human lens cell growth and induce pigmentation

PURPOSE

The expression of the Sigma 1 receptor and the ability of receptor antagonists to inhibit growth and induce pigment formation were investigated in human lens epithelial cells.

METHODS

Capsular bags were formed for experimental purposes by performing sham cataract operations on donor lenses. The resultant bags were cultured in Eagle's minimum essential medium (EMEM) alone or supplemented with the Sigma receptor antagonists rimcazole (3 microM) and BD1047 (10 microM). Cell growth was monitored by phase microscopy. Tyrosine incorporation was quantified by culturing in the presence of 14-C tyrosine for 24 hours. At the end of the culture period, some bags were fixed in 4% paraformaldehyde for electron microscopy, and others were plunged into liquid nitrogen for later immunoblot and PCR analyses. Protein levels of tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2) were quantified by Western blot analysis. The presence of pigment granules within epithelial cells were monitored by phase and electron microscopy techniques.

RESULTS

The Sigma-1 receptor was expressed in native human lens cells and in cultured capsular bag cells. The Sigma receptor antagonists BD1047 and rimcazole inhibited lens cell growth and, surprisingly, lens cells accumulated pigment granules in the presence of the antagonists. The antagonists raised preexisting levels of TYR and TYRP1, whereas there was no change in TYRP2.

CONCLUSIONS

The human lens normally expresses components of the melanin synthesis pathway, and this suggests a possible origin for the pigment granules that have been observed under certain conditions in the human lens. Exposure of lens cells to Sigma receptor antagonists leads to growth inhibition and pigment granule production.

Characterization and Functional Activity of Thrombin Receptors in the Human Lens

PURPOSE

To investigate the expression of thrombin receptors in the human lens, the activation of downstream signaling pathways, and the ability of thrombin to regulate lens cell growth.

METHODS

Thrombin receptor function in the human lens was determined first by measuring changes in intracellular calcium in response to thrombin and protease-activated receptor-activating peptides (PAR-APs). In the human capsular bag model, cell growth was assessed by phase microscope inspection of the cell coverage of the posterior capsular surface. In the human lens cell line FHL124, it was assessed by [(3)H]thymidine incorporation. Changes in p42/p44 ERK phosphorylation (p-ERK) and protein kinase B (PKB/Akt) phosphorylation (p-Akt) were monitored by Western blot. Reverse transcription-polymerase chain reaction (RT-PCR) applied to isolated lens epithelia and ex vivo capsular bag preparations as well as FHL124 cells determined expression of mRNA for the PARs.

RESULTS

Brief exposures to thrombin (10 nM) and PAR1-AP (10 microM) induced an increase in cytosolic calcium in both anterior and equatorial lens cells, but activating peptides for PAR2, -3, and -4 failed to produce responses. Repeated exposure to thrombin produced a significant increase in cell coverage in the capsular bag model and increased [(3)H]thymidine incorporation into FHL124 cells. In the latter, exposure to thrombin (10 nM) and PAR1-AP (10 microM) induced biphasic increases in the phosphorylation of p42/p44 (p-ERK), with peak responses at 20 minutes and 12 hours. Thrombin also produced a 20-fold increase in p-Akt at 12 hours compared with the control, whereas PAR1-AP (10 microM) induced a much smaller response. PAR1-AP did not induce a significant increase in [(3)H]thymidine incorporation and PAR2-AP, PAR3-AP, and PAR4-AP failed to reproduce any of the thrombin-stimulated effects. mPAR1 and -3 were expressed in native lens cells, and this expression was conserved in ex vivo capsular bag preparations as well as in FHL124 cells.

CONCLUSIONS

This study identifies thrombin receptors coupled to calcium, ERK, and Akt signaling that modulate growth in native lens tissue and cultured cells, and it appears that the PAR1 subtype is mainly responsible. PAR3 mRNA was also detected, but the receptor itself, if present, was not coupled to the above signaling elements.

Stress-induced ATP release from and growth modulation of human lens and retinal pigment epithelial cells

ATP release has been shown to occur following stimulation in several cellular systems. This study was undertaken to determine if lens and retinal epithelial cells release ATP in response to physiological stresses and to elucidate a possible role for ATP. Analysis of human aqueous humour samples showed a mean ATP level of 37.8+/-7.7 nM. Hyper-osmotic stress induced a dose- and time-dependent release of ATP. Both cell types were found to proliferate in serum-free medium, and the addition of ATP and adenosine at concentrations as low as 0.1 nM inhibited growth. Gene profiling also demonstrated the presence of the ectonucleotidases CD39 and CD73 and the A1 adenosine receptor on both cell types.

Regional Differences in Tyrosine Kinase Receptor Signaling Components Determine Differential Growth Patterns in the Human Lens

PURPOSE

The lens epithelium can be separated into two regions, the nondividing central zone and the equator, the site of all division in the normal lens. In the present study, the distribution of epithelial growth factor (EGF)/epithelial growth factor receptor (EGFR) signaling components was investigated and related to mitotic distribution in the lens.

METHODS

Anterior and equatorial regions of the native epithelium were prepared separately from donor lenses. In vitro capsular bags were prepared from donor eyes and cultured. Receptor distribution was determined by immunocytochemistry and RT-PCR. Western blot analysis of phospholipase C (PLC)-gamma and extracellular signal-regulated kinase (ERK; total and active) was performed on cell lysates. Function was determined by calcium imaging of Fura-2-AM-loaded cells and also, in the case of capsular bags, by cell growth.

RESULTS

Immunocytochemistry and RT-PCR showed an even distribution of EGFR across the native epithelium. Whole lenses, however, exhibited only a calcium response to EGF (10 ng/mL) at the equatorial region. Western blot analysis demonstrated significantly greater expression of PLCgamma and ERK (total and active) in the equator than in the central region. Addition of EGF increased growth rates of cells in capsular bags and an EGFR inhibitor decreased rates. EGF also induced a calcium response in posterior capsule cells in the capsular bags.

CONCLUSIONS

EGFR is evenly distributed across the entire epithelium, whereas related calcium signaling and expression of PLCgamma and ERK have a marked bias to the equator. Therefore, levels of downstream enzyme components rather than changes in receptor expression dictate EGFR signaling output in the normal lens. In the wounded lens (capsular bag) EGFR signaling persists in cells growing on the posterior capsule.

Bacteraemia and antibiotic use in respiratory syncytial virus infections

AIMS

To examine the frequency of and risk factors for bacteraemia in children hospitalised with respiratory syncytial virus (RSV) infection; and to determine current use of antibiotics in hospitalised children with RSV infection.

METHODS

Retrospective study of all children, aged 0-14 years, admitted to a tertiary children's hospital with proven RSV infection over a four year period. Children with concurrent bacteraemia and RSV infection were identified, and risk factors examined for bacteraemia. The case notes of a randomly selected comparison sample of 100 of these RSV infected children were examined to assess antibiotic use and population incidence of risk factors for severe RSV infection.

RESULTS

A total of 1795 children had proven RSV infection, and blood cultures were sent on 861 (48%). Eleven (0.6%) of the 1795 RSV positive children had bacteraemia. RSV positive children had a significantly higher incidence of bacteraemia if they had nosocomial RSV infection (6.5%), cyanotic congenital heart disease (6.6%), or were admitted to the paediatric intensive care unit (2.9%). Forty five (45%) of the random comparison sample of RSV infected children received antibiotics.

CONCLUSIONS

Bacteraemia is rare in RSV infection. Children with RSV infection are more likely to be bacteraemic, however, if they have nosocomial RSV infection, cyanotic congenital heart disease, or require intensive care unit admission.

Characterisation of TGF-β2 signalling and function in a human lens cell line

There is increasing evidence implicating Transforming growth factor beta (TGF-beta) in pathological states of the lens. However, the underlying signalling mechanisms in human cells have not been fully examined. We have therefore investigated in a human lens cell line, FHL 124, the signalling characteristics of TGF-beta and Smad proteins. Moreover, we have tested the effectiveness of a fully human monoclonal anti-TGF-beta2 antibody, CAT-152, in suppressing TGF-beta2 induced changes in a number of conditions. FHL 124 cells were routinely cultured in Eagle's minimum essential medium (EMEM) supplemented with 10% FCS. Characterisation of the cell line was determined using Affymetrix gene microarrays and compared to native human lens epithelium. Cells were serum starved for 24 hr prior to exposure to TGF-beta2 in the presence and absence of CAT-152. Non-stimulated cells served as controls. Smad 4 localisation was observed by immunocytochemistry. To study Smad-dependent transcriptional activity, cells were transfected with SBE4-luc, an artificial smad-specific reporter, using Fugene-6. Transcriptional activity was determined by luciferase activity. Gene expression was assessed using reverse transcriptase-polymerase chain reaction (RT-PCR). Proliferation was determined by 3H-thymidine DNA incorporation. Growth and contraction were assessed using a scratch and patch assay. Affymettrix gene microarrays identified 99.5% homology between FHL 124 cells and the native lens epithelium with respect to expression pattern of the 22,270 genes on the chip. Moreover, FHL 124 cells expressed phenotypic markers, alphaA-crystallin and pax6 along with lens epithelial cell specific marker FoxE3. Immunocytochemical studies revealed the presence of Smad 4 which following TGF-beta2 exposure accumulated in the cell nucleus. Furthermore, Smad-dependent transcriptional activity was also stimulated. TGF-beta2 enhanced the expression of mRNA levels of alpha smooth muscle actin (alphaSMA) and connective tissue growth factor (CTGF). Exposure to TGF-beta2 resulted in a relatively small inhibition of 3H-thymidine incorporation of FHL 124 cells. However, a more marked contractile effect was also observed. In serum-supplemented medium, growth rates and TGF-beta induced contraction were enhanced. Treatment with 0.1-10 microg ml(-1) CAT-152 dose-dependently inhibited 10 ng ml(-1) TGF-beta2 induced effects in the presence and absence of serum. Exposure of FHL 124 cells to TGF-beta therefore induces Smad translocation, transcription, expression of transdifferentiation markers and induces marked contraction. Treatment with CAT-152 can effectively inhibit these responses. TGF-beta2 induced changes can also persist long after the period of exposure and when in the presence of serum TGF-beta induced contraction is enhanced. The work presented therefore demonstrates a platform technology to study TGF-beta2 signalling in human lens epithelial cells and provides evidence to show TGF-beta2 can be a potent factor in the development of posterior capsule opacification following cataract surgery.

Spatial characteristics of receptor-induced calcium signaling in human lens capsular bags

PURPOSE

Despite recent improvements in intraocular lens (IOL) design, posterior capsule opacification (PCO) arising from lens cell growth remains a major problem. Calcium signaling has been shown to play a major role in driving human lens cell growth, and therefore it is necessary to understand the underlying mechanisms.

METHODS

Calcium signaling was studied in capsular bags (ex vivo) removed from donors who had undergone earlier cataract surgery. Fresh capsular bags were also produced from intact donor lenses and cultured in serum-free EMEM for up to 8 weeks. Both preparations were loaded with Fura-2, and ratiometric imaging of cytoplasmic calcium was performed using epifluorescence techniques. Changes were monitored in response to 10 microM ATP (adenosine triphosphate), 10 microM acetylcholine, and 10 ng/mL epidermal growth factor (EGF), and data were collected from equatorial, posterior, and anterior regions. Calcium transients were also recorded from anterior epithelial specimens in response to pilocarpine.

RESULTS

All equatorial cells of ex vivo bags responded to ATP and EGF, but not to acetylcholine, and this pattern was maintained in the cultured bags. Posterior capsule cells of both preparations also had similar properties, in which a large proportion of the cells responded to ATP and EGF, but not to acetylcholine. Conversely, most anterior cells of the in vivo bags responded to pilocarpine, whereas no cells in the cultured bags responded. All cells in the fresh anterior epithelium responded to pilocarpine.

CONCLUSIONS

Ex vivo capsular bags retain the region-specific calcium-signaling characteristics of the native lens. Apart from losing M1 muscarinic expression properties, the in vitro capsular bags also reflect region-specific signaling properties and therefore provide a good model for the investigation of the contribution of calcium-signaling to PCO.

A new method to obtain epithelial and stromal explants from human Corneo-Scleral Discs for the routine culture of corneal epithelial and fibroblast cells

Acquisition of human corneal cells for culture is hindered not only by the scarcity of donor tissues but also by some of the standard enzymatic and mechanical isolation techniques. Good yields have been reported from full-thickness explant and sclero-limbal pieces. However, due to their greater proliferative capacity, fibroblasts will encroach and subsequently overwhelm epithelial cultures whichever technique is used. The novel approach presented here is to minimise this by removal of the whole stroma from the epithelial layers at the outset. This is achieved by selective sectioning with the Webb mini-microtome developed in the Norwich Eye Research Laboratory. The microtome can be sterilised by alcohol spraying or autoclaving and is small enough to use in the culture hood. A selective cut in the region of the Bowman's membrane results in the isolation of the epithelium from the stroma and thus exposed, the basal epithelial layers are released from contact inhibition to allow growth. The stroma is further cut to produce multiple sections for the culture of fibroblasts. Both pure epithelial and stromal fibroblast cultures have been successfully generated in serum-enriched medium as well as defined serum-free media with growth supplements, from the corneo-scleral discs of donors of all ages.

D1S80 Single-Locus Discrimination Among African Populations

The highly polymorphic D1S80 locus has no known genetic function. However, this variable number of tandem repeats (VNTR) locus has been highly valuable in forensic identification. In this study we report the allele and genotype frequencies of five African populations (Benin, Cameroon, Egypt, Kenya, and Rwanda), which can be used as databases to help characterize populations and identify individuals. The allele frequencies were used to infer genetic associations through phylogenetic, principal component, and G test statistical analyses. Compliance with Hardy-Weinberg equilibrium expectations was determined as were F(ST) estimates, theta p values, and power of discrimination assessment for each population. Our analyses of 28 additional populations demonstrate that the D1S80 locus alone can be used to discriminate geographic and ethnic groups. We have generated databases useful for human identification and phylogenetic studies.

Nasal fracture manipulation: a comparative study of general and local anaesthesia techniques

Nasal injuries are common conditions treated in either Otolaryngology or Plastic Surgical departments. Manipulation for deformity can be conducted in various ways. The aim of this study is to determine if the anaesthetic technique used for manipulation influences outcomes. Five hundred and fifty-five patients had either local anaesthetic (LA) or general anaesthetic (GA) nasal fracture manipulations in our departments over a 6-year period. Three hundred and twenty-four of these could be contacted and questioned as to subsequent surgical treatments received. Rhinoplasty, septorhinoplasty or septoplasty had been subsequently performed in 3.2% of the GA group and in 17.2% of the LA group (P < 0.0001). We recommend considering this result when treating nasal fractures in conjunction with other important issues of patient preference, financial costs, associated risks, morbidity and facilities available.

Marek's disease, candidiasis and megabacteriosis in a flock of chickens (Gallus gallus domesticus ) and Japanese quail (Coturnix japonka )

An outbreak of mortality in chickens and Japanese quail sharing the same airspace was investigated. Marek's disease was diagnosed in five of 11 chickens examined, and in 20 of 24 quail; crop candidiasis was found in four of the chickens and in five of the quail, and moderate to large numbers of organisms referred to as megabacteria were observed in eight of the chickens and 16 of the quail. The disease was so severe that almost all of the quail in the flock died or were culled during the following six months. In contrast, only approximately 5 per cent of the chickens died from Marek's disease.