Selectively coated contact lenses by nanoelectrospray (nES) to fabricate drug-eluting contact lenses for treating ocular diseases

Drug-eluting contact lenses (DECLs) incorporated with poly(lactic-co-glycolic acid) (PLGA) and various model drugs (ketotifen fumarate, bimatoprost and latanoprost) were fabricated using nanoelectrospray (nES) approach. The resulting DECLs demonstrated outstanding optical transmittance within the optical zone, indicating that the employed coating procedure did not compromise visual acuity under the prescribed spraying parameters. In vitro drug release assessments of the model drugs (ketotifen fumarate (KF), bimatoprost (BIM), and latanoprost (LN)) revealed a strong correlation between the model drug's hydrophobicity and the duration of drug release. Changing the drug loading of the more hydrophilic model drugs, BIM and KF, showed no impact on the drug release kinetics of DECLs loaded with BIM and KF. However, for the hydrophobic model drug, LN, the highest LN loading led to the most extended drug release. The conventional steam sterilisation method was found to damage the PLGA coating on the DECLs fabricated by nES. An alternative sterilisation strategy, such as radiation sterilisation may need to be investigated in the future study to minimise potential harm to the coating.

Electronic field effect detection of SARS-CoV-2 N-protein before the onset of symptoms

As part of the efforts to contain the pandemic, researchers around the world have raced to develop testing platforms to detect the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the Coronavirus disease 2019 (COVID-19). Within the different detection platforms studied, the field effect transistor (FET) is a promising device due to its high sensitivity and fast detection capabilities. In this work, a graphene-based FET which uses a boron and nitrogen co-doped graphene oxide gel (BN-GO gel) transducer functionalized with nucleoprotein antibodies, has been investigated for the detection of SARS-CoV-2 nucleocapsid (N)-protein in buffer. This biosensor was able to detect the viral protein in less than 4 min, with a limit of detection (LOD) as low as 10 ag/mL and a wide linear detection range stretching over 11 orders of magnitude from 10 ag/mL-1 μg/mL. This represents the lowest LOD and widest detection range of any COVID-19 sensor and thus can potentially enable the detection of infected individuals before they become contagious. In addition to its potential use in the COVID-19 pandemic, our device serves as a proof-of-concept of the ability of functionalized BN-GO gel FETs to be used for ultrasensitive yet robust biosensors.

30-Day postoperative COVID-19 outcomes in 398 patients from regional hospitals utilising a designated COVID-19 minimal surgical site pathway

INTRODUCTION

Postoperative pulmonary complications and mortality rates during the COVID-19 pandemic have been higher than expected, leading to mass cancellation of elective operating in the UK. To minimise this, the Guy's and St Thomas' Hospital NHS Foundation Trust elective surgery hub and the executive team at London Bridge Hospital (LBH) created an elective operating framework at LBH, a COVID-19 minimal site, in which patients self-isolated for two weeks and proceeded with surgery only following a negative preoperative SARS-CoV-2 polymerase chain reaction swab. The aim was to determine the rates of rates of postoperative COVID-19 infection.

METHODS

The collaboration involved three large hospital trusts, covering the geographic area of south-east London. All patients were referred to LBH for elective surgery. Patients were followed up by telephone interview at four weeks postoperatively.

RESULTS

Three hundred and ninety-eight patients from 13 surgical specialties were included in the analysis. The median age was 60 (IQR 29-71) years. Sixty-three per cent (252/398) were female. In total, 78.4% of patients had an American Society of Anesthesiologists grade of 1-2 and the average BMI was 27.2 (IQR 23.7-31.8) kg/m2. Some 83.6% (336/402) were 'major' operations. The rate of COVID-19-related death in our cohort was 0.25% (1/398). Overall, there was a 1.26% (5/398) 30-day postoperative all-cause mortality rate. Seven patients (1.76%) reported COVID-19 symptoms, but none attended the emergency department or were readmitted to hospital as a result.

CONCLUSION

The risk of contracting COVID-19 in our elective operating framework was very low. We demonstrate that high-volume major surgery is safe, even at the peak of the pandemic, if patients are screened appropriately preoperatively.

Ascher's syndrome: a rare cause of lip swelling

Ascher's syndrome is a rare, benign entity with just over 100 reported cases. The condition is characterised by a 'double' upper lip, blepharochalasis and non-toxic thyroid enlargement. It presents before the age of 20 years in the majority of cases and shows no racial or gender differences. While the exact cause is unknown, hormonal dysfunction and autosomal dominant inheritance have been suggested as possible aetiological factors. We present two cases of Ascher's syndrome referred for investigation of lip swelling.

Ginsenosides Act As Positive Modulators of P2X4 Receptors

We investigated the selectivity of protopanaxadiol ginsenosides from Panax ginseng acting as positive allosteric modulators on P2X receptors. ATP-induced responses were measured in stable cell lines overexpressing human P2X4 using a YOPRO-1 dye uptake assay, intracellular calcium measurements, and whole-cell patch-clamp recordings. Ginsenosides CK and Rd were demonstrated to enhance ATP responses at P2X4 by ∼twofold, similar to potentiation by the known positive modulator ivermectin. Investigations into the role of P2X4 in mediating a cytotoxic effect showed that only P2X7 expression in HEK-293 cells induces cell death in response to high concentrations of ATP, and that ginsenosides can enhance this process. Generation of a P2X7-deficient clone of BV-2 microglial cells using CRISPR/Cas9 gene editing enabled an investigation of endogenous P2X4 in a microglial cell line. Compared with parental BV-2 cells, P2X7-deficient BV-2 cells showed minor potentiation of ATP responses by ginsenosides, and insensitivity to ATP⁻ or ATP⁺ ginsenoside-induced cell death, indicating a primary role for P2X7 receptors in both of these effects. Computational docking to a homology model of human P2X4, based on the open state of zfP2X4, yielded evidence of a putative ginsenoside binding site in P2X4 in the central vestibule region of the large ectodomain.

Neuroprotective Effects of Human Mesenchymal Stem Cells and Platelet-Derived Growth Factor on Human Retinal Ganglion Cells

Optic neuropathies such as glaucoma occur when retinal ganglion cells (RGCs) in the eye are injured. Strong evidence suggests mesenchymal stem cells (MSCs) could be a potential therapy to protect RGCs; however, little is known regarding their effect on the human retina. We, therefore, investigated if human MSCs (hMSCs), or platelet‐derived growth factor (PDGF) as produced by hMSC, could delay RGC death in a human retinal explant model of optic nerve injury. Our results showed hMSCs and the secreted growth factor PDGF‐AB could substantially reduce human RGC loss and apoptosis following axotomy. The neuroprotective pathways AKT, ERK, and STAT3 were activated in the retina shortly after treatments with labeling seen in the RGC layer. A dose dependent protective effect of PDGF‐AB was observed in human retinal explants but protection was not as substantial as that achieved by culturing hMSCs on the retina surface which resulted in RGC cell counts similar to those immediately post dissection. These results demonstrate that hMSCs and PDGF have strong neuroprotective action on human RGCs and may offer a translatable, therapeutic strategy to reduce degenerative visual loss. Stem Cells2018;36:65–78

The impact of immunoglobulin in acute HIV infection on the HIV reservoir: a randomized controlled trial

OBJECTIVES

Antiretroviral therapy (ART) during acute HIV infection (AHI) restricts the HIV reservoir, but additional interventions are necessary to induce a cure. Intravenous immunoglobulin (IVIG) is not HIV-specific but is safe and temporarily reduces the HIV reservoir in chronic HIV infection. We present a randomized controlled trial to investigate whether IVIG plus ART in AHI reduces the HIV reservoir and immune activation compared with ART alone.

METHODS

Ten men with AHI (Fiebig II-IV) initiated ART (tenofovir, entricitabine, ritonavir boosted darunavir and raltegravir) at HIV-1 diagnosis and were randomized to ART alone or ART plus 5 days of IVIG, once virally suppressed (week 19). Blood samples were evaluated for viral reservoir, immune activation, immune exhaustion and microbial translocation. Flexible sigmoidoscopy was performed at weeks 19, 24 and 48, and gut proviral DNA and cell numbers determined.

RESULTS

IVIG was well tolerated and no viral blips (> 50 HIV-1 RNA copies/mL) occurred during IVIG therapy. From baseline to week 48, total HIV DNA in peripheral blood mononuclear cells (PBMCs) (cases: -3.7 log₁₀ copies/10⁶ CD4 cells; controls: -3.87 log₁₀ copies/10⁶ CD4 cells) declined with no differences observed between the groups (P = 0.49). Declines were observed in both groups from week 19 to week 48 in total HIV DNA in PBMCs (P = 0.38), serum low copy RNA (P = 0.57) and gut total HIV DNA (P = 0.55), but again there were no significant differences between arms. Biomarkers of immune activation, immune exhaustion and microbial translocation and the CD4:CD8 ratio were similar between arms for all comparisons.

CONCLUSIONS

Although safe, IVIG in AHI did not impact total HIV DNA, immune function or microbial translocation in peripheral blood or gut tissue.

THE PITTING TEST; AN INVESTIGATION OF AN UNSTANDARDIZED ASSESSMENT OF LYMPHEDEMA

Soft tissue pitting is the occurrence of a temporary indentation on the body surface after the release of sustained thumb or finger pressure. In the management of lymphedema, presence or absence of pitting can contribute to clinical reasoning and guide healthcare management. However, the pitting test and its application has not been described consistently nor is it a standardized part of assessment. Therefore investigations are needed to assess the outcome measures of pitting identification and characterization of lymphedematous tissue. To determine valid testing parameters for a future study, we evaluated six therapists of varying lymphedema experience who assessed a range of locations on six patients with lymphedema representing the breadth of pitting assessment techniques used clinically. The consequence of an unstandardized assessment is demonstrated by the large variation in techniques observed for test duration (1.1 to 76.0 seconds), pressure (1.3 to 14.4 N/cm2) and contact area (0.2 to 6.8 cm2). Experienced therapists performed the pitting test with a significantly different technique from their inexperienced counterparts, involving a longer duration (p < 0.001), higher pressure (p < 0.001) and a larger contact area (p < 0.001). The results of this pilot study support the need for evaluation of the underlying tissue response to sustained pressure and release, in order to inform the development of a standardized procedure.

Human organotypic retinal cultures (HORCs) as a chronic experimental model for investigation of retinal ganglion cell degeneration

There is a growing need for models of human diseases that utilise native, donated human tissue in order to model disease processes and develop novel therapeutic strategies. In this paper we assessed the suitability of adult human retinal explants as a potential model of chronic retinal ganglion cell (RGC) degeneration. Our results confirmed that RGC markers commonly used in rodent studies (NeuN, βIII Tubulin and Thy-1) were appropriate for labelling human RGCs and followed the expected differential expression patterns across, as well as throughout, the macular and para-macular regions of the retina. Furthermore, we showed that neither donor age nor post-mortem time (within 24 h) significantly affected the initial expression levels of RGC markers. In addition, the feasibility of using human post mortem donor tissue as a long-term model of RGC degeneration was determined with RGC protein being detectable up to 4 weeks in culture with an associated decline in RGC mRNA and significant, progressive, apoptotic labelling of NeuN(+) cells. Differences in RGC apoptosis might have been influenced by medium compositions indicating that media constituents could play a role in supporting axotomised RGCs. We propose that using ex vivo human explants may prove to be a useful model for testing the effectiveness of neuroprotective strategies.

Hydrostatic pressure does not cause detectable changes in survival of human retinal ganglion cells

PURPOSE

Elevated intraocular pressure (IOP) is a major risk factor for glaucoma. One consequence of raised IOP is that ocular tissues are subjected to increased hydrostatic pressure (HP). The effect of raised HP on stress pathway signaling and retinal ganglion cell (RGC) survival in the human retina was investigated.

METHODS

A chamber was designed to expose cells to increased HP (constant and fluctuating). Accurate pressure control (10-100 mmHg) was achieved using mass flow controllers. Human organotypic retinal cultures (HORCs) from donor eyes (<24 h post mortem) were cultured in serum-free DMEM/HamF12. Increased HP was compared to simulated ischemia (oxygen glucose deprivation, OGD). Cell death and apoptosis were measured by LDH and TUNEL assays, RGC marker expression by qRT-PCR (THY-1) and RGC number by immunohistochemistry (NeuN). Activated p38 and JNK were detected by Western blot.

RESULTS

Exposure of HORCs to constant (60 mmHg) or fluctuating (10-100 mmHg; 1 cycle/min) pressure for 24 or 48 h caused no loss of structural integrity, LDH release, decrease in RGC marker expression (THY-1) or loss of RGCs compared with controls. In addition, there was no increase in TUNEL-positive NeuN-labelled cells at either time-point indicating no increase in apoptosis of RGCs. OGD increased apoptosis, reduced RGC marker expression and RGC number and caused elevated LDH release at 24 h. p38 and JNK phosphorylation remained unchanged in HORCs exposed to fluctuating pressure (10-100 mmHg; 1 cycle/min) for 15, 30, 60 and 90 min durations, whereas OGD (3 h) increased activation of p38 and JNK, remaining elevated for 90 min post-OGD.

CONCLUSIONS

Directly applied HP had no detectable impact on RGC survival and stress-signalling in HORCs. Simulated ischemia, however, activated stress pathways and caused RGC death. These results show that direct HP does not cause degeneration of RGCs in the ex vivo human retina.

Autologous stem cell transplantation in severe treatment-resistant Crohn's disease: long-term follow-up of UK patients treated on compassionate basis

BACKGROUND

Although autologous stem cell transplantation (ASCT) may achieve disease control in severe treatment-resistant Crohn's disease (CD), relapse is frequent, and there is little information regarding long-term outcomes in terms of response to subsequent treatments and complications of ASCT.

DESIGN

Retrospective evaluation of UK patients treated on a compassionate basis from three UK tertiary centres.

METHODS

We summarize long-term outcomes of six previously unreported patients with severe treatment-resistant CD treated with ASCT according to international guidelines between 2003 and 2009. Median duration of CD before ASCT was 14 (7-22) years. Following stem cell mobilization, patients were treated with high-dose cyclophosphamide (200 mg/kg) and rabbit anti-thymocyte globulin (7.5 mg/kg) followed by ASCT.

RESULTS

All patients tolerated ASCT with routine toxicities and no treatment-related mortality and are alive at 50-123 months post-ASCT. Clinical and endoscopic remissions of CD were confirmed at 3 months post-ASCT in five patients, although median time to next treatment for inflammatory disease was 10 months (range: 3-16 months). Subsequently, disease control was achieved with previously ineffective and newer treatments, with surgery performed predominantly for pre-existing fibrotic strictures. Two patients became independent of home total parenteral nutrition (TPN). Reported late complications of ASCT included hypothyroidism and ovarian failure.

CONCLUSION

Long-term follow-up supports the safety and feasibility of ASCT as a means of achieving short-term control of severe CD whilst potentially re-sensitizing the disease to medical therapy and reducing requirements for surgery and TPN. Given the inevitability of relapse, pre-emptive salvage and/or maintenance treatments post-ASCT should be the focus of future trials.

Purines in the eye: recent evidence for the physiological and pathological role of purines in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland

This review highlights recent findings that describ how purines modulate the physiological and pathophysiological responses of ocular tissues. For example, in lacrimal glands the cross-talk between P2X7 receptors and both M3 muscarinic receptors and α1D-adrenergic receptors can influence tear secretion. In the cornea, purines lead to post-translational modification of EGFR and structural proteins that participate in wound repair in the epithelium and influence the expression of matrix proteins in the stroma. Purines act at receptors on both the trabecular meshwork and ciliary epithelium to modulate intraocular pressure (IOP); ATP-release pathways of inflow and outflow cells differ, possibly permitting differential modulation of adenosine delivery. Modulators of trabecular meshwork cell ATP release include cell volume, stretch, extracellular Ca(2+) concentration, oxidation state, actin remodeling and possibly endogenous cardiotonic steroids. In the lens, osmotic stress leads to ATP release following TRPV4 activation upstream of hemichannel opening. In the anterior eye, diadenosine polyphosphates such as Ap4A act at P2 receptors to modulate the rate and composition of tear secretion, impact corneal wound healing and lower IOP. The Gq11-coupled P2Y1-receptor contributes to volume control in Müller cells and thus the retina. P2X receptors are expressed in neurons in the inner and outer retina and contribute to visual processing as well as the demise of retinal ganglion cells. In RPE cells, the balance between extracellular ATP and adenosine may modulate lysosomal pH and the rate of lipofuscin formation. In optic nerve head astrocytes, mechanosensitive ATP release via pannexin hemichannels, coupled with stretch-dependent upregulation of pannexins, provides a mechanism for ATP signaling in chronic glaucoma. With so many receptors linked to divergent functions throughout the eye, ensuring the transmitters remain local and stimulation is restricted to the intended target may be a key issue in understanding how physiological signaling becomes pathological in ocular disease.

Reassessment of Crohn's disease treated with at least 12 months of anti-TNF therapy: how likely is treatment withdrawal?

OBJECTIVE

To assess methods of disease reassessment and rates of treatment withdrawal in patients with Crohn's disease (CD) treated with biologics and to report retrospective risk stratification for treatment withdrawal as suggested by the STORI trial in the context of this cohort.

DESIGN

A retrospective observational cohort study of all patients with CD treated with antitumour necrosis factor (anti-TNF) therapy for >12 months in 2011.

SETTING

Tertiary care.

PATIENTS

Patients with CD treated with anti-TNF therapy.

MAIN OUTCOME MEASURES

Method and outcome of reassessment and whether patient was withdrawn from therapy; also, whether patients met low-risk criteria for withdrawal as identified by the STORI trial, and outcome of those meeting low-risk criteria.

RESULTS

73 patients (infliximab n=48, adalimumab n=25) underwent disease reassessment. Nine patients were deemed to have achieved remission and were withdrawn from treatment: 6 (67%) maintained remission at 12 months, three patients relapsed and were successfully retreated. 52 patients had sufficient data available for STORI criteria to be applied retrospectively. 37% (19/52) fulfilled low-risk criteria for withdrawal-of these, 26% (5/19) were withdrawn from anti-TNF therapy and three had sustained clinical remission at 1 year. Reasons for non-withdrawal included ongoing endoscopic activity (n=8), radiological activity (n=2) and clinical concern due to previous disease behaviour (n=4).

CONCLUSIONS

Relatively few patients were deemed in sufficient depth of remission to warrant a trial of withdrawal of anti-TNF therapy. Many patients were not withdrawn, despite meeting STORI low-risk criteria, due to ongoing disease activity highlighting the limitations of applying such criteria in a 'real world' setting.

Gentamicin use in neonates: should we have a change of practice?

Background

Gentamicin, one of the most commonly used antibiotics in neonates, has potential toxicity. This study was performed to determine the incidence of potential toxicity of gentamicin in term and preterm neonates.

Methods

A one-year retrospective study in neonates admitted to Special Baby Care Units at University Hospital of North Durham and Darlington Memorial Hospitals. We reviewed each admission and looked through the case notes in detail to document information about gentamicin administration, dosage and elevated gentamicin levels in the blood. Pre-third dose gentamicin levels >2 mg/L were classified as elevated.

Results

Overall, 192 babies (83 term and 109 preterm) had documented gentamicin levels. Of these, 43% (84/192) manifested elevated gentamicin levels. Of the babies with elevated gentamicin levels, 67% (56/84) weighed less than 2.5 kg. When a combination of gestation period and weight was considered, 61% (51/84) of preterm infants weighing <2.5 kg had elevated levels whereas only one term infant <2.5 kg exhibited elevated levels.

Conclusion

Preterm neonates and specifically low birth weight neonates tolerate gentamicin poorly. Dosage and/or interval of administration of the medication may need modification in this group to minimise toxicity.

P2X7 receptor activation mediates retinal ganglion cell death in a human retina model of ischemic neurodegeneration

PURPOSE

There is evidence implicating ischemia and excitotoxicity in the pathogenesis of glaucoma. ATP-mediated excitotoxicity via activation of the P2X7 receptor (P2X7R) has been proposed to play a role in retinal ganglion cell (RGC) degeneration in this disease. The aim of this research was to determine whether stimulation of the P2X7R mediated ischemia-induced RGC death in the human retina.

METHODS

Human organotypic retinal cultures were exposed to the P2X7R agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) and simulated ischemia (oxygen/glucose deprivation) in the presence or absence of the P2X7R antagonist, Brilliant Blue G (BBG). Neuronal death in the RGC layer was quantified by neuronal nuclei (NeuN)-positive cell counts and quantitative real-time PCR for THY-1 mRNA. The P2X7R was localized by immunohistochemistry and P2X7R mRNA profiling using a cryosectioning technique.

RESULTS

P2X7R stimulation by BzATP (100 μM) induced loss of RGC markers in human organotypic retinal cultures (HORCs), which was inhibited by BBG (1 μM). Simulated ischemia led to loss of RGCs that was also inhibited by BBG, indicating that ischemia-induced RGC degeneration was mediated by the P2X7R. The P2X7R was immunolocalized to the outer and inner plexiform layers of the human retina, and P2X7R mRNA expression was confirmed in the inner retina and ganglion cell layer.

CONCLUSIONS

These studies demonstrated that stimulation of the P2X7R can mediate RGC death and that this mechanism plays a role in ischemia-induced neurodegeneration in the human retina.

The impact of introducing thioguanine nucleotide monitoring into an inflammatory bowel disease clinic

BACKGROUND

Thioguanine nucleotides (TGNs) are the active product of thiopurine metabolism. Levels have been correlated with effective clinical response. Nonetheless, the value of TGN monitoring in clinical practice is debated. We report the influence of introducing TGN monitoring into a large adult inflammatory bowel disease (IBD) clinic.

PATIENTS AND METHODS

Patients with IBD undergoing TGN monitoring were identified from Purine Research Laboratory records. Whole blood TGNs and methylated mercaptopurine nucleotides were hydrolysed to the base and measured using HPLC. Clinical and laboratory data were obtained retrospectively.

RESULTS

One hundred and eighty-nine patients with 608 available TGN results were identified. In non-responders, TGNs directed treatment change in 39/53 patients. When treatment was changed as directed by TGN, 18/20 (90%) improved vs. 7/21 (33%) where the treatment decision was not TGN-directed, p < 0.001. Where treatment change was directed at optimisation of thiopurine therapy, 14/20 achieved steroid-free remission at 6 months vs. 3/10 where the TGN was ignored, (p = 0.037). Six per cent of patients were non-adherent, 25% under-dosed and 29% over-dosed by TGN. Twelve per cent of patients predominantly methylated thiopurines, this group had low TGN levels and high risk of hepatotoxicity. In responders, adherence and dosing issues were identified and TGN-guided dose-reduction was possible without precipitating relapse. Mean cell volume (MCV), white blood cell count (WBC) and lymphocyte counts were not adequate surrogate markers. MCV/WBC ratio correlated with clinical response, but was less useful than TGN for guiding clinical decisions.

CONCLUSIONS

Monitoring TGNs enables thiopurine therapy to be optimised and individualised, guiding effective treatment decisions and improving clinical outcomes.

Sigma 1 receptor stimulation protects against oxidative damage through suppression of the ER stress responses in the human lens

Stimulation of sigma-1 receptors is reported to protect against oxidative stress. The present study uses cells and tissue from the human lens to elucidate the relationship between the sigma 1 receptor, ER stress and oxidative stress-induced damage. Exposure of the human lens cell line FHL124 to increasing concentrations of H(2)O(2) led to reduced cell viability and increased apoptosis. In response to 30 μM H(2)O(2), levels of the ER stress proteins BiP, ATF6 and pEIF2α were significantly increased within 4h of exposure. Expression of the sigma 1 receptor was markedly increased in response to H(2)O(2). Application of 10 and 30 μM (+)-pentazocine, a sigma 1 receptor agonist, significantly inhibited the H(2)O(2) induced cell death. (+)-Pentazocine also suppressed the oxidative stress induced reduction of pro-caspase 12 and suppressed the induction of the ER stress proteins BiP and EIF2α. When applied to cultured human lenses, (+)-pentazocine protected against apoptotic cell death, LDH release and against H(2)O(2) induced opacification. These data demonstrate that stimulation of the sigma 1 receptor provides significant protection from oxidative damage and is, therefore, a putative therapeutic approach to delay the onset of diseases that may be triggered by oxidative damage, including cataract formation.

The development of human organotypic retinal cultures (HORCs) to study retinal neurodegeneration

AIMS

To develop human organotypic retinal cultures (HORCs) to study retinal ganglion cell (RGC) death in response to ischaemic and excitotoxic insults, both known to cause loss of RGCs and proposed as mechanisms involved in glaucomatous retinal neurodegeneration.

METHODS

Human donor eyes were obtained within 24 h post mortem. The retina was isolated and explants cultured using two techniques. THY-1 mRNA (assessed by real-time quantitative PCR) and neuronal nuclei (NeuN) (assessed by immunohistochemistry) were used as markers of RGCs. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL).

RESULTS

The distribution of THY-1 mRNA and NeuN-labelling within the human retina was consistent with the expected distribution of RGCs. Gross morphology and retinal architecture remained stable over a 96 h culture period. THY-1 mRNA and NeuN-labelled RGC layer cells decreased over the culture period, and there was an increase in TUNEL-labelling with time, but HORCs cultured in serum-free DMEM/HamF12 medium were useful for up to 48 h in culture. N-methyl-d-aspartate (10 μM) caused a reduction in THY-1 mRNA by 24 h and decreased the numbers of NeuN-labelled RGC layer neurons by 48 h, suggesting that the loss of THY-1 mRNA was a marker of RGC stress prior to death. Simulated ischaemia (60 min oxygen/glucose deprivation) caused a reduction at 24 h in both THY-1 mRNA and the numbers of NeuN-labelled neurons of HORCs.

CONCLUSION

HORCs provide a useful model to investigate RGC insult by neurodegenerative mechanisms that may lead to glaucoma in human eyes.

N-acetylhistidine, a novel osmolyte in the lens of Atlantic salmon (Salmo salar L.)

Volume homeostasis is essential for the preservation of lens transparency and this is of particular significance to anadromous fish species where migration from freshwater to seawater presents severe osmotic challenges. In Atlantic salmon ( Salmo salar L.), aqueous humor (AH) osmolality is greater in fish acclimated to seawater compared with young freshwater fish, and levels of lens N-acetylhistidine (NAH) are much higher in seawater fish. Here we investigate NAH as an osmolyte in the lenses of salmon receiving diets either with or without histidine supplementation. In the histidine-supplemented diet (HD) histidine content was 14.2 g/kg, and in the control diet (CD) histidine content was 8.9 g/kg. A transient increase in AH osmolality of 20 mmol/kg was observed in fish transferred from freshwater to seawater. In a lens culture model, temporary decreases in volume and transparency were observed when lenses were exposed to hyperosmotic conditions. A positive linear relationship between extracellular osmolality and lens NAH content was also observed, whereas there was no change in lens histidine content. Hypoosmotic exposure stimulated [14C]-histidine efflux by 9.2- and 2.6-fold in CD and HD lenses, respectively. NAH efflux, measured by HPLC, was stimulated by hypoosmotic exposure to a much greater extent in HD lenses. In vivo, lens NAH increased in response to elevated AH osmolality in HD but not CD fish. In conclusion, NAH has an important and novel role as a compatible osmolyte in salmon lens. Furthermore, it is the major osmolyte that balances increases in AH osmolality when fish move from freshwater to seawater. A deficiency in NAH would lead to a dysfunction of the normal osmoregulatory processes in the lens, and we propose that this would contribute to cataract formation in fish deficient in histidine.

Low-dose azathioprine or mercaptopurine in combination with allopurinol can bypass many adverse drug reactions in patients with inflammatory bowel disease

BACKGROUND

The thiopurine drugs, azathioprine and mercaptopurine (MP), are established treatments for IBD. However, therapeutic failure caused by adverse drug reactions occurs frequently.

AIM

To study combination of allopurinol with reduced-dose thiopurine in an attempt to avoid adverse drug reactions in the treatment of IBD.

METHODS

Patients with drug reactions to full-dose thiopurines were recruited for combination therapy in two IBD centres in this retrospective study. Dosing was guided by measuring thiopurine methyltransferase (for UK patients) or thioguanine nucleotides and methyl-6MP (Australian patients). Response was monitored by clinical activity indices.

RESULTS

Of 41 patients, 25 had non-hepatic and 16 had hepatitic reactions. Clinical remission was achieved in 32 patients (78%) with a median follow-up of 41 weeks (range 0.5-400). Patients who did not respond to combination therapy tended to fail early with the same adverse reaction. The relative risk of having an adverse reaction with methyl-6MP in the top interquartile range was 2.7 (1.3-28) times that with methyl-6MP in the lower three quartiles (95% confidence interval).

CONCLUSION

The combined experience from our centres is the largest reported experience of this combination therapy strategy in IBD, and the first to provide evidence for benefit in thiopurine and allopurinol co-therapy to avoid non-hepatitic adverse drug reactions.

Prospective evaluation of the pharmacogenetics of azathioprine in the treatment of inflammatory bowel disease

AIM

To investigate whether pharmacogenetic loci or metabolite concentrations explain clinical response or side effects to AZA.

METHODS

Patients with IBD were given 2 mg/kg of AZA without dose escalation or adjustment. Serial clinical response, thiopurine methyl transferase (TPMT) activity and thioguanine nucleotide (TGN) concentrations were measured over 6 months. All patients were genotyped for inosine triphosphatase (ITPase) and TPMT. Clinical response and side effects were compared to these variables.

RESULTS

Two hundred and seven patients were analysed. Thirty-nine per cent withdrew due to adverse effects. Heterozygous TPMT genotype strongly predicted adverse effects (79% heterozygous vs. 35% wild-type TPMT, P < 0.001). The ITPA 94C>A mutation was associated with withdrawal due to flu-like symptoms (P = 0.014). A baseline TPMT activity below 35 pmol/h/mg/Hb was associated with a greater chance of clinical response compared with a TPMT above 35 pmo/h/mg/Hb (81% vs. 43% respectively, P < 0.001). Patients achieving a mean TGN level above 100 were significantly more likely to respond (P = 0.0017).

CONCLUSIONS

TPMT testing predicts adverse effects and reduced chance of clinical response (TPMT >35 pmol/h/mg/Hb). ITPase deficiency is a predictor of adverse effects and TGN concentrations above 100 correlate with clinical response.

Long-term outcome of using allopurinol co-therapy as a strategy for overcoming thiopurine hepatotoxicity in treating inflammatory bowel disease

BACKGROUND

Hepatotoxicity results in the withdrawal of thiopurines drugs, azathioprine (AZA) and mercaptopurine (MP), in up to 10% of patients with inflammatory bowel disease. Our group previously demonstrated that allopurinol with AZA/ciclosporin/steroid 'triple therapy' improved renal graft survival.

AIM

To confirm the hypothesis that allopurinol may alleviate thiopurine hepatotoxicity by similar mechanisms as proposed in our renal study.

METHODS

Unselected patients with acute thiopurine hepatotoxicity were offered allopurinol co-therapy with low-dose AZA or MP. The starting AZA/MP dose was determined by thiopurine methyltransferase (TPMT) activity (two patients were intermediate TPMT); then this dose was reduced to 25% for allopurinol co-therapy. Response to treatment was assessed by clinical severity indices, endoscopy and blood tests.

RESULTS

Of 11 patients (three Crohn's disease, eight ulcerative colitis) treated, nine (82%) remain in long-term remission (median 42 months) with normal liver tests. One patient also successfully bypassed flu-like symptoms. Two stopped: one nausea, one abnormal liver function (stealosis on biopsy). Leucopenia occurred in two cases and resolved with minor dose reductions.

CONCLUSIONS

Allopurinol co-therapy with low-dose AZA/MP can alleviate thiopurine hepatotoxicity. It appears safe and effective for long-term use, but requires monitoring for myelotoxicity. Assessing the TPMT activity helps tailor the AZA/MP doses.

Influence of xanthine oxidase on thiopurine metabolism in Crohn's disease

BACKGROUND

The thiopurines, azathioprine (AZA) and mercaptopurine are extensively used in Crohn's discase (CD). Thiopurine bioactivation can be diverted by either thiopurine methyltransferase (TPMT), or by xanthine oxidase/dehydrogenase (XOD) which forms 6-thiouric acid (6TU).

AIM

To investigate whether chronic inflammation could influence small intestinal XOD activity using urinary excretion of 6TU as a surrogate marker of XOD activity.

METHODS

6-Thiouric acid excretion was compared between 32 CD patients and nine dermatology patients (control group), on AZA. Six CD patients were interesting: five with low TPMT activity (one deficient, four intermediate), and one receiving AZA/allopurinol co-therapy.

RESULTS

There was no statistical difference in 6TU excretion between the CD and control group. CD location, severity or surgery did not affect excretion. The TPMT-deficient patient excreted 89% of daily AZA dose as 6TU, but excretion by TPMT carriers was essentially normal. Concurrent 5-aminosalicylic acid therapy increased 6TU excretion significantly (median 32.9%), consistent with inhibiting TPMT. 6TU was undetectable in the patient on AZA/allopurinol co-therapy.

CONCLUSIONS

The results refuted our hypothesis, but fitted a model where most of an oral thiopurine dose effectively escapes first-pass metabolism by gut XOD, but is heavily catabolized by TPMT. Bioavailability of thiopurines may be competitively inhibited by dietary purines.

Distinct P2Y receptor subtypes regulate calcium signaling in human retinal pigment epithelial cells

PURPOSE

Nucleotide signaling plays a role in retinal pigment epithelial (RPE) function, and receptors for nucleotides are potential therapeutic targets for various ocular diseases. The purpose of this study was to investigate the expression of P2Y receptor subtypes in native and cultured human RPE cells.

METHODS

Intracellular Ca(2+) levels were monitored using real-time fluorescence imaging in cultured human RPE cells loaded with Fura-2. Expression of P2Y receptors in native and cultured RPE cells was determined by quantitative RT-PCR and Western blot analysis.

RESULTS

Adenosine triphosphate (ATP), uridine triphosphate (UTP), adenosine diphosphate (ADP), 2-methylthio ATP (2MeSATP), and uridine diphosphate (UDP) produced concentration-related increases in [Ca(2+)](i) in cultured RPE cells. However, differences between the magnitude and shape of agonist responses were observed. ATP and UTP showed similar response characteristics, including a distinct Ca(2+) influx component. ATP and UTP were equipotent (EC(50), 6 muM) and maximum responses were equivalent, suggesting activation of a P2Y(2) receptor. Maximal responses to ADP and 2MeSATP were equivalent with EC(50)s of 1 muM and 0.3 muM. The P2Y(1) antagonist MRS 2179 (10 muM) inhibited these responses, confirming functional expression of P2Y(1) receptors. The presence of a response to UDP suggested P2Y(6) expression. There was no influx component to P2Y(1)- and P2Y(6)-mediated responses. mRNA for P2Y(1), P2Y(2,) P2Y(4), and P2Y(6) receptor subtypes was found in cultured RPE cells, and for P2Y(1), P2Y(2,) P2Y(4,) P2Y(6), and P2Y(12) it was found in native RPE cells. Expression of P2Y(1), P2Y(2), and P2Y(6) protein was found in native and cultured RPE cells.

CONCLUSIONS

These data define the expression profile of P2Y receptors in human RPE and show that different P2Y subtypes control distinct calcium responses in these cells.

Estimating risks of common complex diseases across genetic and environmental factors: the example of Crohn disease

BACKGROUND

Progress has been made in identifying mutations that confer susceptibility to complex diseases, with the prospect that these genetic risks might be used in determining individual disease risk.

AIM

To use Crohn disease (CD) as a model of a common complex disorder, and to develop methods to estimate disease risks using both genetic and environmental risk factors.

METHODS

The calculations used three independent risk factors: CARD15 genotype (conferring a gene dosage effect on risk), smoking (twofold increased risk for smokers), and residual familial risk (estimating the effect of unidentified genes, after accounting for the contribution of CARD15). Risks were estimated for high-risk people who are siblings, parents and offspring of a patient with CD.

RESULTS

The CD risk to the sibling of a patient with CD who smokes and carries two CARD15 mutations is approximately 35%, which represents a substantial increase on the population risk of 0.1%. In contrast, the risk to a non-smoking sibling of a patient with CD who carries no CARD15 mutations is 2%. Risks to parents and offspring were lower.

CONCLUSIONS

High absolute risks of CD disease can be obtained by incorporating information on smoking, family history and CARD15 mutations. Behaviour modification through smoking cessation may reduce CD risk in these people.