Role for G protein-coupled receptor kinase in agonist-specific regulation of μ-opioid receptor responsiveness

The G protein-coupled μ-opioid receptor (μOR) mediates the physiological effects of endogenous opioid peptides as well as the structurally distinct opioid alkaloids morphine and etorphine. An intriguing feature of μOR signaling is the differential receptor trafficking and desensitization properties following activation by distinct agonists, which have been proposed as possible mechanisms related to opioid tolerance. Here we report that the ability of distinct opioid agonists to differentially regulate μOR internalization and desensitization is related to their ability to promote G protein-coupled receptor kinase (GRK)-dependent phosphorylation of the μOR. Although both etorphine and morphine effectively activate the μOR, only etorphine elicits robust μOR phosphorylation followed by plasma membrane translocation of β-arrestin and dynamin-dependent receptor internalization. In contrast, corresponding to its inability to cause μOR internalization, morphine is unable to either elicit μOR phosphorylation or stimulate β-arrestin translocation. However, upon the overexpression of GRK2, morphine gains the capacity to induce μOR phosphorylation, accompanied by the rescue of β-arrestin translocation and receptor sequestration. Moreover, overexpression of GRK2 also leads to an attenuation of morphine-mediated inhibition of adenylyl cyclase. These findings point to the existence of marked differences in the ability of different opioid agonists to promote μOR phosphorylation by GRK. These differences may provide the molecular basis underlying the different analgesic properties of opioid agonists and contribute to the distinct ability of various opioids to induce drug tolerance.     

The clinical relevance of ultra-widefield angiography findings in patients with central retinal vein occlusion and macular oedema receiving anti-VEGF therapy

AimsTo report, using ultra-widefield angiography (UWFA) the area, distribution, and change in retinal capillary nonperfusion (RCNP) at baseline and 100 weeks in eyes with central retinal vein occlusion (CRVO) receiving anti-VEGF for macula oedema.MethodsProspective longitudinal multi-centre cohort study. Adults with CRVO treated with anti-VEGF therapy for macular oedema underwent UWFA at baseline and week-100. The area, distribution, and change in total, peripheral and posterior pole RCNP were determined.ResultsOf 153 eyes at baseline, mean area of RCNP was 34.3DA and 12 (7.8%) had ≥75DA RCNP. More than 10DA RCNP was present in the temporal periphery in 75.8% of eyes vs. 10.5% in the nasal periphery. At week-100, mean RCNP was 42.1DA with a median change from baseline of 3.3DA 95% CI [0.4, 7.3]; p < 0.01. Of 146 eyes with ≤10DA of posterior pole RCNP at baseline, 16/146 (11.0%) progressed to >10DA at week-100. These eyes had a median increase in total RCNP of 69.7DA [95% CI 27.2–85.4] vs 0DA [0.0–1.4]; p < 0.001 for those who did not, and two developed neovascular glaucoma. Larger baseline area of RCNP and history of glaucoma were risk factors for posterior pole RCNP developing.ConclusionsWith UWFA, significant baseline RCNP was identified in the majority of CRVO patients, notably in the temporal periphery, but large increases over 100 weeks were uncommon. Development of >10DA posterior pole RCNP is a marker for widespread RCNP and in such cases the risk of anterior segment neovascularisation is not abolished by concomitant anti-VEGF therapy.Subject terms: Retinal diseases, Vision disorders     

Combined efficacies of lipoic acid and meso-2,3-dimercaptosuccinic acid on lead-induced erythrocyte membrane lipid peroxidation and antioxidant status in rats

One of the most intriguing phenomenon observed during lead toxicity has been attributed to lead-induced oxidative stress. The combined effect of DL-alpha-lipoic acid (LA) and meso-2,3-dimercaptosuccinic acid (DMSA) on lead-induced alterations in selected parameters, which are indicators of oxidative stress in erythrocytes, have been studied. Lead acetate (Pb, 0.2%) was administered in drinking water for 5 weeks to induce toxicity. LA (25 mg/ kg body weight per day i.p.) and DMSA (20 mg/kg body weight per day i.p.) were administered individually and also in combination during week 6. Clinical evidence of toxic exposure was evident from the elevated blood lead levels (BPb) along with lowered levels of haemoglobin (Hb) and haematocrit (Ht). Lead-exposed animals showed enhanced membrane lipid peroxidation (LPO) in the erythrocytes. Damage to the erythrocyte membrane was evident from the decline in the activities of the transmembrane enzymes, viz., Na+, K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase. Lead-exposed rats also suffered an onslaught on the antioxidant defence system witnessed by lowered activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH). Serum glutamic-oxoloacetic transaminase (SGOT) and serum glutamic-pyruvic transaminase (SGPT) were also elevated in lead-exposed rats. Treatment with either LA or DMSA reversed the lead-induced biochemical disturbances encountered by the erythrocytes, but combined treatment with LA and DMSA was very effective in mitigating all the parameters indicative of oxidative stress.     

Transdermal iontophoresis of insulin. Part 1: A study on the issues associated with the use of platinum electrodes on rat skin

We have studied the issues associated with the use of platinum electrodes for transdermal iontophoretic delivery of peptides, using insulin as a model peptide. Insulin permeation was studied using full-thickness rat skin by varying the donor solution pH as a function of electrode polarity. The stability of insulin under the iontophoretic conditions was studied using TLC, SDS-polyacrylamide gel electrophoresis and HPLC. Large pH shifts were observed during anodal iontophoresis (AI), when the donor solution pH was above the isoelectric point of insulin and in cathodal iontophoresis (CI), when the donor solution pH was below the isoelectric point of insulin. The direction and magnitude of electroosmotic flow was influenced by pH of the donor solution and the electrode polarity. On the other hand, the buffer used to maintain the pH governed the contribution of electrorepulsion to the overall transport of insulin. Electrochemical degradation of insulin was significant during AI at pH 7.4. Among the pH investigated, AI of insulin at pH 3.6 and CI at pH 8.35 were better, as the pH shift was relatively less and electrochemically more stable during iontophoresis as compared with other pH. In summary, the pH shift caused by platinum electrodes had a significant influence on the permeation and stability of insulin.     

Transfusion transmitted diseases

Transfusion transmitted disease (TTD) is a major challenge to the transfusion services all over the world. The problem of TTD is directly proportionate to the prevalence of the infection in the blood donor community. In India, hepatitis B/C, HIV, malaria, syphilis, cytomegalo virus, parvo-virus B-19 and bacterial infections are important causes of concern. Hepatitis B and C infections are prevalent in India and carrier rate is about 1–5% and 1%, respectively. Post transfusion hepatitis B/C is a major problem in India (about 10%) because of low viraemia and mutant strain undetectable by routine ELISA. HIV prevalence among blood donors is different in various parts of the country. It may not be so alarming as projected by some agencies. In one study from north India, confirmed HIV positivity was found in 0.2/1000 blood donor. Post transfusion CMV is difficult to prevent but use of leukocyte filters may help to reduce it significantly. Parvo virus B-19 infection in blood donors is 39.9% which may increase morbidity in multitransfused or immunocompromised patients. Current symphilis tests may not be sensitive but it should be continued to exclude high-risk donors. Malaria is a real problem for India due to the lack of a simple and sensitive screening test. Incidence of bacterial contamination is greatly reduced due to improved collection/ preservation techniques and use of antibiotics in patients. However, proper vigilance and quality control is needed to prevent this problem. Total dependence of altruistic repeat voluntary donors and use of sensitive laboratory tests may help Indian blood transfusion services to reduce incidences of TTDs.     

Micropulse diode laser photocoagulation for central serous chorio-retinopathy

Purpose:  Central serous chorioretinopathy (CSC) is usually characterized by a localized detachment of the neurosensory retina that is self-limiting. However, some cases may persist or recur leading to degenerative changes of the retinal pigment epithelium and the neurosensory retina resulting in severe visual loss and requiring intervention.
Methods:  This retrospective case series reports the long-term visual outcome of the use of micropulse laser photocoagulation for this condition with a review of literature.
Results:  The mean follow up was 17.1 months. Four of the five patients had complete resolution of symptoms whereas one patient had recurrent CSC from a new leak that failed to resolve after repeat micropulse treatment despite improvement in symptoms.
Discussion:  The outcomes in this case series confirm the long-term efficacy of micropulse laser in the management of CSC. It produces therapeutic effects that appear comparable to those of conventional photocoagulation with no detectable signs of laser-induced iatrogenic damage.     

Using Patient-Level Data to Develop Meaningful Cross-Trial Comparisons of Visual Impairment in Individuals with Diabetic Macular Edema

Introduction

The aim of this study was to assess the impact of baseline characteristics on visual outcome of patients with diabetic macular edema and compare the results of clinical trials with different patient populations.

Methods

A model was created with patient-level data from the RESPOND/RESTORE trials to estimate the impact of baseline characteristics on increases in best-corrected visual acuity (BCVA) with anti-vascular endothelial growth factor therapies, measured by letters gained on the Early Treatment Diabetic Retinopathy Study scale from baseline to month 12. Mean BCVA gains with ranibizumab 0.5 mg pro re nata or laser photocoagulation monotherapy were predicted, assuming baseline characteristics equivalent to those in the VIVID-DME/VISTA-DME trials. These results were compared with the gain with aflibercept 2.0 mg every 8 weeks in VIVID-DME/VISTA-DME. Sensitivity analyses assessed outcome robustness.

Results

Baseline BCVA and central retinal thickness differed significantly between trials. In unadjusted data, patients in RESPOND/RESTORE receiving ranibizumab gained an additional 6.6 letters [95% confidence interval (CI): 4.5–8.7] compared with patients receiving laser monotherapy. After adjusting data to assume baseline characteristics equivalent to VIVID-DME/VISTA-DME, patients receiving ranibizumab were predicted to gain an additional 9.9 letters (95% CI: 7.3–12.4) compared with those receiving laser monotherapy. These results were similar (0.1-letter difference in favor of aflibercept; 95% CI: ?2.9 to 3.2; P = 0.94) to the gain in BCVA in patients receiving aflibercept in VIVID-DME/VISTA-DME compared with those receiving laser monotherapy (10.0 letters, 95% CI: 8.3–11.7).

Conclusion

After adjusting for baseline characteristics, the difference in letters gained between patients receiving ranibizumab versus aflibercept was non-significant across trials, highlighting the importance of adjusting for baseline characteristics in future comparisons.

Funding

Novartis Pharma AG.

     

Development of samarium [P] phosphate colloid for radiosynoviorthesis applications: Preparation, biological and preliminary clinical studies experience

A new therapeutic radio colloid for radiosynoviorthesis (RS) applications is reported. The method of preparation involves the reaction of SmCl₃ carrier with carrier added [³²P]H₃PO₄ in the presence of gelatin. The pure colloid was recovered by dialysis purification leading to radiochemical yield of around 90%. The radiochemical purity of the pure colloid formulated in isotonic saline was over 98%, for the usage period of 14 days, as assessed by paper chromatography. Ninety percent of colloid particles were in the size of 1–10 μm as evident from the laser diffraction particle size analysis, ideally suitable for the intended end use. Animal studies revealed complete retention of the radio colloid in the rabbit knee joint. The results of clinical trials in humans are satisfactory and encouraging, satisfactory retention of the colloid in the knee joint and negligible leakage into the systemic circulation.     

Dietary change for macular health of older people: Eating for Eye Health,a pilot community kitchens intervention

Background

Dry age-related macular degeneration (AMD) is a leading cause of untreatable, progressive central vision loss, social isolation, and disability in older people. Evidence suggests that diet (eg, the Mediterranean dietary pattern or increased oral carotenoid intake) might protect against dry AMD progression. The aim of this pilot study was to test the feasibility of a participant-informed community kitchens intervention (Eating for Eye Health project) to implement dietary behaviour change, to benefit macular health of older adults.