An electrophysiological method for detecting diabetic retinopathy in rats

To determine the value of electroretinography (ERG) and visual evoked potential (VEP) in predicting visual outcome in patients undergoing osteo-keratoprosthesis (OKP) or osteo-odonto-keratoprosthesis (OOKP) surgery. We performed a retrospective cohort study of 143 eyes in 101 patients who underwent OKP or OOKP surgery. The subjects underwent ERG, VEP testing or both up to 6 months prior to surgery. The ERG and VEP results were classified into four categories based on wave amplitude, latency and configuration. The main outcome was the maximum best-corrected visual acuity (maxBCVA) reached at any time postoperatively. One hundred thirty-four cases had undergone preoperative ERG, 82 VEP and 73 both examinations. The sensitivities of ERG and VEP to detect maxBCVA≥0.05 were 68.5% and 87%, respectively, while the specificity was 63.2% for ERG and 47.4% for VEP. The maxBCVA was significantly better in patients with normal ERG (p=0.033) and those with normal VEP (p=0.048), once having defined appropriate normal and abnormal cut-off levels. When comparing fellow eyes in patients who underwent surgery in both eyes, maxBCVA was better in the eyes that had better VEP results (p=0.013). Eyes demonstrating normal ERG or VEP achieved better visual outcome than those with abnormal results. In addition, VEP proved instrumental in determining the eye with the best prognosis when comparing both eyes of a given patient.

Visual electrophysiological responses in subjects with cerebral autosomal arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)

The full-field electroretinogram (ERG) and visual evoked potential (VEP) are useful tools to assess retinal and visual pathway integrity in both laboratory and clinical settings. Currently, preclinical ERG and VEP measurements are performed with anesthesia to ensure stable electrode placements. However, the very presence of anesthesia has been shown to contaminate normal physiological responses. To overcome these anesthesia confounds, we develop a novel platform to assay ERG and VEP in conscious rats. Electrodes are surgically implanted sub-conjunctivally on the eye to assay the ERG and epidurally over the visual cortex to measure the VEP. A range of amplitude and sensitivity/timing parameters are assayed for both the ERG and VEP at increasing luminous energies. The ERG and VEP signals are shown to be stable and repeatable for at least 4 weeks post surgical implantation. This ability to record ERG and VEP signals without anesthesia confounds in the preclinical setting should provide superior translation to clinical data.

Receptor advanced glycation end products (RAGE) activation plays an essential role in diabetic retinopathy (DR) progression. This study was aimed to explore the role of anti-RAGE antibodies (RAGE antagonists) in inhibiting DR progression through their hypoglycemic and anti-inflammatory mechanism in diabetic retinopathy induced rats. A total of 30 male Wistar rats were randomly divided into five group. The group was consisted of normal control group, DR group without treatment, DR group with anti-RAGE 1 ηg/kg BW, 10 ηg/kg BW, and 100 ηg/kg BW. To assess the diabetic retinopathy, fundus photographs were taken every week using a camera with 16x magnification placed in front of the rat's eyes. Blood glucose was checked by the glucose oxidase-peroxidase method. Retinal TNF-α levels and VEGF were examined using an enzyme-linked immunosorbent assay (ELISA) kit. The finding of this study showed that anti-RAGE treatment at dose of 10 and 100 ηg/kg BW, HbA1c levels were significantly higher (p< 0.05) compared to the normal control group but significantly lower (p< 0.05) than in the diabetes group. The mean blood vessel diameter in the DR+anti-RAGE 10 and 100 ηg/kg BW groups was significantly lower than in the diabetic retinopathy group (p< 0.05). The administration of anti-RAGE 10 and 100 ηg/kg BW showed the ability to significantly reduce VEGF levels compared to the DR group (p< 0.05). This study revealed at doses of 10 and 100 ηg/kg BW, anti-RAGE antibodies improved diabetic retinopathy in Wistar rats through hypoglycemic effects and anti-inflammatory mechanisms.

Three months after single injection of streptozotocin (50.0 mg/kg, i.p.), average activities of superoxide dismutase (SOD) and glutathione reductase (GTR) in tissues of the retina of Wistar rats were lower by 47.5 and 42.2%, respectively, while the content of malondialdehyde (MDA) was about 330% of the norm. Recording of electroretinogram (ERG) showed that the amplitude of wave a in these animals was significantly lower (by 57.3%), while the latencies of waves a and b exceeded normal values by 27.5 and 11.8 %, respectively (P < 0.05). After injections of δ sleep-inducing peptide (δSIP, 0.05 mg/kg, i.p., once every three days for two months), SOD and GTR activities did not differ significantly from normal values, while the MDA level was higher by 53.7% (P < 0.05). The mean amplitude of ERG wave a demonstrated no considerable difference from the norm; at the same time, the latencies of waves a and b still exceeded normal values by 13.2 and 10.4 %, respectively. Therefore, negative changes in the functional state of the retina observed because of the development of diabetic retinopathy undergo noticeable moderation under the influence of δSIP.

Objective: To examine the effect of shikonin against streptozotocin (STZ)-induced diabetic retinopathy in rats and elucidate the underlying mechanisms. Methods: Intraperitoneal administration of STZ (65 mg/kg) was used for the induction of diabetic retinopathy in rats. Rats received oral administration of shikonin (10, 20, and 30 mg/kg). The blood glucose level, insulin, body weight, and organ weight were estimated. Advanced glycation end products (AGEs) levels in serum and lens as well as protein carbonyl content of the lens were determined. The parameters related to oxidative stress and inflammation, and the levels of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1) were also measured. In addition, quantitative RT-PCR was performed to determine the mRNA expressions. Results: Shikonin treatment decreased glucose level and boosted insulin level, along with an increase in body weight and improved organ weight. It also lowered O2 •-, ONOO-, serum and lens AGEs, and protein carbonyl content. Furthermore, shikonin treatment significantly alleviated oxidative stress and inflammation, as evidenced by reduced malonaldehyde, nitric oxide, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, cyclooxygenase-2, prostaglandin E2, protein carbonyl content, and nuclear factor kappa-B, and increased superoxide dismutase, glutathione, catalase, and glutathione peroxidase. Markedly decreased levels of ICAM-1 and VCAM-1, as well as heightened levels of Nrf2 and HO-1, were noticed after treatment with shikonin. Furthermore, the mRNA expressions of TNF-α, IL-1β, IL-6, ICAM-1, VCAM-1, RAGE, collagen IV, and fibronectin were significantly downregulated. Conclusions: Shikonin exhibits protective effects against STZ-induced diabetic retinopathy in rats via modulating the Nrf2/HO-1 and NF-κB signaling pathways.

Normalisation of the visual evoked potential (VEP) in patients with optic neuritis (ON) appears to be a rare phenomenon. However, although several workers have indicated that it can happen, they have not followed up with subsequent VEP tests to confirm how long the VEP latency of the affected eye remains in the normal range. To resolve this, 18 patients with a clinical diagnosis of acute unilateral ON were followed for 5 years with repeated VEP tests to determine if the latency of the P2 wave from affected eye could return to the normal range. Furthermore, in cases where the latency returned to normal, the length of time that it remained so was also assessed. The normal range for the latency of the P2 wave was determined by measuring VEPs from a group of 18 healthy control subjects with a similar age distribution to the patients. This established an upper limit of 115.9 ms. At presentation the mean P2 latency of the affected eyes of the patients was 140 ms with a standard deviation of 16 ms. In general, the VEP latencies remained constant over the period of the investigation. However two patients demonstrated a return to normal latencies but this was only temporary. Their latencies become prolonged again within 2 years. These results provide evidence that the delayed P2 latency observed in patients with ON can return to the normal range in a small percentage of cases. However, this improvement may spontaneously deteriorateonce more as a result of further episodes of subacute demyelination.

Effects of Prenatal Substance Exposure: Altered Maturation of Visual Evoked Potentials

HuoXue JieDu formula improves diabetic retinopathy in rats by regulating microRNAs

Purpose/aim: The aim of the study was to investigate the long-term functional changes that may occur in the retina and visual cortex in a rat ocular hypertension (OHT) model of glaucoma, used in our lab for treatment studies, using electroretinogram (ERG) and visual-evoked potential (VEP) cortical recordings in order to test the hypothesis that experimental glaucoma has differential retinal and central effects.Materials and methods: Experimental glaucoma was induced unilaterally in Dark Agouti rats using hypertonic saline injection into the episcleral veins. After 3, 8, 16 and 26 weeks, ERGs and VEPs were recorded under scotopic conditions using brief full-field white flashes (10 μcd s m−2 to 10.4 cd s m−2) and under photopic conditions using a rod-adapting background and white light flashes (0.13–10.4 cd s m−2).Results: At 16 and 26 weeks after OHT induction, there was a significant reduction in the amplitudes of the a- (50% and 30% of unoperated eye values, respectively) and b-waves (55% and 40%, respectively) of the scotopic ERG and the b-waves of the photopic ERG (55% and 45%, respectively) in the glaucomatous eyes. However, no significant changes in the VEPs simultaneously recorded over the visual cortex were seen at any of the time points.Conclusions: The reductions in ERG amplitudes suggest that this model of glaucoma not only causes retinal ganglion cell (RGC) degeneration but also degeneration of the outer retinal cells, and this was confirmed by histology showing a reduction in the outer retinal layers in the glaucomatous eyes. Cortical VEPs did not show detrimental effects suggesting that the retinal damage in this model was not extensive enough to be detected with the VEP methods used or that there could be central compensation in this model of glaucoma.

Reactive oxygen species (ROS) is known to play a significant role in the activation of chronic inflammatory processes in diabetic retinopathy. This study was aimed to evaluate activated growth factor (AGF) from platelet for diabetic retinopathy treatment, utilizing an in vivo investigation to regulate the antioxidant-oxidative stress pathway. The activated growth factor was initially derived by extracting intravenous blood from the rats. Advanced glycation end products (AGEs), p38 mitogen activated protein kinase (p38 MAPK), nuclear factor-κβ (NF-κβ), reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), superoxide dismutase (SOD) and vascular endothelial growth factor (VEGF) was assessed using enzyme linked immunoassay (ELISA). In vivo, diabetic retinopathy rat models were induced by streptozotocin injection and were evaluated by retinal funduscopy. The mean diameter of the retinal artery was significantly reduced when activated growth factor with transforming growth factor-β concentration of 10 ng/mL or 100 ng/mL was administered (p<0.05). The retinal tissue of diabetic rats showed a decline in antioxidant activity due to oxidative stress. AGF containing TGF-β (10 ng/mL and 100 ng/mL) significantly increased SOD activity (p<0.05). AGF administration effectively decreased proinflammatory cytokines like TNF-α and IL-1β. The study shows that AGF, with TGF-β concentrations of 10 ng/mL and 100 ng/mL, can reduce AGEs, p38MAPK, Nf-κβ, ROS, TNF-α, IL-1β, VCAM-1, ICAM-1, and VEGF in diabetic retinopathy rats' retinal tissue, while increasing antioxidant SOD concentration, suggesting AGF may help treat diabetic retinopathy by reducing inflammation and oxidative stress.

The oscillatory potentials (OPs) in electroretinogram (ERG) have clinical values in measuring retinal functions of the early stage of diabetic retinopathy. However, OPs have, until now, been evaluated as components of total ERG recorded with a full field stimulus over the entire retina. Therefore, little information could be obtained about the macular condition (diabetic retinopathy). Using focal stimuli, we successfully recorded OPs in the human macular region. We modified our previously reported system for recording local macular ERG under the fundus monitor with an infrared television fundus camera. We evaluated macular OPs with simultaneously recorded a- and b-waves in many patients with diabetic retinopathy. In some kinds of early diabetic maculopathy, the macular OPs were selectively reduced, leaving the a- and b-waves intact. The macular OPs can be a valuable indicator in assessing the macular function in diabetic maculopathy.

Apocynin ameliorates diabetic retinopathy in rats: Involvement of TLR4/NF-κB signaling pathway

The diagnostic application of averaged visual evoked potentials (VEPs) is illustrated in the investigation of hysterical amblyopia and multiple sclerosis. Averaged VEPs elicited either by a flash of light or a presentation of a grating lasting 100 ms were recorded from the occiput of patients. All the VEPs in hysterical amblyopia were normal. In multiple sclerosis the flash VEPs looked normal for both eyes, whereas the VEPs elicited by grating (2 and 5 c/deg) showed an increase in the latency of the first positive wave, again for both eyes. After physical exercise the VEPs from the right eye were dramatically reduced in amplitude (Uhthoff's sign).

To assess the effect of photoactivated chromophore for keratitis crosslinking (PACK-CXL) in case of severe keratitis with melting on the electrophysiological function of the retina and the optic nerve. The study included 32 eyes of 32 patients with smear positive severe infectious keratitis with corneal melting. The patients were randomly divided into two groups. Group I (control group) included 16 eyes received systemic and topical antimicrobial drugs guarded by culture and sensitivity test. Group II underwent CXL and then continued their antimicrobial treatment. Full field electroretinogram (ERG) and flash visual evoked potential (VEP) were done for each patient in both groups basically and then 1wk, 1 and 3mo post-treatment to assess the changes in the electrophysiological function of the retina and optic nerve. Healing of 10 eyes in group I in comparison to 14 eyes in group II was recorded. The mean duration of healing was 36.56±5.21d in group I vs 20.2±4.4d in group II (P<0.005). In group II, ERG showed an insignificant reduction of all parameters of ERG and VEP after CXL. The amplitude of scotopic rod response, oscillatory potential amplitude, flicker amplitude and photopic cone response were insignificantly decreased (P=0.4, 0.8, 0.1, and 0.3 respectively). There were insignificant prolongation of latencies of scotopic rod, oscillatory potential, flicker and photopic cone response (P=0.2, 0.7, 0.5 and 0.1). There was slight delay in latency of VEP without a significant reduction in amplitude. CXL is an effective technique in treatment of severe infectious keratitis with melting as it halts the melting process with acceptable safety on the retinal and optic nerve function.