Two cases of occupational acute and severe methyl acetate poisoning

Alterations in neurofilament light in optic nerve in rat kainate and monkey ocular hypertension models

To determine the effects of cumulative IOP exposure and axonal damage on retinal gene expression in DBA/2 mice. DBA/2J, DBA/2J(pe) (pearl), and C57BL/6 mice from 3 to 12 months of age were used. IOP was measured with a rebound tonometer, and optic nerve (ON) damage was determined by grading of ON sections. Retinal RNA was subjected to microarray analysis. Comparisons explored the effects of cumulative IOP exposure (cIOPx) as well as ON damage (ONd) in the DBA/2J animals compared with that in the C57BL/6 and pearl mice. RT-PCR was performed to confirm some of the genes and bioinformatic analysis to identify affected gene networks. Microarrays revealed that an increasing number of genes were up- or downregulated in 9- and 12-month DBA/2J mice with various degrees of ONd. A smaller number of genes were expressed differentially between eyes with different cIOPx at the same age, from 6 months on. Expression of 1385 and 1133 genes differed between DBA/2J animals and C57BL/6 or pearl mice, respectively, and some them were confirmed by RT-PCR. Bioinformatics analysis identified functional gene networks, including members of the complement system, that appeared to be related to cIOPx, ONd, or both. Gene expression changes occur in retinas of DBA/2 mice with various amounts of cIOPx as well as ONd. Genes involved, code for proteins with diverse cellular functions and include among others the complement system. cIOPx and ONd affect common as well as unique gene sets.

Optic Nerve Cupping Represents Neuronal Loss

There is a number of literature data on ischemic optic neuropathy development in acute hemorrhage. However, ocular disorders in prolonged chronic hemorrhage and iron-deficiency anemia are not well studied. We present a clinical case of optic nerve and retinal damage in a patient with prolonged chronic gastrointestinal bleeding. 53-year-old patient S. presented with complaints on dramatic sudden loss of vision of his right eye (visual acuity was 0/02 and was not improving with correction). Visual acuity of the left eye was good. Ophthalmoscopy revealed right optic nerve swelling, flame-shaped disc and peripapillary hemorrhages, and multiple soft exudates along blood vessels of the right eye. Optic nerve head of the left eye was pale pink, with well-defined borders. Multiple soft exudates along blood vessels and few flame-shaped hemorrhages were identified as well. Clinical examination revealed iron-deficiency post-hemorrhagic anemia. The diagnosis of anterior ischemic neuropathy of the right eye, ischemic neuroretinopathy of left eye associated with post-hemorrhagic anemia was established. Conservative treatment increased hemoglobin level up to 82 g/l, the red blood cells count - up to 2,88×1012/L, hematocrit was 0.25%, platelet count reached 344×109/L, but the signs of rectal bleeding remained. The patient underwent surgery for hemorrhoids. After the increase of hemoglobin level, visual acuity of the right eye improved to 0.1, the visual acuity of the left eye was 1.0. According to the results of computed peripheral vision test (Humphrey Full Field 120 Point Screening Test), central scotoma and scotomas in the lower half of the field of vision of the right eye remained. In the field of vision of the left eye, the area of absolute arcuate scotoma in the lower-nasal quadrant decreased significantly. Reduced visual acuity was the main complaint of the patient with a longstanding gastrointestinal bleeding. A careful history and thorough clinical examination allowed to establish the cause of the optic nerve and retinal damage, to assign pathogenetically based treatment, which led to an improvement in visual function.

Intravitreal injection of endothelin-1 caused optic nerve damage following to ocular hypoperfusion in rabbits

To correlate the five phases of optic nerve (ON) damage staging, as assessed by means of confocal tomography (HRT) with the five stages of visual field, assessed by conventional perimetry (standard automatic perimetry, SAP) and classified in five stages according to the "GLAUCOMA STAGING SYSTEM". The second step was to correlate the same optic nerve staging system with the results of the visual field tested with non-conventional perimetry using the frequency doubling technology (FDT) employing the Humphrey-Zeiss and Welch-Allyn perimeter. The five stages of FDT visual field data evolution were classified according to the new "FDT STAGING SYSTEM". 58 visual fields of 58 consecutive selected patients with either ocular hypertension or glaucoma with an age-range between 15 and 65 years. Visual field examination was performed with conventional (Octopus G2 threshold test) and non-conventional perimetry (FDT N30 threshold test), and the ON was assessed with confocal tomography (Heidelberg Retina Tomograph). In 40 % of the visual fields tested normal with conventional perimetry, non-conventional perimetry (FDT) detected glaucomatous visual field defects corresponding topographically with the optic nerve damage revealed by HRT. New non-conventional perimetric techniques such as FDT enable the very early detection of visual field defects topographically correlated to optic nerve damage.

PurposeThe purpose of our study was to evaluate the effectiveness of CPAP in increasing the thickness of retinal layers. Other aims were to assess retinal and optic nerve damage predictors in OSA and establish predictors of poor response to CPAP treatment in optic nerve damage.MethodsA prospective cohort study with consecutive inclusion of the first 3 patients who attended for treatment each day. All patients underwent a diagnostic polygraph, and patients with moderate-severe OSA treated with CPAP were recruited. Optical Coherence Tomography (OCT) was performed within 3 days of the patient’s inclusion and 12 months after the start of CPAP treatment.ResultsData from 37 patients with OSA were analysed. After 12 months of CPAP treatment, there was a significant improvement in the thickness of the superotemporal Bruch’s membrane opening-minimum rim width (BMO-MRW) (316.54 to 318.23 μm, p-value = 0.08). There was a non-significant improvement in the thickness of nasal, inferonasal and superonasal retinal nerve fibre layers. In a multivariate analysis, HB and Type 2 diabetes mellitus have been associated with an increased odds ratio (OR) of retinal and optical nerve damage (OR = 3.58, p = 0.03 and OR = 4.344, p = 0.042, respectively).ConclusionBMO-MRW thickness may assess early damage induced by OSA and the response to CPAP. HB is a predictor of retinal and optic nerve damage in patients with OSA. CPAP treatment has a long-term protective effect on the retina and optic nerve.

Kynurenines, products of tryptophan (TRP) metabolism, display neurotoxic (e.g., 3-hydroxykynurenine; 3-HK), or neuroprotective (e.g., kynurenic acid; KYNA) properties. Imbalance between the enzymes constituting the kynurenine pathway (KP) plays a role in several disease, including neurodegeneration. In this study, we track changes in concentrations of tryptophan and its selected metabolites after damage to retinal ganglion cells and link this data with expression of KP enzymes. Brown-Norway rats were subjected to intravitreal N-methyl-D-aspartate (NMDA) injection or partial optic nerve crush (PONC). Retinas were collected 2 and 7 days after the completion of PONC or NMDA injection. Concentrations of TRP, kynurenine (KYN), and KYNA were determined by high performance liquid chromatography (HPLC). Data on gene expression in the rat retina were extracted from GEO, public microarray experiments database. Two days after NMDA injection concentration of TRP decreased, while KYN and KYNA increased. At day 7 compared to day 2 decrease of KYN, KYNA and further reduction of TRP concentration were observed, but on day 7 KYN concentration was still elevated when compared to controls. At day 2 and 7 after NMDA injection no statistically significant alterations of 3-HK were observed. TRP and 3-HK concentration was higher in PONC group than in controls. However, both KYN and KYNA were lower. At day seven concentration of TRP, 3-HK, and KYN was higher, whereas concentration of KYNA declined. In vivo experiments showed that retinal damage or optic nerve lesion affect TRP metabolism via KP. However, the pattern of changes in metabolite concentrations was different depending on the model. In particular, in PONC KYNA and KYN levels were decreased and 3-HK elevated. These observations correspond with data on expression of genes encoding KP enzymes assessed after optic nerve crush or transection. After intraorbital optic nerve crush downregulation of KyatI and KyatIII between 24 h and 3 days after procedure was observed. Kmo expression was transiently upregulated (12 h after the procedures). After intraorbital optic nerve transsection (IONT) Kmo expression was upregulated after 48 h and 7 days, KyatI and KyatIII were downregulated after 12, 48 h, 7 days and upregulated after 15 days. Collected data point to the conclusion that development of therapeutic strategies targeting the KP could be beneficial in diseases involving retinal neurodegeneration.

Endothelin-1 (ET-1), a potent vasoconstrictor, is involved in retinal vascular dysregulation and oxidative stress in glaucomatous eyes. Taurine (TAU), a naturally occurring free amino acid, is known for its neuroprotective and antioxidant properties. Hence, we evaluated its neuroprotective properties against ET-1 induced retinal and optic nerve damage. ET-1 was administered intravitreally to Sprague-Dawley rats and TAU was injected as pre-, co- or post-treatment. Animals were euthanized seven days post TAU injection. Retinae and optic nerve were examined for morphology, and were also processed for caspase-3 immunostaining. Retinal redox status was estimated by measuring retinal superoxide dismutase, catalase, glutathione, and malondialdehyde levels using enzyme-linked immuosorbent assay. Histopathological examination showed significantly improved retinal and optic nerve morphology in TAU-treated groups. Morphometric examination showed that TAU pre-treatment provided marked protection against ET-1 induced damage to retina and optic nerve. In accordance with the morphological observations, immunostaining for caspase showed a significantly lesser number of apoptotic retinal cells in the TAU pre-treatment group. The retinal oxidative stress was reduced in all TAU-treated groups, and particularly in the pre-treatment group. The findings suggest that treatment with TAU, particularly pre-treatment, prevents apoptosis of retinal cells induced by ET-1 and hence prevents the changes in the morphology of retina and optic nerve. The protective effect of TAU against ET-1 induced retinal and optic nerve damage is associated with reduced retinal oxidative stress.

IntroductionDiabetic patients routinely have high levels of high mobility group box 1 (HMGB1) protein in their plasma, vitreous and ocular membranes, which is strongly correlated with subclinical chronic inflammation in the eye. Our previous work has suggested that high HMGB1 in diabetes plays a role in retinal inflammation and angiogenesis, but its role in the optic nerve damage is unclear. Therefore, our goal is to examine the role of HMGB1 in optic nerve damage in diabetes.MethodsGene expression of HMGB1 was quantified in the optic nerve from streptozotocin-induced diabetic mice by qRT-PCR, and their protein expressions by Western blot analysis and immunofluorescence staining. Using immunohistochemical technique, expression of reactive astrogliosis (indicator of neuroinflammation) and nerve demyelination/damage were determined by quantifying glial fibrillary acid protein (GFAP) and myelin basic protein (MBP), respectively. The role of HMGB1 in the optic nerve damage and alteration visual pathways was confirmed in mice receiving glycyrrhizin, a HMGB1 inhibitor. Similar parameters were measured in the optic nerve from human donors with diabetes.ResultsCompared to normal mice, diabetic mice exhibited increased levels of HMGB1, higher GFAP expression, and decreased MBP in the optic nerve. Double immunofluorescence microscopy revealed that diabetes induced increased HMGB1 immunoreactivities were significantly colocalized with GFAP in the optic nerve. Glycyrrhizin supplementation effectively reduced HMGB1 and maintained normal axonal myelination and visual conduction. Results from mice optic nerve confirmed the results obtained from human donors with diabetes.DiscussionsThus, diabetes-induced HMGB1 upregulation promotes optic nerve demyelination and inflammation. The regulation of HMGB1 activation has potential to protect optic nerve damage and the abnormalities of visual pathways in diabetic patients.

Objective: To study the correlation between the 24-hour blood pressure parameters and optic nerve damage in primary open-angle glaucoma (POAG). Methods: In this case control study, 60 patients with POAG were assigned to POAG group, and 55 normal subjects were assigned to control group. Synchronous monitoring of 24-hour intraocular pressure (IOP) and blood pressure was conducted in both groups. Blood pressure parameters, optic perfusion pressure, and intraocular pressure for the two groups were compared. We also evaluated the connections among the blood pressure parameters, optic perfusion pressure, and IOP with visual function. Inter-group comparisons were made by independent samples t-tests and multiple linear regression. Results: ①The average IOP, IOP fluctuation, the ocular perfusion pressure fluctuation, and pulse pressure fluctuation of POAG group were significantly higher than those of control group (t=3.22, 6.57, 2.29, 2.39, respectively, all P<0.05). ②The mean systolic blood pressure of POAG group was significantly higher than that of control group (t=3.02, P=0.003). The highest systolic blood pressure, systolic blood pressure fluctuations, nighttime average systolic blood pressure, highest nighttime systolic blood pressure value and fluctuation of POAG group were also significantly higher than those of control group (t=4.38, 5.27, 4.13, 4.13, 4.14, all P<0.001). ③The mean 24-hour diastolic pressure, the maximum diastolic pressure, the mean nighttime diastolic pressure, and the maximum nighttime diastolic pressure of POAG group were significantly higher than those of control group (t=2.22, 2.50, 2.29, 2.10, all P<0.05). ④In POAG group, the mean IOP was negatively correlated with the visual field mean defect in POAG (b=-0.44, P=0.004), and the RNFL thickness was negatively correlated with mean IOP (b=-0.956, P=0.001), IOP fluctuation (b=-1.125, P=0.003). The mean nighttime diastolic pressure (b=0.395, P<0.001) and the mean nighttime arterial pressure (b=0.046, P=0.001) were positively correlated with AP100 and AP50 values, respectively. Conclusions: ①There was a correlation between the blood pressure parameters and the optic nerve damage in POAG. ②The nighttime optic perfusion pressure, the nighttime diastolic blood pressure, and the nighttime arterial pressure may be influential factors affecting optic nerve damage of POAG. ③In the treatment of POAG, a stable normal blood pressure and stable target IOP are beneficial to maintain an effective and stable optic perfusion pressure. This suggests that we should pay attention to the treatment of POAG with IOP reduction and changes of blood pressure at the same time. Key words: 24-hour blood pressure; blood pressure parameters; primary open-angle glaucoma; optic nerve damage

Purpose To evaluate the therapeutic effects of methylprednisolone, the CoenzymeQ10 (CoQ10) structural analogue idebenone, and both together on the optic nerve (ON) and retinal layers following methanol intoxication in rats with histopathological and biochemical methods. Materials and methods This experimental study was conducted with 30 male Wistar rats. The rats were divided into five equal groups depending on the treatment protocol:healthy controls (HC), methanol (M), methanol + methylprednisolone (MM), methanol + idebenone (MI), and methanol + methylprednisolone + idebenone (MMI).Distilled water was provided orally to the HC group, while 20% methanol was administered orally at a dose of 3 g/kg with a nasogastric tube to all rats in groups except the HC group. Four hours later, group MM received 1 mg/kg of intraperitoneal methylprednisolone for 10 days using an insulin syringe, and group MI received 20 mg/kg idebenone by nasogastric catheter for 28 days. MMI group was administered oral idebenone and intraperitoneal methylprednisolone at the same dose. Serum samples were obtained on the 28th day for biochemical analysis and afterwards the rats were euthanized for histopathological examination and eyes were enucleated. ON was evaluated for circumference thickness, vascularization and number of astrocytes, also retinal layers were examined for structural changes by histopathological examination. Results Comparison of the antioxidant and oxidative stress biomarkers between the groups revealed no statistically significant difference (p > 0.05). By histopathological evaluation the most marked results were obtained by MMI group with an improvement of all parameters mentioned. There was no statistically significant difference between MM group and M group for RD score (p = 0.123). In addition, ON vacuolization in MI group (p < 0.001) and ON astrocyte increase in both MI and MMI groups were statistically significantly lower than in M group (p = 0.001, p = 0.001, respectively). Conclusions The early use (within hours) of idebenone and short-term methylprednisolone treatment together may protect against the retinal and ON damage developing after methanol ingestion in rats as guided by the histopathological data.

The Rgcs1 quantitative trait locus, on mouse chromosome 5, influences susceptibility of retinal ganglion cells to acute damage of the optic nerve. Normally resistant mice (DBA/2J) congenic for the susceptible allele from BALB/cByJ mice exhibit susceptibility to ganglion cells, not only in acute optic nerve crush, but also to chronic inherited glaucoma that is characteristic of the DBA/2J strain as they age. SNP mapping of this QTL has narrowed the region of interest to 1 Mb. In this region, a single gene (Spink2) is the most likely candidate for this effect. Spink2 is expressed in retinal ganglion cells and is increased after optic nerve damage. This gene is also polymorphic between resistant and susceptible strains, containing a single conserved amino acid change (threonine to serine) and a 220 bp deletion in intron 1 that may quantitatively alter endogenous expression levels between strains. Overexpression of the different variants of Spink2 in D407 tissue culture cells also increases their susceptibility to the apoptosis-inducing agent staurosporine in a manner consistent with the differential susceptibility between the DBA/2J and BALB/cByJ strains.

Exploring experimental autoimmune optic neuritis using multimodal imaging

PurposeInhibition or targeted deletion of histone deacetylase 3 (HDAC3) is neuroprotective in a variety neurodegenerative conditions, including retinal ganglion cells (RGCs) after acute optic nerve damage. Consistent with this, induced HDAC3 expression in cultured cells shows selective toxicity to neurons. Despite an established role for HDAC3 in neuronal pathology, little is known regarding the mechanism of this pathology.MethodsInduced expression of an HDAC3-mCherry fusion protein in mouse RGCs was accomplished by transduction with AAV2/2-Pgk-HDAC3-mCherry. Increased susceptibility to optic nerve damage in HDAC3-mCherry expressing RGCs was evaluated in transduced mice that received acute optic nerve crush surgery. Expression of HDAC3-FLAG or HDAC3-mCherry was induced by nucleofection or transfection of plasmids into differentiated or undifferentiated 661W tissue culture cells. Immunostaining for cleaved caspase 3, localization of a GFP-BAX fusion protein, and quantitative RT-PCR was used to evaluate HDAC3-induced damage.ResultsInduced expression of exogenous HDAC3 in RGCs by viral-mediated gene transfer resulted in modest levels of cell death but significantly increased the sensitivity of these neurons to axonal damage. Undifferentiated 661W retinal precursor cells were resilient to induced HDAC3 expression, but after differentiation, HDAC3 induced GFP-BAX recruitment to the mitochondria and BAX/BAK dependent activation of caspase 3. This was accompanied by an increase in accumulation of transcripts for the JNK2/3 kinases and the p53-regulated BH3-only gene Bbc3/Puma. Cell cycle arrest of undifferentiated 661W cells did not increase their sensitivity to HDAC3 expression.ConclusionsCollectively, these results indicate that HDAC3-induced toxicity to neurons is mediated by the intrinsic apoptotic pathway.