VEGF-A165b is an endogenous neuroprotective splice isoform of vascular endothelial growth factor A in vivo and in vitro

Vascular endothelial growth factor (VEGF) A is generated as two isoform families by alternative RNA splicing, represented by VEGF-A165a and VEGF-A165b. These isoforms have opposing actions on vascular permeability, angiogenesis, and vasodilatation. The proangiogenic VEGF-A165a isoform is neuroprotective in hippocampal, dorsal root ganglia, and retinal neurons, but its propermeability, vasodilatatory, and angiogenic properties limit its therapeutic usefulness. In contrast, a neuroprotective effect of endogenous VEGF-A165b on neurons would be advantageous for neurodegenerative pathologies. Endogenous expression of human and rat VEGF-A165b was detected in hippocampal and cortical neurons. VEGF-A165b formed a significant proportion of total VEGF-A in rat brain. Recombinant human VEGF-A165b exerted neuroprotective effects in response to multiple insults, including glutamatergic excitotoxicity in hippocampal neurons, chemotherapy-induced cytotoxicity of dorsal root ganglion neurons, and retinal ganglion cells (RGCs) in rat retinal ischemia-reperfusion injury in vivo. Neuroprotection was dependent on VEGFR2 and MEK1/2 activation but not on p38 or phosphatidylinositol 3-kinase activation. Recombinant human VEGF-A165b is a neuroprotective agent that effectively protects both peripheral and central neurons in vivo and in vitro through VEGFR2, MEK1/2, and inhibition of caspase-3 induction. VEGF-A165b may be therapeutically useful for pathologies that involve neuronal damage, including hippocampal neurodegeneration, glaucoma diabetic retinopathy, and peripheral neuropathy. The endogenous nature of VEGF-A165b expression suggests that non-isoform-specific inhibition of VEGF-A (for antiangiogenic reasons) may be damaging to retinal and sensory neurons.

Evaluation of intraocular pressure elevation in a modified laser-induced glaucoma rat model

The main drawbacks of currently described pressure induced glaucoma animal models are, that intraocular pressure (IOP) either rises slowly, leading to a heterogeneous onset of glaucoma in the treated animals or that IOP normalizes before significant damage occurs, necessitating re-treatment. Furthermore, a variable magnitude of IOP increase often results when particles are introduced into the anterior chamber. In order to develop a simple and reproducible rat glaucoma model with sustained IOP elevation after a single treatment we induced occlusion of the chamber angle by anterior chamber paracentesis and subsequent laser coagulation of the limbal area with 35, 40 or 45 laser burns. Right eyes served as controls. IOP was measured three times weekly using TonoLab rebound tonometry in awake animals. After four weeks, retinal tissue was harvested and processed for whole mount preparation. The number of prelabeled, fluorogold-positive retinal ganglion cells (RGCs) was analyzed under a fluorescence microscope. The eyes were further analyzed histologically. Results are expressed as means and standard deviation. Amplitude and duration of the IOP elevation increased with the number of laser burns. Two weeks after 35, 40 or 45 translimbal laser burns the IOP difference between treated and control eye was 7.5 ± 5, 14 ± 8 or 19 ± 9 mmHg, respectively; the RGC density/mm(2) 28 days after treatment was 1488 ± 238 for control eyes (n = 31) and 1514 ± 287 (n = 10), 955 ± 378 (n = 10) or 447 ± 350 (n = 11) for the respective laser groups. Mean IOP of all control eyes over the observation period was 12.4 ± 0.8 mmHg. The chamber angle showed pigment accumulation in the trabecular meshwork of all laser groups and confluent peripheral anterior synechia after 40 and 45 laser burns. Histologic examination of the retina revealed increasing glia activation in a pressure dependant manner. In this study, >91% of laser treated rats developed secondary glaucoma with sustained IOP elevation for at least 2 weeks. The amount of IOP elevation and RGC loss correspond with the number of laser burns applied. This relatively high success rate after a single procedure may constitutes an advantage over established glaucoma models, as this decreases the risk of complications (e.g. corneal decompensation, intraocular bleeding or inflammation) and, thus, improves the outcome.

Effect of ischemia duration on autoantibody response in rats undergoing retinal ischemia-reperfusion

Both the innate and the adaptive immune systems are involved in the pathogenic processes following ischemia-reperfusion injury. We analyzed the possible correlation between the duration of ischemia and autoantibody diversification in a model of ocular ischemia. Rats were subjected to 30, 45, or 90 min of ischemia, and retinal ganglion cell (RGC) density and antibody reactivity were analyzed via customized protein microarray slides. After ocular ischemia, significant alterations in antibody response were observed, while increasing exposure caused more severe RGC damage. Distinct antibody responses after ischemia were detected; these alterations comprised decreased reactivities against cyclophilin A and glyceraldehyde-3-phosphate dehydrogenase, possibly due to increased binding of circulating antibodies to debris material. Other antibodies, like those against α(5)β(1)-integrin or β(2) -adrenergic receptor, were upregulated after ischemia.

[Ophthalmoplegia with bilateral mydriasis]

We report the case history of a 41-year-old patient who, following bronchial infection, presented with progressive ophthalmoplegia in both eyes, dilated pupils unresponsive to light or convergence and ataxia. The suspected diagnosis of Miller-Fisher syndrome was confirmed by the detection of anti-ganglioside GQ1b antibodies.

Pattern electroretinogram in glaucoma suspects: new findings from a longitudinal study

PURPOSE

Early detection of glaucoma remains a challenging problem and needs long-term, prospective studies. The pattern electroretinogram (PERG) directly reflects retinal ganglion cell function. The PERG was evaluated by extending a prospective study of patients with ocular hypertension and evaluated amplitude, PERG ratio, peak time, and trends thereof.

METHODS

One hundred twenty eyes of 64 patients with intraocular pressure greater than 25 mm Hg (or ≥ 23 mm Hg with additional risk factors), normal visual fields, normal optic disc appearance, and visual acuity ≥ 0.8 were included in the study. Mean follow-up time was 10.3 years. The per-visit measures of amplitude at 15 reversals/s to 0.8° check size, PERG ratio (0.8°/16°), peak time, visual field, and their trends were analyzed.

RESULTS

Over the course of the study 13 eyes converted to glaucoma according to a visual field definition. Amplitude to 0.8° check size, PERG ratio, and peak time were significantly lower in converters. Amplitude and PERG ratio predicted conversion 4 years ahead with a sensitivity/specificity of 67%/64% and 75%/76%, respectively. At this time, the ROC area was already significantly above chance for the PERG ratio. Comparison of the trends of converters and nonconverters revealed significant differences in the PERG ratio; however, trends did not predict conversion as successfully as single-visit measures.

CONCLUSIONS

The PERG, especially the PERG ratio, detected glaucoma patients 4 years before visual field changes occurred, with a sensitivity/specificity of 75%/76%. Slope analysis required multiple visits, but provided little additional information in detecting converters.

Face-to-face upright seated positioning for cataract surgery in patients who cannot lie flat

We describe a technique for cataract surgery in patients unable to adopt the conventional face-to-ceiling position. A standard reclining operating chair and operating microscope are used. Patients are seated instead of lying down, with the chair back elevated 30 to 80 degrees above the horizontal and the operating microscope rotated 45 to 60 degrees to vertical. The surgeon is seated or standing, facing the patient. A clear corneal incision is used via an inferior, temporal, or inferotemporal approach under topical intracameral anesthesia without sedation. Results of this technique in a case series comprising 32 eyes are reported. The technique is useful for patients unable to adopt the traditional approach for cataract surgery and at high risk for complications from general anesthesia. It is technically challenging so should be attempted by experienced surgeons only.

Methylprednisolone fails to preserve retinal ganglion cells and visual function after ocular ischemia in rats

PURPOSE

Methylprednisolone (MP) is commonly used to treat traumatic optic neuropathy and optic neuritis, but its benefit in terms of neuronal survival remains controversial. The aim of this study was to investigate the effects of MP on retinal ganglion cell (RGC) survival and visual function after ischemia in rats.

METHODS

Ocular ischemia was induced by elevated intraocular pressure. Rats were treated with NaCl, 1 mg/kg/d, or 30 mg/kg/d intraperitoneal MP over 3 days. RGCs were labeled retrogradely 4 days after ischemia and were quantified 6 days later. Post-ischemic retinal function was assessed by scotopic and photopic electroretinography (ERG). Optic nerve function was investigated on days 4 and 10 after ischemia by visual evoked potentials (VEPs).

RESULTS

Compared with nonischemic eyes, ischemia reduced RGCs with NaCl to 47% +/- 3% (mean +/- SEM) and to 46% +/- 3% and 43% +/- 6% with 1 mg/kg/d and 30 mg/kg/d MP. ERG did not differ significantly for any parameter among the three groups. Four days after ischemia, the VEPs of rats receiving any dose of MP were significantly higher than the control. VEPs in both steroid groups fell to control levels 10 days after ischemia.

CONCLUSIONS

Treatment with MP did not improve RGC survival or retinal function. The VEP showed a short-term benefit because of steroids.

Quantification of ischemic damage in the rat retina: a comparative study using evoked potentials, electroretinography, and histology

PURPOSE

To identify objective criteria to quantify visual function in the rat for developing therapeutic strategies to protect neuronal cells after ischemia. The impact of ocular ischemia on luminance and frequency-modulated contrast vision was compared with the function of outer retinal cells and the number of intact retinal ganglion cells (RGCs).

METHOD

Ischemia was induced in Brown-Norway rats by elevating the intraocular pressure to 120 mm Hg for 30, 45, 60, and 90 minutes. Visual function was evaluated by visual evoked potentials (VEPs) in awake, freely moving rats. Retinal function was analyzed with scotopic and photopic electroretinography (ERG). RGCs were quantified in retinal flatmounts after postischemic injection of tracer into the superior colliculus.

RESULTS

The response to flicker stimulation in VEP recordings decreased as the ischemic episodes increased. The susceptibility to ischemic damage was more pronounced when potentials were evoked with stimuli at higher frequencies. In ERG recordings, ischemia reduced oscillatory potentials and photopic flicker responses more intensely than scotopic a- and b-waves. In counting the RGCs, the reduced cell density correlated significantly with all electrophysiological parameters. The duration of ischemia with half-maximal inhibitory effect was between 36 and 58 minutes for VEPs and between 36 and 41 minutes for ERG, and it was 51 minutes for RGCs.

CONCLUSIONS

The amounts of reduction in VEPs, ERG, and RGCs differed as the duration of ischemia increased. The electrophysiological parameters presented in this study may serve as a useful addition to morphologic evaluations in future neuroprotection studies in vivo.

[Basiliximab following penetrating risk-keratoplasty--a prospective randomized pilot study]

BACKGROUND

Until now cyclosporin A (CSA) and mycophenolate mofetil (MMF) are the only available systemic immunosuppressants for patients undergoing risk keratoplasty. Basiliximab is a chimeric monoclonal interleukin 2-receptor antibody, which inhibits T-cell proliferation. Basiliximab is approved for the treatment in patients after kidney transplantation. The aim of this study was to prove the efficacy and safety of Basiliximab after penetrating risk keratoplasty.

PATIENTS AND METHODS

20 patients undergoing risk keratoplasty received as postoperative medication fluocortolon 1 mg/kg/d (tapered off within three weeks) and prednisolone acetate eye-drops 5x/d (tapered off within five months). In addition, 10 patients received 20 mg basiliximab immediately following surgery and four days postoperatively. 10 patients in the control group received oral CSA adapted to the blood-trough level (120-150 ng/mL) for six months.

RESULTS

After a mean follow-up time of 477 +/- 263 days 4 patients of the basiliximab group showed corneal immune reactions (2 irreversible), while no side effects were observed. In the CSA group 2 immune reactions occurred (1 irreversible). In 2 CSA-treated patients the CSA administration had to be stopped due to side effects.

CONCLUSIONS

Basiliximab has a lower efficacy in preventing immune reactions after risk keratoplasty than CSA. However, the side effect profile of basiliximab is more favourable than that of CSA.

Effects of an extreme endurance race on energy balance and body composition - a case study

The aim of this case study was to examine energy expenditure (EE) in one cyclist during an extreme endurance cycling race - the "XXAlps 2004" (2,272 km distance and 55,455 m altitude) which was completed in 5 days and 7 hours - and whether the energy deficit derives primarily from the degradation of subcutaneous adipose tissue or loss of muscle mass. Energy intake (EI) was continuously recorded. EE was estimated using two different methods: 1) Continuous heart rate recording using a portable heart rate monitor (POLAR(®) S710) and 2) using the individual relationship between heart rate and oxygen uptake (VO2) determined under laboratory conditions. Body composition was assessed by measuring body mass, skinfold thickness and extremity circumferences. The cyclist lost 2.0 kg body mass, corresponding to 11,950 kcal (50 MJ). Fat mass was reduced by 790 g (7,110 kcal; 30 MJ) and fat free mass by 1.21 kg (4,840 kcal; 20 MJ). Circumferences of the lower extremities were reduced, in contrast skinfold thickness at the lower limbs increased. Energy deficit (ED) was calculated as the difference between EI and EE. Energy deficit using continuous heart rate monitoring was 29,554 kcal (124 MJ), and using the individual relationship between heart rate and VO2 was 7,111 kcal (30 MJ). The results show that the difference between ED due to decreased body mass and ED estimated from continuous heart rate monitoring was 74 MJ (124 MJ - 50 MJ). In contrast the difference between ED due to decreased body mass and ED estimated from laboratory data was 20 MJ (30 - 50 MJ). This difference between methodologies cannot properly be explained. Body mass and skinfold thickness may be overestimated due to hypoproteinemic oedemas during endurance exercise. Data from the present study suggests the individual relationship between heart rate and VO2 may provide a closer estimation of EE during extreme endurance exercise compared with corresponding data derived from continuous heart rate monitoring using the POLAR(®) S710. Key PointsDuring an extreme endurance cycling race, energy expenditure can not be covered by energy intake and an energy deficit results.The energy deficit seems to be covered by degradation of subcutaneous adipose tissue and muscle mass.Determination of energy expenditure during extreme endurance may be properly determined with the individual correlation of heart rate - VO2 instead of continuous heart rate monitoring.

Energy Turnover at the Race Across AMerica (RAAM) - a Case Report

We report about energy intake and energy expenditure in an official finisher of the Race Across AMerica (RAAM) in 2003. Energy intake from nutrition was continuously recorded. Energy expenditure was measured by continuous heart rate recording with a portable heart rate monitor POLAR S710 to estimate energy expenditure during physical activity. Our athlete (33 years, 179 cm, 73 kg, VO (2)max 60 ml . min (-1) . kg (-1), lactate threshold at 77%VO (2)max) finished the 4701-km cycling race with altitude differences amounting to 25,826 meters in 9 days 16 hours and 45 minutes in 4th place. He completed 470+/-72.9 km (372-541 km) per day with 2,582+/-1,576 (683-5,047) meters of altitude. During the whole race, he expended a total energy of 179,650 kcal with 17,965+/-2165 (15,100 - 23,280) kcal per day. Total energy intake was 96,124 kcal with an average of 9,612+/-1,500 (7,513-12,735) kcal per day. Of total ingested calories, 75.2% derived from carbohydrates, 16.2% from fat, and 8.6% from protein. He ingested an energy of 9,612+/-1,550 (7,513 - 12,735) kcal daily, consisting of 1,814+/-310 (1,336 - 2,354) g of carbohydrates, 172+/-47 (88-251) g of fat, and 207+/-52 (128-286) g of protein. The average daily energy deficiency amounted to 8,352+/-2,523 (4,425-13,631) kcal. A total deficiency of 83,526 kcal resulted after the race while the athlete lost 5 kg of body weight. These results provide data about energy intake and energy expenditure in the RAAM for future athletes, nutritionists and coaches. Further investigation should be performed in order to determine whether either muscle mass or body fat will be lost in extreme endurance cycling.

Mice transgenic for exon 1 of Huntington's disease: properties of cholinergic and dopaminergic pre-synaptic function in the striatum

In Huntington's disease (HD), neuronal loss is most prominent in the striatum leading to emotional, cognitive and progressive motor dysfunction. The R6/2 mice, transgenic for exon 1 of the HD gene, develop a neurological phenotype with similarities to these features of HD. In striatal tissue, electrically evoked release of tritiated acetylcholine (ACh) and dopamine (DA) were compared in wild-type (WT) and R6/2 mice. In R6/2 mice, the evoked release of ACh, its M2 autoreceptor-mediated maximum inhibition and its dopamine D2 heteroreceptor-mediated maximum inhibition was diminished to 51%, 74% and 87% of controls, respectively. Also, the activities of choline acetyltransferase and of synaptosomal high-affinity choline uptake decreased progressively with age in these mice. In the DA release model, however, electrical stimulation elicited equal amounts of [3H]-DA both in WT and R6/2 mice. Moreover, high-affinity DA uptake into striatal slices was similar in WT and R6/2 mice. In order to confirm these findings in vivo, intrastriatal levels of extracellular DA were measured by intracerebral microdialysis in freely moving mice: striatal DA levels were found to be equal in WT and R6/2 mice. In conclusion, in the transgenic R6/2 mice changes occur mainly in striatal cholinergic neurones and their pre-synaptic modulation, but not in the dopaminergic afferent terminals. Whether similar events also contribute to the pathogenesis of HD in humans has to be established.

[The effect of gabapentin and gabapentin-lactam on retinal ganglion cell survival. Situation after acute retinal ischemia in animal models]

BACKGROUND

Reduction in the excitatory and potentially toxic neurotransmitter glutamate can protect retinal ganglion cells. What are the effects of the antiepileptic drug gabapentin, for which antiglutamatergic effects have been described, and the new substance gabapentin-lactam (GBP-L) on retinal ganglion cell survival after retinal ischemia?

METHODS

In 3 groups of 10 rats each, ischemia was induced by elevating the intraocular pressure of the left eye to 120 mmHg for 1 h. Saline, gabapentin (2 x 50 mg/kg intraperitoneally) and GBP-L (2 x 50 mg/kg intraperitoneally) were injected before and 5 h after ischemia. Two weeks later ischemic damage was quantified histologically by counting the number of neurons in the ganglion cell layer. In vitro transmitter release experiments were performed to obtain information on the effect of gabapentin and GBP-L on ischemia-induced glutamate release and the mechanism of action of GBP-L.

RESULTS

In the control group 17% of the retinal ganglion cells survived ischemia. GBP-L doubled the number of the surviving cells while gabapentin was not effective in these experiments. In vitro gabapentin and GBP-L reduced ischemia-induced glutamate release by 35.7% and 42.5%, respectively. The blockade of ATP-sensitive potassium channels antagonized the effect of GBP-L completely.

CONCLUSION

GBP-L is neuroprotective in retinal ischemia and diminishes the release of the excitatory neurotoxic amino acid glutamate. The effect of GBP-L might be mediated by ATP-sensitive potassium channels. Also gabapentin reduced glutamate release but was not neuroprotective in vivo.

Gabapentin-lactam (8-aza-spiro[5,4]decan-9-on; GBP-L) inhibits oxygen glucose deprivation-induced [3H]glutmate release and is a neuroprotective agent in amodel of acute retinal ischemia

The modulation of the enhanced release of [3H]glutamate following ischemia-like conditions was studied in rat hippocampal slices using a superfusion system. Ischemia was simulated by a glucose-free medium equilibrated with 95% N2 and 5% CO2. In this model the potential neuroprotective effects of several substances on [3H]glutamate release induced by ischemia-like conditions were investigated. Gabapentin-lactam (8-aza-spiro-5,4-decan-9-on; GBP-L) was synthesised and patented in our laboratory. GBP-L (100 microM) reduced the oxygen glucose deprivation-induced [3H]glutamate release by 42.5%, CI95=[33.4%, 51.5%]. The KATP channel antagonist glibenclamide (1 microM) blocked this effect completely. The high antagonist potency was reflected by an apparent pA2-value of glibenclamide of 8.3, CI95=[6.8, 9.4]. Minoxidil sulfate (10 microM), a KATP channel opener, mimicked the effect of GBP-L (inhibition by 22.8%, CI95=[13.2%, 32.5%]). Similarly to its lactam, also gabapentin (100 microM) reduced the oxygen glucose deprivation-induced [3H]glutamate release by 30.6%, CI95=[15.5%, 45.7%], whereas the "antiglutamatergic" drug riluzole was ineffective. GBP-L and gabapentin were also tested in an in vivo model of acute retinal ischemia in rats. The intraocular pressure was elevated for 1 h above the systolic blood pressure. In the control group, 17.5%, CI95=[13%, 22%], of retinal ganglion cells had survived after 2 weeks. GBP-L doubled the number of surviving ganglion cells up to 35%, CI95=[27%, 43%], while gabapentin had no effect. This difference between gabapentin and its lactam may be due to different pharmacokinetic properties: In contrast to the gamma-amino acid gabapentin, GBP-L is uncharged and therefore might diffuse more easily through biological membranes, e.g. the plasma membrane, to get access to an intracellular locus of action. Thus, the neuroprotective properties in vivo and the diminished oxygen glucose deprivation-induced [3H]glutamate efflux in vitro of the presumed KATP channel agonist GBP-L suggest that this substance might be therapeutically applied in pathological situations induced by a rise in extracellular glutamate and/or neuronal cell death.

Effects of riluzole on electrically evoked neurotransmitter release

1. The main purpose of the present study was to investigate the effects of the neuroprotective agent riluzole on the electrically evoked release of [(3)H]-glutamate ([(3)H]-Glu) in mouse neocortical slices. The reported selectivity of riluzole for excitatory amino acids was tested in release experiments with further neurotransmitters. Also distinct species, mouse, rat and man were compared. 2. [(3)H]-Glu was formed endogenously during incubation of slices with [(3)H]-glutamine ([(3)H]-Gln). Released [(3)H]-Glu and tissue [(3)H]-Glu was separated by anion exchange chromatography. Electrically evoked [(3)H]-Glu release was strongly diminished by tetrodotoxin (TTX) and Ca(2+)-withdrawal. 3. Riluzole (100 microM) depressed the release of [(3)H]-Glu up to 77% (IC(50)=19.5 microM). Riluzole was also able to inhibit strongly the electrically evoked release of [(3)H]-acetylcholine ([(3)H]-ACh) (at 100 microM by 92%, IC(50)=3.3 microM, and [(3)H]-dopamine ([(3)H]-DA) (at 32 microM by 72%, IC(50)=6.8 microM). However, the release of [(3)H]-serotonin ([(3)H]-5-HT) was less diminished (at 100 microM by 53%, IC(50)=39.8 microM). Riluzole up to 100 microM did not affect [(3)H]-noradrenaline ([(3)H]-NA) release. 4. Between species, i.e. in mouse, rat and human neocortex, no significant differences between the effects of riluzole could be observed. 5. The NMDA-receptor blocker MK-801 (1 microM) and the AMPA/Kainate-receptor blocker NBQX (1 microM) did neither affect the electrically evoked [(3)H]-ACh release nor its inhibition by riluzole, indicating that effects of riluzole on transmitter release were neither due to modulation of ionotropic Glu receptors, nor due to indirect inhibition of Glu release through these receptors. 6. Taken together, riluzole inhibits the release of distinct neurotransmitters differently, but is not selective for the excitatory amino acid Glu.

[Acute therapy of ischemic cerebral infarct]

The ischaemic cerebral attack is a disease prevailingly of older age. Its prognosis is distinguished by a mortality rate as high as ever. From 1975 to 1985, 520 patients with ischaemic cerebral attack have been treated in hospital, with specific acute therapy changing from the so-called vasodilator therapy via osmotherapy into haemodilution therapy with lowmolecular dextrane. Since during vasodilator therapy any early mobilisation nor continuous physiotherapy were carried out and the patients prevailingly died of bronchopneumonia, the significantly lower mortality rate under osmotherapy and haemodilution therapy cannot be attributed to the specific drug therapy. In all probability it is a result of the improvement of care and of the active early mobilisation of the patients.