Nogo-A is a negative regulator of CNS angiogenesis.

Nogo-A is an important axonal growth inhibitor in the adult and developing CNS. In vitro, Nogo-A has been shown to inhibit migration and cell spreading of neuronal and nonneuronal cell types. Here, we studied in vivo and in vitro effects of Nogo-A on vascular endothelial cells during angiogenesis of the early postnatal brain and retina in which Nogo-A is expressed by many types of neurons. Genetic ablation or virus-mediated knock down of Nogo-A or neutralization of Nogo-A with an antibody caused a marked increase in the blood vessel density in vivo. In culture, Nogo-A inhibited spreading, migration, and sprouting of primary brain microvascular endothelial cells (MVECs) in a dose-dependent manner and induced the retraction of MVEC lamellipodia and filopodia. Mechanistically, we show that only the Nogo-A-specific Delta 20 domain exerts inhibitory effects on MVECs, but the Nogo-66 fragment, an inhibitory domain common to Nogo-A, -B, and -C, does not. Furthermore, the action of Nogo-A Delta 20 on MVECs required the intracellular activation of the Ras homolog gene family, member A (Rho-A)-associated, coiled-coil containing protein kinase (ROCK)-Myosin II pathway. The inhibitory effects of early postnatal brain membranes or cultured neurons on MVECs were relieved significantly by anti-Nogo-A antibodies. These findings identify Nogo-A as an important negative regulator of developmental angiogenesis in the CNS. They may have important implications in CNS pathologies involving angiogenesis such as stroke, brain tumors, and retinopathies.

Nogo-A deletion increases the plasticity of the optokinetic response and changes retinal projection organization in the adult mouse visual system.

The inhibitory action of Nogo-A on axonal growth has been well described. However, much less is known about the effects that Nogo-A could exert on the plasticity of neuronal circuits under physiological conditions. We investigated the effects of Nogo-A knock-out (KO) on visual function of adult mice using the optokinetic response (OKR) and the monocular deprivation (MD)-induced OKR plasticity and analyzed the anatomical organization of the eye-specific retinal projections. The spatial frequency sensitivity was higher in intact Nogo-A KO than in wild-type (WT) mice. After MD, Nogo-A KO mice reached a significantly higher spatial frequency and contrast sensitivity. Bilateral ablation of the visual cortex did not affect the OKR sensitivity before MD but reduced the MD-induced enhancement of OKR by approximately 50% in Nogo-A KO and WT mice. These results suggest that cortical and subcortical brain structures contribute to the OKR plasticity. The tracing of retinal projections to the dorsal lateral geniculate nucleus (dLGN) revealed that the segregation of eye-specific terminals was decreased in the adult Nogo-A KO dLGN compared with WT mice. Strikingly, MD of the right eye led to additional desegregation of retinal projections in the left dLGN of Nogo-A KO but not in WT mice. In particular, MD promoted ectopic varicosity formation in Nogo-A KO dLGN axons. The present data show that Nogo-A restricts visual experience-driven plasticity of the OKR and plays a role in the segregation and maintenance of retinal projections to the brain.

New mouse retinal stroke model reveals direction-selective circuit damage linked to permanent optokinetic response loss.

PURPOSE: Ischemic insults give rise to severe visual deficits after blood vessel occlusion. In this study we investigated the effects of retinal stroke on the direction-selective circuit of the inner retina in a new adult mouse model. METHODS: The inner retinal blood flow was interrupted for 60 minutes by ligating the ophthalmic arteries and veins in the optic nerve sheath. The optokinetic response (OKR) was measured to assess ischemia/reperfusion-mediated functional deficits and structural changes were studied by immunohistochemistry. RESULTS: Ischemia/reperfusion induced reactive gliosis and degeneration of the inner retina. The OKR was almost completely abolished from 7 days after reperfusion, whereas approximately 40% of retinal ganglion cells were still alive. Ischemia led to severe degeneration of the processes of starburst amacrine cells (SAC), which cell bodies are in the ganglion cell layer (ON SACs), and to a lesser extent of the dendrites of SACs, which cell bodies are in the inner nuclear layer (OFF SACs). In addition, the elimination of retinal ganglion cells, direction-selective ganglion cells, and ON SACs was much greater at 10 days and 21 days than that of OFF SACs. After reperfusion, P-Stat3 was transiently activated in ganglion cells, whereas P-Erk1/2 signal was specifically detected in Müller glia. CONCLUSIONS: These results show a pronounced destruction of the ON direction-selective circuit in the inner retina that correlated with the irreversible loss of the OKR early after ischemia/reperfusion.

Status epilepticus evokes prolonged increase in the expression of CCL3 and CCL4 mRNA and protein in the rat brain.

CCL3 and CCL4 are proinflammatory chemokines belonging to the CC family. Increase in expression of mRNA coding for various chemokines including CCL3 and CCL4 has been often detected with global transcriptome profiling of brain tissue following epileptogenic stimuli as well as in epilepsy in experimental models and in human patients. Despite this, little is known about the expression of these proteins in epileptogenesis or epilepsy. In the present work CCL3 and CCL4 mRNA and protein expression were studied in the amygdala stimulation model of temporal lobe epilepsy using quantitiative PCR and immunohistochemistry. Expression of CCL3 and CCL4 mRNA in the block of tissue containing enthorinal and piriform cortices, amygdala and piriform nucleus was markedly up-regulated at 1, 4, 14 and 30 days following stimulation and in hippocampal CA1 was significantly increased at 1 and 4 days following stimulation. Expression of CCL3 and CCL4 proteins was elevated in astrocytes in the enthorinal and piriform cortices, amygdala, and hippocampus showing the largest increase at 4D after status epilepticus. Increase in mRNA and protein levels of CCL3 and CCL4 in the animal model of temporal lobe epilepsy suggests their role in disease development or recovery form epileptogenic insult. Existence of multiple targets for these chemokines in the damaged brain allows several possibilities of influencing neuronal and glial functions.