MSG-indukálta retinális degeneráció és a PACAP neuroprotektív hatásának vizsgálata = MSG-induced retinal degeneration and the neuroprotective effect of PACAP

A monosodium-glutamát (MSG) egy ismert ízfokozó, amelyet a kínai konyha nagy mennyiségben adagol ételeihez. E vegyület retinakárosító hatását, valamint annak kivédésének lehetséges módszereit vizsgáltuk patkányban. Újszülött patkányokba subcutan MSG-t injektáltunk. Három hét elteltével vizsgáltuk a retinákat. Az kísérletek egy részeben a MSG injekciókkal együtt neuroprotektív szereket, főleg PACAP-ot, alkalmaztunk a degeneratív hatások kivédésére. Munkánk során a MSG-modellt optimalizáltuk és kifejlesztettünk egy ischemiás modellt is, amikor 2 hetes állatokon bilaterális carotis communis lekötést alkalmaztunk és 1 hét elteltével vizsgáltuk a retinákat. Ebben a modellben is lehetőség nyílt a protektív ágensek alkalmazására. Mindezen modellekben morfológiai, morfometriai, immuncitokémiai, és biokémiai módszerekkel vizsgáltuk a sejt- és molekuláris szintű eseményeket. Főbb eredményeink a következőkben foglalhatók össze: 1. A MSG modellben elsősorban a belső retinális rétegek károsodnak. 2. Az ischemiás modellben minden sejtrétegben találtunk károsodott sejteket. 3. A PACAP intravitreálisan adagolva mindkét modellben protektív hatású. 4. A PACAP protektív hatását a proapoptikus faktorok gátlásával és az anti-apoptotikus faktorok serkentésén keresztül éri el. 5. A védő hatás következtében a retina rétegei és sejttípusai megtartottak maradnak, a javulás funkcionális vizsgáló módszerrel (elektroretinogram) is igazolható. 6. Védő hatást gyakorol az ingergazdag környezet is. | Monosodium-glutamát (MSG) is a well-known aromatizer which is widely used in the Chinese cuisine. The retinotoxic effects of this substance and the possible neuroprotective strategies against this compound were examined in rats. Newborn rats were injected subcutaneously with MSG and their retinas were examined after three weeks. In some experiments neuroprotective agents were simulatneously applied with MSG. During the project we optimized the MSG model and also developed an ischemic retina model, in which the common carotid arteries of 2-week-old rats were ligated and the retinas were processed one week after the ligation. Also, a screen for neurorotective agents was executed. The experimental results were obtained with morphological, morphometric, immunocytochemical and biochemical methods. The main results are as follows: 1. After MSG treatment the inner retinal layers were damaged. 2. In the ischemic modell we found damaged cells in all cellular layers of the retina. 3. PACAP is neuroprotective in both models. 4. This effect of PACAP is mediated through inhibition of proapoptotic and stimulation of anti-apopototic factors. 5, Due to this protective effect, the histological layers and the cells of the retina remain relatively intact. These results are also supported by functional examinations (electroretinogram). 6. Enriched environments proved to be retinoprotective too

Urocortin 2 treatment is protective in excitotoxic retinal degeneration

Urocortin 2 (Ucn 2) is a corticotrop releasing factor paralog peptide with many physiological functions and it has widespread distribution. There are some data on the cytoprotective effects of Ucn 2, but less is known about its neuro- and retinoprotective actions. We have previously shown that Ucn 2 is protective in ischemia-induced retinal degeneration. The aim of the present study was to examine the protective potential of Ucn 2 in monosodiumglutamate (MSG)-induced retinal degeneration by routine histology and to investigate cell-type specific effects by immunohistochemistry. Rat pups received MSG applied on postnatal days 1, 5 and 9 and Ucn 2 was injected intravitreally into one eye. Retinas were processed for histology and immunocytochemistry after 3 weeks. Immunolabeling was determined for glial fibrillary acidic protein, vesicular glutamate transporter 1, protein kinase Cα, calbindin, parvalbumin and calretinin. Retinal tissue from animals treated with MSG showed severe degeneration compared to normal retinas, but intravitreal Ucn 2 treatment resulted in a retained retinal structure both at histological and neurochemical levels: distinct inner retinal layers and rescued inner retinal cells (different types of amacrine and rod bipolar cells) could be observed. These findings support the neuroprotective function of Ucn 2 in MSG-induced retinal degeneration

Az óragének és a környezeti fényviszonyok szerepe az N-acetiltranszferáz génexpressziójának szabályozásában csirke retinában = The role of clock-genes and environmental lighting conditions in the regulation of N-acetyltransferase gene expression in the chicken retina

Csirke retina és tobozmirigy sejtekben a melatonin (MT) szintézis kulcsenzimének, az arilalkilamin N-acetiltranszferáznak génje (cAanat) co-expresszálódik az óragénekkel. Emellett a dopamin (DA) a fő katekolamin a retinában, mely neuroregulatorként hat. Tanulmányoztuk: 1. a cBmal1 és cAanat mRNS expressziók dinamikáját retinális/pineális sejtekben in vivo és in vitro RT-PCR-ral. A cBmal1 mRNS csúcsa a fényes fázisban volt Zeitgeber idő (ZT) 8 és 10 között, megelőzve az a cAanat expresszió éjszakai emelkedését ZT 16-17-nál. A retinális/pineális cBmal1 és cAanat mRNS ritmusainak fázisai arra utalnak, hogy kapcsolat van az expressziók között; 2. locked nucleinsav tartalmú cBmal1 antisense oligonukleotidok (AON) hatását a cAanat transzkriptumokra és az MT termelésre pinealocita kultúrában, melyet szuperfúziós rendszerben transzfektáltunk. Az AON, mely vagy az RNáz H-t aktiválta, vagy a transzlációs masinériához való kötődést blokkolta szignifikánsan csökkentette a cAanat transzkripcióját és az MT szekrécióját jelezvén a cBmal1 kulcsszerepét az indol metabolizmus szabályozásában; 3. két fő DA-receptor család (D1 és D2) szerepét a circadián retinális MT ritmus szabályozásában eye-cup modellen. A D2 agonista Quinpirol szignifikánsan csökkentette az MT szekrécióját sötét fázisban, míg a D1 agonista SKF hatástalan volt, amely arra utal, hogy a DA gátló hatást fejt ki a retinális MT szekrécióra (reciprok negativ feed-back), melyet elsősorban a D2 receptorok mediálnak. | In chicken retinal and pineal cells gene of arylalkylamine N-acetyltransferase (cAanat), the key enzyme of melatonin (MT) synthesis is co-expressed with clock genes. In addition, dopamine (DA) is the major catecholamine in the retina serving as a neuroregulator. We studied: 1. the temporal profile of cBmal1 and cAanat mRNA expressions in retinal/pineal cells in vivo and in vitro using RT-PCR. cBmal1 mRNA had a peak in the light phase between Zeitgeber time (ZT) 8 and 10, preceding the nocturnal increase in cAanat expression at ZT 16 to 17. The phase of the rhythms of retinal/pineal cBmal1 and cAanat mRNAs suggests a link between their expressions; 2. the effect of cBmal1 antisense oligonucleotides (AONs) containing locked nucleic acid on cAanat transcripts and MT production in cultured pinealocytes transfected in superfusion system. These AONs synthesized for activating RNase H or blocking the binding of the translation machinery were able to reduce significantly cAanat transcription and MT secretion indicating the key role of cBmal1 in the regulation of indole metabolism; 3. the role of the two major DA-receptor families (D1 and D2) in the regulation of circadian retinal MT rhythm on an eye-cup model. Quinpirole (D2 agonist) reduced significantly MT secretion in dark phase, whereas SKF (D1 agonist) was ineffective suggesting that DA exerts an inhibitory effect on retinal MT secretion (reciprocal negative feed-back), which is mediated primarily via D2 receptors

PACAP promotes neuron survival in early experimental diabetic retinopathy

Metabolic changes induced by diabetes lead to a multifactorial progressive disease of the retina with an extremely complex pathogenesis. One of the mechanisms of retinal cell death in diabetes is via apoptosis. Our previous results show that pituitary adenylate cyclase activating polypeptide (PACAP) attenuates the morphological and neurochemical changes in a rat model of diabetic retinopathy. The aim of this study was to investigate the mechanisms of this protective effect. Retinas of streptozotocin-induced diabetic rats were analyzed using apoptosis detection combined with immunolabeling. Western blot was used to measure levels of pro- and anti-apoptotic pathways. Intraocular PACAP injection markedly attenuated diabetic retinal injury: increased levels of the anti-apoptotic p-Akt, p-ERK1, p-ERK2, PKC, Bcl-2, while decreased levels of the pro-apoptotic p-p38MAPK and activated caspases (8, 3, 12) were detected. The number of apoptotic cells increased in all nuclear layers of diabetic retinas, but significantly decreased after PACAP treatment. Our results clearly demonstrate that the protective effects of PACAP are mediated, at least partly, by attenuating apoptosis, including also that of the dopaminergic amacrine cells. Inhibition of apoptosis is one of the PACAP-induced pathways with therapeutic potential in early experimental diabetic retinopathy

PACAP application improves functional outcome of chronic retinal ischemic injury in rats – evidence from electroretinographic measurements

Retinoprotective effects of pituitary adenylate cyclase activating polypeptide (PACAP) are well-known and have been demonstrated in various pathological conditions, such as diabetic retinopathy, excitotoxic retinal injury, UV light-induced degeneration and ischemic retinal lesion. The neuronal degeneration observed in the different retinal layers under the above pathological conditions can be successfully decreased by PACAP, however, whether this morphological improvement is also reflected in functional amelioration remains unknown. Therefore, our purpose was to investigate the protective effect of PACAP on the rat retina after bilateral common carotid artery occlusion (BCCAO) with electroretinography (ERG) to parallel the functional data with the previous morphological and neurochemical observations. Control eyes received saline treatment while PACAP was injected into the vitreous space of the other eye immediately after the induction of ischemia. Retinal damage and protective effects of PACAP were quantified by the changes in the wave forms and amplitudes. On postoperative days 2 and 14 several parameters were assessed with special attention to the changes of b wave. The results confirm that the previously described morphological protection induced by PACAP treatment is reflected in functional improvement in ischemic retinal lesions

PARP Inhibitor Protects Against Chronic Hypoxia/Reoxygenation-Induced Retinal Injury by Regulation of MAPKs, HIF1α, Nrf2, and NFκB

In the eye, chronic hypoxia/reoxygenation (H/R) contributes to the development of a number of ocular disorders. H/R induces the production of reactive oxygen species (ROS), leading to poly(ADP-ribose) polymerase-1 (PARP1) activation that promotes inflammation, cell death, and disease progression. Here, we analyzed the protective effects of the PARP1 inhibitor olaparib in H/R-induced retina injury and investigated the signaling mechanisms involved.A rat retinal H/R model was used to detect histologic and biochemical changes in the retina.H/R induced reductions in the thickness of most retinal layers, which were prevented by olaparib. Furthermore, H/R caused increased levels of Akt and glycogen synthase kinase-3β phosphorylation, which were further increased by olaparib, contributing to retina protection. By contrast, H/R-induced c-Jun N-terminal kinase and p38 mitogen-activated protein kinases (MAPK) phosphorylation and activation were reduced by olaparib, via mitogen-activated protein kinase phosphatase 1 (MKP-1) expression. In addition, H/R-induced hypoxia-inducible factor 1α (HIF1α) levels were decreased by olaparib, which possibly contributed to reduced VEGF expression. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression was slightly increased by H/R and was further activated by olaparib. Nuclear factor-κB (NFκB) was also activated by H/R through phosphorylation (Ser536) and acetylation (Lys310) of the p65 subunit, although this was significantly reduced by olaparib.Olaparib reduced H/R-induced degenerative changes in retinal morphology. The protective mechanisms of olaparib most probably involved Nrf2 activation and ROS reduction, as well as normalization of HIF1α and related VEGF expression. In addition, olaparib reduced inflammation by NFκB dephosphorylation/inactivation, possibly via the PARP1 inhibition-MKP-1 activation-p38 MAPK inhibition pathway. PARP inhibitors represent potential therapeutics in H/R-induced retinal disease