Acylphloroglucinol derivatives with ATP citrate lyase inhibitory activities from Syzygium oblatum Wall.

Nine undescribed acylphloroglucinol derivatives, oblatones A-I, along with three known ones, were isolated from Syzygium oblatum. Their structures were determined on the basis of extensive spectroscopic analysis, including NMR and MS data interpretation. Oblatones A and B possess an alkylated chromanone scaffold featuring a hemiketal moiety. Oblatones C and D are the first acylphloroglucinol derivatives with an α,ß-unsaturated ketone lipid chain. Some of the isolates showed inhibitory effects on ATP citrate lyase in vitro. The binding mode of oblatone A was predicted by molecular docking.

Enhanced survival of melanopsin-expressing retinal ganglion cells after injury is associated with the PI3 K/Akt pathway.

In the present study, we studied the factors that contribute to the injury-resistant property of melanopsin-expressing retinal ganglion cells (mRGCs). Since phosphatidylinositol-3 kinase (PI3 K)/Akt signaling pathway is one of the well-known pathways for neuronal cell survival, we investigated the survival of mRGCs by applying the PI3 K/Akt specific inhibitors after injury. Two injury models, unilateral optic nerve transection and ocular hypertension, were adopted using Sprague-Dawley rats. Inhibitors of PI3 K/Akt were injected intravitreally following injuries to inhibit the PI3 K/Akt signaling pathway. Retinas were dissected after designated survival time, immunohistochemistry was carried out to visualize the mRGCs using melanopsin antibody and the number of mRGCs was counted. Co-expression of melanopsin and phospho-Akt (pAkt) was also examined. Compared to the survival of non-melanopsin-expressing RGCs, mRGCs showed a marked resistance to injury and co-expressed pAkt. Application of PI3 K/Akt inhibitors decreased the survival of mRGCs after injury. Our previous study has shown that mRGC are less susceptible to injury following the induction of ocular hypertension. In this study, we report that mRGCs were injury-resistant to a more severe type of injury, the optic nerve transection. More importantly, the PI3 K/Akt pathway was found to play a role in maintaining the survival of mRGCs after injury.

Melanopsin-expressing retinal ganglion cells are more injury-resistant in a chronic ocular hypertension model.

PURPOSE: To investigate the survival of melanopsin-expressing retinal ganglion cells (mRGCs) after the induction of chronic ocular hypertension. METHODS: Intraocular pressure (IOP) was elevated in adult Sprague-Dawley rats using an argon laser to photocoagulate the episcleral and limbal veins. IOP was measured with a calibrated tonometer and monitored for a period. Seven days before the animals were killed, a piece of sterile foam soaked with gold fluorescent dye was placed onto the superior colliculus (SC) to label the SC-projecting retinal ganglion cells (scRGCs) retrogradely. mRGCs were visualized by free floating immunohistochemistry on whole-mounted retinas. The number of surviving scRGCs and mRGCs were counted on flatmounted retinas. The branching pattern of dendrites and soma size of mRGCs were examined. RESULTS: An approximately 1.7-fold increase of IOP and a significant loss of scRGCs were found in experimental eyes after laser photocoagulation. However, no significant cell loss or morphologic changes on mRGCs and their dendrites after the induction of chronic ocular hypertension are noticed over a 12-week period. CONCLUSIONS: Although the degeneration of retinal ganglion cells (RGCs) is a major concern in glaucomatous damage, the findings show that mRGCs are less susceptible to death after the induction of chronic ocular hypertension. This result indicates that mRGCs carry some unique properties that are different from those of other subpopulations of RGCs. The immunohistochemistry approach can be used to distinguish easily these mRGCs from other subtypes. This method provides a useful tool to investigate their injury-resistant properties that are informative for the development of effective neuroprotective treatment for glaucoma.

Transgenic mice expressing Cre-recombinase specifically in retinal rod bipolar neurons.

PURPOSE: To establish a transgenic mouse line that expresses Cre-recombinase in retinal rod bipolar cells for the generation of rod bipolar cell-specific knockout mutants. METHODS: The IRES-Cre-cDNA fragment was inserted into a 173-kb bacterial artificial chromosome (BAC) carrying the intact Pcp2 gene, by using red-mediated recombineering. Transgenic mice were generated with the modified BAC and identified. The Cre-transgenic mice were crossed with ROSA26 and Z/EG reporter mice to detect Cre-recombinase activity. RESULTS: X-gal staining showed that strong Cre-recombinase activities were present in retinal inner nuclear layers and cerebellar Purkinje cells. Double staining with an anti-GFP antibody and an anti-PKCalpha antibody (specific for retinal rod bipolar cells) revealed that Cre-recombinase activity localized exclusively to the rod bipolar cells in the retina. CONCLUSIONS: A mouse BAC-Pcp2-IRES-Cre transgenic line that expresses Cre-recombinase in retinal rod bipolar neurons has been established. Because mutations in some ubiquitously expressed genes may result in retinal degenerative diseases, the mouse strain BAC-Pcp2-IRES-Cre will be a useful new tool for investigating the effects of retinal rod bipolar cell-specific gene inactivation.