PURPOSE. Mice with moderate/severe hyperhomocysteinemia due to deficiency or absence of the cbs gene encoding cystathionine-beta-synthase (CBS) have marked retinal disruption, ganglion cell loss, optic nerve mitochondrial dysfunction, and ERG defects; those with mild hyperhomocysteinemia have delayed retinal morphological/functional phenotype. Excess homocysteine is a risk factor for cardiovascular diseases; however, it is not known whether excess homocysteine alters retinal vasculature. METHODS. Cbs, and cbs À/À mice (age~3 weeks) were subjected to angiography; retinas were harvested for cryosections, flat-mount preparations, or trypsin digestion and subjected to immunofluorescence microscopy to visualize vessels using isolectin-B4, to detect angiogenesis using anti-VEGF and anti-endoglin (anti-CD105) and activated glial cells (anti-glial fibrillary acidic protein [anti-GFAP]) and to investigate the blood-retinal barrier using the tight junction markers zonula occludens-1 (ZO-1) and occludin. Expression RESULTS. Angiography revealed vascular leakage in cbs À/À mice; immunohistochemical analysis demonstrated vascular patterns consistent with ischemia; isolectin-B4 labeling revealed a capillary-free zone centrally and new vessels with capillary tufts midperipherally. This was associated with increased vegf mRNA and protein, CD105, and GFAP in cbs À/À retinas concomitant with a marked decrease in ZO-1 and occludin. Homocysteine-treated HRECs showed increased permeability.CONCLUSIONS. Severe elevation of homocysteine in cbs À/À mutant mice is accompanied by alterations in retinal vasculature (ischemia, neovascularization, and incompetent bloodretinal barrier). The marked disruption of retinal structure and decreased visual function reported in cbs À/À mice may reflect vasculopathy as well as neuropathy. (Invest Ophthalmol Vis Sci. 2013;54:939-949)

Antenatal steroids like dexamethasone (DEX) are used to augment foetal lung maturity and there is a major concern that they impair foetal growth. If delivery is delayed after using antenatal DEX, placental function and hence foetal growth may be compromised even further. To investigate the effects of DEX on placental function, we treated 9 pregnant C57/BL6 mice with DEX and 9 pregnant mice were injected with saline to serve as controls. Placental gene expression was studied using microarrays in 3 pairs and other 6 pairs were used to confirm microarray results by semi-quantitative RT-PCR, real-time PCR, in situ hybridization, western blot analysis and Oligo ApopTaq assay. DEXtreated placentas were hydropic, friable, pale, and weighed less (80.0±15.1 mg compared to 85.6.8 ±7.6 mg, p=0.05) (n=62 placentas). Foetal weight was significantly reduced after DEX use (940±32 mg compared to 1162±79 mg, p=0.001) (n=62 foetuses). There was > 99% similarity within and between the three gene chip data sets. DEX led to down-regulation of 1212 genes and up-regulation of 1382 genes. RT-PCR studies showed that DEX caused a decrease in expression of genes involved in cell division such as cyclins A2, B1, D2, cdk 2, cdk 4 and M-phase protein kinase along with growth-promoting genes such as EGF-R, BMP4 and IGFBP3. Oligo ApopTaq assay and western blot studies showed that DEX-treatment increased apoptosis of trophoblast cells. DEX-treatment led to up-regulation of aquaporin 5 and tryptophan hydroxylase genes as confirmed by real-time PCR, and in situ hybridization studies. Thus antenatal DEX treatment led to a reduction in placental and foetal weight, and this effect was associated with a decreased expression of several growth-promoting genes and increased apoptosis of trophoblast cells.

We have investigated the gross, microscopic and molecular effects of carnitine deficiency in the neonatal gut using a mouse model with a loss-of-function mutation in the OCTN2 (SLC22A5) carnitine transporter. The tissue carnitine content of neonatal homozygous (OCTN2−/−) mouse small intestine was markedly reduced; the intestine displayed signs of stunted villous growth, early signs of inflammation, lymphocytic and macrophage infiltration and villous structure breakdown. Mitochondrial β-oxidation was active throughout the GI tract in wild type newborn mice as seen by expression of 6 key enzymes involved in β-oxidation of fatty acids and genes for these 6 enzymes were up-regulated in OCTN2−/− mice. There was increased apoptosis in gut samples from OCTN2−/− mice. OCTN2−/− mice developed a severe immune phenotype, where the thymus, spleen and lymph nodes became atrophied secondary to increased apoptosis. Carnitine deficiency led to increased expression of CD45-B220+ lymphocytes with increased production of basal and anti-CD3-stimulated pro-inflammatory cytokines in immune cells. Real-time PCR array analysis in OCTN2−/− mouse gut epithelium demonstrated down-regulation of TGF-β/BMP pathway genes. We conclude that carnitine plays a major role in neonatal OCTN2−/− mouse gut development and differentiation, and that severe carnitine deficiency leads to increased apoptosis of enterocytes, villous atrophy, inflammation and gut injury.

Background-Carnitine is essential for mitochondrial β-oxidation of long-chain fatty acids. Deficiency of carnitine leads to severe gut atrophy, ulceration and inflammation in animal models of carnitine deficiency. Genetic studies in large populations have linked mutations in the carnitine transporters OCTN1 and OCTN2 with Crohn's disease (CD), while other studies at the same time have failed to show a similar association and report normal serum carnitine levels in CD patients.

Purpose Cystathionine β-synthase (CBS), a key enzyme in the transsulfuration metabolic pathway, converts homocysteine to cystathionine, which is converted to cysteine required for synthesis of the major retinal antioxidant glutathione (GSH). Enzyme activity assays suggest that CBS is present in human and pig retina, however recent studies reported that CBS is not expressed in mouse retina. We found this species difference puzzling. Given the plethora of studies using mouse retina as a model system, coupled with the importance of GSH in retina, we investigated CBS expression in mouse retina at the molecular and cell biological level. Methods Wildtype (WT) mice or mice lacking the gene encoding CBS (cbs−/−) were used in these studies. RNA and protein were isolated from retinas and liver (positive control) for analysis of cbs gene expression by RT-PCR and CBS protein expression by Western blotting, respectively. CBS was analyzed by immunofluorescence in retinal cryosections and primary retinal cells (ganglion, Müller, RPE). CBS enzyme activity was measured in primary Müller cells. Results RT-PCR revealed robust cbs expression in WT liver, brain and retina. Western blotting detected CBS in retina, brain and liver of WT mice, but not in cbs−/− mice liver. In immunohistochemical studies, CBS was present abundantly in the ganglion cell layer of retina; it was detected also in primary isolations of Müller, RPE and ganglion cells. CBS activity was detected in Müller cells by fluorescent detection of H2S. Conclusions We have compelling molecular evidence that CBS is expressed in mouse retina at the gene and protein level. Our immunofluorescence data suggest that it is present in several retinal cell types and the data from the enzyme activity assay suggest activity in Müller cells. These findings set the stage to investigate the role of CBS and the transsulfuration pathway in generation of GSH in mouse retina.