The role of nitric oxide in the apoptosis of neurons in the retina of the human fetal eye

Gaseous transmitters in human retinogenesis

Endogenous gaseous transmitters (nitric oxide, carbon monoxide, and hydrogen sulphide) form a special neuromodulation system mediating the development and modification of nerve centers. Here, we examined the localization of key gaseous transmitter enzymes: cystathionine β-synthetase (CBS), cystathionine γ-lyase (CSE), heme oxygenase 2 (HO-2), and constitutive NO synthase (nNOS) in the fetal human retina at different stages of development. The number of CBS- and CSE-positive photoreceptors and intermediate retinal neurons was high in trimester I and gradually decreased to the end of trimester III. The number of HO-2-positive cells followed the same trend. The number of nNOS-positive intermediate retinal neurons and neurons within the ganglion cell layer showed the opposite dynamics with the peak in trimester III. The results are interpreted in terms of the role of gaseous transmitters in retinogenesis and cytoprotection.

Prenatal exposure to traffic-related air pollution and risk of early childhood cancers

Exposure to air pollution during pregnancy has been linked to the risk of childhood cancer, but the evidence remains inconclusive. In the present study, we used land use regression modeling to estimate prenatal exposures to traffic exhaust and evaluate the associations with cancer risk in very young children. Participants in the Air Pollution and Childhood Cancers Study who were 5 years of age or younger and diagnosed with cancer between 1988 and 2008 were had their records linked to California birth certificates, and controls were selected from birth certificates. Land use regression-based estimates of exposures to nitric oxide, nitrogen dioxide, and nitrogen oxides were assigned based on birthplace residence and temporally adjusted using routine monitoring station data to evaluate air pollution exposures during specific pregnancy periods. Logistic regression models were adjusted for maternal age, race/ethnicity, educational level, parity, insurance type, and Census-based socioeconomic status, as well as child's sex and birth year. The odds of acute lymphoblastic leukemia increased by 9%, 23%, and 8% for each 25-ppb increase in average nitric oxide, nitrogen dioxide, and nitrogen oxide levels, respectively, over the entire pregnancy. Second- and third-trimester exposures increased the odds of bilateral retinoblastoma. No associations were found for annual average exposures without temporal components or for any other cancer type. These results lend support to a link between prenatal exposure to traffic exhaust and the risk of acute lymphoblastic leukemia and bilateral retinoblastoma.

Murine cytomegalovirus infection and apoptosis in organotypic retinal cultures

PURPOSE

An organotypic retinal culture model was used to determine the pattern of murine cytomegalovirus (MCMV) infection and whether apoptosis is induced in MCMV-infected cultured retinas.

METHODS

Retinas harvested from C57BL/6 mice were individually cultured at 37 degrees C on 3-microm filter inserts placed in 24-well plates. Some retinas were infected with MCMV (5 x 10(5) PFU/well). At days 4, 7, and 11 after infection (pi), the culture medium and cultured retinas were collected for examination.

RESULTS

Replicating virus was recovered and viral early antigen (EA)- and late antigen (LA)-positive cells were observed in the MCMV-infected retinal cultures. Most MCMV-infected cells were glia and horizontal cells. Infection resulted in atrophy of the photoreceptor cells and cytomegaly. Apoptosis of uninfected bystander cells, including photoreceptor cells and horizontal cells, was observed. TNF-alpha was produced by activated microglia during MCMV infection of the retina. Mouse apoptosis microarray studies, caspase activity studies, and RT-PCR studies showed that the genes involved in both the death receptor-mediated apoptotic pathway and the mitochondrial pathway were upregulated.

CONCLUSIONS

Many aspects of MCMV infection of retinal cultures parallel those observed during MCMV retinitis in mice. Thus, this in vitro system may be used to explore the role of apoptosis of uninfected retinal cells and the contribution of cytokines and other modulators to the pathogenesis of CMV retinitis.