Background: Circadian rhythm disruption occurs during spaceflight, leading to crew health and performance decrements. Spaceflight-related retinal changes, including oxidative stress and neuronal loss, have been previously reported in mice. Methods: Animal tissue from experiments aboard shuttle missions STS-133 (BALB/cJ mice, albino strain) and STS-135 (C57BL mice, pigmented strain), along with ground controls, was examined to determine survival of intrinsically photosensitive retinal ganglion cells (iPRGC) and melanopsin expression in retinas of mice exposed to the spaceflight environment. Real-time qPCR (RTqPCT) and microarray approaches were used to analyze Opn4 (melanopsin) gene expression, while immunohistologic studies were conducted to detect melanopsin localization in the retina. Results: Opn4 expression was decreased in albino BALB/cJ mice exposed to spaceflight, as measured by RTqPCR, but not in C57BL mice samples as analyzed by microarray. Opn4 expression returned to control levels at 7 d postreturn in the BALB/cJ samples. Melanopsin positive RGCs were found in the expected proportion in all samples, except for the BALB/cJ samples at 1 d after flight, where virtually no immunoreactive cells were found. Discussion: Spaceflight environmental factors may affect the nonvisual function of the retina, mediated by a reduction in melanopsin expression and ipRGC survival, contributing to circadian disruption.
- Circadian rhythm
- Opsin 4
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health