Hippocampal cystathionine beta synthase in young and aged mice.

Cystathionine beta synthase (CBS) is the main contributor to the production of hydrogen sulfide (H2S) in the brain. Exogenously administered H2S has been reported to protect neurons against hypoxic injury, ischemia and LPS-induced neuro-inflammation and in the facilitating of long term potentiation (LTP). Dysregulation of CBS leads to different diseases, which all have mental retardation in common. Although multiple studies have implicated a link between the CBS/H2S pathway and neurodegeneration, no studies have been performed examining the pathway in healthy aging animals. We hypothesize that CBS/H2S pathway plays an important role in the protection of learning and memory functions in the brain at the level of the hippocampus. Thus, we studied a set of 8 young (4 months) and 14 aged (24 months (n=6) and 28 months (n=8)) C57Bl6 mice. The 24-month-old mice displayed a significant decrease of CBS immunoreactivity in the MoDG only, compared to 4-month-old mice. In 28-month-old mice, we observed a significant increase of CBS immunoreactivity in the MoDG, compared to 4-month-old mice. When comparing 28-month-old mice to 24-month-old mice, all areas showed a significant increase of CBS immunoreactivity. Thus, throughout aging, CBS expression is maintained in the hippocampus, and many other forebrain regions as well. Mice at the unusual age of 28 months even have a higher hippocampal CBS expression than young mice. Maintenance (and increase) of CBS levels may sustain memory and learning by precluding neuronal loss in areas of the hippocampus.