Abstract
Purpose:
We continue our investigation into effects of cigarette smoke on mouse retina by examining Müller cells (MC) and retinal pigment epithelium (RPE). Previous studies have demonstrated that cigarette smoke (CS) in mice causes age-related macular degeneration-like pathology in RPE, and oxidative stress induces adaptive MC responses. However, it is unknown whether complement activation is required for these effects. The effects of long-term CS on MCs and RPE were examined in wildtype mice and mice in which the alternative pathway (complement factor B, CfB-/-) or the common terminal pathway (complement component 3, C3-/-) was removed. MC and RPE were analyzed using computational molecular phenotyping (CMP), focusing on metabolites involved in oxidative stress.
Methods:
Mice were exposed to CS or filtered air. CS was generated using an automated cigarette-smoking machine (TE-10, Teague Enterprises) by burning 3R4F reference cigarettes. Mice were exposed to CS for 6 months. Age-matched filtered air-exposed mice were used as controls. Eyes were enucleated immediately post-mortem, fixed in 1% paraformaldehyde, 2.5% glutaraldehyde, dehydrated in graded methanols, embedded in eponates and histologically analyzed with CMP.
Results:
The RPE of CS CfB-/- animals show decreases in glutamate, glutamine and glutathione as well as CRALBP relative to control CfB-/- animals. MCs in CS CfB-/- animals show increases in glutathione, glutamine and arginine relative to control CfB-/- animals. In CS C3-/- mice, RPE shows an increase in glutamate labeling along with decreases in glutamine and glutathione concentrations relative to control C3-/- animals. Additionally, MCs in CS C3-/- animals show higher concentrations of glutamate, glutamine, glutathione and arginine than in control C3-/- animals and in higher concentrations than seen in CfB-/- CS animals.
Conclusions:
Metabolic profiles in MCs and RPE are affected by CS in a genotype-dependent manner. Alterations were most dramatic in C3-/-, whereas the changes in wildtype and CfB-/- were intermediate, suggesting that complement activation has both damaging as well as protective effects. Alterations in glutathione and glutamine might reveal cells that are undergoing cellular/oxidative stress, while arginine upregulation may reveal alterations in gene expression as cells alter metabolism to stabilize gene translation.
Keywords: 412 age-related macular degeneration •
726 stress response •
688 retina