title: Glaucoma alters the circadian timing system.
abstract: Glaucoma is a widespread ocular disease and major cause of blindness characterized by progressive, irreversible damage of the optic nerve. Although the degenerative loss of retinal ganglion cells (RGC) and visual deficits associated with glaucoma have been extensively studied, we hypothesize that glaucoma will also lead to alteration of the circadian timing system. Circadian and non-visual responses to light are mediated by a specialized subset of melanopsin expressing RGCs that provide photic input to mammalian endogenous clock in the suprachiasmatic nucleus (SCN). In order to explore the molecular, anatomical and functional consequences of glaucoma we used a rodent model of chronic ocular hypertension, a primary causal factor of the pathology. Quantitative analysis of retinal projections using sensitive anterograde tracing demonstrates a significant reduction (approximately 50-70%) of RGC axon terminals in all visual and non-visual structures and notably in the SCN. The capacity of glaucomatous rats to entrain to light was challenged by exposure to successive shifts of the light dark (LD) cycle associated with step-wise decreases in light intensity. Although glaucomatous rats are able to entrain their locomotor activity to the LD cycle at all light levels, they require more time to re-adjust to a shifted LD cycle and show significantly greater variability in activity onsets in comparison with normal rats. Quantitative PCR reveals the novel finding that melanopsin as well as rod and cone opsin mRNAs are significantly reduced in glaucomatous retinas. Our findings demonstrate that glaucoma impacts on all these aspects of the circadian timing system. In light of these results, the classical view of glaucoma as pathology unique to the visual system should be extended to include anatomical and functional alterations of the circadian timing system.
authors.affiliation: Department of Chronobiology, INSERM, U846, Stem Cell and Brain Research Institute, Bron, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Drouyer
authors.forename: Ouria
authors.initials: O
authors.lastname: Dkhissi-Benyahya
authors.forename: Christophe
authors.initials: C
authors.lastname: Chiquet
authors.forename: Elizabeth
authors.initials: E
authors.lastname: WoldeMussie
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Ruiz
authors.forename: Larry A
authors.initials: LA
authors.lastname: Wheeler
authors.forename: Philippe
authors.initials: P
authors.lastname: Denis
authors.forename: Howard M
authors.initials: HM
authors.lastname: Cooper
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology* / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects; D005829:Geniculate Bodies / Q000166:cytology / Q000528:radiation effects; D005901:Glaucoma / Q000503:physiopathology*; D007429:Intraocular Pressure / Q000502:physiology / Q000528:radiation effects; D017075:Laser Coagulation; D008027:Light; D008297:Male; D009043:Motor Activity / Q000502:physiology; D055355:Opsins / Q000235:genetics / Q000378:metabolism; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D013477:Superior Colliculi / Q000166:cytology / Q000528:radiation effects; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000528:radiation effects; D013997:Time Factors; D014795:Visual Pathways / Q000503:physiopathology / Q000528:radiation effects
chemical_list: D015415:Biomarkers; D055355:Opsins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012333:RNA, Messenger