Elevated intraocular pressure increases melatonin levels in the aqueous humour.
OBJECTIVE
To study the levels of melatonin in the aqueous humour of normotensive and hypertensive intraocular pressure (IOP) patients and to compare them to an animal model of glaucoma.


METHODS
A total of 37 eyes of 37 patients who underwent cataract surgery were included in the study and were divided into normotensive patients, with IOP below 21 mmHg (n = 23), and hypertensive patients, with IOP > 21 mmHg (n = 14). Glaucomatous DBA/2J (n = 6) and control C57BL/6J (n = 6) mice presenting 3 and 12 months of age for each strain were also used. Human and mice aqueous humours were aspirated using a 30-gauge Rycroft cannula on a tuberculin syringe and further processed to quantify melatonin by high-performance liquid chromatography analysis.


RESULTS
Melatonin levels in normotensive patients (IOP below 21 mmHg) presented values as medians (first quartile; third quartile) of 14.62 (5.38;37.99) ng/ml (n = 23), while hypertensive patients (IOP above 21 mmHg) showed melatonin concentrations of 46.63 (10.28; 167.28) ng/ml (n = 14; p < 0.039). Glaucoma mice presented melatonin values of 0.37 (0.34; 0.59) ng/ml (at 3 months of age, before the pathology starts), which increased to 1.55 (0.94; 1.88) ng/ml (at 12 months of age, when the pathology is fully developed and IOP is maximum; n = 6, p < 0.001). Control mice did not significantly modified melatonin concentrations between 3 and 12 months of age.


CONCLUSIONS
Patients with high IOP present increased concentrations of melatonin in their aqueous humour compared to normotensive patients. This has been confirmed in a glaucomatous animal model in which it has been possible to see a correlation between the development of the pathology, with an increase in IOP, and a concomitant elevation of melatonin in the aqueous humour.
Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Hanan
H
Alkozi
Department of Ophthalmology, Balear Institut of Ophthalmology, Palma de Mallorca, Spain.
Juan
J
Sánchez-Naves
Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Maria Jesús Perez
MJ
de Lara
Department of Optics II (Optometry and Vision), Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Gonzalo
G
Carracedo
Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Begoña
B
Fonseca
Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Alejandro
A
Martinez-Aguila
Department of Biochemistry and Molecular Biology IV, Faculty of Optics and Optometry, University Complutense of Madrid, Madrid, Spain.
Jesús
J
Pintor
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004195:Disease Models, Animal; D005260:Female; D005901:Glaucoma / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008875:Middle Aged; D009798:Ocular Hypertension / Q000378:metabolism* / Q000503:physiopathology
D015415:Biomarkers; D008550:Melatonin
aqueous humour; glaucoma; high-performance liquid chromatography; humans; melatonin; mice