Differential Expression of AQP1 and AQP4 in Avascular Chick Retina Exposed to Moderate Light of Variable Photoperiods.
Aquaporins (AQPs) are integral membrane proteins which maintain cellular water and ion homeostasis. Alterations in AQP expression have been reported in rod-dominated rodent retinas exposed to light. In rodents and also in birds, light of moderate intensities (700-2000 lux) damages the retina, though detailed changes were not examined in birds. The aim of our study was to see if light affects cone dominated retinas, which would be reflected in expression levels of AQPs. We examined AQP1 and AQP4 expressions in chick retina exposed to 2000 lux under 12 h light:12 h dark (12L:12D; normal photoperiod), 18L:6D (prolonged photoperiod) and 24L:0D (constant light). Additionally, morphological changes, apoptosis (by TUNEL) and levels of glutamate and GFAP (a marker of injury) in the retina were examined to correlate these with AQP expressions. Constant light caused damage in outer and inner nuclear layer (ONL, INL) and ganglion cell layer (GCL). Also, there were associated increases in GFAP and glutamate levels in retinal extracts. In normal photoperiod, AQP1 was expressed in GCL, outer part of INL and photoreceptor inner segments of. AQP4 was additionally expressed in nerve fiber layer. Immunohistochemistry and Western blotting revealed over all decreased AQP1 and AQP4 expression in constant light condition compared to those in other two groups. The elevated GFAP and glutamate levels might be involved in the reduction of AQPs in constant light group. Such decreases in AQP expressions are perhaps linked with retinal cell damage seen in constant light condition, while their relatively enhanced expression in two other conditions may help in maintaining a normal retinal architecture, indicating their neuroprotective potential.
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
Kumar Abhiram
KA
Jha
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India. tapas_nag@yahoo.com.
Tapas Chandra
TC
Nag
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
Vivek
V
Kumar
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
Pankaj
P
Kumar
Ocular Pharmacology Lab, Department of Pharmacology, DIPSAR, New Delhi, 110017, India.
Binit
B
Kumar
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
Shashi
S
Wadhwa
Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
Tara Sankar
TS
Roy
D000818:Animals; D051398:Aquaporin 1 / Q000096:biosynthesis* / Q000235:genetics; D051401:Aquaporin 4 / Q000096:biosynthesis* / Q000235:genetics; D002642:Chick Embryo; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008027:Light; D017440:Photoperiod; D012160:Retina / Q000378:metabolism* / Q000528:radiation effects*; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000528:radiation effects
D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein; D051398:Aquaporin 1; D018698:Glutamic Acid
Aquaporins; Chick retina; Light damage; Müller cells; Neuroprotection; Photoreceptors