Accelerated retinal aging in PACAP knock-out mice

Area of Science:

• Neuroscience
• Ophthalmology
• Aging Research

Background:

• Pituitary adenylate cyclase activating polypeptide (PACAP) is a peptide with known neurotrophic and neuroprotective functions.
• PACAP and its receptors are present throughout the retina, suggesting a role in retinal health.
• Previous studies indicate PACAP's neuroprotective effects in various retinal degeneration models.

Purpose of the Study:

• To investigate the role of endogenous PACAP in age-related retinal changes.
• To compare retinal cell-type specific differences between young and aged wild-type (WT) and PACAP knockout (KO) mice.
• To examine the impact of PACAP deficiency on neurochemical markers and signaling pathways during aging.

Main Methods:

• Histological and immunocytochemical analyses of retinal tissues from young and aged WT and PACAP KO mice.
• Western blot analysis to assess protein expression and phosphorylation states, including MAPK signaling pathway components.
• Evaluation of specific neurochemical markers for dopaminergic, horizontal, and rod bipolar cells.

Main Results:

• Young PACAP KO retinas showed no significant changes in major neurochemical markers compared to WT, except for the absence of PAC1-R in bipolar and horizontal cells.
• Aged PACAP KO mice exhibited age-related alterations not seen in WT mice, including dendritic sprouting of horizontal and rod bipolar cells and reduced ganglion cell numbers.
• Elevated GFAP expression in Müller glial cells and altered ERK1/2 and JNK phosphorylation were observed in PACAP KO mice, indicating MAPK pathway dysregulation.

Conclusions:

• Endogenous PACAP plays a crucial role in protecting the retina against age-related damage.
• PACAP deficiency leads to accelerated retinal aging phenotypes and disruptions in key signaling pathways.
• These findings highlight PACAP's importance in maintaining retinal integrity during the aging process.