Lack of P4H-TM in mice results in age-related retinal and renal alterations

Abstract

Age-related macular degeneration (AMD), affecting the retinal pigment epithelium (RPE), is the leading cause of blindness in middle-aged and older people in developed countries. Genetic and environmental risk factors have been identified, but no effective cure exists. Using a mouse model we show that a transmembrane prolyl 4-hydroxylase (P4H-TM), which participates in the oxygen-dependent regulation of the hypoxia-inducible factor (HIF), is a potential novel candidate gene for AMD. We show that P4h-tm had its highest expression levels in the mouse RPE and brain, heart, lung, skeletal muscle and kidney. P4h-tm mice were fertile and had a normal life span. Lack of P4h-tm stabilized HIF-1α in cortical neurons under normoxia, while in hypoxia it increased the expression of certain HIF target genes in tissues with high endogenous P4h-tm expression levels more than in wild-type mice. Renal erythropoietin levels increased in P4h-tm mice with aging, but the resulting ∼2-fold increase in erythropoietin serum levels did not lead to erythrocytosis. Instead, accumulation of lipid-containing lamellar bodies in renal tubuli was detected in P4h-tm mice with aging, resulting in inflammation and fibrosis, and later glomerular sclerosis and albuminuria. Lack of P4h-tm was associated with retinal thinning, rosette-like infoldings and drusen-like structure accumulation in RPE with aging, as is characteristic of AMD. Photoreceptor recycling was compromised, and electroretinograms revealed functional impairment of the cone pathway in adult P4h-tm mice and cone and rod deficiency in middle-aged mice. P4H-TM is therefore imperative for normal vision, and potentially a novel candidate for age-induced diseases, such as AMD.

Loss of NRF-2 and PGC-1α genes leads to retinal pigment epithelium damage resembling dry age-related macular degeneration

“…We tested the retinal function in three-month-old (referred to as “young”; WT, n = 6; dKO, n = 6) and one-year-old mice (referred to as “old”; WT, n = 6; dKO, n = 7) by ERG (electroretinography, Thorlabs PM100D, Thorlabs, NJ, USA). The ERG method has been described in detail previously [41] . The animals were dark-adapted overnight for at least 12 h. They were anesthetized with isoflurane (induction: concentration 4–4.5%; maintenance: concentration ~ 1.2%) and placed into a customized stereotaxic frame and kept warm with a physiological heating pad at 38 °C.…”

“…A strong flash (2.00 log cd·s/m 2 ) was delivered to evoke transient rod saturation and 400 ms later a second probe flash (2.00 log cd·s/m 2 ) was delivered to generate a cone-specific response. Rod-saturation at 400 ms after flash was assumed based on a previous ex vivo ERG saturation test [41] , where the strongest flash was estimated to yield ~ 14,000 photoisomerizations (*R) per mouse rod. The light intensity was quantified with an energy meter (Thorlabs PM100D, Thorlabs, NJ, USA).…”

Retinal Degeneration In A Mouse Model Of CLN5 Disease Is Associated With Compromised Autophagy

“…The maximum flash yielded ~4500 photoisomerizations (*R) per mouse rod (calibration described in ref. 69). After scotopic recordings a monitor in faraday cage was turned on to reflect grey light, at 17 lux, to the animal.…”

Null mutation in P4h-tm leads to decreased fear and anxiety and increased social behavior in mice

“…(3) While P4H-TM can hydroxylate the prolines in HIFα targeted by HIF-P4Hs in vitro, it also hydroxylated to a small extent HIFα in which these prolines were M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT mutated to alanines suggesting it may have additional substrates to HIFα (Koivunen et al 2007). Finally, the physiological role of collagen-P4Hs and HIF-P4Hs 1-3 is established (Myllyharju and Koivunen 2013), but the role and function of P4H-TM remain still largely unknown (Leinonen et al 2016), although its inhibition associates with renal EPO production and induction of erythropoiesis similarly to inhibition of HIF-P4Hs 1-3 (Laitala et al 2012).…”

“…Genetic studies on P4h-tm gene homolog in morpholino knockdown zebrafish provided the first evidence of the significance of P4H-TM in living vertebrates (Hyvarinen et al 2010), later followed by mouse knockout studies (Leinonen et al 2016). P4H-tm gene is not vital since P4h-tm -/mice are fertile and have a normal lifespan (Leinonen et al 2016).…”