FTO alleviates Aβ1-40 induced retinal pigment epithelium degeneration via PKA/CREB signaling pathway

Abstract

Background Amyloid-β (Aβ), a component of age-related macular degeneration (AMD) hallmark drusen, induces retinal pigment epithelium (RPE) cell degeneration and promotes the progress of AMD. Evidence shows that epigenetics mechanism is involved in the regulation of AMD. In this study, we aimed to investigate the roles of N6-methyladenosine (m6A) and its demethylase the fat mass and obesity-associated gene (FTO) in Aβ-mediated degeneration. Methods The molecular characteristics and morphology of FTO were examined by quantitative Real-Time PCR (qRT-PCR), Western blot and immunofluorescence. Inhibition of FTO was conducted to analyze its function on cell survival. Ocular Coherence Tomography and Fundus Photography was performed to evaluate the fundus of animal models. m6A-mRNA Epi-transcriptomic microarray, bioinformatics analysis and experimental verification were used to explore the potential molecular mechanism and signaling pathway. Results We found overexpression of FTO in Aβ model and demonstrated that inhibition of FTO by the sodium form of Meclofenamic acid (MA1) aggravated RPE impairment. Mechanistically, we identified protein kinase A (PKA) as FTO’s mediating target and found that FTO epigenetically demethylated PKA mRNA and decreased PKA expression, leading to suppressed PKA/ cyclin AMP-responsive element binding (CREB) signaling pathway. Moreover, inhibition of FTO promoted PKA/CREB signaling pathway inducing greater RPE degeneration and death. Conclusions These data demonstrated the functional significance of FTO in Aβ-induced RPE degeneration and the regulatory mechanism of PKA/CREB signaling pathway, implying FTO as a potentially therapeutic target for AMD.

Potential Impact of N6-Methyladenosine RNA Methylation on Vision Function and the Pathological Processes of Ocular Diseases: New Discoveries and Future Perspectives

“…The expression of m6A writers (METTL1, METTL3, METTL14 and WTAP), erasers (FTO and ALKBH5) and readers (YTHDF1-3, YTHDC1 and 2, eIF3 and IGF2BP1-3) in ocular tissues has been reported in our previous study and other studies as well [11][12][13]15,39]. The expression of m6A modification factors (METTL3, METTL14, WTAP, FTO, ALKBH5, YTHDF1, YTHDF3 and YTHDC1) can be found in numerous ocular tissues (cornea, lens, retina, retinal pigmental epithelium [RPE], extraocular muscles and uveal melanoma cells) [41][42][43]45,51,[72][73][74][75][76]. m6A methylation usually varies among different tissues [77,78], indicating that m6A methylation is not only variable but also dynamic, and data obtained from one specific tissue or cell cannot represent the status of m6A methylation in other tissues or cells.…”

“…RPE cell dysfunction is closely related to the pathogenesis of AMD, and RPE degeneration may lead to photoreceptor death. Amyloid-β (Aβ), the major causative factor of Alzheimer's disease [142] and one of the components of drusen, contributes to RPE degeneration [143], and RPE degeneration induced by Aβ1-40 is correlated with the reduced expression of FTO, suggesting that enhanced expres-sion of FTO can protect RPE cells from degeneration [72]. Systemically, increased expression of METTL3 has been observed in an experimental mouse model of Alzheimer's disease and was associated with the reduced expression of FTO [61].…”

“…Amyloid-β (Aβ), one of the factors deposited in Bruch membranes and an inducer of oxidative stress, can induce RPE degeneration [167,168]. As mentioned above, Aβ-induced RPE degeneration may be related to m6A modifications [72].…”

“…A study of the effects of m6A modification on the pathogenesis of age-related cataracts by m6A-IP-seq and RNA-seq analysis showed that major enriched and meaningful host cir-cRNA genes are involved in the processes of autophagy, DNA repair, and aging in age-related cataracts [51,[237][238][239]. In addition, Aβ induces senescence [240], and the role of m6A demethylase FTO in Aβ-induced RPE degeneration has been suggested [72]. Therefore, m6A modifications seem to be of importance in senescence in eye diseases.…”

RNA N6-Methyladenosine Modifications and Its Roles in Alzheimer’s Disease

“…Importantly, METTL3 overexpression rescued synaptic damage and cognitive impairment in Aβ-induced AD mice. In addition, the demethylase FTO was reported to alleviate Aβ-induced cell degeneration via the PKA/CREB signaling pathway ( Hu et al, 2020 ). In addition to targeting Aβ, m 6 A methylation also altered the expression levels of Aβ production-related proteins, such as Aβ precursor protein (APP) and the β-site APP-cleaving enzyme (BACE1) ( Kolisnyk et al, 2017 ; Edens et al, 2019 ).…”