Loss of Complement Factor H impairs antioxidant capacity and energy metabolism of human RPE cells

Abstract

polymorphisms in the complement factor H (CFH) gene, coding for the factor H protein (fH), can increase the risk for age-related macular degeneration (AMD). AMD-associated CFH risk variants, Y402H in particular, impair FH function leading to complement overactivation. Whether this alone suffices to trigger AMD pathogenesis remains unclear. in AMD, retinal homeostasis is compromised due to the dysfunction of retinal pigment epithelium (Rpe) cells. to investigate the impact of endogenous fH loss on Rpe cell balance, we silenced CFH in human hTERT-RPE1 cells. FH reduction led to accumulation of C3, at both RNA and protein level and increased RPE vulnerability toward oxidative stress. Mild hydrogen-peroxide exposure in combination with CFH knock-down led to a reduction of glycolysis and mitochondrial respiration, paralleled by an increase in lipid peroxidation, which is a key aspect of AMD pathogenesis. in parallel, cell viability was decreased. the perturbations of energy metabolism were accompanied by transcriptional deregulation of several glucose metabolism genes as well as genes modulating mitochondrial stability. our data suggest that endogenously produced fH contributes to transcriptional and metabolic homeostasis and protects Rpe cells from oxidative stress, highlighting a novel role of fH in AMD pathogenesis. Retinal pigment epithelium (RPE) cells are crucial for the maintenance of retinal homeostasis. RPE cells are located on a thin membrane called Bruch´s membrane (BM), and together provide a barrier between the neuroretina and the choroid capillary network. In addition, RPE cells fulfil several key functions, such as phagocytosis of the photoreceptor outer segments, transport of nutrients, preservation of the retinal structure and, most importantly, due to their high antioxidant capacity, RPE cells protect the retina from photo-oxidation and oxidative damage 1. RPE dysfunction and degeneration are key features of age-related macular degeneration (AMD), a complex degenerative disease, and the primary cause of blindness in the elderly population 2. AMD is characterized by a progressive degeneration of the macula, the cone-rich area of the retina, where damage in this area leads to central vision loss and ultimately blindness 3. The aetiology of AMD involves ageing processes, genetic predisposition and environmental factors, however a full understanding of AMD pathogenesis is lacking, which makes drug discovery challenging 4. A defining hallmark of AMD is the presence of deposits, called drusen, between the BM and the RPE layer 5. In the presence of drusen or altered extracellular matrix (ECM) of BM, the functionality of RPE cells may be impaired 6. The retinal microenvironment is already highly oxidized in physiological conditions, due to a very high energy demand and photo-oxidation. Ageing processes, in combination with external stressors including smoking or a high fat diet 7,8 , force RPE cells to deal with excessive levels of oxidative stress. Disturbed RPE cell homeostasis, and in particular RPE cell ...

Impaired Mitochondrial Function in iPSC-Retinal Pigment Epithelium with the Complement Factor H Polymorphism for Age-Related Macular Degeneration

“…A significant decline in retinal ATP and a significant increase in heat shock protein 60 (Hsp60), a marker of mitochondrial stress, was observed in CFH knockout (Cfh−/−) mice compared to WT mice [ 40 ]. In hTERT-RPE1 cells, silencing CFH expression using siRNA resulted in impaired mitochondrial respiration and upregulation of the mitophagy (mitochondria-specific autophagy) genes, PTEN-induced kinase-1 (PINK1) and PARKIN, compared to the negative control [ 41 ]. Additional studies show CFH also influences other cell processes.…”

The CD36 Ligand-Promoted Autophagy Protects Retinal Pigment Epithelial Cells from Oxidative Stress

“…The human telomerase reverse transcriptase subunit-immortalized RPE cell line hTERT RPE-1 has previously been used to study the impact of oxidative stress on RPE cell energy metabolism [ 30 ], as well as the cytoprotective role of autophagy in the RPE [ 31 ]. Oxidative damage to hTERT RPE-1 cells was induced using NaIO 3 as oxidant.…”

Subretinal Rather Than Intravitreal Adeno-Associated Virus–Mediated Delivery of a Complement Alternative Pathway Inhibitor Is Effective in a Mouse Model of RPE Damage

“… 65 Of note, in hTERT-RPE1, silencing of fH impaired mitochondrial respiration and glycolysis, altered expression of genes involved in mitophagy and mitochondrial dynamics, and impacted the cells’ antioxidant functions. 66 It will be of great interest to determine whether intracellular CR2-fH can contribute to this noncanonical signaling.…”