Inhibiting HIF-1 signaling alleviates HTRA1-induced RPE senescence in retinal degeneration

Background: Age-related macular degeneration (AMD), characterized by the degeneration of retinal pigment epithelium (RPE) and photoreceptors, is the leading cause of irreversible vision impairment among the elderly. RPE senescence is an important contributor to AMD and has become a potential target for AMD therapy. HTRA1 is one of the most significant susceptibility genes in AMD, however, the correlation between HTRA1 and RPE senescence hasn't been investigated in the pathogenesis of AMD.

Methods: Western blotting and immunohistochemistry were used to detect HTRA1 expression in WT and transgenic mice overexpressing human HTRA1 (hHTRA1-Tg mice). RT-qPCR was used to detect the SASP in hHTRA1-Tg mice and ARPE-19 cells infected with HTRA1. TEM, SA-β-gal was used to detect the mitochondria and senescence in RPE. Retinal degeneration of mice was investigated by fundus photography, FFA, SD-OCT and ERG. The RNA-Seq dataset of ARPE-19 cells treated with adv-HTRA1 versus adv-NC were analyzed. Mitochondrial respiration and glycolytic capacity in ARPE-19 cells were measured using OCR and ECAR. Hypoxia of ARPE-19 cells was detected using EF5 Hypoxia Detection Kit. KC7F2 was used to reduce the HIF1α expression both in vitro and in vivo.

Results: In our study, we found that RPE senescence was facilitated in hHTRA1-Tg mice. And hHTRA1-Tg mice became more susceptible to NaIO3 in the development of oxidative stress-induced retinal degeneration. Similarly, overexpression of HTRA1 in ARPE-19 cells accelerated cellular senescence. Our RNA-seq revealed an overlap between HTRA1-induced differentially expressed genes associated with aging and those involved in mitochondrial function and hypoxia response in ARPE-19 cells. HTRA1 overexpression in ARPE-19 cells impaired mitochondrial function and augmented glycolytic capacity. Importantly, upregulation of HTRA1 remarkably activated HIF-1 signaling, shown as promoting HIF1α expression which mainly located in the nucleus. HIF1α translation inhibitor KC7F2 significantly prevented HTRA1-induced cellular senescence in ARPE-19 cells, as well as improved the visual function in hHTRA1-Tg mice treated with NaIO3.

Conclusions: Our study showed elevated HTRA1 contributes to the pathogenesis of AMD by promoting cellular senescence in RPE through damaging mitochondrial function and activating HIF-1 signaling. It also pointed out that inhibition of HIF-1 signaling might serve as a potential therapeutic strategy for AMD. 

 

Comments:

The study described above investigated the role of HTRA1 (high-temperature requirement A serine peptidase 1) in the pathogenesis of age-related macular degeneration (AMD), specifically focusing on its correlation with retinal pigment epithelium (RPE) senescence. AMD is a leading cause of irreversible vision impairment in older individuals, and RPE senescence is known to contribute to its development.

The researchers utilized various methods to study the effects of HTRA1 on RPE senescence and retinal degeneration. They conducted experiments using transgenic mice overexpressing human HTRA1 (hHTRA1-Tg mice) and ARPE-19 cells infected with HTRA1. They also performed molecular analyses such as Western blotting, immunohistochemistry, RT-qPCR, and RNA sequencing (RNA-Seq).

The results of the study revealed several important findings. Firstly, the overexpression of HTRA1 in hHTRA1-Tg mice and ARPE-19 cells accelerated cellular senescence in the RPE. This suggests that elevated levels of HTRA1 contribute to RPE senescence in the pathogenesis of AMD.

Additionally, the study found that hHTRA1-Tg mice were more susceptible to NaIO3, an oxidative stress-inducing agent that leads to retinal degeneration. This indicates that elevated HTRA1 levels exacerbate oxidative stress-induced retinal damage in AMD.

The RNA-Seq analysis identified an overlap between genes associated with HTRA1-induced aging and those involved in mitochondrial function and the hypoxia response in ARPE-19 cells. HTRA1 overexpression in these cells impaired mitochondrial function and increased glycolytic capacity, suggesting that HTRA1 negatively affects cellular energy metabolism.

Furthermore, the study showed that upregulation of HTRA1 significantly activated HIF-1 (hypoxia-inducible factor 1) signaling. HIF-1 is a transcription factor involved in the cellular response to low oxygen levels. Increased HIF-1 signaling, demonstrated by elevated HIF1α expression in the nucleus, contributed to HTRA1-induced cellular senescence in ARPE-19 cells.

To explore potential therapeutic strategies for AMD, the researchers used KC7F2, an inhibitor of HIF1α translation. They found that KC7F2 prevented HTRA1-induced cellular senescence in ARPE-19 cells and improved visual function in hHTRA1-Tg mice treated with NaIO3.

In conclusion, this study highlights the role of elevated HTRA1 in promoting cellular senescence in RPE, impairing mitochondrial function, and activating HIF-1 signaling. These findings suggest that targeting HIF-1 signaling could be a potential therapeutic approach for AMD.