Implications of Senescent Cell Burden and NRF2 Pathway in Uremic Calcification: A Translational Study

Abstract

Increased senescent cell burden and dysregulation of the nuclear factor erythroid 2–related factor 2 (NRF2) pathway have been associated with numerous age-related pathologies; however, their role in promoting vascular calcification (VC) in chronic kidney disease (CKD) has yet to be determined. We investigated whether senescence and NRF2 pathways may serve as drivers of uremia-induced VC using three complementary approaches: a novel model of induced VC in 5/6-nephrectomized rats supplemented with high phosphate and vitamin D; epigastric arteries from CKD patients with established medial calcification; and vascular smooth muscle cells (VSMCs) incubated with uremic serum. Expression of p16Ink4a and p21Cip1, as well as γ-H2A-positive cells, confirmed increased senescent cell burden at the site of calcium deposits in aortic sections in rats, and was similarly observed in calcified epigastric arteries from CKD patients through increased p16Ink4a expression. However, uremic serum-induced VSMC calcification was not accompanied by senescence. Expression of NRF2 and downstream genes, Nqo1 and Sod1, was associated with calcification in uremic rats, while no difference was observed between calcified and non-calcified EAs. Conversely, in vitro uremic serum-driven VC was associated with depleted NRF2 expression. Together, our data strengthen the importance of senescence and NRF2 pathways as potential therapeutic options to combat VC in CKD.

Phenylacetylglutamine and trimethylamine N‐oxide: Two uremic players, different actions

“…Interventional therapies have yet to be developed; however, the fact that free radical generation persists after generation of both toxins is of clinical importance. Using a novel animal model of 5/6 nephrectomised rats, we reported dysregulated NRF2 is linked to ectopic vascular calcification 48 . Hence therapeutically targeting the NRF2 pathway using NRF2 agonists may have positive clinical implications.…”

“…Strengths of the current study include a reasonably large kidney failure cohort that was carefully phenotyped. We also implemented a translational approach to test our hypothesis in a clinical cohort and an in vitro calcification model, as recapitulating uremic components in vitro has been difficult 48 . In addition, we assessed the magnitude of calcification in two separate locations of the vascular tree—coronary and epigastric arteries.…”

“…Using a novel animal model of 5/6 nephrectomised rats, we reported dysregulated NRF2 is linked to ectopic vascular calcification. 48 Hence therapeutically targeting the NRF2 pathway using NRF2 agonists may have positive clinical implications. However, further experimental studies are needed to determine the optimal window of intervention.…”

The NRF2/ID2 Axis in Vascular Smooth Muscle Cells: Novel Insights into the Interplay between Vascular Calcification and Aging

“…Aging is associated with an accumulation of senescent cells resistant to apoptosis, contributing to medial calcification and increased expression of osteogenic markers 7,42 . Silencing Nrf2 has been found to speed up the senescence of vascular cells 43,44 , with both senescent cell accumulation and Nrf2 dysregulation implicated in medial VC pathogenesis 20 . The burgeoning body of evidence suggests that activating NRF2 could provide protective effects against age-related VC by mitigating cellular senescence.…”

“…However, it is imperative to acknowledge that NRF2 activators lack specificity and may induce activation of alternative pathways, such as the NF-κB signaling pathway, which has also been implicated in inhibiting VC 18,19 . Interestingly, NRF2 levels are higher in animal models of CKD and in end-stage renal disease (ESRD) patients with VC, even though uremic serum from these patients paradoxically increases VSMC calcification and decreases NRF2 20 . Molecules associated with NRF2, both upstream and downstream, have been identified as inhibitors of VC.…”