The erythropoietin receptor is a downstream effector of Klotho-induced cytoprotection

Abstract

Although the role of the erythropoietin (Epo) receptor (EpoR) in erythropoiesis has been known for decades, its role in non-hematopoietic tissues is still not well defined. Klotho has been shown and Epo has been suggested to protect against acute ischemia-reperfusion injury in the kidney. Here we found in rat kidney and in a rat renal tubular epithelial cell line (NRK cells) EpoR transcript and antigen, and EpoR activity signified as Epo-induced phosphorylation of Jak2, ErK, Akt, and Stat5 indicating the presence of functional EpoR. Transgenic overexpression of Klotho or addition of exogenous recombinant Klotho increased kidney EpoR protein and transcript. In NRK cells, Klotho increased EpoR protein, enhanced Epo-triggered phosphorylation of Jak2 and Stat5, the nuclear translocation of phospho-Stat5, and protected NRK cells from hydrogen peroxide cytotoxicity. Knock-down of endogenous EpoR rendered NRK cells more vulnerable, and overexpression of EpoR more resistant to peroxide-induced cytotoxicity, indicating that EpoR mitigates oxidative damage. Knock-down of EpoR by siRNA abolished Epo-induced Jak2, and Stat5 phosphorylation, and blunted the protective effect of Klotho against peroxide-induced cytotoxicity. Thus in the kidney, EpoR and its activity are downstream effectors of Klotho enabling it to function as cytoprotective protein against oxidative injury.

αKlotho Mitigates Progression of AKI to CKD through Activation of Autophagy

“…We mimicked IRI with H 2 O 2 and found that H 2 O 2 -induced lactate dehydrogenase (LDH) release was reduced by coincubation with aKlotho ( Figure 8A) as previously reported. 16 The new finding, however, was that aKlotho increased the LC3-IIto-LC3-I ratios and decreased p62 protein in OK cells ( Figure 8B) and increased the number of GPF-LC3 punctae (autophagosomes) in OK cells transfected with GFP-LC3 ( Figure 8, C and D), thereby confirming the in vivo findings of higher baseline autophagic flux in the kidney of Tg-Kl mice compared with WT mice ( Figure 7B). Bafilomycin A1 (Baf), an inhibitor of lysosomal acidification and also, an autophagy inhibitor, 68 increased the ratios of LC3-II to LC3-I and p62 ( Figure 8B), increased GPF-LC3 punctae ( Figure 8, C and D), and also, blunted aKlotho-induced elevation of autophagic flux ( Figure 8, B and C).…”

“…OK cells were treated with H 2 O 2 and/or autophagy modulators (inducers or suppressors) in the presence or absence of aKlotho protein. Cell lysates were prepared 16,17 and immunoblotted for LC3 protein. Supernatants from cell culture media were used for measurement of LDH release as we described previously.…”

“…13,14 aKlotho is involved in cytoprotection, antiapoptosis, anticell senescence, and antifibrosis, all of which may be crucial in tissue protection and regeneration. 15,16 Animal studies have shown that (1) AKI from ischemic injury and AKI from cisplatin nephrotoxicity are transient states of aKlotho deficiency, 17,18 (2) aKlotho protects the kidney from ischemic AKI when given immediately after the insult, 18 and (3) restoration of aKlotho after established unilateral ureteral obstruction can prevent subsequent renal fibrosis. 19,20 Clinical observational studies have shown aKlotho deficiency in both AKI 18 and CKD.…”

The Connotation of Kidney Stores Essence Theory and Kidney Endocrine Substance

“…α-Klotho and EPO can be regulated by each other [38,39]. Obviously, the role of α-klotho is very similar to the TCM theory of "kidneys essence generating marrow and producing blood."…”

Role of alternative phosphorylation and O-glycosylation of erythropoietinreceptor in modulating its function: an in silico study

“…Early studies on EPO-R showed that this receptor is only expressed in cells of the erythroid lineage, emphasizing that the action of EPO is limited to red blood cell manufacturing, while further studies divulged the wide expression of the EPO-R, increasing the likelihood of extra-hematopoietic effect of EPO (Wang et al, 2014). The detection of EPO-R mRNA in the brain, heart, retinal, skeletal, muscle, and kidney cells makes it a promising target to study its untold functions (Morishita et al, 1997;Wu et al, 1999;Noguchi et al, 2008;Hu et al, 2013).…”