Dataset Information

Microtubule associated protein 4 phosphorylation-induced epithelial-to-mesenchymal transition of podocyte leads to proteinuria in diabetic nephropathy

ABSTRACT:

Background

Diabetic nephropathy (DN) involves various structural and functional changes because of chronic glycemic assault and kidney failure. Proteinuria is an early clinical manifestation of DN, but the associated pathogenesis remains elusive. This study aimed to investigate the role of microtubule associated protein 4 (MAP4) phosphorylation (p-MAP4) in proteinuria in DN and its possible mechanisms.

Methods

In this study, the urine samples of diabetic patients and kidney tissues of streptozotocin (STZ)-induced diabetic mice were obtained to detect changes of p-MAP4. A murine model of hyperphosphorylated MAP4 was established to examine the effect of MAP4 phosphorylation in DN. Podocyte was applied to explore changes of kidney phenotypes and potential mechanisms with multiple methods.

Results

Our results demonstrated elevated content of p-MAP4 in diabetic patients’ urine samples, and increased kidney p-MAP4 in streptozocin (STZ)-induced diabetic mice. Moreover, p-MAP4 triggered proteinuria with aging in mice, and induced epithelial-to-mesenchymal transition (EMT) and apoptosis in podocytes. Additionally, p-MAP4 mice were much more susceptible to STZ treatment and showed robust DN pathology as compared to wild-type mice. In vitro study revealed high glucose (HG) triggered elevation of p-MAP4, rearrangement of microtubules and F-actin filaments with enhanced cell permeability, accompanied with dedifferentiation and apoptosis of podocytes. These effects were significantly reinforced by MAP4 hyperphosphorylation, and were rectified by MAP4 dephosphorylation. Notably, pretreatment of p38/MAPK inhibitor SB203580 reinstated all HG-induced pathological alterations.

Conclusions

The findings indicated a novel role for p-MAP4 in causing proteinuria in DN. Our results indicated the therapeutic potential of MAP4 in protecting against proteinuria and related diseases. Video Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12964-022-00883-7.

SUBMITTER: Li L

PROVIDER: S-EPMC9331595 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Purpose:Renal injury with the loss of podocyte was characteristic pathology of diabetic nephropathy (DN) and correlated with increased albuminuria. Many studies have found the nephroprotective effect of the novel inhibitors of sodium-glucose cotransporter 2 (SGLT2-is), like Dapagliflozin, delaying the progression of DN. However, the underlying mechanisms of SGLT2 associated with podocyte injury are still not fully elucidated. Methods: Through mRNA sequencing, streptozotocin-induced and Dapagliflozin-intraperitoneal injection mice models were established to explore potential mechanism between Dapagliflozin and renal phenotype. And all changes referring this observed pathway were proven repeatedly in podocyte. Results: Here, we generated the streptozotocin-induced DN models and found the accumulation of nephrotoxin and pathological lesions of the kidney, including interstitial inflammatory infiltration, mesangial expansion and glomerular sclerosis, while low expression of SGLT2 mitigated these injuries in Dapagliflozin-treated mice. Moreover, mRNA expression profile in these treated models determined the significance of insulin-like growth factor-1 receptor (IGF1R)/PI3K regulatory axis in glomerular injury. Particularly, SGLT2-is inhibited the increase of mesenchymal marker, α-SMA and the decrease of podocyte marker, nephrin at the gene or protein level. KEGG analysis also showed the enrichment of phosphatidylinositol signaling system and TGF-β/smad pathway. In parallel, the protein level of IGF1R, phosphorylated PI3K, and α-SMA were increased in high-glucose stimulated human podocyte, and reduced in Dapagliflozin (50nM and 100nM) or OSI-906 (inhibitor of IGF1R, 60nM) used groups. Notably, combination of the two inhibitors produced an accumulative effect in the protection of podocyte integrity. Mechanistically, IGF1 or IGF2 could bind to IGF1 receptors to mediate the epithelial-mesenchymal transition (EMT) of diabetic podocyte in response to the upregulation of SGLT2. Indeed, we enrolled the urine and plasma samples from a cohort consisting of 13 healthy people, and a cohort of 19 patients with DN using SGLT2-inhibitors (n=9) or not (n=10). Compared with pure DN patients, Elisa results suggested an increased circulation and excretion level of IGF1/2 in SGLT2-is used DN cohort. Conclusions: Taken together, our study reported the key role of SGLT2/IGF1R/PI3K signaling in regulating podocyte EMT. Modulating the IGF1R expression may provide a novel idea for DN therapy.