Autophagy Inhibits Renal Tubule Inflammation in Diabetic Kidney Disease Mice Via Inhibition of NLRP3 Inflammasome

Abstract Background Diabetic kidney disease (DKD) has become the leading cause of chronic kidney disease and numerous reports have validated that renal tubule inflammation participate in DKD progression. However, the molecular mechanism underlying renal tubular inflammatory damage in DKD remains to be completely elucidated. The aim of this study is to investigate the effect of rapamycin-induced autophagy on Nod-like receptor family protein 3 (NLRP3) inflammasome and inflammation of renal tubular epithelial cells in DKD. Methods We collected kidney tissue specimens from patients with DKD and transplanted kidney donors for histopathological examination and performed urine and blood samples. The STZ-induced DKD mice model was established for in vivo study. The mice were divided into three groups: Ctrl, DKD, DKD+Rapa. Collected the serum for 24 h protein quantification, blood glucose, C-peptide and insulin level investigations. PAS staining and electron microscopy were used to visualize the pathological changes in the kidney and the expressions of Beclin1, P62, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) protein, interleukin (IL)-1β, IL-18, β2-microglobulin (β2-MG); 24 urine protein, and creatinine in the kidney tissue were detected. Moreover, human renal proximal tubule cells (HK-2) were cultured in vitro, and high glucose was used to induce the model, followed by rapamycin treatment. The protein expression of Beclin1, P62, ASC protein, IL-1β, IL-18, 24 urine protein, and creatinine were analyzed. Results Compared with the model group mice, after rapamycin treatment, urinary protein decreased quantitatively, blood glucose decreased, C-peptide and insulin levels increased (P<0.01), glomerular basement membrane did not thicken obviously, and the expressions of P62, NLRP3, ASC protein, IL-1β and IL-18 protein in renal tissue decreased, while Beclin-1 level increased (P<0.05). After high glucose intervention in vitro, the expression of NLRP3, ASC protein, IL-1β and IL-18 protein in HK-2 cells increased, while the level of Beclin-1 decreased. The expression of NLRP3, ASC, IL-1β and IL-18 decreased and Beclin-1 level increased after rapamycin intervention (P<0.05). Conclusion The findings of the present study indicated that the NLRP3 inflammasomemediated inflammatory response was activated in DKD. Rapamycin can inhibit the activation of NLRP3 inflammasome in DKD by enhancing autophagy.