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  Objective  To investigate the role of histone deacetylase 6 (HDAC6) in podocyte injury in diabetic kidney disease (DKD) in mice.

  Methods  1) The 8-week-old male CD-1 mice were selected to construct the model of DKD with streptozocin (STZ). After the model was established, the mice were intraperitoneally injected with HDAC6 inhibitor CAY10603 (5mg/kg/daily) or same volume vehicle as control. The mice were divided into four groups, control (CTL)+vehicle (Veh) (n=5), CLT+CAY10603 (n=3), STZ+Veh (n=9), and STZ+CAY10603 (n=7). Mice in STZ+Veh and STZ+CAY10603 groups developed DKD, while mice in the CTL+Veh and CTL+CAY10603 groups were served as normal controls. The therapeutic effect was evaluated through urine albumin-to-creatinine ratio (uACR) and renal pathology after the 2-week treatment with CAY10603. 2) Human podocytes were cultured in vitro and were divided into four groups as follows: CTL, transforming growth factor-β (TGFβ), TGFβ+CAY10603 (250 nmol/L), and TGFβ+CAY10603 (500 nmol/L) groups. The control group did not receive any treatment, the last three groups were given 36-h TGFβ treatment at 5 ng/µL, with or without CAY10603 as indicated for an additional 12 h. Western blot was performed to determine the inhibitory effect of CAY10603 on NLRP3 inflammasome. 3) HDAC6 knockout (KO) mice were generated and used to create STZ-induced model of DKD. The mice were divided into four groups: C57BL/6J wild type (WT) (n=6), HDAC6 KO (n=6), WT+STZ (n=10), and HDAC6 KO+STZ (n=9). Samples were collected 16 weeks after successful modeling and changes in uACR and renal pathology were evaluated accordingly.

  Results  After 2 weeks of treatment, mice in the STZ+CAY10603 group exhibited reduction in uACR (P<0.05) and inhibition of glomerular mesangium expansion (P<0.05) compared with those of the mice in the STZ+Veh group. There was no statistically significant difference in the indicators between the CTL+Veh group and the CTL+CAY10603 group. In vitro cultured podocytes, compared with the control group, NLRP3 inflammasome activation was seen in the TGFβ group. CAY10603 treatment significantly inhibited the activation of NLRP3 in the dosage-dependent manner (P<0.05). Compared with those of the WT group, the WT+STZ group showed increased uACR (P<0.05), obvious glomerulosclerosis and loss of podocytes numbers. Compared with those of the WT+STZ group, the HDAC6 KO+STZ group showed effectively reduction of uACR (P<0.05) and improvement in the renal pathological changes in mice. There was no significant difference in these aspects between the WT and HDAC6 KO groups.

  Conclusion  Inhibition of HDAC6 alleviates proteinuria and podocyte injury in the mouse model of DKD by suppressing the activation of NLRP3 inflammasome.