Effects and mechanism of ROS/NF-κB signaling on MuRF1-mediated BK-β1 degradation on aortic smooth muscle in diabetic mice

AIM To explore the effects and mechanisms of reactive oxygen species(ROS)/NF-κB signaling on muscle RING finger protein 1(MuRF1)-mediated β1 subunit of the large conductance Ca²⁺-activated K⁺ channel(BK-β1) degradation on aortic smooth muscle in diabetic mice. METHODS Diabetes was induced by a single intraperitoneal(i.p.) injection of streptozotocin. Male C57/BL6J mice were randomly divided into six groups(n=15)control group, control+NAC(ROS scavenger) group, control+PDTC(NF-κB inhibitor) group, diabetes group, diabetes+NAC group, and diabetes+PDTC group. Control+NAC group and diabetes+NAC group were administered a dose of 100 mg/(kg·day) NAC and control+PDTC group and diabetes+PDTC group were given a dose of 50 mg/(kg·day) PDTC. Control group and diabetes group received normal saline injection i.p. After 12 weeks, Western blot was used to determine the expression of BK-β1, MuRF1 and RelA/p65. Concentration-response of NS-1619(BK channel activator) to vasodilatation was measured by functional vasoreactivity test. Aortic smooth muscle cells were isolated acutely by enzyme digestion and BK currents were recorded by patch clamp technique in whole cell configuration. RESULTS Compared with those in the control group, control+NAC group and control+PDTC group, expressions of BK-β1 decreased significantly in diabetes group(P<0.05), with significantly increased expressions of MuRF1 and RelA/p65(P<0.05) as well as reduced NS-1619-mediated aortic dilation(P<0.05). There was a reduction of BK current densities when test potential was >50 mV in diabetes group(P<0.05). Compared with those in the diabetes group, protein levels of BK-β1 increased significantly(P<0.05), whereas protein levels of both MuRF1 and RelA/p65 reduced significantly(P<0.05) with restored NS-1619-mediated aortic dilation(P<0.05) and increased BK currents densities(P<0.05) with treatment with NAC and PDTC in diabetes+NAC group and diabetes+PDTC group. CONCLUSION NAC and PDTC inhibit MuRF1-mediated BK-β1 degradation on aortic smooth muscle, restore the response to NS-1619 and increase BK current densities in diabetic mice. ROS/NFκB signaling may be involved in the regulation of MuRF1-mediated BK-β1 degradation.