Effects of Proteasome Inhibition on the Kidney in Experimental Hypercholesterolemia

Abstract

Hypercholesterolemia (HC) and atherosclerosis often accompany and aggravate renal disease. Proteasome inhibitors (PSI) can decrease proliferation and inflammation, likely by reducing activation of the proinflammatory NF-B. However, chronic proteasome inhibition has never been demonstrated in the HC kidney. Four groups of pigs (n ‫؍‬ 7 each) were studied after a 12-wk normal (N) or 2% HC diet alone or supplemented (N؉PSI and HC؉PSI) with MLN-273 (0.08 mg/kg subcutaneously twice weekly). Renal hemodynamics and function were quantified in vivo using electron-beam computed tomography at baseline and after vasodilator challenge using acetylcholine. Renal tissue was studied ex vivo using immunoblotting, PCR, and immunohistochemistry. Serum cholesterol was similarly elevated in HC and HC؉PSI. Basal renal blood flow was similar among the groups, whereas GFR was decreased in both N؉PSI and HC؉PSI. The blunted renovascular and functional responses to acetylcholine in HC were normalized in HC؉PSI (suggesting renal endothelial function improvement), which was accompanied by decreased renal endothelin, NF-B, and augmented endothelial nitric oxide synthase expression. In parallel, HC؉PSI animals also showed elevated NAD(P)H oxidase expression and circulating oxidized LDL, suggesting a potential for increased oxidative stress. This study shows that chronic PSI intervention in HC improves renal endothelial functional responses to challenge, possibly by modulating nitric oxide availability and endothelin. Furthermore, PSI may decrease intrarenal inflammation through modulation of the NF-B pathway but may potentially increase oxidative stress, which warrants further investigation. This study may support a role for the ubiquitin/proteasome system in the kidney in HC and early atherosclerosis.

Proteasome inhibitor MG132 suppresses number and function of endothelial progenitor cells: Involvement of nitric oxide synthase inhibition

“…They showed that bortezomib, another proteasome inhibitor which was approved by the FDA in 2003 for the therapy of relapsed and refractory multiple myeloma (30), exerted a double-edged effect on human umbilical vein cells (HUVECs): at low doses it allowed cell proliferation and angiogenesis, whereas at high doses, still achievable in vivo, it induced growth arrest and angiogenesis blockade. In line with the above observations, the beneficial effect of proteasome inhibitors in endothelial function has been shown by many other experiments, accompanied by enhanced expression of eNOS (15,16,(31)(32)(33). Thus, it seems that partial proteasome inhibition appears to offer beneficial effects on endothelial function.…”

Role of Renal Cortical Neovascularization in Experimental Hypercholesterolemia

“…Furthermore, increased TNF-␣ in HC may have favored renal vasoconstriction by stimulating ET, 43 and we have shown previously that diet-induced HC upregulates both renal ET-1 and its ET-A receptor. 5,25 This study suggests that thalidomide treatment may also exert its effects by downregulating the ET-A receptor, an effect that may have, in turn, contributed to restore eNOS. 18 Furthermore, downregulation of the ET-A receptor can offset the vasoconstrictor effects of TNF-␣.…”

“…In vivo electron-beam computed tomography (CT) flow studies were then performed to assess basal and challenged renal blood flow (RBF) and glomerular filtration rate (GFR). We have shown previously that, using electron-beam CT, we can obtain accurate, repeated, and noninvasive quantifications of RBF and GFR 5,6,11,19,[21][22][23][24][25][26] in the intact single kidney in vivo, allowing evaluation of renal and renovascular function. Briefly, a sequential acquisition of 40 consecutive scans followed a central venous injection of the contrast medium iopamidol (0.5 cc/kg per 2 seconds).…”

Pathways of Renal Fibrosis and Modulation of Matrix Turnover in Experimental Hypercholesterolemia

“…The flow studies were followed by a volume study in which the kidneys were scanned from pole to pole for subsequent measurement of cortical, medullary, and renal volume. Venous blood samples were collected for measurement of plasma lipid profile (Roche Ltd.), total prostaglandin F2 ␣-isoprostanes (enzyme immunoassay; Cayman Chemical Company), 6 superoxide dismutase (SOD) activity (spectrophotometry; Cayman Chemical Company), 12 and circulating oxidized LDL (Ox-LDL) levels (ELISA; Mercodia), 23 as described previously.…”