Vittoria Esposito

Low-protein diet supplemented with ketoacids reduces the severity of renal disease in 5/6 nephrectomized rats: a role for KLF15

Dietary protein restriction is an important treatment for chronic kidney disease. Herein, we tested the effect of low-protein or low-protein plus ketoacids (KA) diet in a remnant kidney model. Rats with a remnant kidney were randomized to receive normal protein diet (22%), low-protein (6%) diet (LPD), or low-protein (5%) plus KA (1%) diet for 6 months. Protein restriction prevented proteinuria, decreased blood urea nitrogen levels, and renal lesions; however, the LPD retarded growth and decreased serum albumin levels. Supplementation with KA corrected these abnormalities and provided superior renal protection compared with protein restriction alone. The levels of Kruppel-like factor-15 (KLF15), a transcription factor shown to reduce cardiac fibrosis, were decreased in remnant kidneys. Protein restriction, which increased KLF15 levels in the normal kidney, partially recovered the levels of KLF15 in remnant kidney. The expression of KLF15 in mesangial cells was repressed by oxidative stress, transforming growth factor-β, and tumor necrosis factor (TNF)-α. The suppressive effect of TNF-α on KLF15 expression was mediated by TNF receptor-1 and nuclear factor-κB. Overexpression of KLF15 in mesangial and HEK293 cells significantly decreased fibronectin and type IV collagen mRNA levels. Furthermore, KLF15 knockout mice developed glomerulosclerosis following uninephrectomy. Thus, KLF15 may be an antifibrotic factor in the kidney, and its decreased expression may contribute to the progression of kidney disease.

CHOP deficiency results in elevated lipopolysaccharide-induced inflammation and kidney injury

C/EBP homologous protein (CHOP) is an important mediator of endoplasmic reticulum (ER) stress-induced cell and organ injury. Here we show that lipopolysaccharide (LPS)-induced acute kidney injury (AKI) is associated with ER stress and elevated CHOP. We postulated that CHOP(-/-) mice would be protected against LPS-induced-AKI. Unexpectedly, while Toll-like receptor 4 (TLR4) expression levels were comparable in kidneys of CHOP(-/-) and wild-type (WT) mice, CHOP(-/-) mice developed more severe AKI after LPS injection. Furthermore, the severe kidney injury in CHOP(-/-) mice was associated with an exaggerated inflammatory response. Serum TNF-α levels were more elevated in LPS-treated CHOP(-/-) mice. There was a 3.5-fold higher amount of renal neutrophil infiltrates in LPS-treated CHOP(-/-) than in WT mice. Additionally, the kidneys of LPS-treated CHOP(-/-) mice had a more prominent increase in NF-κB activation and further upregulation of proinflammatory genes, i.e., c-x-c motif ligand 1 (CXCL-1), macrophage inflammatory protein-2 (MIP-2), and IL-6. Finally, proximal tubules, glomeruli, and podocytes isolated from CHOP(-/-) mice also had an exaggerated proinflammatory response to LPS. Since LPS directly increased CHOP in glomeruli and podocytes of WT mice, together these data suggest that the LPS-induced increase of CHOP in kidneys may inhibit inflammatory response in renal cells and provide protection against AKI.

Pharmacologic control of oxidative stress and inflammation determines whether diabetic glomerulosclerosis progresses or decreases: A pilot study in sclerosis-prone mice

Diabetic kidney disease (DKD) is characterized by progressive glomerulosclerosis (GS). ROP mice have a sclerosis-prone phenotype. However, they develop severe, rapidly progressive GS when rendered diabetic. Since GS also develops in aged C57Bl6 mice, and can be reversed using bone marrow from young mice which have lower oxidative stress and inflammation (OS/Infl), we postulated that this might also apply to DKD. Therefore, this pilot study asked whether reducing OS/Infl in young adult sclerosis-prone (ROP) diabetic mice leads to resolution of existing GS in early DKD using safe, FDA-approved drugs.After 4 weeks of stable streptozotocin-induced hyperglycemia 8–12 week-old female mice were randomized and treated for 22 weeks as follows: 1) enalapril (EN) (n = 8); 2) pyridoxamine (PYR)+EN (n = 8); 3) pentosan polysulfate (PPS)+EN (n = 7) and 4) PPS+PYR+EN (n = 7). Controls were untreated (non-DB, n = 7) and hyperglycemic (DB, n = 8) littermates. PPS+PYR+EN reduced albuminuria and reversed GS in DB. Treatment effects: 1) Anti-OS/Infl defenses: a) PPS+PYR+EN increased the levels of SIRT1, Nrf2, estrogen receptor α (ERα) and advanced glycation endproduct-receptor1 (AGER1) levels; and b) PYR+EN increased ERα and AGER1 levels. 2) Pro-OS/Infl factors: a) PPS+PYR+EN reduced sTNFR1, b) all except EN reduced MCP1, c) RAGE was reduced by all treatments. In summary, PYR+PPS+EN modulated GS in sclerosis-prone hyperglycemic mice. PYR+PPS+EN also decreased albuminuria, OS/Infl and the sclerosis-prone phenotype. Thus, reducing OS/Infl may reverse GS in early diabetes in patients, and albuminuria may allow early detection of the sclerosis-prone phenotype.